JP2009042513A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue good quality printing by suppressing fixing failure even when paper in any one of a plurality of storage cassettes runs out. <P>SOLUTION: For example, when an image forming apparatus has the storage cassettes corresponding to two lines, lines a and b, and a thermistor for measuring the temperature of a heat roller is disposed at one end of a paper non-passage area on the line-b side, and paper in the line-b side storage cassette runs out and printing is carried out using only the line-a side one, a control section sets the temperature of the heat roller to a temperature T3 higher than a regular temperature T1 assigned for fixing on two parallel sheets of paper. When paper in the line-a side storage cassette runs out and printing is continued using only the line-b side one, the control section sets the temperature T2 of the heat roller to the regular temperature T1 or to a temperature slightly lower than the regular temperature T1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that simultaneously forms an image on a plurality of recording media using a heating roller.

2. Description of the Related Art An image forming apparatus that has a plurality of storage cassettes, feeds paper from each storage cassette at the same time, attaches a toner image, fixes the toner images on the plurality of paper using a heating roller, and performs printing. ing. Conventionally, as described in Patent Document 1, such an image forming apparatus is configured to remove a sheet from another storage cassette having a sheet when a sheet in one of the plurality of storage cassettes is exhausted. Paper was fed and printing continued.
JP-A-5-162423

  In general, the surface temperature of the heating roller is measured by a thermistor or the like, and the surface temperature is controlled based on the measurement result. For example, when there is no more paper that passes in the immediate vicinity of the location where the thermistor performs temperature measurement, and printing of paper that passes through an area away from the temperature measurement location is continued, the area through which the paper on the heating roller passes is heated by the paper. Is taken away. Accordingly, a temperature difference is generated between the measured temperature of the thermistor and the region through which the paper passes. That is, when printing only paper that passes through a region away from the location where temperature measurement is performed, it becomes difficult to control the entire heating roller to a temperature suitable for image fixing, which causes fixing failure.

  The present invention has been made to solve the above-described problem, and even when the paper in any of the plurality of storage cassettes is exhausted, fixing failure can be suppressed and high-quality printing can be continued. It is an object of the present invention to provide an image forming apparatus that can be used.

  According to the first aspect of the present invention, there are provided a plurality of storage means for storing recording media, a plurality of presence / absence detecting means for detecting the presence / absence of the recording medium in each storage means, and a plurality of the recording media. On the other hand, a fixing unit that simultaneously fixes an image using a heating roller, a conveyance unit that takes out the recording medium from each storage unit and conveys the plurality of recording media in parallel in the axial direction of the heating roller, and the heating Temperature detecting means for detecting the temperature of a predetermined location on the surface of the roller, and control means for controlling each of the means, the control means according to the detection results of the presence / absence detecting means and the temperature detecting means An image forming apparatus characterized in that the control is variable.

  The invention according to claim 2 is the image forming apparatus according to claim 1, wherein the control means sets the heating roller to a predetermined fixing temperature based on the temperature detected by the temperature detecting means. The presence / absence detecting means detects that there is no recording medium in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature. And when the presence / absence detecting means detects that there is no recording medium in the storage means for storing the recording medium that passes through a region not closest to the predetermined location. The temperature control is variable.

  According to these configurations, by varying control of each unit included in the image forming apparatus according to the detection result of the presence / absence detection unit, there is no recording medium in at least one storage unit among the plurality of storage units, Even when the image fixing to the recording medium conveyed from the storage means is continued, it is possible to fix the image at an appropriate temperature to suppress the fixing failure.

  According to a third aspect of the present invention, the control means of the image forming apparatus according to the second aspect stores the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature. When the presence / absence detecting means detects that the recording medium is not in the storage means, temperature control for holding the heating roller at a predetermined temperature higher than the fixing temperature may be performed.

  According to this configuration, when there is no recording medium in the storage means for storing the recording medium that passes immediately close to the predetermined location where the temperature detection means detects the temperature, the recording medium that passes through the non-nearest area is stored. The temperature control of the heating roller is varied depending on when there is no recording medium in the storage means. Specifically, there is no recording medium in the storage means for storing the recording medium passing through the most recently, and it is separated from the nearest. When continuously performing image fixing on a recording medium that passes through an area, the heating roller is set to a temperature higher than the normal temperature (predetermined fixing temperature), so that the recording medium passes through an area away from the nearest area. Even when only image fixing is performed, image fixing can be performed at an appropriate temperature, and fixing defects can be suppressed.

  According to a fourth aspect of the invention, there is provided the image forming apparatus according to the first aspect, wherein the control unit takes out the recording medium from the storage units at a predetermined time interval and conveys the recording medium. The presence / absence detecting means detects that there is no recording medium in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature. And the predetermined time interval is variable when the presence / absence detecting unit detects that the recording medium is not in the storage unit that stores the recording medium that passes through an area not close to the predetermined location. It is characterized by doing.

  According to a fifth aspect of the present invention, the control unit of the image forming apparatus according to the fourth aspect stores the recording medium that passes immediately adjacent to the predetermined location where the temperature detecting unit detects the temperature. When the presence / absence detecting means detects that there is no recording medium in the storage means, the conveying means is controlled so that the recording medium is taken out at a predetermined time interval longer than the predetermined time interval. It may be done.

  According to these configurations, when there is no recording medium in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature, and the recording medium that passes through the non-adjacent area The printing time interval is varied when there is no recording medium in the storing means for storing. In particular, in the case of the invention described in claim 4, when there is no recording medium in the storage means for storing the recording medium passing through the most recent time, and image fixing is continuously performed on the recording medium that passes through an area away from the nearest. By setting the printing time interval longer than the normal printing time interval (predetermined time interval), image fixing can be performed at an appropriate temperature even when image fixing is performed only on a recording medium that passes through the area away from the nearest point. It is possible to suppress the fixing failure.

  The invention according to claim 6 is the image forming apparatus according to claim 1, wherein the control unit detects the recording medium that passes immediately near the predetermined location where the temperature detecting unit detects the temperature. When the presence / absence detecting means detects that the recording medium is not in the storage means to be stored, the fixing of the image by the heating roller is stopped, and the recording medium passing through a region not closest to the predetermined location is stored. When the presence / absence detecting means detects that the recording medium is not in the storage means, the fixing of the image by the heating roller is continued.

  According to this configuration, it is possible to prevent printing with poor fixability by not performing image fixing only on a recording medium that passes through an area where accurate temperature detection by the temperature detection means is difficult.

  Further, as in the seventh aspect of the invention, the temperature detecting means of the image forming apparatus according to the first to sixth aspects may be a thermistor.

  According to the first and second aspects of the present invention, even when there is no recording medium in at least one of the plurality of storage units and the image fixing to the recording medium conveyed from the other storage unit is continued. Therefore, the image can be fixed at an appropriate temperature, and fixing defects can be suppressed.

  According to the third aspect of the present invention, there is no recording medium in the storage means for storing the recording medium passing through the immediate vicinity of the predetermined place where the temperature measuring means measures the temperature, and the recording passes through the area away from the nearest. When image fixing to the medium is continuously performed, the image is fixed only to the recording medium passing through the region away from the nearest by setting the heating roller to a temperature higher than the normal temperature (the predetermined fixing temperature). Even in the case of performing image fixing, image fixing can be performed at an appropriate temperature, and fixing defects can be suppressed.

  According to the fourth and fifth aspects of the present invention, there is no recording medium in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature, and the recording medium passes through an area away from the nearest. When the image fixing to the recording medium to be performed is continued, the printing time interval is made longer than the normal printing time interval (the predetermined time interval), so that the image is only applied to the recording medium passing through the region far from the nearest. Even when fixing, image fixing can be performed at an appropriate temperature, and fixing defects can be suppressed.

  According to the sixth aspect of the invention, it is possible to prevent printing with poor fixability by not performing image fixing only on the recording medium that passes through an area where accurate temperature detection by the temperature detecting means is difficult.

  According to invention of Claim 7, there exists an effect similar to the effect of said 1st to 6 described above.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. The image forming apparatus according to the present invention can be applied to an electronic device that prints an image or characters by fixing a toner image using a heating roller such as a printer, a copier, or a facsimile machine. In the following embodiments, a printer is described as an example of an image forming apparatus. However, the present invention can be applied to a copying machine, a facsimile, a scanner, or a multifunction machine having these functions. In addition, as an example of a recording medium, a general printing paper (hereinafter simply referred to as “paper”) will be described. However, any other medium that can fix a toner image even with a transparent film or the like will be described. Good. Furthermore, in order to simplify the explanation, a case will be described in which the sheets conveyed in parallel to the heating roller are two rows of a row and b row. However, even if the configuration is such that three or more rows of paper are conveyed in parallel. Good.
[First Embodiment]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus 1 according to the first embodiment, and FIGS. 2 and 3 are a cross-sectional view and a side cross-sectional view, respectively, illustrating a parallel sheet feeding mechanism. Regarding the constituent elements described below, a constituent element installed at a position corresponding to the row a is given a at the end of the reference numeral, and a constituent element installed at a position corresponding to the column b is attached with a suffix b. To distinguish.

  The image forming apparatus 1 includes a storage cassette 4A for normal paper, a storage cassette 4B for parallel paper feeding, a paper feed roller 50, paper feed rollers 5a and 5b, a separating roller 6, a registration roller 7, a photoconductor 8, and the photoconductor. 8, a charging device 10 disposed around the image forming unit 8, an unillustrated image forming unit, a light emitting unit 91 having a printing laser optical unit, a polygon mirror 92, a transfer unit 11, a heating roller 31, a pressure roller 34, a discharge It comprises rollers 13 and 15, a discharge guide 14, and a discharge tray 16. Although not shown, an operation unit for a user to input various operation commands and a display unit for displaying an operation screen, an error message, and the like are installed on the upper part of the image forming apparatus 1.

  The heating roller 31 incorporates a heater lamp 32 and is heated to a predetermined fixing temperature by the heater lamp 32. Further, the surface temperature of the heating roller 31 is measured by the thermistor 33, and a control unit described later controls the heating temperature of the heater lamp 32 based on the measurement result.

  As shown in FIG. 2, the storage cassette 4B has paper alignment units 40a and 40b inside. Paper feed rollers 5 a and 5 b, separating roller 6, registration roller 7, photoconductor 8, heating roller 31, and pressure roller so that the sheets taken out from sheet alignment units 40 a and 40 b are conveyed in parallel to heating roller 31. 34 is installed such that the respective rotation axes are parallel to each other, and the sheet aligning units 40a and 40b are preferably arranged in parallel in the direction of the rotation axis. In the paper alignment units 40a and 40b, paper sensors 1a and 1b for detecting the presence / absence of paper are provided, respectively.

  Returning to FIG. 1, the image forming apparatus 1 further includes a double feed sensor 17 that detects the double feed of paper, registration sensors 18 a and 18 b for driving timing of the registration roller 7, and a timing sensor for light emission start timing such as the light emitting unit 91. 19 and each sensor such as a discharge sensor 20 that detects discharge of the paper. These sensors are arranged in parallel at positions corresponding to the a row and the b row so that the detection operations can be performed for the sheets fed in parallel. Here, when three or more sheets are fed in parallel, the number of sensors is set according to the number of sheets.

  Next, the configuration of the paper sensors 1a and 1b will be described with reference to FIGS. The paper sensors 1a and 1b are disposed at appropriate positions in the paper alignment units 40a and 40b, and detect the presence or absence of paper in the paper alignment units 40a and 40b, respectively. The paper sensors 1a and 1b include, for example, photointerrupters 2a and 2b made up of a pair of light emitting elements and light receiving elements, and detection members 3a and 3b that are rotatably interposed between the photointerrupters 2a and 2b. Each is arranged. The detection members 3a and 3b are configured such that the leading ends of the detection members 3a and 3b come into contact with the uppermost stage of the paper placed on the paper placement plates 41a and 41b of the paper alignment units 40a and 40b.

  Further, elongate holes 43a and 43b are formed at appropriate positions on the paper placement plates 41a and 41b, for example, in parallel with the paper supply direction. When the paper runs out, the detection members 3a and 3b rotate to the vertical position due to their own weight. It is made to move. As indicated by the solid line in FIG. 3, the photo interrupter 2b is turned off when the leading end of the detection member 3b comes into contact with the sheet and the detection member 3b is positioned between the light emitting element and the light receiving element. As indicated by a two-dot chain line in FIG. 3, when the detection member 3b is suspended in the long hole 43b, the photo interrupter 2b is turned on, and a detection signal indicating that the sheet has run out is output. The paper placement plates 41a and 41b are urged upward by coil springs 42a and 42b so that the uppermost stage of the loaded paper comes into contact with the paper feed rollers 5a and 5b with appropriate pressure.

  Next, the flow from paper feeding to image formation will be described with reference to FIGS. FIG. 4 is a plan view schematically showing transport paths of the papers Pa and Pb stored in the paper alignment units 40a and 40b. The sheets Pa and Pb are taken out from the sheet aligning units 40a and 40b by the sheet feeding rollers 5a and 5b, conveyed in two rows to the separating roller 6 (not shown in FIG. 4), and further conveyed to the registration roller 7 by the separating roller 6. The The registration roller 7 is driven and controlled by a control unit 51 (shown in FIG. 5) based on signals from the registration sensors 18a and 18b. The paper feed rollers 5a and 5b and the registration roller 7 are driven by, for example, one main motor (not shown), and each of the paper feed roller drive clutches 21a and 21b and the registration roller drive clutch 22 for transmitting the driving force of the main motor is provided. Comes with the roller. At the start of feeding, the main motor and the feed roller drive clutches 21a and 21b are connected to rotate the feed rollers 5a and 5b. Then, after the registration sensors 18a and 18b detect the papers Pa and Pb, respectively, the main motor and the registration roller driving clutch 22 are connected and the registration roller 7 rotates. Note that the connection and disconnection of each clutch is controlled by a control unit described later in accordance with the detection result of each sensor.

  The photosensitive member 8 is driven by the control unit 51 based on the signal from the timing sensor 19, the image signal transmitted from the external device is optically modulated, and the light emitting unit 91 emits modulated light (laser light). The photosensitive member 8 is exposed by the laser beam through the polygon mirror 92. That is, the surface of the photoconductor 8 is charged by the charging device 10, and an electrostatic latent image is formed in parallel on the charged region by exposure, and is visualized as a toner image by a developing device (not shown). The visualized toner image is transferred onto each sheet by the transfer unit 11, and the toner image is fixed to the sheet when the sheet passes through the nip portion between the heating roller 31 and the pressure roller 34. The sheet on which the image is fixed in this manner is discharged to the discharge tray 16 through the discharge guide 14 by the discharge rollers 13 and 15.

  FIG. 5 is a block diagram illustrating a schematic configuration of the image forming apparatus 1. In addition, about the component demonstrated above, the same sign is attached | subjected and description is abbreviate | omitted. The control unit 51 is configured by a CPU or the like, and executes processing based on a predetermined program in accordance with an input instruction signal or the like, and outputs an instruction signal to each functional unit, transfers data, or the like to perform an image forming apparatus Control 1 centrally. Specifically, when an operation signal is output from the operation unit 52 by a button operation by the user, the control unit 51 detects the paper sensors 1a and 1b, the double feed sensor 17, the registration sensors 18a and 18b, the timing sensor 19, and the discharge sensor 20. The main motor 54, the paper feed roller drive clutches 21a and 21b, the registration roller drive clutch 22 and the like are controlled according to the detection signal from.

  Further, the control unit 51 also receives a temperature signal indicating the temperature of the heating roller 31 from the thermistor 33, and controls the heater lamp 32 so that the heating roller 31 has a predetermined temperature.

  The communication unit 53 includes an interface for performing data communication with an external device. The main motor 54 is for driving the paper feed rollers 5a and 5b, the separating roller 6, the registration roller 7 and the like via the paper feed roller drive clutches 21a and 21b and the registration roller drive clutch 22.

  The image forming controller 56 performs a predetermined process on the image data received by the communication unit 53 and outputs the image data to the control unit 51 so that the image formation is performed in parallel in the rotation axis direction of the photoconductor 8. The control unit 51 performs light modulation based on the image signal and causes the light emitting unit 91 to output modulated light.

  The general configuration of the image forming apparatus 1 that can form an image by conveying two sheets of paper in parallel and fix the image with the heating roller 31 has been described. Here, for example, when there is no paper on the b-row side and printing is performed only on the a-row side, heat is taken away by the paper on the a-row side of the heating roller 31, but heat is taken away from the b-row side because the paper does not pass through. And a temperature difference occurs between the row a side. However, since the thermistor 33 for measuring the temperature of the heating roller 31 is disposed only at one end of the non-sheet passing region on the b row side, it is difficult to accurately detect the temperature on the a row side of the heating roller 31. That is, when the sheet passes only on the row a of the heating roller 31, even if the temperature control is performed so that the heating roller 31 maintains the fixing temperature based on the measured temperature of the thermistor 33 as in the past, The row a side did not reach an appropriate temperature for image fixing, causing fixing failure.

  Therefore, the temperature of the heating roller 31 is varied in accordance with the presence or absence of the paper on the a row side and the b row side so that image fixing is performed at an appropriate temperature even when printing is performed only on the a row side. Hereinafter, the flow of temperature control of the heating roller 31 will be described with reference to the flowchart of FIG. In response to reception of image data from the external device by the communication unit 53, output of a print instruction operation signal from the operation unit 52, the control unit 51 confirms that there is no sheet in the sheet alignment unit 40a from the sheet sensor 1a. It is determined whether or not the detected detection signal is output (step S11). When the detection signal is not output from the sheet sensor 1a, that is, when there is a sheet in the sheet alignment unit 40a (step S11; YES), the control unit 51 has no sheet in the sheet alignment unit 40b from the sheet sensor 1b. It is determined whether or not a detection signal indicating is output (step S12). When the detection signal is not output from the sheet sensor 1b, that is, when there is a sheet in the sheet alignment unit 40b (step S12; YES), the controller 51 controls the heater so that the temperature of the heating roller 31 is maintained at T1. The heating control of the lamp 32 is performed (step S13), and the paper feed roller drive clutches 21a and 21b are driven to convey two sheets in parallel. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed on the a-row side and the b-row side of the photoconductor 8, and executes printing processing (step S14). Here, T1 indicates a set temperature of the heating roller 31 when two images are simultaneously fixed, and is hereinafter referred to as “normal temperature”.

  When there is paper in the paper alignment unit 40a but no paper in the paper alignment unit 40b (step S11; YES, step S12; NO), the controller 51 holds the temperature of the heating roller 31 at T3. Thus, the heating control of the heater lamp 32 is performed (step S15), and only the paper feed roller driving clutch 21a is driven to transport the paper on the a-row side. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed only on the row a of the photoconductor 8, and executes printing processing (step S16).

  Here, T3 indicates a set temperature of the heating roller 31 when image fixing is performed only on the paper on the a-row side, and T1 <T3. Specifically, if the temperature of the heating roller 31 when printing in two rows in parallel on the a-row side and the b-row side is 180 ° C., T1 is the temperature on the a-row side of the heating roller 31 is kept at 180 ° C. A predetermined temperature consisting of 180 ° C. + α. When printing paper only on the a-row side, the paper passes only on the a-row side of the heating roller 31, so the temperature on the a-row side decreases and a temperature difference occurs between the b-row side. For this reason, even if the measurement result of the thermistor 33 is used to control the temperature to the normal temperature T1, it is difficult to set the row a side to an appropriate temperature for fixing. Therefore, when printing only on the a row side, the set temperature of the heating roller 31 is set to a temperature T3 higher than the normal temperature T1, whereby the a row side of the heating roller 31 can be set to a temperature suitable for fixing.

  On the other hand, when there is no paper in the paper aligning unit 40a but there is paper in the paper aligning unit 40b (step S11; NO, step S17; YES), the controller 51 holds the temperature of the heating roller 31 at T2. Then, the heater lamp 32 is controlled to be heated (step S18), and only the paper feed roller driving clutch 21b is driven to convey the b-th row side paper. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed only on the b-row side of the photoconductor 8, and executes printing processing (step S19).

  Here, T2 indicates a set temperature of the heating roller 31 when image fixing is performed only on the paper on the b row side, and T2 ≦ T1. Since the b row side of the heating roller 31 is closest to the thermistor 33, the heating roller 31 is maintained at the normal temperature T1 based on the measured temperature of the thermistor 33 in principle. However, since there is a concern that the temperature on the a-line side where the sheet does not pass is excessively high, a temperature slightly lower than the normal temperature T1 that does not deteriorate the fixability may be set as T2.

  When there is no sheet in both the sheet alignment units 40a and 40b (step S11; NO, step S17; NO), the control unit 51 outputs a print stop instruction signal to the image forming controller 56 and stops the main motor 54. Then, printing is stopped (step S20).

As described above, even when the image is fixed only on one side of the a row side or the b row side by varying the set temperature of the heating roller 31 according to the presence or absence of the paper in the paper alignment units 40a and 40b. Image fixing can be performed at an appropriate temperature, and fixing defects can be suppressed.
[Second Embodiment]
In the first embodiment, the image forming apparatus 1 has been described in which the set temperature of the heating roller 31 is varied according to the presence / absence of sheets in the sheet aligning units 40a and 40b to suppress fixing defects. In the second embodiment, the heating roller 31 is held at a predetermined fixing temperature, but the image forming apparatus 1 that varies the printing time interval according to the presence / absence of paper in the paper alignment units 40a and 40b will be described. . Note that the configuration and block diagram of the image forming apparatus 1 in the present embodiment are the same as those described in the first embodiment, and thus the description thereof is omitted.

  FIG. 7 is a flowchart for explaining the flow of processing for changing the printing time interval according to the presence / absence of paper in the paper alignment units 40a and 40b. Here, the printing time interval is a time difference between the image fixing times of the sheet conveyed first and the sheet conveyed immediately thereafter, and indicates the interval between the sheets.

  In response to reception of image data from an external device by the communication unit 53, output of an operation signal for a print instruction from the operation unit 52, etc., the control unit 51 has no sheet in the sheet alignment unit 40a from the sheet sensor 1a. It is determined whether or not a detection signal indicating is output (step S21). When the detection signal is not output from the sheet sensor 1a, that is, when there is a sheet in the sheet alignment unit 40a (step S21; YES), the control unit 51 has no sheet in the sheet alignment unit 40b from the sheet sensor 1b. It is determined whether or not a detection signal indicating is output (step S22). When the detection signal is not output from the sheet sensor 1b, that is, when there is a sheet in the sheet alignment unit 40b (step S22; YES), the control unit 51 sets the printing time interval to t1 (step S23) and supplies the sheet. The paper roller driving clutches 21a and 21b are driven to convey two sheets in parallel. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed on the a-row side and the b-row side of the photoconductor 8, and executes printing processing (step S24). Here, t1 indicates a printing time interval when image fixing is performed simultaneously on two sheets, and hereinafter, t1 is expressed as a “normal printing time interval”.

  When there is paper in the paper alignment unit 40a but no paper in the paper alignment unit 40b (step S21; YES, step S22; NO), the control unit 51 sets the printing time interval to t3 (step S25). ) Only the paper feed roller driving clutch 21a is driven to convey the paper on the a-row side. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed only on the row a of the photoconductor 8, and executes printing processing (step S26).

  Here, t3 indicates a printing time interval when image fixing is performed only on the paper on the a-row side, and t1 <t3. Specifically, t3 is a time that can stabilize the temperature on the a row side of the heating roller 31 and is a time that is a predetermined time t1 + β. When the sheet is conveyed only on the a-row side, increasing the printing time interval means that the interval between the sheet conveyed first and the sheet conveyed immediately thereafter is increased. If the interval between the sheets is increased, the temperature on the a-row side of the heating roller 31 is stabilized while the sheet is not passing, and the temperature difference from the b-row side can be reduced. Therefore, when the sheet is conveyed only on the a-row side, the printing time interval is lengthened so that the heating roller 31 is heated even if the temperature control of the heating roller 31 is performed based on the measurement result by the thermistor 33 arranged on the b-row side. The a row side of the roller 31 can be set to an appropriate temperature for fixing, and fixing failure can be suppressed.

  On the other hand, when there is no paper in the paper alignment unit 40a but there is paper in the paper alignment unit 40b (step S21; NO, step S27; YES), the control unit 51 sets the printing time interval to t2 (step S28). ), Only the paper feed roller driving clutch 21b is driven to transport the b-row side paper. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed only on the row b side of the photoconductor 8, and executes printing processing (step S29).

  Here, t2 represents a printing time interval when image fixing is performed only on the paper on the b row side, and t1 ≦ t2. In principle, when printing only on the row b side, printing is performed at the normal printing time interval t1. However, since there is a concern that the temperature on the a-line side that does not pass through the paper rises too much and a temperature difference from the b-line side occurs, a time slightly longer than the normal printing time interval t1 is required so as to promote heat dissipation of the heating roller 31. It may be t2.

  When there is no sheet in both the sheet alignment units 40a and 40b (step S21; NO, step S27; NO), the control unit 51 outputs a print stop instruction signal to the image forming controller 56 and stops the main motor 54. Thus, printing is stopped (step S30).

As described above, the heating roller 31 is used even when only the paper on the one side of the a row side or the b row side is fixed by changing the printing time interval according to the presence or absence of the paper in the paper alignment units 40a and 40b. Can be maintained at a temperature suitable for fixing, and fixing defects can be suppressed.
[Third Embodiment]
In the second embodiment, the image forming apparatus 1 has been described in which the printing time interval is varied according to the presence / absence of paper in the paper alignment units 40a and 40b to suppress fixing failure. In the third embodiment, a description will be given of the image forming apparatus 1 that stops printing when there is no more sheet passing through the thermistor 33. Note that the configuration and block diagram of the image forming apparatus 1 in the present embodiment are the same as those described in the first embodiment, and thus the description thereof is omitted.

  FIG. 8 is a flowchart for explaining the flow of processing for determining whether or not to execute print processing according to the presence / absence of paper in the paper alignment units 40a and 40b. In response to the reception of image data from the external device by the communication unit 53, the output of a print instruction operation signal from the operation unit 52, etc., the control unit 51 has no sheet in the sheet alignment unit 40b from the sheet sensor 1b. It is determined whether or not a detection signal indicating is output (step S31). When the detection signal is not output from the sheet sensor 1b, that is, when there is a sheet in the sheet alignment unit 40b (step S31; YES), the control unit 51 has no sheet in the sheet alignment unit 40a from the sheet sensor 1a. It is determined whether or not a detection signal indicating is output (step S32). When the detection signal is not output from the sheet sensor 1a, that is, when there is a sheet in the sheet alignment unit 40a (step S32; YES), the control unit 51 drives the sheet feeding roller driving clutches 21a and 21b to drive two sheets. Paper in parallel. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed on the a-row side and the b-row side of the photoconductor 8, and executes print processing (step S33).

  When there is no sheet in the sheet aligning unit 40a (step S32; NO), the control unit 51 drives only the sheet feed roller driving clutch 21b to convey the sheet on the b row side. Then, the control unit 51 outputs an instruction signal to the image forming controller 56 so that image formation is performed only on the b-row side of the photoconductor 8, and executes print processing (step S34).

  On the other hand, when there is no paper in the paper alignment unit 40b (step S31; NO), the control unit 51 outputs a print stop instruction signal to the image forming controller 56, stops the main motor 54 and stops printing (step S35). ).

  As described above, when there is no paper in the paper aligning unit 40a but there is paper in the paper aligning unit 40b, the printing process is performed only on the b-row side, and when there is no paper in the paper aligning unit 40b, the paper is aligned. Printing is stopped even if there is paper in the unit 40a. If only the a-row side is printed, the a-row side of the heating roller 31 is away from the thermistor 33, so that it becomes difficult to control the temperature to an appropriate temperature for fixing, which causes a fixing failure. Therefore, only the a column side is not printed. On the other hand, the b-row side located in the immediate vicinity of the thermistor 33 is easily controlled to a temperature suitable for fixing based on the measured temperature of the thermistor 33. Accordingly, since the b row side can secure a good fixing property, only one side printing on the b row side is performed.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus. FIG. 3 is a cross-sectional view illustrating a parallel sheet feeding mechanism of the image forming apparatus. FIG. 3 is a side sectional view showing a parallel sheet feeding mechanism of the image forming apparatus. FIG. 3 is a plan view schematically showing a conveyance path of paper stored in a paper alignment unit. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus. 6 is a flowchart illustrating a flow of printing processing according to the first embodiment. 10 is a flowchart illustrating a flow of printing processing according to the second embodiment. 10 is a flowchart illustrating a flow of printing processing according to the third embodiment.

Explanation of symbols

1a, 1b Paper sensor 4A, 4B Storage cassette 5a, 5b, 50 Paper feed roller 8 Photoconductor 10 Charging device 13, 15 Discharge roller 14 Discharge guide 16 Discharge tray 17 Double feed sensor 18a, 18b Registration sensor 19 Timing sensor 20 Discharge sensor 21a, 21b Feed roller driving clutch 22 Registration roller driving clutch 31 Heating roller 32 Heater lamp 33 Thermistor 34 Pressure roller 91 Light emitting unit 92 Polygon mirror 51 Control unit 52 Operation unit 53 Communication unit 54 Main motor 55 Display unit 56 Image controller

Claims (7)

  A plurality of storage means for storing the recording medium, a plurality of presence / absence detection means for detecting the presence / absence of the recording medium in each storage means, and a plurality of the recording media are fixed simultaneously using a heating roller. A fixing unit; a conveying unit that takes out the recording medium from each storage unit and conveys the plurality of recording media in parallel in the axial direction of the heating roller; and detects a temperature at a predetermined location on the surface of the heating roller. An image forming apparatus comprising: a temperature detection unit; and a control unit configured to control each of the units. The control unit varies the control according to detection results of the presence / absence detection unit and the temperature detection unit. apparatus.   The control means performs temperature control for holding the heating roller at a predetermined fixing temperature based on the temperature detected by the temperature detection means, and the temperature detection means detects the temperature at the predetermined location. When the presence / absence detecting unit detects that there is no recording medium in the storage unit that stores the recording medium that passes most recently, and the storage medium that stores the recording medium that passes through a region not closest to the predetermined location. The image forming apparatus according to claim 1, wherein the temperature control of the heating roller is varied when the presence / absence detecting unit detects that the recording medium is not present in the storage unit.   When the presence / absence detecting means detects that the recording medium is not in the storage means for storing the recording medium passing immediately adjacent to the predetermined location where the temperature detection means detects the temperature, the control means The image forming apparatus according to claim 2, wherein temperature control is performed to maintain the roller at a temperature higher than the fixing temperature in advance.   The control unit controls the transport unit so that the recording medium is taken out from the storage unit at a predetermined time interval and transported, and the temperature detection unit detects a position closest to the predetermined position where the temperature is detected. The storage means for storing the recording medium that passes through an area not close to the predetermined location when the presence / absence detecting means detects that the recording medium is not in the storage means for storing the recording medium that passes through. The image forming apparatus according to claim 1, wherein the predetermined time interval is varied when the presence / absence detecting unit detects that the recording medium is not present therein.   When the presence / absence detecting means detects that the recording medium is not in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detection means detects the temperature, the control means The image forming apparatus according to claim 4, wherein the conveying unit is controlled so that the recording medium is taken out at a predetermined time interval longer than the time interval.   When the presence / absence detecting means detects that the recording medium is not in the storage means for storing the recording medium that passes immediately adjacent to the predetermined location where the temperature detecting means detects the temperature, the control means When the presence / absence detecting unit detects that the recording medium is not stored in the storage unit that stores the recording medium passing through a region not close to the predetermined location, the fixing of the image by the heating roller is stopped. The image forming apparatus according to claim 1, wherein the fixing of the image by the roller is continued.   The image forming apparatus according to claim 1, wherein the temperature detection unit is a thermistor.

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