JP3066396B2 - Vehicle suspension system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling a damping coefficient of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping coefficient of a shock absorber, for example, Japanese Utility Model Laid-Open No.
One described in Japanese Patent Application No. 117510 is known.

[0003] In this conventional apparatus, during roll control, the damping coefficient is kept high so as to suppress a change in the attitude of the vehicle body.

[0004]

However, in the above-mentioned prior art, when the vehicle is running on a rough road while performing roll control, unsprung vibrations are transmitted to the vehicle body, and the riding comfort is significantly deteriorated. There was a problem of doing.

The present invention has been made in view of the above-mentioned conventional problems. Therefore, in an apparatus for performing control for enhancing the steering stability during rolling or the like, it is possible to achieve both the steering stability and the riding comfort. It is an object to provide a vehicle suspension device.

[0006]

Therefore, according to the present invention, when the steering stability condition is satisfied, the damping coefficient is determined by calculating the ratio of the sprung vertical velocity to the threshold value or the peak value from the α-th power used during normal control. The above object is achieved by setting the attenuation coefficient in proportion to the value raised to the power of β by the small value β.

That is, the vehicle suspension system of the present invention is shown in FIG.
As shown in the claim correspondence diagram, the shock absorber b interposed between the vehicle body side and the wheel side and formed so that the damping coefficient can be arbitrarily changed by the damping coefficient changing means a, and the sprung vertical speed of the car body is detected. Sprung vertical speed detecting means c
A steering condition determining means d for determining a predetermined steering stability condition; and a ratio between the threshold value and the sprung vertical speed when the absolute value of the sprung vertical speed is less than a predetermined threshold value. While the damping coefficient is set by making the damping coefficient proportional to a value raised to the power of α, when the absolute value of the sprung vertical speed exceeds the threshold, the sprung vertical speed is exceeded after the threshold value is exceeded. Until the peak value is detected, the damping coefficient is fixed to the maximum damping coefficient, and when this peak value is detected, damping coefficient control is performed to set the damping coefficient in proportion to the sprung vertical velocity based on the peak value. When the stability condition is satisfied,
Damping coefficient control means e for performing a damping coefficient control for setting a damping coefficient by proportionally setting the damping coefficient to a value obtained by raising the ratio of the sprung vertical velocity to the threshold value or the peak value by a value β smaller than the α, Was provided. In addition, the shock absorber b can be changed by the damping coefficient changing means a so that the damping coefficient on the extension side can be changed in multiple stages, and the compression side has the extension side hardware characteristic fixed to a low attenuation coefficient and the damping coefficient on the compression side in multiple stages. It may be formed so that the characteristic can be changed to a compression side hard characteristic which is variable and the extension side is fixed to a low damping coefficient.

[0008]

In the normal case where the steering stability condition is not satisfied, if the absolute value of the sprung vertical speed is less than a predetermined threshold value, the ratio between the threshold value and the sprung vertical speed is set to α.
The attenuation coefficient is set by making the attenuation coefficient proportional to the multiplied value.
On the other hand, when the absolute value of the sprung vertical speed becomes equal to or more than the threshold, after exceeding the threshold, until the peak value of the sprung vertical speed is detected, after being fixed to the maximum damping coefficient,
When this peak value is detected, damping coefficient control for setting the damping coefficient in proportion to the sprung vertical velocity based on the peak value is performed.

By performing sudden steering, sudden braking, sudden acceleration, etc.,
When the steering stability condition is satisfied, the damping coefficient is set by making the damping coefficient proportional to a value obtained by raising the ratio of the sprung vertical velocity to the threshold value or the peak value to the βth power by a value β smaller than α. Perform coefficient control. Therefore,
As a result, the damping coefficient is controlled to be higher than that in the normal state and to be proportional to the sprung vertical speed.

[0010] In the second aspect of the invention, while the extension side or the compression side is controlled to have a high damping coefficient in order to control the shock absorber, the opposite stroke side has a low damping coefficient. Therefore, when there is a road surface input in the direction opposite to the vibration suppression side, transmission of this input to the vehicle body can be suppressed, and the riding comfort at the time of vibration suppression can be improved.

[0011]

An embodiment of the present invention will be described with reference to the drawings. First, the configuration of the vehicle suspension system according to the embodiment of the present invention will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system according to an embodiment of the present invention, which is interposed between a vehicle body and each wheel, and is provided with front-wheel-side shock absorbers SA _FR and SA _FR and rear-wheel-side shock absorbers. Shock absorbers SA _RR and SA _RR are provided. A vertical acceleration sensor (hereinafter, referred to as a vertical G sensor) 1 for detecting a vertical acceleration is provided on the vehicle body near the position where each of the shock absorbers SA _FR and SA _RR is attached to the vehicle body. Is provided with a steering sensor 2 for detecting a steering angle, a vehicle speed sensor 8a for detecting a vehicle speed in an engine room, and a brake sensor (not shown) which closes when a braking operation is performed. Switch) 8b. The sensors 1 and 2 are located near the driver's seat.
A control unit 4 is provided for inputting signals from 2, 8a and 8b and outputting a drive control signal to the pulse motor 3 of each of the shock absorbers SA _FR and SA _RR .

FIG. 3 is a system block diagram showing the above configuration. The control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c. ,
Signals are input from 8a and 8b. The vertical acceleration is detected as a positive value for upward acceleration and a negative value for downward acceleration.

Next, FIG. 4 shows each shock absorber SA.
One configuration of _FR and SA _RR (each shock absorber S
A cross-sectional view illustrating the A _FR, construction of SA _RR are the same), the shock absorber SA (hereinafter, the shock absorbers SA _FR, when referring to any one of the SA _RR is a simply SA (Shown) is a cylinder 30 and a piston 3 defining the cylinder 30 in an upper chamber A and a lower chamber B.
1, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, a base 34 defining a lower chamber B and the reservoir chamber 32, and a guide for sliding the piston rod 7 connected to the piston 32. Guide member 35, suspension spring 36 interposed between outer cylinder 33 and the vehicle body
And a bumper bar 37.

FIG. 5 is an enlarged sectional view showing a part of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein, and An extension damping valve 12 and a compression damping valve 20 for opening and closing 31a and 31b, respectively, are provided. A communication hole 39 that connects the upper chamber A and the lower chamber B is formed at the tip of the piston rod 7 that penetrates the piston 31, and further changes the cross-sectional area of the communication hole 39. , And an expansion-side check valve 17 and a pressure-side check valve 22 that allow and shut off the flow of the fluid communication hole 39 in accordance with the flow direction of the fluid. The adjuster 40 is rotated by the pulse motor 3 (see FIG. 4).
Also, the first end of the piston rod 7 is
A port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed. Reference numeral 38 in the drawing denotes a retainer on which the pressure-side check valve 22 is seated.

On the other hand, the adjuster 40 has a hollow portion 19, a first horizontal hole 24 and a second horizontal hole 25 communicating between the inside and the outside, and a vertical groove 23 formed in the outer peripheral portion. I have.

Therefore, between the upper chamber A and the lower chamber B, as a flow path through which fluid can flow during the extension stroke, the inside of the extension-side damping valve 12 passing through the through hole 31b is opened to open the lower chamber. B, the first port D on the extension side, the second port 13 and the flute 2
(3) a second expansion passage (E) that opens the outer peripheral side of the expansion damping valve (12) through the fourth port (14) to reach the lower chamber (B);
The extension side check valve 17 is opened via the port 13, the vertical groove 23, and the fifth port 16, and the extension side third valve reaching the lower chamber B is opened.
The flow path F, the third port 18, the second lateral hole 25, and the hollow portion 19
There are four flow paths of a bypass flow path G which leads to the lower chamber B via. Also, as a flow path through which fluid can flow in the pressure stroke,
The upper side chamber A is opened by opening the pressure side first flow path H passing through the through hole 31a and opening the pressure side damping valve 20, and opening the pressure side check valve 22 via the hollow portion 19, the first horizontal hole 24, and the first port 21. Pressure side second flow path J leading to the hollow portion 19, the second lateral hole 2
5, there are three flow paths: a bypass flow path G which reaches the upper chamber A via the third port 18.

That is, the shock absorber SA is configured such that the damping coefficient can be changed in multiple stages with characteristics as shown in FIG. 6 on both the extension side and the compression side by rotating the adjuster 40. That is, as shown in FIG. 7, when the adjuster 40 is rotated to each position in the counterclockwise direction from the position (the position in the figure) where both the extension side and the compression side have a low attenuation coefficient, only the extension side has an attenuation coefficient. Is changed in multiple steps toward the high damping side, and conversely, when the adjuster 40 is rotated to each position in the clockwise direction, only the pressure side changes in multiple steps toward the high damping coefficient side.

By the way, in FIG. 7, the adjuster 40 is arranged at three positions of (the position of the expansion-side maximum damping coefficient), (the position of the expansion / compression minimum attenuation coefficient), and (the position of the compression-side maximum attenuation coefficient). 8, KK, MM, and NN in FIG. 5 are shown in FIGS. 8, 9, and 10, respectively, and the damping force characteristics at each position are shown in FIGS. 13.

Next, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described with reference to the flowcharts of FIGS.

Step 101 is a step for performing initialization.

In step 102, the upper and lower G sensors 1
This is a step of reading the detected sprung vertical acceleration G from.

Step 103 is to integrate the sprung acceleration G read from the vertical G sensor 1 to calculate the sprung vertical velocity V _n
Is the step of calculating That is, the upper and lower G sensor 1
When constitute the sprung mass vertical velocity detection means the claims at the portion for calculating an acceleration G to the spring on the vertical velocity V _n in the control unit 4. Incidentally, the vertical sprung mass velocity V _n is the upward positive, downward given by a negative value.

Step 104 is a step of judging a steering stability control condition. Based on signals from the steering sensor 2, the vehicle speed sensor 8 a, and the brake sensor 8 c, sudden steering at a predetermined speed or more (a predetermined threshold value) is performed. The rate of change of the steering angle described above), or the presence or absence of sudden braking at or above a predetermined deceleration (rate of decrease in vehicle speed at or above a predetermined threshold value at the time of braking detection) is checked. It is determined that it is time to dampen the shock absorber SA to ensure steering stability. That is, it is determined that the steering stability control condition has been satisfied.

[0025] Step 105 is a step of determining whether the value of the vertical sprung mass velocity V _n is positive (including zero), the process proceeds to step 106 the flow of control corresponding to the extension stroke YES, a If the determination is NO, the process proceeds to step 201 (FIG. 15), which is the flow of control corresponding to the pressure stroke.

Step 106 determines whether or not the sprung vertical speed V _n-1 obtained last time is a negative value (not including 0), that is, when the direction of the sprung vertical speed V _n changes. Is determined, and the process proceeds to step 107 with YES, and proceeds to step 108 with NO.

Step 107 is a step for initially setting the extension side threshold value V _S1 .

Step 108 is a step for judging whether or not the sprung vertical speed Vn is _equal to or higher than the extension side threshold value V _S1.
Go to 10.

Step 109 is a step of rewriting the extension threshold value V _S1 to the current sprung vertical velocity V _n .

Step 110 determines whether the steering stability control condition in step 104 is satisfied (ON) or not (OF).
In the step of determining F), if it is ON, the process proceeds to step 112, and if it is OFF, the process proceeds to step 111.

Step 111 is a target position for driving the pulse motor 3 (position of the adjuster 40).
The square current vertical sprung mass velocity V _n divided by the extension side threshold V _S1 value (the ratio of current vertical sprung mass velocity V _n for the extension side threshold V _S1) (the claims (corresponding to the α-th power), and then multiplying it by the extension-side maximum attenuation coefficient (the position that becomes the extension-side maximum attenuation coefficient).

[0032] Step 112, the current sprung mass vertical velocity target position, with respect to the value obtained by dividing the vertical velocity V _n on the current spring in the extension side threshold V _S1 (extension side threshold V _S1 of the pulse motor 3 V _n ) is calculated by multiplying the extension-side maximum attenuation coefficient (the position at which the maximum attenuation coefficient is reached) by itself. For this step 112, the current vertical sprung mass velocity V _n equal to have the first power value obtained by dividing by the extension side threshold V _S1, that is, squared β ranging this first power is claimed Yes, it is.

Step 113 is a step for driving the pulse motor 3 toward the target position.

On the other hand, in the first step 201 of the control flow of the pressure stroke, it is determined whether or not the sprung vertical velocity V _n-1 obtained last time is a positive value (including 0). It is determined whether or not the time has changed. If YES, the process proceeds to step 202, and if NO, the process proceeds to step 203.

Step 202 is a step for initial setting the pressure side threshold value V _S2 .

Step 203 is a step for judging whether or not the sprung vertical speed Vn is _equal to or higher than the pressure side threshold value V _S2.
Go to 05.

Step 204 is a step for rewriting the pressure-side threshold value V _S2 to the current sprung vertical speed V _n .

Step 205 determines whether the steering stability control condition in step 104 is satisfied (ON) or not (OF).
In the step of determining F), if it is ON, the process proceeds to step 207, and if it is OFF, the process proceeds to step 206.

[0039] Step 206, the target position of the pulse motor 3, the current divided by the vertical sprung mass velocity V _n pressure side threshold V _S2 (the pressure side threshold current sprung vertical velocity for V _S2 V _n ) Is squared (α-th power) and multiplied by the pressure-side maximum damping coefficient (position at which the maximum damping coefficient is obtained).

[0040] Step 207, the target position of the pulse motor 3, the current divided by the vertical sprung mass velocity V _n pressure side threshold V _S2 (the pressure side threshold current sprung vertical velocity for V _S2 V _n Is calculated by multiplying the extension-side maximum attenuation coefficient (the position at which the maximum attenuation coefficient is reached) by itself. Also in this case, the β-th power in the claims is the first power.

Next, the operation of the embodiment will be described with reference to the time chart of FIG.

[0042] When the sprung mass vertical velocity V _n as shown in FIG changes, in the region of figure I, from the vertical sprung mass velocity V _n does not exceed the extension side threshold V _S1, the flow chart of step 105 become a flow -106-108-110-111, divided by the extension side threshold V _S1 of the vertical sprung mass velocity V _n (hereinafter, this is simply referred to as sprung mass vertical velocity ratio) squared, The value obtained by multiplying this by the maximum attenuation coefficient on the extension side is set as the target position. Therefore, the target position is
As shown in the figure, it changes to the extension side and the high attenuation side in proportion to the square of the sprung vertical speed ratio.

Next, in a region II from when the sprung vertical velocity V _n exceeds the extension side threshold value V _S1 to when it reaches a peak value,
Steps 105-106-108-1 in the flowchart
In the flow of 09-110-111, the target position is controlled as the position of the extension-side maximum damping coefficient.

Next, in the region of the drawing III to the vertical sprung mass velocity V _n is 0 reached a peak value, will flow in the same flow as in region I, at this time,
Since the expansion threshold value V _S1 has already been rewritten to the immediately preceding peak value, the target position is increased in proportion to the square of the sprung vertical speed ratio with respect to the immediately preceding peak value, as shown in FIG. Control to the side.

Next, in the region of figure IV from the vertical sprung mass velocity V _n is changed to the pressure side to over pressure side threshold V _S2, the flow chart of steps 105-201-202
With the flow of -203-205-206, the target position is controlled to the pressure side high attenuation side in proportion to the square of the sprung vertical speed ratio as shown in the figure.

Next, in the region of figure V from the vertical sprung mass velocity V _n is over the compression side threshold V _S2 until reaches a peak value, the flow chart of steps 105-201-20
With the flow of 3-204-205-206, the target position is controlled to the position of the compression-side maximum damping coefficient as shown in the figure.

Next, the spring in the region of figure VI of the vertical sprung mass velocity V _n exceeds the peak value, a flow of the same flowchart and IV, the target position, to the peak value of the immediately preceding, as shown The pressure is controlled so as to be in proportion to the square of the upper / lower speed ratio to the pressure side and the low attenuation side.

Next, as shown in a region VII, when the steering stability control condition is satisfied by performing the rapid steering or the rapid acceleration / deceleration, step 201-2 of the flowchart.
With the flow of 03-205-207, the target position is made proportional to (the first power of) the sprung vertical speed ratio, and the damping is controlled to be higher than before.

Next, as shown in region VIII, while steering stability control conditions described above is satisfied, when changes in the extension stroke, to the vertical sprung mass velocity V _n reaches the extension side threshold V _S1 is Steps 105-106-107-10 in the flowchart
In the flow of 8-110-112, the target position is controlled in proportion to the sprung vertical speed ratio (the first power) to have a higher damping coefficient than the region I in which the operation control condition is not satisfied. In this region, the shaded portion is the increase in the attenuation coefficient.

[0050] Thereafter, as shown in region IX, When the vertical sprung mass velocity V _n reaches the extension phase threshold V _S1, until reaches a peak value, as in the case of region II, the target position, Shin Control to the maximum side attenuation coefficient.

Next, as shown in a region X, When it sprung mass vertical velocity V _n is the peak value, and a flow of steps 1110-112 of the flowchart, the target position, the target position, immediately before the peak value Is proportional to the ratio of the sprung vertical speed to
Higher attenuation is controlled by the diagonal line compared to III.

[0052] In the embodiment as described above, when the sprung mass vertical velocity V _n is the extension side and less than the compression side threshold V _S1, V _S2, each threshold V _S1, V _S2 or peak value and in proportion to the square of the ratio of the vertical sprung mass velocity V _n determines a target position while performing rapid steering or sudden braking or sudden acceleration, when the steering stability control condition is satisfied, the threshold Ratio (first power) of V _S1 , V _S2 and sprung vertical velocity V _n
Because the target position is decided in proportion to
When it is necessary to enhance the steering stability, the rise of the damping force is quicker than in the normal control (see the hatched portion in FIG. 16), the damping performance on the spring is improved, and at this time, the damping coefficient is maximized. since it's in in proportion to the sprung mass vertical velocity V _n not fix it has given appropriate damping force to ride is improved.

That is, it has a feature that it is possible to achieve both steering stability and riding comfort.

[0054] Further, in the embodiment, the shock absorber SA is in increasing the damping coefficient of the vertical sprung mass velocity V _n directions, since the opposite stroke direction is configured to be secured to a minimum damping coefficient, When the damping coefficient is increased to increase the damping performance, if there is a road surface input in the reverse direction of the stroke direction due to bad road running, etc., the input in this direction is difficult to be transmitted to the vehicle body, and the ride comfort It has the feature of being further improved.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and any change in design without departing from the gist of the present invention is also included in the present invention.

For example, in the embodiment, when one of the expansion and pressure damping coefficients is changed as the shock absorber SA, the other is fixed to a low damping coefficient. The present invention can also be applied to a variable known structure.

Further, in the embodiment, α = 2 and α = 2, respectively, are specific numerical values for raising the sprung vertical speed ratio to the power of α and power of β.
Although β = 1 is shown, if the relationship α> β is satisfied, this numerical value can be appropriately adopted according to the characteristics of the suspension.

[0058]

As described above, in the vehicle suspension system of the present invention, when the steering stability condition is satisfied, the damping coefficient is usually controlled by controlling the ratio of the threshold value or peak value to the sprung vertical speed. Β, which is smaller than the power of α
Because the damping coefficient is set in proportion to the value of the power, when the steering control condition is satisfied by performing sudden steering, sudden braking, or sudden acceleration, the damping force rises compared to normal damping coefficient control. Hastened, the sprung mass damping property has been improved,
In addition, at this time, since the appropriate damping force is given in proportion to the sprung vertical velocity instead of fixing the damping coefficient to the maximum, the riding comfort is also improved, that is, both steering stability and riding comfort are compatible. Is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a vehicle suspension system of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of a vehicle suspension device according to an embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension device according to the embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber applied to the embodiment device.

FIG. 5 is an enlarged sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to a piston speed of the shock absorber.

FIG. 7 is a damping coefficient characteristic diagram corresponding to a step position of a pulse motor of the shock absorber.

FIG. 8 is a perspective view of the shock absorber shown in FIG.
It is -K sectional drawing.

FIG. 9 is a perspective view of the shock absorber shown in FIG.
It is a -M sectional view.

FIG. 10 is a sectional view taken along line NN of FIG. 5 showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram when the shock absorber is on the extension side hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on an extension side and a compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a pressure-side hard state.

FIG. 14 is a flowchart showing the operation of the control unit of the embodiment device.

FIG. 15 is a flowchart showing the operation of the control unit of the embodiment device.

FIG. 16 is a time chart showing the operation of the embodiment device.

[Explanation of symbols]

 a damping coefficient changing means b shock absorber c sprung vertical speed detecting means d operating condition determining means e damping coefficient controlling means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-217312 (JP, A) JP-A-5-169958 (JP, A) JP-A-58-30544 (JP, A) JP-A-61- 64513 (JP, A) JP-A-3-217313 (JP, A) JP-A-3-208717 (JP, A) JP-A-63-11407 (JP, A) JP-A-59-186711 (JP, A) JP-A-61-263815 (JP, A) JP-A-61-163711 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015

Claims (2)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and a wheel side and formed so as to be capable of arbitrarily changing a damping coefficient by damping coefficient changing means, and a sprung vertical speed detecting means for detecting a sprung vertical speed of the vehicle body. Means for judging a predetermined steering stability condition; and a ratio between the threshold value and the sprung vertical speed when the absolute value of the sprung vertical speed is less than a predetermined threshold value. While the damping coefficient is set by making the damping coefficient proportional to a value raised to the power of α, when the absolute value of the sprung vertical speed exceeds the threshold, the sprung vertical speed is exceeded after the threshold value is exceeded. Until the peak value is detected, the damping coefficient is fixed to the maximum damping coefficient, and when this peak value is detected, damping coefficient control is performed to set the damping coefficient in proportion to the sprung vertical velocity based on the peak value. Stability condition satisfied The damping coefficient control for setting the damping coefficient by proportionally setting the damping coefficient to a value obtained by raising the ratio of the sprung vertical velocity to the threshold value or the peak value to the βth power by a value β smaller than α. And a vehicle suspension device. 2. The shock absorber is characterized in that the damping coefficient changing means allows the damping coefficient on the extension side to be changed in multiple stages, and that the compression side has the extension side hard characteristic fixed to a low attenuation coefficient and the compression side damping coefficient in multiple stages. 2. The vehicle suspension system according to claim 1, wherein the characteristic can be changed to a compression-side hard characteristic that is variable and the extension side is fixed to a low damping coefficient.