JPS63145113A - Suspension device for automobile - Google Patents

Abstract

PURPOSE:To prevent a variation to the understeer side at the time of turning from occurring, by setting a suspension characteristic to that state that only one side of front and rear wheels is made into hard from softness in both of these front and rear wheels when a turning state is detected and the making the rest also to be turned to the hard. CONSTITUTION:A steering angle theta being shown by an output signal B out of a steering angle sensor 13 and a car speed V being shown by an output signal C out of a car speed sensor 14 both are inputted into a controller 12 which outputs a hard selector signal A1 to step motors 81 and 81 of suspensions 3 and 3 for front wheels 1 and 1 and solenoid valves 111 and 111 when it detects a fact that lateral acceleration G of more than the specified value has worked there from the steering angle theta and the car speed V, making each suspension characteristic of these front wheels 1 and 1 into hard. After the elapse of the setting time of a timer (unillustrated herein), it outputs a hard selector signal A2 to rear wheels 2 and 2, operating step motors 82 and 82 and solenoid valves 112 and 112, thus each suspension characteristic of these rear wheels is also made into hard. With this constitution aforesaid, at the time of turning, such a trend that it comes to the understeer side is checked, thus turning steerability is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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 in accordance with driving conditions.

(Prior Art) It is already known that the spring constant of a spring and the damping rate of a damper constituting an automobile suspension, that is, the suspension characteristics of the suspension, can be changed depending on the driving condition. For example, according to Japanese Utility Model Application Publication No. 55-109008, in a car equipped with shock absorbers on the front and rear wheels, at high speeds the damping force of the shock absorber on the face wheel side is increased relative to the rear wheel side. An invention related to a [vehicle suspension] characterized by increasing the understeer tendency of the steering characteristics (by making it harder), and weakening the understeer tendency at low speeds as a damping force relationship that is opposite to that at high speeds, or making the understeer tendency tend to be neutral steer or oversteer. is disclosed. This is designed to achieve both straight-line stability at high speeds and turning maneuverability at low speeds.

In addition to changing the suspension characteristics of the suspension from the viewpoint of steering characteristics as described above, the suspension characteristics may also be changed for the purpose of improving the ride comfort of the automobile. This system softens the suspension characteristics during normal straight-line driving to provide a comfortable ride, and hardens the suspension characteristics when turning to suppress unpleasant body rolling caused by lateral acceleration (centrifugal force). The aim is also to ensure good riding comfort.

(Problems to be Solved by the Invention) However, in the above-mentioned vehicle in which the suspension characteristics are switched to soft when driving straight and to hard when turning in order to improve ride comfort, the following problems regarding the steering characteristics when turning are found. Problems like this occur. In other words, when driving straight, both the front and rear wheels shift from a soft state to a turning state,
For example, if both the front and rear wheels are hardened at the same time when the lateral force i acting on the vehicle body exceeds a predetermined value, the steering characteristics will suddenly change to the understeer side during a turn, resulting in poor driving stability during the turn. It will be damaged. Furthermore, as the understeer tendency becomes stronger, turning maneuverability (responsiveness) deteriorates.

The present invention addresses the above-mentioned situation in an automobile suspension system in which the suspension characteristics are variable depending on the driving condition. The object of the present invention is to solve the above-mentioned problem in steering characteristics when transitioning from a straight-ahead state to a turning state in a vehicle designed to improve riding comfort.

(Means for Solving the Problems) That is, the automobile suspension device according to the present invention includes suspension means for suspending the vehicle body on the front wheels and rear wheels, respectively, and suspension characteristic variable means for changing the suspension characteristics of these suspension means. and,
The vehicle is equipped with a turning detection means for detecting a turning state of the automobile, and a controller for operating the suspension characteristic variable means to switch the suspension characteristic when the turning state is detected by the detection means. The vehicle is characterized in that the suspension characteristics are configured to change from a soft state for both the front and rear wheels to a state where only one of the front wheels or the rear wheels is made hard, and then to harden both the front and rear wheels when turning. The characteristics that can be changed by the suspension characteristic variable means include either one of the damping force of the damper and the spring constant of the spring, or both.

(Function) According to the above configuration, when driving straight, the suspension characteristics are soft for both the front and rear wheels, providing a comfortable ride, and when turning, both the front and rear wheels are hardened, suppressing uncomfortable rolling of the vehicle body. It turns out. When transitioning from a straight-ahead state to a turning state, only the front wheels are temporarily hardened or only the rear wheels are hardened, and in the former case, the steering characteristics are neutral. The vehicle transitions from a steer or oversteer state to a weak understeer state and then to a strong understeer state. In other words, in this case, the understeer tendency of the steering characteristics due to the transition from the soft state to the hard state of both the front and rear wheels is avoided, and the deterioration of driving stability during turns due to the sudden change to a strong understeer tendency is avoided. This results in steering characteristics suitable for automobiles where driving stability is important. In addition, in the latter case, at the start of a turn, both the front and rear wheels change from a soft state to a state where the front wheels become soft and the rear wheels become hard, which temporarily increases the oversteer tendency of the steering characteristics. Maneuverability or responsiveness is improved, and steering characteristics suitable for automobiles where agility is important can be obtained.

(Example) Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

As shown in Fig. 1, suspensions 3.3.4, 4 suspend the vehicle body between the left and right front wheels 1, 1 and the left and right rear wheels 2, 2.
Each of these is composed of a coil spring 5, a damper 6, and an air chamber 7, but the damper 6 has a structure that will be described later, and the damping rate can be switched in two stages. The seedling 7 is connected to an accumulator 10 via a vibrator 9, and a solenoid valve 11 is installed between the air chamber 7 and the accumulator 10 to disconnect communication between the two. Then, a drive signal A1 is applied to the step motor 81.81 and the solenoid valves IL+, IL+ in the suspension 3.3 of the front wheel 1°1.
．． Step motor 8 in suspension 4° 4 of 2
2.82 and the drive signal A for the solenoid valve 112.112.
2, and the controller 12 includes signals from a steering angle sensor 13 that detects the steering angle θ of a steering wheel (not shown) and a vehicle speed sensor 14 that detects the vehicle speed V of the vehicle. Signals B and C are input.

Now, to explain the specific structure of the suspension 3 (4), as shown in FIG.
(4) has an upper end fixed to the vehicle body via a mounting member 21 and an elastic body 22, and is movable up and down relative to the upper case 23 forming the air chamber 7; and a lower case 24. 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 interiors of both cases 23 and 24 are partitioned 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.
A main valve 30 provided at the lower end of the piston rod 29 divides the inside of the inner cylinder 28 into an upper oil chamber 31 and a lower oil chamber 32.
It is divided into two parts. Further, a bottom valve 33 is provided at the lower end of the inner cylinder 28, and a 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 bracket 27a for mounting a support mechanism that rotatably supports the wheel.

The main valve 30 also has an extension side orifice 30b which is configured to allow hydraulic 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. , the lower oil chamber 3 is opened by the check valve 30c.
A contraction-side orifice 30d that allows hydraulic oil to pass only from 2 to the upper oil chamber 31 side is provided. This constitutes a damper 6 that quickly damps vibrations between the upper case 23 and the lower case 24, that is, the vehicle body side and the wheel side.

The piston rod 29 in the damper 6 is hollow, and a control rod 35 inserted into the piston rod 29 is rotated by the step motor 8 via a rotation key 36 engaged at its upper end. In addition, the valve body 37 provided at the lower end of the control rod 35 and the valve case 38 provided at the lower end of the piston rod 29 are provided with communication holes 37a and 38 in corresponding positions.
a is formed, and the control rod 35 or valve body 37
The upper oil chamber 31 and the lower oil chamber 32 are communicated with each other when the two speed passage holes 37a and 38a are brought into alignment due to the rotation. As a result, the damping characteristics of the damper 6 are controlled by the upper and lower oil chambers 3 only by the orifice 30b or 30d.
1.32 are in communication with each other, to a soft state in which the upper and lower oil chambers 31 and 32 are communicated with each other through the communication holes 37a and 38a in addition to these orifices.

Further, as shown in FIG. 2, spring receivers 39 and 40 are provided in the upper case 23 and the lower case 24, respectively, and the coil spring 5 is mounted between these, and the coil spring 5 and the air chamber 7 are connected to each other. The air inside is eggplant pension 3 (4
) constitutes the spring. In that 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 air cap that acts as a spring is generated between the closed state and the open state of the solenoid valve 11i. The spring constant is increased or decreased by one, thereby switching the spring constant of the spring 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 receives the steering angle signal B from the steering angle sensor 13, and sets the steering angle θ indicated by the signal B to three set values θ1, ie, small, medium, and large. θ2. θ3(
The vehicle speed signal C from the vehicle speed sensor 14 is inputted to the first to third comparators 41, 42, and 43 for steering angle whose respective output signals turn ON when θ1, θ2, and θ3) or more. There are three set values V+ that indicate the same vehicle speed V: low, medium, and high.

V2, V3. (V+ <V2 <V3) C1,
It has first to third comparators 44, 45, and 46 for vehicle speed whose output signals are ON when the vehicle speed is above. And the first one for the rudder angle.
The output signal of the comparator 41 and the output signal of the third comparator 46 for vehicle speed are sent to the first AND circuit 47, and the output signal of the second comparator 42 for steering angle and the output signal of the second comparator 45 for vehicle combination are sent to the first AND circuit 47. 2A
The output signal of the third comparator 43 for steering angle and the output signal of the first comparator 44 for vehicle association are input to the ND circuit 48 and to the third AND circuit 49, respectively.
.about.49 output signals are input to the OR circuit 50. Therefore, from this OR circuit 50, when the steering angle θ is more than the first Y2 constant value θ1 (small) and the vehicle speed V is more than the third set value V3 (large), both the steering angle θ and the vehicle speed (Medium), V2 (Medium) or higher, the steering angle θ is the third set value θ3 (Large) or more, and the vehicle speed V is the first set value V
1 (small) or more, that is, when the area is in the shaded area in Figure 5, the ON signal angle θ
The lateral acceleration G when the car turns according to the values of and vehicle speed ■
Since it approximately corresponds to the constant value of +in, the above OR circuit 50
From this, an ONN signal is output when the lateral acceleration G is greater than or equal to a predetermined value.

In this controller 12, an OR circuit 5
The ONN signal from 0 is sent to the front wheels 1, 1 via the driver 51.
Step motor 81 in suspension 3.3.
Hard switching signal A to 81 and solenoid valve 1L+, 111
When the timer 52 is outputted as 1, the timer 52 is activated, and when the set time of the timer 52 has elapsed, the timer 52 outputs the signal to the rear wheel via the driver 53.

Step motor 82 in suspension 4.4 of 2
．． A hard switching signal A2 is output to the electromagnetic valve 82 and the solenoid valve 112.112.

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

First, when the vehicle is traveling straight, the steering angle θ indicated by the output signal B of the steering angle sensor 13 is less than the smallest first setting value θ1 set in the controller 12 shown in FIG. Any AND in 12
No ON signal is output from the circuits 47 to 49, and accordingly, the output signal of the OR circuit 50 is also in an OFF state.

Therefore, in this case, the OR circuit 50 or driver 5
1 to the hardware switching signal A1 and the OR circuit 50,
Neither the timer 52 nor the driver 53 outputs the hard switching signal A2, and both the suspensions 3, 3 of the front wheels 1.1 and the suspensions 4.4 of the rear wheels 2.2 are in a soft state. That is, each suspension 3.4
In the damper 6, the communication hole 37a shown in FIG.
38a coincide with each other, and the upper oil chamber 31 and the lower oil chamber 32 are communicated with each other through the orifice 30b or 30d and the communication holes 37a and 38a, reducing the attenuation rate, and between the air chamber 7 and the accumulator 10. The solenoid valve 11 is open and the spring constant due to the air chamber 7 is small. This provides a softer ride when driving straight.

In the case of transitioning from the straight-ahead state to the turning state, when the steering angle θ and the vehicle speed ■ enter the area shown in the shaded area in Fig. 5, in other words, the lateral acceleration G acting on the vehicle body as it turns When the value exceeds a predetermined value, the controller 12
An ON signal is outputted from any one of the first to third AND circuits 47 to 49, and accordingly, an ONN signal is outputted from the OR circuit 50. And this ON
Simultaneously with the output of the N signal, the timer 52 starts operating, and the suspension 3 of the front wheel 1.1 is activated via the driver 51.
．． Step motor 81°81 and solenoid valve 111 in 3
, 111 is output, and first, the suspension 3.3 of the front wheel 1.1 is set to hard.

That is, the step motor 81 rotates the control rod 35 or the valve body 37 shown in FIG.
The lower oil chamber 31 and the lower oil chamber 32 are in communication only through the orifice 30b or 30d, thereby increasing the damping rate of the damper 6. In addition, the solenoid valve 11
1 cuts off between the air chamber 7 and the accumulator 1o to reduce the amount of air that performs the spring action.
The spring constant of will increase.

After the suspensions 3, 3 of the front wheels 1.1 are first switched to hard in this way, when the set time (for example, 1 second) of the timer 52 has elapsed, the timer 52
The step motors 82, 82 and the solenoid valve 11 in the suspension 4.4 of the rear wheels 2, 2 are connected via the driver 53.
2.112, a hard switching signal A2 is output, and the suspension 4.4 of the rear wheels 2, 2 is also set to hard in the same manner as the suspension 3.3 of the front wheels 1.1.

As a result, suspension 3 of front and rear wheels 1, 1.2.2
, 3.4.4 are both hard, suppressing the rolling of the vehicle body when turning and stabilizing the vehicle body posture when turning.In this example, the suspension of the front and rear wheels when driving straight is .4.4 Both of these suspensions 3, 3.4. when turning from a soft state.
While all of the suspensions 4.4 are switched to hard, the suspension 4.4 of the front wheels 1.1 is hard, and the suspension 4.4 of the rear wheels 2.2 is soft. The distribution of the suspension characteristics of each suspension 3.3.4.4 determines the steering characteristics between a neutral steer or oversteer tendency when all suspensions are soft, and an understeer tendency when all suspensions are hard. Therefore, by switching the suspension characteristics as described above at the time of transition from a straight-ahead condition to a turning condition, the steering characteristics change in the direction of increasing the understeer tendency in a stepwise or It will be done slowly. This prevents the running state from becoming unstable when the understeer tendency suddenly becomes stronger during a turn, and improves the running stability during a turn.

Here, contrary to the above embodiment, when transitioning from a straight-ahead state to a turning state, the rear wheel suspension is first switched to hard, and then the front wheel suspension is switched to hard, and all suspensions are changed from soft to hard. During the changeover, the front wheel suspension may be set to soft and the rear wheel suspension may be set to hard. In this case, the distribution of the suspension characteristics as described above makes the steering characteristics tend to oversteer, so that the maneuverability (responsiveness) at the start of a turn is improved, and agile cornering becomes possible.

Further, in the above embodiment, when the lateral acceleration G exceeds a predetermined value, the suspension of either the front wheel or the rear wheel is switched to hard, and then, when the predetermined time set in the timer has elapsed, the suspension of the other wheel is switched to hard. However, instead of this, one suspension is switched to hard when the lateral acceleration G exceeds a relatively small first predetermined value (for example, 0.2G), and the lateral acceleration is further changed to 1ffG. is a relatively large second predetermined value (for example, 01
4G) or higher, the other suspension may also be switched to hard. In this case, the controller is provided with two sets of circuits, one for the front wheels and the other for the rear wheels, each consisting of comparators 41 to 46, AND circuits 47 to 4, and an OR circuit 50 shown in FIG. When the lateral acceleration G exceeds a first predetermined value, the other OR circuit turns ON when the lateral acceleration G exceeds a second predetermined value.
The configuration may be such that a signal (switching signal to hardware) is output.

(Effects of the Invention) As described above, according to the present invention, the suspension characteristics of the suspension means for suspending the vehicle body on the front and rear wheels are variable, and the characteristics are set to be soft for both the front and rear wheels when driving straight, and hard for both the front and rear wheels when turning. In an automobile suspension system that ensures a soft ride when driving straight and suppresses unpleasant body ringing when turning, both the front and rear wheels can be turned from a soft state when driving straight. When both the front and rear wheels transition to a hard state,
Since the system goes through an intermediate state in which only one of the front and rear wheels is set to hard, for example, if only the front wheels are set to hard, the understeer of the steering characteristics due to the change in suspension characteristics as described above will be reduced. The change in the direction in which the tendency becomes stronger will be carried out gradually, improving driving stability when cornering. Also, if only the rear wheels are made hard as the above intermediate state, the turning At the start, the steering characteristics temporarily tend to oversteer, improving maneuverability. In this way,
While ensuring good ride comfort when traveling straight and when turning, it becomes possible to set the steering characteristics when turning to characteristics that suit the characteristics of each vehicle.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a control system diagram of a suspension device, FIG. 2 is a sectional view showing the structure of the suspension device, FIG. 3 is an enlarged sectional view of the main part, and FIG. The figure is a circuit diagram showing the configuration of the controller.
The figure is a graph showing the control area. 1...Front wheel, 2...Rear wheel, 3.4...Suspension means (
suspension), 8.11... Suspension characteristic variable means (
step motor, solenoid valve), 12...controller,
13.14 Turning detection means (steering angle sensor, vehicle speed sensor).

Claims (1)

[Claims] (1) Suspension means for suspending the vehicle body on the front wheels and the rear wheels, respectively;
Suspension characteristic variable means for changing the suspension characteristics of these suspension means; Turning detection means for detecting the turning state of the automobile;
When the turning state of the automobile is detected by the detection means,
and a controller that operates the suspension characteristic variable means to switch the suspension characteristic, and the controller is configured to change the suspension characteristic from a soft state to only one of the front wheels or the rear wheel when switching the suspension characteristic during the turning. A suspension device for an automobile, characterized in that it is configured to switch from a hard state to a hard state for both the front and rear wheels.