JP2006084824A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image quality from degrading, caused by a fogging in the background part of a copied image, and to prevent toner from splashing accompanying fogging, by controlling the drive of a developing roller differently from the drive of a photoreceptor, thereby making the ratio of the peripheral speed of the developing roller to that of the photoreceptor variable. <P>SOLUTION: The image forming apparatus is provided with first and second reflection coefficient measuring sensors S1, S2 for measuring the surface reflection coefficient of the photoreceptor 1; a fogging level detection means for detecting the fogging level on the surface of the photoreceptor 1, on the basis of the reflection factors measured by the first and second reflection coefficient measuring sensors S1, S2; and a peripheral velocity control means for controlling the increase/decrease in the peripheral velocity of the developing roller 20, on the basis of the detected result of the fogging level detection means 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that controls driving of a developing roller so that fogging of an image background portion does not occur.

  The surface potential of the photoreceptor varies greatly with changes in environmental conditions. For example, in the case of an OPC (Oraganic Photo-conductor) photoreceptor, in a low temperature environment, there is a potential drop of about 100 (V) compared to the potential at normal temperature due to the temperature dependence of the mobility of photocarriers.

  Also, as the number of copies progresses, the photosensitive layer causes film slippage due to mechanical stress (such as the polishing effect by the cleaning blade), and the surface potential tends to gradually decrease due to the decrease in film thickness, and the sensitivity decreases. The problem also comes up. Further, the developer also has environmental characteristics and has a problem that it is vulnerable to changes in humidity.

  For this reason, a large change in image quality occurs due to environmental changes. Therefore, process control is performed to maintain the copy image at the optimum image quality even if the environment or the like changes or time elapses. Normally, this control is performed by detecting the image density on the photoreceptor.

  The photosensitive member is driven by a main body drive motor, and is controlled so as to be driven at different peripheral speeds depending on the type of paper and the image forming mode such as monochrome and color. On the other hand, the developing roller is driven by gear transmission between the photosensitive member and the developing roller, and the peripheral speed ratio between the developing roller and the photosensitive member is constant.

  However, with such a conventional control method, optimal control cannot be performed when a certain amount or more of fog occurs in the image background portion, that is, the non-photosensitive portion of the photoconductor. Such fog occurs due to various causes, and the main causes are an increase in the residual potential of the photoreceptor, environmental characteristics of the developer, and deterioration with time.

  When the toner to be replenished is subjected to a thermal history (for example, when left for two days at 50 (° C.)), the toner is subjected to thermal stress and the resin itself softens or becomes an external additive resin. Surface properties change due to the burial of the surface. As a result, the fluidity and charge rising characteristics of the toner are deteriorated, and the background is fogged.

If process control is performed with the above-described conventional method while leaving such fog, the optimum process control becomes impossible at all, and the image quality of the copy image may be reduced. Furthermore, the problem of toner scattering within the apparatus also arises.
Further, as the peripheral speed ratio between the developing roller and the photosensitive member is deviated from 1.0, the effect of the developing roller scraping off the fog toner on the photosensitive member is increased, and the effect of reducing the fog is increased.

However, if the photosensitive member and the developing roller are continuously driven while the peripheral speed ratio between the developing roller and the photosensitive member is larger than 1.0, a filming phenomenon occurs in the photosensitive member.
For this reason, there is a problem that the peripheral speed ratio between the developing roller and the photosensitive member must be set to a value close to 1.0 to drive the apparatus at the expense of the fog reduction effect.

  Therefore, the present invention controls the development roller driving separately from the photosensitive member driving so that the peripheral speed ratio between the developing roller and the photosensitive member can be changed, thereby causing a problem of image quality deterioration due to fogging of the background portion of the copy image. An object of the present invention is to provide an image forming apparatus capable of preventing toner scattering and the like caused by fogging.

The present invention relates to a reflectance measuring sensor for measuring the surface reflectance of a photoreceptor, a fog level detecting means for detecting a fog level on the surface of the photoreceptor based on the reflectance measured by the reflectance measuring sensor, and the fog. And a peripheral speed control means for increasing / decreasing the peripheral speed of the developing roller based on the fog level detected by the level detection means.
In this configuration, the surface reflectance of the photosensitive member is measured by a reflectance measuring sensor, the fog level on the surface of the photosensitive member is detected based on the measured surface reflectance, and the circumference of the developing roller is detected based on the detection result. Speed can be increased or decreased.

  The reflectance measurement sensor includes a first reflectance measurement sensor that measures the surface reflectance of the photoconductor after development, and a second reflectance measurement sensor that measures the surface reflectance of the photoreceptor after cleaning. In this case, the fog level detecting means may detect the fog level on the surface of the photoconductor from the output ratio of the reflectance detected by the first and second reflectance measuring sensors. .

  A correlation table showing the correlation between the surface reflectance of the photoconductor after development and the fog level is prepared, and the fog level detecting means is used to detect the surface of the photoconductor after development measured by a single reflectance measuring sensor. The fog level corresponding to the reflectance may be detected with reference to the correlation table.

  One or two or more developing rollers are provided, and the peripheral speed control means is based on the fog level on the surface of the photosensitive member detected by the reflectance measuring sensor, and each developing roller according to the level of the fog level. The peripheral speed ratio of the photoreceptor can be changed. In this case, after the change of the peripheral speed ratio, the predetermined process control is performed, so that the process control close to the optimum can be performed, the problem of the image quality deterioration due to the fog of the background portion of the copy image, the toner scattering caused by the fog, etc. Can solve the problem.

  The peripheral speed control means changes the peripheral speed ratio between the developing roller and the photosensitive member to a value larger than 1.0 when the fog level is high, and when the reflectance decreases, the peripheral speed ratio between the developing roller and the photosensitive member is set to 1. Alternatively, the peripheral speed ratio between each developing roller and the photosensitive member may be controlled to be a value close to .0. Thereby, the problem of filming can be suppressed while obtaining the fog reduction effect by changing the peripheral speed ratio.

  A drive motor that can drive these developing rollers independently from each other can be connected. In this case, since each developing roller can be driven and controlled independently of each other, the peripheral speed ratio between the developing roller and the photosensitive member can be appropriately changed according to the fog level.

  In addition to the above-described configuration, after changing the peripheral speed ratio between the developing roller and the photoconductor according to the fog level, a determination unit that performs a determination operation for predetermined process control, and based on the determination result, Process control means for executing predetermined process control can be provided.

  As the determination means, the toner voltage is formed on the photosensitive member or the transfer belt by changing the charging voltage and the development voltage in the image forming apparatus, the toner patch density is measured, and together with the input signal from the temperature sensor, The determination can be made by detecting the optimum charging voltage and developing voltage.

  As the determination means, toner patches may be formed by changing the gradation pattern, the density of the toner patches may be measured, and an optimum image formation pattern may be detected and determined.

  The predetermined process control is to control the charging voltage, the developing voltage, the image forming pattern, or a combination thereof.

According to the invention described in claims 1 to 10, the surface reflectance of the photoconductor is measured to detect the fog level on the photoconductor surface, and the driving of the developing roller is controlled according to the detected fog level, The peripheral speed ratio between the developing roller and the photosensitive member can be changed.
As a result, fog and toner scattering that cannot be removed by conventional control can be removed, and filming due to a change in the peripheral speed ratio between the developing roller and the photosensitive member can be suppressed.

In addition to the common effects obtained by the inventions described in claims 1 to 10, the following effects can be obtained according to the invention described in each claim.
According to the second aspect of the present invention, the fog level detecting means can detect the first and second reflectances from the output ratio between the surface reflectance of the photoconductor after development and the surface reflectance of the photoconductor after cleaning. Since the fog level on the surface of the photoreceptor is detected from the output ratio of the reflectance detected by the measurement sensor, the fog level can be detected with high accuracy.

  According to the third aspect of the present invention, the fog level corresponding to the surface reflectance of the photoconductor after development measured by a single reflectance measuring sensor is determined based on the surface reflectance of the photoconductor after development and the fog level. Therefore, a simple configuration can be achieved.

  According to the fourth aspect of the present invention, the peripheral speed ratio between the developing roller and the photoconductor is changed based on the fog level on the surface of the photoconductor detected by the reflectance measuring sensor according to the stage of the fog level. Therefore, fog and toner scattering in the apparatus can be more effectively removed.

  According to the fifth aspect of the present invention, when the fog level is high, the peripheral speed ratio between the developing roller and the photosensitive member is changed to a value that deviates more than 1.0. The peripheral speed ratio between each developing roller and the photosensitive member is changed and controlled by the peripheral speed control means so that the peripheral speed ratio becomes a value close to 1.0. The occurrence of ming can be more effectively suppressed.

  According to the sixth aspect of the present invention, since each developing roller is connected to a driving motor that can drive them independently of each other, each developing roller can be driven and controlled independently of each other.

  According to the seventh aspect of the present invention, after the peripheral speed ratio between the developing roller and the photosensitive member is changed according to the fog level, a determination operation for predetermined process control is performed, and the determination result is based on the determination result. Since the predetermined process control is executed, the predetermined process control can be optimally performed.

  According to the invention described in claim 8, the determination means changes the charging voltage and the development voltage to form toner patches on the photosensitive member, measures the toner patch density, and determines the input signal from the temperature sensor. In addition, since the determination is performed by detecting the optimum charging voltage and developing voltage, more accurate process control can be performed.

  According to the invention described in claim 9, since the determination means determines the toner patch by changing the gradation pattern, measures the toner patch density, and detects the optimum image formation pattern. More accurate process control can be performed.

  According to the invention described in claim 10, since the predetermined process control includes the control of the charging voltage, the developing voltage, the image forming pattern, or a combination thereof, more accurate process control can be performed. .

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the first embodiment of the present invention, specifically, an electrophotographic image forming apparatus.
The photosensitive member 1 is formed by uniformly applying a charge generation layer to a film pressure of 1 (μm) on an aluminum tube having a thickness of 2 (mm), a diameter of 100 (mm), and a length of 340 (mm). It consists of an organic semiconductor coated with a 35 (μ) charge transfer layer.

  Reference numeral 2 denotes a charger, and 3 denotes an optical system for irradiating a document on the document table and coupling reflected light onto the photosensitive member, a CCD 3a, and a writing unit.

  Reference numeral 4 denotes a developing unit for developing the electrostatic latent image with toner, and reference numeral 5 denotes a transfer unit for transferring the toner image on the photoreceptor 1 onto the transfer paper 6. The toner image transferred onto the transfer paper 6 is heated and fixed by the fixing device 7 and is discharged outside the apparatus.

  S <b> 1 is a first reflectance measurement sensor S <b> 1 that measures the surface reflectance of the non-image portion of the photoreceptor 1, and is disposed on the downstream side of the developing device 4.

Reference numeral 8 denotes a cleaner unit that removes residual toner on the surface of the photoreceptor 1 by an internal blade 8a.
Reference numeral 9 denotes a static elimination lamp disposed on the downstream side of the cleaner unit 8. A second reflectance measurement sensor S <b> 2 that measures the surface reflectance of the non-image portion of the photoreceptor 1 after passing through the cleaner unit 8 is disposed on the downstream side of the static elimination lamp 9.
In the present embodiment, the second reflectance measurement sensor S2 and the first reflectance measurement sensor S1 constitute a reflectance measurement sensor that measures the surface reflectance of the photoreceptor 1.
The reflectance measuring sensors S1 and S2 use light emitting diodes in the light emitting section. The light emitted from the light emitting diodes is irradiated onto the photosensitive member 1, and the reflected light is received by the phototransistor. It is a configured optical type.

  Amplifiers 11c and 11b and A / D converters 12c and 12b are connected to the reflectance measurement sensors S1 and S2, and the outputs of the reflectance measurement sensors S1 and S2 are amplified by the amplifiers 11c and 11b, respectively. After being A / D converted via the / D converters 12c and 12b, it is input to the main control unit 13.

  The main control unit 13 has a CPU (Central Processing Unit), the entire apparatus, a ROM (Read Only Memory) storing a control program for carrying out the present invention, and a RAM (Random access Memory) serving as a work area. Configured.

The main control unit 13 detects the fog level of the non-image portion of the photoreceptor 1 from the output ratio of the reflectance measurement sensors S1 and S2, controls the drive motor 14 that drives the developing roller 20, and the process. It has a function of outputting a signal to the control unit 15.
When two or more developing rollers 20 are provided, a configuration in which a driving motor 14 is provided for each developing roller 20 is preferable. In this case, each developing roller 20 can be driven and controlled independently of each other.

That is, the main control unit 13 has the following functions.
(1) A function of detecting the fog level on the surface of the photoreceptor 1 based on the surface reflectance measured by the first and second reflectance measurement sensors S1 and S2 (fogging level detection means).
In this embodiment, the fog level on the surface of the photosensitive member is detected from the output ratio of the reflectance detected by the first and second reflectance measuring sensors S1 and S2. However, the following may be used. .
A correlation table showing the correlation between the surface reflectance of the photoconductor after development and the fog level is prepared and corresponds to the reflectance of the photoconductor surface after development measured by a single reflectance measurement sensor. The fog level is detected with reference to the correlation table.

(2) A function (peripheral speed control means) for increasing / decreasing the peripheral speed of the developing roller based on the fog level detected by the fog level detecting means.
When the fog level is high, the peripheral speed ratio between the developing roller 20 and the photosensitive member 1 is changed to a value that deviates more than 1.0, and when the reflectance decreases, the peripheral speed ratio between the developing roller 20 and the photosensitive member 1 is changed to 1.0. The peripheral speed ratio between the developing roller 20 and the photosensitive member 1 is changed and controlled so as to be a value close to.
In the case where two or more developing rollers are provided, each development is performed according to the level of the fog level based on the fog level of the surface of the photoreceptor 1 detected by the first and second reflectance measuring sensors S1 and S2. The peripheral speed ratio between the roller and the photoreceptor 1 can be changed.

  In the present embodiment, in addition to the first and second reflectance measurement sensors S1 and S2, a temperature sensor 19 for detecting the temperature near the surface of the photoreceptor 1 is provided, and the output of the temperature sensor 19 is amplified. 11a, and input to the process control unit 15 through the A / D converter 12a.

  After receiving the output from the main control unit 13, the process control unit 15 performs a determination operation for predetermined process control, and controls the charging voltage control unit 16, the development voltage control unit 17, and the image formation pattern control unit 18. It is like that.

That is, the process control unit 15 has the following functions.
(1) A function (determination means) for performing a determination operation for predetermined process control after changing the peripheral speed ratio between the developing roller 20 and the photoreceptor 1 in accordance with the fog level.

  In this embodiment, “determination operation for predetermined process control” means that a toner patch is formed on a photoconductor by changing a charging voltage and a development voltage, and the density of the toner patch is measured. Operation to detect the optimum charging voltage and development voltage in combination with the input signal, or operation to form toner patches by changing the gradation pattern and measure the density of those toner patches to detect the optimum image formation pattern It is.

  When a transfer belt (not shown) is adopted, toner patches are formed on the transfer belt by changing the charging voltage and the development voltage, the density of the toner patches is measured, and an input signal from the temperature sensor 19 is measured. In addition, an operation for detecting an optimal charging voltage and a developing voltage, or an operation such as changing the gradation pattern to form toner patches, measuring the toner patch density and detecting an optimal image forming pattern, “Determining operation for predetermined process control”.

  In other words, the toner voltage is formed on the photosensitive member or the transfer belt by changing the charging voltage and the developing voltage, the toner patch density is measured, and the optimum charging voltage and developing are combined with the input signal from the temperature sensor. The determination is performed by detecting the voltage, and the determination is performed by forming toner patches by changing the gradation pattern, measuring the density of the toner patches, and detecting an optimum image formation pattern.

(2) A function (process control means) for executing predetermined process control based on the determination result by the determination means.
The “predetermined process control” is to control the charging voltage, the developing voltage, the image forming pattern, or a combination thereof.

FIG. 2 is a diagram showing the relationship between the output value ratio A of the first and second reflectance measurement sensors: A and the fog level by measurement.
The horizontal axis indicates actual BG (fogging level by measurement), and the vertical axis indicates the output value of the first reflectance measurement sensor S1 disposed downstream of the developing device 4 and the downstream of the cleaner unit 8. A ratio of output values of the second reflectance measurement sensor S2 arranged on the side: A (output value of the first reflectance measurement sensor S1 / output value of the second reflectance measurement sensor S2).

Here, “BG (fogging level by measurement)” is a difference between values obtained by measuring the background portion of the recording paper with a whiteness meter before and after image formation, and indicates a fogging level.
In the present embodiment, the above-described output value ratio: A is 0.94 or more and there is little fogging. In this case, the peripheral speed ratio between the developing roller 20 and the photosensitive member 1 is K (the peripheral speed of the developing roller 20). / Peripheral speed of the photosensitive member 1) is controlled at a normal value of 0.92.

  When the output value ratio A is 0.88 or more and less than 0.94, the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is controlled so as to be driven by changing K to 0.85, and the output value ratio: When A is less than 0.88, the peripheral speed ratio K between the developing roller 20 and the photoconductor 1 is controlled to be changed to 1.25.

FIG. 3 is a flowchart showing the operation of the image forming apparatus according to the first embodiment.
Step T1 (simply abbreviated as T1 in the figure. The same applies hereinafter): When the power is turned on, first, the peripheral speed ratio between the developing roller 20 and the photosensitive member 1: K (the peripheral speed of the developing roller / the peripheral speed of the photosensitive member) ) Is set to 0.92, and the process proceeds to Step T2.

  Step T2: The rotation of the photosensitive member 1 is started, the surface reflectance of the photosensitive member 1 is measured by the first reflectance measuring sensor S1 and the second reflectance measuring sensor S2, and the process proceeds to Step T3.

  Step T3: Using the output value of the first reflectance measurement sensor S1 for detecting the surface reflectance of the photoconductor 1 after development as a numerator, the second reflectance measurement sensor S2 for detecting the same surface reflectance after cleaning. A ratio of output values having the output value as a denominator: A (output value of the first reflectance measurement sensor S1 / output value of the second reflectance measurement sensor S2) is calculated, and the process proceeds to Step T4.

Step T4: It is determined whether or not the ratio of output values: A ≧ 0.94, and if the relational expression is established, the peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 is kept at 0.92. Proceed to T8, otherwise proceed to Step T5.
Step T5: It is determined whether or not the ratio: A ≧ 0.88. If the relational expression is established, the process proceeds to Step T7, and if not, the process proceeds to Step T6.

Step T6: The peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is changed to 1.25, and the process proceeds to Step T8.
Step T7: The peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 is changed to 0.85, and the process proceeds to Step T8.

  Step T8: A determination operation for process control control is performed, and the process proceeds to Step T9.

Step T9: Various process control controls are executed, and the process proceeds to Step T10.
Step T10: Moves to a copy cycle, and after copying 200 sheets, returns to Step T1 again, sets the peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 to 0.92, and sets the first reflectance measurement sensor S1 and the second The density of the surface of the photoreceptor 1 is detected by the reflectance measurement sensor S2.

The effect of this embodiment is shown in FIG. 4 as an aging result. In FIG. 4, the number of copies is shown on the horizontal axis, and B. G (fogging level by measurement) is shown.
Initially, a new cartridge is prepared, and 10,000 sheets of domestic paper are continuously flown for 18 hours. After leaving for 6 hours, the paper is flowed again by replacing with a new cartridge. Repeat this cycle 5 times.

  When a conventional image forming apparatus in which the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is fixed at 0.92, the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is fixed at 1.25. In the case of flowing in the image forming apparatus, B. in the case of flowing in the image forming apparatus according to the present invention. The change with time of G (fogging level by measurement) was compared.

  Both are continuously flowed. G deteriorates, and after being left, it is changed to a new cartridge. The tendency of G to recover is the same, but when it is flowed by the image forming apparatus according to the present invention, B.G. The degree of deterioration of G was greatly improved, and the occurrence of filming was not observed.

  In contrast, in the image forming apparatus in which the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is fixed at 1.25, the B.I. Although deterioration of G was suppressed, filming occurred near 20K, and the number of filming reached 10 or more around 26k, so aging was interrupted.

  When the image forming apparatus of the present invention is used, B.D. In order not only to suppress the deterioration of G, but also to reduce fog toner on the photoreceptor 1 and toner scattering in the apparatus as a whole, There is also an effect that deterioration of G can be suppressed.

FIG. 5 is a block diagram of an image forming apparatus according to the second embodiment of the present invention. The image forming apparatus according to the second embodiment and the image forming apparatus according to the first embodiment shown in FIG. 1 are replaced by a single instead of the first and second reflectance measuring sensors S1 and S2. The difference is that the reflectance measurement sensor S3 is arranged on the downstream side of the peeling static eliminator and that a correlation table described later is stored in the ROM in the main control unit 13.
Accordingly, in this embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, differences will be mainly described.

  In this embodiment, the reflectance measurement sensor S3 measures the surface reflectance of the non-image portion of the photoreceptor after development, and the output of the reflectance measurement sensor S3 is amplified by the amplifier 11b, and the A / D converter 12b. After being subjected to A / D conversion, the data is input to the main control unit 13.

  In the ROM of the main control unit 13, the sensor output of the surface reflectance of the photosensitive member 1 and B.I. A correlation table that correlates with G (fogging level by measurement) is stored, and the output of the single reflectance measurement sensor S3 and the corresponding B.B. The G value (detected fog level) can be detected.

In the present embodiment, the detected B.P. The G value is 1.0 or less and the fog is reduced. The developing roller and the photosensitive member are driven at a peripheral speed ratio K (peripheral speed of the developing roller / peripheral speed of the photosensitive member) with a normal value of 0.92.
B. detected When the G value is higher than 1.0 and lower than or equal to 2.0, the peripheral speed ratio K between the developing roller and the photosensitive member: K is changed to 0.85 and controlled to drive. When the G value is higher than 2.0, the peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 is controlled to be changed to 1.25.

FIG. 6 is a flowchart illustrating a control operation of the image forming apparatus according to the second embodiment.
Step U1 (simply abbreviated as U1 in the figure. The same applies hereinafter): When the power is turned on, first, the peripheral speed ratio between the developing roller 20 and the photosensitive member 1: K (the peripheral speed of the developing roller / the peripheral speed of the photosensitive member) ) Is set to 0.92, and the process proceeds to Step U2.

  Step U2: The rotation of the photoconductor 1 is started, the surface reflectance of the non-image portion of the photoconductor after development is measured by the reflectance measurement sensor S3, and the process proceeds to Step U3.

  Step U3: From the correlation table, B. The G value (detected fog level) is detected, and the process proceeds to Step U4.

  Step U4: It is determined whether the G value is 1.0 or less. If the G value is 1.0 or less, the process proceeds to step U8; otherwise, the process proceeds to step U5.

  Step U5: It is determined whether the G value is 2.0 or less. If the G value is 2.0 or less, the process proceeds to Step U7, and if not, the process proceeds to Step U6.

  Step U6: Change the peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 to 1.25, and proceed to Step U8.

  Step U7: Change the peripheral speed ratio K between the developing roller 20 and the photoreceptor 1 to 0.85, and proceed to Step U8.

Step U8: A determination operation for process control control is performed, and the process proceeds to step U9.
Step U9: Various process control controls are executed, and the process proceeds to Step U10.
Step U10: Moves to a copy cycle, and after copying 200 sheets, returns to Step U1, and again sets the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 to 0.92, and proceeds to Step U2.

The effect of the image forming apparatus according to the present embodiment is shown in FIG. 7 as an aging result. The number of copies is shown on the horizontal axis and B. G (fogging level by measurement) is shown.
Initially, a new cartridge is prepared, and 10,000 sheets of domestic paper are continuously flown for 18 hours. After leaving for 6 hours, the paper is again replaced with a new cartridge. Repeat this cycle 5 times. Peripheral speed ratio between the developing roller and the photosensitive member: When the image is fed by a conventional image forming apparatus in which K is fixed at 0.92, and the peripheral speed ratio between the developing roller and the photosensitive member: image forming apparatus in which K is fixed at 1.25 B. in the case of flowing in the image forming apparatus of the present invention and B. The time course of G was compared.

  Both are continuously flowed. G deteriorates, and after being left, it is changed to a new cartridge. The tendency of G to recover is the same, but when it is flowed by the image forming apparatus of the present invention, it is B.B. It can be seen that the degree of deterioration of G is greatly improved. In addition, no filming was observed.

  On the other hand, in the image forming apparatus in which the peripheral speed ratio K between the developing roller 20 and the photosensitive member 1 is fixed at 1.25, B.I. Although deterioration of G was suppressed, filming occurred near 20k, and further, the number of filming was 10 or more near 26k, and aging was interrupted.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention, specifically, an electrophotographic image forming apparatus. It is a figure which shows the relationship between the ratio of the output value of a 1st, 2nd reflectance measuring sensor, and the fog level by measurement. 3 is a flowchart illustrating a control operation of the image forming apparatus according to the first embodiment. It is a figure which shows the effect of the image forming apparatus which concerns on 1st Embodiment as an aging result. It is a schematic block diagram of the image forming apparatus which concerns on the 2nd Embodiment of this invention. 10 is a flowchart illustrating a control operation of the image forming apparatus according to the second embodiment. It is a figure which shows the effect of the image forming apparatus which concerns on 2nd Embodiment as an aging result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 13 Fog level detection means 13 Peripheral speed control means 14 Drive motor 15 Determination means 15 Process control means 20 Developing roller S1-S3 Reflectivity measuring sensor S1 1st reflectance measuring sensor S2 2nd reflectance measuring sensor

Claims (10)

  A reflectance measuring sensor for measuring the surface reflectance of the photosensitive member, a fog level detecting means for detecting a fog level on the surface of the photosensitive member based on the reflectance measured by the reflectance measuring sensor, and the fog level detecting means. An image forming apparatus comprising: a peripheral speed control unit that increases or decreases a peripheral speed of the developing roller based on the detected fog level. The reflectance measuring sensor has a first reflectance measuring sensor that measures the surface reflectance of the photoconductor after development, and a second reflectance measuring sensor that measures the surface reflectance of the photoconductor after cleaning. And
2. The image forming apparatus according to claim 1, wherein the fog level detecting unit detects the fog level on the surface of the photosensitive member from the output ratio of the reflectance detected by the first and second reflectance measuring sensors. A correlation table showing the correlation between the surface reflectance of the photoconductor after development and the fog level is prepared.
2. The fog level detection unit detects a fog level corresponding to the reflectance of the developed photoreceptor surface measured by a single reflectance measurement sensor with reference to a correlation table. Image forming apparatus. One or more developing rollers are provided,
The peripheral speed control means changes the peripheral speed ratio between each developing roller and the photoconductor according to the level of the fog level based on the fog level of the photoconductor surface detected by the reflectance measurement sensor. The image forming apparatus according to claim 1.   The peripheral speed control means changes the peripheral speed ratio between the developing roller and the photosensitive member to a value that deviates more than 1.0 when the fog level is high, and sets the peripheral speed ratio between the developing roller and the photosensitive member to 1 when the reflectance decreases. 5. The image forming apparatus according to claim 4, wherein the peripheral speed ratio between each developing roller and the photosensitive member is controlled to be a value close to 0.0.   6. The image forming apparatus according to claim 4, wherein a driving motor capable of independently driving the developing rollers is connected to each developing roller.   After changing the peripheral speed ratio between the developing roller and the photosensitive member in accordance with the fog level, a determination unit for performing a determination operation for predetermined process control, and executing predetermined process control based on the determination result The image forming apparatus according to claim 1, further comprising a process control unit configured to perform the process control.   The judging means changes the charging voltage and the developing voltage in the image forming apparatus, forms toner patches on the photoreceptor or the transfer belt, measures the density of those toner patches, and combines them with the input signal from the temperature sensor. The image forming apparatus according to claim 7, wherein the determination is performed by detecting a stable charging voltage and a developing voltage.   8. The image forming apparatus according to claim 7, wherein the determination unit performs determination by changing the gradation pattern to form toner patches, measuring the density of the toner patches, and detecting an optimum image formation pattern. apparatus.   The image forming apparatus according to claim 7, wherein the predetermined process control includes control of a charging voltage, a developing voltage, an image forming pattern, or a combination thereof.

Images