JP4062442B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine.

  As an electrophotographic image forming apparatus, for example, a photosensitive drum is used as an image carrier, an electrostatic latent image is formed on the surface, toner is attached to the electrostatic latent image, and a visible image is formed and transferred onto a sheet. What performs image formation such as “Yes” is known. In such an image forming apparatus, in order to perform an optimal image forming process, it is necessary to constantly adjust in accordance with the deterioration of the toner and the deterioration of the member that occur as the apparatus is used.

For example, in Patent Document 1, in order to guarantee an optimal image, state changes such as the number of printed sheets, environmental changes, jamming, and developing device replacement are determined, and the electrophotographic pre-rotation process is started in the printer itself. It is described that after information is detected and an optimum high-voltage bias value is predicted, the electrophotographic post-rotation process is performed to return to a printable state. Patent Document 2 describes that the main control unit changes the transfer bias according to the number of recording sheets in order to stabilize the transfer conditions and to function the collection / discharge of the toner with the conductive brush roller stably. ing. In Patent Document 3, when the number of continuous double-sided sheets exceeds a predetermined number, a rise in the temperature and resistance of the transfer roller contacting the photosensitive drum is detected, and constant current control is performed on the transfer roller every time the predetermined number of sheets is exceeded. And a transfer bias obtained by adding a predetermined voltage to the voltage at this time is determined by the printer control unit, and this transfer bias is applied to the transfer roller. In Patent Document 4, the voltage value, polarity, timing, and the like of the voltage applied to the transfer roller are controlled based on outputs from a sensor that detects the leading or trailing end position of the transfer material and a counter that counts the transfer material. Are listed. Patent Document 5 describes that a current applied to a primary transfer member for transferring a toner image to an intermediate transfer member is controlled in accordance with the number of images formed during repeated image formation. .
JP-A-7-219391 JP-A-8-95453 Japanese Patent Laid-Open No. 9-244434 Japanese Patent Laid-Open No. 10-301407 Japanese Patent Laid-Open No. 2003-21976

  In the image forming apparatus described above, the toner cartridge or the developing device can be attached and detached so that the toner can be replenished, or the developing device itself can be replaced with a new one. In the type in which the developing device itself is replaced, the amount of toner stored inside increases because the number of sheets on which image formation is performed is increased. For this reason, the toner stirring time becomes longer, and the deterioration of the toner proceeds. In particular, the toner particle diameter gradually increases due to the stirring of the toner, and the toner tends to be used for development from the one having a small particle diameter. Performance will deteriorate.

  When the charging performance of the toner deteriorates, it becomes difficult for the toner to transfer when the toner is transferred to the paper. Further, since the resistance value increases as the transfer roller itself is used, the image quality will be lowered unless image formation is performed in consideration of the deterioration caused by such use.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing deterioration in image quality in a fine manner in response to the deterioration associated with the use described above.

The image forming apparatus according to the present invention includes a photosensitive drum on which an electrostatic latent image is formed, thereby developing by adhering toner to the electrostatic latent image formed on the photosensitive drum to store a predetermined amount of toner a developing device is exchanged by the consumption of the toner, the transfer means for transferring the toner image formed on the photosensitive drum to the sheet while in contact with the photosensitive drum, image on the sheet as well as rotation control of the photosensitive drum In an image forming apparatus comprising a developing unit and a control unit that controls the transfer unit so as to form a temperature detection sensor that detects a temperature in the apparatus, a transfer roller of the transfer unit, and a photosensitive drum and a current value detecting circuit for detecting the FB current flowing between said control means includes a data storage means for accumulating and storing the number of sheets on which image formation has been processed, the current sensing times A data table for setting an optimum transfer voltage value corresponding to a region where n current ranges obtained by dividing current values of n and n temperature ranges obtained by dividing temperature values of the temperature detection sensors are combined. A transfer voltage determining means for storing a plurality of sheets for each range of the accumulated number of sheets and reading a current accumulated number of sheets subjected to image formation processing from the data storage means and determining a transfer voltage value based on the data table ; And a transfer voltage control means for applying a transfer voltage to the transfer means based on the determined transfer voltage value.

  By having the configuration as described above, usage record data relating to image forming processing on paper is accumulated and stored, and the transfer voltage is determined based on the use record data. The transfer voltage can be finely changed, and the toner can be transferred to the paper with the optimum voltage. Here, the usage record data means data accumulated according to the progress of the deterioration of the toner or the deterioration of the transfer means.

  In particular, the transfer voltage can be determined in accordance with the degree of deterioration of the charging performance of the toner by accumulating the number of sheets on which image formation processing has been performed or the driving time of the developing device as usage record data. Therefore, the transfer voltage can be adjusted when the toner amount is large corresponding to the toner amount stored in the developing device.

  Further, by accumulating the driving time of the transfer means as usage record data, the transfer voltage can be determined in accordance with the degree of deterioration of the transfer means. Therefore, the transfer voltage can be adjusted regardless of the toner amount.

  Further, by detecting that the developing device has been replaced and resetting the data storage means, it is possible to count the usage record data from the beginning when the developing device is replaced with a new one.

  In addition, the transfer voltage value stored in advance corresponding to each predetermined range of the accumulated value of the usage record data is read and determined, thereby setting the allowable range of the accumulated value corresponding to the deterioration due to use. Therefore, the transfer voltage value can be finely adjusted for each model.

  Further, by determining a transfer voltage value by adding a predetermined voltage value corresponding to a predetermined increase in the accumulated value of the usage record data, data related to the transfer voltage value to be stored can be reduced and more efficient. Can be controlled.

  Further, by changing the transfer voltage value based on the detection signal from the detection means for detecting the environmental condition in the apparatus, the transfer voltage can be finely adjusted according to the environmental condition. Here, the environmental condition means a parameter that affects the transfer voltage, and examples thereof include temperature and humidity.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic sectional view of the entire image forming apparatus according to the present invention. A document reading unit 2 is arranged at the upper part of the image forming apparatus 1, and a paper feeding unit 3 and a recording unit 4 are arranged at the lower part from the bottom.

  In the document reading section 2, a document placed on a document tray 11 provided with a document cover 10 is transported to a position facing the reading means 5 by a document transport device 12 and a document reading operation is performed, and a document discharge tray. 13 is discharged. When reading a book or the like, the document cover 10 is rotated upward, a portion to be read such as a book is placed on the flat bed platen 14, and a reading operation is performed by the reading means. The above-described configuration is the same as that of a conventional document reading apparatus called a so-called ADF or flat bed type.

  In the paper feed unit 3, a paper feed cassette 15 is disposed, and a plurality of sheets of a predetermined size are stacked on the flapper 16. A pickup roller 17 is disposed at the end of the paper feed cassette 15 (the right end in FIG. 1). The flapper 16 is urged upward so that the upper surface of the stacked paper is pressed against the pickup roller 17. When the pickup roller 17 is rotationally driven in this state, the sheets are fed one by one to the sheet conveyance path by the frictional force.

  The fed paper is first conveyed to the recording unit 4 by a feed roller 18 and a press roller 19. The recording unit 4 includes a developing device 20, a rotating brush 21, a charger 22, a photosensitive drum 23, a transfer roller 24, an LED print head 25, and a fixing roller 26 for recording on the conveyed paper.

  The photosensitive drum 23 has a cylindrical shape, and a photoconductive film having a predetermined thickness is provided on the outer peripheral surface as a photosensitive member. The photosensitive drum 23 is rotationally driven by a main motor, and an image is formed on the surface thereof by the charger 22, the LED print head 25, and the developing device 20. The charging device 22 uses a charging roller, and acts to uniformly charge the outer peripheral surface of the photosensitive drum 23 by applying a charging voltage in contact with the surface of the photosensitive drum 23. A known charging brush may be used instead of the charging roller. The charged state of the photosensitive drum 23 means a state where electric charges are held on the surface of the photosensitive drum 23.

  The LED print head 25 includes a large number of LEDs arranged in parallel, irradiates light on the outer peripheral surface of the photosensitive drum 13 based on the input image information, and forms an electrostatic latent image corresponding to the image information on the outer peripheral surface. . The developing device 20 stores toner therein, and when the toner is consumed, the toner is replaced with a new one without being replenished. The toner is transferred to the surface of the photosensitive drum 23 by the supply roller 27 and the developing roller 28 attached to the developing device 20, and the electrostatic latent image formed on the surface is visualized. A developing voltage is applied to the developing roller 28, and the toner adhering to the surface of the developing roller 28 is moved by a potential difference between the charged charge on the surface of the photosensitive drum 23 and the developing voltage to form a toner image. .

  As the transfer roller 24, an electronic conductive roller or an ion conductive roller is mainly used, and in any case, the toner developed on the surface of the photosensitive drum 23 by the electric field attractive force when a high transfer voltage is applied. Move. When a sheet exists between the photosensitive drum 23 and the transfer roller 24, the toner is transferred to the sheet. When there is no sheet, the transfer roller 24 is in contact with the surface of the photosensitive drum 23. The toner transferred to the paper is removed of electric charge by a neutralizing brush (not shown).

  The rotary brush 21 is disposed on the downstream side of the transfer roller 24, and removes paper dust adhering to the surface by contacting the surface of the photosensitive drum 23, or removing toner remaining on the surface without being transferred. It acts to disperse on the surface of the photosensitive drum 23. A constant voltage is applied to the rotating brush 21 so that the residual toner is efficiently dispersed.

  The transferred toner image is nipped by the fixing roller 26 and the press roller 29 and heated and pressed to be fixed on the paper. A heater lamp is provided in the fixing roller 26 and heats the heater lamp by generating heat. The fixed sheet is nipped between the sheet discharge roller 30 and the press roller 31 and is carried out to the sheet discharge tray 32.

  In FIG. 1, a sheet conveyance path is indicated by a one-dot chain line from the sheet feeding unit 3 to the sheet discharge tray 32. A reversal conveyance unit 40 is detachably mounted on the side surface of the apparatus main body 1, and a paper carry-out port 41 and a paper carry-in port 42 are formed on the mounting side surface. In the transport unit 40, two pairs of transport rollers, a feed roller 43 and a press roller 44, and a feed roller 45 and a press roller 46, are arranged up and down. Then, as shown by a two-dot chain line in FIG. 1, the reverse conveyance path branches off from the sheet conveyance path between the paper discharge roller 30 and the fixing roller 26, and the two pairs of conveyance rollers 43 and 44, 45 and 46 The sheet is formed so as to pass through the sheet and to join the sheet conveyance path between the roller pairs 18 and 19 and the pickup roller 17.

  In the paper conveyance path, a paper detection sensor 33 is disposed between the paper discharge roller 30 and the fixing roller 26 of the recording unit 4, and the paper detection sensor 34 is also provided between the roller pairs 18 and 19 and the pickup roller 17. Is arranged. When recording on only one side of the sheet, the sheet is conveyed to the sheet conveyance path indicated by the alternate long and short dash line, and image formation is performed by appropriately controlling the operation based on the detection signals of the sheet detection sensors 33 and 34. When recording on one side, the single-sided recording paper is once discharged to the paper discharge tray 32, and when the rear end of the paper is detected by the paper detection sensor 33, the paper discharge roller 30 is rotated reversely to reverse the paper. It is controlled so as to be carried into the conveyance path. The sheet carried into the reverse conveyance path is again carried into the conveyance rollers 18 and 19 and conveyed through the sheet conveyance path, and recording is performed on the other side.

  FIG. 2 is an overall block diagram of the image forming apparatus. In this embodiment, a facsimile function and a copying function are provided. Specifically, the MPU 100 as a control means, the NCU 101 that performs communication control with the network, the MODEM 102 that performs facsimile communication control, the ROM 103 that stores programs, data RAM 104 having a storage unit 104a for accumulating and storing usage record data, an image memory 105 for storing received or read image information, a CODEC 106 for encoding or decoding image information, an operator An operation unit 107 that transmits and receives notification information such as input information and warnings, a scanner 108 that reads image information, and a printer interface 109 that receives a print command from an external computer or the like are provided. These functional blocks are connected to each other via a data bus and an address bus, and are controlled by the MPU 100 as a whole. The information received by the facsimile, the information read by the scanner, and the information received together with the print command are transmitted to the recording unit controller 110 to form an image on the paper.

  FIG. 3 is a schematic diagram illustrating a circuit configuration in the recording unit 4. As described above, around the photosensitive drum 23, the charger 22, the LED print head 25, the developing device 20, the transfer roller 24, and the rotating brush 21 are arranged in this order along the rotation direction.

  A charging voltage application circuit 50 is connected to the charger 22, and a charging voltage HVC is applied. When the charging voltage application circuit 50 applies the charging voltage HVC to the charger 22 based on the control signal from the recording unit controller 110, the surface of the photosensitive drum 23 is uniformly charged to about -750V. A recording signal based on image information is transmitted from the recording unit controller 110 to the LED print head 25, and the LED irradiates the surface of the photosensitive drum 23 to expose the uniformly charged surface of the photosensitive drum 23. An electrostatic latent image corresponding to the image information is formed.

  A developing voltage application circuit 51 is connected to the supply roller 27, the developing roller 28, and the blade 35 in the developing device 20, and the developing voltage application circuit 51 applies a voltage to each based on a control signal from the recording unit controller 110. To do. A predetermined supply voltage (−600 V to −700 V, preferably about −650 V) is applied to the supply roller 27 to supply the toner in the developing device 20 to the developing roller 28 while negatively charging the toner. A predetermined developing voltage HVB (−300 V to −400 V, preferably −350 V) is applied to the developing roller 28, and the toner is transferred using the potential difference with the exposed portion while contacting the surface of the photosensitive drum 23. A predetermined bias voltage (−600 V to −700 V, preferably about −650 V) is applied to the blade 35, and the toner layer is pressed against the surface of the developing roller 28 by an elastic force and adhered to the surface of the developing roller 28. The layer thickness is made uniform.

  A transfer voltage application circuit 52 is connected to the transfer roller 24, and the transfer voltage application circuit 52 applies the transfer voltage HVT to the transfer roller 24 based on a control signal from the recording unit controller 110, and the surface of the photosensitive drum 23. The toner image formed on the sheet is transferred to a sheet by an electric field attraction force.

  A heater driving circuit 53 is connected to the fixing roller 26, and the heater driving circuit 53 operates based on a control signal from the recording unit controller 110 to cause the heater lamp in the fixing roller 26 to generate heat. A thermistor 54 is arranged in contact with the surface to detect the surface temperature of the fixing roller 26, and the recording unit controller 110 controls the heater drive circuit 53 based on the detection signal of the thermistor 54, and the surface of the fixing roller 53. The temperature is maintained at a predetermined temperature.

  A distributed voltage application circuit 55 is connected to the rotary brush 21, and the distributed voltage application circuit 55 applies the distributed voltage HVCL to the rotary brush 21 based on a control signal from the recording unit controller 110, so that the surface of the photosensitive drum 23 is exposed. Residual toner is efficiently dispersed.

  The recording unit controller 110 transmits a control signal to the main motor 56 and the sub motor 57 to perform drive control. The main motor 56 controls the pickup roller 17, the feed roller 18, the rotating brush 21, the photosensitive drum 23, the supply roller 27, the developing roller 28, the fixing roller 26, and the press roller 29 based on a control signal from the recording unit controller 110. Drive to rotate. Further, the paper discharge roller 30 is rotated in the direction of discharging the paper via the clutch by the rotational driving force from the main motor 56. The sub motor 57 rotates the feed rollers 43 and 45 based on a control signal from the recording unit controller 110, and rotates the paper discharge roller 30 in the direction of reversing and conveying the paper via the clutch.

  The recording unit controller 110 transmits control signals to the exhaust fan 58 and the intake fan 59 disposed in the apparatus to perform intake / exhaust control in the apparatus. The exhaust fan 58 discharges the air in the apparatus to the outside, and the intake fan 59 acts to take outside air into the apparatus.

  The transfer roller 24 is connected to a current value detection circuit 60 that detects an FB current value flowing between the photosensitive drum 23 and a temperature detection sensor as a sensor for detecting environmental conditions in the apparatus. 61 and a humidity detection sensor 62 are provided.

  In the vicinity of the developing device 20, a new product detection sensor 63 for detecting whether or not the mounted developing device 20 is new is disposed. For example, a metal wire rod and a fuse are electrically connected and attached to a new developing device 20, and the terminal of the new product detection sensor 63 is disposed so as to contact the wire rod and the fuse when the developing device 20 is mounted. To do. A current is passed between the terminals of the new product detection sensor 63 that are in contact with both ends of the wire to detect the presence of the developing device, and a current is passed between the terminals that are in contact with both ends of the fuse to detect the presence or absence of conduction. To detect if it is new. Since the fuse is blown by conduction, once the developing device is mounted, it is not detected as a new product. A detection signal of the new article detection sensor 63 is input to the developing device detection circuit 64 and transmitted to the recording unit controller 110.

  The recording unit controller 110 includes an FB current value storage unit 111 that stores an FB current value flowing between the transfer roller 24 and the photosensitive drum 23, and stores the stored FB current value and usage record data stored in the RAM 104. And a transfer voltage determination unit 112 that determines a transfer voltage based on detection signals from the temperature detection sensor 61 and the humidity detection sensor 62.

  The usage record data includes the number of sheets of paper subjected to image formation processing, the driving time of the developing device 20, or the driving time of the transfer roller 24. As the driving time of the developing device 20, the stirring time of the agitator that affects the charging performance of the toner may be accumulated. Further, as the driving time of the transfer roller 24, the time during which voltage is applied to the transfer roller 24 may be accumulated.

  FIG. 4 shows the transition of the transfer voltage when the number of recorded sheets of paper is used as usage record data. The vertical axis represents the transfer voltage value, and the horizontal axis represents the number of recorded sheets. When the transfer voltage is transferred in an optimum region between the lower limit voltage Vmin and the upper limit voltage Vmax, the toner is favorably transferred from the photosensitive drum 23 to the sheet. When the transfer voltage is lower than the lower limit voltage Vmin, toner transfer to the paper is not performed well, image quality is deteriorated, and residual toner is increased on the photosensitive drum 23. Further, when the transfer voltage becomes higher than the upper limit voltage Vmax, the toner is scattered from the photosensitive drum 23 to contaminate the paper and the inside of the apparatus.

  As shown in FIG. 4, when the number of recording sheets increases, the characteristics of the transfer roller 24 and the charging performance of the toner deteriorate, and the lower limit voltage Vmin and the upper limit voltage Vmax tend to increase. Therefore, as shown in the graph A, when the image forming process is continued while maintaining a constant transfer voltage, the transfer voltage becomes lower than the lower limit voltage Vmin, which causes a problem of image quality deterioration. In order to cope with such a problem, as shown in the graph B, the transfer voltage may be increased in accordance with the increase of the lower limit voltage Vmin. The degree of increase in the transfer voltage is determined based on the measurement results obtained by conducting experiments in advance. Further, a mathematical expression that approximates the measurement result may be calculated and used. If an experiment is performed assuming that the toner amount filled in the developing device 20 is the maximum, the developing device 20 can be applied to a developing device having a smaller toner amount.

  In FIG. 5, in order to increase the transfer voltage so as not to fall below the lower limit voltage Vmin in the modification of FIG. 4, the increment Vo is added when the number of recording sheets increases by a predetermined number. By setting in this way, the storage data for determining the transfer voltage value can be reduced, and the determination process can be performed efficiently.

  FIG. 6 is another modification of FIG. 4, and the transfer voltage is maintained at a constant transfer voltage until the number of recording sheets reaches a predetermined number. When the number exceeds the predetermined number, the transfer voltage is increased as in FIG. Therefore, when the amount of toner filled in the developing device is small, it is not necessary to change the transfer voltage, and the voltage control can be made more efficient.

  FIG. 7 is a graph showing the characteristics of the FB current flowing between the photosensitive drum 23 and the transfer roller 24 when a predetermined constant voltage is applied by the transfer voltage applying circuit 52. The transfer voltage is taken on the vertical axis, and the detected FB current is taken on the horizontal axis. As shown in this graph, the optimum transfer voltage is large when the FB current is small, but the optimum transfer voltage is small when the FB current is large. Such a relationship changes as the number of recorded sheets increases. Graph E shows a state where the number of recorded sheets is 0 (unrecorded state), graph F shows a state where the number of recorded sheets is 10,000, and graph G shows a state where the number of recorded sheets is 20,000, but as the number of recorded sheets increases. It can be seen that the optimum transfer voltage increases.

  Also, the FB current value depends on environmental conditions. For example, when the transfer roller is an ion conductive roller, the resistance is high when the temperature is low and the humidity is low, and the resistance is low when the temperature is high and the humidity is high. As described above, if the optimum transfer voltage is determined in consideration of the environmental conditions, which are short-term fluctuation factors, and the actual usage data (recording number), which is long-term fluctuation factors, finer voltage control is possible. It can be carried out. As an example, a data table as shown in FIG. 8 may be created in advance and stored in the recording unit controller 110, and the transfer voltage determination unit 112 may determine the transfer voltage based on the data table. The data table of FIG. 8 stores the transfer voltage value for each region obtained by dividing the temperature T detected by the temperature detection sensor 61 and the FB current value detected by the current value detection circuit 60 into a plurality of ranges.

In Figure 8, taking the FB current value on the horizontal axis, the range of range from the current value I ₀ to I _n of n _{(I 0 ~I 1, ···,} I i-1 ~I i, ··· , I _{n-1 to} I _n ). The vertical axis represents temperature, and the temperature range from temperature T ₀ to T _n is n ranges (T _{0 to} T ₁ ,..., T _{j-1 to} T _j ,..., T _n-1 It has been divided into ~T _n). The current range which is a region divided in a matrix form; I _{i-1 to} I _i
Because
Temperature range; T _{j-1 to} T _j
For these areas, an optimum transfer voltage value V _ij is stored for each area in advance through experiments or the like. The transfer voltage value stored in the data table is set to decrease as the current value increases (as it goes to the right in the horizontal axis in FIG. 8), and as the temperature increases (in the vertical axis in FIG. 8). It is set so that the value decreases as it goes up. This is based on the characteristics of the transfer roller as described above.

  The data table 111 is set for each range of usage record data in the recording unit. For example, in the case of the number of recorded sheets, a similar data table is set corresponding to the range of the number of sheets, such as 10,000 sheets or less, more than 10,000 sheets, 20,000 sheets or less, more than 20,000 sheets, 30,000 sheets or less. The

  9 to 12 show a processing flow using such a data table, and FIG. 13 shows a time chart thereof.

    When the power source of the apparatus main body is turned on, an initialization process is first performed (S100), and initial setting of the apparatus is performed. Next, it is checked whether or not the developing device is attached based on the detection signal of the new article detection sensor 63 (S101), and if it is not attached, an error is notified (S102). If the developing device is installed, it is checked whether the developing device is new or not by a detection signal of the new product detection sensor 63 (S103), and if it is new, the use result data storage unit 104a of the RAM 104 is reset (S104). ). If it is not a new product, the usage record data is read (S105), and the corresponding data table is selected from the plurality of data tables based on the read usage record data (S106).

Next, when the recording process is started at time t ₀ , a preparation process is performed (S200), rotation control of the main motor 56 is started (S200a), and voltage control is started (S200b). In the voltage control, a charging voltage HVC is applied, and a positive voltage is applied as the developing voltage HVB. A distributed voltage HVCL is applied, and a negative voltage is applied as the transfer voltage HVT. Here, the positive voltage is applied as the developing voltage HVB because the toner remaining on the uncharged portion (portion where the potential is substantially 0 V) on the outer peripheral surface of the photosensitive drum 23 is efficiently developed by the developing roller 28. This is because of the recovery. The reason why the negative voltage is applied as the transfer voltage HVT is to collect the toner adhering to the outer peripheral surface of the transfer roller 24 on the surface of the photosensitive drum 23.

From the time t ₀ the timer T1 and T6 starts counting (S201), the timer T1 is checked whether or not the time is up (S202). When the timer T1 expires, the developing voltage HVB is switched to a negative voltage, and the transfer voltage HVT is turned off (S203).

  The timer T2 starts counting at the timing when the timer T1 expires (S204), and when the timer T2 expires (S205), a test voltage is applied as the transfer voltage HVT (S206). Simultaneously with the application of the test voltage, the timer T3 starts counting (S207). When the timer T3 counts, the current value detection circuit 60 samples the current value (S208), and when the timer T3 times out (S209), the average value of the current values sampled a plurality of times is used as the FB current value. The image is stored in the storage unit 111 (S210), and the transfer voltage HVT is turned off (S211).

  The timer T4 starts counting at the timing when the timer T3 expires (S212), and when the timer T4 expires (S213), a negative voltage is applied as the transfer voltage HVT (S214). The timer T5 starts counting at the timing when the timer T4 expires (S215), and when the timer T5 expires (S216), the transfer voltage HVT is turned off (S217).

  Next, it is checked whether or not the timer T6 expires (S218). When the timer T6 expires, it is checked whether or not the fixing temperature has reached a predetermined temperature (S219). When the fixing temperature reaches a predetermined temperature and the preparation is completed, the paper feed clutch is turned on (S220). Then, 1 is added to the stored use record data (the number of recorded sheets in this example) and stored again (S221). When the paper feed clutch is turned on, the pickup roller 17 rotates and paper is carried from the paper feed cassette 15.

  When the paper feeding operation is performed, the timer T7 starts counting (S222), and it is checked whether the paper detection sensor 34 detects the front edge of the paper and is turned on (S223). It is checked whether or not the timer T7 has expired with the sheet detection sensor 34 turned off (S224). If the timer T7 has expired, the sheet is loaded even though the sheet feeding clutch is turned on. As a result, a paper jam or out of paper is considered. Therefore, a stop process is performed (S225), the rotation of the main motor 56 is stopped, the charging voltage HVC, the development voltage HVB, the transfer voltage HVT, and the dispersion voltage HVCL are turned off, and the heating process of the fixing roller is also stopped. Then, an error is displayed (S226), and the recording process is terminated.

  In step S223, when the paper detection sensor 34 is turned on, the timers T8, T9, T10 start counting (S227), the timer T10 is checked for time-up (S228), and the LED is timed when the timer T10 times up. Exposure by the print head 25 is started (S229). Next, the time up of the timer T8 is checked (S230), and the transfer voltage value is read based on the FB current value stored in the step S210 from the data table selected in the step S106 at the timing when the timer T8 times out. It is issued and determined (S231).

  Then, a positive pre-transfer voltage value smaller than the transfer voltage value determined when the timer T8 times up is applied as the transfer voltage HVT (S232). During the application of the pre-transfer voltage value, residual toner attached to the rotating brush 21 and the charger 22 is transferred to the surface of the photosensitive drum 23, and these residual toner is collected by the developing roller 28. Next, the timer T9 is checked for time-up (S233), and the positive transfer voltage value determined in step S231 is applied as the transfer voltage HVT at the timing when the timer T9 times up (S233). Is done. Thereafter, the recording process similar to the conventional one is continued.

  In the above example, the number of recorded sheets is accumulated and counted as the usage record data. However, the stirring time of the agitator of the developing device 20 may be counted by a timer and accumulated. Further, the time during which the voltage is applied to the transfer roller 24 may be counted by a timer and accumulated. In the above processing flow, the data table is selected when the power is turned on. However, the data table may be selected when an instruction is given by a user operation, when the cover is opened or closed, or when the sleep state is released.

1 is a schematic perspective view of an entire image forming apparatus using an embodiment according to the present invention. It is a whole block diagram regarding the embodiment concerning the present invention. It is a principal part circuit block diagram regarding embodiment which concerns on this invention. It is a figure explaining the relationship between a transfer voltage and the number of recording sheets. It is a figure explaining the relationship between a transfer voltage and the number of recording sheets. It is a figure explaining the relationship between a transfer voltage and the number of recording sheets. It is a figure explaining the relationship between a transfer voltage and FB current. It is a figure explaining the concept of a data table. It is a processing flow figure of an embodiment concerning the present invention. It is a processing flow figure of an embodiment concerning the present invention. It is a processing flow figure of an embodiment concerning the present invention. It is a processing flow figure of an embodiment concerning the present invention. It is a time chart figure of embodiment which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Original reading part 3 Paper feed part 4 Recording part 5 Reading means

Claims (1)

A photosensitive drum on which an electrostatic latent image is formed, and a developing device that stores a predetermined amount of toner, attaches the toner to the electrostatic latent image formed on the photosensitive drum , develops the toner, and replaces the toner when the toner is consumed When the transfer means for transferring the toner image formed on the photosensitive drum to the sheet while in contact with the photosensitive drum, said developing device so that the image formed on the sheet with the photosensitive drum to control the rotation and the In an image forming apparatus comprising a control means for controlling a transfer means, a temperature detection sensor for detecting the temperature in the apparatus, and a current for detecting an FB current flowing between the transfer roller of the transfer means and the photosensitive drum and a value detection circuit, wherein the control means includes data storage means for accumulating and storing the number of sheets on which image formation has been processed, n-number of conductive obtained by dividing the current value of the current sensing circuit A data table for setting an optimum transfer voltage value corresponding to a region obtained by combining a range and n temperature ranges obtained by dividing the temperature value of the temperature detection sensor for each range of the cumulative number of sheets subjected to image formation processing Transfer voltage determining means for storing a plurality of sheets and reading the accumulated number of sheets subjected to current image formation processing from the data storage means and determining a transfer voltage value based on the data table; and based on the determined transfer voltage value An image forming apparatus comprising: a transfer voltage control unit that applies a transfer voltage to the transfer unit.

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