JP2006067242A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect step-out of a stepping motor with a very simple configuration. <P>SOLUTION: A mark m for detecting the rotational speed of a shading roller is formed outside paper passing area of the shading roller driven by the stepping motor, and the mark m for detecting a rotational speed is read to thereby detect the rotational speed of the shading roller and detect step-out of the stepping motor on the basis of a detection result of the rotational speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus that detects a step out of a stepping motor.

  In an image reading apparatus such as a scanner, a copying machine, or a facsimile machine, shading correction of a CCD (Charge Coupled Device) is performed before reading a document to suppress variations in each reading element.

  Recently, image reading apparatuses such as scanners, copiers, and facsimile machines equipped with an ADF (automatic document feeder) are provided with a CIS (Contact Image Sensor) for reading the back side of a document in an ADF document feeder. A method for simultaneously reading both sides of a document has been proposed.

The CIS shading correction is performed by setting the conveying roller facing the CIS to be white and also serving as a shading roller, and rotating the shading roller to capture shading correction data. (Patent Document 1)
The shading roller is driven by a motor, and in particular, a stepping motor is used. The rotation speed of this stepping motor is used in the pull-out region of the stepping motor due to the recent increase in reading speed. As a control method, the driving frequency of the stepping motor is gradually increased from the low frequency of the pull-in region at the start of driving. In general, slow-up control for reaching a target frequency is used.

  Therefore, if the stepping motor steps out and stops rotating for some reason while the shading roller is rotated and the shading correction data is acquired, normal correction data cannot be obtained.

Therefore, in order to detect whether this stepping motor step-out phenomenon has occurred, it has a current sensor that detects the chopping current of the stepping motor, and detects the step-out phenomenon by counting the number of choppings and comparing it with a reference value. Has been proposed. (Patent Document 2)
Japanese Patent Laid-Open No. 10-23253 JP 2003-237978 A

  However, in order to detect whether or not a stepping motor step-out phenomenon has occurred, a new current sensor, a chopping number counter, and the like are required, which is not practical due to problems such as cost.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image reading apparatus capable of detecting step-out at low cost.

    To achieve the above object, according to the present invention, in an image reading apparatus, a shading roller driven by a stepping motor, a mark for detecting a rotation speed of the shading roller outside a paper passing area of the shading roller, and the mark A rotation speed detection means for detecting the rotation speed of the shading roller by reading the motor, and a motor step-out detection means for detecting the step-out of the stepping motor based on the detection result of the rotation speed detection means. It is characterized by.

  With such a configuration, the rotation speed of the shading roller becomes an index of the rotation speed of the stepping motor, and a change in the rotation speed of the shading roller can be detected. That is, the same effect as that obtained when detecting the step-out of the stepping motor is obtained, and can be achieved with a very simple configuration.

  Further, it is preferable to perform an initial activation control operation of the stepping motor when a step-out of the stepping motor is detected.

  According to the present invention, since the stepping motor step-out is detected by detecting the rotation speed of the shading roller, step-out detection can be performed at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  Here, the overall configuration of the image forming apparatus 1 according to the embodiment of the present invention will be described with reference to FIG.

  The image forming apparatus includes an ADF (automatic document feeder) 2, a scanner unit 3, and a printing unit 4. The ADF 2 includes a back side reading unit 30 that reads the back side of the document, and is configured to read both sides of the document at the same time. The ADF 2 and the scanner unit 3 constitute an image reading device.

  The ADF 2 performs document movement type image reading, and includes a document tray 24 on which a document D is set, a paper feed roller 21 that picks up and feeds documents on the document tray 1 one by one, and a paper supply roller 21 A conveying unit 22 that conveys the document D sent out by the paper roller 21 to the front surface reading unit 23, a back surface reading unit 30 (described later) that reads the back surface of the document D, and a stepping that drives each roller of the back surface reading unit 30 A motor 29 is provided. The back side reading unit 30 also has a function of discharging a document to the paper discharge tray 25.

  Further, the outer cover 26 of the ADF 2 that covers the conveyance unit 22 can be opened and closed from a fulcrum 27, and when the document is jammed on the conveyance unit 22, the user can open the cover and remove the document (in the drawing). (Shown as a dotted line). Further, a safety switch 28 is provided to detect the opening of the cover so that the roller of the conveying unit malfunctions during the jam processing when the outer cover 26 is opened and the user is not in danger. The safety switch 28 cuts off the power supply of the ADF 2 as will be described later.

  The scanner unit 3 includes a light source, a reflection mirror, a lens, a CCD, and the like (none of which are shown) for reading the surface of the document D, and reads the surface of the document D conveyed to the surface reading unit 23. Moreover, the control part 40 mentioned later is provided.

  The printing unit 4 includes a cassette for storing transfer paper, a transfer paper transport unit, a photosensitive drum, an exposure unit, a charging unit, a developing unit, a printing unit including a transfer unit, and a fixing unit (all not shown). First, printing is performed on transfer paper from image data read by the image reading device.

  FIG. 2 is a cross-sectional view illustrating a schematic configuration of the back surface reading unit 30.

  The document D sent out from the document tray 24 and transported to the front surface reading unit 23 is transferred to the transport rollers 11, 12, the contact image sensor 300 that reads an image from the document D being transported, and the contact image sensor 300. There is provided a shading roller 13 which is disposed so as to guide the document D being conveyed at the image reading position from the back side (the side opposite to the image reading surface). Here, the contact image sensor 300 and the guide roller 13 extend over the entire width of the document D in a direction orthogonal to the conveyance direction of the document D (the depth direction of the paper surface in FIG. 2, hereinafter referred to as the document width direction). It is formed to stretch.

  The contact image sensor 300 includes a contact glass 304 in contact with the document D being conveyed, a lamp 303 that is a light emitting means for irradiating light on the reading surface of the document through the contact glass 304, and reflected light from the document. A condensing lens 302 such as a self-focus lens for condensing, and a CCD 301 that receives the collected light and performs photoelectric conversion, are unitized (integrated).

  Further, the shading roller 13 and the transport rollers 11 and 12 are driven by a stepping motor 29, and the shading roller 13 has a white surface color. A function as a reference document when performing shading correction of the CCD 301 before a document reading job is provided.

  The shading correction method is performed while the shading roller 13 is rotated, and a known technique is used for the method, and the description thereof is omitted here.

  Further, a rotation speed detection mark m that is read by the contact image sensor 300 is formed on the shading roller 13.

  FIG. 3 is a perspective view of the shading roller 13.

  The shading roller 13 has a circumferential direction on the surface of the shading roller 13 over the entire circumference in a region 32 outside the guide region 31 through which the document D being conveyed passes (region where the document does not pass). The rotation speed detection mark m is formed of a plurality of marks (in FIG. 3, a straight line extending in the axial direction of the shading roller 13) formed at equal intervals.

  The shading roller 13 is configured to be able to read an image in a wider area than the guide area 31 (document passage area), and the rotational speed detection mark m is used to read an image outside the guide area 31. It is formed in a possible area.

  The surface of the guide roller 3 has a white color, and the rotation speed detection mark m has a black color or a dark color (dark color) close thereto.

  Then, the image reading apparatus reads the rotation speed detection mark m by the contact image sensor 300 and detects the rotation speed of the shading roller 13 based on the read image of the rotation speed detection mark m. In addition, motor step-out detecting means for detecting step-out of the stepping motor 29 based on the detection result is provided.

  FIG. 4 is a block diagram showing a schematic configuration of a main part of the image reading apparatus including the control unit 40.

  The image reading apparatus includes a CPU 41 that executes various control processes in the image processing apparatus, a RAM 42 that constitutes a main memory area in which a control program executed by the CPU 41 is expanded, and a ROM 43 that stores the control program in advance. , A drive unit control circuit (not shown) for controlling the drive unit such as the paper feed roller 21 and the transport roller of the transport unit 22 and a display for displaying messages and inputting operations to the user. An operation unit (not shown), an image processing unit 44 that performs various image processing on an image read by the contact image sensor 300, and a shading roller based on the image of the rotation speed detection mark m of the shading roller 13 And a rotational speed detection unit 45 that detects the rotational speed of 13.

  In addition, a stepping motor 29 for driving the shading roller 13 and a motor driver 46 for controlling the driving of the stepping motor are provided. The rotation speed of the stepping motor is determined by the motor driving frequency of the stepping motor CLK from the control unit 40. The

  A 24V power source that is a driving power source for the stepping motor 29 is supplied from a 24V power source 48, and an output from the 24V power source 48 is supplied via the safety switch 28. Therefore, when the outer cover 26 of the ADF 2 that covers the transport unit 22 is closed, the contact of the safety switch 28 is closed and 24V power is supplied to the stepping motor 29. When the outer cover 26 of the ADF 2 covering the transport unit 22 is opened, the contact of the safety switch 28 is opened and the 24V power is not supplied to the stepping motor 29.

  On the other hand, the output from the 24V power supply 48 from the safety switch 28 is supplied to the stepping motor 29, converted to 5V by the voltage level conversion unit 47, and input to the control unit 40 as a cover open / close detection signal. The voltage level conversion unit 47 is obtained, for example, by simply dividing 24V to 5V by a resistor. The controller 40 can detect the open / close state of the outer cover 26 by detecting whether this signal is 5V or 0V.

  The image processing unit 44 is configured by a DSP (Digital Signal Processor) or the like, and performs well-known shading correction processing, MTF correction filter processing, or the like on document image data read from the document being conveyed by the contact image sensor 300. Correction processing is performed.

  The rotation speed detection unit 45 is configured by a DSP (Digital Signal Processor) or the like, and is based on the image of the rotation speed detection mark m of the shading roller 13 that is rotated by the contact image sensor 300. The rotation speed is detected (an example of rotation speed detection means).

  Next, a method for detecting the rotational speed of the shading roller 13 by the rotational speed detector 45 will be described.

  FIG. 5 is a trend graph showing an example of a change in image data (luminance) of the rotation speed detection mark m read while the shading roller 13 is rotating.

  In the image reading apparatus, the shading roller 13 having a function as a reference original is rotated in order to perform the shading correction of the CCD 301 when the power is turned on or before the original reading job. At this time, the number of rotations of the stepping motor is used in the pull-out region of the stepping motor. As a control method, the stepping motor drive frequency is changed stepwise from a low frequency in the pull-in region at the start of driving as the stepping motor initial start control operation. Slow-up control is used to rise to the target frequency.

  The initial activation control operation control is performed by the control unit 40, and the frequency of the slow-up control is stored in the ROM 43 in advance. When the frequency of the target rotation speed (steady rotation speed) is reached after the slow-up control, the rotation speed is maintained until the end of the rotation operation.

  As shown in FIG. 5, the image data of the area 32 (see FIG. 3) outside the guide area 31 during the rotation of the shading roller 13 has its value (luminance) every time the rotational speed detection mark m is read. Go down.

  Here, since a plurality of the rotational speed detection marks m are formed at equal intervals in the circumferential direction of the shading roller 13, the time during which the value of the image data in the outer region 32 becomes a low value (low luminance). The interval tw is inversely proportional to the rotational speed of the shading roller 13.

  Therefore, the rotation speed detection unit 45 (an example of rotation speed detection means) has a low time interval in which the image of the rotation speed detection mark m is read by the contact image sensor 300, that is, the value of the image data is low. The time interval tw is measured, and the rotational speed of the shading roller 13 during the rotation of the shading roller 13 is detected from the time interval tw.

Here, the time interval tw measures the time from the time when the value of the image data in the outer region 32 falls below or exceeds a predetermined threshold value Ds to the next simultaneous point. Measure with

  Based on the detection result of the rotation speed detection means, the control unit 40 detects the step out of the stepping motor (an example of the motor step out detection means). That is, when the detected rotational speed of the shading roller 13 deviates from a predetermined allowable speed range (previously stored in the ROM 43) (usually, when the speed is lower than the lower limit speed), It is determined that the stepping motor 29 that drives the shading roller 13 has stepped out, and in order to redo the shading correction of the CCD 301 from the beginning, the motor driver 46 sets the stepping motor drive frequency as an initial start control operation. Slow-up control is performed again so as to gradually increase from a low frequency in the pull-in region to reach the target frequency.

  Thereby, during the shading correction operation, the user can not detect that the outer cover 26 of the ADF 2 covering the transport unit 22 is opened / closed instantaneously and the control unit 40 is opened / closed. It is possible to prevent the stepping motor from stepping out due to momentary interruption of the 24V power supply of the stepping motor 29 and normal shading correction cannot be performed.

  In the above-described embodiment, the rotational speed detection mark m is composed of a plurality of marks formed at equal intervals in the circumferential direction of the shading roller 13. However, the present invention is not limited to this.

  For example, it is conceivable to provide a mark having a constant density change in the circumferential direction of the shading roller 13. In this case, the rotational speed can be detected from the difference between the density change amount (luminance change amount) per time of the image of the mark and a preset reference change amount.

  In addition, even in the case of a plurality of marks formed at equal intervals, the reflected light is more than the surroundings by using a mirror surface, etc., in addition to making it darker than the surroundings such as black. It does not matter as a mark with high brightness. Of course, it goes without saying that the mark is not limited to a linear mark but may have other shapes.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a schematic configuration of an image reading processing unit in the image reading apparatus. FIG. 3 is a schematic perspective view of a shading roller in the image reading apparatus. 1 is a block diagram illustrating a schematic configuration of a main part of an image reading apparatus. The trend graph showing the change of the read image data of the rotational speed detection mark formed in the shading roller in the image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus m ... Rotation speed detection mark 13 ... Shading roller 21 ... Paper feed roller 22 ... Conveying part 23 ... Front surface reading part 25 ... Discharge tray 28 ... Safety switch 29 ... Stepping motor 30 ... Back surface reading part 300 ... Adhesion Type image sensor 40 ... control unit 44 ... image processing unit 45 ... rotational speed detection unit 46 ... motor driver

Claims (2)

A shading roller driven by a stepping motor;
A mark for detecting the rotational speed of the shading roller outside the paper passing area of the shading roller;
A rotational speed detecting means for detecting the rotational speed of the shading roller by reading the mark;
Motor step-out detection means for detecting step-out of the stepping motor based on the detection result of the rotation speed detection means;
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein when the stepping motor is stepped out, an initial start-up control operation of the stepping motor is performed.

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