DE2921255A1 - DC motor with reduced drive moment fluctuations - generates extra moment acting against alternating component of drive moment - Google Patents

Abstract

The d.c. motor has a device to generate a moment acting against the attenuating component of the drive moment in order to reduce the fluctuations in the drive moment. The counter-moment has a signal opposing that of the average drive moment and is smaller than the latter moment. The control circuit for the drive current pulses also produces the counter-moment and accordingly has a resistor connecting appropriate connections of the winding groups together. The resistor is large compared to the internal resistance of the winding groups, e.g. 30-70 times greater. The motor receives a constant d.c.

Description

G1 calibrator

(Addition to P 27 30 142.4-32) The invention relates to a DC motor according to the preamble of claim 1. Your is based as a task that of a to make such a motor output torque particularly even during operation.

This object is achieved according to the invention by the claims 1 specified measures. These measures are described below using the exemplary embodiment be expanded.

The invention is preferably used in engines that have an im Use a substantial constant supply current. Your preferred area of application are motors with high demands on (ie quality of synchronization, i.e. in particular Motors for drives for phono and video equipment.

Further details and advantageous developments of the invention result from what is described below and shown in the drawing, in no way to be understood as a limitation of the invention, as well as from the subclaims. It shows: FIG. 1 an illustration of an exemplary embodiment of the invention9 in longitudinal section, Fig. 2 is a schematic representation showing the Rotor and the two groups of windings of the motor of FIG. 1 in plan view as an associated, exemplary circuit shows, and Fig. 3 diagrams to explain the finding.

1 and 2 show the same engine as FIGS. 1 and 2 of the associated Parent application P 27 30 142.4-32, on all of its content to avoid lengths is expressly referred to. In particular, it should be noted that the present invention for all engine types shown in the parent application suitable.

In Fig. 1, 1 denotes a rotary source on which with a press fit a hub 2 is attached, which is in a central recess 3 of a soft magnetic Inference washer / is cast. On the disc 4 is an annular, axially magnetized ring magnet 5 attached coaxially to shaft 1. The slide 4 and the Magnet 5 and hub 2 form the upper rotor disc 6.

The hub 2 has a blind hole 7, the end face of which acts as a starting surface 8 is used for a bearing tube 9, which is plugged onto various Lielle 1 with an axial clearance fit. These Axial construction is very compact. The indicated by the double arrow 10 axial Distance between this contact surface 8 and that facing the planar air gap 11 Surface 12 of the upper rotor disk 6 is dimensioned with little tolerance. The bearing tube 9 consists made of sintered metal and is tapered at both ends to form plain bearings 13, 14. On the enlarged central part 15 of the bearing tube 9 sits a flange washer with a press fit 16, on the end face 17 thereof facing away from the rotor disk 6 a stator plate 18 is attached by gluing. In the punched from a suitable plastic plate and printed circuit board stator 18 are two diametrically opposed Coils 19, 20 opposite one another are glued in place. Between the contact surface 8 and the upper end face 21 of the bearing tube 9 are two StahnschBibon 23, 24.

The lower rotor disk 25 is a soft magnetic yoke disk, the seat with play on the Uslle 1 is plugged and as a result of the magnet 5 exerted axial tension on one inserted in a recess 26 of the shaft 1 Locking disk 27 rests. The total air gap is designated 29, the upper distance between rotor and stator with 11 and the lower distance with 11 ". The End faces of the bearing tube 9 are through the locking disk 27 of dm through the magnet 5 exerted axial tension relieved. A clamping ring 32 secures the rotor disk 25 against slipping off the shaft 1.

Fig. 2 shows the mechanical structure to illustrate the invention of the engine only very schematically.

The RotorS is 2-pole in the illustrated nut guide) sbni spi e.l and can be divided into 6 characteristic numbers: a. one ci continuously as the North Pole magnetized zone 35, which extends over approximately 12UO el. (with this 2-pole Magnetic degrees are equal to electrical degrees); b. one continuously as the south pole magnetized zone 36, which is also about 1200 ei. extends; these two zones 35 and 36 are due to their uniform magnetization with only one pole at a time designated as "monopole zones"; c. a first, in the direction of rotation (Arrow 37 of Fig. 2) to the monopole zone 36 adjoining dipole zone 38 with a Angular extension of about 600, and then in the direction of rotation 37 d. one second dipole zone 39, likewise extending over approximately 600 el.

The dipole zones 38 and 39 are - unlike the monopole zones 35 and 36 - not magnetized uniformly over the entire radial width, but longitudinally of an (imaginary) radius vector changes the direction of the magnetic field. So in the dipole zone 38, as shown, the outer ring segment 41 is a south pole, the inner ring segment 42 is a north pole, and in the dipole zone 39 is the outer ring segment 43 a north pole and the inner ring segment 44 a south pole. The radial width and / or the magnetization of the individual ring segments is preferably so chosen that the magnetic fluxes of the ring segments 41 and 42 according to the amount are as equal as possible. The same applies to the magnetic fluxes of the ring segments 43 and 44. This equality of the rivers in the individual segments of the dipole zones is important for generating uniform torque. -It complement each other each a monopole zone and an adjacent dipole zone to a pole pitch, iso to 180 ° el.

The stator coils 19 and 20 of the ironless stator are according to the teaching of the main patent for achieving a graphical torque, approximately pentagonal educated. Their magnetically active sections 47 and 48 or 49 and 50, which are preferred each between 10 and 500 el. wide, each include one as shown Angle of about 120 ° el. With each other. These active sections run in the essentially radially outwards, as are the boundaries between the zones 35, 36, 38 and 39, i.e. if - as shown in sections 49 and 50 - these above such These sections are boundaries and the boundaries are essentially approximately parallel to each other. The outer and inner yoke sections of the coils 19 and 20 can run essentially outside the magnetic field of the rotor. As special It has proven to be expedient if the width of the coil window is in each case is about 90 Vu of the width 8 m of the rotor magnet 5. In Fig. 2, this is preferred Ratio not shown, if the coil window would snnst so small that one could no longer long for the various magnetic zones. However, you need yourself just imagine the individual coils widened slightly towards the inside in order to meet these dimensions to reach.

As shown, the south pole of the monopoly zone 36 goes directly into the South pole of the outer ring segment 41 of the dipole zone 30 over.

Likewise, the north pole of the outer ring segment 43 of the 39 dipole zone goes directly over to the north pole of monopoly zone 35.

The outer orbit of the rotor magnet 5 is thus about 1800 long magnetized with a north pole and 18 [J0 long with a south pole. in the A rotor position sensor is located on the stator plate 18 in the area of this outer orbit Serving Hall generator 53 attached, which is shown again in Fig. 2 below.

This Hall generator 53 is consequently during one half of the Rotation influenced by a north pole and then switches on the right coil 20, and during the other half of the rotor rotation it is influenced by a south pole and then turns on the left coil 19. ne in the transition from a north to a South Pole or vice versa, the current in one coil is reduced and at the same time that increases in the other coil, so that in operation always in one of the two coils 19 or 20 a current flows. This type of commutation is achieved by a Siver circuit 52 controlled by the Hall generator 53, which as an exemplary embodiment is shown in FIG.

The control circuit 52 according to rig. 2 is structured as follows: The Hall generator 53 controls two pnp transistors 54 and 55 of a differential amplifier which in turn serve as drivers for npn output stage transistors 56 and 57, of which 56 the current in the winding 19 and 57 the current in the winding 20 controls the one power connection the halide generator 53 is connected to a positive line 59 via a resistor 58, the other through a resistor 60 to a negative lead 61. The emitters of 54 and 55 are connected to one another and to 59 via a common resistor 64. The collector of 54 is through a resistor 65 to 61 and directly to the base connected by 56.

Likewise, the collector of 55 is connected to 61 and via a resistor 66 connected directly to the base of 57. The two winding groups exist here only from a single coil 19 or 20. One of the connections of this coil are connected to one another and to the positive line 59, and the other connections 67 and 68 are intermediate connected to the collectors of transistors 56 and 57, respectively the connections 67 and 68 are connected to an ohmic resistor 70, the p resistance value of which is large compared to the internal resistance of the winding groups 19 or 20e If z.8. the winding group 19 (or the winding group 20 identical to it) has an internal resistance (measured with an ohmmeter) of 50 ohms, a preferred value for the resistance can be 70 are between about 5 00 and 3,000 ohms.

In a specific case, then z-0. an optimal value of about 2,000 fihm determined. This resistance is determined empirically in practice: A variable resistor is connected as resistor 7fl and this is varied until the synchronization fluctuations have their lowest value. In concrete terms In case the synchronization fluctuations were reduced by inserting the resistor 7n e.g. from n.0% to a \ there van 0.5 ... n.6%, the motor current increased when idling from 90 to 92.5 mA, and the power output only decreased slightly, but what usually in motors for phono or video equipment because of their low power requirements is meaningless.

Naturally, e.g. in the case of a low-power motor, the figure shown in Fig. The control circuit 52 shown in FIG. 2 can also be implemented in one stage, provided that a tiallgenerator 53 is available with a sufficiently high output signal, i.e. the transistors 56 and 57 would then be omitted and the coil connections 67, 60 would then be connected the collectors of the transistors 54 and 55 are connected.

Operation of the engine according to FIGS. 1 and 2: It will first be the Operation without resistor 70 is described.

In the position shown in FIG. 2, the transistor 56 is conductive and the transistor 57 is blocked because the Hall generator 53 has a south pole, namely the Monopole 36, is opposite, and therefore its left output is more negative than its right. The rotor magnet 5 rotates in the direction of arrow 37, rather than clockwise. At the same time, a voltage with the negative amplitude u1 (Fig. 3A), the instant shown in FIG. 2 being approximately the time t which corresponds to FIG. 3A. In Fig. 3A are those induced in coils 19 and 2D Voltages designated with u19 and u20. The emergence of this negative tension with the amplitude u1 one can clearly explain oneself by cutting the won the two monopoles 35 and 36 outgoing magnetic field lines with the active coil sections 47 and 40, thereby inducing those in 47 and 4 [beta] Add up tensions. Since the monopoles 35 and 36 as well as the coil 20 each have 1200 el. are long, this voltage becomes 1200 ol during a rotation angle of ctwn.

induced, being of course by don i7horgangshcercich between the Poles and the relatively large three of said coil sections adjust the voltage accordingly is rounded off.

As the rotor 5 rotates further, the south pole monopole 36 rotates under the Hall generator 53, and this comes into the sphere of influence of the North Pole monopoly 35, so that the coil 19 is de-energized and the coil 20 receives current, see FIG. 38.

The polarity of the voltage induced in the coil 20 is reversed as can be seen from FIG. 3A, and reaches a medium amplitude + u2, which is only about half the size of that of U1, and this amplitude + u2 remains ei for a period of approximately 2400 as shown. received, with as shown here in the transition areas the voltage from the already given reasons is rounded.

Naturally, the induced voltages in the -identical coils 19 and 20 have the same shape and are offset from one another by 180 ° el the symmetry of the stator easily results. 3A shows what is expressly pointed out - the voltages u19 and u2n in the event that the rotor is driven from the outside and the motor is de-energized. During operation, the voltages shown add up nor the voltage drops at the current-carrying winding group.

From Fig. 3A it can also be seen that the positive portions of the voltages u19 and u20 overlap. This fulfills the requirement that the motor can deliver a torque in every rotational position by going through the Winding group 19 or 20 sends a current in which at the moment a positive Voltage is induced, because the equation applies to the torque generated m . # = Uind. i (l) Here uind are momentarily rotary in a winding group induced voltage according to FIG. 3A, i the instantaneously flowing coil current, nt the torque acting on the rotor 5 and the angular speed of the rotor 5. It can be seen without further ado that with an essentially constant current i the Torque m follows the induced voltage practically exactly, i.e. the same curve has like this.

As already explained, the induced voltages do not have a rectangular shape, but are rounded at the corners, and this inevitably results in the Range of commutation run times t1 to t5 Depressions 71 of the torque, that disturb the synchronism. These depressions 71 can only be influenced slightly, for the following reasons: a) between the monopoles of the Rotormagnetm 5 arise through Scattering poll tickness, i.e. areas in which the density of the magnetic field lines is significant is lower than in the middle of the monopoly. This scatter in the area of the pole gaps is inevitable.

b) Due to scattering on the stator slots (not shown), especially but by a distributed, slotless winding as shown in FIGS. 1 and 2 the electromagnetic coupling between the rotor magnet 5 and the stator winding 19, 20 additionally weakened in the area of the rotor pole gaps, as has already been done in detail has been described.

As already mentioned, these effects can only be influenced relatively little, and It therefore initially appeared that the synchronization could only be improved by that the motor current is additionally increased at the commutation times t1 etc., as is also expressly stated in the main application P 27 30 2.4-32.

But the invention takes a different, much simpler way, namely, the Liechsel component is generated by the respective drive winding driving torque, which is shown in Fig. 3 C at 75 and 75 'by an approximately anti-phase electromagnetic additional torque generated by the counter-torque device 70 is generated9 so that overall the ripple on the motor shaft output torque (77 in Fig. 3 C) is reduced.

3B, 3C and 3D show to the left of the dash-dotted line 74 the ratios without the resistance 70, and to the right of the line 74 the ratios with resistance 70. The driving torque 75 (Fig. 3C) fluctuates without the resistance 70 between a minimum, e.g. at time t1S and a maximum, e.g. 0 at time t0. The amplitude of the fluctuations is w1.

The currents i, i19 and i20 alternately become zeroS, see Fig. 3BD Left.

By the resistor 70 is now achieved that whenever a Winding group current also receives the other winding group one in FIG. 38 79 receives electricity, but only in the order of magnitude of a few percent of the current is in the driving winding. At the same time, this causes the current slightly reduced in the driving winding compared to the state without resistance 70, as is indicated in Fig. 3B, on the right, somewhat exaggerated.

The reduced current in the respective driving winding causes a slightly reduced driving torque: while moving without the resistance 70 results in a torque curve 75 (Figo 3 £, left), that is now reduced from the each driving winding generated drive torque and has the course 75.9 of is entered in Fig. 3C, right9 with dashed lines and with the course at 75 largely coincides with regard to the shape of the alternating component.

At the same time causes the small current that was in the previously currentless second winding (or winding group - if it is a multi-pole motor acts) flows that this winding is an alternating electromagnetic Additional torque 76 is generated, the course of which is shown in FIG. 3D. It's about in phase opposition to the Liechsel component of the drive torque 75 'i.e. during e.g. Drive torque 75 'has its minima at times t2, t3, t4, etc. the additional torque 76 its maxima there and is positive, that is to say driving. Vice versa the drive torque 75 'has its maxima in each case in the middle between t2 and t3, or t3 and t4, etc., and there the additional torque 76 has its minima, i.e. it is negative there (braking). In the case of additional torque 76, only the can be seen Form decisive, so its llechel component.

The additional torque 76 is essential in the present invention an image of the lower one highlighted in FIG. 3A with the dash-dotted lines 78 Part of the curve, i.e. it is negative for about 1200 el., Then 600 el. Positive, then negative again, etc. etc., as FIG. 3D shows. It has a negative mean, i.e. a negative balance component, where the expressions equals and alternating components are to be understood in the sense of Fourier analysis, according to which one a periodic function y (t) can decompose into y (t) = aQ + Y1 (t), where ag is the Cleichomponent and y1 (t) is the alternation component, which latter is known in Weis can be represented by periodic functions, cf.

e.g. Stiefel, Applied Mathematics, Zurich 1955, pages 99 to 102.

The additional torque 76 is superimposed on the drive torque directly in the engine 75 ', and an output torque or shaft torque 77 is obtained on shaft 1, its Shape is shown in Fig. 3e, right and its waviness w2 as shown The waviness w1 without the counter-torque device 70 is smaller Man recognizes readily that the amplitude of the additional torque 76 is greater when the resistor 70 is reduced so that the size can be changed in a very simple manner can adjust this additional torque. Varying the resistor 70 gives a great deal quickly an optimization of the equilibrium, as already described. In the area the commutation times t1, t2 etc. the resistor 70 can be seen without Influence, since both transistors 56 and 57 are approximately equally strong at these times are conductive and therefore points 67 and 68 have approximately the same potential. there So the shaft torque is not reduced, as Fig. 3C clearly shows.

Naturally, rotational position-dependent electromagnetic additional moments can be used produce in a wide variety of ways.

By far the simplest way has been disclosed above.

E.g. for certain applications, instead of an ohmic resistor 70 a non-linear resistor arrangement can be provided to a specific To obtain the shape of the shaft moment 77. The arrangement described brings how presented with really minimal additional effort already a very considerable improvement and wi * you excellent synchronism values.

Finally, it should be pointed out that the zones between the monopoly zones - you can see from their function of controlling the Hall generator 53 or another galvanomagnetic sensor - with regard to their magnetic Properties only have to be such that they interact with them stepping stator winding sections no or at least no significant voltage induce.

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Claims (7)

Claims 1. DC motor, preferably brushless DC motor, with a permanent magnetic rotor, which has monopoly zones, which respectively about 120 ° el. long, with two monopoly zones of different names within each an angular range of about 2400 ei. are arranged and the angular range of this monopole pair has such a magnetization to the next monopole zone, that in the event of a relative movement to one that extends over its entire width Conductor in this one in relation to the voltage induced by the monopoly zones low and preferably no voltage induced further with a stator winding, which has two development groups, which in operation, controlled by a rotor position sensor device, for generating a gap-free driving electromagnetic torque alternating drive current pulses are supplied, in particular according to patent application dung P 27 30 142.4-32 (D86 = DT-207), characterized in that to reduce of fluctuations (w) of the driving electromagnetic torque (75; 75 ') a counter-torque device (70) for generating a to the lying part of the driving Moments (75?) Approximately anti-phase additional electromagnetic torque (76) provided is. 2. Motor according to claim 1, characterized in that the mean value of the additional electromagnetic torque (76) to the mean value of the electromagnetic Drive torque (75t) has the opposite sign and is smaller in terms of amount is than this. 3. Motor according to claim 1 or 2, dadur d7 characterized in that the Counter-torque device (70) for alternately supplying a current to the respective no winding group carrying drive current is formed. gl. Motor according to claim 3, characterized in that the control circuit (52) For Antrichs current pulses (i19, iJ)) also designed as t counter-torque device and that for this purpose the connections facing the control circuit (52) (67, 68) of the two groups of windings (19, 20) over in en preferably obmschen resistance (70) are connected to each other 5. Motor according to claim 4, characterized in, that the ohmic resistance (70) is large compared to the respective internal resistance the winding groups (19, 2ü). 6. Motor according to claim 4 or 5, characterized in that the size of the ohmic resistance (70) about 30 ... 70 times the internal resistance of a winding group (19 or 2U). 7. Motor according to at least one of the preceding claims, characterized characterized in that it is supplied with a substantially constant direct current.