JP2000161468A - Synthetic resin mold gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin which can reduce contraction difference between teeth of a gear without adjusting thickness of each part composing a gear main body, improve molding accuracy of the gear, and be easily designed. SOLUTION: A plurality of teeth 11 are integrated with a rim 12 on an outer peripheral surface of a synthetic resin mold gear. In such a mold gear, a circular portion 13 is integrated with the rim 12 and teeth 11, which circular portion 13 has thickness less than that of the rim 12 and is radially projected from the outer peripheral surface of the rim 12 by specified length. The circular portion 13 is formed on such a position of the outer peripheral surface of the rim 12 as to secure large deformation degree of the rim 12 and not to damage function of the gear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic gear molded gear having teeth integrally formed on the outer peripheral side of a rim,
More specifically, the present invention relates to a synthetic resin molded gear that can improve the molding accuracy of a gear by adjusting the difference in shrinkage of the synthetic resin and has a simple design.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional example of this type of gear. A plurality of teeth 11 are provided on the outer peripheral side of the rim 12 to form the gear body 10. The gear is made of a molten material such as a synthetic resin, for example, from a gate (only one is indicated by a two-dot chain line in FIG. 8) provided on a surface on one side of the rim 12 on a concentric circle. Is injected into a mold (not shown) in which a cavity corresponding to the shape of the above is formed. The injected molten material initially flows radially around the gate position, but eventually fills the cavity of the tooth portion 11 and the rim 12. After that, the molten material is cooled and solidified,
The mold is designed so that a synthetic resin molded gear as shown in FIGS. 8A and 8B can be obtained by releasing the mold.

[0003] In such injection molding, it is known that a more or less contracting action acts upon cooling and solidification of the molten material, which affects the formation of a predetermined gear shape. In general, the degree of shrinkage becomes larger as the thickness is larger and the filling amount of the molten material is larger than in a place where the thickness is smaller and the filling amount of the molten material is smaller. Further, in the case of the same thickness, a portion having a smaller contact area with the mold is less likely to escape heat and is likely to be delayed in solidification. Therefore, in general, when a synthetic resin molded gear having a tooth portion on the outer periphery has a tooth width equal to or larger than a predetermined size, the synthetic resin shrinks greatly at an intermediate position of the tooth width to be molded. Of the gear, and the diameter difference within the tooth width of the gear increases.

[0004] For example, a gear in which a cylindrical rim 12 as shown in FIG. In the central portion 12c, heat is less likely to escape in the axial direction than in the both end portions 12a and 12b, solidification is delayed, and the shrinkage action is greatly exerted. For this reason, as shown in FIG. 8 (c), the center portion 12c of the gear is largely curved inward as compared with the both end portions 12a and 12b.

Therefore, in the case of a conventional synthetic gear made of synthetic resin of this type, for example, in the case of a gear having bosses, webs, ribs and the like in addition to the rim, the thickness of the portion connected to the rim is adjusted. This prevents the delay of solidification in the connection area, minimizes the distortion applied to the teeth provided on the outer peripheral side of the rim, minimizes the difference in outer diameter, and reduces the error in the direction of the teeth and the meshing error per tooth pitch. Can be reduced.

[0006]

However, adjusting the thickness of each part connected to the rim requires complicated design for thinning according to various configurations of the gears, and as shown in FIG. It is not possible to reduce the deformation of a gear that does not have a portion connected to a rim.

Accordingly, the present invention can improve the molding accuracy of the gear by reducing the difference in the contraction of the teeth of the gear without adjusting the thickness of each part constituting the gear main body, and improving the design of the gear. It is an object of the present invention to provide a synthetic resin molded gear that can be easily manufactured.

[0008]

In order to solve this problem, a synthetic resin molded gear according to the present invention comprises a synthetic resin having a gear body in which a plurality of teeth and a rim are integrally formed on an outer peripheral surface. Formed gear is formed along a predetermined portion of the outer peripheral surface of the rim while having a thickness smaller than the thickness of the rim and projecting a predetermined length in the radial direction from the outer peripheral surface of the rim. An annular portion is integrally formed with the rim and the plurality of teeth.

In the present invention, preferably, the annular portion is provided at a location where the degree of deformation of the rim when the molten material in injection molding is solidified is large and the function as a gear is not impaired. It is characterized by having been done.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a synthetic resin molded gear according to the present invention, in which (a) is a plan view, (b) is a cross-sectional view of the gear shown in (a), and (c) is (b). It is a state explanatory view which shows the deformation state of the gear in FIG. Note that, for convenience of explanation, the deformed state is exaggerated. The synthetic resin molded gear of the present embodiment is a gear body 10 shown as a conventional example in FIG.
In addition to the above configuration, the annular portion 13 has a plurality of teeth 1 on the outer peripheral surface.
1 and a rim 12 having a cylindrical shape. In this embodiment, the annular portion 13 has a thickness T ₁ of the rim 1.
2 is thinner than the thickness T ₂ of the rim 12 and is located at substantially the same position from both ends 12 a and 12 b of the rim 12 along the outer peripheral surface of the rim 12 (hereinafter, referred to as a central portion 12 c). It is provided so as to protrude with a predetermined length width W ₁ of the more radially.

The formed gear of the present embodiment is manufactured by the same method as the above-described conventional formed gear. That is,
For example, a molten material such as a synthetic resin is formed into a gear shape from a gate provided on one surface of the rim 12 on a concentric circle (only one dot-dashed line is shown in FIGS. 1A and 1B). It is poured into a mold (not shown) having a matching cavity. The injected molten material initially flows radially around the gate position, but eventually the molten material fills the teeth 11, the rim 12, and the cavity of the annular portion 13 as a whole. Thereafter, the molten material is cooled and solidified, and the mold is released, so that a synthetic resin molded gear as shown in FIGS. 1 (a) and 1 (b) is obtained.

At this time, according to the gear of the present embodiment, the thickness of the annular portion 13 is formed to be thinner than the thickness of the rim 12, so that in actual injection molding, the molten material in the cavity is annular. The portion 13 solidifies before the rim 12 and begins to solidify on the rim 12 later than the annular portion 13. Here, the central portion 12c of the rim 12 is harder to escape heat than the two end portions 12a and 12b, so that the solidification is delayed. However, since the central portion 12c is connected to the annular portion 13 in which the molten material has been solidified, the shrinkage rate is kept low. Can be Thus, as shown in FIG. 1C, the rim 12 is formed in a state where the contraction rates of the both ends 12a, 12b and the central part 12c are substantially equal, and the degree of deformation is determined by the tooth width W _2.
Whole is averaged, the diameter difference is reduced in the tooth width W ₂ of the gear. Therefore, according to the gear of the present embodiment, by diameter difference in the tooth width W ₂ of the gear is reduced, reducing the tooth trace direction error, meshing errors per one pitch of the teeth in both the tooth surface meshing also tested Since it is suppressed as much as possible, the accuracy of the gear can be improved. Further, according to the gear of the present embodiment, the diameter difference of the gear can be reduced by a simple design change only by adjusting the arrangement of the annular portion 13, the thickness T _{1, and the} like. Tooth 1 according to
By adjusting the thickness of the other components of the gear body such as the rim 1 and the rim 12, the accuracy of the gear can be further improved. Further, by connecting the annular portion 13 to the tooth portion 11 and the rim 12, the tooth portion 11 itself of the gear can be reinforced.

In the gear according to the present embodiment, the annular portion 13 is formed so that the tooth portion 11 is divided into two parts. In the present embodiment, the pitch of the tooth portion 11 divided into two by the annular portion 13 may be different depending on the application. For example, one may be a flat tooth and the other may be a helical tooth. In the present embodiment, the annular portion 13 is provided at the central portion 12c of the rim 12. However, in addition to the rim 12, a gear having a plurality of members such as a boss, a web, and a rib, and a thickness T _{2 of the} rim 12 are provided. Is the tooth width W
_In the case of gears designed to be different in ₂ , the degree of deformation of the rim 12 is not always maximized at the central portion 12 c of the rim 12. In this case, if the degree of deformation of the rim 12 is large and the annular portion 13 is provided at a position where the function as a gear is not impaired, the diameter difference of the entire gear can be reduced while maintaining the function as a gear. Can be minimized.

FIGS. 2A and 2B show another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example. FIG. 2A is a plan view of the gear of this embodiment, and FIG. Gear B shown
FIG. 3C is a state explanatory view showing a deformed state of the gear in FIG. 2B, and FIG. 4D is a state explanatory view showing a deformed state of the conventional gear corresponding to the present embodiment. In the gear of the present embodiment, a rim 12, a boss 14 disposed concentrically inside the rim 12, and a web 15 disposed concentrically between the rim 12 and the boss 14 are integrally formed. .
The web 15 is connected to the rim 12 and the boss 14.
Conventionally, when trying to form a gear with such a shape,
As shown in FIG. 2D, the shrinkage of the rim 12
The rim 12 is bent at the maximum at the connection portion with the rim 12, but according to the gear of the present embodiment, as shown in FIGS. 2 (a) and 2 (b), the annular portion 13 As shown in FIG. 2C, the shrinkage of the rim 12 and the degree of deformation of the gear at the connection with the web 15 are formed on the outer peripheral surface of the rim 12 along the connection with the web 15. Can be suppressed. Other configurations, operations and effects are almost the same as those of the gear of the embodiment in FIG.

FIG. 3 shows still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example.
(a) is a cross-sectional view of the gear of the present embodiment, (b) is a state explanatory view showing the deformed state of the gear in (a), (c) is a cross-sectional view of the deformed state of the conventional gear corresponding to the present embodiment. FIG. The gear according to the present embodiment includes a rim 12 and a rim 12.
A boss 14 disposed concentrically inside the inside of the rim 12 and a cylindrical portion 16 disposed concentrically between the rim 12 and the boss 14 are integrally formed. The cylindrical portion 16 has a diameter smaller than the diameter of the rim 12 and larger than the diameter of the boss 14. The cylindrical portion 16 has one end 16 a connected to the boss 14 and the other end 16 b connected to one end 12 a of the rim 12.
Conventionally, when trying to form a gear with such a shape,
As shown in FIG. 3C, the contraction rate of the rim 12 is
At the connection with the other end 16b of the rim 1
At the one end 12a of the second gear 2, the force for deforming the gear is applied to the maximum.

According to the gear of this embodiment, as shown in FIG. 3 (a), the annular portion 13 is connected to the one end 12a of the rim 12 along the connection with the other end 16b of the cylindrical portion 16. Since it is formed on the outer peripheral surface, in actual injection molding, the molten material in the cavity is solidified by the annular portion 13 before the one end 12a of the rim 12 and the other end 16b of the cylindrical portion 16, and One end 12a of the rim 12 and the other end 16b of the cylindrical portion 16 are solidified behind the portion 13. Here, rim 1
2 and the other end 16b of the cylindrical portion 16 are already connected to the annular portion 13 in which the molten material has solidified.
The respective shrinkage rates can be kept low. Thereby, the rim 1
2 is formed as shown in FIG. 3 (b) with the difference between the shrinkage rate and the degree of deformation of both ends 12a and 12b being minimized,
Diameter difference in the tooth width W ₂ of the gear is reduced. The diameter difference between the one end 16a and the other end 16b of the cylindrical portion 16 is also reduced. Other configurations, operations and effects are almost the same as those of the gear of the embodiment in FIG.

FIG. 4 shows still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example.
(a) is a cross-sectional view of the gear of the present embodiment, (b) is a state explanatory view showing the deformed state of the gear in (a), (c) is a cross-sectional view of the deformed state of the conventional gear corresponding to the present embodiment. FIG. The gear according to the present embodiment includes a plurality of rims 12 and 17 having different diameters and arranged concentrically, and rims 12 and 17.
A boss 14 having a diameter smaller than any one of the diameters 17 and concentrically arranged, and a concentrically arranged web 1 connected to each end of the boss 14 and the rims 12 and 17.
5 are integrally formed. The rims 12 and 17 are formed integrally with the plurality of teeth 11 and 18 on the outer peripheral surface. The web 15 has an inner periphery connected to the boss 14 and an outer periphery connected to one ends 12 a and 17 a of the rims 12 and 17.
Conventionally, when trying to form a gear with such a shape,
As shown in FIG. 4 (c), the contraction rate of each of the rims 12 and 17 is maximized at the connection portion with the web 15, and at each end 12a and 17a of each of the rims 12 and 17, the force for deforming the gear is reduced. It will take the maximum.

According to the gear of this embodiment, as shown in FIG. 4A, the annular portion 13 is connected to the rims 12 and 17 and the teeth 11 and 18 along the connection with the web 15. In the actual injection molding, the molten material in the cavity is
The first ends 12a and 17a of the rims 12 and 17 are solidified earlier than the first ends 12a and 17a of the rims 2 and 17, respectively. Here, one end portions 12a and 17a of the rim 12 and the rim 17 are connected to the annular portion 13 in which the molten material has been solidified.
The respective shrinkage rates can be kept low. Thereby, the rim 1
As shown in FIG. 4 (b), the moldings 2 and 17 are formed by minimizing the difference between the shrinkage ratio and the degree of deformation between both ends, and the diameter of one end 12a and the other end 12b. The difference and the diameter difference between the one end 17a and the other end 17b are reduced.
Other configurations, operations and effects are almost the same as those of the gear of the embodiment in FIG.

FIG. 5 shows still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example.
(a) is a cross-sectional view of the gear of the present embodiment, (b) is a state explanatory view showing the deformed state of the gear in (a), (c) is a cross-sectional view of the deformed state of the conventional gear corresponding to the present embodiment. FIG. The gear according to the present embodiment includes a plurality of rims 12 and 17 having different diameters and arranged concentrically,
A boss 14 having a smaller diameter than any one of the bosses 17 and concentrically arranged;
And a web 15 arranged concentrically and connected to the end 17a of the rim 17 are integrally formed. Rim 12,
Numeral 17 is formed integrally with the plurality of teeth 11 and 18 on the outer peripheral surface. In order to form the gear in such a shape, conventionally, as shown in FIG. 5C, since the web 15 is connected to the central portion 12c of the rim 12,
Is maximum at the central portion 12c. A rim 17 is connected to the web 15, and the rim 17 is connected to the web 1.
5, the contraction rate increases at the connection portion. For this reason web 1
5 is deformed in its entirety, and the force for deforming the gears acts on the one end 12a to the maximum.

According to the gear of this embodiment, as shown in FIG. 5A, since the annular portion 13 is formed on the outer peripheral surface of the rim 12 along one end 12a of the rim 12, In the injection molding, the molten material in the cavity is solidified at the annular portion 13 before the one end 12a of the rim 12, and the one end 12a of the rim 12 is solidified after the annular portion 13.
Here, since the one end 12a of the rim 12 is connected to the annular portion 13 in which the molten material has already been solidified, the shrinkage is suppressed to be lower than when the annular portion 13 is not provided. As a result, as shown in FIG. 5 (b), the rim 12 is formed while minimizing the difference in the shrinkage ratio and the degree of deformation across both ends 12a and 12b, and the diameter of the one end 12a and the other end 12b is reduced. The difference is reduced. Other configurations, actions and effects
It is almost the same as the gear of the embodiment of FIG.

FIG. 6 shows still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example.
(a) is a cross-sectional view of the gear of the present embodiment, (b) is a state explanatory view showing the deformed state of the gear in (a), (c) is a cross-sectional view of the deformed state of the conventional gear corresponding to the present embodiment. FIG. The gear according to the present embodiment includes a plurality of rims 12 and 17 having different diameters and arranged concentrically,
A boss 14 having a smaller diameter than any one of the rims 17 and concentrically arranged, one end 12a of the rim 12 and the rim 17
A web 15 connected concentrically to one end 17a of the rim 14 and a web 19 concentrically connected to the boss 14 and the other end 17b of the rim 17 are integrally formed. The rims 12 and 17 are formed integrally with the plurality of teeth 11 and 18 on the outer peripheral surface. In order to form the gear in such a shape, conventionally, as shown in FIG. 6 (c), the contraction rate of the one end 12a of the rim 12 increases,
At each end 12a, 17a of the rims 12, 17, the maximum force for deforming the gears is applied.

According to the gear of this embodiment, as shown in FIG. 6 (a), the annular portion 13 extends along the circumferential portion connected to the web 15 and along the one end 12a of the rim 12 along the rim. 1
As shown in FIG. 6B, the rims 12 and 17 are formed on the outer peripheral surface of the rim 2, and the rims 12 and 17 have the contraction rate and the degree of deformation between both ends as shown in FIG. The difference is suppressed as much as possible, and the diameter difference between the one end 12a and the other end 12b and the diameter difference between the one end 17a and the other end 17b are reduced. Other configurations, operations and effects are almost the same as those of the gear of the embodiment in FIG.

The annular portion of the present invention is not limited to the gears of the above embodiments, provided that the annular portion is provided at a position where the degree of deformation of the rim is large and the function as a gear is not impaired. Instead, the present invention can be applied to any type of gear. Further, the number of the annular portions is not limited. Depending on the form of the gear, for example, two or more annular portions can be provided as shown in FIG.

In addition, the type of teeth formed on the outer peripheral surface of the rim of the synthetic resin molded gear according to the present invention is not particularly limited, and may be, for example, flat teeth or helical teeth. Further, the synthetic resin molded gear according to the present invention can be applied to a gear having a configuration in which a plurality of gears are coaxially combined as shown in the above embodiment. Further, the annular portion of the present invention can be applied as a diameter difference improving means such as a pulley made of a synthetic resin or a pipe without a gear, which has no teeth on the rim.

[0025]

As described above, according to the present invention, the gear forming accuracy can be remarkably improved by a simple design change in which only the annular portion is provided on the rib.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a synthetic resin molded gear according to the present invention, wherein (a) is a plan view and (b) is an A- gear of the gear shown in (a).
FIG. 3A is a sectional view, and FIG. 3C is a state explanatory view showing a deformed state of the gear in FIG.

FIG. 2 shows another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, (a) is a plan view of the gear of the present embodiment, and (b) is a gear of the gear shown in (a). BB sectional view,
(c) is a state explanatory view showing the deformed state of the gear in (b),
(d) is a state explanatory view showing, in cross section, a deformed state of the conventional gear corresponding to the present embodiment.

FIG. 3 shows still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, (a) is a cross-sectional view of the gear of the present embodiment, and (b) is a gear of (a). FIG. 3C is a state explanatory view showing a deformed state, and FIG. 3C is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section.

4A and 4B show still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, wherein FIG. 4A is a cross-sectional view of the gear of the present embodiment, and FIG. 4B is a sectional view of the gear in FIG. FIG. 3C is a state explanatory view showing a deformed state, and FIG. 3C is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section.

5A and 5B show still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, wherein FIG. 5A is a cross-sectional view of the gear of the present embodiment, and FIG. 5B is a sectional view of the gear in FIG. FIG. 3C is a state explanatory view showing a deformed state, and FIG. 3C is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section.

6A and 6B show still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, wherein FIG. 6A is a sectional view of the gear of the present embodiment, and FIG. 6B is a sectional view of the gear in FIG. FIG. 3C is a state explanatory view showing a deformed state, and FIG. 3C is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section.

FIG. 7 is a sectional view showing still another embodiment of a synthetic resin molded gear according to the present invention.

8 (a) is a plan view, FIG. 8 (b) is a cross-sectional view taken along the line CC of the gear shown in FIG. 8 (a), and FIG.
It is a state explanatory view showing the deformation state of the gear in (b).

[Explanation of symbols]

 11, 18 Tooth portion 12, 17 Rim 12a, 12b, 17a, 17b End portion 13 Annular portion 14 Boss 15, 19 Web 16 Cylindrical portion

Claims (2)

[Claims] 1. A synthetic resin molded gear having a gear body in which a plurality of teeth and a rim are integrally molded on an outer peripheral surface, wherein the gear has a thickness smaller than the thickness of the rim, and An annular portion formed along a predetermined portion of the outer peripheral surface of the rim while projecting a predetermined length in the radial direction from the outer peripheral surface of the rim is integrally formed with the rim and the plurality of teeth. Molded gear made of synthetic resin. 2. The method according to claim 1, wherein the annular portion is provided at a location where the degree of deformation of the rim when the molten material in the injection molding is solidified is large and the function as a gear is not impaired. The molded gear made of synthetic resin according to claim 1.