JPH045571A - Rotating direction discriminating and rotation detecting device - Google Patents

Abstract

PURPOSE:To discriminate a rotating direction with high detection sensitivity by employing simple constitution which uses a 3rd magneto-resistance element for reference. CONSTITUTION:The outputs of magneto-resistance elements 11 and 12 are inputted to the plus terminals of differential operational amplifiers 14 and 15 and the output of the 3rd magneto-resistance element 13 is connected to the minus terminals in common. The three magneto-resistance elements 11 - 13 are arranged on the same plane perpendicular to the rotary shaft of a magnet 101. The output amplitudes of the three elements are equal because of the symmetrical position relation between the elements and magnet and their output waveforms are 120 deg. out of phase with one another. The output of the element 13 can, therefore, be used for the reference of other outputs and the need for a conventional semi-fixed resistance and its adjusting operation is eliminated. The input difference voltage of the differential operational amplifier 14 is the difference voltage between the outputs of the magneto-resistance elements 11 and 13 and an amplitude which is one and half time as large as the amplitude of the output voltage of one element is obtained in this case because of the position relation between two elements to improve the sensitivity by about 50%. The differential operational amplifier 15 is the same.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to non-contact rotation direction discrimination rotation detection using a magnetic field.

[Summary of the Invention] The present invention uses two magnetoresistive elements and two differential operational amplifiers to non-contactly detect the number of rotations, including identification of the direction of rotation, using a rotating magnetic field caused by the rotation of a magnet attached to a rotating shaft. In the apparatus, one magnetoresistive element is further used as a comparison object for the magnetoresistive element, thereby making it possible to improve the magnetic field detection sensitivity and eliminate adjustment.

[Conventional technology 1] Conventionally, as a simple method for non-contact detection of rotation speed, changes in the magnetic field of a permanent magnet attached to a rotating shaft are detected by a magnetoresistive element, and the minute detection output of this magnetoresistive element is calculated. A common method is to amplify it with an amplifier and then count the number of rotations with a counter or the like. Furthermore, when detecting the rotation of a water meter, for example, the direction of rotation for supplying water and the direction of rotation for reverse flow due to a water outage are identified, and the accurate amount of supplied water is calculated by adding and subtracting. is necessary.

FIG. 3 shows a conventional example.

In FIG. 3(a), 31 and 32 are magnetoresistive elements;
3 is a semi-fixed resistor, 34 and 35 are differential operational amplifiers, 36.
37 are the outputs of the magnetoresistive elements 31 and 32, respectively, and 38
．． 39 are the outputs of differential operational amplifiers 34 and 35, respectively;
310 and 311 are power supply terminals. In FIG. 3(b), 31 and 32 are magnetoresistive elements, and 301 is a two-pole permanent magnet. FIG. 3(b) is a diagram showing the positional relationship between the magnetoresistive element and the permanent magnet, with the upper diagram being a plan view and the lower diagram being a front view.

FIG. 4 shows the waveform of the signal in FIG. 3. In FIG. 4,
The vertical axis is the voltage, the horizontal axis is the clockwise rotation angle of the permanent magnet 301, 41 is the waveform of the output 36 of the magnetoresistive element 31, 42 is the waveform of the output 37 of the magnetoresistive element 32, 40
1 is the waveform of the output 38 of the differential operational amplifier 34, and 402 is the waveform of the output 39 of the differential operational amplifier 35.

401.4 depending on the rotation of the magnet to the output of the differential operational amplifier
The slice level of the output waveform of the magnetoresistive element is adjusted by the semi-fixed resistor 33 so that a rectangular wave like 02 appears.

401 and 402 are two-phase rectangular waves, and the rotation direction of the magnet can be determined by the mutual phase lead or lag, and the rotation speed of the magnet can be calculated by counting the number of pulses of one rectangular wave. can do.

[Problems to be Solved by the Invention] However, in the conventional technology, the output voltage of a magnetoresistive element is minute, and its center value is affected by variations in the magnetic field strength of the magnet, the relative positional relationship between the magnet and the element, and variations in the element itself. Therefore, there was a problem in that the semi-fixed resistance had to be adjusted without fail.

The present invention has been made to solve these problems, and an object thereof is to provide a rotation detection device for discriminating rotation direction with a simple configuration that does not require adjustment of a semi-fixed resistor.

[Means for Solving the Problems] In order to solve the problems, the present invention provides a rotation detection device for detecting rotation direction that detects changes in the magnetic field of a rotating magnet using a magnetoresistive element and a differential operational amplifier. The outputs of the two magnetoresistive elements are connected to one input of each of the two differential operational amplifiers, and the output of the other magnetoresistive element is connected to one input of each of the two differential operational amplifiers. The output of the element is commonly connected to the other input of the two differential operational amplifiers, and the three magnetoresistive elements are arranged on the same plane perpendicular to the rotation axis of the magnet. It is something to do.

[Implementation Example 1] FIG. 1 shows an embodiment of the present invention.

In FIG. 1(a), 11, 12, and 13 are magnetoresistive elements, 14 and 15 are differential operational amplifiers, 16.17 are the outputs of the magnetoresistive elements 11 and 12, respectively, and 18.19 are 14 and 15, respectively. The output of the differential operational amplifier, 110.11
1 is a power supply terminal. In FIG. 1(b), 11
and 12 and 13 are magnetoresistive elements, and 101 is a two-pole permanent magnet. FIG. 1(b) is a diagram showing the positional relationship between the magnetoresistive element and the permanent magnet, with the upper diagram being a plan view and the lower diagram being a front view. The three magnetoresistive elements are arranged at positions of 120 degrees on the same circumference centered on the rotation axis of the magnet.

The outputs of the two magnetoresistive elements 11 and 12 are connected to respective non-inverting inputs of two differential operational amplifiers 14,15,
The output of the other magnetoresistive element 13 is the differential operational amplifier 1.
4.15, and the three magnetoresistive elements are arranged on the same plane perpendicular to the rotation axis of the magnet.

Figure 2 shows the waveform of the signal in Figure 1. In Figure 2,
The vertical axis is the voltage, the horizontal axis is the clockwise rotation angle of the permanent magnet lO1, 21 is the waveform of the output 16 of the magnetoresistive element 11, 22 is the waveform of the output 17 of the magnetoresistive element 12, 23
is the waveform of the output 103 of the magnetoresistive element 13, 201 is the waveform of the output 18 of the differential operational amplifier 14, and 202 is the waveform of the output 19 of the differential operational amplifier 15.

From the symmetrical positional relationship between the three magnetoresistive elements and the magnet, 3
The output amplitudes of the three magnetoresistive elements are the same, and their output waveforms have a phase difference of 120 degrees from each other. Therefore, the output of the third magnetoresistive element is the output of the other two magnetoresistive elements. It can be used as a reference, and the semi-fixed resistor and adjustment work required in the conventional technology can be omitted.

Furthermore, the input differential voltage of the differential operational amplifier 14 is the differential voltage between the outputs of the magnetoresistive elements 11 and 13. In this case, due to the positional relationship between the two magnetoresistive elements, this differential voltage is equal to the output voltage of one element. Since 1.5 times the amplitude can be obtained, the detection sensitivity is improved by 50% compared to the conventional technology. The same applies to the differential operational amplifier 15.

[Effects of the Invention] As described above, according to the present invention, in the rotation direction discrimination rotation detection device that detects changes in the magnetic field of a rotating magnet using a magnetoresistive element and a differential operational amplifier, the third magnetoresistive element With a simple configuration that uses the resistor as a reference, the adjustment work for conventional semi-fixed resistors can be omitted.

Further, according to the present invention, the detection sensitivity of a rotating magnetic field can be made higher than that of the prior art.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams of one embodiment of the present invention. 2(a) and 2(b) are diagrams of waveforms of the signals in FIG. 1. FIGS. 3(a) and 3(b) are diagrams of examples of traffic. 4(a) and 4(b) are waveform diagrams of the signals in FIG. 3. 11, 12゜14, 15 ・ 16, 17. 18, 19 ・ 110, 11 101 ・ ・ ・ 21 ・ ・ ・ 13 ・ 1 ・ ・ 22 ・ ・ ・ ・ ・ ・ ・ 23 ・ ・ ・ ・ ・ ・ ・ ・ Magnetoresistive element, differential operational amplifier, magnetoresistive element Output of the differential operational amplifier, power supply terminal, two-pole permanent magnet, magnetoresistive element 11, magnetoresistive element 11, magnetoresistive element 12, magnetoresistive element 12, output 201, magnetoresistive element 13, output 201.・ ・ ・ ・202 ・ ・
...
・ ・ ・ ・ ・ Blade type / Output waveform of differential operational amplifier 14 / Output waveform of differential operational amplifier 15 / Magnetoresistive element / Semi-fixed resistance / Differential operational amplifier / Output of magnetoresistive element / Differential operational amplifier・Power supply terminal ・Two-pole permanent magnet ・Width-edge type of magnetic resistance element 31 ・Width-edge type of magnetoresistive element 37 ・Output waveform of differential operational amplifier 34 ・Output waveform of differential operational amplifier 35 5f3(α)

Claims (1)

[Claims] In a rotation detection device for detecting rotation direction that detects changes in the magnetic field of a rotating magnet using a magnetoresistive element and a differential operational amplifier, 3
It consists of 2 magnetoresistive elements and 2 differential operational amplifiers.
The outputs of the two magnetoresistive elements are connected to one input of each of the two differential operational amplifiers, and the output of the other magnetoresistive element is connected to the other input of the two differential operational amplifiers. A rotation detection device for discriminating rotation direction, characterized in that the three magnetoresistive elements are commonly connected to an input and arranged on the same plane perpendicular to the rotation axis of the magnet.