JPH042517A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To improve riding comfortableness and control stability by varying damping force property to a low-damping side when damping force generated in a shock absorber operates in an exciting direction to up-and-down vibration on a spring and to a high-damping side when it operates in a damping direction. CONSTITUTION:Each shock absorber to damp up-and-down movement of each wheel has actuators 25a-25d built in and able to vary and change over, across two high and low stages, damping force property, which is controlled by a control unit 8. In the control of the damping force property, absolute velocity above or below a spring and relative velocity between those above and below the spring is detected, and the product of those velocities is computed. When the product is a preset value or larger, the damping force property of the shock absorber is varied to the high-damping side, when it is smaller than the preset value, the damping force property is varied to the low-damping side, and the preset value is changed with road conditions.

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) to damp the vertical movement 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 all kinds of things.

As a control method for such a shock absorber with variable damping force characteristics, for example, Japanese Patent Application Laid-Open No. 61-16301
As disclosed in Publication No. 1, the unsprung absolute velocity and the relative velocity between the sprung mass and the unsprung mass are detected by respective detection means, and the sign of the unsprung absolute velocity and the sign of the relative velocity match. If the signs do not match, it is determined that the damping force generated by the shock absorber is acting in the excitation direction against the vertical vibration of the vehicle body, and the damping force characteristics of the shock absorber are set to the low damping side. (in other words, the soft side), and when the signs match, it is determined that the damping force is working in the damping direction, and the damping force characteristic of the shock absorber is switched to the high damping side (in other words, the hard side), and the It is known that the damping energy is increased relative to the transmitted excitation energy to improve the riding comfort and steering stability of the vehicle.

In addition, the unsprung absolute speed is detected instead of the unsprung absolute speed,
A method of switching the damping force characteristics of the shock absorber depending on whether or not the sign of the absolute speed of the sprung portion matches the sign of the relative speed between the sprung portion and the unsprung portion, or alternatively, the shock The actual damping force of the shock absorber is detected, and the shock absorber is adjusted depending on whether the sign of this damping force matches the sign of the skyhook damper force, which is the ideal damping force calculated from the unsprung absolute speed. A similar effect can be obtained by switching the damping force characteristics.

(Problem to be Solved by the Invention) However, in the conventional control method described above, when the sprung mass of the vehicle undergoes high-frequency vibration due to unevenness of the road surface, the sign of the absolute speed of the sprung mass and the relative velocity between the sprung mass and the sprung mass are The sign of
There is a problem in that the damping force characteristics of the shock absorber change unnecessarily and frequently every time there is a change between mismatches, resulting in loud noises and vibrations. In addition, when the damping force characteristic of the shock absorber is switched to the high damping side, unsprung vibrations generated due to unevenness of the road surface are easily transmitted to the spring, causing a bumpy feeling and worsening ride comfort.

The present invention has been made in view of the above, and its purpose is to prevent the damping force characteristics of the shock absorber from unnecessarily moving toward the high damping side when the sprung mass vibrates at high frequencies due to unevenness of the road surface. It is an object of the present invention to provide a suspension device for a vehicle that can prevent noise and vibration from occurring and improve riding comfort.

(Means for solving the problem) In order to achieve the above object, the invention described in claim (1):
A shock absorber with changeable damping force characteristics provided between a sprung mass and an unsprung mass, a sprung mass/unsprung absolute speed detection means for detecting a sprung mass absolute speed or a sprung mass absolute speed, and a sprung mass and a sprung mass. a relative speed detection means for detecting the relative speed between the lower part and the lower part; and receiving signals from both of the above-mentioned detection means, and calculating the product of the sprung part absolute velocity or the unsprung part absolute velocity and the sprung part relative velocity; control means for controlling the damping force characteristic of the shock absorber to be changed to a high damping side when the product is above a predetermined value, and to change the damping force characteristic of the shock absorber to a low damping side when the product is below a predetermined value; The vehicle is configured to include a predetermined value changing means for changing the value according to the condition of the road surface.

The invention according to claim 2 provides a shock absorber with changeable damping force characteristics provided between a sprung portion and an unsprung portion;
A sprung picture vs. speed detection means for detecting an absolute sprung speed;
a skyhook damper force calculation means that receives a signal from the detection means and calculates a skyhook damper force that is a function value of the unsprung absolute velocity; a damping force detection means that detects the damping force of the shock absorber; Receiving the signal from the skyhook damper force calculation means and the signal from the damping force detection means, calculates the product of the skyhook damper force and the damping force of the shock absorber, and when the product is greater than a predetermined value, the shock absorber is activated. A control means for controlling the damping force characteristic of the shock absorber to be changed to a high damping side and to a low damping side when the damping force characteristic is less than a predetermined value, and changing the predetermined value according to the condition of the road surface. The configuration includes a predetermined value changing means.

The invention set forth in claim (3) is characterized in that the predetermined value changing means in the invention set forth in claim (1) multiplies the square of the sprung upper-spring lower relative speed detected by the relative speed detecting means by a gain value. The configuration is such that a predetermined value is set by

The invention set forth in claim (4) is such that the predetermined value changing means in the invention set forth in claim (2) is set by multiplying the square value of the shock absorber damping force detected by the damping force detection means by a gain value. It is configured to set a value.

The invention described in claim (5) is the invention described in claim (3) or (4) above.
In the invention described in ), the gain value in the predetermined value calculation formula is set to gradually decrease as the vehicle speed increases.

The invention described in claim (6) is based on the above claim (3) or (4).
In the invention described in ), the gain value in the predetermined value calculation formula is set to gradually decrease as the steering angle increases.

(Function) With the above configuration, in the invention described in claim (1), the absolute speed detection means determines the sprung mass absolute speed or the sprung mass absolute velocity, and the relative speed detection means determines the relative speed between the sprung mass and the sprung mass. is detected, and under the control of the control means that receives signals from both of the detection means, when the product of the sprung mass absolute speed or the sprung mass absolute velocity and the sprung mass relative speed is greater than or equal to a predetermined value ( In other words, when the damping force generated by the shock absorber acts in the damping direction against vertical vibration on the spring, the damping force characteristic of the shock absorber is on the high damping side, and when it is below a predetermined value (in other words, when the damping force When the damping force applied to the vertical vibration of the spring acts in the excitation direction), the damping force characteristics of the shock absorber are changed to the lower damping side, thereby reducing the excitation energy transmitted to the spring. The vibration damping energy becomes larger. Moreover, the above predetermined value is changed by the predetermined value changing means according to the condition of the road surface. For example, when the predetermined value is changed to a high value on an uneven road surface where the sprung mass vibrates at high frequency, the damping force characteristic of the shock absorber is changed to a high damping force. It becomes difficult to change sides.

Furthermore, in the invention described in claim (2), the product of the skyhook damper force and the damping force of the shock absorber is used instead of the product of the sprung absolute velocity or unsprung absolute velocity and the sprung-unsprung relative velocity. Depending on whether the product is greater than or equal to a predetermined value (in other words, whether the damping force generated by the shock absorber acts in the excitation direction or in the damping direction with respect to the vertical vibration on the spring). Since the damping force characteristics of the shock absorber are changed to high damping side or low damping side,
As in the case of the invention described in claim (1), damping energy can be increased with respect to excitation energy. Furthermore, the above-mentioned predetermined value can be changed by the predetermined value changing means according to the condition of the road surface, so that the damping force characteristic of the shock absorber can be made difficult to change to the high damping side in the high frequency vibration region.

Here, the predetermined value changing means sets the predetermined value by multiplying the square value of the relative speed between the two springs detected by the relative speed detecting means by a gain value. or when the predetermined value is set by multiplying the value of the square of the shock absorber damping force detected by the damping force detection means by a gain value as in the invention described in claim (4). The predetermined value can be changed to a higher value on an uneven road surface where the sprung mass vibrates at high frequency without requiring a detection means for detecting the state of the road surface.

Further, if the gain value of the predetermined value calculation formula is set to gradually decrease as the vehicle speed increases, as in the invention described in claim (5), or as in the invention as claimed in claim (6), If the damping force characteristics of the shock absorber are set to gradually decrease as the steering angle increases, the damping force characteristics of the shock absorber will be changed depending on the driving condition of the vehicle, such as at high speeds or when turning when the vehicle becomes unstable. At times, the damping force characteristics of the shock absorber are reliably changed to a higher damping side to improve steering stability.

(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 a first embodiment of the present invention.

In FIG. 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), respectively. 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 (two directions) 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 or not the brake is in operation based on the brake fluid pressure (that is, whether or not the brake is being applied). Brake pressure switch 19 detects the damping force characteristics of shock absorbers 1 to 4.
D, 5OFT, C0NTR0I4) This is a mode selection switch that switches to either mode, and these sensors 1
1 to ]7 and the detection signals of 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.
In the ARD state (state that generates high damping force), Figure 2B shows that the damping force characteristics of shock absorbers 1 to 4 are 5O.
This shows the FT state (state that generates low damping force).

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 2. The cylinder 2] and the piston unit 22 are
They are connected to the axle (unsprung) or the vehicle body (spring) via separate connecting 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 the lower chamber 30 in the cylinder 21 and the cavity in the piston unit 22 communicating with this compartment 29,30 are filled with a fluid of appropriate viscosity. This fluid can travel between upper chamber 29 and lower chamber 30 through any of the orifices 2324 described above.

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 downward is set to be stronger than the force of the spring 28b that biases the control rod 27 upward. 27 is pressed downwards, closing the orifice 24 (see Figure 2A). Therefore, the only passage for fluid is the orifice 23, and the damping force characteristics of the shock absorbers 1 to 4 are in a HARD (high damping) state.

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). For this reason,
Both orifices 23 and 24 become fluid passages, and the damping force characteristics of the shock absorbers 1 to 4 are in a 5OFT (low damping) state.

As described above, the damping force characteristics of the shock absorbers 1 to 4 are in the HARD state when the solenoid 26 is de-energized, so even if the control unit 7 should fail, the shock absorbers 1 to 4 will be in the I(ARD maintain the condition,
Deterioration of steering stability can be prevented.

Figure 3 shows the vibration model of the suspension device, with ms
is the sprung mass, rnu is the unsprung mass, ZS is the 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. be.

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 5L on the left side of the vehicle body.
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 25b are connected to the front wheel on the right side of the vehicle body.
c corresponds to the rear wheel 6L on the left side of the vehicle body, and the fourth vehicle height sensor 44, acceleration sensor 14, and actuator 25d correspond to the rear wheel on the right side of the vehicle body. The actuators 25a to 25d are the actuator 25 in FIG.
The vehicle height sensors 41 to 44 are built into the shock absorbers 1 to 4.

Further, r1 to r4 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 zs − between the sprung mass displacement ZS and the sprung mass displacement zu shown in FIG. 3)
zU) is set to zero, and the deviation from this represents the magnitude of relative displacement.

2c+ to 2ca are the first to fourth acceleration sensors 11, respectively.
This is an absolute acceleration signal of the spring 1 in the vertical direction (Z direction) that is 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 vS is positive when the vehicle is moving forward, and negative when the vehicle is moving backward. As seen from the driver's side, the steering angle signal θH is positive when the steering wheel rotates counterclockwise (that is, when turning left) and (7) when the steering wheel rotates clockwise (that is, when turning right). Set as negative.

Furthermore, the brake pressure [q
BP is output 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.

■1 to v4 are actuator control signals output from the control unit 8 to the actuators 25a to 25d, respectively, and these signals are "1" and "0".
” takes two values. When “1”, actuator 25
The solenoid 26 (see FIG. 2) is not energized, and the damping force characteristics of the shock absorbers 1 to 4 are in a HARD state.

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 are in a 5OFT state.

Furthermore, mode selection 1g is selected from the mode selection switch 19.
The number is being output to the control unit 8,
This signal is a plurality of parallel signals, and in this embodiment, HAR
It takes three values: D, 5OFT, and 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 the HARD state, and when 5OFT, the damping force characteristics of all shock absorbers 1 to 4 are fixed to the 5OFT state, and C0
At NTR0L, the damping force characteristics of each of the shock absorbers 1 to 4 are automatically and independently switched to the HARD or 5OFT state depending on the vehicle motion state, road surface state, etc.

FIG. 5 shows the control fly of the control unit 8. This control operation is executed by a control program installed in the hunt roll unit 8. This control program is run at a fixed cycle (
1~10m5) is activated repeatedly. Below, this $-
11! The It operation will be explained along the flow.

First, in step Sl, it is determined whether the mode selection signal is HARD. When this determination is YES (HARD), the actuator control signal vl~
(2) All of 4 are set to "1", and in step 513, the control signals v1 to (4) are output. As a result, the damping force characteristics of all the shock absorbers 1 to 4 become in a HARD state. 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 signal vl~■
4 is set to "0", and the control signals ■1 to v4 are outputted in step S13. As a result, the damping force characteristics of all the shock absorbers 1 to 4 are in the 5OFT state. In this case, the operation ends in step 2.

When the determinations in both steps St and S2 are NO,
That is, when the value of the mode selection signal is C0NTR0L, in step S3, the sprung upper and lower relative displacement signals r1 to r
4 is input, in step S4, these r1 to r4 are differentiated by numerical differentiation method etc., and the relative velocity t between the sprung upper and unsprung lower parts is obtained.
1 to 4 are determined. By the steps S3 and S4 and the vehicle height sensors 41 to 44, the relative speeds t1 to r4 between the sprung mass and the sprung mass are determined. (i sl-之ul) ~(:!54-2u4
) ) is also constructed.

Subsequently, in step S5, the spring ground-to-ground acceleration signal 2c+~
After inputting 2G4, this 2C, 1~2 is input in step S6.
By integrating ca using a numerical integration method or the like, the absolute vehicle body speed in the vertical direction 2c+ to 2G4 is determined. Since this ic+~2ca is the velocity relative to the spring surface in the vertical direction at the positions of the acceleration sensors 11 to 4, it is determined in step S7 that the absolute velocity 2SI'= Convert to ZS4. sI~2S4
Hahe It can be found if two of 2c+ to 2G4 are known, so below we will use 2G1 to 7G3, and 2
G4 is a reserve value. Here, as shown in Figure 1,
The coordinates of the acceleration sensors 11 to 13 are (xG+, ye+
) ~(XG3, yca), the coordinates of shock absorbers 1 to 4 are (xs l+ys+) ~(XS4
, xs4), iS1 to 2s4 are determined by the following formulas.

However, the two coefficient matrices and their product are calculated in advance,
It is given as a constant. Each of the shock absorbers 1-1 through steps 85-S7 and acceleration sensors 1-14
Vertical spring picture vs. speed 2s+-2 at position 4
A spring 1 absolute speed detection means 52 is configured to detect s4.

After 17 steps, the determination function hi is determined using the following equation in step S8.

bf - "i ・:!si (i-1, 2, 3,
4) In other words, this determination function hi is the value of the product of the sprung-upper sprung-lower relative speed l″l and the sprung-top speed versus sprung speed 26i for each wheel.

Subsequently, in step S9, the vehicle speed signal VS and the steering angle signal θ1 are
(After inputting , a gain value g is set in step 510. A pre-stored map shown in FIGS. 6 and 7 is used to set this gain value g, and a gain value g1 corresponding to the vehicle speed is set. The product of the gain value g2 corresponding to the steering angle (gg
It is obtained as l ・g2). The gain g1 is set to gradually decrease as the vehicle speed increases, and the gain value g2 is set to gradually decrease as the steering angle increases. Further, in step Sll, a predetermined value Ki (-g-ri') is set for each wheel by multiplying the gain value g by the square of the relative speed t1 between the sprung and unsprung portions.

After setting the predetermined value to 1, in step 512, if the judgment function hi previously obtained in step S8 is greater than or equal to the predetermined value Ki (hi > Ki), vi -1 is set, and the judgment function h1 is set to 1 to the predetermined value. If the following (hi≦Ki) is satisfied, it is set as vl-0. After this setting, actuator control signals v1 to v4 are output in step S13, and the process returns. Through steps S8, S12, and S13, a determination function h1 is calculated 12, which is the product of the sprung upper-spring lower relative velocity i1 and the sprung upper-spring velocity 2si, and whether or not this determination function hi is larger than a predetermined value Kl. A control means 53 is configured to control the damping force characteristics of each shock absorber 1 to 4 to be changed to a HARD state or a 5OFT state according to the above predetermined value K in steps 89 to Sll.
A predetermined value changing means 54 is configured to change i according to the driving condition of the vehicle and the condition of the road surface. Furthermore, the judgment function h1
When it is equal to the predetermined value ki (hi - Ki), the actuator control signal vi may be left unchanged so that the damping force characteristic is not changed.

Therefore, according to this kind of control, if the driver
When the TR0L mode is selected, the judgment function h1, which is the product of the sprung upper and unsprung relative speed it (-2si-:!ui) and the sprung upper-spring speed 2si, is greater than or equal to the predetermined value K1 ( hi > Ki ) (that is, when the sprung mass moves upward and the shock absorbers 1 to 4 extend and their damping force acts downward), and when the sprung mass moves downward and the shock absorbers 1 to 4 contract. (when the damping force acts upward), shock absorbers 1 to 4
The shock absorber], ~4
The damping force characteristic of is changed to the HARD state.

Further, the above-mentioned judgment function h1 is less than or equal to 1 (hi≦Ki
) (contrary to the above), 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 shock absorber 1
The damping force characteristics of ~4 are changed to the S0FT state. 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, 1 in the above predetermined value is the product of the gain value g and the value of the square of the sprung upper and unsprung relative speed T1 (g x T12), and the spring is adjusted according to the unevenness of the road surface. When the upper part vibrates at a high frequency, the value becomes high, so in the high frequency vibration region, the damping force characteristics of shock absorbers 1 to 4 are difficult to change to the HARD state, and noise and vibration may occur due to unnecessary changes in the damping force characteristics. In addition, it is possible to suppress the occurrence of a bumpy feeling on the springs due to unevenness of the road surface, and it is possible to further improve riding comfort.

Moreover, in the predetermined value changing means 54 that changes the predetermined value Ki according to the unevenness of the road surface or the vibration region of the vehicle caused by the unevenness of the road surface, the detection means for detecting the road surface condition or the vibration region of the vehicle This method is advantageous in terms of implementation, as it can be implemented at low cost.

Further, the Cain value g used to set the predetermined value Ki is set to be a gain value g1 that is set to gradually decrease as the vehicle speed increases, and a gain value g1 that is set to gradually decrease as the steering angle increases. The damping force characteristics of shock absorbers 1 to 4 become HARD at high speeds or sharp turns when vehicle stability is particularly required, and the stability is reduced. It is possible to ensure that security is secured.

8 and 9 show a second embodiment of the invention.

FIG. 8 shows a block configuration of the control section of the suspension device. The difference between this second embodiment and the first embodiment (see FIG. 3) is that the sprung and unsprung parts of each wheel are Instead of the first to fourth vehicle height sensors 41 to 44 that detect the relative displacement of the shock absorbers 1 to 4, the first to fourth vehicle height sensors serve as damping force detection means to detect the damping force of each shock absorber 1 to 4 (see FIG. 1). The pressure sensors 61 to 64 are provided. These pressure sensors 61 to 64 output damping force signals fsl to fs4 to the control unit 8. This signal takes a continuous value, and is positive when the damping force acts upward, and negative when the damping force acts downward.

Note that the other configurations are the same as in the first embodiment, so
Identical members are given the same reference numerals and their explanations will be omitted.

FIG. 9 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
~10m5) is activated repeatedly. This control operation will be explained below along the flow.

First, in step S21, it is determined whether the mode selection signal is HARD. When this determination is YES (HARD), the actuator control signal V1 is activated in step S34.
.about.v4 are all set to "1", and the control signals v1 to v4 are output in step S33. As a result, the damping force characteristics of all the shock absorbers 1 to 4 become in the I(ARD state). At this time, the operation ends.

When the value of the mode selection signal is not HARD, it is then determined in step S22 whether the value of the mode selection signal is 5OFT, and when the determination is YES (5OFT), the actuator control signals v1 to
All of v4 are set to "0", and the control signals V1 to v4 are output in step S33. As a result, the damping force characteristics of all the shock absorbers 1 to 4 are in the 5OFT state. In this case, the operation ends.

Both steps S21. Both judgments in S22 are NO.
In other words, when the value of the mode selection signal is C0NTR0L, the damping force signals fsl to fs4 are set in step S23.
At the same time, in step S24, spring ground acceleration signals 2'c+ to 2G4 are input. Thereafter, in step S25, 2G+ to 2c and a are integrated by numerical integration to obtain the vertical vehicle absolute speed 2c+ to G4. These G1 to G4 are acceleration sensors 11 to 1.
Since this is the vertical spring surface velocity versus velocity at position 4, in step 328 this is converted into the vertical spring mass velocity versus ground at the positions of each shock absorber 1 to 4 si to 2sa. Note that this conversion has already been described in the first embodiment, so its explanation will be omitted. Steps 824-52 above
B and the acceleration sensors 11 to 14 determine the velocity 2 relative to the spring surface in the vertical direction at the position of each shock absorber 1 to 4.
A spring ground speed detecting means 65 is configured to detect s+ to S4.

Subsequently, in step S27, a skyhook damper force fat as an ideal damping force is determined using the following equation.

fai--g-2si (i-1, 2, 3, 4) In other words, this skyhook damper force fat is the value obtained by adding a negative sign to the product of the spring top picture vs. speed 2sl and the gain value g for each wheel. It is. This step S27 constitutes a skyhook damper force calculation means 66 that calculates the skyhook damper force fat.

After calculating the skyhook damper force fa+, step 5
28, the judgment function hi (-fsi・faD
seek. Subsequently, in step 529, the vehicle speed signal VS and steering angle signal θH are input, and then in step 530, a gain value g is set. As in the case of the first embodiment, the pre-stored maps shown in FIGS. 6 and 7 are used to set the gain value g, and a gain value g1 corresponding to the vehicle speed and a gain corresponding to the steering angle are used. It is obtained as a product of the value g2. In addition, in step 531, a predetermined value K is determined for each wheel as the product of the gain value g and the square of the relative velocity ii between the sprung and unsprung parts.
Set i (-g-fai2).

Subsequently, in step S32, step S28 is first performed.
If the judgment function h1 obtained by is 1 or more (hi > Ki
), then it is set as vl ml, and if the determination function hi is less than or equal to a predetermined value of 1 (hi≦Ki), it is set as vi mO. After this setting, actuator control signals (1 to V4) are output in step S33, and the process returns. In steps 52g, S32 and S33, a judgment function h1 is calculated which is the product of the sky footer damper force fa1 and the actual damping force fsi, and depending on whether or not this judgment function h1 is larger than a predetermined value of 1, Each shock absorber 1~4
A control means 67 is configured to control the damping force characteristic to be changed to a HARD state or a 5OFT state, and
Steps S29 to S531 constitute a predetermined value changing means 68 that changes the above predetermined value Ki according to the driving condition of the vehicle and the condition of the road surface. Note that when the determination function hi is equal to the predetermined value ki (hi - KI), the actuator control signal V1 may be left unchanged and the damping force characteristic may not be changed.

Also in such control, if the driver selects the C0NTR0L mode, as in the case of the first embodiment, Skyfutsuku Danno Kuichiriki fai (=g-2s
l) and the actual damping force fs1 of shock absorbers 1 to 4
When the judgment function hi, which is the product (fsl-fai) of When acting on the shock absorbers 1 to 4, the damping force characteristics of the shock absorbers 1 to 4 are changed to a HARD state,
When the judgment function hl is less than or equal to a predetermined value (hi≦Ki), that is, when the damping force generated by the shock absorbers 1 to 4 acts in the excitation direction with respect to the vertical vibration on the spring, the shock absorber 1 ~4 damping force characteristics or 5OF
Since the state is changed to T, damping energy can be increased relative to the excitation energy transmitted to the spring, and ride comfort and steering stability can be improved.

Further, the predetermined value Ki is the product (g・fsl2) of the gain value g and the square value of the shock absorber damping force fsi, and is the value of the product (g・fsl2) of the gain value g and the value of the square of the shock absorber damping force fsi, and is the value of the product (g・fsl2) of the gain value g and the value of the square of the shock absorber damping force fsi. Since the damping force characteristics of shock absorbers 1 to 4 are difficult to change to the HARD state in the high frequency vibration region, it is possible to prevent the generation of noise and vibration due to unnecessary changes in the damping force characteristics. At the same time, it is possible to suppress the occurrence of a bumpy feeling on the springs due to unevenness of the road surface, and it is possible to further improve riding comfort.

Furthermore, as in the case of the first embodiment, there is no need for a detection means for detecting the road surface condition or the vibration area of the vehicle;
It is advantageous in terms of implementation in terms of cost, etc., and the damping force characteristics of the shock absorber are HA at high speeds and sharp turns.
It also has the effect of entering the RD state and ensuring stability.

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

For example, in the first embodiment, the product of the absolute speed is of the spring 1 and the relative speed between the sprung top and the unsprung portion (-is-2u) is the predetermined value Kl (for example, the square of the relative speed between the sprung top and the unsprung bottom). The value g・ (:ls −fu) obtained by multiplying the value by the gain value
2) Depending on whether the shock absorber is larger than 1
Although the damping force characteristics of 4 to 4 are changed to the HARD state or 5OFT state, the present invention has the advantage that the damping force characteristics of
The product of the relative speed r(-is-'lu) between the sprung top and the sprung bottom is the predetermined value Ki (the value G. U) The damping force characteristics of the shock absorbers 1 to 4 may be changed to a HARD state or a 5OFT state depending on whether the value is larger than 2). This is the product of the absolute speed iS of the spring 1 and the relative speed between the upper and lower parts of the spring (-S-U) and the predetermined value K.
i (=g・(〕5−2u)′), the difference F1 between the spring base and the relative speed 2u, and the relative speed between the sprung base and the sprung base r(−2s−
2U) and the predetermined value Kl (=G ・(2s−Zu
)2) and the difference F2 is the same. That is, the differences Fl and F2 are respectively Fl −之S(之S −之u)−g(之S−之u)2−
(之s -2u) 1'ls -g (之S-之u)1- (之s -2u) ((1-g)之s
+g2ulF2-之U(之S-之u)-G(之S-
之u)2-(之5-2u)(之u-G(2s -之u
)1− (之S −之u)f Gfs+(1+G)之U), but if we put l−g −−G and g−1+G, it becomes Fl −F2.

In addition, in each of the above embodiments, the damping force characteristics of the variable damping force characteristic shock absorbers 1 to 4 provided between the sprung portion and the unsprung portion of each wheel were independently changed and controlled. The two left and right shock absorbers 1.2 and the two left and right shock absorbers 3.4 on the rear wheel side may be controlled to have the same damping force characteristics. in this case,
For example, the product of the absolute speed of spring 1 at the left front wheel: lsl and the relative speed between the sprung top and the unsprung part (i Sl - 2ul), and the product of the absolute speed of spring 1 2s2 and the relative speed between the sprung top and the unsprung part (i s2 - i The damping force characteristics of the two left and right shock absorbers 1 and 2 on the front wheel side may be changed to the HARD state or the 5OFT state depending on whether the sum of the product and u2) is larger than a predetermined value.

(Effect of the invention) As described above, in the invention described in claim (1) or (2),
When the damping force generated by a shock absorber acts in the excitation direction on the vertical vibration on the spring, the damping force characteristic of the shock absorber becomes low damping, and when it acts in the damping direction, the damping force of the shock absorber changes. By changing the characteristics to a high damping side, it is possible to increase damping energy with respect to excitation energy, so it is possible to improve riding comfort and steering stability. Furthermore, in the high-frequency vibration region caused by uneven road surfaces, the damping force characteristics of the shock absorber are less likely to be changed to the high damping side, making it possible to prevent the generation of noise and vibration due to unnecessary changes in the damping force characteristics. , it is possible to further improve riding comfort.

Further, in the inventions described in claims (3) and (4), the damping force characteristic of the shock absorber is on the high damping side in the high frequency vibration region without requiring a detection means for detecting the road surface condition or vibration region. This also has the effect of being advantageous in terms of cost and implementation, since it can be made difficult to change.

Furthermore, in the invention described in claim (5) or (6), the damping force characteristics of the shock absorber are changed depending on the driving condition of the vehicle, so that ride comfort and handling stability can be further improved. .

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and are shown in FIGS. 1 to 7.
The drawings show the first embodiment, Fig. 1 is a perspective view showing the parts 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 schematic diagram showing the vibration model of the suspension device. 4 is a block diagram of the control section of the suspension device, FIG. 5 is a flowchart showing the control flow, and FIGS. 6 and 7 are diagrams showing maps for calculating gain values, respectively. Figures 8 and 9 show the second embodiment, and Figure 8 is a diagram corresponding to Figure 4, and Figure 9 is a diagram corresponding to Figure 4.
The figure is a diagram equivalent to Figure 5. 1 to 4...Shock absorber 51...Relative speed detection means 52.65...Spring ground speed detection means 53.67.
...Control means 54.68...Predetermined value changing means 61-64...Pressure sensor (damping force detection means) 66.
...Skyhook damper force calculation means 2A porridge 2B ward

Claims (6)

[Claims] (1) A shock absorber with variable damping force characteristics installed between the sprung mass and the unsprung mass, and a sprung mass that detects the sprung mass absolute speed or unsprung mass absolute speed.
an unsprung absolute speed detecting means; a relative speed detecting means for detecting the relative speed between the sprung mass and the unsprung mass; The product of the product with the relative velocity between the unsprung parts is calculated, and when the product is above a predetermined value, the damping force characteristic of the shock absorber is set to the high damping side, and when it is below the predetermined value, the damping force characteristic of the shock absorber is set to the low damping side. 1. A suspension device for a vehicle, comprising: a control means for changing the predetermined value; and a predetermined value changing means for changing the predetermined value according to a road surface condition. (2) a shock absorber with variable 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 receiving a signal from the detection means; a skyhook damper force calculation means for calculating a skyhook damper force that is a function value of the absolute sprung velocity; a damping force detection means for detecting the damping force of the shock absorber; a signal from the skyhook damper force calculation means; In response to the signal from the damping force detection means, the product of the skyhook damper force and the damping force of the shock absorber is calculated, and when the product is greater than a predetermined value, the damping force characteristic of the shock absorber is changed to the high damping side to a predetermined value. The present invention is characterized by comprising a control means for controlling the damping force characteristic of the shock absorber to be changed to a lower damping side when the damping force characteristic is less than the above value, and a predetermined value changing means for changing the predetermined value according to the condition of the road surface. Suspension equipment for vehicles. (3) The vehicle according to claim (1), wherein the predetermined value changing means sets the predetermined value by multiplying the square of the relative speed between the sprung and unsprung portions detected by the relative speed detection means by a gain value. suspension equipment. (4) The vehicle suspension according to claim 2, wherein the predetermined value changing means sets the predetermined value by multiplying the value of the square of the shock absorber damping force detected by the damping force detection means by a gain value. Device. (5) The vehicle suspension device according to claim (3) or (4), wherein the gain value in the predetermined value calculation formula is set to gradually decrease as the vehicle speed increases. (6) The vehicle suspension device according to claim (3) or (4), wherein the gain value in the predetermined value calculation formula is set to gradually decrease as the steering angle increases.