MXPA00012233A - Gear housing - Google Patents

Abstract

A gear housing for use in a worm gear drive mechanism having an output shaft (20), has an integral backwall adapted to support the shaft. The backwall (48) has a cylindrical central portion (64) for receiving one end (52) of the output shaft. A plurality of equal annulus segments (76) extend radially from the central portion providing support for the central portion in compression. Each segment has a narrow end (78), a wide end, and sides (82). The narrow end of adjacent segments alternately form an integral part of the central portion above and below a plane orthogonal to a central axis of the central portion.

Description

GEARBOX BACKGROUND OF THE INVENTION The field of the invention is on gearboxes, with more particular gearbox for a motor vehicle to raise windows of a motor vehicle.

In a motor for lifting windows of a motorized vehicle, an endless screw shaft moved in a rotary fashion meshes with the teeth of a gear, such as a gear wheel, arranged in a gearbox. The sprocket has a protruding shaft with an end extending radially through the gearbox to rotationally move a lifting mechanism of a window. An opposite end of the projecting shaft extends radially within the retaining wall of the gearbox. The retaining wall supports the projecting shaft by counterbalancing forces exerted on the retaining wall by the projecting shaft.

In addition to the axial forces, the protruding shaft transmits radial and tangential forces developed in the teeth of the gear wheel and the axis interface of Ref. 125709 endless movement. These forces are absorbed by the retaining wall by various means and methods. A known box provides sufficient structural integrity in the retaining wall of the box by the provision of a greater thickness of the retaining wall, a greater thickness of the plastic or metal box adds unnecessary weight to the whole mechanism and requires a more material for its manufacture than other alternatives.

Another known box incorporates reinforcing ribs in the retaining wall to provide support and structural integrity at key locations. This box requires less material and, therefore, provides a lighter box that is less esive in its production than the method described above. However, the ribs require the manufacture of the box with variable wall thicknesses that concentrate the stresses increasing the potential for fatigue failure and require loose manufacturing tolerances increasing the material requirements.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides an improved gearbox for use in an endless gear drive mechanism having a protruding shaft. The box has an integral retaining wall adapted to support the protruding shaft of the drive mechanism. The retaining wall has a cylindrical central portion for receiving one end of the projecting shaft. Numerous equal annular segments extend from the central portion providing support for the central portion in tension and compression. Each segment has a narrow end, a wide end, and sides. The narrow end of adjacent segments alternatively forms an integral part of the central portion above and below a plane orthogonal to the axis of the central portion. The wide end of each segment converges on the plane at the periphery of the retaining wall.

A general objective of the present invention is to provide a plastic gearbox with a retaining wall supporting the protruding shaft without requiring excess plastic material for structural integrity. The retaining wall box of the present invention is formed with a substantially uniform wall thickness that does not require thicker wall sections to adequately support the protruding shaft.

Another object of the present invention is to provide a plastic gearbox that requires less material for its manufacture. The retention wall of the retaining wall of the present invention having a substantially uniform wall thickness can be fabricated for tighter tolerances by reducing the material required to manufacture the article.

Yet another object of the present invention is to provide an improved gearbox that is less susceptible to fatigue failure than the prior art. The retaining wall of the box of the present invention supports the outgoing shaft with retaining parts that are less susceptible to fatigue than the tension parts found in the prior art.

The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings that form a part thereof, and in which a preferred embodiment of the invention is shown by way of illustration.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a window lifter incorporated in the present invention; Figure 2 is a view of a partial section along line 2-2 of Figure 1; Figure 3 is a right front perspective view of the gear box of Figure 1 with the cover of the box removed; Figure 4 is a front elevation view of the gearbox of Figure 1 with the cover of the box removed; Figure 5 is a left rear perspective view of the gearbox of Figure 1; Figure 6 is a sectional view along line 6-6 of Figure 2; Figure 7 is a sectional view along line 7-7 of Figure 2; Y Figure 8 is a top rear perspective view of a prior art gearbox having support ribs.

DETAILED DESCRIPTION OF THE INVENTION As shown in Figures 1 and 2, one embodiment of the present invention is a direct window lift impeller of a current motor vehicle 10. The motor impeller 10 has an endless drive shaft 12 disposed in a motor housing 14 that it is mounted by means of flanges to a gearbox 16. The drive shaft 12 meshes with a snap-in gear 18, or mounted by other methods known in the art, on an axially extending projection 20. The gear 18 is adapted to rotationally move a window lifter mechanism (not shown) that raises or lowers a window of an automobile (not shown).

Looking particularly at Figure 2, the drive shaft 12 has a first end 22 disposed in the motor housing 14. The first end of the drive shaft 22 accommodates a laminated center of a rotor provided with a rotor winding (armature). A distal end of the drive shaft 28 opposite the first end 22 extends into the gear case 16 and is adapted to move the sprocket 18. The drive shaft 12 is rotatably mounted on the motor case 14 by known methods in the art. the art. A motor housing 14 and a drive shaft 12 for use with the present invention are described in US Pat. No. 5,517,070, to Schmidt and is incorporated herein by reference.

The gearbox 16 has a flange mounting portion 30 and a cavity 32. Preferably, the gearbox 16 is made of polybutylene terephthalate with glass fiber filling, such as Valox 420, available from GE Plastics, Pittsfield, MA or Celanex 7246 available from Ticona GmbH, Germany. Other materials exhibiting similar properties may be used without departing from the scope of the present invention. The box 16 is preferably formed by injection molding or other methods known in the art.

The flange mounting portion 30 is flange-mounted to the motor housing 14 by means of screws 24, or the like, received by bolt dies 34 integrally forming part of the gearbox. The distal end of the drive shaft 28 extends into the cavity of the gearbox 32 through an opening 36 in the flange mounting portion 30. The opening 36 is adapted to receive a bearing 38 radially supporting the drive shaft 12. As shown in Figure 6, a vent passage 40 that forms part of the flanged mounting portion 30 receives a filter 42 and allows air to be vented from the motor housing 14.

As shown in Figures 2-4, the cup-shaped recess 32 of the gearbox 16 forms an integral part of the flange mounting portion 30 and is defined by a wall side 44 along the peripheral cavity and a retaining wall 48 supporting the endless gear shaft 20. The cavity 32 is generally circular and is adapted to receive the rotationally mounted gear 18 which tangentially engages the shaft 12. The supports 50 forming an integral part of the side wall 44 of the cavity prevent excessive axial and radial movement of the drive shaft 12 in the gearbox 16. Through the holes in the dies 62 that form an integral part of the The side wall of the gearbox 44 provides attachment points for coupling the assembled impeller 10 for lifting a window of a motor vehicle with the window lifting mechanism (not shown).

With reference to Figure 7, the gear 18 is snapped onto an axially extending boss 20 and rotatably drives the window lift mechanism (not shown). The projecting shaft 20 has an end 52 supported by means of the retaining wall 48 and the opposite end 56 which extends through the opening 57 in the housing cover 58 to be joined with the window lifting mechanism (not shown). shown).

The case cover 58 is mounted on the side wall 44 of the box by methods known in the art, such as pressure adjustment or ultrasonic welding. Preferably, a groove 60 formed in the side wall 44 is adapted to receive the cover 58 and provide a seal that protects the components inside the window lifter impeller 10 from adverse conditions.

The novelty of the present invention resides in the retaining wall of the gearbox 48. As shown in Figures 3-5 and 7, the retaining wall generally has a cylindrical central portion 64 for receiving the end of the projecting shaft 52. and a support portion 66 that is an integral part of the central portion 64.

The central portion 64 has a cylindrical side wall 68, an open top 70, a closed bottom 72, and a central axis 74. The end of the projecting shaft 52 is received in the open top 70 and supported axially by the closed bottom 72 and radially by the side wall of the central portion 68. Although in the preferred embodiment the bottom of the central portion 72 is closed, an open bottom can also be used without departing from the present invention. In an open bottom configuration, the protruding shaft can be supported axially by a bearing or other methods known in the art.

The supporting portion of the retaining wall 66 having a uniform wall thickness is formed by six segments in the form of pie slices 76 that strrally support the central portion 64. Although the six segments are preferred in the form of slices of Any number of segments in the form of cake slices can be used without departing from the scope of the present invention.

Each cake slice segment 76 has a narrow end 78, a broad end 80, and sides 82. With particular reference to Figure 7, the narrow end 78 of adjacent segments 76 alternately forms an integral part of the central portion 64 above and below a common plane 85 which is orthogonal to the central axis of the central portion 74. The segments 76 extend radially away from the central portion 64 towards the side wall of the box 44 converging on the common plane 85 to form the periphery of the retaining wall at the intersection of the segments 76 and the common plane 80.

The sides 82 of the adjacent segments 76 are joined by vertical side walls 84 providing additional strral support to the retaining wall 48. Although vertical side walls are shown and described, angled side walls can be used to join the segments in the form of pie slices. which are narrower or broader than those shown without departing from the scope of the present invention.

The uniform thickness of the retaining wall 48 advantageously requires less material for its manufacture than the rib designs of the prior art. Additionally, more tight manufacturing tolerances can be maintained during fabrication without variations in thickness created by reinforcing ribs.

As shown in Figures 4 and 7, an annular cutting edge 86 forms an integral part of the retaining wall 48 and is concentric with the central axis of the central portion 74 providing a thrust bearing surface for the rotary gear 18. cutting edge 86 is a wear surface whose intention is to wear out over time instead of retaining wall 48, thus prolonging the service life of gearbox 16.

A finite element analysis comparing a gearbox having a rib design, shown in Figure 8, and an embodiment of the present invention as described above reveals a Greater Principle Effort in the embodiment of the present invention which is 42% less than the Greater Principle Effort of the rib design. In the calculations they used the characteristics of the Valox 420 material and a nominal wall thickness of the retaining wall support portion of 2 mm.

The forces exerted on the retaining wall by the rotating projection shaft caused the retaining wall box of the prior art to alternate between compression and tension in order to support the end of the shaft. The alternating segments ensure that the projection is always supported by a compression member, thus reducing the retaining wall thickness required to support the tensioned shaft as required in the rib designs of the prior art.

While it has been shown and described what is currently considered the preferred embodiment of the invention, it will be obvious that those skilled in the art make various changes and modifications without departing from the scope of the invention defined by the appended claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (1)

1. CLAIMS A gearbox retaining wall forming part of a gearbox, characterized in that said retaining wall comprises: a central portion supporting one end of a gear shaft, said central portion having a central axis intersecting an orthogonal plane to said central axis; and a plurality of annular segments surrounding said central portion, each of said segments having a narrow end, a broad end, and sides, whose feature is that the narrow ends of alternating segments form an integral part of said central portion above said flat and the narrow ends of segments adjacent to said alternating segments form an integral part of said central portion below said plane, and the wide ends of all the segments converge on said plane. A gearbox retaining wall according to claim 1, characterized in that the adjacent annular segments are joined by means of side walls. A gearbox retaining wall according to claim 2, characterized in that said side walls are substantially parallel to said central axis. A gearbox retaining wall according to claim 1, characterized in that said box is formed from polybutylene terephthalate. A gearbox retaining wall according to claim 1, characterized in that said box is formed by injection molding. A gearbox retaining wall according to claim 1, characterized in that said retaining wall has an annular cutting edge. A gearbox retaining wall according to claim 1, characterized in that said retaining wall has a nominal wall thickness of not more than 2 mm. A gearbox retaining wall according to claim 1, characterized in that said gear is a gear wheel. A gearbox retaining wall according to claim 1, characterized in that said gear is rotationally driven by an endless driving shaft.