JP2000257699A - Sprocket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure required mechanical strength by providing a sprocket formed by a disc-like inner ring part and a ring-like outer ring part, and integrally connecting the inner peripheral surface of the outer ring part to the outer peripheral surface of the inner ring part. SOLUTION: A sprocket S is so constructed that a ring-like outer ring part 2 is formed on the outer peripheral surface of a disc-like inner ring part 1, the inner ring part 1 is made of low carbon steel, a center hole 3 for mounting an axle is bored in the central part, and in the middle part, there are provided two rows of plural fitting holes 4 for fitting the sprocket S to the boss part of the driving wheel arranged to be concentric at spaces. On the other hand, the outer ring part 2 is made of medium carbon steel, and provided with plural sprocket teeth 5 meshing with a chain over the whole periphery, which are formed on the outer peripheral part. The inner peripheral surface of the outer peripheral ring is closely fitted to the outer peripheral surface of the inner ring part 1, and with spaces in the circumferential direction along the fitting face in plural portions welding connection 6 is performed to constitute the sprocket S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sprocket, and more particularly to a sprocket employed in a chain drive mechanism for driving driving wheels of a vehicle such as a motorcycle or a saddle type vehicle.

[0002]

2. Description of the Related Art Conventionally, in a vehicle such as a motorcycle or a saddle type vehicle, there is known a power transmission device for transmitting a driving force of a traveling engine to driving wheels (rear wheels) via a chain drive mechanism. However, in such a case, the driven sprocket of the chain drive mechanism is integrally attached to the drive wheel, and meshes with an endless chain that is linked to the engine.

[0003] Incidentally, the conventional driven sprocket is formed by integrally molding the entirety of medium carbon steel in order to improve the mechanical strength of the sprocket teeth, especially the wear resistance, durability and toughness. The sprocket teeth are sufficiently carburized and quenched.

[0004]

However, since the conventional sprocket is entirely made of expensive medium-carbon steel (hard steel), there is a problem that the cost is greatly increased.

Accordingly, the present invention has been made in view of such circumstances, and in particular, an outer ring portion having sprocket teeth with high demands such as durability, abrasion resistance, and toughness, and a lower demand for the outer ring portion. It is an object of the present invention to provide a new sprocket that solves the above-mentioned problem by forming an inner ring portion having an attachment portion and a different material from each other and integrating them.

[0006]

According to the first aspect of the present invention, there is provided a sprocket having a sprocket tooth meshing with a chain on an outer peripheral portion thereof, wherein the sprocket is made of a low carbon steel. An inner ring portion and a ring-shaped outer ring portion made of medium carbon steel formed with sprocket teeth on the outer peripheral portion, and the inner peripheral surface of the outer ring portion is integrally connected to the outer peripheral surface of the inner ring portion. According to this feature, the outer ring portion having sprocket teeth is made of a medium carbon steel having high mechanical strength such as wear resistance and toughness.
The inner ring part to be attached to the drive wheel is made of low carbon steel having the required mechanical strength (lower than the required mechanical strength of the outer ring part), and the low carbon steel is made of medium carbon steel. As a result, it is possible to provide a high-precision sprocket at low cost while securing the required mechanical strength. In addition, the medium carbon steel material of the outer ring portion having the sprocket teeth can be arbitrarily changed, and a sprocket having necessary mechanical strength can be easily obtained.

In order to achieve the above object, according to the second aspect of the present invention, in the sprocket according to the first aspect, the inner race portion has a mounting hole for mounting to a driving wheel of a vehicle. The sprocket teeth of the outer ring portion are characterized by being meshed with a chain that is interlocked with a traveling engine of the vehicle. According to such a feature, a low-cost vehicle sprocket is ensured while securing required mechanical strength. Can be provided.

In order to achieve the above object, according to the third aspect of the present invention, in the sprocket according to the second aspect, the mounting hole of the inner ring portion to the drive wheel is formed by punching. According to this feature, the sprocket can be further reduced in cost.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

In this embodiment, a sprocket according to the present invention is applied to a driven sprocket mounted on a driving wheel of a chain drive mechanism in a saddle type vehicle. FIG. 1 is a front view of the sprocket, and FIG. FIG.
FIG. 3 is a side view of a state in which the sprocket is mounted on a drive wheel of a saddle-ride type vehicle, and FIGS. 4 to 6 are views showing a process of manufacturing the sprocket.

In FIGS. 1 and 2, a sprocket S has a disk-shaped inner ring portion 1 and a ring-shaped outer ring portion 2 having sprocket teeth 5 formed on its outer peripheral surface. The inner peripheral surface of the outer ring portion 2 is formed by welding 6.

The disk-shaped inner ring portion 1 is a mild steel made of low carbon steel (carbon <0.3%, tensile strength <45 Kg / mm ² ), and has an axle fitted in the center thereof. Center hole 3 is formed, and the sprocket S
Are attached to the boss portion of the driving wheel W, and a plurality of mounting holes 4 are formed in concentric circles at intervals.

On the other hand, the ring-shaped outer ring portion 2 is a hard steel made of medium carbon steel (carbon: 0.30 to 0.50%, tensile strength: 45 to 45).
60 kg / mm ² ), and a plurality of sprocket teeth 5 meshed with the chain are formed on the outer peripheral portion over the entire circumference.

The inner peripheral surface of the outer ring is closely fitted to the outer peripheral surface of the inner ring portion 1, and the inner peripheral surface is spaced at a plurality of locations (four locations) along the fitting surfaces at intervals in the circumferential direction. A sprocket S is formed by welding 6.

Next, referring to FIGS.
Will be described.

As shown in FIG. 4, the inner ring portion 1 is formed by stamping and forming a steel sheet material 1M made of low carbon steel by a press. Can be punched and formed at the same time when the inner ring part 1 is press-formed, and low carbon steel (mild steel) is softer than medium carbon steel (hard steel), so that its workability can be improved. Is good, and molding at a low cost is possible.

The inner ring portion 1 can omit a cutting process for deburring to reduce costs.

Forming of the ring body 2R to be the outer ring portion 2 (see FIGS. 5, (a) and (b)) On the other hand, as shown in FIGS. 5 and (a), the outer ring portion 2 is first made of medium carbon steel. After cutting the strip material 2M into a predetermined length, the strip material 2M is bent and formed into a ring shape using a known forming jig, and its both end surfaces 2 ₁ and 2 ₂ are abutted.
As shown in (b), the butted surfaces are welded and joined 2We to form a smooth ring body 2R on the inner and outer peripheral surfaces.

Forming of sprocket S (FIG. 6, (a),
(See (b)) As shown in FIG. 6 and (a), the outer peripheral surface of the inner ring portion 1
The inner peripheral surface of the ring body 2R is tightly fitted, and the fitting surfaces are welded and joined at a plurality of places (four places) at intervals in the circumferential direction, and the inner ring portion 1 and the ring body are joined together. 2R and the 2R.

Next, as shown in FIG. 6 (b), sprocket teeth 5 are formed on the entire outer peripheral surface of the ring 2R by a conventionally known sprocket tooth forming machine (not shown). In this case, the welding 2We portion is located at the root of the sprocket tooth 5, and between the root and the inner ring portion 1,
Ensure that a predetermined welding width can be obtained.

Next, if necessary, the sprocket teeth 5 may be subjected to induction hardening treatment or carburizing quenching treatment by a conventionally known heat treatment means to increase the mechanical strength of the sprocket teeth 5. In this case, the sprocket teeth 5 are formed by shaping the strip into a ring shape.
When this is heat-treated, the effect of thermal strain on the sprocket tooth form can be reduced.

With the above, the formation of the sprocket S made of dissimilar material by the welded joint 6 between the inner race 1 and the outer race 2 is completed.

In the sprocket S constructed as described above, the outer race portion 2 having the sprocket teeth 5 is attached to the drive wheel W by medium carbon steel having high mechanical strength such as wear resistance and toughness. Mechanical strength required by the inner ring portion 1 (lower than the required mechanical strength of the outer ring portion 2)
Since the low carbon steel is less expensive than the medium carbon steel, the sprocket S can provide a low cost sprocket S while securing the required mechanical strength. .

As shown in FIG. 3, the sprocket S formed as described above is provided on the side surface of the boss portion of the drive wheel W of the saddle type vehicle with bolts or the like through the mounting holes 4 thereof. The sprocket teeth 5 are fixed to the driven sprocket S by a fixing tool F, and a chain C of a chain drive mechanism interlocked with the driving engine is meshed with the sprocket teeth 5, and the driving force of the engine is transmitted to the drive wheels W through the chain drive mechanism. Is transmitted to

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various embodiments are possible within the scope of the present invention. For example, in the above-described embodiment, a case has been described in which the sprocket of the present invention is applied to a driven sprocket of a chain drive mechanism of a saddle type vehicle. However, it is needless to say that the sprocket can be applied to a general chain transmission mechanism. The inner ring portion and the outer ring portion may be integrally joined by welding or other known joining means.

[0026]

As described above, according to the first aspect of the present invention, in the sprocket, the outer ring portion having the sprocket teeth is formed with a medium having high mechanical strength such as wear resistance, toughness and durability. The inner ring part to be attached to the drive wheel is made of low carbon steel having the required mechanical strength (lower than the required mechanical strength of the outer ring part), and the low carbon steel is made of carbon steel. Since it is less expensive than medium carbon steel, a high-precision sprocket can be provided at low cost while securing the required mechanical strength. In addition, the medium carbon steel material of the outer ring portion having the sprocket teeth can be arbitrarily changed, and a sprocket having necessary mechanical strength can be easily obtained.

Further, according to the second aspect of the present invention, it is possible to provide a low-cost sprocket for a chain drive mechanism of a vehicle while securing required mechanical strength.

According to the third aspect of the present invention,
The cost of the sprocket can be further reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a sprocket.

FIG. 2 is a sectional view of the sprocket taken along line 2-2 of FIG. 1;

FIG. 3 is a side view showing a state in which a sprocket is mounted on drive wheels of a saddle type vehicle.

FIG. 4 is a diagram showing a manufacturing process of a sprocket.

FIG. 5 is a view showing a manufacturing process of a sprocket.

FIG. 6 is a view showing a manufacturing process of a sprocket.

[Explanation of symbols]

 1 ... inner ring part 2 ... outer ring part 4 ... mounting hole 5 ... sprocket teeth W ... ... Drive wheels C ... Chain

Claims (3)

[Claims] 1. A sprocket having a sprocket tooth meshing with a chain on an outer peripheral portion, wherein a disk-shaped inner ring portion (1) made of low carbon steel and a sprocket tooth (5) are formed on an outer peripheral portion. A ring-shaped outer ring portion (2) made of steel;
A sprocket, wherein an inner peripheral surface of the outer ring portion (2) is integrally connected to an outer peripheral surface of the sprocket. 2. The inner race part (1) has a mounting hole (4) to be mounted on a driving wheel (W) of a vehicle, and the sprocket teeth (5) of the outer race part (2) are The sprocket according to claim 1, wherein the sprocket is meshed with a chain (C) that is interlocked with a traveling engine. 3. The sprocket according to claim 2, wherein the mounting hole (4) of the inner race portion (1) to the drive wheel (W) is formed by punching.