An electronically commutated motor is described that has a stator, carrying at least two winding phases, multiple magnet poles and grooves and a rotor, in which a defined position between the rotor and the stator can be detected by way of a position sensing device. A rotation speed and power output of the motor can easily be influenced by the fact that the magnet poles have regions with air gaps of different heights from the rotor; and that onset times of a temporally successively occurring energization of the at least two winding phases can be varied in terms of the position between the rotor and the stator and/or the energization duration of the at least two winding phases.

FIELD OF THE INVENTION
 The present invention relates to an electronically commutated motor that
 has a stator, carrying at least two winding phases, multiple magnet poles
 and grooves and a rotor, in which a defined position between the rotor and
 the stator can be detected by way of a position sensing device.
 BACKGROUND INFORMATION
 In the case of conventional electronically commutated motors of this kind,
 graduation of output is usually implemented by varying the electronic
 activation, e.g. by pulse width modulation of the power output stage of
 the energization device. When the power output stage is cycled, this
 results in additional electronic losses and thus, in a reduction in motor
 efficiency. Attempts have been made to graduate the output by way of
 special winding variants, but this results in increased manufacturing cost
 for of the stator.
 SUMMARY OF THE INVENTION
 An object of the present invention, in the case of an electronically
 commutated motor, is to graduate output and influence rotation speed with
 a simple motor configuration for the stator and with low-loss
 energization.
 According to the invention, this object is achieved in that the magnet
 poles have regions that have air gaps of different heights from the rotor;
 and the onset times of the temporally successively occurring energization
 of the winding phases can be varied in terms of the position between the
 rotor and the stator and/or the energization durations of the winding
 phases.
 With a winding configuration known per se it is possible, merely by way of
 the configuration of the magnet poles on the stator and by varying the
 energization time and/or energization duration, to obtain a different
 working characteristic curve and/or cover a large working field.
 According to an embodiment, energization of the winding phases is
 accomplished periodically. The period duration, energization onset times
 and/or durations of the energization and/or the current determine the
 rotation speed and/or power output of the motor. In this context, for
 energization over the entire period of time, energization of the winding
 phases may occur in immediate succession; while for partial energization,
 activations of the winding phases can be performed with a time interval in
 between.
 The magnet poles of the stator can form air gaps set back in stepped
 fashion from the rotor, or can have regions in which the air gap with
 respect to the rotor continuously changes.
 If, according to an embodiment, the grooves alternately delimit wide magnet
 poles and narrow return flux poles, and for the winding phases to have
 subwindings, alternately nested into one another, that are each wound
 around only one magnet pole and change winding direction from one
 subwinding to another or--if the current direction is different--are wound
 in the same direction, the result is a winding configuration in which the
 winding phases do not overlap. This eliminates winding terminations at the
 axial ends of the stator, thus making production of the stator simpler and
 less expensive. The motor also requires less space and has higher
 efficiency.
 The motor can be configured as an internal-rotor or external-rotor motor.
 It is advantageous in this context if the rotor is equipped with permanent
 magnets. The different working characteristic curves--governed by the
 differing height of the air gaps in the region of the magnet poles--can
 also be achieved with an electrically excited motor.

DETAILED DESCRIPTION
 As shown by the motor configuration according to FIG. 1, in an
 external-rotor motor a stator St is surrounded by a rotor R that
 alternatingly carries north poles N and south poles S. These north and
 south poles can preferably, but not exclusively, be permanent magnets that
 face toward stator St with concave pole surfaces. Stator St itself is
 subdivided by grooves NT that delimit T-shaped magnet poles MP1, MP2, MP3,
 MP4, MP5, MP6, MP7, and MPn, and return flux poles RP1, RP2, RP3, RP4,
 RP5, RP6, RP7, and RPn. As is evident from FIG. 6, magnet poles MP1
 through MPn constitute, with respect to the pole surfaces of rotor R,
 regions B1 and B2 that have short and tall air gaps L1 and L2. Height
 regions B1 and B2 extend over the same angular region of stator St, i.e.
 they are of approximately the same width. Both regions B1 and B2 also
 cover the angular region of the pole surface of the permanent magnets. The
 pole surfaces of return flux magnets RP1 through RP8 extend over only
 approximately half the angular region of magnet poles MP1 through MPn, and
 north and south poles N and S.
 Associated with rotor R is a position sensing device EF that indicates that
 rotor R has reached a defined position with respect to stator St so as to
 yield a time reference variable tO for onset time t1 and t2 for
 energization of winding phases W1 and W2 of stator St.
 FIGS. 2a and 2b depict energization diagrams for winding phases W1 and W2.
 It is assumed in this context that the zero point at t0 corresponds to the
 time at which the defined position between R and stator St is reached. The
 respective associated working characteristic curves are depicted in FIG.
 3.
 If energization of winding phase W1 is begun at time t1, and if
 energization is repeated in pulsed fashion each time with a period P of
 equal length, the result is the motor working characteristic curves
 labeled n1 and l1 in FIG. 3, if energization is performed when air gaps L2
 are effective. The energization duration accounts for only a portion, e.g.
 one-quarter, of period P. As shown by diagram pair I in FIG. 2a,
 energization of winding phase W2 occurs with an offset of half a period P,
 and is periodic in the same fashion, so that an unenergized interval Ta is
 present between energization of winding phase W1 and energization of
 winding phase W2.
 If energization of winding phase W1 does not occur until time t2 (diagram
 pair II), the working characteristic curves obtained--retaining the same
 period P and the same energization conditions for the two winding pairs W1
 and W2--are those labeled n2 and l2 in FIG. 3. Energization then coincides
 with the position of rotor R and stator St when air gaps L1 are active.
 If winding phases W1 and W2 are energized in accordance with diagram pair
 III of FIGS. 2a and 2b, the result is then, assuming an onset time t1 for
 winding phase W1 and an energization duration that corresponds in each
 case to one-half of period P, the working characteristic curves labeled n3
 and l3 in FIG. 3.
 FIG. 3 shows a plot of the proportional torques M1 and M2 and total torque
 Mges of the motor resulting from an energization of winding phases W1 and
 W2 using onset time t1 and the energization profile according to diagram
 pair III.
 FIG. 4 shows a plot of the working characteristic curves obtained using
 energization diagram pairs I and II as shown in FIG. 2. These two
 energization diagram pairs I and II for winding phases W1 and W2 differ
 only in terms of onset times t1 and t2, so that by changing the onset time
 from t1 to t2 it is possible to cover the shaded working range AF1 shown
 in FIG. 4.
 Considering now the working characteristics curve in FIG. 5 for
 energization using diagram pair III shown in FIGS. 2a and 2b, it is
 evident that the substantially larger shaded working range AF2 can be
 covered by changing the onset time from t1 to t2 and changing the
 energization duration from one-quarter to one-half of period P for winding
 phases W1 and W2.
 FIG. 6 shows different embodiments of the pole surfaces for magnet poles
 MPn of stator St. In this context, regions B1, B2, and B3 that have air
 gaps L1, L2, and L3 of different heights can extend over the same angular
 region of the magnet pole or also over angular regions of different sizes.
 The regions also can be of multi-stepped configuration. In addition, air
 gaps L4 also can continuously increase or decrease over region B4, and can
 be a curved configuration. The regions on magnet poles MPn also can be of
 different sizes and can be equipped with different air gaps.
 The present invention is also applicable to stators St wound in different
 fashions, and is not limited to the configuration of stator St and rotor R
 shown in FIG. 1. The motor also can be configured as an internal-rotor
 motor, and the rotor can be electrically excited.