Electronically commutated motor The invention relates to an electronically commutated motor with a permanent magnetic rotor and a stator. Such a motor is the subject of the earlier patent application WO / EP97 / 01078.
It is an object of the invention to provide a new electronically commutated motor.
According to the invention, this object is achieved by an electronically commutated motor with a permanent-magnet rotor and a stator, with a plurality of rotor position sensor arrangements arranged on the stator side, which are connected in series to a DC voltage source for power supply, each having two antivalent signal outputs, and during operation of the motor provide an alternating sensor output voltage between these antivaltent signal outputs, with each rotor position sensor being assigned a phase shifter arrangement which serves to phase-shift this sensor output voltage in order to generate an alternating output signal which leads in time with respect to the sensor output voltage and whose lead angle relative to the sensor output voltage increases with increasing engine speed increases
and which is used to control at least one stator current of the motor via an electronic switching element controlled by this alternating output signal. One obtains in a very simple and energy-saving manner a plurality of output signals which, by appropriate arrangement of the rotor position sensors on the stator, can have the desired phase positions relative to one another, and whose phase positions change in the same sense depending on the speed in order to change the phase position of these signals for the to improve each speed in a simple manner.
The efficiency of such a motor is therefore improved by the fact that the rotor position sensors have a reduced power requirement because they are flowed through by the same current, and on the other hand by the so-called ignition angle, i.e. the phase position of the commutation, to the speed of the motor is adjusted. (The “firing angle” is understood to mean the start of commutation. Because of its clarity, this term has been adopted from automotive technology, although nothing is “ignited” in the case of an electric motor.) Further details and advantageous developments of the invention result from those described below and illustrated in the drawing, in no way to be understood as a limitation of the invention, and from the dependent claims.
1 shows a block diagram of a three-phase collectorless
2A and 2B, details of the circuit according to FIG. 1, FIG. 3 representations of time profiles to explain the exemplary motor according to FIGS. 1 and 2, FIG. 4 a circuit diagram of a Arrangement according to the invention for detecting the rotor position and for changing the speed as a function of speed
5 was a schematic diagram showing the generation of an alternating phase position of the detected rotor position signals
Output voltage u between the two antivalent
6 shows a representation of the alternating output signal u of FIG. 5, FIG. 7 shows a representation analogous to FIG. 4, but only for one phase of the motor, FIG. 8 shows an associated pointer diagram, FIG.
9 the waveforms of voltage curves as used in the
7 occur during operation, FIG. 10 shows a variant of FIG. 7, FIG. 11 shows the voltage forms occurring in the variant of FIG. 10, FIG. 12 shows the arrangement of a galvanomagnetic sensor in the stray field area
FIG. 13 shows a rotor magnet, and FIG. 13 shows a variant of FIG. 12, in which a special and specially magnetized area of the rotor magnet is provided for controlling the galvanomagnetic sensor.
1 shows an overview using the example of a three-strand (= three-phase) electronically commutated motor 10. This has on its stator 12 a stator winding (here, for example, connected in a star) with three strands (phases) 14, 16 and 18, the connections of which with A , B and C are designated. Furthermore, the motor 10 has a permanent magnetic rotor 20 (only indicated schematically), which is shown with four poles.
In its magnetic field, three Hall generators 22, 24, 26 are arranged on the stator at intervals of 120 ° el. These Hall generators (or other rotor position sensors) are usually located in the so-called neutral zone of the stator, and in practice this means that the rotating field generated by the stator winding 14, 16, 18 leads the field of the rotor by approximately 90 ° el. (Average) when the engine 10 is running at low speed. In the context of the present invention, however, the sensors can also be arranged outside the neutral zone.
A full bridge circuit 44, the structure of which is shown in FIG. 2B, is used here as an example to control the stator winding 14, 16, 18. It has three "upper" transistors 52, 54, 56 in the form of pnp transistors, the emitters of which are each connected to a positive line 48 and the collectors of which are connected to the connections A and B and C, respectively. It also has three "lower" bridge transistors 60, 62, 64 in the form of npn transistors, the emitters of which are connected to a negative line 50 and the collectors of which are connected to the connections A and B and C, respectively.
As shown, signals T1, T2, T3 serve to control the upper transistors 52, 54, 56 and signals B1, B2, B3 to control the lower transistors. These signals are derived from signals H1, H2, H3, which signals in turn are derived from the Hall generators 22, 24 and 26.
How this happens is described below. The logical equations are shown in Fig. 2A. For example, transistor 52 is turned on by signal T1 when signal H1 is high and signal H2 is low. The same applies to the other transistors and can be found in the logic equations shown.
The signals T1 to B3 are generated in a programmable logic circuit (PAL) 70 from the signals H1, H2 and H3. The PAL 70 is programmed accordingly. A microprocessor 72 is also provided in FIG. has the function of controlling the direction of rotation of the motor 10 or other desired functions which may vary from case to case, e.g. Regulation of the speed to a predetermined value.
Needless to say, the invention is not limited to three-phase motors, but is suitable for all motors in which a rotor position sensor is used, e.g. even a single rotor position sensor.
Fig. 4 shows the circuit of the Hall generators 22, 24, 26. These are connected in series between a plus line 78 (e.g. + 12 V) and the minus line 50, i.e. they are all fed with the same current, which improves the efficiency of the motor. There is a resistor 80 (e.g. 500 Q) between the top Hall generator 22 and the plus line 78, and a resistor 82 (e.g. 500 Q) between the bottom Hall generator 26 and the minus line 50. Resistors 80, 82 determine the maximum current through the Hall generators, i.e. they represent a current limitation for the maximum voltage, and the resistor 80 causes a potential shift, since the comparator 102 "cannot work with an input voltage which has the same value as its positive operating voltage (on the line 78).
5 shows an arrangement with only one Hall generator 26, which is connected to the negative line 50 via the resistor 82 and to the positive line 78 via a resistor 80 'for better explanation. When the rotor 20 rotates, it generates an alternating sensor output voltage u between its antivalent outputs 84, 86, the course of which is shown in FIGS. 6, 9 and 11. This voltage u has relatively flat edges 49, that is to say a sinusoidal profile; it has a voltage swing S of e.g. 86 mV, and it has an offset 79 of e.g. 0.7 V. As is readily apparent from FIG. 4, the offset (through the resistor 82) is lowest for the Hall generator 26, higher for the Hall generator 24, and highest for the Hall generator 22. However, the different sizes play in the circuit used of these offset voltages does not matter.
It should be noted that the Hall generators used are preferably those in which there is an amplified Hall signal at the outputs 84, 86, e.g. around the Hall generator type HW101C.
The course of the signal u with the relatively flat edges is preferably obtained by an arrangement according to FIG. 12 or 13. The permanent magnetic rotor 20 is shown here as an external rotor, and the Hall generator 26 is open (as are the Hall generators 22 and 24) a printed circuit board 90 arranged as an SMD part. The comparators 102, 102 ', 102 "can also be arranged on this printed circuit board 90, together with the components assigned to them.
In FIG. 12, the Hall generator 26 is located opposite the end face 92 of the rotor 20, at a distance d from the end face of the rotor magnet 20 ′, and it is cut by an enveloping cylinder C which is formed by the inside 20 ″ of the rotor 20. As a result, the Hall generator 26 lies in the leakage flux region of the rotor magnet 20 ', which is radially magnetized, as indicated by the letters S and N. Experiments have shown that the leakage flux from the rotor magnet 20' is strongest in the position of the Hall generator 26 shown, ie Hall generator 26 in the variant according to FIG. 12 is preferably located under the inner edge 20 ″ of the rotor magnet 20 ′. The size of the distance d determines the amplitude of the voltage swing S, i.e. S increases as d decreases, but the shape of the voltage u becomes more favorable as d increases.
In practice, you have to compromise.
13, the rotor magnet 20 has a special control magnet 94 which is axially magnetized in the manner shown and therefore generates a greater magnetic flux density and thus a greater voltage swing S in the halogenerator 26. Experiments have to determine which of the two variants (Fig. 12 or 13) is more favorable for the individual case. With internal rotors, comparable arrangements will be made, as is known to the person skilled in the art.
FIG. 7 again shows an arrangement analogous to FIG. 5, but with additional switching elements which serve to shift the phase of the signal u as a function of speed, namely with a phase shifter arrangement 87.
The output 84 of the Hall generator 26 is connected here via the parallel connection of a resistor 96 and a capacitor 98 to the non-inverting input 100 of a comparator 102. This input 100 is connected via a high-resistance resistor 101 to the output 108 and via a resistor 104 to the inverting input 106, the latter in turn being connected to the output 86 of the Hall generator 26.
During operation, the rectangular signal H3 is obtained at the output 108 of the comparator 102, which signal serves to control the motor 10 according to FIGS. 1 to 3. The output 108 is connected to the positive line 78 via a resistor 110.
The high-resistance resistor 101, if used, gives the arrangement hysteresis behavior, i.e. brief interference pulses or
Voltage peaks in the signal u from the Hall generator 26, as can be seen in FIG. 9, have no influence on the signal H3 at the output 108.
Resistor 101 therefore very simply effects a filtering or interference suppression function and thereby a smoother running of the motor.
Preferred values for Fig. 7 Comparator 102 ... LM2903 Hall generator 26 ... HW300B resistors 80 ', 82 ... 430 fl resistors 96.104 ... 100 kfl resistor 101 2 ... 4 MQ capacitor 98. 10 nF resistor 110 ... 2 kQ voltage on the line 78 ... + 5 V According to FIG. 8, the alternating sinusoidal sensor voltage u (between the outputs 84 and 86) generates a current 1 through the resistor 96 and a voltage u1 across this resistor, the is in phase with i1.
Furthermore, the voltage u generates a current i2 through the capacitor 98, and this current leads the current il by 90 °. The currents ii and i2 add up to the current i which flows through the resistor 104 and generates a voltage u2 thereon which is in phase with i2. The voltages u1 and u add up to the voltage u2.
According to Fig. 8 there is a phase angle ss between the voltage u1 and the voltage u, i.e. the voltage u1 lags the voltage u in phase.
The phase angle lies between the voltage u2 and the voltage u, and as shown in FIG. 8, the voltage u2, which controls the comparator 102, leads the voltage u by this phase angle (.
FIG. 9 shows the measured profile of the alternating sensor output voltage u on the Hall generator 26. As a result of the phase shift by the phase shifter arrangement 87, the rectangular output signal H3 is obtained at the output 108 of the comparator 102, which corresponds to the voltage u by the angle (p (FIG. 9) leads in phase and that - via the PAL 70 to control the bridge circuit 44.
As can be seen, the angle cm is a function of the frequency and hence the speed of the motor 10, i.e. at low speeds is (p small, and increases with increasing speed, so that the signal H3 is shifted more and more in the direction of arrow 110 (FIG. 9) with increasing speed, ie the angle (p increases with increasing speed, and The relevant phase current is switched on earlier, the higher the speed of the motor.
As a comparison between FIGS. 4 and 7 shows, the circuit according to FIG. 7 is used three times in FIG. For this reason, the circuit part for the Hall generator 24 is identified by a trailing apostrophe, e.g. 87 'instead of 87, and the circuit section for the uppermost Hall generator 22 is identified by two apostrophes, e.g. 87 ". The phase-shifted square-wave signal H1 is thus obtained at the output 108" of the comparator 102 ", the phase-shifted square-wave signal H2 at the output 108 'of the comparator 102', and, as already described in detail, this is obtained at the output 108 of the comparator 102 phase-shifted square wave signal H3.
FIGS. 3a, 3b and 3c show these square-wave signals H1, H2, H3, which are offset by 120 ° el. Relative to one another. These signals are shown with solid lines for a low speed and dash-dotted lines 116 for a higher speed, e.g. 40,000 rpm. At this higher speed, all of the square wave signals H1, H2, H3 are shifted in the manner shown earlier by the same angle, e.g.
by 20O el. And with increasing speed, this shift increases, as symbolized in Fig. 3a by arrow 110.
Alternatively, a phase shifter arrangement 187 according to FIG. 10 can also be used. Here, the parallel connection of a resistor 196 and a capacitor 198 is arranged between the output 86 of the Hall generator 26 and the inverting input 106 of the comparator 102. A resistor 204 lies between the inverting input 106 and the non-inverting input 100, and the non-inverting input 100 is connected to the output 84 of the Hall generator 26 and - via a resistor 101 - to the output 108.
Preferred values for Fig. 10 comparator 102 LM2903 Hall generator 26 ... HW300B resistors 80 '. 82 ... 430 fl resistors 196, 204 ... 100 kQ capacitor 98 ... 10 nF resistor 101 ... 2.4 Mfl resistor 110 ... 2 kQ voltage on line 78 ... + 5 V.
In this case, for the square-wave signal H3 'at the output of the comparator 102, the curve according to FIG. 11 results in relation to the alternating sensor voltage u between the outputs 84 and 86 of the Hall generator 26. Here too, there is a phase shift <pin direction early, only that the square wave signal H3 'is inverted in comparison to the square wave signal H3 of FIG. 9.
If the phase shifter arrangement 187 according to FIG. 10 is to be used in the circuit according to FIG. 4, it must be used in the same way instead of the arrangement 87, instead of the arrangement 87 'and instead of the arrangement 87 ", so that the course according to FIG 3a, 3b, 3c.
If the end 106 of the resistor 204 is additionally connected in FIG. 10 to the non-inverting input of a second comparator X (not shown), and the inverting input of the comparator X to the end 100 of the resistor 204, the output of the comparator is obtained X is the square wave signal H3 according to FIG. 9, which is in phase opposition to the square wave voltage H3 '. These antiphase signals H3 and H3 'can then control different currents in one motor.
Naturally, numerous modifications and modifications are possible within the scope of the present invention. In particular, in the case of electronically commutated motors for high speeds, a combination is expedient in the sense that the Hall generators 22, 24, 26 are already mechanically displaced on the printed circuit board 90 in the early direction relative to the neutral zone, e.g. each halo generator by 20O el., in order to obtain a "basic pre-ignition" mechanically, so to speak, and that the phase shift according to the invention results in an additional shift towards the early depending on the speed.
This is particularly advantageous in engines for very high speeds, where phase shifts of over 40 el. Are required for the early ignition; such phase shifts are difficult to achieve with the aid of the phase shifter arrangements described.
A combination of mechanical pre-ignition and electronic pre-ignition gives you optimal conditions and a significant improvement in efficiency over a wide engine speed range without significant additional costs.
For engines with speeds of up to approx. 20,000 rpm, the "mechanical early ignition" is usually not required, and for these engines the "electronic early ignition" as described above and which is also the subject of the main patent and has the advantage that it is equally effective in both directions of rotation, so that such motors run in both directions of rotation with excellent efficiency.
It has also proven to be very advantageous that when the invention is used, the interface between the output stage 44 (FIG. 1), the motor 10, and the control electronics 70 remains unchanged, since the control electronics 70 have the (already phase-shifted) output signals H1, H2, H3 can be supplied by the arrangement according to FIG. 4.