JPS6134211Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a power steering system for agricultural tractors.It shortens the hydraulic piping so that the feeling of steering operation does not change even if the engine speed increases or decreases while the tractor is operating. In addition, part of the purpose of the present invention is to facilitate piping.

When a power steering device is adopted for an agricultural tractor and a hydraulic pump for lifting a working machine is also used as the hydraulic power source, a problem arises in that the operability of the steering changes as the engine speed increases or decreases. That is, as the engine speed increases, the flow rate of the hydraulic pump increases, the steering force becomes lighter, and the steering feel changes. As a countermeasure to this problem, it is possible to insert a flow divider into the discharge side flow path of the hydraulic pump to maintain a constant flow rate to the power steering device even when the engine speed increases or decreases. However, if a common hydraulic pump is used, it is possible to ensure a constant flow rate on the power steering device side due to the action of the flow divider, but the flow rate on the work equipment lift device side may decrease, especially when the engine speed is low. This may cause problems such as a lack of or instability.

In order to solve the above problem, this invention provides a hydraulic pump exclusively for power steering, and a flow divider is inserted between this hydraulic pump and the power steering device, so that the increased flow rate when the engine speed increases is returned to the tank. Next, it will be explained with reference to the drawings.

In Fig. 1 showing the left side of the fuselage of an agricultural tractor to which the present invention is applied, 1 is the engine at the front end of the machine, and a clutch housing 2 is fastened to the rear end face (right end face in the figure) with several bolts. Similarly, a transmission case 3 and a rear axle housing 4 are integrally connected to the rear of the clutch housing 2 in order to form a body that also serves as a frame at the center of the tractor. In front of the engine 1 (to the left in the figure), there is a radiator 6 across a gap or space 5 for arranging a cooling fan (not shown), and this radiator 6 is attached to a front axle bracket ( (not shown).

The oil strainer 7 is fixed to the left side wall (the front side in the figure) of the transmission case 3 with a plurality of bolts, and its suction port 8 is connected to the transmission case through a first low pressure pipe 9 and a joint 10 at its tip. The first low-pressure pipe 9 is connected to the lowest position of the oil reservoir in the transmission case 3, so that the first low-pressure pipe 9 is always filled with the oil in the transmission case 3. The discharge port 11 of the oil strainer 7 passes through the second low pressure pipe 12 to the suction port 14 of the lift arm hydraulic pump 13 and the power steering hydraulic pump 15.
are respectively connected to the suction ports 16. 17,1
8 is a rubber hose joint. Hydraulic pump 13,1
5 is attached with a plurality of bolts to the rear (right side in the figure) and front (left side in the figure) of a gear case 19 that protrudes from the engine 1 to the left side (the front side in the figure). 21 is connected to the engine 1 via a gear in the gear case 19. Specifically, for example, there is a PTO in the gear case 19 that constantly meshes with the intermediate gear in the engine 1.
(Power extraction) The gear is rotatably supported, and this
Input spline shaft 20,2 in the center of PTO gear
1 is provided with spline holes that engage from both sides. Of course, the input spline shaft 20 is located inside the gear case 19.
21 PTOs with different speeds that engage separately
It can also support gears. A small-capacity power steering hydraulic pump 15 is connected to the gear case 1.
9 is attached to the front of radiator 6 and engine 1
In contrast, a large-capacity lift arm hydraulic pump 13 is located behind the gear case 19 in a spacious space on the left side of the engine 1.

The discharge port 23 of the hydraulic pump 13 is connected to the first high pressure pipe 24
It is connected to the inlet 26 of the hydraulic cylinder case 25 through the. The discharge port 27 of the hydraulic pump 15 passes through the second high pressure pipe 28 to the inlet 3 of the flow divider 29.
0 and the outlet 3 of the flow divider 29.
1 is connected to an inlet 34 of a power steering device 33 via a third high-pressure pipe 32. An outlet 35 of the power steering device 33 is connected to a return port 38 of the transmission case 3 through return pipes 36 and 37. 39 and 40 are return ports of the flow divider 29, 41 is a return pipe joint, and 42 is a return pipe.
The flow divider 29 has a function of always supplying a constant amount of hydraulic fluid at a constant pressure to the power steering device 33 even when the rotational speed of the engine 1 changes.

Second low pressure pipe 12 and first and second high pressure pipes 24, 2
8 on the left side wall of the clutch housing 2, a low pressure pipe clamp plate 46 is attached to a pair of upper and lower reinforcing ribs 44 provided on the clutch housing 2 using bolts 45. First and second high pressure pipes 24 and 28 are clamped to the extended lower end portions.

When both hydraulic pumps 13 and 15 are driven by the engine 1 during operation of the tractor, the suction ports 14,
The oil inside the transmission case 3 is sucked through the first and second low pressure pipes 9 and 12 due to the negative pressure generated in the section 16, and the oil passes through the oil strainer 7 in the middle of the low pressure pipe and flows into the hydraulic pumps 13 and 15. flows into. The hydraulic oil pressurized by the hydraulic pump 13 is transferred to the first high pressure pipe 24
It is supplied to the hydraulic cylinder case 25 through the hydraulic cylinder case 25, and is used for raising and lowering the lift arm 22. The hydraulic oil pressurized by the hydraulic pump 15 passes through the second high-pressure pipe 28 and enters the flow divider 29, where it is adjusted to a constant oil amount and oil pressure, and then passes through the third high-pressure pipe 32 to the power steering device. 33 and discharged from the power steering device 33 is discharged into the transmission case 3 through return pipes 36 and 37.

In FIG. 2 showing the vertical left side of the flow divider 29 in FIG.
9 is a cylinder 48 that opens from the bottom and a cylinder 48 that opens from the top.
A stepped cylinder 49 is provided, and an upwardly opening cup-shaped spool 51 is fitted into the cylinder 48 so as to be movable up and down so as to compress a coil spring 50, and the lower end opening of the cylinder 48 is closed by a plug 52. The bottomed hole 53 in the spool 51 is connected to the second high-pressure pipe 28 at the inlet 30 via a throttle hole 54, an annular groove 55, and an inlet port 56. The annular groove 55 connects to the port 58 of the return port 40 through the land 57 of the spool 51, and the return port 40 connects to the tank through the return pipe 42. Ports 59 and 60 are provided so as to be partially closed by the upper edge of the spool 51,
The port 59 is connected to the power steering device through the discharge port 31 and the third high pressure pipe 32, and the port 60 is connected to the return pipe from the return port 39 through the poppet 61 fitted in the small diameter portion 49a of the two-stage cylinder 49. 36
is connected to. The poppet 61 is a coil spring 62
The poppet 61 normally rests in the closed position shown in the figure, and a cross-shaped relief hole 62 is provided in the lower half of the poppet 61. The annular groove 55 of the spool 51 communicates with an operating chamber 64 below the spool through a vertical groove 63.

Power steering hydraulic pump 15 (first
The pressurized hydraulic oil passes through the second high-pressure pipe 28 and enters the flow divider 29 from the inlet 30, and enters the flow divider 29 through the inlet port 56, the annular groove 55, and the throttle hole 5.
4. It enters the cylinder 48 through the bottomed hole 53, and is supplied to the power steering device through the port 59, the discharge port 31, and the third high-pressure pipe 32. Since a throttle hole 54 is provided in the flow path, the flow rate becomes constant due to its orifice action. When the discharge flow rate of the hydraulic pump increases due to an increase in the engine speed, the oil pressure in the annular groove 55 and the working chamber 64 increases due to the action of the throttle hole 54, and the spool 51 rises against the elasticity of the coil spring 50. , the annular groove 55 communicates with a return port 58, and excess hydraulic oil in the annular groove 55 is discharged into the tank through the return port 40 and the return pipe 42. Also, if the oil pressure at port 59 increases abnormally due to sudden power steering operation, etc.
The poppet 61 rises against the elasticity of the coil spring 62, the relief hole 62 communicates with the return port 39, and abnormal hydraulic pressure is released to the return port 39 side. That is, the poppet 61 serves as a safety valve. In this way, the flow divider 29 always supplies hydraulic fluid at a constant flow rate and constant oil pressure to the power steering device.

As explained above, in the present invention, the hydraulic pump 15 dedicated to power steering driven by the engine 1 and the hydraulic pump 13 dedicated to the lift arm are respectively attached to the front and rear of the gear case 19 extending to the side of the engine 1, and The strainer 7, the flow divider 29 that keeps the flow constant from the power steering hydraulic pump 15 to the power steering device 33, and the oil strainer 7 and both hydraulic pumps 15, 13 from the oil reservoir in the transmission case 3. All hydraulic piping leading to the power steering device 33 and the hydraulic cylinder case 25 with lift arm is connected to the engine 1.
Since it is arranged on one side of the integral assembly of the clutch housing 2, transmission case 3, and rear axle housing 4 on the side where both hydraulic pumps are disposed, the following special effects can be obtained. That is, even when the engine speed increases and the discharge flow rate of the hydraulic pump 15 increases, the power steering device 33
The flow rate supplied to the tank becomes constant, and the increased amount of hydraulic oil is returned to the tank, so the steering feel can be kept constant at all times. Also, the flow divider 29 is designed to return the increased flow rate when the engine speed increases to the tank, but since the hydraulic pump 15 is used exclusively for power steering,
Sufficient hydraulic oil can be supplied to the hydraulic cylinder case 25 for lifting the working machine from the hydraulic pump 13 dedicated to the lift arm, and the operation of the working machine lifting device is stabilized. Since the power steering hydraulic pump 15 has a small capacity, it is attached to the front side of the gear case 19 that protrudes to the side of the engine 1 to effectively utilize the limited space (gap 5) between the engine 1 and the radiator 6. Since the large-capacity hydraulic pump 13 for the lift arm can be placed in a relatively spacious space behind the gear case 19, the entire engine can be made compact, and each hydraulic pump 13, 15 can be installed and removed easily. Maintenance and inspection are also easier because they can be performed independently.

Furthermore, according to the present invention, both hydraulic pumps 15, 13
Because the installation locations of the first and second low pressure pipes 9,
12 can be used for both hydraulic pumps 15 and 13, and the required length of the low pressure pipe can be minimized. Also, since the flow divider 29 is placed on the same side as the oil strainer 7 and both hydraulic pumps 15, 13 (the front side in Figure 1), all the piping can be arranged on the same side as both oil pumps 15, 13. This shortens the length of piping and simplifies piping work.

[Brief explanation of the drawing]

FIG. 1 is a schematic left side view showing the piping layout of an agricultural tractor to which the present invention is applied, and FIG. 2 is a vertical left side view of the flow divider in FIG. 1. 15...Hydraulic pump for power steering, 2
9...Flow divider, 33...Power steering device.

Claims (1)

[Scope of utility model registration request] A hydraulic pump 15 dedicated to power steering driven by the engine 1 and a hydraulic pump 13 dedicated to the lift arm are respectively attached to the front and rear of the gear case 19 projecting out to the side of the engine 1, and an oil strainer 7 and a hydraulic pump 15 for power steering are installed. From power steering device 3
Flow divider 2 that maintains a constant flow rate up to 3.
9 and the oil reservoir in the transmission case 3, through the oil strainer 7, both hydraulic pumps 15 and 13, to the power steering device 33, and the hydraulic cylinder case 25 with lift arm. A power steering device for an agricultural tractor, characterized in that the power steering device is disposed on one side of an integral combination of a front case 3 and a rear axle housing 4 on the side where both hydraulic pumps are arranged.