JPH02162108A - Car body posture control device - Google Patents

Abstract

PURPOSE:To suppress the nose dive phenomenon generated in the braking of a vehicle by controlling actuator control valves of the front and the rear wheels to make the car height at the front wheel side higher than that at the rear wheel side, when the braking condition of the vehicle is detected depending on the signal from a brake detecting device. CONSTITUTION:A signal from each suspension stroke sensor (height sensor) 1 is input to a differential circuit 3 and an integral circuit 4, and the differential value of the stroke signal is output from the differential circuit 3, while the integral value of the difference between the object car height signal responding to each wheel from a main control device 2a is output from the differential circuit 4 to an adder circuit 5 respectively. The adder circuit 5 outputs a control signal by the both input values. In this case, plural control patterns responding to the car running conditions are stored in the main control device 2a, the running condition is discriminated by the signal input from a G sensor 6, and a responding pattern is selected. In a high G area of the acceleration in a braking, the object car height at the front wheel side is set to reduce lower than the standard car height, and the object car height at the rear wheel side is set to further reduce lower than the front wheel side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle body posture control device, and particularly to a vehicle body posture control device that changes the body posture of a vehicle according to the braking state of the vehicle and prevents the front part of the vehicle body from sinking during braking. The present invention relates to a vehicle body posture control device that suppresses vehicle body posture.

(Prior art) Generally, in vehicles equipped with suspensions such as automobiles,
There is a problem in that the suspension stroke changes due to an increase or decrease in the number of passengers, and the vehicle height changes.

In addition, when braking or stopping a car, backward acceleration is applied to the car body, which causes the nose dive phenomenon, where the front of the car sinks and the rear of the car rises in height.
When a car starts or accelerates, forward acceleration is applied to the car body, so there is a problem in that the height of the rear part of the car body is lowered and the front part of the car body lifts up, which is a phenomenon called swash.

Therefore, due to the change in vehicle height due to the increase or decrease in the number of passengers as mentioned above,
A vehicle body attitude control device that automatically adjusts attitude changes such as a nose dive phenomenon and a swash phenomenon has been proposed (for example, Japanese Patent Application Laid-Open No. 61-64509).

This conventional vehicle body posture control device includes a suspension unit provided for each of the front and rear wheels, which uses a combination of a fluid spring chamber and a coil spring, and is individually connected to the fluid spring chamber of each suspension unit. A control valve that controls intake and discharge of fluid, an acceleration sensor that detects longitudinal acceleration acting on the vehicle body, a vehicle height sensor that detects the vehicle height at the front and rear of the vehicle body, and the acceleration sensor When forward acceleration or backward acceleration is detected, the front wheel side control valve or the rear wheel side control valve is actuated and the vehicle body is controlled until the vehicle height at the front and rear of the vehicle body detected by the vehicle height sensor reaches the target vehicle height. The vehicle is characterized by a control means for performing attitude control in a direction to counter the change in attitude of the vehicle, and prevents the front part of the vehicle body from sinking (nose dive) that occurs when braking the vehicle and when the vehicle starts. It is used to suppress the sagging of the rear of the vehicle that sometimes occurs, and to adjust the vehicle height.

(Problem to be Solved by the Invention) By the way, attitude control using a conventional vehicle body attitude control device is performed when a forward acceleration or a backward acceleration of a predetermined value or more is detected by an acceleration sensor that detects longitudinal acceleration acting on the vehicle body. A direction in which the control valve on the front wheel side or the control valve on the rear wheel side is driven and controlled to counter changes in the attitude of the vehicle body until the vehicle height of the front and rear portions of the vehicle body detected by the vehicle height sensor reaches a preset target vehicle height. Posture control is now possible.

However, with conventional vehicle body posture control devices,
Normally, the target vehicle height is the same for both the front and rear wheels, and is set so that the vehicle body is horizontal at the front and rear. The method of controlling the wheel control valves to perform attitude control in a direction that counteracts changes in the attitude of the vehicle body until the target vehicle height is reached can reduce nose dive, but only to a small extent.

For this reason, when a large acceleration is applied, such as during sudden braking, there is a delay in attitude control, causing a problem in that the nose dive cannot be suppressed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a vehicle body posture control device that can more effectively suppress the nose dive phenomenon that occurs when braking a vehicle.

(Means for Solving the Problems) In order to achieve the above object, a vehicle body posture control device according to the present invention is a part of a suspension unit provided for each wheel of a vehicle, and is configured to control the amount or pressure of working fluid supplied. an actuator that can increase or decrease the stroke and spring constant of the suspension accordingly; a supply source for supplying working fluid to the actuators of each suspension unit; a conduit connecting the supply source and each actuator; A control valve that is installed in the road and adjusts the amount or pressure of working fluid supplied and discharged from the supply source to each of the actuators, a suspension stroke sensor that detects the suspension stroke of each wheel of the vehicle, and a braking state of the vehicle. and a braking detection means for detecting the vehicle height and the vehicle body posture by controlling the operation of the control valve based on the signal from the suspension stroke sensor and adjusting the amount or pressure of the working fluid supplied to and discharged from the actuator. Equipped with a controller that automatically adjusts to the set state,
When the controller detects the braking state of the vehicle based on the signal from the braking detection means, it controls the control valve of the front wheel actuator and the control valve of the rear wheel actuator to adjust the vehicle height of the front wheels to the vehicle height of the rear wheels. It is characterized by posture control so that it is higher.

(Function) In the vehicle body posture control device according to the present invention, when the controller detects the braking state of the vehicle based on the signal from the braking detection means, the controller controls the control valve of the front wheel actuator and the control valve of the rear wheel actuator. Since the vehicle is configured to control its attitude so that the vehicle height of the front wheels is higher than that of the rear wheels, the sinking of the front wheels during braking is offset and nose dive is almost completely prevented. .

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example.

First, the configuration of a vehicle body posture control device using a hydraulic mechanical system will be described with reference to FIG. 3 as an example of a vehicle body posture control device most suitable to which the present invention is applied.

FIG. 3 shows a schematic configuration diagram of a vehicle body attitude control device using a hydraulic mechanism system, and in the same figure, reference numeral 10
Reference numeral 11 indicates a reserve tank for supplying and recovering oil; reference numeral 11 indicates an oil pump for assembling and pressurizing the oil in the reserve tank 10; and reference numeral 12 indicates an oil pump 1.
A pressure sensor 13 is used to detect the pressure of the oil fed from the oil pump 11, and when the pressure of the oil fed from the oil pump 11 exceeds a preset pressure, the oil is returned to the reserve tank IO. Reference numeral 14 is an oil filter for removing dust etc. from oil, reference numeral 15 is a check valve for preventing backflow, reference numeral 1 is
6a and 16b are accumulators 17a and 17, which are used for adjusting the oil pressure of the main pipe, accumulating pressure, etc., as shown by solid lines in the figure.
b.

17c and 17d are control valves such as proportional pressure reducing valves for hydraulic control; 18a, 18b, 18c, and 18d are gas springs; and 19a, 19b, 19c, and 19.
d is a hydraulic actuator built into the suspension unit of each wheel. Furthermore, as mentioned above,
The route shown by the solid line in the figure is the main pipe for supplying and discharging oil, and the route shown by the broken line is a drain pipe for returning excess oil to the reserve tank 10 and the like.

Here, each control valve 17a of the hydraulic mechanism system shown in FIG.
17b, 17c, and 17d are electrically connected to the controller 2 for controlling the vehicle body attitude and adjusting the vehicle height,
Each control valve 17a, 17b, 17c, 17d controls the oil pump 11 by a signal from the controller 2.
Each of the seven cutout units 19a, 19b, 19c,
The amount of oil supplied and discharged from the suspension unit 19d and the hydraulic pressure are adjusted, and the actuators 19a, 19b, 19c, and 19d are operated to increase or decrease the stroke and spring constant of each suspension unit. Therefore, the controller 2 controls each control valve 17a, 17b, 17c,
By controlling 17d.

Vehicle height adjustment and vehicle body attitude control can be performed.

Each control valve 17a, 17b, 17c of the hydraulic mechanism system,
The controller 2 that controls the control valves 17d includes a main control device consisting of a microcomputer, and control valves 17a and 17b.
, 17c.

The main controller is equipped with an operating circuit, a power supply circuit, etc. for operating the 17d, and the main control device includes a microcomputer unit that performs arithmetic processing for attitude control and vehicle height adjustment control and generates control signals, and ROM and R that store programs, control programs, various discrimination data, etc.
A storage device consisting of AM, etc., an input device for binarizing signals from various sensors, etc. and inputting them to the microcomputer unit, an output device for outputting control signals from the microcomputer to the above-mentioned operating circuit, etc. It is configured.

The input devices of the main control device of the controller 2 include an ignition sensor that detects the state of the ignition switch, a vehicle speed sensor that detects the running speed of the vehicle, a wheel speed sensor that detects the rotational speed of each wheel, and a brake. SW
A brake sensor detects the operating status of the brake, brake stroke speed, and brake stroke amount; a throttle sensor detects the engine throttle opening; a shift position sensor detects the gear shift position of the transmission; a shift position sensor detects the steering angle of the steering wheel. Steering angle sensor, the longitudinal, lateral, and vertical forces that act on the vehicle body when starting, braking, and running the vehicle;
An acceleration sensor (G sensor) that detects the speed, a yaw rate sensor that detects the shaking and tilt of the vehicle body during cornering, a suspension stroke sensor that detects the suspension stroke of each wheel, etc. are connected to the input device. selectively outputs signals from various sensors in response to control signals from the microcomputer unit.
It is converted into a value and input into the microcomputer unit.

Here, during normal driving, the main control device of the controller 2 uses the signal from the suspension stroke sensor as a so-called feedback signal, controls the operation of each control valve 17a, 17b, 17c, and 17d based on the signal, and adjusts the vehicle height. The vehicle height is adjusted so that it reaches a preset target vehicle height, and when the vehicle is cornering, driving on a slope, or when starting or braking, the suspension stroke sensor, G sensor, yaw rate sensor, Each control valve 1 is controlled based on signals from the steering angle sensor, vehicle speed sensor, etc.
7a, 17b.

17c and 17d, the vehicle body posture is controlled to provide the best driving stability.

By the way, in normal attitude control, when the vehicle is running, the controller uses the signal from the suspension stroke sensor as a feedback signal to control the vehicle body to maintain a horizontal state at the target vehicle height value, and also when braking, starting, etc. When the G-sensor detects backward or forward acceleration of a predetermined value or higher, attitude control is performed to maintain the vehicle height at the front and rear of the vehicle at the target vehicle height, thereby suppressing the occurrence of nose dive or swash. It looks like this.

However, the target vehicle height mentioned above is normally set so that the vehicle body is horizontal at the front and rear, so the target vehicle heights for the front and rear wheels are approximately the same vehicle height value. When the acceleration sensor detects a rearward acceleration of a predetermined value or more when the vehicle is stopped, the control valves for the front and rear wheels are controlled to perform attitude control in a direction that counters changes in the attitude of the vehicle body until the target vehicle height is reached. , it is possible to reduce nose dive, but only to a small extent.

For this reason, especially when a large acceleration is applied, such as during sudden braking, there is a delay in attitude control, resulting in a problem in that the nose dive cannot be suppressed.

Therefore, in the present invention, when the controller 2 of the vehicle body posture control device detects the braking state of the vehicle based on signals from the G sensor, brake sensor, etc., the controller 2 controls the control valve of the front wheel side actuator and the rear wheel side actuator. The control valves of the actuators are separately controlled to control the attitude so that the vehicle height of the front wheels is higher than the vehicle height of the rear wheels.

That is, in the vehicle body posture control device according to the present invention, the controller 2 makes the vehicle height of the front wheels higher than the vehicle height of the rear wheels by the estimated amount of sinking of the front of the vehicle body, depending on the braking state of the vehicle. The system actively controls the front wheels to offset the sinking of the front wheels during braking. Therefore, according to the vehicle body attitude control device according to the present invention, the nose dive phenomenon is almost completely prevented.

More specific control means will be explained below.

FIG. 1 is a schematic configuration diagram showing an example of a suspension stroke feedback type attitude control means, and FIG.
In the figure, reference numeral 1 is a suspension stroke sensor attached to each suspension unit,
Signals from each suspension stroke sensor 1 are input to a differentiating circuit 3 and an integrating circuit 4 provided in the controller 2 described above, respectively. Here, each differentiating circuit 3 outputs a signal corresponding to the differential value of the stroke signal from each suspension stroke sensor 1, that is, the amount of change in stroke per unit time. In addition to the signal from the suspension stroke sensor 1, each integration circuit 4 receives a target vehicle height signal corresponding to each wheel set by the main control device 2a of the controller 2. The integrated value of the difference between the signal and the target vehicle height is output. Further, an adder circuit 5 is provided in the controller 2, and the adder circuit 5 is configured to output a signal obtained by adding the signals from the differentiating circuit 3 and the integrating circuit 4 as a control signal. .

Therefore, the circuit consisting of the differentiator circuit 3, the integrator circuit 4, and the adder circuit 5 shown in FIG. 1 constitutes a feedback control circuit based on the so-called PID method (proportional control + integral control + differential control). When the control means having the configuration shown is used, real-time suspension stroke feedback control is performed using the PID method, and the attitude and vehicle height are controlled in accordance with the target vehicle height generated by the main controller 2a. The differentiator circuit 3, the integrator circuit 4, and the adder circuit 5 are provided corresponding to each suspension stroke sensor provided for each wheel, so that control of each wheel is possible.

By the way, the target vehicle height set by the main control device 2a is patterned into a plurality of control patterns corresponding to the driving state of the vehicle and stored in a storage device, and the vehicle height is determined based on signals from various sensors. A control pattern corresponding to the driving condition is called up, and a target vehicle height signal is output in accordance with the control pattern.

Here, FIGS. 2(a) and 2(b) show an example of the above-mentioned control pattern, which is an attitude control pattern corresponding to starting and braking of the vehicle. Note that FIG. 2(a) shows a control pattern for the front wheels, and FIG. 2(b) shows a control pattern for the rear wheels.

Now, in the vehicle body posture control device according to the present invention, when the longitudinal acceleration of the vehicle is detected based on the signal from the G sensor 6, the control pattern shown in FIGS. 2(a) and 2(b) is called, for example. Attitude control corresponding to starting and braking is executed.

Here, to explain according to the control pattern shown in FIGS. 2(a) and 2(b), the main control device 2a of the controller 2
outputs a target vehicle height for the front wheels according to the control pattern shown in FIG. 2(a) in response to the longitudinal acceleration of the vehicle detected by the G sensor 6.

Further, the target vehicle height for the rear wheels is output according to the control pattern shown in FIG. 2(b). Here, FIG. 2(a).

In the control pattern shown in (b), the acceleration during braking is low G
In this area, the standard target vehicle height value during normal driving is output assuming that the nose dive is small, and attitude control is performed so that the vehicle body attitude is in a horizontal state.

Also, when the acceleration during braking is in the medium G range, the front wheel side.

The target vehicle height for both rear wheels is lowered than the standard vehicle height, lowering the entire vehicle height and maintaining the vehicle body in a horizontal state, improving stability during braking and preventing nose dive. Furthermore, when the acceleration during braking is in a high G region, the target vehicle height for the front wheels is lowered than the standard vehicle height, and the target vehicle height for the rear wheels is set even lower than that for the front wheels. Therefore, the vehicle body posture based on the target vehicle height is set to a reverse dive state in which the front wheels are higher than the rear wheels, and the nose dive is offset to maintain a stable vehicle body posture.

Although the above explanation is for the case of braking, when a large starting acceleration is applied to the vehicle body due to a sudden start, etc., as shown in FIG. 2(a).

As shown in (b), the target vehicle height value on the front wheel side is set to be lower than the target vehicle height value on the rear wheel side, thereby preventing the swarm phenomenon.

Now, as explained above, the target vehicle heights of the front and rear wheels are set separately using the control patterns shown in FIGS. By controlling this, it is possible to suppress the nose dive and swat phenomenon of the vehicle body, as shown in FIG. 2(c).

By the way, when a G sensor is used as a braking detection means and the vehicle attitude is controlled according to the control pattern shown in FIGS. 2(a) and (b), the control is performed after detecting the acceleration acting on the vehicle body. Therefore, especially during sudden braking, there is a time lag between the actual time when nose dive occurs and the time when control starts, and as a result, as shown in Figure 2 (Q),
A slight nose dive remains.

Therefore, a more active posture control means will be explained next.

FIG. 4 shows a flowchart of a control program for more actively suppressing nose dive.
In the control according to this control program, the operating state of the brakes is detected as a means of detecting the braking state of the vehicle, and target vehicle heights for the front and rear wheels are set in response to the operating state of the brakes and changes in vehicle speed. , which attempts to obtain a control output, and according to this method, attitude control is performed in advance,
Nose dive can be completely suppressed.

The process will be explained below with reference to the flowchart shown in FIG.

When the ignition switch of the vehicle is turned on and the operation of the controller 2 is started, the main controller 2a
Execution of the program shown in the figure is started, and first, the current vehicle speed V is detected (Sl).

Next, when the vehicle speed V becomes V≧3 km/h, the control program branches into two parts, and the target vehicle height (standard vehicle height) is used for attitude control using normal suspension stroke feedback.
is output (S3), and in parallel with this, the brake S
The operating state of W is detected (S4).

Here, when the brake SW is in the OFF state, the brake stroke speed VB is determined to be zero, the zero point of the brake stroke speed VB is set, and the brake SW is turned ON.
The vehicle remains in a standby state until , and at this time, the target vehicle height (standard vehicle height) for normal posture control based on the previous suspension stroke feedback is output as a control signal.

Next, when the brake SW is turned on, the brake stroke speed VB is immediately detected (S7), and if the brake stroke speed VB exceeds VB≧20 mm/s, the brake stroke vS is detected (S9), and the brake stroke speed VB is detected immediately (S7). 5
A correction value for the target vehicle height is calculated and output according to the control pattern corresponding to the brake stroke vS during braking shown in the figure.
SIO) is added to the target vehicle height (standard vehicle height) for normal attitude control based on the previous suspension stroke feedback (S14).

In addition, the brake stroke speed VB is VB≧20mm/
If the vehicle speed exceeds S, vehicle speed V is detected at parallel °C (
S11), vehicle speed V is V≧30km/h,
According to the control pattern corresponding to the vehicle speed during braking shown in Fig. 6, a correction value for the target vehicle height corresponding to the vehicle speed V is calculated, and the target vehicle height for normal attitude control based on the suspension stroke feedback described above is set to 11 (sub-vehicle height). is added (S1
4).

Therefore, in the control shown in FIG. 4, when the brake is activated and the brake stroke speed VB is large, that is, during sudden braking, the front and rear wheels are The target vehicle height is corrected in real time, and a control signal is output so that the vehicle height of the front wheels is higher than the vehicle height of the rear wheels during sudden braking, so the vehicle body posture is in a reverse dive state and the nose dive is offset.

By changing the control pattern for correcting the target vehicle height shown in FIGS. 5 and 6, the vehicle height difference between the front wheels and the rear wheels can be changed in various ways, so the posture during braking can be changed in various ways. Nose dive can be completely prevented.

In addition, in the control shown in Fig. 4, when braking, the target vehicle height is corrected based on the brake stroke speed and vehicle speed to perform attitude control, but in addition to this, the target vehicle height corresponding to the G sensor is Corrections may be made in parallel and added to the final control output.

(Effects of the Invention) As explained above, in the vehicle body posture control device according to the present invention, when braking the vehicle, especially when braking suddenly,
Because the configuration performs attitude control so that the vehicle height of the front wheels is higher than that of the rear wheels, it is possible to almost completely suppress nose dive during sudden braking, improving braking performance and safety. Further improvement can be achieved.

Further, by setting a large target vehicle height difference between the front wheels and the rear wheels during braking, it is possible to alleviate the forward leaning of the occupant during braking, and it is possible to improve the feeling during braking.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of the configuration of an attitude control means using a suspension stroke feedback method of a vehicle attitude control device according to the present invention, and FIG. 2(a) shows a front wheel side target vehicle height characteristic during braking according to the present invention. FIG. 2(b) is a diagram showing the rear wheel side target vehicle height characteristics during braking according to the present invention, and FIG. 2(c) is a diagram showing the characteristics shown in FIGS. 2(a) and (b). A diagram showing the vehicle body posture when control is performed,
Figure 3 is a circuit diagram of a hydraulic control system showing an example of a vehicle attitude control system, Figure 4 is a flowchart showing an example of a control program during braking, and Figure 5 is a target vehicle height characteristic corresponding to the brake stroke during braking. FIG. 6 is a diagram showing target vehicle height characteristics corresponding to vehicle speed during braking. 1... Suspension stroke sensor, 2...
Controller, 2a... Main control device, 11...
Oil pump, 17a. 17b. 17c. 17d...Control valve. 19a. 19b. 19c, 19d...actuator. Mushrooms ■) 6 bites■

Claims (1)

[Claims] An actuator that is a part of a suspension unit provided for each wheel of a vehicle and can increase or decrease the stroke and spring constant of the suspension according to the amount or pressure of the supplied working fluid, and an actuator that supplies working fluid to the actuator of each suspension unit. A supply source for supplying, a pipe line connecting the supply source and each actuator, and a pipe line provided in the pipe line to adjust the amount or pressure of the working fluid supplied and discharged from the supply source to each actuator. a control valve;
a suspension stroke sensor that detects the suspension stroke of each wheel of the vehicle, a braking detection means that detects the braking state of the vehicle, and a signal that controls the operation of the control valve based on the signal from the suspension stroke sensor and supplies power to the actuator. and a controller that automatically adjusts the vehicle height and body posture to a preset state by adjusting the amount or pressure of the working fluid to be discharged, and the controller detects the braking state of the vehicle based on the signal from the braking detection means. A vehicle body posture control device characterized in that when detecting the above, the control valve of a front wheel side actuator and the control valve of a rear wheel side actuator are controlled to control the posture so that the vehicle height of the front wheels is higher than the vehicle height of the rear wheels. .