JP2005291929A - Electromagnetic induction encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of the detection positional accuracy by change in the frequency of an LC resonance waveform which is a driving signal. <P>SOLUTION: In this electromagnetic induction encoder, using the LC resonance waveform as the driving signal, a position is detected by sample holding the amplitude peak value P of the detection signal induced based on the driving signal. The delay time D by the sample hold or the amplification factor A of the sample hold value is changed according to the change in the amplitude peak position due to the temperature change or the change in the amplitude of the amplitude peak value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electromagnetic induction encoder that uses an LC resonance waveform as a drive signal, detects the position by sample-holding the amplitude peak value of a detection signal induced based on the drive signal, and in particular, detects the temperature. The present invention relates to an electromagnetic induction encoder capable of performing highly accurate position detection regardless of changes.

  As illustrated in FIG. 1, the main scale 12 and the index scale are caused by electromagnetic induction of an encoder pattern 10 including a plurality of coils 14 arranged in the longitudinal direction of the main scale 12 and a transmission coil 18 and a reception coil 19 arranged on the index scale 16. There are known electromagnetic induction encoders that detect 16 relative position changes (see Patent Documents 1 and 2). In the figure, 20 is a driving circuit, and 30 is a receiving circuit.

  Such a conventional electromagnetic induction encoder basically uses, as a drive signal, an LC resonance waveform generated by inputting a single pulse signal to a drive circuit. In the actual position detection, as indicated by a solid line A in FIG. 2, a delay circuit is incorporated so as to sample and hold the amplitude peak value P of the detection signal (attenuated LCR resonance waveform) derived based on this drive signal. . The transmission frequency f of this LC resonance waveform is expressed by the following equation.

    f = 1 / {2π√ (LC)} (1)

JP 2000-180209 A JP 2002-213906 A

  L and C for generating the LC resonance waveform use general-purpose components and both have temperature characteristics. Therefore, as can be seen from the equation (1), the frequency f of the drive signal changes when the capacitance C varies with temperature. Conventionally, however, this drive signal is sampled with a certain delay time D after the ON signal is turned on (falling in the figure), so that the position of the amplitude peak value shifts from P to P ′. In addition, as indicated by a broken line B in FIG. 2, the sampling voltage is lowered, and the encoder reception position accuracy is finally deteriorated.

  In order to solve such problems, a measuring instrument that operates intermittently, such as a digital caliper, can detect the peak voltage by sweeping the delay time D. It cannot be applied to measuring machines that require high-speed operation, such as linear encoders.

  The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to enable high-speed position detection with high accuracy regardless of changes in the LC resonance waveform frequency due to temperature changes.

  The present invention relates to an electromagnetic induction encoder in which an LC resonance waveform is used as a drive signal, and a position is detected by sampling and holding an amplitude peak value of a detection signal derived based on the drive signal. The problem is solved by changing the delay time until the sample hold according to the temperature in accordance with the change of the peak position.

  The present invention also provides an electromagnetic induction encoder in which the LC resonance waveform is used as a drive signal, and the amplitude peak value of a detection signal induced based on the drive signal is sampled and held to detect the position. The problem is solved by changing the amplification factor of the sample hold value according to the temperature in accordance with the change in the amplitude of the amplitude peak value until the hold.

  Further, the temperature is detected by a temperature sensor for correcting thermal expansion of the scale and monitoring the operating temperature.

  According to the present invention, the sample hold value or the sample hold value after amplification can be maintained constant regardless of the change in the LC resonance waveform frequency due to the temperature change. Therefore, even when high-speed measurement is required and the temperature changes, the encoder receiving position accuracy can be maintained with high accuracy.

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

  As shown in FIG. 3, the first embodiment of the present invention includes an encoder pattern 10 including the coil 14 of the main scale 12 and the transmission / reception coils 18 and 19 of the index scale 16 as illustrated in FIG. A drive circuit 20 for driving the transmission coil 18 of the index scale 16 by LCR resonance, a sample hold (S / H) circuit 32 for sample-holding the output of the reception coil 19 of the index scale 16 of the encoder pattern 10; Based on the output of the amplifier 34 that amplifies the output of the sample hold circuit 32, the analog / digital (A / D) converter 36 that converts the output of the amplifier 34 into a digital signal, and the output of the A / D converter 36, Digitally displays the relative position of the main scale 12 and the index scale 16 In addition, in an electromagnetic induction encoder comprising a processor 40 that operates the sample hold circuit 32 after a delay time D from the fall of the drive signal of the drive circuit 20 to the sampling by the sample hold circuit 32, for example, The processor 40 changes the delay time D as shown in FIG. 4 in accordance with the output of the temperature sensor 50 provided for thermal expansion correction and operation temperature monitoring (for example, for a heat generation warning by a linear motor). It is what.

  According to the present embodiment, as illustrated in FIG. 5, the delay time D is changed to, for example, D ′ according to the temperature change, so that the maximum amplitude peak value can always be sampled regardless of the temperature change. Therefore, it is possible to prevent deterioration in accuracy of the encoder reception position.

  Next, a second embodiment of the present invention will be described in detail.

  In the present embodiment, in the same configuration as that of the first embodiment shown in FIG. 3, the delay time D for sample hold is constant, and the amplification factor A of the amplifier 34 is set as the output of the temperature sensor 50 as shown in FIG. Thus, the change is made as shown in FIG.

  According to the present embodiment, as indicated by the alternate long and short dash line C in FIG. 8, the amplification factor A is changed to, for example, A ′ according to the temperature change, so that the sample hold value after amplification is changed regardless of the temperature change. It can be kept constant, and deterioration in accuracy of the encoder reception position can be prevented.

  In any of the above-described embodiments, since the output of the temperature sensor 50 already provided in the scale for thermal expansion correction and operation temperature monitoring is used, the configuration is simple. It is also possible to separately provide a temperature sensor for correction according to the present invention.

Plan view showing an example of an electromagnetic induction encoder pattern Time chart showing an example of the waveform of the received signal to explain the conventional problems The block diagram which shows the structure of 1st Embodiment of this invention. Diagram showing the relationship between temperature and delay time Similarly, a time chart showing an example of the received signal The block diagram which shows the structure of 2nd Embodiment of this invention. Similarly, a diagram showing an example of the relationship between temperature and gain Similarly, a time chart showing an example of the received signal

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Encoder pattern 20 ... Drive circuit 32 ... Sample hold (S / H) circuit D, D '... Delay time 34 ... Amplifier A, A' ... Amplification factor 36 ... Analog / digital (A / D) converter 40 ... Processor 50 ... Temperature sensor

Claims (3)

In an electromagnetic induction encoder that uses an LC resonance waveform as a drive signal, and detects and positions the amplitude peak value of a detection signal derived based on the drive signal,
An electromagnetic induction encoder, wherein a delay time until the sample hold is changed according to a temperature in response to a change in an amplitude peak position due to a temperature change. In an electromagnetic induction encoder that uses an LC resonance waveform as a drive signal, and detects and positions the amplitude peak value of a detection signal derived based on the drive signal,
An electromagnetic induction encoder characterized in that the amplification factor of the sample hold value is changed in accordance with the temperature in accordance with the change in the amplitude of the amplitude peak value until the sample hold.   3. The electromagnetic induction encoder according to claim 1, wherein the temperature is detected by a temperature sensor for correcting thermal expansion of a scale or monitoring an operating temperature. 4.

Images