JPH0648148A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To obtain sufficient damping performance to the moment of inertia with simple constitution so as to improve control stability by controlling the damping characteristic of each shock absorber on the basis of a control signal obtained by a bounce rate based on the sprung vertical speed, a pitch rate and a roll rate. CONSTITUTION:A suspension device for, a vehicle is provided with a shock absorber (b) interposed between the body side and each wheel side and formed in such a way as to be changeable in its damping characteristic by a damping characteristic changing means (a), a sprung vertical acceleration detecting means (c) for detecting the sprung vertical acceleration near a position where each shock absorber (b) is provided, and a sprung vertical speed detecting means (d) for detecting the sprung vertical speed. A damping characteristic control means (e) controls the damping characteristic of the shock absorber (b) on the basis of a control signal obtained by a bounce rate based on the sprung vertical speed, a pitch rate detected from the sprung vertical f acceleration difference between the front and rear sides of a body, and a roll rate detected from the sprung vertical acceleration difference between the right and left sides of the body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling the damping characteristics of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension device for controlling the damping characteristic of a shock absorber, for example, Japanese Patent Laid-Open No. 61-
The one described in Japanese Patent No. 163011 is known.

This conventional vehicle suspension system detects the sprung vertical speed and the relative speed between the sprung and unsprung parts, and when both have the same sign, the damping characteristic is made hard, and when the two have different signs, the damping characteristic. The damping characteristic control based on the skyhook theory, such as softening, was performed independently for the four wheels.

[0004]

However, since the above-mentioned conventional apparatus has the above-mentioned structure, when the characteristics of the hardware are suitable when the vehicle body is moving in the bounce direction, With respect to the body movement in which bounce and pitching are coupled, a moment of inertia of the body around the center of gravity of the body is added to the sprung mass, so the damping force (control force) is insufficient and the steering stability is poor. There was a point.

Further, although a device for controlling the roll and the pitching is also known, these are separately controlled, and other sensors such as a steering sensor are required, which complicates the control and parts. There was a problem that the score also increased.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to improve steering stability by obtaining a sufficient vibration damping property against the moment of inertia while having a simple structure. Is intended.

[0007]

In order to achieve the above-mentioned object, the vehicle suspension system according to claim 1 of the present invention is arranged between the vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. An intervening shock absorber b whose damping characteristic can be changed by the damping characteristic changing means a, a sprung vertical acceleration detecting means c for detecting sprung vertical acceleration in the vicinity of the position where each shock absorber b is provided, and each shock The sprung vertical velocity detecting means d for detecting the sprung vertical velocity in the vicinity of the position where the absorber b is provided, and the damping characteristics of each shock absorber b are the bounce rate based on the sprung vertical velocity and the sprung vertical velocity on the front and rear of the vehicle body. Damping characteristic control means for controlling based on a control signal obtained from the pitch rate detected from the acceleration difference and the roll rate detected from the sprung vertical acceleration difference on the left and right of the vehicle body It has a configuration that has a door.

According to a second aspect of the present invention, in addition to the above structure, the vehicle suspension system includes the shock absorber in which the expansion side has a variable damping characteristic and the compression side has a low damping characteristic and the compression side has a variable damping characteristic. Is formed in a structure having three regions, that is, a compression side hard region where the extension side is fixed to the low damping characteristic and a soft region where both the extension side and the compression side are low damping characteristics, and the damping characteristic control means is provided with a positive control signal. When the threshold value is exceeded, the shock absorber is controlled in the expansion side hard area, and when the control signal is below the negative threshold value, the shock absorber is controlled in the compression side hard area, and the control signal is between the positive and negative threshold values. At the time of, the shock absorber was configured to be controlled in the soft region.

Further, the vehicle suspension system according to the third aspect is provided with a shock absorber b interposed between the vehicle body side and each wheel side, the damping characteristic of which can be changed by the damping characteristic changing means a, and each shock absorber b. Sprung vertical acceleration detecting means c for detecting the sprung vertical acceleration in the vicinity of the specified position
And a sprung vertical velocity detecting means d for detecting the sprung vertical velocity near the position where each shock absorber b is provided.
And a relative speed detecting means f for detecting the relative speed between the sprung and unsprung portions near the position where each shock absorber a is provided, and the damping characteristic of each shock absorber b as a bounce rate based on the sprung vertical speed. When the control signal obtained from the pitch rate detected from the sprung vertical acceleration difference between the front and rear of the vehicle body and the roll rate detected from the left and right sprung vertical acceleration difference of the vehicle body and the relative speed between the sprung and unsprung have the same sign While increasing the damping characteristic, the damping characteristic controlling means e for controlling the damping characteristic to the minimum when the sign is different is adopted.

[0010]

When bounce, pitch and roll are detected by the sprung acceleration detecting means and the sprung speed detecting means, the damping characteristic control means obtains a control signal based on the bounce rate, pitch rate and roll rate. The damping characteristic of the shock absorber is controlled according to the control signal. Therefore, sufficient control force can be obtained not only for bounce but also for pitch and roll.

Further, in the apparatus according to the second aspect, when the control signal is equal to or more than the positive threshold value, the shock absorber is controlled in the expansion side hard region (the compression side is fixed to the low damping characteristic), and the control signal is negative. The shock absorber is controlled in the compression side hard region (fixed to the low damping characteristic on the extension side) when it is below the threshold value, and the shock absorber is controlled in the soft region when the control signal is between the positive and negative threshold values. is there.

According to the third aspect of the present invention, in the damping characteristic control means, the control signal obtained as described above and the sprung / unsprung relative speed detected by the relative speed detection means have the same sign. When the two have different signs, the attenuation characteristic is minimized. On the other hand, the attenuation characteristic is controlled based on the so-called skyhook theory to minimize the attenuation characteristic when the two have different signs. Sufficient control power can be obtained for pitch and roll.

[0013]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system of a first embodiment which is an embodiment of the invention described in claims 1, 2 and 4, and is interposed between a vehicle body and four wheels. Four shock absorbers SA ₁ , SA ₂ , SA ₃ , SA ₄
(Note that in describing the shock absorber, when these four are collectively referred to, and when describing their common configuration, they are simply referred to as SA.). A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 that detects vertical acceleration is provided on the vehicle body in the vicinity of each shock absorber SA. Further, a control unit 4 is provided near the driver's seat to input a signal from each vertical G sensor 1 and output a drive control signal to the pulse motor 3 of each shock absorber SA.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c. Signal is input. In the interface circuit 4a, a set of five filter circuits shown in FIG. 14 is provided for each upper and lower G sensor 1. That is, LP
F1 is a low-pass filter circuit for removing noise in the high frequency range (30 Hz or more) from the signals sent from the upper and lower G sensors 1. The BPF 1 allows a bounce component signal v (v ₁ , v
₂ , v ₃ , v ₄ The numbers ₁ , ₂ , ₃ , ₄ correspond to the positions of the shock absorbers SA. The same applies to the following. ) Is a band pass filter circuit that forms BP
F2 is a bandpass filter circuit that passes the frequency range including the pitch resonance frequency to form the pitch component signal a (a ₁ , a ₂ , a ₃ , a ₄ ). The BPF ₃ is a bandpass filter circuit that passes a frequency range including a roll resonance frequency and forms a roll component signal a ′ (a ₁ ′, a ₂ ′, a ₃ ′, a ₄ ′). The LPF2 is a low-pass filter circuit for integrating a signal indicating the acceleration that has passed through the band-pass filter circuit BPF1 and converting it into a sprung vertical velocity. Incidentally, in this embodiment, the sprung resonance,
Although the case where the pitch resonance and the roll resonance frequencies are different is taken as an example, when the resonance frequencies are similar, only the BPF 1 is required as the bandpass filter.

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

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

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

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

In other words, the shock absorber SA is constructed so that the damping characteristic can be changed in multiple stages with the characteristics shown in FIG. 6 on both the extension side and the compression side by rotating the adjuster 40. That is, as shown in FIG. 7, both the extension side and the compression side are in the soft state (hereinafter, the soft region S
When the adjuster 40 is rotated counterclockwise from (S), the damping characteristic can be changed in multiple steps only on the extension side, and the compression side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the extension side hard region HS). On the contrary, when the adjuster 40 is rotated clockwise, the damping characteristic can be changed in multiple steps only on the compression side, and the extension side becomes a region where the low damping characteristic is fixed (hereinafter referred to as the compression side hard region SH). There is.

By the way, in FIG. 7, the KK cross section, the LL cross section and the MM cross section, and the NN cross section in FIG. 8, FIG. 9, and FIG. 10, and the damping force characteristics at each position are shown in FIGS.

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

In step 101, each vertical G sensor 1,
The vertical acceleration obtained from 1, 1, 1 is applied to each filter circuit L.
This is a step of performing processing by PF1, BPF1, BPF2, BPF3, LPF2 to obtain a bounce component signal v, a pitch component signal a, and a roll component signal a '.

Step 102 uses Equation 1 below,
This is a step of calculating a control signal V (V ₁ , V ₂ , V ₃ , V ₄ ) for the position of each wheel based on each component signal v, a, a ′.

[0025]

[Equation 1] Note that _{α f, β f, γ f} , the proportionality constant alpha _r of the front wheels, beta _r, gamma _r is the proportionality constant of the rear wheel In each formula, are enclosed in the first alpha _f, alpha _r The part 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.

Step 103 is a step of judging whether or not the control signal V is equal to or more than a predetermined threshold value δ _T , and if YES, the process proceeds to step 104, and if NO, the step 1
Go to 05.

Step 104 is a shock absorber S
This is a step of controlling A to the extension side hard area HS.

Step 105 is a step of judging whether or not the control signal V is a value between a predetermined threshold value δ _T and a threshold value −δ _{C. If} YES, then the routine proceeds to step 106, and if NO. Go to step 107.

Step 106 is a shock absorber S
This is a step of controlling A in the soft area SS.

Step 107 is a step which is displayed for the sake of convenience, and N is omitted in steps 103 and 105.
When it is determined to be O, the control signal V is equal to or lower than the predetermined threshold value −δ _C , and in this case, the process proceeds to step 108.

Step 108 is a shock absorber S
This is a step of controlling A to the pressure side hard area SH.

Next, the operation of the embodiment apparatus will be described with reference to the time chart of FIG.

When the sprung vertical speed changes as shown by the control signal V in this figure, as shown in the figure, the control signal V
Is a value between the predetermined thresholds δ _T and −δ _C ,
The shock absorber SA is controlled in the soft area SS.

When the control signal V becomes equal to or higher than the threshold value δ _T , the expansion side hard region HS is controlled to fix the compression side to the low damping characteristic, while the expansion side damping characteristic is made proportional to the control signal V. To change. At this time, the damping characteristic C is controlled so that C = kV.

When the control signal V becomes equal to or lower than the threshold value -δ _{C, the} compression side hard region SH is controlled to fix the extension side to the low damping characteristic, while making the compression side damping characteristic proportional to the control signal V. To change. Also at this time, the damping characteristic C is C = k ·
It is controlled so as to be V.

Further, in the time chart of FIG.
In the region a, the control signal V based on the sprung vertical velocity is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative velocity is still a negative value (shock absorber SA Since the stroke is on the pressure 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,
Therefore, in this area, the shock absorber SA at that time
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 velocity remains a positive value (upward) and the relative velocity is from a negative value to a positive value (the stroke of the shock absorber SA is the extension 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, and the stroke of the shock absorber is also the extension stroke. In this region, the extension side, which is the stroke of the shock absorber SA at that time, has a hardware characteristic proportional to the value of the control signal V.

In the area c, the control signal V based on the sprung vertical velocity is reversed from a positive value (upward) to a negative value (downward), but at this time, the relative velocity is still positive. (The stroke of the shock absorber SA is on the extension side). Therefore, 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 side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

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

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

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

Next, other embodiments will be described, but in describing these embodiments, only the differences from the first embodiment will be described. Also, the first reference numeral
The same reference numerals as those in the embodiment denote 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 when calculating the control signal V, the arithmetic expression shown in the following formula 2 is used.

[0044]

[Equation 2] That is, in the second embodiment, the bounce rate is independently obtained based on the sprung vertical velocity of each wheel, which is control in which the bounce component is emphasized.

(Third Embodiment) In the third embodiment, as the shock absorber SA of a variable damping characteristic type, when the pulse motor 3 is driven, as shown in FIG. , With a well-known structure that changes from high damping to low damping (for example, see Japanese Utility Model Laid-Open No. 63-112914).
This is an example in which the damping characteristic control based on the conventional skyhook theory is performed by using the above (see Japanese Patent Publication).

Therefore, in this third embodiment, as shown in FIG. 19, in addition to the sprung G sensor 1 as an input means, a load sensor (sprung / unsprung relative speed detecting means) 6, 6, is provided.
6, 6 are provided. The load sensor 6 is
As shown in FIG. 17, the damping force (corresponding to the relative speed) F, which is provided on the piston rod 7 below the mounting portion of each shock absorber SA to the vehicle body and is generated by the shock absorber SA, is used as a load. It is designed to detect.

Control unit 300 of the third embodiment
20 will be described with reference to the flowchart of FIG. 20. Step 301 is to determine the damping force F detected by the load sensor 6.
Is a step of reading, and after this processing, steps 101 and 102 similar to those in the first embodiment are performed, and then the process proceeds to step 302.

In step 302, the damping force F and the control signal V
YES in the step of determining whether and are the same sign
Then, the process proceeds to step 303, and if NO (different sign), the process proceeds to step 304.

In step 303, the damping force F is F = k
The attenuation characteristic is changed so that it becomes V.

In step 304, the damping characteristic of the shock absorber SA is controlled so that both the extension and the compression have the minimum damping characteristic.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the invention.

[0052]

As described above, in the vehicle suspension system of the present invention, the damping characteristic control means determines the damping characteristics of the shock absorbers based on the sprung vertical velocity and the sprung vertical acceleration difference between the front and rear of the vehicle body. Since the control is performed based on the control signal obtained from the pitch rate detected from the pitch rate and the roll rate detected from the sprung vertical acceleration difference between the left and right of the vehicle body, not only bounce, but also sufficient control force not only for pitch and roll As a result, a sufficient control force can be secured even with respect to the body movement in which bounce and pitch are coupled, and the effect of being able to improve the riding comfort and steering stability can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a claim showing a vehicle suspension device of the present invention.

FIG. 2 is a structural explanatory view showing a vehicle suspension device of the first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the first embodiment.

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

FIG. 5 is an enlarged cross-sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to the piston speed of the shock absorber.

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

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

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

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

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

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

FIG. 14 is a block diagram showing a main part of a control unit of the first embodiment.

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

FIG. 16 is a time chart showing the operation of the first embodiment device.

FIG. 17 is a sectional view showing a shock absorber applied to the third embodiment.

FIG. 18 is a characteristic diagram of damping characteristics of the shock absorber of the third embodiment device.

FIG. 19 is a system block diagram showing a device of a third embodiment.

FIG. 20 is a flowchart showing the control operation of the control unit of the third embodiment device.

[Explanation of symbols]

 a damping characteristic changing means b shock absorber c sprung vertical acceleration detecting means d sprung vertical speed detecting means e damping characteristic controlling means f relative speed detecting means

Claims (4)

[Claims] 1. A shock absorber which is interposed between a vehicle body side and each wheel side and whose damping characteristic can be changed by a damping characteristic changing means, and a sprung vertical acceleration in the vicinity of the position where each shock absorber is provided is detected. The sprung vertical acceleration detection means, the sprung vertical speed detection means for detecting the sprung vertical speed in the vicinity of the position where each shock absorber is provided, and the damping characteristics of each shock absorber, the bounce rate based on the sprung vertical speed. And a damping characteristic control means for performing control based on a control signal obtained from a pitch rate detected from the difference in sprung vertical acceleration between the front and rear of the vehicle body and a roll rate detected from the difference in sprung vertical acceleration on the left and right sides of the vehicle body. A vehicle suspension device characterized by: 2. The shock absorber includes an expansion side hard area in which the expansion side is variable in damping characteristics and the compression side is fixed in low damping characteristics, and a compression side hard area in which the compression side is variable in damping characteristics and expansion side is fixed in low damping characteristics is expanded. It is formed in a structure having three regions, that is, a soft region having a low damping characteristic on both the compression side and the compression side, and the damping characteristic control means controls the shock absorber in the expansion side hard region when the control signal is a positive threshold value or more. Then
The shock absorber is controlled in the pressure side hard area when the control signal is below the negative threshold value, and the shock absorber is controlled in the soft area when the control signal is between the positive and negative threshold values. The vehicle suspension system according to claim 1. 3. A shock absorber which is interposed between the vehicle body side and each wheel side and whose damping characteristic can be changed by a damping characteristic changing means, and a sprung vertical acceleration in the vicinity of the position where each shock absorber is provided is detected. Sprung up / down acceleration detection means, sprung up / down speed detection means for detecting sprung up / down speed near the position where each shock absorber is installed, and sprung / unsprung position near the position where each shock absorber is installed Relative speed detection means for detecting the relative speed between the vehicle and the damping characteristics of each shock absorber, the pitch rate detected from the bounce rate based on the sprung vertical speed and the sprung vertical acceleration difference between the front and rear of the vehicle When the control signal obtained from the roll rate detected from the difference and the relative speed between the sprung and unsprung have the same sign, the damping characteristics are increased. Is to one, the vehicle suspension system, characterized in that it and a damping characteristic control means for controlling the damping characteristic to a minimum when different signs. 4. In obtaining the control signal, the bounce rate uses a signal that has passed through a bandpass filter including the sprung resonance frequencies of the front and rear wheels, and the pitch rate uses a bandpass filter that includes the pitch resonance frequency. 4. The vehicle suspension system according to claim 1, wherein a signal that has passed through a band pass filter including a roll resonance frequency is used as the roll rate.