JPH08230434A - Vehicle suspension device - Google Patents

Abstract

PURPOSE: To reduce the number of sensors so as to simplify a system by finding a spring upper vertical speed and a relative speed between a spring upper side and a spring lower side on the basis of a spring upper vertical acceleration in respective left and right front wheel positions and relative displacement between the spring upper side and the spring lower side in the rear wheel side center position. CONSTITUTION: A vehicle suspension device is provided with spring upper acceleration sensors d1, d2 for left and right front wheel sides detecting spring upper vertical accelerations in respective left and right front wheel positions in a vehicle body, and from the detection signals of these sensors d1, d2, a roll rate of a vehicle is computed (e). The suspension device is also provided with a relative displacement sensor (f) detecting relative displacement between a spring upper side and a spring lower side in the rear wheel side center position of the vehicle, and from the detection signal of this sensor (f), a spring upper vertical acceleration in the rear wheel side center position is detected (g). On the basis of the found spring upper vertical acceleration in the rear wheel side center position and the roll rate, spring upper vertical accelerations in respective left and right rear wheel positions are computed (h1), (h2), and from these computed results, a spring upper vertical speed and a relative speed between the spring upper side and the spring lower side are detected by means of respective detecting means (i), (j).

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 force characteristic 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, those described in Nos. 2-18 to 19 of Toyota Celsior new model manual are known.

This conventional vehicle suspension system uses a total of four vehicle height sensors for each wheel and three vertical acceleration sensors, two on the front wheel side and one on the rear wheel side. -When the unsprung relative speed is detected and the damping rate characteristic of the shock absorber at that time is set in the damping range where the sprung vertical speed and the bidirectional discriminant sign of the sprung-unsprung relative speed match. By controlling the hardware characteristics according to the speed, the damping force is increased to suppress the vibration of the vehicle body, and the damping force characteristics of the shock absorber are controlled to the soft characteristics in the vibration range where the bidirectional discrimination codes do not match. Thus, the damping force characteristic control is performed based on the Karnop control theory (skyhook control theory) of weakening the excitation force and suppressing the transmission of the unsprung input to the sprung portion.

[0004]

However, in the conventional device, as described above, a total of four sprung vertical acceleration sensors and a total of three sprung-unsprung relative velocity sensors are required for each wheel. Therefore, there is a problem that the system becomes complicated and the cost becomes high.

The present invention has been made in view of the above-mentioned conventional problems. In a system using a sprung vertical velocity signal and a sprung-unsprung relative velocity signal for damping force characteristic control, the number of sensors An object of the present invention is to provide a vehicle suspension device that can simplify the system and reduce the cost due to the reduction.

[0006]

In order to achieve the above-mentioned object, a vehicle suspension system according to claim 1 of the present invention is provided between a 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; A vehicle suspension system including damping force characteristic control means c for performing characteristic control, comprising left and right front wheel side sprung vertical acceleration sensors d ₁ and d ₂ for detecting sprung vertical accelerations at left and right front wheel positions of a vehicle body, Roll rate calculating means e for obtaining the roll rate of the vehicle from the sprung vertical acceleration signals of the left and right front wheel positions detected by the left and right front wheel side sprung vertical acceleration sensors d ₁ and d ₂ , and the rear wheel side center position of the vehicle. A relative displacement sensor f that detects a relative displacement between the sprung and unsprung portions, and a rear wheel side that obtains a sprung vertical acceleration at a rear wheel center position from a relative displacement signal between the sprung and unsprung portions detected by the relative displacement sensor f. Acceleration detecting means g,
Left and right rear wheel side sprung vertical acceleration calculation for obtaining sprung vertical acceleration at each of the left and right rear wheel positions from the sprung vertical acceleration at the rear wheel center position obtained by the rear wheel side acceleration detecting means g and the roll rate. The means h ₁ and h ₂ , the left and right front wheel side sprung vertical acceleration sensors d ₁ and d _2, and the left and right rear wheel side sprung vertical acceleration calculation means h ₁ and h ₂ on the sprung up and down of each wheel position. A sprung vertical velocity detecting means i and a relative velocity detecting means j for obtaining a sprung vertical velocity and a sprung-unsprung relative velocity at each wheel position from the acceleration signal;
It is a means equipped with.

In the vehicle suspension system according to the second aspect, the damping force characteristic changing means a of the shock absorber b has a soft region (SS) in which both the damping force characteristics on the extension stroke side and the damping force side are soft characteristics. Centering on the compression stroke side, while maintaining the soft characteristics on the compression stroke side, only the damping force characteristics on the extension stroke side can be variably controlled to the hard characteristics side.
And a compression side hard region (SH) capable of variably controlling only the damping force characteristic on the compression stroke side to the hard characteristic side while maintaining the soft characteristic on the extension stroke side, the damping force characteristic control means c When the direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means i is near 0, the shock absorber b is controlled to the soft region (SS), and when it is upward positive, the extension side hard region. The damping force characteristics on the extension stroke side on the (HS) side, and the damping force characteristics on the compression stroke side on the compression side hard area (SH) side when the pressure is downward negative, respectively. The means is configured to variably control the hardware characteristics according to the control signal obtained from the gain that is inversely variably set according to the relative speed between unsprung parts.

[0008]

In the vehicle suspension system according to the first aspect of the present invention, as described above, the left and right front wheel side sprung vertical acceleration sensors d ₁ , d.
_From the sprung vertical acceleration of each of the left and right front wheel positions of the vehicle body detected in ₂ and the relative sprung-unsprung displacement at the rear wheel side center position of the vehicle detected by the relative displacement sensor f, the sprung position at each wheel position is determined. The vertical speed and the relative speed between the sprung part and the unsprung part are obtained, which simplifies the system by reducing the number of sensors and reduces the cost.

Further, in the vehicle suspension system according to claim 2,
In the damping force characteristic control means e, when the direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting means i is near 0, the shock absorber b is controlled to the soft region (SS) and the upward direction. When it is positive, the damping force characteristic on the extension stroke side and when it is negative downward, the damping force characteristic on the compression stroke side is inversely proportional to the sprung vertical velocity and the sprung-unsprung relative velocity. While the variability is controlled to the hardware characteristic according to the control signal obtained from the gain variably set to, the damping force characteristic on the reverse stroke side is fixedly controlled to the soft characteristic. For this reason, in the damping region where the direction discrimination codes of the sprung vertical velocity and the sprung-unsprung relative velocity match, the damping force characteristic on the stroke side of the shock absorber b at that time should be variably controlled on the hardware characteristic side. By car In addition to increasing the vibration damping force of the vehicle, in the vibration region where the direction discrimination codes of the two do not match, the damping force characteristic on the stroke side of the shock absorber b at that time is softened to weaken the vehicle vibration force. Basically, switching control of the damping force characteristic is performed based on the skyhook control theory.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a structural explanatory view showing a vehicle suspension device of an embodiment of the present invention, in which four shock absorbers SA _FL , SA _FR , SA _RL , and SA _RR are inserted between a vehicle body and four wheels. , 4 in explaining shock absorbers
When referring collectively to one, and when describing these common configurations, they are simply denoted as SA. Also, the lower right code indicates the wheel position, _FL is the front wheel left, _FR is the front wheel right,
_RL indicates the left rear wheel, and _RR indicates the right rear wheel. ) Is provided. The front and rear shock absorbers SA _FL and SA _{FR on} the left and right of the front wheels are located near the front and rear wheels (hereinafter referred to as wheel positions). 1 _FL and 1 _FR are provided, and the relative displacement (xx ₀ ) between sprung and unsprung is detected on the vehicle body at the intermediate position between the left and right shock absorbers SA _RL and SA _RR on the rear wheel side. A stroke sensor 2 as a relative displacement sensor is provided, and each vertical G sensor 1 (1 _FL , 1 _FL ,
1 _FR ) and the signal from stroke sensor 2
A control unit 4 that outputs a drive control signal to the pulse motor 3 of each shock absorber SA is provided.

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, and the interface circuit 4a includes the vertical G sensors 1 _FL. , 1 _FR from the sprung vertical accelerations G _FL and G _FR signals, and the stroke sensor 2 from the sprung-sprung relative displacement (x−x ₀ ) signals.

As shown in FIGS. 14 and 15, the interface circuit 4a includes sprung vertical accelerations G _FL and G _FR signals at the front and rear left and right wheel positions and an intermediate position between the rear wheel side left and right shock absorbers. The sprung vertical speeds Δx _FL , Δx _FR , Δx _RL , Δx _RR and the sprung sprung of each wheel position from the relative sprung-unsprung relative displacement (x−x ₀ ) signal of −.
Unsprung relative speed (Δx-Δx ₀ ) _FL , (Δx-Δx
₀ ) _FR , (Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR , and low frequency processed signal Vp _{T, C} of the relative speed (Δx−Δx ₀ ) between the sprung and unsprung portions. A signal processing circuit is provided. The details of this signal processing circuit will be described later.

Next, FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 defining the cylinder 30 into an upper chamber A and a lower chamber B, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Defining the base 34 and the piston 31
A guide member 35 that guides the sliding of the piston rod 7 that is connected to the vehicle, a suspension spring 36 that is interposed between the outer cylinder 33 and the vehicle body, and a bumper bar 37.

Next, FIG. 5 is an enlarged cross-sectional view showing the portion of the piston 31. As shown in FIG. 5, the piston 31 has through holes 31a and 31b formed therein, and each through hole is formed. A compression side damping valve 20 and an expansion side damping valve 12 that open and close 31a and 31b respectively are provided. Further, a stud 38 penetrating the piston 31 is screwed and fixed to the bound stopper 41 screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31a and 31b. Communication for forming a flow path (an expansion-side second flow path E, an expansion-side third flow path F, a bypass flow path G, and a compression-side second flow path J described later) that connects the upper chamber A and the lower chamber B with each other. A hole 39 is formed and this communication hole 3
An adjuster 40 for changing the flow passage cross-sectional area of the flow passage is rotatably provided inside the passage 9. Also, the stud 38
The communication hole 3 is formed on the outer peripheral portion of the communication hole 3 depending on the direction of fluid flow.
An expansion-side check valve 17 and a pressure-side check valve 22 that allow and block the flow passage formed by 9 are provided. It should be noted that this adjuster 40 corresponds to the pulse motor 3
Is rotated via the control rod 70 (see FIG. 4). Also, the stud 38 has
A first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 are formed in this order from the top.

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

Therefore, a through hole 31 is provided between the upper chamber A and the lower chamber B as a flow passage through which a fluid can flow in the extension stroke.
The inside of the extension side damping valve 12 is opened through b and the lower chamber B
To the extension side first flow path D, the second port 13, the vertical groove 23,
Via the expansion side second flow path E, which opens the outer peripheral side of the expansion side damping valve 12 to the lower chamber B via the fourth port 14, the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension side check valve 17 is opened to reach the lower chamber B by way of the third side flow passage F extending to the lower chamber B and the third port 18, the second lateral hole 25, and the hollow portion 19. There are four channels, channel G. Further, as a flow path through which the fluid can flow in the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a is used.
Flow path H, hollow portion 19, first lateral hole 24, first port 21
Via the pressure side check valve 22 to the upper chamber A, and the bypass flow to the upper chamber A via the hollow portion 19, the second lateral hole 25, and the third port 18. Road G
There are three channels.

That is, the shock absorber SA is constructed so that the damping force characteristics 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.
Both the pressure side are soft (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, 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, in the control operation of the control unit 4, the sprung vertical acceleration G at each wheel position.
The configuration of the signal processing circuit for _obtaining (G _FL , G _FR , G _RL , G _RR ) will be described based on the block diagram of FIG.

[0020] First, A1 in (roll rate calculating means the claims), the left and right front wheel vertical G sensors 1 _FL, 1 sprung of the detected right and left front wheel position in _FR vertical acceleration G _FL, G _FR
From the signal, the roll rate GR of the vehicle is calculated based on the following equation (1).
Ask for. That is, the A1 constitutes the roll rate calculating means in the claims. GR = (G _FR -G _FL ) / 2 (1) On the other hand, in A2, as shown in the following equation (2), the relative displacement between the sprung part and the unsprung part (x-x ₀₎ ) To the sprung vertical displacement using the transfer function Ga _(S) , the relative displacement between the sprung and unsprung at the intermediate position between the rear wheel side left and right shock absorbers SA _RL and SA _RR detected by the stroke sensor 2 (x -X ₀ )
From this, the sprung vertical displacement x is obtained. Ga _(S) =-(cs + k) / ms ² (2) where m is the sprung mass, c is the damping coefficient of the suspension, and k is the spring constant of the suspension.

At A3, the sprung vertical displacement x signal at the intermediate position between the rear wheel side left and right shock absorbers SA _RL and SA _RR obtained at A2 is differentiated by the second order to obtain the sprung vertical acceleration at the same position. Convert to Gb _S.
That is, the A2 and the A3 constitute the rear wheel side acceleration detecting means in the claims.

At the subsequent A4, as shown in the following equation (3), the rear wheel side left and right shock absorbers SA obtained at A3 are obtained.
The sprung vertical acceleration G _RR at the right rear wheel position is obtained by adding the roll rate GR obtained in A1 to the sprung vertical acceleration Gb _S at the intermediate position between _RL and SA _RR . G _RR = Gb _S + GR (3) In the following A5, the rear wheel side left and right shock absorbers obtained in A3 are obtained as shown in the following expression (4). The sprung vertical acceleration G _RL at the left rear wheel position is obtained by subtracting the roll rate GR obtained in A1 from the sprung vertical acceleration Gb _{S at} the intermediate position between SA _RL and SA _RR . G _RL = Gb _S -GR (4) That is, the left and right rear wheel side sprung vertical acceleration calculating means of the claims is constituted by A4 and A5. There is.

Next, among the control operations of the control unit 4, the sprung vertical acceleration G at each wheel position.
From (G _FL , G _FR , G _RL , G _RR ), the sprung vertical velocity Δx at each wheel position and the sprung-unsprung relative velocity (Δ
x-Δx ₀ ) and the low-frequency processed signal Vp _{T, C} will be described with reference to the block diagram of FIG.

First, in B1, the phase delay compensation formula is used,
The sprung vertical acceleration G (G _FL , G _FR , G _RL , G _RR ) at each wheel position obtained by the signal processing circuit of FIG.
It is converted to a sprung vertical velocity signal at each wheel position. The general equation for phase delay compensation can be expressed by the following transfer function equation (5). G _(S) = (AS + 1) / (BS + 1) ... (5) (A <B) And the frequency band (0.5 Hz to 3) necessary for damping force characteristic control.
Has the same phase and gain characteristics as the case of integrating (1 / S) at (Hz), and as a phase delay compensation formula for lowering the gain on the low frequency side (up to 0.05 Hz), the following transfer function formula (6 ) Is used.

G _(S) = (0.001 S + 1) / (10S + 1) × γ (6) Note that γ is a signal and gain characteristic when the speed is converted by integration (1 / S). Is a gain for matching, and is set to γ = 10 in this embodiment. As a result,
The gain characteristic of the solid line in (a) of 6 and the gain characteristic of FIG.
As shown by the solid line phase characteristics in (b), only the gain on the low frequency side is reduced without deteriorating the phase characteristics in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. . In addition, the dotted lines of (a) and (b) in FIG.
The gain characteristic and the phase characteristic of the sprung vertical velocity signal whose velocity is converted by integration (1 / S) are shown.

At B2, a bandpass filter process for cutting off components other than the target frequency band to be controlled is performed. That is, this bandpass filter BPF is composed of a secondary high-pass filter HPF (0.3 Hz) and a secondary low-pass filter LPF (4 Hz), and has a sprung vertical velocity targeting the sprung resonance frequency band of the vehicle. Δx (Δx _FL ,
Δx _FR , Δx _RL , Δx _RR ) signals are obtained.

On the other hand, in B3, as shown in the following equation (7),
The vertical acceleration G (G _FL , G _FR , G _RL , G _{RR )} detected by each vertical G sensor 1 using the transfer function Gu _(S) from each sprung vertical acceleration to the relative speed between the sprung and unsprung _portions. ) Signal, the relative speed (Δx-
Δx ₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx ₀ ) _FR ,
(Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] signals are obtained. Gu _(S) = -ms / (cs + k) (7) where m is the sprung mass, c is the damping coefficient of the suspension, and k is the spring constant of the suspension. In the subsequent B4, as shown by the dotted line in FIG.
While detecting the absolute value of the peak value of the unsprung relative velocity (Δx−Δx ₀ ), the absolute value of the peak value is detected until the absolute value of the next peak value is detected, as shown by the solid line in FIG. The low-frequency processed signal Vp _{T, C} held during the above period is created.

That is, in this embodiment, B1 and B2 constitute a sprung vertical velocity detecting means at each wheel position in the claims, and B3 and B4 constitute a sprung-spring in the claims. The lower part relative speed detecting means is configured.

Next, of the damping force characteristic control operation of the shock absorber SA in the control unit 4, the contents of the basic control by the basic control unit will be described based on the flowchart of FIG. This basic control is performed for each shock absorber SA _FL , SA _FR , SA _RL , SA _RR .

In step 101, the sprung vertical velocity Δx
Is a positive value. If YES, the process proceeds to step 102 to control each shock absorber SA to the extension side hard region HS, and if NO, the process proceeds to step 103.

In step 103, the sprung vertical velocity Δx
Is a negative value, and if YES, the routine proceeds to step 104, where each shock absorber SA is controlled to the pressure side hard region SH, and if NO, the routine proceeds to step 105.

Step 105 is a processing step when it is judged NO in steps 101 and 103, that is, when the value of the sprung vertical velocity Δx is 0.
At this time, set each shock absorber SA to the soft area SS.
To control.

Next, the operation of damping force characteristic control will be described with reference to the time chart of FIG. When the sprung vertical velocity Δx based on the sprung vertical velocity Δx and the sprung-unsprung relative velocity (Δx−Δx ₀ ) changes as shown in this figure, as shown in the diagram, the sprung vertical velocity Δx is shown. When the value of is 0, the shock absorber SA is controlled in the soft region SS.

When the value of the sprung vertical velocity Δx becomes a positive value, the expansion side hard area HS is controlled to fix the compression side damping force characteristic to the soft characteristic, while the expansion side of the control signal is controlled. Damping force characteristic (Target damping force characteristic position P _T )
Is changed in proportion to the sprung vertical velocity Δx based on the following equation (8). P _T = α ・ Δx ・ Ku (8) where α is a constant on the extension side, and Ku is the relative speed between the sprung part and the unsprung part (Δx The gain is variably set according to the processed signal Vp _{T, C} of −Δx ₀ ). 20 shows the inverse proportional variable characteristic (Ku = a) of the gain Ku with respect to the processed signal Vp _{T, C.}
/ (Δx-Δx ₀₎₎ is a map showing the.

Further, when the value of the sprung vertical velocity Δx becomes a negative value, the compression side hard region SH is controlled to fix the extension side damping force characteristic to the soft characteristic, while the compression side damping force forming the control signal is controlled. Characteristic (target damping force characteristic position P _C )
It is changed in proportion to the sprung vertical velocity Δx based on the following equation (9). P _C = β · Δx · Ku (9) where β is a constant on the pressure side.

Next, of the damping force characteristic control operation of the control unit 4, mainly the switching operation state of the control area of the shock absorber SA will be described with reference to the time chart of FIG.

In the time chart of FIG. 19, area a
Is a state in which the sprung vertical velocity Δx based on the sprung vertical velocity Δx and the sprung-unsprung relative velocity (Δx−Δx ₀ ) is reversed from a negative value (downward) to a positive value (upward). At this time, the relative speed (Δx−Δx ₀ ) is still a negative value (the stroke of the shock absorber SA is on the pressure stroke side). Therefore, at this time, based on the direction of the sprung vertical velocity Δx. The shock absorber SA is controlled in the extension side hard region HS, and therefore, in this region, the pressure stroke side which is the stroke of the shock absorber SA at that time has a soft characteristic.

In the region b, the sprung vertical velocity Δx remains a positive value (upward), and the sprung-unsprung relative velocity (Δx-Δx ₀ ) changes from a negative value to a positive value (shock absorber). Since the stroke of SA is the area switched to the extension side), at this time, the shock absorber SA is controlled to the extension side hard area HS based on the direction of the sprung vertical velocity Δx, and the shock absorber SA is also controlled. Is also an extension stroke, and therefore, in this region, the extension side which is the stroke of the shock absorber SA at that time has a hard characteristic proportional to the value of the sprung vertical velocity Δx.

In the region c, the sprung vertical velocity Δx is reversed from a positive value (upward) to a negative value (downward), but at this time, the sprung-unsprung relative velocity (Δx) is still.
-Δx ₀ ) is a positive value area (the stroke of the shock absorber SA is the extension stroke side), and at this time, the shock absorber SA is in the compression side hard area SH based on the direction of the sprung vertical velocity Δx. Is controlled by
In this region, the extension side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the area d, the sprung vertical velocity Δx remains a negative value (downward), and the sprung-unsprung relative velocity (Δx-Δx ₀ ) changes from a positive value to a negative value (shock absorber). Since the stroke of 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 sprung vertical velocity Δx, and the stroke of the shock absorber is also It is a pressure stroke,
Therefore, in this area, the shock absorber SA at that time
The pressure stroke side, which is the stroke of, has a hard characteristic proportional to the value of the sprung vertical velocity Δx.

As described above, in this embodiment, the sprung vertical speed Δx and the sprung-unsprung relative speed (Δx-Δx
₀ ) has the same sign (area b, area d), the stroke side of the shock absorber SA at that time is controlled to the hardware characteristic,
When the signs are different (area a, area c), the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic.
The same control as the damping force characteristic control based on the skyhook control theory is performed based only on the sprung vertical velocity Δx signal. And further, in this embodiment,
At the time when the stroke of the shock absorber SA is switched, that is, when shifting from the area a to the area b and from the area c to the area d (soft characteristic to hard characteristic), the damping force characteristic position on the stroke side to be changed is the previous area. Since the switching to the hardware characteristic side has already been performed in a and c, the switching from the soft characteristic to the hardware characteristic can be performed without a time delay, and thus high control response can be obtained and the hardware characteristic can be changed. Switching to the soft characteristic is performed without driving the pulse motor 3,
As a result, the durability of the pulse motor 3 is improved and the power consumption is saved.

When the vehicle is being braked, the vehicle body leans due to the so-called dive phenomenon of the vehicle body, in which the front wheel side sinks and the rear wheel side floats up. Force component up and down G sensor 1
Is detected as a downward (negative) sprung vertical acceleration component,
This continuously input low-frequency downward sprung acceleration component causes the signal to drift.

The above is true when the vehicle is accelerating, when the vehicle travels on a long uphill, or when it travels on a long downhill (in this case, the upward sprung vertical acceleration component is detected. ) Also occurs when a low-frequency DC component is input to the signals of the upper and lower G sensors 1.

However, in this embodiment, as the speed conversion means for converting each sprung vertical acceleration G detected by each vertical G sensor 1 into a sprung vertical speed signal at each wheel position,
By using the phase delay compensation formula, the sprung vertical velocity signal with only the low frequency gain reduced can be obtained without deteriorating the phase characteristic in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. To be

Therefore, even in a situation where an extra low frequency component is added to the signal of the vertical G sensor 1, such as during braking, the lowering of the low frequency gain affects the damping force characteristic control. It can be lost.

As described above, the vehicle suspension system of this embodiment has the following effects. From the signals obtained from the two vertical G sensors 1 _RL and 1 _FR and one stroke sensor 2, the sprung vertical speed Δx and the sprung-unsprung relative speed (Δ
x-Δx ₀ ), which gives
By reducing the number of sensors, the system can be simplified and the cost can be reduced.

As a means for converting the sprung vertical acceleration G into the sprung vertical velocity Δx, by using the phase delay compensation formula, a signal drift based on an extra low frequency signal input, such as during braking, is eliminated. Prevent and by this
It becomes possible to prevent the controllability of the damping force characteristic of the shock absorber SA from deteriorating and ensure the riding comfort of the vehicle.

In the damping force characteristic control based on the skyhook theory, switching from the soft characteristic to the hard characteristic is performed without a time delay, and thus, a high control responsiveness is obtained, and at the same time, from the hard characteristic to the soft characteristic. Switching is performed without driving the actuator, which makes it possible to improve the durability of the pulse motor 3 and save power consumption.

Since the gain Ku is variably controlled by the processed signal Vp _{T, C obtained} by transforming the sprung-unsprung relative velocity signal obtained at a high frequency into a low frequency state, the fluctuation of the gain Ku is changed to a low frequency state. As a result, even if the responsiveness of the pulse motor 3 is not so high, the switching of the damping force characteristic can be made to follow the change of the control signal, so that the controllability can be improved without increasing the cost. become.

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 soft region SS is controlled only when the sprung vertical velocity signal is 0.
Control hunting can be prevented by providing a predetermined dead zone centered at 0 and maintaining the damping force characteristic in the soft region SS while the sprung vertical velocity is changing within the dead zone.

[0051]

As described above, the present invention claims 1.
In the vehicle suspension device described above, as described above, the left and right front wheel side sprung vertical acceleration sensors that detect sprung vertical accelerations at the left and right front wheel positions of the vehicle body, and the left and right front wheel side sprung vertical acceleration sensors that are detected by the left and right front wheel side sprung vertical acceleration sensors. Roll rate calculating means for obtaining the roll rate of the vehicle from the sprung vertical acceleration signals at the respective front wheel positions, a relative displacement sensor for detecting relative sprung-unsprung displacement at the rear wheel side center position of the vehicle, and the relative displacement sensor. Of the rear-wheel-side acceleration detecting means for obtaining the sprung vertical acceleration at the rear-wheel-side center position from the unsprung-unsprung relative displacement signal detected by, and the rear-wheel-side center position obtained by the rear-wheel-side acceleration detecting means. Left and right rear wheel side sprung vertical acceleration calculating means for obtaining sprung vertical acceleration at left and right rear wheel positions from the sprung vertical acceleration and the roll rate, and the left and right front wheel side sprung vertical accelerations A sprung vertical velocity for obtaining a sprung vertical velocity and a sprung-unsprung relative velocity at each wheel position from a sprung vertical acceleration signal at each wheel position obtained by the sensor and the left and right rear wheel side sprung vertical acceleration calculation means. Since the detection means and the relative speed detection means are provided, the sprung vertical velocity signal and the sprung-
In a system using the unsprung relative velocity signal, the number of sensors can be reduced, which has the effect of simplifying the system and reducing the cost.

Further, in the vehicle source device according to claim 2,
The damping force characteristic changing means is a soft region (SS) in which the damping force characteristics on the extension stroke side and the compression stroke side are both soft characteristics.
Centering on the compression stroke side, while maintaining the soft characteristics on the compression stroke side, only the damping force characteristics on the extension stroke side can be variably controlled to the hard characteristics side, and the extension side hard area (HS) is maintained on the soft characteristics on the extension stroke side. The damping force characteristic control means is provided with a compression side hard area (SH) capable of variably controlling only the damping force characteristic on the compression stroke side to the hardware characteristic side, and the damping force characteristic control means detects the sprung vertical speed detected by the sprung vertical speed detecting means. Signal direction identification code is 0
If it is in the vicinity, set the shock absorber to the soft area (S
S), and when the upward positive is the extension side hard region (HS) side, the extension side damping force characteristics, and when the downward negative, the compression side hard region (SH) side is the pressure stroke side. The damping force characteristics of each are variably controlled to the hardware characteristics according to the control signal obtained from the sprung vertical speed at that time and the gain variably set in inverse proportion to the sprung-sprung relative speed. Is configured as
It becomes possible to perform damping force characteristic control based on the skyhook theory.

[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 -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 for obtaining a sprung vertical acceleration in the embodiment apparatus.

FIG. 15 is a block diagram showing a signal processing circuit for obtaining the sprung vertical velocity and the sprung-unsprung relative velocity in the apparatus of the embodiment.

FIG. 16 is a gain characteristic (a) and a phase characteristic of the sprung vertical velocity signal obtained by the signal processing circuit in the embodiment apparatus.
It is a figure which shows (b).

FIG. 17 is a time chart showing a generation state of a processed signal in the apparatus of the embodiment.

FIG. 18 is a flowchart showing the details of the damping force characteristic control operation of the control unit in the embodiment apparatus.

FIG. 19 is a time chart showing the details of the damping force characteristic control operation of the control unit in the embodiment apparatus.

FIG. 20 is a map showing a variable characteristic of a gain with respect to a processing signal of a relative speed between unsprung and unsprung portions in the apparatus of the embodiment.

[Explanation of symbols]

a damping force characteristic changing means b shock absorber c damping force characteristic control means d ₁ left front wheel sprung vertical acceleration sensor d ₂ right front wheel sprung vertical acceleration sensor e roll rate calculation means f relative displacement sensor g rear wheel side acceleration detection means h ₁ Left rear wheel sprung vertical acceleration calculation means h ₂ Right rear wheel sprung vertical acceleration calculation means i Spring sprung vertical speed detection means j Relative speed detection means

Claims (2)

[Claims] 1. A shock absorber which is interposed between a vehicle body side and each wheel side and whose damping force characteristic changing means can change the damping force characteristic, and a sprung vertical velocity and a sprung-unsprung portion at each wheel position. A vehicle suspension system comprising damping force characteristic control means for performing damping force characteristic control of each of the shock absorbers based on relative speed, wherein left and right front wheel side springs for detecting vertical sprung acceleration at left and right front wheel positions of a vehicle body A vertical acceleration sensor, roll rate calculation means for obtaining a vehicle roll rate from the sprung vertical acceleration signals of the left and right front wheel positions detected by the left and right front wheel sprung vertical acceleration sensors, and a spring at the rear wheel center position of the vehicle. A relative displacement sensor for detecting relative displacement between the upper and lower unsprung parts, and a sprung sprung at the rear wheel side center position based on the relative displacement signal between the sprung and unsprung parts detected by the relative displacement sensor. The sprung vertical acceleration at each of the left and right rear wheel positions is calculated from the rear wheel side acceleration detecting means for obtaining the acceleration, and the sprung vertical acceleration at the rear wheel side center position obtained by the rear wheel side acceleration detecting means and the roll rate. Each wheel is determined from the sprung vertical acceleration signals of the respective wheel positions obtained by the left / right rear wheel side sprung vertical acceleration calculating means, the left / right front wheel side sprung vertical acceleration sensors, and the left / right rear wheel side sprung vertical acceleration calculation means. A sprung vertical velocity detecting means and a relative velocity detecting means for determining a sprung vertical velocity of a position and a relative velocity between sprung and unsprung portions. 2. The damping force characteristic changing means of the shock absorber is centered on a soft region (SS) where both the damping force characteristics on the extension stroke side and the compression stroke side are soft characteristics, and the compression stroke side is held to the soft characteristic. The extension side hard area (HS) where only the extension stroke side damping force characteristic can be variably controlled to the hardware characteristic side and the extension stroke side is held to the soft characteristic while only the compression stroke side damping force characteristic is hardened. The characteristic side includes a pressure side hard area (SH) capable of variably control, and the damping force characteristic control unit has a direction discrimination code of the sprung vertical velocity signal detected by the sprung vertical velocity detecting unit.
If it is in the vicinity, set the shock absorber to the soft area (S
S), and when the upward positive is the extension side hard region (HS) side, the extension side damping force characteristics, and when the downward negative, the compression side hard region (SH) side is the pressure stroke side. The damping force characteristics of each are variably controlled to the hardware characteristics according to the control signal obtained from the sprung vertical speed at that time and the gain variably set in inverse proportion to the sprung-sprung relative speed. The vehicle suspension system according to claim 1, wherein the vehicle suspension system is configured as follows.