JP2015072498A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to properly set an electrical value of a transfer unit, and to determine the value earlier than before.SOLUTION: Light-emitting means is forced to emit light at the start of a polygon mirror. Transfer control means corrects a transfer voltage, which has been set so that detected currents are equal to a target current, in order to eliminate a difference between the currents to be detected when an exposure part and a non-exposure part of a photoreceptor reach a transfer nip part, to determine a reference transfer voltage, or to determine a transfer voltage obtained by correcting the detected currents to be equal to the target current, as the reference transfer voltage.

Description

  The present invention relates to an image forming apparatus using an electrophotographic method such as a semiconductor laser printer.

  Japanese Patent Application Laid-Open No. 2004-151867 discloses an image forming apparatus that sets a reference voltage (hereinafter referred to as ATVC (Automatic Transfer Voltage Control)) that is applied to a transfer member during image formation during non-image formation. More specifically, in this ATVC, the current transfer current value is detected, and the reference transfer voltage value is set so that the current value becomes a target value. By repeating this operation a plurality of times, an appropriate transfer output voltage is set during image formation.

  Here, the ATVC control sequence will be described with reference to FIG. First, after driving the scanner motor, the semiconductor laser is forcibly turned on continuously or intermittently (hereinafter referred to as forced light emission), and the rotation speed of the scanner motor is detected by a light receiving sensor provided on the laser scanning line. When the polygon mirror is in a stable rotation state by this detection, the semiconductor laser is not irradiated on the surface of the photoconductor (image area), and is repeatedly turned on and off in accordance with a synchronization signal input to the light receiving sensor (hereinafter referred to as “lighting sensor”). , Called unblanking emission). Subsequently, ATVC is executed after the processing is shifted to the unblanking light emission.

  When transferring an actual toner image, the transfer nip is variably set based on the reference transfer voltage set for the reference state when the exposed area of the photosensitive drum is not in contact (arrival) at the transfer nip. To do. For example, when a recording medium to which a toner image is transferred enters the next transfer nip portion, the transfer voltage value (reference transfer voltage) in a state before the recording medium enters is used as a reference after the recording medium enters. Set the transfer voltage value. For this reason, the image forming apparatus normally performs ATVC after shifting control to the previously described unblanking light emission.

Japanese Patent Laid-Open No. 05-6112

  In recent image forming apparatuses, there is an increasing demand for shortening the first printout time from when a print instruction is received until the first printed matter is discharged. In connection with this, it is also desired to end the ATVC described earlier at an early stage. For example, in the ATVC control shown in FIG. 9, this request can be realized by starting ATVC simultaneously with the start of printing.

  However, on the charged photoconductor surface, the potential changes between the photoconductor surface forcibly emitting the semiconductor laser and the photoconductor surface when the unblanking light is emitted, and the value of the current flowing through the transfer member in contact with the photoconductor also varies. It will change. That is, if ATVC is performed while the semiconductor laser is forcibly emitting light, the potential change described above (change in the transfer current value flowing through the transfer member) occurs, and the accuracy of ATVC decreases. Alternatively, the setting value obtained by ATVC is not appropriate.

  On the other hand, as a transfer method in the image forming apparatus, there is also a method of setting a current value with respect to a target voltage value instead of setting a voltage value with respect to the target current value. The problem described above can also be said in such a case.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain an appropriate electrical setting of a transfer portion and obtain it at an earlier timing than in the past.

  The image forming apparatus according to the present invention includes a light emitting means for emitting a light beam and a light beam emitted from the light emitting means on the surface of the photosensitive member charged by the charging means to form an electrostatic latent image on the photosensitive member. A polygon mirror for scanning; a detecting means for detecting a light beam scanned by the polygon mirror; and a developing means for visualizing a toner image by attaching toner to an electrostatic latent image formed on the surface of the photoreceptor; A transfer unit that transfers the toner image to a transfer medium; a transfer voltage application unit that applies a transfer voltage to the transfer unit; and a current that flows through the transfer unit in response to the application of the transfer voltage, and the detection result And a transfer control means for determining a transfer voltage to be applied to the transfer means, and when the polygon mirror is activated, the light emitting means is connected to the image area of the photoconductor and the non-transfer area. Measurement means for continuously forcibly emitting light over an image area and measuring the speed of a polygon mirror based on a detection period of the detection means; and the transfer control means forcibly causes the light emission means to emit light when the polygon mirror is activated. In such a state, the detected current is set to be a target current in order to eliminate the difference between the detected currents when the exposed portion and the non-exposed portion of the photoreceptor reach the transfer nip portion. The transfer voltage is further corrected to determine a reference transfer voltage, or the detected current is corrected to determine the transfer voltage at which the corrected current becomes the target current as the reference transfer voltage.

  According to the present invention, it is possible to obtain an appropriate electrical setting of the transfer portion at an earlier timing than in the prior art.

1 is an overall cross-sectional view of an image forming apparatus. 1 is a block diagram of an image forming apparatus. FIG. 3 is a diagram illustrating a relationship between an engine controller and each unit of the image forming apparatus. 7 is a flowchart showing an operation at the time of starting an image forming apparatus including ATVC. The timing chart of the initial operation including ATVC. Another flowchart showing the operation when starting up the image forming apparatus including ATVC Another timing chart of initial operation including ATVC Another flowchart showing the operation at the time of starting the image forming apparatus including ATVC Timing chart showing conventional ATVC

[Example 1]
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

[Cross Section of Image Forming Apparatus]
A specific example of an image forming apparatus based on the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating the overall configuration of the image forming apparatus according to the present exemplary embodiment. In FIG. 1, reference numeral 100 denotes an image forming apparatus main body. A toner cartridge 101 is detachable from the image forming apparatus. Reference numeral 102 denotes a photoconductor as an image carrier. Reference numeral 103 denotes a semiconductor laser as a light source. The semiconductor laser 103 emits a light beam. A polygon mirror 105 is rotated by the scanner motor 104. Reference numeral 106 denotes a laser beam path that is emitted from the semiconductor laser 103 and scans the photosensitive member 102. A light receiving sensor 107 receives a laser emitted from the semiconductor laser 103. Reference numeral 108 denotes a charging roller for uniformly charging the surface of the photosensitive member 102. Reference numeral 109 denotes a developing unit for developing the toner by attaching (developing) toner to the electrostatic latent image formed on the photosensitive member 102 to visualize the toner. Reference numeral 110 denotes a transfer roller for transferring the toner image developed by the developing unit 109 to a predetermined recording sheet (transfer target medium). Reference numeral 111 denotes a fixing device, and 112 denotes a fixing heater of the fixing device for fusing the toner transferred to the recording paper by heat. The fixing device 111 heats and fixes the toner on the recording paper to the recording paper while the recording paper is conveyed by the fixing heater and the 124 pressure roller by the fixing heater. Reference numeral 113 denotes a paper feed cassette for storing paper, which is attached to the printer 100 from the direction of arrow A in FIG. Reference numeral 114 denotes a paper feed roller that feeds paper from the paper feed cassette 113 and sends it to the transport path by one rotation. The feed roller 115 and the retard roller 116 are a pair of rollers for separating the paper into one sheet and feeding it to the conveyance path when the paper picked up by the pickup roller 114 is a paper bundle. Reference numeral 117 denotes an intermediate roller for conveying paper fed from the cassette to the image forming unit. Reference numeral 118 denotes a pre-transfer roller that feeds the conveyed paper to the photosensitive member 102, and reference numeral 119 denotes that the image writing (recording / printing) on the photosensitive member 102 and paper conveyance are synchronized with the fed paper and the paper is fed. It is a top sensor for measuring the length of the conveyed paper in the conveyance direction. Reference numeral 120 denotes a fixing sensor for detecting the presence or absence of a sheet after fixing; 121, a conveyance roller for discharging the fixed sheet to a discharge conveyance path; and 122, a sheet is discharged to a discharge tray 123 on which the discharged sheets are stacked. A discharge roller.

  In FIG. 1, the image forming apparatus that performs monochrome printing has been described as an example. However, the present invention is not limited to this. For example, Y, M, C, and K toner images developed on the respective photosensitive drums are directly transferred onto a recording paper (transfer medium) in order, and are transferred to a color image forming apparatus that fixes the toner images. The control described in the embodiment can be applied. Further, for example, primary transfer in a color image forming apparatus in which toner images of each color of Y, M, C, and K are primarily transferred and superimposed on an intermediate transfer belt (transfer medium) and then secondarily transferred to a recording medium. In contrast, the control described in each embodiment described later can be applied.

[Block diagram of image forming apparatus]
FIG. 2 is a block diagram of a circuit configuration in the present invention. In FIG. 2, reference numeral 201 denotes a printer controller for expanding image code data sent from an external device such as a host computer (not shown) into bit data necessary for printer printing, and reading and displaying printer internal information. . Reference numeral 202 denotes an engine controller for controlling each part of the printer engine according to an instruction from the printer controller 201 and notifying the printer controller 201 of internal printer information. The engine controller 202 includes a CPU and an ASIC, and firmware is mounted on the CPU. Note that the printer controller 201 and the engine controller 202 may be constructed in a common CPU and ASIC.

  Reference numeral 203 denotes a high voltage control unit that performs high voltage output control in each process such as charging, development, and transfer in accordance with an instruction from the engine controller 202. An optical system control unit 204 performs speed control such as driving and stopping of the scanner motor 104 and speed measurement, and controls lighting of the laser beam in accordance with an instruction from the engine controller 202. Reference numeral 205 denotes a fixing device control unit that drives and stops energization of the fixing heater in accordance with an instruction from the engine controller 202. Reference numeral 206 denotes a sensor input unit that notifies the engine controller 202 of a paper presence / absence state of a top sensor 119, a fixing sensor 120, and a paper surface position sensor (not shown), and a temperature state detected by a temperature detection element described later. A sheet conveyance control unit 207 performs driving / stopping of a motor / roller for recording sheet conveyance in accordance with an instruction from the engine controller 202. The paper conveyance control unit 207 includes a paper feed roller 114, feed retard roller pairs 115 and 116, a pre-transfer roller 118, a photoconductor 102, a fixing film 124, a pressure roller 125, a conveyance roller 121, and a paper discharge roller 122 in FIG. Controls driving and stopping.

[Figure showing relationship between engine controller and each part of image forming apparatus]
FIG. 3 is a diagram illustrating a relationship between the engine controller used in this embodiment and each unit of the image forming apparatus.

  The CPU in the engine controller 202 transmits a PWM signal to each of the high voltage output circuits of the charging roller 108, the developing device 109, and the transfer roller 110. A booster in each high voltage output circuit (charging voltage output circuit, development voltage output circuit, transfer voltage output circuit) applies a high voltage corresponding to the input PWM signal to each high voltage output unit. Further, when the CPU changes the duty ratio of the PWM signal, the high voltage applied to each high voltage output unit changes.

  A transfer current detection circuit is connected to the transfer voltage output circuit (transfer voltage application circuit), and converts the current flowing through the transfer roller 110 into a voltage. This Analog signal is input to the CPU and converted into a digital value by an A / D converter in the CPU. The CPU can know the current flowing through the transfer roller 110 from this digital value. It should be noted that the current flowing through the transfer roller 110 is actually determined by the action of not only the transfer roller 110 but also the photosensitive member 102. Needless to say, the method for detecting the current flowing through the transfer roller 110 may be other than the method described above.

  The ASIC in the engine controller 202 controls the rotation speed of the scanner motor 104 and the on / off state of the semiconductor laser 103. The CPU can set the lighting method of the semiconductor laser 103 for the ASIC. The lighting method can be set to off, forced light emission, unblanking light emission, VIDEO lighting corresponding to a signal transmitted from the printer controller 201, or the like. For example, as shown in the timing chart of FIG. 5 to be described later, the forced light emission here means that a laser beam is continuously turned on in a non-image area and an image area in at least one laser scan (or a plurality of laser scans). Point to. It can also be said that the laser beam is continuously turned on while the n-side polygon mirror rotates at least (1 / n) (or a plurality of rotations). Further, the CPU sets a target rotation speed of the scanner motor 104 and instructs the ASIC to drive the scanner motor 104. The activation of the scanner motor 104 can also be called the activation of a polygon mirror. The ASIC that has received the drive instruction controls the scanner motor 104 to be accelerated or decelerated according to the lighting cycle input from the light receiving sensor 107 so as to reach the target rotation speed. Here, a certain value may be assigned to the target rotational speed, or a certain allowable range may be assigned.

[Flow chart of initial operation including ATVC]
FIG. 4 is a flowchart showing the ATVC process in a state in which the semiconductor laser 103 is forcibly emitted and an exposed portion is formed on the surface of the photosensitive member 102 and reaches the transfer nip portion. It is executed by an engine controller 202 that functions as a transfer control means.

  When instructed to start printing from the printer controller 201, the engine controller 202 instructs to start driving the photosensitive member 102 and the scanner motor 104 (S401). In addition, the high voltage output of the charging roller 108 and the start of forced light emission of the semiconductor laser 103 are also instructed. Further, the start of driving of other members necessary for image formation is also instructed (S401). A state in which these various types of processing are started is shown at T501 in the timing chart of FIG.

  The time required for the application location (application position) of the photoconductor 102 to which a high voltage is applied by the charging roller 108 to reach the transfer nip portion of the photoconductor 102 and the transfer roller 110 in accordance with the rotation of the photoconductor 102. At least, the ATVC is started (S402). The timing of T502 in the timing chart of FIG. 5 corresponds to the timing of starting ATVC, and the ATVC disclosure instruction is given by the engine controller 202. This is performed in parallel with the startup of the scanner motor 104 (polygon motor 105).

  The engine controller 202 sets the voltage of the transfer roller 110 to the current initial value (S403). Then, the transfer roller 110 outputs a high voltage according to the setting of S403 (S404). The engine controller 202 samples the current value flowing through the transfer roller 110 that outputs a high voltage for a certain period of time (S405). The engine controller 202 changes these settings and repeats the predetermined number of times (S406).

Here, if the current value as the detection result in S405 is lower than the target current value, the engine controller 202 sets the transfer voltage value to be higher in the next S403. On the other hand, if the detection result is higher than the target current value, the engine controller 202 sets the transfer voltage value to be lower in the next S403. The predetermined number of times described above is determined by how many times the processes of S403 to S405 can be performed within the time until the unblanking light emission is started by the semiconductor laser 103. More precisely, it depends on how much control can be performed within the position where the forcibly emitted portion to be exposed affects the detection current, that is, within the time when it is in contact with the transfer nip. And after a predetermined number of times embodiment, the engine controller 202, finally multiplied by the correction coefficient α1 to the transfer voltage value determined, to determine the reference transfer voltage value V ₀ by adding the correction sections α1 determined (S407). The reference transfer voltage value V ₀ may be calculated by the CPU of the engine controller 202 or may be obtained using a table provided in the engine controller 202.

[Calculation of correction information]
Here, the correction coefficient α1 and the correction intercept α1 will be described. The correction coefficient α1 and the correction intercept α1 are obtained by the following processing by the engine controller 202. That is, ATVC is performed in a state where the charging roller 108 outputs a certain high voltage and the exposed surface of the photosensitive member due to forced light emission of the semiconductor laser 103 reaches the transfer nip portion, and is described with reference to the flowchart of FIG. As described above, the transfer voltage value V _0L is obtained. Further, the charging roller 108 outputs a certain high voltage, performs unblanking light emission by the semiconductor laser 103, performs ATVC with the non-exposed surface of the photoreceptor reaching the transfer nip portion, and transfers the transfer voltage value V _Calculate from _0D . Further, the engine controller 202 executes the processing just described in a plurality of environments. Specific examples are shown below.

A target current value in ATVC is set to 3 μA, for example. Assume that the voltage value V _0L when performing ATVC with forced light emission in a low temperature and low humidity environment is 1000 V, and the voltage value V _0D when performing ATVC with unblanking light emission is 1300 V. Also in a high temperature and high humidity environment, the voltage value _{V 0L} is 500V in the case of performing ATVC with forced flash, the transfer voltage value _{V 0D} in the case of performing ATVC accompanied by unblanking emission obtained by 700V and the engine controller 202 Suppose. Assume that the following relationship holds.
700 = 500 × correction coefficient α1 + correction intercept α1
1300 = 1000 × correction coefficient α1 + correction intercept α1
Accordingly, the correction coefficient α1 and the correction intercept α1 are as follows.
Correction coefficient α1 = 1.2
Corrected intercept α1 = 100

  The correction coefficient α1 and the correction intercept α1 are determined by the engine controller 202 in each non-image formation, automatically determined, automatically obtained, stored in a non-illustrated non-volatile memory, and read out when necessary. Anyway. In this case, the image forming apparatus main body is provided with an environmental sensor capable of detecting the environment of temperature and humidity, and the engine controller determines the current environment based on the detection result of the environmental sensor and executes ATVC. Alternatively, the ATVC result under a plurality of environments as described above may be measured in advance in a production factory or the like, and stored in a nonvolatile memory provided in the engine controller 202. Further, when the tendency of the correction coefficient α1 and the correction intercept α1 changes depending on the resistance value of the transfer roller 110 and the printing environment (temperature, humidity, etc.), the following forms are also assumed. That is, a plurality of correction coefficients α1 and correction intercept α1 may be stored in a nonvolatile memory, and the engine controller 202 may switch the correction coefficient α1 and the correction intercept α1 to be used depending on the environment.

[Timing chart of initial operation including ATVC]
FIG. 5 is a timing chart when ATVC is performed on the surface of the photoconductor 102 that forcibly emits light from the semiconductor laser 103 in this embodiment.

  The engine starts after the time from when printing is started and the forced light emission is started (T501) until the position where the exposed portion where the forced light is emitted affects the detection current, that is, the time until it reaches the transfer nip has elapsed. The controller 202 starts ATVC (T502). Then, ATVC described in S403 to S405 in the flowchart of FIG. 4 is executed a predetermined number of times. When the rotation speed of the scanner motor 104 reaches a predetermined rotation speed assumed at the time of image formation (T503), the optical system control is switched to unblanking light emission (T503). Then, the ATVC is terminated until the non-exposed portion of the photoconductor 102 formed by unblanking light emission by the semiconductor laser 103 reaches the transfer nip. Therefore, in ATVC, it can be avoided from the timing chart of FIG. 5 that the surface potential conditions of the photoconductor 102 are mixed and the accuracy of ATVC is lowered.

  As described above, the correction coefficient α1 and the correction intercept α1 are set even when ATVC is performed in a state where the exposed portion where the engine controller 202 is forced to emit light influences the detection current, that is, when it reaches the transfer nip. Therefore, an appropriate electrical setting of the transfer portion can be realized. In addition, since the engine controller 202 can start ATVC from the timing of forced light emission, it can obtain the reference transfer voltage value much earlier than the conventional ATVC, and can thereby shorten the first printer time compared to the conventional one. .

[Example 2]
In the second embodiment, an image forming apparatus for obtaining a more accurate ATVC result will be described. 1, 2, and 3 are the same as those in the first embodiment, and a detailed description thereof is omitted here.

  FIG. 6 is a flowchart showing ATVC processing in a state in which the semiconductor laser 103 is forced to emit light and an exposed portion is formed on the surface of the photosensitive member 102 and reaches the transfer nip portion. It is executed by an engine controller 202 that functions as a transfer control means. Here, the processing of S601 to S607 is the same as the processing of S401 to S407 described in the first embodiment, and therefore detailed description thereof will be omitted, and description will be made centering on portions unique to the second embodiment.

  In step S <b> 608, the engine controller 202 determines whether the scanner motor 104 has reached a predetermined rotation speed (predetermined rotation speed) under the control of the optical system control unit 202. More specifically, the rotation speed of the scanner motor 104 is detected by the engine controller 202 in accordance with the detection cycle by the light receiving sensor 107. If the engine controller 202 determines that the rotation speed of the scanner motor 104 has reached the predetermined rotation speed, the engine controller 202 instructs the semiconductor laser 103 to start unblanking light emission (S609).

  When the time required for the unblanking light emission to start and the non-exposed portion to reach the transfer nip has elapsed, the engine controller 202 starts ATVC again (S610).

The engine controller 202 sets the voltage of the transfer roller 110 in a state where the unblanking light emission is performed in parallel and the non-exposed surface reaches the transfer nip portion (S611). First, the temporary reference transfer voltage value obtained in S607 is set by the engine controller 202 in S611. Then, the transfer roller 110 outputs a high voltage according to the setting (S612). The engine controller 202 samples a current value flowing through the transfer roller 110 to which a high voltage is applied for a predetermined time (S613). The engine controller 202 repeats these controls a predetermined number of times (S614). Here, if the current value acquired in S613 is lower than the target current value, the engine controller 202 sets the transfer voltage value to be higher in the next S611. On the other hand, if the current value acquired in S613 is higher than the target current value, the engine controller 202 sets the transfer voltage value to be lower in the next S611. After a predetermined number of times embodiment, the engine controller 202 may be a transfer voltage value finally determined with the reference transfer voltage value V _0. Here, the predetermined number of times is appropriately determined according to the allowable delay of the far printout.

[Timing chart of initial operation including ATVC]
FIG. 7 is a timing chart when ATVC is performed on the surface of the photoconductor 102 that forcibly emits light from the semiconductor laser 103 in this embodiment. Since T701 to T703 are the same as T501 to T503 described with reference to FIG. 5, detailed description thereof is omitted here.

  At the timing of T704, the engine controller 202 performs ATVC again after the non-exposed portion on the surface of the photoreceptor due to the start of unblanking light emission by the semiconductor laser 103 reaches the transfer nip portion. As a result, the engine controller 202 can obtain a more appropriate reference transfer voltage value even if the correction coefficient α1 and the correction intercept α1 described in the first embodiment are slightly shifted.

  As described above, the engine controller 202 performs ATVC while performing forced light emission in parallel, and then switches processing to unblanking light emission, with the non-exposed portion of the photoreceptor surface reaching the transfer nip portion, Perform ATVC again. Thereby, a more appropriate reference transfer voltage value at the time of image formation can be obtained. In addition, since the engine controller 202 performs only final adjustment (fine adjustment) with unbraked lighting, the reference transfer voltage can be obtained earlier than the conventional ATVC.

[Example 3]
In the first and second embodiments described above, it has been described that the value of the transfer voltage obtained in S407 and S607 is corrected to obtain the value of the reference transfer voltage. However, it is not limited to the form. In order to eliminate the difference between the detected currents when the exposed portion and the non-exposed portion of the photoreceptor reach the transfer nip portion, the detected current value is corrected so that the corrected current becomes the target current. Alternatively, the reference transfer voltage may be set. The target current value at this time may be the same as the target current value in the flowcharts of FIGS.

[Example 4]
In the first to third embodiments, the case where the voltage value obtained by ATVC is corrected or the detected current value is corrected has been described. However, the same effect can be obtained by other methods. In the fourth embodiment, a case will be described in which the target current value in ATVC is set in advance so as to eliminate the difference between the detected currents when the exposed portion and the non-exposed portion of the photoreceptor 102 reach the transfer nip portion. 1, 2, and 3 are the same as those in the first embodiment, and a detailed description thereof is omitted here.

  FIG. 8 is a flowchart showing ATVC in a state in which the semiconductor laser 103 is forcibly emitted and an exposed portion is formed on the surface of the photosensitive member 102 and reaches the transfer nip portion. It is executed by the engine controller 202.

  First, in S801 and S802, for example, the same processing as S401 and 402 in FIG. 4 is performed.

Here the engine controller 202, multiplied by the correction coefficient [alpha] 2 with respect to the target transfer current value, determine the reference transfer current value I ₀ by adding the correction sections α2 (S803).

Here, the correction coefficient α2 and the correction intercept α2 will be described. The correction coefficient α2 and the correction intercept α2 are obtained by the following processing by the engine controller 202. That is, the charging roller 108 outputs a certain value of high voltage, and the transfer roller 110 applies a certain value of the transfer voltage in a state where the exposed surface of the photoconductor due to the forced light emission of the semiconductor laser 103 reaches the transfer nip portion. The transfer current value I _{0 L} at the time of output is detected. In addition, the charging roller 108 outputs a certain value of high voltage, and the transfer roller generates a certain value of the transfer voltage in a state where the non-exposed surface of the photoreceptor due to the unblanking light emission of the semiconductor laser 103 reaches the transfer nip portion. The transfer current value I _0D at the time of output is detected. The engine controller 202 obtains a correction coefficient α2 and a correction intercept α2 from the detected transfer current value I _0L and transfer current value I _0D . Specific examples are shown below.

It is assumed that the transfer current value I _0L is detected as 2 uA in a low temperature and low humidity environment with the transfer voltage 500 V and the exposed portion by forced light emission reaching the transfer nip. Similarly, assume that the transfer voltage is 500 V, and the transfer current value I _0D is 4 uA in a state where the non-exposed portion due to unblanking light emission reaches the transfer nip portion. In a high-temperature and high-humidity environment, assume that the transfer current value I _0L and the transfer current value I _0D when the transfer voltage is 500 V are 6 uA and 9 uA, respectively. Assume that the following relationship holds.
4 = 2 × correction coefficient α2 + correction intercept α2
9 = 6 × correction coefficient α2 + correction intercept α2
Accordingly, the correction coefficient α2 and the correction intercept α2 are as follows.
Correction coefficient α2 = 1.25
Corrected intercept α2 = 1.5

  Under which circumstances the correction coefficient α2 and the correction intercept α2 are obtained are the same as in the case of the correction coefficient α1 and the correction intercept α1 described in the first embodiment. Further, when the tendency of the correction coefficient α2 and the correction intercept α2 changes depending on the resistance value of the transfer roller 110 and the printing environment (temperature, humidity, etc.), the following forms are also assumed. That is, a plurality of correction coefficients α2 and correction intercept α2 may be stored in the nonvolatile memory, and the engine controller 202 may switch the correction coefficient α2 and the correction intercept α2 to be used according to the environment.

  As described above, the same effects as those of the first and second embodiments can be obtained by changing the target current value in ATVC.

  The flowchart in FIG. 8 does not perform the processing described in S608 and subsequent steps in the flowchart in FIG. 6. However, after the flowchart in FIG. 8 is executed, the processing in S608 and subsequent steps in FIG. 6 may be performed. In this case, the reference transfer voltage value obtained in the flowchart of FIG. 8 may be used as the temporary transfer voltage value in S607, and the processing after S608 may be performed by the engine controller 202.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Toner cartridge 102 Photoconductor 103 Semiconductor laser 104 Scanner motor 105 Polygon mirror 106 Laser path 107 Light receiving sensor 108 Charging roller 109 Developer 110 Transfer roller

Claims (3)

A light emitting means for emitting a light beam;
A polygon mirror that scans the surface of the photosensitive member charged by the charging unit with a light beam emitted from the light emitting unit to form an electrostatic latent image on the photosensitive member;
Detecting means for detecting a light beam scanned by the polygon mirror;
Developing means for visualizing the toner image by attaching toner to the electrostatic latent image formed on the surface of the photoreceptor;
Transfer means for transferring the toner image to a transfer medium;
A transfer voltage applying means for applying a transfer voltage to the transfer means;
An image forming apparatus comprising: a transfer control unit that detects a current flowing through the transfer unit in response to the application of the transfer voltage, and determines a transfer voltage to be applied to the transfer unit based on the detection result;
A measurement unit that, when the polygon mirror is activated, causes the light emitting unit to continuously emit light over the image area and the non-image area of the photoconductor, and measures the speed of the polygon mirror based on the detection period of the detection unit;
The transfer control means calculates a difference between detection currents when the exposed portion and the non-exposed portion of the photoreceptor reach the transfer nip portion in a state where the light emitting means is forced to emit light when the polygon mirror is activated. In order to eliminate this, the transfer voltage set so that the detected current becomes a target current is further corrected to determine a reference transfer voltage, or the detected current is corrected and the corrected current becomes the target current. The transfer voltage is determined to be the reference transfer voltage. A light emitting means for emitting a light beam;
A polygon mirror that scans the surface of the photosensitive member charged by the charging unit with a light beam emitted from the light emitting unit to form an electrostatic latent image on the photosensitive member;
Detecting means for detecting a light beam scanned by the polygon mirror;
Developing means for visualizing the toner image by attaching toner to the electrostatic latent image formed on the surface of the photoreceptor;
Transfer means for transferring the toner image to a transfer medium;
A transfer voltage applying means for applying a transfer voltage to the transfer means;
An image forming apparatus comprising: a transfer control unit that detects a current flowing through the transfer unit in response to the application of the transfer voltage, and determines a transfer voltage to be applied to the transfer unit based on the detection result;
A measurement unit that, when the polygon mirror is activated, causes the light emitting unit to continuously emit light over the image area and the non-image area of the photoconductor, and measures the speed of the polygon mirror based on the detection period of the detection unit;
The transfer control means calculates a difference between detection currents when the exposed portion and the non-exposed portion of the photoreceptor reach the transfer nip portion in a state where the light emitting means is forced to emit light when the polygon mirror is activated. Set the target current to eliminate,
Further, the transfer control means determines a reference transfer voltage so that the detected current becomes the set target current.   The transfer control unit detects a current flowing through the transfer unit in response to application of the transfer voltage in accordance with a timing at which a non-exposed portion of the photoconductor formed by the forced light emission reaches the transfer nip portion. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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