JP2016023795A - Static hydraulic infinite variable-speed drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a static hydraulic infinite variable-speed drive having a simple structure and capable of easily changing a biasing force of a neutral biasing mechanism for returning a swash plate to the neutral position.SOLUTION: A neutral biasing mechanism 25 comprises a first turning arm 26 integrally attached to a trunnion shaft 24 and having a cam part 29 reentrant toward the trunnion shaft 24 side formed; a second turning arm 27 rotated around an oscillating shaft 32 in parallel with the trunnion shaft 24; a roller 28 rotatably supported at the second turning arm 27 and fitted into the cam part 29 to cause the first turning arm 26 to rotate in a neutral attitude N2 corresponding to a neutral position N1 of a swash plate 23; and two springs 40 and 41 attached to the second turning arm 27 and a fitting member 20 so as to bias the second turning arm 27 in such a way that the roller 28 may be fitted to the cam part 29. A biasing force of the second spring 41 of the two springs 40 and 41 can be changed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a hydrostatic continuously variable transmission that is capable of changing the angle of a swash plate by rotating a trunnion shaft and that includes a neutral urging mechanism that urges the swash plate to a neutral position. About.

  For example, Patent Document 1 below describes a conventional hydrostatic continuously variable transmission. In the hydrostatic continuously variable transmission described in Patent Document 1, a neutral urging mechanism is integrally attached to a trunnion shaft (“Trunnion shaft” in Patent Document 1), and recessed toward the trunnion shaft. A first rotating arm (“cam plate” in Patent Document 1) having a cam portion (“Cam recess” in Patent Document 1) formed therein is provided. Further, the neutral urging mechanism includes a second rotating arm ("L-shaped arm" in Patent Document 1) that rotates about a swing axis parallel to the trunnion shaft, and a second rotating arm that is freely rotatable. And a roller (“roller” in Patent Document 1) that rotates the first rotation arm to a neutral posture corresponding to the neutral position by being fitted into the cam portion. .

  Further, the neutral urging mechanism is provided with a single spring that is attached across the second rotating arm and the machine base and urges the second rotating arm so that the roller fits into the cam portion. It has been.

Japanese Patent Laying-Open No. 2011-152823 (FIG. 8)

  By the way, in the hydrostatic continuously variable transmission, for example, the swash plate is returned to the neutral position by changing the sliding resistance of the component due to use or by increasing or decreasing the viscous resistance of the hydraulic oil due to the temperature change of the usage environment. The force required to fluctuate may vary. Further, for example, the urging force of the neutral urging mechanism may decrease due to deterioration of the spring.

  In such a case, the urging force of the neutral urging mechanism becomes smaller than the force necessary to return the swash plate to the neutral position, and it becomes difficult for the swash plate to return to the neutral position. There arises a disadvantage that the urging force becomes excessively larger than the force necessary for returning the swash plate to the neutral position.

  In the conventional neutral urging mechanism, the swash plate is urged to the neutral position only by the urging force of a single spring whose mounting position is unchanged.To change the urging force of the neutral urging mechanism, It was necessary to exchange a single spring, which was troublesome. In addition, since the spring is exchanged, the biasing force cannot be finely adjusted, and it is necessary to prepare several types of springs.

  In view of the above circumstances, it has been desired to provide a hydrostatic continuously variable transmission that can easily change the urging force of the neutral urging mechanism for returning the swash plate to the neutral position with a simple structure. .

  The present invention relates to a hydrostatic continuously variable transmission that is capable of changing the angle of a swash plate by rotating a trunnion shaft and that includes a neutral urging mechanism that urges the swash plate to a neutral position. The first biasing arm that is integrally attached to the trunnion shaft and is formed with a cam portion that is recessed toward the trunnion shaft, and the trunnion shaft. A second rotating arm that rotates around a parallel swing axis, and is rotatably supported by the second rotating arm, and is fitted into the cam portion, whereby the first rotating arm is A roller that rotates to a neutral posture corresponding to the neutral position, the second rotating arm, and the machine base are attached, and the second rotating arm is fitted so that the roller fits into the cam portion. Two springs for biasing, and the two spring springs In which the biasing force of one spring is configured to be changed.

According to the present invention, the neutral urging mechanism urges the swash plate to the neutral position by the urging forces of the two springs. Specifically, the urging forces of the two springs act on a second rotating arm that rotates about a rocking axis parallel to the trunnion shaft, and a roller that is rotatably supported by the second rotating arm. The cam portion that is recessed on the trunnion shaft side of the first rotating arm is pressed. As a result, the first turning arm with the trunnion shaft integrated is biased so as to return to the neutral posture, and as a result, the swash plate is biased so as to return to the neutral position.
In such a neutral urging mechanism, the urging force of one of the two springs can be changed. Therefore, it is difficult for the swash plate to return to the neutral position, or the urging force of the neutral urging mechanism becomes too large for the swash plate to return to the neutral position. However, the urging force of the neutral urging mechanism can be changed simply by changing the urging force of one of the springs without replacing the spring.
The two springs are both attached across the second rotating arm and the machine base. Therefore, compared to a structure in which the two springs are mounted at completely different locations, the number of parts of the spring mounting member can be reduced, and the two springs can be arranged close to each other to reduce the spring arrangement space. . That is, the neutral biasing mechanism having a simple structure can be provided while the biasing force can be easily changed.
Moreover, in this neutral urging mechanism, the urging force is distributed and distributed between the two springs, and the urging force of one of the two springs can be changed. It can be easily fine-tuned.
As described above, according to the present invention, it is possible to easily change the urging force of the neutral urging mechanism for returning the swash plate to the neutral position with a simple structure.

  In the present invention, a plurality of attachment holes for selectively attaching the attachment portions of the one springs are formed in one of the second rotating arm or the machine base, and the attachment portions include the attachment portions. Based on the biasing force of the one spring in the attached state, the moment force acting on the second rotating arm is set to be different from each other, and the attachment portion is communicated so as to be movable, It is preferable that holding means for holding the attachment portion in each of the attachment holes is provided.

  According to the above configuration, the moment force acting on the second rotating arm from one spring is selected by selecting an attachment hole to which the attachment portion of one spring is attached from the plurality of attachment holes. Thus, the urging force for urging the swash plate to the neutral position is changed. And the attachment part of one spring is not a location opened like a notch, for example, but is attached to an attachment hole, and since it is hold | maintained at an attachment hole by a holding means, it is hard to remove | deviate. Moreover, since a plurality of mounting holes are communicated with each other, the mounting portion of one spring can be easily shifted from the mounting hole being mounted to the mounting hole to be replaced without removing one spring. it can. Therefore, the urging force of the neutral urging mechanism can be changed with a simple operation.

  In the present invention, as the holding means, a projecting portion projecting toward the extending direction side of the one spring at the edge portion on the compressing direction side of the one spring among the communicating portions communicating with the two adjacent mounting holes. Is provided.

  According to the above configuration, in order for the attachment portion of one spring to be changed from the attachment hole being attached to the attachment hole at the replacement destination, the attachment portion of one spring is the compression direction of one spring of the communicating portions. When moving along the edge of each of the springs, it is necessary to get over the protruding portion that protrudes toward the extending direction of one of the springs. That is, the protruding portion of the attachment portion of one spring becomes a resistance and is held in the attachment hole being attached, and does not move between the attachment holes with a small external force such as vibration. Thereby, it is possible to prevent the biasing force of the neutral biasing mechanism from being changed unexpectedly.

  In the present invention, it is preferable that the plurality of mounting holes are positioned so that distances from the swing shaft are different from each other.

  According to the above configuration, since the plurality of mounting holes have different distances from the swing shaft to the mounting hole, the moment force acting on the second rotating arm from one spring is made different for each mounting hole. be able to.

  In the present invention, it is preferable that a fixing portion for mounting one end of the one spring in a fixed position is provided, and the plurality of mounting holes are positioned so that distances from the fixing portion are different from each other.

  According to the above configuration, since the plurality of mounting holes have different distances from the fixing portion that attaches one end of one spring to the fixed position, the amount of extension of one spring differs for each mounting hole. Become. That is, since the force acting on the second rotating arm from one spring differs for each mounting hole, the moment force acting on the second rotating arm from one spring can be made different for each mounting hole.

  In the present invention, the two springs are a first spring and a second spring having a smaller spring constant than the first spring, and it is preferable that the urging force of the second spring is changed.

  According to the said structure, a neutral urging | biasing mechanism utilizes the urging | biasing force of two types of springs, a 1st spring and a 2nd spring whose spring constant is smaller than a 1st spring. In changing the urging force of the neutral urging mechanism, the urging force is changed not for the first spring having a relatively large urging force but for the second spring having a relatively small urging force. For this reason, the biasing force of the neutral biasing mechanism can be changed with a relatively small operating force.

It is a right view of a tractor. It is a top view of a tractor. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in a neutral position. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in the maximum normal rotation position. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in a maximum reverse rotation position. It is a right view which shows replacement of a 2nd spring. It is explanatory drawing of the right side view explaining the position of an attachment hole.

Hereinafter, an embodiment which is an example of the present invention will be described with reference to the drawings.
In the present embodiment, a case will be described in which the hydrostatic continuously variable transmission S is provided in a tractor T that is an example of a work vehicle.

[Basic structure of tractor]
As shown in FIGS. 1 and 2, the front of the traveling body of the tractor T includes an engine 7 and the like, and a pair of left and right front wheels 8 driven by power from the engine 7 can be steered. Is provided. On the rear part of the traveling machine body of the tractor T, a boarding operation unit 11 is formed including a steering wheel 9 and a driver seat 10 linked to the left and right front wheels 8. A pair of left and right rear wheels 12 driven by power from the engine 7 are provided on the left and right outside of the boarding operation unit 11. A hydrostatic continuously variable transmission that functions as a main transmission, together with a transmission case 13 having a gear-type transmission (not shown) that functions as an auxiliary transmission, etc. A device S is provided.

  As shown in FIG. 1, a link mechanism 17 including a left and right lift arms 14, left and right lower links 15, a lift rod 16 that connects the lift arms 14 and the lower links 15, etc. And a hydraulic cylinder 18 for moving the link mechanism 17 up and down, and a power take-out shaft 19. As a result, the tractor T is configured to be able to move up and down a working device such as a rotary tiller or a plow at the rear portion and to extract power from the power take-out shaft 19.

  As shown in FIG. 3 to FIG. 5, a mounting member 20 (an example of “machine base”) made of a plate-like member is fixedly provided on the right side of the body of the mission case 13. Yes. A bracket 22 is fixedly provided on the right side of the body of the mounting member 20 by fastening the bolt 21 with a fastener.

[About hydrostatic continuously variable transmission]
Although the internal structure is not illustrated, the hydrostatic continuously variable transmission S is supplied with an axial plunger type hydraulic pump configured by a variable displacement type driven by the engine 7 and hydraulic oil from the hydraulic pump. Thus, an axial plunger type hydraulic motor that rotates at a speed corresponding to the amount of oil is provided. This hydraulic pump is configured to transmit a traveling driving force to the mission case 13.

  As shown in FIGS. 3 to 5, the hydrostatic continuously variable transmission S includes a swash plate 23 of a hydraulic pump, a trunnion shaft 24 integrally linked to the swash plate 23, and a trunnion shaft. And a neutral urging mechanism 25 that urges the swash plate 23 to the neutral position N1 via the swash plate 24. The hydrostatic continuously variable transmission S rotates the trunnion shaft 24 about the operation axis X1 so that the angle of the swash plate 23 is set to the maximum forward rotation position F1 and the maximum reverse rotation position R1 across the neutral position N1. It is configured to be changeable between.

  The output of the hydrostatic continuously variable transmission S is configured to be capable of stepless shifting between a maximum forward rotation speed (maximum forward speed) and a maximum reverse rotation speed (maximum reverse speed) with zero speed interposed therebetween. . In the hydrostatic continuously variable transmission S, when the swash plate 23 is set to the neutral position N1, the zero speed state appears, and when the swash plate 23 is set to the maximum forward rotation position F1, the speed is increased in the forward rotation direction. The maximum normal rotation state that becomes maximum appears, and the maximum reverse rotation state that causes the maximum speed in the reverse rotation direction opposite to the normal rotation direction appears by setting the swash plate 23 to the maximum reverse rotation position R1.

  As shown in FIGS. 3 to 5, the trunnion shaft 24 protrudes from the right side of the body of the mission case 13 to the right of the body. The cross-sectional shape of the right end portion of the trunnion shaft 24 in a side view is formed in an oval shape. The trunnion shaft 24 can be rotated around the operation axis X1 in the lateral direction of the machine body.

  The neutral biasing mechanism 25 applies a biasing force for rotating the trunnion shaft 24 so that the swash plate 23 is in the neutral position N1. The neutral urging mechanism 25 includes a first rotating arm 26, a second rotating arm 27, a roller 28, and two springs described later.

  The first rotating arm 26 swings around the operation axis X1 of the trunnion shaft 24, thereby sandwiching a neutral posture N2 (see FIG. 3) corresponding to the neutral position N1 of the swash plate 23. The posture can be changed between a maximum forward rotation posture F2 (see FIG. 4) corresponding to the maximum forward rotation position F1 and a maximum reverse rotation posture R2 (see FIG. 5) corresponding to the maximum reverse rotation position R1 of the swash plate 23. ing.

  As shown in FIGS. 3 to 5, the first rotating arm 26 is integrally attached to the trunnion shaft 24. That is, the first turning arm 26 can swing around the operation axis X1 integrally with the trunnion shaft 24. The first rotating arm 26 includes a fan-shaped fan-shaped portion 26A and an operation arm 26B integrated with the fan-shaped portion 26A. A cam portion 29 that is recessed in a V shape toward the trunnion shaft 24 is formed at the edge of the fan-shaped portion 26 </ b> A of the first rotating arm 26. The base end portion of the fan-shaped portion 26 </ b> A is connected to the trunnion shaft 24 by sandwiching the right end portion of the trunnion shaft 24. As will be described later, a seesaw-type shift pedal 31, which is an example of a shift operation tool, is linked to the operation arm 26 </ b> B via a linkage mechanism 30.

  The second rotating arm 27 is supported so as to be rotatable relative to the mission case 13. Specifically, the second turning arm 27 is configured to turn around a swing shaft 32 parallel to the trunnion shaft 24. That is, the swing shaft 32 is configured to rotate around a rotation axis X2 parallel to the operation axis X1.

  The second rotating arm 27 includes a swinging shaft 32 that can swing around the rotation axis X2 and a first arm 33 that extends from the swinging shaft 32 to the cam portion 29 side of the first rotating arm 26. A second arm 34 extending from the swing shaft 32 in a direction different from the first arm 33, and a detection arm 35 extending downward from a location near the center of the second arm 34. Yes. A roller 28 is rotatably supported on the free end of the first arm 33 of the second rotating arm 27.

  The second arm 34 includes a plurality of mounting holes, which will be described later, and a notch-shaped latching portion 37 located on the free end side farther from the rotation axis X2 than the plurality of mounting holes. . The latching portion 37 is a notched portion in which the edge of the second arm 34 is notched downward.

  The roller 28 is fitted into the cam portion 29 to rotate the first rotation arm 26 to the neutral posture N2 corresponding to the neutral position N1 of the swash plate 23 (see FIG. 3). In other words, the swash plate 23 is in the neutral position N1 when the first rotating arm 26 is in the neutral posture N2.

  As shown in FIGS. 3 to 6, the bracket 22 fixed to the mounting member 20 is provided with a sensor 38 that is a detection means capable of detecting the neutral position N <b> 1 of the swash plate 23. . When the first rotating arm 26 is in the neutral posture N2, the detection arm 38A of the sensor 38 is pressed by the detection arm 35 of the first rotating arm 26. The detection signal of the sensor 38 is input to a control device (not shown) and used for various controls.

[About the first spring and the second spring]
As shown in FIGS. 3 to 6, a first spring 40 and a second spring 41 (corresponding to “one spring”) having a smaller spring constant than the first spring 40 are provided as two springs. Yes. The first spring 40 and the second spring 41 are each a tension spring. The first spring 40 and the second spring 41 are attached across the second arm 34 of the second rotating arm 27 and the bracket 22, respectively.

  The bracket 22 is formed with a round hole-shaped first fixing hole 42, and a round hole-shaped second fixing hole 43 (an example of a “fixing portion”) arranged side by side with the first fixing hole 42. Yes. The second fixing hole 43 is located closer to the swing shaft 32 (rotation axis X2) than the first fixing hole 42.

  One end 40 </ b> A of the first spring 40 is attached to the first fixing hole 42 in a fixable state. The other end 40 </ b> B of the first spring 40 is attached to a hooking portion 37 of the second arm 34 in a fixable state. One end 41 </ b> A of the second spring 41 is attached to the second fixing hole 43 in a fixable state. The other end 41 </ b> B (corresponding to “attachment portion”) of the second spring 41 is attached in a position changeable state. The first spring 40 and the second spring 41 are arranged side by side and close to each other. The second spring 41 is located closer to the swing shaft 32 (rotation axis X2) than the first spring 40 is.

  The first spring 40 and the second spring 41 respectively exert a pulling force on the second arm 34 of the second rotating arm 27, thereby being supported rotatably on the first arm 33 of the second rotating arm 27. The roller 28 is urging the second rotating arm 27 so as to fit into the cam portion 29.

  The first spring 40 and the second spring 41 are respectively contracted most when the swash plate 23 is in the neutral position N1 (see FIG. 3), and when the swash plate 23 is in the maximum forward rotation position F1 or the maximum reverse rotation position R1. (See FIGS. 3 and 4). The first spring 40 and the second spring 41 exert a tensile force on the second rotating arm 27 even when the swash plate 23 is in the neutral position N1.

[About mounting holes]
As shown in FIGS. 3 to 6, the second rotating arm 27 is provided with “a plurality of attachment holes” to which the second spring 41 is selectively attached. Specifically, in the second arm 34 of the second rotation arm 27, a first attachment hole 44, a second attachment hole 45 located at a position farther from the rotation axis X2 than the first attachment hole 44, Two mounting holes are formed.

  The other end 41B of the second spring 41 can be attached to the first attachment hole 44 and the second attachment hole 45, respectively. That is, as shown in FIGS. 3 to 6, the other end 41 </ b> B of the second spring 41 can be replaced with the first mounting hole 44 and the second mounting hole 45.

  The neutral urging mechanism 25 is configured such that the urging force of the second spring 41 among the two springs of the first spring 40 and the second spring 41 can be changed. As the second spring 41, one having a smaller spring constant than the first spring 40 is selected.

  The pulling force acting on the second arm 34 of the second rotation arm 27 from the second spring 41 attached to the second attachment hole 45 is from the second spring 41 attached to the first attachment hole 44 to the second rotation arm 27. It becomes larger than the pulling force acting on the second arm 34. That is, the first mounting hole 44 and the second mounting hole 45 are moment forces acting on the second rotating arm 27 based on the biasing force of the second spring 41 in a state where the second spring 41 is mounted. Are positioned differently.

  As shown in FIG. 6, the first attachment hole 44 and the second attachment hole 45 are communicated with each other by a communication portion 46 formed between the first attachment hole 44 and the second attachment hole 45. That is, the first attachment hole 44 and the second attachment hole 45 are communicated as one hole portion. The first mounting hole 44 and the second mounting hole 45 are communicated so that the other end 41B of the second spring 41 can move.

  The extending direction of the second spring 41 is provided at the edge of the second spring 41 in the compression direction of the communication portion 46 that communicates the first mounting hole 44 and the second mounting hole 45 that are adjacent two mounting holes. A protruding portion 47 (an example of “holding means”) that protrudes to the side is provided. The protruding portion 47 has a substantially arc shape. The protruding portion 47 holds the other end 41 </ b> B of the second spring 41 in each of the first mounting hole 44 and the second mounting hole 45. The first mounting hole 44, the second mounting hole 45, and the protruding portion 47 are continuous in a smooth curved shape.

  As shown in FIGS. 6 and 7, the protrusion 47 is provided with a first inclined surface 47A on the first mounting hole 44 side and a second inclined surface 47B on the second mounting hole 45 side. . The angle α formed between the first inclined surface 47A and the virtual line V1 perpendicular to the expansion and contraction direction of the first spring 40 attached to the first attachment hole 44 is the first angle attached to the second inclined surface 47B and the second attachment hole 45. It is larger than the angle β formed by the virtual line V2 orthogonal to the expansion / contraction direction of the spring 40. That is, the inclination angle of the first inclined surface 47A is tighter than the inclination angle of the second inclined surface 47B. In other words, the inclination angle of the second inclined surface 47B is gentler than the inclination angle of the first inclined surface 47A.

  As shown in FIGS. 6 and 7, the first mounting hole 44 and the second mounting hole 45 are positioned so that the distance from the pivot axis X <b> 2 of the swing shaft 32 is different. In other words, the first mounting hole 44 and the second mounting are set such that the distance A1 between the first mounting hole 44 and the rotation axis X2 is larger than the distance A2 between the second mounting hole 45 and the rotation axis X2. The position of the hole 45 is set.

  As shown in FIGS. 6 and 7, one end 41 </ b> A opposite to the other end 41 </ b> B of the second spring 41 is attached to the second fixing hole 43 in a fixed position. The first mounting hole 44 and the second mounting hole 45 are positioned so that the distance from the second fixing hole 43 is different. That is, the distance B1 between the first mounting hole 44 and the second fixing hole 43 is larger than the distance B2 between the second mounting hole 45 and the second fixing hole 43. The position of the hole 45 is set.

  As shown in FIG. 6, the other end 41 </ b> B of the second spring 41 is shifted between the first mounting hole 44 and the second mounting hole 45 along the edge of the second spring 41 on the compression direction side. By moving the second spring 41, it is possible to change the attachment hole to which the second spring 41 is attached, and to change the urging force acting on the second rotating arm 27 from the second spring 41. That is, the neutral urging mechanism 25 can change the urging force of the second spring 41 whose spring constant is relatively smaller than that of the first spring 40.

  In a state where the second spring 41 is attached to the first attachment hole 44, when the urging force of the neutral urging mechanism 25 becomes smaller than the force necessary to return the swash plate 23 to the neutral position N1, By changing the second spring 41 from the first mounting hole 44 to the second mounting hole 45, the urging force of the neutral urging mechanism 25 can be increased, and the swash plate 23 can be adjusted to a state in which it is surely returned to the neutral position N1. .

  On the other hand, in a state where the second spring 41 is attached to the second attachment hole 45, the urging force of the neutral urging mechanism 25 becomes too large with respect to the force necessary to return the swash plate 23 to the neutral position N1. In this case, the urging force of the neutral urging mechanism 25 can be reduced by changing the second spring 41 from the second attachment hole 45 to the first attachment hole 44.

  As described above, the biasing force of the neutral biasing mechanism 25 can be easily adjusted simply by changing the second spring 41 between the first mounting hole 44 and the second mounting hole 45.

[About the speed change pedal]
As shown in FIGS. 3 to 5, a shift pedal 31 is linked to the operation arm 26 </ b> B of the first rotation arm 26 via a linkage mechanism 30. The shift pedal 31 is disposed on the right side of the body of the boarding operation unit 11. That is, the shift pedal 31 is arranged on the same side as the neutral urging mechanism 25 with respect to the mission case 13 in the left-right direction of the machine body. The speed change pedal 31 includes a forward stepping operation portion 31A for forward shifting, a rear stepping operation portion 31B for reverse shifting integrated with the front stepping operation portion 31A, a front stepping operation portion 31A and a rear stepping operation portion 31B. And a pedal arm 31C located integrally therewith.

  The speed change pedal 31 receives a stepping operation on the front stepping operation portion 31A or the rear stepping operation portion 31B and an urging force of the neutral urging mechanism 25, and is coupled to the lower end portion of the pedal arm 31C. The balance swings around the 48 fulcrum axis X3.

  The linkage mechanism 30 is provided with a first connecting pin 49 that faces the vehicle body in the left-right direction, a linkage arm 50 that extends along the front-rear direction of the vehicle body, and a second connection pin 51 that faces the aircraft left-right. The first connecting pin 49 rotatably connects the pedal arm 31C of the speed change pedal 31 and one end of the linkage arm 50. The second connecting pin 51 rotatably connects the pedal arm 31C of the speed change pedal 31 and the free end of the operation arm 26B of the first rotating arm 26.

  The speed change pedal 31 swings between the maximum forward angle F3 (see FIG. 4) and the maximum reverse angle R3 (see FIG. 5) around the fulcrum axis X3 with the neutral angle N3 (see FIG. 3) in between. It is configured to move. By setting the shift pedal 31 to the neutral angle N3, the swash plate 23 is set to the neutral position N1 (see FIG. 3), and by setting the shift pedal 31 to the maximum forward angle F3, the swash plate 23 is set to the maximum forward rotation position F1 ( 4), by setting the shift pedal 31 to the maximum reverse angle R3, the swash plate 23 reaches the maximum reverse rotation position R1 (see FIG. 5).

  As shown in FIGS. 3 and 4, by depressing the front depression operation portion 31A of the shift pedal 31 against the urging force of the neutral urging mechanism 25, the shift pedal 31 is advanced forward from the neutral angle N3. By swinging to the angle F3 side, the angle of the swash plate 23 is changed from the neutral position N1 to the maximum forward rotation position F1. Then, as shown in FIGS. 3 and 5, the shift pedal 31 is depressed to the neutral angle N3 by depressing the rear stepping operation portion 31B of the shift pedal 31 against the biasing force of the neutral biasing mechanism 25. Is swung from the neutral position N1 to the maximum reverse rotation position R1. When the foot is released from the shift pedal 31, the shift pedal 31 is automatically returned to the neutral angle N3 by the action of the biasing force of the neutral biasing mechanism 25, and the swash plate 23 is automatically moved to the neutral position N1. It is restored (see FIG. 3).

[About adding the biasing force of the first spring and the biasing force of the second spring]
Although not particularly illustrated, as in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-152823), the conventional neutral biasing mechanism is given a biasing force that causes the swash plate to return to the neutral position only by a single spring. There is something to do. In the conventional neutral urging mechanism, a single spring having a relatively large spring constant is used to provide a reliable urging force for returning the swash plate to the neutral position even when the swash plate is in the vicinity of the neutral position. ing. However, when only such a single spring is used, since the spring constant is large, the biasing force of the neutral biasing mechanism when the swash plate is in the neutral position and the swash plate at the maximum forward rotation position or the maximum reverse rotation position. The difference from the biasing force of the neutral biasing mechanism at a certain time becomes too large. That is, the operating force required when the shift pedal 31 is depressed to the maximum forward angle or maximum reverse angle becomes excessive.

  In contrast, the neutral urging mechanism 25 of the present invention has an urging force of the first spring 40 and an urging force of the second spring 41 having a smaller spring constant than the first spring 40, as shown in FIGS. The swash plate 23 is urged to return to the neutral position N1 by adding the forces. As described above, since two springs having different urging forces are used, the urging force of the neutral urging mechanism 25 when the swash plate 23 is at the neutral position N1 and the swash plate 23 at the maximum forward rotation position F1 or the maximum reverse rotation. The difference from the urging force of the neutral urging mechanism 25 at the position R1 can be reduced. As a result, when the swash plate 23 is in the vicinity of the neutral position N1, it is possible to apply a biasing force that reliably returns the swash plate 23 to the neutral position N1, and to make the swash plate 23 the maximum forward rotation position F1 or the maximum reverse rotation position T1. Therefore, it is possible to reduce the operating force when the shift pedal 31 is stepped on to the maximum forward angle F3 or the maximum reverse angle R3, and the operability can be improved.

[Another embodiment]
Hereinafter, another embodiment of the present invention will be described. In each of the following embodiments, configurations other than the configuration described are the same as those in the above embodiment. Moreover, the said embodiment and each following another embodiment can mutually be combined unless a contradiction arises. Note that the scope of the present invention is not limited to the above-described embodiment and the following separate embodiments.

  (1) In the above embodiment, the example in which the urging force of the second spring 41 is changed by changing the second spring 41 between the “plurality of mounting holes” is shown as an example. . For example, an operation member capable of changing the extension amount of the second spring 41 may be provided.

  (2) In the above-described embodiment, as an example of the “plurality of mounting holes”, the one in which the two mounting holes of the first mounting hole 44 and the second mounting hole 45 are formed is shown. It is not limited to this. For example, three or more attachment holes may be provided.

  (3) In the above embodiment, the first mounting hole 44 and the second mounting hole 45 are communicated by the communication portion 46 as an example, but the present invention is not limited to this. The first mounting hole 44 and the second mounting hole 45 may not be communicated with each other and may be formed as mutually independent holes.

  (4) In the above-described embodiment, the projecting portion 47 having an arc shape is shown as an example, but the present invention is not limited thereto. For example, another protrusion having a linear portion may be used. In this case, the other protrusions may have a shape such as a triangular shape or a trapezoidal shape.

  (5) In the above embodiment, the second arm 34 of the second rotating arm 27 is formed with “a plurality of mounting holes” for selectively mounting the second spring 41 as “one spring”. Is shown as an example, but is not limited thereto. Instead, “a plurality of attachment holes” to which the second spring 41 that is “one spring” is selectively attached may be formed in the first arm 33 of the second rotating arm 27.

  (6) In the above embodiment, an example is shown in which the second rotating arm 27 is formed with “a plurality of mounting holes” for selectively mounting the second spring 41 which is “one spring”. However, it is not limited to this. Instead of this, “a plurality of attachment holes” to which the second spring 41 that is “one spring” is selectively attached may be formed in the bracket 22 that is the “machine base”. In this case, the second rotating arm 27 is provided with a “fixing portion”.

  (7) In the above embodiment, the second arm 34 of the second rotating arm 27 has the first mounting hole 44 and the second mounting hole 45 formed as an example. I can't. For example, a first mounting hole and a second mounting hole may be formed in the first arm 33 that supports the roller 28 in the second rotating arm 27.

  (8) In the above-described embodiment, the attachment member 20 fixedly attached to the right side of the body of the mission case 13 is shown as an example of the “machine base”, but is not limited thereto. For example, other attachment members fixedly attached to the right side of the machine body such as the hydrostatic continuously variable transmission S may be used as the “machine base”.

  (9) In the above-described embodiment, the first spring 40 and the second spring 41 are illustrated as tension springs, respectively, but are not limited thereto. For example, the first spring 40 and the second spring 41 may be a tension spring, a compression spring, a torsion spring, or the like, respectively.

  (10) In the above-described embodiment, the shift pedal 31 is disposed on the same side as the neutral urging mechanism 25 with respect to the transmission case 13 in the left-right direction of the body, but is not limited thereto. Absent. You may arrange | position on the opposite side to the neutral urging | biasing mechanism 25 with respect to the mission case 13 in the body left-right direction. In this case, the support shaft in the linkage mechanism crosses the vicinity of the mission case 13 in the direction of the body.

  (11) In the above embodiment, the seesaw-type shift pedal 31 is shown as an example of the shift operation tool, but the present invention is not limited to this. For example, a shift operation tool in which a forward pedal and a reverse pedal are provided separately may be used. Further, for example, a manual operation speed change lever may be provided as a speed change operation tool.

  (12) In the above embodiment, left and right expressions are used, but a structure in which the left and right are opposite may be used.

  The hydrostatic continuously variable transmission according to the present invention can be suitably used by being incorporated in a work vehicle such as a combine, a rice transplanter, a mower, or a construction machine in addition to the tractor.

20: Mounting member ("machine stand")
23: swash plate 24: trunnion shaft 25: neutral urging mechanism 26: first rotating arm 27: second rotating arm 28: roller 29: cam portion 32: swing shaft 40: first spring ("two springs" One of the
41: Second spring (one of “two springs”, “one spring”)
41B: The other end ("mounting part")
43: Second fixing hole ("fixing part")
44: First mounting hole (one of "a plurality of mounting holes")
45: Second mounting hole (one of "a plurality of mounting holes")
46: Communication part 47: Protruding part ("holding means")
N1: Neutral position N2: Neutral posture S: Hydrostatic continuously variable transmission

  The present invention relates to a hydrostatic continuously variable transmission that is capable of changing the angle of a swash plate by rotating a trunnion shaft and that includes a neutral urging mechanism that urges the swash plate to a neutral position. About.

  For example, Patent Document 1 below describes a conventional hydrostatic continuously variable transmission. In the hydrostatic continuously variable transmission described in Patent Document 1, a neutral urging mechanism is integrally attached to a trunnion shaft (“Trunnion shaft” in Patent Document 1), and recessed toward the trunnion shaft. A first rotating arm (“cam plate” in Patent Document 1) having a cam portion (“Cam recess” in Patent Document 1) formed therein is provided. Further, the neutral urging mechanism includes a second rotating arm ("L-shaped arm" in Patent Document 1) that rotates about a swing axis parallel to the trunnion shaft, and a second rotating arm that is freely rotatable. And a roller (“roller” in Patent Document 1) that rotates the first rotation arm to a neutral posture corresponding to the neutral position by being fitted into the cam portion. .

  Further, the neutral urging mechanism is provided with a single spring that is attached across the second rotating arm and the machine base and urges the second rotating arm so that the roller fits into the cam portion. It has been.

Japanese Patent Laying-Open No. 2011-152823 (FIG. 8)

By the way, in the hydrostatic continuously variable transmission , the urging force of the neutral urging mechanism may decrease due to , for example, deterioration of the spring due to plastic deformation or the like .

In such a case, the biasing force of the neutral biasing mechanism, smaller than the force required for returning the swash plate to the neutral position, occur a disadvantage that the swash plate is less likely to return to the neutral position.

  In the conventional neutral urging mechanism, the swash plate is urged to the neutral position only by the urging force of a single spring whose mounting position is unchanged.To change the urging force of the neutral urging mechanism, It was necessary to exchange a single spring, which was troublesome. In addition, since the spring is exchanged, the biasing force cannot be finely adjusted, and it is necessary to prepare several types of springs.

  In view of the above circumstances, it has been desired to provide a hydrostatic continuously variable transmission that can easily change the urging force of the neutral urging mechanism for returning the swash plate to the neutral position with a simple structure. .

  The present invention relates to a hydrostatic continuously variable transmission that is capable of changing the angle of a swash plate by rotating a trunnion shaft and that includes a neutral urging mechanism that urges the swash plate to a neutral position. The first biasing arm that is integrally attached to the trunnion shaft and is formed with a cam portion that is recessed toward the trunnion shaft, and the trunnion shaft. A second rotating arm that rotates around a parallel swing axis, and is rotatably supported by the second rotating arm, and is fitted into the cam portion, whereby the first rotating arm is A roller that rotates to a neutral posture corresponding to the neutral position, the second rotating arm, and the machine base are attached, and the second rotating arm is fitted so that the roller fits into the cam portion. Two springs for biasing, and the two spring springs In which the biasing force of one spring is configured to be changed.

According to the present invention, the neutral urging mechanism urges the swash plate to the neutral position by the urging forces of the two springs. Specifically, the urging forces of the two springs act on a second rotating arm that rotates about a rocking axis parallel to the trunnion shaft, and a roller that is rotatably supported by the second rotating arm. The cam portion that is recessed on the trunnion shaft side of the first rotating arm is pressed. As a result, the first turning arm with the trunnion shaft integrated is biased so as to return to the neutral posture, and as a result, the swash plate is biased so as to return to the neutral position.
In such a neutral urging mechanism, the urging force of one of the two springs can be changed. Therefore, even if the swash plate becomes difficult to return to the neutral position, the urging force of the neutral urging mechanism can be changed simply by changing the urging force of one of the springs without replacing the spring. it can.
The two springs are both attached across the second rotating arm and the machine base. Therefore, compared to a structure in which the two springs are mounted at completely different locations, the number of parts of the spring mounting member can be reduced, and the two springs can be arranged close to each other to reduce the spring arrangement space. . That is, the neutral biasing mechanism having a simple structure can be provided while the biasing force can be easily changed.
Moreover, in this neutral urging mechanism, the urging force is distributed and distributed to the two springs, and the urging force of one of the two springs can be changed. It can be easily fine-tuned.
As described above, according to the present invention, it is possible to easily change the urging force of the neutral urging mechanism for returning the swash plate to the neutral position with a simple structure.

  In the present invention, a plurality of attachment holes for selectively attaching the attachment portions of the one springs are formed in one of the second rotating arm or the machine base, and the attachment portions include the attachment portions. Based on the biasing force of the one spring in the attached state, the moment force acting on the second rotating arm is set to be different from each other, and the attachment portion is communicated so as to be movable, It is preferable that holding means for holding the attachment portion in each of the attachment holes is provided.

  According to the above configuration, the moment force acting on the second rotating arm from one spring is selected by selecting an attachment hole to which the attachment portion of one spring is attached from the plurality of attachment holes. Thus, the urging force for urging the swash plate to the neutral position is changed. And the attachment part of one spring is not a location opened like a notch, for example, but is attached to an attachment hole, and since it is hold | maintained at an attachment hole by a holding means, it is hard to remove | deviate. Moreover, since a plurality of mounting holes are communicated with each other, the mounting portion of one spring can be easily shifted from the mounting hole being mounted to the mounting hole to be replaced without removing one spring. it can. Therefore, the urging force of the neutral urging mechanism can be changed with a simple operation.

  In the present invention, as the holding means, a projecting portion projecting toward the extending direction side of the one spring at the edge portion on the compressing direction side of the one spring among the communicating portions communicating with the two adjacent mounting holes. Is provided.

  According to the above configuration, in order for the attachment portion of one spring to be changed from the attachment hole being attached to the attachment hole at the replacement destination, the attachment portion of one spring is the compression direction of one spring of the communicating portions. When moving along the edge of each of the springs, it is necessary to get over the protruding portion that protrudes toward the extending direction of one of the springs. That is, the protruding portion of the attachment portion of one spring becomes a resistance and is held in the attachment hole being attached, and does not move between the attachment holes with a small external force such as vibration. Thereby, it is possible to prevent the biasing force of the neutral biasing mechanism from being changed unexpectedly.

  In the present invention, it is preferable that the plurality of mounting holes are positioned so that distances from the swing shaft are different from each other.

  According to the above configuration, since the plurality of mounting holes have different distances from the swing shaft to the mounting hole, the moment force acting on the second rotating arm from one spring is made different for each mounting hole. be able to.

  In the present invention, it is preferable that a fixing portion for mounting one end of the one spring in a fixed position is provided, and the plurality of mounting holes are positioned so that distances from the fixing portion are different from each other.

  According to the above configuration, since the plurality of mounting holes have different distances from the fixing portion that attaches one end of one spring to the fixed position, the amount of extension of one spring differs for each mounting hole. Become. That is, since the force acting on the second rotating arm from one spring differs for each mounting hole, the moment force acting on the second rotating arm from one spring can be made different for each mounting hole.

  In the present invention, the two springs are a first spring and a second spring having a smaller spring constant than the first spring, and it is preferable that the urging force of the second spring is changed.

  According to the said structure, a neutral urging | biasing mechanism utilizes the urging | biasing force of two types of springs, a 1st spring and a 2nd spring whose spring constant is smaller than a 1st spring. In changing the urging force of the neutral urging mechanism, the urging force is changed not for the first spring having a relatively large urging force but for the second spring having a relatively small urging force. For this reason, the biasing force of the neutral biasing mechanism can be changed with a relatively small operating force.

It is a right view of a tractor. It is a top view of a tractor. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in a neutral position. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in the maximum normal rotation position. It is a right view which shows the periphery of the neutral urging | biasing mechanism in the state which has a swash plate in a maximum reverse rotation position. It is a right view which shows replacement of a 2nd spring. It is explanatory drawing of the right side view explaining the position of an attachment hole.

Hereinafter, an embodiment which is an example of the present invention will be described with reference to the drawings.
In the present embodiment, a case will be described in which the hydrostatic continuously variable transmission S is provided in a tractor T that is an example of a work vehicle.

[Basic structure of tractor]
As shown in FIGS. 1 and 2, the front of the traveling body of the tractor T includes an engine 7 and the like, and a pair of left and right front wheels 8 driven by power from the engine 7 can be steered. Is provided. On the rear part of the traveling machine body of the tractor T, a boarding operation unit 11 is formed including a steering wheel 9 and a driver seat 10 linked to the left and right front wheels 8. A pair of left and right rear wheels 12 driven by power from the engine 7 are provided on the left and right outside of the boarding operation unit 11. A hydrostatic continuously variable transmission that functions as a main transmission, together with a transmission case 13 having a gear-type transmission (not shown) that functions as an auxiliary transmission, etc. A device S is provided.

  As shown in FIG. 1, a link mechanism 17 including a left and right lift arms 14, left and right lower links 15, a lift rod 16 that connects the lift arms 14 and the lower links 15, etc. And a hydraulic cylinder 18 for moving the link mechanism 17 up and down, and a power take-out shaft 19. As a result, the tractor T is configured to be able to move up and down a working device such as a rotary tiller or a plow at the rear portion and to extract power from the power take-out shaft 19.

  As shown in FIG. 3 to FIG. 5, a mounting member 20 (an example of “machine base”) made of a plate-like member is fixedly provided on the right side of the body of the mission case 13. Yes. A bracket 22 is fixedly provided on the right side of the body of the mounting member 20 by fastening the bolt 21 with a fastener.

[About hydrostatic continuously variable transmission]
Although the internal structure is not illustrated, the hydrostatic continuously variable transmission S is supplied with an axial plunger type hydraulic pump configured by a variable displacement type driven by the engine 7 and hydraulic oil from the hydraulic pump. Thus, an axial plunger type hydraulic motor that rotates at a speed corresponding to the amount of oil is provided. This hydraulic pump is configured to transmit a traveling driving force to the mission case 13.

  As shown in FIGS. 3 to 5, the hydrostatic continuously variable transmission S includes a swash plate 23 of a hydraulic pump, a trunnion shaft 24 integrally linked to the swash plate 23, and a trunnion shaft. And a neutral urging mechanism 25 that urges the swash plate 23 to the neutral position N1 via the swash plate 24. The hydrostatic continuously variable transmission S rotates the trunnion shaft 24 about the operation axis X1 so that the angle of the swash plate 23 is set to the maximum forward rotation position F1 and the maximum reverse rotation position R1 across the neutral position N1. It is configured to be changeable between.

  The output of the hydrostatic continuously variable transmission S is configured to be capable of stepless shifting between a maximum forward rotation speed (maximum forward speed) and a maximum reverse rotation speed (maximum reverse speed) with zero speed interposed therebetween. . In the hydrostatic continuously variable transmission S, when the swash plate 23 is set to the neutral position N1, the zero speed state appears, and when the swash plate 23 is set to the maximum forward rotation position F1, the speed is increased in the forward rotation direction. The maximum normal rotation state that becomes maximum appears, and the maximum reverse rotation state that causes the maximum speed in the reverse rotation direction opposite to the normal rotation direction appears by setting the swash plate 23 to the maximum reverse rotation position R1.

  As shown in FIGS. 3 to 5, the trunnion shaft 24 protrudes from the right side of the body of the mission case 13 to the right of the body. The cross-sectional shape of the right end portion of the trunnion shaft 24 in a side view is formed in an oval shape. The trunnion shaft 24 can be rotated around the operation axis X1 in the lateral direction of the machine body.

  The neutral biasing mechanism 25 applies a biasing force for rotating the trunnion shaft 24 so that the swash plate 23 is in the neutral position N1. The neutral urging mechanism 25 includes a first rotating arm 26, a second rotating arm 27, a roller 28, and two springs described later.

  The first rotating arm 26 swings around the operation axis X1 of the trunnion shaft 24, thereby sandwiching a neutral posture N2 (see FIG. 3) corresponding to the neutral position N1 of the swash plate 23. The posture can be changed between a maximum forward rotation posture F2 (see FIG. 4) corresponding to the maximum forward rotation position F1 and a maximum reverse rotation posture R2 (see FIG. 5) corresponding to the maximum reverse rotation position R1 of the swash plate 23. ing.

  As shown in FIGS. 3 to 5, the first rotating arm 26 is integrally attached to the trunnion shaft 24. That is, the first turning arm 26 can swing around the operation axis X1 integrally with the trunnion shaft 24. The first rotating arm 26 includes a fan-shaped fan-shaped portion 26A and an operation arm 26B integrated with the fan-shaped portion 26A. A cam portion 29 that is recessed in a V shape toward the trunnion shaft 24 is formed at the edge of the fan-shaped portion 26 </ b> A of the first rotating arm 26. The base end portion of the fan-shaped portion 26 </ b> A is connected to the trunnion shaft 24 by sandwiching the right end portion of the trunnion shaft 24. As will be described later, a seesaw-type shift pedal 31, which is an example of a shift operation tool, is linked to the operation arm 26 </ b> B via a linkage mechanism 30.

  The second rotating arm 27 is supported so as to be rotatable relative to the mission case 13. Specifically, the second turning arm 27 is configured to turn around a swing shaft 32 parallel to the trunnion shaft 24. That is, the swing shaft 32 is configured to rotate around a rotation axis X2 parallel to the operation axis X1.

  The second rotating arm 27 includes a swinging shaft 32 that can swing around the rotation axis X2 and a first arm 33 that extends from the swinging shaft 32 to the cam portion 29 side of the first rotating arm 26. A second arm 34 extending from the swing shaft 32 in a direction different from the first arm 33, and a detection arm 35 extending downward from a location near the center of the second arm 34. Yes. A roller 28 is rotatably supported on the free end of the first arm 33 of the second rotating arm 27.

  The second arm 34 includes a plurality of mounting holes, which will be described later, and a notch-shaped latching portion 37 located on the free end side farther from the rotation axis X2 than the plurality of mounting holes. . The latching portion 37 is a notched portion in which the edge of the second arm 34 is notched downward.

  The roller 28 is fitted into the cam portion 29 to rotate the first rotation arm 26 to the neutral posture N2 corresponding to the neutral position N1 of the swash plate 23 (see FIG. 3). In other words, the swash plate 23 is in the neutral position N1 when the first rotating arm 26 is in the neutral posture N2.

  As shown in FIGS. 3 to 6, the bracket 22 fixed to the mounting member 20 is provided with a sensor 38 that is a detection means capable of detecting the neutral position N <b> 1 of the swash plate 23. . When the first rotating arm 26 is in the neutral posture N2, the detection arm 38A of the sensor 38 is pressed by the detection arm 35 of the first rotating arm 26. The detection signal of the sensor 38 is input to a control device (not shown) and used for various controls.

[About the first spring and the second spring]
As shown in FIGS. 3 to 6, a first spring 40 and a second spring 41 (corresponding to “one spring”) having a smaller spring constant than the first spring 40 are provided as two springs. Yes. The first spring 40 and the second spring 41 are each a tension spring. The first spring 40 and the second spring 41 are attached across the second arm 34 of the second rotating arm 27 and the bracket 22, respectively.

  The bracket 22 is formed with a round hole-shaped first fixing hole 42, and a round hole-shaped second fixing hole 43 (an example of a “fixing portion”) arranged side by side with the first fixing hole 42. Yes. The second fixing hole 43 is located closer to the swing shaft 32 (rotation axis X2) than the first fixing hole 42.

  One end 40 </ b> A of the first spring 40 is attached to the first fixing hole 42 in a fixable state. The other end 40 </ b> B of the first spring 40 is attached to a hooking portion 37 of the second arm 34 in a fixable state. One end 41 </ b> A of the second spring 41 is attached to the second fixing hole 43 in a fixable state. The other end 41 </ b> B (corresponding to “attachment portion”) of the second spring 41 is attached in a position changeable state. The first spring 40 and the second spring 41 are arranged side by side and close to each other. The second spring 41 is located closer to the swing shaft 32 (rotation axis X2) than the first spring 40 is.

  The first spring 40 and the second spring 41 respectively exert a pulling force on the second arm 34 of the second rotating arm 27, thereby being supported rotatably on the first arm 33 of the second rotating arm 27. The roller 28 is urging the second rotating arm 27 so as to fit into the cam portion 29.

  The first spring 40 and the second spring 41 are respectively contracted most when the swash plate 23 is in the neutral position N1 (see FIG. 3), and when the swash plate 23 is in the maximum forward rotation position F1 or the maximum reverse rotation position R1. (See FIGS. 3 and 4). The first spring 40 and the second spring 41 exert a tensile force on the second rotating arm 27 even when the swash plate 23 is in the neutral position N1.

[About mounting holes]
As shown in FIGS. 3 to 6, the second rotating arm 27 is provided with “a plurality of attachment holes” to which the second spring 41 is selectively attached. Specifically, in the second arm 34 of the second rotation arm 27, a first attachment hole 44, a second attachment hole 45 located at a position farther from the rotation axis X2 than the first attachment hole 44, Two mounting holes are formed.

  The other end 41B of the second spring 41 can be attached to the first attachment hole 44 and the second attachment hole 45, respectively. That is, as shown in FIGS. 3 to 6, the other end 41 </ b> B of the second spring 41 can be replaced with the first mounting hole 44 and the second mounting hole 45.

  The neutral urging mechanism 25 is configured such that the urging force of the second spring 41 among the two springs of the first spring 40 and the second spring 41 can be changed. As the second spring 41, one having a smaller spring constant than the first spring 40 is selected.

  The pulling force acting on the second arm 34 of the second rotation arm 27 from the second spring 41 attached to the second attachment hole 45 is from the second spring 41 attached to the first attachment hole 44 to the second rotation arm 27. It becomes larger than the pulling force acting on the second arm 34. That is, the first mounting hole 44 and the second mounting hole 45 are moment forces acting on the second rotating arm 27 based on the biasing force of the second spring 41 in a state where the second spring 41 is mounted. Are positioned differently.

  As shown in FIG. 6, the first attachment hole 44 and the second attachment hole 45 are communicated with each other by a communication portion 46 formed between the first attachment hole 44 and the second attachment hole 45. That is, the first attachment hole 44 and the second attachment hole 45 are communicated as one hole portion. The first mounting hole 44 and the second mounting hole 45 are communicated so that the other end 41B of the second spring 41 can move.

  The extending direction of the second spring 41 is at the edge of the second spring 41 in the compression direction side of the communication portion 46 that communicates the first mounting hole 44 and the second mounting hole 45 that are adjacent two mounting holes. A protruding portion 47 (an example of “holding means”) that protrudes to the side is provided. The protruding portion 47 has a substantially arc shape. The protrusion 47 holds the other end 41 </ b> B of the second spring 41 in each of the first attachment hole 44 and the second attachment hole 45. The first mounting hole 44, the second mounting hole 45, and the protruding portion 47 are continuous in a smooth curved shape.

  As shown in FIGS. 6 and 7, the protrusion 47 is provided with a first inclined surface 47A on the first mounting hole 44 side and a second inclined surface 47B on the second mounting hole 45 side. . The angle α formed between the first inclined surface 47A and the virtual line V1 perpendicular to the expansion and contraction direction of the first spring 40 attached to the first attachment hole 44 is the first angle attached to the second inclined surface 47B and the second attachment hole 45. It is larger than the angle β formed by the virtual line V2 orthogonal to the expansion / contraction direction of the spring 40. That is, the inclination angle of the first inclined surface 47A is tighter than the inclination angle of the second inclined surface 47B. In other words, the inclination angle of the second inclined surface 47B is gentler than the inclination angle of the first inclined surface 47A.

  As shown in FIGS. 6 and 7, the first mounting hole 44 and the second mounting hole 45 are positioned so that the distance from the pivot axis X <b> 2 of the swing shaft 32 is different. In other words, the first mounting hole 44 and the second mounting are set such that the distance A1 between the first mounting hole 44 and the rotation axis X2 is larger than the distance A2 between the second mounting hole 45 and the rotation axis X2. The position of the hole 45 is set.

  As shown in FIGS. 6 and 7, one end 41 </ b> A opposite to the other end 41 </ b> B of the second spring 41 is attached to the second fixing hole 43 in a fixed position. The first mounting hole 44 and the second mounting hole 45 are positioned so that the distance from the second fixing hole 43 is different. That is, the distance B1 between the first mounting hole 44 and the second fixing hole 43 is larger than the distance B2 between the second mounting hole 45 and the second fixing hole 43. The position of the hole 45 is set.

  As shown in FIG. 6, the other end 41 </ b> B of the second spring 41 is shifted between the first mounting hole 44 and the second mounting hole 45 along the edge of the second spring 41 on the compression direction side. By moving the second spring 41, it is possible to change the attachment hole to which the second spring 41 is attached, and to change the urging force acting on the second rotating arm 27 from the second spring 41. That is, the neutral urging mechanism 25 can change the urging force of the second spring 41 whose spring constant is relatively smaller than that of the first spring 40.

  In a state where the second spring 41 is attached to the first attachment hole 44, when the urging force of the neutral urging mechanism 25 becomes smaller than the force necessary to return the swash plate 23 to the neutral position N1, By changing the second spring 41 from the first mounting hole 44 to the second mounting hole 45, the urging force of the neutral urging mechanism 25 can be increased, and the swash plate 23 can be adjusted to a state in which it is surely returned to the neutral position N1. .

  As described above, the biasing force of the neutral biasing mechanism 25 can be easily adjusted simply by changing the second spring 41 between the first mounting hole 44 and the second mounting hole 45.

[About the speed change pedal]
As shown in FIGS. 3 to 5, a shift pedal 31 is linked to the operation arm 26 </ b> B of the first rotation arm 26 via a linkage mechanism 30. The shift pedal 31 is disposed on the right side of the body of the boarding operation unit 11. That is, the shift pedal 31 is arranged on the same side as the neutral urging mechanism 25 with respect to the mission case 13 in the left-right direction of the machine body. The speed change pedal 31 includes a forward stepping operation portion 31A for forward shifting, a rear stepping operation portion 31B for reverse shifting integrated with the front stepping operation portion 31A, a front stepping operation portion 31A and a rear stepping operation portion 31B. And a pedal arm 31C located integrally therewith.

  The speed change pedal 31 receives a stepping operation on the front stepping operation portion 31A or the rear stepping operation portion 31B and an urging force of the neutral urging mechanism 25, and is coupled to the lower end portion of the pedal arm 31C. The balance swings around the 48 fulcrum axis X3.

  The linkage mechanism 30 is provided with a first connecting pin 49 that faces the vehicle body in the left-right direction, a linkage arm 50 that extends along the front-rear direction of the vehicle body, and a second connection pin 51 that faces the aircraft left-right. The first connecting pin 49 rotatably connects the pedal arm 31C of the speed change pedal 31 and one end of the linkage arm 50. The second connecting pin 51 rotatably connects the pedal arm 31C of the speed change pedal 31 and the free end of the operation arm 26B of the first rotating arm 26.

  The speed change pedal 31 swings between the maximum forward angle F3 (see FIG. 4) and the maximum reverse angle R3 (see FIG. 5) around the fulcrum axis X3 with the neutral angle N3 (see FIG. 3) in between. It is configured to move. By setting the shift pedal 31 to the neutral angle N3, the swash plate 23 is set to the neutral position N1 (see FIG. 3), and by setting the shift pedal 31 to the maximum forward angle F3, the swash plate 23 is set to the maximum forward rotation position F1 ( 4), by setting the shift pedal 31 to the maximum reverse angle R3, the swash plate 23 reaches the maximum reverse rotation position R1 (see FIG. 5).

  As shown in FIGS. 3 and 4, by depressing the front depression operation portion 31A of the shift pedal 31 against the urging force of the neutral urging mechanism 25, the shift pedal 31 is advanced forward from the neutral angle N3. By swinging to the angle F3 side, the angle of the swash plate 23 is changed from the neutral position N1 to the maximum forward rotation position F1. Then, as shown in FIGS. 3 and 5, the shift pedal 31 is depressed to the neutral angle N3 by depressing the rear stepping operation portion 31B of the shift pedal 31 against the biasing force of the neutral biasing mechanism 25. Is swung from the neutral position N1 to the maximum reverse rotation position R1. When the foot is released from the shift pedal 31, the shift pedal 31 is automatically returned to the neutral angle N3 by the action of the biasing force of the neutral biasing mechanism 25, and the swash plate 23 is automatically moved to the neutral position N1. It is restored (see FIG. 3).

[About adding the biasing force of the first spring and the biasing force of the second spring]
Although not particularly illustrated, as in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-152823), the conventional neutral biasing mechanism is given a biasing force that causes the swash plate to return to the neutral position only by a single spring. There is something to do. In the conventional neutral urging mechanism, a single spring having a relatively large spring constant is used to provide a reliable urging force for returning the swash plate to the neutral position even when the swash plate is in the vicinity of the neutral position. ing. However, when only such a single spring is used, since the spring constant is large, the biasing force of the neutral biasing mechanism when the swash plate is in the neutral position and the swash plate at the maximum forward rotation position or the maximum reverse rotation position. The difference from the biasing force of the neutral biasing mechanism at a certain time becomes too large. That is, the operating force required when the shift pedal 31 is depressed to the maximum forward angle or maximum reverse angle becomes excessive.

In contrast, the neutral urging mechanism 25 of the present invention has an urging force of the first spring 40 and an urging force of the second spring 41 having a smaller spring constant than the first spring 40, as shown in FIGS. The swash plate 23 is urged to return to the neutral position N1 by adding the forces. As described above, since two springs having different urging forces are used, the urging force of the neutral urging mechanism 25 when the swash plate 23 is at the neutral position N1 and the swash plate 23 at the maximum forward rotation position F1 or the maximum reverse rotation. The difference from the urging force of the neutral urging mechanism 25 at the position R1 can be reduced. That is, since the neutral biasing mechanism 25 of the present invention uses two springs having different spring constants, only a single spring having a large spring constant is used, or two springs having the same spring constant are used. Compared with such a conventional neutral urging mechanism, the swash plate 23 has a maximum forward rotation position F1 or a maximum reverse rotation position R1 while ensuring a sufficient urging force necessary to return the swash plate 23 to the neutral position N1. There is an advantage that the urging force when it is in can be reduced. As a result, when the swash plate 23 is in the vicinity of the neutral position N1, it is possible to apply a biasing force that reliably returns the swash plate 23 to the neutral position N1, and to make the swash plate 23 the maximum forward rotation position F1 or the maximum reverse rotation position T1. Therefore, it is possible to reduce the operating force when the shift pedal 31 is stepped on to the maximum forward angle F3 or the maximum reverse angle R3, and the operability can be improved.

[Another embodiment]
Hereinafter, another embodiment of the present invention will be described. In each of the following embodiments, configurations other than the configuration described are the same as those in the above embodiment. Moreover, the said embodiment and each following another embodiment can mutually be combined unless a contradiction arises. Note that the scope of the present invention is not limited to the above-described embodiment and the following separate embodiments.

  (1) In the above embodiment, the example in which the urging force of the second spring 41 is changed by changing the second spring 41 between the “plurality of mounting holes” is shown as an example. . For example, an operation member capable of changing the extension amount of the second spring 41 may be provided.

  (2) In the above-described embodiment, as an example of the “plurality of mounting holes”, the one in which the two mounting holes of the first mounting hole 44 and the second mounting hole 45 are formed is shown. It is not limited to this. For example, three or more attachment holes may be provided.

  (3) In the above embodiment, the first mounting hole 44 and the second mounting hole 45 are communicated by the communication portion 46 as an example, but the present invention is not limited to this. The first mounting hole 44 and the second mounting hole 45 may not be communicated with each other and may be formed as mutually independent holes.

  (4) In the above-described embodiment, the projecting portion 47 having an arc shape is shown as an example, but the present invention is not limited thereto. For example, another protrusion having a linear portion may be used. In this case, the other protrusions may have a shape such as a triangular shape or a trapezoidal shape.

  (5) In the above embodiment, the second arm 34 of the second rotating arm 27 is formed with “a plurality of mounting holes” for selectively mounting the second spring 41 as “one spring”. Is shown as an example, but is not limited thereto. Instead, “a plurality of attachment holes” to which the second spring 41 that is “one spring” is selectively attached may be formed in the first arm 33 of the second rotating arm 27.

  (6) In the above embodiment, an example is shown in which the second rotating arm 27 is formed with “a plurality of mounting holes” for selectively mounting the second spring 41 which is “one spring”. However, it is not limited to this. Instead of this, “a plurality of attachment holes” to which the second spring 41 that is “one spring” is selectively attached may be formed in the bracket 22 that is the “machine base”. In this case, the second rotating arm 27 is provided with a “fixing portion”.

  (7) In the above embodiment, the second arm 34 of the second rotating arm 27 has the first mounting hole 44 and the second mounting hole 45 formed as an example. I can't. For example, a first mounting hole and a second mounting hole may be formed in the first arm 33 that supports the roller 28 in the second rotating arm 27.

  (8) In the above-described embodiment, the attachment member 20 fixedly attached to the right side of the body of the mission case 13 is shown as an example of the “machine base”, but is not limited thereto. For example, other attachment members fixedly attached to the right side of the machine body such as the hydrostatic continuously variable transmission S may be used as the “machine base”.

  (9) In the above-described embodiment, the first spring 40 and the second spring 41 are illustrated as tension springs, respectively, but are not limited thereto. For example, the first spring 40 and the second spring 41 may be a tension spring, a compression spring, a torsion spring, or the like, respectively.

  (10) In the above-described embodiment, the shift pedal 31 is disposed on the same side as the neutral urging mechanism 25 with respect to the transmission case 13 in the left-right direction of the body, but is not limited thereto. Absent. You may arrange | position on the opposite side to the neutral urging | biasing mechanism 25 with respect to the mission case 13 in the body left-right direction. In this case, the support shaft in the linkage mechanism crosses the vicinity of the mission case 13 in the direction of the body.

  (11) In the above embodiment, the seesaw-type shift pedal 31 is shown as an example of the shift operation tool, but the present invention is not limited to this. For example, a shift operation tool in which a forward pedal and a reverse pedal are provided separately may be used. Further, for example, a manual operation speed change lever may be provided as a speed change operation tool.

  (12) In the above embodiment, left and right expressions are used, but a structure in which the left and right are opposite may be used.

  The hydrostatic continuously variable transmission according to the present invention can be suitably used by being incorporated in a work vehicle such as a combine, a rice transplanter, a mower, or a construction machine in addition to the tractor.

20: Mounting member ("machine stand")
23: swash plate 24: trunnion shaft 25: neutral urging mechanism 26: first rotating arm 27: second rotating arm 28: roller 29: cam portion 32: swing shaft 40: first spring ("two springs" One of the
41: Second spring (one of “two springs”, “one spring”)
41B: The other end ("mounting part")
43: Second fixing hole ("fixing part")
44: First mounting hole (one of "a plurality of mounting holes")
45: Second mounting hole (one of "a plurality of mounting holes")
46: Communication part 47: Protruding part ("holding means")
N1: Neutral position N2: Neutral posture S: Hydrostatic continuously variable transmission

Claims (6)

A hydrostatic continuously variable transmission that is capable of changing the angle of the swash plate by rotating the trunnion shaft, and provided with a neutral urging mechanism that urges the swash plate to a neutral position,
In the neutral urging mechanism,
A first rotating arm integrally attached to the trunnion shaft and having a cam portion that is recessed toward the trunnion shaft;
A second pivot arm that pivots about an oscillation axis parallel to the trunnion axis;
A roller that is rotatably supported by the second rotation arm and that fits into the cam portion to rotate the first rotation arm to a neutral posture corresponding to the neutral position;
Two springs attached across the second rotating arm and the machine base and biasing the second rotating arm so that the roller fits into the cam portion, and
A hydrostatic continuously variable transmission configured to be able to change the urging force of one of the two springs. A plurality of attachment holes for selectively attaching the attachment portion of the one spring is formed in one of the second rotating arm or the machine base,
The plurality of mounting holes are positioned so that the moment force acting on the second rotating arm is different based on the biasing force of the one spring in a state where the mounting portion is mounted. The part is communicated so that it can move,
The hydrostatic continuously variable transmission according to claim 1, further comprising holding means for holding the mounting portion in each of the mounting holes.   As the holding means, a protruding portion that protrudes toward the extending direction side of the one spring is provided at an edge portion on the compression direction side of the one spring among the communicating portions that connect the two adjacent mounting holes. The hydrostatic continuously variable transmission according to claim 2.   The hydrostatic continuously variable transmission according to claim 2 or 3, wherein the plurality of mounting holes are positioned so that distances from the swing shaft are different from each other. A fixing portion for attaching one end of the one spring to a fixed position;
The hydrostatic continuously variable transmission according to claim 2 or 3, wherein the plurality of mounting holes are positioned so that distances from the fixed portion are different from each other. The two springs are a first spring and a second spring having a smaller spring constant than the first spring,
The hydrostatic continuously variable transmission according to any one of claims 1 to 5, wherein the urging force of the second spring is changed.

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