SK138693A3 - Rotation detector - Google Patents

Abstract

The detector contains a rotor with angular division into several regions with different electromagnetic damping properties opposite sensors forming elements of an oscillator circuit. The oscillations are damped as the rotor turns. The oscillator output signal is fed to a discriminator circuit which measures the rotor rotations and can also measure its rotation direction. Two sensors can be used. A reference sensor (RS) is arranged opposite a region of the rotor with constant damping properties. The other sensor, i.e. the measurement sensor (MS), is arranged opposite an odd number of regions (d0-d2) of the rotor with different damping properties.

Description

The invention relates to a rotation detector, in particular for a volume measuring part, with a rotor comprising a plurality of angularly distributed sections with different damping properties for electromagnetic oscillation against which several sensors are arranged, which are each element of the oscillating circuit. The initial signals of the oscillating circuits are fed to a discriminator circuit which measures the rotor speed and, optionally, the direction of rotation thereof.

BACKGROUND OF THE INVENTION

Such detectors are used for volume measurement parts, for example cold or hot water counters, if they are supplemented with a temperature sensor.

DE 39 23 398 C1 discloses a speed detector having the aforementioned features. Its disk rotor has a total of two sections with different damping properties, which always occupy 180 °. Four detectors are located opposite the rotor and are spaced 90 ° apart. Here, the opposing detectors are connected to each other so as to give a reference signal.

The disadvantage of this known detector is, in particular, the high construction costs resulting mainly from the need for four detectors. While it would be possible to omit one of the measurement detectors without significant detriment to the measurement accuracy, detectors are still needed as oscillating coils, which according to the state of the art have to be custom made to have the necessary sensitivity, so that each detector is relatively expensive .

Starting from this prior art, the invention aims to provide a speed detector with the aforementioned features, which could be produced considerably cheaper without compromising quality.

SUMMARY OF THE INVENTION

Said object is achieved by a rotation detector according to the invention which comprises exactly two sensors, one of which, the reference sensor, is opposite to a rotor region whose damping properties do not change when the rotor is rotated, the rotor having in the rotation region against the measuring sensor, an odd number of sections with different damping properties.

Since a rotor section is located opposite the reference sensor, whose damping properties do not change when the rotor rotates, a single reference sensor is sufficient.

The fact that an odd number of rotor sections with different damping characteristics opposes the measuring sensor results in the output signal of the oscillating circuit of the measuring sensor having an asymmetrical waveform and it is possible to measure the rotational speed of the rotor and the direction of rotation thereof.

While a total of two rotor sections with different damping properties are used in the art, at least three such sections, possibly four, five, etc., are required according to the invention, as explained in more detail below. However, this increase in the number of rotor sections with different damping properties does not entail virtually any additional costs, since it can be achieved by very simple measures, which are described in more detail below.

In a preferred embodiment of the invention, the rotor is a disc. This has the advantage that the rotor needs little space.

It is furthermore advantageous if the measuring sensor is positioned as close to the rotor as possible. This increases the sensitivity of the rotor.

The reference sensor can be mounted against the axis of rotation of the rotor. In this embodiment, an odd number of rotor sections having different damping properties is sufficient. At least it is necessary to have three such sections. In this arrangement, the reference sensor will be influenced in the same way by all sections with different damping properties and therefore emits a reference signal. In this arrangement, the reference sensor must be precisely centered and also a relatively large distance between the two sensors, since it is advantageous, as mentioned, if the sensor is positioned as close as possible to the circumference.

If this is to be avoided, according to a further preferred embodiment of the invention, the reference sensor is situated against a rotor section having other damping properties than those of the rotor sections which lie opposite the measuring sensor. This region with somewhat neutral damping properties can then occupy a certain disc surface so that the reference sensor can be located very close to the measuring sensor. This entails the substantial advantage that external disturbances, for example caused by external magnetic fields, external temperature influences, have practically the same effect on both sensors, so that these external effects are eliminated from each other.

The disc-shaped embodiment is a disc

A particularly simple rotor is characterized in that the rotor is made of plastic with metal coatings which form sections with different damping properties. These metal coatings differ, for example, by different thickness, for example vaporized copper layers, or also by different shapes, for example by different number and / or size of ring.

If the rotor is designed as a hollow cylinder, it is characterized by a particularly low inertia, which is naturally advantageous, especially if the medium flowing at a low speed is to be measured.

It has already been mentioned that the sensors are designed as coils. Cores of the core-free coil can be used, i. coils without steel core or even ferrite coils.

Core-free coils are used because, in contrast to ferrite cores or even ferromagnetic cores, there is no saturation of the core material, which may be caused by external DC-magnetic fields (= interference). The core in the state of saturation can no longer receive further energy, in particular the energy of the sensor oscillating circuit. (The sensor coil with a capacitor, considered to be an oscillating circuit, can no longer perform any oscillations, since the energy reservoir / = coil / does not allow any change in energy.)

Suitable ferrite cores with a high saturation field strength are used to achieve targeted magnetic field guidance and improve sensor coil quality.

The premagnetizing losses can be maintained by appropriately selecting the ferrite core material for the corresponding frequency ranges. Low energy is then consumed.

Ferrite coils can be used with mushroom-shaped cores (e.g., especially for a cup-shaped rotor. The cup-shaped is a semi-shell shape, belongs to the state of the art for magnetic proximity sensors).

The advantages of the core-free coils are that static magnetic fields do not lead to any saturation of magnetic energy in the coil. The sensor oscillating circuit can oscillate without hindrance. The advantages of ferrite core coils are that they provide good pole guidance, amplification and bundling to the damped section of the rotor, and improve the quality of the coil and hence the oscillating circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following description by way of example with reference to the accompanying drawings, in which they are shown;

Fig. 1a shows a schematic view of the essential elements of the detector according to the invention, the rotor having three sections with different damping; 1b shows a view corresponding to FIG. 1a, wherein the detector has four sections with different attenuation, FIG. 1c shows a front view and a side view of an always modified embodiment, wherein the rotor is formed as a hollow cylinder and the coils are coils with ferrite cores; FIG. 1d is a diagram for illustrating the damping versus time and rotation angle of full rotation of the signal obtained by the arrangement of FIG. 1a; FIG. 1e shows a diagram of a further embodiment of the detector, FIG. 2 shows a circuit diagram for the oscillating circuits of both sensors, FIG. 3a is a block diagram of FIG. 3b a state diagram, FIG. 4 shows a block diagram for the evaluation electronics.

DETAILED DESCRIPTION OF THE INVENTION

A possible construction of the sensor device is shown schematically in FIG. Ia. The speed detector consists of a flat rotor disk R with an odd number of three or more rotor segments d0, d1, d2 of different electromagnetic properties, a measuring sensor MS which is mounted on the rotor periphery and a reference sensor RS which is located above the rotor center. The range of the measuring sensor is essentially limited to one rotor sensor. The measuring sensor range includes all rotor segments with equal proportions.

Typically, coils are used as sensors in which the rotor also has a magnetic circuit. Individual rotor segments have the ability to sense energy to the sensor coil by coupling magnetic fields. For example, the rotor segments may be laminated with copper foil of varying thickness. Placing a different number of shorting rings on each or shorting rings with different diameters on each rotor segment is a second possibility. Several segments of k = 3 are used to save costs. This example is further followed without limiting the generality.

Another possible arrangement of the sensor assembly is shown in FIG. lb. It is possible to provide a (k + 1) -the rotor region which is characterized by a moderate damping of the other rotor regions. This is the central rotor region dm.

Fig. 1e shows the rotor in a cup form with a region 12 of buffer material. A mushroom-shaped measuring sensor 13 is mounted in the rotor. Force lines are also indicated. A reference sensor 14, beside the measuring sensor, is also shown in the rotor on the axis of rotation 15.

The sensors are always part of an oscillating circuit that is briefly energized and then performs free damped oscillations. The elimination of electrical oscillations is dependent on the damping of the various rotor segments. Fig. 1d shows the damping d or the quality Q of the oscillating circuit, proportional to the damping, depending on the rotor angle setting.

Depending on the rotor position phi (phi), the measuring sensor generates a periodic attenuation with a period of 2π. After the phase transition from the rotor segment to the next segment, the damping is constant as the rotor segment moves around the measuring sensor.

The course of the reference signal is largely independent of the rotor position. It only changes with the variation in the electromagnetic properties of the entire sensor assembly and can therefore be used as a fault compensation signal for the measuring sensor. It is thus possible to compensate for temperature deviations (for example, system-dependent for volume measuring parts) and the external field. It is also achieved

Ί interference suppression for quasi-static magnetic fields when the magnetic pole time deflection maintains the sensing condition described in the following section.

The two sensor oscillation circuits are energized at a distance t1 for a short time over time tp and the oscillations are evaluated from the directions via the measuring window. The sensor device can thus be regarded as a sensor system.

Quantization of the sensor signal by both counters leads to a digital representation of the sensor signal (i.e., quality or damping). The sensor device can thus be treated as an analog-to-digital reader.

The sensor is operated at a scanning speed of 1 / Ta. Since the reference sensor will also be operated at this scan rate, in order to continuously evaluate the measurement signal to the reference sensor signal, it is also possible to specify the maximum rotational speed at k of the rotor segments, respecting the Shannon sensing condition and taking into account the overshoot coefficient u:

n = 1/2 (2 Ta.k.u), where Ta> tmer + tl + tp.

Fig. 2 shows a wiring diagram of a possible sensor device. To drive the oscillating circuit, the switch S1 is closed (on) for a time tp. The switch S2 of the same sensor is open, the switch of the non-energized sensor is closed to prevent electromagnetic coupling of both sensors.

Fig. 4 shows a flow chart of the sensor signal processing process. Control of the sensor signal processing process is taken over by the control unit. The sensor signals are fed to an analogue demultiplexer that fulfills a hardware-implemented threshold (with hysteresis) with an always connected sensor signal: a hard decision is made. The threshold signal thus obtained represents the time sequence of exceeding the oscillation threshold of the sensor oscillating circuit and is therefore proportional to the current quality Q of the sensor oscillating circuit or damping d. The number of N threshold exceedances is calculated by reference or sensor readers for each individual sensor oscillation, depending on whether the reference or measurement sensor is active. The threshold generation switching network generates k-1 thresholds, with which the following sensor counter state (soft decision) is compared, as these threshold values are stored in k-1 delays. The starting signals K [1] and K [k-1] are processed in the rotation and direction detection apparatus. This provides two time-varying digital starting signals that can be interpreted as a 1 / k direction and pulse.

Fig. 3a shows a detailed block diagram of the rotary recognition device and the direction for k = 3 different rotor segments. It consists of a finite state machine (FSN) and a D-flip-flop.

A sequential circuit state diagram is shown in FIG. 3b. The sequential circuit is modeled as the finite Mealy automaton. The individual states result from the damping shown in FIG. 1a and 1d at k = 3 rotor segments. The S4 state is redundant and will be used as an error state. The generated error signal can be stored and monitored. The transition function from error state S4 is not indicated because it can be triggered in different ways (e.g., asynchronous resetting signal, synchronously by the transition function to the permissible state). The sequential circuit may be formed as a switching sequence circuit with at least two storage components (flip-flops), with a further D-flip-flop needed for direction recognition.

The 1 / k rotation pulses and the direction signal can be further processed from the volume measuring part.

Thus, it is clear that the core of the invention, compared to the prior art, allows a reduction in the number of sensors to two, as well as an increase in the number of damping segments with different electromagnetic properties, thus enabling the invention to perform rotation and direction detection at minimal cost.

The design cost function occupies an absolute minimum of 2 sensors and 3 different rotor segments.

This allows, with unchanged technology, a higher rotor blade scanning speed and thus higher speed detection. At a given maximum number of revolutions, energy can be saved relative to a given sensor system with three, four or more sensors, since fewer sensor readings must be performed per unit of time. The rotation detector is therefore particularly suitable for battery-operated sensor systems.

The angular distribution can be varied by a number of different angular segments within certain limits, which depend on the geometry of the measuring sensor.

The construction of the sensor device shown is effectively carried out by an analysis procedure with computer support. Optimization of the sensor system parameters is not or very difficult to perform analytically, but can provide arbitrary sensor system optimizations,

Algebraic sensor models provide a precise numerical solution or provide optimum system parameters for a given sensor system.

Claims (13)

Rotation detector, in particular for a volume measuring part, with a rotor comprising a plurality of angularly distributed sections having different damping properties for electromagnetic oscillation, against which several sensors are arranged, which are each element of the oscillating circuit, so that the oscillating circuit oscillates attenuated, the initial signals of the oscillating circuits being supplied to a discriminator circuit which measures the rotor speed and, optionally, the direction of rotation thereof, characterized in that it comprises exactly two sensors (MS, RS), one of which is a reference sensor ( RS) lies opposite to the area of the rotor (R), whose damping properties do not change when the rotor (R) rotates, and the rotor (R) has an odd position in the area opposite to the second sensor, the measuring sensor (MS). number of sections (d0, d1, d2) with different damping properties. Rotation detector according to claim 1, characterized in that the rotor (R) is designed as a disc (Fig. 1a, 1b). Rotation detector according to claim 1 or 2, characterized in that the measuring sensor (MS) is arranged as close as possible to the rotor circumference (Fig. 1b). Rotation detector according to any one of claims 1 to 3, characterized in that the reference sensor (RS) is arranged against the axis of the rotor (R) (Fig. 1a). Rotation detector according to any one of claims 1 to 4, characterized in that the reference sensor (RS) is opposite to a section (dm) of the rotor (R) having damping properties other than those of the rotor sections (d0, d1, d2). that lie opposite the measuring sensor (MS). Rotation detector according to claim 5, characterized in that the rotor section (dm) which is opposite the reference sensor (RS) has a damping property corresponding to the diameter of the damping properties of the section opposite the measuring sensor (MS). The rotation detector according to any one of claims 1 to 6, characterized in that the reference sensor and the measuring sensor (MS) lie as close as possible to each other. Rotation detector according to any one of claims 1 to 7, characterized in that the rotor (R) is designed as a plastic disc with metal coatings which form sections (d1, d2) with different damping properties. Rotation detector according to claim 8, characterized in that the metal coatings have different thicknesses in sections with different damping properties. Rotation detector according to claim 8 or 9, characterized in that the metal coatings have different shapes, different electrical conductivity and / or magnetic conductivity in the regions with different damping properties. Rotation detector according to any one of claims 1 to 7, characterized in that the rotor (R) is designed as a hollow cylinder or a cup (Fig. 1c, Fig. 1e). Rotation detector according to claim 11, characterized in that the sensors (RS, MS) are spaced apart axially (Fig. 1c). Rotation detector according to any one of claims 1 to 12, characterized in that the sensors (RS, MS) are designed as coils without ferrous cores or as coils with ferrite cores.