JP2004117734A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To finish adjusting an image forming condition within an optimum time by constituting an image forming apparatus so that the execution of an automatic image forming condition adjusting means required in the midst of an image forming operation can advance at a reference speed peculiar to the automatic adjusting means without depending on the last image forming speed. <P>SOLUTION: When an image forming condition adjusting timing comes in the midst of forming images on several sheets (S163), first, information on the present image forming speed is retreated (S164), the image forming operation is stopped (S164), a toner density adjusting processing is performed (S166 to S169). And when the adjusting processing is finished, the image forming speed is made to return to the previous speed (S170), and then, the subsequent image forming operation proceeds (S171). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to automatic adjustment in an image forming apparatus that forms an image using an electrophotographic method, for example, an image forming apparatus provided in a copying machine, a printer, a facsimile, or the like.
[0002]
[Prior art]
Image forming conditions that need to be adjusted depending on the external environment that changes every day such as temperature and humidity, heat generated in the image forming apparatus due to image forming, consumption of consumables related to image forming, individual differences of image forming media, etc. In the image forming apparatus having the automatic adjustment function, the timing of the automatic adjustment is the timing before the image formation (hereinafter, first timing), the timing during the image formation, or the timing after the image formation (hereinafter, second timing). There is. At the first timing, automatic adjustment is performed by detecting changes in the external environment of the image forming apparatus, such as humidity and temperature, and changes in image forming conditions due to replacement of consumables in the image forming apparatus. At the second timing, after a certain number of images are formed, automatic adjustment of image forming conditions is performed.
[0003]
Further, the image forming apparatus has a plurality of image forming speeds so as to flexibly respond to changes in image forming accuracy and image forming medium. For example, the first speed is a normal image forming speed, and the second speed is a lower speed, such as a 1/2 speed or a 1/4 speed. The image forming speed can be switched for each image page to be formed.
[0004]
[Problems to be solved by the invention]
In addition, among the automatic adjustments, there are those in which the speed at the time of the image formation and the drive system are made to be the same, and the time for these automatic adjustments is affected by the image formation speed. For example, in the case of automatic adjustment at the second timing during image formation, the image formation speed at which the automatic adjustment is performed depends on the image formation speed immediately before the automatic adjustment. On the other hand, the automatic adjustment at the first timing before the image formation is before the image formation, so that the automatic adjustment is performed at the first speed.
[0005]
When automatic adjustment at the second timing is performed during image formation at the first speed, the automatic adjustment is completed in the same occupation time as the first timing.
[0006]
However, when the automatic adjustment at the second timing is performed during the image formation at the second speed, the automatic adjustment is performed at the second speed, and the automatic adjustment at the second timing at the first speed is performed. It takes more time than adjustment. That is, in each of the first speed and the second speed, the contents of the automatic adjustment are the same, but depend on the image forming speed of the image formation immediately before the automatic adjustment.
[0007]
The present invention has been made in view of such a problem, and in executing an automatic adjustment unit of an image forming condition generated during image formation, a reference speed unique to the automatic adjustment unit is set without depending on the immediately preceding image forming speed. It is an object of the present invention to provide an image forming apparatus capable of completing adjustment of image forming conditions within an optimum time and a control method thereof.
[0008]
[Means for Solving the Problems]
In order to solve such a problem, for example, an image processing apparatus of the present invention has the following configuration.
[0009]
An electrostatic latent image is generated by exposing and scanning the surface of the image carrier charged to a predetermined potential based on image data to be recorded, and the electrostatic latent image is visualized with toner, and transferred and fixed on a recording medium. An image forming apparatus having at least two image forming speeds by forming an image by changing the operating speed of the image carrier,
Image forming condition adjusting means for responding to a change in the use situation;
Adjustment timing detecting means for detecting a timing at which the image forming condition adjusting means performs the adjusting operation,
When the adjustment timing detecting means detects the adjustment timing of the image forming conditions during the image forming operation of a plurality of sheets, the information indicating the image forming speed during the image formation is saved, and the image is formed at a predetermined forming speed. The image forming apparatus further includes control means for causing the adjustment by the forming condition adjusting means to be performed, and when the adjustment is completed, returning to the saved image forming speed and continuing the image forming operation.
[0010]
To achieve the above object, an image forming apparatus according to an embodiment of the present invention includes a charging unit that uniformly charges the surface of an image carrier to a predetermined potential, and an electrostatic latent surface on the surface of the image carrier by light irradiation. Exposure means for forming an image, developing means for visualizing an electrostatic latent image formed on the surface of the image carrier with toner to form a toner image, and transfer means for transferring the toner image to an intermediate transfer body or a transfer material An image forming condition adjusting unit having a voltage application unit for applying a predetermined voltage to the charging unit, the developing unit, and the transfer unit; Adjusting timing detecting means for detecting a timing at which the adjusting operation is performed, image forming speed switching means capable of switching the operating speed of the image carrier to at least two or more, and the image forming speed Storage means for storing a reference speed for performing an adjusting operation by the image forming condition adjusting means among speeds switchable by the switching means, wherein the adjusting timing is detected by the adjusting timing detecting means during the image forming operation In this case, when the current image forming speed is different from the reference speed, the image forming speed is switched to the reference speed by the image forming speed switching means.
[0011]
Further, the image forming speed of the image that is continued when the execution of the image forming condition adjusting unit is completed depends on the accuracy of the continued image and the image forming medium, and always depends on the image forming speed before the image forming condition adjusting unit. It is not a thing.
[0012]
Further, when the adjustment timing by the adjustment timing detecting means occurs in the middle of continuous image formation, image formation and discharge are performed for all papers already fed into the image forming apparatus. Thereafter, image formation and paper feeding are stopped for the image. While the image forming is stopped, the adjusting operation by the image forming condition adjusting means is executed, and after the adjustment is completed, the image forming and the sheet feeding are restarted.
[0013]
Further, one of the image forming conditions is a toner density, and the image forming apparatus includes a density detecting unit for detecting the toner density, and a toner density adjusting unit based on the detection result.
[0014]
One of the image forming conditions is a current of the image carrier, and the image forming apparatus includes a means for detecting the amount of the current and a means for adjusting the amount of the current based on the result of the previous detection.
[0015]
Further, one of the image forming conditions is a current of the transfer roller, and has means for detecting the amount of current of the transfer roller, and has means for adjusting the amount of current based on the detection result in the previous period. .
[0016]
Further, one of the image forming conditions is a tilt and a position of the scanning line, and has a detecting means for detecting the tilt and the position of the scanning line. The tilt and the position of the scanning line are adjusted based on the detection result of the previous period. It is characterized by having means.
[0017]
Further, one of the image forming conditions is a density gradation of an image, the image forming apparatus includes means for detecting the image density, and includes means for adjusting the density gradation based on a result of the detection.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0019]
FIG. 1 is a sectional view of an image forming apparatus applied in the embodiment. The image forming apparatus according to the present embodiment is an electrophotographic printing apparatus. However, since the present invention may be applied to a copying machine, a facsimile, or the like, the present invention is not limited by this.
[0020]
In the figure, reference numeral 1 denotes an image forming apparatus, which is roughly classified into an image forming section (four stations a, b, c, and d are arranged side by side, and the configuration itself is the same), a sheet feeding section, and an intermediate transfer. Unit, transport unit, fixing unit, operation unit, and control unit.
[0021]
Next, each unit will be described in detail. The image forming section has the following configuration. Photosensitive drums 11a, 11b, 11c, and 11d as image carriers are pivotally supported at their centers, and are driven to rotate in the direction of arrows by a drive motor (not shown). Roller chargers 12a, 12b, 12c, and 12d, scanners 13a, 13b, 13c, and 13d, and developing devices 14a, 14b, 14c, and 14d are arranged in the rotation direction of the photosensitive drums 11a to 11d so as to face the outer peripheral surfaces thereof. . In the roller chargers 12a to 12d, charges of a uniform charge amount are given to the surfaces of the photosensitive drums 11a to 11d. Next, the scanners 13a to 13d expose the photosensitive drums 11a to 11d with light beams, such as laser beams, modulated in accordance with the recording image signals, thereby forming electrostatic latent images thereon. Further, the electrostatic latent images are visualized by the developing devices 14a to 14d each storing developers (toners) of four colors such as yellow, cyan, magenta, and black. The visualized visible image is transferred to the intermediate transfer body 30. According to the process described above, image formation using each toner is sequentially performed.
[0022]
Next, the paper supply unit includes a portion for storing the recording material P, a roller for conveying the recording material (OHP sheet, recording paper, etc.) P, a sensor for detecting passage of the recording material P, and a recording material P. And a guide (not shown) for transporting the recording material P along the transport path. Reference numerals 21a, 21b, 21c, and 21d denote cassettes, 27 denotes a manual feed tray, and 28 denotes a deck, which stores the recording material P. 22a, 22b, 22c and 22d are pickup rollers for sending out the recording materials P one by one from the cassettes 21a to 21d. A plurality of recording materials P may be sent out by the pickup rollers 22a to 22d, but only one sheet is surely separated by the BC rollers 23a, 23b, 23c, and 23d. The recording material P separated only by one of the BC rollers 23a to 23d is further conveyed by pull-out rollers 24a to 24d, a pre-registration roller 26, and conveyed to a registration roller 25. Further, the recording material P stored in the manual feed tray 27 is separated one by one by a BC roller 29, and is conveyed to a registration roller 25 by a pre-registration roller 26. The recording material P stored in the deck 28 is transported by the pickup roller 60 to a plurality of paper feed rollers 61, is separated by the paper feed roller 61, and is transported to the pull-out roller 62. Further, the recording material P is transported to the registration roller 25 by the pre-registration roller 26.
[0023]
The intermediate transfer unit will be described in detail. An intermediate transfer belt 30 is made of, for example, PET [polyethylene terephthalate] or PVdF [polyvinylidene fluoride]. Reference numeral 32 denotes a drive roller for transmitting drive to the intermediate transfer belt 30, a tension roller 33 for applying an appropriate tension to the intermediate transfer belt 30 by urging of a spring (not shown), and a secondary transfer area sandwiching the intermediate transfer belt. It is supported by a driven roller 34 to be formed. The drive roller 32 has a surface of a metal roller coated with rubber (urethane or chloroprene) having a thickness of several mm to prevent slippage with the belt. The drive roller 32 is driven to rotate by a stepping motor (not shown). Primary transfer rollers 35 a to 35 d to which a high voltage for transferring a toner image to the intermediate transfer belt 30 is applied on the back of the intermediate transfer belt 30 at a position where each of the photosensitive drums 11 a to 11 d and the intermediate transfer belt 30 face each other. Is arranged. A secondary transfer roller 36 is arranged to face the driven roller 34, and forms a secondary transfer area by nip with the intermediate transfer belt 30. The secondary transfer roller 36 is pressed with an appropriate pressure on the intermediate transfer member. A cleaning device 50 for cleaning the image forming surface of the intermediate transfer belt 30 is disposed on the intermediate transfer belt 30 and downstream of the secondary transfer area. The cleaning device 50 includes a cleaner blade 51 (made of a material such as And a waste toner box 52 for storing waste toner. Further, a patch sensor 77 for detecting an image density is provided near the intermediate transfer belt.
[0024]
The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein and a pressure roller 41b pressed on the roller (the roller may also have a heat source), and the recording material discharged from the roller pair. It comprises an inner discharge roller 44 for transporting P.
[0025]
On the other hand, the recording material P conveyed to the registration roller stops the rotation of the roller upstream of the registration roller and temporarily stops the rotation, and rotates the upstream roller including the registration roller 25 in synchronization with the image forming timing of the image forming unit. Driving is resumed. The recording material P is sent to a secondary transfer area described later. After the recording material P on which the image has been transferred in the secondary transfer area and the image has been fixed in the fixing unit 40 passes through the inner discharge roller 44, the transfer destination is switched by the switching flapper 73. When the switching flapper 73 is on the face-up discharge side, the recording material P is discharged to the face-up discharge tray 2 by the external discharge roller 45. On the other hand, when the switching flapper 73 is on the face-down discharge side, the recording material P is conveyed in the direction of the reversing rollers 72a, 72b, 72c and discharged to the face-down discharge tray 3. When images are formed on both sides of the sheet, the sheet is conveyed in the direction of the face-down discharge tray 3, stopped when the rear end of the sheet material P reaches the reversing position R, and moved in the direction of the two-sided rollers 74a to 74d. The sheet is conveyed by reversing the rotation direction of the reversing roller. Thereafter, the sheet material P is conveyed to the image forming unit in the same manner as when conveying sheets from the cassettes 21a to 21d. A plurality of sensors are arranged on the conveyance path of the recording material P in order to detect the passage of the recording material P, and a paper feeding retry sensor 64a, 64b, 64c, 64d, a deck paper feeding sensor 65, a deck pull-out sensor There are a sensor 66, a registration sensor 67, an internal discharge sensor 68, a face-down discharge sensor 69, a double-sided pre-registration sensor 70, a double-sided re-feed sensor 71, and the like. Cassette sensors 63a, 63b, 63c, 63d for detecting the presence or absence of the recording material P are arranged in the cassettes 21a to 21d for storing the recording material P, and the manual tray 27 is used for recording on the manual tray 27. A manual paper tray presence / absence sensor 76 for detecting the presence / absence of the material P is disposed, and a deck paper presence / absence sensor 75 for detecting the presence / absence of the recording material P in the deck 28 is disposed on the deck 28.
[0026]
The operation unit 4 is disposed on the upper surface of the image forming apparatus 1, selects a paper supply unit (the paper supply cassettes 21 a to 21 d, the manual tray 27, the deck 28) in which the recording material P is stored, and selects a paper discharge tray (face). It is possible to select the up tray 2, the face down tray 3), specify a tab sheet bundle, and the like.
[0027]
In the drawing, reference numeral 1000 denotes a control unit, which includes a control board for controlling the operation of the mechanism in each unit, a motor drive board, and the like.
[0028]
FIG. 9 illustrates a schematic configuration block of the control unit 1000 according to the embodiment and a connection relationship between the control unit 1000 and the printer engine illustrated in FIG. In the figure, reference numeral 90 denotes a CPU that controls the entire apparatus, and 91 denotes a ROM that stores processing procedures (programs) of the CPU 90, font data, and the like. Reference numeral 92 denotes a RAM used as a work area of the CPU 90. Image data based on the received print data is also expanded here. Further, the RAM 92 is provided with a counter area for counting the number of sheets on which an image is formed in one job, and an area for holding a toner density reference value N described later.
[0029]
Reference numeral 93 denotes an interface for connecting to a host computer. This interface may be of any type. For example, if this apparatus functions as a network printer, the interface is a network interface. An operation panel 94 includes buttons for performing various settings and a simple display device (such as a liquid crystal display). Reference numeral 95 denotes an A / D converter, which performs a process of converting signals of various sensor groups provided in the printer engine (see FIG. 1) into digital data. The sensor group includes an inductance sensor described later. A driver 96 generates signals for driving various motors mounted on the printer engine. Reference numeral 97 denotes an interface (engine interface) for communicating with the printer engine, and a video signal for printing is also output to the printer engine via this interface. Reference numeral 98 denotes a printer engine which forms an image based on a group of sensors for outputting a signal to the A / D converter 95, a group of motors operated by a driving signal from a driver 96, and received image data (video signal). An image forming unit is included.
[0030]
Next, an explanation will be given according to the operation of the apparatus. As an example, the case where the recording material P is transported from the cassette 21a will be described, but it is needless to say that another paper supply source may be used.
[0031]
In the embodiment, the print data received via the interface 93 is temporarily stored in the RAM 92, and when the data of one page is stored, the task of issuing an image forming operation start signal to the main process is operating. It will be described as. However, when applied to a copying machine, the image forming operation start signal may be a signal generated when an unread document is scanned from, for example, an ADF or the like, and if there is no ADF, a signal for pressing a copy start key may be used.
[0032]
By the way, after a lapse of a predetermined time from the issuance of the image forming operation start signal, first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the transfer material P is transported by the paper feed roller 23 to the registration roller 25 via the pull-out roller 24a and the pre-registration roller 26. At that time, the registration roller 25 is stopped, and the leading end of the paper strikes the nip. Thereafter, the registration roller starts rotating at the timing when the image forming unit starts forming an image. The rotation timing is set so that the transfer material P and the toner image primarily transferred from the image forming unit onto the intermediate transfer belt just coincide in the secondary transfer area.
[0033]
On the other hand, in the image forming section, when an image forming operation start signal is issued, a high voltage is applied to the toner image formed on the photosensitive drum 11d which is the most upstream in the rotation direction of the intermediate transfer belt 30 by the above-described process. The primary transfer is performed on the intermediate transfer belt 30 in the primary transfer area by the transferred transfer roller 35d. The primary-transferred toner image is transported to the next primary transfer area. In this case, the image formation is performed with a delay of the time during which the toner image is conveyed between the image forming sections, and the next toner image is transferred by aligning the leading end of the image with the previous image. Hereinafter, the same steps are repeated, and the toner images of four colors are primarily transferred on the intermediate transfer belt 31 after all.
[0034]
Thereafter, when the recording material P enters the secondary transfer area and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passage timing of the recording material P. Then, the four color toner images formed on the intermediate transfer belt by the above-described process are transferred onto the surface of the recording material P. Thereafter, the recording material P is guided to the fixing roller nip. Then, the toner image is fixed on the paper surface by the heat of the roller pair 41a and 41b and the pressure of the nip. After that, the sheet is discharged to the face-up sheet discharge tray 2 or the face-down tray 3 according to the switching direction of the switching flapper.
[0035]
Next, the adjustment of the image forming conditions during image formation, which is the main point of the present embodiment, will be described, taking as an example the adjustment of the toner density among the image forming conditions to be adjusted to cope with a change in the use situation.
[0036]
First, the toner density adjusting mechanism will be described. Generally, a two-component developer mainly composed of toner particles and carrier particles is used for a developing device provided in an electrophotographic or electrostatic recording type image forming apparatus. In particular, in a color image forming apparatus for forming a full-color or multi-color image, most developing devices use a two-component developer. As is well known, the toner concentration of this two-component developer (that is, the ratio of the weight of toner particles to the total weight of carrier particles and toner particles) is a very important factor in stabilizing image quality. For this reason, a toner concentration adjusting device (ATR) including a toner concentration detecting unit for detecting the toner concentration of the two-component developer and a control unit for replenishing the developing device with toner in accordance with the detected signal is used. The toner concentration of the two-component developer is kept constant.
[0037]
As a toner concentration detecting means for detecting the toner concentration of the two-component developer, a toner concentration detection sensor of an optical reflected light amount detection method of irradiating the two-component developer with light, receiving the reflected light amount and detecting the toner concentration, For example, an inductance detection type toner concentration detection sensor that detects the toner concentration by detecting the inductance of a two-component developer is used.
[0038]
FIG. 2 is a schematic diagram of the developing device 14a out of 14a to 14d. The same applies to 14c to 14d. In the embodiment, a description will be given of toner concentration detection using an inductance detection method.
[0039]
The developing device 100 is disposed so as to face an image carrier 106 such as a photoreceptor or a dielectric. The inside of the developing device 100 is separated from a developing chamber (first chamber) 101 and a stirring chamber (second chamber) by partition walls 103 extending in the vertical direction. (Room 102). The upper part of the partition 103 is open so that the excess two-component developer in the developing chamber 101 is collected in the stirring chamber 102 side. In this embodiment, the developing chamber 101 and the stirring chamber 102 contain a two-component developer containing a non-magnetic toner and a magnetic carrier.
[0040]
Screw-type first and second developer stirring / transporting means 107 and 108 are disposed in the developing chamber 101 and the stirring chamber 102, respectively. The first stirring / transporting means 107 stirs / conveys the developer in the developing chamber 101, and the second stirring / transporting means 102 is located upstream of the stirring / transporting means 108 from a toner supply tank (not shown). The toner supplied through a toner supply port provided in the upper portion of the printer and the developer already in the stirring chamber 102 are stirred and conveyed to make the toner concentration uniform. As is clear from FIG. 2, at both ends of the partition wall 103, a developer passage for communicating the developing chamber 101 and the stirring chamber 102 with each other is formed. The developer in the developing chamber 101 whose toner concentration has been reduced due to the consumption of the toner due to the development moves from one passage into the stirring chamber 102, and the developer whose toner concentration has been recovered in the stirring chamber 102 develops from the other passage. It is configured to move into the chamber 101.
[0041]
The developing chamber 101 has an opening at a position corresponding to a developing area facing the image carrier 106, and a developing sleeve 104 as a developer carrier is rotatably disposed so as to be partially exposed at the opening 110. Have been. The developing sleeve 104 is made of a non-magnetic material, rotates during the developing operation in the direction of the arrow shown in the figure, and has a magnet 105 fixed therein as a magnetic field generating means. The developing sleeve 104 carries and conveys the layer of the two-component developer whose thickness is regulated by the blade, and develops the developer by attaching the developer to the latent image of the image carrier 106 in a development area facing the image carrier 106. In order to improve the development efficiency, that is, the toner application rate to the latent image, a development bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the development sleeve 104.
[0042]
Since the inductance detection type toner concentration detection sensor detects a change in the inductance of the two-component developer, the change in the inductance and the constant flow of the developer on the side and the bottom of the developing device which can stably detect the change in the inductance can be detected. Need to be installed in place. In addition, since the change in the toner density is detected, the change must be provided on the downstream side of the developing chamber 101. Therefore, usually, a toner concentration detection sensor (inductance head) 109 of an inductance detection type is installed on the bottom surface of the developing device on the downstream side of the developing chamber 101, and the inductance that changes according to the change in the toner amount of the two-component developer is reduced. The toner density has been detected.
[0043]
Next, first, second, and third toner density adjustments in the toner density adjustment will be described. FIG. 3 shows a series of relationships between the inductance sensor and the toner supply operation (also the relationship between the sensor group in the printer engine in FIG. 9 and the control controller).
[0044]
First, the initialization of the toner density adjustment will be described. In the toner density adjustment, it is necessary to correct the reference value of the variation amount of the toner density and to correct the blur of the inductance sensor. The reference value of the toner density is stored in the memory 154 (“N” in the RAM 92) in advance. When the developing device 100 is shipped from the factory or is newly attached by replacement, the toner concentration in the developing device 100 has an optimal ratio. The determination that the developing device is new can be made based on the number of uses written in a memory tag (not shown) attached to the developing device. At the start of the operation of the image forming apparatus, if it is determined that the developing device 100 is new, the developing device corrects the blur of the inductance sensor. Since the toner density of the developing device 100 is in an optimum state, it must be equal to the reference value of the toner density stored in the memory 154 in advance.
[0045]
For example, when the detected value of the inductance sensor is N ± 10 when the toner density reference value is N, it is determined that the blur amount of the inductance sensor is ± 10 with respect to the value N. Therefore, the sensor detection value is adjusted by correcting the detection value of the inductance sensor thereafter by ± 10 or adjusting the inductance sensor itself.
[0046]
Next, the first toner density adjustment will be described with reference to FIG.
[0047]
When the image forming operation is started and the developing sleeve 104 and the first and second developer stirring means 107 and 108 start rotating, the inductance sensor (151) detects the toner density. The toner density in the developing device detected by the inductance sensor (151) is amplified as necessary, then converted into a digital signal by an analog-to-digital converter (A / D converter) 152, and sent to the arithmetic circuit 153. Can be The arithmetic circuit 153 compares the input signal with the reference value to obtain a difference between the input signal and the difference, calculates a toner density variation from the difference, and sends a toner density variation signal representing the variation to the toner supply circuit 155. The toner replenishing circuit 155 drives the driving means of the toner replenishing tank for the converted replenishing time to supply a predetermined amount of toner. FIG. 4 is a timing chart showing the above series of relationships. As shown in the chart, the first density adjustment is performed each time an image is formed.
[0048]
Next, the second toner density adjusting means will be described.
[0049]
In a two-component developer containing toner particles and carrier particles as main components, a long-time voltage application may cause deterioration of the toner. As a result, the ratio between the toner particles and the carrier particles detected by the inductance sensor becomes inaccurate. For example, it is assumed that the detection value of the inductance sensor when the toner does not deteriorate is X. In this state, if the voltage is applied for a long time and the toner is deteriorated without using the toner, the detection of the inductance sensor fluctuates as a value X ± 10. Due to this variation, the first toner density adjusting unit may erroneously determine that toner replenishment is unnecessary based on the calculation result from the inductance sensor detection value regardless of the toner density being reduced in the actual image. There is.
[0050]
In order to prevent such a state, as a second toner density adjustment, at a predetermined timing, the toner density of the patch-like reference image formed on the intermediate transfer belt 30 was detected and the toner was excessively replenished. , It is determined whether or not replenishment is insufficient, and a function of correcting the reference value N of the inductance sensor based on the determination is provided.
[0051]
FIG. 5 shows a processing procedure of the second toner density adjustment. Hereinafter, this processing procedure will be described with reference to FIG.
[0052]
Each time an image forming request (step S161) is issued, an image forming process (step S162) is performed, the number of which is stored and updated in a counter of the RAM 92, and the number of image formed is determined by the predetermined value for performing the second toner density adjustment. It is determined whether or not the number has been reached (step S163). If the number of image formations has not reached the predetermined number, image formation is continued.
[0053]
On the other hand, when the number of formed images is equal to or more than the predetermined number, that is, when it is determined that the second toner adjustment timing has come, information on the image forming speed at that time is saved in the RAM 92 (step S164), and the image formation is temporarily performed. The operation is stopped (step S165).
[0054]
However, at this stop timing, if there is any undischarged recording material (recording paper, OHP sheet, etc.) between the paper feed cassette and the external discharge roller 45, the recording operation on the recording material and the discharge operation After the completion of.
[0055]
After the image formation is stopped, a patch image is formed at the maximum image forming speed of the apparatus (step S166). At this time, since the patch image does not need to be transferred onto paper, paper feeding is not required. The image density of the patch image of each color component (Y, M, C, K) on the intermediate transfer member is read by the patch sensor 77 (step S167). The patch sensor is, for example, a photodiode that looks at the reflected light from the transfer body. The output value is low when the image density is high, and the output value is high when the image density is low. From the output value of the patch sensor, it is determined whether the toner density is appropriate (step S168). If it is determined that the toner is oversupplied or insufficiently resupplied, it is considered that the toner density reference value N in the first toner density adjustment has an error with respect to the use situation, so the reference value N is corrected. After cleaning the patch image on the intermediate transfer member (step S169), reading is performed so as to continue a series of image formation at the evacuated image forming speed (step S170), and based on the readout, continuous image formation is restarted (step S170). S171).
[0056]
As described above, the second toner density adjustment is activated every time the toner consumption reaches a certain value, detects an error between the actual image density and the amount of replenished toner according to the inductance sensor detection, and corrects the error. . Thereby, the error of the inductance sensor detection value generated in the first toner density adjustment is periodically corrected. Further, as described above, the second toner density adjustment process is performed at the fastest speed regardless of the series of image forming speeds, so that the time required for the adjustment process can be shortened. Become. In addition to the measurement from the number of sheets as described above, the toner consumption amount can be measured from, for example, a video count value obtained by photoelectrically converting a document image, an image forming time, and an image size.
[0057]
Next, the third toner density adjusting means will be described.
[0058]
In the second toner density adjustment, the toner supply amount is adjusted at regular intervals. For this reason, there is a possibility that a difference in toner density may occur in image formation before and after the occurrence of the second development density control unit as a boundary. In particular, when the fluctuation of the density adjustment due to the second toner density adjustment is large, it is expected that the image density is greatly different between the number of copies at the beginning and the copy image at the end. This can be a fatal problem when copying a number of copies.
[0059]
Therefore, as a third toner density adjustment, a video when an all black image is formed on the total amount of toner adhered to one sheet of recording paper (a recording material P of a predetermined size (for example, 210 mm × 297 mm)) from the bitmap image. Unused toner is detected from the ratio where the count value is 100%, which is hereinafter referred to as an image duty, which is obtained from the video count value. Means for predicting toner deterioration of the toner to which a voltage is applied without being used in the developing device 100 when the number of sheets has been continued, and correcting the toner density more frequently than the second toner density adjustment ing.
[0060]
Hereinafter, the third toner density adjustment will be described with reference to FIG.
[0061]
An image formation request is issued (step S181), and after image formation (step S182), the image density is determined according to the image duty during image formation (step S183). When the pixel density of the image is equal to or less than the reference value, it is determined that the toner used in the image is equal to or less than the reference value. In this case, the number of continuous image formations when the image duty is equal to or less than the reference value is added (step S184).
[0062]
If this number exceeds the predetermined number A and further exceeds the predetermined number B, which is larger than the predetermined number A, it is determined that the toner has been charged for a long time without being used in the developing device 100, and that the toner has deteriorated. In order to refresh the toner, the image forming speed at that time is temporarily saved in the RAM 92 (step S188), and the continuous image forming request is stopped (step S189).
[0063]
After the image formation is stopped, the toner in the developing device 100 is discharged by forming a patch image on the intermediate transfer member (step S190). At this time, since transfer to paper is not performed, paper feeding is unnecessary. After discharging the toner, the transfer member is cleaned (step S191). Thereafter, the saved image forming speed information is read out, the setting relating to the return is made (step S192), and the image formation is continued (step S193). After the toner is discharged, the toner is replenished (step S194). Note that the order of toner supply may be immediately after toner discharge (step S190) or may vary depending on mounting details.
[0064]
If the image duty is equal to or greater than the reference value (step S183), it is considered that the frequency of the image having the low image density is not high, and the continuous number of images having the low image density is cleared (step S185). In addition, when the continuous number does not exceed the predetermined number A (step S186), it is considered that the image having the low image density is not high in frequency yet, so that no particular processing is performed. If the number is equal to or larger than the predetermined number A and equal to or smaller than the predetermined number B (step S187), it is determined that it is not necessary to refresh all of the toner. Since it is predicted that an error is occurring in one toner density adjustment, only toner replenishment is performed (step S194).
[0065]
The above is the third toner density adjustment, and corrects an error generated in the first toner density adjustment during the second toner density adjustment.
[0066]
Next, automatic adjustment of image forming conditions during image formation, which is the main point of the present embodiment, will be described by taking the toner density adjustment as an example.
[0067]
The image forming apparatus has a plurality of image forming speeds, such as M / 2, M / 4, etc., where M is a normal image forming speed, depending on the number of pixels and the image forming target medium. For example, when the image formation target medium is an OHP sheet, the image formation speed is M / 2, which is half the normal speed. The image forming speed can be switched every time one image is formed. Further, as a feature of the present embodiment, a reference speed L at the time of executing the automatic adjusting means is provided. Here, the description is made on the assumption that the reference speed L is the same as the normal image forming speed M.
[0068]
Further, among the first, second, and third toner density adjustments, the image forming operation needs to be temporarily stopped, as described above, with the second toner control for forming a patch image on the intermediate transfer member. This is the third toner density adjustment. During the toner control, the image formation is temporarily stopped, and the image formation is restarted after adjusting the toner density.
[0069]
FIG. 7 shows the execution of toner density adjustment during image formation when the image formation speed is M during image formation. The switching of the image forming speed is determined by a signal from a sensor that detects the type of recording medium (plain paper or OHP sheet), but may be determined according to an instruction command from the host computer. . Further, even when the present invention is applied to a copying machine, it is determined based on a signal from a sensor for detecting the type of a recording medium, but may be determined according to an instruction from an operation panel.
[0070]
As a means for temporarily stopping the image formation in the middle, the execution control is divided between the image formation instructing unit 200 and the image forming unit 201 here, but this changes depending on the details of implementation, and is not limited to this. Absent.
[0071]
The image formation instructing unit 200 sends a request (202) to the image forming unit 201 as to whether image formation and paper feeding are possible. In response to this, the image forming unit 201 makes a response (203) in which image forming and paper feeding responses are possible. Thereafter, image A information (204) is notified from image formation instructing section 200 to image forming section 201, and image A formation is performed (206). When the second or third toner density adjustment request (205) is generated as a result of image formation, the image forming unit 201 does not return a response to the next continuous image formation and paper feed request (207). Hold the response once. Thus, the next image B information 210 from the image forming instruction unit is temporarily stopped. During this time, the toner density adjustment (208) is performed. As described above, the toner density is adjusted by forming a predetermined patch image held in a memory such as the ROM 91 and reading the patch image on the intermediate transfer body 30 with the patch sensor 77 to determine the image density. Then, the reference value N of the inductance sensor 109 is corrected. Since the patch image is not fed, it is not secondarily transferred to the paper by the secondary transfer roller unit 36, is cleaned by the cleaning device 50, and does not affect the next image formation. After the completion of the toner density adjustment, the image forming unit 201 performs the temporarily suspended image formation and paper feed response 209. As a result, the next image B information 210 is notified, and continuous image formation is performed.
[0072]
The above is the execution of the toner density adjustment during image formation when the reference speed at the time of toner density adjustment and the image formation speed during the immediately preceding image formation are the same.
[0073]
FIG. 8 shows the execution of toner density adjustment during image formation when the reference speed during toner density adjustment and the image formation speed during image formation are different. Note that the description of the same portions as those of FIG. 7 described above is omitted.
[0074]
If image formation is being performed at a speed other than the reference speed L at the time of toner density adjustment, the drive speed is converted to the reference speed L (227). Here, the driving device that needs to switch the speed is a driving system used for forming the patch image for adjusting the toner density of the intermediate transfer body 30, depending on the mounting, although it depends on the mounting. Since no paper is fed, there is no need to change the speed of the paper feed drive system.
[0075]
By switching the speed at the time of toner density adjustment to the reference speed L, regardless of the image forming speed at any image forming speed, the speed required for the toner density adjustment does not depend on the speed at the time of image formation. Can be adjusted. For example, when the image forming speed is executed at a half speed of the normal speed M (= 1/2 speed of the reference speed), the toner density adjustment is performed at the reference speed, so that the toner density adjustment is performed at twice the speed of the half speed. The speed can be adjusted, and as a result, the time taken by the toner density adjustment during image formation is reduced.
[0076]
Further, the speed of the continuous image formation after the completion of the toner density adjustment is not necessarily the image formation speed before the toner density adjustment, but is returned to the image formation speed of the image interrupted by the toner density adjustment or the image requested by the continuous image after the toner adjustment. I do. For example, in the example of FIG. 8, since the 1/4 speed request is generated 230, the continuous image formation after the toner density adjustment is switched from the reference speed L to the 1/4 speed.
[0077]
In the above-described embodiment, the speed at the time of image formation ≦ the speed at the time of executing the automatic adjustment unit is described as an example, but the gist of the present invention is that an automatic adjustment is performed in an image forming apparatus having a unit that switches a plurality of image formation speeds. Since the execution speed at the time of executing the means is not made to depend on the speed at the time of image formation, the present invention can be applied to the relationship that the speed at the time of image formation ≧ the speed at the time of execution of the automatic adjustment means. Further, it is natural to adjust the speed at the time of executing the automatic adjustment in a direction to reduce the ratio of the time at the time of executing the automatic adjustment to the image forming time. In consideration of the speed switching time, the speed at the time of executing the automatic adjustment may be selected so that the ratio of the total time of the speed switching time and the time at the time of performing the automatic adjustment to the entire image forming time is reduced.
[0078]
The automatic adjustment process at the normal speed at the time of forming an image other than the normal speed includes the adjustment of the current amount of the image carrier, the adjustment of the current amount of the transfer roller, the inclination of the scanning line, the position adjustment, the density adjustment other than the toner density adjustment. Automatic adjustment means that occurs during image formation, such as gradation adjustment, shares a drive system for image formation and adjustment means, and applies to image forming conditions in which the time required for adjustment depends on the speed of the drive system. You can do it.
[0079]
Hereinafter, each adjustment of the image forming conditions will be briefly described.
[0080]
In adjusting the current amount of the image carrier, which is one of the image forming conditions, it is determined whether or not the charge by the roller chargers 12a to 12d with respect to the photosensitive drums 11a to 11d as the image carrier is a predetermined reference amount. The determination is made by detecting currents at a plurality of fixed points on the outer periphery of each of the 11d. The charge of the roller chargers 12a to 12d is adjusted based on the determination result. Also in this adjustment, as in the case of the toner density adjustment, the adjustment may occur during image formation of a predetermined number or more, and the photosensitive drums 11a to 11d need to be rotated for current measurement. Therefore, in this adjustment as well, the image formation is temporarily stopped and the adjustment at the reference speed L is performed as in the case of the toner density.
[0081]
In the adjustment of the current amount of the transfer roller, which is one of the image forming conditions, the primary transfer rollers 35a to 35d and the secondary transfer roller 36 determine whether or not the charge by the charging device at the time of unillustration is a predetermined reference amount. The determination is made by detecting currents at a plurality of fixed points on the outer circumference of the transfer roller and the secondary transfer roller. The charge is adjusted by the charge device based on the determination result. Also in this adjustment, as in the case of the toner density adjustment, it may occur during image formation of a predetermined number or more, and it is necessary to rotate the primary transfer rollers 35a to 35d and the secondary transfer roller 36 for current measurement. . Therefore, in this adjustment as well, the image formation is temporarily stopped and the adjustment at the reference speed L is performed as in the case of the toner density.
[0082]
In the inclination and position adjustment of the scanning line, which is one of the image forming conditions, a predetermined image is formed on the intermediate transfer body 30, the predetermined image is read into a memory by a detection unit (not shown), and is previously stored on the memory. By comparing with a reference value of a certain image, inclinations and positional deviations of main and sub scanning lines are detected and adjusted. Also in this adjustment, as in the case of the toner density adjustment, this may occur during the formation of a predetermined number of images or more. In order to form a predetermined image, the image formation is temporarily stopped and the reference speed L is set. Make adjustments in.
[0083]
With respect to the density gradation, which is one of the image forming conditions, a predetermined image is formed on the intermediate transfer body 30 and the predetermined image is read out by the density detection sensor 77 to be compared with the density gradation data stored in the memory. Then, by detecting an error between the density gradation formed on the transfer body and the density gradation data stored in the memory, the density gradation in the subsequent image formation is adjusted. Also in this adjustment, as in the case of the toner density adjustment, this may occur during the formation of a predetermined number of images or more. In order to form a predetermined image, the image formation is temporarily stopped and the reference speed L is set. Make adjustments in.
[0084]
As described above, according to the present embodiment, in execution of the automatic adjustment unit of the image forming condition generated during image formation, a reference speed unique to the automatic adjustment unit is used without depending on the immediately preceding image formation speed. Thus, the adjustment of the image forming conditions can be completed within an optimal time.
[0085]
In the embodiment, the present invention is applied to a printing apparatus that receives print data from a host computer and prints the data. However, any apparatus having an image forming apparatus such as a copying machine or a facsimile apparatus may be used. The present invention is not limited by the above embodiments.
[0086]
【The invention's effect】
As described above, according to the present invention, the execution of the automatic adjustment unit of the image forming condition occurring during image formation has a reference speed unique to the automatic adjustment unit without depending on the immediately preceding image forming speed. The adjustment of the image forming conditions can be completed within an optimal time.
[Brief description of the drawings]
FIG. 1 is a sectional structural view of an image forming apparatus to which an embodiment is applied.
FIG. 2 is a sectional structural view of a developing device in the embodiment.
FIG. 3 is a functional block diagram of a first toner density adjusting unit in the embodiment.
FIG. 4 is a timing chart of a first toner density adjustment.
FIG. 5 is a flowchart illustrating a processing procedure of a second toner density adjustment.
FIG. 6 is a flowchart illustrating a processing procedure of a third toner density adjustment.
FIG. 7 is a diagram illustrating a toner density adjustment flow at a timing when an image is being formed at a normal image forming speed.
FIG. 8 is a diagram showing a toner density adjustment flow at a timing when an image is being formed at a speed lower than a normal image forming speed.
FIG. 9 is a diagram illustrating a configuration of a control controller according to the embodiment.

Claims (9)

An electrostatic latent image is generated by exposing and scanning the surface of the image carrier charged to a predetermined potential based on image data to be recorded, and the electrostatic latent image is visualized with toner, and transferred and fixed on a recording medium. An image forming apparatus having at least two image forming speeds by forming an image by changing the operating speed of the image carrier,
Image forming condition adjusting means for responding to a change in the use situation;
Adjustment timing detecting means for detecting a timing at which the image forming condition adjusting means performs the adjusting operation,
When the adjustment timing detecting means detects the adjustment timing of the image forming conditions during the image forming operation of a plurality of sheets, the information indicating the image forming speed during the image formation is saved, and the image is formed at a predetermined forming speed. An image forming apparatus comprising: a control unit that causes an adjustment by a forming condition adjusting unit to be performed, and when the adjustment is completed, returns to the evacuated image forming speed and continues the image forming operation. The image forming apparatus according to claim 1, wherein the image forming speed is determined depending on accuracy of an image to be formed and an image forming medium. When the adjustment timing detection unit detects that the adjustment timing has come, if there is a recording medium that has not been ejected in the apparatus, the control unit completes the image forming process after the ejection process is completed. The image forming apparatus according to claim 1, wherein the adjustment is performed by a condition adjusting unit. Further, a density detecting means for detecting the toner density is provided,
The image forming apparatus according to claim 1, wherein the image forming condition adjusting unit includes adjusting a toner density based on the detected toner density. Further, a means for detecting a current amount of the image carrier is provided,
The image forming apparatus according to claim 1, wherein the image forming condition adjusting unit includes adjusting the amount of current. Further, there is provided a unit for detecting a current amount of a transfer roller for transferring the toner image to the image forming medium,
The image forming apparatus according to claim 1, wherein the image forming condition adjusting unit includes adjusting the amount of current. Furthermore, it has a detecting means for detecting the inclination and position of the scanning line,
The image forming apparatus according to claim 1, wherein the image forming condition adjusting unit includes adjusting a tilt and a position of the scanning line. Furthermore, it has means for detecting the image density,
The image forming apparatus according to claim 1, wherein the image forming condition adjusting unit includes adjusting a density gradation. An electrostatic latent image is generated by exposing and scanning the surface of the image carrier charged to a predetermined potential based on image data to be recorded, and the electrostatic latent image is visualized with toner, transferred to a recording medium, and fixed. Forming an image by changing the operating speed of the image carrier, thereby controlling the image forming apparatus having at least two image forming speeds.
An image forming condition adjusting step for responding to a change in the use situation;
An adjustment timing detecting step of detecting a timing at which the adjusting operation is performed by the image forming condition adjusting step;
When the adjustment timing of the image forming condition is detected during the image forming operation of a plurality of sheets by the adjustment timing detecting step, information indicating the image forming speed during the image formation is saved, and the image is formed at a predetermined forming speed. A control step of performing an adjustment in a forming condition adjusting step, and when the adjustment is completed, returning to the saved image forming speed and continuing the image forming operation.

Images