JPH0450949A - Method for measuring wear of opc photosensitive body and method for correcting degradation in sensitivity thereof - Google Patents

Abstract

PURPOSE:To allow the correction of a change in the sensitivity of the photosensitive body by wear with higher accuracy by detecting the change in the current flowing from Scotron to the photosensitive body and measuring the abrasion loss of the org. photosensitive body. CONSTITUTION:The electrostatic latent images formed by uniformly electrifying the surface of the drum- or endless belt-shaped org. photosensitive body 1 by using a Scotron electrifier 8 and exposing the electrified surface are developed and transferred. The change in the current flowing from the Scotron 8 to the photosensitive body 1 is detected, by which the abrasion degree of the org. photosensitive body 1 is measured. Then, the abrasion loss is measured in real time with the higher exactness than in the case of estimation of the abrasion loss from the rotating amt., etc., of the photosensitive drum 1. The change in the sensitivity of the photosensitive body 1 by the wear is corrected with the higher exactness in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a toner image obtained by developing an electrostatic latent image formed on a photoreceptor such as an electrophotographic copying machine, a printer, or a facsimile machine. The present invention relates to a method for measuring wear of an OPC photoreceptor and a method for correcting a decrease in sensitivity of the OPC photoreceptor based on the measurement results in an image forming apparatus that transfers images onto paper or the like.

[Conventional technology]

Recently, an organic photoreceptor called OPC has been used in place of an inorganic photoreceptor such as selenium in electrophotographic copying machines. As shown in FIG. 10(a), the OPC photoreceptor has a three-layer structure in which an undercoat layer UCL, a charge generation layer CGL, and a charge transport layer CTL are sequentially provided on a conductive substrate CB, or As shown in Fig. 3), there is a two-layer structure in which a charge generation layer CGL and a charge transport layer CTL are provided in this order on a conductive substrate CB, which is a laminated type photoreceptor. Undercoat layer U CL , li
The charge generation layer CGL usually has a thickness of 1 μm or less, and the charge transport layer CTL has a thickness of 10 to 30 μm. Among these layers, the charge transport layer CTL, which is in direct contact with the cleaning member and the current member, is made of an organic material and is therefore generally fragile and easily abraded. This abrasion is caused by the developing system, contact with copying paper, etc., but is most commonly caused by cleaning members (blades, fur brushes, etc.). For this reason, a binder polymer is selected that is resistant to wear and scratches in addition to the electrical properties of the charger and the like and ozone resistance. -Numerically,
Polycarbonate resin, polyester resin, methacrylic resin, etc. are used.

Conventionally, as mentioned above, when the OPCG light body wears out, the background potential of the white background (bright area) increases and background fog occurs, so the amount of wear on the photoconductor was not directly measured. It is known to correct the sensitivity by estimating the amount of wear from the total number of rotations and correcting the exposure amount, etc. (Japanese Patent Laid-Open No. 138287/1987).

Furthermore, methods are known in which the amount of wear on the OPC photoreceptor is measured by measuring eddy currents at a laboratory level, or optically.

[Problem to be solved by the invention]

However, the wear amount of the OPC photoconductor is measured in real time while the image forming apparatus is in use, and based on the measurement results, the OPC photoreceptor is
There is no known method for correcting the sensitivity of a C photoreceptor in real time.

The present invention was made in view of this situation, and
The objective is to provide a method for measuring wear of an OPC photoconductor in real time in an image forming apparatus that develops an electrostatic latent image formed on an OPC photoconductor and transfers the resulting toner image onto paper, etc. To provide a method capable of correcting a decrease in sensitivity of an OPC photoreceptor in real time based on measurement results, preventing background fogging due to increase in white background potential, and extending the life of the OPC photoreceptor.

[Means to solve the problem]

The organic photoreceptor wear measuring method of the present invention achieves the above object by uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger and exposing the charged surface to light. Detecting changes in the current flowing from a scorotron to a photoreceptor in a method for measuring wear of an organic photoreceptor in an image forming apparatus that transfers a toner image obtained by developing an electrostatic latent image onto paper or the like. This method is characterized by measuring the amount of wear of an organic photoreceptor.

Further, the first method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention includes uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger, and exposing the charged surface to light. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image obtained by developing an electrostatic latent image formed by a photoreceptor onto a sheet of paper, a current of 1K flowing from a scorotron to a photoreceptor is used. This method is characterized by detecting and adjusting the required exposure amount 1 of bright areas according to the following formula based on the detected value: 1t = I + AX (id - 1ao) However, in the above formula, is the initial exposure amount when the photoreceptor is attached, i. is the initial current flowing through the photoreceptor when the photoreceptor is mounted, and A is the wear correction coefficient.

The second method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention is as follows:
A toner image obtained by uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger and developing an electrostatic latent image formed by exposing the charged surface to light. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers onto paper, etc.,
This method is characterized by detecting a current of 1K flowing from the scorotron to the photoreceptor, and adjusting the developing bias voltage (2) according to the following formula based on the detected value: Vy = v + BX (i,,i,. ) However, in the above formula, V is the initial developing bias voltage when the photoreceptor is attached, i. is the initial current flowing through the photoreceptor when the photoreceptor is mounted, and B is the wear correction coefficient.

Furthermore, the third method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention includes uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger, and exposing the charged surface to light. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image obtained by developing an electrostatic latent image formed by , and based on the detected value, calculate the required exposure amount 11 of the bright area according to the following formula (a), and as a result, the required exposure amount 1. is less than the predetermined exposure amount 1xz, the required exposure amount is 11
If the required exposure amount IK is larger than the predetermined exposure amount 1.2, the exposure amount is set to 1°, and the shortfall in the exposure amount is C-((lxIx2)/A). X10
0 by adjusting the developing bias voltage VK2 according to the following formula: Ix = r + Ax (+, 1ao)
(a) VKI2=DXC+V
However, in the above equation, ■ is the initial exposure amount when the photoconductor is attached, ldo is the initial current flowing through the photoconductor when the photoconductor is attached, A is the exposure amount correction coefficient for wear, and ■ is the photoconductor. The initial developing bias voltage when the body is attached, D is the exposure amount-developing bias conversion coefficient.

The fourth method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention is as follows:
A toner image obtained by uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger and developing an electrostatic latent image formed by exposing the charged surface to light. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers onto paper, etc.,
To detect the current 1K flowing from the scorotron to the photoreceptor, and based on the detected value, calculate the required exposure amount 11 of the bright area according to the following formula (a), and then give the calculated required exposure amount The voltage to be applied to the illumination light source required for
8 is less than the predetermined applied voltage VK2, the required exposure amount 1r
is adjusted according to the following formula (a), and when the required applied voltage VK is larger than the predetermined applied voltage VK2, the predetermined applied voltage V
K2 is the exposure amount when applied to the illumination light source Ie2, and the shortfall in exposure amount C=((L-I.)/1.)X100 is the development bias voltage "JK2 is adjusted according to the following formula (b) This method is characterized by compensating by: l
x = I+Ax (ia −1ao) (a)
v M 2 = Dx c + v
(b) However, in the above formula, ■ is the initial exposure amount when the photoconductor is attached, ldo is the initial current flowing through the photoconductor when the photoconductor is attached, A is the wear exposure correction coefficient, and ■
is the initial developing bias voltage when the photoreceptor is attached, DI;!
i! This is a light amount-developing bias conversion coefficient.

[Effect]

According to the organic photoreceptor wear measurement method of the present invention, the amount of wear on the organic photoreceptor is measured by detecting the change in the current flowing from the scorotron to the photoreceptor, so the amount of wear can be calculated by the amount of rotation of the photoreceptor drum. It is possible to measure more accurately and in real time than when estimating from, etc., and it is possible to more accurately correct changes in sensitivity of the photoreceptor due to wear.

According to the first method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention, the current id flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount IK of the bright area is calculated as follows: It = I + AX Since it is adjusted according to (L j ++o), even if the organic photoreceptor is worn out, the bright area potential is kept approximately constant, so there is no background fogging on the white background, etc.
As a result, the life of the organic photoreceptor is extended.

According to the second sensitivity reduction correction method, the current id flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the developing bias voltage V is changed to Vx ''V+B
Since the adjustment is made according to i a i ia), even if the organic photoreceptor is worn out and the bright area potential increases, the difference between the developing bias and the bright area potential will remain approximately constant, so background fog on white backgrounds etc. will be avoided. As a result, the life of the organic photoreceptor is extended.

Furthermore, according to the third sensitivity reduction correction method, the current ld flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount 1 of the bright area is calculated as follows: 1x = I + AX (!v ja. ), and after IK reaches the predetermined exposure amount IK2, it is adjusted according to the developing bias voltage V*zwo, Vx2=DxC+V, so even if the organic photoreceptor wears out, the bright area potential remains the same up to a predetermined point. is kept approximately constant, and even if the bright area potential increases thereafter, the difference between the developing bias and the bright area potential is maintained approximately constant, so that background fogging on the white background does not occur over the entire range, and as a result, The lifespan of organic photoreceptors is extended.

Furthermore, since the exposure amount is not increased indefinitely, an increase in lamp temperature, a resulting shortening of lamp life, and an increase in temperature of the optical system can be avoided.

According to the fourth sensitivity reduction correction method, the current i flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount T for the bright area is calculated as It = I + Ax (i
a-i, +. ), and the necessary applied voltage vI+ necessary to give the required exposure amount I is the predetermined applied voltage V.
After reaching X2, the exposure amount is set to the exposure amount I1.2 when the predetermined applied voltage vI2 is applied to the illumination light source, and the shortfall in the exposure amount is adjusted to the developing bias voltage V++2 according to V * 2 = D X C + V Since it is compensated by adjustment, even if the organic photoreceptor wears out, the bright area potential will remain approximately constant until a certain point, and even if the bright area potential increases thereafter, the developing bias and bright area potential will remain constant. Since the difference is kept substantially constant, white background fogging does not occur over the entire range, and as a result, the life of the organic photoreceptor is extended.

Furthermore, since the exposure amount is not increased indefinitely, an increase in lamp temperature, a resulting shortening of lamp life, and an increase in temperature of the optical system can be avoided. Furthermore, the upper limit for correcting the increase in bright area potential by the exposure amount is determined by the value of the voltage applied to the illumination light source, and the exposure amount control based on other factors is performed by the voltage applied to the illumination light source. It is more consistent and more realistic.

〔Example〕

In the laminated OPC photoreceptor shown in FIG. 10, its sensitivity depends on carrier generation efficiency in the charge generation layer CGL, carrier generation efficiency in the charge transport layer CTL, and carrier ease in the charge transport layer CTL. mobility
) is determined. In order to achieve high sensitivity, a charge generation layer CGL material with high carrier generation efficiency and a charge transport layer C with high carrier mobility and good compatibility with the charge generation layer CGL material are required.
A combination with TL material is required. Furthermore, in order to stabilize sensitivity, it is important that carrier generation efficiency, carrier mobility, and carrier injection efficiency have little dependence on electric field and temperature. Incidentally, carrier generation efficiency and carrier injection efficiency generally decrease in the low electric field region of the bright area potential level, but there are some types of photoreceptors that are less susceptible to such decreases. In the case of such a photoreceptor, the bright area potential increases due to abrasion of the charge transport layer CTL by the cleaning system, etc., and background fogging may occur (that is, a change in sensitivity occurs).

). The mechanism by which fogging occurs in the background area due to such thinning of the charge transport layer CTL will be briefly explained. When a photoreceptor is subjected to corona discharge, charges are placed on the surface of the photoreceptor, thereby charging the photoreceptor. Assuming that the charge per unit area on the photoreceptor is 0 and the capacitance per unit area of the photoreceptor is C, the relationship Q=CV (2) holds between these and the surface potential V. For the capacitance C, the relative permittivity of the photoreceptor is ε, and the permittivity of vacuum is ε. , the film thickness of the photoreceptor (mostly the charge transport layer CTL
(equivalent to the film thickness) is 1, then per unit area, C=ε·ε,/1 ■. From formulas ■ and ■, 0=ε・ε, -V/1 ■. In equation (2), let us consider the case where the charge transport layer CTL is worn away by a cleaning system or the like and its film thickness is reduced as described above. For example, when the charging potential V is kept almost constant regardless of the film thickness by a scorotron charger,
The amount of charge Q on the surface of the photoreceptor is expressed by the formula (■), and the charge transport layer CTL
It is a linear expression of the reciprocal of the film thickness l. The thinner the film, the larger the surface charge O, and at the bright potential level, a certain amount of light <
When a light amount) is incident, a larger amount of exposure is required to neutralize this relatively increased amount of charge. In the case of a photoreceptor in which the carrier generation efficiency of the charge generation layer CGL and the injection efficiency of the generated carriers into the charge transport layer CTL do not depend much on the electric field, the relationship between the relative exposure amount and the surface potential is as shown in Figure 11. It is almost a straight line. Charge transport layer C
Under the conditions where the TL film thickness is set to 22 μm, the dark potential is set to -700 V, the light potential is set to -150 V, the rate of change in potential per unit film thickness (that is, per 1 μm) is
．． When irradiating 0, (700-150)/22=25
V/μm. When a charger is used to constantly charge the dark potential to -700V (that is, even when the film thickness decreases), the bright potential increases by 25V per 1 μm of film thinning, especially near the 1-to potential. This will cause the skin to become foggy. In other words, the sensitivity decreases due to the thinning of the charge transport layer CTL. The carrier generation efficiency has an electric field dependence, and the dependence varies depending on the OPC material. When the electric field dependence increases, the electric field increases under the condition of constant charging potential when the film thickness is thin, and the generation efficiency increases. This increase in sensitivity acts to compensate for the apparent decrease in sensitivity due to the decrease in film thickness, but in commonly used OPC sensitive materials, the contribution of the increase in charge amount due to decrease in film thickness is greater. As a result, the bright area potential increases.

Hereinafter, as an example of an OPC photoreceptor, PC Brown, which has a three-layer structure and whose cross-sectional structure and film thickness are shown in FIG. 1, will be specifically explained. The conductive substrate CB is made of aluminum, the undercoat layer UCL is made of a mixture of tributoxyzirconium acetyl acetate and T-aminopropyltrimethoxysilane, and the charge generation layer CGL is made of a mixture of granular trigonal selenium and vinyl chloride-vinyl acetate. The charge transport layer CTL is composed of N, N'-diphenyl-
N, N'-bis(3-methylphenyl)-[1,1'
-biphenyl]-4,4'-diamine and a polycarbonate resin. This OPC brown has extremely low dependence of carrier generation efficiency on electric field, and the relationship between relative exposure amount and surface potential when this photoreceptor is charged to -800V is approximately a straight line as shown in Figure 2. . When an attempt is made to make more than 100,000 copies using such a PC photoreceptor, the charge transport layer CTL on the surface thereof is worn out mainly by cleaning members (blades, fur brushes, etc.) as the copies are made. As the charge transport layer CTL wears out in this manner, its sensitivity decreases as described above. When the CTL wear amount is 1.3 μm, that is, the thickness of the charge transport layer CTL is 23.7 μm, and when the CTL wear amount is 3.5 μm, that is, the thickness of the charge transport layer CTL is 21 μm.
．． The relationship between the relative exposure amount and surface potential at 5 μm is as shown in FIG. Now, set the background potential (bright area potential) corresponding to the white area of the original on the surface of the photoconductor to -1.
When trying to set the voltage to 00V, when the CTL is initially 25μm, the relative light amount to be exposed is 20.
It turns out that 4 is sufficient. However, at this relative exposure when CTL is 23.7μm and 21.5μm, the background potential is 135VK17, respectively.
It becomes 0V. Therefore, if we do not change the illumination light amount of the exposure system, the bright area potential will increase as described above.
Background fogging occurs. To avoid this,
The exposure amount may be increased to adjust the bright area potential to always be 100V. In the case of the above example, the charge transport layer CTL
The relationship between the film thickness and the required relative exposure amount is as shown in FIG. 3, and it can be seen that the CTL film thickness and the required exposure amount have a substantially linear relationship. In this way, in the OPC photoconductor where the carrier generation efficiency has a small dependence on the electric field, if the exposure amount 1K is increased in proportion to the amount of wear Δl of the CTL film thickness,
The bright area potential can always be kept constant, and an increase in the bright area potential due to CTL wear can be corrected.

By the way, when using a scorotron as a charger,
The characteristics of the scorotron are as shown schematically in Figure 4, when the charging potential V of the charged surface (CTL surface) is taken against the current i flowing through the scorotron spray wire.
Even if the current 1 is changed over a relatively wide range, the charging potential V remains approximately constant. Therefore, when a scorotron is used as a charger, the charging potential V is kept constant even if the CTL is worn out, so if the amount of CTL wear is Δl, from the above equation Q
The amount of increase ΔQ is ΔQoeΔl ■. By the way, the scorotron 21 as shown in the circuit diagram in Fig.
When charging the surface of the photoreceptor 22 to a constant potential V,
The total current flowing through the discharge wire 23 of the scorotron 21 is 1 t.
, the return current lr flowing into the shield 24 and the grid 25 , and the current 1 flowing into the photoreceptor 22 . There is l between
a = l t l r [F]
There is a relationship as follows, and the current flowing through the photoreceptor 22 is 1. is proportional to the photoreceptor charge 0, so the equation
It can be rewritten as ■. Here, Δid is the current 1. , and k is a proportionality constant. From the formula ■, when the scorotron charges the surface of the ○PC photoreceptor to a constant potential, OPC
By determining the amount of increase in the current flowing through the photoreceptor, ○P
It can be said that the amount of wear of the C photoreceptor can be measured. Note that the current flowing through the photoreceptor is measured by the ammeter 2 in FIG.
6 are arranged as shown in the figure, or the total current 1 flowing through the discharge wire 23 and the return current 1 flowing into the shield 24 and the grid 25 are measured. All you have to do is to detect and find it according to the formula (■). For reference, FIG. 5 shows the values of the voltages applied to the discharge line, the grid, the shield, the above-mentioned currents, etc. in one example.

By the way, as shown in relation to Figure 3, in the OPC photoreceptor, if the exposure amount I8 is increased in proportion to the amount of wear △p of the CTL film thickness, the surface potential can be kept constant. This makes it possible to correct the increase in bright area potential due to CTL wear. CTL film thickness wear amount △! is the formula [F]
The amount of increase in the current flowing to the photoreceptor from △1. Since it is proportional to the current increase amount Δl, the exposure amount IK may be increased in proportion to this current increase amount Δl. Therefore, if the initial exposure amount when the OPC photoreceptor is attached is 11, and the current flowing through the photoreceptor is ld, and its initial value is ldo, then Ix = I + Ax (L - i 6 ports)
The exposure amount may be corrected so as to satisfy −〇. Here, A is a wear correction coefficient.

The above formula (■) can also be derived from another viewpoint.

That is, as mentioned above, the carrier generation efficiency of the charge generation layer CGL and the charge transport layer CT of the generated carriers are
In the case of a photoreceptor in which the injection efficiency into L does not depend much on the electric field, the required exposure amount (2) is proportional to the surface charge Q of the photoreceptor, so 11=A'XIa (2). Here, 1. is the current flowing into the photoreceptor 22 when it is charged by the scorotron 21, and A' is a proportionality constant. Therefore, when the OPC photoreceptor is attached, the initial exposure amount is 1, and the current flowing into the photoreceptor is 1. . Then, ■=A′×ido1;, A′=I/i −o
■'When the CTL film thickness changes due to wear, the current flowing into the photoreceptor is L, so ia −ido=I* /A'−I/A',',L
=I+A' (ia -ido) -■I.

Since the constant of proportionality A' can be written as A, formula ■' is the same as formula ■. From now on, we will write A' as A and expand this formula ■' a little more. Substituting the formula ■' into the formula ■', 1m = I + I/la. (i,-i,.)=I(1+1
/ia. (i, -j,.))=I (1+A' (
Lia. ))■' Here, A' is a proportionality constant. 1 above. =1+I
/i,. Expanding (i,-i,.), IK
=I+IXia/iao IXlao/
l++.

= IX! a/l a. ■′
becomes. Therefore, it is safe to say that the above formulas ``■'' to ``■'' may be used in place of the above formula ②. Hereinafter, the explanation will be given assuming that equation (2) is used.

Above, we have explained that the sensitivity of an OPC photoreceptor whose bright area potential increases in proportion to the amount of wear △l of the CTL film thickness is corrected according to formula (■). However, depending on the type of OPC photoreceptor, wear It cannot be said that the amount of change and the amount of change in bright area potential are completely proportional. In such a case, the exposure amount Ix that keeps the bright area potential constant with respect to the change in the current flowing through the photoreceptor (lila) is determined in advance, the relationship is created in a table, and the table is set in the storage device. I'll keep it. Then, the current 1K flowing through the scorotron is actually detected, and based on the detected value, the exposure amount is 1K by referring to the above table.
It is only necessary to read out the value and correct the exposure amount so that it becomes the value.

By the way, above we have explained the case where the increase in bright area potential due to wear of the OPC photoconductor is corrected by increasing the exposure amount. , the developing bias voltage V of the developing device
By increasing the photoreceptor, it is also possible to prevent background fog, etc., which is caused by an increase in bright area potential due to wear of the OPC photoreceptor. That is, when the bright area potential increases and approaches the developing bias voltage of the developing device or is further reversed, toner adheres to the bright area and causes background fog.

Therefore, for example, by increasing the developing bias voltage (in the negative direction in the example of FIG. 1) to compensate for the increase in bright area potential due to the decrease in the charge transport layer CTL in FIG.
The difference between the developing bias and bright area potential can be kept substantially constant, and background fogging in bright areas can be prevented. In this case, the formula corresponding to the above-mentioned formula ■ can be written as follows.

VW −V+B In this case, depending on the type of OPC photoreceptor, the developing bias voltage VK that compensates for the rise in bright area potential against the change in the current flowing through the photoreceptor (IdldO) is determined in advance, and the relationship is tabulated. is set in the storage device, the current ld flowing through the scorotron is actually detected, and based on the detected value, the developing bias voltage V8 is read out with reference to the table above, and the developing bias voltage is adjusted to that value. may be corrected.

Furthermore, by combining the above-mentioned exposure amount correction and development bias voltage correction, for example, the increase in bright area potential is corrected by exposure amount correction up to a predetermined correction amount, and beyond that, the temperature of the lamp and optical system is reduced. This will shorten the life of the lamp and consume a lot of power, so no further corrections will be made by increasing the exposure amount, and the exposure amount will be fixed at its predetermined maximum value. It is possible to adopt a configuration in which correction is performed by increasing the bias voltage. Note that even when requests for increasing the amount of light due to enlargement, reduction, etc. overlap, it is necessary to correct the insufficient amount of light at the specified upper limit voltage using the developing bias.

Now, based on the above equation (1) or (2), a correction device for reducing the sensitivity of an <OPC photoreceptor will be explained using the system configuration diagram of FIG. 6 and the flow chart of FIG. 7.

As shown in FIG. 6, the copying machine has an OPC photosensitive drum 1.
, a scorotron charger 8, a developer 9, a platen 2, an exposure lamp 4, a mirror 5, 7, a lens 6, etc. (other transfer devices, cleaning devices, static eliminators, etc. are omitted from illustration), and the exposure The lighting and current of the lamp 4 are controlled by a lamp drive circuit 11, and the charging timing, charging voltage, development bias application timing, and development bias voltage of the scorotron charger 8 and developer 9 are controlled by a high-voltage power supply circuit 12. Current flowing into the OPC photosensitive drum 1 described above 1. or the total current l flowing in the discharge wire and the return current l flowing into the shield and grid
r is detected and the detection signal is sent to the CPU 15. These lamp drive circuit 11 and high voltage power supply circuit 12 are centrally controlled by the CPU 15, and control the lighting timing of the exposure lamp 4, applied current or voltage, etc.
The charging timing and charging voltage of the charger 8, the timing of applying a developing bias to the developing device 9, and the developing bias voltage are each controlled by instructions from the CPU 15. CPU1
5 is connected to a ROM 16 and a RAM 17, which store control parameters for each part of the copying machine and correction coefficients to be described later.

In addition, a standard reflector 3 placed above or below the platen 2
A detector 14 that detects the intensity of reflected light from the lens 6 is placed near the lens 6, and is connected so that the CPU 15 receives the detection signal.

In order to control the current or voltage applied to the exposure lamp 4 so as to satisfy the above formula (2) using an apparatus having such a configuration, as shown in FIG.
5 is connected to the OPC photosensitive drum 1 via a high voltage power supply circuit 12.
The initial current flowing into l,. is detected and stored in the RAM 17. Next, in step (2), the CPU 15 detects the current i constantly flowing into the OPC photosensitive drum 1 via the high voltage power supply circuit 12. In step ■, It
=I+Ax (ia -L.) - Calculate the required exposure amount according to 〇, or calculate the detected ll, 1. . Accordingly, the required exposure amount IK is read from the table stored in the ROM 16. Note that the initial exposure amount 11 and the wear correction coefficient A are stored in the ROM 16 in advance. Next, in step ■, the calculated or read required exposure amount ■
The current or voltage applied to the exposure lamp 4 is controlled so that the For this purpose, the CPU 15 refers to the intensity signal of the reflected light from the standard reflector 3 obtained from the detector 14, and adjusts the exposure lamp 4 so that the value corresponds to the required exposure amount (2). The current or voltage applied to the exposure lamp 4 may be feedback-controlled, or the relationship between the current or voltage determined in advance and the amount of light emitted by the exposure lamp 4 may be determined so that the amount of light is the required exposure amount (2). The current or voltage applied to the exposure lamp 4 may be controlled so that the value corresponds to . By controlling in this way, the drum 1
Sensitivity decrease due to abrasion of the OPC photoreceptor, that is, OPC
The increase in bright area potential of the photoreceptor can be corrected by increasing the exposure amount of the exposure lamp 4. It should be noted that it is clear that the same structure can be used when controlling the developing bias voltage of the developing device 9 based on the above equation (2). Further, FIG. 8 shows a flowchart of an apparatus in which an increase in bright area potential up to a predetermined level is corrected by correcting the exposure amount, and further correction is compensated by correcting the developing bias. Although detailed explanation is omitted, C={(IK-IM2)/I-)X100, which expresses the underexposure as a percentage.
D is an exposure amount-development bias conversion coefficient. Other words and names are the same as above. However, in this case, in practice,
The reason for setting an upper limit on the exposure amount is that, as mentioned earlier, power consumption and other power supply issues are one of the reasons, the exposure amount is controlled by the voltage applied to the lamp, and the amount of light emitted by the lamp is Considering that it varies depending on temperature etc.,
It is more practical to switch between the sensitivity correction by exposure amount correction and the sensitivity compensation by developing bias voltage correction by determining whether or not the voltage applied to the lamp has reached a predetermined upper limit VK12. A flowchart in that case is shown in FIG.

Although detailed explanation is not necessary, vl is the required lamp applied voltage calculated from the lamp characteristics necessary to obtain the required exposure amount 1. However, even when controlling the developing bias voltage, as in the case of the exposure lamp, there is a maximum allowable developing bias voltage in order to prevent problems such as a decrease in contrast potential and the drawing of carriers in the developer.

Although the above description is based on the assumption that an OPC photoreceptor drum is used, the present invention is not limited to this, and can also be applied to image forming apparatuses such as copying machines that use an endless OPC photoreceptor belt. .

〔Effect of the invention〕

In the organic photoreceptor wear measurement method of the present invention, the amount of wear on the organic photoreceptor is measured by detecting changes in the current flowing from the scorotron to the photoreceptor, so the amount of wear can be measured by measuring the amount of rotation of the photoreceptor drum, etc. It is possible to measure more accurately and in real time than when estimating from the data, and it is possible to more accurately correct changes in sensitivity of the photoreceptor due to wear.

In the first method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention, a current of 1K flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount I of the bright area is calculated as follows: Since the adjustment is made according to I+AX (+dida), even if the organic photoreceptor wears out, the bright area potential remains approximately constant, so background fogging on white backgrounds does not occur, and as a result, the bright area potential of the organic photoreceptor is Increases lifespan.

According to the second sensitivity reduction correction method, the current i flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the developing bias voltage Vx is set as vx = v + Bx (i
d i d. ), even if the organic photoreceptor wears out and the bright area potential increases, the difference between the developing bias and the bright area potential remains approximately constant, so background fogging on white backgrounds does not occur. As a result, the life of the organic photoreceptor is extended.

Furthermore, in the third method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention, a current of 1K flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount IK of the bright area is determined as Ix =I+Ax (ia - jd.), and after 18 reaches the predetermined exposure amount IK2, the developing bias voltage ■. is adjusted according to VK2=DXC+V, so even if the organic photoreceptor wears out, the bright area potential will remain approximately constant up to a predetermined point, and even if the bright area potential increases thereafter, the developing bias and bright area will remain constant. Since the potential difference is kept substantially constant, white background fogging does not occur over the entire range, and as a result, the life of the organic photoreceptor is extended.

Furthermore, since the exposure amount is not increased indefinitely, an increase in lamp temperature, a resulting shortening of lamp life, and an increase in temperature of the optical system can be avoided.

In the fourth method of correcting the decrease in sensitivity of an organic photoreceptor of the present invention, a current of 1K flowing from the scorotron to the photoreceptor is detected, and based on the detected value, the required exposure amount IK of the bright area is determined. I + AX (ia - is.), and after the necessary applied voltage vIK necessary to give the required exposure amount 11 reaches the predetermined applied voltage VW2, the exposure amount is adjusted according to Exposure of precious. The shortfall in exposure amount is compensated for by adjusting the developing bias voltage VK2 according to V xx = D Even if the bright area potential increases after that, the difference between the developing bias and the bright area potential remains approximately constant, so background fogging on white backgrounds does not occur over the entire range, and as a result, organic The life of the photoreceptor is extended.

Furthermore, since the exposure amount is not increased indefinitely, an increase in lamp temperature, a resulting shortening of lamp life, and an increase in temperature of the optical system can be avoided. Furthermore, the upper limit for correcting the increase in bright area potential by the exposure amount is determined by the value of the voltage applied to the illumination light source, and the exposure amount control based on other factors is performed by the voltage applied to the illumination light source. It is more consistent and more realistic.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the cross-sectional structure and film thickness of the ○PC Brown photoconductor, Figure 2 is a diagram showing the relationship between relative exposure amount and surface potential when the photoconductor in Figure 1 is charged to -800V, Figure 3 is the first
Figure 4 is a diagram showing the relationship between the film thickness of the charge transport layer of the photoreceptor and the required relative exposure amount; Fig. 5 is a diagram showing the relationship between the equivalent circuit of a scorotron and current, Fig. 6 is a system configuration diagram of a device that implements the correction method of the present invention, and Fig. 7 is a flowchart of one embodiment of the correction method of the device. , FIGS. 8 and 9 are flowcharts of another embodiment of the present invention, FIG. 10 is a cross-sectional view of a PC photoreceptor, and FIG. 11 is a relative exposure amount when the thickness of the charge transport layer is used as a parameter. FIG. 2 is a diagram showing the relationship between surface potential and surface potential. 1... OPC photoreceptor drum, 2... platen, 3...
...Standard reflector, 4...Exposure lamp, 5.7...Mirror, 6...Lens, 8...Scorotron charger,
9...Developer, 11...Lamp drive circuit, 12...
・High voltage power supply circuit, 14...photodetector, 15...CP
U, 16...ROM, 17...RAM, 21...
Scorotron, 22... Photoreceptor, 23... Discharge wire, 24... Shield, 25... Grid, 26...
... Ammeter, CB ... Conductive substrate, UCL ... Undercoat, CGL ... Charge generation layer, CTL ... Charge transport layer Other 7 people) Figure 3 Figure 3 CTL Discipline Diagram Discharge Wire Electricity 4 i Figure Figure 8 Figure 8

Claims (5)

[Claims] (1) Obtained by uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger and developing an electrostatic latent image formed by exposing the charged surface to light. A method for measuring wear of an organic photoreceptor in an image forming apparatus that transfers a toner image onto paper or the like, characterized in that the amount of wear of the organic photoreceptor is measured by detecting changes in the current flowing from a scorotron to the photoreceptor. A method for measuring organic photoreceptor wear. (2) Obtained by uniformly charging a drum-shaped or endless belt-shaped organic photoreceptor using a scorotron charger and developing an electrostatic latent image formed by exposing the charged surface to light. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image onto paper, etc., the current i_d flowing from a scorotron to the photoreceptor is detected, and the required exposure amount for bright areas is determined based on the detected value. I_K
A method for correcting the decrease in sensitivity of an organic photoreceptor, which is characterized by adjusting according to the following formula: I_K=I+A×(i_d−i_d_0) However, in the above formula, I is the initial exposure amount after mounting the photoreceptor, i_d_0 is the initial current flowing through the photoreceptor when the photoreceptor is mounted, and A is the wear correction coefficient. (3) A drum-shaped or endless belt-shaped organic photoreceptor is uniformly charged using a scorotron charger, and an electrostatic latent image formed by exposing the charged surface to light is developed. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image onto paper or the like, a current i_d flowing from a scorotron to the photoreceptor is detected, and the developing bias voltage V_K is adjusted based on the detected value.
A method for correcting the decrease in sensitivity of an organic photoreceptor, which is characterized by adjusting according to the following formula: V_K=V+B×(i_d−i_d_0) However, in the above formula, V is the initial developing bias voltage when the photoreceptor is attached. , i_d_0 is the initial current flowing through the photoreceptor when the photoreceptor is mounted, and B is the wear correction coefficient. (4) A drum-shaped or endless belt-shaped organic photoreceptor is uniformly charged using a scorotron charger, and an electrostatic latent image formed by exposing the charged surface to light is developed. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image onto paper, etc., the current i_d flowing from a scorotron to the photoreceptor is detected, and the required exposure amount for bright areas is determined based on the detected value. I_K
is calculated according to the following formula (a), and as a result, if the required exposure amount I_K is less than the predetermined exposure amount I_K_2, the required exposure amount I_K is adjusted according to the following formula (a), so that the required exposure amount I_K becomes the predetermined exposure amount. When the amount is larger than I_K_2, the exposure amount is set to I_K_2 and the shortfall in the exposure amount C={(I_K
−I_K_2)/I_K}×100 by adjusting the developing bias voltage V_K_2 according to the following formula (b). i_d_0)(
a) V_K_2=D×C+V(b) However, in the above formula, I is the initial exposure amount when the photoreceptor is attached, i_d_0 is the initial current flowing through the photoreceptor when the photoreceptor is attached, and A is the exposure amount for wear. The correction coefficient, V is the initial developing bias voltage when the photoreceptor is mounted, and D is the exposure amount-developing bias conversion coefficient. (5) A drum-shaped or endless belt-shaped organic photoreceptor is uniformly charged using a scorotron charger, and an electrostatic latent image formed by exposing the charged surface to light is developed. In a method for correcting a decrease in sensitivity due to abrasion of a photoreceptor in an image forming apparatus that transfers a toner image onto paper, etc., the current i_d flowing from a scorotron to the photoreceptor is detected, and the required exposure amount for bright areas is determined based on the detected value. I_K
is calculated according to the following formula (a), and then the voltage to be applied to the illumination light source necessary to give the calculated required exposure amount I_K is calculated from the characteristics of the illumination light source, and the calculated required applied voltage V_K is When the predetermined applied voltage V_K_2 is lower than the predetermined applied voltage V_K_2, the required exposure amount I_K is adjusted according to the following formula (a), and when the required applied voltage V_K is greater than the predetermined applied voltage V_K_2, when the predetermined applied voltage V_K_2 is applied to the illumination light source. Set the exposure amount to I_K_2, and the shortfall in exposure amount C = {
(I_K-I_K_2)/I_K}×100 is compensated for by adjusting the developing bias voltage V_K_2 according to the following formula (b): A method for correcting the decrease in sensitivity of an organic photoreceptor: I_K=I+A×( i_d-i_d_0) (a) V_K
_2=D×C+V(b) However, in the above formula, I is the initial exposure amount when the photoreceptor is attached, i_d_0 is the initial current flowing through the photoreceptor when the photoreceptor is attached, and A is the exposure amount correction coefficient for wear. , V is the initial developing bias voltage when the photoreceptor is mounted, and D is the exposure amount-developing bias conversion coefficient.