JPH0631017B2 - Hydraulic circuit of tractor - Google Patents

Description

The present invention relates to a hydraulic circuit for a tractor.

(Prior Art) In a hydraulic circuit of a tractor, a dual pump including a main hydraulic pump and a sub hydraulic pump is used, and the hydraulic oil is supplied from the main hydraulic pump to a working machine lifting hydraulic device and the sub hydraulic pressure is used. There is one in which a certain amount of hydraulic oil is supplied from a pump to a power steering device via a priority valve, and surplus oil from the priority valve is sent to the suction side of the main hydraulic pump.

In this type of hydraulic circuit, conventionally, when a part of the hydraulic oil is cooled, a method of interposing an oil cooler in the surplus flow circuit is adopted.

(Problems to be Solved by the Invention) In the past, since the oil cooler was in the surplus circuit, a high-pressure oil cooler with high pressure resistance had to be used.
There was a drawback that the production cost increased.

In view of such conventional problems, the present invention makes it possible to use an inexpensive oil cooler for low pressure, and to reduce the oil cooled by the oil cooler when the engine speed is high and energy absorption is large. The purpose of this is to supply oil for lubrication to prevent seizure of the hydraulic clutch.

(Means for Solving the Problem) As means for that purpose, the present invention includes a main hydraulic pump 27 that sends hydraulic fluid to a working machine lifting hydraulic apparatus 25, and another hydraulic apparatus 15.
Is provided with a sub hydraulic pump 28 for sending hydraulic oil via the priority valve 35, and the surplus flow circuit 37 of the priority valve 35 is connected to the main hydraulic pump 27.
In the hydraulic circuit of the tractor connected to the suction side of, a check valve 38 is provided in the surplus flow circuit 37 so that the surplus flow from the priority valve 35 flows to the main hydraulic pump 27 side. A lubrication circuit 39 for supplying a part of the surplus flow to the hydraulic clutches 12 and 13 for lubrication is connected to the excess flow circuit 37 between the oil flow path and the oil cooler 21. is there.

(Operation) When the engine 3 is operated, the hydraulic pumps 27 and 28 operate,
Inhale the oil in mission case 5. Then, the main hydraulic pump 27 discharges as hydraulic oil for the hydraulic devices 25 and 34,
In addition, the auxiliary hydraulic pump 28 is the hydraulic oil of the PS device 15, each clutch
11,12,13,18,19 hydraulic fluid and these clutches 11,12,1
Discharge as 3,18,19 lubricating oil.

Of the oil discharged from the sub-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 excess flow is divided from the priority valve 35 to the excess flow circuit 37. To 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 by the main hydraulic pump 27 together with the oil from the mission case 5. A part 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, and lubricates and cools the clutches 12 and 13. In this case, engine 3
Since the excess flow increases as the number of revolutions increases, the amount of lubricating oil increases when the number of revolutions is large and energy absorption is large, and seizure of the clutches 12 and 13 can be reliably prevented. Moreover, since the lubricating oil is cooled by the oil cooler 21, the cooling efficiency is good. Further, the lubricating oil then returns to the mission case 5, so that the oil can be cooled by the oil cooler 21, and since the oil cooler 21 is in the lubricating circuit 39, it is possible to use an inexpensive one for low pressure with low pressure resistance.

(Example) Hereinafter, the Example of this invention is described based on drawing. FIG. 2 shows an agricultural tractor, and 1 is a tractor vehicle body, which comprises a front vehicle bearing stand 2, an engine 3, a clutch housing 4, a mission case 5, and the like. A main clutch 6 is provided in the clutch housing 4, a traveling system forward / reverse switching device 7, a transmission device 8, a differential device 9 and the like are provided in the mission case 5, and a transmission shaft 10 of the PTO system is provided. , PTO clutch 11 and the like are provided. The forward / reverse switching device 7 has a forward clutch 12 and a reverse clutch 13. 14 is the front wheel,
This is a power steering device (hereinafter referred to as PS device)
It can be steered by 15. Reference numeral 16 is a rear wheel, and 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 switched to a high speed during turning.
20 is a radiator, 21 is an oil cooler, 22 is a bonnet,
Reference numeral 23 is a steering wheel linked to the PS device 15, and 24 is a driver's seat. A hydraulic device 25 for raising and lowering the working machine has a lift arm 26. Lubricant oil is stored in the mission case 5, and this oil is also used as hydraulic oil. Multi-plate hydraulic clutches are used for the clutches 11, 12, 13, 18, and 19.

FIG. 1 shows a hydraulic circuit, 27 is a main hydraulic pump, 28 is a sub hydraulic pump, and these are constituted by a dual pump. The suction circuit 29 is common and the transmission case 5 of the mission case 5 is connected via an oil filter 30. It is connected to the lower center. In addition,
The hydraulic pumps 27 and 28 are driven by the engine 3. The discharge circuit 31 of the main hydraulic pump 27 is connected to the hydraulic device 25 via the control valve 32.
Is connected to the hydraulic device 34 of the working machine via the auxiliary control valve 33, and supplies the hydraulic oil from the main hydraulic pump 27 to the hydraulic devices 25 and 34. A priority valve 35 is connected to the discharge side of the sub hydraulic pump 28, and a certain amount of oil from the sub hydraulic pump 28 is passed through the main circuit 36 to the PS device.
15 and supplies the excess flow to the excess flow circuit 37 and check valve 38.
It is returned to the suction side of the main hydraulic pump 27 via and is supplied to the forward clutch 12 and reverse clutch 13 for lubrication via a lubrication circuit 39. PS device 15 is PS
Control valve 40, metering pump 41, hydraulic cylinder for PS
It has 42 mag. The check valve 38 uses the excess flow to the main hydraulic pump 27.
It flows to the side and also functions as a protection for the seals at the lubrication destination. The lubrication circuit 39 is connected to the surplus flow circuit 37 between the priority valve 35 and the check valve 38, and the oil cooler 21 is interposed in the lubrication circuit 39.

A return circuit 43 is connected to the return side of the PS control valve 40, and the forward clutch 12 is connected to the return circuit 43 via a forward / reverse switching valve 44.
The reverse clutch 13 is connected to the low speed clutch 18 and the high speed clutch 19 via the high / low speed switching valve 45, and the PTO clutch 11 is connected via the PTO control valve 46.
Lubrication circuit that supplies lubricating oil to each clutch 11,12,13,18,19
47 is connected. 48 to 51 are relief valves, and 52 is an oil filter. The relief pressure of the relief valve 48 is higher 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 working machine lifting hydraulic device 25, and the auxiliary hydraulic pump 28 that sends hydraulic oil to another hydraulic device 15 via the priority valve 35. In the hydraulic circuit of the tractor in which the excess flow circuit 37 of the priority valve 35 is connected to the suction side of the main hydraulic pump 27, the excess flow from the priority valve 35 is made to flow to the main hydraulic pump 27 side in the excess flow circuit 37. As described above, the check valve 38 is interposed, and the surplus flow circuit 37 is provided between the check 38 and the priority valve 35, and the lubrication circuit 39 for supplying a part of the surplus flow for lubricating the hydraulic clutches 12 and 13 is provided. Since the oil cooler 21 is connected to the lubrication circuit 39, the low-cost inexpensive oil cooler 21 can be used, and the oil cooled by the oil cooler 21 has high engine speed and energy absorption. A large amount can be supplied as lubricating oil for the hydraulic clutches 12 and 13 when it is large. The burning of the latch 12 and 13 can be prevented.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a schematic side view of the tractor. 12 ... Forward clutch, 13 ... Reverse clutch, 15 ... Power steering device, 21 ... Oil cooler, 25 ... Hydraulic device, 27 ... Main hydraulic pump, 28 ... Sub hydraulic pump, 37 ...
… Excess flow circuit, 38 …… Check valve, 39 …… Lubrication circuit.

Claims (1)

[Claims] 1. A main hydraulic pump (27) for sending hydraulic oil to a working machine lifting hydraulic device (25), and a sub hydraulic pump for sending hydraulic oil to another hydraulic device (15) via a priority valve (35). (28) and in the hydraulic circuit of the tractor in which the surplus flow circuit (37) of the priority valve (35) is connected to the suction side of the main hydraulic pump (27), the surplus flow circuit (37) The surplus flow from (35) is transferred to the main hydraulic pump (2
A check valve (38) is installed so as to flow to the (7) side, and a part of the excess flow is hydraulic clutch (12) in the excess flow circuit (37) between this check (38) and the priority valve (35). ) A hydraulic circuit for a tractor, characterized in that a lubrication circuit (39) for supplying lubrication of (13) is connected, and an oil cooler (21) is interposed in this lubrication circuit (39).