JP2005164687A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately discriminating the abnormal state of a photoreceptor drum or the like while fully taking into account the characteristics of the image forming apparatus in which the optimum setting condition of the apparatus is changed according to the operating environment and an operating time, etc. <P>SOLUTION: The image forming apparatus is constituted so that a constant voltage or a constant current is applied by a transfer voltage apply circuit 52 for applying a transfer voltage between the photoreceptor drum 23 and a transfer roller 24, and the current generated on the transfer roller 24 in that case is detected by a current value detection circuit 60. A reference value corresponding to the temperature and the humidity are read from a reference value table 111 by a recording part controller 110 on the basis of the detection signals from a temperature detection sensor 61 and a humidity detection sensor 62, and it is discriminated whether the abnormal state occurs by comparing the reference value with the detected current value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

An electrophotographic image forming apparatus uses, for example, a photosensitive drum as an image carrier, forms an electrostatic latent image on the surface, develops the electrostatic latent image, and transfers the image onto a sheet. Is known to do. In such an image forming apparatus, deterioration of the photosensitive drum progresses as it is used. Therefore, accurately knowing the degree of deterioration of the photosensitive drum is important in maintaining the image quality.
As a method for detecting the deterioration of the photosensitive drum, for example, in Patent Document 1, a current value flowing into the photosensitive drum when the photosensitive drum is charged using a primary charging roller is detected and set in advance. The point which was made to compare with a lifetime electric current value is described. Japanese Patent Application Laid-Open No. H10-228561 describes that a non-image area formed on a photosensitive drum is irradiated with light by a light emitting element, the reflected light is detected by a light receiving element, and the amount of reflected light is compared with a reference value. .
JP-A-9-179559 JP 2002-278383 A

  Since the electrophotographic image forming apparatus is composed of a wide variety of parts and handles different materials such as toner and paper, the optimal setting conditions of the apparatus vary depending on the usage environment and usage time. It is inevitable to come. However, in the above-described prior art, it is difficult to say that the deterioration of the photosensitive drum is determined in consideration of such characteristics of the image forming apparatus.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of accurately determining an abnormal state of a photosensitive drum or the like by sufficiently considering the characteristics of the image forming apparatus as described above. .

  An image forming apparatus according to the present invention includes an image carrier, image forming means for forming an image on the image carrier, and abutting the image carrier and transferring an image formed on the image carrier to a sheet. In the image forming apparatus, comprising: a transfer unit; and a control unit that controls the rotation of the image carrier and controls the image forming unit and the transfer unit so as to form an image on a sheet. The control unit includes at least one control unit. Storage means for storing a reference value predetermined for each of a plurality of ranges related to the parameter; reading means for determining a current value of the parameter and reading a reference value corresponding to the current value from the storage means; An application unit that applies a constant voltage or a constant current to the transfer unit in a state where no sheet exists between the image carrier and the transfer unit; and a constant voltage or a constant voltage applied by the application unit. Detecting means for detecting a voltage or current generated between the image carrier and the transfer means, and comparing the reference value read by the reading means with the value detected by the detecting means. And determining means for determining whether or not a state is present. Further, the storage means stores a reference value for each range divided into a plurality of temperature ranges with respect to the temperature in the apparatus which is one of the parameters, and the reading means has a temperature provided in the apparatus. A current temperature value is determined based on a detection signal from the sensor. Further, the storage means stores a reference value for each range divided into a plurality of humidity ranges with respect to the humidity in the apparatus which is one of the parameters, and the reading means has a humidity provided in the apparatus. The present invention is characterized in that a current value of humidity is determined based on a detection signal from a sensor. Further, the storage means stores a reference value for each range divided into a plurality of sheet number ranges with respect to the number of recorded sheets as one of the parameters, and the reading means is a recording provided in the apparatus. The present invention is characterized in that the current value of the number of recorded sheets is determined based on an output signal from a number counter. Further, the control means operates the application means during a preparatory process performed before the paper is carried between the image carrier and the transfer means.

  With the above configuration, a constant voltage or a constant current is applied to the transfer unit to detect a voltage or current generated between the image carrier and the transfer unit, so that an image is formed on the image carrier. Since the detection is performed at the final stage, it is possible to reliably determine an abnormal state that causes a reduction in image quality. Further, a reference value determined in advance for each of a plurality of ranges related to a parameter that affects the image forming apparatus is stored, and the current value of the parameter is determined and a reference value corresponding to the current value is stored. Since the determination is based on this, the abnormal state can be determined more accurately.

  Furthermore, as parameters that have the greatest effect on the image forming apparatus, reference values are set in advance using parameters related to the use environment such as the temperature inside the apparatus and humidity inside the apparatus, and parameters related to the use time such as the number of recorded images on the paper. By doing so, an accurate determination can be made. Moreover, if a reference value is set by combining a plurality of these parameters, the determination accuracy can be further improved.

  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 unit 2, a document placed on a document tray 11 provided with a document cover 10 is transported to a position facing the reading unit 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. In the recording unit 4, a developer 20, a rotating brush 21, a charger 22, a photosensitive drum 23, a transfer roller 24, and a laser scan unit (hereinafter abbreviated as “LSU”) 25 are used for recording on the conveyed paper. In addition, a fixing roller 26 is provided.

  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 LSU 25, and the developing unit 20. The charger 22 uses a scorotron charger, a charging brush, or a charging roller, and acts to uniformly charge the outer peripheral surface of the photosensitive drum 23 by applying a charging voltage. 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 LSU 25 performs exposure by irradiating the uniformly charged surface of the photosensitive drum 23 with laser light generated by a laser. When irradiating laser light, the surface of the photosensitive drum 23 is scanned by an optical system such as a polygon mirror to form an electrostatic latent image according to image information. The developing device 20 stores toner therein, and transfers the toner to the surface of the photosensitive drum 23 by the supply roller 27 and the developing roller 28 to visualize the electrostatic latent image formed on the surface. 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, toner developed on the surface of the photosensitive drum 23 by the electric field attraction force when a high transfer voltage is applied is used. 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 a network, the MODEM 102 that performs facsimile communication control, a ROM 103 that stores programs, data, and the like RAM 104 for storing image information, image memory 105 for storing received or read image information, CODEC 106 for encoding or decoding image information, operation unit 107 for transmitting and receiving notification information such as input information and warning from an operator, A scanner 108 for reading image information and a printer interface 109 for receiving 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 LSU 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 positive charging voltage HVC is applied thereto. 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 + 800V. A recording signal based on image information is transmitted from the recording unit controller 110 to the LSU 25, and laser light is irradiated on the surface of the photosensitive drum 23 while being irradiated based on the recording signal, and the photosensitive drum 23 is uniformly charged. The exposed surface is exposed to form an electrostatic latent image corresponding to the image information.

  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 (+300 V to +700 V) is applied to the supply roller 27 to supply the toner in the developing device 20 to the developing roller 28 while being positively charged. A predetermined developing voltage HVB (+300 V to +700 V) is applied to the developing roller 28, and the toner is transferred using the potential difference from the exposed portion while contacting the surface of the photosensitive drum 23. In addition, a predetermined bias voltage (+300 V to +700 V) is applied to the blade 35, and the layer thickness of the toner layer attached to the surface of the developing roller 28 is made uniform by being pressed against the surface of the developing roller 28 by an elastic force.

  A transfer voltage application circuit 52 is connected to the transfer roller 24, and the transfer voltage application circuit 52 applies a transfer voltage HVT (1700 V) to the transfer roller 24 based on a control signal from the recording unit controller 110, and the photosensitive drum. The toner image formed on the surface 23 is transferred onto a sheet by electric field attraction.

  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 a current value flowing between the photosensitive drum 23 and a temperature detection sensor 61 and a humidity detection sensor 62 are disposed in the vicinity thereof. Has been. The detection signals of the current value detection circuit 60, the temperature detection sensor 61, and the humidity detection sensor 62 are transmitted to the recording unit controller 110.

  By measuring a current or voltage generated between the transfer roller 24 and the photosensitive drum 23, an abnormality that causes a reduction in image quality such as a pinhole or a charging failure generated in the photoconductive film on the surface of the photosensitive drum 23 is detected. be able to. For example, when a pinhole is generated in the photoconductive film, a short circuit occurs and a current easily flows, and an abnormally high potential state exists between the transfer roller 24 and the photosensitive drum 23. Conversely, when the current is difficult to flow, an abnormal low potential state occurs. In particular, since the transfer roller 24 comes into contact with the photosensitive drum 23 when the charging process and the developing process are completed, there is an advantage that such an abnormality can be easily detected.

  Therefore, a constant voltage (1000 to 1600 V) or a constant current (3 to 5 μA) is applied to the transfer roller 24 by the transfer voltage application circuit 52, and the current generated in the transfer roller 24 at that time is detected by the current value detection circuit 60. Thus, the abnormal state of the recording unit 4 is detected. In this embodiment, the current flowing through the transfer roller 4 is detected by the current value detection circuit 60, but the voltage generated in the transfer roller 4 may be detected.

  However, the transfer roller 24 has a characteristic that the resistance value easily varies depending on temperature and humidity. For example, in the case of an ion conductive roller, the resistance is high at a low temperature and low humidity, and the resistance is low at a high temperature and high humidity. Further, the resistance value of the transfer roller 24 varies as the usage time becomes longer. For example, as the number of recording sheets increases, the resistance value gradually increases, making it difficult for current to flow through the transfer roller.

  Therefore, it is impossible to accurately detect an abnormality that causes a reduction in image quality unless the fluctuation characteristics are grasped corresponding to parameters that affect the characteristics of the transfer roller. Therefore, in the present embodiment, the temperature detection sensor 61 and the humidity detection sensor 62 are disposed in the vicinity of the transfer roller 24, and these detection signals are transmitted to the recording unit controller 110 and stored in advance in the reference value of the reference table 111. I try to compare.

  FIG. 4 is a diagram conceptually illustrating an example of the reference table 111. The reference table 111 refers to the current value detected by the current value detection circuit 60 for each region divided into a plurality of ranges for the temperature St detected by the temperature detection sensor 61 and the humidity Sh detected by the humidity detection sensor 62. The lower limit value a and the upper limit value b are stored as values.

In Figure 4, taking the temperature on the horizontal axis, the range the temperature range from the temperature St ₀ until the temperature St _n of n _{(St 0 ~St 1, ···,} St i-1 ~St i, ···, It has been divided into St _n-1 ~St _n). The vertical axis represents humidity, and the temperature range from humidity Sh ₀ to humidity Sh _n is n ranges (Sh _{0 to} Sh ₁ ,..., Sh _{j-1 to} Sh _j ,..., Sh _{n− 1 to} Sh _n ). And the temperature range which is the area | region divided into matrix form; St _i-1 -St _i
Because
Humidity range; Sh _{j-1 to} Sh _j
Respect of area, the lower limit value in the range of current values which are recognized as the normal range by pre-test or the like; a _ij
Upper limit; b _ij
Is stored for each area. The lower limit value a and the upper limit value b stored in the reference value table 111 are set to increase as the temperature increases (going to the right in the horizontal axis in FIG. 4), and as the humidity increases (see FIG. The value is set to increase (as it goes upward on the vertical axis of 4). As described above, this is because the resistance value of the transfer roller decreases at high temperature and high humidity.

  The reference value table 111 is set for each recording number range in the recording unit. For example, a reference value table similar to that in FIG. 4 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 recording unit controller 110 is provided with a number counter 112 that counts the number of sheets each time a sheet is recorded, and reads a lower limit value and an upper limit value from a reference value table corresponding to the count value. Since the resistance value of the transfer roller increases as the number of recorded sheets increases, the lower limit value and the upper limit value are set to be smaller as the reference value table has a larger number of recorded sheets.

When the recording unit controller 110 receives the detection signals from the temperature detection sensor 61 and the humidity detection sensor 62, respectively, the corresponding area is determined from the temperature data and the humidity data, and the lower limit value a _ij and the upper limit value b _ij are obtained as a reference value table. The current value SI read from 111 and detected by the current value detection circuit 60 is a _ij ≦ SI ≦ b _ij
If the current value SI satisfies this relationship, it is determined to be normal. If the current value SI does not satisfy this relationship, it is determined that there is an abnormality, and abnormality processing such as stopping the apparatus or displaying an error is performed.

  Next, a processing flow relating to the above-described embodiment will be described. FIG. 5 is a flowchart relating to the warm-up process from when the apparatus is turned on to when the apparatus enters a standby state, and FIG. 6 is a time chart thereof.

When the apparatus is turned on at time t ₀ , initialization processing is first performed (S 100), and initial setting of the apparatus is performed. After the initialization process, the recording unit controller 110 transmits a driving signal to the heater driving circuit 53 to start heating the fixing roller 26, and a detection signal from the thermistor 54 that detects the fixing roller temperature is input to the recording unit controller 110 and fixed. The roller temperature is constantly monitored, and control is performed to increase the temperature to the fixing roller temperature Temp2 (for example, 150 ° C.) at which the warm-up process ends (S101).

It is checked whether the heating of the fixing roller 26 is started and the temperature of the fixing roller has increased to Temp1 (for example, 105 ° C.) (S102). When the fixing roller temperature at time t ₁ is to have reached the Temp1, pre-rotation process from time t ₁ (S103) is performed.

  In the pre-rotation process, the polygon motor that rotates the polygon mirror of the LSU 25 starts to rotate (S103a), and at the same time, the main motor 56 starts to rotate (S103b). As the main motor 56 rotates, the photosensitive drum 23, the supply roller 27, the developing roller 28, the transfer roller 24, and the rotating brush 21 are driven to rotate. Also, the timer T11 starts counting from the start of rotation of the main motor 56.

  In the pre-rotation process, the sub motor 57 starts to rotate (S103c), and the presence / absence of paper remaining in the reverse conveyance unit 40 is detected. As shown in the time chart, the auxiliary motor 57 is driven so as to first rotate in the forward direction while the timer T101 is counting, and then rotate in the reverse direction while the timer 102 is counting. The remaining paper is discharged to the paper discharge tray 32 by the rotation processing in the forward and reverse directions, or is detected by the paper detection sensor 34.

  In the pre-rotation process, rotation control of the exhaust fan 58 and the intake fan 59 is started (S103d). The rotation of the exhaust fan 58 is started and the warm air in the vicinity of the fixing roller is exhausted outside the apparatus, and the rotation of the intake fan 59 is started and the outside air is introduced into the vicinity of the power supply unit.

In the pre-rotation process, voltage control for performing a cleaning process on the photosensitive drum 23 is performed (S103e). The driving of the charging voltage application circuit 50 is started from the time t ₁ when the main motor 56 starts to rotate, and the charging voltage HVC is applied to the charger 22, and the surface of the photosensitive drum 23 is uniformly charged by the application of the charging voltage HVC. To go.

Timer T31 which has started counting from the time t ₁ at the timing when the time is up, the developing voltage HVB to the developing roller 28 is applied a developing voltage applying circuit 51 is started driving. The timer T31 is set to a time until the surface of the photosensitive drum 23 charged by the charger 22 comes to a position where it contacts the developing roller 28 by rotation. Accordingly, the development voltage is prevented from being applied in a state where the uncharged portion of the photosensitive drum 23 is in contact with the development roller 28.

  The applied developing voltage HVB is initially set to a voltage (for example, +10 V) smaller than the developing voltage (for example, +400 V) at the time of image formation. When such a small voltage is applied, a large potential difference is generated between the charged surface of the photosensitive drum 23 and the developing roller 28, so that the toner remaining on the surface of the photosensitive drum 23 is efficiently collected by the developing roller 28. can do.

Timer T32 which has started counting from the time t ₁ is a time-up, further polygon motor timer T34 starts counting a stable Ready signal that is in rotation is output timing at a predetermined rotational speed, timer T34 The development voltage application circuit 51 sets the development voltage HVB to a large positive voltage (for example, +400 V) at the timing when the time expires.

Timer T41 which has started counting from the time t ₁ at the timing when the time is up, the transfer voltage HVT to the transfer roller 24 is applied a transfer voltage application circuit 52 is started driving. The timer T41 is set to a time until the surface area of the photosensitive drum 23 charged by the charger 22 reaches a position where it contacts the transfer roller 24 by rotation. The applied transfer voltage HVT is set to a positive transfer voltage (for example, +1000 V) having a polarity opposite to the transfer voltage (negative polarity) applied at the time of image formation.

  Further, the transfer voltage application circuit 52 applies the transfer voltage HVT for the time set by the timer T42. Since the timer T42 is set to a time longer than the time for which the transfer roller 24 makes one rotation, the residual toner adhering to the entire circumferential surface of the transfer roller 24 is transferred between the transfer roller 24 and the surface of the photosensitive drum 23. Due to the potential difference between them, the surface of the photosensitive drum 23 is transferred.

Timer T61 from the time t ₁ starts counting at the timing when the time is up, dispersion voltage HVCL is applied dispersion voltage application circuit 55 is started driving the rotary brush 21. The timer T61 is set to a time until the surface of the photosensitive drum 23 charged by the charger 22 comes to a position where it contacts the rotating brush 21 by rotation. By applying the dispersion voltage HVCL, the adhesive force of the residual toner attached to the surface of the photosensitive drum 23 is weakened.

  After the pre-rotation process as described above is started, a recording unit abnormality detection task is performed (S104). The recording unit abnormality detection task is performed in the processing flow shown in FIG. First, a detection process for sampling the detection signal from the temperature detection sensor 61 is performed (S200), and a detection process for sampling the detection signal from the humidity detection sensor 62 is performed (S201). Then, the corresponding area of the reference value table 111 is determined based on the sampled detection data regarding temperature and humidity (S202), and the upper limit value and the lower limit value stored in the corresponding area are read (S203).

  Next, as shown in FIG. 6, a constant voltage (or constant current) is applied to the transfer roller 24 by the transfer voltage application circuit 52 for the time counted by the timer T43 (S204). The timer 43 is set to a time required for the transfer roller 24 to contact the entire peripheral surface of the photosensitive drum 23. Meanwhile, a current value generated between the photosensitive drum 23 and the transfer roller 24 is detected by the current value detection circuit 60 (S205). The current value may be detected by sampling a plurality of times and obtaining an average value.

  The detected current value is compared with the lower limit value (S206), and further compared with the upper limit value (S207). If the detected current value is lower than the lower limit value or higher than the upper limit value, image forming processing is performed. In addition to stopping, error notification processing is performed (S208). When the detected current value is higher than the lower limit value and lower than the upper limit value, the process proceeds to S105.

  In S105, it is checked whether the timer T11 has timed up and the fixing roller temperature has increased to Temp2, and if both conditions are satisfied, the main motor 56 is stopped (S106) and the process proceeds to standby state control. To do.

  In the above processing flow, the recording unit abnormality detection task is performed in the warm-up process when the power is turned on, but at the time of the warm-up process performed when an instruction by a user operation, opening / closing of the cover, release of the sleep state, etc. You may make it perform. It is also possible to perform a recording unit abnormality detection task in a post-rotation process performed after the sheet image forming process.

It is a schematic sectional drawing which shows the whole structure regarding embodiment which concerns on this 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 conceptual diagram regarding a reference value table. It is a warm-up process flowchart of embodiment which concerns on this invention. It is a time chart figure at the time of the warming-up process of embodiment which concerns on this invention. It is a recording part abnormality detection task processing flowchart 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 (5)

  An image carrier, image forming means for forming an image on the image carrier, transfer means for contacting the image carrier and transferring the image formed on the image carrier to paper, and the image carrier. In the image forming apparatus including the image forming unit and the control unit that controls the transfer unit so as to perform rotation control and form an image on a sheet, the control unit includes a plurality of ranges for at least one parameter. A storage means for storing a reference value determined in advance, a reading means for determining a current value of the parameter and reading a reference value corresponding to the current value from the storage means, and the image carrier and the transfer means. An application unit that applies a constant voltage or a constant current to the transfer unit in a state where no sheet is present between the image carrier and the transfer unit by a constant voltage or a constant current applied by the application unit. A detecting means for detecting a voltage or current generated between the detecting means and a reference value read by the reading means and a value detected by the detecting means to determine whether or not an abnormal state is present; An image forming apparatus comprising: a determination unit.   The storage means stores a reference value for each range divided into a plurality of temperature ranges with respect to the temperature in the apparatus, which is one of the parameters, and the reading means includes a temperature sensor provided in the apparatus. The image forming apparatus according to claim 1, wherein a current temperature value is determined based on the detection signal.   The storage means stores a reference value for each range divided into a plurality of humidity ranges with respect to the humidity in the apparatus, which is one of the parameters, and the reading means includes a humidity sensor provided in the apparatus. The image forming apparatus according to claim 1, wherein the current humidity value is determined based on the detection signal.   The storage means stores a reference value for each range divided into a plurality of sheet number ranges with respect to the number of recorded sheets as one of the parameters, and the reading means has a recording number counter provided in the apparatus. 4. The image forming apparatus according to claim 1, wherein a current value of the number of recorded sheets is determined based on an output signal from the image forming apparatus.   5. The control unit according to claim 1, wherein the control unit operates the application unit during a preparatory process performed before the sheet is carried between the image carrier and the transfer unit. The image forming apparatus described.

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