JP7536525B2 - Image forming apparatus and image forming system - Google Patents

Description

The present invention relates to image forming apparatuses such as electrophotographic copiers and printers that are equipped with an image heating device and form images on recording materials, and to improving throughput for small-sized paper.

Conventionally, the following techniques have been proposed to suppress the temperature rise in non-paper passing areas that occurs in a film fixing device used in an electrophotographic image forming apparatus to a desired value or less. For example, in Japanese Patent Application Laid-Open No. 2003-233999, the throughput (productivity) is changed according to the recording material width. When the recording material width is narrow, the throughput is reduced (the paper feed interval is widened) to control the temperature rise in the non-paper passing areas to be not excessive.
Also, for example, Japanese Patent Application Laid-Open No. 2003-233663 proposes an image forming apparatus that changes the image forming speed according to the recording material width, instead of changing the throughput by changing the paper feed interval according to the recording material width. In Japanese Patent Application Laid-Open No. 2003-233663, the image forming speed has two speeds (mm/sec), 200 mm/sec and 100 mm/sec.
For wide recording materials such as A4, letter, and legal sizes (hereinafter referred to as large size paper), the paper interval (the distance between the rear end of the Nth page and the front end of the N+1th page when continuously fed) is set to 65 mm. In this case, the throughput is 33 sheets/min for A4 size, 34.8 sheets/min for letter size, and 28.5 sheets/min for legal size. Here, the value of 65 mm paper interval is the minimum paper interval that the image forming device can take, and means the minimum paper interval that can be guaranteed due to variations in paper feed timing, variations in response timing of sensors in the conveying path, etc. On the other hand, narrow recording materials (hereinafter referred to as small size paper) such as B5, A5, and EXE size are set as one group, the image formation speed is set to 100 mm/sec, which is half that of large size paper, and the throughput is controlled so that the paper interval is 65 mm. As a result, the throughput of B5, A5, and EXE size is 18 sheets/min. As a result, when the image forming speed is slow, the amount of heat required for fixing is small, so that the temperature of the fixing film can be set low, thereby making it possible to suppress the temperature rise of the non-paper passing portion.
Also, for example, Japanese Patent Application Laid-Open No. 2003-233666 proposes a control for image formation in which, in an image forming apparatus having multiple image forming speeds, when small-sized paper is printed, the image forming speed is switched according to the number of sheets to be printed. In this case, when a small number of sheets are printed, printing is performed at the fastest image forming speed since there is little possibility that the temperature rise in the non-paper passing area will exceed a desired value. On the other hand, when a large number of sheets are printed, printing is performed at a slow image forming speed in order to suppress the temperature rise in the non-paper passing area.

Japanese Unexamined Patent Publication No. 7-199694 JP 2003-50519 A Patent No. 5455493

However, in Patent Document 1, a difference occurs in the throughput between large size paper and small size paper. Only large size paper has an increased throughput in proportion to the image formation speed due to the increase in the speed of the image forming device, and the throughput does not improve for small size paper. In addition, when the throughput decreases, the paper interval increases, so the rotation time of the cartridge in the image forming unit becomes longer for a given number of prints, and the lifespan is shortened. In addition, in order to deal with the temperature rise in the non-paper passing area, it is necessary to increase the paper interval from a small number of sheets to reduce the throughput, and the total productivity (average throughput) when printing a large number of sheets is reduced.
In addition, in the technique disclosed in Japanese Patent Laid-Open No. 2003-133699, the image forming speed is fixed depending on the recording material width, and the image forming speed is always slow for small-sized paper, resulting in a decrease in throughput. Therefore, the throughput also decreases when printing a small number of sheets, in which the effect of the temperature rise in the non-paper passing portion is small.
In addition, in Patent Document 3, the optimal image forming speed is selected according to the number of prints, but the number of prints is not necessarily known when the image forming operation is started. In other words, in the case of a printer, the number of prints is determined after the image controller unit, which converts the image information sent from the host computer into printable information, finishes converting all the image information. Therefore, if the number of prints is large, if the number of prints is waited until the number of prints is determined, the time until printing starts will be extended, and the time until the first print is output (First Print Out Time: FPOT) will be delayed. Therefore, if it is desired to speed up the FPOT, the image forming operation is started at the point when the image controller unit processes the image information of the first sheet, so the number of subsequent prints is not necessarily known.
Similarly, in the case of a copying machine, the image forming operation starts when the first sheet of paper is read by the image reading device, so it is not always clear how many sheets will be subsequently copied.

The present invention aims to provide a technology that can improve productivity regardless of the size of the recording material and extend the life of the device.

In order to achieve the above object, an image forming apparatus according to the present invention comprises:
an image forming section for forming an image on a recording material;
a fixing section having a nip section for nipping and conveying the recording material, the fixing section heating the image in the nip section to fix the image on the recording material;
a storage unit that stores, as a history for each continuous sheet passing, at least a number of narrower recording materials that are narrower than a recording material that has a maximum width in a direction perpendicular to a conveying direction among the recording materials that can be conveyed through the nip portion, the number of narrower recording materials that are continuously passed through the nip portion during continuous sheet passing;
a control unit for controlling a conveying speed of the recording material when passing through the nip portion;
In an image forming apparatus comprising:
The control unit is
When the narrow recording material is continuously passed through,
a first operation mode is executed in which the conveying speed is controlled to a first speed when a representative value of the number of sheets of the narrow recording material in one continuous passing operation acquired from the history is smaller than a predetermined threshold value;
When the representative value is greater than or equal to the threshold value, a second operating mode is executed in which the conveying interval of the recording material during the continuous paper passing is the same as that in the first operating mode, and the conveying speed is controlled to a second speed slower than the first speed.
In order to achieve the above object, the image forming system of the present invention comprises:
an image forming apparatus including: an image forming section that forms an image on a recording material; a fixing section that has a nip section that nip-conveys the recording material and heats the image in the nip section to fix it on the recording material; and a control section that controls a conveying speed of the recording material when passing through the nip section;
a server connected to the image forming apparatus via a bidirectionally accessible network, the server including a storage unit configured to store, as a history for each continuous sheet passing, the number of narrower recording materials successively passed through the nip portion during continuous sheet passing, the number being narrower than the maximum recording material having a width in a direction perpendicular to a conveying direction among the recording materials that can be conveyed through the nip portion;
In an image forming system having
The control unit is
When the narrow recording material is continuously passed through,
a first operation mode is executed in which the conveying speed is controlled to a first speed when a representative value of the number of sheets of the narrow recording material in one continuous passing operation acquired from the history is smaller than a predetermined threshold value;
When the representative value is greater than or equal to the threshold value, a second operating mode is executed in which the conveying interval of the recording material during the continuous paper passing is the same as that in the first operating mode, and the conveying speed is controlled to a second speed slower than the first speed.

The present invention makes it possible to improve productivity regardless of the size of the recording material, and to extend the life of the device.

Schematic cross-sectional view of an image forming apparatus according to first and second embodiments. Schematic cross-sectional view of an image heating apparatus according to embodiments 1, 2, and 3. Control block diagram of the first embodiment Control flow chart of the first embodiment Graph showing throughput of Example 1 Graph showing a use case of the first embodiment Control flow chart of the second embodiment Graph showing throughput of Example 3 Graph showing throughput of Example 3 Control flow chart of the third embodiment Schematic cross-sectional view of an image forming apparatus according to a third embodiment of the present invention. Control block diagram of the fourth embodiment Control block diagram of the fifth embodiment

The following describes in detail the embodiments of the present invention with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments should be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, it is not intended to limit the scope of the present invention to the embodiments described below.

[Example 1]
[Configuration of Image Forming Apparatus]
1 is a schematic diagram illustrating an example of an electrophotographic image forming apparatus according to the present embodiment. Image forming apparatuses to which the present invention can be applied include copying machines and printers that use electrophotographic or electrostatic recording methods, and the present invention will be described here as being applied to a laser printer that forms an image on a recording material P using electrophotographic methods.

The video controller 120 receives and processes image information and print instructions sent from an external device such as a host computer. The control unit 113 is connected to the video controller 120 and controls each part of the image forming device in response to instructions from the video controller 120. When the video controller 120 receives a print instruction from an external device, image formation is performed through the following operations.

In the image forming apparatus 100, a recording material P is fed by a feed roller 102 and conveyed toward an intermediate transfer body 103. A photosensitive drum 104 is rotated counterclockwise at a predetermined speed, and is uniformly charged by a primary charger 105 during the rotation process. A laser beam scanner 106 outputs a laser beam modulated according to an image signal, and selectively scans and exposes the photosensitive drum 104 to form an electrostatic latent image. A developer 107 rotates a developing roller 118 to attach powder toner, which is a developing body, to the electrostatic latent image, thereby visualizing the image as a toner image (developed body image). The toner image formed on the photosensitive drum 104 is primarily transferred onto an intermediate transfer body 103 that rotates in contact with the photosensitive drum 104.

Here, the photosensitive drum 104, the primary charger 105, the laser beam scanner 106, the developer 107, and the developing roller 118 are arranged for four colors, cyan (C), magenta (M), yellow (Y), and black (K). The toner images for the four colors are transferred in the same order onto the intermediate transfer body 103 in a superimposed manner. The toner images transferred onto the intermediate transfer body 103 in a superimposed manner are secondarily transferred onto the recording material P by a transfer bias applied to the transfer roller 108 in a secondary transfer section formed by the intermediate transfer body 103 and the transfer roller 108. Thereafter, a fixing device (image heating device) 200 as a fixing section (image heating section) heats and presses the recording material P to fix the toner image, and the recording material P is discharged outside the machine as an image formation product.
In the above configuration, the configuration involved in forming an unfixed toner image on a recording material corresponds to the image forming section in the present invention.

The control unit 113 manages the conveying status of the recording material P using a conveying sensor 114, a registration sensor 115, a pre-fixing sensor 116, and a fixing discharge sensor 117 on the conveying path of the recording material P. In addition, the control unit 113 has a memory unit that stores a temperature control program for the fixing device 200. A control circuit 400 as a heater driving means connected to a commercial AC power source 401 supplies power to the fixing device 200. In this embodiment, an image forming device with a maximum paper passing width of 216 mm in the direction (width direction) perpendicular to the conveying direction of the recording material P is used, and it is possible to print letter-size (216 mm x 279 mm) recording material.

[Configuration of Fixing Device (Image Heating Device)]
2 is a schematic cross-sectional view of the fixing device 200 in this embodiment. The fixing device 200 has a fixing film 202 as an endless belt, a heater unit 310 that contacts the inner surface of the fixing film 202, a pressure roller 208 that contacts the outer surface of the fixing film 202, and a metal stay 204. The pressure roller 208 forms a fixing nip N together with a heater 300 via the fixing film 202. The heater unit 310 has a heater 300 and a heater holding member 201 that holds the heater 300.

The fixing film 202 is a multi-layered heat-resistant film formed into a cylindrical shape, and a base layer can be made of a thin heat-resistant resin such as polyimide or a metal such as stainless steel. The surface of the fixing film 202 is coated with a heat-resistant resin with excellent releasability such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) to prevent toner adhesion and ensure separation from the recording material P, forming a release layer. Furthermore, in order to improve image quality, particularly in devices that form color images, a heat-resistant rubber such as silicone rubber may be formed as an elastic layer between the base layer and the release layer.

The pressure roller 208, which serves as a pressure member, has a core metal 209 made of iron, aluminum, or the like, and an elastic layer 210 made of silicone rubber or the like.

The heater 300 is heated by a heating element provided on a ceramic substrate 305, and is provided with a surface protection layer 308 provided on the fixing nip N side and a surface protection layer 307 provided on the opposite side of the fixing nip N. Power is supplied from an electrode (not shown) provided on the opposite side of the fixing nip N. A thermistor 212 serving as an element (temperature detection unit) for detecting the temperature of the heater 300 is in contact with the heater 300. The heater 300 is held by a heater holding member 201 made of heat-resistant resin, and heats the fixing film 202. The heater holding member 201 also has a guide function for guiding the rotation of the fixing film 202.

The metal stay 204 receives a pressure force (not shown) and biases the heater holding member 201 holding the heater 300 toward the pressure roller 208, thereby forming a fixing nip portion N between the fixing film 202 and the pressure roller 208.

The pressure roller 208 receives power from the motor 30 and rotates in the direction of the arrow R1. As the pressure roller 208 rotates, the fixing film 202 rotates in the direction of the arrow R2. The unfixed toner image on the recording material P is fixed by applying heat from the fixing film 202 while the recording material P is nipped and conveyed in the fixing nip N.

[Control block configuration]
3 shows a control block diagram of this embodiment. The video controller 120 receives and processes image information and print instructions sent from an external device 501 such as a host computer. When the video controller 120 receives the image information and print instructions, it instructs the control unit 113 to perform a preparation operation. Thereafter, the video controller 120 converts the image information into printable information and instructs the control unit 113 to perform an image forming operation.

The image forming control unit 502 controls preparatory operation 1 according to a preparatory operation instruction before an image forming operation is instructed, preparatory operation 2 according to a print mode after an image forming operation is instructed, and image forming operation in response to an instruction from the video controller 120. In preparatory operation 1, the fixing device 200 and the laser beam scanner 106 are started to be driven. In preparatory operation 2, preparatory operations necessary for the image forming operation that are not performed in preparatory operation 1 are performed. Specifically, in preparatory operation 2, the photosensitive drum 104, primary charger 105, developer 107, intermediate transfer body 103, and transfer roller 108 are started to be driven. The print mode refers to image forming conditions according to the type of recording material, and includes the transport speed, transfer conditions, target temperature for fixing, etc.

A toner image control unit 503 controls the transfer biases of the laser 483, scanner motor 473, drum motor 475, primary charger 477, developing motor 479, intermediate transfer motor 481, and transfer roller 108 in response to an image formation instruction from the image formation control unit 502, to form a toner image.
The temperature adjustment control unit 505 determines a target temperature of the heater 300 to be controlled by the heating element control unit 507 in response to a preparatory operation instruction or an image formation instruction from the image formation control unit 502 .
The print operation history collection unit 506 stores the print operation history in the storage device (storage unit) 469 .

Next, the print operation history will be explained. A print operation starts in response to an instruction from the video controller 120, and one job is defined as the time when all printing (an image forming operation in which multiple sheets of recording material of a specified size are continuously fed and image formation and image fixing are continuously performed on each of the multiple recording materials) is completed. Information on how many sheets were continuously printed in one job and paper size information are stored as the print operation history. An example is shown in Table 1. The history can store the most recent 100 jobs.

(Table 1) Print operation history

Table 2 shows an example of the analysis results of the print operation history. The print operation history analysis unit 508 stores the analysis results of the print operation history in the memory device 469. In the print operation history analysis in this embodiment, the average value of the number of continuous prints per job for each paper size is calculated. For example, in the print operation history shown in Table 1, there are three jobs with a paper size of A5 among the most recent 100 jobs. If the number of continuous prints per job is 2, 4, and 6, respectively, the print operation history analysis result is stored in the memory device 469 as an average value of 4.

(Table 2) Print operation history analysis

In this embodiment, the average number of consecutive prints was used as the representative value of the analysis results, but it is also possible to combine not only the average value, but also the median, mode, and standard deviation.

[Method of controlling image forming operation]
FIG. 4 is a control flow chart in this embodiment.
In S401, when the video controller 120 receives image information and a print instruction transmitted from the external device 501, it starts the operation of converting the image information into information that can be printed, and also instructs the control unit 113 to perform a preparation operation.

In S402, the image forming control unit 502 included in the control unit 113 receives the preparatory operation instruction and determines whether the number of sheets in the print job has been confirmed. For example, if the print job contains only one sheet, the number may have been confirmed when the preparatory operation instruction was received. However, if the print job contains a large number of sheets, it is highly likely that the number has not been confirmed at this point.

If the number of sheets in the print job has been determined in S402, the image forming control unit 502 receives the number of sheets in the print job from the video controller 120 in S403.
In S404, the number of sheets in the print job is compared with a predetermined number of sheets for switching the image forming speed (hereinafter, the speed switching number), and if the number of sheets in the print job is smaller, printing is performed at a first image forming speed in S405 (first operation mode).On the other hand, if the number of sheets in the print job is greater than the predetermined number for switching the speed (equal to or greater than the speed switching number) in S404, printing is performed at a second image forming speed in S406 (second operation mode).

If the number of pages in the print job has not been confirmed in S402, the print operation history analysis unit 508 acquires the print operation history analysis result from the storage device 469 in S407.
In S408, if the print operation history analysis result indicates that the average number of continuous prints for the paper size specified in the print job is less than the predetermined speed switching number, printing is performed at a first image formation speed in S409. On the other hand, if the average value of the continuous print number history is greater than the predetermined speed switching number (equal to or greater than the speed switching number) in S408, printing is performed at a second image formation speed in S410. In other words, if the representative value of the number of sheets in one continuous paper pass is equal to or greater than a predetermined threshold value, the conveying speed of the recording material is slowed down.

When all the print jobs have been printed in S411, the print operation history collection unit 506 stores the number of pages of the print jobs in the storage device 469 in S412.
In step S<b>413 , the print operation history analysis unit 508 acquires the latest print operation history from the storage device 469 , calculates the average number of consecutive prints for each paper size, and stores the average number in the storage device 469 .

[Throughput comparison]
In the image forming apparatus of this embodiment, the first image forming speed is 200 mm/sec, and the second image forming speed is 100 mm/sec. The maximum width of the printable recording material is the width of a letter paper fed vertically (216 mm). The productivity when printing on a B5 size recording material as a small size paper will be described using this embodiment and a comparative example.

Figure 5(a) is a graph showing the relationship between the number of continuous prints [pages] and throughput (ppm: number of prints per minute) when B5 size paper is fed through at a first image formation speed (200 mm/sec) and a second image formation speed (100 mm/sec).

The fixing temperature at the first image forming speed (the control target temperature at which the temperature detected by thermistor 212 should be maintained) is approximately 200°C in this embodiment from the viewpoint of fixability. When paper is passed at the first image forming speed, it starts at 37 ppm, and after about three sheets, the non-paper passing areas heat up to near the heat resistance temperature of the fixing unit due to the rise in temperature of the non-paper passing areas. For this reason, the throughput, which is the number of sheets of recording material passing through the fixing nip per unit time, is gradually reduced from 18 ppm to 5 ppm (the paper interval (the conveying interval of the recording material) is widened).

On the other hand, the fixing temperature at the second image formation speed is set to approximately 150°C, which is a lower temperature than the fixing temperature setting at the first image formation speed, because the image formation speed is slower than the first image formation speed. Therefore, because the fixing temperature itself is low, the temperature rise in the non-paper passing areas is also low, and when paper is passed at the second image formation speed, paper passing begins at an initial temperature of approximately 18.5 ppm, and thereafter, the temperature of the non-paper passing areas does not reach near the heat resistance temperature of the fixing unit. As a result, the throughput can be maintained at 18.5 ppm.

Next, when printing B5 size paper with an image forming apparatus installed in the market, the number of consecutive prints varies depending on the user. In this embodiment, two types of use cases are assumed. FIG. 6A shows the ratio of each print number to all jobs as use case 1. For example, the ratio of 1 print number to all jobs is 25%. Also, when the number of prints is 11 or more, it is set as one section, and the ratio is 4%. Next, FIG. 6B shows use case 2 as the second use case. In use case 2, the tendency of the number of prints is different from use case 1, and it is assumed that 6 and 7 print numbers are the most common in terms of ratio. Also, when the number of prints is 11 or more, it is set as one section, and the ratio is 6%. In other words, in this embodiment, when printing B5 size paper, it is assumed that one user uses it like use case 1, and another user uses it like use case 2.

Next, comparative example 1 will be explained to compare the throughput of B5 size paper. In comparative example 1, the image formation speed is fixed at the first image formation speed (200 mm/sec), and the paper interval is widened to suppress temperature rise in non-paper passing areas. The throughput for each number of prints at this time is shown in the graph of FIG. 5(a) as a solid line (200 mm/sec). In addition, the time from start to finish of printing for each number of prints is shown in Table 3, and when shown graphically, it is shown as the solid line in FIG. 5(b).

(Table 3) Print time at 200 mm/sec

Now, assuming that the user prints at the rate of use case 1, for example, if there are 100 jobs, there will be 25 jobs for printing one sheet, 25 jobs for printing two sheets, and similarly 15 jobs for printing three sheets. If 100 jobs are printed in this use case 1, the total printing time required will be 1,729 seconds, according to Table 4.

(Table 4) Use case 1: Time required for 100 jobs (Comparative example 1)

In other words, jobs with one print per job account for 25% of jobs in use case 1, so it can be assumed that this is 25 jobs out of 100. The time required to print one print is 6.6 seconds, so the total time is 165 seconds. The same calculation can be made for jobs with two or more prints, but although the proportion of jobs with 11 or more prints is 4%, 15 prints is used as the representative value for calculating the print time. This is because it is assumed that the median frequency of jobs with 11 or more prints is 15. Therefore, assuming use case 1 in comparison example 1, it will take 1,729 seconds to process 100 print jobs.

Next, assuming that the user prints at the rate shown in Use Case 2, if 100 jobs are printed, the total printing time required will be 3109 seconds, according to Table 5.

(Table 5) Use case 2: Time required for 100 jobs (Comparative example 1)

Next, Comparative Example 2 will be described. In Comparative Example 2, the image forming speed is controlled to be switched for each paper size. When printing B5 size paper, the second image forming speed (100 mm/sec) is used. The throughput for each number of prints at this time is shown by the dashed line (100 mm/sec) in the graph of FIG. 5(a), and is constant at 18.5 ppm. In addition, the time from start to finish of printing for each number of prints is shown in Table 6, and when shown on a graph, it is shown by the dashed line in FIG. 5(b).

(Table 6) Print time at 100 mm/sec

Assuming that the user prints at the rate shown in Use Case 1, the total printing time required for printing 100 jobs will be 1,838 seconds, according to Table 7.

(Table 7) Use case 1: Time required for 100 jobs (Comparative example 2)

Next, assuming that the user prints at the rate of use case 2, when 100 jobs are printed, the total printing time required is 2755 seconds according to Table 8.

(Table 8) Use case 2: Time required for 100 jobs (Comparative example 1)

Next, the control of this embodiment will be described. In this embodiment, the image formation speed is switched according to the operation history of the image forming device. In other words, print operations are performed using different image formation speeds depending on the use case. The predetermined number of sheets for switching the image formation speed in this embodiment is set to 6 sheets. In other words, if the average number of continuous prints for each paper size calculated by the print operation history analysis unit 508 is less than 6 sheets, printing is performed at the first image formation speed, and if it is 6 sheets or more, printing is performed at the second image formation speed. Here, when a job is executed at the ratio of use case 1, the average number of continuous prints in the operation history is 3.5 sheets. On the other hand, when a job is executed at the ratio of use case 2, the average number of continuous prints in the operation history is 6.3 sheets.

Therefore, when the control of the first embodiment is performed, in the case of use case 1, since B5 size paper is printed at 200 mm/sec, the total print time when 100 jobs are printed is 1729 seconds. Also, in the case of use case 2, since printing is performed at 100 mm/sec, the total print time when 100 jobs are printed is 2755 seconds.
Table 9 shows a comparison of the total printing times when the above 100 jobs were printed.

(Table 9) Comparison of total print time for 100 jobs

In the case of Comparative Example 1, the image formation speed is 200 mm/sec, so when the ratio of jobs with a small number of sheets is high, as in Use Case 1, printing can be completed in less time than in Comparative Example 2. However, when the ratio of jobs with a large number of sheets is high, as in Use Case 2, the printing time is longer than in Comparative Example 2. Conversely, in Comparative Example 2, the printing time is longer in Use Case 1, but printing is completed in a short time in Use Case 2.

In contrast, in the first embodiment, the image formation speed is controlled based on the operation history, so printing can be completed in the shortest possible time in both use case 1 and use case 2.

As described above, in this embodiment, the operation history of the image forming apparatus is stored, the average number of continuous prints is calculated for each paper size, and the image forming speed is determined by comparing this average with the predetermined number of sheets for speed switching. Therefore, it is possible to select the optimal image forming speed for each use case, and print productivity can be maximized. Also, in this embodiment, the predetermined number of sheets for image speed switching is set to 6 sheets for B5 size paper, but the number of sheets for switching may be changed for each paper size.
That is, in this embodiment, the judgment criteria for control selection reflect the operation history that is updated each time it is used. This enables more optimal fixing operation control in accordance with the user's tendency for the number of printed sheets, thereby improving productivity and extending the life of the device by reducing the load on the device components. Note that the history information stored in the memory unit only needs to include at least the number of continuous sheets passed for recording materials of sizes where non-paper passing section temperature rise is a problem, and the memory unit may be configured not to store information for all sizes of recording materials that can be conveyed.

[Example 2]
In this embodiment, the operation history of the image forming apparatus is analyzed for each user ID. The configurations of the image forming apparatus, image heating apparatus, and control block of the second embodiment are the same as those of the first embodiment, and matters in the second embodiment that are not particularly described here are the same as those of the first embodiment.

The print operation history collection unit 506 of this embodiment collects paper size information, continuous print count information, and user ID information for each print job, and stores them in the storage device 469. Here, the user ID information refers to a unique user ID that is set to distinguish each host computer when the image forming device is connected to multiple external devices 501 (host computers) via a network. An example of the operation history stored in the storage device 469 is shown in Table 10. The history can store the most recent 500 jobs. User IDs are assigned numbers starting from "001" for each host computer connected via the network.

(Table 10) Print operation history

Next, an example of the analysis results of the print operation history in this embodiment is shown in Table 11. The average number of continuous prints is calculated for each user ID and paper size, and the results are stored in the storage device 469.

(Table 11) Print operation history analysis

In this embodiment, the average number of consecutive prints was used as the representative value of the analysis results, but it is also possible to combine not only the average value, but also the median, mode, and standard deviation.

[Method of controlling image forming operation]
FIG. 7 is a control flow chart in this embodiment.
In S701, when the video controller 120 receives image information and a print instruction transmitted from the external device 501, the video controller 120 starts the operation of converting the image information into printable information and also instructs the control unit 113 to perform a preparation operation.

At S702, the image forming control unit 502 included in the control unit 113 receives the preparatory operation instruction and determines whether the number of sheets for the print job has been confirmed.

If the number of sheets in the print job has been determined in S702, the image forming control unit 502 receives the number of sheets in the print job from the video controller 120 in S703.
In S704, the number of sheets in the print job is compared with the predetermined speed switching number, and if the number of sheets in the print job is smaller, printing is performed at a first image formation speed in S705. On the other hand, if the number of sheets in the print job is greater than the predetermined speed switching number in S704, printing is performed at a second image formation speed in S706.

If the number of pages for the print job has not been confirmed in S702, user ID information is obtained from the external device 501 in S707.
In step S708, the print operation history analysis unit 508 acquires the print operation history analysis result corresponding to the specified user ID and paper size information from the storage device 469.
In S709, if the print operation history analysis result indicates that the average number of continuous prints for the paper size specified in the print job is less than the predetermined speed switching number, printing is performed at a first image formation speed in S710. On the other hand, if the average number of continuous prints is greater than the predetermined speed switching number (equal to or greater than the speed switching number) in S709, printing is performed at a second image formation speed in S711.

When all the print jobs have been printed in S712, the print operation history collection unit 506 stores the number of pages of the print jobs in the storage device 469 in S713.
In step S<b>714 , the print operation history analysis unit 508 acquires the latest print operation history from the storage device 469 , calculates the average number of continuous prints for each user ID and paper size, and stores the average number of continuous prints in the storage device 469 .

As described above, in this embodiment, a user ID is assigned to each host computer connected via a network, and the operation history for each user ID is analyzed. Therefore, it is possible to envision use cases according to the user ID, and by selecting the optimal image formation speed for each user ID, print productivity can be maximized.

[Example 3]
In this embodiment, the predetermined number of sheets for determining whether to switch the image formation speed is changed is variable depending on the environmental temperature in which the image forming apparatus is installed. The configurations of the image forming apparatus, image heating apparatus, and control block of the third embodiment are the same as those of the first embodiment, except that an environmental temperature detection sensor 490 is provided as an environmental information acquisition unit, as shown in Fig. 11. Items in the third embodiment that are not particularly described here are the same as those in the first and second embodiments.
The information acquired as the environmental information may be humidity, absolute water content, etc., in addition to temperature.

Fig. 8A is a graph showing the relationship between the number of continuous prints [pages] and throughput when B5 size paper is fed at a first image forming speed (200 mm/sec) and a second image forming speed (100 mm/sec) when the environmental temperature is 20° C. Fig. 8B is a similar graph when the environmental temperature is 30° C.
8(b) where the environmental temperature is 30° C., the amount of heat required for fixing is smaller than that in FIG. 8(a) where the environmental temperature is 20° C., so the set temperature of the fixing unit can be lowered. Therefore, the temperature rise in the non-paper passing area is also suppressed, so that even if the throughput is gradually reduced when the image forming speed is 200 mm/sec, the reduction in the throughput is gradual. On the other hand, when the image forming speed is 100 mm/sec, the reduction in throughput due to the temperature rise in the non-paper passing area does not occur regardless of the environmental temperature.

Next, FIG. 9 shows the time from start to finish of printing for each number of prints. FIG. 9(a) shows the time when printing with throughput control when the environmental temperature is 20°C, and FIG. 9(b) shows the time when printing with throughput control when the environmental temperature is 30°C. In FIG. 9(a), when the number of prints is 6 or less, it is more productive to print at 200 mm/sec, but when the number of prints is 7 or more, it is more productive to print at 100 mm/sec. On the other hand, in FIG. 9(b), it can be seen that the productivity of the image formation speed of 200 mm/sec and the image formation speed of 100 mm/sec are reversed at the border of 10 prints. In other words, when the environmental temperature is high, print productivity is maximized by setting the predetermined number of prints for determining the image formation speed change to a large value.

[Method of controlling image forming operation]
FIG. 10 is a control flow chart in this embodiment.
In S101, when the video controller 120 receives image information and a print instruction transmitted from the external device 501, the video controller 120 starts the operation of converting the image information into printable information and also instructs the control unit 113 to perform a preparation operation.

In S102, the control unit 113 acquires the environmental temperature from the environmental temperature detection sensor 490 installed in the image forming apparatus.
In step S103, the number of sheets required for switching the image forming speed for each environmental temperature is set. In this embodiment, when B5 size paper is continuously printed, the number of sheets required for switching the image forming speed for each environmental temperature is shown in Table 12.

(Table 12)

At S104, the control unit 113 determines whether the number of pages for the print job has been confirmed.

If the number of sheets in the print job has been determined in S104, the image forming control unit 502 receives the number of sheets in the print job from the video controller 120 in S105.
In S106, the number of sheets in the print job is compared with the speed switching number set in S103, and if the number of sheets in the print job is smaller, printing is performed at a first image formation speed in S107. On the other hand, if the number of sheets in the print job is greater than the speed switching number in S106, printing is performed at a second image formation speed in S108.

If the number of sheets for the print job has not been determined in S104, then in S109, if the print operation history analysis result shows that the average number of continuous prints for the paper size specified in the print job is less than the speed switching number, then printing is performed at the first image formation speed in S110. On the other hand, if in S109 the average number of continuous prints is greater than the speed switching number (equal to or greater than the speed switching number), then printing is performed at the second image formation speed in S111.

When all the print jobs have been printed in S112, the print operation history collection unit 506 stores the number of pages of the print jobs in the storage device 469 in S113.
In S<b>114 , the print operation history analysis unit 508 acquires the latest print operation history from the storage device 469 , calculates the average number of consecutive prints, and stores it in the storage device 469 .

As described above, in this embodiment, the number of sheets used to determine whether to switch the image formation speed is variable depending on the environmental temperature in which the image forming device is installed. By selecting the optimal image formation speed for each environmental temperature, print productivity can be maximized.

[Example 4]
[Control block configuration]
12 shows a control block diagram of this embodiment. The video controller 120 stores the print operation history and analyzes the print operation history. When the video controller 120 receives image information and a print instruction from the external device 501, it instructs the control unit 113 to perform a preparation operation. Thereafter, the video controller 120 converts the image information into printable information and instructs the control unit 113 to perform a print operation (image forming operation). The control unit 113 starts the print operation in response to the instruction from the video controller 120.

The print operation history collection unit 122 stores the print operation history in the storage device (storage unit) 124. As in the first embodiment, one job is defined as the period until all printing is completed. The print operation history collection unit 122 acquires information on how many sheets have been continuously printed in one job and paper size information as the print operation history, and stores it in the storage device 124. The print operation history collection unit 122 may also collect paper size information, number of continuously printed sheets information, and user ID information for each print job, and store them in the storage device 124. The print operation history collection unit 122 may perform the same processing as that performed by the print operation history collection unit 506 shown in the first to third embodiments.

The print operation history analysis unit 123 stores the analysis results of the print operation history in the memory device 124. The print operation history analysis unit 123 calculates the average number of continuous prints per job for each paper size. The results calculated by the print operation history analysis unit 123 are also stored in the memory device 124. The print operation history analysis unit 123 may perform the same process as that performed by the print operation history analysis unit 508 shown in the first to third embodiments. Information stored in the memory device 469 shown in the first to third embodiments may be stored in the memory device 124. The method of controlling the image forming operation using the analysis results of the print operation history and the method of controlling the throughput in this embodiment are the same as those in the first embodiment, so the description will be omitted.

[Example 5]
An image forming system according to this embodiment will be described.
[Control block configuration]
FIG. 13 shows a control block diagram in this embodiment. The image forming system includes an image forming apparatus 100 and a server 600. The server 600 stores the print operation history and analyzes the print operation history. The server 600 has a calculation device 601 and a server storage device 604, and is connected to the image forming apparatus 100 via a network that allows bidirectional access. When the video controller 120 receives image information and a print instruction from the external device 501, it instructs the control unit 113 to perform a preparation operation. Thereafter, the video controller 120 converts the image information into printable information and instructs the control unit 113 to perform a print operation (image forming operation). The control unit 113 starts the print operation in response to the instruction from the video controller 120.

The print operation history collection unit 602 stores the print operation history in the server storage device (storage unit) 604. As in the first embodiment, one job is defined as the time until all printing is completed. The print operation history collection unit 602 acquires information on how many sheets have been printed continuously in one job and paper size information as print operation history, and stores it in the server storage device 604. The print operation history collection unit 602 may also collect paper size information, number of continuous prints information, and user ID information for each print job, and store it in the server storage device 604. The print operation history collection unit 602 may perform the same processing as that performed by the print operation history collection unit 506 shown in the first to third embodiments.

The print operation history analysis unit 603 stores the analysis results of the print operation history in the server storage device 604. The print operation history analysis unit 603 calculates the average number of continuous prints per job for each paper size. The results calculated by the print operation history analysis unit 603 are also stored in the server storage device 604. The print operation history analysis unit 603 may perform the same process as that performed by the print operation history analysis unit 508 shown in the first to third embodiments. Information stored in the storage device 469 shown in the first to third embodiments may be stored in the server storage device 604. The method of controlling the image forming operation using the analysis results of the print operation history in this embodiment and the method of controlling the throughput are the same as those in the first embodiment, so the description will be omitted.

The above embodiments can be combined with each other as much as possible.

100: image forming apparatus, 113: control unit, 200: fixing device (image heating device), 300: heater, 469: storage device (storage unit), 501: external device, 502: image forming control unit

Claims (16)

an image forming section for forming an image on a recording material;
a fixing section having a nip section for nipping and conveying the recording material, the fixing section heating the image in the nip section to fix the image on the recording material;
a storage unit that stores, as a history for each continuous sheet passing, at least a number of narrower recording materials that are narrower than a recording material that has a maximum width in a direction perpendicular to a conveying direction among the recording materials that can be conveyed through the nip portion, the number of narrower recording materials that are continuously passed through the nip portion during continuous sheet passing;
a control unit for controlling a conveying speed of the recording material when passing through the nip portion;
In an image forming apparatus comprising:
The control unit is
When the narrow recording material is continuously passed through,
a first operation mode is executed in which the conveying speed is controlled to a first speed when a representative value of the number of sheets of the narrow recording material in one continuous passing operation acquired from the history is smaller than a predetermined threshold value;
An image forming apparatus characterized in that, when the representative value is greater than or equal to the threshold value, a second operating mode is executed in which the conveying interval of the recording material during the continuous paper passing is the same as that of the first operating mode, and the conveying speed is controlled to a second speed slower than the first speed. A temperature detection unit that detects the temperature of the fixing unit is further provided,
The image forming apparatus according to claim 1 , wherein the control unit, in the first operating mode, controls the transport interval of the recording material during the continuous paper passing so that the temperature detected by the temperature detection unit is maintained at a predetermined target temperature. 3. The image forming apparatus according to claim 1, wherein the control unit controls the conveying interval to be constant in the second operation mode. The image forming apparatus according to any one of claims 1 to 3, characterized in that the representative value is one of the average value, median value, and mode value of the number of sheets in one continuous paper pass. The image forming apparatus according to any one of claims 1 to 4, characterized in that the storage unit stores the history for each size of recording material that can be conveyed through the nip portion. the image forming apparatus is connected to a plurality of external devices via a network,
6. The image forming apparatus according to claim 1, wherein the storage section stores the history for each of the plurality of external devices. an environmental information acquisition unit that acquires environmental information about an environment in which the image forming apparatus is installed;
7. The image forming apparatus according to claim 1, wherein the threshold value is set in accordance with the environmental information acquired by the environmental information acquisition unit. The fixing unit is
a heater unit having a heater and a holding member for holding the heater;
a cylindrical film whose inner surface is in contact with the heater unit;
a pressure member that contacts an outer surface of the film to form the nip portion between the outer surface and the pressure member;
8. The image forming apparatus according to claim 1, further comprising: an image forming apparatus including: an image forming section that forms an image on a recording material; a fixing section that has a nip section that nip-conveys the recording material and heats the image in the nip section to fix it on the recording material; and a control section that controls a conveying speed of the recording material when passing through the nip section;
a server connected to the image forming apparatus via a bidirectionally accessible network, the server including a storage unit configured to store, as a history for each continuous sheet passing, the number of narrower recording materials successively passed through the nip portion during continuous sheet passing, the number being narrower than the maximum recording material having a width in a direction perpendicular to a conveying direction among the recording materials that can be conveyed through the nip portion;
In an image forming system having
The control unit is
When the narrow recording material is continuously passed through,
a first operation mode is executed in which the conveying speed is controlled to a first speed when a representative value of the number of sheets of the narrow recording material in one continuous passing operation acquired from the history is smaller than a predetermined threshold value;
An image forming system characterized in that, when the representative value is greater than or equal to the threshold value, a second operating mode is executed in which the conveying interval of the recording material during the continuous paper passing is the same as that of the first operating mode, and the conveying speed is controlled to a second speed slower than the first speed. The image forming apparatus further includes a temperature detection unit that detects a temperature of the fixing unit,
The image forming system according to claim 9, wherein the control unit, in the first operating mode, controls the transport interval of the recording material during the continuous paper passing so that the temperature detected by the temperature detection unit is maintained at a predetermined target temperature. 11. The image forming system according to claim 9, wherein the control unit controls the conveying interval to be constant in the second operation mode. The image forming system according to any one of claims 9 to 11, characterized in that the representative value is one of the average value, median value, and mode value of the number of sheets in one continuous paper pass. 13. The image forming system according to claim 9, wherein the storage section stores the history for each size of the recording material that can be conveyed through the nip portion. the image forming apparatus is connected to a plurality of external devices via a network,
14. The image forming system according to claim 9, wherein the storage unit stores the history for each of the plurality of external devices. the image forming apparatus further includes an environmental information acquisition unit that acquires environmental information about an environment in which the image forming apparatus is installed;
15. The image forming system according to claim 9, wherein the threshold value is set in accordance with the environmental information acquired by the environmental information acquisition unit. The fixing unit is
a heater unit having a heater and a holding member for holding the heater;
a cylindrical film whose inner surface is in contact with the heater unit;
a pressure member that contacts an outer surface of the film to form the nip portion between the outer surface and the pressure member;
16. The image forming system according to claim 9, further comprising:

Images