JP2020002974A - Gear change device - Google Patents

Abstract

To provide a gear change device which can switch the engagement and release of the gear engagement of left and right power transmission mechanisms by using left and right common mechanisms, and can favorably achieve the gear engagement.SOLUTION: A power transmission route for transmitting power to left and right traveling devices is formed by the engagement of intermediate gears 112L, 112R and shifter gears 115L, 115R. The engagement of the intermediate gears 112L, 112R and the shifter gears 115L, 115R is released by the movement of the shifter gears 115L, 115R to a right direction from the formation state, and there arises a neutral state that the power is not transmitted to the left and right traveling devices. Shift forks 123L, 123R are connected to the shifter gears 115L, 115R. A shift fork shaft 121 for supporting the shift forks 123L, 123R is arranged so as to be movable to a rotation axial line direction, and energized to a left direction by a spring 129.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a transmission for a work vehicle such as a combine.

  For example, in a combine equipped with an HST (Hydro Static Transmission), an HST hydraulic pump is driven by engine power, and a hydraulic motor is driven by oil discharged from the hydraulic pump. The power of the hydraulic motor is transmitted to the left and right crawlers via a power transmission mechanism including gears. When the left and right crawlers are driven at the same speed, the machine body goes straight back and forth, and when the left and right crawlers are driven with a speed difference, the machine body turns right and left.

JP 2012-62973 A

  In the combine, it is necessary to shift to a neutral state in which power is not transmitted between the hydraulic motor of the HST and the left and right crawlers for adjustment and emergency traction. The neutral state can be generated, for example, by disengaging two gears included in the power transmission mechanism between the hydraulic motor and the left crawler and the power transmission mechanism between the hydraulic motor and the right crawler, respectively.

  However, in the configuration in which the gears are independently disengaged by the left and right power transmission mechanisms, mechanisms for engaging and disengaging the gears are separately required on the left and right, and the size of the transmission including the power transmission mechanism is increased. I do. Further, when the two gears are meshed from the neutral state, the respective gears are at positions where they do not mesh with each other, that is, the teeth of one gear and the tooth grooves of the other gear do not face each other in the rotation axis direction. Gears may not mesh well.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a transmission that can switch between gear engagement and disengagement of a right and left power transmission mechanism by a single mechanism common to the left and right, and that the gear engagement can be favorably achieved. It is.

  To achieve the above object, a transmission according to the present invention is a transmission that changes the power of a drive source and transmits the power to left and right traveling devices, and is provided for each of the left and right traveling devices, A transmission gear to which power is transmitted from a drive source; and a shifter gear movably provided in a rotation axis direction of the transmission gear. A power transmission path is formed by engagement of the transmission gear and the shifter gear, and the shifter gear is arranged in one direction in the rotation axis direction. The right and left power transmission mechanisms, which move in the direction to disengage the transmission gear and the shifter gear so that the power transmission path is cut off, and are provided movably in the direction of the rotation axis and are respectively coupled to the left and right shifter gears. A shift member including a shift fork, and an urging member for urging the shift member in one direction opposite to one direction of the rotation axis direction are included.

  According to this configuration, the power transmission mechanism is provided for each of the left and right traveling devices. Each power transmission mechanism includes a transmission gear to which power is transmitted from a drive source, and a shifter gear movably provided in a rotation axis direction of the transmission gear. In each power transmission mechanism, a power transmission path for transmitting power to the traveling device is formed by the engagement of the transmission gear and the shifter gear. When the shifter gear moves in one direction along the rotation axis from the state where the transmission gear and the shifter gear are engaged, the engagement between the transmission gear and the shifter gear is released, and the power transmission path is disconnected. Thus, the transmission is in a neutral state in which power is not transmitted to the left and right traveling devices.

  A shift fork of a shift member is connected to the left and right shifter gears. The shift member is provided so as to be movable in the rotation axis direction, and is urged by an urging member in another direction opposite to one direction in the rotation axis direction. When the shift member is moved in one direction in the rotation axis direction against the urging force, both the left and right shifter gears are moved in one direction, and the engagement between both the left and right transmission gears and the shifter gear is released. When the force for moving the shift member in one direction is released, the shift member moves in the other direction of the rotation axis by the urging force of the urging member. If the teeth of the shifter gear face the tooth grooves of the transmission gear in the rotation axis direction, the movement of the shift member causes the teeth of the shifter gear to enter the tooth grooves of the transmission gear, and meshing between the transmission gear and the shifter gear is achieved. . On the other hand, when the teeth of the shifter gear do not face the tooth groove of the transmission gear in the rotation axis direction, the shift member moves, so that the teeth of the shifter gear abut the teeth of the transmission gear, and the shifter gear and the transmission gear do not mesh with each other. . Since the shift member is urged in the other direction of the rotation axis, even if the teeth of the shifter gear contact the teeth of the transmission gear, the rotation of the transmission gear causes the tooth groove of the transmission gear to move in the rotation axis direction with the teeth of the shifter gear. When the gears face each other, the teeth of the shifter gear enter the tooth grooves of the transmission gear, and meshing between the transmission gear and the shifter gear is achieved.

  Accordingly, gear engagement (mesh between the transmission gear and the shifter gear) and disengagement in the left and right power transmission mechanisms can be switched by one mechanism common to the left and right, and the gear engagement can be favorably achieved.

  The transmission further includes a unit case that houses the power transmission mechanism, and the shift member extends in the rotation axis direction, is held movably in the rotation axis direction in the unit case, and includes a shift fork shaft that supports left and right shift forks. You may have.

  In this case, one end of the shift fork shaft extends to the outside through the unit case, is connected to one end of the shift fork shaft, and has a pivot about a support shaft extending in a direction orthogonal to the rotation axis direction. It is preferable to further include an operation member for moving the shift fork shaft in the rotation axis direction by a moving operation. Gear engagement and disengagement can be achieved by rotating the operation member.

  The operation member may include a shift operation piece supported by the support shaft and connected to the shift fork shaft, and an operation arm supported by the support shaft and rotating integrally with the shift operation piece. In this case, it is preferable that the length from the support shaft to the distal end of the operation arm is larger than the length from the support shaft to the connection portion of the shift operation piece with the shift fork shaft. This allows the leverage principle to work, so that even if the force applied to the operation arm is small, the shift fork shaft can be favorably moved against the urging force of the urging member.

  It is preferable that a locking portion for locking the operation arm is formed in the unit case in a state where the transmission gear and the shifter gear are disengaged from each other. After the transmission gear and the shifter gear have been disengaged from each other, the operation arm is locked to the locking portion, so that the disengaged state can be maintained.

  The urging member is preferably interposed between the unit case and one of the left and right shift forks. Accordingly, it is not necessary to separately provide a portion for connecting the biasing member to the shift member, and the configuration of the shift member can be simplified.

  An annular groove centered on the rotation axis of the transmission gear is formed on the side surface of the transmission gear, and a plurality of internal teeth protruding toward the rotation axis are formed on the outer peripheral surface of the groove in the circumferential direction of the groove. The shifter gear is provided with a plurality of external teeth protruding outward in the rotational radial direction, and the external teeth fit into the tooth grooves between the adjacent internal teeth of the transmission gear, thereby forming the transmission gear and the shift gear. It may be configured to engage.

  According to the present invention, gear engagement and disengagement of the left and right power transmission mechanisms can be switched by one mechanism common to the left and right, and the gear engagement can be favorably achieved.

It is a right view which shows the front part of the combine in which the transmission which concerns on one Embodiment of this invention is mounted. FIG. 2 is a diagram illustrating a configuration of a part of a transmission. It is sectional drawing which shows a part of transmission, and shows the structure from the hydraulic motor of the left HST and the right HST to the middle of a travel device. It is sectional drawing which shows the structure of a neutral speed change mechanism, and shows the state in which the 2nd left intermediate gear and the left shifter gear meshed, and the 2nd right intermediate gear and the right shifter gear meshed. FIG. 4 is a cross-sectional view illustrating a configuration of a neutral speed change mechanism, in a state where engagement between a second left intermediate gear and a left shifter gear is released, and engagement between a second right intermediate gear and a right shifter gear is released. FIG. 4 is a cross-sectional view illustrating a configuration of a neutral speed change mechanism, showing a state in which engagement of a second left intermediate gear and a left shifter gear has been released and the second right intermediate gear has contacted the right shifter gear. It is sectional drawing which shows the structure of a neutral speed change mechanism, and shows the state which the 2nd left intermediate gear and the left shifter gear contact, and the 2nd right intermediate gear and the right shifter gear mesh.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Combine>
FIG. 1 is a right side view showing a front portion of a combine 1 on which a transmission 32 according to an embodiment of the present invention is mounted.

  The combine 1 is a work vehicle that cuts culms and threshes from culms while traveling in a field. The fuselage 11 of the combine 1 is supported by a pair of right and left traveling devices 12. The traveling device 12 employs a crawler having a rough terrain running capability so that the combine 1 can travel in a field.

  The machine body 11 is provided with a cab 13, a reaper 14, a threshing device 15, and a grain tank 16.

  The cab 13 is arranged above the front end of the traveling device 12. The driver's cab 13 is provided with a driver's seat 17 on which the operator sits. For example, an operation panel 18 operated by the operator is provided from the front of the driver's seat 17 to the left. The operation panel 18 includes a main shift lever 21 and a steering lever 22.

  The main transmission lever 21 is provided so as to be displaceable from a neutral position to a front forward position and a rear reverse position. When the main transmission lever 21 is operated from the neutral position to the forward position, power in the forward direction is transmitted to the left and right traveling devices 12, and the body 11 moves forward. On the other hand, when the main transmission lever 21 is operated from the neutral position to the reverse position, the power in the reverse direction is transmitted to the left and right traveling devices 12, and the body 11 moves backward. When the main shift lever 21 is returned from the forward position or the reverse position to the neutral position, the body 11 stops. Further, the forward or backward speed can be changed by the operation amount of the main shift lever 21.

  The steering lever 22 is provided to be able to tilt left and right and back and forth. The rightward and leftward tilting operations of the steering lever 22 can switch the body 11 between straight running, left turning, and right turning. Further, the mowing device 14 can be moved up and down by tilting the steering lever 22 back and forth.

  The reaper 14 is arranged in front of the traveling device 12. The reaper 14 includes a weeding tool 23 at the front end thereof, and a cutting blade 24 behind the weeding tool 23. The weeding tool 23 and the cutting blade 24 are supported by a reaper frame 25. At the rear end of the mowing device frame 25, a cutting horizontal frame 26 extending in the left-right direction is provided. One end of the main cutting frame 27 is connected to the horizontal cutting frame 26. The reaping main frame 27 extends rearward from the reaping horizontal frame 26, and the other end (provided forward and downward, the rear end) is rotatably connected to the frame of the machine body 11. The cylinder (not shown) can be operated to swing the reaping main frame 27 by the tilting operation of the steering lever 22 in the front-rear direction, whereby the weeding tool 23 and the cutting blade 24 are grounded. From above, and a descending position in which the weeding implement 23 and the cutting blade 24 descend near the ground. When the airframe 11 advances in a state where the weeding tool 23 and the cutting blade 24 are located at the lowered position, the grain culm is planted on the field while the culm is divided by the weeding tool 23, and the grain culm is cut by the cutting blade 24. Reaped by

  The threshing device 15 and the grain tank 16 are arranged side by side at a position above the traveling device 12 and behind the reaper 14. The cut culm is conveyed to the threshing device 15 by the cutting device 14. The threshing apparatus 15 conveys the stem side of the grain stalk backward by a threshing feed chain, and supplies the spike end side of the grain stalk to a handling room for threshing. Then, the grains are transported from the threshing device 15 to the grain tank 16, and the grains are stored in the grain tank 16. A grain discharge auger 28 is connected to the grain tank 16, and the grains stored in the grain tank 16 can be discharged outside the machine by the grain discharge auger 28.

<Transmission device>
FIG. 2 is a diagram showing a partial configuration of the transmission 32 of the combine 1. In FIG. 2, the configuration from the engine 31 to the left HST 33 and the right HST 34 is shown in a skeleton diagram, and the configuration related to the left HST 33 and the right HST 34 is shown in a hydraulic circuit diagram.

  The combine 1 is equipped with an engine 31 and a transmission 32 that changes the power of the engine 31 and transmits the power to the traveling device 12.

  The transmission 32 includes a left HST (Hydro Static Transmission: hydrostatic transmission) 33 and a right HST 34.

  The left HST 33 has a closed circuit configuration in which the hydraulic pump 41 and the hydraulic motor 42 are connected by a first oil passage 43 and a second oil passage 44 so that hydraulic oil circulates between the hydraulic pump 41 and the hydraulic motor 42. have. The first oil passage 43 is connected to a first port 45 of the hydraulic pump 41 and a first port 46 of the hydraulic motor 42. The second oil passage 44 is connected to a second port 47 of the hydraulic pump 41 and a second port 48 of the hydraulic motor 42.

  The left HST 33 is provided with a charge pump 51. The charge pump 51 is a fixed displacement hydraulic pump, and discharges hydraulic oil to a charge oil passage 53 by rotation of a pump rotation shaft 52. The charge oil passage 53 is connected to the first oil passage 43 via a first check valve 54 and is connected to the second oil passage 44 via a second check valve 55. The charge oil passage 53 is connected to an oil tank 57 via a charge relief valve 56.

  By the function of the charge relief valve 56, the oil pressure in the charge oil passage 53 is maintained at a predetermined charge pressure. When the oil pressure in the first oil passage 43 becomes lower than the oil pressure in the charge oil passage 53, that is, the charge pressure, the first check valve 54 is opened, and the first oil passage 53 is connected to the first oil passage 53 via the first check valve 54. Hydraulic oil is supplied to 43. When the oil pressure in the second oil passage 44 becomes lower than the charge pressure, the second check valve 55 is opened, and hydraulic oil is supplied from the charge oil passage 53 to the second oil passage 44 via the second check valve 55. Is done. Thereby, the oil pressure of the first oil passage 43 and the second oil passage 44 is maintained at or above the charge pressure.

  The left HST 33 includes a hydraulic pump 41, a hydraulic motor 42, a first oil passage 43, a second oil passage 44, a first check valve 54, a second check valve 55, a charge relief valve 56, and the like housed in a single case. It is configured as a body type HST.

  The hydraulic pump 41 is a variable displacement swash plate type piston pump, and includes a cylinder block, a plurality of pistons radially arranged in the cylinder block, a pump swash plate on which the piston slides, and the like. The hydraulic pump 41 and the charge pump 51 have a common pump rotation shaft 52, and the cylinder block is provided so as to rotate integrally with the pump rotation shaft 52.

  An electronically controlled servo piston 58 is provided to change the inclination angle of the pump swash plate of the hydraulic pump 41. The servo piston 58 has a first pressure chamber 62 to which oil pressure is supplied from a pressure control valve 61 on the forward side, and a second pressure chamber 64 to which oil pressure is supplied from a pressure control valve 63 on the reverse side. Further, the servo piston 58 has a rod 65 that moves directly by a pressure difference between the first pressure chamber 62 and the second pressure chamber 64, and the linear movement of the rod 65 changes the inclination angle of the pump swash plate. Is done.

  As the inclination angle of the pump swash plate with respect to the axis of the pump rotation shaft 52 of the hydraulic pump 41 (the rotation axis of the cylinder block) increases, the discharge amount of hydraulic oil from the hydraulic pump 41 decreases, and the inclination angle of the pump swash plate increases by 90 degrees. °, the discharge of the hydraulic oil from the hydraulic pump 41 stops. When the inclination angle of the pump swash plate exceeds 90 ° (when the inclination is reversed), the discharge direction of the hydraulic oil from the hydraulic pump 41 is reversed when the inclination angle is less than 90 °.

  The hydraulic motor 42 is a variable displacement swash plate type piston motor, and includes a motor rotating shaft 71, a cylinder block 72 (see FIG. 3) that rotates integrally with the motor rotating shaft 71, and a plurality of radially arranged radially arranged in the cylinder block 72. And a motor swash plate 74 (see FIG. 3) against which the piston 73 is pressed. When the inclination angle of the motor swash plate 74 with respect to the axis of the motor rotation shaft 71 of the hydraulic motor 42 (the rotation axis of the cylinder block 72) is constant, the amount of hydraulic oil supplied to the hydraulic motor 42, that is, discharge from the hydraulic pump 41. The larger the amount of operating oil that is performed, the higher the rotation speed of the motor rotation shaft 71.

  When the amount of the hydraulic oil supplied to the hydraulic motor 42 is constant, the rotational speed of the motor rotation shaft 71 decreases as the inclination angle of the motor swash plate 74 increases. To change the inclination angle of the motor swash plate 74 of the hydraulic motor 42, a sub-transmission piston 75 is provided. A low-speed switching valve 76 and a high-speed switching valve 77 are connected to the sub-transmission piston 75. The low-speed switching valve 76 is turned on, the high-speed switching valve 77 is turned off, and the hydraulic pressure is supplied from the low-speed switching valve 76 to the sub-transmission piston 75, whereby the rod 78 of the sub-transmission piston 75 is positioned at the low-speed position. , The inclination angle of the motor swash plate 74 becomes relatively large. On the other hand, the low-speed switching valve 76 is turned off, the high-speed switching valve 77 is turned on, and the hydraulic pressure is supplied from the high-speed switching valve 77 to the sub-transmission piston 75, whereby the rod 78 of the sub-transmission piston 75 is moved to the high-speed position. As a result, the inclination angle of the motor swash plate 74 becomes relatively small. Therefore, by switching on / off of the low-speed switching valve 76 and the high-speed switching valve 77, a high-speed stage in which the rotation speed of the motor rotation shaft 71 is relatively large, and a low-speed stage in which the rotation speed of the motor rotation shaft 71 is relatively small. It can be switched to two stages, one stage and the other stage.

  Since the right HST 34 has the same configuration as the left HST 33, parts of the right HST 34 corresponding to the respective parts of the left HST 33 are denoted by the same reference numerals as those parts, and description thereof will be omitted.

  The power of the engine 31 is input to each of the pump rotation shafts 52 of the left HST 33 and the right HST 34. Specifically, a pulley 82 is provided on the output shaft 81 of the engine 31 so as not to rotate relatively. The transmission 32 has an input shaft 83 extending in parallel with the output shaft 81 of the engine 31. A pulley 84 is provided on the input shaft 83 so as not to rotate relatively. An endless belt 85 is wound between the pulleys 82 and 84. Further, an input gear 86 is provided on the input shaft 83 so as not to rotate relatively. The input gear 86 meshes with an intermediate gear 87, and the intermediate gear 87 meshes with a pump gear 88 provided on the pump rotation shaft 52 of the right HST 34 so as not to rotate relatively. The pump gear 88 meshes with a pump gear 89 that is provided on the pump rotation shaft 52 of the left HST 33 so as not to rotate relatively.

  Thus, the power of the engine 31 is transmitted from the output shaft 81 to the pulley 84 via the pulley 82 and the belt 85, and rotates the input shaft 83 integrally with the pulley 84. The power (rotation) of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST 34 via the intermediate gear 87, and rotates the pump rotation shaft 52 of the right HST 34 in a predetermined direction together with the pump gear 88. Let it. The power of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST 34 via the intermediate gear 87, further transmitted from the pump gear 88 to the pump gear 89, and integrated with the pump gear 89 to form the pump of the left HST 33. The rotation shaft 52 is rotated in a direction opposite to the predetermined direction. Therefore, when the inclination angles of the pump swash plates of the hydraulic pumps 41 of the left HST 33 and the right HST 34 are the same, the motor rotation shaft 71 of the hydraulic motor 42 of the left HST 33 and the motor rotation shaft 71 of the hydraulic motor 42 of the right HST 34 Rotate in opposite directions.

  FIG. 3 is a cross-sectional view showing a part of the transmission 32, and shows a configuration from the hydraulic motors 42 of the left HST 33 and the right HST 34 to the traveling device 12.

  The hydraulic motors 42 of the left HST 33 and the right HST 34 are arranged such that the motor rotation shafts 71 are arranged on the same axis (to have a common axis) and the axes are parallel to the axes of the left and right axles. They are arranged symmetrically to each other.

  In the following description, the motor rotation shaft 71 of the left HST 33 is referred to as “motor rotation shaft 71L”, and the motor rotation shaft 71 of the right HST 34 is referred to as “motor rotation shaft 71R”.

  Left and right outer ends of the motor rotation shafts 71L and 71R are rotatably supported by a unit case 101 forming an outer shell of the transmission 32 via bearings 102L and 102R, respectively. Motor output gears 103L and 103R are supported at the inner ends in the left-right direction of the motor rotation shafts 71L and 71R, respectively, so as not to rotate relatively.

  A first intermediate shaft 104 and a second intermediate shaft 105 are provided between the motor rotation shafts 71L and 71R and the axle. Each axis of the first intermediate shaft 104 and the second intermediate shaft 105 is parallel to the axes of the motor rotation shafts 71L and 71R. The first intermediate shaft 104 is non-rotatably supported by the unit case 101. The left end of the second intermediate shaft 105 is rotatably supported by the unit case 101 via a bearing 106. A cylindrical sleeve 107 is externally fitted to the right portion 105R of the second intermediate shaft 105. An inner ring of a bearing 108 is externally fitted to the sleeve 107 so as not to rotate relatively. The outer ring of the bearing 108 is fixed to the unit case 101. Thus, the second intermediate shaft 105 is rotatably held by the unit case 101.

  On the first intermediate shaft 104, a first left intermediate gear 111L and a first right intermediate gear 111R are rotatably held side by side. The left motor output gear 103L meshes with the first left intermediate gear 111L, and the right motor output gear 103R meshes with the first right intermediate gear 111R. A second left intermediate gear 112L and a second right intermediate gear 112R are fixedly held on the left and right portions 105L and 105R of the second intermediate shaft 105, respectively, side by side. The first left intermediate gear 111L meshes with the second left intermediate gear 112L, and the first right middle gear 111R meshes with the second right intermediate gear 112R.

  An annular groove 113L centering on the axis of the second intermediate shaft 105 is formed on the left side surface of the second left intermediate gear 112L. At the left end of the groove 113L, a number of internal teeth 114L protruding toward the center of rotation are formed side by side in the circumferential direction. A left shifter gear 115L is provided on the left side of the second left intermediate gear 112L. The left shifter gear 115L is held by the left portion 105L of the second intermediate shaft 105 so as to be relatively non-rotatable and moveable in the axial direction of the second intermediate shaft 105. The left shifter gear 115L has a large number of external teeth 116L on the outer peripheral surface. The outer teeth 116L are formed with a cutout portion 117 cut out over the entire circumference at a portion closer to the right side.

  On the right side surface of the second right intermediate gear 112R, an annular groove 113R centering on the axis of the second intermediate shaft 105 is formed. At the right end of the groove 113R, a number of internal teeth 114R protruding toward the rotation center are formed side by side in the circumferential direction. A right shifter gear 115R is provided on the right side of the second right intermediate gear 112R. The right shifter gear 115R is held by the sleeve 107 so as not to rotate relatively and to be movable in the axial direction of the second intermediate shaft 105. The right shifter gear 115R has a number of external teeth 116R on the outer peripheral surface.

<Neutral transmission mechanism>
4A, 4B, 4C, and 4D are cross-sectional views showing the configuration of the neutral transmission mechanism 120.

  The transmission 32 is provided with a neutral transmission mechanism 120 for generating a neutral state. The neutral speed change mechanism 120 includes a shift member including a shift fork shaft 121, a left shift fork 122L, and a right shift fork 122R.

  The shift fork shaft 121 is provided at a position separated from the second intermediate shaft 105 in a direction orthogonal to the axial direction. The shift fork shaft 121 has a center line extending in parallel with the axis of the second intermediate shaft 105, and is held by the unit case 101 so as to be movable in the center line direction.

  The left shift fork 122L is fixed to the shift fork shaft 121, and extends from the shift fork shaft 121 toward the left shifter gear 115L in a direction orthogonal to the center line of the shift fork shaft 121. On the outer peripheral surface of the left shifter gear 115L, a concave portion 123L is formed over the entire circumference. The tip of the left shift fork 122L is fitted in the recess 123L of the left shifter gear 115L with a play that allows the rotation of the left shifter gear 115L.

  The right shift fork 122R is fixed to the shift fork shaft 121, and extends from the shift fork shaft 121 toward the right shifter gear 115R in a direction orthogonal to the center line of the shift fork shaft 121. A recess 123R is formed on the entire outer peripheral surface of the right shifter gear 115R. The tip of the right shift fork 122R is fitted in the recess 123R of the right shifter gear 115R with a play that allows the right shifter gear 115R to rotate.

  At the left end of the shift fork shaft 121, an operation groove 124 extending in the circumferential direction is formed. The distal end of a cylindrical operation protrusion 126 extending from the distal end of the shift operation piece 125 toward the shift fork shaft 121 enters the operation groove 124 from the radial direction of the shift fork shaft 121. A support shaft 127 that is orthogonal to both the center line direction of the shift fork shaft 121 and the direction in which the shift operation piece 125 extends is fixedly provided at the base end of the shift operation piece 125. The support shaft 127 is rotatably supported by the unit case 101. An operation arm 128 extending in a direction perpendicular to both the axis of the support shaft 127 and the direction in which the shift operation piece 125 extends is supported by the support shaft 127 so as to be relatively non-rotatable. The length from the center of the support shaft 127 to the tip of the operation arm 128 is larger than the length from the center of the support shaft 127 to the center of the operation protrusion 126.

  Between the unit case 101 and the right shift fork 122R, a coil-shaped spring 129 fitted to the shift fork shaft 121 is interposed in a compressed state. Thus, the elastic force of the spring 129 is applied to the right shift fork 122R, and the shift fork shaft 121 is urged to the left by the elastic force.

  When the operation arm 128 is not operated, as shown in FIG. 4A, the shift fork shaft 121 is located at the left end of the movable range, and the external teeth 116L of the left shifter gear 115L are connected to the internal teeth of the second left intermediate gear 112L. The outer teeth 116R of the right shifter gear 115R mesh with the inner teeth 114R of the second right intermediate gear 112R.

  Therefore, the power (rotation) transmitted from the motor rotation shaft 71L to the second left intermediate gear 112L via the first left intermediate gear 111L is transmitted from the second left intermediate gear 112L to the left shifter gear 115L, and from the left shifter gear 115L. The transmission is transmitted to the left axle via a gear train (not shown), and the left traveling device 12 is driven. A left power transmission mechanism is configured by the first left intermediate gear 111L, the second left intermediate gear 112L, the left shifter gear 115L, and a gear train that transmits power from the left shifter gear 115L to the left axle.

  The power (rotation) transmitted from the motor rotation shaft 71R to the second right intermediate gear 112R via the first right intermediate gear 111R is transmitted from the second right intermediate gear 112R to the right shifter gear 115R, and transmitted from the right shifter gear 115R. The transmission is transmitted to the right axle via a gear train (not shown), and the right traveling device 12 is driven. A right power transmission mechanism is configured by the first right intermediate gear 111R, the second right intermediate gear 112R, the right shifter gear 115R, and a gear train that transmits power from the right shifter gear 115R to the right axle.

  When the operation arm 128 is operated to lift the tip, the shift operation piece 125 rotates around the support shaft 127 as a fulcrum with the rotation of the operation arm 128, and the shift fork shaft 121 moves rightward. When the shift fork shaft 121 is located at the right end of the movable range, as shown in FIG. 4B, the meshing between the outer teeth 116L of the left shifter gear 115L and the inner teeth 114L of the second left intermediate gear 112L is released, and the right shifter gear The engagement between the external teeth 116R of the 115R and the internal teeth 114R of the second right intermediate gear 112R is released. Therefore, power (rotation) transmitted from the motor rotation shaft 71 to the second left intermediate gear 112L via the first left intermediate gear 111L is not transmitted from the second left intermediate gear 112L to the left shifter gear 115L and the right shifter gear 115R. That is, the transmission 32 is in a neutral state in which the power from the engine 31 (the left HST 33 and the right HST 34) is not transmitted to the left and right axles.

  An arcuate locking recess 131 that is recessed upward is formed at the tip of the operation arm 128. By locking the locking concave portion 131 with the locking convex portion 132 fixedly provided on the unit case 101, the neutral state of the transmission 32 can be maintained.

  When the locking concave portion 131 is disengaged from the locking convex portion 132 and the force for lifting the tip of the operation arm 128 is released, the shift fork shaft 121 moves leftward due to the urging force (elastic force) of the spring 129. . If the external teeth 116R of the right shifter gear 115R face the tooth grooves between the internal teeth 114R of the second right intermediate gear 112R, the movement of the shift fork shaft 121 causes the external teeth 116R of the right shifter gear 115R to move to the second right intermediate gear. The second right intermediate gear 112R and the right shifter gear 115R mesh with each other into the tooth groove 112R. On the other hand, when the external teeth 116R of the right shifter gear 115R do not face the tooth grooves of the second right intermediate gear 112R, the movement of the shift fork shaft 121 causes the external teeth of the right shifter gear 115R to move as shown in FIG. 4C. 116R abuts against the internal teeth 114R of the second right intermediate gear 112R, and the right shifter gear 115R and the second right intermediate gear 112R do not mesh. At this time, a gap is generated between a portion (hereinafter, simply referred to as “external teeth 116L”) of the left teeth 115L of the left shifter gear 115L on the right side of the cutout 117 and the internal teeth 114L of the second left intermediate gear 112L. ing.

  Since the shift fork shaft 121 is urged leftward by the spring 129, the second right intermediate gear 112R rotates from the state where the external teeth 116R of the right shifter gear 115R abut the internal teeth 114R of the second right intermediate gear 112R. Then, when the external teeth 116R of the right shifter gear 115R face the tooth grooves of the second right intermediate gear 112R, as shown in FIG. 4D, the shift fork shaft 121 further moves to the left, and the external teeth of the right shifter gear 115R. 116R enters the tooth space of the second right intermediate gear 112R.

  Thereafter, if the shift fork shaft 121 further moves to the left, and the external teeth 116L of the left shifter gear 115L face the tooth grooves between the internal teeth 114L of the second left intermediate gear 112L, the external teeth 116L of the left shifter gear 115L. Enters the tooth space of the second left intermediate gear 112L, and the second left intermediate gear 112L and the left shifter gear 115L mesh with each other. On the other hand, when the external teeth 116L of the left shifter gear 115L are not opposed to the tooth grooves of the second left intermediate gear 112L, the movement of the shift fork shaft 121 causes the external teeth 116L of the left shifter gear 115L to move to the second left intermediate gear 112L. And the left shifter gear 115L does not mesh with the second left intermediate gear 112L.

  Since the shift fork shaft 121 is urged leftward by the spring 129, the second left intermediate gear 112L rotates from a state in which the outer teeth 116L of the left shifter gear 115L abut the inner teeth 114L of the second left intermediate gear 112L. Then, when the external teeth 116L of the left shifter gear 115L face the tooth grooves of the second left intermediate gear 112L, the shift fork shaft 121 moves further leftward, and the external teeth 116L of the left shifter gear 115L move to the second left intermediate gear 112L. Into the tooth space.

  Thus, the meshing between the second left intermediate gear 112L and the left shifter gear 115L and the meshing between the second right intermediate gear 112R and the right shifter gear 115R are achieved.

<Effects>
As described above, the neutral transmission mechanism 120 can switch between engagement / disengagement of the second left intermediate gear 112L and the left shifter gear 115L and engagement / disengagement of the second right intermediate gear 112R and the right shifter gear 115R, In addition, the gear mesh can be favorably achieved.

  In order to move the shift fork shaft 121, a distal end of an operation protrusion 126 extending from a distal end of the shift operation piece 125 enters an operation groove 124 formed in the shift fork shaft 121. An operation arm 128 that rotates integrally with the shift operation piece 125 is supported on a support shaft 127 that supports the shift operation piece 125. The length from the center of the support shaft 127 to the tip of the operation arm 128 is larger than the length from the center of the support shaft 127 to the center of the operation protrusion 126. Therefore, the leverage principle operates, and even if the force applied to the operation arm 128 is small, the shift fork shaft 121 can be favorably moved against the urging force of the spring 129.

  Further, the spring 129 is interposed between the unit case 101 and the right shift fork 122R. Accordingly, there is no need to separately provide a portion for connecting one end of the spring 129 to the shift fork shaft 121, and the configuration of the shift fork shaft 121 can be simplified.

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented in another form.

  For example, in the above-described embodiment, the configuration in which the shift fork shaft 121 is moved by the rotation operation of the operation arm 128 is described. However, the operation member operated to move the shift fork shaft 121 is A configuration in which the shift fork shaft 121 is moved by a linear operation along the center line may be employed.

  In addition, the combine 1 is taken up as an example of the work vehicle, but the present invention is not limited to the combine 1, but is applied to a work vehicle other than the combine 1 such as a harvester that harvests vegetables such as ginseng, radish, green soybeans, and cabbage. can do.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

12: Traveling device 32: Transmission 112L: Second left intermediate gear (transmission gear)
112R: second right intermediate gear (transmission gear)
113L, 113R: Grooves 114L, 114R: Internal teeth 115L: Left shifter gear 115R: Right shifter gear 116L, 116R: External teeth 120: Neutral transmission 121: Shift fork shaft 122L: Left shift fork 122R: Right shift fork 125: Shift operation piece 126: operation protrusion 127: support shaft 128: operation arm 129: spring (biasing member)
132: locking protrusion (locking portion)

Claims (7)

A transmission that changes the power of the drive source and transmits the power to the left and right traveling devices,
A transmission gear provided to correspond to each of the left and right traveling devices, and a shifter gear movably provided in a rotation axis direction of the transmission gear to which power is transmitted from the drive source; and the transmission gear and the shifter gear A power transmission path is formed by meshing with the power transmission path, and the shifter gear is moved in one direction in the rotation axis direction to release the meshing between the transmission gear and the shifter gear, whereby the power transmission path is cut off. Power transmission mechanism,
A shift member that is provided so as to be movable in the rotation axis direction and includes a shift fork coupled to the left and right shifter gears,
A biasing member for biasing the shift member in another direction opposite to the one direction of the rotation axis. Further comprising a unit case that houses the power transmission mechanism,
The transmission according to claim 1, wherein the shift member includes a shift fork shaft extending in the rotation axis direction, movably held in the unit case in the rotation axis direction, and supporting the left and right shift forks. One end of the shift fork shaft extends outside through the unit case,
An operation member connected to the one end of the shift fork shaft and moving the shift fork shaft in the rotation axis direction by a rotation operation with a support shaft extending in a direction orthogonal to the rotation axis direction as a fulcrum; The transmission according to claim 2. The operation member includes a shift operation piece supported by the support shaft and connected to the shift fork shaft, and an operation arm supported by the support shaft and rotating integrally with the shift operation piece,
The transmission according to claim 3, wherein a distance from the support shaft to a tip of the operation arm is greater than a distance from the support shaft to a connection portion of the shift operation piece with the shift fork shaft.   5. The transmission according to claim 4, wherein the unit case has a locking portion that locks the operation arm in a state where the transmission gear and the shifter gear are disengaged from each other. 6.   The transmission according to any one of claims 2 to 5, wherein the urging member is interposed between the unit case and one of the left and right shift forks. An annular groove centered on the rotation axis of the transmission gear is formed on a side surface of the transmission gear,
On the outer peripheral surface of the groove, a plurality of internal teeth projecting toward the rotation axis are formed side by side in the circumferential direction of the groove,
The shifter gear includes a plurality of external teeth protruding outward in a rotational radial direction, and the external teeth mesh with the transmission gear by being fitted in tooth grooves between the adjacent internal teeth of the transmission gear. The transmission according to any one of claims 1 to 6.

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