JPH0478485B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention is directed to suppressing pitching of a vehicle due to nose dive at the start of braking and rocking back at the end of braking when the vehicle is in a braking state. The present invention relates to a suspension control device for a vehicle that can be used in a vehicle.

[Prior art]

When a vehicle is braked while driving, the vehicle body sinks forward, resulting in a so-called nose dive. Such a nose dive phenomenon is generally caused by the characteristics of the vehicle suspension.

In order to prevent this nose dive phenomenon, it has been proposed to control the damping force of the shock absorber during braking.

A conventional example of this type is Japanese Utility Model Application Publication No. 56-111009 (name of the invention: vehicle suspension), which was previously proposed by the present applicant. This is a vehicle suspension equipped with a shock absorber, in which at least one of the shock absorbers on the front wheel side and the rear wheel side is configured with a shock absorber having a variable damping force characteristic structure, and also detects the stroke of the brake pedal. The present invention is characterized in that a sensor is provided to detect when the vehicle is braking, and when the output of this sensor exceeds a predetermined value, the damping force of the shock absorber is increased.

In addition, as another conventional example, Japanese Patent Application Laid-Open No. 53-26021 (title of invention: Adjustable Suspension System for Vehicles) also describes a method of detecting the stroke of the brake pedal and increasing the spring constant of the shock absorber in the braking state. Suggested.

However, in such conventional vehicle suspensions, the braking state is detected by the stroke of the brake pedal, so there are large variations due to sensor installation errors.
In addition, the brake is susceptible to changes over time such as wear and tear of various parts of the brake, and air mixing in the brake oil, and there is an unresolved problem that the control characteristics of the damping force cannot be maintained with high accuracy.

Furthermore, in order to solve the above problems,
As shown in Japanese Patent Application Laid-open No. 58-30814 and Japanese Patent Application Laid-open No. 58-30816, a vehicle suspension device that detects the braking state based on changes in brake oil pressure has also been proposed.

These can solve the above-mentioned problems such as aging, but since it is necessary to incorporate a sensor that detects the braking state into the brake hydraulic system, extremely high reliability is required and the manufacturing cost is high. New problems arose, such as increased volume.

[Purpose of the invention]

The present invention has been made by focusing on the problems of the prior art, and uses a detection signal of a braking state and a detection signal for detecting a change in vehicle attitude due to this braking state to detect a sudden braking state. By detecting this, the objective is to accurately suppress pitching of the vehicle due to nose dive and rolling back during sudden braking, improve the ride comfort of the vehicle, and thereby solve the problems of the conventional example. There is.

[Structure of the invention]

In order to achieve the above object, the present invention provides a vehicle equipped with a suspension device on at least one of the front wheel side or the rear wheel side, which suppresses pitching during vehicle braking by changing the damping force or spring constant according to a control signal. a braking operation detection means for detecting a braking state of the vehicle; an attitude change detection means for detecting a change in attitude of the vehicle due to pitching; When the attitude change detection signal exceeds a predetermined value, the damping force or spring constant of the suspension device is temporarily increased, and at least the damping of the suspension is increased at the end of braking based on the detection signal from the braking operation detection means. and a control means for outputting the control signal to temporarily increase the force or spring constant.

[Effect]

The present invention provides a vehicle equipped with a suspension device on at least one of a front wheel side or a rear wheel side that suppresses pitching during vehicle braking by changing a damping force or a spring constant in response to a control signal, and in which a braking state detecting means detects The braking state of the vehicle is detected, and when the attitude change detected by the attitude change detection means exceeds a predetermined value at the time of starting braking, the control means temporarily increases the damping force or spring constant of the suspension device. In addition to suppressing nose dive during sudden braking accompanied by large pitting, the nose dive is suppressed by temporarily increasing the damping force or spring constant of the suspension device at the end of braking based on at least the detection signal from the braking state operation detection means. By reliably suppressing the back-swinging as a reaction force, and maintaining a normal state in which the swaying is not suppressed during the braking operation, vibration components due to road surface irregularities transmitted from the wheels to the vehicle body are absorbed and the ride is improved. Improves comfort.

〔Example〕

The present invention will be explained below based on the drawings.

1 to 4 are diagrams showing one embodiment of the present invention.

First, to explain the configuration, in FIG. 1, 1L and 1R are variable damping force shock absorbers 3 that constitute the suspension inserted between the left and right front wheels 2L and 2R and the vehicle body (not shown).
L and 3R are shock absorbers having a constant damping force that similarly constitute the suspension and are inserted between the left and right rear wheels 4L and 4R and the vehicle body.

Reference numeral 5 denotes a brake pedal for performing a braking operation on the vehicle, and a brake switch 6 as a braking operation detection means fixed to the vehicle body is in contact with the brake pedal 5. Brake switch 6 is
When the brake pedal 5 is not depressed,
When the brake pedal 5 is depressed from the off (or on) state, it becomes the on (or off) state. Therefore, when the switch signal of the brake switch 6 is in the on (or off) state, it can be determined that the brake is in the braking state.

Reference numeral 7 denotes a vehicle height detector as a posture change detector, and as shown in FIG. By measuring the time from the time when the ultrasonic wave is emitted from the ultrasonic transmitter 9 until the reflected wave is received by the ultrasonic receiver 10 when the ultrasonic wave is reflected on the road surface, and by multiplying this measured time by the speed of sound. ,
The distance H between the vehicle body 8 and the road surface is measured, and a vehicle height detection signal DH corresponding to the measured distance is output.

Reference numeral 11 denotes a drive circuit to which a control signal CS from a control device 12, which will be described later, is supplied, and when this control signal CS has a logical value of "1", for example, it sets the variable damping force shock absorbers 1L and 1R to a high damping force state. Conversely, when the control signal CS has a logical value of "0", the variable damping force shock absorbers 1L and 1R are controlled to a low damping force.

12 is a control device, and a brake switch 6
A switch signal from the vehicle speed detector 7 and a vehicle speed detection signal VP from the vehicle speed detector 7 are supplied, and a control signal CS for controlling the damping force of the variable damping force shock absorbers 1L and 1R is output to the drive circuit 11.

The variable damping force shock absorbers 1L and 1R are
As shown in FIG. 3, a cylinder 16 includes an inner cylinder 14 and an outer cylinder 15, a slidable piston rod 17 inside the cylinder, and a damping force generating bottom valve disposed at the bottom of the cylinder 16. 18. The piston rod 17 is divided in the axial direction into an upper piston rod 19 and a lower piston rod 20. A bypass passage 22 is formed to directly communicate B and C, and an actuator 25 having a solenoid 23 and a plunger 24 is installed inside the upper piston rod 19. Furthermore, the plunger 24 is positioned so as to enter the bypass passage 22,
The plunger 24 is actuated depending on whether the solenoid 23 in the actuator 25 is energized or de-energized,
Then, by opening and closing the bypass passage 22, the oil chambers B and C are opened and closed.
It connects or blocks direct communication between the two. Here, the solenoid 23 is connected to the drive circuit 11 via a lead wire 26, and operates the plunger 24 in response to a control signal CS from the control circuit 12.
By operating the damping force, it is possible to switch and control the damping force between high and low. In addition, in the figure, 27, 28 and 29, 30 are damping force generating orifices on the compression side and expansion side, respectively, and 31, 32
is a non-return valve, and 33 is a return spring.

As shown in FIG. 4, the control device 12 has a braking start determining means 34 supplied with a switch signal from the brake switch 6, and a braking start determination means 34 supplied with a vehicle height detection signal DH from the vehicle height detector 7. Attitude change rate calculation means 35 for calculating the attitude change; attitude change rate determination means 36 for determining whether the calculation result exceeds a predetermined value; Control signal that increases the damping force of variable force shock absorbers 1L and 1R for a predetermined period of time
It includes a damping force control means 37 that outputs CS, a braking end determination means 38, an attitude change amount calculation means 39, and an attitude change amount determination means 40 that determines whether the calculation result exceeds a predetermined value. ing. Here, the predetermined time of the damping force control means 37 is for setting times T1 and T2 necessary for suppressing nose dive and swinging back as a reaction force thereof, which will be described later, and these set times T1 ,T2
is set appropriately according to the suspension characteristics of the vehicle.

Next, a description will be given of a processing procedure when a microcomputer is used as the control device 12 and each of the above means is realized by a program mainly based on a microprocessor.

FIGS. 5a, b, and c show this processing procedure. In FIG. The program starts, and first, in step, the vehicle height detection signal DH from the vehicle height detector 7 is read and stored in a predetermined storage area of the storage device as a vehicle height variable Ho. Next, the process moves to step, reads the vehicle height detection signal DH from the vehicle height detector 7 after a predetermined time Δt seconds, and sets this as the vehicle height variable.
It is stored as H ₁ in a predetermined storage area of the storage device.
Next, proceed to step, read out the vehicle speed variables H ₀ and H ₁ stored in step and step, and calculate the vehicle height change rate (change speed) ΔHs represented by the difference value (H ₁ - H ₀ ) between them. Then move on to the step.

In the step, it is determined whether the vehicle height change rate ΔHs calculated in the step exceeds a predetermined value a. In this case, the determination is made by determining whether the deceleration state is sudden or not by determining the vehicle height change rate, that is, the magnitude of the change in the vehicle attitude in response to the braking operation, and the predetermined value is determined. a is selected depending on the rate of change in vehicle height that causes nose dive, which affects the ride comfort of the vehicle. Here, vehicle height change rate ΔHs
If ΔHs≦a, the interrupt process ends, and if ΔHs>a, the process moves to step.

In step, a control signal CS having a logic value of "1", for example, is output to the drive circuit 11 to increase the damping force of the variable damping force shock absorbers 1L and 1R.

Next, the process moves to step 1, where the timer is set to time T1, and the interrupt processing is ended. In this case, the timer setting time T1 is selected to be a sufficient time to suppress a change in attitude when the vehicle nose dives after starting braking.

In addition, in FIG. 5b, the brake switch 6
A falling input signal from the ON state to the OFF state starts the braking end interrupt program for the main program.First, in step 1, the vehicle height detection signal DH from the vehicle height detector 7 is read, and this signal is used to determine the vehicle height. It is stored in a predetermined storage area of the storage device as variable _H2 .

Next, the process moves to a step where the vehicle height variable H ₀ stored in the previous step and the vehicle height variable H ₂ stored in the previous step are read out, and the braking start time expressed by the difference value (H ₀ - H ₂ ) between them is read out. and calculate the vehicle height change amount ΔH _E at the end of braking.

Next, the process moves to step 11, and it is determined whether or not the vehicle height change amount ΔH _E calculated in the step described above exceeds a predetermined value b. The determination in this case is to determine the amount of swing back as a reaction force of the nose dive at the end of the braking operation, and is determined based on the amount of change in vehicle height at the end of the braking operation. Then, when the determination result in this step is ΔH _E ≦b, the interrupt processing is immediately terminated,
When ΔH _E >b, the process moves to step.

In the step, the control signal CS for increasing the damping force of the variable damping force shock absorbers 1L and 1R is outputted to the drive circuit 11 in the same way as the step in FIG.
After setting the flag to 2, the interrupt processing ends. In this case, the set time T2 of the timer is selected to be a sufficient time to suppress a change in attitude when the vehicle rolls back at the end of braking.

Then, when the timer set in step 2 finishes counting time T1 or T2 and times up, the timer interrupt process shown in FIG. 5c is executed. That is, in the step, the variable damping force shock absorbers 1L, 1R
It is determined whether the damping force is on the low side based on whether the control signal CS is output to the damping force.

Here, since the damping force has already been set to the high side in step 1, we move on to step 1 and set the control signal CS to the logic value "0".
As, variable damping force shock absorber 1L, 1
Switch the damping force of R to the lower side. Then, this interrupt processing ends.

Depending on other conditions, the damping force variable shock absorbers 1L and 1R may be
If the damping force has already been returned to the low side, the damping force is determined to be low in step and the process ends here.

In this way, the variable damping force shock absorbers 1L and 1R, which have been set to have a high damping force in the step or step, are returned to their original "low damping force state" after a certain period of time after the braking operation is completed. It will be done.

Incidentally, the processing from step to step in FIG. 5 is a specific example of the posture change amount calculation means 35 in FIG. ;Step and Step;Step and Step processing are specific examples of the damping force control means 37; Step and Step processing are performed by the posture change amount calculation means 39.
This is a specific example of the above, and the processing of the step is a specific example of the posture change amount determining means 40. On the other hand, the braking start state determining means 34 and the braking end state determining means 38 are performed by determining the state of the brake switch 6, and are not particularly shown in the flow.

Next, to explain the operation, when the driver depresses the brake pedal 5 to initiate a braking operation, the brake switch 6 is first activated and is turned off at time _t0 , as shown in FIG. 6a. The state changes from the state to the on state. Upon receiving the input signal from the brake switch 6, the control device 12 detects that the braking operation has started using the braking start state determining means 34, and executes the braking start interrupt process shown in FIG. 5a.

Therefore, first, in step, the current vehicle height detection signal DH from the vehicle height detector 7 is read, vehicle speed data is calculated based on this, and this is used as a vehicle speed variable.
It is stored as H ₀ in a predetermined storage area of the storage device.

Next, in step, the vehicle height detection signal DH at time _t1 after a predetermined time Δt has elapsed is read and similarly stored in a predetermined storage area of the storage device as a vehicle height variable _H1 . Then, in a step, the vehicle height change amount ΔHs per unit time is calculated, and then in a step it is determined whether the vehicle height change amount ΔHs exceeds a predetermined value a. At this time, when the amount of depression of the brake pedal 5 is small, that is, when braking is slow, the sixth
As the vehicle height change amount ΔHs per unit time _Δt1 becomes smaller as shown by the solid line in FIG. In this case, as shown by the solid line in Figure 6b, the amount of attitude change due to the nose dive of the vehicle, that is, the amount of sinking of the front end of the vehicle is small, and the amount of swinging back as a reaction force is small, which has a large effect on ride comfort. Never give up.

On the other hand, when the amount of depression of the brake pedal 5 is large, that is, when braking is sudden, the value of the vehicle height change ΔHs increases as shown by the dotted line in FIG. As the amount of change in the posture of the vehicle becomes large, which affects the ride comfort of the vehicle, it is determined that ΔHs>a, and the process moves to step 1, where the variable damping force shock absorber 1L,
A control signal with a logic value of “1” that makes 1R a high damping force.
CS is output to the drive circuit 11, and in a further step, the timer is set to time T1, and then the main program is returned. In this way, when the control signal CS with the logical value "1" is output from the control device 12,
An excitation current for exciting the solenoids 23 is outputted from the drive circuit 11 to the variable damping force shock absorbers 1L and 1R. For this reason, solenoid 23
is excited, the plunger 24 slides downward against the return spring 33, and closes the bypass passage 22. As a result, the oil chambers B and C are communicated only by the damping force generating orifices 27 and 29, so movement of the hydraulic oil between the two chambers is restricted, and the variable damping force shock absorbers 1L and 1R are connected as shown in FIG. As shown in c, the damping force is increased. As a result, the amount of nose dive can be suppressed compared to the amount of nose dive that occurs when braking is started, in which the front side sinks mainly around the center of gravity of the vehicle body.

When the timer set in step expires, the timer interrupt process shown in FIG. 5c is executed. That is, first, in a step, it is determined whether or not the variable damping force shock absorbers 1L, 1R have low damping force. At this time, the variable damping force shock absorbers 1L and 1 are
Since R is set to a high damping force, proceed to step, set the control signal CS to logical value "0",
Terminates timer interrupt processing. In this way, when the control signal CS is set to the logical value "0", the excitation current from the drive circuit 11 is cut off, so the solenoids 23 of the variable damping force shock absorbers 1L and 1R are de-energized, and the plunger 24 is returned to its original position by the force of the return spring 33. As a result, the bypass passage 22 between the oil chambers B and C becomes open, facilitating the flow of hydraulic oil between the two chambers, reducing the damping force of the shock absorber, and returning to the normal running condition. It is possible to absorb vibration components near the unsprung resonance frequency due to road surface irregularities that are input to the wheels and prevent them from being transmitted to the vehicle body, thereby improving the ride comfort of the vehicle.

Therefore, when the brake pedal 5 is released at time _t2 to complete the braking operation, the brake switch 6 switches to the sixth position.
As shown in FIG. 5A, since the ON state is changed to the OFF state, this is determined by the braking end state determining means 38, and the braking end interrupt process shown in FIG. 5B is executed. In this case, the braking end interrupt process reads the detection signal DH from the vehicle height detector 7 and stores it in a predetermined storage area of the storage device as a vehicle height variable _H2 . Next, in step, the current vehicle height variable H ₂ and the vehicle height variable H ₀ at the start of braking stored in the storage device are read out, and based on these, the amount of change in vehicle height ΔH _E at the time of ending the braking operation is calculated. Then, in step it is determined whether the vehicle height change amount ΔH _E exceeds a predetermined value b, and ΔH _E ≦
When it is b, end the timer interrupt processing,
When ΔH _E >b, the program moves to step and increases the damping force of the variable damping force shock absorbers 1L and 1R in the same way as step, then moves to step, sets the timer to time T2, and then processes the timer interrupt. end.

When the timer set in step expires, the timer interrupt process shown in FIG. 5c is executed in the same manner as described above, the damping force of the variable damping force shock absorber is reduced, and the vehicle returns to the normal running state. In this way, the variable damping force shock absorber 1 is operated for a predetermined time T2 after the braking operation is completed.
By maintaining the damping forces of L and 1R in a high state, it is possible to reliably suppress the amount of swing back as a reaction force of the nose dive shown by the dotted line in FIG. 6b.

Furthermore, if the damping force of the variable damping force shock absorbers 1L, 1R has been reduced by other processing in the main program when the timer times up, the timer interrupt processing is immediately terminated.

In addition, variable damping force shock absorber 1L, 1
R is not limited to the above embodiments, but a magnetic fluid is used, and an excitation coil that forms a magnetic field is disposed in the path of the magnetic fluid, and the magnetic field of the excitation coil increases the flow resistance of the magnetic fluid. The damping force of the shock absorber may be changed as long as it can change the damping force of the shock absorber.

Furthermore, the damping force control of the variable damping force shock absorbers 1L and 1R at the end of braking is not limited to the above embodiment, and in the braking end interrupt program shown in FIG. Instead of the vehicle height change amount ΔH _E , the vehicle height change rate (change speed) per unit time from time _t2 to time _t3 shown in FIG. ) The damping force may be controlled by calculating ΔH as shown in FIG. 6d.

Further, in the above embodiment, a case has been described in which variable damping force shock absorbers 1L and 1R are applied as a suspension device for suppressing pitching of a vehicle, but the invention is not limited to this, and as shown in FIG. Alternatively, the spring constant may be changed. That is, the suspension device 55 in FIG. 7 is composed of a shock absorber 56 and an air chamber 57 that is integrally formed in the upper part of the shock absorber 56 and is expandable and retractable in the vertical direction. This suspension device 55 is attached to the upper end of the piston rod 58 of the shock absorber 56 and the air chamber 5.
The shock absorber 56 is mounted by attaching the upper end of the shock absorber 7 to a member on the vehicle body side and the lower end of the shock absorber 56 to a member on the vehicle body side.

Here, when the on-off valve 59 is closed, the spring constant of the suspension device 55 is
determined solely by the volume of On the other hand, the on-off valve 5
9 is opened to communicate the air chamber 57 and the reservoir tank 60, the spring constant of the suspension device 55 is determined by the volume of the air chamber 57 plus the volume of the reservoir tank 60. Therefore, by opening and closing the on-off valve 59, the spring constant of the air spring of this suspension device 55 can be increased.
It can be changed to small. This change in spring constant is carried out by the control device 1 in FIG.
A drive circuit 11 supplied with a control signal CS from 2
This is done by opening and closing the on-off valve 59,
When the control signal CS has a logical value of “1”, the on-off valve 5
9 is in the closed state and the spring constant is increased, and on the other hand, when the control signal CS is the logical value "0" opposite to the above,
This is done by opening the on-off valve 59 and reducing the spring constant.

In addition, in the figure, 62 is an elastic body such as rubber, and 63
64 is a passage communicating with another suspension device, 65 is an intake/exhaust valve, and 66 is an air supply device.

Furthermore, in the above embodiment, a case has been described in which variable damping force shock absorbers are attached to the left and right front wheels 2L, 2R to suppress the longitudinal rocking of the vehicle. This occurs when the left and right rear wheels 4 swing back and forth around their center of gravity.
Suspension devices that change the damping force or spring constant may be provided on L and 4R, and furthermore, suspension devices that change the damping force or spring constant may be provided on both the front wheel side and the rear wheel side. It's okay.

Further, the braking operation detecting means is not limited to the brake switch 6, but may detect a braking operation by detecting a change in the working pressure of the master cylinder, a change in tension in the brake force transmission system, or the like.

Furthermore, the vehicle attitude change detector is not limited to the vehicle height detector 7 that uses an ultrasonic distance measuring device, but also a vehicle that detects the amount of displacement of the piston rod of the shock absorber as a change in the inductance of the detection coil. A high speed detector, wheel load detector, etc. can be applied.

〔Effect of the invention〕

As explained above, according to the present invention, a vehicle is provided with a suspension device on at least one of the front wheels or the rear wheels, which suppresses pitching during vehicle braking by changing the damping force or spring constant based on a control signal. a braking operation detection means for detecting a braking state of the vehicle; an attitude change detection means for detecting a change in attitude of the vehicle due to pitching; When the attitude change detection signal exceeds a predetermined value, the damping force or spring constant of the suspension device is temporarily increased, and at least the damping of the suspension is increased at the end of braking based on the detection signal from the braking operation detection means. and a control means for outputting the control signal to temporarily increase the force or the spring constant. For this reason, the pitching state of the vehicle is detected according to the vehicle's running condition, and only during sudden braking that causes a change in vehicle posture, the damping force or spring constant is temporarily increased at the start and end of braking to prevent nose dive and Rocking back as a reaction force can be reliably suppressed, and the damping force or spring constant is maintained at a normal state that does not suppress rocking in braking states other than when braking is started and at the end of braking, so rocking is suppressed. The control time required for suppression is short, and vibration components near the spring resonance frequency input from the road surface during this period can be optimally absorbed to improve riding comfort.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 2 is a side view showing a vehicle equipped with a vehicle height detector applicable to the present invention, and Fig. 3 is a schematic diagram showing an embodiment of the present invention. FIG. 4 is a block diagram showing an example of a control device applicable to the present invention, and FIGS. 5 a to 5 c each show processing contents of the control device. 6 is a signal waveform diagram for explaining the operation of the present invention, and FIG. 7 is a sectional view showing another embodiment of the suspension device applicable to the present invention. 1L, 1R...Variable damping force shock absorber (suspension device), 5...Brake pedal, 6
...Brake switch (braking operation detection means), 7...
Vehicle height detector, 11... drive circuit, 12... control device,
22...Bypass passage, 23...Solenoid, 24...
Plunger, 34...Braking start state determining means, 35
... attitude change rate calculation means, 36... attitude change rate determination means, 37... damping force control means, 38... braking end state determination means, 39... attitude change amount calculation means, 40... attitude change amount determination means.

Claims (1)

[Scope of Claims] 1. A vehicle equipped with a suspension device on at least one of the front wheel side or the rear wheel side that suppresses pitching during vehicle braking by changing the damping force or spring constant according to a control signal. a braking operation detection means for detecting a braking state; an attitude change detection means for detecting a change in the attitude of the vehicle due to pitching; and an attitude change detection signal at the time of starting braking based on the detection signals from the braking operation detection means and the attitude change detection means. exceeds a predetermined value, the damping force or spring constant of the suspension device is temporarily increased, and at least the damping force or spring constant of the suspension device is increased at the end of braking based on the detection signal from the braking operation detection means. A suspension control device for a vehicle, comprising: control means for outputting the control signal for temporarily increasing the suspension control device for a vehicle. 2. When the suspension device is configured to change the damping force, the control means adjusts the damping force to at least one of a vehicle pitching change rate at the start of braking, and a vehicle pitching change rate or pitching change amount at the end of braking. 2. The suspension control device for a vehicle according to claim 1, wherein the suspension control device is configured to temporarily increase the suspension when one of the suspensions exceeds a predetermined value. 3. The suspension control device for a vehicle according to claim 1 or 2, wherein the attitude change detector is a distance detector that detects the distance between the vehicle body and the road surface.