JP2018192989A - Vehicle height control system - Google Patents

Abstract

To reduce a difference between an actual amount of change in vehicle height and the target value for an amount of change in vehicle height determined by vehicle height control, which results from overshoot caused by a suspension bush that has become hard due to a low temperature.SOLUTION: In this vehicle height control system, a value smaller than an actual target amount of change, which is a target value for an amount of change in vehicle height, which is determined by vehicle height control, is used as a target amount of change for control. When an actual amount of change, which is an actual amount of change in vehicle height in the vehicle height control, approaches the target amount of change for control, a vehicle height control valve is closed. In addition, the target amount of change for control is determined based on the temperature of outdoor air. After the actual amount of change approaches the target amount of change for control and the vehicle height control valve is closed, overshoot may occur. However, a difference between the actual amount of change in vehicle height and the actual target amount of change, after the overshoot, can be made smaller.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a vehicle height control system for controlling the vehicle height of wheels.

In the vehicle height control system described in Patent Document 1, when the vehicle height is lower than the target vehicle height, the vehicle height is increased by supplying air to the air cylinder, and the vehicle height is higher than the target vehicle height. The vehicle height is lowered by discharging air from the air cylinder.
In the vehicle height control system described in Patent Document 2, in the vehicle height control for reducing the vehicle height, a value larger than the true target vehicle height that is the target vehicle height is set as the control target vehicle height, and the actual vehicle height is set. When the vehicle approaches the control target vehicle height, the vehicle height control valve is closed. The above-described target vehicle height for control is determined based on the magnitude of the overshoot (overshoot amount) caused by the load applied to the wheel, and is determined to be a larger value when the load is large than when the load is small. In vehicle height control to increase the vehicle height, the target vehicle height for control is set to a value smaller than the true target vehicle height, but the target vehicle height for control is determined to be a smaller value when the load is small and larger. Is done. Thus, in the vehicle height control system described in Patent Document 2, the difference between the actual vehicle height and the true target vehicle height due to the overshoot caused by the load can be reduced.

JP-A-3-70615 JP 2006-248278 A

  An object of the present invention is to reduce the difference between the actual change amount of the vehicle height caused by overshoot caused by the suspension bush becoming hard at low temperatures and the target value of the vehicle height change amount determined by the vehicle height control. is there.

Means and effects for solving the problem

  In the vehicle height control system according to the present invention, a value smaller than the true target change amount that is the target value of the vehicle height change amount determined by the vehicle height control is set as the control target change amount, and the actual vehicle in the vehicle height control is determined. The vehicle height control valve is closed when the actual change amount, which is a high change amount, approaches the control target change amount. Further, the control target change amount is determined based on the temperature of the outside air.

  The suspension including the vehicle height control actuator includes a plurality of bushes. The vehicle height control actuator is connected to the wheel side member and the vehicle body side member via a bush. For this reason, the operation of the vehicle height control actuator causes the bush and the like to be elastically deformed, thereby changing the vehicle height. However, since the bush or the like is made of rubber or the like, it becomes harder and harder to be elastically deformed when the temperature is low than when it is high. Therefore, for example, in up control, which is vehicle height control for increasing vehicle height, when the temperature is low, the actual change amount approaches the target change amount and the vehicle height control valve is closed compared to when the temperature is high. A large amount of pressure medium is supplied to the vehicle height control actuator, and the pressure of the pressure medium accommodated in the vehicle height control actuator at the time when the vehicle height control valve 26 is closed becomes higher. Thereafter, the bush or the like is elastically deformed, the vehicle height is increased, the pressure is decreased, and an overshoot occurs. The amount of overshoot, which is the magnitude of this overshoot, becomes larger when the temperature is low than when it is high.

  From the above, in this vehicle height control system, the control target change amount is determined based on the temperature. For example, when the temperature is low, the control target change amount is determined to be a smaller value than when it is high. As a result, the difference between the actual change amount and the true target change amount due to overshoot caused by the suspension bush becoming hard at low temperatures can be reduced.

It is a circuit diagram showing the vehicle height control system which concerns on Example 1 of this invention. It is a figure showing the periphery of the vehicle height control actuator of the said vehicle height control system. It is a conceptual diagram showing the periphery of vehicle height control ECU of the said vehicle height control system. It is a figure showing the state in which the down control which makes vehicle height low is performed in the said vehicle height control system. It is a figure showing the state in which the up control which raises vehicle height is performed in the said vehicle height control system. It is a flowchart showing the vehicle height control program memorize | stored in the memory | storage part of the said vehicle height control ECU. 3 is a map conceptually showing a correction value determination table stored in the storage unit. It is a figure showing the change of the vehicle height when vehicle height control is performed in the said vehicle height control system. In the vehicle height control system which concerns on Example 2 of this invention, it is a figure showing the change of the vehicle height and cylinder pressure when vehicle height control is performed. It is a figure showing the relationship between the variable L (T) memorize | stored in the memory | storage part of the said vehicle height control system, and temperature. It is a map showing the correction value determination table memorize | stored in the memory | storage part of the vehicle height control system which concerns on Example 3 of this invention. It is a figure showing the change of the vehicle height with respect to temperature when vehicle height control is performed in the conventional vehicle height control system. It is a figure showing the change of the vehicle height with respect to the tank pressure at the time of vehicle height control being performed in the conventional vehicle height control system. It is a figure which shows the relationship between temperature and hysteresis width when vehicle height control is performed in the conventional vehicle height control system.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, a vehicle height control system according to an embodiment of the present invention will be described in detail with reference to the drawings. In the vehicle height control system, air is used as a pressure medium.

In the vehicle height control system according to the present embodiment, as shown in FIGS. 1 and 2, the suspension arms 4FL, FR, RL, RR and the vehicle body 3 are arranged at the respective wheels 2FL, FR, RL, RR on the left and right and the front and rear of the vehicle. Are respectively provided in parallel with air cylinders 8FL, FR, RL, RR and shock absorbers 10FL, FR, RL, RR as vehicle height control actuators and suspension springs (not shown).
Hereinafter, in the present specification, when it is necessary to distinguish the above-described air cylinder 8, shock absorber 10, and the like by the position of the wheel 2, symbols FL, FR, RL, and RR representing the position of the wheel 2 are attached. However, when it is not necessary to distinguish between the positions of the wheels 2, and when representing a generic name, the symbols FL, FR, RL, RR, etc., representing the positions of the wheels 2 are omitted.

  For example, the suspension arm 4 is connected to the wheel 2 via a ball joint and to the vehicle body 3 via a rubber bush 3X. The shock absorber 10 includes an absorber main body and an absorber piston. The absorber main body is attached to the suspension arm 4 via a rubber bush 4X. It is attached via a rubber bush 3Y.

Each of the air cylinders 8 includes the cylinder body 11, a diaphragm 12 fixed to the cylinder body 11, and an air piston 14 provided on the diaphragm body of the diaphragm 12 and the shock absorber 10 so as not to be relatively movable in the vertical direction. These interiors serve as an air chamber 19 as a pressure medium chamber.
The air piston 14 is moved up and down relative to the cylinder body 11 by supplying and discharging air in the air chamber 19, whereby the absorber body and the absorber piston are moved up and down relatively in the shock absorber 10. The vehicle height, which is the distance between the suspension arm 4 and the vehicle body 3, is changed.

  As described above, the shock absorber 10 is attached to the suspension arm 4 and the vehicle body 3 via the rubber bushes 4X and 3Y, and the suspension arm 4 is connected to the vehicle body 3 via the rubber bush 3X. Therefore, when the vehicle height is changed, the rubber bushes 3X, 3Y, 4X and the like are also deformed.

  An air supply / discharge device 24 as a pressure medium supply / discharge device is connected to the air chamber 19 of the air cylinder 8 via an individual passage 20 and a common passage 22, respectively. Each individual passage 20 is provided with a vehicle height control valve 26. The vehicle height control valve 26 is a normally closed electromagnetic valve, and is opened and closed by controlling the current supplied to the solenoid. In the open state, bidirectional air flow is allowed, and in the closed state where no current is supplied to the solenoid, the air flow from the air chamber 19 to the common passage 22 is blocked. When the pressure is higher than the set pressure, the air flow from the common passage 22 to the air chamber 19 is allowed.

The air supply / discharge device 24 includes a compressor device 30, an exhaust valve 32 as a discharge valve, a tank 34, a switching device 36, an intake valve 44, a relief valve 46, and the like.
The compressor device 30 includes a compressor 40 and an electric motor 42 that drives the compressor 40, and the compressor 40 is operated by driving the electric motor 42. When the discharge pressure of the compressor 40 increases, air is released to the atmosphere through the relief valve 46.
The tank 34 accommodates air in a pressurized state, and when the amount of air accommodated increases, the tank pressure, which is the pressure of the accommodated air, increases.

The switching device 36 is provided between the common passage 22, the tank 34, and the compressor device 30, and switches the air flow direction and the like therebetween. As shown in FIG. 1, the common passage 22 and the tank 34 are connected by a first passage 50 and a second passage 52 provided in parallel to each other, and two circuit valves 61, 62 is provided, and two circuit valves 63 and 64 are provided in the second passage 52 in series. A third passage 65 is connected between the two circuit valves 61 and 62 of the first passage 50, connected to the intake side portion 40 a of the compressor 40, and between the two circuit valves 63 and 64 of the second passage 52. In addition, a fourth passage 66 connected to the discharge side 40b of the compressor 40 is connected.
The circuit valves 61 to 64 are normally closed electromagnetic valves, and are opened and closed by controlling the current supplied to the solenoid. In the open state in which current is supplied to the solenoids of the circuit valves 61 to 64, bidirectional air flow is allowed, and in the closed state in which no current is supplied to the solenoid, air flow from one side to the other side is blocked. However, when the pressure on the other side becomes higher than the pressure on one side by a set pressure or more, the flow of air from the other side to the one side is permitted.
The circuit valves 61 and 63 prevent the outflow of air from the tank 34 in the closed state, and the circuit valve 62 prevents the outflow of air from the common passage 22 in the closed state. Reference numeral 64 denotes a supply of air to the common passage 22 in the closed state.

An intake valve 44 is provided between the connection portion 65s of the third passage 65 and the atmosphere. The intake valve 44 is a check valve that is closed when the air pressure at the connecting portion 65s is equal to or higher than the atmospheric pressure, and is opened when the pressure is lower than the atmospheric pressure. When the pressure of the air at the connection portion 65 s becomes lower than the atmospheric pressure by the operation of the compressor 40, the air is sucked from the atmosphere through the filter 43 and the intake valve 44.
The exhaust valve 32 is connected to the connection portion 66 s of the fourth passage 66. The exhaust valve 32 is a normally closed solenoid valve, and in the opened state, the discharge of air from the fourth passage 66 to the atmosphere is allowed, and in the closed state, the discharge of air from the fourth passage 66 to the atmosphere is prevented. However, when the pressure of the air in the fourth passage 66 is lower than the set pressure by the atmospheric pressure, the supply of air from the atmosphere to the fourth passage 66 is permitted.
In addition, a dryer 70 and a flow suppression mechanism 72 are provided in series at a portion closer to the second passage than the connection portion 66 s of the fourth passage 66. The flow suppressing mechanism 72 includes a differential pressure valve 72v and a throttle 72s provided in parallel with each other. The differential pressure valve 72v blocks the flow of air from the second passage side to the compressor side. When the pressure on the compressor side becomes higher than the pressure on the second passage side by a set pressure or more, the air pressure from the compressor 40 to the second passage 52 is reduced. Allow flow.

  In this embodiment, the vehicle height control system is controlled by a vehicle height control ECU 80 mainly composed of a computer. The vehicle height control ECU 80 can communicate with another ECU or the like via a CAN (Controller Area Network) 82. As shown in FIG. 3, the vehicle height control ECU 80 includes an execution unit 80c, a storage unit 80m, an input / output unit 80i, a timer 80t, and the like. The input / output unit 80i includes a temperature sensor 82, a vehicle height changeover switch 88, a tank. A pressure sensor 90, a cylinder pressure sensor 91, a vehicle height sensor 93, a boarding / alighting related motion detection device 95, and the like are connected, and a communication device 96, an ignition switch 98, and the like are connected via a CAN 82. In addition, the electric motor 42 is connected via the drive circuit 100, and the exhaust valve 32, the vehicle height control valve 26, and the solenoids of the circuit valves 61 to 64 are connected.

The temperature sensor 82 detects the temperature of the outside air and can be provided, for example, in a trunk room. The temperatures of the bushes 3X, 3Y, 4X, etc. can be estimated to be substantially the same as the outside air temperature detected by the temperature sensor 82. The vehicle height changeover switch 88 is operated by the driver, and is operated when instructing to change the vehicle height to any one of L (Low), N (Normal), and H (High). The The tank pressure sensor 90 detects the tank pressure, and the cylinder pressure sensor 91 is provided in the common passage 22, and when the vehicle height control valve 26 is opened, the vehicle height control valve 26 (wheel) is opened. The cylinder pressure which is the pressure of the air chamber 19 of the corresponding air cylinder 8 is detected. Further, when all the vehicle height control valves 26 are closed, the air pressure in the common passage 22 is detected. The vehicle height sensor 93 is provided for each of the front, rear, left and right wheels, and detects the vehicle height. The getting-on / off-related operation detecting device 95 detects the presence / absence of an action related to getting on / off, and is provided corresponding to each of a plurality of doors provided in the vehicle, and detects a door opening / closing sensor ( A courtesy lamp sensor) 102, a door lock sensor 103 for detecting the lock and unlock of each of the plurality of doors, and the like. Based on the presence / absence of door opening / closing, door locking / unlocking operations, etc., the intention of getting on, getting off, or starting is estimated. The communication device 96 communicates with the portable device 104 possessed by the driver or the like within a predetermined communicable area, and the door may be locked or unlocked by communication. .
In addition, the vehicle height control system and the like in the present embodiment can be operated by the power of the battery 110. The voltage of the battery 110 is detected by the voltage monitor 112, and the voltage monitor 112 is connected to the vehicle height control ECU 80.

  In the vehicle height control system according to the present embodiment, the actual change amount ΔH * that is the change amount of the actual vehicle height H * that is the actual vehicle height for each of the front, rear, left, and right wheels detected by the vehicle height sensor 93 is obtained. The air supply / discharge device 24 and the vehicle height control valve 26 are controlled so as to approach the true target change amount ΔHrefa, which is the target value of the vehicle height change amount determined by the vehicle height control. Done. The true target change amount ΔHrefa is acquired as the difference between the true target vehicle height Hrefa, which is the target vehicle height determined by the vehicle height control, and the actual vehicle height H * 0 at the time when the vehicle height control is started. The true target vehicle height Hrefa is a height that satisfies the original requirements for vehicle height control. For example, when (a) the vehicle height is determined based on the running state of the vehicle, (b) the vehicle height changeover switch 88 Or (c) a predetermined height (for example, a height that facilitates getting on and off). Depending on the vehicle height control, the true target change amount ΔHrefa may be determined.

  (D) When the difference between the target vehicle height determined based on the running state and the actual vehicle height (true target change amount) is equal to or greater than the set value, (e) the vehicle height instructed by the operation of the vehicle height changeover switch 88 When the difference between the target vehicle height and the actual vehicle height (true target change amount) is greater than or equal to the set value, (f) When a predetermined boarding / exiting condition is established, such as when a person's boarding / exiting is estimated, etc. When the vehicle height control start condition is satisfied, the vehicle height control is started.

For example, when down control, which is vehicle height control for lowering the vehicle height, is performed, as shown in FIG. 4, the compressor 40 is operated by driving the electric motor 42, the circuit valves 61 and 64 are closed, and the circuit valves are closed. 62 and 63 are opened, and the vehicle height control valve 26 corresponding to the wheel to be controlled is opened. Air is discharged from the air chamber 19 of the air cylinder 8 of the wheel to be controlled (the case where the four wheels on the front, rear, left and right are the wheels to be controlled in FIG. 4 is the same as the wheel to be controlled) is supplied to the tank 34. Is done.
Further, when up control, which is vehicle height control for increasing the vehicle height, is performed, as shown in FIG. 5, the circuit valves 61 to 64 are opened and the vehicle height control valve 26 corresponding to the wheel to be controlled is used. Is open. The air stored in the tank 34 is supplied to the air chamber 19 of the air cylinder 8 of the wheel to be controlled. Thereby, the vehicle height about a control object wheel becomes high.

  On the other hand, the vehicle height is changed with elastic deformation of the bushes 3X, 3Y, 4X and the like. However, the bushes 3X, 3Y, 4X, etc. are made of rubber or the like. Since the bushes 3X, 3Y, and 4X are harder when the temperature is low than when the temperature is high, the bushes 3X, 3Y, and 4X are not easily deformed and the vehicle height is difficult to change. As a result, in the up-control, when the temperature is low, the actual change amount ΔH * approaches the true target change amount ΔHrefa more than when the temperature is high, and the air chamber 19 is closed until the vehicle height control valve 26 is closed. The cylinder pressure increases when air is supplied and the vehicle height control valve 26 is closed. Thereafter, the bushes 3X, 3Y, 4X, etc. are deformed until they match the cylinder pressure. Although the vehicle height increases and the cylinder pressure decreases, the overshoot amount ΔHo, which is the amount by which the vehicle height increases, becomes larger when the temperature is low than when it is high, as shown in FIG.

Further, in the up control, as shown in FIG. 5, the tank 34 and the air cylinder 2 of the wheel to be controlled are communicated. When the tank pressure is high, the flow rate of air supplied to the air cylinder 2 is larger than when the tank pressure is low, the actual change amount ΔH * in the up control approaches the true target change amount ΔHrefa, and the vehicle height control valve 26 is closed. At this point, the cylinder pressure tends to increase. Therefore, as shown in FIG. 13, the overshoot amount (ΔHo1) when the tank pressure is high is larger than the overshoot amount (ΔHo2) when the tank pressure is low (ΔHo1> ΔHo2).
Thus, when an overshoot occurs, the difference between the actual change amount ΔH * and the true target change amount ΔHrefa increases. As a result, control hunting occurs or the number of times the auto leveling function is activated increases.

  From the above, in the present embodiment, in the up control, the vehicle height control valve 26 is closed when the actual change amount ΔH * approaches the control target change amount ΔHrefs smaller than the true target change amount ΔHrefa. It was to so. The control target change amount ΔHrefs is a target change amount used in vehicle height control. In the present embodiment, a value obtained by subtracting the correction value Ha determined based on the overshoot amount from the true target change amount ΔHrefa. (ΔHrefs = ΔHrefa−Ha).

The correction value Ha is a value determined based on the overshoot amount, that is, the temperature and the tank pressure. In this embodiment, the overshoot amount when the temperature and the tank pressure are changed is acquired in advance by simulation or actual measurement. Then, the correction value Ha is set based on the acquired overshoot amount, and the correction value determination table shown in FIG. 7 is created and stored in the storage unit 80m of the vehicle height control ECU 80.
As shown in FIG. 7, the correction value Ha is larger when the temperature is low than when it is high, and larger when the tank pressure is high than when it is low. For example, when the tank pressure PT is lower than the set pressure PTs (PT <PTs), the correction value Ha is 0 when the temperature T is 0 ° C. or higher (T ≧ 0 ° C.), and the temperature T is 0 ° C. When the temperature is lower than T1 (0> T ≧ T1), the correction value Ha1 is greater than 0, and when the temperature T is lower than T1 (T <T1), the correction value Ha2 is greater than the correction value Ha1 ( Ha2>Ha1> 0). When the tank pressure PT is equal to or higher than the set pressure PTs (PT ≧ PTs), the correction value is 0 when the temperature T is 0 ° C. or higher, and the temperature T is lower than 0 ° C. and equal to or higher than T1 (0>). When T ≧ T1), the correction value Ha3 is greater than 0. When the temperature T is lower than T1 (T <T1), the correction value Ha4 is greater than the correction value Ha3 (Ha4>Ha3> 0). These correction values Ha1, Ha2, Ha3, and Ha4 are larger than the dead zone width dH as will be described later. The correction values Ha3 and Ha4 when the tank pressure is equal to or higher than the set pressure PTs are larger than the correction values Ha1 and Ha2 when the tank pressure is lower than the set pressure PTs, and the difference between the correction values (Ha4-Ha3 ) Is larger than the difference between correction values (Ha2-Ha1).

The vehicle height control program represented by the flowchart of FIG. 6 is executed at predetermined time intervals.
In step 1 (hereinafter abbreviated as S1. The same applies to other steps), the vehicle height sensor 93 detects actual vehicle heights H * that are actual vehicle heights for the four wheels on the front, rear, left, and right. In step S3, the actual tank pressure PT * is detected by the tank pressure sensor 90. In step S3, the actual outside air temperature T * is detected by the temperature sensor 82. Then, in S4, it is determined whether or not the vehicle height control is being performed. If the vehicle height control is not being performed, it is determined in S5 whether or not the vehicle height control start condition is satisfied.

  While the start condition is not satisfied, S1 to S5 are repeatedly executed. When the start condition is satisfied, the determination of S5 is YES, and in S6, the true target change amount ΔHrefa is determined, and S7 The correction value Ha is determined based on the correction value determination table shown in FIG. 7, the tank pressure PT *, and the temperature T *, and the control target change amount ΔHrefs is determined in S8. Thereafter, in S9, a start process is performed, the air supply / discharge device 24 is controlled, the vehicle height control valve 26 of the wheel to be controlled is opened, and the state shown in FIG. 5 is obtained.

Next, S1 to S4 are executed. In S10, it is determined whether or not a vehicle height control termination condition is satisfied. When the actual change amount ΔH *, which is the change amount of the actual vehicle height H *, reaches the range determined by the control target change amount ΔHrefs and the dead band width dH (ΔHrefs + dH ≧ ΔH * ≧ ΔHrefs−dH), that is, the control target When the change amount ΔHrefs is approached, it is determined that the end condition is satisfied.
While the end condition is not satisfied, S1 to 4 and 10 are repeatedly executed. When the end condition is satisfied, the end process is performed in S11, the vehicle height control valve 26 is closed, and the circuit valve 61 is closed. ˜64 are closed.

  As described above, in the present embodiment, the vehicle height control is performed based on the vehicle height change amount, but can be performed based on the vehicle height. For example, the true target vehicle height Hrefa is acquired in S6, and the control target vehicle height Hrefs is acquired in S8. The control target vehicle height Hrefs is a target vehicle height used in vehicle height control, and the vehicle height control valve 26 is closed when the actual vehicle height H * approaches the control target vehicle height Hrefs. In the up control, the formula (1) (ΔHrefa + H * 0 = Hrefa) is established between the true target vehicle height Hrefa and the true target change amount ΔHrefa, and the control target vehicle height Hrefs and the control target change amount Equation (2) (ΔHrefs + H * 0 = Hrefs) holds between ΔHrefs. Further, the equation (3) (ΔHrefs = ΔHrefa−Ha) is established between the control target change amount ΔHrefs and the true target change amount ΔHrefa. By substituting Eqs. (1) and (2) into Eq. (3), the relational expression (Hrefs = Hrefa-Ha) between the target vehicle height for control Hrefs and the true target vehicle height Hrefa is obtained. It is done. As described above, the determination of the control target change amount ΔHrefs corresponds to the determination of the control target vehicle height Hrefs. In S10, it is determined whether or not the actual vehicle height H * is within a range determined based on the control target vehicle height Hrefs and the dead zone width (Hrefs + dH ≧ H * ≧ Hrefs−dH).

FIG. 8 shows changes in vehicle height when the vehicle height control program is executed and up control is performed. The correction value Ha is determined in accordance with the temperature T *, the tank pressure PT *, and the correction value determination table of FIG. 7, and the control target change based on the determined correction value Ha and the target change amount ΔHrefa (target vehicle height Hrefa) An amount ΔHrefs (control target vehicle height Hrefs) is determined.
For example, when the temperature is −30 ° C., the correction value is determined as Ha (−30), and the control target change amount (control target vehicle height) is determined as ΔHrefs (−30) {Hrefs (−30)}. If the temperature is −15 ° C., the correction value is determined as Ha (−15), and the control target change amount (control target vehicle height) is determined as ΔHrefs (−15) {Hrefs (−15)}. When the temperature is 0 ° C., the correction value is determined to be 0, so that the control target change amount (control target vehicle height) is the true target change amount ΔHrefa (true target vehicle height Hrefa). It becomes the same {ΔHrefa = ΔHrefs (0), Hrefa = Hrefs (0)}. The target change amount for control (target vehicle height for control) is the order of ΔHrefs (-30), ΔHrefs (-15), ΔHrefs (0) {Hrefs (-30), Hrefs (-15), Hrefs (0)}. growing. When the actual change amount ΔH * (the actual vehicle height H *) during the up-control approaches the control target change amount (control target vehicle height) ΔHrefs (Hrefs), the vehicle height control valve 26 is closed. However, as shown in FIG. 8, the actual change amount ΔH * (actual vehicle height H *) is brought closer to the true target change amount (true target vehicle height) ΔHrefa (Hrefa) by overshooting thereafter. Can do. As a result, it is possible to suppress control hunting, reduce the number of times the auto leveling function is activated, and the like.

  As described above, in this embodiment, the vehicle height sensor 93, the tank pressure sensor 90, the temperature sensor 82, the part storing the correction value determination table of FIG. 7 of the vehicle height control ECU 80, the vehicle represented by the flowchart of FIG. A vehicle height control unit is configured by a part for storing a high control program, a part for executing, etc., and a supply / discharge control unit is configured by a part for storing S11, a part for executing, etc., and the correction value determination table of FIG. The target change amount determining unit is composed of a part for storing S, a part for storing S2, 3, 7, 8 and a part for executing.

In the flowchart of FIG. 6, the steps S7 and S8 can be executed even when the determination in S4 is YES. In this case, the control target change amount ΔHrefs can be changed with changes in temperature or tank pressure during control.
In the correction value determination table, the correction value when the temperature is 0 ° C. or higher is set to 0. However, the correction value when the temperature is 0 ° C. or higher can be set to a value larger than 0. Further, the correction value may be a value that continuously changes as the temperature changes.
In the down control, as in the up control, the control target change amount is set based on the overshoot, and the vehicle height control valve 26 is closed when the actual change amount approaches the control target change amount. Can be done.

In the present embodiment, vehicle height control is performed based on the vehicle height. Further, the control target vehicle height Hrefs is determined based on the hysteresis of the change between the vehicle height and the cylinder pressure.
An example of changes in vehicle height and cylinder pressure is shown in FIG. FIG. 9 shows the vehicle height control valve 26 when the actual vehicle height H *, which is the actual vehicle height, approaches the true target vehicle height Hrefa at each of −30 ° C., −15 ° C., 0 ° C., and 20 ° C. A change in the actual vehicle height H * and the cylinder pressure Pc when closed is shown.

In the up control, the cylinder pressure Pc increases as the air is supplied to the air chamber 19 and the vehicle height H * increases. For example, when the temperature is −15 ° C., the point P (−15) is reached. When the actual vehicle height H * approaches the true target vehicle height Hrefa, the vehicle height control valve 26 is closed. However, thereafter, the vehicle height H * further increases, the cylinder pressure Pc decreases, and reaches the point Q (−15). Then, down control is performed and air is allowed to flow out of the air chamber 19, whereby the cylinder pressure Pc decreases and the vehicle height H * decreases. When the temperature is −30 ° C., the vehicle height control valve 26 is closed when the point P (−30) is reached and the actual vehicle height H * approaches the true target vehicle height Hrefa. Until the point Q (-30) is reached, the vehicle height H * increases and the cylinder pressure Pc decreases. The ratio of the change amount of the cylinder pressure to the change amount of the vehicle height after the vehicle height control valve 26 is closed until the vehicle height and the cylinder pressure are balanced (portion between the points P to Q) (gradient of the graph) ) -K (cylinder pressure change amount ΔPc / vehicle height change amount ΔH) is known to be substantially constant regardless of the temperature, as shown in FIG.
9 and 14 that the hysteresis is larger when the temperature is low than when the temperature is high.

The point Q at which the cylinder pressure Pc and the vehicle height H * are balanced includes the load Fp applied to the wheel, the force F (Pc) corresponding to the cylinder pressure, the elastic force F (S) of the suspension spring, and the elastic force F of the bush. This is the point where the resultant force of (V) is almost the same.
Fp = F (Pc) + F (S) + F (V)
As the vehicle height increases, the elastic force of the suspension spring and the elastic force of the bush decrease, and the cylinder pressure increases. Therefore, theoretically, the above equation is established when the vehicle height and the cylinder pressure are located on the thin line A in FIG.

  For example, the point where the true target vehicle height Hrefa and the cylinder pressure Pc are balanced is the point B where the line (thin alternate long and short dash line L) representing the vehicle height Hrefa and the thin line A intersect. That is, the vehicle height Hrefa at point B and the cylinder pressure PcB are balanced. Then, a straight line having a slope of −K (thin broken line E) is drawn through the point B, and the broken line E and a line indicating a change in the cylinder pressure and the vehicle height when the temperature is −15 ° C. (thick dashed line) ) Is the point where the up control is terminated. That is, when up control is started and the vehicle height control valve 26 is closed when the intersection C is reached, the vehicle reaches the point B due to the subsequent increase in vehicle height and the decrease in cylinder pressure. is there.

  From the above, in this embodiment, the relationship between the cylinder pressure and the vehicle height, the temperature, the true target vehicle height Hrefa, the thin line A, the broken line E, and the graph representing the relationship between the cylinder pressure and the vehicle height. Then, the intersection point with the broken line E is acquired, and the vehicle height at the intersection point is set as the control target vehicle height Hrefs (−15). When the temperature is −30 ° C., the vehicle height at the intersection D between the broken line E and the graph (thick solid line) representing the relationship between the cylinder pressure and the vehicle height is the control target vehicle height Hrefs (−30). Is done.

In the present embodiment, the correction value Ha corresponds to a value obtained by multiplying the reciprocal (1 / K) of the absolute value K of the inclination −K by the cylinder pressure decrease amount ΔPc. Further, as shown in FIG. 9, the cylinder pressure decrease amount ΔPc is larger when the temperature is low than when it is high, in other words, when the hysteresis is large, it is larger than when it is small. Therefore, in the present embodiment, a value corresponding to the amount of decrease in cylinder pressure ΔPc until reaching point Q from point P, in other words, a value corresponding to hysteresis is obtained in advance as a coefficient L (T), The data was tabulated and stored in the storage unit 80m. An example of this coefficient determination table is shown in FIG. As shown in FIG. 10, the coefficient L (T) has a larger value when the temperature is low and the hysteresis is large than when the temperature is high and the hysteresis is small.
From the above, the correction value Ha is expressed as shown in the following equation,
Ha = L (T) × 1 / K
The target vehicle height for control Hrefs can be obtained according to the following equation.
Hrefs = Hrefa-L (T) × 1 / K

  Thus, in this embodiment, the control target vehicle height Hrefs is set to a value smaller than the true target vehicle height Hrefa by a correction value Ha determined based on hysteresis, and the actual vehicle height H * approaches the control target vehicle height Hrefs. If this happens, the vehicle height control valve 26 is closed. By subsequent overshoot, the actual vehicle height H * approaches the true target vehicle height Hrefa, and the difference between the actual vehicle height H * and the true target vehicle height Hrefa can be reduced.

  In the present embodiment, the control target change amount ΔHrefs is determined to be smaller when the tank pressure is low than when it is high. In other words, the correction value Ha is determined to be larger than when the tank pressure is low and high. When the tank pressure is low, the time required for up-control becomes longer than when the tank pressure is high. Further, when the tank pressure is very low, the actual change amount ΔH * may not be able to approach the control target change amount ΔHrefs. Therefore, when the tank pressure is low, the correction value Ha is increased and the control target change amount ΔHrefs is decreased compared to when the tank pressure is high.

  An example of the correction value determination table in the present embodiment is shown in FIG. In this embodiment, the correction value Ha is determined to be larger when the temperature is low than when it is high, and larger when the tank pressure is low than when it is high. Specifically, when the temperature T is 0 ° C. or higher (T ≧ 0), when the tank pressure PT is equal to or higher than the set pressure PTb (PT ≧ PTb), the correction value is set to 0, and the tank pressure PT is When the pressure is lower than the set pressure PTb (PT <PTb), a correction value greater than 0 is set to Ha5. When the temperature T is lower than 0 ° C. and equal to or higher than T1 (0> T ≧ T1), when the tank pressure PT is equal to or higher than the set pressure PTb, the correction value is set to Ha5 and the tank pressure PT is set to the set pressure PTb. If it is lower, the correction value is set to Ha6 that is larger than Ha5 (Ha5 <Ha6). When the temperature T is lower than the temperature T1 (T <T1), the correction value is set to Ha6 when the tank pressure PT is equal to or higher than the set pressure PTb, and is corrected when the tank pressure PT is lower than the set pressure PTb. The value is assumed to be Ha7 greater than Ha6 (Ha5 <Ha6). The difference between the correction values (Ha6-Ha5) and the difference between the correction values (Ha7-Ha6) are almost the same.

  As described above, in this embodiment, when the tank pressure is low, the correction value is set to a larger value and the control target change amount is set to a smaller value than when the tank pressure is high. As a result, it is possible to satisfactorily avoid that the vehicle height control time becomes long or the control vehicle height is not reached.

  It should be noted that the correction value can be determined to have a magnitude that changes continuously with changes in temperature and tank pressure. It can be carried out in a modified or improved manner.

  3, 4: Bush 8: Air cylinder 19: Chamber 24: Air supply / discharge device 26: Vehicle height control valve 34: Tank 80: Vehicle height control ECU 90: Tank pressure sensor 93: Vehicle height sensor 95: Boarding / alighting related motion detection device 99: Vehicle speed sensor 102: Door open / close sensor 104: Door lock sensor

Patentable invention

The following paragraphs describe the claimed invention.
(1) a vehicle height control actuator provided corresponding to a vehicle wheel;
A pressure medium supply / discharge device for supplying a pressure medium to the vehicle height control actuator or discharging the pressure medium from the vehicle height control actuator;
A vehicle height control valve provided between the pressure medium supply / discharge device and the vehicle height control actuator;
A vehicle height control unit that controls the vehicle height of the wheels by controlling the supply and discharge of the pressure medium in the vehicle height control actuator by the control of the vehicle height control valve and the pressure medium supply / discharge device. A vehicle height control system,
In the state where the vehicle height control unit supplies or discharges the pressure medium to the vehicle height control actuator under the control of the pressure medium supply / discharge device, an actual change amount that is an actual vehicle height change amount is: Based on the temperature of the outside air, the supply / discharge control unit that closes the vehicle height control valve when the vehicle approaches a control target change amount smaller than the target change amount in the vehicle height control, and the control target change amount A vehicle height control system including a target change amount determination unit determined by
In the vehicle height control system described in this section, (a) the vehicle height control valve is closed when the actual change amount, which is the change amount of the actual vehicle height in vehicle height control, approaches the control vehicle height change amount. (B) In up control, the vehicle height control valve is closed when the actual vehicle height, which is the actual vehicle height, approaches the target vehicle height for control that is lower than the true target vehicle height. Vehicle height control system, and (c) vehicle height control system in which the vehicle height control valve is closed when the actual vehicle height approaches the target vehicle height for control higher than the true target vehicle height. It is.

(2) The vehicle height control system according to (1), wherein the target change amount determination unit determines the control target change amount to a value smaller than that when the temperature is low and high.

(3) The pressure medium supply / discharge device includes a tank that pressurizes and stores the pressure medium, and the target change amount determining unit further stores the control target change amount in the tank. The vehicle height control system according to (1) or (2), wherein when the tank pressure that is the pressure of the tank is high, the value is determined to be smaller than when the tank pressure is low.
When the temperature is the same, the control target change amount is determined to be smaller when the tank pressure is higher than when the tank pressure is low.

(4) When the target change amount determination unit determines that the control target change amount has a large hysteresis of change between the actuator pressure that is the pressure of the pressure medium accommodated in the vehicle height control actuator and the vehicle height. The vehicle height control system according to any one of items (1) to (3), which is determined to be a smaller value than when it is smaller.

(5) The pressure medium supply / discharge device includes a tank that pressurizes and stores the pressure medium, and the vehicle height control unit determines the control target change amount by the pressure of the pressure medium stored in the tank. The vehicle height control system according to any one of items (1) to (4), including a tank pressure shortage determining unit that determines a smaller value when a certain tank pressure is low than when it is high.
When the tank pressure is low, the time required to bring the actual change amount closer to the target change amount becomes longer due to insufficient tank pressure. Further, it may be difficult to bring the actual change amount close to the target change amount. Therefore, in the vehicle height control system described in this section, when the tank pressure is low, the control target vehicle height is set to a lower value than when the tank pressure is high, and the time required for vehicle height control can be made difficult to become longer.

Claims (1)

A vehicle height control actuator provided corresponding to the vehicle wheel;
A pressure medium supply / discharge device for supplying a pressure medium to the vehicle height control actuator or discharging the pressure medium from the vehicle height control actuator;
A vehicle height control valve provided between the pressure medium supply / discharge device and the vehicle height control actuator;
A vehicle height control unit that controls the vehicle height of the wheels by controlling the supply and discharge of the pressure medium in the vehicle height control actuator by the control of the vehicle height control valve and the pressure medium supply / discharge device. A vehicle height control system,
In the state where the vehicle height control unit supplies or discharges the pressure medium to the vehicle height control actuator under the control of the pressure medium supply / discharge device, an actual change amount that is an actual vehicle height change amount is: Based on the temperature of the outside air, the supply / discharge control unit that closes the vehicle height control valve when the vehicle approaches a control target change amount smaller than the target change amount in the vehicle height control, and the control target change amount A vehicle height control system including a target change amount determination unit determined by

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