Title of Invention

"A SEAL STRUCTURE FOR A TRANSMISSION CASE IN A VEHICLE POWER UNIT"

Abstract

In a vehicle power unit comprising an engine and a transmission mechanism having a transmission case in which a cover is connected to a case communicated with a crank case of the engine through gaskets made of resilient material, the transmission case can be sealed with the gaskets formed in a relative less-expensive cost irrespective of a variation in vehicle type. The gasket 401 extruded and formed to be a rope with its cross sectional shape being kept at its specified shape is placed between the case part 37 and the cover 38 with both ends of the gasket 401 being approached to each other.

Full Text

This invention relates to a seal structure for a transmission case in a vehicle power unit which is comprised of an engine and a transmission device , having a transmission case in which a cover is- connected to a case part communicated with a crank case of the engine through gaskets made of resilient material. [Prior Art] Such a vehicle power unit as described above is already known in reference to a gazette of the Japanese Utility Model Laid-Open No. Hei 7-42431, for example. [Problems to be Solved by the Invention] Further, the gaskets placed between the case part communicated with the crank case of the engine and the cover connected to the case part and constituting the transmission case are made of resilient material such as rubber for a sake of countermeasure against noisy sound, although the gaskets in the aforesaid prior art vehicle power unit are formed in molded shape in an endless manner in correspondence with the connecting surface between the -case part and the cover, the forming mold becomes relatively large in size to cause its molding cost to be relatively increased. In addition, it becomes necessary to prepare another forming mold every time a connecting surface shape between the case part and the cover is changed in reference to the type of engine. The present invention has been completed in view of the foregoing circumstances .and it is an object of the present invention to provide a seal structure for a transmission case in a vehicle power unit in which the transmission case can be sealed with the gaskets formed in relative less-expensive manner whatever variation in engine type may occur. [Means for Solving the Problem] Accordingly, there is provided a seal structure for a transmission case in a vehicle power unit comprising an engine and a transmission device having a transmission case in which a cover is connected to a case communicated with a crank case of said engine through gaskets made of rubber characterized in that the gaskets extruded to be formed into ropes with their cross sectional shape being kept constant are placed between the case and the cover in an arrangement in which both ends of said gaskets are closely adjacent to each other. In addition, the invention defined in Claim 2 is characterized in that the gaskets are placed between the case part and the cover with their both ends being arranged below the transmission case in a substantial parallel direction and a drain passage communicated within the transmission case and formed between both ends of the gaskets (401' 402) is opened out of .-the vehicle in a rear downward direction in respect to an advancing direction of the vehicle. [Preferred Embodiments of the Invention] The preferred embodiments of the present invention will be described in reference to the examples shown in the accompanying drawings. [Brief Description of the Drawings] (Fig. 1] This is a side elevational view for showing a scooter type motorcycle of a first preferred embodiment. [Fig. 2] This is an enlarged top plan view in cross section for showing a power unit. [Pig. 3] This is a front elevational view for showing a cover as seen from an arrow direction 3 in Fig. 2. [Fig. 4] This is a rear view of the cover. [Fig. 5] This is a sectional view taken along a line 5- 5 of Figs. 3 and 4 for showing the transmission case. [Fig. 6] This is a sectional view taken along a line 6- 6 of Figs. 3 and 4 for showing the transmission case. [Fig. 7] This is a sectional view taken along a line 7- 7 of Figs. 3 and 4 for showing the transmission case. [Fig. 8] This is a cross sectional view for showing a gasket placed in its free state. [Fig. 9] This is a side elevational view as seen from an arrow line 9 in Fig. 8. [Fig. 10] This is a sectional view corresponding to Fig, 6 of the second preferred embodiment. [Fig. 11] This is a cross sectional view for showing a gasket kept in its free state. Figs. 1 to 9 illustrate a first preferred embodiment of the present invention, wherein Fig. 1 is a side elevational view for showing a scooter type motorcycle, Fig. 2 is an enlarged top plan view in cross section for showing a power unit, Fig. 3 is a front elevational view for showing a cover as seen from an arrow direction 3 in Fig, 2, Fig. 4 is a rear view of the cover, Fig. 5 is a sectional view taken along a line 5-5 of Figs. 3 and 4 for showing the transmission case, Fig. 6 is a sectional view taken along a line 6-6 of Figs. 3 and 4 for showing the transmission case, Fig. 7 is a sectional view taken along a line 7-7 of Figs. 3 and 4 for showing the transmission case, Fig, 8 is a cross sectional view for showing a gasket placed in its free state and Fig. 9 is a side elevational view as seen from an arrow line 9 in Fig. 8. At first, in Fig. 1, a body frame F of a scooter type motorcycle V is comprised of a head pipe 15, a down-tube 16 extending downwardly from the head pipe 15 and a rear frame 17 cooperatively arranged at a lower end of the down tube 16 and extending in a rearward direction or the like, wherein a front fork 18 having a front wheel WF is supported at the head pipe 15 in such a manner that it can be steered. In addition, the body frame F is covered by a body cover C. This body cover C is comprised of a front cover 19 covering the front part of the head pipe 15 as well as an upper part of a front wheel WF; a leg shield 20 connected to the front cover 19 so as to cover a front part of the legs of a driver; a pair of right and left front side covers 21 ... connected to the front cover 19 and the leg shield 20 to cover both sides of the front body part; a floor board 22 connected to the leg shield 20 so as to support the feet of the legs of a driver; a pair of rear lower covers 23 ... connected to both front side cover 21 ... and to the floor board .22 so as to cover both side surfaces of the rear body part; and a rear upper cover 24 connected to both rear lower covers 23 ... and to the floor board 22 or the like, wherein a rear fender 25 covering the upper part of the rear wheel WR is installed at the rear part of the rear upper cover 24 and further a seat 26 where a driver sits is arranged at the upper part of the rear upper cover 24. Referring also to Fig. 2, the rear wheel WR is pivotally supported at a rear part of the power unit ? which is supported in oscillation at the body frame F. The power unit P is comprised of a. two-cycle forced, air-cooled engine E, and a continuously variable transmission M acting as a transmission mechanism for transmitting an output of the engine E to the rear wheel WR. In this way, the front part of the power unit P is supported in oscillation at the rear frame 17 in the body frame F through a link mechanism (not shown) having a supporting shaft 27 in parallel with the rotating axis of the rear wheel WR, and a rear cushion 28 is placed between the rear part of the power unit P and the rear frame 17. To the cylinder head 30 of the 2-cycle. forced air-cooled engine E is connected the front end part of the cylinder block 31 having a substantial horizontal line and then the crank case 32 is connected to the rear end of the cylinder block 31. To one end of the crank shaft 33 projected from the crank case 32 is connected a cooling fan 35 through the generator 34, and then the cooling fan 35, the cylinder head 30 and the cylinder block 31 are covered by the shroud 36. The crank case 32 is integrally assembled with the case part 37 extending toward one side of the rear wheel WR and then the transmission case 39 for the continuously variable transmission machine M is constituted by the case part 37 and the cover 38 connected to the case part 37 through the gasket 401. An inner mechanism of the continuously variable transmission machine M is mounted between the other end of the crank shaft 33 projected out of the crank case 32 and a wheel shaft 44 rotatably supported at the rear part of the transmission case 39 and this is a well-known type. Its constitution will be described as follows, wherein the crank shaft 33 is provided with a driving side transmission pulley 47 comprised of a fixed pulley half member 45 fixed to an end part of the crank shaft 33 and comprised of a movable pulley half member 46. A V-shaped annular groove 48 is formed between the fixed pulley half 45 and the rotatable pulley half 46, and an endless V-belt 49 is inserted into the annular groove 48. In addition, at the rear surface of the movable pulley half 46, a ramp plate 50 is fixed to the crank shaft and then a plurality of weight rollers 51 are stored between the ramp plate 50 and the movable pulley half 46 while being floated. Thus, when the number of rotation of the crank shaft 33 is increased during its rotating operation, the weight rollers 51 receiving a centrifugal force are moved in a radial outward direction, the movable pulley half 46 is moved in a direction to approach near the fixed pulley half 45, thereby a contact radius of the V belt 49 against both pulley half members 45, 46 can be increased. In turn, a driven shaft 52 in parallel with the crank shaft 33 is rotatably supported at the transmission case 39 and this driven shaft 52 is connected to a wheel shaft 44 of the rear wheel WR through a row of reducing gears 53. The driven shaft 52 is connected to a driven side transmission pulley 55 coaxial with the driven shaft 52 through the prior art centrifugal clutch 54. The driven side transmission pulley 55 forms a pair of sets with the driving side transmission pulley 47 and then the V-belt 49 is applied to the driving side transmission pulley 47. Referring to Figs. 3 to 7, an installing groove 56 for use in installing the gasket 401 is arranged at the connecting surface of the cover 38 in respect to the case part 37 which forms the transmission case 39 of the continuously variable transmission machine M together with the case part 37. Although the gasket 401 is of a rope form and the installing groove 56 is arranged over an entire circumference of the connecting surface, a starting end 561 and a terminal end 562 of the installing groove 56 are separated from each other. That is, the installing groove 56 is formed over an entire circumference of the cover 38 in such a manner that its starting end 561is arranged at the upper forward side of the terminal end 562 in a lower part of the rear side of the cover 38 at the transmission case 39, i.e. the lower position of the centrifugal clutch 54 and the driven transmission pulley 55. However, both ends of the installing groove 56 are formed at the cover 38 over a relative long distance L from the starting end 561 and the terminal end 562 in such a manner that they may be extended in a substantial parallel orientation while being closely approached to each other along the centrifugal clutch 54 and a rotating direction 57 of the driven transmission pulley 55, and the part where both ends of the installing groove 56 are extended in a substantial parallel direction is basically formed to be directed in a rearward and downward direction. In addition, insertion holes 58 ... are formed at a plurality of locations spaced apart in a circumferential direction at the peripheral part of the cover 38, threaded holes 59 ... are formed at the case part 37 in correspondence with these insertion holes 58 ... Bolts 60 ... inserted into each of the insertion holes 58 ... are threadably fitted to each of the threaded holes 59 ... while an irregular ring 67 made of resilient material for use in position setting the bolts 60 is placed between it and the cover 38. The cover 38 is provided with, at its far inside location from the installing groove 56, a knock hole 61 opened at one end to the connecting surface with the case part 37, and an insertion hole 62 having a smaller diameter than the knock hole 61, coaxially communicated at one end with the other end of the knock hole 62 and opened at the other end to an outer surface of the cover 38. In turn, the case part 37 is provided with a knock hole 63 having the same diameter as that of the knock hole 61 in such a manner that it is opened coaxially with the knock hole 61 at the connecting surface with the cover 38, and concurrently a threaded hole 64 having a smaller diameter than that of the knock hole 63 is arranged to be coaxial with the knock hole 63. Both ends of the knock pin 65 formed in a cylindrical shape are fitted into both knock holes 61, 63, and the bolts 66 inserted into the insertion holes 62 and the knock pins 65 are threadably fitted to the threaded holes 64. Thus, the irregular ring 67 made of resilient material is held between the engaging head 66a of the bolt 66 and the cover 38 so as to perform a position setting of the bolt 66 and a sealing action between the engaging head 66a and the cover 38. In addition, the bolt 66 is provided with an annular projection 66b which is engaged with a step part between the knock hole 63 at the side of the case part 37 and the threaded hole 64 so as to avoid an excessive fastening force acting against the gasket 401 and to prevent an excessive fastening force of the bolt 66 from being applied between the case part 37 and the cover 38. A blind-hole type knock hole 68 opened at one end is arranged at the connecting surface with the case part 37 at a position spaced apart from the knock hole 61 along a circumferential direction of the cover 38 and at a more inner location than that of the installing groove 56 of the cover 38, and the other end of the knock pin (not shown) having one end fitted to the knock hole 68 is fitted to a blind hole type knock hole (not shown) formed in the cover 38. As described above, a reason why the knock holes 61, 63, 68 ... are arranged more inwardly than the installing groove 56 consists in a prevention that external moisture content such as rain water or the like adheres to the knock pins 65 ... to cause corrosion to be produced there due to the fact that the gasket 401 is installed in the installing groove 56. . E00204- In Figs. 8 and 9, the gasket 401 is extruded and projected into a rope shape with resilient material such as rubber or the like and it has a specified cross sectional shape in which an insertion part 40a inserted into the installing groove 56 and an opposing part 40b opposing against the connecting surface of the case part 37 to the cover 38 are connected to each other in a substantial T-shape. Thus, the extremity end of the insertion part 40a is provided with a seal part 41 in which the gasket 401 is placed between them so as to constitute the transmission case 39, it is formed in the cover 38 such that both ends of the installing groove 56 may be approached to each other in a vertical direction and extended in a substantial parallel direction, resulting in that both ends of the gasket 401 are approached to each other in a vertical direction and arranged in a substantial parallel direction and a drain passage 69 communicating within the transmission case 39 is formed between both ends of the gasket 401 Further, at the rear lower part of the transmission case 39, both ends of the installing groove 56 extend in -a substantial parallel direction along the centrifugal clutch 54 and the rotating direction 57 of the driven side transmission pulley 55 and a part where both ends of the installing groove 56 extend in a substantial parallel direction is basically faced in a rearward and downward direction, thereby the drain passage 69 extends along the centrifugal clutch 54 and the rotating direction of the driven side transmission pulley 55, and further basically it faces in a rearward and downward direction and is opened outside. having a trapezoid cross sectional shape resiliently contacted with an inner end closed part of the installing groove 56, and further at both side surfaces of the insertion part 40a, two sets of a pair of projections 42, 42 ... are extended in parallel to each other in a longitudinal direction of the gasket 401. In addition, each of the projections 42, 42 ... restricts an attitude of the insertion part 40a in the installing groove 56 when the insertion part 40a is inserted into the installing groove 56, and further each of .the projections is formed to be resiliently contacted with both inner side surfaces of the installing groove 56 with such a resilient force as one capable of holding of the gasket 401 in the installing groove 56, respectively. In addition, at the opposing part 40b, a pair of seals 43, 43 resiliently contacted with the connecting surface of the case part 37 with the. cover 38 are extended in parallel from each other in a longitudinal direction of the gasket 401 with their cross sectional shapes being semi-circular one. Such a gasket 401 is installed at the installing groove 56, wherein when the case part 37 and the cover 38 are connected to each other under a state Next, an action of the first preferred embodiment will be described, wherein the gasket 401 placed between the case part 37 and the cover 38 constituting the transmission case 39 while being connected to each other is made of resilient material such as rubber or the like with its cross sectional shape being kept in its specified shape and extruded to be formed in a rope shape, so that as compared with the prior art gasket molded into an endless shape with a forming mold, the forming mold can be eliminated, its molding cost can be set in a relative less expenditure, and even if the shape of the connecting surface between the case part 37 and the cover 38 is changed, the gasket 401 of rope form is cut in response to its connecting surface shape to enable the gasket 401 corresponding to the connecting surface between the case part 37 and the cover 38 to be easily attained. Further, since the rope-shaped gasket 401 is constructed such that both ends of the gasket 401 are approached to each other in a substantial vertical parallel direction over a relative long distance L at a lower part of the transmission case 39 and a drain passage 69 is formed between both ends of the gasket 40l, water entering from outside into the transmission case 39 can be prevented as much as possible, arrangement of the drain passage in the transmission case 39 can be eliminated and the structure can be simplified while a sealing characteristic at the transmission case 39 is kept as much as possible. In addition, the drain passage 69 is basically opened outside in a rearward and downward direction in respect to an advancing direction of the motorcycle, thereby it is possible to prevent immersing of water from the drain passage 69 into the transmission case 39 as much as possible and even if water is immersed in the transmission case 39, discharging of water out of the transmission case 39 may easily be carried out. In addition, the drain passage 69 is formed to extend along the rotating direction 57 of the centrifugal clutch 54 and the driven side transmission pulley 55 so as to enable discharging of water to be facilitated. Further, both ends of the installing groove 56 are set to be in a substantial parallel direction over a relative long distance L, thereby even if there is a certain disturbance in an entire length of the gasket 40l, the disturbance can be accommodated at the substantial parallel parts of both ends of the installing groove 56 and the sealing characteristic can be assured. In addition, since the gasket 401 can be installed and held in the installing groove 56 of the cover 38, even though the gasket 401 formed in a straight shape by an extruded molding operation is bent in compliance with the shape of the installing groove 56, it is possible to avoid dropping of the gasket 401 from the gasket 38 as much as possible and improve an assembling operation during assembling of the transmission case 39. Figs. 10 and 11 illustrate a second preferred embodiment of the present invention, wherein Fig. 10 is a sectional view corresponding to Fig. 6, and Fig. 11 is a cross sectional view for showing a gasket kept in its free state. Between the case part 37 and the cover 38 constituting the transmission case 39 while being connected to each other is placed a rope-shaped gasket 402 extruded to be molded by resilient material such as rubber or the like with its cross sectional shape being kept at its specified shape. The cover 38 is provided with an installing projection 70 projected at the case part 37 in the same arrangement and shape as those of the installing groove 56 in the aforesaid first preferred embodiment, and the gasket 402 is resiliently installed at the installing projection 70. That is, the gasket 402 is formed such that a distance L1 between the extremity ends .under a normal state not applying any external force as shown in Fig. 11 becomes smaller than a width L2 of the installing projection 70, thereby it is formed to have a substantial U-shaped cross sectional shape, two -sets of a pair of seals 41', 41' ... resiliently contacted with both side surfaces of the installing projection 70 extend in parallel to each other in a longitudinal direction and each of them is projected at the inner surface of the gasket 402, and a pair of seals 43', 43' resiliently contacted with the case part 37 extend in parallel to each other in a longitudinal direction of the gasket 402 and are projectingly installed at the gasket 402. Also in the second preferred embodiment, it is also possible to attain the effects similar to those of the aforesaid first preferred embodiment. Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the aforesaid preferred embodiments and various modifications in design can be attained without departing from the scope of the invention defined in the claim. For example, both ends of the rope-shaped gasket may be approached to each other or oppositely spaced apart and in this case it is also possible to form the drain passage between both ends of the gasket. [Effects of the Invention] According to the invention defined in Claim 1 as described above, the gasket extruded and molded into a rope with its cross sectional shape being kept- at its specified shape is arranged such that the gasket is installed between the case part and the cover with both ends of the gasket being closely approached to each other, so that the gasket can be formed in a less- expensive manner while Keeping a sealing as much as possible and concurrently it becomes possible to apply the same kind of gasket irrespective of variation in machine type. In addition, according to the invention defined in Claim 2, the gasket is constructed such that, in addition to the constitution of the invention defined in Claim 1, its both ends are arranged at a lower part of the transmission case in a substantial parallel direction between the case part and the cover, the drain passage communicated in the transmission case and formed between both ends of the gasket is directed in a rearward and downward direction against an advancing direction of the vehicle and opened outside, so that an arrangement of the drain passage at the transmission case is eliminated to simplify the structure, immersion of water from the drain passage into the transmission case can be prevented as much as possible and even if water is immersed in the transmission case, it is possible to perform an easy discharging of water from within the transmission case. [Description of the Reference Numerals] 32: crank case 37: case part 38: cover 39: transmission case 401, 402: gasket 69: drain passage E: engine M: continuously variable transmission machine action, as a transmission mechanism P: power unit WE CLAIM : 1. A seal structure for a transmission case in a vehicle power unit comprising an engine (E) and a transmission device (M) having a transmission case (39) in which a cover (38) is connected to a case (37) communicated with a crank case (32) of said engine (E) through gaskets (401,402) made of rubber characterized in that the gaskets (40i, 402) extruded to be formed into ropes with their cross sectional shape being kept constant are placed between the case (37) and the cover (38) in an arrangement in which both ends of said gaskets (401, 402) are closely adjacent to each other. 2. A seal structure for a transmission case in a vehicle power unit as claimed in claim 1 wherein the gaskets (401, 402) are placed between the case part (37) and the cover (38) with their both ends being arranged below the transmission case (39) in a parallel direction and a drain passage (69) communicated within the transmission case (39) and formed between both ends of the gaskets (40i, 40a) is opened out of the vehicle in a rear downward direction in respect to an advancing direction of the vehicle. 3. A seal structure for a transmission case in a vehicle power unit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

2994-del-1996-abstract.pdf

2994-del-1996-claims.pdf

2994-del-1996-correspondence-others.pdf

2994-del-1996-correspondence-po.pdf

2994-del-1996-description (complete).pdf

2994-del-1996-drawings.pdf

2994-del-1996-form-1.pdf

2994-del-1996-form-13.pdf

2994-del-1996-form-19.pdf

2994-del-1996-form-2.pdf

2994-del-1996-form-3.pdf

2994-del-1996-form-4.pdf

2994-del-1996-form-6.pdf

2994-del-1996-gpa.pdf

2994-del-1996-petition-137.pdf

2994-del-1996-petition-138.pdf