JP4314909B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image.
[0002]
[Prior art]
Conventionally, there has been an image forming apparatus that records an image on a recording sheet. In the image forming apparatus, a toner image corresponding to image data to be printed is formed on a photosensitive drum, the toner image is transferred onto a recording sheet fed from a sheet feeding tray, and the recording sheet is transferred by a fixing roller. Pressurize and pressurize to output the recording paper.
[0003]
When a small size recording paper is continuously passed through the fixing roller, the non-sheet passing portion of the fixing roller becomes abnormally hot.For example, if a large size recording paper is printed after printing a small size recording paper, There was a risk of causing multiple failures such as uneven temperature. Therefore, when switching from the small size to the large size, a configuration has been considered in which the image forming operation is temporarily interrupted if the temperature of the fixing roller end portion (small size non-sheet passing portion) exceeds a specified value (for example, Patent Documents). 1).
[0004]
In addition, when switching from the small size to the large size, there has been considered a configuration in which the image forming operation is temporarily interrupted if the temperature difference between the fixing roller end temperature and the fixing roller center temperature exceeds a specified value (for example, Patent Document 2).
[0005]
[Patent Document 1]
JP 2001-272897 A
[Patent Document 2]
JP 2002-214967 A
[0006]
[Problems to be solved by the invention]
[0007]
However, the configurations described in Patent Documents 1 and 2 have the following problems. For example, if the image forming operation is interrupted at a temperature that may cause image unevenness, even if the temperature is not high enough to cause fixing flaws, for example, the printed image may be a black and white character image or the like. If the size of the previously printed recording paper is smaller than the size of the recording paper printed this time, even if it is unnoticeable or unnoticeable, the printing rate of the boundary portion of the previous recording paper size on the recording paper printed this time will be Even when the image irregularity is low and the image unevenness is not conspicuous, the printing operation is forcibly interrupted, and the productivity of the printed matter may be reduced. The printing rate is the ratio of the actual printing area within the predetermined area to the predetermined area of the printing area of the recording medium.
[0008]
Furthermore, if the image forming operation is interrupted and the paper feeding to the fixing roller is interrupted, the temperature of the fixing roller will then increase abnormally (overshoot). The forming operation should not be interrupted.
[0009]
An object of the present invention is to minimize interruption of a printing operation.
[0010]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, the invention according to claim 1 is an image forming apparatus for forming an image on a recording medium based on image data.
  Image forming means for forming a toner image based on image data on a recording medium;
  Fixing means for heating and fixing the toner image on the recording medium;
  Temperature detecting means for detecting the surface temperature of the fixing means;
  Supply means for selectively supplying recording media of different sizes;
  Conveying means for conveying the recording medium supplied from the supplying means via the image forming means and the fixing means;
  If the current recording medium size as the size of the recording medium currently supplied from the supply means is larger than the previous recording medium size as the size of the recording medium supplied last time, the current recording medium size is based on the previous recording medium size. A boundary area defining means for defining a boundary area in a printing area in the supplied recording medium and including a printing area and a non-printing area of the previously supplied recording medium;
  A boundary area printing rate calculating means for calculating a boundary area printing rate of a toner image formed in the defined boundary area;
  The surface temperature of the fixing unit is controlled based on the detected surface temperature of the fixing unit and a preset reference temperature, and the image forming operation of the image forming unit, the conveying operation of the conveying unit, and the fixing are performed. Control means for controlling the fixing operation of the means and the supply operation of the supply means,
  The control means includesThe current recording medium size is larger than the previous recording medium size, andThe calculatedIt is determined whether the border area printing rate is equal to or greater than a predetermined threshold, and the current recording medium size is larger than the previous recording medium size andThe calculatedWhen the border area printing rate is equal to or greater than the predetermined thresholdStop printingAndWhen it is determined that the printing operation is to be interrupted, the printing operation is controlled to be interrupted.
[0011]
  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
  Image development means for developing image data into bitmap data;
  Information storage means for storing image data expanded into the bitmap data,
  SaidBoundary area printing rate calculation meansIs based on the bitmap dataBorder area printing rateIs calculated.
[0018]
  Claim3The invention described in claim 1Or 2In the image forming apparatus described in 1.
  The temperature detecting means detects the surface temperature of the central part and the end part of the nip part through which the recording medium of the fixing means passes;
  The control means determines whether the surface temperature difference between the central portion and the end portion of the fixing means detected by the temperature detection means is larger than a predetermined threshold, and the surface temperature difference is larger than the predetermined threshold. In this case, it is determined that the printing operation is interrupted, and when it is determined that the printing operation is interrupted, the printing operation is controlled to be interrupted.
[0019]
  Claim4The invention according to claim 1 is from3In the image forming apparatus according to any one of the above,
  When it is determined that the printing operation is interrupted, the control unit interrupts the image forming operation by the image forming unit, the conveying operation by the conveying unit, the fixing operation by the fixing unit, and the supplying operation of the supplying unit. The image forming unit, the conveying unit, the fixing unit, and the supplying unit are controlled.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the invention is not limited to the illustrated examples.
[0021]
First, the apparatus configuration of the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 shows a block configuration of an image forming apparatus 10 according to the present embodiment. FIG. 2 shows a configuration of the image output unit 20 in the image forming apparatus 10.
[0022]
As shown in FIG. 1, an image forming apparatus 10 such as a printer that forms image data on a recording medium is communicatively connected to a host computer 1. For example, the image forming apparatus 10 and the host computer 1 are configured to be connected by peer-to-peer communication using a dedicated cable or the like, but may be configured to be connected via a communication network such as a LAN. The host computer 1 stores the image data, and transmits image data to be image-formed among the stored image data to the image forming apparatus 10 by a user's image formation instruction operation or the like.
[0023]
Hereinafter, the image forming apparatus 10 will be described as a configuration for forming an image on a recording sheet as a recording medium, but is not limited thereto. For example, an OHP sheet or the like may be used as the recording medium.
[0024]
The image forming apparatus 10 includes an image development unit 2, an image information storage unit 3, an operation unit 4, a printing rate calculation unit 7, a control unit 8, a color mode selection unit 9, a priority mode setting unit 11, The boundary area defining unit 12, the size detecting unit 13, and the image output unit 20 are configured.
[0025]
The operation unit 4 includes key input means 5 and display means 6. The image output unit 20 includes a fixing unit 14, a temperature detecting unit 15, an image forming unit 16, a paper feeding unit 17, and a conveying unit 18.
[0026]
Here, the internal configuration of the image output unit 20 will be described with reference to FIG. The image output unit 20 includes photosensitive drums 21Y, 21M, 21C, and 21K, chargers 22Y, 22M, 22C, and 22K, exposure units 23Y, 23M, 23C, and 23K, and developing units 24Y, 24M, 24C, and 24K. Photoconductor cleaning means 25Y, 25M, 25C, and 25K. The symbols Y, M, C, and K represent yellow, magenta, cyan, and black, respectively, in order.
[0027]
Around the photosensitive drums 21Y, 21M, 21C, and 21K as image carriers for four colors that rotate in the direction of the arrow in FIG. 2, chargers 22Y, 22M, 22C, and 22K as charging means for four colors Exposure units 23Y, 23M, 23C, and 23K as latent image forming units for four colors, developing units 24Y, 24M, 24C, and 24K as two-component developing units for four colors, and toners of four colors Photoreceptor cleaning means 25Y, 25M, 25C, and 25K to be removed are provided in order.
[0028]
The image output unit 20 includes an intermediate transfer member 26, a transfer roller 27, a separating unit 28, and a cleaner 29. The image forming unit 16 includes units 21 to 29. The image output unit 20 includes a paper feed tray 30, guide plates 31, registration rollers 32 and 33, guide plates 34, a fixing device 35, a switching gate 38, and a paper discharge tray 39. The paper feed tray 30 includes paper feed trays 30a, 30b, and 30c that include recording sheets of different sizes. The paper feed unit 17 includes a paper feed tray 30. The fixing device 35 includes a heating roller 36 and a pressure roller 37. The fixing unit 14 includes a fixing unit 35, and the temperature detection unit 15 is provided in the fixing unit 33.
[0029]
Each part of the image output unit 20 is provided with an inversion path 40, an inversion point 41, and a double-sided path 42. The transport unit 18 includes guide plates 31 and 34, registration rollers 32 and 33, a switching gate 38, a reverse path 40, a reverse point 41, and a double-side path 42. Each unit in the image output unit 20 is controlled by a control unit 8 including a CPU, a RAM, a ROM, and the like on the output timing, output value, output polarity, and the like of the recording paper.
[0030]
Here, the operation of the image output unit 20 will be briefly described. First, the photosensitive drums 21Y, 21M, 21C, and 21K are driven by a main motor (not shown). The surfaces of the photosensitive drums 21Y, 21M, 21C, and 21K are charged to a negative polarity of, for example, −800 [V] by the discharge of the chargers 22Y, 22M, 22C, and 22K that are supplied with a voltage by a power source (not shown). Then, optical writing based on image data to be printed is performed by the exposure means 23Y, 23M, 23C, and 23K that output laser beams, and electrostatic latent images are formed on the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21K. The
[0031]
The developing devices 24Y, 24M, 24C, and 24K are provided with toner that is negatively charged by a power source (not shown). The electrostatic latent images formed on the surfaces of the photoconductor drums 21Y, 21M, 21C, and 21K pass through the developing devices 24Y, 24M, 24C, and 24K, and the latent image is formed by applying the negative polarity phenomenon bias to the toner. A toner image is formed on the surface of the photosensitive drums 21Y, 21M, 21C, and 21K by adhering to the portion. The toner image is transferred to an endless belt-like intermediate transfer member 26. After the transfer, the toner remaining on the surface of the photosensitive drums 21Y, 21M, 21C, and 21K is cleaned by the photosensitive member cleaning means 25Y, 25M, 25C, and 25K.
[0032]
When the toner image is transferred by all of the photosensitive drums 21Y, 21M, 21C, and 21K, the toner image corresponds to full color. When the toner image is transferred only by the photosensitive drum 21K, the toner image corresponds to black and white. When full-color printing is performed (in the case of full-color printing mode), the photosensitive drums 21Y, 21M, 21C, and 21K are in contact with the intermediate transfer body 26, and when monochrome printing is performed (in the monochrome printing mode), only the photosensitive drum 21K. Is brought into contact with the intermediate transfer member 26, and the photosensitive drums 21Y, 21M, and 21C are separated from the intermediate transfer member 26.
[0033]
On the other hand, the recording paper is fed one by one from the paper feed trays 30a, 30b, 30c in which different sizes are set, and is guided by the guide plate 31 to the position of the registration rollers 32, 33. The recording paper is unloaded at the timing when the toner image on the intermediate transfer body 26 and the image forming position coincide after the leading edges of the recording paper are aligned by the registration rollers 32 and 33. The recording paper carried out by the registration rollers 32 and 33 is guided by a guide plate 34 and fed into a nip portion where the intermediate transfer body 26 and the transfer roller 27 are in contact with each other.
[0034]
The transfer roller 27 presses the recording paper toward the intermediate transfer member 26, and on the intermediate transfer member 26 by the action of electrostatic force generated by a bias (for example, +500 [V]) opposite in polarity to the toner applied from a power source (not shown). The toner image is transferred onto the recording paper. The recording paper carrying the toner image is neutralized by the separating means 28 comprising a neutralizing needle, separated from the intermediate transfer member 26, and introduced into the fixing device 35. The toner image is thermally transferred onto the recording paper heated and pressed through the nip portion of the roller pair of the heating roller 36 and the pressure roller 37. In the case of single-sided printing, the switching gate 38 is switched to the single-sided printing path, and the recording paper on which the toner image is fixed is accommodated in the paper discharge tray 39 via the switching gate 38.
[0035]
In the case of double-sided printing, the switching gate 38 is switched to the path on the double-sided printing side, and the recording paper on which the toner image is fixed is sent out to the reversing path 40 via the switching gate 38 and is reversed at the reversing point 41. Then, it is conveyed on the double-sided path 42 and advanced to the registration rollers 32 and 33. After the leading edges of the recording papers are aligned by the registration rollers 32 and 33, the recording paper is stored in the paper discharge tray 39 by forming and fixing a toner image on the back surface in the same manner as the printing operation on the front surface. The Further, after the recording paper passes through the nip portion between the intermediate transfer member 26 and the transfer roller 27, the toner remaining on the intermediate transfer member 26 is cleaned by the cleaner 29. The above image forming operation is repeated.
[0036]
With reference to FIG. 1 again, the overall configuration of the image forming apparatus 10 will be described. The image expansion means 2 expands image formation target image data received from the host computer 1 into bitmap data. The image information storage unit 3 stores (stores) the bitmap data developed by the image development unit 2. The key input unit 5 of the operation unit 4 includes a keypad for receiving an operator's key input, and transmits the operation input information to the control unit 8. The display unit 6 of the operation unit 4 includes a liquid crystal display and displays the display information transmitted from the control unit 8. Moreover, you may comprise the key input part 5 and the display means 6 integrally as a touch panel.
[0037]
The color mode selection means 9 is a full-color mode that forms a full-color image on recording paper using toners of four colors Y, M, C, and K, and a monochrome that forms a black-and-white image using only K-color toner. Select and set one of the color modes. In the monochrome mode, color toner is not used as compared with the full color mode, so the image forming cost is low. Based on the user's operation input via the operation unit 4, the color mode selection unit 9 sets a color mode and outputs the set color mode information to the control unit 8. Even if the image data transmitted from the host computer 1 supports full color, when the user performs an operation input forcibly setting the monochrome color mode, the color mode selection unit 9 sets the monochrome mode. The full color image data can be formed in black and white to reduce the cost.
[0038]
The priority mode setting means 11 is one of an image quality priority mode that prioritizes the image quality of an image formed on the recording paper and prioritizes the image output speed of the recording paper, and a speed priority mode that outputs the image at high speed. Select one of the priority modes. The image quality priority mode is a mode in which image unevenness is never generated for improving the image quality, and the speed priority mode is a mode in which print productivity is prioritized even if image unevenness slightly occurs. The priority mode setting unit 11 sets a priority mode based on a user operation input via the operation unit 4, and outputs the set priority mode information to the control unit 8.
[0039]
Here, in order to simplify the description, any two consecutive recording sheets on which images are formed in order are sequentially designated as a first recording sheet and a second printing sheet. When the image forming operation for the first print starts, the size detection unit 13 obtains the bitmap image data for the first print from the image information storage unit 3, analyzes the size, and stores the analyzed size information. At the same time, it is output to the control means 8.
[0040]
The control means 8 feeds the paper from the paper feed trays 30a, 30b or 30c in which the recording paper having the same size as the size information of the first print input from the size detection means 13 is started. At the same time, the image data input from the image information storage unit 3 is transferred to the image forming unit 16, and the image forming unit 16 is controlled to execute image formation of the first print.
[0041]
The control means 8 controls the conveying means 18 so as to sequentially convey the recording paper fed from the paper feeding means 17 to the image forming means 16 and the fixing means 14, and the recording paper on which the image is formed by the image forming means 16. The fixing unit 14 is controlled so as to fix the toner image, and the conveying unit 18 is controlled so that the recording paper on which the image is fixed is discharged directly or via the double-sided path 42 to the discharge tray 39. When the size of the recording paper for the second print is equal to or smaller than the size of the recording paper for the first print, the control unit 8 controls image formation in the same manner as the recording paper for the first print. As will be described later, when the size of the recording paper for the second print is larger than the size of the recording paper for the first print, the controller 8 controls the surface temperature of the heating roller 36 detected by the temperature detector 15, and The boundary area defined by the boundary area defining unit 12, the color mode set by the color mode selecting unit 9, the priority mode set by the priority mode setting unit 11, and the printing rate calculated by the printing rate calculating unit 7 Based on the above, printing continuation or interruption is controlled.
[0042]
The boundary area defining means 12 defines the boundary area on the recording paper for the first print and the second print based on the bitmap image data stored in the image information storage means 3, and uses the boundary area information as the printing rate. Output to the calculation means 7. Here, an example of the boundary region will be described with reference to FIG. FIG. 3 shows the boundary area A1 on the recording paper P2. When the recording paper P2 fed for the second print (current) is larger than the size of the recording paper P1 fed for the first printing (previous), the fixing is within the printing area of the recording paper P2. A region including the non-sheet passing portion and the sheet passing portion of the recording paper P1 on the heating roller 36 of the container 35 is defined by the boundary region defining means 12 as a boundary region A1.
[0043]
The printing rate calculation means 7 calculates the printing rate in the boundary area on the recording paper based on the bitmap image data stored in the image information storage means 3 and the boundary area information input from the boundary area definition means 12. Then, the printing rate information is output to the control means 8. The printing rate in the boundary region is defined by (actual printing region area in the boundary region) / (boundary region area) × 100 [%]. The size detection means 13 detects the size of the recording paper forming the image data based on the bitmap image data stored in the image information storage means 3, and controls the size information as current paper feed size information. The information is output to the means 8 and stored as the previous paper feed size information.
[0044]
The temperature detection means 15 is a temperature detection means such as a thermistor and detects the surface temperature of the heating roller 36 of the fixing device 35. FIG. 4 shows the configuration of the temperature detection means 15. As shown in FIG. 4, the temperature detection unit 15 includes, for example, a temperature detection unit 15 a provided at the center portion of the heating roller 36, and temperature detection units 15 b and 15 c provided at both ends of the heating roller 36. Composed. The temperature detection means 15 a, 15 b, and 15 c detect the surface temperatures of the central portion and both end portions of the heating roller 36, and output the detected temperature information to the control means 8.
[0045]
Next, a printing process executed in the image forming apparatus 10 will be described with reference to FIGS. FIG. 5 shows the printing process. FIG. 6 shows a print interruption determination process during the print process. Hereinafter, the subject of the processing of each step is assumed to be the control means 8 unless otherwise specified.
[0046]
In addition, the user inputs in advance the setting of the color mode and the priority mode via the operation unit 4, and based on the setting input, the color mode selection unit 9 selects and sets the color mode, and the priority mode setting unit 11. The priority mode is selected and set by.
[0047]
First, it is determined whether or not a print request including image data to be printed has been transmitted from the host computer 1 (step S1). If the print request has not been transmitted (step S1; NO), the process proceeds to step S1. When the print request is transmitted (step S1; YES), the print request is received, the image data to be printed therein is developed into bitmap data by the image development means 2, and the image data of the bitmap data is converted into the bitmap data. The image information is stored in the image information storage means 3 (step S2).
[0048]
Then, the image data of the bitmap data of the next page in the image data is read out by the control means 8, and the image data of the bitmap data of the next page is the current image data as the boundary area defining means 12 and the size detecting means 13. And output to the printing rate calculation means 7 (step S3). When step S3 is first executed, the data of the first page of the image data is read and output.
[0049]
After execution of step S3, the boundary area defining unit 12 defines the boundary area of the input current image data, and the current boundary area information is output to the printing rate calculation unit 7. Similarly, the size detection unit 13 detects the size of the recording paper to be fed this time based on the input current image data, and outputs the size information to the control unit 8 as current paper feed size information. The previous paper feed size information already stored is output to the control means 8. Similarly, the printing rate calculation means 7 calculates the printing rate in the boundary area of the recording paper to be fed this time based on the current image data and the current boundary area information input from the boundary area definition means 12. This time, the printing rate information is output to the control means 8.
[0050]
Then, it is determined whether or not the page to be imaged this time is the first page (step S4). If it is the first page (step S4; YES), the previous paper feed size information stored in the size detection means 13 is updated to the value of the current paper feed size information (step S5). In the case of the first page, there is no previous print page, and there is no cause of image unevenness and fixing flaws.
[0051]
Then, the current image data is transferred to the image forming unit 16, and the printing of the page corresponding to the current image data in the image output unit 20 is controlled (step S6). Then, it is determined whether or not all pages of the image data to be printed have been printed (step S7). If all pages have been printed (step S7; YES), the printing process is terminated. If all the pages are not printed (step S7; NO), the process proceeds to step S3.
[0052]
If it is not the first page (step S4; NO), a print interruption determination process is executed (step S8), and the process proceeds to step S5. Here, the print interruption determination process will be described in detail with reference to FIG.
[0053]
First, it is determined whether or not the current paper feed size information is larger than the previous paper feed size information based on the previous paper feed size information and the current paper feed size information input from the size detection means 13 (step S81). . If the current paper feed size information is not larger than the previous paper feed size information (step S81; NO), the process proceeds to step S5. This is because there is no boundary region in which image unevenness occurs.
[0054]
When the current paper feed size information is larger than the previous paper feed size information (step S81; YES), a boundary region is generated on the current recording paper, and the heating roller input from the temperature detection means 15 (15A, 15b, 15c). Based on the temperature information of 36, the surface temperature difference between the central portion and both ends of the heating roller 36 is calculated, and it is determined whether or not the temperature difference of the heating roller 36 is 25 [° C.] or more (step S82). ). When the temperature difference of the heating roller 36 is 25 [° C.] or more, the non-sheet passing portion of the heating roller 36 may be at a high temperature, and therefore, fixing flaws may occur on the recording paper. .
[0055]
When the temperature difference of the heating roller 36 is 25 [° C.] or more (step S82; YES), the printing operation of the image output unit 20 is controlled to be interrupted (step S83). When the temperature difference of the heating roller 36 is 25 [° C.] or more, there is a possibility that fixing flaws may occur on the recording paper, so that the printing operation is forcibly controlled to be interrupted. The printing operation to be interrupted includes an image forming operation in the image forming unit 16, a fixing operation in the fixing unit 14, a transporting operation in the transporting unit 18, and an image forming operation in the paper feeding unit 17.
[0056]
Then, based on the temperature information of the heating roller 36 input from the temperature detecting means 15, the surface temperature difference between the central portion and both ends of the heating roller 36 is calculated, and the temperature difference of the heating roller 36 is less than 10 [° C.]. Is determined (step S84). When the temperature difference of the heating roller 36 is less than 10 [° C.], there is no possibility of fixing flaws on the recording paper, and there is no possibility of image unevenness in the boundary area of the recording paper.
[0057]
If the temperature difference of the heating roller 36 is not less than 10 [° C.] (step S84; NO), the process proceeds to step S84 in order to naturally cool the heating roller 36. When the temperature difference of the heating roller 36 is less than 10 [° C.] (step S84; NO), since the heating roller 36 has been cooled to such an extent that no image unevenness occurs in the boundary region, the interruption of the printing operation is released, and the step The process proceeds to S5.
[0058]
If the temperature difference of the heating roller 36 is not 25 [° C.] or more (step S82; NO), there is no possibility of fixing flaws on the recording paper, and the color mode information input from the color mode selection means 9 is the monochrome mode. Or full color mode is determined (step S85). In the black and white mode, there is generally a lot of text, and the image unevenness is not visually noticed by the user or the like. On the other hand, in the full color mode, there are generally many images, and the image unevenness is easily noticed by the user and the like, and there is a demand for suppressing the occurrence of image unevenness.
[0059]
In the monochrome mode (step S85; monochrome), it is not necessary to suppress the occurrence of image unevenness, and the process proceeds to step S5. In the full color mode (step S85; full color), it is necessary to suppress the occurrence of image unevenness, and it is determined whether the priority mode information input from the priority mode setting unit 11 is the image quality priority mode or the speed priority mode. (Step S86). In the image quality priority mode, in order to prioritize image quality, there is a request to suppress the occurrence of image unevenness. In the speed priority mode, priority is given to print productivity, so that the occurrence of image unevenness is not noticed by the user.
[0060]
In the speed priority mode (step S86; speed priority), it is not necessary to suppress the occurrence of image unevenness, and the process proceeds to step S5. In the image quality priority mode (step S85; image quality priority), it is necessary to suppress the occurrence of image unevenness, and based on the temperature information of the heating roller 36 input from the temperature detecting means 15, the central portion and both ends of the heating roller 36 are used. The surface temperature difference with the part is calculated, and it is determined whether or not the temperature difference of the heating roller 36 is less than 10 [° C.] (step S87).
[0061]
When the temperature difference of the heating roller 36 is less than 10 [° C.] (step S87; YES), there is no possibility of image unevenness on the recording paper, and the process proceeds to step S5. If the temperature difference of the heating roller 36 is not less than 10 [° C.] (step S87; NO), there is no possibility of fixing flaws on the recording paper, but there is a possibility that image unevenness may occur in the boundary area, so printing. It is determined whether or not the printing rate information input from the rate calculating means 7 is less than 15 [%] (step S88). The value of 15 [%] in the printing rate information is an empirical threshold value as to whether or not the image unevenness occurring in the boundary area of the recording paper is a concern.
[0062]
If the printing rate information is less than 15% (step S88; YES), even if image unevenness occurs in the boundary area of the recording paper, the process proceeds to step S5. If the printing rate information is not less than 15 [%] (step S88; NO), since it is perceived that image unevenness occurs in the boundary region of the recording paper, the process proceeds to step S83.
[0063]
  As described above, according to the present embodiment, the current paper feed size information is larger than the previous paper feed size information, and the surface temperature of the heating roller 36 is increased.differenceIs 10 [° C.] or more and less than 25 [° C.], and there is a possibility of occurrence of image unevenness in the boundary area, and the print rate information in the boundary area is less than 15 [%] and image unevenness is not a concern. The interruption of the printing operation can be avoided, and the interruption of the printing operation to the recording medium can be minimized.
[0064]
  Also, the current paper feed size information is larger than the previous paper feed size information, and the surface temperature of the heating roller 36DifferenceWhen the temperature is less than 25 [° C.] and there is a possibility of image unevenness in the boundary region, it is possible to avoid interruption of the printing operation when the color mode is the monochrome mode and the image unevenness is not noticed.
[0065]
  Also, the current paper feed size information is larger than the previous paper feed size information, and the surface temperature of the heating roller 36DifferenceWhen the temperature is less than 25 [° C.] and there is a possibility of image unevenness in the boundary region, the priority mode is the speed priority mode, so that it is possible to avoid interruption of the printing operation when image unevenness is not a concern.
[0066]
  Also, the surface temperature of the heating roller 36differenceCan be forcibly interrupted when there is a possibility of occurrence of fixing flaws. Further, when the current paper feed size information is less than or equal to the previous paper feed size information, there is no boundary region in which image unevenness occurs, so that it is possible to avoid interruption of the printing operation.
[0067]
The description in the above-described embodiment is an example of a suitable image forming apparatus 10 according to the present invention, and the present invention is not limited to this.
[0068]
  For example, the surface temperature of the heating roller 36differenceThe threshold values (10 [° C.], 25 [° C.]) and the printing rate information threshold value (15 [%]) are not limited to the values in the above embodiment, and other appropriate values are used. May be.
[0069]
【The invention's effect】
  According to the first aspect of the present invention, while controlling the surface temperature of the fixing unit,It is determined whether the current recording medium size is larger than the previous recording medium size and the boundary area printing rate is equal to or greater than a predetermined threshold, and the current recording medium size is larger than the previous recording medium size and the boundary area printing rate is the predetermined threshold. When it is above, it is determined that the printing operation is interruptedIf it is determined that the printing operation is to be interrupted, control is performed to interrupt the printing operation. For this reason,Printing operation when the current recording medium size is larger than the previous recording medium size and there is a possibility of image unevenness in the boundary area of the recording medium, and the boundary area printing rate is low and the image unevenness on the recording medium is not concerned Avoid interruptionThus, the interruption of the printing operation on the recording medium can be minimized.
  According to the invention of claim 2, based on the bitmap dataBorder area printing rateCan be calculated.
[0073]
  Claim3According to the present invention, the surface temperature of the central portion and the end portion of the nip portion through which the recording medium of the fixing unit passes is detected, and the detected surface temperature difference between the central portion and the end portion of the fixing unit is greater than a predetermined threshold value. If the surface temperature difference is larger than the predetermined threshold, it is determined that the printing operation is interrupted, and when it is determined that the printing operation is interrupted, the printing operation is controlled to be interrupted. To do. Therefore, it is possible to more accurately determine the possibility of image unevenness on the recording medium based on the surface temperature difference of the fixing unit, and to more accurately interrupt the printing operation when the image unevenness on the recording medium is not a concern. Can be avoided.
  Claim4According to the invention described in the above, when it is determined that the printing operation is interrupted, the image forming unit, the conveying unit, the fixing unit, and the supplying unit are arranged so as to interrupt the image forming operation, the conveying operation, the fixing operation, and the supplying operation. Can be controlled.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image forming apparatus 10 according to an embodiment of the present invention.
2 is a configuration diagram of an image output unit 20 in the image forming apparatus 10. FIG.
FIG. 3 is a diagram showing a boundary area A1 on the recording paper P2.
FIG. 4 is a diagram showing a configuration of temperature detection means 15;
FIG. 5 is a flowchart illustrating a printing process.
FIG. 6 is a flowchart illustrating print interruption determination processing during print processing.
[Explanation of symbols]
1 ... Host computer
10. Image forming apparatus
2 ... Image development means
3 ... Image information storage means
4. Operation unit
5 ... Key input means
6. Display means
7. Print rate calculation means
8. Control means
9. Color mode selection means
11 Priority mode setting means
12 ... Boundary region definition means
13. Size detection means
20. Image output unit
14: Fixing means
15 ... Temperature detection means
16 Image forming means
17: Paper feeding means
18 ... Conveying means
21Y, 21M, 21C, 21K ... photosensitive drum
22Y, 22M, 22C, 22K ... charger
23Y, 23M, 23C, 23K ... exposure means
24Y, 24M, 24C, 24K ... Developer
25Y, 25M, 25C, 25K ... photoconductor cleaning means
26. Intermediate transfer member
27. Transfer roller
28. Separation means
29 ... Cleaner
30, 30a, 30b, 30c ... paper feed tray
31, 34 ... Guide plate
32, 33 ... Registration roller
35. Fixing device
36 ... Heating roller
37 ... Pressure roller
38 ... Switching gate
39 ... Output tray
40 ... Reverse path
41 ... Reversal point
42 ... Double-sided path

Claims (4)

In an image forming apparatus that forms an image on a recording medium based on image data,
Image forming means for forming a toner image based on image data on a recording medium;
Fixing means for heating and fixing the toner image on the recording medium;
Temperature detecting means for detecting the surface temperature of the fixing means;
Supply means for selectively supplying recording media of different sizes;
Conveying means for conveying the recording medium supplied from the supplying means via the image forming means and the fixing means;
If the current recording medium size as the size of the recording medium currently supplied from the supply means is larger than the previous recording medium size as the size of the recording medium supplied last time, the current recording medium size is based on the previous recording medium size. A boundary area defining means for defining a boundary area in a printing area in the supplied recording medium and including a printing area and a non-printing area of the previously supplied recording medium;
A boundary area printing rate calculating means for calculating a boundary area printing rate of a toner image formed in the defined boundary area;
The surface temperature of the fixing unit is controlled based on the detected surface temperature of the fixing unit and a preset reference temperature, and the image forming operation of the image forming unit, the conveying operation of the conveying unit, and the fixing are performed. Control means for controlling the fixing operation of the means and the supply operation of the supply means,
The control means determines whether or not the current recording medium size is larger than the previous recording medium size and the calculated boundary area printing rate is equal to or greater than a predetermined threshold, and the current recording medium size is the previous recording medium It is determined that the printing operation is interrupted when it is larger than the size and the calculated border area printing rate is equal to or greater than the predetermined threshold, and when it is determined that the printing operation is interrupted, the printing operation is controlled to be interrupted. An image forming apparatus. Image development means for developing image data into bitmap data;
Information storage means for storing image data expanded into the bitmap data,
The image forming apparatus according to claim 1, wherein the boundary area printing rate calculation unit calculates the boundary area printing rate based on the bitmap data. The temperature detecting means detects the surface temperature of the central part and the end part of the nip part through which the recording medium of the fixing means passes;
The control means determines whether the surface temperature difference between the central portion and the end portion of the fixing means detected by the temperature detection means is larger than a predetermined threshold, and the surface temperature difference is larger than the predetermined threshold. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the printing operation is interrupted and controls to interrupt the printing operation when the printing operation is determined to be interrupted. When it is determined that the printing operation is interrupted, the control unit interrupts the image forming operation by the image forming unit, the conveying operation by the conveying unit, the fixing operation by the fixing unit, and the supplying operation of the supplying unit. , the image forming unit, said transfer means, the fixing means and the image forming apparatus according to any one of claims 1 to 3, wherein the controller controls the supply means.

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