JP3124632B2 - 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 vehicle suspension detects the sprung vertical speed and the relative speed between the sprung and unsprung states. When both have the same sign, the damping characteristic is hard, and when both have different signs, the damping characteristic is hard. The control of the damping characteristics based on the Skyhook theory, such as making the software softer, is performed independently for the four wheels.

[0004]

However, in the above-described conventional apparatus, the above-described configuration has the above-described structure. Therefore, when the hardware characteristics are suitable when the vehicle body is moving in the bounce direction, For the roll at the time of steering, since the body moment of inertia around the center of gravity of the body is applied to the sprung mass, the damping force (control force) is insufficient and sufficient damping performance cannot be obtained, resulting in stable steering. Inferiority,
In particular, there is a problem that a controllability is deteriorated because a phase shift occurs in a sprung vertical velocity component due to an influence of a lateral acceleration due to a cornering force.

FIG. 22 is a diagram viewed from the front of the vehicle for explaining the influence of lateral acceleration during cornering. As shown in FIG. 22, the vehicle body moves rightward in the traveling direction during cornering. In the case of rolling, the left and right sprung vertical acceleration sensors are also inclined in the roll direction of the vehicle body, so the sprung vertical acceleration sensor on the right wheel side, which is the roll direction side, is smaller than the actual vertical acceleration. In addition, the sprung vertical acceleration sensor on the left wheel side opposite to the roll direction is detected as a value larger than the actual vertical acceleration. Suitable rolls are detected and controllability is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides sufficient vibration damping performance not only during straight running but also during cornering, thereby improving steering stability. It is intended to be.

[0007]

In order to achieve the above object, a vehicle suspension system according to the first aspect of the present invention, as shown in the claim correspondence diagram of FIG. A shock absorber b which is interposed and whose damping characteristic can be changed by the damping characteristic changing means a; a sprung vertical speed detecting means c which detects a sprung vertical speed near a position where each shock absorber b is provided; The steering angular velocity detecting means d for detecting the steering angular velocity and the damping characteristic of each shock absorber b are obtained by adding the correction term obtained from the value of the steering angular velocity and the direction to the signal obtained from the value of the sprung vertical velocity and its direction. And means for controlling the attenuation characteristic based on the obtained control signal.

According to a second aspect of the present invention, in addition to the above-described structure, the shock absorber includes an extension-side hard region in which the extension side has a variable damping characteristic and the compression side has a low attenuation characteristic, and a compression side in which the attenuation characteristic is variable. To form a structure having three regions: a compression side hard region in which the extension side is fixed to low attenuation characteristics, and a soft region in which the extension side and the compression side have low attenuation characteristics on both the extension side and the compression side. When the control signal is below the negative threshold value, the shock absorber is controlled in the compression side hard range when the control signal is below the negative threshold, and when the control signal is between the positive and negative threshold values. In this case, the shock absorber was controlled to be in the soft range.

Further, the vehicle suspension device according to the third aspect is provided with a shock absorber b interposed between the vehicle body side and each wheel side and capable of changing the damping characteristic by the damping characteristic changing means a, and each shock absorber b. A sprung vertical speed detecting means c for detecting a sprung vertical speed near a set position, a steering angular speed detecting means d for detecting a steering angular speed of a vehicle, and a sprung near a position where each shock absorber b is provided. .Relative speed detecting means f for detecting the unsprung relative speed
A control signal obtained by adding a damping characteristic of each shock absorber b to a signal obtained from the value of the sprung vertical velocity and the direction thereof and a correction term obtained from the value of the steering angular velocity and the direction thereof, and a sprung / spring When the lower relative speed is the same sign, the damping characteristic is increased, and when the relative speed is different sign, the damping characteristic control means e for controlling the damping characteristic to a minimum is employed.

According to a fourth aspect of the present invention, as the signal obtained from the sprung vertical speed, a bounce rate based on the sprung vertical speed and a pitch rate detected from a difference between the front and rear sprung vertical speeds and the vehicle body are used as the signal. The signal obtained from the roll rate detected from the difference between the left and right sprung vertical speeds was used.

In the vehicle suspension system according to the present invention, the control signal is obtained by using a signal passed through a band-pass filter including a sprung resonance frequency of each of the front and rear wheels, and a pitch rate: A signal passed through a band-pass filter including the pitch resonance frequency was used, and a signal passed through a band-pass filter including the roll resonance frequency was used as the roll rate.

[0012]

According to the first aspect of the present invention, when the sprung vertical velocity and the steering angular velocity are detected by the sprung acceleration detecting means and the steering angular velocity detecting means, the damping characteristic control means determines the damping characteristic of each shock absorber. The control is performed based on a control signal obtained by adding a value of the steering angular velocity and a correction term obtained from the direction to the value of the sprung vertical velocity and the signal obtained from the direction.

Therefore, when a roll is generated by the steering, the value of the steering angular velocity which matches the phase of the roll and is not affected by the lateral acceleration applied to the vehicle body increases. To be enhanced
As a result, sufficient vibration damping can be obtained not only during straight running but also during cornering. Also, as mentioned above,
Steering based on the value of sprung vertical speed and the signal obtained from that direction
Determined by adding the correction term obtained from the angular velocity value and its direction
Control is performed on the basis of the control signal
A correction signal corresponding to the steering angular velocity is continuously taken as a control signal.
Cause sudden change of damping force characteristics.
And therefore the rider has trouble riding.
It does not give a pleasant sensation or impair steering stability.
Also, drive at a fixed steering angle, such as at the entrance of a highway.
In this case, the vehicle attitude is stable,
In a constant turning state of the vehicle, the steering angular velocity becomes zero.
Therefore, it does not generate excessive control force,
Therefore, the ride comfort is not degraded.

According to the second aspect of the present invention, when the control signal is equal to or more than the positive threshold value, the shock absorber is controlled in the extension side hard region (the compression side is fixed to a low attenuation characteristic), and the control signal is negative. Controls the shock absorber in the pressure-side hard area when the pressure is below the threshold (the extension side is fixed to low attenuation characteristics), and controls the shock absorber in the soft area when the control signal is between the positive and negative thresholds. Therefore, when the control signal based on the sprung vertical speed and the relative speed between the sprung and unsprung have the same sign, the stroke side of the shock absorber at that time is controlled to a hard characteristic, and when the sign is different, , The stroke side of the shock absorber at that time is controlled to soft characteristics,
Attenuation characteristic control based on the skyhook theory is performed.

Further, in the device according to the third aspect, the damping characteristic control means has the same sign between the control signal obtained as described above and the sprung / unsprung relative speed detected by the relative speed detecting means. At the time, the damping characteristic is increased, while when both have different signs, the damping characteristic is minimized, that is, the damping characteristic control based on the so-called skyhook theory is performed. Sufficient vibration damping can be obtained even when cornering.

Further, in the device according to the fourth aspect, a sufficient vibration damping property can be obtained for the pitch and roll of the vehicle during straight running.

Further, in the device according to the fifth aspect, an appropriate control force can be obtained even when the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different.

[0018]

An embodiment of the present invention will be described with reference to the drawings. (First Embodiment) First, the configuration will be described. FIG.
The first embodiment according to the first, second, fourth and fifth aspects of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a configuration of a vehicle suspension system according to an embodiment, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ , and SA ₄ are interposed between a vehicle body and four wheels. In this regard, when these four are collectively referred to and when the common configuration is described, they are simply indicated as SA.). A vertical acceleration sensor (hereinafter referred to as a vertical acceleration sensor) for detecting an acceleration in the vertical direction is provided on the vehicle body near each shock absorber SA.
A sensor 1) is provided. The steering ST unit includes a steering sensor 2 for detecting a steering angle.
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 outputs a drive control signal to the pulse motor 3 of each shock absorber SA.

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. The interface circuit 4a includes the above-described upper and lower G sensors 1 and Signals from the steering sensor 2 and the vehicle speed sensor 5 are input. The interface circuit 4a includes:
One set of five filter circuits shown in FIG. 14 is provided for each of the upper and lower G sensors 1. That is, the LPF 1 is a low-pass filter circuit for removing noise in a high frequency range (30 Hz or more) from signals sent from the upper and lower G sensors 1. LPF2 is a low-pass filter circuit for integrating a signal indicating acceleration that has passed through low-pass filter circuit LPF1 and converting the signal into a sprung vertical velocity. BPF1
Are passed through a frequency range including a sprung resonance frequency, and bounce component signals v (v ₁ , v ₂ , v ₃ , v ₄ , ₁ , ₂ , ₃ , ₄
Correspond to the position of each shock absorber SA. The same applies to the following. ) Is a band-pass filter circuit. The BPF 2 allows the pitch component signal v ′ (v ₁ ′, v
₂ ′, v ₃ ′, v ₄ ′). The BPF 3 allows the roll component signal v ″ (v ₁ ), v
₂ ″ ′, v ₃ ″, v ₄ ″). In this embodiment, the sprung resonance,
The case where the pitch resonance and the roll resonance have different frequencies is taken as an example. However, when these resonance frequencies are close to each other, only the BPF1 may be used as the bandpass filter.

Next, 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 An expansion damping valve 12 and a compression damping valve 20 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. The adjuster 40 is rotated by the pulse motor 3 via a control rod 70 (see FIG. 4). The first port 21, the second port 13, the third port 18, the fourth port 14, and the fifth port 16 are formed on the stud 38 in 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.

Accordingly, 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 in 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.

In FIG. 7, 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, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described with reference to the flowchart of FIG. This control is performed separately for each shock absorber SA.

In step 101, the steering sensor 2
In conjunction with obtaining a steering angular velocity F _x from the rate of change of the detected steering angle, the filter circuit a vertical acceleration obtained from each vertical G sensor 1,1,1,1 LPF1, LPF2, BP
F1, BPF2, and BPF3 to obtain a bounce component signal v, a pitch component signal v ', and a roll component signal v ". The sprung vertical acceleration signal has a positive value in the upward direction. The steering angular velocity F _X is given by a positive value because the shock absorber SA on the steering direction side is on the rising side (extending stroke side) of the vehicle body. The shock absorber SA on the side opposite to the steering direction is given a negative value because it is on the sinking side (pressure stroke side) of the vehicle body.

Step 102 uses the following equation (1).
A control signal V (V ₁ , V ₂ , V ₃ , V ₄ ) for the position of each wheel based on the steering angular velocity F _X and each component signal v, v ′, v ″.
Is the step of calculating

[0029]

(Equation 1) Note that α _f , β _f , γ _f , and θ _f are proportional constants of the front wheels, α
_r , β _r , γ _r , θ _r are the respective proportional constants of the rear wheels, and in particular, the proportional constants θ _f , θ _r of the steering correction term are set to larger values than other proportional constants. By changing the proportional constants according to the vehicle speed, tuning from a low speed to a high speed is possible. FIG. 17 shows the change characteristics of the proportional constant α of the bounce rate and the proportional constant β of the pitch rate with respect to the vehicle speed.

In each equation, the part bounded by the first α _f and α _r is the bounce rate, and β _f and β _r
The portion between the two is the pitch rate, γ _f , γ _r
The rolled portion is the roll rate, θ _f , θ _r
The portion enclosed by the circle is the steering correction term.

[0031] Step 103, the control signal V is a step equal to or larger than a predetermined threshold value [delta] _T, the process proceeds to step 104 in YES, a step 1 is NO
Go to 05.

Step 104 is a step for controlling the shock absorber S
This is a step of controlling A to the extension-side hard area HS.

[0033] Step 105 is a step of determining whether a value between the control signal V is a predetermined threshold value [delta] _T and the threshold - [delta _C, the process proceeds to step 106 YES, a by NO Proceed to step 107.

Step 106 is a step of shock absorber S
This is the step of controlling A to the soft area SS.

Step 107 is a step displayed for the sake of convenience.
When it is determined that O is the control signal V is less than a predetermined threshold value - [delta _C, in this case, the process proceeds to step 108.

Step 108 is a step of the shock absorber S
This is a step of controlling A to the compression side hard area SH.

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

When the sprung vertical speed changes as shown by the control signal V in this figure, as shown in the figure, the control signal V
Is between predetermined thresholds δ _T , −δ _C ,
The shock absorber SA is controlled to the soft area SS.

When the control signal V becomes equal to or greater than the threshold value δ _{T, the} compression side is controlled to the expansion side hard region HS so that the compression side is fixed to the low attenuation characteristic, while the expansion side attenuation characteristic is made proportional to the control signal V. Change. At this time, the attenuation characteristic C is C = k ₁ · V
Is controlled so that

When the control signal V becomes equal to or less than the threshold value -δ _{C, the} compression side is controlled to the compression side hard area SH to fix the extension side to the low attenuation characteristic, while making the compression side attenuation characteristic proportional to the control signal V. Change. Also at this time, the attenuation characteristic C is C = k ₂
・ V is controlled to be V. The proportional constants k ₁ and k ₂ change according to the vehicle speed.

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

In a region b, the control signal V based on the sprung vertical speed remains a positive value (upward), and the relative speed changes from a negative value to a positive value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA is controlled to the extension-side hard area HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. In this region, the extension stroke which is the stroke of the shock absorber SA at that time has a hardware characteristic proportional to the value of the control signal V.

The area c is a state where the control signal V based on the sprung vertical velocity is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative velocity is still a positive value. (The stroke of the shock absorber SA is the extension stroke side.) 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. In the region, the extension stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the area d, the control signal V based on the sprung vertical velocity remains negative (downward), and the relative velocity changes from a positive value to a negative value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA is controlled to the pressure side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber is also the pressure stroke. Then, the pressure stroke side, 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.

As described above, in this embodiment, when the sprung vertical speed and the relative speed between the sprung and unsprung are the same sign (region b, region d), the shock absorber S at that time is used.
A damping characteristic control based on the skyhook theory, in which the stroke side of A is controlled to a hard characteristic, and when the sign is different (regions a and c), the stroke side of the shock absorber SA at that time is controlled to a soft characteristic. The same control will be performed without detecting the relative speed between sprung and unsprung. Further, 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 damping characteristic is performed without driving the pulse motor 3.

Next, the operation of the control unit 4 when the vehicle is running straight and during steering will be described. (B) Straight running When the vehicle is running straight, the value of the steering correction term is 0, so that the bounce rate based on the sprung vertical speed,
The control signal V is obtained based on the pitch rate and the roll rate. Therefore, sufficient vibration damping properties can be exhibited not only for the bounce but also for the vehicle behavior in which the pitch and the roll are trained.

[0047] (b) the steering when the steering is performed, although the roll of the vehicle is generated, based on the value of the steering angular velocity F _x which is not affected by the lateral acceleration applied to the vehicle body with consistent with this role phase steering The correction term sharply increases by proportional constants θ _f and θ _{r which} are larger than the proportional constants of other rates (bounce, pitch, roll). A) When the vehicle rolls to the right due to left steering,
In the shock absorber SA on the left wheel side is the steering direction, since the steering angular velocity F _x is obtained as a positive value, the control signal V is a positive value, the attenuation characteristics of the extension side of the control signal V value increases in proportion to, also, the steering direction in the shock absorber SA on the right wheel side is reverse, since the steering angular velocity F _x is obtained in a negative value, so the control signal V is a negative value , The pressure-side damping characteristic increases in proportion to the value of the control signal V, so that the rightward roll of the vehicle is appropriately suppressed.

[0048] b) When the right steering vehicle rolls in the left direction, the shock absorber SA on the right wheel side is the steering direction, since the steering angular velocity F _x is obtained as a positive value, the control signal V is As a positive value, the damping characteristic on the extension side increases in proportion to the value of the control signal V. In the shock absorber SA on the left wheel side opposite to the steering direction, the steering angular velocity _Fx is Since the control signal V is obtained as a negative value, the control signal V becomes a negative value, and the damping characteristic on the pressure side increases in proportion to the value of the control signal V. Therefore, the leftward roll of the vehicle is appropriately suppressed. You.

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

When a vehicle travels straight, it is possible to generate a sufficient control force not only for bounces but also for pitches and rolls. Therefore, it is possible to provide a vehicle suspension system that is excellent in ride comfort and steering stability. Can be.

The function of the steering correction term based on the steering angular velocity not only at the time of straight running of the vehicle but also at the time of cornering makes it possible to obtain sufficient vibration damping properties and secure steering stability. Also, as described above, the sprung vertical speed
The steering angular velocity F _x every value and signals obtained from that direction
Value and the steering correction term obtained from that direction.
The control is performed based on the control signal V, that is, the control is always performed.
The correction signal is continuously control signal V in accordance with the steering angular velocity F _x
Because it is taken in, the sudden change of the damping force characteristics
It does not cause
It does not cause discomfort or impair steering stability.
No. In addition, a fixed steering angle such as at the entrance of a highway
The vehicle attitude is stable when traveling with
However, in such a constant turning state of the vehicle, the steering angular velocity
Since the degree F _x becomes zero, excessive control force is generated
There is no deteriorating ride quality.
No. Since different constants α, β, and γ are used in obtaining the bounce rate, pitch rate, and roll rate, even if the sprung resonance frequency, pitch resonance frequency, and roll resonance frequency are different in a vehicle, the sprung rate Each rate can be accurately detected based on the vertical speed.

In obtaining the bounce rate, pitch rate, and roll rate, different constants α,
Since β and γ are used, in the vehicle, even if the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different from each other, each rate can be accurately detected based on the sprung vertical speed.

Next, other embodiments will be described. In describing these embodiments, only differences from the first embodiment will be described. In addition, the first reference
The same reference numerals as those in the embodiments indicate the same objects.

(Second Embodiment) In the second embodiment, a part of the control unit 4 is different from that of the first embodiment, and the following equation (2) is used to obtain the control signal V.

[0055]

(Equation 2) That is, in the second embodiment, the bounce component can be obtained independently based on the sprung vertical velocity of each wheel, thereby performing control that emphasizes the bounce component.

(Third Embodiment) In a third embodiment, as a shock absorber SA, a variable damping characteristic type is used, and when the pulse motor 3 is driven, as shown in FIG. , Both of which have a known structure that changes from high attenuation to low attenuation (for example, Japanese Utility Model Application Laid-Open No. 63-112914).
In this example, damping characteristic control based on the conventional skyhook theory is performed.

Therefore, in the third embodiment, as shown in FIG. 20, in addition to the sprung G sensor 1 as input means, load sensors (spring-spring-unsprung relative speed detecting means) 6, 6,
6, 6 are provided. As shown in FIG. 18, this load sensor 6 is provided on the piston rod 7 below the mounting portion of each shock absorber SA to the vehicle body, and a damping force (relative force) generated by the shock absorber SA is provided. (Corresponding to speed) F is detected as a load.

Control unit 300 of the third embodiment
21 will be described with reference to the flowchart of FIG. 21. In step 301, the damping force F detected by the load sensor 6 is determined.
After this processing, the process goes through steps 101 and 102 similar to the first embodiment, and then proceeds to step 302.

In step 302, the damping force F and the control signal V
Is a step for determining whether or not
The process proceeds to step 303 with NO, and proceeds to step 304 with NO (with a different sign).

In step 303, the damping force F becomes F = k
-Change the attenuation characteristic so that V is obtained.

In step 304, control is performed so that the damping characteristics of the shock absorber SA are the minimum damping characteristics in both the extension and the pressure.

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, as a signal obtained from the sprung vertical speed, a bounce rate based on the sprung vertical speed, a pitch rate detected from a sprung vertical speed difference between the front and rear of the vehicle, and a sprung vertical speed of the left and right of the vehicle. Although the signal obtained from the roll rate detected from the speed difference is used, any one or two of the three rates can be omitted.

[0064]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension device described above, the damping characteristic of each shock absorber is adjusted by the damping characteristic control means so that the signal obtained from the sprung vertical velocity matches the roll phase and the steering angular velocity is not affected by the lateral acceleration applied to the vehicle body. Control based on the control signal obtained by adding the correction term obtained from the above, sufficient vibration damping can be obtained not only when traveling straight ahead but also when cornering, thereby improving ride comfort and steering stability. The effect of being able to improve is obtained.
Also, as described above, the value of the sprung vertical velocity and its direction
From the value of steering angular velocity and its direction
Control is performed based on the control signal obtained by adding the
That is, a correction signal corresponding to the steering angular velocity is always
Since it is continuously captured in the control signal, the damping force characteristics
Without causing a sudden changeover, and therefore the occupant
Gives the driver uncomfortable feeling about riding comfort and poor handling stability.
It does not change. Also, like the entrance of a highway
When traveling at a fixed steering angle, the vehicle attitude is
However, when the vehicle is in a constant turning state,
Generates excessive control force because the steering angular velocity becomes zero.
And therefore cause a deterioration in ride quality.
Not even.

In the vehicle suspension system according to the present invention, the bounce rate based on the sprung vertical speed, the pitch rate detected from the sprung vertical speed difference between the front and rear of the vehicle, and the vehicle right and left as the signal obtained from the sprung vertical speed. By using the signal obtained from the roll rate detected from the difference between the sprung vertical velocity of the vehicle, sufficient vibration suppression can be obtained not only for bounce, but also for pitch and roll, especially during straight running. Become.

In the vehicle suspension according to the fifth aspect,
Even when the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different, an appropriate control force can be 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 a configuration explanatory view showing a vehicle suspension system according to a first embodiment of the present invention.

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

FIG. 4 is a sectional view showing a shock absorber applied to the first 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 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 showing a main part of the control unit of the first embodiment.

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

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

FIG. 17 is a change characteristic diagram of a proportional constant with respect to a vehicle speed in the first embodiment device.

FIG. 18 is a sectional view showing a shock absorber applied to the third embodiment.

FIG. 19 is a characteristic diagram of a damping characteristic of a shock absorber of the device of the third embodiment.

FIG. 20 is a system block diagram showing a device according to a third embodiment.

FIG. 21 is a flowchart showing the control operation of the control unit of the third embodiment.

FIG. 22 is a diagram for explaining the influence of lateral acceleration during cornering.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c sprung vertical speed detecting means d steering angular velocity detecting means e damping characteristic controlling means f relative speed detecting means

Continuation of the front page (56) References JP-A-2-141317 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60G 17/015 B60G 17/08 F16F 9/50

Claims (5)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing damping characteristics by damping characteristic changing means, and detecting a sprung vertical speed near a position where each shock absorber is provided. A sprung vertical velocity detecting means, a steering angular velocity detecting means for detecting a steering angular velocity of the vehicle, and a damping characteristic of each shock absorber, a steering angular velocity value and a direction obtained from a signal obtained from the sprung vertical velocity value and the direction thereof And a damping characteristic control means for controlling based on a control signal obtained by adding a correction term obtained from the vehicle suspension. 2. A compression-side hard region in which the expansion side has a variable damping characteristic and the compression side is fixed to a low attenuation characteristic, a compression-side hard region in which the compression side has a variable attenuation characteristic and the expansion side is fixed to a low attenuation characteristic. The damping characteristic control means is formed in a structure having three regions of a soft region having a low damping characteristic on both the side and the pressure side. When the control signal is equal to or more than a positive threshold value, the shock absorber is controlled in the expanding hard region. And
When the control signal is less than the negative threshold, the shock absorber is controlled in the pressure side hard range, and when the control signal is between the positive and negative thresholds, the shock absorber is controlled in the soft range. The vehicle suspension device according to claim 1, wherein 3. A shock absorber interposed between the vehicle body side and each wheel side and capable of changing damping characteristics by damping characteristic changing means, and detecting a sprung vertical speed near a position where each shock absorber is provided. A sprung vertical velocity detecting means, a steering angular velocity detecting means for detecting a steering angular velocity of the vehicle, a relative speed detecting means for detecting a sprung / unsprung relative velocity near a position where each shock absorber is provided, The damping characteristic of the shock absorber is calculated by adding the correction value obtained from the value of the steering angular velocity and the direction to the signal obtained from the value and the direction of the sprung vertical velocity and the relative value between the sprung and unsprung parts. And a damping characteristic control means for controlling the damping characteristic to a minimum while increasing the damping characteristic when the speed is the same sign. Location. 4. A signal obtained from the sprung vertical speed, a bounce rate based on the sprung vertical speed, a pitch rate detected from a sprung vertical speed difference between the front and rear of the vehicle body, and a sprung vertical speed difference between the left and right vehicle bodies. 4. The vehicle suspension according to claim 1, wherein a signal obtained from the roll rate is used. 5. The control signal is obtained by using a signal passed through a band-pass filter including a sprung resonance frequency of each of the front and rear wheels as a bounce rate, and using a band-pass filter including a pitch resonance frequency as a pitch rate. The vehicle suspension device according to claim 4, wherein a signal passed through a band-pass filter including a roll resonance frequency is used as the roll rate.