Optical Pulse Generator for an Electric-Motor Drive Arrangement

a. Field of Invention

The invention relates to an optical pulse generator for a motor drive arrangement including a light transmitter, a light receiver and a code wheel enclosed in a protective housing.

b. Description of the Prior Art

An optical pulse generator is known from European Patent No. EP-Al-O 066 636. In this patent, an optical pulse generator is fastened to the electric motor on the outside after the latter is completely assembled. For this purpose the protective housing is firmly connected to the stator housing at the end face and the code wheel is placed on an end of the rotor shaft protruding from the motor. In each half of the protective housing, axial openings are provided for the light transmitter and the light receiver, respectively.

It is an objectives of the present invention to provide an optical pulse generator in a production-wise simple manner which improves the operating reliability of the drive arrangement while the overall size is reduced at the same time.

By the arrangement of the optical pulse generator within the stator housing of the electric motor or the transmission housing, a particularly compact electric-motor drive arrangement can be provided in a production-wise and installation-wise simple manner. The support of the protective housing at the code wheel remains unchanged. The arrangement of the code wheel and the transmitting and receiving device which is advantageous for a reliable speed determination, is assured under all operating conditions, especially in the case of position changes of the code wheel due to undesirable axial and/or centrifugal motions. At the same time, great freedom in the arrangement of the optical pulse generator is obtained since the installation of the code wheel can be made at a larger distance from the shaft bearings.

A light transmitter is arranged in the one half of the protective housing and a light receiver in the other half of the protective housing. For the complete encapsulation of the code wheel. The aperture raster of the code wheel is advantageously formed by successive windows or by successive line markings.

The support of the protective housing and the protection of the code wheel against dirt can further be improved by the provision that the code wheel is fastened on the rotor shaft via an axially formed-on projecting hub and the protective housing is supported at the hub.

In the arrangement of the code wheel provided according to the invention on or at the end face of the transmission output gear, the protective housing is formed by the transmission housing wall, the transmission output gear and the sealing rings arranged therebetween. Therefore, separate parts for forming an encapsulated protective housing can largely be dispensed with.

The invention as well as further advantageous embodiments of the invention will be explained in the following in greater detail, in conjunction with the figures, wherein:

FIG. 1 shows in an axial longitudinal partial section, a motor vehicle window lifting drive with a code wheel arranged within a stator housing of an electric motor;

FIG. 2 shows in more detail, an axial longitudinal section through the optical pulse generator; and

FIG. 3, shows a section through the transmission housing of the motor vehicle window lifting drive shown in FIG. 1 taken along the line III--III through the transmission output gear.

FIG. 1 shows in an axial longitudinal partial section, a motor vehicle window lifting drive which consists essentially of a half-shell-shaped transmission housing 20 and a stator housing 10, having on its left side a permanent-magnet-excited commutator motor. The rotor shaft 4 is supported between two spherical bearings 42, 43 and supports in turn a rotor lamination stack 40 with a rotor winding and a commutator 50. A brush system 9 slides on the commutator. The rotor shaft 4 is extended beyond the right spherical bearing 43 to form a worm drive shaft 41 and drives a transmission output gear 5 which is rotatably supported on a drive shaft 30.

A pulse generator is arranged between the commutator 50 and the right spherical bearing 43, and it includes a code wheel 1 fastened on the rotor shaft 4 via an axially projecting protruding hub 2. A protective housing 3 is supported on the hub 2 as shown. A light source 6 and the light receiver 7 are arranged on the housing according to one embodiment of the invention, in the same half of the protective housing 3 whereby the light transmitter generates light which is selectively reflected by the code wheel back to the light transmitter. Connecting leads, not shown here, are disposed in the interior of the stator housing, for the light transmitter 6 and the light receiver 7, and according to one embodiment of the invention, comprise a flat cable. The connecting leads are brought out of the stator housing 10 together with the connecting leads of the brush system 9 and combine to form the common cable 60 shown in FIG. 4. Advantageously, no additional holes are required in the stator housing 10.

The design of the connecting leads of the light transmitter 6 and the light receiver 7 as flat cables has the advantage that the optical pulse generator is kept, on the one hand, flexible in the axial and radial direction, so that the axial play and the shaft offsets can be taken up by the optical pulse generator and on the other hand, undesirable rotation of the protective housing 3 during the rotary motion of the motor shaft 4 can additionally be prevented by the relatively stiff flat cable.

Alternatively, the optical pulse generator can also be slipped onto the other rotor shaft end, especially in the case of other electric-motor drive arrangements.

FIG. 2 shows a more detailed magnification of FIG. 1 in an axial longitudinal section through the optical pulse generator, in which contrary to the pulse generator shown in FIG. 1, a light transmitter 6 is arranged in the one half of the protective housing 3 and a light receiver 7 is arranged in the other half of the housing 3 whereby light from transmitter 6 passes selectively through a raster on the code wheel and is detected by the receiver 7.

According to one embodiment of the invention, the code wheel 1 is fastened on the rotor shaft 4 via an axially formed projecting hub 2 and the protective housing 3 is supported at the hub 2. The mounting of the hub 2 is improved by the external guiding rings 21 extending in the radial direction, which are disposed adjacent to corresponding circular guiding shoulders 31 of the protective housing 3. As an alternative, not shown here, it is also possible to provide the protective housing 3 with external guiding rings extending in the circumferential direction which are disposed adjacent corresponding circular guiding shoulders of the hub 2. Together with the spacer rings 13 which are provided on the two end faces of the code wheel 1 which are projecting axially and are directed against the inside of the protective housing 3. A constant axial distance of the light transmitter 6 and the light receiver 7 from the aperture raster 11 is obtained in the event of axial movements of the rotor shaft 4, so that a reliable speed determination is assured.

The protection of the aperture raster 11, the light transmitter 6 and the light receiver 7 against dirt is advantageously improved by the provision that both end faces of the code wheel 1 and the protective housing 3 are equipped with alternatively axially axial rings 12, 32 which extend the paths for possibly penetrating dirt particles to form a labyrinth seal.

In order to reduce the friction between the rotating code wheel 1 and the protective housing 3 which is supported at the code wheel 1, the code wheel 1 and/or the protective housing 3 consist of a flexible material with a small coefficient of friction, such as a plastic for material.

FIG. 3 shows a section through the transmission housing 20 of the motor vehicle window lifting drive shown in FIG. 1, according to the line III--III. Within the transmission housing 20, the transmission output gear 5 is supported rotatably on an output shaft 30. As an alternative to the arrangement shown in FIGS. 1, 2, the code wheel 1 is arranged on the end face 51 of the transmission output gear 5.

The light transmitter 6 and the light receiver 7 are fastened tightly in the transmission housing wall 201 and their connecting leads 70 are brought out as flat cable is directly from the outside wall of the transmission housing 20. The vicinity of the transmission output gear 5, to which the aperture raster 11 is applied, is protected against dirt by sealing rings 8. The sealing rings 8 can be fastened in this embodiment either with their one end facing the transmission housing wall 201 or the transmission output gear 5. In the first constance, the sealing rings 8 are stationary. In the second constance the sealing rings 8 rotate with respect to the transmission output gear 5. The frictional losses generated by the sealing rings 8 within the electric-motor drive arrangement are reduced by a reduction terminal by the worm drive shaft 41 of 1:50 to 1:70 in accordance with the transmission ratio.

It would seem to be obvious that by the arrangement of the optical pulse generator within the electric motor drive arrangement according to the invention, the operating liability of the drive arrangement is improved in a production-wise and installation-wise simple and thereby inexpensive manner while the overall size is reduced at the same time.