Electric motor with circuit board being held by insulator

Abstract

Insulators each include a plurality of board holding claws projecting from an outer peripheral edge of the circuit board for engaging a plurality of board recesses, the plurality of board holding claws are arranged on the outer peripheral edge of the circuit board such that an interval of board holding claws on a connector-mounted side is smaller than an interval between board holding claws on a counter-connector-mounted side, and a load receiving pin, which receives a radial load, projects at a counter-connector-mounted position, which is opposite to a mounted position of a connector.

Claims

1. An electric motor comprising: a stator core including an annular back yoke and a plurality of pole teeth projecting in a radial direction from the back yoke at predetermined intervals, the stator core including insulators attached to the pole teeth from both sides in an axial direction, and a circuit board including a connector mounted thereon, the circuit board being held by the insulator on a counter-output side, wherein the insulator on the counter-output side includes a plurality of board holding claws projecting from an outer peripheral edge of the circuit board for engaging a plurality of board recesses, the plurality of board holding claws are provided at positions of line symmetry to a connector insertion direction on the outer peripheral edge of the circuit board, the plurality of board holding claws are arranged on the outer peripheral edge of the circuit board such that the board holding claws on a connector-mounted side are formed at an interval having a central angle θ1, and that the board holding claws on a counter-connector-mounted side are formed at an interval having a central angle θ2, 01 is smaller than θ2, and a load receiving member, which receives a radial load, projects from the circuit board at a counter-connector-mounted position, which is opposite to a connector-mounted position.

2. The electric motor according to claim 1, wherein the outer peripheral edge of the circuit board includes the board recesses with which the board holding claws engage and a board notch into which the load-receiving member fits.

3. The electric motor according to claim 1, wherein the circuit board includes a plurality of guide grooves for guiding a coil wire at a winding start position or a winding end position of a coil wound around the insulators, which covers stator pole teeth at a position not interfering with the board holding claws.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a cross-sectional view of a motor taken along an axial direction.

(2) FIG. 1B is a right side view of an insulator holding a circuit board in FIG. 1A.

(3) FIG. 2A is a plan view illustrating an arrangement of the circuit board and board holding claws.

(4) FIG. 2B is a plan view illustrating an arrangement of a circuit board and board holding claws of the related art.

(5) FIG. 3A is a cross-sectional view of a motor of the related art taken along an axial direction.

(6) FIG. 3B is a right side view of an insulator holding a circuit board in FIG. 3A.

DESCRIPTION OF EMBODIMENT

(7) Referring now to the attached drawings, an embodiment of an electric motor according to the present invention will be described below. Schematic configuration of an inner rotor type motor as an example of the electric motor will be described with reference to FIG. 1A.

(8) In FIG. 1A, a motor 1 has the following configuration. A motor case 2 includes a case body 2a and a rear cover 2b. The motor case 2 is made of a metal material, such as a galvanized steel sheet. The motor case 2 contains therein a stator 3 and a rotor 4.

(9) The stator 3 is assembled with a stator core 5 being press-fitted into the case body 2a with the rear cover 2b removed. The stator core 5 includes an annular back yoke having a plurality (six in a case of a three-phase slot) of pole teeth projecting radially toward a center at predetermined intervals (at every 60 degrees in a circumferential direction). A laminated core including a plurality of transposed electromagnetic steel plates is used as the stator core 5. The pole teeth of the stator core 5 are covered with the insulators 6, which are mounted on both sides in an axial direction, and a coil 7 is wound around the pole teeth via the insulators 6. For example, a PBT (polybutylene terephthalate) resin or the like is used for the insulators 6. A circuit board 8 having a wiring pattern for supplying power to the coil 7 is held on the insulator 6 on a counter-output side. A connector 9 is mounted on the circuit board 8, and the connector 9 is connected to a terminal of external connection wiring, not illustrated, and receives a supply of power.

(10) In FIG. 1A, the rotor 4 includes a rotor magnetic pole 4b assembled integrally around a rotor shaft 4a. The rotor shaft 4a is rotatably supported by rolling bearings 10 assembled respectively to the case body 2a and the rear cover 2b, which constitute the motor case 2. The rotor magnetic pole 4b is assembled to face magnetic flux acting surfaces of the pole teeth of the stator core 5. Note that the rolling bearing 10 provided in the rear cover 2b may be preloaded toward an output side in the axial direction by a preload spring 11.

(11) The insulator 6 on the counter-output side includes a plurality of board holding claws 6a projecting therefrom. The board holding claws 6a are provided at four positions as illustrated in FIG. 2A, such that those on a connector-mounted side are provided at different intervals from those on a counter-connector-mounted side. The circuit board 8 includes a plurality of board recesses 8a (8a1, 8a2) provided on an outer peripheral edge thereof. The board holding claws 6a each include hook-shaped claws at an end thereof, and the hook-shaped claws are engaged in the board recesses 8a by a snap-fit. The circuit board 8 is assembled to the insulator 6 with each of the board holding claws 6a engaging the board recesses 8a. The board recesses 8a are also provided at different intervals between the connector-mounted side and the counter-connector-mounted side, such as at four positions on the outer peripheral edge of the circuit board 8 as illustrated in FIG. 2A.

(12) As illustrated in FIG. 1B, the plurality of board holding claws 6a are provided on the outer peripheral edge of the circuit board 8 at positions of line symmetry to a direction of insertion of a connector (direction indicated by an arrow), and intervals between the board holding claws 6a1 on the connector-mounted side are smaller than intervals between the board holding claws 6a2 on the counter-connector-mounted side. Specifically, while the board holding claws 6a2 on the counter-connector-mounted side are formed at an interval having a central angle θ2, the board holding claws 6a1 on the connector-mounted side are formed at an interval having a central angle θ1, which is smaller than θ2 (θ2>θ1), that is, are formed at positions near the connector 9. A load receiving pin 6b (load-receiving member), which receives a radial load, is provided on the circuit board 8 at a counter-connector-mounted position, which is opposite to a connector 9 mounted position. The load receiving pin 6b is configured to be fitted to a board notch 8b provided on the circuit board 8 on the outer peripheral edge (See FIG. 2A). The outer peripheral edge of the circuit board 8 also includes V-shaped guide grooves 8c at three points in an equiangular arrangement to guide a coil wire at a winding start position and a winding end position of the coil 7. The positions of the guide grooves 8c correspond to positions where the coil wire is held in a three-phase delta connection.

(13) As illustrated in FIG. 2A, the motor 1 as described above shares the load acting radially when inserting the terminal of the external connection wiring into the connector 9 in a direction indicated by an arrow P1 by the load-receiving pin 6b, which is provided at the counter-connector-mounted position, and the board holding claws 6a2, which are provided on both sides of the load-receiving pin 6b. When the terminal of the external connection wiring is pulled out from the connector 9 in a direction indicated by an arrow P2, the board holding claws 6a1 provided at a narrow interval on the connector 9 mounted side receive the radial load. This prevents deformations and damages of the board holding claws 6a (6a1, 6a2).

(14) The interval between the board holding claws 6a1 on the connector-mounted side is smaller than the interval between the board holding claws 6a2 on the counter-connector-mounted side. This prevents assembly of the circuit board 8 in a wrong orientation by being rotated by 180 degrees.

(15) In addition, making the interval between the board holding claws 6a1 on the connector-mounted side narrower than the interval between the board holding claws 6a2 on the counter-connector-mounted side eliminates interference with the guide grooves 8c that guide the coil wire at an engaging position of the board holding claws 6a and the winding start position and the winding end position of the coil 7, and also eliminates the interference of the board recesses 8a (8a1, 8a2), which are engaged by the board holding claws 6a (6a1, 6a2) with the guide grooves 8c, so that the wiring process is facilitated.

(16) In the embodiment described above, the inner rotor type motor has been illustrated as an example of the electric motor. However, an outer-rotor type motor including the circuit board on the insulator is also applicable. The number of board holding claws 6a and the board recesses 8a for holding the circuit board 8 has been described by four, but more than four is also applicable.

(17) The three-phase delta connection has been described as a coil connection. However, a three-star connection is also applicable.