Abstract:
A fan unit comprises an electric rotary machine (e.g. electric motor) having a rotor and a fin structure unified with the rotor. The fan unit further comprises a rotation mechanism for rotating the rotor. The rotor is formed to have an opening at a central portion thereof in a direction along which the opening permits fluid to flow. The fin structure is coupled with a peripheral portion of the opening so as to be unified with the rotor. The peripheral portion incorporates the rotation mechanism therein.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The present invention relates to a fan unit that has various uses including electric vehicles, airships, turbine engines, turbine generators, fuel batteries, air conditioners, heat exchangers, and fluid sensor, and in particular, to the fan unit having a motor equipped with a rotor and fins united with the rotor itself. 
   2. Related Art 
   Conventionally, a variety of types of fan units have been used. One type of fan unit has been proposed by Japanese Patent Laid-open No. 11-218092, in which a compact fan with a brushless compact DC motor is explained. Specifically, the fan unit is made compact to the extent of allowing the fan unit to be directly disposed on, for example, a printed wiring assembly. This fan unit has a feature that a brushless DC motor driving a fan wheel is provided as a single-phase single-winding gearing-pole type of motor provided with a non-feedback permanent magnet rotor and at least one magnet for positioning is placed to exert an influence on an activating position of the rotor. 
   However the above conventional fan unit faces a problem that the motor is obliged to position at the center of a flow path for fluid in which the fan unit is arranged. Hence it is unavoidable that the motor becomes resistance against a flow of fluid. 
   In addition, due to the fact that the foregoing conventional fan unit has a driving part located in the flow path, there are various other difficulties to the fan unit. For example, there is a reduction in fluid delivery efficiency, fluid loss is easily caused, and the flow path is difficult to be thinner in construction. Moreover, some kind of restrictions in temperature and types of gas and solvent are easily exerted on the fluid. In cases where the driving part becomes a resistance against the flow of fluid and dirt in the fluid adheres to the driving part, the efficiency of fluid flow will suffer a further decrease. 
   SUMMARY OF THE INVENTION 
   The present invention has been performed in consideration of the drawbacks that the foregoing conventional fan unit has been suffered. An object of the present invention is to provide a fan unit structure that has a motor serving as means for rotating fins and avoid the motor from becoming resistance to the flow of fluid. 
   In order to realize the above object, there is provided a fan unit comprising an electric rotary machine having a rotor; and a fin structure unified with the rotor. 
   Because the fin structure is united with the rotor, so that a mechanism for rotating the motor, that is, the fin structure, can be around an opening formed to allow fluid pass therethrough. Accordingly, there is no need for arranging the rotating mechanism, such as motor, in the opening. Hence the rotating mechanism creates almost no resistance against flow of the fluid passing through the opening. 
   Applying this fan unit to control of flow of fluid, such as gas and air, makes it possible to transmit and/or compress the fluid at higher efficiency. 
   Some practical configurations falling into the gist of the above configuration are as follows. 
   It is preferred that the fan unit further comprises a rotation mechanism for rotating the rotor, wherein the rotor is formed to have an opening at a central portion thereof in a direction along which the opening permits fluid to flow and the fin structure is coupled with a peripheral portion of the opening so as to be unified with the rotor, the peripheral portion incorporating the rotation mechanism therein. 
   Preferably, the electric rotary machine is provided with a first magnetic member, a second magnetic member disposed to face the first magnetic member with a space therebetween, a third magnetic member disposed between the first and the second magnetic members and configured to relatively movable to both the first and second magnetic members in a predetermined direction in the space, wherein each of the first and second magnetic members has a plurality of electromagnetic coils which are current-excitable and disposed in order along each magnetic member so as to have relative differences in disposal pitches of both of the electromagnetic coils of the first magnetic members and the electromagnetic coils of the second magnetic member, and the third magnetic member has a plurality of permanent magnets magnetized to predetermined magnetic poles and disposed in order along the third magnetic member, the third magnetic member being unified with the fin structure so as to serve as the rotor. 
   It is also preferred that the fan unit further comprises exciting circuit means configured to supply excitation current to the electromagnetic coils of at least one of the first and second magnetic members. 
   For example, the exciting circuit means is configured to supply the excitation current to the electromagnetic coils of the first and second magnetic members, the excitation current being set to give the same magnet pole to the electromagnetic coils of each of the first and second magnetic members. In this case, by way of example, the excitation current supplied to the electromagnetic coils of the first magnetic member is different in phase from the excitation current supplied to the electromagnetic coils of the second magnetic member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIGS. 1A and 1B  are perspective views of a fan unit according to an embodiment of the present invention; 
       FIGS. 2-5  illustrate the principle of operation of magnetic members employed by the fan unit, together with the structural configuration of the magnetic members; 
       FIGS. 6A and 6B  are circuitry showing the electrical connections of excitation coils placed on the magnetic members; 
       FIG. 7  is a block diagram showing the electrical configuration of an excitation circuit to feeding pulse current to the excitation coils; 
       FIG. 8  is a block diagram showing the electrical configuration of a driver employed by the excitation circuit; 
       FIG. 9A  is a perspective view detailing the fan unit according to the embodiment, the fan unit being disassembled; 
       FIG. 9B  is a plan view showing a third magnetic member (i.e., rotor) employed by the fan unit in  FIG. 9A ; 
       FIG. 9C  is a plan view showing excitation coils (referred to as A-phase excitation coils) on a first magnetic member (i.e., stator) employed by the fan unit in  FIG. 9A ; 
       FIG. 9D  is a plan view showing excitation coils (referred to as B-phase excitation coils) on a second magnetic member (i.e., stator) employed by the fan unit in  FIG. 9A ; 
       FIGS. 10 and 11  are timing charts of pulse signals showing the processing necessary for exciting the excitation coils, the processing being performed by the driver; 
       FIG. 12  is an electrical circuit showing the configuration of a buffer employed by the driver; 
       FIG. 13A  is a plan view outlining the fan unit to show the entire arrangement configuration thereof; 
       FIG. 13B  is a section taken along an A-A line in  FIG. 13A ; 
       FIG. 14  illustrates an example of applications of the fan unit according to the embodiment; 
       FIGS. 15 to 16  illustrate other examples of applications of the fan unit according to the embodiment; 
       FIG. 17A  is a sectional view showing another example of applications of the fan unit according to the embodiment; 
       FIG. 17B  is a section taken along an A-A line in  FIG. 17A ; 
       FIG. 18A  is a plan view showing another example of applications of the fan unit according to the embodiment; 
       FIG. 18B  is a section taken along an A-A line in  FIG. 18A ; 
       FIGS. 19 to 22  still illustrate other examples of the fan unit according to the embodiment; 
       FIG. 23A  is a plan view showing another example of applications of the fan unit according to the embodiment; 
       FIG. 23B  is a section taken along an A-A line in  FIG. 23A ; 
       FIG. 24A  is a plan view showing another example of applications of the fan unit according to the embodiment; 
       FIG. 24B  is a section taken along an A-A line in  FIG. 24A ; 
       FIG. 25A  is a plan view showing another example of applications of the fan unit according to the embodiment; and 
       FIG. 25B  is a section taken along an A-A line in  FIG. 25A . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1A and 1B  to  13 A and  13 B, a fan unit according to an embodiment of the present invention will now be described. 
     FIGS. 1A and 1B  are perspective front and rear views each showing a fin/frame member of the fan unit, respectively. 
   The fin/frame member, which is structured into a “fin structure,” serves as a rotor of a motor (or generator) incorporated in the fan unit. The fin/frame member, which is formed into an annular shape as a whole, has an annular outer frame  1 , four fins  2 , a boss  3  located at the center of the outer frame  1 , all of which are produced as a single unit. 
   The four fins  2  are formed to connect the outer fame  1  and the central boss  3 . In order to make the outer frame  1  work as the rotor of the motor (or generator), a plurality of permanent magnets are used as part of magnetic members in the outer fame  1  so that the magnets make a line, but in an alternately aligned N/S-pole manner, along a circumferential direction of the outer frame  1 . 
     FIGS. 2-5  each illustrate the structure of magnetic members for rotating the rotor (formed into the fin structure as a single unit) according to the present invention and the principle of operation of the magnetic members. The structure of the magnetic members has a first magnetic member (A-phase coil)  10 , a second magnetic member (B-phase coil)  12 , and a third magnetic member  14  located between the first and second magnetic members  10  and  12 . Practically, each of the sets of magnetic members  10 ,  12  and  14  are disposed in an annular (or arc-like, circular) shape, respectively. As a result, either the third magnetic member or the first and second magnetic members is able to function as the rotor. When considering the configuration shown in  FIGS. 1A and 1B , the third magnetic member corresponds to the annular outer frame  1 . 
   The first magnetic member  10  is arranged together with excitation coils  16  that can sequentially be excited into different magnetic poles. The coils are mapped along the first magnetic member  10  at predetermined intervals, preferably at equal intervals. This first magnetic member  10  has an equivalent circuit shown in  FIG. 6A  or  6 B. As will be detailed later in connection with  FIGS. 2-5 , all of the two excitation coils for the first and second magnetic members  10  and  12  are always subjected to excitation on the already described polarities during the operation (2π). Accordingly, it is possible to drive and rotate an object to be driven, such as the rotor or a slider, at higher torque. 
   The second magnetic pole  12  also has circuitry equivalent to the circuit shown in  FIG. 6A  or  6 B. That is, the equivalent circuit itself of both first and second magnetic members  10  and  12  are the same, but both members  10  and  12  are excited in mutually different patterns to continuously rotate the rotor. Those excitation patterns are controlled as described later. 
   As shown in  FIG. 6A , the first magnetic member  10  has a plurality of excitation coils  16  connected to an excitation circuit  18 A. The plural excitation coils  16 , each composes a unit of magnetization, are arrayed at equal intervals in the circumferential direction and connected in series to each other. 
   The excitation circuit  18 A is connected to the excitation coils  16  to provide a pulse current having a predetermined frequency (serving as an excitation pulse signal) thereto. The windings of the respective excitation coils  16  are previously adjusted to have magnetic poles which are different from each other between adjacent excitation coils  16 . How to array the excitation coils  16  may be modified as shown in  FIG. 6B , in which, of the excitation coils  16 , each pair of coils  16  are mutually connected in series and the respective serially-connected pairs are mutually connected in parallel. 
   The pulse current, which has a frequency capable of switching the magnetic polarities of the excitation coils  16  at predetermined intervals, is fed from the excitation circuit  18 A to the first magnetic member  10 . In response to the pulse current, the excitation coils  16  arrayed in the circumferential direction exhibit magnetic polarities changing in a certain pattern of N, S, N, . . . at their poles facing the third magnetic member  14 , as shown in  FIGS. 2-5 . When the pulse current fed to the excitation coils  16  is reversed in its polarities, the excitation coils  16  arrayed in the circumferential direction exhibit magnetic polarities changing in the opposite pattern of S, N, S, . . . at their poles facing the third magnetic member  14 . Accordingly, the excitation polarity patterns taken on by the first magnetic member  10  can be changed periodically. 
   The second magnetic member  12  is structured in the similar way to the first magnetic member  10 , except that excitation coils  18  arrayed on the second magnetic member  12  are shifted in positions in the circumferential direction, compared to the excitation coils  16  on the first magnetic member  10 . That is, the excitation coils  18  on the second magnetic member  12  are arrayed in different pitches from the excitation coils  16  on the first magnetic member  10 , so that both coils  16  and  18  are arrayed in a predetermined pitch difference (corresponding to a predetermined angular difference) in the circumferential direction. 
   It is preferred that this pitch difference is set to a quantity corresponding to a distance through which the third magnetic member  14  (i.e., the permanent magnet) moves relatively to the excitation coils  16  and  18  during one cycle (2π) of the frequency of the excitation current. In other words, it is preferred that the distance is either the total distance (2π) of each pair of N and S polarities or ¼ (i.e., π/2) of the total distance. 
   The third magnetic member  14  will now be explained. As shown in  FIGS. 2-5 , the third magnetic member  14 , which is disposed between the first and second magnetic members  10  and  12 , is provided a plurality of permanent magnets  20  shown by black rectangles in  FIGS. 2-5 . The plural permanent magnets  20  are aligned at intervals in a linear form or an arc-like form to have their polarities reversed in turn. Preferably, the magnets  20  are arrayed at equal intervals in the circumferential direction. The arc-like form along which the magnets  20  are aligned can be changed into various forms, such as a complete circle, an ellipse, and others (i.e., a closed loop), an uncertain annular structure, a semi-circle, and a sector form. 
   The first and second magnetic members  10  and  12  are, for example, parallel to each other (with an equal distance therebetween). The third magnetic member  14  is arranged at the middle position between the first and second magnetic poles  10  and  12 . The permanent magnets  20  on the third magnetic member  14  are arrayed at equal pitches to the coils  16  and  18  on the first and second magnetic members  10  and  12 . 
   Referring to  FIGS. 2-5 , the operations of the magnetic member structure consisting of the first, second and third magnetic members  10 ,  12  and  14  will now be explained. 
   At a certain time instant, the foregoing excitation circuit  18 A (in  FIG. 6 ; which will be detailed later) allows the excitation coils  16  and  18  of the first and second magnetic members  10  and  12  to have polarities according to an excitation polarity pattern shown in a chart ( 1 ) in  FIG. 2 . 
   At this time, the respective excitation coils  16  on the first magnetic member  10  generate, at their coil ends facing the third magnetic member  14 , the magnetic poles in agreement with the pattern of S, N, S, N, . . . , etc. Concurrently with this, the respective excitation coils  18  on the second magnetic member  12  generate, at their coil ends facing the third magnetic member  14 , the magnetic poles in agreement with the pattern of N, S, N, S, . . . , etc. In the figure, each solid line arrow indicates an attractive force, while each dashed line arrow indicates a repulsive force. 
   At the next time instant, as shown in a chart ( 2 ) in  FIG. 2 , the excitation circuit  18 A inverses the polarities of the pulse current supplied to the first magnetic member  10 . This polarity inversion creates not only repulsive forces between the magnetic poles of the excitation coils  16  of the first magnetic member  10  and those of the permanent magnets  20  on the third magnetic member  14  but also attractive forces between the magnetic poles of the excitation coils  18  of the second magnetic member  12  and those of the permanent magnets  20  on the third magnetic member  14 . Such repulsive and attractive forces enable the third magnetic member  14  to move, in the case of the  FIG. 2 , rightward, as shown in charts ( 2 ) to ( 5 ) in  FIG. 2 . 
   The pulse current fed to the excitation coils  18  of the second magnetic member  12  is different in phase from that to the excitation coils  16  of the first magnetic member  10 . Thus, as shown in charts ( 6 ) to ( 8 ) in  FIG. 3 , the magnetic poles of the excitation coils  18  of the second magnetic member  12  become repulsive to those of the permanent magnets  20  of the third magnetic member  14 , thus further moving the third magnetic member  14  rightward. 
   The charts ( 1 ) to ( 8 ) in  FIGS. 2 and 3  illustrate a move of the third magnetic member  14  (i.e., the permanent magnets) along a distance corresponding to a ´radian. Similarly to this, charts ( 9 ) to ( 16 ) in  FIGS. 4 and 5  illustrate another move of the third magnetic member  14  along a distance corresponding to a second ´radian. Hence, the charts ( 1 ) to ( 16 ) show the third magnetic member  14  which relatively moves to the first and second magnetic members  10  and  12  over a distance corresponding to one cycle ( 2 ´) of the pulse currents, which are fed to the excitation coils  16  and  18  of the first and second magnetic members  10  and  12 . 
   Accordingly, supplying the pulse currents of different phases to the first and second magnetic members  12  and  14  (phases “A” and “B”) enables the third magnetic member  14  to rotate as a rotor. 
   When the first to third magnetic members  12 ,  14  and  16  are shaped circularly, the fin frame member shown in  FIGS. 1A and 1B  can be an electric rotary motor. Various components such as casing and rotor, which are other than the permanent magnets and excitation coils, may be formed of conductive materials, but it is preferred that such components are made of lightweight materials including resin serving as nonmagnetic material, aluminum, and magnesium alloy. Employing such lightweight materials leads to rotary electric machines which are lightweight and higher magnetic efficiency and provide open magnetic circuits. 
   In this magnetic-member structure, the third magnetic member  14  is movable responsively to the magnetic forces from and to the first and second magnetic members  10  and  12 . Hence amounts of torque that is a turning force for the third magnetic member becomes greater, being excellent in balance between the torque and the weight. It is therefore possible to provide a compact and lightweight electric motor that can be driven with higher torque. 
     FIG. 7  exemplifies a block diagram showing the configuration of the excitation circuit  18 A to apply exciting pulse currents to both of the excitation coils  16  (A-phase excitation coils) of the first magnetic member  10  and the excitation coils  18  (B-phase excitation coils) of the second magnetic member  12 . 
   This excitation circuit  18 A has a configuration in which pulse signals whose frequencies are controlled are fed to both of the A-phase and B-phase excitation coils  16  and  18 , respectively. This circuit  18 A is provided, as shown in  FIG. 7 , a quartz oscillator  30  oscillating a predetermined frequency signal and an M-PLL (phase-locked loop) circuit  31  creating a reference pulse signal by dividing the oscillated frequency signal by an arbitrary integer M. 
   The excitation circuit  18 A is also provided with sensors  34 A and  34 B consisting of an A-phase sensor  34 A and a B-phase sensor  34 B. Each sensor  34 A ( 34 B) senses a rotary position (angle) of the third magnetic member  14  (i.e., the rotor in the embodiment) and generates a position pulse signal depending on the rotation of the third magnetic member  14 . Preferably, a sensing piece incorporated in each sensor  34 A ( 34 B) may be a hall element or optical type element. 
   A plurality of holes (not shown) that equal in the number to the permanent magnets are formed in the rotor. When each hole is positioned right before the sensor  34 A ( 34 B) during each rotation, the sensor responds to the arrival of the hole by generating a pulse signal. Incidentally, such holes are unnecessary, provided that a magnetic type sensor is employed as the sensor  34 A ( 34 B), where a magnetic sensing element responding to each permanent magnet  20  on the third magnetic member  14  is used. 
   The A-phase sensor  34 A is in charge of sensing the position pulse signal to be supplied to a driver circuit for the A-phase excitation coils  16 , while the B-phase sensor  34 B is in charge of sensing the position pulse signal to be supplied to a driver circuit for the B-phase excitation coils  18 . Both driver circuits are incorporated in a driver  32  shown in  FIG. 7 . Practically, as illustrated, the position signals (i.e., pulse signals) from both sensors  34 A and  34 B are sent to the driver for feeding excitation currents to the first and second magnetic members  10  and  14 . 
   In addition, the excitation circuit  18 A is provided with a CPU (central processing unit)  33  to control the M-PLL circuit  31  and driver  32 . 
     FIG. 8  details in block form the configuration of the driver  32 , which includes an A-phase polarity switching circuit  32 A, B-phase polarity switching circuit  32 B, A-phase phase correcting circuit  32 C, B-phase phase correcting circuit  32 D, A-phase buffer  32 E, B-phase buffer  32 F, D-PLL circuit  32 G, and rotative direction switching circuit  32 H. 
   Provided to this driver  32  from the M-PLL circuit  31  is a reference signal, which is produced by M-dividing the frequency signal oscillated by the quarts oscillator  30 . This reference signal is subjected to polarity switching in the A-phase polarity switching circuit  32 A, before being supplied to the A-phase phase correcting circuit  32 C for controlling its phase. In the similar manner to this, the reference signal from the M-PLL circuit  31  is also subjected to polarity switching in the B-phase polarity switching circuit  32 B, and then supplied to the B-phase phase correcting circuit  32 D for controlling its phase. 
   Control signal from the CPU  33  are fed to the rotative direction switching circuit  32 H so as to selectively switch the normal rotation (or forward movement) and the reverse rotation (or backward movement) of the rotor (or a slider). This switching circuit  32 H operates under the control of the CPU  33  to control the A-phase and B-phase polarity switching circuits  32 A and  32 B in accordance with CPU-originated commands for the normal/reverse rotations. 
   The outputs, each showing an angular position of the third magnetic member  14 , from the A-phase and B-phase sensors  34 A and  34 B are fed to the A-phase and B-phase phase correcting circuits  32 C and  32 D, respectively. In addition, the polarity-switched reference signals from the A-phase and B-phase polarity switching circuits  32 A and  32 B are fed to the A- and B-phase phase correcting circuits  32 C and  32 D, respectively. Also supplied to each of the phase correcting circuits  32 C and  32 D is a signal which is created from the reference signal and the frequency of which is multiplied by a dividing rate of D after lock of the phase in the D-PLL circuit  32 J. 
   The CPU  33  accepts information regarding how to operate this fan unit from a not-shown operation means. The CPU  33  then uses such information to control the rotation speed of the rotor (or the movement speed of a slider) which is actually the third magnetic member  14 . For this control, the CPU  33  reads out a desired dividing rate for the parameter M (referred to as M dividing rate) from an internal memory in which a plurality of M dividing rates are mapped in advance. Based on the read-out M value, the CPU  33  changes the frequency of the reference signal. The similar control to the M value is applied to the control of the dividing rate D for the D-PLL circuit  32 J, which will be detailed later. These dividing rates are should be changed depending on desired operation characteristics of the third magnetic member  14 , such as rotation speeds of the rotor (or movement speeds of the slider). Such operation characteristics are reflected in the previously mapped data in memory tables in the internal memory. 
   Both of the phase correcting circuits  32 C and  32 D are responsible for providing the A-phase and B-phase excitation coils  16  and  18  with excitation pulse signals whose phases are mutually differentiated one from the other in a controlled manner This control is required for the rotation (or straight movement) of the third magnetic member  14 . Each of the phase correcting circuits  32 C and  32 D performs the correction by synchronizing the phase of each of the A-phase and B-phase excitation pulse signals with the position pulse signal from each of the A-phase and B-phase sensors  34 A and  34 B. 
   Each of the A-phase buffers  32 E and  32 F serves as circuit means for feeding the phase-corrected excitation signal to each of the A-phase and B-phase excitation coils  16  and  18 . 
   Referring to  FIGS. 9A to 9D , the mechanical configuration of the foregoing fan unit serving as an electric motor will now be detailed.  FIG. 9A  shows a perspective view of a disassembled fan unit;  FIG. 9B  is a plan view of the rotor (fins);  FIG. 9C  is a plan view of the A-phase excitation coils (on the first magnetic member); and  FIG. 9D  is a plan view of the B-phase excitation coils (on the second magnetic member). 
   The motor (i.e., fan unit) is provided with the paired A-phase (first) and B-phase (second) magnetic members  10  and  12  which serve as a stator of the motor and the third magnetic member  14  serving as the rotor, as desired. The third magnetic member  14  is disposed between the A-phase and B-phase magnetic members  10  and  12 , as sandwiched therebetween, with the third magnetic member (i.e. rotor)  14  rotatable about a center axis passing a central point O (refer to  FIGS. 9B to 9D ). 
   On the rotor  14 , six permanent magnets  20  (refer to  FIG. 2 , for example) are disposed at equal intervals along a circumferential direction. The polarities of the six permanent magnets  20  are alternately opposite to adjacent one. Similarly to this, six excitation coils  16  are disposed on the stator  10  (the first magnetic member) at equal intervals along the circumferential direction and six excitation coils  18  are disposed on the stator  12  (the second magnetic member) at equal intervals along the circumferential direction. The coils  16  and  18  have also been explained in terms of their functions in for example  FIG. 2 . 
   As shown in  FIGS. 9A and 9C , the A-phase and B-phase sensors  34 A and  34 B, which are formed into optical type sensors, are placed on the inner wall of a casing for the first magnetic member  10 , with an angular difference of π/2 [rad] secured between the two sensors  34 A and  34 B. This angular difference of π/2 [rad] is determined depending on a predetermined phase difference secured between the two types of excitation pulse signals fed to the A-phase and B-phase excitation coils  16  and  18 , respectively. 
   As described, along the circumferential edge of the disk-like rotor, i.e., the third magnetic member  14 , a plurality of holes (notches)  35  are formed at equal angular intervals. In this example, the number of holes  35  is six, which equal to the number of the permanent magnets  20  arrayed at equal intervals along the circumferential direction of the rotor. Each sensor  34 A ( 34 B) is equipped with a light emitter and a light receiver. Each hole  35  is configured to be a hole to absorb an emitted light beam or to be filled with a light absorption material. Thus, the emitted light beam from the light emitter is reflected by a portion of the rotor (the third magnetic member  14 ) other than the holes  35 , but absorbed by the holes  35 . That is, when each hole  35  is positioned in front of each sensor  34 A ( 34 B), the emitted light beam is absorbed and no light reflection is created. 
   Therefore, during each rotation of the rotor, every time when each hole  35  passes before each sensor  34 A ( 35 B), the sensor generates a pulse signal using the fact that there is no light reflection at the position to be detected where each hole  35  is just before each sensor  34 A ( 34 B). Hence each sensor  34 A ( 34 B) is able to generate a pulse signal, called the position pulse signal, whose frequency depends on both of a rotation speed of the rotor and the number of holes  35 . 
   A circular opening  300  is formed in a central part of each of the rotor  14  and stators  10  and  12 , so that a flow of fluid is allowed to pass through. In addition, a set of fins (composing a fan)  302  is attached to the rotor  14  as a one structure thereof and is located to cover the opening  300  of the rotor  14 . Thus, the rotation of the rotor  14  directly leads to the rotation of the fins  302  serving as suction means for fluid to pass through the opening  300 . Since this configuration allows the fins  302  to be located in a path through which the fluid passes, the fluid can be forcibly suctioned to pass along a predetermined direction through the opening  300 . 
   Mechanisms for rotating the rotor, in other words, the foregoing permanent magnets and the A-phase and B-phase excitation coils  16  and  18 , are disposed on the rotor  14  and the stators  10  and  12 , which are assembled to secure the opening  300  of which center axis serves as a common axis of the rotor  14  and the stators  10  and  12 . Hence, the rotation of the rotor  14  causes fluid to be sucked downward through the opening  300 . There exists no electric motor in the opening  300 , which means that no obstacles to resist the flow of fluid are present in the path 
     FIG. 10  illustrates wave patterns to attain the A-phase and B-phase excitation pulse signals, the processing being conducted by the driver  32 . In those wave patterns, the pattern ( 1 ) depicts the reference signal, while the patterns ( 2 ) and ( 3 ) depict the position pulse signals from the A-phase and B-phase sensors  34 A and  34 B, respectively. As described, both A-phase and B-phase sensors  34 A and  34 B are located on the motor so that there is a particular difference in the phases of the detected position pulse signals. In the example shown in  FIG. 10 , such a phase difference is π/2. 
   The foregoing A-phase phase correcting circuit  32 C executes a known PLL control to synchronize the phase of the detected position pulse signal (wave pattern ( 2 )) from the A-phase sensor  34 A with that of the reference pulse signal (wave pattern ( 1 ). As a result, a pulse signal to excite the A-phase excitation coils  16 , which is shown in the pattern ( 4 ), is produced and sent to the A-phase buffer  32 E. The buffer  32 E has a switching transistor circuit to receive, from the phase correcting circuit  32 C, the pulse signal of a particular frequency to perform the PWM control on the signal. 
   The B-phase phase correcting circuit  32 D is configured to operate in the same way as above. The wave pattern ( 5 ) in  FIG. 10  shows a pulse signal of a particular frequency, which is outputted from the B-phase phase correcting circuit  32 D to the B-phase buffer  32 F for the B-phase excitation coils  18 . As compared between the wave patterns ( 4 ) and ( 5 ), there is a relative phase difference of π/2 between the excitation pulse signals fed to the A-phase and B-phase excitation coils  16  and  18 , respectively. 
     FIG. 11  shows wave patterns necessary for inversing the rotation of the motor (or movement of the slider), in which wave patterns ( 1 ) to ( 5 ) illustrated therein correspond to the wave patterns ( 1 ) to ( 5 ) in  FIG. 10 . As clear from the comparison between the wave patterns in  FIGS. 10 and 11 , there is only a difference concerning the excitation pulse signal to be fed to the B-phase excitation coils  18 . Specifically, the polarity of the excitation pulse signal is inverted one from the other, as shown by the wave patterns ( 5 ) in  FIGS. 10 and 11 . When the excitation pulse signal is changed from the pattern ( 5 ) in  FIG. 10  to that in  FIG. 11 , a braking force is applied to the rotation (or sliding) executed under the control of the wave patterns in  FIG. 10 . 
     FIG. 12  details each of the foregoing A-phase and B-phase buffers  32 E and  32 F. This buffer has circuitry including a set of switching transistors TR 1  to TR 4  and an inverter  35 A, which are responsible for producing the excitation pulse signal to be applied to each of the A-phase and B-phase excitation coils. 
   Let assume that a logical signal of “H” is applied to the buffer shown in  FIG. 12 . This signal application causes the transistors TR 1 , TR 2 , TR 3  and TR 4  to turn off, turn on, turn on, and turn off, respectively, resulting in an excitation pulse current Ib (refer to an arrow Ib) through the A-phase or B-phase excitation coils  16  or  18 . 
   In contrast, when a logical signal of “L” is applied to the buffer shown in  FIG. 12 , the transistors TR 1 , TR 2 , TR 3  and TR 4  are turned on, turned off, turned off, and turned on, respectively. Accordingly, an excitation pulse current Ia that is opposite in the direction to the foregoing current Ib (refer to an arrow Ia) flows through the A-phase or B-phase excitation coils  16  or  18 . In consequence, the excitation patterns for the A-phase and B-phase excitation coils  16  and  18  can be changed alternately, as described before. 
   In the present embodiment, the shape of the rotor and/or stator, that is, the third magnetic member  14  and/or the first and second magnetic members  10  and  12  have been explained as having circular contours. However, this is not a definitive list, but those members may have arch-like contours or elliptic contours. Further, the number of holes  35  may also be changed to another value, not limited to the value which is equal to the number of permanent magnets. By way of example, the number of holes may be one or more. 
     FIGS. 13A and 13B  show a fan unit  400  employing the foregoing various structures like the fin/frame structure and rotation mechanisms, but the fan unit  400  is drawn in a simplified manner.  FIG. 13A  is a plan view of the fan unit along the axial direction, while  FIG. 13B  is a sectional view taken along an A-A line in  FIG. 13B . In those figures, a reference  304  depicts a frame portion (including the annular outer frame  1  shown in  FIGS. 1A and 1B ), a reference  306  depicts a guide, and references  308  depict bearings. Within the frame portion  304 , a plurality of the permanent magnets  20  are arrayed along the circumferential direction, which are shown in  FIG. 9 . The frame  304  is supported along the guide  306  using the bearings  308 . 
     FIG. 14  shows one example of practical applications of the fan unit  400 . In this example, the fan unit  400  is applied to a duct  310  having an inlet  311  and an outlet  312  of which diameter is made larger. A single fan unit  400  is placed in the course of the duct  310 . When the foregoing A-phase and B-phase excitation pulse signals are produced in the fan unit  400 , the rotor with the fins are rotated. Thus fluid such as gas or air is drawn in through the inlet  311  and forcibly sent out from the outlet  312 . 
     FIG. 15  shows another example of practical applications of the fan unit  400 . This example uses a plurality of fan units  400  along the same fluid path, which is different from the configuration shown in  FIG. 14 . As shown in  FIG. 15 , the plural fan units  400  (for example, four units) are aligned in series along the duct path so as to constitute a multiple-stage fin structure. 
     FIG. 16  shows another example. This example is similar to that in  FIG. 15  in that the plural fan units  400  are used. However, in this example, those fan units  400  are combined into a single plate to constitute a multiple parallel fin structure. Both structures in  FIGS. 15 and 16  can be combined with each other. 
     FIGS. 17A and 17B  show another example, in which two fan units  400  each composed of the foregoing one are placed in series in a duct  620 , close to a duct opening  620 A of the duct  620 . 
     FIGS. 18A and 18B  show another application, in which the foregoing fan unit  400  is applied to an airship  630  having a weight part  631 . The fan unit  400  serving as a floating part is placed on the weight part  631 . 
   In the foregoing embodiments and its various applications, by stopping supplying the excitation pulse currents to both A-phase and B-phase excitation coils, dynamic braking control is carried out by the rotations of the rotor. Additionally, since the rotor is rotated on magnetic force, the fan unit can be applied to a path through which explosive gas flows. The structure of the motor to rotate the rotor is not limited to the foregoing one. 
   The foregoing explanations are directed to the rotation of fins to generate flow of fluid to be targeted, but the opposite way to the above can also be realized. In other words, it can be configured such that the fan unit  400  is forcibly driven by incoming fluid, whereby the fan unit  400  is able to serve as a generator. Additionally, an integrated application is also possible. For example, the A-phase excitation coils are used as a generator, while the B-phase excitation coils are used for control of rotary load. In this configuration, even when the fins encounter a sharp fluctuation in fluid flow, the load control done by the B-phase excitation coils gives a constant number of rotations of the fan unit  400 , thus easily generating stable voltage. 
     FIG. 19  also shows an application, in which a heat exchange system is constructed by using the foregoing fan unit. In this heat exchange system, there are provided a housing  300  in which a rotor  310  with fins are rotatably contained. The periphery part of the rotor  310 , which is rotatably supported by bearings  306  attached to a recess formed on the housing  300 , is composed of a plate part with permanent magnets  304 . The front and rear of the periphery part, which is an array of the permanent magnets  304 , are respectively opposed excitation coils  308  disposed on both inner walls of the recess of the housing  300 . The bearings  306  are made of ceramics, which are non-magnetic members which can be excluded from magnetic loads. 
   The rotor  310  in the housing  300  acts as a compressor, which pressurizes material to be heat-exchanged (such as alternative Freon) in an upper section  322  and sends the pressurized material into an adjacent lower section  324 . This lower section  324  is connected to a heat exchanging device  312  via a path  301 , for discharging heat accumulated in the pressurized material. The heat exchanging device  312  is combined with warming fins  314 . The heat exchanging device  312  is connected to a further heat exchanging device  320  via a path  303 . This heat exchanging device  320  is combined with cooling fins  316 . While the material passes the heat exchanging device  320 , the material absorbs environmental heat to evaporate, and the evaporated material returns to the upper section  302  via a path  305 . In this heat exchange system, the rotor  310 , that is, the fins, is rotatably supported between the two mutually opposed arrays of excitation coils. Accordingly, both of the support and the drive of the fins can be combined into one structure member, thus making both fins and housing compact. When this cooling system is applied to imaging apparatuses such as projectors, the cooling operation can be more effective, compared to the existing ones. 
     FIG. 20  shows another application which is similar to that in  FIG. 19  except that the cooling heat exchanging device  320  is applied to a heat source  350  of an electronics device. Hence the heat source, such as light source and semiconductor circuit, can be cooled effectively. 
     FIG. 21  shows another application, in which the foregoing fan unit  699  is also used. That is, between mutually opposed two stators  700  with excitation coils, a rotor  702  with permanent magnets is rotatably supported by baring  706  placed on a housing  704 . Large-size fins  708  are attached to the rotor  702 . An opening  707  is formed through the rotor  702  at a central part thereof. Making the fins  708  compact will lead to a pump for circulating blood, which can be applied to the human body. The rotation of the rotor  702  (i.e., the fins  708 ) causes blood to flow downstream through the opening  707 . A sensor  709  to detect the rotary position of the rotor  702  is secured to the housing  704 . 
   The above pump shown in  FIG. 21  can also be used as shown in  FIG. 22 , in which the pump is arranged to discharge nutrient medium for plant. Plural types of nutrient A and B and water on an upstream side are blended together when they are obliged to flow through the opening  707  in response to the rotations of the rotor  702 , and the blended water is discharged downstream. 
     FIGS. 23A and 23B  to  25 A and  25 B show other examples of the fan unit according to the present embodiment, in which the foregoing fan unit  400  is further modified. For the sake of an easier understanding, the references employed in  FIGS. 21 and 22  are used again to explain. 
   In the case of a fan unit  710  shown in  FIGS. 23A and 23B , a housing  704  is formed into an almost cylindrical and short-axis shape to contain fins  708  therein. The fins  708  are disposed to rotate around a rotation shaft  711  placed at the radial center of the housing  704 . The rotation shaft  711  is rotatably supported by a pair of bearings  712  disposed on both axial ends of the rotation shaft  711 . On both axial sides of the housing  704 , each bearing  712  is connected to the circumferential periphery of the housing  704  by three support bars  713 . The remaining components are identical or similar in configurations and operations to those in  FIGS. 21 and 22 . Hence, the fins  708  can be rotated around the central rotation shaft  712  on the basis of the same principle as the foregoing. Since the fins  708  are supported by the central rotation shaft  712 , the support structure for the fins  712  can be simplified. 
   The structure in  FIGS. 23A and 23B  can further be modified that shown in  FIGS. 24A and 24B . This structure is almost similar to those in  FIGS. 23A and 23B , except that the first and second magnetic members with excitation coils  700  are formed in parallel with the axial direction of a fan unit  720 . The third magnetic member with the permanent magnets  702  are inserted between the first and second magnetic members with excitation coils  700  and also in parallel with the axial direction. The fins  708  are coupled with the third magnetic member using L-shaped connections  721 . Hence it is also possible for this fan unit  720  to operate in the same way as the foregoing. 
   In addition, the structure in  FIGS. 25A and 25B  is also a modified fan unit  730 , in which there is a housing  731  formed into a rectangular shape, when viewed along the axial direction thereof. A rotation shaft  732  is arranged at the center, like the above in  FIGS. 24A and 24B , but only one bearing  733  supports the rotation shaft  732 . Thus, support bars connecting the bearing  733  and the housing  704  are arranged only one axial side of the housing  704 . That is, the support on the one-sided bearing system is employed. Each of the first and second magnetic members with excitation coils  700  is divided into four sections each disposed at the four corners as shown in  FIG. 25B . Hence it is also possible for this fan unit  720  to operate in the same way as the foregoing. 
   The present invention will not restricted to the constructions shown in the foregoing embodiments, but a person having ordinary skill in the art can create a variety of constructions adequately altered or deformed within the scope of the claims.