JP2007047630A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an appropriate response according to the abrasion level of a body to be electrified, without increasing the cost of an image forming apparatus, in the image forming apparatus variably controlling an electrifying bias. <P>SOLUTION: The image forming apparatus 10 is provided with a rotatable photoreceptor 1 having an electrostatic latent image formed on a surface thereof and an electrifying device 2 to which the electrifying bias is applied and which electrifies the surface of the photoreceptor 1. A controller 7 calculates the integrated value of the product of the speed of revolution of the photoreceptor 1 and a coefficient corresponding to the electrifying bias at that time and controls image forming conditions such as the electrifying bias, based on the calculated integrated value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a charged body such as a photoconductor on which an electrostatic latent image is formed, and a charging device that charges a surface of the charged body by receiving a charging bias.

  In the image forming apparatus as described above, the surface of the photosensitive member, which is a member to be charged, is worn with use, and the characteristics (charging characteristics, photosensitive sensitivity, etc.) of the photosensitive member change accordingly. For this reason, conventionally, there has been used a technique for estimating the film thickness or film reduction amount of the photoreceptor and controlling the image forming conditions (exposure amount, developing bias, etc.) according to the estimation result.

  For example, Japanese Patent Application Laid-Open No. H10-228561 discloses a technique in which image forming parameters are changed according to the integrated value of the rotation amount of the photosensitive member. Japanese Patent Application Laid-Open No. H10-228561 describes a method of detecting a current flowing into a photoconductor during charging and setting an image forming condition based on the detection result.

JP-A-11-202572 JP-A-4-57068

  By the way, the minimum necessary charging bias for satisfactorily charging the surface of the photoreceptor varies depending on the film thickness of the photoreceptor and the environmental temperature and humidity. Also, the greater the charging bias, the greater the degree of wear of the photoreceptor. Therefore, in order to reduce the wear of the photosensitive member and extend the life, it is preferable to appropriately change the charging bias according to the film thickness and the ambient temperature and humidity, instead of making the charging bias constant.

  However, the technique described in Patent Document 1 cannot cope with a configuration in which the charging bias is variably controlled. This is because in the configuration in which the charging bias is variably controlled, the amount of film reduction per unit rotation speed is not constant, and the integrated value of the photosensitive member rotation amount does not indicate the film reduction amount. On the other hand, the technique described in Patent Document 2 requires a device for detecting the current flowing into the photosensitive member, which increases the cost.

  Therefore, the present invention provides an image forming apparatus capable of taking an appropriate measure according to the degree of wear of a charged body without increasing the cost of the apparatus.

  An image forming apparatus according to the present invention includes a rotatable object to be charged on which an electrostatic latent image is formed, and a charging device that charges the surface of the object to be charged upon application of a charging bias. An image forming apparatus in which a charging bias is variably controlled, a calculation unit that calculates an integrated value of a product of the number of rotations of the charged body and a coefficient corresponding to the charging bias at the time, and a calculation by the calculation unit And image forming condition control means for controlling the image forming condition based on the integrated value.

  In a preferred aspect of the present invention, the image forming condition control means changes the charging bias according to the integrated value.

  An image forming apparatus according to the present invention includes a rotatable charged body on which an electrostatic latent image is formed, and a charging apparatus that charges the surface of the charged body upon application of a charging bias. An image forming apparatus in which the charging bias is variably controlled, a calculating unit that calculates an integrated value of a product of the number of rotations of the member to be charged and a coefficient corresponding to the charging bias at that time; and the calculating unit And an informing means for informing information on the life of the charged body based on the integrated value calculated by the above.

  According to the present invention, it is possible to provide an image forming apparatus capable of taking an appropriate measure according to the degree of wear of the charged body without increasing the cost of the apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 prints an image on a transfer material such as paper using an electrophotographic system, and is, for example, a digital copying machine, an analog copying machine, a printer, a facsimile machine, or the like.

[Overall image forming apparatus]
First, the overall configuration and operation of the image forming apparatus 10 will be described. Since the electrophotographic process is widely known, it will be briefly described here.

  In FIG. 1, an image forming apparatus 10 includes a photoreceptor 1 that rotates in the direction of an arrow R as a rotatable member to be charged on which an electrostatic latent image is formed. Here, the photoreceptor 1 is a laminated organic photoreceptor drum in which a photoconductive layer such as a charge generation layer (CGL) or a charge transport layer (CTL) is laminated on a conductive substrate such as aluminum. However, the photoreceptor 1 may be other types such as a photoreceptor belt.

  A charging device 2 that uniformly charges the surface of the photoconductor 1 to a predetermined potential along the rotation direction (the direction of the arrow R) around the photoconductor 1 and the surface of the charged photoconductor 1 according to an image. An exposure device 3 that forms an electrostatic latent image by irradiating light, a developing device 4 that develops the electrostatic latent image with toner, and a transfer device that transfers the developed toner image onto a recording paper (transfer material) P (here) , A transfer roll) 5 and a cleaning device (here, a cleaner having a cleaning blade) 6 for removing the toner remaining on the surface of the photoreceptor 1 after the transfer are arranged in this order.

  Further, the image forming apparatus 10 includes a control device 7 that controls the entire apparatus. The control device 7 is a motor (not shown) that rotates the photoreceptor 1, a charging bias applied to the charging device 2, an exposure amount by the exposure device 3, a developing bias applied to the developing device 4, and an application to the transfer device 5. The transfer bias to be controlled is controlled. Here, the control device 7 is a circuit board on which a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like are mounted, and the function is stored in a recording medium such as a ROM. The program is implemented by the CPU.

  The image forming apparatus 10 having the above configuration operates as follows. That is, the photoreceptor 1 is rotationally driven in the direction of arrow R by a motor (not shown). At the charging position, the charging device 2 uniformly charges the surface of the photoreceptor 1 to a predetermined potential of, for example, about -600V to -800V. The uniformly charged surface of the photoreceptor 1 is conveyed to the exposure position by the rotation of the photoreceptor 1.

  At the exposure position, the exposure device 3 irradiates the uniformly charged surface of the photoreceptor 1 with light (for example, a laser beam based on image data) corresponding to the image pattern to be formed, and according to the image pattern. The surface of the photoreceptor 1 is neutralized to form an electrostatic latent image. The electrostatic latent image formed in this way is conveyed to the development position by the rotation of the photoreceptor 1.

  At the development position, the development device 4 develops the electrostatic latent image with toner. Specifically, in reversal development, a toner having the same polarity as the latent image charge is electrostatically attached to the neutralized portion of the surface of the photoreceptor 1, and in normal development, the toner has a polarity opposite to that of the latent image charge. The toner is electrostatically attached to the surface of the photoreceptor 1 where the charge is not removed, thereby forming a toner image corresponding to the image pattern. The toner image formed in this way is conveyed to the transfer position by the rotation of the photoreceptor 1.

  At the transfer position, the transfer device 5 transfers the toner image formed on the surface of the photoreceptor 1 onto the recording paper P conveyed to the transfer position in accordance with the rotation of the photoreceptor 1. Specifically, a transfer bias having a polarity opposite to that of the toner is applied to the transfer device 5, and the toner on the surface of the photoconductor 1 is transferred onto the recording paper P by an electrostatic force directed from the photoconductor 1 to the transfer device 5. After the transfer, the surface of the photoreceptor 1 is conveyed to a cleaning position by the rotation of the photoreceptor 1, and residual toner on the surface of the photoreceptor 1 is removed. On the other hand, the recording paper P to which the toner image has been transferred is conveyed to a fixing device (not shown), and the toner image is fixed on the recording paper P by the fixing device.

[Charging device]
The charging device 2 receives the charging bias and uniformly charges the surface of the photoreceptor 1 to a predetermined potential. The charging device 2 is preferably a contact-type charging device that performs charging by contacting the surface of the photosensitive member 1 from the viewpoint of lowering voltage or reducing ozone. As the contact charging device, various types such as a roll shape, a brush shape, a blade shape, and a belt shape can be used. A power supply device 8 is electrically connected to the charging device (hereinafter referred to as a charging roll) 2, and a predetermined charging bias is applied from the power supply device 8 to the charging roll 2.

  The charging method using the charging roll includes an AC charging method in which a charging bias in which an alternating current (AC) voltage is superimposed on a direct current (DC) voltage and a DC charging method in which only a DC voltage is applied. Although a method can also be adopted, an AC charging method is used here. Note that this AC charging method has an advantage in that it has excellent charging uniformity and high image quality compared to the DC charging method, but has a demerit in that the degree of film reduction (scraping) on the surface layer of the photoreceptor 1 is large. .

  As will be described later, the charging bias applied to the charging roll 2, such as the AC peak voltage value Vpp and the DC voltage value Vdc, is determined by the film thickness, environmental temperature / humidity, user setting, or process speed (photosensitive member). 1) and the like.

[About control devices]
As described above, the characteristics (charging characteristics and photosensitivity) of the photoreceptor 1 vary depending on the film thickness. Therefore, the control device 7 has a function of estimating the film reduction amount (scraping amount) of the photosensitive member 1 and controlling the image forming conditions based on the estimation result. Hereinafter, the configuration and operation of the control device 7 according to this function will be specifically described.

  As shown in FIG. 1, the control device 7 includes a film reduction amount calculation unit 7a, a film reduction amount holding unit 7b, and an image forming condition control unit 7c as functional blocks.

  The film reduction amount calculation unit 7a calculates an integrated value of the product of the number of rotations of the photosensitive member 1 and a coefficient corresponding to the charging bias at that time. The amount is estimated.

  The concept of estimating the amount of film loss by the film thickness reduction calculation unit 7a is as follows. As the photoconductor 1 rotates, the surface layer is scraped off by rubbing against the cleaning device 6 and the like. The degree of film reduction at this time increases as the charging bias (particularly the AC peak-to-peak voltage Vpp) increases, and the amount of film reduction per unit rotational speed can be expressed as a function α (b) of the charging bias b. Therefore, the amount of film reduction when the photosensitive member 1 is rotated by the number of rotations Δn is the product Δn of the number of rotations Δn and the amount of film reduction α (b) per unit rotation number corresponding to the charging bias b at the time of rotation. Α (b) can be expressed, and if this product Δn · α (b) is integrated from the start of use of the photoreceptor 1 to the present time, the amount of film reduction from the initial film thickness of the photoreceptor 1 can be obtained. Can do. Therefore, the film reduction amount calculation unit 7a calculates an integrated value of the product of the number of rotations of the photoconductor 1 and a coefficient corresponding to the charging bias at that time as the estimated film reduction amount.

  Here, the coefficient according to the charging bias is a coefficient indicating the degree of film reduction according to the charging bias (specifically, the AC peak voltage value Vpp, the DC voltage value Vdc, or a combination thereof). For example, the amount of film reduction per unit rotation number (μm / 1 rotation) obtained by experiment. Note that the charging bias value itself can be used as the coefficient.

  Further, calculating the integrated value includes calculating a value substantially indicating the integrated value. For example, it includes calculating the integrated value of the product of the rotation time (or travel distance) of the photosensitive member 1 and the coefficient.

  Moreover, the film loss calculation part 7a should just be able to calculate the value which shows the said integrated value substantially as a result, and the specific calculation method is not specifically limited. For example, the film loss calculation unit 7a can obtain an integrated value obtained by integrating the above coefficient with the rotation speed and rotation time of the photosensitive member 1 as the integrated value y as in the following formulas (1) and (2). .

In the above formula (1), n is the rotational speed from the start of use of the photoreceptor 1, b (n) is the charging bias at the time of the rotational speed n, and α {b (n)} is the rotational speed n. it is a coefficient corresponding to the charging bias at the time, n _a is the rotational speed of the current (film reduction amount estimation time). In the above equation (2), t is the rotation time from the start of use of the photoreceptor 1, b (t) is the charging bias at the time of the rotation time t, and α {b (t)} is the rotation time. is a coefficient corresponding to the charging bias at the time of t, t _a is the rotation time of the current (film reduction amount estimation time).

  Further, for example, the film reduction amount calculation unit 7a may obtain the integrated value y by summing up the products of the coefficient for each charging bias and the number of rotations as in the following formula (3).

In the above formula (3), i (0 to k) is a subscript for distinguishing each charging bias, b _i is the i-th charging bias, and α (b _i ) is in accordance with the charging bias b _i . N _i is the cumulative number of rotations when the charging bias b _i is applied.

In the present embodiment, it is assumed that the film reduction amount calculation unit 7a calculates the estimated film reduction amount y (μm) using the above equation (3). Here, k = 25 in the above formula (3), the charging bias b ₀ is [Vdc = 0V, Vpp = 0V], and b _i (i = 1-25) is [Vdc = −700 V, Vpp = (1350 + 10). Xi) V]. The coefficient α (b _i ) is a film reduction amount (μm / 1 rotation) per unit rotation number obtained in advance by experiments, and is a preset constant. Accumulated rotation number N _i is counted by film reduction amount calculating portion 7a, is stored in a predetermined rotational speed holding region, the photosensitive member 1 is cleared to 0 when it is replaced with a new.

  The film loss amount holding unit 7b is a non-volatile storage area that holds the integrated value calculated by the film loss amount calculating unit 7a, and is realized by, for example, NVRAM (Non Volatile RAM). In the present embodiment, the film reduction amount holding unit 7b holds the estimated film reduction amount y (μm) calculated by the film reduction amount calculation unit 7a as the integrated value.

  The image forming condition control unit 7c controls the image forming condition based on the integrated value held in the film reduction amount holding unit 7b. In actuality, the image forming condition control unit 7c is calculated by the film reduction amount calculation unit 7a. The image forming conditions are controlled based on the estimated film reduction amount. In the present embodiment, the image forming condition control unit 7c changes the charging bias according to the estimated film reduction amount y. Specifically, since the discharge start voltage decreases as the film thickness of the photoreceptor 1 decreases, the AC peak voltage Vpp applied to the charging roll 2 decreases so that the AC peak-to-peak voltage Vpp decreases as the estimated film reduction amount increases. The peak-to-peak voltage value Vpp is changed stepwise. More specifically, the image forming condition control unit 7c holds a correspondence table between the estimated film reduction amount and the charging bias shown in FIG. 2, and switches the charging bias step by step according to the correspondence table.

  In this embodiment, the charging bias is controlled based on the integrated value. However, other image forming conditions such as the exposure amount and the developing bias of the exposure apparatus 3 may be controlled based on the integrated value. Good. For example, the photosensitive sensitivity of the photosensitive member 1 decreases as the film thickness of the photosensitive member 1 decreases. Therefore, the exposure amount by the exposure device 3 may be changed so that the exposure amount increases as the integrated value increases.

  FIG. 3 is a timing chart for explaining the operation of the control device 7. Hereinafter, an example of the operation of the control device 7 having the above configuration will be specifically described with reference to FIG. Here, it is assumed that the estimated film reduction amount y = 7.00 μm is currently held in the film reduction amount holding unit 7b.

At time t <b> 0 in FIG. 3, when receiving a copy start instruction from the user via a user interface (not shown), the control device 7 turns on a motor (not shown) to start rotation of the photoreceptor 1. At this time, the charging bias is b _0, that is, off.

Next, in the non-image forming period from time t0 to t1, the image forming condition control unit 7c reads the estimated film reduction amount y from the film reduction amount holding unit 7b, and refers to the preset correspondence table to determine the estimated film A charging bias b ₁₃ (Vdc = −700 V, Vpp = 1480 V) corresponding to the reduction amount y = 7.00 μm is specified. Then, the image forming condition control unit 7c, to the charging bias b ₁₃ identified, environmental temperature and humidity, user settings, performs a correction based on the correction factors such as process speed, to determine the final charging bias. In the present embodiment, the image forming condition control unit 7c, based on the output of a humidity sensor (not shown), according to a difference from the reference when the humidity is higher than the reference according to a preset table or calculation formula. The charging bias is lowered to b ₁₃ → b ₁₂ →..., And when the humidity is lower than the reference, the charging bias is increased to b ₁₃ → b ₁₄ → ... according to the difference from the reference. Here, the humidity is lower than the reference, the charging bias is assumed that has changed from b ₁₃ to b _15.

Then, at time t1, the image forming condition control unit 7c instructs the application of the charging bias b ₁₅ determined above to the power supply 8. As a result, the charging bias b ₁₅ (Vdc = −700 V, Vpp = 1500 V) is applied to the charging roll 2 from the power supply device 8, and the surface of the photoreceptor 1 is uniformly charged to about −700 V. Thereafter, image formation is performed in the period up to time t2.

Then, at time t2, the image forming condition control unit 7c is in a charging bias b _0, or OFF.

In the non-image forming period from time t2 to time t3, the film reduction amount calculation unit 7a performs an update process of the accumulated rotational speed N _i (i = 0 to 25) for each charging bias stored in the rotational speed holding area. . Specifically, film reduction amount calculating portion 7a, the rotational speed holding area read the accumulated rotation number N ₀ of the charging bias b _0, the accumulated rotation number N ₀ read, rotation time {(t1-t0) + (t3-t2)} by adding the rotational speed of the photosensitive member 1 corresponding to the search of a new cumulative rotational speed N _0, and writes it to the rotational speed holding area. Further, the rotational speed holding area read the accumulated rotation number N ₁₅ of the charging bias b _15, the accumulated rotation number N ₁₅ read, added to the rotational speed of the photosensitive member 1 corresponding to the rotation time (t2-t1) seeking new cumulative rotational speed N ₁₅ Te, writes this into rotation number storing region. Note that the rotation speed corresponding to the rotation time is obtained based on the process speed and the circumference of the photoreceptor 1. Then, the film reduction amount calculation unit 7a calculates the estimated film reduction amount y by substituting the updated cumulative number of rotations _Ni into the above formula (3), and retains the film reduction amount as a new estimated film reduction amount. Write to part 7b. This new estimated film reduction amount y is used by the image forming condition control unit 7c in the next print job.

  The operation of the control device 7 in one print job has been described above. When the control device 7 operates in this way, the photoconductor 1 can be seen in a long period from the start of use of the photoconductor 1 to the end of its life. As shown in FIGS. 4 and 5, the AC peak-to-peak voltage value Vpp transitions. 4 shows how the AC peak-to-peak voltage value Vpp changes as the film loss increases, and FIG. 5 shows how the AC peak-to-peak voltage value Vpp changes as the rotational speed of the photoreceptor 1 increases. ing. 4 and 5 show the AC peak-to-peak voltage value Vpp before correction based on the environment and the like.

  As described above, in this embodiment, image formation includes a rotatable charged body on which an electrostatic latent image is formed on the surface, and a charging device that charges the surface of the charged body upon application of a charging bias. In the apparatus, an integrated value of a product of the number of rotations of the member to be charged and a coefficient corresponding to the charging bias at that time is calculated, and image forming conditions are controlled based on the calculated integrated value. Therefore, according to the present embodiment, even when the charging bias is variably controlled based on predetermined conditions (the degree of wear of the object to be charged, environmental temperature and humidity, user settings, etc.) Appropriate image forming conditions can be set according to the degree of wear of the member to be charged without using a special device. That is, it is possible to take an appropriate measure according to the degree of wear of the member to be charged without increasing the cost of the apparatus. Specifically, the amount of film reduction of the photoreceptor 1 can be estimated well without adding a special device, and an appropriate image forming parameter can be set according to the film thickness of the photoreceptor 1. .

  In the present embodiment, since the charging bias is changed according to the integrated value, the charging bias can be controlled to an appropriate magnitude according to the degree of wear of the member to be charged. For this reason, compared to the case where the charging bias is constant, the wear of the member to be charged can be reduced, and the life of the member to be charged can be extended.

  In addition, this invention is not limited to the said embodiment, It can change variously within the range which does not deviate from the summary of this invention. For example, in the above embodiment, the control device 7 controls the image forming conditions based on the integrated value, but may report information on the life of the charged body based on the integrated value. In one aspect of this configuration, the control device 7 displays a screen indicating that the life of the photosensitive member 1 has expired when the estimated film reduction amount calculated by the film reduction amount calculation unit 7a exceeds a predetermined life end film reduction threshold. The user is notified by display or the like. In another aspect, the control device 7 estimates the remaining life (the remaining number of printable sheets and the like) based on the estimated film reduction amount, and notifies the user of the remaining life by screen display or the like. In yet another aspect, the control device 7 notifies the estimated film loss amount to a service center such as a manufacturer via a communication line.

  In the above embodiment, the AC component of the charging bias is controlled at a constant voltage, but it is also possible to control at a constant current. In this case, the film reduction amount calculation unit 7a may calculate an integrated value of the product of the number of rotations of the photosensitive member 1 and a coefficient corresponding to the AC current value at that time. The image forming condition control unit 7c may change the AC current value based on the integrated value. Also, a DC charging method can be used, and in this case, the film reduction amount calculation unit 7a calculates an integrated value of the product of the number of rotations of the photoreceptor 1 and a coefficient corresponding to the DC voltage value at that time. Good. The image forming condition control unit 7c may change the DC voltage value based on the integrated value. In the AC charging method, the AC peak-to-peak voltage may be decreased according to the increase in the integrated value, and the charging DC voltage and the developing DC voltage may be decreased.

  In the above embodiment, the image forming conditions such as the charging bias are controlled based on the estimated film reduction amount. However, the estimated film thickness is obtained from the initial film thickness value and the estimated film reduction amount, and this estimated film is determined. The image forming conditions may be controlled based on the thickness.

  In the configuration in which the process unit including the photosensitive member 1 is detachably attached to the apparatus main body, it is preferable that the film reduction amount holding portion 7b is provided in the process unit.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is a figure which shows the corresponding | compatible table of the estimated film reduction amount and charging bias. It is a timing chart for demonstrating operation | movement of a control apparatus. It is a figure which shows the mode of the change of the voltage value Vpp between AC peaks accompanying the increase in film loss. It is a figure which shows the mode of the change of the voltage value Vpp between AC peaks accompanying the increase in the rotation speed of a photoconductor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Photoconductor, 2 Charging apparatus (charging roll), 3 Exposure apparatus, 4 Developing apparatus, 5 Transfer apparatus, 6 Cleaning apparatus, 7 Control apparatus, 7a Film reduction amount calculation part, 7b Film reduction amount holding part, 7c Image formation conditions Control unit, 8 power supply device, 10 image forming apparatus.

Claims (3)

An image forming apparatus comprising: a rotatable charged object on which an electrostatic latent image is formed; and a charging device that charges the surface of the charged object by applying a charging bias, wherein the charging bias is variably controlled. A device,
A calculating means for calculating an integrated value of a product of the number of rotations of the member to be charged and a coefficient corresponding to the charging bias at that time;
Image forming condition control means for controlling the image forming conditions based on the integrated value calculated by the calculating means;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The image forming condition control means changes the charging bias in accordance with the integrated value. An image forming apparatus comprising: a rotatable charged object on which an electrostatic latent image is formed; and a charging device that charges the surface of the charged object by applying a charging bias, wherein the charging bias is variably controlled. A device,
A calculating means for calculating an integrated value of a product of the number of rotations of the member to be charged and a coefficient corresponding to the charging bias at that time;
Informing means for informing information on the life of the charged body based on the integrated value calculated by the calculating means;
An image forming apparatus comprising:

Images