GB2222316A - Electric motor with suppressor choke and terminal housing - Google Patents

Abstract

In a fractional horsepower PMDC motor a terminal 10 is mounted on the end cap 3 and a choke 13 is connected in series between the terminal 10 and brush 15. The choke and terminal are mounted on the outside of the casing and protected by a cover 18 which also supports the terminal 10. <IMAGE>

Description

ELECTRIC MOTOR The present invention relates to a fractional horsepower PMDC motor including a suppression element electrically connected to brushgear of the motor.

It is known to install suppression elements on electric motors. Typically these may take the form of a capacitor connected between a motor brush and earth, a choke connected in series between the power supply and the motor brush, or even a varistor connected across segments of the commutator.

Suppression of electric motors is very important in modern automobiles where electrical interference may impair the functioning of on-board microprocessors which control the engine or brakes. There is therefore a demand for electric motors with the suppression elements built in to the motor.

The present invention provides a fractional horsepower PMDC motor having a housing comprising a can-like casing closed at one end and an end cap mounted on the open end of the casing, a rotor comprising a shaft and a commutator and wound armature mounted on the shaft, brushgear mounted inside the housing on the end cap, at least one terminal and a suppression element electrically connected to the brushgear and mounted outside of the housing on the end cap, wherein a cover is mounted on the housing, the cover enclosing the suppression element and having an aperture therein through which the terminal extends.

Preferably the terminal is supported by the cover. The end cap may be of plastics and the cover of metal. The terminal may be sleeved in plastics where it passes through the cover.

Preferably the end cap is a drawn can-like metal casing.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side view of a fractional horsepower PMDC motor in accordance with the invention Figure 2 shows a detail of the motor of Figure 1, partly cut away; and Figure 3 is a schematic view on arrow A of Figure 2, partly cut away.

Figures 1 to 3 show a fractional horsepower PMDC motor which in the particular example shown is for driving a windscreen washer pump in an automobile.

The motor comprises a housing 1 having a deep drawn can-like steel casing 2 and a plastics end cap 3. The casing 2 is closed at one end by an integral wall 4 which carries a bearing 5 and at its other end by the end cap 3. End cap 3 carries a bearing 6 and a rotor shaft 7 runs in the bearings 5, 6. Two permanent magnets (not shown) are mounted in the casing 2, and shaft 7 carries a wound armature and a commutator (not shown).

The end cap 3 sits inside the open end of the casing 2 and is located by lugs 8 which fit in cutouts 9 in the end of the casing. The end cap 3 carries two terminal posts 10 which are each rivetted to a respective first contact plate 11 to make electrical contact therewith. The contact plates 11 are electrically connected to respective brush contact plates 12 via respective chokes 13, the choke wire being soldered to tags of the plates 11, 12 which project through the end cap 3. The plates 12 each carry a brushleaf 14 and brush 15. Brushes 15 are arranged to bear on the commutator (not shown).

The chokes 13 each rest in a saddle 16 adjacent a respective terminal 10 and are held lightly in place by a resilient finger 17.

To protect the chokes 13, a deep-drawn can-like steel cover 18 is mounted on the outside of the end cap 3. Cover 18 has two apertures 19 which snugly receive plastics sleeves 20 which surround and support the terminals 10. The sleeves 20 are integrally formed on the end cap 3. The cover 18 has rim 21 with lugs 22 which are received in the cutouts 9, outside of the lugs 8 of the end cap.

The cover 18 and end cap 3 are held on the casing 2 by turning the end 23 of the casing 2 over the rim 21 in the region of the lugs 22.

The cover 18 thus serves to protect the chokes 13 and to support the terminal posts 10, thus providing a more stable assembly for connecting the motor to a power supply.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims (8)

1. A fractional horsepower PMDC motor having a housing comprising a can-like casing closed at one end and an end cap mounted on the open end of the casing, a rotor comprising a shaft and a commutator and wound armature mounted on the shaft, brushgear mounted on the end cap inside the housing, at least one terminal and a suppression element electrically connected to the brushgear and mounted outside the housing on the end cap, wherein a cover is mounted on the housing, the cover enclosing the suppression element and having an aperture therein through which the terminal extends.

2. A motor as claimed in claim 1, wherein the cover supports the terminal.

3. A motor as claimed in claim 1 or 2, wherein the end cap is of plastics.

4. A motor as claimed in claim 1, 2 or 3, wherein the cover is a deep drawn can-like metal casing.

5. A motor as claimed in claim 4, wherein the terminal is sleeved in plastics where it penetrates the cover.

6. A motor as claimed in any one of claim;l to 5, wherein the suppression element is a choke in series between the terminal and a brush of the brushgear.

7. A motor as claimed in claim 6, having two said terminals and two chokes, each in series between a respectlve terminal and brush.

8. A fractional horsepower PVDC motor substantially as hereinbefore described with reference to the accompanying drawings.