JP4511258B2 - Image reading device - Google Patents

Description

  The present invention relates to control of a traveling body drive motor of a pressure plate mode digital copier.

  The image reading apparatus that executes a homing operation when the power is turned on and determines the position of the traveling body based on the ON / OFF position of the HP sensor rotates the step motor, which is a power source of the traveling body, by a predetermined number of pulses. In this case, the traveling body control is performed on the assumption that the traveling body returns to the same position if the step motors are reversed by the same number of pulses.

  Normally, after stopping the rotation of the step motor after the operation is finished, the excitation of the step motor is turned off. Then, at the next drive, the excitation is turned on with the same excitation pattern as when the excitation is turned off, so that the running body deviation does not occur.

  However, in practice, depending on the drive system mechanism (gear, wire, belt, etc.) for controlling the traveling body, the position of the traveling body may be shifted at the moment when the step motor excitation is turned off. This occurs when a tension or the like is generated in a certain direction after the motor rotates and the position is shifted at the moment when the excitation is turned off.

If the amount of deviation is very small and the original position is restored at the next excitation ON, the positional deviation does not become a problem. However, if the amount of deviation is large, it will not return to the original position even with the next excitation ON.
When the traveling body deviation in the same direction repeatedly occurs, the positional deviation amount exceeds the error range, and a traveling body position deviation error or a reading start position deviation occurs.

As a prior art aiming at preventing the displacement of the traveling body, there is a “scanner and a scanner position correction method” disclosed in Patent Document 1. The invention disclosed in Patent Document 1 reads an image on a document table, counts the number of motor pulses until the home position sensor stops after passing through at the end of return, and when the count value is different from a predetermined value, Position correction processing is performed.
JP 2002-158834 A

  However, the invention described in Patent Document 1 is intended to correct the generated positional deviation and is not intended to prevent the positional deviation itself from occurring. For this reason, there is a problem that the position of the traveling body must be frequently corrected when the traveling body shift is likely to occur.

  The present invention has been made in view of such a problem, and an object thereof is to provide an image reading apparatus in which a displacement of a traveling body is prevented.

Image reading apparatus according to the present invention is an image reading apparatus for reading originals by the Rukoto moving the traveling body having a photoelectric conversion unit in the stepping motor to the sub scanning direction, the stepping motor wherein when moving the traveling body, so as to move the traveling body in a predetermined period or longer constant speed, characterized by Rukoto changing the maximum moving speed of the running body Te.

  ADVANTAGE OF THE INVENTION According to this invention, the image reading apparatus which prevented the position shift of the traveling body can be provided.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described. FIG. 1 shows a configuration of an image reading apparatus according to the embodiment. The image reading apparatus according to the present embodiment includes a first carriage 1, a second carriage 2, a home position sensor (HP sensor) 3, an imaging unit 4, a step motor 5, and a contact glass 6. The first carriage 1 includes a xenon lamp 11 and a first mirror 12. The second carriage 2 includes a second mirror 21 and a third mirror 22. The imaging unit 4 includes a lens block 41 and a photoelectric conversion element 42.
The scanning light emitted from the xenon lamp 11 passes through the contact glass 6 and is irradiated on the original, and the reflected light passes through the contact glass 6 again and enters the first mirror 12. The image light incident on the first mirror 12 is sequentially reflected by the second mirror 21 and the third mirror 22 and enters the imaging unit 3. The image light that has entered the imaging unit 4 is focused by the lens block 41 and forms an image on the photoelectric conversion element 42. The electrical signal output from the photoelectric conversion element 42 is processed by an image processing circuit (not shown), and image data corresponding to the document is generated. The step motor 5 is a power source for moving the contact image sensor unit (first carriage 1) during the document reading operation.

  A reading device that optically scans and reads a document placed on the contact glass 6 is configured to set the document on the contact glass 6 provided at the position where the pressure plate is opened. The (traveling body) is moved by the step motor 5 and read. There is also a type in which the reduction optical system is moved and focused on a CCD through a lens and read.

  The traveling body is also provided with a light source (xenon lamp 11) for irradiating the document, and a mechanism for reading the reflected light of the document irradiated by the light source by condensing it on a contact image sensor or a reduction optical system; It has become.

  Further, an HP sensor 3 for detecting the current position of the traveling body is provided, and if this is ON (running body detection), it is recognized that the traveling body is on the reading home position side. (When the traveling body is on the HP side, the HP sensor is always ON.)

FIG. 2 shows the relationship between the operation relating to reading of the document and the position of the traveling body. The BOOK reading is a reading start position when reading a document placed on the contact glass 6.
Further, a shading white reference plate is attached on the scan line via a contact glass 6. The white reference plate has a certain width (for example, 3 to 5 cm), and shading correction can be performed anywhere within the width (here, 15.2 to 19.96 mm from HP).

The image reading apparatus according to the present embodiment performs an operation called homing when the apparatus is turned on. Since it is not known where the traveling body is when the power is turned on, the HP sensor 3 is referred to, and when it is in the HP sensor ON region, the forward rotation (in this case, the direction to move to the rear end side of the pressure plate) Then, after moving to the HP sensor OFF position, this is reversed while detecting the HP sensor ON. Then, the traveling body is stopped at a specified position (here, 6.0 mm) from the position where the HP sensor 3 is turned on. This position is called the home position. The home position is also a position of the traveling body (DF reading position) when reading a document placed on an ADF (not shown).
During the homing operation, the step motor 5 is rotated at a slow speed within the self-starting frequency in order to stop at the correct home position. In addition, if the HP sensor is out of order, there is a risk of collision with the housing if the traveling body is moved at a high speed, but the traveling body is damaged during the homing operation by rotating the step motor 5 at a low speed. You can avoid it. It also serves as a failure detection for the HP sensor 3.

  Thereafter, on the white board (white reference plate), the traveling body is moved to the white board position (here, 17 mm from HP) in order to carry out white board density adjustment, and after the white board density adjustment is carried out, the running body is returned to the home position. The white plate density adjustment is an operation for storing the white density used as correction data at the time of reading a document by reading the white reference plate, but the details are omitted.

  When adjusting the density of the white plate, the fault detection of the HP sensor 3 has already been completed and the traveling body has stopped at the home position. It is returning. During this operation, since the operation may be performed at high speed, the stop position is not determined by the ON / OFF of the HP sensor 3. This is because the timing of ON / OFF of the HP sensor 3 and the actual step This is because the pulse supply of the motor 5 is performed asynchronously, so that there is a possibility that the traveling body cannot be stopped at an accurate position due to a delay according to the speed at the moment when the HP sensor 3 is turned ON / OFF. .

  Therefore, the traveling body is reliably returned to the home position by accurately matching the number of forward rotation pulses and the number of reverse rotation pulses. Similarly, in the normal plate reading operation, the traveling body is always stopped at the home position when the operation ends by accurately matching the number of forward rotation pulses and the number of reverse rotation pulses.

  In the present invention, the excitation is not turned off even after the step motor 5 is stopped, and the step motor 5 is stopped while the excitation is maintained. Thereby, it is possible to prevent the running body from being displaced due to mechanical tension.

  As described above, the image reading apparatus according to the present embodiment does not cause displacement of the traveling body.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described. The configuration of the image reading apparatus according to the present embodiment is the same as that of the first embodiment shown in FIG.

In the first embodiment, the displacement of the traveling body is prevented by not turning off the excitation even after the rotation of the step motor 5 is stopped.
However, the fact that the excitation of the step motor 5 is not turned off means that a current is always supplied to the step motor 5 and the temperature of the step motor 5 and the motor drive circuit is increased, resulting in a decrease in component reliability.
Therefore, if possible, it is preferable to turn off the excitation of the step motor 5 and stop the power supply.

  Although the temperature rise of the step motor 5 and the motor drive circuit can be suppressed by reducing the current (hold excitation current) for maintaining the excitation state when the step motor 5 is stopped, the excitation is performed if possible. It is preferable to turn it off completely.

  Therefore, in the present embodiment, the excitation is kept on for a predetermined time after the step motor 5 is stopped, and the excitation of the step motor 5 is turned off after the predetermined time has elapsed. When the excitation of the step motor 5 is turned off, the homing operation is always performed before starting the next operation. As a result, the reading operation or the like is not performed while the position of the traveling body is displaced.

  Needless to say, it is preferable to allow the user to set the time during which the excitation continues to be turned on after the stepping motor is stopped, which improves the usability of the user.

[Third Embodiment]
A third embodiment in which the present invention is preferably implemented will be described. The configuration of the image reading apparatus according to this embodiment is the same as that of the first embodiment shown in FIG.

  When the traveling body is moved at a speed as fast as possible (such as an operation of moving the traveling body to the bottom of the white plate to perform white reference density adjustment and then returning it to the home position), motor through up / down is necessary.

  In this case, when the moving distance is short, the traveling body may not be stopped at a desired position unless the through-down is started during the through-up.

FIG. 3 shows the relationship between the moving speed of the traveling body and time. When the traveling body is driven by traveling control as shown in FIG. 3, the acceleration of the traveling body changes from positive to negative at point A.
When the inertia of the traveling body is large, the motor and the traveling body cannot follow such a rapid change in acceleration, and there is a possibility that the step motor 5 may lose a pulse or step out. When a pulse drop occurs in the step motor 5, the position where the traveling body stops is different from the desired position, and a traveling body displacement occurs.

  In the present embodiment, a period for driving at a constant speed is always provided regardless of the travel distance of the traveling body, and the traveling body is driven at the maximum speed under the conditions.

  First, the number of steps required for the movement is obtained from the distance to be moved, the excitation method at the time of movement (for example, 2W1-2 phase excitation) and the motor step angle. Here, it is assumed that 300 pulses are required to move the traveling body to a desired position.

  Here, assuming that 200 pulses are required for the slew-up from the stop state to the maximum speed and the slew-down from the maximum speed to the stop state, the conventional drive system performs 150 pulses slew-up and 150 pulses through-down The body will be stopped (through-up and through-down do not necessarily have the same acceleration, so the number of pulses may differ between through-up and through-down).

On the other hand, in the present embodiment, as shown in FIG. 4, if the condition that the traveling body is moved at a constant speed for 100 pulses is set, 100 pulses are slewed up and then travel at a constant speed of 100 pulses. Move body and stop running body with 100 pulse slew down.
As a result, no pulse omission occurs in the step motor 5.

  Needless to say, the minimum number of pulses during the period in which the traveling body is moved at a constant speed is an appropriate number of pulses adjusted for each apparatus.

  As described above, the image reading apparatus according to the present embodiment does not cause a displacement of the traveling body even when the traveling body is moved at a high speed.

  Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to these, and various modifications can be made.

1 is a diagram illustrating a configuration of an image reading apparatus according to the present invention. It is a figure which shows the relationship between the operation | movement at the time of image reading, and the position of a traveling body. It is a figure which shows the relationship between the speed of the traveling body in the conventional image reading apparatus, and time. It is a figure which shows the relationship between the speed of a traveling body and time in the image reading apparatus concerning 3rd Embodiment which implemented this invention suitably.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st carriage 2 2nd carriage 3 HP sensor 4 Imaging part 5 Step motor 6 Contact glass 7 Step motor 11 Xenon lamp 12 1st mirror 21 2nd mirror 22 3rd mirror 41 Lens block 42 Photoelectric conversion element

Claims (3)

An image reading apparatus for reading originals by the Rukoto moving the traveling body having a photoelectric conversion unit in the stepping motor to the sub scanning direction,
Wherein when moving the traveling body in a stepping motor, to move the traveling body in a predetermined period or longer constant speed, the image reading apparatus according to claim Rukoto changing the maximum moving speed of the traveling body. The image reading apparatus according to claim 1 , wherein when the traveling body is stopped, the stepping motor is continuously excited even after the traveling body is stopped . After the stop of the traveling body and after a predetermined time, the excitation to the stepping motor is stopped,
3. The image reading apparatus according to claim 2 , wherein when the traveling body is moved after the excitation of the stepping motor is stopped, the traveling body is homed using a home position sensor .

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