JP2001021382A - Rotary angle-detecting device and ink jet printer with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary angle-detecting device for drastically reducing a detection error caused by the eccentricity of a scale disk, SOLUTION: A rotary angle-detecting device 20 is formed by two detectors 31A and 31B that are arranged oppositely in a scale disk 21 while detection means are shifted by 180 degrees each other with a rotary axis 2 as a center, and a rotary angle detection circuit 50 is formed so that it can generate a detection signal Nc after a new correction where time errors of detection signals Sda and Sdb caused by an amount of eccentricity ε for a rotary axis 2 of the scale disk 21 are corrected by utilizing the two detection signals Sda and Sdb being outputted from the two detectors 31A and 31B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale disk provided with a large number of scales and mounted on a rotating shaft, detecting means including a detector arranged opposite to the scale disk, and an output from the detecting means. And a rotation angle detection circuit capable of detecting a rotation angle of the rotation shaft by performing predetermined processing on the detected signal.

[0002]

2. Description of the Related Art In a rotation angle detecting device for detecting a rotation angle of a rotation shaft or the like, a detection means including a scale disk attached to the rotation shaft and a detector arranged opposite to the scale disk. And a rotation angle detection circuit capable of detecting a rotation angle of the rotation shaft by performing predetermined processing on a detection signal output from the detection means.

A large number of scales (slits) such as an optical slit and an electric slit are provided on a scale disk, and a detector outputs a detection signal every time the slit passes. Then, the rotation angle detection circuit detects the rotation angle of the rotation shaft by performing predetermined processing (for example, counting the detection signal output time) on the detection signal output from the detection means (detector).

Further, if the detection signal is subjected to predetermined processing based on the passage time of one slit (detection signal output time) to the length of the passage time between the front and rear slits, the rotation speed of the rotating shaft can be detected. Further, it can be detected as a rotation speed or a rotation angle per unit time (rotation speed change rate or rotation angle change rate). In other words, the rotation angle detection device is configured to use the rotation speed detection device,
It can also function as a rotation speed change rate detection device, a rotation angle change rate detection device, or an angular speed detection device.

[0005] Such a rotation angle detection device (20P, 50
P) is used as follows. That is, for example,
The ink jet printer shown in FIG. 13 includes a rotating drum 1 that rotates in one direction (R direction) around a rotating shaft 2 and nozzle heads 11C and 1 that are disposed to face the rotating drum 1.
1M, 11Y, and 11K (see FIG. 14), and prints by driving the nozzle heads 11C, 11M, 11Y, and 11K on the rotating print medium (paper P) wound around the rotary drum 1. Is formed. Each nozzle head 11C,
11M, 11Y, and 11K are integrally configured as a nozzle head unit 10 shown in FIG.

That is, the print medium (paper P) sent from the paper feeding means is fed to the rotating drum 1 side at a predetermined timing by the feeding means, and is brought into close contact with the outer peripheral surface of the rotating drum 1 by, for example, electrostatic attraction. It is wound and held. The rotating drum 1 rotates at a reference rotation speed (for example, 120 RPM) around the axis Z in FIG. 13 and in a predetermined rotation (R) direction.
Has been rotated.

A nozzle head 1 for each color having a large number of ink jet nozzles arranged in the main scanning (X = Z) direction and displaced in the R direction as shown in FIG.
1C, 11M, 11Y, 11K can be selectively driven,
The nozzle heads 11C, 11 for each color selectively driven
Printing can be performed while ejecting ink for each color onto the rotating printing medium (P) from the respective inkjet nozzles of M, 11Y, and 11K.

In FIG. 14, the nozzle head unit 1
0 (11C, 11M, 11Y, 11K) is reciprocated in the row (X) direction by a predetermined distance (for example, the pitch between ink jet nozzles) by the reciprocating means, while rotating the rotating drum 1, that is, the print medium in the row direction. Printing (dot D
11 to Dn1), and in the printing (X) direction, for example, during the forward movement, using the rotation of the rotating drum 1 (Y =
R) direction printing (dots D11 to D1m,..., Dn1 to Dn)
nm). That is, the row (X... Main scan)
Since the directional printing and the row (Y... Sub-scanning) directional printing can proceed at the same time, the printing speed can be greatly increased.

More specifically, the printing drive timing control means on the printer side starts detecting the printing start position P0 of the printing medium (P) at the printing reference position detection time point t0.
Based on this, the nozzle heads for each color 11C, 11M,
Arrangement positions Pc, Pm, P in the R direction of 11Y and 11K
time difference T0c, Tcm, Tmy, corresponding to y, Pk,
At times tc, tm, ty, and tk at which Tyk is provided, each of the color nozzle heads 11C, 11M, 11Y, and 11K is printed. Thus, by paying attention to one row, color printing in which cyan C, magenta M, and yellow Y are superimposed can be performed. Also, black K can be printed. In addition,
For example, it may be formed such that the timing of another nozzle head is determined based on the nozzle head 11C.

The printed printing medium (P) is peeled off from the rotating drum 1 and is discharged by a discharging means along a discharging path. Therefore, the higher the rotation speed of the rotating drum 1, the higher the printing speed. For example, if the rotating drum 1 is rotated at a constant and high speed at a reference rotation speed (for example, 120 RPM) by a servo motor of a loop control system, color printing of, for example, 20 PPM or more can be achieved.

However, the rotating shaft 2, that is, the rotating drum 1
There is also a certain limit to stabilizing the rotation speed of the motor due to technical, cost, and time reasons. The rotating shaft 2 when the paper P is wound around the rotating drum 1 or when the paper P is peeled off.
Therefore, it is often necessary to admit that the rotational speed of the rotary shaft 2 fluctuates within a certain range.

Therefore, as shown in FIGS. 13 and 15, a scale disk 21 forming a rotation angle detecting device 20P is attached to the rotary shaft 2, and a detector forming detection means disposed opposite to the scale disk 21 is formed. During the period (T) shown in FIG.
The clock pulse signal CLK output from 1 is counted by the counter 61. The count value Ni is a rotation angle or a rotation speed during the period (T).

Here, the timing correction signal generation / output circuit 81 includes a rotating drum 1 set in the reference value setting unit 71.
The reference value Ns corresponding to the above reference rotation speed is compared with the count value Ni output from the rotation angle detection circuit 50P (51, 61), and the nozzle heads 11C, 11M,
A timing correction signal Sc for correcting the print drive timings of 11Y and 11K is formed so as to be generated and output.

Thus, a change in the rotation speed of the rotary drum 1 is detected in advance using the rotation angle detection device 20P including the detection means (31) and the rotation angle detection circuit 50P,
By controlling the printing drive timing of the nozzle heads 11C, 11M, 11Y, and 11K for each color, the change in the rotation speed of the rotary drum 1 can be corrected, so that high-quality printing can be performed while increasing the printing speed.

[0015]

By the way, the scale disk 21, the detecting means (31) and the rotation angle detecting circuit 50
No matter how carefully processing, adjustment, and setting of component accuracy, assembling accuracy, and electronic and time settings of the P, and further, the timing correction signal generation output circuit 81 and the like are performed within an allowable range, print image quality deteriorates (for example, (A dot shift in the sub-scanning direction).

However, this does not mean that it occurs in all printers in common. One of the causes is scale disk 2.
It is presumed that the eccentricity between 1 and the rotating shaft 2 is involved. For example, assuming that the output time length of the one-slit equivalent detection signal Sd output from the detector 31 when there is no eccentricity shown in FIG. 16 (the eccentricity ε = 0) is “T”, the eccentricity ε
Is larger, the apparent rotation speed when the slit passes through the detector 31 becomes higher.
As shown in FIG. 6, the smaller the eccentricity ε, the lower the apparent rotation speed when the slit passes through the detector 31, so that the output time length Tb becomes longer as shown in FIG.

In other words, in FIG. 15, even if the rotation speed of the rotating shaft 2 is constant, the output time length T of the detection signal Sd varies, so that the count number Ni increases and decreases. It seems that the detection signal Sd (Ni) contains a detection error caused by the eccentricity (ε) of the scale disk 21 with respect to the rotation shaft 2.

However, it is not an exaggeration to say that it is impossible to make the amount of eccentricity ε zero when the scale disk 21 is mounted on the rotating shaft 2 from the technical and assembling time and cost viewpoints.

A first object of the present invention is to provide a rotation angle detecting device capable of greatly reducing a detection error caused by eccentricity of a scale disk. It is a second object of the present invention to provide an ink jet printer which improves printing accuracy by using a rotation angle detecting device capable of greatly reducing a detection error caused by eccentricity of a scale disk.

[0020]

According to the first aspect of the present invention, there is provided a scale disk provided with a large number of scales and mounted on a rotating shaft, a detecting means including a detector arranged opposite to the scale disk, A rotation angle detection circuit capable of detecting a rotation angle of the rotation axis by performing predetermined processing on a detection signal output from the detection means, wherein the detection means sets a 180-degree position around the rotation axis. The rotation angle detection circuit is formed by two detectors disposed to face the scale disk so as to be shifted, and the rotation angle detection circuit uses the two detection signals output from the two detectors to decenter the scale disk with respect to the rotation axis. This is a rotation angle detection device formed so as to be able to generate and output one new corrected detection signal in which the time error of each detection signal caused by the amount is corrected.

In this invention, when the rotating shaft to which the scale disk is connected is rotated, the detection signals are respectively sent from the two detectors disposed opposite to the scale disk by shifting the position by 180 degrees about the rotational axis. Is output. When the scale disk is connected to the rotary shaft without eccentricity, the relative rotation speed between each detector and the scale disk is equal, and the detection signals output from each detector have the same characteristics.

However, when there is eccentricity between the scale disk and the rotating shaft, the relative rotation speed between each detector and the scale disk changes. The degree of change is proportional to the amount of eccentricity.

However, since each of the detectors is opposed to the scale disk in a state of being shifted by 180 degrees about the rotation center of the rotating shaft, the eccentricity included in the detection signal output from each detector. The detection error due to the quantity has a sign inversion relationship and appears periodically.

Here, the rotation angle detection circuit uses (for example, adds / divides) two detection signals output from the two detectors to detect each detection signal caused by the amount of eccentricity of the scale disk with respect to the rotation axis. And generates and outputs one new corrected detection signal in which the time error of the correction is corrected. That is, it is possible to output the corrected detection signal after the errors included in the respective detection signals are canceled out each other.

Therefore, the detection error caused by the eccentricity of the scale disk can be greatly reduced. In addition, the cost of the two detectors is reduced as compared with the cost of a single scale disk and a detector capable of generating and outputting the same detection signal as when the error is corrected. Is easy. Furthermore, the connection of the rotating shaft of the scale disk can be greatly simplified.

According to a second aspect of the present invention, the rotation angle detection circuit adds the value of each of the detection signals output from each of the detectors and divides the added value by two to calculate the average value. This is a rotation angle detection device formed so as to be able to output as a value of a post-detection signal.

According to the present invention, the rotation angle detecting circuit includes:
The values of the respective detection signals output from the respective detectors arranged with a phase shift of 80 degrees are added. For example, the output time length of each detection signal is added as a count value of the number of reference pulse signals. Then, the average value (count value) obtained by dividing the added value by 2 is output as the value of the corrected detection signal. Therefore, in addition to providing the same operation and effect as the case of the first aspect of the present invention, the rotation angle detection circuit can be realized at low cost without excessively modifying and simply adding a simple circuit. it can.

According to a third aspect of the present invention, the detecting means is formed of a plurality of sets each including two detectors whose positions are shifted by 180 degrees, and the rotation angle detecting circuit is configured to detect the rotation angle from each of the detectors of each set. Adding the value of each of the output detection signals and dividing the added value by 2 to obtain an average value of each of the pair of corrected detection signals, and adding the value of each of the pair of corrected detection signals; The rotation angle detection device is formed so that an average value obtained by dividing the added value by the number of sets is output as the value of the corrected detection signal.

In this invention, when the rotating shaft is rotated,
A plurality of sets of detecting means, each of which includes two detectors that are displaced by 180 degrees, perform a detecting operation. Then, the rotation angle detection circuit adds the values of the respective detection signals output from the respective detectors of each group, and divides the added value by 2 to obtain an average value of the corrected detection signals of each group. At the same time, the values of the respective post-correction detection signals are added, and the average value obtained by dividing the added value by the number of pairs is output as the value of the post-correction detection signal.

Therefore, the same operation and effect as those of the second aspect of the invention can be obtained, and
Compared to the case of the detection means having one detector as one set, the effect of reducing the detection error due to the eccentricity can be improved by the number of sets.

Further, the invention according to claim 4 includes a rotating drum which rotates in one direction about a rotating shaft, and a plurality of ink jet nozzles which are arranged in the longitudinal direction of the rotating drum and which is opposed to the rotating drum. The rotation angle detection device according to claim 2 or 3, wherein the rotation angle detection device according to claim 2 or 3 is formed so as to be able to print by driving the nozzle head on a rotating print medium wound around a rotating drum. An ink jet printer having a nozzle head formed so as to be able to control print drive timing using a corrected detection signal generated and output from the rotation angle detection circuit.

According to this invention, the print drive timing of the nozzle head that includes a number of ink jet nozzles arranged in the longitudinal direction of the rotating drum that rotates in one direction about the rotation axis and that is opposed to the rotating drum is Is controlled using the corrected detection signal generated and output from the rotation angle detection circuit. The nozzle head driven at the controlled printing drive timing prints while discharging ink onto the rotating print medium wound around the rotating drum.

Accordingly, high-precision and high-speed printing can be performed while eliminating the detection error caused by the eccentricity of the scale disk.

Further, the invention of claim 5 is an ink jet printer wherein the nozzle heads are formed from nozzle heads for respective colors which are displaced in the rotation direction of the rotary drum.

In this invention, since the nozzle heads are composed of the nozzle heads for the respective colors that are displaced in the rotation direction of the rotary drum, color printing can be performed. Therefore, in addition to providing the same operation and effect as the case of the invention of claim 4, high-quality color printing can be performed regardless of the number of nozzle heads for each color that are displaced in the rotation direction of the rotary drum. Can be performed.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) The present rotation angle detecting device 20 is shown in FIGS.
As shown in FIG.
2 which is arranged opposite to the scale disk 21 by being shifted by 0 degrees
The rotation angle detection circuit 50 is formed of the two detectors 31A and 31B, and uses the two detection signals Sda and Sdb output from the two detectors 31A and 31B to calculate the eccentricity ε of the scale disk 21 with respect to the rotation shaft 2. A new corrected detection signal (Nc) obtained by correcting a time error between the respective detection signals Sda and Sdb due to the correction is generated and output.

The basic configuration and functions are the same as those of the conventional example (FIG. 1).
3 to 15), a scale disk 21 provided with a large number of scales and attached to the rotary shaft 2 and a detector 31 (31A, 3A) disposed opposite to the scale disk 21.
1B), and a rotation angle detection circuit 50 capable of detecting the rotation angle of the rotary shaft 2 by performing predetermined processing on the detection signal Sd (Sda, Sdb) output from the detection means.

In this embodiment, the rotation angle detecting device 20
Are the oscillator 51, the counter 61 (61A, 61B),
The circuit includes a corrected detection signal generation / output circuit 65 (adder 66 and divider 67), a reference value setter 71, and a timing correction signal generation / output circuit 81.

The present rotation angle detecting device is also used to control (correct) the printing drive timing of each nozzle head 11C, 11M, 11Y, 11K of the ink jet printer similar to the case of the previous proposal (FIG. 13). Installed as possible.

That is, as shown in FIG. 2, the color ink-jet printer has nozzle heads 11C, 11M, 11Y, 11Y each having a plurality of ink-jet nozzles integrated into a nozzle head unit 10.
K (see FIG. 14) is formed so as to be able to print on the print medium (P) while supplying the respective color inks and discharging the ink from the selected inkjet nozzle. For example, full-color printing on A4 paper at a high speed of 20 PPM is possible.

More specifically, the color ink jet printer is formed of an image processing section and an engine section, and transmits print data transmitted from an external computer via a data communication line (network, eg, LAN) to a print command. An inkjet printing system for performing printing processing has been constructed.

The image processing unit includes a CPU, a ROM, a RAM,
The operation of the printer as a whole, including an operation panel, a display unit, an interface, an input / output port, and a clock circuit, is controlled by an appropriate amount in a timely manner, such as outputting print data to an engine unit while converting print data into bitmap data depending on the model.

The engine section includes the nozzle heads 11C and 1C.
In addition to 1M, 11Y and 11K, an ink supply means having an ink tank and the like, a rotating drum 1 capable of winding and holding a print medium (P) around an outer peripheral surface and rotatable at a set rotational speed (for example, 120 RPM) by a rotating mechanism. It is provided with other mechanisms including a paper feeding means, a feeding means, a discharging means, etc., and is formed to be capable of color printing and monochrome printing.

When each of the head drivers (print drive timing control means) detects the print start position P0 of the print medium (P) at the time (print reference position detection time) t0 by the present rotation angle detection device (20, 50). From the nozzle heads 11C, 11M, 11Y, 11
Nozzles for each color at times tc, tm, ty, and tk with time differences T0c, Tcm, Tmy, and Tyk corresponding to the respective arrangement positions Pc, Pm, Py, and Pk in the R direction of K. Heads 11C, 11M, 11Y,
Each of 11K is basically set to be drivable.

Specifically, in this embodiment, the timing of the other nozzle heads 11M, 11Y and 11K is determined based on the arrangement position Pc of the cyan nozzle head 11C.

Setting change means (keys on operation panel)
The printing drive timing is set to the printing reference position detection time point t0.
The setting can be changed earlier or later that can correct the positional deviation of the rotary body 1 of each nozzle head in the rotation (R) direction with reference to the reference.

The scale disk 21 shown in FIG. 2 has a number of scales (optical slits) and is attached to the rotating shaft 2 of the rotating drum 1 so as to be able to rotate synchronously.

When the detecting means detects the rotation
2 which is arranged opposite to the scale disk 21 with the position shifted
The rotation angle detection circuit 50 is formed from the two detectors 31A and 31B, and the rotation angle detection circuit 50 uses the two detection signals Sia and Sib output from the two detectors 31A and 31B to calculate the eccentricity ε of the scale disk 21 with respect to the rotation shaft 2. The time error of each detection signal Sia, Sib (Nia, Nib) (△
T) is formed so as to be able to generate and output one new corrected detection signal Nc obtained by correcting T).

The rotation angle detection circuit 50 includes an oscillator 51, counters 61A and 61B, and a corrected detection signal generation / output circuit 6.
5 (adder 66 and divider 67), and are formed so as to be output as the value Nc of the corrected detection signal.

That is, in FIG. 1, each detector 31
During the output periods Ta and Tb (see FIG. 16) of the detection signals Sia and Sib output from A and 31B, each counter 6
1A and 61B count the clock pulse signal CLK output from the oscillator 51 and count values (Nia, N
ib). Each count value (Nia, Nib) is
The rotation speed of the rotation shaft 2 (the rotation angle during the output periods Ta and Tb).

Thereafter, the adder 66 adds each count value (Nia, Nib), and the divider 67 adds the count value N.
iab (= Nia + Nib) divided by 2 to give an average value (N
c) is calculated. That is, the corrected detection signal generation and output circuit 65 generates and outputs a corrected detection signal (value Nc).

Then, the timing correction signal generation / output circuit 81 generates a print drive timing correction signal Sc and outputs it to the print drive timing control means on the printer side.

According to the embodiment having such a configuration, assuming that the amount of eccentricity ε is the same as in the case of the conventional example (FIGS. 13 to 15), the detection error caused by this eccentricity is compared with the case of the conventional example. It can be reduced to 1/20.

That is, in FIG. 3, when the rotation center of the scale disk 21 is displaced from the axis Z of the rotation shaft 2 by the amount of eccentricity ε, the rotation radius “R” of the scale (slit) and the slit When the center is inclined by an angle “θ” with respect to the horizontal axis X, the relationship with the radius of curvature r with one detector 31 is expressed by [Equation 1], and the radius of curvature r is expressed by [Equation 2]. Is required.

[0055]

(Equation 1)

[0056]

(Equation 2)

Here, from the cosine theorem in which the angle between the direction of the rotation axis rotation speed (ω) and the direction of the rotation speed (Ω) of the slit is “α”, [Equation 3] holds. And [Equation 3]
Substituting the radius of curvature “r” obtained by [Equation 2] into [Equation 2] gives [Equation 4].

[0058]

(Equation 3)

[0059]

(Equation 4)

Here, the variation rate “λ” is defined as λ = Ω / ω, and “r” of [Equation 2] and “cos (α)” of [Equation 4] are substituted into [Equation 5]. , [Equation 6].

[0061]

(Equation 5)

[0062]

(Equation 6)

Thus, the vertical axis Y of the detector 31 in FIG.
In the direction, the position R from the axis Z is 28.03 mm, and the detection range of the detector 31 in the vertical axis Y direction is 1.8 m.
m, the outer position R1 is (28.03 + 0.9)
mm and the inner position R2 is (28.03-0.9) m
m. Here, the amount of eccentricity ε is set to the reference position R (28.03
mm) is 1% (0.2803 mm).

Then, theoretically, 360 degrees (θn = 0 to
360), but for convenience and subdivision evaluation, n =
.., 720 and θn = n · 1 · deg, the position R1 is substituted into [Equation 6], and λ1 is obtained from [Equation 7].
When n is obtained, it becomes as shown in FIG. Also,
When λ2n is obtained from [Equation 8] by substituting the position R2 into [Equation 6], the result is as shown in FIG.

[0065]

(Equation 7)

[0066]

(Equation 8)

FIG. 5 is a graph in which the values λ1n and λ2n of FIGS. 4A and 4B thus obtained are combined with n. That is, the amount of eccentricity ε (= 0.2803 m
m), the variation rate λ1n when the slit projects outward due to the eccentricity and the variation rate λ2n when the slit enters the inside.
Then, as shown in FIG. 5 (converted to n = 360), the phase is shifted by 180 degrees, and each value for each n is shown in FIG.
Differences as shown in (A) and (B) occur. This difference (detection error) appears periodically.

Here, N = 0, 1, 2,..., 54
0, and the value “λ1” shifted by 180 degrees in [Equation 9].
N ”and the added value of the value“ λ2 (N + 180) ”to“ 2 ”
The value νN divided by is shown in FIG. 6 and is represented by a graph as shown in FIG. 7 (converted to N = 360).

[0069]

(Equation 9)

Here, the values λ1n, λ2n shown in FIG.
And the two detectors 3 that are 180 degrees out of phase
By comparing the value νN shown in FIG. 7 where 1A and 31B are used and the value when there is no eccentricity is “1”, the detection error can be reduced to about 1/20.

That is, the scale disk 21 whose slit (scale) is guaranteed with a radius of (28.03 ± 0.9 mm) has an eccentricity of 1% (0.2803 m
m) and two detectors 31
The positions R1 and R2 of A and 31B are (28.03 + 0.9
mm) and (28.03-0.9 mm), the detection error due to eccentricity could be reduced to about 0.05%.

Therefore, the colors C, M, and C shown in FIG.
The color shift δ based on the nozzle head 11C when printing in the order of Y and K is represented by [Equation 10], [Equation 11],
[Equation 12], and each value δCMN, δCYN, δCKN
Is as shown in FIGS. 8 (A), 8 (B), and 8 (C), and becomes a graph as shown in FIG.

[0073]

(Equation 10)

[0074]

[Equation 11]

[0075]

(Equation 12)

Thus, the color shift δf after correction using the detectors 31A and 31B is represented by [Equation 13], [Equation 14], and [Equation 15] as F = 0, 1, 2,..., 360. I do. Each value δfCMF, δfCYF, δfCKF is shown in FIG.
0 (A), (B), and (C), and the graph is as shown in FIG. It is understood that the color misregistration can be greatly improved as compared with the case of FIG.

[0077]

(Equation 13)

[0078]

[Equation 14]

[0079]

(Equation 15)

Thus, the printing drive of the nozzle head 11 including a number of ink jet nozzles arranged in the longitudinal direction of the rotating drum 1 rotating in one direction about the rotating shaft 2 and opposed to the rotating drum 1 The timing is based on the corrected detection signal N generated and output from the rotation angle detection circuit 50.
It is controlled using c (Sc). The nozzle head 11 driven at the controlled print drive timing prints while discharging ink onto the rotating print medium wound around the rotary drum 1. Therefore, high-precision and high-speed printing can be performed while eliminating the detection error caused by the eccentricity of the scale disk 21.

Further, the nozzle heads 11 for the respective colors in which the nozzle heads 11 are displaced in the rotation direction of the rotary drum 1 are arranged.
Since this is an inkjet printer formed of 1C, 11M, 11Y, and 11K, high-quality color printing can be performed.

(Second Embodiment) In the second embodiment, as shown in FIG. 12, a scale disk 21 is provided with a gear-shaped scale on the peripheral surface of a disk 25. Others are the same as in the first embodiment. That is, the scale disk is not limited to that of the first embodiment.

(Third Embodiment) The third embodiment has the same basic structure and functions as those of the first embodiment, but further increases the number of detectors 31 to make the slit The detection error due to the eccentricity of the disk 21 can be further reduced.

That is, the detecting means is formed from a plurality of (for example, three) sets each including two detectors 31A and 31B which are displaced by 180 degrees, and the rotation angle detecting circuit 50 controls each of the detectors ( 31A, 31B), add the value (Nia, Nib) of each detection signal (Sda, sdb), and divide the added value (Niab) by 2 to obtain the average value of each group-corrected detection signal. And an average value obtained by adding the values (Nc1, Nc2, Nc3) of the respective group-corrected detection signals and dividing the added value by the number of sets (3) is output as the value of the corrected detection signal (Nc). It is formed to be possible.

That is, referring to FIG.
A, 31B, three sets of counters 61A, 61B and a corrected detection signal generation / output circuit 65 (66, 67) are provided, and an adder similar to the adder 66 and a divider similar to the divider 67 are provided. And an arithmetic unit.

Thus, if one set of the first embodiment in which the detection error reduction rate is 1/20 is set to three sets, one set is obtained.
/ 60 can be improved. With two sets, it can be reduced to 1/40.

[0087]

According to the first aspect of the present invention, the detecting means is formed by two detectors which are disposed opposite to the scale disk by shifting the position by 180 degrees about the rotation axis, and the rotation angle detection circuit is provided with each of the detectors. A rotation angle detection device formed so as to generate and output one new corrected detection signal in which a time error caused by the amount of eccentricity of the scale disk with respect to the rotation axis is corrected using each detection signal output from the detector. Therefore, the detection error caused by the eccentricity of the scale disk can be greatly reduced. In addition, the cost of the two detectors is reduced as compared with the cost of a single scale disk and a detector capable of generating and outputting the same detection signal as when the error is corrected. Is easy. further,
Connection of the rotating shaft of the scale disk can be greatly simplified.

According to the second aspect of the present invention, the rotation angle detection circuit adds the values of the respective detection signals output from the respective detectors and divides the added value by two to obtain an average value obtained by correcting the corrected detection signal. Since it is formed so that it can be output as the value of
In addition to the effect similar to that of the invention, the rotation angle detecting circuit can be realized at low cost without excessively modifying and simply adding a simple circuit.

Further, according to the third aspect of the present invention, the detecting means is formed of a plurality of sets each including two detectors which are displaced by 180 degrees, and the rotation angle detecting circuit is formed by each set of the respective detectors. The values of the output detection signals are added, and the average value obtained by dividing the added value by 2 is used as the value of each pair of corrected detection signals, and the value of each pair of corrected detection signals is added. 3. An average value obtained by dividing the addition value by the number of sets is formed so as to be output as the value of the corrected detection signal.
In addition to the effect similar to that of the invention, the effect of reducing the detection error caused by the eccentricity can be multiplied by the number of sets as compared with the case of the detecting means having two detectors as one set. It can be improved considerably.

According to a fourth aspect of the present invention, the rotary drum includes a rotary drum that rotates in one direction about a rotary shaft, and a number of ink jet nozzles arranged in the longitudinal direction of the rotary drum and faces the rotary drum. 4. The rotation angle detecting device according to claim 2, further comprising a nozzle head disposed therein, wherein the nozzle head is formed so as to be printable by driving the nozzle head to print on a rotating print medium wound around a rotating drum. Since the inkjet printer is provided with a device and the nozzle head is formed so as to be able to control the printing drive timing by using the corrected detection signal generated and output from the rotation angle detection circuit, detection caused by the eccentricity of the scale disk High-precision, high-speed printing can be performed while eliminating errors.

Further, according to the fifth aspect of the present invention, the nozzle heads are formed of the nozzle heads for each color which are displaced in the rotation direction of the rotary drum. In addition to achieving the same effect, high-quality color printing can be performed regardless of the number of nozzle heads for each color that are displaced in the rotation direction of the rotary drum.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is also an external perspective view.

FIG. 3 is also a diagram for explaining an eccentric operation.

FIG. 4 is a diagram for explaining a calculated variation rate before correction.

FIG. 5 is a graph showing the calculated variation rate before correction.

FIG. 6 is a diagram for explaining a calculated variation rate after correction.

FIG. 7 is a graph showing the calculated fluctuation rate after correction.

FIG. 8 is a diagram for explaining a calculated variation rate before correction in the case of color printing.

FIG. 9 is a graph showing the calculated change rate before correction in the case of color printing.

FIG. 10 is a diagram for explaining a calculated variation after correction in the case of color printing.

FIG. 11 is a graph showing the calculated fluctuation rate after correction in the case of color printing.

FIG. 12 is an external perspective view showing a second embodiment of the present invention.

FIG. 13 is an external perspective view for explaining a previously proposed printer and a conventional rotation angle detection device.

FIG. 14 is a view for explaining each nozzle head and an example of a printing mode.

FIG. 15 is a block diagram for explaining a conventional rotation angle detection device.

FIG. 16 is a diagram for explaining a problem of a conventional rotation angle detection device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotating drum 2 rotating shaft 10 nozzle head unit 11C, 11M, 11Y, 11K nozzle head 20 rotation angle detector 21 scale disk 31A, 31B detector 50 rotation angle detection circuit 51 oscillator 61A, 61B counter 65 detection signal generation output after correction Circuit 66 Adder 67 Divider 71 Reference value setting unit 81 Timing correction signal generation / output circuit ε Eccentricity Sda, Sdb detection signal CLK Clock pulse signal Nia, Nib Count value Niab Addition value Nc Correction detection signal Ns Reference value Sc Print drive timing correction signal P paper (print medium)

Claims (5)

[Claims] 1. A scale disk provided with a large number of scales and mounted on a rotating shaft, a detecting means including a detector disposed opposite to the scale disk, and a detection signal output from the detecting means. A rotation angle detection circuit capable of detecting the rotation angle of the rotation axis by processing, wherein the detection means is disposed opposite to the scale disk by shifting the position by 180 degrees about the rotation axis. A temporal error of each detection signal formed by two detectors, wherein the rotation angle detection circuit uses two detection signals output from the two detectors and is caused by an eccentric amount of the scale disk with respect to the rotation axis. A rotation angle detection device formed so as to be able to generate and output one new post-correction detection signal that has been corrected. 2. The rotation angle detection circuit adds the values of the respective detection signals output from the respective detectors and outputs an average value obtained by dividing the added value by 2 as a value of the corrected detection signal. The rotation angle detection device according to claim 1, wherein the rotation angle detection device is formed so as to be capable of being formed. 3. The detection means is formed of a plurality of sets each including two detectors whose positions are shifted by 180 degrees, and each of the detection signals output from each of the sets of the detectors by the rotation angle detection circuit. , And the average value obtained by dividing the added value by 2 is used as the value of each group-corrected detection signal, the value of each group-corrected detection signal is added, and the added value is represented by the number of sets. 3. The rotation angle detecting device according to claim 2, wherein the divided average value is formed so as to be output as a value of the corrected detection signal. 4. A rotary drum rotating in one direction around a rotary shaft, and a nozzle head including a number of ink jet nozzles arranged in the longitudinal direction of the rotary drum and opposed to the rotary drum. And a rotation angle detection device according to claim 2 or 3, wherein the nozzle head is formed so as to be capable of printing by driving a nozzle head on a rotating print medium wound around a rotating drum. An inkjet printer configured to control print drive timing using a corrected detection signal generated and output from the rotation angle detection circuit. 5. An ink jet printer according to claim 4, wherein said nozzle head is formed of nozzle heads for respective colors which are displaced in the rotation direction of said rotary drum.