JPH0528968Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is based on an electromagnetic control valve attached to a cylinder case connected to the upper part of the transmission case, and the oil in the transmission case is suctioned and pressurized by a hydraulic pump. The present invention relates to a hydraulic system for an agricultural tractor configured to supply oil to the control valve and return drain oil from the control valve into the transmission case via a drain circuit.

[Conventional technology]

Agricultural tractors are generally configured to use a pump to suck transmission oil through a strainer, but if the strainer is narrow, it can clog or increase suction resistance, causing cavitation. A coarse strainer (for example, 150 mesh) was used.

[Problem that the invention attempts to solve]

Even if a relatively coarse strainer is used in this way, if the control valve is a manual type, even if there is some dirt in the oil, it will not cause malfunction due to the relatively low accuracy of the valve itself. However, if the control valve is an electromagnetic type with extremely high precision, there is a risk that the valve may become stuck between the spool and the casing, causing malfunction.

The purpose of this invention is to solve the malfunction of electromagnetic control valves by rationally introducing a filter with a finer mesh than a strainer.

[Means for solving problems]

The characteristic structure of this invention to achieve the above purpose is as follows:
An electromagnetic control valve is attached to the cylinder case connected to the upper part of the transmission case, and the oil in the transmission case sucked by a hydraulic pump is supplied to the control valve, and the drain oil from the control valve is passed through the drain circuit. In the hydraulic system for an agricultural tractor configured to be returned to the transmission case, an oil filter for purifying the hydraulic oil is attached to the outside of the cylinder case, and a communication path from the control valve to the oil filter; A communication path from the oil filter to the transmission case is formed in the cylinder case, and a drain circuit from the control valve to the transmission case is configured with these communication paths, so that the oil filter is connected to the drain circuit. It is at the point located at .

[Effect]

The drain circuit from the control valve to the transmission case has a fine mesh (e.g. 400 mesh).
By providing an oil filter, the number of times the circulating oil is filtered increases, extremely small particles can be removed, and the oil in the transmission case is cleaned. Furthermore, since the oil filter is provided on the drain side rather than on the suction side, cavitation will not occur even if the filter is made finer to improve the filtration rate.

Also, even if you remove the filter to clean it or replace the element, the filter is installed high up in the transmission case.
Oil spills are extremely rare.

[Effect of idea]

With the above configuration, extremely small particles can be removed and transmission oil can be cleaned without causing cavitation, and the durability of the control valve and hydraulic pump can be improved.

Furthermore, it is possible to reduce oil leakage when removing the filter, thereby improving maintainability.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 3, a hydraulic pump 2 attached to the side of the engine 1 sucks transmission oil from the rear transmission case 3 through a strainer 4 and a suction pipe 5, and from the pump 2 to the rear. A control valve V (see Fig. 1) attached to the upper right side of the transmission case 3 is used to control the lift cylinder 7 that drives the lift arm 6 and the rolling control of the working device 8 such as a tiller attached to the machine. It is configured to supply pressure oil to hydraulic actuators such as the cylinder 9.

The lift cylinder 7, as shown in FIG.
A piston 7B is provided with a cylinder case 7A serving as a lid that closes the upper part of the transmission case 3, and the control valve V is installed on one side of the cylinder case 7A, as shown in FIG. An oil filter 10 is provided on the other side.

A communication passage 11a leading from the control valve V to the oil filter 10 and a communication passage 11b leading from the oil filter 10 to the transmission case 3 are formed on the wall of the cylinder case 7A, and these communication passages 11a and 11b are used to control the control. A drain circuit 11 from the valve V to the transmission case 3 is configured.

As shown in FIG. 2, the control valve V supplies the control flow branched from the pump port P via the flow priority valve 12 to the rolling solenoid valve 13, and supplies the surplus flow to the lift ascending solenoid valve 14a or the lift solenoid valve 14a. Pressure oil is configured to be supplied to the lift lowering solenoid valve 14b, to the rolling cylinder 9 via the inlet/outlet ports A and B, and to the lift cylinder 7 via the inlet/outlet port C, and further , the drain oil is returned to the transmission case 3 via the drain port D. In the figure, 15 is a relief valve provided in the drain circuit 11, and is a relief valve provided in the oil filter 10.
The construction is such that pressure oil is released directly to the transmission case 3 when the transmission case 3 becomes clogged.

Incidentally, as the oil filter 10, 400
When using filter paper of ~500 mesh as an element and a wire mesh type strainer of about 50 mesh as the strainer 4, extremely small dust could be removed without causing cavitation.

[Another example]

In addition, in the above embodiment, the oil filter 10
is attached horizontally to the side surface of the cylinder case 7A, but it may also be configured to be attached to the lower surface of the adapter 16 via the adapter 16, as shown in FIG. In such a case,
When replacing the oil filter, the oil filter can be replaced without oil leaking out.

[Brief explanation of the drawing]

The drawings show an embodiment of the hydraulic system for an agricultural tractor according to the present invention. Fig. 1 is a partially longitudinal front view of the transmission case, Fig. 2 is a schematic diagram showing the hydraulic system, and Fig. 3 is a side view of the entire tractor. It is a diagram. FIG. 4 is a front view of main parts showing another embodiment. 2... Hydraulic pump, 3... Mission case,
7A...Cylinder case, 10...Oil filter, 11...Drain circuit, 11a, 11b...
Communication path, V... control valve.

Claims (1)

[Claims for Utility Model Registration] An electromagnetic control valve V is attached to the cylinder case 7A connected to the upper part of the transmission case 3, and the oil in the transmission case 3 sucked by the hydraulic pump 2 is supplied to the control valve V. The drain oil from the control valve V is passed through the drain circuit 11 to the transmission case 3.
An oil filter 10 for purifying hydraulic oil, which is a hydraulic system for an agricultural tractor configured to return oil to the interior of the agricultural tractor.
is attached to the outside of the cylinder case 7A, and a communication path 11a from the control valve V to the oil filter 10 and the oil filter 1
By forming a communication path 11b from the control valve V to the mission case 3 in the cylinder case 7A, and configuring the drain circuit 11 from the control valve V to the mission case 3 with these communication paths 11a and 11b. , the oil filter 10
is located in the drain circuit 11 of the agricultural tractor hydraulic system.