JP3550591B2 - Absolute encoder - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an absolute encoder including a communication unit with an external device.
[0002]
[Prior art]
The use of the absolute encoder has been expanding with the progress of automation of the device in various fields, and the application to an AC servomotor, a robot, and the like is also increasing. In such an expanding application, the absolute encoder may be used in combination with a numerical controller to utilize the absolute position data output by the absolute encoder.
[0003]
Absolute encoders are classified into a multi-track type and a one-track type. In either case, if the resolution of the absolute position data is increased, the number of bits of the pattern will increase, and the absolute encoder When used in combination with an external device, the number of connection cables for connecting the absolute encoder to the external device increases. For example, if a linear type absolute encoder is used to represent a distance of 1 m with a resolution of 0.01 μm, the pattern requires 27 bits, that is, 27 patterns are required.
[0004]
In order to avoid such a problem, a serial communication transfer method is used in which absolute position data output from an absolute encoder is output in a serial format and transferred to the external device. In this serial communication transfer method, it is necessary to perform communication in a communication format suitable for the external device for each type of external device to which data is transferred.
[0005]
[Problems to be solved by the invention]
In the conventional absolute encoder, since the communication format must be changed for each external device as described above, the interface circuit for communicating with the external device must be changed according to the external device.
[0006]
Specifically, the IC of the interface circuit has to be replaced or the entire circuit board has to be replaced.
[0007]
However, preparing a plurality of products having different communication formats depending on the connection destination means preparing a plurality of types of products that differ only in the function of the data transfer means, which is a cost and management burden. was there.
[0008]
The present invention has been made in view of such circumstances, and a problem thereof is to provide an absolute encoder that can communicate with an external device having a different communication format without having to exchange an interface circuit for each external device. is there.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an absolute encoder according to the present invention for solving the above-mentioned problem detects a code plate having a pattern and a relative movement between the code plate and absolute data obtained by detecting the pattern. In an absolute encoder including a detection unit that outputs, and a communication unit that serially transfers the absolute data from the detection unit to an external device, the communication format of the communication unit is changed to a communication format corresponding to the type of the external device. There is provided communication format switching means for switching, wherein the communication format switching means switches the communication format based on a communication format identification signal from the external device.
[0010]
[Action]
In the absolute encoder according to the present invention, since the communication format switching means switches the communication format according to the type of the external device based on the communication format identification signal from the external device, an absolute encoder having different communication means for each external device is prepared. No need.
[0011]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a block diagram showing an absolute encoder according to one embodiment of the present invention. The main body of the absolute encoder is provided with an encoder scale 1 on which a pattern is formed, and a signal detector 2 which is provided on the back of the encoder scale 1 and detects relative movement with respect to the encoder scale 1 and outputs absolute data by detecting the pattern. And a connection cable 3 connected to the output end of the signal detector 2.
[0013]
The connection cable 3 is connected to an encoder control unit 4 serving as communication means for serially transferring the absolute data from the signal detector 2 to an external device (here, a numerical control device) 11. An encoder signal processing board 5 on which an encoder signal processing circuit is mounted is mounted on the encoder control unit 4. The encoder signal processing circuit converts an input signal into a digital signal and shapes the waveform of the input signal. 6, an arithmetic circuit 7 for performing arithmetic processing such as counting of absolute signals input from the input signal processing circuit 6, and an interface for converting a signal input from the arithmetic circuit 7 into a communication format corresponding to the type of the external device 11. And a circuit 8. The interface circuit 8 stores a plurality of types of communication formats corresponding to an external device to be connected. Based on a communication format identification signal from the external device 11, an appropriate one of the stored communication formats is selected. The communication format is selected, and the communication format is switched.
[0014]
The encoder control unit 4 is connected to an external device 11 via a connection connector 10a and a connection cable 10b. As shown in FIG. 2, the connector 10a transmits the power supply voltage signal, the 0V signal, and the serial data SD from the encoder control unit 4 to the external device 11, the request signal REQ from the external device 11, and the communication format switching signal FRM0. To FRM2 to the encoder control unit 4.
[0015]
In the absolute encoder of this embodiment, a communication format identification signal (that is, communication format switching signals FRM0 to FRM2) from the external device 11 is transmitted to the interface circuit 8 of the encoder control unit 4 via the connection connector 10a. A communication format suitable for the connected external device 11 is automatically set by the interface circuit 8 based on the signal. Thereby, the communication between the encoder control unit 4 and the external device 11 can be automatically performed with the optimum communication format without changing the interface circuit 8 only by connecting the external device 11 to the encoder control unit 4. Become.
[0016]
In this embodiment, the interface circuit 8 is switched by the electric signal output from the external device 11 using the connector disclosed in FIG. 2 as the connection connector 10a. For example, as shown in FIG. 3, the connector pin 10 a ′ of the external device 11 is subjected to a jumper process suitable for the communication format of the external device 11 to be connected, and the connector corresponding to the external device 11 is connected to the encoder control unit. 4, the communication format identification signal may be transmitted to the interface circuit 8. In the example of FIG. 3, the connector pin 10 a ′ connects the communication format switching signals FRM 0 and FRM 1 to the ground and supplies the power supply voltage to the FRM 2. The communication format corresponding to the format switching signal FRM2 is set in the interface circuit 8. By using such a connector 10a, even if an electrical communication format identification signal is not output from the external device 11, only by connecting the connector 10a corresponding to the external device 11 to the encoder control unit 4, automatic connection is possible. The interface circuit 8 can be switched to a communication format suitable for the connected external device 11.
[0017]
In each of the above-described embodiments and the like, the communication format identification signal is directly input to the interface circuit 8 in any case, and the communication format of the interface circuit 8 is switched. 7, the arithmetic circuit 7 reads the input communication format identification signal, and inputs a command signal for commanding the switching of the communication format to the interface circuit 8.
[0018]
Further, by using a programmable logic device for the interface circuit 8 and enabling the new communication format to be added to the interface circuit 8 when an external device 11 using a communication format other than the previously stored communication format appears, The use period of the absolute encoder can be made longer.
[0019]
【The invention's effect】
As described above, according to the absolute encoder of the present invention, since the communication format is switched based on the communication format identification signal from the external device, the product type of the absolute encoder can be reduced, and as a result, Costs can be reduced.
[0020]
In addition, when the communication format identification signal is input from the outside, the optimum communication format is automatically selected, so that it is not necessary to set the communication format on the absolute encoder side.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an absolute encoder according to one embodiment of the present invention.
FIG. 2 is a schematic diagram showing a configuration of a connector pin of the connection connector of FIG. 1;
FIG. 3 is a schematic diagram showing a configuration of a connector pin of a connection connector according to a modified example of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 encoder scale 2 signal detector 4 encoder control unit 6 input signal processing circuit 7 arithmetic circuit 8 interface circuit 10 a connector 11 external device

Claims (1)

A code plate having a pattern,
Detecting means for detecting relative movement with the code plate and outputting absolute data by detecting the pattern;
Absolute data from the detection means, in an absolute encoder comprising a communication means for serially transferring to an external device,
Communication format switching means for switching the communication format of the communication means to a communication format according to the type of the external device,
An absolute encoder, wherein the communication format switching means switches the communication format based on a communication format identification signal from the external device.

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