Title of Invention

"A SOUND ABSORBING MEMBER"

Abstract

To provide a structure for attaching, to a shroud of an engine, sound absorbing members, which can effectively promote cooling performance of the air-cooled internal combustion engine, effectively mute noise, be easily assembled, and are less expensive. | Means | The shroud 22 surrounding the radiating section of the air-cooled internal combustion engine 3 forms the cooling air passage 38 which surround the engine between a pair of body frames. The sound absorbing member 36 is attached to the side surfaces of the body frames. The sound absorbing member is composed of the plate which has the uniform thickness, and is blanked and partially folded. Specifically, the sound absorbing member 36 is attached to the shrouds 22 with its folded portion being at the downstream side of the cooling air passage 38, and its remaining portion being at the upstream side of the cooling air passage 38. [Selected Drawing| Fig. 2

Full Text

(Detailed Description of the Invention) (Field of the Invention | The present invention relates to a sound absorbing member to shrouds of an air-cooled internal combustion engine installed in a scooter type motorcycle or the like, and more particularly to a structure for attaching a sound absorbing member to shrouds which have excellent cooling and sound absorbing characteristics and is easily assembled to an internal combustion engine. |Related Art | In an existing scooter type motorcycle, a radiator of an internal combustion engine is covered by shrouds, and cooling air is introduced into the shrouds by rotating a cooling fan integral with a crankshaft, via cooling air inlets formed in the shrouds. In such an engine, the shrouds near the cooling air inlets are covered by a shroud cover, and a sound absorbing member made of polyurethane is inserted between the shrouds and the shroud cover in order to improve cooling performance of the radiator and to block sound caused by the cooling air (refer to Japanese Patent Laid-Open Publication No. Hei 6-200757). TProblems to be solved by the Invention) In the foregoing publication, the polyurethane sound absorbing member 036 has a uniform thickness, so that the space for housing the sound absorbing member 036 between the shrouds 024 and the shroud cover 026 should have a uniform width and a uniform shape. When the internal combustion engine is installed to be inclined rearward, the urethane sound absorbing member 036 having the uniform thickness will not cause any problem even if the uniform space is defined by the shrouds 024 and the shroud cover 026. However, when the engine is installed to be inclined forward as shown in Fig. 16, one of a pair of body frames 08 extends immediately over an outer surface of a cover for the sound absorbing member (corresponding to the shroud cover 026 in the cited publication). In order to detour this frame, one of the shrouds 024, i.e., the inner shroud, sandwiching the sound absorbing member 036 should be curved as shown by letter D in Fig. 16, which means that the sound absorbing member 036 projects to the cooling air passage 038, thereby narrowing the cooling air passage 038, and resulting in an area E where the cooling air remains stationary. This has led to reduced cooling efficiency of the internal combustion engine. [Means to solve the Problems and Effect) The present invention is conceived to overcome the problems of the related art, and to provide a structure for attaching a sound absorbing member to shrouds of an internal combustion engine. As defined in claim 1, the structure is for attaching a sound absorbing member to shrouds of an internal combustion engine which is surrounded by a cooling air passage formed between a pair of rear body frames, and the sound absorbing member being fixed to a side of the body frame. The sound absorbing member is formed by blanking and partially folding a plate material having a uniform thickness. Further, the sound absorbing members are housed in the shrouds with the folded part thereof positioned downstream of the cooling air passage and the non-folded part thereof positioned upstream of the cooling air passage. According to the arrangement defined in claim 1, the sound absorbing member includes the non-folded part positioned at the upstream side of the cooling air passage and the folded part positioned at the downstream side of the cooling air passage, and does not have a uniform thickness. This feature and the elasticity peculiar to the sound absorbing members enable the space for housing the sound absorbing members to have a cross section which gradually and smoothly becomes thicker from the narrow upstream part of the air cooling passage toward the downstream part of the cooling air passage. In other words, the sound absorbing member is thin at the upstream part compared with at the downstream part. Even when a body frame extends near the cover of the sound absorbing member around cooling air inlets, it is not necessary to curve shrouds, which hold the sound absorbing members together with the cover, toward the cooling air passage. Therefore, a cross sectional area of the cooling air passage at the upstream part can be kept large, which is effective in introducing a sufficient amount of cooling air to effectively cool the internal combustion engine. Further, the sound absorbing member is substantially tightly fitted in its housing space, thereby effectively blocking noise caused by the cooling air, The sound absorbing member having a varying thickness is formed by folding a plate-shaped material with a uniform thickness, rather than by making a material into a three-dimensional shape. It is possible to manufacture the sound absorbing members at reduced cost. Further, the sound absorbing members are formed by folding one plate-shaped material rather than layering two separate plate-shaped materials having different widths, so that the number of components is reduced, and erroneously assembled or non-assembled components can be also reduced. According to the structure defined in claim 2, the material for the sound absorbing member can be easily folded and reliably assembled. Therefore, the present invention relates to a sound absorbing member attached to shrouds of an internal combustion engine which is surrounded by cooling air passages formed between a pair of rear body frames, and the sound absorbing member being fixed to a side of the body frame, wherein said sound absorbing member is formed by blanking and partially folding a plate material having a uniform thickness, and is housed in the shrouds with the folded part thereof positioned downstream of the cooling air passage and the non-folded part thereof positioned upstream of the cooling air passage. A C compcu-tu I'AO-(Brief Description of theAccompanying Drawings) Fig. I is a right side view of the scooter type motorcycle provided with the structure for attaching the sound absorbing member to the shrouds of the air-cooled internal combustion engine, according to one embodiment of the invention defined in claims I and 2. Fig. 2 is a longitudinal cross section, taken along line II-II in Fig. 1. Fig. 3 is an enlarged longitudinal cross section of the main part shown in Fig. 2. Fig. 4 is a rear view of a part of the cylinder side shroud in the embodiment. Fig. 5 is a right side view of the cylinder side shroud. Fig. 6 is a top plan view of the cylinder side shroud. Fig. 7 is a left side view, and a partly cross sectional view of the cylinder side shroud. Fig. 8 is a top plan view of the cylinder side shroud cover in the embodiment of Fig. I. Fig. 9 is a longitudinal cross section of the cylinder side shroud cover, taken along line IX-IX in Fig. 8. Fig. 10 is atop plan view of the plate formed by blanking the sound absorbing material, in the embodiment of Fig. I. Fig. ! 1 is a longitudinal cross section of the sound absorbing member, taken along line XI-XI in Fig. 10. Fig. 12 shows the process of attaching the sound absorbing member to the shrouds. Fig. 13 is a front view of the fan side shroud assembly. Fig. 14 is a longitudinal cross section of the fan side shroud assembly, taken along line X1V-X1V in Fig. 13. Fig. 15 shows the effect accomplished by the embodiment in Fig. 1. Fig. 16 is a view similar to Fig. 15, showing an example of the related art. (Description of Embodiment) The invention defined in claims 1 and 2 will be described with reference to an embodiment shown in Figs. I to 15. Fig. I is a right side view of a rear part of a scooter type motorcycle in which the sound absorbing member is attached to shrouds of an internal combustion engine, according to the invention. Fig. 2 is a cross sectional view taken along line II-II in Fig. Referring to Figs. I and 2, a swing type power unit 2 installed in the scooter type motorcycle 1 includes: an air-cooled internal combustion engine 3 which is inclined upward toward a front part of the motorcycle I; a V-belt type continuously variable transmission 4 which extends rearward from a left lower part of the engine 3; and a speed reducing gear unit. All of the foregoing members are formed as an integral unit. A rear wheel 12 is fitted to an output shaft (not shown) of the speed reducing gear unit to form an integral part. A hanger (bracket) 7 is present at a position slightly offset rearward from the center of the swing type power unit 2, and is attached to a bracket 9 projecting rearward from the body frame 8 via a link 10, so that the hanger 7 is capable of rocking up and down. A driving pulley 13 is attached to the left end of a crankshaft 12 rotatably fitted in acrankcase 11 of the engine 3. AV-belt 15 extends between the driving pulley 13 and a driven pulley (not shown) rotatably fitted to a rear end of a transmission casing 14. As the crankshaft 12 rotates at an increasing speed, a transmission ratio of the continuously variable transmission 4 is continuously reduced, so that power of the engine 3 is transmitted to the rear wheel 5 via the transmission 4. |OOI3| A plurality of radiating fins 18 are formed in a cylinder 16 above the crankcase 11 and in a cylinder head 17 above the cylinder 16, with predetermined spaces kept therebetween. A rotor 20 of a generator 19 is attached to the right end of the crankshaft 12 as an integral part. A centrifugal cooling fan 21 is attached to the rotor 20 so as to be integral therewith. A synthetic resin shroud 22 covering the engine 3 and the cooling fan 21 includes: a fan side shroud part 23 covering the cooling fan 21 ; a cylinder side shroud part 24 covering the cylinder 16 and cylinder head 17; a fan side shroud cover 25 covering an outer side of the fan side shroud part 23; and a cylinder side shroud cover 26 covering an outer side (right side) of the cylinder side shroud part 24. The fan side shroud part 23 and the cylinder side shroud part 24 respectively have three mounting holes (shown in Figs. 13, 4 and 5), and are detachably attached to the crankcase 11, cylinder head 17 and so on by inserting bolts 27 into the foregoing mounting holes. The bolts 27 are inserted into the mounting holes 44 for the cylinder side shroud part 24 via a hole 45 above the mounting holes 44 (see Fig. 4). Front and rear mounting holes 43, 43 above the fan side shroud part 23 match with front and rear mounting holes 44, 44 below the right lower side of the cylinder side shroud part 24. so that the shrouds 23 and 24 are detachably attached to the crankcase 11 by inserting bolts (not shown) into the holes 43 and 44. The fan side shroud part 23 is provided with a cooling air inlet 28 concentric with the cooling fan 21, and the fan side shroud cover 25 is formed with a cooling air inlet 29 which is in close contact with the cooling air inlet 28. The cooling air inlet 29 includes a grill 30 as an integral part in order to prevent entrance of rainwater and to protect the fan side shroud part 23. The grill 30 includes a plurality of cylindrical members 31 which have different diameters, are thick at central portions, are long enough to prevent the entrance of rainwater, and are concentrically arranged. The cylindrical members 31 are coupled via a plurality of fins 32 which are radially arranged and equally spaced (see Figs. 2, 13, and 14). Referring to Fig. 5, a pair of upper and lower pedestals 33 project from upper and lower parts (the right and left sides in Fig. 5) of a sloped wall overhanging rearward toward the right side 24r of the cylinder side shroud part 24. A partition 34 projects (to the right in Fig. 4) in order to surround the pedestals 33 and define the space covered by the cylinder side shroud cover 26. As shown in Figs. 8 and 9, the cylinder side shroud cover 26 is provided with pedestals 35 at positions corresponding to the pedestals 33, and a peripheral wall 50 projecting inward, which correspond to the partition 34. The sound absorbing member 36 made of a polyurethane sponge or the like is fitted into the space defined by the partition 34 between the fan side shroud part 24 and the cylinder side shroud cover 26. An engaging piece 51 integral with the peripheral wall 50 of the cylinder side shroud cover 26 is engaged in an engaging hole 52 integral with the partition 34 of the cylinder side shroud part 24. The cylinder side shroud part 24 is covered by the cylinder side shroud cover 26. Rivets 37 are fitted to the pedestals 33 and 35 of the fan and cylinder side shrouds part 24 and the cylinder side shroud cover 26. Therefore, the sound absorbing member 36 is sandwiched between the partition 34 and the cylinder side shroud cover 26 (see Fig. 3). The sound absorbing member 36 in the space defined by the partition 34 of the cylinder side shroud part 24 has a plurality of small and large openings 39 which communicate with the cooling air passage in the shroud 22 (see Fig. 5). A pedestal having the hole 45 and positioned at the outer, upper and rear part of the partition 34 is used to fix a member for clamping a high tension cord to a plug. An opening 49 at the rear side surface of the cylinder side shroud part 24 is used to clamp a vacuum tube for supplying a negative pressure from the engine casing to a vacuum fuel pump (not shown) fixed to the body frame 8. A projection 53 atop the cylinder side shroud part 24 is used to control a turning direction of a spark plug cap (not shown) with respect to the spark plug. The partition 34 and the cylinder side shroud cover 26 have a profile and a shape as shown in Figs. 8 and 5. Specifically, they are substantially rectangular as shown by dashed lines, but are cut from one upper corner to the center of the upper side in order to avoid the pedestal having the hole 45. The partition 34 includes a shorter upper rear part 34a (shown at the left side in Fig. 5), and a longer and taller upper rear part 34b which is slightly inclined forward and extends from the upper rear part 34a (shown at the right side in Fig. 5). Both the partition 34 and the cylinder side shroud cover 26 are rounded at their corners. The sound absorbing member 36 will be described referring to Figs. 10 and 11. As shown in these figures, the sound absorbing member 36 is a plate 36a which is formed by blanking a polyurethane material having a uniform thickness, and is folded at a slit 36c, as will be described later. Referring to Fig. 10, the plate 36a has a recess 36b in the shape of a glass having a large mouth, at a substantially left upper half thereof, and the slit 36c at a position slightly below the center of the recess 36b. The sound absorbing member 36 is folded at the slit 36c, so that a folded portion 36d above the slit 36c overlaps with a base portion 36e. The recess 36b of the plate 36a is shaped as described above so that the sound absorbing member 36 is reliably fitted into the space defined by the partition 34 which includes the upper rear partition part 34a having curved ends. The slit 36c is positioned slightly below the center of the recess 36b for the following reason. When the sound absorbing member 36 is fitted into the foregoing space and is covered by the cylinder side shroud cover 26, the folded portion 36d and the base portion 36e may be substantially aligned at their sides in contact with the upper rear partition part 34 (see Fig. 3). Further, the plate 36a has an oval opening 36f and a semicircular opening 36g. When the sound absorbing member 36 is fitted into the predetermined space and is covered by the cylinder side shroud cover 26, the pedestals 33 of the cylinder side fan shroud part 24 come into contact with the pedestals 35 of the cylinder side shroud cover 26 via the oval opening 36f and semicircular opening 36g. Therefore, the foregoing members are coupled by rivets. Fig. 12 schematically shows the process in which the sound absorbing member 36 is fitted into the space defined by the partition 34 between the cylinder side shroud part 24 and the cylinder side shroud cover 26. Another sound absorbing member 42 is fitted into an annular space defined by the fan side shroud part 23 and the fan side shroud cover 25, except for three pedestals 41 which couple the shroud part 23 and the cover 25 using rivets 40. Similarly to the cylinder side shroud part 24, the fan side shroud part 23 is formed with a plurality of openings 46 enabling the sound absorbing member 42 to communicate with the cooling air passage 38 (refer to Figs. 13 and 14). Referring to Fig. 13, the fan side shroud cover 25 is caved in at a position above a boundary F extending to the right and left sides of the pedestal 41. The sound absorbing member 42 is rather thin in the annular space at the caved in portion of the fan side shroud cover 25, compared with at the other part of the annular space (refer to Figs. 2 and 14). The caved in portion of the fan side shroud cover 25 and the cylinder side shroud cover 26 obliquely extending upward toward the center of the motorcycle (as shown in Fig. 2) define a space through which the body frame 7 and a lower part of a body cover 47 extend outward. The cooling air flowing through the cooling air passage 38 cools the cylinder 16 and the cylinder head 17, and is discharged via the shroud 22 as described below. Referring to Fig. 7, the cylinder side shroud part 24 has its left side 241 cut in the shape of an inverted letter L to define a space A shown by letters a, b, c, d, e, and f. The cooling air is discharged via the space A. In Fig. 7, the left side 241 of the cylinder side shroud part 24 has a box-shaped lid 48 as an integral part. The box-shaped lid 48 has a bottom in the shape of a trapezoid, and covers an upper side of the space in the shape of an inverted letter L, and a substantially triangular area at the upper right corner. The lid 48 is open at a slightly curved oblique side 48e of a bottom wall 48a. Therefore, part of the cooling air flowing out via the space A impinges against the bottom wall 48a, and is discharged via the shroud 22 toward a lower front side C of the motorcycle by avoiding the left body cover 47 and the crankcase 11. The remaining cooling air is discharged substantially straight toward the left side B of the motorcycle via the shroud 22 via the oblique side 48e not covered by the bottom wall 48a. The cooling air is discharged via the shroud 22 after passing through the cooling air passage 38 and cooling the cylinder 16 and the cylinder head 17 as described above. Part of the cooling air introduced via the cooling air inlets 29 and 28 flows in front of the cylinder 16 and the cylinder head 17, cools these members, impinges against the bottom wall 48a of the lid 48, and is discharged via the shroud 22 toward lower front part C of the motorcycle. The remaining cooling air is discharged via the shroud 22 substantially straight toward the left side B of the motorcycle. Most of the cooling air circulating behind the cylinder 16 and the cylinder head 17 (the right side in Fig. 7) flows via the upper art of the space A in the shape of an inverted letter L, impinges against the bottom wall 48a of the lid 48, and is discharged obliquely toward the front lower part C of the motorcycle via the shroud 22. In this state, the cooling air flowing a short distance in front of the cylinder 16 and the cylinder head 17 attracts the cooling air flowing a long distance around the rear part of the foregoing members, which is effective in removing heat from the cooling air circulating behind the cylinder 16 and the cylinder head 17. This means that both the cylinder 16 and the cylinder head 17 are effectively cooled by the cooling air both at their front and rear sides. The box-shaped lid 48 includes an upper side wall 48b having the opening 45, a lower side wall 48c which is smaller than the upper side wall 48b and has the mounting opening 44. and a rectangular longitudinal wall 48d. The upper and lower side walls 48b and 48c are substantially in the shape of a trapezoid. The lower side wall 48c is caved in around the mounting opening 44 to form a step. A projecting wall 48f having two sides orthogonal with each other is present around the opening 45 on the upper side wall 48b, and allows the opening 45 to open obliquely toward the front lower side C of the motorcycle. The projecting wall 48f is integral with the upper side wall 48b and the left side surface 241 of the cylinder side shroud part 24 Therefore, a small amount of the cooling air is discharged toward the direction C via the opening 45. The structure according to the invention operates and is effective in the following respects. When the engine 3 is activated followed by the operation of the cooling fan 21, air present outside the right side of the swing type power unit 2 is introduced into the cooling air passage 38 housed in the shroud 22 via the cooling air inlets 29 of the fan side shroud cover 25, and the cooling air inlets 28 of the fan side shroud part 23. While passing through the cooling air passage 38, the cooling air comes into contact with and cools the cylinder 16, cylinder head 17, and radiating fins 18, becomes hot, and is discharged via the shroud 22. Thus, the cylinder 16 and the cylinder head 17 are sufficiently cooled. Noise caused by the operating engine 3 and the radiating fan 21 can be absorbed by the shroud 22 covering the engine 3 and the radiating fan 21, and by the sound absorbing members 36 and 42 communicating with the cooling air passage 38 via the openings 39 and 46. Therefore, noise in the power unit 2 can be remarkably muted. The sound absorbing member 36, fitted between the cylinder side shroud part 24 and the cylinder side shroud cover 26 is constituted by the polyurethane plate 36a having a uniform thickness. The plate 36a is folded at the slit 36c, and the folded portion 36d overlaps with the base 36e. In other words, the sound absorbing member 36 has a varying thickness since it is partly doubled. The space, which houses the elastic sound absorbing member 36, and is defined by the cylinder side shroud part 24 and the cylinder side shroud cover 26, has a cross section which is large at the downstream side of the cooling air passage and gradually becomes smaller toward the upstream side of the cooling air passage. Therefore, even when the body frame 7 extends near the space housing the sound absorbing member 36 around the cooling air inlets 28 and 29, it is not necessary to curve the cylinder side shroud part 24 toward the cooling air passage 38 in order to avoid the body frame 7 and keep the predetermined space from the body frame 7 (see Figs. 2, 3 and 15). The cooling air passage 38 can have a large cross sectional area at its upstream side in order to introduce a sufficient amount of the cooling air, thereby improving the cooling performance of the engine 3. Further, the sound absorbing member 36 is tightly fitted in its housing space in order to assure sufficient sound absorbing performance. The sound absorbing member 36 is constituted by the plate 36a which has the uniform thickness and is folded, without a three-dimensional shaping process. Thus, the sound absorbing member 36 can be manufactured at reduced cost. The sound absorbing member 36 having the varying thickness is obtained by folding the plate 36a with the uniform thickness, not by layering two plates having different thicknesses. This is effective in reducing the number of components, and preventing erroneously assembled or non-assembled parts. in the sound absorbing member 36, the plate 36a has the cross sectional area at the slit 36c smaller than the non-folded portion, so that it can be easily folded and assembled. In addition, the slit 36c is used as the portion to be folded so that the sound absorbing member 36 can be shaped to match with the curved profile of the rear partition portion 34a of the partition 34 of the cylinder side shroud part 24. The structure according to the invention is widely applicable to attach the sound absorbing member to internal combustion engines taking the arrangement of components around the shrouds into consideration. (Reference Numerals| 1 ... scooter type motorcycle, 2 ... swing type power unit, 3 ... air-cooled internal combustion engine, 6 ... rear wheel, 7 ... hanger, 8 ... body frame, 9 ... bracket, 10 ... link, II ... crankcase, 12 ... crankshaft, 13 ... driving pulley, 14 ... continuously variable transmission casing, 15 ... V-belt, 16 ... cylinder, 17 ... cylinder head, 18 ... radiating fins, 19 ... generator, 20 ... rotor, 21 ... cooling fan, 22 ... shroud part, 23 ... fan side shroud part, 24 ... cylinder side shroud, 25 ... fan side shroud cover, 26 ... cylinder side shroud cover, 27 ... mounting bolts, 28 ...cooling air inlet, 29 ...cooling air inlet, 30 ... grill, 31 ... cylindrical member, 32 ... fins, 33 ... pedestals, 34 ... partition, 35 ... pedestals, 36 ... sound absorbing member, 36a ... plate, 36c ... slit (folded portion), 37 ... rivet, 38 ... cooling air passage, 39 ... opening, 40 ... rivet, 41 ... pedestal, 42 ... sound absorbing member, 43 ... mounting openings, 44 ... mounting openings. 45 ... opening, 46... opening, 7 ... body cover, 48 ... box-shaped lid, 50 ... peripheral wall, 51 ... engaging piece, 52 ... engaging opening. WE CLAIM: 1. A sound absorbing member (36) attached to shrouds (23, 24, 25) of an internal combustion engine which is surrounded by cooling air passages (28) formed between a pair of rear body frames, and the sound absorbing member being fixed to a side of the body frame, wherein said sound absorbing member is formed by blanking and partially folding a plate material having a uniform thickness, and is housed in the shrouds (23, 24) with the folded part thereof positioned downstream of the cooling air passage and the non-folded part thereof positioned upstream of the cooling air passage. 2. The sound absorbing member as claimed in claim 1, wherein a cross sectional area of the folded part of the sound absorbing member is smaller than a cross sectional area of the non-folded part thereof extending from the folded part. 3. A sound absorbing member substantially as herein described with reference to the accompanying drawings.

Documents:

734-del-1998-abstract.pdf

734-del-1998-claims.pdf

734-del-1998-correspondence-others.pdf

734-del-1998-correspondence-po.pdf

734-del-1998-description (complete).pdf

734-del-1998-drawings.pdf

734-del-1998-form-1.pdf

734-del-1998-form-13.pdf

734-del-1998-form-19.pdf

734-del-1998-form-2.pdf

734-del-1998-form-3.pdf

734-del-1998-form-4.pdf

734-del-1998-form-6.pdf

734-del-1998-gpa.pdf

734-del-1998-petition-137.pdf

734-del-1998-petition-138.pdf

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