JP2001147631A - Electrophotographic image forming device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly obtain an image having a stable density without unnecessary consumption of toner. SOLUTION: A time t1 of the latest execution of image density control is read out from a memory 20 provided in a process cartridge C to calculate a difference t2-t1 between the time t1 and a present time t2, and this difference is compared with a prescribed time Td (S1). In the case of (t2-t1)>=Td, image density control is executed (S2), and the time t2 is stored as the new time t1 in the memory 20 (S3). In the case of (t2-t1)<Td, image density control is not executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile or a printer, and a process cartridge detachable from the electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic method, a change in an environment in which the image forming apparatus is used,
In order to prevent the image density from fluctuating greatly due to various conditions such as the number of prints, a toner image for density detection (hereinafter referred to as a “patch”) is provided on a photoconductor drum as an electrophotographic photoconductor.
Is formed, and the toner density of the toner image is detected by an optical sensor or the like serving as density detecting means, and the detected toner density is fed back to image forming conditions such as a developing bias, which is a developing process condition, so that the image density becomes a predetermined density. 2. Description of the Related Art An image forming apparatus that performs image density control so as to maintain the image density is known.

In the case of a color image forming apparatus, such image density control must be performed independently for each of the colors Y (yellow), M (magenta), C (cyan), and K (black). Requires a considerable amount of time, so that the response to the image output request may be delayed. Also, if the image density control is executed even when the image forming conditions are not particularly changed, for example, after a short power-off, the user will needlessly wait, and the toner used for creating the patch will be wasted. Will be.

In order to prevent such unnecessary image density control from being performed, the time when the power of the image forming apparatus is turned off is recorded in a nonvolatile memory built in the process cartridge. Japanese Patent Application Laid-Open No. H11-218972 proposes to determine whether to execute image density control based on the length of the apparatus stop time at the time of re-input.

[0005]

However, in the conventional image forming apparatus as described above, for example, when the power is turned on immediately after the power of the image forming apparatus is turned off, or when the process cartridge is once removed from the image forming apparatus main body. When the image forming apparatus is immediately mounted again, the image density control is executed even though it is not necessary to execute the image density control because the image forming condition has not changed. Further, in an image forming apparatus that executes image density control at regular time intervals, for example, during a time period when image output is hardly performed, such as at midnight, only image density control is executed and toner is wasted.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electrophotographic image forming apparatus and a process cartridge capable of rapidly obtaining an image having a stable density without wasting developer.

[0007]

The above object is achieved by an electrophotographic image forming apparatus and a process cartridge according to the present invention. In summary, the present invention relates to an electrophotographic image forming apparatus for forming an image on a recording medium in which a process cartridge is detachable, wherein (a) an electrophotographic photosensitive member and the electrophotographic photosensitive member are acted on. Process means;
Mounting means for removably mounting a process cartridge having a storage means for storing the time t1 at which the image density control was last performed; (b) image density control means for controlling image density; and (c). Means for knowing the current time t2, and operating to execute image density control when the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time. It is a photographic image forming apparatus.

According to a second aspect of the present invention, there is provided an electrophotographic image forming apparatus for detachably mounting a process cartridge and forming an image on a recording medium, comprising: (a) an electrophotographic photosensitive member; Mounting means for removably mounting a process cartridge having a process means acting on the photographic photosensitive member and a storage means for storing a time t1 at which the image density control was last performed; and (b) controlling the image density And (c) means for knowing the current time t2, wherein the time t1 and the current time t2 are determined.
2 is greater than or equal to a predetermined time and the current time t2
Operable to execute the image density control when the time is within a predetermined time zone.

According to a third aspect of the present invention, in an electrophotographic image forming apparatus for forming an image on a recording medium,
(A) an electrophotographic photosensitive member, (b) an electrostatic latent image forming means for forming an electrostatic latent image on the electrophotographic photosensitive member, and (c)
Developing means for developing the electrostatic latent image to obtain an image,
(D) image density control means for controlling the image density; (e)
And (f) means for knowing the current time t2, wherein the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time. An electrophotographic image forming apparatus is provided which operates to execute image density control when.

According to a fourth aspect of the present invention, in an electrophotographic image forming apparatus for forming an image on a recording medium,
(A) an electrophotographic photosensitive member, (b) an electrostatic latent image forming means for forming an electrostatic latent image on the electrophotographic photosensitive member, and (c)
Developing means for developing the electrostatic latent image to obtain an image,
(D) image density control means for controlling the image density; (e)
And (f) means for knowing the current time t2, wherein the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time. , And operates to execute image density control when the current time t2 is within a predetermined time zone.

According to a fifth aspect of the present invention, there is provided a process cartridge detachably mountable to an electrophotographic image forming apparatus main body provided with image density control means for controlling image density.
(A) an electrophotographic photosensitive member, (b) a process unit acting on the electrophotographic photosensitive member, and (c) a storage unit for storing a time t1 at which image density control was last performed. When the difference between the current time t2 by the clock means provided in the photographic image forming apparatus main body and the first time t1 is equal to or longer than a predetermined time, the apparatus operates to execute image density control. A process cartridge is provided.

According to a sixth aspect of the present invention, there is provided a process cartridge detachably mountable to an electrophotographic image forming apparatus main body provided with image density control means for controlling image density.
(A) an electrophotographic photosensitive member, (b) a process unit acting on the electrophotographic photosensitive member, and (c) a storage unit for storing a time t1 at which image density control was last performed. When the difference between the current time t2 by the clock means provided in the main body of the photographic image forming apparatus and the first time t1 is equal to or longer than a predetermined time and the current time t2 falls within a predetermined time zone. A process cartridge operable to execute image density control is provided.

According to one embodiment of the present invention, the clock means that can know the first time t1 is a clock with a battery provided in a printer engine, a clock with a battery provided in a video controller, or a clock in a host computer. Use one of the built-in clocks. Further, the processing means is at least one of a charging means, a developing means and a cleaning means.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophotographic image forming apparatus and a process cartridge according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

The electrophotographic image forming apparatus according to the present embodiment is shown in FIG.
As shown in FIG. 1, a photosensitive drum 1 serving as a drum-shaped electrophotographic photosensitive member on which an electrostatic latent image is formed on an outer peripheral surface, and a photosensitive drum 1
A roller charger 2 serving as charging means for charging the outer peripheral surface of the device to a specified potential; an exposure device serving as an electrostatic latent image forming device for forming an electrostatic latent image on the outer peripheral surface charged to the specified potential by exposure A developing device 4 as a developing unit for developing the electrostatic latent image into a visible image with toner as a developer, and transferring the visible image (visible image) formed on the outer peripheral surface to a transfer paper P as a sheet-shaped recording medium. Roller-like transfer roller 3, fixing device 5 for fixing a visible image to transfer paper P, and cleaning unit 6 for removing toner remaining on photoconductor drum 1
It has.

In FIG. 1, a photoreceptor drum 1 has an organic photoreceptor (OPC) or A
A photoconductor made of Si, CdS, Se or the like is applied, and is rotated in a direction indicated by an arrow in the drawing by a driving means (not shown), and is uniformly charged to a predetermined potential by the roller charger 2. Is done.

The exposing device is disposed above the main body of the image forming apparatus, and has a laser diode 7, a polygon mirror 9 rotated and driven by a high-speed motor 8, a lens 10, and a folding mirror 11.

When an image signal is input to the laser driver 12, the laser driver 12
To emit light. Then, the light from the laser diode 7 passes through the optical path 13 and irradiates the photosensitive drum 1 with optical information corresponding to the image signal, so that a latent image is formed on the photosensitive drum 1.

Further, when the photosensitive drum 1 advances in the direction of the arrow, the bias power supply 14 supplies the frequency 80 between the photosensitive drum 1 and the developing sleeve 4a provided in the developing device 4.
A latent image is developed by applying a developing bias composed of a DC voltage and an AC voltage, which is composed of 0 to 3500 Hz, an amplitude of 400 to 3000 V, and an integrated average value of the waveform VDC of -50 to -550 V. It becomes an image.

The toner visible image developed in this manner is transferred onto the transfer paper P by the transfer roller 3 to which a predetermined bias is applied. Then, the transfer paper P on which the toner image has been transferred is conveyed by conveying means (not shown), and the toner image is fused and fixed by the fixing device 5 to become a permanent image.

The toner remaining on the photoreceptor drum 1 is cleaned by a cleaning means 6 composed of, for example, a fur brush, a blade and the like.

In this embodiment, the photosensitive drum 1 and the roller charger 2, the developing device 4, and the cleaning unit 6 acting on the photosensitive drum 1 as a process unit are integrated into a mounting unit 30 as a process cartridge C. Is configured to be attachable to and detachable from the main body of the apparatus.

In the image density control of this embodiment, when the image density control is started, an image density control circuit 19 serving as an image density control means provided in the image forming apparatus main body.
Generates an image signal representing a patch that is a toner image for density detection from the pattern generation circuit 15, and based on this signal, a latent image for n patches P 1 to Pn along the rotation direction on the photosensitive drum 1. Form an image.

Next, the latent image is developed by the developing device 4. At this time, the developing bias (VDC) is switched for each of the patches P1 to Pn by the high-voltage control circuit 16, and the developing bias V1 is different from each other. ~ Vn
Is developed. Then, the densities D1 to Dn of the patches P1 to Pn formed on the photosensitive drum 1 are measured by the density sensors 17 as density detecting means.

When the latent image of the density detecting patch is developed with different developing biases V1 to Vn, the relationship between the developing bias (VDC) and the patch density (OD) (V−
D characteristic) is as shown in FIG. As is apparent from FIG. 2, the VD characteristic is obtained by the portions A and C where the characteristic change is small.
And a portion B whose characteristics are largely changed. Further, the VD characteristic varies depending on the environment in which the image forming apparatus is installed, and for example, is a characteristic as shown in FIG. In FIG. 3, the characteristic a is the same as that of FIG. 2, the characteristic b is that in a high-temperature and high-humidity environment, and the characteristic c is
Are those in a low-temperature and low-humidity environment.

As shown in FIG. 2, in the VD characteristic,
In the portions A and C, the change in concentration is unstable, and in the portion B, the concentration is stably increasing. Therefore, as shown in FIG. 2, at the time of the density control, the control target DTarget is set to the portion B, and the densities D1 to Dn of the patches are D1 <D2.
<... <Di <Di + 1 <... <Dn, and the developing biases V1 to Vn are set such that the control target density DTarget is approximately halfway between the densities D1 to Dn. Even if the VD characteristic fluctuates slightly and the values of the densities D1 to Dn fluctuate, the values of the developing biases V1 to Vn vary even if the densities D1 to Dn fluctuate.
et is set to a value that falls within the range of D1 to Dn, and the developing bias Vi and the developing bias Vi shown in FIG.
The distance w from +1 is set to about 50V.

As described above, since the VD characteristic fluctuates greatly depending on the environment, if the values of the developing biases V1 to Vn are fixed as shown in FIGS. It goes out of the range of D1 to Dn. Therefore, the developing biases V1 to Vn are also changed according to the respective environments, so that the control target density DTarget becomes the density D1 to D1.
Dn is set to be approximately in the middle. For example, as shown in FIG.
4 to control the image density.

When the density control is started, the developing biases V1 to Vn are changed according to the absolute water content in the apparatus calculated from the temperature / humidity sensor 18 provided in the image forming apparatus.
The one suitable for the image density control at that time is selected. The image density control circuit 19 obtains a control target density DTarget by using the density D1 to Dn of each patch measured by the density sensor 17 and the data of the developing bias V1 to Vn when the patch was created. The optimum developing bias VTarget is calculated.

As described above, the method of calculating the optimum developing bias is as follows. First, a section in which the control target density DTarget is included among the densities D1 to Dn, that is, Di ≦
A section (i to i + 1) in which DTarget ≦ Di + 1 is searched.
If such a section is found, a developing bias VTarget for obtaining DTarget using linear interpolation is used.
Is calculated.

VTarget = {(Vi + 1−Vi) / (Di + 1−Di)} (DTarget−Di) + Vi (1) The optimum developing bias VTarget is calculated by the following equation (1).

Then, the developing bias VTarget is held in the memory 20 as storage means provided in the process cartridge C, and an image is formed using this value until the next image density control is executed.

Next, features of the present invention will be described. FIG. 5 is a flowchart showing a procedure for determining the execution timing of the image density control.

The time t1 at which the image density control was last executed is read from the memory 20 provided in the process cartridge C by a determination circuit 22 provided in the apparatus main body, and the difference t2-t1 from the current time t2 is calculated. (S1). If t2−t1 ≧ Td, image density control is executed (S2), and t2 is stored in the memory 20 as a new t1 (S3). Note that in step S3, if t2−t1 <Td, the image density control is not performed.

By setting the predetermined time Td to an appropriate value, the execution frequency of the image density control can be appropriately maintained, and an image having a stable density can be obtained without wasteful consumption of toner.

Further, in this embodiment, since the memory 20 for storing the time t1 at which the image density control was executed last is provided not in the image forming apparatus main body but in the process cartridge C, the process cartridge C is transferred from the image forming apparatus main body. When the cartridge is temporarily removed and then immediately re-inserted, image density control is not executed unlike when a new process cartridge is installed, so that the user is not wastefully consumed and toner is wasted. Nor.

The above-described image density control execution interval Td is not necessarily required to be a constant value. For example, when the image forming apparatus is turned on after a long-time power-off, the optimum image forming conditions change rapidly. , Td is set to a value smaller than usual to increase the execution frequency of the image density control.

The memory 20 is provided with an area for storing the value of the time t1 at which the image density control was executed last. Each time the image density control is completed, the time at that time is read from the clock 21 and newly stored. Memory 20 as the value of
Write to. The clock 21 may be provided in either the video controller or the printer engine. Alternatively, the clock 21 may be configured to receive time information from a clock provided in the host computer, and the video controller and the printer engine may have no clock.

As described above, according to this embodiment, the image density control is finally performed in the electrophotographic image forming apparatus having the image density control means for controlling the image density by detachably mounting the process cartridge. By providing a storage unit for storing the time t1 in the process cartridge and performing an image density control when the difference between the current times t2 and t1 is equal to or longer than a predetermined time. Since the image density control is executed only when the time during which the change in the image forming conditions is expected actually elapses, an image having a stable density can be obtained without wasteful consumption of toner.

Embodiment 2 Next, an electrophotographic image forming apparatus according to a second embodiment of the present invention will be described. The description of the same configuration as that of the first embodiment will be omitted, and different portions will be described.

FIG. 6 is a flowchart showing the procedure for determining the execution timing of the image density control in this embodiment.

When determining whether to execute the image density control, the determination circuit 22 first determines whether the current time t2 is between the image density control pause time t3 and the image density control restart time t4. Is checked (S11). t4 ≧
If t2 ≧ t3, it is determined that the time period has not entered the image density control, and the image density control is not performed.

If t2 ≧ t4 or t3 ≧ t2, it is determined whether or not to execute image density control as usual based on the determination procedure described in the first embodiment.

That is, the time t1 at which the image density control was last executed by the judgment circuit 22 is set to the process cartridge C.
Is read from the memory 20 to calculate the difference t2-t1 from the current time t2, and is compared with a predetermined time Td (S1).
2). If t2−t1 ≧ Td, image density control is executed (S13), and t2 is stored in the memory 20 as a new t1 (S14). In step S12, t2-t1
If <Td, the image density control is not executed.

In the above control, for example, t3 = 20: 00 and t4 = 8: 00 are set in advance at the time of shipment from the factory for t3 and t4. Change to an appropriate value according to the usage situation. Alternatively, the image forming apparatus main body may be provided with a function of accumulating and analyzing the usage data of the user, so that appropriate values are automatically set in t3 and t4.

In the first embodiment, the time at which the image density control was last performed is stored in the memory.
The image density control was executed at appropriate intervals.However, since the frequency at which the user outputs an image is low during a time period such as at night, for example, the image density control is performed every time when a change in image forming conditions is expected. If it is executed, only the image density control will be executed uselessly. In the present embodiment, as described above, such a waste is avoided by providing a time zone in which the image density control is not performed even if a change in the image forming condition is expected.

Therefore, according to the present embodiment, the time t1 at which the image density control was last performed is stored in the memory 20 provided in the process cartridge C, and the execution of the image density control is performed at the current time t2 and the time t1. Is limited to the case where the difference is equal to or more than a predetermined time and the current time t2 does not fall within the predetermined image density control stop time zone, it is possible to obtain an image having a stable toner density without wasteful consumption of toner. I can do it.

The process cartridge C of the above embodiment is provided with the photosensitive drum 1, the roller charger 2, the developing device 4, and the cleaning device 6 as process means. However, the present invention is not limited to this, and any configuration having the photosensitive drum 1 and at least one of the above-described process units may be used. Also, the present invention
The developing device 4 may have a configuration in which the memory 20 is mounted as a developing cartridge detachable from the apparatus main body.
Further, the present invention is applicable to an image forming apparatus having no cartridge.

[0049]

As is apparent from the above description, according to the electrophotographic image forming apparatus and the process cartridge of the present invention, the storage means for storing the time t1 at which the image density control was last performed, and the current time t2 Means for performing image density control when the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time, or Time t
2 is greater than or equal to a predetermined time and the current time t2
Operates so as to execute image density control when it is within a predetermined time zone, so that an image having a stable density can be quickly obtained without wasteful consumption of the developer, and In addition, workability is improved, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an electrophotographic image forming apparatus according to the present invention.

FIG. 2 is a graph showing a relationship between a developing bias and a patch density;
It is a graph which shows D characteristic.

FIG. 3 is a graph showing a relationship between a developing bias and an image density for explaining a VD characteristic under each environment and a method of determining a developing bias used for image density control.

FIG. 4 is a graph showing a relationship between a developing bias and an image density for explaining a method of determining a developing bias used for image density control in a high-temperature and high-humidity environment.

FIG. 5 is a flowchart illustrating an image density control execution determination procedure according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an image density control execution determination procedure according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum (electrophotographic photoconductor) 2 roller charger (charging means) 4 developing device (developing means) 6 cleaning means 19 image density control circuit (image density control means) 20 memory (storage means) 21 clock 30 mounting means C Process cartridge

Claims (10)

[Claims] 1. An electrophotographic image forming apparatus for detachably attaching a process cartridge and forming an image on a recording medium, comprising: (a) an electrophotographic photosensitive member; and a process means acting on the electrophotographic photosensitive member. Mounting means for removably mounting a process cartridge having storage means for storing a time t1 at which image density control was last performed; (b) image density control means for controlling image density; ) Means for knowing the current time t2.
An electrophotographic image forming apparatus operable to execute image density control when a difference between the time t1 and the current time t2 is equal to or longer than a predetermined time. 2. An electrophotographic image forming apparatus for detachably attaching a process cartridge to form an image on a recording medium, comprising: (a) an electrophotographic photosensitive member, and a process means acting on the electrophotographic photosensitive member. Mounting means for removably mounting a process cartridge having storage means for storing a time t1 at which image density control was last performed; (b) image density control means for controlling image density; ) Means for knowing the current time t2.
When the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time and the current time t2 is within a predetermined time zone, the operation is performed so as to execute the image density control. Electrophotographic image forming apparatus. 3. An electrophotographic image forming apparatus according to claim 1, wherein said processing means is at least one of a charging means, a developing means and a cleaning means. 4. An electrophotographic image forming apparatus for forming an image on a recording medium, comprising: (a) an electrophotographic photosensitive member;
(B) an electrostatic latent image forming means for forming an electrostatic latent image on the electrophotographic photosensitive member; (c) a developing means for developing the electrostatic latent image to obtain an image; Image density control means for controlling the image density; (e) storage means for storing the time t1 at which the image density control was last performed; and (f) current time t.
And an operation for performing image density control when the difference between the time t1 and the current time t2 is a predetermined time or more. apparatus. 5. An electrophotographic image forming apparatus for forming an image on a recording medium, comprising: (a) an electrophotographic photosensitive member;
(B) an electrostatic latent image forming means for forming an electrostatic latent image on the electrophotographic photosensitive member; (c) a developing means for developing the electrostatic latent image to obtain an image; Image density control means for controlling the image density; (e) storage means for storing the time t1 at which the image density control was last performed; and (f) current time t.
And means for knowing the image density when the difference between the time t1 and the current time t2 is equal to or longer than a predetermined time and the current time t2 is within a predetermined time zone. An electrophotographic image forming apparatus operable to execute. 6. The means for knowing the current time t2 includes:
6. The electrophotograph according to claim 1, wherein one of a clock with a battery provided in a printer engine, a clock with a battery provided in a video controller, and a clock built in a host computer is used. Image forming device. 7. A process cartridge detachably mountable to an electrophotographic image forming apparatus main body provided with image density control means for controlling image density, comprising: (a) an electrophotographic photosensitive member;
(B) processing means acting on the electrophotographic photoreceptor;
(C) storage means for storing a time t1 at which the image density control was last performed, and a current time t2 by a clock means provided in the main body of the electrophotographic image forming apparatus;
A process cartridge that operates to execute image density control when the difference from the time t1 is equal to or longer than a predetermined time. 8. A process cartridge detachably mountable to an electrophotographic image forming apparatus main body provided with image density control means for controlling image density, comprising: (a) an electrophotographic photosensitive member;
(B) processing means acting on the electrophotographic photoreceptor;
(C) storage means for storing a time t1 at which the image density control was last performed, and a current time t2 by a clock means provided in the main body of the electrophotographic image forming apparatus;
A process cartridge that operates so as to execute image density control when the difference from the time t1 is equal to or longer than a predetermined time and the current time t2 is within a predetermined time zone. 9. The clock means for knowing the current time,
9. The process cartridge according to claim 7, wherein one of a clock with a battery provided in a printer engine, a clock with a battery provided in a video controller, and a clock built in a host computer is used. 10. The process cartridge according to claim 7, wherein said process means is at least one of a charging means, a developing means and a cleaning means.