Patent Application
20060000303
The subject of the present invention is a geared motor unit, particularly for driving vehicle equipment such as window lifters, sunroofs, etc, and of the type comprising a rotor equipped with a rotor shaft, a reduction gearbox which contains a gearwheel in mesh with a worm belonging to the shaft and capable of driving an output member.
Geared motor units of this type are normally equipped with means for adjusting the axial play between one end of the rotor shaft and the wall of the box. This is because the axial play in the driveline mounted in the geared motor unit is due to the combination of dimensional spreads on the various parts on assembly (shaft, endstop, box, etc.) which, placed end to end, are not as long as their housing.
Hitherto this axial play has been compensated for manually using a screw housed in the end of the box facing the rotor shaft hole and which is immobilized by an adhesive which at the same time provides sealing. Such a method of adjustment is lengthy to perform, expensive, and increases the overall cost of manufacture of the geared motor unit.
It is also known practice (see U.S. Pat. No. 5,169,245) to achieve automatic compensation for the axial play in the driveline of the geared motor unit using a coil spring resting in an axial housing of the end of the box, and a system of end stops designed to limit the compressive axial loading experienced by the coil spring to a predetermined value. This limitation is achieved by a shoulder on the inside of the wall of the box, and against which a piston inserted between the end of the shaft and the coil spring abuts.
These devices for compensating for the axial play have a drawback which lies in the fact that they are not able to eliminate the troublesome noise of the shaft which is caused as it changes direction of rotation.
The object of the invention is therefore to eliminate this drawback by arranging the geared motor unit in such a way that these noises are completely eliminated.
According to the invention, the geared motor unit comprises means for eliminating, under a given compressive axial preload, any axial play between one end of the rotor shaft and the wall of the box.
According to one embodiment of the invention, the said means comprise a plug housed in the end of the box, and a piston inserted between the plug and the end of the shaft, the plug exerting the said compressive axial preload, set at the time of assembly, on the piston and on the shaft, and the geared motor unit also comprises means for immobilizing the piston in its axial position that corresponds to the said compressive preload.
Thus, after assembly and initial adjustment of the play by appropriate positioning of the plug and of the piston against the end of the rotor shaft, using a predetermined axial thrust, for example 100 newtons, the piston is mechanically secured to the wall of the box, in the desired axial location with respect to the rotor shaft. The latter can no longer move axially upon changes of direction of rotation, and therefore cannot cause troublesome noises.
According to one feature of the invention, the means for immobilizing the piston in its axial position comprise irregularities formed on the surface of the piston in contact with the interior wall of the box, such as grooves, the piston being made of metal, and the piston is immobilized with respect to the wall of the box by melting the plastic of which the box is made into the said roughnesses; this melting may be obtained, for example, using a sonotrode, an ultrasonic-welding machine, or alternatively by high-frequency welding.
According to another possible embodiment of the invention, the geared motor unit comprises a metal plug mounted so that it can slide in an axial housing formed in the wall of the box facing the end of the shaft; irregularities are arranged on the surface of this plug in contact with the wall of the housing, and the plug is moved axially until it comes into abutment against the end of the shaft under a given compressive axial preload thrust, then immobilized in this position so as to eliminate any shaft play.
This type of embodiment therefore has no piston, the plug alone fulfilling the function of plug and piston of the previous embodiment, and being immobilized in the desired position to exert appropriate axial thrust on the shaft.
The basic idea underlying the invention therefore consists in eliminating the axial play left in geared motor units of the state of the prior art and in doing so under a given compressive axial preload or thrust, for example of the order of 100 newtons.
Other specific features and advantages of the invention will become apparent during the course of the description which will follow, which is given with reference to the appended drawings which illustrate a number of embodiments thereof by way of non-limiting examples.
The geared motor unit 1 illustrated in
It comprises, housed inside a casing 2, a stator 3 which can be powered by electrical connections 4 in the known way, a rotor 5 equipped with a rotor shaft 6, the ends of which are mounted in rolling bearings 7, 8. This rotor shaft carries a worm 9 in mesh with a gearwheel 11 capable of driving an output member 12 which itself drives the equipment associated with the geared motor unit, for example a window lifter, a sunroof, etc.
The end 6a of the rotor shaft 6 passing through the bearing 7, located near the worm 9 collaborates with a device 12 making it possible, under a given compressive axial preload F (
In the embodiment illustrated in
When the geared motor unit is assembled, the piston 18 is pressed against the plug 15, precompressing it so that it exerts a compressive axial preload thrust F of an appropriate value, such as about 100 newtons, on the piston 18 and on the end 6a of the shaft 6.
Once this compressive preload F has been set to the desired value, the piston 18 is immobilized in the axial position that corresponds to the said compressive preload of the plug 15, and this is done by heating the plastic of the end 13 of the box 14 facing the surface irregularities of the piston 18, so that the molten plastic fills its grooves or channels 19. Subsequent solidification of the plastic by cooling fixes the piston 18 permanently in this position at the end 13 of the box 14. This melting of the plastic may be brought about by appropriate means, not depicted, such as an ultrasound generator or using high-frequency welding.
Once the piston 18 has been secured to the box 14 in this way, changes in direction of rotation of the rotor shaft 6 can no longer cause this shaft to move axially and therefore can no longer generate troublesome noise.
In the second embodiment illustrated in
This device 21 for eliminating axial play in the shaft 6 is adjusted as follows: first of all, the compressive axial preload F of the plug 15 is adjusted to the desired value, so that the piston 22 is positioned exactly at the appropriate axial location, opposite the chamber 26. Next, a liquid adhesive is injected into the lateral duct 25 so that it fills the chamber 26 and the channels 23. The pressure with which the liquid adhesive is injected is arbitrary. After hardening, the adhesive entirely fills the channels 23, the chamber 26 and the duct 25 thus hermetically sealed and immobilizes the piston 22 with respect to the wall 13 of the box 14. As before, the piston 22 eliminates any axial play of the rotor shaft 6 and therefore any parasitic noise as the shaft changes direction of rotation.
In the alternative form of
In the alternative form of
The plug 34 is moved axially in the housing 35 by melting the plastic of the wall 13 using means which are known and have not been depicted, until this plug comes into abutment against the end 6a of the shaft 6 with a given compressive axial preload thrust F (for example 100 newtons). The position of the plug 34 before it is introduced is depicted in chain line in
The plug 34 is positioned axially at the precise desired location in order to place the shaft 6 under compressive preload using an ultrasonic-welding machine which causes the plastic of the wall 13 of the housing 35 to melt into the surface irregularities 36. This machine is associated with a thrusting ram which defines the amount of compressive preload on the driveline. Immobilization is achieved by the hardening of the plastic when the ultrasonic transducer has been shut down.
Use is made, for example, of a hot-melt adhesive, which melts at a temperature lower than the melting point of the plastic of which the box 14 is made (200° C.) at low pressure.
By way of an unlimiting numerical example, if the axial thrust F is 100 newtons, and the cross-sectional area S of the plug 37 is equal to 0.5 cm2, the pressure with which the adhesive is injected must be equal to 20 bar.
Injecting a plastic identical to that of the box 14 is difficult to envisage because it would have to be done at high pressure, which would entail a plug 37 of very low cross section.
The invention is not restricted to the embodiments described and its execution may be varied in a number of ways. Thus, the embodiment of
| Number | Date | Country | Kind |
|---|---|---|---|
| 97 14 950 | Nov 1997 | FR | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10411897 | Apr 2003 | US |
| Child | 11037923 | Jan 2005 | US |
| Parent | 09554959 | Aug 2000 | US |
| Child | 10411897 | Apr 2003 | US |
