JPH0781350A - Vehicle suspension device - Google Patents

Abstract

PURPOSE:To improve the riding comfortableness in controlling any variation in a car body longitudinal position in time of adjustable speed without entailing any damage to a function controlling any springing vertical variations by altering a damping coefficient so as to make the actual damping force of a shock absorber come to the target damping force, while adding a specified regulation to the altering control. CONSTITUTION:A control unit 8 inputs the value of springing absolute acceleration detected four vertical acceleration sensors 11 to 14, finding out a vertical springing absolute speed. In succession, damping force to be actually produced in a shock absorber detected by four pressure sensors 51 to 54 is inputted into the control unit, and then a control signal is outputted to four corresponding actuators 25a to 25d so as to be altered to a damping coefficient set by another damping coefficient of the shock absorber. In addition, a dead zone area is set up in alteration control over the damping coefficient, and when a difference between the actual damping force and the target damping force is within the specified dead zone area, any alteration of the damping coefficient is prohibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension device for a vehicle, and more particularly to an improvement of a shock absorber having a variable damping coefficient between the sprung portion and the unsprung portion, the damping coefficient being variable in multiple stages. Involve

[0002]

2. Description of the Related Art Generally, a suspension device for a vehicle is equipped with a shock absorber for damping vertical vibration of a wheel between a sprung portion on the vehicle body side and an unsprung portion on the wheel side. There are various types of shock absorbers of variable damping coefficient type, such as one in which the damping coefficient can be changed to large and small in two steps, and one in which the damping coefficient can be changed in multiple steps or continuously.

[0006] In such a shock absorber control method of variable damping coefficient, basically, the damping force actually generated by the shock absorber is a target damping force in which the sprung mass does not fluctuate up and down, a so-called skyhook. The damping coefficient of the shock absorber is changed and controlled so that the damper force is obtained. As a specific control method thereof, for example, in Japanese Patent Laid-Open No. 60-248419, the sign of the relative displacement between the sprung mass and the unsprung mass and the sign of the relative velocity between the sprung mass and the unsprung mass, which is a differential value thereof, Check if they match, and if they match, increase the damping coefficient of the shock absorber to increase the damping force generated by the shock absorber, and if they do not match, decrease the damping coefficient of the shock absorber to generate the shock absorber. It is disclosed that the damping force to be reduced is reduced.

In such control, a dead zone is generally provided in order to prevent the damping coefficient of the shock absorber from being frequently switched with respect to the displacement near the neutral position. For example, the actual exploitation 63-40
In Japanese Patent Laid-Open No. 213, in controlling the damping coefficient based on whether the sign of the unsprung-spring-unsprung relative displacement and the sign of the sprung-unsprung relative velocity match or disagree, the sprung-spring unsprung relative displacement is controlled. A dead zone area is provided, and the damping coefficient of the shock absorber is always kept small in the dead zone area, and when the sprung input such as the steering angle or the steering angular velocity is large, the width of the dead zone area is made small to It is disclosed that rolling can be suppressed.

[0005]

By the way, when the vehicle is accelerated or decelerated, the vehicle body tilts in the front-rear direction, which gives an occupant an uncomfortable feeling. In particular, at the time of sudden deceleration, the front part of the vehicle body may largely sink and a large inclination may be generated, which makes the occupant uncomfortable.

The present invention has been made in view of the above points, and an object of the present invention is to focus on a shock absorber whose damping coefficient can be changed in a plurality of stages as described above, and to appropriately set the damping coefficient of the shock absorber. By changing the vehicle, it is possible to improve the riding comfort by suppressing the change in the vehicle body front-rear posture during acceleration / deceleration without impairing the original function of the shock absorber, that is, the function of suppressing the vertical fluctuation on the spring. It is intended to provide the suspension device of.

[0007]

In order to achieve the above object, the invention according to claim 1 is arranged as a suspension device for a vehicle between a sprung part and an unsprung part, and the damping coefficient is changed in a plurality of steps. A possible shock absorber, an actual damping force detecting means for detecting a damping force actually generated by the shock absorber, and a target damping force determining means for determining a target damping force of the shock absorber so that the sprung mass does not fluctuate up and down. A damping coefficient control means for changing and controlling the damping coefficient of the shock absorber so that the actual damping force becomes the target damping force; a restriction means for applying a predetermined restriction to the change control of the damping coefficient control means; Acceleration / deceleration detection means for detecting the acceleration / deceleration in the front-rear direction, and the regulation contents of the regulation means are changed according to the acceleration / deceleration in the vehicle front-rear direction so that the front-rear posture of the vehicle body does not change A configuration and a restriction changing means.

The inventions described in claims 2 and 3 are both dependent on the invention described in claim 1 and show one mode thereof. That is, in the invention according to claim 2, the restriction means prohibits the change of the damping coefficient of the shock absorber when the difference between the actual damping force and the target damping force is within a predetermined dead zone region. The regulation content changing means changes the threshold value of the dead zone area. Further, in the invention according to claim 3, the restriction means limits a number of damping coefficients smaller than a plurality of damping coefficients that can be changed by the shock absorber, and only between the limited damping coefficients. The regulation content changing means changes the range of the damping coefficient limited by the regulation means.

The invention according to claim 4 is dependent on the invention according to claim 2, and more specifically shows the change of the threshold value by the regulation content changing means. That is, the regulation content changing means easily changes the damping coefficient of the shock absorber on the rear wheel side to a higher damping coefficient when the vehicle accelerates, and changes the damping coefficient of the shock absorber on the front wheel side to a higher damping coefficient when decelerating the vehicle. Thus, the threshold value of the dead zone area is changed.

The invention according to claim 5 is dependent on the invention according to claim 3, and more specifically shows the change of the range of the damping coefficient by the regulation content changing means. That is, the regulation content changing means limits the damping coefficient limited by the regulating means so that the damping coefficient of the shock absorber on the rear wheel side is high when the vehicle is accelerating and the damping coefficient of the shock absorber on the front wheel side is high when the vehicle is decelerating. The range of is changed.

[0011]

With the above construction, in the invention according to claim 1,
When the vehicle is running, the actual damping force detection means detects the damping force actually generated by the shock absorber, and the target damping force determination means determines the target damping force of the shock absorber so that the sprung mass does not fluctuate up and down. Then, under the control of the damping coefficient control means that receives the signal of the actual damping force detection means and the signal of the target damping force determination means, the actual damping force of the shock absorber becomes the target damping force. By changing the damping coefficient,
Vertical fluctuations on the spring are effectively suppressed. In this case, the regulation means imposes a predetermined regulation on the change control of the damping coefficient control means. For example, in the invention of claim 2,
When the difference between the actual damping force and the target damping force is within the dead zone region, changing the damping coefficient is prohibited, and frequent changes in the damping coefficient are prevented. Further, in the invention according to claim 3, the damping coefficient of the shock absorber is changed within a limited range, and the generation of sound or vibration due to the drastic change of the damping coefficient is prevented.

On the other hand, when the vehicle is accelerating / decelerating, the acceleration / deceleration detecting means detects it, and the regulation content changing means which receives a signal from the detecting means changes the regulation content of the regulating means according to the acceleration / deceleration. Changes in the front-back posture of the vehicle body are suppressed. That is, when the vehicle is accelerated, the damping coefficient of the shock absorber on the rear wheel side, which is the sinking side of the vehicle body, becomes high, and the sinking of the vehicle body is suppressed. On the contrary, when the vehicle is decelerated, the shock absorber on the front wheel side, which is the sinking side of the vehicle body, has a high damping coefficient, and the sinking of the vehicle body is suppressed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a layout of parts of a vehicle equipped with a suspension device according to a first embodiment of the present invention.

In FIG. 1, reference numerals 1, 2, 3 and 4 are provided to correspond to left and right front wheels 5 (only left front wheel is shown) and rear wheels 6 (only left rear wheel is shown). A shock absorber that damps the vertical movement of each wheel. Each of the shock absorbers 1 to 4 is provided by an actuator 25 (see FIGS. 2 and 3) incorporated therein so that the damping coefficient can be changed to 10 stages, and the magnitude of the damping force actually generated is set. A pressure sensor (not shown) as an actual damping force detecting means for detecting the height is incorporated. Reference numeral 7 is a coil spring arranged on the outer periphery of the upper portion of each of the shock absorbers 1 to 4, and 8 is a control for outputting a control signal to the actuator 25 in each of the shock absorbers 1 to 4 to change and control its damping coefficient. The pressure sensor in each of the shock absorbers 1 to 4 outputs a detection signal toward the control unit 8.

Further, 11, 12, 13, and 14 are four vertical acceleration sensors for detecting the vertical acceleration on the spring of each wheel, and 15 is a vehicle speed sensor for detecting the vehicle speed from the rotational speed of the front wheel 5, which is a driven wheel. Reference numeral 16 is a rudder angle sensor for detecting the steering angle of the steering wheel (that is, steering rudder angle). Reference numeral 17 is a mode selection switch for the driver to switch the damping coefficient of the shock absorbers 1 to 4 between the hard mode, soft mode and control mode. When the hard mode is selected by the mode selection switch 17, a large damping coefficient is selected and the damping force becomes hard. When the soft mode is selected, a small damping coefficient is selected and the damping force becomes soft. Further, when the control mode is selected, the damping coefficient change control of the shock absorbers 1 to 4 is performed based on the map or table stored in the control unit 8 in advance.
This change control will be described later in detail.

FIG. 2 shows the structure of the shock absorbers 1 to 4. However, in this figure, shock absorbers 1-
The pressure sensor built in 4 is omitted for convenience.

In FIG. 2, 21 is a cylinder,
A piston unit 22 formed by integrally forming a piston and a piston rod is slidably fitted in the cylinder 21. The cylinder 21 and the piston unit 22 are coupled to the unsprung portion and the unsprung portion through coupling structures provided separately.

The piston unit 22 is formed with two orifices 23 and 24. One of the orifices 23 is always open, and the other orifice 24 has a passage area (throttle) of the actuator 25.
It is provided so that it can be changed in 10 steps. As shown in FIG. 3, the actuator 25 includes a sleeve 26 fixedly arranged in the piston unit 22, a shaft 27 penetrating through the sleeve 26 and rotatably provided, and the shaft 27. A step motor 28 that rotates at a predetermined angle and a first orifice that is connected to the lower end of the shaft 27 so as to rotate together and has nine circular holes 29, 29, ... Formed at predetermined intervals in the circumferential direction. Attached to the plate 30 and the lower end of the sleeve 26,
And a second orifice plate 32 having a long hole 31 formed in an arc shape along the circumferential direction. And
When the step motor 28 operates and the first orifice plate 30 rotates, the circular hole 29 of the first orifice plate 30 may or may not face the elongated hole 31 of the second orifice plate 32. The number of the circular holes 29 facing each other is also sequentially changed from zero to nine.

An upper chamber 33 and a lower chamber 34 inside the cylinder 21.
And the piston unit 22 communicating with both chambers 33, 34
The inner cavity is filled with a fluid having a moderate viscosity. This fluid moves between the upper chamber 33 and the lower chamber 34 through either of the orifices 23 and 24.

FIG. 4 shows a vibration model of the suspension system. Ms is an unsprung mass, mu is an unsprung mass, Zs is an unsprung displacement, Zu is an unsprung displacement, ks is a spring constant of coil spring 7, and kt is a tire. , Dk is the damping coefficient of the shock absorbers 1-4.

FIG. 5 is a diagram showing the damping coefficients of the shock absorbers 1 to 4, and D1 to D10 are the damping coefficients of the shock absorbers 1 to 4, respectively. In FIG. 5, the vertical axis represents the damping force generated by the shock absorbers 1 to 4, and the horizontal axis represents the displacement speed on the spring, that is, the absolute spring speed Xs.
The difference between (dzs / dt) and the unsprung displacement speed, that is, the unsprung absolute speed Xu (dzu / dt), that is, the relative speed (Xs-Xu) between the sprung and unsprung parts is shown.
The damping coefficients D1 to D10 can be changed in 10 steps by the shock absorbers 1 to 4, D1 is a damping coefficient that produces the softest damping force, and D10 is the hardest damping force. Indicates the damping coefficient. Here, the damping coefficient Dk (k = 1 to 10) is calculated from among the nine circular holes 29, 29, ... formed in the first orifice plate 30.
The (10-k) circular holes 29 are selected by communicating with the long holes 31 formed in the second orifice plate 32. Therefore, the damping coefficient D1 is selected because all nine circular holes 29, 29, ... Of the first orifice plate 30 communicate with the elongated holes 31 of the second orifice plate 32, and the damping coefficient D10 is the first orifice plate. Any of the nine circular holes 29, 29, ... Of 30 are selected because they do not communicate with the elongated hole 31 of the second orifice plate 32.

6 and 7 show the structure of the step motor 28. That is, the step motor 28 has a tubular body 40, a rotor 41 and a stator 42 housed in the tubular body 40, and a lid 43 attached to the tubular body 40. A plurality of rectangular teeth 41a, 41a, ... Are formed on the outer peripheral portion of the rotor 41, and a plurality of rectangular teeth 42a, 42a corresponding to this are formed on the inner peripheral portion of the stator 42. , Are formed, and a solenoid 44 is wound around the stator 42. Two stopper pins 45 and 46 are formed on the rotor 41. On the other hand, on the back surface of the lid 43, as shown in FIG. 8, two grooves 47 and 48 are formed in the circumferential direction at positions corresponding to the stopper pins 45 and 46. Among them, the groove 47 engages with the stopper pin 45 to limit the movable range of the step motor 28, while the groove 48 engages with the stopper pin 46. The stopper pins 45 and 46 are respectively inserted into the grooves 47 and
By engaging with 48, the center of gravity of the rotor 41 coincides with the center of rotation when the lid 43 is covered. Therefore, the circumferential angle of the groove 47, 48 viewed from the center of the lid 43 is set larger in the groove 48 than in the groove 47, and the groove 47 exclusively determines the movable range of the step motor 28. It has become so. When the rotor 41 rotates clockwise in FIG. 7, the damping coefficient Dk of the shock absorbers 1 to 4 becomes larger and the damping force becomes harder. On the other hand, when the rotor 41 rotates counterclockwise, the damping coefficient Dk becomes larger. The smaller it is, the softer the damping force becomes. Further, when the rectangular tooth 41a of the rotor 41 is moved to a position facing the adjacent rectangular tooth 42a of the stator 42, that is, when the step motor 28 rotates one step, the damping coefficient Dk is only one. It is changing. Therefore, when the stopper pin 45 is located at the first reference position which is the left end portion of the groove 47 in FIG. 8, the damping coefficient Dk becomes D10, and the shock absorbers 1 to 4 generate the hardest damping force. When the stopper pin 45 is located at the second reference position which is the right end portion of the groove 47 in FIG. 8, the damping coefficient Dk becomes D1, and the shock absorbers 1 to 4 generate the softest damping force. ing.

FIG. 9 shows a block configuration of a control system of the suspension system. In FIG. 9, the first pressure sensor 51, the vertical acceleration sensor 11 and the actuator 25a are on the front wheel 5 on the left side of the vehicle body, and the second pressure sensor 52, the vertical acceleration sensor 12 and the actuator 25b are on the front wheel 5 on the right side of the vehicle body.
The third pressure sensor 53, the vertical acceleration sensor 13 and the actuator 25c are provided on the rear wheel 6 on the left side of the vehicle body, and the fourth pressure sensor 54, the vertical acceleration sensor 14 and the actuator 2 are provided.
5d are provided corresponding to the rear wheels 6 on the right side of the vehicle body. The actuators 25a to 25d are the same as the actuator 25 in FIG. 2, and the pressure sensors 51 to 54 are built in the shock absorbers 1 to 4, respectively.

Reference numerals 15, 16 and 17 respectively denote the above-mentioned vehicle speed sensor, steering angle sensor and mode selection switch,
Reference numeral 56 denotes a longitudinal acceleration sensor as acceleration / deceleration detecting means for detecting acceleration / deceleration in the vehicle body front-rear direction, reference numeral 57 denotes a yaw rate sensor for detecting a yaw rate of the vehicle, and detection signals of these sensors and switches are all sent to the control unit 8. It has been entered. On the other hand, the control unit 8
Control signals are output to the first to fourth actuators 25a to 25d, respectively, and the damping coefficients Dki of the shock absorbers 1 to 4 are changed and controlled by the operation of the actuators 25a to 25d based on the control signals. It The subscript k on the front side of the damping coefficient Dki means a switching stage and takes a value of 1 to 10. The subscript i on the rear side means the numbers of the actuators 25a to 25d or the shock absorbers 1 to 4 incorporating the actuators 25a to 25d, and takes the values of 1 to 4.

Next, the change control of the damping coefficient Dki of the shock absorbers 1 to 4 by the control unit 8 will be described. This change control is performed according to the flowcharts shown in FIGS. 10 and 11, respectively. FIG. 10 is a flowchart of a basic control for changing and controlling the damping coefficient Dki of the shock absorbers 1 to 4, and FIG. 11 is a threshold setting for setting the thresholds .alpha. And .beta. In the dead zone prior to the basic control. It is a flowchart of a routine.

In FIG. 10, after starting, it is first determined in step S1 whether the control flag F is set to 1. The control flag F is set to 1 when the control mode is selected by the mode selection switch 17 and reset to 0 when the hard mode or the soft mode is selected. When the hard mode or the soft mode is selected, the process directly returns, and when the control mode is selected, the process proceeds to step S2.

In step S2, the vertical acceleration sensors 11-
Sprung absolute acceleration ΔXG1 to ΔXG4 detected by 14
Enter. Then, in step S3, this ΔXG1 ~ Δ
XG4 is integrated by a numerical integration method or the like to obtain vertical sprung mass absolute speeds XG1 to XG4. Since these XG1 to XG4 are vertical sprung absolute speeds at the positions of the acceleration sensors 11 to 14, they are converted to vertical sprung absolute speeds Xs1 to Xs4 at the positions of the shock absorbers 1 to 4 in step S4. .

Then, in step S5, a negative sign is added to the product of the sprung mass absolute speeds Xs1 to Xs4 and the gravitational acceleration g,
The skyhook damper force Fai (= -g · Xsi) (i = 1 to 4) of each shock absorber 1 to 4 is calculated. The skyhook damper force Fai is an ideal damping force in which the sprung top does not fluctuate vertically in the skyhook damper theory.

Subsequently, in step S6, the pressure sensors 51 to 51
After inputting the actually generated damping forces Fs1 to Fs4 of the shock absorbers 1 to 4 detected by 54, step S
7, Y1i and Y2i are calculated according to the following formula: Y1i = Fsi · (Fai−α · Fsi) ... Y2i = Fsi · (Fai−β · Fsi). However, α ≧ 1,0 <
β <1.

Then, in step S8, the above Y1i
Is positive (Y1i> 0), shock absorber 1
The damping coefficient of ~ 4 is set to D (k + 1) i which is one step larger than the current damping coefficient Dki, while Y2i is negative (Y2i <
If 0), the damping coefficient of the shock absorbers 1-4 is
Set D (k-1) i which is one step smaller than the current damping coefficient Dki. Then, in step S9, control signals are output to the corresponding actuators 25a to 25d so that the damping coefficients of the shock absorbers 1 to 4 are changed to the set damping coefficients, and then the process returns.

Here, α and β are threshold values for setting the dead zone for changing control of the damping coefficient Dki. That is, when Fsi and Fai have the same sign, (Fai−
Since αFsi) is α ≧ 1, as compared with the case where α is not multiplied by Fsi, it tends to have a different sign from Fsi, and as a result, hαi tends to become negative, so that the damping coefficient Dki of It becomes difficult to make changes to the hardware side. In addition, in the above equation (F
Since ai−β · Fsi) is 0 <β <1, it is easy to have the same sign as Fsi as compared with the case where Fsi is not multiplied by β, and as a result, hβi tends to be positive. Damping coefficient D
It becomes difficult to change ki to the software side. Furthermore, as the upper limit threshold value α becomes smaller as it approaches 1, the damping coefficient D
It becomes easier to change ki to the hard side, and it becomes more difficult to change the damping coefficient Dki to the soft side as the lower limit threshold value β approaches 0. As described above, in FIG. 12, when α becomes small so as to approach 1, the one of the dead zone regions (the region sandwiched between Fa = αFs and Fa = Fs) that regulates the change of the damping coefficient Dki to the hard side. ) Becomes smaller and β becomes smaller so as to approach 0, the other region (the region sandwiched between Fa = Fs and Fa = βFs) of the dead zone region that regulates the change of the damping coefficient Dki to the soft side expands. You can see from

As described above, of the basic control shown in FIG. 10, the control flow of the first half (steps S2 to S5) causes the target of the shock absorber according to the invention of claim 1 so that the sprung mass does not fluctuate up and down. The target damping force determining means 61 for determining the skyhook damper force Fa, which is the damping force, is configured, and the actual damping force Fs referred to in the invention of claim 1 is obtained by the control flow of the latter half (steps S6 to S9). Damping coefficient control means 62 for independently changing and controlling the damping coefficients of the shock absorbers 1 to 4 so as to obtain the skyhook damper force Fa is configured. Also,
In step S7, the regulation means 63 for setting a dead zone region and regulating the change control of the damping coefficient control means 62.
Has the function of.

In FIG. 11, after starting, it is first determined in step S11 whether the acceleration / deceleration G in the vehicle longitudinal direction detected by the longitudinal acceleration sensor 56 is a positive value. This determination ultimately determines whether the vehicle is accelerating or decelerating.

When the above determination is YES, that is, during acceleration, it is determined in steps S12 and S13 whether the absolute value of the acceleration G is greater than the predetermined values a and b, respectively. Here, the predetermined values a and b have a magnitude relation of a <b. When the acceleration G is greater than the predetermined value b, the dead zone region thresholds α3, β3 or α4, β in the change control of the damping coefficients of the rear wheel side shock absorbers 3, 4 are determined in step S14.
When αc and βc are set to 4 and the acceleration G is medium acceleration which is smaller than the predetermined value b and larger than the predetermined value a, the thresholds α3 and β3 or α4 and β4 are set to αb and βb in step S15, and the acceleration G When the acceleration is smaller than the predetermined value a, in step S16, αa and βa are set to the thresholds α3 and β3 or α4 and β4. Here, there is a magnitude relation of αa>αb>αc> 1 ... 1>βa>βb>βc> 0. Further, αa and βa are reference threshold values of the present embodiment, and in the flowchart of FIG. 11, the dead zone region threshold value in the control of changing the damping coefficient of the shock absorber that is not particularly set is the reference threshold value αa,
Be βa.

On the other hand, when the determination in step S11 is NO, that is, during deceleration, it is determined in steps S17 and S18 whether the absolute value of the deceleration G is greater than the predetermined values c and d, respectively. Here, the predetermined values c and d have a magnitude relationship of c <d. Then, when the deceleration G is large deceleration larger than the predetermined value d, the front wheel side shock absorbers 1 and 2 are determined in step S19.
Threshold α in the dead zone for changing control of damping coefficient
When αc and βc are set to 1, β1 or α2 and β2 and the deceleration G is in the middle deceleration smaller than the predetermined value d and larger than the predetermined value c, in step S20, the threshold value α1, β1 or α2,
When .alpha.b and .beta.b are set to .beta.2 and the deceleration G is small deceleration smaller than the predetermined value c, the above-mentioned threshold values .alpha.1 and .alpha.
Set αa and βa to β1 or α2 and β2.

According to the above flow chart,
According to the invention described above, the vehicle body front-rear posture is not changed according to the longitudinal acceleration / deceleration of the vehicle, that is, when the acceleration G in the longitudinal direction of the vehicle is greater than a predetermined value a, the rear wheel side shock absorbers 3, 4 are The above regulation is made so that the damping coefficient Dki can be easily changed to a higher value, and that the damping coefficient Dki of the front wheel side shock absorbers 1 and 2 can be easily changed to a higher value when the vehicle deceleration G in the front-rear direction is greater than a predetermined value c. A regulation content changing means 64 for changing the dead zone threshold values α and β, which are the regulation content of the means 63, is configured.

Next, to explain the operation and effect of the first embodiment, the shock absorbers 1 to 1 during traveling of the vehicle are described.
Under the control of the control unit 8, particularly the damping coefficient control means 62, the damping force Fs actually generated by the shock absorbers 1 to 4 becomes the skyhook damper force Fa, which is the target damping force, when 4 is expanded and contracted. Since the damping coefficient Dki of the shock absorbers 1 to 4 is changed between D1 to D10, the vertical fluctuation on the spring can be suppressed as much as possible. At this time, when the difference between the actual damping force Fs and the skyhook damper force Fa is within the dead zone, the damping coefficient Dki is prohibited from being changed, so that the damping coefficient Dki can be prevented from being frequently changed.

Further, when the vehicle is accelerated or decelerated, the regulation content changing means 64 of the control unit 8 which receives the signal from the longitudinal acceleration sensor 56 causes the threshold values α and β of the dead zone to be the acceleration and deceleration in the longitudinal direction of the vehicle. Accordingly, the front-rear posture of the vehicle body is changed so as not to change. That is, when the acceleration G of the vehicle is greater than the predetermined value a, the upper limit threshold value α in the change control of the damping coefficient Dki of the rear wheel side shock absorbers 3, 4 on the sinking side of the vehicle body is greater than the reference threshold value αa. The lower threshold β is changed to smaller αb and αc, and βb and βc are smaller than the reference threshold βa, respectively,
It becomes easier to change to a higher damping coefficient Dki. Further, when the deceleration G of the vehicle is decelerated by more than the predetermined value c, the upper limit threshold value α in the change control of the damping coefficient Dki of the front wheel side shock absorbers 1 and 2 on the sinking side of the vehicle body is greater than the reference threshold value αa. The lower threshold β is changed to smaller αb and αc, and βb and βc are smaller than the reference threshold βa, respectively,
It becomes easier to change to a higher damping coefficient Dki. As a result, it is possible to suppress changes in the front-rear posture of the vehicle body and improve riding comfort. In addition, the threshold values α and β are changed in two steps according to the magnitude of the acceleration / deceleration, and the degree to which the damping coefficient Dki is easily changed to a higher value can be changed. Can be suppressed.

FIG. 13 is a flow chart of a damping coefficient limiting routine according to the second embodiment of the present invention. This damping coefficient limiting routine is executed prior to the basic control for changing and controlling the damping coefficient Dki of the shock absorbers 1-4. It is something that will be done. In addition, in the second embodiment, the hardware configuration of the suspension device is exactly the same as that of the first embodiment. Therefore, when referring to the parts and the like, the reference numerals in the first embodiment are used.

In FIG. 13, after starting, first, the acceleration / deceleration G in the vehicle front-rear direction of the vehicle detected by the longitudinal acceleration sensor 56 in step S31 is a positive value, that is, the vehicle is accelerating. Or not. If the determination is YES, that is during acceleration, steps S32 and S33.
And the absolute value of the acceleration G is a predetermined value a, b (a <b).
Determine if greater than. When the acceleration G is greater than the predetermined value b and is large, the hard-side damping coefficients DH3 and DH4 of the rear-wheel-side shock absorbers 3 and 4 are determined in step S34.
Is set to D10, and soft side damping coefficients DS3 and DS4 are set to D9. When the acceleration G is medium acceleration which is smaller than the predetermined value b and larger than the predetermined value a, the hard side damping coefficient D is determined in step S35.
D8 is set to H3 and DH4, and D7 is set to the soft side damping coefficient DS3 and DS4.
When the acceleration G is small and the acceleration is smaller than the predetermined value a, in step S36, the hard damping coefficients DH3 and DH4 are set to D6, and the soft damping coefficients DS3 and DS4 are set to D4.

On the other hand, when the determination in step S31 is NO, that is, during deceleration, it is determined in steps S37 and S38 whether or not the absolute value of the deceleration G is larger than the predetermined values c and d (c <d). . When the deceleration G is large deceleration larger than the predetermined value d, the hard side damping coefficients DH1 and DH2 of the front wheel side shock absorbers 1 and 2 are set to D10, and the soft side damping coefficients DS1 and DS2 are set to D9 in step S39. During deceleration at which the deceleration G is smaller than the predetermined value d and larger than the predetermined value c, in step S40, the hard-side damping coefficients DH1 and DH2 are set to D8,
Set the soft side damping coefficient DS1 and DS2 to D7 and set the deceleration G
When the deceleration is smaller than the predetermined value c, in step S41, the hard side damping coefficients DH1 and DH2 are set to D6, and the soft side damping coefficients DS1 and DS2 are set to D4.

In the case of the second embodiment, the shock absorber 1
Basic control for changing the damping coefficient Dki of 4 to 4 is shown in FIG.
Although it is basically the same as that of the first embodiment shown in FIG. 5, the change of the damping coefficient of the shock absorbers 1 to 4 based on the judgment formula in step S8 is different. That is, in the second embodiment, if Y1i is positive (Y1i> 0), the damping coefficient Dki of the shock absorbers 1 to 4 is set to the hard damping coefficient DHi, while Y2i is negative (Y2i). <
0), the damping coefficient Dki of the shock absorbers 1 to 4
Set the soft side damping coefficient DSi to.

Therefore, in the second embodiment, the regulating means is the damping coefficient D1 to D10 of 10 stages of the shock absorbers 1 to 4.
The two damping coefficients DHi and DSi are limited from among the above, and only the limited two damping coefficients DHi and DSi are changed. However, in the flowchart of FIG. 13, the change control of the damping coefficient of the shock absorber in which the heart side and soft side damping coefficients are not set is the same as that of the first embodiment, and the shock absorber damping control is performed between the damping coefficients D1 to D10. The damping coefficient is changed. In addition, FIG.
According to the flowchart of FIG. 5, the regulation content changing means 64 ′ for changing the two damping coefficients DHi and DSi limited by the regulation means is configured, and the regulation content changing means 64 ′ is
The damping coefficients Dk3, Dk4 of the rear wheel side shock absorbers 3, 4 are high when the vehicle is accelerated, and the damping coefficients Dk1, Dk2 of the front wheel side shock absorbers 1, 2 are high when the vehicle is decelerated so that the two damping coefficients DHi, It is designed to change DSi.

Also in the second embodiment, when the vehicle is running, the damping force Fs actually generated by the shock absorbers 1 to 4 is the target damping force, as in the case of the first embodiment. Since the damping coefficient Dki of the shock absorbers 1 to 4 is changed between D1 to D10 so as to obtain the damper force Fa, the vertical fluctuation on the spring can be suppressed as much as possible.

On the other hand, when accelerating the vehicle, in the rear wheel shock absorbers 3 and 4 which are the sinking sides of the vehicle body, two damping coefficients DHi on the hard side are selected from the damping coefficients D1 to D10 which can be changed in 10 steps. , DSi are limited, and the shock absorbers 3, 4 are only between the two damping coefficients DHi, DSi.
Since the damping coefficient Dki of is changed, the damping coefficients Dk3 and Dk4 of the rear wheel side shock absorbers 3 and 4 are those on the hard side (high damping coefficient). Further, when the vehicle is decelerated, the front wheel side shock absorbers 1, 2
, The two damping coefficients DHi and DSi on the hardware side are limited from the ten adjustable damping coefficients D1 to D10, and the damping coefficients of the shock absorbers 1 and 2 are limited only between the two damping coefficients DHi and DSi. Since ki is changed, the damping coefficients Dk3 and Dk4 of the front wheel side shock absorbers 1 and 2 are on the hard side. As a result, it is possible to suppress changes in the front-rear posture of the vehicle body and improve riding comfort.
Moreover, the damping coefficient Dki of the rear wheel side shock absorbers 3, 4 or the front wheel side shock absorbers 1, 2 can be gradually changed to that on the hard side according to the magnitude of the acceleration / deceleration. It can be suppressed more effectively. Furthermore, it is possible to suppress the sound and vibration generated when the damping coefficient Dki of the shock absorbers 1 to 4 is changed.

The present invention is not limited to the first and second embodiments described above, but includes various modifications. For example, in the above-described first embodiment, the damping coefficient D of the predetermined shock absorbers 1 to 4 is set according to the road surface gradient.
In changing the thresholds α and β in the dead zone so that the ki can be easily changed to a higher one, both the upper limit threshold α and the lower limit threshold β are set to be small. Only one of the upper limit threshold α and the lower limit threshold β may be reduced.

[0048]

As described above, according to the vehicle suspension system of the present invention, the vertical variation on the spring is changed by changing the damping coefficient of the shock absorber so that the actual damping force of the shock absorber becomes the target damping force. While effectively suppressing the above, when the vehicle is accelerated or decelerated, the damping coefficient of the shock absorber on the sinking side of the vehicle body becomes high, and the change in the vehicle body front-rear posture can be suppressed, so that the riding comfort can be improved.

In particular, according to the second aspect of the invention, when the difference between the actual damping force and the target damping force is within the dead zone, it is prohibited to change the damping coefficient of the shock absorber, so that the damping coefficient is changed frequently. It also has the effect of preventing

Further, according to the third aspect of the invention, since the damping coefficient of the shock absorber is changed within a limited range, there is an effect that it is possible to prevent the generation of sound or vibration due to a great change of the damping coefficient.

[Brief description of drawings]

FIG. 1 is a perspective view showing a component layout of a vehicle including a suspension device according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a main part of a shock absorber.

FIG. 3 is an exploded perspective view of an actuator.

FIG. 4 is a schematic diagram showing a vibration model of a suspension device.

FIG. 5 is a diagram showing a damping coefficient of a shock absorber.

FIG. 6 is a perspective view of a step motor.

FIG. 7 is a plan view of a rotor and a stator of a step motor.

FIG. 8 is a bottom view of the lid of the step motor.

FIG. 9 is a block diagram of a control system of the suspension device.

FIG. 10 is a flowchart of basic control for changing and controlling a damping coefficient of a shock absorber.

FIG. 11 is a flowchart of a threshold value setting routine.

FIG. 12 is a diagram for explaining the significance of threshold values α and β.

FIG. 13 is a flowchart of a damping coefficient limiting routine according to the second embodiment.

[Explanation of symbols]

 1 to 4 shock absorber 8 control unit 51 to 54 pressure sensor (actual damping force detection means) 56 longitudinal acceleration sensor (acceleration / deceleration detection means) 61 target damping force determination means 62 damping coefficient control means 63 restriction means 64, 64 ' Means of change

Claims (5)

[Claims] 1. A shock absorber, which is disposed between an unsprung part and an unsprung part and whose damping coefficient can be changed in a plurality of stages, and an actual damping force detecting means for detecting a damping force actually generated by the shock absorber. , A target damping force determination means for determining the target damping force of the shock absorber so that the sprung mass does not fluctuate up and down, and damping for changing and controlling the damping coefficient of the shock absorber so that the actual damping force becomes the target damping force. Coefficient control means, restriction means for applying a predetermined restriction to change control of the damping coefficient control means, acceleration / deceleration detection means for detecting acceleration / deceleration in the longitudinal direction of the vehicle body, A suspension device for a vehicle, comprising: a regulation content changing means for changing the regulation content of the regulation means so that the front-rear posture does not change. 2. The regulation means prohibits the damping coefficient of the shock absorber from being changed when the difference between the actual damping force and the target damping force is within a predetermined dead zone region. The vehicle suspension device according to claim 1, wherein the threshold value of the dead zone region is changed. 3. The limiting means limits a number of damping coefficients smaller than a plurality of damping coefficients which can be changed by the shock absorber, and limits the damping coefficient only between the limited damping coefficients. The suspension device for a vehicle according to claim 1, wherein the regulation content changing means changes the range of the damping coefficient limited by the regulating means. 4. The regulation content changing means makes it easier to change the damping coefficient of the shock absorber on the rear wheel side to a higher damping coefficient when the vehicle accelerates, and increases the damping coefficient of the shock absorber on the front wheel side to a higher damping coefficient when decelerating the vehicle. The vehicle suspension device according to claim 2, wherein the threshold value of the dead zone region is changed so as to be easily changed. 5. The regulation content changing means is limited by the regulating means so that the damping coefficient of the shock absorber on the rear wheel side is high when the vehicle is accelerating and the damping coefficient of the shock absorber on the front wheel side is high when the vehicle is decelerating. The vehicle suspension device according to claim 3, wherein the range of the damping coefficient to be changed is changed.