JPH06293207A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To provide an advantage of ON-OFF switchover control system and eliminate a control delay in switchingover of the characteristics by switching over the damping force characteristic switchover positions of a shock absorber into a soft, extension side, and compression side hard positions with control signals obtained from a sprung vertical speed. CONSTITUTION:A sprung vertical acceleration signal from each vertical G sensor 1 is inputted into an interface circuit 4a of a control unit 4, a control signal is obtained in a CPU 4b, and each pulse motor 3 is driven by a drive circuit 4c to give each shock absorber SA a desired damping characteristics. Namely, when the control signal is within a value in both positive and negative dead band zones, it is switched over to soft position, when it exceeds, it is switched over to extension side hard position, and when it is a negative value, it is switched over to pressure side hard position. Also, when the control signal comes within a range set wider than a value in both positive and negative dead zones after it reaches a peak value, it is switched over from an extension side or compression side hard position to a soft position. Thus an advantage of ON-OFF switchover control system is provided, and a control delay in switchingover of the characteristics can be eliminated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, Japanese Patent Application Laid-Open No. 61-61600.
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 the direction discriminating codes of both are the same, the damping force characteristic is made hard and the two differ. When it is a sign, the damping force characteristic control based on the skyhook theory, such as softening the damping force characteristic, is performed independently for each of the four wheels.

[0004]

However, in the above-mentioned conventional apparatus, since the damping force characteristic switching control is performed in two steps of the hardware characteristic and the soft characteristic as described above, a predetermined value is set. Compared to the case of performing proportional control for signal input, it has the advantage that the structure of the damping force characteristic switching mechanism and the actuator in the shock absorber is simple and the cost is easy.
In the -OFF control, when the input frequency becomes high, the switching control of the damping force characteristic is likely to be delayed, and in particular, the transmissibility is conspicuously deteriorated in a frequency band (2 to 3 Hz) slightly higher than the sprung resonance frequency, There is a problem that a so-called lumpy feeling is generated and the riding comfort is deteriorated.

The present invention has been made by paying attention to the above-mentioned conventional problems, and has the advantage of an ON-OFF type damping force characteristic switching control system, and at the time of switching the damping force characteristic from the hard side to the soft side. An object of the present invention is to provide a vehicle suspension system that can eliminate a control delay.

[0006]

In order to achieve the above-mentioned object, a vehicle suspension system of the present invention is provided between each wheel and a vehicle body as shown in FIG. Switching between three damping force characteristics: an inflatable hard position where the compression side has a soft characteristic, a compression side hard position where the compression side has a hard characteristic and an expansion side has a soft characteristic, and a soft position where both the extension side and the compression side have a soft characteristic. A shock absorber a having a position, a vertical speed detecting means b for detecting a sprung vertical speed, and a control signal obtained from the sprung vertical speed are switched to a soft position when they are within a predetermined positive and negative dead zone threshold value. , When the positive dead zone threshold is exceeded, the extension side hard position is switched, and when the negative dead zone threshold is exceeded, the pressure side hard position is switched to the control signal. After reaching the peak value, when it is within the range of both positive and negative set values set based on the predetermined condition so that it becomes wider than the positive and negative dead zone threshold width, it becomes a soft position from the hard position on the extension side or the hard position on the compression side. And a damping force characteristic control means c for switching to.

[0007]

In the vehicle suspension system of the present invention, as described above,
When the control signal based on the sprung vertical velocity is above the positive dead zone threshold, it is switched to the extend side hard position where the extension side has a hard characteristic and the compression side has a soft characteristic, and is above the negative dead zone threshold. At this time, the pressure side is switched to a hard side where the compression side has a hard characteristic and the extension side has a soft characteristic.
When the direction discrimination codes of the unsprung relative speeds match, the vehicle side vibration suppression force (control force) is increased by making the stroke side of the shock absorber a hard characteristic at that time, and when they do not match, the shock absorber at that time is Damping force characteristic control based on the Skyhook theory, such as weakening the vibration transmission force (excitation force) on the spring by making the stroke side a soft characteristic, is performed without detecting the relative speed. .

Since the switching to the soft characteristic direction is performed without driving the actuator, the frequency of switching is reduced as compared with the conventional damping force characteristic control based on the skyhook theory, and the control response and the actuator are controlled. The durability can be improved.

Further, after the control signal has passed the peak value,
Switching control to the soft position is started from the time when it returns to within the range of both positive and negative set values.After that, by the time the control signal returns to both the positive and negative dead zone thresholds, it has already been switched to the soft position position. Becomes That is, in consideration of the drive time of the actuator, the switching from the expansion side hard position or the compression side hard position side to the soft position direction is started early,
While having the advantage of the N-OFF-like damping force characteristic switching control system, it is possible to eliminate the delay in switching control to the soft position.

[0010]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration will be described. FIG. 2 is a configuration explanatory view showing the vehicle suspension system of the embodiment, in which four shock absorbers SA are provided between the vehicle body and the four wheels. 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 comprises an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a includes the above-mentioned vertical G sensors 1 to The acceleration signal of is input. In the interface circuit 4a, a set of three filter circuits shown in FIG. 13 is provided for each upper and lower G sensor 1. That is,
The LPF1 is a low-pass filter circuit for removing noise in a high frequency range (30 Hz or more) from the signals sent from the upper and lower G sensors 1, and the LPF2 is a signal indicating the acceleration passed through the low-pass filter circuit LPF1. A low-pass filter circuit for integrating and converting to a sprung vertical velocity, and the BPF is a sprung vertical velocity V as a bounce component that passes a frequency range including a sprung resonance frequency.
A bandpass filter circuit for obtaining n.

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 sectional view showing a portion of the piston 31, and as shown in this figure, the piston 31 is formed with through holes 31a and 31b, and each through hole is formed. 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. The adjuster 40 is rotated by the pulse motor 3 via the control rod 70 (see FIG. 4). Further, the stud 38 is formed with a first port 21, a second port 13, a third port 18, a fourth port 14, and a fifth port 16 in order from the top.

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

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

That is, the shock absorber SA is configured to be switchable between three damping positions by rotating the adjuster 40. That is, as shown in FIG. 6, when the adjuster 40 is rotated counterclockwise by 60 ° from the central position (hereinafter referred to as the soft position SS) where both the extension side and the compression side have soft characteristics,
At the position where the extension side has the hard characteristic and the compression side has the soft characteristic (hereinafter referred to as the extension side hard position HS), on the contrary, when the adjuster 40 is rotated clockwise by 60 °,
The structure is such that the compression side has a hard characteristic and the extension side has a soft characteristic (hereinafter, referred to as a compression side hard position SH).

By the way, in FIG. 6, the KK cross section, the LL cross section, the MM cross section, and the MM cross section in FIG. 7, FIG. 8, and FIG. 9, 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.

First, step 101 is a step of reading the sprung vertical velocity Vn. As described above, the sprung vertical velocity Vn is obtained by comparing the vertical acceleration signals obtained from the vertical G sensors 1 with the filter circuits LPF1 and LPF.
2, the sprung vertical velocity Vn as a bounce component obtained by processing with the BPF, that is, in the vicinity of each wheel is read. The sprung vertical velocity Vn is given as a positive value when the sprung vertical acceleration is in the upward direction, and is given as a negative value when it is in the downward direction.

In the following step 102, it is determined whether or not the sprung vertical velocity Vn is a value between a predetermined positive dead zone threshold value δ _T and a negative dead zone threshold value −δ _C, and YES is determined. If there is, proceed to step 103, and shock absorber S
A is switched to the soft position SS and controlled, and N
If it is O, the process proceeds to step 104.

In step 104, the sprung vertical velocity Vn
Is above the predetermined positive dead zone threshold value δ _T , and if YES, the routine proceeds to step 105, where the shock absorber SA is controlled to switch to the extension side hard position HS, and if it is NO. For example, proceed to step 111, and set the shock absorber SA to the compression side hard position S.
Control to switch to H.

In step 106, the sprung vertical velocity Vn
Read. In the following step 107, it is determined whether or not the sprung vertical velocity Vn has reached the positive peak value Vp, and YE
If S, the process proceeds to step 108, and if NO, the process returns to step 106.

At step 108, a positive set value Vx is obtained based on the following arithmetic expression. Vx = Vp * sin {sin- ¹ ([delta] _T / Vp)-[omega] o [Delta] t} Vp: positive peak value of sprung vertical speed [omega]: angular speed = 2 [pi] * fo (fo: sprung resonance frequency) [Delta] t: Pulse motor drive time (switching time) That is, in the above equation, as shown in FIG. 15, the extension side hard position HS is switched to the soft position SS with reference to the sprung vertical velocity input waveform of the sprung resonance frequency fo. The value of the sprung vertical velocity Vn at the point x, which is calculated back from the point w at which the sprung vertical velocity Vn crosses the positive dead zone threshold value δ _T by the time width t required, is determined as the positive set value Vx.

In step 109, the sprung vertical velocity Vn
Read. In step 110, the sprung vertical velocity Vn
Is below the positive set value Vx, it is judged whether YE
If S, the process proceeds to step 103, and if NO, the process returns to step 109.

In step 112, the sprung vertical velocity Vn is read. In the following step 113, it is determined whether or not the absolute value | Vn | of the sprung vertical velocity has reached the absolute value | Vp '| of the negative peak value. If YES, the process proceeds to step 114, and if NO. If there is, return to step 112.

In step 114, a negative set value Vx 'is obtained based on the following arithmetic expression. Vx ′ = | Vp ′ | · sin {sin ⁻¹ (| δ _C | / | Vp ′ |) −ωo · Δt} Vp ′ is a negative peak value of the sprung vertical velocity.

In step 115, the sprung vertical velocity Vn
Read. In step 116, it is determined whether or not the absolute value | Vn | of the sprung vertical velocity has dropped below the negative set value Vx, and if YES, the process proceeds to step 103,
The shock absorber SA is controlled to switch to the soft position SS, and if NO, the process returns to step 115. With the above, one control flow is completed, and thereafter, the above steps are repeated.

Next, the control operation of the control unit 4 will be described with reference to the time chart of FIG. When the sprung vertical velocity Vn changes as shown in this figure, the sprung vertical velocity Vn becomes a predetermined positive / negative dead zone threshold −δ _C , δ _T.
If the value is between the values, the shock absorber SA is controlled to the soft position SS (position where the rotation angle of the pulse motor 3 is 0).

When the sprung vertical velocity Vn exceeds the positive dead zone threshold value δ _T , the extension side hard position HS is switched to control.

The sprung vertical velocity Vn is the peak value Vp.
After passing, when the value falls below the positive set value Vx,
The control for switching the shock absorber SA to the soft position SS is started. After that, at the point w at which the sprung vertical velocity Vn further decreases and crosses the positive dead zone threshold value δ _T , the pulse motor 3 is already started. The rotation angle is switched to the position of 0 (soft position SS position). That is, in consideration of the drive time of the pulse motor 3, by starting the switching from the extension side hard position HS side to the soft position SS direction earlier, it is possible to eliminate the switching control delay to the soft position SS.

After the sprung vertical velocity Vn crosses the zero point, if the absolute value of the sprung vertical velocity | Vn | becomes the negative dead zone threshold absolute value | δ _C | Control is switched to SH.

Further, after the absolute value of the sprung vertical velocity | Vn | exceeds the absolute value of the peak value | Vp '|, a negative set value Vx is obtained.
'When the pressure falls below the value, control for switching the shock absorber SA to the soft position SS is started. After that, the absolute value of the sprung vertical velocity | Vn | further decreases and the negative dead zone threshold value is reached. At a point w ′ crossing the absolute value | δ _C |, the rotation angle of the pulse motor 3 has already been switched to a position of 0 (soft position SS position). That is, the pulse motor 3
By starting the switching from the pressure side hard position SH side to the soft position SS direction earlier in consideration of the driving time of, the control delay to switch to the soft position SS can be eliminated.

Next, the content of the damping force characteristic control based on the skyhook theory will be described with reference to the time chart of FIG.

In FIG. 16, in region a, the sprung vertical velocity Vn is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative velocity is still negative. Since the stroke of the absorber SA is on the pressure stroke side), the shock absorber SA is controlled to the extension side hard position HS based on the direction of the sprung vertical velocity Vn at this time. In the region a, the pressure stroke side, which is the stroke of the shock absorber SA at that time, has soft characteristics.

In the region b, the sprung vertical velocity Vn remains a positive value (upward), and the relative velocity is switched from a negative value to a positive value (the stroke of the shock absorber SA is on the extension stroke side). Since it is a region, at this time, the sprung vertical velocity Vn
The shock absorber SA is controlled to the extension side hard position HS based on the direction of, and the stroke of the shock absorber is also the extension stroke. Therefore, in this area b, the extension side of the shock absorber SA at that time is It has hard characteristics.

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

The area d is an area in which the sprung vertical velocity Vn remains a negative value (downward) and the relative velocity changes from a positive value to a negative value (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 position SH based on the direction of the sprung vertical velocity Vn, and the stroke of the shock absorber is also the pressure stroke. The pressure characteristic side of the shock absorber SA has a hard characteristic.

Areas other than the areas a, b, c, d are controlled to the soft position SS by threshold control, or both the extension side and compression side hard positions H.
It is in the state of being switched from S, SH to the soft position SS.

As described above, in this embodiment, when the sprung vertical speed and the relative speed between the sprung portion and the unsprung portion have the same sign (area b, area d), the shock absorber S at that time.
Damping force characteristic control based on the skyhook theory, in which the stroke side of A is controlled to have a hard characteristic, and when the signs are different (area a, area c), the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic. The same control as above is performed without detecting the relative speed between the sprung and unsprung parts. Further, in this embodiment, when the region a shifts to the region b and the region c shifts to the region d, the damping force characteristic is switched without driving the pulse motor 3.

As described above, in this embodiment, the effects listed below can be obtained. In addition to having the advantage of the ON-OFF type damping force characteristic switching control system, it becomes possible to eliminate the control delay when switching the damping force characteristic from the hardware direction to the software direction.

Compared with the conventional damping force characteristic control based on the skyhook theory, the switching frequency of the damping force characteristic is reduced, so that the control response can be improved and
The durability of the pulse motor 3 can be improved.

Since the damping force characteristic control based on the skyhook theory can be performed only by detecting the sprung vertical velocity as the vehicle behavior, the cost can be reduced.

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.

For example, in the embodiment, the set value is changed and set according to each peak value of the sprung vertical speed.
It is possible to change and set based on other factors,
It can also be a fixed value.

In the embodiment, the sprung vertical velocity signal is used alone as the control signal. However, the control signal may take other factors such as pitch rate and roll rate into consideration.

Further, in the embodiment, the upper and lower G sensors are independently provided at the positions near the respective wheels, but only one is required to perform only the bounce control of the vehicle.

[0047]

As described above, in the vehicle suspension system of the present invention, when the control signal obtained from the sprung vertical velocity is within the predetermined positive and negative dead zone threshold values, both the extension side and the compression side are soft. Switch to the soft position, which is the characteristic, and when the positive dead zone threshold is exceeded, switch to the hard position where the hard side is the stretch side and the soft side is the stretch side.
When the negative dead zone threshold is exceeded, the pressure side hard position is set so that the compression side has a hard characteristic and the extension side has a soft characteristic, so that switching to the soft characteristic direction can be performed without driving the actuator. Therefore, compared with the conventional damping force characteristic control based on the skyhook theory, the switching frequency is reduced, and the control response and the durability of the actuator can be improved.

Further, when the control signal reaches the peak value and becomes within the range of both the positive and negative set values set based on a predetermined condition so as to be wider than the positive and negative dead zone threshold width, the extension side hard position is set. Or by switching from the compression side hard position to the soft position, O
In addition to having the advantage of the N-OFF damping force characteristic switching control system, it is possible to eliminate the control delay when switching the damping force characteristic from the hardware direction to the software direction.

[Brief description of drawings]

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

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

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

FIG. 4 is a cross-sectional view showing a shock absorber applied to the apparatus of the embodiment.

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

FIG. 6 is a damping force characteristic diagram corresponding to a rotation angle of a pulse motor in the shock absorber.

FIG. 7 is a view of K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 8 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. 9 is an N in FIG. 5 showing a main part of the shock absorber.
It is a -N sectional view.

FIG. 10 is a damping force characteristic diagram of the extension side hard position HS of the shock absorber.

FIG. 11 is a damping force characteristic diagram of the soft position SS of the shock absorber.

FIG. 12 is a damping force characteristic diagram of the pressure side hard position SH of the shock absorber.

FIG. 13 is a block diagram showing a main part of a control unit in the apparatus of the embodiment.

FIG. 14 is a flowchart showing the control operation of the control unit in the embodiment apparatus.

FIG. 15 is a time chart showing the control operation of the control unit in the apparatus of the embodiment.

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

[Explanation of symbols]

 a shock absorber b sprung vertical velocity detection means c damping force characteristic control means

Claims (1)

[Claims] 1. An expansion side hard position, which is provided between each wheel and a vehicle body and has a hard characteristic on the expansion side and a soft characteristic on the compression side, and a compression side hard position on which the compression side has a hard characteristic and the expansion side has a soft characteristic. A shock absorber having three damping force characteristic switching positions of soft positions on both the pressure side and the compression side, vertical speed detection means for detecting the sprung vertical speed, and a control signal obtained from the sprung vertical speed are predetermined. When it is within both the positive and negative dead zone thresholds, it switches to the soft position, when it exceeds the positive dead zone threshold, it switches to the extension side hard position, and when it exceeds the negative dead zone threshold, it switches to the pressure side hard position, Both positive and negative settings are set based on predetermined conditions so that they become wider than the positive and negative dead zone threshold width after the control signal reaches the peak value. Vehicle suspension system, characterized as they become within the damping force characteristic control means for switching the soft position from the extension side hard position or pressure side hard positions, further comprising a.