JPH06344749A - Vehicle suspension system - Google Patents

Abstract

PURPOSE:To secure a damping property in generating the extent of damping force characteristics conformed to variations in a spring constant by controlling this damping force characteristic of a shock absorber to a value proportional to a car behavioral value on the basis of a specified reference proportional constant and, when a relative displacement goes beyond the displacement value, compensating the proportional constant to such a value as higher than the reference. CONSTITUTION:This suspension is provided with a spring member (a) whose spring constant, in relation to a relative displacement between both sprung and springing systems to be interposed between a car body and each wheel, and simultaneously it has a damping force characteristic variable type shock absorber (c) with a damping force characteristic altering means (b) being interposed between the car body and the respective wheels, including at least a relative displacement detecting means (d) lying between both these sprung and springing systems, and a car behavior detecting means (e). Likewise, it is also provided with a damping force characteristic control means (f) controlling a damping force characteristic of the shock absorber (c) to such a value as being proportional to a car behavioral value on the basis of the specified reference proportional constant, and a compensation control part (g) being installed in this damping force characteristic control means (f) and compensating the proportional constant to such a value as higher than the reference when the relative displacement goes beyond the specified value.

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 Publication No.
The one described in Japanese Patent No. 502439 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 signs of the both coincide, the stroke side of the shock absorber at that time is sprung at that time. By controlling the damping force characteristics by multiplying the vertical speed by a predetermined proportional constant, the vibration suppression force (damping force) of the vehicle is increased, and when the direction identification codes of the two do not match, the stroke side of the shock absorber at that time The damping force characteristic control based on the Karnop control theory (Skyhook theory), such as weakening the vibration transmission force (exciting force) to the sprung by softening the damping force characteristic of 4 wheels, is performed independently for each of the four wheels. It was a thing.

[0004]

However, in the above-mentioned conventional device, the damping force characteristic of the shock absorber is set to a value proportional to the sprung vertical velocity, as described above. The present invention was applied to a vehicle suspension system having a spring member having a non-linear characteristic in which the spring constant between the sprung and unsprung parts relative to the relative displacement between the upper and unsprung parts (stroke amount of the shock absorber) becomes large on the side of large relative displacement. In this case, there is a problem that the damping force becomes insufficient when the relative displacement becomes large, which deteriorates the vibration damping property.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a vehicle suspension system capable of preventing occurrence of insufficient damping force due to a change in spring constant. It is a thing.

[0006]

In order to achieve the above object, the vehicle suspension system of the present invention is interposed between the vehicle body side and each wheel side as shown in the claim correspondence diagram of FIG. A shock absorber having a variable damping force characteristic, which has a spring member a having a non-linear characteristic of a spring constant with respect to relative displacement between an unsprung part and an unsprung part, and damping force characteristic changing means b interposed between a vehicle body side and each wheel side. c, a vehicle behavior detecting means e for detecting a vehicle behavior including at least a relative displacement detecting means d for detecting a relative displacement between sprung and unsprung, and a damping force characteristic of the shock absorber c based on a predetermined reference proportional constant. The damping force characteristic control means f for controlling to a value proportional to the vehicle behavior amount, and when the relative displacement exceeds a predetermined value provided in the damping force characteristic control means f, the proportional constant of the damping force characteristic control is used as a reference. It's a constant of proportionality A correction control unit g be corrected to a higher value,
And means.

[0007]

In the vehicle suspension system of the present invention, when the vehicle behavior is detected by the vehicle behavior detecting means, the damping force characteristic control means sets the damping force characteristic of the shock absorber to the vehicle behavior amount based on a predetermined reference proportional constant. Control to a proportional value.

When the relative displacement detected by the relative displacement detecting means exceeds a predetermined displacement value, the correction controller corrects the proportional constant of the damping force characteristic control to a value higher than the reference proportional constant. The damping force characteristic of the shock absorber is corrected and controlled to a value higher than that under normal conditions. Therefore, even if the spring constant becomes large, it is possible to secure sufficient vibration damping property.

[0009]

Embodiments of the present invention will be described with reference to the drawings. First, the configuration of the embodiment will be described. FIG. 2 is a configuration explanatory view showing the vehicle suspension system of the embodiment, in which the four shock absorbers SA are interposed between the vehicle body and the four wheels.
Is provided. And each shock absorber SA
A vertical acceleration sensor (hereinafter referred to as a vertical G sensor) 1 for detecting vertical acceleration is provided on the vehicle body in the vicinity of the vehicle body side mounting portion and the wheel side mounting portion of each shock absorber SA. Is provided with a stroke sensor 6 as a relative displacement detecting means for detecting relative displacement between the sprung portion and the unsprung portion. A control unit 4 is provided near the driver's seat to input signals from the vertical G sensor 1 and the stroke sensor 6 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. And the vehicle speed signal from the stroke sensor 2 are input. In the interface circuit 4a, a set of three filter circuits shown in FIG. 14 is provided for each upper and lower G sensor 1. That is, LPF
Reference numeral 1 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 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 a BPF is a band-pass filter circuit for passing a frequency range including a sprung resonance frequency to obtain a sprung vertical velocity V as a bounce component. Is.

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.

FIG. 15 shows the spring constant characteristic of the suspension spring 36 with respect to the relative displacement Sh between the sprung part and the unsprung part. As shown in FIG. 15, a predetermined relative displacement (threshold value) -Ss. When it exceeds the range of Ss to Ss, the spring constant with respect to the relative displacement Sh changes so as to increase in a non-linear characteristic.

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.

In other words, the shock absorber SA is constructed so that the damping force characteristic can be changed in multiple stages on both the extension side and the compression side with the characteristic shown in FIG. 6 by rotating the adjuster 40. That is, as shown in FIG.
Both the pressure side are soft (hereinafter soft area SS
When the adjuster 40 is rotated counterclockwise from
Only the extension side can change the damping force characteristic in multiple stages, and the compression side becomes 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, The damping force characteristic can be changed in multiple steps only on the compression side, and the extension side is a region fixed to the low damping force characteristic (hereinafter, referred to as compression side hard region SH).

Incidentally, in FIG. 7, when the adjuster 40 is arranged in the position of, 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.

First, in step 101, the vertical acceleration signal obtained from each vertical G sensor 1 is converted into each filter circuit LP.
The sprung vertical velocity V as a bounce component at each wheel vicinity position is obtained by processing with F1, LPF2, and BPF.
The sprung vertical velocity V is a positive value when the sprung vertical acceleration V is in the upward direction as the direction determination code, and
In the downward direction, it is given as a negative value.

In the following step 102, the sprung / unsprung relative displacement Sh obtained from each stroke sensor 6 is read, and the sprung / unsprung relative velocity Sv is obtained from the relative displacement Sh signal. The relative displacement Sh and the relative velocity Sv are given as positive and negative values in the extension direction and negative values in the pressure direction as the direction discrimination codes.

In the following step 103, it is judged whether or not the absolute value | Sh | of the relative displacement is less than or equal to the relative displacement (threshold value) Ss which is an inflection point of the rate of change of the spring constant. In step 104, the damping force characteristic C is calculated by the following equation (1)
Then, the process proceeds to step 106. If NO, the process proceeds to step 105 and the damping force characteristic C is calculated by the following equation (2).
Then, the process proceeds to step 106.

C = α (V / Sv) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1) C = α '(V / Sv) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ( 2) In addition, α'is calculated by the following equation (3).

Α ′ = α + β (| Sh | −Ss) (3) (α> 0, β> 0, Ss> 0) In step 106, the sprung vertical velocity V is a positive value. Whether or not (upward) (V> 0) is determined, and if YES (upward), the routine proceeds to step 107, where the shock absorber SA is controlled to the extension side hard area HS side and the extension stroke side is set to the step 104. Alternatively, a drive control signal is output to the pulse motor 3 toward the damping force characteristic C obtained in 105, and the control flow for one time is completed. If NO, the process proceeds to step 108.

In step 108, it is determined whether the sprung vertical velocity V is a negative value (downward) (V <0), and Y
If it is ES (downward), the routine proceeds to step 109, where the shock absorber SA is controlled to the pressure side hard region SH side, and the pressure stroke side is driven to the pulse motor 3 toward the damping force characteristic C obtained at step 104 or 105. A control signal is output, and this completes one control flow, and N
If it is O, the process proceeds to step 110.

Step 110 is a processing step when NO is determined in Steps 106 and 108, that is, when the sprung vertical velocity V is 0. In this step, the shock absorber SA is set in the soft region SS. After controlling, one control flow ends.

After that, the above control flow is repeated.

Next, of the control operation of the control unit 4, switching contents of the control area will be described with reference to the time chart of FIG.

When the sprung vertical velocity V changes as shown in this figure, when the sprung vertical velocity V is 0, the shock absorber SA is controlled to the soft region SS.

When the sprung vertical velocity V becomes a positive value (upward), the shock absorber SA is controlled to the extension side hard area HS.

When the sprung vertical velocity V becomes a negative value (downward), the shock absorber SA is controlled to the pressure side hard region SH.

Further, in the time chart of FIG.
In the region a, the sprung vertical velocity V is reversed from a negative value (downward) to a positive value (upward), but at this time, the relative velocity is still a negative value (the stroke of the shock absorber SA is the pressure stroke). Area). The extension side of the shock absorber SA at this time is controlled in the extension side hard region HS based on the direction of the sprung vertical velocity V. Therefore, in this region a, the compression stroke side, which is the stroke of the shock absorber SA at that time, has a soft characteristic, and on the extension side of the reverse stroke, it is variably controlled toward the extension side maximum damping force characteristic.

In the region b, the sprung vertical velocity V 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 shock absorber SA is controlled to the extension side hard region HS based on the direction of the sprung vertical velocity V, and the stroke of the shock absorber is also the extension stroke. In b, the stroke side, which is the stroke of the shock absorber SA at that time, is variably controlled on the hardware characteristic side.

In the region c, the sprung vertical velocity V 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). The stroke is on the extension side).
The pressure side of the shock absorber SA at this time is controlled to the pressure side hard region SH based on the direction of the sprung vertical velocity V. Therefore, in this region c, the extension side, which is the stroke of the shock absorber SA at that time, has a soft characteristic,
On the pressure side of the reverse stroke, the control is variably controlled toward the pressure-side maximum damping force characteristic.

The area d is an area in which the sprung vertical velocity V 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 stroke side). Therefore, at this time, the shock absorber SA is controlled in the pressure side hard region SH based on the direction of the sprung vertical velocity V, and the stroke of the shock absorber is also the pressure stroke. Therefore, in this region d, The pressure stroke side, which is the stroke of the shock absorber SA, is variably controlled on the hardware characteristic side.

As described above, in this embodiment, when the direction discrimination codes of the sprung vertical velocity V and the sprung / unsprung relative velocity Sv are the same (region b, region d), the shock absorber at that time is determined. Based on the Karnop control theory (skyhook theory), the stroke side of the SA is controlled to have a hard characteristic, and when the opposite sign (area a, area c) is used, the stroke side of the shock absorber SA at that time is controlled to have a soft characteristic. The same control as the damping force characteristic control is performed. 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.

Next, the specific content of the damping force characteristic variable control will be described with reference to the time chart of FIG.

As shown in area (a) of FIG.
When the unsprung relative displacement Sh is within the range of both threshold values −Ss to Ss, an arithmetic expression (C =
Using α (V / Sv), the damping force characteristic is controlled in proportion to the value of the sprung vertical velocity V at that time.

As shown in the area (b) of FIG.
When the unsprung relative displacement Sh exceeds the range of both threshold values −Ss to Ss, the spring constant for the relative displacement Sh changes to a higher value. Therefore, the relative displacement (|
Sh | -Ss) multiplied by an additional proportional constant β, and a value obtained by adding the value to the normal proportional constant α.
(| Sh | −Ss)) using the arithmetic expression (C = α ′ (V / S
Based on v)), the damping force characteristic is controlled in proportion to the value of the sprung vertical velocity V at that time.

That is, by setting the damping force characteristic to be higher as much as the spring constant is higher, it is possible to prevent deterioration of the vibration damping property.

As described above, in this embodiment, the effects listed below can be obtained.

By the correction control of the proportional constant, the shortage of the damping force due to the change of the spring constant can be eliminated, and thus the deterioration of the vibration damping property can be prevented.

Compared with the conventional damping force characteristic control based on the Karnop control theory (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. Can be improved.

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 case where the stroke sensor is used as the relative displacement detecting means is shown, but other known detecting means such as a load sensor and a vehicle height sensor can be used.

Further, in the embodiment, the addition amount of the proportional constant is made proportional to the value of the relative displacement exceeding the threshold value, but a constant value may be increased on / off.

Further, in the embodiment, the case where the sprung vertical velocity is used as the vehicle behavior to perform the control based on the Karnop control theory (skyhook theory) is shown, but the known control method is based on the other vehicle behavior. It can also be applied to the case of controlling by.

The spring member may be an air spring or a combination of an air spring and a coil spring.

[0048]

As described above, in the vehicle suspension system of the present invention, damping force characteristic control means for controlling the damping force characteristic of the shock absorber to a value proportional to the vehicle behavior amount based on a predetermined reference proportional constant. The damping force characteristic control means is provided with a correction control unit that corrects the proportional constant of the damping force characteristic control to a value higher than the reference proportional constant when the relative displacement exceeds a predetermined displacement value. The effect of being able to generate damping force characteristics corresponding to changes in spring constants, which makes it possible to prevent the occurrence of insufficient damping force due to changes in spring constants and to secure damping performance Is 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 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 the piston speed of the shock absorber.

FIG. 7 is a damping force characteristic diagram corresponding to the 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 filter circuit in the apparatus of the embodiment.

FIG. 15 is a spring constant characteristic diagram with respect to relative displacement between the sprung part and the unsprung part of the suspension spring in the embodiment apparatus.

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

FIG. 17 is a time chart showing the switching contents of the control area in the control operation of the control unit in the embodiment apparatus.

FIG. 18 is a time chart showing the specific content of damping force characteristic variable control in the control operation of the control unit in the embodiment apparatus.

[Description of Reference Signs] a Spring member b Damping force characteristic changing means c Shock absorber d Relative displacement detecting means e Vehicle behavior detecting means f Damping force characteristic controlling means g Correction control section

Claims (1)

[Claims] 1. A spring member interposed between a vehicle body side and each wheel side and having a non-linear characteristic of a spring constant against relative displacement between sprung and unsprung parts; and a spring member interposed between the vehicle body side and each wheel side. A shock absorber having a variable damping force characteristic having a damping force characteristic changing means, a vehicle behavior detecting means for detecting a vehicle behavior including at least a relative displacement detecting means for detecting a relative displacement between sprung and unsprung, and a shock absorber for the shock absorber. The damping force characteristic control means for controlling the damping force characteristic to a value proportional to the vehicle behavior amount based on a predetermined reference proportional constant, and the damping force characteristic control means are provided with a predetermined relative displacement between sprung and unsprung portions. A vehicle suspension device comprising: a correction control unit that corrects a proportional constant of damping force characteristic control to a value higher than a reference proportional constant when the value exceeds the value.