JP4869769B2 - Absolute rotary encoder and micrometer - Google Patents

Description

  The present invention relates to an absolute rotary encoder that measures displacement using magnetic flux coupling and a micrometer equipped with the absolute rotary encoder.

The rotary encoder includes a stator in which transmission windings and reception windings are arranged, and a rotor in which tracks capable of magnetic flux coupling are arranged. Among these encoders, the absolute type is disclosed in Patent Documents 1 and 2, for example. In particular, Patent Document 2 discloses a relatively large rotary encoder that is applied to control of an internal combustion engine.
JP-A-10-213407 (FIGS. 2 and 3) US Pat. No. 3,812,481 (column 5, line 68 to column 6, line 3, column 7, line 31 to line 35, FIGS. 1 and 2)

  In the absolute rotary encoder, since a plurality of tracks are arranged on the rotor, the area allocated to each track is small. For this reason, when the absolute rotary encoder is reduced in size, the induced current generated in the track due to the magnetic flux coupling with the transmission winding is reduced. Therefore, a sufficiently strong received signal cannot be obtained from the receiving winding, and the measurement accuracy decreases.

  In addition, when the stator and the rotor are misaligned when the stator and the rotor are assembled in the housing, the magnitude of the misalignment is almost the same regardless of the size of the absolute rotary encoder. Therefore, if the absolute rotary encoder is reduced in size, the influence of the positional deviation is large, which causes a decrease in measurement accuracy.

  An object of the present invention is to provide an absolute rotary encoder capable of performing high-accuracy measurement even if it is miniaturized, and a micrometer equipped with the absolute rotary encoder.

  An absolute rotary encoder according to the present invention includes a shaft, a stator, a rotor having a through hole through which the shaft passes at the center thereof, a rotor disposed to face the stator so as to be rotatable about the shaft, and a track. A group of tracks arranged concentrically on the rotor, a transmission winding group arranged in the stator so as to be magnetically coupled to the track group, and a receiving winding arranged in the stator so as to be magnetically coupled to the track group Each track of the track group includes a linear arc portion having first and second radii arranged alternately on the rotor, and a continuous ring shape around the axis. The at least two tracks of the track group are different in the number of the linear arc portions from each other.

  Each track provided in the absolute rotary encoder according to the present invention includes linear arc portions having first and second radii arranged alternately on the rotor, and one continuous ring-shaped magnetic flux centering on the axis. It is a coupled winding. Therefore, even if the absolute rotary encoder is reduced in size, it is possible to prevent the strength of the received signal from being lowered and to reduce the influence of the displacement of the stator and the rotor.

  In the present invention, the transmission winding group may be arranged outside the innermost one of the plurality of reception windings constituting the reception winding group. According to this, since the transmission winding disposed inside the innermost reception winding is omitted, it is possible to reduce the size of the absolute rotary encoder.

  In the present invention, the transmission winding group may have a configuration in which the transmission windings are connected in a single stroke. According to this, since the transmission winding drive circuit for driving each transmission winding can be shared, the absolute rotary encoder can be reduced in size.

  The absolute rotary encoder can be mounted on a micrometer.

  According to the present invention, even if the absolute rotary encoder is miniaturized, it is possible to prevent the signal strength obtained from the reception winding from being lowered and to reduce the influence of the positional deviation of the stator and the rotor. Therefore, a highly accurate small-sized absolute rotary encoder can be realized.

  Hereinafter, an absolute rotary encoder according to this embodiment (hereinafter, “absolute rotary encoder” may be referred to as “encoder”) will be described with reference to the drawings. In the figure, the same reference numerals are used to designate the same elements as those shown in the drawings already described, and the description thereof is omitted.

  FIG. 1 is a plan view of a stator 1 that is a constituent element of an absolute rotary encoder according to the present embodiment, and FIG. 2 is a plan view of a rotor 3. A through hole 5 is formed at the center of the stator 1, and a shaft 9 is passed through the through hole 5. The rotor 3 also has a through hole 11 through which the shaft 9 passes. The rotor 3 is disposed to face the stator 1 so as to be rotatable about the shaft 9 in the direction of arrow A through a rotor bush (not shown) fitted in the through hole 11. The stator 1 and the rotor 3 are composed of a printed circuit board, a glass substrate, a silicon substrate, or the like.

  The stator 1 shown in FIG. 1 includes an insulating substrate 15 on which ring-shaped receiving windings 17 and 19 are formed concentrically around the shaft 9. The reception winding 17 is located outside and the reception winding 19 is located inside. The reception winding 17 has terminals T1 and T2, and the reception winding 19 has terminals T3 and T4. The reception windings 17 and 19 constitute a reception winding group G1. The configuration of the reception winding will be described using the reception winding 17 as an example.

  FIG. 3 is a plan view of the reception winding 17. The reception winding 17 has a configuration in which a plurality of sets U of upper layer conductors 21 and lower layer conductors 23 that three-dimensionally intersect the upper layer conductors 21 are arranged in a ring shape. An insulating layer (not shown) is disposed between the upper layer conductor 21 and the lower layer conductor 23. The end portion of the upper layer conductor 21 and the end portion of the lower layer conductor 23 are connected via a buried conductor 25 embedded in a through hole or via hole provided in this insulating layer. Therefore, it can be said that the reception winding 17 has a configuration in which a plurality of reception loops 27 each having a substantially rhombus shape are arranged in a ring shape.

  The reception loop 27 can have various closed loop shapes such as a substantially sine wave shape. FIG. 4 is a plan view of a reception winding constituted by a reception loop 27 having a substantially sinusoidal shape. These may be arranged on the stator 1 of FIG.

  FIG. 5 is a plan view of the vicinity of the reception folded portion 29 of the reception winding 17. The reception folded portion 29 is formed at two locations on both the distal end side 31 and the distal end side 33 of the reception winding 17. Specifically, the lower layer conductor 23 is folded at the reception folded portion 29 at the distal end side 31, and the upper layer conductor 21 is folded at the reception folded portion 29 at the distal end 33. The reception folded portion 29 on the distal end side 31 is the lower layer conductor 23, and the reception folded portion 29 on the distal end side 33 is the upper layer conductor 21. Therefore, the reception folding unit 29 on the distal end side 31 and the reception folding unit 29 on the distal side 33 are not connected.

  The reception winding 19 in FIG. 1 has the same configuration as the reception winding 17. However, the rotation angle corresponding to the wavelength λ 2 of the reception winding 19 is different from the rotation angle corresponding to the wavelength λ 1 of the reception winding 17.

  As shown in FIG. 1, the stator 1 includes transmission windings 35 and 37 arranged outside the reception winding 17 and between the reception winding 17 and the reception winding 19, respectively. The transmission windings 35 and 37 have a configuration in which a linear conductor having a constant curvature is formed on the insulating substrate 15 in a ring shape. The transmission winding 35 and the transmission winding 37 are connected in a single stroke and constitute a transmission winding group G2. As a result, the transmission winding drive circuit can be shared and the transmission windings 35 and 37 can be driven simultaneously, so that the encoder can be downsized. T5 and T6 are terminals of the transmission winding group G2.

  The transmission winding group G2 is arranged outside the reception winding 19, that is, outside the innermost one of the reception windings 17 and 19 constituting the reception winding group G1. In this way, the encoder is miniaturized by omitting the transmitter winding disposed inside the receiver winding 19.

  Next, the configuration of the rotor 3 will be described with reference to FIG. The rotor 3 has a disk-shaped insulating substrate 39. Tracks 41 and 43 are concentrically formed on the insulating substrate 39. The track 41 is disposed on the outer side, and can be magnetically coupled to the reception winding 17 and the transmission winding group G2. On the other hand, the track 43 is arranged on the inner side, and can be magnetically coupled to the reception winding 19 and the transmission winding group G2. A track group G3 is constituted by the tracks 41 and 43.

  The track configuration will be described with the track 41 as an example. Ten linear arcs 45 having a radius r1 (an example of a first radius) and ten linear arcs 47 having a smaller radius r2 (an example of a second radius) are alternately arranged. The linear arc portions 45 and 47 are connected by a linear portion 49 extending in the radial direction of the rotor 3. Thus, one continuous ring-shaped magnetic flux coupling winding 51 around the shaft 9 is formed. This magnetic flux coupling winding 51 becomes the track 41. The wavelength λ1 of the magnetic flux coupling winding 51 is equal to the wavelength λ1 of the reception winding 17.

  The magnetic flux coupling winding 53 serving as the track 43 includes a linear arc portion 55 having a radius r3 (an example of the first radius) smaller than the radius r2, and a linear arc having a radius r4 (an example of the second radius) smaller than the radius r2. Nine portions 57 are alternately arranged. The linear arc portions 55 and 57 are connected by a linear portion 59. The wavelength λ2 of the magnetic flux coupling winding 53 is equal to the wavelength λ2 of the reception winding 19. As described above, the magnetic flux coupling windings 51 and 53 have a gear-shaped pattern.

  A block 61 is constituted by the linear arc portion 45 and the linear portions 49 on both sides thereof, and a block 61 is constituted by the linear arc portion 55 and the linear portions 59 on both sides thereof. The number of blocks 61 is 10 for the outer tracks 41 and 9 for the inner tracks 43.

  In the encoder according to the present embodiment configured by the stator 1 in FIG. 1 and the rotor 3 in FIG. 2, since the number of blocks 61 is different between the track 41 and the track 43, the signals obtained from the reception windings 17 and 19 Based on the difference, the absolute position in one rotation of the rotor 3 can be detected.

  Next, the main effects of this embodiment will be described in comparison with a comparative embodiment. FIG. 6 is a plan view of the rotor 71 according to the comparative embodiment, and corresponds to FIG. The rotor 71 is different from the rotor 3 in the track configuration. The track 41 of the rotor 71 is configured by arranging ten magnetic flux coupling windings 73 at a predetermined pitch. On the other hand, the track 43 is configured by arranging nine magnetic flux coupling windings 73 at a predetermined pitch. The magnetic flux coupling winding 73 has a substantially rectangular frame shape.

  Using the encoder according to the present embodiment provided with the rotor 3 and the encoder according to the comparative embodiment provided with the rotor 71, the dimensions of a predetermined measurement object were measured. The conditions were as follows. The radii of the tracks 41 and 43 were 7.4 mm and 6.3 mm, respectively, the deviation amount of the rotation center of the rotor with respect to the stator was about 100 μm, and the deviation of the inclination was about 25 μm in the track 41 portion.

  Measurement errors in the intensity and dimensions of the signal obtained from the receiving winding during the measurement were determined. FIG. 7 is a graph showing the measurement result of the signal intensity, and FIG. 8 is a graph showing the result of the measurement error of the dimension. First, the signal strength will be described. The graph of FIG. 7 represents the signal strength in the present embodiment as a ratio, where the signal strength in the comparative embodiment is 1.

  According to this embodiment, a signal strength about 1.2 times that of the comparative embodiment can be obtained. As described in the section of the problem to be solved by the invention, when the absolute rotary encoder is reduced in size, the induced current generated in the track due to the magnetic flux coupling with the transmission winding becomes small, and the reception signal of sufficient strength is received. Can't get from.

  Since the present embodiment includes tracks 41 and 43 each composed of one continuous ring-shaped (gear-shaped) magnetic flux coupling windings 51 and 53 as shown in FIG. 2, the transmission winding group G2 to the track group are provided. A signal can be efficiently transmitted to G3. Therefore, since the strength of the received signal can be increased, a sufficiently strong received signal can be obtained from the receiving winding even if the encoder is downsized.

  Next, the dimension measurement error will be described. FIG. 8 shows the measurement error ratio of this embodiment when the measurement error of the comparative embodiment is 1. According to the present embodiment, the measurement accuracy can be improved by about 50% compared to the comparative embodiment.

  According to this embodiment, it is considered that the measurement error due to the positional deviation of the stator and the rotor can be reduced for the following reason. As shown in FIG. 9, when the mounting position of the rotor with respect to the stator is shifted, the distance between the stator and the rotor differs depending on the position of the track. Consider the current flowing in the track in this case.

  As shown in FIG. 10, in the rotor 71 of the comparative form, the plurality of magnetic flux coupling windings 73 constituting the track are separated from each other, so that different magnitude induced currents are generated in each of them. For example, the induced current ia flowing through the magnetic flux coupling coil 73a and the induced current ib flowing through the magnetic flux coupling coil 73b are different in magnitude. Accordingly, the magnitude of the induced current differs depending on the position of the track, which causes a reduction in measurement accuracy. For example, even with the same positional deviation of 0.1 mm, the effect increases as the encoder is downsized.

  On the other hand, as shown in FIG. 11, the rotor 3 of the present embodiment is in the form of one ring in which the magnetic flux coupling windings 51 and 53 of one track are continuous, so that the induced current flowing through the track depends on the position of the track. Can be made uniform. Therefore, according to the present embodiment, it is possible to reduce a measurement error due to a misalignment of the stator or the rotor.

  As described above, according to the present embodiment, even if the encoder is downsized, it is possible to prevent a decrease in the strength of the received signal and to reduce the influence of the displacement of the stator and the rotor. A possible small absolute rotary encoder can be realized.

  In addition, as shown in FIG. 1, the case where there is one receiving winding 17 and 19 corresponding to each track (in the case of a one-phase receiving winding) has been described, but there are three receiving windings corresponding to each track. (In the case of a three-phase receiving winding). This is shown in FIG. Three receiving windings 17a, 17b, 17c arranged out of phase with each other correspond to one track, and three receiving windings 19a, 19b, 19c arranged out of phase with each other correspond to the other track. is doing. Further, although not shown in the figure, the number of receiving windings corresponding to each track may be two or four (in the case of two-phase or four-phase receiving windings).

  Further, the rotor 3 is not limited to the configuration shown in FIG. 2, but may have the configuration shown in FIG. In the rotor 81, the outer track 41 is composed of 16 blocks 61, and the inner track 43 is composed of five blocks 61.

  Further, although the case where the number of tracks constituting the track group G3 is two has been described, three or more may be used. In this case, the number of blocks 61 (that is, linear arc portions) may be different from each other in at least two tracks of the track group G3.

  FIG. 14 is a front view of a micrometer 91 equipped with an absolute rotary encoder according to this embodiment. The stator 1 of FIG. 1 is fixed to the frame 93, and the rotor 3 of FIG. According to the present embodiment, high-precision measurement can be realized even with a small micrometer 91 having a diameter of the rotor 3 of, for example, 20 mm or less.

It is a top view of the stator which is a component of the absolute rotary encoder which concerns on this embodiment. It is a top view of the rotor which is a component of the absolute rotary encoder which concerns on this embodiment. It is a top view of an example of the receiving winding arrange | positioned at the stator shown in FIG. FIG. 6 is a plan view of another example of the receiving winding arranged in the stator shown in FIG. 1. FIG. 4 is a plan view of the vicinity of a reception folded portion of the reception winding shown in FIG. 3. It is a top view of the rotor which is a component of the absolute rotary encoder which concerns on a comparison form. It is a graph which shows the measurement result of signal strength. It is a graph which shows the result of the measurement error of a dimension. It is a figure which shows the position shift of the rotor with respect to a stator. It is a figure which shows the electric current which flows into a track | truck when the position shift has generate | occur | produced in the rotor of a comparison form. It is a figure which shows the electric current which flows into a track | truck when the position shift has generate | occur | produced in the rotor of this embodiment. It is a top view of the three phase receiving winding applicable to this embodiment. It is a top view of the other example of the rotor applicable to this embodiment. It is a front view of the micrometer in which the absolute rotary encoder which concerns on this embodiment is integrated.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Stator, 3 ... Rotor, 5 ... Through-hole, 9 ... Shaft, 11 ... Through-hole, 15 ... Insulating substrate, 17, 17a, 17b, 17c, 19, 19a , 19b, 19c: receiving winding, 21 ... upper layer conductor, 23 ... lower layer conductor, 25 ... buried conductor, 27 ... receiving loop, 29 ... receiving folded portion, 31. .. tip side, 33... End side, 35, 37... Transmission winding, 39... Insulating substrate, 41, 43... Track, 45, 47. ..Linear part, 51, 53 ... Magnetic flux coupling winding, 55, 57 ... Linear arc part, 59 ... Linear part, 61 ... Block, 71 ... Rotor, 73 ..Magnetic flux coupling windings, 81 ... rotor, 91 ... micrometer, 93 ... frame, 95 ... thimble, A ... times Direction, G1... Reception winding group, U... Set, T1, T2, T3, T4, T5, T6... Terminal, λ1, λ2. G3: Track group, r1, r2, r3, r4 ... radius.

Claims (7)

The axis,
A stator,
A rotor having a through-hole through which the shaft passes at the center and being arranged to face the stator so as to be rotatable about the shaft;
A group of tracks in which the tracks are arranged concentrically on the rotor;
A transmission winding group disposed on the stator so as to be magnetically coupled to the track group;
A receiving winding group disposed on the stator so as to be magnetically coupled to the track group, and
Each track of the track group includes a linear arc portion having first and second radii arranged alternately on the rotor, and a continuous ring-shaped magnetic flux coupling winding centering on the axis. Yes,
The absolute rotary encoder characterized in that at least two tracks of the track group have different numbers of the linear arc portions. 2. The absolute rotary encoder according to claim 1, wherein the transmission winding group is disposed outside an innermost winding among a plurality of reception windings constituting the reception winding group. The absolute rotary encoder according to claim 1 or 2, wherein the transmission winding group has a configuration in which transmission windings are connected in a single stroke.   The rotation angle corresponding to the wavelength of the outer reception winding among the reception windings constituting the reception winding is different from the rotation angle corresponding to the wavelength of the inner reception winding. Absolute rotary encoder.   2. The absolute rotary encoder according to claim 1, wherein each of the reception windings constituting the reception winding group has a configuration in which a plurality of reception loops having a closed loop shape are arranged in a ring shape.   2. The absolute rotary encoder according to claim 1, wherein a plurality of receiving windings are arranged with a phase shifted corresponding to each track. A micrometer comprising the absolute rotary encoder according to any one of claims 1 to 6.

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