Title of Invention

A REAR CUSHION ARRANGEMENT STRUCTURE OF A MOTORCYCLE

Abstract

A rear cushion arrangement structure of a motorcycle is provided that can avoid a fuel tank from reducing in capacity while ensuring a sufficient stroke of a rear cushion, even if the lower portion of the rear cushion is directly held by a rear fork. In a motorcycle 1 comprising a body frame 2 including main frames 4 and seat rails 9 each of which extends toward the rear of a vehicle body from a corresponding one of the main frames 4, and a rear cushion 3 0 disposed between the body frame 2 and a rear fork supporting a rear wheel for rotation, a fuel tank 50 is disposed to mount on the main frames 4 and the seat rails 9, a fuel pump 60 is disposed on a rear part of a bottom portion of the fuel tank 50, and an upper end of the rear cushion 30 is projected upward from the seat rails 9 and located forward of the fuel pump 60. Fig. 3

Full Text

[Name of Document] Specification [Title of the Invention] Rear Cushion Arrangement Structure of Motorcycle [Technical Field] [0001] The present invention relates to a rear cushion arrangement structure of a motorcycle that prevents a fuel tank from reducing in capacity while ensuring a sufficient stroke of a rear cushion. [Background Art] [0002] There have been known motorcycles that adopt a mono-cushion structure which uses a single rear cushion to absorb a shock transmitted from a rear wheel via a rear fork and then a body frame. The following technique has been proposed as the structure of this type in order to ensure a sufficient stroke of a rear cushion: The lower end of the rear cushion is extended below a rear fork to be coupled to a link and is supported by the lower end of the rear fork via the link, while the upper end of the rear cushion is held by a body frame (see Patent Document 1, for instance). [Patent Document 1] Japanese Patent No. 2673894 [Disclosure of the Invention] [Problem to be Solved by the Invention] [0003] However, some motorcycles are configured such that, for example, the lower end of a rear cushion is supported by a rear fork in a direct manner, that is, without through the above-mentioned link. In this case, the lower end of the rear cushion is positioned at the same height as the position of the rear fork, which makes it difficult that the lower end of the rear cushion is extended below the rear fork. In order to ensure the rear cushion stroke, therefore, the upper end of the rear cushion must be set at a significantly high level. On the other hand, in recent years, motorcycles have been proposed that are configured such that a fuel injector is used to feed fuel to an engine. In this case, a fuel pump needs to be placed in a fuel tank, which enlarges the fuel tank accordingly, causing it to significantly protrude from the body frame. As a result, the fuel tank needs inevitably to be reduced in capacity in order to set the upper end of the rear cushion at a high level and avoid it from interfering with the fuel tank. [0004] The present invention has been made in view of the forgoing, in this invention, it is desirable to provide a rear cushion arrangement structure of a motorcycle that can avoid a fuel tank from reducing in capacity while ensuring a sufficient stroke of a rear cushion, even if the lower portion of the rear cushion is directly held by a rear fork. [Means for Solving the Problem] [0005] In order to solve the above-mentioned problems, the present invention is characterized in that, in a rear cushion arrangement structure of a motorcycle, including a body frame including main frames and seat rails each of which extends toward the rear of a vehicle body from a corresponding one of the main frames, and a rear cushion disposed between the body frame and a rear fork supporting a rear wheel for rotation, a fuel pump is disposed to mount on the main frames and the seat rails, a fuel pump is disposed on a rear part of a bottom portion of the fuel tank, and an upper end of the rear cushion is projected upward from the seat rails and located forward of the fuel pump. In the invention, the lower end of the rear cushion may be directly supported by the rear fork. In addition, the upper end of the rear cushion may be held by a cross member spanned between the pair of left and right main frames. [0006] In the inventions described above, the fuel pump is disposed on the rear part of the bottom portion of the fuel tank. In this case, the fuel tank is generally enlarged. However, the upper end of the rear cushion is projected upward from the seat rails and located forward of the fuel pump. For example, even if the low end of the rear cushion is directly coupled to the rear fork, therefore, the rear cushion assumes a bending-forward posture. This makes it possible to avoid the upper end of the rear cushion from interfering with the fuel tank as well as to enable ensuring of a sufficient stroke of the rear cushion. The fuel tank can be increased or maintained in capacity. In addition, since the upper end of the rear cushion is located above the seat rails, it can be attached and detached from above. [0007] In the invention, a battery and a radiator reserve tank may be symmetrically disposed on both sides of the rear cushion. Effective utilization of left-hand and right-hand spaces makes it possible to arrange the battery and the radiator reserve tank efficiently. [Effects of the Invention] [0008] In the inventions described above, the fuel pump is disposed on the rear part of the bottom portion of the fuel tank. In this case, the fuel tank is generally enlarged. However, the upper end of the rear cushion is projected upward from the seat rails and located forward of the fuel pump. This makes it possible to avoid the upper end of the rear cushion from interfering with the fuel tank as well as to enable ensuring of a sufficient stroke of the rear cushion, which fulfills the increased or maintained capacity of the fuel tank. [Best Mode for Carrying out the Invention] [0009] One preferred embodiment of the present invention will be below described with reference to the accompanying drawings. Note that, in the description, directions such as the front and rear, the left and right, and upside and downside, and the like are based on the vehicle body. Fig. 1 is a side view depicting the general structure of a motorcycle according to the present embodiment, and Fig. 2 is a plan view thereof. This motorcycle 1 includes a body frame 2. This body frame 2 is composed of a head pipe 3, a pair of left and right main frames 4 and a pair of left and right down tubes 5, which are almost annularly joined together by welding. The main frame 4 includes a linear portion and a downward extension 4A. The linear portion extends almost linearly from the head pipe 3 rearward and downward. The downward extension 4A bends downward from the rear end of the linear portion and then loops back in a substantially inverted C-shape. The main frame 4 and the down tube 5 are connected by a reinforcing frame 6 in the vicinity of the head pipe 3. An engine 8 is suspended via a plurality of engine hangers 7 in a lager space surrounded by the main frames 4, down tubes 5 and reinforcing frame 6. [0010] A pair of left and right seat rails 9 extending rearward are each joined to a corresponding one of the upper ends (which correspond to the rear ends of the linear portions of the main frames 4) of the lower extensions 4A included in the main frames 4. The seat rails 9 include a pair of left and right upper tubes 9A, a pair of left and right lower tubes 9B and cross members 9C. The upper tube 9A extends rearward and upward from the upper end of the lower extension 4A of the main frame 4. The lower tube 9B extends rearward and upward from the almost intermediate position of the lower extensions 4A. The cross member 9C is spanned between the upper tube 9A and the lower tube 9B. A seat 10 is supported above the upper tubes 9A and a rear seat cowl 11 is disposed on both sides of the upper and lower tubes 9A, 9B. [0011] A pair of left and right front forks 12 rotatably supporting a front wheel 20F are pivotally supported by the head pipe 3 via a steering stem 13. A top bridge 14 is attached to the upper ends of the front forks 12 and steering stem 13. A steering handlebar 15 provided with a brake lever 15A and a clutch lever 15B is secured to the top bridge 14. A headlamp 17 and a meter 18 are attached to the front forks 12 via stays 16. [0012] A pivot plate 4B is secured to an intermediate portion of each of the lower extensions 4A included in the main frames 4. A pair of left and right rear forks 21 rotatably supporting a rear wheel 2OR are vertically swingably supported by a pivot shaft 19 spanned between the pivot plates 4B. A mono-cushion structure is adopted in which a single rear cushion 30 is interposed between the rear forks 21 and the rear ends of the linear portion of the main frames 4 so as to absorb a shock transmitted from the rear wheel 20R via the rear forks 21 to the body frame 2. The lower extensions 4A are provided with respective foot steps 22, one of the lower extensions 4A is provided with a gear change pedal 23 and the other a brake pedal 24, as shown in Fig, 2. [0013] A master cylinder (not shown) is located in the vicinity of and connected to each of the brake pedal 24 and the brake lever 15A. A hydraulic hose (not shown) extending from the master cylinder is connected to a brake unit 2 0BR (only the brake unit of the front wheel 20F is depicted in Fig. 1) which operates a corresponding one of the front wheel 20F and the rear wheel 20R. Brake fluid is filled in the master cylinder and the hydraulic hose. When the brake pedal 24 and the brake lever 15A are each operated, a corresponding one of the master cylinders increases the pressure of the brake fluid in the hydraulic hose. The increased pressure of the brake fluid operates each brake unit 20BR. [0014] As shown in Figs. 1 and 2, an antilock brake control unit 100 is provided rearward of the rear cushion 30. The antilock control unit 100 detects the slip of the front wheel 20F and the rear wheel 20R on the basis of the detection results of wheel speed sensors for detecting the rotating speed of the front wheel 20F and the rear wheel 20R and a vehicle speed sensor not shown. Upon detecting the slip of the front wheel 20F and the rear wheel 20R, the control unit 100 controls the brake fluid pressure applied to each brake unit 20BR to minimize the slip of the front wheel 20F and the rear wheel 20R. [0015] The engine 8 includes a crankcase 25, a cylinder block 2 6 extending upward from the front of the crankcase 25, and a cylinder head 27 joined to the upper portion of the cylinder block 26. A piston is housed in the cylinder of the cylinder block 26 so as to enable reciprocation therein. A crankshaft 25A connected to the piston via a connecting rod and an output shaft 25B of the engine 8 are journaled by the crankcase 25. A clutch mechanism, a speed change mechanism, a power generation mechanism and the like are housed in the crankcase 25. The clutch mechanism and the speed change mechanism constitute a power transmission mechanism disposed between the crankshaft 25A and the output shaft 25B. The output shaft 25B of the engine 8 and the rear wheel shaft of the rear wheel 20R are provided with sprockets 28A and 28B, respectively. A drive chain 28C is wound around the sprockets 28A, 28B so that power of the engine 8 may be transmitted via the drive chain 2 8C to the rear wheel 20R. [0016] An intake valve and an exhaust valve are housed in a cylinder head 27. The intake valve and the exhaust valve open/close an intake passage and an exhaust passage, respectively, both communicating with the cylinder in a cylinder block 26. An exhaust port 27A of the intake/exhaust passage is formed in the front surface of the cylinder head 27 so as to connect with an exhaust pipe 31. This exhaust pipe 31 extends downward from the exhaust port 27A, further extending rearward below the crankcase, and is joined at its extending end to an exhaust muffler 32. A radiator 29 which cools cooling water for the engine 8 is disposed forward of the cylinder head 27. A radiator reserve tank 80 is connected to the radiator 29 via a hose. This reserve tank 80 is disposed on the right-hand side of the rear cushion 30. An intake port 27B of the intake/exhaust passage is disposed on the back surface of the cylinder head 27 and connected to a throttle body 36 provided with an injector 35. An air cleaner box 40 disposed above the cylinder head 27 is connected to the throttle body 36. A fuel tank 50 is disposed above the cylinder head 27 so as to cover the air cleaner box 40. [0017] The air cleaner box 40 is supported between the main frames 4 as shown in Fig. 3. The air cleaner box 4 0 includes a case dividable into a lower case 41 and an upper case 42 as shown in Figs. 4(A) and 4(B). A filter 43 is disposed between the lower case 41 and the upper case 42 so as to divide the inside of the case into an external air introduction chamber Rl and a clarified air chamber R2. A suction duct 41A is attached to the lower case 41 so as to extend forward therefrom. The external air is introduced into the external air introduction chamber Rl in the lower case 41 via the suction duct 41A. The air (external air) in the external air introduction chamber Rl is clarified by the filter 4 3 and supplied into the clarified air chamber R2 in the upper case 42. This clarified air is supplied, via the exhaust duct 42A formed at the rear portion of the upper case 42, to the throttle body 36 (see Fig. 1) connected to the exhaust duct 42A. [0018] In this way, since the air cleaner box 40 is provided with the intake duct 41A extending forward, as shown in Fig. 1 the external air present forward of the engine 8 is introduced into the air cleaner box 40, in other word, the external air that is wormed up by the engine 8 is prevented from being introduced into the box 40. In addition, the external air introduced from the intake duct 41A is supplied to the throttle body 36 after flowing rearward in the air cleaner box 40. Therefore, during running of the vehicle, the air (driving wind) with higher pressure than the atmospheric pressure can be supplied to the throttle body 36. This makes it possible to increase the charging efficiency of air-fuel mixture fed to the engine 8 via the throttle body 36, thereby enhancing engine performance. [0019] The fuel tank 50 has a bracket 51 located at its rear end as shown in Figs. 5(A) and (B). As shown in Fig. 3, the bracket 51 is turnably connected to a fuel tank stay 52 via a connection shaft 59. The fuel tank stay 52 is disposed on the almost-intermediate portion of the upper tube 9A of the seat rail 9. In this way, the fuel tank 50 is turnably supported with reference to the connection shaft 59 for connecting the bracket 51 and the fuel tank stay 52 as shown in Fig. 1. As shown in Fig. 3, the fuel tank 50 has a front end 50A which is joined, with a bolt, to the main frame 4 in the vicinity of the head pipe 3. In addition, the fuel tank 50 has a rear end 50B which extends beyond the rear end of the linear portion of the main frame 4 and is joined to the upper tube 9A of the seat rail 9 in the vicinity of the fuel tank stay 52. In other words, the fuel tank 50 has a length extending between the main frames 4 and the seat rails 9. Specifically, the fuel tank is formed to have a length from a portion near the head pipe 3 to an almost-intermediate portion of the upper tube 9A and a greater width than that of the pair of left and right main frames 4 as shown in Fig. 2. Thus, the fuel tank 50 is formed as a relatively large-sized fuel tank as compared with the standard-sized fuel tank mounted on a vehicle body of this type. [0020] As shown in Fig. 5(A), the fuel tank 50 is provided at its upper part with a fuel port 53, which is closed with a lid member 54 (Fig. 3). A bottom portion 55 of the fuel tank 50 consists of a front half part 55A and a rear half part 55B. The front half part 55A is formed in a concave shape so as to enable to accommodate the air cleaner box 40 therein. The rear half part 55B is the undermost surface of the fuel tank 50. This bottom surface 55B extends approximately horizontally and as depicted with an imaginary line a fuel pump 60 is placed on the bottom surface 55B. This bottom surface 55B is formed with an opening 55C as shown in Fig. 5(B) and a pump mount seat 55D is formed around the opening 55C. A plurality of bolts 56 are spaced from each other in the pump mount seat 55D. A pump body 61 of the fuel pump 60 is inserted into the opening 55C. The bolts 56 are inserted into holes of a flange 62 formed integrally with the lower portion of the pump body 61. With this inserting state, nuts 5 7 are fastened to the bolts 56, whereby the fuel pump 60 i-s secured to the pump mount seat 55D. The fuel pump 6 0 feeds fuel sucked from the fuel tank 50 by the pump body 61, to an injector 35 connected via a fuel hose to the lower portion of the pump body 61. [0021] A support structure of the rear cushion 3 0 will be next described. As shown in Fig. 1, the rear cushion 3 0 has a lower end 30A which is turnably supported by lower brackets 71 at a position between the connection shaft 59 and the rear wheel 20. The lower brackets 71 are integrally attached to the upper portions of the rear forks 21. The lower brackets 71 are located approximately directly below the connection shaft 59 or the fuel tank stay 52. The rear cushion 30, while its lower end 30A is held by the lower brackets 71, extends forward and obliquely upward as shown in Fig. 3. An upper end 30B of the rear cushion 3 0 is turnably supported by an upper bracket 70, which is secured to the linear portion of the main frame 4 . [0022] A turn-pivot of the upper end 30B of the rear cushion 3 0 is located at a position above the linear portions of the main frames 4, above the upper tubes 9A of the seat rails 9, forward of the fuel pump 6 in the fuel tank 50, and below the pump mount seat 55D of the fuel tank 50. In other words, the turn-pivot is positioned in a triangular space enclosed by the linear portion of the main frame 4, the upper tube 9A and the fuel tank 50. [0023] The upper bracket 70 is joined to the cross member 4C spanned between the main frames 4, and extends rearward from the cross member 4C. The upper end 30B of the rear cushion 3 0 is held by the extension end of the upper bracket 70. In this way, the upper end 30B of the rear cushion 30 is held by the cross member 4C of the main frames 4; therefore, the attachment strength of the rear cushion 30 is increased. In addition, the upper bracket 70 extends rearward from the cross member 4C and the rear cushion 30 is connected to the extension end of the upper bracket 70; therefore, a space can be formed rearward of the cross member 4C and the rear cushion 30. Such a space can be effectively utilized for disposing the pump mount seat 55C of the fuel tank 5 0 therein. [0024] As shown in Fig. 2, the above-mentioned radiator reserve tank 80 and a battery 82 are symmetrically disposed on the right-hand and left-hand spaces of the rear cushion 30, respectively. The battery 8 2 supplies electric power to component parts (e.g., the antilock brake control unit 100 and the headlamp 70) of the vehicle. Thus, the radiator reserve tank 80 and battery 82 which are relatively heavy in weight are arranged in a concentrated manner at the substantially central position of the vehicle. This leads to centralized mass, thereby enhancing vehicle-handling performance. [0025] In the present embodiment, the lower end 30A of the rear cushion 3 0 is directly pin-connected to the lower brackets 71 of the rear forks 21. Therefore, the embodiment can reduce the number of component parts as compared with the conventional technique in which a link is connected to the lower ends of rear forks and via the link the lower ends are supported by rear forks. In addition, the lower end 30A of the rear cushion 30 is turnably pin-connected to the lower brackets 71 located approximately directly below the connection shaft 59 or the fuel tank stay 52. While the rear cushion 30 is extended forward and obliquely upward, its lower end 3 0A is disposed in the triangular space enclosed by the linear portion of the main frame 4, the upper tube 9A and the fuel tank 50, and is turnably pin-connected to the upper bracket 70 located forward of the fuel pump 60. Thus, in addition to the securing of the sufficient stroke of the rear cushion 30, the fuel tank 50 can be increased or maintained in capacity while the rear cushion 3 0 and the fuel tank 50 are avoided from interfering with each other. [0026] In this case, the rear cushion 30 is disposed in such a posture that its upper end 30B is located upward and forward of the position of the lower end 30a held by the rear forks 21. In other words, the rear cushion 30 is disposed in such a posture that the upper end 30B is significantly inclined forward or toward the front of the vehicle. Thus, the sufficient stroke of the rear cushion can be ensured. Further, since the upper end 30B of the rear cushion 30 is disposed above the upper tubes 9A of the seat rails 9, it is attached or detached with ease from above the seat rails 9. As shown in Fig. 3, the upper end 30B of the rear cushion 3 0 is disposed in the triangular space enclosed by the fuel tank 50, the main frame 4 and the seat rail 9, as viewed from the side. Thus, even in a normal state where the fuel tank 50 is disposed on the main frames 4, the upper end 30 can be detached or attached. [0027] While the invention has been described with reference to the embodiment thus far, it is evidently that the present invention is not limited to the embodiment. In the embodiment described above, for example, the lower end 3 0A of the rear cushion 30 is supported by the lower brackets 71 joined to the upper portions of the rear forks 21. However, the present invention is not limited to this configuration. For example, the lower bracket 71 mentioned above may be disposed between the pair of left and right rear forks 21 and the lower end 30A of the rear cushion 30 may be supported by the lower bracket 71. In this case, a supporting position of the lower end 30A of the rear cushion 30 can be lowered, and therefore, a rear cushion 30 with a longer cushion stroke can be applicable. In addition, in the embodiment described above, the present invention is applied to the motorcycle in which the body frame 2 includes the pair of left and right main frames 3. However, the body frame 2 is not limited to the configuration described above. For example, the body frame 2 can be widely applied to motorcycles having any body frame, such as motorcycles having a single main frame that extends in the back-and-forth direction on the general center of the vehicle body. [Brief Description of the Drawings] [0028] [Fig. 1] Fig.lisa side view illustrating the overall configuration of a motorcycle according to the present embodiment. [Fig. 2] Fig. 2 is a top view of the motorcycle. [Fig. 3] Fig. 3 illustrates a body frame of the motorcycle and its peripheral configuration, [Fig. 4] Fig. 4A is a bottom view of an air cleaner box; Fig. 4B is a cross-sectional side view thereof. [Fig. 5] Fig. 5A is a side view of a fuel tank; Fig. 5B is a bottom view thereof. [Description of Reference Symbols] [0029] 1:motorcycle 2:body frame 3:head pipe 4:main frame 4C, 9C:cross member 5:down tube 6:reinforcing frame 7:engine hanger 8:engine 9:seat rail 2 0BR:brake unit 21:rear fork 30:rear cushion 35:injector 36:throttle body 40:air cleaner box 50:fuel tank 60:fuel pump 70:upper bracket 71:lower bracket 80:radiator reserve tank 82:battery 100:antilock brake control unit

Documents:

1288-CHE-2006 CORRESPONDENCE OTHERS.pdf

1288-CHE-2006 CORRESPONDENCE PO.pdf

1288-che-2006-abstract.pdf

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1288-che-2006-claims.pdf

1288-che-2006-correspondence-others.pdf

1288-che-2006-description-complete.pdf

1288-che-2006-drawings.pdf

1288-che-2006-form 1.pdf

1288-che-2006-form 18.pdf

1288-che-2006-form 26.pdf

1288-che-2006-form 3.pdf

1288-che-2006-form 5.pdf

1288-che-2006-priority document.pdf