JP2008005165A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet through type image reader to read an image and to more efficiently clean a platen glass surface. <P>SOLUTION: The sheet through type image reader configured to clean the platen glass surface by reciprocally moving the platen glass in press contact with a cleaning member on its surface in a document conveying direction, so that whether document conveyance intervals T when a plurality of documents are successively conveyed in a set document read mode are larger than a time Tsd needed for one reciprocal motion of the platen glass. (S1). When it is decided that T<Tsd ("NO" in S1), the reciprocal operation (cleaning) of the platen glass is inhibited (S6) and when it is decided that T≥Tsd ("YES" in S1), reciprocal operation of the platen glass is carried out (S3 to S5) after reading of a first document is completed and before a second document is started to be read. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet-through type image reading apparatus that reads an image of a document being conveyed on a translucent member via the translucent member, and in particular, an improvement in technology for preventing image quality deterioration caused by contamination of the translucent member. About.

In an image reading apparatus used for a copying machine or the like, an original is conveyed by an automatic document conveying device, and the original is disposed through the platen glass while passing through a reading position on the platen glass (translucent member). There is a so-called sheet-through system in which light is irradiated from a fixed light source and reflected light from a document portion located on a platen glass is received to read a document image.
In the case of the sheet-through method, if the reading position on the platen glass becomes dirty due to adhesion of dust, dirt, etc., even if this stain is dot-like, this stain is always read when reading the document. Streaks that are continuous in the sub-scanning direction (corresponding to the document transport direction) are generated in the image reproduced from the image data thus obtained.

As an image reading apparatus for preventing the generation of such streaks, Patent Document 1 discloses a sheet-through method in which a cleaning member for cleaning the platen glass surface is pressed against the platen glass surface and the platen glass is moved in the sub-scanning direction. The structure which cleans the dirt adhering to the platen glass surface by moving to is disclosed. The movement of the platen glass is performed immediately before the document conveyance, and the document conveyance is started after the movement is completed.
JP 2003-189060 A

However, in the image reading apparatus disclosed in Patent Document 1, for example, when a document is continuously conveyed, reading of the next document cannot be started until the movement of the platen glass is completed, so that the time required for cleaning the platen glass is adjusted. The document conveyance interval must be lengthened, and the efficiency of the reading process is reduced.
Although it is conceivable to perform cleaning after the document conveyance is finished in order to give priority to the reading process, if dust or the like adheres before the next reading, the dust or the like is read and the image quality deteriorates.

  The present invention has been made in view of the above problems, and in an image reading apparatus of a sheet-through method, an image reading apparatus capable of performing image reading and cleaning of the surface of a translucent member more efficiently. It is intended to provide.

  In order to achieve the above object, an image reading apparatus according to the present invention conveys a document and passes the reading position, while the reading position is set to the reading position by a light source arranged with a light-transmitting member interposed therebetween. A sheet-through-type image reading apparatus that reads a document image by irradiating light to an existing document portion and receiving reflected light from the document portion. A determination means for determining a document conveyance interval indicating a distance between the document and a second document conveyed to the reading position next to the first document; and a cleaning member that contacts the surface of the translucent member; A cleaning unit that cleans the dust adhering to the translucent member by the cleaning member; and the non-reading period from the end of reading of the first document to the start of reading of the second document. By cleaning means The 掃動 operation, characterized in that it comprises a control means for controlling in response to the determination result by the determination unit.

This makes it possible to effectively clean the surface of the light transmissive member without reducing the efficiency of the reading process.
Further, the control means performs cleaning when the determined document conveyance interval is equal to or longer than the time required for the cleaning operation, and prohibits cleaning when the determined time is shorter than the time.
In this way, the cleaning operation can be executed only when the cleaning operation can be completed within the non-reading period, and it is possible to prevent the cleaning operation from being completed at the start of reading the second document.

Here, the time is obtained based on a moving speed V and a moving distance D of the translucent member.
Furthermore, the minimum moving distance required for cleaning the dust is Dmin, the maximum movable distance is Dmax (≧ Dmin), the upper limit of the moving speed at which dust can be effectively removed is Vmax, and the lower limit is Vmin. The time is a value within a range from a value tmin obtained by dividing Dmin by Vmax to a value tmax obtained by dividing Dmax by Vmin.

In this way, the time required for cleaning can be set between tmin and tmax, and the degree of freedom when setting the moving distance and moving speed is increased.
Further, when the determined document conveyance interval is a time T, the control means can move the translucent member at a moving speed V and a moving distance D within a time within the range from the time tmin to the time T. It is characterized by selecting a set of

In this way, it is possible to set an optimum set of moving distance and moving speed.
And a document conveying means for conveying the document by switching between the first and second document reading modes having different document conveying intervals, and a receiving means for accepting selection of the document conveying mode. The determination is performed by reading information indicating a document transport interval preset as a document transport interval corresponding to the document transport mode.

In this way, it is possible to determine the document conveyance interval only by determining which document reading mode is selected, and it is not necessary to provide means for actually measuring the document conveyance interval.
Further, the cleaning means cleans the translucent member by moving the translucent member along the document conveying direction with the cleaning member fixed.
If it does in this way, it will become possible to clean by arranging only the mechanism which moves a translucent member.

Hereinafter, an embodiment of an image reading apparatus according to the present invention will be described by taking as an example a case where it is applied to a digital color copying machine (hereinafter simply referred to as “copying machine”).
(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of the copying machine 1.
As shown in FIG. 1, the copying machine 1 is roughly composed of a scanner unit 2 as an image reading device that reads an original image, and a printer unit 3 that prints and reproduces the read image on a recording sheet. .

  The scanner unit 2 is configured to be able to read a document image by both a sheet-through method that is one of fixed optical systems and a scanner moving method that is one of moving optical systems. Here, the sheet-through method is a method of reading while moving the document while the optical system is stationary (fixed). The scanner movement method is a state in which the optical path length from the original reading position to the CCD sensor is always kept constant by moving the mirror that guides the reflected light from the original surface to the CCD sensor while the original is stationary. This is a reading method.

  The scanner unit 2 includes an automatic document feeder 4 for realizing a sheet-through method. The automatic document feeder 4 separates the documents one by one from the bundle of documents set on the document feed tray 6 and passes the reading position G on the sheet-through platen glass 30 as a translucent member. The paper is discharged to the document discharge tray 24 and functions as a document transport unit. Here, it is configured to be able to switch between a single-sided reading mode for reading only one side of a document and a double-sided reading mode for reversing the document and sequentially reading both sides (front and back) of the document.

  In the single-sided reading mode, the uppermost document in the document bundle set on the document feed tray 6 is separated from the document bundle by the pickup roller 8 and the separating roller 10, and the registration roller pair via the first intermediate roller pair 12. 14 is conveyed. After the inclination (skew) is corrected here, the original is conveyed to the sheet-through platen glass 30 by the registration roller pair 14. A document image is read when the document passes through a reading position G on the sheet-through platen glass 30. The document that has passed over the sheet-through platen glass 30 is conveyed to the discharge roller pair 22 by the second intermediate roller pair 16 and the third intermediate roller pair 20, and discharged to the document discharge tray 24 by the discharge roller pair 22. Is done.

  On the other hand, in the double-sided reading mode, the switching claw 18 is switched to the broken line position in FIG. When the surface of the original is read, the original is conveyed from the second intermediate roller pair 16 to the fourth intermediate roller pair 26 via the switching claw 18, and the fourth intermediate roller pair 26 moves the conveyance path 28 in the direction of arrow B. To be transported. When the vicinity of the trailing edge of the document is conveyed to the position of the fourth intermediate roller pair 26, the fourth intermediate roller pair 26 rotates in the reverse direction and the switching claw 18 is switched to the solid line position.

  As a result, the original whose surface has been read is conveyed through the conveyance path 29 via the switching claw 18 with the conveyance path 28 switched back in the direction of the arrow C and the original rear end at the top. Then, the sheet is conveyed again to the registration roller pair 14 and is conveyed to the sheet-through platen glass 30 by the registration roller pair 14. At that time, the back surface of the document is opposed to the surface of the sheet-through platen glass 30. After the image on the back surface of the document is read when passing through the reading position G, the second intermediate roller pair 16, and discharged to the document discharge tray 24 via the third intermediate roller pair 20 and the discharge roller pair 22.

  Each roller described above is rotationally driven through a power transmission mechanism (not shown) using the motor M1 as a power source. A document registration sensor 15 is provided at a position downstream of the registration roller pair 14 in the document conveyance direction to detect the leading edge and the trailing edge of the conveyed document. Further, a document size detection sensor 11 for detecting the size of the set document is arranged in the document feed tray 6.

  The document passing over the sheet-through platen glass 30 is irradiated by the light source 34 of the scanner 32 that is stationary below the sheet-through platen glass 30. The reflected light from the document surface is changed in optical path by the first mirror 36, the second mirror 38 and the third mirror 40, formed on the CCD sensor 44 by the condenser lens 42, and photoelectrically converted into an image signal by the CCD sensor 44. Is done. The photoelectrically converted image signal is subjected to known image processing in the control unit 46 and then sent to the printer unit 3.

The printer unit 3 is a known electrophotographic image forming apparatus, and forms (prints) a document image on a recording sheet based on an image signal from the control unit 46.
In addition to the sheet-through platen glass 30, the copying machine 1 is provided with an original document placement platen glass 39 at a position facing the automatic document feeder 4.
As described above, when reading a document by the sheet through method, the scanner 32 is moved to a position indicated by a broken line below the platen glass 30 for sheet through, and the document conveyed by the automatic document conveying device 4 at this position. And read the original image.

On the other hand, when the original is placed on the manual placement platen glass 39 and read (when the scanner moving method is used), the automatic document feeder 4 is opened upward and the original is set on the manual placement platen glass 39. Is done.
With the document set, the scanner 32 is moved in the direction of arrow A in FIG. At this time, the second mirror 38 and the third mirror 40 are paired and move in the same direction as the scanner 32 at a speed that is half of the moving speed. The distance (optical path length) of the document is always kept constant, and the reflected light of the original is imaged on the light receiving surface of the CCD sensor 44. The scanner 32, the second mirror 38, and the third mirror 40 are driven to travel via a power transmission mechanism (not shown) using the motor M2 as a power source.

A sheet-through platen glass 30 (hereinafter abbreviated as “platen glass 30”) is movable in the document transport direction (corresponding to the sub-scanning direction).
FIG. 2 is a diagram illustrating a configuration example of a moving mechanism of the platen glass 30.
As shown in the drawing, the platen glass 30 is made of a plate-like glass that is elongated in the main scanning direction and is shown as an example of a translucent member. Here, the arrow Y in the figure indicates the sub-scanning direction, and the arrow X indicates the main scanning direction orthogonal to the sub-scanning direction. Note that the translucent member is not limited to glass, and may be a translucent plastic.

The platen glass 30 is fitted and held in a glass holder 52. A glass holder 53 in which the platen glass 30 is fitted is referred to as a glass unit 53.
The glass holder 52 is slidably held in the sub-scanning direction by a pair of glass holder guides 54 and 56 at both ends in the main scanning direction. The glass holder 52 has a pair of racks 58 and 60 protruding in the sub-scanning direction. A pair of pinions 64 and 66 attached to the shaft 62 are engaged with the racks 58 and 60. A spur gear 68 is attached to one end of the shaft 62, and the spur gear 68 meshes with the spur gear 69. A pulley 70 is integrally provided on one surface of the spur gear 69, and a belt 72 is stretched between the pulley 70 and the output shaft 71 of the motor M3.

  In the mechanism configured as described above, when the motor M3 is rotated in the direction of the arrow D (this is assumed to be normal rotation), the driving force of the motor M3 is the belt 72, the pulley 70, the spur gear 69, the spur gear 68, The light is sequentially transmitted to the shaft 62, the pinions 64 and 66, and the racks 58 and 60, whereby the glass holder 52 and the platen glass 30 are moved in the direction indicated by the sub-scanning direction arrow D. Further, when the motor M3 is rotated in the direction opposite to the arrow D (this is reversed), the glass unit 53 (platen glass 30) moves in the direction indicated by the sub-scanning direction arrow E. Here, the movement of the glass unit 53 (platen glass 30) in the direction indicated by the arrow D is defined as the forward movement, and the movement in the direction indicated by the opposite arrow E is defined as the backward movement.

The figure shows a state in which the glass unit 53 (platen glass 30) is in a position moved in the direction indicated by the arrow E (full side of the paper passing guide 51). This position is the home position.
Whether or not the platen glass 30 is at the home position is detected by the reference position detection sensor 55. The reference position detection sensor 55 is composed of, for example, a gap type photo sensor, and a part of the end portion of the glass holder 52 on the side of the paper passing guide 51 enters the gap of the gap type photo sensor (the platen glass 30). In a home position) and a state in which no gap exists (a state in which the platen glass 30 is not in the home position).

The document is conveyed in the direction of arrow E and passes over the platen glass 30. During this time, the document portion at the reading position G indicated by the alternate long and short dash line is irradiated by the light source 34, and the reflected light of the document portion is reflected by the CCD sensor 44. Will be detected.
The surface of the platen glass 30 is cleaned by a cleaning member 31 disposed on the frame 27 of the automatic document feeder 4 shown in FIG. The cleaning member 31 is made of a plate-like elastic body and is brought into contact with the surface of the platen glass 30 with a constant pressure.

FIG. 3 is a diagram schematically showing a state of cleaning by the cleaning member 31. For easy understanding, the platen glass 30 and the cleaning member 31 when the platen glass 30 is viewed from the direction of the arrow X in FIG. Only shows.
FIG. 3A shows a situation where dust 74 is attached on the position Ga on the surface of the platen glass 30 located at the home position. Here, the position Ga is a position corresponding to the reading position G when the platen glass 30 is located at the home position. Therefore, when reading is performed in a state where the dust 74 is attached as shown in the figure, the dust 74 is read together with the original image, and noise on the line is generated. In the figure, the distance from the downstream end surface 311 of the cleaning member 31 in the document transport direction to the position Ga is defined as d in the document transport direction.

  FIG. 3B shows a state in which the platen glass 30 has moved to the full position upstream in the document transport direction due to the forward movement. Here, the distance Ds indicates a stroke. Since the distance Ds> d, when the platen glass 30 moves, the dust 74 on the position Ga is blocked by hitting the end surface 311 of the cleaning member 31 in the middle of the movement, and the document conveyance direction from the position Ga on the surface of the platen glass 30 is blocked. It is located at a position M shifted by a distance (Ds-d) on the downstream side.

FIG. 3C shows a state when the platen glass 30 returns to the home position by the backward movement. Since the dust 74 exists at the position M on the surface of the platen glass 30 and does not exist (is removed) from the position Ga, the document image can be read without being influenced by the dust 74 after the reciprocation.
The reciprocating operation of the platen glass 30 is the second original that is conveyed to the reading position G next to the first original after the reading of the first original in the case of continuously reading the conveyed original is completed. Is controlled in accordance with the size of the first and second document transport intervals (hereinafter referred to as “document transport interval”) until the start of reading (hereinafter referred to as “non-reading period”). Is done. Details of this movement control will be described later.

Returning to FIG. 1, an operation panel 5 is arranged at a position on the upper surface of the copying machine 1 where it is easy to operate. The operation panel 5 is provided with a numeric keypad for setting the number of copies, a key for switching between double-sided and single-sided, high-resolution and low-resolution scanning, etc. as a document reading mode.
In addition, a non-mixed mode in which a document is continuously conveyed and read one by one from a stack of documents of the same size, and a plurality of documents of different sizes, for example, A3 (vertical) and A4 (horizontal) are stacked. A key or the like for switching between the mixed loading mode in which the originals are continuously conveyed and read one by one from the original bundle is also provided. The user can select each mode by pressing each key.

FIG. 4 is a block diagram illustrating a configuration of the control unit 46.
As shown in the figure, the control unit 46 includes a CPU 101, motor drive ICs 102 to 104 as main components, a ROM 105 storing programs necessary for each control, a RAM 106 serving as a work area during program execution, and an image processing unit. 107, an image memory 108, and a document conveyance interval information storage unit 109.

The motor driving ICs 102 to 104 are driver ICs for driving the motors M1 to M3. Here, stepping motors are used as the motors M1 to M3, and the motor M1 receives the excitation signals φ0 to φ3 from the CPU 101. -M3 is driven to rotate.
The image processing unit 107 performs various processes such as known shading correction and gradation correction on the image signal from the CCD sensor 44 to generate an image signal for printing, and stores the image signal in the image memory 108. The image signal stored in the image memory 108 is read out at the time of printing such as copying and used for printing.

The document conveyance interval information storage unit 109 includes a nonvolatile memory, and is provided with a document conveyance interval information table 121 in which information indicating the document conveyance interval (document conveyance interval information) is stored.
FIG. 5 is a diagram illustrating the contents of the document conveyance interval information table 121.
As shown in the drawing, the document conveyance interval information is information indicating the document reading mode and the document conveyance interval in association with each other. Here, the document conveyance interval indicates an interval when documents are continuously conveyed in the corresponding document reading mode, and the shortest readable time is set in advance. This is for increasing the number of reading processes per unit time and improving the reading efficiency.

For example, in the non-mixed mode, T1 (<Tsd), and in the mixed mode, T2 (≧ Tsd).
The reason why the document conveyance interval is larger in the mixed loading mode than in the non-mixed loading mode is as follows.
That is, in the non-mixed loading mode, all the document sizes are the same, and the document size can be detected before conveyance. Accordingly, the timing of paper feed, conveyance, reading, etc. can be fixed for each size, and the document conveyance interval T1 can be determined to be the shortest value from the document size, document conveyance speed, document reading processing speed, and the like.

  On the other hand, in the mixed loading mode, the sizes of the originals are different, and in the state where the originals are stacked as a bundle of originals, the size of each original cannot be detected before conveyance, and therefore the timing of paper feeding cannot be fixed. Therefore, it is assumed that a document having a size slightly larger than the maximum size is transported, and the timing of paper feeding is determined in advance, and by reading at the timing, what size document is printed for each sheet. Smooth reading can be performed even if the image is conveyed. In this case, since the size of the original document actually transported is smaller than the assumed document size, the document transport interval becomes larger than T1.

Tsd corresponds to the time required for reciprocating the platen glass 30 at a speed at which dust can be removed to a state where the image quality is not affected (time required for cleaning the dust).
In the present embodiment, whether or not the platen glass 30 needs to be reciprocated (cleaned) is determined by the size of the document conveyance interval T with reference to the Tsd. Specifically, the platen glass 30 is cleaned in the document transport mode in which the document transport interval T is Tsd or more, and cleaning is prohibited in the document transport mode shorter than Tsd.

  This is due to the following reason. That is, if the moving speed of the platen glass 30 is increased, the frequency with which small dust cannot be removed increases due to a decrease in the pressure contact force with the cleaning member 31 due to vibrations or an increase in the gap (cleaning capability decreases). Therefore, a document reading mode in which a moving speed Vsd that can remove dust to a state that does not affect the image quality is obtained in advance, and a document transport interval that is equal to or longer than the time Tsd required for one reciprocating operation by the moving speed Vsd can be secured. The reciprocating operation is permitted only when the document transport interval is shorter, and when the other document transport intervals are shorter than the time Tsd, the reciprocating operation is intentionally prohibited and the document transport interval is not extended for the reciprocating operation. This is so as not to lower the temperature.

FIG. 6 is a diagram showing the relationship between the moving speed V of the platen glass 30 and the frequency of occurrence of the case where the dust cannot be completely removed from the experimental results.
As shown in the figure, it can be seen that the frequency increases as the moving speed V increases. Here, the frequency refers to when the platen glass 30 is reciprocated at the moving speed V during the non-reading period every time the non-reading period comes when a predetermined number of documents, for example, 500 sheets are sequentially conveyed and read. Of the 500 originals, this indicates the number of originals in which the generation of streak noise due to dust that cannot be removed is recognized in the read image.

The moving speed V3 is a value indicating an upper limit value of a moving speed range in which dust can be removed up to a state that does not affect the image quality. In other words, when the moving speed is faster than V3, the frequency that the dust cannot be removed increases to the extent that the image quality is affected.
In the present embodiment, from the relationship with the moving distance (stroke) of the platen glass 30, the speed V1 in the figure is set as the above Vsd, and the time required for one reciprocating operation at the time of the V1 is set as the time Tsd. Take the case as an example.

The dust attached to the platen glass 30 has various sizes such as several μm to several hundred μm. The ability to clean such dust is based on the material of the cleaning member 31 and the pressure contact force with the platen glass 30. Needless to say, the values of V1 to V3 are not limited to the example shown in FIG.
Returning to FIG. 5, when the document reading mode is double-sided, two pieces of information T3 and T4 are written as the document conveyance interval. Here, T3 indicates the time required for conveyance from the end of reading of the front surface of the Nth document to the reverse of the N-side document for reading the back surface and the start of reading of the back surface. Indicates the time required from the end of reading the back side of the Nth original to the start of reading the front side of the (N + 1) th original. The reason why T3> T4 is that when the reading surface of the Nth document is switched from the front surface to the back surface, the document is reversed by the conveyance path 28, so that the reversal takes time. Here, an example in which a relationship of T4 <Tsd ≦ T3 is shown.

In the case of high image quality, the normal document conveyance interval other than memory full is T5, and the document conveyance interval when memory is full is T6.
Here, “memory full” means that a buffer (not shown) for storing the read image signal until various processing such as gradation correction is performed becomes full. In the case of low image quality, the speed of the correction process is set faster than the speed of the reading process. Therefore, when the read image signal is stored in the buffer, processing such as correction is performed in the order in which it is stored. Since the image signal is stored in the image memory 108, the buffer does not become full.

  However, in the case of high image quality, the number of pixels is doubled compared to the low image quality, so it takes time for correction, and the reading processing speed is faster than the correction processing speed. The buffer is full. When the buffer is full, thereafter, the original reading operation (original conveying operation) is temporarily stopped, and control for resuming the original conveying is performed after the buffer capacity increases. The document conveyance interval T6 is set as a time corresponding to this waiting time. Here, an example in which a relationship of T5 <Tsd ≦ T6 is shown.

This document conveyance interval information is written in advance in the document conveyance interval information table 121 when the apparatus is manufactured.
Returning to FIG. 4, the CPU 101 controls the operation of each unit such as the scanner unit 2 and the printer unit 3 based on the control program in the ROM 105, thereby realizing a smooth copy operation. Further, the detection signal from the document size detection sensor 11 is received, and the document size set in the document feed tray 6 is determined.

  Further, the detection signal from the document registration sensor 15 is received, and it is determined that the leading edge and the trailing edge of the conveyed document have passed the position of the document registration sensor 15. Further, the detection signal from the reference position detection sensor 55 is received, and it is determined whether or not the platen glass 30 is located at the home position. Further, it accepts a key input from the user via the operation panel 5 and determines which original reading mode is selected by the user. And a glass movement control process is performed.

FIG. 7 is a flowchart showing the contents of the glass movement control process. This process is executed when the feeding of the first document is started.
As shown in the figure, it is determined whether or not the document reading mode selected by the user satisfies the relationship of document transport interval T ≧ Tsd (step S1). This determination is made with reference to the document conveyance interval information table 121. Specifically, for example, when the mixed loading mode is selected, T2 ≧ Tsd, so that the relationship is satisfied, and when the non-mixed mode is selected, it is determined that the relationship is not satisfied. When the duplex reading mode is selected, it is determined that the relationship satisfies the relationship because T3 ≧ Tsd.

If it is determined that the relationship is not satisfied (“NO” in step S1), the cleaning operation of the platen glass 30 is prohibited (step S6), and the process proceeds to step S7.
On the other hand, if it is determined that the relationship is satisfied (“YES” in step S1), it is determined whether or not the trailing edge of the document has passed the reading position G (reading is completed) (step S2). This determination is made based on whether or not a predetermined time has elapsed since the trailing edge of the document being read was detected by the registration detection sensor 15. Here, the predetermined time corresponds to a value obtained by dividing the distance from the position of the registration detection sensor 15 on the conveyance path to the reading position G by the document conveyance speed.

  If it is determined that the trailing edge of the document has passed the reading position G (“YES” in step S2), it is determined whether or not the time is a timing satisfying the document conveyance interval T ≧ Tsd (step S3). This determination is made with reference to the document conveyance interval information table 121. Specifically, for example, in the double-sided reading mode, when T3 ≧ Tsd when the next reading is on the back side of the document, the timing satisfies T ≧ Tsd. When the next reading is on the surface of the document, T4 < Since it is Tsd, it is determined that it is not the timing.

Similarly, in the high image quality mode, for example, when the memory is full, T6 ≧ Tsd, and therefore, T ≧ Tsd is satisfied, and when the memory is not full, T5 <Tsd. To be judged. In the mixed loading mode and the non-mixed loading mode, it is determined that the timing satisfies T ≧ Tsd.
If it is determined that it is not time to satisfy T ≧ Tsd (“NO” in step S3), cleaning of the platen glass 30 is prohibited (step S6), and the process proceeds to step S7.

If it is determined that the timing satisfies T ≧ Tsd (“YES” in step S3), the stroke of the platen glass 30 is set to Ds, and the moving speed is set to V1 (step S4). Here, the moving speed V1 is Vsd.
Then, the platen glass 30 is reciprocated at the set stroke Ds and the moving speed V1 to perform cleaning (step S5), and the process proceeds to step S7. Specifically, an excitation signal for reciprocating the platen glass 30 at the moving speed V1 and the stroke Ds is supplied to the motor M3 via the motor driving IC 104.

Since T ≧ Tsd, the reciprocating operation of the platen glass 30 is completed within the non-reading period, that is, until reading of the next document is started (until the leading edge of the next document reaches the reading position G). It will be.
In step S7, it is determined whether there is a document to be read next. The determination of whether or not there is a document to be read is performed not only when a document that has not been read in the single-sided scanning mode is set, but also when the front side of one document has been read in the double-sided scanning mode. This is also performed when the image is reversed for reading and conveyed to the reading position G again.

If it is determined that there is a document, the process returns to step S1, and the processes after step S1 are executed.
For example, in the high image quality mode, when it is determined in step S3 that the time T ≦ Tsd is satisfied (memory full), the platen glass 30 is caused to reciprocate in steps S4 and S5.

Until it is determined in step S7 that the next document does not exist, the processes in and after step S1 are repeatedly executed. When it is determined that there is no document (“NO” in step S7), the glass movement process is terminated.
FIG. 8 is a timing chart showing the presence or absence of movement of the platen glass 30 in each document reading mode.

FIG. 8A shows an example in the non-mixed mode. Since the document transport interval T1 <Tsd, the time point t1 (when the first document reading (first document reading) ends) to the time point t2 (second document reading (second document reading) starts) ) (Corresponding to the non-reading period), the platen glass 30 remains stopped.
FIG. 8B shows an example in the mixed loading mode. Since the document transport interval T2 ≧ Tsd, the platen glass 30 is reciprocated once between t1 and t2.

FIG. 8C shows an example in the double-sided reading mode. Between time t1 (when reading of the front side of the first sheet (reading of the first document) ends) and time point of t2 (when reading of the back side of the first page (reading of the second document) is started) (corresponding to a non-reading period) In FIG. 5, since the document conveyance interval T3 ≧ Tsd, the platen glass 30 is reciprocated once.
Between time t3 (when reading of the back side of the first sheet (reading of the first original)) and time point of t4 (when starting reading of the front side of the second sheet (reading of the second original)) (corresponding to a non-reading period) The platen glass 30 remains stopped because the document conveyance interval T4 <Tsd.

FIG. 8D shows an example in the case of the high image quality mode. From the time point t1 (when the first sheet reading (first document reading) ends) to the time point t2 (when the second sheet reading (second document reading) starts) (corresponding to a non-reading period), Since the memory is not full, the document conveyance interval T5 <Tsd, and the platen glass 30 remains stopped.
Since the memory is full at the end of reading the second sheet, the time point t3 (at the end of reading the second sheet (reading the first document)) to the time point t4 (reading the third sheet (reading the second document)) ) (Corresponding to a non-reading period), the document conveyance interval T6 ≧ Tsd, and the platen glass 30 is reciprocated once.

As described above, in this embodiment, since the necessity of the cleaning operation of the platen glass 30 in the non-reading period is controlled according to the size of the document conveyance interval in the document reading mode, the efficiency of the reading process is reduced. Therefore, the platen glass 30 can be effectively cleaned.
The moving speed V of the platen glass 30 is preferably a low speed as described above. However, if the speed is too low, the time required for the reciprocating operation increases, and there may be no case where the relationship T ≧ Tsd is satisfied. It is done. As shown in FIG. 6, since there exists a speed range (V1 to V3, etc.) that does not affect the image quality, an optimum value is obtained from an experiment or the like based on the relationship with the minimum required moving distance d of the platen glass 30. It is determined.

(Second Embodiment)
In the above embodiment, the configuration example in which the platen glass 30 is moved at the predetermined speed Vsd has been described. However, in this embodiment, the moving speed and the moving distance are changed according to the size of the document conveyance interval. This point is different from the first embodiment. Hereinafter, for the convenience of description, the description of the same contents as those of the first embodiment is omitted, and the same components are denoted by the same reference numerals.

FIG. 9 is a diagram showing the contents of the document conveyance interval information table 131 according to the present embodiment.
As shown in the drawing, the document conveyance interval information is information in which the document conveyance interval (time), the movement speed, and the movement distance are associated with each other. Here, the moving speed Vmax is an upper limit value of a moving speed range in which dust can be removed until dust does not affect the image quality (which can be effectively cleaned), and indicates a moving speed corresponding to V3 shown in FIG. ing.

Further, the moving speed Vmin is a moving speed that can ensure sufficient cleaning performance (lower limit sufficient to clean the dust) without lowering the speed, and corresponds to V1 shown in FIG. Is shown.
Furthermore, the movement distance Dmin is a movement distance that is the minimum necessary for cleaning the garbage, and indicates a distance corresponding to the distance d shown in FIG. Further, the moving distance Dmax is a maximum movable distance of the cleaning member 31 and indicates a distance corresponding to the distance Ds (stroke) shown in FIG. Note that it is desirable to increase the movement distance D. This is because as the moving distance D increases, the dust can be moved away from the portion corresponding to the reading position G on the platen glass 30 in the sub-scanning direction, and the dust once removed from the reading position G vibrates due to the movement of the platen glass 30. This is because it is possible to further reduce the possibility that the original reading position G is returned to and read.

The document conveyance interval T corresponds to the movement time t of the platen glass 30 and shows a value obtained by dividing the movement distance D by the movement speed V, for example, Tmin = Dmin / Vmax.
Each value of the document conveyance interval T is a value that can be taken as the movement time t of the platen glass 30 from the combination of the movement distance D and the movement speed V in the range of Dmin to Dmax and Vmin to Vmax. . This figure shows an example in which the moving speed V is set so as to decrease as the document conveyance interval T increases from Tmin. Since the document conveyance interval T and the movement time t of the platen glass 30 are set to be equal, the reciprocating operation of the platen glass 30 can be terminated when reading of the next document is started.

Dmin to Dmax means a distance range in which dust adhering to the position Ga (corresponding to the reading position G) on the surface of the platen glass 30 can be removed from the reading position G by the cleaning member 31, and Vmin to Vmax are This means a speed range in which dust can be removed until it does not affect the image quality.
Therefore, if the moving speed V and the moving distance D adapted to the document transport interval T are determined in advance within the above range from experiments and written in the document transport interval information table 131, the document transport interval T depends on the document size and the like. Even in such a case, the movement of the platen glass 30 can be controlled with the moving speed V and the moving distance D suitable for the document conveying interval T.

  The document transport interval T and the movement time t of the platen glass 30 are not limited to the same value. For example, (document transport interval T) = (movement time t of the platen glass 30) + (predetermined time) may be used. Even if the time required for the movement of the platen glass 30 varies, the relationship between the document conveyance interval T> the movement time t of the platen glass 30 can be satisfied by absorbing the variation for a predetermined time. The reciprocating operation can be terminated before the reading of the next original is started.

  FIG. 10 is a flowchart showing the contents of the glass movement control process according to the present embodiment. As shown in the figure, first, the document conveyance interval T is measured (step S11). Here, after receiving from the document registration sensor 15 a signal indicating that the trailing edge of the document being read (first document) has passed the detection position of the document registration sensor 15, the document to be read next (the first document) This is performed by measuring the time until a signal indicating that the leading edge of the second original) has passed the detection position.

Then, it is determined whether or not the relationship of measurement time <Tmin is satisfied (step S12). Here, Tmin corresponds to Tmin written in the document conveyance interval information table 131.
If it is determined that the measurement time <Tmin is satisfied (“YES” in step S12), cleaning of the platen glass 30 is prohibited (step S16), and the process proceeds to step S17.

On the other hand, when it is determined that the measurement time <Tmin is not satisfied, that is, the measurement time ≧ Tmin (“NO” in step S12), the moving speed V and the movement of the platen glass 30 are referred with reference to the document conveyance interval information table 131. A distance D is set (step S13).
For example, when the measurement time is (Tmin + 0.04) [seconds], the combination of the movement speed V and the movement distance D of the platen glass 30 when the movement time of the platen glass 30 becomes (Tmin + 0.04) or less. Is selected.

  Specifically, the following three are: (A) Combination of movement speed (Vmax-4) and movement distance Dmin, (A) Combination of movement speed (Vmax-2) and movement distance Dmin, and (C) Movement speed. One of the combinations of Vmax and the movement distance Dmin is selected. Here, the moving speed and moving distance corresponding to the measurement time, (a) in the above example is selected, and the selected moving speed V and moving distance D are set, but other combinations are taken. It is also good.

Next, it is determined whether or not the trailing edge of the document being read has passed the reading position G (step S14). This determination is made by the method as in step S2.
When it is determined that the trailing edge of the document has passed the reading position G (“YES” in step S14), the platen glass 30 is reciprocated at the moving speed V and the moving distance D set in step S12 to perform cleaning. (Step S15). Specifically, an excitation signal for reciprocating the platen glass 30 at a set moving speed V and moving distance D is supplied to the motor M3 via the motor driving IC 104.

FIG. 11 is a timing chart showing how the platen glass 30 moves.
FIG. 11A shows an example in which the document conveyance interval T is Tmin + n ′ (> Tmin + n) shown in FIG. 9 (moving speed Vmin, moving distance Dmax). FIG. 11B shows an example when the document conveyance interval T is Tmin + m (movement speed Vmin, movement distance Dmin + 2), and FIG. 11C shows the case where the document conveyance interval T is Tmin (movement speed Vmax, movement distance). Dmin) is shown as an example.

Since both satisfy the relationship of movement time t ≦ measurement time (document transport interval T) of the platen glass 30, when the leading edge of the next document reaches the reading position G (within the non-reading period), the platen glass 30. This means that the reciprocating operation has been completed.
Returning to FIG. 10, in step S17, it is determined whether there is a document to be read next. If it is determined that it exists, the process returns to step S11 and the subsequent processing is executed.

Until it is determined in step S17 that there is no next original, the processes in and after step S11 are repeatedly executed. If it is determined that there is no next original ("NO" in step S17), the glass movement process is terminated.
As described above, in the present embodiment, the values of the moving speed and moving distance of the platen glass 30 are set according to the document conveyance interval. Accordingly, for example, if the mechanism is such that even if the moving speed of the platen glass 30 is increased, the cleaning ability is not easily lowered due to vibration or the like, the moving speed is increased to some extent to set the moving distance as long as possible. On the other hand, if the mechanism is prone to decrease in cleaning ability when the moving speed is increased, the moving speed is set to be as slow as possible while securing the minimum moving distance, and the number of times of cleaning is increased as much as possible. Arbitrary settings such as setting the moving speed and the like can be made according to the configuration of the apparatus and the like, so that the degree of freedom of design is widened and the cleaning ability of the platen glass 30 can be further improved.

In the above description, as the document conveyance interval T, the interval immediately after passing through the registration roller pair 14 is measured, but is not limited thereto. The document transport interval T can be known. For example, a sensor similar to the registration sensor 15 is arranged near the first intermediate roller pair 12 and the interval immediately after passing through the first intermediate roller pair 12 is measured as the document transport interval T. Also good.
Moreover, it is not restricted to measuring. For example, if the document conveyance interval is stored in advance in association with each document reading mode as in the first embodiment, the document conveyance interval corresponding to the set document reading mode is read from the storage unit. You can also

  The present invention is not limited to the image reading apparatus, and may be a method for executing the movement control. Furthermore, the method may be a program executed by a computer. The program according to the present invention includes, for example, a magnetic disk such as a magnetic tape and a flexible disk, a light such as a DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, PD, and BD (Blu-ray Disc). It can be recorded on various computer-readable recording media such as recording media, flash memory recording media such as Smart Media (registered trademark), and may be produced, transferred, etc. in the form of the recording media. In some cases, the program is transmitted and supplied via various wired and wireless networks including the Internet, broadcasting, telecommunication lines, satellite communications, and the like.

  Further, the program according to the present invention does not have to include all modules for causing the computer to execute the processing described above. For example, a separate information process such as a communication program or a program included in an operating system (OS) is performed. You may make it make a computer perform each process of this invention using the various general purpose programs which can be installed in an apparatus. Accordingly, it is not always necessary to record all the modules on the recording medium of the present invention, and it is not always necessary to transmit all the modules. Further, there are cases where predetermined processing can be executed using dedicated hardware.

(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above embodiment, as a cleaning means for cleaning the surface of the platen glass 30, the platen glass 30 is conveyed without moving the cleaning member 31 in a state where the cleaning member 31 is pressed against the surface of the platen glass 30. Although an example of a mechanism that reciprocates in the direction has been described, it is needless to say that the mechanism is not limited to this as long as the surface of the platen glass 30 can be cleaned. For example, a mechanism for reciprocating the cleaning member 31 without moving (fixing) the platen glass 30 may be employed, or a mechanism for relatively moving both members so as to create a speed difference may be employed.

(2) The moving mechanism of the platen glass 30 is not limited to the rack and pinion mechanism described above. It is only necessary that the platen glass 30 can be moved in a direction necessary for cleaning. For example, a configuration in which the platen glass 30 is moved by using a so-called screw feeding mechanism can be adopted.
(3) In the above embodiment, an example in which the image reading apparatus of the present invention is applied to a copying machine has been described. However, in general, a sheet-through type image reading apparatus such as a scanner, a facsimile machine, or an MFP (Multiple Function Peripheral) is used. Applicable.

  Further, the above embodiment and the above modification examples may be combined.

  The present invention can be widely applied to sheet-through type image reading apparatuses.

1 is a diagram showing a schematic configuration of a digital color copying machine 1 according to a first embodiment. 3 is a diagram illustrating a configuration example of a moving mechanism of a sheet-through platen glass 30 disposed in the copying machine 1. FIG. It is the figure which showed typically the mode of cleaning of the platen glass 30 surface for sheet through by the cleaning member 31. FIG. 2 is a block diagram illustrating a configuration of a control unit 46 of the copying machine 1. FIG. 6 is a diagram illustrating contents of a document conveyance interval information table 121 of a control unit 46. FIG. It is the figure which showed from the experimental result the relationship between the moving speed V of the platen glass 30 for sheet through, and the frequency that the case where dust cannot be removed completely occurs. It is a flowchart which shows the content of the glass movement control process which the control part 46 performs. 6 is a timing chart showing a state of presence or absence of movement of a platen glass 30 in each document reading mode. It is a figure which shows the content of the document conveyance space | interval information table 131 which concerns on 2nd Embodiment. It is a flowchart which shows the content of the glass movement control process which concerns on 2nd Embodiment. 4 is a timing chart showing how the platen glass 30 moves.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier 2 Scanner part 4 Automatic document conveying apparatus 5 Operation panel 30 Platen glass 31 Cleaning member 46 Control part 121,131 Document conveyance interval information table M3 Motor G Reading position

Claims (7)

While the original is transported and passed through the reading position, light is irradiated to the original portion at the reading position by a light source disposed through the light transmitting member between the reading position and reflected light from the original portion. Is a sheet-through type image reading device that receives an image and reads a document image,
A determination unit for determining a document conveyance interval indicating a distance between a first document and a second document conveyed to a reading position next to the first document in a case where the conveyed document is continuously read;
A cleaning member that contacts the surface of the translucent member, and cleaning means for cleaning the dust adhering to the translucent member by the cleaning member;
Control means for controlling a cleaning operation by the cleaning means in a non-reading period from the end of reading of the first original to the start of reading of the second original in accordance with a determination result by the determination means;
An image reading apparatus comprising: The control means includes
The image reading apparatus according to claim 1, wherein cleaning is performed when the determined document conveyance interval is equal to or longer than a time required for the cleaning operation, and cleaning is prohibited when the determined document transport interval is shorter than the time.   The image reading apparatus according to claim 2, wherein the time is obtained based on a moving speed V and a moving distance D of the translucent member. The minimum moving distance required for cleaning the light transmitting member is Dmin, the maximum movable distance is Dmax (≧ Dmin), the upper limit of the moving speed at which dust can be effectively removed is Vmax, and the lower limit is Vmin. When
The time is
4. The image reading apparatus according to claim 3, wherein the image reading apparatus has a value in a range from a value tmin obtained by dividing Dmin by Vmax to a value tmax obtained by dividing Dmax by Vmin. The control means includes
When the determined document conveyance interval is time T, a set of a moving speed V and a moving distance D at which the translucent member can be moved within a time range between the time tmin and the time T is selected. The image reading apparatus according to claim 4, wherein: A document conveying means for conveying the document by switching between the first and second document reading modes having different document conveyance intervals;
Receiving means for accepting selection of a document transport mode,
The determination means includes
6. The determination according to any one of claims 1 to 5, wherein the determination is performed by reading information indicating a document transport interval preset as a document transport interval corresponding to the selected document transport mode. Image reading apparatus. The cleaning means includes
The image according to any one of claims 1 to 6, wherein the translucent member is cleaned by moving the translucent member along a document conveying direction in a state where the cleaning member is fixed. Reader.

Images