Absolute encoder

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an absolute encoder provided with a means of communicating with an external device.

【0002】

[Conventional technology]

Absolute encoders are expanding their applications with the progress of automation of equipment in various fields, and their applications to AC servomotors, robots, etc. are also increasing. As the application expands in this way, the absolute encoder may be used in combination with a numerical control device in order to utilize the absolute position data output by the absolute encoder.

【0003】

There are two types of absolute encoders, one is a multi-track type and the other is a one-track type. In either type, if the resolution of the absolute position data is increased, the number of bits of the pattern increases, and numerical control devices, etc. When used in combination with an external device, the number of connection cables connecting the absolute encoder and the external device increases. For example, in a linear type absolute encoder, if a distance of 1 m is to be represented with a resolution of 0.01 μm, 27 bits of the pattern are required, that is, 27 connection cables are required.

【0004】

In order to avoid such a problem, a serial communication transfer method is used in which the absolute position data output from the 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 communication with the external device must be changed according to the external device.

【0006】

Specifically, the IC of the interface circuit had to be replaced or the entire circuit board had to be replaced.

【0007】

However, preparing multiple products with different communication formats depending on the other party to connect means preparing multiple types of products that differ only in the function of the data transfer means, which poses a problem of cost and management burden. was there.

【0008】

The present invention has been made in view of such circumstances, and the problem is to provide an absolute encoder capable of communicating 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 problems]

In order to solve the above-mentioned problems, in order to achieve such an object, the absolute encoder of the present invention detects the relative movement between the code plate having a pattern and the code plate, and obtains the absolute data by detecting the pattern. In an absolute encoder including a detection means for output and a communication means for serially transferring absolute data from the detection means to an external device, the communication format of the communication means is changed to a communication format according to the type of the external device. The communication format switching means for switching is provided, and the communication format switching means switches the communication format based on the communication format identification signal from the external device.

【0010】

[Action]

In the absolute encoder in 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 a different communication means for each external device is prepared. No need.

【0011】

[Example]

Hereinafter, examples 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 an embodiment of the present invention. The main body of the absolute encoder is provided on the back surface of the encoder scale 1 on which the pattern is formed and the encoder scale 1, and is a signal detector 2 that detects the relative motion with the encoder scale 1 and outputs the absolute data by detecting the pattern. And the connection cable 3 connected to the output end of the signal detector 2.

【0013】

An encoder control unit 4 serving as a communication means for serially transferring absolute data from the signal detector 2 to an external device (here, a numerical control device) 11 is connected to the connection cable 3. An encoder signal processing board 5 on which an encoder signal processing circuit is mounted is mounted on the encoder control unit 4, and this encoder signal processing circuit is an input signal processing circuit that converts an input signal into a digital signal and shapes the waveform. 6 and the arithmetic circuit 7 that performs arithmetic processing such as counting the absolute signal input from the input signal processing circuit 6, and the interface that converts the signal input from the arithmetic circuit 7 into a communication format according to the type of the external device 11. It is composed of circuit 8. The interface circuit 8 stores a plurality of types of communication formats according to the external device that is expected to be connected, and is appropriate from the stored communication formats based on the communication format identification signal from the external device 11. The communication format is selected and the communication format is switched.

【0014】

The encoder control unit 4 is connected to the external device 11 via the connection connector 10a and the connection cable 10b. As shown in FIG. 2, the connector 10a transmits the power supply voltage signal, 0V signal, and serial data SD from the encoder control unit 4 to the external device 11, and the request signal REQ and communication format switching signal FRM0 from the external device 11 ~ FRM2 is transmitted to the encoder control unit 4.

【0015】

In the absolute encoder of this embodiment, the communication format identification signal (that is, the 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 connector 10a, and the communication format identification is performed. Based on the signal, the interface circuit 8 automatically sets the communication format suitable for the connected external device 11. As a result, simply by connecting the external device 11 to the encoder control unit 4, communication between the encoder control unit 4 and the external device 11 is possible automatically by the optimum communication format without exchanging the interface circuit 8. Become.

【0016】

In this embodiment, the interface circuit 8 is switched by the electric signal output from the external device 11 using the type of connector 10a disclosed in FIG. 2, but the connector 10a of the modified example is used. As shown in FIG. 3, for example, the connector pin 10a'on the external device 11 side is subjected to jumper processing suitable for the communication format of the external device 11 to be connected, and the connector corresponding to the external device 11 is assigned to the encoder control unit. The communication format identification signal may be transmitted to the interface circuit 8 by connecting to 4. In the example of FIG. 3, the connector pin 10a'is used to supply the power supply voltage to the FRM2 by grounding the communication format switching signals FRM0 and FRM1, so that when the connection connector 10a is connected to the encoder control unit 4, communication is performed. 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, the connection connector 10a corresponding to the external device 11 is automatically connected to the encoder control unit 4. The interface circuit 8 can be switched to a communication format suitable for the connected external device 11.

【0017】

Further, in the above-described embodiment or the like, the communication format identification signal is directly input to the interface circuit 8 in any case to switch the communication format of the interface circuit 8, but the communication format identification signal is used as an arithmetic circuit. The interface circuit 8 may be configured to input to the interface circuit 7, read the communication format identification signal input to the arithmetic circuit 7, and input a command signal to command the switching of the communication format to the interface circuit 8.

【0018】

Further, if a programmable logic device is used in the interface circuit 8 and an external device 11 using a communication format other than that stored in advance appears, this new communication format can be added to the interface circuit 8. The period of use of the absolute encoder can be extended.

【0019】

[Effect of the invention]

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 number of product types of the absolute encoder can be reduced, and as a result, the manufacturing is possible. It becomes possible to reduce the cost.

【0020】

Further, since the optimum communication format is automatically selected by inputting the communication format identification signal from the outside, it is not necessary to set the communication format on the absolute encoder side.

[Simple explanation of drawings]

[Figure 1]

FIG. 1 is a block diagram showing an absolute encoder according to an embodiment of the present invention.

[Figure 2]

FIG. 2 is a schematic diagram showing the configuration of the connector pins of the connector of FIG. 1.

[Fig. 3]

FIG. 3 is a schematic view showing the configuration of the connector pin of the connection connector of the modified example of the present invention.

[Explanation of symbols]

1 encoder scale 2 signal detector 4 Encoder control unit 6 Input signal processing circuit 7 Arithmetic circuit 8 interface circuit 10a connector 11 External device