JP5223785B2 - Vehicular steering transmission ratio variable type steering device - Google Patents

Description

  The present invention relates to a steering device for a vehicle such as an automobile, and more particularly to a steering device with a variable steering transmission ratio.

  The steering transmission ratio variable type steering device is provided with a steering transmission ratio variable device capable of changing a steering transmission ratio, which is a ratio of a steering wheel turning amount to a steering input amount to the steering wheel, and changes the steering transmission ratio as necessary. The device is well known in the art. When the steering transmission ratio is changed by the steering transmission ratio variable type steering device, the relationship between the steering operation position of the steering wheel and the steering angle of the steered wheels deviates from the relationship before the steering transmission ratio change, so that a so-called offset occurs. Therefore, in the steering transmission ratio variable type steering device, as described in, for example, Patent Document 1 below, when the steering wheel is turned up or down by the driver after the steering transmission ratio is changed, or the switching back operation is performed. In this case, the steering transmission ratio is returned to the original value, thereby eliminating the offset.

JP 2005-8033 A

[Problems to be Solved by the Invention]
In a vehicle equipped with a steering transmission ratio variable type steering device, if the steering transmission ratio is suddenly returned to the original value after the steering transmission ratio is changed, the relationship of the vehicle behavior to the driver's steering operation is abruptly changed. Therefore, there is a limit to the speed at which the steering transmission ratio can be returned to the original value. For this reason, for example, when a very rapid steering operation such as emergency avoidance steering is performed, or when the steered wheels are suddenly actively steered by the steering transmission ratio variable device for the purpose of ensuring safety during traveling of the vehicle, the steering transmission ratio is restored. In some cases, the offset remains without being canceled even if it is returned to the value of.

  Thus, if the offset remains, the relationship between the steering operation position of the steering wheel and the steering angle of the steered wheels deviates from the relationship that should originally exist, and it is inevitable that the driver feels uncomfortable with the steering operation. For example, if the driver tries to drive the vehicle straight, the steering wheel must be steered and held to cancel the offset. If the driver tries to turn the vehicle, the steering wheel is It must be rotated to a different rotational position. If the driver further rotates the steering wheel to reduce the turning radius of the vehicle, the steering wheel cannot be rotated unless the steering wheel is changed relatively early depending on the direction of the offset.

The present invention has been made in view of the above-described problems in the conventional steering transmission ratio variable type steering device, and the main problem of the present invention is due to the offset remaining after the steering transmission ratio is changed. Thus, it is possible to reduce the uncomfortable feeling that the driver learns during the steering operation.
[Means for Solving the Problems and Effects of the Invention]

  According to the present invention, the main problem described above is the variable steering transmission ratio capable of changing the steering transmission ratio, which is the ratio of the steering wheel turning amount to the steering operation amount to the steering input means. And a control means for controlling the steering transmission ratio variable device, the vehicle steering transmission ratio variable type steering device, wherein the control means changes the steering transmission ratio by the steering transmission ratio variable device. When an offset occurs in the relationship of the steering position of the steering input means with respect to the steering angle of the steered wheels, the steering position of the steering input means when the specific control ends is set as a reference steering position, and the reference steering position Among the two steering areas on both sides of the vehicle, the steering area on the same side as the offset side with respect to the vehicle straight position of the steering input means is the first steering area, and the steering transmission when the offset is 0 Is the standard steering transmission ratio, and when the driver steers the steering input means in the first steering region after the end of the specific control, the steering transmission ratio is the standard steering transmission ratio. This is achieved by a vehicle steering transmission ratio variable type steering apparatus characterized by being larger than that.

  According to the first aspect of the present invention, when the driver steers the steering input means in the first steering region after completion of the predetermined control, the steering transmission ratio is higher than the standard steering transmission ratio. Increased. Therefore, when the driver steers the steering input means in the first steering area where it is difficult to steer the steering input means, the required steering amount of the steering input means can be reduced, and the driver can input the steering input. The desired amount of steering wheel can be steered with a small steering operation amount. Therefore, compared with the case where the steering transmission ratio is not made larger than the standard steering transmission ratio in the situation where the driver steers the steering input means in the first steering region, the driver In this case, the vehicle can be easily turned when the steering input means is steered, thereby reducing a sense of incongruity.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the control means is opposite to the first steering region with respect to the reference steering position. When the driver steers the steering input means in the second steering area, the steering transmission ratio is set to be larger than the standard steering transmission ratio. It is comprised so that it may become small (structure of Claim 2).

  According to the second aspect of the present invention, when the driver steers the steering input means in the second steering region, the steering transmission ratio is made smaller than the standard steering transmission ratio. Therefore, the required steering amount of the steering input means when the steering input means is steered in the second steering region where the driver can easily steer the steering input means can be increased. Therefore, compared with the case where the steering transmission ratio is not made smaller than the standard steering transmission ratio in the situation where the driver steers the steering input means in the second steering area, the driver In this case, it is possible to make it difficult for the vehicle to turn by steering the steering input means, thereby reducing the uncomfortable feeling caused by the fact that the steering input means can be easily steered.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 2, the amount by which the steering transmission ratio is made smaller than the standard steering transmission ratio is the steering The transmission ratio is configured to be smaller than an amount that is larger than the standard steering transmission ratio (configuration of claim 3).

  According to the third aspect of the present invention, the amount that makes the steering transmission ratio smaller than the standard steering transmission ratio is smaller than the amount that makes the steering transmission ratio larger than the standard steering transmission ratio. Therefore, it is possible to effectively prevent the steering operation of the steering input means in the second steering area from becoming excessively difficult while effectively facilitating the steering operation of the steering input means in the first steering area. be able to.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration according to any one of claims 1 to 3, the control means controls the steering according to the magnitude of the offset. The change amount of the transmission ratio is variably set (configuration of claim 4).

  According to the configuration of the fourth aspect, the change amount of the steering transmission ratio is variably set according to the magnitude of the offset. Therefore, the steered wheels are steered according to the degree to which it is difficult to steer the steering input means in the first steering region as compared with the case where the change amount of the steering transmission ratio is constant regardless of the magnitude of the offset. The degree of ease can be variably set.

  According to the present invention, in the configuration according to any one of the first to fourth aspects, when the magnitude of the offset after the start of the change of the steering transmission ratio becomes equal to or less than a reference value, the control means The change of the steering transmission ratio is terminated, and the steering transmission ratio is returned to the standard steering transmission ratio (configuration of claim 5).

  According to the fifth aspect of the present invention, when the magnitude of the offset after the start of the change of the steering transmission ratio becomes equal to or less than the reference value, the change of the steering transmission ratio is terminated, and the steering transmission ratio becomes the standard steering transmission ratio. Returned to Therefore, when the magnitude of the offset decreases after the start of the change of the steering transmission ratio and the degree of difficulty in steering the steering input means in the first steering region decreases, the steering transmission ratio is returned to the standard steering transmission ratio. It is possible to prevent the steering transmission ratio from being changed unnecessarily.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration according to any one of claims 1 to 5, the control means is that the driver has changed the steering input means. When the estimation is made, the change of the steering transmission ratio is terminated, and the steering transmission ratio is returned to the standard steering transmission ratio (configuration of claim 6).

  According to the sixth aspect of the present invention, when it is estimated that the driver has changed the steering input means, the change of the steering transmission ratio is ended, and the steering transmission ratio is returned to the standard steering transmission ratio. Therefore, in a situation where the driver can easily steer the steered wheel by changing the steering input means, the steering transmission ratio is returned to the standard steering transmission ratio, and the change of the steering transmission ratio is continued unnecessarily. This can be prevented.

  According to the present invention, in the configuration of claim 6, the control means steers the steering input means in a direction away from the reference steering position in the first steering region. In this process, when the steering operation speed of the steering input unit becomes equal to or higher than a steering operation speed determination reference value, it is estimated that the driver has changed the steering input unit. ).

  According to the configuration of the seventh aspect, in the process in which the driver steers the steering input means in the direction away from the reference steering position in the first steering region, the steering operation speed of the steering input means is the steering speed. When the operation speed determination reference value is exceeded, it is estimated that the driver has changed the steering input means. Further, the steering operation speed of the steering input means can be determined as the change speed of the steering position of the steering input means. Accordingly, it is possible to estimate the change of the steering input means without requiring a special means for detecting the change of the steering input means.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration according to any one of claims 1 to 7, the control means is the first steering region. When the steering operation amount of the steering input means in the direction away from the reference steering position is equal to or greater than the steering operation amount determination reference value, the change of the steering transmission ratio is terminated, and the steering transmission ratio is changed to the standard steering transmission ratio. It is comprised so that it may return to (structure of Claim 8).

  According to the configuration of the above eighth aspect, when the steering operation amount of the steering input means in the direction away from the reference steering position in the first steering region becomes equal to or larger than the steering operation amount determination reference value, the steering transmission ratio is increased. The steering transmission ratio is returned to the standard steering transmission ratio. In general, when the steering operation amount of the steering input means increases in the direction away from the reference steering position in the first steering region, the driver changes the steering input means. Therefore, by appropriately setting the steering operation amount determination reference value, the change of the steering transmission ratio is finished before and after the driver changes the steering input means without detecting or judging the change of the steering input means. The steering transmission ratio can be returned to the standard steering transmission ratio.

  In the first steering region, the steering transmission ratio is made larger than the standard steering transmission ratio. Therefore, the steering input means steers the steering position relative to the steering position as compared with the case where the steering transmission ratio is the standard steering transmission ratio. The offset in relation to the steering angle of the wheel is reduced. Therefore, even if the change of the steering transmission ratio is finished before the driver changes the steering input means and the steering transmission ratio is returned to the standard steering transmission ratio, the change of the steering transmission ratio at that time is changed to the first steering region. However, the steering transmission ratio is smaller than the case where the steering transmission ratio is not made larger than the standard steering transmission ratio.

  According to the present invention, in the configuration according to any one of the first to eighth aspects, when the vehicle speed is high, the control means increases the amount of increasing the steering transmission ratio compared to when the vehicle speed is low. Thus, the amount of increasing the steering transmission ratio is variably set according to the vehicle speed (configuration of claim 9).

  In general, in a low vehicle speed range, the amount of steering operation of the steering input means is large, so there is a high possibility that the driver will change the steering input means, and the steering operation in the first steering area is high. There is little need to compensate for the difficulty of relieving by increasing the steering transmission ratio. On the other hand, in the high vehicle speed range, the amount of steering operation of the steering input means is small, so it is unlikely that the driver will change the steering input means. There is a high need to compensate for the difficulty of operation by increasing the steering transmission ratio.

  According to the ninth aspect of the present invention, the amount for increasing the steering transmission ratio is variably set according to the vehicle speed so that the amount for increasing the steering transmission ratio is larger when the vehicle speed is high than when the vehicle speed is low. . Therefore, it is necessary to compensate for the difficulty of steering operation of the steering input means in the first steering region by increasing the steering transmission ratio, compared to the case where the amount of increase in the steering transmission ratio is constant regardless of the vehicle speed. It is possible to appropriately change the ease of turning the steered wheels by changing the steering transmission ratio according to the characteristics.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration according to any one of claims 1 to 9, the control means is a steering operation of the steering input means by a driver. The change amount of the steering transmission ratio is variably set according to the steering operation speed so that the change amount of the steering transmission ratio becomes larger when the speed is high than when the steering operation speed is low ( Configuration of claim 10).

  According to the configuration of the above tenth aspect, when the steering operation speed of the steering input means by the driver is high, the change amount of the steering transmission ratio is increased according to the steering operation speed so that the change amount of the steering transmission ratio becomes larger than when the steering operation speed is low. A change amount of the steering transmission ratio is variably set. Accordingly, when the steering operation speed of the steering input means is high and the driver wants to steer the steering wheel quickly, the steering operation speed of the steering input means is low and the driver wants to steer the steering wheel slowly. Thus, it is possible to effectively reduce the difficulty of the steering operation of the steering input means in the first steering region.

  According to the present invention, in any one of the first to tenth aspects, the vehicle has a steering assist force generating means for generating a steering assist force, and the control means is operated by the driver. When the steering input means is steered in the steering area, the steering assist force is increased as compared with the case where the driver steers the steering input means in the second steering area. (Constitution of Claim 11)

  According to the configuration of claim 11, when the driver steers the steering input means in the first steering area, the driver steers the steering input means in the second steering area. Compared to the above, the steering assist force is increased. Therefore, when the driver steers the steering input means in the first steering region, the steering input means can surely be easily steered by the steering assist force.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 11, the steered wheel is a front wheel, and the vehicle steers the rear wheel. And the control means controls the steering in the second steering area when the driver steers the steering input means in the first steering area. Compared to the case where the input means is steered, the rear wheel steering angle is modified so that the rear wheel steering angle changes in the opposite phase to the front wheel.

According to the structure of claim 12, when the driver steers the steering input means in the first steering area, the driver steers the steering input means in the second steering area. As compared with the above, the steering angle of the rear wheel is corrected so that the steering angle of the rear wheel changes in the opposite phase to the front wheel. Therefore, when the driver steers the steering input means in the first steering area, it is easy to reliably turn the vehicle by correcting the steering angle of the rear wheel even if the steering operation amount of the steering input means is small. Can do.
[Preferred embodiment of problem solving means]

  According to one preferred aspect of the present invention, in the configuration of claim 1, the amount by which the steering transmission ratio is made larger than the standard steering transmission ratio is configured to be constant over the entire first steering region. (Preferred embodiment 1)

  According to another preferred aspect of the present invention, in the configuration of claim 1, the control means sets the second steering region in the steering region on the side opposite to the first steering region with respect to the reference steering position. As a region, when the driver steers the steering input means in the second steering region, the steering transmission ratio is set to a standard steering transmission ratio (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the amount by which the steering transmission ratio is made smaller than the standard steering transmission ratio is constant over the entire second steering region. (Preferred Aspect 3)

  According to another preferred aspect of the present invention, in the configuration according to any one of claims 4 to 12 or preferred aspects 1 to 3, the control means increases the steering transmission ratio as the magnitude of the offset increases. It is configured to increase the amount of change (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration according to any one of claims 1 to 12 or preferred aspects 1 to 4, the control means is a deviation between the current steering angle and the reference steering angle. When the value of is less than or equal to the reference value, the change of the steering transmission ratio is terminated and the steering transmission ratio is returned to the standard steering transmission ratio (preferred aspect 5).

  According to another preferred embodiment of the present invention, in the structure according to any one of claims 9 to 12 or preferred embodiments 1 to 5, the control means increases the steering transmission ratio as the vehicle speed increases. (Preferred aspect 6).

  According to another preferred aspect of the present invention, in the structure according to any one of claims 10 to 12 or preferred aspects 1 to 6, the control means has a steering operation speed of the steering input means by the driver. It is comprised so that the change amount of a steering transmission ratio may be enlarged, so that it is high (preferable aspect 7).

  According to another preferred aspect of the present invention, in the configuration of any one of the above-mentioned claims 11 or 12 or the preferred aspects 1 to 7, the steering assist force when the offset is 0 is used as the standard steering force. As the assisting force, the control means is configured to make the steering assisting force larger than the standard steering assisting force when the driver steers the steering input means in the first steering region (preferred aspect 8). .

  According to another preferred embodiment of the present invention, in the configuration of any one of the above-mentioned claims 11 or 12 or the preferred embodiments 1 to 8, the steering assist force when the offset is 0 is used as the standard steering force. As the assisting force, the control means is configured to make the steering assisting force smaller than the standard steering assisting force when the driver steers the steering input means in the second steering region (preferred aspect 9). .

  According to another preferred embodiment of the present invention, in the configuration of any one of the above-described claim 12 and the preferred embodiments 1 to 9, the steering angle of the rear wheel when the offset is 0 is set to the standard rear. When the driver steers the steering input means in the first steering area as the steering angle of the wheel, the steering angle of the rear wheel is opposite to the standard steering angle of the rear wheel relative to the front wheel. It is comprised so that the steering angle of a rear-wheel may be corrected so that it may change (preferable aspect 10).

  According to another preferred embodiment of the present invention, in the configuration of any one of the above-described claim 12 and the preferred embodiments 1 to 9, the steering angle of the rear wheel when the offset is 0 is set to the standard rear. As the wheel steering angle, when the driver steers the steering input means in the second steering area, the rear wheel steering angle changes to the same phase as the front wheel relative to the standard rear wheel steering angle. It is comprised so that the rudder angle of a rear wheel may be corrected (preferable aspect 11).

  According to another preferred aspect of the present invention, in the configuration of any one of the above-mentioned claims 11 or the preferred aspects 1 to 11, the control means changes the steering assist force according to the magnitude of the offset. Is configured to be variably set (preferred aspect 12).

  According to another preferred embodiment of the present invention, in the structure of any one of the above-mentioned claims 11 or the preferred embodiments 1 to 12, the control means steers when the vehicle speed is high compared to when the vehicle speed is low. The amount of increase in the steering assist force is variably set according to the vehicle speed so that the amount of increase in the assist force is increased (preferred aspect 13).

  According to another preferred aspect of the present invention, in the structure according to any one of the above-mentioned claim 11 and the preferred aspects 1 to 13, the control means is configured such that when the steering operation speed of the steering input means by the driver is high. The change amount of the steering assist force is variably set in accordance with the steering operation speed so that the change amount of the steering assist force becomes larger than that when the steering operation speed is low (preferred aspect 14).

  According to another preferred embodiment of the present invention, in the configuration of any one of the above-mentioned claim 12 and the preferred embodiments 1 to 14, the control means adjusts the steering angle of the rear wheel according to the magnitude of the offset. The correction amount is variably set (preferred aspect 15).

  According to another preferred embodiment of the present invention, in the configuration of claim 12 or any one of preferred embodiments 1 to 15, the control means is configured to perform the control when the vehicle speed is high compared to when the vehicle speed is low. The amount of change in the steering angle of the rear wheel in the direction opposite to the front wheel is variably set according to the vehicle speed so that the amount of change in the direction of the opposite phase with respect to the front wheel increases. (Preferred embodiment 16).

  According to another preferred aspect of the present invention, in the structure of any one of the above-described claim 12 and the preferred aspects 1 to 16, the control means is configured such that when the steering operation speed of the steering input means by the driver is high. Compared to when the steering speed is low, the amount of change in the steering angle of the rear wheels in the opposite phase to the front wheels is larger. The amount of change in the direction is variably set (preferred aspect 17).

1 is a schematic configuration diagram showing a first embodiment of a vehicle steering transmission ratio variable type steering apparatus according to the present invention applied to a vehicle equipped with an electric power steering apparatus. It is a flowchart which shows the main routine of steering gear ratio control. 3 is a flowchart showing an offset calculation routine in step 190 of the flowchart shown in FIG. 2. FIG. 3 is a flowchart showing a routine for determining whether a steering gear ratio left / right difference control end condition is satisfied in step 160 of the flowchart shown in FIG. 2; FIG. FIG. 3 is a flowchart showing a target steering gear ratio calculation routine for steering gear ratio left / right difference control in step 210 of the flowchart shown in FIG. 2; It is a flowchart which shows the main routine of steering assist torque control. 7 is a flowchart showing a correction coefficient Kp calculation routine in step 350 of the flowchart shown in FIG. 6. It is a schematic block diagram which shows 2nd embodiment of the steering transmission ratio variable type steering device for vehicles by this invention applied to the vehicle by which a rear-wheel steering device is mounted. It is a flowchart which shows the main routine of rear-wheel steering control. 10 is a flowchart showing a correction coefficient Kr calculation routine in step 440 of the flowchart shown in FIG. 9. It is a map which shows the relationship between steering speed and vehicle speed V, and basic target steering gear ratio Rsbt. It is a map which shows the relationship between the absolute value of offset (phi) o of a pinion angle, and offset correction coefficient Kco and Kso. It is a map which shows the relationship between the vehicle speed V and the vehicle speed correction coefficient Kcvv. It is a map which shows the relationship between the absolute value of steering angular velocity (theta) d, and steering angular velocity correction coefficient Kcsv, Kssv. It is a map which shows the relationship between steering torque Ts and basic assist torque Tab. It is a map which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a map which shows the relationship between the absolute value of offset φo of a pinion angle, and offset correction coefficient Kpco and Kpso. It is a map which shows the relationship between the vehicle speed V and the vehicle speed correction coefficient Kpcv. It is a map which shows the relationship between the absolute value of steering angular velocity (theta) d, and a steering angular velocity correction coefficient Kpcsv, Kpssv. It is a map which shows the relationship between the vehicle speed V and the front-rear wheel steering angle ratio Rs. It is a map which shows the relationship between the absolute value of offset (phi) o of a pinion angle, and offset correction coefficient Krco and Krso. It is a map which shows the relationship between the vehicle speed V and the vehicle speed correction coefficient Krcv. 6 is a map showing a relationship between an absolute value of a steering angular velocity θd and steering angular velocity correction coefficients Krcsv and Krssv. In the case of right-turn offset, the relationship between the steering angle θ and the pinion angle φ when the left / right difference control is performed (solid line) and the relationship when the left / right difference control is not performed (broken line) It is a graph to show. In the case of a left turn offset, the relationship (solid line) between the steering angle θ and the pinion angle φ when the left / right difference control is performed is shown together with the relationship (broken line) when the left / right difference control is not performed. It is a graph. It is a graph which shows the relationship between steering angle (theta) and pinion angle (phi) about the case where an offset has not arisen (solid line) and the case where an offset has arisen (broken line). It is explanatory drawing which shows the holding | maintenance state of the steering wheel 20 by the driver | operator at the time of a straight drive of a vehicle about the case where the offset does not arise (A) and the case where the offset to the right turn direction arises (B). It is explanatory drawing which shows that the relationship between steering angle (theta) and pinion angle (phi) in case right-and-left difference control is performed changes with the magnitude | size of offset (phi) o.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[First embodiment]

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle steering transmission ratio variable type steering apparatus according to the present invention applied to a vehicle equipped with an electric power steering apparatus.

  In FIG. 1, a steering device 10 according to the present invention is mounted on a vehicle 12 and includes a turning angle varying device 14 and an electronic control device 16 for controlling the turning angle varying device 14. In FIG. 1, 18FL and 18FR indicate left and right front wheels as steering wheels of the vehicle 12, and 18RL and 18RR indicate left and right rear wheels, respectively. The left and right front wheels 18FL and 18FR, which are the steering wheels, are driven via a rack bar 24 and tie rods 26L and 26R by a rack and pinion type electric power steering device 22 driven in response to an operation of the steering wheel 20 by a driver. Steered.

  The steering wheel 20 is drivingly connected to a pinion shaft 34 of the power steering device 22 through an upper steering shaft 28, a turning angle varying device 14, a lower steering shaft 30, and a universal joint 32. In the illustrated embodiment, the turning angle varying device 14 is connected to the lower end of the upper steering shaft 28 on the housing 14A side, and the auxiliary is connected to the upper end of the lower steering shaft 30 on the rotor 14B side. A motor 36 for turning driving is included.

  Thus, the turning angle varying device 14 rotationally drives the lower steering shaft 30 relative to the upper steering shaft 28 to drive auxiliary steering of the left and right front wheels 18FL and 18FR relative to the steering wheel 20. Therefore, the turning angle varying device 14 functions as a steering gear ratio varying means for changing the steering gear ratio (reciprocal of the steering transmission ratio), and thus functions as a steering transmission ratio varying device, and is controlled by the steering angle control unit of the electronic control unit 16. The

  If an abnormality in which the lower steering shaft 30 cannot be driven to rotate relative to the upper steering shaft 28 occurs in the turning angle varying device 14, a lock device not shown in FIG. The relative rotation of the housing 14A and the rotor 14B is mechanically prevented so that the relative rotation angle of the lower steering shaft 30 with respect to 28 does not change.

  In the illustrated embodiment, the electric power steering device 22 is a rack coaxial type electric power steering device, and converts the electric motor 38 and the rotational torque of the electric motor 38 into a force in the reciprocating direction of the rack bar 24. For example, it has a ball screw type conversion mechanism 42. The electric power steering device 22 is controlled by an electric power steering device (EPS) control unit of the electronic control device 16, and generates an auxiliary steering force that drives the rack bar 24 relative to the housing 44. It functions as an auxiliary steering assist force generator that reduces the steering burden. The auxiliary steering assist force generator may have any configuration known in the art.

  In the illustrated embodiment, the upper steering shaft 28 is provided with a steering angle sensor 50 for detecting the rotation angle of the upper steering shaft as the steering angle θ and a steering torque sensor 52 for detecting the steering torque Ts. The lower steering shaft 30 is provided with a rotation angle sensor 54 that detects the rotation angle as a pinion angle (rotation angle of the pinion shaft 34) φ. A signal indicating the steering angle θ, a signal indicating the steering torque Ts, and a signal indicating the pinion angle φ are input to the steering angle control unit and the EPS control unit of the electronic control device 16 together with the signal indicating the vehicle speed V detected by the vehicle speed sensor 56. Is done.

  The rotation angle sensor 54 may be replaced with a rotation angle sensor that detects the relative rotation angle θre of the steering angle varying device 14, that is, the relative rotation angle of the lower steering shaft 30 with respect to the upper steering shaft 28.

  The vehicle 12 is provided with a CCD camera 58 for photographing the front of the vehicle and a radar sensor 60 for detecting the distance to the obstacle in front of the vehicle. Image information in front of the vehicle photographed by the CCD camera 58 and a signal indicating the distance to the obstacles ahead detected by the radar sensor 60 are input to the collision prevention control unit of the electronic control unit 16.

  Each control unit of the electronic control device 16 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other via a bidirectional common bus. Further, the steering angle sensor 50, the steering torque sensor 52, and the rotation angle sensor 54 detect the steering angle θ, the steering torque Ts, and the pinion angle φ, respectively, when the steering or turning in the right turning direction of the vehicle is positive.

  As will be described in detail later, the electronic control unit 16 achieves a predetermined steering characteristic based on the vehicle speed V so that it increases as the vehicle speed V increases and increases as the steering speed (the absolute value of the steering angular velocity θd) increases. A basic target steering gear ratio Rsbt is calculated.

  The electronic control unit 16 determines whether or not there is an obstacle ahead of the vehicle based on image information in front of the vehicle photographed by the CCD camera 58, and the vehicle detected by the radar sensor 60 when there is an obstacle. Control a braking device not shown in the figure so that the distance between the obstacle and the vehicle is a safe distance based on the distance to the obstacle ahead, the rate of change, the vehicle speed, etc. To decelerate the vehicle.

  Further, when the electronic control unit 16 cannot reduce the distance between the obstacle and the own vehicle even if the vehicle is decelerated, the electronic control unit 16 detects that the own vehicle has an obstacle based on the image information in front of the vehicle taken by the CCD camera 58. The left and right front wheels 18FL and 18FR are steered by the turning angle varying device 14 so as not to collide with an object (collision prevention steering).

  Note that the steering speed by the driver is high as in emergency avoidance steering, or the left and right front wheels 18FL and 18FR are steered by the turning angle varying device 14 at a turning speed that is greater than or equal to a reference value due to collision prevention steering. A certain control is called “specific control”.

  When the specific control end condition is satisfied and the specific control ends, the electronic control unit 16 stores the steering angle θ at that time as a reference steering angle θs in a storage device not shown in FIG. In addition, when the specific control is finished, the electronic control device 16 determines whether or not the turning angle variable device 14 has an offset θo that is equal to or larger than a reference value.

  The “offset θo” is a deviation in the relationship of the steering position of the steering wheel 20 as steering input means with respect to the steering angle φ of the left and right front wheels 18FL and 18FR that are the steering wheels, specifically, the left and right front wheels 18FL and This is the value of the steering angle θ when 18FR is at the straight traveling position of the vehicle, that is, when the pinion angle φ is zero.

  The electronic control unit 16 performs steering in the first steering region where the steering angle θ is closer to the offset θo than the reference steering angle θs when the steering angle variable device 14 has an offset θo greater than the reference value. When the wheel 20 is steered, the steering angle θ is steered in the second steering region on the side opposite to the offset θo with respect to the reference steering angle θs. Then, the turning angle varying device 14 is controlled so that the steering gear ratio Rst is reduced and the steering transmission ratio is increased (steering gear ratio left / right difference control).

  Further, the electronic control unit 16 calculates a target assist torque Ta for generating a steering assist force based on the steering torque Ts and the vehicle speed V, and controls the electric power steering device 22 so that the assist torque becomes the target assist torque Ta. This reduces the driver's steering burden.

  When the steering angle variable device 14 has an offset greater than the reference value, the electronic control unit 16 uses the second steering region when the steering wheel 20 is steered in the first steering region. In this case, the target assist torque Ta is corrected according to the offset of the turning angle varying device 14 so that the driver can easily rotate the steering wheel 20 as compared with the case where the steering wheel 20 is steered.

  Note that the above-described basic target steering gear ratio Rsbt calculation procedure and steering assist force control itself excluding correction of the target assist torque Ta according to the offset of the turning angle varying device 14 do not form the gist of the present invention. Basic control of the steering assist force may be executed in any manner known in the art.

  Next, the steering gear ratio control in the first embodiment will be described with reference to the flowcharts shown in FIGS. 2 is a flowchart showing a main routine of the steering gear ratio control, FIG. 3 is a flowchart showing an offset calculation routine in step 190 of the flowchart shown in FIG. 2, and FIG. 4 is shown in FIG. FIG. 5 is a flowchart showing a routine for determining whether or not the steering gear ratio left-right difference control is completed in step 160 of the flowchart, and FIG. 5 is a left-right difference control of the steering gear ratio in step 210 of the flowchart shown in FIG. 7 is a flowchart showing a target steering gear ratio calculation routine. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

  In step 110 of the main routine of the steering gear ratio control shown in FIG. 2, the steering angular velocity θd is calculated as a time differential value of the steering angle θ, and the absolute value of the steering angular velocity θd, that is, the steering speed and the vehicle speed. Based on V, the basic target steering gear ratio Rsbt is calculated from the map shown in FIG.

  In step 120, it is determined whether or not specific control is being performed, that is, whether or not the left and right front wheels 18FL and 18FR are being steered by the steered angle varying device 14 at a steered speed that is greater than or equal to a reference value. If a determination is made and an affirmative determination is made, the process proceeds to step 180. If a negative determination is made, the process proceeds to step 130.

  In step 130, for example, by determining whether the steering speed by the driver is equal to or higher than a reference value or whether anti-collision steering is necessary, it is determined whether a specific control start condition is satisfied. Is done. When an affirmative determination is made, specific control is executed at step 140. Thereafter, the process returns to step 110, and when a negative determination is made, the process proceeds to step 150.

  In step 150, it is determined whether or not the left / right difference control of the steering gear ratio is being performed. If a negative determination is made, the process proceeds to step 175. If an affirmative determination is made, the process proceeds to step 160.

  In step 160, it is determined whether or not the steering gear ratio left-right difference termination condition is satisfied according to the determination routine shown in FIG. 4, and if a negative determination is made, the process proceeds to step 210. If the determination is affirmative, the target steering gear ratio Rst is set to the basic target steering gear ratio Rsbt in step 175, and then the routine proceeds to step 240.

  In step 180, it is determined whether or not a specific control termination condition is satisfied. If a negative determination is made, the process proceeds to step 140. If an affirmative determination is made, the process proceeds to step 190. The reference steering angle θs, the offset θo, and the pinion angle offset φo are calculated according to the calculation routine shown in FIG.

  In step 200, it is necessary to determine whether or not the absolute value of the pi-offset θo, which is the magnitude of the offset θo, is greater than or equal to a reference value θa (a positive constant), that is, to start the left / right difference control of the steering gear ratio. If a negative determination is made, the process proceeds to step 175. If an affirmative determination is made, the process proceeds to step 210.

  In step 210, the target steering gear ratio Rst for the left / right difference control of the steering gear ratio is calculated according to the calculation routine shown in FIG. 5. When step 210 is completed, the steering gear ratio is converted to the target steering gear ratio in step 240. The turning angle varying device 14 is controlled so as to be Rst.

  In step 192 of the offset calculation routine shown in FIG. 3, at the time when an affirmative determination is made in step 180, that is, when it is determined that a specific control end condition is satisfied. The steering angle θ is determined to be the reference steering angle θs corresponding to the “reference steering position of the steering input means”. Further, the pinion angle φ at the time point is determined as the reference pinion angle φs corresponding to the reference steering angle θs.

  In step 194, based on the steering speed and the vehicle speed V, the basic target steering gear ratio Rsbt is calculated from the map shown in FIG.

In step 196, the reference steering angle θs is substituted for the steering angle θ of the following equation 1 showing the relationship between the steering angle θ and the target steering gear ratio Rsbt, and the reference pinion angle φs is substituted for the pinion angle φ. The offset φo of the pinion angle that is the pinion angle φ when the steering angle θ is 0 is calculated.
φ = θ / Rsbt + φo (1)

  In step 198, 0 is substituted for the pinion angle φ in the above equation 1, and the value calculated in step 196 is substituted for φo, thereby offsetting the steering angle θ when the pinion angle φ is 0. θo is calculated.

  In step 162 of the steering gear ratio left / right difference control completion condition establishment determination routine shown in FIG. 4, the original steering angle θbt, that is, the current pinion angle φ when the left / right difference control is not performed. Is calculated as the product of the pinion angle φ and the basic target steering gear ratio Rsbt by setting φo in the above equation 1 to zero.

  In step 164, the magnitude of the current offset, that is, the absolute value of the deviation Δθ (= θ−θbt) between the current steering angle θ and the original steering angle θbt is the reference value θb ( It is determined whether or not it is equal to or less than (positive constant). If an affirmative determination is made, the process proceeds to step 174. If a negative determination is made, the process proceeds to step 166.

  In step 166, the absolute value of the corrected steering angle (effective steering angle) θ−θs obtained by subtracting the reference steering angle θs from the steering angle θ is the reference value θc (positive constant) for determining the end of the left / right difference control. It is determined whether or not the above is satisfied, that is, whether or not the steering wheel 20 has been rotated more than the reference angle value with respect to the position of the reference steering angle θs. When a positive determination is made, the process proceeds to step 174, and when a negative determination is made, the process proceeds to step 168.

  In step 168, whether or not the steering wheel 20 has been changed by the driver is determined by estimation. If an affirmative determination is made, the process proceeds to step 174. If a negative determination is made, step 170 is performed. Proceed to The holding of the steering wheel 20 may be determined by, for example, incorporating a grip switch that detects whether or not the steering wheel 20 is gripped into the steering wheel. In addition, the steering wheel 20 is changed by, for example, determining whether or not the steering speed is once more than a reference value variably set according to the vehicle speed V after the steering speed is once decreased in the process of increasing or decreasing the steering angle θ. May be.

  In step 170, the product sign θo · θ of the sign θo of the offset θo and the steering angle θ is a reference value θd (positive constant) for determining the end of the left / right difference control. For example, the steering wheel is statistically changed. A determination is made as to whether or not it is greater than or equal to (determined as the steering angle). That is, it is determined whether or not the steering wheel 20 has been rotated more than the reference value in the direction of the offset θo with respect to the neutral position. If a negative determination is made, it is determined in step 172 that the steering gear ratio left-right difference control termination condition is not satisfied, and if an affirmative determination is made, in step 174 the left-right difference in steering gear ratio is determined. It is determined that the control end condition is satisfied.

  In step 212 of the target steering gear ratio calculation routine for the left / right difference control of the steering gear ratio shown in FIG. 5, the offset on the quick side from the map shown in FIG. 12 based on the absolute value of the offset φo of the pinion angle. The correction coefficient Kco and the slow-side offset correction coefficient Kso are calculated.

  In step 214, the vehicle speed correction coefficient Kcvv on the quick side is calculated from the map shown in FIG. 13 based on the vehicle speed V. In step 216, the map shown in FIG. 14 is calculated based on the absolute value of the steering angular velocity θd. Further, the quick side steering angular velocity correction coefficient Kcsv and the slow side steering angular velocity correction coefficient Kssv are calculated.

  In step 218, the basic target steering gear is calculated as the product of the quick-side basic correction coefficient Kcb (a positive constant smaller than 1), the quick-side offset correction coefficient Kco, the vehicle speed correction coefficient Kcvv, and the steering angular speed correction coefficient Kcsv. A quick-side correction coefficient Kc for the ratio Rsbt is calculated.

  In step 220, the slow-side basic correction coefficient Ksb (a positive constant greater than 1 and the difference between Ksb and 1 is smaller than the difference between 1 and Kcb) and the slow-side offset correction coefficient Kso As the product of the steering angular velocity correction coefficient Kssv, a slow-side correction coefficient Ks for the basic target steering gear ratio Rsbt is calculated.

  In step 222, it is determined whether or not the offset θo is a positive value, that is, whether or not the offset of the turning angle varying device 14 is in the right turn direction, and a negative determination is made. If YES, the process proceeds to step 226. If an affirmative determination is made, the process proceeds to step 224.

  In step 224, it is determined whether or not the steering angle θ is larger than the reference steering angle θs, that is, whether the steering angle of the left and right front wheels 18FL and 18FR is the steering angle on the right turn side with respect to the reference steering angle θs. If a negative determination is made, the process proceeds to step 228. If a negative determination is made, the process proceeds to step 230.

  Similarly, in step 226, it is determined whether or not the steering angle θ is larger than the reference steering angle θs. When a negative determination is made, at step 228, the target steering gear ratio Rst for the left / right difference control of the steering gear ratio is set to the product of the quick side correction coefficient Kc and the basic target steering gear ratio Rsbt. If an affirmative determination is made, in step 230, the target steering gear ratio Rst for the left / right difference control of the steering gear ratio is set to the product of the slow side correction coefficient Ks and the basic target steering gear ratio Rsbt.

  Next, the steering assist torque control in the first embodiment will be described with reference to the flowcharts shown in FIGS. FIG. 6 is a flowchart showing a main routine of steering assist torque control, and FIG. 7 is a flowchart showing a correction coefficient Kp calculation routine in step 350 of the flowchart shown in FIG. The control according to the flowchart shown in FIG. 6 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

  In step 310 of the steering assist torque control routine shown in FIG. 6, the basic assist torque Tab is calculated from the map shown in FIG. 15 based on the steering torque Ts, and based on the vehicle speed V in step 320. A vehicle speed coefficient Kv is calculated from the map shown in FIG.

  In step 330, it is determined whether left / right difference control of the steering gear ratio is being performed. If a negative determination is made, the correction coefficient Kp is set to 1 in step 340, and then step 380 is performed. If the determination is affirmative, the correction coefficient Kp is calculated in step 350 according to the routine shown in FIG.

  In step 380, the target assist torque Ta is calculated as the product of the correction coefficient Kp, the vehicle speed coefficient Kv, and the basic assist torque Tab, and in step 390, a control signal corresponding to the target assist torque Ta is output to the motor 38. Thus, the assist torque is controlled so that the assist torque becomes the target assist torque Ta.

  In step 352 of the correction coefficient Kp calculation routine shown in FIG. 7, the quick side offset correction coefficient Kpco and the slow side offset correction from the map shown in FIG. 17 based on the absolute value of the offset φo of the pinion angle. A coefficient Kpso is calculated.

  In step 354, the vehicle speed correction coefficient Kpcv on the quick side is calculated from the map shown in FIG. 18 based on the vehicle speed V. In step 356, the map shown in FIG. 19 is calculated based on the absolute value of the steering angular velocity θd. The quicker steering angular velocity correction coefficient Kpcsv and the slow steering angular velocity correction coefficient Kpssv are calculated.

  In step 358, the basic target steering gear is calculated by multiplying the quick-side basic correction coefficient Kpcb (a positive constant greater than 1), the quick-side offset correction coefficient Kpco, the vehicle speed correction coefficient Kpcv, and the steering angular speed correction coefficient Kpcsv. A correction coefficient Kpc on the quick side for the ratio Rsbt is calculated.

  In step 360, the product of the slow-side basic correction coefficient Kpsb (a positive constant smaller than 1), the slow-side offset correction coefficient Kpso, and the steering angular velocity correction coefficient Kpssv is the slow-side relative to the basic target steering gear ratio Rsbt. The correction coefficient Kps is calculated.

  In step 362, it is determined whether or not the offset θo is a positive value, that is, whether or not the offset of the turning angle varying device 14 is in the right turn direction, and a negative determination is made. If YES in step 366, the flow advances to step 366. If a positive determination is made, the flow advances to step 364.

  In step 364, it is determined whether or not the steering angle θ is larger than the reference steering angle θs, that is, whether the steering angle of the left and right front wheels 18FL and 18FR is the steering angle on the right turn side with respect to the reference steering angle θs. If a negative determination is made, the process proceeds to step 368. If a negative determination is made, the process proceeds to step 370.

Similarly, in step 366, it is determined whether or not the steering angle θ is larger than the reference steering angle θs. When a negative determination is made, the correction coefficient Kp is set to the quick-side basic correction coefficient Kpc at step 368, and when an affirmative determination is made, the correction coefficient Kp is set to the slow-side correction coefficient Kps at step 370. Set to
[Second Embodiment]

  FIG. 8 is a schematic configuration diagram showing a second embodiment of the vehicle steering transmission ratio variable type steering device according to the present invention applied to a vehicle equipped with a rear wheel steering device. In FIG. 8, members corresponding to those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.

  In the second embodiment, the left and right rear wheels 18RL and 18RR are hydraulic or electric power steering of the rear wheel steering device 64 irrespective of the steering of the left and right front wheels 18FL and 18FR by the driver. The device 66 can be steered via tie rods 68L and 68R. The rear wheel steering device 64 is controlled by a rear wheel steering control unit of the electronic control device 16 as will be described in detail later. A signal indicating the steering angle δr of the rear wheel detected by the steering angle sensor 70 is input to the rear wheel steering control unit of the electronic control unit 16.

  In the second embodiment, the electronic control device 16 controls the turning angle varying device 14 as in the case of the first embodiment described above. The electronic control unit 16 calculates the basic assist torque Tab and the vehicle speed coefficient Kv from the maps shown in FIGS. 15 and 16 based on the steering torque Ts and the vehicle speed V, respectively. The electronic control unit 16 calculates the target assist torque Ta as the product of the basic assist torque Tab and the vehicle speed coefficient Kv regardless of whether or not the turning angle varying device 14 is offset, and the assist torque is the target assist torque. The rear wheel steering device 64 is controlled to reach Ta.

  Further, the electronic control unit 16 calculates a target rear wheel steering angle δrt based on the vehicle speed V, the steering angle θ, and the reference steering angle θo, and rear wheel steering so that the rear wheel steering angle δr becomes the target rear wheel steering angle δrt. The device 64 is controlled. In particular, when the steering angle varying device 14 has an offset and the rear wheel is in reverse phase with respect to the front wheel, when the driver steers the steering wheel 20 in the offset direction, the steering wheel 20 is in the offset direction. The electronic control device 16 increases the size of the target rear wheel steering angle δrt according to the offset of the turning angle varying device 14 so that the vehicle 10 can be easily turned compared to the case where the steering operation is performed in the opposite direction. Correct it.

  Conversely, when the steering angle varying device 14 is offset and the rear wheels are in phase with the front wheels, when the driver steers the steering wheel 20 in the offset direction, the steering wheel 20 is set to the offset direction. Compared with steering in the reverse direction, the electronic control unit 16 reduces the size of the target rear wheel steering angle δrt according to the offset of the turning angle varying device 14 so that the vehicle 10 can turn easily. Correct it.

  Next, rear wheel steering control in the second embodiment will be described with reference to the flowcharts shown in FIGS. FIG. 9 is a flowchart showing a main routine of rear wheel steering control, and FIG. 10 is a flowchart showing a correction coefficient Kr calculation routine in step 450 of the flowchart shown in FIG. Further, the control according to the flowchart shown in FIG. 9 is started by closing an ignition switch (not shown), and is repeatedly executed every predetermined time.

  In step 410 of the rear wheel steering control routine shown in FIG. 9, the front and rear wheel steering angle ratio Rs is calculated from the map shown in FIG.

  In step 420, it is determined whether or not the steering gear ratio left / right difference control is being performed. If a negative determination is made, the correction coefficient Kr is set to 1 in step 430 and then step 470 is performed. When the determination is affirmative, the correction coefficient Kr is calculated in step 440 according to the routine shown in FIG.

  In step 470, the effective steering angle θ−θs, that is, the corrected steering angle obtained by subtracting the reference steering angle θs from the steering angle θ, the correction coefficient Kr, and the front / rear wheel steering angle ratio Rs is set as the target. The wheel steering angle δrt is calculated.

  In step 480, a control signal corresponding to the target rear wheel steering angle δrt is output to the rear wheel steering device 64, so that the rear wheel steering angle δr becomes the target rear wheel steering angle δrt. The control is executed.

  In step 442 of the correction coefficient Kr calculation routine shown in FIG. 10, the offset correction coefficient Krco on the increase side and the offset correction on the reduction side are compared with the map shown in FIG. 21 based on the absolute value of the offset φo of the pinion angle. A coefficient Krso is calculated.

  In step 444, the vehicle speed correction coefficient Krcv on the increase side from the map shown in FIG. 22 is calculated based on the vehicle speed V. In step 446, the map shown in FIG. 23 is calculated based on the absolute value of the steering angular velocity θd. A further increase steering angular velocity correction coefficient Krcsv and a decrease steering angular velocity correction coefficient Krssv are calculated.

  In step 448, the product of the basic correction coefficient Krcb on the increase side (a positive constant greater than 1), the offset correction coefficient Krco on the increase side and the steering angular velocity correction coefficient Krcsv is used as the increase side with respect to the front and rear wheel steering angle ratio Rs. The correction coefficient Krc is calculated.

  In step 450, the product of the reduction-side basic correction coefficient Krsb (a positive constant smaller than 1), the reduction-side offset correction coefficient Krso, and the steering angular velocity correction coefficient Krssv is used to reduce the front-rear wheel steering angle ratio Rs. The correction coefficient Krs is calculated.

  In step 452, it is determined whether or not the offset θo is a positive value, that is, whether or not the offset of the turning angle varying device 14 is in the right turn direction, and a negative determination is made. If YES in step 458, the flow advances to step 458. If a positive determination is made, the flow advances to step 454.

  In step 454, it is determined whether or not the steering angle θ is larger than the reference steering angle θs, that is, whether the steering angle of the left and right front wheels 18FL and 18FR is the steering angle on the right turn side with respect to the reference steering angle θs. If a negative determination is made, the process proceeds to step 460. If an affirmative determination is made, the process proceeds to step 456.

  In step 456, it is determined whether or not the rear wheels are in reverse phase with respect to the front wheels, that is, whether the left and right rear wheels 18RL and 18RR are steered in the opposite direction to the left and right front wheels 18FL and 18FR. When a negative determination is made, the process proceeds to step 464. When an affirmative determination is made, the process proceeds to step 462.

  Similarly, in step 458, it is determined whether or not the steering angle θ is larger than the reference steering angle θs. If a negative determination is made, the process proceeds to step 456, and if an affirmative determination is made, step 460 is performed. Proceed to

  In step 460, as in step 456, it is determined whether or not the rear wheel is in reverse phase with respect to the front wheel. If a negative determination is made, in step 462, the correction coefficient Kr is corrected to increase. If the product of the coefficient Krc and the vehicle speed correction coefficient Krcv is set and an affirmative determination is made, in step 464, the correction coefficient Kr is set to the correction coefficient Krs on the reduction side.

Next, operations and effects common to the steering devices according to the first and second embodiments described above will be described for various traveling situations of the vehicle.
(1) When neither specific control nor left-right difference control is performed

In Steps 120, 130, and 150, a negative determination is made. In Step 175, the target steering gear ratio Rst is set to the basic target steering gear ratio Rsbt. In Step 240, the steering gear ratio is changed to the target steering gear ratio Rst. The turning angle varying device 14 is controlled so that
(2) When specific control is performed and right / left difference control is not performed

First, a negative determination is made at step 120, an affirmative determination is made at step 130, and specific control is started at step 140. Thereafter, an affirmative determination is made at step 120, and a negative determination is made at step 180, whereby specific control is executed at step 140.
(3) When specific control ends

When the specific control end condition is satisfied and the specific control ends, an affirmative determination is made in steps 120 and 180, and in step 190, the reference steering angle θs, the offset θo, and the pinion angle offset φo. Is calculated.
(4) When returning to normal control after specific control is completed

When the magnitude of the offset θo at the time when the specific control is finished is small, the steering gear ratio control returns to the normal control without performing the left-right difference control. That is, a negative determination is made at step 200, the target steering gear ratio Rst is set to the basic target steering gear ratio Rsbt at step 175, and the steering gear ratio becomes the target steering gear ratio Rst at step 240. The turning angle varying device 14 is controlled.
(5) When left-right difference control is performed after specific control is completed

When the magnitude of the offset θo at the time when the specific control is finished is large, the left / right difference control is executed without returning the steering gear ratio control to the normal control. That is, an affirmative determination is made in step 200, a target steering gear ratio Rst for left / right difference control is calculated in step 210, and a turning angle is set so that the steering gear ratio becomes the target steering gear ratio Rst in step 240. The variable device 14 is controlled.
(5-1) When left / right difference control is performed with a right turn offset

  When the offset θo is a right turn offset, the relationship between the steering angle θ and the pinion angle φ when the steering gear ratio is the basic target steering gear ratio Rsbt is indicated by a broken line L in FIG. The offset θo becomes a positive value. Accordingly, an affirmative determination is made at step 222 in the flowchart of FIG. The solid line L0 indicates the relationship when the offset θo is zero.

  The situation where the steering angle θ is larger than the reference steering angle θs is that the steering region on the same side as the offset θo side with respect to the position where the steering angle θ is 0 among the steering regions on both sides of the steering position of the reference steering angle θs, that is, This is a situation in which the steering wheel 20 is steered in one steering area. In this situation, an affirmative determination is made in step 224, and in step 228, the target steering gear ratio Rst is set to the product of the quick-side basic correction coefficient Kc and the basic target steering gear ratio Rsbt. . Therefore, the relationship between the steering angle θ and the pinion angle φ in the first steering region is the relationship indicated by the solid line L1 in FIG.

  Therefore, compared with the case where the target steering gear ratio Rst is the basic target steering gear ratio Rsbt, the target steering gear ratio Rst in the first steering region can be reduced, thereby increasing the steering transmission ratio. Can do.

  Conversely, when the steering angle θ is equal to or smaller than the reference steering angle θs, the steering operation is performed in the second steering region on the side opposite to the first steering region with respect to the steering position of the reference steering angle θs. Is the situation. In this situation, a negative determination is made in step 224, and in step 230, the target steering gear ratio Rst is set to the product of the slow side basic correction coefficient Ks and the basic target steering gear ratio Rsbt. . Therefore, the relationship between the steering angle θ and the pinion angle φ in the second steering region is also the relationship indicated by the solid line L2 in FIG.

Therefore, compared with the case where the target steering gear ratio Rst is the basic target steering gear ratio Rsbt, the target steering gear ratio Rst in the second steering region can be increased, thereby reducing the steering transmission ratio. Can do.
(5-2) When left / right difference control is performed with a left turn offset

  When the offset θo is a left turn offset, the relationship between the steering angle θ and the pinion angle φ when the steering gear ratio is the basic target steering gear ratio Rsbt is shown by a broken line in FIG. 25, for example. The offset θo is a negative value. Accordingly, a negative determination is made at step 222 in the flowchart of FIG.

  The situation where the steering angle θ is equal to or smaller than the reference steering angle θs is that the steering region on the same side as the offset θo side with respect to the position where the steering angle θ is 0 among the steering regions on both sides of the steering position of the reference steering angle θs, that is, the first This is a situation in which the steering wheel 20 is steered in one steering area. In this situation, a negative determination is made in step 226, and in step 228, the target steering gear ratio Rst is set to the product of the quick side basic correction coefficient Kc and the basic target steering gear ratio Rsbt. . Therefore, the relationship between the steering angle θ and the pinion angle φ in the first steering region is the relationship indicated by the solid line L1 in FIG.

  Therefore, compared with the case where the target steering gear ratio Rst is the basic target steering gear ratio Rsbt, the target steering gear ratio Rst in the first steering region can be reduced, thereby increasing the steering transmission ratio. Can do.

  Conversely, when the steering angle θ is larger than the reference steering angle θs, the steering operation is performed in the second steering region on the side opposite to the first steering region with respect to the steering position of the reference steering angle θs. Is the situation. In this situation, an affirmative determination is made at step 226, and at step 230, the target steering gear ratio Rst is set to the product of the slow-side basic correction coefficient Ks and the basic target steering gear ratio Rsbt. . Therefore, the relationship between the steering angle θ and the pinion angle φ in the second steering region is also the relationship indicated by the solid line L2 in FIG.

Therefore, compared with the case where the target steering gear ratio Rst is the basic target steering gear ratio Rsbt, the target steering gear ratio Rst in the second steering region can be increased, thereby reducing the steering transmission ratio. Can do.
(6) When left / right difference control ends

  In the process in which the left / right difference control is performed, for example, if the offset θo is reduced and the end condition for the left / right difference control is satisfied, the left / right difference control is ended, and the steering gear ratio control is changed to the normal control. Return. That is, a negative determination is made in steps 120 and 130, an affirmative determination is made in steps 150 and 160, and the target steering gear ratio Rst is set to the basic target steering gear ratio Rsbt in step 175. Then, the turning angle varying device 14 is controlled so that the steering gear ratio becomes the target steering gear ratio Rst.

  In the above-mentioned “(3) When the specific control is finished”, for example, the steering angle θ and the pinion in the case where the right / left difference control of the present invention is not executed even if the offset θo in the right turn direction occurs. The relationship with the angle φ is not the relationship in which the offset θo indicated by the solid line L0 in FIG. 26 is 0, but the relationship indicated by the wavy line L shifted in the right turn direction with respect to the solid line.

  Therefore, even when the vehicle travels straight, the driver holds the steering wheel 20 with the left and right hands 72L and 72R and holds the steering wheel 20 in the original straight traveling position as shown in FIG. Instead, the vehicle must be held in the right turn position as shown in FIG. In FIG. 27, an arrow 74 indicates the straight direction of the steering wheel 20 in the vehicle.

  Further, when the steering wheel 20 is rotated in the right turning direction that is the offset direction from the holding position shown in FIG. 27B, the steering wheel 20 is turned in the right turning direction from the holding position shown in FIG. This is not as easy as when the steering wheel 20 is rotated. Conversely, rotating the steering wheel 20 from the holding position shown in FIG. 27B to the left turning direction opposite to the offset direction means turning left from the holding position shown in FIG. This is easier than when the steering wheel 20 is rotated in the direction. The driver feels uncomfortable with the change in ease of rotating operation caused by the offset.

  On the other hand, according to the first and second embodiments, as understood from the above description, even when the offset θo is generated at the time when the specific control is finished, the offset θo is the right-turning offset. In both cases, the left and right turn offset, the steering transmission ratio can be made higher in the first steering region than in the case where the left / right difference control is not performed. Accordingly, it is possible to reduce the uncomfortable feeling caused by the difficulty in rotating the steering wheel 20 due to the offset in the first steering region. Further, in the second steering region, the steering transmission ratio can be lowered as compared with the case where the left / right difference control is not performed, thereby causing the steering wheel 20 due to the offset in the second steering region. It is possible to reduce a sense of incongruity that is felt due to the ease of rotating the.

  Further, according to the first and second embodiments, the steering transmission ratio is increased by reducing the target steering gear ratio Rst in the first steering region as compared with the case where the left / right difference control is not performed. In the second steering area, the steering transmission ratio is lowered by increasing the target steering gear ratio Rst as compared with the case where the left / right difference control is not performed. Therefore, the first and second steering gear ratios Rst are reduced only in the first steering region, and the first and second steering gear ratios Rst are increased only in the second steering region. It is possible to effectively reduce the uncomfortable feeling when the steering operation is performed in the second steering region.

  Further, according to the first and second embodiments, the difference between the slow-side basic correction coefficient Ksb and 1 is smaller than the difference between 1 and the quick-side steering angular velocity correction coefficient Kcb, and in the second steering region. The amount by which the target steering gear ratio Rst is increased is smaller than the amount by which the target steering gear ratio Rst is decreased in the first steering region. In other words, the amount by which the steering transmission ratio is lowered in the second steering region is smaller than the amount by which the steering transmission ratio is increased in the first steering region. Accordingly, it is possible to effectively prevent the steering operation in the second steering region from becoming excessively difficult while effectively facilitating the steering operation in the first steering region.

  Further, according to the first and second embodiments, in step 212, the quick-side offset correction coefficient Kco is calculated so as to decrease as the absolute value of the pinion angle offset φo increases within a range of 1 or less. Further, the slow-side offset correction coefficient Kso is calculated so as to increase as the absolute value of the pinion angle offset φo increases in a range of 1 or more. The quick-side correction coefficient Kc for the basic target steering gear ratio Rsbt is calculated to include a quick-side offset correction coefficient Kco, and the slow-side correction coefficient Ks for the basic target steering gear ratio Rsbt is the slow-side offset correction coefficient Kso. Is calculated to a value containing

  Therefore, as shown in FIG. 28, compared to the case where the quick side correction coefficient Kc is constant regardless of the magnitude of the offset, the degree of difficulty in steering the steering wheel 20 in the first steering region. Accordingly, the left and right front wheels 18FL and 18FR can be easily steered. In addition, the left and right front wheels 18FL and 18FR are adjusted according to the degree to which the steering wheel 20 is easily steered in the second steering region, as compared with the case where the slow-side correction coefficient Ks is constant regardless of the magnitude of the offset. Can be difficult to steer.

  In addition, according to the first and second embodiments, if an affirmative determination is made in any of steps 164, 166, 168, 170, the termination condition for the left / right difference control is satisfied in step 172. It is determined. That is, (A) the magnitude of the current offset Δθ is equal to or smaller than a reference value θb for determining the end of the left / right difference control, (B) the steering wheel 20 is rotated more than the reference angle value with respect to the position of the reference steering angle θs If either (C) the steering wheel 20 is changed by the driver or (D) the steering wheel 20 is rotated more than the reference value in the direction of the offset θo with respect to the neutral position, the left / right difference control is performed. Is terminated.

  Therefore, the possibility that the left / right difference control is continued unnecessarily is effectively reduced as compared with the case where it is determined whether or not the right / left difference control end condition is satisfied only by any of steps 164 to 170. can do. In particular, when the driver changes the steering wheel 20 so that the steering speed does not change, an affirmative determination may not be made in step 168, but if the steering angle increases, the process proceeds to step 170. Since the affirmative determination is made in this case, the left / right difference control can be reliably ended.

  For example, as can be seen from FIG. 28, the inclination angles of the solid lines L1 and L2 with respect to the solid line L0 and the wavy line L increase as the magnitude of the offset θo increases, and thereby increase as the distance between the solid line L0 and the wavy line L increases. Become. Therefore, the solid lines L1 and L2 and the solid line L0 between the solid lines L1 and L2 and the solid line L0 are compared with the case where the inclination angles of the solid lines L1 and L2 with respect to the solid line L0 and the broken line L do not increase as the magnitude of the offset θo increases. The change in the position of the intersection is small. Therefore, regardless of the magnitude of the offset θo, it can be determined whether or not the left / right difference control is unnecessary by the determination in step 166.

  Further, in step 168, for example, in the process of increasing or decreasing the steering angle θ, the steering wheel 20 is discriminated by determining whether or not the steering speed has once exceeded a reference value variably set according to the vehicle speed V after the steering speed has once decreased. When it is determined whether or not the steering wheel 20 has been changed, it is possible to estimate whether or not the steering wheel 20 has been changed without requiring a grip switch or the like for detecting whether or not the steering wheel 20 is being held. it can.

  Further, according to the first and second embodiments, the quick side vehicle speed correction coefficient Kcvv is calculated so as to decrease as the vehicle speed V increases in step 214, and in step 218, the quick target vehicle speed correction coefficient Kcvv is calculated with respect to the basic target steering gear ratio Rsbt. The side correction coefficient Kc is calculated as a value including the vehicle speed correction coefficient Kcvv. Therefore, in the low vehicle speed range where the steering wheel 20 is easily changed and therefore the necessity of the left / right difference control is low, the target steering gear ratio Rst is increased to lower the steering transmission ratio, and the steering wheel 20 is changed. Therefore, in a high vehicle speed range where the need for right / left difference control is high, the target steering gear ratio Rst can be reduced and the steering transmission ratio can be increased.

  Further, according to the first and second embodiments, in step 216, the quick-side steering angular velocity correction coefficient Kcsv is calculated so as to decrease as the absolute value of the steering angular velocity θd increases, and the slow-side steering angular velocity correction coefficient Kssv. Is calculated so as to increase as the absolute value of the steering angular velocity θd increases. Accordingly, the higher the driver's steering operation speed and the higher the degree of quick steering of the left and right front wheels, the lower the target steering gear ratio Rst and the higher the steering transmission ratio.

  Next, operations and effects unique to each of the first and second embodiments will be described.

  As described above, in the first embodiment, when the left / right difference control is being performed, an affirmative determination is made in step 330, and the correction coefficient Kp is calculated in step 350. Thus, the target assist torque Ta is corrected to increase or decrease. In particular, in the first steering region where steering operation is difficult, the target assist torque Ta is corrected to be larger than the basic assist torque Tab, and in the second steering region where steering operation is easy, the target assist torque Ta is the basic assist torque. It is corrected to be lower than Tab.

  Therefore, compared to the case where the target assist torque Ta is not corrected for increase / decrease even during the left / right difference control, the steering operation is easier in the first steering region, and the steering operation is performed in the second steering region. The steering assist torque can be controlled to make it difficult to do so. Therefore, compared to the case where the steering assist torque is not controlled, the uncomfortable feeling caused by the offset of the turning angle varying device 14 can be effectively reduced.

  In particular, according to the first embodiment, in steps 352 to 360, the same processing as that in steps 212 to 220 regarding the increase or decrease of the target steering gear ratio Rst is performed for the increase or decrease of the target assist torque Ta. Accordingly, the target assist torque Ta can be appropriately increased or decreased in accordance with the magnitude of the offset θo, the vehicle speed V, and the absolute values of the steering angular velocity θd, as compared with the case where the processing in steps 352 to 360 is not performed.

  As described above, in the second embodiment, when the left / right difference control is being performed, an affirmative determination is made in step 420, and the correction coefficient Kr is calculated in step 440, whereby step 470 is performed. At this time, the target rear wheel steering angle δrt is corrected. Particularly in the first steering area where steering operation is difficult, the target rear wheel steering angle δrt is corrected so as to increase the turning yaw moment of the vehicle more than usual, and in the second steering area where steering operation is easy. The target rear wheel steering angle δrt is corrected so as to reduce the turning yaw moment of the vehicle.

  Therefore, even when the left / right difference control is being performed, the vehicle is easier to turn in the first steering region than in the case where the target rear wheel steering angle δrt is not corrected for increase / decrease. Can control the rear wheel steering angle δr so that the vehicle is difficult to turn. Therefore, compared with the case where the rear wheel steering angle is not controlled, the uncomfortable feeling caused by the offset of the turning angle varying device 14 can be effectively reduced.

  In particular, according to the second embodiment, in steps 442 to 450, the same processing as in steps 212 to 220 regarding the increase or decrease of the target steering gear ratio Rst is performed for the increase or decrease of the target rear wheel steering angle δrt. Accordingly, the target rear wheel steering angle δrt can be appropriately increased / decreased according to the magnitude of the offset θo, the vehicle speed V, and the absolute values of the steering angular velocity θd as compared with the case where the processing of steps 442 to 450 is not performed.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the first and second embodiments described above, in step 212, the quick-side offset correction coefficient Kco is calculated so as to decrease as the absolute value of the pinion angle offset φo increases within a range of 1 or less. The slow-side offset correction coefficient Kso is calculated so as to increase as the absolute value of the pinion angle offset φo increases within a range of 1 or more, but these correction coefficients may be omitted.

  In the first and second embodiments described above, in step 214, the quick-side vehicle speed correction coefficient Kcvv is calculated to decrease as the vehicle speed V increases. In step 218, the basic target steering gear ratio is calculated. Although the correction coefficient Kc on the quick side for Rsbt is calculated as a value including the vehicle speed correction coefficient Kcvv, the vehicle speed correction coefficient Kcvv may be omitted.

  In the first and second embodiments described above, in step 216, the quick-side steering angular velocity correction coefficient Kcsv is calculated so as to decrease as the absolute value of the steering angular velocity θd increases. The correction coefficient Kssv is calculated so as to increase as the absolute value of the steering angular velocity θd increases, but these correction coefficients may be omitted.

  Corresponding to the omission of the correction coefficient, the correction coefficient calculated in any of steps 352 to 356 in the first embodiment described above may be omitted, and the second embodiment described above. The correction coefficient calculated in any one of steps 442 to 446 may be omitted.

  In the first and second embodiments described above, the difference between the slow-side basic correction coefficient Ksb and 1 is set to a value smaller than the difference between 1 and the quick-side steering angular velocity correction coefficient Kcb. However, these differences may be set to the same value.

  In the first and second embodiments described above, it is determined whether or not the right / left difference control end condition is satisfied by the four steps of steps 164 to 170. At least one of the steps 164 to 170 may be omitted.

  In the first embodiment described above, the steering assist torque is controlled so that the steering operation becomes easy in the first steering region and the steering operation becomes difficult in the second steering region. In the second embodiment, the rear wheel steering angle δr is controlled so that the vehicle is easy to turn in the first steering region and the vehicle is difficult to turn in the second steering region. However, it may be modified so that both the steering assist torque control of the first embodiment and the rear wheel steering angle δr control of the second embodiment are performed.

  Conversely, in the first embodiment described above, the steering assist torque control corresponding to the left / right difference control may be omitted, and in the second embodiment described above, the control corresponding to the left / right difference control is performed. The control of the wheel steering angle δr may be omitted.

  DESCRIPTION OF SYMBOLS 10 ... Steering device, 14 ... Steering angle variable device, 16 ... Electronic control device, 20 ... Steering wheel, 22 ... Electric power steering device, 50 ... Steering angle sensor, 52 ... Steering torque sensor, 54 ... Rotation angle sensor, 56 ... Vehicle speed sensor, 58 ... CCD camera, 60 ... Radar sensor, 64 ... Rear wheel steering device, 70 ... Steering angle sensor

Claims (12)

  A vehicle steering system comprising: a steering transmission ratio variable device capable of changing a steering transmission ratio, which is a ratio of a steering wheel turning amount to a steering operation amount to a steering input means; and a control means for controlling the steering transmission ratio variable device. In the transmission ratio variable type steering apparatus, the control means has an offset in the relationship of the steering position of the steering input means with respect to the steering angle of the steered wheel by specific control for changing the steering transmission ratio by the steering transmission ratio variable apparatus. When it occurs, the steering position of the steering input means when the specific control is finished is set as a reference steering position, and the vehicle input position of the steering input means in the two steering areas on both sides of the reference steering position is Driving after the end of the specific control with the steering region on the same side as the offset side as the first steering region and the steering transmission ratio when the offset is 0 as the standard steering transmission ratio When the steering input means is steered in the first steering region, the steering transmission ratio is made larger than the standard steering transmission ratio. apparatus.   The control means uses the steering area opposite to the first steering area as the second steering area with respect to the reference steering position, and the driver uses the steering input means in the second steering area. 2. The vehicle steering transmission ratio variable type steering apparatus according to claim 1, wherein the steering transmission ratio is made smaller than the standard steering transmission ratio when a steering operation is performed.   3. The vehicle according to claim 2, wherein an amount that makes the steering transmission ratio smaller than the standard steering transmission ratio is smaller than an amount that makes the steering transmission ratio larger than the standard steering transmission ratio. Steering device with variable steering transmission ratio.   4. The vehicle steering transmission ratio variable steering apparatus according to claim 1, wherein the control unit variably sets a change amount of the steering transmission ratio according to the magnitude of the offset. 5. .   The control means ends the change of the steering transmission ratio when the magnitude of the offset after the start of the change of the steering transmission ratio becomes a reference value or less, and changes the steering transmission ratio to the standard steering transmission ratio. The vehicle steering transmission ratio variable type steering device according to any one of claims 1 to 4, wherein the steering device is returned.   2. The control unit according to claim 1, wherein when the driver estimates that the driver has changed the steering input unit, the control unit ends the change of the steering transmission ratio and returns the steering transmission ratio to the standard steering transmission ratio. The vehicle steering transmission ratio variable type steering device according to any one of claims 5 to 6.   In the process in which the driver steers the steering input means in a direction away from the reference steering position in the first steering region, the control means determines that the steering operation speed of the steering input means is a steering operation. 7. The vehicular steering transmission ratio variable type steering apparatus according to claim 6, wherein when the speed judgment reference value is exceeded, it is estimated that the driver has changed the steering input means.   The control means changes the steering transmission ratio when a steering operation amount of the steering input means in a direction away from the reference steering position in the first steering region is equal to or greater than a steering operation amount determination reference value. 8. The vehicle steering transmission ratio variable type steering apparatus according to claim 1, wherein the steering transmission ratio is ended and the steering transmission ratio is returned to the standard steering transmission ratio.   The control means variably sets the amount for increasing the steering transmission ratio according to the vehicle speed so that the amount for increasing the steering transmission ratio becomes larger when the vehicle speed is high than when the vehicle speed is low. The vehicle steering transmission ratio variable type steering apparatus according to any one of claims 1 to 8.   The control means controls the steering according to the steering operation speed so that when the steering operation speed of the steering input means by the driver is high, the amount of change in the steering transmission ratio is larger than when the steering operation speed is low. The vehicular steering transmission ratio variable type steering apparatus according to any one of claims 1 to 9, wherein a change amount of the transmission ratio is variably set.   The vehicle has a steering assist force generating means for generating a steering assist force, and the control means is configured such that when the driver steers the steering input means in the first steering region, the driver The vehicle steering transmission ratio variable according to any one of claims 1 to 10, wherein a steering assist force is increased as compared with a case where the steering input means is steered in a steering region. Type steering device.   The steering wheel is a front wheel, the vehicle has a rear wheel steering device for steering a rear wheel, and the control means is used when the driver steers the steering input means in the first steering region. Compared to the case where the driver steers the steering input means in the second steering area, the steering angle of the rear wheel is corrected so that the steering angle of the rear wheel changes in the opposite phase to the front wheel. The vehicular steering transmission ratio variable type steering apparatus according to any one of claims 1 to 11, wherein:

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