JP2008211635A - Document reader - Google Patents

Abstract

An original reading apparatus capable of effectively suppressing a temperature rise of an optical unit or a platen glass is provided.
The temperatures detected by first to third temperature sensors 76 to 78 are compared, the lowest temperature is selected from these detected temperatures, and the first temperature is reached up to the position where the lowest temperature is reached. The scanning unit 15 is moved and positioned, the second scanning unit 16 is also moved and positioned, and the light near the position of the first platen glass 14 where the light from the light source 15a and the reflected light from the document are at the lowest temperature are detected. Since it is made to permeate | transmit, the temperature of the specific part of the 1st platen glass 14 does not rise too much. Further, since the air flow by the fan changes as the first and second scanning units 15 and 16 move, the stagnation of air in the vicinity of the first and second scanning units 15 and 16 and the optical system is eliminated, and the temperature The rise is suppressed.
[Selection] Figure 2

Description

  The present invention relates to a document reading device that is equipped in a copying machine, a facsimile machine, or the like and reads a document placed on a document placement table.

  In this type of document reading apparatus, a document is placed on a platen glass, and the illumination of the document and the reading of the document image are performed by the optical unit below the platen glass through the platen glass. Then, while moving the optical unit in the sub-scanning direction, scanning in the main scanning direction is repeated to read the entire image of the document (so-called document fixing method), or the document itself is conveyed on the platen glass in the sub-scanning direction. The entire original image is read by repeating scanning in the main scanning direction (so-called document conveyance method).

  FIG. 6A is a cross-sectional view partially showing a conventional document reading apparatus adopting a document conveying system. In this apparatus, a CCD (Charge Coupled Device) 202 and a light source 203 are disposed below the platen glass 201, a shading correction plate 204 is disposed above the platen glass 201, and a document is placed on the platen glass 201 by a plurality of conveyance rollers 205. The original is illuminated by the light source 203 through the platen glass 201 and the image of the original is read by the CCD 202.

Furthermore, in Patent Literature 1, when the platen glass 201 is soiled after being configured as shown in FIG. 6A, even if the original is read through the soiled portion of the platen glass 201, good reading cannot be performed. The CCD 202, the light source 203, and the like are moved along the platen glass 201 so that the original is read through a non-stained portion of the platen glass 201.
JP 2003-259087 A

  By the way, a fluorescent lamp, a cold cathode tube, or the like is used as a light source of the document reading device, but in recent years, a cold cathode tube is often used for power saving and heat generation reduction.

  However, in the conventional document transport system, the optical unit including the light source, the reflecting mirror, the lens, and the like is positioned at a fixed position. It was easy to conduct to platen glass, the optical unit and platen glass were heated, and these temperatures rose.

  In addition, a fan for cooling the optical unit and the platen glass is provided, but when the optical unit is positioned at a fixed position, the air flow by the fan is specified and the air near the optical unit stays. There was a tendency, and the temperature rise could not be effectively prevented.

  Furthermore, in recent years, development of an apparatus that has increased the printing processing speed has progressed. For example, an apparatus has been developed in which the number of printing processes is 100 sheets / minute or more. In order to realize such a high printing processing speed, it is necessary to set a document reading speed higher than the printing processing speed. If the document reading speed is slower than the printing process speed, there is a problem that the printing process must be interrupted until the document reading catches up when the document reading is delayed from the printing process.

  However, in order to sufficiently increase the reading speed of the original, it is necessary to increase the light quantity of the light source. In addition, when a large amount of originals are read, the irradiation time of the light source becomes long. For this reason, the temperature of the optical unit and the platen glass increased excessively.

  For example, in the conventional document conveying method, as shown in the graph of FIG. 6B, the temperature of the light transmitting portion 201a of the platen glass 201 through which the light from the light source 203 and the reflected light from the document are transmitted is It rose exceptionally than other parts.

  Further, when the reading speed of the original is increased, as shown in the graph of FIG. 7, the temperature of the light transmitting portion of the platen glass 201 rises to about 80 ° C. when the number of continuous originals to be read becomes close to 300. If the number of originals to be read further increases, the temperature may rise to nearly 95 ° C.

  In this way, when the temperature of the platen glass is raised to near 80 ° C. or higher, a human hand will be burned just by touching the platen glass. In addition, the original touches the part of the platen glass where the temperature is high, and the original is discolored or the moisture distribution of the original is biased, which causes warpage, wrinkles, and eventually jamming. .

  Also, in the state where the air stays, the temperature of the optical unit consisting of the light source support member and the reflecting mirror, lens, etc. is likely to rise, the focal length of the optical system fluctuates, and the image of the document is out of focus. As a result, the image quality is degraded.

  Conventionally, however, there is no way to effectively cope with the temperature rise of such an optical unit or platen glass, and this temperature rise has been left as it is.

  On the other hand, in Patent Document 1, the CCD, the light source, and the like are moved along the platen glass, but this is for avoiding a dirty portion of the platen glass, which increases the temperature of the optical unit or the platen glass. It was not intended to solve the various problems involved, and could not be solved.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a document reading apparatus capable of effectively suppressing an increase in temperature of an optical unit or a platen glass.

  In order to solve the above-described problems, the present invention provides a document reading apparatus that reads an image of a document by an optical unit positioned below the platen glass through the platen glass while conveying the document on the platen glass. The optical unit is moved along the platen glass according to the internal temperature displacement state, the position of the optical unit is changed, and image reading of the document is continued.

  In addition, a temperature sensor is provided for detecting the temperature of the light transmitting portion of the platen glass through which light from the light source of the optical unit or reflected light from the document is transmitted, and according to the temperature displacement detected by the temperature sensor. The light transmission part of the platen glass is changed by moving the light source of the optical unit.

  Furthermore, a number accumulation counter for counting the number of documents continuously read is provided, and when the number of documents counted by the number accumulation counter reaches a certain number that can cause a temperature displacement inside the document reading device, The position of the optical unit is changed by moving the optical unit.

  In addition, a timer for measuring the irradiation time of the light of the light source is provided, and when the irradiation time measured by the timer reaches a certain number that can cause a temperature displacement inside the document reading device, the optical unit is moved, The position of the optical unit has been changed.

  Further, the position of the optical unit is changed by moving the optical unit in the conveying direction of the original on the platen glass.

  The apparatus further includes conveying means for conveying the document on the platen glass, and the conveying means conveys the document while pressing it on the platen glass.

  Further, the transporting means includes a white endless belt that is rotated and moved, and the document is sandwiched and transported between the endless belt and the platen glass.

  According to the present invention as described above, the optical unit is moved along the platen glass in accordance with the temperature displacement state inside the original reading apparatus, the position of the optical unit is changed, and the image reading of the original is continued. . For this reason, the light from the light source of the optical unit or the reflected light from the original is not applied to only the specific portion of the platen glass, and only the specific portion of the platen glass does not rise excessively. For this reason, there are no burns due to contact with the platen glass, discoloration of the original, warping of the original, wrinkles, jams and the like.

  In addition, when a fan for cooling is provided, the flow of air by the fan changes as the optical unit moves, so that the retention of air near the optical unit and platen glass is eliminated, and the optical unit and platen glass Temperature rise is suppressed. For this reason, the focal length of the optical system does not fluctuate, focus does not occur, and image quality does not deteriorate.

  For example, the temperature of the light transmitting portion of the platen glass may be detected by a temperature sensor, and the light transmitting portion of the platen glass may be changed by moving the light source in accordance with the detected temperature displacement.

  Alternatively, when a plurality of originals are continuously read, the light source is continuously turned on. Therefore, if the number of originals continuously read increases, the temperature inside the apparatus rises. Therefore, the number of documents may be counted, and the position may be changed by moving the optical unit when the counted number of documents reaches a certain number that can cause temperature displacement inside the apparatus.

  Further, the longer the irradiation time of the light from the light source, the higher the temperature inside the apparatus. Therefore, the light irradiation time of the light source is measured, and when the measured irradiation time reaches a certain time that can cause temperature displacement inside the apparatus, the position of the optical unit may be moved and changed. Absent.

  Further, the optical unit is moved in the conveying direction of the original on the platen glass. In this case, when reading the front and back documents continuously conveyed, the optical unit starts to move immediately after the reading of the previous document, and the optical unit is moved to follow the gap between the front and back documents. The reading of the subsequent document can be started immediately after the stop. That is, the position of the optical unit can be changed by moving the optical unit with almost no interruption of the reading of the document.

  Further, since the document is conveyed while being pressed onto the platen glass, the positional relationship between the platen glass and the document does not change, and the document can be easily read. For example, a document is sandwiched and conveyed between an endless belt that is rotated and a platen glass. In addition, since the white endless belt is used, this endless belt can be used for shading correction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which a first embodiment of a document reading apparatus according to the present invention is applied. The image forming apparatus 100 acquires image data read from a document, or acquires image data received from the outside, and forms a monochrome image indicated by the image data on a recording sheet. The configuration is roughly divided into a document transport unit (ADF) 101, a document reading device 102, a printing unit 103, a recording paper transport unit 104, and a paper feed unit 105.

  When at least one document is set on the document setting tray 11, the document conveying unit 101 pulls out the document one by one from the document setting tray 11 and conveys the document. The document is read by the first platen glass 14 of the document reading device 102. Then, the document is discharged to the discharge tray 12.

  In the document reading device 102, an optical unit including a first scanning unit 15 and a second scanning unit 16 is disposed below the first platen glass 14, and when the document passes through the first platen glass 14, the first scanning unit 15. The document surface is exposed by the light source of the scanning unit 15, the reflected light from the document surface is guided to the imaging lens 17 by the mirrors of the first and second scanning units 15 and 16, and the image of the document surface is formed by the imaging lens 17. An image is formed on a CCD (Charge Coupled Device) 18. The CCD 18 repeatedly reads an image on the document surface in the main scanning direction and outputs image data indicating the image on the document surface.

  Further, when the document is placed on the second platen glass 19 on the upper surface of the document reading apparatus 102, the first scanning unit 15 moves the first and second scanning units 15 and 16 in the sub-scanning direction, and the second scanning unit 15 performs the second scanning. The document surface on the platen glass 19 is exposed, the reflected light from the document surface is further reflected by the first and second scanning units 15 and 16, and guided to the imaging lens 17. Is imaged on the CCD 18. At this time, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other, and the reflection of the document surface → the first and second scanning units 15 and 16 → the imaging lens 17 → the CCD 18 is reflected. The positional relationship between the first and second scanning units 15 and 16 is always maintained so that the length of the light path of the light does not change, and thereby the focus of the image on the document surface on the CCD 18 is always maintained accurately. Yes.

  The image data output from the CCD 18 is subjected to various types of image processing by a control circuit such as a microcomputer and then output to the printing unit 103.

  Therefore, in the document reading apparatus 102 according to the present embodiment, the document is transported on the first platen glass 14 and the document is placed on the second platen glass 19, and the optical unit (first and second). Both of the document fixing methods in which the scanning units 15 and 16) are moved are also used.

  The printing unit 103 records a document indicated by image data on a sheet, and includes a photosensitive drum 21, a charger 22, an optical writing unit 23, a developing device 24, a transfer unit 25, a cleaning unit 26, and a fixing device. 27 etc.

  The photoconductor drum 21 is an organic photoconductor whose surface layer is made of an organic photoconductive material. The photoconductor drum 21 rotates in one direction, the surface is cleaned by the cleaning unit 26, and the surface is uniformly charged by the charger 22. Is done. The charger 22 may be of a charger type or of a roller type or a brush type that contacts the photosensitive drum 21.

  The optical writing unit 23 is a laser scanning unit (LSU) including two laser irradiation units 28a and 28b and two mirror groups 29a and 29b. In the optical writing unit 23, image data is input, laser light corresponding to the image data is emitted from the laser irradiation units 28a and 28b, and the laser light is transmitted through the mirror groups 29a and 29b. The drum 21 is irradiated to expose the uniformly charged surface of the photosensitive drum 21 to form an electrostatic latent image on the surface of the photosensitive drum 21.

  The optical writing unit 23 employs a two-beam method including two laser irradiation units 28a and 28b in order to cope with high-speed printing processing, thereby reducing the burden associated with increasing the irradiation timing.

  As the optical writing unit 23, an EL writing head or an LED writing head in which light emitting elements are arranged in an array can be used instead of the laser scanning unit.

  The developing device 24 supplies toner to the surface of the photosensitive drum 21 to develop the electrostatic latent image, and forms a toner image on the surface of the photosensitive drum 21. The transfer unit 25 transfers the toner image on the surface of the photosensitive drum 21 onto the recording paper conveyed by the paper conveyance unit 104. The fixing device 27 heats and pressurizes the recording paper to fix the toner image on the recording paper. Thereafter, the recording sheet is further conveyed to the sheet discharge tray 47 by the sheet conveying unit 104 and discharged. The cleaning unit 26 removes and collects the toner remaining on the surface of the photosensitive drum 21 after development and transfer.

Here, the transfer unit 25 includes a transfer belt 31, a drive roller 32, a driven roller 33, an elastic conductive roller 34, and the like, and the transfer belt 31 is stretched between the rollers 32 to 34 and other rollers. Rotating. The transfer belt 31 has a predetermined resistance value (for example, 1 × 10 ⁹ to 1 × 10 ¹³ Ω / cm), and conveys the recording paper placed on the surface thereof. The elastic conductive roller 34 is pressed against the surface of the photosensitive drum 21 via the transfer belt 31, and presses the recording paper on the transfer belt 31 against the surface of the photosensitive drum 21. A transfer electric field having a polarity opposite to the charge of the toner image on the surface of the photosensitive drum 21 is applied to the elastic conductive roller 34, and the toner image on the surface of the photosensitive drum 21 is transferred to the transfer belt by the transfer electric field having the opposite polarity. 31 is transferred to a recording sheet on the recording medium 31. For example, when the toner image has a charge of (−) polarity, the polarity of the transfer electric field applied to the elastic conductive roller 34 is set to (+) polarity.

  The cleaning unit 26 presses the cleaning blade 26 </ b> A against the surface of the photosensitive drum 21 to remove toner and paper dust remaining on the surface of the photosensitive drum 21. The entire toner image on the surface of the photosensitive drum 21 is not transferred onto the recording paper. Generally, it is said that the transfer efficiency is approximately 85 to 95%, although it varies depending on the transfer mechanism. . On the other hand, when the recording paper is subjected to a transfer electric field, the floating matter (cellulose short fiber, extender, bleaching agent, etc.) on the surface of the recording paper is charged to the opposite polarity to the transfer electric field, and the charged floating matter is the photosensitive drum. 21 adsorbs on the surface and becomes a deposit called paper dust.

  If the toner or paper dust remaining on the surface of the photosensitive drum 21 is not removed, the print quality is deteriorated. For this reason, it is necessary to clean the surface of the photosensitive drum 21 by the cleaning unit 26.

  The fixing device 27 includes a heating roller 35 and a pressure roller 36. Pressure members (not shown) are arranged at both ends of the pressure roller 36 so that the pressure roller 36 is pressed against the heating roller 35 with a predetermined pressure. When the recording paper is conveyed to a pressure contact area (referred to as a nip area) between the heating roller 35 and the pressure roller 36, the recording paper is conveyed by the rollers 35 and 36, and unfixed toner on the recording paper. The image is heated and melted and pressed to fix the toner image on the recording paper.

  The paper transport unit 104 includes a plurality of pairs of transport rollers 41, a pair of registration rollers 42, a transport path 43, reverse transport paths 44a and 44b, a plurality of branching claws 45, and a pair of paper discharge rollers 46 for transporting recording paper. Etc.

  In the conveyance path 43, the recording paper is received from the paper supply unit 105, and the recording paper is conveyed until the leading edge of the recording paper reaches the registration roller 42. At this time, since the registration roller 42 is temporarily stopped, the leading edge of the recording paper reaches and contacts the registration roller 42, and the recording paper is bent. The leading edge of the recording sheet is aligned parallel to the registration roller 42 by the elastic force of the bent recording sheet. Thereafter, the rotation of the registration roller 42 is started, the recording paper is conveyed to the transfer unit 25 of the printing unit 103 by the registration roller 42, and the recording paper is further conveyed to the paper discharge tray 47 by the paper discharge roller 46.

  The registration roller 42 is stopped and rotated by switching on and off the clutch between the registration roller 42 and the drive shaft, or by switching on and off the motor that is the drive source of the registration roller 42.

  Also, when recording an image on the back side of the recording paper, each branch claw 45 is selectively switched, the recording paper is guided from the transport path 43 to the reverse transport path 44b, and the transport of the recording paper is temporarily stopped. Further, each of the branch claws 45 is selectively switched again, the recording sheet is guided from the reverse conveying path 44b to the reverse conveying path 44a, the recording sheet is reversed, and the recording sheet is conveyed through the reverse conveying path 44a. Return to the registration roller 42 in the path 43.

  Such conveyance of the recording paper is referred to as switchback conveyance. By this switchback conveyance, the front and back of the recording paper can be reversed, and at the same time, the leading edge and the trailing edge of the recording paper are also switched. Accordingly, when the recording paper is reversed and returned, the trailing edge of the recording paper comes into contact with the registration roller 42 and the trailing edge of the recording paper is aligned in parallel with the registration roller 42. Is transferred to the transfer unit 25 of the printing unit 103 to perform printing on the back surface of the recording paper, and the unfixed toner image on the back surface of the recording paper is heated and melted by the nip area between the rollers 35 and 36 of the fixing device 27. The toner image is fixed on the back surface of the recording sheet by the pressure, and then the recording sheet is conveyed to the discharge tray 47 by the discharge roller 46.

  In the conveyance path 43 and the reverse conveyance paths 44a and 44b, sensors for detecting the position of the recording paper and the like are arranged at various locations, and the conveyance roller and the registration roller are driven and controlled based on the position of the recording paper detected by each sensor. Thus, the recording paper is conveyed and positioned.

  The paper feed unit 105 includes a plurality of paper feed trays 51. Each paper feed tray 51 is a tray for storing recording paper and is provided below the image forming apparatus 100. Each paper feed tray 51 is provided with a pick-up roller or the like for pulling out recording sheets one by one, and sends out the pulled recording sheets to the transport path 43 of the paper transport unit 104.

  Since the image forming apparatus 100 is intended for high-speed printing processing, each paper feed tray 51 has a capacity capable of storing 500 to 1500 standard size recording sheets.

  Further, on the side surface of the image forming apparatus 100, a large-capacity paper feed cassette (LCC) 52 capable of storing a large amount of a plurality of types of recording papers and a manual feed tray 53 for mainly supplying irregular-size recording papers are provided. ing.

  The paper discharge tray 47 is disposed on the side surface opposite to the manual feed tray 53. In place of the paper discharge tray 47, a post-processing device for paper discharge (such as stapling and punching) and a plurality of paper discharge trays can be arranged as options.

  Next, the document reading apparatus 102 of this embodiment will be described in detail.

  In the document reading apparatus 102 of the present embodiment, the first platen glass 14 is elongated in the document transport direction as shown in an enlarged view in FIG.

  For this reason, in the document conveying unit 101, an endless conveying belt 71 is bridged between the driving roller 72 and the driven roller 73 on the upper side of the first platen glass 14, and the conveying belt 71 is brought into contact with the upper surface of the first platen glass 14. Yes. When the document is transported, the driving roller 72 is rotationally driven to rotate the transport belt 71 in the direction of arrow A.

  When a document is conveyed by a pair of conveyance rollers 74 on the upstream side in the document conveyance direction, the document is guided between the first platen glass 14 and the conveyance belt 71, and the document is conveyed by the conveyance belt 71 to the first platen glass 14. The document is conveyed so as to slide upward, and the document is further conveyed by a set of conveyance rollers 75 on the downstream side.

  The surface of the conveyor belt 71 is uniform white and is used for shading correction by the document reader 102.

  In the document reading apparatus 102, the first scanning unit 15 can be positioned by moving to any one of the three positions P1, P2, and P3.

  Regardless of whether the first scanning unit 15 is positioned at each of the positions P1, P2, or P3, the light from the light source (cold cathode tube) 15a of the first scanning unit 15 irradiates the document surface through the first platen glass 14. The reflected light from the original enters the first scanning unit 15 through the first platen glass 14, and the reflected light from the original is reflected by the reflection mirror 15 b of the first scanning unit 15 and the second scanning unit 16. The light is sequentially reflected by the two reflecting mirrors 16 a and 16 b, further guided to the CCD 18 through the imaging lens 17, and an original image is formed on the CCD 18.

  Even if the first scanning unit 15 is positioned at any of the positions P1, P2, and P3, the original surface → first and second scanning units 15, 16 → imaging lens 17 as in the original fixing method. → The positional relationship between the first and second scanning units 15 and 16 is always maintained so that the length of the optical path of the reflected light of the CCD 18 does not change, and the focus of the image on the document surface on the CCD 18 is always maintained accurately. ing.

  When the first scanning unit 15 is positioned at the position P1, the light from the light source 15a of the first scanning unit 15 is transmitted through the portion near the position P1 of the first platen glass 14, and the reflected light from the document is the portion near the same position P1. , And enters the first scanning unit 15. For this reason, the temperature of the position P1 vicinity part of the 1st platen glass 14 rises. Similarly, when the first scanning unit 15 is positioned at the position P2 or P3, the light from the light source 15a of the first scanning unit 15 is transmitted through the vicinity of the position P2 or P3 of the first platen glass 14 and reflected from the document. The light passes through the portion near the position P2 or P3 and enters the first scanning unit 15, and the temperature of the portion near the position P2 or P3 of the first platen glass 14 rises.

  The positions P1, P2, and P3 are spaced apart from each other so as not to be affected by the temperature between the portions near the respective positions in the first platen glass 14. Therefore, in the first platen glass 14, even if the temperature in the vicinity of the position P1 rises, the temperature in the vicinity of the adjacent position P2 hardly increases, and even if the temperature in the vicinity of the position P2 rises, Even if the temperature in the vicinity of the position P1 and the position in the vicinity of the position P3 does not increase, and the temperature in the vicinity of the position P3 further increases, the temperature in the vicinity of the adjacent position P2 hardly increases. Therefore, the first platen glass 14 is long in the document transport direction.

  The first, second, and third temperature sensors 76, 77, 78 detect the temperatures of the respective positions P 1, P 2, P 3 of the first platen glass 14. These temperature sensors 76 to 78 may detect the respective temperatures by directly contacting the respective positions P1, P2, and P3 of the first platen glass 14 outside the region through which the document with the maximum width passes. The temperature may be detected in a non-contact manner with each of the positions P1, P2, and P3 inside the area through which the document passes.

  The control unit 79 inputs the temperatures detected by the first to third temperature sensors 76 to 78, and drives the drive mechanisms (not shown) of the first and second scanning units 15 and 16 based on these temperatures. By driving control, the first scanning unit 15 is moved and positioned to any one of the positions P1, P2, and P3, and the second scanning unit 16 is also moved following the positioning.

  For example, the control unit 79 compares the temperatures detected by the first to third temperature sensors 76 to 78, selects the lowest temperature from these detected temperatures, and is the position at which the lowest temperature is reached. The first scanning unit 15 is moved until positioning, and the second scanning unit 16 is also moved following the positioning. As a result, the light from the light source 15a of the first scanning unit 15 passes through the portion of the first platen glass 14 near the lowest temperature position, and the reflected light from the document also passes through the portion near the same position.

  For this reason, the temperature of a specific portion of the first platen glass 14 does not rise excessively, and burns due to contact with the first platen glass 14, discoloration of the document, warping of the document, wrinkles, jams, and the like may occur. Absent.

  In general, the document reading apparatus 102 is provided with a cooling fan. However, since the air flow by the fan changes as the first and second scanning units 15 and 16 move, the first and second scannings are performed. The stagnation of air in the vicinity of the units 15 and 16, the imaging lens 17, and the CCD 18 is eliminated, and the temperature rise is suppressed. For this reason, the focal length of the optical system does not fluctuate, focus does not occur, and image quality does not deteriorate.

  Next, referring to the flowchart of FIG. 3, a processing procedure for controlling the movement of the first scanning unit 15 based on the temperatures detected by the first to third temperature sensors 76 to 78 when reading the document by the document movement method. Will be explained.

  First, in the standby state of the image forming apparatus 100, when a document is set on the document set tray 11, and a document reading request (step ST1) is made by operating the operation panel, the control unit 79 responds to this by reading the document. It is determined whether there are a plurality of documents on the set tray 11 (ST2). For example, the control unit 79 determines whether or not there are a plurality of documents based on the detection output of the document sensor provided on the document set tray 11 and the document reading conditions designated by the operation of the operation panel.

  If there is only one document (“No” in ST2), the control unit 79 moves the first scanning unit 15 to the position P1, for example, and moves the second scanning unit 16 to follow. Position (ST3). At this time, since it is immediately after the standby state of the image forming apparatus 100, the temperature of any part of the first platen glass 14 has not increased.

  The position of the first scanning unit 15 in step ST3 may be determined in advance and stored in the memory of the control unit 11, or may be a position different from the last reading position in the previous reading process. .

  Subsequently, the control unit 79 energizes the light source 15a of the first scanning unit 15 (ST4) to turn on the light source 15a, control the amount of light emitted from the light source 15a, and shading using the white surface of the conveyor belt 71. Correction is performed (ST5). Then, after the control of the irradiation light amount and the shading correction are finished (“Yes” in ST5), the control unit 79 controls the document conveying unit 101 to pull out the document from the document set tray 11, and to store the document on the first platen. The document is transported and passed on the glass 14, and the document is discharged to the discharge tray 12. At the same time, the document reading device 102 is controlled to perform document reading processing (ST6).

  At this time, since the first scanning unit 15 is positioned at the position P1, the light from the light source 15a of the first scanning unit 15 passes through the portion near the position P1 of the first platen glass 14, and is reflected from the document. Also passes through the vicinity of the same position P1.

  When the reading process of the one original is completed and the original is discharged to the paper discharge tray 12, the process returns to the standby state.

  On the other hand, when it is determined in step ST2 that there are a plurality of documents (“Yes” in ST2), the control unit 79 detects each of the first platen glasses 14 detected by the first to third temperature sensors 76 to 78. The temperatures of the positions P1, P2, and P3 are input, the lowest temperature is selected from these detected temperatures, the first scanning unit 15 is moved to the lowest temperature position, and is positioned. The scanning unit 16 is also moved and positioned (ST8).

  For example, assuming that the temperature at the position P1 is the lowest, the control unit 79 moves and positions the first scanning unit 15 to the position P1, and positions the second scanning unit 16 by following movement.

  Then, the control unit 79 turns on the light source 15a of the first scanning unit 15 (ST9), controls the amount of irradiation light and performs shading correction (“Yes” in ST10), and then controls the document conveying unit 101, The document is pulled out from the document set tray 11, and the document is transported and passed on the first platen glass 14 and discharged. At the same time, the document reading device 102 is controlled to perform document reading processing (ST11).

  Also at this time, the light from the light source 15a and the reflected light from the original are transmitted through the vicinity of the position P1 of the first platen glass 14.

  Thereafter, the control unit 79 determines whether or not there is a next document (ST12). If there is no next document (“No” in ST12), the control unit 79 returns to a standby state.

  Further, if there is a next original to be read (“Yes” in ST12), the control unit 79 sets each of the positions P1, P2, and P3 of the first platen glass 14 detected by the first to third temperature sensors 76 to 78. A temperature is input (ST13). Then, the control unit 79 compares the detected temperature at the position P1 of the first platen glass 14 with a temperature threshold value stored in advance in the memory 79a built in the control unit 79 (ST14), and the position of the first platen glass 14 is determined. If the detected temperature of P1 is less than the temperature threshold value (“Yes” in ST14), that is, if the temperature of the position P1 of the first platen glass 14 has not risen exceptionally, the process returns to ST11 to read the next document. I do.

  In this case, the next original is read with the first scanning unit 15 still positioned at the position P1.

  Further, if the detected temperature at the position P1 of the first platen glass 14 is equal to or higher than the temperature threshold (“No” in ST14), the control unit 79 has a particularly high temperature at the position P1 of the first platen glass 14. Then, returning to ST8, the temperatures of the respective positions P1, P2, and P3 of the first platen glass 14 detected by the first to third temperature sensors 76 to 78 are inputted, and the lowest of these detected temperatures is input. The temperature is selected, the first scanning unit 15 is moved and positioned to the position where the temperature is the lowest, and the second scanning unit 16 is also moved and positioned.

  For example, assuming that the temperature at the position P2 is the lowest, the control unit 79 moves and positions the first scanning unit 15 to the position P2, and positions the second scanning unit 16 by following movement. Then, the process after ST9 is performed, and the next document reading process is performed.

  At this time, the light from the light source 15a of the first scanning unit 15 passes through the portion near the position P2 of the first platen glass 14, and the reflected light from the document also passes through the portion near the position P2.

  Similarly, when the temperature of the position of the first platen glass 14 through which the light from the light source 15a and the reflected light from the document are transmitted becomes equal to or higher than the temperature threshold, the detected temperatures at the positions P1, P2, and P3 of the first platen glass 14 are detected. The lowest temperature is selected, and the first scanning unit 15 is moved and positioned to the position where the lowest temperature is reached. The second scanning unit 16 is also moved and positioned, and then the original is read. Process.

  The temperature threshold is preferably set to a temperature that does not cause burns or a temperature that does not cause discoloration of the document. Specifically, the temperature threshold is preferably set to 60 ° C. or lower.

  As described above, in the present embodiment, the temperatures detected by the first to third temperature sensors 76 to 78 are compared, the lowest temperature is selected from these detected temperatures, and this lowest temperature is obtained. The first scanning unit 15 is moved to the position for positioning, and the second scanning unit 16 is also moved to follow the positioning so that the light from the light source 15a and the reflected light from the document have the lowest temperature of the first platen glass 14. Since the portion near the position is transmitted, the temperature of the specific portion of the first platen glass 14 does not rise excessively. Further, since the air flow by the fan changes as the first and second scanning units 15 and 16 move, the stagnation of air in the vicinity of the first and second scanning units 15 and 16 and the optical system is eliminated, and the temperature The rise is suppressed.

  Next, a second embodiment of the document reading apparatus of the present invention will be described. The document reading apparatus of the present embodiment has the same configuration as that of the document reading apparatus shown in FIG. 2 and is applied to the image forming apparatus 100 of FIG. 1, but controls the movement of the first scanning unit 15. The processing procedure is different from that of the first embodiment.

  In the present embodiment, the first scanning unit 15 is not moved and controlled based on the temperature detected by the first platen glass 14 by the temperature sensor as in the first embodiment, but the first scanning is performed based on the number of documents read. The movement of the scanning unit 15 is controlled.

  Here, if a plurality of documents are continuously read with the first and second scanning units 15 and 16 positioned, the light source 15a of the first scanning unit 15 is continuously turned on, and the light source 15a. Since the light from the document and the reflected light from the document are continuously applied to the specific part of the first platen glass 14, the temperature of the specific part of the first platen glass 14 continues to rise gradually. At this time, the temperature of the specific portion of the first platen glass 14 corresponds to the length of the continuous lighting time of the light source 15a, and the length of the continuous lighting time corresponds to the number of documents to be read. The temperature of a specific portion of the platen glass 14 corresponds to the number of originals to be read.

  Therefore, a plurality of originals are continuously read, and it is obtained in advance whether the temperature of a specific portion of the first platen glass 14 reaches an allowable temperature when reading the original. The number of documents is stored in the memory 79a of the control unit 79 as the number threshold. The control unit 79 has a built-in sheet number counter (not shown) that accumulates the number of read documents.

  The number threshold is obtained and stored under the condition that an A4 size document (210 mm × 299 mm) is conveyed in the short direction.

  Accordingly, when an A4 size document is conveyed and read in the lateral direction, the number of documents may be accumulated one by one for each read document.

  However, the illumination time of the light source 15a required for each original document changes when the original document is transported in the longitudinal direction for reading or when reading an original of another size. Therefore, the integrated value for each read document is corrected according to the length of the document in the conveyance direction.

  For example, the integrated value is set to 2 for conveyance of one A3 size original (299 mm × 420 mm) in the longitudinal direction. For the conveyance of the A4 size original in the longitudinal direction, the integrated value is set to 1.42. As a result, the integrated value of the number of read originals can be made to accurately correspond to the temperature of the specific portion of the first platen glass 14.

  Now, the processing procedure of this embodiment is as shown in the flowchart of FIG. First, in the standby state of the image forming apparatus 100, when a document is set on the document set tray 11, and a document reading request (step ST21) is made by operating the operation panel, the control unit 79 responds to the request by the control unit 79. It is determined whether or not there are a plurality of documents on the set tray 11 (ST22).

  If there is only one document (“No” in ST22), for example, the control unit 79 moves and positions the first scanning unit 15 to the position P1, and moves the second scanning unit 16 to follow. Positioning is performed (ST23).

  Note that the position of the first scanning unit 15 in step ST23 may be determined in advance and stored in the memory of the control unit 11, or may be a position different from the last reading position in the previous reading process.

  Subsequently, the control unit 79 turns on the light source 15a of the first scanning unit 15 (ST24), and controls the irradiation light amount and performs shading correction (ST25). Then, the control unit 79 controls the document conveying unit 101 to convey and pass the document on the first platen glass 14, and simultaneously controls the document reading device 102 to perform the document reading process (ST26). .

  At this time, the light from the light source 15a and the reflected light from the document are transmitted through the portion of the first platen glass 14 near the position P1.

  When the reading process of the one original is completed and the original is discharged to the paper discharge tray 12, the process returns to the standby state.

  On the other hand, if it is determined in step ST22 that there are a plurality of documents (“Yes” in ST22), the control unit 79 moves the first scanning unit 15 to the position P1, for example, and positions the second scanning unit 16. Are also moved following the positioning (ST27). The position at this time is also determined in advance or different from the last reading position in the previous reading process.

  Then, the control unit 79 turns on the light source 15a of the first scanning unit 15 (ST28), controls the amount of irradiation light and performs shading correction (“Yes” in ST29), and then the integrated value of the number of documents by the number integration counter. Is initialized (ST30). Further, the control unit 79 controls the document conveying unit 101 to convey and pass the document on the first platen glass 14, and simultaneously controls the document reading device 102 to perform the document reading process (ST31). Then, according to the length of the document in the conveyance direction, the accumulated value of the number of documents by the number accumulation counter is accumulated.

  Also at this time, the light from the light source 15a and the reflected light from the original are transmitted through the vicinity of the position P1 of the first platen glass 14.

  Thereafter, the control unit 79 determines whether or not there is a next document (ST32). If there is no next document (“No” in ST32), the control unit 79 returns to a standby state.

  If there is a next document (“Yes” in ST32), control unit 79 determines whether the integrated value of the number of documents by the number integration counter is equal to or greater than the number threshold (ST33), and the integrated value is the number of sheets. If it is less than the threshold value (“No” in ST33), the process returns to ST31 to perform the next document reading process.

  Accordingly, the next original is read with the first scanning unit 15 positioned at the position P1.

  Then, ST31 to ST33 are repeated, the originals are read one after another, and when the integrated value of the number of originals by the number integration counter is integrated, the integrated value of the originals by the number integration counter becomes equal to or greater than the number threshold (ST33). "Yes"). At this time, the control unit 79 moves and positions the first scanning unit 15 to the position P2 or P3 different from the position P1, and positions the second scanning unit 16 by following movement (ST34). Then, returning to the process from ST28, the document reading process is continued.

  At this time, the light from the light source 15a and the reflected light from the document are transmitted through the first platen glass 14 near the position P2 or P3.

  Note that the order of changing the position of the first scanning unit 15 in step ST34 may be determined in advance, for example, in a cyclic order of positions P1 → P2 → P3 → P1. In particular, if the position of the first scanning unit 15 is changed in the order of positions P1 → P2 → P3, the first scanning unit 15 is moved in the document conveyance direction. In this case, however, the first scanning unit 15 is continuously conveyed. When reading the front and back documents, the optical unit (first and second scanning units 15 and 16) starts moving immediately after the reading of the previous document, and moves the first scanning unit 15 following the gap between the front and back documents. The reading of the subsequent document can be started immediately after the optical unit is stopped. That is, the position of the optical unit can be changed by moving the optical unit with almost no interruption of the reading of the document.

  As described above, in the present embodiment, when reading a plurality of documents, if the integrated value of the number of documents exceeds the number threshold, the first scanning unit 15 is moved and its position is changed. Therefore, the specific part of the first platen glass 14 is not continuously irradiated with the light and the reflected light from the document without any limit, and the temperature of the specific part of the first platen glass 14 does not increase excessively. Further, since the air flow by the fan changes as the first and second scanning units 15 and 16 move, the stagnation of air in the vicinity of the first and second scanning units 15 and 16 and the optical system is eliminated, and the temperature The rise is suppressed.

  Next, a third embodiment of the document reading apparatus according to the present invention will be described. The document reading apparatus of the present embodiment has the same configuration as that of the document reading apparatus shown in FIG. 2 and is applied to the image forming apparatus 100 of FIG. 1, but controls the movement of the first scanning unit 15. This processing procedure is different from those of the first and second embodiments.

  In the present embodiment, the movement of the first scanning unit 15 is not controlled based on the temperature of the first platen glass by the temperature sensor as in the first embodiment, and the document scanned as in the second embodiment is not controlled. The movement of the first scanning unit 15 is not controlled based on the number of sheets, but the movement of the first scanning unit 15 is controlled based on the continuous irradiation time by the light source 15a of the first scanning unit 15.

  As described above, the temperature of the specific portion of the first platen glass 14 corresponds to the lighting time of the light source 15a continuously.

  Therefore, it is obtained in advance how long the continuous lighting time of the light source 15a is, and the temperature of the specific part of the first platen glass 14 is above the allowable temperature. The length is stored in the memory 79a of the control unit 79 as a time threshold value. In addition, the control unit 79 has a built-in timer (not shown) for measuring the continuous lighting time of the light source 15a.

  Now, the processing procedure of this embodiment is as shown in the flowchart of FIG. First, in the standby state of the image forming apparatus 100, when a document is set on the document set tray 11, and a document reading request (step ST41) is made by operating the operation panel, the control unit 79 responds to the request by the control unit 79. It is determined whether or not there are a plurality of documents on the set tray 11 (ST42).

  If there is only one document (“No” in ST42), for example, the control unit 79 moves and positions the first scanning unit 15 to the position P1, and moves the second scanning unit 16 to follow. Positioning is performed (ST43).

  Note that the position of the first scanning unit 15 in step ST43 may be determined in advance and stored in the memory of the control unit 11, or may be a position different from the last reading position in the previous reading process.

  Subsequently, the control unit 79 turns on the light source 15a of the first scanning unit 15 (ST44), and controls the irradiation light amount and performs shading correction (ST45). Then, the control unit 79 controls the document conveying unit 101 to convey and pass the document on the first platen glass 14, and simultaneously controls the document reading device 102 to perform the document reading process (ST46). .

  At this time, the light from the light source 15a and the reflected light from the document are transmitted through the portion of the first platen glass 14 near the position P1.

  When the reading process for one original is completed and the original is discharged to the paper discharge tray 12, the process returns to the standby state.

  On the other hand, when it is determined in step ST42 that there are a plurality of documents (“Yes” in ST42), the control unit 79 moves the first scanning unit 15 to the position P1, for example, and positions the second scanning unit 16. Is also moved following the positioning (ST47). The position at this time is also determined in advance or different from the last reading position in the previous reading process.

  Then, the control unit 79 turns on the light source 15a of the first scanning unit 15 (ST48), and controls the irradiation light amount and performs shading correction (“Yes” in ST49). At the same time, after the timer is initialized, the timer starts measuring the continuous lighting time of the light source 15a (ST50). Further, the control unit 79 controls the document conveying unit 101 to convey and pass the document on the first platen glass 14, and simultaneously controls the document reading device 102 to perform the document reading process (ST51). .

  Also at this time, the light from the light source 15a and the reflected light from the original are transmitted through the vicinity of the position P1 of the first platen glass 14.

  Thereafter, the control unit 79 determines whether or not there is a next document (ST52). If there is no next document (“No” in ST52), the control unit 79 returns to a standby state.

  If there is a next document (“Yes” in ST52), control unit 79 determines whether or not the continuous lighting time counted by the timer is equal to or greater than the time threshold (ST53). If the lighting time is less than the time threshold (“No” in ST53), the process returns to ST51 to perform the next document reading process.

  Accordingly, the next original is read with the first scanning unit 15 positioned at the position P1.

  If ST51 to ST53 are repeated and the original is read one after another and the continuous lighting time by the timer continues to be measured, the continuous lighting time by the timer becomes equal to or greater than the time threshold (“Yes” in ST53). . At this time, the control unit 79 moves and positions the first scanning unit 15 to a position P2 or P3 different from the position P1, and positions the second scanning unit 16 by following movement (ST54). Then, returning to the process from ST48, the document reading process is continued.

  At this time, the light from the light source 15a and the reflected light from the document are transmitted through the first platen glass 14 near the position P2 or P3.

  The order of changing the position of the first scanning unit 15 in step ST54 may be determined in advance, for example, in a cyclic order of positions P1, P2, P3, and P1. In particular, if the position of the first scanning unit 15 is changed in the order of positions P1 → P2 → P3, the first scanning unit 15 is moved in the document conveyance direction. In this case, however, the first scanning unit 15 is continuously conveyed. When reading the front and back documents, the optical unit (first and second scanning units 15 and 16) starts moving immediately after the reading of the previous document, and moves the first scanning unit 15 following the gap between the front and back documents. The reading of the subsequent document can be started immediately after the optical unit is stopped. That is, the position of the optical unit can be changed by moving the optical unit with almost no interruption of the reading of the document.

  As described above, in the present embodiment, when reading a plurality of documents, if the continuous lighting time of the light source 15a is equal to or longer than the time threshold, the first scanning unit 15 is moved and its position is changed. The light from the light source 15a and the reflected light from the document are not continuously applied to the specific part of the first platen glass 14, and the temperature of the specific part of the first platen glass 14 does not increase excessively. Further, since the air flow by the fan changes as the first and second scanning units 15 and 16 move, the stagnation of air in the vicinity of the first and second scanning units 15 and 16 and the optical system is eliminated, and the temperature The rise is suppressed.

  In addition, this invention is not limited to said each embodiment, It can deform | transform variously. For example, instead of detecting the temperature of the first platen glass 14 with the temperature sensor, the temperature sensor detects the temperature of the first and second scanning units 15 and 16, more specifically the temperature of the reflection mirror and its holding member. Thus, the first and second scanning units 15 and 16 may be moved along the first platen glass 14 based on the detected temperature.

  Further, the positions where the first and second scanning units 15 and 16 are positioned may be increased or decreased.

  Furthermore, the document reading apparatus of the present invention can be applied not only to an image reading apparatus but also to a copier, a scanner, a printer, and a multifunction machine having a facsimile function.

1 is a cross-sectional view showing an image forming apparatus to which a first embodiment of a document reading apparatus of the present invention is applied. FIG. 2 is an enlarged cross-sectional view illustrating a part of the document reading apparatus according to the first embodiment. 6 is a flowchart illustrating a processing procedure for controlling movement of the first scanning unit 15 in the document reading apparatus according to the first embodiment. 10 is a flowchart illustrating a processing procedure for controlling movement of a first scanning unit 15 in a document reading apparatus according to a second embodiment. 10 is a flowchart illustrating a processing procedure for controlling movement of a first scanning unit 15 in a document reading apparatus according to a second embodiment. (A) is sectional drawing which shows partially the conventional original reading apparatus which employ | adopted the conveyance system, (b) is a graph which shows the temperature distribution of the platen glass of (a). It is a graph which shows the mode of the temperature rise of the platen glass in the conventional document reader.

Explanation of symbols

11 Document setting tray 12 Paper discharge tray 14 First platen glass 15 First scanning unit 16 Second scanning unit 17 Imaging lens 18 CCD
21 Photosensitive drum 22 Charger 23 Optical writing unit 24 Developer 25 Transfer unit 26 Cleaning unit 26A Cleaning blade 27 Fixing unit 35 Heating roller 36 Pressure roller 41a-41e Conveying roller 42 Registration roller 61 Pickup roller 62 Sakiki roller 63a-63f Paper Detection sensor 64 Pre-registration roller 71 Conveying belt 72 Drive roller 73 Driven rollers 74, 75 Conveying rollers 76, 77, 78 First, second, and third temperature sensors 79 Control unit 100 Image forming apparatus 101 Document conveying unit 102 Document reading Device 103 Printing section 104 Recording paper transport section 105 Paper feed section

Claims (7)

In an original reading apparatus that reads an image of an original by an optical unit positioned below the platen glass through the platen glass while conveying the original on the platen glass.
The original reading apparatus, wherein the optical unit is moved along the platen glass in accordance with a temperature displacement state inside the original reading apparatus, the position of the optical unit is changed, and image reading of the original is continued. . A temperature sensor for detecting the temperature of the light transmitting portion of the platen glass through which light from the light source of the optical unit or reflected light from the document is transmitted;
2. The document reading apparatus according to claim 1, wherein the light transmitting portion of the platen glass is changed by moving the light source of the optical unit in accordance with the temperature displacement detected by the temperature sensor. A number accumulation counter that counts the number of documents read continuously is provided.
The optical unit is moved to change the position of the optical unit when the number of originals counted by the number integration counter reaches a certain number that can cause a temperature displacement inside the original reading device. Item 2. The document reading device according to Item 1. A timer for measuring the light irradiation time of the light source;
2. The position of the optical unit is changed by moving the optical unit when the irradiation time measured by the timer reaches a certain number of sheets that can cause a temperature displacement in the document reading apparatus. The document reading device described.   2. The document reading apparatus according to claim 1, wherein the position of the optical unit is changed by moving the optical unit in the transport direction of the document on the platen glass. A transport means for transporting the document on the platen glass;
2. The document reading apparatus according to claim 1, wherein the transport unit transports the document while pressing the document on the platen glass.   7. The document reading apparatus according to claim 6, wherein the transport unit includes a white endless belt that is rotated and moves the document between the endless belt and the platen glass.

Images