End cap arrangement

Abstract

An electric motor, comprising an end cap arrangement: The device comprises a base (10) and a cover. The base includes a first chamber (20) suitable for accommodating a commutator, a second chamber (24) suitable for accommodating electronic components, and brush housings (18) with through-holes suitable for accommodating brushes (19). The first and second chambers are located on opposite sides of the base. The through-holes of the brush housings open into the first chamber to allow the brushes to make sliding contact with a commutator located therein. The cover is connected to the base and covers the second chamber.

Description

FIELD OF THE INVENTION

[0001] The invention relates to an end cap assembly for an electric motor and, more particularly, to an end cap assembly for a miniature high voltage DC motor. BACKGROUND OF THE INVENTION

[0002] Many applications require an electric motor with low EMI emissions. Traditionally, this has been achieved by adding EMI / EMC suppression components, such as chokes and capacitors, to the motor circuitry, usually mounted on an end cap within the motor. However, in a miniature electric motor, the end cap is small; for example, the end cap diameter may be less than 30 mm. Therefore, end caps of miniature electric motors may not have enough space to accommodate the required EMI / EMC suppression components. In a high-voltage electric motor, for safety reasons, a distance greater than a safety value must be maintained between adjacent electrical components, known as the creepage distance, to prevent cross-contamination between components.These requirements limit the ability to mount EMI / EMC suppression components in the end cap of a miniature high-voltage motor.

[0003] US 6 927 522 B2 discloses a power supply unit for a commutator of an electric motor. JP 55-68 862 A relates to wiring of an electronic component in a small-format motor. US 5 942 819 A discloses a brush support assembly with a suppression circuit for an electric motor. US 5 243 247 A discloses a brush bridge assembly for an electric motor. US 6 861 775 B2 discloses a permanent magnet DC motor with a speed sensor, and US 4 728 835 A relates to an electric motor with brush support elements having terminals extending through an end cap of the electric motor. DESCRIPTION OF THE INVENTION

[0004] The invention aims to provide an end cap arrangement that solves the above-mentioned problems or at least offers the public a sensible alternative.

[0005] Accordingly, the present invention, in one aspect thereof, provides an end cap assembly for an electric motor comprising a base made of insulating material, the base including a first chamber adapted to receive a commutator, a second chamber adapted to receive electronic components, and brush housings having passages adapted to receive brushes, the first chamber and the second chamber being respectively formed on opposite sides of the base, the passages of the brush housings opening into the first chamber to allow the brushes to slidably contact a commutator disposed in the first chamber; and a cover connected to the base and covering the second chamber.The base includes a hub, a sidewall spaced from the hub and surrounding the hub, and a connecting wall connecting the hub to a first end of the sidewall spaced from the cover, the first chamber being formed in the hub, the second chamber being formed between an outer surface of the hub, an inner surface of the sidewall, the connecting wall, and the cover. Two types of EMI / EMC suppression components are each mounted on two abutment surfaces in the second chamber, the two abutment surfaces being in different planes in the axial direction from the base. Two motor poles are further provided for connection to a power supply, two webs being connected between the hub and the sidewall, each web having a recess, and each of the poles being inserted into a corresponding recess and extending through the cover.

[0006] Preferably, the brush housings extend radially outwardly from the hub, one of the abutment surfaces being formed on one side of the brush housings, the side wall extending over the first abutment surface towards the cover.

[0007] Preferably, the EMI / EMC suppression components comprise a capacitor and a choke, wherein the choke is mounted on one of the contact surfaces and wherein the capacitor is mounted on a side of the connecting wall forming the other contact surface opposite the cover.

[0008] Preferably, the cover has a central opening, and an axial end of the hub spaced from the connecting wall extends through the central opening, the axial end of the hub having a through bore receiving the shaft of the motor.

[0009] Preferably, at least one radially recessed recess is formed in an inner surface of the first chamber.

[0010] According to a second aspect of the invention, the present invention provides an electric motor comprising an end cap assembly as described above.

[0011] Preferably, the electric motor is a miniature high-voltage DC motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A preferred embodiment of the invention will now be described by way of example with reference to the figures of the accompanying drawings. In the figures, identical structures, elements, or parts that appear in more than one figure are designated by the same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for simplicity and clarity of illustration and are not shown to scale. The figures are listed below. Fig. Figure 1 shows an electric motor including an end cap assembly in accordance with a preferred embodiment of the present invention; Fig. Figure 2 is an assembled view of the end cap assembly; Fig. Figure 3 illustrates a base of the end cap assembly showing the EMI / EMC suppression components mounted on the base; Fig. 4 is a view of the base of the Fig. 3 without the suppression components; and Fig. 5 illustrates the basis of the Fig. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Fig. Figure 1 illustrates a miniature high voltage DC electric motor 2 comprising an end cap assembly 6 in accordance with the preferred embodiment of the present invention, as shown in Figures Fig. 2 to 5. The motor 2 comprises a housing 4, preferably a deep-drawn steel tube with a closed end and an open end. The end cap assembly 6 is attached to the open end of the housing. The closed end of the housing and the end cap support bearings in which a shaft 8 of the motor is journaled.

[0014] The preferred end cap assembly 6 according to the present invention is shown in more detail in the Fig. 2 to 5. The end cap arrangement is shown in Fig. 2 in an upright or vertical position, showing the two motor poles 38 and two brush housings. The end cap comprises two parts, a base 14 and a cover 50. In Fig. Figure 3 shows the end cap assembly with the cover removed to show the components within the base. Fig. 4 is one of the Fig. 3 Similar view, but with most components removed to show the structure of the base. Fig. 5 is a view of the underside of the base of the Fig. 4, which shows the structure of the underside or first side of the base, and shows the brushes 19 within the brush housings 18.

[0015] The base 10 and cover 50 are made of an insulating material, such as nylon. The base 10 includes a hub 12 located at its center, a cylindrical sidewall 14 surrounding and radially spaced from the hub 12, a connecting wall 16 radially extending and spacing the hub 12 to a first end of the sidewall 14 spaced from the cover 50, and brush housings 18 extending radially outward from the hub 12 and through the sidewall 14. The brush housings each have a passageway adapted to slidably receive a brush 19.

[0016] The hub 12 forms, at one of its ends adjacent the connecting wall, a first chamber 20 suitable for receiving a commutator (not shown). The passages in the brush housings open into the first chamber 20 and guide the brushes into contact with a brush contact surface of the commutator housed in the first chamber. The other end of the hub, which is spaced from the connecting wall, extends through a central opening 52 of the cover 50. A mounting hole 22 extends through the hub to allow the shaft of the motor to extend through the end cap. The hub 12 has a reduced diameter portion forming a projection for mounting a bearing thereon to support the shaft of the motor.Portions of the inner surface of the chamber 20 are recessed radially and outwardly to form a recess 23 for receiving particles generated by friction between the brushes 19 and the commutator. Recesses 23 are formed in the inner surface of the wall of the chamber 20 to receive dust particles generated by wear of the brushes and the commutator.

[0017] The cover 50 is attached to the second side of the base 10 by crimping the motor poles. Small crimp fingers extend axially along the poles, which are plastically deformed to secure the cover to the base once the cover is in place. The second chamber 24 is defined by the outer surface of the hub 12, the inner surface of the sidewall 14, the connecting wall 16, and the cover 50. EMI / EMC suppression components such as capacitors 26 and chokes 30 are housed in the second chamber 24. The surface of the connecting wall 16 opposite the cover 50 provides a first abutment surface 31 for mounting the capacitors 26 and 20 thereon. The connecting wall 16 has through-holes 28 in the first abutment surface for conducting the capacitors 26 to be mounted on the connecting wall 16.Each capacitor has a lead threaded through the through-holes 28 and then bent to lie along the connecting wall, thereby holding the capacitor in place. The leads are then routed through a small groove in the side wall so that when the end cap is attached to the open end of the housing, the lead is clamped between the base and the housing to establish electrical contact between the housing and the capacitor, thus grounding the capacitor.

[0018] The second axial end of the side wall 14, which is spaced from the connecting wall 16, extends beyond the brush housings 18 in the axial direction of the base 10. The surfaces of the brush housings 18 adjacent to the axial end of the side wall 14 form a second abutment surface 32 for mounting the chokes 30 thereon. Consequently, the capacitors 26 and the chokes 30 are respectively attached to the first and second abutment surfaces 31 and 32, which are located in different axial planes of the base 10, i.e., are axially spaced apart, thereby allowing the capacitors 26 and the chokes 30 to partially overlap in the axial direction. Two webs 34 are formed between the hub 12 and the side wall 14. Each web 34 has a recess 36. A motor pole 38 is inserted into each recess 36 and extends through the cover 50 for connection to a power supply.Alternatively, poles 38 can be replaced by cables.

[0019] In preferred embodiments, the brushes 19 slidably contact the commutator in the first chamber 20 formed on one side of the base 10. EMI / EMC suppression components 26 and 30 are housed in the second chamber 24 formed at the opposite end of the base 10. Accordingly, dust particles generated by friction of the brushes 19 on the commutator in the first chamber 20 do not easily penetrate into the second chamber 24. The cover 50, which substantially closes the open end of the second chamber 24, further prevents dust particles escaping from the first chamber 20 from entering the second chamber and causing short circuits between the EMI / EMC suppression components 26 and 30. Furthermore, the components 26 and 30 are mounted on two abutment surfaces located at different axial planes of the base 10, further increasing the creepage distance between the components 26 and 30.Components 26 and 30 may partially overlap in the axial direction of base 10 to thereby reduce the footprint or the total area occupied by components 26 and 30 in a plane perpendicular to the axial direction of the base. The end cap in accordance with the preferred embodiment of the present invention is particularly suitable for a miniature high-voltage electric motor. An end cap in accordance with the present invention may also be used in a miniature low-voltage electric motor.

[0020] In the description and claims of the present invention, each of the verbs "comprise," "comprise," "include," and "have," and variations thereof, is used in an inclusive sense to specify the presence of the named element and not to exclude the presence of other elements.

[0021] Although the invention is described with reference to several embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Accordingly, the scope of the invention is determined by the following claims.

Claims

[1] An end cap assembly for an electric motor, comprising: a base (10) made of insulating material, the base having a first chamber (20) adapted to receive a commutator, a second chamber (24) adapted to receive electronic components, and Brush housing (18) with passages formed to receive brushes (19), wherein the first chamber and the second chamber are each formed on opposite sides of the base, wherein the passages of the brush housings open into the first chamber to allow the brushes, to slidably contact a commutator arranged in the first chamber; and a cover connected to the base and covering the second chamber, wherein the base (10) comprises a hub (12), a side wall (14) spaced from the hub and surrounding the hub, and a connecting wall (16) connecting the hub to a first end of the side wall spaced from the cover (50), the first chamber (20) being formed in the hub, wherein the second chamber (24) is formed between an outer surface of the hub, an inner surface of the side wall, the connecting wall and the cover, wherein two types of EMI / EMC suppression components (26, 30) are each attached to two contact surfaces (31, 32) in the second chamber (24), the two contact surfaces being in different planes in the axial direction from the base, and wherein the end cap assembly further comprises two motor poles (38) for connection to a power supply, wherein two webs (34) are connected between the hub (12) and the side wall (14), wherein each web (34) has a recess (36) and wherein each of the poles (38) is inserted into a corresponding recess (36) and extends through the cover (50). [2] The end cap assembly of claim 1, wherein the brush housings (18) extend radially outwardly from the hub (12), one of the abutment surfaces (32) being formed on one side of the brush housings (18), the side wall (14) extending beyond the first abutment surface (32) toward the cover (50). [3] The end cap assembly of claim 2, wherein the EMI / EMC suppression components comprise a capacitor (26) and a choke (30), the choke being mounted on one of the engagement surfaces (32) and the capacitor being mounted on a side of the connecting wall forming the other engagement surface (31) opposite the cover. [4] End cap assembly according to one of claims 1 to 3, wherein the cover (50) has a central opening (52) and the axial end of the hub (12) spaced from the connecting wall (16) extends through the central opening, the axial end of the hub having a through bore (22) receiving the shaft of the motor. [5] An end cap assembly according to any one of the preceding claims, wherein at least one radially recessed recess (23) is formed in an inner surface of the first chamber (20). [6] An electric motor comprising the end cap assembly (6) according to any one of the preceding claims. [7] An electric motor according to claim 6, wherein the electric motor is a miniature high voltage DC motor.

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