JP2012207771A - Speed change mechanism for tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed change mechanism for a tractor, which enables reduction of tool cost and setup man-hours for a gear, and reduction of manufacturing cost.SOLUTION: In the speed change mechanism for a tractor in which traveling speed change is performed by transmitting power to a forward/reverse movement speed change mechanism, a main speed change mechanism B, and an auxiliary speed change mechanism, and the main speed change mechanism B is configured such that a plurality of speed change drive gears 27, 28, 30, 31 provided on an input shaft 21 is constantly meshed with a plurality of speed change driven gears 32, 33, 34, 35 provided on an output shaft 22 to perform multi-stage traveling speed change by actuating speed change clutches 25, 26 based on operation of a main speed change lever, combinations of teeth numbers of the speed change drive gears 27, 31, 28, 30 and the driven gears 35, 32, 34, 33 as pairs of a low speed stage side and a high speed stage side of the main speed change mechanism B are made same and configured such that four gears of the low speed stage side and the high sped stage side can be manufactured by two kinds of gear cutting tools.

Description

  The present invention relates to a transmission mechanism for a tractor that performs a multi-stage traveling shift by a main transmission mechanism provided in a transmission case.

2. Description of the Related Art Conventionally, agricultural tractors are configured to perform a traveling shift by transmitting engine power to a forward / reverse transmission mechanism provided in a transmission case, a main transmission mechanism, and a sub-transmission mechanism (for example, Patent Document 1). .
The speed change mechanism of this tractor meshes a plurality of speed change drive gears provided on a speed change shaft (input shaft) and a plurality of speed change driven gears provided on an output shaft so as to form a pair. Based on the operation, by selectively selecting a shift clutch provided on the output shaft, for example, a 1st to 4th traveling shift is performed.

Japanese Patent No. 3875593

In the production of a transmission gear in a conventional tractor main transmission mechanism, the gear module, the center distance and the speed ratio are first determined, and the number of teeth of the drive gear and the driven gear is calculated thereby, so that the number of teeth does not become an integer. At times, or in order to prevent undercuts, the gears are designed to shift.
Therefore, in order to manufacture all gears because each gear has a different number of teeth and tooth type, it is necessary to prepare a dedicated gear cutting tool for each gear, and the gear cutting machine of the gear cutting tool There is a drawback that the manufacturing cost increases due to an increase in the number of setup steps such as attachment to the machine and change of the gear cutting program.

  In order to solve the problem, the present invention transmits the power from the engine 4 to the forward / reverse transmission mechanism A, the main transmission mechanism B, and the auxiliary transmission mechanism C provided in the transmission case 7 to perform a traveling shift, In the main transmission mechanism B, a plurality of transmission drive gears 27, 28, 30, 31 provided on the input shaft 21 and a plurality of transmission driven gears 32, 33, 34, 35 provided on the output shaft 22 are always meshed with each other. In the tractor speed change mechanism configured to operate the speed change clutches 25 and 26 to perform multi-speed travel speed change based on the operation of the speed change lever, the speed change is a pair of the low speed side and the high speed side of the main speed change mechanism B. Using the same number of teeth for the drive gears 27, 31, 28, 30 and the driven gears 35, 32, 34, 33, four gears for the low speed stage and the high speed stage are manufactured using two types of gear cutting tools. Configure to be able to It is characterized by that.

  According to the first aspect of the present invention, a plurality of speed change drive gears provided on the input shaft and a plurality of speed change driven gears provided on the output shaft are always meshed, and a multi-stage traveling speed change is performed by the speed change clutch. In the speed change mechanism, the combination of the number of teeth of the speed change drive gear and the driven gear paired at the low speed stage side and the high speed stage side is made the same, and the four gears on the low speed stage side and the high speed stage side by two kinds of gear cutting tools The gear can be manufactured by reducing the number of expensive gear cutting tools by half. In addition, it is possible to reduce the manufacturing cost by reducing the time and effort for mounting the gear cutting tool on the gear cutting machine and the change of the gear cutting program.

It is a side view of a tractor. It is an expanded view of a transmission. It is sectional drawing which shows the structure of a main transmission mechanism.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an agricultural tractor. This tractor 1 has a traveling machine body 3 having a front wheel 2 and a rear wheel 2a. A steering unit 6 including 6a, a seat 6b, and the like is disposed, and a connecting unit for mounting a work machine such as a tillage device is provided at the rear of the machine body. As a result, the tractor 1 grounds the work implement to the field while traveling and performs the field work and the like. The control unit 6 includes a forward / reverse shift lever that shifts a forward / reverse shift mechanism A, which will be described later, a main shift lever that shifts the main shift mechanism B, a sub shift lever that shifts the first sub shift mechanism C, and a second sub shift lever. A sub-shift lever for shifting the speed change mechanism D, a PTO speed change lever for shifting the PTO speed change mechanism E, and the like are provided, and a clutch pedal for turning on and off the main clutch 10 is provided below the steering handle 6a. .

  As shown in FIG. 2, the transmission case 7 constituting the traveling machine body 3 has a front portion coupled to the engine 4, and includes a main clutch 8, a forward / reverse transmission mechanism A, a main transmission mechanism B, and a first auxiliary transmission mechanism C. The second auxiliary transmission mechanism D, the PTO transmission mechanism E, the front wheel transmission device F, and the rear wheel differential device G are housed.

  Next, each transmission mechanism will be described with reference to FIG. First, in the transmission case 7, a main shaft 10 (transmission shaft) integrally formed with a drive gear 9 is supported. The main shaft 10 is connected to a main clutch 8 of a dry single plate clutch type, and the main clutch 8 is turned on and off by operation of a clutch pedal disposed on the foot side of the control unit 6. The power of the engine 4 is transmitted to the forward / reverse transmission mechanism A via the main clutch 8 and the main shaft 10, and is transmitted to the PTO transmission mechanism E via the joint and the PTO transmission shaft 12.

  The forward / reverse transmission mechanism A includes an input shaft 13, a forward / reverse shaft 14, and a back shaft 14b. An input gear 15 that meshes with the drive gear 9, a forward drive gear 16 and a reverse drive gear 17 that are arranged at the front and rear are fixed to the input shaft 13. A forward driven gear 18 that meshes with the forward drive gear 16 and a reverse driven gear 19 that meshes with the reverse drive gear 17 via the back gear 14a are supported on the free-running shaft 14 and are hydraulically operated between the two gears. The multi-plate type forward / reverse clutch 20 is provided.

  As a result, when the forward clutch 20a of the forward / reverse clutch 20 is engaged and operated based on the operation of the forward / reverse shift lever, the forward / reverse shaft 14 rotates forward (forward rotation) to enter the forward shift state. Further, when the reverse clutch 20b is engaged and operated, the forward / reverse shaft 14 is reversely rotated (reversely rotated) to enter the reverse shift state.

Next, the main transmission mechanism B will be described with reference to FIGS. The main transmission mechanism B includes an input shaft 21 and an output shaft 22 that are hollow shafts each having a spline formed at each connection end.
The input shaft 21 is spline-connected to the forward / rearward movement shaft 14 to transmit power. Further, the output shaft 22 outputs to the auxiliary transmission input shaft 23 of the first auxiliary transmission mechanism C that is splined to the rear end, and performs four-speed transmission from the first speed to the fourth speed. That is, the input shaft 21 is provided with a synchromesh type 1/2 speed transmission clutch 25 and a 3/4 speed transmission clutch 26. A first-speed shift drive gear 27 and a second-speed shift drive gear 28 are rotatably supported on the front side, and a third-speed shift drive gear on the rear side and front side of the third- and fourth-speed shift clutch 26. 30 and a 4-speed transmission gear 31 are supported rotatably.

  On the other hand, the output shaft 22 is engaged with the 1st, 2nd, 3rd and 4th speed shift drive gears 27, 28, 30 and 31, and the 1st, 2nd, 3rd and 4th speed shift driven gears 32, 33, 34 and 35 are fixed by spline fitting. Thus, in the main transmission mechanism B, when the main transmission lever is operated to the first speed position along the transmission guide groove, the first and second speed transmission clutch 25 is shifted backward via the transmission drive gear 27 and the transmission driven gear 32. The power is transmitted to the output shaft 22, and the first speed is changed.

  When the main speed change lever is operated to the 2nd speed position, the 1st and 2nd speed shift clutch 25 shifts forward to transmit power to the output shaft 22 via the speed change drive gear 28 and the speed change driven gear 33, thereby shifting to the 2nd speed shift state. Become. Similarly, when the main speed change lever is operated to the 3rd speed or 4th speed position, the 3rd and 4th speed shift clutch 26 is shifted forward and the output shaft via the 3rd speed or 4th speed driven gears 34 and 35. The power can be transmitted to 22 to obtain a 3rd speed or 4th speed shift state.

In the above-described configuration, the main transmission mechanism B has 23, 27, 31, and 35 teeth of the transmission drive gears 27, 28, 30, and 31 provided on the input shaft 21, respectively. The number of teeth of the variable speed driven gears 32, 33, 34, and 35 provided on the output shaft 22 is set to 35, 31, 27, and 23, respectively. As a result, the main transmission mechanism B performs a four-speed shift according to the gear ratio of the gears that are always meshed in pairs.
That is, the main speed change mechanism B has the same number of teeth on the speed change drive gear 27 and the speed change driven gear 35 at the first speed and the fourth speed for the gears provided on the input shaft 21 and the output shaft 22, and the speed change drive gear 31. The number of teeth of the speed change driven gear 32 is the same. In the second speed and the third speed, the number of teeth of the speed change drive gear 28 and the speed change driven gear 34 is the same, and the number of teeth of the speed change drive gear 30 and the speed change driven gear 33 is the same. Thereby, the main transmission mechanism B can reduce the manufacturing cost, as will be described later.

Next, the first auxiliary transmission mechanism C will be described. The first sub-transmission mechanism C is a sub-transmission output shaft (spline-connected to the sub-transmission input shaft 23 connected to the output shaft 22 and the second sub-transmission input shaft 36 of the second sub-transmission mechanism D to the rear end). (Speed change driven shaft) 37 is provided, and the power output from the main speed change mechanism B is shifted in two stages, high speed and low speed, and is output to the second auxiliary speed change mechanism D.
That is, the auxiliary transmission input shaft 23 has a low-speed drive gear 38 and a high-speed drive gear 39 fixed in the front-rear direction. The auxiliary transmission output shaft 37 supports a low-speed driven gear 40 and a high-speed driven gear 41 that are always meshed with the low-speed driving gear 38 and the high-speed driving gear 39 in the front and rear directions so as to freely rotate. A double cone synchromesh type sub-transmission clutch 42 is interposed between 41.

  Thus, when the first sub-transmission mechanism C is operated to move the sub-transmission lever to the low speed position, the sleeve of the sub-transmission clutch 42 moves forward, and the rotation of the low-speed driven gear 40 is transmitted to the sub-transmission output shaft 37 to enter the low-speed sub transmission state. Become. Further, when the auxiliary transmission lever is operated to the high speed position, the sleeve of the auxiliary transmission clutch 42 moves backward to transmit the rotation of the high speed driven gear 41 to the auxiliary transmission output shaft 37 and to enter the high speed auxiliary transmission state.

Next, the second auxiliary transmission mechanism D will be described. The second auxiliary transmission mechanism D includes a second auxiliary transmission input shaft 36 and a pinion shaft 43 that outputs to the rear wheel differential gear G, and a counter shaft 45 below the second auxiliary transmission input shaft 36. The rotation of the two sub-transmission input shaft 36 is subjected to three-stage sub-shifts of high speed, medium speed, and low speed, and is output from the pinion shaft 43 to the rear wheel differential device G and the front wheel transmission device F.
That is, the second auxiliary transmission input shaft 36 has a low-speed drive gear 46, a medium-speed drive gear 47, and a high-speed drive gear 48 fixed from the front side to the rear side, and the medium-speed drive gear 47 and the high-speed drive gear. A high-speed drive counter gear composed of a small-diameter gear 49 and a large-diameter gear 50 is pivotally supported between the small-diameter gear 49 and the large-diameter gear 50.

  A front wheel drive gear 52 that is output to the front wheel transmission device F is fixed on the front side of the pinion shaft 43, and a low speed driven gear 53 that is always meshed with the low speed drive gear 46 is supported on the rear side so as to be freely rotatable, and the gears are changed. A second auxiliary transmission clutch gear comprising a low / medium speed driven gear 54 having a shifter portion and a high speed driven gear 55 is spline-fitted so as to be slidable in the axial direction. When the low / medium speed driven gear 54 and the high speed driven gear 55 move from the neutral position shown in the drawing to the front side, the low / medium speed driven gear 54 meshes with the medium speed drive gear 47 to become a working speed, and when the gear moves further to the front side, the low speed becomes low. The medium-speed driven gear 54 engages with the internal teeth formed on the side surface of the low-speed driven gear 53 and becomes ultra-low speed. Further, when moving from the neutral position to the rear side, the high-speed driven gear 55 meshes with the large-diameter gear 50 of the high-speed drive counter gear, and the road running speed is reached. The counter large-diameter gear 56 meshed with the small-diameter gear 49 and the counter small-diameter gear 57 meshed with the high-speed drive gear 48 are pivotally supported on the counter shaft 45 in an integrally formed state. .

  Thus, when the second auxiliary transmission mechanism D is operated to move the second auxiliary transmission lever to the low speed position, the low / medium speed driven gear 54 of the second auxiliary transmission clutch gear engages with the internal teeth of the low speed driven gear 53 and the pinion shaft 43 is rotated at a very low speed. When the second sub-shift lever is operated to the medium speed position, the low / medium speed driven gear 54 is engaged with the medium speed drive gear 47 to rotate the pinion shaft 43 at the working speed. Further, when the second auxiliary transmission lever is operated to the high speed position, the high speed driven gear 55 is engaged with the large diameter gear 50 of the high speed drive counter gear, and the pinion shaft 43 is rotated at the road traveling speed. In other words, the second subtransmission mechanism D can shift the power shifted in eight stages by the main transmission mechanism B and the first subtransmission mechanism C into three stages of ultra-low speed, working speed, and road traveling speed. Output from the shaft 43 to the rear wheel differential G and the front wheel transmission F.

Next, the front wheel transmission device F will be described. The front wheel transmission device F includes a front wheel drive input shaft 60 and a front wheel output shaft 61, and transmits power from the front wheel output shaft 61 to a differential device of the front wheels 2 via a transmission shaft (not shown).
The front wheel drive input shaft 60 is fixedly provided with a standard drive gear 62, a front wheel input gear 63 and a front wheel speed increasing drive gear 64, which mesh with the front wheel drive gear 52. The front wheel output shaft 61 has a standard driven gear 65 and a speed increasing driven gear 66 rotatably supported on the front and rear, and a hydraulic multi-plate type front wheel standard clutch 67 and a front wheel speed increasing clutch 68 are provided between both gears. Yes.

  Accordingly, in the front wheel transmission device F, the front wheel input gear 63 meshing with the front wheel drive gear 52 rotates the front wheel drive input shaft 60, and the standard drive gear 62 and the front wheel speed increasing drive gear 64 are replaced by the standard driven gear 65 and the front wheel, respectively. The speed increasing driven gear 66 is driven to rotate. When the front wheel standard clutch 67 is engaged and operated, the standard driven gear 65 and the front wheel output shaft 61 are connected, and the front wheel 2 is driven at substantially the same speed as the rear wheel 2a. When the front wheel acceleration clutch 68 is engaged and operated, the front wheel acceleration driven gear 66 and the front wheel output shaft 61 are connected, and the front wheel 2 is driven at a speed approximately twice that of the rear wheel 2a. That is, the front wheel transmission F is in a two-wheel drive state with only the rear wheel 2a when the front wheel standard clutch 67 and the front wheel acceleration clutch 68 are both disconnected, and is in a standard four-wheel drive state when the front wheel standard clutch 67 is engaged. When the front wheel acceleration clutch 68 is engaged, the front wheel acceleration state is established.

  Next, the PTO transmission mechanism E will be described. The PTO speed change mechanism E includes a PTO input shaft 70 connected to the PTO transmission shaft 12, and includes a reverse rotation shaft 71 on the upper side of the PTO input shaft 70 and a PTO shaft 72 on the lower side. A high speed drive gear 73, a reverse drive gear 75, and a medium speed drive gear 76 are fixed to the PTO input shaft 70 from the front side, and a low speed drive gear 77 is integrally formed on the rear side. A reverse gear 78 that meshes with the reverse drive gear 75 is rotatably supported on the reverse shaft 71.

  The PTO shaft 72 has a high-speed reverse transmission gear 79 that is spline-fitted movably in the front-rear direction from a neutral position so as to selectively engage the high-speed drive gear 73 and the reverse drive gear 75 from the front side, and a medium-speed drive A medium-speed transmission gear 80 that is always meshed with the gear 76 and a low-speed transmission gear 81 that is always meshed with the low-speed drive gear 77 are pivotally supported, and a medium-speed and low-speed clutch 82 is pivotally supported therebetween. .

  Thus, the PTO transmission mechanism E outputs high speed rotation to the PTO shaft 72 when the high speed reverse transmission gear 79 is shifted forward and meshed with the high speed drive gear 73 based on the operation of the PTO transmission lever. When the high-speed reverse transmission gear 79 is shifted backward and meshed with the reverse rotation gear 78, reverse rotation is output to the PTO shaft 72. When the sleeve of the medium-speed low-speed clutch 82 is engaged with the medium-speed transmission gear 80, medium-speed rotation is output to the PTO shaft 72. Further, when the sleeve of the medium-speed low-speed clutch 82 meshes with the low-speed transmission gear 81, low-speed rotation is output to the PTO shaft 72. Therefore, the PTO speed change mechanism E can obtain a shift state of the third forward speed and the first reverse speed.

  The tractor 1 configured as described above can perform a traveling shift required for each type of work by the forward / reverse shift lever, the main shift lever, the sub shift lever, and the second sub shift lever. That is, when plowing work or the like is performed on the field, the operator positions the second auxiliary transmission lever on the low speed side in advance and shifts the second auxiliary transmission mechanism D to the low speed state. In addition, when traveling on the road or the like, the second auxiliary transmission mechanism D is shifted to a high speed state.

Then, the required speed is selected from the first to fourth speeds by operating the main speed change lever, the first subtransmission mechanism C is selected to be high speed or low speed, and the forward / reverse speed change lever is moved from the neutral position to the forward position. When operated, the fuselage is a multi-stage shift combining a four-speed shift by the main transmission mechanism B, a two-speed shift by the first sub-transmission mechanism C, and a three-speed shift by the second sub-transmission mechanism D. The vehicle can travel forward under any one speed change state. Further, when the forward / reverse shift lever is operated from the neutral position to the reverse position, the reverse travel can be performed at a speed substantially equal to the forward travel up to that point.
Further, the front wheel transmission device F can select two-wheel drive or four-wheel drive, and the small turn can be performed by increasing the speed of the front wheel 2 relative to the rear wheel 2a when the vehicle is turning.

  The main transmission mechanism B by the tractor 1 has 23, 27, 31, and 35 teeth of the transmission drive gears 27, 28, 30, and 31 of the input shaft 21 and the output shaft 22. The number of teeth of the transmission driven gears 32, 33, 34, and 35 is 35, 31, 27, and 23, respectively, and the opposing gears are always meshed. Further, in the first speed (low speed stage) and the fourth speed (high speed stage), the transmission drive gear 27 and the transmission driven gear 35 have the same number of teeth of 23, and the transmission driving gear 31 and the transmission driven gear 32 include 35 sheets. In the second speed (low speed stage) and the third speed (high speed stage), the transmission drive gear 28 and the transmission driven gear 34 have the same number of teeth, and the transmission driving gear 30 and the transmission driven gear 33. And the same number of teeth of 31 sheets. Thereby, the main transmission mechanism B has the following characteristics.

  That is, the speed change drive gears 27, 28, 30, and 31 that are mounted on the input shaft 21 and the speed change driven gears 32, 33, 34, and 35 that are mounted on the output shaft 22 perform speed change between the low speed stage and the high speed stage. The combination of the number of teeth of the low-speed gear and the high-speed gear that are meshed in pairs is made the same. In addition, since each of the two gears in the low speed stage and the high speed stage has the same number of teeth and shift coefficient as the module, two types of tooth surface finishing tools such as a gear cutting tool and a shaving cutter are shared. Gears can be made.

  Therefore, the main speed change mechanism B can halve the types of expensive gear cutting tools and can manufacture gears, and can reduce the time and effort required to install the gear cutting tools on the gear cutting machine, or change the gear cutting program. Reduction can be achieved and the manufacturing cost can be reduced. Further, since gears having the same tooth shape and diameter are increased, there is a feature that the types of columnar steel materials (materials) for manufacturing gears can be reduced.

  In the main transmission mechanism B of the embodiment, all the gears that perform the four-speed traveling shift from the first speed to the fourth speed have the same combination of the number of teeth of the low-speed gear and the high-speed gear. The combination of the number of teeth may be the same for only the fourth speed or the second speed and the third speed, or the main transmission mechanism B may change to a four-speed shift and perform a multi-speed traveling shift such as a sixth speed. . Further, the gear shift coefficient is not necessarily the same as long as it can be manufactured with the same gear cutting tool.

DESCRIPTION OF SYMBOLS 1 Tractor 4 Engine 7 Transmission case 21 Input shaft 23 Subtransmission input shaft 25,26 Shift clutch 27,28,30,31 Shift drive gear 32,33,34,35 Shift driven gear A Forward / reverse transmission mechanism B Main transmission mechanism C First subtransmission mechanism

Claims (1)

  The power from the engine (4) is transmitted to the forward / reverse transmission mechanism (A), the main transmission mechanism (B), and the auxiliary transmission mechanism (C) provided in the transmission case (7) to perform the traveling shift, The transmission mechanism (B) includes a plurality of transmission drive gears (27), (28), (30), (31) provided on the input shaft (21), and a plurality of transmission driven gears (provided on the output shaft (22)). 32), (33), (34), (35) are always meshed, and based on the operation of the main speed change lever, the speed change clutches (25), (26) are operated to perform multi-stage running speed change. In the transmission mechanism of the tractor, the transmission drive gears (27), (31), (28), (30) and the driven gear (35) which are a pair of the low speed stage side and the high speed stage side of the main transmission mechanism (B). , (32), (34), (33) A speed change mechanism for a tractor, characterized in that four gears on a low speed side and a high speed side can be manufactured by a tool.

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