JPH02102881A - Hydraulic circuit for tractor - Google Patents

Abstract

PURPOSE:To make an inexpensive oil cooler for low pressure usable by connecting a hydraulic clutch and a lubricating circuit for lubrication both to an excess flow circuit between a check valve and a preferential valve, and installing the oil cooler in this lubricating circuit, in a hydraulic circuit used with a double pump. CONSTITUTION:A hydraulic system 25 is connected to a discharge circuit 31 of a main hydraulic pump 27 driven by an engine via a control valve 32, while a hydraulic system 34 for a farm working machine is connected thereto via an auxiliary control valve 33. Likewise, a preferential valve 35 is connected to the discharge side of a sub hydraulic pump 28 driven by the engine, and a fixed quantity of oil out of this sub hydraulic pump 28 is fed to a power steering system 15 by way of a main circuit 36. In this case, an excess flow is put back to the suction side of the main hydraulic pump 27 via an excess flow circuit 37 and a check valve 38, while it is constituted so as to be fed to a forward clutch 12 and a backward clutch 13 as lubrication use via a lubricating circuit 39 which is connected to the excess flow circuit 37 between the preferential valve 35 and the check valve 38, while an oil cooler 21 is interposingly installed in the midway.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydraulic circuit for a tractor.

(Prior art) In the hydraulic circuit of a tractor, a dual-type pump including a main hydraulic pump and an auxiliary hydraulic pump is used. There is one in which a fixed amount of hydraulic oil is supplied from the pump to the power steering device via a priority valve, and excess oil from the priority valve is sent to the suction side of the main hydraulic pump.

Conventionally, in this type of hydraulic circuit, when a portion of the hydraulic oil is cooled, an oil cooler is installed in the surplus flow circuit.

(Problem to be solved by the invention) Conventionally, the oil cooler was in the surplus flow circuit, so a high-pressure oil cooler with high pressure resistance had to be used.
This had the disadvantage of increasing production costs.

In view of these conventional problems, the present invention makes it possible to use an inexpensive low-pressure oil cooler, and also transfers the oil cooled by the oil cooler to the hydraulic clutch when the engine speed is high and energy absorption is large. The purpose is to supply it as a lubricant for hydraulic clutches and prevent seizing of hydraulic clutches.

(Means for Solving the Problems) As a means for achieving this, the present invention provides a main hydraulic pump 27 that sends hydraulic oil to the hydraulic system 25 for lifting and lowering the working machine, and a separate hydraulic bag y115 through which hydraulic oil is sent via a priority valve 35. A surplus flow circuit 37 of the priority valve 35 is provided.
In the hydraulic circuit of the tractor connected to the suction side of the main hydraulic pump 27, a check valve 38 is connected to the surplus flow circuit 37 so that the surplus flow from the priority valve 35 flows to the main hydraulic pump 27 side.
A part of the surplus flow is transferred to the surplus flow circuit 37 between the check 38 and the priority valve 35 through the hydraulic clutches 12 and 13.
A lubrication circuit 39 for supplying lubrication is connected thereto, and an oil cooler 21 is interposed in this lubrication circuit 39.

(Function) When the engine 3 is operated, the hydraulic pumps 27 and 28 are activated to suck oil in the transmission case 5. The main hydraulic pump 27 discharges hydraulic oil for the hydraulic system 25.34, and the auxiliary hydraulic pump 28 discharges hydraulic oil for the PS device 15, hydraulic oil for each clutch 11, 12, 13, 18, 19, and these clutches. 11, 12, 13.18.19
It is discharged as a lubricating oil.

Of the oil discharged from the auxiliary hydraulic pump 28, a constant amount is always sent from the main circuit 36 to the PS device 15 via the priority valve 35, and the remaining surplus flow is diverted from the priority valve 35 to the surplus flow circuit 37. do. Then, the surplus flow is returned to the suction side of the main hydraulic pump 27 via the check valve 38, and is sent together with the oil from the transmission case 5 by the main hydraulic pump 27. Further, a portion of the surplus flow is supplied to the forward clutch 12 and the renewal clutch 13 for lubrication through the lubrication circuit 39 and the oil cooler 21, thereby lubricating and cooling each clutch 12, 13. In this case, as the rotational speed of the engine 3 increases, the surplus flow also increases, so when the rotational speed is high and energy absorption is large, the amount of lubricating oil increases, ensuring that each clutch 12 and 13 seizes. can be prevented. Moreover, since the lubricating oil is cooled by the oil cooler 21, the cooling efficiency is also good. Further, since the lubricating oil then returns to the transmission case 5, the oil can be cooled by the oil cooler 21, and since the oil cooler 21 is located in the lubrication circuit 39, an inexpensive one for low pressure with low pressure resistance can be used.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an agricultural tractor, where l is the tractor body, which consists of a front wheel bearing stand 2, an engine 3, a clutch housing 4, a transmission case 5, and the like. A main clutch 6 is provided within the clutch housing 4, and a forward/reverse switching device 7, a transmission 8, a differential device 9, etc. of the traveling system are provided within the transmission case 5, as well as a PTO system transmission shaft 10. ,
A PTO clutch 11 and the like are provided. The forward/reverse switching device 7 has a forward clutch 12 and a reverse clutch 13. Reference numeral 14 denotes a front wheel, which can be steered by a power steering device (hereinafter referred to as a PS device) 15. 16 is
The rear wheel 17 is a front wheel power take-off device, which has a low speed clutch 18 and a high speed clutch 19 so that the front wheel speed can be changed to high speed when turning. 20 is a radiator, 21 is an oil cooler, 22 is a bonnet, 23 is a PS device 15
24 is the driver's seat.

25 is a hydraulic system for lifting and lowering the working machine, and has a lift arm 26. Note that lubricating oil is stored in the transmission case 5, and this oil is also used as hydraulic oil. A multi-disc hydraulic clutch is used for the clutches 11, 12, 13, 18, and 19.

1 shows a hydraulic circuit, 27 is a main hydraulic pump, 28 is an auxiliary hydraulic pump, these are composed of two pumps, and their suction circuit 29 is common, and the transmission case 5 is connected to the transmission case 5 through an oil filter 30. Connected to the bottom center. Note that the hydraulic pumps 27 and 2B are driven by the engine 3. The discharge circuit 31 of the main hydraulic pump 27 is connected to the control valve 3
Hydraulic system through 2! 25, and is also connected to the hydraulic system 34 of the working machine via the auxiliary control valve 33, and the hydraulic oil from the main hydraulic pump 27 is supplied to the hydraulic system 25.3.
4. A priority valve 35 is connected to the discharge side of the auxiliary hydraulic pump 28, which supplies a certain amount of oil from the auxiliary hydraulic pump 28 to the PS device 15 via the main circuit 36, and supplies surplus flow to the surplus flow circuit 37, It is returned to the suction side of the main hydraulic pump 27 via the check valve 38, and the forward clutch 12 and reverse clutch 13 are returned via the lubrication circuit 39.
It is designed to be supplied for lubrication. PS device 1
5 is a PS control valve 40, a metering pump 41. It has a PS hydraulic cylinder 42 and the like. The check valve 3B allows surplus flow to flow to the main hydraulic pump 27 side, and also functions to protect the seals of the lubricating light. The lubrication circuit 39 is a priority valve 35
The lubricating circuit 39 is connected to a surplus flow circuit 37 between the lubrication circuit 39 and the check valve 38, and an oil cooler 21 is interposed in the lubrication circuit 39.

A return circuit 43 is connected to the return side of the PSS control area 40,
The forward clutch 12 and the reverse clutch 13 are connected to this return circuit 43 via a forward/reverse switching valve 44, and a high/low speed switching valve 45.
The low speed clutch 18 and the high speed clutch 19 are connected through the PTO control valve 46, and the PTO clutch 11 is connected through the PTO control valve 46.
A lubrication circuit 47 is connected to 18 and 19 for supplying lubricating oil. 48 to 51 are relief valves, and 52 is an oil filter. Note that the reel pressure of the relief valve 48 is greater than that of the relief valve 49.

(Effects of the Invention) According to the present invention, the main hydraulic pump 27 that sends hydraulic oil to the hydraulic system 25 for lifting and lowering the work machine, and the priority valve 3 that is connected to another hydraulic system 15.
5, and a secondary hydraulic pump 28 that sends hydraulic oil through the main hydraulic pump 27.
In the tractor's hydraulic circuit connected to the suction side of A lubrication circuit 39 for supplying a portion of the surplus flow to lubricate the hydraulic clutch 1213 is connected to the surplus flow circuit 37 between the lubrication circuit 39 and the oil cooler 21 interposed in the lubrication circuit 39. In addition to being able to use an inexpensive oil cooler 21 for low pressure, a large amount of oil cooled by the oil cooler 21 can be supplied as lubricating oil for the hydraulic clutches 12 and 13 when the engine speed is high and energy absorption is large. .13 seizure can be prevented.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention, and FIG. 2 is a schematic side view of the same tractor. 12...Forward clutch, 13...Reverse clutch, 1
5... Power steering device, 21... Oil cooler, 25... Hydraulic device, 27... Main hydraulic pump,
28... Sub-hydraulic pump, 37... Surplus flow circuit, 38
...Check valve, 39...Lubrication circuit.

Claims (1)

[Claims] (1) A main hydraulic pump (27) that sends hydraulic oil to a hydraulic system for lifting and lowering work equipment (25), and an auxiliary hydraulic pump (28) that sends hydraulic oil to another hydraulic system (15) via a priority valve (35). )
and a surplus flow circuit (37) of the priority valve (35).
) is connected to the suction side of the main hydraulic pump (27), and the surplus flow circuit (37) is connected to the priority valve (
A check valve (38) is installed so that the surplus flow from the main hydraulic pump (27) flows from the check valve (38) to the main hydraulic pump (27).
) and the priority valve (35), a lubrication circuit (39) is connected to the surplus flow circuit (37) for supplying a portion of the surplus flow for lubrication of the hydraulic clutches (12) and (13), A hydraulic circuit for a tractor, characterized in that an oil cooler (21) is interposed in the lubrication circuit (39).