JPH0911724A - Suspension device for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve running stability when an automobile shifts from a straight traveling state to a turning state while ensuring the good riding comfort in straight traveling and turning in an automobile suspension device in which the suspension characteristics of the suspension device having a spring and a damper for suspending a car body on a front wheel and a rear wheel can be changed. SOLUTION: This device has a controller 12 for changing the suspension characteristics between suspensions 3, 3 of front wheels 1,1 and suspensions 4, 4 of rear wheels 2, 2. The controller 12 makes the suspension characteristics of the front and the rear wheels in a predetermined soft condition when a car runs straight ahead and them in a predetermined hard condition when the car turns. When the car is changed from a straight ahead running state to a turning state, the front wheel is temporarily controlled in a hard condition compared with the rear wheel and a steering characteristic is changed from a neutral steering or an over steering condition to a strong under-steering condition via a slightly under-steering condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension system for an automobile, and more particularly to a suspension system in which suspension characteristics are variably controlled according to driving conditions.

[0002]

2. Description of the Related Art It is already known to change the spring constant of a spring constituting a suspension of an automobile and the damping rate of a damper, that is, the suspension characteristic of a suspension according to a driving condition. For example, according to Japanese Utility Model Laid-Open No. 55-109008, in a vehicle having shock absorbers on front and rear wheels, the damping force of the shock absorber on the front wheel side is relatively increased relative to the rear wheel side at high speed ( A device for a "vehicle suspension" characterized by enhancing the understeering tendency of the steering characteristics (hardening) and weakening the understeering tendency as a damping force relationship opposite to that at high speed at low speed or neutral steering or oversteering tendency at low speed It is disclosed. This is to achieve both straight running stability at high speed and turning maneuverability at low speed.

[0003] In addition to changing the suspension characteristics of the suspension from the viewpoint of the steering characteristics as described above, the suspension characteristics may be changed for the purpose of improving the riding comfort of the automobile. This is because the suspension characteristic is softened during normal straight running to obtain a comfortable ride, and the suspension characteristic is hardened during turning to suppress uncomfortable rolling of the vehicle body due to lateral acceleration (centrifugal force). Is also intended to ensure a good riding comfort.

[0004]

However, as described above, in order to improve the riding comfort, the suspension characteristic is switched between soft when straight ahead and hard when turning.
The following problems occur with respect to the steering characteristics when turning.

In other words, when the front and rear wheels shift from a soft state to a turning state when traveling straight, and if the front and rear wheels are simultaneously hardened when the lateral acceleration acting on the vehicle body exceeds a predetermined value, the steering characteristic is turned. The vehicle suddenly changes to the understeer side on the way, so that the running stability at the time of turning is impaired. In addition, turning maneuverability (responsiveness) due to increased understeer tendency
Will be worse.

The present invention addresses the above-mentioned situation in a vehicle suspension system in which the suspension characteristics are varied according to the driving conditions. The suspension characteristics are made soft when traveling straight, hard when turning, and when traveling straight. It is an object of the present invention to improve the riding comfort when turning, and to solve the above-mentioned problem in steering characteristics at the time of transition from a straight traveling state to a turning state.

[0007]

That is, a vehicle suspension system according to the present invention includes a suspension means having springs and dampers for suspending a vehicle body on front wheels and rear wheels, respectively, and a spring constant of the springs or a damping ratio of the dampers. A suspension characteristic changing means for changing the suspension characteristic of at least one of the above, a turning detection means for detecting a turning state of the vehicle, and a suspension characteristic changing means for detecting a turning state of the vehicle by the turning detection means. A controller provided with a controller that operates to change the suspension characteristics from a predetermined soft state for both the front and rear wheels to a predetermined hard state for both the front and rear wheels. Both the front and rear wheels are switched to a predetermined hard state from a predetermined soft state via the state where the front wheels are harder than the rear wheels Characterized by being configured to so that.

[0008] According to the above configuration, when the vehicle is going straight, the suspension characteristics of both the front and rear wheels are in a predetermined soft state, so that a comfortable ride can be obtained. Rolling of the vehicle body is suppressed. And at the time of transition from the straight running state to the turning state,
Temporarily the front wheels are harder than the rear wheels,
Therefore, the steering characteristic shifts from the neutral steer or oversteer state to the strong understeer state via the weak understeer state.

In other words, the steering characteristic gradually changes in the direction in which the understeering tendency becomes stronger as the front and rear wheels shift from the soft state to the hard state in both the front and rear wheels. Thus, deterioration of running stability at the time of turning due to the change to is avoided, and steering characteristics suitable for an automobile in which running stability is emphasized can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

As shown in FIG. 1, suspensions 3 for suspending the vehicle body on left and right front wheels 1, 1 and left and right rear wheels 2, 2 are provided.
3, 4, and 4 each include a coil spring 5, a damper 6,
The damper 6 is composed of an air chamber 7 and a damper 6 having a configuration which will be described later and the attenuation factor can be switched in two steps.
Is provided. The air chamber 7 is connected to an accumulator 10 via a pipe 9 and an electromagnetic valve 11 is provided between the air chamber 7 and the accumulator 10 to shut off communication between the two.

Then, the suspension 3,
Step motors 8 ₁ , 8 ₁ and solenoid valves 11 ₁ , 1 in 3
1 ₁ and the step motor 8 in the suspension of 4,4 drive signals A _1, the rear wheels 2 relative to the _2, 8 ₂ and the solenoid valve 1
1 _2, 11 ₂ and the drive signal A ₂ controller 12 that respectively output is provided with respect to, and to the controller 12, a steering wheel (not shown) steering angle sensor 13 and the detecting the steering angle θ of Signals B and C from a vehicle speed sensor 14 for detecting the vehicle speed V of the vehicle are input.

Here, the specific structure of the suspension 3 (4) will be described. As shown in FIG. 2, the upper end of the suspension 3 (4) is attached to the vehicle body via a mounting member 21 and an elastic body 22. It has an upper case 23 that is fixed and forms the air chamber 7, and a lower case 24 that can move up and down relative to the case 23. The lower end of the upper case 23 and the upper end of the lower case 24 are connected by a rolling diaphragm 25, and the insides of the two cases 23 and 24 are separated by a seal member 26.

The lower case 24 further includes an outer cylinder 27 and an inner cylinder 28, and a piston rod 29 is inserted into the inner cylinder 28 so as to be relatively slidable up and down. The inside of the inner cylinder 28 is partitioned into an upper oil chamber 31 and a lower oil chamber 32 by a main valve 30 provided at the lower end of 29. Further, a bottom valve 33 is provided at the lower end of the inner cylinder 28, and the inner cylinder 28
The space between the outer cylinder 27 and the outer cylinder 27 is a reservoir chamber 34. Here, the outer cylinder 27 is provided with a mounting bracket 27a of a support mechanism for rotatably supporting the wheels.

As shown in the enlarged view of FIG. 3, the main valve 30 is provided with a check valve 30a.
An extension orifice 30b that allows hydraulic oil to pass only from 1 to the lower oil chamber 32 side, and a check valve 30c allows hydraulic oil to pass only from the lower oil chamber 32 to the upper oil chamber 31 side. A contraction-side orifice 30d is provided. Thereby, the upper case 23 and the lower case 2
4, that is, a damper 6 that rapidly attenuates the vibration between the vehicle body side and the wheel side is configured.

The piston rod 29 of the damper 6 is hollow, and a control rod 35 inserted therein is rotated by the step motor 8 via a rotary key 36 engaged with the upper end. In addition, communication holes 37a and 38a are formed at corresponding positions of a valve body 37 provided at a lower end of the control rod 35 and a valve case 38 provided at a lower end of the piston rod 29. The upper oil chamber 31 and the lower oil chamber 32 are connected when the communication holes 37a and 38a coincide with each other by rotation of the control rod 35 or the valve body 37.

As a result, the damping rate of the damper 6 is controlled by the orifice 30b or 30d alone.
The upper and lower oil chambers 31 and 32 can be switched from a hard state in which the first and second oil chambers are communicated to a soft state in which the upper and lower oil chambers 31 and 32 are communicated with each other through the orifices 37a and 38a.

As shown in FIG. 2, the upper case 23 and the lower case 24 are provided with spring receivers 39 and 40, respectively, and the coil spring 5 is mounted between them.
The coil spring 5 and the air in the air chamber 7 constitute a spring of the suspension 3 (4). In this case, since the air chamber 7 is connected to the accumulator 10 via the pipe 9 and the solenoid valve 11 as described above,
The amount of air acting as a spring is increased or decreased between the closed state and the opened state of 1, whereby the spring constant of the spring is switched between a hard state and a soft state.

On the other hand, the controller 12 is configured as shown in FIG. That is, the controller 12
Is inputted with the steering angle signal B from the steering angle sensor 13, and the steering angle θ indicated by the signal B is set to three small, medium and large setting values θ ₁ ,
Steering angle first to third comparators 41, 42, 43 whose output signals are ON when θ ₂ and θ ₃ (θ ₁ <θ ₂ <θ ₃ ) or more
And a vehicle speed signal C from the vehicle speed sensor 14 is input, and the vehicle speed V indicated by the signal C is also three set values V ₁ , V ₂ , V ₃ (V ₁ <V ₂ <V ₃ ) Vehicle speed first to third comparators 44, 45, 4 whose output signals are turned on respectively in the above cases
6.

The output signal of the steering angle first comparator 41 and the output signal of the vehicle speed third comparator 46 are supplied to a first AND circuit 47, and the output signal of the steering angle second comparator 42 and the vehicle speed 2
The output signal of the comparator 45 is supplied to the second AND circuit 48, and the output signal of the third comparator 43 for the steering angle and the first comparator 4 for the vehicle speed.
4 is input to the third AND circuit 49, and the output signals of these AND circuits 47 to 49 are
The signal is input to the R circuit 50.

Therefore, from the OR circuit 50, the steering angle θ
Is larger than the first set value θ ₁ (small) and the vehicle speed V is larger than the third set value V ₃ (large), both the steering angle θ and the vehicle speed V are set to the second set values θ ₂ (medium) and V ₂ (medium). 5), and when the steering angle θ is equal to or larger than the third set value θ ₃ (large) and the vehicle speed V is equal to or larger than the first set value V ₁ (small), that is, in the region indicated by the hatched portion in FIG. Sometimes ON
Is output.

In this case, the step-shaped line a defining this area substantially corresponds to the constant value line b of the lateral acceleration G during turning of the vehicle based on the steering angle θ and the vehicle speed V.
The ON signal X is output from the OR circuit 50 when the lateral acceleration G is equal to or more than a predetermined value.

In the controller 12, the ON signal X from the OR circuit 50 is transmitted via the driver 51 to the step motors 8 ₁ and 8 ₁ and the solenoid valves 11 ₁ and 11 ₁ in the suspensions 3 and 3 of the front wheels 1 and _1. at the same time the output bets on the switching signal a ₁ to the hard, being adapted to actuate the timer 52, also when the setting time of the timer 52 has elapsed, wheel post through a driver 53 from the timer 52 step motor 8 _2, 8 ₂ and the solenoid valve 11 _2, 11 ₂ and the switching signal a ₂ to the hard is to be outputted in the suspension 4,4 2,2.

Next, the operation of the above embodiment will be described.

First, when the vehicle is traveling straight, the steering angle θ indicated by the output signal B of the steering angle sensor 13 is smaller than the smallest first set value θ ₁ set in the controller 12 shown in FIG. The ON signal is not output from any of the AND circuits 47 to 49 in the controller 12, and accordingly, the output signal of the OR circuit 50 is also in the OFF state.

Therefore, in this case, the switching signal A ₁ to the hardware from the OR circuit 50 or the driver 51 and the O signal
R circuit 50, a timer 52 or not switching signal A ₂ are both output to the hard from the driver 53, the suspension 4,4 are both soft state of suspension 3,3 and the rear wheels 2, 2 of the front wheels 1,1 is there.

That is, in the dampers 6 of the suspensions 3 and 4, the communication holes 37a and 38a shown in FIG. 3 coincide with each other so that the upper oil chamber 31 and the lower oil chamber 32 are orifice 30b.
Alternatively, the damping rate is reduced by communicating with 30d and the communication holes 37a and 38a, and the electromagnetic valve 11 between the air chamber 7 and the accumulator 10 is opened to open the air chamber 7
The spring constant is small. As a result, a soft ride can be obtained during straight running.

In the transition from the straight traveling state to the turning state, when the steering angle θ and the vehicle speed V enter the area shown by the hatched portion in FIG. 5, in other words, the lateral force acting on the vehicle body with the turning. When the acceleration G becomes equal to or more than a predetermined value, an ON signal is output from any of the first to third AND circuits 47 to 49 in the controller 12, and an ON signal X is output from the OR circuit 50 accordingly. Become.

The timer 52 starts operating simultaneously with the output of the ON signal X, and the step motors 8 ₁ , 8 ₁ and the solenoid valves 11 ₁ , 11 in the suspensions 3, 3 of the front wheels 1, 1 via the driver 51. ₁ , a switching signal A ₁ to hardware is output, and first, the suspensions 3, 3 of the front wheels 1, 1 are hardened.

[0030] That is, the step control rod 35 to the valve body 37 shown in FIG. 3 is rotated by the motor 8 ₁ communication hole 37a, by the inter-38a is cut off, upper oil chamber 31 and the lower oil chamber of the damper 6 32 is in communication with only the orifice 31b or 30d, whereby the damping rate of the damper 6 increases. Further, the electromagnetic valve 11 ₁ blocks the space between the air chamber 7 and the accumulator 10 to reduce the amount of air that acts as a spring, thereby increasing the spring constant of the air chamber 7.

Then, after the suspensions 3, 3 of the front wheels 1, 1 are first switched to hardware in this way, when the set time (for example, 1 second) of the timer 52 has elapsed, the driver 53 is released from the timer 52. via step motor 8 _2, 8 ₂ and the solenoid valve 11 _2, 11 ₂ and the switching signal a ₂ to the hard is output in suspension 4,4 of the rear wheels 2, 2, suspension 3 of the front wheels 1,1, Similarly to 3, the suspensions 4, 4 of the rear wheels 2, 2 are made hard.

As a result, the suspensions 3, 3, 4, and 4 of the front and rear wheels 1, 1, 2, and 2 become hard, and rolling of the vehicle body during the turn is suppressed, and the vehicle body posture during the turn is stabilized. However, in this case, the suspensions 3, 3, 4 and 4 of the front and rear wheels when traveling straight are changed from the soft state to the suspensions 3 and 3 when turning.
While all 3,4,4 are switched to hard, the front wheels 1,1
The suspensions 3 and 3 are hard and the suspensions 4 and 4 of the rear wheels 2 and 2 are soft.

Then, each of such suspensions 3,
The distribution of the suspension characteristics of 3, 4, and 4
This is an intermediate characteristic between the state of neutral steering or oversteering when all suspensions are soft and the state of strong understeering when all suspensions are hard, and therefore when transitioning from straight running to turning. As described above, the change in the suspension characteristics causes the steering characteristics to change stepwise or gradually in the direction in which the understeer tendency becomes stronger. This prevents the running state from becoming unstable when the understeer tendency suddenly increases during turning, and improves running stability during turning.

In the above embodiment, when the lateral acceleration G exceeds a predetermined value, the suspensions 3, 3 of the front wheels 1, 1 are switched to hardware, and thereafter, a predetermined time set in the timer 52 elapses. The suspensions 4 and 4 of the rear wheels 2 and 2 are configured to be switched to hard when the lateral acceleration G is increased to a relatively small first predetermined value (for example, 0.2 G) or more. The front wheel suspension is switched to hard, and the lateral acceleration G is relatively large.
The suspension of the rear wheels may be hard-switched when the value exceeds a predetermined value (eg 0.4 G).

In this case, the controller is provided with two sets of comparators 41 to 46, AND circuits 47 to 49, and an OR circuit 50 shown in FIG. 4 for the front wheels and the rear wheels. When the lateral acceleration G becomes equal to or more than the first predetermined value, the lateral acceleration G is output from the OR circuit for the rear wheel.
May be configured to output an ON signal (a switching signal to hardware), respectively, when is greater than or equal to a second predetermined value.

[0036]

As described above, according to the present invention, the suspension characteristics of the suspension means having the spring and the damper for suspending the vehicle body on the front and rear wheels respectively, that is, the spring constant of the spring and the damping rate of the damper are made variable. By setting the characteristics so that the front and rear wheels are in a predetermined soft state when going straight, and the front and rear wheels are in a predetermined hard state when turning, a soft riding comfort is ensured when going straight and uncomfortable rolling of the vehicle body is suppressed during turning. In the vehicle suspension device that is configured to do so, when transitioning from the soft state of both the front and rear wheels to the hard state of both the front and rear wheels when turning, the intermediate state where only the front wheels are hard is passed. The change in the steering characteristics due to the switching of the suspension characteristics as described above is gradually changed in the direction in which the understeer tendency becomes stronger. . As a result, the traveling stability at the time of turning can be improved while securing a good riding comfort at the time of going straight and turning.

[Brief description of the drawings]

FIG. 1 is a control system diagram of a suspension device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of the suspension device.

FIG. 3 is likewise an enlarged cross-sectional view of a main part.

FIG. 4 is a circuit diagram showing a configuration of a controller.

FIG. 5 is a graph showing a control area.

[Explanation of symbols]

1 Front Wheel 2 Rear Wheel 3,4 Suspension Means (Suspension) 6 Damper 7 Spring (Air Chamber) 8,11 Suspension Characteristic Changing Means (Step Motor, Solenoid Valve) 12 Controller 13,14 Turning Detection Means (Steering Angle Sensor, Vehicle Speed Sensor) )

Claims (1)

[Claims] 1. Suspension means having springs and dampers for suspending the vehicle body on the front wheels and rear wheels, respectively, and suspension characteristic variable means for changing suspension characteristics of at least one of the spring constant of the springs and the damping ratio of the dampers. A turning detection means for detecting a turning state of the vehicle; and when the turning state of the vehicle is detected by the turning detection means, the suspension characteristic varying means is operated to change the suspension characteristic from a predetermined soft state to a front and rear state. In a vehicle suspension device equipped with a controller that switches both wheels to a predetermined hard state,
When the suspension characteristics are changed during the turning, the controller changes from a predetermined soft state for both front and rear wheels to a predetermined hard state for both front and rear wheels through a state in which the front wheels are harder than the rear wheels. A vehicle suspension device characterized by being configured to switch.