Vehicle body frame for vehicle and saddle-ridden vehicle

Abstract

A vehicle body frame (1) for a vehicle comprises: a first pipe member (21, 31) which includes a portion having a first thicknesses (t1, t1'); and a second pipe member (22, 32) which includes a portion having a second thickness (t2, t2') smaller than the first thickness. The vehicle body frame (1) has a joint portion (23, 33) where a first end face (ES1, ES1'), which is one end face of the first pipe member, and a second end face (ES2, ES2'), which is one end face of the second pipe member, are butt-joined. At a position spaced apart from the joint portion, either the first pipe member or the second pipe member has a thickness change portion (TC) where the thickness changes in the length direction. The thickness of the first pipe member and the thickness of the second pipe member at the joint portion are the same as one another.

Description

Vehicle body frame for a vehicle and a straddle-type vehicle

[0001] The present invention relates to a vehicle body frame for a vehicle and a straddle-type vehicle.

[0002] Conventionally, various vehicle body frames for straddle-type vehicles have been proposed. For example, Patent Document 1 discloses a vehicle body frame preferably used for a scooter-type motorcycle.

[0003] The vehicle body frame disclosed in Patent Document 1 includes a head pipe portion, a down frame portion extending downward from the head pipe portion, a left side frame connected to the lower portion of the down frame portion and extending in the front-rear direction as a whole on the left side of the head pipe portion, a right side frame connected to the lower portion of the down frame portion and extending in the front-rear direction as a whole on the right side of the head pipe portion, and a connecting frame connecting the left side frame and the right side frame. Each of the head pipe portion, the down frame portion, the left side frame, the right side frame, and the connecting frame is composed of a hollow pipe member.

[0004] Japanese Patent Application Laid-Open No. 2017-121849

[0005] In straddle-type vehicles that require high mobility such as motorcycles, weight reduction is strongly desired, and weight reduction of the vehicle body frame is also desired. As will be described in detail later, the inventor of the present application considered adopting a new structure that can achieve weight reduction for the vehicle body frame, but found that a new problem of strength reduction occurs in that structure.

[0006] An embodiment of the present invention has been made in view of the above problems, and an object thereof is to provide a vehicle body frame for a vehicle that can achieve both weight reduction and strength retention.

[0007] This specification discloses a vehicle body frame for a vehicle and a straddle-type vehicle described in the following items.

[0008] [Item 1] A vehicle body frame comprising: a first pipe member including a portion having a first thickness; and a second pipe member including a portion having a second thickness smaller than the first thickness, wherein a first end face, which is one end face of the first pipe member, and a second end face, which is one end face of the second pipe member, are butt-joined, and one of the first pipe member and the second pipe member has a thickness-changing portion, which changes in thickness in the longitudinal direction, located away from the joint, and the thickness of the first pipe member and the thickness of the second pipe member at the joint are the same.

[0009] A vehicle body frame according to an embodiment of the present invention comprises a first pipe member including a portion having a first thickness and a second pipe member including a portion having a second thickness smaller than the first thickness, and has a joint portion where a first end face, which is one end face of the first pipe member, and a second end face, which is one end face of the second pipe member, are butt-joined. By adopting such a configuration, the weight of the vehicle body frame can be reduced.

[0010] Furthermore, in the vehicle frame according to the embodiment of the present invention, one of the first pipe member and the second pipe member has a thickness-changing portion where the thickness changes in the longitudinal direction, located away from the joint, and the thickness of the first pipe member and the second pipe member at the joint are the same. As a result, the stress concentration point when force (load) is applied to the vehicle frame can be moved away from the joint (i.e., shifted), thereby improving the strength of the vehicle frame.

[0011] [Item 2] The vehicle body frame according to Item 1, wherein the first pipe member has the thickness-changing portion, and the thickness of the first pipe member changes from a first thickness to a second thickness in the thickness-changing portion.

[0012] An embodiment of the present invention may include, for example, a configuration in which the first pipe member has a thickness-changing portion. When the first pipe member has a thickness-changing portion, it can be said that the first pipe member is locally thinned on the side of the second pipe member, and the thickness of the first pipe member changes, for example, from a first thickness to a second thickness at the thickness-changing portion.

[0013] [Item 3] The vehicle body frame according to Item 1, wherein the second pipe member has the thickness-changing portion, and the thickness of the second pipe member changes from the second thickness to the first thickness in the thickness-changing portion.

[0014] An embodiment of the present invention may have a configuration in which the second pipe member has a thickness-changing portion. When the second pipe member has a thickness-changing portion, it can be said that the second pipe member is locally thickened on the first pipe member side, and the thickness of the second pipe member changes, for example, from a second thickness to a first thickness at the thickness-changing portion.

[0015] [Item 4] A vehicle body frame according to any one of items 1 to 3, wherein the distance from the joint to the thickness change portion is set so that stress concentration due to load does not substantially occur at the joint.

[0016] From the viewpoint of improving strength, it is preferable that the distance from the joint to the section with a change in wall thickness is set so that stress concentration due to the load does not substantially occur at the joint.

[0017] [Item 5] A vehicle body frame according to any one of items 1 to 4, wherein the distance from the joint to the thickness change portion is 5 mm or more.

[0018] From the viewpoint of improving strength, it is preferable that the section with a change in wall thickness be located at a certain distance or more from the joint. Specifically, it is preferable that the distance from the joint to the section with a change in wall thickness be 5 mm or more.

[0019] [Item 6] A vehicle body frame according to any one of items 1 to 5, wherein the distance from the joint to the thickness change portion is 50 mm or less.

[0020] From the viewpoint of reducing processing time and improving productivity, it is preferable that the section with a change in wall thickness is not too far from the joint. Specifically, it is preferable that the distance from the joint to the section with a change in wall thickness be 50 mm or less.

[0021] [Item 7] A vehicle body frame according to any one of items 1 to 6, wherein the first end face of the first pipe member and the second end face of the second pipe member are surfaces inclined with respect to the radial direction.

[0022] If the first end face of the first pipe member and the second end face of the second pipe member are inclined with respect to the radial direction, misalignment between the first pipe member and the second pipe member can be prevented, and the joint can be made more stable.

[0023] [Item 8] The vehicle body frame according to Item 7, wherein the first end face of the first pipe member and the second end face of the second pipe member are inclined such that the first end face is located radially outward from the second end face.

[0024] When the first pipe member has a section with a change in wall thickness, it is preferable that the first end face of the first pipe member and the second end face of the second pipe member are inclined such that the first end face is located radially outward from the second end face. By adopting such a configuration, it becomes easy to continuously perform the process of locally thinning the first pipe member and tapering the first end face, thereby simplifying the manufacturing of the first pipe member.

[0025] [Item 9] The vehicle body frame according to any one of items 1 to 8, wherein the joint is a welded joint formed by butt welding of the first end face and the second end face.

[0026] The joint may be, for example, a welded joint formed by butt welding the first end face of the first pipe member to the second end face of the second pipe member. Since the welded joint is a part where the material has become brittle due to the heat input during welding, the configuration in which the joint is a welded joint is significant in that it separates (shifts) the area of ​​thickness change (stress concentration area) from the joint.

[0027] [Item 10] A saddle-type vehicle equipped with a vehicle body frame as described in any of Items 1 to 9.

[0028] [Item 11] The saddle-type vehicle described in Item 10, wherein the first pipe member and the second pipe member are parts of the vehicle body frame that extend in the longitudinal direction of the vehicle as a whole.

[0029] The first pipe member and the second pipe member are, for example, parts of the vehicle frame that extend in the longitudinal direction of the vehicle as a whole. In a saddle-type vehicle, the required rigidity and strength of the parts extending in the longitudinal direction may differ depending on their position in the longitudinal direction. By having the first pipe member and the second pipe member having the above-described configuration in such parts, it is possible to achieve both weight reduction and the securing of rigidity and strength.

[0030] [Item 12] The saddle-type vehicle according to Item 11, wherein the first pipe member is located in front of the second pipe member.

[0031] In the case of a saddle-type vehicle, if a relatively heavy component (e.g., the engine) is supported at the front of the vehicle frame, it is preferable that the first pipe member be located further forward than the second pipe member.

[0032] [Item 13] The saddle-type vehicle according to Item 12, wherein the joint is located aft of the center in the longitudinal direction of the vehicle.

[0033] The center of gravity of a saddle-type vehicle is often set near the center in the longitudinal direction of the vehicle. Therefore, when the first pipe member is located in front of the second pipe member, it is preferable that the joint be located behind the center in the longitudinal direction of the vehicle, from the viewpoint of ensuring rigidity and strength to support relatively heavy components.

[0034] According to embodiments of the present invention, it is possible to provide a vehicle body frame that can achieve both weight reduction and strength.

[0035] This is a left side view showing a motorcycle 100 equipped with a vehicle body frame 1 according to an embodiment of the present invention. This is a perspective view showing the vehicle body frame 1. This is a left side view showing the vehicle body frame 1. This is a right side view showing the vehicle body frame 1. This is a top view showing the vehicle body frame 1. This is an enlarged cross-sectional view showing a part of the left side frame 4 (near the joint 23). This is an enlarged cross-sectional view showing a part of the right side frame 5 (near the joint 33). This is an enlarged cross-sectional view showing a part of the left side frame 4 (near the joint 23). This is an enlarged cross-sectional view showing a part of the right side frame 5 (near the joint 33). This is an enlarged cross-sectional view showing a part of the left side frame 4 (near the joint 23). This is an enlarged cross-sectional view showing a part of the right side frame 5 (near the joint 33). This is a diagram for explaining the inclination angle θi of the first end faces ES1 and ES1' of the first pipe members 21 and 31. This diagram illustrates the inclination angle θi of the second end faces ES2 and ES2' of the second pipe members 22 and 32. This is an enlarged cross-sectional view showing a part of the left side frame 4 (near the joint 23). This is an enlarged cross-sectional view showing a part of the right side frame 5 (near the joint 33).

[0036] The following description will explain, with reference to the drawings, a vehicle body frame according to an embodiment of the present invention and a saddle-type vehicle equipped therewith. A saddle-type vehicle is a vehicle on which a rider straddles and rides. In the following description, a motorcycle will be used as an example of a saddle-type vehicle. The type of motorcycle is not limited and may be any type such as a scooter, moped, off-road, or on-road. Furthermore, the saddle-type vehicle is not limited to a motorcycle and may be an ATV (All Terrain Vehicle), etc.

[0037] Referring to Figures 1 to 5, the overall configuration of a motorcycle 100 equipped with a vehicle body frame (hereinafter simply referred to as "body frame") 1 according to an embodiment of the present invention will be described. The motorcycle 100 illustrated is a scooter type. Figure 1 is a left side view showing the motorcycle 100. Figures 2, 3, 4, and 5 are a perspective view, left side view, right side view, and plan view, respectively, showing the body frame 1.

[0038] In the following explanation, front, rear, left, right, up, and down refer to the front, rear, left, right, up, and down directions as seen from the perspective of a passenger seated on the seat of the motorcycle 100. Up and down refer to the vertical directions when the motorcycle 100 is stopped on a horizontal plane. These directions are also used when describing each part of the vehicle frame 1. Therefore, front, rear, left, right, up, and down in the vehicle frame 1 refer to the front, rear, left, right, up, and down directions when the vehicle frame 1 constitutes part of the motorcycle 100.

[0039] As shown in Figure 1, the saddle-type vehicle 100 comprises a body frame 1, front wheels 41 and rear wheels 42, a seat 43, a power unit 50, a steering device 60, and a body cover 70. In Figure 1, the seat 43 and the body cover 70 are indicated by dashed lines.

[0040] The vehicle frame 1 includes a head pipe section 2, a down frame section 3, a left side frame 4, a right side frame 5, a connecting member 6, and a connecting frame 7. The down frame section 3 extends downward and rearward from the head pipe section 2. Gusset sections 8 are attached to both the head pipe section 2 and the down frame section 3.

[0041] The left side frame 4 includes a left lower frame section 4a and a left rear frame section 4b. The left lower frame section 4a is located to the left of the head pipe section 2. The left lower frame section 4a is connected to the lower part of the down frame section 3. The left lower frame section 4a extends from the lower part of the down frame section 3 to the left and rearward in the vehicle width direction.

[0042] The left rear frame portion 4b is disposed to the left of the head pipe portion 2. The left rear frame portion 4b is connected to the rear portion of the left lower frame portion 4a. The left rear frame portion 4b extends rearward and upward from the left lower frame portion 4a.

[0043] The right side frame 5 includes a right lower frame portion 5a and a right rear frame portion 5b. The right lower frame portion 5a is disposed to the right of the head pipe portion 2. The right lower frame portion 5a is connected to the lower portion of the down frame portion 3. The right lower frame portion 5a extends from the lower portion of the down frame portion 3 to the right side and rearward in the vehicle width direction.

[0044] The right rear frame portion 5b is disposed to the right of the head pipe portion 2. The right rear frame portion 5b is connected to the rear portion of the right lower frame portion 5a. The right rear frame portion 5b extends rearward and upward from the right lower frame portion 5a.

[0045] The left lower frame portion 4a and the right lower frame portion 5a are connected by a cross frame portion 9. The cross frame portion 9 extends in the vehicle width direction. A power unit 50 is attached to the left lower frame portion 4a and the right lower frame portion 5a via a link member 44.

[0046] The rear portion of the left rear frame portion 4b and the rear portion of the right rear frame portion 5b are connected by a cross member 11.

[0047] The connecting frame 7 connects the left side frame 4 and the right side frame 5. More specifically, the connecting frame 7 connects the left rear frame portion 4b and the right rear frame portion 5b. At least a part of the connecting frame 7 is located above the left lower frame portion 4a and the right lower frame portion 5a.

[0048] The connecting frame 7 includes a left support portion 7a, a right support portion 7b, and a central portion 7c. The left support portion 7a is connected to the left rear frame portion 4b. In a side view of the vehicle, the left support portion 7a extends obliquely upward and forward from the left rear frame portion 4b. The right support portion 7b is connected to the right rear frame portion 5b. In a side view of the vehicle, the right support portion 7b extends obliquely upward and forward from the right rear frame portion 5b.

[0049] As shown in FIG. 5, the central portion 7c connects the left support portion 7a and the right support portion 7b. In a plan view of the vehicle, the central portion 7c extends in the vehicle width direction. In a plan view of the vehicle, the left support portion 7a extends forward and inward from the left rear frame portion 4b. In a plan view of the vehicle, the right support portion 7b extends forward and inward from the right rear frame portion 5b.

[0050] Here, the inner side means the direction approaching the center line of the vehicle in the vehicle width direction in the vehicle width direction. Also, the outer side means the direction away from the center line of the vehicle in the vehicle width direction in the vehicle width direction.

[0051] The connecting member 6 extends in the vehicle front-rear direction above the left lower frame portion 4a and the right lower frame portion 5a. The connecting member 6 connects the down frame portion 3 and the connecting frame 7. In a side view of the vehicle, the connecting member 6 is disposed obliquely in the vehicle front-rear direction. The connecting member 6 is inclined forward and upward.

[0052] The front portion of the connecting member 6 is connected to the down frame portion 3 at a position above the lower end portion of the gusset portion 8. The rear portion of the connecting member 6 is connected to the connecting frame 7. More specifically, the rear portion of the connecting member 6 is connected to the central portion 7c of the connecting frame 7 as shown in FIG. 5.

[0053] As shown in Figure 1, the seat 43 is supported by the vehicle frame 1. The rider sits on the seat 43. The seat 43 is supported by the left side frame 4 and the right side frame 5. More specifically, the front part of the seat 43 is supported by the left side frame 4 and the right side frame 5 via the storage compartment 45. The rear part of the seat 43 is supported by the left side frame 4 and the right side frame 5 via the cross member 11. The support structure of the seat 43 may be modified as appropriate. For example, the seat 43 may be directly supported by the left side frame 4 and the right side frame 5, or the seat 43 may be indirectly supported by the left side frame 4 and the right side frame 5 via stays.

[0054] A storage compartment 45 is located below the seat 43. The front of the storage compartment 45 is supported by the connecting frame 7. The storage compartment 45 has a storage space from which the rider's belongings, such as helmets and gloves, can be put in and taken out.

[0055] The power unit 50 is located below the seat 43. The power unit 50 is pivotably supported by the vehicle frame 1. The power unit 50 rotatably supports the rear wheels 42. The power unit 50 includes an engine 51 and a transmission 56.

[0056] The engine 51 includes a crankcase 52, a cylinder block 53, a cylinder head 54, and a cylinder head cover 55. The crankcase 52 is located in front of the rear wheel 42. The cylinder block 53 is located in front of the crankcase 52. The cylinder head 54 is located in front of the cylinder block 53. In a side view of the vehicle, the cylinder head 54 is located below the connecting frame 7. The cylinder head cover 55 is located in front of the cylinder head 54. The cylinder head cover 55 is detachably attached to the cylinder head 54. The connecting frame 7 is connected to the left side frame 4 and the right side frame 5 at a position rearward from at least a portion of the cylinder head cover 55. The upper end of the connecting frame 7 is located above the cylinder head cover 55.

[0057] A portion of the engine 51 is positioned behind the fuel tank 46 and below the storage compartment 45. The engine 51 is suspended from the left side frame 4 and the right side frame 5 via the link member 44 described above.

[0058] The steering system 60 includes a steering shaft 61, a handle member 62, and a suspension 63. The steering shaft 61 is inserted into the head pipe section 2. The steering shaft 61 is supported in the head pipe section 2 so as to be rotatable from side to side. The lower part of the steering shaft 61 is connected to the suspension 63.

[0059] The suspension 63 rotatably supports the front wheel 41. A front fender 47 is positioned above the front wheel 41. The upper part of the steering shaft 61 is connected to a handle member 62. The handle member 62 is operated by the rider to rotate the front wheel 41.

[0060] The vehicle body cover 70 includes a rear cover 71, a lower cover 72, a tunnel section 73, and a front cover 74. The rear cover 71 covers the periphery of the left rear frame section 4b and the right rear frame section 5b. The rear cover 71 is located below the seat 43. The front cover 74 is located in front of the seat 43. The front cover 74 covers the periphery of the head pipe section 2. The front cover 74 also covers the periphery of the down frame section 3. A headlamp 76 is attached to the front cover 74.

[0061] The lower cover 72 is positioned between the front cover 74 and the rear cover 71. The lower cover 72 covers the periphery of the left lower frame portion 4a and the right lower frame portion 5a. The upper surface of the lower cover 72 includes a footrest portion 72a. The footrest portion 72a is located below and in front of the seat 4 and is supported by the left lower frame portion 4a and the right lower frame portion 5a. The footrest portion 72a is located below the connecting member 6.

[0062] The tunnel section 73 is positioned between the front cover 74 and the rear cover 71 in the longitudinal direction of the vehicle. The tunnel section 73 has a cross-sectional shape that bulges upward. The connecting member 6 and the fuel tank 46 are positioned inside the tunnel section 73. Inside the tunnel section 73, the connecting member 6 is positioned above the fuel tank 46.

[0063] Here, with further reference to Figures 6A and 6B, the configurations of the left side frame 4 and the right side frame 5 of the vehicle body frame 2 will be explained in more detail. Figure 6A is an enlarged cross-sectional view showing a part of the left side frame 4, and Figure 6B is an enlarged cross-sectional view showing a part of the right side frame 5. Note that in Figures 6A and 6B, the thickness of the members is exaggerated for clarity (the same applies to subsequent cross-sectional views).

[0064] The left side frame 4 has two pipe members 21 and 22, each being hollow and tubular. The pipe members 21 and 22 are each made of a metal material (e.g., steel). As will be described later, one of the two pipe members 21 and 22, pipe member 21, is relatively thick-walled, and the other pipe member 22 is relatively thin-walled. Hereafter, the pipe member 21, which is relatively thick-walled, will be referred to as the "first pipe member," and the pipe member 22, which is relatively thin-walled, will be referred to as the "second pipe member." Here, the outer diameter of the first pipe member 21 and the outer diameter of the second pipe member 22 are the same.

[0065] The first pipe member 21 and the second pipe member 22 are butt-jointed. The portion 23 where one end face ES1 of the first pipe member 21 (hereinafter also referred to as the "first end face") and one end face ES2 of the second pipe member 22 (hereinafter also referred to as the "second end face") are butt-jointed is hereinafter referred to as the "joint portion". Figure 6A shows the vicinity of the joint portion 23 of the left side frame 4.

[0066] Here, the joint 23 is a "welded joint" formed by butt welding the first end face ES1 of the first pipe member 21 and the second end face ES2 of the second pipe member 22. The method of welding the first pipe member 21 and the second pipe member 22 is not particularly limited, and various welding methods such as TIG welding can be used.

[0067] In the illustrated example, the first pipe member 21 is located in front of the second pipe member 22. The joint 23 is located in the left rear frame portion 4b. Therefore, the first pipe member 21 constitutes the left lower frame portion 4a and a part of the left rear frame portion 4b, while the second pipe member 22 constitutes the remaining portion of the left rear frame portion 4b.

[0068] The first pipe member 21 includes a portion having a first thickness t1. The second pipe member 22 includes a portion having a second thickness t2 which is smaller than the first thickness t1. Here, the second pipe member 22 has the second thickness t2 throughout its entirety. In other words, the thickness of the second pipe member 22 does not change in the longitudinal direction.

[0069] In contrast, the first pipe member 21 has a thickness-changing section TC, where the thickness changes in the longitudinal direction, located away from the joint 23. The first pipe member 21 has a first thickness t1 in front of the thickness-changing section TC (i.e., on the side opposite to the second pipe member 22 with respect to the thickness-changing section TC), and a second thickness t2 in rear of the thickness-changing section TC (i.e., on the side of the second pipe member 22 with respect to the thickness-changing section TC). In other words, the thickness of the first pipe member 21 changes from the first thickness t1 to the second thickness t2 at the thickness-changing section TC. Therefore, the thickness of the first pipe member 21 and the thickness of the second pipe member 22 at the joint 23 are the same.

[0070] In the illustrated example, at the thickness change section TC, the inner circumferential surface 21i of the first pipe member 21 forms an angle of approximately 90° with respect to the length direction, and the thickness of the first pipe member 21 changes in a step-like manner. Also, in the illustrated example, the first end face ES1 of the first pipe member 21 and the second end face ES2 of the second pipe member 22 are surfaces inclined with respect to the radial direction (hereinafter also referred to as "tapered surfaces").

[0071] The right side frame 5, like the left side frame 4, has two pipe members 31 and 32, each being hollow and tubular. The pipe members 31 and 32 are each made of a metal material (e.g., steel). As will be described later, one of the two pipe members 31 and 32, pipe member 31, is relatively thick-walled, and the other pipe member 32 is relatively thin-walled. Hereafter, similar to the pipe members 21 and 22 of the left side frame 4, the pipe member 31, which is relatively thick-walled, will be referred to as the "first pipe member," and the pipe member 32, which is relatively thin-walled, will be referred to as the "second pipe member." Here, the outer diameter of the first pipe member 31 and the outer diameter of the second pipe member 32 are the same.

[0072] The first pipe member 31 and the second pipe member 32 are butt-jointed. The portion 33 where one end face ES1' of the first pipe member 31 (hereinafter also referred to as the "first end face") and one end face ES2' of the second pipe member 32 (hereinafter also referred to as the "second end face") are butt-jointed is hereinafter referred to as the "joint portion". Figure 6B shows the vicinity of the joint portion 33 of the right side frame 5.

[0073] Here, the joint 33 is a "welded joint" where the first end face ES1' of the first pipe member 31 and the second end face ES2' of the second pipe member 32 are butt-welded, similar to the joint 23 of the left side frame 4.

[0074] In the illustrated example, the first pipe member 31 is located in front of the second pipe member 32. The joint 33 is located in the right rear frame portion 5b. Therefore, the first pipe member 31 constitutes the right lower frame portion 5a and a part of the right rear frame portion 5b, while the second pipe member 32 constitutes the remaining portion of the right rear frame portion 5b.

[0075] The first pipe member 31 includes a portion having a first thickness t1'. The second pipe member 32 includes a portion having a second thickness t2' which is smaller than the first thickness t1'. Here, the second pipe member 32 has the second thickness t2' throughout its entirety. In other words, the thickness of the second pipe member 32 does not change in the longitudinal direction.

[0076] In contrast, the first pipe member 31 has a thickness-changing section TC, where the thickness changes in the longitudinal direction, located away from the joint 33. The first pipe member 31 has a first thickness t1' in front of the thickness-changing section TC (i.e., on the side opposite to the second pipe member 32 with respect to the thickness-changing section TC), and a second thickness t2' in rear of the thickness-changing section TC (i.e., on the side of the second pipe member 32 with respect to the thickness-changing section TC). In other words, the thickness of the first pipe member 31 changes from the first thickness t1' to the second thickness t2' at the thickness-changing section TC. Therefore, the thickness of the first pipe member 31 and the thickness of the second pipe member 32 at the joint 33 are the same.

[0077] In the illustrated example, at the thickness change section TC, the inner circumferential surface 31i of the first pipe member 31 forms an angle of approximately 90° with respect to the length direction, and the thickness of the first pipe member 31 changes in a step-like manner. Also, in the illustrated example, the first end face ES1' of the first pipe member 31 and the second end face ES2' of the second pipe member 32 are surfaces inclined with respect to the radial direction (tapered surfaces).

[0078] As described above, in the vehicle frame 1 according to the embodiment of the present invention, the left side frame 4 comprises a first pipe member 21 including a portion having a first thickness t1 and a second pipe member 22 including a portion having a second thickness t2 smaller than the first thickness t1, and has a joint portion 23 where a first end face ES1, which is one end face of the first pipe member 21, and a second end face ES2, which is one end face of the second pipe member 22, are butt-joined. The right side frame 5 comprises a first pipe member 31 including a portion having a first thickness t1' and a second pipe member 32 including a portion having a second thickness t2' smaller than the first thickness t1', and has a joint portion 33 where a first end face ES1', which is one end face of the first pipe member 31, and a second end face ES2', which is one end face of the second pipe member 32, are butt-joined. By adopting such a configuration, the weight of the vehicle frame 1 can be reduced.

[0079] Furthermore, if pipe members with different wall thicknesses are simply butted together, the weight of the vehicle frame can be reduced, but when force (load) is applied to the vehicle frame, stress concentration occurs at the joint (i.e., the joint becomes a stress concentration point), raising concerns about a decrease in strength. In the vehicle frame 1 according to the embodiment of the present invention, the first pipe member 21 of the left side frame 4 has a thickness change section TC where the thickness changes in the longitudinal direction, located away from the joint 23, and the thickness of the first pipe member 21 and the second pipe member 22 at the joint 23 are the same. Also, the first pipe member 31 of the right side frame 5 has a thickness change section TC where the thickness changes in the longitudinal direction, located away from the joint 33, and the thickness of the first pipe member 31 and the second pipe member 32 at the joint 33 are the same. With this configuration, the stress concentration points when force (load) is applied to the vehicle frame 1 can be moved away from (i.e., shifted) from the joints 23 and 33, thereby improving the strength of the vehicle frame 1.

[0080] The first thickness t1 in the left side frame 4 and the first thickness t1' in the right side frame 5 may be the same or different. Similarly, the second thickness t2 in the left side frame 4 and the second thickness t2' in the right side frame 5 may be the same or different. The first thicknesses t1, t1' and the second thicknesses t2, t2' are not particularly limited and are set appropriately according to the specifications of the vehicle frame 1, the required strength, the degree of weight reduction to be achieved, etc.

[0081] The illustrated vehicle frame 1 has a configuration in which the first pipe members 21 and 31 have a thickness variation section TC. When the first pipe members 21 and 31 have a thickness variation section TC, it can be said that the first pipe members 21 and 31 are locally thinned on the side of the second pipe members 22 and 32. Such local thinning can be achieved, for example, by performing machining such as cutting on a part of a pipe member having a uniform thickness. Alternatively, instead of the configuration in which the first pipe members 21 and 31 have a thickness variation section TC, the configurations shown in Figures 7A and 7B may be adopted.

[0082] In the left side frame 4 shown in Figure 7A, the first pipe member 21 has a first thickness t1 throughout its entirety. In other words, the thickness of the first pipe member 21 does not change in the longitudinal direction. In contrast, the second pipe member 22 has a thickness change section TC, where the thickness changes in the longitudinal direction, located away from the joint 23. The second pipe member 22 has a second thickness t2 on the rear side of the thickness change section TC (i.e., on the opposite side of the thickness change section TC from the first pipe member 21), and a first thickness t1 on the front side of the thickness change section TC (i.e., on the side of the thickness change section TC from the first pipe member 21). In other words, the thickness of the second pipe member 22 changes from the second thickness t2 to the first thickness t1 at the thickness change section TC. In the illustrated example, in the thickness change section TC, the inner circumferential surface 22i of the second pipe member 22 forms an angle of approximately 90° with respect to the length direction, and the thickness of the second pipe member 22 changes in a step-like manner.

[0083] In the right side frame 5 shown in Figure 7B, the first pipe member 31 has a first thickness t1' throughout its entirety. That is, the thickness of the first pipe member 31 does not change in the longitudinal direction. In contrast, the second pipe member 32 has a thickness change section TC, where the thickness changes in the longitudinal direction, located away from the joint 33. The second pipe member 32 has a second thickness t2' on the rear side of the thickness change section TC (i.e., on the opposite side of the thickness change section TC from the first pipe member 31), and a first thickness t1' on the front side of the thickness change section TC (i.e., on the side of the thickness change section TC from the first pipe member 31). In other words, the thickness of the second pipe member 32 changes from the second thickness t2' to the first thickness t1' at the thickness change section TC. In the illustrated example, in the thickness change section TC, the inner circumferential surface 32i of the second pipe member 32 forms an angle of approximately 90° with respect to the length direction, and the thickness of the second pipe member 32 changes in a step-like manner.

[0084] As shown in the examples in Figures 7A and 7B, the vehicle frame 1 may have a configuration in which the second pipe members 22 and 32 have a thickness change portion TC. When the second pipe members 22 and 32 have a thickness change portion TC, it can be said that the second pipe members 22 and 32 are locally thickened on the side of the first pipe members 21 and 31.

[0085] From the viewpoint of improving strength, it is preferable that the distance from the joint 23 to the thickness change section TC in the left side frame 4 is set so that stress concentration due to load does not substantially occur at the joint 23. Similarly, it is preferable that the distance from the joint 33 to the thickness change section TC in the right side frame 5 is set so that stress concentration due to load does not substantially occur at the joint 33.

[0086] From the viewpoint of improving strength, it is preferable that the thickness change portion TC of the left side frame 4 be a certain distance or more from the joint portion 23. Specifically, it is preferable that the distance from the joint portion 23 to the thickness change portion TC be 5 mm or more. Furthermore, from the viewpoint of reducing processing time and improving productivity, it is preferable that the thickness change portion TC of the left side frame 4 is not too far from the joint portion 23. Specifically, it is preferable that the distance from the joint portion 23 to the thickness change portion TC be 50 mm or less. Thus, it is preferable that the thickness change portion TC of the left side frame 4 be 5 mm to 50 mm away from the joint portion 23. For similar reasons, it is preferable that the thickness change portion TC of the right side frame 5 be 5 mm to 50 mm away from the joint portion 33.

[0087] In the explanation so far, we have illustrated a configuration in which the thickness changes in a step-like manner in the thickness-changing section TC, but a configuration in which the thickness changes continuously in the thickness-changing section TC may also be adopted. Figures 8A and 8B show examples of such configurations.

[0088] In the left side frame 4 shown in Figure 8A, the inner circumferential surface 21i of the first pipe member 21 forms an acute angle θa with respect to the length direction in the thickness change section TC, and the thickness of the first pipe member 21 changes continuously. Similarly, in the right side frame 5 shown in Figure 8B, the inner circumferential surface 31i of the first pipe member 31 forms an acute angle θa with respect to the length direction in the thickness change section TC, and the thickness of the first pipe member 31 changes continuously. The inclination angle of the inner circumferential surfaces 21i and 31i with respect to the length direction in the thickness change section TC is not particularly limited.

[0089] Furthermore, while the above explanation has illustrated a configuration in which the first end faces ES1 and ES1' of the first pipe members 21 and 31 and the second end faces ES2 and ES2' of the second pipe members 22 and 32 are tapered surfaces, the configurations shown in Figures 9A and 9B may be adopted instead.

[0090] In the left side frame 4 shown in Figure 9A, the first end face ES1 of the first pipe member 21 and the second end face ES2 of the second pipe member 22 are both substantially parallel to the radial direction (i.e., substantially perpendicular to the longitudinal direction) and are not tapered surfaces. Similarly, in the right side frame 5 shown in Figure 9B, the first end face ES1' of the first pipe member 31 and the second end face ES2' of the second pipe member 32 are both substantially parallel to the radial direction (i.e., substantially perpendicular to the longitudinal direction) and are not tapered surfaces.

[0091] As shown in Figures 6A and 6B, if the first end faces ES1 and ES1' of the first pipe members 21 and 31 and the second end faces ES2 and ES2' of the second pipe members 22 and 32 are tapered surfaces, then misalignment between the first pipe member 21 and the second pipe member 22, and between the first pipe member 31 and the second pipe member 32 can be prevented when joining the first pipe member 21 and the second pipe member 22, and when joining the first pipe member 31 and the second pipe member 32, thus enabling more stable joining. Furthermore, if the joints 23 and 33 are welded parts, the effect of suppressing burn-through during welding can also be obtained. When the first end faces ES1 and ES1' and the second end faces ES2 and ES2' are tapered surfaces, the angle θi that these tapered surfaces make with respect to the radial direction (see Figures 10A and 10B) is referred to here as the "angle of inclination" of the tapered surface. This inclination angle θi is, for example, between 30° and 70°.

[0092] In Figures 6A and 6B, the first end faces ES1 and ES1' of the first pipe members 21 and 31, and the second end faces ES2 and ES2' of the second pipe members 22 and 32 are inclined such that the first end faces ES1 and ES1' are located radially outward from the second end faces ES2 and ES2'. Instead of this configuration, the configurations shown in Figures 11A and 11B may be adopted.

[0093] In the left side frame 4 shown in Figure 11A, the first end face ES1 of the first pipe member 21 and the second end face ES2 of the second pipe member 22 are inclined such that the second end face ES2 is located radially outward from the first end face ES1. Similarly, in the right side frame 5 shown in Figure 11B, the first end face ES1' of the first pipe member 31 and the second end face ES2' of the second pipe member 32 are inclined such that the second end face ES2' is located radially outward from the first end face ES1'.

[0094] When the first pipe member 21 has a thickness change section TC, it is preferable to adopt the configuration shown in Figure 6A rather than the configuration shown in Figure 11A. In other words, it is preferable that the first end face ES1 of the first pipe member 21 and the second end face ES2 of the second pipe member 22 are inclined such that the first end face ES1 is located radially outward from the second end face ES2. By adopting such a configuration, it becomes easy to continuously perform the process of locally thinning the first pipe member 21 and tapering the first end face ES1, thus simplifying the manufacturing of the first pipe member 21. For similar reasons, when the first pipe member 31 has a thickness change section TC, it is preferable to adopt the configuration shown in Figure 6B rather than the configuration shown in Figure 11B. In other words, it is preferable that the first end face ES1' of the first pipe member 31 and the second end face ES2' of the second pipe member 32 are inclined such that the first end face ES1' is located radially outward from the second end face ES2'.

[0095] In the explanation so far, the example given is that the joints 23 and 33 are welded joints, but the joints 23 and 33 may be parts that have been joined by methods other than welding. Examples of methods other than welding include adhesive bonding. Since welded joints are parts where the material has become brittle due to the heat input of welding, the configuration in which the joints 23 and 33 are welded joints is significant because it separates (shifts) the thickness change area TC (stress concentration area) from the joints 23 and 33.

[0096] Furthermore, while the explanation so far has shown an example in which the left side frame 4 and right side frame 5 of the vehicle body frame 1 are composed of two pipe members with different wall thicknesses, other parts of the vehicle body frame 1 may be composed of two pipe members with different wall thicknesses (a first pipe member and a second pipe member having the above-described configuration) in addition to (or instead of) the left side frame 4 and right side frame 5. The left side frame 4 and right side frame 5 are parts of the vehicle body frame 1 that extend in the longitudinal direction of the vehicle as a whole. Since the required rigidity and strength of parts extending in the longitudinal direction of a saddle-type vehicle may differ depending on their position in the longitudinal direction, having such parts be first pipe members and second pipe members having the above-described configuration makes it possible to achieve both weight reduction and securing rigidity and strength.

[0097] Furthermore, in the illustrated configuration, the relatively thicker first pipe members 21 and 31 are positioned further forward than the relatively thinner second pipe members 22 and 32. When a relatively heavy component of the motorcycle (saddle-type vehicle) 100 (for example, the engine 51) is supported at the front of the vehicle frame 1, it is preferable that the first pipe members 21 and 31 are positioned further forward than the second pipe members 22 and 32, as illustrated.

[0098] The center of gravity of a saddle-type vehicle is often set near the center in the longitudinal direction of the vehicle (indicated as "cp" in Figure 1). Therefore, when the first pipe members 21 and 31 are located in front of the second pipe members 22 and 32, it is preferable that the joints 23 and 33 are located behind the center in the longitudinal direction of the vehicle, from the viewpoint of ensuring rigidity and strength to support relatively heavy components.

[0099] Conversely to the example configuration, a relatively thicker pipe member (first pipe member) may be located behind a relatively thinner pipe member (second pipe member). Also, a specific part of the vehicle frame 1 (for example, the left side frame 4 or the right side frame 5) may be composed of three or more pipe members, including the first and second pipe members.

[0100] Furthermore, the vehicle body frame according to the embodiment of the present invention can also be used for vehicles other than saddle-type vehicles (for example, golf carts).

[0101] As described above, the vehicle body frame 1 according to an embodiment of the present invention comprises a first pipe member 21(31) including a portion having a first thickness t1(t1') and a second pipe member 22(32) including a portion having a second thickness t2(t2') smaller than the first thickness t1(t1'), and has a joint portion 23(33) where a first end face ES1(ES1'), which is one end face of the first pipe member 21(31), and a second end face ES2(ES2'), which is one end face of the second pipe member 22(32), are butt-joined. One of the first pipe member 21(31) and the second pipe member 22(32) has a thickness-changing portion TC, which has a thickness that changes in the longitudinal direction, located away from the joint portion 23(33), and the thickness of the first pipe member 21(31) and the thickness of the second pipe member 22(32) at the joint portion 23(33) are the same.

[0102] The vehicle body frame 1 according to an embodiment of the present invention comprises a first pipe member 21 (31) including a portion having a first thickness t1 (t1') and a second pipe member 22 (32) including a portion having a second thickness t2 (t2') smaller than the first thickness t1 (t1'), and has a joint portion 23 (33) where a first end face ES1 (ES1'), which is one end face of the first pipe member 21 (31), and a second end face ES2 (ES2'), which is one end face of the second pipe member 22 (32), are butt-joined. By adopting such a configuration, the weight of the vehicle body frame 1 can be reduced.

[0103] Furthermore, in the vehicle frame 1 according to an embodiment of the present invention, one of the first pipe member 21(31) and the second pipe member 22(32) has a thickness-changing portion TC in the longitudinal direction, located away from the joint portion 23(33), and the thickness of the first pipe member 21(22) and the second pipe member 22(32) at the joint portion 23(33) are the same. As a result, the stress concentration point when force (load) is applied to the vehicle frame 1 can be moved away from the joint portion 22(32) (i.e., shifted), thereby improving the strength of the vehicle frame 1.

[0104] In one embodiment, the first pipe member 21(31) has the thickness change portion TC, and the thickness of the first pipe member 21(31) changes from the first thickness t1(t1') to the second thickness t2(t2') in the thickness change portion TC.

[0105] An embodiment of the present invention may include a vehicle frame 1 in which, for example, the first pipe member 21(31) has a thickness change portion TC. When the first pipe member 21(31) has a thickness change portion TC, it can be said that the first pipe member 21(31) is locally thinned on the side of the second pipe member 22(32), and the thickness of the first pipe member 21(31) changes, for example, from a first thickness t1(t1') to a second thickness t2(t2') at the thickness change portion TC.

[0106] In one embodiment, the second pipe member 22(32) has the thickness change portion TC, and the thickness of the second pipe member 22(32) changes from the second thickness t2(t2') to the first thickness t1(t1') in the thickness change portion TC.

[0107] The vehicle frame 1 according to an embodiment of the present invention may have a configuration in which the second pipe member 22(32) has a thickness change portion TC. When the second pipe member 22(32) has a thickness change portion TC, it can be said that the second pipe member 22(32) is locally thickened on the first pipe member 21(31) side, and the thickness of the second pipe member 22(32) changes, for example, from a second thickness t2(t1') to a first thickness t1(t1') at the thickness change portion TC.

[0108] In one embodiment, the distance from the joint 23(33) to the thickness change portion TC is set so that stress concentration due to load does not substantially occur at the joint 23(33).

[0109] From the viewpoint of improving strength, it is preferable that the distance from the joint portion 23 (33) to the thickness change portion TC is set so that stress concentration due to load does not substantially occur at the joint portion 23 (33).

[0110] In one embodiment, the distance from the joint portion 23 (33) to the thickness change portion TC is 5 mm or more.

[0111] From the viewpoint of improving strength, it is preferable that the thickness change portion TC is located a certain distance or more from the joint portion 23 (33). Specifically, it is preferable that the distance from the joint portion 23 (33) to the thickness change portion TC be 5 mm or more.

[0112] In one embodiment, the distance from the joint portion 23 (33) to the thickness change portion TC is 50 mm or less.

[0113] From the viewpoint of reducing processing time and improving productivity, it is preferable that the thickness change portion TC is not too far from the joint portion 23 (33). Specifically, it is preferable that the distance from the joint portion 23 (33) to the thickness change portion TC is 50 mm or less.

[0114] In one embodiment, the first end face ES1 (ES1') of the first pipe member 21 (31) and the second end face ES2 (ES2') of the second pipe member 22 (32) are surfaces inclined with respect to the radial direction.

[0115] If the first end face ES1 (ES1') of the first pipe member 21 (31) and the second end face ES2 (ES2') of the second pipe member 22 (32) are inclined surfaces with respect to the radial direction, misalignment between the first pipe member 21 (31) and the second pipe member 22 (32) can be prevented, and the joint can be made more stable.

[0116] In one embodiment, the first end face ES1 (ES1') of the first pipe member 21 (31) and the second end face ES2 (ES2') of the second pipe member 22 (32) are inclined such that the first end face ES1 (ES1') is located radially outward from the second end face ES2 (ES2').

[0117] When the first pipe member 21(31) has a thickness change portion TC, it is preferable that the first end face ES1(ES1') of the first pipe member 21(31) and the second end face ES2(ES2') of the second pipe member 22(32) are inclined such that the first end face ES1(ES1') is located radially outward from the second end face ES2(ES2'). By adopting such a configuration, it becomes easy to continuously perform the process of locally thinning the first pipe member 21(31) and tapering the first end face ES1(ES1'), thereby simplifying the manufacturing of the first pipe member 21(31).

[0118] In one embodiment, the joint 23 (33) is a welded joint formed by butt welding of the first end face ES1 (ES1') and the second end face ES2 (ES2').

[0119] The joint 23 (33) may be, for example, a welded joint formed by butt welding the first end face ES1 (ES1') of the first pipe member 21 (31) and the second end face ES2 (ES2') of the second pipe member 22 (32). Since the welded joint is a part where the material has become brittle due to the heat input during welding, the configuration in which the joint 23 (33) is a welded joint is significant in that it separates (shifts) the thickness change portion TC (stress concentration portion) from the joint 23 (33).

[0120] A saddle-type vehicle according to an embodiment of the present invention comprises a vehicle body frame 1 having any of the above-described configurations.

[0121] In one embodiment, the first pipe member 21 (31) and the second pipe member 22 (32) are portions of the vehicle body frame 1 that extend in the longitudinal direction of the vehicle as a whole.

[0122] The first pipe member 21 (31) and the second pipe member 22 (32) are, for example, parts of the vehicle frame 1 that extend in the longitudinal direction of the vehicle as a whole. In a saddle-type vehicle, the required rigidity and strength of the parts extending in the longitudinal direction may differ depending on their position in the longitudinal direction. By having such parts be the first pipe member 21 (31) and the second pipe member 22 (32) having the above-described configuration, it is possible to achieve both weight reduction and the securing of rigidity and strength.

[0123] In one embodiment, the first pipe member 21 (31) is located in front of the second pipe member 22 (32).

[0124] In the case of a saddle-type vehicle, if a relatively heavy component (for example, the engine 51) is supported at the front of the vehicle frame 1, it is preferable that the first pipe member 21 (31) is located further forward than the second pipe member 22 (32).

[0125] In one embodiment, the joint portion 23 (33) is located rearward from the center in the longitudinal direction of the vehicle.

[0126] The center of gravity of a saddle-type vehicle is often set near the center in the longitudinal direction of the vehicle. Therefore, when the first pipe member 21 (31) is located in front of the second pipe member 22 (32), it is preferable that the joint 23 (33) be located behind the center in the longitudinal direction of the vehicle, from the viewpoint of ensuring rigidity and strength to support relatively heavy components.

[0127] According to embodiments of the present invention, it is possible to provide a vehicle body frame that can achieve both weight reduction and strength. The vehicle body frame according to embodiments of the present invention can be used in various types of vehicles, and can be suitably used, for example, in saddle-type vehicles.

[0128] 1: Vehicle body frame, 2: Head pipe section, 3: Down frame section, 4: Left side frame, 4a: Left lower frame section, 4b: Left rear frame section, 5: Right side frame, 5a: Right lower frame section, 5b: Right rear frame section, 6: Connecting member, 7: Connecting frame, 7a: Left support section, 7b: Right support section, 7c: Center section, 8: Gusset section, 9: Cross frame section, 11: Cross member, 2 1・31: First pipe member, 21i, 31i: Inner surface of the first pipe member, 22・32: Second pipe member, 22i・32i: Inner surface of the second pipe member, 23・33: Joint, 41: Front wheel, 42: Rear wheel, 43: Seat, 50: Power unit, 60: Steering device, 70: Body cover, 100: Motorcycle, ES1・ES1': First end face, ES2・ES2': Second end face, TC: Thickness change section

Claims

1. A vehicle body frame comprising: a first pipe member including a portion having a first thickness; and a second pipe member including a portion having a second thickness smaller than the first thickness, wherein a first end face, which is one end face of the first pipe member, and a second end face, which is one end face of the second pipe member, are butt-joined, and one of the first pipe member and the second pipe member has a thickness-changing portion, where the thickness changes in the longitudinal direction, located away from the joint, and the thickness of the first pipe member and the thickness of the second pipe member at the joint are the same.

2. The vehicle body frame according to claim 1, wherein the first pipe member has the thickness-changing portion, and the thickness of the first pipe member changes from a first thickness to a second thickness in the thickness-changing portion.

3. The vehicle body frame according to claim 1, wherein the second pipe member has the thickness-changing portion, and the thickness of the second pipe member changes from the second thickness to the first thickness in the thickness-changing portion.

4. The vehicle body frame according to any one of claims 1 to 3, wherein the distance from the joint to the thickness change portion is set so that stress concentration due to load does not substantially occur at the joint.

5. The vehicle body frame according to any one of claims 1 to 4, wherein the distance from the joint to the thickness change portion is 5 mm or more.

6. The vehicle body frame according to any one of claims 1 to 5, wherein the distance from the joint to the thickness change portion is 50 mm or less.

7. The vehicle body frame according to any one of claims 1 to 6, wherein the first end face of the first pipe member and the second end face of the second pipe member are surfaces inclined with respect to the radial direction.

8. The vehicle body frame according to claim 7, wherein the first end face of the first pipe member and the second end face of the second pipe member are inclined such that the first end face is located radially outward from the second end face.

9. The vehicle body frame according to any one of claims 1 to 8, wherein the joint is a welded joint formed by butt welding of the first end face and the second end face.

10. A saddle-type vehicle equipped with a vehicle body frame according to any one of claims 1 to 9.

11. The saddle-type vehicle according to claim 10, wherein the first pipe member and the second pipe member are portions of the vehicle body frame that extend in the longitudinal direction of the vehicle as a whole.

12. The saddle-type vehicle according to claim 11, wherein the first pipe member is located in front of the second pipe member.

13. The saddle-type vehicle according to claim 12, wherein the joint is located rearward from the center in the longitudinal direction of the vehicle.

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