JP3189176B2 - 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 a damping characteristic of a shock absorber, for example, Japanese Patent Laid-Open Publication No.
One described in Japanese Patent Publication No. 02439 is known.

This conventional vehicle suspension detects the sprung vertical speed and the relative speed between the sprung and unsprung speeds, and when the two direction discriminating codes match each other, moves the stroke side of the shock absorber at that time to the relative speed. By adopting a hardware damping characteristic based on the value, the vibration damping force (damping force) of the vehicle is increased, and when the direction discriminating codes do not match, the damping characteristic on the stroke side of the shock absorber at that time is softened. Thus, the damping characteristic control based on the Skyhook theory, such as reducing the vibration transmission force (excitation force) to the sprung, is performed independently for the four wheels.

[0004]

However, in the above-mentioned conventional apparatus, as described above, the damping characteristic of each shock absorber is set based on the relative speed between the sprung and unsprung parts. Therefore, there were the following problems.

That is, the relative speed component between the sprung and unsprung parts is
The high-frequency component near the unsprung resonance point is large, and the switching control of the damping characteristics of the shock absorber is performed based on this high-frequency control signal. Even when is small, the switching of the damping force is switched at a high frequency, so that the riding comfort of the vehicle becomes hard.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is capable of generating an appropriate control force for any road surface input. It is an object of the present invention to provide a vehicle suspension device that can secure the vehicle suspension.

[0007]

In order to achieve the above object, a vehicle suspension system according to the present invention is interposed between a vehicle body side and each wheel side as shown in FIG. Shock absorber b whose damping characteristic can be changed by characteristic changing means a, sprung vertical speed detecting means c for detecting a sprung vertical speed, and unsprung vertical speed detecting means for detecting a signal including at least a unsprung vertical speed component and d, when sprung mass vertical speed detected by the sprung mass vertical velocity detection means c is less than a predetermined threshold, rather than based on the sprung mass vertical velocity signal
The damping characteristic of the shock absorber b is controlled by the control output signal. on vertical velocity signal and based rather control output signal to the signal including at least unsprung vertical velocity component detected by the unsprung vertical velocity detecting means d bundled
And damping characteristic control means e for controlling the damping characteristic of the shock absorber b.

[0008]

According to the vehicle suspension system of the present invention, as described above, when the sprung behavior is small, the sprung vertical speed detected by the sprung vertical speed detecting means is less than a predetermined threshold value. Therefore, the damping characteristic control means, in which the damping characteristic control of the shock absorber is made by based rather control output signal to the sprung mass vertical velocity signals, thereby,
Control is performed with emphasis on the riding comfort of the vehicle.

When the sprung behavior becomes a high frequency, the sprung vertical speed detected by the sprung vertical speed detecting means exceeds a predetermined threshold value.
In based rather control output signal to the signal including at least unsprung vertical velocity component detected sprung detected by the sprung mass vertical velocity detecting means at a vertical velocity signal and the unsprung vertical velocity detecting means
The control of the damping characteristic of the shock absorber is further performed, whereby the control force is generated to make the vibration suppression force (vibration suppression force) of the vehicle appropriate, thereby ensuring the riding comfort and the steering stability.

[0010]

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

FIG. 2 is a structural explanatory view showing a vehicle suspension system according to an embodiment of the present invention. Four shock absorbers SA are provided between a vehicle body and four wheels. 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 each shock absorber SA, and a spring is provided between each wheel and the vehicle body. A stroke sensor 2 for detecting a relative displacement between the upper part and the lower part is provided.
At a position near the driver's seat, there is provided a control unit 4 that receives signals from the upper and lower G sensors 1 and the stroke sensors 2 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA. I have.

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 includes the above-described upper and lower G sensors 1 and A signal from each stroke sensor 2 is input.

As shown in FIG. 14A, a set of four filter circuits is provided for each of the upper and lower G sensors 1 in the interface circuit 4a. That is, in FIG. 14A, LPF1 is a low-pass filter for removing noise in a high frequency range (30 Hz or more) from the sprung vertical acceleration signal G sent from the vertical G sensor 1, and LPF2 is Low-pass filter LPF1
HPF1 is a low-pass filter for integrating the acceleration signal G processed in the above to convert the acceleration signal G into a sprung vertical velocity.
A high-pass filter with a cutoff frequency of 1.0 Hz.
The PF3 is a low-pass filter having a cutoff frequency of 1.5 Hz, and the two filters HPF1 and LPF3 constitute a band-pass filter for obtaining a low-frequency sprung vertical velocity Vn including a sprung resonance frequency.

As shown in FIG. 14B, a set of two filter circuits is provided for each stroke sensor 2 in the interface circuit 4a. That is, the HPF 2 is a high-pass filter that differentiates the relative displacement between the sprung and unsprung sent from the stroke sensor 2 and converts it into a relative sprung / unsprung speed signal.
HPF3 the cut-off frequency for obtaining a high-frequency relative velocity signal V _ST containing unsprung resonance frequency to remove low-frequency components including a sprung resonance frequency from the relative velocity signals between the unsprung on springs 3.0Hz Is a high pass filter.

FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 that defines the cylinder 30 in an upper chamber A and a lower chamber B, an outer cylinder 33 in which a reservoir chamber 32 is formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Base 34 and piston 31
A guide member 35 for guiding the sliding of the piston rod 7 connected to the outer cylinder 33, a suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and a bump rubber 37.

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 formed therein, 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 38 that penetrates the piston 31 is screwed and fixed to the bound stopper 41 screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31a and 31b. Communication for forming flow paths (extension-side second flow paths E, expansion-side third flow paths F, bypass flow paths G, and compression-side second flow paths J to be described later) that communicate the upper chamber A and the lower chamber B. A hole 39 is formed.
An adjuster 40 for changing the flow path cross-sectional area of the flow path is rotatably provided in 9. Also, stud 38
The communication hole 3 is formed on the outer periphery of the communication hole 3 in accordance with the direction of fluid flow.
An expansion-side check valve 17 and a compression-side check valve 22 that allow and shut off the flow on the flow path side formed by 9 are provided. Note that the adjuster 40 is provided with the pulse motor 3.
Is rotated through the control rod 70 (see FIG. 4). Also, studs 38
A first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed in this order from the top.

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, a through-hole 31 is formed as a flow path through which fluid can flow during the extension stroke.
b, the inside of the extension side damping valve 12 is opened to open the lower chamber B
, The second port 13, the vertical groove 23,
Via the second port 13, the vertical groove 23, and the fifth port 16 via the fourth port 14, the outer peripheral side of the extension side damping valve 12 is opened to open the outer peripheral side of the extension side damping valve 12 to reach the lower chamber B, Then, the extension side check valve 17 is opened to open the extension side third flow path F to the lower chamber B, and the bypass to the lower chamber B via the third port 18, the second horizontal hole 25, and the hollow portion 19. There are four flow paths G. In addition, as a flow path through which fluid can flow in the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a.
Channel H, hollow portion 19, first lateral hole 24, first port 21
, The pressure-side second flow path J that opens the pressure-side check valve 22 to reach the upper chamber A through the air passage, and the bypass flow that reaches the upper chamber A through the hollow portion 19, the second horizontal hole 25, and the third port 18. Road G
And three flow paths.

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 state where both the extension side and the compression side are soft (hereinafter, the soft area S
When the adjuster 40 is rotated in the counterclockwise direction from S), the damping characteristic can be changed in multiple stages only on the extension side, and the compression side becomes a region fixed to the low attenuation characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, the attenuation characteristic can be changed in multiple stages only on the compression side, and the expansion side becomes a region fixed to the low attenuation characteristic (hereinafter referred to as a compression side hard region SH). I have.

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

Next, among the control operations of the control unit 4, the control operation for setting the control signal V which is the basis of the damping characteristic control will be described with reference to the flowchart of FIG.
6 will be described. This control is performed separately for each shock absorber SA.

First, in the flowchart of FIG.
In step 101, the vertical acceleration obtained from each vertical G sensor 1 is filtered to determine the sprung vertical speed Vn of each wheel position, and the relative displacement between the sprung and unsprung obtained from each stroke sensor 2 is filtered. A sprung / unsprung relative speed signal _VST at each wheel position is obtained. Each of the sprung vertical speed Vn and the sprung / unsprung relative speed signal _VST is given as a direction discriminating code with a positive value in the upward direction and a negative value in the downward direction.

In step 102, the sprung vertical speed Vn
There is judged whether it is within range of predetermined Shin圧両threshold δ _VN ~δ _VN ', if YES, the process advances to step 103, the process proceeds to step 104 if NO.

In step 103, the control signal V is expressed by the following equation:
Determined by (1). V = G ₁ · Vn (1) G ₁ is a first speed gain.

In step 104, the sprung vertical speed Vn
There is judged whether it exceeds the threshold value [delta] _VN of the extension side, Y
If it is ES, the process proceeds to step 105, and if NO, the sprung vertical speed Vn is less than the pressure side threshold value _δVN ', and in this case, the process proceeds to step 109.

[0026] At step 105, the relative velocity signal V _ST is equal to or within the range of 0 and the extension side of the threshold V _XR, if YES, the process advances to step 106, step 107, if NO Proceed to.

In step 106, the value of the relative speed signal V _ST used in the calculation of the control signal V is changed to the threshold value V on the extension side.
After setting to _XR , go to step 107.

In step 107, the sprung vertical speed Vn
And the direction discrimination code of the relative speed signal _VST matches (V
n · V _ST > 0) is determined, and if YES, proceed to Step 108, and if NO, proceed to Step 103.

In step 108, the control signal V is calculated by the following equation.
Determined by (2). _{V = (G 2 · Vn /} G 3 · V ST) G 4 + δ V · G 1 ·········· (2) In addition, G ₂ is a second speed gain, G _3, the relative The speed gain, G ₄ is a control gain, and δ _V is a raised value of the control signal V.

In step 109, it is determined whether or not the relative speed signal V _ST is within the range of 0 and the threshold value V _{XB on} the pressure side. If YES, proceed to step 110, and if NO, proceed to step 111. move on.

In step 110, the value of the relative speed signal V _ST used in the calculation of the control signal V is changed to the pressure side threshold V
After setting to _XB , the process proceeds to step 111.

In step 111, the sprung vertical velocity Vn
And the direction discrimination code of the relative speed signal _VST matches (V
n · V _ST > 0) is determined. If YES, the process proceeds to a step 112, and if NO, the process proceeds to a step 103.

In step 112, the control signal V is calculated by the following equation.
Determined by (3). V = − (G ₂ · Vn / G ₃ · V _ST ) G ₄ −δ _V ′ · G ₁ (3) One control flow is completed as described above. FIG. 1 to be described later
Go to the flowchart of 7.

Next, based on the time chart of FIG.
A control operation for setting the control signal V will be described. still,
In this figure, the sprung vertical velocity Vn,
The relative speed signal V _ST and the control signal V are shown.

In this time chart, the area (a)
Is that the sprung vertical velocity Vn is equal to a predetermined extension / pressure threshold δ _V
~ Δ _V ′, and the area (b)
Is that the sprung vertical velocity Vn is equal to a predetermined extension / pressure threshold δ _V
Δ _V ′, but the direction of the relative speed signal V _ST is inconsistent with the direction of the sprung vertical speed Vn. In both regions (a) and (b), the control signal V Is set and controlled in step 103 to a value proportional to the control signal Vn. Therefore, when the sprung behavior is small, damping characteristic control is performed with emphasis on the riding comfort of the vehicle.

In the area (c), the sprung vertical speed Vn exceeds the range of the predetermined extension / pressure thresholds δ _{V to} δ _V ′, and the direction of the relative speed signal V _ST is an area to match the direction of the upper vertical velocity Vn, in the region (c), the value of the control signal V is proportional to the value obtained by dividing the sprung mass vertical velocity Vn at a relative speed signal V _ST in step 108 or 112 Is controlled. Therefore, the control force is generated to make the vibration suppression force (vibration suppression force) of the vehicle appropriate, whereby the riding comfort and the steering stability can be secured.

Next, the contents of the switching control of the attenuation characteristic in the control unit 4 will be described with reference to the flowchart of FIG. 17 and the time chart of FIG.

First, in the flowchart of FIG.
In step 201, it is determined whether or not the control signal V is a positive value. If YES, the flow advances to step 202 to control the shock absorber SA to the expansion-side hard region HS so as to control the expansion-side target attenuation position Pt. Is obtained by the following equation (4). Pt = α ₁ × V (4) where α ₁ is a proportional constant on the extension side.

Step 203 is a step for judging whether or not the control signal V is 0. If YES, proceed to step 204 to control the shock absorber SA to the soft area SS, and if NO, step 205 Proceed to.

Step 205 is a step displayed for convenience.
When it is determined to be O, the control signal V is a negative value,
In this case, the routine proceeds to step 206, where the target damping position Pc on the compression side is obtained by the following equation (5) in order to control the shock absorber SA to the compression-side hard region SH. Pc = α ₂ × V (5) Here, α ₂ is a proportional constant on the pressure side.

Next, the time chart of FIG. 18 will be described. The time chart shows the sprung vertical velocity V
The figure shows a case where the control signal V based on n changes in a sine curve.

In the time chart of FIG.
Is a state in which the control signal V is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative speed signal _VST is still a negative value (the stroke of the shock absorber SA is on the pressure stroke side). ), The shock absorber SA is controlled to the extension-side hard region HS based on the direction of the control signal V at this time. Therefore, in this region, the shock absorber SA is moved in the stroke of the shock absorber SA at that time. A certain pressure stroke side has soft characteristics.

In the area b, the control signal V remains at a positive value (upward), and the relative speed signal V _{ST switches} from a negative value to a positive value (the stroke of the shock absorber SA is extended). At this time, based on the direction of the control signal V, the shock absorber SA
, And the stroke of the shock absorber is also the extension stroke. Therefore, in this region, the extension stroke which is the stroke of the shock absorber SA at that time has a hard characteristic proportional to the value of the control signal V.

Area c is a state where the control signal V is reversed from a positive value (upward) to a negative value (downward).
At this time, since the relative speed signal V _ST is still in a region where the value of the relative speed signal V _ST is a positive value (the stroke of the shock absorber SA is on the extension stroke side), at this time, the shock absorber SA is on the compression side based on the direction of the control signal V. The hard region SH is controlled, and therefore, in this region, the extension stroke side, which is the stroke of the shock absorber SA at that time, has a soft characteristic.

A region d is a region in which the control signal V remains negative (downward) and the relative speed signal V _ST changes from a positive value to a negative value (the stroke of the shock absorber SA is on the extension stroke side). Therefore, at this time, the shock absorber SA is controlled to the compression-side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber SA is also the compression stroke. The pressure stroke side, which is the stroke of the shock absorber SA, has a hard characteristic proportional to the value of the control signal V.

As described above, in this embodiment, when the control signal V based on the sprung vertical velocity Vn and the relative speed signal _VST between the sprung and unsprung states have the same sign (area b, area d), ,
Based on the skyhook theory, the stroke side of the shock absorber SA at that time is controlled to hard characteristics, and when the sign is different (regions a and c), the stroke side of the shock absorber SA at that time is controlled to soft characteristics. The same control as the damping characteristic control is performed. And then,
In this embodiment, when shifting from the area a to the area b and from the area c to the area d, the switching of the attenuation characteristic is performed without driving the pulse motor 3.

As described above, in this embodiment, the following effects can be obtained.

[0048] Appropriate control force can be generated for any road surface input, and the riding comfort and steering stability of the vehicle can be ensured.

Since the frequency of switching of the damping characteristic is reduced as compared with the damping characteristic control based on the conventional skyhook theory, the control responsiveness can be improved and the durability of the pulse motor 3 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.

For example, in the embodiment, the extension side hard region in which the extension side has a variable attenuation characteristic and the compression side is fixed to the low attenuation characteristic, the compression side has the attenuation characteristic variable in the compression side and the extension side is fixed in the low attenuation characteristic, -Although the shock absorber having three regions, that is, the soft region having low damping characteristics on both the compression side and the compression side is used, the present invention can be applied to control using a shock absorber having a structure in which the extension side and the compression side change the damping characteristics simultaneously.

Further, in the embodiment, the case where the relative speed signal between the sprung and unsprung is used as the signal including at least the unsprung vertical speed component, but the unsprung vertical speed signal may be used.

[0053]

As described above, the vehicle suspension device of the present invention provides a sprung vertical speed signal when the sprung vertical speed detected by the sprung vertical speed detecting means is less than a predetermined threshold value. performs damping characteristics control of the shock absorber by a group Dzu rather control output signal, when sprung mass vertical speed detected by the sprung mass vertical velocity detecting means is equal to or greater than a predetermined threshold value is detected by the sprung mass vertical velocity detecting means bundled on vertical velocity signal and based rather control output signal including at least unsprung vertical velocity component detected by the unsprung vertical velocity detecting means
And a damping characteristic control means for controlling the damping characteristic of the shock absorber by a signal , so that an appropriate control force can be generated for any road surface input, and the riding comfort and the steering of the vehicle can be improved. The effect that stability can be ensured 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 force 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 an L sectional view and MM 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 block diagram of a signal processing in the apparatus according to the embodiment.

FIG. 15 is a flowchart illustrating a setting operation of a control signal serving as a basis for damping characteristic control among control operations of the control unit in the apparatus of the embodiment.

FIG. 16 is a time chart illustrating a setting operation of a control signal serving as a basis for damping characteristic control among control operations of the control unit in the embodiment device.

FIG. 17 is a flowchart illustrating a switching control operation of a damping characteristic in the control operation of the control unit in the embodiment device.

FIG. 18 is a time chart showing a switching control operation of a damping characteristic in the control operation of the control unit in the embodiment device.

[Explanation of symbols]

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

Continuation of the front page (56) References JP-A-5-178044 (JP, A) JP-A-5-155222 (JP, A) JP-A-4-334614 (JP, A) JP-A-62-20709 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 1/00-25/00

Claims (1)

(57) [Claims] 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 speed detecting means for detecting a sprung vertical speed, at least an unsprung state An unsprung vertical speed detecting means for detecting a signal including a vertical speed component; and a sprung vertical speed signal when the sprung vertical speed detected by the sprung vertical speed detecting means is less than a predetermined threshold. /> performs damping characteristics control of the shock absorber by a group Dzu rather control output signal, when vertical velocity sprung detected by the vertical sprung mass velocity detection means is equal to or greater than a predetermined threshold, in sprung mass vertical velocity detecting means attenuation of the detected sprung mass vertical velocity signal and <br/> shock absorber by based rather control output signal to the signal including at least unsprung vertical velocity component detected by the unsprung vertical velocity detecting means Vehicle suspension system, characterized in that it comprises a damping characteristic control means for performing sexual control, the.