JP2590075Y2 - 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 characteristic of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling damping characteristics of a shock absorber, for example, Japanese Unexamined Patent Publication No.
What is described in 163011 is known.

This conventional device detects a sprung vertical speed and a sprung-unsprung relative speed. When both detected values have the same sign, the damping characteristic is made hard, and when both detected values have different signs, the damping characteristic is made. As software, the damping characteristic control based on the skyhook theory is performed independently for four wheels.

[0004]

However, in the conventional apparatus, as described above, while the damping characteristic is being controlled to the hard side based on the low-frequency road surface input such as a bounce, the high-frequency road surface input such as a protrusion is generated. When the vehicle enters, the high-frequency road surface input under the spring is transmitted to the spring, whereby there is a problem that the riding comfort of the vehicle cannot be secured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is intended to improve the ride comfort of a vehicle when passing through a protrusion while ensuring the vehicle's vibration damping property when inputting a low-frequency road surface. It is an object of the present invention to provide a vehicle suspension device capable of performing the following.

[0006]

The vehicle suspension system according to the present invention is interposed between the vehicle body side and each wheel side, and the damping characteristic is changed by damping characteristic changing means a, as shown in the claim correspondence diagram of FIG. A possible shock absorber b, a sprung vertical acceleration detecting means c for detecting a sprung vertical acceleration of the vehicle,
A sprung vertical speed detecting means d for detecting a sprung vertical speed of the vehicle and a sprung vertical speed detecting means when the sprung vertical acceleration detected by the sprung vertical acceleration detecting means c is less than a predetermined threshold value. A signal for controlling the stroke direction side of the shock absorber b, which is the same as the direction of the sprung vertical speed detected at d, to the optimum damping characteristic proportional to the sprung vertical speed is output to the damping characteristic changing means a, and the sprung vertical acceleration is reduced. If the speed exceeds the specified threshold , the sprung vertical speed at that time is equal to the specified speed.
Judge whether it is more than the threshold, and more than the predetermined threshold
In the case of, a signal for reducing the damping characteristic in the stroke direction of the same shock absorber b as the direction of the sprung vertical speed for a predetermined period from that time to a predetermined value smaller than a value proportional to the sprung vertical speed is output. And a damping characteristic control means e for outputting to the damping characteristic changing means a.

Further, in the vehicle suspension device according to the second aspect,
In addition to the above configuration, the predetermined value of the attenuation characteristic is the reduced
The sprung vertical speed is changed in proportion to the sprung vertical speed when the sprung vertical acceleration becomes equal to or more than a predetermined threshold value .

[0008]

In the vehicle suspension system of the present invention, when the road surface input is in a low frequency state, the sprung vertical acceleration is less than a predetermined threshold value. This controls the stroke direction side of the shock absorber in the same direction as the optimal damping characteristic in proportion to the sprung vertical speed, thereby suppressing the vibration of the vehicle and ensuring the steering stability of the vehicle.

When a high-frequency road surface input such as a projection is made, the sprung vertical acceleration is equal to or higher than a predetermined threshold, and the sprung vertical speed at that time is equal to or higher than the predetermined threshold.
It is determined whether or not the damping characteristic is equal to or greater than a predetermined threshold value, and the damping characteristic control means sets a damping characteristic in the stroke direction of the same shock absorber as the direction of the sprung vertical speed for a predetermined time from that point. A control for reducing the value to a predetermined value smaller than a value proportional to the sprung vertical speed, thereby suppressing transmission of a high-frequency road surface input to the vehicle body and improving the riding comfort of the vehicle. be able to.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. First, the configuration of the vehicle suspension device according to the embodiment of the present invention will be described. FIG. 2 is an explanatory view showing the configuration of the vehicle suspension system according to the embodiment of the present invention. Four shock absorbers SA are provided between the vehicle body and each wheel. A sprung vertical acceleration sensor (hereinafter, referred to as a vertical G sensor) 1 for detecting a vertical acceleration is provided on a vehicle body near a position where each shock absorber SA is mounted on the vehicle body. A control unit 4 that receives a signal from each sensor 1 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA is provided at a nearby position.

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, and the interface circuit 4a receives signals from each of the upper and lower G sensors 1. A signal is input. And this interface circuit 4
14, a set of five filter circuits is provided for each of the upper and lower G sensors 1 as shown in FIG. That, LPF1 is a low-pass filter circuit for removing noise of a high frequency (30H _Z or higher) from the sprung mass vertical acceleration signal sent from the vertical G sensor 1. HPF1
Is a high-pass filter for removing the sprung resonance frequency from the sprung vertical acceleration signal to obtain an acceleration signal including the unsprung resonance frequency. The LPF 2 is a low-pass filter that integrates a sprung vertical acceleration signal and converts the signal into a sprung vertical speed. HPF2 is a high-pass filter cutoff frequency 1.0H _Z, LPF 3 is a cut-off frequency 1.5H
_{Z is} a low-pass filter, and both filters constitute a band-pass filter that obtains a sprung vertical speed signal including a sprung resonance frequency.

Next, FIG. 4 shows each shock absorber SA.
In this shock absorber SA, a cylinder 30, a piston 31 defining the cylinder 30 in an upper chamber A and a lower chamber B, and a reservoir chamber 32 on the outer periphery of the cylinder 30 are formed. An outer cylinder 33, a base 34 defining a lower chamber B and a reservoir chamber 32, a guide member 35 for guiding sliding of a piston rod 7 having a lower end connected to the piston 31, and an outer cylinder 33 and a vehicle body. The suspension spring 36 interposed between the bumper rubber 3
7 is provided.

FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b and A pressure-side damping valve 20 and an extension-side damping valve 12 for opening and closing 31a and 31b, respectively, are provided. A stud 3 penetrating the piston 31 is provided on a bound stopper 41 screwed to the tip of the piston rod 7.
8 is screwed and fixed, and this stud 38 has
A communication hole 39 communicating the upper chamber A and the lower chamber B is formed, and further, an adjuster 40 for changing a flow path cross-sectional area of the communication hole 39 and communication of the fluid in accordance with the direction of fluid flow. Extension side check valve 1 that allows and blocks the flow of hole 39
7 and a pressure side check valve 22 are provided.
The adjuster 40 is rotated by the pulse motor 3 via a control rod 70 (see FIG. 4). Also, the stud 38 has a first port 21, a second port 13, a third port 18,
A fourth port 14 and a fifth port 16 are formed.

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 which passes 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 so that the damping characteristic can be changed in multiple steps by rotating the adjuster 40 with the characteristics shown in FIG. 6 on both the extension side and the compression side. That is, as shown in FIG. 7, a region where both the extension side and the compression side are soft (hereinafter, the soft characteristic S
When the adjuster 40 is rotated in the counterclockwise direction from the S region, the damping characteristic can be changed in multiple stages to the hard side only on the extension side and the compression side is fixed softly (hereinafter, the extension side hard characteristic HS region). Conversely, when the adjuster 40 is rotated clockwise, the attenuation characteristic on the compression side can be changed to the hardware side in multiple stages and the expansion side is fixed softly (hereinafter referred to as the compression-side hard characteristic SH area). The structure is as follows.

In FIG. 7, the KK section, the LL section, the MM section, and the NN section in FIG. 8, 9 and 10 and the damping force characteristics at each position are shown in FIGS.

Next, the operation of the damping characteristic control section in the control unit 4 will be described with reference to the flowcharts of FIGS. 15 and 16 and the time chart of FIG.

First, the overall operation will be described with reference to the flowchart of FIG. 15 and the time chart of FIG.

In step 201, the sprung vertical acceleration G ₁
Is a step of determining whether or not is greater than or equal to a predetermined threshold value g. If YES, proceed to Step 202; if NO, proceed to Step 208.

[0021] Step 202 is sprung mass vertical velocity Vn is determining whether a predetermined threshold value V ₂ or more, YES, the processing advances to step 203, the process proceeds to step 205 if NO.

Step 203 is a step of controlling the damping characteristic to the second low damping position X ₂ , and then proceeds to step 204.

This step 204 is based on the sprung vertical speed V
n is determining whether drops below a predetermined threshold value V _2, the process returns to step 203 in NO, YE
In S, one control flow ends. That is, until sprung mass vertical velocity Vn falls below a predetermined threshold value V _2,
It is held in the second low-attenuation position X ₂ position.

In step 205, the sprung vertical speed V
n is determining whether a predetermined threshold value V ₁ or more, YES, the processing advances to step 206, the process proceeds to step 208 if NO.

Step 206 is a step of controlling the attenuation characteristic to the first low attenuation position X ₁ , and then proceeds to step 207.

In step 207, the sprung vertical speed V
n is determining whether drops below a predetermined threshold value V _1, the flow returns to step 206 in NO, YE
In S, one control flow ends. That is, until sprung mass vertical velocity Vn falls below a predetermined threshold value V _1,
It is held in the first low-attenuation position X ₁ position.

Step 208 is a step in which normal control is performed, and one control flow is completed.

Next, the operation of the normal control in step 208 will be described with reference to the flowchart of FIG.

Step 101 is a step of detecting the sprung vertical acceleration G ₁ from the vertical G sensor 1.

[0030] Step 102 is a step of calculating a vertical velocity Vn sprung by integrating the vertical acceleration G ₁ detected spring. The sprung vertical velocity Vn is given a positive value in the upward direction and a negative value in the downward direction.

Step 103 is a step for determining whether or not the sprung vertical speed Vn is a positive value (upward). If YES (upward), the process proceeds to step 104, and NO
The process proceeds to step 105 (downward).

Step 104 is a step for judging whether or not the previous sprung vertical velocity Vn _-1 is a negative value. If YES, proceed to Step 106; if NO, proceed to Step 1
Proceed to 07. That is, in this step, it is determined whether or not the direction of the sprung vertical speed Vn has been reversed.

Step 106 is a step of initially setting the threshold value V _S1 of the upward sprung vertical speed Vn to a predetermined value.

Step 107 is a step for judging whether or not the sprung vertical speed Vn is equal to or higher than a predetermined threshold value V _S1 .
If NO (less than), the process proceeds to step 109.

Step 108 is a step of updating the initially set value of the threshold value V _{S1 to} the value of the sprung vertical speed Vn at that time.

In step 109, the shock absorber S
The target attenuation position on the extension side at A (TARGET)
Is set, and the pulse motor 3 is driven toward the set target position. This target attenuation position is obtained based on an arithmetic expression of (Vn / _VS1 ) ² * F _{+ MAX} . Note that F _{+ MAX} is the position where the damping force on the extension side is the maximum, and the two values in parentheses in the above-mentioned equation are that the change in the damping characteristic with respect to the sprung vertical velocity Vn is corrected linearly. To do that. Then, this completes one control flow.

Step 105 is a step for judging whether or not the previous sprung vertical velocity Vn _-1 is a positive value. If YES, proceed to Step 110; if NO, Step 1 is performed.
Proceed to 11. That is, in this step, it is determined whether or not the direction of the sprung vertical speed Vn has been reversed.

Step 110 is a step of initially setting the threshold value V _S2 of the downward sprung vertical speed Vn to a predetermined value.

Step 111 is a step for judging whether or not the sprung vertical speed Vn has become equal to or lower than a predetermined threshold value V _S2 . If YES, the process proceeds to step 112, and if NO, the process proceeds to step 113.

Step 112 is a step of updating the initially set value of the threshold value V _{S2 to} the value of the sprung vertical speed Vn at that time.

The step 113 is a step of the shock absorber S
Target damping position on the compression side at A (TARGET)
Set a step of driving the pulse motor 3 towards its set target position, the target damping position is determined based on the arithmetic expression ^{_{(Vn / V S2) 2 ×}} F -MAX. In addition, F- _MAX is a position where the damping force on the _compression side becomes maximum. Then, this completes one control flow.

The control unit 4 repeats the above control flow.

FIGS. 18 and 19 are time charts showing the operation of the control unit 4 in the normal control state. First, the time chart of FIG. 18 will be described. In order from the top, the sprung vertical speed Vn, damping force and stroke It shows changes in the direction, relative speed, and damping position. The sprung vertical speed Vn draws a sine curve and alternately extends on the extension side and the compression side, and the peak values P ₁ and P ₂ are initialized in the vertical direction. Are shown to exceed the threshold values V _S1 and V _S2 of FIG.

In the drawing, a region a is a sprung vertical speed V
The region where n is upward and less than the initial threshold value V _S1 . In this case, the target extension-side damping position is controlled in proportion to the sprung vertical velocity Vn. At this time, since the stroke of the shock absorber SA is a compression stroke, the compression-side soft characteristic is reduced. (Minimum damping position 0) makes it possible to suppress thrust of the vehicle body due to road surface input.

The next area b is an area where the sprung vertical velocity Vn becomes equal to or higher than the initial threshold value V _S1 and reaches the peak value P _{1. In} this case, the flow of steps 107 to 108 in FIG. As a result, the threshold value V _S1 is made to coincide with the sprung vertical velocity at any time. As a result, the attenuation position is held at the extension-side maximum attenuation position F _{+ MAX} until the peak value P ₁ is reached. By increasing the damping characteristic on the extension side in this way, it is possible to suppress the upward vibration of the vehicle body.

The next area c is an area where the sprung vertical speed Vn crosses the peak value P _{1 from the} sprung vertical speed = 0, and in this case, the sprung vertical speed Vn is the peak value P ₁
In at the time became, since the threshold V _S1 is also equal to the peak value P _1, on the basis of the calculation formula shown in step 109 of FIG. 16, sprung mass vertical velocity Vn is the peak value P ₁ primary area d Is a region from when the sprung vertical velocity Vn becomes 0 to when it becomes equal to or more than the threshold value V _S2 of the downward initial setting. In this case, the target damping position on the pressure side is controlled in proportion to the sprung vertical velocity Vn. At this time, the stroke of the shock absorber SA is the extension stroke, so that the soft characteristic of the extension side is increased. (Lowest damping position 0) makes it possible to suppress sinking of the vehicle body due to road surface input.

The next area e is an area where the sprung vertical velocity Vn becomes equal to or higher than the initial threshold value V _S2 and reaches the peak value P _{2. In} this case, the flow of steps 111 to 112 in FIG. As a result, the threshold value V _S2 is made to coincide with the sprung vertical velocity at any time. As a result, the damping position is held at the compression-side maximum damping position F- _MAX until the peak value P ₂ is reached. By thus increasing the compression-side damping characteristic, it is possible to suppress the vibration in the downward direction of the vehicle body.

The next area f is an area where the sprung vertical velocity Vn crosses the sprung vertical velocity = 0 from the peak value P _{2. In} this case, the sprung vertical velocity Vn is the peak value P ₂
At this point, since the threshold value V _S2 is equal to the peak value P ₂ , the sprung vertical velocity Vn changes upward from the peak value P ₂ based on the arithmetic expression shown in step 113 in FIG. From that point, the pressure-side damping position decreases in proportion to the change in the sprung vertical speed Vn.

Referring to the time chart of FIG. 19, the change in the sprung vertical velocity Vn and the damping position is shown in order from the top, and the sprung vertical velocity Vn draws a sine curve to alternate between the extension side and the compression side. , The sprung vertical speed Vn changes below the initially set thresholds V _S1 and V _S2 in the vertical direction, respectively.

As shown in this figure, the sprung vertical velocity Vn
_Are the threshold values V _S1 ,
If it changes below V _S2 , the sprung vertical speed V at that time
The damping position on the stroke side of the same shock absorber as the direction of n is changed in proportion to the value of the sprung vertical speed Vn.

As described above, in the vehicle suspension system of this embodiment, the sprung vertical acceleration G ₁ Is less than the predetermined threshold value g , the stroke direction side of the shock absorber SA, which is the same as the direction of the sprung vertical speed Vn, is controlled to the optimal damping characteristic proportional to the sprung vertical speed Vn. Vertical acceleration
G ₁ Is larger than a predetermined threshold value g , the sprung mass at that time
Der vertical velocity Vn is a predetermined threshold V ₁ or V ₂ or more
To determine Luke, predetermined threshold V ₁ or V ₂ or more
, The sprung up-and-down speed Vn becomes a predetermined threshold value V ₁ from that point. , V ₂ Until the value becomes smaller than the value, the damping characteristic in the stroke direction of the shock absorber SA, which is the same as the direction of the sprung vertical speed Vn, is proportional to the sprung vertical speed Vn.
The low damping position X ₁ , X _{2 is} reduced to a smaller value to ensure the vehicle's vibration damping performance at the time of low-frequency road surface input, while absorbing the road surface input with a low damping characteristic at the time of passing a protrusion. The ride comfort of the vehicle can be improved.

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

[0053]

As described above, when the sprung vertical acceleration is less than a predetermined threshold value, the vehicle suspension of the present invention has the same shock absorber vertical direction as the direction of the sprung vertical speed. Is controlled to an optimal damping characteristic proportional to the sprung vertical speed, and when the sprung vertical acceleration exceeds a predetermined threshold value , the sprung vertical speed at that time becomes a predetermined value.
Judge whether it is more than the threshold, and more than the predetermined threshold
, Damping characteristic control for reducing the damping characteristic in the stroke direction of the same shock absorber as the direction of the sprung vertical speed for a predetermined period from that time to a predetermined value smaller than a value proportional to the sprung vertical speed With the provision of the means, it is possible to improve the ride comfort of the vehicle with a low damping characteristic which is reduced when the vehicle passes through the protrusions, while securing the vibration damping property of the vehicle by the damping characteristic according to the sprung vertical speed when inputting a low frequency road surface. The effect that it can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a vehicle suspension device according to the present invention.

FIG. 2 is an explanatory view showing the configuration of the vehicle suspension device according to the 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 characteristic diagram of a damping characteristic 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 -L and MM sectional drawing.

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 block diagram illustrating a signal processing unit of the control unit.

FIG. 15 is a flowchart illustrating an operation of a damping characteristic control unit in the control unit.

FIG. 16 is a flowchart illustrating an operation of a normal control part of the control operation of the damping characteristic control unit.

FIG. 17 is a time chart illustrating the entire operation of the attenuation characteristic control unit.

FIG. 18 is a time chart illustrating an operation of the damping characteristic control unit during normal control.

FIG. 19 is a time chart illustrating an operation of the damping characteristic control unit during normal control.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c sprung vertical acceleration detecting means d sprung vertical speed detecting means e damping characteristic controlling means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B60G 17/00-23/00 F16F 9/50

Claims (2)

(57) [Scope of request for utility model registration] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping characteristic by damping characteristic changing means, a sprung vertical acceleration detecting means for detecting a sprung vertical acceleration of a vehicle, and a vehicle A sprung vertical speed detecting means for detecting a sprung vertical speed of the motor; and a sprung vertical speed detecting means for detecting when the sprung vertical acceleration detected by the sprung vertical acceleration detecting means is less than a predetermined threshold value. And outputs a signal for controlling the stroke direction side of the same shock absorber as the direction of the sprung vertical speed to the optimum damping characteristic proportional to the sprung vertical speed to the damping characteristic changing means, and the sprung vertical acceleration is equal to or greater than a predetermined threshold. , The sprung vertical speed at that time is equal to or higher than a predetermined threshold.
To determine Luke, time, sprung mass vertical velocity of the stroke direction of the damping characteristics of a given between sprung mass vertical velocity of the directions of the same shock absorber from that point is above a predetermined threshold value
And a damping characteristic control means for outputting a signal for reducing to a predetermined value smaller than a value proportional to the degree to the damping characteristic changing means. 2. The method according to claim 1, wherein the predetermined value of the reduced attenuation characteristic is
The vehicle suspension device according to claim 1, wherein the vertical suspension speed is changed in proportion to the vertical suspension speed when the vertical acceleration exceeds a predetermined threshold value .