JP6414093B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus, it is known to control a transfer voltage value applied to a primary transfer roller. The transfer voltage value is set so that image formation can be performed satisfactorily.

  For example, in the image forming apparatus described in Patent Document 1, a predetermined voltage is applied to the transfer material before the transfer bias is applied to the transfer material by the transfer roller, and a current value corresponding to the predetermined voltage is set. Detected. The current value is compared with the table to determine the applied voltage at the transfer roller capable of forming the desired image. The applied voltage in Patent Document 1 corresponds to a transfer voltage, and the transfer roller corresponds to a primary transfer roller.

  Patent Document 1 describes that, according to the image forming apparatus, it is possible to appropriately set the applied voltage and to always obtain a high-quality image.

JP 2003-248384 A

  However, in the image forming apparatus described in Patent Document 1, it is considered that it is actually difficult to appropriately set the transfer voltage value of the primary transfer roller. A plurality of primary transfer rollers are used for color printing. In general, the resistance in the plurality of primary transfer rollers is different for each individual. In addition, the resistance of one primary transfer roller also varies, for example, when the environmental temperature changes. Therefore, in order to appropriately set the transfer voltage value, it is necessary to consider individual differences and fluctuations in resistance among a plurality of primary transfer rollers (hereinafter, both are collectively referred to as “resistance variation”). .

  In the image forming apparatus described in Patent Document 1, transfer voltage values in a plurality of primary transfer rollers are set without considering variations in resistance in the plurality of primary transfer rollers. Therefore, in the image forming apparatus described in Patent Document 1, it is difficult to set the transfer voltage value appropriately.

  The present invention has been made in view of the above problems, and the transfer voltage values in the plurality of primary transfer rollers can be satisfactorily formed even when there are variations in resistance in the plurality of primary transfer rollers. An object of the present invention is to provide an image forming apparatus capable of setting the above.

  An image forming apparatus of the present invention is an image forming apparatus that forms an image on a recording medium, and includes a plurality of photosensitive drums, a plurality of primary transfer rollers, a plurality of voltage application units, a current detection unit, a storage unit, and A control unit is provided. The plurality of primary transfer rollers are disposed to face each of the plurality of photosensitive drums. The plurality of voltage application units apply a voltage to each of the plurality of primary transfer rollers. The current detection unit detects a current value of a current flowing through each of the plurality of primary transfer rollers. The storage unit stores a transfer voltage value applied to each of the plurality of primary transfer rollers. The control unit updates the transfer voltage value for each of the plurality of primary transfer rollers. The control unit newly calculates the transfer voltage value corresponding to the specific primary transfer roller based on the current value flowing through the specific primary transfer roller among the plurality of primary transfer rollers. To do. In addition, the control unit may store the transfer voltage value stored in correspondence with another primary transfer roller that is different from the specific primary transfer roller among the plurality of primary transfer rollers, and the difference. Based on this, the transfer voltage value corresponding to the other primary transfer roller is newly calculated.

  According to the image forming apparatus of the present invention, it is possible to set the transfer voltage values in the plurality of primary transfer rollers so that the image can be formed satisfactorily even when the resistances in the plurality of primary transfer rollers vary. it can.

1 is a side view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view illustrating configurations of an image forming unit and a transfer unit illustrated in FIG. 1. It is a side view which shows the structure of the power supply part shown in FIG. It is a figure which shows the structure of the control part shown in FIG. 6 is a graph showing variations in voltage-current characteristics among a plurality of primary transfer rollers. It is a graph which shows the voltage value of the detection voltage in a 1st mode. It is a graph which shows the electric current value for calculating | requiring a transfer voltage value in a 1st mode. It is a graph which shows the voltage value of the detection voltage in a 2nd mode. It is a flowchart which shows operation | movement of the voltage control part shown in FIG. 6 is a graph showing transfer voltage values for obtaining a new transfer voltage value in another primary transfer roller in the first mode. It is a graph which shows the voltage value of the detection voltage in a 3rd mode. 12 is a graph showing a current value for obtaining a transfer voltage value in a specific primary transfer roller in a third mode. 6 is a flowchart illustrating an operation of a voltage control unit in the second embodiment. 10 is a flowchart showing an operation of a voltage control unit in Modification 2.

  Embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 14). In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

Embodiment 1
First, an image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 1 according to the present embodiment. In the present embodiment, the image forming apparatus 1 is a color copying machine.

  The image forming apparatus 1 is an apparatus that forms an image on a sheet P, and includes a housing 10, a paper feeding unit 2, a transport unit L, a toner supply unit 3, an image forming unit 4, a transfer unit 5, a power supply unit 6, A fixing unit 7, a discharge unit 8, and a control unit 9 are provided. The paper P corresponds to an example of “recording medium”.

  The paper feed unit 2 is disposed at the lower part of the housing 10 and supplies the paper P to the transport unit L. The paper feed unit 2 can accommodate a plurality of sheets P, and supplies the uppermost sheet P one by one to the transport unit L.

  The transport unit L transports the paper P supplied by the paper feed unit 2 to the discharge unit 8 via the transfer unit 5 and the fixing unit 7.

  The toner supply unit 3 is a container that supplies toner to the image forming unit 4 and includes four toner cartridges 3y, 3c, 3m, and 3k. The toner cartridge 3y contains yellow toner. The toner cartridge 3c contains cyan toner. The toner cartridge 3m contains magenta toner. The toner cartridge 3k contains black toner.

  The image forming unit 4 includes four image forming units 4y, 4c, 4m, and 4k. Yellow toner is supplied from the toner cartridge 3y to the image forming unit 4y. Cyan toner is supplied from the toner cartridge 3c to the image forming unit 4c. Magenta toner is supplied from the toner cartridge 3m to the image forming unit 4m. Black toner is supplied to the image forming unit 4k from the toner cartridge 3k. The configuration of the image forming unit 4 will be described later with reference to FIG.

  The transfer unit 5 includes an intermediate transfer belt 54. The transfer unit 5 transfers the toner image formed on the intermediate transfer belt 54 onto the paper P by the image forming unit 4. The configuration of the transfer unit 5 will be described later with reference to FIG.

  The power supply unit 6 applies a voltage to the transfer unit 5. The power supply unit 6 detects the current value of the current flowing through the transfer unit 5. The configuration of the power supply unit 6 will be described later with reference to FIG.

  The fixing unit 7 is a roller pair that fixes the toner image formed on the paper P by the transfer unit 5, and includes a heating roller 71 and a pressure roller 72. The paper P is heated and pressed by the heating roller 71 and the pressure roller 72. As a result, the fixing unit 7 fixes the unfixed toner image transferred to the paper P in the transfer unit 5. The discharge unit 8 discharges the paper P on which the toner image is fixed to the outside of the apparatus.

  The control unit 9 controls the operation of the image forming apparatus 1. The configuration of the control unit 9 will be described later with reference to FIG.

  Next, the configuration of the image forming unit 4 and the transfer unit 5 will be described with reference to FIG. FIG. 2 is a side view illustrating the configuration of the image forming unit 4 and the transfer unit 5. As shown in FIG. 2, the image forming unit 4 includes four image forming units 4y, 4c, 4m, and 4k.

  Each of the image forming units 4y, 4c, 4m, and 4k includes an exposure device 41, a photosensitive drum 42, a developing unit 43, a charging roller 44, and a cleaning blade 45. The configurations of the four image forming units 4y, 4c, 4m, and 4k are substantially the same except for the color of the supplied toner. Therefore, in this specification, the configuration of the image forming unit 4y will be described, and the description of the configuration of the image forming units 4c, 4m, and 4k other than the image forming unit 4y will be omitted.

  The image forming unit 4y includes an exposure unit 41y (41), a photosensitive drum 42y (42), a developing unit 43y (43), a charging roller 44y (44), and a cleaning blade 45y (45).

  The charging roller 44y charges the photosensitive drum 42y to a predetermined potential. The exposure unit 41y exposes the photosensitive drum 42y by irradiating a laser beam to form an electrostatic latent image on the photosensitive drum 42y. The developing unit 43y includes a developing roller 431y. The developing roller 431y supplies yellow toner to the photosensitive drum 42y to develop the electrostatic latent image to form a toner image. As a result, a yellow toner image is formed on the peripheral surface of the photosensitive drum 42y.

  The front end (upper end in FIG. 2) of the cleaning blade 45y is in sliding contact with the peripheral surface of the photosensitive drum 42y. The yellow toner remaining on the peripheral surface of the photosensitive drum 42y is removed by the sliding contact between the peripheral surface of the photosensitive drum 42y and the tip of the cleaning blade 45y.

  The transfer unit 5 transfers the toner image onto the paper P. The transfer unit 5 includes four primary transfer rollers 51 (51y, 51c, 51m, 51k), a secondary transfer roller 52, a driving roller 53, an intermediate transfer belt 54, a driven roller 55, and a blade 56.

  The transfer unit 5 superimposes the toner images formed on the photosensitive drums 42 (42y, 42c, 42m, and 42k) of the image forming units 4y, 4c, 4m, and 4k on the intermediate transfer belt 54 after overlapping them. The toner image thus transferred is transferred from the intermediate transfer belt 54 to the paper P.

  The primary transfer roller 51y is disposed to face the photosensitive drum 42y with the intermediate transfer belt 54 interposed therebetween. The primary transfer roller 51y can be pressed against the photosensitive drum 42y via the intermediate transfer belt 54 or can be separated from the photosensitive drum 42y by a driving mechanism (not shown). The primary transfer roller 51y is normally pressed against the photosensitive drum 42y via the intermediate transfer belt 54. The other primary transfer rollers 51c, 51m, 51k are also in pressure contact with the corresponding photosensitive drums 42 (42c, 42m, or 42k) via the intermediate transfer belt 54, similarly to the primary transfer roller 51y.

  The drive roller 53 is disposed to face the secondary transfer roller 52 and drives the intermediate transfer belt 54.

  The intermediate transfer belt 54 is an endless belt that is stretched around four primary transfer rollers 51, a drive roller 53, and a driven roller 55. The intermediate transfer belt 54 is driven to rotate counterclockwise by the driving roller 53 as shown by arrows F1 and F2 in FIG. Further, the surface side of the intermediate transfer belt 54 is in contact with the peripheral surface of each photosensitive drum 42 (42y, 42c, 42m, 42k). A toner image is transferred from the photosensitive drum 42 (42y, 42c, 42m, 42k) to the surface of the intermediate transfer belt 54 by the primary transfer roller 51 (51y, 51c, 51m, 51k).

  The driven roller 55 is driven to rotate as the intermediate transfer belt 54 rotates. A blade 56 is disposed at a position facing the driven roller 55 via the intermediate transfer belt 54. The blade 56 removes toner remaining on the surface of the intermediate transfer belt 54.

  The secondary transfer roller 52 is pressed against the drive roller 53. As a result, a nip N is formed between the secondary transfer roller 52 and the drive roller 53. The secondary transfer roller 52 and the drive roller 53 transfer the toner image on the intermediate transfer belt 54 to the paper P when the paper P passes through the nip portion N.

  Next, the power supply unit 6 will be described with reference to FIG. FIG. 3 is a side view showing the configuration of the power supply unit 6. The power supply unit 6 includes a voltage application unit 61 and a current detection unit 62. Further, a voltage is applied to the primary transfer roller 51 by a voltage application unit 61.

  The voltage application unit 61 includes four voltage application units 61y, 61c, 61m, and 61k. The four voltage application units 61y, 61c, 61m, and 61k apply voltages to the primary transfer rollers 51y, 51c, 51m, and 51k, respectively. For example, the voltage application unit 61y applies a voltage to the primary transfer roller 51y. The photosensitive drum 42 (42y, 42c, 42m, 42k) is grounded. As a result, the voltage application unit 61 y applies a voltage between the primary transfer roller 51 and the photosensitive drum 42.

  The current detection unit 62 detects the total current value JS of the current flowing through each of the four primary transfer rollers 51y, 51c, 51m, and 51k. Note that the number of current detection units 62 is not limited to one. Four current detection units 62 (not shown) may be provided corresponding to the four primary transfer rollers 51y, 51c, 51m, and 51k. In this case, each of the four current detection units 62 detects a current flowing through the corresponding primary transfer roller 51.

  Next, the configuration of the control unit 9 will be described with reference to FIG. FIG. 4 is a diagram illustrating a configuration of the control unit 9. The control unit 9 includes a CPU (Central Processing Unit) and a memory. A control program is stored in the memory. The CPU functions as various functional units by executing the control program. Further, the CPU causes the memory to function as various functional units by executing a control program. As a result, various functional units of the control unit 9 control the operation of the image forming apparatus 1. The control unit 9 includes a voltage control unit 911, a current acquisition unit 912, a correction unit 914, and a voltage / current storage unit 92. The voltage controller 911 updates the transfer voltage value applied to the primary transfer roller 51 for each of the four primary transfer rollers 51y, 51c, 51m, and 51k. The voltage control unit 911 corresponds to a “control unit”, and the voltage / current storage unit 92 corresponds to a “storage unit”.

  The voltage / current storage unit 92 stores the voltage value VT of the voltage applied to the primary transfer roller 51 by the voltage application unit 61 and the total current value JS detected by the current detection unit 62 in association with each other. The voltage value VT and the total current value JS of the voltage stored in the voltage / current storage unit 92 are read by the correction unit 914. Further, the voltage / current storage unit 92 stores transfer voltage value information. The transfer voltage value information will be described later.

  First, a method for obtaining the current value of the current flowing through each of the four primary transfer rollers 51y, 51c, 51m, and 51k from the total current value JS will be described.

  The voltage control unit 911 controls the voltage applied by the voltage application unit 61 to the primary transfer rollers 51y, 51c, 51m, and 51k. Specifically, when applying the detection voltage VS to one primary transfer roller 51 among the four primary transfer rollers 51, the voltage control unit 911 applies to all the other primary transfer rollers 51. A first voltage having the same polarity as the detection voltage VS is applied. One primary transfer roller 51 is, for example, a primary transfer roller 51y, and all other primary transfer rollers 51 are, for example, primary transfer rollers 51c, 51m, and 51k. The detection voltage VS is a voltage applied to detect the resistance value R between the primary transfer roller 51 and the photosensitive drum 42, and has a preset voltage value (for example, 1000 V). The first voltage has a voltage value (for example, 100 V) that is 1/200 to 1/10 of the voltage value of the detection voltage VS.

  The voltage controller 911 applies the second voltage to all four primary transfer rollers 51y, 51c, 51m, and 51k.

  Further, the voltage controller 911 applies detection voltages VS having a plurality of different voltage values to one primary transfer roller 51 (for example, the primary transfer roller 51y), and all other primary transfer rollers 51. A first voltage is applied to (for example, the primary transfer rollers 51c, 51m, and 51k).

  The current acquisition unit 912 acquires the total current value JS detected by the current detection unit 62. The current acquisition unit 912 records the total current value JS in the voltage / current storage unit 92 in association with the voltage values of the voltages applied by the voltage application unit 61 to the four primary transfer rollers 51y, 51c, 51m, and 51k. To do.

  The voltage / current storage unit 92 stores transfer voltage values E1y, E1c, E1m, and E1k as transfer voltage value information for each of the four primary transfer rollers 51y, 51c, 51m, and 51k. The transfer voltage value information can be updated under the control of the voltage control unit 911. The initial value of the transfer voltage value information is stored in the voltage / current storage unit 92 when the image forming apparatus 1 is manufactured, for example.

  FIG. 5 is a graph showing variations in voltage-current characteristics among a plurality of primary transfer rollers. The horizontal axis X1 of the graph is a voltage axis, and indicates the voltage value VT of the voltage applied by the voltage application unit 61 to each of the four primary transfer rollers 51y, 51c, 51m, and 51k. The vertical axis Y1 of the graph indicates the current value I of the current flowing through each of the four primary transfer rollers 51y, 51c, 51m, and 51k. Curves L11, L12, L13, and L14 are voltage-current characteristic curves for the four primary transfer rollers 51y, 51c, 51m, and 51k when the environmental temperature T is 23 ° C. and the relative humidity H is 50%. Hereinafter, this is simply referred to as a characteristic curve). Curves L15, L16, L17, and L18 are characteristic curves for the four primary transfer rollers 51y, 51c, 51m, and 51k when the environmental temperature T is 10 ° C. and the relative humidity H is 15%. In this specification, “curve” is used as a concept including “straight line”.

  The resistance values R of the four primary transfer rollers 51y, 51c, 51m, and 51k are different from each other. Therefore, as shown in FIG. 5, the transfer voltage value E1 (E1y, E1c, E1m, E1k) that allows the current of the current value IG to flow through each of the four primary transfer rollers 51y, 51c, 51m, 51k is Different from each other.

  When the environmental temperature T and the relative humidity H change, the resistance value R in the primary transfer roller 51 (51y, 51c, 51m, 51k) also changes. As a result, the characteristic curve of the primary transfer roller 51 (51y, 51c, 51m, 51k) is translated in the direction of the horizontal axis X1. In the illustrated example, when the environmental temperature T is 23 ° C. and the relative humidity H is 50%, the transfer voltage value E1k in the primary transfer roller 51k is 1100 volts, and the transfer voltage value in the primary transfer roller 51y. E1y is 900 volts. On the other hand, when the environmental temperature T is 10 ° C. and the relative humidity H is 15%, the transfer voltage value E1y in the primary transfer roller 51k is 2100 volts, and the transfer voltage value E1k in the primary transfer roller 51y is 1900. It is a bolt.

  In FIG. 5, fluctuations in the environmental temperature T and the relative humidity H are cited as factors that cause the characteristic curves of the primary transfer rollers 51 (51y, 51c, 51m, 51k) to shift. However, the factors that cause the resistance value R to fluctuate in the primary transfer rollers 51 (51y, 51c, 51m, 51k) are not limited to the environmental temperature T and the humidity H. For example, when toner adheres to the intermediate transfer belt 54, the resistance of the intermediate transfer belt 54 (hereinafter referred to as belt resistance) increases. As the belt resistance increases, the resistance value R at the primary transfer rollers 51 (51y, 51c, 51m, 51k) increases, and the characteristic curve shifts in the direction of the horizontal axis X1. Further, even when images are continuously formed on a large number of sheets P, the temperature of the primary transfer roller 51 (51y, 51c, 51m, 51k) rises, and the primary transfer roller 51 (51y, 51c, 51m, The resistance of 51k) increases. As a result, the characteristic curve shifts in the direction of the horizontal axis X1. Even if the resistance value R in the primary transfer rollers 51 (51y, 51c, 51m, 51k) varies due to the belt resistance variation, the resistance values R in the four primary transfer rollers 51y, 51c, 51m, 51k are large or small. The relationship does not change.

  FIG. 6 is a graph showing the voltage value of the detection voltage in the first mode. In the first mode, a plurality of detection voltages having a plurality of voltage values are applied to a specific primary transfer roller. In FIG. 6, graphs G1, G2, G3, and G4 show voltage values VTy, VTc, VTm, and VTk of detection voltages applied by the voltage application unit 61 to the four primary transfer rollers 51y, 51c, 51m, and 51k, respectively. Show. In the example shown in FIG. 6, as shown in the graph G4, a plurality of detection voltages having a plurality of different voltage values V1, V2, and V3 are applied to the primary transfer roller 51k. On the other hand, a detection voltage of 0 (zero) volts is always applied to the other primary transfer rollers 51y, 51c, and 51m, as shown in the graphs G1, G2, and G3.

  In FIG. 6, a period from time T1 to time T2 is a preparation period until the detection voltage is applied to the primary transfer roller 51k. In the preparation period, a process for removing the toner adhering to the surface of the intermediate transfer belt 54 by the blade 56 is performed. At the time T2 when the preparation period ends, the surface of the intermediate transfer belt 54 is in a state where no toner is attached. Specifically, in the intermediate transfer belt 54, at least a region extending from a position facing the primary transfer roller 51y to a position facing the primary transfer roller 51k is in a state where toner is not attached. Then, at time T2, application of a plurality of detection voltages is started.

  FIG. 7 is a graph showing a current value for obtaining a transfer voltage value in the first mode. According to the graph of FIG. 7, the voltage control unit 911 newly calculates a transfer voltage value E1k corresponding to the specific primary transfer roller 51k based on the current value I of the current flowing through the specific primary transfer roller 51k. The horizontal axis X2 of the graph indicates the voltage value VTk at a specific primary transfer roller 51k. The vertical axis Y2 of the graph represents the current value Ik in the primary transfer roller 51k. In FIG. 7, points P1, P2, and P3 indicate the results of the current detection unit 62 detecting the current flowing through the specific primary transfer roller 51k for each of a plurality of voltage values. The current value Ik corresponding to the voltage value VTk of 700 volts is the current value Ik1, the current value Ik corresponding to the voltage value VTk of 1000 volts is the current value Ik2, and the current value Ik corresponding to the voltage value VTk of 1300 volts. Is the current value Ik3.

  The current value IG of the prescribed transfer current is larger than the current value Ik2 at the point P2 and smaller than the current value Ik3 at the point P3. Therefore, the transfer voltage value E1k (= 1100 volts) can be determined from the intersection point P4 of the line segment L1 obtained by linear interpolation between the points P2 and P3 and the straight line L2 indicating the current value IG. A line segment L1 approximately represents a characteristic curve in the primary transfer roller 51k. The line segment L1 has an inclination a1. The method for obtaining the characteristic curve of the primary transfer roller 51k is not limited to linear interpolation, and for example, it can be obtained from the points P1, P2, and P3 by the least square method.

  FIG. 8 is a graph showing the voltage value of the detection voltage in the second mode. In the second mode, a plurality of detection voltages are respectively applied to a predetermined number of all primary transfer rollers. In FIG. 8, graphs G11, G12, G13, and G14 show voltage values VTy, VTc, VTm, and VTk of voltages applied by the voltage application unit 61 to the four primary transfer rollers 51y, 51c, 51m, and 51k, respectively. ing.

  In the example shown in FIG. 8, as shown in the graph G11, a plurality of detection voltages having a plurality of different voltage values V11, V12, and V13 are applied to the primary transfer roller 51y. As shown in the graph G12, a plurality of detection voltages having a plurality of different voltage values V21, V22, and V23 are applied to the primary transfer roller 51c. As shown in the graph G13, a plurality of detection voltages having a plurality of different voltage values V31, V32, and V33 are applied to the primary transfer roller 51m. As shown in the graph G14, a plurality of detection voltages having a plurality of different voltage values V41, V42, and V43 are applied to the primary transfer roller 51k.

  The period from time T1 to time T2 is the preparation period described with reference to FIG. At time T2 when the preparation period ends, a process of applying detection voltages of a plurality of voltage values V11, V12, and V13 to the primary transfer roller 51y is started.

  When the process of applying detection voltages having a plurality of voltage values V11, V12, and V13 to the primary transfer roller 51y is completed at time T21, the primary transfer roller 51c continues to have a plurality of voltage values V21, V22, and V23. Processing for applying the detection voltage is started. Furthermore, when the process of applying the detection voltages having the plurality of voltage values V21, V22, and V23 to the primary transfer roller 51c is completed at time T22, the plurality of voltage values V31, V32, and V33 are continuously applied to the primary transfer roller 51m. The process of applying the detection voltage having is started. Further, when the application process for applying the detection voltages having the plurality of voltage values V31, V32, and V33 to the primary transfer roller 51m is completed at time T23, the plurality of voltage values V41, V42, The process of applying the detection voltage having V43 is started.

  In the embodiment, the polarity of the toner is positive. Therefore, the voltage value VT is actually negative. However, in order to facilitate understanding, in FIGS. 5 to 8 and FIGS. 10 to 12, the voltage value VT is shown as an absolute value. The present invention is also applicable when the toner has a negative polarity and the voltage value VT has a positive polarity.

  Next, the operation of the control unit will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the voltage control unit. In the processing shown in FIG. 9, the voltage control unit 911 performs transfer corresponding to a specific primary transfer roller based on a current value of a current flowing through the specific primary transfer roller among a predetermined number of primary transfer rollers. A new voltage value is calculated. Specifically, first, the voltage control unit 911 acquires status information of the image forming apparatus 1 (S101). The status information indicates the state of the image forming apparatus 1. For example, the status information includes whether the image forming apparatus 1 is in a sleep state, whether the image forming apparatus 1 is immediately after startup, and whether the image forming apparatus 1 is continuously performing image formation. Indicates.

  Next, the voltage control unit 911 performs a determination process for switching between the first mode and the second mode according to the status information (S102). In the determination process in step S102, either the first mode or the second mode is selected. In the first mode, a new transfer voltage value E1k corresponding to a specific primary transfer roller 51k and new transfer voltage values E1y, E1c, E1m corresponding to the other primary transfer rollers 51y, 51c, 51m are calculated. Is done. In the second mode, the transfer voltage values E1y, E1c, E1m, E1k of all four primary transfer rollers 51y, 51c, 51m, 51k are directly calculated.

  The control operation in the second mode is executed when there is no urgent image formation request to the image forming apparatus 1 and there is time allowance, for example, the image forming apparatus 1 is in a ready state after the end of the printing process. . Further, the control operation in the second mode is executed when it is expected that the resistance value R in the primary transfer roller 51 is greatly changed. For example, the control operation of the second mode is executed when image formation on a relatively large number of sheets P is completed and when the environmental temperature T and / or the relative humidity H fluctuate greatly. On the other hand, in the control operation in the first mode, it is expected that the resistance value R in the primary transfer roller 51 varies, but there is an urgent image formation request to the image forming apparatus 1 and there is a time margin. It is executed when there is not. For example, when image formation on a relatively large number of sheets (for example, 1000 sheets) is continuously performed, image formation on a predetermined number of sheets (for example, 100 sheets) is performed. The control operation of the first mode is executed every time it is completed.

  If it is determined in step S102 that the control operation in the first mode is to be performed, as shown in FIG. 6, the voltage application unit 61k has a plurality of detections having a plurality of voltage values V1, V2, and V3 that change stepwise. A voltage is applied to the specific primary transfer roller 51k (S103). At this time, the current detection unit 62 detects the current value Ik of the current flowing through the specific primary transfer roller 51k for each of the plurality of voltage values V1, V2, and V3.

  Next, a new transfer corresponding to the specific primary transfer roller 51k based on the characteristic curve (for example, the line segment L1 in FIG. 7) in the specific primary transfer roller 51k and the current value IG of the specified transfer current. A voltage value E1k is calculated (S104). Next, the difference D11 is calculated (S105). The difference D11 is the transfer voltage value E1k stored in the voltage / current storage unit 92 corresponding to the specific primary transfer roller 51k and the transfer newly calculated in step S104 corresponding to the specific primary transfer roller. It is a difference from the voltage value E1k.

  Next, another primary transfer is performed on the basis of the transfer voltage values E1y, E1c, E1m stored in the voltage / current storage unit 92 corresponding to the other primary transfer rollers 51y, 51c, 51m and the difference D11. Transfer voltage values E1y, E1c, E1m corresponding to the rollers 51y, 51c, 51m are newly calculated (S106). Hereinafter, a case where a new transfer voltage value E1y in the primary transfer roller 51y is calculated in steps S105 and S106 will be described with reference to FIG. Description of the case of calculating the transfer voltage values E1c and E1m at the primary transfer rollers 51c and 51m will be omitted. In FIG. 10, the horizontal axis X <b> 5 indicates the resistance value R in the primary transfer roller 51. The vertical axis Y5 indicates the transfer voltage value E1 in the primary transfer roller 51.

  In the example shown in FIG. 10, the voltage / current storage unit 92 has a transfer voltage value E1k (0): 1100 volts when the resistance value R is the value R (0), and the resistance value R is the value R (0). ), The transfer voltage value E1y (0): 900 volts is stored. Then, for example, a transfer voltage value E1k (1): 1200 volts when the resistance value R is the value R (1) is calculated as a new transfer voltage value. Note that the value R (1) is larger than the value R (0).

  Next, the difference of the transfer voltage value E1k when the resistance value R changes from the value R (0) to the value R (1): (E1k (1) −E1k (0)) is calculated. The difference (E1k (1) -E1k (0)) is 100 (= 1200-1100) volts. By adding the difference (E1k (1) −E1k (0)) to the transfer voltage value E1y (0) when the resistance value R is the value R (0), the resistance value R becomes the value R (1). Transfer voltage value E1y (1) at a certain time: 1000 volts is newly calculated.

  The transfer voltage value E1k (0) at the specific primary transfer roller 51k is obtained by the initial value stored in the voltage / current storage unit 92 at the time of manufacturing the image forming apparatus 1 or the control operation in the previous second mode. The transfer voltage value E1k can be substituted. With respect to the transfer voltage value E1y (0) in the other primary transfer roller 51y, the initial value stored in the voltage / current storage unit 92 at the time of manufacturing the image forming apparatus 1 or the previous second mode control operation is obtained. The transfer voltage value E1y can be substituted.

As described above, the new transfer voltage value E1y (1) at the primary transfer roller 51y is calculated by the following equation (5). The same applies to the primary transfer rollers 51c and 51m.
E1y (1) = E1y (0) + (E1k (1) −E1k (0)) (5)

  Next, with reference to FIG. 9, the processing after step S107 will be described. In step S102, when the second mode is selected, a plurality of detection voltages having a plurality of different voltage values VT are respectively applied to the four primary transfer rollers 51y, 51c, 51m, and 51k. , 61m, 61k (S107). The current detection unit 62 detects the current value I of the current flowing through each of the four primary transfer rollers 51y, 51c, 51m, 51k for each of a plurality of voltage values VT.

  Next, for each of the four primary transfer rollers 51y, 51c, 51m, and 51k, based on the characteristic curve indicating the characteristics of the primary transfer roller and the current values IGy, IGc, IGm, and IG of the specified transfer current. Transfer voltage values E1y, E1c, E1m, and E1k corresponding to the primary transfer rollers 51y, 51c, 51m, and 51k are newly calculated (S108). Next, the transfer voltage value information stored in the voltage / current storage unit 92 is updated to the transfer voltage values E1y, E1c, E1m, and E1k newly calculated in step S108 (S109).

  As described with reference to FIGS. 1 to 10, according to the image forming apparatus 1 of the first embodiment, the primary transfer roller 51 (51 y) due to, for example, fluctuations in the environmental temperature T, the relative humidity H, and the resistance value R. , 51c, 51m, 51k), the transfer voltage value E1 can be set according to the change in the characteristics. Therefore, the transfer voltage value in the primary transfer roller can be set so that image formation can be performed satisfactorily.

  Further, according to the processing shown in FIG. 9, the control operations in the first mode and the second mode are selectively executed according to the status information of the image forming apparatus 1. The control operation in the first mode (see FIG. 6) takes less time than the control operation in the second mode (see FIG. 8). Therefore, for example, when it is necessary for the image forming apparatus 1 to quickly perform image formation in response to a user's image formation instruction and the transfer voltage value E1 is expected to vary, the first mode By performing this control operation, image formation can be performed satisfactorily and quickly.

  On the other hand, when the image forming apparatus 1 is in a ready state after the end of the printing process and there is no urgent image formation request, the actual resistance in the primary transfer roller 51 is performed by performing the control operation in the second mode. Based on the value R, the transfer voltage value E1 can be set. Therefore, image formation can be performed more favorably.

<< Embodiment 2 >>
Hereinafter, Embodiment 2 of the present invention will be described with reference to FIGS. 11 to 13.

  FIG. 11 is a graph showing the voltage value of the detected voltage in the third mode. In the third mode, a single detection voltage is applied to a specific primary transfer roller. In FIG. 11, graphs G21, G22, G23, and G24 show voltage values VTy, VTc, VTm, and VTk of detection voltages applied by the voltage application unit 61 to the four primary transfer rollers 51y, 51c, 51m, and 51k, respectively. Show. In the example shown in FIG. 11, as shown in a graph G24, a single detection voltage having a voltage value V51 is applied to the primary transfer roller 51k by the voltage application unit 61k. On the other hand, a detection voltage of 0 (zero) volts is always applied to the other primary transfer rollers 51y, 51c, 51m as shown in the graphs G21, G22, G23.

  In FIG. 11, the period from time T1 to time T2 is the preparation period described with reference to FIG. Then, at time T2, application of a single detection voltage is started.

  FIG. 12 is a graph showing a current value for obtaining a transfer voltage value in a specific primary transfer roller in the third mode. Based on the graph of FIG. 12, the voltage control unit 911 newly calculates a transfer voltage value E1k corresponding to the specific primary transfer roller 51k based on the current value Ik of the current flowing through the specific primary transfer roller 51k. The horizontal axis X4 of the graph indicates the voltage value VTk at the primary transfer roller 51k which is a specific primary transfer roller. The vertical axis Y4 of the graph represents the current value Ik in the primary transfer roller 51k.

  In the third mode control operation, a characteristic curve obtained by the most recently executed second mode control operation is used. In FIG. 12, a straight line L11 corresponds to a characteristic curve including the line segment L1 shown in FIG. Hereinafter, the straight line L11 is referred to as a characteristic curve L11. Information defining a characteristic curve (for example, characteristic curve L11) obtained by the control operation of the second mode executed most recently is stored in the voltage / current storage unit 92 as characteristic curve information.

  The slope a1 of the characteristic curve L11 is equal to the slope a1 of the line segment L1. A point P11 on the characteristic curve L11 corresponds to the point P4 shown in FIG. Therefore, the voltage value E1 (b) at the point P11 is equal to the transfer voltage value E1k calculated by the most recently executed control operation in the second mode. In FIG. 12, a point P12 is indicated by a voltage value E1 (b) of a single detection voltage and a current value I2 corresponding to the voltage value E1 (b).

  In FIG. 12, a point P12 is a point on the straight line L13. The straight line L13 is a straight line obtained by translating the characteristic curve L11 in the direction of the horizontal axis X4. That is, the straight line L13 shows the voltage value E1 (b) of the single detection voltage, the current value I2 corresponding to the voltage value E1 (b) of the single detection voltage, and the characteristics of the specific primary transfer roller 51k. It is obtained from the characteristic curve L11 shown. A new transfer voltage value E1k (voltage value E1 (p) in the illustrated example) corresponding to the specific primary transfer roller 51k is a voltage value at the intersection P13 between the straight line L13 and the straight line L12 indicating the specified current value IG. Desired.

  Next, the operation of the control unit in the second embodiment will be described with reference to FIG. FIG. 13 is a flowchart illustrating the operation of the voltage control unit according to the second embodiment. In FIG. 13, step S205 corresponds to step S106 shown in FIG. Steps S201 to S202 correspond to steps S101 to S102 shown in FIG. 9, and steps S107 to S109 correspond to steps S107 to S109 shown in FIG. Therefore, only steps S203 and S204 will be described below.

  If it is determined in step S202 that the control operation in the third mode is to be executed, as shown in FIG. 11, the voltage application unit 61k applies a single detected voltage having a voltage value V51, for example, to a specific primary transfer roller 51k. (S203). At this time, the current detection unit 62 detects the current value Ik of the current flowing through the specific primary transfer roller 51k corresponding to the voltage value V51 of the single detection voltage.

  Next, as described with reference to FIG. 12, the voltage value of a single detection voltage (for example, the voltage value E1 (b)) and the current value Ik (for example, the voltage value of the single detection voltage) , Current value I2), a characteristic curve indicating the characteristic of the specific primary transfer roller 51k (for example, characteristic curve L11), and the current value IG of the specified transfer current, the specific primary transfer roller 51k A corresponding new transfer voltage value E1k (for example, E1 (p)) is calculated (S204).

  According to the processing of steps S201 to S205, the transfer voltage value can be appropriately set in a time shorter than the time required for the control operation in the first mode described in the first embodiment. Therefore, for example, when it is necessary for the image forming apparatus 1 to execute image formation promptly in response to a user's image formation instruction and fluctuations in the transfer voltage value E1 are expected, the image formation is performed well and promptly. Can be executed.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof (for example, Modification 1 to Modification 2 shown below). In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. In order to facilitate understanding, the drawings schematically show each component as a main component, and the thickness, length, number, interval, etc. of each component shown in the drawings are actual for convenience of drawing. May be different. In addition, the material, shape, dimensions, and the like of each component shown in the above embodiment are merely examples, and are not particularly limited, and various changes can be made without departing from the effects of the present invention. is there.

Modification 1
Instead of the transfer voltage value information, the voltage-current storage unit 92 can store difference information between the rollers. The inter-roller difference information is information indicating a difference between the transfer voltage value E1k at the specific primary transfer roller 51k and the transfer voltage values E1y, E1c, and E1m at the other primary transfer rollers 51y, 51c, and 51m. . The difference information between rollers can be updated by the control of the voltage control unit 911. The update process for updating the difference information between rollers can be executed, for example, when the control operation in the second mode is executed, similarly to the update process of the transfer voltage value information.

  Specifically, in FIG. 5, the intersections of the straight line L19 indicating the specified current value IG and the curves L11 and L12 are defined as a point P31 and a point P32, respectively. For example, the difference D1 (200 (= 1100-900) volts) between the voltage value VT (= 900 volts) at the point P31 and the voltage value VT (= 1100 volts) at the point P32 is obtained. Similarly, a difference D2 between the transfer voltage value E1k and the transfer voltage value E1c and a difference D3 between the transfer voltage value E1k and the transfer voltage value E1m are obtained. The differences D1, D2, and D3 are stored in the voltage / current storage unit 92 as inter-roller difference information.

  Based on the new transfer voltage value E1k (for example, the transfer voltage value E1k (1) shown in FIG. 10) and the difference D1 in the specific primary transfer roller 51k, the voltage control unit 911 determines another primary transfer roller ( For example, a new transfer voltage value E1y (for example, transfer voltage value E1y (1) shown in FIG. 10) at the primary transfer roller 51y) is calculated. Specifically, the transfer voltage value E1y (1) (= 1000 volts) is calculated by subtracting the difference D1 (= 200 volts) from the transfer voltage value E1k (1) (= 1200 volts).

  In the image forming apparatus 1 of the first modification, as in the image forming apparatuses of the first and second embodiments, for example, the primary transfer roller 51 (51y) is caused by fluctuations in the environmental temperature T, the relative humidity H, and the resistance value R, for example. , 51c, 51m, 51k), the transfer voltage value E1 can be set according to the change in the characteristics. Therefore, the transfer voltage value in the primary transfer roller can be set so that image formation can be performed satisfactorily.

Modification 2
Hereinafter, an image forming apparatus according to Modification 2 will be described with reference to FIG. FIG. 14 is a flowchart showing the operation of the voltage controller in the second modification. In FIG. 14, steps S201 to S205 correspond to steps S201 to S205 shown in FIG. Therefore, only steps S206 to S208 will be described below. In the operation of the control unit shown in FIG. 14, the third mode control operation (steps S203, S204, and S205) and the fourth mode control operation (steps S206, S207, and S208) can be switched and executed. it can. Hereinafter, the control operation in the fourth mode will be described.

  If it is determined in step S202 that the control operation in the fourth mode is to be executed, a single detection voltage is applied to all four primary transfer rollers 51y, 51c, 51m, 51k, and voltage application units 61y, 61c, 61m, Each voltage is applied by 61k (S206).

  Next, transfer voltage values E1y, E1c, E1m, and E1k for all four primary transfer rollers 51y, 51c, 51m, and 51k are newly calculated by the same method as that described in step S204 (S207). . Next, the transfer voltage value information stored in the voltage / current storage unit 92 is updated to the transfer voltage values E1y, E1c, E1m, and E1k newly calculated in step S207 (S208).

  According to the image forming apparatus 1 of Modification 2, it is possible to set transfer voltage values for all the primary transfer rollers 51y, 51c, 51m, and 51k more rapidly than in the second mode.

  The present invention is applicable to an image forming apparatus.

1: Image forming apparatus 4: Image forming unit 9: Control unit 42: Photosensitive drum 51: Primary transfer roller 51c: Primary transfer roller 51k: Primary transfer roller 51m: Primary transfer roller 51y: Primary transfer roller 54 : Intermediate transfer belt 61: Voltage application unit 61c: Voltage application unit 61k: Voltage application unit 61m: Voltage application unit 61y: Voltage application unit 62: Current detection unit 92: Voltage / current storage unit 911: Voltage control unit

Claims (3)

An image forming apparatus for forming an image on a recording medium,
A plurality of photosensitive drums;
A plurality of primary transfer rollers arranged corresponding to each of the plurality of photosensitive drums;
A plurality of voltage application sections for applying a voltage to each of the plurality of primary transfer rollers;
A current detection unit that detects a current value of a current flowing through each of the plurality of primary transfer rollers;
A storage unit for storing a transfer voltage value applied to each of the plurality of primary transfer rollers;
A controller that updates the transfer voltage value for each of the plurality of primary transfer rollers;
The controller is
Based on the current value flowing through the specific primary transfer roller among the plurality of primary transfer rollers, the transfer voltage value corresponding to the specific primary transfer roller is newly calculated,
Calculating a difference between the transfer voltage value stored corresponding to the specific primary transfer roller and the transfer voltage value newly calculated corresponding to the specific primary transfer roller;
Based on the transfer voltage value stored in correspondence with another primary transfer roller different from the specific primary transfer roller among the plurality of primary transfer rollers and the difference, the other 1 The transfer voltage value corresponding to the next transfer roller is newly calculated,
The voltage application unit applies a single voltage to the specific primary transfer roller,
The current detection unit detects a current value of a current flowing through the specific primary transfer roller corresponding to the voltage value of the single voltage,
The control unit includes the voltage value of the single voltage, the current value corresponding to the voltage value of the single voltage, a characteristic curve indicating characteristics of the specific primary transfer roller, Based on the current value of the transfer current, a new transfer voltage value corresponding to the specific primary transfer roller is calculated,
The image forming apparatus, wherein the characteristic curve is determined based on a voltage value of a voltage applied to the specific primary transfer roller and a current value flowing through the specific primary transfer roller. Having a first mode and a second mode;
The control unit switches between the first mode and the second mode according to the state of the image forming apparatus,
In the first mode,
The control unit calculates a new transfer voltage value corresponding to the specific primary transfer roller and a new transfer voltage value corresponding to the other primary transfer roller;
In the second mode,
The voltage application unit applies a plurality of voltages having a plurality of different voltage values to each of the plurality of primary transfer rollers,
The current detection unit detects a current value of a current flowing through each of the plurality of primary transfer rollers for each of the plurality of voltage values;
For each of the plurality of primary transfer rollers, the control unit performs the transfer corresponding to the primary transfer roller based on a characteristic curve indicating the characteristics of the primary transfer roller and a current value of a specified transfer current. Calculate a new voltage value,
The image forming apparatus according to claim 1, wherein the characteristic curve is determined based on the plurality of voltage values and the current value for each of the plurality of voltage values. The image forming apparatus according to claim 1, wherein the current detection unit detects a total current value of currents flowing through the plurality of primary transfer rollers.

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