JPH0386612A - Control for height control system - Google Patents

Abstract

PURPOSE:To prevent the erroneous operation during traveling by carrying out the ground clearance adjustment by the switch operation only in stop state, in the height control for a truck, etc. CONSTITUTION:A controller 34 is installed onto a controller 3, and is connected with a down switch 35, up switch 36, pressure switches 37 and 38, and a driving circuit for a motor 19 of a hydraulic pump 2. Each signal of a car speed sensor 39, a parking brake sensor 40, and an engine revolution speed sensor 41 is inputted into the controller 34, and the ground clearance is adjusted. At this time, the lowering of a load carrying platform is permitted, only in the case when a car stops and the engine is in revolution, and if the vehicle starts traveling in the state where the load carrying platform is at a lower position, the load carrying platform is returned to a normal height independently of the operation of the up switch 36. With this constitution, safety can be improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of controlling a vehicle height adjustment device installed in an automobile.

[Conventional technology]

For example, in the case of a truck with a loading platform at the rear of the vehicle,
Since the height of the cargo bed is generally relatively high, it is not so easy to load and unload heavy cargo, and this is especially true for large vehicles. For this reason, there are low deck type trucks that have smaller tires and lower loading platform height. However, in the case of such a vehicle, since the ground clearance is low, problems arise such as the possibility that the vehicle will come into contact with four objects when driving on an uneven road.

[Question B that the invention attempts to solve]

Therefore, the above problem can be solved by providing a vehicle height adjustment device that can raise and lower the loading platform so that the height of the loading platform can be lowered when necessary, and the height of the loading platform can be returned to the normal position during driving. In this case, the vehicle height adjustment device is provided with a control means and an operation switch composed of a microcomputer, etc., and is configured so that the height of the cargo platform can be adjusted as necessary by operating the switch. be done. However, such a vehicle height adjustment device has the following problems. Raising and lowering the cargo platform while the vehicle is running is not desirable from a safety standpoint. However, while driving, the user may accidentally touch the switch. Therefore, in the case of the vehicle height adjustment device described above, it is necessary to take safety measures to prevent the loading platform from being raised or lowered inadvertently during driving. Generally, the on/off state of a switch is determined according to the type of signal sent to the control means. For example, when the switch is on, the LO14 signal is input, and when the switch is off, the old Gll signal is input. Ru. However, in such a case, if a short-circuit failure occurs in the switch while the LOW signal is being input, a situation may arise in which the cargo platform starts moving by itself.
This is because the switch is mistakenly recognized as being turned on. In this case, if the above-mentioned safety measures are taken, at least the inconvenience of the cargo platform moving by itself during travel can be prevented. However, even if the above safety measures are taken,
If a short-circuit failure occurs in the switch for some reason while the vehicle is running, the platform will automatically start lowering when the vehicle is stopped temporarily, such as waiting at a traffic light. This is because, if the conditions for the loading platform stop state are correct, the control means will operate the device in response to the above-mentioned O■ signal from the switch. The present invention was devised under the above-mentioned circumstances, and when applied to a trunk car, for example, the present invention provides a vehicle height structure that allows the height of the cargo platform to be changed as necessary by operating a switch. In the adjustment device, a control method configured to prevent the device from being activated accidentally during driving due to an erroneous operation of a switch and causing the loading platform to lower, or from being activated automatically due to a short-circuit failure of the switch. Its purpose is to provide.

[Means to solve the problem]

the above! ! In order to solve the problem, the present invention takes the following technical measures. First, the invention according to claim 1 of the present application provides a vehicle height adjustment device that includes a control means and is configured to adjust the vehicle height by operating a switch electrically connected to the control means. The vehicle is characterized in that the vehicle height can be adjusted by operating the switch only when the vehicle is stopped. Further, the invention according to claim 2 of the present application is characterized in that, when the control means detects a change from an off signal to an on signal of the switch, the control means is set to recognize that the switch is on. .

[Operation and effects of the invention]

The vehicle height can be adjusted as necessary by operating a switch, but in the case of the present invention, even if the switch is turned on, the device does not operate when the vehicle is not stopped. Even if you accidentally touch the switch, the device will not operate inadvertently and lower the vehicle height, and the switch will not cause a short-circuit failure when the switch is turned on manually. Even if the vehicle is running, the device will not operate automatically while driving. Further, in the case of the invention described in claim 2, the control means is configured to recognize that the switch has been turned on when detecting a change from an off signal to an on signal of the switch. Therefore, if the switch is short-circuited for some reason while driving, there will be no inconvenience such as the device operating automatically and the vehicle body starting to lower when the vehicle is stopped.
Even if the vehicle is stopped, the signal from the switch remains on and if there is no change,
This is because the control means does not operate the hydraulic pump or hydraulic cylinder. As described above, in the present invention, in a device that adjusts vehicle height by operating a switch, the device may be activated inadvertently due to erroneous operation of the switch while driving, or the device may be activated automatically due to a short circuit failure of the switch. can be prevented,
Safety can be increased.

[Explanation of Examples]

Embodiments of the present invention will be specifically described below with reference to the drawings. This example shows an example in which the present invention is applied to a vehicle height adjustment device configured as a cargo height adjustment device for a truck vehicle. The loading platform height adjustment device is provided below the loading platform at the rear of the vehicle. As shown in FIGS. 4, 5, and 8, this device includes a hydraulic cylinder 1 interposed between a vehicle body and an unsprung member, a hydraulic pump 2 that drives this hydraulic cylinder 1, A control means 3 for controlling the drive of the hydraulic pump 2 is provided. In the case of this example, the hydraulic cylinder 1 is constructed by using the shock absorber of the rear suspension, and as described later, it functions as the original shock absorber during normal times and raises and lowers the cargo platform when adjusting the vehicle height. Function as an actuator. The shock absorber in this example is of a twin tube type, as shown in FIG. A piston rod 8 which has a slidably disposed piston 6 at its lower end and whose upper end protrudes from the upper part of the cylinder is connected to, for example, a vehicle body frame 7, and an outer shell which surrounds the cylinder 5 and forms a reservoir chamber 9. A tube 10 is provided. Piston upper chamber 11 and piston lower chamber 1 in the cylinder 5
2 is communicated with the piston 6 through a passage 13 provided at the lower end of the piston rod 8, and oil is communicated with the passage 13, the lower end of the piston rod 8, and the piston 6. The piston upper chamber 1 is passed through the axial hole 14 and the orifice 44 at the lower end of the piston.
1 and the piston lower chamber 12. Furthermore, in the case of this example, the piston 6 is provided with a check valve 15 that only allows oil to flow from the piston lower chamber 12 to the piston upper chamber 11. Furthermore, a base valve portion 16 is provided at the lower end of the cylinder 5 to partition the lower piston chamber 12 and the reservoir chamber 9. As shown in FIG. 8, the base valve portion 16 is provided with an orifice 17 and a check valve 18 that only allows oil to flow from the reservoir chamber 9 to the lower piston chamber 12. Therefore, in the extension stroke in which the piston rod 8 moves upward, the piston During the contraction stroke in which the rod 9 moves downward, a damping force is generated due to the flow resistance when oil flows from the piston lower chamber 12 through the orifice 17 to the reservoir chamber 9. Furthermore, in this example, the shock absorbers of the left and right suspensions are both used as the hydraulic cylinder l. On the other hand, the hydraulic pump 2 uses a motor 19 that drives the pump and an oil tank 20 that are integrated, and is attached to a cross member 21 that extends in the vehicle width direction between the left and right frames. There is. The hydraulic pump 2 sends oil to the hydraulic cylinder 1, which is originally a shock absorber, and transfers the oil to the vehicle body (
As shown in Figs. 4, 5, and 8, it is connected to the left and right hydraulic cylinders 1.1 through hoses 22 and 22, respectively. has been done. When the hydraulic pump 2 is driven in the normal direction, oil is sucked up from the oil tank 20 through the oil passage 27 into the piston upper chamber 11 of the hydraulic cylinder 1, and when the hydraulic pump 2 is driven in the reverse direction, it is sucked from the piston upper chamber 11 side. Oil is discharged into the oil tank 20 via the oil passage 28. Further, the motor 19 that drives the pump is connected to an alternator or panteri,
It is powered by these sources and operated. The connection between the hydraulic cylinder 1 and the hose 22 is such that the hose 22 is connected to an oil boat 23 provided at the upper end of the piston rod 8.
This is done by connecting to. Further, the piston rod 8 has an upper end connected to the oil boat 23,
An oil hole 24 is formed whose lower end extends in the axial direction following the axial hole I4 formed at the lower end of the piston rod. In this example, as shown in FIGS. 6 and 7, a pilot is provided at the bottom of the oil hole 24 to cut off communication between the piston upper chamber 11 and the piston lower chamber 12 when the hydraulic pressure supplied from the hydraulic pump 2 is generated. A valve 25 is incorporated. This viroft valve 25 has a valve body 26 that is slidably inserted into the oil hole 24 and urged upward by a compression coil spring 43. When the valve body 26 is moved downward against the spring force by the hydraulic pressure supplied from the hydraulic pump 2, it cuts off the communication between the piston upper chamber 11 and the piston lower chamber 12, and also cuts off the communication between the piston upper chamber 11 and the piston upper chamber 12. The hydraulic cylinder 1 is made to function as an actuator. That is, when oil is sent from the hydraulic pump 2 through the hose 22 into the oil hole 24 of the piston rod 8, the oil pressure causes the valve body 26 to move downward from the passage 13 as shown by the imaginary line in FIG. Being pushed down. This results in
The passage 13 is substantially closed and the piston upper chamber 11 and the piston lower chamber 12 are in a non-communicating state, and the oil sent from the hydraulic pump 2 is transferred to the oil hole 24 and the oil hole 24.
a gap between the inner periphery of the valve body 26 and the small-diameter Rondo portion 26a of the valve body 26;
Therefore, at this time, the piston 6 and the piston loft 8 are forcibly pushed down by the hydraulic pressure in the piston upper chamber 11, so the loading platform is pulled down and its height is increased. can be lowered. The hydraulic cylinder 1, which is interposed between the vehicle body and the unsprung member and whose upper end portion of the piston rod 8 is connected to the vehicle body (loading platform) side, applies pressure to the suspension spring 32 in the vertical direction.
This is because the piston rod 8 is moved downward while deforming the vehicle body (loading platform). On the other hand, the hydraulic pump 2 is driven in reverse and the piston upper chamber 1
When the oil in 1 is returned to the oil tank 20 side, the piston loft 8 and the loading platform are moved upward while receiving the elastic restoring force of the suspension spring 32 that has been compressed and deformed. Therefore, the height of the loading platform returns to the normal height. Also,
At this time, due to the pressure drop in the oil hole 24 of the piston rod 8, the valve body 26 of the viroft valve 25 is returned by the spring force to the passage unblocked position as shown by the solid line in FIGS. Since the chamber 11 and the piston lower chamber 12 communicate with each other via the passage 13, the hydraulic cylinder 1 can function as an original shock absorber. Note that the oil passage connecting the hydraulic pump 2 and the hydraulic cylinder 1 (
As shown in FIG. 8, an operating check valve 29 is provided on the hose 22), which is connected to the oil line 28 through a pilot line 30 when oil is discharged from the hydraulic pump 2 to the oil tank 20. It is being The operating check valve 29 allows oil to be sent to the hydraulic cylinder 1 side when the hydraulic pump 2 is driven in normal rotation,
It also functions as a check valve to prevent backflow of oil when the hydraulic pump 2 is driven in normal rotation and when stopped. Therefore, after oil is sent into the piston upper chamber 11 and the piston rod 8 is moved downward to lower the loading platform, the hydraulic pump 2
Even when the piston is stopped, the hydraulic pressure that can maintain the height of the loading platform against the spring force of the suspension spring 32 can be maintained in the upper piston chamber 11. On the other hand, when the hydraulic pump 2 is driven in reverse and oil is discharged from the hydraulic pump 2 to the oil tank 20 via the oil passage 28, the oil pressure in the oil passage 28 is due to the influence of the throttle 31 provided on the oil passage 28. rises, and the oil pressure acts as a biloft pressure that causes the operating check valve 29 to open via the pilot line 30. Therefore, when the hydraulic pump 2 is driven in reverse, oil can be sucked from inside the piston upper chamber ll of the hydraulic cylinder 1 and discharged into the oil tank 20. In addition, since it is generally difficult to achieve a perfect seal between the piston 6 and the cylinder 5, when oil is being fed into the piston upper chamber 11 by the hydraulic pump 2, the pressure in the piston upper chamber 11 increases. If there is a significant increase in
In the event that oil may leak from the piston upper chamber 11 to the piston lower chamber 12,
A problem arises in that the internal pressure of the hydraulic cylinder 1, which is a shock absorber, in its natural state fluctuates. Therefore,
In this example, when oil leaks from the piston upper chamber II to the piston lower chamber 12, a return hose 3 is used to recover the oil from the reservoir chamber 9 to the oil tank 20.
3 between the hydraulic cylinder 1 and the oil tank 20, the above problem can be prevented from occurring. Further, the hydraulic pump 2 is controlled by a control means 3,
Thereby, the vehicle height adjustment mode in which the hydraulic cylinder 1 functions as an actuator and the shock absorber mode in which the hydraulic cylinder 1 functions as a vibration damping device can be appropriately selected. In this example, the control means 3 includes a controller 34 constituted by a microcomputer or the like, and the controller 34 includes an operation switch for changing the mode,
Signals from various sensors are input as control information. The controller 34 also controls the motor 1 of the hydraulic pump 2.
It is connected to a drive circuit 9 (not shown), and controls the drive of the motor 19 or the hydraulic pump 2 based on the above control information. As shown in FIG. 8, there are two types of operation switches, a down switch 35 and an up switch 36, which are mounted, for example, on a continuous section of the instrument panel in the driver's cab. When the down switch 35 is turned on, the motor 19 and the hydraulic pump 2 are driven to rotate in the normal direction, thereby lowering the cargo platform. On the other hand, the up switch 36
When the hydraulic pump 2 is turned on, the hydraulic pump 2 can be driven in reverse to return the loading platform to its normal height. Further, in this example, the above-mentioned sensor is provided with the following. One of them is the hydraulic pump 2 attached to the hydraulic pump 2.
Oil passage 22 between and hydraulic cylinder 1 or hydraulic cylinder 1
This is a pressure switch that detects the oil pressure in the piston upper chamber 11, and is a pressure switch that detects the oil pressure in the piston upper chamber 11.
Two of the 8 are provided. The signals from these pressure switches 37, 38 are used to determine whether the loading platform is in the lowered position or the normal height position. When the loading platform is at a predetermined lowered position, the pressure in the piston upper chamber 11, into which oil is fed from the hydraulic pump 2, exceeds a predetermined upper limit threshold, and when the loading platform is at the normal height position, Since the pressure inside the piston upper chamber 11 is below a predetermined lower limit threshold, the vehicle height state can be known by detecting the pressure inside the piston upper chamber 11. In this example, When the pressure in the piston upper chamber 11 exceeds the upper limit threshold value, in other words, when the loading platform reaches the lowered position, the high pressure side pressure switch 37
A signal is sent to the controller 34, and when the pressure in the piston upper chamber 11 falls below the lower limit threshold, in other words, when the loading platform is returned to the normal height, the signal is sent from the low pressure side pressure switch 38. A LOW signal is sent to controller 34. Then, the controller 34 determines the vehicle height state based on the signals from the pressure switches 37 and 38, and controls the driving of the motor 19 and the hydraulic pump 2. Furthermore, the controller 34 includes a vehicle speed sensor 39 and a parking brake sensor 40 for detecting vehicle conditions.
A signal from the engine rotation speed detection sensor 41 is also sent. In the present invention, in order to improve safety,
Based on the information from the above sensor, when the vehicle is not stopped, the VT position is controlled so that it cannot be activated even if the switch is operated, but in this example, especially when the vehicle is stopped and the engine is The cargo bed can be lowered only when the cargo bed is in the lowered position, and when the cargo bed starts traveling with the cargo bed in the lowered position, the cargo bed is lowered to the normal height regardless of whether the up switch 36 is operated or not. A system will be configured to force a return to When the hydraulic pump 2 is operated with the engine turned off, it relies solely on the battery as its power source, but this is because there is a risk that the battery will be exhausted and the battery will run out. In addition, when the loading platform is lowered, the suspension spring 32 is compressed and becomes almost a rigid body as described above, so if the vehicle is driven in that state, vibrations or shocks during driving will be directly applied to the vehicle body. In addition to significantly impairing driving stability, there is a risk of damage to the vehicle. Therefore, when the vehicle is traveling, the loading platform is reliably returned to its normal height to prevent the above-mentioned problem from occurring. In addition, in this example, it flashes while the loading platform is being lowered.
A warning lamp 42 is provided to alert the driver etc., which lights up when the cargo platform is located at a predetermined lowered position. Incidentally, instead of providing this warning lamp, the down switch 35 may be made to blink and turn on. Next, the operation of this loading platform height adjustment device with the above configuration is as follows.
This will be explained with reference to the flowcharts in FIGS. 1 to 3. Note that these flowcharts are subroutine flowcharts included in the main flowchart. First, the loading platform lowering operation system will be explained based on the flowchart of FIG. The loading platform is lowered by turning on the down switch 35. In this case, the above pressure switch is 37.38
Based on the signal from
and if the height is not being adjusted (S 101.310
2 and 3103), and the parking brake sensor 40. Based on the signals from the engine rotation speed detection sensor 41 and the vehicle speed sensor 39, it is determined whether the loading platform lowering condition is satisfied. Here, if the vehicle is stopped with the parking brake applied and the engine is running (S104.
If 5105 and 5106 are YES>, that is, there is no risk of the pantyhose rising even if the motor 19 and hydraulic pump 2 are operated, and there is no risk that the car will move unexpectedly while adjusting the vehicle height, then the above down switch 35
This operation drives the motor 19 and the hydraulic pump 2, thereby operating the hydraulic cylinder 1 and lowering the loading platform to a predetermined position (Sill). However, in the case of the present invention, the controller 34 controls the change from the OFF signal to the ON signal of the switch in order to prevent the device from operating automatically in the event of a short-circuit failure of the switch. In this example, when a change from an off signal to an on signal of the down switch 35 is detected, the controller 34 recognizes that the down switch 35 is turned on. configured to recognize that the That is, when the controller is turned on,
When the LOW signal is switched off, the HIGH signal is
Generally, the controller is configured to determine whether to turn the switch on or off depending on the type of input signal. However, with this configuration, if the harness that connects the switch and the controller is short-circuited for some reason while the vehicle is running, the following problem will occur. In other words, if a short-circuit failure occurs in the down switch 35, regardless of whether the down switch 35 is on or off, the L〇- signal that causes the controller to recognize that the switch is on continues to be input.In this example, the parking brake is pulled. Since the structure is such that the loading platform can only be lowered when certain conditions are satisfied, such as that the loading switch 35 is closed, the loading platform will not start lowering during traveling even if the down switch 35 is short-circuited. However, if the parking brake is pulled while waiting at a traffic light, the loading platform lowering condition is met and the loading platform will start lowering automatically. If the configuration is such that there is no such problem, the above-mentioned inconvenience can be prevented. A short-circuit failure occurred in the switch while driving, and -
Even if the load platform lowering condition is corrected when the vehicle is stopped, the input signal from the down switch 35 remains the LO- signal.
This is because if there is no change in the input signal, the controller 34 will not recognize that the switch has been turned on. In this example, the above control is achieved by detecting the rise of the down switch 35 as follows. This will be explained based on the flowchart of FIG. 1 and its subroutine flowchart (see FIG. 2). As shown in FIG. 2, when the down switch 35 is not turned on (YES in 3201), the off flag for the down switch 35 is set (3202).
When the down switch 35 is turned on from such a state (YES at 3201), it is determined whether the off flag of the down switch 35 is set, and if the off flag is set (S203). DeYE
S), a rising flag of the down switch 35 is set, indicating that there has been a change in the input signal (3204).
. Then, as shown in FIG. 1, the down switch 35
When the rising flag is set (YES at 3108), the off flag and rising flag of the down switch 35 are cleared (3108).
09), if the amplifier switch 36 is not turned on (S110: YES), the hydraulic pump 2 is driven, the hydraulic cylinder 1 is operated, and the loading platform is lowered to a predetermined lowering position (Sill). On the other hand, when the down switch 35 is short-circuited, an LO- signal is sent to the controller 34 to recognize that the down switch 35 is originally turned on. However, as shown in FIG. 2, when the down switch 35 is short-circuited, (S 2
01 (NO), the off flag of the down switch 35 is not set, and as a result, the down switch 3
5 rising flag cannot be set (NO at 3202)
>, and as long as the rising flag of the down switch 35 is not set (No in 8108 in Fig. 6), the hydraulic cylinder 1 will not operate to lower the loading platform.Therefore, a short circuit of the down switch 35 has occurred. In this state, even if the parking brake is pulled during a temporary stop such as waiting at a traffic light and the conditions for lowering the platform are met, the platform will not start lowering by itself. Next, with reference to the flowchart in FIG. 3, the operation for returning the loading platform to its normal height will be described. In addition,
This loading platform height return operation routine follows the loading platform lowering condition routine, and the vehicle height is basically restored by operating the up switch 36. in particular,
The signal from the low side pressure cusp inch 38 is not the LOh signal indicating that the loading platform is at the normal height position (N at 3301).
O), when the vehicle height is not being restored (No in 3302) and is not in a running state (No in S 303), when the up switch 36 is turned on (YES in S304)
At this time, if the parking brake is pulled (YES in S305), the hydraulic pump 2 is driven and the hydraulic cylinder 1 is activated to return the loading platform to the normal height (3306). The vehicle height is restored when the vehicle is securely stopped. However, even if the amplifier switch 36 is not turned on, if the vehicle is not stopped or the parking brake is released and the vehicle is ready to start driving (S
(YES in 303), the loading platform is forcibly returned to the normal position (3306), in order to prevent the vehicle from starting to move with the loading platform lowered. When the loading platform is returned to its normal height, the hydraulic pressure for operating the pilot pulp 25 that closes the passage 13 of the piston 6 of the hydraulic cylinder 1 is released, and the piston upper chamber 11 of the hydraulic cylinder 1 is closed. and the piston lower chamber 12 are communicated via a passage 13. Therefore, in this state, the hydraulic cylinder 1 functions as a shock absorber. In addition, in this example, the pressure switch has a short-circuit failure,
A fail-safe system is installed that forcibly returns the loading platform to its normal position when the height position of the loading platform cannot be detected properly. This is because the height position of the loading platform is detected by pressure detection by the pressure switches 37 and 38. However, for example, the low-pressure side pressure switch 38 detects that the loading platform has returned to its normal position. If a short-circuit failure occurs while the signal is being input, a situation may occur in which the cargo platform is left in the lowered position and the vehicle is driven. In this case, as described above, problems such as a significant deterioration in running stability occur. Therefore, in order to prevent such a situation and further enhance the safety of the system, the fail system described above is provided, and in this example, this system is specifically incorporated into the loading platform lowering operation routine. ing. That is, as shown in FIG.
When it is determined that the loading platform is in the lowered position by the pressure detection by 7 (S101: YES), failure detection of the low pressure side pressure switch 38 is performed (3112), and here,
If No. 13 from the low-pressure side pressure switch 38 is the L〇- signal (YES at S112), the loading platform is forcibly returned to the normal position (3113), and the high-pressure side pressure switch 3
7 detects that the pressure in the piston upper chamber 11 of the hydraulic cylinder 1 is higher than the upper limit threshold, the signal from the low pressure side pressure switch 38 LOW indicates that the pressure is below the lower threshold and the loading platform is at normal height.
This is because the fact that it is a signal can only occur when the low-pressure side pressure switch 38 is short-circuited. Note that this example is an example of a fail-safe system in the case where only the low-pressure side pressure cusp inch 38 has a short-circuit failure. In addition, if the low pressure side pressure switch 38 is not short-circuited, the signal from the low pressure side pressure switch 38 will not be the L〇- signal (No in S112), and needless to say, in this case, forced return will occur. System does not work. By the way, as described above, in the loading platform height adjusting device according to the present example, by operating the down switch 35 or the amplifier switch 36, the device can be operated to adjust the loading platform height. In this case, the device is configured so that it does not operate even if the switch is operated while driving, so even if the down switch 35 is pressed by mistake while driving, the loading platform will not be inadvertently lowered. Further, the controller 34 recognizes that the down switch 35 has been turned on when it detects a change from the off signal to the on signal of the down switch 35, so that the down switch 35 is short-circuited. Even if the parking brake is pulled and the cargo platform lowering condition is corrected when the vehicle is stopped at - time while the vehicle is running in this state, the device will not operate automatically and the cargo platform will not start lowering against the user's will. Therefore, the security of the system is very high. Further, in the case of this example, since the hydraulic cylinder 1 is teased using a suspension shock absorber, the number of new parts required for constructing the apparatus can be reduced, and the apparatus can be implemented at low cost. Furthermore, before starting, such as when the parking brake is released, or if the pressure switch for detecting the height of the loading platform is malfunctioning, the loading platform will be forcibly moved regardless of whether the up switch 36 is operated. Since it is configured to return to the normal position, it is possible to prevent the vehicle from traveling with the cargo platform lowered, thereby further increasing safety. Note that the scope of the present invention is not limited to the embodiments described above. For example, in the above embodiment, in order to prevent the battery from dying, the platform lowering condition is set so that the platform can be lowered only when the engine is running and the vehicle is stopped with the parking brake applied. However, in order to operate the device and lower the cargo platform, it is basically sufficient as long as the vehicle is stopped. Furthermore, it goes without saying that the type of vehicle height adjustment device is not limited to that of the above embodiment.

[Brief explanation of drawings]

1 to 3 are flowcharts for explaining the operation of the vehicle height adjustment device according to the embodiment of the present invention, FIG. 4 is a diagram of the device according to the embodiment as seen from the side of the vehicle, and FIG. A diagram schematically showing the overall configuration of the device according to the embodiment, FIG. 6 is a longitudinal sectional view of the hydraulic cylinder according to the embodiment, and FIG. 7 is an enlarged view of the piston loft and piston of the hydraulic cylinder in FIG. FIG. 8 is a system circuit diagram of the device according to the embodiment. 1... Hydraulic cylinder, 2... Hydraulic pump, 3...
Control means, 5...Cylinder, 8...Piston Rondo, 35°36...Switch.

Claims (2)

[Claims] (1) In a vehicle height adjustment device that is equipped with a control means and configured to be able to adjust the vehicle height by operating a switch electrically connected to the control means, the vehicle height adjustment by operating the switch is stopped. A control method for a vehicle height adjustment device, characterized in that the control method can be performed only when the vehicle height adjustment device is in a state where (2) The method of controlling a vehicle height adjustment device according to claim 1, wherein the control means is configured to recognize that the switch is on when detecting a change from an off signal to an on signal of the switch.