JPH08238917A - Vehicle suspension controller - Google Patents

Abstract

PURPOSE: To decrease rolling of a vehicle, so as to improve steering stability by switching the rear suspension characteristic to the hard state when plus and minus signs of the steering angle and the steering angle speed to be calculated from the steering angle are equal to each other, and switching the front suspension characteristic to the hard state when the plus and minus signs are different from each other. CONSTITUTION: The steering angle θ is read by a steering angle input sensor 11, and the steering angle speed ω is calculated from the steering angle θ in a controller 9. Whether the signs of the steering angle θ and the steering angle speed ωare equal to each other or not is judged. When the signs are equal to each other, it is judged that turning to be started, the suspension characteristic of the front wheel is switched to the soft state and the suspension characteristic of the rear wheel is switched to the hard state. That is, the turning round performance of the wheel is improved by decreasing the rolling stiffness distribution of the front wheel, and increasing cornering force of the front wheel. When turning is not started, and also when the signs of θ, ωare different from each other, it is judged that turning is completed, the suspension characteristics of the front and rear wheels are contrary switched, and convergence of the yawing of the vehicle is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension device for a vehicle, and more particularly to a technique for controlling suspension characteristics according to a running state of a vehicle.

[0002]

2. Description of the Related Art As one of suspensions mounted on buses, large trucks, etc.
BACKGROUND ART There is known an air suspension device for a vehicle that supports a vehicle body by utilizing air elasticity as disclosed in Japanese Unexamined Patent Publication No. 20 and Japanese Utility Model Laid-Open No. 2-141510.

Further, in recent years, there is a need to improve riding comfort and maneuverability according to the running state of the vehicle.
For this reason, a spring constant variable mechanism of the air spring and a damping force switching mechanism of the shock absorber are provided, and the spring constant of the air spring and the damping force of the shock absorber are controlled according to the running state of the vehicle to reduce rolling of the vehicle. There is a technique (see Japanese Patent Laid-Open No. 5-193324).

On the other hand, as a technique for improving the steering stability of the vehicle, a technique for changing the rolling rigidity distribution of the front and rear suspensions in order to improve the yawing characteristics accompanying the turning of the vehicle is known as an active suspension.

[0005]

By the way, in the conventional technique for reducing the rolling of the vehicle, the improvement of the yawing characteristic for improving the steerability of the vehicle is not taken into consideration, and the active suspension has the following problems. However, there is a problem that it is expensive due to a complicated system.

In view of the above conventional problems, it is an object of the present invention to simultaneously realize a reduction in rolling of a vehicle and an improvement in yawing characteristics with a relatively simple mechanism.

[0007]

For this reason, the invention according to claim 1 provides a suspension mechanism capable of individually switching front and rear suspension characteristics at the front and rear left and right ends between the sprung and unsprung portions of a vehicle. In a vehicle suspension device provided with a switching mechanism for switching the characteristics of the suspension mechanism, a steering angle detecting means for detecting a steering angle of a steering wheel, and a steering angular velocity calculating means for computing a steering angular velocity from the detected steering angle. And a suspension control means for controlling the switching mechanism to control the suspension mechanism based on the detected steering angle and the calculated steering angular velocity. And the sign of the steering angular velocity are the same, the suspension characteristics of the rear part of the vehicle are switched to hardware and the sign Different time was configured vehicle suspension control system to switch the suspension characteristic of the vehicle front hard.

According to a second aspect of the present invention, in the vehicle suspension control device according to the first aspect, instead of the steering angle detecting means and the steering angular velocity calculating means, a lateral acceleration detecting means for detecting a lateral acceleration generated in the vehicle. And a lateral jerk calculating means for calculating a lateral jerk from the detected lateral acceleration,
In place of the configuration of the suspension control means, when the lateral acceleration and the lateral jerk have the same positive / negative sign based on the detected lateral acceleration and the calculated lateral jerk, the suspension characteristic of the rear wheel is switched to hardware, and the positive / negative sign is used. The suspension control device for a vehicle is configured to switch the suspension characteristics of the front wheels to a hard one when the values are different.

[0009]

In the inventions of claims 1 and 2, when the vehicle starts to turn, the suspension characteristics of the front part of the vehicle are made soft and the suspension characteristics of the rear part of the vehicle are made hard, so that the rolling rigidity distribution of the front wheels is small, The cornering force of the front wheels is increased and the turning performance can be improved. On the other hand, when the vehicle finishes turning, the suspension characteristics of the front part of the vehicle are made hard and the suspension characteristics of the rear part of the vehicle are made soft, so that the rolling rigidity distribution of the rear wheels is small, the cornering force of the rear wheels is large, and the yawing is converged. You can improve the property. Further, since the total rolling rigidity of the front wheels and the rear wheels is increased both when the vehicle starts turning and when the vehicle ends turning, rolling can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an overall system configuration of a suspension device for all wheels of a vehicle, and FIG. 2 shows an air suspension device for one wheel of the vehicle, for example, the front left wheel.
That is, in these figures, an air spring 2 (2a to 2f) and a damping force switching mechanism are built in between the vehicle body 18 as an unsprung part of the vehicle and the tire 1 (1a to 1d) as an unsprung part. Shock absorber 7 (7a-7f)
And are provided respectively. Air reservoir tank 3 for storing compressed air and the air spring 2 (2a to 2f)
Is a leveling valve 4 (4a-) for supplying / exhausting compressed air to / from the air spring 2 (2a-2f).
4c). Also, the air spring 2
The inside of (2a to 2f) and the sub tank 5 (5a to 5d) are communicated with each other via a spring constant switching valve 6 (6a to 6f) which is an electromagnetic valve as an opening / closing means for switching the spring constant.

FIG. 3 is a detailed control block diagram of an embodiment according to the invention described in claim 1, and the signal output from the steering angle sensor 11 is transmitted through the steering angle signal detecting means. It is input to the drive pattern calculation means that determines the front and rear suspension characteristics according to the running state. The output from the steering angle signal detecting means is branched and input to the drive pattern calculating means via the steering angular velocity calculating means for calculating the steering angular velocity. The control signal output from the drive pattern calculation means is sent to the spring constant switching valve 6 via the spring constant switching valve signal output means, and the actuator of the damping force switching mechanism of the shock absorber 7 via the shock absorber switching signal output means. Are input respectively.

Next, the control contents of the embodiment of the invention according to claim 1 will be described. The flow chart shown in FIG. 4 shows a spring constant switching valve 6 and a shock absorber 7 by the control device 9.
It is the switching control content of the actuator of the damping force switching mechanism of. Step 1 (abbreviated as S1 in the figure. The same applies hereinafter)
Then, the steering angle θ is read from the steering angle input sensor 11,
The steering angular velocity ω is calculated by the steering angular velocity calculation means. Since the vehicle makes a right turn or a left turn, the steering angle θ and the steering angular velocity ω are values having positive and negative signs.

In step 2, it is judged whether or not the signs of the steering angle θ and the steering angular velocity ω have the same sign (both are positive or negative). When the signs are the same, the vehicle starts turning (the turning radius becomes smaller). If it is not the same, the process proceeds to step 6. In step 3, the control flag indicating during control for distinguishing whether to perform post-processing for improving yawing at the end of control is set to 1, and in step 4, the post-processing counter N is set to 0. In step 5, the suspension characteristics of the front wheels are switched to soft and the suspension characteristics of the rear wheels are switched to hard, and the process returns. That is, in steps 3 to 5,
By preparing for the post-processing at the end of the control and reducing the rolling rigidity distribution of the front wheels and increasing the cornering force of the front wheels at the start of turning of the vehicle, the turning performance of the vehicle is improved.

Next, when it is judged that the vehicle has not started to turn and the routine proceeds to step 6, the steering angle θ and the steering angular velocity ω
Is a different sign (one is positive and the other is negative), and when the sign is different, it is judged that the vehicle is at the end of turning (the turning radius becomes large), and the routine proceeds to step 7, where the different sign If not, proceed to Step 10. In step 7, the aforementioned control flag is set to 1, and in step 8, the post-processing counter N is set to 0. In step 9, the suspension characteristics of the front wheels are switched to hard and the suspension characteristics of the rear wheels are switched to soft, and the routine returns. That is, step 7
In step 9, post-processing preparations are made at the end of control, and at the end of turning of the vehicle, the rolling rigidity distribution of the rear wheels is reduced and the cornering force of the rear wheels is increased to improve the convergence of the yaw of the vehicle. Let

In step 10 when the steering angle θ and the steering angular velocity ω have neither the same sign nor different signs, it is determined whether the steering angle θ and the steering angular velocity ω are both 0. When both are 0, it is determined that the vehicle is in a straight traveling state, and the process proceeds to step 11. When both are not 0, step 1 is performed.
Proceed to 8. In step 11, it is checked whether or not the control flag indicating that the control is in progress is 1 (in control). If control is in progress, the process proceeds to step 12, and if not, the process proceeds to step 17.

[0016] At step 12, a post-processing counter is incremented by one, step 13, to then process the counter is judged whether it is above a predetermined value N _r, if available step 14 with a predetermined value N _r more, If it is less than the predetermined value N _r , the process proceeds to step 16. That is, in steps 12 to 13, as a post-process at the end of the control, a process for continuing the control for improving the yawing of the vehicle for a predetermined time is performed.

In step 14, a control flag indicating whether control is in progress is set to 0 (not in control), and in step 15
Then, the suspension characteristics of both the front wheels and the rear wheels are softly switched, and the process returns. That is, step 14-
In step 15, the processing when the control is completed is performed, and both the suspension characteristics before and after the normal state of the vehicle are switched to soft.

In step 16, when the control is finished, the processing for improving the yawing of the vehicle is continued for a predetermined time, and the suspension characteristics of the front wheels are hardened.
The suspension characteristics of the rear wheels are softly switched, and the car returns. When it is determined in step 11 that the vehicle is not in control, it means that the vehicle is traveling straight ahead,
In step 17, the front and rear suspension characteristics are both switched to soft.

In step 18, when it is determined that the vehicle is not in the straight traveling state, it is determined whether the steering angle θ is not 0 and the steering angular velocity ω is 0, and θ ≠ 0 and ω = 0. For example, it is determined that the vehicle is turning with a constant radius, and the routine proceeds to step 19, and otherwise (step = 0 and ω ≠ 0), the routine proceeds to step 20. In step 19, in order to improve the yawing convergence of the vehicle, the suspension characteristics of the front wheels are switched to hard and the suspension characteristics of the rear wheels are switched to soft, and the routine returns.

In step 20, the suspension characteristics of the front wheels are switched to soft and the suspension characteristics of the rear wheels are switched to hard in order to improve the turning performance of the vehicle, and the routine returns.
Further, FIG. 5 shows a switching operation of the suspension characteristics of the vehicle under the control. This figure shows how the front and rear suspension characteristics of the vehicle are switched when the vehicle changes its course.

FIG. 6 is a detailed control block diagram of an embodiment according to the second aspect of the present invention, in which the signal output from the lateral acceleration sensor 14 is passed through the lateral acceleration signal detecting means. It is input to the drive pattern calculation means that determines the front and rear suspension characteristics according to the running state. Also,
The output from the lateral acceleration signal detecting means is branched and input to the drive pattern calculating means via the lateral jerk calculating means for calculating the lateral jerk. The control signal output from the drive pattern calculation means is sent to the spring constant switching valve 6 via the spring constant switching valve signal output means, and the actuator of the damping force switching mechanism of the shock absorber 7 via the shock absorber switching signal output means. Are input respectively.

Next, the control contents of the embodiment of the invention according to claim 2 will be described. The flow chart shown in FIG. 7 shows the spring constant switching valve 6 and the shock absorber 7 by the control device 9.
It is the switching control content of the actuator of the damping force switching mechanism of. Step 1 (abbreviated as S1 in the figure. The same applies hereinafter)
Then, the lateral acceleration G is read from the lateral acceleration sensor 14,
The lateral jerk calculation means calculates the lateral jerk α. Since the vehicle turns right or left, the lateral acceleration G and the lateral jerk α are values having positive and negative signs.

In steps 2 to 20, the steering angle .theta. Is replaced by the lateral acceleration G and the steering angular velocity .omega. Is replaced by the lateral jerk .alpha. In the flowchart of FIG. 4 of the embodiment of the invention described in claim 1. Since it is the same as the above, it is omitted here. Further, FIG. 8 shows a switching operation of the suspension characteristic of the vehicle by the above control of the invention according to claim 2 of the present invention. This figure shows how the front and rear suspension characteristics of the vehicle are switched when the vehicle changes its course.

In the above embodiment, the spring coefficient of the air spring and the damping force of the shock absorber are changed in order to switch the suspension characteristics of the vehicle.
As shown in, a suspension mechanism may be combined with a stabilizer mechanism capable of changing and controlling rolling rigidity or rolling reaction force separately for the front and rear wheels. In this case, the hydraulic pressure source 20 communicates with the hydraulic cylinder 22 via the hydraulic cylinder operation valve 21, and controls the suspension mechanism based on the steering angle or the lateral acceleration detected by the steering angle sensor 11 or the lateral acceleration sensor 14. The hydraulic cylinder operating valve 21 is switched according to the output signal of the control device 9 that operates. As a result, due to the operation of the hydraulic cylinder 22, a torsion moment is generated in the stabilizer 23 connected to the rod 24 fixed to the vehicle body 18, and the rolling rigidity or rolling reaction force of the suspension mechanism is changed.

[0025]

As described above, according to the first and second aspects of the present invention, the steering angular velocity calculated from the steering angle and the steering angle, or the lateral jerk calculated from the lateral acceleration and the lateral acceleration. When the positive and negative signs are the same, the suspension characteristics of the rear part of the vehicle are switched to hard, and when the positive and negative signs are different, the suspension characteristics of the front part of the vehicle are switched to hard.Therefore, the rolling rigidity distribution of the front wheels is small at the start of turning. In addition, the cornering force of the front wheels is increased and the turning performance is improved, and at the end of turning, the rolling rigidity distribution of the rear wheels is small, the cornering force of the rear wheels is increased, the yawing convergence is improved, and the vehicle maneuverability is improved. can do. In addition, since the total rolling rigidity of the front wheels and the rear wheels increases both at the start of turning and at the end of turning, rolling of the vehicle is reduced.

[Brief description of drawings]

FIG. 1 is an overall system configuration diagram of an embodiment of the present invention

FIG. 2 is a partial system configuration diagram of the above embodiment

FIG. 3 is a control block diagram of an embodiment of the invention described in claim 1.

FIG. 4 is a flowchart showing the control contents of the above embodiment.

FIG. 5 is an operation explanatory view showing the operation of the above embodiment.

FIG. 6 is a control block diagram of an embodiment of the invention according to claim 2;

FIG. 7 is a flowchart showing the control contents of the above embodiment.

FIG. 8 is an operation explanatory view showing the operation of the embodiment.

FIG. 9 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 (1a-1d) Wheel 2 (2a-2f) Air spring 6 (6a-6f) Spring constant switching valve 7 (7a-7f) Shock absorber 9 Control device 11 Steering angle sensor 14 Lateral acceleration sensor 23 Stabilizer

Claims (2)

[Claims] 1. A suspension mechanism capable of individually switching front and rear suspension characteristics at both left and right front and rear sides between a sprung portion and an unsprung portion of a vehicle, and a switching mechanism for switching the characteristic of the suspension mechanism. In a vehicle suspension device, a steering angle detecting means for detecting a steering angle of a steering wheel, a steering angular velocity calculating means for calculating a steering angular velocity from the detected steering angle, and a steering angle detected based on the detected steering angle and the calculated steering angular velocity. And a suspension control means for controlling the switching mechanism to control the suspension mechanism. The suspension control means is a suspension at the rear of the vehicle when the positive and negative signs of the steering angle and the steering angular velocity are the same. If the characteristic is switched to hardware and the positive and negative signs are different, the suspension characteristic at the front of the vehicle is The vehicle suspension control system being characterized in that is configured to switch to. 2. The vehicle suspension control device according to claim 1, wherein instead of the steering angle detecting means and the steering angular velocity calculating means, a lateral acceleration detecting means for detecting a lateral acceleration generated in the vehicle and a detected lateral acceleration. When the lateral jerk calculation means for calculating lateral jerk from the acceleration and the configuration of the suspension control means are used, and the positive and negative signs of the lateral jerk and the lateral jerk are the same based on the detected lateral jerk and the calculated lateral jerk. The vehicle suspension control device is configured to switch the suspension characteristics of the rear wheels to hard and to switch the suspension characteristics of the front wheels to hard when the signs are different.