JP2530038B2 - Hydraulic circuit of working vehicle - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic circuit of a work vehicle such as a tractor having two or more actuators.

(Prior Art) For example, in a tractor, in addition to a hydraulic device (main actuator) for lifting a rear-mounted work machine, a tractor equipped with a hydraulic motor-driven cane cutter or mower and a hydraulic device (secondary actuator) such as a loader work machine is used. Yes, pressure oil can be supplied to each actuator from two engine-driven hydraulic pumps.

(Problems to be Solved by the Invention) By the way, although the sub-actuator is equipped with various conversion devices, for example, in a loader working machine or the like, it is possible to increase the amount of supplied oil and shorten the cycle time. Although a larger amount of oil than the required amount may be required, the auxiliary actuator pump has a constant capacity and cannot meet the demand.

Although it is relatively easy to supply the pump discharge oil for the main actuator to the auxiliary actuator,
Since a relief valve is provided in the oil passage for each actuator, if the relief pressure of both relief valves is the same, when the pump discharge oil is merged, both relief valves will resonate and generate chattering noise. There is, and it is because it was not possible to simply join.

By the way, the relief pressure of various hydraulic devices is substantially constant, and raising the relief pressure individually poses a problem because it impairs versatility, whereas the hydraulic system of the tractor on which it is mounted has It can be set arbitrarily, and it is known that the higher the system pressure, the more compact the design.

(Means for Solving the Problem) According to the present invention, a mode in which pressure oil is independently supplied to the main / subactuator and a junction to the subactuator are provided in an oil passage connecting the first and second pumps to the main / subactuator. By providing a two-position switching valve that can take the form of supplying in the same manner, and setting the relief pressure of the relief valve on the pump side for the main actuator higher than the relief valve on the pump side for the auxiliary actuator, the above-mentioned various problems are solved. I was able to solve it.

That is, the specific configuration for solving the problem in the present invention is such that the first pump 1 and the main actuator 8 have
To connect the second pump 2 and the auxiliary actuator 10 to the second
A two-position switching valve 27, which is connected by an oil passage 9 and is artificially operated in the middle of the first and second oil passages 6 and 9, is provided.
27 is provided with an independent position A for connecting the first and second pumps 1 and 2 to the main and auxiliary actuators 8 and 10, respectively, and a confluence position B for connecting both the first and second pumps 1 and 2 to the auxiliary actuator 10. Two
The relief valve 26 is provided between the position switching valve 27 and the first pump 1, and the relief valve 29 is provided between the second pump 2 and the relief valve 29 so that the relief of the auxiliary actuator 10 at the time of merging is performed only by the relief valve 29. That is, the relief pressure of the valve 26 is set higher than that of the relief valve 29.

(Operation) When the 2-position switching valve 27 is set to the independent position A operation mode,
・ The oil discharged from the 2 pumps 1 and 2 is the main and auxiliary actuators 8 and 1.
Each is independently supplied to 0.

When the two-position switching valve 27 is set to the merging position B working mode,
・ The discharge oil of 2 pumps 1 and 2 joins and the auxiliary actuator 10
It is possible to increase the work efficiency of the loader work machine and the like. At this time, pressure oil flows through the relief valves 26 and 29 for both pumps 1 and 2 at the same time, but since the relief pressure of the first pump relief valve 26 is higher than that of the second pump relief valve 29, it acts as a relief. In this case, only the relief valve 29 for the second pump operates, so that resonance does not occur.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows a hydraulic circuit of a tractor capable of mounting an implement equipped with an actuator such as a front loader working machine, a cane cutter, a mower, a rotary cultivator, and a lift device.

1, 2 and 3 are pumps driven by a tractor engine, which can suck lubricating oil from an oil tank 4 formed in a transmission case through an intake passage 5 and supply pressure oil to the actuator inside and outside the tractor. .

The first pump 1 is connected via a first oil passage 6 to a cylinder of a hydraulic device 7 for lifting the rear-mounted work machine, that is, a first actuator 8 (main actuator), and a second pump 2 is connected to a second oil passage 9 Is connected to a second actuator 10 (sub-actuator) such as a cylinder of an external hydraulic mechanism or a hydraulic motor.

A priority valve is provided in the oil supply passage 13 of the third pump 3.
14, power steering valve 15, PTO speed change valve 16,
A double speed switching valve 17 and a forward / reverse switching valve 18 are connected.

That is, a part of the oil discharged from the third pump 3 is returned to the return oil passage 19 by the priority valve 14 and is preferentially supplied to the power steering valve 15 to operate the power steering cylinder 20 to operate it. The pressure oil via
Supplied to the PTO speed change valve 16 and the PTO speed change hydraulic clutch 21
Is supplied to the double speed switching valve 17, and the hydraulic clutch 22 of the transmission that drives the front wheels of the tractor twice as fast as the rear wheels is operated, and in parallel with this, is supplied to the forward / reverse switching valve 18. Then, the forward / reverse switching hydraulic clutch 22 is operated, and after passing through the PTO speed change valve 16 and the forward / backward switching valve 18, it is returned to the oil tank 4 through the return oil passage 19.

In the first oil passage 6 for the first pump 1, the relief valve 2
6, a 2-position switching valve 27 and a draft control valve 28 are provided, and a relief valve 29, a 2-position switching valve 27 and an auxiliary control valve 30 are provided in the second oil passage 9 for the second pump 2. There is.

The two-position switching valve 27 has both oil passages 6 and 9 communicated with each other, has an independent position A and a merging position B, and can be artificially switched between the positions A and B. Independent position A is the first pump 1
Connected to the first actuator 8 and the second pump 2 to the second
The oil passages 6 and 9 are connected independently to the actuator 10, and the confluence position B is such that the first and second pumps 1 and 2 are both connected to the second actuator 10 so that the combined large flow rate pressure is obtained. It is in the form of supplying oil.

The relief pressures of the two relief valves 26, 29 are different, and the relief valve 26 for the first actuator 8 is set higher than the relief valve 29 for the second actuator 10, for example, the relief valve 29 is 180 kgf / cm. ^{At 2} , the relief valve 26 is set to 200 kgf / cm ² .

As a result, when the pressure oils of the first and second pumps 1 and 2 merge and are supplied to the second actuator 10, the relief pressure thereof becomes 180 kgf / cm ² , and only the relief valve 29 operates and the relief valve 26 Does not work, resonance is prevented and chattering noise is not generated. Further, by setting the relief pressure of the relief valve 26 high, it is possible to increase the operating force of the first actuator 8 or downsize the first actuator 8.

In the hydraulic circuit, the oil tank 4 to the three pumps 1,
Since a large amount of oil must be sucked into the second and third oils, the oil filter 33 can also pass a large flow rate.

This oil filter 33 can be a single large-capacity type, but since the oil filter is usually arranged on the side of the engine, it is not preferable to use a large-diameter filter because it will protrude from the bonnet. Therefore, it is conceivable to use two small-capacity ones. However, if one pipe of two oil filters is forked and simply connected in parallel, a large difference will occur in the hydraulic pressure flow, and one oil filter Filtration efficiency may decrease, and piping is difficult.

2 and 3 illustrate a dual oil filter 33 that solves the above problems.

34 is a common bracket, and two mounting screw bodies 35A and 35B
The case 36A, 36B is detachably screwed to each mounting screw body 35, and the element 3 is placed in each case 36A, 36B.
7 are arranged. Suction ports 39A, 39B are formed in the lid portion 38 of each case 36A, 36B, and the insides of the mounting screw bodies 35A, 35B are discharge ports 40A, 40B.

A suction passage 41 and a discharge passage 42 are formed in the common bracket 34 from the front and rear opposite directions, and the suction passage 41 includes two cases 36A and 36A.
The B suction ports 39A, 39B communicate with each other via the passages 43A, 43B, and the discharge passage 42 also communicates with the discharge ports 40A, 40B for the two cases 36A, 36B.

The suction passage 41 is a tapered hole, has a large thickness up to the suction port 39A in the front in the oil flow direction, and has a sufficient hole cross-sectional area for the oil amount of two oil filters to flow. The cross-sectional area of the hole from the port 39A to the suction port 39B is such that the amount of oil for one oil filter flows.

The discharge passage 42 is a divergent hole, has a narrow hole cross-sectional area from the discharge port 40A on the front side in the oil flow direction to the discharge port 40B on the front side, and is sufficient for the oil amount of one oil filter to flow.
The downstream side from the discharge port 40B is thick and has a hole cross-sectional area through which the oil amount of two oil filters can flow.

Since the suction passage 41 has a tapered shape, it has two cases.
It is possible to flow approximately even oil into 36A and 36B, and the discharge path 4
Since 2 has a divergent shape, almost even oil can be discharged from the two cases 36A and 36B, so that the dual oil filter 33 can sufficiently exert the filtering effect of two pieces. Become. Further, since the suction passage 41 and the discharge passage 42 are tapered in the opposite directions, they can approach each other in the left-right direction.
The left and right width of the common bracket 34 can be made sufficiently small.

Although the suction passage 41 and the discharge passage 42 are each formed of a two-step hole, they may be tapered holes, or may be cast holes instead of drill holes. In the case of a casting hole using a core, the tapered hole is easier to remove the core, and the cross-section can be formed into a non-round shape. 44
Is a magnet filter.

(Effect of the Invention) According to the present invention described in detail above, the two-position switching valve 27 is artificially switched between the independent position A and the merging position B, so that the two pumps 1 and 2 are connected to the main / auxiliary actuators 8. It is possible to adopt a mode in which the pressure oil is sent to each of the first and second pumps 10 and a mode in which the pressure oil is combined and sent to the sub-actuator 10, and the relief pressure of the relief valve 26 for the first pump 1 is set to the relief valve for the second pump 2. Since it is set higher than 29, even if the auxiliary actuator 10 is activated by combining the hydraulic pressures of both pumps 1 and 2, the first pump 1
The relief valve 26 for use does not operate, and the relief of the auxiliary actuator 10 at the time of merging can be performed only by the relief valve 29,
Therefore, resonance of the relief valves 26 and 29 can be prevented, chattering noise can be prevented from occurring, the relief pressure of the main actuator 8 can be set high, and chattering noise can be prevented from occurring.

[Brief description of drawings]

FIG. 1 shows a hydraulic circuit showing an embodiment of the present invention, FIGS. 2 and 3 show an example of a double oil filter, FIG. 2 is a longitudinal sectional view, and FIG. 3 is III- of FIG. It is a III line sectional view. 1 ... First pump, 2 ... Second pump, 6 ... First oil passage, 7 ... Hydraulic device, 8 ... First actuator (main actuator), 9 ... Second oil passage, 10 ... Second actuator (auxiliary actuator), 26 ... Relief valve, 27 ...
… 2-position switching valve, 28… draft control valve, 29… relief valve, 30… auxiliary control valve, A… independent position, B
...... Confluence position.

Claims (1)

(57) [Claims] 1. A first pump (1) and a main actuator (8) are connected by a first oil passage (6), and a second pump (2) is provided.
And a sub-actuator (10) are connected by a second oil passage (9), and a two-position switching valve (27) for artificial operation is provided in the middle of the first and second oil passages (6) and (9). , An independent position (A) that connects the first and second pumps (1) and (2) to the main and auxiliary actuators (8) and (10) to the two-position switching valve (27),
A confluence position (B) for connecting both the first and second pumps (1) and (2) to the auxiliary actuator (10) is provided, and a relief valve is provided between the two-position switching valve (27) and the first pump (1). (26)
The relief valve (29) is provided between the second pump (2) and the second pump (2), and the relief valve (26) is replaced by the relief valve (26) so that the relief of the auxiliary actuator (10) at the time of merging is performed only by the relief valve (29). 29) The hydraulic circuit of the working vehicle is characterized by setting the relief pressure higher than that of 29).