JP3354737B2 - Vehicle suspension system - Google Patents

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.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling the damping force characteristic of a shock absorber, for example, those described in the Toyota Celsior New Car Manual, Nos. 2-18 to 19 are known.

This conventional vehicle suspension system uses a total of four vehicle height sensors for each wheel and a total of three vertical acceleration sensors, two front wheels and one rear wheel, to determine the sprung vertical speed and spring speed at each wheel position. The upper and lower unsprung relative speeds are detected, and in the case of a vibration damping region where both the sprung vertical speed and the sprung and unsprung relative speed discriminating sign match, the damping force characteristic of the shock absorber is adjusted to the sprung at that time. By controlling the hardware characteristics according to the vertical speed, the vibration damping force is increased and the vibration of the vehicle body is suppressed,
In a vibration region where the two-way discrimination code does not match, the carnop control controls the damping force characteristics of the shock absorber to soft characteristics to weaken the vibration force and suppress the transmission of unsprung input to the sprung mass. Damping force characteristic control based on the theory (skyhook control theory) is performed.

[0004]

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

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. In a system using a control signal obtained from a vertical state amount of each wheel position for damping force characteristic control, the number of sensors is reduced. It is an object of the present invention to provide a vehicle suspension device capable of simplifying a system and reducing costs.

[0006]

In order to achieve the above object, a vehicle suspension system according to the first aspect of the present invention, 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 damping force characteristic control of each of the shock absorbers b based on at least a control signal obtained from a vertical state amount of each wheel position. A damping force characteristic control means c for performing
Left and right front wheel side vertical state amount detecting means d ₁ and d ₂ for detecting the vertical state amount of the vehicle body at each of the left and right front wheel positions, and left and right front wheel side vertical state amount detecting means d ₁ and d _2. left and right front wheel side bounce rate computing means e for obtaining the vehicle bounce rate on the front wheel side center position from the average value of the vertical state amount of the vehicle body of the front wheel position, the left and right front wheel vertical state quantity detecting means d _1, d A roll rate calculating means f for calculating a roll rate from a difference in the vertical state amount of the vehicle body at each of the left and right front wheel positions detected in step ₂ , and a vehicle for detecting the vehicle speed
A speed sensor, a bounce rate on the front wheel side of the vehicle obtained by the front wheel side bounce rate calculating means e, and a vehicle speed sensor.
From the front wheel position, which varies according to the vehicle speed detected by the
Based on the transfer function using the road surface input to the position as the transfer path.
There are a wheel side bounce rate computing means g After obtaining the vehicle bounce rate in the rear wheel side central positions, the rear wheel side bounce rate computing means the vehicle rear wheel bounce rate determined by g and the roll rate calculating means and left and right rear wheel side vertical state amount calculating means h ₁ and h _{2 for} obtaining the vertical state amount of the vehicle body at each of the left and right rear wheel positions from addition and subtraction with the roll rate obtained in f.

Further, in the vehicle suspension device according to the present invention, the left and right front wheel side vertical sprung amount detecting means d ₁ and d ₂ detect a sprung vertical acceleration as a vertical state amount. The means comprises acceleration sensors i ₁ and i ₂ .

Further, in the vehicle suspension system according to the third aspect, the left and right front wheel side vertical state amount detecting means d ₁ and d ₂ detect a relative displacement between a sprung and unsprung state as a vertical state amount. The means is constituted by the side relative displacement sensors j ₁ and j ₂ .

According to a fourth aspect of the present invention, there is provided the vehicle suspension device according to the second aspect, wherein the left and right front wheel side sprung vertical acceleration sensors i ₁ and i ₂ are detected and the left and right rear wheel side vertical direction state amount calculating means. h _1, h comprises a sprung mass vertical velocity detection means k _1, k ₂ to obtain the sprung mass vertical velocity of each wheel position from the sprung vertical acceleration of each wheel position obtained by _2, the damping force characteristics of the shock absorber b The changing means a is centered on the soft region (SS) in which both the damping force characteristics on the extension stroke side and the compression stroke side are soft characteristics, and only the damping force characteristic on the extension stroke side is maintained while the compression stroke side is kept in the soft characteristic. The expansion-side hardware area (HS) that can variably control the hardware characteristic side,
The extension stroke side includes a compression-side hard region (SH) capable of variably controlling only the compression-stroke-side damping force characteristic to the hard characteristic side while maintaining the soft characteristic, and the damping-force characteristic control means c.
However, when the direction discrimination code of the sprung vertical speed signal detected by the sprung vertical speed detecting means k ₁ or k ₂ is near 0, the shock absorber b is controlled to the soft region (SS), and the upward direction is positive. In some cases, the damping force characteristic on the extension stroke side is shown on the extension side hard region (HS) side, and when it is negative downward, the damping force characteristic on the compression stroke side is shown on the compression side hard region (SH) side. The means is configured to variably control hardware characteristics according to a control signal based on the vertical speed.

[0010]

In the vehicle suspension system according to the first aspect of the present invention, as described above, the left and right front wheel side vertical state amount detecting means d ₁ , d
_From the bounce rate on the front wheel side of the vehicle obtained from the amount of vertical state of each of the left and right front wheel positions of the vehicle body detected in ₂ , the vehicle speed
Road input from front wheel position to rear wheel position that changes according to
The bounce rates of the left and right rear wheel positions of the vehicle body are obtained based on a transfer function having a transmission path , thereby simplifying the system by reducing the number of sensors and reducing costs. .

Further, in the vehicle suspension device according to the fourth aspect,
When the direction discriminating code of the sprung vertical speed signal at each wheel position detected by the sprung vertical speed detecting means k ₁ and k ₂ in the damping force characteristic control means c is near 0, the shock absorber b is in the soft region. The control signal is controlled based on the sprung up / down speed at that time. When the value is upward positive, the damping force characteristic on the extension stroke side is used, and when the value is negative downward, the damping force characteristic on the compression stroke side is used. The damping force characteristic on the reverse stroke side is fixedly controlled to the soft characteristic, respectively, so that the sprung vertical speed and the sprung-unsprung In the damping region where the direction discriminating sign of the relative speed between the two coincides, the damping force characteristic on the stroke side of the shock absorber b at that time is variably controlled on the hardware characteristic side, thereby increasing the damping force of the vehicle and increasing the damping force in both directions. The discrimination code is Basic vibration damping force characteristics based on the skyhook control theory, in which the vibration range of the shock absorber b at that time is reduced to a soft characteristic in the vibration region where the vibrations coincide, thereby weakening the vehicle vibration force. Switching control is performed.

[0012]

An embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 is an explanatory view showing the structure of a vehicle suspension system according to a first embodiment of the present invention, in which four shock absorbers SA _FL and S _FL are interposed between a vehicle body and four wheels.
A _FR , SA _RL , SA _RR (Note that in describing the shock absorber, when these four are collectively referred to, and when describing their common configuration, they are simply indicated as SA. Indicates the wheel position.
_FL indicates front wheel left, _FR indicates front wheel right, _RL indicates rear wheel left, and _RR indicates rear wheel right. ) Is provided. A vehicle body at a position near each of the left and right front shock absorbers SA _FL and SA _FR (hereinafter referred to as each wheel position) has a left and right front wheel side sprung vertical acceleration sensor (hereinafter, referred to as a sprung vertical acceleration sensor G) that detects a vertical acceleration G on a spring. 1 _FL and 1 _FR are provided, and although not shown, a vehicle speed sensor 2 for detecting the vehicle speed of the vehicle is provided. Further, each of the upper and lower G sensors 1 A control unit 4 for outputting a drive control signal to the pulse motor 3 of each shock absorber SA based on (1 _FL , 1 _FR ) and a signal from the vehicle speed sensor 2 is provided.

FIG. 3 is a system block diagram showing the above configuration. The control unit 4 includes an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the upper and lower G sensors 1 _FL are provided in the interface circuit 4a. , sprung mass vertical accelerations G _FL from 1 _FR, G _FR signal, and the signal from the vehicle speed sensor 2 are inputted.

As shown in FIGS. 14 and 15, the interface circuit 4a calculates the sprung vertical acceleration G _FL and G _FR signals of the front left and right wheel positions and the rear wheel left and right wheels based on the vehicle speed signal. The sprung vertical accelerations G _RL , G _{RR of the} position, the sprung vertical speeds Δx _FL , Δx _FR , Δx _RL , Δx _{RR of} each wheel position and the sprung-unsprung relative velocity (Δx−Δx ₀₎ ) _FL , (Δx−Δx ₀ ) _FR ,
A signal processing circuit for obtaining (Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR , and a low frequency processing signal Vp _{T, C} of the sprung-unsprung relative speed (Δx−Δx ₀ ) is provided. Is provided. The details of this signal processing circuit will be described later.

FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A is a cylinder 30, a piston 31 that defines the cylinder 30 in an upper chamber A and a lower chamber B, an outer cylinder 33 in which a reservoir chamber 32 is formed on the outer periphery of the cylinder 30, a lower chamber B and a reservoir chamber 32. Base 34 and piston 31
A guide member 35 for guiding the sliding of the piston rod 7 connected to the outer cylinder 33, a suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and a bump rubber 37.

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 A compression-side damping valve 20 and an extension-side damping valve 12 for opening and closing 31a and 31b, respectively, are provided. A stud 38 that penetrates the piston 31 is screwed and fixed to a 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 flow paths (extension-side second flow paths E, expansion-side third flow paths F, bypass flow paths G, and compression-side second flow paths J to be described later) that communicate the upper chamber A and the lower chamber B. A hole 39 is formed.
An adjuster 40 for changing the flow path cross-sectional area of the flow path is rotatably provided in 9. Also, stud 38
The communication hole 3 is formed on the outer periphery of the communication hole 3 in accordance with the direction of fluid flow.
An expansion-side check valve 17 and a compression-side check valve 22 that allow and shut off the flow on the flow path side formed by 9 are provided. Note that the adjuster 40 is provided with the pulse motor 3.
Is rotated through the control rod 70 (see FIG. 4). Also, studs 38
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, the adjuster 40 has a hollow portion 19, a first horizontal hole 24 and a second horizontal hole 25 communicating between the inside and the outside, and a vertical groove 23 formed in the outer peripheral portion. I have.

Therefore, between the upper chamber A and the lower chamber B, a through-hole 31 is formed as a flow path through which fluid can flow during the extension stroke.
b, the inside of the extension side damping valve 12 is opened to open the lower chamber B
, The second port 13, the vertical groove 23,
Via the second port 13, the vertical groove 23, and the fifth port 16 via the fourth port 14, the outer peripheral side of the extension side damping valve 12 is opened to open the outer peripheral side of the extension side damping valve 12 to reach the lower chamber B, Then, the extension side check valve 17 is opened to open the extension side third flow path F to the lower chamber B, and the bypass to the lower chamber B via the third port 18, the second horizontal hole 25, and the hollow portion 19. There are four flow paths G. In addition, as a flow path through which a fluid can flow during the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a.
Channel H, hollow portion 19, first lateral hole 24, first port 21
, The pressure-side second flow path J that opens the pressure-side check valve 22 to reach the upper chamber A through the air passage, and the bypass flow that reaches the upper chamber A through the hollow portion 19, the second horizontal hole 25, and the third port 18. Road G
And three flow paths.

That is, the shock absorber SA is configured such that the damping force characteristic can be changed in multiple steps by rotating the adjuster 40 with the characteristics shown in FIG. 6 on both the extension side and the compression side. That is, as shown in FIG.
The state in which both pressure sides are soft (hereinafter, soft area SS
When the adjuster 40 is rotated counterclockwise from
When the damping force characteristic can be changed in multiple stages only on the extension side and the compression side is 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, Only the compression side has a structure in which the damping force characteristic can be changed in multiple stages, and the extension side is a region fixed to the low damping force characteristic (hereinafter referred to as a compression side hard region SH).

FIG. 7 shows the KK section, LL section, MM section, and NN section in FIG. 8, 9 and 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 is calculated.
The configuration of a signal processing circuit for _obtaining (G _FL , G _FR , G _RL , G _RR ) will be described with reference to the block diagram of FIG.

First, in A1, the vehicle sprung vertical acceleration G _FL and G _FR signals at the left and right front wheel positions detected by the left and right front wheel side vertical G sensors 1 _FL and 1 _FR are detected based on the following equation (1). Request bounce rate GB _F in the front wheel center position. That is, this A1 constitutes the front-wheel-side bounce rate calculating means in the claims.

GB _F = (G _FR + G _FL ) / 2 (1) In the following A2, the road surface represented by the following equation (2) is obtained from the bounce rate GB _{F at} the front wheel side center position of the vehicle. based on the transfer function G _B to the rear wheel position _(S) input from the front wheel position of the transmission path, the bounce rate GB _R in wheel side center position after the vehicle
Ask for. That is, the A2 constitutes a rear-wheel-side bounce rate calculating means described in the claims.

G _{B (S)} = G _{1 (S)} G _{2 (S)} G _{3 (S)} (2) G _{1 (S)} is a front wheel side spring Transfer function from the top to the road,
G _{2 (S)} is a transfer function from the rear wheel side road surface to the rear wheel side sprung mass,
G3 _(S) is a delay transfer function of the input time difference between the front and rear of the vehicle. The delay transfer function G _{3 (S)} is given by the following equation:
As shown in (3), the vehicle wheel base W _B and the vehicle speed S
Determined by _V.

G _{3 (S)} = e ^{−s (WB / Sv)} (3) On the other hand, in A 3, detection is performed by the left and right front wheel side vertical G sensors 1 _FL and 1 _FR . Sprung vertical accelerations G _FL , G at each of the left and right front wheel positions
_{From the FR} signal, the roll rate G of the vehicle is calculated based on the following equation (4).
Find R. That is, the roll rate calculating means in the claims is constituted by A3.

GR = (G _FR -G _FL ) / 2 (4) Next, at A4, as shown in the following equation (5), bounce rate GB _R in wheel center position, by adding the roll rate GR obtained in the A3, obtains the sprung mass vertical acceleration G _RR at the right rear wheel position. G _RR = GB _R + GR (5) In A5, as shown in the following equation (6), the center of the rear wheel of the vehicle obtained in A2 is obtained. from bounce rate GB _R at position by subtracting the roll rate GR obtained in the A3, obtains the sprung mass vertical acceleration G _RL on the left rear wheel position.

G _RR = GB _R −GR (6) That is, A4 and A5 are used to calculate the left and right rear wheel side vertical state amount calculating means in the claims. It is composed.

Next, in the control operation of the control unit 4, the sprung vertical acceleration G at each wheel position is calculated.
From (G _FL , G _FR , G _RL , G _RR ), the sprung vertical velocity Δx and the sprung-unsprung relative velocity (Δ
x-Δx ₀ ) and the configuration of a signal processing circuit for obtaining the low-frequency processing signal Vp _{T, C} will be described with reference to the block diagram of FIG.

First, in B1, a 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.
The signal is converted into a sprung vertical speed signal at each wheel position. The general expression of the phase delay compensation can be expressed by the following transfer function expression (7). G _(S) = (AS + 1) / (BS + 1) (7) (A <B) Then, the frequency band (0.5 Hz to 3
Hz), has the same phase and gain characteristics as the case of integration (1 / S), and as a phase lag compensation equation for lowering the gain on the low frequency side (up to 0.05 Hz), the following transfer function equation (8 ) Is used.

G _(S) = (0.001 S + 1) / (10S + 1) × γ (8) where γ is a signal and gain characteristic when speed conversion is performed by integration (1 / S). , And is set to γ = 10 in this embodiment. As a result, FIG.
The gain characteristic of the solid line in FIG.
As shown by the solid line phase characteristics in (b), only the low-frequency gain is reduced without deteriorating the phase characteristics in the frequency band (0.5 Hz to 3 Hz) necessary for damping force characteristic control. . The dotted lines in (a) and (b) of FIG.
9 shows gain characteristics and phase characteristics of a sprung vertical speed signal whose speed is converted by integration (1 / S).

In B2, a band-pass filter process for cutting off components other than the target frequency band to be controlled is performed. That is, the band-pass filter BPF is composed of a second-order high-pass filter HPF (0.3 Hz) and a second-order low-pass filter LPF (4 Hz), and has a sprung vertical velocity that targets a 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 (9),
Using the transfer function Gu _(S) from each sprung vertical acceleration to the sprung-unsprung relative velocity, the vertical acceleration G (G _FL , G _FR , G _RL , G _{RR )} detected by each vertical G sensor 1. ) Signal, the sprung-unsprung relative speed (Δx−
Δx ₀ ) [(Δx−Δx ₀ ) _FL , (Δx−Δx ₀ ) _FR ,
(Δx−Δx ₀ ) _RL , (Δx−Δx ₀ ) _RR ] signal is obtained. Gu _(S) = − ms / (cs + k) (9) where m is a sprung mass, c is a damping coefficient of the suspension, and k is a spring constant of the suspension. In the subsequent B4, as shown by the dotted line in FIG.
The absolute value of the peak value of the unsprung relative velocity (Δx−Δx ₀ ) is detected, and the absolute value of the peak value is changed until the absolute value of the next peak value is detected, as shown by the solid line in FIG. During this period, the held low-frequency processing signal Vp _{T, C} is created. That is, in this embodiment, B1 and B2 constitute a sprung vertical speed detecting means for each wheel position in the claims.

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 with reference to the flowchart of FIG. The basic control is performed for each of the shock absorbers SA _FL , SA _FR , SA _RL , and SA _RR .

In step 101, the sprung vertical speed Δx
Is determined to be a positive value. If YES, the flow proceeds to step 102 to control each shock absorber SA to the extension-side hard region HS. If NO, the flow proceeds to step 103.

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

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

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

When the value of the sprung vertical velocity Δx becomes a positive value, control is performed in the expansion-side hard region HS to fix the compression-side damping force characteristic to the soft characteristic, and on the other hand, to increase the compression-side damping force characteristic. Damping force characteristics (Target damping force characteristic position _PT )
Is changed in proportion to the sprung vertical speed Δx based on the following equation (10). P _T = α · Δx · Ku (10) where α is the extension-side constant, and Ku is the relative speed between the sprung and unsprung (Δx −Δx ₀ ) is a gain that is variably set according to the processing signal Vp _{T, C.} FIG. 20 shows an inverse proportional variable characteristic (Ku = a) of the gain Ku with respect to the processing signal VpT _{, C.}
/ (Δx−Δx ₀ )).

When the value of the sprung vertical velocity Δx becomes a negative value, the compression-side hard region SH is controlled to fix the expansion-side damping force characteristic to the soft characteristic while the compression-side damping force constituting the control signal is controlled. Characteristics (target damping force characteristic position P _C )
Based on the following equation (11), the value is changed in proportion to the sprung vertical speed Δx. P _C = β · Δx · Ku (11) where β is a pressure-side constant.

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

In the time chart of FIG.
Is a state in which the sprung vertical speed Δx based on the sprung vertical speed Δx and the sprung-unsprung relative speed (Δx−Δx ₀ ) is reversed from a negative value (downward) to a positive value (upward). At this time, since the relative speed (Δx−Δx ₀ ) is still a negative value (the stroke of the shock absorber SA is on the pressure stroke side), at this time, the relative speed (Δx−Δx ₀ ) is determined based on the direction of the sprung vertical speed Δx. The shock absorber SA is controlled in the extension-side hard region HS. 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 region b, the sprung vertical speed Δx remains a positive value (upward), and the sprung-unsprung relative speed (Δx−Δx ₀ ) changes from a negative value to a positive value (shock absorber). In this case, the shock absorber SA is controlled to the extension-side hard region HS based on the direction of the sprung vertical speed Δx, and the shock absorber is switched to the extension-side hard region HS. Is also an extension stroke. Therefore, in this region, the extension stroke which is the stroke of the shock absorber SA at that time has a hardware characteristic proportional to the value of the sprung vertical speed Δx.

Region c is a state in which the sprung vertical speed Δx is reversed from a positive value (upward) to a negative value (downward). At this time, the sprung-unsprung relative speed (Δx
−Δx ₀ ) is a region having a positive value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA sets the compression-side hard region SH based on the direction of the sprung vertical speed Δx. , And therefore
In this region, the extension stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the area d, the sprung vertical speed Δx remains a negative value (downward), and the sprung-unsprung relative speed (Δx−Δx ₀ ) changes from a positive value to a negative value (shock absorber). 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 increased. Pressure stroke,
Therefore, in this area, the shock absorber SA at that time is
The pressure stroke side, which is the stroke of the above, has hardware characteristics proportional to the value of the sprung vertical speed Δx.

As described above, in this embodiment, the sprung vertical speed Δx and the sprung-unsprung relative speed (Δx−Δx
₀ ) and the same sign (area b, area d), the stroke side of the shock absorber SA at that time is controlled to hard characteristics,
At the time of the different sign (area a, area c), the stroke side of the shock absorber SA at that time is controlled to 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 speed Δx signal. And furthermore, in this embodiment,
When the stroke of the shock absorber SA switches, that is, when shifting from the area a to the area b and from the area c to the area d (from the soft characteristic to the hard characteristic), the damping force characteristic position on the switching stroke side is the previous area. Since the switching to the hardware characteristics has already been performed at a and c, the switching from the soft characteristics to the hardware characteristics is performed without a time delay. As a result, a high control response can be obtained and the hardware characteristics can be reduced. 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 power consumption is reduced.

When the vehicle is being braked, the vehicle body is tilted by the so-called dive phenomenon of the vehicle body, in which the front wheel side sinks and the rear wheel side floats, and the vehicle body speed is reduced in this lean state, so that the deceleration is reduced. The upper and lower G sensor 1
Is detected as a downward (negative) sprung vertical acceleration component,
The continuously input low-frequency downward sprung acceleration component causes the signal to drift.

The above is when the vehicle is suddenly accelerated to cause a scut phenomenon or when the vehicle accelerates on a long uphill (in this case, the upward sprung vertical acceleration component is detected). Alternatively, it occurs when accelerating on a long downhill, and also occurs when a low-frequency DC component is input to the signal of the vertical G sensor 1.

However, in this embodiment, as a speed conversion means for converting each sprung vertical acceleration G detected by each vertical G sensor 1 into a sprung vertical speed signal of each wheel position,
By using the phase lag compensation formula, it is possible to obtain a sprung vertical velocity signal in which only the low-frequency gain is reduced without deteriorating the phase characteristics in the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control. Can be

Therefore, even in a situation where an extra low frequency component is added to the signal of the upper and lower G sensors 1 such as during braking, the influence on the damping force characteristic control is reduced by lowering the low frequency side gain. Can be eliminated.

As described above, the vehicle suspension system of this embodiment has the following advantages. Two upper and lower G sensors 1 _RL , 1 _FR provided on the front wheel side
From the signals obtained from the above, the sprung vertical velocity Δx and the sprung-unsprung relative velocity (Δx−Δx) at each wheel position
₀ ), thereby simplifying the system and reducing the cost by reducing the number of sensors.

As a means for converting the sprung vertical acceleration G from the sprung vertical acceleration G to the sprung vertical velocity Δx, a signal drift based on an extra low-frequency signal input, such as at the time of braking, is reduced by using a phase lag compensation formula. To prevent
The controllability of the damping force characteristic of the shock absorber SA is prevented from being deteriorated, and the riding comfort of the vehicle can be secured.

In the damping force characteristic control based on the skyhook theory, the switching from the soft characteristic to the hard characteristic is performed without time delay, whereby high control responsiveness is obtained and the hard characteristic is changed to the soft characteristic. Is switched without driving the actuator, thereby improving the durability of the pulse motor 3 and saving power consumption.

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

(Second Embodiment) The vehicle suspension system of the second embodiment differs from the first embodiment in the configuration of the signal processing circuit for obtaining the sprung vertical acceleration. The description is omitted because it is the same as the first embodiment. Also, since the configuration of the signal processing circuit is partly common to that of the first embodiment, the common parts are denoted by the same reference numerals, and description thereof will be omitted. Only different points will be described.

In the signal processing circuit shown in FIG.
Then, based on the transfer function GR _(S) from the front wheel position to the rear wheel position obtained in A3, the vehicle roll rate GR _R on the rear wheel side is calculated from the vehicle roll rate GR detected on the front wheel side.
Ask for.

In A7 and A8, the transfer function G _{HP (S)} from the front wheel position to the rear wheel position using the body as a transmission path.
, The high frequency component _GH of the sprung vertical acceleration transmitted to the rear wheel side is obtained.

In A9 and A10, the following equation (12)
As shown in (13), the A4, the signal obtained by _{A5 (GB R + GR R)} , the (GB _R -GR _R), further wherein A7,
By adding the high frequency components G _{HR ,} G _HL of the sprung vertical acceleration transmitted to the rear wheel side obtained in A8, the sprung vertical accelerations G _RR , G _{RL at the} left and right rear wheel positions are respectively added.
Ask for.

G _RR = (GB _R + GR _R ) + G _HR (12) G _RL = (GB _R -GR _R ) + G _HL . (13) As described above, in this embodiment, the vehicle roll rate GR _R on the rear wheel side is used instead of the vehicle roll rate GR detected on the front wheel side, and the vehicle Component G of sprung vertical acceleration transmitted to the rear wheel side
_HR, With the addition of G _HL, sprung mass vertical acceleration G _RR at the right and left rear wheels, the G _RL, it is possible to estimate more accurately.

Although the embodiment has been described above, the specific configuration is not limited to this embodiment, and any change in the design without departing from the gist of the present invention is included in the present invention.

For example, in the embodiment, the case where the vertical state amount detected by the vertical state amount detection sensor is the sprung vertical acceleration and the sprung vertical acceleration sensor is used as the vertical state amount detecting sensor has been described. A sprung-unsprung relative displacement sensor for detecting a relative displacement between a sprung and unsprung portion can also be used.

In the embodiment, the soft region SS is controlled only when the sprung vertical speed signal is zero.
By providing a predetermined dead zone centered at the center of the dead zone and maintaining the damping force characteristic in the soft region SS while the sprung vertical speed is changing within the range of the dead zone, control hunting can be prevented.

[0062]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension device described above, as described above, a shock absorber interposed between the vehicle body side and each wheel side and capable of changing the damping force characteristics by the damping force characteristic changing means, and at least the vertical state of each wheel position A vehicle suspension device provided with damping force characteristic control means for performing damping force characteristic control of each of the shock absorbers based on a control signal obtained from the control signal obtained from the left and right front wheel side vertical direction state amount detecting means. A front-wheel-side bounce-rate calculating means for obtaining a bounce rate of the vehicle at the front-wheel-side center position from an average value of the vertical-state quantities of the vehicle body at the front-wheel position, and a roll rate from a difference between the vertical-state quantities of the vehicle body at each of the left and right front wheel positions A roll rate calculating means, a vehicle speed sensor for detecting a vehicle speed, a bounce rate on a front wheel side of the vehicle, and a speed detected by the vehicle speed sensor .
Road surface from front wheel position to rear wheel position that changes according to vehicle speed
Based on the transfer function for inputting a transmission path, and wheel bounce rate computing means after obtaining the bounce rate of the vehicle at the rear wheel side central positions, left and right from the subtraction of the bounce rate and roll rate of a vehicle rear wheel each And left and right rear wheel side vertical state amount calculating means for calculating the vertical state amount of the vehicle body at the rear wheel position, so that damping force characteristic control can be performed from the vertical state amount of each wheel position. In a system using a signal, an effect is obtained that the system can be simplified and the cost can be reduced by reducing the number of sensors.

Further, the vehicle source according to claim 4 is an apparatus,
The sprung vertical velocity of each wheel position is determined from the sprung vertical acceleration of each wheel position detected by the left and right front wheel side sprung vertical acceleration sensor and calculated by the left and right rear wheel side vertical state amount calculating means. Detecting means, wherein the damping force characteristic changing means is centered on the 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 kept at the soft characteristic. The expansion side hard region (HS), in which only the damping force characteristic on the extension stroke side can be variably controlled to the hard characteristic side, and only the damping force characteristic on the compression stroke side on the hard characteristic side while the extension stroke side is kept in the soft characteristic. A variably controllable pressure side hard region (SH), wherein the damping force characteristic control means detects a shock when the direction identification code of the sprung vertical speed signal detected by the sprung vertical speed detecting means is near 0. The sober is controlled to the soft region (SS). When it is positive upward, the extension side damping force characteristic is on the extension side hard region (HS) side, and when it is downward negative, the compression side hard region (SH) is on. Is configured to variably control the damping force characteristics on the pressure stroke side to the hardware characteristics according to the control signal based on the sprung vertical speed at that time, so that the damping force characteristics control based on the Skyhook theory can be performed. Will be able to do it.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a vehicle suspension system of the present invention.

FIG. 2 is a configuration explanatory view showing a vehicle suspension system according to a first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system according to a first embodiment.

FIG. 4 is a sectional view showing a shock absorber applied to the first embodiment device.

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 a piston speed of the shock absorber.

FIG. 7 is a damping force characteristic diagram corresponding to a step position of a pulse motor of the shock absorber.

FIG. 8 is a perspective view of the shock absorber shown in FIG.
It is -K sectional drawing.

FIG. 9 is a perspective view of the shock absorber shown in FIG.
It is an L sectional view and MM sectional view.

FIG. 10 is a sectional view taken along line NN of FIG. 5 showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram when the shock absorber is on the extension side hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on an extension side and a compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a pressure-side hard state.

FIG. 14 is a block diagram showing a signal processing circuit for obtaining a sprung vertical acceleration in the device of the first embodiment.

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

FIG. 16 is a diagram showing a gain characteristic (a) and a phase characteristic (b) of a sprung vertical velocity signal obtained by a signal processing circuit in the device of the first embodiment.

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

FIG. 18 is a flowchart showing the content of the damping force characteristic control operation of the control unit in the first embodiment device.

FIG. 19 is a time chart showing the content of the damping force characteristic control operation of the control unit in the first embodiment device.

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

FIG. 21 is a block diagram showing a signal processing circuit for obtaining a sprung vertical acceleration in the device of the second embodiment.

[Explanation of symbols]

a damping force characteristic changing means b shock absorber c damping force characteristic controlling means d ₁ left front wheel side vertical state amount detecting means d ₂ right front wheel side vertical state amount detecting means e front wheel bounce rate calculating means f roll rate calculating means g Rear wheel side bounce rate calculation means h ₁ Left rear wheel side vertical state quantity calculation means h ₂ Right rear wheel side vertical state quantity calculation means i ₁ Left front wheel side sprung vertical acceleration sensor i ₂ Right front wheel side sprung vertical acceleration Sensor j ₁ Left front wheel side relative displacement sensor j ₂ Right front wheel side relative displacement sensor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60G 17/015

Claims (4)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing a damping force characteristic by damping force characteristic changing means, and a control signal obtained at least from a vertical state quantity of each wheel position. A vehicle suspension system provided with damping force characteristic control means for performing damping force characteristic control of each of the shock absorbers based on the left and right front wheel side vertical state for detecting a vertical state amount of the vehicle body at each of left and right front wheel positions of the vehicle body. Front-wheel-side bounce rate calculation for obtaining a vehicle bounce rate at a front-wheel-side center position from an average value of vehicle-body vertical-state quantities at left and right front-wheel positions detected by the left and right front-wheel-side vertical state quantity detection means. Means for calculating a roll rate from a difference between the state quantities of the vehicle body at the left and right front wheel positions detected by the left and right front wheel side vertical state quantity detecting means. Calculation means, a vehicle speed sensor for detecting a vehicle speed, a bounce rate on the vehicle front wheel side obtained by the front wheel side bounce rate calculation means, and a vehicle speed sensor detected by the vehicle speed sensor.
Road surface from front wheel position to rear wheel position that changes according to vehicle speed
A rear-wheel-side bounce-rate calculating means for obtaining a bounce rate of the vehicle at a rear-wheel-side center position based on a transfer function having an input as a transmission path; Left and right rear wheel side vertical state amount calculating means for obtaining the vertical state amount of the vehicle body at each of the left and right rear wheel positions from addition and subtraction of the bounce rate of the vehicle and the roll rate calculated by the roll rate calculating means. A vehicle suspension device characterized by the above-mentioned. 2. The left and right front wheel side vertical state amount detecting means,
2. The vehicle suspension system according to claim 1, further comprising a left and right front wheel side sprung vertical acceleration sensor for detecting a sprung vertical acceleration as a vertical state amount. 3. The left and right front wheel side vertical state amount detecting means,
2. The vehicle suspension system according to claim 1, further comprising a left and right front wheel side relative displacement sensor for detecting a relative displacement between a sprung and unsprung state as a vertical state amount. 4. A sprung vertical velocity at each wheel position from a sprung vertical acceleration at each wheel position detected by the left and right front wheel side sprung vertical acceleration sensor and obtained by the left and right rear wheel side vertical sprung state calculation means. The shock-absorbing damping force characteristic changing means includes a soft region (SS) in which both damping force characteristics on the extension stroke side and the compression stroke side are soft characteristics. The extension side hard region (HS), in which only the extension side damping force characteristic can be variably controlled to the hard characteristic side while the side is maintained at the soft characteristic,
The extension stroke side includes a compression-side hard region (SH) in which only the compression-stroke-side damping force characteristic can be variably controlled to the hard characteristic side while maintaining the soft characteristic, and the damping-force characteristic control means includes: The direction discrimination code of the sprung vertical speed signal detected by the speed detecting means is 0.
When the shock absorber is near the soft area (S
S), and when the value is upwardly positive, the damping force characteristic on the extension stroke side on the extension side hard region (HS) side, and when the value is downwardly negative, the compression stroke side on the compression side hard region (SH) side. 3. The vehicle suspension system according to claim 2, wherein said damping force characteristics are variably controlled to hardware characteristics according to a control signal based on a sprung vertical speed at that time.