CA1205115A - Simple brushless dc fan motor - Google PatentsSimple brushless dc fan motor
- Publication number
- CA1205115A CA1205115A CA000435800A CA435800A CA1205115A CA 1205115 A CA1205115 A CA 1205115A CA 000435800 A CA000435800 A CA 000435800A CA 435800 A CA435800 A CA 435800A CA 1205115 A CA1205115 A CA 1205115A
- Prior art keywords
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D25/00—Pumping installations or systems
- F04D25/02—Units comprising pumps and their driving means
- F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
- F04D25/0606—Units comprising pumps and their driving means the pump being electrically driven the electric motor being specially adapted for integration in the pump
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
- H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices
- H02K29/08—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices using magnetic effect devices, e.g. Hall-plates, magneto-resistors
A simplified fan and brushless DC motor employs an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially mag-netized with respect to the preceding segment as one pro-cedes around the magnet. Fan blades are located within the annular magnet. A coil and electromagnet structure defining two pole pieces reside outside the permanent magnet annulus.
A Hall effect device switches the coil off and on in response to passage of the segments of the rotor magnet. Thus com-mutated, the single coil affects rotation of the rotor and the fan blades. A permanent magnet supported on the stator structure serves to magnetically detent the permanent magnet of the rotor, bringing the rotor to rest correctly for restarting.
, , ~, , SPECIFICATION
_ BACKGROUND OF THE INVENTION
This invention relates to brushless DC motors electronically commutated and more particularly to brushless DC fan motors that are of simple construction, inexpensive to manufacture, and reliable.
A typical goal in the manufacture of fans is a motor that is very simple and consequently has a low manu-facturing cost. In AC motors for fans, the side armature AC
motor comes closest to achieving these goals. However, recently, DC motors for fans have become more and more attractive, particularly for fans used to cool electronics where DC power is available.
Brushless DC motors using ~all effect devices to sense the commutation points as the rotor rotates are well known in the art. One or more stator coils are repeatedly ~2~S~
energized or have their energization reversed to effect relocation of the electromagnetic field produced by poles of the stator core. A permanent magnet rotor is continuously att~acted to the new electromagnetic pole locations. For commutation, one or more Hall effect devices senses the location of the poles of the rotor permanent magnet to control the eneryization of the stator winding or windinys, or a EIall device detects the~position of oIle or more com-mutation magnets mounted to rotate with the rotor and provided especially to indicate, by changing the state of the Hall device, the commutation points as the rotor turns.
Many brushless DC motors have been complex in both their structure and their commutation circuitry. Where simple, low cost and reliable fan motors have been needed these brushless DC motors, whlch might more appropriately have been used for, say, precise disc or tape drives, have been too expensive for the simple purpose of fan rotation.
BRIEF SU~ARY OF THE INVENTION
In accordance with this invention, a simple DC
brushless motor has a rotor with an annular permanent magnet and a stator coil and electromagnet structure outside the annular magnet. The annular magnet of the rotor is mag-netized in segments about its circumference, each succeeding segment being oppositely magnetized in the radial direction.
The electromagnet structure includes pole pieces magnetized by the coil and closely proximate the outer cylindrical surface of the annular magnet. A Hall effect device senses , ~2~5~S
the passage of the rotor magnet segments to turn the coil on and off. The location of the electromagnet pole pieces and of the Hall effect device are such that, each time the coil is energized, the corr~ct magnetic polarities are established at the pole pieces to attract the next approaching s~gments or poles of the annular ma~net.
A further permanent magnet supported on the stator structure close to the periphery of the annular rotor magnet magnetically detents the annular magnet so that the rotor is correctly positioned for start up.
In the fan of the invention, fan blades are located within and affixed to the annular magnet. The magnet and the fan blades are mounted for rotation at a central hub.
The stator includes a housing and support structure extending from proximate the magnet to the hub and supporting the rotor hub for rotation. The housing encircles the annular magnet and the fan blades. The support structure includes mounting means formed in the housing about the periphery of the motor.
~ small compartment in the housing houses the stator coil, the electromagnet structure and all circuit elements of the relatively simple switching circuitry, including the commuta-tion-effecting ~all device~
Whereas, with its large annular rotor and external stator structure, the motor of this invention misht not be adva~tageous for certain other applications, it is particu-larly suitable for fans. The tips of fan blades ordinarily define a circular path and the area within the circle is necessarily used. Driving the fan blades directly from a magnet secured to the blade tips thus re~uires little ~r~
additional space and permits a narrow fan since there is no need to couple a motor to the hub or shaft supporting the blades centrally. The drive is ef~icient and is economically accomplished in that the rotary force applied to the magnet is imparted directly to the blades. Less force is required to move the blades against a load than when force is applied where the blades are centrally supported. Furthermore, using the rotor of the current invention a large proportion of the circular area from the blade tips inward can be devoted to air 10w, inasmuch as no space therein is taken up by motor. The advantages of the combination fan and rotor, then, surpass the apparent sum of the advantages of each.
The above and further features of the invention will be better understood with reference to the several figures of the attached drawings and the following detailed description of a preferred embodiment.
DESCRIPTION OF THE DRAWINGS_ . _ . .. . .
In the drawings:
Figure 1 is a top plan view of the fan and motor according to this invention and shows the rotor's annular permanent magnet magnetized in segments about its periphery and an external coil and electromagnet stator structure.
Figure 2 is a side elevational view of the fan and motor of Figure 1, partially in section, along the line 2-2 of Fig. 1, and illustrates the mounting of the rotor and fan blades on a hub for rotation about a central support section of the stator.
Figure 3 is a schematic diagram of an energizing circuit for the stator coil.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 a fan and motor combination 10 accord-ing to the invention includes a rotor 11 and a stator 12.
The rotor 11 has an annular permanent magnet 14, magnetized in segments about its circumference. As illustrated, each succeeding segment about the circumference is oppositely magneti~ed in the radial direction. The magnet 14 is secured on a ring 16. Fan blades 17 extend from the ring 16 to a central hub 19.
In Figure 2, the hub 19 carries a shat 21 sup-ported in the sleeve bearing 22 located in a bore 23 formed ln a central projecting portion 25 of the stator 12. C-rings 28 and 29 retain the bearing and secure the rotor and stator together. Spacers or shims 31 take up any excess end play in the assembly. The particular mounting employed to locate the rotor assembly and fan blades rotatably ~ithin the stator structure i5 exemplary only and not to be construed as essen-tial to the invention. For example, roller bearings or otherbearing structure can be substituted for the sleeve bearing 22 and other arran~ements than the shaft 21 and bore 23 will readily be envisioned.
Three struts 33 radiate outwardly from the central stator projection 25. These connect to a generally circular housing 34. Mounting bGsses 35 define holes 36 ab~ut t~
periphery of the housing, enabling the entire motor and fan to be mounted by, e.g., bolts passed through the holes 36.
At one location, as seen at the bottom of Figure 1, the housing 34 forms a compartment 40 housing a stator coil 41, electromagnet structure 4~, a Hall effect device Xl, and the remaining circuit elements of the commutation circuit, not shown in Figure 1. The coil 41 is wound on a bobbin 43.
A core 44 o magnetic material extends through the bobbin from end to end and forms a part of the electromagnet structure 42. Alternatively, the bobbin can be a part of the electromagnet structure. That structure also includes a pair of arms 46 and 47 secured in flux conducting relation to the magnetic core 44 and terminating in pole pieces 48 and 49 closely proximate the outer surface of the permanent magnet 14. As can be seen in Figure 1, the spacing of the pole pieces 48 and 49 is such that, with the magnet located as shownr energization of the coil 41 to make pole piece 48 north and pole piece 49 south will affect clockwise rotation of the rotor structure and the fan blades.
A further permanent magnet 50 magnetically detents the annular rotor magnet in a position such that starting of the motor and fan is assured. At start-up, the coil is ener-gized to applyr via the pole pieces 48 and 49, starting torque to the annular magnet. The Hall effect device X1 controls eneryization of the coil 41 such that the coil is energized to attract approaching poles of the annular rotor magnet and then deenergized when the magnetic field of the annular permanent magnet is reversed at the ~all device as a result of movement of a new, oppositely magnetically polar-ized segment into proximity with the deviceO Deenergization of the coil allows passage o= the next poles past the pole , pieces 48 and 49 until the Hall device Xl senses the rever-sal of the magnetic field, signaling the approach of the next segrnents. The coil is reenergized and the pole pieces attract the next two segments. This sequence repeats itself until the rotor comes to an e~uilibrium speed where the aerodynamic load balances the motor power.
This operation allows use of a simplified com-mutation circuit. In Figure 3, the Hall device Xl, which can be a Hall switch, for example, is seen controlling a transistor Ql whose collector-emitter circuit is in series with the stator coil 41. One such Hall switch is the sprague UGN-3013T of Sprague Electric Companyt Worcester, Mass. Exposure of the Hall effect device X1 to a magnetic field o the correct direction or polarity opens (breaks) a conduction path from a line 51 to ground. With this path thus open, a resistor Rl supplies base drive to Ql, biasing Ql into conduction and energizing the coil 41. When the Hall effect device Xl experiences a magnetic field of reverse direction or polarity, or no field at all, the current path from ground to Rl and the base of Ql closes.
This path of conduction, now closed, starves Ql of base drive and Ql no longer conducts, the coil 41 is deenergized until Xl experiences a field of the appropriate direction again. Capacitor Cl damps transients that arise from the abrupt switching of the coil 41. The diode CRl prevents current reversals back through the input leads to, for example, the electronics being cooled. Typically, the input power to this simple circ~it arrangement is taken from the DC bias voltage available nearby in the cooled electronics.
25~76 ~Z~5~5 In a preferred embodiment, the circuit elements are mounted on a printed circuitboard of essentially the same shape as the cavity that forms ~he compartment 40 in E`igure 1. The circuitboard is supported above the cavity with the circuit elements projecting downward and housed within the cavity so that the fan and motor has the compact shape seen in Figure 1 and the narrow profile shown in Figure 2.
From the foregoing it will be seen that a simple and quite original combination of motor and fan has been provided. It will be readily apparent to those skilled in the art that many variations in the foregoing exemplary embodiment can be made without departing from the spirit and scope of the invent.ion, as defined in the depen~ant claims.
a rotor with an annular permanent magnet, the magnet defining magnetic segments, wherein segments of like polarization in the radial outward direction are spaced apart circumferentially about the magnet;
a stator having an electromagnet structure outside said annular magnet, proximate the periphery thereof, the electromagnet structure including, in a location to one side of the annular magnet and extending less than 180° around the magnet, coil means and electromagnetic flux conducting means in flux conducting relation to the coil and located to establish a magnetic field applying rotational torque to the annular magnet;
position detecting means for commutating electrical current to the coil means to repeatedly produce said field and apply torque to succeeding segments as the rotor rotates.
a rotor with a large, narrow annular permanent magnet, the magnet having a large central opening that is at least twice the radial thickness of the magnet, the magnet defining radially magnetized magnetic segments extending circumferentially, segments of like polarization in the radial outward direction being spaced apart circumferentially about the magnet;
a stator outside of the annular magnet with electromagnetic field producing means proximate the periphery of the annular magnet;
means controlling energization of the field producing means to cause said field producing means to apply rotational torque to the annular magnet, said energization controlling means comprising position detecting means for commutating electrical current to the electromagnetic field producing means.
Priority Applications (2)
|Application Number||Priority Date||Filing Date||Title|
|Publication Number||Publication Date|
|CA1205115A true CA1205115A (en)||1986-05-27|
Family Applications (1)
|Application Number||Title||Priority Date||Filing Date|
|CA000435800A Expired CA1205115A (en)||1982-09-10||1983-08-31||Simple brushless dc fan motor|
Country Status (5)
|JP (1)||JPS5967862A (en)|
|BR (1)||BR8304892A (en)|
|CA (1)||CA1205115A (en)|
|DE (1)||DE3332659C2 (en)|
|FR (1)||FR2533085B1 (en)|
Families Citing this family (7)
|Publication number||Priority date||Publication date||Assignee||Title|
|JPS61123664U (en) *||1985-01-21||1986-08-04|
|US4618806A (en) *||1985-02-11||1986-10-21||Rotron, Inc.||Ironless, brushless DC motor with wave-winding|
|DE3638282B4 (en) *||1985-11-08||2006-05-04||Papst Licensing Gmbh & Co. Kg||Axialkleinstgebläse|
|DE29718082U1 (en) *||1997-10-11||1999-02-11||Papst Motoren Gmbh & Co Kg||Small fan unit, particularly for use as a circuit board fan|
|DE10036339A1 (en) *||2000-07-26||2002-02-07||Bayerische Motoren Werke Ag||Extremely thin and powerful fan e.g. for vehicle, comprises motor with external polyphase stator winding and iron magnetic return circuit|
|DE10156941B4 (en) *||2001-11-20||2007-05-31||Sunonwealth Electric Machine Industry Co., Ltd.||A brushless DC motor|
|ES2469440T3 (en)||2009-05-06||2014-06-18||Munters Corporation||Fan for use in agriculture|
Family Cites Families (13)
|Publication number||Priority date||Publication date||Assignee||Title|
|US1996195A (en) *||1933-05-05||1935-04-02||Julian K Ferguson||Electric fan|
|DE819281C (en) *||1948-10-02||1951-10-31||Telefunken Gmbh||Electrically driven fan|
|US3333172A (en) *||1966-03-30||1967-07-25||Harrison D Brailsford||Direct current oscillator fed motor|
|FR1531531A (en) *||1967-05-22||1968-07-05||Radiotechnique Coprim Rtc||DC brushless motor|
|CA971365A (en) *||1971-08-19||1975-07-22||George A. Lane||Pyrotechnic composition for inflation of passive restraint systems|
|US3909643A (en) *||1973-03-30||1975-09-30||Victor Company Of Japan||Direct-driven type phonograph turntable|
|CH612736A5 (en) *||1976-04-27||1979-08-15||Papst Motoren Kg|
|JPS5523711A (en) *||1978-07-29||1980-02-20||Sony Corp||Rotary electric machine|
|CH658348A5 (en) *||1979-11-30||1986-10-31||Papst Motoren Kg||Two-pulse brushless dc motor.|
|DE3026797C2 (en) *||1980-07-15||1986-09-11||Ebm Elektrobau Mulfingen Gmbh & Co, 7119 Mulfingen, De|
|FR2501933B1 (en) *||1981-03-13||1984-11-09||Peugeot Aciers Et Outillage|
|JPS5866553A (en) *||1981-10-13||1983-04-20||Matsushita Electric Works Ltd||Fan motor|
|EP0093817B1 (en) *||1982-05-10||1986-09-10||ACIERS ET OUTILLAGE PEUGEOT Société dite:||Ventilator unit for internal-combustion engines of automotive vehicles|
- 1983-08-31 CA CA000435800A patent/CA1205115A/en not_active Expired
- 1983-09-08 BR BR8304892A patent/BR8304892A/en unknown
- 1983-09-09 DE DE19833332659 patent/DE3332659C2/de not_active Expired
- 1983-09-09 JP JP16641883A patent/JPS5967862A/en active Pending
- 1983-09-09 FR FR8314412A patent/FR2533085B1/en not_active Expired - Lifetime
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