JP2010054752A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply a proper voltage on a developer supply member and a layer forming member to form images of high quality without occurrence of soiling due to excessive charging even when repeating image forming operation by determining the voltage applied on the developer supply member and the layer forming member in response to a current value flowing in a developer carrier and an environment. <P>SOLUTION: An image forming apparatus includes: an image carrier chargeable on a surface; an exposure part for forming an electrostatic latent image on the image carrier; the developer carrier for developing the electrostatic latent image with a developer; the developer supply member for supplying the developer on the developer carrier; the layer forming member for forming the developer on the developer carrier in a thin layer; a current measuring part for measuring the current value flowing in the developer carrier; an environment detection part for detecting the environment; and a voltage correction condition determining part for determining the voltage applied on the developer supply member and the layer forming member in response to the current value measured with the current measuring part and the environment detected with the environment detection part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Conventionally, in an image forming apparatus such as an electrophotographic printer, a photosensitive drum as an image carrier is charged by a charging roller as a charging member, an exposure unit writes an electrostatic latent image on the photosensitive drum, and a developer. A developing roller as a carrier, a toner supplying roller as a developer supplying member that supplies toner as a developer to the developing roller, and a regulating blade as a layer forming member that forms a thin layer of toner on the developing roller The electrostatic latent image on the photosensitive drum is developed by a developing device that includes a toner image to form a toner image, and the toner image is transferred onto a sheet by a transfer roller as a transfer member. The toner remaining on the photosensitive drum after the transfer is collected by a cleaning blade made of a rubber plate. The sheet on which the toner image has been transferred passes through the fixing device and is fixed by the toner image, and then is discharged from the main body of the image forming apparatus.

  As the developing roller, toner supply roller, transfer roller, and charging roller disposed in such an image forming apparatus, a conductive roller having at least a conductive rubber elastic layer around a conductive shaft is used. An independent or common power source is connected to these conductive rollers, and a positive or negative voltage is applied.

  By the way, in the image forming apparatus, since the conductivity of the developing roller and the toner supply roller or the charging characteristics of the toner itself changes depending on the environmental conditions, the charge amount and the adhesion amount of the toner on the developing roller change. As a result, for example, in a low temperature and low humidity environment called LL environment, the toner charge amount and adhesion amount increase, and toner adhesion (hereinafter referred to as “dirt”) occurs on the non-exposed portion. Further, for example, in a high-temperature and high-humidity environment called an HH environment, the toner charge amount decreases and the adhesion amount to the developing roller decreases, resulting in a decrease in toner density or fading.

For this reason, a current measuring unit is provided, and the toner charge amount and adhesion amount are estimated based on the current value of the current flowing through the developing roller (hereinafter referred to as “DB current”) measured by the current measuring unit to develop the toner. An image forming apparatus that determines a voltage to be applied to a roller has been proposed (see, for example, Patent Document 1). In this case, when the measured current value of the DB current is equal to or less than a predetermined value, the warm-up operation before printing is extended according to the current value.
JP 2005-331726 A

  However, in the conventional image forming apparatus, the environmental conditions under which the image forming apparatus is used even if the warm-up operation time is controlled or the voltage to be applied to the developing roller is determined based on the charge amount of the toner. Depending on the case, the quality of the image may deteriorate. For example, dirt may occur in the LL environment. Further, for example, in the HH environment, the back surface of the paper may be stained.

  The present invention solves the problems of the conventional image forming apparatus and determines the voltage applied to the developer supply member and the layer forming member according to the value of the current flowing through the developer carrying member and the environment. An image forming apparatus capable of applying an appropriate voltage to the agent supply member and the layer forming member and capable of forming a high-quality image without causing contamination due to excessive charging even when the image forming operation is repeated. The purpose is to provide.

  Therefore, in the image forming apparatus of the present invention, an image carrier that can be charged on the surface, an exposure unit that forms an electrostatic latent image on the image carrier, and development that develops the electrostatic latent image using a developer. A developer carrier, a developer supply member that supplies the developer to the developer carrier, a layer forming member that forms the developer on the developer carrier into a thin layer, and a current that flows through the developer carrier. A current measuring unit for measuring a value; an environment detecting unit for detecting an environment; a current value measured by the current measuring unit and an environment detected by the environment detecting unit; A voltage correction condition determination unit that determines a voltage to be applied.

  According to the present invention, the image forming apparatus determines the voltage to be applied to the developer supply member and the layer forming member according to the current value flowing through the developer carrying member and the environment. As a result, an appropriate voltage can be applied to the developer supply member and the layer forming member, and even when the image forming operation is repeated, contamination due to excessive charging does not occur, and a high-quality image can be formed. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the first embodiment of the present invention.

  In the figure, reference numeral 10 denotes an image forming apparatus according to the present embodiment. For example, a printer, a facsimile machine, a copier, a printer, a facsimile machine, and a multifunction machine having the functions of a copier, etc. May be. Here, the image forming apparatus 10 will be described as an electrophotographic printer that forms an image by an electrophotographic method. The image forming apparatus 10 may be a device that forms a color image, but is a device that forms a monochrome image.

  Here, reference numeral 21 denotes a sheet as a print medium, such as a print sheet or an OHP (Over Head Projector) sheet. Inside the image forming apparatus 10, an image forming unit unit 24 having an LED (Light Emitting Diode) head 13 as an exposure unit and a fixing unit 25 as a fixing unit are arranged along the conveyance path of the paper 21. Has been.

  Then, the sheets 21 stacked and set in the sheet tray unit 26 composed of a sheet cassette or the like are fed one by one by a hopping roller 27 as a sheet feeding roller, and are fed to the conveyance path of the sheet 21. It is sent to the registration rollers 31 provided.

  Subsequently, the sheet 21 is sent out at a predetermined timing by the registration rollers 31 and is conveyed to an image forming unit including an image forming unit 24 and a transfer roller 22 as a transfer member while being conveyed along the conveying path. Then, the toner image is transferred.

  When the paper 21 is fed into the fixing unit 25, a fixing process is performed by the fixing unit 25, and the toner image is fixed on the paper 21 by being heated and pressurized. Subsequently, the sheet 21 on which the toner image is fixed is discharged by the transport roller 34 and the discharge roller 33 and is stored in a stacker in the upper part of the image forming apparatus 10.

  Next, the configuration of the image forming unit 24 will be described.

  FIG. 1 is a schematic configuration diagram of an image forming unit section according to the first embodiment of the present invention.

  As shown in the drawing, the image forming unit 24 includes a photosensitive drum 11 as an image bearing member rotatably disposed, and a rotatable developer bearing disposed facing the photosensitive drum 11. A developing roller 14 as a body, a toner supply roller 15 as a developer supplying member that supplies toner 16 as a developer to the developing roller 14, and a layer forming member that forms a thin layer of toner 16 on the developing roller 14 A regulating blade 17, a charging roller 12 as a charging member for charging the photosensitive drum 11, and a cleaning blade comprising a rubber plate for collecting fog toner on the photosensitive drum 11, residual toner after transfer, and the like. 23. The developing roller 14, the toner supply roller 15, and the regulating blade 17 are part of the developing device.

  Then, the surface of the photosensitive drum 11 is charged by the charging roller 12 and exposed to light irradiated from the LED head 13, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11. Subsequently, the electrostatic latent image is developed by a developing device including the developing roller 14, the toner supply roller 15, and the regulating blade 17, thereby forming a toner image on the surface of the photosensitive drum 11. The toner image is transferred onto the paper 21 from the surface of the photosensitive drum 11 by the transfer roller 22. The toner 16 remaining on the photosensitive drum 11 after the transfer is collected by the cleaning blade 23.

  Here, the charging roller 12, the developing roller 14, the toner supply roller 15, and the transfer roller 22 are conductive rollers in which at least a conductive rubber elastic layer is provided around the conductive shaft. An independent or common power source is connected to the charging roller 12, the developing roller 14, the toner supply roller 15, and the transfer roller 22, and a positive or negative voltage is applied thereto.

  In the present embodiment, the developing roller 14 is connected to a dedicated high-voltage power supply 46, and the DB current flowing through the developing roller 14 is measured by a current measuring unit 47 as a current detecting unit. The charging roller 12, the toner supply roller 15, the regulating blade 17 and the transfer roller 22 are also connected to dedicated power sources, respectively, and an appropriate voltage is applied according to the measurement result of the current measuring unit 47.

  Next, the configuration of the control system of the image forming apparatus 10 will be described.

  FIG. 3 is a block diagram showing the configuration of the control system of the image forming apparatus according to the first embodiment of the present invention.

  In the figure, a control unit 40 includes a microprocessor, a ROM, a RAM, an interface, and the like, and is a host device connected via a cable such as a USB (Universal Serial Bus) cable or a network such as a LAN (Local Area Network). The print data and the control command are received from 34, and the overall operation of the image forming apparatus 10 is controlled to perform the printing operation.

  The control unit 40 drives an environment detection unit 35 that detects the environment of the image forming apparatus 10, a main storage unit 41 that stores control conditions, an exposure control unit 42 that controls the LED head 13, and the photosensitive drum 11. A motor control unit 43 for controlling the motor 44, a high voltage power source control unit 45 for controlling a high voltage power source 46 for applying a voltage to each member of the image forming apparatus 10, and a current measuring unit 47 are connected. The main storage unit 41 includes a voltage condition determination unit 41a as a voltage correction condition determination unit that determines a voltage to be applied to the toner supply roller 15 and the regulation blade 17.

  Next, the configuration of the current measuring unit 47 will be described in detail.

  FIG. 4 is a diagram showing the configuration of the current measurement unit in the first embodiment of the present invention.

  As shown in the figure, the current measuring unit 47 includes an amplifier circuit U1, an inverting amplifier circuit U2, and an A / D (analog / digital) converter 48.

  A reference resistor R0 (for example, 10K [Ω]) is connected in the middle of the conductive path between the developing roller 14 through which the DB current flows and the high-voltage power supply 46, and the voltage at both ends of the reference resistor R0 is amplified with high impedance. Differential amplification is performed by the circuit U1. Further, the output voltage of the amplifier circuit U1 is inverted and amplified by the inverting amplifier circuit U2. Then, the output voltage of the inverting amplifier circuit U 2 is digitally converted by the A / D converter 48 and sent to the controller 40.

  In the example shown in the figure, for example, when a DB current of 1 [μA] flows, the voltage at both ends of R0 becomes 10 [mV] and is amplified twice by the amplifier circuit U1 and 10 by the inverting amplifier circuit U2. Amplified twice. As a result, the output voltage of the inverting amplifier circuit U2 is 200 [mV].

  Next, a method for measuring the DB current will be described. First, the timing for measuring the DB current will be described.

  FIG. 5 is a time chart showing the timing for measuring the DB current in the first embodiment of the present invention.

  In the present embodiment, the DB current is measured when solid printing is performed by exposing the entire surface of the LED head 13 during the pre-printing operation. That is, when performing solid printing, the current measuring unit 47 measures the DB current flowing through the developing roller 14. In the figure, timing T1 corresponds to the position of point a in FIG. 1, and timing T2 corresponds to the position of point b in FIG.

  Here, the reason why the DB current is measured when performing solid printing is that the DB current is determined by the movement of charges accompanying the movement of the charged toner 16. For example, when there is no movement of the toner 16 as in the case of printing blank paper, the DB current is very small. On the other hand, in the case of solid printing, a large amount of toner 16 moves to the photosensitive drum 11, and thus a large DB current flows. That is, by measuring the DB current when performing solid printing, the measurement accuracy of the DB current is improved, and the charge amount and absolute amount of the toner 16 can be estimated with high accuracy.

  Next, the relationship between the potential of the toner 16 on the developing roller 14 and the DB current value will be described.

  FIG. 6 is a diagram showing the relationship between the potential of the toner on the developing roller and the DB current value in the first embodiment of the present invention.

  In the figure, the potential of the developer on the developer carrying member shown on the horizontal axis, that is, the potential of the toner 16 on the developing roller 14 changes the voltage applied to the developing roller 14 and the toner supply roller 15 to change the toner 16. The amount was measured using a surface electrometer (Treck Mode 1344).

  As shown in the figure, it can be seen that the larger the potential of the toner 16 on the developing roller 14, the more DB current flows. This is because the potential of the toner 16 on the developing roller 14 is determined by the charge amount and absolute amount of the toner 16.

  Further, the potential of the toner 16 on the developing roller 14 varies depending on the environment in which the image forming apparatus 10 is used, the printing conditions used, and the like. As is well known, since the toner 16 is charged by frictional charging, the charge amount is large under a low humidity environment and is small under a high humidity environment. Further, when the toner 16 has a high charge amount, the mirror image force with the developing roller 14 becomes large, the thickness of the toner layer becomes difficult to be regulated by the regulating blade 17, and the toner supply roller 15 scrapes off the toner 16. Since the force also decreases, the absolute amount of toner 16 on the developing roller 14 increases.

  In the conventional image forming apparatus as described in “Background Art”, the toner potential change is measured by an environmental sensor, and the voltage applied to each member of the image forming apparatus is corrected by a preset correction voltage. The amount of charge and the amount of adhesion are adjusted. Further, in an image forming apparatus that does not include an environmental sensor, the potential of toner is predicted by a DB current, and the voltage applied to each member is corrected so that the potential of the toner becomes a predetermined value.

  However, in the case of the conventional image forming apparatus that measures the potential change of the toner with an environmental sensor, the actual charge amount and adhesion amount of the toner are not measured. For example, for a long period of time in a high temperature and high humidity environment called HH environment ( It is difficult to apply an optimum voltage when the chargeability of the toner changes due to leaving it unused or when the toner is deteriorated.

  Further, in the case of a conventional image forming apparatus that does not include an environmental sensor, the potential of the toner at that time can be estimated by detecting the DB current. As a result, it is impossible to determine whether the DB current has changed due to damage to the received toner. In particular, since the conductivity of the developing roller and the toner supply roller changes as the usage environment changes, the optimum DB current value differs. For this reason, in such a correction that makes the DB current constant, a stable image cannot be obtained due to excessive voltage application or insufficient applied voltage.

  Next, the relationship between the environment detection value obtained by quantifying the environment in which the image forming apparatus 10 is used and the DB current value will be described.

  FIG. 7 is a diagram showing the relationship between the environment detection value and the DB current value in the first embodiment of the present invention.

The environmental detection values shown on the horizontal axis in the figure are obtained by arranging an environmental sensor in the image forming apparatus 10 and measuring the temperature and humidity of the environment in which the image forming apparatus 10 is used by the environmental sensor. This is a value calculated according to (2).
Absolute water vapor volume = (saturated water vapor volume) * (humidity / 100)
= (0.0225 * (temperature) * (temperature) + 0.1568 * (temperature) +
5.2058) * (humidity / 100) (1)
Environmental detection value = -0.0001 * (Absolute water vapor) * (Absolute water vapor) *
(Absolute water vapor) + 0.0142 * (Absolute water vapor) *
(Absolute water vapor amount) −0.6249 * (Absolute water vapor amount) +8.9869 Expression (2)
However, the value of the environmental detection value is in the range of 1 to 8, and when the numerical value calculated by the formula (2) is less than 1, the value of the environmental detection value is 1 and exceeds 8. In this case, the value of the environment detection value is 8. Moreover, the value of an environment detection value shall be an integer, and when the numerical value calculated by the said Formula (2) is provided with a numerical value below a decimal point, a decimal point is rounded down. For example, when the numerical value calculated by the equation (2) is 4 or more and less than 5, the environment detection value = 4.

  As shown in the figure, it can be seen that the smaller the environment detection value is, the higher the humidity is, so that the charge amount of the toner 16 is reduced and the DB current is reduced. On the contrary, it can be seen that the greater the environmental detection value, the lower the humidity, so that the charge amount of the toner 16 increases and the DB current increases. As described above, since the charging characteristics of the toner 16 vary greatly depending on the environment, it is difficult to make the DB current constant regardless of the environment.

  Therefore, in the present embodiment, a DB current value (hereinafter referred to as “reference current value”) capable of forming an image with stable image quality in each environment is obtained in advance, and the measured use environment of the image forming apparatus 10 is measured. The voltage applied to the toner supply roller 15, the regulating blade 17 and the like is corrected in accordance with the reference current value determined by the environmental detection value calculated from the temperature and humidity and the DB current value actually measured. ing.

  Next, a supply voltage correction table used for correcting the voltage value applied to the toner supply roller 15 will be described.

  FIG. 8 is a diagram showing an example of a supply voltage correction table for correcting the voltage value applied to the toner supply roller in the first embodiment of the present invention.

  As shown in the figure, the supply voltage correction table applies a correction voltage having a larger absolute value as the DB current value measured from the reference current value obtained in advance by experiment is smaller or the environment becomes humid. Is set to be.

The absolute value of the DB current has become the order of _{X 1 <X 2 ··· <X} 21.

When X ₃ ≦ DB current <X ₄ and 5 ≦ E <6, the voltage applied to the toner supply roller 15 is corrected to a voltage obtained by adding −50 [V] to the reference voltage.

  For example, when the reference voltage is −300 [V], the voltage applied to the toner supply roller 15 is corrected to −350 [V].

On the other hand, when X ₁₈ ≦ DB current <X ₁₉ and 2 ≦ E <3, the voltage applied to the toner supply roller 15 is corrected to a voltage obtained by adding 150 [V] to the reference voltage.

  For example, when the reference voltage is −300 [V], the voltage applied to the toner supply roller 15 is corrected to −150 [V].

  This is because the charging ability of the toner 16 decreases in a high humidity environment, and a high-quality image cannot be obtained unless a larger voltage is applied, and the charging ability of the toner 16 increases in a low humidity environment. This is because the charge amount of the toner 16 changes with a small voltage change.

  In the supply voltage correction table shown in the figure, the shaded range is a DB current range in which a good image can be obtained in each environment, and an average value of the DB current in this range is used as a reference current value. Set. The reference current value can also be set to the upper limit value or the lower limit value of the DB current in the above range.

  In this embodiment, the toner supply roller 15 and the regulation blade 17 are connected so that the same voltage is applied from the same power source.

  In this embodiment, the voltage applied to the toner supply roller 15 is corrected. However, it goes without saying that the voltage applied to the developing roller 14, the charging roller 12, the transfer roller 22, and the like may be corrected. Yes.

  Next, the operation of the image forming apparatus 10 having the above configuration will be described.

  FIG. 9 is a flowchart showing the operation of the image forming apparatus according to the first embodiment of the present invention.

  First, when a print command is received from the host apparatus 34, the image forming apparatus 10 starts operating. The control unit 40 starts motor rotation and high voltage application, causes the motor control unit 43 to start rotation of the motor 44, and causes the high voltage power supply control unit 45 to apply voltage from the high voltage power supply 46 to each member of the image forming apparatus 10. To start.

  Subsequently, the control unit 40 causes the environment detection unit 35 to perform environment measurement. The environment detection unit 35 measures the temperature and humidity of the environment in which the image forming apparatus 10 is used by the environment sensor, calculates the environment detection value, and stores the calculated value in the main storage unit 41.

  Subsequently, the control unit 40 performs the entire surface exposure start and DB current measurement. In this case, the exposure control unit 42 exposes the entire LED head 13 to perform solid printing, and causes the current measuring unit 47 to measure the DB current value.

  Subsequently, the voltage condition determination unit 41a acquires a correction value from the developer supply member voltage correction table. That is, the correction value of the toner supply roller 15 determined by the environment detection value stored in the main storage unit 41 and the measured DB current value is acquired from the supply voltage correction table shown in FIG. The voltage value applied to the regulating blade 17 is determined.

  Subsequently, the control unit 40 starts the printing operation and applies the corrected voltage to the toner supply roller 15 and the regulation blade 17. Then, the image forming apparatus 10 ends the processing after performing a series of printing operations.

  Note that the measurement of the DB current value involves solid printing, so it is not preferable to perform it for each print job. This is because, if solid printing is performed for each print job, the amount of toner 16 consumed increases, so that it is impossible to print on the guaranteed number of sheets 21 or transfer residual toner cannot be collected. End up. Furthermore, there is a problem that throughput is lowered. Therefore, in the present embodiment, the number of prints from the previous measurement of the DB current value exceeds 100 after the power is turned on after being left unused for a long time (for example, after 6 hours have elapsed). Then, it is preferable to carry out the process after the toner cartridge is replaced.

Next, a flowchart will be described.
Step S1 The controller 40 starts motor rotation and high voltage application.
Step S2 The control unit 40 causes the environment detection unit 35 to perform environment measurement.
Step S3 The control unit 40 starts the entire surface exposure and measures the DB current.
Step S4: The voltage condition determination unit 41a acquires a correction value from the developer supply member voltage correction table.
Step S <b> 5 The control unit 40 starts the printing operation and applies the corrected voltage to the toner supply roller 15 and the regulating blade 17.
Step S6 The image forming apparatus 10 ends the process after performing a series of printing operations.

  As described above, in this embodiment, the voltage value applied to the toner supply roller 15 and the regulating blade 17 can be corrected according to the measured environment detection value and DB current value, so that the printing operation is repeated. However, contamination due to excessive charging does not occur, and a high-quality image can be stably formed.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 10 is a block diagram showing the configuration of the control system of the image forming apparatus according to the second embodiment of the present invention.

  As shown in the figure, the main storage unit 41 of the image forming apparatus 10 according to the present embodiment includes an idling operation condition determination unit 41b that determines an idling operation condition of the developing roller 14 in addition to the voltage condition determination unit 41a. A drum counter 41 c that counts the number of rotations of the photosensitive drum 11. Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the idling operation table used for determining the idling operation condition of the developing roller 14 will be described.

  FIG. 11 is a diagram showing an example of an idle operation table for determining an idle operation condition in the second embodiment of the present invention.

  In this embodiment, when the DB current value is smaller than the reference current value, a preliminary operation is performed in advance to increase the charge amount of the toner 16 to approach the normal state, and then perform voltage correction again. The printing operation is started.

  Even a conventional image forming apparatus as described in the “Background Art” section may perform such a preliminary operation. However, the inventor of the present invention has found a novel method for determining the conditions for the preliminary operation according to the environment detection value and the DB current value. By this method, the conditions for the preliminary operation can be determined very efficiently.

  In the present embodiment, the idling operation of the developing roller 22 is determined by determining the idling operation condition of the photosensitive drum 11 on the assumption that the developing roller 22 and the photosensitive drum 11 are connected to each other and rotate simultaneously. Determine the conditions. The idling operation condition is specifically the rotational speed. In the first place, the purpose is to precharge the toner 16 before printing, and in order to frictionally charge the toner 16, the developing roller 22 needs to be rotated.

  “Patent Document 1” discloses a method of determining a preliminary operation condition by measuring a DB current. However, in this method, for example, in a high-temperature and high-humidity environment, warm-up and DB current measurement must be repeated until the current value becomes equal to or higher than the reference current value, which consumes a large amount of toner. In addition, if the warm-up time is increased in order to reduce the number of times the DB current is measured, the toner is excessively charged in a low-humidity environment, resulting in contamination. Further, it is said that the preliminary operation is preferably performed at a constant current value or less, but the definition of the constant current value is not clear and a correction method according to the environment is not disclosed.

  In contrast, in the present embodiment, the idling operation condition of the photosensitive drum 11 is determined according to the environment detection value and the DB current value in accordance with the idling operation table as shown in the figure. Then, the developing roller 14 is rotated by idling the photosensitive drum 11 in accordance with the determined idling operation condition, whereby the charge amount of the toner 16 is increased in advance, that is, preliminary charging is performed.

  The idling operation table is set so that the number of rotations of the photosensitive drum 11 increases as the difference between the reference current value obtained in advance by experiment and the measured DB current value increases, and as the environment becomes higher temperature. ing. On the contrary, the photosensitive drum 11 is set to rotate less as the difference between the reference current value and the DB current value becomes smaller and the environment becomes a low humidity environment.

  Next, the operation timing of preliminary charging in the present embodiment will be described.

  FIG. 12 is a time chart showing the operation timing of the preliminary charging in the second embodiment of the present invention.

  In the present embodiment, the entire surface of the LED head 13 is exposed between timing T1 and timing T2, and solid printing is performed, and the current measuring unit 47 measures the first DB current. Then, the idling operation condition determining unit 41b determines the idling operation condition of the photosensitive drum 11 according to the idling operation table as shown in FIG.

  Subsequently, the idling operation is performed between the timing T3 and the timing T4, and the photosensitive drum 11 is idly rotated by the number of rotations determined as the idling operation condition. Thereby, preliminary charging of the toner 16 is performed.

  Subsequently, during the timing T4 to the timing T5, the entire surface of the LED head 13 is exposed to perform solid printing, and the current measuring unit 47 measures the DB current for the second time. Then, the voltage condition determination unit 41a determines the correction voltage according to the supply voltage correction table as shown in FIG. 8 described in the first embodiment.

  Subsequently, during timing T6 to timing T7, the LED head 13 is exposed in accordance with the actual printing command to perform normal printing, and at timing T8, a series of printing operations are completed, the motor 44 is turned off, and applied to each member. Turn off the voltage.

  Next, the operation of the image forming apparatus 10 in the present embodiment will be described.

  FIG. 13 is a flowchart showing the operation of the image forming apparatus according to the second embodiment of the present invention.

  First, when a print command is received from the host apparatus 34, the image forming apparatus 10 starts operating. Then, the control unit 40 causes the environment detection unit 35 to perform environment measurement. The environment detection unit 35 measures the temperature and humidity of the environment in which the image forming apparatus 10 is used by the environment sensor, calculates the environment detection value, and stores the calculated value in the main storage unit 41.

  Subsequently, the control unit 40 starts motor rotation and high-voltage application, causes the motor control unit 43 to start rotation of the motor 44, and causes the high-voltage power supply control unit 45 to transfer each component of the image forming apparatus 10 from the high-voltage power supply 46. The voltage application is started.

  Subsequently, the control unit 40 performs the entire surface exposure start and DB current measurement. In this case, the exposure control unit 42 exposes the entire LED head 13 to perform solid printing, and causes the current measuring unit 47 to measure the DB current value.

  Subsequently, the idling operation condition determination unit 41b acquires the idling rotation speed Dd from the idling operation table. That is, the idling rotation speed Dd that is the rotation speed for idly rotating the photosensitive drum 11 is acquired from the idling operation table shown in FIG. Also, a drum count D0 that is the number of rotations of the photosensitive drum 11 immediately before starting the idling operation of the photosensitive drum 11 is acquired.

  Subsequently, the control unit 40 starts the idling operation and starts applying a high voltage. In this case, the developing roller 14 is also rotated by idling the photosensitive drum 11, and the charge amount of the toner 16 is increased in advance. A voltage is applied to each member.

  Subsequently, the control unit 40 acquires a drum count Dc that is the number of revolutions at which the photosensitive drum 11 rotates idly. The idling of the photosensitive drum 11 is continued until Dc−D0> Dd.

  Subsequently, when Dc−D0> Dd, the DB current value is measured again, the correction value of the toner supply roller 15 is obtained from the supply voltage correction table shown in FIG. A normal printing operation is performed by applying a corrected voltage. The subsequent operations after Dc−D0> Dd are the same as the operations in steps S1 to S6 described in the first embodiment, and thus the description thereof is omitted.

Next, a flowchart will be described.
Step S11 The control unit 40 causes the environment detection unit 35 to perform environment measurement.
Step S12 The control unit 40 starts motor rotation and high voltage application.
Step S13: The control unit 40 performs full exposure start and DB current measurement.
Step S14 The idling operation condition determination unit 41b acquires the idling rotation speed Dd from the idling operation table.
Step S15 The control unit 40 starts the idling operation and starts applying high voltage.
Step S16 The control unit 40 acquires the drum count Dc.
Step S17 The control unit 40 determines whether or not Dc-D0> Dd is satisfied. If Dc-D0> Dd, the process proceeds to step S18. If Dc-D0> Dd is not satisfied, the process returns to step S16.
Step S18 The control unit 40 starts motor rotation and high voltage application.
Step S19 The control unit 40 causes the environment detection unit 35 to perform environment measurement.
Step S20 The control unit 40 starts the entire surface exposure and measures the DB current.
Step S21: The voltage condition determination unit 41a acquires a correction value from the developer supply member voltage correction table.
Step S <b> 22 The control unit 40 starts the printing operation and applies the corrected voltage to the toner supply roller 15 and the regulating blade 17.
Step S23 The image forming apparatus 10 ends the process after performing a series of printing operations.

  As described above, in the present exemplary embodiment, it is possible to preliminarily charge the toner 16 by determining the idling operation condition of the photosensitive drum 11 before printing in accordance with the environment and the DB current value. Dirt caused by will not occur.

  Further, by the idling operation of the photosensitive drum 11, the charge amount of the toner 16 can be increased to a charge amount at which a good image can be obtained in each environment, and an optimum correction voltage can be determined. As a result, it is possible to prevent the problem that the correction voltage is excessively large during printing and the charge amount of the toner 16 increases greatly, causing a change in image quality and smearing.

  As a modification of the present embodiment, a combination of the first embodiment and the present embodiment can be used. That is, in the modified example, after the first DB current value is measured, the idling number of the photosensitive drum 11 is determined according to the idling operation table as shown in FIG. 11, and at the same time, the supply voltage as shown in FIG. The voltage to be applied to the toner supply roller 15 is determined according to the correction table. Then, when the idling operation of the photosensitive drum 11 is performed, the corrected voltage is applied to the toner supply roller 15, and then the applied voltage value at the time of printing is determined again by the second measurement of the DB current value, and the printing operation is performed. Do.

  By adopting such a method, the toner 16 can be effectively pre-charged by the idling operation of the photoconductive drum 11, so that the idling number of the photoconductive drum 11 can be reduced and the throughput can be reduced. A high quality image can be stably formed without lowering.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming unit in the first embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a block diagram illustrating a configuration of a control system of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of the electric current measurement part in the 1st Embodiment of this invention. It is a time chart which shows the timing which measures DB electric current in the 1st Embodiment of this invention. FIG. 6 is a diagram illustrating a relationship between a potential of toner on a developing roller and a DB current in the first embodiment of the present invention. It is a figure which shows the relationship between the environmental detection value and DB electric current in the 1st Embodiment of this invention. 6 is a diagram illustrating an example of a supply voltage correction table for correcting a voltage value applied to the toner supply roller according to the first exemplary embodiment of the present invention. FIG. 3 is a flowchart showing an operation of the image forming apparatus in the first embodiment of the present invention. FIG. 6 is a block diagram illustrating a configuration of a control system of an image forming apparatus according to a second embodiment of the present invention. It is a figure which shows the example of the idle operation table for determining the idle operation condition in the 2nd Embodiment of this invention. It is a time chart which shows the operation timing of the preliminary | backup charge in the 2nd Embodiment of this invention. 6 is a flowchart illustrating an operation of the image forming apparatus according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Photosensitive drum 13 LED head 14 Developing roller 15 Toner supply roller 16 Toner 17 Control blade 35 Environment detection part 41a Voltage condition determination part 41b Idling operation condition determination part 47 Current measurement part

Claims (5)

(A) an image carrier whose surface can be charged;
(B) an exposure unit that forms an electrostatic latent image on the image carrier;
(C) a developer carrier that develops the electrostatic latent image with a developer;
(D) a developer supply member for supplying a developer to the developer carrying member;
(E) a layer forming member for forming the developer on the developer carrying member into a thin layer;
(F) a current measuring unit for measuring a current value flowing through the developer carrying member;
(G) an environment detection unit for detecting the environment;
(H) a voltage correction condition determining unit that determines a voltage to be applied to the developer supply member and the layer forming member according to the current value measured by the current measuring unit and the environment detected by the environment detecting unit. An image forming apparatus. The image forming apparatus according to claim 1, wherein the current value is measured to detect the environment after the power is turned on, after being left for a long period of time, or after a predetermined number of printing operations are performed. (A) an image carrier whose surface can be charged;
(B) an exposure unit that forms an electrostatic latent image on the image carrier;
(C) a developer carrier that develops the electrostatic latent image with a developer;
(D) a developer supply member for supplying a developer to the developer carrying member;
(E) a layer forming member for forming the developer on the developer carrying member into a thin layer;
(F) a current measuring unit for measuring a current value flowing through the developer carrying member;
(G) an environment detection unit for detecting the environment;
(H) An idle operation condition determining unit that determines an idle operation condition of the developer carrying member according to the current value measured by the current measurement unit and the environment detected by the environment detection unit. Image forming apparatus. The image forming apparatus according to claim 3, wherein the current value is measured to detect the environment after the power is turned on, after being left for a long period of time, or after a predetermined number of printing operations are performed. The image forming apparatus according to claim 3, wherein the idling operation condition is a rotational speed of the image carrier or the developer carrier.

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