JPS62198511A - Suspension control device in vehicle - Google Patents

Abstract

PURPOSE:To make quick turning-round ability and running stability of a vehicle coexist, by deciding whether it is under the turning-round motion or under convergence, depending upon the condition of revolution detecting signal, providing a state of over-steer or neutral of steering characteristics under the turning- round motion, and a state of under-steer of the steering characteristics under convergence. CONSTITUTION:As yaw rate detecting signal phi during the straight running, is approximately zero, differentiated/integrated value dphi output from a differentiating/integrating unit 18 is also approximately zero, and deciding signal Db of the theoretical value 1 is output from a deciding unit 19 to a gain setting circuit 20b. By this matter, gain constants Kf=D and Kr=E (D>E) which under-steer characterize the steering characteristics, are selected, sent to amplifiers 17f, 17r of front/rear wheels, and the steering characteristics is controlled as to be under-steerized, through controllers 22FL-22RR. In the same way, the steering characteristics is controlled as to be in a state of over-steer under the turning-round motion, and as to be in a state of under-steer under the convergence. In this way, quick turning-round ability and running stability of a vehicle can coexist.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention changes the front and rear roll stiffness of a vehicle during cornering by controlling a suspension device, thereby achieving agile turning performance and stable running performance. The present invention relates to a suspension control device for a vehicle that enables both of the following.

[Conventional technology]

Suspension control devices for conventional vehicles include:
For example, there is one described in Japanese Patent Application Laid-Open No. 60-82424.

This conventional example uses a torsional rigidity variable stabilizer as a suspension device whose roll rigidity can be changed by control signals, and a steering condition detector that detects the rotation angle of the steering wheel and a vehicle speed detector that detects the vehicle speed. Based on the detection signal, during steering (that is, when turning), a control signal from the control means is output to the torsional rigidity variable stabilizer to increase the total roll rigidity of the vehicle and change the steering characteristic to neutral steer or oversteer. This improves turning performance.

[Problem that the invention seeks to solve]

However, the suspension control device for the conventional vehicle described above is configured to control the steering characteristics of the vehicle to oversteer when it is determined that the vehicle is in a steering state, so the turning operation becomes agile. Although the controllability at the beginning of a turn was improved, the convergence after that was not sufficient and the vehicle body was difficult to stabilize, which was an unresolved problem.

Therefore, the present invention has been made by paying attention to the above-mentioned problems of the conventional example, and its purpose is to change the steering characteristic during cornering to oversteer or neutral steering characteristic when the vehicle body turns, and the purpose of this invention is to To provide a suspension control device for a vehicle that independently controls the roll stiffness of the front and rear wheels so that an understeer characteristic occurs when the turning movement converges, thereby making it possible to achieve both agile movement and stable running. The purpose is

[Means for solving problems]

In order to achieve the above object, the present invention provides a turning state detection means for detecting a turning state of a vehicle body associated with steering, in a vehicle equipped with a suspension device capable of changing the steering characteristics of the vehicle by inputting a control signal; a turning motion determining means for determining whether the turning state is actually in the vehicle body turning motion or convergence based on the detection signal of the turning state detecting means; and when the determination result of the oral motion determining means is that the vehicle body is in the vehicle turning motion. and control means for outputting to the suspension device a control signal that changes the steering characteristics of the vehicle to oversteer or neutral steering, and a control signal that changes the steering characteristics of the vehicle to understeer at the time of convergence, respectively. do.

[Effect]

In the present invention, in a vehicle equipped with a suspension device that can change the roll stiffness of the vehicle to select the steering characteristic based on a control signal, the initial stage of the vehicle body turning movement, that is, the initial By controlling the suspension by means of the control means so as to oversteer or neutral steer during operation to improve maneuverability, and to understeer during the convergence period of the maneuver to improve steering stability, the suspension is controlled during turning. To simultaneously improve the verbal performance of a vehicle and ensure stable running performance.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 1 to 3 are diagrams showing one embodiment of the present invention.

In Figure 1, IFL, IFR, IRL, I
RR is the vehicle body side member 2 and each wheel 3FL, 3FR, respectively.
, 3RL, and 3RR, and is an active suspension device interposed between wheel side members 4 that individually support a hydraulic cylinder 5, a coil spring 6, a stroke sensor 7, and a working fluid for the hydraulic cylinder 5 as actuators. and a directional switching valve 8 that controls the supply of.

Here, the hydraulic cylinder 5 has its cylinder tube 5a
is attached to the vehicle body side member 2, and the piston rod 5b is attached to the wheel side member 4.

Further, the coil spring 6 is installed between the vehicle body side member 2 and the wheel side member 4 to support the vehicle body load, and under normal conditions, the coil spring 6 is installed between the vehicle body side member 2 and the wheel side member 4 to support the vehicle body load. The amount of variation is adjusted by adjusting the stroke of the hydraulic cylinder 5. Further, the stroke sensor 7 is composed of, for example, a potentiometer, and detects the stroke between the vehicle body side member 2 and the wheel side member 4 from the neutral position, and detects a positive detection when the stroke is displaced upward from the neutral position accordingly. Outputs a negative detection signal when the signal is displaced downward. Furthermore, the directional control valve 8 connects each input boat to a hydraulic unit 10 having a built-in hydraulic pump.
The return ports are each connected to the tank 11, and a damping force is generated by the viscous resistance of the hydraulic oil passing through these directional control valves 8, and the function is similar to that of a conventional Sisic Absorber. High pressure accumulators 12f, 12r and low pressure accumulator 1 are installed in the piping and low pressure side piping, respectively.
3f and j3r are connected, and the directional control valve 8
has improved responsiveness.

The detection signals of the stroke sensors 7 of the respective suspension devices IFL to IRR and the detection signals of the yaw rate sensor 14 which detects the angular velocity around the vertical axis of the vehicle body, that is, the yaw rate, are supplied to the control device 15. Based on the detection signal φ of the yaw rate sensor 14 and the detection signal of the stroke sensor 7, this control device 15 outputs a control signal for controlling the directional control valve 8 of each suspension device IFL to IRIII.

In one example of the control device 15, as shown in the block diagram of FIG. 2, a yaw rate detection signal φ from a yaw rate sensor 14 is supplied to a retrospective movement determination circuit 16.

An example of this verbal motion determination circuit 16 includes a front wheel side amplifier 17f and a rear wheel side amplifier 17r whose gains are adjustable, and a differentiator 1 to which the detection signal of the yaw rate sensor 14 is supplied.
8, and the differential output dφ consisting of the differential value d1≠l/dt of the absolute value 1≠1 of the yaw rate detection signal φ output from the differentiator 18 is supplied to the determiner 19. It is determined whether or not it exceeds a predetermined set value A°, and when the value of the differential output d exceeds the predetermined set value A,
Absolute value of yaw rate 1≠1 with angular acceleration exceeding set value A
This means that the turning operation is being performed, and a judgment signal Da of logical value "1" is sent to the gain setter 20a, and the value of the differential output dφ is less than or equal to the predetermined set value A. Sometimes, when the angular acceleration is less than the set value A, the absolute value of the yaw rate 1≠1 slightly increases or decreases, and this is determined to be the time when the turning operation has converged, and the gain is set to the determination signal Db with the logical value "1". The signals are output to the respective devices 20b.

The gain setter 20a sets the gain constant Kf of the front wheel side amplifier 17f to a predetermined setting value B when the control signal Da is supplied.
, the gain constant Kr of the rear wheel side amplifier 17r is set to a predetermined setting value C of 8 or more, and the gain setter 20
b is the front wheel side amplifier 1 when the control signal Db is supplied.
The gain constant Kf of the rear wheel amplifier 17r is set to a predetermined set value, and the gain constant Kr of the rear wheel side amplifier 17r is set to a predetermined set value E that is less than the set value.
The front wheel side amplifier 17 outputs gain adjustment outputs respectively set to
f and rear wheel side amplifier 17r, and these amplifiers 1
Controls the gains of 7f and 17r.

The amplified output of the front wheel side amplifier 17f is supplied to the comparators 21FL and 2IFR as a stroke target value Tf for controlling the front wheel suspension devices IFL and IFR, respectively, and the amplified output of the rear wheel side amplifier 17r is
Rear wheel suspension W I RL.

The comparison unit 2 uses the stroke target value Tr to control the IRR.
Supplied to 1RL and 21RR. Here, comparison section 2
2FL, 22RL and 22F]? , 22RR are compared with the stroke detection signal of the stroke sensor 7 in such a manner that the target values Tf and Tr have opposite signs, respectively.

The output deviation signals from these comparators 21FL to 21RR are supplied to controllers 22FL to 22RR that output control signals for controlling the directional control valve 8 based on these signals.

Here, assuming that the wheel loads of the front and rear wheels of the vehicle and the characteristics of the hydraulic cylinders 5, hydraulic system loop gains, coil springs 6, etc. of the suspension systems FIFL to IRR are equal, a gain adjustment output can be obtained from the gain setting device 20a. Therefore, the gain constant Kf of the front wheel side amplifier 17f becomes the gain constant Kr of the rear wheel side amplifier 17r.
Since the steering characteristics of the vehicle are controlled as follows, the steering characteristics of the vehicle are changed to neutral steering or oversteer. Conversely, assuming that the gain adjustment output can be obtained from the gain setter 20b,
As a result, the gain constant Kf of the front wheel amplifier 17f is controlled to be thicker than the gain constant Kr of the rear wheel amplifier 17r, so that the steering characteristic of the vehicle becomes understeer.

In this way, the gain constant Kf on the front wheel side and the rear wheel side
The reason why the steering characteristics can be changed by changing the KrO values is as described below.

In other words, depending on the magnitude of the gain constants Kf and Kr, the reverse roll moment for countering centrifugal force when the vehicle turns can be made different between the front and rear wheels, and this is due to the roll stiffness of the conventional suspension. This corresponds to different share ratios. Therefore, if Kf > Kr is selected, the amount of left and right wheel load movement on the front wheels increases during turning, and the left and right total cornering power of the tire decreases compared to that on the rear wheels, which improves stability. The factor Ks increases and the steering characteristics of the vehicle become understeer characteristics. Similarly, if we select Kf<Kr,
Contrary to the above, the amount of left and right wheel load transfer on the rear wheel side increases,
The total left and right cornering power of the tires is reduced compared to that of the front wheels, and this reduces the stability factor Ks, causing the vehicle's steering characteristics to become oversteer characteristics.Furthermore, when Kf=Kr is selected, neutral steering characteristics occur. It can be done.

Next, the operation of the above embodiment will be explained with reference to FIGS. 3(a) to 3(C) showing the behavior of the vehicle when traveling at an S-junction.

Now, time t0~1. Assuming that the vehicle is traveling straight ahead as shown in FIG. 3, the yaw rate detection signal of the yaw rate sensor 14 is approximately zero as shown in FIG. is maintained. Therefore, the differential value dφ output from the differentiator 18
also indicates approximately zero, and the determiner 19 outputs a determination signal Db with a logical value of "1" to the gain setting circuit 20b. For this reason, gain constants Kf=D and Kr=E (D>E) that give the vehicle understeer characteristics are selected by the gain setter 20b, and these are supplied to the front wheel amplifier 17f and the rear wheel amplifier 17r, respectively. The amplification gain of is controlled.

At this time, since the yaw rate detection signal φ from the yaw rate sensor 14 is zero, the front wheel side and rear wheel side amplifiers 17f
, 17r, the target value Tf is zero, that is, the target value Tf that makes the vehicle height a neutral state.
, Tr are output, and the deviation between this and the stroke detection signal of the stroke sensor 7 of each wheel is determined by the controller 22F.
Supplied to L~22RR. As a result, a predetermined switching signal is output from the controllers 2.2FL to 22RR to the directional switching valve 8, and the stroke of the hydraulic cylinder 5 is controlled to the neutral position, and in this state, the steering characteristics of the vehicle are controlled to understeer. , improve straight-line stability.

Then, when the steering wheel is turned to the right at time t from this straight running state to a right turning state, the yaw rate detection signal from the yaw rate sensor 14 changes according to this turning state as shown in FIG. The differential output dφ of the absolute value will gradually increase in the positive direction as shown in FIG.
It increases as shown in Figure (C). Then, at time t2, when the value of the differential output d from the differentiator 18 exceeds the set value A,
In place of the determination signal Db of the determiner 19, the determination signal Da has a logical value of "1" and is supplied to the gain setter 20a. Therefore, the gain constant K that makes the vehicle have oversteering or neutral steering characteristics is set using the gain setting device 20a.
f=B and Kr −C (B≦C) are selected, and these are supplied to the front wheel side amplifier 17f and the rear wheel side amplifier 17r, respectively, to control their amplification gains.

Therefore, the front wheel side amplifier t7 corresponds to the magnitude of the yaw rate detection signal - output from the yaw rate sensor 14.
The target value Tf output from f is the rear wheel side amplifier 17r.
The amount of left and right wheel load movement on the rear wheel side becomes equal to or larger than that on the front wheel side, resulting in neutral steer or oversteer characteristics, and agile turning operation is performed. be able to.

In this right-turning state, the left side of the vehicle sinks from the neutral position due to the lateral acceleration generated by the turning operation, and the output of the stroke sensor 7 becomes negative, and conversely, the right side rises from the neutral position, and the output of the stroke sensor 7 becomes negative. Although the output will be positive, the front wheel side and rear wheel side amplifiers 17
Comparison units 21FL and 21RL assume that target value Tf from f and 17r and Tr are positive for the left wheel and negative for the right wheel.
, 21FR.

21RR, the suspension device for the left wheel is controlled to extend the hydraulic cylinder 5, and the suspension device for the right wheel is controlled to contract the hydraulic cylinder 5. ÷, it is possible to exert an anti-roll effect.

Then, at time t3, when the vehicle approaches the center of the 8-way intersection and transitions from the retrospective operation state in the right turn to the convergence state, and the differential output dφ of the differentiator 18 becomes equal to or less than the predetermined setting value A, the determiner 19 The judgment signal Db becomes a logical value "1", and the gain constants Kf and Kr set by the gain setter 20b are set to the front wheel side and rear wheel side amplifiers 17f and 16r, so that the vehicle changes to understeer characteristics. This makes it easy to return the steering wheel to its neutral position.

Subsequently, at time t4, when the steering wheel is turned to the left and the vehicle shifts to a left turning state, the yaw rate detection signal φ of the yaw rate sensor 14 increases in the negative direction as shown in FIG. 3(b). Since the differential output dφ output from the differentiator 18 increases again in the positive direction as shown in FIG. This allows for agile retrospective performance. At this time, since the yaw rate detection signal φ output from the yaw rate sensor 14 is a negative value, the front wheel side and rear wheel side amplifiers 17f
, 17r are negative values, and in contrast to the right turning state, the suspension device on the left wheel side is controlled to contract the hydraulic cylinder 5, and the suspension device on the left wheel side is controlled to contract. For this suspension device, the hydraulic cylinder 5 is extended so that the anti-roll effect can be achieved.

Next, when reaching the end of the 8-junction at time t, the yaw rate detection signal φΦ value of the yaw rate sensor 14 reaches a peak value in the negative direction, and when the differential output dφ of the differentiator 18 becomes less than the predetermined set value A, the above-mentioned As with the convergence of the right turn,
When the vehicle changes to understeer characteristics, the steering wheel can be easily returned to the neutral position, and then shifts to a straight running state at time t6, the value of the yaw rate detection signal φ of the yaw rate sensor 14 becomes zero, To maintain understeer characteristics and return to normal straight running condition without anti-roll effect.

In the above embodiment, the case where the yaw rate sensor 14 is applied as a means for detecting the turning state of the vehicle has been described, but the invention is not limited to this. The turning state may be detected by detecting a physical quantity that can detect the turning state of the vehicle.

Further, in the above embodiment, the case where an active type suspension device is applied is explained when controlling the steering characteristics of the vehicle, but the invention is not limited to this, and it may be applied to a vehicle having a variable damping force shock absorber as a suspension device. The system increases the damping force of the variable damping force shock absorber on the rear wheel side when turning, and reduces the damping force of the damping force shock absorber on the front wheel side, resulting in neutral steer or oversteer characteristics. The damping force of the variable damping force shock absorber on the rear wheel side can be increased, and the damping force of the variable damping force shock absorber on the rear wheel side can be lowered to control the understeer characteristics. For vehicles equipped with variable rigidity stabilizers, variable spring constant air springs, etc., by controlling their torsional rigidity and spring constant, it is possible to achieve neutral steer or oversteer characteristics during turning operations, and understeer characteristics during retrospective convergence. can be controlled.

〔Effect of the invention〕

As explained above, according to the present invention, the turning state of the vehicle body accompanying the steering of the steering wheel is detected, and based on the detected value, the turning motion determining means determines whether the turning state is in a retrospective operation or when the turning has converged. The suspension system on the front and rear wheels is controlled so that the steering characteristic changes to neutral steer or oversteer if the turning is occurring, and understeer if the turning is convergent. The effect of achieving both agile turning performance and stable running performance when running is achieved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a suspension control device showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the control device, and FIG. 3 is an explanatory diagram providing a detailed explanation of the invention. . In the figure, IFL, IPR, IRL, IRR are suspension devices, 5 is a hydraulic cylinder, 7 is a stroke sensor, 8 is a directional control valve, 14 is a yaw rate sensor, 15
16 is a control device, 16 is a retrospective motion determination circuit, 17f is a front wheel side amplifier, 17f is a rear wheel side amplifier, 18 is a differentiator, 19 is a judger, 20a, 20b are gain setters, 21 is a comparison unit, 22 is a controller It is.

Claims (1)

[Claims] In a vehicle equipped with a suspension device capable of changing steering characteristics of the vehicle by inputting a control signal, a turning state detection means detects a turning state of the vehicle body accompanying steering, and a turning state is determined based on a detection signal of the turning state detection means. A turning motion determining means for determining whether the vehicle body is actually turning or converging; and converting the steering characteristic of the vehicle to oversteer or neutral steering when the determination result of the turning motion determining means is that the vehicle body is currently turning. 1. A suspension control device for a vehicle, comprising: control means for outputting a control signal to each of the suspension devices to make the steering characteristic of the vehicle understeer when the control signal is converged.