JPH11129723A - Suspension control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the turning performance of a vehicle by appropriately controlling the damping coefficient of a shock absorber of inner and outer turning wheels to reduce the height of the center of gravity of a vehicle body in the transitional turn of the vehicle. SOLUTION: A suspension control device of a vehicle in which a suspension having shock absorbers 14FL, 14FR variable in damping coefficient is provided on each wheel, is provided with turning condition detection devices 28, 30, 32FL, 32FR, 32RL, 32RR, and a control device 34 to control the damping coefficient of the shock absorbers. The control device sets the damping coefficient of the shock absorbers on the turning inner wheel side to be relatively higher when the vehicle is in the transitional turning condition, and sets the elongation of the suspension on the turning inner wheel side to be smaller than the contraction of the suspension on the turning outer wheel, to reduce the height of the center of gravity of the vehicle body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension for a vehicle such as an automobile, and more particularly to a suspension control device for a vehicle having a shock absorber in which each wheel suspension has a variable damping coefficient.

[0002]

2. Description of the Related Art As one of air suspension control devices provided with an air spring corresponding to each wheel, for example, as described in Japanese Patent Application Laid-Open No. 62-83210, when a vehicle travels straight, the left and right The air chambers of the air springs are connected to each other to cut off the communication between the air chambers of the left and right air springs when the vehicle turns, and compressed air is supplied to the air chambers of the air springs on the turning outer wheel to supply air to the turning inner wheel. A suspension control device configured to discharge compressed air from an air chamber of a spring is conventionally known.

According to such a suspension control device,
When the vehicle travels straight, the spring constant of each air spring is maintained at a low value to ensure good riding comfort of the vehicle. When the vehicle turns, the spring constant of each air spring is switched to a high value and the vehicle turns. Rolling of the vehicle body is suppressed by increasing the vehicle height on the outer wheel side and decreasing the vehicle height on the turning inner wheel side, thereby improving the steering stability of the vehicle when the vehicle turns.

[0004]

However, in the conventional suspension control device as described above, compared to a case where compressed air is not supplied to and exhausted from the air chambers of the air springs on the turning outer wheel side and the turning inner wheel side. Although the roll of the vehicle body during turning of the vehicle can be suppressed, the height of the center of gravity of the vehicle body during turning can be kept substantially constant and not lowered,
In order to improve the turning performance of the vehicle, there is room for further improvement in the height of the center of gravity of the vehicle body.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional suspension control device, and the main problem of the present invention is that each wheel suspension has a shock absorber with a variable damping coefficient. It is an object of the present invention to reduce the height of the center of gravity of the vehicle body when the vehicle is turning by appropriately controlling the damping coefficient of the shock absorbers of the inner and outer turning wheels in the vehicle, thereby improving the turning performance of the vehicle.

[0006]

According to the present invention, there is provided a suspension control apparatus for a vehicle in which a suspension having a shock absorber with a variable damping coefficient is provided for each wheel. And a turning state detecting means for detecting a turning state of the vehicle, and a damping coefficient control means for controlling a damping coefficient of the shock absorber, wherein the damping coefficient control means is provided when the vehicle is in a transient turning state. This is achieved by a suspension control device configured to set the damping coefficient of the shock absorber on the turning inner wheel side relatively higher than that on the turning outer wheel side.

According to the first aspect of the present invention, when the vehicle is in a transient turning state, the damping coefficient of the shock absorber on the turning inner wheel side is set relatively higher than that of the turning outer wheel side. As compared with the case where the damping coefficient of the shock absorber is controlled to be the same, the extension amount of the suspension on the turning inner wheel side during the transient turning is reduced, and the height of the center of gravity of the vehicle body during the transient turning is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing one embodiment of a suspension control device according to the present invention applied to an air suspension having a variable damping coefficient type shock absorber.

In FIG. 1, 10FR, 10FL, 10RR, 1
0RL is right front wheel 12FR, left front wheel 12FL, right rear wheel 1
The air spring is provided integrally with the shock absorbers 14FR, 14FL, 14RR, and 14RL of the variable damping coefficient type corresponding to 2RR and the left rear wheel 12RL. The air springs 10FR, 10FL, 10RR, and 10RL cooperate with the corresponding shock absorbers to change the volume of the main air chamber 16 which is variable.
FR, 16FL, 16RR, and 16RL are defined, and the auxiliary air chambers 18FR, 18FL, 18RR, and 18RL having a constant volume are defined.

Each wheel control valve as a first control valve for controlling communication between a corresponding main air chamber and a sub air chamber is provided at a partition wall between the main air chamber and the sub air chamber of each air spring. 20FR, 20FL, 20RR, and 20RL are provided. The auxiliary air chambers for the front left and right wheels and the rear left and right wheels are
F and 22R, connected to each other by conduit 22F.
And 22R, common control valves 24F and 24R as second control valves for controlling the communication of the corresponding conduits.
R is provided.

In the illustrated embodiment, each wheel control valve 20
FR, 20FL, 20RR, and 20RL are normally open on-off valves, while common control valves 24F and 24R are normally closed on-off valves. When these control valves are opened and closed, the communication state between the main air chamber and the sub air chamber and the communication state between the sub air chambers of the left and right wheels are controlled, whereby the effective volume of the air chamber of each air spring is adjusted. As shown in Table 1 below for the left and right front wheels, the spring constants of the air springs for each wheel are three levels of "super soft", "normal", and "hard", in five combinations. Controlled.

In Table 1, "=" indicates that the corresponding air chambers are connected to each other. The relationship between the opening and closing of each control valve on the rear wheel side, the communication of the air chamber, and the spring constant of the air spring is also the same as in Table 1 below.

[0014]

[Table 1] Control valve 20FR 20FL 24F Air chamber communication spring constant Case 1 Open Open Open 16FR = 18FR = 16FL = 18FL Super soft Case 2 Open Open Close 16FR = 18FR, 16FL = 18FL Normal case 3 Close Close--- −−− Hard Case 4 Closed Open Closed 16FL = 18FL Right Hard, Left Normal Case 5 Open Closed Closed 16FR = 18FR Right Normal, Left Hard

In the case 1 in particular, the main air chamber and the sub air chamber of each air spring are connected to each other and the sub air chambers of the left and right wheels are connected to each other. Becomes about 1/2 of the normal case,
As a result, as shown in FIG. 5, the sprung resonance point Fbos
Is about 70% of the resonance point Fbon in the normal case, and the vibration gain on the spring in the frequency range of about 0 to 5 Hz is greatly reduced, thereby greatly improving the ride comfort of the vehicle. I do.

Although not shown in detail in FIG. 1, the shock absorbers 14FR, 14FL, 14RR, and 14RL each have a damping force control valve in the body of the piston, and the damping force control valve is provided at the upper end of the piston rod. Actuator 26FR,
As shown in FIG. 4, the damping force is increased or decreased in three stages of "high", "medium" and "low" by controlling the 26FL, 26RR and 26RL to increase or decrease the damping coefficient. ing. Note that the damping force control valve and the actuator may have any conventionally known structures.

Each wheel control valve 20FR-20RL, common control valve 2
4F and 24R, actuators 26FR to 26RL are provided on the vehicle body corresponding to the vehicle speed V detected by the vehicle speed sensor 28, the steering angle θ detected by the steering angle sensor 30 with the right turning direction being positive, and each wheel. Vertical acceleration sensor 32F
Based on the vertical acceleration Gi (i = FR, FL, RR, RL) of the vehicle body detected by R, 32FL, 32RR, 32RL, the electronic control unit 34 controls the acceleration as described later.

As shown in FIG. 2, the electronic control unit 3
4 has a microcomputer 35. The microcomputer 30 may have a general configuration as shown in FIG. 2, and includes a CPU 36, a ROM 38,
It has a RAM 40, an input port device 42, and an output port device 44, which are connected to each other by a bidirectional common bus 46. The input port device 42 includes a vehicle speed sensor 28, a steering angle sensor 30, and a vertical acceleration sensor 32.
A signal indicating the vehicle speed V, a signal indicating the steering angle θ, and a signal indicating the vertical acceleration Gi of the vehicle body are input from FR to 32RL.

The input port device 42 appropriately processes the signal inputted thereto, and in accordance with the instruction of the CPU 36 based on the program stored in the ROM 38, the CPU 36 and the R
The processed signal is output to the AM 40. The ROM 38 stores the control program shown in FIG. The CPU 36 performs various calculations and signal processing based on the control program shown in FIG. The output port device 44 outputs control signals to the respective wheel control valves 20FR to 20RL via the drive circuits 48FR to 48RL, respectively, in accordance with the instructions of the CPU 36, and
A control signal is output to the common control valves 24F and 24R via F and 50R, and a control signal is output to the actuators 26FR to 26RL via drive circuits 52FR to 52RL.

Next, control of the spring constant of the air spring and the damping force of the shock absorber in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 3 is started by closing an ignition switch (not shown).

First, in step 10, the detection result detected by each sensor is read. In step 20, it is determined whether or not the vehicle speed V exceeds a reference value Vc (positive constant). That is, it is determined whether or not the vehicle is in a high vehicle speed state. When a negative determination is made, the process proceeds to step 70, and when an affirmative determination is made, each control valve is set in step 30 of Table 1 in step 30. As described above, the spring constant of the air spring of each wheel is normally controlled.

In step 40, the vertical acceleration G of the vehicle body
By integrating i, the vertical speed Vi of the vehicle body at the portion corresponding to each wheel is calculated, and it is determined whether or not the absolute value of the vertical speed Vi is less than a reference value Ve (positive constant). When an affirmative determination is made, the damping force of the corresponding shock absorber is controlled to a low damping force in step 50, and when a negative determination is made, the damping force of the corresponding shock absorber is set to medium in step 60. Controlled by damping force. Steps 40 to 60 are individually executed for each wheel.

In step 70, it is determined whether or not the absolute value of the steering angle θ exceeds the reference value θc (positive constant), that is, whether or not the vehicle is in a turning state. When it is determined that the vehicle is in a running state, the process proceeds to step 150. When it is determined that the vehicle is in a substantially straight running state, in step 80, each control valve is set as shown in case 1 of Table 1. Control, whereby the spring constant of the air spring of each wheel is super-softly controlled.

In step 90, the vertical speeds VFR and VFL of the vehicle body on the front wheel side are calculated by integrating the vertical accelerations GFR and GFL of the vehicle body on the front wheel side. The vertical speed Vfh of the vehicle body on the front wheel side is set, and it is determined whether or not the absolute value of the vertical speed Vfh is less than a reference value Vfc (positive constant). Step 9
If a positive determination is made in step 0, the damping force of the left and right front wheel shock absorbers is controlled to a low damping force in step 100, and if a negative determination is made, step 11 is executed.
At 0, the damping force of the left and right front wheel shock absorbers is controlled to the medium damping force.

In step 120, the vertical velocities VRR and VRL of the vehicle body on the rear wheel side are calculated by integrating the vertical accelerations GRR and GRL of the vehicle body on the rear wheel side. The value is set as the vertical speed Vrh of the vehicle body on the rear wheel side, and it is determined whether or not the absolute value of the vertical speed Vrh is less than a reference value Vrc (positive constant). If a positive determination is made in step 120, step 13
At 0, the damping force of the left and right rear wheel shock absorbers is controlled to a low damping force. When a negative determination is made, at step 140, the damping force of the right and left rear wheel shock absorbers is controlled to a medium damping force. .

In step 150, the steering angular velocity θd is calculated as, for example, a time differential value of the steering angle θ.
It is determined whether or not the absolute value of the steering angular velocity θd exceeds a reference value θdc (positive constant), that is, whether or not the vehicle is in a very sharp turning state, and the vehicle is not turning very sharply. If it is determined that the vehicle is in the state, step 18
0, and when it is determined that the vehicle is in a very sharp turning state, in step 160, each control valve is controlled as shown in Case 3 of Table 1 so that the spring of the air spring of each wheel is controlled. The constant is hardly controlled, and in step 170, the damping force of the shock absorber for each wheel is controlled to a high damping force.

In step 180, it is determined whether or not the steering angle θ is positive, that is, whether or not the vehicle is turning right, and it is determined whether or not the vehicle is turning right. When the determination is made, the process proceeds to step 240. When it is determined that the vehicle is turning to the left, the control valves are controlled in step 190 as shown in case 4 of Table 1 so that the air of the front and rear right wheels is adjusted. The spring constant of the spring is hardly controlled, and the spring constants of the front and rear left air springs are normally controlled.

In step 200, the system waits for several seconds while the damping force of the shock absorbers of the front and rear left wheels is controlled to a high damping force. In step 210, the vertical acceleration Gi (i = FL) of the vehicle body of the front and rear left wheels , RL) are integrated to calculate the vertical speed Vi of the vehicle body of the front and rear left wheels, and it is determined whether or not the absolute value of the vertical speed Vi is less than a reference value Ve (positive constant). If an affirmative determination is made in step 210, the damping force of the corresponding left front wheel or rear left shock absorber is controlled to a low damping force in step 220, and if a negative determination is made, step 2 is performed.
At 30, the damping force of the shock absorber of the corresponding left front wheel or left rear wheel is controlled to the medium damping force.

In step 240, the control of each control valve is performed as shown in Case 5 in Table 1, whereby the spring constants of the air springs of the front and rear left wheels are controlled hard, and the spring constants of the air springs of the front and rear right wheels are controlled. Is controlled normally. In step 250, the process waits for several seconds while the damping force of the front and rear right wheel shock absorbers is controlled to a high damping force. The standby time in steps 200 and 250 is set at least to a value equal to the transient turning time in the normal turning of the vehicle.

In step 260, the vertical acceleration Vi (i = FR, RR) of the vehicle body of the front and rear right wheels is integrated to calculate the vertical speed Vi of the vehicle body of the front and rear right wheels.
It is determined whether or not the absolute value of i is less than the reference value Ve. When an affirmative determination is made in step 260, the damping force of the corresponding right front wheel or right rear wheel shock absorber is controlled to a low damping force in step 270.
When a negative determination is made, in step 280, the damping force of the corresponding shock absorber for the right front wheel or the right rear wheel is controlled to the medium damping force. Steps 210 to 230
And steps 260 to 280 are individually executed for the front and rear left wheels and the front and rear right wheels, respectively.

Thus, according to the illustrated embodiment, when the vehicle travels substantially straight at low to medium speed, step 2 is executed.
The determination of NO is made in steps 0 and 70. In step 80, the spring constant of each of the air springs 10FR to 10RL is super-softly controlled. In steps 90 to 140, the shock absorbers for the front and rear wheels are set. The damping force is controlled to a low damping force or a medium damping force according to the vertical speed of the vehicle body on the front wheel side and the rear wheel side, thereby ensuring a good ride comfort of the vehicle and the wheels being uneven on the road surface. Vibration of the vehicle body when the vehicle crosses over is effectively attenuated.

If the vehicle is running at a high speed, the determination in step 20 is YES, and in step 30, the spring constant of each air spring is controlled normally.
Further, in steps 40 to 60, the damping force of each shock absorber is controlled to a low damping force or a medium damping force according to the corresponding vertical speed of the vehicle body, thereby ensuring good riding comfort and steering stability of the vehicle. Is done.

If the vehicle is in a very sharp turning state, a YES determination is made in step 150,
In step 160, the spring constant of each air spring is hardly controlled, and in step 170, the damping force of each shock absorber is controlled to a high damping force. Driving stability is ensured.

Further, when the vehicle is in a turning state that is not very sharp, the spring constant of the air spring on the turning inner wheel side is hardly controlled in step 190 or 240 and the spring constant of the air spring on the turning outer wheel side is increased. Normally controlled. As shown in FIG. 6, when the spring constant K1 of the left and right air springs 100L and 100R does not increase or decrease even when the vehicle turns, the strokes of the left and right suspensions caused by the centrifugal force F acting on the vehicle body 102. The magnitudes of the quantities -x and + x are substantially the same, so that a roll occurs in the vehicle body, in which case the height of the center of gravity Hg of the vehicle body is substantially the same as when the vehicle is traveling straight.

On the other hand, according to the illustrated embodiment, the spring constant of the air spring 100R on the turning inner wheel side is, for example, K
1 to K2, and the stroke amount + a of the suspension on the turning inner wheel side becomes smaller than the magnitude of the stroke amount -b of the suspension on the turning outer wheel side. The height of the center of gravity is made smaller than the height Hg, whereby the roll moment acting on the vehicle body is reduced, the roll amount of the vehicle body is reduced, and the turning performance of the vehicle can be improved.

In the above-mentioned conventional suspension control device, a large amount of energy is consumed because compressed air is supplied to and exhausted from the air chambers of the left and right air springs when the vehicle turns, in order to improve the turning performance. Would. On the other hand, according to the illustrated embodiment, it is not necessary to supply and discharge compressed air even when the vehicle turns, so that the energy consumption can be significantly reduced as compared with the conventional suspension control device. .

Also, according to the illustrated embodiment, step 2
At 00 or 250, the damping force of the shock absorber on the turning inner wheel is controlled to a high damping force at least during the transient turning state, and therefore, the extension stroke amount of the suspension on the turning inner wheel side when the vehicle is in the transient turning state. Since a is smaller than the contraction stroke amount b of the suspension on the turning outer wheel side, the height of the center of gravity of the vehicle body during transient turning of the vehicle is reduced, thereby improving the transient turning performance of the vehicle.

In particular, according to the illustrated embodiment, when the vehicle is in a transient turning state, the damping force of the shock absorber on the turning inner wheel side is set higher than when the vehicle is not turning, so that the shock absorber on the turning inner wheel side is turned off. Since the damping coefficient is set relatively higher than the turning outer wheel side, when the vehicle is in a transient turning state, the damping force of the turning outer wheel side shock absorber is reduced, so that the damping coefficient of the turning inner wheel side shock absorber is reduced. Rolling of the vehicle body can be reliably suppressed as compared with the case where the rolling is set relatively higher than the turning outer wheel side.

In both cases of left turn and right turn,
By executing Steps 210 to 230 or Steps 260 to 280 during the steady turning after the transient turning, the damping force of each shock absorber is controlled to a low damping force or a middle damping force according to the vertical speed of the vehicle body. .

In the above-described embodiment, the damping force of the shock absorber on the turning inner wheel side is controlled to a high damping force for a predetermined time during the transient turning of the vehicle. The change in the roll amount of the vehicle body is estimated based on the angle θ or the vertical acceleration GFR to GRL, and the damping force of the shock absorber on the turning inner wheel side is modified to be controlled to a high damping force in the process of increasing the roll amount of the vehicle body. You may.

In the above embodiment, the damping force of each shock absorber is controlled in three stages, but the damping force of the shock absorber is controlled in four or more stages according to the running state of the vehicle. It may be controlled in multiple stages.

In the above embodiment, the suspension spring is an air suspension having a variable spring constant. However, the spring of the suspension to which the present invention is applied is not limited to an air suspension, and the spring constant is constant. May be used.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments may be made within the scope of the present invention. The possibilities will be clear to the skilled person.

[0044]

As is apparent from the above description, according to the present invention, when the vehicle is in a transient turning state, the damping coefficient of the shock absorber on the turning inner wheel side is set relatively higher than that of the turning outer wheel side. Therefore, the extension stroke amount of the suspension on the turning inner wheel side during transient turning is made smaller than the contraction stroke amount of the suspension on the turning outer wheel side as compared with the case where the damping coefficient of the shock absorber of the turning inner and outer wheels is controlled to be the same. As a result, the height of the center of gravity of the vehicle body during a transient turn can be reduced, thereby improving the turning performance (transient turning performance) of the vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a suspension control device according to the present invention applied to an air suspension provided with a variable damping coefficient type shock absorber.

FIG. 2 is a block diagram showing one embodiment of the electronic control device shown in FIG.

FIG. 3 is a flowchart illustrating a control routine of a spring constant of an air spring and a damping force of a shock absorber.

FIG. 4 is a graph showing the vibration gain on the spring when the sub air chambers of the left and right air springs are not communicating (broken line) and when they are communicating (solid line).

FIG. 5 is a graph showing a damping force characteristic of a shock absorber.

FIG. 6 is an explanatory diagram showing a change in the height of the center of gravity of the vehicle body when the spring constant of the air spring is not changed during turning of the vehicle (A) and when the spring constant of the air spring of the turning inner wheel is increased (B). .

[Explanation of symbols]

 10FR to 10RL ... Air spring 14FR to 14RL ... Shock absorber 16FR to 16RL ... Main air chamber 18FR to 18RL ... Sub air chamber 20FR to 20RL ... Each wheel control valve 24F, 24R ... Common control valve 26FR to 26RL ... Actuator 28 ... Vehicle speed sensor Reference numeral 30: steering angle sensor 32FR to 32RL: vertical acceleration sensor 34: electronic control unit

Claims (1)

[Claims] 1. A vehicle suspension control device in which a suspension having a variable damping coefficient shock absorber is provided for each wheel, a turning state detecting means for detecting a turning state of the vehicle, and a damping coefficient of the shock absorber. Damping coefficient control means for controlling, wherein the damping coefficient control means sets the damping coefficient of the shock absorber on the turning inner wheel side relatively higher than the turning outer wheel side when the vehicle is in a transient turning state. A suspension control device characterized by being performed.