JP3095398B2 - Vehicle suspension device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to a vehicle suspension device, and in particular,
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.

[0002]

[Prior art]

2. Description of the Related Art Generally, a suspension device for a vehicle 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 characteristic can be changed in two stages and a type in which the damping force characteristic can be changed in multiple stages or in a continuously variable manner.

[0003] Basically, such a method of controlling a shock absorber having a variable damping force characteristic basically involves damping 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. The damping force characteristic of the shock absorber is changed to the high damping side (that is, the hard side) when the damping force is applied in the damping direction, and the force transmitted to the spring is changed. The purpose of the present invention is to increase the vibration damping energy relative to the vibration energy, thereby improving both the riding comfort and the steering stability of the vehicle.

[0004] 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,
JP 60-248419A examines whether the sign of the relative displacement between sprung and unsprung and the sign of the relative speed between unsprung and unsprung, which is the derivative thereof, match. Is determined as the vibration direction, and when they do not match, the method is determined as the vibration damping direction. A method is disclosed in which it is checked whether or not the signs of the relative speeds match each other, and when they match, it is determined to be the vibration damping direction, and when they do not match, it is determined to be the vibration direction.

In such control, a dead zone is generally provided to prevent the damping force characteristics of the shock absorber from being frequently switched with respect to a displacement near the neutral position. And, in Japanese Utility Model Publication No. 61-110412,
Within the dead zone, the damping force characteristic of the shock absorber is always set to the soft side characteristic, and the width of the dead zone is changed according to the peak value of the stroke displacement of the shock absorber (that is, the relative displacement between the sprung and unsprung portions). Is disclosed. Japanese Utility Model Application Laid-Open No. 63-40213 discloses that the damping force characteristic of the shock absorber is always set to the soft side within the dead zone, and the width of the dead zone is reduced when the steering angle or the steering angular velocity is large. Have been.

[0006]

[Problems to be solved by the invention]

By the way, in the vehicle suspension device, in order to restrict the wheels from bumping or rebounding greatly,
A bump stopper and a rebound stopper are generally provided on a shock absorber or the like.

However, when these stoppers collide with a shock absorber or the like (that is, at the time of restricting bump / rebound of a wheel).
Since this generates considerable vibration and impairs ride comfort, it is desirable to minimize this collision. In particular, when the wheels are deviated from the neutral position in the bump or rebound direction when the vehicle is stopped due to the load weight or the like, collision of the bump / rebound stopper is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a purpose thereof is to provide a shock absorber having a variable damping force characteristic. It is an object of the present invention to provide a vehicle suspension device that can be reduced.

[0009]

[Means for Solving the Problems]

In order to achieve the above object, the invention according to claim 1 provides a shock absorber provided between a sprung portion and a unsprung portion and having a variable damping force characteristic, and a relative displacement between the sprung portion and the unsprung portion. A relative displacement detecting means for detecting, a damping force characteristic controlling means for changing and controlling a damping force characteristic of the shock absorber in accordance with a relative displacement between a sprung portion and an unsprung portion detected by the relative displacement detecting means, and a vehicle. Stop state detection means for detecting the stop state of the vehicle, and receives signals from the relative displacement detection means and the stop state detection means, when the relative displacement between the sprung and unsprung parts is deviated from the neutral position in the stop state of the vehicle A control sensitivity changing means for increasing the control sensitivity of the damping force characteristic control means is provided.

[0010] The inventions according to claims 2 and 3 are all described in claim 1 above.
A more specific configuration of the control sensitivity changing means, which is dependent on the described invention.

That is, in the case of the second aspect of the invention, the control sensitivity changing means increases the control sensitivity by reducing the width of the dead zone for restricting the change of the damping force characteristic in the control of the damping force characteristic control means. is there. Further, in the case of the invention according to claim 3, the control sensitivity changing means increases the control sensitivity by increasing the control gain of the damping force characteristic control means.

[0012]

[Action]

With the configuration described above, in the present invention, when the vehicle is stopped, the relative displacement between the sprung and unsprung parts is deviated from the neutral position (that is, the wheel is deviated from the neutral position by one or more of the bump and the rebound direction by a predetermined value or more). When you are)
In addition, the control sensitivity of the damping force characteristic control means is increased by, for example, reducing the width of the dead zone or increasing the control gain by the control sensitivity changing means. As a result, the shock absorber quickly generates a large damping force with a change in stroke (change in expansion and contraction) as compared with the case where the control sensitivity is normal.

[0013]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

In FIG. 1, reference numerals 1 to 4 denote four shock absorbers provided respectively corresponding to left and right front wheels 5L (only the left front wheel is shown) and rear wheels 6L (only the left rear wheel is shown). Thus, the vertical movement of each wheel is attenuated.
Each of the shock absorbers 1 to 4 has a built-in actuator 25 (refer to FIG. 2) so that the damping force characteristic can be changed between high and low, and can be switched between a vehicle body (sprung) and an axle (unsprung). A vehicle height sensor (not shown) is incorporated as relative displacement detection means for detecting relative displacement between the two. Reference numeral 7 denotes a coil spring disposed on the outer periphery of each of the shock absorbers 1 to 4, and 8 a control for outputting a control signal to an actuator in each of the shock absorbers 1 to 4 to variably control the damping force characteristics. A detection signal is output from the vehicle height sensor in each of the shock absorbers 1 to 4 to the control unit 8.

Further, 11 to 14 are four acceleration sensors for detecting acceleration in a vertical direction (Z direction) on a spring for each wheel, and 15 is a vehicle speed sensor provided in a meter of an instrument panel for detecting a vehicle speed. , 16 is 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 the brake is operating based on the brake fluid pressure 19) is a brake pressure switch that detects whether or not the driver has 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.
In the HARD state (a state where high damping force is generated), the 2B
The figure shows a case where the damping force characteristics of the shock absorbers 1 to 4 are in a SOFT state (a state in which a low damping force is generated). In this figure, the vehicle height sensors built in 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 and 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 to be stronger than the force of the spring 28b for urging the control rod 27 upward. The control rod 27 is pressed downward to close the orifice 24 (see FIG. 2A). For this reason, the passage of the fluid is only the orifice 23, and the damping force characteristics of the shock absorbers 1 to 4 are in the HARD (high damping) state.

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 the orifices 23 and 24 are fluid passages, and the damping force characteristics of the shock absorbers 1 to 4 are in the SOFT (low damping) state.

As described above, the shock absorbers 1 to 4
When the solenoid 26 is de-energized, it enters the HARD state. Therefore, even if the control unit 7 breaks down, the shock absorbers 1 to 4 maintain the HARD state and prevent deterioration of steering stability.

FIG. 3 shows a vibration model of the suspension device, in which ms
Is the sprung mass, mu is the unsprung mass, Zs is the unsprung displacement, Zu is the unsprung displacement, Ks is the spring constant of the coil spring 7, Kt is the tire's spring constant, and v (t) is the damping coefficient of the shock absorber. is there.

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.

Further, r1 to r4 are sprung unsprung relative displacement signals output from the first to fourth vehicle height sensors (relative displacement detecting means) 41 to 44 toward the control unit 8, respectively.
Each of these signals takes a continuous value. This signal is positive when the shock absorbers 1-4 extend and negative when contracting. Note that 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 determined by the deviation from this. Express.

Z _G1 ″ to Z _G4 ″ are first to fourth acceleration sensors 11 to
These are sprung absolute acceleration signals in the vertical direction (Z direction) output from the control unit 14 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. These signals take continuous values. 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 of the actuator 25
No power is supplied to 26 (see FIG. 2), and the damping force characteristics of the shock absorbers 1 to 4 are in the 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 the SOFT state.

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 the case of 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. Then, as described later, in the case of HARD, the damping force characteristics of all the shock absorbers 1 to 4 are fixed to the HARD state, and in the case of SOFT, the damping force characteristics of all the shock absorbers 1 to 4 are fixed to the SOFT state, and Sometimes, the damping force characteristics of each of the shock absorbers 1-4 are HARD or SOFT depending on the driving condition of the vehicle and the condition of the road surface, respectively.
State automatically and independently.

FIG. 5 shows a 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 repeatedly started at a fixed period (1 to 10 ms) by a separately provided start program. Hereinafter, this control operation will be described along the flow.

First, in step S1, it is determined whether or not the mode selection signal is HARD. If the determination is HARD of YES, all of the actuator control signals v1 to v4 are set to "1" in step S15, and the control signals v1 to v4 are set in step S14.
Is output. As a result, all shock absorbers 1
The damping force characteristics of ４4 are in the HARD state. In this case, the operation is ended as follows.

When the value of the mode selection signal is not HARD,
In step S2, it is determined whether or not the value of the mode selection signal is SOFT.
Sets "0" to all of the actuator control signals v1 to v4, and outputs these control signals v1 to v4 in step S14.
Thereby, the damping force characteristics of all the shock absorbers 1 to 4 are in the SOFT state. At this time, the operation is completed.

When the determinations in both steps S1 and S2 are both NO, that is, when the value of the mode selection signal is CONTROL, step S
After inputting the sprung unsprung relative displacement signals r1 to r4 in step 3,
In step S4, the relative displacements r1 to r4 are differentiated by a numerical differentiation method or the like to obtain sprung unsprung relative speeds r1 'to r4'.

Subsequently, in step S5, the sprung absolute acceleration signals Z _G1 ″ to Z _G1
After inputting _G4 ″, in step S6, these Z _G1 ″ to Z _G4 ″ are integrated by a numerical integration method or the like, and the vertical vehicle absolute speed Z
Determine the _G1 '~Z _G4'. Since these Z _G1 ′ to Z _G4 ′ are vertical absolute sprung velocities at the positions of the acceleration sensors 11 to 14, these are applied to the respective shock absorbers 1 to 4 in step S 7.
Absolute vertical sprung speed Z _s1 ′ to Z _s4 ′ at the position
Convert to Z _s1 '~Z _s4', of Z _G1 '~Z _G4', since it is determined if known three is less, Z _G1 '~Z _G3'
And Z _G4 ′ is a reserve value. here,
As shown in FIG. 1, the origin is appropriately set in the horizontal plane, and xy
The coordinates of the acceleration sensors 11 to 13 at the time of taking the coordinates are (x
_G1, when y _G1) ~ where (x _G3, y _G3), the coordinates of the shock absorber 1 to 4 and _{(x s1, y s1) ~} (x s4, y s4), Z s1 '~Z
_s4 'is obtained by the following equation (1). However, the two coefficient matrices and their product are obtained in advance and given as constants.

[0038]

(Equation 1)

[0039] Then, enter the vehicle speed V (speed signal VS) at step S8, and determines whether the absolute value of the vehicle speed V is smaller than the predetermined value V ₀ in step S9. The predetermined value V ₀ is equivalent to a vehicle speed in a state where the vehicle is stopped, at this time the wheel without almost causing bump rebound, there remains stationary.

When the determination in step S9 is YES (when the vehicle is stopped), the dead zone width constant δi is set in step S10, and then the process proceeds to step S11. In such a case, the process immediately proceeds to step S11. The setting of the dead zone width constant δi is performed by using a pre-stored map shown in FIG. 6, in which the dead zone width constant δ is expressed as a function of the sprung-unsprung relative displacement r. When the relative displacement r is in the neutral position (r = 0), the dead zone width constant δ is set to the maximum value, and is set so as to decrease as the relative displacement r becomes closer to the bump side or the rebound side.

In step S 11, if the absolute value of the relative speed ri ′ between the sprung and unsprung components is smaller than the dead zone width constant δi (| ri ′ | <δi), ri ′ = 0. Subsequently, in step S12, a judgment function hi is obtained by the following equation.

Hi = ri ′ · Z _si ′ (i = 1,2,3,4) That is, the determination function hi is based on the sprung unsprung relative speed ri ′ and the sprung absolute speed Z _si ′ at each wheel. And the product of

Subsequently, in step S13, if the judgment function hi is zero or a positive value (hi ≧ 0), vi = 1, and if the judgment function hi is a negative value (hi <0), vi is set. = 0. After a while
In step S14, actuator control signals v1 to v4 are output, and the process returns.

By the above steps S12 to S14, a judgment function hi which is a product of the sprung absolute speed and the sprung unsprung relative speed is calculated,
A damping force characteristic control means 52 for controlling the damping force characteristics of each of the shock absorbers 1 to 4 to be changed to the HARD side or the SOFT side in accordance with whether or not the determination function hi is zero or more is constituted. S11 is the sprung unsprung relative speed ri ′
When the absolute value of is near the neutral position smaller than the dead band width constant δi, the control unit 52 restricts the change of the damping force characteristic, and fixes the damping force characteristic on the SOFT side.
Is composed. In step S9, the stationary state detecting means 55 for detecting the stationary state of the vehicle is configured, and in steps S9 and S10, the relative displacement r between the sprung and unsprung parts is neutral in the stationary state or the stationary state of the vehicle. A control sensitivity changing means 54 configured to increase the control sensitivity of the control force characteristic control means 52 by reducing the dead zone width constant δ according to the deviation when the position is deviated in the bump direction or the rebound direction from the position. I have.

Therefore, according to such control, the driver can control the CONT
When the ROL mode is selected, the judgment function hi is a product ri ′ · Z _si ′ of the sprung unsprung relative velocity ri ′ (= Z _si ′ −Z _ui ′) and the sprung absolute velocity Z _s1 ′. Is zero or a positive value (hi ≧ 0) (i.e., when the sprung mass moves upward and the shock absorbers 1-4 extend to exert their damping force downward, and when the sprung mass moves downward and When the shock absorbers 1 to 4 contract and their damping force acts upward), it is determined that the damping force generated by the shock absorbers 1 to 4 acts on the vertical vibration on the spring in the vibration damping direction,
The damping force characteristics of the shock absorbers 1-4 are changed to the HARD state. When the judgment function hi is a negative value (hi
<0) (in the case opposite to the above), the shock absorber 1
The shock absorbers 1 to 4 determine that the damping force generated by the shock absorbers 1 to 4 acts on the vertical vibration on the spring in the vibration direction.
The damping force characteristic of No. 4 is changed to the SOFT state. This allows
The vibration damping energy is larger than the vibration energy transmitted to the sprung, so that both the riding comfort and the steering stability can be improved.

When the sprung mass vibrates near the neutral position where the absolute value of the sprung unsprung relative speed ri ′ is smaller than the dead zone width constant δi, the damping force characteristics of the corresponding shock absorbers 1 to 4 Is restricted, and the damping force coefficient is fixed in the SOFT state, so that unnecessary and frequent changes in the damping force characteristics can prevent sound and vibration from occurring.

In addition, when the sprung spring-unsprung relative displacement r is deviated from the neutral position due to the amount of load or the like in a stationary state of the vehicle,
The dead band width constant δi decreases in accordance with the deviation, and the damping force characteristics of the shock absorbers 1 to 4 are easily changed from the SOFT state to the HARD state even near the neutral position. As a result, the relative displacement r between the sprung and unsprung portions can be suppressed from further changing in the direction from the biased position, and the bump rebound movement is less restricted by the bump stopper or the rebound stopper. Deterioration of ride comfort due to collision can be prevented.

The present invention is not limited to the above embodiment,
Other various modifications are included. For example, in the above embodiment, the shock absorber is determined in accordance with whether or not the judgment function hi, which is the product ri ′ · Z _si ′ of the sprung unsprung relative speed ri ′ and the sprung absolute speed Z _si ′, is zero or more. In the control law for changing the damping force characteristics of 1 to 4 to HARD or SOFT, a dead zone is provided for the sprung unsprung relative speed ri ', and the sprung unsprung relative displacement r is deviated from the neutral position in a stationary state of the vehicle. In this case, the control sensitivity is increased by reducing the width of the dead zone (dead zone width constant δi). However, in the present invention, the sprung absolute speed Z is used instead of the sprung unsprung relative speed ri ′.
_A dead zone may be provided in _si ′, and when the relative displacement r between the sprung and unsprung parts is deviated from the neutral position in a stationary state of the vehicle, the width of the dead zone may be reduced to increase the control sensitivity. is there.

As a method of increasing the control sensitivity of the damping force characteristic control means 52, in addition to reducing the width of the dead zone as in the embodiment, a control gain may be increased.

Further, the damping force characteristics of the shock absorbers 1-4 are HA
The control rules for changing to RD or SOFT are not limited to those in the embodiment, and other conventionally known control rules may be used.

[0051]

【The invention's effect】

As described above, according to the vehicle suspension device of the present invention, when the vehicle is stopped, the control sensitivity is enhanced when the relative displacement between the sprung and unsprung portions is deviated from the neutral position, and the bump rebound of the wheel is reduced. As a result, the shock absorber quickly generates a large damping force due to the change in expansion and contraction, so that the collision of the bump rebound stopper due to the large bump rebound of the wheel can be suppressed as much as possible, and the riding comfort is improved. Can contribute.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a component layout of a suspension device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view showing a main part of the shock absorber.

FIG. 3 is a schematic diagram showing a vibration model of the suspension device.

FIG. 4 is a block diagram of a control unit of the suspension device.

FIG. 5 is a flowchart showing a control flow.

FIG. 6 is a diagram showing a map for setting a dead zone width constant.

[Explanation of symbols]

 1-4 Shock absorbers 41-44 Vehicle height sensor (relative displacement detecting means) 52 Damping force characteristic controlling means 54 Control sensitivity changing means 55 Stopping state detecting means

Continuation of the front page (72) Inventor Akihiro Kimura 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-1-202511 (JP, A) JP-A-2-81710 ( JP, A) JP-A-2-106418 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (3)

(57) [Claims] A shock absorber provided between the sprung portion and the unsprung portion and having a variable damping force characteristic; a relative displacement detecting means for detecting a relative displacement between the sprung portion and the unsprung portion; Damping force characteristic control means for changing and controlling the damping force characteristic of the shock absorber in accordance with the relative displacement between the sprung and unsprung parts detected by the displacement detecting means; and a stopped state detecting means for detecting a stopped state of the vehicle And receiving signals from the relative displacement detecting means and the stationary state detecting means, and controlling the control sensitivity of the damping force characteristic controlling means when the relative displacement between the sprung and unsprung is deviated from the neutral position in the stationary state of the vehicle. A vehicle suspension device comprising: a control sensitivity changing unit that increases control sensitivity. 2. The vehicle suspension according to claim 1, wherein the control sensitivity changing means increases the control sensitivity by reducing the width of a dead zone for restricting the change of the damping force characteristic in the control of the damping force characteristic control means. apparatus. 3. The suspension apparatus according to claim 1, wherein the control sensitivity changing means increases the control sensitivity by increasing a control gain of the damping force characteristic control means.