JPH07117433A - Suspension control device - Google Patents

Abstract

PURPOSE:To simultaneously ensure that riding comfort is secured and that a damping effect is maximized by setting a dead zone in the sprung velocity in a semi-active suspension control system which controls the damping coefficient of a shock absorber in accordance with the ratio of the absolute velocity of the sprung member to the relative velocity of the sprung member to a lower spring member. CONSTITUTION:When a detected value X of the sprung velocity imply changes from positive to negative or vice versa, the correction Y of the detected value X is set to zero only immediately after the sign of the detected value X has been inverted. This can save much of a damping effect that is wasted for the purpose of securing riding comfort, as compared with the case in which the correction Y is set to zero both before and after the sign of the detected value X is inverted. While the absolute value is not in excess of a set value (a) even if the detected value X is varied in the opposite direction after the correction Y has been set to zero, the correction Y is set to zero. Therefore hunting of damping coefficient control is restrained and riding comfort is enhanced.

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 improvement of 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. 5-24423 of the present applicant.
This is because (a) the sprung speed detecting means for detecting the sprung speed, which is the speed of the sprung member of the vehicle in the vehicle up-down direction, and (b) the sprung member and unsprung member of the vehicle in the vehicle up-down direction. Relative speed detecting means for detecting a relative speed that is a changing speed of relative displacement, and (c) a sprung member based on a speed ratio that is a ratio of the sprung speed (that is, the absolute speed of the sprung member) to the relative speed. And a controller that controls the suspension characteristics of a suspension mechanism that connects the unsprung member to the suspension control device.

The suspension control device of the type that controls the suspension characteristics based on the speed ratio has the following problems. When the vehicle is traveling on a flat road where the vehicle travels on a substantially flat road surface, it is desirable that the suspension characteristics are not substantially changed in order to ensure a comfortable ride. However, the speed ratio is calculated by dividing the sprung speed by the relative speed. On the other hand, even when the road surface is flat, the relative speed is centered at 0 during small vibration running when vibration with a relatively small amplitude is input to the tire from the road surface. It tends to oscillate positively and negatively (ie 0
There is a tendency for small vibrations in the vicinity, and this tendency is strongly affected by signal noise, calculation errors, and the like. Therefore, during small-vibration traveling, the speed ratio tends to vibrate positively and negatively (sensitively), and the sprung speed detection value and the relative speed detection value are used as they are to obtain the speed ratio to obtain the original speed. If the suspension characteristics are controlled based on the ratio, the suspension characteristics are changed frequently even when the vehicle is traveling on a flat road.
It causes the deterioration of riding comfort.

In order to solve this problem, the present applicant previously made the following proposal and disclosed it in Japanese Patent Application No. 5-117741. This is a technique of setting a dead zone for the sprung speed, and the following technique has been proposed as a specific example of this technique. As shown in the graph of FIG. 12, when the detected value X of the sprung speed monotonously changes from one of the positive and negative regions to the other region, the absolute value of the detected value X is the set value. In the area larger than e, the detected value X is directly used as the corrected sprung speed Y, but in the area equal to or smaller than the set value e, the corrected sprung speed Y is 0.

When traveling on a flat road, not only the relative speed detection value but also the sprung speed detection value tends to be almost zero. Therefore, by implementing this sprung mass velocity correction technique and setting a dead band in the sprung mass velocity, the detected value of the sprung mass velocity during small vibration traveling is positive or negative without the absolute value thereof exceeding the set value e. The corrected sprung speed becomes 0 and the speed ratio also becomes 0 when the vehicle is vibrating in a very small amount, so that the suspension characteristics are kept constant and the riding comfort is secured as desired.

[0006]

However, this sprung mass velocity correction technique has the following problems. When implementing this technique, the absolute value of the detection value of the sprung speed is the set value e.
The correction sprung speed is set to 0 and the speed ratio is set to 0 in the entire region below, that is, both immediately before and after the sign of the detected value is reversed. Therefore, when a vehicle is traveling on a non-flat road, large vibration traveling in which vibration of a relatively large amplitude is input to the tire from the road surface requires a large damping effect compared to small vibration traveling. However, there is a problem in that the period in which the speed ratio is considered to be 0 is a little too long, and the vibration damping effect may not be sufficiently exerted.

Against the background of such circumstances, the invention of claim 1 has been made in order to secure a vibration damping effect mainly during a large vibration running in the suspension control utilizing the speed ratio. . When the invention of claim 2 is carried out, an object of the invention is to secure a riding comfort mainly during small vibration traveling. The invention of claim 3 is to solve the problem of the invention of claim 1 or 2 to secure a damping effect during large vibration traveling by setting an appropriate dead zone for the sprung speed. A fourth aspect of the present invention is intended to secure riding comfort during small vibration traveling by setting an appropriate dead zone for the sprung speed in the third aspect of the invention. A fifth aspect of the present invention is to provide a desirable mode of applying each of the first to fourth aspects of the invention to a semi-active suspension control device.

[0008]

The invention according to claim 1 is based on 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 is controlled so that the detected value of the sprung speed changes from one of positive and negative regions to the other. The first characteristic change prohibiting means 4 for prohibiting the change of the suspension characteristic when the detected value becomes 0 and the absolute value of the detected value exceeds the first set value when the respective values monotonously change toward the area To solve the problem.

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

For the "suspension characteristic", for example, a damping coefficient, a spring constant, a stabilizer rigidity, etc. can be selected.

Further, the "controller" may have a mode of controlling the suspension characteristics stepwise or a mode of continuously controlling the suspension characteristics.

According to the second aspect of the invention, as shown in FIG.
In the controller 3 of the invention of claim 1, further, after the detected value of the sprung speed enters the dead zone where the change of the suspension characteristic is prohibited by the first characteristic change prohibiting means 4, the absolute value is the first set value. If it changes in the opposite direction to the current time and exits the dead zone without exceeding, the suspension characteristics change from the time of entering the dead zone until the absolute value of the detected value exceeds the second set value. 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 set value", you can set a fixed value,
For example, it may be a variable value that changes according to the road surface condition, vehicle speed, driver's steering condition, vehicle lateral acceleration, 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 the invention of claim 3, as shown in FIG.
In the first characteristic change inhibiting means 4 in the invention of claim 1 or 2, when the detected value of the sprung speed monotonously changes from one of the positive and negative regions to the other region,
Until the detected value becomes 0, the detected value is used as it is as the corrected sprung speed, but the corrected sprung speed is fixed at 0 until the absolute value of the detected value becomes 0 or more than the first set value. ,
The problem is solved by using the first sprung mass velocity correction means 6 that makes the detected spun velocity the corrected sprung mass velocity as it is after it exceeds.

According to a fourth aspect of the invention, as shown in FIG.
After the second characteristic change prohibiting means 5 in the invention of claim 3 enters the dead zone where the detected sprung mass velocity is fixed to 0 by the first sprung mass velocity correcting device 6, the absolute value is detected. If the value does not exceed the first set value and changes in the opposite direction to the current time and exits the dead zone, the absolute value of the detected value from the time of entering the dead zone is the second set value. The problem is solved by using the second sprung mass velocity correcting means 7 that fixes the correction sprung mass velocity to 0 until the value exceeds.

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

[0018]

In each of the first to fifth aspects of the invention, the first characteristic change inhibiting means 4 optimizes the suspension characteristic during large vibration traveling. Specifically, when the detected value of the sprung speed monotonously changes from one of the positive and negative regions to the other region, the absolute value of the detected value becomes 0 after the detected value becomes 0. Changes in suspension characteristics are prohibited until the value is exceeded.

That is, in the present invention, only the period immediately after the sign of the detected value of the sprung speed is reversed is the dead zone in the relationship in which the sprung speed is input and the suspension characteristic is output, and the sign of the detected value is The period immediately before the reversal is a period in which changes in suspension characteristics are allowed. Therefore, according to the present invention, as compared with the case where the change in the suspension characteristics is prohibited not only immediately after the sign of the detected value is reversed but also immediately before it is reversed, the detected value of the sprung speed is detected during large vibration traveling. However, the loss of the damping effect in the suspension control is reduced when the vehicle travels in which the absolute value of the absolute value fluctuates positively or negatively beyond the first set value.

If only the damping effect is taken into consideration during large vibration traveling and the ride comfort can be ignored at all, the suspension characteristics are controlled by setting no dead zone in the sprung speed during large vibration traveling. Technology is also possible. However, since the original speed ratio suddenly changes in the vicinity of the time when the relative speed becomes 0, when the suspension control is performed without setting the dead zone in the relationship between the sprung speed and the suspension characteristics, the suspension characteristics suddenly change. There is a risk that the occupants will feel uncomfortable. On the other hand, the detected value of sprung speed and the detected value of relative speed are generally shown in FIG.
As shown in the graph in Fig. 8, the sprung speed phase tends to lead the relative speed phase, and the sprung speed zero cross point is earlier than the relative speed zero cross point in time, and The sign reversal tends to occur immediately after the sign reversal of the sensed sprung speed value. Therefore, immediately after the sign of the detected value of the sprung speed is reversed, the relative speed becomes almost 0, and the original speed ratio tends to change suddenly. Therefore, according to the invention of claim 1, there is a tendency that the change of the suspension characteristics is prohibited during the period when the original speed ratio suddenly changes, so that the ride comfort is secured and the damping effect is secured during the large vibration traveling. Will be done.

Particularly, in the second aspect of the present invention, the second characteristic change inhibiting means 5 optimizes the suspension characteristic during the small vibration traveling. Specifically, the detected value of sprung speed changes in the direction opposite to the change direction up to the present time after the absolute value does not exceed the first set value after entering the dead zone where the change in suspension characteristics is prohibited. Then, when exiting from the dead zone, the change of suspension characteristics is prohibited from the time of entering the dead zone until the absolute value of the detected value exceeds the second set value.

Claim 1 without any special measures
In the case of carrying out the invention of (1), when traveling with a small vibration, that is,
The sign of the detected value of sprung speed when the detected value of sprung speed does not exceed the first set value after entering the dead zone, changes in the opposite direction to the current direction, and exits from the dead zone Compared to the case where the suspension characteristics are prohibited both immediately before and after the reversal,
Hunting may occur in suspension control, resulting in poor riding comfort. This is because the dead zone set to the sprung speed has asymmetry with respect to the zero point of the detected value, whereas the detected value of sprung speed fluctuates positively or negatively around 0 during small vibration traveling. In view of this, in the present invention, the change in suspension characteristics is prohibited during low-vibration running, which suppresses hunting in suspension control.

That is, according to the present invention, the first characteristic change prohibiting means 4 and the second characteristic change prohibiting means 5 work together so that the detected value of the sprung speed exceeds the first set value after entering the dead zone. If it changes in the opposite direction to the current direction and exits from the dead zone, the correction sprung speed is fixed to 0 unless the absolute value exceeds the second set value, while the detected value is , When changing in the same direction as when entering the dead zone and exiting the dead zone,
The correction sprung speed is 0 unless the absolute value exceeds the first set value.
According to the present invention, a dead zone having a width wider than that of the dead zone in the invention of claim 1 is set during traveling with a small vibration.

Particularly, in the invention of claim 3,
Prohibition of suspension characteristic change during high vibration running,
That is, the optimization of the suspension characteristics at the time of large vibration traveling is realized by setting the dead zone in the sprung speed. Specifically, as shown in the graph of FIG. 6, when the detected value X of the sprung speed monotonously changes from one of the positive and negative regions to the other region, the detected value X becomes 0. Until the detection value X becomes the correction sprung speed Y as it is, the correction sprung speed Y is fixed to 0 until the absolute value of the detection value X becomes 0 or more than 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 as a result, during this period, the change in suspension characteristics is prohibited.

That is, in the present invention, the dead zone is set in the relationship in which the detected value X of the sprung speed is input and the corrected sprung speed Y is output, and the dead zone has asymmetry. Therefore, the hysteresis in which the value of the correction sprung speed Y is different when the detected value X is increased and when it is decreased is also set.

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

As the suspension control device, there is an active type which controls the suspension mechanism so as to generate a positive damping force when the speed ratio is positive and a negative damping force when the speed ratio is negative. On the other hand, there is also a semi-active type that controls the damping coefficient of the shock absorber, but unlike the active type, this semi-active type cannot generate a negative damping force. Therefore, in this semi-active suspension control device, due to the fact that the original speed ratio tends to be negative immediately after the sign of the detected value of the sprung speed is reversed (see FIG. 18), during this period Corrected sprung speed to 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 velocity is fixed to 0 immediately before the sign of the detected value of the sprung velocity is reversed, a sufficient damping effect is exhibited especially in the semi-active type suspension control device. The problem arises that you cannot do it. Immediately before the sign of the detected value is reversed, as is apparent from FIG. 18, the speed ratio tends to be positive, and it is originally intended that the correction sprung speed is 0 and the speed ratio is 0 during this period. This means that the damping effect that can be achieved is not exerted, and the area shown by hatching in FIG. 19 becomes a loss area of the damping effect.

As described above, some suspension control devices have a form in which there is substantially no effect on suspension control even if the speed ratio is set to 0 immediately after the sign of the detected value of sprung speed is reversed. In the invention of claim 3, as the period for fixing the correction sprung speed to 0,
The sign of the detected value of the sprung speed is selected not immediately before it is inverted, but immediately after it is inverted.

According to the third aspect of the invention, the speed ratio is determined as the ratio of the corrected sprung speed Y and the relative speed, and the suspension characteristic is controlled based on this, but the speed ratio is determined. The relative speed used when doing so can be the detected value itself, but the speed ratio is determined using the corrected relative speed in which the dead band is set for the detected value, in accordance with the case of the sprung speed. It is desirable to do.

Further, in particular, in the invention of claim 4,
Prohibition of suspension characteristic change during small vibration running,
That is, optimization of the suspension characteristics during small vibration traveling is realized by setting a dead zone in the 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 opposite direction to the current change direction, and exits from the dead zone. Indicates that the corrected sprung speed is 0 until the absolute value of the detected value exceeds the second set value from the time of entering the dead zone.
Fixed to.

Further, in particular, in the invention of claim 5,
When each of the inventions of claims 1 to 4 is applied to a suspension control device of a passive type in which a suspension mechanism has a shock absorber, an actuator that changes a damping coefficient of the shock absorber, and a spring, a controller controls the actuator. This makes it a semi-active type that controls suspension.

[0033]

As is apparent from the above description, according to each of the first to fifth aspects of the present invention, the effect of ensuring the vibration damping effect can be obtained during the large vibration traveling. Further, according to each of these inventions, the change in the suspension characteristics tends to be prohibited during the period when the original speed ratio suddenly changes, so that the ride comfort is secured and the vibration damping effect is secured during large vibration traveling. Can also be obtained.

Particularly, according to the invention of claim 2 or 4,
In addition to the effect of the invention of claim 1, hunting for suspension control is suppressed during low-vibration traveling, and the riding comfort is secured. Therefore, claim 2 or 4
According to the invention, after all, it is possible to obtain the effect of easily achieving both the vibration damping effect at the time of large vibration traveling and the riding comfort at the time of small vibration traveling.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention of each claim will be concretely described below based on an embodiment shown in the drawings. The present embodiment is a suspension control device for a four-wheel vehicle. In this suspension control device, the controller controls the damping coefficient of the shock absorber via the actuator based on the signal from the sensor. Also, this suspension control device is a semi-active type, and by making the shock absorber exhibit a function equivalent to that of the skyhook damper, it is possible to satisfactorily suppress the vertical vibration of the vehicle body and realize a flat ride as much as possible. .

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

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

Each sprung acceleration sensor 30 includes an integrating circuit 3
Connected to the input side of the controller 40 via 6,
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 the relative velocity 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 drive circuit 5 is provided on the output side of the controller 40.
The actuator 52 is connected via 0. 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 passage area of the hydraulic oil in accordance with the drive signal supplied from each drive circuit 50, and thereby the damping coefficient of each shock absorber 54 is changed. It changes. It should be noted that FIG. 1 representatively shows only elements related to one wheel.

The controller 40 includes a CPU 60 and a ROM
The computer mainly includes 62 and RAM 64. The ROM 62 stores various programs including the damping coefficient control routine shown in the flowchart of FIG. In addition, various maps and tables 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 uses the CP
The U60 executes the program of the ROM62 while using the RAM64, thereby controlling the damping coefficient of the shock absorber 54 based on the theory of the skyhook damper.

The contents of this damping coefficient control will be described briefly. The motion system including the sprung member, the suspension mechanism (mainly composed of the shock absorber 54 and a spring (not shown)) and the 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: 1/4 mass of sprung member of vehicle (fixed value) c: damping coefficient of shock absorber 54 (variable value) v _S : relative speed k: spring constant of spring ( Fixed value) δ _S : Relative displacement

On the other hand, when the theory of the skyhook damper is applied to the damping coefficient control, the motion system consisting of the sprung member, the suspension mechanism and the 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 fixed 1/4 vehicle sprung member (fixed value) c ′: damping coefficient of skyhook damper (variable value) V: sprung speed k: spring of spring Constant (fixed value) δ _S : Relative displacement

Therefore, in the present embodiment, in order to realize the ride comfort as flat as possible, the damping coefficient control causes the shock absorber 54 to exhibit the same function as that of the skyhook damper. Specifically, in order to match the damping force of the shock absorber 54 with the damping force of the skyhook damper, between the damping coefficient c of the shock absorber 54 and the damping coefficient c ′ 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 expression v _S = c′γ (where γ: speed ratio) is established.
Here, the damping coefficient c'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.

Further, in this embodiment, the sprung speed V and the relative speed v _S are set for the purpose of ensuring a good riding comfort during small-vibration traveling and a sufficient damping effect during large-vibration traveling. A dead zone is set for each of the above, the speed ratio γ is determined using the value affected by the dead zone, and the damping coefficient c is changed based on that. Details of the dead zone setting will be described later.

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

First, step S11 (hereinafter, simply S11
It is represented by. Same for the other steps)
From M64, the current value of the sprung speed V and the current value of the relative speed v _S are read out for all the wheels. Then S
At 12, the optimization process of 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. The four types of motion modes that the occupant feels while the vehicle is traveling: roll, pitch,
This is because the sprung speed V of each wheel is optimized by individually focusing on each of the heave and the warp. The bounce control gain setting is performed, for example, based on the traveling speed, lateral acceleration, longitudinal acceleration, etc. of the vehicle so that the occupant does not feel the convergence of the vertical vibration of the vehicle body. An example of this optimizing process is described in Japanese Patent Laid-Open No. 5-24423, so detailed description will be omitted.

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

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

Furthermore, after the detection value X enters the dead zone where the correction value Y is 0, the absolute value does not exceed the first set value and changes in the opposite direction to the current change direction. When exiting the dead zone, the correction value Y is kept until the absolute value of the detection value X exceeds the second set value (a in the figure).
It also includes a process of fixing the detected value X to 0 as the correction value Y as it is after the value is fixed to 0.

That is, in this embodiment, the detected value X
In the case where the detection value X changes monotonically in the increasing direction and the decreasing direction, respectively, the region between the detected value X and 0 or a or −a becomes the dead zone. The width of the dead zone is expanded, and the area between the detected value X and −a becomes the dead zone.

In the present embodiment, the size 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 sprung speed and the detected value of relative speed. Therefore, 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 The calculated value of is not set to 0. The positive damping force is always generated in the region where the positive damping force is required, and the vibration damping effect is prevented from being unnecessarily sacrificed.

Each process in this sprung mass velocity correction is shown as a subroutine in the flow chart of FIG.
When one execution of this subroutine is completed, S1 in FIG.
4, the following description will be given on the assumption that this subroutine is executed many times in succession 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 as an example. First, S
At 51, it is determined whether the detected value X is a or more. Assuming that it is equal to or larger than a, the determination is YES, and the flag F1 and the flag F2 are set to 1 in S52. Then, in S53, the detection value X is directly used as the correction value Y. This is the end of one execution of this subroutine.

After that, assuming that the detected value X decreases and becomes smaller than a while the execution of S51 to 53 is repeated, the determination in S51 is NO, and in S54,
It is determined whether or not the detected value X has become −a or less. Assuming that it is still larger than -a, the determination is NO and S
At 55, it is determined whether the detected value X is 0 or more. Assuming that it is 0 or more, the determination is YES, and it is determined in S56 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 the flag F2 is 1. Since it is 1 at present, the determination is YES, the process proceeds to S53, and the detected value X is directly used as the correction value Y. This is the end of one execution of this subroutine.

After that, S51, 54, 55, 56, 57
While the executions of 5 and 53 are repeated, the detected value X becomes 0.
Assuming that the value is smaller than −a but not less than −a, the determination in S51 is NO, the determination in S54 is NO, and S55.
Is also NO, and the flag F1 is set to 1 in S58.
Is determined. Since it is 1 at present, the determination becomes YES, the flag F2 is set to 0 in S59, and then the process proceeds to S60, and the correction value Y is set to 0.
The detected value X has entered the dead zone. This is the end of one execution of this subroutine.

After that, S51, 54, 55, 58, 59
And the execution of 60 are repeated, the detected value X becomes −
Assuming that the value is a or less, the determination in S51 is NO, S
The determination of 54 is YES, and the flag F is determined in S61.
After 1 is set to 0 and flag F2 is set to 1, the process proceeds to S53,
The detected value X is directly used as the correction value Y. The detected value X has exited from the dead zone in the negative direction. This is the end of one execution of this subroutine.

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

After that, if it is assumed that the detected value X becomes a value 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 in S54. No judgment, NO in S55
Then, in S58, it is determined whether or not the flag F1 is 1. Since it is currently 0, the determination is NO,
In S62, it is determined whether 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. This is the end of one execution of this subroutine.

After that, S51, 54, 55, 58, 62
While the executions of 5 and 53 are repeated, the detected value X becomes 0.
Assuming that the value is smaller than a, the determination in S51 is NO, the determination in S54 is NO, and S55.
The determination is YES, and it is determined in S56 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.
This is the end of one execution of this subroutine.

After that, S51, 54, 55, 56, 63
While the executions of 60 and 60 are repeated, the detected value X becomes a
Assuming that the above is the case, the determination in S51 is YES, both flags F1 and F2 are set to 1 in S52, and then, in S53, the detection value X is directly used as the correction value Y. This is the end of one execution of this subroutine.

As is clear from the above description, when the detected value X monotonously increases or decreases during large vibration traveling,
The correction value Y is fixed to 0 only immediately after the sign of the detection value X is reversed, and compared with the case where the correction value Y is fixed to 0 immediately before the sign of the detection value X is reversed,
The vibration damping effect is not sacrificed unnecessarily to secure the riding comfort.

In particular, this suspension control device is a semi-active type that changes the damping coefficient of the shock absorber, and in principle is a type that cannot generate a negative damping force, so the sign of the detected value X is Immediately after the reversal, that is, during the period when the original speed ratio becomes negative, the correction value Y
Even if 0 is set, there is no loss of damping effect.

Next, an explanation will be given by taking as an example the case where the detected value X monotonously changes from positive to negative and enters the dead zone, and then it reverses toward positive and exits from the dead zone in the positive direction. .

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

Thereafter, 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.
The determinations in O and S54 are NO, and the determination in S55 is YES, and it is determined in S56 whether the flag F1 is 0. Since it is currently 1, the determination is NO and S5
At 7, it is determined whether the flag F2 is 1. Since it is currently 1, the determination is YES, and the detected value X is directly used as the correction value Y in S53.

Thereafter, the detected value X is 0, which is larger than -a.
Assuming that the value is smaller than that, 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 zero.

If it is assumed that the detected value X thereafter increases and becomes a value of 0 or more but smaller than a, S5
The determination of 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 or not the flag F2 is 1. Since it is currently 0, the determination is NO.
Therefore, the correction value Y is set to 0 in S60. The increase of the detected value X from 0 will be ignored.

Assuming that the detected value X then starts to decrease and becomes smaller than 0 but larger than -a, S
The determination of 55 is NO, and the flag F1 is set in S58.
Is determined. 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.

After that, assuming that the detected 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 value is detected in S53. The value X is directly used as the correction value Y.

As is clear from the above description, when the detected value X enters the dead zone and then exits during the small vibration traveling, the detected value X does not exceed a if the absolute value of the detected value X does not exceed a. Even if X changes in any direction, the correction value Y is fixed to 0. This suppresses hunting in so-called 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 in the graph on the upper side of FIG. 8, the correction value Y
Changes as shown in the graph at the bottom of the figure.

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

In this relative speed correction, as shown in the graph of FIG. 9, when the detected value X monotonously changes from one of the positive and negative regions toward the other, the sign of the detected value X becomes Before reversing, (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 used as the correction value Y as it is, and (ii) if it is less than or equal to the third set value, the correction value Y is fixed to the third set value, while after the sign of the detected value X is reversed, (i) the detected value X While the absolute value of does not exceed the third set value, only the sign of the correction value Y is reversed while the absolute value of the correction value remains the third set value, and after exceeding (ii), the detected value X is corrected as it is. The process of setting the value Y is included.

Further, the detected value X has entered the positive side dead zone between the correction value Y of 0 and the positive third set value or the negative side dead zone of the correction value Y between 0 and the negative third set value. After that, when the user exits each dead zone by changing in the direction opposite to the current direction without exceeding the third set value, the absolute value of the detected value X is the fourth set value (b in the figure). A process of fixing the correction value Y is included as long as it does not exceed.

That is, in this embodiment, the detected value X
After the sign of is inverted, even if the detected value X changes in any direction, as long as the absolute value of the detected value X does not exceed b,
The correction value Y is fixed at b or -b.

Each step in this relative speed correction is shown as a subroutine in the flow chart of FIG.
When one execution of this subroutine is completed, S1 in FIG.
5, the following description will be given on the assumption that this subroutine is continuously executed many times in order to simplify the description.

First, the case where the detected value X monotonously changes from positive to negative will be described as an example. First, in S81,
It is determined whether the detected value X is b or more. Assuming that it is b or more, the determination is YES, and the flag F3 and the flag F4 are set to 1 in S82. Then S
At 83, the detected value X is directly used as the correction value Y.
This is the end of one execution of this subroutine.

After that, assuming that the detected value X decreases and becomes smaller than b while the execution of S81 to 83 is repeated, the determination in S58 becomes NO, and in S58,
It is determined whether or not the detected value X has become -b or less. -B
If it is assumed to be larger, the determination is NO, and it is determined in S85 whether the detection value X is 0 or more.
Assuming that it 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 1 at present, the determination is NO, and in S87, it is determined whether or not 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 detected value X has entered the dead zone on the right side. This is the end of one execution of this subroutine.

After that, S81, 84, 85, 86, 87
And 88 are repeated, the detected value X becomes 0.
Assuming that the flag becomes smaller, the determination in S85 becomes 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 then S9.
In 1, the correction value Y is set to -b. The detected value X enters the negative dead zone from the positive dead zone, and the sign of the correction value Y is inverted. This is the end of one execution of this subroutine.

After that, S81, 84, 85, 89, 8
Assuming that the detected value X becomes -b or less while the execution of 9, 90 and 91 is repeated, the determination in S84 is YES, and after 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 exited in the negative direction from the dead zone on the negative side. This is the end of one execution of this subroutine.

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

After that, if it is assumed that the detected value X becomes a value greater than -b but less than or equal to 0 while the execution of S81, 84, 92 and 83 is repeated, the determination in S84 is NO, and in S85. The determination is also NO, and it is determined in S89 whether the flag F3 is 1 or not. Currently 0
Therefore, the determination is NO, and it is determined in S93 whether the flag F4 is 1 or not. 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. This is the end of one execution of this subroutine.

After that, S81, 84, 85, 89, 93
And the execution of steps 91 and 91 are repeated, the detected 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 the flag F3 is 0 or not. Since it is currently 0, the determination is yes, and in S94, the flag F
4 is set to 0, and then the correction value Y is b in S88.
It is said that The detection value X enters the positive dead zone from the negative dead zone, and the sign of the correction value Y is inverted. This is the end of one execution of this subroutine.

After that, S81, 84, 85, 86, 94
And 88 are repeated, the detected value X becomes b
Assuming that the above is the case, the determination in S81 is YES, both the flags F3 and F4 are 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 exited from the dead zone on the positive side in the positive direction. This is the end of one execution of this subroutine.

As is clear from the above description, the relative speed v _S is prevented from becoming 0 and is kept from approaching 0 above a certain value, and the speed ratio γ, which is the denominator thereof, suddenly changes. It is designed so that it is suppressed from doing.

Next, the detected value X decreases to enter the positive dead zone, further decreases to enter 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.

Thereafter, assuming that the detected value X is a value smaller than b but greater than or equal to 0, the determination in S81 is N.
The determinations in O and S84 are also NO, and the determination in S85 is YES, and it is determined in S86 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 the flag F4 is 1. Since it is currently 1, the determination is yes, the process proceeds to S88, and the correction value Y is set to b.

Thereafter, the detected value X is larger than -b but is 0.
Assuming that the value is smaller than that, 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 after the flag F4 is set to 0 in S90, S
Then, the flow goes to 91, and the correction value Y is set to -b.

If it is assumed that the detected value X thereafter increases and becomes a value greater than 0 but smaller than b, S8
The determination result of 5 is YES, and the flag F3 is determined in S86.
Is determined to be 0 or not. Since it is 1 at present, the determination is NO, and in S87, it is determined whether or not the flag F4 is 1. Since it is currently 0, the determination is NO.
Then, the process proceeds to S91, and 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 constant value other than 0 during traveling with small vibration, whereby hunting in damping coefficient control is suppressed. Of.

For example, the detected value X of the relative speed v _S is as shown in FIG.
When the value changes to the upper side of 1 as shown in the graph, the correction value Y changes to the lower side of the figure as shown in the graph.

Then, 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 correction value of _S.

Then, in S16, the road surface is a swell road, a bad road (for example, a road surface having a large unevenness on the road surface), or a composite road (a swell road and a bad road are combined) based on the characteristics of the vibration input to the tire from the road surface. It is determined that the current value of the skyhook damping coefficient c ′ is set according to the result.

The road surface condition can be determined by detecting the frequency characteristics of the vehicle condition signal such as the sprung acceleration α of the four wheels and the relative speed v _S. 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 intensity of the low-frequency component is larger than the reference value, and thus the intensity of the high-frequency component is the reference value. If it is smaller, it is judged as a swell road, and if the strength of the low frequency component is smaller than the reference value and the strength of the high frequency component is larger than the reference value, it is judged as a bad road and the strength of the low frequency component is larger than the reference value. When the strength of the high frequency component is also larger than the reference value, it is judged as a composite road, and when the strength of the low frequency component is smaller than the reference value and the strength of the high frequency component is smaller than the reference value, it is judged as a good road. be able to.

The relationship between the type of road surface condition and the skyhook damping coefficient c'can be set as follows, for example. That is, it is possible to set the road to become smaller in order of the swell road, the complex 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 determined as described above 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
It is represented graphically in FIG. In this graph,
“Hard” means a state where the actual damping coefficient c is maximum and the riding comfort is the hardest, while “soft” means a state where the actual damping coefficient c is minimum and the riding comfort is the softest. To do. In this embodiment, the actuator 52
However, the shock absorber 54 can be operated substantially continuously between the operating position where the damping force characteristic is hard and the operating position where it is soft, so that the damping coefficient c can be 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 is the end of one execution of this damping coefficient control routine.

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

Further, in the present embodiment, the sprung speed V
When the correction value Y is set to 0 and the detection value X is directly set to the correction value Y, the correction value Y is allowed to change discontinuously.
It is also possible to implement the invention of each claim by performing first-order lag processing, for example, to continuously change the correction value Y so that the correction value Y gradually approaches the detection value X during the transition. In this way, the sudden change of 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 controller, but the inventions of claim 1 or 2 are, for example, full-active type. It can also be applied to a suspension control device. That is, the suspension mechanism can be an active type mainly including a hydraulic pressure source, an electromagnetic valve, and a cylinder, and the controller can be a full active type that controls the electromagnetic valve to perform suspension control.

As is clear from the above description, in this embodiment, the sprung acceleration sensor 30 and the integrating circuit 3 are arranged.
4 constitutes one example of the "spring speed detecting means" in each invention of claims 1 to 5, and the relative displacement sensor 32 and the differentiating circuit 36 constitute one example of "relative speed detecting means",
The controller 40 constitutes an example of a “controller”,
The part of the controller 40 that executes S13 in FIG. 2 is the "first characteristic change inhibiting means" in each of the first, second and fifth inventions, the "second characteristic change inhibiting means" in the third or fifth invention, 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 or fifth inventions is constituted.

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

[Brief description of 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 showing a damping coefficient control routine stored in a ROM shown in FIG.

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

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

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

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

FIG. 7 is a flowchart showing in detail the contents of S13.

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

FIG. 9 is a graph for explaining how the detected value X of the relative speed v _S is corrected in S14 of FIG.

FIG. 10 is a flowchart showing in detail the contents of S14.

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

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

FIG. 13 is a diagram conceptually showing the structure of the invention of claim 1.

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

FIG. 15 is a diagram conceptually showing the structure of the invention of claim 3.

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

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

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

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

Claims (5)

[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. Relative speed detecting means for detecting a relative speed that is a changing 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. In a suspension control device including a controller that controls, when the detected value of the sprung speed monotonously changes from one of the positive and negative regions to the other region, the suspension controller includes a controller that controls the detected value to 0. Since then, the first characteristic change prohibiting means for prohibiting the change of the suspension characteristic until the absolute value thereof exceeds the first set value is provided. And a suspension control device. 2. The controller further includes an absolute value of the first set value after the detected value of the sprung speed enters a dead zone where the change of the suspension characteristic is prohibited by the first characteristic change prohibiting means. If it changes in the opposite direction to the current time and exits the dead zone without exceeding, the suspension characteristics change from the time of entering the dead zone until the absolute value of the detected value exceeds the second set value. The suspension control device according to claim 1, further comprising a second characteristic change prohibiting unit that prohibits a change. 3. The detection value becomes 0 when the first characteristic change prohibiting means monotonously changes from one of the positive and negative regions to the other region of the detection value of the sprung speed. Until then, the detected value is used as the corrected sprung speed as it is, but after the detected value becomes 0, the corrected sprung speed is fixed at 0 until the absolute value thereof exceeds the first set value. 3. The suspension control device according to claim 1, wherein the suspension control device is a first sprung mass velocity correction unit that directly uses the detected value as a corrected sprung mass velocity. 4. The second characteristic change prohibiting means sets an absolute value after the detected value of the sprung speed enters a dead zone where the corrected sprung speed is fixed to 0 by the first sprung speed correcting means. When the exit from the dead zone by changing in the direction opposite to the current direction without exceeding the first set value, 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, which is a second sprung mass velocity correction means for fixing the corrected sprung mass velocity to 0 until the correction value is exceeded. 5. The suspension mechanism is a passive type mainly composed of a shock absorber, an actuator for changing a damping coefficient of the shock absorber, and a spring, and the controller controls the actuator to provide a damping coefficient as the suspension characteristic. The suspension control device according to any one of claims 1 to 4, which is a semi-active type that controls the above.