JPH07232529A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To efficiently restrain a vehicle behavior within an extensive range from low speed to high speed by controlling a damping force characteristic of a shock absorber at a rear wheel position when a pitch rate exceeds a threshold, controlling an extensional stroke side when its directional discrimination code is positive and controlling a pressure side at the time when it is negative. CONSTITUTION:A pitch rate is found by a pitch rate detection means (e) from an average value of front and rear wheel speed from each wheel speed sensor (d) in shock absorbers b1, b2 having a damping force characteristic variation means (a). When the pitch rate is lower than a threshold, a damping force characteristic of the front and rear wheel shock absorbers b1, b2 is controlled in accordance with spring vertical speed of the front wheel by a spring vertical speed detection means (c), and when it exceeds the threshold, the damping force characteristic of the front wheel is controlled after the pitch rate is lowered below the threshold, and simultaneously, the damping force characteristic of the shock absorber b2 of the rear wheel is controlled by a reversal control signal of front wheel. When its direction is positive, an extensional process side is controlled, and when it is negative, a pressure process side is controlled.

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 controlling damping force characteristics of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, Japanese Unexamined Patent Publication No. Heisei 4-
The one described in Japanese Patent No. 1911111 is known.

This conventional vehicle suspension system includes an actuator (shock absorber) which is interposed between a vehicle body and a rear wheel and is capable of increasing or decreasing the supporting force (damping force) of the vehicle body with respect to the rear wheel, and a road surface unevenness. A vertical G sensor for detecting vertical acceleration acting on the vehicle body by vibration input from the front wheels, a vehicle speed sensor for detecting the traveling speed of the vehicle, and control means for controlling the operation of the actuator based on the output of each sensor. When the control means detects that the vertical acceleration of the vehicle body detected by the vertical G sensor exceeds a predetermined value, the control means gives a vertical acceleration of the predetermined value or more based on the output of the vehicle speed sensor. After a delay time until the rear wheel reaches the unevenness, the actuator is operated according to a control signal obtained by inverting the phase of the signal based on the vertical acceleration. It was those that are configured.

That is, in this conventional device, even if a relatively large vibration is generated in the vehicle body when the front wheels pass through the unevenness of the road surface, when the rear wheels pass through the unevenness, the vertical acceleration of the vehicle body is referred to when the front wheels pass through the unevenness. Control is performed in such a direction as to cancel the vertical acceleration of the vehicle body, whereby vibration input can be reduced when the rear wheels pass through the unevenness as compared to when the front wheels pass through the unevenness.

The phase inversion of the signal is carried out in order to exhibit stable performance against noise.

[0006]

However, the above-mentioned conventional device has the following problems.

That is, when the vehicle travels at high speed, the behavior of the vehicle body is in the bounce mode, but when the vehicle travels at low speed to medium speed, the behavior of the vehicle mainly changes to the pitch mode. In addition, it is not possible to effectively suppress the pitching of the vehicle during low / medium speed running only by preview-controlling the shock absorber of the rear wheel by the vertical acceleration of the front wheel position.

The present invention has been made in view of the above conventional problems, and can effectively suppress the vehicle behavior in a wide range from low speed to high speed and improve the riding comfort of the vehicle. It is intended to provide a vehicle suspension system.

[0009]

In order to achieve the above-mentioned object, in a vehicle suspension system of the present invention, a damping is provided between the vehicle body side and each wheel side, and one of the extension side and compression side stroke side damping is provided. When the force characteristics are variably controlled, shock absorbers b ₁ and b ₂ having damping force characteristic changing means a having a structure in which the reverse stroke side is fixed to a low damping force characteristic and at least the sprung vertical velocity at the front wheel position are detected. The sprung vertical speed detecting means c, the wheel speed sensor d for detecting the wheel speed of the left and right front wheels and at least one of the left and right rear wheels, and the front wheel and the rear wheel obtained from each wheel speed sensor d. Pitch rate detecting means e for obtaining the pitch rate of the vehicle from the average value of the wheel speeds
When the pitch rate detected by the pitch rate detecting means e is less than a predetermined threshold value, the damping force characteristics of the shock absorbers b ₁ and b ₂ at the front wheel position and the rear wheel position are set to the sprung up and down at the front wheel position. Controlled by a control signal based on speed,
Further, when the pitch rate becomes equal to or higher than a predetermined threshold value, the damping force characteristic of the shock absorber b _{1 at} the front wheel position is kept at the sprung position at the front wheel position for a predetermined period after the pitch rate is reduced to less than the predetermined threshold value. While controlling by a control signal based on the vertical speed, the shock absorber b ₂ at the rear wheel position is controlled.
The damping force characteristic of is controlled by an inversion control signal which is the inversion of the phase of the control signal based on the sprung vertical velocity at the front wheel position, and the direction discrimination code of the control signal or the inverted control signal (when the sprung vertical velocity is upward, positive, downward negative), variably controlled in response to the positive control signal or the inverted control signal extension phase of the shock absorber b _1, b ₂ when the when the negative controls compression phase of the shock absorber b _1, b ₂ And a damping force characteristic control means f for performing variable control according to a signal or an inversion control signal.

[0010]

Since the vehicle suspension system of the present invention is configured as described above, the damping force characteristic control means f determines the direction discrimination code of the control signal or the reversal control signal (the sprung vertical velocity is upward and positive or downward). in negative), is variably controlled in response to the positive control signal or the inverted control signal extension phase of the shock absorber b _1, b ₂ when the the compression phase when the negative shock absorbers b _1, b ₂ It is variably controlled in accordance with the control signal or the inversion control signal, and the stroke opposite to the variably controlled stroke is fixed to the low damping force characteristic. Therefore, when the direction discrimination code between the control signal based on the sprung vertical speed and the relative speed between sprung and unsprung is the same sign, the stroke side of the shock absorber at that time is controlled to the hardware characteristic side, and the different sign is used. At certain times, the same control as the damping force characteristic control based on the skyhook theory, that is, the stroke side of the shock absorber at that time is controlled to the soft characteristic, is performed without detecting the relative speed between the sprung and unsprung parts. It will be.

When the pitch rate detected by the pitch rate detecting means e is less than a predetermined threshold value, the phase difference between the sprung vertical velocities on the front wheel side and the rear wheel side is the same as during high speed running. Since the small bounce mode is set, the shock absorber b at the front wheel position and the rear wheel position at this time is set.
Bounce of the vehicle can be suppressed by controlling the damping force characteristics of ₁ and b ₂ with a control signal based on the sprung vertical velocity at the front wheel position.

Further, when the pitch rate is equal to or higher than a predetermined threshold value, the pitch mode has a large phase difference between the sprung vertical velocities on the front wheel side and the rear wheel side, as in low to medium speed running. Therefore, at this time, the damping force characteristic of the shock absorber b ₁ at the front wheel position is controlled by the control signal based on the sprung vertical velocity at the front wheel position for a predetermined period after the pitch rate has decreased below the predetermined threshold value. while, by controlling the inversion control signal obtained by inverting the phase of the control signal based on the damping force characteristics of the shock absorber b ₂ of the rear wheel position sprung vertical velocity of the front wheel position, the rear wheel side shock absorbers b ₂ The variable control stroke side of the damping force characteristic is the reverse stroke to that of the front wheel side, and thus the bounce of the vehicle can be effectively suppressed.

[0013]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration of the vehicle suspension system according to the embodiment of the present invention will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system according to an embodiment of the present invention. The four shock absorbers SA (SA _FL , SA _FR ,
SA _RL , SA _{RR In} addition, _FL is the front wheel left side, _FR is the front wheel right side, _RL
Indicates the left side of the rear wheel, and _RR indicates the right side of the rear wheel. The same applies to the following. ) 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 at an intermediate position between the left and right front wheels, and the left and right front wheels and the left and right rear wheels are provided with respective wheels. Wheel speed sensors 2 _FL , 2 _FR ,
2 _RL and 2 _RR are provided. Then, in the vicinity of the driver's seat, the vertical G sensor 1 and each wheel speed sensor 2 _FL ,
A damping force characteristic control circuit for inputting signals from 2 _FR , 2 _RL , 2 _RR and outputting a drive control signal to the pulse motor 3 of each shock absorber SA, and each wheel speed sensor 2 _FL , 2 _FR ,
2 Based on the wheel speed signal from the _RL, the slip condition of the wheel at the time of brake operation is detected, and when the slip ratio is equal to or higher than a predetermined value, the braking force is reduced to prevent the wheel from locking. A control unit 4 having a skid control circuit is provided.

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 has a through hole 31 for communicating the upper chamber A and the lower chamber B with each other.
a, 31b are formed, and each through hole 31a,
A compression side damping valve 20 and an expansion side damping valve 12 that open and close 31b are provided. In addition, the bound stopper 41 screwed to the tip of the piston rod 7
A stud 38 penetrating the piston 31 is screwed and fixed, and the stud 38 has an upper chamber A and a lower chamber B.
Is formed with a communication hole 39 for communicating with, and further, an adjuster 40 for changing the flow passage cross-sectional area of the communication hole 39 and a fluid flow on the communication hole 39 side are allowed depending on the fluid flow direction. An extension side check valve 17 and a pressure side check valve 22 for shutting off 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 has a damping force characteristic based on the rotation of the adjuster 40 when the adjuster 40 is rotated. It is configured so that it can be changed in multiple stages from the characteristic (hereinafter referred to as software) to the high damping force characteristic (hereinafter referred to as hardware). In addition, as shown in FIG.
Adjuster 4 from the position where both pressure side was soft
When 0 is rotated counterclockwise (direction), only the extension side changes to the hard side, and conversely, when the adjuster 40 is rotated clockwise (direction), only the pressure side changes to the hard side. Has become.

Incidentally, in FIG. 7, the KK cross section, the MM cross section, and the NN cross section in FIG. 10 and the damping force characteristics at each position are shown in FIGS.

Next, among the control circuits included in the control unit 4, the damping force characteristic control circuit for controlling the damping force characteristic of each shock absorber SA is input from the vertical G sensor 1 as shown in FIG. The bounce component V _{B of the} vehicle is obtained from the signal obtained by converting the sprung vertical acceleration signal into the sprung vertical velocity, and each wheel speed sensor 2 _FL ,
A necessary speed component arithmetic circuit 4a for obtaining the pitch rate V _P based on the input signals from 2 _FR , 2 _RL , 2 _RR, and a control signal for controlling the damping force characteristic of each shock absorber SA from the bounce component V _B. V and a control signal calculation circuit 4b for obtaining an inverted control signal V'in which the phase of the control signal V is inverted. That is, the required speed component calculation circuit 4a is provided with the processing circuits shown in the block diagrams of (a) and (b) of FIG.

FIG. 14A shows the bounce component V _{B of the} vehicle.
And a low-pass filter LPF for integrating a sprung acceleration G signal sent from each vertical G sensor 1 and converting it into a sprung vertical velocity (bounce component V _B ). There is.

FIG. 14B shows each wheel speed sensor 2 _FL , 2 _FL .
A signal processing circuit for obtaining a pitch rate V _P of a vehicle based on input signals from _FR , 2 _RL , 2 _RR . This signal processing circuit is based on the following equations (1) and (2). It is composed of an arithmetic circuit 5 for obtaining the pitch rate V _{P. VP (n) = (WVFL (} n) + WVFR (n) + WVRL (n) + WVRR (n)) / 4 ······ (1) V P = (VP (n) + VP (n-1) ··・ ・ ＋ VP _(nm) ) / (m + 1) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2) WVFL is the wheel speed of the left front wheel, WVFR is the wheel speed of the right front wheel, and WVRL is the left rear wheel. Wheel speed, WVRR is the wheel speed of the right rear wheel, _(n) is the sampling data at any time, _{(n -1)} is the sampling data at any time _(n) , one sampling before, and _(m) is any Indicates an integer.

FIG. 15 shows the pitch rate V _P obtained by the above equations (1) and (2) and the actual pitch rate measured data by the gyro. As shown in FIG. By determining the average value of the wheel speeds, the pitch rate of the vehicle can be determined.

Next, among the operations of the control unit 4, the control operation of the damping force characteristic control circuit 4a for controlling the drive of the pulse motor 3 will be described with reference to the flowchart of FIG. In addition, this control is performed by each shock absorber S
Do each A separately.

In step 101, the sprung vertical acceleration signals from the vertical G sensors 1 are read, and at the same time as shown in FIG.
The bounce component V _B based on the sprung vertical velocity is obtained by the low-pass filter LPF shown in (a). The bounce component V
_B is obtained with a positive value in the upward direction and a negative value in the downward direction.

In step 102, the control signal V is obtained based on the following equation (3). V = α × V _B ······· (3) In addition, α is a proportional constant.

In step 103, the wheel speed signal of each wheel is read from each wheel speed sensor 2 _FL , 2 _FR , 2 _RL , 2 _RR , and this wheel speed signal is read by the signal processing circuit shown in FIG. By processing, the pitch rate V _P of the vehicle is obtained. The pitch rate V _P is obtained as a positive value when the vehicle is in the scat direction, and is obtained as a negative value when the vehicle is in the dive direction.

In step 104, it is determined whether the pitch rate V _P is greater than or equal to a predetermined threshold Ps, and YES
If so, the process proceeds to step 105, and an inverted control signal V ′ obtained by inverting the phase of the control signal V is obtained as the control signal for the rear wheels, and if NO, the process proceeds to step 106.

In step 106, the previous pitch rate V
_It is determined whether _P is greater than or equal to a predetermined threshold Ps,
If YES, the process proceeds to step 107 to clear and start the timer count of the delay timer, and then to step 1
If NO, proceed to step 108.

In step 108, it is determined whether or not the timer count Tc of the delay timer is less than a predetermined delay time Ts, and if YES, the process proceeds to step 109 to add 1 to the timer count of the delay timer, Step 1
If NO, proceed to step 110.

In step 110, it is judged whether or not the control signal V or the inverted control signal V'is not less than a predetermined threshold value δ _T , and if YES, the routine proceeds to step 111, where N
If it is O, the process proceeds to step 112.

In step 111, the shock absorber SA is controlled to the extension side hard area HS. At this time, the target damping force characteristic C on the extension side is controlled so that C = k _T · V. Note that k _T is a proportional constant on the extension side.

At step 112, the control signal V or the inverted control signal V'is set to a predetermined threshold value δ _T and threshold value −δ _C.
If YES, the routine proceeds to step 113, where the shock absorber SA is controlled to the soft region SS, and if NO, the routine proceeds to step 114.

In step 114, when it is determined to be NO in step 110 and step 112, that is, the control signal V
Alternatively, this is a processing step when the inversion control signal V ′ is equal to or less than a predetermined threshold value −δ _C , and in this step, the target damping force characteristic C on the pressure side is set so as to control the shock absorber SA to the pressure side hard region SH. Are controlled so that C = k _C · V. Note that k _C is a proportional constant on the pressure side.

At step 115, each target damping force characteristic C
To the pulse motor 3 of each shock absorber SA.

Next, among the operations of the control unit 4, the damping force characteristic switching control operation in the damping force characteristic control circuit for controlling the drive of the pulse motor 3 will be described with reference to the time chart of FIG.

In the time chart of FIG. 17, area a
Indicates that 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 negative (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 based on the direction of the control signal V.
In this region, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

The region b is a region where 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 area 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 area, 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 control signal V based on the sprung vertical velocity has the same sign as the relative velocity between the sprung and unsprung portions (region b, region d), the shock at that time is generated. Damping force characteristics based on the skyhook theory that the stroke side of the absorber SA is controlled to have a hard characteristic and the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic when the signs are different (area a, area c). The same control as the control will be performed without detecting the relative speed between the sprung part and the unsprung part. Further, in this embodiment, when the region a shifts to the region b and the region c shifts to the region d, the damping force characteristic is switched without driving the pulse motor 3.

Next, of the control operations of the damping force characteristic control circuit, the control operations during high speed running and during low / medium speed running will be described with reference to the time charts of FIGS. 18 and 19. (A) During high-speed traveling When the vehicle is traveling at high speed, as shown in FIG. 18, the pitch rate V _P obtained from the average value of the front and rear wheel speeds is less than a predetermined threshold Ps. And
Since the bounce mode has a small phase difference between the sprung vertical speeds of the front wheel side and the rear wheel side, at this time, the damping force characteristics of the shock absorbers SA at the front wheel position and the rear wheel position are set to the sprung vertical speeds at the front wheel position. By controlling with a common control signal V based on the above, it is possible to suppress the bounce of the vehicle.

(B) At low / medium speed running When the vehicle is running at low to medium speeds, as shown in FIG. 19, the pitch rate V _P obtained from the average value of the wheel speeds of the front wheels and the rear wheels. Is greater than or equal to a predetermined threshold value Ps and the phase difference between the sprung vertical velocities of the front wheel side and the rear wheel side is large. Therefore, at this time, the pitch rate V _P is then the predetermined threshold value Ps. Until the predetermined delay time Ts elapses after decreasing to less than 1, the damping force characteristics of the shock absorbers SA _FL and SA _FR at the front wheel position are controlled by the control signal V based on the sprung vertical velocity at the front wheel position. , The damping force characteristics of the shock absorbers SA _RL and SA _RR at the rear wheel positions are controlled by an inversion control signal V ′ which is the inverted phase of the control signal V based on the sprung vertical velocity at the front wheel position.

Therefore, the rear wheel side shock absorber S
The variable control stroke side of the damping force characteristics in A _RL and SA _RR is the reverse stroke to the variable control stroke of the front wheel side shock absorbers SA _FL and SA _FR , whereby the bounce of the vehicle can be effectively suppressed.

As described above, in the vehicle suspension system of this embodiment, the effects listed below can be obtained.

Since bounce can be suppressed when the vehicle that is in the bounce mode is running at low / medium speeds, and pitching can be effectively suppressed when the vehicle that is in the pitch mode is running at high speeds, it is possible to change from low speed to high speed. The vehicle behavior can be effectively suppressed over a wide range, and the riding comfort of the vehicle can be improved.

The wheel speed sensor 2 detects the behavior on the spring.
Since it is detected on the input (road surface) side, the initial response of the signal is excellent compared to the case of detecting on the sprung side by obtaining the pitch rate from each wheel speed WVFL, WVFR, WVRL, WVRR signal. Will be things.

The vehicle pitch rate and roll rate are obtained by wheel speed sensors 2 _FL , 2 _FR , 2 _RL and 2 _RR used in the anti-skid control system.
Since it can be obtained from the WVFR, WVRL, and WVRR signals, it is sufficient to provide at least one vertical G sensor for determining the bounce rate of the vehicle as a sensor for damping force characteristic control. The system cost can be reduced.

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

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, the vertical G sensor 1 is set to 1
Although the system using only one unit is shown, the system may be one in which the up and down G sensors 1 and 1 are provided on the vehicle body at both the left and right front wheel positions. In this case, the bounce component V
_B and roll component V _R is both vertical G acceleration signals obtained from the sensors 1,1 and integration on the resulting spring vertical velocity signals FLVn, by FRVn, the following equation (4), calculated based on (5) To be The control signal (LV = left wheel side RV = right wheel side) in this case is obtained based on the following equations (6) and (7). _{V B = (FLVn + FRVn)} / 2 ······· (4) V R = FLVn -FRVn ············· (5) LV = α · V B + β · V _{R ··········· (6) RV = α} · V B -β · V R ··········· (7) in addition, beta is a proportionality constant.

Further, in the embodiment, the system using four wheel speed sensors is shown, but the present invention can be applied to a system using a total of three of either one of the left and right front wheels or the left and right rear wheels. In this case, instead of the above equation (1),
The average value VP is obtained based on (8). VP _(n) = (WVFL _(n) + WVFR _(n) + WVRL _(n)・ 2) / 4 ・ ・ ・ ・ ・ ・ (8) Furthermore, the yaw rate signal Y obtained from the wheel speed signal difference between the left and right front wheels is It may be used as a correction signal for canceling the other axis component due to the lateral acceleration acting on the vehicle body during steering.

Further, the threshold value Ps can be arbitrarily set in accordance with the vehicle speed. Also, the count of the delay timer may be started at the time when the pitch rate crosses zero.

[0055]

As described above, in the vehicle suspension system of the present invention, when the pitch rate detected by the pitch rate detecting means is less than a predetermined threshold value, the shock absorbers for the front wheel position and the rear wheel position are provided. The damping force characteristic of the is controlled by the control signal based on the sprung vertical velocity at the front wheel position,
When the pitch rate becomes equal to or higher than a predetermined threshold value, the damping force characteristic of the shock absorber at the front wheel position is based on the sprung vertical speed at the front wheel position for a predetermined period after the pitch rate falls below the predetermined threshold value. While controlling by the control signal, the damping force characteristic of the shock absorber at the rear wheel position is controlled by the reversal control signal which is the phase of the control signal based on the sprung vertical velocity at the front wheel position, and the direction of the control signal or the reversal control signal. When the discrimination code (positive when the sprung vertical speed is upward, negative when downward) is positive, the extension side of the shock absorber is variably controlled according to the control signal or the reversal control signal, and when it is negative, the shock absorber pressure is changed. Low- and medium-speed running of the vehicle in the bounce mode is achieved by providing the damping force characteristic control means that variably controls the stroke side according to the control signal or the reverse control signal. Sometimes to suppress the bounce, also,
Pitching can be effectively suppressed during high-speed running of the vehicle in the pitch mode. Therefore, vehicle behavior can be effectively suppressed in a wide range from low speed to high speed to improve the ride comfort of the vehicle. The effect of being able to do is 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 an embodiment of the present invention.

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

FIG. 4 is a cross-sectional view showing a shock absorber applied to the apparatus of the 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 damping force characteristic diagram corresponding to the 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 LM 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 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 configuration of a signal processing unit in the device of the embodiment.

FIG. 15: Pitch rate (a) obtained from wheel speed
It is a figure which shows the actual measurement data of, and the pitch rate (b) by gyro.

FIG. 16 is a flowchart showing the control operation of the damping force characteristic control circuit among the control operations of the control unit in the embodiment apparatus.

FIG. 17 is a time chart showing a damping force characteristic switching control operation among the control operations of the damping force characteristic control circuit in the embodiment apparatus.

FIG. 18 is a time chart showing a control operation during high-speed traveling among the control operations of the damping force characteristic control circuit in the apparatus of the embodiment.

FIG. 19 is a time chart showing a control operation at low / medium speed running among the control operations of the damping force characteristic control circuit in the embodiment apparatus.

[Explanation of symbols]

a damping force characteristic changing means b ₁ shock absorber (front wheel side) b ₂ shock absorber (rear wheel side) c sprung vertical velocity detecting means d wheel speed sensor e pitch rate detecting means f damping force characteristic controlling means

Claims (1)

[Claims] 1. When variably controlling the damping force characteristic of one of the extension side and the compression side, which is interposed between the vehicle body side and each wheel side, the reverse stroke side is fixed to a low damping force characteristic. A shock absorber having a structural damping force characteristic changing means, a sprung vertical speed detecting means for detecting at least the sprung vertical speed at the front wheel position, and at least one of the left and right front wheel speeds and the left and right rear wheel wheels The wheel speed sensor for detecting the speed, the pitch rate detecting means for obtaining the pitch rate of the vehicle from the average value of the front and rear wheel speeds obtained from each wheel speed sensor, and the pitch rate detected by the pitch rate detecting means When it is less than the predetermined threshold value, the damping force characteristics of the shock absorbers at the front wheel position and the rear wheel position are controlled by the control signal based on the sprung vertical speed at the front wheel position, and the pitch level is also controlled. When the pitch exceeds a predetermined threshold value, the damping rate characteristic of the shock absorber at the front wheel position is controlled based on the sprung vertical speed at the front wheel position for a predetermined period after the pitch rate drops below the predetermined threshold value. While controlling by the signal, the damping force characteristic of the shock absorber at the rear wheel position is controlled by the reversal control signal that is the reverse of the phase of the control signal based on the sprung vertical velocity at the front wheel position, and the direction of the control signal or the reversal control signal is determined. When the sign (positive when the sprung vertical speed is upward, negative when downward) is positive, the extension side of the shock absorber is variably controlled according to the control signal or the reversal control signal, and when it is negative, the pressure stroke of the shock absorber. And a damping force characteristic control means for variably controlling the side according to a control signal or a reversal control signal.