Polyphase linear motor

• US 4,220,899 A
• Filed: 09/14/1978
• Issued: 09/02/1980
• Est. Priority Date: 09/19/1977
• Status: Expired due to Term

• Current Assignee: Papst Licensing GmbH & Company Kg
• Original Assignee: Papst-Motoren GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Inventors: von der Heide, Johann
• Primary Examiner(s): Duggan, Donovan F.
• Application Number:
  US05/942,288
• Time in Patent Office: 719 Days
• Field of Search: 310/12-14, 104/148 LM, 318/135
• US Class Current: 318/135
• CPC Class Codes: H02K 41/031 of the permanent magnet type

Abstract

The linear motor comprises a stator and an armature mounted for travel along the length of the stator. The stator includes an elongated inner flux-carrying structure extending in the direction of armature travel. A plurality of stationary coils are provided on the inner flux-carrying structure, the stationary coils being spaced in the direction of armature travel. The armature is provided with a plurality of radially magnetized permanent magnet units spaced in the direction of armature travel. The magnetic polarity of successive ones of the permanent magnet units alternates, proceeding in the direction of armature travel from one permanent magnet unit to the next. An outer flux-carrying structure, provided on either the stator or armature, extends in the direction of armature travel and surrounds the armature. Because the polarity of successive permanent magnet units alternates, proceeding from one to the next, the flux passing through the inner and outer flux-carrying structures is not, at any point, equal to the sum of the fluxes from all the permanent magnets, and accordingly the flux-carrying structures can be of smaller flux-conducting cross-sectional areas, and therefore of lower weight.

Claims

1. A polyphase linear motor, particularly for use as a drive motor for peripheral equipment in data-processing installations or the like, the motor comprising a stator and an armature mounted for travel along the length of the stator, the stator including an elongated inner flux-carrying structure extending in the direction of armature travel;

a plurality of stationary coils on the inner flux-carrying structure, the stationary coils being spaced in the direction of armature travel;

a plurality of permanent magnet units on the armature, the permanent magnet units being spaced in the direction of armature travel, each permanent magnet unit surrounding the inner flux-carrying structure and the coils on the latter, the magnetic polarity of successive ones of the permanent magnet units alternating proceeding in the direction of armature travel from one permanent magnet unit to the next; and

an outer flux-carrying structure extending in the direction of armature travel and surrounding the armature.

2. The linear motor defined in claim 1, wherein each permanent magnet unit is of polygonal configuration, is coaxial with the longitudinal axis of the elongated inner flux-carrying structure, and is radially magnetized.

3. The linear motor defined in claim 2, each permanent magnet unit comprising a plurality of magnetic plates arranged to form a polygon.

4. The linear motor defined in claim 2, the polygonal configuration being hexagonal.

5. The linear motor defined in claim 2, the cross-sectional configuration of both the inner and outer flux-carrying structures being polygonal and matching that of the permanent magnet units.

6. The linear motor defined in claim 1, the outer flux-carrying structure being a stationary structure.

7. The linear motor defined in claim 1, the outer flux-carrying structure being coupled to and travelling with the armature.

8. The linear motor defined in claim 1, each permanent magnet unit comprising a single radially magnetized permanent magnet of circular configuration.

9. The linear motor defined in claim 1, each permanent magnet unit comprising a single radially magnetized permanent magnet of polygonal configuration.

10. The linear motor defined in claim 1, the plurality of stationary coils on the inner flux-carrying structure comprising a succession of more than two such coils, the succession of coils extending in the direction of armature travel, each coil being a single annular coil.

11. The linear motor defined in claim 10, each annular coil being a wound strip of flat copper material.

12. The linear motor defined in claim 11, furthermore including insulating elements located intermediate adjoining ones of the coils.

13. The linear motor defined in claim 12, the insulating elements extending radially inward slightly beyond the coils and radially outward slightly beyond the coils.

14. The linear motor defined in claim 10, the coils being electrically interconnected in three-strand configuration.

15. The linear motor defined in claim 1, the armature comprising an injection-molded item, the permanent magnet units being secured thereto.

16. The linear motor defined in claim 15, the permanent magnet units being held in place on the injection-molded item by virtue of the injection-molded item being molded around them.

17. The linear motor defined in claim 1, furthermore including two sleeves of material of high electrical conductivity, each surrounding the inner flux-carrying structure at a respective one of the two ends of the linear motor, whereby if the armature travels so far towards one or the other end of the motor that the motor flux passes through the respective highly conductive sleeve eddy current generation results in braking of the armature.

18. The linear motor defined in claim 1, furthermore including impact-absorbing structures located at the two ends of the linear motor for cushioning the impact of the armature in the event the armature travels so far as to impact against an end of the motor.

19. The linear motor defined in claim 1, the inner flux-carrying structure being hollow and provided with heat dissipating means.

20. The linear motor defined in claim 1, furthermore including commutating means connected to the coils and operative for controlling their energization in dependence upon the position of the travelling armature.

21. The linear motor defined in claim 20, the commutating means including optoelectronic means for detecting the position of the travelling armature.

22. The linear motor defined in claim 1, furthermore including means connected to and controlling the energization of the stationary coils and causing the linear motor to perform as the servo motor of a negative-feedback system.