JPH02199366A - Shift device for hydraulic transmission - Google Patents

Abstract

PURPOSE:To surely stop a motor shaft at the neutral position of a shift lever even if a link mechanism or the like has backlash by providing an opening/ closing valve on a bypass path provided between a pair of oil feed paths and opening the opening/closing valve at the neutral position of the interlockable shift lever. CONSTITUTION:An operation lever 22 is formed so that its cross section shape is protruded to the end section 78a side of a spool valve 78 at the center section and inclined on both the right and left sides apart from the end section 78a. When the operation lever 22 is rotated at the advance, neutral and reverse positions together with an operation main shaft, the end section 78a is pushed in at the neutral position and the spool valve 78 is opened, and a hydraulic motor is not rotated even if pressure oil is generated on a circulating pump side. Even if the oil feeding of the circulating pump is not completely stopped when a shift lever is shifted to the neutral position due to the backlash in a link mechanism or the like, the hydraulic motor can be completely stopped.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a shift device for a hydraulic transmission;
More specifically, the present invention relates to a shift device for a hydraulic transmission used in a working machine such as a riding lawn mower.

[Prior art]

2. Description of the Related Art Some working machines, such as riding lawn mowers, are equipped with a so-called hydraulic transmission as a transmission for transmitting power from an engine to wheels.

This hydraulic transmission is configured such that the input shaft is the pump shaft of a variable capacity circulation pump, and the output shaft is a motor shaft driven by the hydraulic pressure generated by the circulation pump. The direction of circulation is changed according to the rotation angle of a control shaft interlocked with a shift lever, and the motor shaft is switched between normal rotation, neutral rotation, and reverse rotation according to the rotation angle of a control shaft linked to a shift lever. A work machine equipped with such a hydraulic transmission is convenient in that the drive wheels can be switched between forward, neutral, and reverse by simply operating a shift lever without operating a clutch.

However, since the amount of oil fed by the circulation pump changes with slight changes in the angle of the control shaft, it is necessary to set the control shaft accurately to the neutral position when shifting from forward to neutral or from reverse to neutral. Otherwise, it will be difficult to completely stop the motor shaft. Tendency, -
In general, the link mechanism that connects the shift lever to the control shaft is composed of multiple links, but it is inevitable that these links will have looseness due to manufacturing errors and assembly errors, and there are many connection points for the links. As the errors accumulate and the backlash increases, it becomes increasingly difficult to set it to the neutral position accurately.

Although the above play can be absorbed by providing a length adjustment mechanism in the link mechanism, the adjustment work is extremely troublesome. Further, even if an accurate neutral position is temporarily set by adjusting the length, play may occur again due to distortion that occurs during use, so this cannot be said to be a perfect solution.

[Problem to be solved by the invention]

The object of the present invention is to solve the above-mentioned conventional problems, and regardless of whether there is play in the link mechanism between the shift lever and the control shaft, the motor shaft can be moved as long as the shift lever is shifted to the neutral position. An object of the present invention is to provide a shift device for a hydraulic transmission that can reliably stop the transmission.

[Means to solve the problem]

To achieve the above object, the present invention provides a pair of oil supply passages for circulating pressure oil between a circulation pump and a hydraulic motor,
The pump shaft of the circulation pump is used as an input shaft, while the motor shaft of a hydraulic motor driven by the pressure oil generated by the circulation pump is used as an output shaft, and the oil feed amount and circulation direction of the circulation pump are controlled by a shift lever. In the hydraulic transmission, the motor shaft can be switched between normal rotation, neutral rotation, and reverse rotation by changing the rotation angle of an interlocking control shaft, and a bypass path is provided between the pair of oil feed paths. The present invention is characterized in that an on-off valve is provided in the bypass passage, the on-off valve can be interlocked with the shift lever, and the valve is opened when the shift lever is in a neutral position.

The present invention will be explained below with reference to embodiments shown in the figures.

FIG. 7 schematically shows a riding lawn mower equipped with a hydraulic transmission according to the present invention.

In the figure, 1 is the car body, 2 is the engine mounted on the front of the car body l, 3 is the front wheel, 4 is the rear wheel, 5 is the handle,
6 is a sheet. Between the front wheel 3 and the rear wheel 4, a cutter housing 8 housing the cutter 7 is connected to the front and rear links 9.
, 9, and can be raised and lowered via a link mechanism 11 by operating an elevator lever 10.

The engine 2 has a crankshaft 12 extending in the front-rear direction, and a pulley 13 is fixed to an end protruding from the front end of the crankshaft 12. This pulley 13 includes a pulley 1 provided in the cutter housing 8.
A belt 16 is wound between pulleys 14 and 5, and a belt 19 is wound between pulleys 17 and 18 to drive the cutter 7. Further, the rear end of the crankshaft 12 protruding rearward is connected to a hydraulic transmission 20 at the rear of the vehicle body via a propulsion shaft 21, and power is input to the hydraulic transmission 20. The hydraulic transmission 20 transmits input power to the rear wheels 4 via a reduction gear in a gear case 23. By,
The output to the rear wheels 4 is switched between forward rotation (forward), neutral (stop), and reverse rotation (backward).

Further, the vehicle body 1 is provided with a foot brake 26.

When the foot brake 26 is depressed, the I-flange 27 rotates forward around the shaft 28, and the loft 29 connected to the lever 27 is pulled forward, thereby braking the rear wheel 4. It has become. Another rod 30 is connected to the lever 27, and two pairs of arms 31a, 31b; 32a, 32b (see FIG. 3) attached to the rear end are actuated in a scissor-like manner, and the bottle 33 is held between the levers. 45 to the center position, and the main operating shaft 4 of the shift lever 25 to which this lever 45 is fixed, as will be described later.
1 is forced to return to the neutral position.

5 and 6 show the hydraulic transmission 2.
6 shows the details of 0. The hydraulic transmission 20 has a main body composed of a housing portion 50 and a flat cover portion 51, and the main body is provided with a pump shaft 52 serving as an input shaft and a motor shaft 53 serving as an output shaft. Hippo part 5
1, oil feed grooves 71 and 72 are provided on both left and right sides of the pump shaft 52 and motor shaft 53 to communicate between the two wheels, and arc-shaped groove boats 73 are provided on both sides of the pump shaft 52 and motor shaft 53, respectively. 74, 75 and 76 are provided so as to communicate with the oil feed grooves 71 and 72.

The pump shaft 52 includes a variable capacity hydraulic pump. That is, a cylinder block 55 is pivotally supported on the pump shaft 52 so as to rotate integrally therewith, and a plurality of cylinders 54 . -.-154 are provided at equal intervals in the circumferential direction, and the cylinder boats 54a are brought into sliding contact with the inner surface of the cover part 51 by the elastic force of the spring. Further, a cup-shaped piston 56 is inserted into the cylinder 54 and is biased by a spring 57 toward the side opposite to the cylinder port 54a, so that its head is brought into sliding contact with the swash plate 58. The swash plate 58 is in sliding contact with the arcuate lining portion 59 and is connected to the control shaft 60 via an arm 61. The control shaft 60 is pivotally supported at the center of the arc of the lining portion 59, and by rotating the control shaft 60, the swash plate 58 can be tilted alternately between the solid line position and the chain line position. On the other hand, the motor shaft 53 is configured with a hydraulic motor. That is, the cylinder block 6 is attached to the motor shaft 53.
A cylinder block 65 is provided with a plurality of cylinders 64, -, 64 at equal intervals in the circumferential direction, and the cylinder bow 1-64a is partially covered by the elastic force of a spring. It is made to come into sliding contact with the inner surface of 51. A cup-shaped piston 66 is inserted into the cylinder 64, and is urged by a spring 67 toward the opposite side from the cylinder port 64a, so that its head slides into contact with the swash plate 68. This swash plate 68 is
It is fixed in an oblique position as shown in the figure.

In the above configuration, when the pump shaft 52 receives engine power and rotates in the six directions of arrows (see FIG. 6), the plurality of pistons 56. -., 56 slidingly contact the swash plate 58 to change the height, thereby changing the volume of the cylinder 54 into which each is inserted. When each cylinder 54 rotates along the boats 73 and 74 on both sides, the side where the cylinder volume changes from small to large becomes the suction side,
The side that changes from large to small is the discharge side. therefore,
When the swash plate 58 is inclined to the solid line position, the pressure oil flows as shown by the solid line arrow, and when it is inclined to the chain line position, it flows to the opposite side as shown by the chain line arrow.

By inputting such a flow of pressure oil, the hydraulic motor rotates so that the volume of the cylinder 64 of the motor shaft 53 changes from small to large.

Therefore, when the pressure oil flows as a solid line, the rotation is in the forward direction, and when the pressure oil flows as the chain line, the rotation is in the backward direction.

Furthermore, when the variable swash plate 58 is set perpendicular to the pump shaft 52 by operating the control shaft 60, no change in the volume of the cylinder 54 occurs, so no pressure oil flow occurs and the motor The shaft 53 does not rotate. That is, at this time, the hydraulic transmission 20 can be placed in neutral.

In the hydraulic transmission of the present invention, a bypass passage 77 is provided between the oil feed grooves 71 and 72 having the above structure, and a spool valve 78 is provided in the bypass passage 77 as an on-off valve.

When this spool valve 78 is opened, two oil feeding grooves 71.
Since oil can move freely between the pumps 72 and 72, the hydraulic motor can be prevented from rotating even if pressure oil is generated on the circulation pump side.

An end 78a of the spool valve 78 for performing such a hydraulic motor stopping action protrudes outside the hydraulic transmission 20, and an operating lever 22 is provided corresponding to the end 78a of the spool valve 78. As shown in FIG. 3, this operating lever 22 is integrally formed with a lever 45 fixed to an operating main shaft 41, and has a cross-sectional shape that protrudes toward an end 78a side at the center, and slopes on both left and right sides. 7
It is formed so as to move away from 8a. therefore,
This operating lever 22 moves forward, neutral, and
When rotating through each retreat position, the end portion 78a is pushed in at the neutral position to open the spool valve 78.

As described above, when the spool valve 78 is opened, the hydraulic motor does not rotate even if pressure oil is generated on the circulation pump side. In other words, even if the circulation pump does not completely stop supplying oil even if the shift lever is shifted to the neutral position due to looseness in the link mechanism, pressure oil moves through the bypass passage 77 and the hydraulic motor can be completely stopped.

Furthermore, in a normal hydraulic transmission, if the hydraulic motor does not rotate at the neutral position, the brakes will be applied and it will be difficult to tow the vehicle. However, in the case of the hydraulic transmission having the above structure, the oil can be moved via the bypass passage 77, so that the vehicle can be towed with a light force.

Moreover, the hydraulic transmission 20 in this embodiment
, another communication passage 79 is provided between both oil feed grooves 71, 72, and this communication passage 79 further communicates with an oil reservoir 81 via a communication passage 80. Furthermore, at the re-entrance end of the first communicating path 79, a check valve 82 with a small hole 82a is provided on one side, and a check valve 83 without a small hole is provided on the other side. The check valve 82 with the small hole 82a suppresses the initial pressure rise on the oil feed groove 72 side when switching to the reverse side, thereby widening the neutral region.

Figures 1 and 2 show the above-mentioned hydraulic transmission 2.
0 and the link mechanism 40 of the shift lever 25, FIG. 1 is a plan view, and FIG. 2 is a rear view.

The main operating shaft 41 of the link mechanism 40 is rotatably supported by a frame 1a fixed on the vehicle body 1.
A support tube 42 of the shift lever 25 is spline-fitted to one end of the shift lever 1. The shift lever 25 is rotatably supported by a bracket 43 fixed on the support tube 42 and maintained in a vertical position by a spring 44. On the other hand, the other end of the main operating shaft 41 is provided with the lever 4 described above.
5 is fixed so that it rotates together, and this lever 4
5 is provided with a bin 33 and a ti-making lever 22.

A rod 34 is rotatably connected to the bracket 43 supporting the shift lever 25 via a connecting bracket 43a, and a rotary lever 35 is attached to the other end of the rod 34.
are rotatably connected. This rotating lever 35 is designed to be rotated around a support shaft 36 on the bracket la between a forward position F and a reverse position R with a neutral position 1tfN in between as shown in the figure. A pin 37 fixed to a cam lever 35 is engaged with a cam groove 3Sa of a cam lever 38. The cam lever 38 is rotatably supported by a support shaft 39 on the bracket la, and its end is connected to a rotating lever 47 via a rod 46. This rotary lever 47 is connected to the hydraulic transmission 2 described above.
0, and the control shaft 60 is rotated.

Therefore, when the shift lever 25 is shifted toward the arrow F side, the bracket 43 rotates together with the operating main shaft 41, and the rotary lever 35 is rotated via the rod 34. This rotation of the rotary lever 35 causes the cam lever 38 to rotate via the pin 37, and further rotates the rotary lever 4 via the rod 46.
7 rotates, the control shaft 60 is rotated in the direction of arrow F. This rotation of the control shaft 60 causes the swash plate 58 of the hydraulic transmission to tilt as shown by the solid line in FIG. 5, and the hydraulic transmission 20 rotates the motor shaft 53 in the forward direction.

Furthermore, when the shift lever 25 is shifted in the direction of arrow R,
The bracket 43, rotary lever 35, cam lever 38, and rotary lever 47 rotate in the opposite direction to the above, and the swash plate 58 of the hydraulic transmission is tilted as shown by the chain line in FIG. is switched to rotate in the reverse direction.

When the shift lever 25 is set at the center as shown in FIG. 1.2, the swash plate 58 of the hydraulic transmission 20 becomes perpendicular to the pump shaft 52, and the circulation pump becomes neutral N, not sending pressure oil.

Further, when the neutral position N is set, the operating lever 22 provided at the shaft end of the operating main shaft 41 is moved to the spool valve 7 as described above.
8, the spool valve 78 is opened.

Therefore, the pressure oil can move freely in the bypass passage 77, and even if there is play in the link mechanism or the like, a situation is created in which the swash plate 58 of the hydraulic transmission 20 cannot be made completely perpendicular to the pump shaft 52. In other words, even if the circulation pump is in a situation where oil is being supplied, the motor shaft 53 will not be rotated.

In addition, although the above-mentioned embodiment explained the case of a hydraulic transmission applied to a lawn mower, the present invention is similarly applicable to a hydraulic transmission applied to other vehicles other than lawn mowers.

〔Effect of the invention〕

As described above, the present invention provides a pair of oil supply passages for circulating pressure oil between a circulation pump and a hydraulic motor, and uses the pump shaft of the circulation pump as an input shaft, while the circulation pump generates electricity. The motor shaft of a hydraulic motor driven by pressure oil is used as an output shaft, and the oil supply amount and circulation direction of the circulation pump are changed in accordance with the rotation angle of a control shaft linked to a shift lever, so that the motor shaft can be adjusted in the correct direction. In a hydraulic transmission capable of switching to any one of shift, neutral, and reverse, a bypass path is provided between the pair of oil feed paths, an on-off valve is provided in the bypass path, and the on-off valve is interlocked with the shift lever. The valve is opened when the shift lever is in the neutral position.

Therefore, there is a slight play in the link mechanism between the shift lever and the control shaft, which causes the shift lever to
Even in a situation where the oil supply of the circulation pump cannot be completely stopped even if the pump is set to the neutral position, the motor shaft can be reliably stopped by freely moving the pressure oil to the bypass path.

Furthermore, due to the movement of oil via the bypass path, the hydraulic motor does not apply the brakes in the neutral position, making it possible to tow the vehicle with a light force.

[Brief explanation of the drawing]

1 and 2 show essential parts of a shift device and a hydraulic transmission in the lawn mower shown in FIG. 7, with FIG. 1 being a plan view and FIG. 2 being a rear view. Figure 3 is m- of Figure 2.
An arrow view showing the main part in the m arrow view, Fig. 4 is IV-I in Fig. 3.
5 is a longitudinal sectional view of the hydraulic transmission, and FIG. 6 is a view taken along the line VI-VI in FIG. 4. FIG. 7 is a schematic side view of a lawn mower equipped with a hydraulic transmission shift device according to an embodiment of the present invention. 2...Engine, 12...Crankshaft, 20...
Hydraulic transmission, 22...operation lever, 25
...Shift lever-140...Link machine ll, 41
...Operating main shaft, 45...Lever, 52...Pump shaft, 53...Motor shaft, 60...Control shaft, 71.7
2... Oil feed groove (oil feed path), 77... Bypass path, 7
8... Spool valve (on/off valve), 78a... End. ■ Shi diagram diagram

Claims (1)

[Claims] A pair of oil supply passages for circulating pressure oil is provided between the circulation pump and the hydraulic motor, and the pump shaft of the circulation pump is used as an input shaft, while the hydraulic motor driven by the pressure oil generated by the circulation pump is The motor shaft is used as an output shaft, and the oil supply amount and circulation direction of the circulation pump are changed in accordance with the rotation angle of a control shaft linked to a shift lever, and the motor shaft is rotated in the normal direction.
In a hydraulic transmission capable of switching between neutral and reverse, a bypass path is provided between the pair of oil feed paths, an on-off valve is provided on the bypass path, and the on-off valve is interlocked with the shift lever. , a shift device for a hydraulic transmission configured to open a valve when the shift lever is in a neutral position.