JPH0479867B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a suspension in which at least one of damper damping characteristics and spring characteristics (hereinafter referred to as suspension characteristics) is variable;
The steering system is equipped with a steering device that has variable transmission characteristics between the steering wheel and the steered wheels (for example, steering operation characteristics with respect to the front wheel turning angle, steering angle characteristics with respect to the front wheel turning angle (hereinafter referred to as steering system transfer characteristics)). In the vehicle,
The present invention relates to an integrated control system for suspension and steering in which, when changing the suspension characteristics, the steering system transmission characteristics are also changed at the same time as the suspension characteristics are changed. BACKGROUND ART In automobile suspensions, systems have been proposed in which the damping force of a damper is controlled depending on the situation. For example, as shown in Japanese Utility Model Application No. 55-109008, a vehicle is known in which the damping force is changed depending on the vehicle speed so as to always obtain favorable handling characteristics. Suspensions consist of a combination of dampers and springs, and it is conceivable that similar steering characteristics can be obtained by changing the spring characteristics. These systems strengthen understeer characteristics at high speeds to increase straight-line stability, and weaken understeer characteristics to increase turning performance at low speeds, thereby consistently providing favorable handling characteristics in response to changes in vehicle speed. Changing the understeer characteristics will change the handling characteristics (steering feel). In other words, when the understeer characteristic is strengthened, the steering force increases, making the steering heavier, and the response during steering tends to be slower. When the understeer characteristic is weakened, the steering force decreases, the steering becomes lighter, and the steering response becomes slower. The tendency for responsiveness to become sharper is strengthened. Further, the maneuverability can also be changed by changing the steering system transfer characteristics. For example, in power steering, by changing the steering assist force (assist force), and in manual steering, by changing the ratio of the steering wheel steering angle to the front wheel turning angle (hereinafter referred to as the steering reduction ratio), the steering It is possible to change the steering characteristics by changing the system transfer characteristics. In other words, if you reduce the assist force with power steering, or if you increase the steering reduction ratio with manual steering, the stability when driving straight increases and the steering feel becomes dull; When the ratio is increased or when the ratio is decreased by manual steering, the response during steering becomes sharp and the steering feeling becomes sharp. As an example of changing the steering system transmission characteristics, for example, as shown in Japanese Patent Application Laid-Open No. 55-55059, the steering force is changed depending on the vehicle speed, the steering is made heavier at high speeds to increase straight-line stability, and at low speeds It is known that the steering wheel is lightened to improve turning performance. As mentioned above, in the past, the suspension characteristics or steering system transmission characteristics were controlled separately to increase straight-line stability during high-speed driving, where lane changes or relatively gentle curves were mostly involved. Turning performance is increased during low-speed driving where there is a lot of sharp cornering. However, the senses and preferences of drivers vary widely, and it is extremely difficult to create a car with performance that satisfies all drivers. For example, when it comes to steering characteristics, some people prefer a sporty-feeling car that is responsive to steering operations, while others prefer a calm-feeling car that emphasizes stability. People with less power may prefer lighter steering. For this reason, if you place emphasis on the performance of one, you will inevitably end up sacrificing the other. In view of the above circumstances, the present invention sets several combination patterns of suspension characteristics and steering system transmission characteristics that determine handling characteristics depending on the driving condition, and allows the driver to select his or her preferred pattern at will or at the time of design. The objective is to provide a comprehensive control system for suspension and steering. The integrated suspension and steering control device according to the present invention includes a suspension unit that suspends a vehicle body on each of the front, rear, left and right wheels, a steering device that steers a steerable wheel among the wheels, and a damping force of the suspension unit. and a first control means for changing suspension characteristics by controlling at least one of the spring constants and changing at least one of the front wheel to rear wheel damping force ratio and the spring constant ratio; a second control means for variably controlling the steering system transmission characteristic, and the first control means and the second control means so as to change the steering system transmission characteristic at the same time as the suspension characteristic is changed when the suspension characteristic is changed; It is characterized in that it is comprised of a controller that issues control signals. According to the present invention, when the suspension characteristics are changed, the steering system transmission characteristics are also changed at the same time as the suspension characteristics are changed, so that the suspension characteristics are changed and the understeer characteristics are made stronger or weaker. By promoting or offsetting the changes in the steering characteristics caused by changes in the steering system transmission characteristics, it is possible to obtain steering characteristics that meet various demands. In other words, changes in understeer characteristics due to the suspension cause a difference in steering feel between dullness and sharpness, but this can be facilitated by the steering system transmission characteristics, making it even duller or more sensitive, or canceling each other out to eliminate the difference. I can,
This allows a variety of maneuvering characteristics to be obtained. Specifically, if the suspension characteristics can be switched to strong or weak understeer by operating a manual switch, etc., the understeer characteristics can be changed by changing the steering system transmission characteristics at the same time as this switching. Two types of steering characteristics can be obtained: either the change in the steering wheel is clearly felt as a human sense, or the change is not felt. In other words, in the case of power steering, for example, if the steering assist force is set to be smaller when the suspension characteristics are strong understeer, and conversely set to be further increased when the understeer is weak, the understeer characteristics of the suspension characteristics can be adjusted using a switch etc. When Strong is selected, the tendency for the steering force to increase due to stronger understeer is amplified by the smaller assist force, making the steering feel even duller, resulting in a steering characteristic that emphasizes straight-line stability. Conversely, when weak understeer is selected, the tendency for the steering force to decrease due to weakening of understeer is amplified by the increase in assist force, resulting in a sharper steering feel and a steering characteristic that emphasizes responsiveness. Furthermore, the assist power is increased when understeer is strong,
If the assist force is set to be small when understeer is weak, the assist force will offset the increase or decrease in steering force due to changes in understeer, which is exactly the opposite of the case described above, so the car state will improve stability or responsiveness depending on the understeer characteristics. However, the steering feeling is such that you do not feel any change in understeer characteristics. It is possible to set the vehicle to have either one of the above-mentioned two types of driving characteristics, auxiliary type and countervailing type, at the time of design, or it may be possible to switch between them using a switch or other means that the driver can freely select. can. In addition to power steering, manual
In the case of steering, two types of steering characteristics can be similarly obtained by changing the steering reduction ratio. On the other hand, there is a method of automatically controlling the suspension characteristics in accordance with the driving conditions of the vehicle (eg, vehicle speed, load, steering angle, etc.). When the control characteristics are selected using the manual switch mentioned above, there is a problem that if the characteristics are excellent in straight-line stability, the characteristics are inferior when turning, but this problem can be resolved by using an automatic control system. can. In this case as well, two types of steering characteristics can be obtained. For example, if the suspension characteristics are controlled to have strong understeer at high speeds and weak understeer at low speeds depending on the vehicle speed,
At high speeds, the assist force of the power steering is reduced, and at low speeds, this assist force is increased.
There are two completely opposite cases. When the assist force is small at high speeds and large at low speeds, the tendency of increasing steering force at high speeds and decreasing tendency of steering force at low speeds due to changes in understeer characteristics is promoted by changes in assist force, and high-speed stability and low-speed turning performance are emphasized. As a result, so-called sporty steering characteristics can be obtained.Conversely, if the assist force is increased at high speeds and decreased at low speeds, the steering force tends to increase at high speeds due to changes in understeer characteristics, and the steering force decreases at low speeds due to changes in assist force. This offsets the understeer characteristics of the car, and while the car's high-speed stability and low-speed turning performance are adjusted accordingly, the result is a gentle steering characteristic that doesn't give you much of a sense of understeer. In this case, similar characteristics can also be obtained by changing the steering reduction ratio of manual steering instead of the assist force of power steering. The characteristics described above can be summarized as shown in the following table.

[Table] Examples of the present invention will be described in detail with reference to the drawings. FIGS. 1 and 2 each show an example of the relationship between centripetal acceleration and yaw rate with respect to steering force when power steering is provided. The one-dot chain line in the figure is a reference line showing the case of manual steering (M/S), and the power steering assist force does not work when the steering force is small, but starts working when the steering force exceeds a certain value. Solid lines A and C show an example when the steering assist force is reduced, and broken lines (B and D show an example when the steering assist force is increased, and upper lines A and B show an example when the understeer characteristic is strengthened. Lines C and D show an example where the understeer characteristics are weakened.If control is performed so that the relationship shown by lines A and D is achieved according to changes in the understeer characteristics, sporty handling characteristics are obtained, corresponding to the cases shown in Table 1 above. is obtained, and if control is performed so that the relationship shown by lines B and C is obtained, Table 1
In the case shown in Figure 2, quiet handling characteristics can be obtained. FIGS. 3 and 4 respectively show the relationship between centripetal acceleration and yaw rate with respect to steering angle when manual steering is provided. Solid lines (a and c show an example when the steering reduction ratio is increased, broken lines b and d show an example when the steering reduction ratio is reduced, upper lines a and b show an example when the understeer characteristic is strengthened, and the lower line c shows an example when the steering reduction ratio is increased. and d show examples in which the understeer characteristics are weakened. In this case also, Figs.
As in the case shown in the figure, if control is performed so that the relationship shown by lines a and d is achieved according to changes in the understeer characteristics, sporty handling characteristics will be obtained in the case shown in Table 1 above, and lines b and c will be obtained. If the control is performed so that the relationship shown in the following is achieved, quiet maneuvering characteristics can be obtained in this case. 5 and 6 show an automobile equipped with an integrated control device according to an embodiment of the present invention.
The figure shows an embodiment with power steering, and the sixth
The figure shows an embodiment with manual steering. In the embodiment shown in FIG.
1 or the manual switch 32, or both, the controller 30 outputs an output that operates the solenoids 21b, 22b that change the damper damping force, or the solenoids 21a, 22a that change the spring characteristics, or both. At the same time, the controller 30 sends out an output for controlling the discharge amount of the pump 14 to change the steering system transmission characteristics. This output operates the solenoid of the flow rate control valve when the power steering pump is driven by an engine, and controls the rotation speed of the motor when it is driven by an electric motor. In the embodiment shown in FIG.
1 or the manual switch 32, or both, the controller 3 outputs an output that operates the solenoids 21b and 22b that change the damper damping force or the solenoids 21a and 22a that change the spring characteristics, or both.
By outputting from 0, the suspension characteristics are changed, and at the same time, the controller 30 sends out an output that changes the gear ratio of the steering speed reduction device 50 to change the steering system transmission characteristics. FIG. 7 shows a main system diagram of an embodiment of the present invention, which is equipped with a power steering system that obtains assist force from a hydraulic pump driven by an engine. The power steering device of this embodiment is equipped with a rack and pinion type steering as manual steering, and a steering shaft 2 rotated by a steering wheel 1 is connected to a pinion 5 via joints 3 and 4. This pinion 5 is meshed with a rack 6, and at both ends of this rack 6 are knuckle arms 8a, which are rotatably supported around shafts 7a and 7b.
Tie rods 9a and 9b engaged with 8b are connected. Steering wheel 1 is operated,
When the rotation of the steering shaft 2 is transmitted to the rack 6 via the pinion 5, the rack 6 moves in the left-right direction in the figure, rotates the knuckle arms 8a and 8b via tie rods 9a and 9b, and rotates the steering wheels (generally Give the steering angle to the front wheels) 10a and 10b. A piston 11c of a power cylinder 11 is fixed to the rack 6, and a piping 1 communicating with oil chambers 11a and 11b defined by the piston 11c.
2a and 12b are connected to an oil pump 14a via a control valve 13. The control valve 13 has been commonly used in this type of power steering device, and controls the discharge pipe 15 and return pipe 16 of the oil pump 14a to the pipes 12a and 1, respectively, depending on the steering direction.
Switch the hydraulic system to connect to 2b, or 12b and 12a. For example, when the rack 6 is steered to move to the right in the figure, the discharge pipe 1
5 is connected to the pipe 12b, and the return pipe 16 is connected to the pipe 12a. As a result, the hydraulic pressure within the power cylinder 11 assists the movement of the rack 6 to the right.
Further, when the steering shaft 2 is not rotating, the control valve 13 allows the discharge pipe 15 and the return pipe 16 to communicate directly, and does not send pressure oil to the power cylinder 11. The oil pump 14a is directly driven by the engine 18 via a belt 17, and a flow rate control valve 19 is interposed in the discharge pipe 15 of the pump 14a. The flow rate control valve 19 includes a valve body 19b that is formed to be slidable in the vertical direction in the figure within the casing 19a, a spring 19c that biases the valve body 19b downward in the figure, and a flow rate control solenoid 19.
d, and the casing 19a is the discharge pipe 15.
the first and second ports 19e and 19f connected to the , and the third port 19g connected to the return pipe 16
It is equipped with When the flow control solenoid 19d is demagnetized, the valve body 19b is pushed by the spring 19c and the third
Port 19g is closed. At this time, the annular groove 19h carved around the valve body 19b aligns with the first and second ports 19e and 19f, and these first and second ports 19e and 19f communicate with each other (as shown in FIG. condition). On the other hand, the controller 30
Flow control solenoid 19d with an output of 30g
When energized, the valve body 19b is pulled upward in the figure against the biasing force of the spring 19c. Therefore, the third port 19g, which had been closed by the valve body 19b, partially communicates with the first port 19e, and a part of the flow rate from the first port 19e flows through the third port 19e.
To return to the return pipe 16 through port 19g,
The flow rate exiting from the second port 19f decreases. That is, when the flow rate control solenoid 19d is demagnetized, the entire discharge amount of the pump 14a is controlled by the control valve 13.
When the flow control solenoid 19d is energized, part of the discharge amount of the pump 14a is bypassed by the flow control valve 19, so the flow to the control valve 13 decreases and the steering assist force becomes small. . Actually, by changing the ON-OFF duty ratio of this solenoid, control as shown in FIGS. 9, 10, and 11, which will be described later, is performed. In addition to inputs from the power supply, the controller receives inputs 30a from a manual switch 32 when the suspension characteristics and steering system transmission characteristics can be simultaneously switched manually, and an input 30f from the vehicle speed sensor 31 in this embodiment. This input is not limited to vehicle speed, but may also include load, steering angle, etc.), and signals 30b, 30c, and 30 that change the suspension characteristics based on these inputs are input.
d and 30e, and a signal 30g that changes the steering system transmission characteristics. Specifically, the steering system transmission characteristics are as described above, and regarding the suspension characteristics, for example, to change the spring characteristics of the air springs 21 and 22, the solenoids 21a and 22a are excited by the outputs 30b and 30c from the controller 30. Or, to change the damping characteristics of the damper by demagnetizing and turning ON/OFF the communication with the actuators 21A, 21A, outputs 30d, 30 from the controller 30 can be used.
This is done by exciting or demagnetizing the solenoids 21b and 22b with e, and changing the orifice size that determines the damper characteristics. As described above, it is possible to control the steering system transmission characteristics to be changed at the same time as the suspension characteristics are changed by the controller, either by manual switch selection or automatically depending on the vehicle speed (or driving conditions such as load and steering angle). FIG. 8 shows a main system diagram of an embodiment of the present invention, which is equipped with a power steering system that obtains assisting force from a hydraulic pump driven by an electric motor. This embodiment is different from the embodiment shown in FIG. 7 in that the hydraulic pump is not driven by an engine but by a motor.
They are completely the same except that there is no flow control valve, and the same parts are given the same numbers and the explanation will be omitted. In this embodiment, the motor 20 is driven and controlled by the output 30 g from the controller 30, and the steering system transmission characteristics are changed by controlling the discharge amount of the pump 14b. Similar to the example shown in FIG. 7, this controller can also change the suspension characteristics, so it is possible to control the suspension characteristics and the steering system transmission characteristics in a mutually related manner. FIGS. 9, 10, and 11 are graphs illustrating the relationship between the hydraulic pump discharge amount and the steering system transmission characteristic in the embodiments described in FIGS. 7 and 8. The graph in FIG. 9 shows the relationship between the vehicle speed V and the pump discharge amount Q. Generally, at low speeds, that is, when a large steering force is required, the flow rate is large, and as the speed increases, the flow rate decreases, and becomes constant above a certain speed. The difference between the large assist force and the small assist force is determined by changing the deenergization/excitation duty ratio of the solenoid of the flow control valve in the embodiment shown in FIG. 7, and by changing the rotational speed of the motor in the embodiment shown in FIG. For example, vehicle speed V ₁
At , the flow rate changes from Q _L to Q _H. Figure 10 shows the steering torque when the vehicle speed is V ₁ , that is, the flow rate to the power steering is Q _L and Q _H.
This is a graph showing the relationship between T _H and oil pressure P. The oil pressure P does not change much when the steering torque T _H is small.
When the steering torque exceeds a certain value, the oil pressure P increases synergistically. However, to obtain the same oil pressure, the flow rate is
Q _H (less) requires greater torque T _H. Figure 11 is a graph showing the relationship between the centripetal acceleration and the steering torque T _H when the vehicle speed is V ₁ , that is, the flow rate to the power steering is Q _L and Q _H. As the steering torque T _H increases, the centripetal acceleration increases. increase synergistically. To obtain the same centripetal acceleration, the flow rate is Q _H
In other words, the smaller the flow rate to the power steering, the smaller the assist force and the heavier the steering feel. The embodiment shown in FIG. 12 shows a main system diagram of the present invention when manual steering is provided. In this embodiment as well, parts common to the embodiments of FIGS. 7 and 8 are given the same numbers.
The explanation will be omitted. The upper steering shaft 2a rotated by the steering wheel 1 is connected to the pinion 5 via a steering reducer 50, the lower steering shaft 2b, and joints 3 and 4, and the rotation of the steering wheel 1 is decelerated by the steering reducer 50. After that, rotate the pinion 5. This pinion 5 is meshed with a rack 6, and knuckle arms 8a and 8 are supported at both ends of this rack 6 so as to be rotatable about shafts 7a and 7b.
Tie rods 9a and 9b engaged with b are connected. The rotation of the pinion 5 moves the rack 6 in the left-right direction in the figure, rotates the knuckle arms 8a, 8b via tie rods 9a, 9b, and gives steering angles to the steered wheels (generally front wheels) 10a, 10b. The steering reducer 50 is the controller 3
Upper steering shaft 2 due to output from 0
a is slowed down or directly connected to the lower steering shaft 2b to transmit rotation to change the steering characteristics, and details are shown in the enlarged view in the figure. A gear 51a (number of teeth: Z ₁ ) and an external spline 51 are provided at the lower end of the upper steering shaft 2a.
b, and the gear 51a is a gear 52a on the first gear body 52 that freely rotates on the fixed shaft 59.
(Number of teeth: Z ₂ ), and another gear 52b (Number of teeth: Z ₃ ) on the gear body 52 rotates on the lower steering shaft 2b and engages with the outer spline 53.
gear 5 of second gear body 53 having gear 53a and gear 53a;
It meshes with 3a (number of teeth: Z ₄ ). Therefore, from the gear 51a at the end of the upper steering shaft 2a to the second
When the rotation is transmitted to the gear 53a of the gear body 53, the speed is reduced to a reduction ratio: (Z ₁ /Z ₂ )×(Z ₃ /Z ₄ ). The upper end of the lower steering shaft 2b also has an external spline whose axis is aligned with the upper steering shaft 2a, and the external spline 51b on the upper steering shaft and the external spline on the lower steering shaft. 54
b and the spline 53b of the second gear body are adjacent in this order and have the same specifications and are on the same axis, so the sleeve 55 having an internal spline that meshes with this spline will not mesh with any of the three splines. Moreover, it can slide on the spline in the vertical direction in the figure. On the other hand, a reducer case 60 is inserted into a groove 55a provided on the outer circumference of this sleeve.
A protrusion (fork) 56a of a shaft 56 which can be slid up and down in the drawing is fitted inside, and the sleeve 55 also moves up and down in alignment with the up and down of the shaft 56. Further, the shaft 56 is urged downward in the figure by a spring 57, and the solenoid 58 is excited by the output 30g from the controller 30, which overcomes the urging force of the spring 57 and pushes the shaft 56 upward. When the solenoid 58 is demagnetized, it is lowered. Thus, the energization and demagnetization of the solenoid 58 causes the sleeve 55 to move up and down, causing the sleeve 55 to move upward, i.e., when the solenoid 58 is energized in this figure, the sleeve 55 moves up and down.
The internal spline of the upper steering shaft 2
The external spline 51b of a and the external spline 53b of the lower steering shaft 2b are simultaneously engaged to directly connect the upper and lower steering shafts. When the solenoid 58 is demagnetized, the spring 5
With a force of 7, the shaft 56 and sleeve 55 go down, and the internal spline of the sleeve 55
Both the external spline 53b of the gear body 53 and the external spline 54b of the lower steering shaft 2b mesh at the same time, and the rotation of the steering wheel is controlled by the gear train shown in the diagram at a reduction ratio: (Z ₁ /Z ₂ )×(Z ₃ /
Z ₄ ) is decelerated and the pinion 5 is rotated. As described above, the solenoid 58 is deenergized and energized by the output 30 g from the controller 30, and the steering reduction ratio can be changed to change the steering system transmission characteristic. On the other hand, the suspension characteristics can be controlled by the controller 30 according to the driving condition, as in the embodiments shown in FIGS. It can be controlled by As explained in detail above, according to the present invention, the steering system transmission characteristics are changed at the same time as the suspension characteristics are changed, so that, for example, a sporty steering feeling or a calm steering feeling can be achieved.
It becomes possible to select a vehicle with various handling characteristics at the time of design, and the driver can freely select a vehicle, which has many advantages for both the designer and the driver.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the relationship between centripetal acceleration (FIG. 1) and yaw rate (FIG. 2) with respect to steering force in the embodiment of the present invention when power steering is provided, and FIGS. The figure is a graph showing the relationship between the centripetal acceleration (Figure 3) and the yaw rate (Figure 4) with respect to the steering angle in the embodiment of the present invention when the vehicle has manual steering. Figure 5 is a perspective view showing an example of a car equipped with a comprehensive control device. Figure 5 is a car with power steering, Figure 6 is a car with manual steering, and Figure 7 is a car with power steering using an engine-driven hydraulic pump. 8 is a main system diagram of an embodiment of the invention, FIG. 8 is a main system diagram of an embodiment of the invention equipped with power steering by an electric motor-driven hydraulic pump, FIGS.
Figure 1 is a graph showing the relationship between hydraulic pump discharge amount and steering system transmission characteristics in an embodiment of the present invention having power steering, Figure 9 is a graph showing the relationship between vehicle speed and pump discharge amount, and Figure 10 is a graph showing the relationship between hydraulic pressure and steering system transmission characteristics. FIG. 11 is a graph showing the relationship between steering torque and centripetal acceleration, and FIG. 12 is a main system diagram of an embodiment of the present invention equipped with manual steering. 1...Steering wheel, 2, 2a, 2b
... Steering shaft, 3, 4 ... Joint, 5 ... Pinion, 6 ... Rack, 11 ... Power cylinder, 13 ... Control valve, 1
4a, 14b...Hydraulic pump, 18...Engine, 19...Flow control valve, 20...Motor, 21
a, 21b, 22a, 22b...Solenoid, 2
1A, 22A...Accumulator, 30...Controller, 31...Vehicle speed sensor, 32...Manual switch, 50...Steering speed reducer, 5
1a, 52a, 52b, 53a...gear, 51
b, 53b, 54b...external spline, 55...
...Sleeve, 56...Shaft, 57...Spring, 58...Solenoid.

Claims (1)

[Claims] 1. A suspension unit that suspends the vehicle body on each of the front, rear, left and right wheels, a steering device that steers a steerable wheel among the wheels, and at least one of the damping force and spring constant of the suspension unit. a first control means for changing the suspension characteristics by changing at least one of the damping force ratio and the spring constant ratio of the front wheels to the rear wheels; a second control means, and a controller for issuing a control signal to the first control means and the second control means so that when the suspension characteristics are changed, the transmission characteristics are also changed at the same time as the suspension characteristics are changed; Comprehensive steering control device.