JP2009168701A - Electromagnetic induction encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively achieve a high-precision/high-resolution electromagnetic induction encoder for mitigating a design rule without changing a height and a wavelength of a receiving coil, and reducing a signal pitch without using a high-density PCB. <P>SOLUTION: The electromagnetic induction encoder includes: scale coils 14, 16 arrayed on a scale 10 in the measurement direction; and transmitting coils 24, 26 and the receiving coils 20, 22 provided on a grid 12 moved relative to the scale in the measurement direction. When the transmitting coils are excited, the electromagnetic induction encoder detects a relative movement between the scale and the grid based on a change in a magnetic flux detected by the receiving coils through the scale coils. The receiving coil has twisted wiring using a through-hole, and is folded so as to pass through an intermediate point of a sinusoidal shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromagnetic induction encoder, in particular, it can be used for calipers, indicators, linear scales, micrometers, etc., and can relax design rules without changing the height and wavelength of the receiving coil. Therefore, the present invention relates to an electromagnetic induction encoder that can reduce the signal pitch without using a high-density printed wiring board for the grid.

  As described in Patent Documents 1 and 2, as shown in FIG. 1 as an example of Patent Document 2, a large number of scale coils 14 and 16 arranged on the scale 10 along the measurement direction, and the scale 10 Transmission coils 24 and 26 and reception coils 20 and 22 disposed on a grid 12 (also referred to as a slider) that is relatively movable in the measurement direction. When the transmission coils are excited, they are received via a scale coil. 2. Description of the Related Art An electromagnetic induction encoder that detects a relative movement amount of a scale 10 and a grid 12 from a change in magnetic flux detected by a coil is known. In the figure, 18 is a coupling wiring, 28 is a transmission control unit, and 30 is a reception control unit.

Japanese Patent Laid-Open No. 10-318781 Japanese Patent Laying-Open No. 2003-121206 (FIG. 1)

  However, the conventional electromagnetic induction encoder generally employs a rhombus shape (height H, wavelength λ) as shown in FIG. 2 in order to reduce the receiving coil pitch (wavelength λ). The grid had to employ a high density printed circuit board (PCB). That is, in the diamond-shaped receiving coil shape, in order to configure the receiving coil pitch (wavelength) λ, it is necessary to use an expensive PCB capable of realizing a design rule with a small through-hole pitch A and a through-hole diameter φB. It has not been possible to reduce the cost by adopting an inexpensive PCB having a rough design rule for an encoder having the same receiving coil pitch.

  In order to reduce the price while maintaining the required wavelength λ of the receiving coil, it is necessary to relax the design rules for the through-hole pitch A and the through-hole diameter φB. However, if the design rule is to be relaxed while maintaining the current diamond shape and the through-hole pitch is A + a and the through-hole diameter is φB + b, as shown in FIG. Through holes (TH) are in contact with each other and a receiving coil cannot be formed.

  On the other hand, it is conceivable that the height H of the receiving coil is increased or the design rule is relaxed by increasing the wavelength λ. However, both increase the substrate size and degrade the accuracy, and thus cannot be adopted practically.

  On the other hand, it is conceivable to use the sinusoidal receiving coil shown in FIG. 4 without changing both the receiving coil height H and the wavelength λ.

  However, the sinusoidal receiving coil can satisfy the clearance between TH for connecting the receiving coil and the receiving control unit IC, and has good characteristics. I can't.

  The present invention has been made to solve the above-mentioned conventional problems, and can relax the design rule without changing the height and wavelength of the receiving coil. Therefore, the signal can be obtained without using a high-density PCB for the grid. It is an object to be able to reduce the pitch.

  The present invention includes a plurality of scale coils arranged on a scale along a measurement direction, and a transmission coil and a reception coil disposed on a grid that is relatively movable in the measurement direction with respect to the scale. In an electromagnetic induction encoder that detects the relative movement of the scale and grid from the change in magnetic flux detected by the receiving coil via the scale coil, the receiving coil is twisted using a through hole. In addition, the problem is solved by bending the sine wave shape so that it passes through a point in the middle.

  The receiving coil can be bent so as to pass through a point having a height of ½ of the apex at ± 1/6 wavelength across the apex of the sine wave shape.

  According to the present invention, as illustrated in FIG. 5, the design rule can be relaxed to, for example, the through hole pitch A + a and the through hole diameter φB + b without changing the height H and the wavelength λ of the receiving coil. Accordingly, since the signal pitch can be reduced without using a high-density PCB for the grid, an electromagnetic induction encoder with high accuracy and high resolution and good environmental resistance can be realized at low cost. In addition, since a large signal strength can be obtained, an encoder with higher resolution and lower cost can be realized.

  In particular, as shown in detail in FIG. 6, when the vertices are bent so as to pass through a point that is ± 1/6 wavelength and half the height of the vertices, the folds are folded at a sinusoidal H / 2 position. As shown in FIGS. 7 and 8, the simulation results are improved in the signal strength with respect to the conventional rhombus coil (FIG. 7), and the third harmonic that causes the deterioration of accuracy is reduced. (FIG. 8).

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

  In this embodiment, in the electromagnetic induction encoder of the overall configuration illustrated in FIG. 1, as shown in FIGS. 5 and 6, the receiving coil is a twisted wiring using a through hole, and a twisted pair is used. It is bent so that it passes through a point having a height of ½ of the apex at ± 1/6 wavelength across the apex of the sine wave shape.

  According to the present embodiment, a low-cost encoder can be supplied by relaxing the design rule. Further, as shown in FIG. 7, a highly accurate encoder can be supplied by improving the signal strength. Further, as shown in FIG. 8, since the third-order harmonic can be reduced, the distortion of the signal is small, and even a two-phase or four-phase 90 ° phase difference receiving coil configuration encoder can achieve high accuracy. Moreover, since it is an electromagnetic induction type, an encoder resistant to water and oil can be supplied. Further, since the wavelength can be reduced with the same design rule, a highly accurate encoder can be supplied.

  In the above-described embodiment, the receiving coil is bent so as to pass through a point having a height of ± 1/6 wavelength and a half of the apex with the apex of the sinusoidal shape interposed therebetween. The method of bending so as to pass through a point in the middle is not limited to this, and for example, it is possible to bend at two or more points.

  The application object is not limited to the low-price encoder, and can be applied to general electromagnetic induction encoders.

The perspective view which shows the whole structure of an electromagnetic induction type encoder The top view which shows the example of the shape of the conventional rhombus receiving coil Plan view for explaining the problems when the design rules are relaxed with a conventional diamond-shaped receiving coil Plan view showing conventional sinusoidal receiver coil and its problems The top view which shows the shape of embodiment of the receiving coil which concerns on this invention The figure explaining the bending point of the said embodiment The figure which compares and shows the simulation result of the signal strength in the conventional example and the embodiment of the present invention Figure showing comparison of harmonic ratios

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Scale 12 ... Grid 14, 16 ... Scale coil 20, 22 ... Reception coil 24, 26 ... Transmission coil 28 ... Transmission control part 30 ... Reception control part

Claims (2)

A number of scale coils arranged on the scale along the measurement direction;
A transmitter coil and a receiver coil disposed on a grid that is movable relative to the scale in the measurement direction;
In the electromagnetic induction encoder that detects the relative movement of the scale and grid from the change in magnetic flux detected by the receiving coil via the scale coil when the transmitting coil is excited,
An electromagnetic induction encoder characterized in that the receiving coil is twisted using a through-hole and bent so as to pass through a point in the middle of a sine wave shape.   2. The electromagnetic wave according to claim 1, wherein the receiving coil is bent so as to pass through a point having a height of ½ of the apex at ± 1/6 wavelength across the apex of the sine wave shape. Inductive encoder.

Images