JP6287258B2 - Motorcycle swing arm - Google Patents

Description

  The present invention relates to a swing arm of a motorcycle that supports a rear wheel so as to be swingable in a vertical direction.

  Conventionally, a swing arm of a motorcycle has a front end rotatably supported by a vehicle body frame via a rear wheel suspension device (rear suspension), and a rear wheel rotatably supported by a rear end thereof. It has a structure that can absorb the movement in the direction (see, for example, Patent Document 1).

  In recent years, motorcycles equipped with this type of swing arm have been able to keep the bank angle very deep when turning due to technological advances in tires, etc., especially for motorcycles for racing and super sports categories. This is especially true in.

  However, since the suspension system can only absorb the vertical movement of the vehicle body, in a motorcycle that can keep the bank angle deep during turning, the vehicle body frame and the swing arm are deformed to the vehicle body that is received from the unevenness of the road surface. By absorbing lateral force, in addition to improving torsional rigidity that improves straight running stability and steering stability, the need to optimize lateral bending rigidity related to absorption and stability during turning increases. doing.

JP 2012-76612 A

  However, in the conventional motorcycle swing arm disclosed in the above-mentioned Patent Document 1 and the like, there is not much consideration for the lateral bending rigidity, and in order to efficiently improve the torsional rigidity and reduce the weight, The structure is such that the front base portion of the arm has a strong structure and the arm portion for holding the axle is connected thereto.

  In addition, when trying to reduce the lateral bending rigidity in a conventional motorcycle that employs such a structure, it is necessary to adopt a structure in which the arm part that supports the axle of the rear wheel is thinned to greatly deform the arm part. In this case, when a lateral force is applied to the swing arm, stress concentration occurs at the connecting portion between the base portion and the arm portion. Therefore, it is necessary to reinforce this connection part, and the problem that the weight of a vehicle body increases will generate | occur | produce. Further, even if such a structure that reinforces the connection portion is employed, there is a problem that the lateral bending rigidity may not be lowered to a desired value.

  The present invention has been made to solve the above-mentioned problems, and provides a swing arm for a motorcycle having a rigidity balance with high torsional rigidity and low lateral bending rigidity without increasing the vehicle weight. With the goal.

In order to achieve the above-described object, the present invention provides a pivot portion connected to a vehicle body frame by a pivot shaft, a pair of left and right front arm portions extending rearward from the pivot portion, and a rear portion of the pair of left and right front arm portions. The rear wheel is rotatably supported by a cross part connecting the two, a pair of left and right rear arm parts extending rearward of the vehicle so as to sandwich the rear wheel from the cross part, and a rear end part of the pair of left and right rear arm parts A motorcycle having a bracket portion, wherein an opening penetrating in the vertical direction is formed by the pivot portion, the pair of left and right front arm portions, and the cross portion, and a rear wheel suspension device is disposed in the opening portion. Each of the front arm portions has a recess formed on the outer surface thereof, and each recess has a shape curved inward in the vehicle width direction from the pivot portion to the cross portion. Previous Between the most constricted portion of the recess, characterized in that the shortest narrowest section length in the vehicle width direction is formed.

  By having this feature, when the motorcycle is banked when turning, the swing arm can be deformed to easily absorb the lateral force applied to the vehicle body from the unevenness of the road surface. In addition to improving torsional rigidity that improves steering stability, it is possible to improve absorbency and stability when turning the vehicle.

Further, in the motorcycle swing arm according to the present invention, a through hole through which a drive chain that transmits engine power to the rear wheel can pass is formed in a front region of the rear arm portion, characterized in that it is formed on the inner side of the vehicle width direction inner side of the drive chain.

  By providing this feature, the section where the drive chain may come into contact with the outer surface of the swing arm is shortened, so the installation area of the chain buffer can be reduced, and the vehicle can be reduced in weight and cost. .

  In the swing arm of the motorcycle according to the present invention, the pivot portion, the front arm portion, the cross portion, and the rear arm portion have symmetrical shapes with respect to the center of the vehicle body. Also good.

  By providing this feature, the balance of rigidity of the swing arm can be further improved, and the steering stability can be further improved.

  According to the present invention, it is possible to provide a motorcycle swing arm having a rigidity balance with high torsional rigidity and low lateral bending rigidity without increasing the vehicle weight. be able to.

1 is a left side view showing a motorcycle including a swing arm according to an embodiment of the present invention. 1 is a perspective view showing a swing arm of a motorcycle according to an embodiment of the present invention. 1 is a plan view showing a swing arm of a motorcycle according to an embodiment of the present invention. 1 is a left side view showing a swing arm of a motorcycle according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the case where the swing arm of the present invention is applied to an on-road type motorcycle will be described. However, this is merely an example, and the swing arm of the present invention is applied to other types of motorcycles. It is also possible to do.

  First, with reference to FIG. 1, a schematic configuration of an entire motorcycle including a swing arm according to an embodiment of the present invention will be described. FIG. 1 is a left side view showing a motorcycle having a swing arm according to an embodiment of the present invention. In the following description, the front-rear and left-right directions are based on the direction seen from the rider riding the motorcycle, and in the drawing, the front of the vehicle body is indicated by an arrow FR and the rear of the vehicle body is indicated by an arrow RE.

  The motorcycle 10 includes a body frame 11 made of steel or aluminum alloy constituting a framework. The main frame 12 of the vehicle body frame 11 branches leftward and rightward from a head pipe (not shown) located at the front end, and extends obliquely downward. A swing arm bracket 13 extends downward from the rear end side of the main frame 12.

  Below the main frame 12, an engine 15 is mounted so as to be suspended by an engine suspension bracket (not shown) and a swing arm bracket 13. The engine 15 is composed of, for example, a parallel 4-cylinder engine and a transmission. A fuel tank 17 is disposed above the main frame 12, and a rider seat 18 and a pillion seat 19 are connected to the rear of the fuel tank 17. The rider seat 18 and the pillion seat 19 are supported by a pair of left and right seat rails 20 connected to the rear portion of the main frame 12.

  A front fork 22 is rotatably supported at the front end of the vehicle body frame 11 via a steering shaft (not shown). A handlebar (not shown) is provided at the upper end of the steering shaft, and grips 23 are attached to the left and right ends of the handlebar. A front wheel 25 is rotatably supported at a lower portion of the front fork 22, and a brake disk 26 is provided on the front wheel 25.

  A swing arm 30 is connected to the swing arm bracket 13 of the body frame 11 so as to be swingable in the vertical direction, and a rear wheel suspension device (not shown) is attached between the body frame 11 and the swing arm 30. It has been. A rear wheel 32 is rotatably supported at the rear portion of the swing arm 30 via an axle 31 extending in the vehicle width direction. A driven sprocket 33 is provided on the left side of the rear wheel 32 so that the power of the engine 15 is transmitted to the rear wheel 32 by a drive chain 34. Further, the body frame 11 and the like are provided with a cowl 36 as an exterior of the vehicle body, and a gap for taking outside air into the engine 15 from the front of the vehicle body is formed between the cowl 36 and the body frame 11.

  Next, the swing arm 30 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2 to 4. Here, FIG. 2 is a perspective view showing the swing arm of the motorcycle according to the embodiment of the present invention, FIG. 3 is a plan view showing the swing arm of the motorcycle according to the embodiment of the present invention, and FIG. FIG. 6 is a left side view showing a swing arm of the motorcycle according to the embodiment.

  The swing arm 30 is provided at a base portion 41 connected to the swing arm bracket 13 via a pivot shaft 40, a pair of left and right rear arm portions 42 extending rearward from the base portion 41, and a rear end portion of each rear arm portion 42. And a pair of left and right bracket portions 43, and has a symmetrical shape with respect to the center of the vehicle body. In the present embodiment, the base portion 41 and the rear arm portion 42 are formed by a press-formed product having a hollow structure, and the bracket portion 43 is integrally manufactured as a forged product or a cast product.

  The vertical width of the swing arm 30 is maximized in the vicinity of the center in the front-rear direction, where the base portion 41 and the rear arm portion 42 are joined, and gradually decreases from the center toward the front and rear. The lower edge of the swing arm 30 has a shape that bulges downward in the vicinity of the center in the front-rear direction and inclines obliquely upward from the bulged portion toward the front-rear direction. Has a shape in which the vicinity of the center in the front-rear direction slightly swells upward.

  The base portion 41 includes a cylindrical pivot portion 45 extending in the vehicle width direction, and the pivot shaft 40 passes through the pivot portion 45. A pair of left and right front arm portions 46 that extend rearward are formed on the rear side of the pivot portion 45, and a single cross is provided behind the front arm portions 46 so as to connect the rear portions of the front arm portions 46. A portion 47 is formed. As a result, an opening 48 penetrating in the vertical direction is formed in a portion surrounded by the pivot portion 45, the left and right front arm portions 46, and the cross portion 47, and the rear wheel suspension device penetrates the opening 48. Are arranged as follows.

  A concave portion 49 that is curved inward in the vehicle width direction is formed on the outer surface of each front arm portion 46. A narrowest portion having the shortest length in the vehicle width direction is formed between the most constricted portions 49a of the concave portions 49, and each of the front arm portions 46 moves toward the front and rear of the narrowest portion. It is formed so as to spread outward in the width direction.

  The outer surface of the cross portion 47 is formed so as to extend rearward in the vehicle width direction toward the rear, and the pair of left and right front arm portions 46 are respectively connected to the pair of left and right rear arm portions 42 via the cross portion 47. It is formed to be continuous.

  Each rear arm portion 42 extends rearward from the cross portion 47 so as to sandwich the rear wheel 32, and a portion from the rear surface of the rear portion 47a of the cross portion 47 to the front portion of the inner surface of each rear arm portion 42 is seen in a plan view. Are formed in a curved shape similar to an arc or a curve similar to an arc.

  Each rear arm portion 42 extends so that the front-rear direction intermediate region swells most outward in the vehicle width direction, and the left-right separation distance in the vehicle width direction of the left and right rear arm portions 42 is maximum in this intermediate region. It forms so that it may become small gradually toward the front and back from an area | region. Thereby, the left and right outer surfaces of the swing arm 30 extending from the base portion 41 to the rear arm portion 42 are formed so as to form a gentle S shape in a plan view.

  The thickness of each rear arm portion 42 in the left-right direction gradually decreases from the front end portion toward the center portion in the front-rear direction, and is substantially the same from the center portion to the rear end portion. Further, a through hole 51 having a shape approximate to a triangle is formed in a front region of each rear arm portion 42. As shown in FIG. 3, the drive chain 34 passes through the left through hole 51, and the left recess 49 is formed on the inner side of the inner side surface in the vehicle width direction of the drive chain 34.

  Each bracket portion 43 is connected to the rear end portion of each rear arm portion 42 by welding. A hole 52 through which the axle 31 passes is formed at the rear end side of each bracket portion 43, and the axle portion 31 is inserted into the hole 52 and a hub (not shown) of the rear wheel 32, whereby each bracket portion 43. The rear wheel 32 is rotatably supported. The hole 52 has a shape that is longer in the front-rear direction than in the up-down direction, so that the front-rear position of the rear wheel 32 can be adjusted by displacing the axle 31 back and forth within the hole 52.

  As described above, in the swing arm 30 of the motorcycle 10 according to the embodiment of the present invention, the concave portion 49 is formed on the outer surface of each front arm portion 46 and the opening 48 between the pair of left and right front arm portions 46. Therefore, the bending rigidity in the lateral direction of the forearm portion 46 can be reduced. Thereby, the balance of rigidity between the front arm portion 46 and the rear arm portion 42 is improved, and stress concentration at the joint portion between the front arm portion 46 and the cross portion 47 and the joint portion between the cross portion 47 and the rear arm portion 42 is alleviated. can do. Further, since it is not necessary to reinforce the structure in the vicinity of each coupling portion, an increase in vehicle weight can be prevented, and the lateral bending rigidity of the entire swing arm 30 can be reduced.

  Further, even in a motorcycle that can keep a bank angle deep when turning, such as the road-type motorcycle 10 in the above-described embodiment of the present invention, the swing arm 30 is deformed to be received from unevenness on the road surface. Since the lateral force against the vehicle body can be absorbed easily, in addition to improving torsional rigidity that improves straight running stability and steering stability, it is possible to improve absorption and stability when turning the vehicle. .

  Further, since the recess 49 is formed in the front arm portion 46 and this recess 49 is formed inside the inner side surface in the vehicle width direction of the drive chain 34, the drive chain 34 may come into contact with the outer surface of the swing arm 30. The section becomes shorter. Therefore, as shown in FIGS. 2 and 3, the attachment section of the chain buffer 55 can be reduced, so that the weight of the vehicle and the cost can be reduced.

  In the above description of the embodiment, since a preferred embodiment of the swing arm of the motorcycle according to the present invention is described, there may be various technically preferable limitations. The technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the embodiment of the present invention described above does not limit the contents of the invention described in the claims.

DESCRIPTION OF SYMBOLS 10 Motorcycle 11 Body frame 30 Swing arm 32 Rear wheel 34 Drive chain 40 Pivot shaft 42 Rear arm part 43 Bracket part 45 Pivot part 46 Front arm part 47 Cross part 48 Opening part 49 Recessed part 51 Through hole

Claims (2)

A pivot portion connected to the body frame by a pivot shaft, a pair of left and right front arm portions extending from the pivot portion to the rear of the vehicle, a cross portion connecting the rear portions of the pair of left and right front arm portions, and a rear portion from the cross portion. A pair of left and right rear arm portions extending rearward of the vehicle so as to sandwich the wheel, and a bracket portion that rotatably supports the rear wheel at the rear end portion of the pair of left and right rear arm portions, the pivot portion, An opening that penetrates in the vertical direction is formed by the pair of left and right front arm portions and the cross portion, and a swing arm of the motorcycle in which a rear wheel suspension device is disposed in the opening portion,
A concave portion is formed on the outer surface of each forearm portion, and each concave portion has a shape curved inward in the vehicle width direction from the pivot portion to the cross portion, and the most constricted portion of the curved concave portion. The narrowest part with the shortest length in the vehicle width direction is formed between
A through hole through which a drive chain for transmitting engine power to the rear wheel can pass is formed in a front region of the rear arm portion, and the concave portion is formed on the inner side of the drive chain in the vehicle width direction. The swing arm of a motorcycle characterized by being made . 2. The motorcycle swing arm according to claim 1, wherein the pivot portion, the front arm portion, the cross portion, and the rear arm portion have a symmetrical shape with respect to a vehicle body center.

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