Title of Invention	POWER TRANSMISSION UNIT FOR MOTORCYCLE
Abstract	To provide a power transmission unit for a motorcycle which can suppress the entry of foreign matter and can reduce the cost. [Solving Means] Disclosed herein is a power transmission unit 17 for a motorcycle wherein a unit case 18 of the power transmission unit 17 has an opening 33 for connecting an outside air introducing pipe 34 to supply the outside air through the outside air introducing pipe 34 into the unit case 18, thereby cooling the power transmission unit 17. A step supporting member 72 is provided substantially directly above the opening 33 of the unit case 18, and an upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72. Further, a cover member 81 is provided in the vicinity of the upper end portion 34a of the outside air introducing pipe 34. [Selected Drawing] FIG. 2

Title of Invention

POWER TRANSMISSION UNIT FOR MOTORCYCLE

Abstract

To provide a power transmission unit for a motorcycle which can suppress the entry of foreign matter and can reduce the cost. [Solving Means] Disclosed herein is a power transmission unit 17 for a motorcycle wherein a unit case 18 of the power transmission unit 17 has an opening 33 for connecting an outside air introducing pipe 34 to supply the outside air through the outside air introducing pipe 34 into the unit case 18, thereby cooling the power transmission unit 17. A step supporting member 72 is provided substantially directly above the opening 33 of the unit case 18, and an upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72. Further, a cover member 81 is provided in the vicinity of the upper end portion 34a of the outside air introducing pipe 34. [Selected Drawing] FIG. 2

Full Text	[Name of Document] Specification [Title of the Invention] Power Transmission Unit for Motorcycle [Technical Field] [0001] The present invention relates to a power transmission unit for a motorcycle designed to supply the outside air into a unit case of the power transmission unit, thereby cooling the power transmission unit. [Background Art] [0002] Conventionally known is a power transmission unit for a motorcycle designed so that a unit case of the power transmission unit is pivotably mounted to a body frame, and the unit case has an opening for supplying the outside air into the unit case, thereby cooling the power transmission unit (see Patent Document 1, for example). [Patent Document 1] Japanese Patent No. 3064389 (FIG. 2) [0003] Referring to FIG. 2 in Patent Document 1, a unit swing type engine 11 is pivotably mounted to a body frame 10, and a cleaner hose 77 is connected to a transmission case 12 constituting a part of the unit swing type engine 11. The cleaner hose 77 extends obliquely upward from the transmission case 12 toward the rear end of the vehicle, and a cooling air cleaner 7 0 is connected to the upper end (rear end) of the cleaner hose 77. The cooling air cleaner 70 is connected to the upper end of the cleaner hose 77. The cooling air cleaner 70 is fixed to a rear fender 23. With this structure, the outside air is introduced from the cooling air cleaner 70 and supplied through the cleaner hose 77 to the transmission case 12, thereby cooling the inside of the transmission case 12. [0004] However, the cleaner hose 77 extends rearward of the vehicle body and the rear end of the cleaner hose 77 is located above a rear wheel 13. Accordingly, there is a possibility that foreign matter such as dust generated around the rear wheel 13 may enter the cleaner hose 77 from the rear end thereof. To cope with this problem, the cooling air cleaner 70 must be provided to prevent the entry of foreign matter into the cleaner hose 77 in Patent Document 1, causing an increase in production cost for the vehicle. [Disclosure of the Invention] [Problem to be Solved by the Invention] [0005] It is accordingly an object of the present invention to provide a power transmission unit for a motorcycle which can suppress the entry of foreign matter and can reduce the cost. [Means for Solving the Problem] [0006] In accordance with the invention as defined in claim 1, there is provided a power transmission unit for a motorcycle designed so that a unit case of the power transmission unit is pivotably mounted to a body frame to thereby transmit the power from an engine to a rear wheel, and the unit case has an opening for connecting an outside air introducing pipe to supply the outside air through the outside air introducing pipe into the unit case, thereby cooling the power transmission unit, wherein the body frame is provided with a frame member located substantially directly above the opening of the unit case; and the outside air introducing pipe has an upper end portion fixed to the frame member. [0007] In accordance with the invention as defined in claim 2, the frame member is provided by a step supporting member for supporting a passenger step. [0008] In accordance with the invention as defined in claim 3, an inlet member is fixed to the step supporting member, and the upper end portion of the outside air introducing pipe is fixedly fitted to the inlet member. [0009] In accordance with the invention as defined in claim 4, a cover member for covering an upper opening of the outside air introducing pipe is provided in the vicinity of the upper end portion of the outside air introducing pipe. [0010] In accordance with the invention as defined in claim 5, the step supporting member is located substantially directly above the opening of the unit case, and the outside air introducing pipe has a substantially L-shaped structure. [Effect of the Invention] [0011] According to the invention as defined in claim 1, the upper end portion of the outside air introducing pipe is fixed to the frame member located substantially directly above the opening of the unit case. Accordingly, by locating the frame member apart from the rear wheel, the upper end portion of the outside air introducing pipe can be located apart from the rear wheel. As a result, the entry of foreign matter such as dust generated around the rear wheel into the outside air introducing pipe can be suppressed, and no air filter is required at the upper end portion of the outside air introducing pipe, thereby reducing a production cost for the motorcycle. As mentioned above, the frame member is located substantially directly above the opening of the unit case, and the upper end portion of the outside air introducing pipe is fixed to the frame member. Accordingly, the outside air introducing pipe can be reduced in length, thereby reducing a cost for the outside air introducing pipe. [0012] According to the invention as defined in claim 2, the step supporting member is used also as the frame member. In other words, the passenger step is supported by the step supporting member, and the upper end portion of the outside air introducing pipe is also supported by the step supporting member. Thus, the step supporting member serves also as the frame member according to claim 2. Accordingly, as compared with the case that the step supporting member and the frame member are provided as separate members, the number of parts can be reduced. [0013] According to the invention as defined in claim 3, the upper end portion of the outside air introducing pipe is fixedly fitted to the inlet member fixed to the step supporting member. Accordingly, the upper end portion of the outside air introducing pipe oscillating with the power transmission unit can be reliably supported. [0014] According to the invention as defined in claim 4, the cover member is located in the vicinity of the upper end portion of the outside air introducing pipe. Accordingly, the entry of foreign matter such as dust into the outside air introducing pipe can be suppressed. [0015] According to the invention as defined in claim 5, the outside air introducing pipe has a substantially L-shaped structure. Accordingly, foreign matter that has entered the outside air introducing pipe can be stopped at an L-shaped bent portion of this pipe, thereby preventing the entry of foreign matter into the unit case. [Best Mode for Carrying out the Invention] [0016] A preferred embodiment of the present invention will now be described with reference to the attached drawings. In the drawings, the arrows shown by "FRONT", "REAR", "RIGHT", "LEFT", "UPPER", and "LOWER" indicate the directions as viewed from the operator, and the orientation of each drawing is the same as that of the reference numerals included therein. FIG. 1 is a partially sectional, side view of a motorcycle 10 adopting the power transmission unit according to the present invention. As shown in FIG. 1, the motorcycle 10 includes a body frame 11, a link mechanism 14 having a pivot shaft 12, and a power unit 15 pivotably mounted through the link mechanism 14 to a rear portion of the body frame 11. [0017] The power unit 15 is composed of an engine 16 and a power transmission unit 17 provided on the rear side of the engine 16. The power transmission unit 17 is composed of a unit case 18 and a transmission mechanism not shown. The unit case 18 is pivotably mounted to the body frame 11 to thereby transmit the power from the engine 16 to a rear wheel 19. [0018] The body frame 11 is composed of a head pipe 21 provided at the front end, a main frame 22 connected to the head pipe 21 and extending obliquely downward therefrom, a cross frame 23 connected to the rear ends of the main frame 22 so as to extend in the lateral direction of the motorcycle 10, and a pair of right and left rear frames 24R and 24L (only the left rear frame 24L being shown) extending obliquely upward from the cross frame 23 toward the rear end to constitute a rear portion of the body frame 11. [0019] A front fork 25 is steerably mounted to the head pipe 21. A front wheel 28 is mounted to the lower ends of the front fork 25, and a steering handle 29 is mounted to the upper end of the front fork 25. [0020] The rear wheel 19 is mounted to the rear end of the power unit 15 serving also as a rear swing arm. A rear cushion unit 26 is connected between the rear end of the power unit 15 and the rear frame 24L. Reference numeral 27 denotes a cushion bracket. [0021] The link mechanism 14 is interposed between the power unit 15 and the cross frame 23, and has a support shaft 31 in the vicinity of the cross frame 23. A link member 32 extends rearward from the support shaft 31, and the pivot shaft 12 is provided at the rear end of the link member 32. [0022] The unit case 18 has a front portion 18a formed with an opening 33 for introducing the outside air, and an outside air introducing pipe 34 is connected to the opening 33 of the unit case 18. Thus, the unit case 18 has the opening 33, and the outside air introducing pipe 34 is connected to the opening 33, thereby supplying the outside air into the unit case 18 through the outside air introducing pipe 34 to cool the power transmission unit 17. [0023] The engine 16 constituting a front portion of the power unit 15 has a cylinder block 36, and an intake unit 3 7 and an exhaust unit 3 8 are connected to the cylinder block 36 of the engine 16. The intake unit 37 is composed of a primary air cleaner 41, a fuel supply device 42 connected to the primary air cleaner 41, and an intake pipe 43 connected to the fuel supply device 42 to supply an air-fuel mixture to the engine 16. Stays (not shown) project downward from the right and left rear frames 24R and 24L, and the primary air cleaner 41 is mounted to the stays of the rear frames 24R and 24L. [0024] The exhaust unit 3 8 is composed of an exhaust pipe 45 connected to the engine 16 so as to extend rearward, and a muffler 46 connected to the exhaust pipe 45 so as to extend rearward. A secondary air supply device 5 0 is mounted to the exhaust pipe 45 as a part of the exhaust unit 38 to supply a secondary air to the exhaust pipe 45, thereby cleaning exhaust gases from the exhaust unit 3 8. [0025] Reference numeral 51 denotes a secondary air passage for connecting the exhaust unit 3 8 and the secondary air supply device 50, and reference numeral 52 denotes a control pipe for connecting the intake pipe 43 and the secondary air supply device 50. [0026] A luggage box 53 is provided on the upper side of the rear frames 24R and 24L, and a fuel tank 54 is provided on the rear side of the luggage box 53. A dual seat 55 is pivotably mounted on the upper side of the luggage box 53 and the fuel tank 54 so that the dual seat 55 can be opened to expose the luggage box 53 and the fuel tank 54. Although not shown, a fuel pipe is provided to connect the fuel tank 54 and the engine 16. Reference character He denotes a helmet stored in the luggage box 53. [0027] The motorcycle 10 further includes a passenger step 57, stand 58, grab rail 59, front brake unit 61, front fender 62, cowl member 63, rear fender 64, and secondary air supply pipe 67. [0028] FIG. 2 is an enlarged view of an essential part of the motorcycle provided with a transmission unit according to the present invention. As shown in FIG. 2, the power transmission unit 17 has the unit case 18, and the unit case 18 has the opening 33 for introducing the outside air into the power transmission unit 17. The outside air introducing pipe 34 is connected to the opening 3 3 to introduce the outside air through the opening 33 into the unit case 18. [0029] The outside air introducing pipe 34 has a rear end portion 34b, which is fixedly connected to the opening 33 formed at the front portion 18a of the unit case 18. The outside air introducing pipe 34 further has an upper end portion 34a, which is fixedly connected to a step supporting member 72 as a frame member 71 extending downward from the rear frame 24L. [0030] The step supporting member 72 is mounted at an upper end portion thereof to the rear frame 24L and extends obliquely downward from the rear frame 24L. The passenger step 57 is mounted to a lower end portion 72b of the step supporting member 72. The step supporting member 72 serves also as a member for fixing the upper end portion 34a of the outside air introducing pipe 34. [0031] The step supporting member 72 is composed of a main arm 74 extending obliquely downward from the rear frame 24L and an auxiliary arm 75 extending from the rear frame 24L toward the main arm 74 and connected to a lower portion 74c of the main arm 74 to reinforce the main arm 74. The passenger step 57 is fixed to a lower end portion 74b of the main arm 74. [0032] A cover member 81 is provided in the vicinity of the upper end portion 34a of the outside air introducing pipe 34 so as to cover an upper opening 82 of the outside air introducing pipe 34. More specifically, two stay members 83 and 84 project from the auxiliary arm 75, and the cover member 81 is fixed to the auxiliary arm 75 through the stay members 83 and 84 by means of screws 85. [0033] The outside air introducing pipe 34 is a substantially L-shaped tubular member, which is composed of the upper end portion 34a having a flange 86, a vertically extending bellows portion 87, a bent portion 8 8 extending from the lower end of the bellows portion 8 7 and bent horizontally rearward, and the rear end portion 34b connected to the rear end of the bent portion 88. Thus, the upper end portion 34a communicates with the rear end portion 34b through the bellows portion 87 and the bent portion 88. [0034] The positional relation between the opening 33 of the unit case 18 and the step supporting member 72 is set so that the step supporting member 72 as the frame member 71 is positioned substantially directly above the opening 33 of the unit case 18. Reference numerals 91 and 92 denote hose bands, and reference numerals 93 denote tightening bolts for fixing the step supporting member 72 to the rear frame 24L. [0035] The step supporting member 72 serves also as the frame member 71 for supporting the upper end portion 34a of the outside air introducing pipe 34. In other words, the step supporting member 72 serves both as a member for supporting the passenger step 57 and as a member for supporting the upper end portion 34a of the outside air introducing pipe 34. [0036] Thus, the step supporting member 72 serves also as the frame member 71 in this preferred embodiment. Accordingly, as compared with the case that the step supporting member 72 and the frame member 71 are provided as separate members, the number of parts can be reduced. [0037] While the step supporting member 72 for supporting the passenger step 57 is used as the frame member 71 in this preferred embodiment, any other member positioned substantially directly above the opening 33 of the unit case 18 may be used as a member for fixing the upper end portion 34a of the outside air introducing pipe 34. [0038] The cover member 81 is located in the vicinity of the upper end portion 34a of the outside air introducing pipe 34, so that the entry of foreign matter such as dust into the outside air introducing pipe 34 can be prevented. The step supporting member 72 is located substantially directly above the opening 33, and the outside air introducing pipe 34 has a substantially L-shaped structure. Owing to the substantially L-shaped structure of the outside air introducing pipe 34, foreign matter that has entered the outside air introducing pipe 34 can be stopped at the L-shaped bent portion 88 of the pipe 34, thereby preventing the entry of foreign matter into the unit case 18. [0039] FIG. 3 is a cross section taken along the line 3-3 in FIG. 2. As shown in FIG. 3, a inlet member 94 is mounted through an L-shaped bracket 95 to the step supporting member 72, and the upper end portion 34a of the outside air introducing pipe 34 is fitted to a lower portion of the inlet member 94, thereby fixing the outside air introducing pipe 34 through the inlet member 94 to the step supporting member 72. Thus, the inlet member 94 is fixed to the step supporting member 72, and the upper end portion 34a of the outside air introducing pipe 34 is fixed to the inlet member 94. [0040] After fitting the upper end portion 34a of the outside air introducing pipe 34 to the inlet member 94, the outer circumference of the upper end portion 34a is clamped by the hose band 91. Accordingly, the upper end portion 34a of the outside air introducing pipe 34 oscillating together with the power transmission unit 17 can be reliably fixed to the inlet member 94. [0041] Further, the bellows portion 87 of the outside air introducing pipe 34 can contract and expand upon application of an external force. Accordingly, the oscillation of the outside air introducing pipe 34 transmitted from the power transmission unit (notation 17 in Fig. 1) can be absorbed by the bellows portion 87 of the outside air introducing pipe 34. [0042] The inlet member 94 has an upper opening 94a inclined about 45° with respect to the axis of the inlet member 94 and oriented laterally inward of the motorcycle. Further, the cover member 81 is provided so as to cover the upper opening 94a of the inlet member 94. [0043] The upper opening 94a of the inlet member 94 is located in the vicinity of the passenger step (notation 57 in Fig. 2) which is located at a position where it is hardly splashed with mud or the like. Further, the upper opening 94a is covered with the cover member 81. Accordingly, the entry of foreign matter such as dust into the outside air introducing pipe 34 can be suppressed, and it is not necessary to specially provide an air cleaner or the like for cleaning the outside air to be introduced into the outside air introducing pipe 34. [0044] FIG. 4 is an exploded perspective view of an outside air introducing portion including the outside air introducing pipe according to the present invention. As shown in FIG. 4, the inlet member 94 is mounted to the main arm 74 of the step supporting member 72, and the stay members 83 and 84 for mounting the cover member 81 project from the auxiliary arm 75 of the step supporting member 72 in the frontward and laterally inward directions of the motorcycle, respectively. The stay members 83 and 84 have holes 83h and 84h, respectively, and the cover member 81 has two screw mounting portions 81v and 84v respectively adapted to be aligned to the holes 83h and 84h of the stay members 83 and 84. Accordingly, the cover member 81 is fixed to the stay members 83 and 84 by inserting the screws 85 through the holes 83h and 84h and threadedly engaging the screws 85 into the screw mounting portions 81v and 84v, respectively. [0045] The step supporting member 72 is a relatively small member adapted to be mounted on the rear frame 24L. Accordingly, even when it is necessary to perform additional working for fixing the upper end portion 34a of the outside air introducing pipe 34 to the step supporting member 72, the step supporting member 72 can be easily mounted/demounted, handled, and worked. More specifically, the structure for fixing the upper end portion 34a of the outside air introducing pipe 34 to the step supporting member 72 is only a structure of mounting the inlet member 94 and the two stay members 83 and 84 to the step supporting member 72, so that an increase in cost for fixation of the outside air introducing pipe 34 can be avoided. [0046] The operation of the power transmission unit as mentioned above will now be described. Referring back to FIG. 2, the upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72 as the frame member 71 located substantially directly above the opening 33. Further, the step supporting member 72 is located apart from the rear wheel (notation 19 in Fig. 1) . Accordingly, the upper end portion 34a of the outside air introducing pipe 34 can be located apart from the rear wheel 19. As a result, the entry of foreign matter such as dust generated around the rear wheel 19 into the outside air introducing pipe 34 can be suppressed, and no air filter is required at the upper end portion 34a, thereby reducing a production cost for the motorcycle. [0047] As mentioned above, the step suppressing member 72 is located substantially directly above the opening 33, and the upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72. Accordingly, the outside air introducing pipe 34 can be reduced in length, thereby reducing a cost for the outside air introducing pipe 34. In addition, the upper end portion 34a as an air inlet portion is located at a relatively high level, so that it is possible to provide a structure for suppressing the entry of water into the unit case 18. Further, according to the structure of the present invention, no opening is formed in the body frame 11, so that there is no possibility of reduction in rigidity of the body frame 11. [0048] In claim 1, the frame member for fixing the upper end portion of the outside air introducing pipe may be provided as a member separate from the step supporting member. In other words, the frame member and the step supporting member may be separate members. In claim 2, the upper end portion of the outside air introducing pipe may be directly fixed to the step supporting member. [0049] In claims 1 to 3, the cover member may not be provided, that is, it is not an essential member. In claims 2 to 4, the shape of the outside air introducing pipe is not limited, but various shapes such as L-shape, J-shape, and I-shape may be adopted. [Industrial Applicability] [0050] The present invention is suitably applicable to a power transmission unit for a motorcycle. [Brief Description of the Drawings] [0051] [FIG. 1] FIG. 1 is a partially sectional, side view of a motorcycle adopting the power transmission unit according to the present invention. [FIG. 2] FIG. 2 is an enlarged view of an essential part of the motorcycle according to the present invention. [FIG. 3] FIG. 3 is a cross section taken along the line 3-3 in FIG. 2. [FIG. 4] FIG. 4 is an exploded perspective view of an outside air introducing portion for the power transmission unit according to the present invention. [Description of Reference Symbols] [0052] 10: motorcycle 11: body frame 16: engine 17: power transmission unit 18: unit case 19: rear wheel 33: opening 34: outside air introducing, pipe 34a: upper end portion of the outside air introducing pipe 57: passenger step 71: frame member 72: step supporting member 81: cover member 82: upper opening of the outside air introducing pipe 94: inlet member [Name of Document] Drawings [FIG. 1] UPPER LOWER FRONT REAR [FIG. 2] UPPER LOWER FRONT REAR [FIG. 3] UPPER LOWER RIGHT LEFT [FIG. 4] UPPER LOWER FRONT REAR RIGHT LEFT [Name of Document] Claims [Claim 1] A power transmission unit for a motorcycle designed so that a unit case of said power transmission unit is pivotably mounted to a body frame to thereby transmit the power from an engine to a rear wheel, and said unit case has an opening for connecting an outside air introducing pipe to supply the outside air through said outside air introducing pipe into said unit case, thereby cooling said power transmission unit, wherein: said body frame is provided with a frame member located substantially directly above said opening of said unit case; and said outside air introducing pipe has an upper end portion fixed to said frame member. [Claim 2] The power transmission unit for the motorcycle according to claim 1, wherein said frame member is provided by a step supporting member for supporting a passenger step. [Claim 3] The power transmission unit for the motorcycle according to claim 2, wherein an inlet member is fixed to said step supporting member, and said upper end portion of said outside air introducing pipe is fixedly fitted to said inlet member. [Claim 4] The power transmission unit for the motorcycle according to claim 1, 2, or 3, wherein a cover member for covering an upper opening of said outside air introducing pipe is provided in the vicinity of said upper end portion of said outside air introducing pipe. [Claim 5] The power transmission unit for the motorcycle according to claim 2, 3, or 4, wherein said step supporting member is located substantially directly above said opening of said unit case, and said outside air introducing pipe has a substantially L-shaped structure. Dated this 12 day of December 2006

Full Text

[Name of Document] Specification [Title of the Invention]
Power Transmission Unit for Motorcycle [Technical Field] [0001]
The present invention relates to a power transmission unit for a motorcycle designed to supply the outside air into a unit case of the power transmission unit, thereby cooling the power transmission unit. [Background Art] [0002]
Conventionally known is a power transmission unit for a motorcycle designed so that a unit case of the power transmission unit is pivotably mounted to a body frame, and the unit case has an opening for supplying the outside air into the unit case, thereby cooling the power transmission unit (see Patent Document 1, for example). [Patent Document 1]
Japanese Patent No. 3064389 (FIG. 2) [0003]
Referring to FIG. 2 in Patent Document 1, a unit swing type engine 11 is pivotably mounted to a body frame 10, and a cleaner hose 77 is connected to a transmission case 12 constituting a part of the unit swing type engine

11. The cleaner hose 77 extends obliquely upward from the transmission case 12 toward the rear end of the vehicle, and a cooling air cleaner 7 0 is connected to the upper end (rear end) of the cleaner hose 77. The cooling air cleaner 70 is connected to the upper end of the cleaner hose 77. The cooling air cleaner 70 is fixed to a rear fender 23. With this structure, the outside air is introduced from the cooling air cleaner 70 and supplied through the cleaner hose 77 to the transmission case 12, thereby cooling the inside of the transmission case 12.
[0004]
However, the cleaner hose 77 extends rearward of the vehicle body and the rear end of the cleaner hose 77 is located above a rear wheel 13. Accordingly, there is a possibility that foreign matter such as dust generated around the rear wheel 13 may enter the cleaner hose 77 from the rear end thereof. To cope with this problem, the cooling air cleaner 70 must be provided to prevent the entry of foreign matter into the cleaner hose 77 in Patent Document 1, causing an increase in production cost for the vehicle.
[Disclosure of the Invention]
[Problem to be Solved by the Invention]
[0005]

It is accordingly an object of the present invention to provide a power transmission unit for a motorcycle which can suppress the entry of foreign matter and can reduce the cost. [Means for Solving the Problem] [0006]
In accordance with the invention as defined in claim 1, there is provided a power transmission unit for a motorcycle designed so that a unit case of the power transmission unit is pivotably mounted to a body frame to thereby transmit the power from an engine to a rear wheel, and the unit case has an opening for connecting an outside air introducing pipe to supply the outside air through the outside air introducing pipe into the unit case, thereby cooling the power transmission unit, wherein the body frame is provided with a frame member located substantially directly above the opening of the unit case; and the outside air introducing pipe has an upper end portion fixed to the frame member. [0007]
In accordance with the invention as defined in claim 2, the frame member is provided by a step supporting member for supporting a passenger step. [0008]

In accordance with the invention as defined in claim 3, an inlet member is fixed to the step supporting member, and the upper end portion of the outside air
introducing pipe is fixedly fitted to the inlet member.
[0009]
In accordance with the invention as defined in claim 4, a cover member for covering an upper opening of the outside air introducing pipe is provided in the vicinity of the upper end portion of the outside air introducing pipe.
[0010]
In accordance with the invention as defined in claim 5, the step supporting member is located substantially directly above the opening of the unit case, and the outside air introducing pipe has a substantially L-shaped structure.
[Effect of the Invention]
[0011]
According to the invention as defined in claim 1, the upper end portion of the outside air introducing pipe is fixed to the frame member located substantially directly above the opening of the unit case. Accordingly, by locating the frame member apart from the rear wheel, the upper end portion of the outside air introducing pipe

can be located apart from the rear wheel. As a result, the entry of foreign matter such as dust generated around the rear wheel into the outside air introducing pipe can be suppressed, and no air filter is required at the upper end portion of the outside air introducing pipe, thereby reducing a production cost for the motorcycle.
As mentioned above, the frame member is located substantially directly above the opening of the unit case, and the upper end portion of the outside air introducing pipe is fixed to the frame member. Accordingly, the outside air introducing pipe can be reduced in length, thereby reducing a cost for the outside air introducing pipe. [0012]
According to the invention as defined in claim 2, the step supporting member is used also as the frame member. In other words, the passenger step is supported by the step supporting member, and the upper end portion of the outside air introducing pipe is also supported by the step supporting member.
Thus, the step supporting member serves also as the frame member according to claim 2. Accordingly, as compared with the case that the step supporting member and the frame member are provided as separate members,

the number of parts can be reduced.
[0013]
According to the invention as defined in claim 3, the upper end portion of the outside air introducing pipe is fixedly fitted to the inlet member fixed to the step supporting member. Accordingly, the upper end portion of the outside air introducing pipe oscillating with the power transmission unit can be reliably supported.
[0014]
According to the invention as defined in claim 4, the cover member is located in the vicinity of the upper end portion of the outside air introducing pipe. Accordingly, the entry of foreign matter such as dust into the outside air introducing pipe can be suppressed.
[0015]
According to the invention as defined in claim 5, the outside air introducing pipe has a substantially L-shaped structure. Accordingly, foreign matter that has entered the outside air introducing pipe can be stopped at an L-shaped bent portion of this pipe, thereby preventing the entry of foreign matter into the unit case.
[Best Mode for Carrying out the Invention]
[0016]
A preferred embodiment of the present invention

will now be described with reference to the attached drawings. In the drawings, the arrows shown by "FRONT", "REAR", "RIGHT", "LEFT", "UPPER", and "LOWER" indicate the directions as viewed from the operator, and the orientation of each drawing is the same as that of the reference numerals included therein.
FIG. 1 is a partially sectional, side view of a motorcycle 10 adopting the power transmission unit according to the present invention. As shown in FIG. 1, the motorcycle 10 includes a body frame 11, a link mechanism 14 having a pivot shaft 12, and a power unit 15 pivotably mounted through the link mechanism 14 to a rear portion of the body frame 11.
[0017]
The power unit 15 is composed of an engine 16 and a power transmission unit 17 provided on the rear side of the engine 16. The power transmission unit 17 is composed of a unit case 18 and a transmission mechanism not shown. The unit case 18 is pivotably mounted to the body frame 11 to thereby transmit the power from the engine 16 to a rear wheel 19.
[0018]
The body frame 11 is composed of a head pipe 21 provided at the front end, a main frame 22 connected to

the head pipe 21 and extending obliquely downward therefrom, a cross frame 23 connected to the rear ends of the main frame 22 so as to extend in the lateral direction of the motorcycle 10, and a pair of right and left rear frames 24R and 24L (only the left rear frame 24L being shown) extending obliquely upward from the cross frame 23 toward the rear end to constitute a rear portion of the body frame 11. [0019]
A front fork 25 is steerably mounted to the head pipe 21. A front wheel 28 is mounted to the lower ends of the front fork 25, and a steering handle 29 is mounted to the upper end of the front fork 25. [0020]
The rear wheel 19 is mounted to the rear end of the power unit 15 serving also as a rear swing arm. A rear cushion unit 26 is connected between the rear end of the power unit 15 and the rear frame 24L. Reference numeral 27 denotes a cushion bracket. [0021]
The link mechanism 14 is interposed between the power unit 15 and the cross frame 23, and has a support shaft 31 in the vicinity of the cross frame 23. A link member 32 extends rearward from the support shaft 31, and

the pivot shaft 12 is provided at the rear end of the
link member 32.
[0022]
The unit case 18 has a front portion 18a formed with an opening 33 for introducing the outside air, and an outside air introducing pipe 34 is connected to the opening 33 of the unit case 18.
Thus, the unit case 18 has the opening 33, and the outside air introducing pipe 34 is connected to the opening 33, thereby supplying the outside air into the unit case 18 through the outside air introducing pipe 34 to cool the power transmission unit 17. [0023]
The engine 16 constituting a front portion of the power unit 15 has a cylinder block 36, and an intake unit 3 7 and an exhaust unit 3 8 are connected to the cylinder block 36 of the engine 16.
The intake unit 37 is composed of a primary air cleaner 41, a fuel supply device 42 connected to the primary air cleaner 41, and an intake pipe 43 connected to the fuel supply device 42 to supply an air-fuel mixture to the engine 16. Stays (not shown) project downward from the right and left rear frames 24R and 24L, and the primary air cleaner 41 is mounted to the stays of

the rear frames 24R and 24L. [0024]
The exhaust unit 3 8 is composed of an exhaust pipe 45 connected to the engine 16 so as to extend rearward, and a muffler 46 connected to the exhaust pipe 45 so as to extend rearward.
A secondary air supply device 5 0 is mounted to the exhaust pipe 45 as a part of the exhaust unit 38 to supply a secondary air to the exhaust pipe 45, thereby cleaning exhaust gases from the exhaust unit 3 8. [0025]
Reference numeral 51 denotes a secondary air passage for connecting the exhaust unit 3 8 and the secondary air supply device 50, and reference numeral 52 denotes a control pipe for connecting the intake pipe 43 and the secondary air supply device 50. [0026]
A luggage box 53 is provided on the upper side of the rear frames 24R and 24L, and a fuel tank 54 is provided on the rear side of the luggage box 53. A dual seat 55 is pivotably mounted on the upper side of the luggage box 53 and the fuel tank 54 so that the dual seat 55 can be opened to expose the luggage box 53 and the fuel tank 54.

Although not shown, a fuel pipe is provided to connect the fuel tank 54 and the engine 16. Reference character He denotes a helmet stored in the luggage box 53. [0027]
The motorcycle 10 further includes a passenger step 57, stand 58, grab rail 59, front brake unit 61, front fender 62, cowl member 63, rear fender 64, and secondary air supply pipe 67. [0028]
FIG. 2 is an enlarged view of an essential part of the motorcycle provided with a transmission unit according to the present invention. As shown in FIG. 2, the power transmission unit 17 has the unit case 18, and the unit case 18 has the opening 33 for introducing the outside air into the power transmission unit 17. The outside air introducing pipe 34 is connected to the opening 3 3 to introduce the outside air through the opening 33 into the unit case 18. [0029]
The outside air introducing pipe 34 has a rear end portion 34b, which is fixedly connected to the opening 33 formed at the front portion 18a of the unit case 18. The outside air introducing pipe 34 further has an upper end

portion 34a, which is fixedly connected to a step supporting member 72 as a frame member 71 extending downward from the rear frame 24L.
[0030]
The step supporting member 72 is mounted at an upper end portion thereof to the rear frame 24L and extends obliquely downward from the rear frame 24L. The passenger step 57 is mounted to a lower end portion 72b of the step supporting member 72. The step supporting member 72 serves also as a member for fixing the upper end portion 34a of the outside air introducing pipe 34.
[0031]
The step supporting member 72 is composed of a main arm 74 extending obliquely downward from the rear frame 24L and an auxiliary arm 75 extending from the rear frame 24L toward the main arm 74 and connected to a lower portion 74c of the main arm 74 to reinforce the main arm 74. The passenger step 57 is fixed to a lower end portion 74b of the main arm 74.
[0032]
A cover member 81 is provided in the vicinity of the upper end portion 34a of the outside air introducing pipe 34 so as to cover an upper opening 82 of the outside air introducing pipe 34. More specifically, two stay

members 83 and 84 project from the auxiliary arm 75, and the cover member 81 is fixed to the auxiliary arm 75 through the stay members 83 and 84 by means of screws 85.
[0033]
The outside air introducing pipe 34 is a substantially L-shaped tubular member, which is composed of the upper end portion 34a having a flange 86, a vertically extending bellows portion 87, a bent portion 8 8 extending from the lower end of the bellows portion 8 7 and bent horizontally rearward, and the rear end portion 34b connected to the rear end of the bent portion 88. Thus, the upper end portion 34a communicates with the rear end portion 34b through the bellows portion 87 and the bent portion 88.
[0034]
The positional relation between the opening 33 of the unit case 18 and the step supporting member 72 is set so that the step supporting member 72 as the frame member 71 is positioned substantially directly above the opening 33 of the unit case 18.
Reference numerals 91 and 92 denote hose bands, and reference numerals 93 denote tightening bolts for fixing the step supporting member 72 to the rear frame 24L.
[0035]

The step supporting member 72 serves also as the frame member 71 for supporting the upper end portion 34a of the outside air introducing pipe 34. In other words, the step supporting member 72 serves both as a member for supporting the passenger step 57 and as a member for supporting the upper end portion 34a of the outside air introducing pipe 34.
[0036]
Thus, the step supporting member 72 serves also as the frame member 71 in this preferred embodiment. Accordingly, as compared with the case that the step supporting member 72 and the frame member 71 are provided as separate members, the number of parts can be reduced.
[0037]
While the step supporting member 72 for supporting the passenger step 57 is used as the frame member 71 in this preferred embodiment, any other member positioned substantially directly above the opening 33 of the unit case 18 may be used as a member for fixing the upper end portion 34a of the outside air introducing pipe 34.
[0038]
The cover member 81 is located in the vicinity of the upper end portion 34a of the outside air introducing pipe 34, so that the entry of foreign matter such as dust

into the outside air introducing pipe 34 can be prevented.
The step supporting member 72 is located substantially directly above the opening 33, and the outside air introducing pipe 34 has a substantially L-shaped structure.
Owing to the substantially L-shaped structure of the outside air introducing pipe 34, foreign matter that has entered the outside air introducing pipe 34 can be stopped at the L-shaped bent portion 88 of the pipe 34, thereby preventing the entry of foreign matter into the unit case 18. [0039]
FIG. 3 is a cross section taken along the line 3-3 in FIG. 2. As shown in FIG. 3, a inlet member 94 is mounted through an L-shaped bracket 95 to the step supporting member 72, and the upper end portion 34a of the outside air introducing pipe 34 is fitted to a lower portion of the inlet member 94, thereby fixing the outside air introducing pipe 34 through the inlet member 94 to the step supporting member 72.
Thus, the inlet member 94 is fixed to the step supporting member 72, and the upper end portion 34a of the outside air introducing pipe 34 is fixed to the inlet member 94.

[0040]
After fitting the upper end portion 34a of the outside air introducing pipe 34 to the inlet member 94, the outer circumference of the upper end portion 34a is clamped by the hose band 91.
Accordingly, the upper end portion 34a of the outside air introducing pipe 34 oscillating together with the power transmission unit 17 can be reliably fixed to the inlet member 94. [0041]
Further, the bellows portion 87 of the outside air introducing pipe 34 can contract and expand upon application of an external force.
Accordingly, the oscillation of the outside air introducing pipe 34 transmitted from the power transmission unit (notation 17 in Fig. 1) can be absorbed by the bellows portion 87 of the outside air introducing pipe 34. [0042]
The inlet member 94 has an upper opening 94a
inclined about 45° with respect to the axis of the inlet member 94 and oriented laterally inward of the motorcycle.
Further, the cover member 81 is provided so as to cover
the upper opening 94a of the inlet member 94.

[0043]
The upper opening 94a of the inlet member 94 is located in the vicinity of the passenger step (notation 57 in Fig. 2) which is located at a position where it is hardly splashed with mud or the like. Further, the upper opening 94a is covered with the cover member 81. Accordingly, the entry of foreign matter such as dust into the outside air introducing pipe 34 can be suppressed, and it is not necessary to specially provide an air cleaner or the like for cleaning the outside air to be introduced into the outside air introducing pipe 34.
[0044]
FIG. 4 is an exploded perspective view of an outside air introducing portion including the outside air introducing pipe according to the present invention. As shown in FIG. 4, the inlet member 94 is mounted to the main arm 74 of the step supporting member 72, and the stay members 83 and 84 for mounting the cover member 81 project from the auxiliary arm 75 of the step supporting member 72 in the frontward and laterally inward directions of the motorcycle, respectively. The stay members 83 and 84 have holes 83h and 84h, respectively, and the cover member 81 has two screw mounting portions 81v and 84v respectively adapted to be aligned to the

holes 83h and 84h of the stay members 83 and 84. Accordingly, the cover member 81 is fixed to the stay members 83 and 84 by inserting the screws 85 through the holes 83h and 84h and threadedly engaging the screws 85 into the screw mounting portions 81v and 84v, respectively.
[0045]
The step supporting member 72 is a relatively small member adapted to be mounted on the rear frame 24L. Accordingly, even when it is necessary to perform additional working for fixing the upper end portion 34a of the outside air introducing pipe 34 to the step supporting member 72, the step supporting member 72 can be easily mounted/demounted, handled, and worked. More specifically, the structure for fixing the upper end portion 34a of the outside air introducing pipe 34 to the step supporting member 72 is only a structure of mounting the inlet member 94 and the two stay members 83 and 84 to the step supporting member 72, so that an increase in cost for fixation of the outside air introducing pipe 34 can be avoided.
[0046]
The operation of the power transmission unit as mentioned above will now be described.

Referring back to FIG. 2, the upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72 as the frame member 71 located substantially directly above the opening 33. Further, the step supporting member 72 is located apart from the rear wheel (notation 19 in Fig. 1) . Accordingly, the upper end portion 34a of the outside air introducing pipe 34 can be located apart from the rear wheel 19. As a result, the entry of foreign matter such as dust generated around the rear wheel 19 into the outside air introducing pipe 34 can be suppressed, and no air filter is required at the upper end portion 34a, thereby reducing a production cost for the motorcycle. [0047]
As mentioned above, the step suppressing member 72 is located substantially directly above the opening 33, and the upper end portion 34a of the outside air introducing pipe 34 is fixed to the step supporting member 72. Accordingly, the outside air introducing pipe 34 can be reduced in length, thereby reducing a cost for the outside air introducing pipe 34. In addition, the upper end portion 34a as an air inlet portion is located at a relatively high level, so that it is possible to provide a structure for suppressing the entry of water

into the unit case 18.
Further, according to the structure of the present invention, no opening is formed in the body frame 11, so that there is no possibility of reduction in rigidity of the body frame 11. [0048]
In claim 1, the frame member for fixing the upper end portion of the outside air introducing pipe may be provided as a member separate from the step supporting member. In other words, the frame member and the step supporting member may be separate members.
In claim 2, the upper end portion of the outside air introducing pipe may be directly fixed to the step supporting member. [0049]
In claims 1 to 3, the cover member may not be provided, that is, it is not an essential member.
In claims 2 to 4, the shape of the outside air introducing pipe is not limited, but various shapes such as L-shape, J-shape, and I-shape may be adopted. [Industrial Applicability] [0050]
The present invention is suitably applicable to a power transmission unit for a motorcycle.

[Brief Description of the Drawings]
[0051]
[FIG. 1]
FIG. 1 is a partially sectional, side view of a motorcycle adopting the power transmission unit according to the present invention. [FIG. 2]
FIG. 2 is an enlarged view of an essential part of the motorcycle according to the present invention. [FIG. 3]
FIG. 3 is a cross section taken along the line 3-3 in FIG. 2. [FIG. 4]
FIG. 4 is an exploded perspective view of an outside air introducing portion for the power transmission unit according to the present invention. [Description of Reference Symbols] [0052]
10: motorcycle 11: body frame 16: engine 17: power transmission unit 18: unit case 19: rear wheel 33: opening 34: outside air introducing, pipe 34a: upper end portion of the outside air introducing pipe 57: passenger step 71: frame member 72: step supporting member 81: cover member 82: upper opening of the outside

air introducing pipe 94: inlet member

[Name of Document] Drawings
[FIG. 1] UPPER LOWER FRONT REAR
[FIG. 2] UPPER LOWER FRONT REAR
[FIG. 3] UPPER LOWER RIGHT LEFT
[FIG. 4] UPPER LOWER FRONT REAR RIGHT LEFT

[Name of Document] Claims [Claim 1]
A power transmission unit for a motorcycle designed so that a unit case of said power transmission unit is pivotably mounted to a body frame to thereby transmit the power from an engine to a rear wheel, and said unit case has an opening for connecting an outside air introducing pipe to supply the outside air through said outside air introducing pipe into said unit case, thereby cooling said power transmission unit, wherein:
said body frame is provided with a frame member located substantially directly above said opening of said unit case; and
said outside air introducing pipe has an upper end portion fixed to said frame member. [Claim 2]
The power transmission unit for the motorcycle according to claim 1, wherein said frame member is provided by a step supporting member for supporting a passenger step. [Claim 3]
The power transmission unit for the motorcycle according to claim 2, wherein an inlet member is fixed to said step supporting member, and said upper end portion

of said outside air introducing pipe is fixedly fitted to said inlet member. [Claim 4]
The power transmission unit for the motorcycle according to claim 1, 2, or 3, wherein a cover member for covering an upper opening of said outside air introducing pipe is provided in the vicinity of said upper end portion of said outside air introducing pipe. [Claim 5]
The power transmission unit for the motorcycle according to claim 2, 3, or 4, wherein said step supporting member is located substantially directly above said opening of said unit case, and said outside air introducing pipe has a substantially L-shaped structure.
Dated this 12 day of December 2006

Documents:

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Patent Number

232309

Indian Patent Application Number

2301/CHE/2006

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

16-Mar-2009

Date of Filing

12-Dec-2006

Name of Patentee

HONDA MOTOR CO., LTD

Applicant Address

1-1, MINAMI-AOYAMA 2-CHOME, MINATO-KU, TOKYO 107-8556,

Inventors:

#	Inventor's Name	Inventor's Address
1	YANAGIDA, TAKAYUKI	C/O HONDA R&D CO., LTD,, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193,

PCT International Classification Number

B62J15/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2005-363846	2005-12-16	Japan