IE42848B1

IE42848B1 - Stepping motors

Info

Publication number: IE42848B1
Application number: IE1236/76A
Authority: IE
Original assignee: Heliowatt Werke
Priority date: 1975-07-04
Filing date: 1976-06-09
Publication date: 1980-11-05
Also published as: LU74462A1; GB1496619A; SE7602907L; BE839997A; AT341613B; ATA196376A; CH613602B; DE2530410A1; DE2530410C3; IE42848L; CH613602GA3; DE2530410B2; IT1066962B; DK86176A; FR2316779A1; NL7602052A; SE409632B

Abstract

The stepping motor for pulse-controlled electronic clocks is provided with stator laminates of unsplit sheet metal, which have recesses for the rotor at the open ends of the stator laminates. In order to create a pulse-controlled stepping motor which can be assembled at a low assembly cost and requires only a low drive power, the core laminates (1) of the stator have allocated to them externally attached additional laminates (2) whose tabs (21) and steps (22) cover the air gap (11) of the core laminates (1) and whose end opening (23) is smaller than a quarter of the circular cut-out which holds the rotor. In this case, the drive coil is advantageously pushed over the one limb of the stator, after said stator has been bent laterally.

Description

This invention relates to stepping motors and is particularly concerned with stators therefor. The invention is particularly but not exclusively concerned with stepping motors for pulse-controlled electronic clocks.

Electronic motors for driving clocks are usually constructed as miniature motors, the manufacture of which, generally involves difficult and time-consuming assembly.

A stepping motor performs, with each pulse at its exciter windings, a step which is determined by the number of magnetic poles of the rotor; when the rotor has two magnetic poles, it is stepped forward through half its circumference at each pulse.

For prodicing a particular direction of rotation, the stator may be made asymmetrical about the rotor axis.

In addition, motors are known whose direction of rotation 48848 is determined by accummulations of ferromagnetic material through which coil-driving flux does not pass.

According to the present invention there is provided a stator for a stepping motor, wherein the stator comprises a plurality of first laminations which define two limbs, a cylindrical recess between the limbs for receiving a rotor, and an air gap formed by a space between the limbs at one side of the recess, and at least one second lamination which is secured to the first laminations and has a projection which overlaps said air gap.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:Figure 1 shows a first core lamination of a stator in accordance with the invention, of a pulse-control stepping motor for an electric clock; and Figure 2 shows an additional, second, lamination of the stator.

The stator of the motor is composed of a number of first core laminations 1 which have been stamped in one-piece. An advantage of such one-piece core laminations is that the magnetic circuit of the motor is not interrupted, as when two or three stampings are employed for one core lamination. The laminations 1 define two limbs, a circular cylindrical recess between the limbs for receiving a rotor, and two air gaps 11 and 12 formed by spaces between the limbs at opposite sides of the recess. One or more additional, second laminations 2 are provided in association with the laminated core assembly of the stator. The second laminations 2 are also formed as one-piece stampings, and are secured to the first laminations 1 preferably externally thereof. The additional laminations 2 determine the direction of rotation of the rector, because the diametrally magnetised rotor sets itself in the direction of a first projection in the form of a lip 21. This lip 21 overlaps one air gap 11 of the core laminations 1, and a second projection in the form of a shoulder 22 overlaps the other air gap 12. These overlaps bring about a ready starting of the stepping motor with little power consumption. The or each additional lamination 2 defines an end gap 23 between the lip 21 and an other part of the lamination 2. The end gap 23 has a circumferential extent which is less than a quarter of the circumference of the cylindrical recess which receives the rotor.

In order to manufacture the stator, the stator coil is not wound around one limb of the stator as in known stepping motors, but the arrangement is such that one limb of the stator may be resiliently bent laterally, sufficiently for a factory-wound coil to be pushed over one limb, after which the bent limb is returned to its normal position.

A pulse-controlled stepping motor having a stator as illustrated may therefore be assembled at little cost, and requires only a relatively small driving power.

Claims

1. CLAIMS: 1A stator for a stepping motor, wherein the stator comprises a plurality of first laminations which define two limbs, a cylindrical recess between the limbs for receiving a rotor, and an air gap formed by a space between the limbs at one side of the recess, and at least one second lamination which is secured to the first laminations and has a projection which overlaps said air gap.

2. A stator according to Claim 1, wherein each lamination comprises a one-piece stamping.

3. A stator according to claim 1 or 2, wherein there are two said air gaps at opposite sides of the recess and the or each second lamination has two projections each of which overlaps a respective one of the said air gaps.

4. A stator according to claim 1, 2 or 3, wherein the first laminations are assembled together and the second lamination or laminations is or are secured externally of the assembled first laminations.

5. A stator according to claim 1, 2, 3 or 4, wherein the cylindrical recess is adjacent one end of the first laminations.

6. A stator according to claim 5, wherein said air gap or one of said air gaps is at said one end of the first laminations, and the or each second lamination defines an end gap between the respective projection and another part of the lamination, which gap has a circumferential extent which is less than a quarter of the circumference of the cylindrical recess.

7. A stator according to. any preceding claim, *•8 including a coil on one of said limbs.

8. A stator substantially as hereinbefore described with reference to the accompanying drawing.

9. A method of manufacturing a stator according to claim 7, Wherein the^laminations are assembled, said limbs are bent laterally apart, a pre-wound coil is fitted onto one » * I of the limbs, and the limbs are then returned to their original positions.

10. A motor incorporating a stator in accordance with any one of claims 1 to 8.

11. An electronic clock incorporating a stepping motor in accordance with claim 10.