ELECTRONICALLY COMMUTATED DC MOTOR

Abstract

An electronically commutated direct current motor made up of a cylindrically shaped non-ferrous stator winding; a cylindrically shaped, magnetically conductive back iron arranged radially outside of the stator winding; and a cylindrically shaped permanent magnet rotor arranged concentrically within the stator winding, wherein the magnetically conductive back iron has different magnetic conductivities over its circumference

Claims

1. An electronically commutated direct current motor, the motor comprising: a cylindrically shaped non-ferrous stator winding; a cylindrically shaped, magnetically conductive back iron arranged radially outside of the stator winding; and a cylindrically shaped permanent magnet rotor arranged concentrically within the stator winding, wherein the magnetically conductive back iron has different magnetic conductivities over its circumference.

2. The direct current motor according to claim 1, wherein the magnetically conductive back iron has different material thicknesses over its circumference.

3. The direct current motor according to claim 1, wherein the magnetically conductive back iron is multi-part.

4. The direct current motor according to claim 1, wherein the magnetically conductive back iron has a cylindrical shell surface on its inner circumference.

5. The direct current motor according to claim 1, wherein the magnetically conductive back iron has a cylindrical shell surface on its outer circumference.

6. The direct current motor according to claim 1, wherein the magnetically conductive back iron does not have a cylindrical shell surface on its inner circumference or on its outer circumference.

7. The direct current motor according to claim 1, wherein the magnetically conductive back iron serves as a housing.

8. The direct current motor according to claim 1, wherein the direct current motor is one of a series of motors.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] The exemplary embodiments of the invention are subsequently explained in more detail based on the drawings. The following is shown:

[0017] FIG. 1 a conventional electronically commutated direct current motor according to the prior art,

[0018] FIG. 2 a first embodiment of the invention, and

[0019] FIG. 3 a second embodiment of the invention.

[0020] Note: The reference numbers with a subscript and the corresponding reference numbers without a subscript refer to details with the same name in the drawings and the drawing description. This reflects use in another embodiment or the prior art, and/or where the detail is a variant.

DETAILED DESCRIPTION OF THE INVENTION

[0021] In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

[0022] FIG. 1 shows a conventional electronically commutated direct current motor 1 according to the prior art with a hollow-cylindrical magnetically conductive back iron 3, a hollow-cylindrical non-ferrous stator winding 2 abutting against the inner circumference of the back iron 3, and a permanent magnet rotor 4 inside of the stator winding.

[0023] FIG. 2 shows a first embodiment of a direct current motor 1a with a hollow-cylindrical non-ferrous stator winding 2a and a magnetically conductive back iron 3a, which has a cylindrical shell surface 5a on its inner circumference. A closed inner ring 7a has a thickness d.sub.a. Reinforcing regions 8a separated by constrictions 9a abut radially outside of the inner ring. The back iron 3a has a greater thickness D.sub.a in the region of the reinforcements. Since the air gap width remains constant, the achievable holding or braking force is less than in a second embodiment.

[0024] FIG. 3 shows the second embodiment of a direct current motor 1b, which has a magnetically conductive back iron 3b, a hollow-cylindrical non-ferrous stator winding 2b, and a permanent magnet rotor 4b. The back iron 3b has a closed outer cylindrical shell surface 6b. A closed ring 7b has a thickness d.sub.b. Reinforcing regions 8b separated by constrictions 9b abut radially inside of the closed ring. The back iron 3b has a greater thickness D.sub.b in the region of the reinforcing regions 8b than the closed ring thickness d.sub.b. The air gap width varies in this case between the distance between the permanent magnet rotor 4b and the reinforcing region 8b and the distance between the permanent magnet rotor 4b and the closed ring 7b. As a result, the achievable holding or braking force is considerably greater than in the first embodiment. The closed shell surface 6b can also provide the outer surface for the back iron 3b to act as a housing for the motor.

[0025] Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. For Example, the constructions on the magnetively conductive back irons 3a and 3b of FIGS. 2 and 3 can be combined to become a magnetively conductive back iron that has a tooth-like geometry on both its inner and outer circumferences along the lines shown in FIGS. 2 and 3 with a shared closed inner ring 7a or 7b.

LIST OF REFERENCE SYMBOLS

[0026] 1 Direct current motor [0027] 2 Stator winding [0028] 3 Back iron [0029] 4 Permanent magnet rotor [0030] 5 Inner cylindrical shell surface [0031] 6 Outer cylindrical shell surface [0032] 7 Inner ring [0033] 8 Reinforcing region [0034] 9 Constriction