JP2007078000A - Hydrostatic continuously variable transmission for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrostatic continuously variable transmission for a working vehicle which may not start nor stop suddenly even by changing a rotation angle of a trunnion shaft near the neutral position. <P>SOLUTION: An eccentric cam 42 is installed in a crank arm 37 which is an interlocking member between the trunnion shaft 36 and a swash plate 3. Since the inclination angle of the swash plate 3 changes quadratically from the neutral position of an HST toward either positive or negative side with respect to the rotation angle of the trunnion shaft 36, but the inclination angel of the swash plate 3 does not change rapidly, the movement of the swash plate 3 near the neutral position can be minimized compared with the movement of the trunnion shaft 36. Thereby, the neutral position can be easily controlled, while the most subtle operation can be made for the working vehicle near the neutral position, so that the starting and stopping can be smoothly performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrostatic continuously variable transmission for a work vehicle.

Conventionally, work vehicles such as rice transplanters equipped with a hydrostatic continuously variable transmission (sometimes referred to as HST) have been widely used. The hydrostatic continuously variable transmission is connected by a hydraulic closed circuit by the hydraulic pressure of the variable displacement pump along the slope angle of the movable swash plate while rotating by arranging a number of piston cylinders around the shaft. This is a hydraulic continuously variable transmission that performs a continuously variable transmission while hydraulically driving a fixed displacement motor.
Special opening and closing No. 5-288271

  The HST adjusts the oil discharge pressure of the variable displacement pump by adjusting the inclination angle of the swash plate according to the rotation angle of the trunnion shaft, and by rotating the rotation direction of the variable displacement pump forward or reverse. The rotational speed and direction of the output shaft can be changed.

However, in the conventional HST, there is a relationship shown by a dotted line in FIG. 6 between the rotation angle of the trunnion shaft and the inclination angle of the swash plate, and the rotation angle of the trunnion shaft is increased from the neutral position to the forward rotation direction and the reverse rotation direction. The inclination angle of the swash plate rises linearly. Therefore, the HST output suddenly increases or decreases near the neutral position, causing sudden start and stop of the work vehicle.
Accordingly, an object of the present invention is to provide a hydrostatic continuously variable transmission that does not cause the work vehicle to suddenly start or stop even if the rotation angle of the trunnion shaft is increased near the neutral position.

The above-described problems of the present invention are solved by the following solution means.
That is, the manually operated trunnion shaft (36), the swash plate (3) whose inclination angle is changed by the rotation of the trunnion shaft (36), and the discharge oil amount by the inclination angle of the swash plate (3). A variable displacement pump (A) that adjusts the oil discharge direction, and a hydraulic pressure that changes the rotational speed and direction of the output shaft (11) according to the amount of oil discharged from the variable displacement pump (A) and the oil discharge direction. In a hydrostatic continuously variable transmission equipped with a motor (B), a hydrostatic type is mounted with an eccentric cam (42) as one of the interlocking members between the trunnion shaft (36) and the swash plate (3). It is a continuously variable transmission.

  According to the present invention, when the eccentric cam (42) is used as one of the interlocking members, the inclination angle of the swash plate (3) with respect to the rotation operation angle of the trunnion shaft (36) is positive or negative from the neutral position of the HST. Since the inclination angle of the swash plate (3) does not change rapidly, the movement of the swash plate (3) near the neutral position is changed to the movement of the trunnion shaft (36). In comparison, the neutral position can be easily adjusted, and at the same time, the work vehicle can be operated very delicately in the vicinity of the neutral position, so that start and stop can be smoothly performed.

Examples of the present invention will be described.
The configuration of the hydraulic circuit of the hydraulic continuously variable transmission HST of this embodiment is shown in FIG. 1, the front view of the port desk is shown in FIG. 2, the entire side sectional view is shown in FIG. 3, and the entire plan sectional view is shown. 4 shows.

  The case 8 of the variable displacement hydraulic pump A and the fixed displacement hydraulic motor B and the case of the boost pump 9 and the like are superposed on the port body 7 to form an integral structure, and the input shaft 10 and the output shaft are parallel to each other in the axial direction. 11 is supported. A trochoid rotor (not shown) of the pump A and the boost pump 9 is provided around the input shaft 10, and a motor B is provided around the output shaft 11.

  The pump A and the motor B constitute a cylinder block by arranging a large number of cylinders 1 around the input shaft 10 and the output shaft 11 in parallel with the axial direction, and each cylinder 1 slides in the axial direction. A piston 2 is provided. Each of the pistons 2 is supported at its tip by a ball joint of a joint disk 13 so as to be swingable, and is provided so as to be rotatable about axes 10 and 11 with respect to a thrust plate 14 of the swash plate 3. The cylinder block rotates integrally with the shafts 10, 11 and the like. However, the joint disk 13 that rotates together with the piston 2, the thrust plate 14 that is slidably guided, and the swash plate 3 integrated therewith are integrated with the cylinder block. The inclination angle of the swash plate 3 on the motor B side is constant, and the angle of the swash plate 3 on the pump A side is controlled by a control lever or the like. Thus, the stroke amount of the reciprocating movement of the piston 2 on the pump A side is changed, whereby the fixed stroke amount of the piston 2 of the motor B on the other side passes through the hydraulic circuit 4 on the forward side and the hydraulic circuit 5 on the reverse side. The speed is changed by changing the rotation speed at the base.

  Therefore, when the swash plate 3 is at a right angle to the input shaft 10, even if the cylinder 1 on the input shaft 10 side is rotated, each piston 2 does not reciprocate in the axial direction. There is no transmission to and is in a neutral state. Further, when the swash plate 3 on the pump A side increases the inclination angle to the forward rotation side, the stroke of the piston 2 also increases, and the hydraulic pressure acting on the motor B side via the hydraulic circuit 4 also becomes high. At this time, the hydraulic circuit 5 on the opposite side of the hydraulic circuit 4 becomes low pressure, and the oil discharged from the motor B side is sucked into the pump A side. Accordingly, the output shaft 11 by the motor B is sequentially increased from the neutral state to the forward rotation side high speed state.

  Conversely, when the angle of the swash plate 3 on the pump A side is increased from the neutral state to the reverse side, the hydraulic circuit 5 becomes high pressure and oil flows to the motor B side, and the hydraulic circuit 4 becomes low pressure and the pump A As a result, the output shaft 11 is continuously variable in the reverse direction. The boost pump 9 replenishes oil into the hydraulic circuits 4 and 5 from the tank port T, and passes through an oil filter 16, a main relief valve 17, field valves (check valves) 18a and 18b, a neutral valve 19 and the like. It communicates with the hydraulic circuits 4 and 5. A high-pressure relief valve 20 is provided between the hydraulic circuits 4 and 5.

  As described above, the block of the cylinder 1 of the pump A and the motor B rotates together with the input shaft 10 and the output shaft 11, but the cylinder port of each cylinder 1 is disposed on the end surface of the block of each cylinder 1 on the port body 7 side. 25 and 26 are arranged at equal angular intervals, and rotate and slide on the port disk 21 attached to the port body 7. The port disk 21 is formed with a shaft hole 22 through which the input shaft 10 and the output shaft 11 are inserted at the center, and the outer periphery of the shaft hole 22 along the rotational surfaces of the cylinder ports 25 and 26. The arc-shaped oblong holes 23 and 24 are formed over a predetermined rotation angle, and no-hole pressure transition sections (A) and (B) are formed between the upper and lower dead centers of the left and right ports 23 and 24. .

  As a result, the cylinder ports 25 and 26 communicate with the port body 7 formed with the hydraulic circuits 4 and 5 via the ports 23 and 24, but the operation angle of the swash plate 3 is in the forward rotation position. Assuming that one port 23 has a high pressure on the hydraulic discharge side, the other port 24 has a low pressure on the hydraulic suction side. When the operation angle of the swash plate 3 exceeds the neutral position and is in the reverse shift position, the discharge side and the suction side are reversed.

A relief port 27 is provided at the center of the pressure transition section (b) at the bottom dead center of the port disk 21, and the relief valve 6 communicating with the relief port 27 is attached to the port body 7. Thereby, when each cylinder port 25, 26 of the cylinder block of the pump A or the motor B moves from the port 23 on the high pressure region side to the port 24 on the low pressure region side through the pressure transition section (b), the cylinder port 25 is The state of communication with the port 23 is switched to the relief port 27 in the pressure transition section (B), and the oil pressure is absorbed by the relief valve 6. Therefore, when the oil pressure at this time is too high, the oil pressure is relaxed and absorbed by the relief valve 6 and the oil pressure is smoothly lowered in the subsequent switching to the port 24 in the low pressure region.
Such relief port 27 and relief valve 6 may be provided on both port disks 21 of the pump A and the motor B, or may be provided on any one of the port disks 21.

  The adjusting screw 35 is screwed into the case 8 in the direction of the input shaft 10 and moves and adjusts the swash plate 3 along the direction of the input shaft 10 to change and adjust the distance from the cylinder 1. At this time, a trunnion shaft 36 perpendicular to the input shaft 10 is provided, and a pin slider 38 of a crank arm 37 integral with the trunnion shaft 36 is provided at the tip of the trunnion shaft 36 in a roller groove 3 a formed in the swash plate 3. By engaging and rotating the trunnion shaft 36, the pin slider 38 is swung to operate the inclination angle of the swash plate 3.

5A shows an enlarged cross-sectional view of a part of the trunnion shaft 36, the crank arm 37, and the swash plate 3 of FIG. 4, and FIG. 5B shows the AA line arrow of FIG. 5A. The figure is shown.
An eccentric cam 42 is interposed between the crank arm 37 for operating the swash plate 3 and the pin slider 38. In the eccentric cam 42, a pin 42a and a pin 42b are rotatably inserted into the crank arm 37 and the pin slider 38, respectively, and the two pins 42a and 42b are provided at positions eccentric from each other.

  Therefore, when the crank arm 37 is operated according to the rotational position of the trunnion shaft 36, the operation amount is transmitted to the pin slider 38 via the eccentric cam 42, and the pin slider 38 is moved to the groove of the swash plate 3. Slide 3a by a predetermined amount. The inclination angle of the swash plate 3 is determined according to a predetermined amount of sliding of the pin slider 38.

  In FIG. 6, the solid line shows the relationship between the rotation angle of the trunnion shaft 36 and the inclination angle of the swash plate 3 when the eccentric cam 42 is interposed between the crank arm 37 and the pin slider 38. On the other hand, the relationship between the rotation angle of the trunnion shaft 36 and the inclination angle of the swash plate 3 when the pin slider 38 is directly operated by the crank arm 37 without using the cam 42 is shown by a dotted line, but in the case of a solid line, the trunnion When the actual inclination angle of the swash plate 3 changes in a quadratic curve from the neutral position of the HST to either the positive or negative side with respect to the operation rotation angle of the shaft 36, and is shown by a dotted line not using the eccentric cam In comparison, since the inclination angle of the swash plate 3 does not change abruptly, the movement of the swash plate 3 in the vicinity of the neutral position can be minimized compared to the movement of the trunnion shaft 36. Therefore, the neutral position can be easily adjusted, and at the same time, the work vehicle can be operated very delicately in the vicinity of the neutral position, so that start and stop can be smoothly performed.

FIG. 7A shows an enlarged cross-sectional view of a portion of the trunnion shaft 36, crank arm 37, and swash plate 3 of another embodiment, and FIG. B line arrow figure is shown.
A stopper 43 that restricts the amount of rotation of the eccentric cam 42 only on one side is provided. Therefore, in the operation from the neutral position to the forward side, the rotation of the eccentric cam 42 is restricted by the stopper 43, and when the rotation angle of the trunnion shaft from the neutral position to the positive direction in FIG. You can (forward). On the other hand, in the operation from the neutral position to the reverse side, the rotation of the eccentric cam 42 is not restricted by the stopper 43, and the rotation angle of the trunnion shaft from the neutral position to the negative direction in FIG. Even starting (reversing) can be delayed. In this way, the fulcrum position of the eccentric cam 42 is shifted between the vehicle forward side and the reverse side, whereby the relationship between the rotation angle of the trunnion shaft 36 and the inclination angle of the swash plate 3 in FIG. At times, the vehicle can start faster than the reverse operation with respect to the travel lever operation, and can start slowly with respect to the operation of the travel lever when the vehicle travels backward.

  Conventionally, the traveling speed is equally changed with respect to the rotation angle operation amount of the trunnion shaft 36 both when the vehicle is moving forward and when the vehicle is moving backward. For example, when the work vehicle is a tractor, the tractor has a rotary backup mechanism. Therefore, there is a risk of damage if the fuselage is backed before the rotary moves up. However, the configuration shown in FIG. 7 makes it easier to obtain an optimum feeling by changing the forward and backward movements in accordance with the actual movement of the vehicle. In particular, when the vehicle is to be moved back, the vehicle can be started up gently so that the work apparatus can safely move backward after the working device has surfaced.

  FIG. 9 shows a cross-sectional view of the port body 7 of FIG. 3 taken along the line XX. When the oil in the forward hydraulic circuit 4 and the backward hydraulic circuit 5 of the port body 7 is insufficient, respectively. The oil is supplied from the charge oil passage 47, but the oil supply passages from the charge oil passage 47 into the hydraulic circuits 4 and 5 are provided with field valves 18a and 18b, respectively. The hydraulic circuit shown in FIG.

  The HST shown in FIG. 9 has a configuration in which an orifice hole 45 is provided in the field valve (check valve) 18b of the reverse hydraulic circuit 5 to ensure neutrality, but the field valve (check) of the hydraulic circuit 4 on the forward side (high pressure side). The valve 18a is provided with a relief valve 46 (steel ball 46a and spring 46b) that can be opened and closed only from the forward hydraulic circuit 4 to the hydraulic circuit 5 on the reverse side (low pressure circuit side).

  If the high-pressure relief valve 46 is not provided in the field valve (check valve) 18a of the hydraulic circuit 4 on the forward side (high pressure side), the motor is driven by the inertial force of the fuselage when the operation is suddenly returned from the reverse state to the neutral state. B performs a pumping action, a high pressure is suddenly applied to the forward hydraulic circuit 4, and the vehicle may stop suddenly in some cases. Therefore, by providing a relief valve 46 that can be opened and closed only from the forward hydraulic circuit 4 to the hydraulic circuit 5 on the reverse side (low pressure circuit side), high pressure is not applied to the forward hydraulic circuit 4 suddenly.

Further, in the HST shown in FIG. 10, an assist cylinder 48 is provided on the trunnion shaft 36, and the assist cylinder 48 is connected to the high pressure ports of the hydraulic circuits 4 and 5 on the forward side and the reverse side, which are closed circuits of the HST. An example is shown.
If a load is applied during the operation of the shift lever, the operation of the shift lever becomes heavy. At this time, the oil passage pressure in the forward hydraulic circuit 4 or the reverse hydraulic circuit 5 also increases in the HST oil passage. The assist cylinder 48 is actuated by using the pressure in the hydraulic circuit 4 or 5 on the side where the pressure is increased, so as to lighten the operation of the shift lever. Since only the assist cylinder 48 is mounted on the closed circuit of the HST, the operation load of the shift lever is reduced, so that torque can be reduced at a lower cost than when a servo valve or the like is mounted.
In addition, the oil path of the S portion in FIG. 10 is a charge oil path from the push pump 9 (see FIG. 1).

A configuration in which a gear pump is attached to the end of the HST input shaft may be employed to simplify the configuration. In FIG. 11, the input shaft 51 is provided on the gear pump C through the metal 50, and the input shaft 51 is mounted on the end of the HST input shaft 10, and the input for mounting the gear pump C on the HST input shaft 10 is provided. An example is shown in which the pressure oil of the HST charge circuit 52 is supplied to the spline part 51a of the shaft 51 and the lubricating oil is effectively sent to the spline part 51a.
At this time, if the supply of the pressure oil from the HST charge circuit 52 to the spline portion 51 a is directly supplied through the oil passage 7 a provided inside the port body (valve plate) 7, a compact configuration can be obtained.

  The gear pump C is, for example, an oil pump that sends pressure oil to the boost pump 9 or an elevating cylinder of a seedling planting portion of a rice transplanter, etc. In the assembly operation of mounting this gear pump on the end of the HST input shaft 10, Grease is applied to the input shaft 10, but in the conventional configuration, the spline portion 51a may be worn due to scattering and deterioration of the grease. Therefore, when the configuration shown in FIG. 11 is adopted, stable pressure oil is supplied to the spline portion 51a from the HST charge circuit 52, so that a good lubrication state is always maintained and wear is prevented.

  In the HST hydraulic pump A, aeration may occur depending on the binding position of the piston 2, oil may be cut off on the piston sliding surface, and the piston 2 may seize (cause galling). Therefore, as shown in the sectional view of the variable displacement pump A portion of FIG. 12 (a) and the sectional view taken along the line CC of FIG. 12 (a) of FIG. 12 (b), a small hole 7b for releasing the binding pressure is provided in the port. If the check valve 7c is arranged in the body 7, the check valve 7c is disposed in the hole 7b, and an oil passage communicating with the high-pressure side hydraulic circuit 4 or 5 is provided via the hole 7b, the occurrence of the air-conditioning can be prevented.

  The present invention can be used as an HST for a work vehicle that does not have a sudden stop or sudden start.

The structure of the hydraulic circuit of the hydraulic continuously variable transmission of the Example of this invention is shown. The front view of the port desk of the hydraulic continuously variable transmission of FIG. 1 is shown. FIG. 2 is a side sectional view of the entire hydraulic continuously variable transmission of FIG. 1. FIG. 2 is an overall plan sectional view of the hydraulic continuously variable transmission of FIG. 1. FIG. 5A shows an enlarged cross-sectional view of a portion of the trunnion shaft, crank arm and swash plate of the hydraulic continuously variable transmission of FIG. 1, and FIG. 5B shows an AA of FIG. A line arrow figure is shown. The relationship between the rotation angle of the trunnion shaft and the inclination angle of the swash plate when the eccentric cam is interposed between the crank arm and the pin slider and when the eccentric cam is not used in the hydraulic continuously variable transmission of FIG. Shown in solid and dotted lines, respectively. FIG. 7A shows an enlarged cross-sectional view of a portion of a trunnion shaft, a crank arm, and a swash plate of another embodiment of the hydraulic continuously variable transmission of FIG. 1, and FIG. ) Is a view taken along line B-B in FIG. The relationship between the rotation angle of the trunnion shaft in the structure of FIG. 7 and the inclination angle of a swash plate is shown. The XX line partial cross section arrow view of the port body 7 of FIG. 3 is shown. The structure of the hydraulic circuit of the hydraulic continuously variable transmission of the other Example of this invention is shown. The side sectional view of the whole hydraulic continuously variable transmission of other examples of the present invention is shown. Sectional drawing (FIG. 12 (a)) of the pump part of the hydraulic continuously variable transmission of other Example of this invention and CC sectional view taken on the line in FIG. 12 (a) are shown. .

Explanation of symbols

1, 2 Cylinder 2 Piston 3 Swash plate 3a Roller groove 4 Forward hydraulic circuit 5 Reverse hydraulic circuit 6 Relief valve 7 Port body
7a Oil passage 7b Hole 7c Check valve 8 Case
9 Boost pump 10 Input shaft
DESCRIPTION OF SYMBOLS 11 Output shaft 13 Joint disk 14 Thrust plate 15 Ball seat 16 Oil filter 17 Main relief valve 18a, 18b Field valve 19 Neutral valve 20 High pressure relief valve 21 Port disk 22 Shaft hole 23, 24 Port 25, 26 of arc-shaped long hole Port 27 Relief port 35 Adjustment screw 36 Trunnion shaft 37 Crank arm 38 Pin slider 40 Stopper 42 Eccentric cam 42a, 42b Pin 43 Stopper 45 Orifice hole 46 Relief valve 46a Steel ball 46b Spring 47 Charge oil passage 48 Assist cylinder 50 Metal 51 Input Shaft 51a Spline 52 HST charge circuit A Variable displacement hydraulic pump B Fixed displacement hydraulic motor C Gear pump T Tank port

Claims (1)

A manually operable trunnion shaft (36), a swash plate (3) whose inclination angle is changed by the rotation of the trunnion shaft (36), and the amount of oil discharged and the amount of oil depending on the inclination angle of the swash plate (3) A variable displacement pump (A) that adjusts the discharge direction, and a hydraulic motor that changes the rotational speed and direction of the output shaft (11) according to the amount of oil discharged from the variable displacement pump (A) and the direction of oil discharge ( B) with a hydrostatic continuously variable transmission,
A hydrostatic continuously variable transmission comprising an eccentric cam (42) as one of the interlocking members between the trunnion shaft (36) and the swash plate (3).

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