JP2016149001A - Hydrostatic continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrostatic continuously variable transmission capable of easily changing biasing force of a neutral biasing mechanism for returning a cam plate to a neutral position with a simple structure.SOLUTION: A neutral energization mechanism 25 is provided with a cam member 26 attached to a trunnion shaft 24 integrally, a rotation arm 27, a roller 28 rotatably supported by the rotation arm 27 and a plurality of springs 40, 41 and 60 attached over the rotation arm 27 and a machine base 20 and biasing the rotation arm 27. As the plurality of springs 40, 41 and 60, an adjustment spring 41 configured so that biasing force can be changed and other springs 40 and 60 different from the adjustment spring 41 are provided. The adjustment spring 41 and other springs 40 and 60 are independently provided in such a state that attachment positions on the rotation arm 27 and the machine base 20 are away from each other. The adjustment spring 41 and other springs 40 and 60 are attached so as to extend in directions different from each other.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 cam portion that is integrally attached to a trunnion shaft and is recessed toward the trunnion shaft in a neutral urging mechanism (in Patent Document 1, “ A cam member (“cam plate” in Patent Document 1) in which a cam recess “) is formed is provided. Further, the neutral urging mechanism includes a rotating arm (“L-shaped arm” in Patent Document 1) that rotates around a swing axis (“support shaft” in Patent Document 1) parallel to the trunnion shaft, A roller that is rotatably supported by the rotation arm and that is fitted into the cam portion to rotate the cam member to a neutral posture corresponding to the neutral position is provided.

  Further, the neutral urging mechanism is provided with a single spring which is attached over the rotating arm and the machine base and urges the rotating arm so that the roller fits into the cam portion.

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, plastic deformation of the spring due to use over time.

  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, which causes a disadvantage that the swash plate is difficult 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. Moreover, since the spring is exchanged, it is not possible to finely adjust the urging force, 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. A cam member that is integrally attached to the trunnion shaft and formed with a cam portion that is recessed toward the trunnion shaft, and a swing member that is parallel to the trunnion shaft. A rotating arm that rotates around a moving shaft, and is rotatably supported by the rotating arm and fitted into the cam portion, thereby rotating the cam member to a neutral posture corresponding to the neutral position. And a plurality of springs attached to the rotating arm and the machine base and biasing the rotating arm so that the roller fits into the cam portion. As a spring, the biasing force can be changed. Adjustment springs and other springs different from the adjustment springs, and the adjustment springs and the other springs are independent in a state in which the rotating arm and the mounting location on the machine base are separated from each other. The adjustment spring and the other spring are attached so as to extend in different directions.

According to the present invention, the neutral biasing mechanism is provided with the adjustment spring capable of changing the biasing force. 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 the adjusting spring without replacing the spring. .
Furthermore, since the adjustment spring and other springs are located at locations apart from each other, a wide space is secured around the adjustment spring, making it easy to adjust the adjustment spring, and adjusting spring and other springs. Interference with the spring is less likely to occur, and the inconvenience that the springs are entangled can be avoided.
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, it is preferable that the urging force of the adjusting spring on the rotating arm is set to be smaller than the urging force of the other spring on the rotating arm.

  According to the above configuration, since the biasing force of the adjustment spring is smaller than the biasing force of the other springs, the adjustment work for changing the biasing force of the adjustment spring can be easily performed.

  In the present invention, the rotating arm includes a main arm portion to which the adjustment spring is attached, and a sub arm portion that extends in a direction different from the main arm portion and to which the other spring is attached. Is preferred.

  According to the above configuration, the adjustment spring and other springs are arranged in a distributed manner in a space near the main arm portion and a space near the sub arm portion extending in a direction different from the main arm portion. The attachment location with respect to the rotary arm of a spring and another spring can be separated largely. As a result, the adjustment work for the adjustment spring becomes easier, and interference between the adjustment spring and other springs is less likely to occur.

  In the present invention, it is preferable that a plurality of the other springs are provided.

  According to the above configuration, the biasing force of the other springs and the biasing force of the adjustment spring are added together to obtain the biasing force of the neutral biasing mechanism. The urging force borne by each spring is smaller than the urging force of the neutral urging mechanism. That is, since the stress generated inside each spring is small, plastic deformation or breakage of the spring due to repeated use is suitably suppressed.

  In the present invention, a push-type switch that is attached to the machine base and detects the neutral position is provided, and a detection unit that is a detection target of the switch is provided in the rotating arm in a state of facing the switch. It is preferable that the other spring is attached in the vicinity of the detection unit in the rotating arm, and the extension direction of the other spring is along the pressing direction of the switch.

  According to the said structure, the neutral position of a swash plate is detected because the detection part of the rotation arm rotated based on the urging | biasing force of another spring presses the switch facing this detection part. And the other spring which gives urging | biasing force to a rotation arm is attached to the vicinity of the detection part in a rotation arm, and also the extension direction of another spring is a thing along the pressing direction of a switch. . For this reason, when the switch is pressed by the detection unit, the urging force of another spring can be efficiently transmitted to the rotating arm. As a result, the switch is reliably pressed by the detecting portion of the rotating arm based on the urging force of the other spring, and the neutral position of the swash plate can be suitably detected.

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. It is a right view which shows the principal part of the neutral biasing mechanism of another embodiment. It is a right view which shows the principal part of the neutral biasing mechanism of another embodiment. It is a right view which shows the principal part of the neutral biasing mechanism of another embodiment. It is a right view which shows the principal part of the neutral biasing mechanism of another embodiment.

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 is equipped with 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 functioning as a main transmission, together with a transmission case 13 provided with a gear-type transmission (not shown) functioning as a sub-transmission device, etc., below the boarding operation unit 11. 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 FIGS. 3 to 5, a mounting base 20 made of, for example, a plate-like member is fixedly provided on the right side of the body of the mission case 13.

[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. 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 cam member 26, a rotating arm 27, a roller 28, and a plurality of springs.

  The cam member 26 swings around the operation axis X1 of the trunnion shaft 24 so that the forward rotation of the swash plate 23 sandwiches 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 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.

  As shown in FIGS. 3 to 5, the cam member 26 is integrally attached to the trunnion shaft 24. That is, the cam member 26 can swing about the operation axis X1 integrally with the trunnion shaft 24. The cam member 26 is provided with 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 cam member 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 rotating arm 27 includes a swing shaft 32 parallel to the trunnion shaft 24, a first arm 33 extending from the swing shaft 32 toward the cam portion 29 of the cam member 26, and the swing arm 32 to the first arm 33. Includes a second arm 34 (corresponding to a “main arm portion”) extending in a different direction and a detection arm 35 (corresponding to a “sub arm portion”) extending in a direction different from the first arm 33 and the second arm 34. Is provided. The swing shaft 32, the first arm 33, the second arm 34, and the detection arm 35 are moved together. The first arm 33 extends upward from the swing shaft 32. The second arm 34 extends from the swing shaft 32 toward the front side. The detection arm 35 extends downward from the swing shaft 32.

  The rotating arm 27 is supported so as to be rotatable with respect to the machine base 20 fixed to the mission case 13. The rotation arm 27 is configured to rotate around the rotation axis X2 that is the center of the swing shaft 32. The pivot axis X2 of the swing shaft 32 is parallel to the operation axis X1 of the trunnion shaft 24.

  The roller 28 is rotatably supported by the free end portion of the first arm 33 of the rotating arm 27. The roller 28 is fitted into the cam portion 29, thereby pressing the cam member 26 and rotating the cam member 26 toward the neutral posture N2 corresponding to the neutral position N1 of the swash plate 23 ( (See FIG. 3). When the cam member 26 is in the neutral posture N2, the swash plate 23 interlocked with the cam member 26 via the trunnion shaft 24 is in the neutral position N1. In other words, the cam portion 29 is formed in a curved shape such that the roller 28 is closest to the operation axis X1 side of the trunnion shaft 24 when the swash plate 23 is in the neutral position N1.

  As shown in FIGS. 3 to 6, the hydrostatic continuously variable transmission S is provided with a push-type switch 38 that is detection means capable of detecting the neutral position N <b> 1 of the swash plate 23. The switch 38 is attached to the machine base 20 via the attachment bracket 61. The switch 38 is attached to a support portion 61B that is a portion along the rotation axis X2 in the mounting bracket 61 bent in an L shape. The mounting bracket 61 is fixed to the machine base 20 with bolts or the like. The switch 38 outputs a detection signal by pushing the detector 38A in the pressing direction along the pressing axis C4. The detection signal of the switch 38 is input to a control device (not shown) and used for various controls.

  The detection arm 35 of the rotation arm 27 is provided with a detection unit 35 </ b> A that is a detection target of the switch 38. 35 A of detection parts are formed in the location in alignment with the direction of the rotation axis X2 in the L-shaped detection arm 35. As shown in FIG. The detection unit 35A is in a state of facing the switch 38. When the cam member 26 is in the neutral posture N2, the swash plate 23 is in the neutral position N1, and the detector 38A of the switch 38 is pushed in by the detection unit 35A of the detection arm 35. As a result, the switch 38 outputs a detection signal indicating that the swash plate 23 is in the neutral position N1. The detection signal of the switch 38 is input to a control device (not shown) and used for various controls.

[About the first spring, second spring, and third spring]
As the plurality of springs provided in the neutral urging mechanism 25, a first spring 40 (corresponding to “other spring”) configured so that the urging force cannot be changed, and a second spring configured so that the urging force can be changed. There are provided three springs 41 (corresponding to “adjustment spring”) and a third spring 60 (corresponding to “other spring”) configured such that the urging force cannot be changed. In other words, the neutral urging mechanism 25 includes a plurality of “other springs” different from the “adjustment springs”.

  The first spring 40, the second spring 41, and the third spring 60 are each a tension spring. The first spring 40, the second spring 41, and the third spring 60 are respectively contracted most when the swash plate 23 is in the neutral position N1 (see FIG. 3), and the swash plate 23 is in the maximum forward rotation position F1 or the maximum reverse rotation position. It extends most when it is in R1 (see FIGS. 3 and 4). The first spring 40, the second spring 41, and the third spring 60 each exert a pulling force on the rotating arm 27 even when the swash plate 23 is in the neutral position N1. In other words, in the state where the cam member 26 is in the neutral posture N2, the first spring 40, the second spring 41, and the third spring 60 are respectively extended to the rotating arm 27 in a state of being stretched more than the natural length. It is attached.

  The springs 40, 41, and 60 are attached over the rotating arm 27 and the machine base 20, respectively, so as to bias the rotating arm 27 so that the roller 28 fits into the cam portion 29 of the cam member 26. It is configured. In other words, the springs 40, 41, and 60 have a biasing force that biases the rotating arm 27 in a direction in which the roller 28 presses the cam portion 29 of the cam member 26 and the swash plate 23 becomes the neutral position N1. It is configured to grant. That is, the urging force that the neutral urging mechanism 25 urges the swash plate 23 to the neutral position N1 is the sum of the urging force of the first spring 40, the urging force of the second spring 41, and the urging force of the third spring 60. It is based on things.

  The spring constant of the second spring 41 is set smaller than the spring constant of the first spring 40 and the spring constant of the third spring 60. In other words, the urging force of the second spring 41 on the rotating arm 27 is smaller than the urging force of the first spring 40 on the rotating arm 27 and the urging force of the third spring 60 on the rotating arm 27. Is set.

  As shown in FIGS. 3 to 5, the machine base 20 is provided with a fixing bracket 22 to which the first spring 40 and the second spring 41 are attached, and an attachment bracket 61 to which the third spring 60 is attached. Yes. The fixing bracket 22 is fixedly supported on the right side of the machine body 20 by a fastener such as a bolt 21. The mounting bracket 61 is located on the rear side of the fixed bracket 22 and is fixedly supported on the right side of the machine body 20 by a fastener such as a bolt 21.

  The first spring 40 and the second spring 41 are attached across the second arm 34 of the rotating arm 27 and the machine base 20, respectively. The first spring and the second spring 41 are attached to the machine base 20 via a common fixing bracket 22. The third spring 60 is attached across the detection arm 35 of the rotating arm 27 and the machine base 20. The third spring 60 is attached to the machine base 20 via a mounting bracket 61.

  The second arm 34 of the rotating arm 27 is provided with a notch-shaped hooking portion 37. The latching portion 37 is a notched portion in which the upper edge portion of the second arm 34 is notched toward the lower side. The fixing bracket 22 is provided with a round hole-shaped first fixing hole 42 which is an example of a fixing portion. The latching portion 37 and the first fixing hole 42 are attachment locations where the first spring 40 can be attached. 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.

  The second arm 34 of the rotating arm 27 is provided with a first mounting hole 44 and a second mounting hole 45 as a plurality of mounting holes. The first attachment hole 44 and the second attachment hole 45 are located closer to the swing shaft 32 (rotation axis X2) than the hook portion 37. The fixing bracket 22 is provided with a round hole-shaped second fixing hole 43 which is an example of a fixing portion. The first mounting hole 44, the second mounting hole 45, and the second fixing hole 43 are mounting locations where the second spring 41 can be mounted. The second fixing holes 43 are arranged side by side along the front-rear direction with the first fixing holes 42, and are located closer to the rotation axis X <b> 2 than the first fixing holes 42. 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 41B corresponding to the attachment portion of the second spring 41 is attached in a position changeable state. The second mounting hole 45 is located at a location farther from the rotation axis X <b> 2 than the first mounting hole 44. The other end 41 </ b> B of the second spring 41 can be selectively attached to the first attachment hole 44 and the second attachment hole 45. That is, by changing the other end 41 </ b> B of the second spring 41 between the first mounting hole 44 and the second mounting hole 45, the urging force applied from the second spring 41 to the rotating arm 27 can be changed. It has become.

  The detection arm 35 of the rotation arm 27 is provided with a first attachment portion 35B. The first attachment portion 35B is located above the detection portion 35A. The mounting bracket 61 is provided with a second mounting portion 61A. The second attachment portion 61A is located above the switch 38 on the rear side of the support portion 61B. The first attachment portion 35B and the second attachment portion 61A are attachment locations where the third spring 60 can be attached. One end 60 </ b> A of the third spring 60 is attached to the second attachment portion 61 </ b> A of the attachment bracket 61. The other end 60 </ b> B of the third spring 60 is attached to the first attachment portion 35 </ b> B in the detection arm 35 of the rotation arm 27. That is, the third spring 60 is attached in the vicinity of the detection portion 35 </ b> A of the detection arm 35 in the rotating arm 27. Since the third spring 60 is located above the switch 38, the upper side of the switch 38 is protected by the third spring 60. The extension direction of the third spring 60 is along the pressing direction of the switch 38. Further, as shown in FIG. 6, in a state where the switch 38 is pressed by the detection unit 35 </ b> A of the detection arm 35, the third axis C <b> 3 that is the center of the third spring 60 is substantially the same as the pressing axis C <b> 4 of the switch 38. It is set to be parallel.

  That is, as shown in FIGS. 3 to 5, the first spring 40 and the second spring 41 are provided independently with the mounting positions of the rotating arm 27 and the machine base 20 being separated from each other. . The second spring 41 and the third spring 60 are independently provided in a state where the mounting positions on the rotating arm 27 and the machine base 20 are separated from each other. The third spring 60 and the first spring 40 are independently provided in a state where the mounting positions on the rotating arm 27 and the machine base 20 are separated from each other.

  The second spring 41 is located closer to the swing shaft 32 (rotation axis X2) than the first spring 40 is. The third spring 60 is located at a position far away from the first spring 40 and the second spring 41 and is attached in the vicinity of the detection portion 35 </ b> A of the detection arm 35 in the rotating arm 27. If it demonstrates, the 3rd spring 60 is located in the other side on both sides of the detection arm 35 of the rotation arm 27 with respect to the 1st spring 40 and the 2nd spring 41. As shown in FIG. For this reason, a relatively large space is secured at the attachment location of the third spring 60, and it is easy to place the third spring 60 having a large size.

  The pulling force acting on the second arm 34 of the rotation arm 27 from the second spring 41 attached to the second attachment hole 45 is the second arm of the rotation arm 27 from the second spring 41 attached to the first attachment hole 44. It becomes larger than the pulling force acting on 34. That is, the first mounting hole 44 and the second mounting hole 45 have different moments acting on the rotating arm 27 based on the urging force of the second spring 41 when the second spring 41 is mounted. The position is set as follows.

  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. The protrusion part 47 which is an example of the holding means which 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 the urging force acting on the rotating arm 27 from the second spring 41 can be changed.

  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.

  Moreover, as FIG. 6 etc. show, the 1st spring 40 and the 2nd spring 41 are attached so that it may extend in a mutually different direction. The first axis C1 that is the center of the first spring 40 is inclined with respect to the contraction-side second axis C2a that is the center of the second spring 41 that is attached to the first attachment hole 44. Further, the first axis C1 that is the center of the first spring 40 is inclined with respect to the extension-side second axis C2b that is the center of the second spring 41 that is attached to the second attachment hole 45. . If it demonstrates, the 1st spring 40 and the 2nd spring 41 will be attached so that it may space apart as it goes to the 2nd arm 34 from the fixing bracket 22. For this reason, the second spring 41 does not block the space around the first mounting hole 44 and the second mounting hole 45. That is, it is easy to replace the other end 41 </ b> B of the second spring 41 between the first mounting hole 44 and the second mounting hole 45 without the second spring 41 being in the way.

  The second spring 41 and the third spring 60 are attached so as to extend in different directions. The third axis C3 that is the center of the third spring 60 is inclined with respect to the contraction-side second axis C2a that is the center of the second spring 41 in the state of being attached to the first attachment hole 44. The third axis C3 that is the center of the third spring 60 is inclined with respect to the extension-side second axis C2b that is the center of the second spring 41 that is attached to the second attachment hole 45. . For this reason, it is easy to replace the other end 41 </ b> B of the second spring 41 between the first mounting hole 44 and the second mounting hole 45 without the third spring 60 being in the way.

[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 cam member 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 shift pedal 31 includes a forward stepping operation unit 31A for forward shifting, a rear stepping operation unit 31B for reverse shifting integrated with the front stepping operation unit 31A, a front stepping operation unit 31A and a rear stepping operation unit 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 cam member 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, second spring, and third 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.

  On the other hand, as shown in FIGS. 3 to 7, the neutral urging mechanism 25 of the present invention has an urging force of the first spring 40 and a second spring 41 having a smaller spring constant than the first spring 40. The urging force and the urging force of the third spring 60 having a spring constant larger than that of the first spring 40 are added to obtain an urging force for returning the swash plate 23 to the neutral position N1. Thus, since three 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 three springs having different spring constants, the swash plate is compared with a conventional neutral biasing mechanism using only a single spring having a large spring constant. Further, there is an advantage that the urging force when the swash plate 23 is at the maximum forward rotation position F1 or the maximum reverse rotation position R1 can be reduced while sufficiently securing the urging force necessary for returning 23 to the neutral position N1. 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.

  Further, since the urging force of the neutral urging mechanism 25 is distributed to the first spring 40, the second spring 41, and the third spring 60, in each of the first spring 40, the second spring 41, and the third spring 60. The stress applied to the fragile portion where the curvature becomes maximum can be reduced. Thereby, about each of the 1st spring 40, the 2nd spring 41, and the 3rd spring 60, it can be made into the thing which is hard to produce a damage | wound in the weak part of a spring by repeated use. For this reason, the neutral urging | biasing mechanism 25 excellent in durability can be comprised.

[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 third spring 60 is mounted over the detection arm 35 of the rotating arm 27 and the machine base 20 (mounting bracket 61). Not limited to. For example, the attachment location of the third spring 60 may be changed. As shown in FIG. 8, the third spring 60 is connected to the second arm 34 of the rotating arm 27 and the machine base 20 (fixed bracket 22). , And may be attached over the whole area. In this case, the urging forces of the springs 40, 41, and 60 are appropriately adjusted so that the total urging force of the first spring 40, the second spring 41, and the third spring 60 against the rotating arm 27 does not change.

  (2) In the above embodiment, the third spring 60 is provided, but the present invention is not limited to this. For example, as shown in FIG. 9, the third spring 60 may be omitted. In this case, in order to compensate for the omitted urging force of the third spring 60, the urging force of the first spring 40 and the second spring 41 against the rotating arm 27 is the same as that of the first spring 40 and the second spring 41 of the above embodiment. Configured to be larger.

  (3) In the above embodiment, the first spring 40 is attached over the second arm 34 of the rotating arm 27 and the machine base 20 (fixed bracket 22). It is not limited to this. For example, the mounting location of the first spring 40 may be changed. As shown in FIG. 10, the first spring 40 is moved to the detection arm 35 of the rotating arm 27, the machine base 20 (mounting bracket 61), You may make it attach over. In this case, the urging forces of the springs 40, 41, and 60 are appropriately adjusted so that the total urging force of the first spring 40, the second spring 41, and the third spring 60 against the rotating arm 27 does not change.

  (4) In the above embodiment, the second spring 41 is illustrated as being attached across the second arm 34 of the rotating arm 27 and the machine base 20 (fixed bracket 22). It is not limited to this. For example, you may change the attachment location of the 2nd spring 41, and as FIG. 11 shows, the 2nd spring 41, the detection arm 35 of the rotation arm 27, the machine base 20 (attachment bracket 61), You may make it attach over. In this case, the detection arm 35 of the rotating arm 27 may be formed with “a plurality of attachment holes” to which the second spring 41 as the “adjustment spring” is selectively attached. Further, in this case, the mounting location of the third spring 60 is changed, and the third spring 60 is mounted across the second arm 34 of the rotating arm 27 and the machine base 20 (fixed bracket 22). Also good. In this case, the urging forces of the springs 40, 41, and 60 are appropriately adjusted so that the total urging force of the first spring 40, the second spring 41, and the third spring 60 against the rotating arm 27 does not change.

  (5) In the above embodiment, the extension direction of the third spring 60 is exemplified along the pressing direction of the switch 38, but is not limited thereto. For example, the extension direction of the third spring 60 may face a direction different from the pressing direction of the switch 38.

  (6) In the above embodiment, an example in which the urging force of the third spring 60 against the rotating arm 27 is set to be larger than the urging force of the first spring 40 against the rotating arm 27 is illustrated. However, it is not limited to this. For example, the urging force of the first spring 40 on the rotating arm 27 may be set to be larger than the urging force of the third spring 60 on the rotating arm 27.

  (7) 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.

  (8) In the above embodiment, the first mounting hole 44 and the second mounting hole 45 are communicated by the communication portion 46, 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.

  (9) In the above embodiment, the protruding portion 47 having an arc shape is illustrated, but the present invention is not limited to this. 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.

  (10) In the above embodiment, the rotation arm 27 is formed with “a plurality of attachment holes” to which the second spring 41 as the “adjustment spring” is selectively attached. Not limited. Instead of this, “a plurality of attachment holes” to which the second spring 41 as the “adjustment spring” is selectively attached may be formed in the fixed bracket 22 as the “machine base”. In this case, the rotating arm 27 is provided with a “fixing portion”.

  (11) In the above embodiment, the second arm 34 of the turning arm 27 is formed with the first mounting hole 44 and the second mounting hole 45, but the present invention is not limited to this. 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 rotating arm 27.

  (12) In the above embodiment, the first spring 40, the second spring 41, and the third spring 60 are exemplified as the tension springs, but the present invention is not limited thereto. For example, the first spring 40, the second spring 41, and the third spring 60 may be selected from a tension spring, a compression spring, a torsion spring, and the like, respectively.

  (13) In the above 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 machine body, but is not limited thereto. 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.

  (14) 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.

  (15) 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: Machine base 23: Swash plate 24: Trunnion shaft 25: Neutral biasing mechanism 26: Cam member 27: Rotating arm 28: Roller 29: Cam portion 32: Oscillating shaft 34: Second arm (main arm portion)
35: Detection arm (sub arm part)
35A: detection unit 38: switch 40: first spring (other spring)
41: Second spring (adjustment spring)
60: Third spring (other spring)
N1: Neutral position N2: Neutral posture S: Hydrostatic continuously variable transmission

Claims (5)

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 cam member that is integrally attached to the trunnion shaft and has a cam portion that is recessed toward the trunnion shaft;
A pivot arm that pivots about an oscillation axis parallel to the trunnion axis;
A roller that is rotatably supported by the rotating arm and that fits into the cam portion to rotate the cam member to a neutral posture corresponding to the neutral position;
A plurality of springs attached across the pivot arm and the machine base and biasing the pivot arm so that the roller fits into the cam portion;
As the plurality of springs, an adjustment spring configured to change the biasing force and another spring different from the adjustment spring are provided,
The adjustment spring and the other spring are provided independently in a state in which attachment points in the rotating arm and the machine base are separated from each other,
A hydrostatic continuously variable transmission in which the adjustment spring and the other spring are attached to extend in different directions.   2. The hydrostatic continuously variable transmission according to claim 1, wherein an urging force of the adjustment spring against the rotating arm is set to be smaller than an urging force of the other spring against the rotating arm.   The main arm part to which the said adjustment spring is attached to the said rotation arm, and the subarm part which extends in the direction different from the said main arm part, and to which the said other spring is attached are provided. The hydrostatic continuously variable transmission described in 1.   The hydrostatic continuously variable transmission according to any one of claims 1 to 3, wherein a plurality of the other springs are provided. A press-type switch that is attached to the machine base and detects the neutral position is provided,
The rotating arm is provided with a detection unit that is a detection target of the switch in a state of facing the switch,
The said other spring is attached to the vicinity of the said detection part in the said rotation arm, and the extension direction of the said other spring is along the pressing direction of the said switch. The hydrostatic continuously variable transmission described.

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