JP3286899B2 - Control method of image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, electrophotographic devices (copiers, optical printers, etc.), electrostatic recording devices, etc.
A transfer type (indirect type) or direct type image forming process including a step of charging a surface of an image carrier (electrophotographic photosensitive member, electrostatic recording dielectric, etc.) as a member to be charged is applied to form an image. The present invention relates to an image forming apparatus to be executed.

More specifically, the present invention relates to an image forming apparatus using a contact-type charging device as a means for charging a member to be charged, in which a charging member to which a charging bias is applied is brought into contact with the member to be charged to charge the surface of the member to be charged.

[0003]

2. Description of the Related Art For example, Japanese Patent Laid-Open Publication No. Sho 62-514
92 JP, as JP 62-230334 discloses), the contact charging device, an oscillating electric field having more than twice the peak voltage of the charge starting voltage when a DC voltage is applied to the charging member ( An alternating electric field, an electric field (voltage) whose voltage value periodically changes with time) is formed between the charging member and a member to be charged such as a photoreceptor, and further, a charging member having a high resistance layer on the surface layer By using such a material, charging uniformity of the member to be charged and prevention of leakage due to pinholes, scratches and the like on the surface of the member to be charged such as a photoreceptor can be achieved.

Further, as a charging member, a conductive member such as a conductive fiber bristle brush or a conductive elastic roller (conductive potential) is used.
In some cases, the charging member is brought into contact with a member to be charged, and a DC voltage is applied from the outside to directly inject charges into the surface of the member to be charged to charge the surface of the member to be charged to a predetermined potential.

FIG. 4 is a schematic configuration diagram of a conventional image forming apparatus. In FIG. 1, reference numeral 1 denotes a cylindrical photosensitive drum which is long in a direction perpendicular to the paper surface, has a rotation axis in the same direction, and rotates clockwise as indicated by an arrow. Around the photosensitive drum 1, a charging roller 2, a developing device 11,
A transfer unit 12, a cleaning device 13, and the like are provided. When the photosensitive drum 1, which is a member to be charged, is rotationally driven in accordance with a predetermined sequence, a predetermined bias is applied to the charging roller 2 from the power supply 3, whereby a predetermined bias is applied. The outer peripheral surface of the photosensitive drum 1, that is, the charged surface 1a is charged to a predetermined polarity and potential. Then, the charged surface to be charged 1a is subjected to image exposure 5 in accordance with the image content to form an electrostatic latent image. Next, a developer (toner) is applied from the developing device 11 to the surface on which the latent image is formed, and is visualized (toner image), and the transfer material 1 is synchronized with the formation of the toner image.
4 is an opposing portion (transfer portion) between the photosensitive drum 1 and the transfer means 12
The toner image on the photosensitive drum surface side is transferred onto the transfer material 14 by applying a transfer bias to the transfer unit 12. Then, the transfer material 14 onto which the toner image has been transferred is discharged outside the apparatus after the toner image is fixed by the fixing device 19. On the other hand, the transfer residual toner on the surface of the photosensitive drum 1 after the transfer is removed by the cleaning device 13, the charge is removed by the pre-exposure device 15, and the image is supplied to the next image forming apparatus.

[0006]

In the above-described image forming apparatus, the contact charging means or the image carrier sometimes has a temperature characteristic. For example, when the contact charging means has a temperature characteristic, even if an appropriate image is obtained in an environment of about 20 ° C., if left in an environment of 10 ° C. or less for a long time, the temperature of the contact charging means is also set. The temperature will be similar to the environment. At this time, when an image is output, the resistance value of the contact charging means is higher than that of 20 ° C. due to the temperature characteristics of the contact charging means. As a result, the amount of current is reduced, and the dark potential (black background potential) and halftone potential of the photoreceptor are reduced. However, there is a problem that the reproducibility of a thin character image such as a pencil image and a section is deteriorated because the difference from the white background potential becomes small.

On the other hand, if image forming conditions are set in advance so that an appropriate image can be obtained in a low-temperature environment, for example, 20
When the temperature reaches about ° C., the resistance value decreases due to the temperature characteristics of the charging unit, so that the amount of current flowing through the charging unit increases and the surface potential of the photoconductor increases, so that an overall fog image is formed.

Further, when the photoreceptor has a temperature characteristic, the level of the residual potential tends to increase (in absolute value) in a low-temperature environment. For this reason, the potential of the white background increases, and the contrast with the dark potential (black background) decreases, so that the image has a fog and a low density of the black background compared with the room temperature.

Usually, in a low temperature environment, the temperature characteristics of both the photosensitive member and the charging means are affected, so that the image has a problem that the density of the black background is low and fogging occurs.

Therefore, an object of the present invention is to solve the above-mentioned problems.

[0011]

According to the present invention, there is provided a method for controlling an image forming apparatus, comprising the following means.

(1) In a control method of an image forming apparatus for performing image formation by applying an image forming process including a step of charging a surface of a member to be charged, the means for charging the member to be charged includes: Is a contact type in which a charging member to which a charging bias is applied is brought into contact with a member to be charged to charge the surface of the member to be charged,
When the charging member corresponds to the non-image forming area of the member to be charged, the charging bias is controlled by DC constant voltage, and the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected. When the charging member corresponds to the image forming area of the member to be charged, a memory in which a correction value corresponding to a temperature is previously stored in a DC voltage corresponding to the detected DC current amount is referred.
Irradiation to complement determine a correction value corresponding to the temperature the detection
A method for controlling an image forming apparatus, wherein the charging bias is controlled to be DC constant voltage by applying a positive voltage.

(2) Forming an image by applying an image forming process including a step of charging the surface of the member to be charged with a light image containing image information on the surface of the member to be charged. In the method for controlling an image forming apparatus, the charging means of the charged body is a contact type in which a charging member to which a charging bias is applied is brought into contact with the charged body to charge the surface of the charged body. When the member corresponds to the non-image forming area of the member to be charged, the charging bias is DC constant voltage controlled, and the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected, When the charging member corresponds to the image forming area of the member to be charged, a correction amount corresponding to the temperature is added to the exposure amount of the light image irradiation corresponding to the detected DC current amount.
Corresponds to the temperature detected above by referring to the pre-stored memory
A method for controlling an image forming apparatus, comprising: determining an amount of correction to be performed;

(3) Forming an image by applying an image forming process including a step of charging the surface of the member to be charged and a step of irradiating the surface of the charged member with a light image containing image information. In the method for controlling an image forming apparatus, the charging means for the charged object is a contact type in which a charging member to which a charging bias is applied is brought into contact with the charged object to charge the surface of the charged object, The image forming apparatus further includes a time measuring unit configured to detect a pause time and an operation time of the apparatus, and a temperature detecting unit configured to detect a temperature of an environment in which the image forming apparatus is placed, wherein the charging member corresponds to a non-image forming area of the member to be charged. When the charging member is controlled by a DC constant voltage, the amount of DC current at that time is detected, and when the charging member corresponds to the image forming area of the member to be charged, the DC voltage corresponding to the detected DC current amount is detected. In addition, detection of timing means It was in accordance with the value and temperature correction value
The stored with reference to the memory temperature sensing hand stage of the detected and determined from the value obtained temperature compensation in addition to the DC constant voltage control such a charging bias in advance, also the charging bias by at least one value of the timekeeping means and the temperature detecting means Wherein the temperature correction added to the DC constant voltage control is cancelled.

(4) Forming an image by applying an image forming process including a step of charging the surface of the member to be charged, and a step of irradiating the surface of the charged member with a light image containing image information. In the method for controlling an image forming apparatus, the charging means for the charged object is a contact type in which a charging member to which a charging bias is applied is brought into contact with the charged object to charge the surface of the charged object, The image forming apparatus further includes a time measuring unit configured to detect a pause time and an operation time of the apparatus, and a temperature detecting unit configured to detect a temperature of an environment in which the image forming apparatus is placed, wherein the charging member corresponds to a non-image forming area of the member to be charged. When the charging bias is controlled by a DC constant voltage, the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected, and the charging member corresponds to the image forming area of the member to be charged. If the above is detected Exposure of light image irradiation in accordance with the flow amount of current
Refer to the memory that stores the correction amount according to the temperature in advance.
A method for controlling an image forming apparatus, comprising: controlling an exposure amount by performing a correction; and canceling a temperature correction added to the control of the exposure amount by at least one of a time measuring unit and a temperature detecting unit.

<Operation> (1) When the charging member corresponds to the non-image forming area of the member to be charged, the charging bias is controlled with a constant DC voltage, and the DC current amount at that time and the position of the image forming apparatus are controlled. And when the charging member corresponds to the image forming area of the member to be charged, a DC voltage corresponding to the detected DC current amount is subjected to a correction corresponding to the detected temperature. By controlling the charging bias with a DC constant voltage, a change in the charging potential of the member to be charged due to an environmental change is suppressed, and a decrease in contrast, fogging, and the like are prevented.

(2) When the charging member corresponds to the non-image forming area of the member to be charged, the charging bias is controlled by a constant DC voltage, and the amount of DC current at that time and the environment in which the image forming apparatus is placed When the charging member corresponds to the image forming area of the member to be charged, the correction corresponding to the detected temperature is performed on the exposure amount of the light image irradiation corresponding to the detected DC current amount. By controlling the amount of exposure, the fluctuation of the image formed on the member to be charged by light image irradiation due to environmental changes is suppressed, and a decrease in contrast and fogging are prevented.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment Example 1> 1. FIG. 1 is a schematic diagram of an example of an image forming apparatus according to the present invention.

Reference numeral 1 denotes an image bearing member as a member to be charged. In this embodiment, a drum type electrophotograph is basically composed of a conductive substrate 1b of aluminum or the like and a photoconductive layer 1a formed on the outer peripheral surface thereof. It is a photoconductor. It is driven to rotate around the support shaft 1d clockwise in the drawing at a predetermined peripheral speed (process speed). Reference numeral 2 denotes a charging roller which contacts the surface of the photoreceptor 1 to uniformly perform primary charging on the photoreceptor surface to a predetermined polarity and potential.
La . Then, by applying a predetermined direct current (DC) bias from the power supply 3, the peripheral surface of the rotary photoconductor 1 is primarily charged. Photoconductor surface 1 uniformly charged by charging member 2
Next, the exposure means 10 receives an exposure (eg, a slit exposure of a document image, a laser beam scanning exposure, etc.) based on the light beam L based on the target image information, and an electrostatic latent image corresponding to the target image information is formed on the peripheral surface thereof. Is formed. The exposure unit 10 in the apparatus of the present embodiment is a known document table fixed-optical system movable type document image forming slit exposure unit. In the exposure means 10, reference numeral 20 denotes a fixed platen glass, O denotes a document placed and set on the platen glass with the image surface facing down,
21 is a document holding plate, 22 is a document illumination lamp (exposure lamp), 23 is a slit plate, 24 to 26 are moving first to third mirrors, 27 is an image forming lamp, and 28 is a fixed mirror. Lamp 22, slit plate 23, moving first mirror 24
Is moved at a predetermined speed V from one end side to the other end side below the platen glass 20, and the second and third mirrors 25 and 26 are driven to move at a speed of V / 2, so that a downward original surface on the platen glass 20 is moved. Is scanned from one end side to the other end side, and image exposure is performed on the surface of the rotary photoconductor 1 by image forming slit exposure. The latent image formed on the surface of the photoreceptor 1 is subsequently visualized as a toner image by the developing unit 11. The toner image is then transferred by a transfer unit 12 from a paper supply unit (not shown) at an appropriate timing to a transfer unit t between the photoconductor 1 and the transfer unit 12.
Are sequentially transferred onto the surface of the transfer material 14 transported to Transferring means 12 of this embodiment is a contact charging system (transfer low la), the toner image of the photosensitive member 1 surface side by performing the charging of the toner and opposite polarity from the back of the transfer material 14 on the surface side of the transfer material 14 It is transcribed. The transfer material 14 to which the toner image has been transferred is separated from the surface of the photoconductor 1, conveyed to an image fixing unit (not shown), subjected to image fixing, and output as an image. Alternatively, in the case of forming an image on the back surface, the image is conveyed to a re-conveying unit to the transfer unit. The surface of the photoreceptor 1 after transfer is cleaned by a cleaning unit 13 to remove adhered contaminants such as untransferred toner and the like. The surface of the photoreceptor 1 is further subjected to static elimination by a static elimination exposure device 15 to repeatedly provide an image.

2. Correction Control According to Environmental Change When an image is formed at about 20 ° C., which is a normal temperature, using the above-described image forming apparatus, DC voltage control of the charging roller (charging member) 2 is performed prior to the image formation to adjust the photoconductor film thickness. A corresponding DC current amount is detected, and a DC voltage corresponding to the detected DC current amount is output as an image forming output voltage. Normally, DC voltage control is performed so that an appropriate potential is set in this environment, so that it is not necessary to make any particular correction.

However, for example, 5 to 10 as in winter morning
When the image forming apparatus is used in an environment of ° C., the resistance value increases due to the temperature characteristics of the charging roller 2 and the output characteristics of the charging roller 2 change, so that the dark potential (black background portion potential) tends to decrease. . At the same time, the photoconductor may also have temperature characteristics, in which case the dark potential V d
Does not change, V _SL (blank portion potential) increases, and V 1 (white background potential) increases accordingly, so that the latent image contrast (difference between V d and V 1 ) decreases.

FIG. 3 shows the temperature characteristics in this case .

In this embodiment, the temperature characteristic is corrected by the control means 30 using the following method.

2a. At a low temperature, a correction to increase the voltage applied to the charging roller 2 is performed. At a low temperature, the dark potential Vd decreases and the white background potential Vl decreases.
Rise, so that the latent image contrast, which is the difference between the two, decreases. In order to correct this and maintain the contrast, the voltage applied to the charging roller 2 is corrected as the temperature decreases. That is, the voltage for correction at room temperature (around 20 ° C.) is set to 0.
The correction is made to increase the applied voltage as the temperature decreases to V. The correction voltage to be applied at this time is determined in advance by measuring how much the resistance value changes under each environment. For example, in a 5 ° C. environment, the correction voltage is set to 60 to 80V. As a result, the contrast corresponding to the temperature is shown in FIG.
Thus, the fluctuation with respect to the temperature change is suppressed to be small, and an image without fog and without density fluctuation can always be obtained.

2b. At low temperatures, a correction is made to reduce the exposure of the image exposure lamp.

When the temperature characteristic of the photosensitive drum 1 is relatively small, the change in the contrast with respect to the temperature change is small because the change in the white background potential is small. in this case,
The lowering of the black portion potential has little effect on the density reduction, but the halftone potential Vh decreases with the decrease of the black background potential and the difference from the white background potential decreases, so that a pencil image or a thin section, etc. When taking a character image, fog appears.

Therefore, in order to maintain a difference between the halftone potential Vh and the white background portion potential Vl and obtain a thin character image in which the image is fogged, the exposure amount is corrected with respect to the temperature change. That is, at room temperature (20
(Approximately 0 ° C.), the correction amount is set to 0 V, and a correction is made to lower the voltage applied to the image exposure lamp as the temperature decreases. This makes it possible to obtain a thin character image without fogging even when the temperature of the photosensitive drum 1 changes.

In this embodiment, the correction of the voltage applied to the charging roller 2 and the correction of the exposure amount of the image exposure lamp 22 are separately performed. However, the present invention is not limited to this. May be performed, thereby enabling more detailed control.

Further, when the correction of the developing bias is added to the correction of the charging bias, it is possible to obtain an image which is not further affected by the temperature change.

3. Operation Sequence at the Time of Temperature Correction Next, an operation sequence of the control unit 30 that performs correction according to a temperature change will be described.

First, the pause time (switch-off time) of the image forming apparatus is detected by the timer means 33, and if the pause time is equal to or longer than a predetermined value, the arithmetic means 32 causes the charging roller 2 and the photosensitive drum 1 to operate. Judge that the temperature is the same as the external environment. Next, the calculating means 32 includes the temperature detecting means 31
, The environmental temperature in which the image forming apparatus is placed is detected, and a correction value corresponding to the detected temperature is determined with reference to a memory 34 in which correction values corresponding to the respective temperatures are stored in advance. When the charging roller 2 corresponds to the non-image area of the photosensitive drum 1, the charging bias to the charging roller 2 is controlled by DC constant voltage, and the amount of DC current corresponding to the film thickness of the photosensitive drum 1 is detected. An actual applied voltage is determined by adding a correction by a temperature factor to a DC voltage corresponding to the detected DC current amount.

Similarly, when the exposure amount of the exposure unit 10 is corrected, if it is determined that the temperature of the photosensitive drum 1 has reached the same temperature as the external environment, the memory 34 is stored based on the temperature information from the temperature detection unit 31. Referring to the correction amount, the light source 2 is referred to.
2 is determined.

Next, the operation time of the image forming apparatus (the time actually used for the copying operation) is integrated, and if the time used within a certain time exceeds a certain value, the temperature rise due to its use As a result, it is determined that the temperatures of the charging roller 2 and the photosensitive drum 1 have sufficiently increased, and the temperature correction is canceled.

If the usage time is less than a certain value,
The temperature correction is canceled in response to a rise in the temperature of the environment where the image forming apparatus is placed. In this case, the temperature correction may be gradually reduced to cancel the temperature correction.

By performing the above control, it is possible to cope not only with the start of use in a low-temperature environment but also with a temperature change during use of the image forming apparatus.

[0036]

As described above, according to the present invention,
Even when the environmental temperature changes, an image forming apparatus has been achieved in which a reduction in contrast, generation of fog, and the like are prevented by correcting a charging bias and an exposure amount.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between charging potential and temperature after correction of charging bias.

FIG. 3 shows a temperature characteristic of a charged potential of an object to be charged.

FIG. 4 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged body (photosensitive body) 2 Charging roller 3 Charging bias application power supply 10 Image exposure means 11 Developing means 12 Transfer means 13 Cleaning means 14 Transfer material

Continuation of front page (56) References JP-A-5-307315 (JP, A) JP-A-8-95317 (JP, A) JP-A-8-76561 (JP, A) JP-A-8-171261 (JP) JP-A-61-100768 (JP, A) JP-A-8-272202 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 21/00 370-540 G03G 15/02-15/02 103

Claims (4)

(57) [Claims] 1. A method for controlling an image forming apparatus, which performs image formation by applying an image forming process including a step of charging a surface of a member to be charged with the surface of the member to be charged, comprising: This is a contact type in which a charging member to which a charging bias is applied is brought into contact with a member to be charged to charge the surface of the member to be charged, and the charging bias is applied when the charging member corresponds to a non-image forming area of the member to be charged. DC constant voltage control, the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected, and when the charging member corresponds to the image forming area of the member to be charged, the above detection is performed. Refer to the memory in which the correction value corresponding to the temperature is previously stored in the DC voltage corresponding to the amount of DC current.
Irradiation to complement determine a correction value corresponding to the temperature the detection
A method for controlling an image forming apparatus, wherein the charging bias is DC-constant voltage controlled by applying a positive voltage. 2. An image forming process comprising the steps of: charging an object to be charged with a surface of the object to be charged; and irradiating the charged surface of the object to be charged with a light image containing image information. In the control method for an image forming apparatus to be executed, the charging means for the charged member is a contact type in which a charging member to which a charging bias is applied is brought into contact with the charged member to charge the surface of the charged member. When the charging bias corresponds to the non-image forming area of the member to be charged, the charging bias is controlled by DC constant voltage, and the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected. When the charging member corresponds to the image forming area of the member to be charged, light corresponding to the detected DC current amount
A method is used in which a correction amount corresponding to the temperature is stored in advance for the image irradiation exposure amount.
Determine the correction amount corresponding to the detected temperature with reference to the memory.
A method of controlling the exposure amount by applying a correction to the image forming apparatus. 3. An image forming process is performed by applying an image forming process including a step of charging a surface of a member to be charged with a light image containing image information on the surface of the member to be charged. In the control method of the image forming apparatus to be executed, the charging means for the member to be charged is a contact type for charging a surface of the member to be charged by bringing a charging member to which a charging bias is applied into contact with the member to be charged. And a temperature detecting means for detecting a temperature of an environment where the image forming apparatus is placed. The charging member corresponds to a non-image forming area of the member to be charged. When the charging member is controlled by a DC constant voltage, the amount of DC current at that time is detected, and when the charging member corresponds to the image forming area of the member to be charged, the DC voltage is adjusted to a DC voltage corresponding to the detected DC current amount. , Detection of timing means Respond to value and temperature
Refer to the memory that stores the same correction value in advance, and
Adding temperature correction determined from the detected value of the stage such a charging bias to a DC constant voltage control, also DC constant of the charging bias by at least one value of the timekeeping means and the temperature detecting means
A method for controlling an image forming apparatus, comprising: canceling temperature correction added to voltage control . 4. An image forming process comprising the steps of: charging a surface of a member to be charged with a surface of the member to be charged; and irradiating the surface of the member to be charged with a light image containing image information. In the control method of the image forming apparatus to be executed, the charging means for the member to be charged is a contact type for charging a surface of the member to be charged by bringing a charging member to which a charging bias is applied into contact with the member to be charged. And a temperature detecting means for detecting a temperature of an environment where the image forming apparatus is placed. The charging member corresponds to a non-image forming area of the member to be charged. When the charging bias is controlled by a DC constant voltage, the amount of DC current at that time and the temperature in the environment where the image forming apparatus is placed are detected, and the charging member corresponds to the image forming area of the member to be charged. Is detected, the Light according to the amount of current
A method is used in which a correction amount corresponding to the temperature is stored in advance for the image irradiation exposure amount.
Controlling the exposure amount by correcting with reference to memory, also the amount of exposure by at least one value of the timekeeping means and the temperature detecting means
A method for controlling an image forming apparatus, comprising: canceling temperature correction added to control.