JPH07134045A - Absolute encoder - Google Patents

Abstract

PURPOSE:To easily adjust the phases of an absolute signal and an incremental signal during assembly to have a small phase shift. CONSTITUTION:In the absolute encoder-with a detection part for absolute signal for detecting an absolute signal consisting of a code plate where an absolute track and an incremental track are formed concentrically and a plurality of detection elements and a detection part for incremental signal for detecting an incremental signal, sensors 1-4 for detecting A(+) phase, B(+) phase, A(-) phase, and B(-) phase of incremental signal are laid out so that they hold the sensors for detecting absolute signal, namely a sensor 5 for detecting ABS(+) signal and a sensor 6 for detecting ABS (-) signal at the center. Then, an absolute signal detection center and an incremental signal detection center are matched in radial direction of a rotary circular plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute encoder, and more particularly to an absolute encoder in which an absolute track and an incremental track are concentrically formed.

[0002]

2. Description of the Related Art A conventional absolute encoder of this type has a sensor arrangement as shown in FIG. In FIG. 2, the sensor 5 is ABS based on the absolute pattern.
It is a sensor for detecting the (+) signal. The sensor 6 is a sensor for detecting the ABS (-) signal from the absolute inversion pattern. Thus, the sensor 5
And 6 form an absolute signal detection unit. Further, in FIG. 2, the sensors 1 to 4 have A (+) phase, B (+) phase, A (−) phase and B (−) phase of the incremental signal from the incremental pattern, respectively.
It is a sensor for detecting a phase. Thus, the sensor 1
Reference numerals 4 to 4 constitute an incremental signal detector.

FIG. 6 shows an absolute pattern (ABS (+) signal engraved band) and an absolute inversion pattern (ABS (-) signal engraved line) formed on a rotating disk so as to correspond to the conventional sensor arrangement of FIG. FIG. 3 is a diagram showing a band) and an incremental pattern (main signal engraved band). As described above, the absolute track and the incremental track are concentrically formed on the rotating disk. FIG. 8 is a diagram showing a configuration of a signal detection unit having the sensor arrangement of FIG. As illustrated, the ABS (+) signal sensor 5 and the ABS (-) signal sensor 6 are composed of a number corresponding to a predetermined number of bits (in this case, 11 bits, for example), that is, 11 detection elements. As is clear with reference to FIGS. 6 and 8, the ABS (+) signal sensor 5 is in the ABS (+) signal marking band, the ABS (−) signal sensor 6 is in the ABS (−) signal marking band, The main signal sensors (incremental signal detection sensors) 1 to 4 are configured to face the main signal engraved band.

FIG. 3 is a diagram for explaining the phase shift between the incremental signal and the absolute signal in the conventional absolute encoder having the sensor arrangement of FIG. The rotating disc having a pattern as shown in FIG. 6 is attached so that its center coincides with the center of the rotating shaft. However, actually, as shown in FIG. 3, the rotation center O of the rotation shaft and the center P of the disc do not exactly coincide with each other due to the mounting error. Therefore, as the rotation axis rotates, the center P of the disk draws a locus of the circle OC centering on the rotation center O of the rotation axis. The diameter of this circle OC represents the amount of eccentricity ε of the disc. The incremental signal detection center IC is set at one point as the geometric center of the sensors 1 to 4 as shown in the figure. However, there are as many absolute signal detection centers as the number corresponding to the predetermined bit number n as shown in the figure. Hereinafter, the phase deviation will be described based on the absolute signal detection center AC at the left end in the figure.

As shown in FIG. 3, when eccentricity occurs in the rotating disk, a phase shift occurs between the absolute signal and the incremental signal. Specifically, an angle θ1 formed by the absolute signal detection center AC and the incremental signal center IC about a point C1 on the circle OC formed by the locus of the center of the rotating disk and another point C2 on the circle OC are defined. The difference (θ1−θ2) between the angle θ2 formed by the absolute signal detection center AC and the incremental signal center IC as the center constitutes the phase deviation. This phase deviation (θ1−θ2) is an angle θ counterclockwise in the figure with respect to a diameter line segment of a circle OC orthogonal to a radial direction line segment RX connecting the rotation center O of the rotation axis and the incremental signal detection center IC.
Points C1 and C2 of the circle OC and the diameter line segment rotated by
Takes almost the maximum value for. Note that the angle θ is defined by the absolute signal detection center AC and the incremental signal center I.
It is equal to the angle formed by the line segment connecting C and the radial line segment RX.

[0006]

Further, as shown in FIG. 5, the absolute signal 2 from the absolute detection unit is detected.
Looking at the relationship between 0 and the incremental signal 30 from the incremental detector, in the state where there is no phase deviation,
When the absolute signal 20 crosses at the central level 40 (41), the incremental signal 30 reaches the peak value (42). When the phase shift occurs, the phase of the incremental signal 30 becomes the state of the signal 31 or the signal 32.

As described above, in the conventional absolute encoder, the phase deviation occurs due to the eccentricity between the rotation center of the rotating shaft and the geometric center of the rotating disk. If the phase deviation exceeds a predetermined value, it is difficult or impossible to adjust the phase of the absolute signal and the incremental signal during assembly, which in turn causes a malfunction of the absolute encoder. In other words, the allowable eccentricity of the rotating disc is too small, which makes it difficult or impossible to assemble the rotating disc to the rotating shaft. The present invention has been made in view of the above problems, and an object of the present invention is to provide an absolute encoder that has a small phase deviation and that can easily adjust the phases of an absolute signal and an incremental signal during assembly.

[0008]

In order to solve the above-mentioned problems, in the present invention, a code in which an absolute track and an incremental track in which one absolute value is represented by a predetermined number of bits are formed concentrically A board,
Consisting of a plurality of detection elements corresponding to the predetermined number of bits,
An absolute signal detection unit for detecting an absolute signal from the absolute track formed on the code plate, and an incremental signal detection unit for detecting an incremental signal from the incremental track formed on the code plate. In the absolute encoder provided, the detection center of the absolute signal in the absolute signal detection unit and the detection center of the incremental signal in the incremental signal detection unit substantially coincide with the radial direction of the code plate, and the code plate There is provided an absolute encoder characterized in that they exist on substantially the same circumference.

Further, according to the present invention, a code plate in which first and second absolute tracks whose absolute values are expressed by a predetermined number of bits and incremental tracks are provided concentrically, An absolute signal detection unit for detecting an absolute signal from each of the first absolute track and the second absolute track, and an incremental track from the incremental track, each of which includes a plurality of detection elements corresponding to a predetermined number of bits. In an absolute encoder including an incremental signal detection unit for detecting a signal, the absolute track is
A first absolute track on which a pattern in which one absolute value is represented by a predetermined number of bits is formed, and a second reverse pattern formed by reversing the pattern formed on the first absolute track And an absolute track, wherein the incremental track is arranged between the first absolute track and the second absolute track.

[0010]

In the present invention, the above-mentioned phase shift (θ1-θ
2) is not only the eccentricity ε of the rotating disk, but also the absolute signal detection center AC and the incremental signal center IC
Paying attention to the fact that it also depends on the radial distance L2 between and, the sensor arrangement is configured so that the absolute signal detection center AC and the incremental signal detection center IC coincide in the radial direction. As will be described later, the phase deviation (θ1−) is made by matching the absolute signal detection center AC and the incremental signal detection center IC in the radial direction.
θ2) is significantly reduced. As a result, the phase adjustment of the absolute signal and the incremental signal during assembly becomes extremely easy. In other words, an absolute encoder having a large allowable eccentricity of the rotating disk can be realized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, an absolute encoder suitable for applying the present invention will be described. A code plate formed with a one-track absolute pattern formed from a minimum read pattern of a minimum read unit λ and an incremental pattern having a pitch of λ; an absolute detection unit having two sets of elements and detecting an absolute pattern; An absolute encoder having an incremental detector having an incremental element for detecting an incremental pattern has already been proposed (Japanese Patent Laid-Open No. 2-168115). The minimum reading unit λ and the pitch λ of the incremental pattern will be described later with reference to FIG.
Can be referred to.

In the absolute encoder configured as described above, the incremental signal output from the incremental detection section is provided so that the absolute detector does not cause a malfunction such as a pattern reading error when passing through the boundary area of the minimum read pattern. Using, the element group in the boundary area of the absolute pattern and the element group in the minimum reading unit of the absolute pattern are appropriately switched. The application of the present invention to this absolute encoder is most preferable because a malfunction can be avoided by switching between the element group at the boundary of the absolute pattern and the element group within the minimum reading unit of the absolute pattern.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing sensor arrangement examples (a) to (e) of an absolute encoder according to an embodiment of the present invention. In the sensor arrangement of FIG. 1A, the sensor for detecting an incremental signal, that is, A of the incremental signal is used.
The sensors 1 to 4 for detecting the (+) phase, the B (+) phase, the A (-) phase and the B (-) phase are used for detecting the absolute signal, that is, the ABS (+) signal. The sensor 5 and the sensor 6 for detecting the ABS (-) signal are arranged so as to be sandwiched in the center, and the absolute signal detection center and the incremental signal detection center are aligned in the radial direction of the rotating disk.

FIG. 7A shows an absolute pattern (ABS (+) signal engraved band) and an absolute inversion pattern (ABS (-) formed on the rotating disk so as to correspond to the sensor arrangement of FIG. 1A. FIG. 6 is a diagram showing a signal engraved band) and an incremental pattern (main signal engraved band). Corresponding to the sensor arrangement of FIG. 1A, two main signal engraved bands are patterned so as to sandwich the ABS (+) signal engraved band and the ABS (-) signal engraved band in the center. . The absolute pattern and the absolute reverse pattern are patterns of the minimum reading unit λ. In addition, the incremental pattern is composed of a 1-pitch repeating bright and dark pattern.

FIG. 9A is a diagram showing a configuration of a signal detection unit having the sensor arrangement of FIG. 1A. As shown in the figure, the ABS (+) signal sensor 5 and the ABS (-) signal sensor 6 are composed of a predetermined number of bits (in this case, 11 bits, for example) of detection elements, and the main signal sensor (incremental signal detection sensor). ) 1 to 4 are arranged so as to be sandwiched in the center.

As is apparent from FIGS. 7 (a) and 9 (a), the ABS (+) signal sensor 5 is an ABS.
The ABS (-) signal sensor 6 is AB in the (+) signal engraved zone.
The main signal sensors (incremental signal detecting sensors) 1 to 4 are arranged in the S (-) signal engraved band so as to face the main signal engraved band. That is, for the absolute pattern, the ABS (+) signal sensor 5 and the ABS (-) signal sensor 6 are arranged vertically in the drawing. Also, for the incremental pattern, A
(+) Phase sensor 1 and B (+) phase sensor 2 and A (-)
The phase sensor 3 and the B (-) phase sensor 4 are arranged so as to sandwich the two ABS sensors 5 and 6 above and below in the figure.

FIG. 4 is a diagram for explaining the phase shift between the incremental signal and the absolute signal in the absolute encoder having the sensor arrangement of FIG. 1 (a). In addition, in FIG. 4, the incremental signal detection center IC is set at one point as the geometric center of the sensors 1 to 4 as illustrated. However, there are as many absolute signal detection centers as the number corresponding to the predetermined bit number n as shown in the figure. Hereinafter, the phase deviation will be described based on the absolute signal detection center AC at the left end in the figure.

When the eccentricity ε is generated on the rotating disk, a phase shift is generated between the absolute signal and the incremental signal. Specifically, an angle θ1 formed by the absolute signal detection center AC and the incremental signal center IC about a point C1 on the circle OC formed by the locus of the center of the rotating disk and another point C2 on the circle OC are defined. The difference (θ1−θ2) between the angle θ2 formed by the absolute signal detection center AC and the incremental signal center IC as the center constitutes the phase deviation. This phase shift (θ1−θ2) takes almost the maximum value at the intersections C1 and C2 of the radial line segment RX and the circle OC.

Referring to an actual design dimension example, the phase deviation (θ1−θ1 in the conventional absolute encoder of FIG.
θ2) can be quantitatively compared with the phase shift (θ1−θ2) in the absolute encoder of the embodiment of the present invention shown in FIG. Therefore, the distance between the absolute signal detection center AC and the radial line segment RX is set to L1, the distance between the absolute signal detection center AC and the incremental signal detection center IC is set to L2, and the incremental signal detection center IC and rotation are set. Let L3 be the distance along the radial direction from the rotation center O of the shaft, and let the eccentricity of the disc be ε.
Then, these dimension parameters were set with reference to an actual design dimension example, and the conventional example and the example were compared. The conditions and results in the conventional example and the example are shown in the following Table 1 and Table 2, respectively.

[0020]

Table 1 [Conventional example] (Condition) L1 = 0.38 mm L2 = 2.45 mm L3 = 13.6 mm ε = 0.1 mm (Result) θ1 = 1.41855 ° θ2 = 1.29365 ° θ1-θ2 = 0.1249 ° (phase shift)

[0021]

[Example 2] (Condition 1) L1 = 0.38 mm L2 = 0 mm L3 = 13.6 mm ε = 0.1 mm (Result 1) θ1 = 1.61234 ° θ2 = 1.58882 ° θ1-θ2 = 0.02352 ° (Phase deviation) (Condition 2) L1 = 0.38 mm L2 = 0 mm L3 = 16.05 mm ε = 0.1 mm (Result 2) θ1 = 1.36478 ° θ2 = 1.34789 ° θ1-θ2 = 0.01689 ° (phase shift)

In order to match the conditions of the conventional example and the embodiment, in condition 1, L3 matches L3 of the conventional example, and condition 2
Then, L3 was matched with L2 + L3 of the conventional example. Under any of the conditions, it is found that the phase deviation (θ1−θ2) is significantly reduced by making the absolute signal detection center AC and the incremental signal detection center IC coincide with each other in the radial direction.

FIG. 1B is a diagram showing a sensor arrangement of an absolute encoder according to another embodiment. Figure 1
In the sensor arrangement of (b), the incremental signal detection sensor, that is, the A (+) phase of the incremental signal,
The sensors 1 to 4 for detecting the B (+) phase, the A (-) phase and the B (-) phase are absolute signal detecting sensors, that is, the sensor 5 and the ABS (for detecting the ABS (+) signal. -) It is arranged so as to be sandwiched in the center by a sensor 6 for detecting a signal, and is configured so that the absolute signal detection center and the incremental signal detection center coincide with each other in the radial direction of the rotating disk.

FIG. 7B shows an absolute pattern (ABS (+) signal engraved band) and an absolute inversion pattern (ABS (-) formed on the rotating disk so as to correspond to the sensor arrangement of FIG. 1B. FIG. 6 is a diagram showing a signal engraved band) and an incremental pattern (main signal engraved band). Corresponding to the arrangement of FIG. 1B, one main signal engraved band is patterned so as to be sandwiched between the ABS (+) signal engraved band and the ABS (-) signal engraved band.

FIG. 9 (b) is a diagram showing the structure of a detection unit having the sensor arrangement of FIG. 1 (b). As shown, A
The BS (+) signal sensor 5 and the ABS (-) signal sensor 6 are composed of detection elements having a predetermined number of bits (in this case, for example, 11 bits), and four main signal sensors (incremental signal detection sensors) 1 to It is arranged so as to sandwich 4 in the center. 7 (b) and 9
As is clear with reference to (b), the ABS (+) signal sensor 5 is in the ABS (+) signal marking band, the ABS (-) signal sensor 6 is in the ABS (-) signal marking band, and the main signal is The sensors (incremental signal detection sensors) 1 to 4 are configured to face the main signal engraved band.

As another embodiment of the present invention, a sensor arrangement as shown in FIGS. 1 (c) to 1 (e) is also possible. Figure 1
The sensor arrangement of (c) is A of the incremental signal.
It is applicable to the absolute encoder in which the sensors 1 to 4 for detecting the (+) phase, the B (+) phase, the A (-) phase and the B (-) phase are arranged in the circumferential direction. In this embodiment, the A (+) phase and B (+) phase of the incremental signal
The sensors 1 to 4 for detecting the phase, the A (-) phase and the B (-) phase are ABS (+) signal detection sensors 5 and A.
It is configured to be sandwiched by the BS (-) signal detection sensor 6 in the center thereof.

The sensor arrangement shown in FIG. 1 (d) includes sensors 1 to 4 for detecting the A (+) phase, B (+) phase, A (-) phase and B (-) phase of the incremental signal. Is applicable to an absolute encoder in which a plurality of sets are arranged in the circumferential direction. In this embodiment, the A (+) phase, B (+) phase, A (-) phase and B of the incremental signal are used.
The incremental signal detecting sensor including a plurality of sets of sensors 1 to 4 for detecting the (−) phase is an ABS.
The (+) signal detection sensor 5 and the ABS (-) signal detection sensor 6 are sandwiched in the center thereof.

Further, the sensor arrangement of FIG. 1 (e) can be applied to an absolute encoder having only a sensor 5 for detecting an ABS (+) signal as an absolute signal detecting sensor. In this embodiment, the sensors 1 to 4 for detecting the A (+) phase, B (+) phase, A (−) phase and B (−) phase of the incremental signal are
The BS (+) signal detection sensor 5 is configured to be sandwiched in the center.

[0029]

[Effect] As described above, according to the present invention, the detection center of the absolute signal and the detection center of the incremental signal are made to coincide with each other in the radial direction of the rotating disk, so that there is a phase shift between the absolute signal and the incremental signal. Significantly reduced. As a result, the phase adjustment of the absolute signal and the incremental signal at the time of assembly becomes extremely easy, and an absolute encoder with a large allowable eccentricity of the rotating disk can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing sensor arrangement examples (a) to (e) of an absolute encoder according to an embodiment of the present invention.

FIG. 2 is a diagram showing a sensor arrangement of a conventional absolute encoder.

FIG. 3 is a diagram for explaining phase deviation between an incremental signal and an absolute signal in a conventional absolute encoder having the sensor arrangement of FIG.

FIG. 4 is a diagram for explaining phase deviation between an incremental signal and an absolute signal in the absolute encoder having the sensor arrangement of FIG.

FIG. 5 is a signal waveform diagram for explaining the influence of a phase shift on a signal waveform.

FIG. 6 is a diagram showing a pattern formed on a rotating disk so as to correspond to the conventional sensor arrangement of FIG.

FIG. 7 is a view showing a pattern formed on a rotating disc so as to correspond to the sensor arrangements of FIGS. 1 (a) and 1 (b).

FIG. 8 is a diagram showing a configuration of a signal detection unit having the conventional sensor arrangement of FIG.

FIG. 9 is a diagram showing a configuration of a signal detection unit having the sensor arrangements of FIGS. 1 (a) and 1 (b).

[Explanation of symbols]

 1 A (+) phase sensor 2 B (+) phase sensor 3 A (-) phase sensor 4 B (-) phase sensor 5 ABS (+) signal sensor 6 ABS (-) signal sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Morita 471 Nagaodai-cho, Sakae-ku, Yokohama-shi, Kanagawa Nikon Yokohama Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A code plate in which an absolute track and an incremental track, one absolute value of which is represented by a predetermined number of bits, are concentrically formed, and a plurality of detection elements corresponding to the predetermined number of bits. An absolute signal detection unit for detecting an absolute signal from the absolute track formed on the code plate, and an incremental signal detection unit for detecting an incremental signal from the incremental track formed on the code plate. In the absolute encoder provided, the detection center of the absolute signal in the absolute signal detection unit and the detection center of the incremental signal in the incremental signal detection unit substantially coincide with the radial direction of the code plate, the code Absolute encoder, characterized in that present on the substantially same circumference of the plate. 2. A code plate in which first and second absolute tracks whose absolute values are expressed by a predetermined number of bits and incremental tracks are provided concentrically, and which corresponds to the predetermined number of bits. Consisting of multiple detectors,
An absolute signal detecting unit for detecting an absolute signal from each of the first absolute track and the second absolute track, and an incremental signal detecting unit for detecting an incremental signal from the incremental track. In the absolute encoder provided, the absolute track includes a first absolute track on which a pattern in which one absolute value is represented by a predetermined number of bits is formed, and the first absolute track formed on the first absolute track. A second absolute track having an inverted pattern formed by reversing the pattern, wherein the incremental track is provided between the first absolute track and the second absolute track. Absolute encoder, characterized in that it is location. 3. A code plate in which first and second absolute tracks and an incremental track, one absolute value of which is represented by a predetermined number of bits, are concentrically provided, and a plurality of code plates corresponding to the predetermined number of bits. It consists of the detection element of
An absolute signal detecting unit for detecting an absolute signal from each of the first absolute track and the second absolute track, and an incremental signal detecting unit for detecting an incremental signal from the incremental track. In the absolute encoder provided, the incremental track includes a first incremental track and a second incremental track in which a repeating pattern with an equal pitch is formed, and the absolute track is the first incremental track. An absolute encoder arranged between a track and the second incremental track.