JPH07191570A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of preventing soil of transfer paper caused by soil of the roller of a fixing device, and preventing the paper from being wrapped around the roller. CONSTITUTION:In the copying device 2, the image density of an original, which is transmitted to a photosensitive drum 42, is detected by an automatic exposure sensor 40. The image density detected by the automatic exposure sensor 40 is used in order to alter the time required to clean the surfaces of the upper heat roller 62a and lower heat roller 62b of the fixing device 62. That is, because the heat rollers 62a, 62b are likely to get soiled when the image density of the original is high, the heat rollers 62a, 62b are rotated for a long time according to the image density detected by the sensor 40, thus the surfaces of the heat rollers 62a, 62b are securely cleaned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which forms an image on an image bearing member by an electrostatic photography process, develops the image with toner and outputs it on a sheet.

[0002]

2. Description of the Related Art In an image forming apparatus, for example, an electrostatic copying apparatus, a photosensitive drum which is charged in advance to a predetermined polarity is irradiated with light from an original based on reflected light reflected from the original surface. A latent image is formed. The latent image formed on the photoconductor drum is developed by supplying toner from the developing device, and is transferred as a copy image onto a transfer sheet attracted to the photoconductor drum by electrostatic force.

The copy image, that is, the toner image transferred onto the transfer paper is separated from the photosensitive drum together with the transfer paper and is fixed on the transfer paper via a fixing device. At this time, the toner image, that is, the toner is melted by the heat of the heater of the fixing device. The melted toner penetrates between the fibers of the transfer paper, so that the paper and the toner are firmly adhered to each other and are discharged as a copy.

By the way, the toner melted by the heat of the heater of the fixing device is not only adhered to the paper but also adhered to the surface of the roller of the fixing device. The toner attached to the surface of the roller not only provides undesired dirt on the transfer paper by adsorbing paper dust or dust generated from the transfer paper, but also at a position equal to the outer peripheral length of the roller as the roller rotates. It is known that an offset image is generated on a transfer sheet.

Therefore, a fixing device having a cleaning member for removing the toner adhering to the surface of the roller has already been proposed.

[0006]

However, since the amount of toner adhering to the surface of the roller of the fixing device is increased as the image density of the original is higher (higher), the image density of the original to be copied is predetermined. If the value exceeds the value, there is a problem that toner adheres to the surface of the roller even in the fixing device in which the cleaning member is arranged.

Further, when a fixing device provided with a cleaning member is used, even if the image density of the original is relatively low (low), a continuous copying operation, that is, a large number of sheets of the same original are printed. When the copying is performed, there is a problem that the cleaning cannot catch up and the contamination of the roller increases.

An object of the present invention is to provide an image forming apparatus capable of preventing the transfer sheet from being contaminated and the sheet from being rolled up by removing the toner attached to the roller of the fixing device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems, and detects an image carrier on which an image corresponding to the information of an original is formed and the density of the information of the original to detect the density. Density detecting means for outputting a numerical value corresponding to, transfer means for transferring the image formed on the image carrier to a medium, and the number of times the image is transferred from the image carrier by the transfer means. A first means, which is arranged so that the axes thereof are substantially parallel to each other, and which is rotatably formed.
Fixing means for fixing the image on the medium by passing the medium having the image transferred by the transfer means between the pressure members, the fixing means including the second pressing member; Drive means for rotating at least one of the first and second pressure members, and contacting arrangements on the respective surfaces of the first and second pressure members, and the first and second pressure members by the drive means. The cleaning means for cleaning the respective surfaces of the first and second pressure members, the number of times the image counted by the counting means is transferred, and the density detecting means are detected during the entire rotation of The driving means is urged so that the conditions for cleaning the surfaces of the first and second pressing members by the cleaning means are changed at a predetermined ratio based on the density of the original document. There is provided an image forming apparatus characterized by comprising a cleaning condition changing means for changing that condition.

Further, according to the present invention, a document reading means for transmitting information of a document as light / dark information of light, and an image carrier on which an image corresponding to the light / dark information transmitted by the document reading means is formed. Photoelectric conversion means for photoelectrically converting the light / dark information transmitted by the document reading means according to the brightness to provide a numerical value corresponding to the light / dark information, and the image formed on the image carrier to be transferred. A transfer means for transferring the image onto the material, a fixing means for fixing the image transferred onto the transfer material by the transfer means onto the transfer material, and an area of the fixing means which is in contact with the image or the transfer material. The cleaning means for cleaning, the driving means for rotating the area of the fixing means in contact with the image or the material to be transferred at a predetermined speed, and the driving means are provided from the photoelectric conversion means. An image forming apparatus having a biasing means for biasing at a predetermined rate corresponding to the serial number is provided.

Further, according to the present invention, the original reading means for transmitting the information of the original as light / darkness information of the original, the instruction means for instructing the start of the operation of the original reading means, and the original reading means for transmitting the information. An image carrier on which an image corresponding to the light / dark information is formed, and a photoelectric conversion unit for photoelectrically converting the light / dark information transmitted by the document reading unit according to the brightness to provide a numerical value corresponding to the light / dark information. Transfer means for transferring the image formed on the image carrier to the transfer material, fixing means for fixing the image transferred to the transfer material by the transfer means to the transfer material, Counting means for counting the number of times the image is transferred to the transfer material by the transfer means, cleaning means for cleaning a region of the fixing means in contact with the image or the transfer material, and Driving means for rotating the area of the means in contact with the image or the material to be transferred at a predetermined speed, and a means for urging the driving means at a predetermined ratio according to the numerical value provided from the photoelectric conversion means. An image forming apparatus having a biasing means is provided.

[0012]

According to the image forming apparatus of the present invention, the image density of the document transmitted to the image carrier is detected by the density detecting means. The image density detected by the detection unit is used as an index for urging the cleaning unit for cleaning the first and second pressure members of the fixing unit. That is, when the original image has a high image density, the first and second pressing members are easily contaminated. Therefore, the cleaning unit causes the first and second pressing members to be responsive to the image density detected by the detecting unit. By changing the conditions for cleaning the surface of the first and second pressure members, the first and second pressure members are reliably cleaned.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

According to FIG. 1, the image forming apparatus or copying apparatus 2 reproduces an image on the basis of the image reading unit 4 for taking out an image of a document as light and dark information of light, and the light and dark information taken by the image reading unit 4. Image forming unit 6 and image reading unit 4
In addition, it has a control unit 8 for operating the image forming unit 6 according to a predetermined rule.

The image reading section 4 is formed so as to be openable and closable with respect to the original table 10 on which an object to be read, that is, the original D is placed, and the original D placed on the original table 10 is made into an original document. It has a document holder 12 that is brought into close contact with the table 10.

Below the document table 10, an exposure lamp 22 for illuminating the document D placed on the document table 10, a reflector 24 for converging the illumination light generated by the exposure lamp 22 on the document D, and A first mirror 26 that bends the reflected light from the document D is integrally formed, and a first carriage 20 that reflects the reflected light from the document D toward a second carriage 30 (described later) is arranged. The first carriage 20 is arranged so as to be movable in parallel with the platen 10, and by a pulse motor (not shown),
It is reciprocated along the platen 10. The exposure lamp 22 is
It is connected to a lamp regulator (not shown) and is turned on by a voltage adjusted so as to generate various light amounts corresponding to the exposure amount input from an operation panel (not shown).

The second carriage 30 includes the first carriage 20.
The second mirror 32 and the third mirror 34, which sequentially bend the reflected light from the document D that is bent via the first mirror 26, are arranged at right angles to each other. The second carriage 30 is driven by the first carriage 20 by a toothed belt or the like (not shown) that drives the first carriage 20, and is parallel to the document table 10 at a speed half that of the first carriage 20. Be moved to.

Below the first carriage 20, in a plane including the optical axis of the light reflected by the second carriage 30, it is movably formed by a drive mechanism (not shown).
While giving converging property to the reflected light from the second carriage 30, the imaging lens 36 that forms an image of the reflected light at a predetermined magnification by moving itself, and the focusing property corresponding to the predetermined magnification by the lens 36. A folding mirror 38 and the like for converging the given reflected light at a predetermined position on the photosensitive drum 40 described later are arranged. The folding mirror 38 can be moved along the optical axis of the lens 36 via a driving mechanism (not shown) in order to correct the variation of the focal length that changes according to the copy magnification, like the imaging lens 36. Is formed in.

In the same plane as the plane in which the lens unit 36 is arranged (shown by the chain double-dashed line in FIG. 2), that is, in the region through which the light transmitted from the third mirror 34 to the folding mirror 38 passes. At a position that does not block the light traveling toward the folding mirror 38, an automatic exposure sensor (for detecting the density of the image information of the document D in order to maintain the image density of the copy obtained by the copying operation at a constant level). AES) 40 (see Figure 2)
Are fixed via a fixing member (not shown). Incidentally, A
The output signal of ES40 is taken out after being stabilized by the circuit as shown in FIG. 2 and input to the input circuit of the control circuit described later.

A recording medium, that is, a photosensitive drum 42, on which an image corresponding to the image of the original is formed by the light transmitted through the folding mirror 38, is arranged at approximately the center of the image forming section 6. The photosensitive drum 42 is rotated in the direction of arrow R at a predetermined speed by a main motor (not shown).

Around the photosensitive drum 42, a charging device 44 for charging the drum 42 with a predetermined electric charge, and a developing device for developing the electrostatic latent image formed on the drum 42 by supplying toner thereto.
46, a transfer device 48 for transferring the toner image formed on the drum 42 to the paper P, and a cleaning static eliminator 50 for scraping off the toner remaining on the surface of the drum 42 and removing the electric charges remaining on the surface of the drum 42. Are arranged in order.

The charging device 44 is connected to a charging transformer, which will be described later, and is connected to a corona wire 44a which provides the photosensitive drum 42 with a predetermined amount of electric charge, that is, a charging potential, and a grid bias adjusting circuit, which will be described later. And includes a grid screen 44b that provides a grid bias voltage to control the amount of charge radiated through the photoreceptor drum 42.

The developing device 46 conveys a two-component developer (not shown) composed of toner and carrier (not shown), and at the same time holds the developer, attaches only the toner to the electrostatic latent image formed on the photosensitive drum 40. It has a developing roller 46a. A developing bias voltage is applied to the developing roller 46a via a developing bias transformer (not shown).

The transfer device 48 is connected to a transfer transformer (not shown), and is connected to a transfer charger wire 48a used for transferring the toner image on the photosensitive drum 42 to the paper P, and an AC voltage supply circuit (not shown). Further, it has a separation charger wire 48b for separating the sheet P electrostatically adsorbed on the photoconductor drum 42 from the photoconductor when the toner image is transferred.

The cleaning static eliminator 50 is a photosensitive drum.
It is constituted by a blade 50a that is pressed against the surface 42 of the drum 42 to remove the toner on the surface of the drum 42, and a discharge lamp 50b that removes the potential remaining on the surface of the photosensitive drum 42.

An image, that is, a toner image formed on the photosensitive drum 42 is transferred to a position corresponding to the upstream side in the direction in which the photosensitive drum 42 is rotated, that is, to the right of the apparatus 2 in this embodiment. Slots 52a and 52b into which the first and second sheet cassettes 14a and 14b for holding sheets P for storing are attached and detached
Are arranged.

Photoreceptor drum 42 and slot 52a (cassette
14a), the paper feed roller 54a that draws out the paper P one by one from the paper cassette 14a, and the paper P that is drawn out via the paper feed roller 54a and the paper feed roller 54b is sent to the photosensitive drum 42. A conveyance roller 56a for performing the operation is arranged. Similarly, the photosensitive drum 42 and the slot 52b (cassette
14b), a sheet feeding roller 54b for pulling out the sheets P one by one from the sheet cassette 14b, and a conveying roller for feeding the sheets P pulled out through the sheet feeding roller 54b to the photosensitive drum 42. 56b is arranged.

Between the photosensitive drum 42 and the conveying rollers 56a and 56b, the inclination of the paper P taken out from each cassette is corrected and the photosensitive drum 42 is also corrected.
A timing roller 58 that aligns the leading edge of the upper toner image and the leading edge of the sheet P and feeds the sheet P at the same speed as the moving speed of the outer peripheral surface of the photosensitive drum 42 is arranged.

The toner image formed on the photosensitive drum 42 is transferred to a position corresponding to the downstream side of the transfer device 48 along the direction in which the photosensitive drum 42 is rotated, and the toner is electrostatically attached. A conveying device 60 for conveying the sheet P in the running state,
The toner transferred to the paper P is heated to melt,
It has a fixing device 62 for fixing it on the paper P, and a pair of discharge rollers 64 for discharging the paper P on which the toner image is fixed to the outside of the device 2. Further to the left of the discharge roller 64,
A discharge tray 16 is arranged on which the paper P on which the toner image is fixed is stocked.

In the fixing device 62, an upper heat roller 62a having a heater 62c inserted therein is pressed against the upper heat roller 62a via a spring (not shown), and a lower heat roller 62b having an auxiliary heater (not shown) incorporated therein. The toner image is fixed on the paper P by heating the toner held on the paper P to melt the toner image and pressurize the toner image and the paper P. The heater 62c
The auxiliary heater (not shown) is turned on at a predetermined timing by a heater control circuit described later. The upper heat roller 62a is rotated at a predetermined speed by a motor 62m via a transmission mechanism such as a gear.

As is apparent from FIG. 3, the upper heat roller
On the outer peripheral surface of 62a, a cleaning roller 62d for removing the toner on the transfer paper which may adhere to the roller 62a,
The cleaning felt roller 62e that supplies silicon oil to the roller 62a in order to reduce toner adhesion to the outer peripheral surface of the roller 62a, the thermistor 62f that detects the surface temperature of the roller 62a, and the paper P from the upper heat roller 62a. An upper peeling claw 62g for peeling is arranged so as to contact the outer peripheral surface of the roller 62a. Further, a thermal fuse 62h for preventing abnormal heat generation of the roller 62a is arranged at a predetermined distance from the outer peripheral surface of the upper heat roller 62a.

A cleaning felt 62i is provided on the outer peripheral surface of the lower heat roller 62b to remove the toner transferred from the toner attached to the outer peripheral surface of the upper heat roller 62a, and the paper P is wound on the lower heat roller 62b. A lower peeling claw 62j for preventing and a thermistor 62k for detecting the surface temperature of the roller 62b are arranged so as to come into contact with the outer peripheral surface of the roller 62b.

FIG. 4 schematically shows an electrical connection between the control section 8 and the image forming section 6 and the image reading section 4 in the apparatus 2.

According to FIG. 4, the controller 8 has a CPU 70 as a main controller.

The CPU 72 has a ROM 72a in which data necessary for operating the apparatus 2 and a surface potential control routine, which will be described later, are written in advance, and the number of copies or copy magnification input via an operation panel (not shown). RA used for temporary storage of numerical data such as
A memory 72 including M72b and the like is connected.

The CPU 70 also includes a motor for the fixing device 62.
A motor driver 74 for rotating the 62m (and a main motor (not shown) and a scan motor (not shown)) at a predetermined speed, a heater 62c of the fixing device 62, and an auxiliary heater (not shown) (and an illumination lamp 22) are turned on at a predetermined timing. An input circuit for inputting an analog signal from the heater control circuit 76 and the automatic exposure sensor (AES) 40 to the CPU 70 (A
/ D converter) 78 etc. are also connected. The input circuit 78 includes the thermistors 62f and 62k, a thermal fuse 62,
Alternatively, an output from a temperature sensor (not shown) or the like is also input.

The CPU 70 further includes a high voltage transformer 80 for supplying a predetermined high voltage to the corona wire 44a of the charging device 44 and the transfer wire 48a of the transfer device 48, the grid screen 44b of the charging device 44 and the developing roller of the developing device 46. Bias voltage generating circuit 8 for supplying a predetermined bias voltage to 46a
2, an AC voltage generating circuit 84 for supplying an AC electric field to the separation charge wire 48b of the transfer device 48, an input port to which a paper detection signal output from many paper position detection switches (not shown) is input, many solenoids (not shown) or The data input from the mechanical controller that activates the electromagnetic clutch and the operation panel (not shown)
An interface or the like for transmitting the output (for example, data display) corresponding to the instruction from the CPU 70 to the operation panel while being transmitted to the U70 is also connected.

Next, the copying machine 2 according to the embodiment of the present invention.
The operation of will be described in detail.

When the power switch (not shown) is turned on, the apparatus 2 is warmed up and the standby (copyable) state is defined. During the warm-up period, the fixing device 62
The motor 62m for rotating the upper heat roller 62a and the lower heat roller 62b is rotated at a lower speed than during the copying operation. As a result, the upper and lower heat rollers 62a and 62b
Heating time required for the surface temperature of the product to reach a specified value
(Most of the time required for warm-up is spent to heat the heat roller of the fixing device, so the warm-up time can be substantially shortened.

The number of copies made via an operation panel (not shown),
Copying is started by inputting copy condition data such as copy magnification, enlargement / reduction, paper size selection, or mode selection, and turning on a copy start key (not shown). That is, the exposure lamp 22 is turned on by activating a lamp regulator (not shown) in accordance with an instruction from the CPU 70, and the scan motor (not shown) is urged to move the first carriage 20 and the second carriage 30 to the original table 10. The reflected light (that is, image information) from the document D placed on the document table 10 as it is moved along is sequentially transmitted to the photosensitive drum 42. In this case, a part of the reflected light of the illumination light from the exposure lamp 22 reflected by the document D is incident on the automatic exposure sensor (AES) 40 and converted into a voltage corresponding to the intensity of the input light. The output voltage output from the AES40 is, for example, as shown in FIG.
As shown in (1), the predetermined value is proportional to the amount of light reflected from the document D, that is, the image density of the document D. Where AES
If the output voltage range of 40 is, for example, 0 volt to 5 volt, the voltages shown by 4 volt, 3 volt, 2 volt ... Are output according to the amount of light reflected from the document D. . In this case, if the image density of the original document D is low, that is, if it is a white original document, a voltage close to 5 V is applied, and if the image density of the original document D is high, that is, if it is a black original document or an original document containing many solid black images. For example, voltages close to 0 volt are output.

On the other hand, in the image forming section 6, when the reading of the image information of the document D is started, the main motor (not shown) is energized to rotate the photosensitive drum 42 at a desired speed.
At the same time, by applying a predetermined voltage to each of the corona wire 44a and the grid screen 44b of the charging device 44, a predetermined amount of electric charge is supplied to the photosensitive drum 42 by corona discharge. Further, the fixing motor 62m of the fixing device 62 is energized to rotate the upper and lower heat rollers 62a and 62b. This substantially means that the cleaning roller 62d cleans the upper heat roller 62a, while the cleaning felt roller 62e cleans the surface of the roller 62a with silicon oil for reducing the adhesion of toner to the roller 62a. Useful for applying (hereinafter referred to as pre-cleaning).

In this state, the surface of the photosensitive drum 42 is illuminated with light from the illumination lamp 22 which is controlled so as to generate a light amount corresponding to the image density of the document D detected by the automatic exposure sensor (AES) 40. The first mirror 26 of the first carriage 20, the second mirror 32 of the second carriage 30, and the third mirror
The reflected light of the document D transmitted through the mirror 34, the imaging lens 36, and the folding mirror 38 is imaged, and the photosensitive drum
An electrostatic latent image corresponding to the image of the document D is formed on the surface of 42.

The electrostatic latent image formed in this manner is developed by the toner supplied by the developing roller 46a of the developing device 46 to which a predetermined developing bias voltage is applied, and is transferred through the transfer device 48 to the copy sheet. The toner image is transferred to P.

The toner image transferred to the copy paper P is separated from the surface of the photosensitive drum 40 together with the paper P,
The transfer device 60 transfers the fixing device 62 to the fixing device 62.
It is fixed to the sheet P via the.

The sheet of paper P to which the toner image is fixed is placed on the outside of the apparatus 2 via the ejection roller 64 and is placed in the ejection tray.
It is sequentially discharged to 66.

The photosensitive drum 42 on which the toner image has been transferred to the paper P is rotated as it is, and the residual toner is removed through the cleaning and neutralizing device 50, and then the electric charge is removed to be used for the next image formation.

Needless to say, the above series of copying operations are repeated when the number of copies is two or more or when the next original exists.

By the way, the fixing device is usually heated to a predetermined temperature by the above warm-up, and then the copy start key is turned on, so that the transfer sheet on which the toner image is transferred is conveyed to the fixing device 62. Until time is rotated for the above pre-cleaning. After that, the toner image is transferred, and the transfer paper in a state where the toner image is electrostatically held on the transfer paper is the upper heat roller 62a and the lower heat roller 62b.
The toner image is fixed on the sheet by being conveyed to a pressure contact area between the transfer sheet and the transfer sheet and passing through the pressure contact area. On the other hand, when the trailing edge of the sheet has completely passed through the pressure contact area, the upper heat roller 62a and the lower heat roller of the fixing device 62 are
The motor 62b, that is, the motor 62m, is rotated for a predetermined time and then stopped. This means that the next transfer sheet is supplied with toner that may be attached to the rollers 62a and 62b as the transfer sheet passes through the pressure contact area (the next copying operation is executed). Useful to get rid of before. That is, as described above, the cleaning roller 62d cleans the upper heat roller 62a, while the cleaning felt roller 62e causes the silicone oil on the surface of the roller 62a to reduce the adhesion of toner to the roller 62a. It is applied (hereinafter referred to as post-cleaning).

However, when the image density of the original D is high (dark) or a large number of copies are continuously copied from one original despite the above-mentioned pre-cleaning and post-cleaning. On the heat roller
Toner that cannot be completely cleaned is deposited on the surface of 62a, the lower heat roller 62b, or both rollers.

The amount of accumulated toner, the number of copies to be continuously copied, and the image density of the original are measured, for example, as shown in FIG.

FIG. 6A shows the degree of contamination of the roller with respect to the total number of copies with the image density of the original as the axis. According to FIG. 6A, by setting the image density of the original on the horizontal axis, when the image of the original having many solid black images is copied, the image of the original having the image density close to the blank sheet is copied. Compared with the case, it can be seen that dirt is conspicuous on the roller even with a small number of copies.

FIG. 6 (b) shows the number of copies per original, that is, the degree of contamination of the roller with respect to the total number of copies centered on the number of copies. According to FIG. 6 (b),
The horizontal axis represents the number of intermittent copies, that is, when the copy start key is turned on, the fixing roller is rotated, and the fixing roller is stopped after fixing the toner image on the sheet on which the toner image is transferred. When the number of intermittent copies is 1, the fixing roller is stopped when one copy is completed, and when the number of intermittent copies is 5, 5 copies are continuously completed. By doing so, the fixing roller is stopped, and by repeating the copying operation with one unit,
It can be seen that the smaller the number of sheets of paper passing through the fixing device, the less the dirt of the rollers.

That is, according to FIGS. 6 (a) and 6 (b), the smaller the number of intermittent copies and the lower the image density of the original, the higher the heat roller 62a and the lower heat roller 62b of the fixing device 62 are. You can see that the surface is hard to get dirty. This means that the cleaning mechanism of the fixing device 62 shown in FIG. 3, that is, the upper heat roller 62a, the cleaning roller 62d and the cleaning felt roller 62e, and the lower heat roller 62b and the cleaning felt 62i are in contact with each other ( It is shown that a sufficient cleaning effect can be provided by sufficiently securing the fixing cleaning time (hereinafter referred to as the fixing cleaning time) in comparison with the amount of toner conveyed by the transfer paper, that is, the number of copies.

FIG. 7 shows an example of control of the copying machine useful for removing the dirt on the rollers shown in FIG.

As described above, when the copy start key (not shown) is turned on, the motor 62m is energized to rotate the upper heat roller 62a and the lower heat roller 62b of the fixing device 62 for a predetermined time (STP 1 ). Then, one copy sheet is pulled out from the already selected cassette and is fed toward the timing roller 58 (STP 2).

At the same time when the paper is pulled out from the cassette or at a predetermined timing, a scanning motor (not shown) is energized, and the first carriage 20 and the second carriage 30 in which the illumination lamp 22 is turned on move along the document table 10. Then, the image of the document D is read (STP 3). Subsequently, the reflected light from the document D enters the AES 40, and the output voltage from the AES 40 is input to the CPU 70 via the input circuit 78.
(STP 4). By moving the first carriage 20 and the second carriage 30, the document D corresponding to a predetermined sampling section
Point when reflected light from AES40 is incident (STP 5)
Then, the CPU 70 averages the output voltage from the AES 40 input so far and stores it in the RAM 72b of the memory 72 (STP 6). Incidentally, in parallel with the STPs 3 to 5, the photosensitive drum 42 to which a predetermined potential is applied by the charging device 44.
The document light corresponding to the image information of the document transmitted via the first and second carriages 20 and 30, the lens unit 36, and the folding mirror 38 is supplied to the drum 42.
An electrostatic latent image is formed on the surface and is developed by the developing device 46,
The transfer device 48 transfers the toner image onto the copy sheet.

After the image of the original is transferred to the copy sheet by STP 3 to 5, it is determined whether or not the copy is completed.
(STP 7), when copying is completed (STP 7-Y), CP
AES40 stored in ROM72b by STP 6 by U70
The output voltage of the
The fixing cleaning time standard value (stored in 72a) is compared (STP 8 and 9).

When the STP 8 determines that the output of the AES 40 exceeds 3 volts, it is determined that the roller is not dirty, and the motor 62m of the fixing device 62 is rotated for a normal cleaning time. Stopped (STP 10).
If STP 8 and 9 determine that the output of AES40 exceeds 2 volts and is 3 volts or less, it is determined that the roller is slightly dirty, and the motor 62m of the fixing device 62 uses the normal cleaning time. Is rotated for an additional cleaning time, for example, 1 second added, and then stopped.
(STP 11). When the STP 9 determines that the output of the AES 40 is 2 volts or less, it is determined that the roller is considerably dirty, and the motor 62m of the fixing device 62 adds the normal cleaning time to the additional cleaning time, for example, It is rotated for an additional 2 seconds and then stopped (STP 12).

Incidentally, it is known that once the rollers 62a and 62b are soiled, the toner adhesion is accelerated. Therefore, if it is clear that all the copies have not been completed by STP 7 (STP 7-N)
Even by monitoring the output voltage of AES40,
It is determined whether or not the document has a risk that the roller may be soiled (STP 13), and if the output voltage of AES 40 is, for example, 2 V or less, the same addition as described above with STP 12 is made. Cleaning is carried out (STP 14)
. Since the motor 62m can change the rotation speed by the motor drive circuit 74, STP 11, STP 12, and STP
The rotation speed may be increased as the rotation time is increased at 14.

FIG. 8 shows a modification of the control for removing the dirt on the roller shown in FIG.

According to FIG. 8, when the copy start key (not shown) is turned on, the upper heat roller 62a and the lower heat roller 62b of the fixing device 62 are rotated for a predetermined time (STP 21),
When the number of copies is two or more, N = 1 is set to the copy number counter N for cleaning the rollers 62a and 62b during the continuous copying operation (STP 22). The copy number counter N is easily provided, for example, by securing a predetermined area in the RAM 72b and using it as a register. Further, as the counter N, an integration counter (not shown) incorporated in the device 2 may be used.

Subsequently, one copy sheet is pulled out from the already selected cassette and is fed toward the timing roller 58 (STP 23), and the first and second carriages 20 and
The image of document D is read by 30 (STP 24)
, The voltage corresponding to the image density of the original converted into a predetermined voltage by being incident on the AES 40 is input to the CPU 70 (STP 25).

By the movement of the first and second carriages 20 and 30, when the reflected light from the document D corresponding to a predetermined sampling section is incident on the AES 40 (STP 26), the CP
By U70, the output voltage from AES40 input so far is averaged and stored in RAM72b of memory 72.
(STP 27), "1" is added to the copy number counter N
(STP 28).

In parallel with the STPs 23 to 26, the first and second carriages 20 and 30, the lens unit 36, and the folding mirror 38 are provided to the photosensitive drum 42 to which a predetermined potential is applied by the charging device 44. The original light corresponding to the image information of the original transmitted is supplied to form an electrostatic latent image on the drum 42, the electrostatic latent image is developed by the developing device 46, and the toner image is transferred to the copy sheet by the transfer device 48. To be done.

Next, it is judged whether or not N has reached a predetermined number, that is, whether or not the number has reached a predetermined number of intermediate cleanings determined by α = 2, 4, 6, ...
(STP29) If the number of sheets is other than the predetermined number (STP29-N), it is determined whether copying is completed (STP30). If copying is completed (STP30-Y), the CPU 70 causes STP27 And R
The output voltage of AES40 stored in OM72b and (ROM72
The fixing cleaning time standard value (stored in a) is compared (STP 31 and 32).

If it is determined in STP 31 that the output of AES 40 exceeds 3 volts, it is determined that the rollers are less contaminated, and the motor 62m of the fixing device 62 is rotated for a normal cleaning time. Stopped (STP 33).
When STP 31 and 32 determine that the output of AES40 is more than 2 volts and less than 3 volts, it is determined that the roller is slightly dirty, and the motor 62m of the fixing device 62 uses the normal cleaning time. Is rotated for an additional cleaning time, for example, 1 second added, and then stopped.
(STP 34). When the STP 32 determines that the output of the AES 40 is 2 volts or less, it is determined that the roller is considerably soiled, and the motor 62m of the fixing device 62 adds the normal cleaning time to the additional cleaning time, for example, It is rotated for an additional 2 seconds and then stopped (STP 35).

By the way, even if it is clear from the STP 29 that all copying is not completed (STP 29-Y), for example, α = 2, during the continuous copying operation.
By monitoring the output voltage of the AES40 with the number of sheets specified by 4, 6, ... x 10, it is determined whether the document has a risk that the roller will be soiled (STP 36).
When the output voltage of ES 40 is, for example, 2 V or less, additional cleaning similar to that already described by STP 35 is periodically performed according to the number of continuous copies (STP 37). After that, the process is returned to STP 30 which determines whether the set number of copies have been completed. In this case, α × 1
The midway cleaning point defined by 0 is the cleaning roller 62d and the cleaning felt roller 62 of the fixing device 62.
e and the cleaning capability provided by the cleaning felt 62i. Also, "α"
Is set so that the total number of copies, which is not shown, is increased and the number of copies is reduced, so that it is possible to prevent an increase in dirt due to a decrease in cleaning ability.

[0068]

As described above, according to the image forming apparatus of the present invention, the time for cleaning the heat roller of the fixing device is increased in accordance with the image density of the document, so that the roller becomes dirty. It is possible to prevent the copied image from becoming dirty.

When the original image has a high image density, the heat roller is cleaned at a predetermined timing according to the total number of copies, even during the continuous copying operation. Therefore, it is possible to prevent the copied image from becoming dirty even after long-term use.

Further, by removing the stains on the heat roller according to the image density, it is possible to prevent the entrainment or jamming of copy paper which may occur due to the adhesion of toner to the roller.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a copying machine in which an embodiment of the present invention is incorporated.

2 is a schematic diagram showing an example of the position and signal output circuit of the automatic exposure sensor of the copying apparatus shown in FIG.

FIG. 3 is a schematic sectional view illustrating a fixing device used in the copying apparatus shown in FIG.

FIG. 4 is a schematic block diagram showing an example of a control unit of the copying apparatus shown in FIG.

5 is a graph showing the relationship between the output voltage from the automatic exposure sensor shown in FIG. 2 and the image density of a document.

6 is a graph showing the degree of contamination of the heat roller of the fixing device of the copying machine shown in FIG.
Is a graph showing the relationship between the image density of the original and the number of copies,
And, (b) is a graph showing the relationship with the number of copies provided by one copy operation.

7 is a flowchart showing an example of control of a fixing device of the copying apparatus shown in FIGS. 1 to 4. FIG.

8 is a flowchart showing a modified example of control of the fixing device shown in FIG.

[Explanation of symbols]

2 ... Copier (image forming apparatus) 4 ... Image reading unit 6 ...
Image forming unit, 8 ... Control unit, 10 ... Document table, 12 ... Document holder, 14a, 14b ... Paper cassette, 16 ... Tray, 20 ... First carriage, 22 ... Exposure lamp, 24 ... Reflector plate, 26 ... First Mirror, 30 ... Second carriage, 32 ... Second mirror, 34 ... Third
Mirror, 36 ... Imaging lens, 38 ... Folding mirror, 40 ... Automatic exposure sensor (AES), 42 ... Photosensitive drum, 42a ... Photosensitive layer, 44 ... Charging device, 46 ... Developing device, 48 ... Transfer device, 50 ...
Cleaning static eliminator, 52a, 52b ... slot, 54a,
54b ... Paper feeding roller, 56a, 56b ... Conveying roller, 58 ... Timing roller, 60 ... Conveying device, 62 ... Fixing device, 62a ... Upper heat roller, 62b ... Lower heat roller, 62c ... Heater,
62d ... Cleaning roller, 62e ... Cleaning felt roller, 62f ... Thermistor, 62g ... Upper peeling claw, 62h ...
Thermal fuse, 62i ... Cleaning felt, 62j ... Lower peeling claw, 62k ... Thermistor, 62m ... Motor, 64 ... Ejection roller, 70 ... CPU, 72 ... Memory, 72a ... ROM, 72b ...
RAM, 74 ... Motor driver, 76 ... Heater control circuit, 78
Input circuit (A / D converter), 80 ... High voltage transformer, 82 ... Bias voltage generating circuit, 84 ... AC voltage generating circuit.

Claims (5)

[Claims] 1. An image carrier on which an image corresponding to information of an original is formed, density detecting means for detecting the density of information on the original and outputting a numerical value corresponding to the density, and formed on the image carrier. A transfer means for transferring the image onto the medium, a counting means for counting the number of times the image is transferred from the image carrier by the transfer means, and the axes are arranged so as to be substantially parallel to each other, and each is rotatable. Including first and second pressure members formed on the
Fixing means for fixing the image on the medium by passing the medium on which the image is transferred by the transfer means between the pressure members, and at least one of the first and second pressure members. A driving means for rotating the first and second pressing members, and the driving means is disposed in contact with the respective surfaces of the first and second pressing members. While the driving means rotates the first and second pressing members, the first and second pressing members are rotated. Cleaning means for cleaning the surfaces of the first and second pressure members, a predetermined number based on the number of times the image counted by the counting means has been transferred, and the density of the original document detected by the density detecting means. At a rate of 5%, the cleaning means changes the condition for urging the driving means so that the conditions for cleaning the surfaces of the first and second pressing members are changed. An image forming apparatus comprising: the ring condition changing means. 2. A document reading means for transmitting information of a document as light / dark information of light, an image carrier on which an image corresponding to the light / dark information transmitted by the document reading means is formed, and the document reading means. Photoelectric conversion means for photoelectrically converting the transmitted light / dark information according to brightness to provide a numerical value corresponding to the light / dark information, and a transfer means for transferring the image formed on the image carrier to a transfer material. Fixing means for fixing the image transferred to the transfer material by the transfer means to the transfer material, and cleaning means for cleaning an area of the fixing means in contact with the image or the transfer material, Driving means for rotating an area of the fixing means, which comes into contact with the image or the transfer material, at a predetermined speed, and a predetermined driving means for driving the area according to the numerical value provided from the photoelectric conversion means. And an urging unit that urges the image forming apparatus. 3. The urging means, when the numerical value provided from the photoelectric conversion means is smaller than a predetermined value, a predetermined ratio predetermined according to the magnitude of the numerical value. 3. The image forming apparatus according to claim 2, wherein the time for energizing the drive means is increased by. 4. An original reading means for transmitting information of an original as light / dark information of light, an instruction means for instructing start of operation of the original reading means, and the light / dark information transmitted by the original reading means. An image carrier on which an image is formed; photoelectric conversion means for photoelectrically converting the light-dark information transmitted by the document reading means according to the brightness to provide a numerical value corresponding to the light-dark information; Transfer means for transferring the image formed on the transfer material to the transfer material; fixing means for fixing the image transferred to the transfer material by the transfer means to the transfer material; and transfer means for transferring the image to the transfer material. Counting means for counting the number of times the transfer material is transferred, cleaning means for cleaning the image of the fixing means or a region in contact with the transfer material, and the image or the image of the fixing means. Drive means for rotating an area in contact with the transferred material at a predetermined speed, and biasing means for biasing the drive means at a predetermined ratio according to the numerical value provided from the photoelectric conversion means. An image forming apparatus having. 5. The urging means, in advance, is provided with the numerical value provided from the photoelectric conversion means when the number of times the image counted by the counting means is transferred to the transfer material reaches a predetermined number. If the numerical value is smaller than the predetermined value, the driving means is energized at a predetermined ratio according to the magnitude of the numerical value. Further, when the operation of the document reading means is finished, the time for urging the driving means again at a predetermined ratio defined according to the magnitude of the numerical value is increased. The image forming apparatus according to claim 4, wherein