JPH02176885A - Stamp detector by magnetic sensor - Google Patents

Abstract

PURPOSE:To detect a stamp without being affected by ambient leakage magnetism or electrical noise by detecting difference between the magnetic field of the stamping part and that of the non-stamping part of an object to be detected. CONSTITUTION:A magnetic 1 is magnetized in one direction, and is a magnetic sensor on which the one end of a substrate 3 forming a ferromagnetic magneto-resistance element(MR element) 4 to apply magnetic force on a stamping part is adhered. In the case of making the magnetic sensor approach the non-stamping part of a ferromagnetic body, the magnetic flux of the plane 2 of the magnet of the ferromagnetic body passes entire parts of the MR element 4. Next, in the case of making the magnetic sensor approach the stamping part 6 of the ferromagnetic body, the magnetic flux of the plane 2 of the magnet advances in the directions of both ends 7 and 8 of the non-stamping part 5 and the stamping part 6 of the ferromagnetic body, however, magnetic poles are generated at both side ends 7 and 8, and since both polarity of the magnetic flux are the same polarity, the magnetic fluxes are repulsed with each other, and the magnetic fluxes advance in a direction separated from the stamping part 6, and the magnetic fluxes which pass the MR element 4 are reduced, which enables the presence/absence of the stamp to be identified by an electrical circuit.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is directed to the use of a magnetic spatula to print engraved characters on a ferromagnetic material.
”, a device that reads an electric circuit using a magnetic sensor such as a fi1 electric conversion element;

Conventional technology Traditionally, high-pressure gas containers, internal combustion engines, etc. have been individually engraved with different symbol numbers and used for management purposes. This method of pasting nameplates has the drawback that they are easily removed and separated, so a method is used in which different symbol numbers are stamped on each nameplate, making it impossible to prevent alterations and to erase them.

However, when it is necessary to read the symbol number, the user reads the symbol while looking at the stamp and writes it on the paper, but since the color of the stamp and the surrounding area are the same, it is difficult to read it easily, resulting in misreading and reduced work efficiency. Due to the decline in numbers, there is a serious problem in management, which is the basic purpose of symbol numbers.

For this reason, attempts have been made to coat the engraving with ink or the like to make it easier to read, or to read it optically using optical sensors, but due to the variety of environmental conditions, no practical method has yet been completed. do not have.

Problems to be Solved by the Invention The present invention utilizes the fact that when a magnetic field is applied to the stamped part, there is a difference in magnetic flux density between the stamped part and the non-warped marked part, and a magnetic sensor is used to detect the marking. This is to read the symbol number in 1fi5+ manner and eliminate the above problem.

Operation First, the operation of the present invention will be explained with reference to FIGS. 1 to 6 as an example using a ferromagnetic magnetoresistive element (hereinafter referred to as MR element).

In Figure 1, 1 is a magnet that is magnetized in one direction,
This is a magnetic sensor in which a substrate 3 on which an MRg element 4 is formed is adhered to one end of a magnet in order to apply magnetic force to the engraved portion.

Now, to explain the flow of magnetic flux when the 81-ki sensor shown in Figure 1 is brought close to a ferromagnetic material, Figure 2 shows the flow of magnetic flux when the 81 sensor shown in Figure 1 is brought close to a ferromagnetic material.
This is the case when the magnetic sensor is placed close to the magnetic sensor 5, and at this time the magnetic flux of the magnet surface 2 passes through all parts of the MR element 4. Next, when a magnetic sensor is placed close to the engraved part 6 of the ferromagnetic material, the magnetic flux of the magnet surface 2 is transferred to the non-engraved part 5 of the ferromagnetic material and both ends 7.8 of the engraved part 6, as shown in FIG. However, magnetic poles are generated at both ends 7.8, and the polarity of the magnetic flux is the same, so the magnetic fluxes repel each other, and the magnetic fluxes pass through the MR element 4 in the direction far from the stamped part 6. becomes less.

By guiding such changes in magnetic flux to the electric path of the electric circuit shown in FIG. 4, presence or absence of markings can be identified as shown in FIG.

In FIG. 4, 10 is a load resistance for converting changes in resistance due to the magnetic field of MR element 4 into changes in voltage, and resistor 9
．． Reference numeral 11 denotes a bias resistor for adjusting the output P1 of the differential amplifier 12 to take a value of O when the magnetic sensor approaches the non-engraved portion.

Therefore, when the magnetic sensor is close to the non-engraved f15, the output of P1 is naturally O.

When the 81% sensor is close to the marking part 6, the MR element 4
Since the magnetic flux passing over the MR element 4 decreases, the resistance value of the MR element 4 decreases, so the output of Pl increases.

The output of Pl is shaped by a waveform shaping circuit 13 as shown in FIG. 5, and a detection signal corresponding to the presence or absence of a marking can be obtained.

EXAMPLE Next, this example will be explained with reference to FIGS. 6 to 10. Since there are naturally many types of engraved character shapes to be detected, in order to judge characters based on detection signals, it is necessary to use detection signals from as many points as possible. I have to get it. Therefore, the magnetic sensor unit 17 of this embodiment has MR elements arranged in series as shown in the MR element array 14 in FIG. 6, and one end of each MR element MO to Ml is connected in common as shown in FIG. Connect to ground G. This MR element array 14 is adhered to a magnetic force applying magnet to constitute the magnetic sensor unit 17 of this embodiment ηII.

On the other hand, the other ends MO'' to M7' of each MR element are connected to the power of the differential amplifier 15, respectively.

Generally, in a magnetic detection device such as this embodiment, a differential amplifier requires an amplification factor of at least several hundred times because the detection signal becomes weak at C. However, of course, there is magnetic noise in this device and circuit. , 7. Since there is unspecified noise such as electrical noise, it has an adverse effect on the magnetic signal detection port '7□3.

In order to detect accurate signals without being affected by these noises, the MR element MO closely outputs the resistance value on the non-engraved part, as shown in FIG. The circuit is configured such that all inputs are the difference from the resistance of the MR elements M1 to Ml for marking detection, with the resistance value of the MR element MO as a reference. As a result, the differential amplifier 15
The common mode noise of the antenna is removed, and the adverse effects due to the temperature characteristics of the MRN element are also improved. Therefore, the differential amplifier 15 is supplied with only a voltage that is exactly proportional to the difference in magnetic flux from M1 to M1 with respect to MO.

In FIG. 7, R7 from RO is rl! lUpper air unit 1
A resistor 7 is set so that the output of Pl of the waveform shaping circuit 16 is set to 0 when the resistor 7 is on the non-engraved part of the ferromagnetic material.

Now, when the magnetic sensor unit 17 moves in the X direction over the character 19 marked zlJ on the ferromagnetic material 1B in the perspective view of this embodiment in FIG.
Each of the MR elements moves eight points x7 from XO in the X direction. By this operation, the signal output of each output P1 to Pl of the waveform shaping circuit 16 is changed to each MR as shown in FIG.
The output is output according to the strength of the magnetic field that the element receives. Output Pl
to P7 can be used for each purpose after being subjected to time-division processing for each suitable moving distance in the X direction, introduced into a storage circuit such as a computer, and subjected to character recognition processing by software.

Effects of the Invention As described above, the present invention detects the difference in the magnetic field between the engraved part and the non-engraved part of a non-detecting object, and can detect the engraved mark without being affected by surrounding magnetic leakage or electrical noise. , the structure can be easily provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a magnetic sensor as an example for explaining the present invention, and FIG. 2 is a view taken along the line A-A' in FIG. longitudinal section,
Fig. 3 is a vertical cross-sectional view when the sensor is close to the marking part, Fig. 4 is an electronic circuit diagram when an example of the present invention is implemented, and Fig. 5 is stamped by the electronic circuit shown in Fig. 4. FIG. 6 is an explanatory diagram showing the state of the MR array array when this embodiment is implemented using an MR element of an 81 air sensor, and FIG. 7 is an electronic circuit diagram of this embodiment. FIG. 8 shows that the magnetic sensor unit 17 has the number (4) in FIG. 10.
)19 when moving in the X direction from MO to M7 and the letters (
4) An explanatory diagram showing the relationship with 19. Fig. 9 is an explanatory diagram showing the states of outputs P1 to P7 when the magnetic sensor unit 17 detects the number (4) 19, and Fig. 10 is a perspective view showing the relationship between the marking of this example and the 81 sensor unit. It is. Figure 1 Figure 4 Figure 5 Figure 2 Figure 3 Figure 6 Figure Boat Figure Figure

Claims (1)

[Claims] 1. Regarding the reading of characters engraved on ferromagnetic material, magnetic force is applied to the engraved part of the ferromagnetic material, and the difference in magnetic flux density in the magnetic circuits between the magnet and the engraved part, and between the magnet and the non-engraved part is utilized. An engraving detection device attempts to detect the presence or absence of an engraving by comparing the difference between the detection signal output of a magnetic sensor that detects an engraving part and the detection signal output of a magnetic sensor that detects an engraving part as a reference.