Image forming apparatus and control method

Abstract

Embodiments of the present application relate to an image forming apparatus and a control method. An image forming apparatus of an embodiment includes a photoreceptor, a charger, an exposure section, and a control section. The charger charges a surface of the photoreceptor. The exposure section exposes the photoreceptor charged by the charger using a light emitting diode. The control section controls the exposure section so that an exposure energy of the exposure section is constant.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to an image forming apparatus and a control method. BACKGROUND

[0002] There is an image forming apparatus that exposes a photoreceptor using a light emitting diode. The light amount of the light emitting diode gradually decreases. When the light amount decreases, exposure energy decreases. SUMMARY

[0003] An image forming apparatus of an embodiment includes a photoreceptor, a charger that charges a surface of the photoreceptor, an exposure section that exposes the photoreceptor charged by the charger using a light emitting diode, and a control section that controls the exposure section so that exposure energy of the exposure section is constant.

[0004] A control method of an embodiment controls an image forming apparatus that includes a photoreceptor, a charger that charges a surface of the photoreceptor, and an exposure section that exposes the photoreceptor charged by the charger using a light emitting diode. The control method includes a control step in which the exposure section is controlled so that exposure energy of the exposure section is constant. BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 is an appearance view that shows one example of an image forming apparatus 1 of an embodiment.

[0006] Figure 2 is a view that shows one example of a schematic configuration of the image forming apparatus 1 of an embodiment.

[0007] Figure 3 is a view that shows a degree of decrease in light emission amount of an organic light emitting diode.

[0008] Figure 4 is a view that shows a degree of increase in duty ratio.

[0009] Figure 5 is a view that shows exposure energy.

[0010] Figure 6 is a flowchart that shows a processing flow common to three control methods.

[0011] Figure 7 is a flowchart that shows a flow of processing A.

[0012] Figure 8 is a flowchart that shows a flow of processing B.

[0013] Figure 9 is a flowchart that shows a flow of processing C. DETAILED DESCRIPTION

[0014] The image forming apparatus of the embodiment has a photoreceptor, a charger, an exposure section, and a control section. The charger charges a surface of the photoreceptor. The exposure section exposes the photoreceptor charged by the charger using a light emitting diode. The control section controls the exposure section so that an exposure energy of the exposure section is constant.

[0015] Hereinafter, the image forming apparatus of the embodiment will be described with reference to the drawings.

[0016] Figure 1 is an appearance view showing one example of the image forming apparatus 1 of the embodiment. The image forming apparatus 1 is, for example, a multifunction peripheral (MFP). The image forming apparatus 1 reads an image formed on a sheet-like recording medium such as paper and generates digital data (an image file). The image forming apparatus 1 forms an image on paper using toner according to the digital data.

[0017] The image forming apparatus 1 has a display section 110, an image reading section 120, an image forming section 130, and a paper feeding section 140.

[0018] The display section 110 functions as an output interface that displays characters and images. The display section 110 also functions as an input interface that accepts an instruction from a user. The display section 110 is, for example, a liquid crystal display having a touch panel.

[0019] The image reading section 120 is a color scanner. The image reading section 120 reads an image formed on a sheet-like recording medium such as paper. The image reading section 120 converts the read image on the medium into digital data. The image reading section 120 has, for example, a CIS (Contact Image Sensor) or a CCD (Charge Coupled Devices).

[0020] The image forming section 130 forms an image on a recording medium using toner. The image forming section 130 forms an image on a recording medium according to image data read by the image reading section 120 or image data received from an external device.

[0021] The paper feeding section 140 accommodates a recording medium. The paper feeding section 140 supplies the recording medium to the image forming section 130.

[0022] In the image forming section 130 of the embodiment, at least a colored toner is used. The colored toner is a toner that contains a yellow (Y), a magenta (M), a cyan (C), and a black (K) pigment respectively.

[0023] Figure 2 is a diagram showing one example of a schematic configuration of an image forming apparatus 1 of an embodiment.

[0024] The image forming apparatus 1 is an image forming apparatus of an intermediate transfer method. The image forming apparatus 1 includes a paper discharge section 11, a primary transfer section 30, a secondary transfer section 12 (a counter roller 122 and a secondary transfer roller 121), an intermediate transfer belt 13, a fixing section 14, a control section 15, and a paper feed section 140.

[0025] The control section 15 controls the entire image forming apparatus. The control section 15 includes an arithmetic device and a storage device. The paper discharge section 11 discharges the paper 40, on which a fixing process has been performed by the fixing section 14, to a paper discharge space not shown.

[0026] The primary transfer section 30 includes an image forming station 20Y, an image forming station 20M, an image forming station 20C, an image forming station 20K, a primary transfer roller 30Y, a primary transfer roller 30M, a primary transfer roller 30C, and a primary transfer roller 30K.

[0027] The image forming station 20Y is disposed upstream of the image forming station 20M. The image forming station 20Y includes a photoreceptor 21Y, a photoreceptor cleaner 22Y, a charging device 23Y, an exposure device 24Y, and a developing device 25Y.

[0028] The image forming station 20M is disposed upstream of the image forming station 20C. The image forming station 20M includes a photoreceptor 21M, a photoreceptor cleaner 22M, a charging device 23M, an exposure device 24M, and a developing device 25M.

[0029] The image forming station 20C is disposed upstream of the image forming station 20K. The image forming station 20C includes a photoreceptor 21C, a photoreceptor cleaner 22C, a charging device 23C, an exposure device 24C, and a developing device 25C.

[0030] The image forming station 20K is disposed downstream of the image forming station 20C. The image forming station 20K includes a photoreceptor 21K, a photoreceptor cleaner 22K, a charging device 23K, an exposure device 24K, and a developing device 25K.

[0031] The photoreceptors 21Y, 21M, 21C, and 21K have an organic photoconductor (OPC) on their surfaces.

[0032] The photoreceptor cleaners 22Y, 22M, 22C, and 22K remove residual toner on the surfaces of the photoreceptors 21Y, 21M, 21C, and 21K. The residual toner is toner that remains on the surface of the photoreceptor after the primary transfer.

[0033] The charging devices 23Y, 23M, 23C, and 23K uniformly charge the surfaces of the respective photosensitive bodies 21Y, 21M, 21C, and 21K. The charging devices 23Y, 23M, 23C, and 23K are, for example, grid-controlled corona chargers.

[0034] The exposure devices 24Y, 24M, 24C, and 24K acquire image data from the control section 15. The exposure devices 24Y, 24M, 24C, and 24K irradiate laser light corresponding to the acquired image data onto the photosensitive bodies 21Y, 21M, 21C, and 21K. The exposure devices 24Y, 24M, 24C, and 24K scan the laser light in the axial direction of the photosensitive bodies 21Y, 21M, 21C, and 21K. Electrostatic latent images are formed on the photosensitive bodies 21Y, 21M, 21C, and 21K by the scanning exposure of the laser light.

[0035] The developing devices 25Y, 25M, 25C, and 25K each include a developing roller and a developing motor.

[0036] The developing agent Y is accommodated in the developing device 25Y. The developing agent M is accommodated in the developing device 25M. The developing agent C is accommodated in the developing device 25C. The developing agent K is accommodated in the developing device 25K. The developing agents are mixtures of toners and magnetic carriers.

[0037] In the developing device 25Y, a developing bias is applied to the developing roller. By the developing bias, the developing agent Y is supplied to the photosensitive body 21Y. Also, the electrostatic latent image formed on the photosensitive body 21Y by the exposure device 24Y is formed as a toner image of the yellow toner.

[0038] In the developing device 25M, a developing bias is applied to the developing roller. By the developing bias, the developing agent M is supplied to the photosensitive body 21M. Also, the electrostatic latent image formed on the photosensitive body 21M by the exposure device 24M is formed as a toner image of the magenta toner.

[0039] In the developing device 25C, a developing bias is applied to the developing roller. By the developing bias, the developing agent C is supplied to the photosensitive body 21C. Also, the electrostatic latent image formed on the photosensitive body 21C by the exposure device 24C is formed as a toner image of the cyan toner.

[0040] In the developing device 25K, a developing bias is applied to the developing roller. By the developing bias, the developing agent K is supplied to the photosensitive body 21K. Also, the electrostatic latent image formed on the photosensitive body 21K by the exposure device 24K is formed as a toner image of the black toner.

[0041] The intermediate transfer belt 13 is in contact with the primary transfer section 30. The intermediate transfer belt 13 is supported by the support roller 17, the driven roller 18, and the tension roller 19. The intermediate transfer belt 13 rotates in the direction of the arrow m.

[0042] The primary transfer roller 30Y is pressed against the photosensitive body 21Y via the intermediate transfer belt 13. In addition, a transfer bias is applied to the primary transfer roller 30Y. Thus, the toner image of yellow toner is transferred (primary transfer) to the intermediate transfer belt 13.

[0043] The primary transfer roller 30M is pressed against the photosensitive body 21M via the intermediate transfer belt 13. In addition, a transfer bias is applied to the primary transfer roller 30M. Thus, the toner image of magenta toner is transferred (primary transfer) to the intermediate transfer belt 13.

[0044] The primary transfer roller 30C is pressed against the photosensitive body 21C via the intermediate transfer belt 13. In addition, a transfer bias is applied to the primary transfer roller 30C. Thus, the toner image of cyan toner is transferred (primary transfer) to the intermediate transfer belt 13.

[0045] The primary transfer roller 30K is pressed against the photosensitive body 21K via the intermediate transfer belt 13. In addition, a transfer bias is applied to the primary transfer roller 30K. Thus, the toner image of black toner is transferred (primary transfer) to the intermediate transfer belt 13. The transfer bias is applied to the primary transfer roller 30Y, the primary transfer roller 30M, the primary transfer roller 30C, and the primary transfer roller 30K in this order.

[0046] Paper is fed from the paper feed section 140 to the secondary transfer section 12. The secondary transfer section 12 includes a secondary transfer roller 121 and a counter roller 122.

[0047] The secondary transfer section 12 is disposed downstream of the image forming station 20K. The secondary transfer roller 121 is disposed so as to face the counter roller 122 via the intermediate transfer belt 13. The secondary transfer roller 121 is a conductive roller. A prescribed secondary transfer bias is applied to the secondary transfer roller 121. Thus, the secondary transfer roller 121 transfers (secondary transfer) the toner images of yellow toner to black toner on the intermediate transfer belt 13 to the paper from the paper feed section 140. The toner images of yellow toner, magenta toner, cyan toner, and black toner, which are sequentially stacked on the intermediate transfer belt 13, are secondary transferred to the paper 40. Thus, an image in which the toner images of black toner, cyan toner, magenta toner, and yellow toner are sequentially stacked is formed on the paper 40. Note that the intermediate transfer belt 13 is cleaned by a belt cleaner, not shown, after the secondary transfer is completed.

[0048] The fixing section 14 performs heating and pressure fixation on the paper on which the toner images are transferred. For example, the fixing section 14 is a fixing device that uses electromagnetic induction heating.

[0049] Next, a control method of controlling the exposure devices 24Y, 24M, 24C, and 24K so that the exposure energy of the exposure devices 24Y, 24M, 24C, and 24K is constant will be described. Hereinafter, without particularly distinguishing the respective exposure devices 24Y, 24M, 24C, and 24K, any one of them will be described as the exposure device 24. Without particularly distinguishing the respective photosensitive bodies 21Y, 21M, 21C, and 21K, any one of them will be described as the photosensitive body 21. Without particularly distinguishing the respective charging devices 23Y, 23M, 23C, and 23K, any one of them will be described as the charging device 23.

[0050] In the exposure device 24 of the present embodiment, the photosensitive body 21 charged by the charging device 23 is exposed using an organic light emitting diode (OLED (Organic Light Emitting Diode)). The organic light emitting diode has a greater degree of reduction in the amount of light emitted than a general light emitting diode. Figure 3 is a graph showing the degree of reduction in the amount of light emitted by the organic light emitting diode. Figure 3 In the graph shown, the horizontal axis represents the light emission time, and the vertical axis represents the amount of light emitted. As shown, Figure 3 The amount of light emitted by the organic light emitting diode decreases over time.

[0051] When the amount of light emitted by the organic light emitting diode decreases, the exposure energy to the photosensitive body 21 decreases. The exposure energy is determined by the amount of light emitted and the light emission duty ratio (hereinafter, simply referred to as "duty ratio"). In order to obtain the same exposure energy, it is possible to consider increasing the amount of light emitted and decreasing the duty ratio, or decreasing the amount of light emitted and increasing the duty ratio.

[0052] The organic light emitting diode is more likely to deteriorate when the amount of light emitted is increased and the duty ratio is decreased than when the amount of light emitted is decreased and the duty ratio is increased. For this reason, in the present embodiment, the exposure energy is kept constant by the control of decreasing the amount of light emitted and increasing the duty ratio, and the deterioration of the organic light emitting diode is suppressed.

[0053] Figure 4 is a graph showing the degree of increase in the duty ratio. In Figure 4 In the graph shown, the horizontal axis represents the light emission time, and the vertical axis represents the duty ratio. As shown, Figure 4 The control unit 15 increases the duty ratio over time, as shown.

[0054] Figure 5 is a graph showing the exposure energy. In Figure 5 In the graph shown, the horizontal axis represents the light emission time, and the vertical axis represents the exposure energy. The control unit 15 controls the exposure device 24 so that the exposure energy is constant by increasing the duty ratio, as shown. Figure 5 ​

[0055] A specific control method will be described with a flowchart. There are three control methods in this embodiment. Figure 6 is a flowchart showing a processing flow common to the three control methods.

[0056] The control section 15 determines whether or not image formation is instructed (ACT 101). The image formation instruction here includes, for example, an image formation instruction by a user on the display section 110 and an image formation instruction from another device via a network.

[0057] In a case where image formation is instructed (ACT 101: YES), the control section 15 acquires the duty ratio r stored in the storage device. The duty ratio r is stored in a nonvolatile storage device. The control section 15 performs image formation processing (ACT 103). In the image formation processing here, the control section 15 controls the exposure device 24 so as to perform exposure using the duty ratio r acquired in ACT 102.

[0058] The control section 15 determines whether or not the image formation processing is ended (ACT 104). In a case where the image formation processing is ended (ACT 104: YES), the control section 15 performs duty ratio derivation processing (ACT 105) of deriving a duty ratio and ends the present processing. In the duty ratio derivation processing, there are three kinds of processing as described above. The three kinds of processing are processing A, processing B, and processing C, respectively. Further, the derived duty ratio is stored as the duty ratio r acquired in ACT 102. That is, the duty ratio derivation processing is processing of updating the duty ratio r.

[0059] Figure 7 is a flowchart showing a flow of processing A. The processing A is processing of deriving a duty ratio from a light amount of an organic light emitting diode, a duty ratio of the organic light emitting diode, and a light emission time of the organic light emitting diode.

[0060] The control section 15 acquires the light emission time t (ACT 201). The light emission time here is a light emission time of the organic light emitting diode in the image formation processing of ACT 103. The control section 15 substitutes a*P*r*t / F into d (ACT 202). Here, "*" is a multiplication operator.

[0061] In a*P*r*t / F, a is a coefficient. P is a light amount. r is the duty ratio acquired in ACT 102. t is the light emission time acquired in ACT 201. F is a life determination value. This F and a are constants determined in advance in accordance with the performance of the organic light emitting diode or the like. Note that P, r, and t in a*P*r*t / F are values in the image formation processing of ACT 103. Therefore, d is a value determined for each of the image formation processings in ACT 103. Further, d is a value indicating a degree of use of the organic light emitting diode in the present image formation processing.

[0062] The control section 15 substitutes the sum of the current s and d (ACT 203) as a new s. The s is the cumulative value of d obtained by the above-described ACT 202 in each image forming process. In addition, the s is stored in a nonvolatile storage device.

[0063] The control section 15 substitutes the product of the current duty ratio r and (1 + d) as a new duty ratio r (ACT 204). The control section 15 stores the new duty ratio r in a nonvolatile storage device (ACT 205) and ends the process. The new duty ratio r thus stored is acquired in the ACT 102 and used in the next image forming process.

[0064] As described above, the d is a value decided for each image forming process, so the s which is the cumulative value thereof is a value indicating the degree of use of the organic light emitting diode so far. In addition, since the d is positive, the s monotonically increases. The a and F are decided in a manner that the s reaches F when the life of the organic light emitting diode is exhausted.

[0065] Figure 8 is a flowchart showing the flow of the process B. The process B is a process of deriving a duty ratio from the cumulative value of the energization time of the organic light emitting diode and the energization limit time of the organic light emitting diode.

[0066] The control section 15 acquires the energization time t (ACT 301). The energization time here is the energization time of the organic light emitting diode in the image forming process of the ACT 103. The control section 15 substitutes the sum of the current Tt and t as a new Tt (ACT 302). The Tt is the cumulative value of the energization time. In addition, the Tt is stored in a nonvolatile storage device.

[0067] The control section 15 substitutes b * Tt / Tm for d (ACT 303). Here, "*" is a multiplication operator. The b is a coefficient. The Tm is the energization limit time. The Tm and b are constants decided in advance in accordance with the performance or the like of the organic light emitting diode. The b and Tm are decided in a manner that the Tt reaches Tm when the life of the organic light emitting diode is exhausted.

[0068] The control section 15 substitutes the product of the initial value R of the duty ratio and (1 + d) as a new duty ratio r (ACT 304). The initial value R of the duty ratio is stored in a nonvolatile storage device. The control section 15 stores the new duty ratio r in a nonvolatile storage device (ACT 305) and ends the process. The new duty ratio r thus stored is acquired in the ACT 102 and used in the next image forming process.

[0069] Thus, in the process B, the duty cycle is derived from the cumulative value of the energization time of the organic light emitting diode and the energization limit time of the organic light emitting diode. Thereby, the control section 15 can keep the exposure energy constant and suppress the deterioration of the organic light emitting diode.

[0070] Figure 9 is a flowchart showing the flow of the process B. The process C is a process of deriving the duty cycle from the number of sheets on which images are formed in the image forming apparatus 1.

[0071] The control section 15 acquires the number p (ACT401). The number p here is the number of sheets on which images are formed in the image forming process of the ACT103. The control section 15 substitutes the sum of the current Up and p as a new Up (ACT402). The Up is counted by the number of sheets. In addition, the Up is stored in the nonvolatile storage device.

[0072] The control section 15 substitutes c*Up / Um as d (ACT403). Here, "*" is a multiplication operator. The c is a coefficient. The Um is counted by the number of sheets. The Um and the c are constants decided in advance in accordance with the performance of the organic light emitting diode or the like. The c and the Um are decided in a manner that the Up reaches the Um when the life of the organic light emitting diode is exhausted.

[0073] The control section 15 substitutes the product of the initial value R of the duty cycle and (1+d) as a new duty cycle r (ACT404). The initial value R of the duty cycle is stored in the nonvolatile storage device. The control section 15 stores the new duty cycle r to the nonvolatile storage device (ACT405) and ends the process. The new duty cycle r thus stored is acquired in the ACT102 and used in the next image forming process.

[0074] Thus, in the process C, the duty cycle is derived from the number of sheets on which images are formed in the image forming apparatus 1. Thereby, the control section 15 can keep the exposure energy constant and suppress the deterioration of the organic light emitting diode.

[0075] The processes A, B, and C described above all derive the duty cycle in accordance with the actual usage degree (emission time, energization time, number of sheets passed) of the organic light emitting diode. Therefore, the control section 15 can perform the control in accordance with the actual state.

[0076] In addition, in the present embodiment, the control is performed by the duty cycle rather than the emission amount. Thereby, in the present embodiment, the life of the organic light emitting diode can be extended compared to the case where the emission amount is increased.

[0077] In the present embodiment, the organic light emitting diode is exemplified, but is not limited thereto. As long as it is a light emitting device that can control the exposure energy by the duty cycle, it can be any light emitting device.

[0078] Figure 7 、 Figure 8 、 Figure 9 The mathematical expression for obtaining d described in the above is not limited to this. The mathematical expression for obtaining d can be appropriately determined in accordance with the characteristics of the organic light emitting diode so that the exposure energy is constant.

[0079] A program (control program) for realizing all or part of the functions of the above-described control section 15 is recorded in a computer-readable recording medium. Furthermore, the program recorded in the recording medium can be realized by the CPU.

[0080] In addition, the "computer-readable recording medium" refers to a removable medium and a storage section. For example, the removable medium is a floppy disk, a magnetic disk, a ROM, a CD-ROM. For example, the storage section is a hard disk built in a computer system. Furthermore, the "computer-readable recording medium" refers to a network, a medium that dynamically holds a program for a short time, and a medium that holds a program at a timing. For example, the network is the Internet. For example, the medium that dynamically holds a program is a communication line when a program is transmitted via a communication line. For example, the medium that holds a program at a timing is a volatile memory inside a computer system that becomes a server or a client. In addition, the above-described program can also be used to realize part of the above-described functions. Furthermore, it can also be combined with a program already recorded in a computer system to realize the above-described functions.

[0081] Although several embodiments have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and equivalents thereof as recited in the claims.

Claims

1. An image forming apparatus comprising: a photoreceptor; a charger that charges a surface of the photoreceptor; an exposure section that exposes the photoreceptor charged by the charger using a light emitting diode; and a control section that controls the exposure section so as to make an exposure energy of the exposure section constant by adjusting a light emission duty cycle of the light emitting diode in such a manner that a light emission light amount is reduced and the light emission duty cycle is increased in accordance with an actual usage degree of the light emitting diode, the control section performing a duty cycle derivation process that derives the light emission duty cycle in a case where an image forming process ends, the duty cycle derivation process being a process of updating the light emission duty cycle.

2. The image forming apparatus according to claim 1, wherein the control section controls the exposure section so as to make the exposure energy of the exposure section constant in accordance with a light amount of the light emitting diode, the light emission duty cycle of the light emitting diode, and a light emission time of the light emitting diode.

3. The image forming apparatus according to claim 1, wherein the control section controls the exposure section so as to make the exposure energy of the exposure section constant in accordance with a cumulative value of an energization time of the light emitting diode and an energization limit time of the light emitting diode.

4. The image forming apparatus according to claim 1, wherein the control section controls the exposure section so as to make the exposure energy of the exposure section constant in accordance with a number of sheets on which images are formed in the image forming apparatus.

5. The image forming apparatus according to any one of claims 1 to 3, wherein the light emitting diode is an organic light emitting diode.

6. A control method of controlling an image forming apparatus, wherein the image forming apparatus comprises: a photoreceptor; a charger that charges a surface of the photoreceptor; and an exposure section that exposes the photoreceptor charged by the charger using a light emitting diode, the control method comprises a control step in which the exposure section is controlled so as to make an exposure energy of the exposure section constant by adjusting a light emission duty cycle of the light emitting diode in such a manner that a light emission light amount is reduced and the light emission duty cycle is increased in accordance with an actual usage degree of the light emitting diode, in the control step, a duty cycle derivation process that derives the light emission duty cycle is performed in a case where an image forming process ends, the duty cycle derivation process being a process of updating the light emission duty cycle.

7. The control method according to claim 6, wherein in the control step, the exposure section is controlled so as to make the exposure energy of the exposure section constant in accordance with a light amount of the light emitting diode, the light emission duty cycle of the light emitting diode, and a light emission time of the light emitting diode.

8. The control method according to claim 6, wherein in the control step, the exposure section is controlled so as to make the exposure energy of the exposure section constant in accordance with a cumulative value of an energization time of the light emitting diode and an energization limit time of the light emitting diode.

9. The control method according to claim 6, wherein In the control step, the exposure section is controlled so that the exposure energy of the exposure section is constant, in accordance with the number of sheets on which images are formed in the image forming apparatus.

10. The control method according to any one of claims 6 to 8, wherein The light emitting diode is an organic light emitting diode.

Images