The present invention relates to a motor. More particularly, the present invention pertains to a motor that has short-circuit members for connecting segments of a commutator.
Japanese Laid-Open Patent Publication No. 10-174403 discloses a motor that has a stator and a rotor (armature). The stator has permanent magnets, which form magnetic poles. The armature has exciting coils. The armature is rotated when electric current is supplied to the exciting coils through an anode supply brush and a cathode supply brush.
U.S. Laid-Open Patent Publication No. 2002/0121831A1 discloses a motor that includes a stator and a rotor (armature). The stator has permanent magnets that form six magnetic poles. The armature has eight exciting coils. The force applied to the armature in the radial direction during rotation is very small. Therefore, vibration of the armature is very small.
In the above mentioned motor, the commutator has twenty-four segments arranged along the outer circumferential surface of the commutator. Three anode supply brushes and three cathode supply brushes slide against the commutator. That is, the total number of the supply brushes is six. However, with this structure, a process for assembling a brush device is not only complicated, but also increases the size of the brush device since there are many supply brushes.
Accordingly, it has been proposed to reduce the number of supply brushes by connecting some of the segments of the commutator that have the same potential.
Short-circuit members are used to connect the segments. However, although the short-circuit members are effective in reducing the number of the supply brushes, the short-circuit members can increase the size of the motor. Therefore, it is desired to design and arrange the short-circuit members without increasing the size of the motor.
Accordingly, it is an objective of the present invention to reduce the size, particularly the axial size, of a motor that includes short-circuit members.
To achieve the above objective, the present invention provides a motor, which includes a stator, a rotor, an anode supply brush, and a cathode supply brush. The stator has a plurality of magnetic poles. The number of the magnetic poles is represented by 2x (x is an integer number greater than or equal to one). The magnetic poles are arranged along the circumferential direction of the stator. The rotor faces the magnetic poles. The rotor includes an armature core, a commutator, and short-circuit members. The armature core has a plurality of teeth. The number of the teeth is represented by 2y (y is an integer number greater than or equal to three). A coil is wound about each tooth. The commutator has a plurality of segments. The number of the segments is represented by 2xy. The segments are arranged along the circumferential direction of the commutator. Each short-circuit member is connected to a predetermined number of the segments. The number of the segments that are connected to one short-circuit member is B. The number of the short-circuit members is at least 2xy/B. The anode supply brush and the cathode supply brush slide against the commutator. The supply brushes are arranged at a predetermined angular interval about the axis of the commutator. Each short-circuit member extends in an arcuate form in an angular range corresponding to the arranging positions of the segments to be connected to the short-circuit member. The short-circuit members are laminated to form a multi-layer structure in the axial direction of the commutator, and form a substantially cylindrical laminated body. The short-circuit members are formed and arranged such that at least parts of two or more of the short-circuit members are in the same layer of the laminated body so that the number of layers of the laminated body is less than the number of short-circuit members.
The present invention also provides a motor, which includes a stator, a rotor, an anode supply brush, and a cathode supply brush. The stator has six magnetic poles. The magnetic poles are arranged along one circumferential direction of the stator. The magnetic poles are arranged such that the magnetic poles that are adjacent to each other in the circumferential direction have different polarities. The rotor faces the magnetic poles. The rotor includes an armature core, a commutator, short-circuit members. The armature core has eight teeth. A coil is wound about each tooth. The commutator has twenty-four segments. The segments are arranged in the circumferential direction of the commutator. Each short-circuit member is connected to three of the segments. The anode supply brush and the cathode supply brush slide against the commutator. The supply brushes are arranged at an angular interval of 180 degrees about the axis of the commutator. The segments are classified into first to eighth segment groups in order along the one circumferential direction of the commutator. Each segment group includes first to third segments. Each coil is connected to the second and third segments of one of the segment groups. The short-circuit members include first short-circuit members and second short-circuit members. Each of the first short-circuit members is connected to the first segment of an odd number segment group, the third segment of an even number segment group that is adjacent to the odd number segment group in the one circumferential direction, and the third segment of an odd number segment group that is adjacent to the even number segment group in the one circumferential direction. Each of the second short-circuit members is connected to the first segment of an even number segment group, the second segment of an odd number segment group that is adjacent to the even number segment group in the one circumferential direction, and the second segment of an even number segment group that is adjacent to the odd number segment group in the one circumferential direction.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.