JP2009139637A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect present electrical state of an image holder at high precision. <P>SOLUTION: The image holder 22 includes a cylindrical conductive supporting body 96 and a photoreceptor layer 98 covering an outer surface of the conductive supporting layer 96. The photoreceptor layer 98 is comprised of a charge generating layer 100, a charge transporting layer (CT layer) 102 and a protective layer (OC layer) 104. A control unit 66 contains a correction section 90 composed as a program, a charge amount detection section 92 and a layer thickness calculating section 94. The correction section 90 corrects the present direct current which is detected by a direct current detection section 86 according to the direct current stored within the latest prescribed period by a memory 76, alternating current detected by an alternating current detection section 88, rotational speed (process speed) of the image holder 22 and the calculated result by the layer thickness calculating section 94. For example, the correction section 90 corrects direct current Idc detected by the direct current detection section 86 by using a correction term which is varied according to passage of time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses an image forming apparatus that detects and stores a current amount according to the film thickness of an image carrier and corrects a detection result based on a temporal transition such as a change in environmental conditions to control process setting conditions. Disclose.

JP 2004-334063 A

  An object of the present invention is to provide an image forming apparatus capable of accurately detecting the current electrical state of an image carrier.

  In order to achieve the above object, the present invention according to claim 1 is directed to a rotating image carrier that is coated with a plurality of coating layers, and a charging member that charges the image carrier in contact with or in proximity to the image carrier. A power supply means for applying a voltage obtained by superimposing an alternating voltage and a direct current voltage to the charging member, a direct current detection means for detecting a direct current flowing through the charging member, and the direct current detection means for a predetermined period. Storage means for storing the DC current detected at the time, and correction means for correcting the current DC current detected by the DC current detection means based on the DC current stored in the most recent predetermined period by the storage means. An image forming apparatus.

  The present invention according to claim 2 further includes environmental condition detection means for detecting at least one of temperature and humidity around the image carrier as an environmental condition, and the correction means is detected by the environmental condition detection means. The image forming apparatus according to claim 1, wherein the current direct current is corrected based on the result.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the correction unit corrects a current direct current based on a rotation speed of the image carrier.

  The present invention according to claim 4 further includes an alternating current detecting means for detecting an alternating current flowing through the charging member, wherein the correcting means is based on the alternating current detected by the alternating current detecting means. The image forming apparatus according to claim 1, wherein the current is corrected.

  According to a fifth aspect of the present invention, there is provided a charge amount detection means for detecting a charge amount of the image carrier, and a layer for calculating a layer thickness of the plurality of coating layers based on a detection result of the charge amount detection means. The image forming apparatus according to claim 1, further comprising a thickness calculating unit.

  The present invention according to claim 6 is the image forming apparatus according to claim 5, wherein the correction unit corrects a current direct current based on a calculation result of the layer thickness calculation unit.

  According to the first aspect of the present invention, the current electrical state of the image carrier can be detected with higher accuracy than when the present configuration is not provided.

  According to the second aspect of the present invention, in addition to the effect of the present invention according to the first aspect, even if at least one of the temperature and the humidity around the image carrier changes, the electricity of the current image carrier is changed. The target state can be detected with high accuracy.

  According to the third aspect of the present invention, in addition to the effect of the present invention according to the first or second aspect, the electrical state of the current image carrier is accurately determined in consideration of the influence of the rotation speed of the image carrier. Can be detected well.

  According to the fourth aspect of the present invention, in addition to the effect of the present invention according to any one of the first to third aspects, the electrical state of the current image carrier is considered in consideration of the influence of the alternating current flowing through the charging member. Can be detected with high accuracy.

  According to the present invention of claim 5, in addition to the effects of the present invention of any one of claims 1 to 4, the thickness of the plurality of coating layers is more accurate than when the present configuration is not provided. It can be calculated well.

  According to the sixth aspect of the present invention, in addition to the effect of the present invention according to the fifth aspect, even if the thickness of the plurality of coating layers changes, the current electrical state of the image carrier is accurately detected. can do.

Next, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming unit 12 and a document reading device 14. The image forming unit 12 is of a xerographic type, for example, and has, for example, four stages of paper feed trays 16a, 16b, 16c, 16d on which recording media such as paper are stacked, and a manual feed tray 18, and these trays 16a to 16a. An image is formed on the recording medium supplied to the recording medium conveyance path 20 from 16d and 18.

  In other words, the image forming unit 12 includes, for example, a cylindrical rotating image holding body 22, a charging member 24 made of, for example, a charging roll that uniformly charges the image holding body 22, and the charging member 24. An exposure device (optical writing device) 26 that forms an electrostatic latent image on the charged image carrier 22 and a developing device 28 that visualizes the latent image on the image carrier 22 formed by the exposure device 26 with a developer. And a transfer device 30 that transfers the developer image formed by the developing device 28 to a recording medium, and a cleaner 32 that cleans the developer remaining on the image carrier 22.

  The charging member 24 has a member having elasticity, such as rubber, on the surface thereof, and rotates in contact with the image carrier 22. The exposure device 26 is of a laser scanning type and outputs, for example, an image of a document read by the document reading device 14 instead of a laser on / off signal. The transfer device 30 is composed of, for example, a transfer roll, and the recording medium onto which the developer image has been transferred by the transfer device 30 is sent to the fixing device 34, and the developer image is fixed to the recording medium by the fixing device 34. The recording medium on which the developer image is fixed is discharged to the discharge tray 36.

  A plurality of recording medium conveying rolls 38 are provided in the recording medium conveying path 20. As one of the recording medium transport rolls 38, a registration roll 40 is disposed in the vicinity of the upstream side of the transfer device 30. The registration roll 40 is controlled so as to temporarily stop the supplied recording medium and supply the recording medium to the transfer device 30 in synchronization with the timing at which the latent image is formed on the image holding member 22.

The document reading device 14 includes an optical system 42 that optically reads a document and an automatic document feeder 44.
The optical system 42 has a function of flowing and reading a document sent by the automatic document feeder 44 and a function of reading a document placed on the document table glass 54 by scanning a reflection mirror or the like.

  The automatic document feeder 44 includes a document placement table 56 on which a large number of documents are placed, a document conveyance path 58 that conveys the document, and a discharge table 60 that ejects the document after the image is read.

The image forming apparatus 10 includes a control unit 66, a temperature / humidity sensor 67, a user interface device (UI device) 68 including a display device and a keyboard, a storage device 70 such as an HDD / CD device, a communication device 72, and the like. The control unit 66 includes a CPU 74, a memory 76, and the like, and controls each unit constituting the image forming apparatus 10. The memory 76 is configured to store, for example, a direct current detected by a direct current detection unit 86 described later during a predetermined period. The temperature / humidity sensor 67 detects the ambient temperature and humidity (environmental conditions) of the image forming apparatus 10 and outputs them to the control unit 66.
As described above, the image forming apparatus 10 includes a function as a computer, and performs processing such as printing by executing the program received via the storage medium 78 or the communication device 72.

Next, the image carrier 22, the charging member 24, and the periphery thereof will be described in detail.
FIG. 3 is a schematic diagram showing details of the configuration of the image carrier 22, the charging member 24, and the periphery thereof. A high voltage power source 82 is connected to the charging member 24. The high voltage power supply 82 has an AC power supply (AC) and a DC power supply (DC), and applies a voltage obtained by superimposing the AC voltage Vac on the predetermined DC voltage Vdc to the charging member 24 in accordance with the control of the control unit 66. For example, the high voltage power supply 82 applies an AC voltage with a frequency of 1000 Hz and a peak-to-peak voltage Vpp of about 800 to 2500 V to the charging member 24, and applies a DC voltage Vdc of about −750 V to the charging member 24. A predetermined current is supplied to the charging member 24. The current detection unit 84 includes a DC current detection unit 86 and an AC current detection unit 88. The current detection unit 84 detects a DC current and an AC current that the high-voltage power supply 82 passes through the charging member 24, and outputs the DC current and the AC current to the control unit 66.

  The control unit 66 includes, for example, a correction unit 90, a charge amount detection unit 92, and a layer thickness calculation unit 94 configured as a program. The correction unit 90 includes the current DC current detected by the DC current detection unit 86, the DC current stored in the memory 76 within the most recent predetermined period, the AC current detected by the AC current detection unit 88, and the rotation of the image carrier 22. Correction is performed according to the speed (process speed) and the calculation result of a layer thickness calculation unit 94 described later. The charge amount detection unit 92 detects the charge amount of the charging member 24 according to the detection result of the direct current detection unit 86 or the alternating current detection unit 88. The layer thickness calculation unit 94 calculates the layer thickness of the photosensitive layer 98 described later according to the detection result of the charge amount detection unit 92.

  The image carrier 22 includes a cylindrical conductive support 96 made of, for example, grounded aluminum, and a photosensitive layer 98 that covers the outer surface of the conductive support 96. As shown in FIG. 4, the photosensitive layer 98 includes, for example, a charge generation layer 100, a charge transport layer (CT layer) 102, and a protective layer (OC layer) 104. The charge generation layer 100 has a layer thickness (film thickness) of 0.15 μm, for example, and covers the conductive support 96 including a charge carrier generating material. The charge transport layer 102 is made of a member containing a charge carrier transport material, for example, having a relative dielectric constant of 3, has a layer thickness of about 20 μm, and is laminated outside the charge generation layer 100. The protective layer 104 is made of, for example, a member having a relative dielectric constant of 4.5, has a thickness of about 5 μm, and is laminated outside the charge transport layer 102. The protective layer 104 has a higher hardness than the charge transport layer 102. For example, the charge transport layer 102 has about 30 nm of wear after 1000 cycles of processing, whereas the protective layer 104 has about 3 nm of wear after 1000 cycles of processing.

FIG. 5 is a graph showing the direct current Idc detected by the direct current detector 86 when the image carrier 22 is used for a predetermined period in a constant environment (predetermined temperature and humidity).
When the photosensitive layer 98 of the image carrier 22 is a single layer, the direct current Idc detected by the direct current detection unit 86 is expressed by the following formula 1, and the direct current detection unit 86 detects it for several tens of minutes. It is considered that the direct current does not change as shown in FIG.

Idc = (V−V0) · ε0 · ε · L · VP / D (1)
Idc: DC current value (current value)
V: Applied voltage of high-voltage power supply 82
V0: initial surface potential of the image carrier 22
ε0: Dielectric constant of vacuum
ε: relative dielectric constant of photosensitive layer 98
VP: Process speed
D: Layer thickness of photosensitive layer 98
L: Effective charging length of the image carrier 22

Here, the range that each value can take is roughly as follows.
Idc: DC current value (current value) 0 to 200 μA
V: Applied voltage of high-voltage power supply 82 -300 to -1000 V
V0: Initial surface potential of the image carrier 22 0 to −300V
ε0: Dielectric constant of vacuum 8.85E-12
ε: relative dielectric constant of photosensitive layer 98 1-10
VP: Process speed 50-400mm / s
D: Layer thickness of photosensitive layer 98: 10 to 40 μm
L: Effective charging length of the image carrier 22 100 to 400 mm

  On the other hand, when the photosensitive layer 98 of the image carrier 22 is composed of the charge generation layer 100, the charge transport layer 102, and the protective layer 104 (consisting of a plurality of layers) as described above, the surface potential of the image carrier 22 is The present inventor has found that the DC current Idc detected by the DC current detector 86 changes as shown in FIG. 5 even if it does not change. Therefore, the correction unit 90 provided in the control unit 66 needs to correct the DC current Idc detected by the DC current detection unit 86 using, for example, the following equation 2.

Idc = (V−V0) · ε0 · ε · L · VP / D + A (2)
Idc: DC current value (current correction value)
V: Applied voltage of high-voltage power supply 82
V0: initial surface potential of the image carrier 22
ε0: Dielectric constant of vacuum
ε: relative dielectric constant of photosensitive layer 98
VP: Process speed
D: Layer thickness of photosensitive layer 98
L: Effective charging length of the image carrier 22
A: Correction term

  Here, the correction term A is expressed by the following equation 3, for example.

FIG. 6 is a graph showing the change of the coefficient a (t) shown in Equation 3 with respect to the elapsed time t. As shown in FIG. 6, the coefficient a (t) has a value close to 1 when the elapsed time t is short, and suddenly becomes a value close to 0 when the elapsed time t becomes long. Therefore, the correction value of the DC current Idc before t minutes has a greater influence on the correction term A as the elapsed time t is shorter.
Note that the DC current Idc corrected by the correcting unit 90 is stored in the memory 76 at least for the most recent predetermined period (for example, each DC current Idc corrected by the correcting unit 90 during 60 minutes).
Here, when a time longer than a predetermined period (for example, 60 minutes) has elapsed after the DC current Idc is detected, the correction unit 90 determines that the value of the DC current Idc that has passed a predetermined time after the detection is the current value. In order to correct the direct current Idc, it is unnecessary (does not affect).

FIG. 7 is a graph showing the relationship between the DC current Idc corrected by the correction unit 90 and stored in the memory 76, and the correction amount corrected by the correction unit 90 according to the elapsed time.
When an image is formed in the image forming apparatus 10, a direct current Idc flows through the image carrier 22, and the direct current Idc corrected by the correction unit 90 is stored in the memory 76. The correction amount corrected by the correction unit 90 according to the elapsed time increases after the image formation time and decreases after the image formation stop time.

  Further, the direct current value Idc includes the temperature and humidity (environmental conditions) detected by the temperature / humidity sensor 67, the rotational speed (process speed) of the image carrier 22, the alternating current Iac detected by the alternating current detector 88, and the layer thickness. The correction accuracy is improved by correcting the correction term A to change using the coefficient for the direct current Idc (t) that changes in accordance with the change in the layer thickness of the photosensitive layer 98 calculated by the calculation unit 94. .

FIG. 8 is a graph showing coefficients for the direct current Idc (t) used to calculate the correction term A.
As shown in FIG. 8A, the coefficient for the direct current Idc (t) that changes according to the change in temperature is close to 1 when the temperature is low, and rapidly close to 0 when the temperature is high. To be value.
As shown in FIG. 8B, the coefficient for the direct current Idc (t) that changes according to the change in humidity is close to 1 when the humidity is low, and rapidly close to 0 when the humidity is high. To be value.
As shown in FIG. 8C, the coefficient for the direct current Idc (t) that changes according to the change in the layer thickness of the photosensitive layer 98 is close to 1 when the layer thickness of the photosensitive layer 98 is thick. As the layer thickness of the photosensitive layer 98 decreases, the value becomes closer to zero.
As shown in FIG. 8D, the coefficient for the direct current Idc (t) that changes according to the change in the rotation speed (process speed) of the image carrier 22 is close to 1 when the process speed is slow. As the process speed increases, the value becomes smaller.
As shown in FIG. 8E, the coefficient for the direct current Idc (t) that changes according to the change in the alternating current Iac detected by the alternating current detector 88 is a value close to 1 when the alternating current Iac is large. As the alternating current Iac becomes smaller, the value becomes smaller.

  FIG. 9 shows the detected DC current value, the correction term A, and the corrected DC current value when the above-described correction is performed on the characteristics shown in FIG. Although the detected direct current increases, it can be set to a substantially constant value by correction.

1 is a side view illustrating an outline of an image forming apparatus according to an embodiment of the present invention. 1 is a configuration diagram illustrating an overview of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating details of an image carrier, a charging member, and the surrounding configuration. It is a schematic diagram which shows the structure of a photosensitive layer. It is a graph which shows the direct current Idc which the direct current detection part detected when the image holding body was used for a predetermined period in a fixed environment (predetermined temperature and humidity). It is a graph which shows the change with respect to the elapsed time t of the coefficient a (t) shown in Formula 3. It is a graph which shows the relationship between the direct current Idc which the correction | amendment part correct | amended and memorize | stored in memory, and the correction amount which the correction | amendment part correct | amended according to elapsed time. It is a graph which respectively shows the coefficient with respect to the direct current Idc (t) used in order to calculate the correction | amendment term A. FIG. FIG. 5 is a graph showing a DC current Idc detected by a DC current detector, a correction term A at that time, and a corrected DC current Idc when the image carrier is used for a predetermined period in a constant environment (predetermined temperature and humidity). is there.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image forming part 22 Image holding body 24 Charging member 66 Control unit 67 Temperature / humidity sensor 74 CPU
76 Memory 82 High-voltage power supply 84 Current detection unit 86 DC current detection unit 88 AC current detection unit 90 Correction unit 92 Charge amount detection unit 94 Layer thickness calculation unit 96 Conductive support 98 Photosensitive layer 100 Charge generation layer 102 Charge transport layer 104 Protection layer

Claims (6)

  An image holding body that is coated and rotated by a plurality of coating layers, a charging member that charges the image holding body in contact with or close to the image holding body, and an AC voltage and a DC voltage are superimposed on the charging member. A power supply means for applying the applied voltage; a direct current detection means for detecting a direct current flowing through the charging member; a storage means for storing the direct current detected by the direct current detection means for a predetermined period; and the direct current detection An image forming apparatus comprising: a correction unit that corrects a current direct current detected by the unit based on a direct current stored in the most recent predetermined period by the storage unit.   An environmental condition detection unit that detects at least one of a temperature and humidity around the image carrier as an environmental condition, and the correction unit is configured to detect a current direct current based on a detection result of the environmental condition detection unit. The image forming apparatus according to claim 1, wherein the correction is performed.   The image forming apparatus according to claim 1, wherein the correction unit corrects a current direct current based on a rotation speed of the image carrier.   4. An AC current detection unit that detects an AC current flowing through the charging member, and the correction unit corrects the current DC current based on the AC current detected by the AC current detection unit. Any one of the image forming apparatuses.   The charge amount detection means for detecting the charge amount of the image carrier, and the layer thickness calculation means for calculating the layer thickness of the plurality of coating layers based on the detection result of the charge amount detection means. The image forming apparatus according to any one of 1 to 4.   The image forming apparatus according to claim 5, wherein the correction unit corrects a current direct current based on a calculation result of the layer thickness calculation unit.

Images