Permanent magnet motor

Abstract

Permanent magnet motor (20), comprising a stand and a rotor rotatably mounted on the stand, wherein the stand comprises a housing (21) with n convex side regions (23a-23d) and n connecting regions (25a-25d) alternately distributed, the connecting regions (25a-25d) being arranged at corners of the housing (21), wherein n is an integer equal to or greater than 3, preferably 4, wherein adjacent convex side regions are connected by a respective connecting region, each of the n convex side regions (23a-23d) having a convex outer surface and a convex inner surface; wherein the radial cross-section of each convex side region (23a-23d) is a convexly curved line which is curved outwards relative to the straight line passing through the two ends of the convexly curved line; wherein permanent magnets (27) are attached to an inner surface of the housing (21), the permanent magnets (27) each being attached to an inner surface of the connection areas (25a-25d); and wherein an end cap (31) is mounted at one end of the housing, the end cap (31) having a base (33) and n side walls (34) extending from the base (33), wherein a flat mounting surface (35) is formed on the outer surface of a first of the side walls (34) of the end cap (31) and is located outside the housing (21) when the end cap (31) is attached to the housing (21).

Description

AREA OF INVENTION

[0001] The invention relates to a permanent magnet motor and in particular a permanent magnet direct current small motor (PMDC motor) such as a motor for a door locking system of a vehicle or for a tailgate of a vehicle. BACKGROUND OF THE INVENTION

[0002] The size of a PMDC motor is a crucial factor in some applications. A smaller motor with the same or higher power output is desired. In other words, a motor with a higher power density is needed. Published US patent application US 2010 / 0231072A1 describes a PMDC motor that has a higher power density compared to a conventional flat-sided motor. The motor has a steel housing with four side sections and four connection sections. Adjacent side sections are connected by a corresponding connection section. Magnets are attached to the connection sections. The radial cross-section of each side section resembles a convex or curved line that bulges outward relative to a straight line passing through its two ends.Compared to a conventional two-flat-sided motor, this motor has a higher power density and is quieter, according to finite element analysis (FEA) testing.

[0003] However, the housing with its curved sides makes it difficult to install the motor.

[0004] US Patent 4,453,097 A discloses a motor housing and stator assembly, wherein the housing has a plurality of arcuate, recessed seats, each to which a permanent magnet with a convex side is attached. JP Patent H07-194,063 A discloses a small motor with female terminals detachably connected to a male terminal for power supply. JP Patent 2009-165,209 A discloses a housing cover assembly consisting of a brush holder and a resin terminal holder integrally mounted on both sides of a metal plate for supporting a bearing.JP S62-125,366 U discloses a motor with an armature iron core around which an armature coil is wound, a magnet, and a housing on an outer circumference of the armature iron core. At least two circular arc surfaces with a larger diameter than the outer circumference of the armature iron core are formed on an inner circumferential surface of the housing, and a uniform, flexible magnet is closely attached to the circular arc surface. US 6,515,389 B1 discloses a permanent magnet-excited small motor with an armature rotatably mounted about a pivot axis, at least two permanent magnet poles surrounding the armature at opposite locations, and a pole housing connecting the permanent magnet poles.

[0005] The invention aims to provide an improved motor that offers the same or a higher power density while being easy to install.

[0006] To solve this problem, the invention provides a permanent magnet motor according to claim 1. Advantageous embodiments are the subject of the dependent claims, the following description and the figures. BRIEF DESCRIPTION OF THE INVENTION

[0007] According to one aspect of the present invention, a permanent magnet motor is provided, comprising a stator and a rotor rotatably mounted on the stator, the stator having a housing with alternately distributed n convex side regions and n connection regions, the connection regions being arranged at corners of the housing and n being an integer equal to or greater than 3, adjacent convex side regions being connected by a respective connection region, each of the n convex side regions having a convex outer surface and a convex inner surface, the radial cross-section of each convex side region being a convexly curved line that is curved outwards relative to a straight line passing through the ends of the convexly curved line; permanent magnets being attached to an inner surface of the housing, the permanent magnets each being attached to an inner surface of the connection regions;and wherein an end cap is mounted at one end of the housing and has a base and n side walls extending from the base, wherein a flat mounting surface is formed on the outer surface of a first of the side walls of the end cap and is located outside the housing when the end cap is attached to the housing.; Preferably, n equals 4.

[0008] Preferably, the entire outer surface of the first side wall forms the flat mounting surface.

[0009] Preferably, a part of the outer surface of the first side wall forms the flat mounting surface, and the flat mounting surface lies substantially parallel to the plane containing the two axial edges of the first side wall.

[0010] Preferably, the convexly curved line has a straight segment and an arc segment.

[0011] Preferably, the rotor comprises a shaft, a commutator, a rotor core mounted on the shaft, and rotor windings wound around the rotor core. The end cap carries a first brush and a second brush for sliding contact with the commutator, a first terminal and a second terminal for connection to the power supply and electrically connected to the respective brushes, and a thermistor electrically connected between the first brush and the first terminal for overcurrent protection.

[0012] Preferably, the end cap carries a chip capacitor that is electrically connected to the first terminal and the second terminal.

[0013] Preferably the end cap has a first yoke and a second yoke, wherein the first yoke is electrically connected in series with the first brush, the thermistor and the first terminal, and the second yoke is electrically connected in series with the second brush and the second terminal.

[0014] Preferably, the motor has a cup-shaped cover that is mounted on the end cap in the axial direction of the motor.

[0015] Preferably the cover has a base and a side wall with a flat mounting surface, wherein the flat mounting surface is aligned with the flat mounting surface of the end cap.

[0016] Preferably, the motor includes a printed circuit board mounted in the cover.

[0017] Preferably the motor comprises a position magnet mounted on the shaft, located on the outside of the end cap and received in the cover, wherein the motor comprises at least one Hall sensor received in the cover for detecting the magnetic field of the position magnet.

[0018] Preferably the motor comprises a position magnet mounted on the shaft, located on the outside of the end cap and received in the cover, wherein the motor comprises at least one Hall sensor mounted on the printed circuit board for detecting the magnetic field of the position magnet.

[0019] Preferably, the cover is attached to the end cap by elastic fingers which are integrally formed as part of the cover and arranged in recesses in the end cap. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred embodiments of the invention will now be described by way of example, with reference to the accompanying drawings. Identical structures, elements, or parts that appear in more than one figure bear the same reference numerals in all figures in which they appear. The dimensions of components and features shown in the figures are generally chosen for the sake of clarity and are not necessarily to scale. The figures are listed below. Fig. Figure 1 shows a PMDC motor according to a first embodiment of the present invention; Fig. Figure 2 shows a stand of the engine from Fig. 1; Fig. Figure 3 shows another view of the engine of Fig. 1; Fig. 4 shows how the engine of Fig. 1 is mounted; Fig. 5 and Fig. Figure 6 shows the end cap of the motor. Fig. 1; Fig. 7 and Fig. Figure 8 shows the end cap of a PMDC motor according to a second embodiment of the present invention; Fig. Figure 9 shows a PMDC motor according to a third embodiment of the present invention; Fig. Figure 10 shows an internal structure of an end cap cover, which is part of the engine of Fig. 9 is; Fig. Figure 11 is an end view of the end cap cover of Fig. 10; Fig. 12 is an end view of the assembled end cap cover and end cap; and Fig. Figure 13 is a longitudinal section view of the assembled end cap cover and end cap of Fig. 12. DETAILED DESCRIPTION OF THE PREFERRED EXECUTION FORMS

[0021] As in the Fig. 1, Fig. 2, Fig. 3 to Fig. As shown in Figure 4, the PMDC motor 20 according to the first preferred embodiment of the invention comprises a stator and a rotor rotatably mounted on the stator. A radial cross-section of the stator is shown in Fig. The stator 2 comprises a housing 21, an end cap 31 mounted at one end of the housing 21, and permanent magnets 27 attached to inner surfaces of the housing 21. The rotor comprises a shaft 29, a commutator (not shown), a rotor core (not shown) mounted on the shaft 29, and rotor windings (not shown) wound around the rotor core and terminating at the commutator. The shaft 29 is rotatably supported by bearings 28 mounted on the end cap 31 and on the housing 21. The end cap is arranged in a bearing hub or in a bearing holder 36.

[0022] The housing 21 has four side regions 23a-23d and four connecting regions 25a-25d, which are alternately distributed along the circumferential direction of the motor. Adjacent side regions are connected by a corresponding connecting region. The magnets 27 are attached to an inner surface of the respective connecting regions 25a-25d, preferably conforming to the adjacent side regions 23a-23d. In the radial cross-section, each of the side regions 23a-23d is a convexly curved line that curves outwards with respect to a straight line passing through the respective ends of the curved line. In this embodiment, the convexly curved line is an arc with a radius extending from a center O'. The center O' is offset from the center of rotation O of the rotor.

[0023] As the Fig. 1 and Fig. As shown in Figure 3, the end cap 31 has a base 33 and four side walls 34 extending axially from the edge of the base 33. A flat mounting surface 35 is formed in a first side wall 34. The flat mounting surface 35 is parallel to the plane containing the two axial edges of the first side wall 34. The flat mounting surface 35 can be formed by a portion or substantially the entire outer surface of the first side wall 34. The bearing holder 36 is formed similarly to a hub in the center of the end cap 31 and has a through-opening for the rotor shaft. The rotor shaft 29 is rotatably mounted by the bearing 28 received in the bearing holder 36.

[0024] As in Fig. As shown in Figure 4, a motor mounting 39 has a horizontal and a vertical section. The vertical section engages with the hub-like bearing holder 36. The horizontal section has a flat surface for contact with the flat mounting surface 35 of the end cap 31. In other words, the curved side sections give this motor a high power density and low noise, while the flat mounting surface 35 facilitates installation. The larger the flat mounting surface 35, the more stable the motor should be.

[0025] As in Fig. 5 and Fig. As shown in Figure 6, two brushes 41 and 42, a thermistor 47 (such as a positive temperature coefficient resistor, or PTC resistor), a chip capacitor 48, and two terminals 45 and 46 are mounted in the end cap 31. The thermistor 47 is electrically connected in series between the first terminal 45 and the first brush 41. Specifically, the first terminal 45 is electrically connected to the thermistor 47 by a strip-like conductor 43 (e.g., a copper strip). The first brush 41 is electrically connected to the thermistor 47 by a brush blade and a brush holder. Similarly, the second terminal 46 is electrically connected to the second brush 42 by a strip-like conductor 44 and by the brush blade and brush holder of the second brush 42. Terminals 45 and 46 are used for connection to an external power supply.The two brushes 41 and 42 are pressed into sliding contact with a commutator by their respective elastic brush blades to supply current to the rotor windings. The thermistor 47 provides overcurrent protection for the motor. Two contacts of the chip capacitor 48 are electrically connected to the respective terminals 45 and 46 to reduce electrical noise. Fingers 43a and 44a are integrally formed with the terminals 45 and 46 and prevent the capacitor 48 from moving out of its slot in the end cap 31.

[0026] An end cap according to a second embodiment is in the Fig. 7 and Fig. Figure 8 shows the end cap 31 and further comprises two yokes 49 and 50. The first yoke 49 is electrically connected in series between the first terminal 45 and the thermistor 47. The second yoke 50 is electrically connected in series between the second terminal 46 and the second brush 42 via the conductor 44, the brush holder, and the brush blade of the second brush 42. The addition of the two yokes improves the EMI (electromagnetic interference) suppression of the end cap 31.

[0027] Another motor according to a third embodiment of the present invention is in Fig. 9 shown. This motor further comprises an end cap cover 51, which is mounted on the end cap 31 to provide additional functions in the axial direction. Fig. 10 shows the cup-shaped cover 51, and Fig. Figure 11 is an end view of cover 51. Fig. 12 is an end view of the mounted cover 51 and end cap 31, and Fig. Figure 13 is a longitudinal section view of the mounted cover 51 and end cap 31.

[0028] The cup-shaped cover 51 has a base 52 and four side walls 53 extending axially from the edge of the base 52. One of the side walls 53 is essentially flat and rests against the flat mounting surface 35 of the cover 31 ( Fig. 12) aligned. Four legs 54 are integrally formed with the cover 51 and extend axially from respective corners of the cover 51. How Fig. Figure 9 shows that four guide grooves 37 are formed at the corners of the end cap 31 for the frictional engagement of the four legs 54, providing guidance during the axial attachment of the cover 51 to the end cap 31. Two spring-loaded locking fingers 55 are integrally formed with the cover 51 and extend axially into recesses formed in the end cap for locking the cover 51 to the end cap 31.

[0029] In this embodiment, the cover 51 primarily performs Hall effect functions such as speed control, rotation detection, position detection, etc. A position magnet (not shown), preferably a ring magnet, is mounted on the rotor shaft 29 and rotates with the shaft 29. A chamber 59 is formed in the cover 51 between the two spring-loaded fingers 55 to accommodate the position magnet. A printed circuit board (PCB) 56 is mounted in the cover 51, and a Hall sensor (Hall sensors) 57 is (are) mounted on the PCB 56 to detect the magnetic field of the position magnet. As shown in Fig.As can be seen in Figure 9, the cover 51 has slots 58 formed in one of the side walls 53. Connectors for the power supply and signal lines of the PCB 56 and the Hall sensors 57 can run through the slots 58. Similarly, the end cap 31 also has slots 38 formed in one of the side walls 34 so that external connectors can be plugged into the motor to supply it with power. In this embodiment, the slots 58 and 38 are formed in the side walls opposite the flat mounting surface 35 of the end cap. However, this is not essential. For example, instead of being located opposite the flat mounting surface 35, the slots 38 could be formed in a side wall 34 that is adjacent to or adjoins the flat mounting surface 35.

[0030] In the embodiment described above, the radial cross-section of each side region of the motor housing 21 is a convexly curved line formed as an arc. However, the convexly curved line can also be formed by one or more arc segments, or by one or more straight segments, or combinations thereof.

[0031] The invention is applicable to a motor whose housing has n side regions and n connection regions, where n is an integer equal to or greater than 3. Preferably, n is an even number greater than 3.

[0032] Verbs such as "to encompass," "to exhibit," "to contain," and "to have," as well as their variations in description and in claims, are to be understood in an inclusive sense. They indicate that the mentioned element is present, but do not preclude the presence of further elements.

[0033] Although the invention has been described with reference to several preferred embodiments, the person skilled in the art will recognize that various modifications are possible, which is why the protective framework of the invention is defined by the attached claims.

Claims

[1] Permanent magnet motor (20) comprising a stator and a rotor rotatably mounted on the stator, wherein the stand comprises a housing (21) with n convex side regions (23a-23d) and n connecting regions (25a-25d) alternately distributed, the connecting regions (25a-25d) being arranged at corners of the housing (21), wherein n is an integer equal to or greater than 3, preferably 4, wherein adjacent convex side regions are connected by a respective connecting region, each of the n convex side regions (23a-23d) having a convex outer surface and a convex inner surface; wherein the radial cross-section of each convex side region (23a-23d) is a convexly curved line which is curved outwards relative to the straight line passing through the two ends of the convexly curved line; wherein permanent magnets (27) are attached to an inner surface of the housing (21), the permanent magnets (27) each being attached to an inner surface of the connection areas (25a-25d); and wherein an end cap (31) is mounted at one end of the housing, the end cap (31) having a base (33) and n side walls (34) extending from the base (33), wherein a flat mounting surface (35) is formed on the outer surface of a first of the side walls (34) of the end cap (31) and is located outside the housing (21) when the end cap (31) is attached to the housing (21). [2] Permanent magnet motor (20) according to claim 1, wherein the entire outer surface of the first side wall forms the flat mounting surface (35). [3] Permanent magnet motor (20) according to claim 1, wherein a part of the outer surface of the first side wall forms the planar mounting surface (35) and wherein the planar mounting surface (35) is substantially parallel to the plane containing the two axial edges of the first side wall. [4] Permanent magnet motor (20) according to claim 1, wherein the convexly curved line has a straight segment and an arc segment. [5] Permanent magnet motor (20) according to claim 4, wherein the rotor has a shaft (29), a commutator, a rotor core attached to the shaft and rotor windings wound around the rotor and wherein the end cap (31) carries a first brush (41) and a second brush (42) for sliding contact with the commutator, a first terminal (45) and a second terminal (46) which serve for connection to a power supply and are electrically connected to the respective brushes, and a thermistor (47) which is electrically connected in series between the first brush (41) and the first terminal (45) as overcurrent protection. [6] Permanent magnet motor (20) according to claim 5, wherein the end cap (31) carries a chip capacitor (48) electrically connected to the first terminal (45) and the second terminal (46), a first yoke (49) electrically connected in series with the first brush (41), the thermistor (47) and the first terminal (45), and a second yoke (50) electrically connected in series with the second brush (42) and the second terminal (46). [7] Permanent magnet motor (20) according to claim 5, wherein the motor comprises a cup-shaped cover (51) which is mounted on the end cap (31) in the axial direction of the motor, wherein the cover (51) comprises a bottom (52) and a side wall (53) with a flat mounting surface, wherein the flat mounting surface of the cover (51) is aligned with the flat mounting surface (35) of the end cap (31). [8] Permanent magnet motor (20) according to claim 7, wherein the motor comprises a position magnet mounted on the shaft (29) which is located outside the end cap (31) and is received in the cover (51), wherein the motor comprises at least one Hall sensor (57) received in the cover for detecting the magnetic field of the position magnet. [9] Permanent magnet motor (20) according to claim 7, wherein the motor comprises a position magnet which is attached to the shaft (29) and is received in the cover (51); a printed circuit board (56) which is mounted in the cover (51) and at least one Hall sensor (57) which is mounted on the printed circuit board (56) to detect the magnetic field of the position magnet. [10] Permanent magnet motor (20) according to claim 7, wherein the cover (51) is attached to the end cap (31) by elastic fingers which are integrally formed as part of the cover and are arranged in recesses in the end cap.

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