JP2002238309A - Hydraulic system of tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a tractor (lawn mower) starts a mowing work, when the grounding rollers and a gauge wheel of an implement (mower) mounted on the tractor is grounded on the surface of the ground and then when the control valve of the hydraulic valve of a lifting unit is operated to a lower position, but can not carry out the mowing work in a precise mowing height, because the implement has a large weight to sink the grounding rollers and the gauge wheel in soil. SOLUTION: A power steering unit 3 for steering front wheels, a lifting or lowering unit 6 for lifting or lowering an implement, and a hydraulic change unit 7 for changing a travel power are allowed to communicate with each other in series through a series of hydraulic circuits. On the basis of the lowering state operation of the hydraulic valve 9 of the lifting or lowering unit 6, the charge pressure of the hydraulic stepless change device 25 of the hydraulic change unit 7 is utilized to impart a back pressure to a hydraulic cylinder 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for applying a back pressure to a hydraulic cylinder in a hydraulic circuit having a structure in which a power steering unit, a lifting / lowering unit, and a hydraulic transmission unit are connected in series by a series of hydraulic paths. Yes, and can be used as a hydraulic device for tractors.

[0002]

2. Description of the Related Art A hydraulic device for a tractor (for example, a lawn mower) includes a power steering unit for steering front wheels based on an operation angle of a steering handle, and a working machine (for example, a mower) supported on a traveling vehicle body so as to be able to move up and down. And a hydraulic transmission unit for shifting the traveling power are connected in series through a series of hydraulic paths. The hydraulic cylinder for raising and lowering the mower is supplied with hydraulic oil, stopped, and operated by switching a control valve that is connected to a raising circuit, a lowering circuit, and a neutral circuit provided in the lifting unit 6 through a neutral circuit.
The system is configured so that each operation of ascent, stop, and descent can be performed by draining the oil.

In the conventional hydraulic device, when a predetermined cutting height is set by operating a vertical position of a gauge wheel,
The mower's grounding roller and the gauge wheel run while touching the ground, and when the work is started by operating the control valve of the hydraulic valve of the elevating unit of the hydraulic device to the lowered position, the mower is set to a predetermined predetermined value. The mower is controlled to be lowered by the operation of the hydraulic cylinder so as to reach the cutting height, so that the ground roller and the gauge wheel are always controlled to be in contact with the ground so as to cut at a predetermined cutting height, The turf is cut.

[0004]

The mower's ground roller and the gauge wheel are grounded to the ground, and the lawn mowing operation is started by operating the control valve of the hydraulic valve of the elevating unit to the lowered position. If the weight is heavy, the ground roller and the gauge wheel of the mower may sink into the ground, and the mowing height of the turf is set from the ground position of the gauge wheel. When the sun sinks into the soil, the lawn is cut low, and the set cutting height cannot be obtained, or the sunken parts are damaged. The present invention is intended to solve these problems.

[0005]

For this purpose, the present invention provides a power steering unit 3 for steering a front wheel 2 by operating a steering handle 1, and a lifting unit 6 for a working machine 5 supported on a traveling vehicle body 4 so as to be able to move up and down. And a hydraulic transmission unit 7 for shifting the traveling power in a series of hydraulic paths in a hydraulic circuit, wherein the hydraulic valve 9 of the elevating unit 6 is operated in a lowered state to operate the hydraulic transmission unit. 7. A tractor hydraulic device characterized in that it is provided to apply back pressure to the hydraulic cylinder 8 using the charge pressure of the hydraulic continuously variable transmission 25.

[0006]

The hydraulic device of the tractor (mower) includes a power steering 3 for steering the front wheels 2 based on an operation angle of a steering handle 1, and a work machine (mower) 5 supported on a traveling body 4 so as to be able to move up and down. Lifting control unit 6 of
This is a configuration in which a hydraulic transmission unit 7 for shifting the traveling power is connected in series through a series of hydraulic paths. And working machine 5
The hydraulic cylinder 8 that raises and lowers the hydraulic oil is supplied, stopped, and drains the hydraulic oil by switching a control valve that is communicated via a raising circuit and a lowering circuit of a hydraulic valve 9 of the lifting and lowering unit 6 to raise and stop. , Each operation of descent can be performed. Further, the lowering operation of the control valve of the hydraulic valve 9 causes the hydraulic transmission unit 7 to operate.
The back pressure is applied to the hydraulic cylinder 8 using the charge pressure of the hydraulic continuously variable transmission 25.

In the lawn mowing operation, when the vertical position of the gauge wheel is operated to a predetermined cutting height, the ground roller of the working machine 5 and the gauge wheel can be brought into contact with the ground and run, and the lifting unit of the hydraulic device can be moved. When the work is started by operating the control valve of the hydraulic valve 9 to the lowered position, the work machine 5
The working machine 5 is controlled to be lowered by the operation of the hydraulic cylinder 8 so as to achieve the set predetermined cutting height, so that the grounding roller and the gauge wheel are always moved to cut the lawn at the predetermined cutting height. At the same time as the grounding state is controlled to the ground, the charge pressure of the hydraulic continuously variable transmission 25 of the hydraulic transmission unit 7 further acts as a back pressure on the hydraulic cylinder 8, and the working load of the working machine 5 is reduced as it floats. The turf is being harvested.

[0008]

The charge pressure of the hydraulic continuously variable transmission 25 of the hydraulic transmission unit 7 is applied to the hydraulic cylinder 8 as back pressure, so that the ground load of the working machine 5 is reduced, and the ground roller of the working machine 5 The gauge wheel can be prevented from sinking into the soil, and thereby, the lawn can be mowed while maintaining the predetermined cutting height that has been set.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The tractor 15 will be described as a lawn mower 15 in the embodiment, for example. The working machine 5 installed below the traveling body 4 of the lawn mower 15 is, for example, in the embodiment,
The description will be made with the mower 5 attached. The hydraulic device of the lawn mower 15 includes a power steering unit 3 for steering a front wheel 2 by operating a steering handle 1 provided at a front portion of a body frame 16, and a mower 5 supported on a traveling body 4 so as to be able to move up and down.
Is a hydraulic circuit having a configuration in which a lifting unit 6 for raising and lowering the hydraulic power unit and a hydraulic transmission unit 7 for shifting the traveling power are connected in series through a series of hydraulic paths, and a hydraulic device formed by the hydraulic circuit is mainly illustrated. explain.

As shown in the figure, the lawn mower 5 supports a front wheel 2 which is steered from a steering handle 1 via a power steering unit 3 at a front portion of a body frame 16 and a driving wheel at a rear portion. The rear wheel 17 is provided. The engine 18 is mounted inside an engine room covered by a hood cover 19 on the front side of the vehicle body frame 16, and the rotational power is transmitted to a traveling transmission case 20, a hydraulic pump 21 and a mower 5 which are driven backward. It is a configuration for transmitting. 34 is an oil tank.

The mower 5 is provided with a cutting blade that rotates on the vertical axis inside the cutting blade housing 22, and
Are supported by a main link 23a and a front link 23b at the center lower left and right, respectively, in a suspended state. The mower 5 is provided by mounting a projecting lower end of a crank arm 23c having an upper end connected to the hydraulic cylinder 8 to a substantially intermediate portion of a support frame 40 integrated with the mower 5 via a lift link 23d. The mower 5 is configured to be able to move up and down by the expansion and contraction operation of.

The mower 5 has an input shaft 22a extending from the front side as shown in FIG. 3, and further has a ground roller 24a on the lower surface of the front part and a gauge wheel 24b on the rear part. Each unit 3, 6, 7 on the hydraulic circuit of the hydraulic device
1, the power steering unit 3 connected to the steering handle 1 is provided on the basis of a hydraulic pump 21 driven by the engine 18 as shown in FIG. 1, and the lifting unit 6 connected to the hydraulic cylinder 8 is provided. And a hydraulic transmission unit 7 that constitutes the hydraulic continuously variable transmission 25 is provided.

The hydraulic circuit shown in FIG. 1 will be described. This hydraulic circuit is connected to the power steering unit 3 using a port orbit roll from the side close to the hydraulic pump 21 via a high-pressure oil passage 50, and if a pressure oil of a predetermined flow rate or more is flowing through a branch valve 51. When the pressure oil is connected to the hydraulic valve 9 at 52 and the flow rate is equal to or less than a predetermined flow rate, the pressure oil passing through the power steering unit 3 is connected to and supplied to the hydraulic valve 9 as a pump oil passage 53. Further, an oil passage exiting from the hydraulic valve 9 is provided with an unload circuit 31 and a tank circuit 30 described later.
, The lifting oil passage 5 connected to the hydraulic cylinder 8 for lifting
4 are provided.

The unload circuit 31 is configured to communicate in series with a hydraulic transmission unit 7 for shifting the traveling power through a series of hydraulic paths. The power steering unit 3 is configured to steer the front wheels 2 left and right via the two-chamber cylinder 41 by switching a valve 26 which is operated by an operation angle of the steering handle 1.

The raising / lowering control unit 6 of the mower 5 includes a raising circuit 10 with the control valve 9a of the hydraulic valve 9 in the U position.
And the lowering circuit 11 at the position D, the mower 5 is connected to the hydraulic cylinder 8 so as to be able to move up and down.
The hydraulic transmission unit 7 includes a variable hydraulic pump 27,
A hydraulic continuously variable transmission 25 including a hydraulic motor 28 is configured to change the traveling power.

The hydraulic circuit shown in FIG.
The lifting unit 6 will be further described. The lifting unit 6 includes a pump circuit 29 that communicates with the hydraulic pump 21 to supply hydraulic oil, and a tank circuit 30 that discharges hydraulic oil.
And a raising circuit 10 for supplying hydraulic oil to the hydraulic cylinder 8, a lowering circuit 11 for discharging the hydraulic oil, and an unloading circuit 31 for feeding the hydraulic oil to the charge oil passage of the hydraulic transmission unit 7.

The control valve 9a of the hydraulic valve 9 is a switching valve that slides left and right based on the operation of the hydraulic lever 42. The control valve 9a is provided with a neutral position (N) at the center and a lowered position (N) at one side. D), and a lifting position (U) is provided on the other side. Therefore, when the control valve 9a is switched to the raising position (U), the unload circuit 31 is closed, and the pressure oil of the pump circuit 29 is supplied to the check valve 12 via the throttle 43.
Is opened to communicate with the lifting circuit 10. When switching to the lowering position (D), the pressure oil of the pump circuit 29
The pilot circuit 32 opens the pilot check valve 13 and acts on the hydraulic cylinder 8 via the throttle 45, thereby causing the mower 5 to act in the floating direction. Further, the pilot check valve 13
When the pressure is not applied to the pilot circuit 32, the pilot circuit 32 is connected so that the opening operation can be performed by the pressing pin 14 which can be manually pushed from the outside.

The hydraulic cylinder 8 is supplied or discharged with hydraulic fluid by a raising circuit 10 and a lowering circuit 11 in conjunction with a switching operation of a control valve 9a of a hydraulic valve 9, and the mower 5 is raised and lowered. The pilot check valve 13 of the lowering circuit 11 opens when the pilot pressure of the oil supplied from the control valve 9a side to the pilot circuit 32 is generated as described above, and the hydraulic oil flows to the unload circuit 31 side. The mower 5 is ejected, and the mower 5 is lifted up, and a resistance is given to the lowering operation of the lowering operation.

When the mower 5 performs mowing work, the gauge wheel 24b is adjusted to a predetermined height position according to the mowing height of the lawn, and the control valve 9a of the hydraulic valve 9 of the elevating unit 6 is lowered to the lower position. (D), the lowering circuit 11 and the unloading circuit 31 are in communication with each other, and when the lawn mowing operation is started, the ground roller 24a and the gauge wheel 24b provided on the cutting blade housing 22 are moved to the ground. The mower 5 is driven up and down to control the mower 5 to a predetermined cutting height, and the mower 5 is controlled to descend to cut the grass at a predetermined cutting height. In order to keep the ground roller 24a and the gauge wheel 24b
Means that the ground is in contact with the ground and is controlled so that it rises to the ground, and is cut to prevent sinking into the ground.

At this time, the port of the hydraulic cylinder 8 communicates with the unload circuit 31 of the hydraulic continuously variable transmission 25 of the hydraulic transmission unit 7, and the charge pressure of the relief valve 33 of the hydraulic continuously variable transmission 25 is controlled. For example, 5kg / c
utilizing m ^2, is added to the back pressure to the hydraulic cylinder 8, the force to lift the mower 5 is generated by the pressure cylinder 8, the ground contact load of the mower unit 5 is configured to be reduced, The mower 5 has a configuration in which the ground roller 24a and the gauge wheel 24b provided on the mowing housing 22 are prevented from sinking.

For example, 5 kg / c of the charge pressure
m ² is a mower 5 completely lifted, rather than pressure to float, merely, the mower 5 is a structure capable of traveling to follow the ground. As a result, although the weight of the mower 5 is large, the charge pressure is applied to the hydraulic cylinder 8 as back pressure, so that the ground load of the mower 5 is reduced, and the ground roller 24a and the gauge wheel 24b
It is possible to prevent sinking in the soil, and thereby, it is possible to mow the turf while maintaining the set predetermined cutting height.

FIG. 2 shows another example of the pilot check valve 13 in detail, which will be described below. A pilot piston 36 for pushing and opening the pilot check switch 35 at the time of lowering the mower 5 is provided. The pilot piston 36 has a larger cross-sectional area in the radial direction than the poppet 37 of the pilot check switch 35. Thus, when the pressing pin 14 is pressed, the pilot check switch 35 can be pressed and opened at a low pressure. 38 is a spring for pressing resistance.

In the neutral state N of the control valve 9a in FIG. 2, the pressure oil from the hydraulic pump 21 is supplied to the unload circuit 31 of the hydraulic continuously variable transmission 25 through the position of the control valve 9aN.
When the control valve 9a is in the lowered state D, the control valve 9a, which is a spool, moves to the right, and the pressure oil from the hydraulic pump 21
While being supplied to the unloading circuit 31 of the hydraulic continuously variable transmission 25, it communicates with the back of the pilot check switch 35 in the pilot check valve 13 and the pilot piston 36 through the oil drain passage 44 as shown by an arrow (c). The poppet 37 is pressed and moved in the direction of the arrow (d) due to the difference in the cross-sectional area to open the pilot check valve 13.

The pilot piston 36 is actuated to push and open the poppet 37, and the unloading circuit 31 of the hydraulic continuously variable transmission 25 is moved from the arrow E through the throttle 45 to the lifting circuit 10.
And the charge pressure to the hydraulic cylinder 8, for example, 5
It is configured to apply a back pressure of kg / cm ² .

Thus, the conventional pilot piston 3
In the configuration without 6, the pressure difference is small to apply pressure directly to the back 46 of the pilot check switch 35, and a high pressure is required to push and open the poppet 37, resulting in a loss of horsepower and an increase in oil temperature. However, since the large-diameter pilot piston 36 is formed by the configuration of this another drawing, a difference in cross-sectional area from the poppet 37 is provided, so that even if the pressure is low or the same, the poppet Opening 37 and applying back pressure to the hydraulic cylinder 8 became possible because the radial dimensional difference was increased.

In the configuration shown in FIGS. 1 and 2 (N state), the control valve 9a of the hydraulic valve 9 is in the neutral position (N).
In this case, the pilot check switch 35 and the pilot piston 36 are connected directly to the oil tank 34 port as shown by the arrow.

Thus, conventionally, when the engine 18 is stopped and the mower 5 is attached or detached, when the back pressure is left behind the pilot piston 36 and the pressing pin 14 is pushed back, the manual operation of pushing the pressing pin 14 is performed. Although the operation could not be performed, according to the present invention, by connecting the back of the pilot piston 36 to the oil tank 34 port at the time of neutral operation, the hydraulic cylinder 8 can be freely moved at the time of manual operation, and Desorption is easy.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic device.

FIG. 2 is an enlarged sectional side view of a pilot check switch unit.

FIG. 3 is an overall side view of the lawn mower.

FIG. 4 is a side view of each hydraulic unit arrangement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering handle 2 Front wheel 3 Power steering unit 4 Traveling platform 5 Work machine (Mower) 6 Elevating unit 7 Hydraulic transmission unit 8 Hydraulic cylinder 9 Hydraulic valve 25 Hydraulic continuously variable transmission

Claims (1)

[Claims] 1. A front wheel 2 is operated by operating a steering handle 1.
Power steering unit 3 for steering the vehicle and traveling vehicle body 4
The hydraulic circuit has a configuration in which an elevating unit 6 of a working machine 5 supported so as to be movable up and down and a hydraulic transmission unit 7 for shifting the traveling power are connected in series through a series of hydraulic paths. 9 based on the operation of the lower state,
A hydraulic system for a tractor provided to apply back pressure to a hydraulic cylinder (8) by utilizing charge pressure of a hydraulic continuously variable transmission (25) of a hydraulic transmission unit (7).