JP6617370B2 - Transfer device, image forming apparatus, and life judgment method - Google Patents

Description

  The present invention relates to a transfer device, an image forming apparatus, and a life determination method.

  In general, an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology irradiates (exposes) a charged photosensitive drum (image carrier) with laser light based on image data. To form an electrostatic latent image. Then, by supplying toner from the developing device to the photosensitive drum on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, after the toner image is directly or indirectly transferred to the sheet, the toner image is formed on the sheet by fixing it by heating and pressing at the fixing nip.

  By applying a transfer bias to a transfer member that forms a transfer nip with the photosensitive drum, a transfer electric field is generated between the photosensitive drum and the transfer member, and the charged toner is transferred from the photosensitive drum to the paper. Move to the side. The resistance value of such a transfer member varies as it is used for a long time. When the fluctuation of the resistance value of the transfer member becomes excessive, even if the set transfer bias is applied to the transfer member, the toner cannot be properly transferred to the sheet passing through the transfer nip.

  For example, Patent Document 1 describes a technique for determining the life of a transfer member by detecting the electrical characteristics of the entire transfer member when fluctuations in the resistance value of the transfer member become excessive.

JP 2003-195700 A

  However, if there is a portion where the resistance value fluctuates partially on the transfer member, when a transfer bias is applied to the transfer member, an excessive current flows through the portion where the resistance value of the transfer member is low. Easy to progress. For this reason, the uneven resistance between the portion where the resistance value is low and the portion where the resistance value is not low tends to increase as the life of the transfer member advances, so that the transfer charge applied to the paper becomes uneven. End up. When unevenness occurs in the transfer charge, there arises a problem that an image defect occurs. In addition, when a sheet is electrostatically attracted to a transfer member such as a transfer belt, a problem of separation failure of the sheet with respect to the transfer member occurs due to a marked increase in unevenness of the transfer charge.

  Further, in the configuration described in Patent Document 1, since the life of the transfer member is determined by detecting the electrical characteristics of the entire transfer member, when the partial resistance unevenness of the transfer member as described above occurs, it is accurate. In addition, the life of the transfer member cannot be determined.

  An object of the present invention is to provide a transfer device, an image forming apparatus, and a life determination method capable of accurately determining the life of a transfer member by detecting partial resistance unevenness in the transfer member.

The transfer device according to the present invention is:
An image carrier for carrying a toner image;
A plurality of transfer members used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
Equipped with a,
The life determination unit calculates a cycle of the change amount of the electrical characteristics, specifies the transfer member having a large change amount of the electrical characteristics from the cycle, and determines the life of the specified transfer member. .

An image forming apparatus according to the present invention includes:
An image carrier for carrying a toner image;
A plurality of transfer members used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
Equipped with a,
The life determination unit calculates a cycle of the change amount of the electrical characteristics, specifies the transfer member having a large change amount of the electrical characteristics from the cycle, and determines the life of the specified transfer member. .

The life judging method according to the present invention is:
An image carrier that carries a toner image, a plurality of transfer members that are used to form a transfer nip between the image carrier, and a toner image on the image carrier onto a sheet that passes through the transfer nip. A bias applicator for applying a transfer bias for transferring to the transfer member,
Detecting an electrical characteristic of the transfer member to which the transfer bias is applied;
Calculating a change amount of the electrical characteristic according to a detection result, determining a life of the transfer member based on the calculated change amount of the electrical characteristic;
The cycle of the change amount of the electrical characteristic is calculated, the transfer member having the larger change amount of the electrical property is specified from the cycle, and the life of the specified transfer member is determined .

  According to the present invention, it is possible to accurately determine the life of the transfer member by detecting partial resistance unevenness in the transfer member.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. It is a figure which shows a photoconductive drum and a transfer roller. It is an enlarged view of a transfer nip portion. FIG. 6 is a diagram illustrating an example of a sheet potential with respect to a position in a sheet conveyance direction. It is a figure which shows an example of the fluctuation | variation of the applied voltage in the transfer roller whose change of resistance nonuniformity is wavy. It is a figure which shows the fluctuation | variation of the applied voltage in the state which the deterioration of the transfer roller in FIG. 6 advanced. It is a figure which shows an example of the fluctuation | variation of the applied voltage in the transfer roller in which the resistance value of one part became extremely smaller than the resistance value of another part. It is a figure which shows the fluctuation | variation of the applied voltage in the state in which deterioration of the transfer roller in FIG. 8 advanced. It is a figure which shows the fluctuation | variation of the applied voltage in the state in which deterioration of the transfer roller in FIG. 8 advanced. It is a figure which shows the fluctuation | variation of the applied voltage in a transfer roller after making the output of a transfer bias small. 5 is a flowchart illustrating an example of an operation example when executing transfer roller life determination control in the image forming apparatus. It is a flowchart which shows an example of detailed operation | movement of the lifetime determination control of a transfer roller.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus 1 according to the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the present embodiment.

  The image forming apparatus 1 shown in FIGS. 1 and 2 is a direct transfer type monochrome image forming apparatus using electrophotographic process technology. In other words, the image forming apparatus 1 forms an image by directly transferring a K component (black) toner image formed on the photosensitive drum 213 to a sheet.

  As shown in FIGS. 1 and 2, the image forming apparatus 1 includes an image reading unit 11, an operation display unit 12, an image processing unit 13, an image forming unit 20, a paper feed unit 14, a paper discharge unit 15, a paper transport unit 16, A control unit 17, a bias application unit 80, and a voltage detection unit 81 are provided.

  The control unit 17 includes a CPU (Central Processing Unit) 171, a ROM (Read Only Memory) 172, a RAM (Random Access Memory) 173, and the like. The CPU 171 reads a program corresponding to the processing content from the ROM 172 or the storage unit 182, develops it in the RAM 173, and performs centralized control of the operation of each block of the image forming apparatus 1 in cooperation with the developed program.

  The communication unit 181 includes various interfaces such as a network interface card (NIC), a modem-demodulator (MODEM), and a universal serial bus (USB).

  The storage unit 182 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive. The storage unit 182 stores, for example, a lookup table that is referred to when controlling the operation of each block.

  The control unit 17 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 181. Do. For example, the control unit 17 receives image data (input image data) in a page description language (PDL) transmitted from an external device, and forms an image on a sheet based on the received image data.

  The image reading unit 11 includes an automatic document feeder 111 called an ADF (Auto Document Feeder), a document image scanning device 112 (scanner), and the like.

  The automatic document feeder 111 conveys the document placed on the document tray by the conveyance mechanism and sends it out to the document image scanning device 112. The automatic document feeder 111 can continuously read images (including both sides) of a large number of documents placed on the document tray.

  The document image scanning device 112 optically scans a document conveyed on the contact glass from the automatic document feeder 111 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) Form an image on the light receiving surface of the sensor and read the original image. The image reading unit 11 generates input image data based on the reading result by the document image scanning device 112. The input image data is subjected to predetermined image processing in the image processing unit 13.

  The operation display unit 12 includes, for example, a liquid crystal display (LCD) with a touch panel, and functions as the display unit 121 and the operation unit 122. The display unit 121 displays various operation screens, an image status display, an operation status of each function, and the like according to a display control signal input from the control unit 17. The operation unit 122 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 17. The display unit 121 corresponds to the “notification unit” of the present invention.

  The image processing unit 13 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 13 performs gradation correction based on the gradation correction data under the control of the control unit 17. The image processing unit 13 performs various correction processes such as color correction and shading correction on the input image data. The image forming unit 20 is controlled based on the image data subjected to these processes.

  The image forming unit 20 forms a toner image with a K component toner based on the input image data, and a transfer unit 22 that transfers the toner image formed by the toner image forming unit 21 to a sheet. And a fixing unit 23 for fixing the toner image transferred onto the paper.

  The toner image forming unit 21 includes an exposure device 211, a charging device 212, a photosensitive drum 213, a developing device 214, a drum cleaning device 215, and the like.

  The photosensitive drum 213 has, for example, an undercoat layer (UCL), a charge generation layer (CGL), a charge transport layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube). It is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) in which CTL (Charge Transport Layer) is sequentially laminated.

  The charging device 212 is constituted by a corona discharge generator such as a scorotron charging device or a corotron charging device. The charging device 212 uniformly charges the surface of the photosensitive drum 213 to a negative polarity by corona discharge.

  The exposure apparatus 211 includes, for example, an LED array in which a plurality of light emitting diodes (LEDs) are linearly arranged, an LPH driving unit (driver IC) for driving individual LEDs, and emitted light from the LED array Is formed of an LED print head having a lens array or the like that forms an image on the photosensitive drum 213. One LED of the LED array corresponds to one dot of the image. When the LPH driving unit is controlled by the control unit 17, a predetermined driving current flows through the LED array, and a specific LED emits light.

  The exposure device 211 irradiates the photosensitive drum 213 with light corresponding to a monochrome image. The positive charge generated in the charge generation layer of the photosensitive drum 213 upon receiving light irradiation is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 213 is neutralized. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 213 due to a potential difference from the surroundings.

  The developing device 214 contains a K-component developer (for example, a two-component developer composed of toner and a magnetic carrier). The developing device 214 visualizes the electrostatic latent image to form a toner image by attaching a K component toner to the surface of the photosensitive drum 213. Specifically, a developing bias is applied to the developer carrying member (developing roller), and an electric field is formed between the photosensitive drum 213 and the developer carrying member.

  The drum cleaning device 215 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 213 and removes transfer residual toner remaining on the surface of the photosensitive drum 213 after transfer.

  The transfer unit 22 includes a transfer belt 221, a transfer roller 222, a plurality of support rollers 223, and the like. The transfer belt 221 and the transfer roller 222 correspond to the “transfer member” of the present invention.

  The transfer belt 221 is an endless belt, and is stretched around a plurality of support rollers 223 in a loop shape. At least one of the plurality of support rollers 223 is configured by a driving roller, and the other is configured by a driven roller. As the driving roller rotates, the transfer belt 221 travels and the paper is conveyed at a constant speed.

  The transfer roller 222 is disposed on the inner peripheral surface side of the transfer belt 221 so as to face the photosensitive drum 213. The transfer roller 222 is pressed against the photosensitive drum 213 with the transfer belt 221 interposed therebetween, thereby forming a transfer nip for transferring the toner image from the photosensitive drum 213 to the sheet.

  The bias applying unit 80 is connected to the cored bar 222 </ b> A (see FIG. 4) of the transfer roller 222. A predetermined transfer current flows from the transfer roller 222 to the photosensitive drum 213 by controlling the output of the bias applying unit 80, that is, the transfer bias, by the control unit 17.

  The voltage detector 81 detects the voltage at the transfer belt 221. The voltage detection unit 81 detects the voltage applied to the transfer belt 221 by applying a transfer bias to the transfer roller 222 by the bias application unit 80 and outputs the detected voltage to the control unit 17. The voltage detection unit 81 corresponds to the “detection unit” of the present invention.

  When the paper passes through the transfer nip, the toner image on the photosensitive drum 213 is transferred to the paper. Specifically, a transfer bias is applied to the transfer roller 222 by the bias applying unit 80, and a charge (positive charge) having a polarity opposite to that of the toner is applied to the back side of the sheet, that is, the side in contact with the transfer belt 221. Thus, the toner image is electrostatically transferred onto the paper. The sheet on which the toner image is transferred is conveyed toward the fixing unit 23.

  The fixing unit 23 includes an upper fixing unit 231 having a fixing surface side member disposed on a fixing surface of a sheet, that is, a surface on which a toner image is formed, and a back surface of the sheet, that is, a surface opposite to the fixing surface. A lower fixing unit 232 having a rear surface side support member to be arranged, a heating source 233 for heating the fixing surface side member, and the like are provided.

  The sheet on which the toner image has been transferred and conveyed along the sheet passing path is heated and pressurized when passing through the fixing unit 23. As a result, the toner image is fixed on the paper.

  The paper feed unit 14 includes a paper feed tray unit 141 and a manual paper feed unit 142. In the paper feed tray unit 141, sheets (standard paper, special paper) identified based on basis weight, size, and the like are stored for each preset paper type. The paper feed unit 14 feeds the paper fed from the paper feed tray unit 141 or the manual paper feed unit 142 to the paper transport unit 16.

  The paper discharge unit 15 includes a paper discharge roller unit 151 and the like, and discharges the paper sent from the paper transport unit 16 to the outside of the apparatus. The paper transport unit 16 includes a main transport unit 161, a switchback transport unit 162, a back surface print transport unit 163, and the like.

  The paper fed from the paper feeding unit 14 is conveyed to the image forming unit 20 by the main conveying unit 161. Then, when the sheet passes through the transfer nip, the toner image on the photosensitive drum 213 is collectively transferred to the first surface (front surface) of the sheet, and the fixing unit 23 performs a fixing process. The paper on which the image is formed is discharged out of the apparatus by the paper discharge unit 15. When images are formed on both sides of a sheet, the sheet on which the image is formed on the first side is sent to the switchback conveyance unit 162 and is reversed by returning to the main conveyance unit 161 through the backside printing conveyance unit 163. An image is formed on the second surface (back surface).

  By the way, as shown in FIGS. 3 and 4, for example, when there is a low resistance portion X whose resistance value is partially smaller than other portions in the roller portion 222 </ b> B of the transfer roller 222, transfer is performed to the transfer roller 222 by the bias application unit 80. When a bias is applied, a larger current flows in the low resistance portion X than in other portions. For this reason, the low resistance portion X of the transfer roller 222 is more likely to deteriorate than the other portions. Therefore, the resistance unevenness between the low resistance portion X and the other portions becomes larger as the transfer roller 222 deteriorates.

  FIG. 5 is a diagram illustrating the potential of the sheet with respect to the position in the sheet conveyance direction. A solid line E indicates a detection potential for each position in the sheet conveyance direction. When the deterioration of the transfer roller 222 progresses in this way, only the portion corresponding to the low resistance portion X jumps through and increases as shown in FIG. As a result, the transfer charge transferred to the paper is uneven, and an image defect occurs. In addition, when the unevenness in the transfer charge becomes remarkably large, a separation defect occurs between the transfer belt 221 and the sheet when the sheet is electrostatically attracted to the transfer belt 221.

  Therefore, in the present embodiment, the control unit 17 calculates the amount of change in the voltage value detected by the voltage detection unit 81, and determines the lifetime of the transfer roller 222 and the transfer belt 221 according to the amount of change. Hereinafter, the life determination of the transfer roller 222 and the transfer belt 221 in the control unit 17 will be specifically described.

  In the following description, the transfer roller 222 and the transfer belt 221 are also simply referred to as “transfer members”. Further, the photosensitive drum 213, the transfer belt 221, the transfer roller 222, the bias applying unit 80, the voltage detecting unit 81, and the control unit 17 correspond to the “transfer device” of the present invention, and the control unit 17 of the present invention “ Corresponds to the “life determination unit”.

  The control unit 17 drives the transfer roller 222, the transfer belt 221, and the photosensitive drum 213 during non-image formation, and causes the bias application unit 80 to apply a certain transfer bias to the transfer roller 222.

  The control unit 17 causes the voltage detection unit 81 to detect the voltage applied to the transfer roller 222 and the transfer belt 221 a plurality of times at a constant period for a predetermined time. Specifically, the control unit 17 acquires a detection value of the applied voltage of the transfer belt 221 in the transfer nip from the voltage detection unit 81 every time the transfer belt 221 travels a predetermined distance within a fixed time. The applied voltage corresponds to the “electrical characteristics” of the present invention.

  The fixed time is set to a time required for the transfer belt 221 that is the transfer member having the longer peripheral length of the transfer roller 222 and the transfer belt 221 to make one or more rounds. The predetermined distance is set to a distance that the transfer roller 222 and the predetermined portion of the transfer belt 221 move at a cycle shorter than the time required to pass through the transfer nip because the resistance value on the peripheral surface of the transfer member needs to be detected without shortage. The

Control unit 17, a measured applied voltage V _n, calculating the absolute value of the difference between the applied voltage V _n-1 measured in the previous applied voltage V _n as a voltage change amount [Delta] V _n. Note that n is an arbitrary natural number, and V _n indicates an applied voltage detected n times within a predetermined time. The applied voltage V _n corresponds to the “first electrical characteristic” of the present invention, and the applied voltage V _n−1 corresponds to the “second electrical characteristic” of the present invention.

The control unit 17 selects a maximum value among a plurality of voltage change amounts ΔV _n detected within a predetermined time. The controller 17 sets the maximum absolute value ΔV _{max of the} voltage change amount (hereinafter also simply referred to as “the maximum value of the voltage change amount”) as a first determination value TH1 (for example, 2 V) set in advance. Compare. When it is larger than the first determination value TH1, the control unit 17 determines that the transfer member is at the end of its life because the partial resistance change amount of the transfer member is large. The voltage change amount corresponds to the “change amount of electrical characteristics” of the present invention.

This will be described in detail with reference to FIGS.
First, an example of the transfer roller 222 in which the variation in resistance unevenness in the rotation direction of the transfer roller 222 is wavy will be described. The travel distance of the transfer roller 222 corresponding to the transfer nip in FIGS. 6 to 9 is 2 mm.

  FIG. 6 is a diagram illustrating an example of a variation in applied voltage in the transfer roller 222 in which the variation in resistance unevenness is wavy, and FIG. 7 is a diagram of a variation in applied voltage in a state where the deterioration of the transfer roller 222 in FIG. 6 has advanced. FIG.

Also, solid lines E1, E2, E3, E4, E5, and E6 in FIGS. 6 to 11 indicate measured values of the applied voltage with respect to the travel distance of the transfer roller 222, and broken lines D1, D2, D3, D4 in FIGS. D5, D6 shows the voltage variation [Delta] V _n with respect to the running distance of the transfer roller 222. In addition, a one-dot chain line TH1 in FIGS. 6 to 11 is a first determination value TH1, and is shown as a positive value and a negative value in consideration of an absolute value.

As shown in FIG. 6, when the measured value of the applied voltage, that is, the resistance unevenness of the transfer roller 222 is gentle as a whole, the voltage change amount ΔV _{n at} that time becomes small. This is because if the resistance unevenness of the entire transfer roller 222 is moderate, the amount of fluctuation in the resistance value of the adjacent portion in the rotation direction of the transfer roller 222 becomes small. In the case of FIG. 6, since the voltage change amount is smaller than the first determination value TH1, the control unit 17 does not determine that the transfer roller 222 is at the end of its life.

  When the deterioration of the transfer roller 222 progresses, as shown in FIG. 7, the difference between the maximum value and the minimum value of the applied voltage increases, but the applied voltage fluctuates at a gradual cycle. The fluctuation amount of the resistance value of the adjacent portions in the rotation direction is difficult to increase.

For this reason, in the transfer roller 222 in which the variation in resistance unevenness is wavy, even if the transfer roller 222 is slightly deteriorated and the difference between the maximum value and the minimum value of the applied voltage is increased, image defects are less likely to occur. In FIG. 7, similarly to the case of FIG. 6, the voltage variation [Delta] V _n, is smaller than the first determination value TH1, the control unit 17, the transfer roller 222 is not judged to be life.

  Next, an example of the transfer roller 222 in which the resistance value of one part is extremely smaller than the resistance value of another part will be described. FIG. 8 is a diagram showing an example of fluctuations in the applied voltage in the transfer roller 222 in which the resistance value of one part is extremely smaller than the resistance value of the other part, and FIG. 9 shows the deterioration of the transfer roller 222 in FIG. It is a figure which shows the fluctuation | variation of the applied voltage in the advanced state.

As shown in FIGS. 8 and 9, in the case of the transfer roller 222 in which the resistance value of one part is extremely smaller than the resistance value of the other part, the resistance value fluctuation amount between the part where the resistance value fluctuation is large and the adjacent part. That is, since the partial resistance unevenness is large, the voltage change amount ΔV _n in the part tends to be large. As the deterioration of the transfer roller 222 progresses, the voltage change amount ΔV _n tends to further increase.

When FIG. 7 is compared with FIG. 9, the difference between the maximum value and the minimum value of the applied voltage is substantially the same, but the amount of voltage variation ΔV _n is also gradual as compared with FIG. In FIG. 9 where the fluctuation of the instantaneous resistance value is large, the voltage change amount ΔV _n tends to be large in a portion where the fluctuation of the resistance value is large. Therefore, in the case of the transfer roller 222 in which the resistance value in one part is smaller than the resistance value in the other part, the voltage change amount ΔV _n tends to exceed the first determination value TH1, and image defects are likely to occur.

  Here, in the configuration in which the life of the transfer member is determined based on the electrical characteristics of the entire transfer member, even if the voltage change in a part is large, the transfer member is determined as a whole, and thus such partial resistance unevenness occurs. In some cases, the life of the transfer member cannot be accurately determined. However, in the present embodiment, such partial resistance unevenness can be accurately identified, so that the life of the transfer member can be accurately determined.

If the transfer member has partial resistance unevenness, the voltage change amount ΔV _n tends to exceed the first determination value TH1, so it is desirable to detect the life of the transfer member earlier. FIG. 10 is a diagram illustrating fluctuations in the applied voltage in a state where the deterioration of the transfer roller 222 in FIG. 8 has progressed. A two-dot chain line TH2 in FIG. 10 is the second determination value TH2, and is shown as a positive value and a negative value in consideration of the absolute value.

Therefore, as shown in FIG. 10, when the voltage change amount ΔV _n becomes equal to or larger than the second determination value TH2 (for example, 1V) whose absolute value is smaller than the first determination value TH1, the control unit 17 Judge that life is near. When determining that the life of the transfer member is near, the control unit 17 predicts when the voltage change amount ΔV _n becomes equal to or greater than the first determination value TH1.

Specifically, the control unit 17 causes the storage unit 182 to store the maximum value ΔV _max of the voltage change amount and the number of printed sheets that is the durability count value of the transfer member at that time. Then, the control unit 17 calculates the rate of change of the maximum value ΔV _max of the voltage change amount with respect to the number of printed sheets from the number of printed sheets and the maximum value ΔV _max of the voltage change stored so far, and from the rate of the change The number of printed sheets where the maximum value ΔV _max of the voltage change amount reaches the first determination value TH1 is predicted.

When determining that the life of the transfer member is near, the control unit 17 outputs information indicating that the life of the transfer member is near to the communication unit 181. Specifically, the control unit 17 outputs to the communication unit 181 the number of printed sheets where the maximum voltage change amount ΔV _max reaches the first determination value TH1. The communication unit 181 notifies the information to the outside, that is, a trader who replaces the transfer member. This makes it possible to replace the transfer member at an appropriate time.

  Further, the first determination value TH1 and the second determination value TH2 can be changed values, and can be appropriately set according to the image quality level requested by the user.

When the maximum value ΔV _max of the voltage change amount reaches the first determination value TH1 before the transfer member is replaced, the control unit 17 outputs a warning command for prompting replacement of the transfer member to the display unit 121. When the display unit 121 receives the warning command, the display unit 121 displays a notification that prompts replacement of the transfer member. Thereby, it is possible to prompt the user to replace the transfer member at an appropriate timing.

Further, the control unit 17 controls the bias applying unit 80 so that the transfer bias is such that the maximum value ΔV _max of the voltage change amount is smaller than the first determination value TH1. FIG. 11 is a diagram illustrating fluctuations in the applied voltage at the transfer roller 222 after the transfer bias output is reduced.

For example, in FIG. 9, when the maximum value ΔV _max of the voltage change amount reaches the first determination value TH1, the applied voltage at the set transfer bias is 1600 V, but as shown in FIG. After the maximum value ΔV _max reaches the first determination value TH1, the control unit 17 sets the transfer bias so that the voltage applied to the transfer member becomes small. Specifically, the control unit 17 performs control to reduce the transfer bias by a certain amount (for example, 10 μA when the transfer bias is 100 μA).

As a result, the applied voltage at the transfer bias becomes 1200 V and the maximum value ΔV _max of the voltage change amount becomes small. Therefore, an image defect occurs after the transfer member is determined to have reached the end of its life and before the transfer member is replaced. Can be suppressed.

  Note that when the control unit 17 performs control to reduce the transfer bias, the control unit 17 may control the bias application unit 80 so as to adjust the magnitude of the transfer bias to the extent that no image defect occurs.

By the way, in this embodiment, since the transfer member is composed of a plurality of members such as the transfer roller 222 and the transfer belt 221, when measuring the voltage change amount ΔV _n at the transfer nip, both of the transfer roller 222 and the transfer belt 221 are used. The amount of change obtained by adding the amount of voltage change ΔV _n is measured. Therefore, when the deterioration amount of one member is remarkably larger than the deterioration amount of the other member, it is not preferable from the viewpoint of cost to replace both members.

Therefore, in the present embodiment, the control unit 17 calculates the cycle of the measured voltage change amount ΔV _n , identifies a member having a larger voltage change amount ΔV _n from the cycle, and determines the life of the identified transfer member. Judging. Specifically, the control unit 17 can specify a transfer member having a large deterioration by performing a known analysis method such as frequency analysis such as FFT (Fast Fourier Transform).

An example of the operation when executing the life determination control of the transfer roller 222 in the image forming apparatus 1 including the control unit 17 as described above will be described. FIG. 12 is a flowchart illustrating an example of an operation example when the life determination control of the transfer roller 222 in the image forming apparatus 1 is executed. The process in FIG. 12 is executed when, for example, an instruction to execute life determination control is received. The controller 17 initializes the maximum voltage change amount ΔV _max used in the life determination control when executing the life determination control.

As shown in FIG. 12, the control unit 17 drives the photosensitive drum 213 and the transfer member to turn on the transfer bias (step S101). Next, the control unit 17 measures the applied voltage _{V n} (step S102). Next, the control unit 17 calculates a voltage change amount ΔV _n (step S103).

The control unit 17 compares the maximum voltage change amount ΔV _max used in this control with the calculated voltage change amount ΔV _n and determines whether or not the maximum voltage change amount ΔV _max is smaller than the voltage change amount ΔV _n. (Step S104). As a result of the determination, when the maximum value ΔV _max of the voltage change amount is _{equal to} or greater than the voltage change amount ΔV _n (step S104, NO), the process transitions to step S106. On the other hand, if the maximum value ΔV _max of the voltage change amount is smaller than the voltage change amount ΔV _n (YES in step S104), the control unit 17 calculates the voltage change amount ΔV _max that calculates the maximum value ΔV _max of the voltage change amount used in this control. Update to _n (step S105).

Next, after starting the measurement, the control unit 17 determines whether or not the applied voltage is measured while the transfer member makes one or more turns (step S106). As a result of the determination, when the transfer member has not made one or more turns after the start of measurement (step S106, NO), the process transitions to step S102. On the other hand, if the transfer member has made one or more turns after the start of measurement (step S106, YES), the control unit 17 stores the number of printed sheets and the maximum voltage change amount ΔV _max in the storage unit 182 (step S107). ).

  Next, the controller 17 executes transfer member life determination control (step S108). After step S108, the controller 17 stops the photosensitive drum 213 and the transfer member, turns off the transfer bias (step S109), and ends this control.

  Next, an example of a detailed operation example of the life determination control (step S108 in FIG. 12) of the transfer roller 222 will be described. FIG. 13 is a flowchart illustrating an example of a detailed operation example of the life determination control of the transfer roller 222.

As illustrated in FIG. 13, the control unit 17 determines whether or not the maximum value ΔV _max of the voltage change amount is equal to or greater than the second determination value TH2 (step S201). As a result of the determination, when the maximum value ΔV _max of the voltage change amount is less than the second determination value TH2 (step S201, NO), the control unit 17 ends this control. On the other hand, when the maximum value ΔV _max of the voltage change amount is equal to or greater than the second determination value TH2 (step S201, YES), the control unit 17 determines whether the maximum value ΔV _max of the voltage change amount is equal to or greater than the first determination value TH1. It is determined whether or not (step S202).

As a result of the determination, when the maximum value ΔV _max of the voltage change amount is equal to or greater than the first determination value TH1 (step S202, YES), the control unit 17 controls the communication unit 181 to indicate that the transfer member has reached the end of its life. Notify the outside (step S203). Next, the controller 17 reduces the transfer bias by a certain amount (step S204).

Next, the control unit 17 measures the applied voltage _{V n} of the transfer member (step S205). Next, the control unit 17 calculates a voltage change amount ΔV _n (step S206). Next, the control unit 17 determines whether or not the maximum voltage change amount ΔV _max stored in the storage unit 182 is smaller than the voltage change amount ΔV _n (step S207).

As a result of the determination, when the maximum value ΔV _max of the voltage change amount is _{equal to} or greater than the voltage change amount ΔV _n (NO in step S207), the process transitions to step S209. On the other hand, when the maximum value ΔV _max of the voltage change amount is smaller than the voltage change amount ΔV _n (YES in step S207), the control unit 17 updates the maximum value ΔV _max of the voltage change amount in the storage unit to the voltage change amount ΔV _n . (Step S208).

Next, after starting the measurement, the control unit 17 determines whether or not the applied voltage is measured while the transfer member makes one or more turns (step S209). If the result of determination is that the transfer member has not made more than one turn after the start of measurement (step S209, NO), the process transitions to step S205. On the other hand, when the transfer member has made one or more rounds after the start of measurement (step S209, YES), the control unit 17 determines whether or not the maximum value ΔV _max of the voltage change amount is smaller than the first determination value TH1 (step S209). S210).

As a result of the determination, when the maximum value ΔV _max of the voltage change amount is equal to or greater than the first determination value TH1 (step S210, NO), the process transitions to step S204. On the other hand, when the maximum value ΔV _max of the voltage change amount is smaller than the first determination value TH1 (step S210, YES), the control unit 17 changes the transfer bias (step S211).

Returning to the determination in step S202, when the maximum value ΔV _max of the voltage change amount is smaller than the first determination value TH1 (step S202, NO), the control unit 17 performs frequency analysis on the applied voltage to calculate the period of resistance unevenness. (Step S212).

Next, the control unit 17 identifies a transfer member that has deteriorated from the frequency analysis result (step S213). Next, the control unit 17 calculates a rate of change of the maximum value ΔV _max of the voltage change amount with respect to the specified number of prints of the transfer member (step S214). Next, the control unit 17 predicts the number of printed sheets from which the maximum value ΔV _max of the voltage change amount reaches the first determination value TH1 from the change rate (step S215).

  Next, the control unit 17 controls the communication unit 181 to notify the outside of the number of printed sheets that reach the life of the transfer member (step S216). After step S211 and step S216, the image forming apparatus 1 ends this control.

As described above in detail, the image forming apparatus 1 according to the present exemplary embodiment uses the transfer roller 222 used to form a transfer nip between the photosensitive drum 213 that carries the toner image and the photosensitive drum 213. And a transfer belt 221, a bias applying unit 80 for applying a transfer bias for transferring the toner image on the photosensitive drum 213 to a sheet passing through the transfer nip, and a transfer bias in the range of the transfer nip. The voltage detection unit 81 that detects the applied voltage of the transfer roller 222 and the transfer belt 221 and the voltage detected by the voltage detection unit 81 are acquired a plurality of times at a constant period, and the voltage change amount ΔV _n acquired from the voltage detection unit 81 And a control unit 17 for determining the life of the transfer member according to the above.

According to the present embodiment configured as described above, even when there is partial resistance unevenness in the transfer member, the voltage change amount ΔV _n in the resistance unevenness can be accurately identified, so that the life of the transfer member Can be accurately determined. For this reason, it is possible to suppress the occurrence of image defects due to uneven transfer charges caused by the influence of resistance unevenness, and the transfer belt due to extremely large transfer charge unevenness when the sheet is electrostatically attracted to the transfer belt 221. Occurrence of poor separation between the paper 221 and the paper can be suppressed.

  In addition, since the life of the transfer member can be accurately determined, it is possible to prompt the user to replace the transfer member at an appropriate timing.

  Further, since the applied voltage of the transfer member is acquired at a cycle shorter than the time required for the predetermined portion of the transfer member to pass through the transfer nip, it is possible to detect a deteriorated portion on the transfer member without being insufficient.

Further, since the voltage change amount ΔV _n is calculated from the voltage value at the adjacent portion in the rotation direction of the transfer member, the partial resistance unevenness can be accurately detected.

Further, the rate of change of the maximum value [Delta] V _max of the voltage variation with respect to the number of printed sheets, so predicts the number of copies that the maximum value [Delta] V _max of the voltage change amount reaches a first determination value TH1, the replacement timing of the precise transfer member Can be notified outside.

Further, since specifying the larger becomes the transfer member of the periodic by the voltage variation [Delta] V _n of the voltage variation [Delta] V _n, can transfer member not progressed deterioration can be inhibited from being wastefully replaced.

Further, since the transfer bias is controlled so that the maximum value ΔV _max of the voltage change amount becomes small until the transfer member is replaced after the maximum value ΔV _max of the voltage change amount becomes equal to or greater than the first determination value TH1, It is possible to suppress the occurrence of defects such as image defects before the transfer member is replaced.

  In the above embodiment, the voltage is exemplified as an example of the electrical characteristics. However, the present invention is not limited to this, and for example, when the transfer bias is a voltage, a current may be used. In addition, a resistance value calculated from the acquired voltage or current may be used as the electrical characteristic.

  In the above embodiment, the detection value of the voltage applied to the transfer belt 221 in the transfer nip is acquired from the voltage detection unit 81 every time the transfer belt 221 travels a predetermined distance. However, the present invention is not limited to this. . For example, the voltage applied to the transfer belt 221 in the transfer nip may be acquired from the voltage detection unit 81 every predetermined time. The predetermined time is set to a cycle shorter than the time during which the predetermined portions of the transfer roller 222 and the transfer belt 221 pass through the transfer nip.

  In the above embodiment, the voltage change amount is calculated using the applied voltage of the transfer belt 221 acquired at a cycle shorter than the time during which the predetermined portion of the transfer member passes through the transfer nip. It is not limited to. For example, the detection value of the applied voltage of the transfer belt 221 may be acquired constantly, and the voltage change amount may be calculated using the applied voltage of the transfer belt 221 at regular intervals during the acquisition period.

  Further, in the above embodiment, the portion where the resistance value variation is generated is exemplified by the resistance value lower than that of the other portion. However, in the present invention, the portion where the resistance value variation occurs is more than the other portion. However, the present invention is also applicable to those having a high resistance value.

  In addition, each of the above-described embodiments is merely an example of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 17 Control part 22 Transfer part 80 Bias application part 81 Voltage detection part 213 Photosensitive drum 221 Transfer belt 222 Transfer roller

Claims (22)

An image carrier for carrying a toner image;
A plurality of transfer members used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
Equipped with a,
The life determination unit calculates a cycle of the change amount of the electrical characteristics, specifies the transfer member having a large change amount of the electrical characteristics from the cycle, and determines the life of the specified transfer member. ,
Transfer device. The plurality of transfer members include a transfer roller that forms a transfer nip with the image carrier, and a transfer belt disposed between the transfer roller and the image carrier.
The transfer device according to claim 1. Before Symbol detector, while the transfer member is more than one turn, it detects the electrical properties,
The transfer device according to claim 1 or 2 . The amount of change in the electrical characteristics includes a first electrical characteristic detected by the detection unit and a second electrical characteristic detected by the detection unit one time before the first electrical characteristic is detected. The amount is based on the difference between
The transfer device according to claim 3 . The lifetime determining unit determines the lifetime of the transfer member based on a maximum value of the change amount of the electrical characteristics;
The transfer device according to claim 4 . When the maximum absolute value of the change amount of the electrical characteristics is equal to or greater than a second determination value that is smaller than the first determination value for determining the life of the transfer member, the life determination unit prints The ratio of the change of the maximum absolute value of the change amount of the electrical characteristics to the number of sheets is calculated, and the maximum absolute value of the change amount of the electrical characteristics is determined according to the change ratio. Predict the number of prints to reach
The transfer device according to claim 5 . Before Symbol detection unit, among the plurality of transfer members, detects the electrical characteristic between the most peripheral length long transfer member is more than one turn,
The transfer device according to any one of claims 1-6. The life determination unit controls the bias application unit to reduce the transfer bias when it is determined that the transfer member has a lifetime.
The transfer device according to claim 1. The life determination unit controls the bias applying unit so that the transfer bias becomes such that the maximum value of the change amount of the electrical characteristic is reduced until the transfer member is replaced.
The transfer device according to claim 8. The electrical characteristic is a voltage applied to the transfer member;
The transfer device according to claim 1. The electrical property is a current applied to the transfer member;
The transfer device according to claim 1. The electrical property is a resistance of the transfer member;
The transfer device according to claim 1. An image carrier for carrying a toner image;
A plurality of transfer members used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
Equipped with a,
The life determination unit calculates a cycle of the change amount of the electrical characteristics, specifies the transfer member having a large change amount of the electrical characteristics from the cycle, and determines the life of the specified transfer member. ,
Image forming apparatus. An informing unit for informing the replacement of the transfer member;
The image forming apparatus according to claim 13. A communication unit that communicates information indicating that the life of the transfer member is near to the outside;
The image forming apparatus according to claim 13 or 14. An image carrier that carries a toner image, a plurality of transfer members that are used to form a transfer nip between the image carrier, and a toner image on the image carrier onto a sheet that passes through the transfer nip. A bias applicator for applying a transfer bias for transferring to the transfer member,
Detecting an electrical characteristic of the transfer member to which the transfer bias is applied;
Calculating a change amount of the electrical characteristics according to a detection result, determining a life of the transfer member based on the calculated change amount of the electrical characteristics;
Calculating a cycle of the change amount of the electrical characteristics, specifying the transfer member having a large change amount of the electrical characteristics from the cycle, and determining a life of the specified transfer member;
Life judgment method. An image carrier for carrying a toner image;
A transfer member used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
With
The life determination unit controls the bias application unit to reduce the transfer bias when it is determined that the transfer member has a lifetime.
Transfer device. The life determination unit controls the bias applying unit so that the transfer bias becomes such that the maximum value of the change amount of the electrical characteristic is reduced until the transfer member is replaced.
The transfer device according to claim 17. An image carrier for carrying a toner image;
A transfer member used to form a transfer nip with the image carrier;
A bias applying unit that applies a transfer bias to the transfer member for transferring a toner image on the image carrier to a sheet passing through the transfer nip;
A detection unit for detecting electrical characteristics of the transfer member to which the transfer bias is applied;
A life determination unit that calculates a change amount of the electrical characteristic according to a detection result of the detection unit, and determines a life of the transfer member based on the calculated change amount of the electrical characteristic;
With
The life determination unit controls the bias application unit to reduce the transfer bias when it is determined that the transfer member has a lifetime.
Image forming apparatus. The life determination unit controls the bias applying unit so that the transfer bias becomes such that the maximum value of the change amount of the electrical characteristic is reduced until the transfer member is replaced.
The image forming apparatus according to claim 19. An image carrier for carrying a toner image, a transfer member used for forming a transfer nip between the image carrier and a toner image on the image carrier to a sheet passing through the transfer nip. A bias application unit that applies a transfer bias to the transfer member for determining the life of the transfer device,
Detecting electrical characteristics of the transfer member to which the transfer bias is applied;
Calculating a change amount of the electrical characteristic according to a detection result, and determining a life of the transfer member based on the calculated change amount of the electrical characteristic;
If it is determined that the transfer member has a lifetime, controlling the bias application unit to reduce the transfer bias; and
Lifetime judgment method having In the step of controlling the bias application unit, the bias application unit is controlled so that the transfer bias is such that the maximum value of the change amount of the electrical characteristic is reduced until the transfer member is replaced.
The life judging method according to claim 21.

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