JPH0648140A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To obtain sufficient damping performance not only during rectilinear travel but also during cornering travel so as to improve maneuvering stability. CONSTITUTION:A suspension device for a vehicle is provided with a shock absorber (b) interposed between the body side and each wheel side in such a way as to be changeable in its damping characteristic by a damping characteristic changing means (a), a sprung vertical speed detecting means (c) for detecting the sprung vertical speed near a position where each shock absorber (b) is provided, a steering angle speed detecting means (d) for detecting the steering angle speed of the vehicle, and a damping characteristic control means (e) for controlling the damping characteristic of each shock absorber (b) on the basis of a control signal obtained by adding a correction term, obtained from the steering angle speed, to a signal obtained from the sprung vertical speed.

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 the damping characteristics of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling the damping characteristic of a shock absorber, for example, Japanese Patent Laid-Open No. 61-
The one described in Japanese Patent No. 163011 is known.

This conventional vehicle suspension system detects the sprung vertical speed and the relative speed between the sprung and unsprung parts, and when both have the same sign, the damping characteristic is made hard, and when the two have different signs, the damping characteristic. The damping characteristic control based on the skyhook theory, such as softening, was performed independently for the four wheels.

[0004]

However, since the above-mentioned conventional apparatus has the above-mentioned structure, when the characteristics of the hardware are suitable when the vehicle body is moving in the bounce direction, For the roll during steering, the moment of inertia of the vehicle body around the center of gravity of the vehicle body is added to the sprung mass, so the damping force (control force) is insufficient and sufficient vibration damping cannot be obtained, resulting in stable steering. Inferior in sex,
In particular, there is a problem in that the sprung vertical velocity component is out of phase due to the influence of the lateral acceleration due to the cornering force, which leads to deterioration in controllability.

That is, FIG. 22 is a diagram viewed from the front side 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. When the roll is rolled, the left and right sprung vertical acceleration sensors are also tilted in the rolling direction of the vehicle body.Therefore, the sprung vertical acceleration sensor on the right wheel side, which is the rolling direction, is smaller than the actual vertical acceleration. In addition, the sprung vertical acceleration sensor on the left wheel side, which is the opposite side to the roll direction, detects a value larger than the actual vertical acceleration. Appropriate rolls are detected and controllability is reduced.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to obtain sufficient vibration damping performance not only when traveling straight ahead but also when cornering, and thereby improving steering stability. Is intended.

[0007]

In order to achieve the above-mentioned object, the vehicle suspension system according to claim 1 of the present invention is arranged between the vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. An intervening shock absorber b whose damping characteristic can be changed by the damping characteristic changing means a, a sprung vertical speed detecting means c for detecting a sprung vertical speed in the vicinity of the position where each shock absorber b is provided, and a vehicle The steering angular velocity detecting means d for detecting the steering angular velocity and the damping characteristics of each shock absorber b are added to the signal obtained from the value of the sprung vertical velocity and its direction by adding the correction term obtained from the value of the steering angular velocity and its direction. A damping characteristic control means e for controlling based on the obtained control signal is provided.

According to a second aspect of the present invention, in addition to the above structure, the vehicle suspension system includes the shock absorber in which the expansion side has a variable damping characteristic and the compression side has a low damping characteristic and the compression side has a variable damping characteristic. Is formed in a structure having three regions, that is, a compression side hard region where the extension side is fixed to the low damping characteristic and a soft region where both the extension side and the compression side are low damping characteristics, and the damping characteristic control means is provided with a positive control signal. When the threshold value is exceeded, the shock absorber is controlled in the expansion side hard area, and when the control signal is below the negative threshold value, the shock absorber is controlled in the compression side hard area, and the control signal is between the positive and negative threshold values. At the time of, the shock absorber was configured to be controlled in the soft region.

Further, the vehicle suspension system according to the third aspect is provided with a shock absorber b interposed between the vehicle body side and each wheel side, the damping characteristic of which can be changed by the damping characteristic changing means a, and each shock absorber b. The sprung vertical velocity detecting means c for detecting the sprung vertical velocity in the vicinity of the fixed position, the steering angular velocity detecting means d for detecting the steering angular velocity of the vehicle, and the sprung portion in the vicinity of the positions where the shock absorbers b are provided. .Relative speed detecting means f for detecting the relative speed between unsprung parts
And a control signal obtained by adding the correction term obtained from the value of the steering angular velocity and the direction thereof to the signal obtained from the value of the sprung vertical velocity and its direction, and the sprung / spring When the relative velocity between the lower parts has the same sign, the damping characteristic is increased, while when it has a different sign, the damping characteristic control means e for controlling the damping characteristic to the minimum is provided.

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

Further, in the vehicle suspension system according to a fifth aspect of the present invention, in obtaining the control signal, the bounce rate uses a signal that has passed through a band pass filter including the sprung resonance frequencies of the front and rear wheels, and the pitch rate is A signal passed through a bandpass filter including the pitch resonance frequency was used, and a signal passing through a bandpass filter including the roll resonance frequency was used as the roll rate.

[0012]

In the device according to the first aspect, when the sprung acceleration detection means and the steering angular velocity detection means detect the sprung vertical velocity and the steering angular velocity, the damping characteristic control means determines the damping characteristic of each shock absorber. The control is performed based on the control signal obtained by adding the correction term obtained from the value of the steering angular velocity and its direction to the signal obtained from the value of the sprung vertical velocity and its direction.

Therefore, when a roll occurs due to steering, the value of the steering angular velocity that matches the phase of the roll and is not affected by the lateral acceleration applied to the vehicle body increases, so that the control signal is appropriate according to the roll direction. To
As a result, sufficient damping performance can be obtained not only when traveling straight ahead but also when cornering.

Further, in the apparatus according to the second aspect, 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 the low damping characteristic), and the control signal is negative. The shock absorber is controlled in the compression side hard region (fixed to the low damping characteristic on the extension side) when it is below the threshold value, and the shock absorber is controlled in the soft region when the control signal is between the positive and negative threshold values. 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 the hardware characteristic, and when the sign is different, , At that time, the stroke side of the shock absorber is controlled to have a soft characteristic.
Attenuation characteristic control based on the skyhook theory is performed.

Further, in the apparatus according to the third aspect, the damping characteristic control means has the same sign as the control signal obtained as described above and the sprung / unsprung relative speed detected by the relative speed detecting means. In this case, the damping characteristic is increased based on the so-called skyhook theory, which minimizes the damping characteristic when the two have different signs. Sufficient vibration damping is obtained even during cornering.

Further, in the apparatus according to the fourth aspect, sufficient damping performance can be obtained even with respect to the pitch and roll of the vehicle when traveling straight ahead.

Further, in the apparatus 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]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described. Figure 2
The first embodiment which is an embodiment of the invention described in claims 1, 2, 4, 5
A configuration diagram showing a vehicle suspension system embodiment, is interposed between the vehicle body and four wheels, four shock absorbers _{SA 1, SA 2, SA 3} , SA 4 ( Incidentally, illustrating a shock absorber In the description, when these four are collectively referred to, and when describing a common configuration of these, simply referred to as SA) is provided. A vertical acceleration sensor (hereinafter, vertical G sensor) for detecting vertical acceleration is provided on the vehicle body near each shock absorber SA.
1) is provided. Further, the steering ST section has a steering sensor 2 for detecting a steering angle.
Is provided. Further, a control unit 4 is provided near the driver's seat to input a signal from each vertical G sensor 1 and output a drive control signal to the pulse motor 3 of each shock absorber SA.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a includes the above-mentioned vertical G sensors 1 and Signals from the steering sensor 2 and the vehicle speed sensor 5 are input. In the interface circuit 4a,
One set of five filter circuits shown in FIG. 14 is provided for each upper and lower G sensor 1. That is, the LPF 1 is a low-pass filter circuit for removing noise in the high frequency range (30 Hz or higher) from the signals sent from the upper and lower G sensors 1. The LPF2 is a low-pass filter circuit for integrating a signal indicating the acceleration that has passed through the low-pass filter circuit LPF1 and converting it into a sprung vertical velocity. BPF1
Is a bounce component signal v (v ₁ , v ₂ , v ₃ , v ₄ by passing through a frequency range including the sprung resonance frequency, ₁ , ₂ , ₃ , ₄
The number of corresponds to the position of each shock absorber SA. The same applies to the following. ) Is a band pass filter circuit that forms The BPF 2 passes the frequency range including the pitch resonance frequency to pass 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) to pass through a frequency range including the roll resonance frequency.
₂ ″ ′, v ₃ ″, v ₄ ″). By the way, in this embodiment, the sprung resonance,
Although the case where the pitch resonance and the roll resonance frequencies are different is taken as an example, when the resonance frequencies are similar, only the BPF 1 is required 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 defining the cylinder 30 into an upper chamber A and a lower chamber B, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Defining the base 34 and the piston 31
A guide member 35 that guides the sliding of the piston rod 7 that is connected to the vehicle, a suspension spring 36 that is interposed between the outer cylinder 33 and the vehicle body, and a bumper bar 37.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 is formed with through holes 31a and 31b, and each through hole is formed. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b, respectively, are provided. Further, a stud 38 penetrating 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 a flow path (an expansion-side second flow path E, an expansion-side third flow path F, a bypass flow path G, and a compression-side second flow path J described later) that connects the upper chamber A and the lower chamber B with each other. A hole 39 is formed and this communication hole 3
An adjuster 40 for changing the flow passage cross-sectional area of the flow passage is rotatably provided inside the passage 9. Also, the stud 38
The communication hole 3 is formed on the outer peripheral portion of the communication hole 3 depending on the direction of fluid flow.
An expansion-side check valve 17 and a pressure-side check valve 22 that allow and block the flow passage formed by 9 are provided. The adjuster 40 is rotated by the pulse motor 3 via the control rod 70 (see FIG. 4). Further, the stud 38 is formed with a first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 in order from the top.

On the other hand, in the adjuster 40, a hollow portion 19 is formed, a first lateral hole 24 and a second lateral hole 25 which communicate the inside and the outside are formed, and a vertical groove 23 is formed in the outer peripheral portion. There is.

Therefore, the through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which the fluid can flow in the extension stroke.
The inside of the extension side damping valve 12 is opened through b and the lower chamber B
To the extension side first flow path D, the second port 13, the vertical groove 23,
Via the expansion side second flow path E, which opens the outer peripheral side of the expansion side damping valve 12 to the lower chamber B via the fourth port 14, the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension side check valve 17 is opened to reach the lower chamber B by way of the third side flow passage F extending to the lower chamber B and the third port 18, the second lateral hole 25, and the hollow portion 19. There are four channels, channel G. Further, as a flow path through which the 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 is used.
Flow path H, hollow portion 19, first lateral hole 24, first port 21
Via the pressure side check valve 22 to the upper chamber A, and the bypass flow to the upper chamber A via the hollow portion 19, the second lateral hole 25, and the third port 18. Road G
There are three channels.

That is, the shock absorber SA is constructed so that the damping characteristic can be changed in multiple stages with the characteristics shown in FIG. 6 on both the extension side and the compression side by rotating the adjuster 40. That is, as shown in FIG. 7, both the extension side and the compression side are in the soft state (hereinafter, the soft region S
When the adjuster 40 is rotated counterclockwise from (S), the damping characteristic can be changed in multiple steps only on the extension side, and the compression side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the extension side hard region HS). On the contrary, when the adjuster 40 is rotated clockwise, the damping characteristic can be changed in multiple steps only on the compression side, and the extension side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the compression side hard region SH). There is.

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

Next, the operation of the control unit 4 for controlling the drive of the pulse motor 3 will be described with reference to the flowchart of FIG. Note that this control is separately performed for each shock absorber SA.

Step 101 is the steering sensor 2
The steering angular velocity F _x is obtained from the rate of change of the steering angle detected in step S1, and the vertical acceleration obtained from each vertical G sensor 1, 1, 1, 1 is applied to each filter circuit LPF1, LPF2, BP
This is a step of performing processing by F1, BPF2, 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 as a positive value because the vehicle body is on the upside (extension side) of the shock absorber SA on the steering direction side. Since the shock absorber SA on the side opposite to the steering direction is on the sinking side (pressure stroke side) of the vehicle body, it is given as a negative value.

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

[0029]

[Equation 1] Note that α _f , β _f , γ _f , and θ _f are the proportional constants of the front wheels, α
_r , β _r , γ _r , and θ _r are respective proportional constants of the rear wheels, and in particular, the proportional constants θ _f and θ _r of the steering correction term are set to values larger than other proportional constants. By varying each of the proportional constants according to the vehicle speed, tuning from low speed to 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 first part bounding by α _f and α _r is the bounce rate, and β _f and β _r
The part enclosed by is the pitch rate, and γ _f and γ _r
The part enclosed by is the roll rate, and θ _f and θ _r
The part indicated by is the steering correction term.

Step 103 is a step of determining whether or not the control signal V is equal to or greater than a predetermined threshold value δ _T , and if YES, the process proceeds to step 104, and if NO, step 1
Go to 05.

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

Step 105 is a step of judging whether or not the control signal V is a value between a predetermined threshold value δ _T and a threshold value −δ _{C. If} YES, then the routine proceeds to step 106, and if NO. Go to step 107.

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

Step 107 is a step which is displayed for the sake of convenience, and N is omitted in steps 103 and 105.
When it is determined to be O, the control signal V is equal to or lower than the predetermined threshold value −δ _C , and in this case, the process proceeds to step 108.

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

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

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

When the control signal V becomes equal to or higher than the threshold value δ _T , the expansion side hard region HS is controlled to fix the compression side to the low damping characteristic, while the expansion side damping characteristic is made proportional to the control signal V. To change. At this time, the attenuation characteristic C is C = k ₁ · V
Control so that.

When the control signal V becomes equal to or lower than the threshold value -δ _{C, the} compression side hard region SH is controlled to fix the extension side to a low damping characteristic, while making the compression side damping characteristic proportional to the control signal V. To 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 are adapted to change according to the vehicle speed.

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

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

In region c, 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 positive. Since the stroke of the shock absorber SA is on the extension side, the shock absorber SA is controlled to the pressure side hard area SH side based on the direction of the control signal V at this time. In the region, the extension side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

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

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

Next, the operation of the control unit 4 during straight running and steering of the vehicle will be described. (A) When traveling straight ahead When the vehicle is traveling straight ahead, the value of the steering correction term becomes 0, so the bounce rate based on the sprung vertical speed and
The control signal V is obtained based on the pitch rate and the roll rate. Therefore, not only the bounce, but also the vehicle behavior in which the pitch and the roll are kneaded can be sufficiently exerted.

(B) Steering When steering is performed, rolling occurs in the vehicle, but steering based on the value of the steering angular velocity F _x that matches the phase of this rolling and is not affected by the lateral acceleration applied to the vehicle body. The correction term sharply increases due to the large proportional constants θ _f and θ _r as compared with the proportional constants of other rates (bounce, pitch, roll). That is: a) When the vehicle rolls to the right due to left steering,
In the shock absorber SA on the left wheel side, which is the steering direction, since the steering angular velocity F _x is obtained as a positive value, the control signal V becomes a positive value and the extension side damping characteristic becomes the value of the control signal V. In the shock absorber SA on the right wheel side, which is in the opposite direction to the steering direction, the steering angular velocity F _x has a negative value, so the control signal V has a negative value. , The damping characteristic on the compression side is increased in proportion to the value of the control signal V, so that the rightward roll of the vehicle is appropriately suppressed.

B) When the vehicle rolls to the left by steering to the right, the shock absorber SA on the right wheel side, which is in the steering direction, produces a positive steering angular velocity F _x , so the control signal V is It becomes a positive value, the damping characteristic on the extension side increases in proportion to the value of the control signal V, and the steering angular velocity F _x is increased in the shock absorber SA on the left wheel side, which is the opposite direction to the steering direction. Since it is obtained with a negative value, the control signal V becomes a negative value, and the damping characteristic on the compression side becomes higher in proportion to the value of the control signal V, and therefore, the leftward roll of the vehicle is properly suppressed. It

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

Since a sufficient control force can be generated not only for bounce but also for pitch and roll when the vehicle travels straight ahead, it is possible to provide a vehicle suspension system excellent in riding comfort and steering stability. You can

By the function of the steering correction term based on the steering angular velocity, not only when the vehicle is traveling straight ahead but also when cornering, sufficient vibration damping property is obtained and steering stability can be secured.

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

Next, other embodiments will be described, but in describing these embodiments, only the differences from the first embodiment will be described. Also, the first reference numeral
The same reference numerals as those in the embodiment denote 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 in calculating the control signal V, the arithmetic expression shown in the following formula 2 is used.

[0055]

[Equation 2] That is, in the second embodiment, the bounce rate can be independently obtained based on the sprung vertical velocity of each wheel, and the control in which the bounce component is emphasized can be performed.

(Third Embodiment) In the third embodiment, as the shock absorber SA of the damping characteristic variable type, when the pulse motor 3 is driven, as shown in FIG. , With a well-known structure that changes from high damping to low damping (for example, see Japanese Utility Model Laid-Open No. 63-112914).
This is an example in which the damping characteristic control based on the conventional skyhook theory is performed by using the above (see Japanese Patent Publication).

Therefore, in this third embodiment, as shown in FIG. 20, in addition to the sprung G sensor 1 as an input means, a load sensor (sprung / unsprung relative speed detecting means) 6, 6,
6, 6 are provided. As shown in FIG. 18, the load sensor 6 is provided on the piston rod 7 below the mounting portion of each shock absorber SA to the vehicle body, and the damping force (relative force) generated by the shock absorber SA (relative Equivalent 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, the step 301 is to determine the damping force F detected by the load sensor 6.
Is a step of reading, and after this processing, steps 101 and 102 similar to those in the first embodiment are performed, and then the process proceeds to step 302.

In step 302, the damping force F and the control signal V
YES in the step of determining whether and are the same sign
Then, the process proceeds to step 303, and if NO (different sign), the process proceeds to step 304.

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

At step 304, the damping characteristic of the shock absorber SA is controlled so that both the extension and the compression have the minimum damping characteristic.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the invention.

For example, in the embodiment, as the signal obtained from the sprung vertical velocity, the bounce rate based on the sprung vertical velocity, the pitch rate detected from the sprung vertical velocity difference before and after the vehicle body, and the sprung vertical direction on the left and right of the vehicle body Although the signal obtained by 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 vehicle suspension system of the present invention is obtained by eliminating the deviation of the phase / detection value of the sprung vertical velocity that occurs during cornering using the correction term obtained from the steering angular velocity. Since damping characteristic control means that performs control based on the control signal is used, sufficient damping performance can be obtained not only when traveling straight ahead but also when cornering, thereby improving riding comfort and steering stability. In addition to the effect that it is possible to obtain, there is an effect that it is possible to cope with the delay in the control in the initial stage of turning.

Further, in the vehicle suspension system according to the present invention, as a signal obtained from the sprung vertical velocity, the bounce rate based on the sprung vertical velocity and the pitch rate and the vehicle left-right direction detected from the difference between the sprung vertical velocity before and after the vehicle body. By using the signal obtained from the roll rate detected from the sprung vertical speed difference, it is possible to obtain not only bounce, but also pitch and roll sufficient damping performance, especially when traveling straight ahead. Become.

Further, in the vehicle suspension system according to claim 5,
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 drawings]

FIG. 1 is a conceptual diagram of a claim showing a vehicle suspension device of the present invention.

FIG. 2 is a structural explanatory view showing a vehicle suspension device of the first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the first embodiment.

FIG. 4 is a sectional view showing a shock absorber applied to the device of the first embodiment.

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

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

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

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

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 of the shock absorber when the extension side is hard.

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

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

FIG. 14 is a block diagram showing a main part of a control unit of the first embodiment.

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

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

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

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

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

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

FIG. 21 is a flow chart showing the control operation of the control unit of the third embodiment device.

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 velocity detecting means d steering angular velocity detecting means e damping characteristic controlling means f relative speed detecting means

Claims (5)

[Claims] 1. A shock absorber which is interposed between a vehicle body side and each wheel side and whose damping characteristic can be changed by a damping characteristic changing means, and a sprung vertical velocity near the position where each shock absorber is provided is detected. The sprung vertical velocity detection means, the steering angular velocity detection means for detecting the steering angular velocity of the vehicle, and the damping characteristics of each shock absorber are converted into a signal obtained from the sprung vertical velocity value and its direction to obtain the steering angular velocity value and its direction. And a damping characteristic control means for performing control based on a control signal obtained by adding the correction term obtained from the vehicle suspension device. 2. The shock absorber includes an expansion side hard area in which the expansion side is variable in damping characteristics and the compression side is fixed in low damping characteristics, and a compression side hard area in which the compression side is variable in damping characteristics and expansion side is fixed in low damping characteristics is expanded. It is formed in a structure having three regions, that is, a soft region having a low damping characteristic on both the compression side and the compression side, and the damping characteristic control means controls the shock absorber in the expansion side hard region when the control signal is a positive threshold value or more. Then
The shock absorber is controlled in the pressure side hard area when the control signal is below the negative threshold value, and the shock absorber is controlled in the soft area when the control signal is between the positive and negative threshold values. The vehicle suspension system according to claim 1. 3. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping characteristic by a damping characteristic changing means, and a sprung vertical velocity near a position where each shock absorber is provided is detected. A sprung vertical speed detecting means, a steering angular speed detecting means for detecting a steering angular speed of the vehicle, a relative speed detecting means for detecting a relative speed between unsprung and unsprung parts near a position where each shock absorber is provided, The damping characteristics of the shock absorber are calculated by adding the correction term obtained from the value of the steering angular velocity and its direction to the signal obtained from the value of the sprung vertical velocity and its direction, and the relative value between the sprung and unsprung parts. A vehicle suspension characterized by comprising: a damping characteristic control means for increasing the damping characteristic when the speed has the same sign, and controlling the damping characteristic to the minimum when the speed has the different sign. Location. 4. The signal obtained from the sprung vertical velocity is detected from the bounce rate based on the sprung vertical velocity, the pitch rate detected from the sprung vertical velocity difference between the front and rear of the vehicle body, and the sprung vertical velocity difference between the left and right sides of the vehicle body. 4. The vehicle suspension system according to claim 1, wherein the signal obtained from the roll rate is used. 5. In obtaining the control signal, the bounce rate uses a signal that has passed through a bandpass filter including the sprung resonance frequencies of the front and rear wheels, and the pitch rate uses a bandpass filter that includes the pitch resonance frequency. 5. The vehicle suspension system according to claim 4, wherein a signal that has been passed through a band pass filter including a roll resonance frequency is used as the roll rate.