JPH05208609A - Damping force control device - Google Patents

Abstract

PURPOSE:To achieve cost reduction and improve damping performance and the riding comfortableness by reducing the number of parts, causing no delay in control response, and preventing generation of noises and vibrations due to oil shocks. CONSTITUTION:When the spring speed operated from the accelerations obtained by a shock absorber 10 which is interposed between a vehicle body and wheels, and whose tension side and compression side damping factor are formed variable through the control signal, and an acceleration sensor 30 which measures the spring acceleration to measure the spring speed, is upward, the control signal is outputted where the damping factor on the tension side is changed according to the spring speed under the condition where the compression side is fixed to the low-damping factor. On the other hand, when the spring speed is downward, a controller 20 to output the control signal which changes the damping factor on the compression side under the condition where the tension side is fixed to the low-damping factor is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force control device for controlling the damping force of a shock absorber according to the running condition.

[0002]

2. Description of the Related Art As a conventional damping force control device, for example,
The one described in JP-A-61-163011 is known.

This conventional damping force control apparatus comprises a shock absorber of variable damping force, sprung speed measuring means for measuring sprung speed, and relative speed measuring means for measuring relative speed between sprung and unsprung. And a means for controlling the damping force of the shock absorber based on the input signals from both measuring means. The damping force control means determines whether the sign of the sprung speed and the sign of the relative speed match. And a control signal output means for outputting a control signal for making the damping force a low damping force when the codes do not match and a high damping force when the codes match, based on the determination result of the code determining means. It has a different structure.

[0004]

However, the above-mentioned conventional techniques have the problems listed below.

A) Since two measuring means, a sprung speed measuring means and a relative speed measuring means, are required as the input means, the number of parts is increased and the cost is increased.

B) Input components of the shock absorber include a low frequency component of vehicle body vibration and a high frequency component of road surface input. When there is such a composite input of low-frequency components and high-frequency components, the system response requires a speed to respond even to high-frequency components. The control delay occurs due to the delay, etc., and the vibration damping property and the riding comfort deteriorate.

C) Because the switching of the damping force is two positions, soft and hard, especially when the sprung speed changes from the upward direction to the downward direction or from the downward direction to the upward direction (crosses speed 0), the damping force is rapidly increased. Since it changes from hard to soft, noise and vibration (see FIG. 9) are generated by the oil hammer. In addition, the generated damping force becomes too large in some cases, which distorts the sprung mass velocity waveform and gives an occupant a discomfort.

The present invention has been made by paying attention to the above-mentioned problems. The number of parts is reduced, the control response delay is prevented from occurring, and the sound and vibration due to oil hammer are prevented from occurring. It is an object of the present invention to provide a damping force control device capable of achieving cost reduction, vibration control and improvement of riding comfort.

[0009]

In the present invention, the above-described object is achieved by measuring only the sprung speed indicating the sprung state and controlling the damping coefficient. That is, of the high frequency components due to the road surface input, those that do not affect the sprung mass are ignored, and the ignored unsprung components are low-damped on the opposite stroke side from the damping coefficient. The coefficient is fixed and the input is absorbed to achieve the purpose.

The damping force control device of the present invention measures the sprung speed, and a shock absorber which is interposed between the vehicle body and the wheels and has a variable damping coefficient on the extension side and the compression side by the input of a control signal. Based on the sprung speed measuring means and the input from this sprung speed measuring means, when the sprung speed is in the upward direction, the expansion side damping coefficient is adjusted according to the sprung speed with the compression side fixed to a low damping coefficient. A damping coefficient control means for outputting a control signal for changing the sprung speed and outputting a control signal for changing the damping coefficient on the compression side according to the sprung speed when the extension side is fixed to a low damping coefficient when the sprung speed is in the downward direction. And.

It should be noted that the damping coefficient control means maximizes the damping coefficient regardless of whether the sprung speed is in the upward or downward direction as long as the sprung speed does not exceed a preset threshold value. If the sprung mass speed is changed in proportion to the sprung mass speed within the range less than the damping coefficient and the sprung mass speed exceeds the initial setting threshold value within the same cycle, the damping coefficient shall be the maximum damping coefficient until the speed peak value is detected. , When the sprung speed reaches the peak value, the damping coefficient is changed according to the sprung speed until the sprung speed exceeds the previously detected peak value or the direction changes in the opposite direction. When the peak value detected in the same cycle is exceeded, the maximum damping coefficient is maintained until the next peak value is detected.When the next peak value is detected, the damping is performed according to the sprung speed. Change the coefficient It may be used as the stage.

[0012]

When the sprung speed is in the upward direction, the damping coefficient on the extension side is changed according to the sprung speed, and the compression side is fixed at a low damping coefficient. In this case, in the case of the device according to claim 2,
If the sprung speed in the upward direction does not exceed the initial setting threshold value, the damping coefficient on the extension side is changed in proportion to the sprung speed within a range less than the maximum damping coefficient. In addition, if the sprung speed exceeds the initial setting threshold within the same cycle,
The damping coefficient is the maximum damping coefficient until the velocity peak value is detected. Then, when the sprung speed reaches the peak value, the damping coefficient is changed according to the sprung speed until the sprung speed exceeds the previously detected peak value or the direction is changed downward. When the sprung speed exceeds the previously detected peak value in the same cycle, the maximum damping coefficient is maintained until the next peak value is detected. The damping coefficient is changed according to the speed.

On the other hand, when the sprung speed is downward,
Change the damping coefficient on the compression side to fix the extension side to a low damping coefficient.

Thus, since only the sprung speed is measured, the number of measuring means can be reduced. In addition, since the low-frequency sprung component and the high-frequency unsprung component are controlled only in response to those that affect the sprung, the response delay of the control is unlikely to occur, and the damping coefficient control is performed. Since the opposite stroke side is fixed to a low damping coefficient, it is possible to absorb the high frequency component on that stroke side.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an overall view showing a damping force control device of an embodiment. In this figure, 10 indicates a shock absorber, which is interposed between each wheel of the vehicle and the vehicle body. The shock absorber 10 has a so-called inverted type configuration in which a piston 10a is connected to an axle side and a cylinder 10b is connected to a vehicle body side.
Then, an outer cylinder 10c provided outside the cylinder 10b
Is provided with a step motor 10d at the upper end thereof, and by driving the step motor 10d to rotate the adjuster 10f provided on the base 10e, as shown in FIG. It is formed so that the damping coefficient can be changed. And this shock absorber 10
One of the expansion side and the compression side is N, (N-1), (N-2) ... 2,
When changing to the damping position in the ranges A and B shown in FIG. 1, the other is formed in a structure that is fixed to the damping position of the lowest damping coefficient shown by position 0 in the figure. Incidentally, as a shock absorber having such a structure, Japanese Patent Application Laid-Open No. 3-61736 filed by the applicant of the present application.
In the example shown in FIG. 8 of this publication, when changing the damping position on the extension side, the orifice of 27c is closed and 27a,
When the opening degree of the orifice of 27b is changed and the damping position on the compression side is changed, the orifice of 27b is closed and the opening degrees of the orifices of 27a and 27c are changed. It is possible to form various structures. For details, refer to the above-mentioned publication.

The controller 20 drives the step motor 10d. The controller 20 has an acceleration sensor (hereinafter referred to as a G sensor) 30 that detects vertical acceleration of the vehicle body as an input unit.
Based on the input from, the control is performed according to the flow shown in the flowchart 200 of FIG.

Explaining the flowchart 200, the first step 201 is a processing step of integrating the sprung acceleration read from the G sensor 30 to calculate the sprung speed V _n . That is, the G sensor 30 and the portion of the controller 20 that calculates the sprung mass velocity V _n from the acceleration thus constitute the sprung mass velocity measuring means in the claims. The sprung speed is given a positive value in the upward direction and a negative value in the downward direction.

The following step 202 is a step of determining whether or not the sprung mass velocity V _n has a positive value.
If S, the process proceeds to step 203, and if NO, the process proceeds to step 204. Further, step 204 is a step of determining whether or not the sprung mass velocity V _n is 0. If YES, the process returns to step 201, and if NO, step 20.
Go to 5.

That is, the flow continuing from step 203 is the control flow when the sprung speed V _n is upward, and the flow continuing from step 205 is the sprung speed V _n.
This is a control flow when _n is downward.

Step 203 is a step of determining whether or not the sprung mass velocity V _n-1 read immediately before is negative. If YES, the process proceeds to step 206, and if NO, the process proceeds to step 207. That is, this step 203 determines whether or not the direction of the sprung speed has changed.

Step 206 is a processing step for initializing the threshold value V _t of the upward sprung speed to a predetermined value.

The following step 207 is a step of determining whether or not the sprung mass velocity V _{n at} this time is _{equal to} or more than the threshold value V _t . If YES, then the process proceeds to step 208, and if NO, the process proceeds to step 209.

Step 208 is a processing step in which the threshold value V _t is reset to the current sprung speed V _n from the value initialized in step 206.

Step 209 is a processing step for setting a target damping position n, and n = (N _t / V
_t ) · V _n Note that N _t is the maximum position on the extension side. This completes the control when the sprung speed is upward.

On the other hand, if the sprung mass velocity is downward, in step 205, the sprung mass velocity V _n-1 read immediately before is determined.
Is determined to be positive, and if YES, step 210
And proceeds to step 211 with NO. This determines whether or not the direction of the sprung speed is switched, as in the case of the sprung speed being upward.

Step 210 is a processing step for initializing the threshold value V _c of the downward sprung speed to a predetermined value.

The following step 211 is a step of determining whether or not the sprung mass velocity V _c this time is less than or equal to the threshold value V _c . If YES, the process proceeds to step 212, and if NO, the process proceeds to step 213.

Step 212 is a step of resetting the threshold value V _c to the present sprung mass speed V _n .

Step 213 is a processing step for setting a target damping position n, and n = (N _C / V
_c) a · V _n obtained by the arithmetic expression. Note that N _C is the maximum damping position on the compression side. Due to the above, the sprung speed V
The control when _n is downward ends.

Next, the operation of the embodiment will be described with reference to the time charts of FIGS.

First, the basic control shown in FIG. 4 will be described.

FIG. 4 shows changes in the sprung speed, damping force, stroke direction, relative speed, and damping position in order from the top. The sprung speed draws a sine curve and travels alternately on the extension side and the compression side. Also, an example is given in which the peak values P ₁ and P ₂ change so as to exceed the initially set threshold values V _t and V _c in both up and down directions.

In the figure, region a is a region in which the sprung speed is directed upward and does not exceed the initial threshold value V _t . In this case, the target damping position on the extension side is controlled in proportion to the sprung speed. At this time, the shock absorber 10 is on the compression side stroke, but since it is moving toward the extension side stroke, the damping effect is obtained by increasing the extension side damping coefficient in this way, and the damping coefficient is the spring. Since the damping force does not change abruptly because it changes in steps in proportion to the upper speed, it is possible to prevent the occurrence of noise and vibration due to oil hammer. At this time, the pressure side is at the minimum damping position 0, and the pressure side input from the road surface is absorbed.

The next region b is a region in which the sprung mass velocity exceeds the initial threshold value V _t and reaches the peak value P ₁ , and in this case, according to the flow of steps 207 to 208 of FIG. As a result of performing the process of matching the threshold value V _t with the sprung speed at any time, the damping position is held at the maximum damping position N _t on the extension side until the peak value P ₁ is reached. By thus increasing the extension side damping force, the shock absorber 10 is damped.

In the next region c, the sprung mass velocity has a peak value P.
_In the region from when the sprung mass velocity exceeds ₁ to when the sprung mass velocity crosses 0, in this case, when the sprung mass velocity exceeds the peak value P ₁ , the threshold value V _t becomes equal to the peak value P ₁ at this point. Therefore, when the sprung speed exceeds the peak value P ₁ based on the arithmetic expression shown in step 209 of FIG. 3, the damping position decreases in proportion to the decrease in the sprung speed. As a result, the damping of the extension side stroke is continued.

The next region d is a region from when the sprung mass velocity becomes 0 to when the sprung mass velocity exceeds the downward threshold value V _c, and the damping position on the compression side is proportional to the increase in the sprung mass velocity. Increase. At this time, the shock absorber 10 is in the extension side stroke state, but is in the state of performing the stroke toward the compression side, so that the vibration damping action is obtained.

The next region e is a region from when the sprung mass velocity exceeds the initially set threshold value V _c to when it reaches the peak value P _{2. In} this case, the target damping position is set to the maximum damping on the pressure side. Position N _c .

After that, the target damping position is changed as in the case of the above-mentioned upward direction.

Next, in FIG. 5, the sprung mass velocity is the threshold value V.
The control when the sine curve is changed without _{exceeding t} and Vc is shown. Thus, the sprung mass velocity is the threshold value V _t ,
If V _c is not exceeded, the threshold remains at the default value and n = n in steps 209 and 213 of FIG.
(N _t / V _t ) · V _n and n = (N _C / V _c ) · V _n
Based on the arithmetic expression, sprung velocity (v _1, v ₂₎ proportional damping position (n _1, -n ₂₎ is changed to.

FIG. 6 shows that the sprung speed has peak values P ₁ , P ₂ and P ₃ which continuously exceed the initially set threshold value V _{t a} plurality of times in the same cycle without changing the sine curve. It shows the case where it changes.

In this figure, region a is a region in which the sprung mass velocity does not exceed the threshold value V _t , so the damping position is changed in proportion to the sprung mass velocity.

The region b is a region until the sprung speed exceeds the threshold value V _t and reaches the peak value P ₁ , and holds the target damping position as the maximum damping position N _t on the extension side.

Next, the area c is an area in which the peak value P ₁ is exceeded, and the target damping position is changed in proportion to the sprung speed, as in the basic control. In this case, as shown in the figure, the peak value P _{2 that} does not reach the previous peak value P ₁
However, the control proportional to the sprung speed continues.

The area d is an area until the peak value P ₃ larger than the previous peak value P ₁ is reached. Based on the control of step 208 in FIG. 3, the threshold value is exceeded when the peak value P ₁ is exceeded. Rewrite V _t to the sprung speed at that time. Therefore, like the region b, the maximum damping position N _t on the extension side is maintained.

The region e is a region where the peak value P ₃ is reached and the sprung mass velocity becomes 0, and the damping position is decreased in proportion to the decrease in the sprung mass speed.

Since the apparatus of the first embodiment of the present invention is as described above, the following effects can be obtained.

A) Since only the G sensor 30 is used as the measuring means, the number of parts is small and the cost can be reduced, and the control factor is small, so that the control can be simplified and the cost can be reduced.

B) Since the damping coefficient control is mainly performed only for the low-frequency sprung component, the control response delay hardly occurs and the riding comfort is improved. Moreover, although the sprung-unsprung relative velocity is not measured in this way, the unsprung component of the high frequency is controlled corresponding to the one that affects the sprung, and
Since the input side is fixed with a low damping coefficient on the side opposite to the side where the damping coefficient control is performed, this also improves the riding comfort.

C) In the range where the sprung mass velocity does not exceed the threshold values V _t and V _c , the damping coefficient is controlled in small steps in proportion to the sprung mass velocity, so that abrupt changes in damping force are suppressed. It is possible to prevent the generation of noise and vibration due to oil hammer,
In addition, while performing such proportional control, the threshold value V
_{When t} and _Vc are exceeded, the maximum damping position is controlled all at once, so no response delay occurs.

Next, a second embodiment of the present invention will be described.

The second embodiment is different from the first embodiment in part of the control contents of the controller 20. That is, FIG. 7 shows a control flow of the apparatus of the second embodiment, and the formula for obtaining the target position in steps 301 and 302 is different from that of the first embodiment, and is a function of speed square. .. The rest of the configuration is the same as that of the first embodiment, so the explanation is omitted.

Therefore, as shown in FIG. 8, the relationship between the position and the speed is shown by a solid line, and in comparison with the characteristic of the first embodiment, in the second embodiment, as shown by a chain line, the sprung speed is in a low speed region. Has a characteristic of being a low damping position and having a high damping position in the high speed range. This allows
Compared to the first embodiment, the riding comfort when traveling on an uneven terrain is improved, and the vibration damping property is also improved.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and even if there is a design change or the like within the scope not departing from the gist of the present invention. Included in the present invention. For example, in the embodiment, the upright type shock absorber is shown as an example, but an upright type shock absorber may be used. Further, in the embodiment, as the shock absorber, only one adjuster for changing the damping coefficient is provided.
In the state where one damping coefficient on the compression side is changed, the other damping coefficient is shown to have a low damping position.However, the adjuster is provided separately for the extension side and the compression side, and each is independently Such characteristics may be obtained by controlling. That is, although the above-mentioned characteristics are obtained mechanically in the embodiment, they may be obtained controllably.

[0055]

As described above, in the damping force control device of the present invention, only the sprung speed measuring means is used as the input means, and the damping coefficient control means is used when the sprung speed is in the upward direction. With the compression side fixed to a low damping coefficient, a control signal is output to change the expansion side damping coefficient according to the sprung speed.When the sprung speed is downward, the expansion side is fixed to a low damping coefficient. Since the means for outputting the control signal for changing the damping coefficient on the compression side according to the sprung speed is used, the number of measuring means can be reduced, the number of parts can be reduced, and the control can be simplified to achieve cost reduction. Since the damping coefficient control is performed mainly in response to only the low-frequency sprung component, the response delay of the control is unlikely to occur, and the effect of improving the riding comfort is obtained.
Thus, although the sprung-unsprung relative velocity is not measured, the high-frequency unsprung component is controlled according to the one that affects the sprung, and the damping coefficient control is performed. Since the input is absorbed by fixing the low damping coefficient on the side opposite to that performed, the effect of improving the riding comfort is also obtained. further,
Since the damping coefficient is controlled in accordance with the sprung speed, it is possible to suppress an abrupt change in the damping force and prevent the occurrence of noise or vibration due to an oil hammer.

In addition, in the apparatus according to claim 2,
In the range where the sprung speed does not exceed the threshold value, the damping coefficient is changed according to the sprung speed to prevent the occurrence of noise and vibration due to oil hammer as described above.
For a sudden change exceeding the threshold value, the damping coefficient can be changed all at once to the maximum damping coefficient to prevent the control response delay. Further, when the peak value is exceeded within the same cycle, the threshold value is changed to the peak value, so that the above-described effect can be obtained even if a plurality of peak values occur within the same cycle.

[Brief description of drawings]

FIG. 1 is an overall view showing a damping force control device of a first embodiment of the present invention.

FIG. 2 is a graph showing a damping coefficient characteristic diagram of the shock absorber of the first embodiment of the present invention.

FIG. 3 is a flowchart showing a control flow of a controller of the first embodiment device of the present invention.

FIG. 4 is a time chart showing an operating state at the time of basic control of the first embodiment of the present invention.

FIG. 5 is a time chart showing an operating state of the first embodiment of the present invention.

FIG. 6 is a time chart showing an operating state of the first embodiment of the present invention.

FIG. 7 is a flowchart showing a control flow in a controller of the damping force control system of the second embodiment of the present invention.

FIG. 8 is a graph showing the relationship between the damping position n and the sprung speed v of the first and second embodiments of the present invention.

FIG. 9 is a time chart showing the operation of the conventional technique.

[Explanation of symbols]

10 shock absorber 20 controller (sprung speed measuring means; damping coefficient control means) 30 acceleration sensor (sprung speed measuring means)

Claims (2)

[Claims] 1. A shock absorber, which is interposed between a vehicle body and a wheel and has a variable damping coefficient on the expansion side and the compression side when a control signal is input, and a sprung speed measuring means for measuring sprung speed. Based on the input from the sprung speed measuring means, when the sprung speed is in the upward direction, a control signal for changing the expansion side damping coefficient according to the sprung speed is output while the compression side is fixed to a low damping coefficient. When the sprung speed is in the downward direction, a damping coefficient control means for outputting a control signal for changing the damping coefficient on the compression side according to the sprung speed in a state where the expansion side is fixed to a low damping coefficient is provided. A characteristic damping force control device. 2. The damping coefficient control means, regardless of whether the sprung speed is in an upward or downward direction, if the sprung speed does not exceed a preset initial setting threshold value,
If the damping coefficient is changed in proportion to the sprung speed within a range less than the maximum damping coefficient, and if the sprung speed exceeds the initial setting threshold value within the same cycle, the damping coefficient is changed until the speed peak value is detected. With the maximum damping coefficient, when the sprung speed reaches the peak value, the damping coefficient is changed according to the sprung speed until the sprung speed exceeds the previously detected peak value or the direction changes in the opposite direction. , When the sprung speed exceeds the previously detected peak value within the same cycle, the maximum damping coefficient is maintained until the next peak value is detected, and when the next peak value is detected, the sprung speed is The damping force control device according to claim 1, wherein the damping coefficient is changed according to the above.