JPH07205628A - Suspension controller - Google Patents

Abstract

PURPOSE:To enhance turning performance and drivability of a car by providing a suspension controller which detects the turning conditions of the car and changes damping characteristics of a shock absorber in order to restrict the rolling of the car. CONSTITUTION:A turning condition detecting means 22 detects turning conditions of a car; especially on a car speed and a steering angle. Meanwhile, an absorber control computer 26 intensifies the damping characteristic of a turning inner- wheel-side supporting means 24 and, after the elapse of a delay time set based on the car speed and steering angle detected, intensifies the damping characteristic of turning outer-wheel-side supporting means 25.

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 which detects a turning state of a vehicle and changes damping characteristics of a shock absorber to suppress rolling.

[0002]

2. Description of the Related Art Conventionally, as one of the functions of a suspension device used in an automobile or the like, a damping characteristic of a shock absorber is changed in order to suppress rolling of the vehicle during turning. One of such suspension devices is described in, for example, Japanese Patent Laid-Open No. 59-120508.

The suspension device described in this publication is equipped with shock absorbers for adjusting the damping force in response to electric signals on all of the wheels (four wheels) of an automobile, and the steering angular velocity (Operation speed)
Is a parameter for adjusting the damping force of the shock absorber.

That is, when the steering position is more than a predetermined preparation angle from the center position, the damping force of all shock absorbers is made hard at the same time according to the angular velocity of the steering movement.

As a result, the traveling feeling can be improved and the roll angle of rolling during cornering can be suppressed. In this case, the driving feeling during cornering is related to the cornering force together with the roll angle. The cornering force is a centripetal force generated in the tire against centrifugal force during turning, and the greater this force, the more stable the cornering.

Therefore, FIG. 8 shows a diagram for explaining the balance of the forces acting on the tire during turning, and FIG. 9 shows a graph of the relationship between the slip angle and the cornering force. In FIG. 8, when the automobile 11 is cornering, the centrifugal force G causes the vehicle body 12 to roll and the outer tire 13
The outer ring's moment center becomes O _OUT , and the inner ring side tire 1
The moment center of the inner ring of 4 becomes O _IN .

At this time, as shown in FIG.
Is expressed by (geometry reaction force + spring system reaction force) for both the outer wheel side tire 13 and the inner wheel side tire 14. The geometric reaction force is the geometric reaction force from the suspension, and the spring reaction force is the sum of the spring reaction force (SP), the shock absorber reaction force (SA), and the stabilizer reaction force (ST). It should be noted that the suspension geometry is determined by the length dimensions and arrangement of the members that form the suspension, and is set so as to maximize exercise performance such as riding comfort and maneuverability, and suppress tire uneven wear.

Here, as shown in FIG. 8, the load movement amount (ΔW) and the stabilizer reaction force (ST) are the same in the inner and outer rings, but the directions are opposite, and generally the geometry reaction force (GF).
_{Since O} and GF _I are different for the inner and outer rings, the spring reaction force (SF
_O and SF _I ) are also balanced with different values for the inner and outer rings. Since the spring reaction forces (SF ₀ , SF _I ) are different depending on the stroke amount, the wheel stroke amounts of the inner and outer wheels are different, which changes the height of the vehicle 12 on the inner and outer wheel sides.

Therefore, since the geometric reaction force is determined by the vehicle, the load movement amount ΔW can be controlled by controlling the characteristics of the spring system.

Further, as shown in FIG. 9, general tire characteristics are represented by cornering forces (CF _O , CF _{I in} FIG. 8) with respect to slip angle (deg), that is, cornering power, and at the same slip angle. If so, the cornering force is proportional to the ground load, and if the ground load increases, the cornering force increases.

[0011]

However, since the damping force of the shock absorber is made hard at the same time as the inner and outer wheels at the time of cornering as described above, the amount of load movement on the outer wheel side is reduced at the initial stage of turning, and the ground load is sufficient. Does not increase.
As a result, the necessary cornering force cannot be obtained,
There is a problem that optimum tire characteristics cannot be derived.

Therefore, the present invention has been made in view of the above problems, and improves the turning performance and drivability by changing the damping characteristic of the inner wheel side during turning and changing the damping characteristic of the outer wheel side after a predetermined time. An object of the present invention is to provide a suspension control device.

[0013]

FIG. 1 shows the principle of the present invention. In FIG. 1, the suspension control device 21
The rolling state is detected by the turning state detecting means 22 to harden the hard and soft characteristics of the supporting means 23 of each wheel portion to suppress rolling, and the turning state detecting means 22 detects turning. Inner ring side support means 24
The suspension characteristic control means 26 for hardening the soft / soft characteristics of the above and hardening the soft / soft characteristics of the turning outer wheel side supporting means 25 after a predetermined time.

[0014]

As shown in FIG. 1, when the suspension characteristic control means 26 makes the hardness of the support means harder than the turning state of the vehicle from the turning state detection means 22, first, the suspension characteristic control means 26 determines the hardness of the turning inner wheel side support means 24. Make it hard. Then, after delaying for a predetermined time, the hardness of the outer ring side support means 25 is made hard.

That is, the outer ring side support means 25 is hardened in hardness and softness after the load is sufficiently moved to the outer ring side and the ground load is sufficiently increased.

This means that the cornering force is increased and the turning performance and drivability are improved.

[0017]

FIG. 2 is a block diagram of an embodiment of the present invention. In the suspension control device 21 shown in FIG. 2, the turning state detecting means 22 includes at least a steering sensor 31, a suspension stroke sensor 32, a speed sensor 33, a throttle sensor 34 (engine control computer 35), a stop lamp switch 36, and an absorber control switch 37 ( The indicator 38) and the check connector 39 are used to send respective signals to the absorber control computer 26 which is suspension characteristic control means. The absorber control computer 26 controls the support means 23.

The buffer means 23 is a turning inner wheel side support means 24.
Is composed of an inner ring front absorber control actuator 24a and an inner ring rear absorber control actuator 24b, and the turning outer ring side support means 25 is an outer ring front absorber control actuator 25a and an outer ring rear absorber control actuator 25b.
Composed of. Absorber control computer 2 for inner and outer wheels from left front, left rear, right front, right rear
6 selects.

Here, the steering sensor 31 detects the rotation of the steering wheel (steering angle θ). The suspension stroke sensor 32 detects a stroke at the time of controlling each shock absorber. The speed sensor 33 detects the vehicle speed (V). The throttle sensor 34 detects the accelerator depression amount and sends it to the engine control computer 35, and sends a throttle opening control signal from the engine control computer 35 to the absorber control computer 26. The stop lamp switch 36 detects whether or not the brake has been depressed especially during turning. Absorber control switch 37
Switches to various modes of the damping force of the shock absorber. The indicator 38 is turned on and signals of various modes are sent. The check connector 39 is a connector for detecting an abnormality.

On the other hand, each actuator 2 of the buffer means 23
4a, 24b, 25a, 25b constitute a part of each shock absorber to change the damping characteristic, that is, harden the soft characteristic.

Here, FIG. 3 shows a vertical sectional view of the shock absorber, and FIG. 4 shows an enlarged vertical sectional view for explaining the mechanism for switching the damping force of FIG. 3 and 4, the hydraulic shock absorber 40 uses a rotary valve 41 to make its damping force variable. The shock absorber 40 has a lower end fixed to a wheel (not shown), a cylinder 42, a piston 43 sliding inside the cylinder 42, a piston 43 connected to the piston 43, and a vehicle body (not shown) at the other end. It is composed of a piston rod 44 to be connected, and a cap 45 that closes the cylinder 42 in a state in which the piston rod 44 is slidably held at the center thereof.

At this time, the cylinder 42 filled with differential oil
The internal space of is divided into a first oil chamber 46 and a second oil chamber 47 by a piston 43, and the piston 43 is provided with a passage for properly communicating these oil chambers 46, 47. The rotary valve 42 is incorporated in a part of the passage.

More specifically, as shown in FIG. 4, which is an enlarged view of the periphery of the piston 43, the outer cylinder 48 is composed of a piston rod 44. And the piston rod 44
The rotary valve 41 is realized by incorporating the inner cylinder 49 and the guide cylinder 50 in a predetermined space provided on the inner circumference of the. The inner cylinder 49 has a piston rod 4
4 through the central portion of the actuator 24a (24b,
The shaft 51 fixed to 25a, 25b) is connected.

A piston valve 52 and a sub valve 53 are arranged on the outer circumference of the piston rod 44. As a result, in the shock absorber 40 incorporating the rotary valve 41 of the present embodiment, as shown in FIG. 4, between the first oil chamber 46 and the second oil chamber 47, from the internal passage of the piston valve 52. A hydraulic passage 54 communicating with the outer circumference of the sub valve 53 and a hydraulic passage 55 communicating with the central portion of the piston rod 44 and above the sub valve 53 via the rotary valve 41 are formed.

The actuator 24a (24b,
25a, 25b) are appropriately driven to rotate the shaft 51, the opening area of the orifice formed in the rotary valve 41 is changed and the flow resistance of the hydraulic passage 55 is changed. Therefore, the piston 43 in the cylinder 42 is changed. The flow resistance of the hydraulic oil changes due to the displacement of, and the damping force of the shock absorber 40 changes accordingly.

Therefore, FIG. 5 shows a flow chart of the control of the present invention, and FIG. 6 shows a graph of the setting of the delay time at the vehicle speed (V) and the steering angle (θ).

In FIG. 5, the turning state detecting means 2 is provided in the absorber control computer 26 while the vehicle is running.
Various detection signals are input from 2 and, of which, FIG. 6 (A)
The vehicle speed (V) from the speed sensor 33 and the steering angle (θ) detection signal (step (ST) 1) from the steering sensor 31 are input to perform roll determination (normal V
(Rolling size judgment by θ and θ) is performed (ST
2). And the absorber control computer 2
6 drives the inner ring front absorber control actuator 24a and the inner ring rear absorber control actuator 24b to make the damping force of the inner ring side shock absorber hard (ST3).

On the other hand, the absorber control computer 26 sets the delay time based on the roll judgment described above (ST4). The delay time is set by the regions Ta and Tb preset with the vehicle speed (V) and the steering angle (θ) as shown in FIG. 6 (B). By the way, the delay time T _a > the delay time T
_{When b} is set, the smaller the lateral acceleration G, the longer the delay state. Further, the set delay time (t ₁ -t ₀ ) (FIG. 2) is set shorter than the time of the turning transient state until the roll reaches the steady state.

Then, the set delay time (t ₁ −
After t ₀ ), the outer ring front absorber control actuator 25a and the outer ring rear absorber control actuator 25b are driven to make the damping force of the outer ring side shock absorber hard (ST5). That is,
In the latter half of the above-mentioned transient state, the outer ring side is hardened to suppress rolling.

As a result, the shock absorber on the inner ring side
When the damping force of the becomes hard, the outer ring side becomes hard.
However, the load is moved to the outer ring side. That is,
The load movement amount ΔW shown in FIG. 8 is (geometry reaction force GF
_O+ Spring system reaction force SFa: ΔW = GF_O+ SA + SP + S
T), of which geometric reaction force GF _O
And the stabilizer reaction force ST are the values determined by the vehicle.
Therefore, the absorber reaction force SA can be controlled with the above delay time.
With, it is possible to change (increase) the load movement amount ΔW.
Further, as shown in FIG. 9 described above, the load movement amount ΔW is increased.
Then cornering force CF_OWill increase.

Further, FIG. 7 shows a graph of the relationship between the ground load and the cornering power, and in detail, as shown in FIG. 7, the cornering power increases almost in proportion to the ground load in the low load region. This is cornering power C
P = K {1-0.0166 (K / μL)} cornering power CP _O The greater the vertical load L is as is clear from (Hideo Sakai et al., "Tire Technology") increases. In the above equation, K is the cornering stiffness, and μ is the friction coefficient between the road surface and rubber (tire).

Further, the cornering force on the outer wheel side is dominant during turning, and the influence of the damping force is large at the initial stage of steering (there is no influence of the damping force because relative displacement does not occur during steady turning).

Therefore, the damping force on the outer wheel side is applied to the inner wheel at the initial stage of steering.
It is controlled by delaying from the side and making it hard.
This increases the ground contact load on the outer ring side and increases the cornering force.
CF _OTo improve turning performance (operational stability).
You can In addition, the height of the center of gravity of the vehicle body decreases,
The steering feel is improved and the outer ring side is soft at the beginning of turning.
The ride comfort is improved and the drivability is improved.
Can be improved. Furthermore, the turning state is steady
The roll angle (low
Ring) can be suppressed.

In the above embodiment, the delay time is set based on the vehicle speed and the steering angle, but it may be set based on the roll angular velocity (differential roll angle). Also,
It may be uniformly set and set by the tread (constant depending on the vehicle type). Further, the roll determination in ST2 of FIG. 5 may be performed by the combination of the steering angular velocity and the vehicle speed or the lateral acceleration. Further, the applied shock absorber 40 is not limited to the one in which the motor is used as the actuator for switching the damping force as in the present embodiment, but may be an electrostrictive element, a solenoid or the like.

In the above embodiment, the damping force of the shock absorber is changed. However, in a suspension provided with a spring (air spring, hydropneumatic suspension) having a variable spring characteristic, damping force control is replaced or added. Alternatively, the spring characteristics may be changed.

[0036]

As described above, according to the present invention, the damping characteristic of the inner wheel side is changed at the time of turning, and the damping characteristic of the outer wheel side is changed after a predetermined time. The performance can be improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a vertical sectional view of a shock absorber.

FIG. 4 is an enlarged vertical sectional view for explaining a mechanism for switching the damping force of FIG.

FIG. 5 is a flowchart of control of the present invention.

FIG. 6 (A) is a graph showing a roll control region, and FIG. 6 (B) is a graph showing setting of delay time at vehicle speed (V) and steering angle (θ).

FIG. 7 is a graph showing the relationship between ground load and cornering power.

FIG. 8 is a diagram for explaining a balance of forces acting on the tire during turning.

FIG. 9 is a graph of tire characteristics showing the relationship between slip angle and cornering force.

[Explanation of symbols]

 21 Suspension Control Device 22 Turning State Detection Means 23 Supporting Means 24 Turning Inner Wheel Side Supporting Means 25 Turning Outer Wheel Side Supporting Means 26 Suspension Characteristic Control Means 24a Inner Ring Front Absorber Control 24b Inner Ring Rear Absorber Control 25a Outer Ring Front Absorber Control 25b Outer Ring Rear Absorber Control 31 Steering sensor 32 Suspension stroke sensor 33 Speed sensor 34 Throttle sensor 35 Engine control computer 36 Stop lamp switch 37 Absorber control switch 38 Indicator 39 Check connector

Claims (1)

[Claims] 1. A suspension control device for suppressing rolling by detecting a turning state of a vehicle that is turning by a turning state detecting means and changing a hard-soft characteristic of a supporting means of each wheel portion, wherein the turning state detecting means detects the turning state. The suspension control device is characterized by comprising: suspension characteristic control means for increasing the hardness and softness of the turning inner wheel side support means and hardening the hard and soft characteristics of the turning outer wheel side support means after a predetermined time.