This application is based on and claims priority under 35 U.S.C. ยง 119 to Japanese Patent Application 2006-176515, filed on Jun. 27, 2006, the entire content of which is incorporated herein by reference.
This invention relates to a resin-made worm wheel driven by a worm and a worm gear (worm speed reducer) having the same.
A known worm wheel is disclosed in JP2002-310267A (hereinafter, refers to as a reference. The worm wheel is formed with resin and driven by a worm. The worm wheel is provided with: an engaging portion having a plurality of teeth engaged with the worm; and tooth spaces defined between the neighboring teeth and of which bottom surface is recessed radially inwardly. The worm wheel is structured by integrating two members divided perpendicularly to the axis thereof.
Generally at a resin molding with a die, undercut is formed by tooth spaces when the bottom surfaces of each tooth space is recessed radially inwardly. If the amount of the undercut is large, it may be difficult to die-cut the worm wheel after molding the worm wheel in the die, which structures the worm wheel disclosed in this reference with two members.
The worm wheel disclosed in the reference needs to be structured by resin-molding two members separately and by bonding the two members perpendicularly along the axis direction, thus leading to an inevitable increase of man-hours to connect two members.
As a worm wheel, which is not established with plural divided members, a resin base material of the worm wheel can be formed with toothed portions at a peripheral portion by cutting. However, the cutting work is not cost efficient and a certain improvement is considered to be necessary for this method from the viewpoint of productivity.
The present invention has been made in view of the above circumstances and provides a resin worm wheel manufactured with improved productivity.
According to an aspect of the present invention, a resin worm wheel is formed by injection molding and includes a first end and a second end. The worm wheel is adapted to be driven by a worm. The worm wheel further includes: an engaging portion including a plurality of teeth engageable with the worm and a tooth space formed between the neighboring teeth; a first non-engaging portion adjacent to the engaging portion at the first end of the worm wheel and not engaging with the worm; and a first cutout portion formed at the first non-engaging portion continuously from the tooth space. The first cutout portion extends axially.
The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:
Embodiments of the present invention will be descried below with reference to the attached drawing figures.
In the embodiment shown in the
In the embodiment shown in the
It is preferable that the insertion portions 31 protrude at one surface of the ring-shaped reinforcement member 30.
The reinforcement member 30 is formed separately from the worm wheel 10 by injection molding. The reinforcement member 30 is ring-shaped, having a hole 32 at the center thereof, and is provided with the insertion portions 31 that are equally spaced in the circumferential direction (the insertion portion 31 are only partially attached with reference numerals in
As an embodiment of present invention, the worm gear 1 can include a helical gear 40 instead of the worm wheel 10 as described above.
As described above, the worm wheel 10 and the worm wheel 10 configuring the worm gear 1 according to the embodiment, each includes cutout portions, which are provided at the non-engaging portions 12 and are formed continuously through the tooth spaces 14 extending to the axial direction of the worm wheel 10. With this structure, the amount of the undercut will be reduced and it can be easier to die-cut the worm wheel 10 after resin molding. Accordingly, according to the embodiment, the worm wheel 10 does not include a block configuration and is entirely formed by thereof is formed by resin molding, which enhances productivity of the worm wheel 10 (worm gear 1).
It is preferable that the first cutout portion extends into an end surface of the first end of the worm wheel.
It is further preferable that the resin worm wheel further includes a second non-engaging portion adjacent to the engaging portion at the second end of the worm wheel and not engaging with the worm. The first cutout portion is formed at the first non-engaging portion and a second cutout portion is formed at the second non-engaging portion.
It is still further preferable that the worm wheel further includes a first ring-shaped reinforcement member having at least one insertion portion fitted into the first cutout portion and attached to the end of the worm wheel.
It is preferable that the insertion portion of the first ring-shaped reinforcement member includes multiple protrusions provided at one surface of the first ring-shaped reinforcement member.
It is still further preferable that the worm wheel and the worm structures a worm gear.
As described above, the worm wheel and the worm wheel configuring the worm gear is each provided with the non-engaging portion. The worm wheel is formed with cutout portions formed continuously from the tooth space and extending axially. In such structure, because the amount of undercut by the tooth space is reduced, the worm wheel is easily die-cut from a die. As a result, the entire body of the worm wheel is formed in one operation by injection molding, which leads to an improvement in productivity of the worm wheel.
The principles, of the preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention, which is intended to be protected, is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
Number | Date | Country | Kind |
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2006-176515 | Jun 2006 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6354395 | Cheng et al. | Mar 2002 | B1 |
20020046897 | Kurokawa et al. | Apr 2002 | A1 |
20050115343 | Sakamaki | Jun 2005 | A1 |
20050269478 | Woehrle et al. | Dec 2005 | A1 |
20060213302 | Hoffmann et al. | Sep 2006 | A1 |
Number | Date | Country |
---|---|---|
10 2004 013 009 | Oct 2005 | DE |
2002-310267 | Oct 2002 | JP |
2003-160052 | Jun 2003 | JP |
WO 2005-015054 | Feb 2005 | WO |
Number | Date | Country | |
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20070295129 A1 | Dec 2007 | US |