HU195008B - Speed indicator - Google Patents

Abstract

The rotational velocity-type transducer comprises a permanent magnet (1), which is fabricated as a disk provided with poles alternating circle-wise and with an axial opening (2) adapted for a rotary shaft (3). In front of the poles of the permanent magnet (1) there are disposed electronic conductors (7a) of a winding (4a) arranged on a base, which electronic conductors are connected in series through the frontal portions (8a) of the winding (4a). Just like the winding (4a), there is arranged a winding (4b) of which the electronic conductors (7b) and the frontal portions (8b) are mounted closely to the electronic conductors (7a) and the frontal portions (8a) and so that they form the displacement therebetween in the range from 30 to 330 electrical degrees. The taps of the windings (4a, 4b) are connected to a differential amplifier (9) whilst their other taps are linked with a common bus (10) of said amplifier (9).

Description

The present invention relates in particular to a speed encoder for use in the field of measuring technology.

In contrast to measuring instruments and transducers, it is often a requirement that they have a high degree of accuracy in the measurement of particular parameters. Therefore, the encoders are constructed on the basis of principles and in such a way that the effect of the distortion factors affecting the final measurement result is kept to a minimum. These factors include various interfering signals.

A known embodiment of a tachometer comprises a disc-shaped permanent magnet having radially or axially magnetized poles circumferentially circumferentially, and having a central bore for picking up a rotary axis and a coil mounted on a holder made of insulating material. The active coil turns, whose number (2n + l) -p, where n is a fixed integer and p is the number of poles, lie opposite the poles of the permanent magnet and are connected in series through the coil heads. Such a speed encoder is disclosed in GB 2022326 and US 4093897. In order to overcome unwanted interference signals generated during their operation, which necessarily cause errors in speed determination, in both embodiments of said patent, winding is compensated by winding. For this purpose, the encoder winding is divided into 180 electrified sections, which are connected in series (see, e.g., LN Safonov, VN Wolnyansky, et al., "Precision Angle Encoders with Printed Coils", Mashinostrojenie, Moscow, 1977 7-13, 58-60). pages).

As the permanent magnet rotates, a useful signal-electromotive force of variable polarity is induced in the active coil conductors. In addition, external magnetic or electromagnetic fields in the active conductors and the coil heads induce interference electromotive forces, which, although active in the coil conductors, are compensated by their series opposed connections, but in the coil heads are added because the coil heads are connected in series.

Thus, in the case of the said encoders, the interfering signals cannot be fully compensated because the compensation coil is located at a certain distance from the coil construction relative to the coil heads. This is particularly noticeable in asymmetric external electromagnetic fields, such as the power transformer spraying on the encoder. In these speed encoders, the interference signals that are induced in the connecting wires between the coils and subsequent devices cannot be compensated for.

It is an object of the present invention to provide a speed encoder whose accuracy, by perfectly compensating for external interference signals, is significantly higher than the accuracy of current encoders.

The object is solved by a rotary encoder having a disc-shaped permanent magnet having circumferential magnetic poles, a central receiving hole for the shaft, and a coil on an insulating holder, the active conductors of which lie across the poles of the permanent magnet are turned on. This speed encoder has been further developed in accordance with the present invention by having auxiliary winding having active conductors and a series of winding coils thereof, similar to the active conductors and coil heads of the main winding, located in close proximity to each other and offset by an angle of 30-330 degrees. one end of the coil winding and the auxiliary winding are connected, while the other end of the main winding and the auxiliary winding is connected to the common power supply line of the differential amplifier.

According to a preferred embodiment of the speed transmitter according to the invention, the differential amplifier of the speed transmitter is designed as a voltage comparator.

The speed encoder of the present invention allows for the accurate determination of any speed by completely compensating for the electromagnetic interfering signals it receives.

Other features of the invention will now be described in more detail with the help of the drawing, which shows an exemplary embodiment of a speed encoder. In the drawing it is

Fig. 1 is a schematic diagram of a possible embodiment of the tachometer according to the invention, a

Figure 2 is a sectional view taken along line II-II of the speed transmitter of Figure 1, a

Figure 3 shows an section of an insulating material holder on an enlarged scale, the grooves of which are provided with coils according to the invention,

Figure 4 is a schematic diagram of the section shown in Figure 3 showing the directions of electromotive forces generated by electromagnetic disturbances;

Fig. 5 is a schematic diagram of a coil of a rotary encoder according to the invention and a differential amplifier formed as a voltage comparator, and

Figure 6 shows the waveforms observed at the input and output of the differential amplifier.

-2195008

An exemplary embodiment of the tachometer according to the invention comprises a permanent magnet 1 which is formed as a disk and alternates north and south poles N and S radially magnetized along the periphery of the disk. The disk of the permanent magnet 1 has a central bore 2 in which 3 axes are located. The rotary encoder described further comprises a main winding 4a and an auxiliary winding 4b, which are located in the grooves 5 of the insulating material holder 6 shown in Fig. 3. The main winding 4a and the auxiliary winding 4b consist of active conductors 7a, 7b in rows 8a, 8b. on. The active conductors 7a and 7b are located in close proximity to the poles of the permanent magnet 1. Accordingly, the coil heads 8a, 8b are arranged in close proximity to one another, as shown in FIG. The main winding 4a and the auxiliary winding 4b are offset by a given angle, which is in the range of 30 to 330 degrees. The limits of said angle range are determined by the permissible magnitude of the output signal. In the exemplary speed transmitter shown in the figure, the main winding 4a and the auxiliary winding 4b are offset from each other by 180 degrees (or π-p where p represents the number of poles), which represents an optimum offset angle.

The speed transmitter of the present invention further comprises a differential amplifier 9 having its inputs to which the same ends of the main winding 4a and the auxiliary winding 4b are connected, while the other end of the main winding 4a and the auxiliary winding 4b is connected to a common power supply . The same end in this case means the beginning or end of the coils.

For the rectangular output signal, the differential amplifier 9 is configured as a voltage comparator 11, see Figure 5.

According to another embodiment of the tachometer according to the invention, the permanent magnet 1 has axially magnetized N, S poles. In this embodiment, the active conductors 7a, 7b are positioned as described above but in a radial direction.

Preferably, the main winding 4a and the auxiliary winding 4b are formed on both sides as a printed circuit winding.

The operation of the tachometer according to the invention is as follows:

During the rotation of the permanent magnet 1, the main winding 4a connected to the inverter input of the voltage comparator 11 induces a voltage 12 directly related to the speed of the speed encoder. We noted this process in the

6 shows the amplified rectangular output signal 14 of the voltage comparator 11 in the top row of the figure.

When an external interfering electromagnetic field is applied to the speed transmitter of the present invention, interfering electromotive forces are induced in the active conductors 7a, 7b and the coil heads 8a, 8b. In the active conductors 7a, 7b, which are connected in series and face to face, the interfering electromotive forces ex are compensated, but they are summed in the coil heads 8a, 8b. In this case, the interfering electromotor forces ex superpolarize to, and add to, the voltages 12, 13 generated by the rotating permanent magnet 1 and, in the form of _this electromotive force, are applied to the voltage comparator 11. Since the interfering signals are input to the voltage comparator 11 in the same phase, the state of the output signal 14 of the voltage comparator 11 does not change.

Thus, the two complete coils of the invention are identical coils, the active conductors of which are offset from one another at a given angle of 30 to 330 degrees, but just as the coil heads are placed in close proximity, and the voltage comparator connected to the coils allows practically perfect compensation of the influence of external electromagnetic fields and thus increase the accuracy of the measured speed.

The speed transmitter of the present invention is preferably used for measuring and controlling the electric motors of turntables, tape recorders and VCRs.

Claims (2)

A rotary encoder having a disc-shaped permanent magnet having alternating magnetic poles around its circumference, having an axial bore for receiving a shaft, and winding disposed on an insulating material holder, the active conductors of which lie opposite the poles of the permanent magnet, characterized in that it has an auxiliary winding (4b) having active conductors (7b) and interleaving coil heads (8b) thereof, similar to active conductors (7a) and coils (8a) of winding (4a) and in close proximity to each other, —Located offset by electrical degrees within an angle range of 330 °, and comprising a differential amplifier (9) having input terminals connected at the same end of the main winding (4a) and auxiliary winding (4b), while the main winding (4a) and auxiliary winding winding (4b) alternatively The end of the k is connected to the common power line (10) of the differential amplifier (9). -3195008 5 6 The speed amplifier (9) of claim 1 as a voltage comparator (11), characterized in that it is differentially configured.