JP2010169187A - Transmission for tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission for a tractor, operating for speed change a single shift fork acting on the first transmission and the second transmission by a single speed change operation tool. <P>SOLUTION: This transmission for the tractor includes the speed changing shift fork 50 provided with: the first engaging recessed part 50a fit around the first shift sleeve S6, in the first shift fork part 50A for operating for speed change a super deceleration mechanism 16; and the second engaging recessed part 50b fit around the second shift sleeve S7, in the second shift fork part 50B for operating for speed change an overdrive mechanism 45. A common leg portion 50e engaged with the first shift sleeve S6 and the second shift sleeve S7 is formed in an intermediate position between the first engaging recessed part 50a and the second engaging recessed part 50b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a transmission for a tractor including an operation tool for performing a shift operation on a first transmission and a second transmission.

As the transmission, a first reduction gear, a super reduction mechanism that performs a gear change with a larger reduction ratio than the main transmission mechanism, and a second transmission, an overdrive mechanism that increases the power from the previous stage, are provided. The structure which operates with one shift operation tool was taken (refer patent document 1).
In the above configuration, since the two transmissions can be operated with a single transmission operation tool, the operation structure can be simplified as compared with the operation structure operated with the two transmission operation tools.

However, a single shift operation tool is arranged between the shift fork for the first transmission and the shift fork for the second transmission, and the operation path of the shift operation tool is set higher and lower than the first transmission. The first shift path to be shifted in parallel with the second shift path for shifting the second transmission device to the height is arranged in parallel, and is orthogonal to these first and second shift paths. The shift operation tool is temporarily moved in the direction to select the first shift path and the second shift path.
Then, the structure for selectively engaging the shift operating tool with respect to the two shift forks becomes complicated, and the shift operation is performed in the orthogonal direction in order to select the first shift path and the second shift path. The tool had to be operated once, and the operation was complicated.

Therefore, as a means for simplifying the operation structure of the speed change operation tool, a first shift fork portion (publication number: 122) for operating a creep transmission device (super deceleration mechanism) (publication number: 43) as a first transmission device. ) And a second shift fork portion (publication number: 123) for operating a secondary transmission (subtransmission mechanism) (publication number: 42) as a second transmission device is integrally formed. There is a thing of the structure which takes the form which operates this with a single transmission operation tool (gazette number: 125) (refer patent document 2).

JP 2001-130281 A (paragraph numbers [0038] to [0041] and FIG. 13) JP-A-2006-234010 (paragraph numbers [0038] to [0042] and FIGS. 6 and 12)

In the configuration of Patent Document 2, the second shift fork portion for sub-shifting (publication number: 123) is engaged with a sub-shifting shift sleeve (publication number: 104) as a second operated member. It has two engaging recesses and both leg portions located at the peripheral edge of the second engaging recess, and extends a leg base end portion in which both leg portions are converged to a narrow width, and a sub-shift on the leg base end portion. A shift hole is provided by providing a support hole as a support part for slidably supporting the second shift fork part for use, and externally fitting the support hole to a support shaft (name in publication: fourth shift rod 124). A fork is attached to the support shaft. On the other hand, the first shift fork portion forms a first engagement recessed portion and both leg portions located at the peripheral edge portion of the first engagement recessed portion, and the both leg portions are converged without converging the both leg portions. Is integrally connected to the lateral side surface of the leg base end of the second shift fork.

Considering the above points, when considering the invention described in Patent Document 2, a support portion serving as an operating force application position in a shift fork for shifting, in which the first shift fork portion and the second shift fork portion are combined. Is provided at the base end of the leg in which both legs of the second shift fork are converged (for example, on an extended line extending in a direction orthogonal to the assumed virtual line assuming a virtual line connecting the two legs). Although there is no position where both legs of the first shift fork are converged, the direction orthogonal to or substantially perpendicular to the imaginary line connecting the centers of the first engagement recess and the second engagement recess It is in a position deviated from the extended line extending in the direction.

For this purpose, the distance from the support portion serving as the operating force application position to the center position of the first engagement recess portion in the first shift fork portion, and the center of the second engagement recess portion in the second shift fork portion from the support portion. Since the distance to the position is greatly different, the driving movement force when driving the shift fork for shifting is hardly applied to both shift forks, and the eccentric force is applied to the shift shift fork. There was a risk of lack of smoothness in movement.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tractor travel transmission capable of smoothly shifting a single shift fork acting on a first transmission and a second transmission with a single transmission operation tool.

〔Constitution〕
According to a first aspect of the present invention, there is provided a shift fork for shifting in which a first shift fork portion for shifting the first transmission and a second shift fork portion for shifting the second transmission are integrally formed. The first shift fork is provided with a first engagement recess for engaging the first operated member of the first transmission, and the second operated fork of the second transmission is provided in the second shift fork. A second engagement recess portion that engages the first engagement member and the second engagement recess portion at an intermediate position between the first engagement recess portion and the second engagement recess portion. Forming a common leg portion to be joined, and extending the common leg portion in a direction perpendicular to or substantially perpendicular to a virtual line connecting the centers of the first engagement recessed portion and the second engagement recessed portion. The base end of the leg is formed to be supported by the support shaft of the shift fork for shifting. That the support portion is in the point that is formed on the Ashimoto end, the effects thereof are as follows.

[Action]
In the present invention having the two shift forks 50A and 50B, the first engaging recess 50a surrounded by both the legs 50c and 50e in the first shift fork 50A and the both legs in the second shift fork 50B. The center positions a and b of the second engaging recess 50b surrounded by 50d and 50e are respectively extended on an extension line extending in a direction orthogonal or substantially orthogonal from a bisecting position of a virtual line z that can be connected. When the support portion 50f is disposed, the operating force applied to the support portion 50f is transmitted to the first shift fork portion 50A and the second shift fork portion 50B substantially equally, so that the first shift fork portion 50A and the second shift fork portion 50B This is based on the viewpoint that the shift fork portion 50B operates smoothly (see FIG. 5).

Therefore, in the present invention, as shown in FIG. 5, the support portion 50f of the shift fork 50 connects the centers a and b of the first engagement recess 50a and the second engagement recess 50b. Since it is formed in the leg base end portion 50g extending in a direction orthogonal to or substantially orthogonal to the imaginary line z, the distance between the support portion 50f and the first engagement recess 50a, the support portion 50f and the first The interval between the two engaging recessed portions 50b is not greatly different, and the shift fork 50 for shifting can exert substantially the same operation driving force on the first and second operated members S6 and S7 without causing kinks. .
Therefore, an appropriate operation stroke is given to the first shift fork portion 50A and the second shift fork portion 50B, and a smooth speed change operation is performed.

〔effect〕
It is possible to provide a transmission structure for a tractor capable of performing a reliable and smooth operation while driving a single shift fork with a single shift operation tool to shift two transmissions simultaneously. It was.

(Constitution)
According to a second aspect of the invention, in the first aspect of the invention, the first or second operated member is supported on an input shaft of an output differential mechanism, and the shift fork for shifting is disposed above the input shaft. The shift shift fork is arranged near the side wall of the transmission case, the shift operation tool provided in the operation unit is linked to the linkage operation unit, and the shift shift fork is connected to the shift operation tool. The operation and effect are as follows.

(Function and effect)
In addition to the operational effects of the first aspect of the invention, the following operational effects can be achieved.
In other words, the shift shift fork is connected to the transmission case while the shift fork for shifting is arranged near the output differential mechanism and the installation interval between the shift operation fork provided in the driving unit is minimized. The transmission operation mechanism can be configured by arranging the transmission operation tool and the linking operation unit in the vicinity of the side wall of the, and shortening the mechanism as simple as possible.

It is a whole side view showing a tractor. It is a block diagram which shows a transmission system. It is a schematic block diagram which shows a transmission system. FIG. 3 is a hydraulic circuit diagram for shift control. It is a front view which shows the linkage state of the speed change operating tool and speed change shift fork which carry out speed change operation of a super deceleration mechanism and an overdrive mechanism. It is a perspective view which shows the shift fork for a speed change operation of a super deceleration mechanism and an overdrive mechanism. It is a vertical side view which shows a super deceleration mechanism and an overdrive mechanism. It is a side view which shows a transmission lever part. It is a rear view which shows a transmission lever part. It is a top view which shows the lever guide part for transmission. It is a perspective view which shows the base of a subtransmission lever. It is a perspective view which shows the state before attachment of the forward / reverse switching lever provided integrally with a detection sensor. It is a block diagram which shows the state provided with the detection sensor with respect to the shift rod operated with the forward / reverse switching lever and the forward / backward switching lever without the detection sensor. FIG. 6 is a side view showing a state before the lever shaft of the PTO speed change lever and the linkage shaft of the PTO speed change mechanism are linked together. It is a side view which shows the linkage coupling state of the lever shaft of the PTO transmission lever and the linkage shaft of the PTO transmission mechanism. (A) A longitudinal front view showing a configuration of a detent mechanism that acts on a shift rod operated by a PTO shift lever; (b) a state in which the PTO shift lever is urged from the operation position to the original reference position by the detent mechanism. FIG. It is a vertical side view which shows the structure of the shift rod operated with the shift lever for PTO.

  FIG. 1 shows an entire side surface of the tractor, and FIG. 2 shows a block diagram showing an outline of a transmission system. The tractor in this example is configured such that a rotary cultivator K is connected to a rear portion of a tractor main body 2 provided with an operation cabin 75 that covers the operation unit 1 so that the rotary cultivator K can be driven up and down by an external lift cylinder 3 to perform riding cultivation work. The output of the engine 4 mounted on the front of the fuselage is transmitted to the transmission case 6 via the main clutch 5, where it is branched into a traveling system and a PTO system. After the speed change, the rear wheel 7 as the main propulsion wheel and the front wheel 8 as the steering wheel are driven. The power of the branched PTO system is also appropriately shifted and then transmitted to the rotary tiller K via the PTO shaft 9 at the rear of the machine body.

  FIG. 3 shows an outline of the transmission built in the mission case 6. The engine output transmitted to the mission case 6 via the main clutch 5 is branched into the traveling system and the PTO system via the counter shaft 10. The traveling system includes a main transmission mechanism 11 that performs a four-speed shift, a multi-plate shift hydraulic clutch 12, a forward / reverse switching mechanism 13, a high / low transmission mechanism 14 that performs a two-speed shift with a small transmission ratio, and a large transmission ratio. A sub-transmission mechanism 15 that performs two-step shift in high and low and a super deceleration mechanism 16 are arranged in series, and an overdrive mechanism 45 is arranged in parallel with the sub transmission mechanism 15 and the super deceleration mechanism 16. Has been.

  The power shifted by each speed change mechanism is transmitted to the rear wheel 7 via the rear differential mechanism 17 and is also transmitted to the front wheel 8 via the transmission shaft 18 and the front differential mechanism 19. Further, the PTO system is provided with a PTO transmission mechanism 20 that shifts the power branched by the counter shaft 10 to three forward rotations and one reverse rotation and transmits it to the PTO shaft 9.

[PTO shift lever]
A linkage structure between the PTO transmission lever 73 and the PTO transmission mechanism 20 will be described. As shown in FIGS. 14 and 15, the PTO speed change is performed by the lever shaft 73A of the PTO speed change lever 73 and the linkage shaft 74 that receives the operation of the lever shaft 73A and transmits it to the shift rod (not shown) of the PTO speed change mechanism 20. An operation linkage mechanism is configured.

  A linkage boss 73a is provided at the lower end position of the lever shaft 73A, and a linkage rod 74a is formed at the upper end position of the linkage shaft 74. The lever shaft 73A is provided in the operation cabin 75 and is attached to an operation guide panel (not shown). The linkage shaft 74 is attached to the transmission case 6 and, as shown in FIG. The shaft 73A and the linkage shaft 74 are in a separated state.

  As shown in FIG. 15, when the operating cabin 75 is attached at a predetermined position, the linkage boss 73a of the lever shaft 73A is engaged with the linkage rod 74a of the linkage shaft 74, and both are linked. Then, the plate-like bracket 76 that prevents the lever shaft 73A from being shaken is bolted to the outer surface of the transmission case 6, thereby establishing the linkage between the lever shaft 73A and the linkage shaft 74.

  As shown in FIGS. 14 and 15, the linkage shaft 74 is linked by a shift rod 77 and a coupling 77 </ b> A supported in a bearing portion 6 </ b> C projecting to the side of the mission case 6. As shown in FIG. 16, in the bearing portion 6C, the shift rod 77 is provided with a shift fork 78 for PTO, and the three shifters 80A, 80B, 80C are rotated by rotating the shift rod 77 around the axis. The shift operation can be performed by selecting and engaging the gears to select the shift position and sliding the shift rod 77 in the axial direction.

  Although not shown, the PTO gear shift pattern is a five-speed gear that allows forward and reverse rotation, and the forward rotation first is centered on the transmission path between the second forward rotation and the fourth forward rotation. A speed change path between the first speed and the third forward speed is provided on one of the left and right sides, and a speed change path for reverse rotation is provided on the other side of the left and right sides. It is necessary to bias the position so as to return to the speed change path.

In other words, if the state is kept engaged with the second shifter 80B located in the center among the three shifters 80A, 80B, 80C, the shift path between the forward second speed and the forward fourth speed is selected. When the first shifter 80A located on the left or right side is selected, the speed change path between the first forward rotation and the third forward speed is selected, and when the third shifter 80C located on the other side is selected, the reverse rotation The position shift path is selected.
Therefore, as shown in FIGS. 16 and 17, a detent mechanism 79 is provided at the shift fork 78 mounting portion of the shift rod 77, and the PTO speed change lever 73 is moved along the speed change path between the forward rotation second speed and the forward rotation fourth speed. It is configured to return.

  As shown in FIGS. 16 and 17, an engagement groove 78a along the shift rod 77 is provided in the proximal boss 78A of the shift fork 78, and a detent ball 79a is accommodated in the engagement groove 78a. . A spring 79b that presses and urges the ball 79a is provided in the bearing portion 6C, and the ball 79a and the spring 79b constitute a detent mechanism 79.

  As shown in FIGS. 16 (a) and 16 (b), in order to switch from the speed change path connecting the normal rotation first speed and the normal rotation third speed to the speed change path connecting the normal rotation second speed and the normal rotation fourth speed, Even when the shift rod 77 is rotated around the axis, the shift rod 77 is returned to the speed change path connecting the second forward speed and the fourth forward speed by the biasing force of the spring 79b. .

[Main transmission mechanism]
As shown in FIG. 3, the main speed change mechanism 11 is configured to shift the two shift sleeves S1, S2 alternatively to perform a four-speed shift. With the shift sleeve S2 kept neutral, the shift sleeve S1 is shifted backward to obtain the first speed, and the shift sleeve S1 is shifted forward to obtain the second speed, while the shift sleeve S1 is kept neutral. The third speed can be obtained by shifting the shift sleeve S2 rearward, and the fourth speed can be obtained by shifting the shift sleeve S2 forward. The shift sleeves S1 and S2 are shifted by hydraulic cylinders C1 and C2 that also function as sequence valves.

  The hydraulic cylinders C1 and C2 for operating the main transmission mechanism 11, the hydraulic cylinder C5 for operating the auxiliary transmission mechanism 15, the hydraulic cylinder C4 for operating the high / low transmission mechanism 14, and the hydraulic control circuit for the transmission hydraulic clutch 12 are illustrated. 4. In FIG. 4, P is a hydraulic pump, V1 to V7 are electromagnetic unloading valves, V8 is an electromagnetic proportional control valve, V9 is a pilot unloading valve, and 30 is swung back and forth on the left side of the driver's seat 28. A shift lever 31 movably provided is a potentiometer for detecting the operation position of the shift lever 30, and is connected to the control device 32 together with the electromagnetic unload valves V 1 to V 6 and the electromagnetic proportional control valve V 7.

  As shown in FIGS. 8 to 10, the transmission lever 30 protrudes from a guide groove 35 of a lever guide 34 fixed to the inside of the left rear wheel fender 33, and the last end of the operation stroke is set to the neutral N. As well as being set, 12 forward forward speeds and 8 reverse speed positions are set.

A support bracket 36 made of sheet metal is fixed inside the rear wheel fender 33, and a lever fulcrum member 38 is fixed to a support shaft 37 that is rotatably mounted on the support bracket 36, and a shift lever is fixed to the lever fulcrum member 38. The base end of 30 is pivotally connected via a front / rear fulcrum x perpendicular to the support shaft 37 so as to be able to swing left and right. As shown in FIG. 8, a potentiometer 31 is attached to a support side 36a connected to the support bracket 36. The operation shaft 31a and the support shaft 37 are concentrically connected to each other, and the shift lever 30 is moved back and forth. The moving position can be detected by the potentiometer 31.
The transmission lever 30 is always urged to swing to the left by a torsion spring 39 provided at its left and right swing fulcrum x so that it is guided and moved along the left edge of the guide groove 35 formed in a step shape. It has become.

  Further, the support bracket 36 is provided with a sector-shaped positioning plate portion 36b as viewed from the side in an upright manner. On the outer peripheral edge of the positioning plate portion 36b, a positioning concave portion 41 corresponding to the neutral and 12-speed shift positions is formed, and the lever fulcrum member 38 can be swung up and down around the fulcrum y and downward by a spring 42. The detent arm 43 that is urged to swing is attached, and the roller 44 provided in the detent arm 43 is elastically engaged with the positioning recess 41 on the outer peripheral edge of the positioning plate portion 36b, so that the speed change lever 30 is neutralized. It is configured so that it can be stably held at the 12-speed shift position.

[Forward / reverse switching mechanism]
The forward / reverse switching mechanism 13 can move forward by shifting the shift sleeve S3 forward and reverse by shifting backward. The forward / reverse switching mechanism 13 is provided with a forward / reverse switching lever 22 provided on the left side of the steering handle 21. A shift sleeve S3 is linked.
When the forward / reverse switching mechanism 13 is switched forward, the power of the output side transmission shaft 23 of the transmission hydraulic clutch 12 is transmitted to the high / low speed transmission mechanism 14 via the intermediate idle shaft 24. The power changed by the high / low speed change mechanism 14 is transmitted to the subtransmission mechanism 15 via the speed change shaft 25. When the forward / reverse switching mechanism 13 is switched to reverse, the power of the output transmission shaft 23 is directly transmitted to the transmission shaft 25 without passing through the high / low transmission mechanism 14.

An operation structure for operating the forward / reverse switching mechanism 13 will be described. As shown in FIGS. 12 and 13, two types of forward / reverse switching operation structures will be described. Here, first, a detection sensor 60 is provided near the forward / reverse switching lever 22, and an electronically controlled forward / reverse switching operation for switching forward / backward by switching the hydraulic clutch by hydraulic control based on the detection result of the detection sensor 60. Structure and a mechanical forward / reverse switching operation structure (manually switching a shift fork and the like to perform a shifting operation by operating a forward / reverse switching operation tool (feeding control is performed by providing a detection sensor 71 near the shift rod 73) ) Will be described at a low cost.
As the electronically controlled forward / reverse switching operation structure, a structure using a hydraulic cylinder C4 that also serves as a sequence valve described later may be employed.

First, the electronically controlled forward / reverse switching operation structure in which the detection sensor 60 is provided near the forward / reverse switching lever 22 will be described.
As shown in FIG. 12, a mounting frame 61 is provided on the handle post, a semicircular arc-shaped recessed portion 61A is formed at the distal end portion of the mounting frame 61, and an operation shaft 62 is disposed inside the recessed portion 61A.

  The operation shaft 62 is attached to a mounting frame 63, and the mounting frame 63 is folded into a channel shape and an upper frame portion 63A and a lower frame portion 63B that is bent in an angle from the upper frame portion 63A to the lateral side. It consists of. An operation shaft 62 is rotatably supported by the upper frame portion 63A, and the operation shaft 62 is protruded vertically through the upper frame portion 63A, and a forward / reverse switching lever is provided on the upper square shaft portion 62A of the operation shaft 62 protruding upward. 22 is detachably attached.

  A rotating plate 64 is attached and fixed to the lower end portion protruding from the lower end of the upper frame portion 63A, and an engagement hole 64a for a detent mechanism is formed in the peripheral portion of the rotating plate 64. A drive pin 64b extends on the lower surface of the rotating plate 64, and is configured to transmit the amount of rotation to a detection sensor 60 described later.

  On the other hand, a detection sensor 60 is attached to the lower frame portion 63B, and a passive rotating plate 65 is attached to an upward detection shaft 60A of the detection sensor 60 so as to be integrally rotatable. The passive rotation plate 65 is provided with an engagement long hole 65a along the longitudinal direction of the passive rotation plate 65, and a drive pin 64b extending from the rotation plate 64 is engaged with the engagement long hole 65a. .

  In order to attach the mounting frame 63 configured as described above to the mounting frame 61, mounting holes 61a are formed in the left and right leg portions 61B sandwiching the recessed portion 61A of the mounting frame 61, and the mounting holes 61a and the upper frame portion are formed. A mounting hole 63a formed in the left and right projecting portion 63C of 63A is connected with a bolt to adopt a detachable configuration.

  Next, a mechanical forward / reverse switching operation structure will be described. First, it is necessary to remove the mounting frame 63 from the mounting frame 61. The forward / reverse switching lever 22 is removed from the operation shaft 62, the above-mentioned bolts are disconnected, and the mounting frame 63 is removed from the mounting frame 61.

  As shown in FIG. 13, what is replaced with the attachment frame 61 is a plate frame 68 having a universal join 67, and attachment holes 68 a are formed in the left and right projecting portions 68 </ b> A of the plate frame 68. The universal join 67 has an operation shaft 62 extending therethrough, and an upper square shaft portion 62A for attaching the forward / reverse switching lever 22 is formed in a portion of the operation shaft 62 protruding above the universal joint 67.

  As described above, by attaching the plate-like frame 68 to which the operation shaft 62 is attached to the attachment frame 61 through bolts, it is possible to replace the plate-like frame 68 with the structure of the operation shaft 62 that is not equipped with the detection sensor 60. .

  As shown in FIG. 13, when the forward / reverse switching lever 22 is not provided with the detection sensor 60, the detection sensor 71 is provided for the shift rod 66 operated by receiving a driving force from the operation shaft 62. The detection sensor structure will be described. As shown in FIG. 13, a shift rod 66 is slidably supported on a support wall 6A in the mission case 6 and one end thereof is linked to the operation shaft 62 described above.

Three non-contact type detection sensors 71 are embedded and fixed on the support wall 6A, and three annular grooves 66A formed on the surface of the shift rod 66 can be detected. As the detection sensor 71, a capacitance type, an optical type, a proximity sensor type, or the like can be adopted.
In this way, by adopting a configuration in which the detection sensor 71 is directly applied to the shift rod 66, it is necessary to adjust the limit sensor based on the manufacturing error of the lever as compared with the configuration in which the position of the forward / reverse switching lever 22 is detected by the limit sensor. In addition, it is possible to improve the assembly workability and the reliability.

[High and low speed change mechanism]
The high / low speed change mechanism 14 obtains a low speed “Lo” by shifting the shift sleeve S4 forward, and obtains a high speed “Hi” by shifting the shift sleeve S4 forward. It is set to be smaller than the transmission ratio between the respective speed stages in the transmission mechanism 11. The shift sleeve S4 is shifted by a hydraulic cylinder C4 that also serves as a sequence valve.

[Sub-transmission mechanism]
The auxiliary transmission mechanism 15 obtains a low speed “L” by shifting the shift sleeve S5 forward, and obtains a high speed “H” by shifting backward. The transmission ratio in the transmission mechanism 11 is set to be larger than the transmission ratio between the gears. The shift sleeve S5 is shifted by a hydraulic cylinder C5 that also serves as a sequence valve.

A link structure between the auxiliary transmission lever 53 and the transmission operation shaft 54 will be described. As shown in FIG. 11, the auxiliary transmission lever 53 is supported on the differential lock operation shaft 55, the passive arm 56 is attached to the transmission operation shaft 54 extended from the transmission case 6, and the auxiliary transmission lever 53 and the passive arm 56 are connected. The link rod 57 is linked, and the sub-shift lever 53 is linked so that the shift operation shaft 54 can be operated.
An angle sensor 58 that detects the rotation angle of the speed change operation shaft 54 is attached to the boss portion 54A that supports the speed change operation shaft 54, and detects the operation position of the sub speed change lever 53. As the angle sensor 58, a potentiometer or a rotary encoder can be used.

As described above, since the auxiliary speed change lever 53 and the speed change operation shaft 54 are linked via the link mechanism, it is not necessary to change the operation angle of the speed change operation shaft 54 beyond the difference for each model. That is, the length of the auxiliary transmission lever 53 differs between the small model and the large model. Then, if the amount of movement in the operation direction is the same, the rotation angle of the speed change operation shaft 54 tends to be smaller for larger models, and the shift of the subtransmission mechanism 15 that performs the speed change operation by the rotation angle of the speed change operation shaft 54 is shifted. The amount is not enough.
Therefore, correction can be performed by changing the connecting portion of the linkage rod 57 and the passive arm 56 in the longitudinal direction of the passive arm 57.
Such a structure is not limited to the structure of the auxiliary transmission lever 53 but may be applied to the main transmission lever and other transmission levers.

[Super deceleration mechanism and overdrive mechanism]
The configurations of the super deceleration mechanism 16 as the first transmission and the overdrive mechanism 45 as the second transmission will be described. As shown in FIG. 3, an overdrive mechanism 45 is provided between the rear end portion of the transmission shaft 25 of the auxiliary transmission mechanism 15 and the final transmission shaft 26 output to the rear differential mechanism 17. At a position parallel to the overdrive mechanism 45, the super speed reduction mechanism 16 is provided across the final speed change shaft 26 and the speed reduction shaft 27 installed in parallel to the final speed change shaft 26.

  As shown in FIGS. 3 and 7, a large-diameter output gear 45A of the overdrive mechanism 45 is loosely fitted to the rear end portion of the transmission shaft 25 via a needle bearing, and faces the front of the large-diameter output gear 45A. A long boss portion 45 a extending in a straight manner is directly fitted to the transmission shaft 25.

  A large-diameter clutch portion 25A of the transmission shaft 25 is formed on the front end side of the long boss portion 45a. The long-diameter clutch portion 25A of the transmission shaft 25 and the long-diameter output gear 45A of the overdrive mechanism 45 are long. A spline structure is formed on the outer peripheral surface with the boss portion 45a. A shift sleeve S7 (an example of a second operated member) is fitted on the spline portion so as to be slidable and integrally rotatable across the large-diameter clutch portion 25A and the long boss portion 45a.

On the other hand, on the final transmission shaft 26, a composite gear in which a large-diameter input gear 15B and a small-diameter output gear 15C of the sub-transmission mechanism 15 and a small-diameter output gear 16B of the super speed reduction mechanism 16 are integrally formed is idled via a needle bearing. Has been transferred. A clutch boss portion 15D that is idle-supported on the final transmission shaft 26 extends further to the rear end side than the small-diameter output gear 15C of the auxiliary transmission mechanism 15.
A clutch sleeve 52 is splined to the final transmission shaft 26 on the rear end side of the clutch boss portion 15D, and sliding movement in the axial direction of the final transmission shaft 26 is restricted by a shaft retaining ring. .

  On the rear end side of the clutch sleeve 52, the large-diameter gear 16 </ b> A of the super speed reduction mechanism 16 is idled and supported on the final transmission shaft 26, and the clutch boss portion 16 a extends toward the clutch sleeve 52.

  Three of them are supported by the final transmission shaft 26 and are supported by the clutch boss 15D of the small-diameter output gear 15C of the auxiliary transmission mechanism 15, the clutch sleeve 52, and the clutch boss 16a of the large-diameter gear 16A of the super-deceleration mechanism 16. A spline structure is formed on each outer peripheral surface. A shift sleeve S6 (an example of a first operated member) is externally fitted to the spline portion, and is configured to be slidable and integrally rotatable across the clutch boss portion 15D, the clutch sleeve 52, and the clutch boss portion 16a. It is.

  The super-deceleration shift sleeve S6 and the overdrive shift sleeve S7 are operated by a single shift fork 50 described later. The super-deceleration shift sleeve S6 and the overdrive shift sleeve S7 are simultaneously shifted forward and positioned at the position (a) shown in FIG. Thus, the overdrive shift sleeve S7 is engaged with the large-diameter clutch portion 25A of the transmission shaft 25 (in this case, the super-deceleration shift sleeve S6 is engaged with the clutch boss portion 15D loosely fitted to the final transmission shaft 26. And is operated to a position where it does not receive power transmission from the deceleration shaft 27). As a result, an “overdrive-on state” and an “super-deceleration cut-off state” are brought about.

  Next, the shift sleeve S6 for super deceleration and the shift sleeve S7 for overdrive are simultaneously shifted slightly rearward to be positioned at the position (b) shown in FIG. As a result, the overdrive shift sleeve S7 is separated from the large-diameter clutch portion 25A of the auxiliary transmission mechanism 15, and at the same time, the state where the shift sleeve S7 is engaged with the clutch boss portion 15D loosely fitted to the final transmission shaft 26 is maintained. 26 is engaged with a clutch sleeve 52 which is spline-fitted to the clutch 26. As a result, an “overdrive cut-off state” and an “ultra-deceleration cut-off state” are brought about, and the low output “L” and the high speed “H” output from the auxiliary transmission mechanism 15 are transmitted to the final output shaft 26 as the travel output. The

  The super-deceleration shift sleeve S6 and the overdrive shift sleeve S7 are simultaneously and further rearwardly shifted to the position (c) shown in FIG. Thus, while maintaining the state where the overdrive shift sleeve S7 is separated from the large-diameter clutch portion 25A of the auxiliary transmission mechanism 15, the super-deceleration shift sleeve S6 is connected to the clutch boss portion 16a of the large-diameter gear 16A for deceleration. And the clutch sleeve 52 that is spline-fitted to the final transmission shaft 26. As a result, the “overdrive cut-off state” is maintained, and the output from the sub-transmission mechanism 15 is converted into power bypassing the speed reduction shaft 27 and transmitted to the final speed change shaft 26, and the “super deceleration on state” appears. Is done.

  Next, the shift fork 50 for operating the shift sleeve S6 and the shift sleeve S7 will be described. As shown in FIGS. 5 and 6, the transmission shaft 25 and the final transmission shaft 26 are arranged in parallel vertically, and the shift sleeve S6 is arranged on the transmission shaft 25 and the shift sleeve S7 is arranged on the final transmission shaft 26.

  The shift fork 50 for shifting is integrally formed with a first shift fork portion 50A for shifting the super deceleration mechanism 16 and a second shift fork portion 50B for shifting the overdrive mechanism 45. The first shift fork 50A is provided with a first engagement recess 50a that engages with the shift sleeve S6, and the second shift fork 50B is provided with a second engagement recess 50b that engages with the shift sleeve S7.

  A leg portion 50c that forms a semi-arc-shaped edge of the first engagement recess 50a and a leg portion 50d that forms a semi-arc-shaped edge of the second engagement recess 50b are formed. Of the leg portions 50c and 50d, a portion located between the first engagement recess 50a and the second engagement recess 50b is formed between the first engagement recess 50a and the second engagement recess 50b. It is formed in a common leg portion 50e that is also used as an edge.

  The common leg portion 50e is extended in a direction perpendicular or substantially perpendicular to a virtual line z connecting the center a of the first engagement recess 50a and the center b of the second engagement recess 50b. A base end portion 50g is formed. A support portion 50f that supports the shift fork 50 for speed change movement is formed on the leg base end portion 50g. The support portion 50f is externally fitted to a shift operation support shaft 51, and the shift shift fork 50 can be operated by a shift operation tool 29 described later.

  As described above, since the support portion 50f that receives the operation force is provided at the leg base end portion 50g, the operation force received by the support portion 50f is applied to the first shift fork portion 50A and the second shift fork portion 50B substantially equally. Thus, the shift fork 50 for shifting can be operated without causing stagnation or the like.

A shift fork 50 for shifting is disposed above the final transmission shaft 26 (an example of an input shaft), and a linkage operation unit 50D provided at the base end of the shift fork 50 for shifting is disposed near the side wall of the transmission case 6. is there.
As shown in FIGS. 1 and 5, in the vicinity of the driver's seat 28 of the driving unit 1, the speed change operation tool 29 is provided at the outer projecting end portion of the rotary operation shaft 84 arranged in the state of penetrating the lateral side of the mission case 6. Is attached. A drive arm 85 that drives and operates the shift fork 50 for shifting is attached to the projecting end portion of the rotation operation shaft 84 so as to be integrally rotated.

On the other hand, the support shaft 51 of the shift shift fork 50 is disposed along the vicinity of the side wall of the transmission case 6 and is shown in FIG. As described above, a recessed portion is formed, and the recessed portion is configured as a linkage operation portion 50D in which the tip end portion of the drive arm 85 is engaged and linked. As described above, the front end portion of the drive arm 85 is linked to the linkage operation portion 50D of the shift shift fork 50, and the shift shift fork 50 can be operated by the shift operation tool 29.
As described above, since a configuration in which the gearbox is directly operated by the speed change operation tool 29 is adopted, the operation structure is simpler than that in which a link mechanism is interposed between the speed change operation tool 29 and the speed change shift fork 50.

  Next, a shift position restricting mechanism is provided between the shift sleeve S6, the shift sleeve S7, and the spline structure that supports them slidably so that the shift position of the shift fork 50 is not easily changed. It is configured. This shift position restricting structure will be described.

  Although not shown, outer peripheral surfaces of the large-diameter clutch portion 25A of the transmission shaft 25, the clutch boss portion 15D of the small-diameter output gear 15C of the auxiliary transmission mechanism 15, and the clutch boss portion 16a of the large-diameter gear 16A of the super reduction gear mechanism 16 are illustrated. As for the structure of the spline part provided in the large-diameter clutch part 25A of the transmission shaft 25, the spline tooth part of the shift sleeves S6 and S7 enters the space between the mating spline tooth parts and is difficult to come off. The distance between adjacent tooth portions of the clutch boss portion 15D of the small-diameter output gear 15C of the mechanism 15 and the clutch boss portion 16a of the large-diameter gear 16A of the super reduction gear mechanism 16 is configured to be narrower as it is closer to the rear side. The spline teeth of the shift sleeves S6 and S7 are configured to be tightened from the lateral side.

  On the other hand, as the structure of the spline part formed on the outer peripheral surface of the clutch sleeve 52 located in the middle, the tooth height of the tooth part of the spline part is set to a different height along the axial direction, and the clutch Compared to the case where the contact between the spline tooth portions of the sleeve 52 and the shift sleeves S6 and S7 is configured to be partial along the axial direction, and the tooth portion contacts the entire length in the axial direction. On the other hand, the structure that can increase the resistance is adopted.

[Another embodiment]
The present invention can also be implemented in the following forms.
(1) In the above embodiment, the super-deceleration mechanism 16 as the first transmission device and the overdrive mechanism 45 as the second transmission device have been selected and described. However, the main transmission mechanism 11, the auxiliary transmission mechanism 15, and The structure of the shift fork 50 described above may be applied to the high / low speed change mechanism 14 or the like.
(2) The first operated member S6 and the second operated member S7 may be not only the shift sleeve but also a shift gear itself shifted by a shift fork.

  The present invention describes a traveling speed change structure that uses a hydraulic device as an actuator in a tractor, but it can be applied to a traveling speed change device that is operated by an artificial operating tool that does not use an actuator, or an electric cylinder or the like as an actuator. You may apply to the used traveling transmission structure. Furthermore, the present invention may be applied to PTO speed change.

1 Driving part 16 Super deceleration mechanism (first transmission)
17 Output differential mechanism 26 Final transmission shaft (input shaft)
29 Shifting operation tool 45 Overdrive mechanism 50 Shifting shift fork 50A First shift fork part 50B Second shift fork part 50D Linking operation part 50a First engagement recess part 50b Second engagement recess part 50e Common leg part 50f Support 50g Leg base end 51 Support shaft S6 Shift sleeve (first operated member)
S7 Shift sleeve (second operated member)
z virtual line

Claims (2)

A shift fork for shifting, in which a first shift fork for shifting the first transmission and a second shift fork for shifting the second transmission is integrally formed, is provided, and the first shift fork is provided with the first shift fork. A first engagement recess for engaging with a first operated member of the transmission is provided, and a second engagement recess for engaging with a second operated member of the second transmission is provided in the second shift fork. A common leg portion that engages with the first operated member and the second operated member is formed at an intermediate position between the first engaging recessed portion and the second engaging recessed portion; The leg portion extends in a direction orthogonal to or substantially orthogonal to a virtual line connecting the centers of the first engagement recess and the second engagement recess to form a leg base end, A support portion supported by a support shaft in the shift fork for shifting is formed at the base end portion of the leg. And Aru transmission of the tractor. The first or second operated member is supported on the input shaft of the output differential mechanism, the shift fork for shifting is disposed above the input shaft, and the linkage operating portion of the shift fork for shifting is near the side wall of the transmission case The tractor shift according to claim 1, wherein the shift shift fork can be operated by the shift operation tool by linking the shift operation tool provided in the driving section and the linkage operation section. apparatus.

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