JP2014221627A - Wheel structure and motorcycle provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel structure which does not cause relative deviation between a boss and a hub even when a large driving force is transmitted from an axle.SOLUTION: When a driving force is transmitted from an axle to a boss 16 and the boss 16 rotates in an A direction in the figure, the torque acts in the direction perpendicular to the contact surface between an octagonal cylindrical part 19 of the boss 16 and a hub 10, as shown with a solid-line arrow, without causing deviation from the rotation direction like conventional wheel structures. When a brake force is caused to act on a wheel by operating a brake unit 12, a force rotating in a B direction from the hub 10 to the boss 16 acts. The torque acts in the direction perpendicular to the contact surface between the octagonal cylindrical part 19 of the boss 16 and the hub 10 as the same as above, as shown with a broken-line arrow, without causing deviation from the rotation direction, like conventional wheel structures.

Description

  The present invention relates to a wheel structure in which rotation of an axle is transmitted to a wheel via a boss and a hub, and a motorcycle including the wheel structure.

  As a motorcycle drive type, the engine power is transmitted to the axle, the rotational force of this axle is transmitted to the boss that is splined to the axle, and the rotational force of this boss is coupled to the boss (integrated casting). There is a type that transmits to the wheel hub.

  In the type of motorcycle described above, a problem has been pointed out that abnormal noise is generated from the vicinity of the wheel shaft center when a large engine driving force is generated by widening the throttle at the start.

In Patent Document 1, a gap generated between the boss and the hub is cited as a cause of the abnormal noise.
That is, the wheel has a cast iron boss set in a mold, and in this state, a light alloy molten metal such as a molten aluminum alloy is gravity cast to integrally cast the hub and the boss. Since it is gravity casting, no pressure is applied to the molten metal, and a gap is easily formed between the boss and the hub. Due to this gap, the adhesion between the boss and the hub is not sufficient, and when the engine driving force is increased to shift from the static friction state to the dynamic friction state, the gap that cancels the above gap is the difference between the boss and the hub. It occurs in the middle and abnormal noise is generated by this deviation.

  In the above, the gap between the boss and the hub does not occur over the entire circumference, but occurs in a part and the remaining part is in contact, so the rotation of the boss is transmitted to the hub and the wheel Rotates. However, if the above state is not the most closely contacted state, an abnormal noise is generated by shifting to the closest contact point when the engine driving force is increased. Incidentally, there is also a vehicle that is in the most closely contacted state from the beginning, and no abnormal noise is generated in this case.

  In Patent Document 1, in order to solve the above problem, a plating film having a small friction coefficient is formed on the surface of a boss set in a mold, and the most stable position before a large driving force is transmitted. This prevents the noise from being generated and causes a large noise.

JP 2007-112387 A

  In Patent Document 1, there is a problem that the plating film is worn or lost. In other words, the hub is made of a light alloy such as aluminum, and when casting the hub, a cast iron boss is set and cast into the mold. However, there is a disadvantage that the gap between the boss and the hub becomes larger.

  In particular, in a motorcycle in which the braking force of the wheel (hub) is transmitted to the axle through the boss during braking, the rotational force in the opposite direction is applied to the joint between the boss and the hub each time driving and braking are repeated. Therefore, abnormal noise due to the gaps frequently occurs.

  In order to solve the above-described problems, a wheel structure according to the present invention includes a tooth portion for transmitting power to a hub on the outer periphery of an axially intermediate portion of a boss that is spline-fitted outside an axle to which engine driving force is transmitted. (Rib) is formed, and at least one of the outer peripheral shapes of the cylindrical portions on both sides of the tooth portion is a polygonal cylindrical shape.

  As described above, the hub is generally manufactured by casting a light alloy such as an aluminum alloy, and a boss is set in the mold at the time of casting. Since the boss is spline-fitted to the axle, when braking is applied to the hub by the brake, the braking force is transmitted to the axle via the boss.

  According to the wheel structure of the present invention, since the shape of the joint portion between the boss and the hub is not a circle but a polygon, a large driving force is transmitted to the boss from the axle, or a large braking force is applied to the hub. Even if it is applied, the force that the boss tries to contact the hub (force perpendicular to the joint surface) is generated in both cases, and there is no relative displacement in the circumferential direction between the boss and the hub. No noise is generated near the wheel center during braking or braking.

Side view of a motorcycle having a wheel structure according to the present invention. Cross section of the rear wheel of the motorcycle Boss side view End view of the boss The figure explaining the direction of the force which acts at the time of driving and braking (A) And (b) is a figure similar to FIG. 4 which shows another Example.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In the motorcycle 1, a front wheel 4 is supported by a front fork 3 that is steered by a handle 2, and a rear wheel 7 is supported via an axle 6 at a rear end of a rear arm 5 whose tip is supported by an engine.

  In the rear wheel 7, a tire 9 is mounted on a rim 8 of an aluminum alloy wheel, and a hub 10 serving as a wheel shaft core portion is connected by a plurality of spokes 11. The rim 8, hub 10 and spoke 11 are integrally cast.

  The hub 10 has an outwardly bulging shape, and a drum-type brake device 12 is disposed on the inner side. The brake device 12 includes a brake shoe 13, a brake cam 14 for expanding the brake shoe 13, and an iron brake drum 15.

  A boss 16 is cast on the inner periphery of the hub 10. The boss 16 is formed by pre-molding by gravity casting and setting in a mold at the time of wheel casting.

  A serration 17 for spline fitting with the axle 6 is formed in the inner hole of the boss 16, and a tooth portion (rib) 18 that transmits rotational force to the hub 10 at an intermediate position of the outer surface of the boss 16. Is formed.

  The left side portion of the tooth portion (rib) 18 of the outer surface of the boss 16 is an octagonal cylindrical portion 19 and the right side portion is a cylindrical portion 20. The right side portion may also be a polygonal cylinder shape such as an octagonal cylinder shape, or only the right side portion may be a polygonal cylinder shape.

  In the above, when the driving force is transmitted from the axle 6 to the boss 16 as shown in FIG. 5 and the boss 16 rotates in the direction A in the figure, the rotational force is the eight corners of the boss 16 as shown by the solid line arrows. It acts in a direction perpendicular to the contact surface between the cylindrical portion 19 and the hub 10, and does not become a force in a direction in which a rotational displacement occurs as in the prior art.

  Further, when a braking force is applied to the wheel by operating the brake device 12, a force rotating in the B direction from the hub 10 is applied to the boss 16. As indicated by the dotted arrow, this rotational force acts in the vertical direction with respect to the contact surface of the octagonal cylindrical portion 19 of the boss 16 and the hub 10 as described above, and a deviation in the rotational direction as in the prior art occurs. There is no direction force.

  6 (a) and 6 (b) are views similar to FIG. 4 showing another embodiment, and the outer peripheral surface shape of the boss 16 is not limited to the octagonal cylinder-shaped portion 19; It is good also as the triangular cylinder shape part 19b.

  However, it is necessary to ensure a necessary thickness from the viewpoint of durability and the like, and from this viewpoint, a polygonal cylinder shape and a polygonal cylinder of an octagonal cylinder or more are more preferable. It is possible up to a cylinder.

  In the embodiment, the cast wheel in which the rim, the hub and the spoke are integrally cast has been described. However, in the present invention, at least the hub may be made of a light alloy such as an aluminum alloy, and the rim, the hub and the spoke are integrated. It is not limited to what was cast.

  Furthermore, the wheel structure according to the present invention can be applied to a motorcycle to which a disc brake is applied instead of a drum brake device.

  DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 2 ... Handle, 3 ... Front fork, 4 ... Front wheel, 5 ... Rear arm, 6 ... Axle, 7 ... Rear wheel, 8 ... Rim, 9 ... Tire, 10 ... Hub, 11 ... Spoke, 12 ... Brake Device: 13 ... Brake shoe, 14 ... Brake cam, 15 ... Brake drum, 16 ... Boss, 17 ... Serration, 18 ... Tooth part (rib), 19 ... Octagonal cylindrical part, 19a ... Hexagonal cylindrical part, 19b ... Triangular cylindrical part, 20 ... Cylindrical part.

Claims (3)

  In a wheel structure in which a hub is coupled to a boss that is spline-fitted to the outside of an axle to which the driving force of the engine is transmitted, a tooth portion for power transmission is formed on the outer periphery of the axial intermediate portion of the boss, A wheel structure characterized in that at least one outer peripheral shape of the cylindrical portions on both sides sandwiching the tooth portion is a polygonal cylindrical shape.   2. The wheel structure according to claim 1, wherein the rotational force of the axle is transmitted to the hub via the boss during driving, and the braking force of the hub is transmitted to the axle via the boss during braking. A motorcycle comprising the wheel structure according to claim 1 or 2.

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