JPH07246819A - Suspension controller - Google Patents

Abstract

PURPOSE:To restrain the vibration of a car body more effectively than that of conventional car bodies for improving the riding comfort of a vehicle when one wheel gets over projections or the like. CONSTITUTION:When vibration is inputted to a right front wheel 10FR, the damping coefficient of a shock absorber for the vibration input wheel and a left rear wheel 10RL in the diagonal direction is increased in low speed and the damping coefficient of a shock absorber for the vibration input wheel and a left and right rear wheels 10RR, 10RL is increased in medium and high speed so as to restrain the large vibration. Thus, the sway of the vehicle produced when one of left and light front wheels gets over a projection in the low speed, i.e., the sway having the large vertical vibration of the car body in positions corresponding to the vibration input wheel and the wheel in the diagonal direction is restrained and the sway of the vehicle produced when one of left and right front wheels gets over the projection in the medium and high speed, i.e., the sway having the large vertical vibration of the car body in the positions corresponding to the vibration input wheel and left and right rear wheels is restrained.

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 a damping force of a suspension connecting a wheel and a vehicle body.

[0002]

2. Description of the Related Art Conventionally, as a device for controlling the damping force of a shock absorber of a suspension provided in an automobile or the like, as shown in, for example, Japanese Patent Application Laid-Open No. 60-183216, front wheel vibration detection for detecting vibration of front wheels. And a rear-wheel vibration detector that detects the vibration of the rear wheels, and a control circuit that controls the damping force based on the output signals from these detectors.At least immediately after the front wheels vibrate, the rear wheels vibrate. It is known that the damping force is kept in a low state until the time when the rear wheel is driven and the damping force is returned to the original state immediately after the rear wheel vibrates.

According to such a suspension control device, the damping force of the shock absorber of the rear wheels is kept low after the front wheels have passed over the protrusions, so that the impact is transmitted to the vehicle body when the rear wheels pass over the protrusions. The damping force is suppressed and the damping force is returned to the original damping force immediately after the rear wheel has passed over the projection or the like, so that the vibration of the vehicle body is effectively damped. Therefore, it is possible to improve the riding comfort of the vehicle when the wheels pass over the protrusions and the like.

[0004]

However, in the above-mentioned conventional technique, the vibration of the vehicle body (vibration called "flapping" near the sprung resonance frequency) when one of the left and right wheels crosses a protrusion or the like is Since it appears remarkably not only on the input wheel but also on the wheels in the diagonal direction with respect to the wheel, depending on the conventional damping force control device as described above in which the damping force of the shock absorber of the rear wheel is controlled based on the vibration of the front wheel, It has not been possible to effectively suppress the vibration of the vehicle body when one wheel gets over a protrusion or the like.

The present invention has been made in view of these problems, and more effectively suppresses the vibration of the vehicle body when one wheel gets over a protrusion or the like, and improves the riding comfort of the vehicle. Is intended.

[0006]

In order to achieve such an object, the following constitution is adopted as a means for solving the above problems.

That is, the suspension control device according to claim 1 of the present invention is a suspension control device that can independently control the damping force of the suspension that connects the wheel and the vehicle body for each wheel, and Vertical vibration detection means for respectively detecting vertical vibrations of the vehicle body at both parts corresponding to the right front wheel, low frequency component extraction means for respectively extracting low frequency components of the detected vertical vibrations, and each of the extracted low frequencies A vibration determining means for determining whether or not the component exceeds a predetermined value, and when the low frequency component of any one of the low frequency components is determined to exceed the predetermined value by the vibration determining means, A wheel corresponding to the frequency component is used as a vibration input wheel, and damping force increasing means for increasing the damping force of the suspension for the vibration input wheel and each of the left and right rear wheels are provided. , Has as its gist.

In the suspension control device having the above construction, a vehicle speed detecting means for detecting the speed of the vehicle, a low speed area judging means for judging whether or not the detected vehicle speed is in a predetermined low speed area, and the low speed area. And a prohibiting means for prohibiting an increase of the damping force of the suspension for the rear wheel on the vibration input wheel side by the damping force increasing means when the range determining means determines that the vehicle speed is in a predetermined low speed range. It may have a different configuration (the suspension control device according to claim 2).

Further, a suspension control device according to a third aspect of the present invention is a suspension control device capable of independently controlling, for each wheel, a damping force of a suspension connecting a wheel and a vehicle body. Vehicle speed detecting means for detecting, vertical vibration detecting means for detecting vertical vibrations of the vehicle body at both parts corresponding to the left front wheel and right front wheel of the vehicle, and low frequency components for extracting low frequency components of the detected vertical vibrations. Extraction means, vibration determination means for determining whether or not each of the extracted low frequency components exceeds a predetermined value, and any one of the low frequency components exceeds a predetermined value by the vibration determination means. And a damping force increasing means for increasing the damping force of the suspension for the wheels, which is determined based on the speed of the vehicle detected by the vehicle speed detecting means. That, it has as its gist.

[0010]

According to the suspension control device of the present invention, the low frequency components of the vertical vibrations of the vehicle body at both the parts corresponding to the left front wheel and the right front wheel detected by the vertical vibration detection means are respectively detected by the low frequency component extraction means. The vibration determining means determines whether or not each extracted low-frequency component exceeds a predetermined value. And
When it is determined by the vibration determination means that any of the low frequency components exceeds the predetermined value, the wheels corresponding to the exceeded low frequency components are set as the vibration input wheels, and the suspension of the vibration input wheels and the left and right rear wheels is determined. The damping force is increased by the damping force increasing means.

The graph of FIG. 12 shows the vibration level of each wheel when the vehicle speed is 80 [km / h] and the right front wheel gets over the projection or the like. As shown in this figure, when the right front wheel crosses over a protrusion, etc., it is near the sprung resonance frequency (2 [H
z] or less), the vertical vibration GFR of the vehicle body at the portion corresponding to the right front wheel and the vertical vibrations GRR, GRL of the vehicle body at the portion corresponding to the left and right rear wheels reach large peak values, and the other left front wheel The vertical vibration GFL of the vehicle body at the portion corresponding to (3) has a relatively small peak value. Therefore, according to the first suspension control device, the damping forces of the shock absorbers of the right front wheel and the left and right rear wheels, which are the vibration input wheels, are increased at the same time, so that the vertical vibrations GFR, GR reaching the large peak values are reached.
R and GRL are effectively suppressed. That is, in this suspension control device, the damping force of the vibration input wheels and the shock absorbers of the left and right rear wheels are simultaneously increased, so that the vibration of the vehicle body when the left and right front wheels pass over the protrusions or the like is effectively suppressed. It

In the graph of FIG. 13, the vehicle speed is 100
The vibration level of each wheel is shown when the right front wheel climbs over the protrusion in the condition of [km / h]. Also from this figure, when the right front wheel passes over the protrusion, the vibration near the sprung resonance frequency is the vertical vibration GFR of the vehicle body at the portion corresponding to the right front wheel and the vertical vibration GRR of the vehicle body at the portion corresponding to the left and right rear wheels. It can be seen that the GRL and GFL reach a large peak value, and the vertical vibration GFL of the body corresponding to the other left front wheel has a relatively small peak value. Therefore, even when the vehicle speed is 100 [km / h], the vertical vibration of the wheel portion reaching the large peak value is effectively suppressed.

According to another aspect of the suspension control device of the present invention, when the speed of the vehicle detected by the vehicle speed detecting means is within a predetermined low speed range, the vibration input wheel by the damping force increasing means is determined by the low speed range determining means. The increase of the damping force of the suspension for the rear wheel on the side is prohibited by prohibiting means. The graph of FIG. 11 shows the vibration level of each wheel when the right front wheel gets over a protrusion or the like in a low speed range of 50 [km / h]. As shown in this figure,
When the right front wheel gets over the protrusion, vibration near the sprung resonance frequency (about 2 [Hz] or less) is in a direction diagonal to the vertical vibration GFR of the body of the part corresponding to the right front wheel and the right front wheel. Vertical vibration GRL of the body corresponding to the left rear wheel
Has a large peak value, and the other vertical vibrations GFL, GRR of the vehicle body in the parts corresponding to the left front wheel and the right rear wheel have relatively small peak values.

Therefore, according to the suspension control device of the second aspect, the increase of the damping force of the suspension for the right rear wheel which is the rear wheel of the vibration input wheel is prohibited, and the right front wheel and the left wheel which are the vibration input wheels are prohibited. Since the damping force of the rear wheel shock absorber is increased at the same time, the vertical vibrations GFR and GRL reaching their large peak values are effectively suppressed. That is, in this suspension control device, the damping force of the vibration input wheel and the suspension of the rear wheel in the diagonal direction of the vibration input wheel are simultaneously increased, so that the left and right front wheels can overcome the protrusions at low speed. The vibration of the vehicle body in the case of being damaged is effectively suppressed.

According to a third aspect of the suspension control device of the present invention, the predetermined low frequency component of the vertical vibration of the vehicle body of both parts corresponding to the left front wheel and the right front wheel of the vehicle, which is extracted by the low frequency component extracting means, is predetermined. When the value exceeds the value, when the vibration determining means determines, the damping force of the suspension for the wheel, which is determined based on the vehicle speed detected by the vehicle speed detecting means, is increased by the damping force increasing means. On the other hand, the inventor of the present invention has found that the vibration of the vehicle body when one of the left and right front wheels passes over the protrusion or the like varies depending on the vehicle speed. At a certain vehicle speed, the left and right rear wheels shake significantly in addition to the vibration input wheel, and at a different vehicle speed, one side rear wheel shakes greatly in addition to the vibration input wheel. Change. On the other hand, the suspension control device according to the third aspect controls the damping force of the suspension for different wheels according to the vehicle speed, so that the vibration of the vehicle body when one of the left and right front wheels gets over the protrusion or the like. Effectively suppress.

[0016]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above.

FIG. 1 is a schematic configuration diagram of a suspension control device as an embodiment of the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the suspension control device shown in FIG.

As shown in FIG. 1, a strut-type front suspension 12 is attached to the right front wheel 10FR and the left front wheel 10FL of the vehicle, and strut-type front suspension 12 is also attached to the right rear wheel 10RR and the left rear wheel 10RL. The rear suspension 14 is attached. In the front suspension 12 and the rear suspension 14, shock absorbers 20FR, 20FL, 20RR, 20RL used as columns (struts) for positioning the wheels 10FR, 10FL, 10RR, 10RL, and coil springs 22FR, 22FL, 22RR. , 22RL are provided respectively.

Shock absorber 20FR, 20FL, 20
The RR and 20RL are variable orifice types that open and close a bypass orifice by rotating a control rod by driving a step motor, and have a well-known configuration that adjusts the damping force by the amount of flowing oil.

In the vehicle 10, as sensors for detecting various parameters related to the running state, accelerations GR in the vertical direction of the vehicle body in the vicinity of the right front wheel 10FR and the left front wheel 10FL,
Vertical acceleration sensors 25FR and 25F for detecting GL respectively
L, a steering angle sensor 27 that detects a steering angle θ, a vehicle speed sensor 29 that detects a vehicle speed (vehicle speed) V, and the like are provided. These sensors are connected to the suspension control unit 30. Further, the suspension control unit 30 includes a shock absorber 20.
FR, 20FL, 20RR, and 20RL step motors are connected to these shock absorbers 20FR and 20F.
The suspension control unit 30 controls L, 20RR, and 20RL.

As shown in FIG. 2, the suspension control unit 30 includes a microcomputer 32. The microcomputer 32 has a very general configuration, and includes a central processing unit (CPU) 32a,
Read-on memory (ROM) 32b, random access memory (RAM) 32c, and input port device 32d
And an output port device 32e, which are connected to each other by a bidirectional common bus 32f.

The input port device 32d receives signals from the vertical acceleration sensors 25FR and 25FL, the steering angle sensor 27 and the vehicle speed sensor 29 indicating the vertical accelerations GR and GL of the vehicle body corresponding to the right front wheel and the left front wheel, and the steering angle. a signal indicating θ,
A signal indicating the vehicle speed V is input respectively. The CPU 32a appropriately reads a signal input from the input port device 32d and performs various arithmetic processes based on a program stored in advance in the ROM 32b.
The CPU 32a uses the results of the arithmetic processing as the driving circuits 34, 3
Shock absorber 20FR, 2 via 5, 36, 37
By outputting to 0FL, 20RR, 20RL step motors, each shock absorber 20FR, 20FL, 20RR, 2
The damping force of 0RL is controlled to increase or decrease.

Suspension control unit 30
Next, the damping force control of the shock absorber executed by the above will be described. Suspension control unit 30
When the vehicle starts running after the power is turned on, the damping force control routine shown in FIG. 3 is executed as an interrupt process activated by a built-in timer every predetermined time when the vehicle starts traveling. By the initialization process immediately after the power is turned on, variables and flags are set to initial values.

When the damping force control routine shown in FIG. 3 is started, the CPU 32a executes the following processing. First, the vertical acceleration GR of the vehicle body at the parts corresponding to the right front wheel and the left front wheel detected by the vertical acceleration sensors 25FR and 25FL.
, GL, a signal indicating the steering angle θ detected by the steering angle sensor 27, and a signal indicating the vehicle speed V detected by the vehicle speed sensor 29 are read (step S100).

Next, it is judged whether or not the damping force control of the shock absorber for suppressing the roll of the vehicle body is necessary (step 110). This determination is made, for example, in the map corresponding to the graph shown in FIG. 4 as to whether or not the vehicle speed V and the steering angle θ read in step S100 are in the shaded area in the drawing. If it is determined by this determination that the roll control of the vehicle body is not necessary, each wheel 10FR, 10FR required to suppress the roll of the vehicle body
FL, 10RR, 10RL shock absorbers 20FR, 20
Attenuation coefficient C (1), C (2), C of FL, 20RR, 20RL
(3) and C (4) are calculated (step S120). The damping coefficients C (1) to C (4) are increased in accordance with an increase in the absolute value of the steering angular velocity obtained by, for example, differentiating the steering angle θ, and when the absolute value of the steering angular velocity reaches the maximum value. The value may be maintained at a constant value for a predetermined time, and thereafter, the damping coefficient may be gradually returned to a low value.

After that, the CPU 32a advances the process to step S130, and sends a control signal corresponding to the damping coefficients C (1) to C (4) calculated in step S120 to each wheel 1
0FR, 10FL, 10RR, 10RL shock absorber 2
Output to 0FR, 20FL, 20RR, 20RL step motors. As a result, each shock absorber 20FR-20
The damping force of RL is controlled to the optimum size to suppress the roll of the vehicle body. After that, the process proceeds to "return", and this process is once ended.

On the other hand, when it is determined in step S110 that the damping force control for restraining the roll of the vehicle body is not necessary, the low-pass filter is applied to the vehicle body vertical accelerations GR and GL detected by the vertical acceleration sensors 25FR and 25FL. Vertical acceleration GLR, G after processing and filtering
LL is calculated (step S140). The low pass filter process is a process for extracting only a predetermined low frequency component of the vertical acceleration sensors 25FR and 25FL, for example, a component of 2.0 [Hz] or less.

Subsequently, a process for calculating the weighting factors K1, K2, K3 according to the vehicle speed V read in step S100 is performed (step S150). The weighting factors K1, K2, K3 are the right front wheel 10FR or the left front wheel 10FL.
5 is a coefficient used for predicting the level of vertical vibration of the vehicle body at the portion corresponding to each wheel 10FR to 10RL when the vibration is input to the vehicle speed V in FIGS. It is obtained by comparing with the map shown. That is, as shown in FIGS. 5 and 7, the weighting factors K1 and K3 are constant values, for example 1.0, regardless of the vehicle speed V. The weighting coefficient K2 is shown in FIG.
As shown in, the vehicle speed V is a predetermined value V1 (for example, 60 [km
/ h]) at a low speed, the value becomes 0, and then gradually increases, and the vehicle speed V becomes a predetermined value V2 (for example, 70
[Km / h]) The value is 1.0 at medium and high speeds.

Then, using the weighting factors K1, K2 and K3 calculated in step S150, each wheel 10FR, 10FR
A process of calculating values G (1), G (2), G (3), and G (4) that predict vertical vibrations of the vehicle body at the portions corresponding to FL, 10RR, and 10RL is performed (step S160). This calculation process is performed using the following equations (1) to (4).

G (1) = K1 · GLR (1) G (2) = K1 · GLL (2) G (3) = K2 · GLR + K3 · GLL (3) G (4) = K2 · GLL + K3 · GLR (4)

Thereafter, the CPU 32a causes the step S17.
By executing 0 to S195, each wheel 10FR ~
The processing of calculating the damping coefficient of all the shock absorbers 20FR to 20RL of 10RL is performed. Specifically, the initial value 1 is set to the variable r (step S170), and then the damping coefficient calculation routine is started (step S180). This damping coefficient calculation routine is performed by the wheel 1 at the position determined by the variable r.
It calculates the damping coefficient of the shock absorbers 20FR to 20RL of 0FR to 10RL, which will be described later in detail.

Subsequently, the variable r is incremented by 1 (step S190), and then the variable r is changed to the number of wheels 4
It is determined whether or not it is larger (step S195). Here, when it is determined that the variable r is smaller than the value 4,
The process returns to step S180, and the processes of steps S180 to S195 are repeatedly executed. Step S19
If it is determined in step 5 that the variable r is larger than the value 4, the process proceeds to step S130. In step S130, step S
Attenuation coefficients C (1) to C (4) calculated in 180
The control signal corresponding to is output to the step motors of the shock absorbers 20FR to 20RL of the wheels 10FR to 10RL.
Thereby, the damping force of each shock absorber 20FR to 20RL is controlled. After that, the process proceeds to "return", and this process is once ended.

Next, the damping coefficient calculation routine executed in step S180 will be described in detail with reference to the flowchart of FIG. This damping coefficient calculation routine is performed in step S in the damping force control routine (FIG. 3) described above.
When the process moves to 180, the subroutine is called and activated.

When the damping coefficient calculation routine shown in FIG. 8 is started, the CPU 32a first selects the variable r set in step S170 from among G (1) to G (4) calculated in step S160. Determined by G
(R) is selected, and a process of determining whether or not the absolute value of G (r) exceeds a preset threshold value G0 is performed (step S200). That is, here, the vertical vibration G of the vehicle body at the portion corresponding to the wheel determined by the variable r.
It is determined whether or not the absolute value of (r) exceeds a preset threshold value GO, and if it is determined that | G (r) |> G0, the process proceeds to step S210.

In step S210, a value 1 is set in the flag S (r) indicating the damping force control process.
The flag S (r) is a flag S (1) prepared in advance,
Among the steps S (2), S (3) and S (4), the step S
It is determined by the variable r set in 170. For example, when the variable r is set to the value 2 in step S170, the flag S (2) is set to the value 1 in step S210. For each variable used in the damping coefficient calculation routine, as in the case of the flag S, four data with subscripts of values 1 to 4 are prepared in advance, and for the position determined by the variable r set in step S170, Each processing shall be performed.

Next, shock absorbers 20FR, 20FL, 20RR, 20 corresponding to the wheels determined by the variable r.
The attenuation coefficient C (r) of RL is incremented by a predetermined value ΔCi (a minute positive constant) (step S220). Each shock absorber 20FR, 20FL, 20RR, 2
It is assumed that the damping coefficients C (1) to C (4) of 0RL are each set to an initial value 0 when the damping force control routine shown in FIG. 3 is started.

Next, the damping coefficient C (r) is the maximum value Cu.
(Positive constant) It is determined whether or not (step S2
30), if it is determined that C (r) ≧ Cu, the damping coefficient C (r) is set to the value Cu, and at the same time, the timer count value T (r) described later is set to the value 0. ,
The value 2 is set to the flag S (r) (step S24).
0). After that, the process proceeds to “EXIT”, the damping coefficient calculation routine is once finished, and the process proceeds from step S180 to step S190 of the damping force control routine. On the other hand, when a negative determination is made in step S230, that is, when it is determined that C (r) <Cu, the process of step S240 is not executed, and the process directly proceeds to “EXIT”.

In step S200, a negative determination is made, that is, G
When it is determined that the absolute value of (r) is less than or equal to the threshold value G0,
In step S250, it is determined whether the flag S (r) is 1 or not. Here, if it is determined that the flag S (r) has the value 1, the process proceeds to step S220.
On the other hand, when it is determined in step S250 that the flag S (r) is not the value 1, then it is determined whether the flag S (r) is the value 2 (step S26).
0).

When it is determined in step S260 that the flag S (r) has the value 2, the process proceeds to step S270, and the timer count value T (r) is incremented by ΔT (a minute positive constant). Then, the timer count value T
It is determined whether (r) is equal to or greater than the reference value Tc (step S280). If it is determined that T (r) ≧ Tc, the timer count value T (r) is reset to the value 0 and the flag S (r) is set to the value 3 (step S290). After that, the processing is "EXIT".
Then, the attenuation coefficient calculation routine is once ended. On the other hand, a negative determination is made in step S280, that is, T (r) <T
If it is determined to be c, the process of step S290 is not executed and the process is directly advanced to “EXIT”.

If it is determined in step S260 that the flag S (r) is not the value 2, then the flag S
It is determined whether or not (r) is 3 (step S300). Here, if it is determined that the flag S (r) has the value 3, the process proceeds to step S310, and the shock absorbers 20FR to 2FR corresponding to the wheels determined by the variable r.
The damping coefficient C (r) of 0RL is decremented by a predetermined value ΔCd (a minute positive constant). Then, the damping coefficient C (r)
Is determined to be equal to or smaller than the minimum value Cb (a positive constant) (step S320), and if it is determined that C (r) ≦ Cb, a value 0 is set in the flag S (r). Along with (step S330), the damping coefficient C (r) is set to the minimum value Cb.
Is set (step S340). After that, the process
"XIT", and the damping coefficient calculation routine is once ended.

On the other hand, when the negative determination is made in step S320, that is, when it is determined that C (r)> Cu, the processes of steps S330 and S340 are not executed, and the process proceeds directly to "EXIT". Also, step S300
When it is determined that the flag S (r) is not 3, the process proceeds to step S340, the damping coefficient C (r) is set to the minimum value Cb, and then the process proceeds to "EXIT" to calculate this damping coefficient. Finish the routine once.

How the damping coefficient of the shock absorbers 20FR to 20RL is controlled to increase or decrease by the damping coefficient calculation routine thus constructed will be described below with reference to the timing chart of FIG. At time t1, if the absolute value of the vertical vibration G (r) of the vehicle body of the portion corresponding to the wheel determined by the variable r exceeds the threshold value G0, an affirmative decision is made in step S200, and the flag S (r) becomes the value 1. It is set (step S210). As a result, an affirmative determination is made in step S250 even if the absolute value of G (r) becomes less than or equal to the threshold value G0, and step S22 is performed.
0 and S230 are repeatedly executed, and as a result, the damping coefficient C (r) of the shock absorber is gradually increased,
The maximum value Cu is reached at time t2.

When the damping coefficient C (r) exceeds the maximum value Cu at the time t2, the damping coefficient C (r) is set to Cu and the flag S (r) is set to the value 2 (step S240). This results in steps S250 and S
A negative determination and an affirmative determination are made in 260, respectively, and in step S270, the timer count value T
(R) is incremented, and when the damping coefficient C (r) is set to the maximum value Cu, the timer count value T (r)
The damping coefficient C (r) is maintained at a constant value of Cu until the time reaches Tc.

At time t3 when the time Tc has passed,
An affirmative decision is made in step S280, and step S2
At 90, the flag S (r) is set to the value 3. As a result, an affirmative decision is made in step S300, and the damping coefficient C (r) is gradually reduced to the minimum value Cb by repeatedly executing step S310. Time t4
At, the damping coefficient C (r) reaches a minimum value Cb and thereafter maintains this value.

Therefore, the absolute value of the vertical vibration G (r) of the vehicle body at the portion corresponding to the wheel determined by the variable r is the threshold value G0.
When it exceeds, the damping coefficient C (r) of the shock absorber of the wheel in accordance with the trapezoidal pattern shown in FIG.
It is gradually increased and maintained at the maximum value Cu for the time Tc, and then gradually reduced to the minimum value Cb.

By the way, the vertical vibration G (r) is obtained from the equations (1) to (4) as described above, and has a different magnitude for each wheel 10FR to 10RL. Formula (1)-
Looking at (4), when the vertical acceleration (after low-pass filtering) GLR of the vehicle body at the portion corresponding to the right front wheel 10FR gets over the protrusion and the right front wheel 10FR becomes large, the weighting coefficient K1 has the value 1. Therefore, the vertical vibration G (1) on the right front wheel side becomes large, and the vertical vibration G (2) on the left front wheel side remains small. On the other hand, the vertical vibration G on the right rear wheel 10RR side
(3) is determined from the value obtained by multiplying the weighting coefficient K2 by GLR because GLL is small. However, the value of K2 takes a value 0 at low speed and a value 1 at medium and high speeds as described above. , Vertical vibration G (3) has a small value at low speed,
Large value at medium and high speeds. Further, the vertical vibration G (4) on the left rear wheel 10RL side is determined by a value obtained by multiplying the weighting K3 by GLR because GLL is small, and takes a large value.

That is, when a vibration is input to the right front wheel 10FR, the vertical vibration G of the portion corresponding to the vibration input wheel and the left rear wheel 10RL in the diagonal direction thereof at low speed is obtained.
(1), G (4) becomes large, and at middle and high speeds, vertical vibrations G (1), G (3), G (of the parts corresponding to the vibration input wheel and the left and right rear wheels 10RR, 10RL. 4) becomes large. Therefore, as shown in FIG. 10, the right front wheel 10
If there is vibration input to FR, the vibration input wheel (right front wheel 10F)
R) and the diagonally opposite wheels (left rear wheel 10RL) of the shock absorbers 20FR and 20RL have increased damping coefficients, and at middle and high speeds, the vibration input wheel and the left and right rear wheels 10RR and 10RL are shocked. Absorber 20FR, 20R
The damping factors of R and 20RL are increased.

Therefore, according to the suspension control system of this embodiment, the vehicle shakes when the front wheels on either side pass over the protrusion at low speed, that is, the vibration input wheel and the wheels in the diagonal direction thereof. It is possible to suppress the swaying such that the vertical vibration of the vehicle body at the portion corresponding to the above becomes large by increasing the damping coefficient of the shock absorbers of both wheels. In addition, at the time of medium and high speeds, one of the left and right front wheels rides over the protrusion, which causes the vehicle to shake. This can be suppressed by increasing the damping coefficient of the wheel shock absorber. Therefore, regardless of the vehicle speed, it is possible to improve the riding comfort of the vehicle when the wheels pass over the protrusion or the like.

Further, according to this suspension control device, since the damping coefficient of the shock absorber of the wheel corresponding to the portion where vertical vibration is small is not increased and is maintained at the same value, the damping coefficient of the shock absorber of all the wheels is maintained. It is possible to improve the riding comfort of the vehicle even when the vehicle is increased. Furthermore, since the damping coefficient of the shock absorber is increased by the trapezoidal pattern as shown in FIG. 9, there is no sudden change in the damping coefficient, and therefore the riding comfort of the vehicle can be further improved. .

In the above-described embodiment, the speed for determining the low speed region by the low speed region determining means is set to 60 [km / h] determined by the graph shown in FIG.
Any value may be used as long as it is between 70 [km / h]. Further, as in the present embodiment, a gray zone is not provided between 60 and 70 [km / h] and an intermediate weighting value is not taken, but when the judgment speed is exceeded, the larger weighting is immediately performed. May be configured to take the value of. Furthermore, the upper limit of the extraction of the low frequency component by the low frequency component extraction means is set to 2.
Although it is set to 0 [Hz], preferably 0.7 to 2.5 [H]
z], any value may be used.

Further, in the above-mentioned embodiment, the control of the damping coefficient for suppressing the posture change of the vehicle body is performed in step S1.
Although the steps 10 and S120 are performed only on the roll of the vehicle body, they may be performed on both the roll and the pitch of the vehicle body.

Further, in the above-described embodiment, the time Tc for maintaining the damping coefficient C (r) at the constant value of the maximum value Cu.
However, instead of this, the time Tc may be variably controlled so that it becomes longer as the absolute value of the vehicle speed or the vertical acceleration of the vehicle body increases.

In the above-described embodiment, the damping coefficient of the shock absorber is controlled so as to be substantially continuously increased / decreased, but the damping coefficient is controlled to be increased / decreased stepwise in multiple stages. May be.

Although the conventional suspension has been described in the above-mentioned embodiments, the present invention may be applied to the active suspension instead. In the active suspension, since the vibration of the vehicle body can be suppressed by changing the pneumatic cylinder pressure, in this case, step S16
The control gain that determines the pneumatic cylinder pressure is changed in accordance with the predicted values G (1) to G (4) of the vertical vibration of the vehicle body of the part corresponding to each wheel calculated by 0. With such a configuration, even in the active suspension, it is possible to improve the riding comfort of the vehicle when the wheels pass over the protrusions and the like.

The embodiment of the present invention has been described above.
The present invention is not limited to these embodiments. For example, unlike the embodiments, the low frequency component extracting means is not configured by software executed by the suspension control unit 30, but a discrete electronic circuit. It is needless to say that the present invention can be implemented in various modes without departing from the scope of the present invention, such as the one configured by the low-pass filter.

[0056]

As described above, according to the suspension control device of the first aspect of the present invention, when the front wheel on the left or right passes over the protrusion, the vehicle shakes, that is, the vibration input wheel and the left and right rear wheels. It is possible to suppress the swaying such that the vertical vibration of the vehicle body in the part corresponding to the above becomes large by increasing the damping force of the suspension for these three wheels. Therefore, it is possible to improve the riding comfort of the vehicle when the wheels pass over the protrusions and the like.

According to the suspension control device of the second aspect, the vehicle vibration generated when one of the left and right front wheels passes over the protrusion at a low speed, that is, a portion corresponding to the vibration input wheel and the wheels in the diagonal direction thereof. It is possible to suppress the swaying such that the vertical vibration of the vehicle body becomes large by increasing the damping coefficient of the shock absorbers of both wheels.
Therefore, the riding comfort of the vehicle can be improved regardless of the vehicle speed even when the vehicle speed is in the low speed range.

According to the suspension control device of the third aspect, since the damping force of the suspension for the different wheels is controlled according to the vehicle speed, the damping force of the suspension can be precisely controlled, and the wheels are projected. It is possible to improve the riding comfort of the vehicle when riding over the vehicle.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a suspension control device as an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the suspension control device shown in FIG.

FIG. 3 is a flowchart showing a damping force control routine of a shock absorber executed by a suspension control unit 30.

FIG. 4 is a graph showing a region where the vehicle body rolls by a predetermined amount or more, which is determined by a steering angle θ and a vehicle speed V.

FIG. 5 is a graph showing changes in weighting coefficient K1 according to vehicle speed V.

FIG. 6 is a graph showing changes in weighting coefficient K2 according to vehicle speed V.

FIG. 7 is a graph showing changes in weighting coefficient K3 according to vehicle speed V.

FIG. 8 is a flowchart showing a damping coefficient calculation routine that is activated by being called as a subroutine in a damping force control routine.

FIG. 9 is a timing chart showing changes in the attenuation coefficient according to the attenuation coefficient calculation routine.

FIG. 10 is an explanatory diagram showing wheels for which the damping coefficient of the shock absorber is increased in the embodiment, distinguishing between low speed and medium / high speed.

FIG. 11 is a graph showing the vibration level of each wheel when the vehicle speed is 50 [km / h] and the right front wheel gets over a protrusion or the like.

FIG. 12 is a graph showing a vibration level of each wheel when the vehicle speed is 80 [km / h] and the right front wheel gets over a protrusion or the like.

FIG. 13 is a graph showing the vibration level of each wheel when the vehicle speed is 100 [km / h] and the right front wheel passes over a protrusion or the like.

[Explanation of symbols]

 10FL ... left front wheel 10FR ... right front wheel 10RL ... left rear wheel 10RR ... right rear wheel 12 ... front suspension 14 ... rear suspension 20FR, 20FL, 20RR, 20RL ... shock absorber 22FR, 22FL, 22RR, 22RL ... coil spring 30 ... suspension control Unit 32 ... Microcomputer 32a ... CPU 32b ... ROM 32f ... Common bus 34, 35, 36, 37 ... Drive circuit

Claims (3)

[Claims] 1. A suspension control device capable of independently controlling, for each wheel, a damping force of a suspension connecting a wheel and a vehicle body, the vertical vibration of the vehicle body at both parts corresponding to the left front wheel and the right front wheel of the vehicle being controlled. Vertical vibration detection means for detecting each, low frequency component extraction means for extracting each low frequency component of the detected vertical vibration, and whether each of the extracted low frequency components exceeds a predetermined value. And a vibration determining unit that determines whether any of the low-frequency components exceeds a predetermined value, and a wheel that corresponds to the exceeded low-frequency component is used as a vibration input wheel. A suspension control device comprising: a vibration input wheel and damping force increasing means for increasing the damping force of the suspension for each of the left and right rear wheels. 2. The suspension control device according to claim 1, wherein a vehicle speed detecting means for detecting a vehicle speed, and a low speed range for judging whether or not the detected vehicle speed is within a predetermined low speed range. When the determination means and the low-speed range determination means determine that the vehicle speed is within a predetermined low-speed range, the damping force increase means prohibits the increase of the damping force of the suspension for the rear wheel on the vibration input wheel side. And a suspension control device provided with a prohibition means. 3. A suspension control device capable of independently controlling, for each wheel, a damping force of a suspension connecting a wheel and a vehicle body, a vehicle speed detecting means for detecting a speed of the vehicle, a left front wheel and a right front wheel of the vehicle. Vertical vibration detection means for detecting vertical vibrations of the vehicle body in both parts corresponding to the above, low frequency component extraction means for extracting low frequency components of the detected vertical vibrations, and each of the extracted low frequency components Vibration determining means for determining whether each exceeds a predetermined value, and when the vibration determining means determines that any low frequency component exceeds a predetermined value, the vehicle speed detecting means detects And a damping force increasing means for increasing the damping force of the suspension for the wheel determined based on the speed of the vehicle.