JPH0747366B2 - Suspension device for automobile - Google Patents

Description

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

(Prior 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 the suspension according to a driving state. For example, according to Japanese Utility Model Publication 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 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.

In addition to changing the suspension characteristic of the suspension in terms of the steering characteristic as described above, the suspension characteristic 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.

(Problems to be solved by the invention) However, in the case where the suspension characteristic is switched to soft when traveling straight and hard when traveling in order to improve the riding comfort as described above, the steering characteristic regarding turning is as follows. Such a problem occurs. In other words, transition from a state where the suspension characteristics when traveling straight ahead is soft to a turning state,
For example, when the lateral acceleration acting on the vehicle body exceeds a predetermined value, especially when the suspension characteristics of the front wheels are made hard, the understeering tendency of the steering characteristics suddenly becomes strong during turning, and the running stability during turning is impaired. become. Also,
As the understeer tendency becomes stronger, turning maneuverability (responsiveness) deteriorates.

The present invention addresses the above situation in a vehicle suspension system in which the suspension characteristics are variable according to the driving state. In particular, when shifting from a straight running state to a turning state, the front wheels are By appropriately changing the suspension characteristics of the vehicle, it is intended to improve running stability, turning controllability, and stability of the vehicle body posture.

(Means for Solving the Problems) That is, the vehicle suspension device according to the present invention has a suspension means for suspending the vehicle body on each of the front wheels and the rear wheels, and at least the suspension characteristics of at least the front wheel among these suspension means. Suspension characteristic changing means for changing independently, turning detection means for detecting a turning state of an automobile, and a controller for operating the suspension characteristic changing means when the turning state is detected by the detecting means to switch at least the suspension characteristics of the front wheels. In addition to this, this controller switches from the state where both the left and right front wheels have a soft suspension characteristic when turning, to the state where both front wheels on the outside of the turn are hard, and both left and right front wheels are hard. It is characterized in that it is configured as follows. Regarding the suspension characteristics of the rear wheels, it is desirable to make both left and right soft when going straight from the viewpoint of riding comfort, but when making both left and right soft when turning, and when making both left and right hard in terms of vehicle body posture stability. There is. Further, when the front wheels on the outside of the turn are hard when the straight traveling state is changed to the turn state, only the rear wheels on the inside of the turn may be hard. Further, the characteristics that can be switched by the suspension characteristic changing means include one of the damping force of the damper and the spring constant of the spring, or both of them.

(Operation) According to the above configuration, the suspension characteristics of at least the front wheels are soft on both sides when going straight, and a comfortable riding comfort is obtained,
Further, at the time of turning, the suspension characteristics of at least the front wheels are hard on both the left and right sides, and unpleasant rolling of the vehicle body is suppressed. During the transition from the straight-ahead state to the turning state, only the front outer wheel of the left and right front wheels is temporarily in a hard state, and the steering characteristics of both the left and right front wheels tend to be a soft neutral steer or an oversteer tendency. Therefore, only the front wheels on the outside of the turn are in a state of a hard weak understeer tendency, and then the right and left front wheels are changed to a state of a strong strong understeer tendency. That is, the steering characteristics are gradually changed to the understeer tendency at the time of turning, and the deterioration of the running stability at the time of turning due to the rapid change to the understeer tendency is prevented. At the start of turning, one of the front wheels remains soft, so the maneuverability at the beginning of turning is improved compared to the case where both the left and right front wheels are made hard immediately. By doing
Rolling around the axis connecting the front wheel on the inside of the turn and the rear wheel on the outside of the turn, which is likely to occur at the start of turning, that is, the diagonal roll is effectively suppressed.

(Example) Hereinafter, the present invention will be described based on an example shown in the drawings.

As shown in FIG. 1, left and right front wheels 1, 2 and left and right rear wheels 3, 4
Each of the suspensions 5, 6, 7, 8 for suspending the vehicle body is composed of a coil spring 9, a damper 10, and an air chamber 11, but the damper 10 has a configuration as described later and has a two-stage damping rate. The step motor 12 is provided as an actuator that is switchable. Further, the air chamber 11 is connected to an accumulator 14 via a pipe 13, and a solenoid valve 15 is installed between the air chamber 11 and the accumulator 14 to cut off the communication between them.
A controller 16 for outputting switching signals A _{1 to} A ₄ to the step motors 12 _{1 to} 12 ₄ and the solenoid valves 15 ₁ to 15 4 in the suspensions 5 to 8 of the wheels ₁ to ₄ is provided, and The controller 16 receives signals B and C from a lateral G sensor 17 that detects a lateral acceleration acting on the vehicle body during turning and a turning direction sensor 18 that detects a turning direction.

Here, the specific structure of the suspensions 5 to 8 will be described. As shown in FIG.
Reference numeral 8 denotes an upper case 23 that has its upper end fixed to the vehicle body via a mounting portion 21 and an elastic body 22, respectively, and an upper case 23 that forms the air chamber 11, and a lower portion that can move up and down relative to the case 23. And a case 24. Then, 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 inside of both cases 23, 24 is a seal member 26.
It is partitioned by. Further, the lower case 24 is further composed of 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 vertically, and the lower end of the piston rod 29 is lower. 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 in the. Further, a bottom valve 33 is provided at the lower end of the inner cylinder 28, and the space between the inner cylinder 28 and the outer cylinder 27 is a reservoir chamber 34. Here, the outer cylinder 27 is provided with a mounting mechanism mounting bracket 27a for rotatably supporting the wheels.

Further, the main valve 30 is provided with an extension side orifice 30b, which is configured to allow the working oil to pass only from the upper oil chamber 31 to the lower oil chamber 32 side by a check valve 30a, as shown in an enlarged view in FIG. , Check valve 30c from lower oil chamber 32 to upper oil chamber 31
A contraction side orifice 30d adapted to pass hydraulic oil is provided only on the side. This allows the upper case 2
3 and the lower case 24, that is, the damper 10 that quickly damps the vibration between the vehicle body side and the wheel side.

Further, the piston rod 29 of the damper 10 is hollow, and the control rod 35 is inserted into the piston rod 29.
Is rotated by the step motor 12 via a rotary key 36 engaged with the upper end, and a valve element 37 provided at the lower end of the control rod 35,
Communication holes 37a and 38a are formed at positions corresponding to the valve case 38 provided at the lower end of the piston rod 29. The upper oil chamber 31 and the lower oil chamber 32 are communicated with each other when the communication holes 37a, 38a are aligned by the rotation of the control rod 35 or the valve body 37, and the damping characteristic of the damper 10 is the orifice 30b or 30b. Only by this, the upper and lower oil chambers 31 and 32 can be switched from a hard state in which they are communicated to a soft state.

Further, 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 9 is mounted between them, and the coil spring 9 and the air chamber 11 are provided. It constitutes the spring of the air and suspension inside. In that case, since the air chamber 11 is connected to the accumulator 14 via the pipe 13 and the solenoid valve 15 as described above, the amount of air acting as a spring when the solenoid valve 15 is closed and when it is opened. Is increased or decreased, whereby the spring constant of the spring is switched between a hard state and a soft state.

On the other hand, the controller 16 is configured as shown in FIG. That is, the controller 16 receives the output signal B of the lateral G sensor 17, and the lateral acceleration G at the time of turning indicated by the signal B has a relatively small first predetermined value G1 (for example, 0.2).
G) or more, a first comparator 41 that outputs an ON signal, and a second predetermined value G ₂ (for example 0.4 G) in which the lateral acceleration G is relatively large.
The second comparator 42 that outputs an ON signal at the above time and the output signal C of the turning direction sensor 18 are input, and the ON signal is output when the turning direction (steering direction) indicated by the signal C is on the left side. It has three comparators 43 and a fourth comparator 44 which outputs an ON signal when the turning direction is on the right side. The output signals of the first and third comparators 41 and 43 are sent to the first AND circuit 45 and the second and third comparators 4 and 4.
The output signals of 2,43 are sent to the second AND circuit 46 and the first and fourth comparators 41,4
The output signal of 4 is sent to the third AND circuit 47, and the second and fourth comparators 42, 42,
The output signal of 44 is input to the fourth AND circuit 48. Therefore, from the first AND circuit 45, when turning left and the lateral acceleration G is the first predetermined value G ₁ or more, the ON signal Xl ₁ is changed to the second AN.
Similarly, the D circuit 46 outputs the ON signal Xl ₂ when the vehicle is turning left and the lateral acceleration G becomes equal to or more than the second predetermined value G _2, and the third AND circuit 47 outputs the signal when turning right. When the lateral acceleration G is the first predetermined value G ₁ or more, the ON signal Xr ₁ changes to the fourth AND circuit 4
From FIG. 8, the ON signal Xr ₂ is output when the lateral acceleration G is equal to or more than the second predetermined value G ₂ when the vehicle is turning right. The ON signals Xrl ₁ and Xr ₂ output from the first and fourth AND circuits 45 and 48 are transmitted to the step motor 1 in the suspensions 6 and 7 of the right front wheel 2 and the left rear wheel 3 via the driver 49.
2 ₂ and 12 ₃ and solenoid valves 15 ₂ and 15 ₃ are output as switching signals A ₂ and A ₃ to the hardware, and ON signals Xl _{2 and} Xr ₁ are output from the second and third AND circuits 46 and 47. Is the step motor 1 in the suspensions 5 and 8 of the left front wheel 1 and the right rear wheel 4 via the driver 50.
2 ₁ and 12 ₄ and solenoid valves 15 ₁ and 15 ₄ are output as hardware switching signals A ₁ and A ₄ .

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

First, when the vehicle is traveling straight ahead, the lateral G sensor
Since the lateral acceleration G acting on the vehicle body indicated by the output signal B of 17 is zero, the first and second comparators 41, 4 in the control 16 are
The output signal of 2 is OFF, and the output signals of the first to fourth AND circuits 45 to 48 are all OFF accordingly. Therefore, in this case, the switching signals A _{1 to} A ₄ to the hardware are not output to any of the step motors 12 _{1 to} 12 ₄ and the solenoid valves 15 ₁ to 15 4 in the suspensions 5 to 8 of the wheels ₁ to ₄ , All suspensions 5-8 are in soft condition. That is, in the damper 10 of each suspension 5-8, the communication holes 37a, 38a shown in FIG. 3 are aligned, and the upper oil chamber 31 and the lower oil chamber 32 are connected to the orifice 30b or 30d and the communication holes 37a, 38a. And the damping force is reduced, and the solenoid valve 15 between the air chamber 11 and the accumulator 14 is opened so that the spring constant of the air chamber 11 is small. As a result, a soft riding comfort can be obtained when driving straight ahead.

Then, if the lateral acceleration G acting on the vehicle body becomes a relatively small first predetermined value G ₁ or more as a result of turning operation to the left from this straight traveling state, the first comparator 41 and the third comparator 41 in the controller 16 ON signal is output from 43 and ON, and these signals are input from the first AND circuit 45
The signal Xl ₁ will be output. Therefore, driver 4
Via step 9 to the step motor 12 ₂ and the solenoid valve 15 ₂ in the suspension 6 of the right front wheel 2 and the step motor 12 ₃ and the solenoid valve 15 ₃ in the suspension 7 of the left rear wheel 3 respectively, a switching signal A ₂ to the hardware, A ₃ is output and these suspensions 6 and 7 are hardened. That is, the step motors 12 ₂ and 12 ₃ rotate the control 35 or the valve body 37 shown in FIG. ₃ to shut off the communication holes 37a and 38a, so that the upper oil chamber 31 and the lower oil chamber 32 of the damper 10 are closed. And are communicated with each other only by the orifice 30b or 30d, and the damping force of the damper 10 is increased. Also solenoid valve
The spring constant of the air chamber 11 is increased by blocking the space between the air chamber 11 and the accumulator 14 by 15 ₂ and 15 ₃ and reducing the amount of air that acts as a spring.

Then, when turning to the left in this way, first the right front wheel 2
And after the suspensions 6 and 7 of the left rear wheel 3 are switched to hard, the lateral acceleration G further acts on the vehicle body as the turning state progresses further.
Becomes a relatively large second predetermined value G ₂ or more, the output signal of the second comparator 42 is turned on next, and the signal and the ON signal from the third comparator 43 are input to the second AND. The ON signal Xl ₂ will be output from the circuit 46. And this ON signal Xl ₂
Via the driver 50 with the suspension 5 on the left front wheel 1,
Step motors 12 ₁ , 12 ₄ of suspension 8 for right rear wheel ₄
Also, by outputting to the solenoid valves 15 ₁ and 15 ₄ as switching signals A ₁ and A ₄ to the hardware, respectively, these suspensions 5 and 8 are also hard as in the case of the suspensions 6 and 7. .

As a result, the suspension 5 of all the wheels 1 to 4 is finally obtained.
~ 8 becomes hard and rolling of the vehicle body due to turning is effectively suppressed, but at the start of turning, when all the suspensions 5 to 8 are switched from the soft state to the hard state as described above, As an intermediate state, only the suspensions 6 and 7 of the right front wheel 2 (the front wheel on the outside of the turn) and the left rear wheel 3 (the rear wheel on the inside of the turn) go through a hard state. The suspension characteristics of the suspensions 5 to 8 are distributed between the steering characteristics such as a neutral steering or oversteering tendency when all the suspensions are soft and a strong understeering tendency when all the suspensions are hard. Since the intermediate characteristics are used, the steering characteristics change gradually or gradually in the direction in which the understeer tendency becomes stronger due to the switching of the suspension characteristics as described above at the time of the transition from the straight traveling state to the turning state. It will be. As a result, instability of the running state is prevented when the understeer tendency sharply increases, and the running stability during turning is improved. Also, in the intermediate state at the start of turning, one of the left and right front wheels 1 and 2 is held soft, so maneuverability at the beginning of turning is better than when both front wheels are hard at the start of turning. Will be improved. Further, in this case, the suspension of the front wheel on the outside of the turn (the suspension 6 of the right front wheel 2 in the above left turn) is made hard, and in this embodiment, the suspension of the rear wheel on the inside of the turn (the left rear wheel 3). Suspension 7)
Since it is also hardened, the diagonal roll that tends to occur at the beginning of turning, that is, the phenomenon in which the entire vehicle body on the outside of the turning sinks around the axis connecting the front wheel on the inside of the turning and the rear wheel on the outside of the turning, is effectively suppressed, and turning starts. The body posture at that time will be stabilized.

Although the above description is for the case of turning to the left, the suspension characteristics of the suspensions 5 to 8 are similarly switched when turning to the right. That is, in this case, at the start of turning, the suspensions 5 and 8 for the left front wheel 1 and the right rear wheel 4 are made hard first, and then the suspensions for the right front wheel 2 and the left rear wheel 3 are made.
6,7 are considered hard. Further, in the above embodiments, the suspension of all the wheels is finally made hard, but the rear wheels may be made to be soft on both the left and right, and in the intermediate state, the front wheels on the outside of the turning are hard. At this time, the rear wheel on the inside of the turn may remain soft. In short, at the time of the transition from the straight traveling state to the turning state, the left and right front wheels may be made hard via the state in which the left and right front wheels are in the soft state and the front wheels on the outside of the turning are made hard. The same effect as can be obtained.

Further, in the above-described embodiment, the two-stage switching is performed according to the increase of the lateral acceleration G at the time of turning, but instead of this, the turning is performed when the lateral acceleration G becomes a predetermined value (for example, 0.2 G) or more. The outer front wheel may be hardened, and then, the front wheel on the inside of the turn may be hardened when a predetermined time (for example, 1 second) has elapsed. In this case, the second comparator 42 shown in FIG. 4 may be omitted and a timer 42 'may be provided as shown by the chain line in FIG.

As described above, according to the present invention, the suspension characteristic of at least the suspension means of the front wheels is made variable among the suspension means for suspending the vehicle body on the front and rear wheels, respectively, and the characteristics are softened to the left and right front wheels when going straight. By making both the left and right front wheels hard when turning, a soft riding comfort is ensured when going straight and uncomfortable rolling of the vehicle body when turning is suppressed,
At the time of transition from the soft state of both the left and right front wheels when going straight to the hard state of both the left and right front wheels when turning, only the front outside wheels of the turn are set to be in a hard state. The change in the steering characteristic is gradually changed in the direction in which the understeer tendency becomes stronger, and the traveling stability at the time of turning is improved. In addition, as described above, the front wheel on the outside of the turn is hard at the start of turning and the front wheel on the inside of the turn is soft, so the maneuverability at the beginning of turning is improved compared to the case where both the front and left front wheels are immediately made hard at the start of turning. At the same time, the diagonal roll is suppressed, and the stability of the vehicle body posture is further improved.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a control system diagram of a suspension device, FIG. 2 is a sectional view showing the structure of the suspension device, and FIG. The figure is a circuit diagram showing the configuration of the controller. 1,2 …… Front wheel, 5,6 …… Suspension means, 1
2,15 ... Suspension characteristic changing means (step motor, solenoid valve), 16 ... Controller, 17,18 ... Turning detection means (lateral G sensor, turning direction sensor).

Claims (1)

[Claims] 1. A suspension means for suspending a vehicle body on each of front and rear wheels, a suspension characteristic variable means for changing at least the suspension characteristic of at least the front wheel independently of left and right among these suspension means, and a turning state of an automobile is detected. A turning detection means and a controller for switching the suspension characteristics of at least the front wheels by activating the suspension characteristic changing means when the turning state of the vehicle is detected by the detection means are provided, and the controller controls the left and right sides when turning. A suspension device for an automobile, characterized in that the front wheels on both sides are switched to a hard state from a state in which both front wheels are in a soft state and a state in which only the front wheel on the outside of the turning of both front wheels is in a hard state .