JPS59230110A - Electromagnetic type rotation detector - Google Patents

Abstract

PURPOSE:To detect a rotation of a shaft whose rotational angle and rotating direction are varied remarkably, by providing two pickups placed opposingly by making them have a phase difference of 90 deg. against a tooth of a rotation detecting gear provided on a shaft to be measured. CONSTITUTION:A pickup has a structure in which both ends of a magnetic path constituted of a permanent magnet 3 and a magnetic material 4 connected to said magnet are opposed to a gear, and a Hall element 5 is placed on the end face of the permanent magnet 3, and it is utilized that a magnetic path length is varied in accordance with a position of a tooth, and a direction of the magnetic path is varied on the end face of the magnet. When the gear rotates at an angular velocity omega, an output is frequency-modulated by the angular velocity omega, and by frequency-demodulating it, a rotating speed omega is derived. Also, a phase of the gear is derived from a phase difference to a reference signal, and when a prescribed current is made to flow as a control current to pickups 12a, 12b from a carrier generator, Hall voltage is modulated, an output to be modulated is obtained by addition of a pickup output in an adding circuit, and a rotation detecting quantity can be known.

Description

[Detailed description of the invention] The present invention relates to an electromagnetic rotation detector.

The method for measuring the rotation speed of equipment with a rotating shaft is as follows:
In addition to methods that use a tachometer generator or rotary encoder, there is a method that uses a combination of an electromagnetic pickup and gears. In particular, when measuring the rotational speed of a large rotating device, this method of providing a gear for rotation detection on the shaft to be measured is widely used. It was possible to directly apply a rotary encoder to a relatively large piece of equipment. This is because problems often arise in terms of the strength of the encoder bearing.

The above method using an electromagnetic pickup can use existing gears, and unlike the photoelectric method, it is resistant to dirt from oil and the like, so it is widely used as a simple, inexpensive, and stable method. However, it measures the number of pulses within a unit time. Since this is a so-called zero-uniform rotation speed measurement, unlike a tacho generator, it is not suitable for detecting rapidly changing rotation speeds. Also, since the direction of rotation cannot be detected, a method for detecting this is, for example, by preparing two pickups with SO degrees shifted in phase with respect to the pitch of the gear, and determining from the phase of these two output signals. must be taken. Furthermore, if the rotation direction changes within the gate time, the counting method of the counter must be devised.

In view of the above problem, the present invention aims to provide an electromagnetic rotation detector using gears, which is advantageous when the rotation speed fluctuates greatly, especially when there are many changes in the rotation direction. It is something.

In order to achieve this object, the rotation detector of the present invention includes two pick amplifiers that are arranged facing each other with a phase difference of 90 degrees with respect to the teeth of a rotation detection gear provided on the shaft to be measured. The output signal changes sinusoidally with respect to the geometric phase difference between the teeth and the pickup, and the pickup is connected to a carrier generator that outputs a control current for modulation, and the output signal is sent to the pickup amplifier. An adder circuit is connected, and this output signal is frequency demodulated to determine the rotational angular velocity, and the phase of the gear is determined from the phase difference with the reference signal. It is possible to obtain an electromagnetic rotation detector that can detect

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, an electromagnetic pickup 2. When pick amplifiers 2a and 2b are arranged with a phase shift of 80 degrees with respect to the tooth period of the gear, the pick amplifiers 2a and 2b
b is a normal electromagnetic induction type or magnetic density response type (for example,
If it is an electromagnetic pickup (one that uses a magnetoresistive element or a pole element), the electrical angle from the two pink ups 2a and 2b is 80 degrees or -9 depending on the rotation direction of the gear.
A sinusoidal output signal shifted by 0 degrees is obtained.

Therefore, for these pickups, the output signal is 5 inches (
O++φ) or a variable equivalent thereto is used.

An example of a pickup that satisfies this requirement is shown in FIGS. 2 to 4.

The pickup shown in FIG. 2 has both ends of a magnetic path made up of a permanent magnet 3 and a magnetic material 4 connected thereto facing the teeth of a gear 1, and the permanent magnet 3 in a magnetic circuit made up of these and the gear 1. This structure has a Hall element 5 disposed on the end face, and utilizes the fact that the length of the magnetic path changes depending on the position of the teeth, and the direction of the magnetic path at the end face of the magnet changes.

In the figure, 5a indicates a magnetically sensitive part. Note that a magnetoresistive element may be used in place of the Hall element 5.

When the above pickup is used, the change in magnetic field strength H takes the form H=5In(Ol+φ)+. k is the magnitude of the magnetic field in the phase state shown by the chain line in the figure, and this is the bias.

This bias due to k can be eliminated if necessary, and an example of a pickup with this method is shown in the third example.
As shown in the figure. In this structural example, the magnetic path constituted by the magnetic material 4 is made into two loops 4a and 4b, and the permanent magnets 3a and 3b are set in opposite phases with respect to the teeth so that the direction of magnetization is opposite. ing. Therefore, when the length of the magnetic path in the loop formed by the magnetic material 4a becomes shorter, the loop formed by the magnetic material 4b becomes longer, and the Hall element 5 placed astride both loops receives the signal. The magnitude of the magnetic field changes in proportion to sin θ1.

The third method uses a divider type magnetoresistive element (eg, magnetically sensitive element SDME manufactured by Sony Corporation), and an example of its structure is shown in FIG. This magnetoresistive element 6
The output changes by sin 2α with respect to the rotation angle α of the magnetic field in the magnetically sensitive plane, and uses a magnetized ring in which a large number of equal-length magnetic domains are arranged in a ring-shaped magnetic body, and It is known that if the spacing between the magnetized ring and the magnetized ring is selected, the output changes sinusoidally with respect to the rotation angle of the magnetized ring. This characteristic can be utilized when using a magnetized ring.

When using a gear, an element with a bias magnet 7 (magnetized in the direction of the arrow in the figure) is installed parallel to the rotating surface of the gear, and the direction of the magnetic field is aligned depending on the phase relationship with the teeth. The tooth size and the element size may be selected so as to vary within the range of 90° to +90′. However, since the shape of the element is generally fixed, it is not practical to select an element that matches the dimensions of the tooth. For this reason, it is practical to tilt the element as shown in the figure and find an arrangement in which the direction of the magnetic field changes sufficiently.

When using such a magnetoresistive element, the optimal method for arranging the magnetoresistive element varies depending on the size of the teeth, and in some cases, it is necessary to add a magnetic circuit.

Next, we will describe the processing of the output signal of the pickup when the above-mentioned pickup is set so that the output changes sinusoidally as the gear rotates.

If the number of teeth of the gear is N and the rotation angle of the gear is θ, the pitch of the teeth corresponds to N・or'ad, so one pickup 2a has an output that changes in a relationship of 5 inNeθ, whereas the other The pickup 2b has cos
An output that changes in the relationship N·θ appears.

When using a Hall element in this state, the pin-up 2
The control current of a is I cosω. Pickup 2b at t
The control current of I sinω. If modulated by t, the output of the pickup 2a will be Icos ω. t @sin Noθ The output of pickup 2b is l5in c++. t @Co5N・θ, and adding this output gives l5inω. tacosN*θ+IC03CII. t
*sin No 0=Isin(ω.t+N− of −−
--(1)=E sin (C1l.t+NIIωt)
=Esin(ω.+Nω)1--...(2) However, ω
−5(=zπf).

Therefore, when O does not change in equation (1), the output frequency becomes fo=- and remains constant, and only the phase 2π shifts by N·θ.

Furthermore, if the gear rotates at the angular velocity ω, the output will be frequency modulated by the angular velocity ω of the gear according to equation (2) 8.

Therefore, by frequency demodulating this output signal, the rotational angular velocity ω can be determined. Furthermore, by measuring the phase difference from the reference value, the phase of the gear can be determined.

5 to 7 show circuit configurations for processing the output signals of the pickups shown in FIGS. 212 to 4, respectively, and the pickup 12 in FIG.
The pickups 13a and 13b in FIG. 6 are those shown in FIG. 3, and the pickups 14a and 14b in FIG. 7 are those shown in FIG. 4. There is.

In the circuit having the configuration shown in FIGS. 5 and 6, Icosωot is applied to the pickups 12a and 13a from the carrier generator as control currents, and l5inω is applied to the pinkups 12b and 13b. When t flows, the Hall voltages are c and osω, respectively. t, sinω. t, and a modulated output is obtained by adding the pickup outputs in an adder circuit.

Figure 6 shows a case where a Hall element is used in the configuration shown in Figure 3, and therefore there is no bias in the Hall element output, but when a bias magnetic field is applied to the Hall element as shown in Figure 2, In this case, it is necessary to add a bias magnet circuit 15 as shown in FIG. 5 to correct the output due to bias.

This means that the change in the magnetic field in the Hall element is sin
Since NmO+k and cos Noθ+, -IS1nω in the circuit of FIG. t, to *l5inc+>
. This will cancel the value t.

Figure 7 shows the tooth path configuration when a divider type magnetic resistance element as shown in Figure 4 is used as a pickup. It doesn't matter if it's a mold. The figure illustrates the case of three terminals.

In the case of the Hall element described above, the control current was modulated, whereas in this case, the drive voltage or current applied to the bridge was changed to CO3ω. It suffices to modulate by t and sinω01, and thereby the same result as in the case of a Hall element can be obtained (!).

In addition, to improve the quality of the modulated signal, it is better to arrange the magnetically sensitive 2) ↓ elements in multiple stages with gear pinches or integer multiples of pinches, but in this case, the elements are made by vapor deposition. Therefore, it is also possible to manufacture a dedicated array of multiple elements. The geometric precision at this time is determined by the manufacturing precision of the mask pattern, so high precision can be expected.

Figure 8 shows the same gear 21 at both ends of the torsion/<-20.
．． 22 and utilizes the fact that the phases of both gears change depending on the torque received by the torsion bar 20, which is a so-called phase difference type torque meter, in which the present invention is applied.

When a normal rotation detector is used, it is naturally impossible to detect the phase difference between the two gears because there is no signal from the pulse pickup when the rotation speed of the shaft is small or when the shaft is stopped. For this reason, when measurement is required even at low speeds or when stopped, a method is adopted in which the detector is rotated at a constant speed by another motor.

On the other hand, according to the rotation detector of the present invention, the output from each detector is a signal with the same wave number of the carrier phase even when the gear is stopped, and the phase difference between this signal and the carrier is It shows the geometric phase of gears and pickups. Therefore, by measuring the phase difference between the output signals of the two sets of detectors attached to the two gears, the three phase differences of the gears can be detected and can be effectively used as a torque meter.

Further, by demodulating the output of one of the two sets of detectors, a DC voltage proportional to the rotation speed including the polarity can be obtained. To know the rotation angle, it is also possible to use an up-down counter that performs addition based on the output signal of the detector and subtraction based on the carrier signal, thereby obtaining an output signal proportional to the rotation angle.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the phase relationship of the pickup, Figures 2 to 4 are front or oblique views showing configuration examples of the pickup amplifier, and Figures 5 to 7 are diagrams showing the configuration of the pickup amplifier. FIG. 8 is a circuit configuration diagram of a rotation detector of the present invention, and FIG. 8 is a configuration diagram of an application example of the present invention. 1... Gear, 2a, 2b, 12a ~ 14a, 12b ~ 14
b = pickup. Figure 1 Figure 2 Figure 3 Figure 4 WA Figure 8

Claims (1)

[Claims] 1.9 against the teeth of the gear for rotation detection provided on the shaft to be measured
Two pickups are arranged facing each other with a phase difference of 0 degrees, and the output signal changes sinusoidally with respect to the geometric phase difference between the teeth and the pickups, and the pickups are controlled to modulate the pickups. In addition to connecting to a carrier generator that outputs a current, an adder circuit that adds the output to the pickup is connected, and this output signal is frequency demodulated to obtain the rotational angular velocity, and the rotational angular velocity is determined based on the phase difference with the reference signal. An electromagnetic rotation detector characterized by determining the phase of gears.