JPH06168351A - Bar code reader - Google Patents

Abstract

PURPOSE:To make a bar code reader compact, to attain power saving and to eliminate the necessity of centering rubber by changing the number of permanent magnets and their arrangement in a galvanomirror driving voice coil motor. CONSTITUTION:Two permanent magnets 105 having respectively different polarity are arranged correspondingly to one driving coil 101. Namely the polarity of a permanent magnet 105a opposed to one side 101a of a driving coil 101 formed like a square shape is inverted from that of a permanent magnet 105b opposed to one side 101b opposed to the side 101a. Consequently the driving force of the coil 101 and that generated by a current flowing into the coil 101 are applied to the same direction, so that a bobbin 11 and a reflection mirror can be oscillated. The effective part, i.e., effective length, of the coil 101 can be increased, so that a current to be applied in order to driving force can be reduced and the number of coils and their number of turns can also be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bar code reader,
In particular, in the voice coil motor for driving the galvano mirror rotation, the use efficiency of the drive coil provided on the moving part side is improved, the moving part is made smaller and lighter, and further, the voice coil motor and the galvano mirror are made small and save. The present invention relates to a bar code reader designed for electric power conversion.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view showing a general example of a bar code reader, FIG. 7 is a front view thereof, FIG. 8 is a front view of a galvanometer mirror thereof, and FIG. 9 is a plan view thereof. First, the main configuration of the bar code reader will be described with reference to FIGS. In these figures, 1 is a bar code reader, 2 is a galvanometer mirror, 2a is a reflection mirror, 3 is a laser diode, 4 and 4a are laser beams, 5 is a photodiode, and 6 is a bar code. The laser light 4 emitted from the laser diode 3 is
The optical axis is changed by the reflection mirror 2a attached to the galvano mirror 2, and the laser beam 4a is irradiated onto the barcode 6. Laser light 4 irradiated on the bar code 6
The reflected light 4b of a is captured by the photodiode 5 provided in the vicinity thereof, and the information on the barcode 6 is read.

Here, the bar code 6 has a plurality of bars 6a formed over a certain width, and one bar or a plurality of pieces of information as a whole. In order to read all the bars 6a, it is necessary to move the bar code 6 or the laser beam 4a. here,
By changing the reflection angle of the laser beam 4 by swinging the reflection mirror 2a for changing the optical axis of the laser beam 4 about an axis perpendicular to the optical axis, the position where the laser beam 4a hits the barcode 6 is changed ( (Scanning, scanning).

Next, the structure of the galvanometer mirror will be described with reference to FIGS. In these figures, 11 is a bobbin, 12 is a ball bearing, 13 is a drive coil, 14 is a magnetic circuit, 15 is a side yoke, 16
Is a center yoke, 17 is a permanent magnet, 18 is a rotating shaft, 1
Reference numeral 9 is a compression coil spring, and 20 is a stopper. That is, a plurality of ball bearings 12 are attached to the central portion 11a of the cylindrical bobbin 11, and four rectangular drive coils 13 are fixed to the outer peripheral portion 11b of the bobbin 11. There is.

The magnetic circuit 14 is composed of a side yoke 15, a center yoke 16 and a permanent magnet 17, and the permanent magnet 17 is fixed to the opposing surfaces of the side yoke 15 and the center yoke 16 which are formed in a U shape. Rotating shaft 1
8 has one end fixed to the magnetic circuit 14, and the bobbin 11
Through the ball bearing 12 attached to the bobbin 11
Is swingably supported around the rotary shaft 18. The compression coil spring 19 is provided below the movable portion through the rotary shaft 18, and pushes up the ball bearing 12 and presses the ball bearing 12 against the stopper 20, thereby eliminating play in the ball bearing 12.

The reflecting mirror 2a is fixed to the upper surface 11d of the bobbin 11 as shown in FIG. 8, and the reflecting mirror 2a can be swung as the bobbin 11 is swung. When assembling the bobbin 11 in which the magnetic circuit 14 and the reflection mirror 2a are fixed, the center yoke 16 is provided with the groove 1 inside the bobbin 11.
1c, the side yoke 15 and the permanent magnet 17 are located outside the bobbin 11, and the drive coil 13 is located in the magnetic gap 14a. As shown in FIG. 9, each side 13a of each drive coil 13 enters the magnetic gap 14a, and the opposing side 13b has the magnetic gap 1a.
It is fixed so as not to enter 4a. In addition, the driving coil 13 is connected to each side 13a of the driving coil 13 in the magnetic gap 14a when a current is applied to the driving coil 13.
Are connected so that the currents flow in the same direction.

The operation will be described. By supplying a predetermined current to the four drive coils 13 connected in series or in parallel, a driving force is generated by the current and the magnetic flux of the magnetic circuit 14, and the bobbin 11 is rotated. At this time, the bobbin 11 and the reflection mirror 2a are oscillated by making the current flowing through the drive coil 13 sinusoidal, thereby changing the optical axis of the laser beam 4 and scanning the entire bar code 6. Or you can scan.

10 and 11 show another example of the galvano mirror. The reflection mirror 2a is fixed to the end surface of the rotor 21 formed in a column shape, and the pin 22 is provided on the other end surface and the end surface of the reflection mirror 2a. This pin 2
Reference numeral 2 is fixed to the inner rings of the ball bearings 23 and 24, and the rotor 21 and the reflection mirror 2a are rotatably supported.
The outer ring of the ball bearing 23 is fixed to the yoke 26 formed in an annular shape, and the outer ring of the ball bearing 24 is fixed to the frame 31.

The yoke 26 and the frame 31 are fixed at a position where the central axes of the ball bearings 23 and 24 are aligned. Two permanent magnets 25 having different polarities are fixed to the inner wall of the yoke 26. The rotor 21
Also serves as an inner yoke, and a magnetic circuit is formed by the rotor 21, the yoke 26, and the permanent magnet 25. The two drive coils 27 are wound in a substantially rectangular shape, and the rotor 2
It is fixed to the outer peripheral surface of 1. The drive coil 27 is configured to be positioned in the gap 28 between the permanent magnet 25 and the rotor 21 when the rotor 21 that is the movable portion and the magnetic circuit that is the fixed portion are assembled. As shown in FIG. 11, each drive coil 27 has each side 27a arranged in a space 28a so as to face the permanent magnet 25a, and one opposite side 27b arranged in a space 28b so as to face the permanent magnet 25b. Also,
The driving coil 27 is connected such that when a current is applied to the driving coil 27, each side 27a of the coil 27 in the air gap 28a is connected so that the current flows in the same direction.

The coil spring 29 is located outside the ball bearing 24 and is pressed against the ball bearing 24 by the holder 30, whereby the flange portion of the ball bearing 23 is pressed against the yoke 26. As a result, the backlash of the ball bearings 23 and 24 is eliminated.
Further, the centering rubber 32 is formed of silicon rubber or the like in a square shape, one end of which is formed on the yoke 26,
The other ends are fixed to the rotor 21, respectively, and are mounted at a position where the tension is minimized at the center of the operating range.
As a result, when the rotor 21 rotates, the centering rubber 32 is deformed, and the reference position for swinging the reflection mirror 2a is determined by the restoring force that attempts to restore this deformation.

The operation is as follows. That is,
By supplying a predetermined current to the two drive coils 27 connected in series or in parallel, a driving force is generated by this current and the magnetic flux of the magnetic circuit, and the rotor 21 is rotated.
At this time, the rotor 21 and the reflection mirror 2a are caused to oscillate by making the current flowing through the drive coil 27, for example, sinusoidal so that the oscillating range determined by the centering rubber 32 is always symmetrical with respect to the center. . Thereby, the optical axis of the laser beam 4 shown in FIGS. 6 and 7 is changed so that the entire bar code 6 can be stably scanned.

[0012]

However, as shown in FIG.
In the configuration as shown in FIG. 9, the effective portion for one of the drive coils 13 is only one side 13a of the drive coil 13 formed in a rectangular shape, and the other three sides are not involved in the driving force. That is the part. Therefore, in order to obtain a large driving force, the number of drive coils or the number of turns, the magnetic flux density,
It is necessary to increase the applied current. As a result, the weight of the movable part is increased, the voice coil motor is increased in size, and the galvanometer mirror is increased in electric power. Also, FIG.
0, FIG. 11 has a problem that the reference point for swinging the rotor 21 and the reflection mirror 2a is obtained by the centering rubber 32, so that the structure is complicated and the cost becomes high. . Therefore, an object of the present invention is to reduce the size and power consumption of a galvano mirror and to omit the centering rubber.

[0013]

In order to solve such a problem, in the first invention, a laser diode for emitting a laser beam, a galvano mirror having a reflecting mirror for changing the optical axis of the laser beam, and a center yoke are provided. A voice coil motor that has at least a magnetic circuit including a side yoke and a permanent magnet and a drive coil, and that drives the galvano mirror; and a photodiode that receives laser light that is emitted from the barcode and reflected from the barcode. In the bar code reader provided, permanent magnets are arranged at positions facing two sides of the drive coil wound in a substantially rectangular shape and fixed to the movable portion, and the polarities of the permanent magnets corresponding to the respective sides are reversed. It is characterized by doing.

In the second invention, a laser diode emitting a laser beam, a galvano mirror having a reflecting mirror for changing the optical axis of the laser beam, a rotor having the reflecting mirror fixed thereto, a yoke, a permanent magnet and the rotor fixed thereto. A bar code reader comprising a voice coil motor for driving the galvano mirror and a photodiode for receiving a laser beam emitted to a bar code and reflected from the bar code. Is made of a magnetic material, and its cross-sectional shape is substantially rectangular.

[0015]

The permanent magnet of the swing coil voice coil motor for changing the optical axis of the laser beam is arranged on a plurality of sides of the rectangular drive coil to increase the effective portion of the drive coil. At the same time, the polarities of the permanent magnets on the respective sides are made different from each other to achieve size reduction and power saving. In addition, the rotor is made of a magnetic material,
By making the cross-sectional shape substantially rectangular, the centering rubber is unnecessary.

[0016]

FIG. 1 is a front view showing an embodiment of the present invention, and FIG.
Is also a plan view thereof. This embodiment is different from the conventional one shown in FIGS. 8 and 9 in the structure of the voice coil motor for swinging the reflection mirror 2a, and the other basic structure is the same as the conventional one. That is, in FIG. 8 and FIG. 9, two drive coils 13 are provided for one permanent magnet 17.
However, in this embodiment, one drive coil 10 is provided.
Two permanent magnets 10 with different polarities
5 is provided. That is, the permanent magnet 105a facing the one side 101a of the drive coil 101 formed in a rectangular shape.
The polarity of the permanent magnet 105b facing the side 101b facing 101a is opposite. As a result, the driving forces generated by the driving coil 101 and the current flowing therethrough are in the same direction, which allows the bobbin 11 and the reflection mirror 2a to swing.

FIGS. 3 to 5 are for explaining another embodiment of the present invention, which is an improved example corresponding to FIGS. This embodiment is different from that shown in FIGS. 10 and 11 in the centering method for obtaining the center of the reflecting mirror 2a when the reflecting mirror 2a is driven. In other words, conventionally, centering rubber was used for centering,
Here, the centering rubber is not used, but the centering is performed by utilizing the property that the rotor is stable at the position of the largest magnetic flux in the magnetic field.

That is, as shown in FIG. 3, the reflection mirror 2
The rotor 201 to which "a" is fixed is made of a magnetic material, and has a substantially rectangular shape with the surface facing the permanent magnet 25 being the longitudinal direction. By doing so, the magnetic flux density in the radial direction of the air gap 28 between the rotor 201 and the permanent magnet 25 is small at the end of the permanent magnet 25 and the largest at the center thereof, as shown in FIG. Therefore, the largest magnetic flux is obtained when the rotor 201 is at the position as shown in FIG. 5A, and the magnetic flux is evenly distributed from the rotor 26 to the rotor 20 as shown by the magnetic force lines 203.
It will go around 1.

On the other hand, when the rotor 201 rotates to the position shown in FIG. 5B, the magnetic flux becomes smaller than that in the case of FIG. Not only that, the magnetic flux 203a at a position away from the surface of the rotor 201 facing the permanent magnet 25 causes the rotor 2
It returns to the yoke 26 without passing 01. As a result, the magnetic flux passing through the rotor 201 is reduced, and as a result, the rotor 201 is at a position where the magnetic flux is large.
A force will be generated to return to the position of (a), and eventually it will stabilize at the same position.

[0020]

According to the present invention, the effective portion of the drive coil, that is, the effective length can be increased by a simple modification by changing the arrangement and number of the permanent magnets in the galvano mirror driving voice coil motor. As a result, it is possible to reduce the applied current for obtaining the same driving force as the conventional one, reduce the number of coils and the number of turns, and further reduce the size of the barcode reader and save power. In addition, since the rotor is made of a magnetic material and its cross-sectional shape is substantially rectangular, it is possible to eliminate the need for centering rubber, reduce the size, reduce the number of parts, and further reduce the cost by not adjusting the centering. It is possible to obtain advantages such as.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a plan configuration diagram showing an embodiment of the present invention.

FIG. 3 is a plan view showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a magnetic flux density in the case of FIG.

5 is an explanatory diagram for explaining the operation of FIG. 3. FIG.

FIG. 6 is an external view showing a conventional example of a barcode reader.

FIG. 7 is a plan view of FIG.

FIG. 8 is a front view showing a conventional example of a galvanometer mirror.

FIG. 9 is a plan view showing a conventional example of a galvanometer mirror.

FIG. 10 is a front view showing another conventional example of a galvanometer mirror.

FIG. 11 is a plan view showing another conventional example of a galvanometer mirror.

[Explanation of symbols]

1 ... Bar code reader, 2 ... Galvano mirror, 2a ... Mirror, 3 ... Laser diode, 4, 4a ... Laser light, 5 ... Photo diode, 6 ... Bar code, 11 ... Bobbin, 12 ... Ball bearing, 13, 27, 101,
202 ... Coil, 14, 102 ... Magnetic circuit, 15, 1
6, 26, 103, 104 ... Yoke, 17, 25, 10
5 ... Permanent magnet, 18 ... Rotating shaft, 19, 29 ... Coil spring, 20 ... Stopper, 21,201 ... Rotor, 22 ... Pin, 23, 24 ... Bearing, 28 ... Void, 30 ... Holder, 31 ... Frame, 203 ... Magnetic field lines.

Claims (2)

[Claims] 1. A laser diode that emits laser light,
A galvanometer mirror having a reflecting mirror that changes the optical axis of laser light, a magnetic circuit including a center yoke, a side yoke, and a permanent magnet, and at least a drive coil,
A voice coil motor for driving the galvano mirror,
In a bar code reader equipped with a photodiode for receiving a laser beam emitted to a bar code and reflected from the bar code, in a position facing two sides of the drive coil fixed in a movable part and wound in a substantially rectangular shape. A bar code reader characterized by arranging permanent magnets respectively and reversing the polarities of the permanent magnets corresponding to the respective sides. 2. A laser diode which emits laser light,
A galvano mirror having a reflecting mirror for changing the optical axis of laser light, a rotor having the reflecting mirror fixed thereto, a yoke, a permanent magnet, and a drive coil having a substantially rectangular shape fixed to the rotor, and driving the galvano mirror. In a bar code reader including a coil motor and a photodiode that receives laser light that is emitted from the bar code and reflected from the bar code, the rotor is made of a magnetic material and its cross-sectional shape is substantially rectangular. Bar code reader characterized by.