Abstract:
A brushless motor pump includes a case; a motor disposed in the case, and including a rotor and a stator; a rotary blade assembly connected to one end of the rotor; a blade housing mounted to the case and encompassing the rotary blade assembly; an excitation unit for energizing the stator; and a control unit for generating an operating frequency which increases gradually from an initial low value to a constant high value so that the rotor starts to operate at a low speed and continues its operation to a high constant speed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority of Taiwanese Application No. 094100632, filed on Jan. 10, 2005.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a pump, and more particularly to a brushless motor pump.  
         [0004]     2. Description of the Related Art  
         [0005]     Referring to  FIGS. 1 and 2 , a conventional single-phase brushless motor pump  1  includes a motor  10 , a hollow case  11 , a fan blade member  14 , and a front cover  15 .  
         [0006]     The hollow case  11  includes a main housing  112  that defines a chamber  111  and has a front face  114 . The case  11  further includes a circular boss  115  that projects from the front face  114  of the main housing  112 , a cylinder  116  extended into the chamber  111  from the circular boss  115 , an opening  117  formed in the circular boss  115  at a location corresponding to the cylinder  116 , and a pair of L-shaped connectors  118  formed symmetrically about the circular boss  115 .  
         [0007]     The motor  10  includes a coil  12  and a rotor  13 . The rotor  13  includes a rotating shaft  131 , and an annular magnetic member  132  surrounding an outer circumference of the rotating shaft  131 . The fan blade member  14  is mounted on a front end of the rotating shaft  131  of the rotor  13 , and the rotor  13  is inserted into the cylinder  116  through the opening  117  such that the fan blade member  14  is positioned outside the opening  117 . The coil  12  is mounted in the chamber  111  surrounding the cylinder  116 . Silicon steel laminations  121  of the coil  12  oppose the magnetic member  132  of the rotor  13  so that the coil  12  is subjected to the magnetic attraction force of the magnetic member  132 . The front cover  15  includes a front wall  151 , a circumferential wall  152  extending from an outer circumference of the front wall  151  to thereby define a hollow  150 , and a pair of flanges  154  extending from a distal end of the circumferential wall  152 . Gaps  153  are formed between the pair of the flanges  154 . A hollow intake tube  156  is formed protruding from the front wall  151  such that a center axis of the intake tube  156  substantially corresponds to an axis of rotation of the fan blade member  14 , and a hollow exhaust tube  157  is formed protruding from the circumferential wall  152 .  
         [0008]     The front cover  15  is secured to the hollow case  11  by first aligning the gaps  153  of the front cover  15  to the connectors  118  of the hollow case  11 , then rotating the front cover  15  by approximately a half turn.  
         [0009]     Referring to  FIG. 3A , the conventional synchronous motor pump further includes an excitation circuit  16 . When external power is supplied to the excitation circuit  16 , the coil  12  is operated to generate a magnetic flux effect to thereby induce the rotor  13  to rotate. Through such operation of the motor  10 , water enters through the intake tube  156 , then is exhausted via the exhaust tube  157  by the rotation of the fan blade member  14  fixed to the rotating rotor  13 . Hence, pumping of a liquid substance such as water is realized.  
         [0010]     Although the conventional pump can achieve its intended purpose, it nevertheless suffers from many drawbacks as follows:  
         [0011]     1. With reference to  FIG. 4 , there is a lag between when power is first provided to the motor pump  1  and when the rotor  13  reaches its desired final rotational speed. Since full power is supplied to the motor  10  at this initial stage prior to when the rotor  13  reaches its final speed, there is a loss of energy.  
         [0012]     2. Referring to  FIG. 3B , since the conventional single-phase synchronous motor pump does not have a starting coil, there is a minimal starting torque and the rotational direction is not fixed. Therefore, the rotor  13  must be rotatably interconnected with the fan blade member  14  (i.e., rotatable over a fixed range). When the rotating shaft  131  of the rotor  13  starts to operate, it rotates up to 270 degrees to cause a protuberance  1311  of the rotating shaft  131  to collide against a blocking member  141  of the fan blade member  14 . If the rotation of 270 degrees does not actuate the fan blade member  14 , the direction of the rotor  13  will reverse so that the rotating shaft  131  moves in the opposite direction by 270 degrees to collide with an opposite side of the blocking member  141  to drive the fan blade member  14 . However, since the fast starting resistance of the conventional pump is large, when the rotor  13  is instantly rotated one direction then in the reverse direction, the high-speed collision between the protuberance  1311  and the blocking member  141  results in easy damage to the fan blade member  14 , the protuberance  1311 , and the blocking member  141 .  
       SUMMARY OF THE INVENTION  
       [0013]     Therefore, the object of the present invention is to provide a brushless motor pump that minimizes use of power, and that can operate and discharge water smoothly.  
         [0014]     According to the present invention, a brushless motor pump comprises: a case; a motor disposed in the case, and including a rotor and a stator; a rotary blade assembly connected to one end of the rotor; a blade housing mounted to the case and encompassing the rotary blade assembly; an excitation unit for energizing the stator; and a control unit for generating an operating frequency which increases gradually from an initial low value to a constant high value so that the rotor starts to operate at a low speed and continues its operation to a high constant speed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:  
         [0016]      FIG. 1  is a partly exploded perspective view of a conventional brushless motor pump;  
         [0017]      FIG. 2  is a sectional view of the conventional brushless motor pump, illustrating the flow of water in the brushless motor pump;  
         [0018]      FIG. 3A  is a schematic circuit block diagram of an excitation circuit and a motor of the conventional brushless motor pump;  
         [0019]      FIG. 3B  is a partly sectioned view illustrating a rotor and a fan blade assembly of the conventional brushless motor pump;  
         [0020]      FIG. 4  is a timing diagram of a signal used to drive the motor of the conventional brushless motor pump;  
         [0021]      FIG. 5  is a partly exploded perspective view of a brushless motor pump according to a first preferred embodiment of the present invention;  
         [0022]      FIG. 6  is a sectional view of the first preferred embodiment, illustrating the flow of water in the brushless motor pump;  
         [0023]      FIG. 7  is a schematic circuit block diagram of a control unit and a motor of the first preferred embodiment;  
         [0024]      FIG. 8  is a timing diagram of a signal used to drive a motor of the first preferred embodiment;  
         [0025]      FIG. 9  is a partly exploded perspective view of a modified example,of the brushless motor pump of the first preferred embodiment;  
         [0026]      FIG. 10  is a partly exploded perspective view of a brushless motor pump according to a second preferred embodiment of the present invention;  
         [0027]      FIG. 11  is a schematic circuit block diagram of a control unit, a motor, and a magnetism detector of the second preferred embodiment;  
         [0028]      FIG. 12  is a circuit diagram of the control unit of the second preferred embodiment;  
         [0029]      FIG. 13  is a partly sectioned view illustrating a rotor and a rotary blade assembly of the preferred embodiments when having a fixed connection; and  
         [0030]      FIG. 14  is a partly sectioned view illustrating the rotor and the rotary blade assembly of the preferred embodiments when having a pivotable connection. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.  
         [0032]     Referring to  FIGS. 5 and 6 , a brushless motor pump according to a first preferred embodiment of the present invention includes a case  2 , a motor  3 , a rotary blade assembly  4 , a control unit  5 , and a blade housing  6 . The brushless motor pump may be a single-phase brushless motor pump.  
         [0033]     The case  2  includes a main housing  22  that defines a chamber  21  therein. The main housing  22  has a rear end that is open, and a front end that is closed to form a front face  24 . The case  2  also includes a rear cover  23  sealing the open rear end of the main housing  22 . A circular boss  25  projects from the front face  24  of the main housing  22 , and an opening is formed in the circular boss  25 . A cylinder  26  is extended into the chamber  21  from the circular boss  25  starting from the opening  27 . A pair of connectors  28  of L-shaped cross-section is formed symmetrically about the circular boss  25 .  
         [0034]     The motor  3  includes a coil unit  30  and a rotor  33 . The rotor  33  includes a rotating shaft  331 , and an annular magnetic member  332  surrounding an outer circumference of the rotating shaft  331 . The rotary blade assembly  4  is rotatably mounted on a front end of the rotating shaft  331  of the rotor  33  in substantially a coaxial position with the rotating shaft  331 , and the rotor  33  is inserted into the cylinder  26  through the opening  27  such that the rotary blade assembly  4  is positioned outside the opening  27 . The coil unit  30  is mounted in the chamber  21 . The coil unit  30  includes a plurality of silicon steel laminations  310  that form a core  31  of a substantially U-shaped cross-section, and a plurality of coils  32  provided partly surrounding the core  31 . The coil unit  30  is positioned over the outer circumference of the cylinder  26  such that the core  31  opposes the magnetic member  332  of the rotor  33 . The coil unit  30  is subjected to the magnetic attraction force of the magnetic member  332 .  
         [0035]     The blade housing  6  includes a front wall  61 , a circumferential wall  62  extending from an outer circumference of the front wall  61  to thereby form a hollow  610 , and a pair of flanges  64  extending from an outer circumference of the circumferential wall  62  at a distal end portion thereof. Gaps  63  are formed between the pair of the flanges  64 . A hollow intake tube  65  is formed on the front wall  61  that extends away from the same. A center axis of the intake tube  65  substantially corresponds to an axis of rotation of the rotary blade assembly  4 . A hollow exhaust tube  66  is formed on the circumferential wall  62  and extends away from the same. The blade housing  6  is mounted to the case  2  in a conventional manner and such that the blade housing  6  encompasses the rotary blade assembly  4 .  
         [0036]     The control unit  5  is mounted in the case  2  as shown in  FIG. 6 . Referring to  FIGS. 7 and 8 , the control unit  5  includes a signal control unit  51  and an excitation unit  52 . The excitation unit  52  energizes the coil unit  30 . That is, the excitation unit  52  is connected to an input terminal  301  of the coil unit  30 , and effects a magnetic excitation of the coil unit  30  so that the rotor  33  rotates. The signal control unit  51  supplies power to the excitation unit  52 , and is able to generate signals of differing frequencies which increase gradually from an initial low frequency level to a high frequency level. In the preferred embodiment, the signal control unit  51  generates a continuous train of pulse signals of increasing frequencies as shown in  FIG. 8 . When the signal control unit  51  starts its operation, it provides a pulse signal of a low frequency. Hence, at the beginning of operation, the coil unit  30  is operated such that the rotor  33  rotates slowly. The signal control unit  51  gradually increases the frequency of the pulse signal until it reaches a predetermined level, at which point the pulse signal is maintained at a constant level. In this state, the rotor  33  rotates at a higher speed.  
         [0037]     Referring to  FIGS. 10, 11 , and  12 , a second preferred embodiment of the present invention includes a case  2 , a motor  3 , a rotary blade assembly  4 , a control unit  5 , and a blade housing  6 . Except for the control unit  5 , all other aspects of the second preferred embodiment are identical to the first preferred embodiment. Therefore, only the control unit  5  will be described in the following.  
         [0038]     The control unit  5  of the second preferred embodiment further includes a magnetism detector  53 . As an example, the magnetism detector  53  may be a Hall sensor. The magnetism detector  53  is electrically connected to both the signal control unit  51  and the motor  3 . The magnetism detector  53  produces signals indicative of angular positions of N and S poles of the rotor  33 , then transmits the signals to the signal control unit  51 . The supply of the signals is uninterrupted, and the signal control unit  51  uses these signals to optimize driving of the rotor  33  so that the rotor  33  rotates more smoothly.  
         [0039]     Referring again to  FIG. 6 , in the first and second preferred embodiments, the core  31  functions as the stator of the motor  3 , and are therefore positioned surrounding the rotor  33 . When the coil unit  30  is supplied power, the core  31  creates a magnetic field. However, the single phase coil laminations produce parallel attraction and repulsion forces without rotational forces.  
         [0040]     The core  31  has the U-shaped cross section as described above and includes a bottom segment  3110 , and a pair of opposing side arms  3111  that extend upwardly from the bottom segment  3110 . The bottom segments  3110  of the core  31  cooperate with inner walls  3112  of the side arms  3111  thereof to define a channel  311  to receive the rotor  33 . The inner walls  3112  of the core  31  respectively have recessed surfaces  312  that confront the rotor  33 . Each of the recessed surfaces  312  includes a shallow region  3121  and a deep region  3122 . A distance D between the shallow region  3121  and the rotor  33  is smaller than a distance D 1  between the deep region  3122  and the rotor  33 . The shallow regions  3121  of the recessed surfaces  312  are arranged substantially at two diametrically opposed positions relative to the rotor  33 . Similarly, the deep regions  3122  of the recessed surfaces  312  are arranged substantially at two diametrically opposed positions relative to the rotor  33 .  
         [0041]     As a result of the difference in the distances D 1 , D, magnetic flux densities of differing intensities are created around the rotor  33 , thereby resulting in different magnetic forces. This, in turn, causes the N and S poles of the rotor  33  to alternate. Hence, the force needed for the initial rotation of the rotor  33  is formed.  
         [0042]     With reference to  FIG. 9 , in a modified example, the depth of recessed surfaces  312 ′ of the core  31  is gradually increased so that there is a smooth transition between shallow regions  3121 ′ and deep regions  3122 ′. As with the configuration described with reference to  FIG. 6 , the distance D 1  between each deep region  3122 ′ and the rotor  33  is greater than the distance D between each shallow region  3121 ′ and the rotor  33 . Also, the pair of the shallow regions  3121 ′ and the pair of the deep regions  3122 ′ are formed at diametrically opposed positions relative to the rotor  33  such that the distances D 1 , D are positioned opposite to one another. A magnetism detector  53  may be included in the configuration of the modified example as in the second preferred embodiment described above.  
         [0043]     Referring back to  FIGS. 11 and 12 , the excitation unit  52  includes a number of power transistors  521  (Q 6  and Q 7 ), and is connected to the input terminal  301  of the coil unit  30 . When the excitation unit  52  receives power, it performs an excitation function by causing the coil unit  30  to undergo quick conversion between positive and negative poles to thereby drive the rotor  33  by the rapid conversion between N and S poles of the coil unit  30 . Hence, rapid driving is achieved.  
         [0044]     The brushless motor pump of the present invention described above has advantages over the conventional configuration as follows:  
         [0045]     1. Power saving: Since the signal control unit  51  supplies power of differing frequencies to the excitation unit  52 , the rotor  33  is rotated starting from a slow speed and increasing to a fast speed. When the motor  3  is initially started, it does not produce any output, and, therefore, requires a relatively small supply of power. Power consumption may be reduced by supplying a small initial power that gradually increases.  
         [0046]     2. Smooth driving: With the addition of the magnetism detector  53  in the second preferred embodiment, and with the different depths between the shallow regions  3121  and the deep regions  3122  of the silicon steel laminations  31 , the magnetism detector  53  is able to sense changes in the north and south poles of the rotor  33 , and transmit corresponding signals to the signal control unit  51 . The supply of the signals is uninterrupted, and the rotor  33  that is excited to undergo rotation does so more smoothly by the use of this data by the signal control unit  51 .  
         [0047]     With reference to  FIG. 13 , since the rotor  33  of the present invention is driven from a slow speed to a fast speed, the resistance against rotation is small during initial operation. Therefore, the rotary blade assembly  4  of the present invention may be fixedly connected to the rotating shaft  331  of the rotor  33 . When the rotor  33  starts to rotate, it can easily make the rotary blade assembly  4  achieve the necessary rotational speed.  
         [0048]     Referring to  FIG. 14 , the rotary blade assembly  4  may also have a pivotable structure. In this case, the rotary blade assembly  4  includes a blocking member  41  that extends over a range of approximately  90  degrees, and the rotating shaft  331  of the rotor  33  includes a protuberance  3311 . When the rotor  33  rotates, after rotating 270 degrees, the protuberance  3311  collides against an opposite side  411  of the blocking member  41  of the rotary blade assembly  4  opposite an initial side  410  where the protuberance  3211  is initially positioned. The rotor  33  then rotates in the opposite direction, and again drives the rotary blade assembly  4  until reaching the desired speed. Since the rotor  33  is initially driven at a slow speed, the prior art drawbacks of damage to the rotary blade assembly  4  and/or the protuberance  3311  are not encountered in the present invention.  
         [0049]     In addition, in the coil unit  30  of the present invention, the coils  32  cover the U-shaped silicon steel laminations  310 . As a result, the structure is simple, and is therefore suitable for automated manufacture. In addition, the number of power elements of the present invention (i.e., the power transistors  521 ) is smaller than that used in two-phase or three-phase winding coils. Manufacturing costs are reduced since fewer parts are needed.  
         [0050]     While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.