JP2001153207A - Forming gear made of synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming gear made of a synthetic resin capable of improving the forming accuracy of a gear by reducing a difference in shrinkage of teeth part of the gear. SOLUTION: In this forming gear made of a synthetic resin in which a rim 12 integrated with a plurality of teeth parts 11 on the outer peripheral surface, a boss 13 disposed concentrically inside the rim 12, and a web 14 connecting the inner peripheral part of the rim 12 and the outer peripheral part of the boss 13 are integrally formed, the web 14 is has a wall thickness T1 smaller than the wall thickness T2 of the rim 12, plural ribs 15 having a width T3 smaller than the wall thickness T1 of the web 14 are formed radially between the rim 12 and the boss 13 to be integrated with the web 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin molded gear provided with a web on an inner peripheral side of a rim having a tooth portion on an outer peripheral side, and more particularly, by adjusting a difference in shrinkage of the synthetic resin. The present invention relates to a molded gear made of a synthetic resin that can improve molding accuracy of a gear.

[0002]

2. Description of the Related Art In general, a synthetic resin molded gear having a tooth portion on the outer periphery has a large shrinkage action of the synthetic resin when the tooth width exceeds a predetermined size. As a result, the distortion of the gear to be formed becomes large, so that the lightening is performed to secure the accuracy of the gear.

FIG. 10 shows a conventional example of this kind of gear. The cylindrical rim 12 is integrated with the plurality of teeth 11 on the outer peripheral surface. The boss 13 is arranged concentrically inside the rim 12. The web 14 is provided between the inner peripheral portion of the rim 12 and the boss 1.
3 is integrally connected to the outer peripheral portion.

[0004] A gear of this kind is provided with a molten material such as a synthetic resin by, for example, a gate provided with a predetermined number of concentric circles on one surface of the web 14 (in FIG. Only shown) into a mold (not shown) having a cavity that matches the shape of the gear. The injected molten material initially flows radially around the gate position, but eventually flows as a whole in the outer diameter direction and the inner diameter direction of the web 14, and the tooth portion 11 and the rim 1
The cavity 2 and the cavity of the boss 13 are filled. Thereafter, the molten material is cooled and solidified and released from the mold to obtain a synthetic resin molded gear as shown in FIGS. 10 (a) and 10 (b).

[0005] 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 tends to be larger at a portion where the thickness is larger and the amount of the molten material filled is larger than at a portion where the thickness is smaller and the amount of the molten material is smaller and the solidification is delayed. It is in. 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.

For this reason, in this type of gear, the solidification of the molten material tends to be slower than that of the teeth at the portion near the connection portion with the web, and the teeth at the portion far from the connection portion with the web. There is a difference between the degree of shrinkage in the vicinity of the part and the degree of shrinkage in a part away from the web. The more the teeth are farther away from the side ends, the greater the distortion of the formed gear and the greater the difference in diameter within the tooth width of the gear.

For example, a gear in which a cylindrical rim 12 as shown in FIG. 10 (a) is designed so as to be integrated with a plurality of teeth 11 on the outer peripheral surface is used in actual injection molding.
The vicinity of the connection portion 12a of the rim 12 with the web 14 is the connection portion 1
Heat is less likely to escape in the axial direction than at the end 12b away from the end 2a, so that the solidification is delayed and the shrinkage action is significant. For this reason,
As shown in FIG. 10C, the connection portion 12a of the gear is largely curved inward as compared with the end portion 12b.

Therefore, the applicant of the present invention reduced the thickness of the web 14 connected to the rim to prevent the solidification delay in the connection area with the web far from the end of the rim, The present inventors have attempted to improve the gear forming accuracy by minimizing the difference in outer diameter by minimizing the distortion applied to the provided teeth, and have completed the present invention.

[0009]

According to the present invention, there is provided a molded gear made of synthetic resin according to the present invention, comprising: a rim integrated with a plurality of teeth on an outer peripheral surface; and an annular portion arranged concentrically inside the rim. In a synthetic resin molded gear in which a web connected to an inner peripheral portion of the rim and an outer peripheral portion of the annular portion is integrally molded, the thickness of the web is thinner than the thickness of the rim. It is characterized by being formed.

[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 has a rim 12 integrated with a plurality of teeth 11 on the outer peripheral surface, and a concentric annular portion of the present invention disposed inside the rim 12. The boss 13 and a web 14 connected to the inner peripheral portion of the rim 12 and the outer peripheral portion of the boss 13 are integrally formed. Also, the web 14 is arranged is not biased position at the center of the tooth width W _1. In these respects, the configuration is the same as that of the conventional gear shown in FIG. The molded gear of the present embodiment differs from the conventional gear in the following points.

In the formed gear of the present embodiment, the thickness T ₁ of the web 14 is formed smaller than the thickness T ₂ of the rim 12. In addition, one end of the web 14
A plurality of ribs 15 radially provided between the rim 12 and the boss 13 are integrally formed with the rib 15 connected to the rim 12 and the boss 13.

The ribs 15 are formed as needed for reinforcement. It is preferable that the width T ₃ in a direction perpendicular to the longitudinal direction is smaller than the thickness T ₁ of the web 14. Further, in the present embodiment, the ribs 15 are formed on only one surface of the web 14, but the ribs 15 may be formed on both surfaces of the web 14 as needed. When the ribs 15 are formed on both sides of the web 14, it is preferable that the ribs 15 are formed alternately on one side of the web 14 and on the other side so that the ribs 15 do not overlap. In forming the rib 15,
It is preferable that the sum T _{4 of the} thickness of the rib 15 and the thickness of the web 14 be equal to or less than the thickness T ₂ of the rim 12.

The formed gear of the present embodiment thus constructed is manufactured by the same method as the above-described conventional formed gear. That is, a molten material such as a synthetic resin is fed from a gate (only one is indicated by a two-dot chain line in FIG. 1) provided concentrically on one surface of the web 14 between the rim 12 and the boss 13. 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 the molten material fills the teeth 11, the rim 12, and the cavity of the boss 13 as a whole. After that, the molten material is cooled and solidified, and is released from the mold.
A synthetic resin molded gear as shown in (b) is obtained.

At this time, according to the molded gear of the present embodiment, the thickness T ₁ of the web 14 is formed to be smaller than the thickness T ₂ of the rim 12, so that the cavity is not actually used in the injection molding. In the molten material, heat is easily released in the web 14 as compared with the conventional material as shown in FIG. 10 and solidification is accelerated, and the amount of resin in the connection portion 12a between the rim 12 and the web 14 is small. Rim 12
As shown in FIG. 1 (c), the connecting portion 12 with the web 14
a and the end 12b furthest from the connecting portion 12a can minimize the difference in shrinkage, and the tooth width W _{1 of the} gear can be reduced.
The difference in diameter along the direction is reduced.

The web 14 is provided with a rib 15 so that the thickness of the web 14 is reduced.
4 can be prevented from decreasing in strength. Furthermore, rib 15
The width T ₃ of, since the thinner than the thickness T ₁ of the web 14, the rib 15 is not be solidified as compared with the web 14 and the rim 12 is delayed, the connecting portion and the rim 1 between the web 14
There is no adverse effect on the degree of shrinkage at the connection with No. 2.

[0017] Therefore, according to the molding wheel of the present embodiment, while maintaining the strength of the web, thereby reducing the diameter difference along the tooth width W ₁ direction of the gear, to improve the molding accuracy of the gear it can.

The formed gear according to the present embodiment includes a gear in which the web is arranged at a position deviated to one side in the face width direction as shown in FIG. Even when the present invention is applied to a gear having a large diameter as shown in FIG. In particular, a gear having a large diameter requires a web having higher strength than a gear having a small diameter, and therefore, the gear of the present embodiment in which ribs are formed so as not to adversely affect the degree of shrinkage is particularly effective. Further, the rib 15 may be provided on the surface of the web 14 on the side opposite to that of FIG. 1 (the lower side of the web 14). However, in order to minimize the adverse effect due to shrinkage, the rib 15
Is preferably formed on the surface of the web 14 on the side where the gate is provided.

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 plan view of the gear of the present embodiment, (b) is a cross-sectional view taken along the line BB of the gear shown in (a), (c) is a state explanatory view showing the deformed state of the gear in (b), (d) () Is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in a cross section.

In the molded gear of the present embodiment, an annular rib 16 as an annular portion of the present invention is provided on a concentric circle of a boss 13, and the web 14 is connected to the inner peripheral portion of the rim 12 and the annular rib 1.
6 is connected to one end of the boss 13 and an outer peripheral portion of the boss 13. Further, a plurality of ribs 17 are connected to one surface of the web 14, and both ends are connected to the annular rib 16 and the boss 13.
Are formed integrally with each other in a state of being radially provided between them.

In this embodiment, the web 14
Is formed so that its thickness T ₁ is smaller than the thickness T ₂ of the rim 12. On one surface of the web 14, the rim 12 is connected to the rim 12 and the annular rib 16 at both ends.
The plurality of ribs 15 radially provided between the web 14 and the annular rib 16 have a width T ₃ in a direction orthogonal to the longitudinal direction of the plurality of ribs 15 larger than the thickness T _{1 of the} web 14 as in the above-described embodiment. It is formed integrally so as to be thin. Other configurations are almost the same as those of the formed gear of FIG. In this embodiment, the same effects as those of the formed gear of the embodiment in FIG. 1 can be obtained.

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 plan view of the gear of the present embodiment, (b) is a cross-sectional view of the gear shown in (a), and (c) is a state explanatory view showing the deformed state of the gear in (b), (d) () Is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in a cross section.

The molded gear of the present embodiment has a so-called rim 19 integrated with a plurality of teeth 18 on the outer peripheral surface, which is provided separately from the rim 12 on a concentric circle of the boss 13 as an annular portion of the present invention. This is a multi-stage gear. Also in this embodiment, the ribs 17 are radially arranged between the rim 19 and the boss 13, and the webs 14 are integrally formed in a state of being connected to the inner peripheral portion of the rim 12 and the outer peripheral portion of the rim 19. ing.

In this embodiment, the web 14
Is formed so that its thickness T ₁ is smaller than the thickness T ₂ of the rim 12. On one surface of the web 14, a plurality of ribs 15 radially provided between the rim 12 and the rim 19 with both ends connected to the rim 12 and the rim 19 are provided.
As in the above-described embodiment, the width T ₃ in the direction orthogonal to the longitudinal direction is integrally formed so as to be smaller than the thickness T ₁ of the web 14. Other configurations are almost the same as those of the formed gear of FIG.

In this embodiment, the same effects as those of the formed gear of the embodiment shown in FIG. 1 can be obtained. The ribs in the gears of the above embodiments are not limited to those shown in FIGS. 1 to 4, but may be a combination of annular ribs.

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 plan view of the gear of the present embodiment, (b) is a cross-sectional view of the gear shown in (a) along DD line, (c) is a state explanatory view showing the deformed state of the gear in (b), (d) () Is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in a cross section.

The gear according to the present embodiment includes a rim 12 integrated with a plurality of teeth 11 on an outer peripheral surface, an annular portion 20 arranged concentrically inside the rim 12, and an inner peripheral portion of the rim 12. The web 14 connected to the outer peripheral portion of the annular portion 20 is integrally formed. The annular rib 21 is arranged concentrically between the rim 12 and the annular portion 20, and a plurality of ribs 22 are formed between the rim 12 and the annular rib 21.
A plurality of ribs 23 are provided radially between the and the annular portion 20. The annular rib 20 and the ribs 22 and 23 are integrally formed on one surface of the web 14.

The rib 22 has one end connected to the annular rib 21 and the other end connected to the rim 12. The rib 23
Has one end connected to the annular rib 21 and the other end connected to the annular portion 20. The thickness T ₁ of the web 14 is formed smaller than the thickness T ₂ of the rim 12. Further, the reinforcing ribs 22 and 23 have a width T ₃ smaller than the thickness T ₁ of the web 14.
have.

According to the gear of the present embodiment, the thickness T ₁ of the web 14 is formed to be thinner than the thickness T ₂ of the rim 12, so that the molten material in the cavity in actual injection molding is formed. As shown in FIG. 5 (d), heat is easily released from the conventional web as shown in FIG. 5 (d), solidification is accelerated, and the amount of resin at the connection portion 12 a between the rim 12 and the web 14 is reduced. As a result, the rim 12 is
As shown in the figure, the connecting portion 12a with the web 14 and the connecting portion 1
2a as much as it is possible to suppress the differential shrinkage in the farthest end 12b from the diameter difference along the tooth width W ₁ direction of the gear is reduced.

Further, by providing the web 14 with the annular ribs 21 and the ribs 22 and 23, a decrease in the strength of the web 14 due to the reduced thickness of the web 14 can be suppressed. Further, since the width T ₃ of the ribs 22 and 23 is formed smaller than the thickness T ₁ of the web 14, the ribs 22 and 23 are not delayed in solidification as compared with the web 14 and the rim 12. It does not adversely affect the degree of contraction at the connection portion and the connection portion with the rim 12. Other configurations, operations and effects are substantially the same as those of the molded gear of the embodiment in FIG.

In FIG. 5, the width T _{3 of the} ribs 22 and 23 is shown.
Although both are also formed thinner than the thickness T ₁ of the web 14, the thickness T ₁ of the width T ₃ of the web 14 of at least the rib 22
If it is formed thinner, the same effect can be obtained. Further, in the molded gear of the present embodiment, if at least the width T _{3 of the} rib 22 is formed smaller than the thickness T ₁ of the web 14 as described above, the annular portion 20 can be formed as the boss 13 in FIG. The same effect as that of the molded gear of the embodiment of FIG. 1 can be obtained regardless of the configuration corresponding to any of the rib 16 and the rim 19 of FIG.

In addition, the gears of the above embodiments can be applied to various types of gears, for example, as shown in FIG. FIG.
It is sectional drawing which shows further another embodiment of the synthetic resin molded gear by this invention.

The formed gear of this embodiment is formed by combining two gears having substantially the same configuration as that of the embodiment of FIG. 1 coaxially and in opposite directions.
The thickness T ₁ , T ′ _{1 of} 4 ′ is the thickness T ₂ ,
T 'together are thinner than _2, the web 14,
On one surface of the rim 14 ', the both ends are respectively connected to the rim 12 and the boss 13 and the rim 12' and the boss 13 '. A plurality of ribs 15 and 15 ′ radially provided between the ribs 15 and 15 ′ have a width (not shown in FIG. 6) in a direction perpendicular to the longitudinal direction, similarly to the above-described embodiment.
As but it becomes thinner than the thickness T ₁ of the web 14, 14 ',
It is formed integrally. The molded gear according to the present embodiment also has the same effects as those of the above embodiments.

The synthetic resin molded gear according to the present invention is applicable to a gear having a configuration in which a gear body having a web is coaxially combined in a plurality of stages. FIGS. 7A and 7B show still another embodiment of the synthetic resin molded gear according to the present invention and a corresponding conventional example, wherein FIG. 7A is a plan view of the gear of this embodiment, and FIG. 7B is a gear shown in FIG. (C) is a state explanatory view showing the deformed state of the gear in (b), and (d) is a state explanatory view showing the deformed state of the conventional gear corresponding to the present embodiment in cross section. is there.

In the molded gear of this embodiment, a rim 19 integrated with a plurality of teeth 18 on the outer peripheral surface is provided separately from the rim 12 on the concentric circle of the boss 13, A web 24 is connected to the outer periphery of the
Are connected to the inner peripheral portion of the rim 12 and the outer peripheral portion of the rim 19 and are integrally formed.

In the present embodiment, the web 14
The wall thickness T ₁₁ is formed thinner than the thickness T ₁₂ of the rim 12. Further, on one surface of the web 14, a plurality of ribs 15 radially provided between the rim 12 and the rim 19 with both ends connected to the rim 12 and the rim 19 are provided. Similarly, the width T ₁₃ in the direction perpendicular to the longitudinal direction is integrally formed so as to be smaller than the thickness T _{11 of the} web 14.

In this embodiment, the web 24
Is formed such that the thickness T ₂₁ is smaller than the thickness T ₂₂ of the rim 19. Further, on one surface of the web 24, a plurality of ribs 25 radially provided between the rim 19 and the boss 13 with both ends connected to the rim 19 and the boss 13 are provided. similar to the width T ₂₃ in the direction perpendicular to the longitudinal direction such that thinner than the thickness T ₂₁ of the web 24, are integrally formed.

[0038] According to the gear of the present embodiment. Thus the thickness T ₁₁ of the web 14 is formed thinner than the thickness T ₁₂ of the rim 12, molten material in the cavity in the actual injection molding As shown in FIG. 7 (d), heat is easily released from the conventional web as shown in FIG. 7 (d), solidification is accelerated, and the amount of resin at the connection portion 12 a between the rim 12 and the web 14 is reduced. As a result, the rim 12 is
As shown in the figure, the connecting portion 12a with the web 14 and the connecting portion 1
2a as much as it is possible to suppress the differential shrinkage in the farthest end 12b from the diameter difference along the tooth width W ₁ direction of the gear is reduced.

The web 14 is provided with a rib 15 so that the thickness of the web 14 is reduced.
4 can be prevented from decreasing in strength. Furthermore, rib 15
The width T ₁₃ of, since the thinner than the thickness T ₁₁ of the web 14, the rib 15 is not be solidified as compared with the web 14 and the rim 12 is delayed, the connecting portion and the rim 12 of the web 14 It does not adversely affect the degree of shrinkage at the connection.

Since the thickness T ₂₁ of the web 24 is formed to be thinner than the thickness T ₂₂ of the rim 19, the molten material in the cavity in the actual injection molding does not As shown in (d), the heat easily escapes and the solidification speeds up as compared with the conventional one, and the amount of resin at the connecting portion 19a between the rim 19 and the web 24 decreases. as shown in 7 (c), it is possible to suppress the differential shrinkage in the farthest end 19b from the connecting portion 19a and the connection portion 19a of the web 24 as much as possible, the diameter along the tooth width W ₂ direction of the gear The difference is reduced.

Further, the ribs 25 are provided on the web 24 to reduce the thickness of the web 24 so that the web 2
4 can be prevented from decreasing in strength. Furthermore, the rib 25
The width T _23, since the thinner than the thickness T ₂₁ of the web 24, the rib 25 is not to be solidified as compared with the web 24 and the rim 19 is delayed, the connection portion of the web 24 and the rim 1
There is no adverse effect on the degree of shrinkage at the connection with the substrate 9. Other configurations, operations and effects are substantially the same as those of the molded gear of the embodiment in FIG. Note that, in the gear as in this embodiment, a combination of a radial rib and an annular rib as shown in the embodiment of FIG. 5 may be used.

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. When the configuration of the synthetic resin molded gear according to the present invention is applied to a plurality of gears as shown in the embodiment of FIG. As shown, ribs 15, 25 may be provided on both sides of each web 14, 24. Of course, the ribs 15, 25 may be provided on only one surface of each of the webs 14, 24. In addition, when the present invention is applied to a helical two-stage gear, as shown in FIG.
Preferably, 5 and 25 are provided on opposite sides of the respective webs 14 and 24.

[0043]

As described above, according to the present invention, it is possible to reduce the difference in shrinkage of the tooth portion of the gear and to improve the molding accuracy of the gear.

[Brief description of the drawings]

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

2A and 2B show another embodiment of a synthetic resin molded gear according to the present invention, wherein FIG. 2A is a sectional view, and FIG. 2B is a state explanatory view showing a deformed state of the gear 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 plan view,
(b) is a BB cross-sectional view of the gear shown in (a), (c) is a state explanatory view showing a deformed state of the gear in (b), (d) is a gear of a conventional example corresponding to this embodiment. It is a state explanatory view which shows a deformation state by a 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 plan view of the gear of the present embodiment, and FIG. 4B is a gear shown in FIG. (C) is a state explanatory view showing a deformed state of the gear in (b), and (d) is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section. is there.

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 plan view of the gear of the present embodiment, and (b) is a gear shown in (a). (C) is a state explanatory view showing a deformed state of the gear in (b), and (d) is a state explanatory view showing a deformed state of a gear of a conventional example corresponding to the present embodiment in cross section. is there.

FIG. 6 is a sectional view showing still another embodiment of a synthetic resin molded gear according to the present invention.

7A and 7B show still another embodiment of a synthetic resin molded gear according to the present invention and a corresponding conventional example, wherein FIG. 7A is a plan view of the gear of the present embodiment, and FIG. 7B is a gear shown in FIG. (C) is a state explanatory view showing the deformed state of the gear in (b), and (d) is a state explanatory view showing the deformed state of the conventional gear corresponding to the present embodiment in cross section. is there.

FIG. 8 is a partial cross-sectional view of a two-stage spur gear having another embodiment of a synthetic resin molded gear according to the present invention.

FIG. 9 is a partial sectional view of a helical two-stage gear showing still another embodiment of a synthetic resin molded gear according to the present invention.

FIG. 10 shows a conventional example of a synthetic gear made of synthetic resin,
(a) is a plan view, (b) is a sectional view taken along line FF of the gear shown in (a), (c)
FIG. 4 is a state explanatory view showing a deformed state of the gear in (b).

[Explanation of symbols]

11, 11 ', 18 Tooth 12, 12', 19 Rim 12a, 12'a Web connection 12b, 12'b End 13, 13 'Boss 14, 14' Web 15, 15 ', 22, 23 ribs 16, 21 annular rib 17 rib 20 annular portion _{T 1, T '1, T} 11, T 21 the thickness of webs _{T 2, T' 2, T} 12, T 22 thickness of the rim T _3, T _13, T ₂₃ Rib width T ₄ , T ' ₄ , T ₁₄ , T ₂₄ Sum of web thickness and rib width W ₁ , W ₂ Tooth width

Claims (1)

[Claims] A rim integrated with a plurality of teeth on an outer peripheral surface; an annular portion disposed concentrically inside the rim;
In a synthetic resin molded gear in which a web connected to an inner peripheral portion of the rim and an outer peripheral portion of the annular portion is integrally molded, the web has a thickness smaller than a thickness of the rim. A synthetic resin molded gear characterized by being formed.