Patent Application
20140060963
This application is based on and claims Convention priority to Japanese patent application No, 2012-193796, filed Sep. 4, 2012, the entire disclosure of which is herein incorporated by reference as a part of this application.
1. (Field of the Invention)
The present invention relates to an exhaust system for a motorcycle, which includes an exhaust chamber and a muffler for silencing noises generated by exhaust gases then flowing therethrough from a combustion engine towards the atmosphere.
2. (Description of Related Art)
A certain motorcycle having a combustion engine employed as a drive source therefor has been known, in which an exhaust chamber of a large capacity is provided at a location upstream of a muffler and beneath the combustion engine. This type of motorcycle is disclosed in, for example, the JP Laid-open Patent Publication No. H05-262272. The use of the exhaust chamber in the way as discussed in the above mentioned patent document is effective to allow the use of a downsized muffler at a location downstream of the exhaust chamber, resulting in an improvement in and of the appearance of the motorcycle.
It has however been found that where no space is available for the installation of a large sized exhaust chamber, it has been difficult to downsize the muffler. It has also been found that if a space for installation of the exhaust chamber is sought at a location below the combustion engine, the necessity will arise that the combustion engine must be positioned above the exhaust chamber a distance corresponding to the size of such exhaust chamber in order to secure the minimum ground clearance, accompanied by elevation of the center of gravity of the motorcycle as a whole.
The present invention has been devised in view of the foregoing problems and inconveniences and is intended to provide a motorcycle of a kind in which while a sufficient silencing effect is maintained, the length of the muffler as measured in a direction substantially or generally parallel to the longitudinal sense of the motorcycle is reduced to thereby improve the appearance of the motorcycle.
In order to accomplish the foregoing object, the present invention provides a motorcycle of a type using a combustion engine as a drive source, which motorcycle includes an exhaust chamber having defined therein a chamber expansion compartment for exhaust gases and also having a first outer peripheral wall; and a muffler having defined therein a muffler expansion compartment for the exhaust gases and also having a second outer peripheral wall, the muffler being positioned downstream of the exhaust chamber with respect to the direction of flow of the exhaust gases. In such case, the exhaust chamber is positioned between the combustion engine and a rear wheel; the first and second outer peripheral walls of the exhaust chamber and the muffler are formed by a common casing; a partition wall divides the casing in an anteroposterior direction to define the chamber expansion compartment, which is positioned forwardly of the partition wall, and the muffler expansion compartment which is positioned rearwardly of the partition wall, a rear end shape of the chamber expansion compartment and a front end shape of the muffler expansion compartment being identical with each other; the exhaust chamber has an inner side surface that is positioned inwardly of an outer side surface of the rear wheel in a motorcycle body widthwise direction; and the muffler has a rear portion that is positioned on an outer side of the rear wheel. It is to be noted that the term “common casing” referred to above and hereinafter is to be construed as a single casing including the respective outer peripheral walls of the exhaust chamber and the muffler. It is also to be noted that the term “chamber expansion compartment” referred to above is to be construed as including a resonance compartment.
According to the features, since the exhaust chamber is positioned intermediate between the combustion engine and the rear wheel and the inner side surface of the exhaust chamber is positioned inwardly of the outer side surface of the rear wheel in the motorcycle body widthwise direction, without the space below the combustion engine being compressed, the exhaust chamber of an increased capacity can be disposed. As a result, a sufficient silencing effect can be maintained, and also the muffler can be downsized to enhance the appearance of the motorcycle. Also, since the outer peripheral wall of the exhaust chamber and the outer peripheral wall of the muffler are formed by the common casing and the rear end shape of the chamber expansion compartment and the front end shape of the muffler expansion compartment are made identical with each other, the expansion space, which is defined foremost within the muffler communicated with the exhaust chamber of the increased capacity, can be increased. As a result, a further downsizing of the muffler and a further increase of the silencing effect can be accomplished.
As discussed above, since the muffler can be downsized, the length of the muffler in the anteroposterior direction can be shortened and the position of the exhaust device including the muffler can therefore be brought to a location close to the center of gravity of the motorcycle body. As a result, the straightforward travel characteristic and the steerability of the motorcycle increase. Yet, since the exhaust chamber and the muffler do not compress the space below the combustion engine, the position of the combustion engine can be lowered to lower the center of gravity of the motorcycle. The partition wall referred to above is preferably disposed in a portion of the casing where a change in longitudinal sectional area is moderate.
In a preferred embodiment of the present invention, a motorcycle body inner side end of a front wall of the muffler is positioned inwardly of the outer side surface of the rear wheel in the motorcycle body widthwise direction and a motorcycle outer side end of the front wall of the muffler is positioned outwardly of the outer side surface of the rear wheel in the motorcycle body widthwise direction. According to this construction, the motorcycle body widthwise dimension of the front portion of the muffler becomes large and, therefore, the expansion space positioned foremost within the muffler can be increased further.
In another preferred embodiment of the present invention, the motorcycle may include a pipe extending through the chamber expansion compartment to form a part of an exhaust passage, and the pipe may have a peripheral wall provided with communicating holes to communicate with the chamber expansion component. The use of the perforated pipe makes it possible to obtain an enhanced silencing effect by increasing an effect of silencing a particular frequency band with the utilization of the resonance effect.
In a further preferred embodiment of the present invention, the muffler is disposed on one side of the rear wheel with respect to a motorcycle body widthwise direction, in which case a rear wheel shock absorbing mechanism is positioned on the opposite side of the motorcycle body widthwise direction with respect to a longitudinal mid-center line and also is juxtaposed to the exhaust chamber in the motorcycle body widthwise direction. According to this construction, it is easy to dispose the exhaust chamber at a location inwardly of the motorcycle body.
In a still further preferred embodiment of the present invention, the motorcycle preferably include an exhaust device to regulate an exhaust passage sectional area, in which case the exhaust device is disposed upstream of the exhaust chamber. According to this construction, a reaction of the exhaust characteristic change relative to the valve operation will be good as compared with the disposition of the exhaust device at a position immediately preceding the muffler.
Any combination of at least two constructions, disclosed in the appended claims and/or the specification and/or the accompanying drawings should be construed as included within the scope of the present invention. In particular, any combination of two or more of the appended claims should be equally construed as included within the scope of the present invention.
In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:
Hereinafter, a preferred embodiment of the present invention will be described in detail with particular reference to the accompanying drawings. It is to be noted that the terms “left” and “right” are used to denote opposite positions or directions, respectively, relative to a motorcycle rider or motorist then occupying a motorcycle rider's seat and looking forwards in a direction parallel to the longitudinal sense of the motorcycle.
Referring first to
The main frame 1 has a front end portion provided with a head tube 5, and an upper bracket 6 and a lower bracket 8 are supported by this main frame 1 through a steering shaft (not shown) which is rotatably inserted into the head tube 5. A front fork assembly 10 is supported by the upper and lower brackets 6 and 8 with a front wheel 12 rotatably supported at a lower end portion of the front fork assembly 10. The upper bracket 6 at an upper end portion of the front fork assembly 10 has a steering handlebar 14 mounted thereon for angular movement together with the front fork assembly 10.
A rear end portion of the main frame 1 is inclined rearwardly slantwise, and a swingarm bracket 16 is formed at this rear end portion of the main frame 1. A swingarm 18 is pivotally supported by the swingarm bracket 16 through a pivot shaft 20, with a rear wheel 22 rotatably supported by a rear end portion of the swingarm 18. A motorcycle combustion engine E, which is a drive source for the motorcycle, is mounted on an intermediate portion of the main frame 1 with respect to the longitudinal sense of the motorcycle, in a fashion tilted forwardly. The rear wheel 22 referred to above is driven by the combustion engine E through a transmission member 21 such as, for example, a substantially endless chain.
The motorcycle combustion engine E referred to above is an internal combustion engine and, in describing the preferred embodiment, is a parallel multi-cylinder, water cooled internal combustion engine such as, for example, a four-cylinder, four-stroke water-cooled internal combustion engine. The combustion engine E includes a crankcase 24, a cylinder block 26 protruding upwardly from the crankcase 24, a cylinder head 28 mounted atop the cylinder block 26, and a head cover 29 enclosing the cylinder head 28.
Four exhaust header tubes 30 are connected with a front surface of the cylinder head 28 in communication with respective engine cylinders, which are defined in the cylinder block 24 in cooperation with the cylinder head 28, and those exhaust tubes 30 have their downstream ends merged together at a collecting tube 32. This collecting tube 32 has a downstream end with respect to the direction of flow of exhaust gases towards the atmosphere and this downstream end of the collecting tube 32 is fluid connected through a connecting tube 36 with an exhaust silencing device 34 that is positioned rightwardly of the rear wheel 22. The exhaust silencing device 34 is of a type having a small length, i.e., short in length, having a rear end thereof positioned forwardly of an axle A of the rear wheel 22.
The exhaust tubes 30, the collecting tube 32, the exhaust silencing device 34 and the connecting tube 36 cooperate with each other to define a motorcycle exhaust system 40. Of the components defining the motorcycle exhaust system 40, the connecting tube 36 and the collecting tube 32, both positioned on an upstream side of the exhaust silencing device 34, have a vertical dimension that is smaller than the exhaust silencing device 34.
The exhaust silencing device 34 includes a single casing 69, in which an exhaust chamber 82 for temporarily reserving exhaust gases and subsequently discharging those exhaust gases and a muffler 84 for accomplishing a noise reduction by cyclically repeating expansion and contraction of the exhaust gases discharged from the exhaust chamber 82 are accommodated. A region of the exhaust system 40 ranging from a rear half of the collecting tube 32 to a front half of the muffler 84 is enclosed from outside by a covering 39 made of a steel material. The details of each of the exhaust silencing device 34 and the exhaust system 40 will be discussed later.
A fuel tank 44 is mounted atop the main frame A headlamp unit 46 is supported at a front surface portion of the front fork assembly 10, and a front cowl or fairing 48 made of a resinous material is supported by the headlamp unit 46 so as to enclose an area forwardly of and above the front fork assembly 10.
A radiator 50 for dissipating an engine coolant medium is disposed forwardly above the combustion engine E. A pair of left and right cowls 52 are mounted on the main frame 1 so as to extend from laterally upwardly of the radiator 50 to respective upper end portions of the left and right subframe 4 and laterally outwardly of the front portion of the main frame 1. A lower cowl 54 is supported beneath the combustion engine E so as to enclose a lower portion of the combustion engine E from laterally outwardly.
A seat assembly comprised of a rider's seat 56 and a fellow passenger's seat 58 is mounted on an upper portion of the rear frame 2. Rear half portions of the left and right subframes 4 are covered from outside with respective side coverings 60 each extending from a location below the rider's seat 56 to a rear portion of the cylinder block 26 of the combustion engine E. Subframe coverings 62, one on each side of the motorcycle, are supported by the subframe 4 so as to extend from respective front end portion of the associated side coverings 60 to corresponding lower portion of the side cowls 52 to thereby cover the front half portion of the subframe 4 from outside.
An upper frame covering; 64 and a lower frame covering 66 are disposed at upper and lower locations, respectively, with each side covering 60 sandwiched therebetween. The upper frame covering 64 extends from the adjacent side cowl 52 to the associated side covering 60 along a lower edge of the fuel tank 44 to thereby cover the main frame 1 from outside. On the other hand, the lower frame covering 66 extends downwardly from the associated side covering 60 to cover the swingarm bracket 16 from outside.
A bracket 72 for supporting a brake pedal 68, a rider's footrest 70 and a fellow passenger's footrest 71 is fixed to a rear portion of the swingarm bracket 16. This bracket 72 extends rearwardly slantwise from the swingarm bracket 16 along the exhaust silencing device 34.
A rear suspension unit 74 for connecting the rear wheel 22 and the motorcycle body is disposed at a location rearwardly of the swingarm bracket 16. This rear suspension unit 74 is in the form of a single, generally or substantially vertically extending suspension and has a lower end portion fitted to the swingarm 18 through a link mechanism 76 and an upper end portion connected with the main frame 1. A connecting portion where the rear suspension unit 74 and the link mechanism 76 are connected with each other, when viewed from side, overlaps the exhaust chamber 82. The rear suspension unit 74 and the link mechanism 76, both referred to above, cooperate with each other to define a rear wheel shock absorbing mechanism. As best shown in
As shown in
The connecting tube 36 and the collecting tube 32, each having a smaller vertical dimension than the exhaust silencing device 34 of the exhaust system 40 best shown in
Referring to
The connecting tube 36 referred to above has an exhaust device 43 disposed therein for adjusting the cross sectional area of the exhaust passage, which is leading to the exhaust silencing device 34, by means of a valve opening. The provision of the exhaust device 43 referred to above is effective to optimize the engine performance characteristic by driving the exhaust device 43 in dependence on an engine operating condition. Also, the positioning of the exhaust device 43 at a location on an upstream side of the exhaust silencing device 34 makes it possible to allow the use of only one exhaust device 43 even where the exhaust silencing device is disposed on opposite lateral sides of the motorcycle body.
This exhaust device 43 has an operating member 43a disposed laterally outwardly of the motorcycle body and also has a valve shaft 43b inclined upwardly so as to extend towards the outside of the motorcycle body in the widthwise direction of the motorcycle. Accordingly, it is possible to suppress the dimension of projection of the operating member 43a in a direction laterally outwardly of the motorcycle to thereby gain the bank angle. The operating member 43a referred to above is a source for rotating the valve shaft 43b and is in the form of, for example, a motor.
A first covering fitting bracket 45 necessitated for the covering 39 (best shown in
The exhaust silencing device 34 best shown in
The first casing region 86 is divided circumferentially into first casing halves 86a and 86h as shown by the line L of division in
The exhaust chamber 82 is partitioned from the muffler 84 by a partition wall 98. In other words, with the casing 69 divided by the partition wall 98, a chamber expansion compartment 90 as will be described in detail later is defined forwardly of the partition wall 98 and a first muffler expansion compartment 92 as will be described in detail later is defined rearwardly of the partition wall 98. Hence, the partition wall 90 referred to above forms a rear wall of the exhaust chamber 82 and, at the same time, a front wall of the muffler 84 and, therefore, a rear end shape of the chamber expansion compartment 90 and a front end shape of the first muffler expansion compartment 92 can be formed to the same shape. Speaking differently, the sectional shape of the chamber expansion compartment 90 along a front surface of the partition wall 98 and the sectional shape of the first muffler expansion compartment 92 along a rear surface of the partition wall 98 are formed to the same shape.
As shown in
On the other hand, a motorcycle body outer end 98b of the front wall 98 and a motorcycle body outer end of the muffler front portion in the vicinity of the front wall 98 are positioned laterally outwardly of the outer side surface 22a of the rear wheel 22 in the motorcycle body widthwise direction. Since the collecting tube 32 including the catalytic unit 42, the exhaust chamber 82 and the muffler 84 are thus disposed on a right side of the motorcycle body with respect to the longitudinal mid-center plane C, a range from the collecting tube 32 to the exhaust chamber 82 can be formed as a simple path with minimized number of curves, and also a region below the combustion engine E will not be compressed. Accordingly, with the combustion engine E positioned low, an oil pan 85 and the rear suspension unit 74 can be disposed in a side by side relation with the exhaust system 40 in a direction widthwise of the motorcycle body.
As shown in
The chamber expansion compartment 90, which is the most foremost inner space, is formed intermediate between the connecting tube 36 and the first partition wall 98. A pipe 104 communicated with the connecting tube 36 extends through the chamber expansion compartment 90 while upwardly curved within the chamber expansion compartment 90. The pipe 104 has a downstream end fluid connected with a first communicating tube 105 by means of welding. The first communicating tube 105 is, after having extended through the first partition wall 98, communicated with the first muffler expansion compartment 92 of the muffler 84 neighboring rearwardly thereof. This pipe 104 is formed with a plurality of communicating holes 106. A portion of the exhaust gases flowing inside the pipe 104 flows into the chamber expansion compartment 90 through the communicating holes 106 and is then expanded and silenced. The pipe 104 and the first communicating tube 105 are connected together within the chamber expansion compartment 90 and the first communicating tube 105 is welded to the first partition wall 98.
The first muffler expansion compartment 92 of the muffler 84 is formed intermediate between the first and second partition walls 98 and 100. In other words, the second partition wall 100 forms a rear wail 100 of the first muffler expansion compartment 92 which is the most upstream expansion compartment of the muffler 84. As shown in
The second muffler expansion compartment 94 is formed intermediate between the third partition wall 102 and the rear end wall 73 fitted to the casing 69. In the second muffler expansion compartment 94, the exhaust gases flowing from the second communicating tube 108 are expanded and silenced. This third partition wall 102 is provided with a fourth communicating tube 112 for fluid connecting the second muffler expansion compartment 94 and the third muffler expansion compartment 96 together.
The third muffler expansion compartment 96 referred to above is formed intermediate between the second and third partition walls 100 and 102. In this third expansion compartment 108, the exhaust gases flowing from the third communicating tube 110 and the fourth communicating tube 112 are expanded and silenced. The third and fourth communicating tubes 110 and 112 referred to above are disposed so as to face in a direction of flow of the exhaust gases. The exhaust gases, flowing from the first muffler expansion compartment 92 through the third communicating tube 110, and the exhaust gases, flowing from the third muffler expansion chamber 96 through the fourth communicating tube 112 collide against each other within the third muffler expansion compartment 96. Accordingly, expansion and silencing of the exhaust gases are further accelerated.
The third partition wall 102 is provided with two, fifth and sixth communicating tubes 114 and 116 for communicating the third muffler expansion compartment 96 with the outside of the casing 69. The exhaust gases which have been expanded and silenced within the third muffler expansion compartment 96 are discharged to the outside through the exhaust ports 71 and 71 by way of the fifth and sixth communicating tubes 114 and 116.
First to third heat insulating materials 118, 120 and 122 such as, for example, wools are fitted to a lower surface of an inner wall of the chamber expansion compartment 90, an upper surface of an inner wall of the first muffler expansion compartment 92 of the muffler 84 and an outer side surface of the inner wall of the first muffler expansion compartment 92 of the muffler 84, respectively. As best shown in
As shown in
Second and third covering fitting brackets 130 and 132, each made of a steel material, are fixedly welded to a front side portion of and a rear upper portion of the first casing region 86, respectively. The covering 39 (best shown in
As described above, the second and third heat insulating materials 120 and 122 are fitted to the inner surface of the first casing region 86 forming the first muffler expansion compartment 92, and the heat insulating plate 128 is provided in the outer surface of the first casing region 86 and the first casing region 86 is enclosed from the outside by the covering 39. Accordingly, even though the brake pedal 68 or the rider's footrest 70, both shown in
As hereinabove described, the first casing region 86 forming the contour of the first muffler expansion compartment 92 of the exhaust chamber 82 and the muffler 84 both shown in
A major portion of the second casing region 88 defining the contour of the second and third muffler expansion chambers 94 and 96 of the muffler 84 is not covered by the covering 39. Accordingly, as best shown in
A first fitting piece 136 is fixed to a portion of an outer peripheral surface of the first casing region 86 adjacent a front end portion thereof by means of welding. This first fitting piece 1.36 is formed with a bolt insertion hole 136a. Also, a second fitting piece 138 is fixed to a portion of an outer peripheral surface of the second casing region 88 adjacent a rear end portion thereof by means of welding. Even this second fitting piece 138 is formed with a bolt insertion hole 138a in the form of a slot.
Each of upstream end portions of the exhaust tubes 30 is inserted in a corresponding fitting hole (not shown), which is defined in the cylinder head 28, to allow a front portion of the exhaust system 40 to be supported by the motorcycle body through the cylinder head 28 (combustion engine E). While in this condition, a bolt (not shown) is inserted from the outside of the motorcycle body into the bolt insertion hole 136a in the first fitting piece 136 provided in the first casing 86 and is in turn fastened into a threaded hole (also not shown) defined in the swingarm bracket 16. By so doing, a longitudinal intermediate portion of the exhaust system 40 is supported by the swingarm bracket 16 on the main frame 1, that is, by the motorcycle body.
Also, a bolt 140 best shown in
With the exhaust system of the motorcycle so constructed as described hereinabove, as best shown in
As best shown in
As best shown in
Since as shown in
Since as shown in
Since as shown in
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings which are used only for the purpose of illustration, those skilled in the art will readily conceive numerous changes and modifications within the framework of obviousness upon the reading of the specification herein presented of the present invention. By way of example, although in describing the preferred embodiment reference has been made to a so-called naked type motorcycle in which the headlamp unit 46 is supported by the front fork assembly 10, the present invention can be equally applied to any type of motorcycles.
Accordingly, such changes and modifications are, unless they depart from the scope of the present invention as delivered from the claims annexed hereto, to be construed as included therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-193796 | Sep 2012 | JP | national |
