JPH0655920A - Vehicular suspension device - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a vehicle suspension system capable of obtaining sufficient vibration damping property against moment of inertia and improving steering stability. [Structure] A shock absorber b interposed between a vehicle body side and each wheel side and capable of changing a damping characteristic by a damping characteristic changing means a, and a sprung vertical velocity near a position where each shock absorber b is provided are detected. The sprung vertical velocity detecting means c, the lateral acceleration detecting means d for detecting the rate of change in the lateral acceleration of the vehicle, and the damping characteristics of the shock absorbers b are the bounce rate based on the sprung vertical velocity and the springs before and after the vehicle body. A damping characteristic control means e is provided for controlling based on a control signal obtained from a pitch rate detected from an upper / lower speed difference and a roll rate based on a rate of change of lateral acceleration.

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 sprung and unsprung, and when both have the same sign, the damping characteristic is made hard, and when the two have different signs, the damping characteristic is made soft. The four wheels independently controlled the damping characteristics based on the skyhook theory.

[0003]

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, In addition to bounce, for body movements in which pitches and rolls are coupled, the moment of inertia of the body around the center of gravity of the body is added to the sprung mass,
There was a problem that the damping force (control force) was insufficient and the steering stability was poor.

In the damping characteristic control based on the skyhook theory, it is necessary to drive the actuator to switch the damping characteristic each time the signs of the sprung vertical velocity and the relative velocity are changed to match or not match. Therefore, there is a problem that the control response is deteriorated and the number of times the actuator is driven is increased, so that the durability is reduced.

The present invention has been made by paying attention to the above-mentioned conventional problems, and a first object thereof is to obtain sufficient vibration damping property with respect to the moment of inertia and to improve steering stability. The second object is to improve the control response and the durability of the actuator.

[0006]

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 lateral acceleration detecting means d for detecting the rate of change of the lateral acceleration, and the damping rate of each shock absorber b are detected from the bounce rate based on the sprung vertical velocity and the sprung vertical velocity difference between the front and rear of the vehicle body and the lateral direction. A damping characteristic control means e for controlling based on a control signal obtained by a roll rate based on a rate of change of acceleration and a control signal is provided.

In addition to the above configuration, the vehicle suspension system according to a second aspect of the present invention is characterized in that, in the shock absorber, the expansion side hard region 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, 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 controls the positive value of the control signal. When, the shock absorber is controlled in the expansion side hard area, when the control signal is a negative value, the shock absorber is controlled in the compression side hard area, and when the control signal is 0, the shock absorber is controlled in the soft area. did.

[0008]

When the sprung vertical velocity detecting means and the lateral acceleration detecting means detect the bounce, the pitch and the roll, the damping characteristic control means obtains a control signal based on the bounce rate, the pitch rate and the roll rate. The damping characteristic of the shock absorber is controlled according to the signal. Therefore, sufficient control force can be obtained not only for bounce but also for pitch and roll.

Further, in the apparatus according to the second aspect, when the control signal has a positive value, the shock absorber is controlled in the expansion side hard region (the compression side is fixed to the low damping characteristic), and when the control signal has a negative value. The shock absorber is controlled in the compression side hard area (fixed to the low damping characteristic on the extension side), and when the control signal is 0, the shock absorber is controlled in the soft area. Therefore, the control signal based on the sprung vertical speed is used. When the relative speed between sprung and unsprung has 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,
The same control as the damping characteristic control based on the skyhook theory that the stroke side of the shock absorber at that time is controlled to a soft characteristic can be performed without detecting the relative speed between the sprung and unsprung parts. The switching of the damping characteristics toward the low damping characteristics direction is performed without driving the actuator. Therefore, the switching frequency of the damping characteristics is reduced compared to the conventional damping characteristics control based on the skyhook theory, and the control response is reduced. The improvement and the durability of the actuator can be improved.

[0010]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described. Figure 2
FIG. 3 is a configuration explanatory view showing a vehicle suspension system of the first embodiment of the present invention, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ , SA ₄ (shocks are interposed between a vehicle body and four wheels). In explaining the absorber, these 4
When referring to one together, and when describing these common configurations, they are simply referred to as SA. ) Is provided. A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 for detecting vertical acceleration is provided on the vehicle body in the vicinity of each shock absorber SA. A lateral acceleration sensor (hereinafter referred to as lateral G sensor) 2 for detecting directional acceleration is provided. In addition, signals from the respective vertical G sensors 1 are input to a position near the driver's seat so that each shock absorber SA
A control unit 4 for outputting a drive control signal to the pulse motor 3 is provided.

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 A signal from the lateral G sensor 2 is input. In the interface circuit 4a, a set of four 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. The BPF 1 allows a bounce component signal v (v ₁ , v
₂ , v ₃ , v ₄ The numbers ₁ , ₂ , ₃ , ₄ correspond to the positions of the shock absorbers SA. The same applies to the following. ) Is a band pass filter circuit that forms BP
F2 is passed through a frequency range including the pitch resonant frequency pitch component signal _{v '(v 1', v} 2 ', v 3', v
₄ ') is a bandpass filter circuit. By the way, in the present embodiment, the sprung resonance and the pitch resonance have different frequencies, but when the two resonance frequencies are close to each other, the bandpass filter of FIG.
Only PF1 is required. Further, the interface circuit 4
As shown in FIG. 15, a set of two filter circuits for processing the signal sent from the lateral G sensor 2 is provided in a. That is, the HPF 1 differentiates the signal indicating the lateral acceleration sent from the lateral G sensor 2 and converts the signal into the rate of change in lateral acceleration (lateral jerk) to generate the roll component signal G.
It is a high-pass filter circuit for forming _G. LP
F3 is a phase delay generated by passing through the high pass filter circuit HPF1 (45 near the roll resonance frequency).
This is a low-pass filter circuit for correcting high-frequency components above the roll resonance frequency where the phase delay further progresses while correcting the deg.

As described above, in this embodiment, the vertical G sensor 1 and the filter circuit of FIG. 14 constitute the sprung vertical speed detecting means in the claims, and the lateral G sensor 2 and FIG.
The filter circuit of 5 constitutes lateral acceleration detecting means in the claims.

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 cross-sectional view showing the portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein, and each through hole is formed. A compression side damping valve 20 and an expansion side damping valve 12 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. It should be noted that this adjuster 40 corresponds to the pulse motor 3
Is rotated via the control rod 70 (see FIG. 4). Also, the stud 38 has
A first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed in this 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, a through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which a 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, when the adjuster 40 is rotated in the counterclockwise direction from the state in which both the expansion side and the compression side are soft (hereinafter referred to as the soft region SS), only the expansion side has multi-stage damping characteristics. It can be changed and the compression side becomes a region fixed to the low damping characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, only the compression side can change the damping characteristic in multiple stages. The structure is such that the extension side is a region fixed to the low damping characteristic (hereinafter referred to as the compression side hard region SH).

Incidentally, in FIG. 7, when the adjuster 40 is arranged in the position of, the KK section, the LL section, the MM section, and the NN 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 driving 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.

In step 101, the upper and lower G sensors 1,
1, 1, 1 and the vertical acceleration signal and the lateral acceleration signal obtained from the lateral G sensor 2 are used as filter circuits LPF1 and LPF, respectively.
2, BPF1, BPF2 or HPF1, LPF
3, in the process to bouncing component signal v, the pitch component signal v ', a step of performing a process of obtaining a roll component signal G _G. The bounce component signal v and the pitch component signal v '
Is given as a positive value when the sprung vertical acceleration is in the upward direction, and is given as a negative value in the downward direction. Further, the roll component signal G _G is the shock absorber SA on the acceleration direction side.
Is given as a negative value because it is on the sinking side (pressure stroke side) of the vehicle body, and is a positive value because it is on the rising side (extension stroke side) of the shock absorber SA on the opposite side to the acceleration direction. Given in.

Step 102 uses Equation 1 below,
Each component signal v, v ', a step of computing the control signal V of the position of each wheel _{(V 1, V 2, V} 3, V 4) based on G _G.

[0022]

[Equation 1] Note that α _f , β _f , and γ _f are proportional constants α _r , β _r , and γ _r of the front wheels, respectively.

In each equation, the first part bounded 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 marked with is the roll rate.

Step 103 is a step of determining whether or not the control signal V has a positive value. If YES, the process proceeds to step 104, and if NO, the process proceeds to step 105.

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 for judging whether or not the control signal V is 0, and if YES, step 1
The procedure proceeds to 06, and if NO, the procedure proceeds 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 a negative value,
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 control signal V changes as shown in this figure, when the control signal V is 0 as shown in the figure,
The shock absorber SA is controlled in the soft area SS.

When the control signal V has a positive value, the expansion side hard area HS is controlled to fix the compression side to the low damping characteristic, while the expansion side damping characteristic is changed in proportion to the control signal V. . At this time, the damping characteristic C is controlled so that C = k ₁ · V. The k ₁ is a proportional constant on the extension side.

When the control signal V becomes a negative value, the compression side hard region SH is controlled to fix the extension side to the low damping characteristic, while the compression side damping characteristic is changed in proportion to the control signal V. Also at this time, the damping characteristic C is controlled so that C = k ₂ · V. The k ₂ is a proportional constant on the pressure stroke side.

Further, in the time chart of FIG.
In the region a, the control signal V 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 stroke of the shock absorber SA is the pressure stroke side). Therefore, 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 therefore, the stroke of the shock absorber SA at that time is in this area. The pressure stroke side has soft characteristics.

The region b is a region in which the control signal V remains a positive value (upward) and the relative speed is switched from a negative value to a positive value (the stroke of the shock absorber SA is the extension stroke side). Therefore, at this time, the shock absorber SA is controlled in the extension side hard region HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. Therefore, in this region, the shock at that time is present. The extension side, which is the stroke of the absorber SA, has a hardware characteristic proportional to the value of the control signal V.

In the area c, the control signal V is reversed from a positive value (upward) to a negative value (downward).
At this time, the relative speed is still a positive value (shock absorber S
Since the stroke of A is on the extension side), at this time, the shock absorber SA is controlled to the compression side hard zone SH based on the direction of the control signal V. Therefore, in this zone, The extension side, which is the stroke of the shock absorber SA, has soft characteristics.

In the area d, the control signal V remains a negative value (downward) and the relative speed changes from a positive value to a negative value (the stroke of the shock absorber SA is on the extension 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, and the stroke of the shock absorber is also the pressure stroke.
Therefore, in this area, the shock absorber SA at that time
The pressure stroke side, which is the stroke of, 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 lateral acceleration does not act on the vehicle, so that the roll component signal G _G becomes 0. Therefore, the bounce rate and pitch based on the sprung speed are set. The damping characteristic of each shock absorber SA is controlled by the control signal obtained from the rate.

Therefore, not only the bounce, but also the vehicle behavior in which the bounce and the pitch are trained can be sufficiently damped.

(B) At the time of steering When steering is performed, a roll is generated in the vehicle and a lateral acceleration acts on the vehicle at the same time, so that the roll component signal G _G increases in accordance with the rate of change, whereby control is performed. The signal V increases.

That is, in the shock absorber SA on the steering direction side (the side opposite to the acting direction of the lateral acceleration), the roll component signal G _G is given as a positive value, so the damping characteristic on the extension side is the control signal. In the shock absorber SA on the side opposite to the steering direction (on the side in which the lateral acceleration acts), the roll component signal G increases in proportion to the increase in V.
_{Since G} is given as a negative value, the damping characteristic on the compression side becomes higher in proportion to the increase of the control signal V, whereby rolling of the vehicle body can be sufficiently suppressed.

As described above, in this embodiment, the effects listed below can be obtained. Since sufficient control force can be generated not only for bounce but also for pitch and roll, it is possible to provide a vehicle suspension system that is excellent in riding comfort and steering stability.

As compared with the conventional damping characteristic control based on the skyhook theory, the frequency of switching the damping characteristics is reduced, so that the control response can be improved and the durability of the pulse motor 3 can be improved.

In determining 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 when calculating the control signal V, the arithmetic expression shown in the following formula 2 is used.

[0049]

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

(Third Embodiment) In the third 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 expression 3 is used.

[0051]

[Equation 3] That is, in this third embodiment, the bounce rate component is independently calculated on the front wheel side and the rear wheel side by the average value of the bounce component signals on the left and right wheels, respectively, and the pitch rate component is calculated on the left and right sides of the front wheel. This is obtained by the difference between the average value of the component signals and the average value of the pitch component signals on the left and right rear wheels. Therefore, the influence of the detection value of the acceleration sensor due to the roll of the vehicle is eliminated because the average value of the left and right wheels is taken, and it is possible to advantageously control the vehicle with low vehicle body rigidity.

(Fourth Embodiment) In the fourth embodiment, as shown in the diagram of FIG. 18, the upper and lower G sensors 1, 1, 1, 1 are arranged on the left and right sides of the vehicle in the widthwise central axis direction of the vehicle. By mounting the both detection direction axes h, h in an upward direction so as to approach each other in an inclined manner, the actual springs at the positions of the vertical G sensors 1, 1, 1, 1 are based on the signals from the vertical G sensors 1, respectively. The bounce rate component and the pitch rate component based on the upper and lower velocities and the roll component signal based on the change rate of the lateral acceleration acting on the vehicle body are respectively calculated. Therefore, in this embodiment, the first embodiment is performed. The lateral G sensor 2 in the example is omitted.

That is, in this embodiment, each vertical G sensor 1
As shown in the diagram of FIG. 18, the detection value Gg of each vertical G sensor 1 is different from the actual vertical sprung vertical acceleration value G _X acting in the vertical direction. Since it corresponds to the component force, the actual sprung vertical acceleration value G _X can be calculated from the detected value Gg, and the bounce rate component and the pitch rate component can be calculated based on each detected value Gg. You can In this arithmetic expression, the point that the bounce component signal v and the pitch component signal v ′ processed by the filter circuit shown in FIG. 14 are used is the same as in the case of the first embodiment.

Further, in this embodiment, as shown in the diagram of FIG. 19, when the lateral acceleration G acts on the vehicle, one of the left and right upper and lower G sensors 1, 1 has a lateral acceleration G acting direction. The vertical G sensor 1 detects the downward acceleration value (negative value), while the vertical G sensor 1 on the side opposite to the acting direction of the lateral acceleration G detects the upward acceleration value (positive value). Since it is detected, both left and right upper and lower G
By subtracting the detected acceleration value of the other upper and lower G sensor 1 from the detected acceleration value of the upper and lower G sensor 1 on the side where the roll component signal is obtained, among the detected acceleration values of the sensors 1 and 1,
Lateral acceleration direction side and vehicle body sinking side (pressure stroke side)
On the shock absorber SA side, the lateral acceleration value G _K approximated to the actual lateral acceleration G is given as a negative value, and the lateral acceleration value G _K is opposite to the lateral acceleration direction. On the shock absorber SA side which is the stroke side), the lateral acceleration value G _K approximated to the actual lateral acceleration G value is given as a positive value. The lateral acceleration value G _k is processed by a pair of filter circuits HPF1 and LPF3 shown in FIG. 15 to obtain a roll component signal G _G as a rate of change in lateral acceleration (lateral jerk). Is converted to.

Therefore, in this embodiment, in calculating the control signal V, the arithmetic expression shown in the following formula 4 is used.
In this embodiment, the bounce rate component and the pitch rate component are calculated based on the left and right average values.

[0056]

[Equation 4] That is, in the fourth embodiment, as in the case of the third embodiment, the sprung vertical acceleration values G on the left and right wheels are independently set for the bounce rate component independently on the front wheel side and the rear wheel side.
The pitch rate component is obtained by integrating the average value of x, and the difference between the average value of the left and right sprung vertical accelerations Gx on the front wheel side and the average value of the sprung vertical acceleration values Gx on the left and right rear wheels is integrated. It is something that I was asked for.

As described above, in this embodiment, since the lateral G sensor can be omitted, the number of parts can be reduced and the cost can be reduced, and the assembling labor, assembling space and weight can be reduced. It has the characteristics of

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 without departing from the scope of the invention.

For example, if the inclination direction of each vertical G sensor in the fourth embodiment is the width direction of the vehicle, it may be inclined in the opposite direction to the fourth embodiment. In this case, the roll component signal is positive. -Negative is the reverse of the fourth embodiment.

Further, in each equation for obtaining the control signal,
The method of obtaining the portion of each rate component can be applied by being arbitrarily interchanged among the mathematical expressions.

[0061]

As described above, in the vehicle suspension system of the present invention, the damping characteristic control means determines the damping characteristic of each shock absorber by the bounce rate based on the sprung vertical velocity and the sprung vertical velocity difference between the front and rear of the vehicle body. Since the control is performed based on the control signal obtained by the pitch rate detected from and the roll rate based on the change rate of the lateral acceleration,
In addition to bounce, sufficient control force can be obtained not only for pitch and roll, but this has the effect of improving riding comfort and steering stability.

According to a second aspect of the present invention, in the vehicle suspension system, each shock absorber has an expansion side hard region 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 and the expansion side has a low damping characteristic. It is formed in a structure having three regions of a compression side hard region fixed to the characteristic and a soft region having low damping characteristics on both the extension side and the compression side, and the damping characteristic control means is a shock absorber when the control signal has a positive value. By controlling in the expansion side hard area, controlling the shock absorber in the compression side hard area when the control signal is a negative value, and controlling the shock absorber in the soft area when the control signal is 0, the relative It is possible to control the damping characteristics based on the skyhook theory without using speed detection means, and compare the damping characteristics control based on the conventional skyhook theory with the switching frequency of the damping characteristics. Because can be reduced, it is possible to improve the control response, and the effect is obtained that it is possible to improve the durability of the damping characteristic switching actuator.

[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 block diagram showing a main part of a control unit of the first embodiment.

FIG. 16 is a flowchart showing the control operation of the control unit of the first embodiment device.

FIG. 17 is a time chart showing the operation of the first embodiment device.

FIG. 18 is a diagram illustrating a structure of a fourth embodiment device and a detection state of vertical acceleration.

FIG. 19 is a diagram for explaining the structure of the fourth embodiment device and the state of detection of lateral acceleration.

[Explanation of symbols]

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

Claims (2)

[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 lateral acceleration detection means for detecting the rate of change in the lateral acceleration of the vehicle, and the damping characteristics of each shock absorber are calculated by measuring the bounce rate based on the sprung vertical velocity and the sprung vertical velocity difference between the front and rear of the vehicle body. And a damping characteristic control means for controlling based on a control signal obtained from a pitch rate detected from the roll rate and a roll rate based on a change rate of the lateral acceleration, and a 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, a soft region having a low damping characteristic on both the side and the compression side, and the damping characteristic control means controls the shock absorber in the extension side hard region when the control signal has a positive value. The shock absorber is controlled in the pressure side hard region when the signal has a negative value, and the shock absorber is controlled in the soft region when the control signal is 0.
The vehicle suspension system described.