JPH0427612A - Suspension device of vehicle - Google Patents

Abstract

PURPOSE:To provide rolling restraint effect sufficiently by changing a damping characteristics in a deadband at springing absolute speed to the low damping side for good ride comfortability in an ordinary case, and to the high damping side when springing input is large. CONSTITUTION:Respective shock absorbers 1-4 installed at front wheels 51, and rear wheels 6L on the right and left is designed so that the damping characteristics may be changed to two stages of high and low through built-in actuators, and houses a vehicle height sensor which a relative displacement between a vehicle body (springing) and an axle (unspringing). For a control unit 8 which outputs control signals for the respective actuators and variably controls the damping characteristics, detected signals are outputted from the vehicle height sensor. The control unit 8 makes a change to the high damping side in a deadband at a springing absolute speed when a springing input such as steering angle and steering speed is large.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension system for a vehicle, and particularly relates to an improvement in a suspension system that includes a shock absorber with variable damping force characteristics between a sprung portion and an unsprung portion.

(Prior Art) Generally, in a vehicle suspension system, a shock absorber is provided between a sprung mass (on the vehicle body side) and an unsprung mass (on the wheel side) for damping vertical motion of the wheel. This shock absorber has a variable damping force characteristic, one in which the damping force characteristic (characteristics with different damping coefficients) can be changed in two stages, high and low, and one in which the damping force characteristic can be changed in multiple stages or continuously. There are a lot of things.

The control method for such a shock absorber with variable damping force characteristics basically changes the damping force characteristics of the shock absorber when the damping force generated by the shock absorber acts in the excitation direction against the vertical vibration of the vehicle body. Set it to the low damping side (that is, the soft side), and set the damping force characteristics of the shock absorber to the high damping side (that is, the hard side) when the damping force acts in the damping direction.
This is to increase the allocated energy with respect to the excitation energy transmitted to the spring, thereby improving both ride comfort and handling stability of the vehicle.

Various methods have been proposed for determining whether the damping force of the shock absorber acts in either the excitation direction or the damping direction of the sprung ball under-ball vibration. For example, JP-A-6
In '0-248419, it is investigated whether the sign of the relative displacement between the sprung mass and the sprung mass and the sign of the relative velocity of the sprung mass and the sprung mass, which is its differential value, match. A method is disclosed in which the direction is determined to be the vibration excitation direction when the time is different, and the direction is determined to be the vibration damping direction when there is a discrepancy.
Publication No. 011 states that it is checked whether the sign of the absolute speed of the sprung mass matches the sign of the relative speed of the sprung mass, and if they match, it is determined that the damping direction is applied, and if they do not match, the direction of vibration is suppressed. A method for determining the direction is disclosed.

In addition, in such control, a dead zone region is generally provided to prevent the damping force characteristics of the shock absorber from being frequently switched in response to displacements near the neutral position. For example, Japanese Utility Model Application Publication No. 63-40213 discloses that in changing and controlling the damping force characteristics based on the coincidence or mismatch between the sign of the relative displacement between the sprung top and the sprung bottom and the sign of the relative velocity between the sprung top and the bottom, A dead band area is provided for relative displacement between the sprung and unsprung parts, and within the dead band area, the damping force characteristic of the shock absorber is always maintained on the low damping side, and when the main spring input such as the steering angle or steering angular velocity is large, the above-mentioned It is disclosed that rolling of a vehicle can be suppressed by reducing the width of a dead zone region.

(Issue 8 to be solved by the invention) However, since the sprung mass relative displacement occurs at a relatively late point in the process in which rolling occurs due to the action of the spring main input, this sprung mass Merely reducing the width of the relative displacement dead zone region cannot expect a sufficient effect of suppressing rolling.

The present invention has been made in view of the above, and its purpose is to reduce the absolute displacement of the sprung mass compared to the relative displacement of the sprung mass and the sprung mass, especially in the process where rolling occurs due to the action of the spring main input. The speed is faster (see what happens,
The present invention aims to provide a vehicle suspension system that controls the damping force characteristics of a shock absorber based on the sprung absolute speed, etc., and that can appropriately control the dead zone and sufficiently exert the effect of suppressing rolling. .

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides a shock absorber with changeable damping force characteristics provided between a sprung mass and a sprung mass, and a sprung mass absolute velocity. A sprung mass absolute speed detection means detects the relative speed between the sprung mass and the sprung mass, and a relative speed detection means detects the relative speed between the sprung mass and the sprung mass. When the product is greater than a predetermined value, the damping force characteristic of the shock absorber is changed to a high damping side, and when the product is below a predetermined value, the damping force characteristic of the shock absorber is changed to a low damping side. and control means for controlling. Furthermore, for the control of the control means, a dead zone region is provided for regulating changes in the damping force characteristics when the absolute value of the sprung mass absolute speed is at least a predetermined value or less, and within the dead zone region, the damping force of the yoke absorber is controlled. A dead band setting means that maintains the characteristics on the low damping side, and a correction for the dead band setting means to change the damping force characteristic within the dead band region of the sprung mass absolute speed to the high damping side when the spring main input is large. The present invention is configured to include dead zone correction means.

(Function) With the above configuration, in the present invention, when the spring input such as the steering angle or the steering angular velocity is large, the damping force characteristic within the dead zone head of the spring mass ground speed is shifted to the high damping side by the dead zone correction means. As a result of this change, the shock absorber generates a large damping force from an early point in the process when the vehicle rolls from the sprung input.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a component layout of a suspension device according to an embodiment of the present invention.

In FIG. 1, 1 to 4 are four shock absorbers provided corresponding to the left and right front wheels 5L (only the left front wheel is shown) and the rear wheel 6L (only the left rear wheel is shown), This dampens the vertical movement of each wheel.

Each of the shock absorbers 1 to 4 has a built-in actuator 25 (see Fig. 2) that allows the damping force characteristics to be changed to two levels, high and low.
It has a built-in vehicle height sensor (not shown) that detects the relative displacement between the vehicle and the axle (unsprung). Reference numeral 7 denotes a coil spring disposed on the upper outer periphery of each of the above-mentioned shock absorbers 1 to 4, and 8 a control that outputs a control signal to the actuator in each of the above-mentioned shock absorbers 1 to 4 to variably control its damping force characteristics. unit, each of the above-mentioned stock absorbers 1 to 4 toward the control unit 8.
A detection signal is output from the vehicle height sensor inside.

Further, 11 to 14 are four acceleration sensors that detect the acceleration in the vertical direction (Z direction) on the springs of each wheel, 15 is a vehicle speed sensor installed in the meter of the instrument panel that detects the vehicle speed, and 16 is a vehicle speed sensor that detects the vehicle speed. A steering angle sensor detects the steering angle of the front wheels from the rotation of the steering shaft, 17 is an accelerator opening sensor that detects the accelerator opening, and 18 is a sensor that detects whether the brake is in operation (that is, whether or not it is braking) based on the brake fluid pressure. ), and 19 is a brake pressure switch that detects the damping force characteristics of shock absorbers 1 to 4.
This is a mode selection switch that switches to either mode D, 5OFT, or C0NTR0L, and these sensors 11
17 and switches 18 and 19 are all outputted to the control unit 8.

FIG. 2 shows the structure of the shock absorbers 1 to 4,
Figure 2A shows that the damping force characteristics of shock absorbers 1 to 4 are H.
When the characteristics are ARD (characteristics with high damping coefficient), the second B
The diagram shows the damping force characteristics of shock absorbers 1 to 4 as 5OFT.
Indicates when the characteristic is low (low damping coefficient). Note that vehicle height sensors built into the shock absorbers 1 to 4 are omitted in this figure.

In FIG. 2, 21 is a cylinder, and a piston unit 22 formed by integrally molding a piston and a piston rod is slidably inserted into the cylinder 21. The cylinder 21 and piston unit 22 are
They are connected to the axle (unsprung) or the vehicle body (sprung) via separate connection structures.

The piston unit 22 has two orifices 23.
24 are provided. Orifice 2 of one of them
3 is always open. Further, the other orifice 24 is provided so as to be openable and closable by an actuator 25. The actuator 25 includes a solenoid 26 and a control rod 2.
7 and two springs 28a and 28b. The control rod 27 is configured to move up and down within the piston unit 22 by the magnetic force received from the solenoid 26 and the urging force received from both springs 28a and 28b, thereby opening and closing the orifice 24.

The upper chamber 29 and lower chamber 30 in the cylinder 21 and the cavities in the piston unit 22 communicating with these two chambers 29, 30 are filled with a fluid having an appropriate viscosity. This fluid can move between the upper chamber 29 and the lower chamber 30 through any of the orifices 23,24.

In the above configuration, the shock absorbers 1 to 4 perform the following operations.

That is, when the solenoid 26 is not energized, the force of the spring 28a that biases the control rod 27 in the γ direction is set to be stronger than the force that biases the control rod 27 upward by the spring 28b. rod 2
7 is pressed downward, closing the orifice 24 (see Figure 2A). Therefore, the fluid path is through orifice 2.
3, and the damping force characteristics of these shock absorbers 1 to 4 are HA and RD (high damping) characteristics.

Further, when the solenoid 26 is energized, the control rod 27 is pulled upward by the magnetic force of the solenoid 26, and the orifice 24 is opened (see FIG. 2B). Therefore, both the orifices 23 and 24 serve as passages for fluid, and the damping force characteristics of the shock absorbers 1 to 4 become 5OFT (low damping) characteristics.

As mentioned above, the shock absorbers 1 to 4 have HARD characteristics when the solenoid 26 is not energized, so
Even if the control unit 7 should fail, the shock absorbers 1 to 4 can maintain the HA and RD characteristics and prevent deterioration of steering stability.

Figure 3 shows the vibration model of the suspension device, with ms
is sprung mass, mu is sprung mass, ZS is sprung displacement,
ZU is the unsprung displacement, ks is the spring constant of the coil spring 7, kt is the spring constant of the tire, and v (t) is the damping coefficient of the shock absorber.

FIG. 4 shows a block configuration of the control section of the suspension device. In FIG. 4, the first vehicle height sensor 41, acceleration sensor 11, and actuator 25a are connected to the front wheel '5 on the left side of the vehicle body.
L, the second vehicle height sensor 42, acceleration sensor 12 and actuator 25b are connected to the front wheel on the right side of the vehicle body, and the third vehicle height sensor 43, acceleration sensor 13 and actuator 2 are connected to the front wheel on the right side of the vehicle body.
5c is a fourth vehicle height sensor 44 on the rear wheel 6L on the left side of the vehicle body;
The acceleration sensor 14 and the actuator 25d each correspond to the rear wheel on the right side of the vehicle body. Incidentally, the actuators 25a to 25d are the actuator 2 in FIG.
The vehicle height sensors 41 to 44 are built into the shock absorbers 1 to 4.

In addition, r1 to "4 are the first to fourth vehicle height sensors 4, respectively.
These are sprung and unsprung relative displacement signals outputted from 1 to 44 toward the control unit 8, and all of these signals take continuous values. This signal is positive when the shock absorbers 1 to 4 extend, and negative when they contract.

Note that the relative displacement when the vehicle is stationary (that is, the difference between the sprung mass displacement ZS and the sprung mass displacement ZU shown in Fig. 3) is
ZU) is set to zero, and the deviation from this represents the magnitude of relative displacement.

zG1 to 2Ga are the first to fourth acceleration sensors 11, respectively.
These are absolute sprung acceleration signals in the vertical direction (Z direction) outputted from ~14 toward the control unit 8, and all of these signals take continuous values. This signal is positive when the sprung mass is subjected to upward acceleration, and negative when the sprung mass is subjected to downward acceleration.

In addition, the vehicle speed signal ■S is sent from the vehicle speed sensor 15, the steering angle signal θH is sent from the steering angle sensor 16, and the accelerator opening sensor 1
7 outputs an accelerator opening signal TVO to the control unit 8, and all of these signals take continuous values.

The vehicle speed signal S is positive when the vehicle is moving forward, and negative when the vehicle is moving backward by 1-1. As seen from the driver's side, the steering angle signal θ11 is positive when the steering wheel rotates counterclockwise (that is, when turning left), and negative when it rotates clockwise (that is, when turning right). do.

Furthermore, a brake pressure signal BP is output from the brake pressure switch 18 to the control unit 8, and this signal has two values: ON and OFF. ON means that the brake is being operated, and OFF means that it is not.

vl~■4 are actuator control signals output from the control I/roll unit 8 to the actuators 25a~25d, respectively, and these signals are "1" and "
It takes a binary value of 0. When “1”, actuator 2
No. 5 solenoid 26 (see FIG. 2) is not energized, and the damping force characteristics of the shock absorbers 1 to 4 become HARD characteristics.

When the value is "0", the solenoid 26 of the actuator 25 is energized, and the damping force characteristics of the shock absorbers 1 to 4 become 5OFT characteristics.

Furthermore, a mode selection signal is output from the mode selection switch 19 to the control unit 8, and this signal is a plurality of parallel signals, and in the case of this embodiment, a HARD
, '5OFT, C0NTR0L. HARD
indicates that the driver has selected HARD mode.
FT indicates that 5OFT mode is selected, C0NT
R0L means that the C0NTR0L mode is selected. As described later, when HARD, the damping force characteristics of all shock absorbers 1 to 4 are fixed to HARD characteristics, and when 5OFT, damping force characteristics of all shock absorbers 1 to 4 are fixed to 5OFT characteristics, and C0
At NTR0L, the damping force characteristics of each of the shock absorbers 1 to 4 are automatically and independently switched to HARD or 5OFT characteristics depending on the vehicle motion state, road surface state, etc.

FIG. 5 shows the control flow of the control unit 8.

This control operation is executed by a control program installed in the control unit 8. This control program is run at a fixed period (1
~10 m, s). This control operation will be explained below along the flow.

First, in step S1, it is determined whether the mode selection signal is HARD. When this determination is YES (HARD), in step S19 the actuator control signals v1 to
All of v4 are set to "1", and in step S13, the control signals ■1 to V4 are output. As a result, the damping force characteristics of all the shock absorbers 1 to 4 become HARD characteristics. In this case, the operation ends.

When the value of the mode selection signal is not HARD, it is subsequently determined in step S2 whether the value of the mode selection signal is 5OFT, and when the determination is YES (5OFT), the actuator control signals v1 to v are activated in step S20.
4 is set to "0", and in step 313, the control signals (1) to (4) are output. As a result, the damping force characteristics of all the shock absorbers 1 to 4 become 5OFT characteristics. In this case, the operation ends.

The determinations in both steps SL and S2 are N.

In other words, when the value of the mode selection signal is C0NTR0L, in step S3, after inputting the sprung/unsprung relative displacement signals "1 to r4," in step S4, the relative displacements r1 to r4 are differentiated by numerical differentiation. Then, the relative velocity 11 to t4 between the sprung top and the sprung bottom is determined.The above step S3
．． S4 and the vehicle height sensors 41 to 44 determine the relative speed between the sprung mass and the unsprung mass.
(2s4-2u4)) Relative speed detection means 51 for detecting
is configured.

Subsequently, in step S5, the sprung mass absolute acceleration signal 2G1~
After inputting 2ca, in step S6 this 2c+~2c
Integrate a using numerical integration method etc. to find the absolute sprung mass speed z
Find c+~iG4. These 2G1 to 2G4 are the absolute sprung mass velocities in the vertical direction at the positions of the acceleration sensors 11 to 14, so in step S7 they are set as the absolute sprung mass velocities in the vertical direction i5 at the positions of the shock absorbers 1 to 4.
Convert to 1-2S4. 231~ZS4 is zc~fc
If you know 3 of 4, you can find it, so below,
It is assumed that fc+~2G3 is used, and ia4 is a preliminary value. Here, as shown in Fig. 1, when the origin is appropriately set in the horizontal plane and the xy coordinates are taken, the acceleration sensor 1
The coordinates of 1 to 13 are (xc+, yc+) ~ (XG
3, XG3), the coordinates of shock absorbers 1 to 4 are (xs+, ys+) to (XS4 rys4
), 2s+ to fs4 can be obtained using the following formula.

However, the two coefficient matrices and their product are calculated in advance,
It is given as a constant. Each shock absorber 1-
Absolute speed of spring 1 in the vertical direction at position 4 2s+~2
A sprung absolute speed detection means 52 is configured to detect s4.

Subsequently, after inputting the steering angle (steering angle signal) θH in step S8, the absolute value of this steering angle θH is set to a predetermined value θ in step S9.
Determine whether it is greater than 0.

If this determination is No, in step SIO, the absolute speed of spring 1 for each wheel: lsi (l −1, 2, 3° 4
) is smaller than a predetermined value δ.

When the determination in step SIO is No, the determination function h1 is determined in step Sll using the following equation.

hz -il ・2si (i-1, 2, 3, 4
) In other words, this determination function h1 is the value of the product of the relative speed N between the sprung and unsprung parts of each wheel and the absolute sprung speed deficit s1.

Subsequently, in step SL2, if the judgment function hi is zero or a positive value (hi≧0), it is set to vl-1, and if the judgment function h1 is a negative value (hl < 0), it is set to vi-0. do. Thereafter, in step S13, actuator control signals 1 to v4 are output, and the process returns. Step S above
A determination function hi, which is the product of the absolute speed of the spring 1 and the relative speed between the upper and lower parts of the spring, is calculated using Ll~81B, and the determination function hi for each shock absorber 1~4 is calculated depending on whether the determination function h1 is greater than or equal to zero. The damping force characteristics of HARD characteristics or 5OFT
A control means 53 is configured to control changes to the characteristics.

On the other hand, when the determination in step SIO is YES,
The corresponding actuator control signal v1 in step S14
This control signal v is set in step S15.
Returns after outputting i. Here, the predetermined value δ of the determination formula in step lO has the meaning of the dead zone constant and (-) for the spring mass absolute velocity vs. When the absolute value of fs+ is less than or equal to this predetermined value δ, a dead zone region is provided that restricts changes in the damping force characteristics, and within the dead zone region, the damping force characteristics of shock absorbers 1 to 4 are set to 5.
A dead zone setting means 54 is configured to maintain the OFT characteristic.

Further, when the determination in step S9 is YES, that is, when the steering angle θ11 is greater than or equal to the predetermined value 00, step 31
In step 6, it is determined for each wheel whether the absolute value of the absolute speed 2si of the spring 1 is smaller than a predetermined value δ which is a dead zone constant, and if the determination is No, the process moves to step Sll, whereas if the determination is YES, the process moves to step Sll. In step S17, the corresponding actuator control signal Vj is set to "1", and in step S1
After outputting this control signal vi at step 8, the process returns. Such step S9. By SL6 to S18, when the steering angle θH which is the spring force is large, the absolute speed of the spring 1 is 2si
A dead zone correction means 55 is configured to change and correct the damping force characteristic within the dead zone region to a HARD characteristic.

Therefore, according to such control, driver f)<C
When the 0NTR0L mode is selected, the judgment function h1 is the product of the sprung top/spring bottom relative speed ri (-2si-fui) and the spring 1 absolute speed 2si, 1"1 ・fsl.
When is zero or a positive value (h1≧O) (that is, when the sprung mass moves upward, shock absorbers 1 to 4 extend and their damping force acts downward, and the sprung mass moves downward. and when the shock absorbers 1 to 4 contract and their damping force acts upward), the shock absorbers 1 to 4
It is determined that the damping force generated by the shock absorbers 1 to 4 acts in a damping direction against the vertical vibration on the spring, and the damping force characteristics of the shock absorbers 1 to 4 are changed to HARD characteristics.

Also, when the above judgment function h1 is a negative value (hl 0) (
In the opposite case), it is determined that the damping force generated by the shock absorbers 1 to 4 acts in the excitation direction against the vertical vibration on the spring, and the damping force characteristics of the shock absorbers 1 to 4 are 5OFT. changed to a characteristic. As a result, the damping energy becomes larger than the excitation energy transmitted to the spring, and both riding comfort and steering stability can be improved.

Moreover, the absolute value of the sprung mass absolute speed zS1 is the predetermined value δ.
When the sprung mass vibrates within a dead band region smaller than , changes in the damping force characteristics of the corresponding shock absorbers 1 to 4 are restricted, so noise and vibration due to unnecessary and frequent changes in the damping force characteristics are prevented. This can be prevented from occurring. Further, in this case, the damping force characteristics of the shock absorbers 1 to 4 are maintained at 5OFT characteristics, and riding comfort is improved.

Furthermore, when the steering angle θH is manipulated to a large extent and the vehicle rolls due to this, the sprung absolute speed 2s
The damping force characteristic in the dead zone region of l has been changed to a HARD characteristic, and since the sprung absolute speed f61 itself changes relatively quickly with the operation of the steering angle θH, the damping force characteristic is changed from an early point in the rolling process. Shock absorber 1
~4 generates a large damping force, and can fully exhibit the effect of suppressing rolling.

It should be noted that the present invention is not limited to the above embodiments, but includes various other modifications.

For example, in the above embodiment, the relative velocity ri between the sprung and unsprung parts
The damping force characteristics of the shock absorbers 1 to 4 are changed to HARD or 5OFT depending on whether the judgment function hi, which is the product of zsi and the absolute sprung speed zsi, is equal to or greater than zero. In the present invention, the damping force characteristics of the shock absorbers 1 to 4 may be changed depending on whether or not the judgment function hJ is larger than a predetermined value other than zero. It may also be a variable that changes depending on the steering angle. In this case, if the predetermined value is a positive value, the damping force characteristic of the shock absorber will be closer to 5OFT,
If the predetermined value is a negative value, the damping force characteristic of the shock absorber will be closer to HARD.

In addition, in the above embodiment, the dead zone correction means 55 is configured to correct the damping force characteristic within the dead zone region of the sprung absolute speed 2si to a high damping side when the steering angle θH is large. Similarly, when other sprung inputs such as steering force and deceleration are large, the damping force characteristic within the dead zone region of the sprung absolute speed 2si may be similarly corrected to change to the high damping side.

Further, in the above embodiments, the damping force characteristics of the shock absorbers 1 to 4 can be changed to two stages of high and low levels, but the present invention provides for changing the damping force characteristics of the shock absorbers to three or more stages or continuously. Of course, the same can be applied to cases where it is possible to change the structure.

(Effects of the Invention) As described above, according to the vehicle suspension device of the present invention, the damping force characteristic within the dead zone region of the sprung absolute speed is normally set to the low damping side to provide good ride comfort.
By changing to the high damping side when the sprung mass input is large, the shock absorber generates a large damping force from an early point in the rolling process caused by the sprung mass input, thereby fully demonstrating the rolling suppression effect. I can do it.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a perspective view showing the component layout of the suspension device, FIG. 2 is a vertical side view showing the main parts of the shock absorber, and FIG. 3 is a vibration model of the suspension device. FIG. 4 is a block configuration diagram of the control section of the suspension device, and FIG.
The figure is a flowchart diagram showing the control flow. 1 to 4...Shock absorber 51...Relative speed detection means 52...Spring 1 Absolute speed detection means 53...Control means 54...Dead band setting means 55/Dead band correction means 2nd A section closed 2B section

Claims (1)

[Claims] (1) A shock absorber with changeable damping force characteristics provided between the sprung mass and the unsprung mass, a sprung mass absolute speed detection means for detecting the sprung mass absolute speed, and a shock absorber between the sprung mass and the unsprung mass. Relative speed detection means for detecting relative speed; Receiving signals from both of the above-mentioned detection means, calculates the product of the absolute sprung speed and the relative speed between the sprung portion and the sprung portion, and when the product is greater than a predetermined value, the above-mentioned shock is applied. a control means for controlling the damping force characteristic of the shock absorber to a high damping side and changing the damping force characteristic of the shock absorber to a low damping side when the damping force characteristic is lower than a predetermined value; a dead zone setting means for providing a dead zone region that restricts changes in damping force characteristics when the absolute value of the speed is less than a predetermined value, and maintaining the damping force characteristics of the shock absorber on the low damping side within the dead zone region; and a sprung mass input. A suspension for a vehicle, characterized in that it is provided with a dead band correction means for correcting the dead band setting means so as to change the damping force characteristic within the dead band region of the sprung absolute speed to a high damping side when the dead band setting means is large. Device.