JP3102230B2 - Suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device for controlling suspension characteristics of a vehicle, and more particularly to an improvement in control of the suspension control device.

[0002]

2. Description of the Related Art One type of suspension control device is described in Japanese Patent Application Laid-Open No. Hei 5-24423 of the present applicant.
This means (a) a sprung speed detecting means for detecting a sprung speed which is a speed of the sprung member of the vehicle in the vehicle vertical direction, and (b) a sprung member and a unsprung member of the vehicle in the vehicle vertical direction. (C) a sprung member based on a speed ratio that is a ratio of the sprung speed (ie, the absolute speed of the sprung member) to the relative speed; And a controller that controls suspension characteristics of a suspension mechanism that connects the suspension mechanism and the unsprung member.

A suspension control device of the type that controls suspension characteristics based on a speed ratio has the following problems. When the vehicle travels on a flat road surface on a substantially flat road surface, it is desirable to keep the suspension characteristics substantially unchanged in order to secure ride comfort. However, the speed ratio is obtained by dividing the sprung speed by the relative speed.On the other hand, when the vehicle is running on a small vibration where a relatively small amplitude of vibration is input from the road surface to the tire even when the road surface is flat, the relative speed is centered around 0. The tendency to vibrate positively and negatively (ie, 0
(A tendency of small vibration in the vicinity), and this tendency is strongly affected by signal noise, calculation error and the like. Therefore, when traveling with small vibration, the speed ratio tends to vibrate positively and negatively (sensitively), and the speed ratio is calculated using the sprung speed detection value and the relative speed detection value as they are to obtain the original speed. If the suspension characteristics are controlled based on the ratio, the suspension characteristics are frequently changed even when the vehicle is traveling on a flat road, and the vehicle body shock and the like may be changed.
Causes a deterioration in ride quality.

[0004] In order to solve this problem, the present applicant has previously made the following proposal and disclosed it in Japanese Patent Application No. 5-117774. This is a technique for setting a dead zone in sprung speed, and the following technique has been proposed as a specific example of this technique. As shown by the graph in FIG. 12, when the detected value X of the sprung speed changes monotonically from one of the positive and negative regions to the other region, the absolute value of the detected value X becomes the set value. In a region larger than e, the detected value X is used as the corrected sprung speed Y as it is, but in a region below the set value e, the corrected sprung speed Y is set to 0.

When traveling on a flat road, not only the detected value of the relative speed but also the detected value of the sprung speed tends to be substantially zero. Therefore, if the dead zone is set for the sprung speed by implementing this sprung speed correction technique, the detected value of the sprung speed can be positive or negative during small vibration traveling, that is, the absolute value of the detected value does not exceed the set value e. When the vehicle travels with a small vibration, the corrected sprung speed becomes 0 and the speed ratio also becomes 0, so that the suspension characteristics are kept constant as desired and the riding comfort is secured.

[0006]

However, this sprung speed correction technique has the following problems. When implementing this technique, the absolute value of the detected value of the sprung speed is equal to the set value e.
The corrected sprung speed is set to 0 and the speed ratio is set to 0 in both the following regions, that is, immediately before and immediately after the sign of the detected value is inverted. For this reason, when the vehicle travels on an uneven road, such as when traveling on a non-flat road, a large vibration is input to the tires from the road surface during a large-vibration run, although a large vibration damping effect is required compared to a small-vibration run. In addition, there is a problem that the period in which the speed ratio is regarded as 0 is slightly too long, and the vibration damping action may not be sufficiently exerted.

[0007] Against this background, the invention of claim 1 has been made in the suspension control using the speed ratio, mainly to ensure the vibration damping effect during running with large vibration. . The second aspect of the present invention, when the first aspect of the present invention is implemented, has been made with the main object of ensuring ride comfort during small-vibration traveling. A third aspect of the present invention is directed to the first or second aspect of the invention, in which an appropriate dead zone is set for the sprung speed so as to secure a vibration damping effect during a large vibration traveling. A fourth aspect of the present invention is directed to a third aspect of the present invention, in which an appropriate dead zone is set for the sprung speed so as to ensure a comfortable ride during running with a small vibration. It is an object of the invention of claim 5 to provide a desirable aspect when the inventions of claims 1 to 4 are applied to a semi-active suspension control device.

[0008]

Means for Solving the Problems The first aspect of the present invention is shown in FIG.
As shown in FIG. 3, in the suspension control device including the sprung speed detecting means 1, the relative speed detecting means 2 and the controller 3, the controller 3 sends the detected value of the sprung speed from one of the positive and negative areas to the other. The first characteristic change prohibiting means 4 for prohibiting the change of the suspension characteristic until the detected value becomes 0 and the absolute value thereof exceeds the first set value when monotonously changing toward the region of Solves the problem.

The "first set value" here may be a fixed value or a variable value that changes according to, for example, the road surface condition, vehicle speed, driver's steering condition, vehicle lateral acceleration, vehicle yaw rate, and the like. it can.

As the "suspension characteristics", for example, a damping coefficient, a spring constant, a stabilizer rigidity and the like can be selected.

[0011] The "controller" may be a mode for controlling the suspension characteristics stepwise or a mode for continuously controlling the suspension characteristics.

According to a second aspect of the present invention, as shown in FIG.
The controller (3) according to claim 1, further comprising, after the sprung speed detection value enters a dead zone in which a change in suspension characteristics is prohibited by the first characteristic change prohibiting means (4), sets the absolute value to a first set value. If it changes in the direction opposite to the change direction up to the current point and exits from the dead zone, the suspension characteristics will not change until the absolute value of the detected value exceeds the second set value after entering the dead zone. The problem is solved by providing the second characteristic change prohibiting means 5 for prohibiting the change.

The "second set value" here is also
As in the case of the “first setting value”, a fixed value may be used.
For example, it may be a variable value that changes according to a road surface condition, a vehicle speed, a driver's steering condition, a vehicle lateral acceleration, a vehicle yaw rate, and the like.

The "second set value" can be the same value as the "first set value" or a different value.

According to a third aspect of the present invention, as shown in FIG.
The first characteristic change prohibiting means 4 according to the first or second aspect of the present invention is configured such that when the detected value of the sprung speed changes monotonically from one of the positive and negative regions to the other region,
Until the detected value becomes 0, the detected value is used as the corrected sprung speed as it is, but the corrected sprung speed is fixed at 0 until the detected value becomes 0 and the absolute value exceeds the first set value. ,
The problem is solved by using the first sprung speed correction means 6 which uses the detected value as it is as the corrected sprung speed after exceeding.

According to a fourth aspect of the present invention, as shown in FIG.
After the detected value of the sprung speed enters the dead zone in which the corrected sprung speed is fixed to 0 by the first sprung speed correcting means, the second characteristic change inhibiting means in the invention according to the third aspect of the present invention is used. If the value changes in the direction opposite to the change direction up to the present point and leaves the dead zone without exceeding the first set value, the absolute value of the detected value will be changed to the second set value from the time of entering the dead zone. The second problem is solved by using the second sprung speed correction means 7 for fixing the corrected sprung speed to 0 until the speed exceeds the value.

In the fifth aspect of the present invention, as shown in FIG. 17, each of the first to fourth aspects of the present invention is different from the first aspect in that the suspension mechanism 8 mainly includes a shock absorber 9, an actuator 10 for changing the damping coefficient thereof, and a spring 11. When applied to a passive type suspension control device, the controller 3 in each of the first to fourth aspects of the present invention controls an actuator 10 to control a damping coefficient as a suspension characteristic. Solves the problem.

[0018]

In each of the first to fifth aspects of the present invention, the first characteristic change prohibiting means 4 optimizes suspension characteristics during large-vibration running. Specifically, when the sprung speed detection value monotonically changes from one of the positive and negative regions to the other region, the absolute value of the detection value becomes zero after the detection value becomes zero. Changes in suspension characteristics are prohibited until the value exceeds the value.

That is, in the present invention, only the period immediately after the sign of the detected value of the sprung speed is inverted is regarded as the dead zone in the relationship of inputting the sprung speed and outputting the suspension characteristics, and the sign of the detected value is determined. The period immediately before the inversion is a period during which a change in suspension characteristics is allowed. Therefore, according to the present invention, when the vehicle travels with a large vibration, that is, the detected value of the sprung speed is compared with the case where the change of the suspension characteristic is prohibited not only immediately after the sign of the detected value is inverted but also immediately before the inverted. However, when the vehicle travels whose absolute value fluctuates positively or negatively beyond the first set value, loss of the vibration suppression effect in suspension control is reduced.

If only vibration damping action is taken into account during running with great vibration and ride comfort can be neglected at all, suspension characteristics are controlled by setting no dead zone at sprung speed during running with large vibration. Technology is also conceivable. However, the original speed ratio changes abruptly near the time when the relative speed becomes 0. Therefore, when the suspension control is performed without setting any dead zone in the relationship between the sprung speed and the suspension characteristics, the suspension characteristics suddenly change. The occupants may feel uncomfortable. On the other hand, the detected value of the sprung speed and the detected value of the relative speed generally have the values shown in FIG.
As shown by the graph in FIG. 8, the phase of the sprung speed tends to be ahead of the phase of the relative speed, and the zero-cross point of the sprung speed is earlier in time than the zero-cross point of the relative speed. Sign reversal tends to occur immediately after sign reversal of the sprung velocity detection value. Therefore, immediately after the sign of the detected value of the sprung speed is inverted, the relative speed becomes almost zero, and the original speed ratio tends to change suddenly. Therefore, according to the first aspect of the present invention, a change in suspension characteristics tends to be prohibited during a period in which the original speed ratio changes suddenly. Will be done.

In particular, in the second aspect of the present invention, the second characteristic change inhibiting means 5 optimizes the suspension characteristic during running with small vibration. Specifically, after the sprung speed detection value enters the dead zone where the change in suspension characteristics is prohibited, the absolute value does not exceed the first set value and changes in the direction opposite to the change direction up to the present time. When the vehicle exits the dead zone, the change in suspension characteristics is prohibited until the absolute value of the detected value exceeds the second set value after entering the dead zone.

Claim 1 without taking any special measures
When the invention of the present invention is carried out, during small vibration traveling, that is,
When the sprung speed detection value changes into the direction opposite to the change direction up to the present point without exceeding the first set value after entering the dead zone and exits the dead zone, the sign of the sprung speed detection value In comparison with the case where the suspension characteristics are prohibited both immediately before and immediately after the inversion,
Hunting may occur in suspension control, and riding comfort may be degraded. This is because the dead zone set at the sprung speed has asymmetry with respect to the zero point of the detected value, whereas the detected value of the sprung speed fluctuates in both positive and negative directions around 0 during small vibration traveling. Therefore, in the present invention, a change in suspension characteristics is prohibited during small-vibration traveling, thereby suppressing suspension control hunting.

That is, in the present invention, the first characteristic change prohibiting means 4 and the second characteristic change prohibiting means 5 cooperate to make the detected value of the sprung speed exceed the first set value after entering the dead zone. However, when the vehicle moves out of the dead zone by changing in the direction opposite to the change direction up to the present time, the corrected sprung speed is fixed to 0 as long as the absolute value does not exceed the second set value. , When changing in the same direction as when entering the dead zone and exiting the dead zone,
Unless the absolute value exceeds the first set value, the corrected sprung speed is 0
According to the present invention, a dead zone wider than the dead zone according to the first aspect of the present invention is set during small vibration traveling.

[0024] In particular, in the invention of claim 3,
Prohibition of suspension characteristics change during high vibration running,
In other words, optimization of suspension characteristics during large-vibration running is realized by setting a dead zone in sprung speed. Specifically, as shown in the graph of FIG. 6, when the detected value X of the sprung speed changes monotonically from one of the positive and negative regions to the other region, the detected value X becomes zero. Until the detected value X becomes the corrected sprung speed Y, the corrected sprung speed Y is fixed at 0 until the detected value X becomes 0 and the absolute value thereof exceeds the first set value a. The detected value X is directly used as the corrected sprung speed Y. If the corrected sprung speed Y is fixed to 0, the speed ratio is also fixed to 0, and during that time, as a result, a change in suspension characteristics is prohibited.

That is, in the present invention, a dead zone is set such that the detected sprung speed X is input and the corrected sprung speed Y is output, and the dead zone has asymmetry. Thus, the hysteresis in which the value of the corrected sprung speed Y is different when the detected value X increases and when the detected value X decreases is also set.

Here, the reason why the period immediately after the sign of the detected value of the sprung speed is inverted is selected as the period for fixing the corrected sprung speed to 0 will be specifically described.

There is an active suspension control device that controls a suspension mechanism so as to generate a positive damping force when the speed ratio is positive and to generate a negative damping force when the speed ratio is negative. On the other hand, there is a semi-active type that controls the damping coefficient of a shock absorber, but unlike the active type, the semi-active type cannot generate a negative damping force. Therefore, in this semi-active type suspension control device, the original speed ratio tends to be negative immediately after the sign of the detected value of the sprung speed is inverted (see FIG. 18). Correction sprung speed is 0
Even if the speed ratio is set to 0, there is substantially no effect on suspension control.

On the other hand, when the corrected sprung speed is fixed to 0 immediately before the sign of the sprung speed detection value is inverted, a sufficient vibration damping action is exhibited particularly in a semi-active type suspension control device. A problem arises. As is apparent from FIG. 18, immediately before the sign of the detected value is inverted, the speed ratio tends to be positive. In this period, setting the corrected sprung speed to 0 and setting the speed ratio to 0 is originally effective. This means that the damping effect that can be performed is not exhibited, and the region indicated by hatching in FIG. 19 becomes a loss region of the damping effect.

As described above, there is a type of suspension control device in which even if the speed ratio is set to 0 immediately after the sign of the detected value of the sprung speed is inverted, there is substantially no effect on suspension control. According to the third aspect of the present invention, as the period in which the corrected sprung speed is fixed to 0,
Instead of immediately before the sign of the detected value of the sprung speed is inverted, immediately after the inversion is selected.

In the third aspect of the present invention, the speed ratio is determined as the ratio between the corrected sprung speed Y and the relative speed, and the suspension characteristics are controlled based on the speed ratio. The relative speed used when performing the detection can be the detected value itself, but the speed ratio is determined using the corrected relative speed in which the dead band is set to the detected value, according to the sprung speed. It is desirable to do.

In particular, in the invention of claim 4,
Prohibition of suspension characteristics change during small vibration running,
That is, optimization of suspension characteristics during running with small vibration is realized by setting a dead zone in sprung speed. Specifically, when the detected value of the sprung speed enters the dead zone, the absolute value does not exceed the first set value, changes in the direction opposite to the change direction up to the present time, and exits from the dead zone. Means that the corrected sprung speed is 0 from the time of entry into the dead zone until the absolute value of the detected value exceeds the second set value.
Fixed to

In particular, in the invention of claim 5,
In the case where each of the inventions according to claims 1 to 4 is applied to a passive suspension control apparatus mainly including a shock absorber, an actuator for changing a damping coefficient of the shock absorber and a spring, the controller controls the actuator. As a result, it is a semi-active type that performs suspension control.

[0033]

As is clear from the above description, according to each of the first to fifth aspects of the present invention, an effect of ensuring a vibration damping effect during large vibration traveling can be obtained. Furthermore, according to each of these inventions, a change in suspension characteristics tends to be prohibited during a period in which the original speed ratio changes suddenly. Is also obtained.

In particular, according to the invention of claim 2 or 4,
In addition to the effect of the first aspect of the invention, hunting of suspension control during running with small vibration is suppressed, and an effect of ensuring riding comfort is obtained. Therefore, claim 2 or 4
According to the invention, after all, an effect that can easily achieve both the vibration damping effect at the time of large vibration traveling and the riding comfort at the time of small vibration traveling can be obtained.

[0035]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; This embodiment is a suspension control device for a four-wheel vehicle. In this suspension control device, a controller controls a damping coefficient of a shock absorber via an actuator based on a signal from a sensor. In addition, this suspension control device is a semi-active type, and by making the shock absorber perform the same function as the sky hook damper, the vertical vibration of the vehicle body is suppressed well and the ride comfort is as flat as possible. .

Specifically, as shown in FIG. 1, the sprung acceleration sensor 30 and the relative displacement sensor 32 are used as sensors.
Is provided. The sprung acceleration sensor 30 is disposed on a sprung member for each wheel, and detects acceleration of the sprung member in the vehicle vertical direction (hereinafter, referred to as sprung acceleration α). On the other hand, relative displacement sensor 32 is caused to cooperate on the sprung and unsprung members in each wheel, and detects a relative displacement [delta] _S in both the vertical direction of the vehicle.

In general, the sprung acceleration sensor 30 does not need to be mounted on a vehicle for one of the four wheels. This is because the sprung member can be obtained by calculation from the sprung accelerations α of the other three wheels, on the assumption that the sprung member can be regarded as a rigid body.

Each sprung acceleration sensor 30 is connected to each integration circuit 3
6 and is connected to the input side of the controller 40,
The sprung speed V, which is a value obtained by integrating the sprung acceleration α with respect to time, is input to the controller 40 for each wheel. On the other hand, each relative displacement sensor 32 is connected to the input side of the controller 40 via each differentiating circuit 42 so that a relative speed v _S which is a value obtained by differentiating the relative displacement δ _S with respect to time is input for each wheel. It has become.

The driving circuit 5 is provided on the output side of the controller 40.
0 is connected to the actuator 52. The drive circuit 50 and the actuator 52 are provided for each shock absorber 54 of each wheel. Each actuator 52 changes the valve opening degree of each shock absorber 54, that is, the effective flow path area of the hydraulic oil in accordance with the drive signal supplied from each drive circuit 50, thereby reducing the damping coefficient of each shock absorber 54. To change it. FIG. 1 representatively shows only various elements related to one wheel.

The controller 40 includes a CPU 60, a ROM
It is mainly configured by a computer including a RAM 62 and a RAM 64. The ROM 62 stores various programs including a damping coefficient control routine shown in the flowchart of FIG. Various maps, tables, and the like are also stored. On the other hand, the RAM 64 is provided with a sprung speed memory, a relative speed memory, various flag memories, and the like. Then, the controller 40
The U60 controls the damping coefficient of the shock absorber 54 based on the skyhook damper theory by executing the program of the ROM 62 using the RAM 64.

The contents of the damping coefficient control will be schematically described. A motion system including a sprung member, a suspension mechanism (mainly a shock absorber 54 and a spring (not shown)), and a unsprung member can be modeled as shown in FIG. 3 in terms of vibration engineering. In this vibration model, the following equation of motion is established. mα = −cv _S −kδ _{S where} , m: mass of a sprung member of a 1/4 vehicle (fixed value) c: damping coefficient of shock absorber 54 (variable value) v _S : relative speed k: spring constant of spring ( fixed value) [delta] _S: relative displacement

On the other hand, when the skyhook damper theory is applied to damping coefficient control, a motion system including a sprung member, a suspension mechanism, and a unsprung member can be modeled as shown in FIG. . In this vibration model, the following equation of motion is established. mα = −c′V−kδ _S where m: mass of a 1/4 vehicle sprung member (fixed value) c ′: skyhook damper damping coefficient (variable value) V: sprung speed k: spring of the spring Constant (fixed value) δ _S : Relative displacement

Therefore, in this embodiment, the damping coefficient control is made to cause the shock absorber 54 to perform the same function as the skyhook damper in order to realize a flat ride comfort as much as possible. Specifically, in order to match the damping force of the shock absorber 54 with the damping force of the skyhook damper, c = c'V / The damping coefficient c of the shock absorber 54 is changed via the actuator 52 so that the relationship represented by the equation v _S = c′γ (where γ: speed ratio) is satisfied.
Here, the damping coefficient of the skyhook damper (hereinafter referred to as the skyhook damping coefficient) c ′ is set based on the state of the road surface. The details will be described later.

[0044] Further, in this embodiment, intended to ensure a sufficient damping effect when a large vibration traveling with to ensure a good riding comfort at the time of a small oscillation travel, sprung velocity V and the relative speed v _S Are set to a dead zone, the speed ratio γ is determined using the value affected by the dead zone, and the damping coefficient c is changed based on the speed ratio γ. Details of the dead zone setting will be described later.

The above-described damping coefficient control is executed by the damping coefficient control routine. Hereinafter, the contents of this routine will be specifically described with reference to FIG.

First, in step S11 (hereinafter simply referred to as S11
Expressed by The same applies to the other steps).
M64 and the current value of the current value and the relative velocity v _S of to the spring on the speed V is read for all the wheels, respectively. Next, S
At 12, the optimization process for sequentially performing the motion mode decomposition, the bounce control gain setting, and the motion mode synthesis is performed on the sprung speeds V of all the wheels. Four types of motion modes that the occupant feels while driving the vehicle: roll, pitch,
This is to optimize the sprung speed V of each wheel by individually focusing on the heave and the warp. The bounce control gain setting is performed based on, for example, the traveling speed, the lateral acceleration, the longitudinal acceleration, and the like of the vehicle so that the convergence of the vertical vibration of the vehicle body does not make the occupant feel uncomfortable. An example of this optimizing process is described in the above-mentioned Japanese Patent Application Laid-Open No. 5-24423, and a detailed description thereof will be omitted.

Thereafter, in S13, the sprung speed V is corrected by setting a dead zone in the sprung speed V of each wheel.

This sprung speed correction is performed when the detected value X of the sprung speed V monotonically changes from one of the positive and negative regions to the other region, as shown by the graph in FIG. Until the detection value X becomes 0, the detection value X is used as it is as the correction value Y of the sprung speed V (that is, the corrected sprung speed), and after the detection value X becomes 0, the absolute value thereof becomes the first setting. Until the value (a in the figure) is exceeded, the correction value Y is fixed to 0, and after that, the detection value X is directly used as the correction value Y.

Further, after the detection value X enters the dead zone where the correction value Y is set to 0, the absolute value does not exceed the first set value and changes in the direction opposite to the change direction up to the present time. When leaving the dead zone, the correction value Y is maintained until the absolute value of the detection value X exceeds the second set value (a in the figure).
Is fixed to 0, and after exceeding, the detected value X is directly used as the correction value Y.

That is, in this embodiment, the detected value X
When the detection value X monotonically changes in the increasing direction and the decreasing direction, a region where the detection value X is between 0 and a or −a becomes a dead zone. The width of the dead zone is enlarged, and a region where the detection value X is between -a and a becomes the dead zone.

In this embodiment, the magnitude of "a" is set so as to correspond to a value slightly smaller than the general value of the phase difference between the detected value of the sprung speed and the detected value of the relative speed. Before the detected value of the relative speed becomes 0, the state in which the correction value Y of the sprung speed V is corrected to 0 is released, and after the original speed ratio in FIG. 19 becomes positive, the speed ratio γ Is not set to 0. In a region where a positive damping force is required, a positive damping force is always generated, so that the damping effect is not sacrificed uselessly.

Each step in the sprung speed correction is shown as a subroutine in a flowchart in FIG.
When one execution of this subroutine is completed, S1 in FIG.
4, the following description will be made assuming that this subroutine is executed many times successively for the sake of simplicity.

First, a case where the detected value X of the sprung speed V monotonously changes from positive to negative will be described. First, S
At 51, it is determined whether the detection value X is equal to or greater than a. Assuming that it is equal to or greater than a, the determination is YES, and both the flag F1 and the flag F2 are set to 1 in S52. Thereafter, in S53, the detected value X is directly used as the correction value Y. Thus, one execution of this subroutine is completed.

Thereafter, assuming that the detection value X decreases during execution of S51 to S53 and becomes smaller than a, the determination in S51 becomes NO, and in S54,
It is determined whether the detection value X has become equal to or less than -a. Assuming that it is still larger than -a, the determination is NO and S
At 55, it is determined whether the detection value X is 0 or more. Assuming that it is 0 or more, the determination becomes YES, and in S56, it is determined whether or not the flag F1 is 0. Since it is currently 1, the determination is NO and S5
At 7, it is determined whether or not the flag F2 is 1. Since the current value is 1, the determination becomes YES, and the flow shifts to S53, where the detected value X is directly used as the correction value Y. Thus, one execution of this subroutine is completed.

Thereafter, S51, 54, 55, 56, 57
While the execution of steps 53 and 53 is repeated, the detection value X becomes 0
Is smaller than -a, the determination in S51 is NO, the determination in S54 is NO, and the determination in S55 is NO.
Is also NO, and in S58, the flag F1 is set to 1
Is determined. Since the current value is 1, the determination is YES, and in S59, the flag F2 is set to 0. Thereafter, the flow shifts to S60, where the correction value Y is set to 0.
The detection value X has entered the dead zone. Thus, one execution of this subroutine is completed.

Thereafter, S51, 54, 55, 58, 59
While the execution of steps 60 and 60 is repeated, the detection value X becomes −
a, the determination at S51 is NO, S
The determination at 54 is YES, and at S61, the flag F
After 1 is set to 0 and the flag F2 is set to 1, the flow shifts to S53,
The detected value X is directly used as the correction value Y. The detection value X has left the dead zone in the negative direction. Thus, one execution of this subroutine is completed.

Next, a case where the detected value X monotonously changes from negative to positive will be described as an example. Assuming that the detection value X is currently negative, the determination in S51 is NO, and in S54, it is determined whether the detection value X is equal to or less than -a.
−a, the determination is YES, and S
At 61, the flag F1 is set to 0 and the flag F2 is set to 1. Thereafter, at S53, the detected value X is directly used as the correction value Y. Thus, one execution of this subroutine is completed.

Thereafter, if it is assumed that the detection value X becomes larger than -a but smaller than 0 while the execution of S51, 54, 61 and 53 is repeated, the determination in S51 is NO, and the determination in S54 is NO. Determination is also NO, determination of S55 is also NO
In S58, it is determined whether the flag F1 is 1. Since it is currently 0, the determination is NO,
In S62, it is determined whether or not the flag F2 is 1. Since it is currently 1, the determination is YES and S53
In, the detected value X is directly used as the correction value Y. Thus, one execution of this subroutine is completed.

Thereafter, S51, 54, 55, 58, 62
While the execution of steps 53 and 53 is repeated, the detection value X becomes 0
As described above, assuming that the value becomes smaller than a, the determination in S51 is NO, the determination in S54 is NO, and the determination in S55 is NO.
Is YES, and in S56, it is determined whether the flag F1 is 0 or not. Since it is currently 0, the determination is YES, the flag F2 is set to 0 in S63, and then the correction value Y is set to 0 in S60.
Thus, one execution of this subroutine is completed.

Thereafter, S51, 54, 55, 56, 63
The detection value X is a
Assuming that this is the case, the determination in S51 is YES, the flags F1 and F2 are both set to 1 in S52, and then the detected value X is directly used as the correction value Y in S53. Thus, one execution of this subroutine is completed.

As is apparent from the above description, when the detected value X monotonously increases or decreases during the large vibration traveling,
The correction value Y is fixed to 0 only immediately after the sign of the detection value X is inverted. Compared with the case where the correction value Y is fixed to 0 immediately before the sign of the detection value X is inverted,
In other words, the damping action is not sacrificed for securing a comfortable ride.

In particular, this suspension control device is a semi-active type in which the damping coefficient of the shock absorber is changed, and is of a type in which a negative damping force cannot be generated in principle. Immediately after reversing, that is, during the period when the original speed ratio is negative, the correction value Y
Is zero, there is no loss of the damping effect.

Next, a case where the detected value X monotonously changes from positive to negative and enters the dead zone, and then changes toward positive and exits from the dead zone in the positive direction will be described as an example. .

Assuming that the detection value X is initially equal to or larger than a, the determination in S51 becomes YES, the flags F1 and F2 are set to 1 in S52, and the detection value X is determined in S53.
Is directly used as the correction value Y.

Assuming that the detected value X is a value smaller than a but greater than or equal to 0, the determination in S51 is N
O, the determination in S54 is also NO, and the determination in S55 is YES, and in S56, it is determined whether the flag F1 is 0 or not. Since it is currently 1, the determination is NO and S5
At 7, it is determined whether or not the flag F2 is 1. Since the current value is 1, the determination is YES, and the detection value X is directly used as the correction value Y in S53.

The detected value X is then greater than -a but 0
Assuming that the value is smaller than the above, the determination in S55 is NO, and in S58, it is determined whether or not the flag F1 is 1. Since it is currently 1, the determination is YES, and after the flag F2 is set to 0 in S59, S
At 60, the correction value Y is set to 0.

The detection value X then starts increasing, and assuming that it is a value greater than 0 but smaller than a, S5
5 is YES, and in S56, the flag F1
Is determined to be 0 or not. Since it is currently 1, the determination is NO, and in S57, it is determined whether the flag F2 is 1. Since it is currently 0, the determination is NO
The correction value Y is set to 0 in S60. The increase of the detection value X from 0 will be ignored.

Assuming that the detected value X subsequently decreases and becomes a value smaller than 0 but larger than -a, S
The determination at 55 is NO, and at S58, the flag F1
Is 1 or not. Since it is currently 1, the determination is YES, the flag F2 is set to 0 in S59, and then the correction value Y is set to 0 in S60.

If it is assumed that the detection value X further decreases and becomes −a or less, the determination in S54 becomes YES, the flag F1 is set to 0 and the flag F2 is set to 1 in S61, and then the detection is performed in S53. The value X is directly used as the correction value Y.

As apparent from the above description, when the detected value X enters the dead zone and exits from the dead zone during the small vibration traveling, the detected value X is not changed unless the absolute value of the detected value X exceeds a. Regardless of the direction in which X changes, the correction value Y is fixed to 0, thereby suppressing so-called hunting of damping coefficient control in which the damping coefficient c is frequently changed during small vibration traveling, and Comfort is secured.

For example, when the detected value X of the sprung speed V changes as shown by the graph in the upper part of FIG.
Changes as shown in the graph on the lower side of FIG.

After the sprung speed V is corrected as described above, the flow shifts to S14 in FIG. This S14
In the relative velocity v _S is corrected by setting the dead zone to the relative speed v _S of each wheel.

As shown in the graph of FIG. 9, when the detected value X monotonously changes from one of the positive and negative regions to the other region, the sign of the detected value X is changed. Before the inversion, (i) while the absolute value of the detected value X is larger than the third set value (b in the figure), the detected value X
Is directly used as the correction value Y. (ii) When the value becomes equal to or less than the third set value, the correction value Y is fixed to the third set value. On the other hand, after the sign of the detected value X is inverted, (i) the detected value X As long as the absolute value of does not exceed the third set value, the sign is inverted with respect to the correction value Y while the absolute value remains at the third set value, and (ii) after that, the detected value X is corrected as it is. The processing for setting the value to Y is included.

Further, the detected value X has entered a positive dead zone where the correction value Y is between 0 and the third positive set value or a negative dead zone between the zero and the negative third set value. Thereafter, when the vehicle moves out of each dead zone in a direction opposite to the change direction up to the present time without exceeding the third set value, the absolute value of the detected value X becomes the fourth set value (b in the figure). As long as the value does not exceed, processing for fixing the correction value Y is also included.

That is, in this embodiment, the detected value X
After the sign of is inverted, no matter which direction the detection value X changes, unless the absolute value of the detection value X exceeds b,
The correction value Y is fixed at b or -b.

Each step in the relative speed correction is shown as a subroutine in a flowchart in FIG.
When one execution of this subroutine is completed, S1 in FIG.
5, the following description will be made assuming that this subroutine is executed many times successively for the sake of simplicity.

First, a case where the detected value X monotonously changes from positive to negative will be described. First, in S81,
It is determined whether the detection value X is equal to or greater than b. If it is assumed that it is equal to or more than b, the determination becomes YES, and in S82, both the flag F3 and the flag F4 are set to 1. Then, S
At 83, the detected value X is directly used as the correction value Y.
Thus, one execution of this subroutine is completed.

Thereafter, assuming that the detection value X decreases during execution of steps S81 to S83 and becomes smaller than b, the determination in step S58 becomes NO.
It is determined whether or not the detection value X has become -b or less. -B
If it is assumed to be larger, the determination is NO, and in S85, it is determined whether or not the detected value X is 0 or more.
If it is assumed that the value is 0 or more, the determination is YES and S8
At 6, it is determined whether the flag F3 is 0 or not. Since it is currently 1, the determination is NO, and in S87, it is determined whether the flag F4 is 1. Since it is currently 1, the determination is YES, and in S88,
The value of the correction value Y is set to b. The detection value X has entered the right dead zone. Thus, one execution of this subroutine is completed.

Thereafter, S81, 84, 85, 86, 87
The detection value X becomes 0 while the execution of
Assuming that the value has become smaller, the determination in S85 is NO, and in S89, it is determined whether or not the flag F3 is 1. Since it is currently 1, the determination is YES,
In S90, the flag F4 is set to 0, and thereafter, in S9
At 1, the correction value Y is set to -b. The detection value X enters the negative dead zone from the positive dead zone, and the sign of the correction value Y is inverted. Thus, one execution of this subroutine is completed.

Thereafter, S81, 84, 85, 89, 8
If it is assumed that the detection value X has become −b or less while the execution of 9, 90 and 91 is repeated, the determination in S84 becomes YES, and the flag F3 is set to 0 and the flag F4 is set to 1 in S92. , S83, and the detected value X is directly used as the correction value Y. The detected value X has left in the negative direction from the negative dead zone. Thus, one execution of this subroutine is completed.

Next, a case where the detection value X monotonously changes from negative to positive will be described as an example. Since the detection value X is currently assumed to be negative, the determination in S81 is NO, and the determination in S81 is NO.
At 84, it is determined whether the detection value X is equal to or less than -b. Assuming this is the case, the decision is YES
In S92, the flag F3 is set to 0, and the flag F4
Is set to 1 and thereafter, in S83, the detected value X is directly used as the correction value Y. Thus, one execution of this subroutine is completed.

Thereafter, if it is assumed that the detection value X becomes a value larger than -b but equal to or less than 0 while the execution of S81, 84, 92 and 83 is repeated, the determination in S84 is NO, and the determination in S85 is NO. The determination is also NO, and in S89, it is determined whether the flag F3 is 1. Currently 0
Therefore, the determination is NO, and in S93, it is determined whether the flag F4 is 1. Since it is currently 1, the determination is YES, and the correction value Y is set to −b in S91. The detected value X has entered the negative dead zone. Thus, one execution of this subroutine is completed.

Thereafter, S81, 84, 85, 89, 93
And 91 are repeated, the detection value X becomes 0
As described above, assuming that the value is smaller than b, the determination in S85 is YES, and in S86, it is determined whether or not the flag F3 is 0. Since it is currently 0, the determination is YES, and in S94, the flag F
4 is set to 0, and then in S88, the correction value Y is set to b
It is said. The detection value X enters the positive dead zone from the negative dead zone, and the sign of the correction value Y is inverted. Thus, one execution of this subroutine is completed.

Thereafter, S81, 84, 85, 86, 94
And 88 are repeated, the detection value X becomes b
Assuming that this is the case, the determination in S81 is YES, the flags F3 and F4 are both set to 1 in S82, and then the detected value X is directly used as the correction value Y in S83. The detected value X has left in the positive direction from the positive dead zone. Thus, one execution of this subroutine is completed.

As is clear from the above description, the relative speed v _S is prevented from becoming 0 and is not made to approach 0 beyond a certain value, and the speed ratio γ, which becomes the denominator, changes suddenly. It is made to be suppressed.

Next, the detected value X decreases and enters the positive dead zone, further decreases and enters the negative dead zone, and then changes toward positive and exits from the negative dead zone. The case will be described as an example.

Assuming that the detected value X is initially b or more, the determination in S81 is YES, the flags F3 and F4 are set to 1 in S82, and the detected value X is determined in S83.
Is directly used as the correction value Y.

Assuming that the detected value X is smaller than b but greater than or equal to 0, the determination in S81 is N
O, S84 is also NO, S85 is YES, and in S86, it is determined whether the flag F3 is 0 or not. Since it is currently 1, the determination is NO, and S8
At 7, it is determined whether or not the flag F4 is 1. Since it is currently 1, the determination is YES, and the flow shifts to S88, where the correction value Y is set to b.

Thereafter, the detection value X is larger than -b but 0
If it is assumed that the value is smaller than the above, the determination in S85 is NO, and in S89, it is determined whether or not the flag F3 is 1. Since it is currently 1, the determination is YES, and in S90, after the flag F4 is set to 0,
The flow shifts to 91, where the correction value Y is set to -b.

The detection value X then starts increasing, and assuming that it is a value greater than 0 but smaller than b, S8
5 is YES, and in S86, the flag F3
Is determined to be 0 or not. Since it is currently 1, the determination is NO, and in S87, it is determined whether the flag F4 is 1. Since it is currently 0, the determination is NO
Then, the flow shifts to S91, where the correction value Y is set to -b.

As is clear from the above description, the correction value Y of the relative speed v _S is fixed to a non-zero constant value during the small vibration traveling, whereby the hunting of the damping coefficient control is suppressed. It is.

For example, the detected value X of the relative speed v _S is calculated as shown in FIG.
In the case where the correction value Y changes as shown by a graph on the upper side of FIG. 1, the correction value Y changes as shown by a graph on the lower side of FIG.

Subsequently, S15 of FIG. 2 is executed. In S15, the correction value of the sprung speed V is set to the relative speed v.
_The speed ratio γ is calculated by dividing by the _S correction value.

Then, in S16, based on the characteristics of the vibration inputted from the road surface to the tire, the road surface is a undulating road, a rough road (for example, a road surface with severe unevenness of the road surface), and a composite road (the winding road and the rough road are combined). ) Or a good road (substantially flat road surface), and the current value of the skyhook damping coefficient c 'is set according to the result.

The determination of the road surface condition can be made by detecting the frequency characteristics of the vehicle state signal such as the sprung acceleration α and the relative speed v _{S of the} four wheels. For example, a low-frequency component (for example, about 3 Hz or less) and a high-frequency component (for example, about 3 Hz or more) are extracted from the vehicle state signal, and the strength of the low-frequency component is greater than the reference value, and the strength of the high-frequency component is If it is smaller, it is determined to be a undulating road, and if the low-frequency component intensity is smaller than the reference value and the high-frequency component intensity is larger than the reference value, it is determined to be a bad road, and the low-frequency component intensity is smaller than the reference value. If it is large and the intensity of the high frequency component is also larger than the reference value, it is determined that the road is a composite road. If the intensity of the low frequency component is smaller than the reference value and the intensity of the high frequency component is also smaller than the reference value, it is determined that the road is good. be able to.

The relationship between the type of road surface condition and the skyhook damping coefficient c 'can be set, for example, as follows. In other words, it can be set so as to become smaller in the order of the undulating road, the composite road, the good road and the bad road.
This relationship is stored in the ROM 62 in advance.

Subsequently, in S17, the current value of the target damping coefficient c ^* is determined as the product of the speed ratio γ thus determined and the skyhook damping coefficient c '. Thereafter, in S18, according to the relationship between the pre-stored valve opening degree of the target damping coefficient c ^* and the shock absorber 54 to the ROM 62, the valve opening degree corresponding to the current value of the target damping coefficient c ^* is determined. The relationship between the target damping coefficient c ^* and the valve opening is
FIG. 5 is a graph. In this graph,
“Hard” means a state where the actual damping coefficient c is maximum and the ride comfort is the hardest, while “soft” means a state where the actual damping coefficient c is minimum and the ride comfort is the softest. I do. In this embodiment, the actuator 52
Can be operated substantially continuously between an operating position where the damping force characteristic of the shock absorber 54 is hard and an operating position where the damping force characteristic is soft, so that the damping coefficient c is continuously changed. Has become.

Further, in this step, a drive signal suitable for realizing the current value of the target damping coefficient c ^* is supplied to the actuator 52 via the drive circuit 50.
This completes one execution of the attenuation coefficient control routine.

In this embodiment, the set values a and b are both fixed values. However, the set values a and b may be variable values that change according to the road surface condition. For example, the road surface condition is determined as described above. For example, when the road is determined to be a bad road, the values of the set values a and b are set smaller than when the road is determined to be a good road, and the frequency of the damping coefficient control is reduced. It is also possible to implement it in a way that allows for an increase.

In this embodiment, the sprung speed V
When the correction value Y shifts from the state where the correction value Y is set to 0 to the state where the detection value X is directly set to the correction value Y, it is allowed that the correction value Y changes discontinuously.
At the time of the transition, it is also possible to carry out, for example, a first-order lag process so that the correction value Y changes continuously, and the correction value Y gradually approaches the detection value X, so that the invention of each claim can be implemented. In this way, a sudden change in the damping coefficient c is prevented, and the riding comfort is further improved.

The present embodiment is an example in which the inventions of claims 1 and 2 are applied to a semi-active suspension control device. The present invention can also be applied to a suspension control device. That is, the suspension mechanism can be of an active type mainly composed of a hydraulic pressure source, an electromagnetic valve and a cylinder, and the controller can be of a fully active type of controlling a suspension by controlling the electromagnetic valve.

As is clear from the above description, in this embodiment, the sprung acceleration sensor 30 and the integrating circuit 3
4 constitutes an example of the "spring speed detecting means" in each of the first to fifth aspects of the present invention, and the relative displacement sensor 32 and the differentiating circuit 36 constitute an example of the "relative speed detecting means";
The controller 40 forms an example of a “controller”,
The part of the controller 40 that executes S13 in FIG. 2 is a "first characteristic change prohibiting means" in each of the first, second or fifth inventions, a "second characteristic change prohibiting means" in each of the third or fifth inventions, This constitutes an example of each of the "first sprung speed correction means" in each of the third to fifth inventions and the "second sprung speed correction means" in each of the fourth and fifth inventions.

Although the invention of each claim has been specifically described based on the embodiments, various modifications and improvements are made based on the knowledge of those skilled in the art without departing from the scope of the claims. The invention of each of those claims can be implemented.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an electrical configuration of a suspension control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a damping coefficient control routine stored in a ROM in FIG. 1;

FIG. 3 is a diagram showing a vibration model of a suspension mechanism.

FIG. 4 is a diagram showing a vibration model when a shock absorber in the suspension mechanism is replaced with a skyhook damper.

FIG. 5 is a graph showing a relationship between a target damping coefficient c ^* stored in a ROM in FIG. 1 and a valve opening degree of a shock absorber.

FIG. 6 is a graph for explaining how a detected value X of a sprung speed V is corrected by S13 of FIG. 2;

FIG. 7 is a flowchart showing details of step S13.

FIG. 8 is a graph for explaining the effect of S13.

FIG. 9 is a graph for explaining how the detection value X of the relative speed v _S is corrected by S14 of FIG. 2;

FIG. 10 is a flowchart showing details of step S14.

FIG. 11 is a graph for explaining the effect of S14.

FIG. 12 is a graph for explaining the content of a sprung speed correction technique proposed by the present applicant prior to the present invention.

FIG. 13 is a diagram conceptually showing the configuration of the first embodiment.

FIG. 14 is a diagram conceptually showing a configuration of the invention of claim 2;

FIG. 15 is a diagram conceptually showing the configuration of the third aspect of the present invention.

FIG. 16 is a diagram conceptually showing the configuration of the invention of claim 4;

FIG. 17 is a diagram conceptually showing the configuration of the invention of claim 5;

FIG. 18 is a graph for explaining a general relationship between a detected value of a sprung speed, a detected value of a relative speed, and an original speed ratio.

FIG. 19 is a graph for explaining a problem of a sprung speed correction technique proposed by the present applicant prior to the present invention.

Claims (5)

(57) [Claims] 1. A sprung speed detecting means for detecting a sprung speed which is a speed of a sprung member of a vehicle in a vertical direction of the vehicle, and a relative displacement of the sprung member and the unsprung member of the vehicle in a vertical direction of the vehicle. A relative speed detecting means for detecting a relative speed that is a change speed; and a suspension characteristic of a suspension mechanism that connects the sprung member and the unsprung member based on a speed ratio that is a ratio of the sprung speed to the relative speed. A controller for controlling the suspension, wherein the controller sets the detected value of the sprung speed to 0 when the detected value of the sprung speed changes monotonically from one of the positive and negative regions to the other region. The first characteristic change inhibiting means for inhibiting the change of the suspension characteristic until the absolute value of the suspension characteristic exceeds the first set value is provided. And a suspension control device. 2. The controller according to claim 1, wherein the detected value of the sprung speed enters a dead zone in which a change in suspension characteristics is prohibited by the first characteristic change prohibiting means. If it changes in the direction opposite to the change direction up to the current point and exits from the dead zone, the suspension characteristics will not change until the absolute value of the detected value exceeds the second set value after entering the dead zone. The suspension control device according to claim 1, further comprising a second characteristic change prohibiting unit that prohibits the change. 3. The first characteristic change prohibiting means, wherein when the detected value of the sprung speed changes monotonically from one of the positive and negative regions to the other region, the detected value becomes zero. Until the detected value is used as the corrected sprung speed as it is, the corrected sprung speed is fixed at 0 until the absolute value of the detected value exceeds 0 until the absolute value exceeds the first set value. 3. The suspension control device according to claim 1, wherein the first control unit is a first sprung speed correction unit that uses the detected value as it is as a corrected sprung speed. 4. The method according to claim 1, wherein said second characteristic change prohibiting means sets an absolute value after the detected value of the sprung speed enters a dead zone in which the corrected sprung speed is fixed to 0 by the first sprung speed correcting means. Is changed in the direction opposite to the change direction up to the present time without exceeding the first set value and exits from the dead zone, the absolute value of the detected value from the time of entering the dead zone is the second set value 4. The suspension control device according to claim 3, wherein the second sprung speed correction means fixes the corrected sprung speed to 0 until the speed exceeds a predetermined value. 5. The suspension mechanism is of a passive type mainly comprising a shock absorber, an actuator for changing the damping coefficient of the shock absorber and a spring, and the controller controls the actuator so that the damping coefficient as the suspension characteristic is obtained. The suspension control device according to any one of claims 1 to 4, wherein the suspension control device is of a semi-active type that performs the following control.