JP4534653B2 - Differential - Google Patents

Description

  The present invention relates to a differential device disposed between the left and right wheels of a front wheel or a rear wheel of a four-wheeled vehicle.

  Conventionally, as a differential device disposed between the left and right wheels of a driven wheel of a four-wheeled vehicle, for example, the rotational difference between the left and right wheels is positively generated so as to absorb the difference between the inner wheels when the four-wheeled vehicle turns. There is what is constituted so that it may be made (refer to patent documents 1). In this differential device, it is intended to improve running stability during turning by actively absorbing the difference between the inner wheels when the four-wheeled vehicle turns. In such a differential device, the rotational torque of the differential motor is converted to the differential torque of the left and right wheels. Further, the differential device configured as described above is configured to restrict the rotation difference between the left and right wheels by restricting the rotation of the differential motor so as to improve traveling stability in a straight traveling state. is there.

  However, the conventional differential device has the following problems. That is, an appropriate rotational difference is generated between the left and right wheels in a traveling state with a large turning radius close to a complete straight traveling state or when the diameter difference between the left and right wheels is different due to tire air pressure or the like. If the rotation of the differential motor is restricted in such a running state to restrict the rotation difference between the left and right wheels, the running stability may be impaired, and the engine power of the four-wheeled vehicle may be lost.

Japanese Patent Laid-Open No. 11-91383 JP 2000-203295 A

  The present invention has been made in view of the above-described conventional problems, and in a differential device disposed between the left and right wheels of a front wheel or a rear wheel of a four-wheeled vehicle, it is possible to suppress power loss and improve straight running stability. The present invention aims to provide an excellent differential device that satisfies both requirements at a high level.

The present invention is a differential device disposed between the left and right wheels of a front wheel or rear wheel of a four-wheel vehicle,
The differential device includes two output elements independently connected to the left and right wheels, a differential motor for controlling a differential between the two output elements, and a turning radius of the four-wheel vehicle. A measurement sensor for measuring an index value having a correlation with the magnitude, a motor control unit for controlling the differential motor, a straight-ahead determination sensor for obtaining a measurement value for determining a straight-ahead state of the four-wheeled vehicle, The motor control unit determines that the four-wheeled vehicle is in a straight traveling state based on a rotation difference sensor for directly or indirectly measuring the rotation difference between the left and right wheels and the measured value of the straight traveling determination sensor. Storage means for storing the rotation difference between the left and right wheels measured by the rotation difference sensor as a straight rotation difference ,
When the motor control unit determines that the turning radius is large and the four-wheeled vehicle is in a traveling state close to a straight traveling state by performing threshold processing on the index value measured by the measuring sensor, The difference is characterized in that a straight running stability control is executed to control the differential motor so that the rotation difference between the left and right wheels measured by the rotation difference sensor coincides with the straight rotation difference stored in the storage means. (Claim 1).

The differential device of the present invention includes a measurement sensor that measures an index value correlated with the magnitude of the turning radius, a motor control unit that controls the differential motor, and the left and right when the four-wheeled vehicle goes straight. Storage means for storing a straight rotation difference which is a rotation difference of the wheel.
Then, the motor control unit, based on the index value, the rotational difference between the left and right wheels are controlled so as to coincide with the straight rotational difference.

In the present invention, the storage means arranges the upper limit value of the torque generated by the differential motor with respect to the index value, and the upper limit value monotonously increases as the turning radius increases. The torque map set as described above is further stored, and the motor control unit obtains a value obtained by referring to the torque map stored in the storage unit based on the index value measured by the measurement sensor. It is preferable that the straight running stability control is executed with the upper limit of the generated torque as defined above (claim 2).
That is, the differential motor of the differential device generates a generated torque that serves as an assist force for maintaining the straight traveling state in a straight traveling state or a traveling state having a large turning radius close to the straight traveling state. Here, the upper limit value of the generated torque (hereinafter referred to as the differential limiting torque as appropriate ) is set so as to increase monotonically as the turning radius of the four-wheeled vehicle increases and approaches a completely straight running state. . In addition, that the differential limiting torque increases monotonously means that the differential limiting torque is changed by a monotonic increase in a broad sense. That is, it means that the differential limiting torque T1 for the turning radius R1 (> R2) and the differential limiting torque T2 for the turning radius R2 always satisfy the relationship of T1 ≧ T2.

  The differential device controls the differential motor using the differential limiting torque obtained by referring to the torque map as an upper limit torque value so that the rotational difference between the left and right wheels matches the linear rotational difference. To control. That is, according to the differential device, the torque generated by the differential motor increases in order to maintain the straight traveling as the turning radius increases and the straight traveling state is approached. That is, as the turning radius increases and approaches a completely straight traveling state, the assist force for maintaining the straight traveling state increases.

  Therefore, the driver who drives the above-mentioned four-wheeled vehicle equipped with the above-mentioned differential device has excellent straight running stability such that the steering becomes slow (the reaction is dull) as it approaches the complete straight running state. A feeling of operation can be obtained. Therefore, according to the differential device, it is possible to improve the straight running stability of the four-wheeled vehicle and improve the traveling safety.

  On the other hand, in the differential device, the turning radius is reduced, and the differential limiting torque is reduced and the generated torque of the differential motor is reduced as the turning away from the complete straight traveling state. Thereby, the power loss in the traveling state in which there is a high possibility that the rotation difference between the left and right wheels is generated is suppressed. In this way, in the above-described differential device, power loss during straight running stability control is suppressed.

As described above, it is possible to achieve both improvement of the straight running stability and the suppression of the power loss at a high level.
As the torque map in which the differential limiting torque is arranged, the differential limiting torque is calculated based on the index value in addition to a data map in which the value of the differential limiting torque is arranged according to the index value. It may be a calculation formula or a logical formula. That is, the torque map means anything configured to be able to determine the differential limiting torque based on the index value.
Furthermore, when there is no difference in diameter between the left and right wheels, the straight rotation difference is zero. On the other hand, when there is a difference in diameter between the left and right wheels, the straight rotation difference has a value other than zero.

  The motor control unit can execute the straight running stability control by operating the differential motor in the regeneration mode.

In this case, when it is determined that the four-wheeled vehicle is in a straight traveling state, the differential motor is operated in the regeneration mode. At this time, the driving torque required for the differential motor to generate power acts as a torque that limits the differential between the left and right wheels. Therefore, in the four-wheel vehicle equipped with the differential device, when the differential motor performs the regeneration mode, the differential between the left and right wheels is suppressed, and the straight running stability is improved.
Note that the straight traveling state means a traveling state in which the turning radius is sufficiently large and close to the complete straight traveling state with the complete straight traveling state as a center. For example, the straight traveling state may be a traveling region having a turning radius of about 300 m to 400 m or more.

In the present invention, the differential device measures, as the measurement sensor, a vehicle speed sensor that measures a vehicle speed that is the speed of the four-wheeled vehicle as the index value, and a steering angle that is a steering operation amount as the index value. has a steering angle sensor, the torque map is preferably one obtained by arranging an upper limit value of the generated torque with respect to the vehicle speed and the steering angle (claim 3).
In this case, the turning radius of the four-wheeled vehicle can be estimated with high accuracy based on the vehicle speed and the steering angle. And based on the vehicle speed and steering angle which can estimate a turning radius accurately, the said differential device can be controlled exactly.

In addition, the differential device includes a straight-ahead determination sensor that obtains a measurement value for determining a straight-ahead state of the four-wheeled vehicle, and a rotation difference sensor for directly or indirectly measuring a rotation difference between the left and right wheels. The differential control unit determines whether or not the four-wheeled vehicle is in a straight traveling state based on the measurement value of the straight traveling determination sensor, and determines the rotation difference between the left and right wheels in the straight traveling state. It is configured to learn as the straight rotation difference .
As a result , for example, it is possible to cope with a case where the rotation difference between the left and right wheels in a straight traveling state does not become zero due to the difference in diameter between the left and right wheels. That is, the differential device can appropriately improve the straight running stability of the four-wheeled vehicle regardless of the diameter difference between the left and right wheels.

Moreover, the straight travel determination sensors are preferably have a yaw rate sensor or lateral G sensor for measuring the rotational angular velocity of the four-wheeled vehicle (claim 4). Further, as the rotation differential sensor, it is preferable to have a motor rotation sensor which measures the rotational direction and the rotational speed of the wheel speed sensor or the differential motor individually detecting the rotational speed of the left and right wheels.
If the yaw rate sensor or the lateral G sensor is used, the straight traveling state of the four-wheeled vehicle can be accurately determined. The rotation difference between the left and right wheels when it is determined that the four-wheeled vehicle is in the straight traveling state can be learned as the straight traveling rotation difference. The rotation difference between the left and right wheels can be directly measured using the wheel speed sensor, or can be indirectly measured using the motor rotation sensor.

Further, when the motor control unit determines that the turning radius is large and the four-wheeled vehicle is in a traveling state close to a straight traveling state by performing threshold processing on the index value, the rotation of the left and right wheels is determined. When the differential motor is controlled so that the difference matches the straight rotation difference, and when it is determined that the vehicle is in another running state, the rotation difference between the left and right wheels is made to match the straight rotation difference. The control of the differential motor is not performed .

In this case, the differential motor is controlled so that the rotational difference between the left and right wheels substantially coincides with the linear rotational difference in a traveling region having a large turning radius and a predetermined range centered on a complete straight traveling state. To do. As a result, it is possible to improve the straight running stability of the four-wheeled vehicle in the traveling region within the predetermined range.
In addition, as a control range which controls the said differential motor so that the rotation difference of the said right-and-left wheels may correspond with the said linear advance rotation difference, the said turning radius can be set to the range of about 300 m-radius 400 m or more, for example. .

Even when the differential motor is operated in the regenerative mode, the differential device is a vehicle speed sensor that measures the vehicle speed that is the speed of the four-wheeled vehicle as the index value as the measurement sensor, and a steering operation amount. It is preferable to have a steering angle sensor that measures the steering angle as the index value .
In this case, it can be accurately determined whether or not the four-wheeled vehicle is in a straight traveling state based on the vehicle speed and the steering angle. When the four-wheeled vehicle is traveling straight ahead, the differential motor can be operated in the regenerative mode at an appropriate timing.

When the differential motor is operated in the regenerative mode, it is preferable that the measurement sensor has a wheel speed sensor that measures the rotation speed of the left and right wheels as the index value .
In this case, the rotation difference between the left and right wheels can be easily calculated based on the rotation speed of the left and right wheels. Based on the rotation difference between the left and right wheels, it can be determined relatively easily whether or not the four-wheeled vehicle is in a straight traveling state. When the four-wheeled vehicle is traveling straight ahead, the differential motor can be operated in the regenerative mode at an appropriate timing.

Example 1
This example is an example related to the differential device 1 disposed between the auxiliary drive wheels 50L and 50R of the four-wheel automobile 100. The contents will be described with reference to FIGS.
As shown in FIG. 1, the differential device 1 of the present example is disposed between the left and right wheels (hereinafter referred to as auxiliary drive wheels 50 </ b> L, R) of the four-wheeled vehicle 100. is there.
As shown in FIG. 2, the differential device 1 includes two output elements that are independently connected to the auxiliary drive wheels 50L and 50R, and a differential motor 40 that generates a differential between the two output elements. A measurement sensor that measures an index value correlated with the turning radius of the four-wheel vehicle 100, a motor control unit 6 for controlling the differential motor 40, and the differential motor 40 for the index value. auxiliary drive wheel 50L when the torque map and four-wheel motor vehicle 100 has been arranged a differential limiting torque is the upper limit of Ru generation torque is generated is straight, the storage unit 604 for storing the straight rotational difference is the rotational difference R It has.

The motor control unit 6 obtains a differential limiting torque by referring to the torque map based on the index value, and the rotational difference between the auxiliary drive wheels 50L, R with the differential limiting torque as an upper limit torque value The differential motor 40 is controlled to match the rotation difference. In the torque map, the differential limiting torque monotonously increases as the turning radius estimated based on the index value increases.
In this example, a vehicle speed sensor 61 that measures the vehicle speed of the four-wheel vehicle 100 and a steering angle sensor 62 that is a steering operation amount are used as the measurement sensor.
This content will be described in detail below.

As shown in FIGS. 1 and 2, the differential device 1 controls a differential between two output elements (in this example, the output shafts 32 </ b> L and 32 </ b> R of the equally distributed differential 30).
The differential 1 includes three parts: a sun gear 23, a ring gear 22 coaxially arranged on the outer peripheral side of the sun gear 23, and a carrier 21 that holds a planetary gear 24 that is gear-engaged with the ring gear 22 and the sun gear 23. In the planetary gear mechanism set 2 in which two (20a and 20b) planetary gear mechanisms 20 including a selection component that is a gear element are combined, a housing 25 that houses the planetary gear mechanism set 2, and one planetary gear mechanism 20b. A differential motor 40 that rotates any one of the constituent elements of the ring gear 22, the sun gear 23, and the carrier 21 (in this example, it also serves as a secondary prime mover; hereinafter referred to as the secondary prime mover 40); The other planetary gear mechanism 20a includes a brake mechanism 251 configured to stop the rotation of any one of the above-described components. In FIG. 2, the vehicle engine 8 and the main drive wheels 80L and 80R (FIG. 1) are omitted.

In the planetary gear mechanism set 2, the gear ratio which is the ratio of the number of teeth of the sun gear 23 and the number of teeth of the ring gear 22 matches.
And the carrier 21 which is the 1st element of each said selection component is connected with the carriers 21a and 21b of each planetary gear mechanism 20a and 20b.
In addition, the ring gear 22 which is the second element among the selected components is configured such that the ring gear 22a of one planetary gear mechanism 20a can stop rotating by the brake mechanism 251 and the other planetary gear. The ring gear 22b of the mechanism 20b is connected to the motor shaft of the sub prime mover 40.
Further, in the sun gear 23 which is the third element among the selection components, the sun gears 23a and 23b of the planetary gear mechanisms 20a and 20b are directly or indirectly connected to the output shaft 32L or 32R, respectively. .

  As shown in FIGS. 1 and 2, the differential device 1 of this example includes a bevel gear type equally distributed differential 30 including a single input shaft 31 and two output shafts 32 </ b> L and 32 </ b> R as output elements. It becomes. One sun gear 23b is connected to the input shaft 31 of the equally distributed differential 30, and the other sun gear 23a is connected to the output shaft 32L. In the front and rear wheel drive device 10, the output shafts 32 </ b> L and 32 </ b> R of the equally distributed differential 30 are output elements of the differential device 1.

As shown in FIGS. 1 and 2, the front and rear wheel drive device 10 of the present example using this differential device 1 is a main prime mover 8 that drives main drive wheels 80L and 80R of front wheels or rear wheels of a four-wheeled vehicle 100. (Hereinafter, referred to as the vehicle engine 8 as appropriate) and the auxiliary prime mover 40 for driving the auxiliary driving wheels 50L and 50R.
The drive shafts 51L and 51R of the auxiliary drive wheels 50L and 50R are connected to the output shafts 32L and 32R of the equally distributed differential 30 in the differential device 1, respectively. The motor shaft of the secondary prime mover 40 is connected to the input shaft 31 of the equally distributed differential 30 via the clutch mechanism 41. The main drive wheels 80L and 80R are connected to the vehicle engine 8 via a power transmission unit 82.

  As shown in FIGS. 1 and 2, the planetary gear mechanism set 2 of the present example combines the planetary gear mechanisms 20 a and 20 b having the same specifications (hereinafter abbreviated as appropriate) and a common housing 25. The unit is housed integrally. Each planetary gear mechanism 20 includes a sun gear 23 disposed on the inner periphery, a plurality of planetary gears 24 that are rotatably supported by the carrier 21 and revolve around the sun gear 23, and an outer periphery thereof. It has an engagement structure with the ring gear 22 arranged on the side.

In the planetary gear mechanism set 2 of this example, as shown in the figure, the carrier 21 is configured as the first element. That is, each planetary gear 24 of each planetary gear mechanism 20 has a structure that is held by a common carrier 21.
In this example, the ring gear 22 is configured as the second element. That is, the ring gear 22a of one planetary gear mechanism 20a is configured to be stopped by the brake mechanism 251, and the ring gear 22b of the other planetary gear mechanism 20b is connected to the motor shaft of the differential motor. Has been. In this example, since the differential motor and the secondary prime mover 40 are shared, the motor shaft of the secondary prime mover 40 is connected to the ring gear 22b.

  Furthermore, in this example, as shown in FIGS. 1 and 2, the sun gear 23 is configured as the third element. The sun gear 23b of one planetary gear mechanism 20b is connected to the input shaft 31 of the equal distribution differential 30, and the sun gear 23a of the other planetary gear mechanism 20a is connected to one output shaft 32L and one of the equal distribution differential 30. Is connected to the drive shaft 51L of the drive wheel 50L.

  Here, the operation of the planetary gear mechanism set 2 of this example will be briefly described with reference to FIGS. 1 and 2. The number of teeth of each sun gear 23 is the same number of Zs, and the number of teeth of each ring gear 22 is the same number of Zr. When one ring gear 22a is stopped by the brake mechanism 251 and the rotational speed ωi input to the other ring gear 22b is set to zero, when one sun gear 23b is rotated at the rotational speed ω1, the carrier that is the first element The rotational speed of 21 is ωc = Zs / (Zs + Zr) × ω1. At this time, the other sun gear 23a rotates at the same ω1 as the one sun gear 23b.

  In order to rotate the other sun gear 23b at ω2 = ω1 + Δω with respect to the sun gear 23a having the rotational speed ω1 while the one ring gear 22a is stopped by the brake mechanism 251, the carrier 21 which is the first element is used. Needs to be rotated at ωc = Zs / (Zs + Zr) × ω1. In order to obtain the rotation speed of the carrier 21, it is necessary to input the rotation of ωi = (− Zr) / Zs × Δω to the other ring gear 22b.

  As shown in FIGS. 1 and 2, the equally distributed differential 30 of this example is configured using a bevel gear. The input shaft 31 of the equally distributed differential 30 is connected via a clutch mechanism 33 to a speed reducer 42 that is connected to the motor shaft of the sub prime mover 40. That is, the clutch mechanism 33 is intermittently connected so that the transmission of the rotational torque from the sub prime mover 40 to the equally distributed differential 30 can be interrupted. The right output shaft 32R of the equally distributed differential 30 is connected to a drive shaft 51R connected to the right sub drive wheel 50R. Further, as described above, the left output shaft 32L is coupled to the drive shaft 51L coupled to the left sub drive wheel 50L together with the sun gear 23a of one planetary gear mechanism 20a.

  For example, in the differential device 1 configured as described above, if the auxiliary prime mover 40 is rotationally driven in a state where the clutch mechanism 33 is disconnected and the rotation of the ring gear 22a is restricted by the brake mechanism 251, FIG. And as shown to FIG. 4 (B), a differential arises in the sub drive wheels 50L and R. As shown in FIG. Here, in FIG. 3 (A) and FIG. 4 (B), the rotation direction of the sub prime mover 40 is reversed.

In addition, as shown in FIG.5 and FIG.6, what was comprised using the double pinion gear instead of what was comprised using the bevel gear of this example as the equal distribution differential 30 is also applicable. In particular, in the case of the equally distributed differential 30 using a double pinion, as shown in FIG. 4, the sun gears 23a and 23b, which are the third elements of the planetary gear mechanisms 20a and 20b, are provided on the two output shafts 32L and 32R. Each can also be linked.
The clutch mechanism 33 may be a clutch having various structures such as a multi-plate clutch, a single-plate clutch, a hydraulic clutch, and an electromagnetic clutch.

  The front and rear wheel drive device 10 of this example is configured to be controlled by a motor control unit 6 as shown in FIGS. 2 and 7. The motor control unit 6 is configured to take in sensor outputs of the connected sensors and output control signals to the sub motor motor 40, the clutch mechanism 33, and the brake mechanism 251. Signals from the sensors may be input directly to the motor control unit 6 or may be input indirectly via an engine ECU or the like for controlling the vehicle engine 8 (FIG. 1).

  The vehicle speed sensor 61 is configured to detect the traveling speed of the four-wheeled vehicle 100 and generate an output signal corresponding to the traveling speed. The steering rudder angle sensor 62 is configured to detect a steering rudder angle as an operation amount of the steering wheel by the driver and generate an output signal corresponding to the steering rudder angle. The motor rotation sensor 401 is configured to measure the rotation direction and the number of rotations of the sub prime mover 40. The motor torque sensor 402 is configured to measure an energization current value that has a high correlation with the torque generated by the sub prime mover 40.

  As shown in FIG. 7, the motor control unit 6 of this example includes a CPU 601, an I / O unit 602 as an input / output interface, and a RAM 603 and a ROM 604 as storage means. The motor control unit 6 is connected to the vehicle speed measured by the vehicle speed sensor 601, the steering angle measured by the steering angle sensor 602, the motor rotation number measured by the motor rotation sensor 401, and the motor torque via the I / O circuit unit 602. A motor current value measured by a current sensor as the sensor 402 is captured. The motor control unit 6 is configured to control the differential motor 40 via the I / O circuit unit 602.

  Here, the ROM 604 of the motor control unit 6 stores a first program for determining the straight traveling state of the four-wheeled vehicle 100 and a second program for executing the straight traveling stability control when the straight traveling state is determined. And a motor characteristic map for estimating the motor torque based on the motor current value, and a torque map for obtaining the differential limiting torque of the auxiliary prime mover 40 based on the vehicle speed and the steering angle. Further, the ROM 604 stores a straight rotation difference that is a rotation difference between the auxiliary drive wheels 50L and 50R when the four-wheeled vehicle 100 is traveling in a completely straight traveling state. In this example, this straight rotation difference is set to zero.

  The characteristic map is a map of the relationship between the energization current value of the sub motor 40 and the rotational torque. As shown in FIG. 8, this characteristic map is a map that represents the relationship between the current value energized in the sub prime mover 40 and the generated torque. If this characteristic map is used, the magnitude of the actual torque generated by the secondary prime mover 40 can be obtained based on the value of the current supplied to the secondary prime mover 40. In the figure, the horizontal axis defines the current value, and the vertical axis defines the torque generated by the auxiliary prime mover 40.

The torque map is an array of differential limiting torques of the sub prime mover 40 in the straight-ahead stability control. As shown in FIG. 9, this torque map is an array of the above-mentioned differential limiting torque, which is the upper limit value of the generated torque when controlling the sub prime mover 40 with respect to the steering angle. In this example, a plurality of torque maps having different specifications are prepared for each vehicle speed. The torque map shown in FIG. 9 is an array of differential limiting torques with respect to the steering angle at a certain vehicle speed. In the figure, the horizontal axis defines the steering angle, and the vertical axis defines the absolute value of the differential limiting torque.

Next, a control method of the front and rear wheel drive device 10 of the present example will be described while explaining the contents of the first and second programs.
As shown in FIG. 10, the first program estimates the turning radius R of the four-wheeled vehicle 100 based on the captured vehicle speed and steering angle, and is the quasi-straight-running state close to the complete straight-running state or the complete straight-running state? Determine whether or not. Then, depending on the determination result, switching is performed between whether to perform straight-line stability control or normal control.

As shown in the figure, the first program first takes in the vehicle speed and the steering angle in step S110. In step S120, the turning radius R of the four-wheeled vehicle 100 is estimated based on the captured vehicle speed and steering angle.
In step S130, it is determined whether or not the estimated turning radius R is larger than a predetermined turning radius threshold value Rth. That is, in step S130, it is determined whether the turning radius R is sufficiently large and the vehicle is in the straight traveling state or the semi-straight traveling state, or the turning radius R is small.

When the traveling state of the four-wheeled vehicle 100 is in a straight traveling state or a semi-straight traveling state, the process proceeds to step S140. In this step S140, the differential torque limit Tlim is obtained by referring to the torque map based on the vehicle speed and the steering angle. Specifically, a torque map corresponding to the vehicle speed is selected, and the torque limit map Tlim is obtained by referring to the torque map based on the steering angle. In step S160, straight running stability control is performed.
On the other hand, when it is determined that the turning radius R of the four-wheeled vehicle 100 is small and the vehicle is in a turning state, the process proceeds to step S150, and predetermined normal control programmed in advance is performed.

  The second program executes the straight running stability control in step S160. Here, the front-rear wheel drive device 10 of this example opens the clutch mechanism 33 and engages the brake mechanism 251 as shown in FIG. In this state, the sub prime mover 40 is controlled using the differential limiting torque Tlim obtained by referring to the torque map as an upper limit torque value. Specifically, the difference between the third elements sun gears 23a and 23b is set so that the rotation difference between the auxiliary drive wheels 50L and R becomes a straight rotation difference by applying the torque generated by the auxiliary prime mover 40 to the ring gear 22b. Control the movement. To achieve a desired rotational difference.

  In the second program, as shown in FIG. 12, first, in step S210, the rotational speed of the differential motor (in this example, the secondary prime mover 40) measured by the motor rotation sensor 401 is fetched. In step S220, the rotation difference Δr between the auxiliary drive wheels 50L, R is calculated based on the rotation speed of the auxiliary prime mover 40, which is a differential motor.

  Thereafter, in step S230, Δr is compared with the straight rotation difference. If Δr does not substantially match the straight rotation difference, the processing step of Step S240 is performed. Here, “Δr substantially coincides with the straight rotation difference” means that Δr belongs to a predetermined range with the straight rotation difference as the center value. Further, the predetermined range may be set so that a preferable hysteresis is generated in terms of control.

  In step S240, the motor current value measured by the motor torque sensor 402, which is a current sensor, is captured. In step S250, Treal, which is the actual torque of the auxiliary prime mover 40 (differential motor), is calculated based on the motor current value. Thereafter, in step S260, the actual rotational torque Treal is compared with the differential limiting torque Tlim obtained in step S140. When Treal <Tlim is satisfied, the process proceeds to step S270, and when not satisfied, the process proceeds to step S280.

  In step S270, the sub prime mover 40 (differential motor) is controlled such that Δr substantially coincides with the linear rotation difference with the differential limiting torque Tlim as the upper limit torque value. On the other hand, in step S280, the energization current value for energizing the sub prime mover 40 (differential motor) is gradually decreased so that the actual torque Treal of the sub prime mover 40 (differential motor) is equal to or less than the differential limit torque Tlim. Go.

  In this example, the turning assist control is performed in the normal control (step S280) in which the straight running stability control is not performed. In this turning assist control, an appropriate rotational difference between the auxiliary drive wheels 50L and 50R for traveling at the turning radius R estimated based on the steering angle and the vehicle speed is obtained, and the auxiliary differential is actively applied so as to obtain this rotational difference. The motor 40 is rotationally controlled. In this turning assist control, the sub prime mover 40 is controlled to rotate while the clutch mechanism 33 is released and the brake mechanism 251 is engaged.

  When the four-wheel automobile 100 starts, the front and rear wheel drive device 10 releases the brake mechanism 251 to freely rotate the ring gear 22a and engages the clutch mechanism 33 to equally distribute from the auxiliary prime mover 40. Drive torque is transmitted toward the differential 30. As a result, the rotational torque of the auxiliary prime mover 40 is transmitted to the auxiliary drive wheels 50L and 50R, thereby realizing a four-wheel drive traveling state.

  As described above, the motor control unit 6 of the differential device 1 obtains the differential limit torque by referring to the torque map based on the vehicle speed and the steering angle, and uses the differential limit torque as the upper limit torque value. 40 is controlled. As a result, control is performed such that the rotation difference between the auxiliary drive wheels 50L and 50 becomes zero, which is a straight rotation difference. Here, in each torque map defined for each vehicle speed, the differential limiting torque monotonously increases as the steering angle decreases (the turning radius increases).

  That is, the sub prime mover 40 of the differential device 1 is for maintaining the straight traveling state with the differential limiting torque as the upper limit torque value in a completely straight traveling state or a traveling state having a large turning radius close to the complete straight traveling state. Generate assist force. Here, the differential limiting torque is set so as to increase monotonously as the turning radius of the four-wheeled vehicle increases (the steering angle decreases) and the vehicle approaches a completely straight running state.

  The differential device 1 controls the auxiliary prime mover 40 using the differential limiting torque obtained by referring to the torque map as an upper limit torque value, and the rotational difference between the auxiliary driving wheels 50L and 50R is the linear rotational difference. Control to match zero. That is, according to the differential device 1, the torque generated by the auxiliary prime mover 40 is increased to maintain the straight traveling as the turning radius becomes larger and the straight traveling state is approached. That is, as the turning radius increases and the vehicle approaches a completely straight traveling state, the assist force for maintaining the straight traveling state increases.

  Therefore, the driver who drives the four-wheeled vehicle 100 equipped with the differential device 1 of the present example has a straight running stability as if the steering became slow (the reaction was dull) as it approached the complete straight running state. A high feeling of steering operation can be obtained. Therefore, according to the differential device 1 of the present example, the straight traveling performance of the four-wheeled vehicle 100 can be improved, and the traveling safety can be enhanced.

  The torque map includes a data map in which differential limit torque data is arranged according to the steering angle, and a calculation formula, a logical formula, and the like for calculating the differential limit torque based on the vehicle speed and the steering angle. Also good. In other words, the torque map in the present invention means all those configured so that the differential limiting torque can be determined based on the vehicle speed and the steering angle.

As shown in FIG. 13, instead of omitting the speed reducer 42, the clutch mechanism 33, and the auxiliary prime mover 40 from the front and rear wheel drive device 10 (FIG. 1) of this example, a differential motor 45 is added to the differential device 1. Can also be configured. According to the differential device 1, the differential between the output shafts 32L and 32R can be suppressed using the differential motor 45.
Furthermore, the differential device 1 shown in FIG. 14 can be configured by omitting the equally distributed differential from the front and rear wheel drive device 10 shown in FIG. The output elements of the differential 1 are shafts 571L and 571R connected to the driven wheels 57L and 57R. The sun gears 23a and 23b, which are third elements, are directly connected to the shafts 571L and 571R, respectively. According to the differential device 1, the differential between the driven wheels 57 </ b> L and 57 </ b> R can be controlled using the differential motor 45.

  Furthermore, as shown in FIG. 15, a differential motor 45 dedicated to the planetary gear mechanism set 2 can be provided separately from the auxiliary prime mover 40 for the front and rear wheel drive device 10 of this example. In this case, the rotational difference between the sub drive wheels 50L and 50R can be controlled by using the differential motor 45 while the sub motors 40 rotate and drive the sub drive wheels 50L and 50R in the same direction. .

  Further, as shown in FIG. 16, the front and rear wheel drive device in which the clutch mechanism and the sub prime mover are omitted, and the propeller shaft 310 driven by the vehicle engine 8 and the input shaft 31 of the equally distributed differential 30 are connected via a hypoid gear or the like. 10 can also be configured. According to the front and rear wheel drive device 10, the driving torque of the vehicle engine 8 is transmitted to the auxiliary driving wheels 50 </ b> L and 50 </ b> R while controlling the rotational difference between the auxiliary driving wheels 50 </ b> L and 50 </ b> R using the rotation of the differential motor 45. can do.

(Example 2)
This example is an example in which the first program for switching between the straight traveling assist control and the normal control is changed based on the differential device of the first embodiment. This will be described with reference to FIG.
In the first program of this example, as shown in FIG. 17, first, in step S131, it is determined whether or not the vehicle speed is 30 km / h and the steering angle is less than 30 degrees. When the condition is met, the process proceeds to step S141, where the differential limiting torque Tlim is obtained by referring to the torque map based on the steering angle. Note that the torque map of this example is configured to correspond to the entire vehicle speed region. Then, it transfers to step S160 and implements straight running stability control. On the other hand, when the above conditions are not met, the process proceeds to step S150 and normal control similar to that in the first embodiment is performed.
Other configurations and operational effects are the same as those in the first embodiment.

(Example 3)
This example is an example in which the straight running stability control in which the secondary prime mover is operated in the regeneration mode based on the second embodiment. This will be described with reference to FIG.
In this example, the sub prime mover (reference numeral 40 in FIG. 1) is controlled using the control flowchart shown in FIG. As shown in the figure, in step S131, when the vehicle speed is 30 km / h or more and the steering angle is less than 30 degrees, it is determined that the vehicle is traveling straight. When the vehicle is in the straight traveling state, the process proceeds to step S161 to perform the straight traveling stability control. In other cases, the process proceeds to step S150 and the normal control is performed.

Unlike the straight running stability control according to the second program of the second embodiment, the straight running stability control of this example does not actively control the sub prime mover. The straight running stability control of the present example suppresses the differential between the auxiliary drive wheels 50L and R by operating the auxiliary prime mover in the regeneration mode. Further, by suppressing the differential between the auxiliary driving wheels 50L and 50R, the straight running stability of the four-wheeled vehicle is improved.
Other configurations and operational effects are the same as those in the second embodiment.

Example 4
This example is an example in which a learning function of a straight rotation difference is added based on the differential device of the first embodiment. This will be described with reference to FIG.
In addition to the configuration of the first embodiment, the motor control unit 6 of this example is configured to capture an output signal of a yaw rate sensor 403 that measures the rotation angular velocity of a four-wheeled vehicle via the I / O circuit unit 602. is there. Then, the motor control unit 6 determines that the four-wheeled vehicle is in the straight traveling state when the output signal of the yaw rate sensor 403 is sufficiently small and the vehicle speed is equal to or higher than the threshold value. Then, in this straight traveling state, a rotational difference between the auxiliary drive wheels 50L and R (see FIG. 1) calculated from the measured rotational speed of the motor rotation sensor 401 is obtained, and the rotational rotation is performed using the rotational difference as a sample rotational difference. Learn the difference. In determining the sample rotation difference, the sample rotation difference is measured in a state where no motor current is supplied to the differential motor 45 in order to eliminate the influence of the output torque of the differential motor 45 on the rotation difference. good.

Specifically, in this example, the straight rotation difference is stored in the RAM 603 serving as a storage unit, and the straight rotation difference is updated based on the sample rotation difference calculated as described above. For example, the straight rotation difference can be learned by an equation for obtaining a moving average of (new straight rotation difference = current straight rotation difference × 0.9 + sample rotation difference × 0.1).
Other configurations and operational effects are the same as those in the first embodiment.

  In addition, it can replace with the said yaw rate sensor 403, and can determine the straight-ahead state of a four-wheeled vehicle using a lateral G sensor. Furthermore, instead of the yaw rate sensor 402, it is possible to determine the straight traveling state of the four-wheeled vehicle using a GPS positioning sensor. In general, a GPS positioning sensor can measure the relative positional relationship between different positioning points with relatively high accuracy. Therefore, if this GPS positioning sensor is used, the straight traveling state can be accurately determined based on the positional relationship of three or more positioning points. Furthermore, instead of the yaw rate sensor 402, a navigation system can be electrically connected. If the road curvature data is taken from the navigation that has the positioning function of the own vehicle position and can refer to the road data at the own vehicle position, it is possible to easily determine whether or not the vehicle is traveling on a straight road. And, on a straight road, the straight-ahead rotation difference can be learned on the assumption that the four-wheeled vehicle is in a straight traveling state.

(Example 5)
In this example, the configuration of the planetary gear mechanism set 2 is changed based on the front and rear wheel drive device of the first embodiment. This content will be described with reference to FIGS.
In the planetary gear mechanism set 2 of Embodiment 1 (see FIG. 1), the carrier 21 is a first element, the ring gear 22 is a second element, and the sun gear 23 is a third element (configuration shown in FIG. 20). .) This configuration is characterized in that the structure is relatively simple and can be realized at low cost and in a compact manner. In particular, in this configuration, since the output is increased with respect to the input, this is particularly effective when the difference in the rotational speed between the left and right wheels is large, such as a vehicle having a small tire diameter.

  Instead of the configuration of the first embodiment, FIG. 21 shows a configuration in which the ring gear 22 is a first element, the carrier 21 is a second element, and the sun gear 23 is a third element. This configuration is advantageous in that it has a simple structure and can be realized at low cost and in a compact manner. In particular, in this configuration, it is possible to secure the largest speed increasing ratio, which is a rotation ratio of output to input.

FIG. 22 shows a configuration in which the sun gear 23 is a first element, the ring gear 22 is a second element, and the carrier 21 is a third element. This configuration can simplify the structure and can be realized at low cost. And this structure has the feature of a large torque type balance type that the output torque can be increased because the output is decelerated with respect to the input, and the load on the gear can be reduced, so that the planetary gear mechanism can be miniaturized. .

  FIG. 23 shows a configuration in which the ring gear 22 is a first element, the sun gear 23 is a second element, and the carrier 21 is a third element. In this configuration, the reduction ratio, which is the rotation ratio of output to input, can be increased, which is effective when a large torque is required for output.

FIG. 24 shows a configuration in which the sun gear 23 is a first element, the carrier 21 is a second element, and the ring gear 22 is a third element. This configuration has the advantage that the load on the gear can be reduced and the size can be reduced as compared with other combinations in which the sun gear 23 is the third element, although the structure is slightly complicated.
Other configurations and operational effects are the same as those in the first embodiment. In addition to the above, although the structure is complicated, the carrier can be the first element, the sun gear can be the second element, and the ring gear can be the third element.

(Example 6)
This example is another application example of the differential device shown in FIG. 16 in the first embodiment. This will be described with reference to FIG.
The differential device 1 of this example is for giving a rotational difference to main drive wheels 60L and 60R of a two-wheel drive four-wheeled vehicle. In the differential device 1, the propeller shaft 310 driven by the vehicle engine 8 and the input shaft 31 of the equally distributed differential 30 are connected via a hypoid gear or the like. According to the differential device 1, the differential difference between the main drive wheels 60 </ b> L and 60 </ b> R can be controlled using the differential motor 45.
In addition, about another structure and an effect, it is the same as that of the differential apparatus shown in FIG.
In addition to the above, the differential device 1 of this example can be used as a main drive wheel of a four-wheel drive four-wheeled vehicle or a differential device of a sub drive wheel. Furthermore, it can also be used as a differential device that provides a rotational difference between the front and rear wheels of a four-wheel drive four-wheeled vehicle.

(Example 7)
In this example, the configuration of the differential device 1 is changed based on the front and rear wheel drive device of the first embodiment. This will be described with reference to FIG.
In the differential device 1 of this example, as shown in the figure, the rotation of the ring gear 22a of one planetary gear mechanism 20a is restricted. A differential clutch mechanism 252 for interrupting torque transmission is disposed between the ring gear 22b of the other planetary gear mechanism 20b and the speed reducer 42 that decelerates the rotation of the auxiliary prime mover 40. In the differential device 1 of this example, the rotation of the ring gear 22a is restricted by indirectly engaging the housing 25 and the ring gear 22a.

Next, a control method of the front and rear wheel drive device 10 of this example will be described.
The difference from the front and rear wheel drive device of the first embodiment is that the clutch mechanism 33 is opened and the differential clutch mechanism 252 is engaged when the rotational difference between the auxiliary drive wheels 50L and 50R is controlled. . In this state, if the rotation of the ring gear 22b is controlled by the auxiliary prime mover 40, the differential between the sun gears 23a and 23b as the third element can be controlled. In this example, the drive shaft 51L of the left auxiliary drive wheel 50L is directly connected to one sun gear 23a as described above. The other sun gear 23b is directly connected to the input shaft 31 of the equally distributed differential 30, and is connected to the drive shaft 51R of the right auxiliary drive wheel 50R via the equally distributed differential 30. Therefore, if the front and rear wheel drive device 1 is controlled as described above, the rotational difference between the auxiliary drive wheels 50L and 50R can be controlled.

When the four-wheel automobile 100 is started, the differential clutch mechanism 252 is opened and the clutch mechanism 33 is engaged to transmit the drive torque from the sub prime mover 40 toward the equally distributed differential 30. Thereby, the four-wheel drive state of the four-wheel automobile 100 is realized.
Other configurations and operational effects are the same as those in the first embodiment.

(Example 8)
This example is an example in which the configuration of the differential device is changed based on the other front and rear wheel drive devices (see FIG. 16) of the first embodiment. This will be described with reference to FIG.
In the differential device 1 of this example, as shown in the figure, the rotation of the ring gear 22a of one planetary gear mechanism 20a is restricted. A differential clutch mechanism 252 is disposed between the ring gear 22b of the other planetary gear mechanism 20b and the speed reducer 42 that decelerates the rotation of the differential motor 45.
Other configurations and operational effects are the same as those in the first embodiment.

FIG. 2 is a block diagram showing a configuration of a front and rear wheel drive device in the first embodiment. FIG. 3 is a system diagram showing a control system of the front and rear wheel drive device in the first embodiment. Explanatory drawing (A) explaining the flow of the transmission torque in the front-and-rear wheel drive device at the time of turning travel in Example 1. FIG. Explanatory drawing (B) explaining the flow of the transmission torque in the front-and-rear wheel drive device at the time of turning travel in Example 1. FIG. The block diagram which shows the structure of the other front-and-rear wheel drive device in Example 1. FIG. The block diagram which shows the structure of the other front-and-rear wheel drive device in Example 1. FIG. FIG. 3 is a block diagram illustrating a configuration of a motor control unit according to the first embodiment. FIG. 3 is a graph showing a characteristic map showing the characteristics of the auxiliary prime mover in Embodiment 1. FIG. FIG. 3 is a torque map showing the relationship between the steering angle and the absolute value of the differential limiting torque in the first embodiment. FIG. 3 is a flowchart for explaining a first program according to the first embodiment. Explanatory drawing explaining operation | movement of the front-and-rear wheel drive device in the straight running stability control in the first embodiment. FIG. 6 is a flowchart for explaining a second program for performing straight running stability control in the first embodiment. FIG. 3 is a block diagram illustrating a configuration of another differential device according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration of another differential device according to the first embodiment. The block diagram which shows the structure of the other front-and-rear wheel drive device in Example 1. FIG. The block diagram which shows the structure of the other front-and-rear wheel drive device in Example 1. FIG. FIG. 9 is a flowchart for explaining a first program in the second embodiment. FIG. 10 is a flowchart for explaining a first program in the third embodiment. FIG. 9 is a block diagram showing a configuration of a motor control unit in Embodiment 4. FIG. 3 is a configuration diagram illustrating a configuration of a planetary gear mechanism set according to the first embodiment. The block diagram which shows the 1st structure of the planetary gear mechanism group in Example 5. FIG. The block diagram which shows the 2nd structure of the planetary gear mechanism group in Example 5. FIG. FIG. 10 is a configuration diagram showing a third configuration of the planetary gear mechanism set according to the fifth embodiment. FIG. 10 is a configuration diagram showing a fourth configuration of the planetary gear mechanism set according to the fifth embodiment. FIG. 10 is a block diagram illustrating a configuration of a differential device according to a sixth embodiment. FIG. 10 is a block diagram showing a configuration of a front and rear wheel drive device in a seventh embodiment. FIG. 10 is a block diagram showing a configuration of a front and rear wheel drive device in an eighth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Differential device 10 Front-and-rear wheel drive device 2 Planetary gear mechanism group 20a, 20b Planetary gear mechanism 21 Carrier 22 Ring gear 23 Sun gear 24 Planetary gear 25 Housing 251 Brake mechanism 30 Equal distribution differential 31 Input shaft 32L, 32R Output shaft 33 Clutch mechanism 40 secondary prime mover 42 reduction gear 45 differential motor 50L, 50R secondary drive wheel 51L, 51R drive shaft 6 motor control unit

Claims (5)

A differential device disposed between a front wheel or a rear wheel of a four-wheeled vehicle,
The differential device includes two output elements independently connected to the left and right wheels, a differential motor for controlling a differential between the two output elements, and a turning radius of the four-wheel vehicle. A measurement sensor for measuring an index value having a correlation with the magnitude, a motor control unit for controlling the differential motor, a straight-ahead determination sensor for obtaining a measurement value for determining a straight-ahead state of the four-wheeled vehicle, The motor control unit determines that the four-wheeled vehicle is in a straight traveling state based on a rotation difference sensor for directly or indirectly measuring the rotation difference between the left and right wheels and the measured value of the straight traveling determination sensor. Storage means for storing the rotation difference between the left and right wheels measured by the rotation difference sensor as a straight rotation difference ,
When the motor control unit determines that the turning radius is large and the four-wheeled vehicle is in a traveling state close to a straight traveling state by performing threshold processing on the index value measured by the measuring sensor, The difference is characterized in that a straight running stability control is executed to control the differential motor so that the rotation difference between the left and right wheels measured by the rotation difference sensor coincides with the straight rotation difference stored in the storage means. Moving device.   The storage means is arranged so that the upper limit value of the torque generated by the differential motor is arranged with respect to the index value, and the upper limit value increases monotonously as the turning radius increases. A torque map is further stored, and the motor control unit obtains a value obtained by referring to the torque map stored in the storage unit based on the index value measured by the measurement sensor. The differential device according to claim 1, wherein the straight running stability control is executed as an upper limit value.   The measurement sensor includes a vehicle speed sensor that measures the vehicle speed of the four-wheeled vehicle and a steering angle sensor that measures a steering angle that is a steering operation amount, and the torque map relates to the vehicle speed and the steering angle. The differential device according to claim 2, wherein upper limit values of the generated torque are arranged.   The differential device according to any one of claims 1 to 3, wherein the straight traveling determination sensor includes a yaw rate sensor or a lateral G sensor that measures a rotation angular velocity of the four-wheeled vehicle.   5. The differential motor according to claim 1, wherein the motor control unit performs the linear stability control by operating the differential motor in a regenerative mode. 6.

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