JPS61175111A - Car level control device for rear wheels - Google Patents

Abstract

PURPOSE:To aim at improvements in a feeling of driving comfortableness and prevention of contact between a car bottom and a road surface, by constituting a controller so as to make a rear-wheel car level higher at a time when a front-wheel car level is out of the specified range and to cause it to be restored after the elapse of the specified time, in case of a device which adjusts a car level with road unevenness. CONSTITUTION:A front-wheel car level is inputted into an electronic control part 300 from each of front-wheel car level detecting devices 1 and 2. Simultaneously a car speed 250 is also inputted. The control part 300 finds a mean car level of the inputted car level, comparing the existing car level with the mean car level, and when the existing car level is more displaced than the mean car level as far as more than the specified value, rear-wheel suspensions 3 and 4 are driven, making rear wheels go up, in order to cope with riding across an uneven road. And, after the elapse of the specified time required for riding across the uneven road, these rear wheels is made to go down by these rear- wheel suspensions and they are restored. With this constitution, a bottoming limitation is made larger whereby car bottom drag prevention and improvements in a feeling of driving comfortableness are promoted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vehicle height control device for rear wheels having means for detecting unevenness of the road surface and adjusting the vehicle height when the vehicle is running. .

[Prior Art] Conventionally, as this type of device, for example, Japanese Patent Laid-Open No. 57-1
72808, Japanese Unexamined Patent Publication No. 59-23713, or 59-23712 have been proposed. In other words, while the vehicle is running, the vehicle height sensor detects the vehicle height and the vertical acceleration of the vehicle body, and if the detected value is greater than a predetermined value,
Moreover, when the road continues to be rough for a predetermined period of time, it is determined that the road is rough and the height of the vehicle is raised to improve ride comfort and prevent contact between the bottom of the vehicle and the road surface.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional control, the vehicle height does not increase unless the vehicle travels on a rough road for a predetermined period of time, so the vehicle height does not increase when driving over a joint or a one-off unevenness. For this reason, when the rear wheels go over a single unevenness that the front wheels passed,
As the vehicle body shakes back, the vehicle height of the rear wheels may drop further, causing the bottom of the vehicle to come into contact with the road surface.Also, if the vehicle height remains low, the shock absorber will easily reach its compression limit and cause the vehicle to bounce. A bottoming condition occurs in which vibrations are directly transmitted to the vehicle body via the stopper, which can cause severe vibrations to be transmitted to the vehicle body, impairing ride comfort.

[Means for Solving the Problems] The present invention employs the following configuration as a means for solving the above problems. That is, as shown in FIG. 1, in a vehicle height control device for the rear wheels of a vehicle that is provided with vehicle height adjustment means between the vehicle body M1 and the wheels, the distance between the front wheel WF and the vehicle body M1 is detected as the vehicle height. a front wheel height detecting means M2 for detecting the vehicle height; a determining means M3 for determining whether or not the vehicle height data obtained from the detected value of the vehicle height detecting means M2 is outside a predetermined range; a return means M4 that determines to return to m based on the middle height of the rear wheel WR after a predetermined time has elapsed after it is determined that the vehicle height data is outside the predetermined range; Rear wheel height adjustment means M6 raises the vehicle height of the rear wheel WR and returns to the original vehicle height based on the determination from the return means.
It is characterized by having the following.

Here, the front wheel height detection means M2 detects the distance between the front wheels and the vehicle body and determines the vehicle height, and vehicle height data can be obtained from this detected value. This vehicle height data may be the displacement from the previous average vehicle height, the speed of displacement or acceleration,
Or it may be the amplitude of vehicle height vibration. In the case of the present invention,
The front wheels mainly capture individual road surface irregularities as vehicle height data.

The determining means M3 obtains vehicle height data from the detected value of the vehicle height, determines a predetermined range in which the vehicle height of the rear wheels should be maintained, and compares it with the vehicle height data to produce a result.

The return means M4 is, for example, a means for determining whether or not to return based on the vehicle height based on vehicle height data from a rear wheel height detection means provided on the rear wheels, or a means for determining whether or not the vehicle is restored based on the vehicle height, or for detecting irregularities over which the front wheels have gone over. It is a means of measuring the time it takes for the toonawa to overcome.

The vehicle height adjustment means M6 means that, if the determination result of the determination means M3 is vehicle height data outside a predetermined range, the vehicle height adjustment means M6, for example, uses a compressor to adjust the gas chamber of the air suspension provided at the rear wheel or the liquid chamber of the hydraulic circuit. A device that raises or lowers the height of a vehicle by supplying gas or pressurized liquid, or by mechanical driving force.

[Operation] When a concave or convex portion of the road surface is detected by the front wheel height detecting means M2, the degree of the convexity or convexity is determined by the determining means M3. This determination result is transmitted to the rear wheel height adjustment means. At this time, if the concavity or convexity is large enough to exceed a predetermined range, the vehicle height at the rear wheel section is increased by the rear wheel vehicle height adjustment means, so the bottoming limit is increased, the ride comfort is improved, and the rear side prevent the bottom of the vehicle from coming into contact with the road surface.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 shows a vehicle height control device for rear wheels of an automobile using an air suspension, which is an embodiment of the present invention.

Reference numeral 1 represents a right front wheel height sensor installed between the right front wheel and the vehicle body of the own VJ vehicle, and detects the distance between the right suspension arm that follows the movement of the wheel and the vehicle body. 2 represents a left front wheel height sensor provided between the left front wheel and the vehicle body, and detects the distance between the left suspension arm and the vehicle body. Short cylindrical bodies 1a and 2a of the vehicle height sensor 1.2
are fixed to the vehicle body side, and links 1b and 2b are provided approximately perpendicularly to the central axes of the main bodies 1a and 2a. A turnbuckle Ic is provided at the other end of the links Ib and 2b.

2C is rotatably attached, and the other ends of the turnbuckles 1c, 2c are rotatably attached to a part of the suspension arm.

The main body of the vehicle height sensor 1.2 has a built-in potentiometer whose electrical resistance value changes in accordance with the rotation of its central axis, and which can detect changes in vehicle height as changes in voltage.

In addition, as the vehicle height sensor 1.2, the one of the above type is used in this embodiment, but in addition, a plurality of photo interrupters are arranged inside the main body, and a slit coaxial with the center axis of the vehicle height sensor is installed. It is also possible to use a disc plate which detects the vehicle height by turning a photointerrupter 0N10FF according to changes in the vehicle height.

Reference numerals 1B and 2B are vehicle height sensors provided on the left and right rear wheels (or only one of them may be provided), and have the same configuration as the vehicle height sensor 1.2 described above.

3 is air suspension (air spring type suspension)
represents. The air suspension 3 is provided in parallel with a suspension spring (not shown) between a suspension arm (not shown) of the right rear wheel and the vehicle body. The air suspension 3 mainly includes a shock absorber 3a, a main air chamber 3b, a sub-air chamber 3c, and an actuator 3d, and has an air spring function, a vehicle height adjustment function, and a shock absorber function. Further, air suspensions 4 to 6 represent similar air suspensions, and air suspension 4 is provided for the left rear wheel, air suspension 5 is provided for the right front wheel, and air suspension 6 is provided for the left front wheel.

Figures 3(a) and 3(b) show examples of the configuration of the main parts of the air suspension 3.Other air suspensions 4.5.6 have completely similar configurations.

This air suspension 3, as shown in FIG. 3(a), uses a conventionally well-known piston.

A shock absorber 3a consisting of a cylinder and an air spring device 14 provided in relation to the shock absorber 3a
including.

Cylinder 12a of shock absorber 3a (1! shock absorber)
An axle (not shown) is supported at the lower end of the piston rod 12b, which extends from a piston (not shown) slidably disposed within the cylinder 12a.
A cylindrical elastic assembly 18 is provided for elastically supporting the piston rod 12b on the vehicle body 16. In the illustrated example, the shock absorber 3a is a conventionally well-known variable damping force shock absorber whose damping force can be adjusted by operating a valve function provided on the piston. The control rod 20 is connected to the seal member 22
The piston rod 12b is fluid-tightly and rotatably connected via the piston rod 12b.
located within.

The air spring device 14 includes a peripheral wall member 26 including a bottom portion 26a provided with an opening 24 that allows the piston rod 12b to pass therethrough, and a peripheral wall portion 26b rising from the edge of the bottom portion, and a peripheral wall member 26 disposed over the peripheral wall member and attached to the vehicle body. A fixed upper housing member 28a, and a lower housing member 28 with an open lower end connected to the lower end of the housing member 28a.
b, and a diaphragm 30 made of an elastic member that closes the lower end of the lower housing member 28b. The chamber 32 has an opening 3 corresponding to the opening 24 provided in the bottom 26a of the peripheral wall member.
4 and fixed to the bottom portion 26a.
Therefore, the lower one air chamber 3b and the upper sub air chamber 3c
Both chambers 3b and 3C are filled with compressed air. The partition member 36 is provided with a conventionally well-known buffer rubber 4o that can come into contact with the upper end of the cylinder 12a, and the buffer rubber 40 has a rubber cushion 4o that communicates both the openings 24 and 34 with the main air chamber 3b. A passage 42 is formed for this purpose.

The cylindrical elastic assembly 18 is arranged around the piston rod 12b inside the circumferential wall member 26 that defines the inner circumferential wall of the sub-air chamber 3c with the circumferential wall 26b. A valve device 244 is provided to control communication between the rain air chambers 3b and 3C.

The cylindrical assembly 18 includes an outer cylinder 18a, a cylindrical elastic body 18b, and an inner cylinder 18C, which are arranged concentrically with each other,
The cylindrical elastic member 18b is fixed to both cylinders 18a and 18b. The outer cylinder 18a of the cylindrical assembly 18 is press-fitted into the peripheral wall portion 26b of the peripheral wall member 26 fixed to the vehicle body via the upper housing member 28a. Also,
The valve number body 44a of the pulp device 44, which allows the piston rod 12b to pass therethrough, is fixed to the inner cylinder 18c, and the piston rod 12b is fixed to the recovery body 44a, so the piston rod 12b is inserted into the cylinder. It is elastically supported by the vehicle body via a shaped elastic assembly 18. An annular air seal member 4 is provided between the outer cylinder 18a and the peripheral wall portion 26b.
6, and an annular air seal member 48 seals between the piston rod 12b and the collection container 44a. In addition, the inner cylinder 18c and the collection container 44
A is sealed by an annular air seal member 50.

A hole 52 that extends parallel to the piston rod 12b and is open at both ends is formed in the collection container 44a, and a rotary valve 44b is rotatably housed in the hole. The valve body 44b includes a main body portion 56a that can come into contact with a lower positioning ring 54a disposed at the lower end of the hole 52;
It includes a small-diameter operating portion 56b that protrudes above the cylindrical elastic assembly 18 from the main body portion. The upper end of the hole 52 is provided with the valve body 4 in cooperation with the lower positioning ring 54a.
An upper positioning ring 54b is arranged to prevent the upper positioning ring 54b from falling off from the hole 52 of the upper positioning ring 54b.
An annular seal base 60 having an inner air seal member 58a and an outer air seal member 58b for sealing the hole 52 is disposed between the body portion and the hole 52. Further, between the seal base 60 and the main body portion 56a of the valve body 44b, there is a groove for smoothing the rotational movement of the valve body 44b when the main body portion 56a of the valve body is pressed against the seal base 60 by air pressure. A friction reducing member 62 is arranged.

Below the cylindrical elastic assembly 18 is the opening 24.34.
A chamber 64 is formed which communicates with the main air chamber 3b through the passage 42 of the buffer rubber 40, and the valve body 44b is connected to the main air chamber 3b.
A recess 66 that opens into the chamber 64 is formed in the main body portion 56a. Further, a communication passage 68 is formed in the main body portion 56a, passing through the main body portion in the diametrical direction and crossing the recess 66.

The collection container 56b that receives the valve body 56a includes a third
As clearly shown in Figure (B), one end is connected to the communication path 6.
8 are provided with a pair of air passages 70 that can communicate with each other, and the air passages extend outward in the diametrical direction of the hole 52 on substantially the same plane toward the outer peripheral surface of the valve body 44b.
The other end is open to the outer circumferential surface of the collection container 44a through a seat hole 72.

Further, between the pair of ventilation passages 70 in the circumferential direction of the hole 52, a ventilation passage 74 whose one end can be communicated with the communication passage 68 is arranged so that the ventilation passage 74 and the ventilation passage 70 are substantially on the same plane toward the outer circumferential surface of the collection container 44a. Stretch. The diameter of the ventilation passage 74 is smaller than that of the ventilation passage 70, and the other end of the ventilation passage 74 has a seat hole 75.
It opens to the outer circumferential surface of the collection container 44a. On the inner circumferential surface of the inner cylinder 18c that covers the outer circumferential surface of the collection container 44a,
An annular groove 76 is formed surrounding the outer peripheral surface of the collecting container 44a to communicate the seat holes 72, 75 of the ventilation passages 70 and 74.

The inner cylinder 18c is formed with an open lower portion 8 that opens into the groove 76 forming an annular air passage, and the cylindrical elastic member 18b has an elastic member that corresponds to the open lower portion 8. A through hole 80 is formed that extends radially outward. Further, each through hole 80 opens to the outer peripheral surface of the outer cylinder 18a through an opening 82 provided in the outer cylinder 18a. Accordingly, the intermediate lower part 8 82 and the through hole 80 are provided corresponding to the air passage 70 and define an air passage passing through the cylindrical elastic assembly 18 .

The open lower part 8.82 and the through hole 80 are connected to the sub air chamber 3.
A plurality of openings 84 open to the sub air chamber 3C are provided at equal intervals in the circumferential direction on the outer circumferential surface of the circumferential wall portion 26b of the circumferential wall member that covers the outer cylinder 18a so as to communicate with the sub-air chamber 3C. . In order to communicate all the openings 84 with the opening lower part 8.82 and the through hole 80, the outer peripheral surface of the outer cylinder 18a is provided with:
An annular groove 86 surrounding the outer cylinder is formed at the portion where the opening 82 opens, and the opening 84 opens into the groove 86 forming an annular air passage.

In the example shown in FIG. 3(b), the open lower lower part 8.82 and the through hole 80 are provided corresponding to the two ventilation passages 70 of the collection container 44a, but the inner cylinder 18C and the collection container 44a
Since the annular air passage 76 is formed between the elastic member 18b and the air passages 7° and 74, the air passage can be formed at a desired position in the circumferential direction of the elastic member 18b. .

Referring again to FIG. 3(a), the piston rod 12b
A control rod 20 for adjusting the damping force of the shock absorber 3a and a conventionally well-known actuator 3d for rotating the valve body 44b of the pulp device 44 are provided at the upper end. 3d rotates the valve body 44b.

The present air suspension 3 is configured as described above and has the following effects.

First, the valve body 44k) is placed in the closed position as shown in FIG. When the suspension is held, the communication between the sub air chamber 3C and the main air chamber 3b is cut off, so that the spring constant of the suspension 3 is set to a large value.

Further, the communication passage 68 of the valve body is actuated by the actuator 3d.
When the main air chamber 3b is moved to a position where it communicates with the large-diameter ventilation passage 70 of the holding body 44a, the main air chamber 3b is connected to the communication passage 68, the large-diameter ventilation passage 70. The spring constant of the suspension 3 is set to a small value because it communicates with the auxiliary air chamber 3C via the open lower portion 8, the through hole 80, and the openings 82 and 84 of the elastic assembly 18.

Also, by adjusting the actuator 3d, the valve body 441
) is the small-diameter ventilation passage 7 of the holding body 44a.
When the main air chamber 3b is operated to the position where it communicates with the air chamber 3b, the communication passage 68 and the small diameter ventilation passage 7 communicate with the air chamber 3b.
4, through the air passage 76, the open lower portion 8 of the elastic assembly 18, the through hole 80, and the openings 82 and 84;
It communicates with II air chamber 3C. Since the small-diameter air passage 74 provides greater air resistance than the large-diameter air passage 70, the spring constant of the suspension 3 is set to an intermediate value.

Returning to FIG. 2 again, 151 to 154 represent leveling valves, which are provided in pairs with the air suspensions 3 to 6, respectively. The leveling valves 151 to 154 open or close the spaces between the compressed air supply and exhaust system 200 (described later) and the main air chambers 3b to 6b of the air suspensions 3 to 6, depending on whether or not the electromagnetic solenoids 151a to 154a are energized.

When the leveling valves 151 to 154 are opened, compressed air can be supplied to and exhausted from the air suspensions 3 to 6, and when the air is supplied, the vehicle height becomes higher, and when the air is exhausted, the vehicle height is lowered. Furthermore, the vehicle height can be maintained by closing the leveling valves 151 to 154.

200 represents a compressed air supply/exhaust system, which operates a compressor 200b by a motor 20Qa to generate compressed air. The air dryer 200C dries the compressed air supplied to the air suspensions 3 to 6, protects the piping and components of the air suspensions 3 to 6 from moisture, and also protects the main air chambers 3b to 6b in the air suspensions 3 to 6.
, pressure abnormalities due to phase changes of moisture within the sub-air chambers 3C to 6C are prevented. In the check valve 200d with a fixed throttle, the check valve part opens when compressed air is supplied, and when the compressed air is discharged, the check valve part closes and the compressed air is discharged only from the fixed throttle part. The discharge solenoid valve 200e is driven when compressed air is discharged from the air suspensions 3 to 6, and discharges the compressed air discharged from the air suspensions 3 to 6 into the atmosphere via the fixed throttle check valve 200d and the air dryer 200C. discharge. By controlling this solenoid valve 200e, it is possible to change the volume of the main air chamber 5b of the air suspensions 3 to 6 and adjust the vehicle height.

Further, 250 represents a vehicle speed sensor, which is provided within a speedometer, for example, and outputs a pulse signal corresponding to the vehicle speed in conjunction with the axle.

Signals from the vehicle height sensors 1 and 2 and the vehicle speed sensor 250 described above are input to an electronic control circuit (ECU>300.The electronic control circuit 300 inputs these signals, processes the data, and performs processing as necessary. In order to perform appropriate control, the actuators 3d to 5d of the air suspensions 3 to 6, the leveling valves 151 to 154, and the compressed air supply and exhaust system 200
A drive signal is output to the motor 200a and solenoid valve 200e.

FIG. 4 shows the configuration of the electronic control circuit 300.

301 is a central processing unit (hereinafter simply referred to as CPLJ) that inputs and calculates data output from each sensor according to a control program and performs processing for controlling the operation of various devices; 302 is a central processing unit (hereinafter simply referred to as CPLJ); 302 is a central processing unit that inputs and calculates data output from each sensor according to a control program; A read-only memory (hereinafter simply referred to as ROM) in which 303 is stored is an electronic control circuit 3.
Random access memory (hereinafter referred to simply as RAM) is used to read data input to 00 and data necessary for arithmetic control.
), 304 is a backup random access memory (hereinafter simply referred to as backup RAM) backed up by a battery so as to retain necessary data even when the key switch is turned off, and 305 is an input (not shown). It represents an input section equipped with a board, a waveform shaping circuit provided as necessary, a multiplexer that selectively outputs the output signal of each sensor to the CPU 301, an A/D converter that converts an analog signal into a digital signal, etc. There is. Reference numeral 306 denotes an output boat (not shown), an output unit equipped with a drive circuit etc. that drives each actuator according to a control signal from the CPU 301 as necessary; 307,
Each element such as CPU 301 and ROM 302 and input section 30
5. Each represents a path line connecting the output section 306 and through which each data is sent. Also, 308 is CPt+301
1, a clock circuit that sends a clock signal serving as a control timing to the ROM 302, RAM 303, etc. at predetermined intervals.

If the signal output from the vehicle height sensor 1 is a digital signal, it is transmitted to the CP (+301) via the input section 305 equipped with a buffer as shown in FIG.
A vehicle height sensor 1 that outputs an analog signal may have a configuration as shown in FIG. 5(b), for example. The vehicle height sensor here outputs a signal representing the vehicle height value as an analog voltage value. This analog voltage signal is O-
After being converted into a voltage value VHF (OR) indicating the average vehicle height value by the OR filter circuit 305a which is a bus filter, the voltage value VHF (S) is inputted to the A/D converter 305b and directly indicating the current vehicle height value. The signal is input to the A/D converter 305b as follows. The A/D converter 305b digitizes each signal using a multiplexer, and then transmits each signal to the CPL +301. Left front wheel height sensor 2
The same applies to

Next, the process executed by the electronic control circuit 300 is executed in the sixth step.
This will be explained based on the flowchart in Figure (a).

FIG. 6(a) shows a flowchart of processing performed in the electronic control circuit 300 using a linear vehicle height sensor that outputs the analog signal shown in FIG. 5(b) as the vehicle height sensor 1. This process is performed every predetermined time, for example, 5 m5
It is executed repeatedly for each ec.

The outline of the processing in this flowchart is as follows.

■First, current vehicle height VHF (S) and average vehicle height VHF (CR)
(Steps 540 and 550).

(2) Next, it is determined whether the current vehicle height is a displacement exceeding a predetermined who from the average vehicle height (step 580).

■Next, if the displacement exceeds the predetermined value ho, the vehicle height of the rear wheels is increased to cope with overcoming the bumps (step 620).
. That is, the leveling valve 151,1 shown in FIG.
By energizing the electromagnetic solenoids 151a and 152a of 52, the pulp 151 and 152 are opened, and the air from the compressor 200b is transferred to the main air chamber 3b of the air suspension 3.4.

4b to raise the feed vehicle height.

■After the rear wheels go over the bumps, return the rear wheels to their original height (
Step 660>.

Next, details of this process will be explained. This process is 51se
It is executed repeatedly every c. The numbers in parentheses indicate the step numbers of the process.

First, it is determined whether the process is the first one after the electronic control circuit 300 is activated (510). If the current processing is the first processing, initial settings are performed (520), various variables are cleared, and various flags are reset. Initial setting <52
0), or if the process of this routine is the second or subsequent time, as the first process of determination (510), the vehicle speed V
is detected (530). This is detected by a signal from vehicle speed sensor 250. Next, the current vehicle height VHF (S)
is detected (540). The output value of the vehicle height sensor for either the right front wheel or the left front wheel can be used for the vehicle height, but since the same shock will be caused to the rear wheels regardless of which front wheel rides up or down, the front wheel The average value of both vehicle height sensors may be used, or the larger value of both may be used.

Next, the past average of the output values of the vehicle height sensor 1 is calculated, and a reference vehicle height is set (<550). In this example, Fig. 5 (b)
CR filter circuit 3 using the low-pass filter shown in
05a, the reference vehicle height VHF (OR>) as an average value is directly determined from the output signal of the vehicle height sensor 1. If the vehicle height sensor 1 is outputting a digital signal, it is determined in the electronic control circuit 300. Calculation may be performed using the vehicle height VHF(S) measured in the past.For example, by adopting the process shown in FIG. 7 instead of steps 540 and 550 in FIG. executed. The process in FIG. 7 first detects the current vehicle height VHF(8)n (710
a＞. Next, every predetermined calculation unit time tms (720a>)
Average value VHFa,n calculation processing (730a1740a) is performed. Calculations are then performed in step 730a.

VHFa, n 4- ((k -1) VHFa, n-1
+VHFb, n-1 +VHF (Sin)/kk:
Number of measured values to be averaged VHFa, n: Current (nth) average value to be calculated VHFa, n-1: Previously (n-1st) calculated average value VHF (Sin: Current medium/high measurement value VHFb, n-
1: To calculate the average value VHFa,n, the value previously calculated for convenience In step 740a, the above VHFb,n is calculated by the following calculation.

VHFb, n 4-nod (k) ((k
-1) VHFa.

n-1+VHFb, n-1+VHF (S)n) where ll1Od (A> (B) means the value of the remainder when B is divided by A.

The processing in steps 730a and 740a described above is a simple method for calculating the average value, and a value close to the average value can be calculated simply by storing VHFa,n, VHFa,n-1, and VHFb,n-1 in memory. and in the past
Since it is not necessary to store individual pieces of data, memory and calculation time are saved.

If memory and calculation time are available, the average of the required number of measured values may be calculated.

Next, returning to Fig. 6 (a), after detecting the average value (550),
It is determined whether the suspension control is in auto mode (560). For example, if the driver has not instructed the auto mode using the manual switch, the processing of this routine ends. If the auto mode has been instructed, the process moves to a determination as to whether or not the vehicle is running (570). The output of the vehicle speed sensor 250 is detected, and if the output is equal to or higher than a predetermined value, it is determined that the vehicle is running.

If it is running, then the average vehicle height VH of the current vehicle height VHF (S)
Displacement from F (CR) 1VHF (S) - VHF (
It is determined whether CR)1 exceeds a predetermined reference value hO (580). If the displacement is less than ho, flag Fh is reset (590).

Flag Fh is a flag for determining that this is the first process in which the displacement exceeds ho.

If it is determined that the displacement exceeds ho, timer T1 is started and flags Fr and Fh are set. The timer T1 is a timer for checking the time for changing the vehicle height of the rear wheels, and the flag Fr is a flag for determining whether to count up the timer T1 as shown in FIG.

FIG. 8 is a flowchart showing a routine that is repeatedly executed at predetermined time intervals. If flag Fr is set (810), timer T1 is counted up (810).
20) It is configured as follows.

Next, returning to FIG. 6(a), after step 610, the vehicle height of the rear wheels is raised (620).

That is, by energizing the electromagnetic solenoids 151a and 152a of the leveling pulp 151 and 152 for a certain period of time Δ[1, the valves 151 and 152 are released, and the air supplied from the compressor 200b is transferred to the main air chambers 3b and 4b of the air suspension 3.4. to raise the vehicle height. Due to this vehicle height raising process, even if the vehicle body shakes back and forth when the rear wheels pass over an uneven surface, the rear bottom of the vehicle does not come into contact with the uneven road surface.

That is, at five points on the road surface, there is no contact with the top, and on the other hand, at the concave place, there is no contact at the upper corner.

Furthermore, since the vehicle height is raised, even when there are large irregularities, it is difficult for the suspension to reach its compression limit, that is, it is difficult for the suspension to reach the bottoming state, which improves ride comfort.

Next, after the rear wheel vehicle height raising process (620), the time TV from when the rear wheel detects an unevenness on the front wheel until it crosses the unevenness is calculated using the following formula based on the vehicle speed ■. <630
).

Tv←(AI/V)+A2 A1: Wheelbase A2: Correction term (constant) The above A2 is determined by taking into consideration the detection delay of the vehicle height sensor 1.2, the time required for the rear wheels to pass over unevenness, etc.

Next, start raising the vehicle height of the rear wheels and then step 6 above.
Timer T1 determines whether the TV determined at 30 has elapsed.
(640). If T1 is less than or equal to TV, the processing of this routine is ended as is. T
1 exceeds TV, that is, if Tv has elapsed after the vehicle height of the rear wheels started rising, timer T1 is reset, and flag Fr is also reset (650).
.

Therefore, while flag Fr is being set, in step 810 of the timer T1 count-up process shown in FIG.
”, and the count-up of the timer T1 is stopped.

Finally, the rear wheel height is returned to its original height (660).
. That is, by stopping the compressor 200b and opening the discharge solenoid valve 200e for a certain period of time Δt2 to discharge the air from the main air chambers 3b and 4b, the vehicle height can be lowered to the original height. It will be done.

In addition, in the above-described vehicle height raising and lowering process, air is supplied from the compressor 200b for a certain period of time Δt1,
The release solenoid valve 200e is opened for a certain period of time Δt2 to further raise and lower the vehicle height.
The setting is not limited to this, and may be set in multiple stages depending on the size of the unevenness. Further, the above-mentioned Δtl and Δt2 may be set variably according to the vehicle speed V, that is, the vehicle height may be raised until just before the rear wheels pass over the unevenness. That is, the sixth
Timer T1 and flag l in step 610 in Figure (a)
By setting r, the flowchart shown in FIG.
1-AI/V is calculated to measure the time until just before the rear wheel passes the bump (624), and when T1 has passed Δt1, the vehicle height raising process is ended (626, 628).

On the other hand, in order to make the time for the vehicle height lowering process variable, first, do not reset T1 in step 650 of FIG. 6(a), but perform the process in step 660 according to the flowchart of FIG. 6(c). . In other words, start the vehicle height lowering process 662), then calculate Δt2−mΔt1 664), where m is m−(time required to lower the vehicle height to a certain level)/(−time required to raise the castor height). time required). Then, when T1 has passed TV+Δt2, the vehicle height lowering process is finished.
666.668).

In this way, when an unevenness is detected on the front wheels, the vehicle height of the rear wheels is raised to prevent contact with the road surface on the rear side.
Additionally, the suspension compression limit before bottoming has been increased to improve ride comfort. Additionally, the time taken for the rear wheels to pass over the bumps is measured and the rear wheels are quickly returned to their original height, so there is no problem with subsequent driving.

FIG. 9 shows an example of the above-mentioned processing in a time chart. Before time t1, the vehicle is traveling on a flat road surface. The vehicle height VHF (S) obtained from the vehicle height sensor 1.2 depicts a wave with a small amplitude. Average vehicle height VH obtained from CR filter circuit 305a
F (CR) changes in a smoothed form. When the front wheels start to ride up on the bumps on the road, the vehicle height VHF (S)
falls sharply. Then, at time t1, VHF(S)
is smaller than VHF (CR) −h O. That is,
Step 580 of the flowchart shown in FIG. 6(a)
At l VHF (S)-VHF (OR>I>ho
It will be determined that At this point t1, the electronic control circuit 300 opens the leveling valves 151 and 152, and the air suspension 3.4 is moved to the compressor 200.
By supplying air from time t1 to time t2 after Δt1, the middle height of the rear wheels gradually increases. Then, at time t3, the rear wheels ride on the convex portion, and the vehicle height of the rear wheels becomes low. However, since the vehicle height on the rear wheel side has already risen, even if the rear wheels bounce on the convex portion, the vehicle height will not drop below normal driving, and the vehicle height will not come into contact with the road surface. Moreover, it does not become a bottoming state.

Next, when the compressor 200b is driven, the discharge solenoid valve 200e is opened from time t4 after a time Tv to Δt2 from time t5, and the vehicle height returns to the normal running state.

In the case of boarding down, the peak of the vehicle height is upward, and when the current vehicle height VHF (S) exceeds VHF (CR) - h O, the vehicle height raising process is performed in the same way as in the case of boarding up.

In the above embodiment, the vehicle height sensor 1.2 is used as a vehicle height detection means, the compressed air supply and exhaust system of the compressor 200b, the leveling valves 151 and 152, and the air suspensions 3 and 4 are used as a vehicle height adjustment means, and , Figure 6 (
Step 580 in the flowchart of A) is used as the determination means in Steps 61016'30 to 6501 of FIG. 6(A).
Figures (c) and 8 correspond to the return means, respectively.

Next, a second embodiment of the present invention will be described. In the second embodiment, in addition to the configuration shown in FIG. 2, a vehicle height sensor is also provided at the rear wheel portion, and the distance between the intermediate suspension and the rear wheel is also detected as the vehicle height at the rear wheel portion.

The detection signal is sent from the ECU 3 as well as the front wheel height sensor 1.2.
00 is input. And in ECU300, the 6th
Instead of the processing in Figures and Figure 8, Figures 10 (a) and (b)
The processing shown in is performed. The second embodiment is characterized by this processing.

The details of FIGS. 10(a) and 10(0) will be explained. 1st
The process in Figure 0 (a) is the same as in Figure 6 (a), when the front wheels detect unevenness on the road surface, the rear wheels raise the vehicle height, and after a predetermined period of time, the vehicle height returns to the original height, but if the front wheels detect an unevenness on the road surface, the vehicle height is returned to the original height. The aim is to accurately detect the height of the rear wheels and restore the vehicle height of the rear wheels as quickly as possible, thereby ensuring even more appropriate control.

First, the initial steps 701 to 703, 706.7 of the process
07, step 51 Cl-5 of the first embodiment
(1) is the same as 30, 560, and 570, and its explanation will be omitted.

Next, the current front wheel vehicle height VHF (S) and the average vehicle height VH
F (CR) is detected (704), and the current rear wheel aVHR (S) and average vehicle VHR (OR) are detected (705). These, vehicle height VHF (S), VH
R(S) and average vehicle height Vl-IF(CR), VHR(O
R) is obtained in the same manner as the treatment of Sten 7540.550 in the first embodiment.

Next, when it is determined that the vehicle is in auto mode (706) and that the vehicle is running (707), it is determined whether the flag Fr is set (708).

The flag F" is a flag indicating that the vehicle height raising process for the rear wheels is being performed. In the initial setting, it is in the reset state.

If Fr-0, the average vehicle height VHF of the current vehicle height VHF (S)
Displacement from (OR) I VHF (S) −VHF(
It is determined whether CR)l exceeds a predetermined reference value ho (709). If the displacement is less than ho, the processing of this routine ends.

If it is determined that the displacement exceeds ho, timer T1 is started and flag Fr is set.

Timer T1 is a timer for checking the time for changing the vehicle height of the rear wheels, and flag Fr is a flag for determining whether to count up timer T1 as shown in Figure 10 (b). It is.

FIG. 10(0) is a flowchart showing a routine that is repeatedly executed at predetermined time intervals. If the flag 1"r is set (751), the timer T1 is counted up (752), and the flag Rr, which will be described later, is set.
If it is set to 2 (753), it is configured to count up the timer T2 (754).

Next, returning to FIG. 10 (a), after step 710, the minimum time Tvl for prohibiting the vehicle height of the rear wheels from lowering from the time when the front wheels detect an unevenness until the rear wheels cross the unevenness is determined by the vehicle speed
It is calculated using the following formula based on (711).

Tv 1←(AI/V) +A2 A1: Wheelbase A2: Correction term (constant) The above A2 is determined in consideration of the detection delay of the vehicle height sensors 1 and 2, the time required for the rear wheels to pass over unevenness, etc. Tv is sufficient time for unevenness to pass through the wheel base at normal driving speed.
If set as l, Tvl may be a fixed time.

Next, the maximum time Tv2 for which the rear wheels have completely overcome the unevenness and there is no need to keep the vehicle height of the rear wheels raised is calculated using the following formula based on the above minimum setting time Tvl. <712).

TV 24-TV 1+A3 A3: Correction term (constant) The above A3 is determined in consideration of the time it takes for the rear wheels to completely overcome the unevenness.

Next, processing for raising the vehicle height of the rear wheels is performed (713).

This raising process is the same as step 620 in the first embodiment, so it will be omitted.

In this way, the processing of this routine ends.

The processing of this routine is started again, but if rYEsJ was determined in the previous step 709, the flag Fr is set (710). Therefore, this time, rYEsJ is determined in step 708.

In this way, it is then determined whether the flag Rr1 is set (714). Flag Rr1 is a flag indicating that the vehicle height sensor provided on the rear wheel has detected an unevenness.

Since the unevenness has not yet reached the rear wheels and the flag Rr1 is in the initial reset state, it is determined in step 714 that rNOJ.

Next, the current vehicle height of the rear wheels V) - the average vehicle height of IR(S) V)(
Displacement from R(CR) I VHR(S) - VHR(CR
)1 exceeds a predetermined standard 1ah1 is determined (
715). If the rear wheel has not yet reached the unevenness and the displacement is less than h1, then it is determined whether the value of timer T1, which has already been started in step 710, exceeds the maximum set time Tv2.

(717). If it has not yet been exceeded, the processing of this routine is temporarily terminated. In this state, the front wheels have overcome the unevenness, but the rear wheels have not yet overcome the unevenness.

Then, as time continues to pass and when TI>Tv2, rYEsJ is determined in step 717, flags l''r, Rr 1.Rr 2 are reset, and timer T1.72 is cleared (718). Next, the vehicle height of the rear wheels is returned to the original height (719).

In this way, even if the rear wheel height sensor does not detect any irregularities (715), the TV 2 performs a process (719) to return the vehicle height to its original level without leaving it elevated for a long time. This is because the rear wheel height sensor made a detection error or the object that caused the unevenness moved after the front wheel passed and could not be detected, so the rear wheel height sensor was left raised for a long time. This is to prevent a decrease in ride comfort, maneuverability, and stability, and to prevent nose dive.

Next, in the above situation, in step 717 T
Consider a case where the rear wheel height sensor detects an unevenness before 1>Tv2.

In this case, the rear wheel vehicle height VHR (S) and its average vehicle height V
HR(OR) let, l VHR(S) -VHR(
OR) l > hl. hl is a value set to detect rear wheel overtaking. In this way, in step 715, it is determined as "YESJ", and flag Rrl is set (716), and then T1>
If it is Tv2 (717), this process ends once.

Next, when the process starts again, it is Rrl-1, so
At step 714, it is determined that rYEsJ, and the flag Rr
It is determined whether or not 2 is set (720).

Flag Rr2 indicates that the rear wheel height is I VHR(S) - VHR
(CR) This is a flag indicating a state in which the relationship of l <Δh is satisfied. However, there is a relationship such as hl>Δh, and Δh becomes the standard for determining the situation in which the vehicle height of the rear wheels should be returned to the original level if l VHR(S)−VHR(CR)1 falls below Δh. be.

Here, if l VHR (S) - VHR (OR > 1 and Δh) has not yet reached the state, rNOJ is determined in step 720, and in subsequent step 721, l V
Since the determination is HR(S)-VHR(CR)l<Δh, it is determined as rNOJ, and if it is determined in step 717 that TI>Tv2 is not established, this processing is temporarily terminated.

After this, the process continues in steps 701 to 708.71 until the vehicle height (7) displacement ff1l VHR(S) - VHR(CR)l of the rear wheels, which once rose beyond h1, becomes less than 61.
4,720,721,717 and then repeating the process. However, this is a case where the condition that T1≦TV2 is satisfied, and if TI>TV2, step 7
At step 17, it is immediately determined to be rYEsJ, and the vehicle height of the rear wheels returns to the original height (719).

Next, IR (S) - VHR (CR) 1 decreases by 1, and 6
If it is less than 1, it is determined as rYEsJ in step 721, timer T2 is started, and flag Rr2 is set. The timer T2 is provided to restore the vehicle height of the rear wheels to the original height after a time ΔT after the rear wheels have overcome the unevenness.

In this way, when the process returns to step 720, Rr 2
-1, it is determined as rYESJ, and timer T2 is set to Δ
It is determined whether or not T is exceeded (723). If it has not exceeded T1≦Tv2, proceed to step 717.
If so, the rear wheel height will not return to its original height.

After this, if T2>6, in step 723 rY
EsJ has been determined, and just to be sure, the control will not be inappropriate due to false detection or the detection of other continuous irregularities.
At step 724, it is checked whether Tl>TV 1 or not.
If "YES", steps 718 and 719 are processed and the vehicle height of the rear wheels is returned to the original height. If T1≦Tv1 in step 724, the vehicle height is returned to its original value.
There is a risk that the bumps will pass through the rear wheels right after, so ``NO''
It is determined that this is the case, and the process is terminated without returning to the original state.

The above-described processing is shown in a timing chart as shown in FIG. (a) is a timing chart of front wheel height;
(b) is a timing chart of the compressor drive signal,
(C) shows a timing chart of the rear wheel height, and (d) shows a flow chart of the exhaust valve. Here, running onto a road surface depression is illustrated.

At time t11, front wheel height VHF(S) becomes VHF(CR)
When the value -ho is exceeded, the compressor drive signal is output by Δt1 from that point on, and the vehicle height increases. Also, at this point, considering the vehicle speed, wheelbase, and vehicle height rise speed,
Time Tv1 and Tv2 are set. Tv1 is the minimum setting time for prohibiting the vehicle height lowering process. This is because, considering the driving situation, it is considered that the rear wheels will not meet the six points until after time t12, which is from time t11 to Tv1.

Further, Tv2 is the maximum setting time for starting the vehicle height lowering process. In other words, this indicates that the rear wheel always passes through the recess detected by the front wheel at time t11 between time t11 and before time t13 of Tv2.

In this example, the rear wheel vehicle height V at time t21 after time t12
Since HR(S) exceeded VHR(CR)+h1 and then became less than V)(R(CR)+61 at time t22, the time t22 was determined considering the time for the rear wheel vibration to subside.
At time t23, when time ΔT has elapsed since then, the process of lowering the vehicle is started. Then, the descending process is completed after Δt2.

In another situation, if the rear wheel does not detect a recess for some reason such as a detection error until time t13, the maximum set time Tv2 to wait before starting the vehicle height lowering process is set. At step 13, the descending process is started. For example, time t
Even if five locations are detected on the rear wheel between 11 and t13, the time t2
2 or time t23 becomes time t1]1, the vehicle height starts lowering at time t13.

On the other hand, if the time points t21 to t23 fall within the range t11 to t12, the vehicle height lowering process is prohibited until at least time t12, in consideration of erroneous detection or the like.

According to this embodiment, there are two types of setting time Tv 1 and maximum setting time 7v2 for prohibiting the rear wheel vehicle height from returning to the original height, and Tv 1 is set depending on the time point when the rear wheel vehicle height is detected.
and Tv 2 are used, and depending on the situation, the vehicle height of the rear wheels is controlled to return to the original height depending on when irregularities on the rear wheels are detected. Therefore, it is possible to control the rear wheel height more appropriately and precisely even when the vehicle continuously passes over different unevenness or when there is a detection error.

In the first and second embodiments described above, the average vehicle height VHF (C
R) and the current vehicle height vHF(S) exceeded the range of ±hO to determine whether the vehicle height had increased. Alternatively, the determination may be made based on the amplitude.

Judgment based on speed and acceleration reveals the initial state of the front wheel over unevenness, so it can be dealt with quickly, and when using amplitude, it is particularly effective when emphasis is placed on maneuverability and stability.

[Effects of the Invention] As explained above, according to the present invention, when the vehicle height detecting means provided on the front wheels detects the unevenness of the road surface, the vehicle height of the rear wheels is increased, so that the rear wheels can detect the unevenness. This prevents the bottom of the car from coming into contact with uneven surfaces even if the car body is shaking when passing through the road. It also increases the compression limit of the suspension, improving ride comfort. Furthermore, since a return means is provided to quickly return the rear wheels to the original vehicle height after passing over the bumps, there is no problem with subsequent driving.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic contents of the present invention, Fig. 2 is a system block diagram showing an embodiment of the present invention, and Fig. 3 (A) is a cross-section of the main parts of the air suspension used in this embodiment. Figure 3 (B) is a sectional view taken along line A-A, Figure 4 is a block diagram for explaining the electronic control circuit, and Figure 5 (A) is a block diagram showing the digital vehicle height sensor signal input circuit. ,
Figure 5 (b) is a block diagram showing the analog vehicle height sensor signal input circuit, Figures 6 (a) to 6 (c) are flowcharts of the processing executed by the electronic control circuit, and Figure 7 is a block diagram showing the analog vehicle height sensor signal input circuit. Flowchart showing the average value calculation processing part, FIG. 8 is a flowchart of timer count-up, FIG. 9 is a timing chart of front and rear wheel vehicle heights and actuator drive signals in the control of this embodiment, and FIGS. 1
FIG. 0 (0) is a flowchart showing another embodiment, No. 11
The figure is a timing chart of another embodiment. Ml...Vehicle body WF, WR...Front and rear wheels M2...Front wheel height detection means M3...Judgment means M4...Returning means M6...Vehicle height adjustment means ) Figure 5 "7 ＼300 '$l'1.v@Route E+fl umbrella height C-/"7 Figure 5 (T) Figure 7 Figure 8 Figure 9 L-1Δt2-1〒

Claims (1)

[Scope of Claims] 1. A vehicle height control device for the rear wheels of a vehicle having a vehicle height adjustment means between the vehicle body and the wheels, comprising: a front wheel height detection means for detecting the distance between the front wheels and the vehicle body as a vehicle height; , determination means for determining whether or not the vehicle height data obtained from the detected value of the vehicle height detection means is outside the predetermined range; and after the determination means determines that the vehicle height data is outside the predetermined range. a return means for determining whether to restore the vehicle height based on the vehicle height of the rear wheels after a predetermined time has elapsed, and raising the vehicle height of the rear wheels when the determination means determines that the vehicle height data is outside a predetermined range; A rear wheel vehicle height control device comprising: rear wheel vehicle height adjusting means for returning to the original vehicle height based on judgment from the return means.