JPH11301235A - Vehicle suspension - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance comfortability to ride against an input of an unsprung resonance frequency band by controlling a suspension rigidity to a predetermined strength or more within a predetermined time. SOLUTION: In the case where an unsprung damping judging signal exceeds a predetermined threshold value, an unsprung controlling means d controls a suspension rigidity to a predetermined strength or more within a predetermined time from the time after a predetermined time passed. Namely, at the time that the unsprung damping judging signal exceeds the predetermined threshold value, since an input from a road surface is forcedly transmitted to the unsprung, it is prevented that an unsprung forced vibration during road surface inputting is transmitted to a car body (springing) by withholding beginning of unsuprung damping controlling for the time that a predetermined time for which the road surface input passes passes, and controlling is carried out such that the suspension rigidity becomes a predetermined strength or more against an unsprung free vibration after the road surface input passed.

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.
In particular, the present invention relates to a vehicle suspension device that performs unsprung vibration control.

[0002]

2. Description of the Related Art Conventionally, as an example of a vehicle suspension system for performing unsprung mass damping control, an "electronic control suspension system" described in Japanese Patent Application Laid-Open No. 7-315029 is known. That is, when the unsprung resonance frequency component exceeds a predetermined threshold value, the conventional device suppresses unsprung fluttering by prohibiting the suspension rigidity from becoming softer than the predetermined strength. It was what was done.

[0003]

However, according to the conventional apparatus, as described above, the unsprung vibration suppression control is started immediately when the unsprung resonance frequency component exceeds a predetermined threshold value. Therefore, a vibration damping effect can be obtained with respect to free vibration after passing through the road surface input, but as a result, unsprung fluttering is transmitted to the sprung portion (vehicle body) with respect to forced vibration during road surface input, As a result, there is a problem that the flapping feeling may be worsened instead.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and prevents transmission of unsprung flutter to the vehicle body during road surface input while preventing unsprung flutter after passage of the road surface input. It is an object of the present invention to provide a vehicle suspension device capable of suppressing free vibration and thereby improving ride comfort with respect to an input of an unsprung resonance frequency band.

[0005]

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 suspension a that is interposed and capable of changing suspension rigidity, an unsprung vertical behavior detecting means b for detecting at least a front unsprung vertical behavior on the front wheel side, and a unsprung vertical direction detected by the unsprung vertical behavior detecting means b An unsprung damping determination signal creating means c for creating an unsprung damping determination signal from the behavior; and a unsprung damping determination signal created by the unsprung damping determination signal creating means c exceeds a predetermined threshold. The time is a means provided with unsprung mass damping control means d for controlling the suspension rigidity to be equal to or higher than a predetermined strength within a predetermined time after a predetermined time has elapsed. According to a second aspect of the present invention, in the vehicle suspension according to the first aspect, the unsprung vibration suppression determination signal generated by the unsprung vibration suppression determination signal generating means c exceeds a predetermined threshold value. Until the control by the lower vibration suppression control means d is started, the suspension rigidity is controlled to a predetermined soft characteristic. According to a third aspect of the present invention, in the vehicle suspension according to the first or second aspect, the unsprung mass damping control means d is provided.
However, the suspension rigidity is fixed to a fixed value equal to or higher than a predetermined strength. Claim 4
The vehicle suspension according to any one of claims 1 to 3, wherein the vehicle suspension detection unit detects a vehicle speed, and the unsprung vibration suppression determination generated by the unsprung vibration suppression determination signal generation unit c. Control time variable control means for variably controlling a predetermined time from when the signal exceeds a predetermined threshold value to when control by the unsprung vibration damping control means d is started according to the vehicle speed detected by the vehicle speed detection means Means. In the vehicle suspension device according to claim 5, claim 1 is
4. In the vehicle suspension device according to any one of 4, the vehicle speed detecting means for detecting a vehicle speed, and a calculating means for calculating a wheel base passing time from the vehicle speed detected by the vehicle speed detecting means,
The unsprung vibration damping control means d performs the calculation when the unsprung vibration damping determination signal for the front wheels generated by the unsprung vibration damping determination signal generating means c exceeds a predetermined threshold value. Means for controlling the suspension stiffness of the rear-wheel suspension to be equal to or greater than a predetermined strength after a predetermined time has elapsed after the passage of the wheelbase passing time calculated by the means. .

[0006]

In the vehicle suspension system according to the first aspect of the present invention, when forced vibration is generated below the spring due to road surface input, the vibration is detected by the unsprung vertical movement detecting means b as unsprung vertical movement, and The lower vibration suppression determination signal creating means c creates an unsprung vibration suppression determination signal from the unsprung vertical behavior. When the unsprung mass damping control signal exceeds a predetermined threshold, the unsprung mass damping control means d sets the unsprung mass damping control means d within a predetermined time after a predetermined time has elapsed thereafter. In, control is performed so that the suspension rigidity is equal to or higher than a predetermined strength. That is, when the unsprung mass damping determination signal exceeds a predetermined threshold value, the input from the road surface is forcibly transmitted to the unsprung portion, and the predetermined time during which the road surface input passes elapses. In the meantime, the start of the unsprung vibration suppression control is reserved to prevent the unsprung forced vibration during the road surface input from being transmitted to the vehicle body (sprung up) and to prevent the vibration from being transmitted after the road surface input is passed. For the unsprung free vibration, the unsprung free vibration is suppressed by performing control such that the suspension rigidity is equal to or more than a predetermined strength for a predetermined time. Further, in the vehicle suspension system according to the second aspect, the control by the unsprung vibration suppression control means d is performed after the unsprung vibration suppression judgment signal created by the unsprung vibration suppression judgment signal creation means c exceeds a predetermined threshold value. Until the start of the suspension, the suspension rigidity is controlled to a predetermined soft characteristic, whereby the effect of preventing the transmission of the unsprung forced vibration to the vehicle body (spring up) during road surface input increases. In the vehicle suspension device according to the third aspect, in the unsprung vibration suppression control means d, the suspension rigidity is fixed to a predetermined value equal to or higher than a predetermined strength with respect to unsprung free vibration after a road surface input has passed. Control is performed, thereby preventing flapping when switching the suspension rigidity. In the vehicle suspension device according to the fourth aspect, a predetermined time from when the unsprung vibration suppression determination signal exceeds a predetermined threshold value to when control by the unsprung vibration suppression control means d is started is determined according to the vehicle speed. Variable control,
Thereby, the start point of the unsprung vibration suppression control can be made to correspond to the switching point from the unsprung vibration state due to the road surface input to the free vibration state after the end of the road surface input. improves. Claim 5
In the vehicle suspension device described above, when the front-wheel-side unsprung vibration damping determination signal generated by the unsprung vibration damping determination signal generating means c exceeds a predetermined threshold, the unsprung vibration damping control means d The control is performed such that the suspension stiffness of the rear wheel-side suspension becomes equal to or more than a predetermined strength after a lapse of a predetermined time after the passage of the wheelbase calculated by the calculation means. By
Based on the unsprung vertical movement signal detected by the unsprung vertical movement detecting means on the front wheel side, accurate unsprung vibration suppression control on the rear wheel side is performed.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a configuration explanatory view showing a vehicle suspension system according to an embodiment of the present invention, and is interposed between a vehicle body and four wheels and is provided with four shock absorbers SA _FL and SA _FL .
_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 denoted 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. Each wheel position has a vertical acceleration G (G _FL , G _FR , G _RL , G
_RR ) to detect a sprung vertical acceleration sensor
Sensor _{as) 1 (1 FL, 1 FR} , 1 RL, 1 RR) is provided, also on the left and right front wheels, the wheel speed WS _FL, the wheel speed sensors 2 _FL for detecting the WS _FR, 2 _FR is provided Although not shown in the figure, a vehicle speed sensor 5 for detecting the vehicle speed BS of the vehicle is provided, and further, the upper and lower G sensors 1 ( _1FL , _1FR , _1RL) are provided near the driver's seat. , 1 _RR ), the left and right wheel speed sensors 2 _FL , 2 _FR and the signals from the vehicle speed sensor 5, and the respective shock absorbers SA _FL ,
A control unit 4 for outputting a drive control signal to the pulse motor 3 for SA _FR , SA _RL , and SA _RR 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 interface circuit 4a includes the upper and lower G sensors 1 (1).
_FL , 1 _FR , 1 _RL , 1 _RR )
_FL , G _FR , G _RL , G _RR ) signals, the wheel speed WS _FL , WS _FR signals from the left and right wheel speed sensors 2 _FL , 2 _FR , and the vehicle speed BS signal from the vehicle speed sensor 5. Then, based on these input signals, each shock absorber SA (SA _FL , SA _FR , SA _RL , SA
_RR ) is performed.

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. 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 in 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, and the second port 13, the vertical groove 23, and the fifth port 16. Then, the extension-side check valve 17 is opened to open the extension-side third flow path F leading to the lower chamber B, and a bypass reaching 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, of the control operation of the control unit 4, the structure of a signal processing circuit for obtaining the sprung vertical speed Δx and the sprung-unsprung relative speed (Δx−Δx ₀ ) is shown in FIG. Description will be made based on the drawings.

First, in B1, a phase delay compensation formula is used,
Each vertical G sensors _{1 (1 FL, 1 FR,} 1 RL, 1 RR) on each spring is detected by the vertical acceleration _{G (G FL, G FR,} G RL, G RR)
Is converted into a sprung vertical speed signal at each tower position.

The general expression of the phase delay compensation can be expressed by the following transfer function expression (1). G _(S) = (AS + 1) / (BS + 1) (1) (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 (2 ) Is used. G _(S) = ((0.001 S + 1) / (10S + 1)) × γ (2) where γ is a signal and gain characteristic when the speed is converted by integration (1 / S). This is a gain for matching, and is set to γ = 10 in the embodiment of the present invention. As a result, as shown in the gain characteristic of the solid line in FIG. 15A and the phase characteristic of the solid line in FIG. 15B, the frequency band (0.5 Hz to 3 Hz) required for damping force characteristic control is obtained.
2), only the gain on the low frequency side is reduced without deteriorating the phase characteristics. Note that FIG.
Dotted lines (a) and (b) show the gain characteristic and phase characteristic of the sprung vertical velocity signal that has been velocity-converted by integration (1 / S).

In B2, band-pass filtering is performed to cut off components other than the target frequency band to be controlled. 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 (3),
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 from the sprung-unsprung relative velocity (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) (3) where m is a sprung mass, c is a damping coefficient of the suspension, and k is a spring constant of the suspension.

Next, of the control operation of the damping force characteristic of the shock absorber SA in the control unit 4, the contents of the normal control by the basic control unit will be described with reference to the flowchart of FIG. Note that this normal control is performed by each of the shock absorbers SA _FL , SA _FR , SA _RL , SA
_Performed for each _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. The sprung vertical speed Δx is
When the value changes as shown in this figure, as shown in the figure, when the value of the sprung vertical velocity Δx is 0, the shock absorber SA is controlled to the soft area SS.

When the value of the sprung vertical velocity Δx becomes a positive value, the compression-side damping force characteristic is controlled to the extension-side hard region HS to fix the compression-side damping force characteristic to the soft characteristic, while the extension-side damping force characteristic (target The damping force characteristic position P _T ) is changed in proportion to the sprung vertical speed Δx based on the following equation (4). P _T = α · Δx · Ku (4) where α is a constant on the extension side and Ku is a distance between the sprung and unsprung state shown in FIG. Based on the control gain variable characteristic map for the relative speed, the sprung-unsprung relative speed (Δx−Δx ₀ )
Is a control gain variably set to a value inversely proportional to.

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 characteristic (target damping force) is set. The characteristic position P _C ) is calculated based on the following equation (5).
It changes in proportion to the sprung vertical speed Δx. P _C = β · Δx · Ku (5) 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 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 (shock absorber SA).
Is a pressure stroke side), and at this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the sprung vertical speed Δx,
Therefore, in this area, the shock absorber SA at that time is
The pressure stroke side, which is the stroke of, has soft characteristics.

In region b, the sprung vertical speed Δx remains a positive value (upward), and the relative speed (Δx−Δx ₀ ) changes from a negative value to a positive value (the stroke of the shock absorber SA is the extension stroke). Side), the shock absorber SA is controlled to the extension side hard area HS based on the direction of the sprung vertical speed Δx at this time, and the stroke of the shock absorber is also the extension stroke. Accordingly, 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.

Area c is a state in which the sprung vertical speed Δx is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative speed (Δx−Δx ₀ ) is still positive. (The stroke of the shock absorber SA is on the extension stroke side), and at this time, the sprung vertical velocity Δx
The shock absorber SA is controlled to the pressure side hard region SH based on the direction of the shock absorber SA. Therefore, in this region, the extension stroke which is the stroke of the shock absorber SA at that time has the soft characteristic.

In the area d, the sprung vertical speed Δx remains a negative value (downward), and the relative speed (Δx−Δx ₀ ) changes from a positive value to a negative value (the stroke of the shock absorber SA is the extension stroke). 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 the compression stroke. In this region, the pressure stroke 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 speed Δx.

As described above, in the embodiment of the present invention, when the sprung vertical speed Δx and the relative speed (Δx−Δx ₀ ) have the same sign (region b, region d), the shock absorber SA at that time is used. And the damping force characteristic control based on the skyhook theory, in which the stroke side of the shock absorber SA is controlled to a hard characteristic, and the stroke side of the shock absorber SA at the time of the different sign (region a, region c) is controlled to a soft characteristic. The same control will be performed. Further, in the embodiment of the present invention, when the stroke of the shock absorber SA is switched, that is, when shifting from the region a to the region b and from the region c to the region d (from the soft characteristic to the hard characteristic), the switching is performed. Since the position of the damping force characteristic on the switching side has already been switched to the hardware characteristic in the previous areas a and c, the switching from the soft characteristic to the hardware characteristic is performed without time delay.

Next, of the control operation of the control unit 4, the contents of the unsprung vibration control will be described. First, the configuration of a signal processing circuit for obtaining the unsprung vibration suppression determination signal RH from the front wheel left and right wheel speed WS _FL and WS _FR signals detected by the front left and right wheel speed sensors 2 _FL and 2 _FR is shown in the block of FIG. This will be described with reference to FIG. 20 and the time chart of FIG.
The unsprung vibration damping determination signal RH is obtained separately and independently for the left and right wheels.

First, at C1, the wheel speed change amount is obtained by subtracting the wheel speed WS _{n-1 one time} before the sampling time n from the wheel speed WS _{n at} the sampling time n.

In the following C2, the absolute value of the wheel speed change amount is obtained, and in the following C3, the moving average value of the absolute value of the wheel speed change amount is obtained.

In C4, a 1 Hz low-pass filter L
By processing with the PF, the unsprung vibration suppression determination signal RH as the unsprung resonance component is obtained.

Next, the contents of the unsprung mass damping control based on the unsprung mass damping determination signal RH obtained as described above are as follows.
A description will be given based on the flowcharts of FIGS. This control is performed independently for each wheel.

First, the operation of the timer process will be described with reference to the flowchart of FIG. In step 201, it is determined whether or not the unsprung mass damping determination signal RH is equal to or greater than a threshold value THUS. If YES, the process proceeds to step 202,
When the result is NO, the process proceeds to step 203 without passing through step 202.

In step 202, it is determined whether or not the previous unsprung vibration damping determination signal RH _n-1 is equal to or less than the threshold value THUS. If YES, the threshold value RH is already crossed. Since the timer count has already started,
Proceed to step 203. If NO, it means that the threshold RH is crossed for the first time.
Proceeding to 6, the timer count TMUS is set to 1, and one flow is completed.

In step 203, the timer count TMUS determines the wheel base passage time TD (= wheel base m / vehicle speed BSm / s), the unsprung vibration control start time.
It is determined whether it is less than the total time of the TMS and the unsprung vibration suppression control hold time TMH. If YES (less than the total time), the process proceeds to step 204, where 1 is added to the timer count TMUS, If NO (total time or more), the routine proceeds to step 205, where the timer count TM
US is reset to 0, and this ends one flow.

Next, the unsprung mass damping command operation on the front wheels will be described with reference to the flowchart of FIG. In step 301, the timer count TMUS is equal to or longer than the unsprung vibration suppression control start time TMS and the unsprung vibration suppression control start time
It is determined whether or not it is less than the total time of TMS and the unsprung vibration suppression control hold time TMH.
Go to 02 and set the unsprung vibration suppression control flag to 1,
If NO, the process proceeds to step 303, where the unsprung vibration suppression control flag is cleared, and one flow is completed.

Next, the unsprung mass damping command operation on the rear wheel side will be described with reference to the flowchart of FIG. In step 401, the timer count TMUS is equal to or longer than the total time of the wheelbase passing time TD and the unsprung vibration suppression control start time TMS, and the wheelbase passing time TD, the unsprung vibration suppression control start time TMS, and the unsprung vibration suppression Control hold time TM
It is determined whether or not it is less than the total time of H. If YES, the process proceeds to step 402, and the unsprung vibration suppression control flag is set to 1. If NO, step 403 is executed.
To clear the unsprung damping control flag, thereby ending one flow.

Next, the unsprung mass damping control operation will be described with reference to the flowchart of FIG. In step 501, it is determined whether the unsprung vibration suppression control flag is set to 1 or not. If NO, the one-time flow is ended. If YES, the flow proceeds to step 502. move on.

In step 502, it is determined whether or not the target damping force characteristic position P in the normal control is greater than the pressure side position threshold value PTHC and less than the extension side position threshold value PTHT. At this time, one flow is completed, and if YES, the routine proceeds to step 503, where the target damping force characteristic position P is set to the unsprung vibration suppression control position PUS (= PTHT). Ends the flow.

Next, the contents of the above-described unsprung mass damping control operation will be described with reference to the time chart of FIG. (B) Normal control When the unsprung flapping does not occur, the unsprung vibration suppression determination signal RH is equal to or lower than the threshold value THUS. By performing the damping force characteristic control (skyhook control) of the shock absorber SA based on the speed Δx signal, the riding comfort of the vehicle when traveling on a good road can be ensured.

(B) At the time of the normal control hold When the front wheel side unsprung due to the road surface input, the unsprung vibration suppression determination signal RH exceeds the threshold value THUS. Vibration control start time TM
During S), the road surface input is being performed, and the road surface input is forcibly transmitted to the front-wheel-side unsprung portion, and during that time, the front-wheel-side shock absorbers SA _FL and SA _{FR use} the above-described operation. The normal control state is maintained.

On the rear wheel side, when fluttering occurs on the unsprung side of the front wheel side, the unsprung vibration suppression determination signal RH is set to a threshold value.
THUS, but after a lapse of the wheelbase passing time TD from that point, a predetermined time (the unsprung vibration suppression control start time
TMS), the road surface input is being performed on the rear wheel side, and the road surface input is forcibly transmitted to the rear wheel unsprung, and during that time, the rear wheel side shock absorber SA _RL , S
In the _ARR , the normal control state described above is maintained. Therefore, on both the front wheel side and the rear wheel side, the unsprung forced vibration during the road surface input can be prevented from being transmitted to the sprung portion (vehicle body).

(C) At the time of unsprung vibration suppression control After a predetermined time (unsprung vibration suppression control start time TMS) elapses after fluttering occurs at the front wheel side unsprung due to road surface input, the road surface input changes to the front wheel side. After that, the unsprung state becomes a free vibration state. At that time, the target damping force characteristic position of the front wheel side shock absorbers SA _FL and SA _FR is maintained for a predetermined time (the unsprung vibration suppression control hold time TMH). An unsprung vibration control is performed in which P is fixed to the unsprung vibration control position PUS.

On the rear wheel side, after fluttering occurs on the front wheel side under the spring, after a lapse of the wheelbase passing time TD from that point, a further predetermined time (the unsprung vibration suppression control start time TMS) elapses. Then, since the road surface input passes through the rear wheel side and the unsprung portion is in a free vibration state, at that time, after a lapse of the wheel base passing time TD from that time, a predetermined time (the unsprung vibration suppression control hold Time TMH
), The rear wheel side shock absorbers SA _RL and SA _RR
Of the target damping force characteristic position P is fixed to the unsprung vibration suppression control position PUS. Therefore, it is possible to suppress the unsprung flapping after the road surface input has elapsed on both the front wheel side and the rear wheel side.

As described above, according to the vehicle suspension system of the embodiment of the present invention, during normal running of the vehicle, the vehicle is controlled by the damping force characteristic control of the shock absorber SA based on the skyhook control theory. Comfort and steering stability can be ensured, while preventing unsprung flutter from being transmitted to the vehicle body during road input, and damping unsprung free vibration after passing the road input. Thus, it is possible to improve the ride comfort with respect to the road surface input in the unsprung resonance frequency band.

Further, based on the unsprung vibration suppression control judgment signal RH detected on the front wheel side, accurate unsprung vibration suppression control on the rear wheel side is performed, and the system cost is reduced by reducing the number of parts. Will be able to

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the embodiments of the present invention, and even if there is a design change or the like within a range not departing from the gist of the present invention, the present invention is not limited thereto. Included in the invention.

For example, in the embodiment of the present invention, when one of the damping force characteristics of the extension stroke and the compression stroke is variably controlled, the damping force characteristic of the other stroke side is soft. Although the example in which the shock absorber having the structure fixed to the characteristic is used has been described, the present invention can be applied to a case where the shock absorber having a structure in which the damping force characteristics of the extension stroke and the compression stroke are simultaneously changed.

In the embodiment of the present invention, the soft region SS is controlled only when the sprung vertical speed signal is 0. However, a predetermined dead zone centered at 0 is provided and the spring is controlled within the range of the dead zone. By maintaining the damping force characteristic in the soft region SS while the up-down speed is changing, control hunting can be prevented.

In the embodiment of the present invention, the normal control state is held until the unsprung vibration suppression control is started after the unsprung vibration suppression determination signal RH exceeds the threshold value THUS. However, by controlling the target damping force characteristic position P of the shock absorber SA to a predetermined soft damping force characteristic, the effect of preventing the unsprung forced vibration from being transmitted to the vehicle body (sprung up) during road surface input is enhanced. Will be able to do it.

In the embodiment of the present invention, the predetermined time from when the unsprung mass damping determination signal RH exceeds the threshold value THUS to when the unsprung mass damping control is started is fixedly set to a fixed time. However, by performing variable control according to the vehicle speed BS, the unsprung vibration suppression control is started at the point where the unsprung force vibration state during the road surface input switches to the free vibration state after the road surface input is completed. The time points can be made to correspond, whereby the unsprung vibration suppression control effect can be further improved.

Further, in the embodiment of the present invention, the unsprung vibration damping determination signal RH is obtained from the wheel speed. However, the unsprung vibration damping determination signal RH may be obtained based on a signal detected by a vertical acceleration sensor provided below the spring. Alternatively, an unsprung resonance frequency band component can be extracted from a sprung-unsprung stroke signal detected by a stroke sensor using a filter or the like, and can be obtained based on this signal.

[0058]

As described above, the first aspect of the present invention is as follows.
In the vehicle suspension device described above, as described above, when the unsprung mass damping determination signal created by the unsprung mass damping determination signal creation means exceeds a predetermined threshold value, a predetermined time elapses thereafter, and then a predetermined time elapses. Within this time, the unsprung vibration suppression control means for controlling the suspension stiffness to be equal to or higher than a predetermined strength is provided to prevent the transmission of unsprung flutter to the vehicle body during road surface input. At the same time, the unsprung free vibration after passing through the road surface input is damped, whereby the effect of improving the riding comfort with respect to the input of the unsprung resonance frequency band can be obtained. According to a second aspect of the present invention, in the vehicle suspension according to the first aspect, the unsprung vibration damping determination signal generated by the unsprung vibration damping determination signal generating means exceeds a predetermined threshold value. Until the control by the vibration damping control means is started, the suspension rigidity is controlled to a predetermined soft characteristic, so that the vehicle body (spring-up) which is subjected to unsprung forced vibration during road surface input. Can be enhanced. In the vehicle suspension according to claim 3, in the vehicle suspension according to claim 1 or 2,
Since the unsprung mass damping control means is configured to fix the suspension rigidity to a constant value equal to or higher than a predetermined strength, it is possible to prevent flapping when switching the suspension rigidity. In the vehicle suspension device according to claim 4,
4. The unsprung mass damping control according to claim 1, wherein the unsprung mass damping judgment signal created by the unsprung mass damping judgment signal creating means exceeds a predetermined threshold. Control time variable control means for variably controlling a predetermined time until the control by the means is started in accordance with the vehicle speed detected by the vehicle speed detection means. The starting point of the unsprung vibration suppression control can be made to correspond to the switching point from the forced vibration state to the free vibration state after the end of the road surface input, so that the unsprung vibration suppression control effect can be further improved. According to a fifth aspect of the present invention, in the vehicle suspension according to any one of the first to fourth aspects, a vehicle speed detecting means for detecting a vehicle speed, and a wheelbase passing time is calculated from the vehicle speed detected by the vehicle speed detecting means. Calculating means for calculating, when the unsprung vibration suppression control signal generated by the unsprung vibration suppression judgment signal generating means exceeds a predetermined threshold value. Is configured to control the suspension stiffness of the rear wheel suspension to be equal to or greater than a predetermined strength after a lapse of a predetermined time after the passage of the wheelbase calculated by the calculation means. This makes it possible to perform accurate unsprung vibration suppression control on the rear wheel side based on the unsprung vertical movement signal detected by the unsprung vertical movement detecting means on the front wheel side.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating a configuration of a vehicle suspension device according to an embodiment of the present invention.

FIG. 3 is a system block diagram illustrating a vehicle suspension device according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a shock absorber applied to the vehicle suspension device according to the embodiment of the present invention.

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.

8 is a cross-sectional view showing a state where the adjuster of the shock absorber is arranged at a position shown in FIG. 7;
5 is a sectional view taken along line KK of FIG. 5, (b) is a sectional view taken along line LL and MM of FIG. 5, and (c) is a sectional view taken along line NN of FIG.

FIG. 9 is a cross-sectional view showing a state where the adjuster of the shock absorber is arranged at a position shown in FIG. 7;
5 is a sectional view taken along line KK of FIG. 5, (b) is a sectional view taken along line LL and MM of FIG. 5, and (c) is a sectional view taken along line NN of FIG.

FIG. 10 is a sectional view showing a state in which the adjuster of the shock absorber is arranged at the position shown in FIG. 7;
(A) is a sectional view taken along the line KK of FIG. 5, (B) is a sectional view taken along the line LL and MM of FIG. 5, and (C) is a sectional view taken along the line NN of FIG.

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 speed and a sprung unsprung relative speed signal from a sprung vertical acceleration in the vehicle suspension system according to the embodiment of the present invention.

FIG. 15 is a diagram showing a gain characteristic (a) and a phase characteristic (b) of the sprung vertical velocity signal converted by using the phase lag compensation equation.

FIG. 16 is a flowchart showing a damping force characteristic normal control operation of a control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 17 is a time chart showing a damping force characteristic normal control operation of the control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 18 is a control gain variable characteristic map with respect to a sprung-unsprung relative speed in the vehicle suspension system according to the embodiment of the present invention.

FIG. 19 is a block diagram illustrating a configuration of a signal processing circuit that obtains an unsprung vibration suppression determination signal from a front wheel speed signal in the control operation of the control unit 4 in the vehicle suspension system according to the embodiment of the present invention.

FIG. 20 is a time chart illustrating a processing state of a signal processing circuit for obtaining an unsprung vibration suppression determination signal from a front wheel speed signal among control operations of the control unit 4 in the vehicle suspension system according to the embodiment of the present invention. is there.

FIG. 21 is a flowchart showing a timer processing operation in the damping force characteristic control operation of the control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 22 is a flowchart showing a content of a unsprung control command operation on a front wheel side in a damping force characteristic control operation of the control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 23 is a flowchart showing the contents of a unsprung control command operation on the rear wheel side in the damping force characteristic control operation of the control unit in the vehicle suspension system according to the embodiment of the present invention.

FIG. 24 shows the contents of the control operation for switching between the normal control and the unsprung vibration suppression control and the contents of the unsprung vibration suppression control in the damping force characteristic control operation of the control unit in the vehicle suspension system according to the embodiment of the present invention. It is a flowchart which shows.

FIG. 25 shows the contents of the switching control operation between the normal control and the unsprung vibration control and the contents of the unsprung vibration control among the damping force characteristic control operations of the control unit in the vehicle suspension system according to the embodiment of the present invention. FIG.

[Explanation of symbols]

 a suspension b unsprung vertical movement detecting means c unsprung vibration suppression determination signal creating means d unsprung vibration suppression controlling means

Claims (5)

[Claims] 1. A suspension interposed between a vehicle body side and a wheel side and capable of changing suspension rigidity, an unsprung vertical behavior detecting means for detecting at least a front unsprung vertical behavior on a front wheel side, Under-sprung vibration-damping determination signal creating means for creating an unsprung vibration-damping determination signal from the unsprung vertical movement detected by the up-down behavior detecting means, and an unsprung vibration-damping determination signal created by the unsprung vibration-damping determination signal creating means When a predetermined threshold value is exceeded, the unsprung mass damping control means for controlling the suspension rigidity to be equal to or higher than a predetermined strength within a predetermined time after a predetermined time has elapsed. A vehicle suspension device comprising: 2. The apparatus according to claim 1, wherein said unsprung mass damping determination signal generated by said unsprung mass damping determination signal generation means exceeds a predetermined threshold value and starts control by said unsprung mass damping control means. 2. The vehicle suspension according to claim 1, wherein the suspension rigidity is controlled to a predetermined soft characteristic. 3. The vehicle suspension according to claim 1, wherein the unsprung mass damping control means is configured to fix the suspension rigidity to a fixed value equal to or higher than a predetermined strength. apparatus. 4. A vehicle speed detecting means for detecting a vehicle speed, and after the unsprung vibration suppression judging signal generated by said unsprung vibration damping judging signal generating means exceeds a predetermined threshold value, said unsprung vibration damping control means. The control time variable control means for variably controlling a predetermined time until the control is started according to the vehicle speed detected by the vehicle speed detection means, wherein the control time variable control means is provided. The vehicle suspension according to any one of the preceding claims. 5. A vehicle speed detecting means for detecting a vehicle speed, and a calculating means for calculating a wheelbase passing time from the vehicle speed detected by the vehicle speed detecting means, wherein the unsprung vibration suppression control means comprises: When the front-wheel-side unsprung vibration-damping determination signal created by the vibration-damping determination signal creation means exceeds a predetermined threshold, the wheelbase passing time calculated by the calculation means elapses, and then the predetermined time elapses. The vehicle suspension device according to any one of claims 1 to 4, wherein the suspension rigidity of the rear wheel-side suspension is controlled so as to be equal to or higher than a predetermined strength after a lapse of time.