JPH0615287B2 - Suspension - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to suspension systems.

(Prior Art) It is widely known that a suspension device is provided between an axle and a vehicle body, and the two are coupled to each other to absorb an impact from a road surface and improve riding comfort. The suspension device is roughly composed of a coil spring that absorbs a shock from the road surface and a shock absorber that suppresses free vibration of the coil spring. The shock absorber, in particular, the coil spring itself has no damping action. Therefore, as a means for suppressing the free vibration of the coil spring, it plays an important role in the suspension device.

(Problems to be Solved by the Invention) However, using a shock absorber together in a suspension system means that the damping force of the shock absorber acts on the vehicle body in addition to the spring force of the coil spring. Compared with this, the vertical acceleration of the vehicle body was increased.

That is, the vertical acceleration of the vehicle body due to the input from the road surface is
It is derived by dividing the sum of the spring force of the coil spring and the damping force of the shock absorber by the vehicle mass. The spring force acting on the vehicle body in the coil spring is large due to the relative expansion and contraction of the coil spring with respect to the reference length. And the direction (downward if larger than the reference length, upward if smaller) are determined, and the damping force acting on the vehicle body in the shock absorber expands or contracts between the maximum length and the minimum length of the piston rod. By moving, its size and direction (downward when extended, upward when shortened) are determined. Therefore, the direction and magnitude of the spring force of the coil spring and the damping force of the shock absorber change according to their own unique conditions, and the acting direction of the spring force and the acting direction of the damping force are the same. In some cases, the two may conflict with each other. When the acting direction of the spring force acting on the vehicle body is the same as the acting direction of the damping force (when the extension is larger than the reference length or when the extension is shorter than the reference length), the sum of the spring force and the damping force is large. Therefore, the vertical acceleration of the vehicle body increases.

Therefore, an increase in vertical acceleration of the vehicle body causes an occupant to feel discomfort.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent an increase in vertical acceleration of a vehicle body and improve riding comfort of the vehicle by reducing a force acting on the vehicle body due to an input from a road surface. is there.

(Means for Solving the Problems) In order to achieve such an object, in the present invention, a spring means provided between an axle of a vehicle and a vehicle body for absorbing an impact from a road surface and vibration of the vehicle body are provided. In a suspension system including a damping damper, at least two levels of damping force characteristics can be selected on the extension side and the contraction side of the damping force characteristic of the shock absorber, and further, the vehicle body and the axle of the vehicle can be selected. Detecting means for detecting whether the distance between the vehicle body and the axle is larger or smaller than the reference state, and the damping force of the shock absorber when the distance between the vehicle body and the axle is larger than the reference state. When the characteristic is a combination of low damping force on the extension side and high damping force on the contraction side, and when the distance between the vehicle body and the axle is smaller than the reference state, the damping force characteristic of the shock absorber is that the extension side is high damping force and the contraction side is Low damping force pair The control means for matching is provided.

(Operation) With the above configuration, when the distance between the vehicle body and the axle is larger than the reference state, the control means sets the damping force characteristics of the shock absorber to a combination of low damping force on the extension side and high damping force on the contraction side. When the distance between the vehicle body and the axle becomes large against the spring force of the vehicle and the vehicle departs from the standard state (the spring force acting on the vehicle body and the direction of the damping force are the same), a low damping force acts as the shock absorber extends. Therefore, the vertical acceleration of the car body becomes small,
When the distance between the vehicle body and the axle becomes smaller due to the spring force and the reference state approaches (the direction of the spring force acting on the vehicle body and the direction of the damping force differ), a high damping force acts as the shock absorber shortens. Convergence of vertical acceleration is promoted. Also,
When the distance between the vehicle body and the axle is smaller than the reference state, the control means sets the damping force characteristics of the shock absorber to a combination of a high damping force on the extension side and a low damping force on the contraction side, so that the vehicle body is resistant to the spring force of the spring means. When the vehicle departs from the standard state due to the small distance between the vehicle and the axle (the direction of the spring force acting on the vehicle and the direction of the damping force are the same), a low damping force acts as the shock absorber shortens, so the vertical acceleration of the vehicle body is small. Therefore, when the spring force increases the distance between the vehicle body and the axle and approaches the reference state (the spring force acting on the vehicle body and the direction of the damping force differ), a high damping force acts as the shock absorber extends. Convergence of vertical acceleration of the vehicle body is promoted.

(Effects of the Invention) Therefore, according to the present invention, the vertical acceleration of the vehicle body is reduced and the convergence thereof is promoted, so that the occupant is not uncomfortable and the riding comfort is improved. it can.

(Example) Hereinafter, the Example of this invention is described.

In FIGS. 1 to 10, reference numeral 1 denotes a vehicle, and a vehicle body 2 and an axle 3 of the vehicle 1 are connected via a suspension device 4,
Wheels 5 are connected to the axle 3. The suspension device 4 is provided for each wheel 5, and FIG. 1 shows one of the suspension devices 4.

The suspension device 4 includes a coil spring 6 as a spring.
And a hydraulic shock absorber 7 as a shock absorber, and a displacement sensor 8 as a detection means. The inside of one end of the coil spring 6 is provided on the axle 3 and is fitted and held in the rubber cushion 9, and the inside of the other end of the coil spring 6 is provided on the side of the vehicle body 2 facing the rubber cushion 9. It is fitted and held in the cushion receiver 10.

The hydraulic shock absorber 7 is shown in detail in FIG.

That is, the free piston 12 is slidably inserted in the cylinder 11, and the free piston 12 is inserted in the cylinder 11.
It is divided into two chambers, a gas chamber 13 and an oil chamber 14. The gas chamber 13 is filled with high-pressure gas, and the oil chamber 14 is filled with oil liquid.

A piston 15 is slidably fitted in the oil chamber 14, and the oil chamber 14 is defined by the piston 15 into a lower chamber R1 and an upper chamber R2. A piston rod 16 is connected to the piston 15, and the piston rod 16 extends outside the cylinder 11 through the upper chamber R2.

The piston 15 is provided with a first communication passage 17 and a second communication passage 18 that connect the lower chamber R1 and the upper chamber R2. When the piston rod 16 is shortened, the lower chamber R1
When the pressure in the lower chamber R1 and the pressure in the upper chamber R2 reach a certain value due to the increase in the pressure in the first chamber, the normally closed first damping valve 19 that opens the first communication passage 17 is opened.
On the other hand, if the pressure in the upper chamber R2 becomes high when the piston rod 16 extends and the pressure difference between the lower chamber R1 and the upper chamber R2 reaches a certain value, the second communication passage 18 A normally closed second damping valve 20 is installed which opens.

The piston 15 is formed with third and fourth communication passages 21 and 22 that face each other with the axis of the piston rod 16 in between, and the third and fourth communication passages 21 and 22 are respectively connected to the upper chamber R2. It communicates with the lower chamber R1. Check valves 23 and 24 are provided in the third and fourth communication passages 21 and 22, respectively. The check valve 23 allows only the flow of the oil liquid from the lower chamber R1 to the upper chamber R2, and the check valve 24 is provided. Allows only the flow of oil liquid from the upper chamber R2 to the lower chamber R1. A disk-shaped movable plate 25 is rotatably held inside the piston 15 about the axis of the piston rod 16.
The plate surface of the movable plate 25 crosses the third and fourth communication passages 21 and 22. A pair of elongated holes 26, 27 are concentrically formed in the movable plate 25, and the pair of elongated holes 26, 27 face each other. The elongated holes 26, 27 extend in the circumferential direction of the movable plate 25, and the opening area of one elongated hole 26 increases in the clockwise direction in FIG. 3, while the other elongated hole 27. Is
In FIG. 3, the opening area decreases in the clockwise direction. The elongated holes 26, 27 are formed by rotating the movable plate 25 about its axis, thereby forming the third and fourth communication passages 2.
It is possible to approach 1, 22 and the damping force characteristics at this time are shown in FIG. To explain this concretely, for example, the b1 point of the long hole 26 is made to face the third communication passage 21,
When the b2 point of the long hole 27 is exposed to the fourth communication passage 22, a rising characteristic curve as shown by B1 and B2 in FIG. 5 is shown (medium damping force on both the extension side and the contraction side). When the a1 point of the long hole 26 faces the third communication passage 21 and the a2 point of the long hole 27 faces the fourth communication passage 22, a characteristic curve with a sharper rise than the characteristic curve B1 A1 and a characteristic curve A2 that rises more gently than the characteristic curve B2 are shown (extension side: low damping force, contraction side: high damping force), and the c1 point of the long hole 26 faces the third communication passage 21. , 4th
When the point c2 of the long hole 27 is made to face the communication passage 22 of, the characteristic curve C1 that rises more gently than the characteristic curve B1 and the characteristic curve
It shows a characteristic curve C2 that rises more rapidly than B2 (extension side: high damping force, contraction side: low damping force). When each of the initial rising damping forces exceeds a predetermined value, the first and second damping valves 19 and 20 are opened, and the hydraulic shock absorber 7
Indicates each predetermined damping force. The first and second damping forces 19,
At the time of opening 20, the points P1 and
Equivalent to P2.

An operation rod 28 is connected to the movable plate 25 at its axial center, and the operation rod 28 rotatably passes through the piston rod 16 in the axial direction. An actuator 29 is connected to the operation rod 28, and the actuator 29 allows the operation rod 28 to be appropriately rotated about its axis.

The displacement sensor 8 is interposed between the vehicle body 2 and the axle 3, and the displacement sensor 8 extends and contracts in a distance between the vehicle body 2 and the axle 3 in a reference state, that is, a distance between the axle 3 and the reference length L. Detect displacement. The reference length L may be a distance between the vehicle body 2 and the axle 3 when the vehicle 1 is left stationary on a flat ground, or the vehicle 1 is allowed to travel on a predetermined road surface for a predetermined time, and then the vehicle body 2 It may be an average value of the distance from the axle 3.

Each displacement sensor 8a, 8b, 8c, 8d in each suspension device 4 and each actuator in each hydraulic shock absorber 7 of each suspension device 4
29a, 29b, 29c and 29d are connected via a control circuit 30 as shown in FIG. The control circuit 30 has a function of controlling the corresponding actuators 29a to 29d based on the detection signals from the displacement sensors 8a to 8d. That is,
The control circuit 30 determines the spring force Fs of the coil spring 6 based on the detection signal from the displacement sensor 8 (hereinafter, one of the displacement sensors and the actuator corresponding to the displacement sensor) regarding the magnitude and direction thereof. Along with the calculation, the time-dependent expansion / contraction change of the distance between the vehicle body 2 and the axle 3 with respect to the reference length L, that is, the suspension speed (piston speed) is calculated. Calculate the force Fa.

Fa = K × gravitational acceleration × piston velocity K = coefficient (Kg · m / sec ² ) Then, the control circuit 30 controls the acting direction of the spring force Fs and the damping force Fa.
Compare with the action direction of. Here, when the axial length of the coil spring 6 is shorter than the action reference length L of the spring force Fs with respect to the vehicle body, the coil spring 6 is in the extending direction (upward direction), and the coil spring 6 is longer than the reference length L. When the axial length is long, the coil spring 6 contracts (downward). Also, the acting direction of the damping force Fa is such that when the piston rod 16 is extended, the piston rod is
16 is the direction of shortening (downward), and when the piston rod 16 is shortened, it is in the extending direction (upward) of the piston rod 16.

When the control circuit 30 compares the acting direction of the spring force Fs and the acting direction of the damping force Fa and determines that they are the same, the control circuit 30 operates the actuator 29 to rotate the movable plate 25. The predetermined position of the predetermined elongated hole 26 or 27 is made to face the third communication passage 21 or the fourth communication passage 22 so that the damping force Fa is not generated. That is, when the distance between the vehicle body 2 and the vehicle body 3 is smaller than the reference length L, the point c ₁ of the elongated hole 26 is set to
Face 21 and reduce the damping force on the contraction side to a low damping force. At this time, since the point c ₂ of the long hole 27 faces the fourth communication passage 22, the extension side damping force becomes a high damping force. When the distance between the vehicle body 2 and the vehicle body 3 is larger than the reference length, the a ₂ of the long hole 27 is set to the fourth communication passage.
Facing 22 and reducing the damping force on the extension side to a low damping force. At this time, since the point a ₁ of the elongated hole 26 faces the third communication passage 21, the damping force on the contraction side becomes a high damping force. When the control circuit 30 compares the acting direction of the spring force Fs and the acting direction of the damping force Fa and determines that they are in conflict, the control circuit 30 determines that the actuator 29
Is operated to rotate the movable plate 25, and the predetermined position of the predetermined elongated hole 26 or 27 is set to the third communication passage 21 or the fourth communication passage 21 or the fourth position so that the magnitude of the damping force Fa becomes equal to the magnitude of the spring force Fs. It faces the passage 22 of. The details will be described later.

Next, as shown in FIG. 6, the vehicle 1 has a convex portion 31a on the road surface 31.
The operation of the above configuration will be described by taking the case of traveling as an example.

The calculation is performed by modeling the suspension device 4 as shown in FIG. 7. In this model, the body mass M = 300 Kg, the spring constant of the coil spring 6 k = 1207 × gravitational acceleration (Kgm / sec) ² m), and three types of hydraulic shock absorbers were used in which the damping force Fa was calculated by the following equation.

Fa = Ka x gravity acceleration x piston speed Ka = -20 (Kgm / sec ² ) Fa = Kb x gravity acceleration x piston speed Kb = -200 (Kgm / sec ² ) Fa = Kc x gravity acceleration x piston speed Kc =- 20 to −300 (Kgm / sec ² ) is the case where the damping force Fa is almost zero, is the case of the conventional suspension device, and is the case of the suspension device according to the present invention. Indicates the range that can be taken by.

Then, the vertical acceleration α of the vehicle body 2 is obtained by the following equation based on the above relationship.

α = (Fa + Fs) / M For this result, the type of the above hydraulic shock absorber,
Each of them is shown in FIG. 8, FIG. 9 and FIG.

Hereinafter, description will be given based on four sections A, B, C, and D in each drawing.

(I) Section A When the vehicle 1 rides on the convex portion 31a of the road surface 31, both the coil spring 6 and the hydraulic shock absorber 7 are contracted.
In the figure, a spring force Fs is generated in the coil spring 6 and a damping force Fa is generated in the hydraulic shock absorber 7. At this time, the spring force
Since both Fs and damping force Fa act upward in FIG. 7, the vertical acceleration α of the vehicle body 2 is obtained based on the sum of them, and the vertical acceleration α of the vehicle body 2 in FIG. It becomes larger than the vertical acceleration α of the vehicle body 2 in FIG.

On the other hand, in FIG. 10, when the coil spring 6 and the piston rod 16 of the hydraulic shock absorber 7 start to contract, the point c1 of the elongated hole 26 faces the third communicating passage 21, and the fourth communicating passage 22 has an elongated hole. 27
C2 points. Therefore, in the hydraulic shock absorber 7, the damping force Fa becomes extremely small when the piston rod 16 is shortened (C1 in FIG. 5), and the fluctuation of the vehicle body 2 is almost controlled by the spring force Fs. Therefore, the vertical acceleration α of the vehicle body 2 is determined based on the spring force Fs, and its value is substantially equal to that in the case of FIG.

(II) Section B When the vehicle 1 reaches the boundary between the section A and the section B, the distance between the vehicle body 2 and the axle 3 starts to be restored, and the coil spring 6 and the piston rod 16 of the hydraulic shock absorber 7 are extended. Will be done. At this time, the coil spring 6 has a reference length L.
The spring force Fs acts upward in the figure because it is shorter than the above, and the damping force Fa of the hydraulic shock absorber 7 as the piston rod 16 extends in the hydraulic shock absorber 7 is:
In the figure, it acts downward. in this way,
Since the directions of the spring force Fs and the damping force Fa are opposite,
In the cases of Fig. 10 and Fig. 10, the spring force Fa and the damping force Fa try to cancel each other out.

However, in the case of FIG. 9, since the damping force Fa is not set for the purpose of completely canceling the spring force Fs, the spring force is not set.
The total sum of Fs and the damping force Fa becomes large, and becomes large as the vertical acceleration α of the vehicle body 2 increases.

On the other hand, in the case of FIG. 10, the c2 point of the elongated hole 27 faces the fourth communication passage 22 in the section A already, and the damping force Fa when the piston rod 16 is extended at this time is Fa.
Becomes extremely large (C2 in Fig. 5). The damping force Fa is adjusted so as to be substantially equal to the spring force Fs in the section B, and the movable plate 25 is moved to correspond to the change of the spring force Fs in order to make the damping force Fa equal to the spring force Fs. , Rotate slightly clockwise. Therefore, the sum of the spring force Fs and the damping force Fa is
Since the respective directions are opposite to each other, they cancel each other almost completely, and the vertical acceleration α of the vehicle body 2 becomes substantially zero.

(III) Section C At the boundary between Section B and Section C, the vehicle body 2 and the axle 3
Although the interval between and becomes the reference length L, when entering the section C, both the coil spring 6 and the piston rod 16 of the hydraulic shock absorber 7 are extended. At this time, in the case of FIG. 9, since the coil spring 6 is longer than the reference length L, its spring force Fs acts downward in the figure,
In the hydraulic shock absorber 7, since the piston rod 16 extends, the damping force Fa thereof acts downward in the figure. Therefore, the sum of the two Fs and Fa becomes large, and the vertical acceleration α of the vehicle body 2 becomes larger than that in the case of FIG.

On the other hand, in the case of FIG. 10, when the coil spring 6 and the piston rod 16 of the hydraulic shock absorber 7 begin to expand, the movable plate 25 rotates and the point a2 of the long hole 27 is generated in the fourth communication passage 22. Facing
The a1 point of the long hole 26 faces the third communication passage 21. Therefore, in the hydraulic shock absorber 7, the damping force Fa becomes extremely small when the piston rod 16 is extended (see A in FIG. 5).
2), the fluctuation of the vehicle body 2 is mostly controlled by the spring force Fs. Therefore, the vertical acceleration α of the vehicle body 2 is determined based on the spring force Fs, and its value is substantially equal to that in the case of FIG. 8 and smaller than that in the case of FIG. 9.

(IV) Section D When entering section D from section C, the distance between the vehicle body 2 and the axle 3 starts to be restored, and the coil spring 6 and the piston rod 16 of the hydraulic shock absorber 7 contract. At this time, since the coil spring 6 is longer than the reference length L, its spring force Fs acts downward in the drawing, and in the hydraulic shock absorber 7, as the piston rod 16 shortens. The damping force Fa acts upward in the figure. Thus, the spring force Fs and the damping force Fa
Since the directions of and are opposite to each other, the spring force Fs and the damping force Fa try to cancel each other out in the cases of FIGS. 9 and 10.

However, in the case of FIG. 9, since the damping force Fa is not set for the purpose of completely canceling the spring force Fs, the spring force is not set.
The sum of Fs and damping force Fa becomes large, and the vertical acceleration α of the vehicle body 2 becomes large.

On the other hand, in the case of FIG. 10, in the section A, the point a1 of the elongated hole 26 faces the third communication passage 21, and when the piston rod 16 is shortened at this time, the damping force Fa
Becomes extremely large (A1 in Fig. 5). The damping force Fa is adjusted so as to be substantially equal to the spring force Fs in the section D, and the movable plate 25 corresponds to the change in the spring force Fs in order to make the damping force Fa equal to the spring force Fs. , Rotate slightly counterclockwise. Therefore, the sum total of the spring force Fs and the damping force Fa cancels each other out substantially because the respective directions are opposite to each other, and the vertical acceleration α of the vehicle body 2 becomes substantially zero.

As described above, the vertical acceleration α of the vehicle body 2 is made extremely small with the sections A to D as one cycle, and the vertical acceleration α prevents the occupant from feeling uncomfortable.

Although one embodiment has been described above, the present invention includes the following modes.

Instead of the long holes 25 and 26, the movable plate 25 is provided with a plurality of orifices that can face the third and fourth communication passages 21 and 22,
The damping force Fa may be adjusted by changing the opening area of each orifice and selecting the orifice.

In order to detect the spring force Fs, the mounting portion of the coil spring 6 or the strain of the spring itself may be detected.

In order to detect the piston speed (suspension speed), the speed itself may be directly detected.

The acceleration sensor utilizing the inertial force of the weight may be used to detect the vertical acceleration α of the vehicle body 2 and perform feedback control such that the damping force Fa of the hydraulic shock absorber 7 is controlled according to the detected state. .

The vertical acceleration α of the vehicle body 2 may be detected by detecting strain or the like at the mounting portion of the hydraulic shock absorber 7.

The spring is a leaf spring having a damping action,
It may be an air spring or the like.

[Brief description of drawings]

FIG. 1 is a conceptual view showing a suspension device according to the present invention mounted on a vehicle, FIG. 2 is a longitudinal sectional view showing a hydraulic shock absorber according to the present invention, FIG. 3 is a plan view showing a movable plate, and FIG. Is a control system diagram according to the present invention, FIG. 5 is a damping force characteristic diagram according to the present invention, FIG. 6 is a schematic diagram showing a running state of a vehicle, and FIG. 7 is a coil spring, a hydraulic shock absorber, and a vehicle body mass. A schematic diagram, FIG. 8 is a characteristic diagram showing each characteristic in the case of a damping force characteristic depending on a coil spring, and FIG. 9 is a conventional damping force characteristic when a coil spring and a hydraulic shock absorber are used. FIG. 10 is a characteristic diagram showing each characteristic in the case, and FIG. 10 is a characteristic diagram showing each characteristic in the case of the present invention. 1 ... Vehicle, 2 ... Car body 3 ... Axle, 4 ... Suspension device 6 ... Coil spring 7 ... Hydraulic shock absorber, 8 ... Displacement sensor 30 ... Control circuit, 31 ... Road surface Fa ... Damping Force, Fa …… Spring force L …… Standard length

Claims (1)

[Claims] 1. A suspension system provided between an axle of a vehicle and a vehicle body, comprising spring means for absorbing impact from a road surface and a shock absorber for damping vibration of the vehicle body, wherein a damping force characteristic of the shock absorber is provided. A detection means capable of selecting at least two stages of high and low damping force characteristics on the extension side and the contraction side, respectively, and further detecting whether or not the distance between the vehicle body and the axle of the vehicle is smaller than the reference state. Based on the detection result of the detection means, when the distance between the vehicle body and the axle is larger than the reference state, the damping force characteristic of the shock absorber is a combination of low damping force on the extension side and high damping force on the contraction side, and When the distance between the vehicle body and the axle is smaller than the reference state, there is provided a control means for combining the damping force characteristics of the shock absorber with a high damping force on the extension side and a low damping force on the contraction side. Suspension system.