JP2016114703A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem such that with a configuration in which a voltage is applied to a discharge member, a high voltage power supply device for the discharge member is necessary and downsizing and low cost of an image formation device is prevented.SOLUTION: An image formation device includes a first high voltage output terminal connected with first high voltage output means and second high voltage output means and a second high voltage output terminal connected with the second high voltage output means. A transfer member is connected with the first high voltage output terminal. The discharge member is connected with the second high voltage output terminal. Based on a voltage applied by the first high voltage output means and a current value detected by a current detection unit, it is determined whether the second high voltage output means applies a voltage to the discharge member or not.SELECTED DRAWING: Figure 2

Description

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

  In an electrophotographic image forming apparatus, a toner image formed on a photosensitive drum or an intermediate transfer member is electrostatically applied by applying a voltage having a polarity opposite to that of the toner to a transfer member disposed opposite to the photosensitive drum or the intermediate transfer member. The image is transferred onto a recording material. Thereafter, the recording material is nipped and conveyed by the fixing device, whereby the toner image is fixed to the recording material by heat and pressure.

  As a method of applying a voltage to the transfer member, the current flowing through the transfer member (hereinafter referred to as transfer current) is sequentially detected, and the detection result is fed back to the voltage applied to the transfer member (hereinafter referred to as transfer voltage). There is known a constant current control method for controlling the current constant. The constant current control method is easy to ensure good transferability regardless of the electric resistance of the transfer member or recording material. Also, as a technique for cleaning toner adhering to the transfer member, a voltage having the same polarity as that of the toner is applied to the transfer member, and the toner adhering to the surface of the transfer roller is moved onto the photosensitive drum or intermediate transfer member by electrostatic force. Technology is known.

  In a system in which a toner image is electrostatically transferred onto a recording material, the recording material is charged during transfer, and a transfer defect may occur due to a discharge generated between the recording material and the transfer portion when the recording material is separated from the transfer portion. . For this reason, Patent Document 1 discloses a configuration in which a neutralizing member is disposed in the vicinity of the separation portion from the transfer portion, and the recording material is neutralized when the recording material is separated from the transfer portion by applying a voltage having the same polarity as the toner. Is disclosed.

Japanese Patent Laid-Open No. 5-100593

  However, in the configuration of Patent Document 1, there are a plurality of high-voltage output means for applying a voltage to the charge removal member and a high-voltage output means for applying a voltage to the transfer member for cleaning, despite applying the same polarity voltage. High voltage output means was required.

  In addition, since the voltage applied to the charge removal member for charge removal and the voltage applied to the transfer member for transfer are opposite in polarity, when a voltage is applied to the charge removal member and the transfer member from the common voltage application means, the voltage is applied to the transfer member. It is difficult to maintain proper voltage application.

  Therefore, an object of the present invention is to provide an image forming apparatus capable of maintaining an appropriate voltage application to a transfer member even when a voltage is applied to a charge removal member and a transfer member from a common high-voltage output unit. .

  In order to solve the above-described problems, the present invention provides an image carrier that carries a toner image, a transfer member that forms a transfer portion that transfers the toner image on the image carrier to a recording material, Neutralizing member, first high voltage output means for outputting a voltage of a predetermined polarity, second high voltage output means for outputting a voltage having a polarity opposite to that of the first high voltage output means, and the first high voltage A first high voltage output terminal connected to the output means and the second high voltage output means; a second high voltage output terminal connected to the second high voltage output means; and a current flowing through the first high voltage output terminal. An electric current detection unit for detecting, the transfer member is connected to the first high-voltage output end, the static elimination member is connected to the second high-voltage output end, and the second high-voltage output means When the reverse polarity voltage is output to the static elimination member, the first high voltage output terminal Voltage of the opposite polarity to the copy member, characterized in that is output.

  In order to solve the above-described problems, the present invention provides an image carrier that carries a toner image, a transfer member that forms a transfer portion that transfers the toner image on the image carrier to a recording material, and a recording material. A neutralizing member for neutralizing, a first high-voltage output means for outputting a voltage of a predetermined polarity, a second high-voltage output means for outputting a voltage having a polarity opposite to that of the first high-voltage output means, and the first A high-voltage output means, a first high-voltage output end connected to the second high-voltage output means, a second high-voltage output end connected to the second high-voltage output means, and the first high-voltage output end A current detection unit for detecting current, wherein the transfer member is connected to the first high-voltage output end, the neutralizing member is connected to the second high-voltage output end, and the first high-voltage output means On the basis of the voltage applied by the current detector and the current value detected by the current detector. Characterized in that the high-voltage output means for determining whether to apply a voltage to said discharging member.

  According to the present invention, it is possible to provide an image forming apparatus capable of maintaining an appropriate voltage application to a transfer member even when a voltage is applied to a charge removal member and a transfer member from a common high-voltage output unit. .

1 is a diagram illustrating an outline of an image forming apparatus to which the present invention can be applied. 1 is a diagram illustrating a high-voltage power supply of an image forming apparatus to which the present invention can be applied. The figure which showed the electric current path | route of the positive voltage high voltage power supply which can apply this invention. The figure which showed the electric current path | route of the negative voltage high voltage power supply which can apply this invention. The figure explaining operation | movement of the 1st Example which can apply this invention. The figure explaining the transcription | transfer constant voltage target value of 1st Example which can apply this invention. The figure explaining the threshold value K of 1st Example which can apply this invention. The figure explaining the effect confirmation result of the 1st example which can apply the present invention. The figure explaining operation | movement of the 2nd Example which can apply this invention. The figure explaining the detail of operation | movement of the 2nd Example which can apply this invention. The figure explaining the threshold value K of the 2nd Example which can apply this invention. The figure explaining operation | movement of the 3rd Example which can apply this invention. The figure explaining the threshold value K of the 3rd Example which can apply this invention.

  The preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following examples should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

Example 1
FIG. 1A is a configuration diagram of the image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 includes a deck 101 that stores a recording material P that is a recording sheet. The image forming apparatus 100 also includes a deck paper presence sensor 102 that detects the presence or absence of the recording material P in the deck 101, and a paper size detection sensor 103 that detects the size of the recording material P in the deck 101. Yes. The image forming apparatus 100 also includes a pickup roller 104 that feeds the recording material P from the deck 101 onto the transport path, and a deck paper feed roller 105 that transports the recording material P fed by the pickup roller 104. ing. In addition, the image forming apparatus 100 includes a retard roller 106 that is paired with the deck paper feed roller 105 and suppresses double feeding of the recording material P. The image forming apparatus 100 includes a paper feed sensor 107 that detects the conveyance state of the recording material P from the deck 101 or a double-side reversing unit described later on the downstream side in the conveyance direction of the deck paper supply roller 105. . In addition, the image forming apparatus 100 includes a paper feed conveyance roller 108 for conveying the recording material P further downstream, and a registration roller pair 109 for conveying the recording material P in synchronization with the printing timing. Further, the image forming apparatus 100 includes a pre-registration sensor 110 that detects a conveyance state of the recording material P to the registration roller pair 109.

  Further, on the downstream side in the conveying direction of the registration roller pair 109, a process cartridge that emits laser light from the laser scanner unit 111 based on image information transmitted from the video controller 128 and forms a toner image on the photosensitive drum 1. 152 is disposed. A transfer roller 113 as a transfer means (first member) for transferring the toner image formed on the photosensitive drum 1 onto the recording material P is disposed at a position facing the photosensitive drum 1 as an image carrier. It is installed. Further, at a position facing the photosensitive drum 1, a static elimination member that is a static elimination means (second member) for accelerating the separation of the recording material P from the photosensitive drum 1 by removing the charge on the recording material P. 114 is arranged. Further, a conveyance guide 115, a fixing device 116, a fixing paper discharge sensor 119, and a double-sided flapper 120 are disposed on the downstream side in the conveyance direction of the charge removal member 114. The fixing device 116 thermally fixes the toner image transferred onto the recording material P. The fixing paper discharge sensor 119 detects the conveyance state of the recording material P from the fixing device 116. The double-sided flapper 120 switches the conveyance destination of the recording material P conveyed from the fixing device 116 to a paper discharge unit or a double-side reversing unit.

  A paper discharge sensor 121 that detects the conveyance state of the recording material P in the paper discharge unit and a paper discharge roller pair 122 that discharges the recording material P to the outside of the apparatus are disposed on the downstream side of the paper discharge unit. . On the other hand, the double-side reversing unit is provided for reversing the recording material P after the single-sided printing is completed in order to print on both sides of the recording material P, and transporting the recording material P again to the image forming unit. A reversing roller pair 123, a reversing sensor 124, a D-cut roller 125, a double-sided sensor 126, and a double-sided conveying roller pair 127 are disposed on the double-side reversing unit side. The reverse roller pair 123 switches back the recording material P on the transport path by forward and reverse. The reverse sensor 124 detects the conveyance state of the recording material P to the reverse roller pair 123. The D-cut roller 125 is a roller for transporting the recording material P from a lateral registration portion (not shown) for aligning the position of the recording material P in the width direction. Here, the width direction of the recording material P refers to a direction (also a main scanning direction) orthogonal to the conveyance direction of the recording material P. The double-sided sensor 126 detects the conveyance state of the recording material P in the double-side reversing unit. The duplex conveying roller pair 127 is a roller for conveying the recording material P from the duplex reversing unit to the sheet feeding unit. The high-voltage power supply device 3 is a device that generates a voltage used in the electrophotographic process. The high-voltage power supply device 3 applies a high voltage to, for example, the charger 23, the developing roller 134, the transfer roller 113, the charge removal member 114, and the like. A series of control of the image forming apparatus 100 of this embodiment is performed by an MPU (microprocessor) 5 mounted on the engine controller 4. The high-voltage power supply device 3 includes a voltage generation circuit 31 that applies a voltage to the transfer roller 113 and the charge removal member 114.

Next, the transfer unit and the charge removal member 114 of the image forming apparatus of this embodiment will be described.
FIG. 2 is a schematic diagram of the transfer unit, the charge removal member 114, and the high-voltage power supply device 3 of the image forming apparatus according to the present exemplary embodiment. As shown in FIG. 2, the transfer unit of the image forming apparatus includes a photosensitive drum 1 and a transfer roller 113 that is pressed against the surface of the photosensitive drum 1 to form a transfer nip N. The photosensitive drum 1 is rotationally driven by a motor (not shown), and the transfer roller 113 is driven to rotate with respect to the photosensitive drum 1. In the transfer nip portion N, the toner image on the surface of the photosensitive drum 1 is transferred to the recording material by the transfer voltage applied to the transfer roller 113 from the transfer / discharge voltage generating circuit 31 which is a voltage generating circuit while nipping and conveying the recording material. The transfer voltage is a voltage having a predetermined polarity, and a voltage value to be applied will be described later. Here, the normal polarity of the toner is a negative polarity, and the positive polarity that is the opposite polarity is a voltage of a predetermined polarity. The transfer roller 113 is a rubber roller in which a foamed sponge-like medium resistance elastic layer mainly composed of NBR and epichlorohydrin rubber is formed on a core metal such as iron or SUS.

  The neutralizing member 114 is disposed on the recording material discharge side of the transfer nip N, that is, downstream of the transfer roller 113 with respect to the moving direction of the recording material. The recording material that has passed through the transfer nip N is neutralized by the neutralizing voltage applied from the transfer / static voltage generating circuit 31. The static elimination voltage is a voltage having a polarity opposite to that of the transfer voltage applied to the transfer roller 113. In the present image forming apparatus, -1000 V is applied as the static elimination voltage.

  Next, the internal configuration of the transfer / static discharge voltage generating circuit 31 mounted inside the high voltage power supply device 3 will be described. As shown in FIG. 2, the transfer / discharge voltage generating circuit 31 includes a negative voltage high voltage power supply 31b as a second voltage application means, a positive voltage high voltage power supply 31a as a first voltage application means, and a current as a current detection unit. The detection circuit 31c is configured.

  The positive voltage high voltage power supply 31a generates a voltage having a predetermined polarity (positive polarity). The positive transfer voltage is output when a charge having a polarity (positive polarity) opposite to that of the toner image is applied to the recording material and the toner image on the photosensitive drum 1 is transferred onto the recording material.

  The negative voltage high voltage power supply 31b generates a negative transfer negative voltage and a negative charge removal voltage. The transfer negative voltage is output when the transfer residual toner on the surface of the transfer roller 113 after the toner image is transferred is collected and cleaned on the photosensitive drum 1 side. The neutralization voltage is output when the recording material that has passed through the transfer nip N is neutralized. The current detection circuit 31c is a circuit that detects the current output from the positive voltage high-voltage power supply 31b.

  The configuration of the positive voltage high voltage power supply 31a will be described below. Similar to the negative voltage high voltage power supply 31b, the positive voltage high voltage power supply 31a includes a step-up transformer 310, a primary drive circuit 312 and rectifying / smoothing elements (313, 314). Further, the positive voltage high voltage power supply 31a generates AC high voltage in the secondary winding by supplying AC power to the primary winding by the primary drive circuit 312 composed of a switching element. The AC high voltage generated in the secondary winding is rectified as a positive DC high voltage by the diode 313 and the high voltage capacitor 314 which are rectifier elements. Here, the resistor 311 is a bleeder resistor of the positive voltage high voltage power supply 31a. The negative voltage high voltage power supply 31b and the positive voltage high voltage power supply 31b are connected in series with each other, and the generated DC high voltage is supplied to the transfer roller 113 via each bleeder resistor (316, 311). . The voltage detection circuit 325 divides the DC high voltage applied to the transfer roller 113 by resistance and feeds back to the MPU 5 (not shown). The MPU 5 performs constant voltage control of the positive voltage high voltage power supply based on the feedback of the voltage detection circuit 325. The output of the positive voltage high voltage power supply 31a is output to the transfer roller 113 connected to the first high voltage output terminal 40a.

  FIG. 3 is a diagram showing a current path of the positive voltage high voltage power supply 31a. The output of the positive voltage high voltage power supply 31a is in the on state, and the output of the negative voltage high voltage power supply 31b is in the off state.

  A current path that flows when a positive transfer positive voltage is applied to the transfer roller 113 from the positive voltage high-voltage power supply 31 a includes paths 334 and 336. A path 334 is a path through which a positive current from the positive voltage high voltage power supply 31a flows to the GND (not shown) of the photosensitive drum 1 via the transfer roller 113 and the recording material. The path 336 is a path through which the positive current from the GND of the current detection circuit 31c returns to the positive voltage high-voltage power supply 31a via the operational amplifier 321, the resistor 322, and the resistor 316 of the current detection circuit 31c.

  Since the reverse voltage is applied to the diode 320 through the path 336, the diode 320 returns from the GND (not shown) of the photosensitive drum 1 to the positive voltage high voltage power supply 31a via the recording material, the charge removal member 114, and the diode 320. There is no negative current path. More specifically, assuming that the resistance 316 is 10 MΩ and the current value flowing through the path 336 is 20 uA, a voltage drop of 200 V occurs at both ends of the resistance 316. The voltage on the anode side of the diode 320 is approximately −200 V because the negative input of the operational amplifier 321 of the current detection circuit 31 c described later is about several volts. On the other hand, the voltage on the cathode side of the diode 320 is approximately the same potential as the negative input of the operational amplifier 321 and is about several volts because the output of the negative voltage high voltage power supply 31b is off. Therefore, the diode 320 is in a state where a reverse voltage is applied.

  As described above, there is no negative current path from the GND (not shown) of the photosensitive drum 1 to the positive voltage high voltage power supply 31a via the recording material, the charge removal member 114, and the diode 320 by the diode 320. Therefore, the current flowing in the path 334 and the current flowing in the path 336 coincide with each other, and the positive transfer positive voltage flowing in the transfer roller 113 can be detected by the current detection circuit 31c. Further, as a current path that does not flow to the process member, there is a path 335 that returns from the positive voltage high-voltage power supply 31a to the positive voltage high-voltage power supply 31a via the resistor 311.

  The configuration of the negative voltage high voltage power supply 31b will be described below. The negative voltage high voltage power supply 31b includes a primary drive circuit 317 that drives the step-up transformer 315 by a control signal from the step-up transformer 315 and the MPU 5, and a rectifying / smoothing element (319, 320). The step-up transformer 315 generates AC high voltage in the secondary winding when AC power is supplied to the primary winding by the primary drive circuit 317 including a switching element. The AC high voltage generated in the secondary winding is rectified as a negative DC high voltage by the diode 318 and the high voltage capacitor 319 which are rectifying elements. Here, the resistor 316 is a bleeder resistor of the negative voltage high voltage power supply 31b. The voltage detection circuit 326 divides the DC high voltage of the negative voltage high voltage power supply 31b by resistance and feeds back to the MPU 5 (not shown). The MPU 5 performs constant voltage control of the negative voltage high voltage power supply 31b based on the feedback of the voltage detection circuit 326. The cathode voltage of the diode 320 supplies the negative DC high voltage of the negative voltage high voltage power supply to the static elimination member 114, and the anode voltage of the diode 320 supplies the negative DC high voltage of the negative voltage high voltage power supply to the transfer roller 113 via the resistor 311. Supply. The output of the negative voltage high voltage power supply 31b is output to the transfer roller 113 connected to the second high voltage output terminal 40b.

  FIG. 4 is a diagram showing a current path of the negative voltage high voltage power supply 31b. The output of the positive voltage high voltage power supply 31a is in an off state, and the output of the negative voltage high voltage power supply 31b is in an on state.

  A current path that flows when a negative transfer negative voltage is applied to the transfer roller 113 from the negative voltage high-voltage power supply 31 b includes paths 330 and 333. A path 330 is a path through which a negative current from GND (not shown) of the photosensitive drum 1 reaches the negative voltage high voltage power supply 31b via the recording material, the transfer roller 113, the resistor 311 and the diode 320. A path 333 is a path through which the current from the negative voltage high voltage power supply 31b flows to the GND of the current detection circuit 31c via the resistor 322 and the operational amplifier 321 of the current detection circuit 31c.

  A current path that flows when a negative charge removal voltage is applied to the charge removal member 114 from the negative voltage high-voltage power supply 31 b includes paths 331 and 333. A path 331 is a path through which a negative current from GND (not shown) of the photosensitive drum 1 reaches the negative voltage high-voltage power supply 31b via the recording material and the charge removal member 114. Since the path 333 is the same as the case where a negative transfer negative voltage is applied to the transfer roller 113 from the negative voltage high voltage power supply 31b, the description is omitted.

  Further, as a current path that does not flow to the process member, there is a path 332 that returns from the negative voltage high voltage power supply 31b to the negative voltage high voltage power supply 31b via the resistor 316.

  Next, the current detection circuit 31c will be described. The current detection circuit 31c includes an operational amplifier 321 and resistors 322, 323, and 324 connected to the step-up transformer 315, and feeds back the output of the operational amplifier 321 to the MPU 5.

  A voltage: Vt obtained by dividing the power supply voltage Vcc by resistors 323 and 324 is input to the positive input of the operational amplifier 321. The voltage value of Vt is set to about several volts in consideration of the rating of the operational amplifier 321. Here, since the operational amplifier 321 constitutes a negative feedback circuit by R322, the potential difference between the positive input and the negative input of the operational amplifier 321 becomes 0V. That is, the positive input and the negative input of the operational amplifier 321 are in a state where Vt is input.

When the output of the positive voltage high voltage power supply 31a is turned on, a voltage is generated in the transfer roller 113 and a current flows. At this time, since the current paths are the paths 334 and 336 described above, a current having the same level as the current flowing through the transfer roller 113 flows through the resistor 322. As a result, a voltage is generated across the resistor 322, and the output of the operational amplifier 321: Visns is at the following voltage level.
Visns = Vt + R322 × Io (Formula 1)

  Here, R322 is a resistance value of the resistor 322, and Io is a current value flowing through the transfer roller 113. The relationship between the voltage level of Visns and the current flowing through the transfer roller 113 is stored in advance in a storage device (not shown) in the MPU 4.

  As described above, the configuration of the high-voltage power supply according to the present embodiment described above makes it possible to share a negative voltage high-voltage power supply that applies a negative charge removal voltage to the charge removal member 114 and a negative voltage high-voltage power supply that applies a negative voltage to the transfer roller 113. The negative voltage high voltage power supply can be reduced.

  Further, since the charge removal member 114 is disposed in the vicinity of the transfer roller 113 and the transfer timing to the recording material and the charge removal timing substantially overlap, the timing at which a negative voltage is applied from the negative voltage high voltage power source to the transfer roller 113 and the charge removal member 114. Can be made substantially the same.

  However, since the negative voltage high-voltage power supply for the static elimination member 114 and the transfer roller 113 is made common, the problems described below occur.

  In the image forming apparatus according to the present exemplary embodiment, when a neutralization voltage is applied, a positive transfer positive voltage is applied to the transfer roller 113 to transfer the toner image on the photosensitive drum 1 onto the recording material, and a neutralization neutralization is applied to the neutralization member 114. In some cases, the recording material is neutralized by applying a voltage. Therefore, both the outputs of the positive voltage high voltage power supply 31a and the negative voltage high voltage power supply 31b are turned on. At this time, the superimposed voltage of the positive voltage high voltage power supply 31a and the negative voltage high voltage power supply 31b has the same polarity as the output voltage of the positive voltage high voltage power supply 31a.

  At this time, the current of the positive voltage high voltage power supply 31 a and the current of the negative voltage high voltage power supply 31 b flow through the transfer roller 113 simultaneously. Therefore, a current flows through all the paths 330, 331, 333, 334, and 336 shown in FIGS. The current flowing through the transfer roller 113 is the sum of the currents of the paths 330 and 334, and the current flowing through the current detection circuit 31 c is the sum of the currents flowing through the paths 333 and 336. The currents in the paths 334 and 336 are the same, but the currents flowing in the paths 330 and 333 are different.

  Therefore, in the power supply configuration of this embodiment, if the negative voltage high voltage power supply 31b and the positive voltage high voltage power supply 31a are simultaneously output, the current detection circuit 322 cannot correctly detect the transfer current flowing through the transfer roller 113. For this reason, the constant current control of the transfer current cannot be performed while the voltage is applied to the charge removal member 114, and good transferability may not be obtained.

  In addition, when a static elimination voltage is applied to the static eliminator 114 and the recording material has a low resistance, if a static eliminator is applied to the static eliminator 114 when the recording material has a low resistance, the transfer current may leak from the transfer roller 113 to the static eliminator 114 via the recording material. is there.

  Therefore, the impedance of the transfer part is calculated from the transfer voltage and transfer current at the time of transfer to the first surface of the recording material, and only when the calculated impedance is larger than a preset threshold value, the neutralization voltage is applied at the time of transfer to the second surface of the recording material. carry out.

Based on the flowchart shown in FIG. 5, the detail of the operation | movement used as the characteristic of a present Example is demonstrated. When the image forming apparatus receives an image signal and starts printing, first, in step S101, the moisture content M (g / m ³ ) in the air is calculated from the temperature and humidity detection results of the environmental sensor 6. In step S102, a transfer voltage target value (hereinafter, transfer constant voltage target value) when the transfer voltage is controlled at a constant value (hereinafter referred to as transfer constant voltage control) during transfer is calculated. Transfer constant voltage target value as shown in FIG. 6 is calculated based on the water content M (g / ^{m 3),} the water content M is to 2000V is 5 (g / ^{m 3)} than the low-humidity environment. In a high humidity environment where the water content is 20 (g / m ³ ) or more, 500 V, and in an environment where the water content is 5 (g / m ³ ) or more and less than 20 (g / m ³ ), 5 (g / m ^3). ) Is a value obtained by linearly interpolating 2000 V, which is a transfer constant voltage target value in the case of less than 20), and 500 V, which is a transfer constant voltage target value in the case of 20 (g / m ³ ) or more, in accordance with the amount of moisture M.

After calculating the transfer constant voltage target value, the threshold value K is calculated in S103. The threshold value K is used when determining whether or not to apply a static elimination voltage when transferring to the second surface of the recording material P. As shown in FIG. 7, the threshold value K is calculated based on the moisture content M, and is 200 in a low humidity environment with a moisture content of less than 5 (g / m ³ ), and a high humidity with a moisture content of 20 (g / m ³ ) or more. In an environment where the water content is 50 (g / m ³ ) or more and less than 20 (g / m ³ ), the set values are 200 and 20 (g / m ³ ). ³ ) It is calculated as a value obtained by linearly interpolating 50, which is a set value in the above case, according to the amount of moisture M. As described above, S101 to S103 are the pre-transfer operations of the image forming apparatus according to the present exemplary embodiment.

  After the above-described pre-transfer start operation from S101 to S103, it is determined in S104 whether or not the print to be performed is the first print, and if it is determined that the print is the first print, the following transfer operation is performed. carry out.

  First, in S105, it is determined whether or not the recording material P has reached the transfer portion based on the leading end position of the recording material P detected by the pre-registration sensor. If it is determined in S105 that the recording material P has reached the transfer portion, the process proceeds to S106, and constant transfer current control is started. Here, the transfer constant current control is a method for controlling the transfer voltage so that the transfer current flowing through the transfer member is constant, and the transfer current target value during the transfer constant current control (hereinafter referred to as the transfer constant current target value). Is 10 μA.

After the start of the transfer constant current control, the process proceeds to S107, where the calculation of the impedance R1 of the transfer portion is started, and then the average value R1 _Ave. The calculation of is started. R1 is calculated from the transfer current detected by the current detection circuit 31c every 30 msec and the transfer voltage output by the positive voltage high-voltage power supply 31a at that time. R1 _Ave. Is calculated by dividing the integrated value of R1 calculated so far by the number of R1 calculations so far.

Thereafter, in S109, it is determined whether the recording material P is discharged from the transfer portion based on the rear end position of the recording material P detected by the pre-registration sensor. If it is determined in step S109 that the recording material P has been discharged from the transfer portion, the process proceeds to step S110 to finish calculating R1, and then in step S111, R1 _Ave. The transfer constant current control is terminated in S112. As described above, the operation from S104 to S112 is the transfer operation at the time of printing the first page in this embodiment.

  After the transfer operation of the first-side print is completed, it is determined in S113 whether or not the print input this time to the image forming apparatus has been completed. If it is determined that the print has not been completed, the process returns to S104. When it is determined that the printing is finished, the printing operation of the image forming apparatus is finished.

After the first side print is completed and the process returns to S104, if it is determined that the print to be performed is not the first side print, that is, the second side print, the following transfer operation is executed. First, the process proceeds to S114, and R1 _Ave. Is greater than or equal to the threshold value K calculated in S103. In S114, R1 _Ave. Is determined to be greater than or equal to K, the process proceeds to S115, and R1 _Ave. Is determined to be less than K, the process proceeds to S121.

First, the transfer operation at the time of printing on the second side when the process proceeds to S115 will be described. In step S115, it is determined whether or not the recording material P has reached the transfer portion. If it is determined in step S115 that the recording material has reached the transfer portion, the process proceeds to step S116 and the transfer constant voltage target value calculated in step S102. To start transfer constant voltage control. In addition, after starting the transfer constant voltage control, application of the static elimination voltage is started in S117. Thereafter, in S118, it is determined whether or not the recording material P has been discharged from the transfer portion. If it is determined that the recording material P has been discharged, the application of the static elimination voltage is terminated in S119, and then the transfer is performed in S120. Ends constant voltage control. As described above, the operations from S113 to S120 are the same as R1 _Ave. Is a transfer operation at the time of printing the second side when the value is equal to or greater than the threshold value K.

  Next, the transfer operation at the time of printing on the second side when the process proceeds to S121 will be described. In S121, it is determined whether or not the recording material P has reached the transfer portion. If it is determined in S121 that the recording material has reached the transfer portion, the process proceeds to S122, and a constant transfer current control is performed with 15 μA as a target value. To start. Thereafter, in S123, it is determined whether or not the recording material P is discharged from the transfer portion. If it is determined that the recording material P is discharged, the transfer constant current control is ended in S124. As described above, the operation from S121 to S124 is a transfer operation at the time of second-side printing when R1 in this embodiment is less than the threshold value K.

  After the second-side print transfer operation is completed, it is determined in S113 whether or not the print input this time to the image forming apparatus has been completed. If the print has not been completed, the process returns to S104, and the operations described so far are performed. Perform again. If it is determined in S113 that printing has ended, the printing operation of the image forming apparatus is ended.

In this example, the calculated R1 _Ave. Is applied at the time of transfer to the second surface only when is greater than a preset threshold value K.

First, since the impedance R1 of the transfer portion is calculated from the transfer voltage and transfer current at the time of transfer to the first surface of the recording material, R1 in the state including the recording material P is calculated. Can be predicted. Also, R1 to R1 _Ave. Can be calculated with higher accuracy.

Since the recording material is easily charged when the resistance is large, the calculated R1 _Ave. It is determined that the static elimination voltage application is performed at the time of transfer to the second surface only when is greater than a preset threshold value K. With this configuration, the neutralization voltage can be applied only when there is a possibility of charging of the recording material and the associated transfer failure. Therefore, the application of an unnecessary neutralization voltage and the associated transfer failure can be suppressed.

  In order to confirm the effect of this example, the following experiment was conducted. With the image forming apparatus of this example that was allowed to stand in a high temperature and high humidity environment of 30 ° C. and 80% for 24 hours, single-color halftone double-sided printing was performed, and image defects and transfer defects that occurred during second-side printing were confirmed. Here, the image defect is a discharge mark on the toner image generated by a discharge generated between the recording material and the transfer roller 113 or the photosensitive drum 1 when the recording material is separated from the transfer portion. Further, the transfer failure is a transfer failure of the toner image from the photosensitive drum 1 to the recording material, which occurs when the transfer voltage is not appropriate or the transfer current leaks.

The recording material used for printing was a thin paper of 60 (g / m ² ), and left paper left in a high temperature and high humidity environment of 30 ° C. and 80% for 24 hours and open paper immediately after opening the package were prepared. In a high humidity environment, the left paper absorbs moisture and becomes a low resistance paper, and the open paper does not absorb moisture and becomes a high resistance paper.

In addition, single-sided halftone double-sided printing was performed with the image forming apparatus of this example that was left in a low-temperature and low-humidity environment at 15 ° C. and 10%, and image defects and transfer defects that occurred during the second-side printing were confirmed. The recording material used for printing was a thin paper of 60 (g / m ² ), and left paper left in a low temperature and low humidity environment of 15 ° C. and 10% for 24 hours and open paper immediately after opening the package were prepared. In the low-humidity environment, the leaving paper Z becomes a high resistance paper because moisture is taken away, and the open paper becomes a low resistance paper because moisture is not taken away.

  Furthermore, the same effect confirmation experiment was implemented also about the following comparative examples.

(Comparative Example 1)
In the image forming apparatus of the present embodiment, the neutralizing member 114 is not connected to the negative voltage high voltage generator 31b, the negative voltage high voltage power source 31b dedicated to the neutralizing member 114 is provided, and the neutralizing voltage is set to R1 _Ave. Regardless of the image forming apparatus, it is applied every time the second surface is transferred.

(Comparative Example 2)
In contrast to the image forming apparatus of the present embodiment, the image forming apparatus does not have the negative voltage high voltage power source 31b for the charge eliminating member 114 without connecting the charge eliminating member 114 to the negative voltage high voltage source 31b.

  FIG. 8 shows the result of the effect confirmation experiment of the present embodiment and each comparative example. In the table of FIG. 8, O, Δ, and X are the image defect and the occurrence / non-occurrence level of the image defect that occurred during the transfer of the second surface, respectively, and the “present” and “absent” notations in the table are the second surface transfer, respectively. The presence / absence of application of a static elimination voltage at the time is shown.

  As shown in FIG. 8, no image defect or transfer defect occurred in this example. On the other hand, in Comparative Example 1, a poor transfer level occurred in the low-humidity environment open paper and the high-humidity environment paper. In the present example, the neutralization voltage was not applied between the open paper in the low humidity environment and the left paper in the high humidity environment, whereas in Comparative Example 1, the open paper in the low humidity environment and the left paper in the high humidity environment. This is because a static elimination voltage is applied.

  In Comparative Example 1, since the open paper in the low humidity environment and the left-side paper in the high humidity environment are papers having relatively low resistance in each environment, the transfer current leaks to the static eliminator 114 through the paper, resulting in transfer failure. It was easy to occur.

  Further, in this example, there was no occurrence of image failure or transfer failure, whereas in Comparative Example 1, transfer failure occurred even in a low humidity environment left-sided paper and a high humidity environment open paper. This is because the transfer voltage can be made to follow the resistance of the recording material and the impedance of the transfer part in the transfer constant voltage control in which the transfer constant voltage target value is set to a constant 1000 V regardless of the environment as in Comparative Example 1. This is because a transfer defect was likely to occur.

In contrast, in this embodiment, the smaller the amount of moisture M (g / m ³ ), the larger the constant transfer voltage target value is calculated, so that the recording material and the transfer roller 113 release moisture to increase the resistance. The lower the humidity environment, the larger the transfer constant voltage target value. As a result, the transfer voltage can be made to follow the resistance of the recording material and the impedance of the transfer portion, so that no transfer failure occurred.

  Further, in this embodiment, no image defect or transfer defect occurred, whereas in Comparative Example 2, an image defect with a poor level occurred in the low humidity environment left paper and the high humidity environment open paper. In this example, the neutralization voltage was applied to the low humidity environment left paper and the high humidity environment open paper, whereas in Comparative Example 2, the low humidity environment left paper and the high humidity environment open paper were neutralized. This is because no voltage was applied.

  In Comparative Example 2, a discharge occurred between the charged paper and the photosensitive drum 1 at the time of separation from the transfer portion, and an image defect of the toner image occurred. On the other hand, in this embodiment, by applying a static elimination voltage to the left-side paper in a low-humidity environment and the open paper in a high-humidity environment, the paper charged during transfer can be sufficiently neutralized. For this reason, no discharge occurred between the paper and the transfer roller 113 during separation, and no image defect occurred.

As described above, according to the present embodiment, the impedance R1 _Ave. calculated from the transfer voltage and transfer current at the time of transfer to the first surface of the recording material. Is applied at the time of transfer to the second surface of the recording material only when is larger than a preset threshold value. With this configuration, it is possible to suppress unnecessary static elimination voltage application and the accompanying transfer failure.

Further, in this embodiment, the target voltage of the static elimination voltage is made constant. However, as described above, the recording material is more easily charged when the resistance of the recording material is higher, so that the R1 _Ave. The target voltage of the static elimination voltage may be increased as the value of increases.

(Example 2)
Since the configuration of the image forming apparatus of the present embodiment is the same as that of the first embodiment, description thereof is omitted.

The feature of this embodiment is that the transfer portion impedance R0 and its average value R0 _{Ave. in the} state where the recording material is not sandwiched between the transfer nip portion N and the average value R0 _Ave. Add an operation to calculate. Furthermore, R1 _Ave. To R0 _Ave. That is, the neutralization voltage application condition at the time of the second surface transfer is changed so that the neutralization voltage is applied at the time of the second surface transfer only when the value obtained by subtracting is greater than the threshold value K.

As shown in FIG. 9, R0 and R0 _Ave. This calculation is performed as S203 after the transfer constant voltage target value in S202 is calculated. 10 shows R0 and R0 _Ave. FIG. 9 shows the details of the calculation operation of S2031, S2031 to S2038 are R0 and R0 _Ave. This is the calculation operation. As shown in FIG. 10, R0 and R0 _Ave. First, in step S2031, transfer constant current control is started with a transfer current of 15 μA as a target value. Next, when it is determined in S2032 that the transfer current detected by the current detection circuit has become 15 μA or more, R0 calculation is started in S2033, and then R0 _Ave. The calculation of is started. Here, R0 is calculated from the transfer current detected by the current detection circuit every 30 msec and the transfer voltage output at that time, and R0 _Ave. Is calculated by dividing the integrated value of R1 calculated so far by the number of R1 calculations so far. If it is determined in S2035 that the number of R0 calculations has reached 100, R0 calculation ends in S2036, and then R0 _Ave. The calculation of is terminated. Thereafter, the transfer constant current control is terminated in S2038, and the process proceeds to calculation of the threshold value K in S204.

As shown in FIG. 9, in the image forming apparatus of this embodiment, R1 _Ave. To R0 _Ave. Only when the value obtained by subtracting is greater than the threshold value K, it is determined whether or not the neutralization voltage is applied during the second surface transfer so that the neutralization voltage is applied during the second surface transfer.

In this embodiment, R1 _Ave. To R0 _Ave. The value of the threshold value K was changed as shown in FIG. 11 in accordance with the change in the method for determining whether or not the neutralization voltage was applied during the second-side transfer so that the value obtained by subtracting the threshold value and the threshold value K were compared. 120 in a low humidity environment with a moisture content of less than 5 (g / m ³ ) and 30 in a high humidity environment with a moisture content of 20 (g / m ³ ) or more. Further, water content of 5 (g / ^{m 3)} or more, 20 in (g / ^{m 3)} than the environment, 5 (g / ^{m 3)} is the setting value of less than 120 and 20 (g ^{/ m} 3) The set value 30 in the above case is calculated as a value obtained by linear interpolation according to the amount of moisture M.
Since other operations are the same as those in the first embodiment, description thereof is omitted.

  With this configuration, even when the impedance of the transfer roller 113 or the photosensitive drum 1 fluctuates, it is possible to maintain the accuracy of determining the necessity of applying a static elimination voltage during the second surface transfer.

(Example 3)
Since the configuration of the image forming apparatus of the present embodiment is the same as that of the first embodiment, description thereof is omitted.

The feature of this embodiment is that the setting value of the threshold value K is changed depending on the paper type to be printed. Specifically, as shown in FIG. 12, the printing mode to be executed in S302 is read, and the threshold value K is calculated based on the moisture amount M (g / m ³ ) according to the printing mode read in S305. Do. The image forming apparatus according to the present embodiment has a thin paper mode, a plain paper mode, and a thick paper mode as print modes. As shown in FIG. 13, the thin paper mode has a moisture content of less than 5 (g / m ³ ) in a low humidity environment. 120, 30 in a high humidity environment with a moisture content of 20 (g / m ³ ) or more. Further, water content of 5 (g / ^{m 3)} or more, 20 in (g / ^{m 3)} than the environment, 5 (g / ^{m 3)} is the setting value of less than 120 and 20 (g ^{/ m} 3) The set value 30 in the above case is calculated as a value obtained by linear interpolation according to the amount of moisture M.

In the plain paper mode, 160 is set in a low-humidity environment where the water content is less than 5 (g / m ³ ), and 40 is set in a high-humidity environment where the water content is 20 (g / m ³ ) or more. In an environment where the amount of water is 5 (g / m ³ ) or more and less than 20 (g / m ³ ), the set values in the case of less than 5 (g / m ³ ) are 1600 and 20 (g / m ³ ) or more. The set value 40 in this case is calculated as a value obtained by linear interpolation according to the amount of moisture M.

In the cardboard mode, the moisture content is set to 200 in a low humidity environment with a moisture content of less than 5 (g / m ³ ) and 50 in a high humidity environment with a moisture content of 20 (g / m ³ ) or more. In an environment where the amount of water is 5 (g / m ³ ) or more and less than 20 (g / m ³ ), the set values in the case of less than 5 (g / m ³ ) are 200 and 20 (g / m ³ ) or more. In this case, the set value 50 is calculated as a value obtained by linear interpolation according to the amount of moisture M.

  As described above, by setting the threshold value K for each print mode and changing the determination condition for applying the charge removal voltage according to the ease of charging depending on the paper type, unnecessary charge removal voltage application and accompanying transfer failure are generated. An image forming apparatus can be provided.

  In this embodiment, the transfer constant voltage target value was not changed in accordance with the print mode. However, as described above, the moisture content decreases due to the sheet passing through the fixing device on the first surface of plain paper and thick paper compared to thin paper. Is small. For this reason, since it is difficult to increase the resistance after the fixing device on the first surface is passed, the target value of the transfer constant voltage may be set smaller as the printing mode has a larger basis weight.

  In this embodiment, the neutralization voltage is not changed according to the print mode. However, the neutralization voltage may be set smaller as the print mode has a larger basis weight.

(Other examples)
The present invention is also applicable to the image forming apparatus described with reference to FIG. The image forming apparatus in FIG. 1B is different from the image forming apparatus in FIG. 1A in that it includes a plurality of image carriers (photosensitive drums) and an intermediate transfer body (intermediate transfer belt). In FIG. 1B, subscripts a, b, c, and d are added to the reference numerals of the image forming unit. Subscripts a, b, c, and d are omitted unless necessary.

  FIG. 1B shows an image forming apparatus having an intermediate transfer member (hereinafter referred to as an intermediate transfer belt) 140. The intermediate transfer belt 140 is stretched by rollers 141, 142, and 143. In the image forming apparatus 100, at the time of image formation, the toner image on the photosensitive drum 1 developed by the developing device 112 is transferred onto the intermediate transfer belt 140 (by a transfer voltage applied to the transfer roller 113 from a primary transfer power source (not shown). The images are sequentially superimposed and transferred onto the intermediate transfer member. Thereafter, a positive transfer voltage is applied from a secondary transfer positive power source (not shown) to the secondary transfer roller 144 as a transfer means (first member), and the toner image on the intermediate transfer belt 140 is applied to the recording material P. Transcribed. The toner not transferred to the recording material P but remaining on the intermediate transfer belt 140 is subjected to intermediate transfer belt cleaning by a positive voltage applied to the intermediate transfer belt cleaning brush 145 from an intermediate transfer belt cleaning positive power source (not shown). It is temporarily collected by the brush 145. Hereinafter, the intermediate transfer belt cleaning positive power source is simply referred to as a cleaning positive power source, and the intermediate transfer belt cleaning brush 145 serving as a removing unit (second member) is simply referred to as a cleaning brush 145.

  On the other hand, during the cleaning process, the toner attached to the secondary transfer roller 144 is transferred onto the intermediate transfer belt 140 by the negative voltage applied to the secondary transfer roller 144 and removed from the secondary transfer roller 144. . The toner temporarily collected and collected by the cleaning brush 145 is discharged onto the intermediate transfer belt 140 by the negative voltage applied to the cleaning brush 145. Thereafter, the toner discharged onto the intermediate transfer belt 140 is transferred from the intermediate transfer belt 140 to the photosensitive drum 1 (that is, reversely transferred) and collected in a cleaner container (not shown) in the photosensitive drum 1.

  Even in such an image forming apparatus, in order to separate the recording material from the intermediate transfer belt 10, a negative high voltage power source that applies a negative voltage to the neutralizing member 114 and the secondary transfer roller 144 is used in common. The same effect as Example 1 is obtained.

DESCRIPTION OF SYMBOLS 1 Image carrier 113 Transfer member 114 Static elimination member 3 High voltage power supply device 31a Positive high voltage power supply 32b Negative high voltage power supply

Claims (10)

An image carrier that carries a toner image, a transfer member that forms a transfer portion that transfers the toner image on the image carrier to a recording material, a static elimination member that neutralizes the recording material, and outputs a voltage of a predetermined polarity The first high voltage output means, the second high voltage output means for outputting a voltage having a polarity opposite to that of the first high voltage output means, the first high voltage output means and the second high voltage output means. A first high-voltage output end, a second high-voltage output end connected to the second high-voltage output means, and a current detection unit that detects a current flowing through the first high-voltage output end,
When the transfer member is connected to the first high-voltage output end, the static elimination member is connected to the second high-voltage output end, and the second high-voltage output means outputs the reverse polarity voltage to the static elimination member. The image forming apparatus, wherein the reverse polarity voltage is output to the transfer member via the first high-voltage output end.   The image forming apparatus according to claim 1, wherein the voltage output to the charge removal member is a constant value at least as the voltage output from the second high voltage output unit.   2. The voltage output from the first high-voltage output means and the voltage output from the second high-voltage output means are both set to a constant value when outputting the voltage to the static elimination member. Item 3. The image forming apparatus according to Item 2.   When outputting the voltage to the static elimination member, the superimposed voltage of the voltage output from the first high voltage output means to the transfer member and the voltage output from the second high voltage output means to the transfer member is the first voltage. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus has the same polarity as a voltage output from the high-voltage output means. A fixing unit configured to fix the toner image transferred to the recording material to the recording material; the recording material having the toner image fixed on the first surface by the fixing unit is reversed; When transferring in
Based on the voltage applied by the first high-voltage output means when transferring the toner image for the first surface and the current value detected by the current detector, the first image is transferred when transferring the toner image for the second surface. 5. The image forming apparatus according to claim 1, wherein two high-voltage output units determine whether to apply a voltage to the charge removal member.   Only when the value calculated based on the voltage applied by the first high-voltage output means and the current value detected by the current detection unit when transferring the toner image on the first surface is larger than a threshold, the second 6. The image forming apparatus according to claim 5, wherein the second high-voltage output means applies a voltage to the charge removal member when transferring the toner image to the face.   When the second high voltage output means applies a voltage to the charge removal member when transferring the toner image to the second surface, the voltage applied by the first high voltage output means is a constant voltage. The image forming apparatus according to claim 6. An image carrier that carries a toner image, a transfer member that forms a transfer portion that transfers the toner image on the image carrier to a recording material, a static elimination member that neutralizes the recording material, and outputs a voltage of a predetermined polarity The first high voltage output means, the second high voltage output means for outputting a voltage having a polarity opposite to that of the first high voltage output means, the first high voltage output means and the second high voltage output means. A first high-voltage output end, a second high-voltage output end connected to the second high-voltage output means, and a current detection unit that detects a current flowing through the first high-voltage output end, A transfer member is connected to the first high-voltage output end, and the static elimination member is connected to the second high-voltage output end;
Based on the voltage applied by the first high-voltage output means and the current value detected by the current detection unit, the second high-voltage output means determines whether to apply a voltage to the static elimination member. An image forming apparatus. A fixing means for fixing the toner image transferred to the recording material to the recording material;
When the recording material on which the toner image is fixed on the first surface by the fixing unit is reversed and the toner image is transferred to the transfer surface on the second surface, the second high-voltage output unit applies a voltage to the charge eliminating member. The image forming apparatus according to claim 8, wherein:   The second high voltage output means only when the value calculated from the voltage applied by the first high voltage output means and the current value detected by the current detection unit when the recording material is not sandwiched is larger than a threshold value. The image forming apparatus according to claim 9, wherein a voltage is output to the charge removal member.

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