JPH07232531A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To provide a vehicle suspension device capable of securing riding comfortability of a vehicle at the time of straight traveling, securing operational stability of the vehicle at the time of steering and doubly securing the riding comfortability and the operational stability under any traveling condition. CONSTITUTION:A shock absorber (b) interposed between the side of a car body and the side of each wheel and free to vary a damping force characteristic by a damping force characteristic variation means (a) and a front wheel side spring vertical speed detection means c1 and a rear wheel side spring vertical speed detection means c2 to detect spring vertical speed on the front wheel side and the rear wheel side of a vehicle are provided. Additionally, a front wheel side cross acceleration detection means d1 and a rear wheel side cross acceleration detection means d2 to detect cross directional acceleration on the front wheel side and the rear wheel side of the vehicle and a damping force characteristic control means (e) to carry out damping force characteristic control of each shock absorber (b) in accordance with a control signal acquired from a both front and rear spring vertical speed signal and a both front and rear cross acceleration signal are furnished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling a damping force characteristic of a shock absorber, and more particularly to a vehicle suspension system which suppresses vehicle roll due to steering.

[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 Patent Application Laid-Open No. 61-61600.
The one described in Japanese Patent No. 163011 is known. This conventional vehicle suspension system detects the sprung vertical velocity and the sprung / unsprung relative velocity of the vehicle at each wheel position, and when the direction discrimination codes of both are the same, the damping force characteristic of each shock absorber is determined. The four wheels are independently configured to perform damping force characteristic control based on the skyhook theory, such as making the damping force characteristic soft when the hardware has a different sign.

[0003]

However, in the conventional device, when lateral acceleration acts on the vehicle to cause a roll, such as when the vehicle turns by steering, a spring is generated by the roll angle. Since the detection axis direction of the upper vertical acceleration sensor is inclined, the other axis component due to the lateral acceleration (the vertical acceleration component of the lateral acceleration due to the roll angle)
Therefore, the control based only on the sprung vertical velocity signal cannot perform accurate damping force characteristic control adapted to all running conditions.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to secure the riding comfort of the vehicle when traveling straight ahead and to secure the steering stability of the vehicle at the time of steering, so that all traveling is possible. It is an object of the present invention to provide a vehicle suspension device that can ensure both ride comfort and steering stability even under conditions.

[0005]

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. A shock absorber b which is interposed and whose damping force characteristic can be changed by the damping force characteristic changing means a, and a front wheel side sprung vertical speed detecting means c ₁ for detecting sprung vertical speeds on the front wheel side and the rear wheel side of the vehicle; Rear-spring-side sprung vertical velocity detecting means c ₂ , front-wheel-side lateral acceleration detecting means d ₁ and rear-wheel-side lateral acceleration detecting means d ₂ for detecting lateral acceleration on the front-wheel side and rear-wheel side of the vehicle, and both front and rear Damping force characteristic control means e for controlling the damping force characteristic of each shock absorber b based on the control signals obtained from the sprung vertical velocity signal and the front and rear lateral acceleration signals.

Further, in the vehicle suspension system according to claim 2,
The damping force characteristic control means e in claim 1 includes a steering state determination unit f for determining the steering state of the vehicle from both the front and rear lateral acceleration signals, and the front and rear springs when the vehicle is not in a steering state above a predetermined level. A straight running control unit g for performing damping force characteristic control of each shock absorber by a straight running control signal based on a bounce rate and a pitch rate obtained from the vertical velocity signal and a roll rate obtained from both front and rear lateral acceleration signals.
And a steering control section h for performing damping force characteristic control of each shock absorber by a steering control signal based on a roll rate and a yaw rate obtained from both front and rear lateral acceleration signals when in a steering state above a predetermined level. It has a structure.

Further, in the vehicle suspension system according to claim 3,
In the damping force characteristic control means e in claim 1,
A pure sprung vertical speed signal at each wheel position is obtained by subtracting the front and rear lateral acceleration signals from the front and rear sprung vertical speed signals, and a bounce rate based on this pure front and rear sprung vertical speed signals, The damping force characteristic control of each shock absorber is performed by a control signal based on a pitch rate obtained from pure front and rear sprung vertical velocity signals and a roll rate obtained from front and rear lateral acceleration signals.

[0008]

In the vehicle suspension system according to the first aspect of the present invention, as described above, in the damping force characteristic control means e, the control signals for controlling the damping force characteristic of each shock absorber are the front and rear sprung vertical velocity signals and It is obtained from both front and rear lateral acceleration signals, which enables accurate damping force characteristic control suitable for all driving conditions such as straight running and steering, ensuring ride comfort and steering stability under any driving condition. It is possible to achieve both securing and securing.

Further, in the vehicle suspension system according to claim 2,
The steering state determination unit of the damping force characteristic control unit determines the steering state of the vehicle based on the front and rear lateral acceleration signals.

When the vehicle is not in a steering state above a predetermined level as a result of the steering state determination unit, the straight-ahead control unit controls the bounce rate and pitch rate obtained from the front and rear sprung vertical velocity signals and the front and rear lateral directions. The damping force characteristic control of each shock absorber is performed in the direction to suppress the transmission of the road surface input to the sprung by the straight running control signal based on the roll rate obtained from the acceleration signal. Is less than or equal to a predetermined amount or the vehicle speed is low, so that the ride comfort and steering stability of the vehicle can be secured when the vehicle roll is less than or equal to a predetermined amount. When the vehicle is in a steering state above a predetermined level as a result of determination by the steering state determination unit, the steering control unit controls the steering control signal based on the roll rate and yaw rate obtained from the front and rear lateral acceleration signals. The damping force characteristic control of each shock absorber is performed in the direction that minimizes the posture change, so that during steering (when the steering amount is more than a predetermined amount or the vehicle roll is greater than a predetermined amount because the vehicle speed is high) It is possible to ensure the steering stability of the vehicle in.

Further, in the vehicle suspension system according to claim 3,
By subtracting the front-rear lateral acceleration signals from the front-rear sprung vertical velocity signals, a pure sprung vertical velocity signal at each wheel position is obtained, and a bounce rate based on the pure front-rear sprung vertical velocity signals, Damping force characteristic control of each shock absorber is performed by a control signal based on a pitch rate obtained from pure front and rear sprung vertical velocity signals and a roll rate obtained from front and rear lateral acceleration signals.

Therefore, when the vehicle is traveling straight (when the steering amount is less than a predetermined amount or the vehicle roll is less than a predetermined amount because the vehicle speed is low), the front and rear lateral acceleration signals are also less than the predetermined amount, so that the front-back direction is mainly performed. The damping force characteristic control of each shock absorber is performed in a direction to suppress the transmission of road surface input to the sprung by a control signal based on each sprung vertical velocity signal. Can be secured.

During steering (when the steering amount is greater than a predetermined amount or the vehicle speed is greater than a predetermined amount due to a high vehicle speed), the front and rear lateral acceleration signals also exceed the predetermined amount. The bounce rate and pitch rate are corrected by the acceleration signal, and the damping force characteristic control of each shock absorber is performed by the control signal in which the roll rate is incorporated, which changes the posture of the vehicle during steering. The steering stability of the vehicle can be secured by suppressing it to the minimum.

[0014]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 is a system block diagram showing a vehicle suspension system according to a first embodiment of the present invention, in which four shock absorbers SA are interposed between a vehicle body and four wheels.
_FL , SA _FR , SA _RL , SA _RR (Note that _FL is the front wheel left side, _FR
Indicates the right side of the front wheel, _RL indicates the left side of the rear wheel, and _RR indicates the right side of the rear wheel. In describing the shock absorber, when these four are collectively referred to, and when describing their common configuration, they are simply indicated as SA. ) Is provided. Further, at the front wheel side center position and the rear wheel side center position of the vehicle body, a front wheel side vertical acceleration sensor and a rear wheel side vertical acceleration sensor (hereinafter, vertical G level) for detecting the vertical accelerations G _F and G _R at the respective positions. Sensors) 1f, 1r and front wheel side lateral acceleration sensor and rear wheel side lateral acceleration sensor (hereinafter referred to as lateral G sensor) for detecting lateral accelerations G _SF , G _SR at respective positions.
2f and 2r are provided. As shown in FIG. 15, the vertical accelerations G _F and G _R are obtained as positive values when the acceleration direction is upward and are obtained as negative values when the acceleration direction is downward.
The lateral accelerations G _SF and G _SR are positive values when the acceleration direction is from the right wheel to the left wheel direction (the right turning direction of the vehicle), and are the opposite directions (the left turning direction of the vehicle). Obtained with a negative value.

The above configuration is shown in the system block diagram of FIG. 3, in which the control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c. G sensors 1f, 1r and front and rear lateral G sensors 2f
, 2r are input.

In the interface circuit 4a, the signal processing circuits shown in (a) to (f) of FIG. 14 are provided for both the upper and lower G sensors 1 and the both lateral G sensors 2.

In FIGS. 14A and 14B, the LPF
Reference numeral 1 is a low-pass filter for integrating the sprung vertical acceleration signals G _F and G _R sent from the vertical G sensors 1f and 1r to convert them into a sprung vertical velocity.
Is a bandpass filter for obtaining the bounce velocities Vn-F and Vn-R of the sprung vertical velocity including the sprung resonance frequency.

In FIGS. 14C and 14D, the LPF
Reference numeral 2 is a low-pass filter for integrating the lateral acceleration signals G _SF , G _SR sent from both the front and rear lateral G sensors 2 f, 2 r to convert it into a lateral velocity, and the BPF 2 is a lateral direction including a roll resonance frequency. A bandpass filter for obtaining the velocities Vs-F and Vs-R, and the HPF is for differentiating the lateral acceleration signals sent from the front and rear lateral G sensors 2f and 2r to convert them into lateral acceleration change rates. The BPF 3 is a high-pass filter and is a band-pass filter for obtaining the lateral acceleration change rates Gs-F and Gs-R including the roll resonance frequency.

In FIG. 14 (e), E ₁ is the difference between the front and rear accelerations G _F and G _R , which are sent from the front and rear upper and lower G sensors 1f and 1r, and the front and rear acceleration difference Gp (= G _F −
An arithmetic circuit for obtaining G _R ), an LPF 3 is a low pass filter for integrating the G p signal and converting it into a sprung vertical velocity, and a BPF 4 is a band pass for obtaining a pitch velocity V p including a pitch resonance frequency. It is a filter.
The pitch speed Vp is obtained as a positive value when the vehicle is in the scat direction and a negative value when the vehicle is in the dive direction.

In FIG. 14F, E ₂ is the lateral acceleration G _SF , which is sent from the front and rear lateral G sensors 2f and 2r.
Arithmetic circuits for calculating the two acceleration difference Gr (= G _SF -G _SR) before and after the G _SR, LPF 4 is a low-pass filter for converting the lateral velocity by integrating both acceleration difference Gr signal, BPF 5 Is a bandpass filter for obtaining the yaw rate signal V _Y including the roll resonance frequency. The yaw rate signal V _Y is the lateral acceleration G in both front and rear directions.
_{In place of SF} and G _SR , the front and rear lateral velocities Vs-F and Vs-R
You can also ask from.

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 through holes 31a and 31b formed therein and each through hole. 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 that 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 force characteristic can be changed in multiple stages on both the extension side and the compression side by the characteristic shown in FIG. 6 by rotating the adjuster 40. That is, as shown in FIG.
A soft area on both sides (hereinafter soft area SS
When the adjuster 40 is rotated counterclockwise from
Only the extension side can change the damping force characteristic in multiple stages, and the compression side becomes a region fixed to the low damping force characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, The damping force characteristic can be changed in multiple steps only on the compression side, and the extension side is a region fixed to the low damping force characteristic (hereinafter, referred to as compression side hard region SH).

Incidentally, in FIG. 7, when the adjuster 40 is arranged in the displacement position of, the KK section, the LL section, the MM section, and the NN section in FIG.
Sections are shown in FIGS. 8, 9 and 10, respectively, and
The damping force characteristics at each displacement position are shown in Figs.
It is shown in 13.

Next, regarding the damping force control operation of the control unit 4, the flowchart of FIG. 16 and FIG.
This will be explained based on the time chart of. Note that this control is separately performed for each shock absorber SA.

First, in the flow chart of FIG.
In step 101, the sprung vertical accelerations of the front wheel and the rear wheel detected by the front wheel vertical G sensor 1f, the rear wheel vertical G sensor 1r, the front wheel lateral G sensor 2f, and the rear wheel lateral G sensor 2f. G _F , G _R and lateral acceleration G _SF , G _SR
Are processed by the respective signal processing circuits shown in FIG. 14, the front and rear bounce velocities Vn-F and Vn-R, the front and rear lateral velocities Vs-F and Vs-R, and the front and rear lateral acceleration change rates Gs. -F, Gs-R, pitch velocity Vp, and yaw rate signal _VY are obtained.

In step 102, it is judged whether or not the absolute value | V _Y | of the yaw rate signal is equal to or more than a predetermined steering condition threshold value Vs, and if YES, the process proceeds to step 103,
If NO, the process proceeds to step 104.

In step 103, the following arithmetic expressions (1)
Based on (4), the control signals V '(V'FR, V'FL, V'RR at steering of the shock absorber SA at each wheel position,
V'RL) is calculated. Front wheel right V'FR = α _f · Vn-F + β _f · Vp + γ _f · Gs-F ···· (1) Front wheel left V'FL = α _f · Vn-F + β _f · Vp -Γ _f · Gs-F ··· (2) Rear wheel right V′RR = α _r · Vn-R −β _r · Vp + γ _r · Gs-R ···・ ・ (3) Rear wheel left V'RL = α _r・ Vn-R −β _r・ Vp −γ _r・ Gs-R ・ ・ ・ ・ ・ ・ ・ (4) Note that α _f , β _f , γ _f is the control gain on the front wheel side, α _r ,
β _r and γ _r are the control gains on the rear wheel side. And α
_The part multiplied by _f and α _r is the bounce rate, and β _f and
The part multiplied by β _r is the pitch rate, and the part multiplied by γ _f and γ _r is the roll rate.

In step 104, the following arithmetic expression (5)
Based on (8), the control signals V (VFR, VFL, VRR, VRL) of the shock absorber SA at each wheel position are obtained. Front right _{VFR = δ f · Gs-F} + ε f · V Y ········· (5) the front wheel left _{VFL = -δ f · Gs-F} -ε f · V Y ······・ ・ ・ (6) Rear wheel right VRR = δ _r・ Gs-R + ε _r・ V _Y・ ・ ・ ・ ・ ・ ・ ・ ・ (7) Rear wheel left VRL = −δ _r・ Gs-R −ε _r・V _Y ... (8) where δ _f and ε _f are control gains on the front wheel side, and δ _r and ε _r are control gains on the rear wheel side. The portion multiplied by δ _f and δ _r is the steering roll rate, and the portion multiplied by ε _f and ε _r is the yaw rate.

In step 105, the control signal V (V ')
Is a positive value. If YES, the process proceeds to step 106, and if NO, the process proceeds to step 107.
In step 106, the shock absorber SA is controlled to the extension side hard region HS side, and the pulse motor 3 is drive-controlled toward the extension side target damping force position P obtained based on the following equation. P = Vθt where θt is a control gain on the extension side.

In step 107, the control signal V (V ')
Is 0, and if YES, step 1
Proceed to 08 to set shock absorber SA to soft area SS
The pulse motor 3 is drive-controlled to control so that if NO, the process proceeds to step 109.

In step 109, when NO is determined in steps 105 and 107, that is, since the control signal V has a negative value, in this case, the shock absorber SA is controlled to the pressure side hard area SH side, and The pulse motor 3 is drive-controlled toward the target damping force position P on the compression side obtained based on the equation. P = Vθc where θc is the pressure side control gain.

Next, the above control operation will be described with reference to the time chart of FIG. First, when the absolute value | V _Y | of the yaw rate signal is less than the predetermined steering condition threshold value Vs, steering is not performed, or even if steering is performed, the steering amount is small or the vehicle speed is low. Is a low speed and the vehicle does not roll over a predetermined amount. At this time, the control is switched to the straight-ahead control (steering FLAG is OFF), and the straight-ahead drive is the basis for the damping force characteristic control of the shock absorber SA. The time control signal V is obtained by synthesizing the bounce rate and pitch rate based on the sprung vertical accelerations G _F and G _R signals and the roll rate based on the lateral acceleration change rates Gs-F and Gs-R. As a result, when the vehicle is traveling straight ahead, damping force characteristic control is performed in a direction in which transmission of road surface input to the spring is suppressed, and the ride comfort of the vehicle can be ensured.

When the absolute value | V _Y | of the yaw rate signal is equal to or greater than the predetermined steering condition threshold value Vs, it means that the vehicle rolls more than a predetermined value as a result of the steering operation. At the time of steering control (steering FLAG is ON)
The steering control signal V ′, which is the basis of the damping force characteristic control of the shock absorber SA, is obtained by combining the roll rate and the yaw rate based on the lateral acceleration change rates Gs-F and Gs-R. Accordingly, during steering, damping force characteristic control is performed in a direction that minimizes a change in vehicle attitude, and steering stability of the vehicle can be ensured.

Next, the time chart of FIG. 18 will be described. In the time chart of FIG. 18, the area a is
The control signal V (V ') is in a state of being 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 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 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 in the pressure side hard area SH based on the direction of the control signal V, and the stroke of the shock absorber SA is also the pressure stroke. Therefore, in this area, the shock absorber SA at that time is present. 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 Vn and the relative speed between the sprung and unsprung portions have the same sign (region b, region d), Damping force based on the skyhook theory, in which the stroke side of the shock absorber SA is controlled to have a hard characteristic, and when the shock absorber SA has a different sign (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 as the characteristic control is performed. 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.

As described above, in this embodiment, it is possible to secure the riding comfort of the vehicle during straight traveling and the steering stability of the vehicle during steering without using a steering sensor, and under any traveling condition. Also, it is possible to obtain both the ride comfort and the driving stability.

(Second Embodiment) Next, a vehicle suspension system according to a second embodiment of the present invention will be described. In the description of this embodiment, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and only different points will be described. In this embodiment, the control contents of the signal processing circuit and the control unit 4 are different from those of the first embodiment.

19 (a) to 19 (e) show the signal processing circuit of this embodiment. In FIGS. 19 (a) and 19 (b), E ₃ and E ₄ are upper and lower springs, respectively. Acceleration G _F , G
Each lateral acceleration before and after the _R G _SF, G _SR correction signal G _F corrected for _{· '(= G F -a ·} G SF), G R' (= G R -b
2 shows an arithmetic circuit for _obtaining G _SR ). The a and b are correction gains. Therefore, in this signal processing circuit, pure bounce velocities Vn-F and Vn-R in which the lateral acceleration component due to the roll of the vehicle is corrected can be obtained.

Further, in (c) of FIG. 19, E ₅ is
This is an arithmetic circuit for obtaining the vehicle pitch speed Vp (= Vn-F-Vn-R) from the front and rear bounce speeds Vn-F and Vn-R.

Since (d) and (e) in FIG. 19 are the same as the signal processing circuit portion for obtaining the lateral acceleration change rates G _S -F and G _S -R in the first embodiment, The description is omitted.

In this embodiment, the following arithmetic expression (9)
~ Control signal V "(V" FR, obtained based on (12),
V "FL, V" RL, V "RR) performs damping force characteristic control of the shock absorber SA at each wheel position.

Front wheel right V "FR = α _f · Vn-F + β _f · Vp + γ _f · Gs-F ··· (9) Front wheel left V” FL = α _f · Vn-F + β _f・ Vp-γ _f・ Gs-F ・ ・ ・ ・ ・ ・ ・ (10) Rear wheel right V "RR = α _r・ Vn-R −β _r・ Vp + γ _r・ Gs-R ・ ・ ・ ・ ・ ・ ・(11) Rear wheel left V "RL = α _r · Vn-R −β _r · Vp −γ _r · Gs-R ··· (12) As described above, in this embodiment, the vehicle travels straight ahead. At a time (when the steering amount is less than a predetermined amount or the vehicle speed is less than a predetermined amount due to a low vehicle speed), the front-rear lateral accelerations G _SF , G _SR and the front-rear lateral acceleration change rates G _S -F, G
_{Since S-} R is also a predetermined amount or less, the damping force characteristic control of each shock absorber SA is performed mainly in the direction of suppressing the transmission of the road surface input to the sprung by the control signal V "based on the front and rear sprung vertical velocity signals. As a result, it is possible to ensure the riding comfort of the vehicle when traveling straight ahead.

Further, during steering (when the steering amount is equal to or greater than a predetermined amount or the vehicle speed is greater than a predetermined amount due to a high vehicle speed), front and rear lateral accelerations G _SF and G _SR and front and rear lateral acceleration changes. Since the rates G _S -F and G _S -R also exceed a predetermined amount, the front and rear lateral accelerations G _SF and G _SR correct the bounce rate and pitch rate, and the front and rear lateral acceleration change rates are also corrected. The damping force characteristic control of each shock absorber SA is performed by the control signal V "in which the roll rate based on G _S -F and G _S -R is incorporated, thereby minimizing the change in the attitude of the vehicle during steering. It is possible to suppress and secure the steering stability of the vehicle.

As described above, also in this embodiment, it is possible to secure the riding comfort of the vehicle during straight running and the steering stability of the vehicle during steering without using a steering sensor, and all driving conditions can be ensured. Also in this case, it is possible to obtain both the ride comfort and the driving stability.

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 extension side hard region where the extension side has a variable damping force characteristic and the compression side has a low damping force characteristic fixed, and the compression side hard region where the compression side has a variable damping force characteristic and the extension side has a low damping force characteristic fixed. And a shock absorber having three regions, a soft region with low damping force characteristics on both the extension side and compression side, was used, but it is also possible to control using a shock absorber with a structure in which the damping force characteristics on the extension side and compression side change simultaneously. Can be applied.

Further, in the embodiment, the case where only two vertical G sensors and two lateral G sensors are used is shown, but they may be provided at each wheel position.

[0054]

As described above, in the vehicle suspension system of the present invention, the front wheel sprung vertical speed detecting means for detecting the sprung vertical speed on the front wheel side and the rear wheel side of the vehicle and the rear wheel sprung upper and lower speeds. From the speed detecting means, the front wheel side lateral acceleration detecting means and the rear wheel side lateral acceleration detecting means for detecting the lateral acceleration on the front wheel side and the rear wheel side of the vehicle, and the front and rear sprung vertical speed signals and the front and rear lateral acceleration signals. By providing the damping force characteristic control means for performing the damping force characteristic control of each shock absorber based on the obtained control signal, ensuring the ride comfort of the vehicle during straight running,
It is possible to ensure the steering stability of the vehicle at the time of steering, and it is possible to obtain both the riding comfort and the steering stability under all driving conditions.

[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 device according to the first embodiment of the present invention.

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 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 -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 signal processing circuit in the device of the first embodiment.

FIG. 15 is an explanatory diagram showing a mounting positional relationship of each of the vertical G sensor and the lateral G sensor in the first embodiment device and a direction of a signal based on an acceleration direction.

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

FIG. 17 is a time chart showing a control switching state between straight-ahead traveling control and steering control during a control operation of the control unit in the first embodiment device.

FIG. 18 is a time chart showing a straight-ahead operation of the control operations of the control unit in the embodiment apparatus.

FIG. 19 is a block diagram showing a signal processing circuit in a vehicle suspension system according to a second embodiment of the present invention.

[Explanation of symbols]

a Damping force characteristic changing means b Shock absorber c ₁ Front wheel side sprung vertical speed detecting means c ₂ Rear wheel side sprung vertical speed detecting means d ₁ Front wheel side lateral acceleration detecting means d ₂ Rear wheel side lateral acceleration detecting means e Damping force Characteristic control means f Steering state determination unit g Straight traveling control unit h Steering control unit

Claims (3)

[Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping force characteristic by a damping force characteristic changing means, and a sprung vertical velocity on a front wheel side and a rear wheel side of a vehicle are detected. Front-wheel-side sprung vertical velocity detecting means and rear-wheel-side sprung vertical velocity detecting means, and front-wheel lateral acceleration detecting means and rear-wheel lateral-acceleration detecting means for detecting lateral acceleration on the front wheel side and rear wheel side of the vehicle And a damping force characteristic control means for performing damping force characteristic control of each shock absorber based on control signals obtained from both front and rear sprung vertical velocity signals and front and rear lateral acceleration signals. Suspension system. 2. The damping force characteristic control means includes a steering state determination unit that determines a steering state of the vehicle from both front and rear lateral acceleration signals, and both front and rear spring upper and lower springs when the vehicle is not in a steering state above a predetermined level. A straight-ahead control unit that controls the damping force characteristics of each shock absorber by a straight-ahead control signal based on the bounce rate and pitch rate obtained from the speed signal and the roll rate obtained from both front and rear lateral acceleration signals, and a steering state above a certain level. And a steering control section for performing damping force characteristic control of each shock absorber by a steering control signal based on a roll rate and a yaw rate obtained from both front and rear lateral acceleration signals. Item 3. The vehicle suspension device according to item 1. 3. The damping force characteristic control means obtains a pure sprung vertical velocity signal at each wheel position obtained by subtracting each of the front and rear lateral acceleration signals from each of the front and rear sprung vertical velocity signals, and the pure sprung vertical velocity signal is obtained. The bounce rate based on the front and rear sprung vertical speed signals, the pitch rate obtained from the pure front and rear sprung vertical speed signals, and the control signal based on the roll rate obtained from the front and rear lateral acceleration signals The vehicle suspension system according to claim 1, wherein damping force characteristic control is performed.