JPH0436775A - Image forming device - Google Patents

Abstract

PURPOSE:To accurately detect the density of a pattern by arranging a density detecting sensor more backward than a transfer position for an intermediate transfer medium and controlling a reference density pattern for adjusting image density (AIDC pattern) so that it is not cleaned. CONSTITUTION:An AIDC sensor 73 for detecting the reference pattern for adjusting image density is constituted of a light emitting diode and a photodetector and arranged more backward than the transfer position for a transfer belt 11 on the circumferential surface of a photosensitive drum 3 and the toner of the AIDC pattern is prevented from adhereing to the belt 11 to the utmost. The part where the AIDC pattern passes inside of the surface of the belt 11 is controlled so that a belt cleaner 19 may be in a non-actuated state. Then, the image density is adjusted in accordance with the variation of humidity and the utilization condition of the photosensitive drum 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus having an intermediate transfer medium, such as a color copying machine.

[Conventional technology]

Conventionally, in general color copying machines, a photoreceptor is used to separate an image of a document into three primary colors and form a toner image for each color, and a photoreceptor is used to transfer and hold the toner image on the photoreceptor. A transfer belt is provided for overlapping toner images of each color.

Then, an AIDC pattern (a reference pattern for adjusting image density) is formed on the photoreceptor at a certain timing, and this is detected (read) by a photoelectric AIDC sensor, and the image density is adjusted based on this detection signal. It is being done.

In conventional copying machines, the above-mentioned AIDC sensor is arranged to detect the AIDC pattern on the photoconductor in front of the transfer position from the photoconductor to the transfer belt (Japanese Patent Laid-Open No. 60-23868). ).

[Problem to be solved by the invention]

However, in front of the transfer position, a charger, an eraser, a developer for each color, etc. are arranged along the surface of the photoreceptor, so in the conventional copying machine mentioned above, the AIDC sensor is arranged. There was very little space to do so, and layout design, assembly, and maintenance were not easy.

In addition, the area around the developing device is easily contaminated by toner, so
In the above-mentioned conventional copying machine, there was a problem in that the AIDC sensor was contaminated with toner and its sensitivity was reduced, making it difficult to accurately detect density.

On the other hand, it is conceivable to place the AIDC sensor behind the transfer position, but in that case, the AIDC pattern formed on the photoconductor comes into contact with the transfer belt, so that the toner of the AIDC pattern Part of the image is transferred to the transfer belt and the AI detected
There is a problem in that the toner image of the DC pattern becomes thinner, making it difficult to accurately detect the density.

In view of the above-mentioned problems, an object of the present invention is to arrange an AIDC sensor at a position after the transfer position to facilitate assembly and maintenance, and to accurately detect the density of an AIDC pattern.

[Means to solve the problem]

In order to solve the above-mentioned problems, an image forming device according to the present invention has the following features:
A density detection sensor is arranged to detect a reference density pattern on the photoreceptor at a position after the transfer position from the photoreceptor to the intermediate transfer medium, and the density detection sensor is arranged to detect the reference density pattern on the surface of the intermediate transfer medium. The cleaning device is controlled to be inactive for the portion through which the density pattern passes.

[For production]

A reference density pattern is created on the surface of the photoreceptor, and the created reference density pattern is detected by a density detection sensor placed at a position after the transfer position from the photoreceptor to the intermediate transfer medium.

Base 1! When the density pattern passes in contact with the surface of the intermediate transfer medium, the surface of the intermediate transfer medium is free from unnecessary electrical charges due to the inactivation of the cleaning device for electrostatically cleaning the intermediate transfer medium. This minimizes the adhesion of toner of the reference density pattern to the intermediate transfer medium.

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

FIG. 1 is a sectional front view showing the general structure of a copying machine 1 according to the present invention.

A photoreceptor drum 3 is arranged to be rotatable clockwise (in the direction of arrow M1) at the upper left of the center of the copying machine 1.A charger 4, an editing eraser 5, and a developer 6 are arranged around the photoreceptor drum 3. ~9. Transfer belt 1 as intermediate transfer medium
1. A cleaning device W22 and a maintenance device 23 are provided.

The surface of the photoreceptor drum 3 is uniformly charged by the charger 4, but the charged portion remaining when the exposure (scanning light) from the optical system 27 is cut off is selectively erased by the editing eraser 5. By doing so, AI
A latent image APE of the DC pattern AP is formed.

FIG. 2 is a diagram showing a state in which a latent image APR of the AIDC pattern AP is formed by the editing eraser 5.

The editing eraser 5 includes a large number of LEDs 5a in a holder arranged along the axial direction of the photoreceptor drum 3.

5a... are arranged in a row, and the latent image or charge on the photosensitive drum 3 can be partially erased by controlling the lighting of each LED 5a, 5a... ing.

Latent image A of AIDC pattern AP by editing eraser 5
To form PR, L corresponding to the latent image APEO width L1 is required.
The LED 5a is controlled to be turned off at the timing corresponding to the length L2, and the other LEDs 5a are turned on at the timing. The latent image APR is developed by the developing devices 6 to 9 and A
IDC pattern AP is created 0 Created AIDC
The density of pattern AP is detected by AIDC sensor 73.

The timing at which the latent image APR of the AIDC pattern AP is formed and the method of blocking the scanning light will be described later.

Each developing device 6, 7, 8.9 has yellow (Y) color.
, magenta (M), cyan (C), black (BK)
Toner density sensors (ATDC sensors: specifically, a magnetic detection type ATDC sensor is used here) 71y, 71m, 71c, and 71k are provided to control the density of the toners of each color.

Further, above the developing device 6, a humidity sensor 70 for detecting the humidity inside the copying machine 1 is provided.

The transfer belt 11 is used to temporarily hold the toner image developed on the photoreceptor drum 3 by the developing devices 6 to 9 to transfer (secondary transfer) onto the paper P.
2 to 16 are extended, and are supported so as to be rotatable in the counterclockwise direction (in the direction of arrow M4) while always being in contact with the photoreceptor drum 3.

A transfer charger 17 for primary transfer of the toner image from the photosensitive drum 3 onto the transfer belt 11 is arranged inside the transfer belt 11, and a transfer charger 17 for secondary transfer is arranged outside the transfer belt 11. 20, Transfer paper P with bell)
A belt cleaner 19 is provided having a separation charge +21 separating from the transfer belt 11 and a fur brush 190 for cleaning the outer surface of the transfer belt 11. This heald cleaner 19 corresponds to the cleaning device of the present invention. The fur brush 190 can be brought into pressure contact with the transfer heald 11 or retracted by turning a solenoid 195 on and off.

Belt mark sensors 72.7 are provided between the rollers 15 and 16 and between the rollers 12 and 13, respectively, for detecting the rotational angular position of the transfer heald 11.
2s are fixedly arranged.

FIG. 3 is a sectional front view of the belt cleaner 19.

The belt cleaner 19 cleans the transfer belt 11 using a cylindrical fur brush 190 disposed to face the roller 15 that supports the transfer belt 11.
a collection roller 191 that collects the toner scraped off from the
It is composed of a blade 192 that removes toner attached to the surface of the collection roller 191, an exterior support 193 that supports these members, etc., and rotates about a support shaft 194 to connect the fur brush 190 and the transfer belt 11. The operating position where the fur brush 190 and the transfer belt 1 are in contact with each other, and the fur brush 190 and the transfer belt 1
1 and a retracted position separated by a predetermined distance.

FIG. 3 shows the state in which the belt cleaner 19 is in the operating position, and when it moves to the retracted position, it is in the state shown by the dashed line in the figure.

The mechanism for moving the belt cleaner 19 is a rotating shaft 196.
ae-attached disk-shaped eccentric cam 196, rotating shaft 1
96a, a solenoid 195 that rotates the ankle lever 198, a spring 199 that always pushes the belt cleaner 19 toward the transfer belt 11, and a rotation shaft 1.
It is comprised of a mechanical clutch (not shown), etc., which urges 96a to always rotate in the direction of arrow M9.

The ankle lever 19 is provided with a stopping claw and a stopping head (not shown) at its tip.
The rotation of the rotating shaft 196a causes the rotating shaft 196a to rotate such that projections (not shown) provided on the rotating shaft 196a alternately abut against the stopper claws or the stopper head, and thereby the rotating shaft 196a
are positioned every 180 degrees.

The solenoid 195 is turned on and off by a drive section 195a controlled by a drive control signal S9 output from the CPU 401, which will be described later.

When the solenoid 195 is off, the belt cleaner 19
is in the operating position. At this time, the eccentric cam 196 is in the state shown in the figure, and the roller 197 rotatably fixed to the upper part of the exterior support 193 contacts the eccentric cam 196, so that the fur brush 190 is appropriately pressed against the transfer belt 11. The heald cleaner 19 is positioned so as to.

A drive control signal S9 is applied to the drive unit 195a, the solenoid 195 is turned on, and the rod 195b is connected to the spring 1.
When the ankle lever 198 moves downward against the biasing force of the lever 98a, the ankle lever 198 rotates around the support shaft 198b, and the state in which the rotation of the rotating shaft 196a is inhibited by a restraining pawl or a restraining head (not shown) changes. As a result, the rotating shaft 196a rotates half a rotation, the eccentric cam 196 pushes the roller 197 against the urging force of the spring 199, and the belt cleaner 19 moves to the retracted position.

When removing toner remaining on the surface of the transfer belt 11, that is, cleaning the transfer belt 11, the belt cleaner 19 is moved to the operating position and the fur brush 190 is moved to the operating position.
is brought into contact with the transfer belt 11, and the high voltage power source 4 for the cleaner is connected to the transfer belt 11.
05, the fur brush 190 and the collection roller 191 are rotated while the charging voltage HV (cleaner bias HV) is applied to the fur brush 190 and the collection roller 191. As a result, the toner on the transfer belt 11 is scraped off by the fur brush 190 and electrostatically attracted to the charged fur brush 190.

Since the cleaner bias HV is set so that the amount of charge on the collection roller 191 is greater than the amount of charge on the fur brush 190, the toner adsorbed on the fur brush 190 is transferred to the collection roller 191, which has a large adsorption force. The toner adsorbed on the collection roller 191 is scraped off from the collection roller 191 by a blade 192 and stored in a waste toner bottle (not shown).

In the following explanation, moving the belt cleaner 19 to the operating position by turning off the solenoid 195 is referred to as "pressing the fur brush 190", and applying the cleaner bias HV to the fur brush 190 and the collection roller 191 is referred to as "pressing the fur brush 190". "Cleaner bias HV on"
That's what it means.

Returning to FIG. 1 again, at the top of the copying machine 1 there is an optical system 27.
is located. The optical system 27 includes a scanner 30 which is movable back and forth in the direction of arrow M5 (forward movement direction) and the direction of arrow M6 (return movement direction) below the document platen glass 28, and a scanner 30 whose position is adjusted according to the copying magnification. A lens 35, a mirror device 36 for performing color separation exposure, a fixed mirror 37 that guides the scanning light reflected by the mirror attached to the mirror device 36 to an exposure point on the photoreceptor drum 3, and a mirror of the mirror device 36. The scanner 3 consists of a color image sensor 38 that receives transmitted scanning light.
During the forward movement of 0, the document tray is scanned and the photosensitive drum 3 is exposed.

The scanner 30 includes a first slider 31 having an exposure lamp 33 and a mirror 34, and a second slider 32 having mirrors 35a and 35b. End of the return movement of the scanner 30,
That is, the return of the scanner 30 to the reference position (home position) is detected by the scanner home switch 74, which is a photo sensor.

The mirror device 36 includes a half mirror 36ND (the ratio of transmission and reflection is 6:4) and three filter mirrors 36YB, 36MG, and 36CR that are parallel to the axis 36a and make an angle of 90 degrees to each other. By rotating the mirrors, one of these mirrors can be selectively switched and positioned. Filter mirrors 36YB, 36MG, and 36CR are each blue (B
), green (G), and red (R) color separation filters are attached to the mirror surface to integrate the mirror and filter, and each corresponds to Y, M, and C toner colors. used.

During exposure scanning for image formation, the reflective surface of the selected mirror is positioned so as to be tilted approximately 10 degrees clockwise with respect to the vertical plane, so that the scanning light is directed toward the photoreceptor drum 3.
is guided to the exposure point.

In addition, in the preliminary scan to read the image of the document sheet prior to the exposure scan, the half mirror 36
ND is selected and vertically positioned perpendicular to the direction of incidence of the scanning light in order to improve the MTF (imaging power) of the image sensor 38. Reference numeral 77 is a rotational position detection sensor for determining the indication position of the mirror device 36. Note that FIG. 1 shows a state in which the filter mirror 36CR has been selected and positioned at the image forming position.

In the following description, the half mirror 36ND, filter mirrors 36YB, 36MG, and 36CR may be referred to as an ND filter, a B filter, a G filter, and an R filter, respectively, based on their color separation characteristics. Further, the entirety of these may be referred to as a mirror 36b.

On the other hand, an upper paper cassette 42 and a lower paper cassette 43 containing paper P are installed at the bottom of the copying machine I, and a door is provided on the left side of the copying machine I11 for manually feeding the paper P. A manual paper feed port 41 is provided which is opened by opening 41a, and these paper cassette 42, paper cassette 43, and manual paper feed port 41 are used selectively when feeding paper.

The paper cassettes 42, 43 each include pickup rollers 44, 45 that feed out the paper P one by one, and paper size sensors 81, 8 that detect the size of the paper P.
2. Paper empty sensors 83 and 84 are installed to detect the lack of paper P, and the manual paper feed slot 4
1 is provided with a manual feed sensor 87 for detecting insertion of paper P.

The paper P fed out from the paper cassette 42 is conveyed to the timing roller 46 by the paper feed roller 47, and the paper P fed out from the paper cassette 43 is conveyed to the timing roller 46 by the paper feed rollers 4B and 47, and is put on standby there. do.

Further, the paper P inserted into the manual paper feed port 41 is conveyed to the timing roller 46 by the manual paper feed roller 49 .

A paper detection sensor 85 is provided near the paper feed roller 47 to detect the presence or absence of paper P in the paper feed path R1 between the paper feed roller 47 and the timing roller 46. A timing sensor 86 for detecting the position of the leading edge of the paper P is provided.

The waiting paper P is conveyed in synchronization with the transfer belt 11 by the rotation of the timing roller 46, and the toner image is secondarily transferred from the transfer belt 11 to the paper P at the transfer position. Thereafter, the paper P is sent to the fixing unit 51 by a conveyor belt 50 having a linear distance corresponding to an A4 size paper.

The fixing unit 51 includes an upper roller 52 having heater lamps 54 and 55 and a lower roller 53 having a heater lamp 56, and fuses the toner image to the paper P. Temperature sensors 91 and 92 made of thermistors are provided near each roller 52 and 53, respectively.

The paper P on which a desired copy image has been formed by fixing the toner image is transferred to the ejection roller 5 with an ejection sensor 88 disposed nearby.
7 to the sorter 2 and discharged to the storage tray 61 of the sorter 2 or the sorting pen (shelf) 62.

Further, the copying machine 1 of this embodiment is equipped with a return bag 260 for re-fixing, which is used during OHP mode copying. The return device 60 includes a transport mechanism 58 having a return path R2.
, a switching claw 59, and a return paper detection sensor 89 are provided.

In FIG. 1, 24 is a main motor that mainly drives various parts related to feeding and transporting paper P, and 25
26 is a PC motor that drives the photosensitive drum 3, transfer belt 11, etc., and 26 is a cooling fan.

In the copy Ill configured as above, the above Y, M
, a monochrome copy image of each single toner color of C and BK,
R (Y and M), G (Y and C), obtained by superimposing toner images of two of the three primary colors Y, M, and C.
The color (
It is possible to create full-color (full color) copied images. Such copy mode switching is performed using various switches or keys arranged on an operation panel (not shown).

In forming a single toner color and a composite monochrome copy image, a half mirror 36ND is used to expose and scan the original, and the latent image formed on the photoreceptor drum 3 is developed according to the specified color. The toner image is developed using any one of the containers 6 to 9 and transferred onto the transfer belt 11. Furthermore, in the case of a composite monochrome copy image, the same original document is exposed and scanned again by the half mirror 36ND, and the toner image developed using the developing devices 6 to 9 different from the previous one is transferred to the transfer belt 11. The toner images of the two colors are superimposed on the transfer belt 11.

In addition, in forming a color copy image, the copying machine 1:
To improve the reproducibility of black areas, four toner colors, including Y, MC, and BK, are sequentially used. That is, a total of four exposure scans are performed on the same document, and for each scan, B,
The G, R, and ND mirrors and the developing devices 6 to 9 are selectively switched to form and develop a latent image in which the original is color-separated, and the toner images are sequentially transferred to the transfer belt 11. The toner images of each color are superimposed on top.

When overlapping toner images (hereinafter referred to as "multiple transfer"), it is necessary to transfer each toner image to the same position on the transfer belt 11. Therefore, in the copying machine 1 of this embodiment, the above-mentioned belt mark sensor is used. The scanner 30 uses the generation timing of the belt mark signal from 72 or 72s as a reference.
The start timing of movement of the photosensitive drum 3, that is, the start timing of forming a latent image on the photosensitive drum 3 is controlled.

Next, the positioning operation of each mirror 36b will be explained.

As the mirror device 36 rotates, each mirror 36b is sequentially positioned at an image forming position where the scanning light is reflected and guided to an exposure point on the photoreceptor drum 3. Also, half mirror 36
The ND is also positioned in a vertical position that transmits the scanning light and guides it to the image sensor 38. Each mirror 36b does not guide the scanning light to the exposure point of the photosensitive drum 3 at a position other than the image forming position.

FIG. 4 is a diagram showing the AIDC sensor 73.

The AIDC sensor 73 includes a light emitting diode 73a and a light receiving element 73b.

The light emitting diode 73a is arranged so that the light it emits is directed toward the photoreceptor drum 3, and the light receiving element 73b is arranged so that it does not receive regular reflection from the photoreceptor drum 3.

That is, when toner adheres to the surface of the photoreceptor drum 3, the light from the light emitting diode 73a is diffusely reflected by the toner, and the light receiving element 73b receives the light and outputs the detection signal Sl. If there is no light, no light enters the light receiving element 73b.

FIG. 5 is a diagram showing an example of the relationship between the amount of toner adhered to the photosensitive drum 3 and the detection signal S1.

The amount of light received by the light receiving element 73b increases as the amount of toner attached to the photoreceptor drum 3 increases, that is, as the density of the toner image increases. In addition, the detection signal S1 outputted by the light receiving element 73b
The magnitude increases as the amount of received light increases.

Therefore, since the detection signal S1 increases according to the density of the toner image, the magnitude of the detection signal S1 is compared with a reference value,
The result is fed back to the grind voltage of the charger 4 and the voltage applied to the exposure lamp 33 to adjust the image density.

It should be noted that the variation in the amount of toner adhering to the photoreceptor drum 3 due to environmental changes or changes over time is considered to be almost the same for each color of Y, M, and CBK, so the AIDC pattern for all these four colors is considered to be approximately the same. There is no need to create an AP to detect the density, AIDC pattern AP for only one color.
, and calculate the density of other colors based on the detection signal S1.

In this example, an ATDC pattern AP is created only for Y, and for each of the other colors M, C, and BK, the ATDC pattern AP is created for Y only.
The correction is made based on the detection signal SI for.

Now, since the A, IDC sensor 73 is arranged on the circumferential surface of the photosensitive drum 3 at a position behind the transfer position to the transfer belt 11, its assembly and maintenance are easy. However, since the density of the AIDC pattern AP is detected after it comes into contact with the transfer belt 11, in order to improve the detection accuracy,
It is necessary to prevent the toner of the AIDC pattern AP from adhering to the transfer belt 11 as much as possible.

6 and 7 show the AI formed on the photoreceptor drum 3.
7 is a diagram showing changes in the output of the AIDC sensor 73 before and after the DC pattern AP contacts the transfer belt 11. FIG.

In these figures, white circles are before contact, and black circles are after contact. In addition, all cases show the case where the fur brush 17 is turned off during transfer charging, and FIG. 6 shows the state where the fur brush 190 is in pressure contact with the transfer belt 11 and the cleaner bias HV is turned on (operating state), and FIG. This is a state in which the brush 190 is retracted from the transfer belt 11 and the cleaner bias HV is turned off (non-operating state).

As can be seen by comparing FIG. 6 and FIG. 7, by turning off the cleaner bias HV, the transfer belt 1
1 is not unnecessarily charged, and as a result, the amount of toner adhering from the photosensitive drum 3 to the transfer belt 11 is significantly reduced, and changes in the output of the AIDC sensor 73 are reduced.

Therefore, in this embodiment, the belt cleaner 19 is controlled to be inactive for the portion of the surface of the transfer belt 11 through which the AIDC pattern AP passes.

Next, the timing of creating the AIDC pattern AP will be explained.

The amount of toner adhering to the photoreceptor drum 3 changes depending on the humidity of the toner, that is, the humidity inside the developing units 6 to 9, even when there is no change in the control state of each part.

FIG. 10 is a diagram showing the amount of toner adhering to the photosensitive drum 3 with respect to changes in humidity.

In FIG. 10, it is assumed that the potential difference between the developing bias potential and the surface potential of the photosensitive drum 3 and the T/C ratio (mixing ratio of toner and carrier) are constant.

According to FIG. 10, as the humidity increases, the amount of toner adhering to the photosensitive drum 3 increases.

The reason for this is that the amount of charge on the toner is large when the humidity is low, and decreases when the humidity is high.

Therefore, even if the toner concentration in the developing units 6 to 9 is constant, the amount of toner adhering to the photoreceptor drum 3 changes depending on the humidity. It is necessary to stabilize the amount and adjust the image density.

However, changes in humidity not only cause changes in the amount of toner adhering, but also affect the characteristics of the photoreceptor drum 3 and cause problems in response. Therefore, it is not possible to correct the density using only the detected humidity value. is not enough.

Note that when the humidity reaches 60% RH or more, the density of the developer increases, so the output value of the magnetic detection type ATDC sensor that detects the toner concentration in the developing devices 6 to 9 increases significantly. . Therefore, it is necessary to stabilize the T/C ratio in the developing units 6 to 9 by increasing the control level based on the output value of the ATDC sensor.

FIG. 9 is a diagram showing how the humidity inside the copying machine 1 and the humidity inside the developing units 6 to 9 change over time.

According to FIG. 9, even if the humidity inside the copying machine 1 drops rapidly, the humidity inside the developing units 6 to 9 gradually decreases until the humidity reaches the same level as the humidity inside the copying machine 1. takes more time. In other words, the humidity responsiveness inside the developing units 6 to 9 is poor.

Therefore, if the humidity inside the copying machine 1 is simply detected (measured), a large error will occur between the humidity inside the developing units 6 to 9 (therefore, the humidity of the toner), and the detected value will be Even if used as is, the amount of toner adhering to the photoreceptor drum 3 cannot be accurately controlled. This is more noticeable when there is a sudden change in humidity.

FIG. 8 is a sectional view of the humidity sensor 70.

The humidity sensor 70 includes a case 70 having a ventilation hole 70b.
It is provided inside a. Therefore, when the humidity inside the copying machine 1 changes, the air enters the inside of the case 70a through the ventilation hole 70b, so that the change in humidity is transmitted to the humidity sensor 70 with a delay.

Then, the humidity inside the case 70a is determined by the developing unit 6.
~ Case 70 so as to approximate the internal humidity state of Case 9.
The volume of a, the size of the ventilation hole 70b, etc. are set.

As a result, the detected value of the humidity sensor 70 (detected humidity)
can be approximated to the humidity inside the developing units 6 to 9, and it is possible to eliminate the risk of contamination with toner as in the case where the humidity sensor 70 is provided inside the developing units 6 to 9, and toner adhesion can be avoided. The amount etc. can be controlled accurately.

Note that since the influence of changes in humidity is the same for each of the Y, M, and CBK developing units 6 to 9, each can be corrected based on the detected value by one humidity sensor 70.

The timing of creating the AIDC pattern AP is controlled using the humidity detected by the humidity sensor 70 having such a structure.

In other words, if the AIDC pattern AP is created every time the print key is pressed or a predetermined number of copies are made, as in the past, there is no change in image density. Even so, an AIDC pattern AP will be created, and toner will be wasted.

Therefore, in this embodiment, if the amount of change in the detected humidity value at each predetermined first interval is smaller than the reference amount of change, the AIDC pattern AP is not created;
If the amount of change is greater than the reference amount, an AIDC pattern AP is created and image density adjustment is performed.

Further, at every second interval that is larger than the first interval, the amount of change in the detected humidity value is checked, and when the amount of change is greater than the reference amount, an ATDC pattern AP is created and image density adjustment is performed. As a result, even if the humidity changes extremely slowly, image density adjustment is performed when the amount of change accumulates and reaches the reference value.

In this embodiment, the humidity sensor 70 detects humidity every time the print key is pressed.

Furthermore, since the characteristics of the photosensitive drum 3 deteriorate with use regardless of whether there is a change in humidity, the image density is adjusted by creating an A/Dc pattern AP depending on the usage situation.

In other words, when the drive time of the PC motor 25 that rotates the photosensitive drum 3 reaches a predetermined value, or when the copy count data stored in the non-volatile memory inside the CPU 401 reaches a predetermined value, etc. , related to the amount of change in humidity (image density adjustment is performed).

In this way, the amount of change in humidity is checked at each first and second interval, and the image density is adjusted according to the usage status of the photoreceptor drum 3, so an image with an appropriate density can be obtained and the image quality can be improved. Stabilization is achieved, and since unnecessary AIDC patterns AP are not created, wasteful consumption of toner is prevented, and since no time is required for this purpose, the time for first copying is shortened.

FIG. 11 is a block diagram of the control circuit 8400 of the copying machine 1.

The control circuit 400 controls the entire operation of the copying machine 1.
A controller 402 that controls the drive of various parts such as a scanner 30, an exposure lamp 33, a main lens 35, an electrostatic charger 4, and a PC motor 25, centered on a PU (central processing unit) 401, and an operation panel (not shown) are arranged. Various switches 403 and display unit 404, cleaner bias to belt cleaner 19) (high voltage power supply 405 that applies V, drive unit 195a that drives solenoid 195,
An image processing unit 100 for performing image processing using an image sensor 38 and the like is provided.

Although not shown, the above-mentioned humidity sensor 70,
AIDC sensor 73, scanner home spin chia 4,
Each sensor such as the rotational position detection sensor 77 is also connected to the CPU 401 via a suitable interface.

The controller 402 controls the editing eraser 5 to
It also performs control for creating a DC pattern AP. The regulator for the exposure lamp and the control circuit for the charger 4, which are part of the controller 402, each have several bit data lines controlled by the CPU 401, and the output voltage can be changed by changing data from the CPU 401. It is designed to be variable.

The drive unit 195a receives a drive control signal S from the CPU 401.
9, the solenoid 195 is turned on and off.

The high voltage power supply 405 is controlled by the control signal S8 from the CPU 401 to turn on or turn off the application of the cleaner bias HV to the fur brush 190 and the collection roller 191.

Note that the CPU 401 has a built-in memory that stores programs, various data such as humidity data 1 and humidity data 2, and a data table for obtaining correction data.

Next, referring to the flowchart, AIDC pattern A
The operation of the copy tla1 related to the creation of P and the control of the belt cleaner 19 will be explained.

FIG. 12 is a main flowchart schematically showing the operation of the CPU 401.

When the power is turned on and the program starts, first,
Initial settings are made for registers and peripheral interfaces (step #1), and an internal timer is set to specify the length of one routine of the CPU 401 (step #2).
.

In step #3, image forming processing related to the electrophotographic process is performed, and in step #4, scanning processing for scanning the original document is performed.

Next, belt mark detection processing (step #5) for determining the timing of multiple transfer, AIDC pattern AP
AIDC pattern processing to create (step #6
), humidity detection processing (step #7), fur brush processing when creating AIDC pattern AP (step #8)
Execute each.

Step #9 includes a paper feeding process that controls the paper feeding and conveyance of the paper P, a manual feed reception process that determines the timing of manual paper feeding using the manual paper feed port 41, a temperature control process that adjusts the temperature of the fixing unit 51, and a transfer process. From various processes such as belt cleaning processing to perform normal cleaning of the belt 11, lens processing to control the movement of the main lens 35 according to the copying magnification, and input processing to accept and receive signals from the operation keys on the operation panel. A series of copy sequence processing is executed.

After executing these processes, an internal timer is waited in step #10, and the process returns to step #2. As a result, the length of one routine is kept constant, and each process from step #2 to step #10 is repeated while the power is turned on.

FIGS. 13(a) to 13(d) are flowcharts of image forming processing.

In this routine, first, in step #20, the image forming state indicated by the count value of the state counter is checked, and the following processing is executed depending on each state.

Note that the state is "0" in the initial state immediately after the power is turned on and in the standby state after the copying operation is completed.

In state "0", the print key is first checked (step #21). When the print key is turned on (pressed down), the main motor 24 and the PC motor 25 are turned on, and the photosensitive drum 3, etc. The rotational drive of each part is started (step #22).

Next, step #23L state is set to "1" to set a motor start-up timer for waiting for the rotation of each motor 24, 25 to become stable (step #24).

In state "1", the motor start-up timer is updated by counting up (step #26),
Wait for the relevant timer to finish counting (step #
27), the state is set to "2" (step #28).

In state "2", the presence or absence of a pattern creation request, which is a flag set in the humidity detection process, is checked (step #31).

If the pattern creation request is not set, return as is.

If the pattern creation request is set, set the belt cleaning timer (step #32), turn on the cleaner bias HV (step #33), press the fur brush 190 (step #34), and change the state to [3 commands]. (Step #35).

In state "3", the belt cleaning timer is updated (step #36), and after waiting for the timer to end (step #37), the L state is set to "4" (step #38).

In state "4", check whether the copy mode specified by the operation panel is monochrome mode or full color mode (step #41), and perform the following processing according to each mode. do.

If the monochrome mode is designated, a mirror rotation request (ND request), which is a flag for requesting positioning of the half mirror 36ND, is set (step #42).

As a result, the filter mirror processing is started, and the half mirror 36ND is positioned at the image forming position.

Next, the charger 4 and the exposure lamp 33 are turned on (Step #43), and a scan request is set to start scanning by the scanner 30 (Step #43).
44), turn on any of the developing devices 6 to 9 selected by the operation panel (step #45), and set the state to "5".
” (Step #46).

In state 5j, the completion of scanning of the document is confirmed (step #61), and the charger 4 is turned on.
Then, the exposure lamp 33 is turned off (step #62), and the developing device in operation is turned off (step #63).

Then, check whether the next copy is requested or not (step #64), and if there is no next copy request, turn off the cleaner bias HV (step #65), and retract the fur brush 190 (step #66L).
Then, the PC motor 25 is turned off and the step #67L state is returned to "0" (step #68).

As a result, the copying machine 1 enters a standby state.

If there is a next copy request, the state is returned to "4" (step #69).

On the other hand, in step #4 of state [4] above, if full color mode is specified, the mirror rotation request for positioning the half mirror 36ND (
Step #47L turns on the exposure lamp 33 (Step #48), issues a preliminary scan request (Step #49), and sets the state to "6" (Step #50).

In state "6", the completion of the preliminary scan is confirmed (step #75), the exposure lamp 33 is turned off (step #76), and a mirror rotation request (B request) is made to position the filter mirror 36YB at the image forming position. )
Please set the stamp #77L belt mark sensor 7
2. Set mark detection permission to start scanning at the on-timing of 72 seconds (step #78), and set the state to "7" (step #79).

In state "7", the scanner 30 waits for the scanner 30 to start scanning based on the heald mark signal (step #81), turns off the fur brush output at the start of scanning (step #82), and turns on the Y toner developer 6. Step #83), set the state to "8".

In state "8", the completion of scanning is confirmed (step #91), the charger 4 and the exposure lamp 33 are turned off (step #92), and the Y toner developer 6 is turned off.
Step #93), then turn off the filter mirror 3.
The mirror rotation request (G request) for positioning the 6MG at the image forming position is sent as "#94L state" to "9".

In states "9" to "14", a series of processes for forming each of M, C, and BK toner images is executed, similar to the formation of the Y toner image described above. That is, turning on and off the developing devices 7 and 8.9 corresponding to each color, turning off the exposure lamp 33 and charger 4 when the scanner 30 finishes scanning, and turning off the filter mirror 36 corresponding to the next scan.
Positioning of the CR or half mirror 36ND is performed.

In addition, if there is no next copy request in step #124 of step)r14J, turn off the main motor 24 and PC motor 25, step #125), reset mark detection permission (step #126), and set the state to "0".
(Step #127).

FIG. 14 is a flowchart of scan processing.

First check the scan state (step #
200), the following processing is executed according to each state.

In state "0", the presence or absence of a scan request is checked (step #201), and if there is a scan request, the forward movement of the scanner 30 is started (step #202).
).

If there is no scan request, it is checked whether scan permission is available (step #204). The scan permission flag is set when it becomes possible to start scanning based on the belt mark signal.

If scanning is permitted, set the state to “1” (
Step #205).

In state "l", the scanner 30 starts forward movement (step #212) after waiting for the belt mark signal to be output (step #211). The toner images of each color are superimposed at the same position.

In state "2", it is checked whether the scanner 30 moving forward has reached the rear end of the document tray and scanning has been completed (step #215).

When the scan is completed, the scanner 30 immediately starts returning (step #216), and the state is set to "3".
(Step #217).

In state "3", the scanner home switch 7
After confirming that the scanner 30 has returned to the home position and the return has been completed, the scan request is reset (Step #219), and the state is returned to the initial value "0".

FIG. 15 is a flowchart of belt mark detection processing.

First check the mark state (step #3
00), the following processing is executed according to each state.

In state "0", if the print key on the operation panel is turned on and full color mode is specified (YES in both steps #301 and 302), the state is set to "1" (step #303).

In state "1", wait for mark detection permission to be set in image creation processing (step #311).
, the state is set to "2" (step #312).

In state "2", the belt mark signal is checked (step #321).

When the belt mark signal turns on (occurs), the exposure lamp 3
Set the exposure lamp on timer consisting of a counter to determine the lighting timing of Step #322)
, the state is set to "3" (step #323).

That is, the transfer belt 11 is rotationally driven at a constant speed (system speed), and the generation cycle of the belt mark signal is constant. Therefore, in the copying process 111, in order to stabilize the light intensity of the exposure lamp 33 in a scan that is started based on the belt mark signal, the exposure is timed from the generation timing of the belt mark signal immediately before the start of the scan. In order to turn on the lamp 33, an exposure lamp on timer is provided. As a result, the exposure lamp 33
It is possible to prevent unnecessary lighting and scanning when the amount of light is unstable.

In state "3", first, the exposure lamp on timer is updated (step #331), and a check is made to see if the timer has finished counting (step #332).

At this time, if the exposure lamp on timer is counting,
Check the mark detection flag again Step #337
), when the mark detection flag is reset in the image forming process, the state is returned to "0" to put the copying machine 1 in a standby state.

When the exposure lamp on timer finishes counting, the exposure lamp 33 and the charger 4 are turned on in preparation for scanning (step #333), and the scan permission checked in the above scan process is set (step #33).
4), return the state to "2" (step #335)
.

FIG. 16 is a flowchart of AIDC pattern processing.

First check the AIDC state (step #
400), the following processing is executed according to each state.

In state rQJ, wait for a pattern creation request to be set by image creation processing (step #401).
.

If yes, set the fur brush-off request step #402), set the pattern creation in progress step #403), turn on the Y toner developer 6 for pattern creation step #404), turn on the charger 4 and Turn on the editing eraser 5 (all LEDs 5a) (Step #405), turn on the rising timer (Step #406), and set the state to "1" (Step #40)
7).

At this time, the grid voltage VG of the charger 4 is A
This is a fixed value determined for creating an IDC pattern AP. The rise timer is set with a time that takes into account the width of the charger 4 and the distance to the editing eraser 5, and an AIDC pattern AP is created at a position on the photosensitive drum 3 corresponding to this time.

In state 1j, update the rise timer (Step #411), wait for the end of the rise timer (Step #412), and output eraser data to the editing eraser 5 to create the AIDC pattern AP (Step #413). , starts forming the latent image APE.

Next, step #414 sets a pattern creation timer to define the length L2 of the AIDC pattern AP.
), and the state is set to "2" (step #415).

In state "2", update the pattern creation timer, step #421L, wait for the corresponding timer to end (step #422), and update the m-set eraser 5 (all LEDs).
5a) is turned on in step #423), the electrification charger 4 is turned off in step #424), and an erase-off delay timer for turning off the W collection eraser 5 is set (step #425).

Next, the developer off-delay timer is set (step #426L), and the pattern passage wait timer is set (step #427), and the state is set to "3" (step #428).

Here, the developer off-delay timer includes the latent image APE.
In order to develop the entire area, a time corresponding to the distance between the editing eraser 5 and the Y developing device 6 is set. The time required for the image to pass through the transfer position is set.

In state "3", the erase-off delay timer is updated (step #431), the end of the timer is waited for (step #432), and the editing eraser 5 is turned off (step #433).

Also, update the developer off-delay timer (step #434) and wait for the timer to end (step #434).
435), turn off the Y developer 6 (stencil #436)
).

Then, update the pattern passage wait timer (step #437), wait for the timer to end (step #43B), reset the pattern creation process, press the fur brush 190 on the image forming side, and turn the cleaner bias HV on. The pattern read counter is cleared (step #440), and the state is set to "4" (step #441).

The pattern read counter counts the number of times the AIDC pattern AP is read.
Count 0 times.

In state "4", the detection signal S1 of the AIDC sensor 73 is read (step #451), the pattern read counter is updated (step #452), and the process waits until the count value reaches 10 (step #45).
3), average the 10 detection data (step #4
54).

The reason why the detection is performed 10 times is to take into account the variation in the detection signal SL, and by averaging this, the reliability is improved.

Next, the difference between the detected data and the reference value is calculated (step #455).

This allows the user to recognize how much the current image density deviates from the standard.

Then, correction data for the charging mode 4 and the exposure lamp 33 in each mode is determined (step #456).
.

This correction data is read from the data table based on the value calculated in step #455. The data table includes the grid voltage VG of the charger 4 and the exposure lamp 33 in each mode (full color yellow, full color magenta, full color cyan, monocolor).
Correction data for each voltage is stored.

As a result, correction data for all other colors can be determined simply by creating the AIDC pattern AP for one color.

Then, reset the pattern creation request in step #4.
Step #45 of returning the 57L state to "0" B)
, wait for the next boot to take.

FIG. 17 is a flowchart of the humidity detection process.

First check the humidity state (step #50)
0), the following processing is executed according to each state.

In state "0", it is first checked whether the print key on the operation panel has been pressed (step #
501).

Here, it is checked whether this is the first copy after the power of the copying machine 1 is turned on. first 1
This is because the correction data for the output voltages of the charger 4 and the exposure lamp 33 have not been determined in the first sheet, so the AIDC pattern AP must be created to determine the correction data.

If YES in step #501, set a pattern creation request (step #502), and detect the humidity at that time from the output of the humidity sensor 70 (step #503).
, the detected humidity (detected humidity) is stored in the memory as temperature data 1 and humidity data 2. Steps #504 and 5
05), set the state to “1” (step #506)
.

Here, humidity data 1 is used to compare the amount of change in humidity each time the print key is pressed, and humidity data 2 is used to compare the amount of change in humidity each time the print key is pressed, and humidity data 2 is used to compare the amount of change in humidity every time the print key is pressed.
This is to save the data until the DC pattern AP is created.

In other words, every time the print key is pressed, the humidity sensor 7
0 is detected, and when the difference (amount of change in humidity) from the humidity when the print key was pressed last time exceeds a predetermined reference amount of change, an AIDC pattern AP is created.

Also, each time the print key is pressed, the previous AIDC
It checks the difference in humidity from when the pattern AP was created, and can also respond to long-term changes in humidity.

In state "1", it is checked whether the PC motor 25 is on (step #511), thereby determining whether the image forming operation started in state "0" is continuing.

If the PC motor 25 is off, set the state to "2"
(Step #516).

When the PC motor 25 is on, the photoconductor rotation timer is updated (step #512), and when the timer exceeds the specified amount (step #513), the AIDC
Set the pattern unconditional creation to create pattern AP unconditionally (step #514), and set the state to "3".
” (Step #515).

The photoconductor rotation timer is a timer for measuring the total time that the photoconductor drum 3 has rotated, and if the value exceeds a preset value, the print key is activated regardless of the amount of change in humidity. AIDC pattern AP is created unconditionally every time is pressed. This prevents deterioration in image quality due to a decrease in sensitivity of the photoreceptor drum 3 or the like.

In state "2", a check is made to see if the print key has been pressed (step #521).

When the print key is pressed, it is checked whether pattern unconditional creation is set (step #52).
2).

If yes, set pattern creation request and AI
Start up the DC pattern processing side (step #523L)
The state is set to "3" (step #524).

If no in step #522, the humidity sensor 70
Step #525: Detect the humidity at that time from the output of
), the detected humidity is compared with humidity data 1 (step #526).

If the difference is small (within the reference amount of change), then comparison with humidity data 2 is performed (step #527).

If the difference is also small, the humidity detected in step #525 is stored in humidity data 1 without creating the AIDC pattern AP (step #530), and the state is changed to "1".
” (Step #531).

If the difference is large in either step #526 or step #527 (if it exceeds the standard change amount), a pattern creation request is set (step #528), and the detected humidity is stored in temperature data 2 (step #529).

In state "3", if the rotation time of the photosensitive drum 3 exceeds a specified amount, after creating the AIDC pattern AP,
This is a state in which the image forming operation waits for completion.

In state "3", wait until the PC motor 25 is turned off (step #541), and change the state to "2".
Step #542) and waits for the print key to be pressed.

FIG. 18 is a flowchart of fur brush processing.

The fur brush process is for controlling the operation of the belt cleaner 19 when creating the AIDC pattern AP, and a pattern creation request is set in the humidity detection process, and a fur brush off request is set in the AIDC pattern process. Executed when

First check the brush state (step #6
00), the following processing is executed according to each state.

In state "0", first, the presence or absence of a fur brush-off request set in AIDC pattern processing is checked (step #601).

If the fur brush-off request is set, reset the fur brush-off request (step #602).
, turn on the cleaner bias HV step #603)
, press the fur brush 190 into step (#604).
, set the fur brush off timer Step #6
05), set the state to “IJ” (step #606)
.

Here, a time is set in the fur brush-off timer so that the position on the transfer belt 11 when the belt cleaner 19 is not activated matches the position of the A, IDC pattern AP on the photosensitive drum 3. Ru.

In state "1", update the fur brush-off timer (step #611), wait for the timer to end (step #612), and then set the cleaner bias H.
Turn off the V stepper #613), fur brush 1
90 is saved (step #614), the fur brush ion timer is set (step #615), and the state is set to "2" (step #61.6).

Here, the fur brush ion timer is used to specify the time from when the belt cleaner 19 is inactive to when it is activated, and is set to a time longer than the time corresponding to the length L2 of the AIDC pattern AP. be done.

In state "2", update the fur brush ion timer (step #621), wait for the timer to end (step #622), and then update the cleaner bias HV.
Turn on the fur brush 190 (step #623), press the fur brush 190 (step #624), and return the state to "0" (step #625).

FIG. 19 is a timing diagram showing the operation of each part related to the creation of the AIDC pattern AP.

The timing diagram in FIG. 19 is based on the above-mentioned flowchart, and T1 shown in FIG. 19 is the rise timer of step #406, T2 is the pattern creation timer of step #414, and T3 is the developer off-delay timer of step #426. T4 corresponds to the erase-off delay timer in step #425, T5 corresponds to the pattern passage wait timer in step #427, T6 corresponds to the fur brush-off timer in step #605, and T7 corresponds to the fur brush-on timer in step #615.

As can be seen from FIG. 19, when the print key is pressed with predetermined conditions met, a latent image APR of the AIDC pattern AP is formed for a time T2 after a time T1.
After that, the latent image APR is developed by the Y developing device 6 within a time T3, and after a time T5 has elapsed after the latent image APR is formed, detection (reading) is performed ten times by the AIDC sensor 73.

On the other hand, the belt cleaner 19 is in an operating state in which the fur brush 190 is pressed and the cleaner bias HV is turned on for a time T6 after the print key is pressed, and is then in an inactive state for a time T7. After that, it becomes operational again.

During time T7, unnecessary charging does not occur on the transfer belt 11, so that portion is transferred to the AIDC on the photoreceptor drum 3.
The toner of the AIDC pattern AP is prevented from adhering to the transfer belt 11 by contacting the pattern AP, and detection by the AIDC sensor 73 is performed accurately.

In the above embodiment, the AIDC pattern AP was created using the Y developer 6, but other specific color developers 7 to 9 may be used.

In the embodiment described above, the fur brush 190 was retracted and the cleaner bias HV was turned off in order to put the belt cleaner 19 into a non-operating state, but it is also possible to perform only one of these. good.

In the above embodiment, the exposure lamp 33 is turned off when forming the latent image APE for the AIDC pattern AP, but even if the exposure lamp 33 is turned on,
The light from the exposure lamp 33 may be blocked from reaching the photoreceptor drum 3 by rotating the mirror device 36 and removing it from the image forming position. Humidity sensor 7
Although the amount of change in humidity detected by 0 is checked at each first interval and second interval, the reference amount of change used for comparison at that time may be different values or the same value.

In addition, the content and order of the flowchart, the structure, shape, dimensions, materials, timing, etc. of each part of the editing eraser 5, belt cleaner 19, AIDC sensor 73, control unit 400, and copying machine 1 may be changed in various ways other than those described above. be able to.

〔Effect of the invention〕

According to the present invention, the density detection sensor is disposed at a position after the transfer position to facilitate assembly and maintenance of the density detection sensor and the like, and the density of the reference density pattern can be accurately detected.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view showing the general configuration of a copying machine according to the present invention, FIG. 2 is a view showing the state of formation of a latent image of an AIDC pattern by an editing eraser, and FIG. 3 is a cross-sectional front view of a belt cleaner. Figure 4 shows AID
FIG. 5 is a diagram showing an example of the relationship between the amount of toner adhered to the photoreceptor drum 3 and the detection signal S1, and FIG. formed A
A diagram showing changes in the output of the AIDC sensor before and after the IDC pattern contacts the transfer belt. Figure 7 shows the AIDC pattern formed on the photoreceptor drum contacts the transfer belt when the belt cleaner is inactive. Figure 8 is a cross-sectional view of the humidity sensor, Figure 9 is a diagram showing how the temperature inside the copying machine and the humidity inside the developing unit change over time. 10 is a diagram showing the amount of toner adhering to the photoconductor drum with respect to humidity changes. FIG. 11 is a block diagram of the control circuit of the copying machine, and FIGS.
FIG. 18 is a flowchart showing the operation of the copying machine, and FIG. 19 is a timing diagram showing the operation of each part related to the creation of an AIDC pattern. 1... Copying II (imaging bag W), 3... Photosensitive drum (photosensitive member), 11... Transfer belt (intermediate transfer medium),
19...Belt cleaner (cleaning device), 73
...AIDC sensor (concentration detection sensor), 195
a... Drive unit, 401... CPU, 405... High voltage power supply, AP... AIDC pattern (reference density pattern), S8... Control signal, S9... Drive control signal.

Claims (1)

[Claims] (1) a photoconductor on which a toner image is formed; an intermediate transfer medium to which the toner image formed on the photoconductor is transferred and secondarily transfers the transferred toner image to paper; An image forming device comprising: a cleaning device that cleans the surface of an intermediate transfer medium using static electricity; and a density detection sensor that detects a reference density pattern for adjusting image density formed on the photoreceptor. The density detection sensor is located at a position after the transfer position from the photoreceptor to the intermediate transfer medium,
The cleaning device is arranged to detect a reference density pattern on the photoreceptor, and the cleaning device is inactive for a portion of the surface of the intermediate transfer medium through which the reference density pattern passes. An image forming device characterized in that it is controlled.