JPH0349369B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a noise-resistant optical encoder.

The optical encoder according to the present invention is used, for example, to detect and control the rotation of a servo motor in the field of numerically controlled machine tools.

[Prior art and problems to be solved by the invention]

Generally, in an optical encoder, a light emitting diode LED is used as a light source, a rotating slit plate fixed to the rotating shaft of a motor, a fixed slit plate facing the rotary slit plate, and the light from the light source is transmitted to the rotating slit plate and the fixed slit plate. and a light-receiving element that receives light that has passed through.

In a conventional optical encoder, as shown in FIG. 7, power from a power supply energizes the encoder and light source, and part of the power passes through a printed circuit board 71 and is applied to a light receiving element 73 via a connection line 72. There is. The light receiving element 73 is attached to a recessed portion of a fixed slit stand 75 that supports a fixed slit 74. The output voltage of the light receiving element generates a pulse in the processing circuit. In this case, since a weak current from the light receiving element flows through the connection line 72 connecting the light receiving element 73 and the printed board 71, there is a problem in that it is easily influenced by noise. Therefore, the optical encoder tends to generate noise in the signal of the minute current path, and therefore needs to be shielded.

[Means for solving problems]

According to the present invention, a printed circuit board for a light receiving element of an optical encoder and a printed circuit board including a light emitting part are connected by a plurality of connection wires, and the plurality of connection wires are integrated by resin molding and assembled at once. At the same time as resin molding, a metal shield foil is formed using the on-sert method, and a metal film that acts as a shield film is formed on the outer surface of the resin body in which a large number of connection wires that conduct microcurrent are buried. , a noise-resistant optical encoder characterized in that the metal coating is connected to the through-hole portion of the light receiving part and the reference potential point of the printed circuit board on the power supply side, and eliminates noise of electromagnetic induction components from outside the encoder. provided.

〔Example〕

FIG. 1 is a diagram showing an outline of a noise-resistant optical encoder as an embodiment of the present invention. Reference numeral 2 denotes a printed circuit board including a light emitting section, and power and light from the cable and optical fiber bundle section are sent to the light receiving element via the printed circuit board 2. Reference numeral 1 is a connecting wire portion, and reference numeral 13 is a metal shielding foil. Metal shielding foils are formed as so-called onserts, for example by applying paint or by applying metal foil. The metal shield foil 13 is connected to a grounding connection line 115 at a connection portion 114 .
111 to 114 are non-grounded connection lines. 31 is a rotating shaft, 32 is a rotating slit plate, 41 is a fixed slit plate, and 5 is a printed board for a light receiving element. 42
is a fixed slit base, and 6 is a flange.

The assembly situation of the device shown in FIG. 1 is shown in FIGS. 2, 3, and 4.

In FIG. 2, connection wires 111 to 115 are buried in the resin molded part 12, and a ground connection wire 115 is connected to the metal shield foil 13 through the connection part 14.

FIG. 3 shows a top view of FIG.

Figure 4 is an exploded view of connecting wires with shield foil attached to a pair of printed boards, and shows a plurality of connecting wires 111.
A pair of upper and lower printed circuit boards 2 and 5 are attached to the circuit boards 115 to 115. 2 indicates a printed circuit board for the LED circuit, and 5 indicates a printed circuit board for the light receiving element.

Figure 5 shows the deformation of the connection line in the device shown in Figure 1.
It is shown in FIG. FIG. 6 is a top view of FIG. 5. The metal shield foil 16 is connected to the non-grounded connection wire 11
1, 112, 113, and 114. The grounding connection wire 115 is provided to penetrate the metal shield foil 16.

If the on-sert method is adopted for forming the metal shield foil in manufacturing the device shown in FIG. 1, the metal shield foil will be formed at the same time as the resin molding, and the manufacturing process can be simplified. In other words, in general, when coating a metal plate or metal foil over a connection wire, the process is as follows: inserting the connection wire → soldering → pasting insulating tape →
At least 6 steps are required, such as pasting the metal foil → connecting a part of the metal foil to the shield wire, so the first step is
The simplifications in the manufacturing process of the device are significant.

〔Effect of the invention〕

According to the present invention, in the optical encoder,
A shielding film such as metal foil is adopted for the minute current path, and the connection wire for the return path of the output of the light receiving section is buried in the resin body, and a metal film is formed on the surface of the resin body by the so-called on-sert method, and the printed board on the power supply side is The ground potential point and the through-hole portion of the light receiving portion are connected to the metal coating, so that a shielding effect can be exhibited. Thereby, the noise resistance of the optical encoder can be improved, and pulse counting errors after waveform shaping due to noise in the amplified waveform can be prevented. In addition, the connection wires are embedded in resin so that a metal coating is formed on the outer surface.
The manufacturing process can be simplified.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part showing an embodiment of an optical encoder according to the present invention, FIGS. 2 and 3 are a side view and a top view of a buried part of a connecting wire with shielded foil according to the present invention, and FIG. 4 Figure 5 is an exploded view of connecting wires with shielded foil inserted into a pair of printed circuit boards, and Figure 5 is a top view of the connecting wires that bring the inner and outer metal foil parts into a conductive state.
FIG. 6 is a top view of a connection line in the case where a metal shield foil is applied to a resin by an on-sert method, and FIG. 7 is a front view of an encoder including a conventional connection line portion. 1... Connecting wire section, 2... Printed circuit board, 5...
...printed circuit board for photodetector, 6...flange,
111-114... Connection wire (non-grounded), 115
...Grounding connection wire, 12...Resin molding part, 13,
16... Metal shield foil, 14... Grounding connection part, 31... Rotating shaft, 32... Rotating slit plate,
41...Fixed slit plate, 42...Fixed slit stand.

Claims (1)

[Scope of Claims] 1. A printed circuit board for a light-receiving element of an optical encoder and a printed circuit board including a light emitting part are connected by a plurality of connection wires, and the plurality of connection wires are integrated by resin molding to be integrated at once. They are buried so as to be attached all at once, and at the same time as resin molding, a metal shielding foil is formed using the on-sert method, thereby forming a metal coating that acts as a shielding coating on the outer surface of the resin body in which a large number of connection wires that carry minute currents are embedded. A noise-resistant optical encoder, wherein the metal coating is connected to a through-hole portion of the light receiving portion and a reference potential point of a printed circuit board on the power supply side, and removes noise of electromagnetic induction components from outside the encoder.