DC brushless motor for electrical power steering and the production method thereof

• US 20050269895A1
• Filed: 05/25/2005
• Published: 12/08/2005
• Est. Priority Date: 06/03/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ishigami, Takashi, Innami, Toshiyuki, Koizumi, Osamu, Kitamura, Masashi, Yagai, Masamichi, Mirumachi, Mitsuaki
• Granted Patent: US 7,242,128 B2
• Time in Patent Office: Days
• US Class Current: 310/429
• CPC Class Codes: B62D 5/0403 characterised by constructional features, e.g. common housing for motor and gear box
• CPC Class Codes: H02K 1/148 Sectional cores H02K1/141 takes precedence
• CPC Class Codes: H02K 1/185 to outer stators
• CPC Class Codes: H02K 11/00 Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection casings, enclosures or supports H02K5/00
• CPC Class Codes: H02K 11/33 Drive circuits, e.g. power electronics H02K11/38 takes precedence
• CPC Class Codes: H02K 29/06 with position sensing devices H02K29/03 takes precedence
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02K 5/1732 radially supporting the rotary shaft at both ends of the rotor H02K5/1737 takes precedence
• CPC Class Codes: H02K 5/225 Terminal boxes or connection arrangements specially adapted for submersible motors H02K5/132
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine

Abstract

The stator core of a motor comprises an annular back core, and a plurality of tees created separately from the back core and secured onto the inner periphery of the back core. A stator coil is wound on each of the tees by a distributed or concentrated winding method. The stator core and stator coil are formed by molding.

Claims

1. A DC brushless motor for electrical power steering, driven by polyphase alternating current power, for outputting steering torque, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame; and

a rotor arranged opposite to said stator through an air gap;

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

a slot being formed on said tee core adjacent to said stator core, and said stator coil being incorporated in said slot,

said rotor comprising;

a rotor core; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said stator core and stator coil being molded by a molding agent, with the stator coil incorporated in the stator core.

2. The DC brushless motor for electrical power steering described in claim 1, said split core pieces comprising:

core pieces corresponding to said back core; and

core pieces corresponding to said tee core;

said stator core being formed by bonding the core pieces corresponding to said tee core, to the core pieces corresponding to said back core.

3. The DC brushless motor for electrical power steering described in claim 1, said slit core pieces being T-shaped pieces formed by integration of:

one of core pieces obtained by splitting said back core in multiple numbers in the circumferential direction; and

one of core pieces corresponding to said tee core;

said stator core being formed by connecting a plurality of said T-shaped core pieces in the circumferential direction.

4. A DC brushless motor for electrical power steering, driven by polyphase alternating current power, for outputting steering torque, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame; and

a rotor arranged opposite to said stator through an air gap;

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

a slot being formed on said tee core adjacent to said stator core, and said stator coil being incorporated in said slot,

said rotor comprising;

a rotor core; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said stator core and stator coil being molded by a molding agent, with the stator coil incorporated into the stator core, and

the surface opposite to the rotor as an integral mold obtained by said molding process, being provided with machining.

5. A DC brushless motor for electrical power steering, driven by polyphase alternating current power, for outputting steering torque, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame; and

a rotor arranged opposite to said stator through an air gap;

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

said stator core being press-fit into said frame;

a slot being formed on said tee core adjacent to said stator core, and said stator coil being incorporated in said slot,

said rotor comprising;

a rotor core; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said stator core and stator coil being molded by a molding agent, while the stator coil incorporated in the stator core is fixed on the frame.

6. The DC brushless motor for electrical power steering described in claim 5 wherein said stator core is press-fitted into said arm partially at a plurality of positions in the circumferential direction, the space between the stator core and the frame being filled with said molding agent.

7. The DC brushless motor for electrical power steering described in claim 5 wherein an engagement section is provided between said stator core and frame, said engagement section intended to avoid rotation of the stator core in the circumferential direction with respect to the frame.

8. A DC brushless motor for electrical power steering, driven by polyphase alternating current power, for outputting steering torque, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame; and

a rotor arranged opposite to said stator through an air gap;

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

a slot being formed on said tee core adjacent to said stator core, and said stator coil being composed of a wire rod whose diameter is smaller than the circumferential space between the closest sections, out of the circumferential spaces between said adjacent tee cores, and said stator coil being incorporated in said slot,

said rotor comprising;

a rotor core; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said stator core and stator coil being molded by a molding agent, with the stator coil incorporated in the stator core.

9. A DC brushless motor for electrical power steering, controlled by a power conversion apparatus for converting the electric power supplied from a 14-volt or 42-volt on-board power source, into polyphase alternating current power, for outputting steering torque, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame; and

a rotor arranged opposite to said stator through an air gap;

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

a slot being formed on said tee core adjacent to said stator core, and said stator coil composed of a plurality of unit coils and incorporated in said slot,

said unit coils, composed of a wire rod whose diameter is smaller than the circumferential space between the closest sections, out of the circumferential spaces between tee cores, and continuously wound on the tee core;

said rotor comprising;

a rotor core; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said stator core and stator coil being molded by a molding agent, while the stator coil incorporated in the stator core is fixed on the frame;

a 8-pole 9-slot, 10-pole 9-slot or 10-pole 12-slot relationship holding between the number of said magnets (in the plural) and the number of said slots.

10. The DC brushless motor for electrical power steering described in claim 9, said split core pieces comprising:

core pieces corresponding to said back core; and

core pieces corresponding to said tee core;

said stator core being formed by bonding the core pieces corresponding to said tee core, to the core pieces corresponding to said back core.

11. The DC brushless motor for electrical power steering described in claim 9, said slit core pieces being T-shaped pieces formed by integration of:

one of core pieces obtained by splitting said back core in multiple numbers in the circumferential direction; and

one of core pieces corresponding to said tee core;

said stator core being formed by connecting a plurality of said T-shaped core pieces in the circumferential direction.

12. The DC brushless motor for electrical power steering described in claim 9, the surface opposite to the rotor as an integral mold obtained by said molding process, being provided with machining.

13. The DC brushless motor for electrical power steering described in claim 9, wherein said stator core is press-fitted into said frame, said stator core press-fitted into the arm partially at a plurality of positions in the circumferential direction, and the space between the stator core and the frame being filled with said molding agent.

14. The DC brushless motor for electrical power steering described in claim 9, wherein said stator core is press-fitted into said frame, and an engagement section is provided between said stator core and frame, said engagement section intended to avoid rotation of the stator core in the circumferential direction with respect to the frame.

15. The DC brushless motor for electrical power steering described in claim 9, wherein

both ends of said frame in the axial direction are blocked by a flange;

the stator coil comprises a coil end;

said coil end protrudes in the axial direction from both ends of the stator core in the axial direction, and is covered by the molding agent so that the entire portion is wrapped inside;

the molding agent covering one of the coil ends is kept in close contact with the surface to which the stator core of the frame is secured;

an air gap is formed between the molding agent covering the other end of the coil ends and the surface of the frame to which the stator core is secured; and

one end of the flange is partly inserted into this air gap.

16. The DC brushless motor for electrical power steering described in claim 9, wherein

the stator coil comprises a coil end;

said coil end protrudes in the axial direction from both ends of the stator core in the axial direction, and is covered by the molding agent so that the entire portion is wrapped inside;

said unit coils are electrically connected by a connection member for each phase on one side of the coil end;

the connection member is electrically connected with a cable extending outside from the frame,

one side of the coil end, including the connection member and part of the cable, is covered with the molding agent.

17. The DC brushless motor for electrical power steering described in claim 16, wherein said connection member is a tabular conductor, said conductor covered with the molding agent.

18. The DC brushless motor for electrical power steering described in claim 9, wherein said magnets are covered by the non-magnetic tubular member from the outer periphery and are secured on the outer peripheral surface of the rotor core.

19. The DC brushless motor for electrical power steering described in claim 9, wherein the stator coil is formed by electric connection of a plurality of phase coils by delta connection, and wherein a plurality of phase coils are composed of series connections of a plurality of unit coils which are arranged in a plurality of electrical parallel connections.

20. A DC brushless motor for electrical power steering for outputting the steering torque, controlled by a power conversion apparatus for converting the power obtained from an on-board power source, into polyphase a.c. power and for outputting the power, said DC brushless motor for electrical power steering comprising:

a frame;

a stator secured on said frame;

a rotor arranged opposite to said stator through an air gap;

a flange for blocking both ends of the frame in the axial direction; and

a sensor for checking the magnetic pole position of the rotor

said stator comprising;

a stator core; and

a polyphase stator coil built in said stator core;

said stator core, formed by connecting a plurality of split core pieces, comprising;

an annular back core; and

a plurality of tee cores projected radially from said back core;

wherein a slot is formed on said tee core adjacent to said stator core, and said stator coil is composed of a plurality of unit coils, and is incorporated in said slot;

said rotor comprising;

a shaft;

a rotor core provided on the shaft; and

a plurality of magnets fixed onto the surface of the outer periphery of the rotor core;

said DC brushless motor for electrical power steering further characterized in that said stator core and stator coil are molded by a molding agent, with the stator coil incorporated in the stator core, said shaft being rotatably supported by a bearing, said bearing being arranged on the flange, one side of said flange being provided with a recess, said recess, as a cylindrical member concentric with the shaft, being located inward of the axial end of the frame and extending to the position opposed to the coil end, and one side of said bearing being arranged on the position of the recess radially opposite to the coil end.

21. The DC brushless motor for electrical power steering described in claim 20, wherein the sensor is arranged on the axial end of the frame, and the flange with the recess arranged thereon blocks one of the axial ends of the frame, equipped with the sensor.

22. The DC brushless motor for electrical power steering described in claim 21, wherein one end of said shaft in the axial direction expends further in the axial direction than one side of the bearing and reaches said recess, and said sensor is arranged in the air gap between the outer peripheral surface of the shaft and the peripheral surface of the recess.

23. The DC brushless motor for electrical power steering described in claim 22, said sensor comprising:

a census tester with a coil wound on the core; and

a sensor rotor arranged opposite to the census tester;

wherein said census tester is secured on the peripheral surface of the recess, while the sensor rotor is secured on the outer peripheral surface of the shaft so as to be positioned opposite to the census sensor through the air gap.

24. The DC brushless motor for electrical power steering described in claim 20, wherein a plurality of unit coils are electrically connected for each phase by the connection member arranged on one side of the coil end, and the flange equipped with said recess blocks the end on the side axially opposite to the coil end equipped with said connection member.

25. The DC brushless motor for electrical power steering described in claim 20, wherein the other end of the flange has a recess on the side axially opposite to the coil end, said recess on the other end of the flange being engaged with the tip of the coil end.

26. The DC brushless motor for electrical power steering described in claim 20, wherein the coil end opposite axially to the other end of the flange is covered with said molding agent so that an air gap is formed between the frame and air space;

the other end of said flange provided with an annular protrusion extending in the axial direction, and said protrusion being engaged with the air gap when the other end of the flange is secured on the frame.

27. A DC brushless motor for electrical power steering manufacturing method, driven by polyphase alternating current power, for outputting steering torque, said manufacturing method comprising:

a first step of assembling a stator coil into a stator core;

a subsequent second step of press-fitting into the frame a plurality of positions of the stator core incorporating the stator coil in the circumferential direction, and obtaining a structure composed of the stator core incorporating the stator coil, secured to the frame;

a subsequent third step of mounting a jig on said structure in such a way that the jig and frame will enclose the stator core and the coil end of the stator coil protruding axially from the axial end of the stator core;

a subsequent fourth step of injecting the molding agent into the space enclosed by the jig and frame, thereby filling the molding agent into the air gap between the coil end and stator core, the air gap of the stator coil, the air gap between stator core and stator coil, and the air gap between the stator core and frame;

a subsequent fifth step of solidifying the molding agent; and

a subsequent sixth step of removing the jig.

28. The DC brushless motor for electrical power steering manufacturing method described in claim 27, further comprising the steps of

preparing a plurality of serrated coil pieces with coil by winding a coil on the serrated core piece;

and

connecting a plurality of serrated coil pieces with coil, to annular core pieces, thereby obtaining said stator core incorporating the stator coil.

29. The DC brushless motor for electrical power steering manufacturing method described in claim 27, further comprising the steps of:

preparing a plurality of T-shaped core pieces with coil, by winding the coil on the protruded portion of the T-shaped core piece; and

connecting a plurality of T-shaped core pieces in the circumferential direction, thereby obtaining said stator core incorporating the stator coil.

30. The DC brushless motor for electrical power steering manufacturing method described in claim 27, further comprising the steps of:

electrically connecting one side of the coil end to a plurality of unit coils constituting the stator coil using a connection member;

electrically connecting said connection member to a cable extending outside from the frame; and

molding one side of the coil end with said molding agent in such a way that the connection member and part of the cable are molded together with one side of the coil end by the molding agent.