JP4006354B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer.
[0002]
[Prior art]
In an image forming apparatus that forms an image on a sheet by an electrophotographic method, a primary sheet feeding unit that feeds sheets one by one from a sheet cassette (or a sheet tray), and a sheet fed to the registration roller by the primary sheet feeding. Paper feeding to the image forming unit is achieved by a two-stage paper feeding operation including a secondary paper feeding to the image forming unit at a timing by the registration rollers. The image forming unit includes a photoconductive drum, and after the toner image formed on the surface of the photoconductive drum is transferred to the paper in the image forming unit, the paper on which the toner image is transferred is fixed to the fixing device. Then, the toner image is fixed on the paper by this fixing device, whereby the formation of the image on the paper is achieved (for example, see Patent Document 1).
[0003]
The processing speed (copy speed, print speed) in this type of image forming apparatus is determined by the time interval (secondary paper feed interval) from the start of the previous secondary paper feed to the start of the next secondary paper feed. For example, in a model in which the secondary paper feed interval is set to 1000 msec when image formation is continuously performed on a plurality of sheets, a maximum of 60 sheets can be sent to the image forming unit per minute. The maximum processing speed is 60 cpm (copy per minute) for a copying machine, and 60 ppm (print per minute) for a printer.
[0004]
[Patent Document 1]
JP 2002-116590 A
[0005]
[Problems to be solved by the invention]
5A and 5B show that in a copying machine with a maximum processing speed of 60 cpm, (a) when the primary paper feeding is performed normally and (b) when the primary paper feeding is delayed, It is a time chart which shows a timing.
When the primary paper feeding is performed normally without causing paper slip (slip of the roller for paper transport) during the primary paper feeding, as shown in FIG. Before the timing to start rotation arrives, the paper reaches the registration roller, and a registration switch for detecting the arrival of the paper at the registration roller is turned on. In other words, the sheet to be secondarily fed next reaches the registration roller before 1000 msec from the start of the previous secondary sheet feeding. Accordingly, in this case, a new secondary paper feed can be started every 1000 msec, and copying onto 60 sheets can be completed in one minute.
[0006]
However, if a paper slip or the like occurs during the primary paper feeding, there is a situation where the paper to be secondarily fed does not reach the registration roller when 1000 msec has elapsed since the start of the secondary paper feeding. Can occur. In that case, the secondary paper feeding is started simultaneously with the arrival of the paper on the registration roller, and the next secondary paper feeding is in response to 1000 msec from the start of the secondary paper feeding performed late. Done. For this reason, the time required for copying onto a predetermined number of sheets is equal to the time that the start of the secondary paper feed is delayed compared to the case where all the primary paper feeds are normally performed (the delay time of the primary paper feed). Min).
[0007]
For example, as shown in FIG. 5B, during the continuous copying on 60 sheets of paper, the primary feed of a certain sheet is delayed, and that sheet is the previous secondary feed. When 1100 msec has passed since the start of the printing, when the registration roller is reached, the time required for copying onto 60 sheets of paper is 100 msec than the time required for the primary feeding of all sheets to be normal. Will only get longer.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to perform primary feeding even when primary feeding delay occurs due to slipping of paper during primary feeding when image formation is continuously performed on a plurality of sheets. An object of the present invention is to provide an image forming apparatus capable of completing image formation on a plurality of sheets in the same time as when no paper delay occurs.
[0008]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the invention according to claim 1 is characterized in that an image forming unit (2) for forming an image on a sheet, and a sheet set at a sheet setting position (4) are transported (51). Primary sheet feeding means (52, 54) for feeding and conveying one sheet at a time, and for feeding the sheet fed by the primary sheet feeding means to the image forming section. A registration roller (53), and a sheet detection means (55) provided in the vicinity of the registration roller and at a position upstream of the registration roller in the sheet conveyance direction, and for detecting the presence or absence of the sheet at the position. A storage means (TMR_BUF) for storing the time to be secured from the previous secondary paper feed to the next secondary paper feed by the registration roller, and in response to the start of the secondary paper feed by the registration roller Start timing operation The first time measuring means (TMR1) that finishes the time measuring operation in response to the elapse of the time stored in the storage means, and the next secondary paper feeding from the start of the previous secondary paper feeding by the registration roller. The second time measuring means (TMR2) for measuring the elapsed time until the start of the printing, and after the start of the previous secondary paper feeding by the registration roller, the paper detection means detects the paper to be secondarily fed next. And the means (6, S3) for starting the next secondary sheet feeding by the registration roller and the next secondary feeding by the registration roller on the condition that the timing operation by the first timing unit has been completed. At the start of paper, the difference between the elapsed time measured by the second time measuring means and the time stored in the storage means is obtained, and the difference is subtracted from the processing speed limit time determined according to the paper size. can get During the an image forming apparatus which comprises a means (6, S9) to be stored in the storage means.
[0009]
In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
According to the above configuration, when a paper slip or the like occurs during the primary paper feeding and the paper reaches the registration roller later than the end of the time measuring operation (time up) of the first time measuring means, the delay occurs. When secondary paper feeding of the arrived paper is started, a time obtained by subtracting the delay time from the processing speed limit time determined according to the paper size is stored in the storage means. Therefore, the first time measuring means starts the time measuring operation in response to the start of the secondary paper feeding of the paper that arrives with a delay, and is a time shorter than the processing speed limit time by the delay time (stored in the storage means). The timekeeping operation ends when the specified time elapses. Therefore, if the next paper arrives at the registration roller when a time shorter by the delay time than the processing speed limit time has elapsed since the start of secondary paper feeding, the paper that has reached the registration roller is The secondary paper is immediately fed. That is, when a situation occurs in which the primary paper feed delay occurs and the secondary paper feed is delayed by a predetermined time, the next secondary paper feed is limited in processing speed from the start of the previous secondary paper feed. It is performed earlier by the delay time than when the time has elapsed. As a result, the delay of the previous secondary paper feed can be recovered, and as a result, the image formation on a plurality of sheets can be completed in the same time as when the primary paper feed delay does not occur. Can do.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic sectional view showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is, for example, a digital copying machine that forms an image on a sheet by an electrophotographic method, and includes a laser scan unit 1 that emits laser light corresponding to image data input from a scanner (not shown), and toner An image forming unit 2 that forms an image by transferring the image onto a sheet; a fixing unit 3 that fixes the toner image transferred onto the sheet by the image forming unit 2; and a plurality of sheets (for example, 100 to 200 sheets) ) And a paper feeding unit 5 for feeding the paper one by one from the paper cassette 4 and supplying the fed paper to the image forming unit 2.
[0011]
The image forming unit 2 includes a photosensitive drum 21, a main charger 22, a developing device 23, and a transfer charger 24 arranged around the photosensitive drum 21. Laser light emitted from the laser scan unit 1 passes between the main charger 22 and the developing device 23 and enters the surface of the photosensitive drum 21.
At the time of image formation, the photosensitive drum 21 is rotationally driven at a constant speed in a predetermined direction. When the surface of the photosensitive drum 21 faces the main charger 22, it is charged to a constant potential by the discharge from the main charger 22, and then the laser beam from the laser scan unit 1 is irradiated to the portion charged to the constant potential. Is done. The charged electric charge is removed from the portion irradiated with the laser beam, whereby an electrostatic latent image corresponding to the image to be formed on the paper is formed on the surface of the photosensitive drum 21. The electrostatic latent image then faces the developing device 23 and is supplied with toner from the developing device 23 to be visualized as a toner image. The toner image formed on the surface of the photosensitive drum 21 in this way is formed between the photosensitive drum 21 and the transfer charger 24 by the discharge from the transfer charger 24 when the photosensitive drum 21 is further rotated and faces the transfer charger 24. It is transferred to the paper that entered between them.
[0012]
The sheet on which the toner image is transferred is guided to the fixing unit 3 by the conveyance belt 25. The fixing unit 3 includes a heat roller 31 and a press roller 32. The sheet guided to the fixing device 3 enters between the heat roller 31 and the press roller 32. Then, the toner image is conveyed while being held between the heat roller 31 and the press roller 32. At this time, the toner image transferred in the image forming unit 2 is fixed on the sheet by being heated and pressed. The sheet after the fixing process is discharged by a discharge roller 33 to a discharge tray (not shown) provided outside the apparatus.
[0013]
The paper feed unit 5 includes a paper feed path 51 from the paper cassette 4 to the image forming unit 2, a pickup roller 52 for separating the sheets stored in the paper cassette 4 one by one and feeding them to the paper feed path 51. , A registration roller 53 for performing secondary paper feeding at the timing of paper feeding to the image forming unit 2, and a conveyance roller 54 for conveying the paper fed by the pickup roller 52 to the registration roller 53. Yes. In the vicinity of the registration roller 53 and upstream of the registration roller 53 in the sheet conveyance direction, a registration switch 55 for detecting the presence or absence of the sheet at that position is provided. The registration switch 55 is turned on when the leading edge of the sheet sent through the paper feed path 51 is detected, the sheet is fed from the registration roller 53 toward the image forming unit 2, and the trailing edge of the sheet has passed. It is a switch that sometimes turns off.
[0014]
Instead of the registration switch 55, a registration sensor that detects the presence / absence of a sheet in the vicinity of the upstream side of the registration roller 53 in a non-contact manner and outputs a signal (Hi / Low signal) corresponding to the presence / absence of the sheet. It may be provided.
FIG. 2 is a block diagram showing an electrical configuration relating to secondary sheet feeding control of the image forming apparatus. This image forming apparatus includes a microcomputer 6 including a CPU, a RAM, and a ROM. In the RAM of the microcomputer 6, a timer buffer TMR_BUF for storing a time value to be secured from the previous secondary paper feed to the next secondary paper feed, and the time value stored in the timer buffer TMR_BUF are set. The first timer TMR1 for measuring the set time value and the time from the start of the previous secondary paper feed until the next secondary paper feed can be started are measured. The second timer TMR2 is provided. The microcomputer 6 receives an on / off signal of the registration switch 55.
[0015]
A driving force from the motor M is applied to the registration roller 53 via a registration clutch (CL) 56. The microcomputer 6 switches the registration clutch 56 on / off based on the on / off signal from the registration switch 55 and the states of the first timer TMR1 and the second timer TMR2, and the like, thereby performing the secondary operation by the registration roller 53. Control feeding.
FIG. 3 is a flowchart showing the flow of processing performed by the microcomputer 6. When an instruction to form an image on a sheet is input by the user of the image forming apparatus (for example, when the copy start key for starting copying is pressed after the number of copies is set), first, the image Is set a processing speed limit time Amsec corresponding to the size of the paper to be formed (step S1). The processing speed limit time Amsec is set such that, for example, when copying (image formation) onto a plurality of sheets is continuously performed, the interval (distance) between the trailing end of the preceding sheet and the leading end of the succeeding sheet is a predetermined interval. The time interval is set to be (for example, 100 mm). The processing speed limit time Amsec thus set is stored in the timer buffer TMR_BUF (step S2).
[0016]
In the meantime, the pickup roller 52 and the transport roller 54 are driven to perform so-called primary paper feeding. That is, by the action of the pickup roller 52, one sheet is sent out from the sheet cassette 4 to the sheet feeding path 51, and the sheet is conveyed to the registration roller 53 by the conveying roller 54. At this time, the registration roller 53 is stopped, and the sheet conveyed to the registration roller 53 stops in a state where the leading end is nipped between a pair of rollers constituting the registration roller 53. The primary feeding of the second and subsequent sheets is performed in synchronization with the start of the secondary feeding by the registration roller 53 of the preceding sheet, for example.
[0017]
After the processing speed limit time Amsec is stored in the timer buffer TMR_BUF, when the secondary paper feeding timing comes, the registration clutch 56 is turned on and the registration roller 53 is driven so that the registration roller 53 is nipped. The stopped paper is secondarily fed (step S3). Then, the processing speed limit time Amsec stored in the timer buffer TMR_BUF is set in the first timer TMR1, and time measurement by the first timer TMR1 is started (step S4). Further, the time measurement by the second timer TMR2 is started at the same time as the time measurement by the first timer TMR1 is started (step S5).
[0018]
After the secondary paper feed is started, it is repeatedly determined whether or not all conditions (secondary paper feed conditions) for starting the secondary paper feed for the succeeding paper are satisfied (step S6). For example, whether the condition that the time limit by the first timer TMR1 has been typed up after the processing speed limit time Amsec has elapsed since the start of the secondary sheet feeding and the condition that the registration switch 55 is turned on are satisfied. It is determined whether or not. When both secondary paper feed conditions are satisfied (YES in step S6), the time measurement by the second timer TMR2 is stopped, and the time measured by the second timer TMR2 so far is stored in the timer buffer TMR_BUF. It is checked whether or not it is longer than the speed limit time Amsec (step S7). That is, the time from the start of the previous secondary paper feed until the secondary paper feed conditions for starting the next secondary paper feed are all satisfied from the processing speed limit time Amsec stored in the timer buffer TMR_BUF. Whether it is too long or not is determined.
[0019]
The sheet to be secondarily fed when the time is counted up by the first timer TMR1 and is normally performed without causing slippage (slip of the transport roller 54, etc.) during the primary feeding. Has reached the registration roller 53 (NO in step S7), the processing speed limit time Amsec set in step S1 is stored in the timer buffer TMR_BUF (step S8). That is, in this case, the processing speed limit time Amsec stored in the timer buffer TMR_BUF is stored and held as it is. Then, the next secondary paper feeding is started (step S3), and the processing speed limit time Amsec stored in the timer buffer TMR_BUF is set in the first timer TMR1, and the time measurement by the first timer TMR1 is started. (Step S4). Further, the time measurement by the second timer TMR2 is started (step S5). Thereafter, it is repeatedly determined whether or not all the conditions for starting the secondary sheet feeding of the succeeding sheet are satisfied (step S6). If this determination is affirmed, the second timer TMR2 until that time determines It is checked again whether or not the measured time is longer than the processing speed limit time Amsec stored in the timer buffer TMR_BUF (step S7).
[0020]
As described above, while the primary paper feeding is normally performed, the processes in steps S3 to S8 are repeatedly performed, and the secondary paper feeding is performed every time the processing speed limit time Amsec elapses. Therefore, it is possible to continuously form images on a plurality of sheets at a processing speed according to the specification of the image forming apparatus.
On the other hand, if a paper slip or the like occurs during the primary paper feeding, the next time until the processing speed limit time Amsec elapses from the start of the previous secondary paper feeding (by the time count by the first timer TMR1 times up) In some cases, the sheet to be secondarily fed does not reach the registration roller 53. In this case, even if the processing speed limit time Amsec elapses, the next secondary paper feeding is not performed until the secondary paper feeding condition that the registration switch 55 is turned on is satisfied, and the process waits. The next secondary paper feeding is performed in response to the paper reaching the registration roller 53 and the registration switch 55 being turned on. Therefore, when the next secondary paper feed is started, the elapsed time from the start of the previous secondary paper feed exceeds the processing speed limit time Amsec stored in the timer buffer TMR_BUF, The determination whether the time measured by the two timer TMR2 is longer than the processing speed limit time Amsec stored in the timer buffer TMR_BUF is affirmed (YES in step S7). In this case, the difference between the time measured by the second timer TMR2 and the processing speed limit time Amsec stored in the timer buffer TMR_BUF is obtained, and the difference is calculated as the processing speed limit time calculated in step S1. The time “Amsec− (TMR2−TMR_BUF)” obtained by subtracting from Amsec is stored in the timer buffer TMR_BUF (step S9).
[0021]
Subsequently, the next secondary paper feed is started (step S3), and the time “Amsec− (TMR2−TMR_BUF)” stored in the timer buffer TMR_BUF is set in the first timer TMR1, and the first timer is set. Time measurement by TMR1 is started (step S4). Further, the time measurement by the second timer TMR2 is started (step S5). Thereafter, it is repeatedly determined whether or not all the conditions for starting the secondary paper feeding of the succeeding paper are satisfied (step S6). That is, the condition that the time “Amsec− (TMR2−TMR_BUF)” has elapsed from the start of the secondary sheet feeding and the time measurement by the first timer TMR1 has been typed up, and the condition that the registration switch 55 is turned on are as follows. It is determined whether both are satisfied. When both secondary paper feed conditions are satisfied (YES in step S6), the time measured by the second timer TMR2 until that time is stored in the timer buffer TMR_BUF “Amsec− (TMR2−TMR_BUF)”. Whether it is longer or not (step S7).
[0022]
As described above, when a paper slip or the like occurs during the primary paper feeding and the paper reaches the registration roller 53 after the time-up of the first timer TMR1, processing is performed for the delayed time “TMR2-TMR_BUF”. Since the time “Amsec− (TMR2−TMR_BUF)”, which is shorter than the speed limit time Amsec, is set in the first timer TMR1, one of the conditions for starting the next secondary paper feeding is the previous secondary paper feeding. This is satisfied when the time “Amsec− (TMR2−TMR_BUF)”, which is shorter than the processing speed limit time Amsec, has elapsed since the start of the paper. Therefore, when image formation is continuously performed on a plurality of sheets, even if a primary paper feed delay occurs due to a paper slip during the primary paper feed, the primary paper feed delay results. It is possible to complete image formation on a plurality of sheets in the same time as when no occurrence occurs.
[0023]
FIG. 4 is a time chart showing the timing of secondary paper feeding in this image forming apparatus when (a) primary paper feeding is performed normally and (b) primary paper feeding delay occurs. It is.
The maximum processing speed of the image forming apparatus is set to a speed at which copying can be performed up to 60 times per minute on a Japanese Industrial Standard A row No. 4 (A4) sheet, that is, 60 cpm (copy per minute). If it is, the processing speed limit time Amsec is calculated as 1000 msec.
[0024]
In this case, while the primary paper feeding is normally performed without causing a paper slip or the like during the primary paper feeding, before 1000 msec elapses from the start of the previous secondary paper feeding, The sheet to be secondarily fed reaches the registration roller 53, and the registration switch 55 is turned on. Therefore, in this case, as shown in FIG. 4A, a new secondary paper feed can be started every 1000 msec. Therefore, copying on 60 sheets of paper can be completed in one minute, and copying at 60 cpm of the maximum processing speed (processing speed as specified) of the image forming apparatus can be achieved.
[0025]
On the other hand, as shown in FIG. 4B, while the copying to a plurality of sheets is continuously performed, the primary feeding of a certain sheet is delayed, and that sheet is the second secondary feeding. When 1100 msec has elapsed from the start of the printing, when the paper reaches the registration roller 53, secondary paper feeding of the paper that has arrived after the delay is started, and the processing speed limit time Amsec is shorter by 100 msec than 1000 msec. 900 msec is set in the first timer TMR1, and time measurement by the first timer TMR1 is started. Therefore, when the time measured by the first timer TMR1 is timed up (when 900 msec has elapsed since the start of the secondary paper feeding of the paper that has arrived after reaching the registration roller 53), the next paper reaches the registration roller 53. If so, the secondary feeding of the paper is started immediately. That is, when the primary paper feed delay occurs and the secondary paper feed is delayed by 100 msec from 1000 msec, the next secondary paper feed is 1000 msec from the start of the previous secondary paper feed. It is performed at a time point that is 100 seconds earlier than the time point when the time elapses. As a result, the delay of the previous secondary paper feed can be recovered, and as a result, the image formation on a plurality of sheets can be completed in the same time as when the primary paper feed delay does not occur. Can do.
[0026]
Note that the delay of the primary paper feed of a certain sheet is large, and when the time shorter than the processing speed limit time Amsec has elapsed since the secondary paper feed of the delayed sheet, the next sheet is If the registration roller 53 has not been reached, the difference between the time measured by the second timer TMR2 until the next sheet reaches the registration roller 53 and the time stored in the timer buffer TMR_BUF is obtained. The time obtained by subtracting the difference from the processing speed limit time Amsec is stored in the timer buffer TMR_BUF. Then, secondary feeding of the next sheet is started, and the time stored in the timer buffer TMR_BUF is stored in the first timer TMR1.
[0027]
For example, a certain sheet reaches the registration roller 53 when 1300 msec has elapsed from the start of the previous secondary paper feed, and 700 msec (= 1000-300 msec) is the first timer TMR1 when the secondary paper feed of the paper starts. When the first timer TMR1 starts counting, the next paper arrives at the registration roller 53 when 800 msec has elapsed from the start of the secondary paper feeding of the paper that arrived earlier. A difference of 100 msec between the time of 800 msec measured by the second timer TMR2 and the time of 700 msec stored in the timer buffer TMR_BUF is obtained, and the difference of 100 msec is obtained by subtracting from the processing speed limit time of 1000 msec to 900 msec. Is the timer buffer TMR_BU It is stored in. Then, secondary feeding of the next sheet is started, and the time 900 msec stored in the timer buffer TMR_BUF is stored in the first timer TMR1. That is, when a certain sheet arrives at the registration roller 53 with a large delay, the subsequent secondary sheet feeding interval of the plurality of sheets is shortened from the processing speed limit time Amsec of 1000 msec.
[0028]
Although one embodiment of the present invention has been described above, the present invention can be implemented in other forms. For example, in the above embodiment, the case where the present invention is applied to a digital copying machine is taken as an example, but the present invention can also be applied to a digital printer. In this case, the image data to be formed on the paper is input to the laser scan unit 1 via a communication cable from a personal computer (not shown) or the like.
[0029]
Further, not limited to a digital image forming apparatus, a so-called analog copying machine that guides reflected light from a document to the surface of the photosensitive drum 21 to form an electrostatic latent image on the surface of the photosensitive drum 21. The present invention can also be applied to.
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an internal configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating an electrical configuration related to secondary sheet feeding control of the image forming apparatus.
FIG. 3 is a flowchart showing a flow of processing performed by a microcomputer.
FIG. 4 is a time chart showing the timing of secondary paper feeding in the image forming apparatus when (a) primary paper feeding is performed normally and (b) primary paper feeding delay occurs. It is.
FIGS. 5A and 5B are diagrams illustrating a timing of secondary sheet feeding when (a) primary sheet feeding is normally performed and (b) primary feeding delay occurs in a conventional image forming apparatus. It is a chart.
[Explanation of symbols]
2 Image forming unit
4 Paper cassette
5 Paper feeder
6 Microcomputer
51 Paper path
52 Pickup roller
53 Registration Roller
54 Transport roller
55 resist switch
56 resist clutch
TMR_BUF Timer buffer
TMR1 first timer
TMR2 second timer

Claims (1)

An image forming unit for forming an image on paper;
A primary paper feeding unit that feeds the paper set at the paper setting position one by one to the transport path;
A registration roller for secondarily feeding the sheet fed through the conveyance path by the primary sheet feeding unit to the image forming unit;
A sheet detection means provided in the vicinity of the registration roller and at a position upstream of the registration roller in the sheet conveying direction, for detecting the presence or absence of the sheet at the position;
Storage means for storing the time to be secured from the previous secondary paper feed to the next secondary paper feed by the registration roller;
First timing means for starting a timing operation in response to the start of secondary paper feeding by the registration roller and ending the timing operation in response to elapse of the time stored in the storage means;
Second time measuring means for measuring an elapsed time from the start of the previous secondary paper feed by the registration roller to the start of the next secondary paper feed;
On the condition that after the start of the secondary feeding by the registration roller, the paper to be secondarily fed is detected by the paper detection means, and the timing operation by the first timing means is completed. Means for starting the next secondary paper feeding by the registration roller;
At the start of the next secondary paper feeding by the registration roller, the difference between the elapsed time measured by the second time measuring means and the time stored in the storage means is obtained, and the difference is determined according to the paper size. And a means for storing in the storage means a time obtained by subtracting from the processing speed limit time.

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