JP4633607B2 - Rotation drive - Google Patents

Description

  The present invention relates to a rotation driving device that rotationally drives a rotating body including a photosensitive member of an image forming apparatus including a facsimile machine, a copying machine, and a printer.

Conventionally, an encoder provided with a scale for detecting the number of rotations of a rotating body (rotation detection scale) and an eccentricity detection scale (eccentricity detection scale), and a rotation for detecting transmitted light or reflected light of light irradiated on the rotation detection scale A detector for detecting the number of light beams, and a light detector for detecting eccentricity for detecting transmitted light or reflected light of the light irradiated on the eccentricity detection scale, and using the detection values of the two light detectors. There has been a rotary drive device (see, for example, Patent Document 1) that detects the rotational speed and the amount of eccentricity of a rotating body.
JP 2003-130688 A

However, the conventional rotary drive device requires two light source units and a photodetector in order to detect the rotation detection scale and the eccentricity detection scale of the encoder, and the structure of the device becomes large and complicated. was there.
The present invention has been made in view of the above points, and an object thereof is to simplify the configuration for detecting the rotational speed of a rotating body.

In order to achieve the above object, the present invention provides the following rotary drive device.
(1) A rotating body, a detection means connected to the rotating body via a rotation shaft, and having a plurality of openings arranged annularly around the rotation shaft, the rotation body, and the detection means And a motor for transmitting rotational force to the rotating body and the detected means via the rotating shaft and simultaneously driving the rotating body and the detected means to rotate, and the detected means Detecting means for detecting each of the openings, and control means for controlling the rotational speed of the motor based on the detection result of each opening by the detecting means, and a part of each opening is detected Rotation drive device comprising a combination of a portion in which the width of the opening portion is gradually changed in the radial direction of the means and a portion in which the width of the opening portion is formed in a constant width in the radial direction of the detected means .

(2) In the rotational drive device of (1), there is provided means for detecting the amount of eccentricity of the detected means relative to the rotation shaft of the rotating body based on the detection result of each opening by the detecting means. Rotation drive device.
(3) The rotation drive device according to (2), wherein a correction means for correcting the amount of mounting eccentricity is provided.

  The rotary drive device according to the present invention can simplify the configuration for detecting the rotational speed of the rotating body.

Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
〔Example〕
FIG. 1 is a block diagram showing a functional configuration of a rotary drive device according to an embodiment of the present invention.
This rotational driving device is a device that is mounted on an image forming apparatus including, for example, a facsimile machine, a copying machine, and a printer, and rotationally drives a cylindrical rotating body 1 including a photosensitive drum.
The rotating shaft 3 of the motor 2 is connected to the rotation center of the rotating body 1, and the rotating shaft 3 is provided with a disk-shaped encoder 4 between the rotating body 1 and the motor 2. Is transmitted to the rotating body 1 and the encoder 4 via the rotating shaft 3 to simultaneously rotate the rotating body 1 and the encoder 4 at the same speed.

On the encoder 4, a scale 5 as a plurality of openings (slit shape) is annularly arranged around the rotating shaft 3, and the laser light emitting diode is disposed so as to face each other with the scale 5 of the encoder 4 interposed therebetween. A detector 6 is provided that includes a light source including a sensor and a sensor. When the encoder 4 rotates, the scale 5 on the encoder 4 is irradiated with light from the light source and transmitted through the scale 5. A detection signal when the light is detected by the sensor is output to the control unit 7.
The control unit 7 rotates the motor 2 and controls the rotation speed of the rotating body 1 by adjusting the rotation speed of the motor 2 based on the detection signal from the detecting unit 6 while the rotating body 1 is rotating. In this case, the function unit is realized by a microcomputer including a CPU that detects the amount of eccentricity of the encoder 4 and corrects the detected amount of eccentricity of the encoder 4 to rotate the rotating body 1 at a predetermined rotational speed. is there.

FIG. 2 is an explanatory diagram of the shape of each scale 5 on the encoder 4 shown in FIG.
Each scale 5 of the encoder 4 is annularly arranged with respect to the center.
There are two positions, an arbitrary position on the encoder 4 and a position shifted by 180 ° from the position, a portion in which the width of the opening is gradually changed in the radial direction of the encoder 4, and a radial direction of the encoder 4. And a portion in which the width of the opening has a constant width.
As shown in the figure, the scales 5 a and 5 b are provided at positions facing each other across the center of the encoder 4, and the opening length (opening width) increases as the distance from the center of the encoder 4 increases. An opening A, a rectangular opening B whose opening length is constant regardless of the distance from the center, and a triangular opening C whose opening length decreases as the distance from the center increases are arranged next to each other. ing.
In this embodiment, the shape of the openings A and C is described as being a right triangle, but may be an isosceles triangle or a trapezoid.

FIG. 3 is a waveform diagram showing an example of an output waveform of a detection signal of each scale 5 of the encoder 4 by the detection unit 6 shown in FIG.
In the figure, a, b, and c are the pulse widths (unit: time) of the openings A, B, and C, respectively.
Regarding the output waveform when the detection unit 6 detects the scales 5a and 5b, the output waveform when the opening B is detected is constant regardless of the sensor detection point when detecting any part in the longitudinal direction of the opening B. However, for the output waveform when the openings A and C are detected, the pulse width varies depending on the relative distance between the center of the encoder 4 and the sensor detection point. That is, if the relative distance between the center of the encoder 4 and the sensor detection point is long, a> c, and conversely if it is short, a <c.

FIG. 4 shows the relationship between the rotation axis center O that is the center of the rotation shaft 3 and the encoder 4 when the eccentricity of the encoder 4 shown in FIG. 1 occurs (when the center of the rotation shaft 3 and the center of the encoder 4 are shifted). It is the schematic showing the positional relationship of encoder center O 'which is a center, and sensor detection point P.
Here, for example, in order to detect the actual rotation speed of the rotating body 1, it is assumed that “the time for which the rotating body 1 rotates 180 ° needs to be measured”.
In this case, in the conventional method, from the pulse width detected from the scale 5 of any encoder 4, the scale 5 at the position where the encoder 4 is rotated by 180 °, for example, the scale at the position of the point X in FIG. The time until the pulse width obtained when passing through the detection point P is measured. However, when the rotation axis center O and the encoder center O ′ are at the positions shown in FIG. 4, the position of the scale 5 of the encoder 4 when the rotating body 1 is actually rotated 180 ° is the Y point. When the point data is measured, an accurate rotation speed cannot be measured, and the influence of the eccentricity of the encoder 4 is affected.

Next, the encoder attachment eccentricity detection process will be described.
The relationship between the opening lengths of the openings A and C and the distance from the encoder center O ′ is stored in advance in a storage unit (not shown) including the ROM of the control unit 7.
First, a deviation angle (θ in FIG. 4) between the rotation axis center O and the encoder center O ′ shown in FIG.

However, at this time, it is unclear whether the encoder center O ′ is eccentric to the left or right with respect to the rotation axis center O.
Therefore, in order to determine the direction of the encoder mounting eccentricity, arithmetic processing based on the following equations 2 to 4 is executed.

Based on the results of the arithmetic processing of the above formulas 2 to 4, the following (1) and (2) can be determined for the direction of encoder mounting eccentricity.
(1) When l × (a / b)> l × (c / b), if l × {1− (a / b)}> l × (c / b), the encoder center O ′ rotates. It is eccentric to the right with respect to the axis center O. If l × {1− (a / b)} <l × (c / b), the encoder center O ′ is eccentric to the left with respect to the rotation axis center O.
(2) In the case of l × (a / b) <l × (c / b), if l × {1− (a / b)}> l × (c / b), the encoder center O ′ rotates. It is eccentric to the left with respect to the axis center O. If l × {1− (a / b)} <l × (c / b), the encoder center O ′ is eccentric to the right with respect to the rotation axis center O.

Next, using the relationship between the opening lengths of the openings A and C stored in the control unit 7 and the distance from the encoder center O ′, the pulse width a of the opening A or the pulse width b of the opening C is used. Thus, the distance S1 between the encoder center O ′ and the sensor detection point P is calculated.
Further, the distance S2 between the point X and the encoder center O ′ is determined from the pulse width a ′ of the opening A or the pulse width b ′ of the opening C at the point where the encoder 4 is rotated 180 ° (point X in FIG. 4). calculate.
Then, calculation processing based on the following equation 5 is performed based on the values of the distances S1 and S2, and the distance r between the sensor detection point P and the rotation axis center O, that is, the amount of eccentricity of the encoder is obtained.

Next, a control process for correcting the mounting eccentricity obtained by the above process will be described.
First, as shown in FIG. 4, the Y point is calculated by the arithmetic processing based on the following equation 6 from the distance S1 between the encoder center O ′ and the sensor detection point P and the distance r between the sensor detection point P and the rotation axis center O. The distance m of the encoder center O ′ is obtained.

  Further, by using the above values including the distance m between the Y point and the encoder center O ′, an angle φ formed by the X point and the Y point with respect to the encoder center O ′ is obtained by arithmetic processing based on the following equation (7).

Here, since the number of scales of one rotation of the encoder 4 is determined by the shape of the encoder 4, the number of scales between the X point and the Y point is formed by the X point and the Y point with respect to the encoder center O ′. If the encoder center O ′ is decentered to the right with respect to the rotation axis center O, the number of scales between the X point and the Y point can be determined from the Y point scale to the left. to correct.
Further, when the encoder center O ′ is eccentric to the left with respect to the rotation axis center O, correction is made from the scale of the Y point by the number of scales between the X point and the Y point to the right.

  In this way, this rotary drive device can provide a difference between the pulse width detected from the scale having a structure in which the opening length changes in the radial direction of the encoder and the pulse width detected from the conventional scale having a constant opening length. By utilizing this, the amount of eccentricity of the encoder can be detected and the motor's rotational speed can be adjusted by performing correction control of the amount of eccentricity of the encoder, so the configuration for detecting the rotational speed of the rotating body is simplified. In addition, the rotational speed of the rotating body can be adjusted correctly even if the encoder is eccentric.

  The rotary drive device according to the present invention can also be applied to personal computers such as desktop personal computers and notebook personal computers.

It is a block diagram which shows the function structure of the rotational drive apparatus of the Example of this invention. It is explanatory drawing of the shape of each scale 5 on the encoder 4 shown in FIG. It is a wave form diagram which shows an example of the output waveform of the detection signal of each scale 5 of the encoder 4 by the detection part 6 shown in FIG. FIG. 2 is a schematic diagram showing a positional relationship among a rotation axis center O, an encoder center O ′, and a sensor detection point P when mounting eccentricity of the encoder 4 shown in FIG. 1 occurs.

Explanation of symbols

1: Rotating body 2: Motor 3: Rotating shaft 4: Encoder 5, 5a, 5b: Scale 6: Detection unit 7: Control unit

Claims (3)

  A rotating body, a detecting means connected to the rotating body via a rotating shaft, and having a plurality of openings disposed annularly around the rotating shaft; the rotating body, the detected means, and the rotating shaft; And a motor that transmits rotational force to the rotating body and the detected means via the rotating shaft to simultaneously drive the rotating body and the detected means to rotate, and each opening of the detected means Detection means for detecting a portion, and control means for controlling the rotation speed of the motor based on the detection result of each opening by the detection means, and a part of each opening is provided by the detected means. A portion formed by gradually changing the width of the opening in the radial direction and a portion formed by changing the width of the opening in the radial direction of the detection means are combined. Rotation drive device.   2. The rotation drive device according to claim 1, further comprising means for detecting an amount of eccentricity of the detected means with respect to a rotation shaft of the rotating body based on a detection result of each opening by the detecting means. Rotation drive device. 3. The rotation drive device according to claim 2, further comprising correction means for correcting the amount of eccentricity of attachment.

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