Linear motor

• US 5,808,381 A
• Filed: 08/08/1995
• Issued: 09/15/1998
• Est. Priority Date: 08/09/1994
• Status: Expired due to Term

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Shimizu, Yutaka, Aoyama, Hiroyuki
• Primary Examiner(s): Dougherty, Thomas M.
• Assistant Examiner(s): WILLIAMS, TIMOTHY A J
• Application Number:
  US08/512,684
• Time in Patent Office: 1,134 Days
• Field of Search: 310/12, 310/194, 335/281, 336/199, 336/208, 336/233, 174/138 G
• US Class Current: 310/12.29
• CPC Class Codes: H02K 41/03 Synchronous motors; Motors moving step by step; Reluctance motors H02K41/035 takes precedence

Abstract

In the linear motor including (a) a plurality of permanent magnet members 1 fixed to a pair of ferromagnetic yokes 3 such that longitudinally adjacent magnetic poles have different polarities and that the magnetic poles of different polarities face each other via a magnetic gap 7, (b) a polyphase coil 2 disposed in the magnetic gap 7, either one of the polyphase coil 2 and the permanent magnet members 1 being caused to move relative to each other when the polyphase coil 2 is energized; and (c) a coil-supporting member 4 to which the polyphase coil 2 is fixed, the coil-supporting member 4 is made of non-magnetic ceramics having excellent heat conductivity and insulation.

Claims

1. A linear motor comprising:

a plurality of permanent magnet members defining a magnetic gap on one side thereof;

a polyphase coil disposed in said magnetic gap, one of said polyphase coil and said permanent magnet members being caused to move relative to the other when said polyphase coil is energized; and

a coil-supporting member to which said polyphase coil is fixed, said coil-supporting member being made of a non-magnetic, heat conducting and electrically insulating ceramic selected from the group consisting of aluminum nitride and a composite sintered ceramic comprising 50-97 weight % of aluminum nitride and 3-50 weight % of boron nitride.

2. The linear motor according to claim 1, wherein said ceramic has a resistivity of 10¹ Ω

·

cm or more, a heat conductivity of 1 W/m·

K or more and a Young'"'"'s modulus of 0.5×

10⁴ kgf/mm² or more.

4. The linear motor according to claim 1, wherein said coil-supporting member provides a temperature distribution such that a difference between T_H and T_L is less than or equal to 40 degrees Celsius, where T_H is the highest surface temperature of the polyphase coil and T_L is the lowest surface temperature of the coil supporting member.

3. A linear motor comprising:

(a) a pair of ferromagnetic yokes;

(b) a plurality of permanent magnet members fixed to each of said pair of ferromagnetic yokes such that longitudinally adjacent magnetic members have different polarities, the pair of ferromagnetic yokes each having the plurality of permanent magnet members fixed thereto being arranged to oppose one another with a magnetic gap therebetween such that permanent magnet members having different polarities face each other across the magnetic gap;

(c) a polyphase coil disposed in said magnetic gap, one of said polyphase coil and said permanent magnet members being caused to move relative to the other when said polyphase coil is energized; and

(d) a coil-supporting member to which said polyphase coil is fixed, said coil-supporting member being made of a non-magnetic, heat conducting and electrically insulating ceramic selected from the group consisting of aluminum nitride and a composite sintered ceramic comprising 50-97 weight % of aluminum nitride and 3-50 weight % of boron nitride.

5. The linear motor according to claim 3, wherein said coil-supporting member provides a temperature distribution such that a difference between T_H and T_L is less than or equal to 40 degrees Celsius, where T_H is the highest surface temperature of the polyphase coil and T_L is the lowest surface temperature of the coil supporting member.

6. A linear motor comprising:

(a) a pair of stationary ferromagnetic yokes;

(b) a plurality of permanent magnet members fixed to each of said pair of stationary ferromagnetic yokes such that longitudinally adjacent magnetic members have different polarities, the pair of ferromagnetic yokes each having the plurality of permanent magnet members fixed thereto being arranged to oppose one another with a magnetic gap therebetween such that permanent magnet members having different polarities face each other via across the magnetic gap;

(c) a polyphase coil disposed in said magnetic gap such that said polyphase coil is longitudinally movable with respect to said permanent magnet members;

(d) a coil-supporting member to which said polyphase coil is fixed, said coil-supporting member being made of a non-magnetic heat conducting and electrically insulating ceramic selected from the group consisting of aluminum nitride and a composite sintered ceramic comprising 50-97 weight % of aluminum nitride and 3-50 weight % of boron nitride; and

(e) a driving circuit for supplying sinusoidal current to said polyphase coil to longitudinally move the polyphase coil with respect to the permanent magnetic members.

8. The linear motor according to claim 6, wherein said coil-supporting member provides a temperature distribution such that a difference between T_H and T_L is less than or equal to 40 degrees Celsius, where T_H is the highest surface temperature of the polyphase coil and T_L is the lowest surface temperature of the coil supporting member.

9. The linear motor according to claim 8, wherein said coil-supporting member provides a temperature distribution such that a difference between T_H and T_L is less than or equal to 40 degrees Celsius, where T_H is the highest surface temperature of the polyphase coil and T_L is the lowest surface temperature of the coil supporting member.

7. A linear motor comprising:

(a) a pair of movable ferromagnetic yokes;

(b) a plurality of permanent magnet members fixed to each of said pair of movable ferromagnetic yokes such that longitudinally adjacent magnetic members have different polarities, the pair of ferromagnetic yokes each having the plurality of permanent magnet members fixed thereto being arranged to oppose one another with a magnetic gap therebetween such that permanent magnet members having different polarities face each other via across the magnetic gap;

(c) a polyphase coil stationarily disposed in said magnetic gap such that said permanent magnetic members are longitudinally movable with respect to said polyphase coil;

(d) a coil-supporting member to which said polyphase coil is fixed, said coil-supporting member being made of a non-magnetic, heat conducting and electrically insulating ceramic selected from the group consisting of aluminum nitride and a composite sintered ceramic comprising 50-97 weight % of aluminum nitride and 3-50 weight % of boron nitride; and

(e) a driving circuit for supplying sinusoidal current to said polyphase coil to longitudinally move the polyphase coil with respect to the permanent magnetic members.