JP4777120B2 - Backup power supply for absolute encoder - Google Patents

Description

  The present invention relates to an improvement of a backup power supply for an absolute encoder.

  Absolute encoders are connected to non-control devices such as industrial machinery, machine tools, industrial robots, etc., and rotating parts, motor shafts, etc., and detect and hold the position of various rotating parts of non-control devices or the position on a straight line. It is. Here, the control device that drives the non-control device is not always in an operating state. For example, when the operation by the non-control device is completed or a power failure occurs, the power supply to the control device is cut off. Therefore, since the power supply to the absolute encoder is also cut off, there arises a problem that the position detection operation of the non-control device by the absolute encoder cannot be performed or the detected position information is lost. For this reason, a backup power source is prepared in the past, and when the power supply to the control device is cut off, power is supplied from the backup power source to the absolute encoder.

  FIG. 1 is a block diagram showing a configuration of an entire system including a conventional absolute encoder. In the figure, 11 is a control device that controls a servo motor 12 as an example of a non-control device, 13 is an absolute encoder, 14 is a backup power source (primary battery that cannot be charged), 15 is a power cable, and 16 is a position feedback cable. It is.

  In operation, while the main power supply in the control device 11 is being supplied, drive power is supplied from the control device 11 to the servo motor 12 via the power cable 15, and the main power supply and backup in the control device 11 are also supplied. Electric power is supplied from the power source 14 to the absolute encoder 13 through the position feedback cable 16. The position information held in the absolute encoder 13 is returned to the control device 11 via the position feedback cable 16 and used for controlling the servo motor 12.

  When the main power supply in the control device 11 is turned off, electric power is supplied from only the backup power supply 14 via the position feedback cable 16 to the absolute encoder 13 and the detection operation of the rotational position of the servo motor 12 is continued. As a result, it is possible to keep the information of the position of the motor shaft and the table position of the machine as a non-control device in the absolute encoder 13.

  As described above, conventionally, a primary battery such as an alkaline battery or a lithium primary battery is used as a backup power source for the absolute encoder. However, since the primary battery cannot be charged, a user who uses the absolute encoder is one to three years. This battery must be replaced every year, which is a big burden especially for a large user who uses a large number of CNC machine tools.

In addition, a method using a rechargeable secondary battery instead of the primary battery is also known (see Patent Document 1). However, since it is difficult to design a charging circuit for the following reasons, it is still in practical use. Has not been.
(1) Absolute encoders are different in character from general electronic devices such as mobile phones. If the battery runs out even once, the machine runs out for a long time due to the work of positioning the machine coordinates. Has a large influence on the battery, and it is necessary to charge the battery before it runs out.
(2) There is a limit to the number of times of charging (hundreds of times). For example, if the machine is charged every time the power is turned on every day, it is frequently charged before the expected life of 10 to 20 years. The battery reaches the end of its life due to operation.

Japanese Patent Laid-Open No. 10-227659 JP2003-18761

  In view of the problems in the prior art described above, the object of the present invention is to set the power supply timing to the secondary battery for supplying power to the absolute encoder with a timer efficiently, thereby extending the battery replacement period as much as possible. The purpose is to extend the usable time of the battery for the backup power source for supplying power to the absolute encoder.

  In order to achieve the above object, what is provided by the first aspect of the present invention includes a secondary battery, a charging circuit, and a timer circuit, and the charging circuit is a secondary battery according to an output signal of the timer circuit. This is a backup power source for an absolute encoder, characterized in that it is charged.

  According to the second aspect of the present invention, the charging circuit is supplied with power from an external power supply provided outside the backup power supply, the timer circuit is supplied with power from the secondary battery, and the timer circuit outputs a charging start signal. When the power is supplied to the charging circuit from the external power source, the charging circuit charges the secondary battery.

  According to the third aspect of the present invention, the main power supplied from the control circuit to the absolute encoder is used as the external power while the power of the control device is on.

  According to the fourth aspect of the present invention, the timer circuit detects the on / off state of the external power source and switches the speed of the timer operation according to the state. In this case, the timer circuit decreases the count value per unit time when the external power supply is on, and increases the count value per unit time when the external power supply is off.

  According to the fifth aspect of the present invention, the backup power source is built in the absolute encoder.

  Since the secondary battery is charged according to the output signal of the timer circuit, the battery will not run out. Therefore, the work of aligning the machine coordinates becomes unnecessary, and it is possible to avoid the machine from being stopped for a long time. . Moreover, since the charging frequency of the secondary battery can be reduced, the usable time of the secondary battery can be made longer than the life of the machine.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a block diagram showing the configuration of a backup power source for an absolute encoder according to the first embodiment of the present invention. In the figure, an absolute encoder backup power source 21 includes a charging circuit 22, a timer circuit 23, and a secondary battery 24. The external power source (A) 25 is connected to the charging circuit 22 by a power line 26 and a ground line 27. The output of the charging circuit 22 is connected to the timer circuit 23 via a line 28. The output of the timer circuit 23 is input to the charging circuit 22 via the line 29. The output of the charging circuit 22 is connected to the positive electrode of the secondary battery 24. The secondary battery 24 is connected to the absolute encoder 201.

  In operation, the timer circuit 23 is reset when the charging circuit 22 is fully charged. After resetting the charging circuit 22, the timer circuit 23 starts counting. In this case, when the external power supply 25 is not connected to the charging circuit 22 or is disconnected due to a power failure or the like, the count value per unit time of the timer circuit 23 is relatively large and the external power supply 25 is not disconnected. When connected to the charging circuit 22, the count value per unit time of the timer circuit 23 is made relatively small. This is because the current consumption of the secondary battery 24 is small when the external power supply 25 is on, and the current consumption of the secondary power supply 24 is large when the external power supply 25 is off. When the count value of the timer circuit 23 reaches a predetermined value and the external power supply 25 is on, the timer circuit 23 gives a charging start signal to the charging circuit 22, and in response to the charging start signal, the charging circuit 22 The secondary battery 24 is charged by the power from the external power supply 25 while the power supply 25 is on.

  In this way, since the charging timing of the secondary battery 24 is set by the timer circuit 23, the battery does not run out, and the charging time of the secondary battery is not shortened by frequently charging. .

  FIG. 3 is a block diagram showing the configuration of a backup power source for an absolute encoder according to the second embodiment of the present invention. In the figure, an absolute encoder backup power supply 31 includes a charging circuit 32, a timer circuit 33, an on / off detection circuit 34, and a secondary battery 35. The charging circuit 32 is supplied with power from a main power supply 37 in the control device 36 as an external power supply through a main power supply line 301 and a 0 V ground line 302. The output of the charging circuit 32 is connected to the timer circuit 33 and the positive electrode of the secondary battery 35 via the backup power line 304. The secondary battery 35 is connected to an absolute encoder 38 via a backup power line 304. Reference numeral 39 denotes a servo motor as an example of a non-control device. The position feedback cable 300 includes a main power supply line 301 connected to the main power supply 37, a 0 V ground line 302, a position data communication signal line 303, and a backup power supply line 304.

  FIG. 4 is a graph for explaining the operation of the absolute encoder backup power source shown in FIG. Assume that the timer circuit 33 is initially reset. In this state, the output of the main power supply 37 is repeatedly turned on and off as shown. The servo motor 39 is driven in the on period, and the servo motor is not driven in the off period. Even during the off period, the secondary battery 35 is used to store the rotational position held in the absolute encoder until immediately before. As shown in the figure, the timer count value per unit time is relatively large when the main power supply 37 is off, and the timer count value per unit time is relatively small when the main power supply 37 is on. . This is because, as described above, the current consumption of the secondary battery 35 is small when the main power supply 37 is on, and the current consumption of the secondary power supply 35 is large when the main power supply 37 is off. The on / off detection circuit 34 detects whether the main power source 37 is on or off. When the count value of the timer circuit 33 reaches the timer set value and the external power source 37 is on, the timer circuit 33 gives a charging start signal to the charging circuit 32, and in response to the charging start signal, the charging circuit 32 The secondary battery 35 is charged by the power from the main power supply 37 while the main power supply 37 is on. The timer set value is determined by a time t before the voltage of the secondary battery drops to a voltage that can hold the data in the absolute encoder due to the discharge of the secondary battery 35. When charging of the secondary battery 35 is completed, the timer circuit 33 is reset by the output of the charging circuit 32. If the charging of the secondary battery is not completed within one ON period of the main power supply 37, the charging is continued during the next ON period and the timer circuit 37 is reset according to the completion of charging.

When the main power supply is on and the current consumption on the backup power supply side is about 1/10 of that when the main power supply is off, the timer count operation is, for example, 1/10 of that when the main power supply is off. The entire timer count operation is set in consideration of not only the current consumption of the absolute encoder 38 but also the self-discharge current and the current consumption of the timer circuit 33. Furthermore, by changing the speed of the timer operation along with the elapsed time, the closeness with the actual discharge characteristics can be improved.
In addition, the timer circuit 33, the on / off detection circuit 34, the charging circuit 32, and the secondary battery 35 may be optimally arranged in separate devices instead of being provided in the absolute encoder backup power source. Furthermore, a backup power supply for an absolute encoder can be built in the absolute encoder.

  In this way, since the charging timing of the secondary battery 35 is set by the timer circuit 33, the battery will not run out, and the charging time of the secondary battery will not be shortened by frequent charging. .

  According to the present invention, by efficiently setting the power supply timing to the secondary battery for supplying power to the absolute encoder by the timer, the replacement period of the battery replacement is extended, and thereby the backup power supply for supplying power to the absolute encoder The battery can be used for a long time.

It is a block diagram which shows the structure of the whole system containing the conventional absolute encoder. It is a block diagram which shows the structure of the backup power supply for absolute encoders by the 1st Example of this invention. It is a block diagram which shows the structure of the backup power supply for absolute encoders by the 2nd Example of this invention. It is a graph explaining operation | movement of the backup power supply for absolute encoders shown in FIG.

Explanation of symbols

201 Absolute encoder 202 Servo motor (non-control device)
21 Absolute Encoder Backup Power Supply 22 Charging Circuit 23 Timer Circuit 24 Secondary Battery 25 External Power Supply 31 Absolute Encoder Backup Circuit 32 Charging Circuit 33 Timer Circuit 34 On / Off Detection Circuit 35 Secondary Battery 36 Control Circuit 37 Main Power Supply 38 Absolute Encoder 39 Servo motor (non-control device)

Claims (5)

A backup power supply that supplies power to an absolute encoder in order to perform at least one of position detection and position information holding of the controlled device when the control device that controls the controlled device is turned off.
The backup power source includes a secondary battery, a charging circuit, and a timer circuit, and the charging circuit charges the secondary battery according to an output signal of the timer circuit, and the timer circuit turns on / off the external power source. An off state is detected, and the speed of the timer operation in the on state of the external power source is set to a first value exceeding zero set by at least one of a self-discharge current and power consumption of the timer circuit, and the external power source A backup power supply for an absolute encoder , wherein the timer operation speed in the off state is set to a second value larger than the first value . The timer circuit sets the count value per unit time to the first value when the external power source is turned on, and sets the count value per unit time to the second value when the external power source is turned off. The backup power supply for an absolute encoder according to claim 1. The charging circuit is supplied with electric power from an external power source provided outside the backup power source, the timer circuit is supplied with electric power from the secondary battery, the timer circuit outputs a charging start signal, and The absolute power supply for an absolute encoder according to claim 1 or 2 , wherein when the electric power is supplied from an external power source to the charging circuit, the charging circuit charges the secondary battery. During the power of the control device is on, any one of 3 to supply main power to said absolute encoder from the control device from claim 1, characterized in that it has to be used as the external power source Backup power supply for absolute encoders. The absolute power supply for an absolute encoder according to any one of claims 1 to 4 , wherein the backup power supply is built in an absolute encoder.

Images