DC Brushless Motor for Electrical Power Steering and the Production Method Thereof

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.

1 . 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.   
   
   
       2 . The DC brushless motor for electrical power steering described in  claim 1 , 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. 
   
   
       3 . The DC brushless motor for electrical power steering described in  claim 2 , 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. 
   
   
       4 . The DC brushless motor for electrical power steering described in  claim 3 , 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.   
   
   
       5 . The DC brushless motor for electrical power steering described in  claim 1 , 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. 
   
   
       6 . The DC brushless motor for electrical power steering described in  claim 1 , 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. 
   
   
       7 . The DC brushless motor for electrical power steering described in  claim 1 , 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. 
   
   
       8 . 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.   
   
   
       9 . The DC brushless motor for electrical power steering manufacturing method described in  claim 8 , 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.   
   
   
       10 . The DC brushless motor for electrical power steering manufacturing method described in  claim 8 , 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.   
   
   
       11 . The DC brushless motor for electrical power steering manufacturing method described in  claim 8 , 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.