Mounting structure of vibration isolating member to shroud

Abstract: To mount a vibration isolating member easily at low costs, mounting holes 20 are formed through a platelike vibration isolating member 10, and projections 17 integrally projecting from a shroud 9 are forced into the mounting holes 20, thereby temporarily mounting the vibration isolating member 10 on the shroud 9. In this condition, the shroud 9 is mounted to the cylinder head 8, thereby holding the vibration isolating member 10 between the inner surface of the shroud 9 and fins 22 of the cylinder head 8. Many similar vibration isolating members 10 can be continuously formed by punching a belt-shaped stock.

Description: The present invention relates to a structure for mounting a vibration isolating member on a shroud provided so as to cover an air-cooled engine for a motorcycle or the like. In Japanese Utility Model Laid-open No. 59-139514, there is shown a forced air-cooled engine for a motorcycle provided with a shroud, and there is disclosed a structure of sandwiching a vibration isolating member between fins of a cylinder head and the inner surface of the shroud. As another known structure for mounting a vibration isolating member to a shroud, the vibration isolating member is formed with projections, and the projections are forced into engaging holes formed through the shroud, thereby mounting the vibration isolating member to the shroud. In the former method of sandwiching the vibration isolating member as disclosed in the above publication, it is sometimes troublesome to precisely position the vibration isolating member. On the other hand, in the latter method of forming the projections on the vibration isolating member, the vibration isolating member must be formed integrally with the projections by using a mold, causing an increase in cost. Furthermore, since the projections are formed of an elastic material, it is sometimes troublesome to mount the vibration isolating member to the shroud. According to the present invention solving the above problem, there is provided a mounting structure having the features of claim 1. The projections are formed on the inner surface of the shroud, and the mounting holes to be engaged with the projections are formed through the vibration isolating member. The vibration isolating member can be mounted on the shroud by forcing the projections of the shroud into the mounting holes preliminarily formed through the vibration isolating member. The projections are integral with the shroud and are relatively rigid, whereas the mounting holes are formed through the vibration isolating member which is an elastic member. Accordingly, the projections can be easily forced into the mounting holes, so that the vibration isolating member can be mounted on the shroud quickly and simply. Furthermore, since the vibration isolating member can be temporarily mounted on the shroud as mentioned above, the vibration isolating member can be precisely positioned. Furthermore, the vibration isolating member must only be formed with the mounting holes. Accordingly, the mounting holes can be formed simultaneously with or after the step of forming the vibration isolating member from a platelike stock. Further, unlike the prior art, it is unnecessary to use an expensive mold including portions for molding projections in forming the vibration isolating member. A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is an enlarged sectional view of an essential part according to a preferred embodiment of the present invention. FIG. 2 is a horizontal sectional view of a swing type power unit according to the preferred embodiment. FIG. 3 is a plan view of a vibration isolating member. FIG. 4 is a plan view of a shroud. FIG. 2 is a horizontal sectional view of a swing type power unit for a scooter. The swing type power unit is provided with a two-cycle engine 1, a V-belt transmission 4 connected to one end of a crankshaft 3 traversing a crankcase 2, and a forced-air cooling fan 5 mounted on the other end of the crankshaft 3. The forced-air cooling fan 5 is surrounded by a duct cover 6. A cylinder 7 and a cylinder head 8 of the two-cycle engine 1 are surrounded by a shroud 9. A vibration isolating member 10 is mounted on the inner surface of the shroud 9. The duct cover 6 and the shroud 9 are continuously connected, so that the outside air taken from slits of the duct cover 6 is fed to around the cylinder 7 and the cylinder head 8 inside the duct cover 6 and the shroud 9 by the forced-air cooling fan 5 as shown by the arrows in FIG. 2, thereby forcibly cooling the cylinder 7 and the cylinder head 8. FIG. 1 is an enlarged sectional view of a portion surrounding the cylinder head 8, in which the cross section of the shroud 9 is taken substantially along the line 1-1 in FIG. 4. FIG. 3 is a plan view of the vibration isolating member 10, and FIG. 4 is a plan view of the shroud 9. As apparent from FIGS. 1 and 4, the shroud 9 is formed at its top with a plug hole 12 for allowing insertion of a plug 11, and also with a plurality of bolt insert holes 15 for allowing insertion of bolts 14 for mounting the shroud 9 to bosses 13 of the cylinder head 8. A rubber seal 16 is preliminarily mounted on each bolt 14, so that after the bolts 14 have been inserted through the respective bolt insert holes 15 and secured to the respective bosses 13, the bolt insert holes 15 are automatically sealed by the respective rubber seals 16. The shroud 9 is integrally formed with a plurality of (four in this preferred embodiment) projections 17 projecting downward from the inner surface of the shroud 9 (i.e., toward the cylinder head 8). The projections 17 are so located as to surround the plug hole 12. The shroud 9 is formed by molding a suitable synthetic resin. As apparent from FIGS. 1 and 3, the vibration isolating member 10 is formed of a suitable elastic material such as rubber, and has a platelike shape and a size enough to cover the top portion of the cylinder head 8. The vibration isolating member 10 is formed with a plug hole 18, bolt insert holes 19, and mounting holes 20 respectively corresponding to the plug hole 12, the bolt insert holes 15, and the projections 17 of the shroud 9. Reference numerals 21 denote escape portions cut out to insert bolts. Each mounting hole 20 is smaller in diameter than each projection 17, so that when each projection 17 is forced into the corresponding mounting hole 20, the diameter of each mounting hole 20 is enlarged by elastic deformation of the vibration isolating member 10, and simultaneously each projection 17 is held within the corresponding mounting hole 20 by the elastic restoring force of the vibration isolating member 10. Thus, the vibration isolating member 10 can be temporarily mounted on the inner surface of the shroud 9. When the shroud 9 with the vibration isolating member 10 is mounted around the two-cycle engine 1, the vibration isolating member 10 temporarily mounted on the inner surface of the shroud 9 is held between the shroud 9 and a plurality of fins 22 formed on the cylinder head 8 so as to project in parallel to each other toward the shroud 9. The operation of the preferred embodiment will now be described. First, the vibration isolating member 10 is placed on the inner surface of the shroud 9 before mounting the shroud 9 around the two-cycle engine 1. In this condition, the projections 17 of the shroud 9 are forced into the respective mounting holes 20 of the vibration isolating member 10, with the result that the vibration isolating member 10 is elastically curved along the inner surface of the shroud 9 and is temporarily mounted on the inner surface of the shroud 9. At this time, the projections 17 can be easily forced into the respective mounting holes 20, because the projections 17 are relatively rigid, whereas the vibration isolating member 10 is an elastic member. Accordingly, as compared with the prior art structure that the projections formed as a part of an elastic member are forced into the engaging holes of the shroud, the engagement of the projections 17 into the mounting holes 20 can be easily carried out. Then, the shroud 9 with the vibration isolating member 10 is so placed as to surround the cylinder 7 and the cylinder head 8, so that the inner surface of the vibration isolating member 10 abuts against the upper end surfaces of the fins 22 of the cylinder head 8. In this condition, the shroud 9 is fixed to the cylinder head 8 by using the bolts 14, thereby securely holding the vibration isolating member 10 between the shroud 9 and the fins 22. Since the vibration isolating member 10 is temporarily mounted on the shroud 9, the parts can be well handled. Further, since the vibration isolating member 10 can be precisely positioned, the workability in mounting the vibration isolating member 10 can be greatly improved. Moreover, after mounting the shroud 9 around the two-cycle engine 1, the vibration isolating member 10 can be stably fixed with no slip of position by the engagement of the projections 17 with the mounting holes 20 and by the holding pressure between the shroud 9 and the fins 22. In addition, since the vibration isolating member 10 is formed in a platelike shape, all of the plug hole 18, the bolt insert holes 19, the mounting holes 20, and the escape portions 21 can be simultaneously formed only by punching a belt-shaped stock. Further, many similar vibration isolating members can be continuously manufactured with a high efficiency. Accordingly, unlike the prior art vibration isolating member integrally formed with projections, any specific mold for forming the vibration isolating member 10 is not necessary, thereby realizing high mass-productivity and cost reduction. The formation of the mounting holes 20 may be carried out after punching the belt-shaped stock. Furthermore, since the mounting holes 20 are formed in the vibration isolating member 10, the shroud 9 must only have the projections 17 instead. Accordingly, the number of openings to be formed in the shroud 9 can be reduced to thereby allow the forced cooling air to be efficiently introduced to the surrounding area of the cylinder 7 and the cylinder head 8. To mount a vibration isolating member easily at low costs, mounting holes 20 are formed through a platelike vibration isolating member 10, and projections 17 integrally projecting from a shroud 9 are forced into the mounting holes 20, thereby temporarily mounting the vibration isolating member 10 on the shroud 9. In this condition, the shroud 9 is mounted to the cylinder head 8, thereby holding the vibration isolating member 10 between the inner surface of the shroud 9 and fins 22 of the cylinder head 8. Many similar vibration isolating members 10 can be continuously formed by punching a belt-shaped stock.

Claims: A mounting structure for mounting a vibration isolating member (10) on a shroud (9), wherein said shroud (9) is adapted to sourround at least a cylinder head (8) of an air cooled engine (1), wherein said isolating member (10) is interposed between said shroud (9) and said cylinder head (8), and wherein projections (17) formed on an inner surface of said shroud (9) engage mounting holes (20) formed in said vibration isolating member (10), wherein said isolating member (10) is made of an elastic material, said mounting holes (20) are preliminarily formed in said isolating member (10) and have a diameter that is smaller than a diameter of the projections (17) so that each projection (17) is elastically held within said respective mounting hole (20), and said shroud (9) is further adapted so that said isolating member (10) is fixable between said shroud (9) and fins (22) formed on said cylinder head (8) by a holding pressure between said shroud (9) and said fins (22).

Inventors: HANAWA KAORU, HANAWA, KAORU, Hanawa, Kaoru, c/o Kabushiki Kaisha
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1996
Main classification: F02B77
IPC codes: B62M7, F01P5, F02B77, F02B75, B60K11, B62J99