JP6385776B2 - Image forming apparatus - Google Patents

Description

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

  In an electrophotographic image forming apparatus, it is necessary to replace the unit due to the life or failure of a unit important for image formation. However, if the entire unit is replaced, parts that are not the cause of failure may be replaced together. Therefore, in recent years, there are increasing cases in which only some parts of the unit are replaced in order to reduce the running cost of the unit. At this time, unless image adjustment, adjustment of applied bias, etc. are individually optimized according to the characteristic data of the replaced unit, it may cause image defects. In addition, when a life counter that stores individual operation histories is installed, the operation history cannot be managed unless an exchange history is input. Therefore, when replacing the unit, the image forming apparatus is individually optimized by manually inputting characteristic data of the unit to be replaced by a serviceman.

  However, there is a problem that an input error occurs due to manual input, and there is also a problem that it is impossible to determine whether the input data is a correct value. Therefore, there is a method using a bar code instead of manual input. However, in this case, it is expensive to provide the barcode reader in the apparatus main body of the image forming apparatus, and the size of the barcode reader is large. Go backwards

  In addition, with regard to a unit to be replaced by a user, for example, a unit in which parts such as a photosensitive drum or a charging member as an image carrier are integrated, conventionally, when individually optimizing, a memory in which an optimum value is input to each unit. A method is employed in which an image forming apparatus reads the image data and optimizes it.

  However, when more detailed characteristic data such as characteristics of the photosensitive drum and charging member is obtained and individual optimization is to be performed, it is necessary to increase the memory capacity. For this reason, there is a problem in that the price of replacement parts constituting the unit increases, and the running cost of the image forming apparatus increases.

  As described above, Japanese Unexamined Patent Publication No. 9-62152 (Patent Document 1) is disclosed as a technique using a non-volatile memory for investigating unit operation history of an image forming apparatus. In Patent Document 1, the operation history of a unit is obtained and recorded using a rewritable nonvolatile memory. However, since the nonvolatile memory is rewritable and requires a memory capacity for storing operation history data and the like, there is a problem that the cost of the nonvolatile memory and the cost of the transmission / reception unit for reading and writing to the memory are high. there were.

JP-A-9-62152

  As described above, in the conventional image forming apparatus, when the unit is replaced for reasons such as life or failure, there is a problem that labor and cost for adjusting the replaced image forming apparatus are increased.

  Furthermore, when a non-volatile memory is attached to store the operation history of the entire unit as in Patent Document 1, it cannot be detected until the individual parts constituting the unit are replaced. In the market in recent years, there are an increasing number of cases where a part of a unit is replaced for the purpose of reducing the running cost of the unit. For the purpose of dealing with such a case, when one nonvolatile memory is mounted on each part, there is a problem that the cost is increased due to an increase in memory and the cost of a transmission / reception unit that reads from and writes to the memory.

Therefore, an object of the present invention is to easily and inexpensively determine a new part of a part of a unit.

In order to achieve the above object, the present invention comprises an image carrier that carries an image to be formed on a recording medium, and a charging member that charges the image carrier, and the image carrier and the charging member are each replaced. An image forming apparatus capable of applying a voltage to the charging member, a current detecting unit for detecting a current flowing in the image carrier when the voltage applying unit is applied, and the current A storage unit that stores a detection result by the detection unit, and a detection current detected by the current detection unit is greater than or equal to a predetermined difference amount from a previous detection result stored in the storage unit, and in a predetermined current value range. If there is, it is determined that both the image carrier and the charging member have been replaced with new ones, and the first current value range in which the detected current is equal to or greater than the predetermined difference amount and lower than the predetermined current value range If It determines that the image bearing member is the charging member is replaced with a new has not been replaced with a new, second current value range in which the sensed current exceeds the above is a predetermined difference amount or more and the predetermined current value range The charging member is replaced with a new one, and the control unit determines that the image carrier is not replaced with a new one.

According to the present invention, it is possible to easily and inexpensively determine a new part of a part of a unit.

Schematic cross-sectional view showing schematic configuration of image forming apparatus Schematic sectional view showing the layer structure of the photoreceptor The figure which shows the operation | movement sequence of an image forming apparatus. Block diagram showing block circuit of charging bias application system The figure which shows the relationship between the applied voltage and alternating current amount in Example 1. The flowchart which shows the flow of control which judges whether the unit in Example 1 or some parts was replaced | exchanged. Table showing the judgment results for each detected current value in Example 1 The figure which shows the relationship between the applied voltage and alternating current amount in Example 2. The flowchart which shows the flow of control which judges whether the unit in Example 2 or some parts was replaced | exchanged. Table showing the judgment results for each detected current value in Example 2 (A) (b) is a figure which shows the relationship between the applied voltage for every environment in Example 3, and an alternating current amount. The flowchart which shows the flow of control which judges whether the unit in Example 3 or some parts was replaced | exchanged. The flowchart which shows the flow of control which judges whether the unit in Example 3 or some parts was replaced | exchanged. Table showing the judgment results for each detected current value in Example 3

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

[Example 1]
FIG. 1 is a schematic configuration model diagram of an image forming apparatus according to the present embodiment. The image forming apparatus of this example exemplifies a laser beam printer that can change a process speed of image formation and a pixel density of image formation by using a transfer type electrophotographic process, a contact charging method, and a reversal development method.

(1) Overall schematic configuration of printer a) Image carrier 1 is a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier for carrying an image. The photosensitive drum 1 is a negatively chargeable organic photoconductor (OPC) having an outer diameter of 25 mm, and is rotated clockwise as indicated by an arrow with a process speed (peripheral speed) of 100 mm / sec centered on the central support shaft during normal image formation. It is rotationally driven in the direction.

  As shown in the layer configuration model diagram of FIG. 2, the photosensitive drum 1 has an undercoat layer 1b that suppresses light interference and improves the adhesion of an upper layer on the surface of an aluminum cylinder (conductive drum base) 1a. The photocharge generation layer 1c and the charge transport layer 1d (thickness t μm) are applied in order from the bottom.

b) Charging means 2 is a contact charging device (contact charger) as a charging means for uniformly charging the peripheral surface of the photosensitive drum 1, and in this example, a charging roller (roller charger).

  The charging roller 2 is rotatably held at both ends of a cored bar (supporting member) 2a by a bearing member (not shown), and is biased toward the photosensitive drum 1 by a pressing spring 2e. It is in pressure contact with a predetermined pressing force. The charging roller 2 rotates following the rotation of the photosensitive drum 1. A pressure contact portion between the photosensitive drum 1 and the charging roller 2 is a charging portion (charging nip portion) a.

  The charging roller 2 applies a charging bias voltage of a predetermined condition to the cored bar 2a from a power source S1 as a charging voltage applying means, so that the peripheral surface of the photosensitive drum 1 is uniformly negative in this example. Contact charging treatment. The configuration of the charging roller 2 and the discharge current control will be described in detail in the section (4).

c) Information writing means 3 is an exposure device as information writing means for forming an electrostatic latent image on the surface of the charged photosensitive drum 1, and this example is a laser beam scanner using a semiconductor laser. A laser beam modulated in response to an image signal sent from a host device such as an image reading device (not shown) to the printer side is output, and the uniformly charged surface of the photosensitive drum 1 is laser scanned at the exposure position b. (Image scanning exposure). As the laser scanning exposure L lowers the potential of the photosensitive drum 1 surface irradiated with the laser light, electrostatic latent images corresponding to the scanned and exposed image information are sequentially formed on the photosensitive drum 1 surface. .

d) Developing means 4 is a jumping developing device (developer) in this example as developing means for supplying a developer (toner) to the electrostatic latent image on the photosensitive drum 1 to visualize the electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 1 is reversely developed by the developing device 4 with one-component magnetic toner (negative toner) negatively charged.

  4a is a developing container, and 4b is a non-magnetic developing sleeve. The developing sleeve 4b is rotatably disposed in the developing container 4a with a part of its outer peripheral surface exposed to the outside. Reference numeral 4c denotes a magnet roller that is fixed in a non-rotating state and is inserted into the developing sleeve 4b. 4d is a developer coating blade, 4e is a one-component magnetic toner as a developer contained in the developer container 4a, and S2 is a power supply for applying a developing bias to the developing sleeve 4b.

  Then, the surface of the developing sleeve 4b rotating in the counterclockwise direction of the arrow is coated as a thin layer, and the one-component magnetic toner conveyed to the developing unit c is converted into an electrostatic latent image on the surface of the photosensitive drum 1 by an electric field due to the developing bias. Correspondingly selectively adheres. As a result, the electrostatic latent image on the photosensitive drum 1 is developed as a toner image. In the case of this example, the toner adheres to the exposed bright portion of the surface of the photosensitive drum 1 and the electrostatic latent image is reversely developed.

  The developer thin layer on the developing sleeve 4b that has passed through the developing portion c is returned to the developer reservoir in the developing container 4a with the subsequent rotation of the developing sleeve.

e) Transfer means / fixing means / cleaning means 5 is a transfer device, and in this example is a transfer roller. The transfer roller 5 is brought into pressure contact with the photosensitive drum 1 with a predetermined pressing force, and the pressure nip portion is a transfer portion d. A transfer material (recording medium, recording material) P is fed to the transfer portion d from a paper feed mechanism portion (not shown) at a predetermined control timing.

  The transfer material P fed to the transfer part d is nipped and conveyed between the rotating photosensitive drum 1 and the transfer roller 5, and during that time, the negative polarity that is the normal charging polarity of the toner from the power source S 3 is transferred to the transfer roller 5. A positive polarity transfer bias having a reverse polarity is applied. As a result, the toner image on the surface of the photosensitive drum 1 is sequentially electrostatically transferred onto the surface of the transfer material P that is nipped and conveyed by the transfer portion d.

  The transfer material P that has received the transfer of the toner image through the transfer portion d is sequentially separated from the surface of the photosensitive drum 1 and is transported to the fixing device 6 (for example, a heat roller fixing device or a fixing device) to fix the toner image. And output as an image formed product (print, copy).

  Reference numeral 7 denotes a cleaning device. The surface of the photosensitive drum 1 after the toner image is transferred to the transfer material P is rubbed by the cleaning blade 7a to be cleaned to remove the transfer residual toner, and is repeatedly used for image formation. . e is the photosensitive drum surface contact portion of the cleaning blade 7a.

(2) Printer Operation Sequence FIG. 3 is an operation sequence diagram of the printer.

a. Initial rotation operation (front multiple rotation process)
This is a start operation period (start operation period, warming period) when the printer is started. When the power switch is turned on, the photosensitive drum is rotationally driven, and a preparatory operation for a predetermined process device such as raising the fixing device to a predetermined temperature is executed.

  In this embodiment, a determination program for detecting the replacement history of the photosensitive drum 1 that is a photosensitive member or a photosensitive member that is a part of the photosensitive unit and the charging roller 2 that is a charging unit is executed during this initial rotation operation period. This will be described in detail in section (4). Note that the photosensitive unit integrally includes the photosensitive drum 1 and the charging roller 2, and the photosensitive drum 1 and the charging roller 2 can be independently replaced. The photosensitive unit is detachable from the apparatus main body of the image forming apparatus.

b. Print preparation rotation operation (pre-rotation process)
Print signal-This is a preparatory rotation operation period before image formation from when the image formation (printing) process operation is actually performed, and is executed following the initial rotation operation when a print signal is input during the initial rotation operation. Is done. When the print signal is not input, the main motor is temporarily stopped after the initial rotation operation is completed, and the photosensitive drum is stopped from rotating. The printer is kept in a standby (standby) state until the print signal is input. When the print signal is input, the print preparation rotation operation is executed.

  In the present embodiment, during this printing preparation rotation operation period, an appropriate peak-to-peak voltage value (or alternating current value) calculation / determination program for the applied alternating voltage in the charging step of the printing step is executed. This will be described in detail in section (C) of (3).

c. Printing process (image forming process, image forming process)
When the predetermined print preparation rotation operation is completed, an image forming process for the photosensitive drum is subsequently executed, and the toner image formed on the photosensitive drum surface is transferred to a transfer material, and the toner image is fixed by the fixing device. The formation is printed out.

  In the continuous printing (continuous printing) mode, the above printing process is repeated for a predetermined set number of prints n.

d. Inter-sheet process In the continuous printing mode, after the rear end of one transfer material passes the transfer position d, the transfer material at the transfer position until the front end of the next transfer material reaches the transfer position d. This is a non-paper passing period.

e. Post-rotation operation This is a period during which a predetermined post-operation is performed by continuing to drive the main motor for a while after the last transfer material printing process is completed and rotating the photosensitive drum.

f. Standby When the predetermined post-rotation operation is completed, the drive of the main motor is stopped and the rotation of the photosensitive drum is stopped, and the printer is kept in a standby state until the next print start signal is input.

  In the case of printing only one sheet, after the printing is completed, the printer goes into a standby state through a post-rotation operation. When the print start signal is input in the standby state, the printer proceeds to the pre-rotation process.

  The printing process of c is the time of image formation, and the initial rotation operation of a, the printing preparation rotation operation of b, the paper gap process of d, and the post-rotation operation of e are non-image formation.

(3) Detailed description of charging means A) Charging roller The longitudinal length of the charging roller 2 as a contact charging member is 320 mm, and the lower layer 2b and the outer layer of the cored bar 2a as shown in FIG. The intermediate layer 2c and the surface layer 2d are laminated in order from the bottom. The lower layer 2b is a foamed sponge layer for reducing charging noise, the intermediate layer 2c is a conductive layer for obtaining uniform resistance as a whole charging roller, and the surface layer 2d has defects such as pinholes on the photosensitive drum 1. Even if it exists, it is a protective layer provided to prevent leakage.

More specifically, the specification of the charging roller 2 of this example is as follows. The core metal 2a was a stainless steel round bar having a diameter of 6 mm. The lower layer 2b was made of carbon-dispersed foamed EPDM, specific gravity 0.5 g / cm ³ , volume resistivity 10 ³ Ωcm, layer thickness 3.0 mm, and length 320 mm. The intermediate layer 2c was made of carbon-dispersed NBR rubber, a volume resistance value of 10 ⁵ Ωcm, and a layer thickness of 700 μm. The surface layer 2d was made of tin resin and carbon dispersed in a fluororesin resin, volume resistivity 10 ⁸ Ωcm, surface roughness (JIS standard 10-point average surface roughness Ra) 1.5 μm, and layer thickness 10 μm.

B) Charging Bias Application System FIG. 4 is a block circuit diagram of a charging bias application system for the charging roller 2.

  A predetermined vibration voltage (bias voltage Vdc + Vac) obtained by superimposing an AC voltage having a frequency f on a DC voltage from the power source S1 is applied to the charging roller 2 through the cored bar 2a, whereby the peripheral surface of the rotating photosensitive drum 1 is predetermined. Is charged to a potential of. A power source S1 that is a voltage applying unit capable of applying a voltage to the charging roller 2 includes a direct current (DC) power source 11 and an alternating current (AC) power source 12.

  A control circuit 13 serving as a control unit controls on / off of the DC power source 11 and the AC power source 12 of the power source S1 so as to apply a DC voltage, an AC voltage, or a superimposed voltage of both to the charging roller 2. It has a function to control. The control circuit 13 has a function of controlling the DC voltage value applied from the DC power source 11 to the charging roller 2 and the peak-to-peak voltage value of the AC voltage applied from the AC power source 12 to the charging roller 2.

  The AC current value measurement circuit 14 is current detection means for measuring (detecting) the AC current value flowing through the photosensitive drum 1 when a voltage is applied from the power source S1 to the charging roller 2. The measured alternating current value information is input from the alternating current value measurement circuit 14 to the control circuit 13.

  The environment sensor 15 is an environment detection unit (temperature / humidity detection unit, thermometer and hygrometer) that detects an environment such as temperature and humidity where the printer is installed. The detected environmental information (temperature and humidity information) is input from the environmental sensor 15 to the control circuit 13.

  Then, the control circuit 13 determines from the AC current value information input from the AC current value measurement circuit 14 and the environmental information input from the environmental sensor 15 between appropriate peaks of the AC voltage applied to the charging roller 2 in the charging process of the printing process. It has a function of executing a voltage value calculation / determination program.

C) Constant Current Control Next, a method for controlling the alternating current applied to the charging roller 2 during printing will be described. An “AC constant current control method” has been proposed in which an alternating current value that flows by applying an alternating voltage to a charging member is controlled. According to this AC constant current control system, the peak voltage value of the AC voltage is increased in an L / L environment where the material resistance increases, and conversely, the peak voltage value is decreased in an H / H environment where the material resistance decreases. Therefore, increase / decrease in discharge can be suppressed as compared with the AC constant voltage control method. Here, the charging member is not necessarily in contact with the image carrier surface. If even a dischargeable region determined by the gap voltage and the corrected Paschen curve is reliably ensured between the charging member and the image carrier, for example, a gap (gap) of several tens of μm exists and is arranged in a non-contact manner. (Proximity charging). In the present invention, this proximity charging also falls within the category of contact charging.

(4) Operation History Detection of Photosensitive Unit or Part of Photosensitive Member and Charging Member In this embodiment, in the initial rotation operation period, the control circuit (control means) 13 uses the photosensitive unit or part of the photosensitive unit. A determination program for detecting the replacement history of the body (photosensitive drum 1 in this example) and the charging member (charging roller 2 in this example) is executed.

  Specifically, description will be made with reference to FIGS. 5, 6, and 7. FIG. 5 is a graph showing the transition of the amount of current flowing into the photoreceptor via the charging member with respect to the applied voltage. FIG. 6 is a flowchart showing the flow of control for determining whether or not a unit or a part of a unit has been replaced. FIG. 7 is a table showing the determination result based on the detected current value.

  After the initial rotation operation (S6-1) is started, the replacement history detection control (after S6-2) is started. As a method, when a predetermined voltage X (1.0 kV in the present embodiment) as a detection voltage is applied to the charging roller 2, an AC current value flowing through the photosensitive member through the charging member at that time is determined as an AC current value. Measured by the measurement circuit 14 and input to the control circuit 13.

  Next, the control circuit 13 compares the measured current value α (S6-3) with the predetermined current value range set as the predetermined current so that the photosensitive unit or only the photosensitive member is charged. It is possible to detect whether or not some parts such as only members have been replaced. In addition to this, when the current detection result (detection current) is outside the predetermined current value range, an abnormality is detected, and the image forming apparatus is adjusted such that the warning or the printing operation is stopped to prevent the malfunction of the main body. Do. In addition, after performing the replacement history detection control after the initial rotation operation is started and determining the presence or absence of replacement, the determination of the presence or absence of replacement is not performed until the initial rotation operation is performed a predetermined number of times. Even if several print jobs are executed, the measured current value does not change. Therefore, if it is determined each time, for example, after the photoconductor is replaced once, it may be erroneously determined that it has been replaced every time the measurement is performed. is there.

  For example, in the case where the current value α when the voltage of 1.0 kV is applied as the control voltage as in the present embodiment is 700 μA, it is not in the range of 1100 μA (γ) ≧ α> 920 μA (δ). -4). Furthermore, since it is not in the range of 920 μA (δ) ≧ α> 750 μA (ε), which is the predetermined current value range that has been set, it becomes No determination (S6-7), and the first current value as the first current value that falls below this is determined Since the range is 750 μA (ε) ≧ α> 600 μA (ψ), the determination is Yes (S6-10). In this case, in FIG. 7, since it is within the range of case 1 which is the first current value range lower than the range of case 2 which is the predetermined current value range, only the photoconductor is replaced with a new one as the photoconductor unit. It is determined that the member has not been replaced (second-hand goods) (S6-11). Then, the optimum applied bias (1600 μA in this case) corresponding to case 1 as the determination result is determined as the applied bias to the charging means (S6-12), the applied bias control is terminated (S6-16), and the initial rotation is performed. The operation is terminated (S6-17).

  Further, when the current value α when the voltage of 1.0 kV is applied as the control voltage is 800 μA, it is not in the range of 1100 μA (γ) ≧ α> 920 μA (δ), so the determination is No (S6-4). Furthermore, since it is in the range of 920 μA (δ) ≧ α> 750 μA (ε), a Yes determination is made (S6-7). In this case, since it is within the range of case 2 in FIG. 7, it is determined that the photoconductor unit and the charging member have not been replaced or one of them has been replaced with a used product (S6-8). Then, an optimum applied bias (1550 μA in this case) corresponding to the case 2 as the determination result is determined as the applied bias (S6-9), the applied bias control is terminated (S6-16), and the initial rotation operation is terminated. (S6-17).

  Further, when the current value α when a voltage of 1.0 kV is applied as the control voltage is 1000 μA, the second current value range as the second current value exceeding the predetermined current value range is 1100 μA (γ ) ≧ α> 920 μA (δ), so a Yes determination is made (S6-4). In this case, in FIG. 7, since it is within the range of case 3 which is the second current value range exceeding the range of case 2 which is a predetermined current value range, only the charging member is replaced with a new one as the photosensitive unit. It is determined that the body has not been exchanged (second-hand goods) (S6-5). Then, an optimum applied bias (1500 μA in this case) corresponding to Case 3 as the determination result is determined as the applied bias (S6-6), the applied bias control is terminated (S6-16), and the initial rotation operation is terminated. (S6-17).

  Further, when the current value α when the voltage of 1.0 kV is applied as the control voltage is 100 μA, it is not in the range of 1100 μA (γ) ≧ α> 920 μA (δ) which is the second current value range. It becomes a judgment (S6-4). Further, since the predetermined current value range is not in the range of 920 μA (δ) ≧ α> 750 μA (ε), the determination is No (S6-7). Furthermore, since it is not in the range of 750 μA (ε) ≧ α> 600 μA (ψ), which is the first current value range, No determination is made (S6-10). Since 600 μA (ψ) ≧ α, which is lower than the first current value range, a Yes determination is made (S6-13). In this case, in FIG. 7, since it is within the range of Case 4 below the first current value range, it is determined that there is an abnormality in the photoconductor unit (photoconductor or charging means) (S6-13). In addition, the current value α is not the predetermined current value range, the first current value range, and the second current value range, and exceeds the second current value range (α> γ). Similarly, it is determined that there is an abnormality in the photoconductor unit. Then, it is determined to perform error display (notification of abnormality) according to case 4 which is the determination result (S6-15), the applied bias control is terminated (S6-16), and the initial rotation operation is terminated ( S6-17).

  The reason why the relationship between the applied voltage and the current amount changes as shown in FIG. 6 or FIG. 7 when the part of the photosensitive member or the charging member is replaced as the photosensitive member unit, and the optimum at that time. The necessity of changing the applied bias will be described.

[Case 1: Only the photoconductor is replaced]
When the number of operations as a photoconductor unit increases and image defects occur, and the cause is the exhaustion or failure of the photoconductor, replace only the photoconductor that is part of the unit to reduce running costs Is implemented.

  As the number of operations increases as a characteristic of the single photoconductor, the charge transport layer 1d is consumed and the thickness is reduced. As a result, the amount of electric charge that moves per unit time increases due to an increase in the capacitance of the photosensitive member itself, and the amount of current that flows through the photosensitive member via the charging member tends to increase with a constant applied voltage.

  As the characteristics of the charging member alone, as the number of operations increases, the surface resistance increases due to the external additive, which is a high-resistance substance contained in the toner, adhering to the surface layer 2d of itself. Therefore, the amount of current flowing through the photosensitive member via the charging member tends to decrease with a constant applied voltage. In addition, the resistance increases due to the dirt substance adhering to the surface layer 2d, and the amount of current necessary for the disappearance of charging failure increases.

  When the photosensitive member and the charging member are started to be used at the same time as a new photosensitive member unit and the number of operations is repeated (in the case 2), the entire photosensitive member unit of this embodiment has a current due to an increase in the resistance of the charging member. Since the amount of increase in current due to the thinning of the surface layer of the photoreceptor is greater than the amount of decrease in amount, the amount of current flowing to the photoreceptor via the charging member with respect to the applied voltage increases. In addition, since the polarization of the photosensitive layer is promoted by increasing the electrostatic capacity due to the thinning of the surface layer of the photosensitive member, the amount of current required to eliminate the charging failure is reduced.

  However, as in the case of this time, when the surface layer 1d is the thickest in the new state and the photosensitive member that tends to hardly flow current is combined with the charging member in which resistance increases due to contamination of the external additive and current does not flow easily. (Case 1 range) is a case where the photosensitive member and the charging member as a photosensitive unit are used at the same time from a new state and the end of use is reached (the case 2 range). Therefore, the amount of current flowing through the photoconductor decreases, and the amount of current necessary to prevent a defective image such as a charging failure from increasing increases. Therefore, it is necessary to increase the applied bias.

[Case 2: A single item has not been replaced or is equivalent]
As described above, when the photosensitive member and the charging member are started to be used at the same time as a new photosensitive member unit and the number of operations is repeated (in the case 2), the entire photosensitive member unit of this embodiment is charged. Since the amount of current increase due to the thinning of the photoreceptor surface layer is greater than the amount of current decrease due to the increase in resistance, the amount of current flowing to the photoconductor via the charging member with respect to the applied voltage increases.

[Case 3: Only the charging member is replaced separately]
If the number of operations of the photoconductor unit increases and image defects occur, and the cause is the exhaustion or failure of the charging member, replace only the charging member, which is part of the unit, to reduce running costs. Is implemented.

  When the photosensitive member in a state where the film is thinned and the current easily flows as in the case of this time and the charging member in which the resistance does not increase due to the external additive contamination and the current easily flows are combined (case 3) In the case of the photosensitive member unit, the photosensitive member and the charging member are used at the same time from a new state and are used at the end of use (the case 2 range). Since the amount of current flowing through the body increases and the amount of current necessary for not producing a defective image such as a charging failure decreases, the applied bias needs to be lowered.

[Case 4: Abnormal state other than cases 1, 2, 3]
If the amount of current flowing through the charging member via the charging member with respect to an arbitrary applied voltage is outside the range assumed in the cases 1, 2, and 3, the overall resistance or capacity of the photosensitive unit is too high. It is conceivable that there is an abnormality such as the above, or the overall resistance or capacity is too low.

  Examples of the state in which the overall resistance or capacity of the photosensitive unit is detected unexpectedly high include an installation error of the photosensitive unit or a case where it is not installed in the first place. If the printing operation is started without the photoconductor unit being installed, the toner that should originally adhere to the photoconductor unit is scattered in the machine, or the intermediate transfer member that should be originally conveyed along the photoconductor unit This may cause failure such as contact with an unintended part.

  The state in which the overall resistance or capacity of the photoconductor unit is detected unexpectedly low includes an abnormal component assembly state in addition to an installation error of the photoconductor unit. If the assembled state of the photosensitive unit is abnormal and the current easily flows, it may cause a malfunction of the main body such as a current leak to the main body.

  Since the case described above is conceivable, when the range of case 4 is detected, it is determined that there is an abnormality, and it is necessary to prevent a failure by displaying an error display and shifting to a non-printable state.

  As described above, according to the present exemplary embodiment, the process of adjusting the image forming apparatus after replacement of the photosensitive unit or some of the parts thereof is simple and inexpensive without bothering the user or the serviceman. Can be realized. In addition, when an abnormality is detected, the image forming apparatus can be adjusted such that a warning or operation is stopped in order to prevent failure of the apparatus main body.

[Example 2]
This embodiment is an invention that prevents erroneous determination when the initial rotation operation is performed in a short period of time.

  The image forming apparatus according to the present exemplary embodiment includes an operation history of the photosensitive member and / or the charging member in addition to the configuration of the first exemplary embodiment described above in order to prevent erroneous determination when the initial rotation operation is performed in a short period of time. It has a non-volatile memory as a storage means capable of storing at least one control detection current value α ′ before the previous time. In the image forming apparatus according to the present embodiment, the control program 13 executes a determination program for detecting the replacement history of the photosensitive unit or the photosensitive unit that is a part of the photosensitive unit and the charging unit during the initial rotation operation period. The operation history of the photosensitive member and / or the charging member stored in the nonvolatile memory is reset according to the difference between the (detection current) and the control detection current value α ′ as the previous detection result. In addition, depending on the detected value, a process for stopping the printing operation is performed.

  Specifically, description will be made with reference to FIGS. FIG. 8 is a graph showing the transition of the amount of current flowing into the photoconductor via the charging member with respect to the applied voltage. FIG. 9 is a flowchart showing a flow of control for determining whether or not a unit or a part of a unit has been replaced. FIG. 10 is a table showing the determination result based on the detected current value.

  After the initial rotation operation is started, replacement history detection control is started (S8-1), and life counter control of the photosensitive member / charging member is performed (S8-2). As a method, when a predetermined voltage X (1.0 kV in the present embodiment) as a detection voltage is applied to the charging roller 2, an AC current value flowing through the photosensitive member through the charging member at that time is determined as an AC current value. Measured by the measurement circuit 14 and input to the control circuit 13.

  Next, the control circuit 13 compares the measured current value α with the predetermined current value range set as the predetermined current, and the detected current value α ′ at the previous control, thereby comparing the photoconductor unit. However, it is possible to detect whether or not some parts such as only the photoconductor and only the charging means have been replaced. In addition to this, when the current detection result (detection current) is outside the predetermined current value range, an abnormality is detected, and the image forming apparatus is adjusted such that the warning or the printing operation is stopped to prevent the malfunction of the main body. Do.

  For example, when the current value α when the voltage of 1.0 kV is applied as the control voltage is 600 μA as in the present embodiment and the previous control detection current value α ′ is 700 μA (S8-3), it is set. Since the first current value range below the predetermined current value range is 625 μA (g) ≧ α ≧ 575 μA (h), the determination is Yes (S8-14), and the previous detected current value α ′ Since the difference (100 μA) is equal to or greater than a predetermined amount (here, 50 μA or more), a Yes determination is made (S8-15). In this case, since it is within the range of case 1 in FIG. 10, it is determined that only the photoconductor has been replaced with a new one (S8-16). Then, based on the determination result, the life counter of the photoconductor is reset (S8-17), the life counter control is ended (S8-24), and the initial rotation operation is ended (S8-25). Even if the determination is Yes in S8-14, if the difference from the previous detected current value is less than the predetermined amount in S8-15, the determination is No. In this case, since it is case 2 in FIG. 10, based on the determination result, the counter reset is not performed (S8-18), the life counter control is terminated (S8-24), and the initial rotation operation is terminated (S8-). 25).

  Further, when the current value α when a voltage of 1.0 kV is applied as the control voltage is 700 μA and the previous control detection current value α ′ is 600 μA (S8-3), a predetermined predetermined current value range is set. Since it is in the range of 750 μA (e) ≧ α ≧ 700 μA (f), the determination is Yes (S8-9), and the difference (100 μA) from the previous detected current value α ′ is a predetermined amount or more (here, 50 μA or more). Since there is, it becomes Yes judgment (S8-10). In this case, since it is within the range of case 3 in FIG. 10, it is determined that the photoconductor unit and the photoconductor and the charging member are both replaced (S8-11). Then, based on the determination result, the life counters of the photosensitive member and the charging member are reset (S8-12), the life counter control is ended (S8-24), and the initial rotation operation is ended (S8-25). Even if a Yes determination is made at S8-9, if the difference from the previous detected current value is less than a predetermined amount at S8-10, a No determination is made. In this case, since it is case 4 in FIG. 10, from the determination result, the counter reset is not performed (S8-13), the life counter control is terminated (S8-24), and the initial rotation operation is terminated (S8-). 25).

  Further, when the current value α when a voltage of 1.0 kV is applied as the control voltage is 1100 μA and the previous control detection current value α ′ is 900 μA (S8-3), a predetermined current value range that is set Is within the range of 1125 μA (c) ≧ α ≧ 1075 μA (d), which is the second current value range that exceeds the threshold value, the judgment is Yes (S8-4), and the difference (200 μA) from the previous detected current value α ′ is Since there is a predetermined amount or more (here, 50 μA or more), a Yes determination (S8-5) is made. In this case, since it is within the range of case 5 in FIG. 10, it is determined that only the charging member has been replaced with a new one (S8-6). Then, based on the determination result, after resetting the life counter of the charging member (S8-7), the life counter control is finished (S8-24), and the initial rotation operation is finished (S8-25). Even if a Yes determination is made in S8-4, a No determination is made if the difference from the previous detected current value is less than a predetermined amount in S8-5. In this case, since it is case 6 in FIG. 10, based on the determination result, the counter reset is not performed (S8-8), the life counter control is terminated (S8-24), and the initial rotation operation is terminated (S8-). 25).

  When the current value α when the voltage of 1.0 kV is applied as the control voltage is 100 μA (S8-3), the second current value range of 1125 μA (c) ≧ α ≧ 1075 μA (d) Since it is not within the range, the judgment is No (S8-4). Further, since the predetermined current value range is not in the range of 750 μA (e) ≧ α ≧ 700 μA (f), the determination is No (S8-9). Furthermore, since it is not in the range of 625 μA (g) ≧ α ≧ 575 μA (h), which is the first current value range, No determination is made (S8-14). Then, since 575 μA (c)> α, which is lower than the first current value range, is Yes (S8-19). In this case, in FIG. 10, since it is within the range of Case 7 which is lower than the first current value range, it is determined that there is an abnormality in the photoconductor unit (photoconductor or charging means) (S8-20). Note that the current value α is not the predetermined current value range, the first current value range, and the second current value range, and exceeds the second current value range (α> h). Similarly, it is determined that there is an abnormality in the photoconductor unit. Then, it is determined to perform error display (notification of abnormality) according to case 7 which is the determination result (S8-21), the life counter control is finished (S8-24), and the initial rotation operation is finished (S8). -25).

  Further, when the current value α when the voltage of 1.0 kV is applied as the control voltage is 675 μA (S8-3), the current value range falls below the predetermined current value range and exceeds the first current value range. Since it is in the range of 700 μA (f)> α> 625 μA (g), a Yes determination is made (S8-22). The same applies to the case where the current value α falls within the range of 1075 μA (d)> α> 750 μA (e), which is a current value range that falls below the predetermined current value range and exceeds the second current value range. It becomes Yes judgment. In this case, since it is case 8 in FIG. 10, it is determined that no action is taken (S8-23), the life counter control ends (S8-24), and the initial rotation operation ends (S8-25).

  The life counter reset described above sets the operation history of the applicable member to “0”. The unit of the life counter at this time may be the operating time or the number of printed sheets, and it is desirable to select an appropriate unit depending on the product.

  As described above, according to the present exemplary embodiment, the process of adjusting the image forming apparatus after replacement of the photosensitive unit or some of the parts thereof is simple and inexpensive without bothering the user or the serviceman. Can be realized. In addition, when an abnormality is detected, the image forming apparatus can be adjusted such that a warning or operation is stopped in order to prevent failure of the apparatus main body.

Example 3
In the image forming apparatus according to the present embodiment, in addition to the configuration of the first embodiment described above, the control circuit 13 detects the replacement history of the photosensitive unit or a part of the photosensitive unit and the charging unit in the initial rotation operation period. The program is executed by reflecting the environment detection result by the environment sensor 15.

  Specifically, description will be made with reference to FIGS. 11, 12, 13, and 14. FIG. 11 is a graph showing the transition of the amount of current flowing into the photoreceptor via the charging member with respect to the applied voltage. 12 and 13 are flowcharts showing the flow of control for determining whether or not a unit or a part of a unit has been replaced. FIG. 14 is a table showing the determination result based on the detected current value.

  As the resistance value fluctuates in accordance with the temperature / humidity state / durability state of the charging roller, the curve of the amount of current with respect to the applied voltage fluctuates as shown in FIGS. 11 (a) and 11 (b). In this embodiment, the temperature and humidity data detected by the environmental sensor 15 is estimated for the state of the charging roller, and the control flow in the program is changed according to the result of calculating the absolute humidity by the control circuit 13.

  As shown in FIGS. 12 and 13, the printing bias control is started (S10-2) during the initial rotation operation (S10-1). First, the absolute humidity Y introduced by the environmental sensor 15 and the control circuit 13 is determined as an absolute value. It is compared with the reference value α ′ of the water content (S10-3). Here, when the absolute humidity Y is 6.0, compared with the absolute water content reference value α ′ (here, 7.0), since it is in the range of α ′ ≧ Y, a Yes determination is made, and the control circuit 13 performs control flow. Change (transfer) to A. On the other hand, when the absolute humidity Y is 8.0, compared with the absolute water content reference value α ′ (here 7.0), it is not in the range of α ′ ≧ Y, so the determination is No, and the control circuit 13 controls the control flow B. Change (migrate) to.

  In each control flow, when a predetermined voltage X (1.0 kV in the present embodiment) as a detection voltage is applied to the charging roller 2, the AC current value flowing through the photosensitive member through the charging member at that time is determined as the AC current. Measured by the value measuring circuit 14 and input to the control circuit 13.

  Next, as in the first embodiment, the control circuit 13 compares the measured current value α (or current value β) with a predetermined current value range to set the photosensitive unit or It is possible to detect whether or not some parts such as only the photoconductor and only the charging means have been replaced. In addition to this, when the current detection result is outside the predetermined current value range, an abnormality is detected, and the image forming apparatus is adjusted such that the warning or the printing operation is stopped in order to prevent the malfunction of the main body.

  The control flow A after the Yes determination in S10-3 described above is the same as the control flow after S6-3 described in the first embodiment with reference to FIG. The description is omitted. Further, the control flow B after S11-3 after No determination in S10-3 described above is also described in the first embodiment with reference to FIG. 6 although the setting of the current value β and each current value range to be compared is different. Since it is the same as that of the control flow after S6-3, description is abbreviate | omitted.

  As described above, according to the present exemplary embodiment, the process of adjusting the image forming apparatus after replacement of the photosensitive unit or some of the parts thereof is simple and inexpensive without bothering the user or the serviceman. Can be realized. In addition, when an abnormality is detected, the image forming apparatus can be adjusted such that a warning or operation is stopped in order to prevent failure of the apparatus main body.

[Other Examples]
In the above-described embodiments, only the printing operation in mono color (single color) has been described. However, the present invention is not limited to this, and the same effect can be achieved in the printing operation in full color.

  In the embodiment described above, an appropriate peak-to-peak voltage value or alternating current value calculation / determination program is executed in the charging process of the printing process during the print preparation rotation operation period when the printer is not forming an image. However, the present invention is not limited to this. For example, it may be performed during other non-image formation, that is, during initial rotation operation, during a sheet-to-sheet process, during post-rotation process, or may be performed during formation of a plurality of non-images.

Further, the image carrier may be of a direct injection charging type provided with a charge injection layer having a surface resistance of 10 ⁹ to 10 ¹⁴ Ω · cm. Even when the charge injection layer is not used, for example, the same effect can be obtained when the charge transport layer is in the above resistance range. An amorphous silicon photoreceptor having a surface layer volume resistance of about 10 ¹³ Ω · cm may also be used.

  In addition to the charging roller, a flexible contact charging member having a shape or material such as a fur brush, felt, or cloth can be used. Further, by combining various materials, it is possible to obtain more appropriate elasticity, conductivity, surface property, and durability.

  Further, as a waveform of an alternating voltage component (AC component, voltage whose voltage value periodically changes) of the oscillating electric field applied to the contact charging member or the developing member, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. It may be a rectangular wave formed by periodically turning on / off a DC power supply.

  In addition to the laser scanning unit of the above-described embodiment, the image exposure unit as the information writing unit for the charged surface of the photosensitive member as the image carrier is a digital exposure unit using a solid light emitting element array such as an LED. It may be. An analog image exposure unit using a halogen lamp or a fluorescent lamp as a document illumination light source may be used. In short, any device capable of forming an electrostatic latent image corresponding to image information may be used.

  Further, the toner developing method and means for the electrostatic latent image are arbitrary. A reversal development method or a regular development method may be used.

  In general, the electrostatic latent image is developed by coating a non-magnetic toner on a developer carrying member such as a sleeve with a blade or the like, and magnetic toner on a developer carrying member. A method in which an electrostatic latent image is developed in a non-contact state with respect to an image carrier by coating and conveying by force (one-component non-contact development), and coating on a developer carrying member as described above A method for developing an electrostatic latent image by applying toner in contact with an image carrier (one-component contact development), and a developer obtained by mixing a magnetic carrier with toner particles (two-component developer) And a method of developing the electrostatic latent image by conveying it by magnetic force and applying it in contact with the image carrier (two-component contact development), and applying the two-component developer to the image carrier. Apply electrostatic latent image in contact It is roughly divided into four 顛 the method (two-component non-contact development) to the image.

  Further, the transfer means is not limited to the roller transfer of the above-described embodiment, but may be a blade transfer, a belt transfer, other contact transfer charging methods, or a non-contact transfer charging method using a corona charger.

  Further, the present invention can be applied not only to the formation of a single color image by using an intermediate transfer member such as a transfer drum or a transfer belt, but also to an image forming apparatus that forms a multicolor or full color image by multiple transfer or the like.

  In the above-described embodiments, the photosensitive unit is exemplified as a unit that can be attached to and detached from the apparatus main body of the image forming apparatus. However, the present invention is not limited to this. For example, in addition to the photosensitive drum and the charging roller, a unit having a developing unit or a cleaning unit as a process unit that acts on the photosensitive drum may be used. The present invention is also effective when applied to an image forming apparatus in which these units are detachable.

S1, S2, S3 ... power source 1 ... photosensitive drum 2 ... charging roller 3 ... laser beam scanner 4 ... developing device 5 ... transfer roller 7 ... cleaning device 11 ... DC power source 12 ... AC power source 13 ... control circuit 14 ... AC current value measurement Circuit 15: Environmental sensor

Claims (9)

An image forming apparatus comprising: an image carrier that carries an image to be formed on a recording medium; and a charging member that charges the image carrier, wherein the image carrier and the charging member can be respectively replaced.
Voltage applying means for applying a voltage to the charging member;
Current detecting means for detecting a current flowing in the image carrier when the voltage applying means is applied; and
Storage means for storing a detection result by the current detection means;
When the detected current detected by the current detecting means is not less than a predetermined difference amount from the previous detection result stored in the storage means and is in a predetermined current value range, the image carrier and the charging member When the detected current is in the first current value range that is equal to or larger than the predetermined difference amount and lower than the predetermined current value range, the image carrier is replaced with a new one . When it is determined that the charged charging member has not been replaced with a new one and the detected current is equal to or greater than the predetermined difference amount and is in a second current value range exceeding the predetermined current value range, An image forming apparatus comprising: a control unit that determines that a member is replaced with a new one and that the image carrier is not replaced with a new one . The control unit changes a voltage value applied to the charging member by the voltage applying unit when an image is formed on a recording medium in accordance with the image carrier or the charging member determined to be replaced with a new one. The image forming apparatus according to claim 1. Wherein, the detection current, when a current value lower than the first current value range, or when the a second current value greater than the current value range is that error display on the display unit The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   4. The image forming apparatus according to claim 1, wherein the image carrier and the charging member are each attached to a replacement unit that is replaceable with respect to the image forming apparatus in a replaceable manner. 5. . It further has a counting means for counting the operation history of the image carrier and the charging member,
5. The control unit according to claim 1, wherein the control unit resets an operation history counted by the counting unit of the image carrier or the charging member that has been determined to be replaced with a new one . 6. Image forming apparatus. It further has an environment detection means for detecting the environment,
The control means, in response to a detection result of said environment detection means, the image forming apparatus according to any one of claims 1 to 5, wherein changing the value of said predetermined current value range. An image forming apparatus comprising: an image carrier that carries an image to be formed on a recording medium; and a charging member that charges the image carrier, wherein the image carrier and the charging member can be respectively replaced.
Voltage applying means for applying a voltage to the charging member;
Current detecting means for detecting a current flowing in the image carrier when the voltage applying means is applied; and
Storage means for storing a detection result by the current detection means;
Control means capable of changing a voltage value applied to the charging member by the voltage applying means when forming an image on a recording medium,
When the detected current detected by the current detecting means is equal to or greater than a predetermined difference amount from the previous detection result stored in the storage means and is in a predetermined current value range, the control means A voltage value applied to the charging member when both the body and the charging member are replaced with a new one are applied to the voltage applying means, and the detected current is equal to or greater than the predetermined difference amount and the predetermined current When the first current value range is lower than the value range , a voltage value applied to the charging member when the image carrier is replaced with a new one and the charging member is not replaced with a new one is supplied to the voltage applying unit. When the detected current is in a second current value range that is equal to or greater than the predetermined difference amount and exceeds the predetermined current value range, the charging member is replaced with a new one , and the image carrier is a new one. Has been replaced An image forming apparatus comprising a voltage applied to the charging member be applied in the voltage applying means when had. Wherein, the detection current, when a current value lower than the first current value range, or when the a second current value greater than the current value range is that error display on the display unit The image forming apparatus according to claim 7 . An image forming apparatus comprising: an image carrier that carries an image to be formed on a recording medium; and a charging member that charges the image carrier, wherein the image carrier and the charging member can be respectively replaced.
Voltage applying means for applying a voltage to the charging member;
Current detecting means for detecting a current flowing in the image carrier when the voltage applying means is applied; and
Storage means for storing a detection result by the current detection means;
Counting means for counting the operation history of the image carrier and the charging member,
The counting unit is configured to perform the image holding when the detected current detected by the current detecting unit is equal to or greater than a predetermined difference amount from the previous detection result stored in the storage unit and is in a predetermined current value range. The operation history counted by both the body and the charging member is reset, and when the detected current is the first current value range that is equal to or larger than the predetermined difference amount and lower than the predetermined current value range, the count is performed. The operation history of the image carrier is reset , the operation history of the charging member is not reset, and the detected current is equal to or greater than the predetermined difference amount and exceeds the predetermined current value range. An image forming apparatus characterized by resetting the counted operation history of the charging member and not resetting the operation history of the image carrier when it is within the range .