Patent Publication Number: US-2013234569-A1

Title: Direct current motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a “continuation” application and claims benefit of the filing date of U.S. patent application Ser. No. 12/831307 filed on Jul. 7, 2010 and entitled “Direct Current Motor,” which, in turn, is based upon and claims priority to Chinese Patent Application 200910174206.5 filed on Sep. 23, 2009. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The invention relates to, in general, a motor and, in particular, a series-excited direct-current (DC) motor. 
     2. Description of Related Art 
     For a DC motor capable of rotating in forward and inverse directions, the rotating direction is changed by changing a direction of the current supplied to the exciting coil. Conventionally, the controller capable of changing the direction of the current supplied to the exciting coil is disposed outside the motor (for example, mounted on the outer surface of the motor shell) and usually includes four contactors so that the controller has a plurality of wires and connection points. 
     Therefore, the motors of the type commonly known n the related art have a large volume, are not compact in structure, and occupy a large mounting space. Moreover, the controller needs to be enclosed, and the wires and connection points thereof need to he sealed and insulated, respectively. These requirements increase the cost and reduce the operating efficiency of the motors. 
     Additionally, due to the large number of the wires and connection points, the work load of sealing and insulating the motor is large, the operation is complex, and the power consumption is increased. Further, because the controller is disposed outside the motor, the current-direction controller and wires and connection points thereof tend to be damaged, thus causing higher maintenance cost. 
     SUMMARY OF INVENTION 
     The invention overcomes problems existing in the related art in a direct-current motor comprising a stator including a shell, a main magnetic. pole, and an exciting coil. A rotator is disposed inside the stator, A brush holder is disposed at an end of the shell. First and second carbon brushes are disposed on the brush holder and contacted with the rotator, respectively. A current-direction controller is disposed on the brush holder and connected with the first and second carbon brushes and first and second ends of the exciting coil, respectively, to control a direction of a current supplied to the exciting coil, A over is disposed at the end of the shell to enclose the brush holder. 
     Accordingly, a DC motor is provided, in which a current-direction controller is disposed inside the motor so that wires and connection points may he decreased, the power consumption may be reduced, the operating efficiency may be improved, the current-direction controller and wires and connection points thereof are not easy to damage, the work load of sealing and insulating may he reduced, and the structure of the motor may be compact. 
     The motor according to the embodiment of the invention is compact in structure, small in volume, and occupies a small mounting space, and the work load of sealing and insulating is reduced so that e cost is reduced and the manufacture efficiency is improved. 
     The above summary of the invention is not intended to describe each disclosed embodiment or every implementation of the invention. The drawing and detailed description that follows more particularly exemplify illustrative embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF EACH FIGURE OF DRAWING OF INVENTION 
       These and other aspects and advantages of the invention should become apparent and more readily appreciated from the following detailed description taken in conjunction with the drawing in which: 
         FIG. 1  is a partially sectioned perspective view of the DC motor according to an embodiment of the invention; 
         FIG. 2  is an exploded view of the DC motor according to an embodiment of the invention; 
         FIG. 3  is a perspective view of the brash holder of the DC motor according to an embodiment of the invention; 
         FIG. 4  is a plan view of the brush holder shown in  FIG. 3 ; 
         FIG. 5  is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in a “de-energized” state; 
         FIG. 6  is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in an “energized” state and the motor rotates in a first direction; and 
         FIG. 7  is a principle diagram of the current-direction controller according to an embodiment of the invention in which the current-direction controller is in an “energized” state and the motor rotates in a second direction opposite to the first direction. 
     
    
    
     DETAILED SCRIPT ION OF EMBODIMENTS OF INVENTION 
     Reference is made in detail to embodiments of the invention. The embodiments described herein with reference to the drawing are explanatory and illustrative and used to generally understand the invention. The embodiments should not be construed to limit the invention. The DC motor according to an embodiment of the invention is described below in detail referring to the drawing. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the description. 
     As shown in  FIGS. 1 and 2 , the DC motor according to an embodiment of the invention includes a stator  1 , a rotator M, a brush holder  3 , first and second carbon brushes T 1 , T 2 , a current-direction controller  4 , and a cover  2 . Each of these components is described in greater detail below. 
     The stator  1  includes a shell  11 , a main magnetic pole  12 , and an exciting coil X disposed in the shell  11 . The rotator M is disposed in the stator  1  to rotate under the action of the magnetic field in the shell  11 . The brush holder  3  is mounted at an end of the shell  1  (for example, the right end of the shell  1  as illustrated in  FIGS. 1 and 2 ). The first and second carbon brushes T 1 . T 2  are mounted on the brush holder  3  and in contact with the rotator M, respectively. For example, the first and second carbon brushes T 1 , T 2  are in sliding contact with the commutator of the rotator M. The current-direction controller  4  is disposed on the brush holder  3  and connected with the first and second carbon brushes T 1 , T 2  and first and second ends X 1 , X 2  of the exciting coil X, respectively, to control or change a direction of a current supplied to the exciting coil X. The cover  2  is mounted into an end of the shell  11  to seal the brush holder  3 . For example, the cover  2  and the brush holder  3  may be mounted at the end of the shell  11  via a bolt  5 . Therefore, as shown in  FIG. 1 , in an assembled state, the brush holder  3  and the current-direction controller  4  mounted thereon are mounted at an end of the shell  11  and enclosed by the cover  2 . As a result, the motor may have a compact structure and occupy a small mounting space. Moreover, because the current-direction controller  4  is disposed inside the cover  2 , the current-direction controller  4  and the wires and connection points thereof may not need to be sealed and insulated from outside so that the cost is reduced and the safety and the manufacture efficiency are improved. 
     In some embodiments of the invention, the DC motor may be a series-excited DC motor. More particularly, as shown in  FIGS. 3-7 , the current-direction controller  4  includes first and second contactors A 1 , A 2 . The first contactor A 1  has a pair of normally open contacts K 11 , K 12 , a pair of normally closed contacts B 11 , B 12 , and a contactor coil KM 1 . The second contactor A 2  has a pair of normally open contacts K 21 , K 22 , a pair of normally closed contacts B 21 , B 22 , and a contactor coil KM 2 . 
     One normally open contact K 11  of the first contactor A 1  is connected with one normally closed contact B 11  thereof and the first end X 1  of the exciting coil X via a conducting wire L 3  and a conducting wire L 8 , respectively. One normally open contact K 22  of the second contactor A 2  is connected with one normally closed contact B 22  thereof and the second end X 2  of the exciting coil X via a conducting wire L 4  and a conducting wire L 9 , respectively. The other normally closed contact K 12  of the first contactor A 1  is connected with the other normally open contact K 21  of the second contactor A 2  via a conducting wire L 1 . The other normally open contact K 21  of the second contactor A 2  is also connected with one end of each of the contactor coils KM 1 , KM 2  of the first and second contactors A 1 , A 2 , respectively, via a conducting wire L 7  and connected with the second carbon brush T 2  via a power supply E. The other end of each of the contactor coils KM 1 , KM 2  of the first and second contactors A 1 , A 2  is configured to connect with an end of an external control switch K. Moreover, the one end of each of the contactor coils KM 1 , KM 2  of the first and second contactors A 1 , A 2  (and the other normally open contact K 21  of the second contactor A 2 ) is also connected with the negative pole of the power supply E. The other end of the external control switch K is connected with the positive electrode of the power supply E. Therefore, by controlling the external control switch K, the contactor coil KM 1  of the first contactor A 1  may be energized while the contactor coil KM 2  of the second contactor A 2  may he de-energized (as shown in  FIG. 6 ). The contactor coil KM 1  of the first contactor A 1  may he de-energized while the contactor coil KM 2  of the second contractor A 2  may be energized (as shown in  FIG. 7 ). In addition, the contactor coil KM 1  of the first contactor A 1  and the contactor coil KM 2  of the second contactor A 2  may be do-energized simultaneously (as shown in  FIG. 5 ). 
     The other normally closed contact B 12  of the first contactor A 1  is connected with the other normally closed contact B 21  of the second contactor A 2  via a conducting wire L 2  and with the first carbon brush T 1  via a conducting wire L 5 . 
     Therefore, as shown in  FIG. 5 , when the external control switch K is in its normally “open” position, both the contactor coils KM 1  of the first contactor A 1  and the contactor coil KM 2  of the second contactor A 2  are de-energized. The two normally open contacts K 11 , K 12  of the first contactor A 1  are disconnected from each other while the two normally closed contacts B 11 , B 12  thereof are connected with each other. In addition, the two normally open contacts K 21 , K 22  of the first contactor A 2  are disconnected from each other while the two normally closed contacts B 21 , B 22  thereof are connected with each other so that the DC motor is stopped. 
     As shown in  FIG. 6 , when the external control switch K is in its first position (i.e., the “left” position in  FIG. 6 ), the contactor coil KM 1  of the first contactor A 1  is energized while the contactor coil KM 2  of the second contactor A 2  is de-energized. The two normally open contacts K 11 , K 12  of the first contactor A 1  are connected with each other while the two normally closed contacts B 11 , B 12  thereof are disconnected from each other so that the motor rotates in a first direction. 
     As shown in  FIG. 7 , when the external control switch K is in its second position (i.e., the “right” position in Fig. the contactor coil KM 2  of the second contactor A 2  is energized while the contactor coil KM 1  of the first contactor A 1  is de-energized. The two normally open contacts K 21 , K 22  of the second contactor A 2  are connected with each other while the two normally closed contacts B 21 , B 22  thereof are disconnected from each other so that the motor rotates in a second direction opposite to the first direction. 
     As shown in  FIGS. 3-5 , in some embodiments of the invention, the first carbon brush T 1  includes two sub-carbon brushes T 11 , T 12  disposed on the brush holder  3  opposite to each other in a radial direction. Similarly, the second carbon brush T 2  includes two sub-carbon brushes T 21 , T 22  disposed on the brush holder  3  opposite to each other in the radial direction, in one embodiment, a first line connecting the two sub-carbon brushes T 11 , T 12  of the first carbon brush T 1  is substantially perpendicular to a second line connecting the two sub-carbon brushes T 21 , T 22  of the second carbon brush T 2 . As shown in  FIGS. 3 and 4 , the two sub-carbon brushes T 11 , T 12  are connected to each other in series via the conducting wire L 7 , and the two sub-carbon brushes T 21 , T 22  are connected with the shell  11 , respectively 
     As shown in FIGS.  4  and  5 - 7 , the other normally open contact K 21  of the second contactor A 2  is connected with a negative pole of the power supply F via the conducting wire L 7  such that the other normally open contact K 12  of the second contactor A 1  is connected with the negative pole of the power supply E via the conducting wire L 2 , the normally open contact K 22  of the second contactor A 2 , and the conducting wire L 7 , and the second carbon brush  12  is connected with the positive pole of the power supply F via the conducting wire L 6 . 
     Therefore, in the series-excited DC motor according to some embodiments of the invention, the current-direction controller  4  includes two contactors, thus reducing the number of the contactors. Moreover, the contacts of the two contactors, the contactor coils, and the wires. are all disposed on the brush holder  3  and enclosed inside the cover  2  such that there are no wires and contactors outside the shell  11 . As a result, the motor is compact in structure and small in volume, and the wires and connection points thereof are decreased in number, thus reducing the power consumption. Furthermore, because the current-direction controller  4  is enclosed inside the cover  2 , the current-direction controller  4  and the wires and connection points thereof are not necessary to seal and insulate so that the manufacture is much more simple, the cost s reduced, and. the safety is improved. 
     The operation of the series-excited DC motor according to embodiments of the invention is described below in detail with reference to  FIGS. 5-7 . 
     Firstly, as shown in  FIG. 5 , when the external control switch K is in the “disconnected” position, both the contactor coil KM 1  of the first contactor A 1  and the contactor coil KM 2  of the second contactor A 2  are de-energized. The two normally open contacts K 11 , K 12  of the first contactor A 1  are disconnected from each other while the two normally closed contacts B 11 , B 12  thereof are connected with each other. Meanwhile, the two normally open contacts K 21 , K 22  of the second contactor A 2  are disconnected from each other while the two normally closed contacts B 21 , B 22  thereof are connected with each other. In this way, no current flows through the exciting coil X so that the DC motor is stopped. 
     When the motor needs to rotate in the first direction, the external control switch K is switched to the first position (i.e., the “left” position as shown in  FIG. 6 ), the contactor coil KM 1  of the first contactor A 1  is energized, and the two normally open contacts K 11 , K 12  thereof are connected with each other while the two normally closed contacts B 11 , B 12  thereof are disconnected from each other. Meanwhile, the contactor coil KM 2  of the second contactor A 2  is de-energized, and the two normally open contacts K 21 , K 22  thereof are disconnected from each other while the two normally closed contacts B 21 , B 22  thereof are connected with each other. In this way, the current flows from X 2  to X 1  in the exciting coil X so that the motor rotates in a first direction (for example, the forward direction), as shown in  FIG. 6 . 
     When the motor needs to rotate in a second direction (for example, the reverse direction) opposite to the first direction, the external control switch K is switched to the second position (i.e., the “right” position in FIG.  7 ),, the contactor coil KM 1  of the first contactor A 1  is de-energized, and the two normally open contacts K 11 , K 12  thereof are disconnected from each other while the two normally closed contacts B 11 , B 12  thereof are connected with each other. Meanwhile, the contactor coil KM 2  of the second contactor A 2  is energized, and the two normally open contacts K 21 , K 22  thereof are connected with each other while the two normally closed contacts B 21 , B 22  thereof are disconnected from each other. In this way, the current flows from X 1  to X 2  in the exciting coil X so that the motor rotates in the second direction, as shown in  FIG. 7 . 
     Thus, with the DC motor according to embodiments of the invention, the current-direction controller  4  is mounted onto the brush holder  3  and enclosed by the cover  2  such that the motor is small. in volume and compact in structure, the number of the wires and connection points of the current-direction controller  4  is decreased, and the current-direction controller  4  and the wires and connection points thereof are not necessary to seal and insulate from outside. Therefore, the power consumption and the cost are reduced, and the manufacture efficiency and aesthetics are improved. 
     Although explanatory embodiments have been shown and described, it should be appreciated by those skilled in the related art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents can he made in the embodiments without departing from spirit and principles of the invention. 
     Reference throughout this specification to “one embodiment,” “some embodiments,” “an example,” or “some examples” means that a particular feature, structure, material, or characteristic- described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment,” “an example,” or “some examples” in various places throughout this specification are not necessarily referring to the same embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.