JP4783698B2 - Electromagnetic induction encoder - Google Patents

Description

  The present invention relates to an electromagnetic induction encoder adapted to detect displacement of a slider relative to a scale from an output obtained by using an encoder track formed on the scale. In particular, the present invention relates to an electromagnetic induction encoder that can correct a yaw tilt angle of a slider with respect to a scale, which is suitable for use in a caliper or a linear encoder.

  In a contact-type measuring instrument in which a slider having a measuring element is slidably provided on the scale body, the measuring element is placed at a position off the measuring axis of the measuring means for detecting the moving amount of the slider. Positioned measuring instruments, for example calipers, are known. As shown in FIG. 1, the vernier caliper is provided with a slider 2 slidably provided on the main scale 1, and an outer measurement jaw 3 and an inner measurement jaw 4 that are measuring elements are perpendicular to the main scale 1 and the slider 2 ( Since the structure is provided at a right angle with respect to the longitudinal direction of the main scale 1, there is an advantage that the jaws 3, 4 as measuring elements are not on the main scale 1 constituting the length measuring means, and are easy to use. .

  However, in a contact type measuring instrument in which the measuring element is located away from the measuring axis of the measuring means, such as a caliper, the sliding of the main body (main scale 1 in the caliper) that slidably guides the slider 2. The slider 2 is tilted with respect to the main body (main scale 1) by the straightness of the reference end face, and the slider 2 is moved to the main body (main scale 1) by the measuring force when the measuring element (4) comes into contact with the object to be measured. However, there is a problem that a measurement error occurs with respect to each inclination.

  In order to solve such a problem, the applicant is described in Patent Document 1, and as shown in FIG. 1, the slider 2 is obtained from a pair of Y-axis length measuring sensors 12y and 13y and the difference between the displacement amounts of the sensors 12y and 13y. An inclination amount calculation circuit 25 for calculating the inclination angle θ of the jaw 4 is provided, and the error δ at the measurement point P of the jaw 4 based on the inclination angle θ of the slider 2 obtained by the error correction circuit 22 is detected by the X-axis length measurement sensor 11. It is proposed to correct from the amount of movement x of the slider 2. In the figure, 21 is a counting circuit for counting the output of the X-axis length measuring sensor 11, 23 and 24 are counting circuits for counting the outputs of the Y-axis length measuring sensors 12y and 13y, and 27 is a display.

  As described above, in a length measuring device that causes Abbe error such as calipers, a change in the attitude of the slider due to the measurement pressure applied to the probe causes a measurement error. In particular, as proposed by the applicants in Patent Documents 2 and 3, a plurality of different wavelengths (three in coarse, medium, and fine in Patent Document 2, and Coarse, Medium, Fine in Patent Document 3) are formed on a scale. In the electromagnetic induction type absolute encoder that determines the absolute position of the slider by synthesizing the output obtained from the three tracks, the combination of the outputs of the multiple tracks changes due to the change in the attitude of the slider. As a result, discontinuous display of values with incorrect display values is possible.

  On the other hand, although not an electromagnetic induction encoder that is the subject of the present invention, as related to a photoelectric encoder, Patent Document 4 arranges a scale scale for detecting an inclination angle above and below an encoder track for detecting an absolute position, It is described that the inclination is read by the difference between the counts.

  In addition, although not an electromagnetic induction encoder that is the subject of the present invention, the applicant has disclosed a sensor for detecting an inclination angle in a direction orthogonal to the length measuring direction in Patent Document 5 as relating to a capacitive encoder. Thus, it is proposed to detect a displacement amount other than the length measuring direction (a displacement perpendicular to the length measuring direction, a yaw angle, a pitch angle, etc.).

JP 9-49722 A JP 2005-345375 A JP 2006-98139 A JP 7-324948 A JP 2001-249001 A

  However, the techniques described in Patent Documents 1 and 5 relate to a capacitive encoder and cannot be used as it is for an electromagnetic induction encoder.

  Further, the technique described in Patent Document 4 has a problem in that the resolution of inclination detection is lowered unless the scale width is narrow and the interval between the scale marks arranged above and below the encoder track is not sufficient.

  The present invention has been made to solve the above-described conventional problems. In an electromagnetic induction encoder, the inclination of the slider attitude can be detected with high accuracy and low power, the encoder output can be corrected, and the cost can be reduced. It is another object of the present invention to provide an electromagnetic induction encoder with high accuracy and high resolution.

  The present invention relates to an electromagnetic induction encoder configured to detect displacement of a slider with respect to a scale from an output obtained by using an encoder track formed on the scale, in a measurement direction disposed on the scale. A plurality of inclination detection scale coils that are long in a direction perpendicular to the measurement direction, a three-phase inclination detection transmission coil disposed on the slider, and a position 3 away from the transmission coil in the measurement direction. A three-phase signal obtained by adding three sets of output signals of the phase inclination detection coil and nine sets of transmission / reception by a predetermined calculation is converted into a two-phase signal to obtain a yaw inclination angle of the slider with respect to the scale. And a means for correcting the displacement obtained by using the encoder track according to the calculated yaw inclination angle. That.

  The plurality of inclination detecting scale coils can be connected in series to one to enable stable detection.

  According to the present invention, since the length between the transmission / reception coils for inclination detection can be taken in the longitudinal direction of the detector, the angular resolution can be increased. In addition, since only the change in the yaw tilt of the slider with respect to the scale can be captured, the yaw tilt angle can be detected by eliminating the variation factors other than the yaw tilt. Furthermore, since a detection circuit of a conventional electromagnetic induction encoder can be used, detection can be performed with low power.

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

  In the present embodiment, as shown in detail in FIG. 2, the displacement of a slider (also referred to as a grid) 40 with respect to the scale 30 is detected from the output obtained by using the encoder track 32 formed on the scale 30. In the electromagnetic induction type encoder, a plurality of (four in the figure) inclination detection scale coils (hereinafter simply referred to as scales) disposed on the scale 30 are long in the measurement direction (left-right direction in the figure) and perpendicular to the measurement direction. 34), a three-phase tilt detection transmission coil (hereinafter also simply referred to as a transmission coil) 44 disposed on the slider 40, and a position 3 away from the transmission coil 44 in the measurement direction. A three-phase signal obtained by adding together three sets of output signals of the phase inclination detection receiving coil 46 and nine sets of transmission / reception by a predetermined calculation is converted into a two-phase signal, and then scaled. And a signal processing IC 48 that obtains the yaw tilt angle θ of the slider 40 with respect to 0 and corrects the displacement obtained by using the encoder track 32 and the encoder grid 42 based on the obtained yaw tilt angle θ. is there.

  As the encoder track 32, for example, as described in Patent Documents 2 and 3, three tracks having different pitches are formed, and the encoder grid 42 is formed on the slider 40 correspondingly.

  As shown in detail in FIG. 3, the four scale coils 34 are, for example, four long rectangular coils connected in series in one longitudinal direction. The scale coils 34 may be independent from each other without being connected in series. However, the same current flows more uniformly when they are connected in series as shown in FIG. It becomes possible. The width W of the scale coil 34 only needs to be wider than the width V of the transmission coil 44 and the reception coil 46 shown in FIG. It will be a margin when leaning against.

  As shown in FIG. 4, the transmission coil 44 and the reception coil 46 are arranged at a distance L with a signal processing IC 48 interposed therebetween. As shown in detail in FIG. 5, the transmission coil 44 and the reception coil 46 are arranged on a slider 40 made of, for example, a build-up substrate, as shown in detail in FIG. 5 such as a first phase 0 °, a second phase 120 °, and a third phase 240 ° Phased.

  As shown in FIG. 4, the signal processing IC 48 includes a drive circuit 50 for the transmission coil 44 and a reception circuit 52 for the reception coil 46. The connection between the driving circuit 50 and the transmission coil 44 and the connection between the reception coil 46 and the reception circuit 52 are shown in FIG.

  An arithmetic circuit 54 is connected to the receiving circuit 52, and the arithmetic circuit 54 performs the calculation as follows. That is, assuming that the transmission coil 44 has three phases of A, B, and C and the reception coil 46 has three phases of 0, 1, and 2, the transmission coils A, B, and C are driven in order, and the combination of transmission and reception is 3 X3 = 9 outputs are obtained.

  For this output signal, when only the transmission coil A is driven, the output obtained by the reception coil 0 is A0, the output obtained by the reception coil 1 is A1, the output A2 is also obtained by the reception coil 2, and only the transmission coil B is obtained. The output obtained by the receiving coil 0 when the signal is driven is B0, the output obtained by the receiving coil 1 is B1, the output obtained by the receiving coil 2 is B2, and the receiving coil 0 is driven when only the transmitting coil C is driven. If the output obtained in step C0 is C1, the output obtained by the receiving coil 1 is C1, and the output obtained by the receiving coil 2 is C2, the nine outputs are converted into three-phase signals R0, R1, and R2 by the following equation: Convert to

R0 = (A2 + B1 + C0) / 3 (1)
R1 = (A1 + B0 + C2) / 3 (2)
R2 = (A0 + B2 + C1) / 3 (3)

FIGS. 7 and 8 show the results of calculating the three-phase signals R0, R1, and R2 from the actually measured values when the yaw inclination is given and when the translation is performed in the lateral direction perpendicular to the length measurement direction. From FIG. 7, it can be seen that each of the slider positions changes corresponding to the yaw inclination change, and each changes in a sine wave shape having a phase difference of 120 °. The yaw tilt angle θ can be calculated by converting the three-phase signals R0, R1, and R2 into a two-phase signal by a known method and calculating tan ⁻¹ .

  That is, the three-phase signals R0, R1, and R2 having a phase difference of 120 ° are set to X, Y, and Z as shown in the following equation.

X (θ) = Asinθ (4)
Y (θ) = Asin {θ− (2π / 3)} (5)
Z (θ) = Asin {θ− (4π / 3)} (6)

  If the three-phase signals X, Y, and Z are calculated as follows, they can be converted into a two-phase signal of a sin component and a cos component.

(3/2) ^* Asin θ = X− (Y / 2) − (Z / 2) (7)
(3/2) ^* Acos θ = {(− 2Y / √3) + (2Z / √3)} (8)

  From this, θ can be obtained by calculating the following equation.

θ = tan ^-1 (sinθ / cosθ)
= Tan ^-1 [{X- (Y / 2)-(Z / 2)} / {-2 (Y / √3) + (2Z / √3)}]
... (9)

Note that the three-phase to two-phase conversion and the tan ^-1 calculation are not performed each time, but can be quickly performed using a conversion table obtained in advance.

  On the other hand, as shown in FIG. 8, the three-phase signals R0, R1, and R2 do not change with respect to changes in the lateral direction. Therefore, according to the present invention, a sensor capable of detecting only the yaw tilt can be realized.

  Based on the yaw angle θ obtained as described above, the absolute position calculation result obtained using the encoder track 32 and the grid 42 is corrected in the same manner as in the prior art.

  As described above, for the jaw tilted by the measurement pressure (in the case of a caliper), the correction value is calculated from the length of the jaw and the yaw angle θ, thereby enabling accurate measurement.

  Here, as a detection circuit, a conventional electromagnetic induction encoder system can be used as it is, and operation is possible with low power.

  The present invention is particularly effective for an absolute encoder in which a measurement value changes discontinuously due to a change in yaw inclination. However, the scope of application of the present invention is not limited to this, and even an incremental encoder may be used. ,effective.

Plan view including a partial block diagram showing the configuration of the contact-type measuring instrument proposed by the applicant in Patent Document 1 The perspective view which shows the whole structure of embodiment of this invention. The top view which shows the scale coil of the said embodiment The top view which similarly shows a transmission coil, a reception coil, and signal processing IC Explanatory drawing which shows the specific arrangement | positioning of a transmission coil and a receiving coil similarly The block diagram which similarly shows the connection of a transmission coil, a reception coil, and signal processing IC The diagram which shows the change of the three-phase output signal when giving a yaw inclination for demonstrating the principle of this invention Similarly, a diagram showing changes in three-phase output signal when lateral displacement is applied

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 ... Scale 32 ... Encoder track 34 ... Scale coil for inclination detection 40 ... Slider 42 ... Encoder grid 44 ... Transmit coil for inclination detection 46 ... Receive coil for inclination detection 48 ... Signal processing IC
50 ... Drive circuit 52 ... Receiver circuit 54 ... Operation circuit R0, R1, R2 ... Three-phase output signal

Claims (2)

In an electromagnetic induction encoder adapted to detect the displacement of the slider with respect to the scale from the output obtained using the encoder track formed on the scale,
A plurality of scale coils for detecting inclination in a direction perpendicular to the measurement direction and disposed on the scale;
A three-phase inclination detection transmission coil disposed on the slider, and a three-phase inclination detection reception coil at a position away from the transmission coil in the measurement direction;
Means for converting a three-phase signal obtained by adding three sets of transmission / reception output signals by a predetermined calculation to a two-phase signal to obtain a yaw tilt angle of the slider with respect to the scale;
Means for correcting the displacement obtained using the encoder track according to the determined yaw tilt angle;
An electromagnetic induction encoder characterized by comprising:   The electromagnetic induction encoder according to claim 1, wherein the plurality of inclination detecting scale coils are connected in series to one.

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