JP4475363B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, as an image forming apparatus such as a color electrophotographic printer, for example, a plurality of image forming units are arranged side by side along a belt for paper conveyance, and each image forming unit for paper conveyed on the belt And the like in which toner images of respective colors are sequentially transferred. In such an image forming apparatus, if an image forming position shift (color shift) with respect to the sheet occurs between the image forming units, the quality of the formed image deteriorates.

  Therefore, in order to ensure image quality, a technique called registration or the like that corrects the deviation of the image forming position of each color is employed. According to this technique, a predetermined pattern is formed on the belt surface by each image forming unit, the position of the pattern is detected by an optical sensor, and the amount of deviation of the image forming position of each color is obtained, and according to the amount of deviation. The image forming position of each image forming unit is corrected.

  By the way, in the image forming apparatus, when the cover is opened and closed, the accuracy of the image forming position is likely to change. Thus, for example, in the device described in Patent Document 1, when it is detected that the cover is closed, the above-described misregistration detection is performed to obtain a correction value. Thereafter, when a print request is received, based on the correction value. It is configured to perform printing.

Japanese Patent Laid-Open No. 11-95628

  However, the above-described one has a problem that misalignment detection is performed every time the cover is opened and closed. In other words, if the cover is opened and closed many times without printing, misalignment correction is wasted each time, causing problems such as deterioration of parts and consumption of colorants. there were. In addition, when it is preferable to perform detection immediately after the cover is closed, the timing for executing the detection process cannot be appropriately selected by the user.

  The present invention has been completed based on the above-described circumstances, and it is possible to suppress execution of useless misalignment correction and to appropriately select a timing for executing detection processing by the user. An object of the present invention is to provide a simple image forming apparatus.

As means for achieving the above object, an image forming apparatus according to a first invention includes a main body casing, a cover that can be opened and closed with respect to the main body casing, an open / close detection means that detects an open / closed state of the cover, A forming unit that forms an image, a detecting unit that performs a detection process for detecting a shift amount of the image forming position based on a position of a mark formed on the carrier by the forming unit, and a deviation detected by the detecting unit When the opening / closing operation of the cover is detected by the correction means for correcting the image forming position by the forming means according to the amount, the input means for inputting a print request, and the opening / closing detection means after the previous detection processing, the printing Control that causes the detection unit to execute the detection process based on a request input, and then causes the forming unit to perform image formation based on the print request. The detection process is executed by the detection unit triggered by the detection of the closure of the cover by the opening / closing detection unit, or the print request is input after the closure of the cover is detected. Selection means for selecting whether to execute the detection process as an opportunity.
According to the present invention, when a cover opening / closing operation is performed, detection processing is not performed each time, but detection is performed as long as a print request is not input even if the cover opening / closing operation is performed after the previous detection processing. Do not execute processing. Then, a detection process is executed based on the input of the print request, and thereafter, an image is formed on the carrier at an image forming position corresponding to the shift amount detected by the detection process. Therefore, for example, even when the opening / closing of the cover is repeated without inputting a print request, it is possible to suppress wasteful position correction.
In addition, since it may be preferable to perform detection immediately after the cover is closed, it is preferable that the user can appropriately select the timing for executing the detection process as in the present invention.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the invention, the input unit includes a paper jam detection unit that can specify a printing condition and detects the occurrence of a paper jam. When the opening / closing operation of the cover is detected by the opening / closing detection unit after the occurrence of a paper jam is detected by the paper jam detection unit, the detection is performed according to whether the printing condition satisfies a predetermined requirement. When the printing process is executed after the process is executed or the printing process is executed without executing the detection process, and the occurrence of the paper jam is not detected, the detection process is performed regardless of the printing condition. Execute print processing after executing.
When printing is performed after a paper jam (jam) has occurred, the possibility of a paper jam occurring again is often higher than usual. For this reason, if the detection process is always performed before printing, the detection process is repeatedly performed in vain when paper jams occur repeatedly. Therefore, when a paper jam occurs, execution of detection processing can be suppressed by limiting the execution of detection processing only when a predetermined condition is satisfied.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the input unit includes a paper jam detection unit that can specify a printing condition and detects occurrence of a paper jam. If the occurrence frequency of the paper jam in the paper jam detection unit is equal to or higher than a reference and the opening / closing operation of the cover is detected by the open / close detection unit, whether the printing condition satisfies a predetermined requirement or not. Accordingly, the print condition is switched between executing the print process after executing the detection process or executing the print process without executing the detection process, and if the occurrence frequency of the paper jam is less than the reference, Regardless, the print processing is executed after the detection processing is executed.
When printing is performed after a paper jam (jam) has occurred, the possibility of a paper jam occurring again is often higher than usual. For this reason, if the detection process is always performed before printing, the detection process is repeatedly performed in vain when paper jams occur repeatedly. Therefore, when the occurrence frequency of the paper jam is high, it is possible to suppress the execution of the useless detection process by limiting the execution of the detection process only when a predetermined condition is satisfied.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the forming unit can form an image using a plurality of colorants, and the control unit When image formation using a plurality of colorants is specified as a print condition, the print process is executed after the detection process is performed, and the image formation is performed using a single colorant as the print condition. Is specified, the printing process is executed without executing the detection process.
According to the present invention, when printing using a single colorant, the need for detecting misregistration is low, and therefore the waiting time of the user can be shortened by omitting the detection process. Further, consumption of parts and consumption of colorant can be suppressed.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects of the present invention, the image forming apparatus includes a paper jam detection unit that detects the occurrence of a paper jam, and the control unit performs the printing process after the detection process. When occurrence of a paper jam is detected continuously a predetermined number of times, the printing process is executed without executing the detection process.
When a paper jam occurs during printing, the operation of clearing the paper jam by opening and closing the cover, and causing the paper jam again during the printing process due to the subsequent print request may be repeated many times. In such a case, it is preferable not to execute misalignment correction.

According to a sixth invention, in the image forming apparatus according to any one of the first to fifth inventions, at least a part of the forming means is supported by the cover.
Since at least a part of the forming means is supported by the cover, the opening / closing operation of the cover tends to affect the image quality. Therefore, the application of the present invention is particularly effective.

  According to the present invention, it is possible to suppress execution of useless misalignment correction.

1 is a side sectional view showing a schematic configuration of a printer according to Embodiment 1 of the present invention. Block diagram schematically showing the electrical configuration of the printer Flow chart of printing / misalignment correction control processing Diagram showing misalignment correction pattern Time chart showing the relationship between cover opening / closing, misalignment detection processing, and print request (comparative example) Time chart showing the relationship between cover open / close, misregistration detection processing and print request (when color printing is specified) Time chart showing the relationship between cover opening / closing, misalignment detection processing, and print request (when monochrome printing is specified) Flowchart of printing / misalignment correction control processing according to the second embodiment Time chart showing the relationship between cover opening / closing, misregistration detection processing, print request, etc. FIG. 10 is a flowchart illustrating a part of the printing / misalignment correction control process according to the third embodiment. Time chart showing the relationship between cover opening / closing, misregistration detection processing, print request, etc. Flowchart of printing / misalignment correction control processing of embodiment 4 Time chart showing the relationship between cover opening / closing, misregistration detection processing, print request, etc. Flowchart of printing / misalignment correction control processing of embodiment 4 (part 1) Flowchart of printing / misalignment correction control process of embodiment 4 (part 2)

<Embodiment 1>
Embodiment 1 of the present invention will be described with reference to FIGS.
(Entire printer configuration)
FIG. 1 is a side sectional view showing a schematic configuration of a printer 1 (an example of an image forming apparatus) according to the present embodiment. In the following description, the left side in FIG. The printer 1 is a color printer that forms a color image with colorants of four colors (black BK, yellow Y, magenta M, and cyan C). It is assumed that BK (black), Y (yellow), M (magenta), and C (cyan) indicating each color are added to the end of the reference numerals of the component parts.

The printer 1 includes a main body casing 3, and a supply tray 7 on which sheets 5 serving as recording media are stacked is provided at the bottom of the main body casing 3. A front cover 3A (an example of a cover) is provided on the front side of the main body casing 3 so as to be openable and closable around the lower end portion, and an upper cover 3B (an example of a cover) is provided on the upper surface of the main body casing 3 at the rear end portion. It can be opened and closed around.

  A paper feed roller 9 is provided above the front end of the supply tray 7, and the uppermost sheet 5 stacked in the supply tray 7 is sent out to the registration roller 11 as the paper feed roller 9 rotates. The registration roller 11 corrects the skew of the sheet 5 and then conveys the sheet 5 onto the belt unit 15 of the image forming unit 13.

The image forming unit 13 (an example of a forming unit) includes a belt unit 15, an exposure unit 17, a process unit 19, a fixing unit 21, and the like.
The belt unit 15 has a configuration in which a belt 25 made of polycarbonate or the like is stretched between a pair of front and rear belt support rollers 23 and 23. Then, the belt support roller 23 on the rear side is rotationally driven, whereby the belt 25 circulates counterclockwise on the paper surface, and the paper 5 on the upper surface of the belt 25 is conveyed backward. Further, on the inner side of the belt 25, transfer rollers 29 are provided at positions facing each photosensitive drum 27 of the process unit 19 to be described later across the belt 25, respectively.

  Further, a pair of pattern detection sensors 26 (an example of detection means) that detect a pattern formed on the belt 25 are provided facing the lower surface of the belt 25. The pattern detection sensor 26 irradiates the surface of the belt 25 with light, receives the reflected light with a phototransistor or the like, and outputs a signal having a level corresponding to the amount of light received. A cleaning device 28 that collects toner, paper dust, and the like attached to the surface of the belt 25 is provided below the belt unit 15.

  The exposure unit 17 includes four LED units 17BK, 17Y, 17M, and 17C (an example of part of a forming unit) corresponding to each color. Each LED unit 17BK, 17Y, 17M, 17C has an arm 16 whose upper end is supported so as to be suspended from the lower surface of the upper cover 3B, and an LED head 18 provided at the lower end of the arm 16. The LED head 18 has a plurality of light emitting units made of LEDs arranged in the left-right direction. A CPU 61, which will be described later, controls the light emission of each light emitting unit based on the image data to be formed, thereby irradiating the surface of the photosensitive drum 27 with the light emitted from each light emitting unit and exposing it.

  The process unit 19 includes a frame 31 and a plurality of developing cartridges 33 (an example of 33BK, 33Y, 33M, and 33C cartridges) corresponding to the four colors mounted on the frame 31. Below each developing cartridge 33, a photosensitive drum 27 whose surface is covered with a positively chargeable photosensitive layer and a scorotron charger 37 are provided.

  The developing cartridge 33 is replaced by opening the upper cover 3B, or a paper jam removal process (jam processing) is performed with the developing cartridge 33 removed or the front cover 3A opened.

Each developing cartridge 33 is provided with a toner storage chamber 39 for storing toner of each color as a developer (coloring agent) on the inner upper part of a box-shaped casing, and a supply roller 41, a developing roller 43, a layer thickness are provided below the toner storing chamber 39. A regulation blade 45, an agitator 47, and the like are provided. The toner discharged from the toner storage chamber 39 is supplied to the developing roller 43 by the rotation of the supply roller 41, and is positively frictionally charged between the supply roller 41 and the developing roller 43. Further, the toner supplied onto the developing roller 43 enters between the layer thickness regulating blade 45 and the developing roller 43 as the developing roller 43 rotates, and is further sufficiently frictionally charged to have a constant thickness. It is carried on the developing roller 43 as a thin layer.

  At the time of image formation, the photosensitive drum 27 is rotationally driven, and accordingly, the surface of the photosensitive drum 27 is uniformly positively charged by the charger 37. The positively charged portion is exposed by high-speed scanning of light from the exposure unit 17, and an electrostatic latent image corresponding to the image to be formed on the paper 5 is formed on the surface of the photosensitive drum 27.

  Next, the electrostatic latent toner formed on the surface of the photosensitive drum 27 when the positively charged toner carried on the developing roller 43 comes into contact with the photosensitive drum 27 by the rotation of the developing roller 43. Supplied to the image. As a result, the electrostatic latent image on the photosensitive drum 27 is visualized, and the surface of the photosensitive drum 27 carries a toner image with toner attached only to the exposed portion.

  Thereafter, the toner image carried on the surface of each photosensitive drum 27 is transferred to the transfer roller 29 while the sheet 5 conveyed by the belt 25 passes through each transfer position between the photosensitive drum 27 and the transfer roller 29. The images are sequentially transferred onto the paper 5 by the applied negative transfer voltage. The sheet 5 having the toner image transferred thereon is then conveyed to the fixing unit 21.

  The fixing unit 21 includes a heating roller 49 having a heat source and a pressure roller 51 that presses the paper 5 toward the heating roller 49, and heat-fixes the toner image transferred onto the paper 5 on the paper surface. The sheet 5 thermally fixed by the fixing unit 21 is conveyed upward and discharged onto a discharge tray 53 provided on the upper surface of the main body casing 3.

(Electrical configuration of printer)
FIG. 2 is a block diagram schematically showing the electrical configuration of the printer 1. As shown in FIG. 1, the printer 1 includes a CPU 61, a ROM 63, a RAM 65 and NVRAM 67 (nonvolatile memory) as an example of a storage unit, and a network interface 69, and the image forming unit 13 and the pattern detection sensor 26 described above. In addition, a display unit 73, an operation unit 75 (an example of an input unit), a paper jam detection sensor 76 (an example of a paper jam detection unit), a cover open / close detection sensor 78 (an example of an open / close detection unit), and the like are connected.

  The ROM 63 stores a program for executing various operations of the printer 1 such as a printing / misalignment correction control process to be described later. The CPU 61 stores the processing result in the RAM 65 or in accordance with the program read from the ROM 63. Each unit is controlled while being stored in the NVRAM 67 (hereinafter referred to as “RAM 65 or the like”). The network interface 69 is connected to an external computer 79 or the like via a communication line 77, thereby enabling mutual data communication.

  The display unit 73 includes a liquid crystal display, a lamp, and the like, and can display various setting screens and operation states of the apparatus. The operation unit 75 includes a plurality of buttons, and various input operations can be performed by the user. For example, an input operation for a print request, an input operation for designating a predetermined printing condition, and the like can be performed. The designation of the predetermined printing condition includes, for example, designation of color printing or monochrome printing, designation of normal image quality or high image quality higher than a predetermined level, and the like. The print request and the print conditions can also be specified via the network interface 69 by an input operation using an external computer 79, for example. In this case, the network interface 69 is an example of input means.

For example, a plurality of paper jam detection sensors 76 are arranged on the conveyance path of the paper 5 and detect the presence or absence of the paper 5 at each position. For example, after receiving a print request, the CPU 61 determines that a paper jam has occurred when a detection signal indicating the presence of the paper 5 is not received from the paper jam detection sensor 76 at a predetermined timing. The cover open / close detection sensor 78 detects the open / closed state of the front cover 3 </ b> A and the upper cover 3 </ b> B (hereinafter simply referred to as “cover”).

(Printing and misalignment correction control processing)
The printing / misalignment correction control process executed by the CPU 61 will be described. FIG. 3 is a flowchart of the printing / misalignment correction control process, and FIG. 4 is a diagram showing misalignment correction patterns.

  When the printer 1 is turned on, the CPU 61 executes a printing / misalignment correction control process shown in FIG. The CPU 61 first functions as control means. That is, when the opening / closing detection means detects the opening / closing operation of the cover after the previous positional deviation detection process (an example of the detection process will be described later), the positional deviation detection process is executed based on the input of the print request. Thereafter, the image forming unit 13 executes image formation based on the print request.

  Specifically, the CPU 61 monitors whether a cover opening / closing operation has been performed based on a detection signal from the cover opening / closing detection sensor 78 in S1, and monitors whether there has been a print request in S3. While the opening / closing operation of the cover is not detected after the previous misalignment detection process (S1: NO), the misalignment detection request not required state (specifically, for example, the misalignment detection request flag is set in the RAM 65 or the like). Record the information to the effect that they cannot stand up). On the other hand, if a cover opening / closing operation is detected after the previous positional deviation detection process (S1: YES), a positional deviation detection requested state (specifically, for example, in the position of the RAM 65 or the like) that requests the positional deviation detection process in S5. Information to set a deviation detection request flag is recorded). However, even if this misregistration detection request is entered, the misregistration detection process is not performed immediately, and the misregistration detection process is not performed until there is a print request.

  If there is a print request (S3: YES), a print request flag is set in the RAM 65 or the like, and it is determined in S7 whether or not there is a positional deviation detection request. Here, when a print request is made without detecting the opening / closing operation of the cover after the previous misalignment detection process (S1: NO and S3: YES), it is determined that there is no misalignment detection request. (S7: NO). In this case, the image forming unit 13 is caused to execute the printing process for one page by using the correction value X currently recorded in the RAM 65 or the like as it is without performing the misregistration detection process (S9).

  On the other hand, when the cover opening / closing operation has already been detected after the previous misregistration detection process and a print request is made after that (S1: YES and S3: YES), the misregistration detection is requested. It is determined that there is (S7: YES). Then, the CPU 61 executes the printing process after executing the misregistration detection process when the printing condition specified by the operation unit 75 or the like satisfies the predetermined requirement, and when the printing condition does not satisfy the predetermined requirement, The printing process is executed without executing the deviation detection process.

  Specifically, in S11, it is determined whether the printing condition satisfies a predetermined requirement. Here, the “predetermined requirement” means that at least one of color printing and high image quality printing is designated as a printing condition. When monochrome printing or normal image quality printing has been designated as the printing condition (S11: NO), the correction value X currently recorded in the RAM 65 or the like is used as it is without performing misregistration detection processing for one page. The image forming unit 13 is caused to execute the printing process (S9).

On the other hand, when color printing or high-quality printing is specified as the printing condition (S11: YES), image formation is performed based on the position of the mark formed on the carrier by the image forming unit 13 in S13. A misregistration detection process for detecting the misregistration amount is performed. Specifically, the CPU 61 first causes the image forming unit 10 to form a misalignment correction pattern P on the belt 25 (an example of a carrier). The correction pattern P may be the sheet 5 (an example of a carrier) conveyed from the supply tray 7 instead of the belt 25.

  The misregistration correction pattern P has a plurality of marks 81 arranged in a line on both sides of the belt 25 as shown in FIG. The pair of pattern detection sensors 26 described above are disposed at positions facing the marks 81 in each row. Each mark 81 is arranged at a predetermined interval in the conveyance direction of the paper 5, and a set of four marks 81 formed in each color used in the process unit 19, and a plurality of sets of marks 81 are in a certain order (for example, black 81BK). , Yellow 81Y, magenta 81M, cyan 81C in this order).

  The CPU 61 measures the amount of misregistration of each color based on all the patterns P formed on the belt 25. Specifically, the CPU 61 detects the position of each mark 81 by comparing the output level of the pattern detection sensor 26 with a predetermined threshold value. At this time, the CPU 61 and the pattern detection sensor 26 function as detection means.

  Next, in S15, for each set of marks 81 described above, the marks 81 of the other three colors (hereinafter referred to as “correction colors”) with respect to the position of the black (hereinafter referred to as “reference color”) mark 81BK. A positional shift amount (more specifically, a shift amount with respect to a regular distance interval from the position of the reference color) is obtained. With respect to the above-described misregistration amounts of the respective correction colors, an average value of all sets is calculated, and this average value is set as a new correction value for each correction color, and these correction values are overwritten in the RAM 65 or the like as the correction value X. Update. Thereafter, in S17, the misalignment detection requested state is changed to a misalignment detection not requested state, and the process proceeds to S9.

  In S9, the CPU 61 corrects the image forming position by the image forming unit 13 in accordance with the position shift amount (new correction value X) detected in the position shift detection process (S13). At this time, the CPU 61 functions as a correction unit. That is, the light emission timing of the LED head 18 with respect to each correction color is adjusted so as to cancel out the positional deviation amount (correction value X) of each correction color with respect to the reference position. Thereafter, in S19, it is determined whether or not printing of all pages of the print data corresponding to the current print request has been completed. If printing has not been completed (S19: NO), the process returns to S1 and printing is completed. (S19: YES) After the above-described print request flag is deleted (S21), the process returns to S1 to enter a cover opening / closing operation and a print request standby state.

(Operational effect of this embodiment)
(1) The operation and effect of the present embodiment by the printing / misalignment correction control process will be described in comparison with a comparative example.
The CPU 61 monitors the status of the printer 1 and performs the above-described misregistration detection process (S13) even when the status of the printer 1 satisfies other conditions than opening and closing of the cover. When the other conditions are satisfied, the misregistration detection process is performed without waiting for a print request. Other conditions include, for example, when the printer 1 is turned on, when there is no printing request for a predetermined time, and when the number of printed sheets from the previous correction reaches a predetermined number.

A. Comparative Example Here, as shown in FIG. 5, when the cover is opened and closed, the misalignment detection process is performed immediately without waiting for a print request, as in the case where other conditions are satisfied. become. That is, every time the cover is opened and closed as shown in (1) and (4) of FIG. 5, the positional deviation detection process (see FIGS. 5 (3) and (6)) is performed. In particular, as shown in the figure, for example, when a cover is repeatedly opened and closed and a subsequent print request (see FIGS. 5 (7) and (8)) is made within a relatively short time, a misalignment detection process is performed. As a result, parts are deteriorated and toner is consumed.

In addition, since the opening and closing of the cover is performed at the time of replacement of the developing cartridge 33 or jam processing, there is a high possibility that the cover is repeated more frequently than other conditions. On the other hand, since the printer 1 has a configuration in which each LED head 18 is suspended from the upper cover 3B via the arm 16 as described above, the image forming position is particularly easily displaced by opening and closing the upper cover 3B. Therefore, it is not preferable that the position shift detection process is not performed at all when the cover is opened or closed just because the cover is frequently opened and closed.

B. Therefore, unlike the case where other conditions are satisfied, the printer 1 of this embodiment has a print request when the cover is opened and closed (S1: YES) (S3). : YES), the positional deviation detection process (S13) is performed.

For example, as shown in FIG. 6, even if the cover is repeatedly opened and closed (see FIGS. 6 (1) and (4)), the misalignment detection process is performed only at the time when the misalignment detection is requested (S5). Not (see FIGS. 6 (2) and (5)). If there is a color print request (S11: YES)
First, the misregistration detection process (see FIG. 6 (6)) is performed, and then the printing process (see FIG. 6 (8)) is performed. Therefore, for example, when the opening and closing of the cover is repeated without inputting a print request, it is possible to suppress the misalignment correction.

  (2) When there is a request for monochrome printing (an example of image formation using a single colorant) in a state where there is a positional deviation detection request (S7: YES and S11: NO), FIG. As shown in FIG. 7, while monochrome printing is being requested (see FIGS. 7 (3), (5), and (9)), monochrome printing is performed without performing misregistration detection processing (FIGS. 7 (4) and (6)). 10)). Then, when a request for color printing (an example of image formation using a plurality of colorants) is made (see FIG. 7 (11)), color misalignment detection processing is performed and then color printing processing is performed (FIG. 7 (FIG. 7)). 12) (see 13)).

  As described above, when a predetermined condition (for example, color printing, printing in a high image quality mode or printing of a predetermined number of sheets or more) is specified as a printing condition (for example, a condition that requires print quality is specified). In the case), the printing process is executed after the misregistration detection process, so that the print quality can be ensured. Further, when the predetermined condition is not specified (for example, when high print quality is not required), the printing process is executed without executing the misregistration detection process, so that the waiting time of the user can be shortened. In the case of monochrome printing, there are few problems due to image formation misregistration and the need for misregistration detection is low. Therefore, the waiting time of the user can be shortened by omitting misregistration detection processing. Further, consumption of parts and consumption of colorant can be suppressed.

<Embodiment 2>
8 and 9 show the second embodiment. The difference from the first embodiment lies in a part of the process during the printing / misalignment correction control process, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next. FIG. 8 is a flowchart of the printing / misalignment correction control process.

  Once a paper jam occurs, for example, the jammed paper pieces have not been sufficiently removed, and thereafter there may be repeated paper jams every time there is a print request. Therefore, in this embodiment, when the paper jam occurs repeatedly more than a predetermined number of times after the cover is opened and closed, even if there is a print request, the misregistration detection process is prohibited and the print process is performed. In such a case, the positional deviation detection process is allowed.

Specifically, when the CPU 61 first detects opening / closing of the cover (S1: YES), the CPU 61 determines whether the opening / closing of the cover has been performed in a paper jam state in S31. This is determined, for example, by whether or not information indicating that a paper jam flag is set is recorded in the RAM 65 or the like. For example, when the cover is opened and closed when the paper cartridge is not jammed, such as replacement of the developing cartridge 33 (S31: NO), the position deviation detection request is always set in S5.

  On the other hand, when the cover is opened and closed in a paper jam state (S31: YES), the paper jam state is once canceled in S33 (information indicating that the paper jam flag is not set is recorded in the RAM 65 or the like). Next, in S35, it is determined whether or not the normal printing is not performed after the opening and closing of the cover and the paper jam is continuously generated a predetermined number of times. This is determined by whether or not a paper jam counter, which will be described later, is a predetermined number of times (for example, twice) or more. If the paper jam counter is less than the predetermined number of times (S35: NO), the process proceeds to S3 after setting the position deviation detection request in S5, but if it exceeds the predetermined number of times (S35: YES), it indicates that there is no position deviation detection request. Continue to S3.

  Even if a print request is made (S3: YES), if the paper jam state has not been resolved (S37: YES), the printing process cannot be performed and the process returns to S3 again, while if the paper jam state has been resolved ( (S37: NO), the process proceeds to S7.

  The CPU 61 detects the occurrence of a paper jam during the printing process in S9. Specifically, during the printing process, the detection signal from the paper jam detection sensor 76 is monitored, and the occurrence of paper jam is detected based on the detection signal. If no paper jam occurs during the printing process (S39: NO), assuming that the printing process for one page is normally completed, the paper jam counter is initialized to “zero” in S41, and the process proceeds to S19. . On the other hand, when a paper jam occurs during the printing process (S39: YES), the paper jam state is set at S43, and "1" is added to the paper jam counter at S45.

  Next, the relationship between the cover open / close, the position shift detection process, the print request, and the like is as shown in FIG. For example, if a paper jam occurs during printing of a certain page (see FIG. 9 (1)) (see FIG. 9 (2)) (S39: YES), the CPU 61 sets a paper jam flag to set the paper jam state, and the paper jam occurs. “1” is added to the counter (S43, S45).

  After that, when the cover is opened and closed for the paper jam removal process (see FIG. 9 (3)) (S1: YES), this is the opening and closing of the cover in the paper jam state (S31: YES). The clogged state is released (S33). At this time, the paper jam counter is still “1” (S35: NO), so that the position deviation detection request is made (S5). In other words, if there is a next print request (see FIG. 9 (5)) (S3: YES), as long as the printing conditions satisfy the predetermined requirements (S11: YES), a misregistration detection process (see FIG. 9 (6)), etc. Implement (S13-S15).

Thereafter, when a paper jam occurs again (see FIG. 9 (8)) during the printing process (see FIG. 9 (7)) in S9, the cover is opened and closed again for the paper jam removal process (FIG. 9 (9)). )) (S1: YES), but the paper jam counter is already “2” at this time (S35: YES), and therefore no misregistration detection request is maintained. That is, even if there is a next print request (see FIG. 9 (10)) (S7: YES), the printing process of S9 is performed without performing the misregistration detection process regardless of whether the printing condition satisfies the predetermined requirement. (See FIG. 9 (11)). Accordingly, even after the cover is opened and closed, the misregistration detection process is not performed as long as a paper jam occurs during the printing process (unless the printing process is normally completed).

On the other hand, if the printing process is successful without occurrence of paper jam (see FIG. 9 (16)) (S39: NO), the paper jam counter is initialized to “zero” (S41). Therefore, after this, when a paper jam occurs again and the cover is opened and closed (S1: YES and S31: YES), the position deviation detection request is again made.

  According to the above configuration, when paper jams frequently occur, it is possible to prevent the misregistration detection process due to the reprint request after opening / closing the cover from being wasted.

<Embodiment 3>
10 and 11 show the third embodiment. The printing / misalignment correction control process of the present embodiment is different from the process (between A and B) surrounded by the dotted line in FIG. 8 of the second embodiment, and this part of the process is shown in FIG. The other points are the same as in the second embodiment. Therefore, the same reference numerals as those in the second embodiment are given and the redundant description is omitted, and only different points will be described next.

  In the present embodiment, when the CPU 61 detects the occurrence of a paper jam and then detects the opening and closing of the cover, the CPU 61 attempts to print a test page by the image forming unit 13, and after the printing process has been normally completed, the misalignment occurs. Perform detection processing. Thereafter, a recovery process can be performed in which a page printed before the misregistration detection process is reprinted.

  Specifically, if no paper jam has occurred during the printing process in S9 (S39: NO), in S51, the positional deviation detection process is performed during the period from the last opening / closing of the cover to the printing process in S9. It is determined whether (S13) has been performed. This determination is made based on whether the paper jam counter is equal to or greater than the predetermined number of times. If the misregistration detection process is performed during this period (S51: NO), it is not necessary to perform a new process here, so that the process proceeds to S41, and the misalignment detection request state is entered when the cover is opened and closed next time.

  On the other hand, when the position shift is not detected during the synchronization (S51: YES), it is highly possible that the image forming position is shifted. Therefore, it is necessary to perform the position shift detection process as necessary. . In the present embodiment, in S53, it is determined whether the printing conditions in the printing process in S9 satisfy the predetermined requirement. If the printing process is normal printing or monochrome printing (S53: NO), the process proceeds to S41.

  On the other hand, if the printing process is color printing or high-quality printing (S53: YES), the user is inquired of whether or not reprinting after the positional deviation detection process is necessary in S55. Specifically, the inquiry message or the like is displayed on the display unit 73. If the user's instruction is input through the operation unit 75 or the external computer 79 (an example of the first selection means) (S57: YES), and if it is not an instruction for reprinting (S59: NO) ), The process proceeds to S41.

  On the other hand, if the instruction is to instruct reprinting (S59: YES), the same page printed in S9 is set to an unprinted state (S61), and is changed to a misalignment detection requested state. After that, when a reprint request is made (S3: YES in FIG. 8), the process proceeds to S13 and the misregistration detection process and the like (S13 to S17) are performed, so that the same page as the test page is corrected after correcting the image forming position Can be reprinted.

Next, the relationship between the cover opening / closing, the position shift detection process, the print request, and the like is as shown in FIG. After the occurrence of a paper jam (see FIG. 11 (12)), the cover is opened and closed (see FIG. 11 (13)), a reprint request is made (see FIG. 11 (14)), and the printing process (see FIG. 11 (15)) is performed. Executed. If this printing process is completed normally without paper jams (S39: NO), the paper jam counter has reached a predetermined number of times or more at this point (S51: YES), and the printing process is color printing. Therefore (S53: YES), when there is a reprint instruction from the user (see FIG. 11 (16)) (S59: YES), after the misalignment detection process (see FIG. 11 (17)), FIG. 11 (15). The reprinting process (see FIG. 11 (18)) is performed for the same page as the printing process.

  As described above, the opening / closing operation of the cover after the occurrence of the paper jam is highly likely to be performed to eliminate the paper jam. Further, when a paper jam occurs, a paper jam may occur continuously because a piece of paper remains in the apparatus even if the cover is opened and the paper is removed. Therefore, by performing the misalignment detection process after the test page has been printed normally, it is possible to suppress the execution of useless misalignment correction.

  In addition, the test page is an image page corresponding to the print request, and the test page is printed again after the positional deviation detection processing. Therefore, it is not necessary to provide a special test page for determining whether printing has been normally completed without causing a paper jam. In addition, since the image page as the test page is reprinted after the detection process, the quality of the page can be ensured in the same manner as other pages.

  Further, the reprinting is configured to determine whether or not to perform the reprinting according to a user input instruction. This allows the user to select whether or not printing is necessary again by looking at the test page image before the misregistration detection process.

<Embodiment 4>
12 and 13 show a fourth embodiment. The difference from the first embodiment lies in a part of the process during the printing / misalignment correction control process, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next.

  In the present embodiment, the CPU 61 determines whether or not the printing condition satisfies a predetermined requirement when the cover is opened / closed after the occurrence of a paper jam is detected by the paper jam detection sensor 76. After the misregistration detection process (S13) is executed, the image forming unit 13 is switched between the printing process (S9) and the printing process without executing the misregistration detection process. If not detected, the print processing is executed after the misregistration detection processing is executed regardless of the printing conditions.

  Specifically, when the CPU 61 first detects opening / closing of the cover (S1: YES), the CPU 61 determines whether the opening / closing of the cover has been performed in a paper jam state in S31. This is determined, for example, by whether or not information indicating that a paper jam flag is set is recorded in the RAM 65 or the like. For example, when the cover is opened and closed when the developing cartridge 33 is not in a paper jam state (S31: NO), in S71, a “position misalignment detection request state not due to a paper jam” (information indicating that fact is stored in the RAM 65). And the process proceeds to S3.

  On the other hand, when the cover is opened and closed in a paper jam state (S31: YES), the paper jam state is once canceled in S33 (information indicating that the paper jam flag is not set is recorded in the RAM 65 or the like). Next, in S73, the “position misalignment detection requested state due to paper jam” is set (information to that effect is recorded in the RAM 65 or the like), and the process proceeds to S3.

  Even if a print request is made (S3: YES), if the paper jam state is not resolved (S37: YES), the printing process cannot be performed, and the process returns to S3 again, but if the paper jam condition is resolved ( (S37: NO), the process proceeds to S75. When there is a misregistration detection request that does not depend on a paper jam (S75: YES), that is, when the cover is opened and closed in S1 due to a factor other than a paper jam, whether or not the printing conditions satisfy a predetermined requirement. First, a misalignment detection process or the like (S13 to S17) is performed, and the process proceeds to S9.

On the other hand, there is a request for detection of misregistration due to a paper jam (S75: NO and S7).
7: YES), that is, when the cover is opened and closed in S1 due to the occurrence of a paper jam, if the printing conditions satisfy the predetermined requirements (S11: YES), the misregistration detection process and the like (S13 to S17) are performed. However, if the predetermined requirement is not satisfied (S11: NO), the process proceeds to S9 without performing the positional deviation detection process.

  Further, the CPU 61 monitors the detection signal from the paper jam detection sensor 76 during the printing process of S9, and detects the occurrence of paper jam based on the detection signal. If no paper jam occurs during the printing process (S39: NO), the process proceeds to S19. On the other hand, if a paper jam occurs during the printing process (S39: YES), the paper jam state is set in S43, and the process returns to S1.

  Next, the relationship between the cover opening / closing, the position shift detection process, the print request, and the like is as shown in FIG. When the cover is opened and closed (see FIG. 13 (1)) when no paper jam has occurred, the misalignment detection requested state (S71) does not occur due to paper jam (see FIG. 13 (2)). When there is a print request (see FIG. 13 (3)) (S3: YES and S75: YES) ”, the print processing is performed after performing the misregistration detection process (see FIG. 13 (4)) regardless of the printing conditions. (See FIG. 13 (5)).

  On the other hand, when the cover is opened and closed (see FIG. 13 (7)) when a paper jam occurs (see FIG. 13 (6)), a misalignment detection requested state due to paper jam (S73) is entered (FIG. 13). 13 (8)), when there is a monochrome printing request (see FIG. 13 (9)) (S3: YES and S77: YES), the printing conditions do not satisfy the predetermined requirements (S11: NO). Monochrome printing processing (see FIG. 13 (10)) is performed without performing misregistration detection processing.

  On the other hand, when there is a color printing request (see FIG. 13 (11)) (S3: YES and S77: YES), the printing condition satisfies a predetermined requirement (S11: YES), so a misregistration detection process (FIG. 13). After performing (see (12)), color printing processing (see (13) in FIG. 13) is performed.

  As described above, according to the present embodiment, when a printing process is performed after a paper jam occurs, the possibility that a paper jam will occur again is higher than usual. Therefore, if the misregistration detection process is always performed before the printing process, the misregistration detection process is repeatedly performed unnecessarily when a paper jam occurs repeatedly. Thus, when a paper jam occurs, the execution of the misregistration detection process can be suppressed only when the printing condition satisfies the predetermined condition, thereby suppressing the unnecessary misregistration detection process.

  <Fifth Embodiment> FIGS. 14 and 15 show a fifth embodiment. The difference from the first embodiment lies in a part of the process during the printing / misalignment correction control process, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next.

  In the present embodiment, the CPU 61 satisfies the predetermined condition when the occurrence frequency of the paper jam in the paper jam detection sensor 76 is a reference value (for example, 5 times) or more and the cover is opened and closed. Whether to cause the image forming unit 13 to execute the printing process after performing the misregistration detection process or whether to execute the printing process without performing the misregistration detection process depending on whether the misregistration detection process is performed or not. Is less than the reference value, the printing process is executed after the misregistration detection process is performed regardless of the printing conditions.

Specifically, the CPU 61 counts the number of occurrences of paper jam during the printing process for the most recent predetermined page (hereinafter referred to as “paper jam occurrence frequency”). The CPU 61 monitors the detection signal from the paper jam detection sensor 76 during the printing process of S9, and detects the occurrence of paper jam based on this detection signal. If a paper jam occurs during the printing process (S39: YES), the paper jam state is set in S43, and "1" is added to the paper jam counter in S45.

  On the other hand, if no paper jam occurs during the printing process (S39: NO), “1” is added to the printing counter in S91, and the printing process for the most recent predetermined page or the most recent predetermined number of sheets is performed in S93. Determine whether the process completed successfully. This is determined by whether or not the print counter has exceeded a predetermined value (for example, 10). When the printing process for the last predetermined page has been completed normally (S93: YES), the print counter and the paper jam counter are initialized to “zero” in S95 and S41, and the process proceeds to S19. On the other hand, if the printing process for the most recent predetermined page has not been completed normally (S93: NO), the process proceeds to S19 without initializing the print counter and the paper jam counter.

  If the CPU 61 detects opening / closing of the cover (S1: YES), the CPU 61 determines in S31 whether the opening / closing of the cover has been performed in a paper jam state. For example, when the cover is opened and closed when the paper is not jammed, such as when the developing cartridge 33 is replaced (S31: NO), the process proceeds to S81. On the other hand, when the paper jammed, the paper jammed condition is cleared once in S33. The process proceeds to S81. In S81, it is determined whether or not the paper jam occurrence frequency is high. Specifically, when the paper jam occurrence frequency is equal to or higher than a reference value (for example, 5) (S81: YES), in S83, a high frequency misalignment detection request is made, and the paper jam occurrence frequency is less than the reference value. If this is the case (S81: NO), in S85, a low-frequency misalignment detection request is made.

  Thus, when a print request is made (S3: YES), if the occurrence frequency of the paper jam during the printing process for the most recent predetermined page is less than the reference value (S87: YES), the misregistration is detected regardless of the printing conditions. After performing the processing (S13 to S17), the printing process (S9) is performed.

  On the other hand, when there is a print request (S3: YES), if the above-mentioned paper jam occurrence frequency is equal to or higher than a reference value (S89: YES), the positional deviation is made on condition that the printing condition satisfies the above predetermined requirement. After performing the detection process and the like, the printing process is performed. On the other hand, when the printing condition does not satisfy the predetermined requirement, the printing process is performed without performing the misregistration detection process.

  As described above, when printing is performed after a paper jam (jamming) occurs, the possibility of the paper jam occurring again is often higher than usual. For this reason, if the detection process is always performed before printing, the detection process is repeatedly performed in vain when paper jams occur repeatedly. Therefore, when the occurrence frequency of the paper jam is high, the execution of the detection process can be suppressed by restricting the execution of the detection process only when a predetermined condition is satisfied.

<Other Embodiments> The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In each of the above-described embodiments, the case where color printing or high-quality printing is used as an example of the predetermined requirement has been described. However, the present invention is not limited to this, and misregistration detection is triggered when the cover is closed. The user can select, for example, the operation unit 75 or the external computer 79 to execute the processing or to execute the misregistration detection processing when a print request is input after the cover is closed. May be. At this time, the operation unit 75 or the external computer 79 is an example of a selection unit. Since it may be preferable to perform detection immediately after the cover is closed, it is preferable that the user can appropriately select the timing for performing the positional deviation detection process.

  (2) The “image forming apparatus” may be an electrophotographic printer provided with a laser scanning device having a polygon mirror or the like, or an ink jet printer.

  (3) In the above-described embodiment, when monochrome printing or normal image quality is designated, the misregistration detection process or the like is not performed. However, even when such designation is designated, the misregistration detection process or the like is performed. Also good. For example, when printing on a form such as a slip, it is necessary to accurately print characters and the like in each item column. In this case, it is preferable to perform a printing process after performing a misregistration detection process.

1 ... Printer (image forming apparatus)
3 ... Main body casing 3A ... Front cover (cover)
3B ... Upper cover (cover)
13: Image forming section (forming means)
26: Pattern detection sensor (detection means)
76: Paper jam detection sensor (paper jam detection means)
78. Cover open / close detection sensor (open / close detection means)
75 .. operation unit (input means)
25 ... Belt (supporting body)
61 ... CPU (detection means, control means, correction means)
81 ... Mark

Claims (6)

A body casing;
A cover that can be opened and closed with respect to the main body casing;
Open / close detecting means for detecting the open / closed state of the cover;
Forming means for forming an image;
Detecting means for performing detection processing for detecting a shift amount of the image forming position based on the position of the mark formed on the carrier by the forming means;
A correcting unit that corrects an image forming position by the forming unit according to a shift amount detected by the detecting unit;
An input means for inputting a print request;
When the opening / closing operation of the cover is detected by the opening / closing detection means after the previous detection process, the detection means is caused to execute the detection process based on the input of the print request, and then the printing means is executed by the forming means. Control means for executing image formation based on the request;
When the opening / closing detection means detects that the cover is closed, the detection means executes detection processing, or when the cover request is detected and the print request is input, A selection means for selecting whether to execute the detection process;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The input means can specify printing conditions,
Equipped with paper jam detection means to detect the occurrence of paper jam,
When the opening / closing operation of the cover is detected by the opening / closing detection unit after the occurrence of a paper jam is detected by the paper jam detection unit, the control unit determines whether the printing condition satisfies a predetermined requirement. Accordingly, the printing process is switched between the execution of the detection process and the execution of the print process without executing the detection process, and if the occurrence of the paper jam is not detected, the printing is performed. The print process is executed after executing the detection process regardless of the conditions. The image forming apparatus according to claim 1.
The input means can specify printing conditions,
Equipped with paper jam detection means to detect the occurrence of paper jam,
When the occurrence frequency of the paper jam in the paper jam detection unit is equal to or higher than a reference and the opening / closing operation of the cover is detected by the open / close detection unit, the control unit determines that the printing condition is a predetermined requirement. When the print process is executed after the detection process is executed or the print process is executed without executing the detection process depending on whether or not the condition is satisfied, and the occurrence frequency of the paper jam is less than the reference In addition, the printing process is executed after the detection process is executed regardless of the printing conditions. The image forming apparatus according to any one of claims 1 to 3,
The forming means can form an image using a plurality of colorants,
When the image forming using a plurality of colorants is specified as the printing condition, the control unit executes a printing process after executing the detection process, and a single colorant as the printing condition. When image formation using is designated, printing processing is executed without executing the detection processing. The image forming apparatus according to claim 1, wherein:
Equipped with paper jam detection means to detect the occurrence of paper jam,
When the occurrence of a paper jam is continuously detected a predetermined number of times in the printing process after the detection process, the control unit executes the printing process without executing the detection process. The image forming apparatus according to any one of claims 1 to 5,
At least a part of the forming means is supported by the cover.