JP2003255629A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image deterioration such as lowering of density by predicting toner deterioration in a developing unit and varying processing conditions. <P>SOLUTION: An image forming apparatus is provided with a transfer material detecting means detecting passage of a transfer material in a carrying path of the transfer material, a measuring means to measure the time of a detecting signal of the transfer material detecting means and a control means to control an image forming action. When the time measured by the measuring means is equal to or longer than the specified time, the controlling conditions for each control means carrying out the image forming action are varied. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat. No. 2,297,961 and JP-B-42-23910 are known.
A large number of methods are known, as described in Japanese Patent Publication No. 43-24748 and Japanese Patent Publication No. 43-24748. In general,
An electrical latent image is formed on a photoreceptor, which is a recording body using a photoelectric substance, by various means, and then the latent image is developed with toner, and the obtained toner image is transferred onto a transfer material such as paper as necessary. Then, the transfer material is separated from the photoconductor by the action of the claw-shaped member and the separation bias, and the toner image is fixed on the transfer material by heating or solvent vapor to obtain an image.

Various developing methods are known for visualizing an electric latent image using a developer. For example,
The magnetic brush developing method described in U.S. Pat. No. 2,874,063, the powder cloud method described in U.S. Pat. No. 2,21,776, a fur brush developing method, a liquid developing method, etc. There is a way. Among these developing methods, a magnetic brush developing method using a two-component developer mainly composed of a toner and a carrier has been widely put into practical use. Of the two-component developer, that is, deterioration of the toner and fluctuation of the mixing ratio of the toner and the carrier.

In order to avoid such drawbacks, various developing methods using a one-component developer consisting of only toner have been proposed. According to this developing method, it is not necessary to control the mixing ratio of the toner to the carrier, which has the advantage of simplifying the apparatus.

In the above-mentioned one-component developing method, it is difficult to apply a charge to the toner because no carrier is used. Therefore, various methods for charging the toner have been studied.

[0006] For example, Japanese Patent Laid-Open No. 50-4539 discloses
A method of imparting an electrostatic charge by frictional charging with a toner carrier, and JP-A-54-2100 describe a method of providing a friction member and imparting an electrostatic charge by frictional charging with the friction member. ing. Further, a method of applying a voltage to the friction member, a method of charging the toner by a charging member such as corona charging, and the like have been devised.

By the way, in recent years, the number of digital copiers for office use not only as stand-alone copiers but also as network printers and finishing mechanisms as light printing devices is increasing. Further, as the number of these functions increases, the control unit for controlling each function in the apparatus also becomes complicated, but each function operates independently in order not to reduce the processing speed. . As a result, for example, when a complicated finishing process such as saddle stitch binding is performed, a space between transfer sheets on which an image is formed is vacant. Further, when used as a network printer, if there is large expanded data in the middle of the job, the printer engine will continue to operate even though it is not forming an image.

[0008]

However, in such an image forming apparatus according to the related art, if many idle rotations are performed in a state where image formation is not performed, various output image quality deteriorations, mainly density reductions, occur. There was a problem of inviting.

Further, as the developing method, in the electric field flying developing method and the jumping developing method using a one-component magnetic developer, especially when the image forming apparatus is started in a high humidity environment, the developer absorbs moisture while being left. However, the surface resistance of the developer particles decreases, the amount of charge that the developer should hold cannot be maintained, and the developing efficiency decreases.

Therefore, as in the technique disclosed in Japanese Unexamined Patent Publication No. 2000-181321, a preparation period at the time of starting the image forming apparatus in an environment of a predetermined humidity (mainly for heating the fixing device is intended. ), The deteriorated toner staying in the vicinity of the developer carrying member is forcibly transferred to the cleaning device via the photoconductor to prevent the deteriorated toner from being supplied to the image output. But not
2. Description of the Related Art Rotation of a developer carrying member that does not consume toner in order to increase the charge amount of the toner whose charge amount has temporarily decreased due to a long pause has been actively performed.

However, in the prior art, the above-mentioned forced discharge of deteriorated toner is always operated under a certain environment, and the toner is forcibly discharged even if it is not actually deteriorated. Wasted, leading to an increase in running costs.

The present invention has been made in view of the above circumstances. Even when the image forming apparatus is used as a multi-print system, the deteriorated toner in the developing device is appropriately predicted and the image forming condition is changed. Accordingly, it is an object of the present invention to provide an image forming apparatus that can prevent deterioration of output image quality, can provide a high-quality output image for a long period of time, and can save toner, at low cost.

[0013]

In order to achieve such an object, the present invention provides a transfer material detecting means for detecting passage of a transfer material in a transfer material conveying path during an image forming operation of an image forming apparatus. The image forming operation is performed when the measuring means for measuring the time of the detection signal of the transfer material detecting means and the control means for controlling the image forming operation are provided, and when the time measured by the measuring means is a specific time or more. The control condition of each control means is changed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an example of a digital copying machine according to the present invention.

The document placing portion 20 of the automatic document feeder 201
The document placed on the sheet No. 3 is separated and fed by the paper feed roller 204, and is conveyed to the reading device 202 via the conveyance guide 206. Further, it is conveyed at a constant speed by the conveyor belt 208, and is ejected out of the machine by the paper ejection roller 205. During this time, the image illuminated by the illumination system 209 at the reading position of the reading device 202 is reflected by the reflecting mirrors 210, 2.
The image reading unit 213 is configured by the optical system including the reference numerals 11 and 212.
Is converted into an image signal. The image reading unit 213 is a lens,
It is composed of a CCD which is a photoelectric conversion element, a driving circuit of the CCD, and the like. When reading a document, the document is conveyed at a constant speed and the reading system is stopped to read the document.
There is a fixed mode in which the illumination system 209 and the mirrors 210, 211, 212 are moved on the original glass table 214 and moved at a constant speed for reading. Normally, a sheet-like document is read in the flow-reading mode, and a bound document is read in the fixed mode.

The image signal is processed by the image processing unit 103 (not shown), and then the image reproducing apparatus 301 is processed page by page.
It is reproduced on recording paper with. The image signal is modulated into an optical signal by a semiconductor laser (not shown) or the like. The modulated laser light is an optical scanning device 31 using a polygon mirror.
1, through the mirrors 312 and 313, the photosensitive drum 309 whose surface is uniformly charged by the charger 310 is exposed to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 314.
Is developed with the toner of No. 1 and the toner image is transferred to the recording paper by the transfer separator 315. Recording paper is paper cassette 3
02 and 304. In this embodiment, standard paper is stored in the paper cassette 302 and tab paper is stored in the paper cassette 304. Paper cassette 302
The recording paper (standard paper in this embodiment) from the paper feed roller 3
The sheet is fed by 03, conveyed by the conveying roller 306, adjusted in timing with the image by the registration roller 308, and conveyed to the transfer position of the photosensitive drum. On the other hand, the recording paper (tab paper in this embodiment) of the paper cassette 304 is fed by the feed roller 305,
It is conveyed by 306, adjusted in timing with an image by the registration roller 308, and conveyed to the transfer position of the photosensitive drum. Here, in the case of forming an image on the tab portion of the tab sheet, as described later, when the timing of the registration roller 308 is adjusted, the tab sheet is fed earlier by the amount of the tab to align the image position with the tab portion of the tab sheet. To be transported. The recording paper on which the toner image is transferred is the conveyor belt 3
At 17, the toner is conveyed to the fixing device 318 and the toner on the recording paper is fixed.

When the single-sided mode is set, the recording paper from the fixing device 318 is discharged outside the machine by the fixing paper discharge roller 319 and the paper discharge roller 324. When the double-sided mode is set, the recording paper is conveyed from the fixing paper ejection roller 319 via the conveyance roller 320 to the reversing path 325 by the reversing roller 321. further,
Immediately after the trailing edge of the recording paper passes through the confluence point with the double-sided path 326, the rotation of the reversing roller 321 is reversed, so that the recording paper is reversed and is conveyed to the double-sided path 326. The recording paper conveyed to the double-sided path is conveyed by the rollers 322 and 323, and after the timing adjustment with the back side image is performed again by the registration roller 308 via the conveyance roller 306,
Transferred, fixed and discharged outside the machine.

When the front and back sides of the recording paper from the fixing device 318 are reversed and discharged to the outside of the machine, the recording paper is once conveyed to the conveying roller 320 and the rear end of the recording paper is conveyed. Immediately before passing through the roller 320, the rotation of the transport roller 320 is reversed, and the sheet is discharged to the outside by the sheet discharge roller 324.

FIG. 3 is a block diagram of the copy controller 105 of this apparatus.

All the devices are system controller 15
It is totally controlled by 1. The system controller 151 mainly plays a role of driving each load in the apparatus, collecting and analyzing information of sensors and the image controller 100 described above, and also exchanging data with the operation unit 600, that is, a user interface. There is. The internal configuration of the system controller 151 has the function of C
The PU 151a is installed, and the CPU 151a is the ROM 1 similarly installed in the system controller 151.
The program stored in 51b executes various sequences related to a predetermined image forming sequence. In addition, at that time, in order to store rewritable data that needs to be temporarily or permanently stored, a RAM is used.
151c is also installed. The RAM 151c stores, for example, a high voltage set value for the high voltage control unit 155, which will be described later, various data described later, image formation command information from the operation unit 152, and the like.

The system controller 151 sends to the image control section 100 the specification setting value data of each section necessary for the image processing section 102, and also receives signals from each section, such as a document image density signal. Then, the high voltage control unit 105 and the image processing unit 103, which will be described later, are controlled to make settings for optimal image formation.

In addition to obtaining information such as a copy magnification and a density setting value set by the user, the operating unit 600 receives information about the state of the image forming apparatus, for example, whether the number of images is being formed or whether images are being formed. It sends out information and data to indicate the occurrence of jam and its location to the user. Further, as will be described later, various settings for tab sheets and exchanges for displaying a warning for tab sheets are performed.

Next, driving of each load in the apparatus and information collection and analysis of sensors will be described. This device is equipped with DC load such as motor, clutch / solenoid, etc.
Sensors such as a photo interrupter and a micro switch are arranged. In other words, various sensors are used to convey the transfer material and drive each unit by appropriately driving the motor and each DC load, and monitoring the operation thereof. Therefore, the system controller 151
Based on the signals from various sensors 159, the motor control unit 157 controls each motor, and at the same time,
The DC load control unit 158 operates the clutch / solenoid to smoothly advance the image forming operation.

Further, by sending various high voltage control signals to the high voltage controller 155, various chargers constituting the high voltage unit 156, which are the primary charger 310, the transfer charger 315,
Appropriate high voltage is applied to the developing roller of the developing device 314. Further, each of the fixing rollers in the fixing device 318 described above has a built-in heater 161 for heating the roller, and each heater is turned on by the AC driver 160.
N / OFF controlled. At this time, each fixing roller is provided with a thermistor 154 for measuring the temperature thereof, and after the A / D 503 converts the resistance value change of the thermistor 154 according to the temperature change of each fixing roller into a voltage value, System controller 151 as a digital value
Entered in. The AC driver 160 described above is controlled based on this temperature data.

FIG. 1 is a block diagram of the image processing unit 102 of the present invention.

The image data read by the image reading unit 101 is input to the image processing unit 102 and the image processing circuit 40.
After predetermined image processing is performed in 2, the data is input to the memory control circuit. Under the control of the CPU 401, the memory control circuit 403 stores the input image data in the memory 404, reads the image data for forming an image from the memory 404, and outputs the image data to the image writing unit 103.

The CPU 401 controls the memory control circuit 403 to store the input image data in the memory 404 and the image writing unit 1 for the image data stored in the memory 404.
03, the image data stored in the memory 404 is read out, the image area in which the image data to be actually imaged is present is detected in the image data of one page, and the copy control unit 105 To notify.

The characteristic parts of this patent will be described below.

FIG. 4 shows the registration roller 30 in FIG.
8 is a layout diagram showing a layout of a registration sensor 501 arranged in front of FIG. The recording paper fed at the start of the image forming operation is temporarily stopped by the registration roller 308 and the image forming timing is adjusted. If there is a recording paper at this position, the registration sensor 501 is turned on.
It becomes a state. When the image forming data is prepared in the image processing unit 102, the registration roller starts driving and sends the recording paper to the transfer position. However, when the recording paper is sent, until the next recording paper arrives, The registration sensor 501 is turned off. The signal from the registration sensor 501 is one of the signals from the various sensors 159 described above and is input to the system controller 151.

Further, in the case of image formation based on the image data from the external I / F 106 in FIG. 1, in order to expand the print data if it is a complicated image, the image processing unit 102 does some image processing. It takes time. However,
Since the density of the image data input to 106 is unknown at the time of input and the data expansion may end instantaneously, the image forming apparatus starts the image forming operation together with the data input. That is, the recording paper also starts the paper feeding operation and stands by at the registration roller 308.
9 means that the developing device 314 is also operating.
Therefore, when the data sent from the external I / F is large like an image, the image forming operation is started, and the fed recording paper stands by at the registration roller 308 for a considerable time. Until the processing work in the image processing unit 102 is completed, the photoconductor 309 and the developing device 3 are
14 continues to rotate idly. At this time, it may take several minutes for large image data.

FIG. 5 shows a specific paper feeding sequence. In this sequence, two recording sheets are fed, and the black part is the timing when each component is turned on. When the copy start key is turned on, the paper feed motor is operated, the paper feed clutch and the pickup solenoid are turned on, and the paper feed operation is started. Then, the recording sheet moving on the conveying path is controlled by the sheet feeding clutch and the pickup solenoid according to the outputs of the sheet feeding sensor and the vertical path roller 1 sensor. After that, the recording paper reaches the registration roller 308, and the registration sensor 501 is turned on. The image forming operation for the first sheet is a little longer because it is necessary to stabilize the process state around the photoconductor 309, but the speed for the second and subsequent sheets is the same as the speed of the apparatus. Tb in the figure is the transit time of the recording paper during normal copying, T
a is the distance between the recording sheets. Since the device of this patent has the ability to print at a speed of 85 sheets per minute, it is usually Ta = 0.2392 seconds Tb = in A4 transverse feeding.
It becomes 0.4667 seconds.

The above-mentioned control uses the copy start as a trigger, but the same applies when image data is input to the external I / F, and when the first external input image data is expanded, From the image processing unit 102 to the copy control unit 10
A trigger for starting the image forming operation is input to 5. In the case of image formation based on the image data from the external I / F 106 described above, the image processing unit 102 processes the image data in order to expand the print data if the image is a complicated image. If it takes a long time, the waiting time at the registration roller 308, that is, the time Ta described above becomes long. Therefore, the idle rotation time of the developing device 314 can be detected by measuring the time Ta. When the system controller 151 determines that Ta exceeds the predetermined time Ti, the light amount of the laser with which the photosensitive drum 309 is exposed is changed.

FIG. 6 is an explanatory diagram of the internal structure of the writing unit 103. The image data sent from the image processing unit 102 is
After being modulated by the image processor circuit 510, it is sent to the laser driver circuit 511, and by the laser drivers 516 and 517 of the laser driver circuit 511,
The emission of lasers 512 and 513 is controlled. Since this apparatus is a high speed machine, it has two lasers for exposure as described above. The emission intensity of the laser is based on the data stored in the EEPROMs 514 and 515 in the laser driver circuit 511.
14 and 515 can be rewritten from the image processor circuit 510 by serial communication control.

Therefore, the system controller 151
When it is determined that Ta exceeds the predetermined time Ti, the system controller 151 sends information for changing the laser power to the image processing unit 102, and the information is transferred from the image processing unit 102 to the image writing unit 103. Will be done. Here, if the laser emission intensity during normal image formation is P0, the actual laser emission intensity Pr
When Ta> Ti, Pr = Ta / Ti × P0 However, the MAX of Ta / Ti is controlled to be 1.5. Here, the MAX light amount is defined because the light amount of the laser is normally monitored in order to avoid the destruction of the laser, and a limiter function of stopping the laser emission when the light amount exceeds a certain amount is provided. . Further, even if the emission intensity of the laser is increased too much, the potential on the photosensitive drum is saturate, and the original effect is lost.

By performing the above control, it is possible to accurately predict the deterioration of the toner, and it is possible to supply a stable image quality.

However, with the above control method, the emission intensity of the laser cannot be changed when there are many idle rotations that do not reach the predetermined time. The toner is deteriorated even after idling for a long time at a time, but the toner is deteriorated even after a relatively long number of idling. Therefore, after the job is completed, the total of Ta and Tb in one job is calculated,
It is effective to operate the black band sequence at the ratio of the total idle rotation and the idle rotation during the job. Therefore, the system controller 151 changes the laser emission intensity under the following conditions.

ΣTa> Ti and ΣTa / ΣTb> a where a is a constant obtained from experiments.
The laser emission intensity at this time is Pr = ΣTa / Ti × P0, where MAX of ΣTa / Ti is controlled to be 1.5.

By performing the above control, it becomes possible to more accurately predict the deterioration of the toner, and it becomes possible to stably supply the image quality.

(Second Embodiment) In the first embodiment,
By changing the emission intensity of the laser that exposes the photosensitive drum 309, deterioration of the image quality (mainly a decrease in density) is prevented, but the same effect can be obtained by controlling the developing bias of the developing device 314. Therefore, in the second embodiment, a method for controlling the developing bias will be described.

FIG. 7 is a control block diagram of the developing bias.
The developing bias control amount determined by the system controller 151 is sent to the high-voltage control unit 155, and a high-voltage unit 156 generates a high-voltage according to the control amount, and the developing device 3
14 are supplied. Here, assuming that the normal developing bias voltage is VDCi, T measured by the measuring means is
The actual developing bias VDCr is controlled by a as follows.

When Ta> Ti, VDCr = 1.1 × VDCi When Ta> 2Ti, VDCr = 1.2 × VDCi Setting the upper limit of the developing bias causes a problem of fogging when the developing bias is too large. Because it does. By the way, as in the first embodiment, the total time between the sheets Ta is controlled as follows.

In the case of ΣTa> Ti and ΣTa / ΣTb> a, VDCr = 1.1 × VDCi In the case of ΣTa> 2Ti and ΣTa / ΣTb> a, VDCr = 1.2 × VDCi It becomes possible to accurately predict the deterioration of the image quality, and it becomes possible to supply a stable image quality.

(Third Embodiment) Further, in the case of using the jumping development using a one-component magnetic developer as a developing system like this apparatus, the toner is changed depending on the amount of water in the air around the apparatus. It is known that the degree of deterioration of the changes. When the amount of water in the air increases, the toner absorbs the water and the surface resistance of the developer particles decreases, so that the amount of charge that the toner should hold cannot be maintained and the developing efficiency decreases.

The sensors 159 also include an environmental sensor for detecting the temperature / humidity around the apparatus, and the environmental sensor can calculate the amount of water in the air around the apparatus. Since the degree of toner deterioration changes according to the amount of water in the air, in the image forming apparatus of the first embodiment, the system controller 151 sets the laser emission intensity determined in the first embodiment to Pr1. Then, the laser emission intensity to be actually emitted is as follows: Water content <9 g / kg Pr = Pr1 Water content <16 g / kg Pr = 1.1 × Pr1 Water content> 16 g / kg Pr = 1.2 × Pr1 However, control is performed so that the MAX of Pr is 1.5P0.

In the image forming apparatus of the second embodiment, the system controller 151 sets the developing bias voltage determined in the second embodiment to VDCr2.
The voltage VDCr actually applied to the developing unit 314 is as follows: When water content is <9 g / kg VDCr = VDCr1 When water content is <16 g / kg VDCr = 1.1 × VD
Cr1 Moisture amount> 16g / kg VDCr = 1.2 × VD
Control is performed so that Cr1 is obtained.

By performing the above control, more stable image quality can be supplied.

[0047]

As described above, according to the present invention, even when the image forming apparatus is used as a multi-print system, by predicting the toner deterioration in the developing device, it is possible to prevent the deterioration of the output image quality, and An image forming apparatus that can provide high-quality output images for a long time and save toner
It can be provided at a low price.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an image processing unit of the present invention.

FIG. 2 is a sectional configuration diagram showing an example of an image forming apparatus of the present invention.

FIG. 3 is a block diagram showing an example of a copy control unit of the present invention.

FIG. 4 is an explanatory view of a sensor arrangement in the vicinity of the registration roller in FIG.

FIG. 5 is an explanatory diagram of a paper feeding sequence.

FIG. 6 is an explanatory diagram of an internal configuration of the writing unit 103.

FIG. 7 is a control configuration diagram of a developing bias.

[Explanation of symbols]

101 image reading unit 102 image processing unit 402 image processing circuit 403 memory

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA14 DA38 DC04 DC05 DE07                       EA02 EA05 EC06 EC14 EC20                       ED16                 2H073 AA02 BA13 BA25 BA33 CA02                 2H076 AB05 AB12 AB22 DA09 DA10                       DA17 DA19

Claims (4)

[Claims] 1. A charging unit for uniformly charging the surface of an image bearing member, an exposing unit for exposing the charged surface of the image bearing member according to image data to form an electrostatic latent image, and the electrostatic latent image. Developing means for developing a toner image by attaching toner to the image;
Transfer means for transferring the toner image formed on the image carrier to a transfer material, fixing means for fixing the toner image on the transfer material, and cleaning means for cleaning the surface of the image carrier after the toner image transfer. A transfer material detecting means for detecting passage of the transfer material in the transfer material conveying path during an image forming operation of an image forming apparatus including a measuring means for measuring a time of a detection signal of the transfer material detecting means, an image A control means for controlling the forming operation, and when the time measured by the measuring means is a specific time or longer, the control condition of each control means for performing the image forming operation is changed. Forming equipment. 2. The control condition controls an exposure unit that forms an electrostatic latent image by exposing the charged surface of the image carrier according to image data according to the amount of time measured by the measuring unit. The image forming apparatus according to claim 1, wherein: 3. The control condition controls a developing unit that adheres toner to the electrostatic latent image and develops it as a toner image according to the amount of time measured by the measuring unit. The image forming apparatus according to Item 1. 4. The image forming apparatus is provided with a water content detecting means for detecting the water content of the surrounding environment, and sets the control condition of each control means for performing the image forming operation according to the water content detected by the water content detecting means. The image forming apparatus according to claim 1, 2 or 3, wherein the image forming apparatus is changed.