JPH06106939A - Vehicle suspension - Google Patents

Abstract

(57) [Summary] [Purpose] When the input from the road surface is large, the input from the road surface that travels on the road surface with a small sprung mass amplitude is ensured while ensuring sufficient damping energy for the excitation energy. If it is small, suppress the sprung displacement to improve the flatness. When the damping force characteristic control means d determines that the traveling state determination means e determines that the vehicle is traveling on a good road, when the damping force generated in the suspension unit b is acting in the vibration direction, the damping force characteristic control means d changes the stroke direction to a low damping force. On the contrary, when the damping force is acting in the damping direction, conversely, the damping control is performed to output an operation signal having a high damping force characteristic in the stroke direction to each suspension unit, and it is determined that the vehicle is running on a rough road. In some cases, flat control is performed to output an actuation signal to each suspension unit b based on a control signal obtained by a control equation having a sprung vertical velocity term and a relative displacement correction term.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension system for optimally controlling a damping force characteristic (hard or soft) of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, as a vehicle suspension system for controlling a damping force characteristic of a shock absorber, for example, Japanese Patent Application Laid-Open No. 61-61600.
The one described in Japanese Patent No. 163011 is known.

This conventional vehicle suspension system detects the sprung vertical velocity and the relative velocity between the sprung and unsprung portions, and when both have the same sign, the damping force characteristic is a hard characteristic, and when both have different signs. The damping force characteristic control based on the skyhook theory, such as making the damping force characteristic soft, was performed independently for the four wheels. As a result, the vibration damping energy can be increased with respect to the vibration energy transmitted to the vehicle body, the vibration of the vehicle body can be suppressed, and an excellent riding comfort can be obtained. It was possible to suppress steering and improve steering stability.

[0004]

However, in the above-mentioned conventional apparatus, the sprung mass velocity is mainly detected by detecting the acceleration and using a filtering process or an integrator to calculate the sprung velocity. Since a delay occurs and the phases do not match in the entire frequency band required for control, control is performed with a signal with some delay or advance, so the amplitude on the spring is small like a good road. It was difficult to get a flat feeling when driving on a rough road surface. In addition, as a characteristic of the shock absorber, it is difficult to obtain a large damping force when the piston speed is low, so when driving on a good road as described above, it is difficult to increase the damping force due to the low piston speed, which also gives a flat feeling. It was one of the causes of difficulty.

The present invention has been made by paying attention to the above-mentioned conventional problems, and when the input from the road surface is large, the sprung mass amplitude is ensured while sufficiently securing the damping energy for the exciting energy. When the input from the road surface such as traveling on a minute road surface is small, the object is to suppress the sprung displacement and improve the feeling of flatness.

[0006]

Therefore, in the present invention, vibration control called so-called "skyhook control" is performed to dampen the vehicle body when traveling on a bad road, and the sprung vertical velocity and It was decided to achieve the above-mentioned object by performing flat control that suppresses the relative displacement in proportion to the relative displacement.

That is, the vehicle suspension system of the present invention is shown in FIG.
As shown in the corresponding claim diagram, the suspension unit b is interposed between the sprung part and the unsprung part of the vehicle, and the damping force characteristic can be changed by the damping characteristic changing means a; and the suspension unit b by the input from the input means c. When it is determined that the generated damping force is acting in the vibration direction, the stroke direction is set to the low damping force characteristic. Conversely, when it is determined that the damping force is acting in the damping direction, the stroke direction is set to the high damping force. In a vehicle suspension system including damping force characteristic control means (d) for performing damping control that outputs a characteristic actuation signal to each suspension unit, the damping force characteristic control means (d) is driven on a good road by a traveling state determination means (e). When it is determined that the vehicle is in a state, the vibration suppression control is performed, and when it is determined that the vehicle is traveling on a rough road,
It is configured to perform flat control for outputting an actuation signal to each suspension unit b based on a control signal obtained by a control equation having a sprung vertical velocity term and a relative displacement correction term.

In the flat control, the damping force characteristic control means d determines the coefficient of the relative displacement term of the control formula based on the magnitude of at least one or both of the sprung vertical velocity and the sprung vertical acceleration. It may be changed by changing.

Further, the suspension unit b is
The extension side hard characteristic with the variable extension side damping force characteristic and the compression side damping force characteristic fixed to the low damping force characteristic, and the compression side hard characteristic with the variable compression side damping force characteristic with the low extension side damping force characteristic fixed to the extension side Both the pressure side and the compression side are configured to be able to form three characteristics, a low damping force characteristic and a fixed soft characteristic, and the damping force characteristic control means d sets the coefficient of the correction term of the control equation at the time of vibration damping control. Based on the control signal obtained by the control equation set to 0, and at the time of flat control, the control is performed based on the control signal obtained by the control equation, and the control signal indicates the extension side threshold value. If it exceeds, it is controlled to the extension side hard characteristic, and if the control signal exceeds the compression side threshold value, it is controlled to the compression side hard characteristic and the control signal is between the extension side threshold value and the compression side threshold value. In the case of, the operation signal for controlling to the soft characteristic is output. It may be so.

[0010]

[Function] When driving on a bad road, when it is determined that the damping force generated by the suspension unit is acting in the damping direction, as in the conventional technique, the stroke direction is set to a high damping force characteristic and the damping generated by the suspension unit is performed. When it is determined that the force acts in the vibration direction with respect to the vertical vibration of the vehicle body, the vibration control of the vehicle body is suppressed by performing the vibration damping control with the low damping force characteristic in the stroke direction. By the way, whether the damping force generated by the suspension unit acts in the vibration direction or the damping direction depends on the signs of the sprung vertical velocity and the relative velocity, for example, if the signs match, the damping direction If they do not match, it can be determined as the excitation direction.

When traveling on a good road, a flat control for outputting an operation signal to the suspension unit based on a control signal obtained by a control equation having a term proportional to the sprung vertical velocity and a correction term proportional to the relative displacement. I do. Therefore, the damping force characteristic of the suspension unit corresponds to the relative displacement, and the relative displacement can be suppressed by the damping force generated in this suspension unit, and the vehicle body posture can be kept flat.

Further, in the apparatus according to the second aspect, the coefficient of the correction term is changed based on either or both of the sprung vertical velocity and the sprung vertical acceleration. Therefore, the sprung vertical velocity is changed. Is larger, or the sprung vertical acceleration is larger, the suspension unit is controlled so that a large damping force is generated, so that the vehicle body posture can be surely kept flat.

Further, in the apparatus according to the third aspect of the present invention, at the time of damping control, the coefficient of the correction term of the relative displacement is set to 0 and the sprung vertical velocity term is included, but the relative displacement correction term is not included. The control signal is obtained by the following equation, and during the flat control, the control signal is obtained by the control equation having the relative displacement correction term. Therefore, if the sprung vertical speed is the same, the control signal tends to be larger during the flat control. When the control signal proportional to the sprung vertical velocity exceeds the extension side threshold value, the extension side hardware characteristic is controlled, and when the control signal exceeds the compression side threshold value, the compression side hardware characteristic is controlled. When the control signal is controlled to the characteristic, and the control signal is between the extension side threshold value and the compression side threshold value, the operation signal for controlling the soft characteristic is output.

That is, in the damping control, when the extension side hard characteristic or the compression side hard characteristic is controlled, the suspension unit has a high damping force characteristic in the direction of sprung vertical velocity and a low damping force in the opposite direction. It is a characteristic. Therefore, in the situation where the direction of the relative velocity matches the direction of the sprung vertical velocity and the damping force generated in the suspension unit acts in the damping direction, the stroke direction is a high damping force and the generated damping force Vibration is controlled by
In the situation where the direction of relative velocity does not match the direction of sprung vertical velocity and the damping force generated in the suspension unit acts in the vibration direction, the stroke direction is low damping force and the generated damping force To weaken. Then, two states in which the damping force generated in the suspension unit suppresses the vibration or the excitation force is weakened can be obtained without switching the damping force characteristics of the suspension unit. Further, during soft control, both the extension side and the compression side have low damping force characteristics, weakening the excitation force in any stroke. In addition,
In the state where the stroke direction has the high damping force characteristic as described above, the reverse stroke direction has the low damping force characteristic, so that the transmission of the road surface input in this direction is weakened and the riding comfort is improved.

Also in the case of flat control, the damping force characteristic of the suspension unit is switched in the same manner as described above, but in this case, since the damping force characteristic corresponds to the relative displacement, the damping force generated by the suspension unit is used. Since the relative displacement is suppressed, a flat feeling can be obtained.

[0016]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure will be described.

FIG. 2 is a structural explanatory view showing a vehicle suspension system of a first embodiment which is an embodiment of the invention described in each claim, and is interposed between a vehicle body and four wheels, and four Shock absorber (suspension unit) SA ₁ , S
A ₂ , SA ₃ , and SA ₄ (in the explanation of the shock absorber, when these four are collectively referred to and when describing their common configuration, they are simply indicated as SA) are provided. . A sprung vertical acceleration sensor (hereinafter, referred to as vertical G sensor) 1 for detecting vertical acceleration is provided on the vehicle body near each shock absorber SA. Further, a control unit 4 is provided near the driver's seat to input a signal from each vertical G sensor 1 and output a drive control signal to the pulse motor 3 of each shock absorber SA.
Further, each shock absorber SA is provided with a stroke sensor 8 that detects the stroke amount of the shock absorber SA.

FIG. 3 is a system block diagram showing the above-mentioned configuration. The control unit 4 is provided with an interface circuit 4a, a CPU 4b, and a drive circuit 4c, and the interface circuit 4a includes the above-mentioned vertical G sensors 1 and A signal from each stroke sensor 8 is input. In the interface circuit 4a, the filter circuit group shown in FIG. 14 is provided for each vertical G sensor 1. That is, the signal g sent from the vertical G sensor 1 is
6 Hz H. P. In addition to being processed into a sprung vertical acceleration G (hereinafter referred to as "acceleration G") in which low frequency components have been cut by F, 30 Hz L. P. F and 0.1Hz L.F. P. F, AMP and 1.0Hz
H. P. F and 1.5Hz L.F. P. By F, the integrated sprung vertical velocity v (hereinafter referred to as velocity v) is processed.

Next, FIG. 4 is a sectional view showing the structure of the shock absorber SA.
A cylinder 30, a piston 31 defining the cylinder 30 into an upper chamber A and a lower chamber B, an outer cylinder 33 having a reservoir chamber 32 formed on the outer periphery of the cylinder 30, and a lower chamber B and a reservoir chamber 32 are defined. The base 34, the guide member 35 for guiding the sliding movement of the piston rod 7 connected to the piston 31, the suspension spring 36 interposed between the outer cylinder 33 and the vehicle body, and the bumper bar 37. Reference numeral 7 in the drawing denotes a piston rod, and a control rod 70 rotated by the pulse motor 3 is provided through the piston rod 7.

Further, as shown, the piston rod 7
On the side, a stroke sensor 8 is provided near the bumper bar 37. In the stroke sensor 8, the detection light emitted downward is used as the outer cylinder 33.
The stroke amount of the shock absorber SA is detected by finding the distance to the reflection plate 8a from the time it takes to hit the reflection plate 8a provided on the upper part and return.

Next, FIG. 5 is an enlarged sectional view showing a portion of the piston 31. As shown in FIG. 5, the piston 31 is formed with through holes 31a and 31b, and each through hole is formed. An expansion side damping valve 12 and a compression side damping valve 20 that open and close 31a and 31b respectively are provided. A stud 38 penetrating the piston 31 is fixed to the bound stopper 41 screwed to the tip of the piston rod 7 by screwing.
Is a flow path (an expansion side second flow path E, an expansion side third flow path F, a bypass flow path G, a compression side) which communicates the upper chamber A and the lower chamber B by bypassing the through holes 31a and 31b. A communication hole 39 for forming the second flow path J) is formed, and an adjuster 40 for changing the flow path cross-sectional area of the flow path is rotatably provided in the communication hole 39. ing. Also, stud 3
An expansion side check valve 17 and a pressure side check valve 22 are provided on the outer peripheral portion of 8 to allow and block the flow on the side of the flow path formed by the communication hole 39 depending on the direction of flow of the fluid. The control rod 70 is connected to the adjuster 40. In addition, the stud 38 has a first port 21, a second port 13, and a third port in order from the top.
A port 18, a fourth port 14 and a fifth port 16 are formed.

On the other hand, in the adjuster 40, the hollow portion 19 is formed, the first lateral hole 24 and the second lateral hole 25 which communicate the inside and the outside are formed, and the vertical groove 23 is formed in the outer peripheral portion. ing.

Therefore, between the upper chamber A and the lower chamber B, the inside of the extension side damping valve 12 is opened by passing through the through hole 31b as a flow passage through which the fluid can flow in the extension stroke. First side flow path D extending to B, second port 13, vertical groove 2
The expansion side second flow path E which opens the outer peripheral side of the expansion side damping valve 12 to the lower chamber B via the third and fourth ports 14, and the second
The extension side check valve 17 is opened via the port 13, the vertical groove 23, and the fifth port 16 to reach the lower chamber B.
Channel F, third port 18, second lateral hole 25, hollow portion 19
There are four flow paths, a bypass flow path G, which leads to the lower chamber B via. Also, as a flow path through which the fluid can flow in the pressure stroke,
The pressure-side first flow path H that opens the pressure-side damping valve 20 through the through hole 31a and the pressure-side check valve 22 through the hollow portion 19, the first lateral hole 24, and the first port 21 to open the upper chamber A. Pressure side second flow path J leading to the hollow part 19, the second lateral hole 2
5, There are three flow paths, a bypass flow path G reaching the upper chamber A via the third port 18.

That is, the shock absorber SA can be changed in characteristics from a low damping force (soft) characteristic to a high damping force (hard) characteristic on both the extension side and the compression side by rotating the adjuster 40. In the embodiment, this characteristic change is proportionally changeable in multiple stages as shown in FIG. 6, so this characteristic is expressed by the term attenuation coefficient.

Further, in the present embodiment, as shown in FIG. 7, the adjuster 40 is rotated counterclockwise from the state in which both the expansion side and the compression side are soft (hereinafter referred to as the soft characteristic SS). And, it is possible to change the damping coefficient in multiple steps only on the extension side,
The compression side has a characteristic that is fixed to a low damping coefficient (hereinafter referred to as the extension side hard characteristic HS). Conversely, when the adjuster 40 is rotated clockwise, the damping coefficient can be changed in multiple steps only on the compression side.
The extension side is configured to have a region where the low damping coefficient is fixed (hereinafter referred to as compression side hard characteristic SH).

By the way, in FIG. 7, when the adjuster 40 is arranged in the position of ,, KK of FIG.
The cross section, the LL cross section, the MM cross section, and the NN cross section are shown in FIGS. 8, 9, and 10, respectively, and the damping force characteristics at each position are shown in FIGS.

Next, the operation of the control unit 4 for controlling the driving of the pulse motor 3 will be described with reference to the flowchart of FIG. Note that this control is separately performed for each shock absorber SA.

In step 101, the velocity v and the acceleration G obtained by processing the signals from the respective vertical G sensors 1 are read, and the stroke amount X obtained from each stroke sensor 8 is read.

Step 102 is for velocity v and acceleration G.
Is a step of determining which area of the map shown in FIG. 16 is included. That is, this map is a map for determining the value of the coefficient β of the correction term of the control equation described later, and as the value of β, there are three values of 0, β ₁ , and β ₂ (0 <β ₁ < beta ₂ is a) is being prepared, each value v, a G, a first threshold value v _1, G ₁ and the second threshold between v _2, as compared to the G ₂ beta = 0, respectively If it is determined, the process proceeds to step 103, if β = β ₁ is determined, the process proceeds to step 104, and if β = β ₂ is determined, the process proceeds to step 105.

In step 103, the control expression (α
Is a coefficient), that is, a step of calculating the control signal V based on a control expression of only the term of the speed v.

In step 104, V = α [v + β ₁ (X
_1- X ₀ )], that is, a step of calculating the control signal V based on a control expression having a speed term and a relative displacement (X ₁ -X ₀ ) correction term. The relative displacement (X ₁ −X ₀ ) is obtained by the change in the stroke amount X within a predetermined time (X ₁ is the sprung displacement, X ₀ is the road surface displacement).

In step 105, V = α [v + β ₂ (X
_1- X ₀ )], that is, a step of calculating the control signal V based on a control equation having a velocity term and a relative displacement correction term.

In step 106, it is judged whether the absolute value of the control signal V is a predetermined threshold value K or more, and YE
In S, the process proceeds to step 107, and when NO, the process proceeds to step 110. By the way, in the control signal V, the positive side indicates the extension side, the negative side indicates the compression side, + K is the extension side threshold value, and −K.
Is the pressure side threshold.

In step 107, it is determined whether or not the control signal V is positive, and if YES, the process proceeds to step 108, and NO
This is the step for proceeding to step 109.

Step 108 is a shock absorber S
This is a step of outputting an operation signal to the pulse motor 3 so as to control A to the extension side hardware characteristic. The expansion side damping coefficient at this time is proportional to the magnitude of the control signal V.

Step 109 is a shock absorber S
This is a step of outputting an operation signal to the pulse motor 3 so as to control A to the pressure side hardware characteristic. The compression-side damping coefficient at this time is proportional to the magnitude of the control signal V.

Step 110 is a shock absorber S
This is a step of outputting an operation signal to the pulse motor 3 so as to control A to have a soft characteristic.

Next, the operation of the embodiment apparatus will be described.

A) When traveling on a bad road When traveling on a bad road, the speed v or the acceleration G on the spring becomes a large value, and each of the values v and G is larger than the first threshold values v ₁ and G _1. If it is larger, β in the control equation for calculating the control signal V is determined to be 0 based on the map shown in FIG.

Therefore, the control signal V is calculated by a calculation formula of V = αv (steps 102 → 103), and the shock absorber SA is set on the basis of the control signal V to the extension side hardware characteristic HS, the compression side hardware characteristic SH, and the software. Characteristic SS
And the attenuation coefficient is switched in proportion to the magnitude of the control signal V. That is, if the control signal V is a positive value and larger than the threshold value K, the extension side hardware characteristic HS is set, and if the control signal V is a negative value and the absolute value is larger than the threshold value K, the pressure side hardware characteristic SH is set. If the absolute value of the control signal V is smaller than the threshold value K, the soft characteristic SS
And When traveling on a rough road, the speed v increases, so that the absolute value of the control signal V rarely becomes smaller than the threshold value K, and therefore the soft characteristic SS hardly occurs.

By the way, as described above, in the embodiment, the shock absorber S is generated only in accordance with the direction of the speed v on the spring.
By switching the characteristics of A, sprung like the prior art-
Although not compared with the sign of the relative speed of the spring, the damping control (skyhook control) can be performed by the above-described control for the reason described below. For example, when controlling to the extension side hard characteristic HS, the shock absorber SA
Has a high damping coefficient on the extension side and a low damping coefficient on the compression side. Therefore, in a situation where the direction of the relative speed is the extension direction and the damping force generated by the shock absorber SA is acting in the damping direction, damping is performed by the generated damping force because the extension side has a high damping coefficient. On the contrary, in the situation where the direction of the relative speed is the compression side direction and the damping force generated by the shock absorber SA is acting in the vibration direction, the compression side has a low damping coefficient and therefore the vibration is generated by the generated damping force. There is nothing to do. In addition, the shock absorber S
It is possible to form two states in which the generated damping force damps the damping force or weakens the excitation force without switching while keeping A as the extension side hard characteristic HS, thereby reducing the switching frequency. , High durability and operation response can be obtained. The same applies to the pressure side hardware characteristic SH.

Further, in the state where the stroke direction has a high damping coefficient as described above, since the reverse stroke direction has a low damping coefficient, the transmission of the road surface input in this direction is weakened,
The riding comfort is improved.

B) When traveling on a good road When traveling on a good road, the speed v and the acceleration G are smaller than those when traveling on a bad road. Then, based on the map of FIG. 16, neither of the respective values v and G exceeds the first threshold values v ₁ and G ₁ , and neither is the second threshold values v ₂ and G _2. Is greater than, then β = β _1, and
If neither exceeds the second threshold values v ₂ and G ₂ , β
= Β ₂ .

As described above, β = β ₁ or β = β ₂
When, the sprung-unsprung relative displacement (X ₁ -X
_The control signal V is obtained based on the control equation having the correction term of ( ₀ ) (steps 104 and 105).

FIG. 17 shows a slip line expression based on this control expression. When β = 0, the control signal V
Overlaps with the horizontal axis and becomes skyhook control. Further, as described above, whether the vehicle is traveling on a good road or traveling on a bad road is determined by the map of FIG. 16 based on the speed v and the acceleration G and the first threshold v.
_Since the determination is made by comparing ₁ and G ₁ (step 102), the up / down G sensor 1, the portion for calculating the speed v in the control unit 4, and the portion for performing the determination in step 102 are also claimed. Thus, the traveling state detecting means in the range will be configured.

Then, as described above, the relative displacement (X ₁ -X
_When the control signal V is obtained using the correction term of ( ₀ ), the velocity v
Compared with the case of the vibration suppression control based on the control expression of only the term, the value of the control signal V is the relative displacement (X ₁
The value tends to be high in proportion to −X ₀ ), and the high damping coefficient is controlled accordingly. Further, since β ₂ > β ₁ , the control equation using β ₂ as a coefficient is more easily controlled to have a higher damping coefficient than the control equation using β ₁ . The fact that the damping coefficient is easily controlled here does not mean that the damping coefficient actually becomes large, but means that the damping coefficient easily becomes larger than the value of the speed v, that is, , If the speed v is the same, the control signal having the correction term of the coefficient of β ₂ has the largest control signal V, and then the control signal obtained by the control expression having the correction term of the coefficient of β ₁ The control signal V obtained by the control formula at the time of damping control in which V is large and β = 0 is the lowest value, but in reality, the velocity v becomes larger in the latter case. Does not mean that the damping coefficient is larger.

As described above, the speed v and the acceleration G on the spring are
When the vehicle is running on a small road, the damping coefficient of the shock absorber SA is largely controlled in proportion to the relative displacement (X ₁ −X ₀ ), so that the relative displacement can be suppressed and the body posture can be kept flat. . Further, since it is determined whether to perform such flat control or the above-described vibration suppression control (skyhook control) based on both the speed v and the acceleration G, for example, relatively small unevenness Various bad roads such as a road surface where the vibration amplitude of the vehicle body is small and the speed v is small but the acceleration G is large, or conversely, a "waviness road" where the acceleration G is small but the speed v is large. It is possible to perform the vibration suppression control corresponding to the above, and to improve the control quality.

Incidentally, the switching of the characteristics and the damping coefficient of the shock absorber SA by the device of this embodiment is shown in the time chart of FIG.

(Second Embodiment) Next, the second embodiment will be described. Only the points different from the first embodiment will be described.

In this embodiment, the operation of the control unit 4 is different from that of the first embodiment, and as shown in the flowchart of FIG.
Step 201 of determining V = α [v + β
(X ₁ −X ₀ )] is provided to provide a step 202 for obtaining the control signal V.

The step 201 will be described in detail.
The basic rule of this control is that "if the sprung vertical velocity v and the sprung vertical acceleration are small, the coefficient β of the correction term is increased."
Three grades GL, GM, and GB are set according to the acceleration G as the first membership function, and as shown in FIG. 21, three grades GL, GM, and GB are set according to the speed v as the second membership function. Grades VL, VM and VB are set. Then, when the likelihood of a good road is detected in this way, the value of the coefficient β is determined by slightly prioritizing the magnitude of the velocity v over the acceleration G as shown in the rule table of FIG. According to the above rule, it is configured to conclude that it is a good road and to determine the coefficient β by the map shown in FIG. When β is 0 or less in this map, β = 0.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like without departing from the scope of the invention.

For example, in the embodiment, whether the road is good or bad,
That is, the determination as to whether to perform the vibration suppression control (skyhook control) or the flat control is made based on the sprung vertical velocity v and the sprung vertical acceleration G, but based on only one of them, It may be determined.

In the embodiment, the extension side hard characteristic HS,
Although an example using a suspension unit capable of forming the pressure side hard special SH and soft characteristics SS is shown, as shown in the prior art, a suspension unit in which the expansion side and the compression side simultaneously change from hard to soft is used. Good. In this case, it is necessary to detect the relative speed when performing the vibration suppression control.

[0055]

As described above, the vehicle suspension system of the present invention has a low damping characteristic in the stroke direction in a situation where the damping force of the suspension unit acts in the exciting direction during traveling on a rough road, and the vibration damping is performed. In the situation where it is acting in the direction of the direction, the damping control is performed so that the stroke direction has a high damping characteristic, while at the time of running on a good road, the control signal is calculated by the control formula having the correction term for the relative sprung-unsprung displacement. Since the characteristics of the suspension unit are controlled by this control signal, when the traveling condition determination means determines that the vehicle is traveling on a rough road, vibration control is performed so that the road surface energy is not input to the vehicle body and a good ride comfort is obtained. To improve the feeling of flatness by performing flat control that suppresses displacement of the vehicle body due to the damping force generated in the suspension unit when driving on a good road. An effect that can be obtained. By the way, if this flat control is performed on a bad road, the transmission force of the road surface input will increase and the riding comfort will deteriorate, and operating noise and oil hammer will occur in the suspension unit, causing unpleasant vibration and noise. I will end up.

Further, in the apparatus according to the second aspect, the suspension unit is controlled so that a larger damping force is generated as the sprung vertical velocity is larger or the sprung vertical acceleration is larger. The effect that the flatness can be further improved is obtained.

Further, in the apparatus according to the third aspect, the suspension unit is configured such that the extension side has high damping force characteristics and the compression side has low damping force characteristics, and the compression side has high damping force characteristics and the extension side has low damping force characteristics. Since it is possible to form the compression side hard characteristic and the soft characteristic of the low damping force characteristic on both the extension side and the compression side, the sign of the relative velocity will change if the direction of the sprung vertical velocity is constant, as in the past. However, since it is not necessary to change the characteristics of the suspension unit, the switching frequency is reduced, and the operation response and durability are improved. In addition, in the extension side hard characteristic and the compression side hard characteristic, since the reverse stroke direction has the low damping force characteristic, the transmission of the road surface input in this direction is weakened, and the riding comfort is improved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a claim showing a vehicle suspension device of the present invention.

FIG. 2 is a structural explanatory view showing a vehicle suspension device of the first embodiment of the present invention.

FIG. 3 is a system block diagram showing a vehicle suspension system of the first embodiment.

FIG. 4 is a cross-sectional view showing a shock absorber (suspension unit) applied to the device of the first embodiment.

FIG. 5 is an enlarged cross-sectional view showing a main part of the shock absorber.

FIG. 6 is a damping force characteristic diagram corresponding to the piston speed of the shock absorber.

FIG. 7 is a characteristic diagram of damping force characteristics corresponding to the step position of the pulse motor of the shock absorber.

FIG. 8 is a K of FIG. 5 showing a main part of the shock absorber.
FIG.

FIG. 9 is an L of FIG. 5 showing a main part of the shock absorber.
It is a -L cross section and a MM cross section.

FIG. 10 is a sectional view taken along line NN of FIG. 5, showing a main part of the shock absorber.

FIG. 11 is a damping force characteristic diagram of the shock absorber when the extension side is hard.

FIG. 12 is a damping force characteristic diagram of the shock absorber in a soft state on the extension side and the compression side.

FIG. 13 is a damping force characteristic diagram of the shock absorber in a compression side hard state.

FIG. 14 is a block diagram showing a main part of a control unit of the first embodiment.

FIG. 15 is a flowchart showing the control operation of the control unit of the first embodiment device.

FIG. 16 is a diagram showing a map for determining a coefficient of the apparatus of the first embodiment.

FIG. 17 is a diagram showing a slip line of the device of the first embodiment.

FIG. 18 is a time chart showing the operation of the first embodiment device.

FIG. 19 is a flowchart showing the control operation of the control unit of the second embodiment device.

FIG. 20 is a characteristic diagram showing a grade in which the sprung vertical acceleration of the second embodiment is used as a membership function.

FIG. 21 is a characteristic diagram showing a grade in which the sprung vertical velocity of the second embodiment is used as a membership function.

FIG. 22A is a map showing rules, and FIG.
Is a diagram showing a conclusion.

[Explanation of symbols]

 a damping force characteristic changing means b suspension unit c input means d damping characteristic control means e running state determination means

Claims (3)

[Claims] 1. A suspension unit interposed between a sprung part and an unsprung part of a vehicle and capable of changing a damping force characteristic by a damping characteristic changing means, and a damping force generated in the suspension unit by an input from an inputting means. When it is determined that the suspension force is acting on the suspension, a low damping force characteristic is set in the stroke direction. Conversely, when it is determined that the damping force acts in the damping direction, a high damping force characteristic is set in the stroke direction. In a vehicle suspension device including damping force characteristic control means for performing damping control output to a unit, when the damping force characteristic control means determines that the vehicle is in a good road traveling state, the damping control is performed. Done,
When it is determined that the vehicle is traveling on a rough road, it is configured to perform flat control by outputting an actuation signal to each suspension unit based on a control signal obtained by a control equation having a sprung vertical velocity term and a relative displacement correction term. A vehicle suspension system characterized by the above. 2. When the damping force characteristic control means is in flat control, the coefficient of the term of relative displacement of the control formula is based on at least one or both of sprung vertical velocity and sprung vertical acceleration. A vehicle suspension system characterized in that the vehicle suspension system is changed. 3. The suspension unit, wherein the extension side damping force characteristic is variable and the compression side damping force characteristic is low, the extension side hard characteristic is fixed, and the compression side damping force characteristic is variable, and the extension side damping force characteristic is low damping. It is possible to form three characteristics, that is, a compression side hard characteristic with a fixed force characteristic and a soft characteristic with a fixed low damping force characteristic on both the extension side and the compression side, and the damping force characteristic control means, during damping control, The control is performed based on a control signal obtained by the control equation in which the coefficient of the correction term of the control equation is 0, and during flat control, based on the control signal obtained by the control equation. When the signal exceeds the extension side threshold value, the extension side hardware characteristic is controlled, and when the control signal exceeds the compression side threshold value, the compression side hardware characteristic is controlled and the control signal is extended side. Between threshold and pressure side threshold The vehicle suspension system according to claim 1 or 2, characterized in that to output an actuation signal for controlling the soft characteristic.