Image forming apparatus

Abstract

To prevent the occurrence of faulty cleaning in initial rotation for allowing a new process cartridge to perform printing.SOLUTION: An image forming apparatus comprises a control unit 100 that executes an initialization operation for allowing a new photoconductor drum 1 to perform printing, and an image forming operation for forming a toner image on a transfer material P. The control unit 100 controls a transfer voltage power supply 20 to apply, to a transfer roller 4, a constant voltage (-150 V) ((v) example 1 of transfer voltage) different from that during an image forming operation, in a time T11 until immediately before [2] a toner supply period for supplying toner in a developing area 31 from a developing device 3 to the photoconductor drum 1 in the initialization operation, and controls the transfer voltage power supply 20 so as to adjust the constant voltage to be applied to the transfer roller 4 in the time T11 to have a normal electrification polarity of the toner and a voltage value at which electric discharge does not occur between the photoconductor drum 1 and the transfer roller 4.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, electrophotographic image forming devices uniformly charge the surface of a photosensitive drum using a charging member, then expose the charged photosensitive drum surface to light in accordance with image information to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image on the photosensitive drum is then developed using toner by a developing device to form a toner image on the photosensitive drum, which is then transferred to a recording material such as paper by a transfer member. Any toner remaining on the photosensitive drum after transfer is removed and collected by a cleaning blade. In this image forming device, consumables such as the photosensitive drum, charging member, developing device, and cleaning blade are integrated into a detachable process cartridge, facilitating maintenance.

[0003] When a brand new process cartridge is installed in an image forming apparatus, an initial operation is required to transition the apparatus to a printable state. This initial operation mainly involves a toner supply operation, which supplies toner from the developing device to the cleaning blade. By sending the fine particles added to the toner between the photosensitive drum and the cleaning blade, lubrication is achieved between the photosensitive drum and the cleaning blade, preventing damage caused by the cleaning blade curling up. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-038973 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a toner supply operation is performed during the initial operation, toner may slip through the cleaning blade and soil the charging member, resulting in so-called cleaning defects. Normally, the tip of a cleaning blade has a barrier layer made of fine particles of external additives, called a blocking layer, which maintains cleaning performance. However, the tip of a cleaning blade in a brand new process cartridge does not yet have a blocking layer, making it prone to cleaning defects.

[0006] The present invention has been made under these circumstances, and has as its object to prevent poor cleaning during the initial rotation that prepares a brand new process cartridge for printing. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0008] (1) An image forming apparatus comprising: a rotatable image carrier; a developing member that supplies toner to the surface of the image carrier in a development area abutting the image carrier to form a toner image; a transfer member that transfers the toner image from the image carrier to a transfer material; an application means that applies a voltage to the transfer member; a cleaning blade that cleans toner remaining on the image carrier after the toner image has been transferred to the transfer material; and a control unit that executes an initial operation to transition the image carrier to a new, printable state and an image forming operation to form the toner image on the transfer material, wherein the control unit controls the application means to apply a constant voltage to the transfer member that is different from that applied during the image forming operation during a second period that is immediately before a first period in which toner is supplied from the developing member to the image carrier in the development area during the initial operation, and controls the application means so that the constant voltage applied to the transfer member during the second period is the normal charging polarity of the toner and a voltage value that does not cause discharge between the image carrier and the transfer member. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent poor cleaning during the initial rotation for bringing a brand new process cartridge into a printable state. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram of the image forming apparatus according to the first to third embodiments [Figure 2] Block diagram of an image forming apparatus according to first to third embodiments [Figure 3] 1 is a diagram showing the cleaning state of the tip of the cleaning blade in Examples 1 to 3. [Figure 4] Sequence diagram of the initial operation of Example 1 [Figure 5] Sequence diagram of the initial operation of Example 2 [Figure 6] Sequence diagram of the initial operation of the third embodiment DETAILED DESCRIPTION OF THE INVENTION [Example]

[0011] In Example 1, we will explain the toner supply operation when performing the initial operation to install a brand new process cartridge 13 in the image forming device 12 and transition it to a printable state, and the voltage control applied to the transfer roller 4 immediately before that.

[0012] <Explanation of Image Forming Apparatus and Image Forming Operation> FIG. 1 shows a schematic configuration of an electrophotographic laser beam printer as an image forming apparatus according to the first embodiment. FIG. 2 shows a block diagram of the image forming apparatus according to the first embodiment. The image forming apparatus 12 using electrophotographic technology according to the first embodiment includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image carrier. Around the photosensitive drum 1, a charging roller 2, an exposure device 6, a developing device 3, a transfer roller 4, and a cleaning device 5 are arranged in this order along the rotation direction (clockwise direction) of the photosensitive drum 1 as indicated by the arrow in FIG. 1. A fixing device 7 is arranged downstream of a transfer nip N formed between the photosensitive drum 1 and the transfer roller 4 in the transport direction of a transfer material P.

[0013] The image forming apparatus 12 also includes a control unit 100. The control unit 100 includes, for example, a CPU 101, a ROM 102, a RAM 103, and a timer 104. The CPU 101 executes programs stored in the ROM 102 and controls the overall operation of the image forming apparatus 12 while using the RAM 103 as a work area and a temporary storage area. The CPU 101 manages time using the timer 104 when performing timing control in controlling the image forming apparatus 12. The control unit 100 controls a high-voltage unit 200 (see FIG. 2). The control unit 100 also reads information from and writes information to a non-volatile memory 9 serving as a storage unit. The high-voltage unit 200 includes a charging voltage power supply 19, a developing voltage power supply 18, and a transfer voltage power supply 20 (see FIG. 2).

[0014] <Detailed Description of Image Forming Apparatus> In Example 1, the photosensitive drum 1 has an OPC (organic photoconductor) photosensitive layer on an aluminum drum base. The photosensitive drum 1 is driven to rotate in the direction of the arrow (clockwise) at a predetermined peripheral speed by a drive unit 220 (see FIG. 3 ), which is a drive means provided on the main body of the image forming apparatus 12. A charging roller 2 as a charging member uniformly charges the photosensitive drum 1 to a predetermined polarity and potential by a charging voltage applied from a charging voltage power supply 19 as a second application means. A DC voltage of −1100 V is applied as the charging voltage, so that the potential on the photosensitive drum 1 (hereinafter referred to as the photosensitive drum potential) becomes a potential Vd=−500 V.

[0015] The exposure device 6 outputs laser light (exposure beam L) from a laser output unit (not shown) that has been modulated by a video controller (not shown) in response to time-series electrical digital image signals based on image information input from a personal computer (not shown). The exposure beam L scans and exposes the surface of the charged photosensitive drum 1, thereby forming an electrostatic latent image corresponding to the image information. In Example 1, the exposure beam L was irradiated so that the light area potential Vl on the photosensitive drum 1 was −150 V. The developing device 3 will be described in detail later.

[0016] A transfer roller 4 as a transfer means comes into contact with the surface of the photosensitive drum 1 with a predetermined pressing force to form a transfer nip N, and a transfer voltage is applied from a transfer voltage power supply 20 as a first application means (application means). This transfer voltage causes the toner image on the surface of the photosensitive drum 1 to be transferred to a transfer material P such as paper at the transfer nip N between the photosensitive drum 1 and the transfer roller 4.

[0017] The fixing device 7 has a heating roller equipped with an internal halogen heater (not shown) and a pressure roller. The fixing device 7 heats, melts, and pressurizes the unfixed toner image transferred onto the surface of the transfer material P while nipping and conveying the transfer material P at the fixing nip between the fixing roller and the pressure roller, thereby thermally fixing the toner image to form a permanent image. After the fixing is completed, the transfer material P carrying the permanent image is discharged outside the image forming apparatus 12.

[0018] A cleaning blade 5a serving as cleaning means cleans off any toner remaining on the photosensitive drum 1 that has not been transferred, and the photosensitive drum 1 is then used again for image formation. The photosensitive drum 1, charging roller 2, developing device 3, and cleaning blade 5a are integrated into a unit to form a process cartridge 13 (cartridge) that is detachable from the main body of the image forming apparatus 12. A nonvolatile memory 9 that stores various information related to the process cartridge 13 is installed in the process cartridge 13.

[0019] <Details of the developing device> Further, referring to FIG. 1, the details of the developing device 3, which is a developing member, will be described. The developing device 3 includes a developing container 3a that stores toner T containing externally added particles, an agitating member 10 that agitates the toner T, a developing roller 8 as a toner carrier, a supply roller 14 that supplies toner T to the developing roller 8, and a developing blade 11 that regulates the thickness of the toner T layer. The toner T is normally charged to a negative polarity (minus polarity), and a magnetic single-component toner with an average particle size of 7 μm is used. That is, in Example 1, the normally charged polarity of the toner is negative. Furthermore, silica particles with a particle size of 20 nm are added to the surface of the toner T as an external toner additive (external particles). The agitating member 10 includes a support rod and an agitating sheet. The support rod is supported at both ends by the developing container 3a and rotates clockwise in FIG. 1. The agitating sheet is made of a 100 μm-thick PPS (polyphenylene sulfide) sheet, and one of its short ends is pressure-bonded to the support rod.

[0020] The developing roller 8 faces and contacts the surface of the photosensitive drum 1, and both ends of the developing roller 8 are rotatably supported in the opening of the developing device 3, rotating in the same direction as the photosensitive drum 1. The photosensitive drum 1 and the developing roller 8 are always in contact with each other, and the image forming apparatus 12 of Example 1 does not have a separation mechanism for separating the developing roller 8 from the photosensitive drum 1. The developing area 31 is the area where the developing roller 8 and the photosensitive drum 1 are in contact with each other. A developing voltage power supply 18 is connected to the developing roller 8 as a developing voltage application means disposed in the main body of the image forming apparatus 12, and the developing voltage power supply 18 applies a DC developing voltage Vdc = -400 V during printing. When the process cartridge 13 is new, the surface of the developing roller 8 is coated with Tospearl (particle size 1 to 2 μm) as a lubricant.

[0021] The supply roller 14 is disposed opposite to and in contact with the surface of the developing roller 8, and rotates in the opposite direction to the developing roller 8. The developing blade 11 is a 1 mm thick stainless steel sheet metal blade fixed to a supporting plate. The supporting plate is fixed to the developing container 3a so that it comes into contact with the developing roller 8 with an appropriate contact pressure in order to appropriately regulate the thickness of the toner T layer and to frictionally charge it. In the case of a new process cartridge 13, a seal member (not shown) is adhered to the inside of the developing container 3a to prevent toner T from leaking from the area shown in Figure 1 during transportation, etc. Figure 1 shows the state after the seal member has been removed.

[0022] With this configuration, the toner T is supplied to the surface of the developing roller 8 by the supply roller 14. Thereafter, the toner T on the surface of the developing roller 8 is charged by frictional charging while the layer thickness is optimized by the developing blade 11. The charged toner T visualizes the electrostatic latent image on the photosensitive drum 1 as a toner image in the developing region 31.

[0023] <Initial operation when using a new process cartridge> When a brand new process cartridge 13 is installed in the image forming apparatus 12, a special initial operation is required (hereinafter, this operation will be referred to as the initial operation). The initial operation is mainly divided into three periods: "(1) Run-in rotation period," "(2) Toner supply operation period" (first period), and "(3) Blocking layer formation period" (third period). These initial operations are controlled by the control unit 100.

[0024] During the "(1) run-in rotation period," rotating bodies such as the developing roller 8 inside the process cartridge 13 are rotated (hereinafter referred to as "run-in rotation"), and during this period, the toner T is properly coated over the entire longitudinal area (also the direction of the rotation axis) of the developing roller 8. Next, during the "(2) toner supply operation period," the toner coated on the developing roller 8 is supplied to the cleaning blade 5a via the rotating photosensitive drum 1. In Example 1, the entire longitudinal area, i.e., an amount of toner equivalent to an area of ​​250 mm in length, is supplied. Finally, during the "(3) blocking layer formation period," the toner T supplied to the cleaning blade 5a is rolled by the force of the rotational drive of the photosensitive drum 1, and the silica particles externally added to the toner T are transferred to the photosensitive drum 1.

[0025] FIG. 3 is an enlarged schematic diagram of a key portion of the tip of the cleaning blade 5a. By transferring silica particles to the photosensitive drum 1, the silica particles are collected at the tip of the cleaning blade 5a as shown in FIG. 3, forming a barrier layer called a blocking layer 15, which prevents the toner T from slipping through the cleaning blade 5a. In Example 1, a constant voltage is applied to the transfer roller 4 for a predetermined time, for example, 5 seconds, immediately before the "(2) toner supply operation period." In Example 1, the drive speed by the drive unit 220 during the initial operation is half the speed during image formation, but the effects of Example 1 can be obtained at any drive speed.

[0026] <Explanation of Initial Operations in Example 1 and Comparative Examples 1 to 3> FIG. 4 shows the detailed initial operation sequence of Example 1 and Comparative Examples 1 to 3. In FIG. 4, (i) indicates the drive (ON) or stop (OFF) of the drive unit, (ii) indicates the charging voltage [V] applied to the charging roller 2, (iii) indicates the developing voltage [V] applied to the developing roller 8, and (iv) indicates exposure by the exposure device 6. Note that exposure by the exposure device 6 is full emission, where the light source emits the maximum amount of light, and exposure by full emission is ON, and no exposure is OFF. In FIG. 4, (v) indicates the transfer voltage [V] applied to the transfer roller 4 of Example 1 to Comparative Examples 1 to 4. The horizontal axis indicates time, and t11 to t16 indicate each timing.

[0027] The initial operation of Example 1 and Comparative Examples 1 to 3 is the same as that of Comparative Examples 1 to 3, with respect to the drive unit 220, the application of the charging voltage by the charging voltage power supply 19, the application of the developing voltage by the developing voltage power supply 18, and the operation of the exposure device 6. Specifically, the drive unit 220 of the image forming device 12 is first turned on at timing t11 to rotate the photosensitive drum 1 and the developing roller 8. After timing t12, a voltage of −1100 V is applied to the charging roller 2 and −400 V is applied to the developing roller 8 for run-in rotation. Then, at timing t14, the exposure device 6 emits the exposure beam L at maximum output (full emission) to form an electrostatic latent image on the photosensitive drum 1, and the toner T is developed onto the photosensitive drum 1. This toner supply operation continues until timing t15, followed by a blocking layer formation period, at which the initial operation ends at timing t16. At the end of the initial operation at timing t16, the drive unit 220 is turned off, the voltage application to the charging roller 2 is stopped, and the voltage application to the developing roller 8 is stopped. The period from timing t11 to timing t14 is the (1) run-in rotation period, the period from timing t14 to timing t15 is the (2) toner supply operation period, and the period from timing t15 to timing t16 is the (3) blocking layer formation period.

[0028] In Example 1 and Comparative Examples 1 to 3, during the run-in rotation period and time T11 (second period) from timing t13 to timing t14 immediately before the toner supply operation period, for example, 5 seconds, transfer voltage is applied to transfer roller 4 by transfer voltage power supply 20. Here, the voltage value of the constant voltage applied to transfer roller 4 differs between Example 1 and Comparative Examples 1 to 3. Specifically, in Example 1, −150 V, which is the same polarity as the normal (negative) charge polarity of the toner, is applied to transfer roller 4; −1000 V in Comparative Example 1; +1000 V, which is the opposite polarity to the normal charge polarity of the toner, is applied to transfer roller 4 in Comparative Example 2; and +150 V in Comparative Example 3. Furthermore, in Comparative Example 4, −150 V is first applied to transfer roller 4 at timing t11 when the run-in rotation period begins, and then it is reset to 0 V at timing t13, and the toner supply operation is performed from timing t14 onwards. That is, in Comparative Example 4, the voltage is reset to 0 V immediately before the toner supply operation period and then the toner supply operation period begins.

[0029] <Verification of the effects of Example 1> The effects of Example 1 are shown in Table 1. The test method was to output a 50% halftone image after performing the initial operation in Example 1 and Comparative Examples 1 to 3, and to check whether the output image had vertical streaks due to poor cleaning, and to evaluate the vertical streak occurrence level. The test was also conducted in an environment where the image forming apparatus 12 was installed at 15°C / 10%. [Table 1] Vertical streak occurrence level: 〇: No vertical streaks, △: A few vertical streaks, ×: Many vertical streaks As shown in Table 1, no vertical streaks occurred in Example 1, but vertical streaks occurred in images of Comparative Examples 1 to 4. In particular, in Comparative Example 2, images with many vertical streaks occurred.

[0030] (Example 1: Vertical streak occurrence level: 0) The reason why vertical streaks did not occur in Example 1 will be explained below. During the run-in rotation period, some of the Tospearl (particle size 1 to 2 μm) initially applied to the surface of the developing roller 8 and some of the toner that is subsequently coated on the developing roller 8 are transferred to the photosensitive drum 1. At this time, by applying a constant voltage of −150 V to the transfer roller 4, only negative (negative polarity) toner particles transferred to the photosensitive drum 1 are sent to the cleaning blade 5a, and positive (positive polarity) toner particles are retained on the transfer roller 4.

[0031] As a result, a blocking layer 15 is quickly formed on the edge of the cleaning blade 5a, as described in FIG. 3. The reason for sending a negative-type toner to the cleaning blade 5a is that negative-type toner has weaker adhesion to the photosensitive drum 1, making it less likely to slip through the cleaning blade 5a and more likely to form a blocking layer. In this way, a simple blocking layer is formed in advance during the run-in rotation period, and then the toner supply operation is performed. This prevents poor cleaning caused by toner slipping through the edge of the cleaning blade 5a, even if a large amount of toner reaches the cleaning blade 5a during the toner supply operation. Note that the blocking layer 15 during the run-in rotation period in Example 1 has a circumferential width of approximately 10 μm on the surface of the photosensitive drum 1. Thereafter, a final blocking layer is formed during the blocking layer formation period. The blocking layer 15 of Example 1 during the blocking layer formation period has a circumferential width of 20 μm or more on the surface of the photosensitive drum 1.

[0032] (Comparative Example 1: Vertical streak occurrence level △) The reason for the slight vertical streaks in Comparative Example 1 is that negative discharge occurred between the transfer roller 4 and the photosensitive drum 1 when a transfer voltage of -1000V was applied to the transfer roller 4. This discharge created tiny holes on the surface of the photosensitive drum 1, reducing the contact area with the cleaning blade 5a and reducing the friction between the photosensitive drum 1 and the cleaning blade 5a. This reduced the amount of the tip of the cleaning blade 5a that was caught, reducing the stress generated when the rubber was caught. This reduced the pressure of the cleaning blade 5a against the photosensitive drum 1, making it easier for toner to slip through. Another issue is that negative discharge occurred between the transfer roller 4 and the photosensitive drum 1, causing the potential of the photosensitive drum 1 to continue to rise during the run-in rotation period. As a result, even when the exposure device 6 was fully illuminated during the toner supply period, the bright-area potential Vl was only about -250V, reducing the amount of toner supplied to the photosensitive drum 1 and resulting in an inadequate supply of toner to the cleaning blade 5a.

[0033] (Comparative Example 2: Vertical streak occurrence level ×) The reason for the numerous vertical streaks in Comparative Example 2 is that a voltage of +1000V was applied to the transfer roller 4, causing positive discharge between the transfer roller 4 and the photosensitive drum 1. As in Comparative Example 1, this discharge reduced the friction between the photosensitive drum 1 and the cleaning blade 5a, reducing the pressure of the cleaning blade 5a against the photosensitive drum 1 and making it easier for toner to slip through. Furthermore, the toner and toner transferred from the developing roller 8 to the photosensitive drum 1 during the run-in period were strongly positively charged (positively polarized) by the positive discharge as they passed through the transfer roller 4, resulting in strong adhesion to the photosensitive drum 1 and entering the cleaning blade 5a. Such strongly positively charged substances (strongly positively charged substances) easily slip through the cleaning blade 5a and are less likely to form the blocking layer 15, making cleaning failures more likely to occur during the toner supply period. These two factors were significant in Comparative Example 2, resulting in images with more vertical streaks than in Comparative Example 1.

[0034] (Comparative Example 3: Vertical streak occurrence level △) The reason why some vertical streaks occurred in Comparative Example 3 is that, unlike Example 1, a voltage of +150V was applied to the transfer roller 4, which resulted in positive-type Tospearl and toner being supplied to the cleaning blade 5a during the run-in rotation period. Positive-type toner has a high adhesive strength with the photosensitive drum 1 and is therefore difficult to form a blocking layer, so a sufficient blocking layer could not be formed by the time the toner supply period began, resulting in some vertical streaks.

[0035] (Comparative Example 4: Vertical streak occurrence level △) The reason why slight vertical streaks occurred in Comparative Example 4 is that the timing of applying -150V to the transfer roller 4 was not immediately before the toner supply period. If -150V was applied to the transfer roller 4 once and then returned to 0V before the toner supply operation was performed, simple blocking layer formation would be difficult in the 0V section (t13 to t14), and the amount of toner that escaped from the cleaning blade 5a would be greater, resulting in the depletion of the blocking layer that had been formed. Therefore, slight vertical streaks occurred in Comparative Example 4.

[0036] As explained above, as in Example 1, by applying a negative transfer voltage that does not cause discharge to the transfer roller 4 during the run-in rotation period immediately before the toner supply operation period during initial operation, it is possible to provide an image forming apparatus that does not cause cleaning failures.

[0037] Note that the toner supply during the toner supply period in Example 1 may be divided into segments. For example, a cycle of "supplying 25 mm of toner and not supplying 25 mm of toner" may be repeated 10 times. In other words, the control unit 100 does not need to continuously supply toner in the toner supply section, and may control the toner supply section to have multiple segments where toner is supplied and multiple segments where toner is not supplied. As described above, the control unit 100 may alternate between supplying and stopping toner supply. This prevents toner T from continuously entering the cleaning blade 5a, further reducing the possibility of the simple blocking layer created during the break-in rotation period breaking down.

[0038] Furthermore, Example 1 can also be applied when the negative voltages of the transfer roller 4 and the charging roller 2 in Example 1 use the same high voltage in the image forming apparatus 12, i.e., are supplied from the same power source. That is, Example 1 can also be applied to a configuration in which a charging voltage of -1100 V is applied to the charging roller 2 and the same voltage of -1100 V is applied to the transfer roller 4. In this case, a constant voltage of +950 V is applied to the transfer roller 4 as a positive voltage. This results in a net voltage of -150 V (= -1100 V + 950 V) being applied to the transfer roller 4, achieving the same effect as Example 1. This configuration also applies to the transfer voltage applied during the blocking layer formation period, which will be described in the following examples.

[0039] As described above, according to the first embodiment, it is possible to prevent the occurrence of poor cleaning during the initial rotation for bringing a brand new process cartridge into a printable state. [Example]

[0040] In the second embodiment, the transfer voltage applied to the transfer roller 4 is adjusted even during the blocking layer formation period (3) during the initial operation. By applying the second embodiment, it is possible to prevent poor cleaning even when the installation temperature of the image forming apparatus 12 is 5°C / 30%, which would cause the cleaning blade to have poor performance.

[0041] <Explanation of Initial Operations in Example 2 and Comparative Examples 5 to 7> FIG. 5 shows the detailed initial operation sequence of Example 2 and Comparative Examples 5 to 7. (i) to (iv) in FIG. 5 are the same as in Example 1. Also, t21 to t26 indicate the respective timings. As in Example 1, Example 2 and Comparative Examples 5 to 7 share the same drive unit 220, the application of charging voltage to charging roller 2, the application of developing voltage to developing roller 8, and the operation of exposure device 6. Furthermore, a voltage other than 0 V is applied to transfer roller 4 during the pre-running rotation period. That is, during time T21, from timing t23 to timing t24 as the second period, a transfer voltage of −150 V is applied to transfer roller 4. The period from timing t21 to timing t24 is [1] the pre-running rotation period, the period from timing t24 to timing t25 is [2] the toner supply operation period, and the period from timing t25 to timing t26 is [3] the blocking layer formation period.

[0042] The voltage value of the constant voltage applied to the transfer roller 4 during the blocking layer formation period differs between Example 2 and Comparative Examples 5 to 7. Specifically, -150 V is applied to the transfer roller 4 in Example 2, -1000 V in Comparative Example 5, +1000 V in Comparative Example 6, and +150 V in Comparative Example 7. Furthermore, since the configuration other than that described up to this point is the same as that of Example 1, a description thereof will be omitted.

[0043] <Verification of the effect of Example 2> The effects of Example 2 are shown in Table 2. The test method was to output a 50% halftone image after performing the initial operation in Example 2 and Comparative Examples 5 to 7, and to check whether the output image had vertical streaks due to poor cleaning, and to evaluate the vertical streak occurrence level. The test was also conducted in the installation environments of the image forming apparatus 12 at 15°C / 10% and 5°C / 30%. [Table 2] Vertical streak occurrence level: 〇: No vertical streaks, △: A few vertical streaks, ×: Many vertical streaks

[0044] As shown in Table 2, no vertical streaks occurred in any of the installation environments of the image forming apparatus 12 at 15°C / 10%. However, in the installation environment of the image forming apparatus 12 at 5°C / 30%. Although no vertical streaks occurred in Example 2, slight vertical streaks occurred in Comparative Examples 5 and 6. Furthermore, no vertical streaks occurred in Comparative Example 7 either.

[0045] (Example 2: Vertical streak occurrence level: 0) The reason why vertical streaks did not occur in Example 2 will be explained. During the blocking layer formation period in Example 2, the voltage applied to the transfer roller 4 was -150 V, so no discharge occurred between the transfer roller 4 and the photosensitive drum 1. Therefore, the frictional force between the cleaning blade 5a and the photosensitive drum 1 was maintained, and the tip of the cleaning blade 5a was properly wrapped around and generated pressure. As a result, no cleaning defects occurred even in an installation environment of 5°C / 30%. For the same reason, no cleaning defects occurred in Comparative Example 7. In Comparative Example 7, the voltage application during the break-in rotation period was the same as in Example 2, and the absolute value of the voltage application during the blocking layer formation period was the same but the polarity was different. From Example 2 and Comparative Example 7, it was found that good results could be obtained regardless of the polarity, either + or -, for the voltage application during the blocking layer formation period, as long as the absolute value was a voltage at which no discharge occurred (e.g., 150 V).

[0046] On the other hand, in Comparative Examples 5 and 6, discharge occurs between the transfer roller 4 and the photosensitive drum 1, which weakens the frictional force between the cleaning blade 5a and the photosensitive drum 1, as explained in Example 1. During the blocking layer formation period, a large amount of toner supplied during the toner supply period remains on the edge of the cleaning blade 5a, causing a decrease in the pressure of the cleaning blade 5a against the photosensitive drum 1. This causes poor cleaning.

[0047] As explained above, it is possible to provide an image forming apparatus in which cleaning defects do not occur by applying a voltage that does not cause discharge to the transfer roller 4 during the blocking layer formation period during initial operation as in Example 2. For example, even if the image forming apparatus is installed in an environment of 5°C / 30%, it is possible to prevent cleaning defects from occurring during initial operation.

[0048] As described above, according to the second embodiment, it is possible to prevent the occurrence of poor cleaning during the initial rotation for bringing a brand new process cartridge into a printable state. [Example]

[0049] In the third embodiment, there are two or more types of process cartridges 13 that can be installed in the image forming apparatus 12, and each process cartridge 13 uses a different surface layer material for the photosensitive drum 1. Therefore, when a durability test is conducted on each process cartridge 13, the amount of wear on the surface layer of the photosensitive drum 1 per 1,000 sheets (hereinafter referred to as the photosensitive drum wear rate) is different. For each process cartridge 13, by controlling the voltage applied to the transfer roller 4 during the [1] break-in rotation period and the [3] blocking layer formation period during initial operation, it is possible to prevent poor cleaning.

[0050] <Description of Configurations and Initial Operations of Examples 3-1, 3-2, and Comparative Examples 8 and 9> First, the difference between the surface layer materials of the two types of photosensitive drums 1 used in Example 3 will be described. In Example 3-1 and Comparative Examples 8 to 9, the surface layer material of the photosensitive drum 1 is softer than that used in Examples 1 and 2 and Comparative Examples 1 to 7. Specifically, the surface layer material of the photosensitive drum 1 used in Example 3-1 and Comparative Examples 8 to 9 is polycarbonate resin. On the other hand, the surface layer material of the photosensitive drum 1 used in Example 1, Example 2, Example 3-2, and Comparative Examples 1 to 7 is polyarylate resin.

[0051] As a result, the photosensitive drum wear rate per 1000 sheets is 0.4 μm for polycarbonate resin and 0.2 μm for polyarylate resin. Furthermore, these values ​​are stored as information in a nonvolatile memory 9 installed in the process cartridge 13. This information on the photosensitive drum wear rate is configured to be communicable by contact between the control unit 100 of the image forming apparatus 12 and the nonvolatile memory 9 via electrical contacts (not shown). Note that the information on the photosensitive drum wear rate may also be stored in ROM 102.

[0052] In the third embodiment, when two types of photosensitive drums 1 having different wear rates are used, the range of voltage applied to the transfer roller 4 during initial operation is changed using information on the photosensitive drum wear rate stored in the nonvolatile memory 9. Specifically, when the photosensitive drum is the second image carrier having a high photosensitive drum wear rate of 0.4 (second value), the control unit 100 controls the voltage applied to the transfer roller 4 during initial operation to be between −200 V and −100 V. On the other hand, when the photosensitive drum is the first image carrier having a low photosensitive drum wear rate of 0.2 (first value), the control unit 100 controls the voltage applied to the transfer roller 4 during initial operation to be between −550 V and 0 V. In other words, when the photosensitive drum wear rate is high, the control unit 100 narrows the range of voltage that can be applied to the transfer roller 4 compared to when the photosensitive drum wear rate is low.

[0053] FIG. 6 shows the detailed initial operation sequence of Example 3-1, Example 3-2, and Comparative Examples 8 to 9. (i) to (iv) in FIG. 6 are the same as in Example 1. Also, t31 to t36 indicate the respective timings. As in Example 1, in Examples 3-1, 3-2, and Comparative Examples 8 to 9, the drive unit 220, the voltage application to the charging roller 2, the voltage application to the developing roller 8, and the operation of the exposure device 6 are the same. Note that the period from timing t31 to timing t34 is [1] the run-in rotation period, the period from timing t34 to timing t35 is [2] the toner supply operation period, and the period from timing t35 to timing t36 is [3] the blocking layer formation period. Since the configurations other than those described up to this point are the same as in Example 1, their explanations will be omitted.

[0054] In this configuration, the differences in the initial operation sequences between Example 3-1, Example 3-2, and Comparative Examples 8 and 9 will be described. Specifically, the voltage value of the constant voltage applied to the transfer roller 4 is different. In Example 3-1, the voltage value of the constant voltage applied to the transfer roller 4 during the run-in rotation period and the blocking layer formation section is set to -150V. In Example 3-2, the voltage value of the constant voltage applied to the transfer roller 4 during the run-in rotation period and the blocking layer formation section is set to -500V. In Comparative Example 8, the voltage value of the constant voltage applied to the transfer roller 4 during the running-in rotation period is −500V, and the voltage value of the constant voltage applied to the transfer roller 4 during the blocking layer formation section is +500V. In Comparative Example 9, the voltage value of the constant voltage applied to the transfer roller 4 during the run-in rotation period and the blocking layer formation section is +150V.

[0055] <Verification of the effects of Examples 3-1 and 3-2> The effects of Example 3-1 and Example 3-2 are shown in Table 3. The test was conducted by performing the initial operation in Example 3-1, Example 3-2, and Comparative Examples 8 and 9, and then outputting a halftone 50% image to check whether vertical streaks occurred in the output image due to poor cleaning. The image forming apparatus 12 was installed in an environment of 15°C / 10%. [Table 3] Vertical streak occurrence level: 〇: No vertical streaks, △: A few vertical streaks, ×: Many vertical streaks As shown in Table 3, no vertical stripes occurred in Examples 3-1 and 3-2, but slight vertical stripes occurred in the images in Comparative Examples 8 and 9.

[0056] (Example 3: Vertical streak occurrence level: 0) The reason why vertical streaks did not occur in Example 3-1 will be explained. The photosensitive drum 1 of Example 3-1 has a higher photosensitive drum abrasion rate than Example 1, and is more susceptible to abrasion. In other words, the photosensitive drum 1 of Example 3-1 corresponds to the photosensitive drum abrasion rate of 0.4, which is high as described above. As a result, more photosensitive drum abrasion powder is interposed between the photosensitive drum 1 and the cleaning blade 5a, and the frictional force between the photosensitive drum 1 and the cleaning blade 5a decreases. As a result, the amount of entrapment of the tip of the cleaning blade 5a decreases, and the pressure on the photosensitive drum 1 also decreases, making it more susceptible to poor cleaning.

[0057] Even in this state, by setting the transfer voltage applied to the transfer roller 4 to -150 V during the run-in rotation period (time T31) and the blocking layer formation period, cleaning performance is maintained for the reasons explained in Example 1. The voltage value of -150 V is within the range of -200 V or more and -100 V or less of the voltage value applied to the transfer roller 4 when the photosensitive drum abrasion rate is 0.4, which is large as described above.

[0058] Next, the reason why vertical streaks did not occur in Example 3-2 will be explained. In Example 3-2, the photosensitive drum wear rate was smaller than in Example 3-1. In other words, the photosensitive drum 1 in Example 3-2 corresponds to the above-mentioned photosensitive drum wear rate of 0.2, which is small. Therefore, the amount of entrapment of the tip of the cleaning blade 5a was also larger than in Example 3-1. Therefore, since cleaning defects were unlikely to occur, no cleaning defects occurred even when the voltage applied to the transfer roller 4 during the break-in rotation period (time T31) and the blocking layer formation period was -500 V. The voltage value of -500 V is within the range of voltage values, from -550 V to -0 V, that are applied to the transfer roller 4 when the above-mentioned photosensitive drum wear rate is small, 0.2.

[0059] (Comparative Examples 8 and 9: Vertical streak occurrence level △) Furthermore, in Comparative Example 8, the target voltage was close to the voltage (-550V) at which discharge occurs between the transfer roller 4 and the photosensitive drum 1. However, due to variations in the high-voltage components of the image forming device 12, discharges did occur in practice. This created a situation where cleaning defects were likely to occur for the reasons described in Example 1. Furthermore, the photosensitive drum 1 used had a soft surface that was prone to cleaning defects, resulting in the occurrence of slight vertical streaks. The photosensitive drum 1 in Comparative Example 8 corresponds to the photosensitive drum wear rate of 0.4, which is described above as being high. Neither of the voltage values ​​of -500V nor +500V falls within the range of -200V or more and -100V or less that is the voltage value applied to the transfer roller 4 when the photosensitive drum wear rate is 0.4, which is described above as being high.

[0060] In Comparative Example 9, +150 V was applied to the transfer roller 4 during the run-in rotation period, so no discharge occurred, but the toner supply operation was performed without forming a simple blocking layer as described in Example 1, resulting in the occurrence of some vertical streaks. The photosensitive drum 1 of Comparative Example 9 also corresponds to the photosensitive drum abrasion rate of 0.4, which is high as described above. The voltage value of +150 V is not included in the range of voltage values, from -200 V to -100 V, that are applied to the transfer roller 4 when the photosensitive drum abrasion rate is 0.4, which is high as described above.

[0061] As explained above, even in a situation like that of Example 3 where the photosensitive drum wear rate is high and cleaning defects are likely to occur, by making the target value of the voltage applied to the transfer roller 4 more appropriate, it is possible to provide an image forming apparatus in which cleaning defects do not occur. As described above, according to the third embodiment, it is possible to prevent the occurrence of poor cleaning during the initial rotation for bringing a brand new process cartridge into a printable state.

[0062] <Other embodiments> In the above-described embodiment, the image forming apparatus is described in which the developing roller is always in contact with the photosensitive drum and does not have a contact / separation mechanism, but the image forming apparatus may also have a contact / separation mechanism. That is, the control unit 100 may cause the photosensitive drum and the developing roller to contact each other using the contact / separation mechanism before rotating the photosensitive drum 1 by the drive unit 220 in the initial operation. The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0063] The disclosure of this embodiment includes the following configuration. (Configuration 1) a rotatable image carrier; a developing member that supplies toner to the surface of the image carrier in a developing region that contacts the image carrier to form a toner image; a transfer member for transferring the toner image from the image carrier to a transfer material; an application means for applying a voltage to the transfer member; a cleaning blade for cleaning the toner remaining on the image carrier after the toner image has been transferred to a transfer material; a control unit that executes an initial operation for shifting the image carrier from a brand new state to a printable state, and an image forming operation for forming the toner image on the transfer material; Equipped with The control unit controls the application means to apply a constant voltage different from that applied during the image forming operation to the transfer member during a second period immediately before a first period in which toner is supplied from the developing member to the image carrier in the development area during the initial operation, and controls the application means so that the constant voltage applied to the transfer member during the second period has the normal charging polarity of the toner and a voltage value that does not cause discharge between the image carrier and the transfer member. (Configuration 2) The image forming apparatus according to configuration 1, characterized in that the control unit controls the application means so that the constant voltage applied to the transfer member during the second period is greater than or equal to -550 V and less than 0 V when the normal charging polarity of the toner is negative. (Configuration 3) 2. The image forming apparatus according to claim 1, wherein the control unit controls the applying unit so that the constant voltage applied to the transfer member during the second period is between −200V and −100V. (Configuration 4) The image forming apparatus according to any one of configurations 1 to 3, wherein the control unit controls the application unit to apply a constant voltage to the transfer member during a third period after the first period so that the constant voltage is a voltage value that does not cause discharge between the image carrier and the transfer member. (Configuration 5) 5. The image forming apparatus according to claim 4, wherein the control unit controls the applying unit so that the constant voltage applied to the transfer member during the third period is between −550 V and +550 V. (Configuration 6) When the application means is a first application means, a charging member for uniformly charging the surface of the image bearing member; a second applying means for applying a voltage to the charging member; Equipped with The image forming apparatus according to Structure 4 or 5, wherein the control unit controls the first application means and the second application means so that, during the third period, the second application means applies to the transfer member the same voltage as that applied to the charging member, and the first application means applies to the transfer member a voltage of opposite polarity to that of the voltage applied by the second application means, and the voltage applied to the transfer member becomes the constant voltage. (Configuration 7) 7. The image forming apparatus according to any one of configurations 1 to 6, wherein the control unit controls the first period so that there are multiple sections in which toner is supplied and multiple sections in which toner is not supplied. (Configuration 8) When the application means is a first application means, a charging member for uniformly charging the surface of the image bearing member; a second applying means for applying a voltage to the charging member; Equipped with The image forming apparatus according to any one of configurations 1 to 7, wherein the control unit controls the first application means and the second application means so that, during the second period, the same voltage as that applied to the charging member by the second application means is applied to the transfer member, and the first application means applies a voltage of opposite polarity to the polarity of the voltage applied by the second application means to the transfer member, and so that the voltage applied to the transfer member becomes the constant voltage. (Configuration 9) the image forming apparatus is mountable with a first image carrier having a first abrasion rate of the surface of the image carrier, and a second image carrier having a surface softer than the first image carrier and a second abrasion rate greater than the first value; The image forming apparatus according to any one of configurations 1 to 8, wherein a range of voltages including the constant voltage applied to the transfer member when the second image carrier is attached is narrower than a range of voltages including the constant voltage applied to the transfer member when the first image carrier is attached. (Configuration 10) a storage unit that stores information about the scraping rate; a cartridge having the storage unit and the image carrier; 10. The image forming apparatus according to claim 9, further comprising: (Configuration 11) the developing member has a toner carrier that contacts the image carrier; 11. The image forming apparatus according to any one of configurations 1 to 10, wherein the toner carrier, when new, is coated on its surface with a lubricant containing at least a lubricant having the same polarity as the normal charging polarity of the toner. [Explanation of symbols]

[0064] 1 Photosensitive drum 3. Developing device 4 Transfer roller 5a cleaning blade 20 Transfer voltage power supply 100 control section

Claims

1. a rotatable image carrier; a developing member that supplies toner to the surface of the image carrier in a developing region that contacts the image carrier to form a toner image; a transfer member for transferring the toner image from the image carrier to a transfer material; an application means for applying a voltage to the transfer member; a cleaning blade for cleaning the toner remaining on the image carrier after the toner image has been transferred to a transfer material; a control unit that executes an initial operation for shifting the image carrier from a brand new state to a printable state, and an image forming operation for forming the toner image on the transfer material; Equipped with an image forming apparatus characterized in that the control unit controls the application means to apply a constant voltage different from that applied during the image forming operation to the transfer member during a second period immediately before a first period in which toner is supplied from the developing member to the image carrier in the development area during the initial operation, and controls the application means so that the constant voltage applied to the transfer member during the second period is a voltage value that has the normal charging polarity of the toner and does not discharge between the image carrier and the transfer member.

2. 2. The image forming apparatus according to claim 1, wherein the control unit controls the application means so that the constant voltage applied to the transfer member during the second period is greater than or equal to -550 V and less than 0 V when the normal charging polarity of the toner is negative.

3. 3. The image forming apparatus according to claim 2, wherein the control unit controls the applying unit so that the constant voltage applied to the transfer member during the second period is −200 V or more and −100 V or less.

4. 2. The image forming apparatus according to claim 1, wherein the control unit controls the application means so that, during a third period after the first period, the constant voltage applied to the transfer member is a voltage value that does not cause discharge between the image carrier and the transfer member.

5. 5. The image forming apparatus according to claim 4, wherein the control unit controls the applying unit so that the constant voltage applied to the transfer member is between −550 V and +550 V during the third period.

6. When the application means is a first application means, a charging member for uniformly charging the surface of the image bearing member; a second applying means for applying a voltage to the charging member; Equipped with The image forming apparatus according to claim 4, wherein the control unit controls the first application means and the second application means so that, during the third period, the second application means applies to the transfer member a voltage that is the same as the voltage applied to the charging member, and the first application means applies to the transfer member a voltage of opposite polarity to the polarity of the voltage applied by the second application means, and the voltage applied to the transfer member becomes the constant voltage.

7. 2. The image forming apparatus according to claim 1, wherein the control unit controls the first period so that there are a plurality of sections in which toner is supplied and a plurality of sections in which toner is not supplied.

8. When the application means is a first application means, a charging member for uniformly charging the surface of the image bearing member; a second applying means for applying a voltage to the charging member; Equipped with 2. The image forming apparatus according to claim 1, wherein the control unit controls the first application means and the second application means so that, during the second period, the second application means applies to the transfer member a voltage that is the same as the voltage applied to the charging member, and the first application means applies to the transfer member a voltage of opposite polarity to the polarity of the voltage applied by the second application means, and the voltage applied to the transfer member becomes the constant voltage.

9. the image forming apparatus is capable of mounting a first image carrier having a first abrasion rate of the surface of the image carrier, and a second image carrier having a surface softer than the first image carrier and having a second abrasion rate greater than the first value; 2. The image forming apparatus according to claim 1, wherein the range of voltages including the constant voltage applied to the transfer member when the second image carrier is installed is narrower than the range of voltages including the constant voltage applied to the transfer member when the first image carrier is installed.

10. a storage unit that stores information about the scraping rate; a cartridge having the storage unit and the image carrier; The image forming apparatus according to claim 9, further comprising:

11. the developing member has a toner carrier that contacts the image carrier; 11. The image forming apparatus according to claim 1, wherein the toner carrier, when new, is coated on its surface with a lubricant containing at least a lubricant having the same polarity as the normal charging polarity of the toner.

Images