JP5157212B2 - Optical encoder - Google Patents

Description

  The present invention relates to an inspection method for an optical encoder capable of guaranteeing encoder characteristics when a light amount of a light emitting element is reduced.

  Conventionally, in an optical encoder, a current is supplied to a light emitting element by electrical processing using a resistor, an amplifier, or the like. This light-emitting element has a high possibility that the encoder characteristics will be hindered when the light amount decreases with time and is generally halved.

On the other hand, in order to check the encoder characteristics when the light intensity of the light emitting element is reduced, the resistor mounted on the circuit board is replaced and the constant is changed to reduce the supply current to the light emitting element and check the encoder characteristics A method has been proposed (see, for example, Patent Document 1).
JP 2004-309203 A

  In the method of Patent Document 1, in order to reduce the light amount of the light emitting element, it is necessary to increase the resistance value of the resistor. On the other hand, after attaching a protective cover to prevent foreign matter from adhering to the rotating code plate and light receiving and emitting elements, aging is performed at high temperatures to ensure the reliability of the optical encoder, and initial changes due to thermal stress are detected. Confirmed and screened.

  The problem to be solved is that the amount of light can be reduced in advance only when the circuit board is exposed, that is, only before the protective cover is attached. It is a point that cannot verify the encoder characteristics. For this reason, the reliability of the optical encoder is reduced.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a highly reliable optical encoder capable of confirming encoder characteristics when a light amount of a light emitting element is reduced in a final state where a protective cover is attached.

  In order to solve the above-described problems, the present invention includes a light amount control circuit that obtains a reference light amount by applying a reference voltage to a light emitting element, and optically transmits position data detected by a serial signal that is a data transmission request signal from the outside. The encoder includes a current switching circuit that suppresses a current supplied to the light emitting element, and controls the current switching circuit by an external serial signal.

  The current switching circuit includes at least one set of a switch controlled by an external serial signal and a resistor connected in parallel or in series to the switch, and is connected in parallel or in series to the light emitting element. .

  Furthermore, the current switching circuit includes at least one set of a switch controlled by a serial signal from the outside and a resistor connected in series to the switch, and a voltage dividing resistor is connected in series to the current switching circuit, The reference voltage of the light amount control circuit may be divided.

According to the optical encoder of the present invention, since the supply current to the light emitting element can be suppressed by an external serial signal without touching the electronic component, the light amount is reduced even in the final state where the protective cover is attached. You can verify the encoder characteristics at any time.

  If a plurality of current switching circuits are used, it is possible to confirm a decrease in the amount of light in a plurality of patterns, and it is possible to grasp the degree of deterioration of the light emitting element during use.

  Therefore, it is possible to provide a highly reliable optical encoder without worrying about foreign matter adhering to the light emitting / receiving element after verification of the encoder characteristics when the amount of light is reduced.

  An optical encoder according to the present invention includes a rotating unit including a rotation code plate, a fixing unit that fixes a signal processing circuit board to which a light receiving element and a light emitting element are attached, at a predetermined position facing the frame, and a protective cover. The data detected by the serial signal which is a data transmission request signal from the outside is transmitted.

  The fixed portion includes a current switching circuit that suppresses a current supplied to the light emitting element. The current switching circuit includes a switch controlled by a serial signal from the outside, and a resistor connected in series to the switch. At least one set, and the switch is closed by a serial signal from the outside, and the current supplied to the current light-emitting element is suppressed by the resistor, so that the encoder characteristics at the time of light quantity decrease can be verified.

  FIG. 1 is an overall configuration diagram of an optical encoder. In FIG. 1, the rotating portion of the optical encoder is composed of a rotary code plate 1 and a boss 2, and is fixed to the motor shaft 3 after centering and fixing. The fixed portion includes an analog signal processing circuit board 4 on which a light receiving element 5 and the like to which a fixed code plate 6 is attached, a power circuit board 7 on which a light emitting element 8 is mounted, a frame 9, a rotary code plate 6, the light receiving element 5, and a light emitting element. 8 and a protective cover 10 that prevents foreign matter from adhering to 8, and the analog signal processing circuit 4 and the power supply circuit board 7 are fixed to a predetermined position of the frame 9.

  FIG. 2 is an explanatory diagram of the data communication unit. In FIG. 2, the bidirectional bus 21 is composed of a line driver receiver for switching between transmission and reception of serial data with the outside. The receiver 22 receives a serial signal that is a data transmission request signal from the outside, outputs a transmission start signal after completion of normal reception, and if the serial signal is a signal that requests switching of a supply current to the light emitting element. A current switching signal for switching the supply current of the light emitting element is generated. The transmitter 23 converts the position data into serial data in response to the transmission start signal.

  FIG. 3 shows a light amount control circuit according to the first embodiment. The light quantity control circuit 30 is composed of a resistor 39 that is connected in series with the light emitting element 38 and limits the supply current, and ensures a steady light emission amount.

  Here, the main part of the present invention will be described. The current switching circuit 31 according to the first embodiment is configured by connecting a switch 32 and a resistor 33 in series, and is connected to the light emitting element 38 in parallel.

  Since the current switching circuit 31 closes the switch 32 by a current switching signal from the outside, the current supplied to the light emitting element 38 is also shunted to the resistor 33, and the current supplied to the light emitting element 38 can be reduced. . In general, when the light amount of the light emitting element is reduced by half, the encoder characteristic is hindered. Therefore, the resistance value is set so that the steady light amount is reduced by half.

  Thereby, even when the protective cover is attached, the encoder characteristics when the light amount of the light emitting element is reduced can be verified, and a highly reliable optical encoder can be obtained.

In the first embodiment, the case where the current switching circuit 31 is one set has been described. However, if a plurality of resistors having different resistance values are provided and the switch is controlled by an external current switching signal, the amount of light can be reduced. It is possible to verify the encoder characteristics with a plurality of patterns.

  These mean that the degree of deterioration of the light emitting element can be grasped not only in the initial stage but also in any environment.

  In Example 2, a current switching circuit is connected in series to the light emitting element to suppress the light emission current, which will be described with reference to FIG.

  In FIG. 4, the light amount control circuit 40 according to the second embodiment includes a light emitting element 48 and a resistor 49 that limits a supply current, and ensures a steady light emission amount. The current switching circuit 41 is provided in series with the current limiting resistor 49 and the light emitting element 48, and is configured by connecting a switch 42 and a resistor 43 in parallel.

  The switch 42 of the current switching circuit 41 according to the second embodiment is closed in a steady state, and is controlled so that the switch 42 is opened by a current switching signal from the outside. In a steady state, the current supplied to the light emitting element 48 by (Vcc−VF) / (resistor 40) becomes a form in which the resistor 43 is connected in series to the resistor 49 by opening the switch 42.

  Therefore, the supply current to the light emitting element 48 is reduced by (Vcc−VF) / (resistor 49 + resistor 43), and the light emission amount is suppressed.

  Thereby, even when the protective cover is attached, the encoder characteristics when the light amount of the light emitting element is reduced can be verified, and a highly reliable optical encoder can be obtained.

  As in the first embodiment, if a plurality of current switching circuits 41 are installed and the switch is controlled by a current switching signal from the outside, the encoder characteristics when the amount of light is reduced can be verified by a plurality of patterns. Even inside, the degree of deterioration of the light emitting element can be grasped.

  The current switching circuit of the third embodiment suppresses the light emission current by changing the light amount reference voltage value of the light amount control circuit, and will be described with reference to FIGS.

  In FIG. 5, the light amount control circuit 50 compares the light emission amount (light amount reference voltage value) of the light emitting element 58 with the light reception amount (voltage value) of the light receiving element 55, and controls the light emission current of the light emitting element 58. Note that the light quantity reference voltage value of the light emitting element 58 is a design value for obtaining the light emission amount in a steady state, and is determined in consideration of the lifetime of the light emitting element.

  In FIG. 6, the current switching circuit 61 is configured by connecting a switch 62 and a resistor 63 in series, and is connected to a light amount setting power source between ground levels via a resistor 64. The switch 62 is closed during normal operation, and the voltage divided by the resistors 63 and 64 is input to the light amount control circuit 50 as a light amount reference voltage value.

  Here, when the switch 62 of the current switching circuit 61 is opened by an external current switching signal, the light quantity reference voltage value changes. At this time, since it is necessary to reduce the light quantity of the light emitting element 58, it is necessary to set the resistance ratio of the resistor 63 and the resistor 64 so that the light quantity reference voltage value after the change becomes high.

Thereby, the switch 62 can be closed by an external current switching signal to reduce the light emission current, and the encoder characteristics when the light quantity is reduced can be verified.

  As in the first and second embodiments, a plurality of current switching circuits 61 may be connected in parallel, and the encoder characteristics when the light amount is reduced can be verified with a plurality of patterns of supply current.

  As described above, when the optical encoder of the present invention is used, the light quantity of the light emitting element can be forcibly reduced by an external serial signal even after being incorporated in a device such as a motor. It can be confirmed from the outside as needed.

  The optical encoder of the present invention is useful for a servo motor or the like that requires long life and reliability, and can also be used for maintenance and inspection work.

Cross-sectional view of structure of optical encoder in the present invention Block explanatory diagram of the data communication unit in the present invention Operation explanatory diagram of light quantity reduction in Example 1 of the present invention Operation explanatory diagram of light quantity reduction in Example 2 of the present invention Explanatory drawing of the light quantity control circuit in Example 3 of this invention Operation explanatory diagram of light quantity reduction in Example 3 of the present invention

Explanation of symbols

1 Rotation Code Plate 2 Boss 3 Motor Shaft 4 Analog Signal Processing Circuit Board (Circuit Board)
5, 55 Light receiving element 6 Fixed code plate 7 Power supply circuit board 8, 38, 48, 58 Light emitting element 9 Encoder frame 10 Protective cover 21 Bidirectional bus 22 Receiver 23 Transmitter 30, 40, 50 Light quantity control circuit 31, 41, 61 Current switching circuit 32, 42, 62 Switch 33, 43, 63 Resistor

Claims (3)

By applying a reference voltage to a light-emitting element includes a light amount control circuit for obtaining a reference amount of light, when a serial signal from the outside is Ru data transmission request signal der, converts the detected position data to a serial signal optical to be transmitted to the outside In the encoder
A current switching circuit for switching the magnitude of the current supplied to the light emitting element, if the signal for requesting switching of the supply current of the serial signal from the outside to the light emitting element, wherein the serial signal from the external optical encoder controls the current switching circuit, to suppress a current flowing through the light emitting element, and wherein the reducing the amount of light of the light emitting element. It said current switching circuit includes a switch controlled by a serial signal from the external, at least 1 Kumisonae parallel or series connected resistors connected to the switch, to claim 1 connected in parallel or in series to the light emitting element The optical encoder described. Said current switching circuit includes a switch controlled by a serial signal from the external, at least 1 Kumisonae a resistor connected in series with the switch, the voltage dividing resistors to said current switching circuit connected in series, wherein The optical encoder according to claim 1, wherein the reference voltage of the light quantity control circuit is divided.