DD222176A1 - SPEED MEASUREMENT OF ELECTRICAL MACHINES FOR THE PURPOSE OF THE SPEED CONTROL - Google Patents

Abstract

The invention relates to an arrangement for speed detection of electric machines for the purpose of speed control, especially in small machines, where low space requirements, low power consumption and imprecision are required against pollution and extraneous light influence and high pulse counts per revolution are favorable for the control process. The object of the invention has been achieved by arranging one or two Hall effect sensor circuits radially or axially to a rotating multi-pole ring magnet. The air gap can be increased, if auxiliary circuits are additionally attached to the circuits.

Description

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Field of application of the invention:

Electrical machines, in particular power tools, in which the speed detection is a prerequisite for control processes, with a high number of pulses per revolution and low installation volume is required.

Characteristic of the known technical solutions:

Solutions are already known in which a tachogenerator with ring magnet and generator coil supplies a rotational count-dependent pulse frequency for the speed detection. The tachogenerator has certain advantages in that there is no inherent disturbance requirement, it is relatively simple in construction and provides high output voltages at a corresponding magnetic flux change rate.

The disadvantage, however, is that the induction of several pulses per revolution require a magnet, which is very large due to high Polpaarzahlen unfavorable field characteristics. The generator coil is expensive to produce and quite voluminous.

Furthermore, it has been proposed to use an opto-electronic pulse generator (fork coupler) for the speed detection.

With the opto-electronic pulse generator large numbers of pulses per revolution can be generated advantageously even with a small shaft diameter. The necessary components are mainly produced automatically.

With the opto-electronic pulse generator, the transmitter's relatively high inherent power consumption is disadvantageous, especially in the case of direct power supply via ballast resistors from the network. A further disadvantage is that the decisive for the speed detection components transmitter and receiver must be protected against light and dust.

Object of the invention

The aim of the invention is an arrangement for speed detection with low power consumption and relatively simple and inexpensive construction. The speed detection should be insensitive to contamination and require a small footprint.

Explanation of the essence of the invention:

The object of the invention is to provide an arrangement for speed detection, which is also on small electrical machines, such as hand-held tool drives, household appliances, etc., applicable and can be produced with relatively little technical effort. The arrangement should be insensitive to external influences, such as light and pollution, and have a low power consumption. , ,

The object is achieved in that the speed detection takes place by means of a multi-pole rotating ring magnet and one or two radially or axially arranged Hall effect sensor circuits. These circuits advantageously combine sensor, amplifier and Schmitt trigger. By using 2 circuits can be at the same ₀

Magnets the number of pulses will be doubled if their sensitive on the same Pol surfaces at an angle of 2§2_

be arranged with respect to the center of the shaft, wherein for ρ the number of poles of the magnet and η is a natural number is used. By attaching small magnets (auxiliary magnets) behind the sensor circuits, the unfavorable field pattern of multi-pole small ring magnets can be improved and thus enable larger air gaps. The or the sensor circuit (s) are arranged on a circuit board, which extends into the immediate vicinity of the rotating magnet and on which the possibly used auxiliary magnets are mounted.

invention description

The invention relates to an arrangement for speed detection of a shaft, especially for small electrical machines. By this arrangement, magnetic flux fluctuations are converted into electrical impulses. The pulse repetition frequency is proportional to the speed. The further processing of the pulses is carried out according to the intended use, z. B. in a f / U converter. The output pulses can also be digitally processed since they are TTL compatible. In the embodiment shown, a multi-pole ring magnet 2 is mounted on the known design of an el. Small machine 1 at the shaft end of the rotor. Furthermore, a circuit board 4 is arranged on the small machine so that the Hall effect sensor circuits 3 or only one with their magnetically sensitive surface intersect the field lines of the magnet 2. To reinforce the circuit penetrating field lines, it is possible to arrange small permanent magnet 5 whose induction is slightly below the switching shaft of the circuit or circuits 3, behind the circuit or circuits that the field lines of Permantentmagneten 5 have the same direction as that of Ring magnets that control the switching process

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in the circuit. When using two circuits 3, the number of pulses per revolution can be doubled with the same magnet 2, wherein the advantageous open collector outputs of the circuits 3 are to be connected in parallel via a common working resistor and the arrangement of the circuits 3 in the angle of 2§2_ (2n-1) is made to the axis of rotation (Fig.2). As a result, always unequal poles are on the circuits.

The integration of Hall element, amplifier and Schmitt trigger on a semiconductor chip results in small dimensions and low power consumption high voltage pulses at the output, which can be conveniently processed in subsequent circuits.

A radial arrangement of the circuits 3 on the ring magnet 2 is also possible (Fig.2).

Claims (3)

-1- 258 761 Invention claims: 1. means for speed detection for the purpose of speed control on the shaft of a small electrical machine carrying a multi-pole ring magnet, characterized in that the ring magnet (2) axially or radially opposite one or two Hall effect sensor circuits (3) are arranged, in addition can be provided with 2 auxiliary magnets (5). 2. Composition according to claim 1, characterized in that the Hall sensors IC (3) are arranged on a printed circuit board which extends into the immediate vicinity of the ring magnet (2). 3. Composition according to claim 1, characterized in that the output voltage of the Hall sensors IC (3) are converted by means of f / U converter into a controlled variable, wherein the f / U converter and the own power requirement of the Hall sensors IC (3).