JP2000046154A - Two-piece sprocket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a manufacturing work process, and reduce a cost by forming the shaft hole part so as to become the specific relationship between a radius of the shaft hole part and a shaft radius of a shaft, and forming a difference between the abutting surface part and the level difference plane part so as to become larger than a difference between the radius of the shaft hole part and the shaft radius of the shaft. SOLUTION: Two sprocket half bodies are installed on a shaft to be fastened by a bolt. Then, the shaft hole part 5 is formed so as to become the relationship of (R1>=R2) between the radius R1 and a shaft radius R2 of a shaft, and since a quantity S of a level difference between the abutting surface part 11 and the level difference plane part 13 is formed larger than a radial difference (R1-R2=T) between the radius R1 of the shaft hole part and the shaft radius R2 of the shaft, the shaft hole part 5 contacts with the surface of the shaft in the first place. However, at this time, since clearance of almost (S-T)×2 remains between the opposed level difference plane part 13, when the bolt is fastend further, the shaft hole part 5 of the shaft is brought into pressure contact with the bolt so as to fix a sprocket.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin two-piece sprocket used for driving a chain.

[0002]

2. Description of the Related Art If a split sprocket made of synthetic resin is damaged or worn during a long period of use, when replacing a sprocket, a bearing unit or a shaft fixed to a conveyor frame is removed. Without splitting the sprocket into two pieces and removing
It has been widely used since it can be easily mounted, especially when a plurality of sprockets are mounted on one shaft (see JP-A-9-118).
No. 415).

FIG. 4 shows a state where a two-piece sprocket 20 made of a synthetic resin is assembled to a shaft 30.
The half-moon-shaped sprocket half 21 includes a joint surface portion 22 and a shaft hole portion 23. The joint surface portion 22 is formed with a convex portion 24 and a concave portion 25 for fitting the convex portion.
The boss 26 is provided with a hole 29 for fitting a nut 27 or a bolt 28, and one sprocket half 21 is provided with a keyway 10. Then, the two sprocket halves 21, 21 'are fastened and fixed to the shaft 30 such that the joining surface portions 22 face and join as shown in FIG. 4B.

[0004]

As shown in FIG. 4, the conventional two-piece sprocket 20 has a shaft hole for securely fastening the two sprocket halves 21, 21 'to the shaft 30. The radius R3 of 23 is smaller than the radius R4 of the shaft 30, and is formed in a relationship of R3 <R4. That is, the sprocket half 2
1,21 'comrades are tightened with bolts 28 and the joint surface 22
Are tightly attached to each other so that the shaft 30 is tightened by the shaft hole 23 so that the shaft 30 and the shaft hole 23 have, for example, about 0.05. Therefore, in order to have such a shimeshiro,
Without the shaft, the sprocket halves are tightened with bolts to make the joint surfaces adhere closely, and then it is necessary to precisely turn and finish to leave the exact dimension of the shimeshiro, but in this way it is quite Performing precise turning has the disadvantage that the work takes time and costs increase.

Further, in the case of the two-piece sprocket, half-moon-shaped sprocket halves are manufactured by injection molding. After injection molding, post-shrinkage of a synthetic resin (plastic) occurs. In general, due to the influence of shrinkage after this, FIG.
As shown in (A), the sprocket half 21 that is deformed in the arrow X direction and the arrow Y direction and has a shaft hole dimension originally smaller than the outer dimension of the shaft 30 is:
Due to the corners 29, the L dimension of the shaft hole 23 is further reduced. Then, when the sprocket halves 21 and 21 ′ are joined to the shaft 30 and assembled, the joint surface 22 is separated by the contact of the shaft 30 and the corner 29, and the bolt 28 and the nut 27 are aligned at the time of the bolt tightening work. There is a drawback that the fitting becomes difficult due to displacement, the tightening resistance increases, and the tightening stroke of the bolt 28 increases, resulting in poor working efficiency. An object of the present invention is to solve these disadvantages and to provide an object.

[0006]

In order to solve the above-mentioned problems, the present invention provides a method of fixing a pair of synthetic resin sprocket halves each having a joint surface and a shaft hole to a shaft. In such a two-piece sprocket, contact surfaces located at the same level as the center point of the sprocket are formed on both side ends of the joint surface of each sprocket half. A stepped flat portion located on the top side of the sprocket is formed, and the shaft hole is formed such that a relationship of R1 ≧ R2 is established between the radius R1 and the shaft radius R2 of the shaft. The difference S between the radius of the shaft hole radius R1 and the radius R2 of the shaft is T (R1
-R2 = T) and is formed in a relationship of S> T ", and a combination of a pair of synthetic resin sprocket halves having a joint surface and a shaft hole. In the two-piece sprocket, a corner formed by the joint surface portion of the sprocket half and the shaft hole is cut or chamfered in the thickness direction of the sprocket half. "

In the present invention, the center point of the sprocket is defined by a combination of two sprocket halves, which are tightened with a bolt or the like, or are fastened and fixed to a shaft, so that the outer peripheral circle is formed as a perfect circle. It is the center point of the sprocket.

[0008]

With the above construction, when the two sprocket halves are assembled to the shaft and fastened by, for example, bolts, the shaft hole portion has a gap between the radius R1 and the shaft radius R2 of the shaft. R2, and the amount of step S between the contact surface portion and the step flat portion is formed.
Is larger than the radius difference T (R1−R2 = T) between the shaft hole radius R1 and the shaft radius R2 of the shaft, and is formed in a relationship of S> T. At this time, a gap of approximately (ST) × 2 remains between the opposing step plane portions. Then, when the bolt is further tightened, the shaft hole is pressed against the shaft, and the sprocket is fixed.

In a two-piece sprocket made by combining a pair of synthetic resin sprocket halves each having a joint surface and a shaft hole, a corner formed by the joint surface of the sprocket half and the shaft hole is formed. Notch or chamfered over the thickness direction of the sprocket half, so the chamfered portion, notch serves as a guide when attaching the sprocket to the shaft, and the shaft enters the shaft hole even before fastening, Shortening the bolt tightening stroke.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.

(Embodiment 1) FIGS. 1A to 1D show:
A two-piece sprocket half 1 made of synthetic resin is shown,
The sprocket half 1 is obtained by injection molding of polyamide and glass fiber reinforced polyamide, and the sprocket is formed by combining and fastening the sprocket half 1 and another sprocket half (not shown). You.

The sprocket half 1 comprises a boss 2 and teeth 2 arranged in two rows, and has joint surfaces 4, 4 and a shaft hole 5, and the joint surface 4 functions for positioning. Protrusions 6, 6 such as protrusions and pins and recesses 7, 7 for fitting the protrusions
Is provided. The recesses 7, 7 have play so that the projections can be displaced in the recesses when tightening the bolts, and are preferably formed in a substantially elliptical shape. The boss portion 2 is provided with a bolt insertion hole 8 and a nut insertion hole 9. In the figure, reference numeral 10 denotes a keyway.

This sprocket half 1 is opposed to another sprocket half (not shown, having the same structure as the sprocket half 1 and not having a key groove) and its joining surface 4 so as to be joined to each other. , Shaft 1 in the same manner as the prior art
5 and tightened and fixed to the shaft 15 by tightening bolts to nuts provided in the nut insertion holes.

By the way, as shown in FIG. 2A, both end portions 1A, 1A of the sprocket half are provided on the joint surface portion 4.
At the same level as the center point 11 of the sprocket, when the paired sprocket halves are joined, abutting surfaces 12 and 12 are formed which come into contact with each other. A step flat portion 13 is formed closer to the top 1B (see FIG. 1), and the step flat portion 13 is substantially parallel to an imaginary line connecting the contact surface portion 12 and the center point 11 of the sprocket. It is formed so as to be positioned. The contact surface portion 12 and the stepped flat portion 13 are formed continuously via a stepped portion 14 formed of an inclined surface. The contact surface portion 12 and the stepped flat portion 13
The amount S of the step in the step portion 14 is a minute interval, and the amount S of the step is maintained toward the center point of the sprocket in the design drawing.

Here, the center point of the sprocket is defined as the case where the two outer sprocket halves are combined and tightened and fixed to a shaft by a bolt or the like, so that the outer peripheral circle is formed into a perfect circle. Center point of the sprocket.

On the other hand, as shown in FIG. 2B, the shaft hole 5 has a radius R1 larger than the shaft radius R2 of the shaft 15. That is, the shaft hole 5 is formed between R1 and R
2 are formed so as to satisfy the relationship of R1 ≧ R2, and have a radius difference of R1−R2 = T. When the sprocket half is assembled to the shaft, the radius difference T is equal to R1−R2 = T. Has an apparent clearance T, and the difference T between the radii is also small.

The amount S of the step is larger than the difference T in the radius, and is set so as to satisfy S> T.

When a pair of sprocket halves formed as described above is assembled to a shaft and fastened with bolts or the like, S
> T, the shaft 15 and the shaft hole 5 first contact on the surface. At this time, the step flat portion 1 of the pair of opposing half sprockets
A gap of approximately (S−T) × 2 remains between 3 and 13. When the bolt is further tightened, the gap is reduced, the shaft hole 5 is pressed against the shaft 15, and the two sprocket halves are fastened and fixed to the shaft 15.

In the above embodiment, the two-split sprocket is formed with a stepped flat portion 13 at the joint surface 4 on the top 1B side from the level of the center point 11 of the sprocket.
Since the amount S of the step is set so as to satisfy the relationship of S> T between the radius R1 of the shaft hole 5 and the radius T of the shaft radius R2 of the shaft 15, the amount of the step S is set at the time of fastening to the shaft 15. Since there is always a gap between the stepped flat portions 13 facing each other in a state where the shaft hole portion 5 and the shaft 15 first contact each other, it is possible to further tighten and fix the shaft 15 to the shaft 15 by pressing. The finish of the shaft hole is not done by finishing the shaft hole by leaving the shimeshiro portion of the exact size as in the above, so the finished size of the shaft hole can be made slightly rough, and consequently turning The finishing process can be omitted and the device can be used in the state of the injection molding level, so that the manufacturing operation process can be shortened.

(Embodiment 2) Embodiment 2 will be described below with reference to FIG. 3. However, since the joint surface portion, shaft hole, and the like of the sprocket half are substantially the same as those in Embodiment 1, detailed description is omitted. .

A corner portion 16 is formed at the intersection of the step flat portion 13 of the joint surface portion 4 of the sprocket half 1 and the shaft hole portion 5. The corner portion 16 is subjected to notch processing, chamfering, and the like, and has a cutout portion having a linear cross section or a chamfered portion 17 having a curved cross section over the thickness direction of the sprocket half 1.
The W dimension (see FIG. 3) of the corner 16 after chamfering is larger than the outer diameter dimension 2 × R2 of the shaft. The size of the notch or the curved chamfered portion should be such that the sprocket half does not hit the shaft at the time of attachment to the shaft or can be pushed in consideration of the deformation as shown in FIG. Is set.

As described above, since the notch or the curved chamfered portion 17 is formed in the corner portion 16, the shaft 1
When a pair of sprocket halves are assembled and fixed to the shaft 5, a notch or a curved chamfer 17 functions as a guide, so that the sprocket halves can be easily assembled to the shaft 15 and fastened and fixed. The tightening stroke can be shortened.

While the embodiment of the present invention has been described above, other embodiments are possible.

For example, in each embodiment, the step portion 14 may be a flat or curved inclined surface. Also, the step flat portion 13 is connected to the center point 11 of the sprocket and the contact surface portion 1.
2 may be parallel to the line connecting the two ends, or may be away from the center point, ie, the sprocket half 1
May be formed slightly inclined toward the top 1B. In short, two sprocket halves are connected to shaft 15
When the shaft 15 and the shaft hole 5 first contact with each other by tightening with a bolt or the like, the opposed corners 16 do not come into contact with each other, and at least the stepped flat portion 13 is left so as to leave a gap equal to or more than Shimeshiro. What is necessary is just to be formed.

In the second embodiment, the bonding surface 4 is replaced by the first embodiment.
As described above, without forming the stepped flat portion 13, the entire bonding surface portion is in close contact, that is, the bonding surface portion is formed only of the contact surface portion (prior art), the cutout portion at the corner portion, A chamfer may be formed.

[0026]

According to the present invention, the contact surfaces of the sprocket halves are formed at both ends with contact surfaces located at the same level as the center point of the sprocket. A stepped flat portion located closer to the top of the sprocket is formed, and the shaft hole is formed so as to satisfy a relationship of R1 ≧ R2 between the radius R1 and the shaft radius R2 of the shaft. The amount S of the step between the surface portion and the stepped flat portion is larger than the difference T between the radius of the shaft hole portion and the radius of the shaft of the shaft, and the relationship is set so that S> T. Sometimes, there is always a gap between the stepped flat portions 13 facing each other in a state where the shaft hole portion 5 and the shaft 15 are initially in contact with each other. That It is not necessary to form the gaps with extremely precise dimensions, and it is not necessary to consider the degree of the gap after the fastening, so the finished dimensions of the shaft hole can be made slightly rough, and the injection molding level state It can be used, and the turning finishing process can be omitted, thereby shortening the manufacturing process and reducing the cost.

Further, according to the present invention, since the notch or the curved chamfer 17 is formed in the corner 16, when the pair of sprocket halves are assembled and fixed to the shaft 15, the notch or the curved chamfer 17 is formed. The chamfer 17 acts as a guide, so that the sprocket half can be easily assembled and fixed to the shaft 15, and the bolt tightening stroke can be shortened.

[Brief description of the drawings]

FIG. 1 is an overall view of a sprocket half, (A) is a plan view, (B) is a front view, (C) is a bottom view, and (D) is a side view.

FIGS. 2A and 2B are front views of a contact surface portion of a half sprocket and a partially cut-away portion of a shaft hole portion, wherein FIG. 2A is a relation between a contact surface portion and a stepped flat portion, and FIG. It is explanatory drawing which shows an association.

FIG. 3 is an explanatory view of a corner formed by a joint surface and a shaft hole in another embodiment.

4A and 4B are explanatory views before and after assembling of a conventional two-piece sprocket, wherein FIG. 4A is an explanatory view before assembling and FIG. 4B is an explanatory view after assembling and fastening.

FIG. 5 is an explanatory view of a modification of the conventional two-piece sprocket, where (A) is an explanatory view showing a state before assembling and (B) is an explanatory view showing an aspect after assembling.

[Explanation of symbols]

1 ... Sprocket half 2 ...
・ Boss part 3 ・ ・ ・ Tooth part 4 ・ ・
・ Joint surface part 5 ・ ・ ・ Shaft hole part 6 ・ ・
・ Protrusion 7 ・ ・ ・ Recess 8 ・ ・
・ Bolt insertion hole 9 ・ ・ ・ Nut insertion hole 10 ・
・ Keyway 11 ・ ・ Central point of sprocket 12 ・
・ Contact surface part 13 ・ ・ Stepped surface part 14 ・
・ Step 15 ・ ・ Shaft 16 ・
・ Corner 17 ・ ・ Notch S ・ ・
・ Amount of step difference T ・ ・ ・ Difference in radius between shaft hole and shaft

Claims (2)

[Claims] In a two-piece sprocket in which a pair of synthetic resin sprocket halves each having a joint surface portion and a shaft hole portion are fastened and fixed to a shaft, a joint surface portion of each sprocket half has two sides. At the end, a contact surface portion located at the same level as the center point of the sprocket is formed, and a step flat portion located at the top side of the sprocket from the level of the center point of the sprocket is formed. Is formed so as to satisfy the relationship of R1 ≧ R2 between the radius R1 and the shaft radius R2 of the shaft, and the amount S of the step between the contact surface portion and the step flat portion is determined by the relationship between the shaft hole radius and the shaft. A two-piece sprocket, characterized in that it is larger than the difference T in radius from the shaft radius and is formed in a relationship of S> T. 2. The sprocket half according to claim 1, wherein the corner formed by the joint surface and the shaft hole is cut or chamfered in the thickness direction of the sprocket half. 2 split sprocket.