JP2013032809A - Transmission of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission of a working vehicle in which a shift operation device for turning a trunnion shaft is arranged around the trunnion shaft which is formed by protruding from a side of a transmission case.SOLUTION: A spring for neutral return which is attached to a cam follower is configured with a spiral spring. A hydraulic actuator 45 is arranged on the side of the transmission case 12 below the trunnion shaft and the cam follower with the expansion and contraction direction thereof as the cross direction.

Description

  The present invention relates to a transmission for a work vehicle including a hydrostatic continuously variable transmission, and more particularly to a shift operation device for a hydrostatic continuously variable transmission.

  In general, a work vehicle such as a tractor has a transmission equipped with HSТ (hydrostatic continuously variable transmission). HSТ is provided with a trunnion shaft, and it is known that gear shifting by HST is performed by rotating the trunnion shaft.

  Conventionally, a shift operation device that rotates a trunnion shaft has been devised (for example, see Patent Document 1). The speed change operation device includes a trunnion arm connected to the trunnion shaft, a cam follower engaged with the trunnion arm, and a hydraulic actuator.

  A tension spring is attached to the cam follower, and this tension spring is arranged side by side with the hydraulic cylinder of the hydraulic actuator. Since the hydraulic actuator is arranged to be offset from the transmission case to the side by the amount of the tension spring, the speed change operation device is enlarged by the offset space.

  The speed change operation device is connected to the end of the trunnion shaft protruding from the side of the transmission case, but the bulging portion containing the main clutch is provided in the transmission case in front of the trunnion shaft, A rear axle case that extends from the mission case to the left and right is provided. In addition, the floor of the control unit is provided above the trunnion shaft, the height is restricted by the minimum ground height below, and a brake rod or the like is arranged on the side of the transmission case. Thus, since many other devices and members are provided around the trunnion shaft, the space for arranging the speed change operation device is limited.

JP 2010-76646 A

  If the speed change device itself is large, there is a possibility that it cannot be placed around the trunnion shaft.In such a case, the placement position of another device or member is changed, or the speed change device is placed away from the trunnion shaft. In the case of changing the arrangement, it takes time, and when the speed change operation device is arranged away from the trunnion shaft, the relay link for connecting the speed change operation device and the trunnion shaft has a complicated configuration. turn into.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission for a work vehicle that solves the above-described problems by making the shift operation device compact by using a spiral spring as a neutral return spring attached to a cam follower.

The present invention relates to a hydraulic actuator (45) in which a trunnion shaft (29) of a hydrostatic continuously variable transmission (21) protruding from the side of a mission case (12) is disposed on the side of the mission case (12). ) To change the speed of the hydrostatic continuously variable transmission (21). In the transmission (23) of the work vehicle (1),
A trunnion arm (42) connected to the trunnion shaft (29) and having a cam (42a) at the tip;
A neutral return spring (46) for urging the cam follower (43) engaged with the cam (42a) so that the trunnion shaft (29) returns to the neutral position;
A relay link (47) connecting the trunnion arm (29) and the hydraulic actuator (45);
The neutral return spring (46) is a spiral spring, and the hydraulic actuator (45) is arranged in the mission case (with the expansion / contraction direction in the front-rear direction below the neutral return spring (46) and the cam follower (43). 12) It is arranged on the side.

For example, referring to FIG. 3, the hydraulic actuator (45) is fixed to a mounting base (44) fixed to the mission case (12).
A valve assembly (41) for controlling the hydraulic actuator (45) is mounted on the mounting base (44) on the opposite side to the transmission case (12) of the hydraulic actuator (45).

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on description of a claim by this.

  According to the first aspect of the present invention, the neutral return spring is constituted by a spiral spring, and the hydraulic actuator is disposed below the trunnion arm and the cam follower and on the side of the transmission case with the expansion / contraction direction as the front-rear direction. Can be arranged with the amount of offset from the transmission case to the side suppressed, the speed change operation device can be made compact, and it can be arranged on the side of the transmission case without interfering with other members and devices. Can do.

  According to the second aspect of the present invention, since the valve assembly is disposed on the opposite side of the transmission case and on the side of the hydraulic cylinder, the speed change device can be made compact, and other members and devices It can be placed on the side of the mission case without interference. In addition, since the hose connecting the valve assembly and the hydraulic actuator can be shortened, the hydraulic pressure loss can be suppressed and the response of the hydraulic actuator can be improved.

The side view of the tractor which is a work vehicle. (A) is a development view of the transmission, (b) is a diagram showing an ultra-low speed transmission mechanism. The perspective view of a mission case. It is a figure which shows a mission case, Comprising: (a) is a top view, (b) is a side view. It is a figure which shows the speed change operation apparatus, Comprising: (a) is a perspective view from a front, (b) is a perspective view from a back surface. It is a figure which shows the speed change operation apparatus of an advance state, Comprising: (a) is a top view, (b) is a side view, (c) is a side view of the state which removed the valve assembly. It is a figure which shows the transmission operation apparatus of a neutral state, Comprising: (a) is a top view, (b) is a side view, (c) is a side view of the state which removed the valve assembly. It is a figure which shows the speed change operation apparatus of a reverse drive, Comprising: (a) is a top view, (b) is a side view, (c) is a side view of the state which removed the valve assembly. The block diagram of a control part. The hydraulic circuit diagram of a tractor.

  Hereinafter, embodiments of a tractor that is an example of a work vehicle including a transmission according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the tractor 1 has a traveling machine body 5 supported by the front wheels 2 and the rear wheels 3, and an engine (not shown) is mounted in front of the traveling machine body 5 by being covered with a bonnet 6. Has been. A transmission case 12 (see FIGS. 2 and 3) is disposed below the engine toward the rear of the machine body, and a driving operation unit 11 is disposed behind the bonnet 6. The driving operation unit 11 includes an operation panel 7, a steering handle 9, a driver seat 10, and the like.

  As shown in FIGS. 2 and 3, the outer shape of the transmission case (hereinafter simply referred to as a mission case) 12 is formed in a vertically long substantially rectangular parallelepiped. As shown in FIG. 2, a clutch housing 13 in which a main clutch 19 is accommodated is formed in front of the mission case, and an HSТ case 15 in which an HST 21 is accommodated is adjacent to the clutch housing 13. A center case 16 in which a gear transmission 22 and a PTO drive shaft 24 are housed is formed next to the HSТ case 15, and a PTO transmission 25 and a center case 16 are formed next to the center case 16. A rear case 17 in which the PTO shaft 26 is accommodated is formed.

  The transmission 23 of the tractor 1 includes an HST 21 and a gear transmission 22, and the gear transmission 22 is arranged side by side with the input shaft 30 and the input shaft 30 as shown in FIG. 2. A pinion shaft 32 and a front wheel drive shaft 31 are provided. The input shaft 30, the pinion shaft 32, and the front wheel drive shaft 31 are each provided with a transmission gear (gear) that changes the speed of rotation. The gear transmission 22 can change the rotation to a high speed or a low speed, and when the ultra-low speed transmission mechanism 35 is provided in the gear transmission 22 as shown in FIG. . In the high speed transmission, an external tooth 36a provided on an intermediate gear 36 rotatably attached to the input shaft 30 and an external tooth 37a provided on a driven gear 37 slidably connected to the pinion shaft 32 by a spline. In meshing and low speed shifting, the external teeth 36b provided on the intermediate gear 36 and the external teeth 37b provided on the driven gear 37 are meshed, and in super low speed shifting, the input shaft 30 is slidable in the axial direction. The external teeth 34a of the spline-coupled transmission gear 34 and the ultra-low speed gear 38 provided in the ultra-low speed transmission mechanism 35 mesh with each other, and the external teeth 37b and external teeth 36c provided on the driven gear 37 mesh with each other. Thus, the speed is changed.

  As shown in FIGS. 3 and 4, a trunnion shaft 29 protrudes from the mission case 12 at the approximate center on the side of the mission case 12, and the trunnion shaft 29 rotates around the trunnion shaft 29. A moving speed change operation device 39 is provided.

  As shown in FIGS. 4 and 5, the speed change operating device 39 is disposed on a mounting base 44 made of a metal plate having a substantially rectangular shape in plan view and having one end fixed to the transmission case 12. And a valve assembly 41 including a plurality of valves.

  The main body 40 has a trunnion arm 42 connected to one end of the trunnion shaft 29 as shown in FIGS. 5 to 8, and the outer shape of the trunnion arm 42 is substantially as shown in FIG. It is formed in a T shape, and a cam 42a is formed at one end. An engaging portion 43b provided at the tip of the cam follower 43 is engaged with the cam 42a, and a spiral spring as a neutral return spring 46 is attached to the shaft portion 43a of the cam follower.

  A hydraulic actuator 45 is disposed below the cam follower 43. The hydraulic actuator 45 includes a hydraulic cylinder 45a and a piston rod 45b. As shown in FIG. 6, the hydraulic actuator 45 is arranged on the side of the transmission case 12 with the expansion / contraction direction of the piston rod 45b in the front / rear direction in a state where the hydraulic cylinder 45a overlaps the trunnion arm 42 and the cam follower 43 in plan view. Has been. The piston rod 45 b of the hydraulic actuator is connected to the trunnion arm 42 via a relay link 47. The relay link 47 has a plate 47b pivotally supported on a shaft 51. One end of the plate 47b is connected to the rod 47a, and the other end is connected to the piston rod 45b. Abuts against the stopper 50 to restrict the rotation range of the relay link. A trunnion angle sensor 49 is connected to the trunnion arm 42 through a rod 48.

  The valve assembly 41 has a valve case 58 in which a relief valve, two pilot check valves (not shown) and the like are accommodated, and a solenoid valve (electromagnetic valve) 54. It arrange | positions at the side of the cylinder 45a. Connected to the valve case 58 are hoses 52 and 53 for supplying hydraulic pressure, a drain rod 55 for returning the oil in the valve assembly 41 into the transmission case 12, and an arrangement 56 from the priority valve 57.

  As shown in FIG. 9, the control unit 60 that controls the operation of the speed change operation device 39 includes a microcomputer 60 (hereinafter simply referred to as a microcomputer). A switch 62, a main clutch switch 63, a shift lever sensor 65, and a trunnion angle sensor 49 are connected. On the output side of the microcomputer 60, a microcomputer fuse 67, a buzzer 69, a solenoid valve (extension) 70, Various switches of a solenoid valve (contraction) 71 are connected. Signals of various switches connected to the input side are input to the microcomputer 60, and based on these signals, signals are output from the microcomputer 60 to the solenoid valves 70, 71 and the like.

  Next, the operation of the speed change operation device 39 will be described. When the driver operates the speed change lever, various switches connected to the input side of the microcomputer 60 detect the operation, a signal is input to the microcomputer 60, and the microcomputer 60 outputs a signal based on this signal. Based on the signal, oil is supplied from the valve assembly 41 to the hydraulic cylinder 45a, and the piston rod 45b of the hydraulic actuator expands and contracts by the inflow of oil into the hydraulic cylinder 45a.

  When the piston rod 45b expands and contracts (see FIGS. 6 and 8), the trunnion arm 42 and the trunnion shaft 29 rotate, and the angle of a swash plate (not shown) in the HSТ 21 changes in conjunction with the rotation. The forward and reverse shifts are performed by HSТ21, and this shift rotation is input to the gear transmission 22 for gear shift. When the trunnion arm 42 rotates, the cam follower 43 engaged with the cam 42a of the trunnion arm also rotates downward about the shaft portion 43a of the cam follower. At this time, the urging force that returns the trunnion shaft 29 to the neutral position by the spiral spring 46 acts on the cam 42a. Further, as the trunnion arm 42 rotates, the inclination angle of the arm 49a of the trunnion angle sensor 49 changes, and the rotation angle of the trunnion shaft 29 is detected by this change. Then, feedback control is performed to operate the speed change operation device 39 so that the trunnion shaft 29 becomes a rotation angle suitable for the speed change operation from this rotation angle.

  As shown in FIG. 10, the hydraulic pressure for operating the speed change operation device 39 is divided by the priority valve 57 and supplied to the hydraulic cylinder 45a of the hydraulic actuator via the valve assembly 41, while the power steering device is supplied from the priority valve 57. Further, the hydraulic pressure divided from the hydraulic pressure is supplied to a steering assist device 75 such as an auto brake turn or a front wheel double speed.

  As described above, the neutral return spring 46 is formed of a spiral spring, and the hydraulic actuator 45 is disposed below the trunnion arm 42 and the cam follower 43 and on the side of the transmission case 12 with the expansion / contraction direction as the front-rear direction. The actuator 45 can be arranged with the offset amount to the side from the mission case 12 being suppressed, the transmission operation device 39 can be configured compactly, and the mission case 12 side without interfering with other members and devices. Can be arranged in the direction.

  Further, since the valve assembly 41 is arranged on the opposite side of the transmission case 12 and on the side of the hydraulic cylinder 45a, the speed change operation device 39 can be made compact and can interfere with other members and devices. And can be arranged on the side of the mission case 12. In addition, since the hoses 52 and 53 connecting the valve assembly 41 and the hydraulic actuator 45 can be shortened, it is possible to increase the responsiveness of the hydraulic actuator by suppressing the hydraulic pressure loss.

  Further, since the hydraulic actuator 45 is arranged along the side of the mission case 12 with the expansion / contraction direction as the front-rear direction, the force acting on the mounting base 44 that supports the speed change operation device 39 can be suppressed.

  Further, since the drain is directly returned from the valve assembly 41 to the transmission case 12, it is sufficient to arrange one high-pressure arrangement from the priority valve 57 to the valve assembly 41, and the arrangement of the arrangement can be facilitated.

  In the present embodiment, the tractor 1 has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied to transmissions such as other agricultural work vehicles and construction work vehicles.

1 Work vehicle (tractor)
12 Mission case 21 Hydrostatic continuously variable transmission (HST)
23 Transmission 29 Trunnion shaft 41 Valve assembly 42 Trunnion arm 42a Cam 43 Cam follower 44 Mounting base 45 Hydraulic actuator 46 Neutral return spring (spiral spring)
47 Relay link

Claims (2)

The trunnion shaft of the hydrostatic continuously variable transmission protruding from the side of the mission case is operated by a hydraulic actuator disposed on the side of the mission case, and the hydrostatic continuously variable transmission is shifted. In a work vehicle transmission,
A trunnion arm connected to the trunnion shaft and having a cam at the tip;
A neutral return spring that biases the cam follower engaged with the cam so that the trunnion shaft returns to a neutral position;
A relay link that connects the trunnion arm and the hydraulic actuator,
The neutral return spring is a spiral spring, and the hydraulic actuator is disposed on the side of the transmission case with the expansion / contraction direction in the front-rear direction below the neutral return spring and the cam follower.
A transmission for a work vehicle. The hydraulic actuator is fixed to a mounting base fixed to the mission case;
A valve assembly for controlling the hydraulic actuator is mounted on the mounting base on the opposite side to the transmission case of the hydraulic actuator;
The transmission for a work vehicle according to claim 1.

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