FR2825340A1 - Controlled rigidity swinging arm for off road motor cycle has curved sections in fork legs to allow controlled vertical deflection of legs under load - Google Patents

Abstract

The off road motorcycle swinging arm has a mounting pivot assembly at the front end (53) and wheel mountings (56) at the rear ends of the fork. The end sections are made rigid in the torsional and bending directions. The swinging arm fork legs have curved sections (55) to give torsional rigidity with controlled flexion in the vertical direction. Loads applied from below provide a greater flexion than those applied from above.

Description

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REAR OSCILLATING ARM FOR MOTORCYCLES Technical field of the invention
The present invention relates to a rear swingarm for motorcycles.

Description of the Related Art
In motorcycles, the balance of the vehicle body frame weight in the longitudinal direction varies slightly with the size or position of the engine to be mounted on the body frame of the vehicle, which influences the maneuverability and the quality of driving. Therefore, the front fork and the rear swingarm for suspension of the front and rear of the engine as well as the frame of the body of the vehicle are very important elements that affect the maneuverability and the driving quality.

For example, it is desirable that the rear swingarm has stiffness properties in some cases and flexural properties in other cases to create an equilibrium with the engine or frame of the vehicle body.

 Stiffness is a deformation resistance for a load, and this usually implies torsional and flexural rigidity.

 The torsional rigidity is defined by a product of an elastic shear coefficient (G) and a geometrical polar moment of inertia (Ip) in the case of a straight rod having a uniform section, which is considered as an indicator in maintaining the basic stiffness of the rear swingarm. Flexural stiffness is defined by a product of a

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 elastic coefficient in the vertical direction (E) and a geometrical moment of inertia (I) in the case of a straight rod having a uniform section, which is considered as an indicator for providing the bending properties in the oscillating arm back.

 Since torsional rigidity is related to flexural stiffness, when torsional rigidity is increased, flexural rigidity is also increased.

 In the case of a motorcycle rear swingarm taking into account torsional stiffness and flexural stiffness, for example, (1) Japanese Patent Laying-Open N0314683 / 1992 entitled "Swing arm for motorcycles", or (2) the registration of Japanese utility model Nc'2536050 entitled "Reinforcing structure in hollow structure for vehicles" are known.

 The aforementioned invention (1) is, according to Fig. 1 of the same publication, a rear swingarm comprising an arm tube 5 having a recessed curve surface 11 extending rearwardly from the body 4 having a centering hole 3 and a shaft hole 1.

 The utility model in document (2) is, according to Figure 1 of this publication, a rear swingarm having the shape of an inverted V in side view.

Problems to be solved by the invention
Although the rear swingarm mentioned in document (1) above must have bending properties, it is likely to have a lack of rigidity.

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 Although the rear swingarm mentioned in document (2) above must be rather hard with high rigidity, it is likely to have a lack of flexural properties, because rigidity is required.

 Therefore, a technique for providing bending properties in the rear swingarm while maintaining sufficient rigidity is desired.

 Accordingly, an object of the present invention is to provide a rear swing arm having bending properties while maintaining sufficient rigidity.

Means to solve problems
In order to achieve the above-mentioned purpose, the present invention provides a motorcycle rear swingarm comprising a hinge shaft fixing portion for hingedly attaching the rear swingarm to the vehicle body frame via the hinge shaft, a rear suspension fixing portion of the hinge shaft fixing portion and a rear wheel support portion for supporting the rear wheel at the rear end of the hinge portion; arm extending rearwardly from the suspension attachment portion, wherein the section between the hinge shaft attachment portion and the suspension attachment portion is constructed to be highly torsionally rigid and at bending in the vertical direction, and the arm portion is constructed to be highly torsionally stiff and slightly flexural in the vertical direction.

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 The section between the hinge pin attachment portion and the suspension attachment portion is constructed to be highly torsionally rigid and vertically bent to provide sufficient rigidity in the rear swingarm. As a result, the maneuverability can be improved.

 The arm portion is constructed to be highly torsionally stiff and weakly flexural in the vertical direction, for example to provide sufficient rigidity in the rear swingarm and to mitigate consecutive and rapidly repetitive shocks that can be barely absorbed. by the suspension. As a result, driving quality is improved.

 According to a first improvement, the rear wheel support portion is constructed to be highly rigid at vertical torsion and bending.

 The rear wheel support portion is constructed to be highly rigid to vertical torsion and bending so that the rear wheel can be supported firmly. As a result, the maneuverability can be improved.

 According to a second improvement, the arm portion is adapted to be convex downward in a side view.

 The section between the hinge shaft fixing portion and the hanger mounting portion is constructed to be highly torsionally rigid and vertically bent, and the arm portion is adapted to be convex to the hinge. down in side view, for example, so that the arm portion acts as a curved beam in

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 overhang whose section between the hinge shaft fixing portion and the suspension fixing portion is fixed. Generally, the cantilever curved beam designed to be downwardly convex is easily flexed by a load applied from below, and can not be easily flexed by a load applied from above.

 In other words, since the main component of the vertical load applied to the rear swingarm by the rear wheel is a load applied from below, the arm portion is adapted to be convex downward in a side view, such as so that it can be manufactured to have low flexural stiffness in the vertical direction while maintaining high torsional stiffness. As a result, the rear swingarm can have sufficient rigidity and the consecutive and rapidly repetitive shocks that can barely be absorbed by the suspension are mitigated.

 The arm portion is adapted to be downwardly convex in a side view, so that any interference with the other body members of the vehicle during oscillation is avoided and the angle of rotation of the rear swingarm can be increases.

Brief description of the drawings
Figure 1 is a side view of a motorcycle comprising a rear swing arm according to the present invention mounted thereon.

 FIG. 2 is a perspective view of the frame of the body of the vehicle comprising a rear oscillating arm

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 for motorcycles according to the present invention mounted thereon.

 Figure 3 is a plan view of the rear motorcycle swingarm according to the present invention.

 Figure 4 is a side view of the rear motorcycle swingarm according to the present invention.

 Figure 5 is a comparative explanatory drawing of the rear motorcycle swingarm according to the present invention.

 Fig. 6 is a first comparative explanatory drawing showing the operation of the rear motorcycle rear arm according to the present invention.

 Fig. 7 is a second comparative explanatory drawing showing the operation of the rear motorcycle rear arm according to the present invention.

Description of the embodiments
Referring now to the accompanying drawings, an embodiment of the present invention will be described hereinafter. The drawings must be displayed in the direction in which the reference numbers are oriented.

 Figure 1 is a side view of the motorcycle including a rear swing arm according to the present invention mounted thereon. Motorcycle 10 is an example of an off-road motorcycle comprising a vehicle body frame 11, a head tube 12 provided on the front of the vehicle body frame, front forks 13,13 (13 on the hidden side is not shown) hingedly mounted on the head tube 12, a handlebar 14 mounted on the

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 upper part of the front forks 13,13, a front wheel 15 rotatably mounted to the lower part of the front forks 13,13, a front fender 16 to cover the front wheel 15, a fuel tank 17 mounted on the frame 11 of the vehicle body at the rear of the head tube 12, a seat 18 located at the rear of the fuel tank 17, an engine block 22 comprising a motor 19 located under the fuel tank 17 and the seat 18, and a transmission 21, a rear swingarm 50 fixed to the frame 11 of the vehicle body at the rear of the engine block 22 for oscillation movement, a rear wheel 24 rotatably mounted on the rear swingarm 50 and driven by the engine block 22, and a rear fender 25 located above the rear wheel 24.

 Reference numeral 26 designates a radiator shell, number 27 designates a side cover, number 28 designates a suspension, number 29 designates an exhaust pipe, number 31 designates a silencer, number 32 designates a caliper, the number 33 designates a hinge shaft, the number 34 designates a drive chain, the number 35 designates an axle of the front wheel 15, the number 36 designates an axle of the rear wheel 24.

 The rear oscillating arm 50 of the motorcycle according to the present invention is, as described below, a rear swing arm having bending properties while maintaining sufficient rigidity.

 Figure 2 is a perspective view of the vehicle body frame having a rear motorcycle swingarm according to the present invention mounted thereto.

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 The vehicle body frame 11 includes a pair of main frames 41, 41 extending from the head tube 12 rearwards on the left side and the right side, the main frames 41, 41 having end portions. 42,42 extending downwardly, an oblique tube 43 extending downwardly from the head tube 12, a pair of parallel tubes 44,44 extending from the intermediate section of the oblique tube 43 rearwardly on the left and right sides, the end portions of the parallel tubes 44, 44 and the end portions 42, 42 of the main frames 41, 41 being respectively connected to form two connecting portions 46, 46, and a tube transverse 47 located between the connecting portions 46,46. The reference numerals 48,48 (one of the numbers 48,48 is not shown) designate passage holes of the hinge shaft 33, the number 49 designates a reinforcing tube extending from the oblique tube 43 to senior managers 41,41.

 Figure 3 is a plan view of the rear motorcycle swingarm according to the present invention.

 The rear swingarm 50 comprises a pair of left and right projections portions 52, 52 towards the front of the base portion 51, hinge shaft attachment portions 53, 53 formed at the ends of the projection portions 52 , 52, a transverse member 54 interconnecting the portions, in the area around the hinge shaft mounting portions 53,53, a pair of left and right arm portions 55,55 extending rearwardly from the base portion 51, thick-walled rear wheel support portions 56, 56 attached to the ends of the arm portions 55, 55, a

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 reinforcing member 57 being integrally mounted on the upper surface of the base portion 51 and suspension attachment portions 58,58 formed downwardly of the base portion 51.

 FIG. 4 is a side view of the motorcycle rear oscillating arm according to the present invention, showing that the arm portion 55 is formed of a square tube in cross-section so as to be downwardly convex in a side view, and is tapered; from the base portion 51 to the rear wheel support portions 56. As will be described later, since the main component of the vertical load applied to the rear swing arm 50 by the rear wheel 24 (see Fig. 1) is a load applied from below, the arm portion 55 is designed to be downwardly convex in a side view, so that it has low vertical bending rigidity while maintaining high rigidity at the torsion. The arm portion 55 is tapered in shape with a radius of curvature on the lower surface R2 smaller than the radius of curvature on the upper surface R1.

 The motorcycle rear swingarm 50 includes hinge shaft mounting portions 53, 53 (not shown on the hidden side) for hingedly mounting the rear swingarm to the vehicle body frame. (see Figure 2) via the hinge shaft 33, the suspension attachment portions 58,58 (58 on the hidden side is not shown) to the rear of the attachment parts 53,53 of the hinge shaft, rear wheel support parts 56,56 (56 on the hidden side is not

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 shown) to support the rear wheel 24 (see Fig. 1) at the rear end of the arm portions 55,55 (55 on the hidden side is not shown) extending rearwardly from the attachment portions of suspension 58,58, in which the parts neighboring the attachment parts 53,53 of the hinge shaft are interconnected by a transverse member 54, and a reinforcing member 57 is integrally mounted on the base portion 51, such that the section between the attachment portions 53, 53 of the hinge shaft and the fixing portion 58 of the suspension is constructed to have a high torsional and bending rigidity in the vertical direction, and the arm portion 55 is formed of a square tube in cross-section so as to be downwardly convex in a side view, so that the arm portion 55 is constructed to have high torsional rigidity and low rigidity. bending in the vertical direction.

 The section between the attachment portion 53 of the hinge shaft and the attachment portion 58 of the suspension is constructed to have high torsional and bending rigidity in the vertical direction to provide sufficient rigidity to the swingarm As a result, the maneuverability can be improved.

 The arm portion 55 is constructed to have high torsional stiffness and low vertical bending stiffness to provide, for example, sufficient rigidity to the rear swingarm 50 and to mitigate the consecutive and rapidly repetitive shocks which can to

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 hardly be absorbed by the suspension 28. As a result, the driving quality is improved. In other words, a rear swingarm 50 having bending properties while maintaining sufficient rigidity is obtained.

 In order to construct an arm portion 55 having high torsional stiffness and low vertical flexural stiffness, the arm portion 55 is formed to be convex downward in a side view. As will be described later, the rear swingarm 50, whose section between the attachment portion 53 of the hinge shaft and the fixing portion 58 of the suspension has a high torsional stiffness and flexion in the vertical direction and whose arm portion 55 is downwardly convex in a lateral view, can act as a cantilevered curved beam whose section between the attachment portion 53 of the hinge shaft and the fixing portion 58 of the suspension is fixed. Generally, the cantilever curved beam formed to be convex downward is easily flexed by a load applied from below and can not be flexed easily by a load applied from above.

 Since the main component of the vertical load applied to the rear swingarm 50 by the rear wheel 24 (see FIG. 1) is a load applied from below, the arm portion 55 is designed to be convex downward in a side view. so that it can have low flexural stiffness in the vertical direction while maintaining high torsional rigidity. As a result, the rear swingarm 50 can be

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 provided with sufficient rigidity and the consecutive and rapidly repetitive shocks that can barely be absorbed by the suspension 28 (see Figure 1) are mitigated.

 In other words, the rear swingarm 50 includes thick walled rear wheel support portions 56 attached to the end of the arm portions 55 respectively, such that the rear wheel support portions 56 are designed to have high torsional and bending stiffness in the vertical direction.

 The rear wheel support portion 56 is designed to have high torsional and bending stiffness in the vertical direction so that the rear wheel can be supported firmly. As a result, the maneuverability can be improved.

 We will now proceed to the description of the operation of the rear swing arm 50 described above.

 Parts (a) and (b) of FIG. 5 are comparative explanatory drawings of the motorcycle rear oscillating arm according to the present invention, in which (a) represents a rear oscillating arm 100 of the comparative example and (b) represents a rear swingarm 50 of the embodiment.

 Generally, since the torsional rigidity is related to the bending stiffness, when the torsional rigidity is increased, the bending rigidity is also increased. Torsional rigidity is required for the stability of the vehicle body, and when the torsional rigidity of the rear swingarm is improved, the bending stiffness is also improved accordingly. However, when

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 the rear swingarm (in particular, the bending stiffness of the arm portion in the vertical direction) has a high rigidity, in the area in which the rear swingarm moves the fastest (ie, on a very steep road); bumpy), the subsequent reaction of the rear swingarm can become slower under the influence of the shock absorber of the suspension. As a result, driving quality and maneuverability can be reduced.

 Therefore, it is preferable that only the torsional rigidity can be improved and that the same bending stiffness is maintained in the vertical direction.

 In (a), the rear swingarm 100 of the comparative example is a rear oscillating arm of a generic form comprising a pair of left and right projections 102, 102 formed forwardly from the base portion 101, portions 103, 103 of the hinge shaft formed at the ends of the projections 102,102, a pair of arms 105,105 extending rearwardly from the base portion 101 on the left and right sides, and parts of thick-walled rear wheel support 106, 106 formed at the ends of the arm portions 105, 105.

 In (b), the rear swingarm 50 according to the described embodiment is an improved rear swingarm comprising a crossmember 54 interconnecting the rear swingarm portions 100 shown in (a) in the area around the attachment portions 53 53 of the articulation shaft, the arm portions 55, 55 which are designed to be convex downwards,

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 56,56 rear wheel support portions designed with thick walls and a reinforcing member 57 integrally mounted on the upper surface of the base portion 51, wherein only the torsional rigidity is improved while maintaining rigidity at the bending in the vertical direction to the same value as that of the rear swingarm 100 in the comparative example.

 As will be described in connection with the following drawing, it is a rear swingarm which provides a sufficient angle of rotation to the rear swingarm 50.

 Parts (a) to (c) of FIG. 6 represent the first explanatory drawings of the operation of the rear motorcycle rear arm according to the present invention, among which (a) represents a rear oscillating arm 110 of comparative example 1, ( b) shows a rear swingarm 120 of Comparative Example 2 and (c) shows a rear swingarm 50 of the embodiment.

 In (a), the rear swingarm 110 is a rear swingarm having an arm portion 115 designed to be straight in a side view.

 In (b), the rear swingarm 120 is a rear swingarm having an arm portion 125 adapted to be upwardly convex in a side view, assuming that the element on the side of the vehicle body is positioned at the height H from the horizontal level passing through the center of the hinge shaft fixing portion 123 and a rotation angle of the rear swing arm 120 when its oscillation is 82 as indicated by the arrow b.

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 In (c), the rear swingarm 50 is a rear swingarm having an arm portion 55 adapted to be downwardly convex in a side view, assuming that the element on the vehicle body side is positioned at the same position. height H that in (b) from the horizontal level passing through the center of the attachment portion 53 of the hinge shaft, and the angle of rotation of the rear swing arm 50 when its oscillation is 8 as indicated by the arrow c.

 In (b) and (c), it is clear that the relation between the possible angle of rotation 82 of the rear swingarm 120 and the angle of rotation 8 of the swingarm 50 is 8> 82, and since the arm portion 55 of the rear swingarm 50 is designed to be downwardly convex in side view, any interference with the other parts of the vehicle body when it is oscillated is avoided and the angle of rotation of the rear swingarm 50 may be increases. In other words, the rear swingarm 50 is an oscillating arm adapted for an off-road motorcycle in which the angle of rotation is set to a large value. Therefore, the design possibility of the motorcycle 10 (see FIG. 1) can be extended.

 It is assumed that the cross-sections taken at the same distance from the respective base portions 111, 121, 51 are identical, and that the work has no influence on the arm portions 115, 125, 55, such as hardening, deformation thermal or the like.

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 In (a) and (b), the rear oscillating arms 110, 120 comprise elements equivalent to the reinforcing member 57 integrally mounted on the base portions 111, 121 respectively, and elements equivalent to the cross member 54 located at the portions 113,123 of the hinge shaft and elements equivalent to the thick-walled rear wheel support portion 56 attached to the ends of the arm portions 115,125.

 Since the zone considered is the zone in which the subsequent reaction of the rear swingarms 110, 150, 50 becomes slower due to the influence of the suspension damper, the rear swingarms 110, 120, 50 can almost be regarded as beams. cantilevered when a predicted load W is applied to the ends of the arm portions 115, 125, 55 from below, the fixed base portions 111, 121, 51 being shown in (a) to (c). A deformation resistance (vertical bending rigidity) of the rear oscillating arms 110, 120, 50 will be considered in connection with the following drawing.

 The indication L denotes a distance between the articulation A and the position B on which a predicted load W is applied in the case where the arm portions 115, 125, 55 are considered to be cantilevered.

 Parts (a) to (c) of FIG. 7 are the second explanatory drawings showing the operation of the motorcycle rear oscillating arms according to the present invention, among which (a) represents the rear oscillating arm 100 of Comparative Example 1, (b) represents the arm

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 rear oscillator 100 of Comparative Example 2 and (c) represents the rear swingarm 50 of the embodiment.

 In (a), when the arm portion 115 is a generic simple beam (right beam) and a predicted load W is applied from below, a deformation amount 81 is generated. For example, when an established load W is applied from above, the same amount of strain 81 is generated.

 In (b), when the arm portion 115 is an upwardly convex curved beam, a deformation amount 82 generated by the established load W applied from below is less than the amount of deformation 51 shown in (a).

 In (c), when the arm portion 55 is a downward convex curved beam, a deformation amount Ò3 generated by the established load W is greater than the amount of strain 81 shown in (a). In other words, the relation between the strain quantities represented in (a) to (c) is Ò2 <Òl <Ò3.

 In other words, as described above, since the bending stiffness is a resistance to deformation, the smaller the amount of deformation, the lower the deformation resistance will be.

 A load applied to the rear swingarm is a load from the underside applied when the rear wheel makes contact with the ground, and therefore a load applied from above is not affected in this case.

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 Thus, as shown in (c), by designing the arm 55 as a downward convex curved beam to provide a directionality to the vertical bending stiffness, the bending stiffness with respect to a load applied from the underside can be reduced while the torsional rigidity of the arm 55 is increased. As a result, a rear swingarm 50 having bending properties while maintaining sufficient rigidity is provided.

 In the embodiment, as shown in FIG. 4, the arm portion is made of tapered shape by forming a radius of curvature on the bottom surface R2 less than the radius of curvature on the upper surface R1, but it is not limited to to that. When the realization of the curvature on the lower surface is related to the curvature on the upper surface, it is also possible to realize it of tapered shape by shifting the center of the curvature on the lower surface with respect to the center of the curvature on the upper surface.

 In the embodiment, as shown in FIG. 4, the cross member 54, the reinforcing member 58, and the thick-walled rear wheel support portions 56, 56 are used to improve the torsional rigidity, but the means to improve torsional rigidity are not limited to these. The combination of the cross member 54, the reinforcing member 58 and the thick-walled rear wheel support portions 56, 56 is arbitrary and can be improved by increasing the wall thickness of the rear swingarm, modifying the material of the rear swingarm or the like.

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Advantages
The present invention constructed as described above offers the following advantages.

 Since the section between the hinge pin securing portion and the hanger mounting portion is designed to have high torsional and bending rigidity in the vertical direction, the trailing arm has stiffness sufficient. As a result, the maneuverability can be improved.

 In addition, since the arm portion is designed to have high torsional rigidity and low vertical bending stiffness, for example, the rear swing arm is provided with sufficient rigidity and consecutive shocks and quickly repetitive which can hardly be absorbed by the suspension are attenuated. As a result, driving quality can be improved. In other words, a rear swingarm having bending properties while maintaining sufficient rigidity is achieved.

 Since the rear wheel support portion is constructed to have extreme torsional and bending rigidity in the vertical direction, the rear wheel can be supported firmly. As a result, the maneuverability can be improved.

 Since the arm portion is adapted to be convex downward in a side view, for example, the arm portion may act as a cantilevered cantilever beam, the section between the hinge shaft attachment portion. and the suspension attachment portion being fixed. Generally, the

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 Cantilever curved beam designed to be convex down can be easily flexed by a load applied from below and can not be easily flexed by a load applied from above.

 In other words, since the main element of the vertical load applied to the rear swingarm by the rear wheel is a load applied from below, the arm portion is designed to be convex downward in a side view, so that it can be designed to have low flexural rigidity in the vertical direction while maintaining high torsional stiffness. As a result, the rear swingarm can be provided with sufficient rigidity and consecutive and rapidly repetitive shocks that can barely be absorbed by the suspension are attenuated.

 Since the arm portion is adapted to be convex downward in a side view, for example, any interference with the other body members of the vehicle when it is swayed is avoided and the angle of rotation of the rear swingarm can be prevented. to be increased. As a result, the design potential of the motorcycle can be extended.

Claims (3)

A motorcycle rear oscillating arm (50) (10) comprising: a hinge shaft fixing portion (53) for hingedly attaching the rear swingarm (50) to the body of the vehicle via the hinge shaft (33); a suspension attachment portion (58) at the rear of the attachment portion of the hinge shaft (53) and a rear wheel support portion (56) for supporting the rear wheel at the rear end of the hinge shaft (53); the arm portion (55) extending rearwardly from the suspension attachment portion (58), characterized in that the section between the hinge shaft attachment portion (53) and the portion suspension fastener (58) is designed to have high torsional and bending stiffness in the vertical direction, and the arm portion (55) is designed to have high torsional rigidity and low rigidity at the same time. bending in the vertical direction.  A motorcycle rear swing arm (50) as claimed in claim 1, characterized in that the rear wheel support portion (56) is designed to have high torsional and bending stiffness in the vertical direction. .  Rear swingarm (50) for motorcycles (10) according to claim 1, <Desc / Clms Page number 22>  characterized in that the arm portion (55) is adapted to be convex downwardly in a side view.