JPH0371311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a track tension adjustment device for tracked vehicles such as hydraulic excavators and cranes.

[Background of the invention]

Japanese Patent Publication No. 57-16033 is known as a track tension adjustment device for a tracked vehicle using hydraulic pressure. With this configuration, if an external force higher than the pressure set by the relief valve continues to act on the idler that supports the track, the piston of the adjuster cylinder (hereinafter simply referred to as "cylinder") connected to the idler will reach the end of its stroke. When the external force is released, the piston and idler are moved by pressure oil from the hydraulic source, and the tension of the crawler track is restored. Further, even if the truck bushing etc. wear out in proportion to the running time during running, the piston and idler are moved by pressure oil from the hydraulic source to compensate for the amount of wear. As a result, the stroke amount of the piston of the cylinder becomes longer, and when the piston reaches the stroke end due to external force in this state, the crawler track becomes more slack than if the track bushing etc. were not worn. At this time, if a steering operation is performed during driving, the track will come off.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to provide a track tension adjustment device for a tracked vehicle that can make the stroke amount of a cylinder piston constant.

[Summary of the invention]

In order to achieve the above object, the present invention provides track tension adjustment for a tracked vehicle, which is equipped with a first cylinder into which a main piston is inserted, a hydraulic power source and a first relief valve connected to the head side chamber of the first cylinder. In the apparatus, a second cylinder whose piston stroke is smaller than that of the first cylinder is provided, one chamber of the second cylinder defined by the sub-piston is connected to the head side chamber of the first cylinder, and the other chamber of the second cylinder is connected to the head side chamber of the first cylinder. The chamber is characterized in that the chamber is connected to an oil pressure source and a second relief valve whose set pressure is lower than that of the first relief valve.

[Embodiments of the invention]

An embodiment of the present invention will be explained with reference to FIG. In the figure, 1 is a cylinder device attached to a side frame (not shown), 2 and 3 are a first cylinder and a second cylinder respectively provided in the cylinder device 1.
4 is the main piston inserted into the first cylinder 2, 5 is the rod of the main piston 4, 6 is the idler to which the rod 5 is in contact, 7 is the first cylinder 2
The head side chamber 8 is connected to the head side chamber 7 via a conduit 9.
10 is a pressure reducing valve 12 provided in the pipe line 11, a hydraulic power source connected to the pipe line 9 via check valves 13 and 14, and 15 is a hydraulic power source 10.
16 is an on-off valve provided in a bypass pipe 17 connected to a pipe 9 in parallel with the first relief valve 8; 18 is a relief valve for setting the maximum pressure of pressure oil discharged from the second cylinder 3; The inserted secondary piston, 19 is a passage connecting the head side chamber 7 of the first cylinder 2 and one chamber 20 of the second cylinder 3 defined by the secondary piston 18, and 21 is the other chamber of the second cylinder 3. 22 is a spring contained in the chamber 22; 23 is a pipe connecting the chamber 22 and the pipe 11 between the check valves 13 and 14; 24 is a second relief valve connected to the chamber 22 via a pipe 25; Second relief valve 2
A fixed throttle is provided on the outlet side of 4, and 27 is a tank. The stroke amount of the main piston 4 of the first cylinder 2 is the same as that of the sub piston 1 of the second cylinder 3.
The stroke amount is set to be larger than the stroke amount of 8. Further, the set pressure of the first relief valve 8 is set higher than the set pressure of the second relief valve 24.

The effect of the above configuration will be explained using FIG. 2.

The tension of the crawler track around the idler 6 is maintained by the pressure oil from the hydraulic source 10 passing through the pipe line 11, the pressure reducing valve 12, the check valves 13, 14, the pipe lines 9, 23, and the head side chamber 7 of the first cylinder 2. Chamber 2 of second cylinder 3
2, the main piston 4 and the sub piston 18 move to the left, and the rod 5 of the main piston 4 pushes the idler 6 to the left. At this time, the chambers 20 and 22 of the second cylinder 3 have the same pressure, but the spring 21 moves the sub-piston 18 to the left. Further, the pressures in the head side chamber 7 of the first cylinder 2 and the chamber 22 of the second cylinder 3 are set by the pressure reducing valve 12.

Next, the buffering effect will be explained.

When an external force is applied to the idler 6 to push the rod 5, the pressure reducing valve 12 is applied to the head side chamber 7 and the chambers 20 and 22.
When a pressure higher than the set pressure α is generated and that pressure reaches the set pressure β of the second relief valve 24, the pressure oil in the chamber 22 is discharged to the tank 27 through the second relief valve 24 and the fixed throttle 26, The sub-piston 18 moves rightward against the spring 21 up to the maximum δ amount, and the pressure oil in the head side chamber 7 is guided into the chamber 20 through the passage 19, and both the main piston 4 and the idler 6 move rightward up to the maximum δ amount. Move to. At this time, the external force applied to the idler 6 is absorbed by the hydraulic pressure set by the second relief valve 24, the passage 19 that acts like a fixed throttle, and the fixed dead throttle 26. Further, when an excessive external force is suddenly applied to the idler 6, after the main piston 4 and the idler 6 move to the right by an amount δ which is the stroke end of the sub piston 18, the pressure in the chamber 7 is reduced by the first relief valve 8. The pressure increases to the set pressure γ, the pressure oil in the chamber 7 is discharged to the tank 27 through the first relief valve 8, and the main piston 4 and idler 6 both move rightward to the maximum amount δ'. In other words, in this configuration, the stroke of the sub-piston 18 (maximum δ
The idler 6 and the main piston 4 are moved within a certain amount of the idler 6 to prevent the crawler track from coming off due to excessive displacement of the idler 6. When the external force is released from the idler 6, pressure oil is supplied from the hydraulic source 10 to the chamber 22, the sub piston 18 moves to the left, and the pressure oil in the chamber 20 is returned to the head side chamber 7 through the passage 19. At the same time, the insufficient pressure oil in the head side chamber 7 is replenished from the pressure oil source 10, the main piston 4 and the idler 6 move to the left, and the tension of the crawler track is restored. In the above, the check valve 14 prevents backflow from the head side chamber 7 to the chamber 22, and the check valve 13 prevents backflow from the chamber 22 to the hydraulic pressure source 10. Further, the on-off valve 16 is for discharging the pressure oil in the head side chamber 7 into the tank 27 when the crawler belt is loosened.

According to the present embodiment described above, the external force applied to the idler 6 can be absorbed with a constant stroke amount determined by the stroke amount (maximum δ) of the sub-piston 18 at all times, so it is possible to prevent the crawler track from coming off. Further, even if an excessive external force is suddenly applied to the idler 6, it can be sufficiently absorbed.

〔Effect of the invention〕

According to the crawler belt tension adjustment device for a tracked vehicle of the present invention described above, the stroke amount of the piston of the cylinder for tensioning the crawler belt can be made constant.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing an embodiment of the track tension adjustment device for a tracked vehicle according to the present invention, and Fig. 2 is a characteristic showing the relationship between the stroke amount of the main piston and the pressure in the main and sub cylinders. It is a line diagram. 2...First cylinder, 3...Second cylinder, 4
...Main piston, 7...Head side chamber, 8...First
Relief valve, 10... Hydraulic source, 18... Sub-piston, 19... Passage, 20, 22... Chamber, 24...
Second relief valve.

Claims (1)

[Claims] 1 The first cylinder into which the main piston is inserted, and the first
A hydraulic power source connected to the head side chamber of the cylinder and the first
In a track tension adjustment device for a tracked vehicle equipped with a relief valve, a second cylinder whose piston stroke is smaller than that of the first cylinder is provided, and one chamber of the second cylinder defined by the sub-piston is connected to the first cylinder. A track tension adjustment device for a tracked vehicle, characterized in that the head side chamber of the cylinder is connected to the head side chamber, and the other chamber of the second cylinder is connected to a hydraulic source and a second relief valve having a lower set pressure than the first relief valve. .