JPH0880754A - Transmission structure for tractor - Google Patents

Abstract

PURPOSE: To facilitate the assembling of a transmission structure and make it compact by providing an auxiliary transmission at the rear section in the front housing of a tractor and a main transmission in a transmission case. CONSTITUTION: A bearing frame 4 fixedly installed near the rear end in a front housing 1 is supported on a housing, and the drive shaft 12 of a main transmission 14 and the front end section of a speed change shaft 13 are supported on the bearing frame 4. The speed change is transmitted to a rotation output member 10 from a driving shaft 7 supported on a partition wall 1a at the middle in the front housing 1, the rotation output member 10 is coupled and supported on the front end section of the drive shaft 12, the rear end section of a counter shaft 11 supported on the partition wall 1a at the front end section is supported on the speed change shaft 13, and they are supported on the bearing frame 4 via the drive shaft 12 and speed change shaft 13 respectively in an auxiliary transmission 9. A circular hole section 4c temporarily holding the rotation output member 10 is preferably provided on the bearing frame 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a transmission structure for a tractor,
In particular, the present invention relates to a transmission structure in which an auxiliary transmission is provided in the rear half of a front housing that is arranged in front of a mission case that incorporates a speed change transmission mechanism and forms a vehicle body of a tractor together with the transmission case.

[0002]

BACKGROUND OF THE INVENTION A typical tractor transmission structure as described above is disclosed in US Pat. 5,058,455 and N
o. 5,058,459. In each of the transmission structures disclosed in these U.S. patents, the front housing is formed to have a rear end open, and the mission case is formed to have a front end open. A bearing frame installed near the rear end is used for axial support of the auxiliary transmission in the front housing and the main transmission in the transmission case.
That is, each of the transmission structures has a driving shaft that penetrates through a partition wall in the middle of the front housing, and the auxiliary transmission has a rotation output member (rotation output shaft or gear) for changing the speed of rotation by the driving shaft. It is said that the main transmission is provided with a counter shaft parallel to the shaft, and the main transmission performs speed change transmission between the drive shaft rotationally driven by the rotation output member and the speed change shaft arranged in parallel therewith. ． 5,0
In the case of 58 and 455, the rear ends of the drive shaft and the counter shaft, the front ends of which are supported by the partition wall, and the front ends of the drive shaft and the speed change shaft are supported by the bearing frame. Also, US Patent No. In the case of No. 5,058,459, the bearing frame has a frame structure in which bearing plate portions which are spaced apart from each other in the front and back are integrally connected to each other, and the bearing plate portion on the front side is provided with the drive shaft and the counter shaft. The front end side and the rear side bearing plate portion respectively support the rear end portion of the counter shaft and the front end portions of the drive shaft and the speed change shaft.

In all of these US patents, the auxiliary transmission is preliminarily assembled to the front of the transmission case as a preassembly by using a bearing frame which is fixedly supported by the transmission case as a support member, and the auxiliary transmission is mounted. Although it is intended to complete the assembly by inserting it into the housing to obtain the required final shaft support, it is not always easy to perform the final assembly while positioning the shaft. That is, US Pat. 5,058,4
In the No. 55 type, the auxiliary transmission is inserted into the front housing by the front-rear width, and the front end sides of the drive shaft and the counter shaft are positioned on the partition wall in the middle of the housing at a position greatly separated from the rear end opening of the housing. The bearing frame is used for axial support of both the auxiliary transmission and the main transmission, and the front and rear bearings are used to support the bearing. However, the auxiliary transmission including the bearing frame has a large front-rear width, which is not low. Also, US Patent No. For 5,058,459, the auxiliary transmission is attached to the front of the transmission case as a pre-assembly with the drive shaft not inserted, and then the long drive shaft is installed in the middle of the front housing. Since the wall and the front bearing plate portion of the bearing frame are inserted and assembled, the insertion length of the shaft is large, and it is difficult to position and support the shaft, which makes final assembly difficult.

Further, the bearing frame used in these US patents has a large size and a complicated shape, which is not preferable in terms of manufacturing and transmission compactness. US Patent No. 5,058,
A bearing frame having front and rear bearing plate portions, such as that of 459, requires a transmission member such as a gear to be laterally inserted into the frame to be supported by the shaft, which is awkward to assemble, and the front housing. The midway partition wall shall not be used as an active support member of the auxiliary transmission.

Therefore, a main object of the present invention is to provide a novel transmission structure for a tractor which facilitates assembly, particularly final assembly for positioning and supporting the shaft.

The accompanying object is to simplify the shape of the bearing frame fixedly installed in the vicinity of the rear end in the front housing and to make the bearing frame small in size, which contributes to cost reduction and compact transmission. It is to provide the transmission structure.

Another attendant object is to provide a novel transmission structure in which the arrangement of the members is devised to increase the compactness of the transmission.

Another attendant object is to provide a novel transmission structure which aims to reduce the number of parts as much as possible to reduce the cost.

[0009]

SUMMARY OF THE INVENTION A transmission structure for a tractor according to the present invention includes a front housing (1) having a partition wall (1a) in the middle thereof and an open rear end, and a front housing having an open front end. A mission case (2) connected to the rear end, a bearing frame (4) fixedly installed near the rear end in the front housing, and a drive shaft (which penetrates the partition wall and is supported by the partition wall). 7), an auxiliary transmission arranged in the front housing on the rear side of the partition wall so as to transmit a speed change between the driving shaft and the rotation output member (10) supported by the bearing frame. And an auxiliary transmission device (9) having a counter shaft (11) supported by the partition wall and the bearing frame, a drive shaft (12) and a transmission shaft (13) having front end portions supported by the bearing frame, respectively. Speed change transmission between A main transmission (14) having the drive shaft thereof interlockingly connected to the rotation output member, the main transmission being disposed in the transmission case, and the bearing frame (4) being provided at a front portion of the main transmission. While fixedly supporting the housing (1), the drive shaft (12) is concentrically arranged with the rotation output member (10), and the speed change shaft (13) is concentrically arranged with the counter shaft (11). The drive shaft and the counter shaft of the drive shaft are projected forward of the bearing frame (4), and the rotation output member (10) is fitted on the drive shaft to be supported by the bearing frame via the drive shaft. (11) The rear end portion is supported by the transmission shaft and is supported by the bearing frame via the transmission shaft.

According to the invention, the auxiliary transmission (9) is utilized by utilizing the partition wall (1a) in the middle of the front housing and the bearing frame fixedly supported by the front housing and installed near the rear end of the housing. Can be installed in the front housing (1) on the rear side of the partition wall as a substantially complete preassembly. That is, even if the rotation output member (10) which is supported by the bearing frame (4) via the drive shaft (12) of the main transmission (14) is temporarily held by some means, the partition wall (1a). ) The driving shaft (7) and the counter shaft (11) whose front end side is supported by
By assembling the members of the transmission from the rear end opening of the front housing and fixing and supporting the bearing frame (4) to the front housing, the assembly of the auxiliary transmission in a substantially completely assembled state can be obtained. it can. In order to temporarily hold the rotation output member (10) that can be configured as a gear or a shaft having a relatively short length, the bearing frame (4) itself is used to position and hold the rotation output member on the bearing frame. It is preferable to provide a hole (4c). Then, after obtaining the above-mentioned incorporation of the auxiliary transmission into the front housing, the front ends of the drive shaft (12) and the transmission shaft (13) of the main transmission (14) incorporated into the mission case (2). Through the bearing frame (4) and the rotation output member (1
0) is fitted and the rear end of the counter shaft is supported by the front end of the speed change shaft, and at the same time the front end of the drive shaft and the speed change shaft is supported by the bearing frame. The assembly is completed by abutting the two together and then fastening them together. The relative position between the front housing (1) and the mission case (2) for positioning and supporting the shaft in this way is as follows. The moving distance is limited to a distance required for causing the front ends of the drive shaft (12) and the speed change shaft (13) to project slightly forward through the bearing frame (4), and the front and rear of the auxiliary speed change device (9). It can be much smaller than the width, thus facilitating final assembly. Since the rotation output member (10) and the rear end of the counter shaft (11) are supported by the bearing frame (4) via the drive shaft and the speed change shaft, respectively, the drive shaft and the speed change shaft front end are provided on the bearing frame. Since only the bearing portion for supporting the bearing frame is provided, and thus the front and rear width of the bearing frame can be made small, the moving distance described above is correspondingly reduced, and final assembly is further facilitated, and the transmission is Becomes a compact one with the front and rear width reduced accordingly.

The above-mentioned bearing frame (4) extends inward from the flange portion (4a) at the outer peripheral end attached to the rear end surface of the front housing (1), and extends toward the inside of the front housing so that the drive shaft (12) and the transmission shaft are It is preferable to form the plate-like one with the bulging portion (4b) supporting the front end portion of (13). That is, by supporting the front ends of the drive shaft and the speed change shaft of the main transmission (14) in the mission case (2) by the bulging portion (4b) in the front housing having a relatively large front and rear space, The main transmission can be arranged from the front end position in the transmission case, and the front-rear width of the transmission and thus the length of the tractor can be shortened by that much.

In order to further enhance the effect of the compactness in the axial direction, the transmission gear train of the main transmission (14) arranged between the drive shaft (12) and the transmission shaft (13) is arranged. Gears of one gear train (62, 66)
Is preferably provided so as to face the inside of the bulging portion (4b) so that the front-back width of the bearing frame can be used generally.

The auxiliary transmission provided in the front housing is often constructed as a forward / reverse switching type as shown in the above-mentioned US Pat. Although an idler gear and a clutch for rotating the rotation output member of the vehicle in the backward direction of the vehicle are provided, the present invention also provides such an idler gear (4
It is also proposed to provide 5) and the shifter member (51) of the clutch (50) on a single support shaft (42) supported by the partition wall (1a) and the bearing frame (4). Is. This structure contributes to the reduction of the number of parts and hence the cost.

In order to further simplify the structure of the forward / reverse switching auxiliary transmission and further reduce the cost, the drive shaft (12) is arranged concentrically with the drive shaft (7), and the front end portion of the drive shaft is arranged. The rotation output member fitted to the counter shaft (1) is attached to the drive gear (39) loosely fitted on the driving shaft.
1), two gears (40, 40) fixedly installed on the counter shaft
41) and the driven gear (10) connected via the idler gear (45), while the clutch is
The shifter member (5) is installed on the rear end of the driving shaft (7).
It is preferable to construct a double clutch (50) operated by 1) to selectively connect the driving gear (39) and the driven gear (10) to the driving shaft (7). That is, according to this structure, the forward / reverse switching can be switched by operating the single shifter member, and the forward / rearward switching clutch and the rotation output member constituted by the driven gear compress the front / rear width of the auxiliary transmission as much as possible. I decided to.

Other features and advantages of the present invention can be clearly understood from the following description with reference to the accompanying drawings.

[0016]

FIG. 1 schematically shows the entire transmission system of a tractor equipped with a preferred embodiment of the present invention. The body of the illustrated tractor is composed of a front housing 1, a transmission case 2 and a rear housing 3, which are arranged in series in the front and rear and connected. The front housing 1 is formed to have a partition wall 1a opened in the front and rear, and a bearing frame 4 fixed to the rear end of the housing 1 is arranged in the rear end of the housing 1. The mission case 2 is formed such that the front and rear are open and the partition wall 2a is provided in the middle. The rear housing 3 has a front wall 3a
And a standing wall 3b standing upright on the inner bottom surface in the rear end portion, and the rear end opening is closed by a rear lid 3c.

Similarly, as shown in FIG. 1, the engine 5 is arranged at the forefront of the machine body, and a traveling system drive shaft 7 and a PTO system drive shaft 8 driven by the engine 5 via a main clutch mechanism 6, It is arranged in the front housing 1. The traveling system drive shaft 7 extends through the partition wall 1a, and the PTO drive shaft 8 extends back and forth through the hollow drive shaft 7. The main clutch mechanism 6 includes a traveling system main clutch 6a and a P clutch which are operated by separate operating mechanisms (not shown).
A TO-system main clutch 6b is provided.

An auxiliary transmission device 9 is arranged in the front housing 1 between the partition wall 1a and the bearing frame 4. This auxiliary transmission device 9 is arranged concentrically with the driving shaft 7 and is provided on the front side of the bearing frame 4 as a driven gear 1 as a rotation output member.
0 and a counter shaft 11 arranged below the drive shaft 7, and is configured to perform speed change transmission between the drive shaft 7 and the gear 10.

A bearing frame 4 is provided in the mission case 2.
And the hollow drive shaft 12 supported by the partition wall 2a, respectively.
And the transmission shaft 13 are arranged vertically, and these drive shafts 1
2 and the speed change shaft 13 are a drive shaft 7 and a counter shaft 1, respectively.
It is arranged concentrically with 1 and projects forward of the bearing frame 4. The gear 10 is fitted to the front end of the drive shaft 12, and the rear end of the counter shaft 11 is supported by the front end of the speed change shaft 13. In the front half of the mission case 2, a main transmission device 14 that transmits a speed change between a drive shaft 12 and a speed change shaft 13 is arranged.

In the rear half of the mission case 2, a hollow intermediate shaft 15 and a transmission shaft 13 are provided on an extension of the drive shaft 12.
And a propeller shaft 16 arranged on an extension line of the auxiliary transmission device 1 for performing speed change transmission between the speed change shaft 13 and the propeller shaft 16.
7 are arranged. Propeller shaft 16 is rear housing 3
A small bevel gear 18 is provided at the rear end of the left end of the left and right rear wheels by meshing the bevel gear 18 with a large input bevel gear 19 of a differential device for the left and right rear wheels (above, not shown). It is said that the vehicle is driven by driving the wheels.

The PTO system drive shaft 8 is connected to a transmission shaft 20 penetrating the hollow drive shaft 12 and the intermediate shaft 15, and further connected to two transmission shafts 21 and 22 arranged in the rear housing 3. There is. A PTO shaft 23 supported by the support wall 3b and the rear lid 3c and extended rearward of the machine body is provided, and the transmission shaft 22 is connected to the PTO shaft 23 by gears 24 and 25 reduction gears.

FIG. 2 shows a longitudinal side surface of the rear half of the front housing 1 and the front end of the mission case 2, and FIG. 3 shows the front housing 1 with the mission case 2 removed from the state of FIG. FIG. 4 shows a rear surface, and FIG. 4 shows a cross section taken substantially along the line IV-IV in FIG. As shown in these figures, the front housing 1 and the mission case 2 are
Between the front housing 1 and the front end surface of the mission case 2 by abutting the flange on the outer periphery of the front housing 1, and by fastening the bolt 27 through the bolt insertion hole of the flange to the screw hole 2b of the mission case 2. Has been done. Positioning pins 28 are used to perform positioning prior to fastening.

Similarly, as shown in FIG. 2-4, the bearing frame 4 is formed in a plate-like shape having a bulging portion 4b which is bulged in the forward direction over substantially the entire surface except the mounting flange portion 4a at the outer peripheral end. The front housing 1 with the bolt 29 that is inserted through the bolt insertion hole of the mounting flange portion 4a.
It is attached to the rear end surface of the housing 1 by being screwed into a screw hole 30 of a boss 1b protruding from the inner surface of the rear end. Positioning pins 31 are used to position the bearing frame 4 prior to mounting with the bolts 29. Bulge 4
In b, two holes for projecting the drive shaft 12 and the transmission shaft 13 from the inside of the mission case 2 to the front side of the bearing frame 4 and annular bearing portions 32, 33 located at the outer ends of the holes are provided.
And the front end portions of the drive shaft 12 and the speed change shaft 13 are held by the bearing portions 32 and 33, respectively.
It is supported by the bearing frame 4 via 4, 35.

As shown in FIG. 2, the driving shaft 7 penetrating the partition wall 1a is supported by the partition wall 1a via a ball bearing 36, and the front end of the counter shaft 11 is partitioned by a ball bearing 37. It is supported by 1a. The driven gear 10, which is to be fitted to the drive shaft 12 on the front surface side of the bearing frame 4 as described above, is formed by engaging the spline 10a on the inner peripheral surface with the spline 12a on the outer peripheral surface of the front end portion of the drive shaft 12. Drive shaft 12 by fitting
And the bearing frame 4 is supported via the drive shaft 12. Further, the front end portion of the transmission shaft 13 projecting forward of the bearing frame 4 has a shaft support portion 13 having a reduced diameter.
a is formed in the rear end portion of the counter shaft 11 and the rear end portion of the counter shaft 11 is supported by inserting the shaft support portion 13a into the hole 11a formed in the rear end portion of the counter shaft 11 and supporting the counter shaft 11 through the needle bearing 38. The portion is supported by the bearing frame 4 via the transmission shaft 13. An annular shoulder portion 10b is provided on the boss portion of the gear 10, and an annular hole portion 4c which is substantially in contact with the shoulder portion 10b is provided on the bearing frame 4 on the front end side of the bearing portion 32 as shown in FIGS. Has been. This annular hole 4c is for temporarily holding the gear 10 before fitting it onto the drive shaft 12, and as shown in FIG. 6 showing the state during assembly, the hole 4c holds the gear 10 at a predetermined position. Position and hold.

The structure of the illustrated auxiliary transmission 9 will be described. As shown in FIG. 2, a drive gear 39 is loosely fitted on the driving shaft 7 behind the partition wall 1a. Further, a gear 40 aligned with the drive gear 39 and a gear 41 aligned with the driven gear 10 are fixedly installed by spline fitting on the counter shaft 11 when viewed in the front-rear direction, and the rear gear 41 is a driven gear. Meshed with 10. Figure 3,
4, a support shaft 42 supported by the partition wall 1a and the bearing frame 4 is provided at an intermediate level between the drive shaft 7 and the counter shaft 11, and the support shaft 42 is provided on the support shaft 42 as shown in FIG. And an idler gear 45 through a bearing 44 held between an annular step portion 42a on the support shaft 42 and a nut 43.
Is freely rotatable. A split pin 46 for locking the nut 43 and the rotation of the support shaft 42 is mounted on the front end of the support shaft 42, and a pin 47 for locking the support shaft 42 is mounted on the rear end thereof. . Then, as shown schematically in FIG. 2, the idler gear 45 is engaged with both the drive gear 39 and the gear 40 on the front end of the counter shaft 11, and the drive gear 39 causes the gears 45, 40 and the counter shaft 1 to rotate.
The driven gear 10 can be rotated via the gear 1 and the gear 41.

As shown in FIG. 2, on the rear end portion of the driving shaft 7, there is a double type structure in which the drive gear 39 and the driven gear 10 can be selectively coupled to the driving shaft 7 by the displacement of the shift sleeve 49. A friction plate type synchronous clutch 50 is provided. As shown in FIGS. 4 and 5, a shifter fork 51 is slidably provided on the support shaft 42.
Is engaged with the shift sleeve 49, and the shifter fork 51 is slid on the support shaft 42 to obtain the displacement of the shift sleeve 49. In order to perform a sliding operation of the shifter fork 51, a rotatable operation shaft 52 is provided so as to extend inside and outside one side wall of the front housing 1, and an operating arm 53 attached to the inner end of the operation shaft 52 is attached to the shifter fork. It is engaged with 51. The operation shaft 52 is connected to a forward / reverse switching lever (not shown). The support shaft 42 is provided with detent annular grooves 54N, 54F, 54R for restricting the position of the shift sleeve 49 at the neutral position shown in FIG. 2 and the forward and rearward positions thereof.
Ball 55 for detent that can enter each of these grooves,
The shifter fork 51 is urged to move by the spring 56.
Is equipped with.

The friction plate type synchronous clutch 50 shown in FIG.
Are, for example, US Pat. 4,830,159 (corresponding to Japanese Unexamined Patent Publication No. 1-224546), the shift sleeve 49 is spline-fitted to the spline hub 57 fixedly installed on the driving shaft 7, and each gear 10 is rotated. , 39 attached to the spline ring 10c, 39
a and the above-mentioned spline hub 57.
8 is supported by the hub 57 and is interposed, and the gears 10, 39
A plurality of friction elements are slidably supported on each of the synchronous rings 58 and each synchronization ring 58, and further, a plurality of detent pins 59 supported by the hub 57 and a plurality of inserts 60 supported by the shift sleeve 49 are provided. It is configured. The insert 60 has a sleeve 49 and a synchronization ring 58.
The movement of the sleeve 49 is controlled, and the synchronous rotation is obtained by the complete engagement between the friction elements, and the sleeve 49 is displaced to the position where the spline ring 10c or 39a is engaged with the spline ring 10c or 39a. is there.

As shown in FIG. 1, the main transmission 14 has four gears 62, 63, 64, 65 loosely fitted on the drive shaft 12 and four gears meshed with these gears. 66, 67, 68, 69 are fixedly installed on the transmission shaft 13, and four transmission gear trains are provided. On the drive shaft 12, between the gears 62 and 63 and the gear 64,
Two sets of double cone type synchronous clutches 70, 71 between 65
The gears 62-65 are selectively connected to the drive shaft 12 by the clutches 70, 71 so as to obtain four speeds. In particular, as shown in FIG. 2, the gears 62 and 66 of the gear train located at the forefront of the four transmission gear trains are arranged so as to face the bulging portion 4b of the bearing frame 4. There is.

The partition wall 1 as shown in FIGS. 2 and 4 and 5.
A pressing plate 73 for preventing the ball bearings 36 and 37 from being pulled out is attached to the rear surface of a using a pair of bolts 74. As is clear from FIGS. 2 and 3, the plate-shaped bearing frame 4 has a size that allows the front housing 1 behind the partition wall 1a to freely communicate with the inside of the mission case 2 on the outer peripheral side thereof. Lubricating oil is stored in the transmission case 2.

The structure of the auxiliary transmission device 17 will be described with reference to FIG. 1. The transmission shaft 13 is connected to the intermediate shaft 15 by a series of reduction gears 76 and 77. Intermediate shaft 15
Two transmission gears 78 and 79 are fixedly installed on the upper side.
A support frame 80 is provided which is inserted into the mission case 2 through an opening (not shown) provided on one side wall near the rear end of the mission case 2 and is attached to the case 2. A reduction gear mechanism 81 that significantly reduces the rotation of the gear 79 on the smaller diameter side of the transmission gears 78 and 79 is provided, and the final gear 82 thereof is configured as a transmission gear for creep travel. On the propeller shaft 16, a shift gear 83 capable of selectively meshing with the gears 82 and 79 and a shift gear 84 selectively meshing with the gear 78 are installed so as to be slidable only. Between the speed change shaft 13 and the propeller shaft 16,
Clutch 8 that can be selectively engaged by shift gear 84
5 is provided. As described above, the auxiliary transmission device 17 operates the gear 8
The creep speed is increased by the engagement between the gears 2, 83 and the gears 79, 8
The third gear meshes with the first gear, the gears 78, 84 mesh with the second gear, and the clutch 85 couples the shafts 13, 16 with each other.
It is said that the third speed is applied to the propeller shaft 16 by the direct connection between the two. On the intermediate shaft 15, in a state where the auxiliary transmission 9 and the main transmission 14 are in the neutral state and the auxiliary transmission 17 is in any one of the shift stages, some torque or torque that can be transmitted from the engine side is provided. A braking mechanism 87 having a weak braking force is provided to prevent the vehicle from unintentionally starting due to the torque that can be transmitted from the wheels on the sloping ground. A braking rotation member 88 of a parking brake (not shown) is fixedly installed on the propeller shaft 16.

FIG. 6 is for explaining the assembling method. The auxiliary transmission 9 is in a completely assembled state as shown by using the partition wall 1a as a main supporting member and the bearing frame 4 as an auxiliary supporting member in advance. Is assembled in the front housing 1. In this state, the driven gear 10 has its annular shoulder 10
It is positioned and held at a predetermined position in the annular hole 4c of the bearing frame 4 by b. Further, the main transmission 14 is
The rear end of the drive shaft 12 and the transmission shaft 13 is supported by the partition wall 2a in the middle of the mission case 2 shown in FIG. 1 and is assembled in the front half of the mission case 2 in a completely assembled state in advance. When the housing 1 and the case 2 are relatively close to each other from the separated state of the front housing 1 and the mission case 2 shown in FIG. The spline 10a on the inner peripheral surface of the driven gear 10 meshes with the spline 12a on the outer peripheral surface of the front end portion of the drive shaft 12 to obtain the fitted state of the gear 10 on the front end portion of the drive shaft 12, and at the rear end of the counter shaft 11. The shaft bearing portion 13a at the front end of the speed change shaft 13 is fitted together with the needle bearing 38 thereon to support the rear end portion of the counter shaft 11, and the drive shaft 12 and the speed change shaft 13 are preliminarily set on the drive shaft 12 and the speed change shaft 13. The ball bearings 34 and 35 to be fitted are held by the annular bearing portions 32 and 33 of the bearing frame 4. In the illustrated example, the drive shaft 8 of the PTO system and the transmission shaft 20 are connected by a spline coupling 90 in the rear end portion of the hollow drive shaft 7, but the coupling 90 is connected to the drive shaft 8 as shown in the figure. By pre-fitting on the rear end part (or conversely on the front end part of the transmission shaft 20), the connection between the shafts 8 and 20 can be obtained at the same time. After that, the bolts 27 are fastened to complete the assembly.

In the embodiment described above, the rotation output member of the auxiliary transmission 9 is constituted by the gear 10, but the rotation output member is a short shaft having a gear corresponding to the gear 10 fixed thereto. You can also do it. Further, although the spline fitting structure using the splines 10a and 12a is adopted for fitting the gear 10 to the front end portion of the drive shaft 12, a structure using a key may be used. Further, the auxiliary transmission 9 can be variously modified within the scope of the present invention, for example, a high-low switching type transmission in which the idler gear 45 is eliminated and gears corresponding to the gears 39 and 40 are directly meshed. Therefore, the present invention is not limited to the illustrated embodiment,
It should be understood that the same embodiment can be implemented with various changes and modifications.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional side view showing an entire transmission mechanism of a tractor equipped with a preferred embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a rear half of a front housing of the tractor and a front end of a transmission case.

FIG. 3 is a rear view of the front housing seen from the state shown in FIG. 2 with the mission case removed.

FIG. 4 is a cross-sectional view substantially along the line IV-IV in FIG.

5 is a vertical cross-sectional view substantially along the line VV in FIG.

FIG. 6 is a vertical sectional side view similar to FIG. 2 for explaining an assembling method.

[Explanation of symbols]

 1 Front Housing 1a Partition Wall 1b Boss 2 Mission Case 2b Screw Hole 4 Bearing Frame 4a Mounting Flange 4b Expansion 4c Annular Hole 5 Engine 7 Driving Shaft 9 Auxiliary Transmission 10 Driven Gear 10a Spline 11 Counter Shaft 11a Hole 12 Drive shaft 12a Spline 12b Shoulder 13 Shift shaft 13a Shaft support 14 Main transmission 27 Bolt 29 Bolt 32,33 Annular bearing 39 Gear 40,41 Gear 42 Spindle 45 Idler gear 49 Shift sleeve 50 Friction plate synchronous clutch 51 Shifter Forks 62, 63, 64, 65 Gears 66, 67, 68, 69 Gears 70, 71 Cone type synchronous clutch

Claims (6)

[Claims] 1. A front housing (1) having a partition wall (1a) in the middle and a rear end opened, and a mission case (2) having a front end opened and connected to a rear end of the front housing. ), A bearing frame (4) fixedly installed near the rear end in the front housing, a drive shaft (7) penetrating through the partition wall and supported by the partition wall, the drive shaft and the bearing frame. An auxiliary transmission arranged in the front housing on the rear side of the partition wall so as to transmit a speed change between the rotation output member (10) and the supported rotation output member (10), the auxiliary transmission device including the partition wall and the bearing frame. Auxiliary transmission (9) having a supported counter shaft (11), inside a transmission case so as to perform a speed change transmission between a drive shaft (12) and a speed change shaft (13) whose front ends are respectively supported by the bearing frame. Main change that is located in A transmission structure for a tractor, comprising a main transmission (14), which is a speed device, the drive shaft of which is interlockingly connected to the rotation output member, wherein the bearing frame (4) includes a front housing (1). On the other hand, the drive shaft (12) is concentrically arranged with the rotation output member (10) and the speed change shaft (13) with the counter shaft (11). The counter shaft is projected to the front of the bearing frame (4), the rotation output member (10) is fitted on the drive shaft to be supported by the bearing frame via the drive shaft, and the counter shaft (11) A transmission structure in which a rear end portion is supported by a speed change shaft and is supported by a bearing frame via the speed change shaft. 2. The transmission structure according to claim 1, wherein the bearing frame (4) is provided with an annular hole (4c) for positioning and temporarily holding the rotation output member (10). 3. The bearing frame (4) and a drive flange (4) extending inward of the front housing and a mounting flange portion (4a) at the outer peripheral end which is mounted on the rear end surface of the front housing (1). 2. The transmission structure according to claim 1, wherein the transmission structure is formed in a plate shape having a bulging portion (4b) supporting a front end portion of the speed change shaft (13). 4. A gear (62, 66) of one gear train of the gear trains of the main transmission (14), which is arranged between the drive shaft (12) and the gear shift shaft (13). The transmission structure according to claim 3, wherein the transmission structure is provided so as to face the bulged portion (4b). 5. The auxiliary transmission (9) is configured to include an idler gear (45) and a clutch (50) for rotating the rotation output member (10) in a backward direction of the vehicle, and the idler gear. And clutch shifter members (51)
Is provided on a single support shaft (42) supported by the partition wall (1a) and the bearing frame (4).
Transmission structure. 6. The drive shaft (12) is replaced with the drive shaft (7).
The rotation output member concentrically arranged with the drive shaft fitted to the front end of the drive shaft is fixedly installed on the counter shaft (11) and the counter shaft with respect to the drive gear (39) loosely fitted on the drive shaft. Of the driven gear (10) connected via the two gears (40, 41) and the idler gear (45), while the clutch is installed on the rear end of the driving shaft (7). 6. A dual clutch (50) operated by the shifter member (51) to selectively connect the drive gear (39) and the driven gear (10) to a driving shaft (7). Transmission structure.