JP2019109301A - Image formation apparatus - Google Patents

Abstract

To suppress the adhesion of the unnecessary toner to a photoreceptor, and suppress the extension of FPOT.SOLUTION: An image formation apparatus includes control means which controls a start-up operation of driving a photoreceptor, electrification means, irradiation means and development means at the print start, and controls a shut-down operation of stopping the photoreceptor, the electrification means, the irradiation means and the development means at the print finish. The control means stops each member after electrifying the photoreceptor by the electrification means as the shut-down operation, performs a first start-up operation of applying a first development voltage and a second development voltage smaller than the first development voltage to the development means when performing the start-up operation after the elapse of a prescribed period from the electrification of the photoreceptor in the shut-down operation, and performs a second start-up operation of applying the second development voltage to the development means having the shorter start-up period than the first start-up operation when performing the start-up operation before the elapse of the prescribed period from the electrification of the photoreceptor in the shut-down operation.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus for forming an image by a contact development method.

  2. Description of the Related Art Conventionally, laser beam printers, copying machines, facsimiles and the like of an electrophotographic system have been known as an example of an image forming apparatus. In such an image forming apparatus, a contact developing system is known as a developing unit for developing an electrostatic latent image formed on a photosensitive member. In this contact development method, the electrostatic latent image on the photosensitive member is developed in a state where the developing sleeve is in contact (contact) with the photosensitive member.

  In such a contact development method, since the photosensitive member and the developing sleeve are in contact with each other, for example, when a portion not appropriately charged on the surface of the photosensitive member faces the developing sleeve, the toner is unnecessarily developed on the photosensitive member. A phenomenon called fogging may occur. As unnecessary toner is developed, the inside of the image forming apparatus may be soiled or toner may be wasted. In view of such a situation, Patent Document 1 discloses a method of suppressing unnecessary adhesion of toner to a photosensitive member when the image forming apparatus is started by a print request. Specifically, when driving of the photosensitive body is started, after applying a voltage having a reverse polarity to that at the time of image formation to the developing unit, and then rotationally driving the photosensitive body, unnecessary toner adheres to the photosensitive body To suppress

JP, 2017-49405, A

  As in the prior art, by applying a voltage of the reverse polarity to that at the time of image formation to the developing unit, it is possible to suppress the adhesion of unnecessary toner to the photosensitive member. However, before starting the driving of the photosensitive member, a control step of applying a voltage of the opposite polarity to that at the time of image formation must be added to the developing unit, which may increase the time to start image formation. was there. That is, there is a possibility that FPOT (First Print Out Time), which is the time from the start of startup of the image forming apparatus to the completion of the first print, may be long.

  The invention according to the present application has been made in view of the above circumstances, and while suppressing the adhesion of unnecessary toner to the photosensitive body, it is also possible to suppress the FPOT becoming long. With the goal.

  In order to achieve the above object, a photosensitive member, a charging unit for charging the photosensitive member, an irradiating unit for emitting light to form an electrostatic latent image on the photosensitive member, and a contact with the photosensitive member A developing unit for developing the electrostatic latent image formed on the photosensitive member, and a start-up operation for driving the photosensitive member, the charging unit, the irradiating unit, and the developing unit before starting printing. And control means for controlling a falling-down operation for stopping the photosensitive member, the charging means, the irradiation means, and the developing means after the printing is completed, the control means comprising, as the falling-off operation, the control means. When each member is stopped after charging the photosensitive member by the charging unit, and when the rising operation is performed after a predetermined period has elapsed since the photosensitive member was charged in the falling operation, the developing unit The first rising operation is performed to apply one developing voltage and a second developing voltage smaller than the first developing voltage, and the predetermined period has elapsed since the photosensitive member is charged in the falling operation. When the start-up operation is performed before the second start-up operation, the second start-up operation is performed to apply the second developing voltage to the developing unit, which has a shorter period of time required for the start-up than the first start-up operation. It is characterized by

  According to the present invention, it is possible to suppress that the FPOT becomes long while suppressing the unnecessary toner from adhering to the photosensitive member.

Schematic Configuration of Image Forming Apparatus 1 Control block diagram showing control functions of image forming apparatus 1 A diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount of unwanted toner adhering to the photosensitive drum 3a. Diagram showing start-up sequence of image forming apparatus 1 A diagram showing the falling sequence of the image forming apparatus 1 Flow chart for selecting startup sequence Control block diagram showing control functions of image forming apparatus 1 A diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount of unwanted toner adhering to the photosensitive drum 3a. Diagram showing setting values of charging voltage and developing voltage according to the environment Control block diagram showing control functions of image forming apparatus 1 A diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount of unwanted toner adhering to the photosensitive drum 3a. A diagram showing set values of charging voltage and developing voltage according to the film thickness of the photosensitive drum 3a

  Hereinafter, embodiments of the present invention will be described using the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of the features described in the embodiments are not necessarily essential to the solution means of the invention.

First Embodiment
FIG. 1 is a schematic block diagram of an image forming apparatus. Although the following description will be made using a monochrome image forming apparatus, the present invention is not limited to this. For example, the present invention can be applied to a color image forming apparatus. The color image forming apparatus may be an in-line method using an intermediate transfer belt, a rotary method, or a direct transfer method.

  The image forming apparatus 1 includes a photosensitive drum 3a as a photosensitive member, a photosensitive drum unit 3 for holding the photosensitive drum 3a, and a charging unit 2 for charging the photosensitive drum 3a. Furthermore, a developing sleeve 4a, which is a developing roller for developing the electrostatic latent image formed on the photosensitive drum 3a with toner in contact (contact) with the photosensitive drum 3a, and a developing unit 4 for holding the developing sleeve 4a are provided. ing. In the present embodiment, the developing sleeve 4a is in contact (contact) with the photosensitive drum 3a both during printing and before and after printing. Furthermore, the laser scanner unit 5 scans the photosensitive drum 3a by reflecting the laser light 5a by a polygon rotated by a scanner motor, and forms an electrostatic latent image on the photosensitive drum 3a. Furthermore, a pre-exposure unit 40 for performing pre-exposure to adjust the potential on the photosensitive drum 3a before charging, and a transfer unit 8 for transferring a toner image developed on the photosensitive drum 3a to the recording material S ing. Hereinafter, the photosensitive drum unit 3 and the developing unit 4 are collectively referred to as a cartridge. Further, the image forming apparatus 1 is a roller for conveying the recording material S, the sheet feeding roller 6 and the conveying roller pair 7, the heating member 9 for fixing the recording material S on which the toner image is transferred, and pressure A roller 10 is provided. Furthermore, a discharge roller pair 11 for discharging the fixed recording material S to the outside of the machine, and a double-sided conveyance roller pair 14 for conveying the fixed recording material S to a double-sided conveyance path are provided.

  Next, the print operation in the image forming apparatus 1 will be described. When the image forming apparatus 1 receives a print request, the image forming apparatus 1 performs start-up operations of the cartridge, the laser scanner unit 5, the heating member 9, and the transfer unit 8. Thereafter, when it is determined that the recording material S can be fed, the recording material S stacked on the sheet feeding tray 12 is fed sheet by sheet. The recording material S is conveyed to the registration sensor 21 by the conveyance roller pair 7. When the registration sensor 21 detects the recording material S, the image formation on the photosensitive drum 3a is started. Thereafter, the recording material S conveyed to the registration sensor 21 is conveyed toward a transfer nip portion including the photosensitive drum 3 a and the transfer unit 8.

  The photosensitive drum 3a rotates in the direction of the arrow in FIG. 1 (clockwise direction). Before charging the photosensitive drum 3a, the surface potential of the photosensitive drum 3a is made to be near 0 [V] by the pre-exposure unit 40. After the surface potential of the photosensitive drum 3 a is equalized by the pre-exposure unit 40, the photosensitive drum 3 a is charged by the charging unit 2. An electrostatic latent image is formed on the photosensitive drum 3 a by irradiating the charged photosensitive drum 3 a with the laser beam 5 a from the laser scanner unit 5. The formed electrostatic latent image is developed by the developing sleeve 4a to form a toner image. The formed toner image is moved to a transfer nip portion composed of the photosensitive drum 3a and the transfer unit 8, and is transferred to the recording material S at the transfer nip portion.

  The recording material S to which the toner image has been transferred is conveyed to a fixing nip portion formed of the heating member 9 and the pressure roller 10, and is heated and pressed to fix the toner image on the recording material S. The recording material S on which the toner image is fixed is discharged onto the paper discharge tray 13 by the paper discharge roller pair 11. When the requested printing is completed, the image forming apparatus 1 performs the falling operation of the cartridge, the laser scanner unit 5, the heating member 9, and the transfer unit 8 which are started by the rising operation.

  FIG. 2 is a control block diagram showing control functions of the image forming apparatus 1 in the present embodiment. The main control unit 200 includes an exposure control unit 220, a drive control unit 230, a charge output control unit 240, a development output control unit 250, a transfer output control unit 260, a fixing control unit 270, and the like.

  The exposure control unit 220 controls the scanner laser 221 and the scanner motor 222 to control the start-up operation of the laser scanner unit 5. By the start-up operation, the rotary polygon mirror of the laser scanner unit 5 is controlled to accelerate and decelerate from the stop state so as to stably rotate at a predetermined speed. Further, the laser beam is irradiated onto the photosensitive drum 3a to control the operation of forming an electrostatic latent image. Furthermore, when the image formation is completed, the control unit 20 controls the lowering operation of the laser scanner unit 5. The rotating polygon mirror rotating at a predetermined speed is stopped by the lowering operation. The drive control unit 230 controls the drive of the main motor 231. In the image forming apparatus 1 according to this embodiment, the main motor 231 rotates the photosensitive drum 3a, the developing sleeve 4a, the sheet feeding roller 6, the conveying roller pair 7, the heating member 9, the pressure roller 10, and the sheet discharging roller pair 11. ing. However, the number of motors is not limited to one, and each member may be rotationally driven by a plurality of motors.

  The charging output control unit 240 controls the charging unit 2 to apply a charging voltage. The development output control unit 250 controls the development unit 4 to apply a development voltage. The transfer output control unit 260 controls the transfer unit 8 to apply a transfer voltage. The fixing control unit 270 controls the temperature control of the heating member 9 by controlling the heating member 9.

  FIG. 3 is a diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount by which unnecessary toner adheres to the photosensitive drum 3a. Hereinafter, the phenomenon in which unnecessary toner adheres is referred to as fogging, and the amount of unnecessary toner is also referred to as fogging amount. Moreover, in the following detailed description, it demonstrates, showing an example of the specific numerical value in this embodiment.

  FIG. 3A shows on the horizontal axis the potential difference obtained by subtracting the surface potential of the photosensitive drum 3a from the voltage applied to the developing sleeve 4a as Vb. Further, the amount of fogging of the toner on the photosensitive drum 3a with respect to the amount of solid black toner, which is an image formed at a density of 100%, is shown as the vertical axis. From FIG. 3A, the fog amount (1%) is the smallest when the potential difference is Vb2 (200 V). Also, it can be seen that the fogging amount tends to increase even if the potential difference becomes smaller or larger than Vb2. If there is a possibility that the inside of the image forming apparatus may become dirty or the toner may be unnecessarily consumed if a large amount of unnecessary toner fog is generated on the photosensitive drum 3a, the amount of fog is as large as possible It is desirable to reduce it.

  Therefore, the allowable fog amount (5%) is set as the fog threshold, and the potential difference Vb1 (100 V) at that time is set as the threshold voltage. That is, it can be said that the potential difference Vb1 is a threshold value for preventing the toner from adhering to the photosensitive drum 3a by more than a predetermined amount. Here, as an example, the threshold voltage of Vb1 having a smaller potential difference than Vb2 is determined, and the threshold voltage having a potential difference larger than Vb2 is omitted. Although this will be described in detail with reference to FIG. 3B, since the charged photosensitive drum 3a approaches 0 V by natural discharge, the threshold voltage on the side having a larger potential difference than Vbpr may not necessarily be set. It is for. However, of course, the threshold voltage higher than Vb2 may also be set. Furthermore, the allowable fog amount may be different between the smaller threshold voltage and the larger threshold voltage. For example, the allowable fogging amount on the large side may be 10%, and the threshold voltage may be 700V. Vbpr represents a potential difference during printing, and the fogging amount at Vbpr is smaller than the fogging amount (5%) of Vb1. The amount of fogging (5%) at the threshold voltage Vb1 is set to be smaller in order to suppress image quality deterioration due to unnecessary fogging during printing.

  FIG. 3B shows the time transition of the surface potential of the photosensitive drum 3a after the charging output control unit 240 of the photosensitive drum 3a applies the charging voltage of the predetermined output setting to the photosensitive drum 3a at the time of post-rotation control. . The output setting at the time of post-rotation control is an output setting of the charging unit such that the potential difference Vb becomes the same Vbpr as at the time of printing even when the output of the developing unit 4 is stopped. The surface potential of the photosensitive drum 3a at this time is Vpr (-500 V). When the output of the charging unit 2 is stopped, the surface potential of the photosensitive drum 3a approaches 0V. As the surface potential of the photosensitive drum 3a approaches 0 V, the potential difference Vb increases. As a result, when the potential difference Vb becomes larger than the threshold voltage Vb1, the amount of fog generated on the photosensitive drum 3a exceeds the allowance. After stopping the developing unit 4 and the charging unit 2, the potential of the photosensitive drum 3a in a state where the amount of toner fogging on the photosensitive drum 3a is acceptable is up to Vth (-150 V). The time from when the photosensitive drum 3a is charged to Vpr to when it reaches Vth is Tth (10 sec). FIG. 3C is a table showing values of Vb1, Vpr, Vth, and Tth. As described above, Vb1 is 100 V, Vpr is -500 V, Vth is -150 V, and Tth is 10 sec.

  FIG. 4 is a diagram showing a start-up sequence which is a start-up operation of the image forming apparatus 1. FIG. 4A is a first start-up sequence (first start-up operation) for applying a developing voltage for suppressing fog on the photosensitive drum 3a. FIG. 4B is a second start-up sequence (second start-up operation) which can omit the application of the developing voltage for suppressing fog on the photosensitive drum 3a.

  First, the start-up sequence of FIG. 4A will be described. The start-up sequence is performed at the start of normal printing, for example, at the time of power on. t11 is the timing of starting the start in response to the print request. When the start-up is started, a first developing voltage (120 V) is applied to the developing unit 4. The development voltage is a voltage for suppressing the fog on the photosensitive drum 3a. t12 is a waiting time for applying a first developing voltage to the developing unit 4. The first developing voltage is set to a value such that Vb, which is the potential difference between the voltage of the developing sleeve 4a and the surface potential of the photosensitive drum 3a, is smaller than Vb1, which is the allowable potential difference of the fogging amount. By setting in this manner, fogging on the photosensitive drum 3a can be suppressed. When the first developing voltage is applied to the developing unit 4, acceleration of the main motor 231 is started.

  t13 is a timing at which the acceleration of the main motor 231 is completed. When acceleration of the main motor 231 is completed, activation of the laser scanner unit 5 is started. First, without causing the scanner laser 221 to emit light, the scanner motor 222 for rotating the polygon mirror, which is a rotary polygon mirror, is forcedly accelerated. After the scanner motor 222 is forcibly accelerated for a predetermined time, the laser is emitted. At this time, in order to stabilize the laser light amount, the laser is kept emitting for a predetermined time. That is, it becomes the first irradiation operation in which the laser is scanned also on the photosensitive drum 3a, and the exposed surface potential approaches 0V. Therefore, by applying the first developing voltage to the developing unit 4, the potential difference Vb is controlled so as not to be larger than Vb 1 to suppress fog.

  Although not shown, the image forming apparatus 1 is provided with a BD sensor as detection means disposed outside the irradiation area of the photosensitive drum 3a to detect a horizontal synchronization signal (BD signal). When the laser light amount is stabilized, from t14, the photosensitive drum 3a is not irradiated with the laser light, and the operation is switched to the second irradiation operation in which the BD sensor is irradiated with the laser light. This is also called unblanking control. The rotational speed of the scanner motor 222 can be determined by detecting the cycle of the BD signal. Based on this, switching is made to discreet control in which acceleration / deceleration control is performed so that the scanner motor 222 has a predetermined rotational speed, and then started up. Discrimination control is control for accelerating and decelerating the scanner motor 222 in order to cause the rotational speed of the scanner motor 222 to converge to the target rotational speed. More specifically, the scanner motor 222 is controlled to rotate at the target speed by obtaining the difference between the target speed and the current speed, and adding or subtracting the value obtained by the difference × predetermined coefficient to the current output. .

  Further, the charging voltage (−1300 V) at the time of printing is applied to the charging unit 2. By applying the charging voltage, the photosensitive drum 3a is charged, and the surface potential also changes. Therefore, the developing voltage applied to the developing unit 4 from t15 is switched to the second developing voltage (−300 V). The second developing voltage is also set to a value such that Vb, which is the potential difference between the voltage of the developing sleeve 4a and the surface potential of the photosensitive drum 3a, is smaller than Vb1, which is the allowable potential difference of the fogging amount. By setting in this manner, fogging on the photosensitive drum 3a can be suppressed. Then, when the startup of the transfer output control unit 260 and the fixing control unit 270 is completed, at t16, the developing voltage applied to the developing unit 4 is switched to the developing voltage (−300 V) at the time of printing. In the present embodiment, as an example, the second developing voltage and the developing voltage at the time of printing are the same -300V.

  Next, the start-up sequence of FIG. 4B will be described. The second start-up sequence is performed when the start-up sequence is performed within a predetermined time after the start-down sequence is performed after the end of printing. For example, it is a case where a request for intermittent printing with a short printing interval is received. The start-up sequence of FIG. 4A is different from the case where the scanner laser 221 and the scanner motor 222 of the laser scanner unit 5 are not stopped and the surface potential of the photosensitive drum 3a. At the timing when the start-up sequence of FIG. 4B is performed, since the start-up is performed within a predetermined time after the end of the stop sequence, Vb is the threshold even if the developing voltage is not applied to the developing unit 4 It does not exceed Vb1. Therefore, the sequence for applying the first developing voltage to the developing unit 4 becomes unnecessary. Therefore, the start-up operation can be performed in a shorter time than the start-up sequence of FIG. The shutdown sequence will be described in detail later with reference to FIG.

  In the start-up sequence of FIG. 4B, the laser scanner unit 5 has already performed unblanking control when it receives a print request of t21. Therefore, in the start-up sequence, it is not necessary to expose the photosensitive drum 3a with laser light. Furthermore, even when the developing voltage is not applied to the developing unit 4, the amount of fogging on the photosensitive drum 3a is within the allowable range. This is because, as described above with reference to FIG. 3B, the surface potential of the photosensitive drum 3a after the falling sequence is kept at a potential at which fogging is suppressed until the period of Tth elapses. It is for. Therefore, it is not necessary to apply the first developing voltage to the developing unit 4 as described with reference to FIG.

  Because of this state, at t21, the developing unit 4 starts to accelerate the main motor 231 in a stopped state. Then, the charging voltage at the time of printing is applied to the charging unit 2. By applying the charging voltage, the photosensitive drum 3a is charged, and the surface potential also changes. Therefore, the developing voltage applied to the developing unit 4 from t22 is switched to the second developing voltage (−300 V). The second developing voltage is also set to a value such that Vb, which is the potential difference between the voltage of the developing sleeve 4a and the surface potential of the photosensitive drum 3a, is smaller than Vb1, which is the allowable potential difference of the fogging amount. By setting in this manner, fogging on the photosensitive drum 3a can be suppressed. Then, when the startup of the transfer output control unit 260 and the fixing control unit 270 is completed, at t23, the developing voltage applied to the developing unit 4 is switched to the developing voltage (−300 V) at the time of printing. FIG. 4C is a table showing the charging voltage and the developing voltage. The charging voltage during printing is -1300V, the developing voltage during printing is -300V, the first developing voltage is 120V, and the second developing voltage is -300V.

  FIG. 5 is a diagram showing a falling sequence which is a falling operation of the image forming apparatus 1. The shutdown sequence is performed in a post-rotation period for stopping the image forming apparatus after printing is completed.

  When printing is completed, the falling sequence is started at t31. The charging voltage applied to the charging unit 2 is changed to the charging voltage at the time of the post-rotation as described in FIG. Thereby, the surface potential of the photosensitive drum 3a becomes the surface potential (Vpr) according to the charging voltage at the time of the post-rotation. At t32, when the surface of the photosensitive drum 3a is charged by the charging unit 2 for one rotation with the charging voltage at the time of post-rotation, the developing voltage of the developing sleeve 4a is stopped. Furthermore, the charging voltage of the charging unit 2 is also stopped. By setting the surface potential of the photosensitive drum 3a to Vpr as described with reference to FIG. 3, the fog can be suppressed even in the state where both the charging unit 2 and the developing sleeve 4a are stopped.

  When the falling of the transfer output control unit 260 and the fixing control unit 270 is completed at t33, the driving of the main motor 231 is stopped, and the falling of the devices other than the laser scanner unit 5 is completed. The scanner laser 221 continues the unblanking control also after t32. Also, the scanner motor 222 does not go down and continues the discriminative control. The target rotational speed of the scanner motor 222 at the time of the post-rotation may be set to a speed slower than that at the normal time.

  The timing for stopping the laser scanner unit 5 is t34. This is Tth seconds after the charging voltage of the post-rotation is applied to the charging unit 2 to charge the photosensitive drum 3a. As described with reference to FIG. 3, when Tth seconds elapse, the surface potential of the photosensitive drum 3a decreases from Vpr to Vth. Therefore, after Tth seconds have elapsed, when the start-up sequence is performed again after the start-up sequence, in order to suppress the fog on the photosensitive drum 3a, as described in FIG. 4A, the developing unit It is necessary to apply the first developing voltage to the fourth. Therefore, even if the laser scanner unit 5 is continuously driven, the start-up sequence of FIG. 4B can not be performed, so the laser scanner unit 5 is stopped at t34 in view of the life of the laser scanner unit.

  Summarizing the relationship between FIG. 4 and FIG. 5, when performing a normal start-up such as when the power is turned on, the start-up sequence of FIG. 4A is performed. Then, when the printing is completed, the falling sequence of FIG. 5 is performed. After the fall sequence is performed and the charging voltage at the post-rotation is applied to the charging unit 2 to charge the photosensitive drum 3a, if the start-up sequence is performed to restart printing before Tth seconds elapse, The potential difference Vb is in a state where fog can be suppressed. Therefore, by performing the startup sequence of FIG. 4B, the time required for startup can be shortened, and the FPOT can also be shortened.

  FIG. 6 is a flowchart for selecting a start-up sequence. As described above, after the charging unit 2 is stopped after applying the charging voltage at the time of post-rotation to the charging unit 2 in the falling sequence, the potential difference Vb can suppress fogging until Tth seconds elapse. ing. Therefore, the main control unit 200 determines in S601 whether or not Tth second has elapsed since the charging unit 2 was stopped in the falling down sequence. If Tth seconds have elapsed, the main control unit 200 performs the first start-up sequence described in FIG. 4A in S602. If Tth seconds have not elapsed, the main control unit 200 performs the second start-up sequence described in FIG. 4B in S603.

  In addition, in this embodiment, although the setting of FIG.3 (c) and FIG.4 (c) was demonstrated as an example, it is not restricted to these. If it is a value of FIG. 3C, it can be set to a value according to how much fogging amount is allowed for the photosensitive drum 3a. With the values shown in FIG. 4C, it is possible to set an appropriate value for each apparatus in consideration of how much the image quality at the time of printing is tolerable, the influence of individual variation of the image forming apparatus 1, and the like.

  As described above, when the start-up sequence is performed again before Tth seconds have elapsed after the charging unit 2 is stopped in the falling-off sequence, the rising-up sequence can be shortened. Therefore, it is possible to shorten the FPOT while suppressing the adhesion of unnecessary toner to the photosensitive drum 3a.

Second Embodiment
In the first embodiment, the example in which the elapsed time Tth has a predetermined value corresponding to the charging voltage applied at the time of post-rotation has been described. However, for example, due to the influence of the surrounding environment where the image forming apparatus 1 is installed, the time during which the surface potential of the photosensitive drum 3a changes is different. Therefore, in the present embodiment, a method of changing the elapsed time Tth in accordance with the surrounding environment in which the image forming apparatus 1 is installed will be described. A detailed description of the same configuration as that of the first embodiment, such as the configuration of the image forming apparatus, is omitted here.

  FIG. 7 is a control block diagram showing control functions of the image forming apparatus 1 in the present embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 7, an environment detection control unit 700 is added, and the temperature sensor 701 and the humidity sensor 702 detect the temperature and humidity of the environment in which the image forming apparatus 1 is installed. That is, the temperature sensor 701 and the humidity sensor 702 can be said to be environment detection means. The temperature sensor 701 is a sensor that detects a temperature. The humidity sensor 702 is a sensor that detects the amount of water, and obtains the humidity from the temperature detected by the temperature sensor 701 and the amount of saturated water vapor. In the present embodiment, it is determined that the high humidity is 65% or more, the normal humidity is 25% or more and less than 65%, and the low humidity is less than 25%.

  FIG. 8 is a diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount by which unnecessary toner adheres to the photosensitive drum 3a, as in FIG. In FIG. 8, the relationship between high humidity and low humidity is also added, with FIG. 3 as normal humidity. The values defined in FIG. 3 have the same meaning in FIG.

  FIG. 8A describes how the potential difference and the fogging amount change at each humidity. First, in the case of high humidity, the fogging amount tends to increase when Vb is larger than Vb2 as compared with the ordinary humidity, and the fogging amount tends to decrease when Vb is smaller than Vb2. Therefore, Vbpr is set smaller than normal humidity. Furthermore, Vth can be made smaller than that of normal humidity. The Vth of the high humidity is -140 V while the Vth of the normal temperature is -150 V.

  In the case of low humidity, when Vb is larger than Vb2 as compared with normal humidity, the fogging amount decreases, and when Vb is smaller than Vb2, the fogging amount tends to increase. Therefore, Vb1 is set to be larger than that at normal humidity. The low humidity Vb1 is 110 V with respect to the normal humidity Vb1 of 100 V.

  Next, FIG. 8B will be described. For low humidity and normal humidity, the photosensitive drum 3a is charged so that Vpr is equal to -500V. In this case, it can be considered from FIG. 8B that although the surface potential of the photosensitive drum 3a is less likely to drop slightly in the low humidity than in the normal humidity, it is approximately the same. Therefore, for low humidity and normal humidity, the time from Vpr to Vth is 10 seconds.

  High humidity requires Vbpr to be smaller than normal humidity, as described in FIG. 8 (a) above. Therefore, Vpr is also set to -400 V lower than normal humidity. Since Vpr is low, the time until the surface potential asymptotically approaches 0 V is also fast. That is, the time from Vpr to Vth is also shorter in high humidity than in normal humidity. Here, the time from the high humidity Vpr to the Vth is 6 seconds.

  FIG. 8C is a table showing each value of low humidity, normal humidity, and high humidity in the present embodiment. As described above, Vb1 sets the low humidity larger and the high humidity smaller than the normal humidity. Therefore, the low humidity Vb1 is 110 V, the normal humidity Vb1 is 100 V, and the high humidity Vb1 is 90 V. Furthermore, Vpr is the same for low humidity and normal humidity, and high humidity is set small. Therefore, the low humidity Vpr is −500 V, the normal humidity Vpr is −500 V, and the high humidity Vpr is −400 V. In addition, the setting of Vth according to the humidity is also changed. The low humidity is -160 V, the normal humidity is -150 V, and the high humidity is -140 V. Furthermore, these conditions also change the period of Tth according to humidity. The low humidity Tth is 10 seconds, the normal humidity Tth is 10 seconds, and the high humidity Tth is 6 seconds. That is, in the first humidity, the predetermined period is the first period, and in the second humidity higher than the first humidity, the predetermined period is the second period shorter than the first period.

  FIG. 9 is a table showing setting values of the charging voltage and the developing voltage according to the environment in the present embodiment. As described above, since it is necessary to lower Vbpr at high humidity, the charging voltage and the developing voltage at high humidity are set to different values from low humidity and normal humidity. The charging voltage during printing is set to −1300 V for low humidity, −1300 V for normal humidity, and −1250 V for high humidity. Furthermore, the developing voltage at the time of printing is -300 V for low humidity, -300 V for normal humidity, and -350 V for high humidity. The first developing voltage is 120 V for low humidity, 120 V for normal humidity, and 120 V for high humidity. The second developing voltage is -300 V for low humidity, -300 V for normal humidity, and -350 V for high humidity.

  Although the settings in FIG. 8C and FIG. 9 have been described as an example in the present embodiment, the present invention is not limited to these. With the values shown in FIG. 8C, the acceptable Vth of the photosensitive drum 3a can be determined for each environment, and can be set to a value corresponding thereto. With the values shown in FIG. 9, it is possible to set an appropriate value for each apparatus in consideration of how much the image quality at the time of printing is tolerable, the influence of individual variation of the image forming apparatus 1, and the like. Moreover, in this embodiment, although high humidity, normal humidity, and low humidity were divided using humidity as an example, it is not restricted to this. It is also possible to divide into more stages as needed. If the fogging amount of the photosensitive drum 3a has a high correlation with the temperature, a division by the temperature may be provided. Changes in the amount of fogging of the photosensitive drum 3a and the attenuation of the surface potential of the photosensitive drum 3a may be measured, and the values shown in FIG. 8C and FIG. 9 may be appropriately set from the above viewpoint. That is, for example, at the first temperature, the predetermined period is the first period, and at the second temperature higher than the first temperature, the humidity is such that the predetermined period is the second period shorter than the first period. Control should be based on the same policy as in.

  As described above, by changing Tth according to the environment, it is possible to shorten the FPOT while suppressing the adhesion of unnecessary toner to the photosensitive drum 3a.

Third Embodiment
In the first embodiment, the example in which the elapsed time Tth has a predetermined value corresponding to the charging voltage applied at the time of post-rotation has been described. However, for example, the time during which the surface potential of the photosensitive drum 3a changes varies depending on the amount of use of the photosensitive drum 3a. Therefore, in the present embodiment, a method of changing the elapsed time Tth in accordance with the amount of use of the photosensitive drum 3a will be described. A detailed description of the same configuration as that of the first embodiment, such as the configuration of the image forming apparatus, is omitted here.

  FIG. 10 is a control block diagram showing control functions of the image forming apparatus 1 in the present embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof will be omitted. In FIG. 10, a photosensitive drum deterioration determination unit 1000 is added. The photosensitive drum deterioration determining unit 1000 determines how much the surface film thickness of the photosensitive drum 3 a has been scraped from the driving time of the photosensitive drum 3 a which is information related to the film thickness stored in the non-volatile memory 1001.

  FIG. 11 is a diagram showing the relationship between the potential difference between the photosensitive drum 3a and the developing sleeve 4a and the amount by which unnecessary toner adheres to the photosensitive drum 3a, as in FIG. FIG. 11A shows the change of the fogging amount according to the film thickness of the photosensitive drum 3a. In the present embodiment, since the fogging amount of the photosensitive drum 3a is substantially not affected by the film thickness of the photosensitive drum 3a, Vb1 is set to the same value.

  Next, FIG. 11B will be described. FIG. 11B shows the change in the surface potential of the photosensitive drum 3a described with reference to FIG. 3B and the change in the surface potential in the state where the film thickness of the photosensitive drum 3a is thinner than that. The state described in FIG. 3B is a film thickness of 18 μm, and the case of a film thickness of 10 μm is added as a comparison. When the attenuation of the surface potential starts from the same Vpr, the thinner the film thickness of the photosensitive drum 3a, the faster it tends to be attenuated. Therefore, the photosensitive drum with a film thickness of 10 μm has a shorter decay time to Vth than the photosensitive drum with a film thickness of 18 μm. That is, Tth also becomes short.

  FIG.11 (c) is the table | surface which showed each value according to the difference in the film thickness in this embodiment. Since the fogging amount of the photosensitive drum 3a is not easily affected by the film thickness of the photosensitive drum 3a, Vpr and Vth described in FIG. 3 have the same value. However, since the attenuation of the surface potential of the photosensitive drum 3a differs according to the film thickness, Vpr, Vth, and Tth are appropriately set according to the film thickness. The Vpr of the film thickness 18 to 16 μm is −500 V, the Vpr of the film thickness 15.9 to 13 μm is −500 V, and the Vpr of the film thickness 12.9 to 10 is −500 V. Furthermore, the Vth of the film thickness 18 to 16 μm is −150 V, the Vth of the film thickness 15.9 to 13 μm is −150 V, and the Vth of the film thickness 12.9 to 10 is −150 V. The Tth of the film thickness 18 to 16 is 10 seconds, the Tth of the film thickness 15.9 to 13 is 7 seconds, and the Tth of the film thickness 12.9 to 10 is 5 seconds. That is, it can be said that the predetermined period is the third period in the first film thickness, and the fourth period is shorter than the third period in the second film thickness thinner than the first film thickness.

  FIG. 12 is a table showing setting values of the charging voltage and the developing voltage according to the film thickness of the photosensitive drum 3a in the present embodiment. As described above, the fogging amount is not easily influenced by the film thickness of the photosensitive drum 3a, but it is necessary to make Vb constant, so each value is set according to the film thickness of the photosensitive drum 3a. The charging voltage during printing is set to −1300 V for the film thickness of 18 to 16 μm, −1320 V for the film thickness of 15.9 to 13 μm, and −1350 V for the film thickness of 12.9 to 10 μm. The developing voltage at the time of printing is -300 V for the film thickness of 18 to 16 μm, -300 V for the film thickness of 15.9 to 13 μm, and -300 V for the film thickness of 12.9 to 10 μm. The first developing voltage is 120V for a film thickness of 18 to 16 μm, 120V for a film thickness of 15.9 to 13μm, and 120V for a film thickness of 12.9 to 10m. The second developing voltage has a thickness of 18 to 16 μm, a Vth of -300 V, a thickness of 15.9 to 13 μm, a Vth of -300 V, and a thickness of 12.9 to 10, a Vth of -300 V.

  Although the settings in FIG. 11C and FIG. 12 have been described as an example in this embodiment, the present invention is not limited to these. If it is the value of FIG. 11C, it is possible to set the allowable Vth of the photosensitive drum 3a to the value corresponding to the film thickness of the photosensitive drum 3a. With the values shown in FIG. 12, it is possible to set an appropriate value for each apparatus in consideration of how much the image quality at the time of printing is tolerable, the influence of individual variation of the image forming apparatus 1, and the like. Further, in the present embodiment, the film thickness of the photosensitive drum 3a is divided into three steps as an example, but the present invention is not limited to this. It is also possible to divide into more stages as needed. The environment detection control unit 700 described in the second embodiment can be added to the configuration of the third embodiment, and each value can be set according to the life and environment of the photosensitive drum 3a.

  As described above, by changing Tth according to the film thickness of the photosensitive drum 3a, it is possible to shorten the FPOT while suppressing the adhesion of unnecessary toner to the photosensitive drum 3a.

2 charging unit 3a photosensitive drum 4a developing sleeve 5 laser scanner unit 200 main control unit

Claims (13)

A photoconductor,
Charging means for charging the photosensitive member;
Irradiating means for irradiating light to form an electrostatic latent image on the photosensitive member;
Developing means for contacting the photosensitive member and developing an electrostatic latent image formed on the photosensitive member;
The start-up operation for driving the photosensitive member, the charging unit, the irradiating unit, and the developing unit is controlled before starting printing, and the photosensitive unit, the charging unit, the irradiating unit, and the printing unit are controlled after the printing is finished. And control means for controlling a lowering operation for stopping the developing means.
The control unit stops each member after charging the photosensitive member by the charging unit as the lowering operation.
In the case where the rising operation is performed after a predetermined period of time has elapsed since the photosensitive member was charged in the falling operation, the developing unit is configured to perform a first developing voltage and a second smaller than the first developing voltage. Perform a first start-up operation to apply a development voltage,
In the case where the rising operation is performed before the predetermined period elapses after the photosensitive member is charged in the falling operation, the developing unit has a shorter period of time for starting than the first rising operation. An image forming apparatus for performing a second rising operation for applying the second developing voltage to the image forming apparatus. And a detection unit disposed outside the irradiation area of the photosensitive member for detecting the light emitted from the irradiation unit.
The first raising operation applies the first developing voltage to the developing unit before the first irradiating operation of irradiating the photosensitive member and the detecting unit by the irradiating unit, the irradiating unit After the first irradiation operation is performed, and then switching to the second irradiation operation of irradiating the detection unit without irradiating the photosensitive member, the second of the second development unit is smaller than the first development voltage. Switching operation to apply the development voltage of
In the second rising operation, the irradiation unit performs the second irradiation operation without performing the first irradiation operation, and the developing unit does not apply the first development voltage. The image forming apparatus according to claim 1, which is an operation of applying two developing voltages.   In the falling operation, the potential difference between the surface potential of the photosensitive member and the developing voltage of the developing unit is that the toner does not adhere to the photosensitive member more than a predetermined amount by charging the photosensitive member by the charging unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is smaller than a predetermined potential difference.   4. The developing device according to any one of claims 1 to 3, wherein the developing device continues to apply a developing voltage at the time of printing in a period in which the photosensitive member is charged by the charging device in the falling operation. The image forming apparatus according to claim 1. In the start-up operation, by applying the first developing voltage to the developing unit, the potential difference between the surface potential of the photosensitive member and the developing voltage of the developing unit is equal to the potential difference between the surface potential of the photosensitive member and the developing unit. It is smaller than the predetermined potential difference for the toner not to adhere more than the predetermined amount
By applying the second developing voltage to the developing means, the potential difference between the surface potential of the photosensitive member and the developing voltage of the developing means is determined by the fact that toner is present on the photosensitive member even if the second irradiation operation is performed. The image forming apparatus according to any one of claims 2 to 4, wherein the image forming apparatus is smaller than a predetermined potential difference for not adhering more than a fixed amount.   In the rising operation, the charging unit does not apply the charging voltage while the first developing voltage is being applied to the developing unit, and the second developing voltage is applied to the developing unit. The image forming apparatus according to claim 5, wherein the charging unit applies a charging voltage during a period of   The image forming apparatus according to any one of claims 1 to 6, wherein the driving of the irradiating unit is continued until a predetermined time during which the photosensitive member is charged in the falling operation has elapsed. .   The irradiating unit does not irradiate the photosensitive member in the lowering operation, but is disposed outside the irradiated area of the photosensitive member, and irradiates a detecting unit that detects light emitted from the irradiating unit. The image forming apparatus according to claim 7, wherein the irradiation operation is continued. An environment detection means for detecting the humidity or temperature around the image forming apparatus;
The image forming apparatus according to any one of claims 1 to 8, wherein the control unit changes the length of the predetermined period in accordance with the humidity or the temperature detected by the environment detection unit. .   In the case of the first humidity, the control means sets the predetermined period as the first length, and in the case of the second humidity where the humidity is higher than the first humidity, the predetermined period is the first length. The image forming apparatus according to claim 9, wherein the second length is shorter than the second length.   In the case of a first temperature, the control means sets the predetermined period to a first length, and in the case of a second temperature higher than the first temperature, the predetermined period is a first length. The image forming apparatus according to claim 9, wherein the second length is shorter than the second length.   The image forming apparatus according to any one of claims 1 to 8, wherein the control unit changes the length of the predetermined period according to information on the film thickness of the photosensitive member. When the film thickness of the photoconductor is a first thickness, the control means sets the predetermined period to a third length, and the film thickness of the photoconductor is a second thickness thinner than the first thickness. 13. The image forming apparatus according to claim 12, wherein the predetermined period is a fourth length shorter than the third length.

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