JPH0553651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a vehicle height adjustment device.

(Prior art) Recently, as shown in Japanese Patent Application Laid-open No. 123514/1983, vehicles such as trucks and box cars are
A fluid actuator, such as a pneumatic spring, is interposed between the sprung weight and the unsprung weight, and when loading and unloading cargo, the air pressure of the pneumatic spring is released to extremely low the vehicle height, that is, to lower the floor. Increasingly, vehicles are designed to facilitate the loading and unloading of cargo.

However, in the case of such a product, if an abnormality occurs in the air pressure generation source and air pressure cannot be obtained when the floor is lowered, for example, if an abnormality occurs in the compressor or the motor driving it, etc. This creates a problem in that the height of the vehicle cannot be raised from the low floor condition, making it virtually impossible to drive after loading and unloading cargo. In particular, as shown in Japanese Utility Model Publication No. 58-24567, if the floor is lowered by more than the bump clearance, it becomes completely impossible to drive.

(Object of the Invention) The present invention has been made in consideration of the above-mentioned circumstances, and provides a vehicle height that makes it possible to raise the vehicle height to a driving state without fail when the floor is lowered. The purpose is to provide a regulating device.

(Structure of the Invention) In order to achieve the above-mentioned object, the present invention includes a pressure storage tank for supplying fluid to a fluid actuator that adjusts the vehicle height according to supply and discharge of fluid pressure. On the premise that the pressure inside the pressure storage tank is at a reference pressure sufficient to raise the vehicle height, lowering the floor is allowed.In other words, the pressure inside the pressure storage tank is When the pressure is lower than the standard pressure, the floor is prevented from lowering.

Specifically, in addition to the above-mentioned pressure storage tank, there is also a floor lowering control circuit that receives a signal from an operating switch and outputs an operating signal for lowering the vehicle body to at least the bump clearance range, and the pressure storage tank. a pressure sensor that directs the pressure in the tank;
a comparison circuit that compares the pressure signal from the pressure sensor with a signal corresponding to the reference pressure mentioned above; and a comparison circuit that receives the output from the comparison circuit and activates the activation switch when the pressure in the pressure storage tank is lower than the reference pressure. A lowering prevention means is provided for preventing lowering of the floor regardless of the operation of the lowering of the floor.

(Example) In FIG. 1, 1 is a pneumatic spring as a fluid actuator provided on the rear wheel suspension, 2 is a bump stopper made of a rubber material, and the pneumatic spring 1 is, for example, of a bellows type. Its upper end is fixed to the sprung weight F ₁ , and its lower end is fixed to _{the unsprung weight F 2 .} The distance from the weight _F2 , that is, the vehicle height, is increased. Further, the bump stopper 2 is fixed to, for example, the sprung mass _F1 ,
As will be described later, there is a predetermined gap, ie, bump clearance L, between the upper end and the unsprung weight _F2 .
(for example, 80 mm), the supply pressure to the pneumatic spring 1 is adjusted according to the load.

The pneumatic spring 1 is connected to a pressure storage tank 4 via a pipe 3.
is connected via a check valve 5 to a compressor 7 driven by a motor 6. Said piping 3
An electromagnetic first on-off valve 8 is connected in the middle, and a second on-off valve 8 is connected to a pipe 9 branched from a branch part a between the first on-off valve 8 and the pneumatic spring 1.
An on-off valve 10 is connected. Further, the branch part a and the pressure storage tank 4 are connected by a pipe 11 that bypasses the first on-off valve 8, and this pipe 11
A manual on-off valve 12 that is manually operated is connected in the middle.

Reference numeral 13 in FIG. 1 is a control unit, and this control unit 13 includes a pressure sensor 14 that detects the pressure in the pressure storage tank 4, an actuation switch 15 that is manually operated when lowering the floor, and a control unit that controls the vehicle height. Each signal from the vehicle height sensor 16 to be detected is inputted, and from this control unit 13, the motor 6 and the first and second on-off valves 8, 1 are inputted.
It is designed to be output to 0.

The control unit 13 has a control function that adjusts the vehicle height according to the load, a control function that lowers the vehicle floor based on a command signal from an operating switch 15, and an operating switch that adjusts the vehicle height according to the pressure in the pressure storage tank 4. It has a control function to prevent this lowering of the floor regardless of the command signal from 15, and the configuration of the control function related to this lowering of the floor will be explained with reference to FIG. First, reference numeral 17 denotes a lowering control circuit, and the actuating switch 15 is connected to this lowering control circuit 17 via a contact 18a of a relay 18 as a lowering preventing means, and this contact 18a
and the actuation switch 15 are both closed,
An activation signal for lowering the floor, which will be described later, is output. Reference numeral 19 in the figure is a comparison circuit, which receives the signal from the pressure sensor 14 and compares the pressure signal from the pressure sensor with a predetermined reference pressure signal to determine whether the pressure is stored in the pressure storage tank 4. Only when the pressure is higher than the reference pressure, current from the battery 20 is passed through the coil 18a of the relay 18 to excite the coil 18a and close the contact 18a. In addition, in the example, the reference pressure is set to a pressure that can secure the above-mentioned predetermined bump clearance L at the maximum load when the floor is lowered (when the internal pressure of the pneumatic spring 1 is zero). has been done. Of course, this reference pressure may be a pressure that is smaller than the predetermined bump clearance L and that ensures the minimum necessary clearance for running the vehicle.

Next, the operation of the above-mentioned configuration will be explained, focusing on the control function of the control unit 13. Air pressure above the reference pressure is always stored in the pressure storage tank 4 based on the signal from the pressure sensor 14. As shown, motor 6 or compressor 7
are to be operated as appropriate. On this premise, normal vehicle height adjustment according to the load is performed based on the output from the vehicle height sensor 16 while the manual on-off valve 12 is always kept closed. That is, if the vehicle height is too high, by closing the first on-off valve 8 and opening the second on-off valve 10, the air pressure in the pneumatic spring 1 is reduced and the vehicle height is lowered. If it is too high, the second on-off valve 10 is closed and the first on-off valve 8 is opened to supply air pressure from the pressure storage tank 4 into the pneumatic spring 1 to raise the vehicle height. In this way, by opening and closing the first and second on-off valves 8 and 10, a predetermined bump clearance L is secured regardless of the load, and the state of the vehicle A in which this bump clearance L is secured is determined as follows. It is shown in Figure 3.

Next, when lowering the floor, the operating switch 15 is closed. At this time, if the pressure inside the pressure storage tank 4 is equal to or higher than the reference pressure, the coil 1 of the relay 18
8b is excited and its contact 18a is closed, whereby the lowering control circuit 17 outputs an activation signal. This actuation signal closes the first on-off valve 8 and opens the second on-off valve 10. Due to the low floor design, the second on-off valve 10 is closed until the air pressure in the pneumatic spring 1 becomes zero. be opened. As a result, the state of vehicle A changes from the state shown in FIG. 3 to the state shown in FIG. 4 (bump stopper 2 is in contact with unsprung weight _F2 in FIG. 1), and the rear wheel 1
The vehicle height on the 9 side becomes extremely low, resulting in a low-floor state. After the cargo is loaded and unloaded in this low-floor state, when the operating switch 15 is operated (opened) again, the second on-off valve 10 is closed, while the first
The on-off valve 8 is opened and air pressure from the pressure storage tank 4 is supplied to the pneumatic spring, and the state of the vehicle A returns to the state shown in FIG. 3. Note that when the first on-off valve 8 does not open due to a failure or the like when raising the vehicle height from the low floor state, the vehicle height is raised by opening the manual on-off valve 12.

Now, if the pressure inside the pressure storage tank 4 becomes lower than the reference pressure due to a failure of at least one of the motor 6 or the compressor 7, or due to an airtight leak in the pressure storage tank 4, the relay 18 coil 18
Since energization to b is blocked and its contact 18a remains open, even if the operating switch 15 is closed, this closing signal is not input to the floor lowering control circuit 17, and as a result, the floor is lowered. This means that it will not happen. In this way, if the air pressure necessary to raise the vehicle height from a low-floor state to a drivable state is not secured, the floor-lowering itself will be prevented, making it impossible to drive after the floor has been lowered. It is possible to reliably prevent such a situation from occurring.

FIG. 5 shows another embodiment of the present invention, in which the same components as those in the previous embodiment are given the same reference numerals and their explanation will be omitted. In this embodiment, the pressure storage tank 20 is used exclusively for supplying air pressure to raise the vehicle height from a low-floored state, while the air pressure supply for adjusting the vehicle height according to the load is handled separately. This is done directly from the compressor 7 without going through a tank. Along with this, there are three positions in which the compressor 7 can be selectively communicated with the piping 3 (first on-off valve 8) or the pressure storage tank 20, and both 3 and 20 can be cut off from the compressor 7. A type electromagnetic switching valve 21 is provided. This switching valve 21 is controlled by the control unit 13, and raising the vehicle height from a low floor condition is normally done by operating the compressor 7. and,
When the compressor 7 is out of order, the vehicle height is raised by opening the manual on-off valve 12 (air pressure is supplied from the pressure storage tank 20 to the pneumatic spring 1). In addition, air pressure may be supplied from the pressure storage tank 20 when raising the vehicle height from a lowered floor condition. In this case, the compressor 7 is switched by switching the switching valve 21.
You can replenish it from there.

Next, an example of a suspension mechanism in which the aforementioned pneumatic spring 1 and bump stopper 2 are actually incorporated into a vehicle will be explained with reference to FIG. 6. In this embodiment, the chassis frame 22 has a rigid suspension in which a mechanical spring consisting of a pneumatic spring 1 and a leaf spring 23 is used together,
The chassis frame 22 is supported so that the bump clearance L is maintained by both spring forces. The ratio of the spring strength of the leaf spring 23 as a suspension spring and the pneumatic spring 1 is set to 3:7 in the embodiment, and the spring strength of the leaf spring 23 is set to the spring strength of the leaf spring 23 when the suspension spring is not loaded (when the loading platform is empty). The spring strength is set to be weaker than the upper weight, that is, weaker than the spring strength necessary to secure the bump clearance L mentioned above. Therefore, as described above, if the air in the pneumatic spring 1 is discharged to approximate the spring force to zero, the chassis frame 22 will be supported only by the spring strength of the leaf springs 23, and the vehicle height will decrease. I will do it.

The leaf spring 23 is disposed in the longitudinal direction of the vehicle through the lower surface of the axle 24, and its rear end is connected to the chassis frame 2 through the shaft 25.
2, and its central portion is connected to an axle 24 via a U bolt 26. pneumatic spring 1
has its upper end fixed to the lower surface of the chassis frame 22, and its lower end fixed at a position offset from the axle mounting position of the leaf spring 23.
The pneumatic springs 1 on both the left and right sides are symmetrical with respect to the differential gear case 27.
That is, by arranging the leaf spring 23 in such a manner that one of the left and right sides is arranged in front of the axle 24 and the other side is arranged in the rear of the axle 24.
The wind-up (wavy phenomenon) of the steel is being suppressed.

Further, the bump stopper 2 is fixed on a leaf spring 23. The bump stoppers 2 on both the left and right sides are arranged symmetrically with respect to the differential gear case 27, similarly to the pneumatic spring 1. Of course, the upper weight F ₁ against which the bump stopper 2 comes into contact is the chassis frame 22 .

In the embodiments described above, the relay 18 as a lowering prevention means is configured to prevent the signal from the actuating switch 15 from being input to the lowering control circuit 17. The configuration may be such that the output is blocked.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
It is possible to reliably avoid situations where the vehicle is left with a low floor and becomes unable to drive, and also situations where cargo or workers are caught between the vehicle body and the road surface when the vehicle floor is lowered. However, this situation can be quickly resolved by surely raising the vehicle height.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention.
FIG. 2 is a main circuit diagram showing an embodiment of the present invention. FIG. 3 is a side view showing the vehicle state in which the vehicle height is raised and the vehicle is ready to travel. FIG. 4 is a side view showing the vehicle in a state where the floor has been lowered and the vehicle cannot run. FIG. 5 is a system diagram of main parts showing another embodiment of the present invention. FIG. 6 is a side view showing an example of a suspension mechanism to which the present invention is applied. 1: Pneumatic spring, 2: Bump stopper, 4,
20: Pressure storage tank, 13: Control unit, 14: Pressure sensor, 15: Operation switch,
18: Relay (lowering prevention means), 19: Comparison circuit, A: Vehicle, L: Bump clearance.

Claims (1)

[Claims] 1. A floor lowering control circuit that receives a signal from an operating switch and outputs an operating signal for lowering the vehicle body to at least a bump clearance range; a pressure storage tank for supplying fluid pressure to a hydraulic actuator that adjusts the height; a pressure sensor that detects the pressure in the pressure storage tank; and a pressure signal from the pressure sensor and a predetermined reference pressure signal. a comparator circuit for comparison; and a comparator circuit that operates in response to a signal from the comparator circuit and prevents the lowering of the floor level when the pressure in the pressure storage tank is lower than the reference pressure regardless of the operation of the operating switch. A vehicle height adjustment device for a vehicle, comprising: a means for preventing floor lowering; and a vehicle height adjustment device.