Patent Grant
6940194
1. Field of the Invention
The invention is directed to an electric drive unit and particularly to such drive units useful in motor vehicles.
2. Description of the Prior Art
From German patent disclosure DE 32 35 622 A1 and U.S. Pat. No. 4,572,979, a design of an electric drive unit is known. Among other elements, it comprises an electric motor with a stator and a magnet in a pole housing, a rotor with an armature, and a gear in a gear housing. The pole housing and gear housing are joined together, making for a high number of parts to be assembled and high production costs.
The gear housing is made from plastic.
In the prior art, the motor housing either has a pole piece or is a pole housing that takes the form of a cup of a magnetically conductive material and thus acts as a pole piece. In both cases, two magnetic half shells are mounted on the inside in the housing. They are partly fixed by retention springs in the pole housing and/or, because of the incident vibration and also to reduce noise, they are adhesively bonded between the magnet and the pole housing.
The pole pot bottom contains a cylindrical or homelike bearing, which acts as a radial bearing for supporting the rotor.
After their manufacture, these parts, comprising an electric motor, magnet and bearing, exist in the form of separate components or a component group that have to be connected to the gear housing by screws or wedging.
Often, to reduce the longitudinal armature play, a spacer is also mounted between a face end of the rotor and a bearing in the pole housing, in order to compensate for tolerances of the rotor and pole housing.
From German patent disclosure DE 43 20 005 A1 and U.S. Pat. No. 5,895,207, it is already known to make the pole housing of an electric drive unit of plastic and for the magnets to be retained in the plastic. However, the gear housing and the pole housing are screwed together.
From German patent disclosure DE 197 24 920 A1, it is already known to accommodate a motor and a substantial portion of the gear in one housing. A separate gear housing is always still necessary, however. Furthermore, this reference provides no information about how the motor is accommodated in the housing or what material comprises the housing.
The electric drive unit of the invention has the advantage over the prior art that in a simple way, the number of parts to be assembled and the production cost are reduced.
The use of plastic for the housing is advantageous, because in this way, watertight pole and gear housings can be produced, and the weight of the drive unit can be reduced.
It is especially advantageous for magnets and/or a pole piece and/or an armature bearing to be injected into the pole housing, since this reduces the production cost and the number of parts to be assembled.
The use of a one-piece pole piece has advantages because it reduces the number of parts to be assembled.
It is also advantageous in the event of corrosion problems to spraycoat the pole piece with plastic on the outside.
By positive and nonpositive engagement, the at least one magnet or the pole piece can advantageously be secured in the pole housing, so that no further securing elements are necessary.
It is advantageous to keep the longitudinal armature play very slight by the insertion of an end shield with the motor bearing after a shaft has been installed.
Other features and advantages of the invention will become apparent from the detailed description contained below, taken in conjunction with the drawings, in which:
a-e show various possible ways of integrating the at least one magnet and the pole piece into the pole housing.
An electric motor 15 is located in the pole housing 10. The electric motor 15 comprises a stator 18 and a rotor 20. The rotor 20 is formed of an armature 22, a commutator 25, and a shaft 28. The shaft has a longitudinal axis 30.
The stator 18 comprises a magnet 32 and a pole piece 36. The magnet 32 can be in one piece or can comprise multiple parts 32.1, 32.2.
The pole piece 36 can comprise two steel half-shells, for instance, or be in one piece, for instance comprising a steel ring, and can thus form the magnetic short circuit for the magnets 32. The pole piece 36 can be made from any magnetically conductive material.
This may also be a mixture of plastic and a magnetically conductive material that is injected into the pole housing 10.
The at least one magnet 32 and the pole piece 36 are integrated with the pole housing 10.
The shaft 28 is supported at at least two points. On an end 40 of the shaft 28 toward the motor, an end shield 43 with a motor bearing 45 is present which initially is still axially adjustable. The end shield 43 and the motor bearing 45 can be embodied in one piece and can for instance be of plastic. The end shield 43 can also comprise a metal motor bearing 45 spray-coated with plastic. One indentation 44, for example, is provided in the pole housing 10, and the end 40 of shaft 28 can be introduced into this indentation.
Downstream of the electric motor 15, viewed in the direction of the gear housing, and in this case downstream of the commutator 25, for example, there is an armature bearing 48 which is injected for instance into the pole housing 10. A further bearing, a so-called gear bearing 50, is located on an end 53, toward the gear, of the shaft 28 in the gear housing 5. The end 53 toward the gear and the end 40 toward the motor of the shaft 28 are shaped as a run-up cup 55, for instance.
In the production of the electric drive unit 1, magnets 32 (32.1, 32.2) and pole pieces 36, for instance, are placed in an injection molding tool and then, by injection of plasticized plastic into the injection-molding tool, the bottom 6 of the gear housing 5 and the pole housing 10 are formed.
After the assembly of the rotor 20, gear 8, and so forth, the end shield 43 with the motor bearing 45 is inserted into the pole housing 10 axially in such a way that the longitudinal armature play is minimal. Shims to compensate for tolerances of the shaft and housings are unnecessary.
The end shield 43 can for instance be screwed into a thread 57 present in the pole housing 10, or glued by a bead of adhesive, or joined to the pole housing 10 by ultrasonic welding or lasers. All this produces a watertight connection.
Given a suitable choice of material for the end shield 43, the motor bearing 45 can not only perform radial support but can also absorb the axial run-up forces of the rotor 20. Furthermore, the end shield 43 with the motor bearing 45 can be pressed axially with slight prestressing force against a steel run-up cup 55 of the shaft 28 and be fixed to the pole housing 10 in an axially play-free state of the shaft 28.
a through 2e show various possible ways of integrating the at least one magnet 32 and the pole piece 36 into the pole housing 10. The same reference numerals as in
a shows that the magnet 32 has a first protrusion 60, which rests on a second protrusion 63, toward the rotor 20, of the pole housing 10 and thus forms a positive engagement with the plastic. The pole housing 10 is injection-molded for instance, around a third protrusion 65 of the pole piece 36, which is thus secured in the pole housing 10. The other ends of the magnet 32 and of the pole piece 36 are embodied similarly and are surrounded by the pole housing 10. The short-circuit element 36 and the magnet 32 rest tightly against one another, creating a nonpositive engagement for the magnet 32, which is retained on the second protrusion 63 of the pole housing 10.
b shows the magnet 32 with a first protrusion 60, which as in the case of the pole piece 36 in
In
d shows how the pole housing 10 on the outside surrounds the circumference of the pole piece 36, for instance completely, and that the pole piece 36 has no protrusion and is secured in its position by positive engagement by the pole housing 10 and nonpositive engagement by the magnet 32. The magnet 32, as in
The protrusions 60, 63, 65 extend completely or partially all the way around radially on at least one end face of the magnet 32 or of the pole piece 36.
The pole housing 10 can also be produced directly, without injection of the magnet 32 and the pole piece 36. Then, as shown in
In
To achieve a good, tight binding of the pole piece or pole pieces 36 to the pole housing 10, an appropriate peripheral region of the pole pieces 36 can be embodied in perforated or ribbed fashion, for instance. Vibration between the magnet 32 and the short-circuit element 36 cannot occur, since both the magnet 32 and/or the pole piece 36 are injected firmly into the pole housing or secured firmly in it.
In general, the described design is suitable for achieving watertight electric drive units, because the already tight plastic gear housing can also be welded in watertight fashion toward the gear to a plastic cap. The foregoing relates to preferred exemplary of embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 199 54 966 | Nov 1999 | DE | national |
This application is a 35 USC 371 application of PCT/DE 00/04020 filed on Nov. 14, 2000.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE00/04020 | 11/14/2000 | WO | 00 | 10/22/2001 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO01/37399 | 5/25/2001 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4572979 | Haar et al. | Feb 1986 | A |
| 5184039 | Kraft | Feb 1993 | A |
| 5881823 | Kabatnik | Mar 1999 | A |
| 5925962 | Kobman | Jul 1999 | A |
| 5942827 | Neumann et al. | Aug 1999 | A |
| 6058594 | Neumann et al. | May 2000 | A |
| 6286199 | Bobay | Sep 2001 | B1 |
| Number | Date | Country |
|---|---|---|
| 196 14 217 | Oct 1997 | DE |
| 2014371 | Aug 1979 | GB |
| 1 596 374 | Aug 1981 | GB |
| WO 98 10971 | Mar 1998 | WO |
