Image forming device

Abstract

To provide an image forming apparatus that can estimate the state of deterioration of a cleaning blade.SOLUTION: An image forming apparatus 100 comprises: an image carrier 65; a developing device that has a developer carrier 641; a voltage application unit 121; a measuring unit 101; a cleaning blade that is in contact with the image carrier 65; and an estimation unit 102. The voltage application unit 121 applies, to the developer carrier 641, a bias voltage including a DC (direct current) bias and an AC (alternating current) bias. The measuring unit 101 measures a developing current Id flowing between the developer carrier 641 and the image carrier 65. The estimation unit 102 changes the DC bias to a first value and a second value, calculates a current ratio indicating the ratio between a first magnitude Id1 of the developing current Id with respect to the first value and a second magnitude Id2 of the developing current Id with respect to the second value Vdc2, and estimates the state of deterioration of the cleaning blade according to the value of the current ratio.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] The image forming apparatus described in Patent Document 1 includes a photosensitive drum, a cleaning blade, and a control unit. The control unit estimates the distribution of the smoothness of the cleaning blade in the axial direction of the photosensitive drum based on the load fluctuation associated with the driving of the photosensitive drum when removing residue from the surface of the photosensitive drum with the cleaning blade. Depending on the estimation result, developing toner is supplied to positions with poor smoothness, thereby making the distribution of smoothness uniform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-26122 A Summary of the Invention [Problem to be solved by the invention]

[0004] The image forming apparatus described in Patent Document 1 was unable to detect the deterioration of the lubricity of the entire cleaning blade, and also had a problem that the amount of toner consumed increases as the number of locations of the cleaning blade where the lubricity is deteriorated increases.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of estimating the deterioration state of a cleaning blade. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes an image carrier, a developing device, a voltage application unit, a measurement unit, a cleaning blade, and an estimation unit. The image carrier carries an electrostatic latent image. The developing device has a developer carrier that carries a developer containing at least a toner. The voltage application unit applies a bias voltage including a DC bias and an AC bias to the developer carrier so as to move the toner from the developer carrier to the image carrier. The measurement unit measures a development current flowing between the developer carrier and the image carrier. The cleaning blade contacts the image carrier so as to remove residual toner on the image carrier after the transfer of a toner image. The estimation unit changes the DC bias to a first value and a second value, respectively, calculates a current ratio indicating a ratio between a first magnitude of the development current relative to the first value and a second magnitude of the development current relative to the second value, and estimates a deterioration state of the cleaning blade according to the value of the current ratio. Effect of the Invention

[0007] According to the present invention, there is provided an image forming apparatus capable of estimating the deterioration state of a cleaning blade. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing an example of a detailed configuration of a developing device. [Diagram 3] FIG. 2 is a block diagram showing an example of a circuit configuration of an image forming apparatus. [Figure 4] 10 is a flowchart illustrating an example of a process of a control unit. [Diagram 5] 10 is a flowchart illustrating an example of a process of a control unit. [Figure 6] 10 is a flowchart illustrating an example of a process of a control unit. [Figure 7] 10 is a flowchart illustrating an example of a process of a control unit. [Figure 8]10 is a flowchart illustrating an example of a process of a control unit. [Figure 9] FIG. 11 is a diagram showing an example of the correlation between a DC bias and a developing current. [Figure 10] FIG. 13 is a diagram showing an example of a predicted curve of a current ratio value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0010] An image forming apparatus 100 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the image forming apparatus 100. The image forming apparatus 100 is, for example, a color printer. In Fig. 1, for the sake of convenience, the direction from left to right is defined as the positive direction of the X axis, the direction from front to back is defined as the positive direction of the Y axis, and the direction from bottom to top is defined as the positive direction of the Z axis.

[0011] As shown in FIG. 1, the image forming apparatus 100 includes an operation unit 2, a paper feed unit 3, a transport unit 4, a toner supply unit 5, an image forming unit 6, a transfer unit 7, a fixing unit 8, and a discharge unit 9.

[0012] The operation unit 2 receives instructions from a user. The operation unit 2 includes a liquid crystal display 21 and a plurality of operation keys 22. The liquid crystal display 21 displays, for example, various processing results. The operation keys 22 include, for example, a numeric keypad and a start key.

[0013] The paper feed unit 3 includes a paper feed cassette 31 and a paper feed roller group 32. The paper feed cassette 31 can accommodate a plurality of sheets of paper P. The paper feed roller group 32 feeds the sheets of paper P accommodated in the paper feed cassette 31 to the transport unit 4 one sheet at a time.

[0014] The transport unit 4 includes a roller and a guide member. The transport unit 4 extends from the paper feed unit 3 to the discharge unit 9. The transport unit 4 transports the paper P from the paper feed unit 3 to the discharge unit 9 so as to pass through the image forming unit 6 and the fixing unit 8.

[0015] The toner supply unit 5 supplies toner to the image forming unit 6. The toner supply unit 5 includes a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

[0016] A first toner container 52Y is attached to the first mounting portion 51Y. Similarly, a second toner container 52C is attached to the second mounting portion 51C, a third toner container 52M is attached to the third mounting portion 51M, and a fourth toner container 52K is attached to the fourth mounting portion 51K. The first mounting portion 51Y to the fourth mounting portion 51K have the same configuration except for the type of toner container that is attached.

[0017] The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain a toner. In this embodiment, the first toner container 52Y contains yellow toner. The second toner container 52C contains cyan toner. The third toner container 52M contains magenta toner. The fourth toner container 52K contains black toner.

[0018] The image forming section 6 includes an exposure device 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K.

[0019] Each of the first to fourth image forming units 62Y to 62K includes a charging device 63, a developing device 64, a photoconductor drum 65, and a cleaning device 66. The photoconductor drum 65 corresponds to an example of an "image carrier".

[0020] The charging device 63, the developing device 64, and the cleaning device 66 are disposed along the circumferential surface of the photoconductor drum 65. In this embodiment, the photoconductor drum 65 rotates in the direction indicated by the arrow R1 in FIG.

[0021] The charging device 63 uniformly charges the photoconductor drum 65 to a predetermined polarity by discharging. In this embodiment, the charging device 63 charges the photoconductor drum 65 to a positive polarity. The exposure device 61 irradiates the charged photoconductor drum 65 with laser light. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 65.

[0022] The developing device 64 forms a toner image by developing the electrostatic latent image formed on the surface of the photoconductor drum 65. The developing device 64 is replenished with toner from the toner replenishing section 5. The developing device 64 supplies the toner replenished from the toner replenishing section 5 to the surface of the photoconductor drum 65. As a result, a toner image is formed on the surface of the photoconductor drum 65.

[0023] In this embodiment, the developing device 64 of the first image forming unit 62Y is connected to the first mounting portion 51Y. Therefore, the developing device 64 of the first image forming unit 62Y is supplied with yellow toner. A yellow toner image is formed on the surface of the photoconductor drum 65 of the first image forming unit 62Y.

[0024] The developing device 64 of the second image forming unit 62C is connected to the second mounting portion 51C. Therefore, the developing device 64 of the second image forming unit 62C is supplied with cyan toner. A cyan toner image is formed on the surface of the photoconductor drum 65 of the second image forming unit 62C.

[0025] The developing device 64 of the third image forming unit 62M is connected to the third mounting portion 51M. Therefore, the developing device 64 of the third image forming unit 62M is replenished with magenta toner. A magenta toner image is formed on the surface of the photoconductor drum 65 of the third image forming unit 62M.

[0026] The developing device 64 of the fourth image forming unit 62K is connected to the fourth mounting portion 51K. Therefore, the developing device 64 of the fourth image forming unit 62K is supplied with black toner. A black toner image is formed on the surface of the photoconductor drum 65 of the fourth image forming unit 62K.

[0027] The transfer unit 7 transfers each toner image formed on the surface of each photoconductor drum 65 of the first image forming unit 62Y to the fourth image forming unit 62K, superimposed on the paper P. In this embodiment, the transfer unit 7 transfers each toner image onto the paper P by a secondary transfer method. In detail, the transfer unit 7 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

[0028] The intermediate transfer belt 72 is an endless belt that is stretched around four primary transfer rollers 71, a driving roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in response to the rotation of the driving roller 73. In FIG. 1, the intermediate transfer belt 72 rotates counterclockwise. The driven roller 74 is driven to rotate in response to the driving of the intermediate transfer belt 72.

[0029] The first to fourth image forming units 62Y to 62K are disposed facing the lower surface of the intermediate transfer belt 72 along the driving direction D of the lower surface of the intermediate transfer belt 72. In this embodiment, the first to fourth image forming units 62Y to 62K are disposed in this order from the upstream side to the downstream side of the driving direction D of the lower surface of the intermediate transfer belt 72.

[0030] Each primary transfer roller 71 is disposed opposite to each photoconductor drum 65 via the intermediate transfer belt 72, and is pressed against each photoconductor drum 65. Therefore, the toner images formed on the surfaces of the respective photoconductor drums 65 are sequentially transferred to the intermediate transfer belt 72. In this embodiment, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are transferred onto the intermediate transfer belt 72 in this order, superimposed thereon.

[0031] The cleaning devices 66 included in the first to fourth image forming units 62Y to 62K remove residual toner from the photoconductor drums 65 after the toner images are transferred to the intermediate transfer belt 72.

[0032] The secondary transfer roller 75 is disposed opposite the drive roller 73 across the intermediate transfer belt 72. The secondary transfer roller 75 is pressed against the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. When the paper P passes through the transfer nip, the toner image stacked on the intermediate transfer belt 72 is transferred to the paper P. The paper P with the transferred toner image is transported by the transport unit 4 toward the fixing unit 8.

[0033] The fixing unit 8 includes a heating member 81 and a pressure member 82. The heating member 81 and the pressure member 82 are disposed opposite each other to form a fixing nip. The paper P conveyed from the image forming unit 6 passes through the fixing nip and is pressurized while being heated at a predetermined fixing temperature. As a result, the toner image is fixed onto the paper P. The paper P is conveyed from the fixing unit 8 to the discharge unit 9 by the conveying unit 4.

[0034] The discharge section 9 has a discharge roller pair 91 and a discharge tray 93. The discharge roller pair 91 transports the paper P to the discharge tray 93 through a discharge opening 92. The discharge opening 92 is formed in the upper part of the image forming apparatus 100.

[0035] Next, a detailed configuration of the developing device 64 will be described with reference to Fig. 1 and Fig. 2. Fig. 2 is an enlarged cross-sectional view showing an example of a detailed configuration of the developing device 64. Note that in Fig. 2, the charging device 63 is omitted from illustration.

[0036] 2, in this embodiment, the developing device 64 has a developing container 640 that contains a two-component developer. The developing device 64 has a developing roller 641, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside the developing container 640. In detail, the developing roller 641 is disposed opposite the second stirring screw 644. The blade 645 is disposed opposite the developing roller 641.

[0037] The developing container 640 is divided into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640c extends in the axial direction (Y-axis direction) of the developing roller 641. The first stirring chamber 640a and the second stirring chamber 640b communicate with each other on the outer sides of both longitudinal ends of the partition wall 640c.

[0038] A first stirring screw 643 is disposed in the first stirring chamber 640a. A magnetic carrier is accommodated in the first stirring chamber 640a. Non-magnetic toner is supplied to the first stirring chamber 640a through a toner supply port 640h.

[0039] The second stirring chamber 640b is provided with a second stirring screw 644. A magnetic carrier is housed in the second stirring chamber 640b.

[0040] The toner is mixed with the carrier by being stirred by the first stirring screw 643 and the second stirring screw 644. As a result, a two-component developer consisting of the carrier and the toner is formed. The two-component developer corresponds to an example of a "developer".

[0041] The first stirring screw 643 and the second stirring screw 644 circulate and stir the developer between the first stirring chamber 640a and the second stirring chamber 640b. As a result, the toner is charged to a predetermined polarity. In this embodiment, the toner is charged to a positive polarity.

[0042] The developing roller 641 is composed of a non-magnetic rotating sleeve 641a and a magnet body 641b. The magnet body 641b is fixedly disposed inside the rotating sleeve 641a. The magnet body 641b includes a plurality of magnetic poles. The developer is attracted to the developing roller 641 by the magnetic force of the magnet body 641b. As a result, a magnetic brush is formed on the surface of the developing roller 641.

[0043] In this embodiment, the developing roller 641 rotates in the direction indicated by the arrow R (counterclockwise) in FIG. 2. The developing roller 641 rotates to transport the magnetic brush to a position facing the blade 645. The blade 645 is disposed so that a gap is formed between the developing roller 641 and the blade 645. Therefore, the thickness of the magnetic brush is determined by the blade 645. The blade 645 is disposed upstream of the position where the developing roller 641 and the photoconductor drum 65 face each other in the rotation direction of the developing roller 641.

[0044] A predetermined voltage is applied to the developing roller 641. As a result, the developer layer formed on the surface is transported to a position facing the photoconductor drum 65, and the toner in the developer adheres to the photoconductor drum 65.

[0045] The cleaning device 66 has a cleaning blade 661 that comes into contact with the photoconductor drum 65. The cleaning device 66 is made of, for example, rubber. The cleaning blade 661 is disposed downstream in the rotation direction of the photoconductor drum 65 from the position where the primary transfer roller 71 and the photoconductor drum 65 face each other.

[0046] 1 to 3, a circuit configuration of the image forming apparatus 100 will be described. FIG. 3 is a block diagram showing an example of the circuit configuration of the image forming apparatus 100.

[0047] As shown in FIG. 3, the image forming apparatus 100 includes a control unit 10, a storage unit 11, and a high-voltage application board 12 in addition to the photoconductor drum 65 and the developing roller 641.

[0048] The storage unit 11 includes a storage device and stores data and computer programs. The storage unit 11 includes a main storage device such as a semiconductor memory and an auxiliary storage device such as a hard disk drive.

[0049] The control unit 10 includes a processor such as a CPU (Central Processing Unit), and controls each component of the image forming apparatus 100 by executing a computer program stored in the storage unit 11. Specifically, the control unit 10 functions as a measurement unit 101 and an estimation unit 102 by executing a computer program stored in the storage unit 11.

[0050] The high voltage application board 12 has a voltage application section 121 and a current detection section 122. The voltage application section 121 applies a bias voltage to the development roller 641 so as to move the toner from the development roller 641 to the photoconductor drum 65. The bias voltage is a voltage in which an AC (alternating current) bias is superimposed on a DC (direct current) bias. The current detection section 122 is an ammeter for measuring a development current Id flowing between the development roller 641 and the photoconductor drum 65.

[0051] The measurement unit 101 measures the development current Id by controlling the operations of the voltage application unit 121 and the current detection unit 122. In a measurement mode for the development current Id, the control unit 10 controls the exposure device 61 so that an electrostatic latent image representing a rectangular patch pattern having a predetermined area is formed on the photoconductor drum 65.

[0052] The estimation unit 102 changes the DC bias Vdc to a first value Vdc1 and a second value Vdc2. Then, the estimation unit 102 calculates a current ratio R indicating a ratio between a first magnitude Id1 of the development current Id for the first value Vdc1 and a second magnitude Id2 of the development current Id for the second value Vdc2. Furthermore, the estimation unit 102 estimates the deterioration state of the cleaning blade 661 according to the calculated value of the current ratio R.

[0053] Furthermore, the estimation unit 102 changes the value of the AC bias Vac while maintaining the first value Vdc1 and the second value Vdc2, and obtains a specific value Vx of the AC bias Vac that maximizes the current ratio R. Then, the estimation unit 102 sets the AC bias Vac used for estimating the deterioration state of the cleaning blade 661 to the specific value Vx.

[0054] Furthermore, the estimation unit 102 generates a prediction curve C that indicates a prediction of a change over time in the value of the current ratio R, and determines the next state estimation timing for the cleaning blade 661 based on the prediction curve C.

[0055] Furthermore, the estimation unit 102 updates the prediction curve C when the value of the current ratio R obtained after generating the prediction curve C deviates from the prediction curve C.

[0056] Furthermore, the estimation unit 102 compares the value of the current ratio R with a first threshold value X1, and if the value of the current ratio R is not greater than the first threshold value X1, calculates the current ratio R for each of the multiple sections into which the photoconductor drum 65 is divided. Then, the estimation unit 102 compares the value of the current ratio R for each of the multiple sections with a second threshold value X2 that is smaller than the first threshold value X1, and if the value of the current ratio R in all of the multiple sections is greater than the second threshold value X2, issues a warning of the end of life of the cleaning blade 661.

[0057] Furthermore, the estimation unit 102 compares the value of the current ratio R with a first threshold value X1, and if the value of the current ratio R is not greater than the first threshold value X1, calculates the current ratio R for each of the multiple sections into which the photoconductor drum 65 is divided. Then, the estimation unit 102 compares the value of the current ratio R for each of the multiple sections with a second threshold value X2 that is smaller than the first threshold value X1, and recommends replacement of the cleaning blade 661 if there is a section among the multiple sections in which the value of the current ratio R is not greater than the second threshold value X2.

[0058] For example, the direction of the development current Id flowing from the development roller 641 to the photoconductor drum 65 is defined as the positive direction of the development current Id. When the potential difference (Vdc-V0) between the DC bias Vdc of the development roller 641 and the surface potential V0 of the photoconductor drum 65 after exposure is a positive value, a forward bias is applied between the development roller 641 and the photoconductor drum 65. When the potential difference (Vdc-V0) is a negative value, a reverse bias is applied between the development roller 641 and the photoconductor drum 65.

[0059] The first value Vdc1 of the DC bias Vdc is set, for example, so that the potential difference (Vdc-V0) is a positive value. Therefore, the first magnitude Id1 of the development current Id is a positive value. The second value Vdc2 of the DC bias Vdc is set, for example, so that the potential difference (Vdc-V0) is a negative value. Therefore, the second magnitude Id2 of the development current Id is a negative value. The current ratio R is, for example, the absolute value of Id1 / Id2.

[0060] When the cleaning blade 661 deteriorates and the performance of removing the residual toner on the surface of the photoconductor drum 65 decreases, the first magnitude Id1 of the development current Id decreases even if the first value Vdc1 of the DC bias Vdc remains unchanged. This is because the positive toner is prevented from flying from the development roller 641 to the photoconductor drum 65 by the positive residual toner. Also, when the cleaning blade 661 deteriorates and the performance of removing the residual toner on the surface of the photoconductor drum 65 decreases, the absolute value of the second magnitude Id2 of the development current Id increases even if the second value Vdc2 of the DC bias Vdc remains unchanged. This is because the positive residual toner on the surface of the photoconductor drum 65 is returned to the development roller 641 by the reverse bias. Therefore, when the cleaning blade 661 deteriorates, it is expected that the current ratio R decreases.

[0061] Next, the processing of the control unit 10 will be described with reference to Fig. 1 to Fig. 5. Fig. 4 and Fig. 5 are flowcharts showing an initialization processing, which is an example of the processing of the control unit 10. The initialization processing is executed only once when the image forming apparatus 100 is shipped from the factory, for example.

[0062] 4, the control unit 10 sets the DC bias Vdc to a first value Vdc1 and a second value Vdc2. When the process of step S101 is completed, the process of the control unit 10 proceeds to step S103.

[0063] Step S103: The control unit 10 initializes a variable n for controlling the repetitive processing to 1. When the process of step S103 is completed, the process of the control unit 10 proceeds to step S105.

[0064] Step S105: The control unit 10 sets the AC bias Vac to a specific value Vac_n. The specific value Vac_n varies depending on the value of the variable n. When the process of step S105 is completed, the process of the control unit 10 proceeds to step S107.

[0065] Step S107: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641, and obtains a first magnitude Id1 of the developing current Id with the bias Vdc1+Vac_n. When the process of step S107 is completed, the process of the control unit 10 proceeds to step S109.

[0066] Step S109: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641, and obtains the second magnitude Id2 of the developing current Id with the bias Vdc2+Vac_n. When the process of step S109 is completed, the control unit 10 proceeds to the process of step S111.

[0067] Step S111: The control unit 10 calculates the value of the current ratio R based on the first magnitude Id1 and the second magnitude Id2 of the development current Id. In steps S105 and S107, the exposure device 61 is controlled so that an electrostatic latent image representing a rectangular patch pattern having a predetermined area is formed over the entire axial direction of the photoconductor drum 65. When the process of step S111 is completed, the process of the control unit 10 proceeds to step S113 shown in FIG.

[0068] 5, the control unit 10 determines whether or not the value of the variable n is equal to 1. If the control unit 10 determines that the value of the variable n is equal to 1 (Yes in step S113), the process of the control unit 10 proceeds to step S115. If the control unit 10 determines that the value of the variable n is not equal to 1 (No in step S113), the process of the control unit 10 proceeds to step S119.

[0069] Step S115: The control unit 10 stores the value of the current ratio R calculated in step S111 as a maximum value Rx. The control unit 10 also stores the specific value Vac_n of the AC bias Vac used in steps S107 and S109 as an optimal value Vx. When the process of step S115 is completed, the process of the control unit 10 proceeds to step S117.

[0070] Step S117: The control unit 10 updates the value of the variable n by incrementing it by 1. When the process of step S117 is completed, the control unit 10 advances the process to step S121.

[0071] Step S119: The control unit 10 judges whether the value of the current ratio R calculated in step S111 is greater than the maximum value Rx. If the control unit 10 judges that the value of the current ratio R is greater than the maximum value Rx (Yes in step S119), the process of the control unit 10 proceeds to step S115 so that the maximum value Rx is updated. If the control unit 10 judges that the value of the current ratio R is not greater than the maximum value Rx (No in step S119), the process of the control unit 10 proceeds to step S117.

[0072] Step S121: The control unit 10 judges whether the value of the variable n is equal to or greater than the threshold value nx. If the control unit 10 judges that the value of the variable n is equal to or greater than the threshold value nx (Yes in step S121), the process of the control unit 10 proceeds to step S123. If the control unit 10 judges that the value of the variable n is not equal to or greater than the threshold value nx (No in step S121), the process of the control unit 10 returns to step S105.

[0073] Step S123: The control unit 10 sets the value of the AC bias Vac used to estimate the deterioration state of the cleaning blade 661 to an optimum value Vx. The optimum value Vx is a specific value Vac_n of the AC bias Vac that maximizes the value of the current ratio R, as shown by the processes from step S103 to step S121. During the search for the optimum value Vx, the first value Vdc1 and the second value Vdc2 of the DC bias Vdc are maintained. When the process of step S123 is completed, the process of the control unit 10 proceeds to step S125.

[0074] Step S125: The control unit 10 saves the maximum value Rx of the current ratio R stored in step S115 as an initial value X0. When the process of step S125 is completed, the process of the control unit 10 proceeds to step S127.

[0075] Step S127: The control unit 10 generates a prediction curve C that indicates a prediction of a change over time in the value of the current ratio R. When the process of step S127 is completed, the control unit 10 proceeds to the process of step S129.

[0076] Step S129: The control unit 10 sets the value of the execution interval Tp of the state estimation to an initial value T0. When the process of step S129 is completed, the initialization process of the control unit 10 ends.

[0077] Next, the processing of the control unit 10 will be further described with reference to Fig. 1 to Fig. 8. Fig. 6, Fig. 7, and Fig. 8 are flowcharts showing a state estimation processing, which is an example of the processing of the control unit 10.

[0078] 6, the control unit 10 determines whether or not the execution interval Tp of the state estimation has elapsed. If the control unit 10 determines that the execution interval Tp of the state estimation has elapsed (Yes in step S201), the process of the control unit 10 proceeds to step S203. If the control unit 10 determines that the execution interval Tp of the state estimation has not yet elapsed (No in step S201), the state estimation process of the control unit 10 ends.

[0079] Step S203: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641, and obtains a first magnitude Id1 of the developing current Id with the bias Vdc1+Vx. When the process of step S203 is completed, the process of the control unit 10 proceeds to step S205.

[0080] Step S205: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641, and obtains the second magnitude Id2 of the developing current Id at the bias Vdc2+Vx. When the process of step S205 is completed, the control unit 10 proceeds to the process of step S207.

[0081] Step S207: The control unit 10 calculates the value of the current ratio R based on the first magnitude Id1 and the second magnitude Id2 of the development current Id. In steps S203 and S205, the exposure device 61 is controlled so that an electrostatic latent image representing a rectangular patch pattern having a predetermined area is formed over the entire axial direction of the photoconductor drum 65. When the process of step S207 is completed, the control unit 10 proceeds to the process of step S209.

[0082] Step S209: The control unit 10 determines whether the value of the current ratio R calculated in step S207 is greater than the first threshold value X1. If the control unit 10 determines that the value of the current ratio R is greater than the first threshold value X1 (Yes in step S209), the process of the control unit 10 proceeds to step S211. If the control unit 10 determines that the value of the current ratio R is not greater than the first threshold value X1 (No in step S209), the process of the control unit 10 proceeds to step S215.

[0083] Step S211: The control unit 10 determines whether or not the value of the current ratio R calculated in step S207 deviates from the predicted curve C. If the control unit 10 determines that the value of the current ratio R deviates from the predicted curve C (Yes in step S211), the process of the control unit 10 proceeds to step S213. If the control unit 10 determines that the value of the current ratio R does not deviate from the predicted curve C (No in step S211), the state estimation process of the control unit 10 ends.

[0084] Step S213: The control unit 10 updates the prediction curve C so as to fit the value of the current ratio R calculated in step S207. When the process of step S213 is completed, the state estimation process of the control unit 10 ends.

[0085] Step S215: The control unit 10 determines whether the value of the current ratio R calculated in step S207 is greater than the second threshold value X2 (<X1). If the control unit 10 determines that the value of the current ratio R is greater than the second threshold value X2 (Yes in step S215), the process of the control unit 10 proceeds to step S219 shown in FIG. 7. When the process of the control unit 10 proceeds to step S219, it means that the value of the current ratio R satisfies the inequality X2 < R ≤ X1. If the control unit 10 determines that the value of the current ratio R is not greater than the second threshold value X2 (No in step S215), the process of the control unit 10 proceeds to step S217.

[0086] Step S217: The control unit 10 uses the liquid crystal display 21 to provide an alert to the user recommending replacement of the unit including the cleaning blade 661. When the process of step S217 is completed, the state estimation process of the control unit 10 ends.

[0087] Step S219: As shown in FIG. 7, the control unit 10 initializes a variable m for controlling the repetitive process to 1. When the process of step S219 is completed, the process of the control unit 10 proceeds to step S221.

[0088] Step S221: The control unit 10 controls the exposure device 61 so that an electrostatic latent image representing a rectangular patch pattern having a predetermined area is formed only in the axial section m of the photoreceptor drum 65. To check for partial defects of the cleaning blade 661, the photoreceptor drum 65 is virtually divided into, for example, eight sections in the Y-axis direction. When the process of step S221 is completed, the process of the control unit 10 proceeds to step S223.

[0089] Step S223: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641 to obtain a first magnitude Id1 of the developing current Id at the bias Vdc1 + Vx. When the process of step S223 is completed, the process of the control unit 10 proceeds to step S225.

[0090] Step S225: The control unit 10 causes the voltage application unit 121 to apply a bias to the developing roller 641, and obtains the second magnitude Id2 of the developing current Id at the bias Vdc2+Vx. When the process of step S225 is completed, the control unit 10 proceeds to the process of step S227.

[0091] Step S227: The control unit 10 calculates the value of the current ratio R based on the first magnitude Id1 and the second magnitude Id2 of the development current Id. When the process of step S227 is completed, the control unit 10 proceeds to the process of step S229.

[0092] Step S229: The control unit 10 updates the value of the variable m by incrementing it by 1. When the process of step S229 is completed, the control unit 10 advances the process to step S231.

[0093] Step S231: The control unit 10 judges whether the value of the variable m is equal to or greater than the threshold mx. If the control unit 10 judges that the value of the variable m is equal to or greater than the threshold mx (Yes in step S231), the process of the control unit 10 proceeds to step S233 shown in Fig. 8. If the control unit 10 judges that the value of the variable m is not equal to or greater than the threshold mx (No in step S231), the process of the control unit 10 returns to step S221. For example, when the photoconductor drum 65 is divided into 8 in the Y-axis direction, the threshold mx is set to 9.

[0094] 8, the control unit 10 judges whether the value of the current ratio R repeatedly calculated in step S227 is greater than the second threshold value X2 in all sections of the photoconductor drum 65. If the control unit 10 judges that the value of the current ratio R is greater than the second threshold value X2 in all sections (Yes in step S233), the process of the control unit 10 proceeds to step S235. If the control unit 10 judges that the value of the current ratio R is not greater than the second threshold value X2 in any section (No in step S233), the process of the control unit 10 proceeds to step S243. Note that the second threshold value X2 in step S215 and the second threshold value X2 in step S233 may be different values.

[0095] Step S235: The control unit 10 determines whether it is possible to change the transfer conditions of the transfer unit 7 so as to compensate for the deterioration of the function of the cleaning blade 661. If the control unit 10 determines that the transfer conditions can be changed (Yes in step S235), the process of the control unit 10 proceeds to step S237. If the control unit 10 determines that the transfer conditions cannot be changed (No in step S235), the process of the control unit 10 proceeds to step S239.

[0096] Step S237: The control unit 10 changes the transfer conditions of the transfer unit 7. When the process of step S237 is completed, the state estimation process of the control unit 10 ends.

[0097] Step S239: The control unit 10 uses the liquid crystal display 21 to provide the user with a display including a life warning of the cleaning blade 661. When the process of step S239 is completed, the process of the control unit 10 proceeds to step S241.

[0098] Step S241: The control unit 10 changes the value of the execution interval Tp of the state estimation to a predetermined value T1 (T1 < T0). That is, the next state estimation timing of the cleaning blade 661 is determined based on the prediction curve C. When the process of step S241 is completed, the state estimation process of the control unit 10 ends.

[0099] Step S243: The control unit 10 uses the liquid crystal display 21 to provide the user with an alert recommending replacement of the unit including the cleaning blade 661. When the process of step S243 is completed, the state estimation process of the control unit 10 ends.

[0100] According to the state estimation process of FIG. 6 to FIG. 8, when the value of the current ratio R calculated for the entire photoconductor drum 65 is not greater than the first threshold value X1, the control unit 10 calculates the current ratio R for each of the multiple sections into which the photoconductor drum 65 is divided. Then, the control unit 10 compares the value of the current ratio R for each of the multiple sections with a second threshold value X2 that is smaller than the first threshold value X1. When the value of the current ratio R is greater than the second threshold value X2 in all of the multiple sections, the control unit 10 issues a warning about the end of life of the cleaning blade 661. Conversely, when the value of the current ratio R is not greater than the second threshold value X2 in the multiple sections, the control unit 10 recommends replacing the cleaning blade 661. That is, a warning display about the end of life of the cleaning blade 661 or an alert recommending unit replacement is provided to the user according to the value of the current ratio R. EXAMPLES

[0101] Next, an embodiment of the present invention will be described. The driving conditions, bias conditions, and toner conditions of the embodiment are as follows. Note that the present invention is not limited to the scope of the embodiment.

[0102] [Drive condition] Printing speed: 60 sheets / min Photoreceptor peripheral speed: 280mm / sec Developer carrier linear speed: 504 mm / sec [Bias conditions] Development DC bias: -110V~130V Developing AC bias: 1000Vpp / 1200Vpp Developing AC frequency: 8000Hz Development AC duty ratio: 50% Potential difference between photoconductor and developer carrier (Vdc-V0): -130V to 110V [Toner conditions] Toner particle size: 6.8μm Toner polarity: positive charge

[0103] Next, the correlation between the DC bias Vdc and the developing current Id in the embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the correlation between the DC bias Vdc and the developing current Id. In Fig. 9, the horizontal axis indicates the potential difference (Vdc-V0) [V] between the developing roller 641 and the photoconductor drum 65, and the vertical axis indicates the developing current Id [μA].

[0104] 9 shows the measurement results when there is no deterioration of the cleaning blade 661. In the range of the DC bias Vdc indicating a forward bias (Vdc-V0>0), as the DC bias Vdc increases, the amount of positive toner flying from the developing roller 641 to the photoconductor drum 65 increases, and therefore the positive developing current Id increases. On the other hand, in the range of the DC bias Vdc indicating a reverse bias (Vdc-V0<0), the toner or carrier charged with the opposite polarity flies from the developing roller 641 to the photoconductor drum 65, and therefore a negative developing current Id is generated. However, the absolute value of the developing current Id in the case of the reverse bias is smaller than the absolute value of the developing current Id in the case of the forward bias.

[0105] According to the example of FIG. 9, in the initialization process, Vdc1-V0=110V and Vdc2-V0=-130V are set. If V0=20V, then Vdc1=130V and Vdc2=-110V. When the value of the AC bias Vac is 1000Vpp under these DC bias conditions, the value of the current ratio R is 3.57. When the value of the AC bias Vac is 1200Vpp under the same DC bias conditions, the value of the current ratio R is 3.89. Therefore, the optimal value Vx of the AC bias Vac is set to 1200Vpp. The initial value X0 of the current ratio R is 3.89.

[0106] Finally, the prediction curve C will be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of the prediction curve C of the value of the current ratio R. In Fig. 10, the horizontal axis indicates the drive time of the image forming apparatus 100, and the vertical axis indicates the value of the current ratio R.

[0107] As shown in FIG. 10, the value of the current ratio R at the driving time “0” is the initial value X0. As long as the value of the current ratio R does not deviate from the prediction curve C, the state estimation processes of FIGS. 6 to 8 are executed every initial value T0 of the execution interval Tp of the state estimation. Thereafter, when the cleaning blade 661 deteriorates to such an extent that the value of the current ratio R satisfies the inequality X2 < R ≦ X1, a life warning display is provided to the user. Further, when the cleaning blade 661 deteriorates further to such an extent that the value of the current ratio R satisfies the inequality R ≦ X2, a unit replacement recommendation alert is provided to the user. The first threshold value X1 and the second threshold value X2 can be set so as to satisfy, for example, X1 = 0.5X0 and X2 = 0.3X0 with reference to the initial value X0 of the current ratio R.

[0108] According to an embodiment, there is provided an image forming apparatus 100 capable of estimating the deterioration state of the cleaning blade 661.

[0109] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Further, by appropriately combining a plurality of components disclosed in the above embodiments, various inventions can be formed. For example, some components may be deleted from all the components shown in the embodiments. The drawings are schematically shown mainly for each component for easy understanding, and the number of each component shown in the drawings may be different from the actual one for convenience of drawing creation. Further, each component shown in the above embodiments is an example and is not particularly limited, and various changes can be made without substantially departing from the effects of the present invention.

[0110] In the embodiment, the image forming apparatus 100 is a color printer, but it is not limited thereto. The image forming apparatus 100 may be an apparatus that forms an image by an electrophotographic method.

[0111] Also, in the embodiment, the developer is a two-component developer, but it is not limited thereto. The developer may be a one-component developer. [Industrial Applicability]

[0112] The present invention can be used in the field of image forming apparatuses. [Explanation of symbols]

[0113] 64 Developing device 65 Photoconductor drum (image carrier) 100 Image forming device 101 Measuring section 102 Estimation part 121 Voltage application section 122 Current detection unit 641 Developing roller (developer carrier) 661 Cleaning Blade

Claims

1. an image carrier that carries an electrostatic latent image; a developing device having a developer carrier that carries a developer containing at least a toner; a voltage application unit that applies a bias voltage including a DC bias and an AC bias to the developer carrier so as to move the toner from the developer carrier to the image carrier; a measurement unit for measuring a development current flowing between the developer carrier and the image carrier; a cleaning blade that contacts the image carrier so as to remove residual toner on the image carrier after the toner image is transferred; an estimation unit that changes the DC bias to a first value at which a potential difference with respect to a surface potential of the image carrier after exposure is either positive or negative and a second value at which the potential difference is either positive or negative, calculates a current ratio that indicates a ratio between a first magnitude of the developing current with respect to the first value and a second magnitude of the developing current with respect to the second value, and estimates a deterioration state of the cleaning blade in accordance with the value of the current ratio; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the estimation unit changes a value of the AC bias while maintaining the first value and the second value, obtains a specific value of the AC bias at which the current ratio is maximized, and sets the AC bias used for estimating the deterioration state to the specific value.

3. 3 . The image forming apparatus according to claim 1 , wherein the estimating section generates a prediction curve indicating a prediction of a change over time in the value of the current ratio, and determines a next timing for estimating the state of the cleaning blade based on the prediction curve.

4. The image forming apparatus according to claim 3 , wherein the estimation unit updates the predicted curve when the value of the current ratio obtained after generating the predicted curve deviates from the predicted curve.

5. 5. The image forming apparatus according to claim 1, wherein the estimation unit compares the value of the current ratio with a first threshold value, and if the value of the current ratio is not greater than the first threshold value, calculates the current ratio for each of a plurality of sections into which the image carrier is divided, compares the value of the current ratio for each of the plurality of sections with a second threshold value that is smaller than the first threshold value, and if the value of the current ratio in all of the plurality of sections is greater than the second threshold value, warns of the end of the life of the cleaning blade.

6. 5. An image forming apparatus according to claim 1, wherein the estimation unit compares the value of the current ratio with a first threshold value, and if the value of the current ratio is not greater than the first threshold value, calculates the current ratio for each of a plurality of sections into which the image carrier is divided, compares the value of the current ratio for each of the plurality of sections with a second threshold value that is smaller than the first threshold value, and if there is a section among the plurality of sections in which the value of the current ratio is not greater than the second threshold value, recommends replacement of the cleaning blade.

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