JPH05294124A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To enhance drive in comfort and operating stability by surely obtaining sufficient vibration damping properties even when a car body is tilted because of inertia moment. CONSTITUTION:The device is equipped with each shock absorber (b) which is interposed between an car body side and each wheel side, and can change its attenuation characteristics by an attenuation characteristics changing means (a), a suspended structure vertical speed detecting means (c) detecting the vertical speed of each suspended structure at a place close to the center of gravity, a tilting rate detecting means (d) detecting the tilting rate of the car body, and with an attenuation characteristics control means (e) controlling the attenuation characteristics of each shock absorber (b) on the basis of control signals obtained by both a bouncing rate and the tilting rate of the car body, which are determined based on the vertical speed of each suspended structure.

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 system for controlling a damping characteristic of a shock absorber, for example, Japanese Patent Laid-Open No. 61-
The thing described in 163011 gazette 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 is made soft. The four-wheel independent damping characteristic control based on the skyhook theory is performed.

[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, With respect to the body movement in which bounce and pitching are coupled, a moment of inertia of the body around the center of gravity of the body is added to the sprung mass, so the damping force (control force) is insufficient and the steering stability is poor. There was a point.

Further, in the damping characteristic control based on the skyhook theory, it is necessary to drive the actuator to switch the damping characteristics each time the signs of both the sprung vertical velocity and the relative velocity are switched to each other. 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 it is possible to obtain a sufficient vibration damping property even with respect to the inclination of the vehicle body due to the moment of inertia, thereby improving the riding comfort and the steering stability of the vehicle. The first purpose is to enable improvement, and the second purpose is to improve control response and durability of the actuator.

[0006]

In order to achieve the above object, the vehicle suspension system according to claim 1 of the present invention is, as shown in the claim correspondence diagram of FIG. 1, arranged between the vehicle body side and each wheel side. A shock absorber b interposed and capable of changing the damping characteristic 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 center of gravity of the vehicle body, and an inclination rate for detecting an inclination rate of the vehicle body. And a damping characteristic control means e for controlling the damping characteristic of each shock absorber b based on a control signal obtained from a bounce rate based on the sprung vertical velocity and a lean rate of the vehicle body. did.

According to a fifth aspect of the present invention, in addition to the above-mentioned 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, a compression side hard region where the extension side is fixed to a 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, the shock absorber is controlled in the pressure side hard area when the control signal is a negative value, and the shock absorber is controlled in the soft area when the control signal is 0. ..

[0008]

When the sprung speed detecting means and the respective inclination rate detecting means detect the bounce rate and the inclination rate, the damping characteristic control means obtains a control signal based on the bounce rate and the inclination rate, and the control signal The damping characteristic of each shock absorber is controlled in accordance with. Therefore, sufficient control force can be obtained not only for bounce but also for inclination of the vehicle body such as pitch and roll.

Further, in the apparatus according to the fifth aspect, when the control signal has a positive value, the shock absorber is controlled in the extension side hard region (the compression side has a low damping characteristic fixed), and when the control signal has a negative value. The shock absorber is controlled in the compression side hard area (fixed to the low side damping characteristic), 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 the sprung part and the unsprung part 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,
It is possible to perform the same control as the damping characteristic control based on the skyhook theory, that is, controlling the stroke side of the shock absorber at that time to a soft characteristic without detecting the relative speed between the sprung and unsprung parts. , In this case, since the switching of the damping characteristic to the low damping characteristic direction is performed without driving the actuator, the switching frequency of the damping characteristic is reduced as compared with the conventional damping characteristic control based on the skyhook theory. The control response 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.

FIG. 2 is a structural explanatory view showing a vehicle suspension system of a first embodiment which is an embodiment of the invention described in claims 1, 2, 3 and 5, and is between a vehicle body and four wheels. Intervened,
Four shock absorbers SA ₁ , SA ₂ , SA ₃ , S
A ₄ (In the explanation of the shock absorber,
When referring to these four collectively, and when describing these common configurations, they are simply referred to as SA. ) Is provided. A vertical acceleration sensor (hereinafter referred to as vertical G sensor) 1 for detecting vertical acceleration is provided at the center of gravity of the vehicle body. A control unit 4 is provided near the driver's seat to input signals from the sensors 1 and 5 and to output drive control signals 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 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a includes the above-mentioned vertical G sensor 1 and each of them. A signal from the stroke sensor 5 is input. In addition,
This stroke sensor 5 is used for each shock absorber SA.
Is provided between the vehicle body side and each wheel side in the vicinity of. Further, in the interface circuit 4a,
In the high frequency range (30
There is provided a filter circuit 6 including a low-pass filter for removing noise of Hz or higher) and a low-pass filter for integrating an acceleration signal passed through the low-pass filter and converting the acceleration signal into a sprung vertical velocity.

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. Which defines 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 through holes 31a and 31b formed therein and each through hole. An expansion-side damping valve 12 and a compression-side damping valve 20 that open and close 31a and 31b, respectively, are provided. A stud 38 penetrating the piston 31 is screwed and fixed to a bound stopper 41 screwed to the tip of the piston rod 7. 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 pressure-side second flow path J, which will be described later) that connects the upper chamber A and the lower chamber B. A hole 39 is formed and the 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 provided on the outer peripheral portion of the communication hole 3 in accordance with 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, 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.
Open the inside of the extension side damping valve 12 through b and open 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 extension side third flow path F reaching 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
Channel H, hollow 19, first lateral hole 24, first port 21
The pressure-side second flow path J that opens the pressure-side check valve 22 to the upper chamber A via 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 expansion 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 property 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 and 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 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 vertical acceleration of the vehicle body center of gravity obtained from the vertical G sensor 1 is processed by the filter circuit 6 to obtain the sprung vertical velocity Vn, and the shocks from the stroke sensors 5, 5, 5 and 5 are calculated. Absorber SA
Stroke speed of V _ST (V _{ST 1} , V _ST2 , V _ST3 , V
_ST4 ) is the step of detecting. Step 102 is
This is a step of obtaining a pitch determination signal A (A ₁ , A ₂ , A ₃ , A ₄ ) of the vehicle at each wheel position based on the following formula. That is, in this step, the stroke speed V _ST of both shock absorbers SA in the vehicle longitudinal direction is
Is for determining whether the vehicle pitch is generated or not. As shown in FIG. 16, no pitch is generated in the in-phase (region s), and in the opposite-phase (region t). There will be a pitch.

Front wheel right A ₁ = _FR V _ST × _RR V _ST Front wheel left A ₂ = _FL V _ST × _RL V _ST Rear wheel right A ₃ = _RR V _ST × _FR V _ST Rear wheel left A ₄ = _RL V _ST × _FL V _ST step 103 is a step of determining whether or not the pitch determination signal A has a positive value (the phases of the stroke speeds of the front wheel side and the rear wheel side are the same phase), and the step is YES (positive value). The process proceeds to step 104, and if NO (negative value), the process proceeds to step 105.

Step 104 is a step of setting the pitch component V _P ( _FR V _P , _FL V _P , _RR V _P , _RL V _P ) of each wheel to -A.

Step 105 is a step of setting the pitch components V _P ( _FR V _P , _FL V _P , _RR V _P , _RL V _P ) of each wheel to zero.

In step 106, the vehicle roll judgment signal B (B
₁ , B ₂ , B ₃ , B ₄ ) These are the steps to obtain. That is,
In this step, whether the stroke speed V _ST of both shock absorbers SA in the left-right direction of the vehicle body is the same phase or opposite phase,
When the rolling state of the vehicle is determined, as shown in FIG. 17, no rolling occurs in the in-phase (region u),
When the phase is reversed (region w), rolls are generated.

Front wheel right B ₁ = _FR V _ST × _FL V _ST Front wheel left B ₂ = _FL V _ST × _FR V _ST Rear wheel right B ₃ = _RR V _ST × _RL V _ST Rear wheel left B ₄ = _RL V _ST × _{The RR} V _ST step 107 is a step of determining whether or not the roll determination signal B has a positive value (the phases of the stroke speeds of the front wheel side and the rear wheel side are the same phase), and the step is YES (positive value). The process proceeds to 108, and if NO (negative value), the process proceeds to step 109.

[0026] Step 108 is a step of setting the roll component V _R at each wheel _{(FR V R, FL V R} , RR V R, RL V R) to -B.

[0027] Step 109, the roll component V _R at each wheel _{(FR V R, FL V R} , RR V R, RL V R) which is a step of setting to zero.

Step 110 is a step of determining whether or not the stroke speed V _ST is a positive value (shock absorber SA is in the stroke). If YES (extension), the process proceeds to step 111, and NO (NO). In the pressure stroke), the process proceeds to step 112.

Step 111 is a step for obtaining the control signals V ( _FR V, _FL V, _RR V, _RL V) on the extension side based on the following equations. Front wheel right _FR V = α ₁ · Vn + β ₁ · _FR V _P + γ ₁ · _FR V _R Front wheel left _FL V = α ₁ · Vn + β ₁ · _FL V _P + γ ₁ · _FL V _R Rear wheel right _RR V = α _{2 · Vn + β 2 · RR V} P + γ 2 · RR V R rear wheel left _{RL V = α 2 · Vn +} β 2 · RL V P + γ 2 · RL V R _{Incidentally, α 1, β 1, γ} 1 is the front wheel The proportional constants α ₂ , β ₂ and γ ₂ represent the proportional constants of the rear wheel.

In each equation, the first part bounded by α ₁ and α ₂ is the bounce rate, and β ₁ and β ₂
The part enclosed by is the pitch rate, and γ ₁ , γ ₂
The part marked with is the roll rate.

Step 112 is a step for obtaining the control signal V ( _FR V, _FL V, _RR V, _RL V) on the pressure stroke side based on the following equation. Front right _{FR V = α 1 · Vn -β} 1 · FR V P -γ 1 · FR V R front wheel left _{FL V = α 1 · Vn -β} 1 · FL V P -γ 1 · FL V R rear wheel right _RR V = α ₂ · Vn −β ₂ · _RR V _P −γ ₂ · _RR V _R Rear wheel left _RL V = α ₂ · Vn −β ₂ · _RL V _P −γ ₂ · _RL V _R Step 113 is a control signal This is a step of determining whether or not V is a positive value (upward), and YES (upward)
To proceed to step 114, and NO (downward) to step 1
Proceed to 15.

Step 114 is a step for determining whether or not the previous control signal V _-1 has a negative value, and YES.
Then, the process proceeds to step 116, and if NO, the process proceeds to step 117. That is, in this step, it is determined whether or not the direction of the control signal V is reversed.

Step 116 is a step of initializing the threshold value V _S1 of the upward control signal V to a predetermined value.

Step 117 is a step of judging whether or not the control signal V has become _{equal to} or higher than a predetermined threshold value V _S1 , and if YES, the routine proceeds to step 118, and if NO, step 1
Proceed to 19.

Step 118 is a step of updating the initially set threshold value V _S1 to the value of the control signal V at that time.

In step 119, the extension side target position Pn ( _FR Pn, _FL Pn, _RR Pn, _RL Pn) in the shock absorber SA is calculated based on the following formula, and the calculated target position Pn is set. This is a step of driving the pulse motor 3. Front wheel right _FR Pn = (P _{+ MAX} / V _S1 ) × _FR V Front wheel left _FL Pn = (P _{+ MAX} / V _S1 ) × _FL V Rear wheel right _RR Pn = (P _{+ MAX} / V _S1 ) × _RR V rear Wheel left _RL Pn = (P _{+ MAX} / V _S1 ) × _RL V Step 115 is a step of determining whether or not the previous control signal V ₋₁ has a positive value, and if YES, step 1
20. If NO, the process proceeds to step 121. That is, in this step, it is determined whether or not the direction of the control signal V is reversed.

Step 120 is a step of initializing the threshold value V _S2 of the downward control signal V to a predetermined value.

In step 121, the absolute value of the control signal | V
Is a step of determining whether or not | is equal to or greater than the absolute value of a predetermined threshold value | V _S2 |
And proceeds to step 123 with NO.

Step 122 is a step of updating the initially set threshold value V _S2 to the value of the control signal V at that time.

In step 123, the pressure side target position Pn ( _FR Pn, _FL Pn, _RR Pn, _RL Pn) in the shock absorber SA is calculated based on the following formula, and the pulse is directed toward the calculated target position Pn. This is a step of driving the motor 3. Front right _{FR Pn = (P -MAX / V} S2) × FR V front left _{FL Pn = (P -MAX / V} S2) × FL V rear wheel right _{RR Pn = (P -MAX / V} S2) × RR V after Wheel left _RL Pn = (P- _MAX / V _S2 ) × _RL V The control flow is completed once, and the above control flow is repeated thereafter.

Next, the operation of the embodiment apparatus will be described with reference to the time chart of FIG. In the drawing, the control signal V, the damping force F and the relative speed, the control direction (stroke) of the shock absorber SA, and the target position Pn are shown in order from the top, and the control signal V draws a sine curve and extends.
The figure shows the case where the pressure side alternates, and the peak values P ₁ and P _{2 change} in the vertical direction so as to exceed the threshold values V _S1 and V _S2 of the initial setting values, respectively.

In the figure, a region a is a region in which the control signal V is upward and is less than the initial threshold value V _S1 . In this case, the target extension side target position Pn is controlled in proportion to the control signal V. At this time, since the stroke of the shock absorber SA is the pressure stroke,
Due to the soft characteristic on the compression side (minimum damping position), it is possible to suppress push-up of the vehicle body due to road surface input.

The next region b is a region until the control signal V becomes equal to or higher than the initial threshold value V _S1 and reaches the peak value P ₁ , and in this case, according to the flow of steps 117 to 118 in FIG. As a result of performing the process of matching the threshold value V _S1 with the control signal V at any time, the target position is held at the maximum extension side damping position P _{+ MAX} until the peak value P ₁ is reached. By thus increasing the damping characteristic on the extension side, it is possible to suppress vibration in the upward direction of the vehicle body.

In the next area c, the control signal V has a peak value P ₁
From the point where the direction of the control signal V reverses,
In this case, since the threshold value V _S1 is also equal to the peak value P ₁ when the control signal V reaches the peak value P ₁ , the control signal V is calculated based on the arithmetic expression shown in step 119 of FIG. Is lower than the peak value P ₁ , the target position Pn on the extension side decreases from that point in proportion to the decrease of the control signal V.

The next area d is an area from when the direction of the control signal V is reversed to when it becomes the downward downward threshold V _S2 or more. In this case, the target position Pn is controlled in proportion to the control signal V, but at this time, since the stroke of the shock absorber SA is the extension stroke, it depends on the extension side soft characteristic (minimum damping position). It is possible to suppress the sinking of the vehicle body due to the road surface input.

The next area e is an area until the control signal V becomes equal to or more than the initial threshold value V _S2 and reaches the peak value P ₂ , and in this case, according to the flow of steps 121 to 122 in FIG. As a result of performing the process of matching the threshold value V _S2 with the control signal V at all times, the target position Pn is held at the compression side maximum damping position P _-MAX until the peak value P ₂ is reached. By thus increasing the damping characteristic on the compression side, it is possible to suppress downward vibration of the vehicle body.

In the next area f, the control signal V has a peak value P ₂
From the point where the direction of the control signal V reverses,
In this case, when the control signal V reaches the peak value P ₂ , it becomes equal to the threshold value V _S2 peak value P _2, and therefore, based on the arithmetic expression shown in step 123 of FIG.
When the control signal V changes upward from the peak value P ₂ , the target position Pn on the extension side decreases from that point in proportion to the change in the control signal V.

Further, in the time chart of FIG.
The region g is a state in which the control signal V based on the control signal V is reversed from a negative value (downward) to a positive value (upward),
At this time, the relative speed is still a negative value (shock absorber S
Since the stroke of A 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. Therefore, in this area, The pressure stroke side, which is the stroke of the shock absorber SA, has soft characteristics.

The region h 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 on 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 that is proportional to the value of the control signal V.

In the region j, 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.

The region k is a region where 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 the extension side). At this time, the shock absorber SA is controlled to the pressure side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber is also the pressure stroke,
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 h, region k), the shock at that time is generated. Damping characteristic control based on the skyhook theory, in which the stroke side of the absorber SA is controlled to have a hard characteristic, and when the shock absorber SA has a different sign, the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic. The same control as above will be performed without detecting the relative speed between the sprung and unsprung parts. Further, in this embodiment, when the region g is shifted to the region h and the region j is shifted to the region k, the damping characteristic is switched without driving the pulse motor 3.

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, it is possible to provide a vehicle suspension system with excellent riding comfort and steering stability.

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

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) This second embodiment is an example in which a gyro is used as means for detecting the pitch rate and the roll rate, and as shown in the configuration explanatory view of FIG.
At the position of the center of gravity of the vehicle body, a rate gyro 2 for detecting the inclination state (pitch, roll) of the vehicle body is provided in addition to the vertical G sensor 1. That is, in this embodiment, as shown in the system block diagram of FIG. 19, the interface circuit 4a includes a pitch rate gyro 2a and a roll rate gyro 2b, which are composed of the above-mentioned vertical G sensor 1 and the rate gyro 2. The signal from is input.

Then, in this embodiment, the control signal is obtained based on the following equation. Front wheel right _FR V = α ₁ · Vn + β ₁ · L ₁ · θ + γ ₁ · X ₁ · φ Front wheel left _FL V = α ₁ · Vn + β ₁ · L ₁ · θ-γ ₁ · X ₂ · φ Rear wheel right _RR V = α ₂ · Vn −β ₂ · L ₂ · θ + γ ₂ · X ₁ · φ Rear wheel left _RL V = α ₂ · Vn −β ₂ · L ₂ · θ-γ ₂ · X ₂ · φ where θ is The pitch component, φ indicates a roll component, the pitch component θ is detected as a head-up direction, and the roll rate φ is detected as a positive value in the left roll direction. Further, as shown in FIG. 20, X ₁ is the distance from the center line m extending in the front-rear direction of the vehicle body through the body weight center position Q to the center of the right wheels (FR, RR), and X ₂ is the left wheel from the center line m. The distance to the center of (FL, RL), L ₁ is the distance from the center line n extending in the width direction of the vehicle body through the vehicle body center of gravity position Q to the front wheel (FR, FL) ground contact point, and L ₂ is from the center line n. Rear wheels (RR, R
L) Indicates the distance to the grounding point.

In each equation, the first part bounded by α ₁ and α ₂ is the bounce rate, and β ₁ and β ₂
The part enclosed by is the pitch rate, and γ ₁ , γ ₂
The part marked with is the roll rate.

That is, in this embodiment, a sufficient control force can be generated not only for bounce but also for pitch and roll. Therefore, as in the case of the first embodiment,
It is possible to provide a suspension system for a vehicle having excellent riding comfort and steering stability, and it is possible to improve the control response because the frequency of switching the damping characteristic is reduced compared to the conventional damping characteristic control based on the skyhook theory. In addition, the durability of the pulse motor 3 can be improved.

Further, in this embodiment, the pitch rate and the roll rate of the vehicle body are detected by the gyro, so that the control content can be simplified and even when a centrifugal force acts on the vehicle. Since no error occurs, the vehicle tilt control can be performed more accurately.

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, in the embodiment, the control content is such that the stroke of the one controlling to the hardware characteristic side is determined depending on whether the sprung vertical velocity is a positive value or a negative value. A value is provided, and while the sprung vertical velocity is within this positive / negative threshold, the soft region SS is controlled so that both the extension side and the compression side have soft characteristics, and when the positive / negative threshold is exceeded, the hard characteristic (extension It is also possible to control to the side hard region HS or the pressure side hard region SH) side.

Further, in the embodiment, the target position is obtained based on the arithmetic expression, but it may be obtained based on the map shown in FIG. In this figure, (a) is a map for extension side and (b) is a map for compression side, and the target position P corresponding to the value of the control signal V is shown.
n is set.

Further, in this embodiment, when controlling one side of both the extension and compression strokes to the high damping characteristic side, a shock absorber having a structure in which the reverse stroke side is fixed to a predetermined low damping characteristic is provided. Although used, a shock absorber having a structure in which both the extension and compression strokes change simultaneously can be used.

In this embodiment, the control signal is obtained based on the bounce rate, the pitch rate and the roll rate.
Alternatively, the control signal can be obtained based on the bounce rate and the roll rate.

[0066]

As described above, in the vehicle suspension system of the present invention, the damping characteristic control means obtains the control signal from the sprung vertical velocity near the vehicle body center position and the lean rate of the vehicle body, and based on this control signal. Since the damping characteristics of each shock absorber are controlled, not only bounce but also
Sufficient vibration damping property can be obtained even with respect to the inclination of the vehicle body due to the moment of inertia, and as a result, riding comfort and steering stability can be improved.

Further, in the vehicle suspension device according to the fourth aspect of the invention, the vehicle body inclination rate detecting means is constituted by a gyro, so that the control contents can be simplified and even when a centrifugal force acts on the vehicle. The inclination control of the vehicle can be performed more accurately without causing a detection error.

According to a fifth aspect of the present invention, in the vehicle suspension system, each shock absorber has a hard region in which the expansion side has a variable damping characteristic and the compression side has a low damping characteristic fixed, and the compression side has a variable damping characteristic and the expansion side has a low damping characteristic. When the control signal is equal to or more than a positive threshold value, the damping characteristic control means is formed in a structure having three regions of a compression side hard region fixed to the characteristic and a soft region of low damping characteristic on both the extension side and the compression side. The shock absorber is controlled in the expansion side hard area, the shock absorber is controlled in the compression side hard area when the control signal is below the negative threshold, and the shock absorber is controlled when the control signal is between the positive and negative threshold values. Since it is possible to control the damping characteristic based on the skyhook theory without using the relative velocity detecting means by configuring to control in the soft region, it is possible to reduce the number of parts and cost. In addition, assembling labor, assembling space, and weight can be reduced, and the switching frequency of the damping characteristics can be reduced compared to the conventional damping characteristic control based on the skyhook theory, so that the control response can be improved. In addition, the durability of the damping characteristic switching actuator can be improved.

[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 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 the step position of the pulse motor of the shock absorber.

FIG. 8 is a part of the shock absorber shown in FIG.
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 pressure side hard state.

FIG. 14 is a flowchart showing a control operation of a control unit in the first embodiment device.

FIG. 15 is a time chart showing the control operation of the control unit in the device of the first embodiment.

FIG. 16 is a time chart illustrating a method of determining a pitch occurrence state in the device of the first embodiment.

FIG. 17 is a time chart illustrating a method of determining a roll occurrence state in the apparatus according to the first embodiment.

FIG. 18 is a structural explanatory view showing a vehicle suspension device of a second embodiment of the present invention.

FIG. 19 is a system block diagram showing a second embodiment device.

FIG. 20 is a perspective view for explaining the control contents of the control unit in the second embodiment device.

FIG. 21 is a map showing another example of how to obtain a target position.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c sprung vertical velocity detecting means d tilt rate detecting means e damping characteristic controlling 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 speed detecting means for detecting a sprung vertical speed in the vicinity of a vehicle body center position. An inclination rate detecting means for detecting an inclination rate of the vehicle body, and an attenuation characteristic control for controlling the attenuation characteristics of each shock absorber based on a control signal obtained from a bounce rate based on the sprung vertical velocity and an inclination rate of the vehicle body. A vehicle suspension system comprising: 2. The vehicle suspension system according to claim 1, wherein the inclination rate detected by the inclination rate detecting means is a pitch rate in the longitudinal direction of the vehicle body and a roll rate in the lateral direction of the vehicle body. 3. The vehicle according to claim 1, wherein the lean rate detecting means of the vehicle body is a means for detecting a lean rate from a stroke speed difference of each shock absorber detected by a stroke sensor. Suspension system. 4. The vehicle suspension system according to claim 1, wherein the vehicle body inclination rate detecting means is a gyro. 5. An expansion side hard region in which the expansion side is variable in damping characteristics and the compression side is fixed in low damping characteristics, and a shock side hard region in which the compression side is variable in damping characteristics and expansion side is fixed in low damping characteristics is formed. It is formed in a structure having three regions, a soft region having a low damping characteristic on both the pressure 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 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.