JP3035317B2 - Vehicle suspension device - Google Patents

Description

The present invention relates to a suspension device for a vehicle, and more particularly, to a suspension device for a vehicle.
The present invention relates to an improvement of a device having a shock absorber having a variable damping force characteristic between a sprung portion and a unsprung portion.

(Prior Art) Generally, a vehicle suspension device is provided with a shock absorber between a sprung portion (body side) and an unsprung portion (wheel side) to attenuate the vertical movement of a wheel. This shock absorber has a damping force characteristic variable type (a characteristic with a different damping coefficient).
There are various types such as a type in which the damping force can be changed in two steps and a type in which the damping force can be changed in multiple steps or steplessly continuously.

Such a method of controlling a shock absorber having a variable damping force characteristic basically reduces the damping force of the shock absorber when the damping force generated by the shock absorber acts in the vibration direction with respect to the vertical vibration of the vehicle body. Change the damping force of the shock absorber to a high damping side (that is, the hard side) when the damping force is applied in the damping direction. The purpose is to increase the damping energy and thereby improve both the riding comfort and the steering stability of the vehicle.

Various methods have been proposed for determining whether the damping force of the shock absorber acts in the vibration direction or the vibration damping direction of the sprung vertical vibration. For example,
Japanese Patent Laid-Open No. 60-248419 examines whether the sign of the relative displacement between the sprung portion and the unsprung portion and the sign of the relative speed between the sprung portion and the unsprung portion, which is a derivative thereof, match. A method is disclosed in which, when they match, the vibration direction is determined, and when they do not match, the vibration is determined to be the vibration damping direction. A method is disclosed in which it is determined whether or not the sign of the relative speed between the upper part and the unsprung part matches, and if they match, it is determined to be the vibration suppression direction, and if they do not match, it is determined to be the vibration direction.

(Problems to be Solved by the Invention) In such a control method, when a signal for switching the damping force characteristic of the shock absorber is output based on a predetermined control law, the switching is generally performed immediately. However, there is a possibility that the switching control of the damping force characteristic is erroneously performed due to the noise mixed with the input signal as the control information such as the sprung absolute speed.

The present invention has been made in view of the above circumstances, and a purpose thereof is to improve erroneous control due to noise mixing by improving the switching control of the damping force characteristic of the shock absorber. It is intended to provide a suspension device for a vehicle that can be used.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a shock absorber (1) having a variable damping force characteristic disposed between a sprung portion and a unsprung portion as a vehicle suspension device. ~ 4)
And damping force characteristic switching determining means for inputting control information such as a sprung absolute speed at predetermined time intervals, and for each time determining a switching of the damping force characteristics of the shock absorbers (1 to 4) based on a predetermined control law. And (53) a damping force characteristic change control means for controlling to change the damping force characteristics of the shock absorbers (1 to 4) when the switching signal is continuously output from the determination means (53) a predetermined number of times. 54), and the shock absorber (1) is provided by the damping force characteristic change control means (54).
When the damping force characteristics of the shock absorbers (1 to 4) are changed to the low damping side, the number of continuous switching signals when changing the damping force characteristics of (4) to (4) is higher than when the damping force characteristics are changed to the high damping side. The configuration is such that the number is set to a small number.

According to the present invention, the damping force characteristic switching determination means (53) inputs control information such as sprung absolute speed at predetermined time intervals, and in each case, executes a shock absorber based on a predetermined control law. The switching determination of the damping force characteristic of (1-4) is performed, and only when the switching signal is continuously output from the determination unit (53) a predetermined number of times, the shock absorber (54) is changed by the damping force characteristic change control unit (54). The damping force characteristics of 1-4) are changed. The number of continuous switching signals is set to a smaller number when the damping force characteristics of the shock absorbers (1 to 4) are changed to the low damping side than when the damping force characteristics are changed to the high damping side.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

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

In FIG. 1, reference numerals 1 to 4 denote four shock absorbers respectively provided for left and right front wheels 5L (only the left front wheel is shown) and rear wheels 6L (only the left rear wheel is shown). It attenuates the vertical movement of each wheel.
Each of the shock absorbers 1 to 4 has a built-in actuator 25 (see FIG. 2) whose damping force characteristics can be switched between high and low and can be switched between a vehicle body (spring up) and an axle (unsprung). A vehicle height sensor (not shown) for detecting a relative displacement between them is built in. Reference numeral 7 denotes a coil spring disposed on the outer periphery of each of the shock absorbers 1 to 4, and 8 denotes a control for outputting a control signal to an actuator in each of the shock absorbers 1 to 4 to change and control the damping force characteristics. And the above-mentioned shock absorbers 1-4 for the control unit 8.
A detection signal is output from a vehicle height sensor in the vehicle.

Also, 11 to 14 are four acceleration sensors for detecting acceleration in a vertical direction (Z direction) on a spring for each wheel, 15 is a vehicle speed sensor provided in a meter of an instrument panel, and 16 is a vehicle speed sensor. A steering angle sensor that 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 whether or not the brake is operating based on the brake fluid pressure (that is, whether or not braking is being performed). 19) is a brake pressure switch that detects whether the driver is HARD, SOFT, CONTRO
This is a mode selection switch for switching to any of the modes L. The detection signals of these sensors 11 to 17 and the switches 18 and 19 are both output to the control unit 8.

FIG. 2 shows the structure of the shock absorbers 1-4, and FIG. 2A shows the damping force characteristics of the shock absorbers 1-4.
HARD characteristics (characteristics that generate high damping force)
FIG. 2B shows a case where the damping force characteristics of the shock absorbers 1 to 4 are SOFT characteristics (characteristics generating a low damping force). still,
In this figure, the vehicle height sensors built into the shock absorbers 1 to 4 are omitted.

In FIG. 2, reference numeral 21 denotes a cylinder.
In the piston 21, a piston unit 22 formed by integrally molding a piston and a piston rod is slidably fitted.
The cylinder 21 and the piston unit 22 are connected to an axle (unsprung) or a vehicle body (upspring) via separately provided connecting structures.

The piston unit 22 has two orifices 23, 24
Is provided. One of the orifices 23 is always open. The other orifice 24 is provided so as to be opened and closed by an actuator 25. The actuator 25 includes a solenoid 26, a control rod 27, and two springs 28a and 28b. The control rod 27 is connected to the solenoid 2
The orifice 24 is opened and closed by moving up and down in the piston unit 22 by the magnetic force received from 6 and the biasing force received from both springs 28a and 28b.

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

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

When the solenoid 26 is energized, the solenoid 26
The control rod 27 is pulled up by the magnetic force of 26, and the orifice 24 is opened (see FIG. 2B). For this reason, both orifices 23 and 24 are fluid passages, and the damping force characteristics of the shock absorbers 1 to 4 are SOFT (low damping) characteristics.

As described above, the shock absorbers 1 to 4
When the solenoid 26 is de-energized, the HARD characteristic is obtained. Therefore, even if the control unit 8 fails, the shock absorbers 1 to 4 maintain the HARD characteristic and prevent the steering stability from deteriorating.

FIG. 3 shows a vibration model of the suspension device, and m
s is the sprung mass, mu 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 absorbers 1-4.

FIG. 4 shows a block configuration of a control unit of the suspension device. In FIG. 4, a first vehicle height sensor 41, an acceleration sensor
11 and the actuator 25a are on the left front wheel 5L of the vehicle body, the second vehicle height sensor 42, the acceleration sensor 12 and the actuator 25b are on the right front wheel of the vehicle body, and the third vehicle height sensor 43, the acceleration sensor 13 and the actuator 25c are on the left side of the vehicle body. Rear wheel 6
In L, the fourth vehicle height sensor 44, the acceleration sensor 14, and the actuator 25d respectively correspond to the rear wheels on the right side of the vehicle body. The actuators 25a to 25d are the same as the actuators 25 in FIG.
Are built in the shock absorbers 1-4.

Also, r1 to r4 are first to fourth vehicle height sensors 41 to
This is a sprung-unsprung relative displacement signal output from the control unit 44 to the control unit 8, and these signals take continuous values. This signal is output from shock absorber 1
4 is positive when it expands and negative when it shrinks. The relative displacement when the vehicle is stationary (that is, the difference zs-zu between the sprung displacement zs and the unsprung displacement zu shown in FIG. 3) is set to zero, and the magnitude of the relative displacement is calculated from the deviation from this. Express.

_G1 to _G4 are first to fourth acceleration sensors 11 to 14, respectively.
Are the sprung absolute acceleration signals in the vertical direction (Z direction) outputted from the control unit 8 to the control unit 8, and these signals take continuous values. This signal is positive when the sprung body receives an upward acceleration and negative when it receives a downward acceleration.

In addition, a vehicle speed signal VS is output from the vehicle speed sensor 15, a steering angle signal θH is output from the steering angle sensor 16, and an accelerator opening signal TVO is output from the accelerator opening sensor 17 to the control unit 8, respectively. Take a continuous value. The vehicle speed signal VS is positive when the vehicle moves forward and negative when the vehicle moves backward. The steering angle signal θH is positive when the steering wheel rotates counterclockwise (that is, when turning left) and negative when clockwise (that is, when turning right) as viewed from the driver's side. I do.

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

v1 to v4 are actuator control signals output from the control unit 8 to the actuators 25a to 25d, respectively, and these signals take two values of "1" and "0". When "1", the solenoid 26 (see FIG. 2) of the actuator 25 is not energized, and the damping force characteristics of the shock absorbers 1 to 4 become HARD characteristics. When it is “0”, the solenoid 26 of the actuator 25 is energized,
The damping force characteristics of the shock absorbers 1 to 4 are SOFT characteristics.

Further, 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. In this embodiment, HARD, SOF
It takes three values, T and CONTROL. HARD means that the driver has selected the HARD mode, SOFT means that the SOFT mode has been selected, and CONTROL means that the CONTROL mode has been selected. In the case of HARD, the damping force characteristics of all shock absorbers 1-4 are fixed to the HARD characteristics, and in the case of SOFT, the damping force characteristics of all shock absorbers 1-4 are SOFT.
In the case of CONTROL, the damping force characteristics of each of the shock absorbers 1 to 4 are automatically and independently switched to HARD or SOFT characteristics according to the motion state of the vehicle, the state of the road surface, and the like.

FIGS. 5 and 6 show a control flow of the control unit 8 when the CONTROL mode is selected (specifically, a flow for determining the switching of the damping force characteristic and a control flow for changing the damping force characteristic).
Is shown. Each of these control operations is executed by a control program installed in the control unit 8. This control program is sequentially and repeatedly started at a fixed period (about 5 ms) by a separately provided start program.

In the switching determination flow of the damping force characteristic shown in FIG. 5, first, in step S1, the sprung-unsprung relative displacement signal r1
After inputting ~ r4, in step S2, these r1 ~ r4 are differentiated by numerical differentiation or the like, and the relative speed 1e
Ask for 4. Steps S1 and S2 and vehicle height sensors 41 to 44
The sprung and unsprung relative speed for each wheel
A relative speed detecting means 51 for detecting the speed 4 is constituted.

Subsequently, after entering the vertical direction of the spring absolute acceleration signals _G1 ~ _G4 in step S3, the _G1 ~ in step S4
_G4 is integrated by a numerical integration method or the like to obtain vertical sprung absolute velocities _G1 to _G4 . Since _G1 to _G4 are sprung absolute speeds at the positions of the acceleration sensors 11 to 14,
In step S5, these are converted into sprung absolute speeds _S1 to _S4 at the positions of the respective shock absorbers 1 to ₄ . _S1 ~
_{Since S4} is obtained if three of _G1 to _G4 are known, _G1 to _G3 will be used hereinafter, and _G4 will be a spare value. Here, as shown in FIG. 1, take the appropriate origin in the horizontal plane, when taking the xy coordinates, the coordinates of the acceleration sensor _{11~13 (x G1, y G1)} ~ (x G3, y G3 ), The coordinates of the shock absorbers 1-4 are ( _xS1 , _yS1 )-( _xS4 ,
y _S4 ), _S1 to _S4 are obtained by the following equations.

However, the two coefficient matrices and their product are obtained in advance and given as constants. The above-mentioned steps S3 to S5 and the acceleration sensors 11 to 14 constitute sprung absolute speed detecting means 52 for detecting the sprung absolute speeds _S1 to _S4 in the vertical direction at the positions of the respective shock absorbers 1 to ₄ .

Subsequently, in step S6, a judgment function hi is obtained by the following equation.

hi = i · si (i = 1,2,3,4) That is, this judgment function hi is the relative speed between the sprung and unsprung portions of each wheel.
This is the value of the product of i and the sprung absolute speed si.

After determining the judgment function hi, in step S7, if the judgment function hi is zero or a positive value (hi ≧ 0), a damping force characteristic to be a switching target (hereinafter referred to as a target damping force characteristic).
Nit = 1, the judgment function hi is a negative value (hi <0)
Then, the target damping force characteristic Nit = 0. Step S6 above,
At S7, a judgment function hi is calculated which is the product of the sprung absolute speed and the sprung unsprung relative speed, and each of the shock absorbers 1-4 is determined according to whether the judgment function hi is zero or more.
The target damping force characteristic is set, and the damping force characteristic switching determining means 53 for judging whether or not the changeover of the damping force characteristic is required is configured. The determination by the determining means 53 is repeatedly executed by the control program. This is performed every time (ie, at intervals of about 5 ms).

In the damping force characteristic change control flow shown in FIG. 6, first, in step S11, each of the shock absorbers 1-4
The current damping force characteristic (hereinafter referred to as the current damping force characteristic) Ni selected at the present time is recognized, the target damping force characteristic Nit is recognized in step S12, and thereafter, the target damping force characteristic Nit is compared with the current damping force characteristic Nit in step S13. The difference from the damping force characteristic Ni is a positive value (+
1) It is determined whether the value is a negative value (-1) or zero.

When the difference is zero (that is, when it is not necessary to change the damping force characteristics of the shock absorbers 1 to 4), the routine immediately returns. When the difference is a positive value (that is, when the damping force characteristic needs to be changed to the HARD side), in step S14, for each count number I _S , I _H , I _S = 0, I _H = I Set _H +1. Then, in step S15, the count number I _H
Is a predetermined number of times α (I _H = α), and if the determination is NO, the routine returns. On the other hand, when the determination is YES, after clearing the count number I _H to zero at step S16, the value of the target damping force characteristic Nit to the actuator control signal vi (this time "1") is set at step S17, the The control signal vi is output, and the process returns.

Further, when the difference between the target damping force characteristic Nit and the current damping force characteristic Ni is a negative value (that is, when it is necessary to change the damping force characteristic to the SOFT side), in step S18, each count number I _H ,
For I _S , set I _H = 0 and I _S = I _S +1. Then, in step S15, the count number I _S
Is a predetermined number β (I _S = β), and the process returns when the determination is NO. On the other hand, when the determination is YES, after clearing the count number I _S to zero at step S20, the value of the target damping force characteristic Nit to the actuator control signal vi (this time "0") is set at step S21, the The control signal vi is output, and the process returns.

According to the above change control flow, when the damping force characteristics of the shock absorbers 1 to 4 are changed and switched to either the HARD side or the SOFT side, the switching signal (current damping force characteristic) is used.
Only when the signal of the target damping force characteristic Nit different from Ni) is continuously output a predetermined number of times, the shock absorbers 1 to
A damping force characteristic change control means 54 for controlling to change the damping force characteristic of No. 4 is provided. Here, the continuous number of switching signals (that is, the predetermined number β) when changing the damping force characteristics of the shock absorbers 1 to 4 to the SOFT side is the same as when changing the damping force characteristics of the shock absorbers 1 to 4 to the HARD side. The number is set equal to or less than the continuous number of switching signals (that is, the predetermined number α).

Therefore, in such damping force characteristic change control, the sprung unsprung relative speed i and the sprung absolute speed i
The control information of si is input every predetermined time (5 ms) to determine a judgment function hi (= i · si) which is a product of the two. Each time, each shock is determined according to whether or not the judgment function hi is zero or more. It is determined whether or not the changeover of the damping force characteristics of the absorbers 1 to 4 is required (setting of the target damping force characteristics Nit). In this determination, when it is determined that the damping force characteristics of the shock absorbers 1 to 4 are changed from the SOFT side to the HARD side a predetermined number of times α, or when the damping force characteristics of the shock absorbers 1 to 4 are changed to the HARD side. The damping force characteristic is changed only when the determination to change from to SOFT is repeated a predetermined number of times β. Therefore, even if noise is accidentally mixed into the input signal as control information,
This prevents the damping force characteristic from being erroneously switched and changed.

In particular, the damping force characteristics of shock absorbers 1-4 are SOFT
If the number of repetitions of the determination when changing to the HARD side (that is, the predetermined number β) is set to a number smaller than the number of repetitions of the determination when changing to the HARD side (that is, the predetermined number α), the damping force characteristics Is easily changed to the low attenuation side, which can contribute to improvement of the riding comfort.

In the above embodiment, the shock absorber 1 is determined according to whether or not the determination function hi, which is the product i · si of the sprung unsprung relative speed i and the sprung absolute speed si, is zero or more.
Although the damping force characteristics of the shock absorbers 1 to 4 are changed to HARD or SOFT, the damping force characteristics of the shock absorbers 1 to 4 may be changed based on other conventionally known control rules.

Further, in the above embodiment, the case where the damping force characteristics of the shock absorbers 1 to 4 can be changed between high and low two stages has been described. However, the present invention provides a multi-stage or stepless continuous damping force characteristic of the shock absorber of three or more stages. It is needless to say that the same can be applied to a case where it can be changed in a practical manner.

(Effects of the Invention) As described above, according to the vehicle suspension device of the present invention, each time control information such as sprung absolute speed is input at predetermined intervals, switching determination of the damping force characteristic of the shock absorber is performed, and the switching is performed. Since the damping force characteristic of the shock absorber is changed only when the determination is continuously performed a predetermined number of times, it is possible to reliably prevent the damping force characteristic from being erroneously controlled due to mixing of noise into the input signal. Moreover, the number of continuous switching signals when changing the damping force characteristics of the shock absorber is set to a smaller number when the damping force characteristics of the shock absorber are changed to the low damping side than when the damping force characteristics are changed to the high damping side. As a result, the damping force characteristic is likely to change to the low damping side, which can contribute to improvement in ride comfort.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention. FIG. 1 is a perspective view showing a component layout of a suspension device, FIG. 2 is a longitudinal side view showing a main part of a shock absorber, and FIG. FIG. 4 is a block diagram of a control unit of the suspension device, and FIG.
Fig. 6 is a flowchart showing a flow for determining the switching of the damping force characteristic, and Fig. 6 is a flowchart showing a control flow for changing the damping force characteristic. 1-4 Shock absorber 53 ... Attenuation force characteristic switching determination means 54 ... Damping force characteristic change control means

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Uchida 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-59-140113 (JP, A) JP-A-61 JP-A-38481 (JP, A) JP-A-2-74411 (JP, A) JP-A-60-47709 (JP, A) JP-A-61-160808 (JP, A) JP-A-62-106684 (JP, A) ) Actually open sho 59-120608 (JP, U) Actually open sho 61-73411 (JP, U) Actually open sho 62-153108 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (1)

(57) [Claims] 1. Shock absorbers (1 to 4) disposed between sprung and unsprung and having variable damping force characteristics, and control information such as sprung absolute speed are input at predetermined time intervals. A damping force characteristic switching determining means (53) for determining switching of the damping force characteristics of the shock absorbers (1 to 4) based on a predetermined control law each time; And a damping force characteristic change control means (54) for changing the damping force characteristics of the shock absorbers (1 to 4) when output is performed. When the damping force characteristics of the shock absorbers (1 to 4) are changed, the number of continuous switching signals is changed to a higher damping force when the damping force characteristics of the shock absorbers (1 to 4) are changed to a lower damping side. Set fewer times than Suspension device for a vehicle, characterized in that it is.