JP2021060559A - Image forming apparatus - Google Patents

Abstract

To reduce an unnecessary image forming operation with an inexpensive configuration without reducing throughput as much as possible.SOLUTION: An image forming apparatus comprises: an intermediate transfer belt; a cleaning device; a toner recovery container; a recording material loading member, a recording material presence/absence sensor; and a CPU that, when the recording material presence/absence sensor detects the absence of a recording material on the recording material loading member during continuous printing, performs a cleaning operation to remove a toner on the intermediate transfer belt with the cleaning device to recover the toner in the toner recovery container. The CPU controls throughput during the continuous printing (S104, S109) according to the number of times the recording material presence/absence sensor detects the absence of the recording material on the recording material loading member during continuous printing (CNT_MISPRINT) (S103).SELECTED DRAWING: Figure 5

Description

The present invention relates to an image forming apparatus, and more particularly to a printing apparatus, particularly an image forming apparatus such as a copier, a laser beam printer, and a facsimile.

As an image forming apparatus adopting a conventional electrophotographic method, an image forming apparatus using an intermediate transfer body is known. In this method, a plurality of component color images based on multicolor image information are sequentially formed on an intermediate transfer body and laminated. Next, the image formed on the intermediate transfer body is transferred to the recording material fed after the start of image formation and fixed. In such an image forming apparatus, when the recording material is exhausted, an extra image is formed on the intermediate transfer body, and the intermediate transfer body needs to be cleaned. Hereinafter, such an operation is referred to as "misprint without recording material", and toner that has been cleaned without being transferred to the recording material is referred to as untransferred toner. If misprints without recording material occur frequently, a large amount of untransferred toner may be generated, and the collection container for untransferred toner may fill up earlier than expected.

In view of these problems, in the past, for example, the following control is performed. That is, when it is detected that the number of recording materials has decreased, the throughput is reduced, the paper feed interval is widened, and the time interval for image formation (the next n + 1th image from the start of exposure by the exposure device for the nth image). The time until the start of exposure of the image by the exposure device) is lengthened. At this time, after confirming that there is a recording material to be transferred so that the exposure start time of an image is later than the paper feeding start time of the recording material to be transferred, the image is transferred to the recording material. The formation of the image to be performed is started (see, for example, Patent Document 1). This addresses the issue of misprinting without recording material.

Japanese Unexamined Patent Publication No. 2001-337575

By detecting the remaining amount of paper in the recording material as in the conventional example, unnecessary image forming operations can be reduced. However, a dedicated hardware configuration is required to detect the remaining amount of paper in the recording material, which may lead to an increase in cost or size of the image forming apparatus. On the other hand, there is a possibility that the throughput may decrease simply by lengthening the time interval between image formation and paper feeding without having a mechanism for detecting the remaining amount of paper as in the conventional example.

The present invention has been made under such circumstances, and an object of the present invention is to reduce unnecessary image forming operations without reducing the throughput as much as possible with an inexpensive configuration.

In order to solve the above-mentioned problems, the present invention includes the following configurations.

(1) An image forming apparatus that forms an image on a recording material, and is used for cleaning the photoconductor, the intermediate transfer body on which the toner image formed on the photoconductor is transferred, and the toner on the intermediate transfer body. The means, the collection container for collecting the toner cleaned by the cleaning means, the loading portion on which the recording material is loaded, and the first detecting means for detecting the presence or absence of the recording material in the loading portion are continuously provided. When the first detecting means detects that there is no recording material in the loading portion during the continuous image forming in which the image is formed, the cleaning means cleans the toner on the intermediate transfer body and the collection container. The control means is provided with a control means for performing a cleaning operation for collecting the data, and the control means is in the process of forming the continuous image according to the number of times it is detected that there is no recording material in the loading portion during the continuous image formation. An image forming apparatus characterized in that the interval of image forming is controlled.

According to the present invention, it is possible to reduce unnecessary image forming operations without reducing the throughput as much as possible with an inexpensive configuration.

Schematic cross-sectional view of the image forming apparatus of Examples 1 and 2. The figure which shows the system configuration of Examples 1 and 2. The figure which shows the state when the recording material is exhausted during the continuous printing of Example 1. The figure which shows the state of switching the throughput of Example 1. Flow chart showing the throughput switching determination process of the first embodiment The figure which shows the state of switching the throughput of Example 2. Flow chart showing the throughput switching determination process of the second embodiment

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The operation of cleaning the intermediate transfer body in order to remove the toner image formed on the intermediate transfer body when the recording material is exhausted is called "misprint without recording material". Toner that has been cleaned without being transferred to the recording material is called untransferred toner.

In the first embodiment, a method of switching the throughput according to the number of occurrences of misprint without recording material will be described.

(Image forming device configuration)
FIG. 1 is a schematic cross-sectional view of an image forming apparatus. The image forming apparatus 1 is an in-line type multicolor image forming apparatus using an intermediate transfer belt 8 which is an intermediate transfer body. The intermediate transfer belt 8 of the endless band is stretched on the drive roller 9, the tension roller 10, and the secondary transfer inner roller 11. The intermediate transfer belt 8 is orbitably conveyed in the direction of arrow B by a drive roller 9 driven by a motor (not shown). The image forming portions SY, SM, SC, and SK forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K) are in contact with the vertically upper surface of the intermediate transfer belt 8. They are arranged at regular intervals. The configuration and operation of the image forming units SY, SM, SC, and SK of the first embodiment are substantially the same except that the colors of the formed images are different. Therefore, unless otherwise specified, the subscripts Y, M, C, and K given to the symbols to indicate that the elements are provided for any color will be omitted. The photosensitive drums 2Y, 2M, 2C, 2K and the primary transfer rollers 7Y, 7M, 7C, 7K sandwich the intermediate transfer belt 8 to form the primary transfer nip portions N1Y, N1M, N1C, N1K. Further, the secondary transfer outer roller 12 is pressed by the secondary transfer inner roller 11 with the intermediate transfer belt 8 interposed therebetween, forming a secondary transfer nip portion N2 which is a transfer means. The cleaning device 14 of the intermediate transfer belt 8 is brought into contact with the intermediate transfer belt 8 along the intermediate transfer belt 8 downstream of the secondary transfer nip portion N2. The image forming unit S includes a photosensitive drum 2 which is a photoconductor, a charging roller 3 arranged around the photosensitive drum 2, an exposure device 4, and a developing device 5. The exposure devices 4Y, 4M, 4C, and 4K are arranged so as to scan the laser beam for each of the photosensitive drums 2Y, 2M, 2C, and 2K in the axial direction of the photosensitive drum 2. Hereinafter, the axial direction of the photosensitive drum 2 is defined as the main scanning direction. Further, the direction orthogonal to the main scanning direction is defined as the sub-scanning direction.

(Image forming device block diagram)
Here, FIG. 2 is a system configuration diagram of the image forming apparatus 1 of the first embodiment. The members overlapping with FIG. 1 are designated by the same reference numerals. The controller unit 401 can communicate with each other of the host computer 400 and the engine control unit 402. When the controller unit 401 receives the image information and the print command from the host computer 400, the controller unit 401 analyzes the received image information and converts it into bit data. Then, the controller unit 401 transmits a print reservation command, a print start command, and a video signal to the engine control unit 402 for each recording material P via the video interface unit 410. The controller unit 401 transmits a print reservation command for notifying the engine control unit 402 of the print conditions from the host computer 400 in the print order. The controller unit 401 transmits a print start command to the engine control unit 402 at the timing when the image forming apparatus 1 is ready for printing.

The engine control unit 402 prepares to execute the printing operation in the order of the print reservation commands received from the controller unit 401, and waits until the print start command is transmitted from the controller unit 401. Upon receiving the print start command from the controller unit 401, the engine control unit 402 performs the following control. That is, the engine control unit 402 outputs the / TOP signal (reference in the sub-scanning direction) and / BD signal (reference in the main scanning direction), which are the reference timings for the output of the video signal, to the controller section 401, and receives the print reservation. Start the print operation according to the command. The controller unit 401 transmits the bit data corresponding to the converted image information to the engine control unit 402 with the / TOP signal as the base point. In the engine control unit 402, the CPU 411, which is a control means, controls the charging roller 3, the exposure device 4, the developing device 5, the primary transfer roller 7, the secondary transfer outer roller 12, the paper transport unit 500, and the fixing device 13. , Perform image formation processing necessary for printing operation. The CPU 411 controls each of the above-described parts while using the RAM 411b as a work area according to various programs stored in the ROM 411a. The engine control unit 402 and the controller unit 401 display an appropriate message for the user on the display unit 403.

(Image formation operation)
The image forming operation will be described with reference to FIGS. 1 and 2. When the image forming apparatus 1 starts the image forming operation, the photosensitive drum 2 is driven by a motor (not shown) and rotates in the direction of arrow A. A voltage of, for example, -1100V is applied to the charging roller 3 to charge the surface of the photosensitive drum 2 having a photoconducting layer to form a uniform background potential of, for example, −500V. Next, the exposure apparatus 4 scans and exposes the surface of the photosensitive drum 2 with laser light according to the laser drive signal to form an electrostatic latent image on the photosensitive drum 2. The surface potential of the photosensitive drum 2 in the portion that receives the maximum amount of light drops to, for example, about -100V. The developing device 5 coats the developing roller 6 with toner charged in a negative electrode property having a normal polarity. The developing roller 6 is arranged so as to be in contact with and separated from the photosensitive drum 2, and a voltage of, for example, −300 V is applied. When the electrostatic latent image formed on the photosensitive drum 2 (on the photoconductor) comes into contact with the developing roller 6 of the developing device 5, the toner has a latent image potential due to the electrostatic latent image of the photosensitive drum 2 and the electric field of the developing roller 6. Adhering (developing) to the portion, the electrostatic latent image of the photosensitive drum 2 becomes a toner image. Since the background potential portion of the photosensitive drum 2 other than the electrostatic latent image has an electric field opposite to that of the electrostatic latent image portion, toner charged with normal polarity does not adhere.

For example, a voltage of + 600 V is applied to the primary transfer roller 7. The toner image formed on the photosensitive drum 2 is transferred to the intermediate transfer belt 8 by the electric field between the photosensitive drum 2 and the primary transfer roller 7 in the process of passing through the primary transfer nip portion N1 (hereinafter, 1). Next transcription). In the process in which the intermediate transfer belt 8 sequentially passes through the primary transfer nip portions N1Y, N1M, N1C, and N1K, the toner images formed by the image forming portions S on the intermediate transfer belt 8 (on the intermediate transfer body) are sequentially 1 Next transcribed. In this way, a toner image in which toners of a plurality of colors are superimposed is formed on the intermediate transfer belt 8. Further, after the image forming operation, the paper feed roller 17, which is a paper feed means, is rotated to feed one sheet of the recording material P of the paper feed trays 16 (16-1, 16-2). The recording material P is separated into one by friction with the separation pad 18, and is conveyed in the direction of the arrow C. Then, the recording material P is stopped while correcting the skew with the registration roller (hereinafter referred to as the registration roller) to 19. For example, a voltage of + 1500V is applied to the secondary transfer outer roller 12. The register roller pair 19 rotates at the timing when the tip of the toner image formed on the intermediate transfer belt 8 and the tip of the recording material P reach the secondary transfer nip portion N2 at the same time. As a result, the recording material P enters the secondary transfer nip portion N2. The toner image formed on the intermediate transfer belt 8 is transferred to the recording material P by the electric field between the intermediate transfer belt 8 and the secondary transfer outer roller 12 (hereinafter referred to as secondary transfer).

As described above, in the image forming apparatus 1 of the first embodiment, the "distance Li from the exposure position of yellow (Y) to the secondary transfer nip portion N2" is "the recording material P of the paper feed tray 16 (16-1)". It is longer than the distance Lp from the tip position of the secondary transfer nip portion N2 (Li> Lp). The distance Li is secondarily determined by the secondary transfer outer roller 12 from the position where the photosensitive drum 2 arranged on the most upstream side in the moving direction of the intermediate transfer belt 8 among the plurality of photosensitive drums 2 is exposed from the exposure apparatus 4. The distance to the position where the transfer is performed. Further, the distance Lp is the distance from the position of the tip of the recording material P loaded on the paper feed tray 16-1 to the position where the secondary transfer is performed.

In such a case, the image forming operation is performed first, and then the paper feeding operation is performed. After the secondary transfer, the recording material P to which the unfixed toner image is transferred is transferred to the fixing device 13. The fixing device 13 driven in the direction of the arrow D by a motor (not shown) heats the recording material P while pressurizing the recording material P to fix the toner image on the recording material P. Then, the recording material P on which the toner image is fixed is discharged to the discharge tray 25. The toner remaining on the intermediate transfer belt 8 after the secondary transfer is called the secondary transfer residual toner. The secondary transfer residual toner is collected by the cleaning device 14 which is a cleaning means for the intermediate transfer belt 8. The cleaning device 14 is, for example, a rubber blade supported by a metal sheet metal, and the edge is brought into contact with the intermediate transfer belt 8 to scrape off the toner and remove the secondary transfer residual toner on the intermediate transfer belt 8. The removed toner is collected in the toner collection container 15, which is a collection container. In this way, the cleaning device 14 performs a cleaning operation in which the secondary transfer residual toner is collected in the toner collection container 15.

(Explanation of paper feed section)
The configuration of the paper feed unit will be described with reference to FIG. The paper feed tray 16 is inserted into the main body of the apparatus from the right side of the cross-sectional view of FIG. The CPU 411 can detect that the paper feed tray 16 has been inserted into the main body of the apparatus by the paper feed tray presence / absence sensor (not shown). The paper feed tray 16 has a recording material loading member 22 which is a swingable loading unit, and a lift arm (not shown) which is a lifting means for lifting the recording material loading member 22. When lifting the recording material loading member 22, the CPU 411 rotates a drive motor (not shown), applies a voltage to the solenoid (not shown), and releases the regulation of the missing tooth gear. After the release, the drive is transmitted to the downstream side in the transmission direction of the driving force, the lift arm rotates, and the recording material loading member 22 is lifted. The elevating position sensor (not shown) has an elevating position detection flag, and the elevating position detection flag (not shown) makes contact with the elevating position detection flag on the uppermost surface of the recording material P when the recording material P is lifted. It is provided as follows. At this time, the signal of the elevating position sensor is switched from off (transmission) to on (light shielding). The CPU 411 stops the solenoid and the drive motor when the signal of the elevating position sensor is switched from off to on, and stops the operation of the recording material loading member 22. By this control, the uppermost surface of the recording material P is raised to the optimum position.

The recording material presence / absence detection flag 20 is provided so as to come into contact with the uppermost surface of the recording material P when the ascending operation of the recording material loading member 22 is completed. When there is a recording material P, the recording material presence / absence detection flag 20 is lifted by the recording material P, and the signal of the recording material presence / absence sensor 21 which is the first detection means is switched from off to on. The recording material loading member 22 directly below the recording material presence / absence detection flag 20 is provided with a hole so that the recording material presence / absence detection flag 20 can pass through. When the recording material P is exhausted, the recording material presence / absence detection flag 20 hangs down due to its own weight, and the signal of the recording material presence / absence sensor 21 is switched from on to off. The CPU 411 can detect that the recording material P has run out based on the signal of the recording material presence / absence sensor 21 being switched from on to off.

When the paper feed tray 16 is removed from the main body of the apparatus, the recording material loading member 22 is lowered, and the signals of the elevating position sensor (not shown) and the recording material presence / absence sensor 21 are turned off. With the above configuration, the CPU 411 determines that the recording material P is “present” when the signal of the recording material presence / absence sensor 21 is on, and determines that the recording material P is “absent” when it is off. In the first embodiment, the paper feed tray 16 has two paper feed trays, an upper paper feed tray 16_1 and a lower paper feed tray 16_2, both of which have the above-described configuration. Further, it is assumed that the maximum load capacity of the recording material P is 500 sheets (assumed to be plain paper).

(First throughput)
The throughput in Example 1 will be described. In the first embodiment, image formation is performed while switching between two types of throughput, a first throughput controlled to be the first interval and a second throughput controlled to be the second interval. Switching between the first throughput and the second throughput means switching between the first interval and the second interval. The recording material P is performed from the paper feed tray 16-1.

First, the operation when the image is formed at the first throughput will be described. The first throughput is the case where the image is formed at the minimum interval that can be fed, and the image formation interval here is 35 mm. Here, the image formation interval is an interval from the end of image formation of a predetermined page to the start of image formation of the next page following the predetermined page. The throughput can be expressed as a distance, specifically as a distance interval, such as "35 mm", or as a time (for example, seconds), specifically as a time interval. Further, the image formation interval can be defined as the time from the start time of exposure of the nth image by the exposure device 4 to the start time of exposure of the next n + 1th image by the exposure device 4. In the case of continuous printing (continuous image formation) in which images are continuously formed on a plurality of recording materials P at the first throughput, if the recording material P runs out in the middle of continuous printing, it is already formed on the intermediate transfer belt 8. There is no recording material to be transferred to the toner image. Therefore, it leads to toner consumption. The situation will be described with reference to FIG. Note that FIG. 3 shows only the main part of the image forming apparatus 1.

FIG. 3A shows the state at the moment when the misprint without recording material occurs at the first throughput. The recording material presence / absence detection flag 20 enters the hole of the recording material loading member 22, and the signal of the recording material presence / absence sensor 21 is switched from on to off. When the CPU 411 can determine "none" of the recording material P based on the detection result of the recording material presence / absence sensor 21, two pages of images have already been formed on the intermediate transfer belt 8. Specifically, assuming that the last recording material P of the paper feed tray 16 is the Nth sheet, the toner images (images) of the N + 1th page and the N + 2nd page are formed on the intermediate transfer belt 8. The N-1st recording material P, which is the preceding recording material P, is transported downstream in the transport direction of the Nth recording material P. Due to the relationship between PPM (number of recording materials P that can be input / output per minute per page) and the main body dimensions, the Nth recording material P is present or absent at the time when image formation on the N + 2nd page is started. It is on the detection flag 20. Therefore, the timing at which the CPU 411 can detect that there is no recording material P under the Nth recording material P is after the image formation on the N + 2nd page.

When a misprint without recording material occurs, the CPU 411 executes a sequence for performing post-image forming operation (hereinafter referred to as a back rotation sequence) to clean the untransferred toner on the intermediate transfer belt 8. Further, in the above-mentioned case, the untransferred toner for 2 pages (N + 1 page, N + 2 page) is collected in the toner collection container 15. Further, the CPU 411 causes the display unit 403 to display information (hereinafter, referred to as a message) prompting the user to replenish the paper feed tray 16 with the recording material P.

Although FIG. 1 does not show a double-sided transfer path for double-sided printing, a unit called a page is used for the toner image, and a unit called a sheet is used for the recording material P. The toner image when printing on one side of one recording material P is one page, and the toner image when printing on both sides of one recording material P is two pages. The following will be described assuming that single-sided printing is performed.

(Second throughput)
Next, the operation when the image is formed with the second throughput lower than the first throughput (in other words, the interval is long) will be described. The second throughput is the throughput when image formation is started after confirming the presence or absence of the recording material P, and here, it is assumed that the image formation interval is 440 mm. When continuous printing is performed with the second throughput, even if the recording material P is exhausted in the middle of continuous printing, unnecessary image formation is not performed on the intermediate transfer belt 8, so that toner consumption can be suppressed. In the second throughput, the fact that the image is not formed at the time when "none" of the recording material P is detected means that the toner image is not formed at least on the intermediate transfer belt 8. The situation will be described with reference to FIG. 3 (b).

FIG. 3B shows the state at the moment when the recording material P disappears during continuous printing (during continuous image formation) at the second throughput. In the second throughput, the image formation and the paper feed interval are longer than those in the first throughput. Therefore, when the CPU 411 can determine “absence” of the recording material P by the recording material presence / absence sensor 21, the image of the subsequent page (N + 1 page) is not yet formed on the intermediate transfer belt 8. Therefore, immediately before starting the image formation on the N + 1th page, the CPU 411 stops (interrupts) continuous printing and causes the display unit 403 to display a message prompting to replenish the recording material P. As described above, in the second throughput, since the image is formed after confirming the presence or absence of the recording material P, the throughput is lower than that of the first throughput, but unnecessary image formation (untransferred toner) is generated. Does not occur.

(How to switch between the first throughput and the second throughput)
In the first embodiment, the throughput is not reduced as much as possible while preventing the toner recovery container 15 from becoming full before reaching the life of the main body (a period during which the quality of image formation can be guaranteed in terms of specifications). In order to achieve this purpose, the first throughput and the second throughput described above are switched at an appropriate timing.

As described above, although the first throughput has a high throughput, unnecessary image formation may occur depending on the usage state of the user. On the other hand, in the second throughput, although the throughput is low, unnecessary image formation is not performed. Therefore, in the first embodiment, the control is performed as follows. First, the default (preset) throughput is set as the first throughput. Then, the number of occurrences of misprint without recording material is monitored, and when the number of occurrences of misprint without recording material increases, the throughput is switched to the second throughput. After that, when the number of occurrences of misprints without recording material being monitored decreases, the throughput is returned to the first throughput again. The number of misprints without recording material can be said to be the number of cleaning operations. Hereinafter, a specific description will be given.

In the first embodiment, the determination timing for switching the throughput is performed at a periodic timing (hereinafter, also referred to as a determination timing) using the total page count. It is assumed that the CPU 411 manages the total number of prints since the new image forming apparatus 1 is installed and started to be used as a total page count. The CPU 411 also functions as a measuring means. The life of the main body is assumed to be, for example, 50,000 pages. Whether or not the CPU 411 switches the throughput at the timing when the total page count managed reaches 1000 × n (n = 1 to 50) pages, in other words, every time 1000 sheets are printed (every time the third number of sheets is printed). To judge. It should be noted that 1000 sheets is an example, and the judgment may be made for each of the other sheets.

Table 1 is a table showing the number of occurrences of misprint without recording material in the standard case and the worst case up to each judgment timing. “1K” or the like in the first row of each column indicates the number of printed sheets “1000” of the recording material P or the like. For example, in the standard case, the number of misprints without a recording material that occurs until 3000 sheets (3K) of the recording material P are printed is 6 times or less. On the other hand, in the worst case, the number of misprints without a recording material that occurs until 3000 sheets (3K) of the recording material P are printed is 12 times or less. Further, as shown in Table 1, when the maximum load capacity of 500 recording materials P is inserted into the paper feed tray 16, the number of misprints without recording material is 0 to 2 when 1000 sheets are reached in the standard case. Times.

Here, the case of 0 times is a case where continuous printing is not performed from page 500 to page 501 and from page 1000 to page 1001. In other words, it can be said that the continuous printing of the 500th page or the 1000th page has just finished. It is also assumed that the user has added (replenished) the recording material P before the maximum load capacity of 500 sheets is exhausted. The two cases are cases where continuous printing is performed from page 500 to page 501 and from page 1000 to page 1001.

In this way, when the total page count reaches 1000 pages, the case where the number of misprints without recording material occurs up to 2 times is assumed to be a standard user's usage state, and is called a standard case. In the standard case, as shown in Table 1, when the total page count reaches 50,000 sheets (50K), the maximum number of misprints without recording material is 100 times.

On the other hand, depending on the user, when the recording material P of the paper feed tray 16 is exhausted, it may be assumed that the maximum load capacity of 500 sheets is not inserted. In this case, the number of misprints without recording material is likely to be higher than in the standard case. The toner recovery container 15 in the first embodiment is designed to have an allowable capacity up to 200 times (predetermined number of times) when the number of occurrences of misprint without recording material reaches 50,000 sheets (first number of sheets). .. Here, the allowable capacity is, for example, the number of times that the toner recovery container 15 is not full. Depending on the specifications of the image forming apparatus, a capacity other than the full capacity may be an acceptable capacity. The case where misprints without recording material occur 200 times when the number of sheets reaches 50,000 is called the worst case. Table 1 shows the number of occurrences for each page count.

In the first embodiment, in order not to exceed the worst case shown in Table 1, in other words, in order to prevent the toner collection container 15 from becoming full when 50,000 sheets are reached, the number of occurrences of misprints without recording material (cumulative). ) Is counted. Then, when the worst case is exceeded in the above-mentioned determination timing, the number of occurrences of misprint without recording material is suppressed by switching from the first throughput to the second throughput. At each determination timing, the worst case in Table 1 is set to the number of sheets that the toner collection container 15 is expected to fill up when the number of sheets reaches 50,000 if printing is continued in the current usage state of the user. That is, in the worst case of Table 1, for example, when the number of occurrences exceeds 8 when 2000 sheets are reached, the toner collection container 15 becomes full before reaching 50,000 sheets if the usage state is continued as it is. It means that.

(Throughput transition)
Hereinafter, a specific description will be given with reference to FIG. FIG. 4 is a graph showing the total page count (K (1000) pages) on the horizontal axis and the number of occurrences (times) of misprints without recording material on the vertical axis, and shows how the throughput is switched. .. The number of misprints without recording material is plotted in the black part. The solid line shows the number of occurrences of misprint without recording material at each determination timing of the worst case shown in Table 1, and is the threshold number (corresponding to a predetermined number) in the switching determination of Example 1. Hereinafter, the number of printed sheets of the recording material P will be described in units of K (1000). The CPU 411 controls to operate at the first throughput, which is the default throughput, while the total page count is 0 to 1K. When the total page count reaches 1K, the number of misprints without recording material is 2 times, which is less than 4 times in the worst case (2 <4). Therefore, the CPU 411 controls so that it continues to operate at the first throughput while the total page count is 1 to 2K.

When the total page count reached 2K, the number of misprints without recording material was 6 times, which is less than 8 times in the worst case (6 <8). Therefore, the CPU 411 controls the CPU 411 to continue operating at the first throughput while the total page count is 2 to 3K. When the total page count reaches 3K, the number of misprints without recording material is 13 times, which exceeds the worst case of 12 times (13> 12). Therefore, the CPU 411 switches to the second throughput while the total page count is 3 to 4K so as not to cause misprint without recording material and controls to suppress toner consumption.

At this time, the CPU 411 notifies the user of a message to the effect of, for example, the following to the display unit 403.
-Since the toner recovery container 15 may fill up earlier than expected, the throughput should be temporarily reduced.-If the recording material P of the paper feed tray 16 runs out, insert 500 sheets with the maximum load capacity as much as possible. To do

When the total page count reached 4K, the number of misprints without recording material was 13 times (no change), which is less than 16 times in the worst case (13 <16). Therefore, the CPU 411 returns to the first throughput and controls to operate at the first throughput while the total page count is 4 to 5K. After that, the same control is performed until it reaches 50K.

(Throughput switching judgment processing)
Hereinafter, the process of the first embodiment described above will be described with reference to the flowchart of FIG. When the power of the image forming apparatus 1 is turned on, the CPU 411 starts the processes of step 100 and subsequent steps (hereinafter referred to as S). In S100, the CPU 411 reads out the following information stored in the RAM 411b, which is rewritable such as a non-volatile memory and can maintain the information even when the power is turned off.
・ Total page count (hereinafter also referred to as CNT_PAGE)
-Number of misprints without recording material (hereinafter also referred to as CNT_MISPRINT)
-Latest throughput (hereinafter also referred to as THR)

In S101, the CPU 411 determines whether or not a print instruction (print request) has been received from the controller unit 401. When the CPU 411 determines in S101 that the print instruction has not been received, the process returns to S101, and when it determines that the print instruction has been received, the CPU 411 proceeds to the process in S102 and shifts to the print operation. In S102, the CPU 411 determines whether or not it is a timing for determining whether or not to switch the throughput (hereinafter, referred to as a switching determination timing). Specifically, the CPU 411 determines whether or not the total page count CNT_PAGE has reached 1K × n (n = 1 to 50).

If the CPU 411 determines in S102 that it is the switching determination timing, the process proceeds to S103, and if it determines that it is not the switching determination timing, the process proceeds to S105. In S103, the CPU 411 determines whether or not the number of occurrences of misprint without recording material CNT_MISPRINT is equal to or less than the worst case threshold number described in Table 1. When the CPU 411 determines in S103 that the number of occurrences of misprint without recording material CNT_MISPRINT is less than or equal to the threshold number (less than or equal to a predetermined number of times), the process proceeds to S104. If the CPU 411 in S103 determines that the number of occurrences of misprint without recording material CNT_MISPRINT is greater than the threshold number, the process proceeds to S109. In S104, the CPU 411 sets the throughput to the first throughput (THR = first throughput). In S109, the CPU 411 sets the throughput to the second throughput (THR = second throughput) and advances the processing to S105.

In S105, the CPU 411 forms an image according to the throughput set in THR. In S106, the CPU 411 increments the total page count CNT_PAGE by one. After starting image formation in S107, the CPU 411 determines the presence / absence of the recording material P in the paper feed tray 16 by the recording material presence / absence sensor 21. When the CPU 411 determines in S107 that the recording material P is “present” in the paper feed tray 16, the process proceeds to S108 and the printing operation is continued. In S108, the CPU 411 determines whether or not continuous printing has been completed, in other words, whether or not there is a print request for the subsequent recording material P. In S108, the CPU 411 returns the process to S102 when it is determined that the continuous print is not completed, and ends the process when it is determined that the continuous print is completed. When the CPU 411 determines in S107 that the recording material P is “none”, the process proceeds to S110. In S110, the CPU 411 counts up the number of occurrences of misprint without recording material CNT_MISPRINT by one. In S111, the CPU 411 executes a cleaning operation and ends the printing operation.

As described above, by switching the throughput according to the number of occurrences of misprint without recording material, it is possible to reduce unnecessary image formation without reducing the throughput as much as possible with an inexpensive configuration. In the first embodiment, it is possible to prevent the toner recovery container from becoming full before reaching the end of the life of the main body, and to prevent the throughput from being reduced as much as possible.

As described above, according to the first embodiment, it is possible to reduce unnecessary image forming operations without reducing the throughput as much as possible with an inexpensive configuration.

In the second embodiment, a method of monitoring the user's operation regarding the insertion of the recording material P after switching to the second throughput and returning to the first throughput will be described. The description of the main parts such as the configuration is the same as that of the first embodiment, and only the parts different from the first embodiment will be described here. In the first embodiment, in order to return from the second throughput to the first throughput, the total page count is used and it is performed at a regular timing. As a result, as shown in FIG. 4, since the throughput remains low while the total page count is 3 to 4K, it may be inconvenient for a user who frequently performs continuous printing. If it is expected that the toner recovery container 15 can be prevented from filling up earlier than expected, it is desirable from the viewpoint of usability to return to the first throughput as soon as possible. In Example 2, this idea is applied to the following cases.

(Assumed case)
Between switching to the second throughput and reaching the page count at the next determination timing, the user inserts the recording material P having a maximum load capacity of 500 sheets (or a number close to 500 sheets) into the paper feed tray 16. This is the case. In this case, the number of times of misprint without recording material occurs 0 to 2 times until the next determination timing. If this number of times is used during the printing period with a total page count of 1K, it can be said that the effect on the toner recovery container 15 is small even if the throughput is returned to the first throughput.

As described above, in the second embodiment, the user's operation regarding the insertion of the recording material P is monitored, and when the user's operation as described above is detected, the second throughput is immediately returned to the first throughput. As a result, the usability is further improved while suppressing the risk that the toner collection container 15 becomes full. Hereinafter, a method for detecting the above-mentioned case will be described.

(Load capacity detection method)
As described above, in the second embodiment, the CPU 411 can detect that the paper feed tray 16 has been taken out of the device main body and inserted into the device main body by the paper feed tray presence / absence sensor (not shown). When the paper feed tray 16 is inserted into the main body of the apparatus by the user, the CPU 411 raises the recording material loading member 22 from off to on until the signal of the elevating position sensor (not shown), which is the second detection means, is turned on. I do.

The time for the ascending operation of the recording material loading member 22 varies depending on the loading capacity of the recording material P. In the second embodiment, it is known in advance that it takes 10 seconds in the case of 0 recording material P and 5 seconds in the case of 500 recording material P (maximum loading number) (assuming plain paper). That is, the larger the load capacity of the recording material P on the recording material loading member 22, the shorter the time required for the ascending operation. Therefore, the CPU 411 can roughly estimate the load capacity of the recording material P by the following equation (1) by measuring the ascending operation time using a timer (not shown). That is, the CPU 411 also functions as an estimation means.
Load capacity (sheets) = 500-((rise time-5) x (500-0) / (10-5)) ... Equation (1)

In the second embodiment, the number of sheets (second number of sheets) close to the maximum load capacity of 500 sheets in the paper feed tray 16 is set to, for example, 480 sheets as a threshold value. Therefore, the CPU 411 determines the ascending time for the load capacity to be 480 sheets to be 5.2 seconds according to the equation (1). When the CPU 411 detects that the rise time measured by the timer is 5.2 seconds or less, which is equivalent to 480 sheets, in other words, when it detects that the load capacity is 480 sheets or more, it is the first from the second throughput. Judge to return to the throughput of. The load capacity of the recording material P may be estimated by measuring the number of steps of the motor when the drive motor for lifting the recording material loading member 22 is a stepping motor.

(Switching throughput)
Hereinafter, a state in which the throughput is switched by the above-mentioned load capacity detection method will be described with reference to FIG. FIG. 6 is a graph similar to that of FIG. In FIG. 6, the total page count is the same as in the first embodiment while the total page count is 0 to 3K. When the total page count reaches 3K, the number of misprints without recording material is 13 times, which exceeds the worst case of 12 times (13> 12). Therefore, the CPU 411 switches to the second throughput while the total page count is 3 to 4K to prevent the occurrence of misprint without recording material and suppresses toner consumption. At this time, the CPU 411 issues the above-mentioned alert message to the user on the display unit 403. After switching to the second throughput, the CPU 411 monitors whether or not the above-mentioned assumed case occurs. The CPU 411 detects that the assumed case has occurred at the timing t1 of FIG. That is, since the CPU 411 determines that the user has inserted 480 or more recording materials P at the timing t1, the throughput is returned to the first throughput at the timing t1.

The difference from the first embodiment is that since the throughput is returned to the first throughput, a misprint without recording material occurs when the total page count is between 3 and 4K. That is, when the total page count reaches 4K, the number of occurrences of misprint without recording material was 13 in Example 1, but it is 14 in Example 2. However, for the reasons mentioned above, even when the total page count reaches 4K, it is still below the worst case of 16 times (14 <16). Therefore, the effect on the toner recovery container 15 is small. On top of that, since the second throughput is returned to the first throughput at an earlier stage, the usability can be improved. Even after the total page count reaches 4K, the same switching control is performed until it reaches 50K.

(Throughput switching judgment processing)
Hereinafter, the process of the second embodiment described above will be described with reference to the flowchart of FIG. 7. The processing of S200 and S201 of FIG. 7 is the same as the processing of S100 and S101 of FIG. 5 of the first embodiment, and the description thereof will be omitted. In S202, the CPU 411 determines whether or not the current throughput THR is the first throughput. When the CPU 411 determines in S202 that the throughput THR is the first throughput, the CPU 411 proceeds to the process in S203. In S203, the CPU 411 determines whether or not it is the switching determination timing of the throughput, and if it is determined that it is the switching determination timing, the process proceeds to S204, and if it is determined that it is not the switching determination timing, the process proceeds to S206. The determination method is the same as that of the first embodiment, and the description thereof will be omitted. In S204, the CPU 411 determines whether or not the number of occurrences of misprint without recording material CNT_MISPRINT is greater than the threshold number of times.

If the CPU 411 determines in S204 that the number of occurrences of misprint without recording material CNT_MISPRINT exceeds the threshold number, the process proceeds to S205. If the CPU 411 determines in S204 that the number of occurrences of misprint without recording material CNT_MISPRINT is equal to or less than the threshold number, the process proceeds to S206. In S205, the CPU 411 sets the current throughput as the second throughput (THR = second throughput). The processing of S206 to S211 is the same as the processing of S105 to S108, S110, and S111 of FIG. 5, and the description thereof will be omitted.

When the CPU 411 determines in S202 that the current throughput THR is the second throughput, the CPU 411 proceeds to the process in S212. In S212, the CPU 411 determines whether or not the user "has a history of inserting a large amount of the recording material P when the recording material P is exhausted". As described above, the CPU 411 determines whether or not the recording material loading member 22 has been inserted in excess by comparing the ascending time of the recording material loading member 22 with, for example, the ascending time corresponding to the loading capacity of 480 sheets.

When the CPU 411 determines in S212 that there is a history of inserting a large number of recording materials P (for example, 480 sheets or more (predetermined number of sheets or more)), the process proceeds to S213. In S213, the CPU 411 returns the current throughput to the first throughput (THR = first throughput). When the CPU 411 determines in S212 that there is no history of inserting a large number of recording materials P (less than a predetermined number of sheets), the processing proceeds to S206 while maintaining the current throughput THR at the second throughput.

From the above, according to the second embodiment, after switching to the second throughput, the user's operation regarding the insertion of the recording material P is monitored and returned to the first throughput, so that the throughput is not reduced as much as possible with an inexpensive configuration. In addition, unnecessary image formation can be reduced. As a result, the risk that the toner recovery container 15 fills up earlier than expected can be reduced. The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as the paper feed tray, only the case of cassette paper feed has been described, but the same effect can be obtained with a manual feed tray or the like.

Further, as a method of switching the throughput, when the total page count reached a predetermined page count, the number of times of misprint without recording material and the number of threshold values were compared. However, for example, the rate at which misprints without recording material occur and the threshold rate may be compared for each page. In the worst case of Table 1, the threshold ratio per page has the following values.
(200 times / 50K) x 100 = 0.4%
The CPU 411 may calculate the rate at which misprints without recording material occur for each page, and switch the throughput in comparison with the above-mentioned threshold rate (for example, 0.4%).

Further, when the total page count reaches a predetermined page count in the latter half of the life of the main body, the throughput switching determination may be made. At this time, if the number of times the misprint without recording material occurs exceeds the threshold number, the first throughput may be switched to the second throughput, and thereafter, the second throughput may remain.

Further, the warning message to the user displayed on the display unit 403 may be before switching to the second throughput. For example, when it is detected that the number of occurrences of misprint without recording material approaches the threshold number of the worst case, a warning message may be displayed on the display unit 403 before switching the throughput.

Further, in Examples 1 and 2, the first throughput is the maximum throughput, and the second throughput is a case where the throughput is reduced to the point where misprint without recording material does not occur. However, a throughput intermediate between the first throughput and the second throughput may be provided. The intermediate throughput refers to a throughput in which, for example, misprinting without recording material occurs, but there are few unnecessary toner images to be cleaned. When the relationship of 1st throughput> 2nd throughput> 3rd throughput is established, the throughput is gradually reduced from the first throughput to the second throughput and from the second throughput to the third throughput. It may be a method of switching as follows.

As described above, according to the second embodiment, it is possible to reduce unnecessary image forming operations without reducing the throughput as much as possible with an inexpensive configuration.

8 Intermediate transfer belt 14 Cleaning device 15 Toner recovery container 21 Recording material presence / absence sensor 22 Recording material loading member P Recording material

Claims (12)

An image forming apparatus that forms an image on a recording material.
Photoreceptor and
An intermediate transfer body on which the toner image formed on the photoconductor is transferred, and
A cleaning means for cleaning the toner on the intermediate transfer body and
A collection container for collecting toner cleaned by the cleaning means, and a collection container.
A loading section for loading recording materials and
A first detecting means for detecting the presence or absence of a recording material in the loading portion, and
When the first detecting means detects that there is no recording material in the loading portion during the continuous image forming in which the image is continuously formed, the cleaning means cleans the toner on the intermediate transfer body. A control means for performing a cleaning operation for collecting in the collection container, and
With
The control means is characterized in that it controls the interval of image formation during the continuous image formation according to the number of times it is detected that there is no recording material in the loading portion during the continuous image formation. apparatus. When the number of times that the control means detects that there is no recording material in the loading unit is equal to or less than a predetermined number of times, the control means controls the interval to be the first interval, and the recording material is placed in the loading unit. The image according to claim 1, wherein when the number of times absent is detected is greater than the predetermined number of times, the interval is controlled to be a second interval longer than the first interval. Forming device. Equipped with a measuring means to measure the number of recording materials for which image formation has been performed,
The predetermined number of times is such that when the number of sheets measured by the measuring means reaches the first number, the collection container is not filled with the toner collected by the cleaning operation of the predetermined number of times. The image forming apparatus according to claim 2, wherein the image forming apparatus is set in advance. A paper feeding means for feeding recording material from the loading unit is provided.
2. The first interval is set to the minimum interval among the intervals at which the recording material can be fed by the paper feeding means in the image forming apparatus. The image forming apparatus according to 3. When the second interval is controlled so that the toner image on the photoconductor is transferred to the intermediate transfer body after the presence of the recording material in the loading portion is detected by the first detection means. The image forming apparatus according to claim 4, wherein the interval is set to. While the image forming operation is being performed at the second interval, the control means switches from the second interval to the first interval according to the information regarding the insertion of the recording material into the loading portion. The image forming apparatus according to claim 4 or 5, wherein the image forming operation is performed. 6. The information regarding the insertion of the recording material into the loading unit is a second number of sheets corresponding to the maximum number of recording materials that can be loaded on the loading unit. The image forming apparatus according to. An ascending means for raising the loading unit to a position where the recording material can be fed by the paper feeding means,
A second detecting means for detecting the position of the loading portion raised by the raising means, and
An estimation means that raises the loading unit by the raising means after the recording material is inserted into the loading unit, and estimates the number of recording materials inserted into the loading unit based on the detection result of the second detecting means. When,
With
When the number of images estimated by the estimation means is equal to or greater than the second number, the control means switches from the second interval to the first interval, and the number of images estimated by the estimation means is said. The image forming apparatus according to claim 7, wherein when the number of images is less than the second number, the second interval is maintained. Equipped with a display unit that displays information
When the control means detects that there is no recording material in the loading unit by the first detecting means, the control means causes the display unit to display information prompting the insertion of the recording material into the loading unit. The image forming apparatus according to claim 7 or 8. The image forming apparatus according to claim 9, wherein the control means causes the display unit to display information prompting the loading unit to insert the second number of recording materials. A second to tenth aspect of the present invention, wherein the control means makes a determination to switch the interval to the first interval or the second interval every time the image forming operation is performed for a third number of sheets. The image forming apparatus according to any one of the above. With the plurality of the photoconductors
An exposure device that forms a latent image on the photoconductor,
A transfer means for transferring the toner image on the intermediate transfer body to the recording material, and
With
The distance from the position where the photoconductor arranged on the most upstream side in the moving direction of the intermediate transfer body among the plurality of photoconductors is exposed from the exposure apparatus to the position where the transfer is performed by the transfer means is the load. The image forming apparatus according to any one of claims 1 to 11, wherein the distance is longer than the distance from the position of the tip of the recording material loaded on the unit to the position where the transfer is performed.

Images