JPH03225224A - Magnetic scale signal detector - Google Patents

Abstract

PURPOSE:To display a picture with fine resolution by reading out a magnetic signal from a magnetic scale with rough magnetizing pitch by a detecting head. CONSTITUTION:A 2mm-pitch signal recorded on the magnetic scale 25 is read out by the detecting head 19 and converted into A and B phase pulses with 0.4mm pitches and the pulses are transmitted to a display counter 24, which displays a picture with 0.1mm resolution. Since display with fine resolution can be attained by using the easily producible magnetic scale 25 prevented from being demagnetized in the lapse of time and having the rough magnetizing pitch and the read signal is converted into two signals having a 90 deg. phase difference (A and B phase pulses) by the detecting head 19 and then transmitted to the counter 24, the highly reliable position display system stabilized against an external magnetic field and noise as compared with a system for transmitting an analog signal can be offered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic scale signal detection device that can obtain a position display with fine resolution from a magnetic scale with a target magnetization pitch in a magnetic scale digital position display system used for displaying the position of industrial machinery. It is something.

``Prior Art'' One conventional magnetic scale digital position display system uses a saturable coil in the detection head. As shown in FIG. 4, two sets of saturable coils 1 detect two sets of sine and cosine signals 3 from the magnetic scale 2, and a detector 4 receives the scale signals from the head 5 to determine the resolution (reading unit). ) corresponding to the right and left rows of the head.
A DOWN pulse voltage is output and displayed on the counter 6.

In some cases, the detector is built into the head or counter.

In addition, as a detection head using a ferromagnetic metal thin film magnetoresistive element, for example, as is known from Jikai Publication No. 60-35215, etc., the magnetoresistive element piece is There is a method to obtain the necessary display resolution by arranging them in parallel, arranging them facing each other with an air gap to detect the signal, and interpolating the obtained analog signal using a phase modulation detection method etc. .

For example, as shown in the circuit conceptual diagram in FIG. A square wave 11 with a phase difference is taken out and the tarok pulse 15 is converted into a game 1 using this square wave 11.
-12 L, and by counting the pulses 13 obtained as its output, the position of the detection head can be digitally displayed with the required display resolution (reading unit).

``Problems to be solved by the invention'' Magnetic scales that use saturable coils in their detection heads use magnetic flux responsive coils that require precision machining and are arranged at regular intervals according to the required display resolution. , requiring many windings, high-precision machining, and assembly. Further, an AC bias peculiar to the magnetic flux responsive coil is required, and as the moving speed of the head increases, a commensurate high frequency AC bias is required.

In addition, in a detection head using a ferromagnetic metal thin film magnetoresistive element, a method for obtaining the necessary display resolution by interpolating the analog voltage waveform obtained from a conventional element using a phase modulation detection method, etc. The higher the inner seed coat, the more likely distortion of the original analog voltage waveform becomes an interpolation error, and to improve accuracy it is necessary to make the magnetization pitch itself of the magnetic signal recorded on the magnetic scale finer. The present invention is based on a magnetic scale with a targeted magnetization pitch.
This is a device whose purpose is to detect position indicating signals with fine resolution.

"Means for solving the steering point problem" The present invention consists of a row of ferromagnetic metal thin film magnetoresistive elements arranged at a pitch of the same length as the resolution (reading unit) required in a display system, and A differential input comparator converts the analog signal obtained by forming a bridge using a magnetoresistive element, an OR circuit generates a 90° phase difference AB signal from each of the obtained pulses, and the transmitted 90°
This device is characterized by comprising a counter that receives the phase difference AB signal multiplied by 4 and displays the position corresponding to the right row and left row of the detection head for each resolution. The detection head is composed of a magnetoresistive element, a differential input comparator, and an OR circuit, and the length of the transmission cable connecting the detection head and the display counter varies depending on the needs of the display system.

"Operation" Using a magnetic linear scale on which a magnetic signal 16 is recorded at a magnetized pitch, the purpose is to display a digital position at a resolution (reading unit) λ finer than the magnetized pitch ρ. do. Assuming that the magnetization pitch g and the resolution input have a relationship of j=nλ, the detection device is required to have an n multiplication function. In the present invention, by having a detection head having a structure in which 2n magnetoresistive element arrays are arranged at intervals of pitch λ, information corresponding to the resolution on a one-to-one basis can be obtained from linear elements without using interpolation. This increases the accuracy and reliability of reading. Four resistive elements form one bridge circuit, and each intermediate potential VR1
7 and VR18 to the differential comparator 35, a pulse waveform is output.

Next, by inputting each pulse output from the differential comparator 35 to the OR circuit, 90
Two signals with a phase difference are obtained. At this time, the A-phase and B-phase are pulses each having a wavelength of 4λ.

The 90° phase 2 signal (AB phase pulse) obtained by the magnetoresistive element array 20, the differential comparator 21, and the OR circuit 22 that constitute the detection head 19 is transmitted to the transmission cable 2.
3 and is input to the display counter 24.

The display counter 24 shows the rise of each AB phase pulse,
By detecting the falling edge, the resolution of the AB phase pulse can be multiplied by 4, and the direction can be determined and counted. The configuration and operation of this counter can be realized using known techniques. According to the above explanation, corresponding to the detection head moving to the right or left on the magnetic scale with the magnetization pitch g,
The position is displayed on a display counter in reading units λ (ρ=nλ).

"Example" Next, we read the signals recorded with a magnetization pitch of 2 mm,
The present invention will be specifically explained using an example in which display is performed with a resolution of 0.1 mm.

FIG. 6 shows an external view of the magnetic scale and detection head. The magnetic scale 25 is now widely used as a signal recording scale for digital position display systems in industrial machinery. The most common is stainless steel base26
Rubber magnet 2 with a certain thickness (for example, 0.4 mm)
9 is glued with an adhesive such as epoxy resin. For the magnetic scale, a rubber magnet is magnetized in the thickness direction, and N and S poles are alternately magnetized and recorded at regular intervals (2 mm in this example). This interval is the magnetization pitch, and it is known that the coarser the magnetization pitch, the greater the amount of magnetic flux generated from the magnetic graduations recorded on the scale, and the easier the magnetization work is.

Therefore, it is advantageous to have the magnetization pitch as targeted as possible in terms of the influence on the external magnetic field and in the manufacturing process of the magnetic scale, but it is disadvantageous in making the reading unit (resolution) finer.

In the case of the magnetization pitch of 2 mm in this example, the surface magnetic flux density is approximately 120G (Gauss), and in the normal usage environment, the influence of external magnetic fields is small, and the magnetization process in scale production is also performed using a coiled yoke. It is known to be simple because one-shot magnetization is possible. However, in general industrial machinery, a reading unit of at least 0.1 mm resolution is required, so it is necessary to read 1/20 from the scale of 2 ImT + pitch.

Therefore, in the present invention, as shown in FIG. 1, arrays of ferromagnetic metal thin-film magnetoresistive elements arranged at 0.1 inch intervals are used as detection sensors.

As a known technique, as shown in FIGS. 2 and 7, 4
By assembling a magnetoresistive element into a bridge, the N pole,
It is known that one cycle of a sine wave can be extracted as a sensor signal from the magnetic signal of each S pole. At this time, there is a relationship of 1-2λO between the magnetization pitch g and the interval λ0 between the four elements forming a pair. Therefore, for example, element Δ130, element A131, element At'32, element A1°
33 are spaced by 1 mm each, but At , At ,
By constructing a bridge circuit as shown in Figure 2 with the four At 'A1' lines, intermediate potentials VR17 and VR18 can be set.
are output as two signals 34 with a 180° phase shift shown in FIG. These signals are input to the differential comparator 35. In the case of this embodiment, the sensor output 34 is
Since each voltage is about 50 mV (P-P>(5V drive)), there is no problem in the operation of the comparator, and as shown in FIG. It is output from the comparator 35.

FIG. 3 shows a timing chart that is the principle of the present invention. With the magnetic signal 16 of the magnetic scale, from the above explanation, one cycle of pulse waveform 36 is obtained for one pole of the magnetic signal.

In exactly the same way, a total of 1 of A, ~A5, and B1-B5 in FIG.
Zero types of pulse waveforms 36 are obtained.

By inputting these pulse waveforms to the OR circuit 38 shown in FIG. 9, two signals 39 with a 90° phase difference between the A phase and the B phase are obtained. At this time, as shown in FIGS. 3 and 9, the A-B phase pulse has a wavelength of 4λ, which in this embodiment is 0.4 mm.

As described above, the detection head 27 consisting of the magnetoresistive element array 37, the differential input comparator 35, and the OR circuit 38 detects magnetic signals at a pitch of 2 mm and detects magnetic signals at a pitch of 0.4 mm.
Output as a pitch A-B phase pulse. Here, the gap 40 between the detection head 27 and the magnetic scale 25 is approximately 0.5 mm ±0.1 mm in this embodiment.

As is well known, the distance between the magnetic scale attached to the machine and the display counter is usually 1 m to 10 m, and when transmitting analog waveforms, a relay amplifier etc. is required, but in the case of this example. Since the transmitter transmits the AB phase pulse waveform, it does not require a relay amplifier or the like. Even when used in places with poor noise environments, it is easy to apply to line driver transmission. The transmitted signal is multiplied by 4 in the counter as described above, and the signal is multiplied by 0. 1m+n
Displayed in resolution.

FIG. 10 shows a conceptual diagram of the present invention.

The 2 nym pitch signal recorded on the magnetic scale 25 is read by one detection head, and the AB of 0.4 mm pitch is detected.
It is converted into a phase pulse, transmitted to a counter, and displayed on a display counter with a resolution of 0.1 mm.

[Effect of the Invention J] The present invention is an apparatus characterized in that a magnetic signal on a magnetic scale with a small magnetization pitch is read by a detection head and displayed with fine resolution.

According to the present invention, in the digital position display system,
By using a magnetic scale with a coarse magnetization pitch that is easy to manufacture and does not demagnetize over time, it is possible to display fine resolution.Moreover, it is possible to display two signals with a 90° phase difference (AB phase pulse) at the detection head. Since the signal is converted and transmitted to the display counter, it is possible to provide a highly reliable position display system that is stable against external magnetic fields and noise, compared to systems that transmit analog signals.

[Brief explanation of drawings]

Fig. 1 is a principle diagram showing the positional relationship between the magnetic signal of the magnetic scale and the magnetoresistive element array, which is a feature of the present invention, Fig. 2 is a principle diagram of the blade Tsuji circuit, and Fig. 3 represents the principle of the present invention. FIG. 4 is a conceptual diagram of an example of a conventional technique; FIG. 5 is a conceptual diagram of an example of a conventional technique; FIG. 6 is an external view of the magnetic scale and detection head of the present invention;
The figure shows an example of a bridge combination of resistive elements, Figures 8 and 9.
The figure is an explanatory diagram of the operation of the differential comparator and OR circuit in the present invention, and FIG. 10 is a conceptual diagram of the present invention. 25...One magnetic scale...Detection head 16...Magnetic signal of magnetic scale 20...
... Magnetoresistive element array 21 ... Differential comparator 22 ... OR circuit 24 ... Display counter

Claims (1)

[Claims] In a magnetic scale type digital position display system, the magnetic signal recorded on a magnetic linear scale is read by a detection head and displayed on a counter. The purpose is to display the position with resolution, and the analog signal obtained by forming a bridge with a detection sensor with ferromagnetic metal thin film magnetoresistive elements arranged at a pitch corresponding to the resolution and four magnetoresistive elements is converted from analog to digital. A magnetic scale signal detection device comprising a detection head with a built-in circuit and a counter that quadruples and displays two 90° phase rectangular signals obtained by A-D conversion.