JPS6235650Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cylinder device used for lifting the cab of a large motor vehicle or the like.

Generally, in large vehicles, the engine portion is inspected by lifting and tilting the cab. Because such cabs are heavy and must be tilted beyond the load balance point, a cylinder device is interposed between the cab and the vehicle body (frame), and the expansion and contraction of this cylinder device allows the cab to tilt. A cab tilt device is used to perform the operation.

For example, as a general cab tilt device,
There is something like the one shown in Figure 1. In Fig. 1, the cab 1 has its front lower end attached to the frame 2 with a hinge 3.
A cylinder device 4 is interposed between the frame 2 and the frame 2 so as to be rotatable. A hydraulic supply device 5 disposed behind the cab 1 on the frame 2 is connected to the cylinder device 4 via a hose 6. Then, the cylinder device 4 is expanded and contracted by the hydraulic pressure supplied from the hydraulic pressure supply device 5, and the cab 1 is tilted.

However, in the case of such a cab tilt device, the hose connecting the cylinder device and the hydraulic pressure supply device is long, making it difficult to bleed air from the hose during assembly or maintenance, and the outside of the work floor etc. There was a problem of contamination.

An object of the present invention is to provide a cylinder device that can simplify air removal work.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 2 is a circuit diagram showing an example of a cab tilt device using an embodiment of the cylinder device according to the present invention, FIG. 3 is a partially cutaway side view showing an embodiment of the cylinder device according to the present invention, and FIG. Figure 3 -
FIG. 3 is an enlarged cross-sectional view taken along the line.

In this embodiment, the cab tilt device includes a cylinder device 4 and a hydraulic pressure supply device 5, the former 4 being interposed between the cab and the frame, and the latter 5.
is installed in the frame. The lower end of the cylinder 11 in the cylinder device 4 is rotatably supported by the frame 2 via a shaft 7, and the upper end of a rod of a piston 12, which is slidably fitted into the cylinder 11, is rotatably supported by the cab 1 via a shaft 8. They are movably connected (see Figure 1).

A valve body 13 is provided at the lower end of the cylinder 11, and a first main flow path 1 is provided inside the valve body 13.
4 and a second main flow path 15 are formed, respectively. One end of each of the main flow channels 14, 15 is connected to the hydraulic pressure supply device 5 via a pressure hose 6, etc., and filters 16, 17 are interposed near both connection ports.
The other end of the first main flow path 14 communicates with the frame side pressure chamber 11a in the cylinder 11 via a port 18, and the other end of the second main flow path 15 communicates with the cab side pressure chamber 11b via a communication pipe 19. ing. Pilot-operated check valves 20 and 21 are interposed in both main channels 14 and 15, respectively, and both check valves 20 and 21 open the other only when pilot pressure from one of the main channels 14 or 15 acts. It is configured to open the main flow path 15 or 14 of.
Therefore, when the oil supply from the hydraulic supply device 5 is stopped, both the check valves 20 and 21 are closed, and the cab is fixed in any position before or after the load balance point C, and is prevented from falling. It is safe.

Both check valves 20 and 21 are provided between both main channels 14 and 15.
A detour passage 22 bypasses the check valve 2 at both ends.
0 and 21 and the filters 16 and 17, respectively, and this bypass flow path 22 has an on-off valve 2 that normally closes this flow path 22.
3 is interposed. Specifically, the on-off valve 23 includes a valve seat 23a formed in the middle of the detour flow path 22, and a needle-shaped valve body 23b that is screwed into the valve body 13 and is seated on and off the valve seat 23a. When the valve body is screwed in and seated, the detour flow path 22
The detour passage 22 is opened when the valve body is loosened and unseated.

The hydraulic supply device 5 includes an oil tank 24, a hydraulic pump 25 that is driven manually or by an arbitrary means such as a motor to pump oil from the oil tank 24, and a manual directional control valve 26 with, for example, 2 positions and 4 ports. We are prepared. Each port of the directional switching valve 26 is connected to the discharge side of the hydraulic pump, the return side of the oil tank, and one end of each of the two main channels, and this valve switches the direction of the pressure oil supplied to the cylinder between forward and reverse. It is configured as follows.

Next, air venting during initial assembly and reassembly after maintenance and inspection will be explained.

The cylinder device 4 and the hydraulic supply device 5 are assembled at predetermined positions on the cab and frame, and are communicated with each other by appropriately connecting hoses 6. The detour passage 22 in the cylinder device 4 is opened when the valve body 23b of the on-off valve 23 is separated from the valve seat 23a. When the hydraulic pump 25 is driven,
Oil is supplied to the oil tank 24, pump 25, and directional control valve 2.
6, one hose 6, one filter 16 or 17, one main channel 14 or 1
5, detour flow path 22, other main flow path 15 or 1
4, the other filter 17 or 16, the other hose 6, the other flow path of the switching valve 26, and the oil tank 24. Due to this oil circulation, air remaining in each channel is pushed out and forcibly discharged from the channel.

Normally, the cylinder 11 and the valve body 13 are filled with oil in advance or oil remains naturally therein, so most of the air bleeding work is done to bleed air between the valve body 13 and the hydraulic pressure supply device 5. However, even if some air remains inside the valve body 13, it will be guided out during the air purge operation.

When the air is completely removed, the on-off valve 23 is opened by screwing in the valve body 23b, the bypass passage 22 is closed, and both main passages 14 and 15 are shut off, creating a normal operating state.

For example, when pressure oil from the hydraulic pump 25 is supplied to the first main flow path 14 by the switching valve 26, since the detour flow path 22 is closed, oil is supplied to the check valve 22.
0 in the forward direction to flow into the frame side pressure chamber 11a of the cylinder and push up the piston 12. At this time, a pilot signal based on the oil pressure opens the check valve 21 of the second main flow path 15 in a direction that allows backflow, so that oil is drained from the cab side pressure chamber 11b of the cylinder through the second main flow path. This causes the piston 12 to extend and lift the cab.

When the valve 26 is switched, the second main flow path 15 is supplied with oil. To supply oil, push open the check valve 21 in the forward direction, flow into the cab side pressure chamber 11b, and feed the piston 12.
Press down. At this time, the check valve 20 of the first main flow path 14 is opened in a direction allowing backflow by the pilot signal, so that oil is drained from the frame side pressure chamber 11a through the first main flow path. As a result, piston 1
2 performs a shortening operation to lower the cab 1.

As explained above, according to the present invention, a detour passage having an on-off valve is interposed between the main passages that respectively supply fluid to a pair of pressure chambers of the cylinder, thereby circulating fluid between the two main passages. Therefore, the main flow path, the piping connected thereto, and various devices can be vented in the assembled state. This simplifies the air removal work and improves work efficiency.
In addition, dripping of fluid can be avoided, and harmful effects such as contamination of the workplace can be prevented.

Furthermore, by arranging the connection position of the bypass flow path to the main flow path closer to the cylinder than the filter in the main flow path, the fluid always passes through the filter during air purge circulation, so dust does not flow into the main flow during air purge operation. It is possible to prevent the liquid from entering the channel, and to prevent the occurrence of clogging of the channel.

It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the gist thereof.

For example, the structure of the detour flow path and the on-off valve is not limited to the above embodiment.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a general cab tilt device, Figs. 2 to 4 show an embodiment of the present invention, Fig. 2 is a circuit diagram, Fig. 3 is a partially cutaway side view, FIG. 4 is an enlarged sectional view taken along the - line in FIG. 3. 1... Cab, 2... Frame, 4... Cylinder device, 5... Hydraulic supply device, 6... Hose, 1
1... Cylinder, 12... Piston, 13... Valve body, 14, 15... Main flow path, 16, 17...
Filter, 20, 21... Pilot operated check valve, 22... Detour flow path, 23... Open/close valve, 25...
...Oil pump, 26...Directional switching valve.

Claims (1)

[Claims for Utility Model Registration] (1) One end of a main flow passage whose other end is connected to a fluid supply device is connected to both chambers of a piston in a cylinder interposed between the driver's cab and the vehicle body. A cylinder device characterized in that a detour passage that detours around the cylinder is interposed between the two main flow passages, and a normally closed on-off valve is interposed in the detour passage. (2) The cylinder device according to claim 1, wherein the connection position of the detour flow path to the main flow path is located closer to the cylinder than a filter interposed in the main flow path.