JPH0634302A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To afford a margin to positioning precision between a magnetic body assembly and an outer case to reduce assembling processes, and provide an inexpensive magnetic sensor in which fluctuation of offset output is little and a stable characteristic can be obtained all the time. CONSTITUTION:A columnar inner magnetic body 2 is arranged nearly at a center part inside of a cylindrical outer magnetic body 1. Nearly at a center part in the length direction of the inner magnetic body 2, a primary coil 4 for excitation is wound, and on both sides thereof a first and a second secondary coils 5a, 5b are respectively wound. The first and the second secondary coils 5a, 5b are connected to each other in reversed polarity to constitute a differential transformer wherein a difference of output of both the coils is taken out. In order to fit a magnetic body assembly composed of the outer magnetic body 1 and the inner magnetic body 2, a cylindrical outer case 8 made of resin is provided in the outer circumferential part of the outer magnetic body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a coin processing machine for processing coins, particularly a large-sized coin sorting machine or coin depositing / dispensing machine having a forced coin conveying means, a coin feeding device, a coin sorting device and the like. In a coin processing machine, the present invention relates to a magnetic sensor used as a material sensor for detecting the material of a coin in order to determine the denomination and authenticity of the coin.

[0002]

2. Description of the Related Art Conventionally, for example, in a coin processor for sorting coins by type, coins are dispensed one by one from a hopper containing coins of mixed denominations to be sorted by a coin dispensing device. The fed coins are conveyed by a coin forced conveying means such as a conveyor belt, and during the conveyance, the discriminating section consisting of an optical sensor and a magnetic sensor (material sensor) determines the denomination and authenticity of the conveyed coins. The coins to be conveyed are discriminated, the coins to be conveyed are discriminated by the coin discriminating device, and are stored in the stacker of the corresponding denomination.

In a large coin processing machine having such a coin forced transfer means, a coin feeding device, a coin sorting device, etc., the magnetic sensor used as the material sensor is, for example,
It was fixed to a sensor fixing block that was fixed to the coin sorter by screwing or the like. The sensor fixing block has a structure in which the upper surface is pressed by a conveyor belt to convey coins, and a considerable pressing force is also applied to the sensor fixing block via the coins.

Therefore, the sensor fixing block is formed of a non-metal material such as aluminum.
Further, the outer case of the outer magnetic body of the magnetic sensor fixed to the sensor fixing block is made of metal (brass, for example).

As is well known, metals have a characteristic that eddy currents are generated so as to prevent interlinking magnetic flux. Therefore, if this external case of the magnetic sensor is removed,
The positional relationship between the sensor fixing block and the external magnetic body becomes a problem, and rather than accurately matching them, a metal external case is used in advance for magnetic shielding, and the magnetic sensor and the external case are accurately separated by polishing with the magnetic sensor alone. Since it is easier to perform the positioning, the non-magnetic metal outer case was used as described above.

[0006]

Heretofore, in this type of magnetic sensor, ferrite has been used as a magnetic material.
It was easy to crack. Therefore, for the purpose of reinforcement, a cylindrical outer case is used outside. The lower part of the outer case is inevitably longer than the upper part due to the reinforcement of the lead wire. The length of this lower part is linked with the leakage magnetic flux, and if the length varies between solids, the amount of metal with which the magnetic flux links changes, and the output voltage (offset when the coin is not present) Voltage) will vary.

Therefore, it is needless to say that the alignment accuracy between the inner magnetic body and the outer magnetic body is required, and also the assembling precision between the magnetic body assembly and the outer case to be fitted.
Since this type of magnetic sensor is a differential transformer type sensor, the output level is determined by the balance of the amount of magnetic flux linked to the two secondary coils.

As in the conventional case, in the case of the metal outer case, since an eddy current is generated so as to prevent the interlinking magnetic flux,
If the positioning accuracy between the magnetic body assembly and the outer case is poor, 2
An imbalance will occur between the outputs of the next coil,
The sensor output fluctuates when there is no detected object (hereinafter,
We call this output the offset).

Normally, this kind of magnetic sensor is adjusted for each machine body by adjusting the output level when the reference piece is set to a specified value when adjusting the gain of the amplifier for amplifying the sensor output. Was taken. In the case of this method, the variation in the offset output becomes the variation in the sensor performance as it is, so there is no mutual relation between the aircrafts, it is necessary to make the sensor circuit and the magnetic sensor one to one, and the assembly adjustment in the manufacturing line, In addition, it takes a lot of time and trouble to provide services when a machine breaks down, which has been a problem.

On the other hand, as described above, since the variation in the offset output largely depends on the mechanical accuracy, a high assembly accuracy is required in manufacturing the magnetic sensor, the number of manufacturing processes increases, and the cost increases.

Therefore, according to the present invention, the positioning accuracy between the magnetic body assembly and the outer case is roughened, the assembling process is reduced, the variation in offset output is small, and stable characteristics are always obtained, and the magnetic sensor is inexpensive. The purpose is to provide.

[0012]

The magnetic sensor of the present invention comprises:
A cylindrical outer magnetic body, a columnar inner magnetic body provided substantially centrally inside the outer magnetic body, and a primary coil for excitation wound substantially centrally in the longitudinal direction of the inner magnetic body. When,
First and second secondary coils that are respectively wound around both sides of the primary coil of the internal magnetic body and are connected to each other with opposite polarities and are electromagnetically induced by the primary coil;
And a cylindrical outer case made of a non-magnetic and non-conductive substance that is fitted to the outer peripheral portion of the outer magnetic body.

[0013]

The magnetic flux generated from the exciting primary coil wound around the internal magnetic body is linked to each secondary coil while the internal magnetic body is linked to the external magnetic body to generate an induced voltage. Occurs,
The differential output is taken out. The amount of magnetic flux interlinking with the secondary coil depends on whether the longitudinal end faces of the inner magnetic substance and the outer magnetic substance are aligned, and whether or not there is a metal or the like that interferes with the magnetic flux near the both end faces. As is well known, metals produce eddy currents that interfere with interlinking magnetic flux. Therefore, when the outer case is made of metal as in the conventional case, the amount of magnetic flux linked to the secondary coil on one side is reduced due to the positional deviation (displacement of the end surface) between the magnetic body assembly and the outer case. , The differential output fluctuates, and the characteristics are deteriorated. However, when the outer case is non-magnetic and is made of a non-conductive material as in the present invention, the AC loss does not occur, so that stable output characteristics can always be obtained regardless of the assembly accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 schematically shows a coin discriminating portion of a large-sized coin processing machine in which the magnetic sensor according to the present invention is used. In the figure, reference numeral 21 denotes a coin feeding device, which feeds coins of mixed denominations inserted into a hopper (not shown) one by one and conveys them to a coin identifying unit 22. Coin feeding device 21
The coins C fed out in 1 are sent to the coin sorting device 23 through the coin discriminating unit 22, and are sorted into the same type based on the discrimination result of the coin discriminating unit 22. Reference numeral 24 denotes a conveyor belt, which compulsorily conveys the coins C fed by the coin feeding device 21 by frictional force while pressing the coins C on the feeding surfaces of the coin identifying part 22 and the coin sorting device 23.

The coin discriminating section 22 is composed of a sensor fixing block 27 fixed to a fixing section 25 provided in the coin sorting device 23 with a screw 26, and a magnetic sensor 28 housed and supported by the sensor fixing block 27. ing. The sensor fixing block 27 is formed of a non-magnetic metal such as aluminum in terms of strength in order to withstand vibration caused by the conveyance of the coin C and vibration caused by driving of the conveying belt, the feeding belt, and the like.

Conventionally, a major cause of forming the outer case of the magnetic sensor from metal was the sensor fixing block. That is, when the magnetic body is directly housed in the sensor fixing block, the positioning accuracy between the both magnetic bodies and the sensor fixing block is required. Since it is easier to provide an outer case made of metal and position the outer case and both magnetic bodies by polishing or the like, the outer case made of metal has been conventionally used. Also,
In addition, in order to improve the mounting accuracy, the outer case is required to have high dimensional accuracy, and it is also convenient that brass or the like, which is made of metal, has good machinability and has little corrosion, is convenient.

Next, the structure of the magnetic sensor 28 will be described with reference to FIG. In the figure, reference numeral 1 denotes a cylindrical outer magnetic body, and a cylindrical inner magnetic body 2 is arranged substantially in the center thereof. The internal magnetic body 2 has flange-shaped projections 3a, 3b, 3c, 3d formed at four locations in the lengthwise direction. The primary coil 4 for excitation is provided between the protrusions 3b, 3c in the substantially central portion, and the protrusions 3a, 3 on both sides thereof are provided.
A first secondary coil 5a is wound between b and a second secondary coil 5b is wound between the protrusions 3c and 3d.

A sine wave signal having a predetermined frequency is input from the oscillator 13 to the primary coil 4. Further, the secondary coils 5a and 5b wound with the primary coil 4 sandwiched therebetween are
The differential transformers are connected to each other in opposite polarities, and the output of each coil is taken out as a difference.

The outer magnetic body 1 and the inner magnetic body 2 have positioning rings 7a and 7b formed of resin or the like on the stepped portions 6a and 6b formed on the inner side surface of the outer magnetic body 1 at both ends in the longitudinal direction thereof. By fitting them, they are positioned and fixed. At this time, positioning of both magnetic bodies 1 and 2 in the longitudinal direction, that is, end face alignment is performed. The positioning ring 7b at the lower end of the drawing is a so-called C ring for drawing the coil lead wire to the outside.
It has a ring shape.

A cylindrical outer case 8 is provided on the outer peripheral portion of the outer magnetic body 1 in order to fit the magnetic body assembly consisting of the outer magnetic body 1 and the inner magnetic body 2 as described above. The outer case 8 is made of non-magnetic and non-conductive material such as resin. Recently, some resins are comparable to metals having excellent dimensional accuracy and environmental resistance, and the material cost is low.

The outer case 8 has a stepped portion at a position slightly shallower than the length of the magnetic bodies 1 and 2, and a stepped portion made of resin is provided there.
The C-plate fixing base 9 is inserted and fixed. Then, the above-mentioned magnetic body assembly is inserted and fitted and fixed to this. The PC board fixing base 9 is for positioning in the depth direction when the magnetic body assembly is fitted. At this time, the positioning of the magnetic body assembly is performed so that the end surface of the magnetic body assembly (the upper end surface with respect to the drawing) slightly projects outward from the end surface of the outer case 8.

The PC board fixing base 9 is provided with a so-called D-cut portion or notch portion in order to draw out the lead wire of each coil. In addition, the coil lead wire and the lead wire 10
PC board (printed circuit board) 11 for connection with
The PC board fixing base 9 is inserted and fixed through a protrusion provided at the center of the PC board fixing base 9.

Lead wires 10 for connecting the differential outputs to an external electric circuit (not shown) are soldered to the PC board 11 in a predetermined order and led out to the outside. PC
The solder connection portion on the plate 11 is fixed by bonding with a mold resin (for example, silicone rubber) 12 for fixing.

Next, in such a structure, the flow of the magnetic flux generated by the primary coil will be described with reference to FIG. 1
The generated magnetic flux of the secondary coil 4 is mainly concentrated on the four protrusions 3a to 3d of the internal magnetic body 2 and the secondary coils 5a and 5b.
, But a part of it is linked to the end face of the magnetic body assembly. As in the conventional case, the outer case 8 is made of metal (for example,
In the case of brass), a part of the magnetic flux interlinking with the end surface of the magnetic body assembly fluctuates due to variations in positional accuracy between the magnetic body assembly and the outer case 8.

As is well known, metals have the property of generating eddy currents in the direction in which the magnetic fluxes that interlink are blocked. When the magnetic body assembly is aligned with the end surface of the outer case 8, when the outer case 8 is protruded, or when the magnetic body assembly is protruded from the end surface, all the magnetic fluxes linked to the secondary coil 5a change. Become. On the other hand, since the magnetic flux interlinking with the secondary coil 5b does not change, the differential output (offset output) changes when there is no object to be detected (metal or the like) in the sense portion, which deteriorates the characteristics. Usually, for the initial adjustment of this type of magnetic sensor, a method has been used in which the gain of the circuit is made constant, or a reference piece is set and the output at that time is adjusted to a specified value. In the case of the conventional adjustment method, variations in offset output cause variations in the magnetic sensor itself, which is a problem.

In order to improve the positioning accuracy, not only the number of steps such as polishing increases and the cost increases, but also the projection 3 of the internal magnetic body 2 must be controlled unless the polishing amount is controlled.
The thickness of a and 3d in the longitudinal direction fluctuates, the magnetic resistance becomes unbalanced, and the performance is further deteriorated. However, in the case of the magnetic sensor according to the present invention, since the outer case 8 is made of resin, AC loss unlike in the case of metal is not generated, and only the positioning accuracy of the magnetic bodies is the cause of the characteristic variation. Therefore, it is possible to inexpensively manufacture a magnetic sensor with a small variation in characteristics due to assembly accuracy.

As described above, according to the above-mentioned embodiment, if the magnetic body assembly is slightly projected from the end face of the outer case, the positioning accuracy is not required, and the conventional positioning jig is used. Further, steps such as polishing of the tip after assembling can be eliminated, so that assemblability and assembly cost can be reduced.

Further, since the AC loss due to the magnetic flux interlinking in the outer case does not occur, the fluctuation of the differential output depends only on the positioning accuracy of the magnetic bodies, and is not affected by other machine accuracy. , Always stable output characteristics can be obtained. Furthermore, since the material itself is inexpensive, the material cost can be reduced.

[0030]

As described above in detail, according to the present invention, the positioning accuracy between the magnetic body assembly and the outer case is roughened, the assembling process is reduced, and the variation of the offset output is small, so that the stable characteristics are always obtained. In addition, it is possible to provide an inexpensive magnetic sensor.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a configuration of a magnetic sensor according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a flow of magnetic flux generated by a primary coil of a magnetic sensor.

FIG. 3 is a configuration diagram schematically showing a coin identification unit of the coin processing machine.

[Explanation of symbols]

1 ... External magnetic material, 2 ... Internal magnetic material, 3a-3d ...
Protrusion, 4 ... Primary coil, 5a, 5b ... Secondary coil,
8 ... Outer case, 21 ... Coin feeding device, 22 ...
Coin identification unit, 23 ... Coin sorter, 24 ... Conveyor belt, 27 ... Sensor fixing block, 28 ... Magnetic sensor, C ... Coin.

Claims (1)

[Claims] 1. A cylindrical outer magnetic body, a columnar inner magnetic body provided substantially in the center of the inside of the outer magnetic body, and an excitation wound around the center of the inner magnetic body in the longitudinal direction. Primary coil and a second coil that is wound around both sides of the primary coil of the internal magnetic body and is connected to each other with opposite polarities and is electromagnetically induced by the primary coil. A magnetic sensor comprising: a secondary coil; and a cylindrical outer case made of a non-magnetic and non-conductive material that fits around the outer magnetic body.