JP3555323B2 - Electronically controlled suspension - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled suspension system that effectively controls a roll of a vehicle body by adjusting a damping force of a hydraulic shock absorber and a spring constant of an air spring in response to a change in a running state of a vehicle.
[0002]
[Prior art]
In the conventional electronically controlled suspension system, when the condition for stopping the roll control is satisfied, the solenoid on-off valve for adjusting the spring constant of the air spring and the control valve for adjusting the damping force of the hydraulic shock absorber are switched to software immediately. . However, in the above-described control, when the steering direction continuously changes as in slalom running, the electromagnetic on-off valve that switches the spring constant of the air spring changes from the closed position during roll control to the closed position via the open position. Therefore, the number of times of operation of the solenoid on-off valve increases, and the durability decreases. Further, since the operation sound of the electromagnetic on-off valve is continuous, there is a possibility that passengers and the like may feel uncomfortable. On the other hand, if the damping force of the hydraulic shock absorber is kept high, a rugged feeling appears and the ride comfort deteriorates. Therefore, it is desirable to reduce the damping force of the hydraulic shock absorber as low as possible when it is not necessary to increase the damping force. .
[0003]
In the electronically controlled suspension disclosed in Japanese Patent Publication No. 2-34803, the damping force of only the hydraulic shock absorber is adjusted according to the running conditions of the vehicle. The comfort and stability of the body posture are not enough.
[0004]
[Problems to be solved by the invention]
In view of the above problems, an object of the present invention is to provide an electronically controlled suspension that variably controls a damping force of a hydraulic shock absorber and a spring constant of an air spring. It is an object of the present invention to provide an electronically controlled suspension that returns the air spring to normal softness with a delay.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the configuration of the present invention is an electronically controlled suspension that variably controls the damping force of a hydraulic shock absorber and the spring constant of an air spring. The damping force is made soft immediately, the spring constant of the air spring is made soft after a lapse of a predetermined time, and then the roll control is released.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
An electronically controlled suspension system according to the present invention includes an electromagnetic on-off valve for adjusting the spring constant of the air spring by adjusting the volume of the air spring, a control valve for adjusting the damping force of the hydraulic shock absorber in multiple stages, and a vehicle speed. Detecting means for detecting the lateral acceleration and the steering speed, and an electronic control device that determines the running state based on a signal from the detecting means, controls the electromagnetic on-off valve and the control valve, and suppresses the roll of the running vehicle body. Have.
[0007]
Normally, the roll control of the vehicle body is not performed, and when the vehicle speed, the lateral acceleration, and the steering speed satisfy predetermined conditions (roll control conditions), the roll control of the running vehicle body is started, and the vehicle speed, the lateral acceleration, and the steering are controlled. When the speed does not satisfy the predetermined condition, the roll control of the vehicle body is stopped.
[0008]
The vehicle speed V is higher than V0, the steering speed W is higher than the predetermined value WO, the relationship between the direction of the lateral acceleration G and the steering direction is normal (if the steering wheel is turned right, the lateral acceleration is leftward), and When the absolute value of the acceleration G is larger than the predetermined value G0, roll control 1 or roll control 2 is performed. That is, when the above condition is satisfied, the roll control 1 is performed when the lateral acceleration change rate ΔG is smaller than the predetermined value g, and the lateral acceleration change rate ΔG is larger than the predetermined value g, When the absolute value is larger than a predetermined value G1 (where G0 <G1), the roll control 2 is performed.
[0009]
In the roll control 1, for example, when the steering wheel is turned to the right, the spring constants of the air springs of the right and left front wheels are set to be soft, the spring constants of the air springs of the left and right front wheels are set to be hard, and the damping force of the hydraulic shock absorber of all the wheels is set to medium. I do. In the roll control 2, the spring constants of the air springs of all the wheels are made hard, and the damping forces of the hydraulic shock absorbers of all the wheels are made hard.
[0010]
Roll control is stopped when the relationship between the direction of the lateral acceleration and the steering direction is abnormal (the lateral acceleration is rightward if the steering wheel is turned right) or the absolute value of the lateral acceleration G becomes smaller than a predetermined value G0. I do. When the condition for stopping the roll control is satisfied, the damping forces of the hydraulic shock absorbers of all the wheels are immediately switched to software, while the spring constants of the air springs of all the wheels are a predetermined time (tailing time, about 1.5 to 2 seconds). Switch to software with a delay. It is preferable to add a time when sensors for detecting the vehicle speed, the lateral acceleration, and the steering speed respectively fail to the condition for stopping the roll control.
[0011]
【Example】
As shown in FIGS. 1 and 2, in the air-spring suspension system for the front wheel 2, a suspension arm 3 a is supported on a vehicle frame 8 by an air spring 3, and the air spring 3 is connected to a sub air tank 4 via an electromagnetic on-off valve 5. . The air spring 3 is configured such that pressurized air is supplied from a main air tank (not shown) via a known leveling valve and a solenoid-operated switching valve, or air from the air spring 3 is discharged to the outside via the leveling valve. I'm familiar. In the air spring type suspension device for the rear wheel 12, the end of the beam 13 a in the front-rear direction supporting the rear wheel 12 is supported by the vehicle frame 8 by a pair of front and rear air springs 13. The pair of air springs 13 is connected to a sub air tank 14 via an electromagnetic on-off valve 15. The air spring 13 is configured such that pressurized air is supplied from a main air tank (not shown) via a leveling valve, or air from the air spring 13 is discharged to the outside via the leveling valve. A hydraulic shock absorber 10 is connected between the suspension arm 3a supporting the front wheel 2 and the vehicle frame 8, and a hydraulic shock absorber 10 is similarly connected between each end of the beam 13a supporting the rear wheel 12 and the vehicle frame 8. . Each hydraulic shock absorber 10 is integrally provided with a rotary damping force control valve 50 that adjusts the damping force in three stages of soft, medium, and hard.
[0012]
As shown in FIG. 3, the present invention provides an electromagnetic on-off valve based on signals from a vehicle speed sensor 22, a steering speed sensor 23, a lateral acceleration sensor 24, and a rate of change in lateral acceleration obtained from the lateral acceleration sensor 24. 5 and 15 are driven to increase or decrease the spring constant of the air spring, and the control valve 51 is driven by the output of the electronic control unit 21 to increase or decrease the damping force of the hydraulic shock absorber 10.
[0013]
As shown in FIGS. 4 and 5, in the hydraulic shock absorber 10 for suspending each wheel, a piston 44 is inserted into a cylinder 41 to define a chamber 43 and a chamber 45. In addition, a cylinder 41 is connected to each of the suspension members. The hydraulic shock absorber 10 is provided with a control valve 51 inside the piston 44. That is, a valve chamber 46 is provided inside the piston 44, and an inverted cup-shaped valve body 47 is inserted into the valve chamber 46. The valve body 47 is connected with a rod 42a projecting upward. The rod 42a is inserted into the hollow rod 42 and, when rotated by a known electromagnetic actuator or electric motor disposed at the upper end of the rod 42, adjusts the area of the passage 48 connecting the chamber 43 and the chamber 45, It is configured to increase or decrease the damping force of the hydraulic shock absorber 10.
[0014]
Therefore, as shown in FIG. 5, the valve chamber 46 of the control valve 51 communicates with the chamber 43 through a pair of passages 48 extending radially outward, while the lower end of the valve chamber 46 communicates with the chamber 45. The valve body 47 fitted into the valve chamber 46 has a large-diameter through hole s, a medium-diameter through-hole m, and a small-diameter through-hole h that can communicate with the passage 48 on the peripheral wall. When the valve body 47 is rotated in the counterclockwise direction from the state shown in the drawing in which s communicates with the passage 48, the through hole m communicates with the passage 48, and when the valve body 47 is rotated clockwise, the through hole h becomes the passage. Connect to 48.
[0015]
In the present invention, the vehicle speed V is lower than V0 (for example, 20 km / h), the steering speed W is lower than the predetermined value WO, or the relationship between the direction of the lateral acceleration G and the steering direction is abnormal (if the steering wheel is turned right). If the lateral acceleration is in the right direction) or the absolute value of the lateral acceleration G is smaller than a predetermined value G0, it is determined that there is almost no roll in the vehicle body and roll control is not performed, and the air springs of all wheels are And the damping forces of the hydraulic shock absorbers of all wheels are made soft. At this time, as shown in FIG. 5, the control valve 51 is set so that the large-diameter through hole s communicates with the passage 48.
[0016]
The vehicle speed V is higher than V0, the steering speed W is higher than the predetermined value WO, the relationship between the direction of the lateral acceleration G and the steering direction is normal (if the steering wheel is turned right, the lateral acceleration is leftward), and When the absolute value of the acceleration G is larger than the predetermined value G0, roll control 1 or roll control 2 is performed. That is, when the above condition is satisfied, the roll control is performed when the lateral acceleration G is larger than the first predetermined value G0 and smaller than the second predetermined value G1, and the lateral acceleration change rate ΔG is smaller than the predetermined value g. The roll control 2 is performed when the change rate ΔG of the lateral acceleration is larger than a predetermined value g or when the absolute value of the lateral acceleration G is larger than a predetermined value G1 (G0 <G1).
[0017]
Roll control is stopped when the relationship between the direction of the lateral acceleration and the steering direction is abnormal (the lateral acceleration is rightward if the steering wheel is turned right) or the absolute value of the lateral acceleration G becomes smaller than a predetermined value G0. I do. At this time, the damping forces of the hydraulic shock absorbers of all wheels are immediately switched to soft, while the spring constants of the air springs of all wheels are switched to soft after a predetermined time (tailing time, about 1.5 to 2 seconds).
[0018]
FIG. 6 is a flow chart of a control program for executing the above-mentioned control by the electronic control unit 21 composed of a microcomputer. In FIG. 6, p08 to p31 represent each step of the control program, and it is determined whether to release the roll control holding state from p13 to p16, and whether to start the roll control from p17 to p21. Roll control is released in p27 to p30, and the roll control mode is selected when roll control is required in p23 to p26. This control program is repeatedly executed at predetermined time intervals. This control program starts at p08, initializes the calculation unit at p09, reads the vehicle speed V, the steering angular velocity W, and the lateral acceleration G at p10, and obtains the lateral acceleration change rate ΔG at p11.
[0019]
It is determined whether or not the flag is 1 at p12. If the flag is 1, it is determined at p13 whether the lateral acceleration G is smaller than a first predetermined value G0. If the lateral acceleration G is smaller than the first predetermined value G0, the flag is set to 0 at p16, and the process proceeds to p22. If the lateral acceleration G is greater than the first predetermined value G0 at p13, it is determined at p14 whether the vehicle speed V is 0 (stop or not). If the vehicle speed V is 0, the process proceeds to p16. If the vehicle speed V is not 0, it is determined at p15 whether the direction of the lateral acceleration G is different from that detected previously. If the direction of the lateral acceleration G is different from that detected last time, the process proceeds to p16, and if the direction of the lateral acceleration G is the same as that detected last time, the process proceeds to p22.
[0020]
If the flag is not 1 at p12, it is determined at p17 whether the vehicle speed V is lower than a predetermined value V0. If the vehicle speed V is lower than the predetermined value V0, the process proceeds to p22. If the vehicle speed V is higher than the predetermined value V0, it is determined at p18 whether the steering speed W is lower than the predetermined value W0. If the steering speed W is lower than the predetermined value W0, the process proceeds to p22. If the steering speed W is higher than the predetermined value W0, the process determines whether the direction of the lateral acceleration G is the same as the steering direction at p19 (whether or not there is an abnormality). Is determined. If the direction of the lateral acceleration G is the same as the steering direction, the process proceeds to p22. If the direction of the lateral acceleration G is opposite to the steering direction, it is determined at p20 whether the lateral acceleration G is smaller than the first predetermined value G0. I do. When the lateral acceleration G is smaller than the first predetermined value G0, the process proceeds to p22. When the lateral acceleration G is larger than the first predetermined value G0, the flag is set to 1 at p21 and the process proceeds to p22.
[0021]
It is determined whether or not the flag is 1 in p22. If the flag is not 1, the damping force of the hydraulic shock absorber 10 is made soft at p27, the predetermined time T is counted at p28, and the spring constant of the air spring 5 is made soft after the predetermined time T has elapsed at p29. The roll control mode is released at p30, and the process ends at p31.
[0022]
If the flag is 1 at p22, it is determined at p23 whether the lateral acceleration G is greater than the second predetermined value G1. If the lateral acceleration G is larger than the second predetermined value G1, the roll control mode is set to 2 at p24. That is, the spring constants of the air springs of all the wheels are made hard, the damping force of the hydraulic shock absorber 10 is made hard, and the process ends at p31.
[0023]
If the lateral acceleration G is smaller than the second predetermined value G1 in p23, it is determined whether or not the change rate ΔG of the lateral acceleration is larger than the predetermined value g in p25. When the change rate ΔG of the lateral acceleration is larger than the predetermined value g, the process proceeds to p24, and when the change rate ΔG of the lateral acceleration is smaller than the predetermined value g, the roll control mode is set to 1 at p26. That is, the spring constant of the air spring of the predetermined wheel is set to be hard, the damping force of the hydraulic shock absorber 10 is set to be medium, and the process ends at p31.
[0024]
In the above embodiment, the damping force of the left and right hydraulic shock absorbers 10 is switched in the same manner regardless of the turning direction of the vehicle, but the damping force of only one hydraulic shock absorber 10 is switched according to the turning direction. It may be.
[0025]
【The invention's effect】
As described above, the present invention provides an electronically controlled suspension that variably controls the damping force of a hydraulic shock absorber and the spring constant of an air spring. Alternatively, the vehicle is made softer from a medium, which improves ride comfort.The spring constant of the air spring is changed from harder to softer after a lapse of a predetermined time, so that the stability of the vehicle body posture is improved, and the electromagnetic on-off valve is improved. Operation frequency can be reduced and durability can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view of a large bus having an electronically controlled suspension system for a vehicle according to the present invention.
FIG. 2 is a schematic configuration diagram of the electronically controlled suspension device.
FIG. 3 is a block diagram of the electronically controlled suspension.
FIG. 4 is a side sectional view of a hydraulic shock absorber in the electronically controlled suspension.
FIG. 5 is a plan sectional view of a control valve incorporated in the hydraulic shock absorber.
FIG. 6 is a flowchart showing a control program of the electronically controlled suspension system according to the present invention.
[Explanation of symbols]
h, m, s: valve hole 2: front wheel 3, 13: air spring 3a: suspension arm 4, 14: auxiliary air tank 5, 15: solenoid on-off valve 10: hydraulic shock absorber 12: rear wheel 13a: beam 21: electronic Control device 22: Vehicle speed sensor 23: Steering speed sensor 24: Lateral acceleration sensor 41: Cylinder 42: Rod 44: Piston 46: Valve chamber 47: Valve body 48: Passage 51: Control valve

Claims (1)

In an electronically controlled suspension that variably controls the damping force of a hydraulic shock absorber and the spring constant of an air spring, when the conditions for terminating roll control are met, the damping force of the hydraulic shock absorber is immediately softened, and the spring constant of the air spring becomes An electronically controlled suspension system wherein the suspension is made soft after a predetermined time has elapsed, and then the roll control is released.

Images