JPH11194560A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reduction in productivity resulted from the difference in carrying passage length in switching of a paper feed tray, and prevent a malfunction such as generation of wasteful paper in the switching by judging the propriety of execution of a paper feeding interval keeping tray switching processing. SOLUTION: A paper feed tray 50 detects the paper sheet residue in multistage by detecting the detecting element of an elevator tray raised according to the consumption of paper sheets by a main body-side paper residue sensor 51. The numerical value every total output image is inputted by use of an input means, and the initial value of the number of residual feed papers is set. It is judged whether the execution of a paper feeding interval keeping tray switching is proper or not when a tray switching is not in execution. When the number of residue feed papers is a prescribed value or less, it is judged that the execution of the paper feeding interval keeping tray switching is not proper regardless of the detection result of the paper residue sensor 51, and a single tray switching is selected. On the other hand, when the number of residual feed papers is more than the prescribed value, the execution of paper feeding interval keeping tray switching is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, etc., and more particularly, to an automatic paper feed tray used when paper in a currently used paper feed tray runs out. The present invention also relates to an image forming apparatus having a sheet feeding device for performing a limitless sheet feeding process for switching to another sheet feeding tray.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, when sheets in a tray are completed during continuous output of images (for example, during continuous copying or continuous printing) (that is, in the case of paper end), the operation is temporarily suspended. Things are common.
On the other hand, when a plurality of transfer material storage units (for example, a paper feed cassette, a paper feed tray, etc .; hereinafter, referred to as a “paper feed tray”) are provided, and sheets of the same size are stored in another paper feed tray. The limitless paper feed function automatically switches to another paper tray and continues output when the paper in the paper tray that is being used runs out during continuous image output (that is, during continuous paper feed). There is also known an image forming apparatus having:

Normally, during continuous paper feeding, it is not possible to determine whether or not there is the next paper, that is, whether it is the paper end, until the paper is completely removed from the paper feeding tray. For this reason, in an apparatus such as an image forming apparatus provided with an intermediate transfer belt, which has a long image path (time from the start of writing an image (for example, the start of a scanner in a copying machine) to the transfer of an image to a sheet), the image Depending on the relationship between the path and the paper feed path (the time from the start of paper feed for each paper until the paper reaches the transfer position), the repeat interval of continuous output, the combination of paper sizes, etc. Even if an attempt is made to interrupt the image forming process at the time of detection, the image forming operation may already be started at that time. In such a case, the paper feed path of the paper feed tray (hereinafter, referred to as “switch destination tray”) switched by the limitless paper feed is the paper end in use (hereinafter, “in use paper tray”). If the length is longer than the paper feeding path of the "tray", the paper does not reach the transfer position at the transfer timing to the paper even if the limitless paper feeding is performed, and there is a disadvantage that the image forming operation is wasted.

In order to eliminate such inconveniences, Japanese Patent Application Laid-Open No. Hei 7-112080 discloses that an intermediate transfer belt is provided which allows transfer points of a photoconductor and a paper transfer unit to be independently contacted and separated from each other. In the image forming apparatus for transferring the image formed on the photoreceptor at the end of the paper during the continuous image forming operation, the image forming apparatus transfers the image formed on the photoreceptor to the paper via the intermediate transfer belt. While the transfer of the image from the photoconductor to the intermediate transfer belt is continued, the transfer operation of the transferred image to the paper is interrupted, and the intermediate transfer belt is switched to another sheet feeding means while the intermediate transfer belt idles. An image forming apparatus, comprising: a control unit that feeds an image on the intermediate transfer belt that spins on the fed sheet at a timing to transfer the image on the fed sheet, thereby continuing the image forming operation. Forming apparatus "has been proposed. In this apparatus, when a paper end occurs during continuous image formation output by feeding from a sheet feeding tray, if image formation on a photoconductor is started at that time, the formed image is transferred to an intermediate transfer belt. And the paper transfer unit is separated from the intermediate transfer belt to interrupt the paper transfer. Then, the intermediate transfer belt is also separated from the photoreceptor, and while the intermediate transfer belt idles once, it is switched to another sheet cassette by limitless sheet feeding and fed, and an image on the belt is taken at a transfer timing. Transfer to paper. Since the intermediate transfer belt runs idle, limitless sheet feeding can be performed by switching to a cassette having a longer sheet feeding path.

[0005] However, when performing limitless paper feeding, when the paper transport path length (or paper feeding path) of the switched paper tray becomes longer than that of the paper tray before switching, for example, the used tray is not used. If the paper supply from the switching destination tray is started at the time when it is confirmed that there is no paper, the paper supply interval may be widened at the time of switching. This results in reduced productivity. In the technique disclosed in Japanese Patent Application Laid-Open No. 7-112080, it is intended that the toner image already formed on the intermediate transfer belt is not wasted when the paper feed tray is switched. Therefore, it is not possible to prevent a decrease in productivity due to an increase in the paper feed interval when the paper feed tray is switched.

FIG. 11 shows that there is no paper in the paper tray being used.
Switch, change the paper tray and feed paper.
Tray cut in conventional limitless paper feed control
FIG. 9 is a schematic diagram illustrating a paper feed delay at the time of replacement. here
If the paper feed path is lengthened by switching the paper tray,
Is shown. FIG. 11A shows a paper feed tray switch.
Tray in use (tray A) at the time of
This is to explain the sheet feeding timing of B). here
Is the paper feed path difference L between tray A and tray B
If it is larger than C, L> CT_DThe condition
I am thinking of satisfying. Where T_DIs for each
When it takes from the start of paper feeding to the detection of the remaining amount of paper
Between. The remaining paper level is detected when the paper being fed is
It was decided that this would be possible after completely leaving Ray.
In the example of FIG. _ThreeAfter paper is fed,
Switch trays as soon as the par end is confirmed
And from tray B to B₁Paper is being fed. this
Time, the paper feed interval (time) C from the same paper feed tray is always
It is constant. However, tray B is supplied more than tray A.
Since the paper path is long and satisfies the above conditions, FIG.
As shown, the final sheet A from tray A_ThreeAnd tray B
Their first form B₁, The paper feed interval C ′ (C <
C '). Therefore, in this case, cut the paper tray.
Feeding is delayed when changing.

On the other hand, as a technique for shortening the paper feeding interval, there is known an alternate paper feeding system in which paper feeding operations are alternately performed using a plurality of paper feeding trays (for example, Japanese Patent Laid-Open No. 6-8 / 1994).
0263). However, this technology
It does not correspond to the limitless sheet feeding, and cannot prevent the above-described decrease in productivity when the sheet tray is switched in the limitless sheet feeding.

[0008]

SUMMARY OF THE INVENTION The present invention prevents a decrease in productivity due to a difference in transport path length (paper feed path) when switching paper feed trays when performing limitless paper feed. In particular, it is an object of the present invention to prevent a malfunction such as the generation of wasted paper when switching the paper feed tray.

[0009]

According to the present invention, there is provided a transfer material storing means for storing a transfer material, and a transfer material capable of detecting a remaining amount of the transfer material stored in the transfer material storage means. The transfer material remaining means of the transfer material storage means being used during continuous output of a plurality of images is not more than a preset value. A feed interval maintaining tray switching process that switches the transfer material storage unit used for feeding without changing the feed interval when the paper remaining amount detecting unit detects the feed interval; The image forming apparatus is provided with a sheet feeding control unit that determines whether the process is appropriate or not, and executes the sheet interval maintaining tray switching process only when the process is determined to be appropriate. .

The above-mentioned preset value as a condition for starting the paper feed interval switching process depends on the configuration of the image forming apparatus.
In particular, it is determined based on the relationship of the paper feed path between the paper feed tray in use and the paper feed tray after switching. At that time, when performing conventional limitless paper feeding, the paper feed interval is delayed between the last paper from the paper tray before switching and the first paper from the paper tray after switching. When the paper feed path is related, the paper feed from the paper feed tray after switching is started so that at least the number of papers to compensate for the delay remains in the paper feed tray before switching. A value needs to be set.

As materials for judging whether or not the sheet feeding interval maintenance tray switching process is appropriate, the remaining sheet number of sheets for continuous output (output image sheet value) and the image forming time are selected according to the configuration of the image forming apparatus and the processing procedure. It is advantageous to use the remaining output copy value, the remaining document number value, and the like for the document.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a copying machine as an example of an image forming apparatus to which the present invention is applied. The copying machine 1 shown in FIG. 1 mainly includes a copying machine main body 10, a sheet feeding device 20, an automatic document feeder 30, and an optional device (sorter stapler) 40. This copying machine is a conventionally well-known electrophotographic analog copying machine, and its basic operation and the like will not be described. Further, the sheet feeder 20 and the automatic document feeder 3
The configuration and operation of the 0 and the sorter stapler 40 are the same as those of the conventional well-known device, and thus the description thereof is omitted.

The copier body 10 includes an image forming unit 2, an exposure device 3,
The image forming apparatus includes a fixing device 4, a double-sided unit 5 serving as a transfer material storage unit, a paper feed tray 6, and the like. The paper feeder 20 is provided with three-stage paper feed trays 7, 8, and 9 as transfer material storage means. Therefore, the copying machine 1 has a total of four levels of paper feed trays including the main body 10 and the paper feeder 20. Each sheet feed tray including the duplex unit 5 has a transfer material remaining amount detecting means (hereinafter, referred to as a transfer material remaining amount detecting means) for detecting the remaining amount of paper.
This is referred to as “paper remaining amount detection means”. As the paper remaining amount detecting means, an arbitrary structure can be used. For example, the remaining amount of paper is multi-stage (in stages)
A mechanism with a detectable mechanism can be considered. FIG. 2 shows an example of the remaining paper amount detecting means usable in the present invention.

FIG. 2 is a perspective view showing a schematic configuration of a paper feed tray attached to a copying machine, a printer, or the like.
The paper feed tray 50 is provided with a paper remaining amount sensor 51 on the main body side, and a plurality of detectors are provided on an elevator tray side (not shown). Then, the main body side paper remaining amount sensor 51 detects the detector of the elevator tray that rises with the consumption of the paper, so that the remaining paper amount is detected in multiple stages. In addition, the present invention is not limited to the configuration illustrated here, and a sheet remaining amount detection unit having an arbitrary configuration can be used in the present invention.

Here, in the limitless sheet feeding performed by the image forming apparatus to which the present invention is applied, the sheet feeding control for switching the sheet feeding tray while maintaining the sheet feeding interval (in this specification, “sheet feeding interval maintaining tray switching processing” ) Will be described with reference to FIG. Although FIG. 3 shows the operation of the image forming apparatus in detail, a basic concept will be briefly described here. FIG. 3A illustrates a tray before switching (a tray in use and a tray A) when the paper feed tray is switched.
This is for explaining the timing of feeding the sheet to and from the post-switching tray (switching destination tray, tray B). When the remaining amount of paper in tray A is detected to be low by the remaining paper amount detecting means, a tray switching process is started, and a paper feed from tray B is instructed. Here, the relationship between the paper feed path of the tray A and tray B, B ₁ sheet of paper feed from the tray B to A ₃ sheets of the paper feed before the tray A is started. In this example, since the sheet feeding path of tray B is longer than the sheet feeding path of tray A, as shown in FIG. 3B, the sheet position on the transport path receives the sheet feeding command with a delay in timing. a ₃ towards the sheet is located in front of the B ₁ sheet which has received the paper feed command to the first. As a result, when switching from tray A to tray B, the same sheet interval C as before is maintained, and sheet feeding is continued. That is, in order to feed paper from the tray B (B ₁ paper) make do with (to maintain the same feeding interval and far), and feeding one sheet (A ₃ paper) from the tray A. The above is the basic concept of the sheet feeding control and the sheet feeding interval maintaining tray switching process used in the image forming apparatus to which the present invention is applied. Further, even after the reference timing of the sheet feeding to the tray B has been shifted by the sheet interval maintaining tray switching process, the tray A
Executing the substitute feeding (Figure 3, A ₄ paper) from the tray A If paper remains on. This will be described later.

By this paper feed control, when the paper feed tray is switched at the time of limitless paper feed, the paper feed interval before the tray change can be maintained. Next, the paper feed control shown in FIG. 3 will be described with reference to the flowcharts shown in FIGS. 4 to 6 show the sheet feeding interval maintaining tray switching process of the sheet feeding tray as a whole. FIG. 4 is a flowchart showing an initial preliminary process in the paper feed interval maintaining tray switching process. FIG. 5 is a flowchart showing preliminary processing such as timing determination prior to the actual tray switching processing. FIG. 6 is a flowchart showing the main body (actual tray switching process) of the actual paper interval maintaining tray switching process, that is, the paper feeding process in which the trays are switched. The paper feed control is performed by the copying machine body 1
This is performed by control means (not shown) of 0.

First, a description will be given with reference to the flowchart of FIG. First, it is determined whether or not the tray switching process is being executed based on ON / OFF of the tray switching process execution flag (S
1). The tray switching process execution flag is set to OFF as an initial value at the start of the image forming process, and is set to “ON” while the tray switching process is being performed, and is set to “OFF” when the tray switching process is completed. In the feeding interval maintaining tray switching process, it is necessary to perform a preliminary process (FIG. 5) such as determination of the feeding timing before the actual tray switching. Therefore, in order to eliminate the trouble of performing the initial preliminary processing (the processing in FIG. 4) again during the execution of the processing, the determination is made by providing the tray switching processing execution flag.

However, other than providing the tray switching process execution flag, there are other methods for determining whether or not the tray switching process is being executed, and these methods can be used. Further, it is also possible to adopt a method in which the preliminary processing is executed only at the start of the actual tray switching processing. Furthermore, although the actual tray switching process becomes complicated, a method that does not determine in advance whether the tray switching process is being executed may be used.

Returning to the flowchart, if the tray switching process is being executed, the process proceeds to the flowchart of FIG.
The sheet feeding process by the actual tray switching process is performed without performing the preliminary process shown in FIG. When the tray switching process is not being executed, the actual tray switching process is executed when the following five conditions are satisfied.

As a first condition, it is determined whether or not the remaining amount of paper in the in-use tray is equal to or less than a preset value based on information on the amount of remaining paper in the currently used paper supply tray (in-use tray) (S2). . If the remaining amount of paper is equal to or greater than the value, the tray switching process is not performed.

As a second condition, it is determined whether or not there is a sheet tray (switch destination tray) that can be switched (S3). Whether the paper feed tray can be switched is determined by using the tray information and confirming that the paper feed tray is in a paper available state. If it is determined that there is no switching destination tray, the tray switching process is not executed.

As a third condition, it is determined whether or not there is a sheet in the tray in use (whether or not there is the next sheet) (S).
4). Depending on the configuration of the sheet remaining amount detecting means, there may be a case where only the sheet remaining amount “none” can be detected. Therefore, if there is no remaining paper in the in-use tray, it is assumed that paper is fed from the switching destination tray previously confirmed in Condition 2 (the in-use tray is switched to another paper feed tray; In the specification, such control of switching the paper feed tray is referred to as “simple tray switching processing”).

As a fourth condition, it is determined whether or not the sheet feeding path of the switching destination tray is longer than the in-use tray (S
5). When comparing the paper feed path of the used tray and the paper feed path of the switch destination tray, if the paper feed path of the used tray is longer, Even if paper feeding is started, the paper can be made in time (the same paper interval can be maintained as before).
After the used tray is completely used, a simple tray switching process using the switching destination tray is performed. The switching destination tray here is the tray confirmed under condition 2.

As a fifth condition, it is determined whether or not the paper is in time when the paper is immediately fed from the switching destination tray (S6). Depending on the configuration of the sheet remaining amount detecting means, when each sheet is fed from the sheet feeding tray, the remaining amount of the sheet (there is no sheet or the remaining amount is equal to or less than the set value) after starting the sheet feeding
It may take some time before it can be determined. Since this time is usually shorter than the paper feed interval, even when a paper feed tray with a slightly longer paper feed path is selected as the switching destination tray (satisfies condition 4), the remaining amount of paper can be confirmed. If the sheet feeding is started immediately after the sheet feeding, there is a possibility that the sheet can be made in time (the same sheet feeding interval can be maintained as before). So, judging this condition, in time (this is,
In other words, if the paper feed tray is switched when the remaining amount of paper is known, this means that the currently used tray is used as it is and the use is continued until there is no remaining amount. If not, the "tray switching process execution flag" is turned on to execute the tray switching process (S7). Then, the process proceeds to the next preliminary processing.

As described above, five conditions are set, and when those conditions are satisfied, an actual tray switching process is executed.
If these conditions are not satisfied, the tray switching process is not executed at that timing, and the feeding from the tray in use is continued unless the condition 3 is satisfied. If the condition 3 is not satisfied, the sheet feeding tray is simply switched to the switching destination tray selected in the condition 2 to execute sheet feeding (simple tray switching processing).

Here, five conditions are set to execute the actual tray switching process. However, the present invention is not limited to the five conditions. For example, when the conditions 2 and 5 are satisfied (the switching destination tray exists However, the actual tray switching process may be executed when the sheet feeding from the switch destination tray cannot be performed in a normal manner.

Next, preliminary processing such as determination of paper feed timing will be described with reference to the flowchart of FIG. When the actual tray switching process is started, the feeding timing from the tray in use and the feeding timing from the switching destination tray are determined as preliminary processing before the actual tray switching process is performed. This is because, as described above, the actual tray switching process is performed only when the paper feed tray is switched and paper is fed immediately after it is determined that the remaining amount of paper is equal to or less than the predetermined value. This is the case where the maintained image formation cannot be performed (the paper feeding process is delayed and cannot be made) (see condition 5).
(In other cases, the simple tray switching process may be performed when the paper end of the used tray is detected.) Therefore, the feeding from the used tray is performed in order to make the paper fed from the switching destination tray in time. This is because it is necessary to control paper as well. That is, in FIG. 3, the paper (A ₃ ) from the in-use tray is also combined to compensate for the deviation of the paper supply interval when the paper (B ₁ ) is supplied from the switching destination tray and to make the paper supply in time. You need to control.

There are the following three items as preliminary processing relating to the paper feed timing. 1) Determination of the number of sheets fed from the tray in use. That is, the number of sheets to be fed from the in-use tray to calculate the number of sheets to be fed in order to make the feeding from the switching destination tray timely is calculated. That is, by feeding 0 to a plurality of sheets from the in-use tray in accordance with the sheet feeding path of the switching destination tray, the sheets from the switching destination tray are in time. If the feeding path of the switching destination tray is shorter than the feeding path of the used tray, the feeding interval can be maintained without feeding any sheet from the used tray. In this case, the number of sheets fed from the in-use tray determined here is zero. on the other hand,
If the paper feed path of the switching destination tray is long, the paper from the switching destination tray will not be able to keep up unless multiple sheets are fed from the busy tray. Become.

2) Determination of paper feed timing of paper fed from a tray in use. 3) Determination of the paper feed timing of the paper fed from the switching destination tray. In the flowchart of FIG. 5, in the first half, the number t of sheets to be fed (to be fed) from the used tray is obtained.
Assuming that the speed at which the paper moves on the transport path is s, and the difference between the transport distances of the in-use tray and the switching destination tray is d, the condition 4 indicates that the switching destination tray having a longer paper feed path than the in-use tray has The fed sheet is transported on the transport path with a delay of time L (L = d / s). C is a paper feed interval (the time required for the next sheet to pass the same point after passing a point on the sheet conveyance path, that is, the sheet conveyance required to keep the image forming speed from decreasing. spacing), if the time required for a T _D from the sheet feed start until the residual paper check, the positional relationship between the paper feed tray is L <C-T
_{In the case of D,} the number of sheets fed from the in-use tray necessary for timely feeding from the switching destination tray is zero.
When the L = C-T _D by performing the paper feed from the paper feed and switching destination tray from the tray in use at the same time, it is possible to make do with paper feed from switching destination tray. Here, assuming that the number of sheets fed simultaneously is not counted as one, the number of sheets fed from the busy tray is L ≦ C−T _D
0 sheets, one when L> C-T _D, 2 sheets when _{L> 2C-T D, L} > 3 sheets when 3C-T _D, the same applies hereinafter, the paper feed is required when the.

[0030] With reference to the flowchart, first substitutes -T _D to k (S8). Next, a counter t for counting the number of sheets to be fed from the tray in use is reset (S9). Then, the value obtained by adding C to the above k is substituted for k (S10). Next, L and k are compared, and L
Is greater than or equal to k (S11). If L is larger than k, the counter t is incremented and the process returns to before S10.

By the way, at the start of the actual tray switching process, since the immediately preceding sheet feed uses the used tray, the sheet feed timing of the sheet fed from the used tray is Assuming that the paper feed timing is T ₀ , T ₁ = T ₀ + C, T ₂ = T ₁ + C, T ₃ = T ₂ + C,...
.., T _i = T _i-1 + C, and paper is fed at intervals of the paper feeding interval C.

Therefore, if L is not larger than k in S11, the paper feed timing is obtained at intervals of the paper feed interval C from T ₁ = T ₀ + C (S13, S14, S15), and the process ends when i = t. (S16).

Here, the first sheet fed from the switching destination tray only needs to be at a position delayed by the time C from the last sheet fed from the busy tray (the paper fed from the busy tray). It only needs to be connected to paper at regular intervals). Therefore, assuming that the paper feed timing of the switching destination tray is Tx,
x = Tt + CL. Tt indicates the timing of feeding the last sheet fed from the tray in use.

This formula indicates that the sheet fed from the switching destination tray must be at a position delayed by C from the last sheet fed from the busy tray. This means that it must be performed at a timing earlier by the time L.

Returning to the flowchart, Tx is obtained as the feed timing information of the switching destination tray (S17), and the process proceeds to the actual tray switching process (FIG. 6). Thus, the preliminary processing for the actual tray switching processing is completed. By determining the first sheet feed timing of the switching destination tray, it is possible to move the sheet feeding tray serving as a reference for feeding from the currently used tray to the switching destination tray. By performing the subsequent sheet feeding on the basis of the switching destination tray, the sheet feeding operation without delay can be continued.

In this case, by executing the actual tray switching process when the above condition 5 (FIG. 4) is satisfied, the process is limited to the case where one or more sheets need to be fed from the tray in use. However, it is easy to include the case where there is no need to feed paper from the tray being used in the actual execution of the tray switching process. That is, it is not always necessary to set the condition 5. In that case, the loop start condition from S14 in FIG. 5 is changed from i = 2 to i = 1,
The processing of T ₁ = T ₀ + C of 13 may be deleted.

In the above example, the initial value 0 of the counter t is set as the number of sheets t fed from the tray in use. However, the initial value is not limited, and any value may be used. Processing can be realized.

Next, the actual part of the paper feed interval maintaining tray switching process (actual tray switching process) will be described. The basic operation of the actual tray switching process is characterized in that it is always aware that paper is fed from the switching destination tray. If it is time to feed paper from the switching destination tray, and there is paper remaining in the used tray, the paper feeding from the used tray is substituted for the paper feeding that should have been performed from the switching destination tray, If it is not possible to determine the presence or absence of paper in the used tray (the paper feeding process performed from the used tray has not been completed, that is, there is a possibility that the paper may run out after paper is fed) The operation is to feed paper. This is based on the fact that the transport path of the tray in use is shorter than the transport path of the switching destination tray (from condition 4 above).

In the above-mentioned case, when it is time to feed paper from the switching destination tray, if there is any paper remaining in the used tray, the paper feeding from the switching destination tray should be started. the substitute "by the paper feeding from the, in FIG. 3, is shown by feeding a sheet a ₄ from the next tray a paper B ₁ from the tray B.

The actual tray switching process shown in FIG.
It is executed from two routes. That is, it is determined that the tray switching process is being executed (when the “tray switching process execution flag” is ON) after (the route from) after the execution of the initial preliminary process in FIG. 4 and in S1 of FIG. 2)
One.

In the flowchart of FIG.
When the paper feed timing Ti from the busy tray is reached, paper is fed from the busy tray. Similarly, in S19,
When the paper feed timing Tx from the switching destination tray comes, paper is fed from the switching destination tray. However, there is an exception that the sheet is not fed from the switching destination tray even when the timing Tx comes. That is, when the paper feed timing Tx is determined by the route (A) shown in the latter half of the flowchart, and when the paper passes from this route (A), the paper feed from the in-use tray becomes the paper feed from the switching destination tray. This is because it is performed as a substitute for. This processing will be described later in detail.

After the paper is fed, a timing T (T = T) when a time C has elapsed from the paper feed timing Tx from the switching destination tray.
(Tx + C) is determined (S20), and when the timing T is reached, the process of determining the next paper feed tray and the paper feed timing is started. Timing T
If not, paper feeding is not performed because it is not the time to perform paper feeding.

Here, since C means a paper feed interval, this timing T is a paper feed timing assuming that the next paper feed will be performed from the switching destination tray. By setting the next paper feed tray as the destination tray longer than the paper feed path, it is possible to prevent a paper feed delay even when the actual paper feed is performed from the used tray with the short paper feed path. .

At the time T, it is checked whether or not there is any scheduled paper feed processing that has not been executed from the used tray (S21). Is generated (S25), and the sheet is immediately fed unconditionally from the switching destination tray. At this time, T
The value of x is set as Tx = Tx + C. This means that if paper feeding from the used tray is not completed, the remaining amount of paper in the used tray cannot be checked and substitute paper feeding by the used tray cannot be performed (paper in the used tray runs out). Because it will happen.

At the time T, it is checked whether or not there is any scheduled sheet feeding process that has not been performed from the tray in use (S21). If the scheduled sheet feeding is completed, Next, it is determined whether it is time to check the remaining amount of paper in the tray in use by the remaining paper amount detecting means (S22). Even when the timing is not reached, the sheet is immediately supplied from the switching destination tray. At this time,
The value of Tx is set as Tx = Tx + C. Normally, it often takes some time after the start of feeding of each sheet until the remaining amount of sheets in the sheet feed tray can be checked. This is because the sheet that has started feeding may interfere with the remaining amount detection. Therefore, there is a timing at which the remaining amount of paper cannot be confirmed even after the last paper feeding timing. Therefore, in that case, paper is fed from the switching destination tray.

If it is time to check the remaining amount of paper, it is next determined whether there is any paper in the tray being used (S23). That is, if all the scheduled paper feeds from the used tray have been executed at the timing T and the timing T is after the timing at which the remaining paper amount can be confirmed by the remaining paper detecting means, the remaining paper of the used tray is Check the quantity. If there is paper, it can be determined that substitute paper feeding by the in-use tray is possible, so that this time paper feeding is performed using the in-use tray and the switching destination tray is not used.
In order to perform the substitute sheet feeding using the used tray, “used tray sheet feeding timing information Ti” is generated (S24).
The paper feed timing Ti of the tray in use is expressed by the following equation: Ti = Tx + C + L. In this case, the sheet feeding process of the switching destination tray is replaced with the sheet feeding from the tray in use.
The process proceeds from S24 to S25, where Tx is updated to Tx + C in the same manner as when the switching destination tray is used, and the next paper feed tray is assumed to be the switching destination tray. That is, the switching destination tray feed timing information is generated through the route (A).

However, as described above, in this case, paper is not fed even at the timing Tx. This is T
This is because the paper originally fed at the timing of x is fed from the busy tray at the timing of Ti. Whether Tx is obtained through the route (A) can be determined by providing a flag or the like that is turned on when the vehicle passes through the route (A).

Thereafter, the same processing is repeated until there is no more paper in the busy tray. When there is no more paper in the used tray, the "tray switching process execution flag" is turned off to indicate that the tray switching process has been completed (S
26). As a result, it can be determined that the normal sheet feeding state in which the tray switching process has not been performed.

In the above-described paper feed interval maintaining tray switching process,
The most significant feature is that the paper feeding process during the actual tray switching process is performed based on the switching destination tray instead of the in-use tray. If the paper feed tray is switched after confirming that there is no remaining paper, the paper feed from the switch destination tray may be delayed. Therefore, before the remaining amount of paper becomes zero, the paper supply interval is widened (paper supply is delayed).
At the timing when it can be confirmed that the paper remains in the used tray, the paper is fed to the used tray in such a manner that it is interrupted during the paper feeding from the switching destination tray.

As described above, when the reference of the paper feed control is shifted to the paper feed tray after the switching, when the paper in the used tray runs out, the paper is fed from the tray to be switched to as it is, and the paper is fed to the used tray. When there is still a sheet, the operation of replacing the sheet to be fed from the switching destination tray with the sheet from the currently used tray can be performed, and the sheet feeding delay due to the tray switching can be eliminated. Also, there is a possibility that a paper feeding delay may occur when the paper feeding reference tray is moved from the used tray to the switching destination tray. Therefore, that part is processed in advance as preliminary processing, and the necessary paper feeding operation is performed. Timing is determined.

With reference to FIG. 3, a description will be given of the paper feed timing in the paper feed interval maintaining tray switching process in the image forming apparatus to which the present invention is applied, and the paper position on the transport path due to the paper feed timing.

As shown in FIG. 3, when it is determined that the remaining amount of paper in the tray A (in-use tray) is small, the tray switching processing in the paper supply interval maintaining tray switching processing is started, and the tray B (switch destination tray) is started. Tray) is determined.
In order to prevent the delay of the paper on the paper transport path when the tray is switched, that is, the paper (B
To compensate for opening the feeding interval due to ₁ sheet) transport time is performed one sheet feed from tray A to (A ₃ paper). A ₃ paper from the tray A is, B ₁ from the tray B
Although delayed sheet feeding is started from the sheet, it is positioned in front of the B ₁ sheet on the conveyance path by the difference between the sheet feeding path.
Further, as described above, after the reference of the sheet feeding control is shifted to the tray B also, if paper remains in the tray A, executes a substitute paper feed from the tray A (A ₄ paper is fed ).

The above-described limitless sheet feeding (sheet feeding interval maintenance tray switching) based on sheet feeding control using the detection result of the sheet remaining amount detecting means, which is performed in the image forming apparatus to which the present invention is applied. Processing). A feature of the present invention is that the paper feed interval maintaining tray switching process is not always executed when the remaining amount of paper in the used tray becomes equal to or less than a predetermined value. Only when all outputs in the continuous image formation being executed in the middle are not completed, the sheet feeding operation according to the sheet interval maintaining tray switching process is performed using a plurality of sheet trays including the tray in use. . According to the present invention, by performing such a paper feed control, it is possible to prevent a malfunction such as generation of waste paper that may occur when performing limitless paper feed based on the above-described paper feed interval maintaining tray switching process. be able to.

Next, a description will be given of a process for determining whether or not to execute the paper feed interval maintaining tray switching process according to the present invention. First,
As a first embodiment of the present invention, a case will be described in which it is determined whether the execution of the paper feed interval maintaining tray switching process is appropriate, taking into account the remaining paper number (the expected output image number). FIG. 7 is a schematic flowchart showing an example of a process based on this embodiment. In the image forming apparatus according to the present embodiment, the total number of sheets fed (the total number of output images) is stored in a recording unit such as a memory. (This means the total number of output images to be output from the image forming apparatus in the image forming / outputting process (in this embodiment, continuous copying)). Further, it has an input unit as a unit for recognizing the total output image number value. It is the remaining output image number value calculated from the total output image number value (that is, the remaining sheet number) that is actually used to determine whether it is appropriate to perform the sheet feeding interval maintaining tray switching process. Instead of the total output image number value, the remaining sheet number value may be input.

There are various methods for inputting the total output image number value. For example, it is as follows: 1) The user of the image forming apparatus directly inputs a total output image number value using a numeric keypad or the like attached to the image forming apparatus, and stores it in a memory or the like; 2) A total output image number value is input from outside using some communication means, particularly like an image forming apparatus such as a printer (for example, transmission of information on total number of pages of scheduled output from a computer to a printer). .

Hereinafter, description will be made with reference to the flowchart of FIG. First, a total output image sheet number value (that is, a total sheet feed number value) S is input using the input means as described above (S
101), the initial value of the remaining sheet number W is set to S (S102). Next, it is determined whether or not the tray switching process is currently being executed (S103). If the tray switching process is already being executed (if YES is determined in S103), the sheet feeding is continued based on the currently executed tray switching process. If the tray switching process is not being executed, it is determined whether it is appropriate to execute the paper feed interval maintaining tray switching process (S104). The remaining sheet number W is used as a material for this determination. If the remaining sheet number W is equal to or smaller than the predetermined value Y (W ≦ Y), it is determined that the execution of the sheet feed interval maintaining tray switching process is inappropriate regardless of the value of the detection result of the paper remaining amount sensor 51. Then, a simple tray switching process used in the conventional limitless sheet feeding operation (that is, the sheet feeding tray is switched while allowing an increase in the sheet feeding interval accompanying a change in the sheet feeding path at the time of tray switching) is selected. On the other hand, the condition W ≦
If Y is not satisfied, execution of the paper feed interval maintaining tray switching process is selected. On the basis of the selection result, the sheet feeding process for the next sheet is started (S105), and the remaining sheet number W is set to W-
1 is updated (S106). Here, it is determined whether or not sheet feeding for all output images has been completed (W = 0 or not) (S10).
7) If not completed yet, repeat the processing from S103.

The remaining number of sheets W is the total number of input output images and the number of images fed so far (not yet transferred, but sheets for transferring the image have already been fed. And OT is the value of the number of images fed up to the present in the continuous image forming / outputting process. Meanwhile, Y is determined as follows based on the difference of the feeding path between the tray and the switching destination tray in use: L <in the case of _{C-T D Y = 0;} L
≧ In the case of C-T _D is Y = 1; in the case of L ≧ 2C-T _D is Y = 3; in the case of _{L ≧ 3C-T D Y =} 5; .... As described above, L is the difference between the paper feeding path and the switching destination tray of the paper feed path of the tray in use, C is feeding interval, T _D is the start feeding of the paper from the start of each of the sheets This is the time required for detecting the remaining amount of paper. The relationship between the two is that the remaining number of sheets is fed from both trays until the paper fed from the destination tray is connected to the paper fed from the busy tray at the same paper feed interval. If the total number of sheets is less than the total number of sheets to be fed, it means that the tray switching process based on the paper feed interval maintaining tray switching process is not performed. For example, when two sheets need to be fed from the busy tray before the sheets fed from the switching destination tray are connected while maintaining the sheet feeding interval C (L ≧ 2C−T _D
At this time, while two sheets are being fed from the busy tray, another sheet is fed from the switching destination tray following the first sheet. This is because the sheet is continuously supplied so that the switching destination tray maintains the sheet interval. in this case,
Since a total of four sheets are to be fed, it is necessary to determine that the tray switching process based on the feed interval maintaining tray switching process is not to be performed when the remaining number of sheets is three or less.

In the tray switching process based on the feed interval maintaining tray switching process, the sheet feeding from the switching destination tray is performed in order to keep the paper fed from the switching destination tray in time (maintaining the current feeding interval). It is necessary to continue feeding paper from the tray in use even after the paper. Thus, for example, if all paper feeding according to the continuous image formation by B ₁ sheet of paper feed from the switching destination tray in the example of FIG. 3 is completed, if the original A ₃ sheets of paper feeding is not required is there. However, feeding of the A ₃ paper if trying to keep feeding interval is essential, B ₁ paper that has already been starts feeding the resulting wasted paper. In order to prevent this situation, it is determined whether or not to execute the feed interval maintaining tray switching process based on the remaining number of fed sheets. That is, for W and Y determined from the above relationship, when the relationship of W ≦ Y is satisfied, the feeding interval maintaining tray switching process is not performed, so that the feeding interval at the time of tray switching is prevented from increasing. It is possible to prevent the sheet that has been fed from remaining on the sheet transport path at the end of the continuous image formation.

Next, a second embodiment of the present invention, based on the number of output copies O _B per sheet of original image (original)
A case where it is determined whether or not the execution of the paper feed interval maintaining tray switching process is appropriate will be described. The number of output copies is often input in a normal operation procedure even in a conventional image forming apparatus. For example, in a copying machine, when copying a document, after setting the document on a pressure plate (contact glass) or an automatic document feeder, information on how many copies are to be made (also referred to as the number of copies and the number of copies). Is directly input as a numerical value from a numeric keypad or the like to obtain a required number of copies of an image. In the case of a printer as well, it is common to input the number of output copies when setting printing conditions. Therefore, by using the number of output copies as the basis for execution determination as in the present embodiment, it is necessary to newly input special information (such as the total number of output images) for determining execution of the paper feed interval maintaining tray switching process. Since there is no work efficiency, it is possible to make an execution decision without lowering work efficiency.

[0060] In this embodiment, when the remaining output copies W _B about the original image currently being image formation is less than a predetermined value Y, that is, when the W _B ≦ Y is, execution of the feeding interval maintaining tray switching process not Judgment is appropriate, and execution of the simple tray switching process is selected. Here, the predetermined value Y may be set in the same manner as in the above embodiment.

Next, as a third embodiment of the present invention, illustrating a case where the number of documents with output copies O _B (original image count) even considering the execution propriety determination process of tray switching process. FIG. 8 is a flowchart schematically illustrating an example of a processing procedure based on the present embodiment. The number of originals used here does not always require an accurate number of originals. This embodiment can be applied to any image forming apparatus that can determine at least whether or not there is a next original.

[0062] In the present embodiment, the number of output copies O _B input in S201, the untreated original number value n is detected in each case
And (necessarily untreated need not be the exact value of the number of documents), the current image formation is updated by subtracting 1 at S206 the initial value in step S202 after the start feeding of the set and each of the paper O _B with the remaining output copy number W _B of the document in the estimates whether the output of the number of sheets after this minimum is carried out. Then, when the condition that the remaining output number of sheets W _B + nO _B is equal to or less than a predetermined value Y described in the first embodiment simply select tray switching process as unsuitable execution of paper feeding interval maintaining tray switching process, If this condition is not satisfied, the paper feed interval maintaining tray switching process is selected (S20).
4).

The following is a description along the flowchart of FIG.
I will tell. Remaining output copies W_BIs the number of output copies O_BSet to
Is performed (S202). Next, is the tray switching process in progress?
It is determined whether or not it is (S203). Tray switching process is executed
If it is medium, continue. Tray switching process is in progress
If not, is it possible to execute the feed interval maintenance tray switching process?
Whether the condition W_B+ NO_B≤ Y
Is determined (S204). Condition is satisfied in S204
If so, select to execute the simple tray switching process, and
If the condition is not satisfied, the feed interval maintenance tray switching process is executed.
Select a row. Remaining output copies W_BThe value of
Or, each time the sheet is fed, 1 is subtracted (S
206). Where W_BWhen the value of becomes zero,
W_BIs O _BIs set to (S208). In S209
If the feeding of all the images has not been completed,
Repeat the process.

In the image forming apparatus used in this embodiment, when there are a plurality of originals, the presence or absence of the next original (not only the next original, but at least several originals after the current original) The more effective the number of documents, the better.) In S202 and S208, the next document presence / absence information is checked, and the number of remaining documents is set in n. That is,
As the determination condition in S204, if the presence or absence of the next original is unknown or if there is no next original, it is determined that W _B ≦
Y, if the remaining original (untreated document) has been determined that if the W _B + O _B ≦ Y has been finalized that the one at least some, the remaining original is two at least W _B + 2O _B ≦
Y,... Are used. By using this information, the range in which the paper feed interval maintaining tray switching process is determined to be appropriate can be expanded as compared with the case of the second embodiment.

As in the case of the image forming apparatus described in the second embodiment, when the image forming apparatus to be used cannot use (or does not use) the next document presence / absence information on the number of remaining documents, In the flowchart, n = 0 is always set, and the determination condition in S204 is set to W _B ≦ Y.

Next, as the fourth and fifth embodiments of the present invention, a case will be described in which it is determined whether or not the feed interval maintaining tray switching process is to be performed using the input total number of documents.
As the means for inputting the total number of originals, for example, the following can be used: 1) As in the case of the means for inputting the total number of output images in the first embodiment, the number of originals is input by communication or direct input. 2) Automatically count the number of documents using an automatic document feeder (ADF); 3) Automatically count the number of documents using a circulation type automatic document feeder (RDH). In the case where the original is reset after counting the number of originals, the work of resetting the original can be omitted as compared with the above 2). Regardless of which of these means or any other input means is used to input the total number of originals, when the total number of originals G is determined, the total number of originals is added to the judgment material to execute the feed interval maintaining tray switching process. Is determined. If the number of output copies is multiple, even the purpose of deciding the third embodiment as well as the remaining output number of copies W _B.

As a process of making a judgment in consideration of both the total number of originals and the number of output copies, there are roughly two types of image forming procedures used in the conventional image forming apparatus, namely, I.I. An image forming procedure in which a set of image formation for a set number of output copies is collectively performed for each document, and this cycle is repeated for the number of documents; and II. At least two types of processes can be considered in accordance with an image forming procedure in which one cycle is defined as forming an image for the number of documents and this cycle is repeated for the number of copies.

Maintaining the paper feed interval when the present invention is applied to an apparatus (for example, an analog copying machine using an automatic document feeder (ADF)) that forms an image according to the above procedure I (fourth embodiment) FIG. 9 shows a schematic flowchart of an example of the execution suitability determination process of the tray switching process. In this case, when the remaining number of originals was W _G, W _B at S306 +
When the condition that W _G O _B ≦ Y is satisfied, without executing the paper feed interval maintaining tray switching process, which determines to perform a simple tray switching process. At that time, as the initial value of the remaining number of documents W _G is set with G-1 (S302),
The count is decremented by one each time an individual document is processed (feeding for the number of copies) (S311). The initial value of the remaining output copies W _B is set number of output copies O _B (S
304), each time the paper is fed (each time the paper is started), the count is decremented by one (S308). A few minutes of the feeding all for that document has been performed in S309 (which is started), i.e. has become W _B = 0, W _B again O _B
Is set to (S310). If it is determined in step S312 that the sheet feeding for all the sheets (all the images) has not been completed (the term “completed” here means that the sheet feeding for all the images has been started, not the completion of the image transfer). State), and the processing from S305 is repeated.

Next, a case where the present invention is applied to an apparatus for forming an image in accordance with Procedure II (for example, an analog copying machine or a digital copying machine using a recirculating document feeder (RDH)) (fifth embodiment) FIG. 10 shows a schematic flowchart of an example of the processing of determining whether or not the paper feed interval maintaining tray switching processing is appropriate. In this case, W _G + W _{B G} ≦ with S409
When the condition of Y is not satisfied, a paper feed interval maintaining tray switching process is executed. The initial value of the remaining number of documents W _G, inputted document sheets G is set (S406), will be decremented by one count for each start sheet feeding (S41
1). The initial value of the remaining output copy number W _B, O _B is set (S402), is subtracted every time the original number of sheets of paper feeding is performed, that is, by one count each time becomes W _G = 0 (S414) . In this case, W _G is set to re-G (S413). If all paper feeding has not been completed in S415, the processing up to that time (S404 to S415) is repeated.

In the present embodiment, for example, in a digital copying machine capable of storing document information, the number of documents is counted at the time of output processing of the first copy, and the counted number of documents is determined from the time of image output of the second copy and thereafter. It can be modified to use as a material.

FIGS. 7 to 1 used in the description of the above embodiment.
The flowchart shown in FIG. 0 shows only the work steps related to the processing for determining whether or not to execute the paper feed interval maintaining tray switching processing. The determination as to whether or not to execute the sheet feeding interval maintaining tray switching process is not always performed for each image output. In the actual image forming procedure, a step (S10) related to the determination as to whether or not to execute the paper feed interval maintaining tray switching process is performed.
4, S204, S306, and S409) may be incorporated, for example, after S5 of the initial preliminary processing process of the paper feed interval maintaining tray switching process shown in FIG. Further, it may be incorporated in another appropriate position depending on the configuration of the device.

As described above, a copying machine has been described as an example of an image forming apparatus to which the present invention is applied. However, the present invention is applicable to digital copying machines in addition to analog copying machines.
Needless to say, the present invention can be applied to an image forming apparatus such as a printer or a facsimile other than the copying machine.

[0073]

According to the image forming apparatus of the present invention, when the remaining amount of paper becomes smaller than the set value during continuous image formation, paper is fed from the switching destination tray and fed from the busy tray. It is possible to execute the paper feed interval maintenance tray switching process that switches the paper feed tray while feeding paper so that the paper feed interval is kept constant with the paper. It is possible to prevent the occurrence of a paper feed delay problem due to a difference in the paper feed path between the in-use tray and the switching destination tray at the time of switching, and to improve the productivity of image formation. In addition, the image forming apparatus is provided with a paper feed control unit that determines whether or not it is appropriate to execute the paper interval maintaining tray switching process, and executes the paper interval maintaining tray switching process only when it is determined to be appropriate. Therefore, it is possible to avoid such a problem that the output of all the images is completed in the middle of the operation of switching the paper feed tray and waste paper is generated.

The image forming apparatus according to the second aspect determines whether or not the sheet interval maintaining tray switching process is appropriate based on the remaining output image sheet value (that is, the remaining sheet number). It is possible to accurately determine whether the processing can be executed.

In the image forming apparatus according to the third aspect, it is determined whether or not the execution of the paper feed interval maintenance tray switching process is appropriate based on the number of remaining output copies when forming a plurality of copies of an image from the same document. The remaining output part value can be calculated from the output part value specified first. Generally, the output copy number information is indispensable information for image formation specified by the user of the image forming apparatus. Therefore, it is possible to minimize the information to be input by using this information. It is. For example, in a normal use procedure such as a copying machine, the total number of output images cannot be determined, and in an image forming apparatus requiring a new input procedure, the work efficiency is improved by eliminating the trouble of inputting the total number of images.

In the image forming apparatus according to the fourth aspect, by adding the value of the number of unprocessed originals to the judgment material, the paper feed interval maintaining tray switching process can be performed more accurately than the image forming apparatus according to the third aspect. Applicability can be determined. If the apparatus can detect the presence or absence of an unprocessed document in the image forming process, the same working efficiency as the image forming apparatus according to the third aspect can be maintained. Also, for example, some copying machines have a mechanism for counting the number of documents using an automatic document feeder or the like, and this mechanism may be incorporated in the image forming procedure. Such a device eliminates the need for the user to input the total number of documents. In the case of such an image forming apparatus, information on the total number of documents and information on the number of output copies can be obtained by the conventional operation procedure, and the information can be used together. It is also possible to obtain the same effect as using the number.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a copying machine according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration of an example of a paper feed tray attached to the copying machine shown in FIG.

FIG. 3 is a schematic diagram illustrating a sheet feeding timing and a sheet position on a conveyance path in a tray switching process performed in the image forming apparatus to which the present invention is applied;

FIG. 4 is a flowchart illustrating a preliminary process in a tray switching process executed by the image forming apparatus to which the present invention is applied;

FIG. 5 is a flowchart illustrating a preliminary process such as timing determination in a tray switching process executed by the image forming apparatus to which the present invention is applied;

FIG. 6 is a flowchart illustrating an actual tray switching process in a tray switching process performed by the image forming apparatus to which the present invention is applied;

FIG. 7 is a schematic flowchart of one embodiment of a sheet feeding interval maintenance tray switching processing execution suitability determination process according to the present invention.

FIG. 8 is a schematic flowchart of another embodiment of the sheet feeding interval maintenance tray switching processing execution suitability determination processing according to the present invention.

FIG. 9 is a schematic flowchart of another embodiment of the sheet feeding interval maintenance tray switching processing execution suitability determination processing according to the present invention.

FIG. 10 is a schematic flowchart of another embodiment of the sheet feeding interval maintenance tray switching processing execution suitability determination processing according to the present invention.

FIG. 11 is a schematic diagram illustrating a paper feed delay at the time of tray switching in a conventional apparatus that performs paper feeding by switching trays after confirming that there is no paper in a paper feed tray in use. This is a case where the transport path of the paper feed tray at the switching destination is larger than the paper feed tray in use.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 2 Image forming part 3 Exposure device 4 Fixing unit 5 Duplex unit 6, 7, 8, 9 Paper feed tray 10 Copier main body 20 Paper feeder 30 Automatic document feeder

Claims (6)

[Claims] A plurality of transfer material storage means for storing the transfer material; and a transfer material remaining amount detection means capable of detecting a remaining amount of the transfer material stored in the transfer material storage means. When the transfer material remaining amount detection unit detects that the transfer material remaining amount of the transfer material storage unit being used is equal to or less than a preset value when performing continuous output of a plurality of images, It is determined whether or not it is possible to perform a paper feed interval maintenance tray switching process for switching the transfer material storage unit used for paper feeding without changing the paper feed interval, and to judge whether or not the paper feed interval maintenance tray switching process is appropriate. An image forming apparatus provided with a sheet feeding control unit for executing the sheet feeding interval maintaining tray switching process only when it is determined that the sheet feeding interval is maintained. 2. The method according to claim 1, wherein the sheet feeding control unit recognizes and uses a remaining sheet number in the continuous image output during execution as a material for determining whether or not the sheet feeding interval maintaining tray switching process is appropriate. The image forming apparatus according to claim 1, wherein: 3. The method according to claim 1, wherein the sheet feeding control unit recognizes and uses a remaining output unit value in the continuous image output being executed as a material for determining whether or not the sheet feeding interval maintaining tray switching process is appropriate. The image forming apparatus according to claim 1. 4. The method according to claim 1, wherein the sheet feeding control unit recognizes and uses the number of unprocessed documents in the continuous image output being executed as a material for determining whether or not the sheet feeding interval maintaining tray switching process is appropriate. The image forming apparatus according to claim 1. 5. The image forming apparatus according to claim 2, further comprising means for recognizing and storing the total number of sheets fed in the continuous image output to be executed. 6. The image forming apparatus according to claim 2, further comprising: means for recognizing and storing a numerical value of the output unit; and means for recognizing and storing the value of the number of originals. apparatus.