JP4842578B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using a two-component developer, such as a copying machine, a facsimile machine, and a printer.

  Conventionally, in an electrophotographic apparatus using a two-component developer, how to control the toner concentration in the developer has been an important issue. Since the toner density in the developer affects the image density, it is desirable to keep the toner density constant in order to obtain a good image.

  As a toner density control method, for example, as disclosed in Patent Document 1, there is a technique for supplying toner so that a constant toner density is obtained using a toner density sensor. In this case, as shown in Patent Document 2, in order to suppress variations in the output of the toner density sensor, some circuit is added to adjust the output of the toner density sensor within a predetermined range. there were.

  However, in the case of such a technique for controlling the toner density to be constant, there are the following problems in the electrophotographic image forming apparatus. That is, even if the toner density is controlled to a predetermined value, the density of the output image changes depending on the temperature and humidity of the surrounding environment and the usage conditions of the developer. This is due to the fact that image formation by electrophotography is developing by frictionally charging toner. Therefore, the above phenomenon is a very essential problem in an image forming apparatus using an electrophotographic system.

As a toner density control method for solving such a problem, a reference image (hereinafter sometimes referred to as a reference pattern or a reference pattern ) is formed on a photoconductor so that the density of the reference pattern becomes constant. In addition, there is a technique in which a target value of toner density is set and toner is replenished based on the target value.

  As the toner density control method, for example, in Patent Document 3, an output value Vti of a toner density sensor (T sensor) immediately after loading a new developer is detected, and a reference value Vref is matched with the output value Vti to output the toner density sensor. Based on the data table showing the correspondence between the value Vti and the toner density change amount ΔTC, the upper limit value VrefH of the reference value Vref and the output value of the T sensor deviated by a certain toner density from the output value of the T sensor at that time The lower limit value VrefL is calculated, and the upper limit value VrefH and the lower limit value VrefL are recorded in the memory. In normal operation, the correction of the reference value based on the detection result of the P sensor is VrefH to VrefL until the next developer replacement. The toner density of the new developer is set to the maximum toner density acceptable in the electrophotographic apparatus, and the upper limit of the toner density is specified. Toner density control apparatus characterized by the output value Vti of VrefL and T sensor is set to be equal, and an image forming apparatus having the same are disclosed. According to the above method, the toner density sensor can be omitted, and the toner density control apparatus can control the image density stably with an inexpensive apparatus configuration.

  In Patent Document 4, the density of the reference image formed on the photoconductor 5 is detected by the P sensor 14, and at this time, Vsp / Vsg, the T sensor value VT2 and the correction amount ΔVT when the P sensor 14 is detected are obtained. The T sensor control target value VTref is obtained from the relational expression VTref = VT2 + f (Vsp / Vsg), VTref is stored, and VT1 after the end of the previous image forming operation and VT2 at the start of the next image forming operation When the difference is larger than a predetermined threshold value, the T sensor control target value VTref uses the calculated value, determines the toner replenishment time t, and the toner replenishment is turned on, so that the toner is supplied to the developing device. Supplied. That is, a toner density control capable of preventing a change in toner density caused by a great change in the characteristics of the developer and an image forming apparatus that performs this have been proposed.

Japanese Patent Laid-Open No. 1-154179 JP 63-58472 A Japanese Patent Laid-Open No. 10-186830 JP-A-11-305497

  However, Patent Documents 3 and 4 have a problem that a normal image state cannot be maintained because there is no correction for a change in sensitivity of the toner density sensor (T sensor) in any control.

  By the way, when a toner using a modified polyester resin is used in an image forming apparatus, it is easy to control the shape, unlike the suspension polymerization method. As can be seen, there is an advantage that the surfactant does not remain inside the toner, and further, this does not cause a problem that the photosensitive member and the developing roller are contaminated to inhibit charging of the toner.

  However, on the other hand, the toner using the modified polyester resin usually has a toner particle itself that is weakly positively charged with the opposite polarity to the charged polarity. There is also a problem that the stirring time is longer than that of the conventional toner.

  In the electrophotographic image forming apparatus, when the modified polyester resin toner is used and the control method for controlling the reference image density as described above is used, there are the following problems.

  That is, when the distribution period from the production of the developer to loading into the image forming apparatus or the storage period after loading for a long period of time, the charge amount of the developer decreases during this period, and the image forming apparatus Even if the developer is stirred, the charge amount of the developer is difficult to recover, so that a sufficient toner charge amount cannot be obtained. For this reason, there arises a problem that the toner on the photosensitive member becomes excessively attached or that offset occurs due to insufficiently charged toner.

  On the other hand, when the developer leaving time is short, there is little decrease in the charge amount of the toner, so that the image density is lowered or the toner near end is turned on.

  In addition, when installing the image forming apparatus at the user's site, the developer and the recording paper are often carried in at the same time. In winter, both the developer and the recording paper are cooled by the external environment, so the offset is further increased. Getting worse.

  Moreover, in recent years, in order to shorten the installation time of the user destination, kitting is often performed in which the image forming apparatus is finished in a place such as a warehouse in advance so that only the image forming apparatus needs to be placed at the user destination. Even in such a case, the state of the image forming apparatus is confirmed by an image tailored in a place such as a warehouse. In such a place, the recording paper is often cold, and an abnormal image such as an offset is likely to occur.

  As described above, when a toner whose charge amount is likely to decrease, such as a modified polyester resin toner, is used in an electrophotographic image forming apparatus, the toner state depends on the length of storage period, its conditions, or the temperature of the recording paper. Thus, there is a problem that proper toner density control is hindered, and as a result, abnormal images such as excessive density and offset are generated.

  An object of the present invention is to obtain an image forming apparatus capable of maintaining an appropriate image output setting state and suppressing abnormal images such as excessive density and offset.

In order to solve the above problems, the invention described in claim 1 is:
The surface of the image carrier is uniformly charged by the charging device , and the latent image on the image carrier formed according to the content of the original is developed with toner by the developing unit, and the toner image thus obtained is recorded on the recording material. In an image forming apparatus that forms an image by transferring it to the top,
Pattern density detection means for detecting the reflection density of a toner pattern for image density detection formed on the image carrier;
When a new toner is supplied into the developing unit, based on manufacturing information of the supplied new toner, a leaving time detecting means for detecting a leaving time from the date of manufacture to the time of supply;
A temperature detecting means for detecting the temperature of the recording material to which the toner image is transferred when the leaving time detected by the leaving time detecting means is outside a predetermined range;
Standing time with the toner, the density of each reference pattern created in advance under various combinations of certain temperature of the recording material (hereinafter, referred to as a reference pattern density.) The lower limit Vsp0 and the upper limit of Vsp1 a storage means for said temperature sensing means and standing time in which the standing time detection unit detects that stores the Matrigel Tsu box table determinable from the temperature of the recording material detected,
Image output correction means for correcting an image output set value when outputting an image from the image forming apparatus,
The image output correction means, the said Matrigel Tsu hex table information temperature and the storage unit of the recording material in which the temperature sensing means and standing time in which the standing time detection unit detects that it detects the sensed has stored patterns based on a reference pattern density concentration detecting unit detects the image output settings so that the image density becomes a predetermined density value serving developing bias Vb, made from the control means for correcting the charging bias Vr,
The control means uses the reference developing bias Vb0 and the reference charging bias Vr0 when the toner leaving time detected by the leaving time detecting means is within the upper and lower limits of the leaving time as the control when the developer is charged. Normal control,
Determined from when the standing time of the toner in which the standing time detecting means has detected is determined to be outside the range of upper and lower limit of exposure time, the standing time outside this range, the temperature of the recording material and the temperature detection unit detects after determining based on the lower limit Vsp0 and the upper limit Vsp1 reference pattern concentration to be in the matrix table,
This is a difference between the development bias Vbp at the time of creating the reference pattern and the default bias value Vbp0 at the time of the reference pattern when the reference pattern is formed with the default bias value Vbp0 at the time of the reference pattern and falls between the lower limit value Vsp0 and the upper limit value Vsp1. A correction voltage Vs is obtained, and a charging bias Vr at the time of image output is obtained by subtracting the correction voltage Vs from the reference charging bias Vr0, and a developing bias Vb at the time of image output is obtained by subtracting the correction voltage Vs from the reference developing bias Vb0. it was decided to perform the required Ru control.
The invention described in claim 2 is the image forming apparatus according to claim 1,
At the time of image output, the image output set value is returned to the original value when the output value of the pattern density detecting means falls within a certain threshold .
The invention described in claim 3 is the image forming apparatus according to claim 1 or 2,
The toner is an aqueous medium containing resin fine particles formed by dissolving or dispersing a modified polyester resin capable of reacting with a compound having at least an active hydrogen group, a colorant, and a release agent in an organic solvent. The organic solvent was removed from the dispersion obtained by dispersing in the resin and reacting with a crosslinking agent and / or an extender, and the resin fine particles adhering to the toner surface were washed and desorbed . .
The following technical features can be provided.
(1): In an image forming apparatus in which a latent image on an image carrier is developed with toner by a developing unit and the resulting toner image is transferred onto a recording material to form an image. From the date of manufacture based on the pattern density detection means for detecting the reflection density of the formed image density detection toner pattern and the new toner supply information when the new toner is supplied into the developing unit. A leaving time detecting means for detecting a standing time until the supply time, and a temperature detection for detecting the temperature of the recording material to which the toner image is transferred when the leaving time detected by the leaving time detecting means is outside a predetermined range. The image output setting value when the image is output so that the image density becomes a predetermined density is corrected based on the means, the leaving time detected by the leaving time detecting means, and the temperature of the recording paper detected by the temperature detecting means. Image output Characterized in that it comprises correction means.

(2): In the invention described in (1) , the target value of the output value detected by the pattern density detecting means based on the leaving time detected by the leaving time detecting means and the temperature of the recording paper detected by the temperature detecting means. The image output correcting means includes a developing means for forming a toner pattern until the density of the toner pattern detected by the pattern density detecting means reaches a target value determined by the determining means. And the image output set value is corrected by the correction amount of the developing bias when the toner pattern reaches the target value.

(3): In the invention described in (1) , the image output correction unit determines a bias correction value based on the temperature of the recording paper detected by the temperature detection unit and the output value of the pattern density detection unit, The image output set value when the image is output is corrected by the bias correction value.

(4): In the invention described in any one of (1) to (3) , when the image is output, when the output value of the pattern density detection means falls within a certain threshold value, the image output set value is changed to the original value. It is characterized by returning to a value.

(5): In the invention described in any one of (1) to (4) , as a toner, a modified polyester resin, a colorant, a release agent capable of reacting with a compound having at least an active hydrogen group in an organic solvent. The dissolution or dispersion formed by dissolving or dispersing the mold is dispersed in an aqueous medium containing resin fine particles, reacted with a crosslinking agent and / or an extender, and the organic solvent is removed from the obtained dispersion. In addition, the resin fine particles are obtained by washing and removing resin fine particles adhering to the toner surface.

  According to the present invention, the image output setting value when the image is output so that the image density becomes a predetermined density based on the leaving time detected by the leaving time detecting means and the temperature of the recording paper detected by the temperature detecting means. Therefore, even when the toner left for a predetermined period from the manufacture is supplied to the developing unit, or even when the temperature of the recording material to be used is low, an appropriate image output setting state is maintained and the density is excessive. And abnormal images such as offset can be suppressed.

  Hereinafter, an embodiment in which the present invention is applied to a copying machine as an image forming apparatus will be described. In the present embodiment, a monochrome image forming apparatus will be described as an example, but the present invention can be similarly applied to a color image forming apparatus.

  First, the configuration of the copying machine according to the first embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of the entire copying machine according to the present embodiment. In FIG. 1, an image reading apparatus 200 is attached to the copying machine main body 100 and placed on a sheet bank 300. Mounted on the image reading apparatus 200 is an automatic document feeder 400 configured to be rotatable about the back side (the back side of the paper in the figure) as a fulcrum.

  Inside the copying machine main body 100, a drum-shaped photoconductor 10 is provided as an image carrier. Around the photosensitive member 10, a charging device 11 using a charging roller, a developing device (developing unit) 12, a transfer device 13, and a cleaning device are arranged along a rotation direction (counterclockwise direction in the drawing) A of the photosensitive member 10. 14 are arranged in order.

  The developing device 12 uses a polymerized toner produced by a polymerization method as a toner, and attaches the polymerized toner to an electrostatic latent image on the photoconductor 10 using a developing roller as a developer carrier. Visualize.

  The transfer device 13 includes a transfer belt 17 wound around two rollers 15 and 16, and the transfer belt 17 is pressed against the peripheral surface of the photoconductor 10 at the transfer position B. Further, the copying machine main body 100 is provided with a toner replenishing device 20 for replenishing the developing device 12 with new toner on the left side of the charging device 11 and the cleaning device 14 in the drawing.

  Further, the copying machine main body 100 is provided with a sheet conveying device 60 that conveys the sheet S sent from the sheet cassette 61 of the sheet bank 300 to the stack unit 39 via the transfer position B. The sheet conveying apparatus 60 conveys the sheet S along the supply path R1 or the manual feed path R2 and the sheet conveyance path R. On the sheet conveyance path R, a registration roller 21 is provided upstream of the transfer position B in the sheet conveyance direction.

  On the other hand, a thermal fixing device 22 is provided on the downstream side in the sheet conveyance direction of the sheet conveyance path R with respect to the transfer position B. The heat fixing device 22 performs heat and pressure fixing by sandwiching the sheet S between a heating roller (heating member) 30 and a pressure roller (pressure member) 32. A discharge branch claw 34, a discharge roller 35, a first pressure roller 36, a second pressure roller 37, and a stiffness roller 38 are provided further downstream in the sheet conveyance direction of the heat fixing device 22. A stack unit 39 is also provided for stacking sheets on which images have been formed through the thermal fixing device 22.

  Further, the copying machine main body 100 is provided with a switchback device 42 on the right side in the drawing. The switchback device 42 reverses the reversing path R3 branched from the position where the discharge branch claw 34 of the sheet conveying path R is arranged, and the position of the registration roller 21 on the sheet conveying path R again after passing the reversing path R3. The sheet S is conveyed along the re-conveying path R4 that leads to the point. A pair of switchback rollers 43 and a plurality of other rollers 66 are provided in the reversing path R3 and the re-transport path R4.

  Further, the copying machine main body 100 is provided with a laser writing device 47 on the left side of the developing device 12 in the drawing. The laser writing device 47 includes a scanning optical system such as a laser light source (not shown), a rotary polygon mirror 48 for scanning, a polygon motor 49, and an fθ lens (not shown).

  The image reading apparatus 200 includes a light source 53, a plurality of mirrors 54, an imaging optical lens 55, an image sensor 56 such as a CCD, and the like, and a contact glass 57 is provided on the upper surface thereof.

  The automatic document feeder 400 is provided with a document setting table (not shown), and a document stacking table (not shown) is provided at the document discharge position. The automatic document transport device 400 includes a plurality of document transport rollers, and the document transport rollers transport the document from the document setting table to the document stack table through the reading position on the contact glass 57 of the image reading device 200. The

  The sheet bank 300 is provided with a plurality of sheet cassettes 61 for storing sheets S such as paper and OHP film as recording materials. Each sheet cassette 61 is provided with a call roller 62, a supply roller 63, and a separation roller 64, respectively. On the right side of the sheet cassette 61 in the drawing, the above-described supply path R1 leading to the sheet conveyance path R of the copying machine main body 100 is formed. Several sheet conveying rollers 66 for conveying the sheet are also provided in the supply path R1.

  Further, the copying machine main body 100 is provided with a manual feed unit 68 on the right side in the drawing. The manual feed unit 68 is provided with a manual feed tray 67 that can be opened and closed. The manual feed path R <b> 2 that guides the manual sheet set on the manual feed tray 67 to the sheet conveyance path R is formed. Similarly to the sheet cassette 61, the manual feed unit 68 is also provided with a calling roller 62, a supply roller 63, and a separation roller 64.

  Next, the operation of the copying machine will be described. When making a copy using the copying machine, first, a main switch (not shown) is turned on, and a document is set on a document setting table of the automatic document feeder 400. In the case of a book document, the automatic document feeder 400 is opened, a document is set directly on the contact glass 57 of the image reading device 200, and the automatic document feeder 400 is closed and pressed. When a start switch (not shown) is pressed, when an original is set on the automatic document feeder 400, the original is moved onto the contact glass 57 through the document feeding path by the document feeding roller, and then the image reading device 200 is driven. Then, the document contents are read and discharged onto the document stacking table.

On the other hand, when the document is set directly on the contact glass 57, the image reading device 200 is immediately driven to read the content of the document. When reading the content of the original, the image reading apparatus 200 irradiates the original surface on the contact glass 57 with light from the light source 53 while moving the light source 53 along the contact glass 57. Then, the reflected light is guided to the imaging optical lens 55 by a plurality of mirrors 54 and put into the image sensor 56, and the document content is read by the image sensor 56.

  On the other hand, simultaneously with the reading of the document content, the photoconductor 10 is rotated by a photoconductor drive motor (not shown). First, the surface of the photoconductor 10 is uniformly charged by the charging device 11, and then writing is performed by irradiating the laser beam from the laser writing device 47 in accordance with the content of the original read by the image reading device 200 described above. Then, an electrostatic latent image is formed on the surface of the photoconductor 10. Thereafter, the developing device 12 attaches toner to the electrostatic latent image to make it visible.

  At the same time as the start switch is pressed, the sheet S is sent out by the calling roller 62 from the one corresponding to the selected size among the plurality of sheet cassettes 61 provided in the sheet bank 300. Then, the fed sheet S is separated one by one by the supply roller 63 and the separation roller 64, and the one sheet is guided to the supply path R 1, and is guided to the sheet conveyance path R by the sheet conveyance roller 66. The sheet S conveyed to the sheet conveyance path R hits the registration roller 21 and is stopped.

  When the manual paper feed unit 68 is used, the manual feed tray 67 is opened and the sheet S is set on the manual feed tray 67. In this case as well, only one sheet S is conveyed to the manual feed path R2 by the calling roller 62, the supply roller 63, and the separation roller 64, and is guided to the sheet conveyance path R by the sheet conveyance roller 66. Stopped by hitting. In this way, the sheet S stopped by the registration roller 21 starts to rotate at the timing when the leading end of the visible toner image of the photoreceptor 10 enters the transfer position B. 21 to the transfer position B.

  The sheet S fed to the transfer position B is transferred with the toner image on the photoreceptor 10 by the transfer device 13 and carries the image on the surface thereof. Residual toner remaining on the surface of the photoconductor 10 after the transfer is removed by the cleaning device 14, and the residual potential on the photoconductor 10 is also removed by a neutralization device (not shown) to prepare for the next image formation starting from the charging device 11. . On the other hand, the sheet S carrying the image is conveyed by the transfer belt 17 and enters the heat fixing device 22. Then, heat and pressure are applied while being conveyed between the heating roller 30 and the pressure roller 32, and the image on the sheet S is fixed. After that, the sheet S is discharged onto the discharge stack unit 39 with a stiffness by the discharge roller 35, the first pressure roller 36, the second pressure roller 37, and the roller with stiffness 38, and is stacked there. The

  When images are formed on both sides of the sheet S, the discharge branch claw 34 is switched, and the toner image is transferred to one side of the sheet S. Then, the toner image is transferred from the sheet conveying path R to the reversing path R3. The sheet S is conveyed by the sheet conveying roller 66 and put into the switchback position 44, and then switched back by the switchback roller 43. This time, the sheet S is put in the re-conveying path R4, and the sheet conveying roller 66 again conveys the sheet. It is led to the path R. Then, the toner image is transferred to the opposite surface of the sheet in the same manner as described above.

  FIG. 2 is a perspective view of the toner bottle 23 set in the toner replenishing device 20. The toner bottle 23 includes a cylindrical bottle body 24 and a cap portion 25. A storage space for storing replenishing toner is formed inside the bottle main body 24, and a spiral protrusion is formed in the storage space. When the toner bottle 23 is set in the toner replenishing device 20, first, the bottom portion of the bottle body 24 (the opposite end portion of the cap portion 25) and the drive shaft of the bottle drive motor 26 are engaged. At the same time, the cap unit 25 is fixed to the toner supply device 20. And if the lever 25a provided in the cap part 25 is operated, the bottle opening 24a will open. Further, when the bottom of the bottle body 24 and the drive shaft of the bottle drive motor 26 are engaged, the shutter pin 27 a is guided upward by the inclined surface of the protrusion 12 a of the developing device 12. As a result, the shutter 27 is opened and the toner discharge port 28 is opened.

  FIG. 3 is a diagram illustrating how toner is supplied to the developing device 12. When the bottle drive motor 26 is driven after the toner bottle 23 is set, the bottle main body 24 rotates, and the toner in the accommodation space is conveyed into the cap portion 25 by the spiral protrusion of the bottle main body. The toner in the cap unit 25 is scraped out to the toner discharge port 28 by the toner replenishment mylar 25b and conveyed into the developing device 12. With such a configuration, the amount of toner (toner replenishment amount) supplied to the developing device 12 can be adjusted by controlling the driving of the bottle drive motor 26.

  Next, toner concentration control by the toner concentration control apparatus in the present embodiment will be described. FIG. 4 is a block diagram showing the configuration of the toner concentration control apparatus in the present embodiment.

  In the present embodiment, a toner density sensor (T sensor) 102 is provided in the developing device 12, and toner for image density detection formed on the photoconductor 10 so as to face the surface of the photoconductor 10. A pattern density sensor (P sensor) 103 is provided as pattern density detection means for detecting the reflection density of the pattern. The T sensor 102 detects the magnetic permeability in a part of the developer, and is a general magnetic permeability sensor in which the output voltage (detection value) increases as the magnetic permeability increases.

  Specifically, when the output voltage Vt of the T sensor 102 is low, it means that the magnetic permeability of the developer is small. Therefore, it is determined that the toner concentration is high, and conversely, the output voltage Vt of the T sensor 102 is high. This means that the toner density is low because it means that the magnetic permeability of the developer is high.

  In this embodiment, a magnetic permeability sensor is used as the T sensor 102. However, if a parameter related to the developer density can be detected for a part of the developer accommodated in the developing device 12, this may be used. Not limited to.

  The P sensor 103 is a reflection type optical sensor, and detects the reflection density of a toner pattern for image density detection formed on the photoconductor 10 from the amount of reflected light that varies depending on the change in the toner amount. The output voltage of the P sensor 103 is lower as the toner amount is smaller, that is, as the toner pattern density is lower. The P sensor is not limited to this as long as the density of the toner pattern on the photoconductor 10 can be detected. The output signals of these sensors 102 and 103 are input to the control unit 101 as image output correction means and determination means.

  In this toner density control apparatus, the detection timing by the T sensor 102 is preferably when the developer is being stirred, and is therefore performed between images during an image forming operation or during continuous image formation. Since it is desirable that the detection interval by the T sensor 102 be as short as possible, in this embodiment, it is performed for each image forming operation.

  On the other hand, the detection operation by the P sensor cannot be performed during the image forming operation because a toner pattern needs to be formed on the photoreceptor 10. Therefore, the detection timing by the T sensor 102 is performed between images (between pages) during a non-image forming operation or during continuous image formation. However, in the detection operation by the P sensor 103, while the toner pattern is formed on the photoconductor 10, the normal image formation operation is made to wait, so this detection operation is performed between images during continuous image formation, for example. In this case, the continuous image forming speed is reduced. Therefore, the detection operation by the P sensor 103 cannot be performed as frequently as the T sensor 102.

  Therefore, in this embodiment, it is set so that the detection operation by the P sensor 103 is performed once every 30 images are output. The detection timing by the P sensor 103 is preferably changed as appropriate according to the system and required specifications.

Whenever the image forming operation is performed, the control unit 101 receives the detection value Vt from the T sensor 102 and compares the detection value Vt with the target value Vtref. If it is determined that the detected value Vt is equal to or greater than the target value Vtref, it is determined that the toner concentration in the agent is lower than the target value Vtref, and a control signal for driving the bottle drive motor 26 is output. As a result, the bottle drive motor 26 is driven to supply toner to the developer in the developing device 12.

  On the other hand, if it is determined that the detected value Vt is lower than the target value Vtref, it is determined that the toner concentration in the agent is higher than the toner concentration at the target value Vtref, and a control signal for stopping the driving of the bottle drive motor 26 is output. To do. As a result, the driving of the bottle drive motor 26 is stopped, and the toner supply is stopped. In this way, the toner density in the developing device 12 is controlled.

  In addition, the control unit 101 receives the detection value Vsp from the P sensor 103 and performs a correction process on the target value Vtref. Specifically, if it is determined that the detected value Vsp is lower than a specified value (target toner pattern density) Vspref, the target value Vtref is corrected to be low. As a result, even if the detection value Vt of the T sensor 102 has been below the target value Vtref so far, if it is equal to or greater than the corrected target value Vtref, the toner supply operation is started and the image density increases.

  On the other hand, if it is determined that the detection value Vsp of the P sensor 103 is greater than or equal to the specified value Vspref, the target value Vtref is corrected so as to increase. As a result, even if the detection value Vt of the T sensor 102 has been equal to or higher than the target value Vtref so far, if the target value Vtref after correction falls below the corrected target value Vtref, the toner supply operation is stopped and the image density is lowered.

  The T sensor 102 also monitors the toner end and toner near end in the developing device 12. In monitoring of the toner end and the toner near end, a value obtained by subtracting a predetermined real number from the target value Vtref is set as a threshold value of the toner near end. When the detection value Vt of the T sensor 102 falls below the toner near-end threshold, it is determined that the toner is near-end, and the user is notified.

  Here, the toner used in the present embodiment uses a modified polyester resin as a base material. Specifically, it is manufactured as follows. That is, a modified polyester resin, a colorant, and a release agent that can react with at least a compound having an active hydrogen group are dissolved or dispersed in an organic solvent. The solution or dispersion thus obtained is dispersed in an aqueous medium containing resin fine particles and reacted with at least one of a crosslinking agent and an extender. Then, the organic solvent is removed from the resulting dispersion, and the resin fine particles are washed to obtain a toner.

  When the toner is left for a long time, the charge amount decreases. In addition, it takes time for the toner to reach a predetermined charge amount. Since the toner has the above properties, it is replaced with a deteriorated developer, and if the toner charge amount in the developer newly filled in the developing device is not within a predetermined range, an image defect occurs at the initial filling stage. End up.

  In the toner density control, when the toner density is high, it takes a certain time until the toner is consumed. Until then, the high toner density state cannot be resolved. For this reason, with only the above control, when performing image formation after a long time has elapsed since the last image output, there is a tendency that excessive density and offset are not easily recovered. In addition, when the sheet S is cold, the sheet S is deprived of heat, so that it becomes insufficient to melt the toner and fix it on the sheet S, so that the offset deteriorates.

  Therefore, in the present embodiment, the time for which the developer to be filled is left standing from the date of manufacture to the present time is detected, the temperature of the sheet S is detected, and image output is performed when an image is output based on these detection results. An image output control device that corrects the developing bias and the charging bias as set values is provided.

  FIG. 5 is a block diagram showing the configuration of the image output control apparatus of this embodiment. As shown in FIG. 5, the image output control apparatus includes an unattended time detection unit 104, a temperature detection sensor (temperature detection unit) 107, a storage unit 106, a control unit 101, a P sensor 103, and a developing device 12. And the charging device 11.

  The leaving time detection unit 104 detects a leaving time T0 of the developer to be filled from the date of manufacture to the present time based on manufacturing information such as the date of manufacture of the developer to be filled in the developing device 12 input from the numeric keypad. To do. The temperature detection sensor 107 is provided in the sheet bank 300 and detects the temperature Tk of the sheet S stored in the sheet cassette 61 of the sheet bank 300.

  The storage unit 106 stores in advance a lower limit value Vsp0 and an upper limit value Vsp1 of the toner pattern density (reference pattern density) at the temperature Tk for a certain standing time T0. In the present embodiment, for example, a matrix (table) is stored in which each standing time T0 is arranged in a vertical column and each temperature Tk is arranged in a horizontal column, and the intersection of each standing time T0 and each temperature Tk is stored. Each stores a lower limit value Vsp0 and an upper limit value Vsp1 of the toner pattern density (reference pattern density).

  The control unit 101 determines whether or not to correct the image output based on the leaving time T 0 detected by the leaving time detection unit 104 and the temperature Tk detected by the temperature detection sensor 107. The control unit 101 corrects the developing bias Vb and the charging bias Vr, which are image output setting values, based on the pattern density output value Vsp of the P sensor.

  FIG. 6 is a flowchart showing a control flow when the developer is charged in the present embodiment. First, it replaces with a deteriorated developing device in the developing device and detects the leaving time T0 of the newly filled developer (S1). The developer leaving time T0 detection is performed by, for example, writing the developer production date in a bag containing the developer, inputting the production date with a numeric keypad, etc., and leaving the developer from the entered production date to the present time. Time T0 is calculated and detected in the apparatus. Further, the developer leaving time T0 up to the present time from the date of manufacture described by the user may be calculated, and the calculated value may be input using a numeric keypad to detect the developer leaving time T0. . Further, the developer production date may be described on the bag as a barcode, the production date may be read with a barcode reader, and the toner developer leaving time T0 from the production date to the present time may be calculated and detected.

  If the leaving time T0 is detected, it is checked whether or not the leaving time T0 is within the upper limit (Trefl) lower limit (Trefs) threshold value range (S2). If it is within the threshold range (YES in S2), the toner charge amount in the replaced developer has a predetermined charge amount, so normal control using the reference development bias Vb0 charge bias Vr0 is performed. (S3).

  On the other hand, when the leaving time T0 is outside the upper and lower threshold values (NO in S2), the toner charge amount in the developer is not a predetermined charge amount, and therefore the development bias Vb and the charge bias Vr are corrected. Do.

  To correct the developing bias Vb and the charging bias Vr, first, the temperature detection sensor 107 measures the temperature Tk of the sheet S and then inputs these values to the control unit 101 (S4). Next, the control unit 101 refers to the matrix of the leaving time T0 and the temperature Tk stored in the storage unit 106 (S5), and determines the lower limit value Vsp0 and the upper limit value Vsp1 of the reference pattern density based on this matrix ( S6).

  In the matrix of the storage unit 106, when the temperature Tk is low, the reference density is set low, and when the temperature Tk is high, the density is set high. As a result, when the temperature Tk is low, the reference density is low and the amount of toner adhering to the sheet S is reduced, so the amount of heat required for fixing is reduced and offset is suppressed. On the other hand, when the temperature Tk is high, the image density can be reliably maintained by increasing the amount of adhesion.

  Subsequently, a reference pattern (reference pattern) is created on the photoconductor 10 (S7). The created reference pattern is detected by the P sensor 103, and it is checked whether or not the pattern density output value Vsp at this time is higher than the reference pattern density output lower limit value Vsp0 (S8). When the reference pattern density output lower limit value Vsp0 is equal to or lower (NO in S8), the developing bias Vbp at the time of creating the reference pattern is subtracted by a predetermined correction amount ΔV (S9).

  Then, a reference pattern is created with the corrected developing bias Vbp at the time of creating the reference pattern (S7), and it is checked whether or not the output value Vsp of the P sensor 103 is higher than the reference pattern density output lower limit value Vsp0 (S8). ). When the reference pattern density output lower limit value Vsp0 is below (NO in S8), the flow after S9 is repeated.

  On the other hand, when the output value Vsp of the P sensor 103 is higher than the reference pattern density output lower limit value Vsp0 (YES in S8), the developing bias Vbp when the output value Vsp is higher than the reference pattern density output lower limit value Vsp0. A reference pattern is created (S10). At this time, it is checked whether or not the reference pattern density output value Vsp of the P sensor 103 is lower than the reference pattern density output upper limit value Vsp1 (S11). When the density output value Vsp is equal to or higher than the density output upper limit value Vsp1 (NO in S11), a predetermined correction amount ΔV is added to the developing bias Vbp at the time of creating the reference pattern (S12).

  Then, a reference pattern is created with the developing bias Vbs to which the correction amount ΔV is added (S10), and it is checked whether the density output value Vsp is lower than the density output upper limit value Vsp1 (S11). If the reference pattern density output upper limit value Vsp1 or more (NO in S11), the flow after S12 is repeated.

On the other hand, when the density output value Vsp of the P sensor 103 is lower than the reference pattern density output upper limit value Vsp1 (YES in S11), a correction voltage Vs for correcting the developing bias Vb and the charging bias Vr during image formation is obtained. (S13).
The correction voltage Vs is obtained by subtracting the default bias value Vbp0 for the reference pattern from the development bias Vbp for creating the reference pattern when the density output value Vsp of the P sensor is lower than the reference pattern density output upper limit value Vsp1. be able to.
After obtaining the correction voltage Vs, the charging bias Vr at the time of image output is obtained by subtracting the obtained correction voltage Vs from the reference charging bias Vr0.
Further, the developing bias Vb 0 reference, by subtracting the correction voltage Vs obtained, obtains the developing bias Vb at the time of image output (S14).

  In this way, by correcting the charging bias Vr and the developing bias Vb, the image output set value is corrected, and even when the charged amount of toner in the replaced developer is not within an appropriate range, the image at the time of arrival is obtained. The density is corrected and the proper density can be maintained. For this reason, excessive density and offset images can be suppressed.

  Here, even if the charge amount of the toner in the replaced developer is not within the proper range, the charge amount of the toner in the developer falls within the proper range by passing the time. In other words, the toner in the developer that has been left for a long period of time and has a reduced charge amount is agitated in the developing device 12 so that the charge amount is restored to a predetermined charge amount.

  On the other hand, the toner in the developer is replaced as soon as the developer is manufactured, and the toner in the developer whose toner is charged more than necessary is consumed, or new toner is supplied from the toner replenishing device. Recovers to a predetermined amount of charge. Therefore, in this embodiment, when the toner charge amount in the developer returns to a predetermined range, control is performed so as to return to the reference developing bias Vb and the reference charging bias Vr.

  FIG. 7 is a flowchart showing a control flow for returning to the reference developing bias Vb and the reference charging bias Vr.

  First, in S14 of the flow of FIG. 6, after correcting the voltage between the charging bias and the developing bias of the image output at the time of arrival, it is detected whether or not the image forming operation is completed (S21). If the image forming operation is completed (YES in S21), the corrected developing bias Vbp is returned to the reference developing bias value Vbp0 during normal control (S22), and a reference pattern is created with this reference developing bias value Vbp0 (S23). ).

  It is checked whether the reference pattern density output value Vsp of the P sensor 103 at this time is within the range of the reference pattern density output upper limit value Vsp1 lower limit value Vsp0 (S24). If it is not within the range (NO in S24), the toner in the developer does not reach the charge amount within the predetermined range, so the flow from S21 is repeated.

On the other hand, when the reference pattern density output value Vsp of the P sensor 103 is within the range of the reference pattern density output upper limit value Vsp1 lower limit value Vsp0 (YES in S24), the toner charge amount in the developer is restored to the charge amount within the predetermined range. Therefore, the developing bias Vb and the charging bias Vr are returned to the reference biases Vb 0 and Vr 0 , respectively (S25).

  As described above, according to the image forming apparatus of the present embodiment, when a new developer is filled in the developing device 12, when the leaving time T0 of the filled developer is outside the predetermined range, The development bias Vb and the charging bias Vr, which are image output set values, are corrected so that the image density becomes a predetermined density based on the standing time T0 and the temperature Tk of the sheet S. As a result, it is possible to maintain the image density at a predetermined density even when the developer image which has been left for a long period or a short period from the manufacture is filled, even if the temperature of the sheet S is the case. Images can be suppressed.

  Further, even when a developer that has been left for a long time is filled, the toner concentration of the developer does not fall below the toner near-end threshold. Therefore, erroneous detection of toner near end can be suppressed.

  The developing bias Vb and the charging bias Vr are corrected based on the reference pattern density output value Vsp detected by the P sensor 103. Thus, by correcting the image output set value based on the toner density actually attached to the photoconductor 10, the developing bias Vb and the charging bias Vr for setting the image density to a predetermined density can be set with high accuracy. it can.

  In the image forming apparatus of the present embodiment, the developing bias at the time of forming the reference pattern is corrected until the reference pattern density output value Vsp detected by the P sensor is within a predetermined range, and the correction amount of the developing bias is corrected. Based on Vs, the developing bias Vb and the charging bias Vr are corrected. As described above, by correcting the developing bias Vb and the charging bias Vr based on the correction amount Vs corrected so that the toner density actually attached to the photoconductor becomes a predetermined density, the image density is surely set to the predetermined density. be able to.

Further, a pattern for image density detection is created on the photoconductor 10 at a predetermined timing, which is detected by the P sensor 103. When the density of the toner pattern detected by the P sensor 103 is within a predetermined range, correction is performed. The developed developing bias Vb and charging bias Vr are returned to the reference developing bias Vb 0 and the reference charging bias Vr 0 before correction.

  The toner in the filled developer gradually recovers to a predetermined charge amount in the developing device. When the toner is charged more than necessary at the initial stage of filling, the image density gradually increases as the charged amount is restored. Accordingly, when the P sensor detects the toner density, the target value of the T sensor is gradually lowered, and the toner density of the developer is gradually lowered.

  As a result, when the developer toner concentration further decreases due to the environment, the developer toner concentration becomes extremely thin and the absolute amount of toner adhering to the developing roller becomes insufficient, and the carrier adheres to the photoreceptor. It may cause problems such as failure. On the other hand, when the toner is less than the predetermined charge amount at the initial stage of filling, the image density gradually decreases as the charge amount is restored. Accordingly, when the P sensor 103 detects the toner concentration, the target value of the T sensor is gradually increased, and the toner concentration of the developer is gradually increased. As a result, when the toner density of the developer further increases due to the environment or the like, the toner density in the developer may become extremely high, and the toner may blow out from the developing device and stain the inside of the device.

  However, if the toner pattern is created with the developing bias before correction at a predetermined timing and the density of the toner pattern detected by the P sensor is within the predetermined range, the charge amount of the toner in the developer is recovered. Therefore, the developing bias and charging bias before correction are restored. As a result, it is possible to prevent the developer from being excessively concentrated and blowing out from the developing device. Further, it is possible to prevent the toner concentration of the developer from becoming extremely thin and the carrier from adhering to the photoreceptor 10.

  In this embodiment, a toner based on a modified polyester resin is used as the toner. As described above, such a toner has advantages that it is easy to improve the removal efficiency when cleaning with a blade, and that the surfactant does not remain inside the toner or inhibit charging of the toner. On the other hand, if the toner particles themselves are left without stirring, there is a demerit that the charge of the toner is lowered and the toner is charged to a weak plus opposite to the charge polarity at the time of use. Further, there is a demerit that more stirring time is required than the conventional toner until the charged toner is charged. When a toner based on a modified polyester resin having such disadvantages is used in an image forming apparatus that controls the toner density by using the P sensor 103 and the T sensor 102 together, the above-mentioned problem appears remarkably. .

  That is, it is an abnormal image at the initial stage when the developing device 12 is filled with a developer having a short standing time or a long developer. However, this can be sufficiently suppressed by correcting the developing bias Vb and the charging bias Vr as described above, so that the above-mentioned merit can be enjoyed in a state where abnormal images at the initial stage are suppressed.

  Next, a second embodiment will be described. In the description, the same parts as those described above are denoted by the same reference numerals, and the description will be simplified.

  In the present embodiment, the storage unit 106 of the image output control device stores a correction voltage (bias correction value) at a temperature Tk of the sheet S with respect to a matrix (reference table) as shown in FIG. Vs is stored in advance. Specifically, as shown in FIG. 8, a matrix is stored in which each output value Vsp is arranged in a vertical column and each temperature Tk is arranged in a horizontal column, and each output value Vsp and each temperature Tk is stored. A correction voltage Vs is stored at each intersection. Based on this matrix, the correction voltage Vs is determined.

  As shown in the flowchart of FIG. 8, first, the developer leaving time T0 in the developing device 12 is detected in the same manner as in the first embodiment (S31). Next, after the temperature Tk of the sheet S is measured by the temperature detection sensor 107, this value is input to the control unit 101 (S32).

If the standing time T0 is within the upper limit (Trefl) lower limit (Trefs) threshold range (YES in S33), the image output is controlled with the normal reference developing bias Vb 0 and charging bias Vr 0 (S34). ).

  When the leaving time T0 is not within the upper limit (Trefl) lower limit (Trefs) threshold range (NO in S12), a reference pattern is created (S35), and the reference pattern density output value Vsp of the P sensor 103 at this time is obtained. . When the standard pattern density output value Vsp of the P sensor 103 is obtained, the correction bias Vs is determined by referring to the reference table of the storage unit 106 (S36) (S37).

After determining the corrected voltage Vs, the charge bias Vr 0 reference, by subtracting a correction voltage Vs, determine the charging bias Vr at the time of image output. Further, the developing bias Vb 0 reference, by subtracting a correction voltage Vs, obtain the developing bias Vb at the time of image output (S38).

  Also in the second embodiment, even if the toner charge amount of the replaced developer is not in the proper range, the developing bias Vb and the charging bias Vr are set to the reference pattern density output value Vsp of the P sensor 103 and the temperature Tk of the sheet S. By correcting based on the above, it is possible to suppress defective images at the initial stage of developer replacement.

  Note that the control shown in FIG. 7 may be performed after S38 as in the first embodiment, and even in this case, the same function and effect are obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, a copying machine has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and the same effects can be obtained even when applied to an image forming apparatus such as a facsimile, a printer, or a multifunction machine thereof. obtain.

1 is a diagram schematically showing a copier according to a first embodiment. FIG. 3 is a schematic view of a toner bottle set in the toner supply device according to the first embodiment. FIG. 3 is a diagram illustrating a state in which toner is supplied to the developing device according to the first embodiment. 1 is a block diagram illustrating a configuration of a toner concentration control apparatus according to a first embodiment. FIG. It is a block diagram which shows the structure of the image output control apparatus which concerns on 1st Embodiment. 6 is a flowchart illustrating a control flow when a developer is charged according to the first embodiment. 6 is a flowchart illustrating a control flow for returning to a reference developing bias and a reference charging bias after image formation according to the first embodiment. It is a flowchart which shows the flow of control at the time of the developer filling which concerns on 2nd Embodiment.

Explanation of symbols

10 Photoconductor (image carrier)
12 Development device (development unit)
101 control unit (image output correction means, determination means)
103 pattern density sensor (pattern density detection means)
104 Standing time detection means 107 Temperature detection sensor (temperature detection means)
S sheet (recording material)

Claims (3)

The surface of the image carrier is uniformly charged by the charging device , and the latent image on the image carrier formed according to the content of the original is developed with toner by the developing unit, and the toner image thus obtained is recorded on the recording material. In an image forming apparatus that forms an image by transferring it to the top,
Pattern density detection means for detecting the reflection density of a toner pattern for image density detection formed on the image carrier;
When a new toner is supplied into the developing unit, based on manufacturing information of the supplied new toner, a leaving time detecting means for detecting a leaving time from the date of manufacture to the time of supply;
A temperature detecting means for detecting the temperature of the recording material to which the toner image is transferred when the leaving time detected by the leaving time detecting means is outside a predetermined range;
Standing time with the toner, the density of each reference pattern created in advance under various combinations of certain temperature of the recording material (hereinafter, referred to as a reference pattern density.) The lower limit Vsp0 and the upper limit of Vsp1 a storage means for said temperature sensing means and standing time in which the standing time detection unit detects that stores the Matrigel Tsu box table determinable from the temperature of the recording material detected,
Image output correction means for correcting an image output set value when outputting an image from the image forming apparatus,
The image output correction means, the said Matrigel Tsu hex table information temperature and the storage unit of the recording material in which the temperature sensing means and standing time in which the standing time detection unit detects that it detects the sensed has stored patterns based on a reference pattern density concentration detecting unit detects the image output settings so that the image density becomes a predetermined density value serving developing bias Vb, made from the control means for correcting the charging bias Vr,
The control means uses the reference developing bias Vb0 and the reference charging bias Vr0 when the toner leaving time detected by the leaving time detecting means is within the upper and lower limits of the leaving time as the control when the developer is charged. Normal control,
Determined from when the standing time of the toner in which the standing time detecting means has detected is determined to be outside the range of upper and lower limit of exposure time, the standing time outside this range, the temperature of the recording material and the temperature detection unit detects after determining based on the lower limit Vsp0 and the upper limit Vsp1 reference pattern concentration to be in the matrix table,
This is a difference between the development bias Vbp at the time of creating the reference pattern and the default bias value Vbp0 at the time of the reference pattern when the reference pattern is formed with the default bias value Vbp0 at the time of the reference pattern and falls between the lower limit value Vsp0 and the upper limit value Vsp1. A correction voltage Vs is obtained, and a charging bias Vr at the time of image output is obtained by subtracting the correction voltage Vs from the reference charging bias Vr0, and a developing bias Vb at the time of image output is obtained by subtracting the correction voltage Vs from the reference developing bias Vb0. image forming apparatus and executes the determined Ru control. The image forming apparatus according to claim 1.
At the time of image output, the image output apparatus returns the set image output value to the original value when the output value of the pattern density detecting means falls within a certain threshold value . The image forming apparatus according to claim 1, wherein
The toner is an aqueous medium containing resin fine particles formed by dissolving or dispersing a modified polyester resin capable of reacting with a compound having at least an active hydrogen group, a colorant, and a release agent in an organic solvent. It was obtained by dispersing in, reacting with a crosslinking agent and / or an extender, removing the organic solvent from the obtained dispersion, and washing and desorbing resin fine particles adhering to the toner surface. An image forming apparatus .

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