JP2007206414A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a inexpensive and compact image forming apparatus, where when one high voltage transformer in a high-voltage power source provided in the apparatus outputs a plurality of high voltages and concurrently voltages having different polarities, the high-voltage transformer superimposes the voltages, having different polarities and outputs a target voltage. <P>SOLUTION: A positive DC high voltage is supplied to a transfer roller 5 as a transfer voltage by a transformer 474 for transfer power source with a transfer power source drive circuit 402 on, and a negative DC high voltage is supplied to the transfer roller 5 as a transfer cleaning voltage by a transformer 414 for charging bias power source with a charging bias drive circuit 404 on. When the transfer voltage and the transfer cleaning voltage are concurrently output at the same time, the transfer voltage and the transfer cleaning voltage are superimposed and the resultant voltage is output to the transfer roller 5 as a target voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an electrophotographic image forming apparatus having a high voltage output for supplying positive or negative DC high voltage and AC high voltage, and a high voltage power source for supplying the high voltage output. About.

  Here, the electrophotographic image forming apparatus includes, for example, an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer, etc.), an electrophotographic facsimile apparatus, and the like.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus that copies an image onto a recording sheet by electrophotography has been widespread. In this electrophotographic image forming apparatus, a light image is projected onto an image carrier that is uniformly charged positively or negatively corresponding to the image to be copied, and a charge pattern is generated on the surface of the image carrier according to the pattern. To obtain a latent image of electrostatic charge. Next, a developer charged with a polarity opposite to the charge pattern of the latent image is supplied, and the developer is adsorbed to the charge pattern of the latent image and developed. The recording paper is superimposed on the developed developer image, and a charge having a polarity opposite to that held by the developer is applied from the back surface thereof, and the developer is electrostatically adsorbed onto the surface of the recording paper and transferred. Thereafter, heat and pressure are applied to the transfer paper to fix the transferred developer image, and the image is copied.

  Here, as a method for transferring the developed developer to the recording paper, corona transfer for applying a charge to the recording paper by corona discharge, charging by applying a DC voltage to the conductive roller, and applying an appropriate pressure There is a roller transfer that gives electric charge to the recording paper by rolling on the recording paper. In the case of roller transfer, it is necessary to apply a high voltage of about several hundred volts to 6 kilovolts to a conductive roller (hereinafter referred to as transfer roller), but there is no generation of ozone as in corona transfer, and the transferred developer. The image is less disturbed and can be transferred with good quality.

  However, in the roller transfer method, when no recording paper is inserted between the image carrier and the transfer roller, the transfer roller directly contacts the image carrier. Therefore, when the recording paper is not conveyed due to the occurrence of a jam, the developer adheres to the surface of the transfer roller and becomes dirty. Further, even during the initial operation or between the recording sheets during continuous printing, if the developer remains on the image carrier, the surface of the transfer roller becomes dirty. In this case, the developer adhesion amount is very small, but if the developer is used for a long time, there is a possibility that the stain gradually becomes worse.

  Thus, it is inevitable that the transfer roller is contaminated with the developer, and it is necessary to clean the transfer roller. The transfer roller is cleaned by applying a voltage having a reverse polarity to that of the transfer roller during non-transfer to move the developer attached to the surface of the transfer roller to the image carrier by electrostatic force. Therefore, the transfer roller needs a high-voltage power supply device that can switch and output a positive and negative high voltage.

  As a high-voltage power supply device that switches between applying positive and negative voltages, for example, a positive-negative switching high-voltage power supply device as disclosed in Patent Document 1 has been proposed. The positive / negative switching high-voltage power supply device is shown in a schematic circuit diagram of FIG.

  A transfer power source drive circuit 102, a charging bias drive circuit 104, and a sine wave generation circuit 144 are connected to the output end of the controller 100, and are ON / OFF controlled, respectively. The output of the charging bias driving circuit 104 is connected to the base of the transistor 108. The collector of the transistor 108 is connected to the positive side of the DC power supply 110. The negative electrode side of the DC power supply 110 is grounded. In the charging bias driving circuit 104, the base current of the transistor 108 is controlled by a signal from the controller 100, and ON / OFF control of the current flowing from the collector to the emitter is performed.

  The emitter of the transistor 108 is connected to the primary winding 118 of the charging bias power source transformer 114. The charging bias power supply transformer 114 includes a secondary winding 122 corresponding to the primary winding 118, and boosts the voltage on the primary side to output a high voltage. The secondary winding 122 is connected to the diode 126 in series. The secondary winding 122 is connected in parallel with a capacitor 142 and resistors 138 and 140 connected in series. The resistors 138 and 140 are connected to the resistors 140 and 138 from the forward direction side of the diode 126, and the one not connected to the resistor 138 of the resistor 140 is grounded. Therefore, when a signal for turning on the charging bias driving circuit 104 is input from the controller 100, a negative DC high voltage is obtained.

  The output of the transfer power supply driving circuit 102 connected to the controller 100 is connected to the base of the npn transistor 106. The collector of the transistor 106 is connected to the positive electrode side of the DC power supply 110. The DC power supply 110 is grounded on the negative electrode side. In the transfer power supply driving circuit 102, the base current of the transistor 106 is controlled by a signal from the controller 100, and ON / OFF control of the current flowing from the collector to the emitter is performed. The emitter of the transistor 106 is connected to the primary winding 116 of the transfer power source transformer 112. The transfer power supply transformer 112 includes a secondary winding 120 corresponding to the primary winding 116 and boosts the voltage on the primary side to output a high voltage. The secondary winding 120 is connected to the diode 124 in series. The diode 124 is connected so as to have a polarity opposite to that of the diode 126. In addition, a capacitor 170 and a resistor 128 are connected to the secondary winding 120 in parallel.

  One end of the resistor 128 and the forward direction side of the diode 124 are connected to the transfer roller 208. Therefore, when a signal for turning on the transfer power supply driving circuit 102 is input from the controller 100, a positive DC high voltage is applied to the transfer roller 208. The other end of the resistor 128 is connected to the collector of the npn transistor 130. The base of the transistor 130 is connected to the collector of the npn transistor 134 via a resistor 132. The emitter of the transistor 130 is connected to the resistor 138. The emitter of the transistor 134 is connected to the positive side of the DC power source 136, and the base is connected to the controller 100. The negative electrode side of the DC power source 136 is grounded. Therefore, the current flowing from the emitter to the collector of the transistor 134 is ON / OFF controlled by the controller 100, so that the current flowing from the collector to the emitter of the transistor 130 is ON / OFF controlled.

  If the transistor 130 is turned on and the transfer power supply drive circuit 102 is turned off while the charging bias drive circuit 104 is in the ON state, a negative DC high voltage is applied to the transfer roller 208. On the other hand, when the transistor 130 is turned off and the transfer power supply driving circuit 102 is turned on, a positive DC high voltage is applied. That is, the transistor 130 serves as a switch for switching between a positive transfer voltage applied to the transfer roller and a negative transfer cleaning voltage. This eliminates the need to provide a transfer cleaning voltage alone, which is advantageous for downsizing.

In FIG. 10, 201 is a photosensitive drum, 206 is a charging member, and 207 is a developing member. Reference numeral 146 denotes a capacitor, and 148 denotes a charging AC transformer. Reference numeral 150 denotes a primary winding of the charging AC transformer 148, and 152 denotes a secondary winding.
JP 2000-137423 A JP 2002-182498 A

  However, since the transistor 130 performs high voltage ON / OFF, a high voltage is applied between the collector and the emitter. Therefore, a high voltage transistor must be used as the transistor 130. High voltage transistors are expensive and have been a problem in realizing low prices.

  The present invention has been made paying attention to the above points. When a plurality of high-voltage outputs are supplied from one high-voltage transformer and different polar voltages are output simultaneously, the different polar voltages are superimposed and outputted. Therefore, an object is to provide a low-cost and compact image forming apparatus.

  In order to solve the above problems, an image forming apparatus of the present invention has the following configuration.

  (1) Charging means for charging an image carrier having a photosensitive layer, latent image means for irradiating light to form a latent image on the image carrier, and developing a developer on the latent image pattern of the image carrier And a transfer means for transferring the developer onto the recording material by applying a transfer voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. A transfer roller cleaning unit that removes the developer attached by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller, and a fixing unit that fixes the developer transferred to the recording material. In the image forming apparatus, each means except at least one of the charging means, the latent image means, the developing means, the transfer means, the transfer roller cleaning means, and the fixing means has a high voltage output means. , When a positive or negative high voltage is supplied to at least one means, the high voltage output means supplies a high voltage having the same polarity as the positive or negative high voltage. Image forming apparatus.

  (2) The one high voltage output unit is the high voltage output unit included in the charging unit, and the at least one unit is the transfer roller cleaning unit. Image forming apparatus.

  (3) Charging means for charging the image bearing member having the photosensitive layer, latent image means for irradiating light to form a latent image on the image bearing member, and developing the developer in the latent image pattern of the image bearing member And a transfer means for transferring the developer onto the recording material by applying a transfer voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. Means, a transfer roller cleaning means for removing the developer adhered by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller, and a fixing means for fixing the developer transferred to the recording material. In the image forming apparatus, the charging unit, the latent image unit, the developing unit, the transfer unit, the transfer roller cleaning unit, and the fixing unit are applied with a high voltage that applies voltages of different polarities to at least one unit. Output means, and the high voltage output means for applying the voltages of different polarities includes superimposing means for superimposing the simultaneously output voltages and outputting a target voltage when simultaneously outputting voltages of different polarities. An image forming apparatus.

  (4) The image forming apparatus according to (3), wherein the superimposing unit is the transfer unit.

  (5) Charging means for charging the image bearing member having the photosensitive layer, latent image means for irradiating light to form a latent image on the image bearing member, and developing the developer in the latent image pattern of the image bearing member And a transfer means for transferring the developer onto the recording material by applying a voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. A transfer roller cleaning unit that removes the developer attached by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller, and a fixing unit that fixes the developer transferred to the recording material. In the image forming apparatus, a common unit for supplying a voltage from one high-voltage power source to the charging unit and the transfer roller cleaning unit, and a target voltage by superimposing voltages of different polarities when the transfer unit outputs a voltage. The A voltage superimposing unit that varies the voltage supplied to the charging unit, and a voltage that is superimposed on the transfer unit according to the voltage variable amount when the voltage variable amount is generated by the voltage variable unit. An image forming apparatus comprising voltage correction means for correcting the above.

  (6) The image forming apparatus according to (5), wherein the voltage correction unit adds or subtracts the voltage variable amount to a voltage superimposed on the transfer unit.

  According to the present invention, when a plurality of high-voltage outputs are supplied from a single high-voltage transformer and different polarity voltages are output simultaneously, the different polarity voltages are superimposed and output, thereby reducing the cost and size of the image forming apparatus. Can be realized. Further, a switching element such as a transistor for turning on / off the high voltage output is not required, and the accuracy of the transfer voltage output to the transfer roller can be improved.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

(First embodiment)
In this embodiment, a laser beam printer will be described as an example of the image forming apparatus. The laser beam printer is configured as shown in FIG. FIG. 1 is a schematic sectional view of an image forming apparatus according to the present invention. Reference numeral 1 denotes a photosensitive drum as an image carrier that rotates in the a direction. Reference numeral 3 denotes an exposure unit (corresponding to a latent image means) having a semiconductor laser (not shown) as a light source and a rotating polygon mirror (not shown) rotated by a scanner motor (not shown). L is a laser beam emitted from the semiconductor laser and scanned on the photosensitive drum 1. The laser beam L is reflected by the reflection mirror 3a. 2 is a charging roller (equivalent to charging means) for uniformly charging the surface of the photosensitive drum 1, and 4 is a developing device for developing the electrostatic latent image formed on the photosensitive drum 1 with toner ( Equivalent to developing means). Reference numeral 5 denotes a transfer roller (corresponding to a transfer unit and a transfer roller cleaning unit) that rotates in the b direction and transfers a toner image developed by the developing device 4 to a predetermined recording sheet P (corresponding to a recording material). . A cleaning unit 6 cleans the photosensitive drum 1 with the cleaning member 6a. Reference numeral 18 denotes a fixing device (corresponding to fixing means) for fusing the toner transferred to the recording paper by heat at the nip T.

  Reference numeral 14 denotes a paper feed cassette that has a function of identifying the size of the recording paper P (hereinafter simply referred to as paper P) and stores the paper P. Reference numeral 15 denotes a cassette paper feed roller that feeds the paper P from the paper feed cassette 14 by one rotation and sends it to the transport path. Reference numeral 20 denotes a transport roller that transports the paper P fed from the cassette. Reference numeral 10 denotes a pre-feed sensor for detecting the leading edge and the trailing edge of the fed paper P, and 11 denotes a pre-transfer roller for feeding the conveyed paper P to the photosensitive drum 1. 12 is for synchronizing the writing (recording / printing) of the image on the photosensitive drum 1 and the sheet conveyance with respect to the fed sheet P and measuring the length of the fed sheet P in the conveyance direction. It is a top sensor. 22 is a paper discharge sensor for detecting the presence or absence of the paper P after fixing, 19 is a paper discharge roller for transporting the paper P after fixing to the paper discharge tray 16 or 17, and 21 is a paper P transported from the paper discharge roller. Is a paper discharge roller for discharging the paper to the paper discharge tray 17. Reference numeral 7 denotes a manual feed tray, and 8 denotes a manual feed roller. A is a driving means for driving the photosensitive drum 1, and B is a driving means for driving the transfer roller 5.

  A control system block diagram for controlling such an image forming apparatus is shown in FIG. In FIG. 2, reference numeral 300 denotes an image forming apparatus main body. A printer controller 301 expands image code data sent from an external device such as a host computer (not shown) into bit data necessary for printing by the printer, and reads and displays printer internal information. A printer engine control unit 302 controls the printing operation of each unit of the printer engine in accordance with an instruction from the printer controller 301 and notifies the printer controller 301 of printer internal information. A high voltage control unit 303 performs high voltage output control in each process such as charging, development, and transfer in accordance with an instruction from the printer engine control unit 302. An optical system control unit 304 controls driving / stopping of the scanner motor and lighting of the laser beam L in accordance with an instruction from the printer engine control unit 302. Reference numeral 305 denotes a fixing device temperature control unit that drives / stops energization of the fixing heater in accordance with an instruction from the printer engine control unit 302. Reference numeral 306 denotes a sensor input unit that notifies the printer engine control unit 302 of paper presence / absence states of the pre-feed sensor 10, the top sensor 12, and the paper discharge sensor 22. A sheet conveyance control unit 307 drives / stops a motor / roller or the like for conveying a recording sheet in accordance with an instruction from the printer engine control unit 302. It controls the drive / stop of the paper feed roller 15, the transport roller 20, the pre-transfer roller 11, the roller of the fixing device 18, and the paper discharge roller 21 in FIG. 1.

  FIG. 3 shows a schematic circuit diagram of a high voltage power supply of the image forming apparatus of this embodiment. The controller 100 is connected to a transfer power supply drive circuit 402, a charging bias drive circuit 404 and a development DC power supply 444. The controller 100 controls ON / OFF of the transfer power supply driving circuit 402, the charging bias driving circuit 404, and the development DC power supply 444. The output of the charging bias driving circuit 404 is connected to the base of the npn transistor 408. The collector of the transistor 408 is connected to the DC power supply 410, and the base current of the transistor 408 is controlled by a signal from the controller 100 to control ON / OFF of the current flowing from the collector to the emitter. The emitter of the transistor 408 is connected to a primary winding 418 of a charging bias power supply transformer 414 (corresponding to high voltage output means). The charging bias power supply transformer 414 includes a secondary winding 422 corresponding to the primary winding 418 and boosts the voltage on the primary side to output a high voltage. The secondary winding 422 is connected to the diode 426 in series. In addition, a capacitor 445 and a resistor 438 are connected in parallel to the secondary winding. When a signal for turning on the charging bias drive circuit 404 is input from the controller 100, a negative DC high voltage is output.

  Next, the output of the transfer power supply driving circuit 402 connected to the controller 100 is connected to the base of 406 to the npn transistor. The collector of the transistor 406 is connected to the DC power supply 410, and the base current of the transistor 406 is controlled by a signal from the controller 100, and ON / OFF control of the current flowing from the collector to the emitter is performed. The emitter of the transistor 406 is connected to the primary winding 416 of a transfer power supply transformer 474 (corresponding to high voltage output means). The transfer power supply transformer 474 includes a secondary winding 420 corresponding to the primary winding 416, and boosts the voltage on the primary side to output a high voltage. The secondary winding 420 is connected to the diode 424 in series. The diode 424 is connected so as to have a polarity opposite to that of the diode 426. In addition, a capacitor 470 and a resistor 456 are connected to the secondary winding 420 in parallel. One end of the resistor 456 and the forward direction side of the diode 424 are connected to the transfer roller 5. Therefore, when a signal for turning on the transfer power supply driving circuit 402 is input from the controller 100, a positive DC high voltage is applied to the transfer roller 5.

  Therefore, when the charging bias driving circuit 404 is in an ON state and the transfer power supply driving circuit 402 is OFF, a negative DC high voltage is output from the charging bias power supply transformer 414 to the transfer roller 5 via the resistor 456 ( Equivalent to common means). Therefore, when the image is not formed on the photosensitive drum 1, the charging bias driving circuit 404 is turned on to output a negative DC high voltage to the transfer roller 5 for cleaning. That is, the charging bias voltage is a transfer cleaning voltage, and the charging bias voltage is hereinafter also referred to as a transfer cleaning voltage.

  The controller 100 is also connected with a development DC power supply 444 that outputs a negative DC high voltage, and a development AC power supply 480 that superimposes AC on the output of the development DC power supply 444 and supplies it to the developing device 4. The details will be omitted.

  Next, FIG. 4 shows a schematic diagram of the transfer voltage output during image formation. FIG. 4 is a diagram showing the relationship between the transfer voltage and the charging bias voltage according to this embodiment. FIG. 4A shows the output voltage when only the transfer power supply driving circuit 402 is turned on with the aim of outputting 3000 V to the transfer roller 5. . In this embodiment, the diode 426 connected in series to the charging bias power supply transformer 414 and the transfer roller 5 are connected via a resistor 456 (corresponding to the superimposing means). Therefore, when the transfer power supply driving circuit 402 is ON, a negative DC high voltage boosted by the charging bias power supply transformer 414 is output to the transfer roller 5. FIG. 4B is a diagram showing an output voltage when the transfer power supply driving circuit is ON and the charging bias driving circuit is ON. As shown in FIG. 4B, the positive DC high voltage (3000 V) that is the transfer voltage is superimposed on the negative DC high voltage that is the charging bias voltage. Therefore, if the negative DC high voltage that is the charging bias voltage is −1000 V, 2000 V (3000 V−1000 V = 2000 V) is output to the transfer roller 5 with respect to the output of the transfer power supply 3000 V.

  Next, timing for applying a high voltage to the charging roller 2, the developing device 4, and the transfer roller 5 is shown in FIG. In FIG. 5, the charging DC voltage (a) applied to the charging roller 2, the developing AC voltage (b) and developing DC voltage (c) applied to the developing device 4, and the transfer voltage (d) applied to the transfer roller 5. ) And the ON / OFF timing of the transfer cleaning voltage (e) with time taken on the horizontal axis. According to FIG. 5, when the charging DC voltage (a) is turned on, the transfer cleaning voltage (e) is turned on and the transfer roller 5 is cleaned. Thereafter, the development AC voltage (b), the development DC voltage (c), and the transfer voltage (d) are turned ON / OFF at a predetermined timing according to the image forming process. Also, before and after the image forming process, the charging DC voltage is turned on to output a negative DC high voltage to the transfer roller 5 for cleaning. That is, the charging DC voltage (a) is always ON before and after image formation and during image formation.

  By adopting the above configuration, it is not necessary to provide a transfer cleaning power supply that outputs negative DC high voltage, and it is not necessary to use a high-voltage transistor, so a low-cost and compact image forming apparatus is provided. can do.

  In this embodiment, a diode 426 is connected in series to the charging bias power transformer 414, and a charging bias and a transfer cleaning bias are output from a terminal connected to the resistor 438. As a configuration for supplying the charging bias and the transfer cleaning bias from the charging bias power transformer 414, a configuration in which the diode 426 and the diode 3000 are separately connected to the secondary winding 422 of the charging bias power transformer 414 as shown in FIG. Very similar effects can be obtained. Here, 3001 is a capacitor, and 3002 is a resistor.

(Second embodiment)
In the first embodiment, the transfer cleaning bias power supply can be eliminated by supplying the negative DC high voltage of the charging bias high voltage power supply transformer 414 to the charging roller 2 and the transfer roller 5. In addition, by superimposing a positive DC high voltage that is a transfer voltage and a negative DC high voltage that is a charging bias, a high-voltage transistor that turns ON / OFF the transfer cleaning bias can be eliminated. However, as can be seen from FIG. 4, if a transfer voltage corresponding to the superposed charging bias voltage is not output, a deviation occurs from the target value of the transfer voltage. Therefore, this embodiment is characterized in that a transfer voltage corresponding to the charging bias voltage is output.

  In the description of the present embodiment, portions overlapping with those of the first embodiment are omitted.

  The setting of the transfer voltage corresponding to the charging bias voltage will be described with reference to FIG. FIG. 7A is a diagram in which only the transfer power supply driving circuit 402 is turned on with the transfer voltage of 3000 V as a target (corresponding to the target voltage). In this configuration, the diode 426 connected in series to the charging bias power supply transformer 414 and the transfer roller 5 are connected via a resistor 456. Therefore, when the transfer power supply driving circuit 402 is ON, a negative DC high voltage boosted by the charging bias power supply transformer 414 is output to the transfer roller 5. Therefore, as shown in FIG. 7B, a positive DC high voltage (3000 V) that is a transfer voltage is superimposed on a negative DC high voltage that is a charging bias voltage. Therefore, if the negative DC high voltage that is the charging bias voltage is −1000 V, 2000 V (3000 V−1000 V = 2000 V) is output to the transfer roller 5 with respect to the output of the transfer power supply 3000 V. In this case, when the target value (3000 V) is output to the transfer roller 5, the transfer power supply driving circuit 402 turns on the positive DC high voltage as the transfer voltage in consideration of the negative DC high voltage value as the charging bias voltage. / OFF control and output. FIGS. 7C and 7D show transfer voltages when the charging bias voltage is taken into consideration. In order to output 3000 V to the transfer roller 5, the negative DC high voltage (−1000 V) superimposed as a charging bias voltage is raised to a positive DC high voltage as a transfer voltage, and 1000 V higher 4000 V is output. By doing so, a target value of 3000 V can be output to the transfer roller 5.

  As described above, when the charging bias voltage and the transfer cleaning bias voltage are output from the charging bias power supply transformer 414 as in this configuration, even if the transfer cleaning bias is always output, the optimum transfer voltage is output to the transfer roller 5. It becomes possible.

(Third embodiment)
In the second embodiment, the charging bias voltage (transfer cleaning voltage) superimposed on the transfer voltage is constant, and the transfer voltage corresponding to the charging bias voltage is output.

  Recently, however, means for varying the charging bias voltage (corresponding to voltage varying means) are generally used in order to improve image quality and adjust density. When such a control is used, in a configuration in which the transfer cleaning voltage (charging bias voltage) is always turned on and superimposed on the transfer voltage, variations in the voltage output to the transfer roller 5 occur. Therefore, in this embodiment, when the charging bias voltage (transfer cleaning voltage) is varied, the superimposed transfer voltage is varied according to the variable width of the charging bias voltage (transfer cleaning voltage).

  In the description of the present embodiment, portions that overlap with the first and second embodiments are omitted.

  With reference to FIG. 8, a description will be given of changing the transfer voltage according to the variable width of the charging bias voltage when the charging bias voltage is changed. FIG. 8A is a diagram in which the transfer power supply driving circuit 402 is turned on with the transfer voltage of 3000 V as a target. FIG. 8B shows a case where the superposed portion when the negative DC high voltage that is the charging bias voltage is −1000 V is raised to the positive DC voltage that is the transfer voltage, and the transfer voltage target value 3000 V is obtained. Output. FIGS. 8C and 8D are diagrams in which the superimposed transfer voltage is similarly varied when the charging bias voltage is varied to perform density adjustment or the like. From FIG. 8D, when the charging bias voltage (transfer cleaning voltage) is varied by −250 V (corresponding to the variable amount of voltage) to −1250 V output, the transfer voltage is changed by the same variable width from FIG. + 250V is added (corresponding to voltage correction means). As a result, when the charging bias voltage (transfer cleaning voltage) is varied, the transfer voltage can be accurately output to the transfer roller 5.

  FIG. 9 shows a high voltage output flowchart in the image forming operation according to the present embodiment. First, the power is turned on (step S901), and a standby state is entered (step S902). At the start of printing (step S903), the controller 100 detects whether the charging bias is varied by changing the density setting or the like (step S904). If the density setting has not been changed, the charging bias is turned on (step S905), and a voltage obtained by adding the charging bias voltage corresponding to the density center setting value to the transfer voltage (step S906) is output to the transfer roller 5. (Step S907). Thereafter, the development voltage is turned on (step S908), and image formation is performed. After the image formation is completed, all the high-voltage voltages are turned off (steps S913 to S915). If the controller 100 detects that the density setting has been changed, the charging bias is turned on (step S909), and the charging bias voltage change from the density center setting value is added to the transfer voltage (step S910). A transfer voltage including the charge bias voltage change is output to the transfer roller 5 (step S911). Thereafter, the developing voltage is turned on (step S912), and image formation is performed. After the image formation is completed, all the high-voltage voltages are turned off (steps S913 to S915).

  As described above, when the charging bias voltage and the transfer cleaning voltage are output from the charging bias power supply transformer 414, the optimum transfer voltage is output to the transfer roller 5 even if the charging bias voltage is changed and the transfer cleaning voltage is changed. It becomes possible to do.

Schematic configuration cross-sectional view of an image forming apparatus of the present invention Control system block diagram of image forming apparatus of the present invention High-voltage power supply schematic configuration circuit diagram according to the first embodiment FIG. 3 is a relationship diagram between a transfer voltage and a charging bias voltage according to the first embodiment, where (a) shows a transfer voltage, and (b) shows an output voltage on which the transfer voltage and the charging bias voltage are superimposed. (A) ON / OFF timing of charging DC voltage applied to charging roller, (b) ON / OFF timing of developing AC voltage applied to developing unit, (c) ON of developing DC voltage The figure which shows ON / OFF timing, (d) The figure which shows the ON / OFF timing of the transfer voltage applied to a transfer roller, (e) The figure which shows the ON / OFF timing of the transfer cleaning voltage High-voltage power supply schematic configuration circuit diagram according to the first embodiment FIG. 6 is a relationship diagram between a transfer voltage and a charging bias voltage according to the second embodiment, where (a) shows a transfer voltage, (b) shows an output voltage on which the transfer voltage and the charging bias voltage are superimposed, and (c) ) Is a diagram showing the increased transfer voltage, and (d) is a diagram showing the output voltage in which the increased transfer voltage and the charging bias voltage are superimposed. FIG. 6 is a relationship diagram between a transfer voltage and a charging bias voltage according to the third embodiment, where (a) shows a raised transfer voltage, and (b) shows the raised transfer voltage and the charging bias voltage superimposed. FIG. 8C is a diagram showing the output voltage, FIG. 10C is a diagram showing the transfer voltage considering the charging bias voltage variable width, and FIG. 10D is a diagram showing the output voltage superimposed with the charging bias voltage and the transfer bias considering the variable width. High Voltage Output Flowchart in Image Forming Operation According to Third Embodiment Schematic configuration circuit diagram of a conventional high voltage power supply device

Explanation of symbols

1 Photosensitive drum (equivalent to an image carrier)
2 Charging roller (equivalent to charging means)
3 Exposure section (equivalent to latent image means)
4 Developer (equivalent to developing means)
5 Transfer roller (equivalent to transfer means and transfer roller cleaning means)
18 Fixing device (equivalent to fixing means)
100 Controller 301 Printer Controller 302 Printer Engine Control Unit 303 High Voltage Control Unit 402 Transfer Power Supply Driving Circuit 404 Charging Bias Driving Circuit 406 Transistor 408 Transistor 410 DC Power Supply 414 Charging Bias Power Supply Transformer (corresponding to high voltage output means)
424 Diode 426 Diode 438 Resistor 445 Capacitor 456 Resistor 470 Capacitor 474 Transformer for transfer power supply (corresponding to high voltage output means)
P Recording paper (equivalent to recording material)

Claims (6)

A charging means for charging an image carrier having a photosensitive layer; a latent image means for irradiating light to form a latent image on the image carrier; and a developing means for developing a developer on the latent image pattern of the image carrier. And a transfer means for transferring the developer to the recording material by applying a transfer voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. An image forming apparatus comprising: a transfer roller cleaning unit that removes the developer attached by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller; and a fixing unit that fixes the developer transferred to the recording material. In
Each means except at least one of the charging means, the latent image means, the developing means, the transfer means, the transfer roller cleaning means, and the fixing means has a high voltage output means,
When a positive or negative high voltage is supplied to the at least one means, the high voltage output means supplies the high voltage having the same polarity as the positive or negative high voltage. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the one high voltage output unit is the high voltage output unit included in the charging unit, and the at least one unit is the transfer roller cleaning unit. A charging means for charging an image carrier having a photosensitive layer; a latent image means for irradiating light to form a latent image on the image carrier; and a developing means for developing a developer on the latent image pattern of the image carrier. And a transfer means for transferring the developer to the recording material by applying a transfer voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. Image forming comprising: a transfer roller cleaning unit that removes the developer attached by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller; and a fixing unit that fixes the developer transferred to the recording material In the device
At least one of the charging unit, the latent image unit, the developing unit, the transfer unit, the transfer roller cleaning unit, and the fixing unit includes a high voltage output unit that applies voltages of different polarities,
The high voltage output means for applying the voltages of different polarities includes superimposing means for superimposing the simultaneously output voltages and outputting a target voltage when simultaneously outputting voltages of different polarities. apparatus.   The image forming apparatus according to claim 3, wherein the superimposing unit is the transfer unit. A charging means for charging an image carrier having a photosensitive layer; a latent image means for irradiating light to form a latent image on the image carrier; and a developing means for developing a developer on the latent image pattern of the image carrier. And a transfer means for transferring the developer to the recording material by applying a voltage having a polarity opposite to the charge held by the developer from the back surface of the recording material to the transfer roller. An image forming apparatus comprising: a transfer roller cleaning unit that removes the developer attached by applying a voltage having a polarity opposite to the transfer voltage to the transfer roller; and a fixing unit that fixes the developer transferred to the recording material. In
A common means for supplying a voltage from one high-voltage power source to the charging means and the transfer roller cleaning means;
A superimposing unit that superimposes voltages of different polarities when outputting a voltage by the transfer unit, and outputs a target voltage;
Voltage varying means for varying the voltage supplied to the charging means,
When a voltage variable amount is generated by the voltage variable means,
An image forming apparatus comprising: a voltage correction unit that corrects a voltage superimposed on the transfer unit according to the voltage variable amount.   6. The image forming apparatus according to claim 5, wherein the voltage correction unit adds or subtracts the voltage variable amount to a voltage superimposed on the transfer unit.

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