DC brushless motor and method for controlling the same

Patent metadata

Field	Value
Publication number	US-10355625-B2
Application number	US-201113989010-A
Country	US
Kind code	B2
Filing date	Nov 18, 2011
Priority date	Dec 1, 2010
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

This DC brushless motor (1) is provided with a stator (2) that has exciting coils (31, 32) and a rotor (4) that is positioned coaxially to the stator (2). The stator (2) has a quasi-E-shaped cross-section in the axial direction at the radius part; a plurality of protrusions (212, 222, 232) serving as magnetic poles are formed on the respective 3 parallel sections (211, 221, 231) of the E in the same number in the circumferential direction; and of the magnetic poles (212, 222, 232) formed at the 3 parallel sections (211, 221, 231) of the E, the top and the bottom magnetic poles (212, 232) are respectively positioned so as to be shifted in the opposite directions in the circumferential direction with respect to the center line of the middle magnetic pole (222). Changes in the magnetic resistance between the stator (2) and the rotor (4), which are caused by the flow of a magnetic flux generated around the exciting coils (31, 32), are utilized as a driving force. The DC brushless motor (1) configured in said manner exhibits excellent space efficiency at low cost and is less affected by temperature changes.

First claim

The invention claimed is:

1. A switched-reluctance (SR) DC brushless motor, comprising:
a stator including ring-shaped exciting coils;
a rotor, which does not include a permanent magnet, provided coaxially to the stator; and
a driving circuit, which provides current to the ring-shaped exciting coils, including a switch element, which controls application of rectangular-wave current to the driving circuit, and each ring-shaped exciting coil having one respective selection switch element connected thereto,
wherein the stator includes
an iron core member having a substantially E-shaped cross-section in an axial direction at a radius part and having a plurality of protrusions, which serve as magnetic poles and are formed in a circumferential direction at each of three parallel sections of the E shape, and the ring-shaped exciting coils housed in two recesses of the E shape, said three parallel sections correspond to a top parallel section, a middle parallel section, and a bottom parallel section, and said plurality of protrusions include at least top protrusions formed on the top parallel section, and middle protrusions formed on the middle parallel section; wherein the rotor includes an iron core member having a plurality of protrusions, which serve as magnetic poles formed in the circumferential direction, each of said plurality of protrusions extending straight along an axial direction of the rotor;

wherein numbers of the magnetic poles at the three parallel sections of the E shape are equivalent,
wherein, from among the magnetic poles at the three parallel sections of the E shape, the corresponding top and bottom magnetic poles are positioned to be shifted in opposite directions in the circumferential direction with respect to a center line of the corresponding middle magnetic pole,
wherein a change in magnetic resistance between the stator and the rotor caused by a flow of a magnetic flux, which is generated around the ring-shaped exciting coils, is utilized as a driving force, and wherein a ratio “γ” of the stator in relation with a ratio “α” of the rotor meets the following mathematical relation,
30%≤γ≤α

where the ratio “γ” is defined as a ratio of a sum of circumferential lengths of top protrusions of the stator with respect to a circumferential length of a circle drawn along the distal ends of the top protrusions of the stator; and the ratio “α” is defined as a ratio of a sum of circumferential lengths of the protrusions of the rotor with respect to a circumferential length of a circle drawn along the distal ends of the protrusions of the rotor,
the exciting coils are individually controlled by configuring the switch element and the selection switch elements to determine a forward or reverse direction of current applied to each ring-shaped exciting coil, and
a ratio “β” is defined as a ratio of a sum of circumferential lengths of middle protrusions of the stator with respect to a circumferential length of a circle drawn along the distal ends of the middle protrusions of the stator, such that β≤55%.

2. The DC brushless motor according to claim 1 , wherein the corresponding top and bottom magnetic poles are positioned to be shifted in the opposite directions in the circumferential direction by the same distance with respect to the center line of the corresponding middle magnetic pole.

3. The DC brushless motor according to claim 1 ,
wherein the rotor is housed at an inner periphery side of the stator, and
wherein the ratio α meets 30%≤α≤55%.

4. The DC brushless motor according to claim 1 , wherein the ring-shaped exciting coils are each formed by winding a strip-shaped conductive member so that a width direction of the conductive member extends along a rotation axis direction of the ring-shaped exciting coil.

5. The DC brushless motor according to claim 1 , wherein the iron core members of the stator and the rotor are each formed of any of a powder magnetic core made of iron-base soft magnetic powder, a ferrite magnetic core, and a magnetic core made of a soft magnetic material in which soft magnetic alloy powder is dispersed in resin.

6. A method for controlling the DC brushless motor according to claim 1 , comprising applying plus current to one of the two ring-shaped exciting coils if the rotor is activated in a forward rotation direction; and applying minus current to the other ring-shaped exciting coil if the rotor is activated in a reverse rotation direction that is reverse to the forward rotation direction.

7. The method for controlling the DC brushless motor according to claim 6 , wherein the rotor is accelerated or normally rotated by applying the rectangular-wave current after the rotor is activated to be rotated.

8. A switched reluctance (SR) DC brushless motor, comprising:
a stator including ring-shaped exciting coils;
a rotor, which does not include a permanent magnet, provided coaxially to the stator; and

a driving circuit, which provides current to the ring-shaped exciting coils, including a switch element, which controls application of rectangular-wave current to the driving circuit, and each ring-shaped exciting coil having one respective selection switch element connected thereto,
wherein the stator includes
an iron core member having a substantially E-shaped cross-section in an axial direction at a radius part and having a plurality of protrusions, which serve as magnetic poles and are formed in a circumferential direction at each of three parallel sections of the E shape, and the ring-shaped exciting coils housed in two recesses of the E shape, said three parallel sections correspond to a top parallel section, a middle parallel section, and a bottom parallel section, and said plurality of protrusions include at least top protrusions formed on the top parallel section, and middle protrusions formed on the middle parallel section, such that a thickness of the middle protrusions is at least 1.5 times a thickness of the top protrusions; wherein the rotor includes an iron core member having a plurality of protrusions, which serve as magnetic poles formed in the circumferential direction, each of said plurality of protrusions extending straight along an axial direction of the rotor;

wherein a numbers of the magnetic poles at the three parallel sections of the E shape are equivalent,
wherein, from among the magnetic poles at the three parallel sections of the E shape, the corresponding top and bottom magnetic poles are positioned to be shifted in opposite directions in the circumferential direction with respect to a center line of the corresponding middle magnetic pole,
wherein the ring-shaped exciting coils are individually controlled by configuring the switch element and the selection switch elements to determine a forward or reverse direction of current applied to each ring-shaped exciting coil,
wherein a change in magnetic resistance between the stator and the rotor caused by a flow of a magnetic flux, which is generated around the ring-shaped exciting coils, is utilized as a driving force, and wherein a ratio “γ” of the stator in relation with a ratio “α” of the rotor meets the following mathematical relation,
30%≤γ≤α

where the ratio “γ” is defined as a ratio of a sum of circumferential lengths of top protrusions of the stator with respect to a circumferential length of a circle drawn along the distal ends of the top protrusions of the stator; and the ratio “α” is defined as a ratio of a sum of circumferential lengths of the protrusions of the rotor with respect to a circumferential length of a circle drawn along the distal ends of the protrusions of the rotor.

Assignees

• Tsutsui Akira
• Inoue Kenichi
• Zaitsu Kyoji
• Kobe Steel Ltd

Inventors

• Tsutsui Akira
• Inoue Kenichi
• Zaitsu Kyoji

Classifications

• H02K1/02

  characterised by the magnetic material · CPC title

• H02K1/145

  having an annular coil, e.g. of the claw-pole type · CPC title

• H02P6/08 Primary

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• H02K19/103

  Motors having windings on the stator and a variable reluctance soft-iron rotor without windings · CPC title