WO2011072915A1

WO2011072915A1 - Electric motor comprising a noise filter

Info

Publication number: WO2011072915A1
Application number: PCT/EP2010/065965
Authority: WO
Inventors: Stephen Nicholls; Frank Kopf; Roland Eidher
Original assignee: Robert Bosch Gmbh
Priority date: 2009-12-16
Filing date: 2010-10-22
Publication date: 2011-06-23
Also published as: EP2513928A1; JP2013514750A; DE102009054717A1; CN102667981A

Abstract

The invention relates to an electric motor (110) for use in a motor vehicle comprising an electric feed line (130) and a capacitor (140), which is accommodated in a passage of a housing of the electric motor and is connected to the electric feed line (130) and the housing (120), wherein a further capacitor is accommodated in the passage, and the capacitors are electrically connected in parallel to each other.

Description

Description title

Electric motor with noise filter

State of the art

It is known that electric motors tend to emit high-frequency noise during operation, which propagate both wirelessly and along electrical feeds to the electric motor and may affect a function of other devices. For example, in a motor vehicle, a fan motor in operation emit high-frequency interference, which are audible via a loudspeaker of a radio of the motor vehicle or visible on a display of a video device of the motor vehicle.

The emitted interference signals are usually broadband and their suppression requires filters, which are preferably arranged close to the electric motor. Different filters for suppression of electric motors are known in the art.

It is an object of the invention to provide an improved electric motor with noise filter for use in a motor vehicle.

Disclosure of the invention

The invention solves this problem by an electric motor with the features of claim 1. Subclaims give advantageous embodiments again. According to the invention, an electric motor for use in a motor vehicle comprises an electrical supply line and a feedthrough capacitor, which in the is rich recorded a passage of a housing of the electric motor and the at least two electrically connected in parallel with each other and with the electrical lead and the housing connected capacitors for filtering interference signals of different frequencies.

Each of the capacitors may filter noise occurring on the electrical lead of the electric motor at a predetermined frequency in a predetermined bandwidth. By appropriate dimensioning of the electrically parallel capacitors, the limited filter effects of the individual capacitors can be combined to form a broadband filter effect of the entire feedthrough capacitor. In addition, the filter effects of the individual capacitors can be dimensioned as a function of known spectrums of interference signals of the electric motor, for example, in a fan motor with a plurality of selectable, fixed speeds set frequencies that correspond to these speeds or their harmonics. As a result, a noise filter is provided which can be handled for use on an electric motor in a motor vehicle.

The implementation may be such that wirelessly propagating interfering signals are retained in the housing so that no interference signals pass the capacitors. The implementation can be carried out for example tubular.

The capacitors can be arranged one behind the other in the feedthrough along the electrical supply line, and at least one of the capacitors can enclose the supply line in the radial direction. In this way, a feedthrough capacitor with a plurality of, mechanically connected in series and electrically parallel capacitors. Such a feedthrough capacitor is easy to assemble and can be well tuned to a power input of the electric motor.

In an embodiment, a plurality of the capacitors are accommodated in a common capacitor housing. The capacitor housing is accommodated in the implementation. As a result, the capacitors do not have to be individually inserted into the bushing during the assembly of the electric motor. but can be used as an integrated component, whereby production costs can be saved.

The housing of the electric motor can have in the region of the leadthrough an electrically connected to the housing holding element, in which the capacitors are accommodated electrically conductive. In this way, it is possible to use capacitors which are not designed as feedthrough capacitors and are therefore inexpensive.

The holding element may comprise a tube or a spring and preferably be arranged at an axial end of the electric motor.

Brief description of the figures

The invention will now be described in more detail with reference to the attached figures, in which:

Figure 1 is a schematic representation of an electric motor;

Figure 2 is an electrical circuit diagram of the feedthrough capacitor of Figure 1;

FIG. 3 shows attenuation curves of the capacitors from FIG. 2;

Figure 4 shows a mechanical structure of the feedthrough capacitor of Figures 1 and 2;

Figure 5 shows another embodiment of a mechanical construction of the feedthrough capacitor of Figures 1 and 2; and

FIG. 6 shows embodiments of a mechanical construction of feedthrough capacitors at bushings of the electric motor of FIG. FIG. 1 shows a schematic representation of an electric motor 110 in a motor vehicle 105, the electric motor 100 comprising a housing 120, an electrical supply line 130 and a feedthrough capacitor 140 accommodated in a feedthrough 150 through the housing 120. The electric motor 1 10 is a DC motor with brushes. A first connection of the electric motor

1 10 is electrically connected to the housing 120. A second terminal of the electric motor 1 10 is connected within the housing 120 by means of the electrical lead 130 to the feedthrough capacitor 140. On the outside of the housing 120, the electrical supply line 130 from the feedthrough capacitor 140 continues further.

In alternative embodiments, multi-pole and / or brushless electric motors 110 may also be used. It is also not necessary that one of the brushes or terminals of the electric motor 1 10 is connected to the housing 120. In other embodiments, multiple or all terminals of the electric motor 1 10 are guided with or without dedicated feedthrough capacitors 140 on an outer side of the housing 120. In one embodiment, the housing 120 is connected to a vehicle ground of the motor vehicle 105 and / or an electrical negative terminal of a supply voltage. The feedthrough 150 includes a recess through the housing 120, and preferably means for connecting the feedthrough capacitor 140 to the housing 120 in a highly frequency-tight manner, for example an electrically conductive tube. The electrically conductive housing 120 of the electric motor 1 10 acts as a Faraday cage and serves inter alia an electromagnetic encapsulation of the electric motor 1 10 in terms of electromagnetic compatibility (EMC). The feedthrough capacitor 140 typically has an ohmic resistance of or near zero with respect to the electrical lead 130. Further, the feedthrough capacitor 140 provides a predetermined capacitance between the electrical lead 130 and the housing 120.

FIG. 2 shows an electrical circuit diagram of the feedthrough capacitor 140 from FIG. 1. A first capacitor 210, a second capacitor 220 and a third capacitor 230 are accommodated within a capacitor housing 240.

Horizontal through the capacitor housing 240 and the capacitors 210 bis 230, the electrical supply line 130 runs. The illustrated electrical circuit diagram of the feedthrough capacitor 140 makes it clear that power-relevant currents, which are transmitted by means of the electrical supply line 130, the feedthrough capacitor 140 along the continuous electrical Zulei- device 130 can pass unhindered. The capacitances of the capacitors 210 to 230 respectively interpose between portions of the electrical lead 130 and counter electrodes electrically connected to the capacitor housing 240. High-frequency voltages between the electrical supply line 130 and the capacitor housing 240, which can cause disturbances on other devices, are derived via the capacitors 210 to 230, wherein in each case a capacitance of one of the capacitors 210 to 230 is assigned to a relatively narrow-band damped frequency range of the voltages ,

Figure 3 shows a diagram of damping curves of the capacitors 210 to 230 of Figure 2. In the horizontal direction, a frequency is applied, in the vertical direction an attenuation, wherein a high attenuation value of a strong attenuation or suppression of a voltage corresponding frequency corresponds. Damping curves 310, 320 and 330 are associated with the capacitors 210, 220 and 230 of FIG. Each of the attenuation curves 310 to 330 is relatively narrow-band, which means that each of the capacitors 210 to 230 can only attenuate signals within a relatively narrow frequency range. By appropriate dimensioning of the capacitors 210 to 230, the relative positions of the damping curves 310 to 330 in the horizontal direction can be influenced. In one embodiment of the invention, the capacitors 210 to 230 are dimensioned such that the attenuation curves 310 to 330 in their sum result in a single, relatively broadband attenuation curve that applies to the entire feedthrough capacitor 140.

Figure 4 shows a mechanical structure of the feedthrough capacitor 140 of Figures 1 and 2. The capacitors 210, 220 and 230 are each in

Substantially cylindrically shaped and arranged coaxially with the electrical supply line 130. The electrical supply line can be continued in the interior of each of the capacitors 210 to 230 or each connected to a conductor portion of the capacitor 210 to 230. Each of the capacitors 210 may comprise an electrically conductive sleeve, which is arranged coaxially around the electrical supply line or the conductor piece by means of an insulator. A distance between such Sleeve and the electrical lead 130, a size of a surface of the sleeve or the electrical supply line 130 in the region of the sleeve, and a dielectric constant of the insulator determine the capacitance of the capacitor. Preferably, an outer diameter of the feedthrough capacitor 140 is in a range of about 4 to 15 mm, more preferably between 6 and 10 mm.

Usual capacities for the capacitors 210 to 230 are in the range of 5 to 1200 nF.

For reasons of clarity, the capacitors 210 to 230 and the electrical supply line 130 are shown separately from a tube 410 which receives the capacitors 210 to 230, as indicated by the arrow. In the assembled state, outer surfaces of the capacitors 210 to 230 are conductively connected to the tube 410. This results in a total of the finished feedthrough capacitor 140 of Figures 1 and 2. In another embodiment, instead of the tube 410, another holder can be used, for example, a flat sheet metal spring, a coil spring or a hollow braid of electrical conductors.

FIG. 5 shows a further embodiment of a mechanical construction of the feedthrough capacitor 140 from FIGS. 1 and 2. In this embodiment, the capacitors 210 to 230 are arranged in the capacitor housing 240. According to the embodiment in Figure 4, and as shown in Figure 2, the capacitances of the capacitors 210 to 230 respectively between the electrical supply line 230 and the capacitor housing 240. It can be used capacitors of any design and design, such as film capacitors, metal paper capacitors, plastic capacitors , Electrolytic capacitors or others. As a result, an axial configuration of the individual capacitors 210 to 230 does not have to be complied with and the capacitors 210 to 230 can be arranged in an arbitrary manner within the capacitor housing 240. The mechanical structure of the feedthrough capacitor 140 shown in FIG. 5 corresponds functionally to miniaturization and encapsulation of the structure shown in FIG. 4 and can be produced, for example, with dimensions known from feedthrough capacitors with only one internally used capacitance value. Externally, a collar 510 may be provided on the capacitor housing 240 to limit axial movement of the feedthrough capacitor 140 in a recess, such as the feedthrough 150 of FIG. Other fasteners may be provided on the capacitor housing 240 of the feedthrough capacitor 140 of FIG. 5, such as a flange, a clamp, a bore, a crimp rim, a solder rim, a clip receptacle, a rivet head, and others.

FIG. 6 shows embodiments of a mechanical construction of feedthrough capacitors 140 at bushings 150 of the electric motor 105 of FIG. 1. An axial section of the housing 120 of the electric motor 110 of FIG. 1 extends in the vertical direction. At an upper end face of the housing 120, a first feedthrough capacitor 140 is inserted in the axial direction according to the design shown in Figure 5. The feedthrough 150 here consists of a recess in the housing 120 matching the capacitor housing 240. As stated above with reference to FIG. 5, the first feedthrough capacitor 140 may be connected to the housing 120 by any known technique. In this case, care is taken to ensure good electrical contact between the feedthrough capacitor 140 and the housing 120; In addition, the connection preferably leaves no passages for electromagnetic radiation. A preferred type of connection includes soldering.

A second feedthrough capacitor 140 according to the design shown in Figure 4 extends parallel to the axial extent of the housing 120 on the outside thereof. The feedthrough 150 here comprises, in addition to a suitable cutout, also the tube 410 of the leadthrough capacitor 140 shown in FIG. 4, wherein the tube 410 has a bend at its lower end at an angle of approximately 90 °, at the end of which the tube 410 with the housing 420 is connected, for example by soldering or welding. In an alternative embodiment, not shown, the second feedthrough capacitor 140 may also extend on an inner side of the housing 120. The bending of the tube 410 is not absolutely necessary and serves mainly a saving of space. A third feedthrough capacitor 140 extends in a radial direction relative to the housing 120. The feedthrough corresponding thereto 150 comprises a recess in the housing 120, a clamping spring 610. Substantially cylindrical capacitors 210, 220 are received by the clamping spring 610, which is connected in any manner with the housing 120, for example by soldering or welding.

All shown in Figure 6 variants of the feedthrough capacitor 140 extend between an inner and an outer side of the housing 120 and are e- lektrisch connected to the housing 120. To achieve a good quality of filtering, it is important to provide the electrical connection between the feedthrough capacitor 140 and the housing as possible in the entire connection area. Remains an opening of the housing 120, for example in the region of a passage 150 of the feedthrough capacitors 140, so can escape through this opening electromagnetic interference from the housing 120 and thus avoid filtering the feedthrough capacitors 140.

The invention makes it possible to carry out a simple and miniaturizable suppression of an electric motor in a motor vehicle, with a given spectrum of interference frequencies of the electric motor 1 10 can be targeted by suitable dimensioning of a plurality of capacitors 210 to 230.

Claims

claims

1 . Electric motor (1 10) for use in a motor vehicle (105), with an electrical supply line (130) and a feedthrough capacitor (140), which in the region of a passage (150) of a housing (120) of the electric motor (1 10) and recorded the electrical supply line (130) and the housing (120) is connected,

characterized in that the feedthrough capacitor (140) comprises at least two capacitors (210-230) electrically connected in parallel for filtering interference signals of different frequencies.

2. Electric motor (1 10) according to claim 1, characterized in that the capacitors (210-230) along the electrical supply line (130) are arranged one behind the other in the passage (150).

3. Electric motor (1 10) according to claim 1 or 2, characterized in that at least one capacitor (210-230) encloses the electrical supply line (130) in a radial direction.

4. Electric motor (1 10) according to any one of the preceding claims, characterized in that a plurality of the capacitors (210-230) are accommodated in a common capacitor housing (240) which is received in the passage (150).

5. Electric motor (1 10) according to any one of the preceding claims, characterized in that the housing (120) in the region of the passage (150) has an electrically connected to the housing (120) holding element (410, 610), in which the capacitors are electrically conductive recorded.

Electric motor (1 10) according to claim 5, characterized in that the holding element comprises a tube (410).

7. Electric motor (1 10) according to claim 5, characterized in that the holding element comprises a spring plate (610).

8. Electric motor (1 10) according to any one of claims 5 to 8, characterized in that the holding element (410, 610) at an axial end of the electric motor (1 10) is arranged.

9. Electric motor (1 10) according to one of claims 5 to 8, characterized in that the holding element (410, 610) is electrically connected to a vehicle ground of the motor vehicle (105).

10. Electric motor (1 10) according to any one of the preceding claims, characterized in that the housing (120) of the electric motor (1 10) is electrically connected to a vehicle ground of the motor vehicle (105).