GB2130663A - A transmission case for motor cultivators and a method of assembling gears in the case - Google Patents

Abstract

A casing body (20) is integrally formed to be open upwardly, the casing body comprising front (24) and rear (25) walls, a pair of opposing side walls (21, 22) and a bottom wall (23). A transmission assembly method using the integrally formed case comprises the steps of bringing from an upper opening into the case a jig with fittings such as gears fitted thereon in advance and arranged in a predetermined order, placing the jig in alignment with a coaxial line of first and second support holes bored either in both of the side walls, abutting a shaft through the first support hole alignedly on the jig as supported by the support holes, and forcing the shaft into the case to push the jig through the second support hole outside of the case, thereby shifting the fittings from the jig onto the shaft and bringing either end of the shaft into both of the first and second support holes. <IMAGE>

Description

SPECIFICATION Transmission case for motor cultivators, transmission assemblying method using same case, and jig for same method The present invention relates to an improvement in a transmission case for motor cultivators, to a transmission assemblying method for assemblying a small-size transmission for motor cultivators by fitting the improved transmission case with such as gears and shafts, and to a jig for the transmission assemblying method.

Conventionally, there has been known a case for a transmission for motor cultivators, the transmission being equipped with a multi-staged speed shift mechanism, which case is composed of a pair of case halves as jointed to be integrated with each other after being fitted therein with the speed shift mechanism.

To such conventional case structure, there have been various drawbacks such that a machining process is needed to the joint surface of case halves, besides the necessity such as of a sealant for the leakage prevention of lube oil at a joint part. Moreover, both case halves require troublesome processes such as a boring work to be executed in a similar manner. Further, due to the reduced rigidity of each case half, necessary reinforcement such as by the formation of a rib and the increase in the wall thickness results in an inevitable increase in the weight of transmission case.

Such drawbacks might be eliminatable with a case for transmissions composed of a single enclosure integrally formed from the beginning.

However, with such enclosing case which may well be considerably narrow and deep, more serious problems would arise such as that it might become difficult to efficiently install a speed shift mechanism in the case.

For such reason, the conventional transmission case for motor cultivators have been submitted to such drawbacks as described above.

The present invention has been achieved to effectively overcome such conventional circumstances.

According to the present invention, there is provided a transmission case for motor cultivators comprising a casing body having a front wall, a rear wall, a pair of side walls opposing each other, a bottom wall, and an opening for opening the interior upwardly, the walls being formed to be all integral.

According to the present invention, there is further provided a method for assemblying a multi-speed transmission for motor cultivators using the transmission case, in which a shaft is supported by first and second support holes bored in the side walls of the transmission case, the shaft having a plurality of fittable members including a gear fitted thereon, comprising the steps of fitting the fittable members on a jig in a predetermined order, the jig having a smaller diameter than the shaft, bringing the jig through the opening of the transmission case into the transmission case, placing the jig in alignment with a coaxial line of the first and second support holes, abutting the shaft through the first support hole to the jig rendering same coaxial therewith, and forcing the shaft into the transmission case, while keeping same coaxial with the jig and pushing the jig out of the second support hole, thereby shifting the fittable members from the jig to the shaft and fitting thereon one by one and bringing both ends of the shaft either in the first and second support holes.

According to the present invention, there is furthermore provided a jig for use in the transmission assemblying method, the jig being provided at its end with an engagement element engageable with either end of the shaft.

Accordingly, an object of the present invention is to provide a case for multi-speed transmissions for motor cultivators, which is easy of the formation and processing and free from the fear of the leakage of lube oil, while concurrently enabling an increase in the rigidity as well as a lightweighted design with minimized wall thickness.

Another object of the present invention is to provide a method for assemblying a multi-speed transmission for motor cultivators, which permits an integrally formed case for small-size transmissions to be fitted with a speed shift mechanism in a simplified and efficient manner.

Still another object of the present invention is to provide a jig which enables an integrally formed case for small-size transmissions to be fitted with a speed shift mechanism efficiently and with ease.

The above and further features, objects and advantages of the present invention will more fully appear from the following detailed description of the preferred embodiments of the invention when the same is read in conjunction with the accompanying drawings.

In the drawings: Fig. 1 is a schematic side view of a motor cultivator including a multi-speed transmission with a transmission case according to the present invention; Fig. 2 is an enlarged side view of an essential part, including the transmission case, of the motor cultivator of Fig. 1; Fig. 3 is an enlarged side view of the transmission of Fig. 1; Fig. 4 is an enlarged longitudinal sectional view taken along line "4"--"4" of Fig. 3; and Fig. 5 is an explanatory sectional view showing a jig and a step of a transmission assemblying method according to the present invention.

Referring first to Figs. 1 and 2, generally designated at reference character 1 is a motor cultivator. The motor cultivator 1 includes a transmission case 2 having at its front side 2a upper and lower bosses 2b, 2c formed thereon, thereby supporting an engine mount base 3 fixed thereto for mounting thereon an engine 4 provided with a fuel tank 5 placed thereon. Moreover, on the upper end of the transmission case 2, there is provided a handle column 6 secured thereto, the handle column 6 rising rearwardly to support by holding to fix the proximal end of a bifurcate handle 7.Further, the transmission case 2 is provided at its rear side 2d with upper and lower bosses 2e, 2f to which a plow bar 8 is hitched through a hitch box 9 fixed thereto and, in the lower part of the transmission case 2, there is transversely supported a drive axle 10 on which a pair of plow rotors 11 are mounted. The plow rotors 11 may be replaced by road wheels or other sort of machinery for plowing or tiliing use.

Referring now to Figs. 3 and 4, the transmission case 2 is formed to be, of the dimension in the longitudinal direction of the motor cultivator 1 or in the left to right direction in Fig. 3, somewhat the larger, as the upper. As for the dimension in the transverse direction of the cultivator 1 or in the left to right direction in Fig. 4, that is, the width, the transmission case 2 is formed to be relatively small in its lower part 29, while its upper part 2h projecting outwardly at a stepped portion 2i is made relatively wide. The transmission case 2 comprises a casing body 20 arranged to be relatively long substantially in the vertical direction.For the later described use, the casing body 20 has an integral form consisting of a left side wall 21, a right side wall 22 and a bottom wall 23 shown in Fig. 4 as well as a front wall 24 and a rear wall 25 shown in Fig. 3, and defining at the upper end thereof an opening 26 open upwardly for the access to the inside. The left and right side walls 21, 22 have in the lower parts thereof left and right bosses 70, 80 integrally formed therewith, respectively, the bosses 70, 80 being disposed coaxially relative to each other and provided with left and right support holes 12, 13 bored therethrough, respectively. Also the support holes 12, 1 3 are coaxial to each other, while the left support hole 12 has a larger diameter than the right support hole 13.In the left and right support holes 12, 1 3, there are respectively fitted left and right bearings 76, 77 and left and right oil seals 78, 79 fitted all on the drive shaft 10 provided therethrough.

Further, the left and right side walls 21, 22 have in the upper parts thereof left and right bearing banks 75, 85 integrally formed therewith, respectively, and bulged both outwardly, the banks 75, 85 constituting the projecting upper part 2h of the transmission case 2. In these left and right banks 75, 85, there are bored in a coaxially opposing manner respectively, in the lower parts thereof, left and right support holes 14, 1 5 for supporting a reduction or final shaft 30; in the upper rear parts thereof in Fig. 4 or in the upper right in Fig. 3, left and right support holes 1 6, 17 for supporting a counter shaft 38; in front of these holes 16, 1 7 in Fig. 4 or in the left thereof in Fig. 3, left and right support holes 1 8, 19 for supporting an input shaft 45; and in the uppermost parts thereof, in front of the these holes 18, 19, left and right through holes 24, 25 for passing a shift rod 51. The left support holes 14, 16 and 18 formed in the left side wall 21 are larger in the diameter than the opposing right support holes 1 5, 1 7 and 19 formed in the right side wall 22, respectively. The final, counter and input shafts 30, 38 and 45 are borne at the left and right ends thereof by left and right bearings 31, 32; 39, 40; and 46, 47 fitted in the corresponding left and right support holes 14, 1 5; 16, 17; and 18, 19, respectively.

There will be detailed hereinbelow the constitution of a speed shift mechanism installed in the transmission case 2.

The input shaft 45 is projected outwardly from the transmission case 2 at either end thereof, at the left end in this embodiment, and there is secured to this projected end a drive pulley 49 interconnected by a V-belt 58 with an output shaft (not shown) of an engine 4 shown in Fig. 1, while the engine 4 and the transmission case 2 are covered at both sides thereof with either of a pair of common covers 59. The remaining part of the input shaft 45 in the transmission case 2 has a plurality of splines 64 formed thereon and a slide gear 48 slidably fitted thereon, the slide gear 48 being integrally provided with right and left drive gears 48a, 48b, so that these drive gears 48a, 48b are integrally shiftable to a plurality of predetermined positions with a yoke 52 secured to a shift rod 51.Also the shift rod 51 is projected out of the transmission case 2 at either end thereof, at the left end in this embodiment, and there is operatively connected to this projected end a shift lever 81 shown in Fig. 1. With this shift lever 81 to be operated, the shift rod 51 is to be slided while causing a click mechanism to effect a click feeling, the click mechanism consisting of a plurality of slots 53 formed in the distal part of the shift rod 51 and a ball 54 resiliently biased to be engageable with the slots 53.

On the counter shaft 38, there are fitted in a spline engagement manner left and right driven gears 41,42 meshable either at a time with the left and right drive gears 48a, 48b, respectively.

The counter shaft 38 has at either end thereof, at the left end in this embodiment, a pinion 63 integrally fitted thereon, the pinion 63 meshing with a reduction gear 35 fitted on the final shaft 30 and engaged therewith through a plurality of splines 62 formed therealong. Moreover, on the final shaft 30, at the right, there is relatively rotatably fitted a reverse gear 33 with a collar 61 inserted therebetween, the reverse gear 33 being meshed with the right driven gear 42 fitted on the counter shaft 38 and driving a certain apparatus (not shown). Further, on the intermediate part of the final shaft 30, there is fitted a sprocket 34 engaged with the splines 62, the sprocket 34 being axially spaced from the reduction gear 35 with a collar 60 put therebetween.

At the lower part 29 of the transmission case 2, there is arranged another sprocket 29 fitted in a spline engagement manner on the drive shaft 10 driving the plow rotors 11. This sprocket 29 is driven by the sprocket 34 fitted on the final shaft 30 through a drive chain 37 stretched therebetween.

The upper part 2h of the transmission case 2 is open upwardly at the opening 26 of the casing body 20, through which various internal components such as gears and collars of the speed shift mechanism are installed before closing with a top cover 56.

As shown in Fig. 4, in the right side wall 22, the support holes 15, 17, 19 and the through hole 25 are closed to be sealed from outside with three flat caps 50 and a convexed cap 55, respectively, to prevent the leakage of internal lube oil as well as the intrusion of foreign matter. In the left side wall 21, the support hole 1 8 supporting the projecting end of the input shaft 45 is sealed with an oil seal 65. Moreover, the remaining two left support holes 1 4, 16 are closed to be sealed from outside with a common cover plate 44, with collars 66, 67 put between this cover plate 44 and the left bearings 31,39 respectively.The cover plate 44 serves to restrict respective axial movements of the final and counter shafts 30, 38, in cooperation with stepped stoppers 1 Sa, 1 7a formed for positioning the corresponding right bearings 32, 40 in the right support holes 1 5, 17, respectively. Further, the top cover 56 of the upper end opening 26 and the common cover plate 44 of the left support holes 1 4, 1 6 are kept oil-tight with seal rings 57 provided inside thereof.

In the above speed shift mechanism, when the shift rod 51 is caused to travel axially, shifting the drive gears 48a, 48b along the input shaft 45 thereby to have, for example, the left drive gear 48a mesh with the left drive gear 41, the torque as transmitted from the engine to the drive pulley 49 will then be transmitted through the input shaft 45 and the drive gear 48a to the driven gear 41 and further therefrom through the pinion 63, the reduction gear 35, the final shaft 30, the sprocket 34 and the chain 37 to the sprocket 29, which will rotate the drive axle 10, thereby driving the plow rotors 11.On the other hand, when the right drive gear 48b is caused to mesh with the right driven gear 42, the torque as given to the drive pulley 49 will then be transmitted through the input shaft 45, the drive gear 48b and the driven gear 42 to the counter shaft 38 and further from the pinion 63, which is integrally rotatable with the counter shaft 38, through the reduction gear 35, the final shaft 30, the sprocket 34 and the chain 37 to the sprocket 29, which will rotate the drive shaft 10 at a speed different from that of the former example.

There will be described hereinbelow a method for fitting the integrally formed transmission case 2 with some essential internal components such as shafts and gears of the before mentioned speed shift mechanism. More particularly, with reference to Fig. 5, there will be detailed below a procedure for fitting the transmission case 2 with the final shaft 30 as a shaft to be installed in the deepest position, while this installation procedure of the final shaft 30 substantially overlaps with that of the counter shaft 38.

The installation procedure of the final shaft has the first step of fitting the support hole 1 5 of the right side wall 22 of the transmission case 2 with the right bearing 32. The second step includes fitting the reduction gear 35, the collar 60, the sprocket 34, the collar 61 and the reverse gear 33 as arranged in this order from the left on a shaftlike jig 71, which has a diameter slightly smaller than that of a right small diameter portion 30a of the final shaft 30, and positioning this assembiy along the axis of the coaxial left and right support holes 14, 1 5. This positioning may be performed with ease by hanging the jig 71 with the above members fitted thereon from the upper end opening 26 (Fig. 4) of the casing body 20 down to the described position, whereas the jig 71 has a length substantially equal to or shorter than the distance between the left and right side walls 21,22 of the transmission case 2.

Incidentally, the final shaft 30 is formed at both ends thereof with either of pair of center holes 72, 72 supported on a tooling machine when machining, and the jig 71 has an engagement projection 73 axially formed at either end thereof, at the left in this embodiment, so as to be engageable with either one, the right one in this embodiment, of the center holes 72, 72 of the final shaft 30.To this point, the third step of the installation procedure of the final shaft 30, following the step of placing the jig 71 in the described position relative to the left and right support holes 14, 1 5, comprises passing the final shaft 30 from outside of the transmission case 2 through the support hole 14 in the left side wall 1 4 till it abuts at the right end thereof on the left end of the jig 71 , thereby bringing the right center hole 72 in engagement with the engagement projection 73, and forcing the final shaft 30 inwardly of the transmission case 2, thus pushing away the jig 72 outwardly of the support hole 1 5 in the right side wall 22, thereby having in place thereof the final shaft 30 fitted forth into the reduction gear 35, the collar 60, the sprocket 34 and the reverse gear 33 one by one from the left, while properly rotating the final shaft 30 to effect a smooth engagement of the splines 62.

The fourth step consists of driving forth the final shaft 30, as having reached at the right end thereof to the right bearing 32, to have the right small diameter portion 30a fitted in this bearing 32 by hitting with a suitable implement and, subsequent thereto, hitting to drive forth from outside of the left side wall 21 the left bearing 31 (Fig. 4) to be fitted on a left small diameter portion 30b of the final shaft 30, while as an intermediate step, the jig 71 is to be taken out from the right support hole 1 5 when the final shaft 30 is assembled in position.

After the final shaft 30 is properly assembled in the transmission case 2 together with necessary gears and collars through the foregoing steps, the common cover plate 44 (Fig. 4) and the flat cap 50 (Fig. 4) are to be fastened to the transmission case 2 as a final step.

In the above embodiment, the jig 71 may preferably be provided with a flange-like projection at the right end thereof, to prevent the fitting members such as gears and collars from coming out of the right end, particularly in those arrangements in which a washer is placed between the right bearing 32 and the reverse gear 33.

Moreover, the jig 71 may preferably be tapered toward the right end to further facilitate the fitting such as of the gears 33, 35 onto the final shaft 30.

Further, it will be apparent that the foregoing shaft installation procedure, which is described about the final shaft 30, may preferably be applied to the counter shaft 38 as well as to various shafts such as a final shaft of a smail-size speed shift mechanism for other vehicles than motor cultivators, the speed shift mechanism being provided with a casing therefor of an integral structure.

Besides above, for the before mentioned speed shift mechanism, in which the counter shaft 38 is located near the upper end opening 26 of the casing body 20, there will be described below an easy and simplified procedure for fitting the transmission case 2 with the counter shaft 38, without using the jig 71.

With reference to Fig. 4, the simplified installation procedure of the counter shaft 38 has the first step of fitting the right bearing 40 in the diametrically small right support hole 1 7 of the right side wall 22 of the transmission case 2, while positioning by an engagement with the stepped stopper 1 7a formed in the support hole 1 7. The second step consists of inserting the counter shaft 38 through the diametrically large left support hole 16 of the left side wall 21 into the transmission case 2, while bringing the left driven gear 41, the collar 68, the right driven gear 42, the collar 69 and other fitting members if any through the opening 26 one by one in the transmission case 2 to fit them in such order on the counter shaft 38.In this step, the counter shaft 38 is to be properly rotated to enable the driven gears 41, 42 to be easily splined onto the counter shaft 38. As following the state in which the counter shaft 38 has reached at the right end thereof to the right bearing 40, the third step includes driving forth the counter shaft 38 to have a small diameter portion 38a as the right end thereof fitted in the right bearing 40 by hitting with a suitable implement. Then, as a fourth step, the left bearing 39 is to be fitted from outside of the left side wall 20 into the left support hole 1 6 and onto a small diameter portion as the left end of the counter shaft 38.Then, the final step comprises fitting the collar 67 in the diametrically large left support hole 16, placing thereon the cover plate 44, and securing this cover plate 44 to the outside of the left side wall 21 , thereby completing the installation of the counter shaft 38 into the transmission case 2.

The above installation procedure of the counter shaft 38 is effectively permitted by the employment of a transmission case for motor cultivators, the transmission case having an integral structure, in which a pair of opposed side walls are formed either with a diametrically large support hole and the other with a diametrically small support hole with a stepped stopper.

In this concern, such installation procedure may preferably be applied to an input shaft of a speed shift mechanism of the before mentioned type as well as to the installation of various shafts in an integrally formed transmission case for speed shift mechanisms for other vehicles than motor cultivators.

In addition to the foregoing installation procedures, there will be described hereinbelow an installation procedure for fitting the transmission case 2 with the drive shaft 10 to be arranged in the lower part 29 thereof.

First, the installation procedure of the drive shaft 10 takes the steps of fitting the right bearing 77 in the right support hole 13 of a relatively small diameter in the right side wall 22 of the transmission case 2, and positioning the bearing 77 by an engagement with a stepped stopper 1 3a integrally formed in the support hole 13. Then, it follows the step of inserting the drive shaft 10 through the left support hole 12 of a relatively large diameter of the left side wall 21 into the transmission case 2, while fitting the driven sprocket 29 as accommodated inside of the transmission case 2 onto the drive shaft 10 in a spline engagement manner. In this step, the drive shaft 10 is to be properly rotated to make easy the spline engagement.Following the state in which the drive shaft 10 has reached to the right bearing 77, the procedure enters the steps of fitting the drive shaft 10 in the bearing 77, and fitting the left bearing 76 from outside of the left side wall 21 into the left support hole 12 and onto the drive shaft 10. After placing a circle clip 36 in a ring-like engagement slot formed in the left support hole 12, there comes the next step of abutting the circle clip 36 on the left face of an outer race of the left bearing 76 thereby to restrict the axial movement of the drive shaft 10 in cooperation with the stepped stopper 13a. The final step includes sealing the left and right support holes 12, 13 from outside with the oil seals 78, 79.

As will be understood from the description hitherto, according to the present invention, there is provided a transmission case for motor cultivators which is integrally formed, thereby enabling an effective elimination of such joint that otherwise may leak lube oil and a favorable increase in the case rigidity as compared with separate types, thus permitting a light-weighted case design by minimized wall thickness as well as a remarkable simplification in the manufacture of transmission case.

Moreover, according to a transmission assemblying method using the integrally formed transmission case, a simple and efficient assembly of transmission is enabled by no more than using a jig of an extremely simple structure and without the need of troublesome installation work in the transmission case.

Claims (14)

1. A transmission case for motor cultivators, comprising: a casing body having a front wall, a rear wall, a pair of side walls opposing each other, a bottom wall, and an opening for opening the interior upwardly; and said walls being formed to be all integral.

2. A transmission case according to Claim 1, wherein: said opposing side walls have at least one set of first and second shaft support holes bored therein either both; and said first and second support holes have a coaxial axis thereof perpendicular to said side walls.

3. A transmission case according to Claim 2, wherein: said first support hole has a larger diameter than said second support hole.

4. A method for assemblying a multi-speed transmission for motor cultivators using a transmission case according to Claim 2 or 3, in which a shaft is supported by said first and second support holes bored in said side walls of said transmission case, said shaft having a plurality of fittable members including a gear fitted thereon, comprising the steps of: fitting said fittable members on a jig in a predetermined order, said jig having a smaller diameter than said shaft; bringing said jig through said opening of said transmission case into said transmission case; placing said jig in alignment with said coaxial line of said first and second support holes; abutting said shaft through said first support hole to said jig, rendering same coaxial therewith; and forcing said shaft into said transmission case, while keeping same coaxial with said jig and pushing said jig out of said second support hole, thereby shifting said fittable members from said jig to said shaft and fitting thereon one by one and bringing both ends of said shaft either in said first and second support holes.

5. A method according to Claim 4, wherein: said forcing step has the step of rotating said shaft to smooth said shifting of said fittable members.

6. A method according to Claim 4, wherein: said jig bringing step follows the step of fitting a second bearing in said second support hole; and said forcing step has the steps of driving said shaft to said second bearing, and pressing the distal end of said shaft into said second bearing.

7. A method according to Claim 6, wherein: said pressing step is followed by the step of forcibly fitting a first bearing through said first support hole onto the proximal end of said shaft.

8. A method according to Claim 6 wherein: said shaft has said distal end reduced in advance.

9. A method according to Claim 7 or 8, wherein: said shaft has said proximal end reduced in advance.

10. A jig for use in a method according to any one of Claims 4 to 9, wherein: said jig is provided at one end thereof with an engagement element engageable with either end of said shaft.

11. A jig according to Claim 10, wherein: said shaft has a machining center hole formed in said either end; and said engagement element comprises a projection engageable with said machining center hole.

12. A transmission case for motor cultivators, substantially as hereinbefore described, with reference to the accompanying drawings.

1 3. A method for assembling a multi-speed transmission for motor cultivators using a transmission case as claimed in Claim 2, 3 or 12, substantially as hereinbefore described, with reference to the accompanying drawings.

14. A jig for use in a method according to any one of Claims 4 to 9, substantially as hereinbefore described, with reference to the accompanying drawings.