JP3121922B2 - 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 characteristic of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling a damping characteristic of a shock absorber, for example, Japanese Unexamined Patent Publication No.
One described in Japanese Patent No. 284013 is known.

When the sprung vertical acceleration is less than a threshold value determined by a function of a relative displacement between a sprung mass and a unsprung mass, the conventional vehicle suspension device switches the damping force hard and sets the threshold value to a hard value. When it exceeds, in addition to the basic control to switch the damping force to software, when the brake operation is performed irrespective of the vehicle condition, the correction control to switch the damping force to hardware is performed during that time. .

[0004]

However, in the above-mentioned conventional device, since the above-mentioned configuration is employed, when the vehicle gets over a projection or the like during a brake operation, the road surface input is hardened by a hard damping force. Is transmitted to the sprung, thereby deteriorating the ride comfort of the vehicle, and when the brake operation is released during traveling, the damping force switches to soft from that point, causing the vehicle to swing back and the running stability of the vehicle There was a problem that impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. The present invention suppresses a dive of a vehicle due to a brake operation and a subsequent swingback, and a vehicle riding by a protruding road surface input during a brake operation. It is an object of the present invention to provide a vehicle suspension device capable of preventing a deterioration in comfort.

[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 interposed and capable of changing the damping characteristic by the damping characteristic changing means a, a sprung vertical speed detecting means c for detecting a sprung vertical speed near a position where each shock absorber b is provided, and a brake operation The brake sensor d that detects the state and the damping characteristics of each shock absorber b are calculated from the bounce rate based on the sprung vertical speed and the pitch rate detected from the sprung vertical speed difference between the front and rear of the vehicle and the sprung vertical speed difference between the left and right of the vehicle. A control unit f having an attenuation characteristic control unit e for controlling based on a control signal obtained from the detected roll rate and provided on the control unit f;
When the brake operation is performed, the correction control unit g that increases the proportional constant of the pitch rate during a half cycle of the pitch resonance frequency after the brake operation is released is provided.

In the vehicle suspension system according to the present invention, in obtaining the control signal, the bounce rate uses a signal passed through a band-pass filter including a sprung resonance frequency of each of the front and rear wheels. A signal passed through a band-pass filter including the pitch resonance frequency was used, and a signal passed through a band-pass filter including the roll resonance frequency was used as the roll rate.

[0008]

When the bounce, pitch, and roll are detected by each sprung speed detecting means, the damping characteristic control section obtains a control signal based on the bounce rate, the pitch rate, and the roll rate. This provides sufficient control force not only for bounce, but also for pitch and roll.

When a brake operation is performed while the vehicle is running, the correction control section performs a correction to increase the proportional constant of the pitch rate, whereby the damping characteristic increases and the brake characteristic is increased. The generated vehicle dive is suppressed.

The above state is maintained for a half cycle of the pitch resonance frequency even after the brake operation is released, so that the swingback of the vehicle body when the brake operation is released is suppressed. You.

During the braking operation, the proportional constant of the pitch rate is increased, but the bounce rate changes according to the sprung vertical speed at that time. Transmission to the sprung can be suppressed.

Further, in the device according to the second aspect, even when the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different, proper damping control can be performed.

[0013]

An embodiment of the present invention will be described with reference to the drawings. (First Embodiment) First, the configuration will be described. FIG.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a configuration of a vehicle suspension system according to a first embodiment, in which four shock absorbers SA ₁ , SA ₂ , SA ₃ , and SA ₄ are provided between a vehicle body and four wheels. In the description, when these four are collectively referred to, and when the common configuration is described, they are simply indicated as SA.). And, on the vehicle body in the vicinity of each shock absorber SA,
A vertical acceleration sensor that detects vertical acceleration (hereinafter
An upper and lower G sensor 1 is provided. At a position near the driver's seat, there is provided a control unit 4 that receives signals from the upper and lower G sensors 1 and outputs a drive control signal to the pulse motor 3 of each shock absorber SA.

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. , An ON / OFF signal from a brake switch (brake sensor) 2, and a vehicle speed signal from a vehicle speed sensor 5. In the interface circuit 4a, a set of five filter circuits shown in FIG. That is, the LPF 1 is a low-pass filter circuit for removing noise in a high frequency range (30 Hz or more) from signals sent from the upper and lower G sensors 1. LPF2 is a low-pass filter circuit for integrating a signal indicating acceleration that has passed through low-pass filter circuit LPF1 and converting the signal into a sprung vertical velocity. The BPF ₁ passes a bounce component signal v (v ₁ , v ₂ , v
_3, v ₄ Numerals _{1, 2, 3 and 4} correspond to the position of the shock absorbers SA. The same applies to the following. ) Is a band-pass filter circuit. BPF2 is
This is a bandpass filter circuit that forms a pitch component signal v ′ (v ₁ ′, v ₂ ′, v ₃ ′, v ₄ ′) by passing a frequency range including a pitch resonance frequency. The BPF ₃ is a band-pass filter circuit that forms a roll component signal v ″ (v ₁ ″, v ₂ ″, v ₃ ″, v ₄ ″) by passing through a frequency range including the roll resonance frequency. In the example, the sprung resonance, pitch resonance, and roll resonance frequencies are
Although different cases are taken as an example, when these resonance frequencies are close to each other, the band-pass filter is set to BPF1.
Only need.

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 An expansion damping valve 12 and a compression damping valve 20 for opening and closing 31a and 31b, respectively, are provided. A stud 38 that penetrates the piston 31 is screwed and fixed to the bound stopper 41 screwed to the tip of the piston rod 7, and the stud 38 bypasses the through holes 31a and 31b. Communication for forming 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 fluid can flow in the pressure stroke, the pressure side first valve that opens the pressure side damping valve 20 through the through hole 31a.
Channel H, hollow 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 so that the damping 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. 7, a state where both the extension side and the compression side are soft (hereinafter, the soft area S
When the adjuster 40 is rotated in the counterclockwise direction from S), the damping characteristic can be changed in multiple stages only on the extension side, and the compression side becomes a region fixed to the low attenuation characteristic (hereinafter referred to as the extension side hard region HS). Conversely, when the adjuster 40 is rotated clockwise, the attenuation characteristic can be changed in multiple stages only on the compression side, and the expansion side becomes a region fixed to the low attenuation characteristic (hereinafter referred to as a compression side hard region SH). I have.

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, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described with reference to the flowchart of FIG. This control is performed separately for each shock absorber SA.

In step 101, the upper and lower G sensors 1,
The vertical acceleration obtained from each of the filter circuits L
PF1, BPF1, BPF2, BPF3, and LPF2 to perform processing for obtaining a bounce component signal v, a pitch component signal v ', and a roll component signal v ". Each component is also determined according to the vehicle speed based on a map shown in FIG. The signals v, v ',
v ”proportional constants α (α _f , α _r ), β (β _f , β _r ),
This is a step of setting γ (γ _f , γ _r ). Each component signal v, v ', v "is given a positive value when the sprung vertical acceleration is in the upward direction, and a negative value when the sprung vertical acceleration is in the downward direction.

Step 102 is a step for determining whether or not the brake switch 2 is ON. If NO, proceed to Step 103, and if YES, proceed to Step 104.

Step 103 is as follows.
This is a step of determining whether or not within a predetermined time (1/2 cycle of the pitch resonance frequency) after the FF.
Go to 5 and proceed to step 104 with YES.

In step 104, the proportional constant α of the bounce component signal v is set to α + α _B and the pitch component signal v ′
The proportionality constant beta, a step of switching to β + β _B. Note that α _B and β _B are correction constants for increasing the values of the proportional constants α and β in step 101, and are set according to the vehicle speed as shown in the map of FIG.

Step 105 uses the following equation (1).
Each component signal v, v'v "and each proportional constant α (or α +
This is a step of calculating control signals V (V ₁ , V ₂ , V ₃ , V ₄ ) for the position of each wheel based on α _B ), β (or β + β _B ), and γ.

[0027]

(Equation 1) Note that α _f , β _f , and γ _f are the respective proportional constants of the front wheels α _r , β _r , and γ _r are the respective proportional constants of the rear wheels. Also,
In each equation, the part bounded by the first α _f and α _r is the bounce rate, the part bounded by β _f and β _r is the pitch rate, and the part bounded by γ _f and γ _r is the roll Rate.

[0028] Step 106, the control signal V is a step equal to or larger than a predetermined threshold value [delta] _T, the process proceeds to step 107 in YES, a step 1 is NO
Proceed to 08.

In step 107, the shock absorber S
This is a step of controlling A to the extension-side hard area HS.

[0030] Step 108, the control signal V is determining whether a value between a predetermined threshold value [delta] _T and the threshold - [delta _C, the process proceeds to step 109 YES, a by NO Proceed to step 110.

In step 109, the shock absorber S
This is the step of controlling A to the soft area SS.

Step 110 is a step displayed for the sake of convenience.
When it is determined that O is the control signal V is less than a predetermined threshold value - [delta _C, in this case, the process proceeds to step 111.

Step 111 is a step performed by the shock absorber S
This is a step of controlling A to the compression side hard area SH.

Next, the operation of the embodiment will be described with reference to the time chart of FIG. If the vertical sprung mass velocity is varied as shown in the control signal V in the figure, as shown in FIG, when the control signal V is a value between the predetermined threshold value [delta] _T, - [delta _C is shock Absorber SA in soft area S
Control to S.

When the control signal V becomes equal to or larger than the threshold value δ _{T, the} compression side is controlled to the expansion side hard region HS to fix the compression side to a low attenuation characteristic, while making the expansion side attenuation characteristic proportional to the control signal V. Change. At this time, the attenuation characteristic C is C = k ₁ · V
Is controlled so that

When the control signal V becomes equal to or smaller than the threshold value -δ _{C, the} compression side is controlled to the compression side hard area SH to fix the extension side to the low attenuation characteristic, while making the compression side attenuation characteristic proportional to the control signal V. Change. Also at this time, the attenuation characteristic C is C = k ₂
・ V is controlled to be V.

In the time chart of FIG.
The area a is a state in which the control signal V based on the sprung vertical speed is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative speed is still a negative value (the shock absorber SA has a negative value). Since the stroke is a pressure stroke side), at this time, the shock absorber SA is controlled to the extension side hard region HS based on the direction of the control signal V.
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 the region b, the control signal V based on the sprung vertical speed remains a positive value (upward), and the relative speed changes from a negative value to a positive value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA is controlled to the extension-side hard area HS based on the direction of the control signal V, and the stroke of the shock absorber is also the extension stroke. In this region, the extension stroke, which is the stroke of the shock absorber SA at that time, has a hard characteristic proportional to the value of the control signal V.

Area c is a state in which the control signal V based on the sprung vertical velocity is reversed from a positive value (upward) to a negative value (downward). At this time, the relative velocity is still a positive value. (The stroke of the shock absorber SA is on the extension stroke side.) At this time, the shock absorber SA is controlled to the compression-side hard region SH based on the direction of the control signal V. Then, the extension stroke side, which is the stroke of the shock absorber SA at that time, has the soft characteristic.

In the area d, the control signal V based on the sprung vertical speed remains a negative value (downward), and the relative speed changes from a positive value to a negative value (the stroke of the shock absorber SA is on the extension stroke side). At this time, the shock absorber SA is controlled to the compression-side hard region SH based on the direction of the control signal V, and the stroke of the shock absorber is also the compression stroke. Therefore, in this region, The pressure stroke side, which is the stroke of the shock absorber SA at that time, has hardware characteristics proportional to the value of the control signal V.

As described above, in this embodiment, when the sprung vertical speed and the relative speed between the sprung and unsprung have the same sign (region b, region d), the shock absorber S at that time is used.
A damping characteristic control based on the skyhook theory, in which the stroke side of A is controlled to a hard characteristic, and when the sign is different (regions a and c), the stroke side of the shock absorber SA at that time is controlled to a soft characteristic. The same control will be performed without detecting the relative speed between sprung and unsprung. Further, in this embodiment, when shifting from the area a to the area b and from the area c to the area d, the switching of the damping characteristic is performed without driving the pulse motor 3.

Next, the operation of the control unit 4 during normal running of the vehicle and during brake operation will be described. (A) During normal traveling During normal traveling of the vehicle, control is performed based on the bounce component signal v, the pitch component signal v ', the roll component signal v ", and the proportional constants α, β, γ set according to the vehicle speed. Signal V
Is required. Therefore, a sufficient control force can be generated not only for the bounce but also for the roll and the pitch.

(B) During Brake Operation When a brake operation is performed while the vehicle is running, the proportional constant α + α _B of the increased bounce component signal v, the proportional constant β + β _{B of} the increased pitch component signal v ′, and , A control signal V based on a proportional constant γ set according to the vehicle speed.
Is required, whereby the control signal V has a larger value than during normal running. Therefore, the bounce and dive of the vehicle that occur at the time of the brake operation can be suppressed by the increased damping characteristics.

The above state is maintained for a half cycle of the pitch resonance frequency even after the brake operation is released, so that the bounce and dive swingback due to the brake operation also increase. It can be suppressed by the provided attenuation characteristics.

(C) When the vehicle climbs over a protrusion during the braking operation During the braking operation, as described above, the control signal V has a larger value than during normal running, but the damping characteristic is proportional to the sprung vertical speed at that time. Since the above-described control is performed, the damping characteristic control according to the input condition from the road surface is performed, and therefore, the riding comfort of the vehicle can be ensured even for a protruding road surface input during the brake operation.

As described above, in this embodiment, the following effects can be obtained. Since a sufficient control force can be generated not only for the bounce but also for the roll and the pitch, it is possible to provide a vehicle suspension system excellent in ride comfort and steering stability.

Bounce, dive, and brake operation
In addition, it is possible to suppress the swing back when the brake operation is released.

[0048] Even for a protruding input during a brake operation, damping characteristic control according to a change in sprung vertical speed is performed, so that the riding comfort of the vehicle can be ensured.

In obtaining the bounce rate, pitch rate, and roll rate, different constants α,
Since β and γ are used, in the vehicle, even if the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different from each other, each rate can be accurately detected based on the sprung vertical speed.

Next, other embodiments will be described. In describing these embodiments, only differences from the first embodiment will be described. In addition, the first reference
The same reference numerals as those in the embodiments indicate the same objects.

(Second Embodiment) In the second embodiment, a part of the control unit 4 is different from that of the first embodiment, and the following equation 2 is used to obtain the control signal V.

[0052]

(Equation 2) That is, in the second embodiment, the bounce rate is independently obtained based on the sprung vertical speed of each wheel.

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

For example, in the embodiment, when variably controlling the damping characteristic on one stroke side on the extension side or the compression side, a shock absorber having a structure in which the reverse stroke side is maintained at a predetermined low damping characteristic is used. Control using a shock absorber having a structure in which the damping characteristics of the pressure side and the compression side simultaneously change can be performed.

[0055]

As described above, in the vehicle suspension system according to the present invention, the damping characteristics of each shock absorber are controlled by the damping characteristics control means to determine the difference between the bounce rate based on the sprung vertical speed and the sprung vertical speed between the front and rear of the vehicle. Control based on the control signal obtained from the pitch rate detected from the vehicle and the roll rate detected from the difference between the sprung up and down speeds of the right and left sides of the vehicle, so that not only bounce but also sufficient control force for pitch and roll This has the effect of improving ride comfort and steering stability.

When the brake operation is performed, the brake operation is released and then the pitch resonance frequency becomes 1
By providing a correction control unit that increases the proportional constant of the pitch rate during the / 2 cycle, it is possible to suppress dive during brake operation and swing back when releasing the brake operation, For protruding input,
By controlling the damping characteristic, the riding comfort of the vehicle can be ensured.

Further, in the device according to the second aspect, even when the sprung resonance frequency, the pitch resonance frequency, and the roll resonance frequency are different, proper damping control can be performed.

[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 characteristic diagram of a damping characteristic 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 main part of the control unit of the first embodiment.

FIG. 15 is a flowchart showing a control operation of the control unit of the first embodiment.

FIG. 16 is a time chart showing the operation of the control unit in the first embodiment.

FIG. 17 is a map showing a proportional constant with respect to a vehicle speed in the first embodiment.

FIG. 18 is a map showing a correction constant for a vehicle speed in the device of the first embodiment.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c sprung vertical speed detecting means d brake sensor e damping characteristic control unit f control means g correction control unit

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

Claims (2)

(57) [Claims] 1. A shock absorber interposed between a vehicle body side and each wheel side and capable of changing damping characteristics by damping characteristic changing means, and detecting a sprung vertical speed near a position where each shock absorber is provided. A sprung vertical speed detecting means, a brake sensor for detecting a brake operation state, a damping characteristic of each shock absorber, a pitch rate detected from a bounce rate based on a sprung vertical speed and a sprung vertical speed difference between front and rear of the vehicle and a vehicle body Control means having a damping characteristic control unit for controlling based on a control signal obtained from a roll rate detected from a difference between left and right sprung vertical speeds; provided in the control means; A correction control unit that increases the proportional constant of the pitch rate during a half cycle of the pitch resonance frequency after the release. Vehicle suspension system, characterized by that example. 2. The control signal is obtained by using a signal passed through a band-pass filter including a sprung resonance frequency of each of the front and rear wheels as a bounce rate, and using a band-pass filter including a pitch resonance frequency as a pitch rate. 2. The vehicle suspension device according to claim 1, wherein a signal passed through a band-pass filter including a roll resonance frequency is used as the roll rate.