JPH06106941A - Suspension characteristic control device for vehicle - Google Patents

Abstract

PURPOSE:To attach most importance to running stability of a vehicle and further to improve its riding comfort as for as possible by decreasing a reference value, by which a suspension characteristic is switched to a soft side or a hard side, by a predetermined amount when a 2-wheel drive condition is selected by a driving gear. CONSTITUTION:In shock absorbers 11a to 11d, damping force against vertical moving of a car body can be changed by a valve opening controlled by actuators 14a to 14d, and in subair chambers 13a to 13d, a spring constant for vertical moving of the car body is changed by a valve for switching communication with main air chambers 12a to 12d by actuators 15a to 15d. In the case of suppressing a squat of the case body with a driving gear DR being normal, a computer 25 maintains a suspension characteristic to a soft side as far as possible even at the time of quick starting or accelerating a vehicle. In the case of failure generation in the driving gear DR to drive the vehicle with two wheels, the suspension characteristic is made to be easily switched to a hard side, to suppress the squat of the car body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension characteristic control device for a vehicle, in which the suspension characteristic is set to a hard side when the vehicle suddenly starts and suddenly accelerates to suppress the squat of the vehicle body.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Laid-Open Patent Publication No. 7611, the degree of sudden start or sudden acceleration of the vehicle is detected by the amount of depression of the accelerator pedal (throttle opening), the depression speed (throttle opening speed), etc., and the detection degree is predetermined. When the value is larger than the standard value, the suspension mechanism is controlled to switch the suspension characteristics of the vehicle to the hard side to suppress the squat of the vehicle body. In addition, conventionally, for example, the actual development Sho 61-500.
As disclosed in Japanese Patent Publication No. 07 and Japanese Utility Model Laid-Open No. 61-50008, it is possible to select a two-wheel drive state or a four-wheel drive state by a driving torque difference between front and rear wheels, a rotational speed difference, a vehicle speed, a manual operation, or the like. Four-wheel drive vehicles equipped with a drive are also well known.

[0003]

However, in the former conventional device described above, the suspension characteristic is set to the hard side when the vehicle suddenly starts and accelerates.
While the posture change of the vehicle body is suppressed and the running stability of the vehicle is improved, there is an incompatible problem that the riding comfort of the vehicle is deteriorated. On the other hand, in the four-wheel drive vehicle equipped with the drive device shown as the latter prior art, if the four-wheel drive state is selected when the vehicle suddenly starts and suddenly accelerates, the vehicle squat is suppressed. The running stability of the vehicle is maintained good, but if the two-wheel drive state is selected by fail, manual selection, etc. when the vehicle suddenly starts or accelerates, the vehicle running stability is not suppressed and the squat of the vehicle body is not suppressed. There is a problem that the property is not good.

The present invention has been made in consideration of the above-mentioned problems comprehensively, and its purpose is to place the most importance on the running stability of the vehicle by controlling the suspension characteristics of the vehicle according to the state of the drive device. The present invention also provides a suspension characteristic control device for a vehicle in which the ride comfort of the vehicle is improved as much as possible.

[0005]

In order to achieve the above object, the structural features of the present invention are applied to a vehicle equipped with a drive device capable of selecting a two-wheel drive state or a four-wheel drive state. Of the suspension mechanism capable of changing the suspension characteristics, a sudden start detecting means for detecting the degree of sudden start or rapid acceleration of the vehicle, a comparing means for comparing the detected degree with a predetermined reference value, and a comparing means A switching control that controls the suspension mechanism according to the comparison result, sets the suspension characteristic to the soft side when the detection degree is smaller than the reference value, and switches the suspension characteristic to the hard side when the detection degree is larger than the reference value. In the suspension characteristic control device for a vehicle, the reference value is reduced by a predetermined amount when the drive device selects the two-wheel drive state. In the provision of the reduction control means for.

[0006]

In the present invention constructed as described above, when the drive unit selects the four-wheel drive state, the comparing means determines the degree of sudden start or sudden acceleration detected by the sudden start detecting means and a predetermined reference. Compare with the value, and depending on the result of this comparison,
The switching control means controls the suspension mechanism to set the suspension characteristic of the vehicle to the soft side when the detection degree is lower than the reference value, and switches the suspension characteristic to the hard side when the detection degree is higher than the reference value. On the other hand, when the drive device selects the two-wheel drive state, the reduction control means reduces the reference value by a predetermined amount. Therefore, in this case, the suspension characteristic of the vehicle can be switched to the hard side even if the degree of sudden start and sudden acceleration of the vehicle is smaller than that in the above case. As a result, when the vehicle is in the two-wheel drive state, the suspension characteristics of the vehicle are more likely to be switched to the hard side with respect to the degree of sudden start and sudden acceleration of the vehicle, as compared with when the vehicle is in the four-wheel drive state.

[0007]

As can be understood from the above description of the operation,
According to the present invention, when the vehicle is traveling in the four-wheel drive state, this drive state suppresses the squat of the vehicle body at the time of sudden start and sudden acceleration of the vehicle, and the traveling stability of the vehicle becomes good, and Since it becomes difficult to switch the suspension characteristics of the vehicle to the hard side, the riding comfort of the vehicle becomes good, and both traveling stability and riding comfort of the vehicle can be achieved. Further, when the vehicle is traveling in the two-wheel drive state, the suspension characteristics of the vehicle are easily switched to the hard side, so that the traveling stability of the vehicle at the time of sudden start and sudden acceleration is secured.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a vehicle suspension device SU and a drive device DR.

The suspension unit SU includes shock absorbers 11a to 11d, main air chambers 12a to 12d, and sub air chambers 13a to 13 provided between the left and right wheels respectively corresponding to the front and rear wheels.
have d. The shock absorbers 11a to 11d can change the damping force with respect to the vertical movement of the vehicle body in three stages (small, medium, and large) according to the valve opening degrees controlled by the actuators 14a to 14d. The main air chambers 12a-12d are (main air chambers 12a-1
2d and the sub air chambers 13a to 13d are in communication with each other, the sub air chambers 13a to 13d) can continuously change the vehicle height at each wheel position in accordance with the amount of stored air. There is. Sub air chambers 13a to 13d
Is a two-step spring constant for the vertical movement of the vehicle body (small, large) in cooperation with the main air chambers 12a-12d by turning on / off a valve whose communication with the main air chambers 12a-12d is switched by the actuators 15a-15d.
To change to.

A supply / discharge device for supplying / discharging air to / from the main air chambers 12a to 12d is connected to the main air chambers 12a to 12d. The supply / discharge device includes a compressor 17 driven by an electric motor 16. The compressor 17 includes a check valve 18, an air dryer 19, a check valve 21 and an orifice 22 connected in parallel, and electromagnetic switching provided for each wheel. It is connected to the main air chambers 12a to 12d via the valves 23a to 23d. These electromagnetic switching valves 23a to 23d are normally in the off state, and are turned on by energization to turn on the check valve 2.
1 and orifice 22 and each air chamber 12a-12
Allow each communication with d. Further, an electromagnetic switching valve 24 is connected to a connection point between the check valve 18 and the air dryer 19, and the valve 24 is normally in an off state, and is turned on by energizing to make the connection point communicate with the atmosphere.

Next, the above-mentioned actuators 14a-1
4d, 15a to 15d and electromagnetic switching valves 23a to 2
An electric control device for controlling 3d and 24 will be described.
This electric control device includes stroke sensors 31a to 31.
d, a mode switch 32, a vehicle speed sensor 33, a depression amount sensor 34, and a microcomputer 35. The stroke sensors 31a to 31d are provided at the respective wheel positions, and the downward displacement amount (hereinafter, stroke amount) S _FL , S _FR , with respect to the reference height of the vehicle body at the same position.
Each of S _RL and S _RR is detected and their detection signals are output. The mode switch 32 is operated by the driver,
This is an operation switch that selectively switches the suspension characteristics between normal mode and sports mode. The vehicle speed sensor 33 detects the vehicle speed V and outputs a detection signal indicating the same speed V. The depression amount sensor 34 detects a depression amount A of an accelerator pedal (not shown) and outputs a detection output signal indicating the depression amount A. Microcomputer 35
Is composed of CPU, ROM, RAM, timer, etc.
The "main program" shown in Fig. 3 is repeatedly executed, and during execution of the "main program", the "abrupt start detection program" shown in Fig. 3 is interrupted and executed at predetermined intervals.

The drive unit DR includes a drive force distribution mechanism 43 for inputting the drive force from the engine 41 via the transmission 42. The driving force distribution mechanism 43 is controlled by the four-wheel drive electric control unit 44, and the input driving force is controlled by the front propeller shaft at a ratio determined according to the rotational speed difference between the front and rear wheels, the rotational torque difference between the front and rear wheels, the vehicle speed, and the like. Four
5a and the rear propeller shaft 45b are distributed and supplied to the front wheels and the rear wheels. At least when the vehicle starts and accelerates, the driving force is distributed to both the front wheels and the rear wheels. Further, the four-wheel drive electric control device 44 is provided with various sensors included in the device 44, means such as a microcomputer, and means for detecting a failure of the driving force distribution mechanism 43, and the driving force distribution is performed when the failure is detected. The mechanism 44 is controlled to the two-wheel drive state, that is, the driving force from the engine 41 is transmitted only to the rear wheels, and a signal indicating fail is output to the microcomputer 35.

Next, the operation of the embodiment configured as described above will be described with reference to the above flow chart. When the ignition switch (not shown) is turned on, the microcomputer 35 starts executing the "main program" in step 100 of FIG. 2 and the antisquat flag ASQF indicating that antisquat control is performed in step 102. After initializing "0" to step 10,
The circulation process of 4 to 116 is repeatedly executed. In this circulation processing, since the anti-squat flag ASQF is initially "0", the microcomputer 35 determines "NO" in step 104 and advances the program to steps 106 and 108. In step 106, it is determined whether or not the vehicle is traveling at high speed by comparing the vehicle speed V detected by the vehicle speed sensor 33 with the predetermined vehicle speed V ₁ . Further, in step 108, it is determined whether the normal mode or the sports mode is selected as the suspension characteristic depending on the setting state of the mode switch 32.

If the vehicle is not traveling at a high speed and the normal mode is selected, the microcomputer 35 makes a "NO" determination in step 106 and a "YES" determination in step 108 to execute the program. Proceed to 110. In step 110, the damping force of the shock absorbers 11a to 11d is set to "small", that is, soft by controlling the actuators 14a to 14d, and the actuators 15a to 15d are controlled to control the main air chambers 12a to 12d and the auxiliary air chambers. The air chambers 13a to 13d are communicated with each other so that both chambers 1
2a-12d, 13a-13d spring constant "small"
That is, set to soft. If the vehicle is traveling at high speed or the sports mode is selected, the microcomputer 35 determines “YES” in step 106 or “NO” in step 108,
The program proceeds to step 112. Step 112
, The damping force of the shock absorbers 11a to 11d is set to "medium", that is, the middle by controlling the actuators 14a to 14d, and the main air chamber 1 is controlled by controlling the actuators 15a to 15d.
2a to 12d and the sub-air chambers 13a to 13d are released from communication with each other so that both chambers 12a to 12d and 13a to 13d are released.
Set the spring constant by to "large" or hard.

After the processing of steps 110 and 112, the microcomputer 35 in step 116 detects the stroke amounts S _FL , S _FR , S _RL and S detected by the stroke sensors 31a to 31d and the vehicle speed sensor 34, respectively.
Solenoid switching valves 23a-2a based on _RR , vehicle speed V, etc.
The vehicle height at each wheel position is adjusted by controlling 3d and 24.

On the other hand, during the circulation processing consisting of steps 104 to 116, the microcomputer 35 interrupts and executes the "abrupt start detection program" of FIG. 3 every predetermined time. In this "rapid start detection program", the microcomputer 35 starts its execution in step 200, reads the vehicle speed V and the depression amount A detected by the vehicle speed sensor 33 and the depression amount sensor 34 in step 202, and executes the step. The amount of depression A at 204
The stepping speed B is calculated by differentiating. Next, the microcomputer 35 proceeds to step 4 at step 206.
It is determined whether or not a signal indicating a failure of the drive device DR is input from the wheel drive electric control device 44.

First, a case where the drive device DR has not failed will be described. In this case, since the signal indicating the failure of the driving device DR is not input from the four-wheel drive electric control device 44, the microcomputer 35 determines “NO” in step 206, and determines the reference depression amount Aref and the reference depression amount in step 208. The speed Bref is set to a relatively large predetermined depression amount A ₀ and a predetermined depression speed B _0, and the reference time Tref is set to a relatively small predetermined time T ₀ (for example, 2 seconds). Next, the microcomputer 35 determines the necessity of anti-squat control in steps 212 to 216. If the vehicle speed V is equal to or higher than the predetermined vehicle speed V ₂ (for example, 40 km / h), it is determined to be “YES” in step 212, the anti-squat flag ASQF is set to “0” in step 228, and the program proceeds to step 230. Proceeded to. Further, the vehicle speed V is smaller than the predetermined vehicle speed V ₂ by a predetermined vehicle speed V ₃ (for example, 3
If it is 0 km / h) or more, it is determined as “NO” in step 214 and the program proceeds to step 224.
If the depression amount A is less than the reference depression amount Aref and the depression speed B is less than the reference depression speed Bref,
Both of the determinations at steps 216 and 218 are "NO", and the program proceeds to step 224. Step two
In 24, the anti-squat flag ASQF is "1".
Or not. If the flag ASQF is maintained at "0" as in the initial state, the microcomputer 35 determines "NO" in step 224,
The program proceeds to step 230. Therefore, in the running state of the vehicle as described above, the microcomputer 35 ends the execution of the "abrupt start detection program" in step 232 after the processing of step 230. In this case, the anti-squat flag ASQF is still "0".
The damping force of the suspension device SU is “small” (soft) or “medium” depending on the selection mode (normal mode or sports mode) as described above.
The spring constant of the device SU is set to "small" (soft) or "large" (hard) while being set to (middle).

On the other hand, if the accelerator pedal is deeply depressed or suddenly depressed due to sudden start or rapid acceleration while the vehicle is traveling below the predetermined vehicle speed V ₃ , that is, the depression amount A becomes the reference depression amount Aref or more. When the depression speed B becomes equal to or higher than the reference depression speed Bref, the microcomputer 35 determines “NO” in step 212, “YES” in step 214, “YES” in step 216 or step 218, and determines the program in step 220. , 222. In step 220, the anti-squat flag ASQF is changed to "1",
In step 222, the anti-squat timer value
Initialize ASQT to "0". After these processes, the microcomputer 35 completes the execution of this "squat detection program" in step 232 through the process of step 230.

In this way, the anti-squat flag AS
When QF is set to "1", the microcomputer 35
At step 104 of the "main program", select "YE
S ”, and the program proceeds to step 114. In step 114, the actuator 14a
The shock absorber 11 is controlled by controlling ~ 14d.
The main air chambers 12a to 12d and the sub air chambers 13a to 13d are set by setting the damping forces of a to 11d to "large" (hard) and controlling the actuators 15a to 15d.
13d to release communication with both chambers 12a-12d,
The spring constant according to 13a to 13d is set to "large" (hard). From this state, the accelerator pedal depression amount A
Becomes less than Aref and the pedaling speed B of the same pedal
If the reference depressing speed Bref is less than the reference depressing speed Bref, the microcomputer 35 determines "N" in steps 216 and 218.
It is determined to be “O” and the program proceeds to step 224.
Also, when the vehicle speed V becomes equal to or higher than the predetermined vehicle speed V ₃ , the microcomputer 35 determines “NO” in step 214 and advances the program to step 224. In these cases, since the anti-squat flag ASQF is set to "1", the microcomputer 35 determines "YES" in step 224, and the anti-squat timer value ASQT corresponds to 1 second in step 226. It is determined whether or not the value is greater than or equal to the value. This anti-squat timer value ASQT is initialized to "0" in step 222 and is incremented by "1" in step 230, and is a small value if there is a short time after the change in the state. Is kept at. Therefore, in this case, the microcomputer 35 returns “NO” in step 226.
Is determined, and the processing of step 230 is performed before step 23.
At 2, the execution of this "quick start detection program" is terminated. As a result, even if the depression amount A and the depression speed B of the accelerator pedal become smaller, the reference time Tre
The damping force and spring constant of the suspension device SU continue to be set to “large” (hard) until f has elapsed.

On the other hand, when the reference time Tref elapses after the depression amount A and the depression speed B of the accelerator pedal have decreased, the anti-squat timer value ASQT becomes equal to or greater than the reference time Tref. In step 226, it is determined to be "YES", and in step 228, the antisquat flag ASQF is set to "".
0 ". Therefore, the microcomputer 3
5 is "N" in step 104 of the "main program".
Since it is determined to be “O” and the program proceeds to step 106 and subsequent steps, as described above, depending on the selection mode (normal mode or sports mode), the suspension device S
U damping force is "small" (soft) or "medium" (middle)
And the spring constant of the device SU is "small"
(Soft) or "Large" (Hard) will be set. Further, when the vehicle speed V becomes equal to or higher than the predetermined vehicle speed V _{2 due to} the sudden start or rapid acceleration of the vehicle, the microcomputer 35 makes a “YES” determination at step 212, and at step 228 the anti-squat flag AS.
Since the QF is changed to "0", the damping force of the suspension device SU is "small" (soft) or "medium" in this case as well.
While being set to (middle), the spring constant of the device SU is set to "small" (soft) or "large" (hard).

On the other hand, during such a sudden start or sudden acceleration, the four-wheel drive electric control unit 44 controls the driving force distribution mechanism 43 in accordance with the difference in rotational speed or the rotational torque between the front wheels and the rear wheels, The driving force from the engine 41 is distributed to the front wheels and the rear wheels, that is, the four-wheel drive state is controlled. Therefore, the vehicle is driven by the front wheels and the rear wheels to suddenly start or suddenly accelerate.

As can be understood from the above description of the operation, when the vehicle suddenly starts or accelerates in a state where the drive device DR does not fail, the drive device DR starts or accelerates the vehicle in the four-wheel drive state. The vehicle body squat is suppressed by the drive device DR, so that the running stability of the vehicle is kept good. On the other hand, in the suspension device SU, the reference depression amount A
Since the ref and the reference depression speed Bref are set to relatively large values and the reference time Tref is set to a relatively short value, it is difficult to set both the damping force and the spring constant of the suspension device SU to "large". The ride quality is also kept good. The degree of sudden start or sudden acceleration is extremely large, and the stepping amount A is equal to the reference stepping amount Are.
If it is f or more or the stepping speed B is the reference stepping speed Bref or more, the damping force and the spring constant are set to “large”, so that the suspension device SU suppresses the squat of the vehicle body together with the drive device DR, and the suspension device SU suppresses the vehicle by the squat. Driving stability does not deteriorate.

Next, the case where the drive device DR fails will be described. In this case, the four-wheel drive electric control device 44 controls the four-wheel drive mechanism 43 to set the vehicle to the drive state with only the rear wheels, that is, the two-wheel drive state. Further, the four-wheel drive electric control unit 44 outputs a signal indicating failure to the microcomputer 35. Therefore, the microcomputer 35 uses the step 206 of FIG.
In the step 21.
Advance to 0. In step 210, the reference depression amount Aref and the reference depression speed Bref are predetermined amounts ΔA, Δ from the predetermined depression amount A ₀ and the predetermined depression speed B _0.
The values A ₀ −ΔA and B ₀ −ΔB smaller by B are set, respectively, and the reference time Tref is set to a time T ₀ + ΔT longer than the predetermined time T ₀ by a predetermined amount ΔT. Next, the microcomputer 35 performs steps 212 to 212 similar to the above.
232 is executed.

Therefore, when a failure occurs in the drive device DR and the device DR suddenly starts or accelerates in the two-wheel drive state, both the damping force and the spring constant of the suspension device SU are "large". And the damping force and the spring constant are set to “large” for a long time. As a result, the tendency of the drive device DR to suppress the squat of the vehicle body increases, so that at least the running stability of the vehicle is maintained.

In the above embodiment, the depression amount A of the accelerator pedal is detected and the depression amount A is detected.
The accelerator pedal depression speed B by differentiating
Was calculated and the sudden start and the rapid acceleration of the vehicle were determined based on the depression amount A and the depression speed B. However, the rotation angle (opening) of the throttle is detected and the rotation angle (opening) is determined. By calculating the rotational angular velocity (opening speed) of the throttle by differentiating, it is possible to determine whether the vehicle suddenly starts or suddenly accelerates based on the rotational angle (opening) and the rotational angular velocity (opening speed) of the throttle. Good.

Further, in the above embodiment, the drive unit DR is automatically determined to be the two-wheel drive state or the four-wheel drive state.
Although an example in which the suspension device SU according to the present invention is applied to a vehicle equipped with the above is shown, the present invention is also applicable to a vehicle equipped with a drive device DR that manually switches between a two-wheel drive state and a four-wheel drive state. Applicable. In this case, the four-wheel drive control device 44 controls the driving force distribution mechanism 43 in response to the manual switching operation to switch between the two-wheel drive state and the four-wheel drive state, and also causes the microcomputer 35 to fail the above embodiment. A selection signal indicating the driving state of the two wheels / 4 wheels is also supplied together with the signal. The microcomputer 35 determines in step 206 of FIG. 3 whether or not the fail or two-wheel drive state is selected, and a failure occurs in the drive device DR or the two-wheel drive state is selected by the device DR. If so, step through the program
If not, the program may proceed to step 208 otherwise. In this case, too,
If a failure occurs in the drive device DR, the drive force distribution mechanism 43 is automatically switched to the two-wheel drive state by the four-wheel drive electric control device 44, as in the above embodiment.

The present invention is also applied to a four-wheel drive vehicle, which is close to a rear-wheel drive vehicle in which the base distribution of the driving force between the front wheels and the rear wheels is 3: 7. In this case, when the drive device DR fails, the distribution of the driving force between the front wheels and the rear wheels is fixed to 3 to 7.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a suspension device and a drive device showing an embodiment of the present invention.

FIG. 2 is a flowchart corresponding to a “main program” executed by the microcomputer of FIG.

FIG. 3 is a flowchart corresponding to a “sudden start detection program” executed by the computer.

[Explanation of symbols]

SU ... Suspension device, DR ... Drive device, 11a ...
11d ... Shock absorber, 12a-12d ... Main air chamber, 13a-13d ... Sub-air chamber, 14a-
14d, 15a to 15d ... Actuator, 17 ... Compressor, 23a to 23d, 24 ... Electromagnetic switching valve, 3
1a to 31d ... Stroke sensor, 33 ... Vehicle speed sensor,
34 ... Depression amount sensor, 35 ... Microcomputer, 43 ... Driving force distribution mechanism, 44 ... Four-wheel drive electric control device.

Claims (1)

[Claims] 1. A suspension mechanism, which is applied to a vehicle equipped with a drive device capable of selecting a two-wheel drive state or a four-wheel drive state, and which has a suspension mechanism capable of changing the suspension characteristics of the vehicle and a degree of sudden start or sudden acceleration of the vehicle. Sudden start detection means for detecting, comparison means for comparing the detected degree with a predetermined reference value, and the suspension mechanism is controlled according to the comparison result of the comparison means, and the detection degree is smaller than the reference value. In the suspension characteristic control device for a vehicle, the suspension device is set to the soft side, and when the detection degree is larger than the reference value, the suspension characteristic is switched to the hard side. A vehicle suspension characterized by comprising reduction control means for reducing the reference value by a predetermined amount when the driving state is selected. Pension characteristic control device.