JP2006053398A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recording apparatus capable of performing an optimum printing control in accordance with the whole moisture content of a recording paper by measuring the moisture content at multiple points of the recording paper. <P>SOLUTION: Regarding the image forming apparatus where the recording paper P is fed to a printing section by a plurality of carrying rollers 22a, then, an image is printed on the fed recording paper P by an ink head 120, a moisture sensor 100 is arranged on the recording paper P carrying path, and the moisture content of the recording paper P is measured by the moisture sensor 100 while carrying the recording paper P. and the moisture content at the multiple points of the recording paper P in the carrying direction is detected, and the ink discharge rate of the ink head 120 is controlled in accordance with the moisture content at the multiple points of the recording paper P detected by the moisture sensor 100. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, or an ink jet printer that forms an image on a sheet-like recording paper, and more particularly to an image forming apparatus that detects the water content of the recording paper.

  In an image forming apparatus such as an electrophotographic copying machine or an ink jet printer, the image quality is affected by changes in the paper quality and moisture content of the transfer paper used. For this reason, a sensor for detecting the moisture content of the transfer paper is provided, and it is configured to perform good recording by controlling the mechanism part of the image forming apparatus and printing control such as transfer current according to the sensor output. . FIG. 1 shows a configuration of a general electrophotographic copying machine.

  FIG. 1 shows the internal structure of an electrophotographic copying machine. A photoconductive drum 12 is disposed in the approximate center of the main body 11 of the electrophotographic copying machine 10. Around the photosensitive drum 12, there are provided a charging device 13, an exposure position 14 a by the optical device 14, a developing device 16, a transfer peeling charger 17, a cleaning device 18, and a static elimination lamp 20.

  Further, on the right side of the main body 11, a paper feed cassette 21 that stores sheet-like recording paper P is provided. The recording paper P in the paper feed cassette 21 is sequentially fed to the transfer portion between the photosensitive drum 12 and the transfer peeling charger 17 through the paper feed portion.

  In the main body 11, the recording paper P taken out from the paper feeding cassette 21 by the pickup roller 22 and fed through this paper feeding portion passes through the transfer portion of the photosensitive drum 12 and is discharged on the left side of the main body 11. A paper conveyance path 24 for leading to the tray 23 is formed.

  A separation roller 25 and a registration roller pair 26 are provided on the upstream side of the photosensitive drum 12 in the paper conveyance path 24, and a conveyance belt 27, a fixing roller pair 28, and a paper discharge roller pair 30 are provided on the downstream side. ing.

  On the upper surface of the main body 11, a document table (transparent glass) 34 on which the document D is placed and a white platen sheet 35 a are provided, and a document cover 35 that covers the document table 34 is provided, and an operation unit (not shown). Not provided). A document scale 32 serving as a guide for placing the document D is provided on the front end side (paper discharge side) of the document around the document table 34.

  The optical device 14 includes an exposure lamp 36, mirrors 37a, 37b, 37c, 37d, 37e, and 37f, and a lens block 15.

  The exposure lamp 36 and the mirrors 37a, 37b, and 37c are moved in the direction of the arrow S in the drawing along the lower surface of the document table 34. With this movement, the document D on the document table 34 is exposed and scanned. .

  The document D placed on the document table 34 is irradiated with light from the exposure lamp 36 as the optical system moves. The reflected light from the document D is guided to the exposure position 14a of the photosensitive drum 12 through the mirrors 37a, 37b, and 37c, the lens block 15, and the mirrors 37d, 37e, and 37f in this order, and the surface is uniformed by the charging device 13. The image is formed on the surface of the photosensitive drum 12 charged with a negative voltage.

  By exposing the image at the exposure position 14a, an electrostatic latent image is formed on the surface. The electrostatic latent image is visualized by attaching toner by the developing device 16. On the other hand, the recording paper P taken out from the paper feeding cassette 21 is sent in the direction of the photosensitive drum 12 by the registration roller pair 26 in synchronization with this.

  The toner image on the photosensitive drum 12 is transferred to the recording paper P by the action of the transfer peeling charger 17 in the transfer portion. The transferred recording paper P is sent to the fixing roller pair 28 by the transport belt 27, and after the transfer image is fixed here, it is discharged onto the paper discharge tray 23 outside the main body 11 by the paper discharge roller pair 30. Is done.

  The transferred photosensitive drum 12 is returned to the initial state by removing the residual toner on the surface by the cleaning device 18 and erasing the residual image by the charge eliminating lamp 20.

  As described above, the recording paper P taken out from the paper feed cassette 21 is fed from the direction of the arrow in the drawing, passes through the paper feed guides 41 and 42 in order, and is temporarily stopped at the position of the registration roller pair 26. Thereafter, the paper is guided on the paper conveyance guide 43 by the registration roller pair 26 and guided to the transfer portion between the photosensitive drum 12 and the transfer peeling charger 17.

  In the electrophotographic copying machine as described above, the moisture content of the recording paper P is measured, and when the moisture content is high, the transfer current is controlled to increase when the moisture content is high. When the amount is small, there is a method of obtaining a high-quality image by reducing the transfer current and optimizing the transfer condition of the transfer portion (see, for example, Patent Document 1).

In addition, there is an apparatus in which a humidity sensor is used to measure the moisture content of the recording paper, and the humidity sensor is provided in a paper feed cassette (see, for example, Patent Document 2).
JP-A-6-266249 JP-A-6-262794

  As described above, it is known that the water content of paper greatly affects the print quality and paper conveyance. For this reason, a humidity sensor or the like is provided, the water content of the paper is measured, and control according to the humidity is performed. In the conventional image forming apparatus, one location of the recording paper is measured with a moisture sensor, and the moisture content of the recording paper is measured. However, in the measurement method described above, only the moisture content of a part of the recording paper is measured, and when the moisture content of the recording paper is unevenly distributed depending on the location, the difference from the measured location becomes large, and the moisture sensor When the control is performed based on the detected output, there is a case where the control is not preferable for the entire recording paper, and there is a problem that the print quality is deteriorated.

  The present invention has been made in view of the above-described conventional problems, and can measure the moisture content of recording paper at a plurality of locations and perform optimum printing control according to the entire moisture content of the recording paper. An object is to provide an image recording apparatus.

  The present invention provides an image forming apparatus in which a recording sheet is fed to a printing unit by a recording sheet conveying unit, and an image is formed on the fed recording sheet by a printing unit. Measure the moisture content of the recording paper with the moisture sensor in the transported state, detect the moisture content of the recording paper from a plurality of locations in the recording paper transport direction, and according to the moisture content of the recording paper at the plurality of locations detected by the moisture sensor The printing control of the image forming apparatus is performed.

  An optical humidity sensor may be used as the moisture sensor.

  Furthermore, the present invention may be configured such that a plurality of moisture sensors are arranged in a direction orthogonal to the recording paper conveyance direction.

  According to the above configuration, it is possible to easily detect the moisture content of a plurality of locations on the recording paper, and therefore it is possible to accurately measure the moisture content of the entire recording paper, which is suitable for the moisture content of the recording paper. Printing control can be performed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the arrangement of the moisture sensor of the image forming apparatus according to the first embodiment of the present invention, FIG. 3 is a diagram showing the output of the moisture sensor, and FIG. 4 is according to the first embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an image forming apparatus.

  As shown in FIGS. 2 and 4, the conveyance path of the image forming apparatus according to the present invention is provided with a plurality of conveyance rollers 22a as recording paper conveyance means. The recording paper P taken out from the paper feeding unit is fed into the printing unit. A moisture sensor 100 is provided in this transport path. The moisture sensor 100 includes a light emitting unit 101 made of a light emitting diode having a light emission intensity in the near infrared region, and a light receiving unit 102 that receives the reflected light emitted from the light emitting unit 101 and reflected by the object to be measured. The reflectance according to the reflected light received by the light receiving unit 102 is obtained, and the water content of the recording paper P is obtained from the calculated reflectance.

  As described above, the moisture sensor 100 includes the near-infrared region, that is, a light emitting diode having an emission intensity in the water absorption wavelength band of 1.45 μm or 1.9 μm, and the near-infrared region, ie, the water absorption wavelength band. It is composed of an optical sensor having a sensitivity of 1.45 μm or 1.9 μm. The absorption band of water is 1.45 μm and 1.9 μm, and the light emitted from the light emitting diode is absorbed according to the water content, the reflected light reflected from the recording paper changes, and the output of the optical sensor changes. . The water content is detected from this change in output. The water content is expressed as a moisture content (%), and is expressed as a percentage of the original weight of the difference between the weight of an arbitrary state of the sample and its absolute dry weight.

  In the above example, the moisture sensor 100 is provided in the conveyance path on the downstream side from the paper feed unit, but the moisture sensor 100 may be arranged on the upstream side of the pickup roller of the paper feed cassette 21.

  After the moisture content of the recording paper P is measured by the moisture sensor 100, the printing unit 120, in this embodiment, is applied to an ink jet printer, and therefore the recording paper P is conveyed to the ink head 120. Then, the ink head 120 is driven under printing conditions suitable for the calculated water content of the recording paper P, and an image is formed on the recording paper P.

  In this embodiment, the moisture content of the recording paper P is measured in a state where the recording paper is transported by the transport roller 22a, that is, in a state where the recording paper is moving. Since the moisture sensor 100 measures the moving recording paper P, the moisture content from the leading edge to the trailing edge of the recording paper P is measured in time series. That is, as the output of the moisture sensor 100, as shown in FIG. 3, an output that changes with time is obtained, and it is possible to grasp which position of the recording paper P is measured over time from the relationship with the conveyance speed. As a result, a single moisture sensor 100 can measure moisture at a plurality of locations on the recording paper P, for example, at a plurality of locations such as the leading edge, middle portion, and trailing edge of the recording paper. Then, according to the measurement results at a plurality of locations, the moisture content of the entire recording paper is estimated, and the printing control suitable for the recording paper can be performed by performing the printing control according to the estimated moisture content. There are various methods for estimating the water content. For example, the average moisture content is calculated from a plurality of detection results, the value is used as the moisture content of the recording paper, the maximum moisture content is calculated, the value is controlled as the moisture content, and the minimum moisture content is calculated. The moisture measurement may be appropriately selected depending on the printing control location and application such as a method of controlling the value as the water content.

  The moisture sensor 100 obtains reflected light amounts at a plurality of locations while the recording paper P is being conveyed. The reflectivity by the amount of reflected light is obtained in the range of 5% <reflectance <80%, for example.

  FIG. 5 is a block diagram showing the configuration of the image forming apparatus according to the present invention. The light emitting unit 101 of the moisture sensor 100 is configured by a light emitting diode having a light emission intensity in the near infrared region, that is, a water absorption wavelength band of 1.45 μm or 1.9 μm, and lighting control is performed by the light emitting unit driving circuit 103. . The light emitting unit driving circuit 103 is controlled by a control unit 110 configured with a microcomputer or the like.

  The light receiving unit 102 of the moisture sensor 100 is composed of an optical sensor having sensitivity in the near infrared region, that is, the water absorption wavelength band of 1.45 μm or 1.9 μm, and a voltage corresponding to the amount of light received detected by the light receiving unit 102. Is converted into digital data by the A / D conversion circuit 104 and supplied to the control unit 110.

  The received light amount data converted into digital data is stored in the memory 111, and a plurality of data along the conveyance direction of the recording paper P is stored in the memory 111. The control unit 110 controls the paper control unit 105 such as the conveyance roller 22a and controls the conveyance of the recording paper P.

  The control unit 110 includes a table indicating a relationship between reflectance and moisture content based on data obtained by measuring reference paper having a predetermined reference moisture content that is set in advance as a reference. Based on this table, the water content is calculated by the output from the light receiving unit 102.

  In this table, for example, a reference paper having a predetermined reference moisture content that is set in advance as a reference is measured by the moisture sensor 100, and the reflectance of the paper is calculated from the amount of received light detected by the light receiving unit 102. Then, a conversion table of the reflectance and a predetermined reference moisture content (water content) is created.

  Table 1 shows an example of a conversion table showing the relationship between the calculated reflectance and moisture content.

  Note that when color paper is used as recording paper, the reflectance is different from that of white paper, so the value of the conversion table is different from that of white paper. In such a case, by adding a light-emitting unit and a light-receiving unit having a band in the visible light region, it is possible to perform more accurate control if the conversion table is switched by the sensor output in the visible light band. Yes.

  The control unit 110 calculates the moisture content of the recording paper based on the calculated reflectance, and calculates the moisture content at a plurality of locations in the conveyance direction of the recording paper P. Print control of the ink head 120 is performed.

  When the recording paper P runs out, the sensor output outputs an abnormal value. The control unit 110 may be configured to determine that there is no recording paper based on the abnormal value. Further, when the moisture sensor 100 detects the reflectance within the assumed range, the moisture content is detected based on the detected reflectance, and the moisture content of the recording paper P as a whole is estimated according to the measurement results at a plurality of locations. Then, the control unit 110 controls the ink head 120 according to the estimated water content.

  For example, when the present invention is used in an ink jet printer, the amount of ejected ink is increased when the moisture content of the recording paper is low, and the amount of ejected ink is decreased when the moisture content is large. That's fine.

  Next, the operation of the control unit of the first embodiment in which the present invention is used in an ink jet printer will be described with reference to the flowchart of FIG. When the operation is started, the process waits until a print request is issued (step S1). When the print request is issued, the paper conveyance unit 105 is controlled to start conveyance of the recording paper P (step S2). And the data of the some location of a recording paper conveyance direction are taken in from the moisture sensor 100, and the moisture content corresponding to a some location is measured (step S3).

  Subsequently, in this embodiment, the average water content is calculated from the calculated water content at a plurality of locations (step S4).

  Subsequently, it is determined whether or not the calculated water content is a low water content, and whether or not the water content is less than 5% (step S5). If the calculated water content is less than 5%, it is determined that the water content is low, and ink ejection is performed. Printing is performed with an increased amount (step S6), and after printing, the conveyance is stopped (step S10), and it is determined whether or not printing is finished (step S11). When printing is finished, the operation is finished.

  It is determined whether or not the calculated water content is a low water content and whether or not the water content is less than 5% (step S5). If the calculated water content is 5% or more, subsequently, whether or not the calculated water content is a high water content. It is determined whether or not the water content exceeds 10% (step S7). If the water content exceeds 10%, it is determined that the water content is high, the ink discharge amount is reduced and printing is performed (step S8), and After printing, the conveyance is stopped (step S10), and it is determined whether or not printing is finished (step S11). When printing is finished, the operation is finished.

  In step S7, if the calculated water content is determined to be 10% or less, it is determined that the water content is optimal, and printing is performed with an appropriate ink discharge amount (step S9). Then, the conveyance is stopped (step S10), and then it is determined whether or not the printing is finished (step S11). When the printing is finished, the operation is finished.

  Next, another embodiment of the present invention will be described with reference to FIGS. In the above-described embodiment, one moisture sensor 100 is provided in the conveyance path, but in other embodiments, a plurality of moisture sensors 100a to 100e are arranged in a direction orthogonal to the conveyance direction. In the first embodiment, since only one moisture sensor 100 is arranged in the direction orthogonal to the transport direction, only one line of water content can be obtained in the direction orthogonal to the transport direction. In this other embodiment, the plurality of moisture sensors 100a to 100e are arranged in a direction orthogonal to the transport direction. As shown in FIG. 8, the water content on the scanning line can be obtained from each of the moisture sensors 100a to 100e. Then, by arranging a plurality of sensors in a direction orthogonal to the conveyance direction, a plurality of points can be detected from end to end in the direction orthogonal to the conveyance direction. As a result, the water content of the entire recording paper P can be detected with higher accuracy.

  Next, the operation of the control unit when another embodiment of the present invention is used in an ink jet printer will be described with reference to the flowchart of FIG. In this embodiment, the ink head is configured to scan and print in a direction orthogonal to the transport direction.

  When the operation is started, the process waits until a print request is issued (step S21). When the print request is issued, the paper conveyance unit 105 is controlled to start conveyance of the recording paper P (step S22). And the data of the some location of a recording paper conveyance direction are each taken in from the moisture sensor 100a-100e arrange | positioned in the direction orthogonal to a conveyance direction, respectively, and the moisture content corresponding to a some location is measured (step S23).

  Subsequently, the water content for each region is calculated (step S24), a table of each position and water content is created, the data is stored (step S25), and printing is started (step S26).

  Subsequently, the ink head is moved to the initial position (step S27), and the water content at the position of the ink head is read from the table (step S28). It is determined whether or not the read water content is a low water content, and whether or not the water content is less than 5% (step S29). If it is less than 5%, it is determined that the water content is low, and the ink discharge amount is increased. Then, printing is performed (step S31), and it is determined whether or not printing is finished (step S34). If it is determined that printing has not ended, the process returns to step S37, and the ink head is moved.

  Then, the water content at the position of the ink head is read from the table (step S28). It is determined whether or not the read water content is a low water content and whether or not the water content is less than 5% (step S29). Then, it is determined whether or not the water content exceeds 10% (step S30). If it exceeds 10%, it is determined that the water content is high, printing is performed with a reduced ink discharge amount (step S32), and printing is completed. Is determined (step S34). If it is determined that printing has not ended, the process returns to step S37, and the ink head is moved.

  Subsequently, the water content at the position of the ink head is read from the table (step S28). It is determined whether or not the read water content is a low water content, and whether or not the water content is less than 5% (step S29). If the water content is 5% or more, subsequently, whether or not the read water content is a high water content. That is, it is determined whether or not the water content exceeds 10% (step S30). If the water content is 10% or less, it is determined that the water content is optimal, and printing is performed with an appropriate ink discharge amount (step S33). Then, it is determined whether or not printing is finished (step S34). In the case of the end of printing, after stopping the conveyance (step S35), it is determined whether or not all operations are to be ended (step S36). If the operation is not ended, the process returns to step S21 and the above-described operation is repeated. . Then, when it is determined that the operation is finished, the operation is finished.

  In the above-described embodiment, the example of the printing control of the ink jet printer has been described. However, other types of printers may perform control suitable for the water content. For example, in an electrophotographic copying machine, depending on the water content of the recording paper P, when the water content is high, the transfer current is controlled to be large, and conversely when the water content is low, the transfer current is reduced, Control is performed so as to obtain a high-quality image by optimizing the transfer condition of the transfer portion.

  In the case of a thermal sublimation type printer, the transfer temperature may be controlled to be low when the moisture content of the recording paper is low, and the transfer temperature may be increased when the moisture content is high.

  Further, the sheet conveyance speed may be controlled. In the case of the paper conveyance speed, it can be controlled to be slow when the moisture content of the recording paper is large and to be fast when the moisture content is small. Further, when the recording paper has a function of drying, the paper drying fan is rotated at a low speed when the moisture content of the recording paper is low, and is rotated at a high speed when the moisture content is high. In this case, the strength of the heater may be controlled to be weak when the water content of the recording paper is low, and may be controlled to be strong when the water content is high.

1 is a schematic configuration diagram showing an internal configuration of a general electrophotographic copying machine. 1 is a schematic configuration diagram illustrating an arrangement of moisture sensors of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the output of the moisture sensor used for the image forming apparatus by 1st Embodiment of this invention. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a flowchart which shows operation | movement of the control part of 1st Embodiment of this invention. It is a schematic block diagram which shows arrangement | positioning of the moisture sensor of the image forming apparatus by other Embodiment of this invention. It is a figure which shows the output of the moisture sensor used for the image forming apparatus by other Embodiment of this invention. It is a flowchart which shows operation | movement of the control part of other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Moisture sensor 101 Light-emitting part 102 Light-receiving part 22a Conveyance roller

Claims (3)

In the image forming apparatus in which the recording paper is fed to the printing section by the recording paper conveying means and the printing section forms an image on the fed recording paper, the moisture sensor is arranged on the recording paper conveying path, and the recording paper is conveyed. The moisture content of the recording paper is measured by the moisture sensor, the moisture content of the recording paper is detected from a plurality of locations in the conveyance direction of the recording paper, and the image forming apparatus is configured according to the moisture content of the recording paper at the plurality of locations detected by the moisture sensor An image forming apparatus that performs printing control. The image forming apparatus according to claim 1, wherein an optical humidity sensor is used as the moisture sensor. The image forming apparatus according to claim 1, wherein a plurality of moisture sensors are arranged in a direction orthogonal to the recording paper conveyance direction.

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