Resin gear

Abstract

A resin gear comprises a rim in an outer peripheral part of a plate, teeth provided on an outer periphery of the rim, a boss provided in a central part of the plate, and a circular rib between the boss and the rim. The resin gear is manufacturable by injection molding that a molten material is injected into a cavity through a plurality of gates arranged at almost equally spaced intervals circumferentially on a forming portion for the circular rib in a direction perpendicular to a side of the plate. The resin gear includes a plurality of inner thin-wall portions on the plate between the circular rib and the boss and a plurality of outer thin-wall portions on the plate between the circular rib and the rim, each of the inner thin-wall portions and the outer thin-wall portions being symmetrically shaped with respect to the radial line passing through each gate corresponding point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention.

In the drawings,

FIG. 1 is a sectional plan view of an electronically controlled throttle valve system;

FIG. 2 is a front view of a valve housing from which an end frame has been detached;

FIG. 3 is a front view of an intermediate gear;

FIG. 4 is a sectional view of the intermediate gear taken along a line A-A in FIG. 3;

FIG. 5 is a sectional view of the intermediate gear taken along a line B-B in FIG. 3;

FIG. 6 is a sectional view of the intermediate gear taken along a line C-C in FIG. 3;

FIG. 7 is a front enlarged view of part of FIG. 3;

FIG. 8 is a front view of another intermediate gear;

FIG. 9 is a sectional view of the intermediate gear taken along a line D-D in FIG. 8;

FIG. 10 is an enlarged view of a modification example of a part circled with a chain line in FIG. 3;

FIG. 11 is an enlarged view of a modification example of the part circled with a chain line in FIG. 3;

FIG. 12 is an enlarged view of another modification example of the part circled with a chain line in FIG. 3;

FIG. 13 is a front enlarged view of the part circled with a chain line in FIG. 8;

FIG. 14 is an enlarged view of a modification example of the part circled with a chain line in FIG. 8;

FIG. 15 is an enlarged view of another modification example of part circled with a chain line in FIG. 8; and

FIG. 16 is a front view of a conventional resin gear.

Claims

1. A resin gear comprising: a circular plate;a rim provided in an outer peripheral part of the plate;teeth formed on an outer periphery of the rim;a boss provided in a central part of the plate; anda circular rib provided on the plate between the boss and the rim and concentrically with the plate;the resin gear being manufacturable by injection molding in which a molten material is injected into a cavity through a plurality of gates arranged at almost equally spaced intervals circumferentially on a forming portion for the circular rib in a manner that the molten resin is injected in a direction perpendicular to a side of the plate,wherein the resin gear is formed with inner thin-wall portions on the plate between the circular rib and the boss, each of the inner thin-wall portions being symmetrical with respect to a radial line passing through each of a plurality of gate corresponding points which correspond to the gates respectively.

2. The resin gear according to claim 1, wherein each inner thin-wall portion is of a length in a radius direction, which is shorter in a section closer to a midpoint between adjacent two of the gate corresponding points.

3. The resin gear according to claim 2, wherein the inner thin-wall portions respectively aligned with the gate corresponding points are equal in shape so that a thick-wall portion has one of a polygonal outer shape and a petaloid outer shape on the plate between the circular rib and the boss.

4. The resin gear according to claim 1, further comprising a boss on a back side of the plate including an axially protruding cylindrical portion on an outer periphery of which a small-diameter gear is formed.

5. The resin gear according to claim 1, further including outer thin-wall portions on the plate between the circular rib and the rim, the outer thin-wall portion being symmetrical with respect to the radial line passing through each of the gate corresponding points which correspond to the gates respectively.

6. The resin gear according to claim 2, further including outer thin-wall portions on the plate between the circular rib and the rim, the outer thin-wall portion being symmetrical with respect to the radial line passing through each of the gate corresponding points which correspond to the gates respectively.

7. The resin gear according to claim 3, further including outer thin-wall portions on the plate between the circular rib and the rim, the outer thin-wall portion being symmetrical with respect to the radial line passing through each of the gate corresponding points which correspond to the gates respectively.

8. The resin gear according to claim 5, wherein each outer thin-wall portion is of a length in the radius direction, which is shorter in a section closer to the midpoint between adjacent two of the gate corresponding points.

9. The resin gear according to claim 6, wherein each outer thin-wall portion is of a length in the radius direction, which is shorter in a section closer to the midpoint between adjacent two of the gate corresponding points.

10. The resin gear according to claim 7, wherein each outer thin-wall portion is of a length in the radius direction, which is shorter in a section closer to the midpoint between adjacent two of the gate corresponding points.

11. The resin gear according to claim 8, wherein the outer thin-wall portions respectively aligned with the gate corresponding points are equal in shape so that the outer thin-wall portions wholly have one of a polygonal outer shape and a petaloid outer shape on the plate between the circular rib and the rim.

12. The resin gear according to claim 9, wherein the outer thin-wall portions respectively aligned with the gate corresponding points are equal in shape so that the outer thin-wall portions wholly have one of a polygonal outer shape and a petaloid outer shape on the plate between the circular rib and the rim.

13. The resin gear according to claim 10, wherein the outer thin-wall portions respectively aligned with the gate corresponding points are equal in shape so that the outer thin-wall portions wholly have one of a polygonal outer shape and a petaloid outer shape on the plate between the circular rib and the rim.

14. The resin gear according to claim 5, further comprising a boss on a back side of the plate including an axially protruding cylindrical portion on an outer periphery of which a small-diameter gear is formed.

15. A resin gear comprising: a circular plate;a rim provided as an outer peripheral part of the plate;teeth formed on an outer periphery of the rim;a boss provided in a central part of the plate; anda circular rib provided on the plate between the boss and the rim and concentrically with the plate;the resin gear being manufacturable by injection molding that a molten material is injected into a cavity through a plurality of gates arranged at almost equally spaced intervals circumferentially on a forming portion for the circular rib in a manner that the molten resin is injected in a direction perpendicular to a side of the plate,wherein the resin gear is formed with an outer thin-wall portion on the plate between the circular rib and the rim, the outer thin-wall portion being symmetrical with respect to a radial line passing through each gate corresponding point corresponding to each gate.

16. The resin gear according to claim 15, wherein each outer thin-wall portion is of a length in the radius direction, which is shorter in a section closer to the midpoint between adjacent two of the gate corresponding points.

17. The resin gear according to claim 16, wherein the outer thin-wall portions respectively aligned with the gate corresponding points are equal in shape so that the outer thin-wall portions wholly have one of a polygonal outer shape and a petaloid outer shape on the plate between the circular rib and the rim.