JP2014215575A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer combining suppression of deterioration in image quality due to rise in temperature, with productivity.SOLUTION: The printer includes a printing part 14 for printing an image on a printing paper 5 which is a sheet, and a control part 80. The control part 80 performs determination processing S90 and temperature-dropping promotion processing S90 to S140. In the determination processing S90, the control part 80 determines whether temperature around the printing part exceeds a prescribed level or not. In the temperature-dropping promotion processing S90 to S140, when a sheet to be printed that is scheduled to be printed after the temperature around the printing part is determined to exceed the prescribed level is a first kind, temperature-dropping of the temperature around the printing part is more promoted than a case where the sheet to be printed is a second kind whose deterioration in image quality when printing is performed in a state where the temperature around the printing part exceeds the prescribed level is less than that of the first kind.

Description

  The present invention relates to a technology that achieves both suppression of deterioration in image quality due to temperature rise and productivity.

  A technique for maintaining transfer efficiency even when the type of paper changes by controlling the transfer voltage according to the type of paper is disclosed (Patent Document 1 below).

Japanese Patent Application Laid-Open No. 07-064212

  However, for example, when the apparatus is not equipped with a fan, or when paper that has passed through the fixing device during double-sided printing is transported again, the temperature of the image forming unit may rise above the normal temperature if continuous printing continues. However, there are paper types that maintain the image quality even if the same printing as before the temperature rise is continued after the temperature rise, but the same as before the temperature rise after the temperature rise due to, for example, a transfer failure. There is a type of paper whose image quality deteriorates when printing is continued, and there is a possibility that the image quality cannot be maintained.

  The present invention provides a technique for achieving both reduction in image quality degradation due to temperature rise and productivity.

  The printing apparatus disclosed in this specification includes a printing unit that prints an image on a sheet, and a control unit, and the control unit determines whether or not the temperature around the printing unit exceeds a specified level. And when the print-scheduled sheet that is scheduled to be printed after it is determined that the temperature around the printing unit exceeds the specified level is the first type, the print-scheduled sheet is The temperature of the periphery of the printing unit is decreased as compared with the case where the deterioration in image quality when the printing is performed in a state where the temperature around the printing unit exceeds the specified level is the second type, which is less than the first type. And a temperature lowering promotion process that promotes.

  When the print-scheduled sheet is the first type, the temperature drop around the printing unit is promoted as compared with the case where the print-scheduled sheet is the second type, so that it is possible to suppress a decrease in image quality. On the other hand, when the print-scheduled sheet is the second type, the image quality is less likely to be lower than when the print-scheduled sheet is the first type, and the temperature lowering promotion process can be suppressed, so that a decrease in productivity can also be suppressed. . Therefore, it is possible to achieve both the reduction in productivity and the reduction in image quality.

The following configuration is preferable as an embodiment of the printing apparatus.
The printing unit includes an image carrier and a transfer unit that transfers a developer image formed on the image carrier onto the sheet, and the first type sheet is orthogonal to the sheet conveyance direction. The sheet width, which is the length in the direction of the sheet, is smaller than the second type sheet width.

  A sheet having a small sheet width is liable to deteriorate in image quality when the temperature around the printing unit exceeds a specified level as compared with a sheet having a large sheet width. In this configuration, a sheet with a small sheet width is classified as the first type of sheet, and when a sheet with a small sheet width is scheduled to be printed after the temperature exceeds a specified level, a temperature lowering promotion process is performed. , Temperature drop is promoted. Therefore, it is possible to suppress a decrease in image quality for a sheet having a small sheet width.

  In the temperature lowering promotion process, the control unit transfers the print scheduled sheet to the printing unit when the print scheduled sheet is the first type, compared to when the print scheduled sheet is the second type. On the other hand, this is processing for delaying the conveyance timing of conveyance. The conveyance timing is intended to mean the timing at which the sheet reaches the printing unit, and methods for adjusting this include a method for adjusting the paper feed timing and a method for adjusting the conveyance speed.

  In this configuration, when the print-scheduled sheet is the first type, the conveyance timing is delayed as compared with the second type. Therefore, when the print-scheduled sheet is the first type, the temperature drop around the printing unit is promoted and the deterioration of the image quality can be suppressed as compared with the second type. On the other hand, when the print-scheduled sheet is the second type, the conveyance timing is earlier than in the case of the first type, so that the productivity can be increased.

  In the temperature decrease promotion process, the control unit prints the conveyance timing before determining that the temperature around the printing unit exceeds the specified level when the print-scheduled sheet is the second type. When the sheet to be printed is of the first type, the conveyance timing is set to be later than the normal conveyance timing.

  In this configuration, when the print-scheduled sheet is the second type, the conveyance timing is maintained at the normal conveyance timing. Therefore, when the temperature around the printing unit exceeds a specified level, the productivity is higher than when the conveyance timing of the second type of sheet is delayed from the normal conveyance timing.

  A sheet feeding unit that feeds sheets is provided, and the control unit adjusts the conveyance timing according to a sheet feeding timing at which the sheet to be printed is fed by the sheet feeding unit. In this configuration, the conveyance timing is adjusted by adjusting the paper feed timing.

  The control unit executes a counting process that counts the amount of sheets that are continuously printed. If the amount of sheets counted in the counting process exceeds a specified value in the determination process, It is determined that the temperature exceeds the specified level. In this configuration, it is possible to determine whether or not the temperature around the printing unit exceeds a specified level without a sensor that detects the temperature around the printing unit. It should be noted that the meaning of counting “sheet quantity” is to count parameters that are correlated with the total quantity of sheets to be printed, that is, to count “number of sheets” or “sheet printing time”. Is included.

  A fixing unit that heat-fixes the image printed on the sheet by the printing unit; and a re-transport mechanism that re-transports the sheet on which the image is heat-fixed by the fixing unit to the printing unit. In the counting process, the amount of sheets continuously re-conveyed by the re-conveying mechanism is counted.

  When performing double-sided printing on a sheet, the temperature of the printing unit is likely to exceed a specified level because the temperature of the printing unit is increased by the heat of the re-conveyed sheet. By applying the present invention to a printing apparatus that enables double-sided printing, it is possible to suppress a decrease in productivity while suppressing a decrease in image quality due to a temperature rise.

  The sensor includes a sensor that detects a temperature around the printing unit, and the control unit determines whether the temperature around the printing unit exceeds the specified level based on a detection value of the sensor in the determination process. It is possible to accurately determine whether the temperature around the printing unit exceeds a specified level.

  According to the printing device disclosed in the present specification, it is possible to achieve both suppression of deterioration in image quality due to temperature rise and productivity.

FIG. 3 is a side sectional view of a main part of the laser printer according to the first embodiment. Block diagram showing the electrical configuration of the laser printer Graph showing the temperature rise of the transfer roller during the printing process Diagram showing the positional relationship between the transfer roller and printing paper The flowchart figure which shows the execution sequence of a temperature fall promotion process FIG. 3 is a block diagram illustrating an electrical configuration of a laser printer according to a second embodiment. The flowchart figure which shows the execution sequence of a temperature fall promotion process Cross-sectional side view of main parts of a laser printer according to another embodiment

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
(1) Configuration of Printer FIG. 1 is a side sectional view of an essential part of a laser printer 1 (an example of a printing apparatus). The laser printer 1 (hereinafter referred to as “printer”) includes a main body frame 11, a paper feeding unit 12, a transport mechanism 13, a printing unit 14, a re-transport mechanism 15, a fixing unit 40, and the like.

  The paper feed unit 12 includes a paper feed tray 16 on which a recording medium such as the printing paper 5 is stacked, a pressing plate 17, and a paper feed roller 18. The pressing plate 17 is rotatable around its rear end, and the printing paper 5 on the pressing plate 17 is pressed toward the paper feed roller 18. As the paper supply roller 18 rotates, the printing paper 5 is sent out one by one to the conveyance path.

  The transport mechanism 13 includes a pair of registration rollers 19 and a pair of paper discharge rollers 20. The printing paper 5 sent out from the paper feed unit 12 to the transport path L 1 is registered by the registration rollers 19 and then transferred to the transfer position X. Sent to. The transfer position X is a position at which the toner image on the photosensitive drum 30 is transferred to the printing paper 5, and is a contact position between the photosensitive drum 30 and the transfer roller 31.

  The printing unit 14 includes a scanner unit 34, a process cartridge 35, a transfer roller (an example of a transfer unit) 31, and the like. The scanner unit 34 includes a polygon mirror 37, a laser diode (not shown), and the like. A light beam (one-dot chain line in the figure) emitted from the laser diode is irradiated onto the surface of the photosensitive drum 30 while being deflected by the polygon mirror 37.

  The process cartridge 35 includes a developing roller 38, a photosensitive drum (an example of an image carrier) 30, and a scorotron charger 39. The charger 39 uniformly charges the surface of the photosensitive drum 30 to a positive polarity. The photosensitive drum 30 has a drum body grounded and a surface formed of a positively chargeable material such as an organic photosensitive member mainly composed of polycarbonate. The surface of the photosensitive drum 30 charged to positive polarity is exposed by the light beam emitted from the scanner unit 34, and an electrostatic latent image is formed. Next, toner (developer image) carried on the surface of the developing roller 38 is supplied to the electrostatic latent image formed on the photosensitive drum 30 and developed.

  The transfer roller 31 is opposed to and contacted with the photosensitive drum 30 from the lower side in the vertical direction, and is disposed so as to form a nip with the photosensitive drum 30. In the transfer roller 31, a metal roller shaft is covered with a roller made of a conductive rubber material, and a predetermined transfer bias is applied. When the printing paper 5 passes through the transfer position X, a transfer bias is applied to the transfer roller 31, so that the toner image carried on the surface of the photosensitive drum 30 is transferred to the printing paper 5. Can be transferred.

  The fixing unit 40 is disposed behind the photosensitive drum 30 (on the left side in FIG. 1). The fixing unit 40 includes a heating roller 41 and a pressing roller 42, and thermally fixes the toner image transferred while the printing paper 5 passes between the heating roller 41 and the pressing roller 42 to the printing paper 5. The heat-fixed printing paper 5 is discharged onto a paper discharge tray 46 via a paper discharge path 45.

  After the image is formed on one side (front surface) of the printing paper 5, the re-transport mechanism 15 automatically turns the printing paper 5 over and forms the image on the other side (back side). Transport toward 14. Specifically, the re-transport mechanism 15 includes a flapper 32, a switchback path 33, and re-transport rollers 26 to 29.

  When the trailing edge of the printing paper 5 is nipped by the paper discharge roller 20, the flapper 32 rotates clockwise as indicated by the broken line in FIG. Is rotated in the reverse direction, whereby the printing paper 5 is sent out from the rear end side to the switchback path 33. The printing paper 5 sent out to the switchback path 33 is sent out to the conveyance path L1 from the rear end side by the re-conveyance rollers 26 to 29 in an inverted state. Thereby, an image can be formed on the back surface.

  A manual feed tray 50 is provided on the front wall of the main body frame 11. The conveyance path L <b> 2 of the manual feed tray 50 joins the conveyance path L <b> 1 before the registration roller 19, and the printing paper 5 can be fed from the manual feed tray 50.

(2) Electrical Configuration of Printer FIG. 2 is a block diagram showing the electrical configuration of the printer 1. The printer 1 includes a control unit 80, a paper feeding unit 12, a transport mechanism 13, a printing unit 14, a fixing device 40, a display unit 63, an operation unit 65, a network interface 67, and the like.

  The control unit 80 includes a CPU 81, a RAM 83, a ROM 85, a timer T1, and a timer T2. The control unit 80 controls each unit of the printer 1 and executes an execution sequence of a temperature lowering promotion process described later.

  The ROM 85 stores various programs executed by the CPU 81, for example, an operation program of an execution sequence of a temperature lowering promotion process described later, a table that the CPU 81 refers to in various processes, and the like. The RAM 83 is used as a main storage device for the CPU 81 to execute various processes. The timer T1 measures the continuous printing time for double-sided printing, and the timer T2 measures the time from the end of double-sided printing to the start of the next printing.

  The display unit 63 includes various lamps and a liquid crystal panel. The operation unit 65 is configured by an input panel or the like, and the user can perform a print instruction by operating the operation unit 65 while referring to the display unit 63. The network interface 67 functions to connect the printer 1 to an external device such as an information terminal device, and the user can instruct printing from the external device via the network interface 67.

(3) Relationship between temperature, paper, and image quality Printing includes single-sided printing and double-sided printing. In single-sided printing, an image is formed on the front surface, passes through the fixing device 40, and heats up the printing paper 5 to be discharged to a discharge tray 46 outside the main body frame 11. On the other hand, in double-sided printing, an image is formed on the surface, passes through the fixing device 40, and heats the printing paper 5 through the re-conveying mechanism 15 to be conveyed again to the printing unit 14. Therefore, in the case of double-sided printing, the ambient temperature of the printing unit 14 is likely to increase compared to single-sided printing.

  In particular, when double-sided printing continues, the temperature of the printing unit 14 rises above the normal temperature, and the temperature of the transfer roller 31 exceeds an allowable temperature (for example, 45 ° C.) that is a specified level as shown in FIG. End up. After exceeding the allowable temperature, the temperature of the transfer roller 31 gradually increases as shown in FIG. 3, and is saturated at a predetermined temperature (48 ° C. in this example). The allowable temperature is a limit temperature that does not cause transfer failure.

  By the way, the printing paper 5 includes a first type printing paper and a second type printing paper. The first type of printing paper is a printing paper whose image quality deteriorates due to transfer failure or the like when the same printing as before the temperature rise is continued after the temperature rises to an allowable temperature. On the other hand, the second type of printing paper is printing paper that maintains the image quality even if the same printing as before the temperature rise is continued after the temperature rise.

  An example of the first type of printing paper is a printing paper S1 having a small sheet width, and an example of the second type of printing paper is a printing paper S2 having a large sheet width. The sheet width means the length of the printing paper 5 in a direction (left and right direction in FIG. 4) orthogonal to the sheet conveyance direction (up and down direction in FIG. 4).

  The following points can be cited as factors that cause a difference in image quality depending on the sheet width. Transfer, which is an important process for maintaining the image quality, electrically attracts the toner image formed on the photosensitive drum 30 to the printing paper 5 by an electric field from the photosensitive drum 30 toward the transfer roller 31. To do. Therefore, in order to maintain image quality, it is desirable to make the electric field applied between the two uniform during transfer.

  However, as shown in FIG. 4, the overlapping range of the printing paper 5 with respect to the transfer roller 31 can be made due to the difference in sheet width. That is, for example, in the printing sheet S2 having a large sheet width such as A4 size or letter size, the printing sheet overlaps almost the entire transfer roller 31, whereas, for example, the sheet like B5 size or A5 size. In the printing paper S1 having a small width, the printing paper overlaps only in the central area A of the transfer roller 31, and the area B where the printing paper does not overlap is formed on both sides.

  When the area B where the printing paper 5 does not overlap becomes wide and the temperature rise around the printing unit 14 such as the transfer roller 31 overlaps, the electric field is likely to be disturbed at the boundary C. Due to the disturbance of the electric field at the boundary C, the image quality is liable to deteriorate. Therefore, if the first type of printing paper is printed in a state where the temperature of the transfer roller 31 exceeds the allowable range, the image quality is likely to be deteriorated.

  In particular, the printer 1 is provided with a manual feed tray 50. After the paper is fed from the paper feed tray 16 side and continuously printed on both sides, the printer 1 is classified as the first type without taking time. There are cases where printing is performed by feeding a printing sheet having a small sheet width from the manual feed tray 50. Therefore, when the double-sided printing is performed, the first type of printing paper may be printed in a state where the temperature around the printing unit 14 such as the transfer roller 31 exceeds the allowable temperature.

  In order to suppress the deterioration of the image quality, printing on all types of printing paper 5 may be performed after the temperature around the printing unit 14 becomes equal to or lower than the allowable temperature. However, since the execution of all the printing processes is restricted until the temperature is lowered, there is a problem that productivity (the number of printable sheets per unit time) is lowered. Therefore, in the printer 1 disclosed in the present embodiment, the following temperature decrease promotion process (the processes of S90 to S140 shown in FIG. 5) is executed.

  The temperature lowering promotion process is performed when the printing paper 5 as a printing scheduled sheet to be printed after it is determined that the temperature of the transfer roller 31 exceeds the allowable temperature (specified level) is the first type. Compared to the case where the printing-scheduled sheet is of the second type, the temperature of the transfer roller 31 is accelerated.

  That is, the process of lowering the temperature around the printing unit 14 such as the transfer roller 31 is differentiated according to the type of the print-scheduled sheet. If the print-scheduled sheet is the first type, the process of lowering the temperature is positively performed. This is performed to increase the temperature decrease range, and printing is performed after the temperature around the printing unit 14 has decreased to an allowable temperature. On the other hand, when the print-scheduled sheet is of the second type, printing is performed even if the temperature decrease around the printing unit 14 is made small or zero and the temperature around the printing unit 14 is higher than the allowable temperature. In other words, when the print-scheduled sheet is the first type, priority is given to the process of lowering the temperature around the printing unit 14 and printing is restricted. When the print-scheduled sheet is the second type, printing is performed. Printing is prioritized by avoiding the process of lowering the temperature around the section 14. By doing so, the first type of printing paper is suppressed from deterioration in image quality, and the second type of printing paper is suppressed from reducing productivity. For this reason, it is possible to achieve both reduction in productivity and reduction in image quality.

3. Execution Sequence of Temperature Reduction Promotion Process Next, an execution sequence of the temperature reduction promotion process executed by the control unit will be described with reference to FIG. The execution sequence of the temperature lowering promotion process shown in FIG. 5 includes the processes of S10 to S140, and starts when a print job is received from an external device such as an information terminal device.

  When the process is started in response to the reception of the print job, first, in S10, the CPU 81 performs a process for determining the presence / absence of double-sided print data. If the received print job contains double-sided print data, YES is determined in S10, and the process proceeds to S20. When the process proceeds to S20, the count operation of the timer T1 is started by the instruction of the CPU 81 (count process). The timer T1 measures the continuous printing time for double-sided printing.

  Then, when the count operation of the timer T1 is started, the process proceeds to S30. In S <b> 30, in response to a command from the CPU 81, the printing paper 5 is started to be fed from the paper feeding tray 16, and the duplex printing process is executed in the printing unit 14. While the double-sided printing process is continued, NO is determined in S40. When the double-sided printing process is completed, a YES determination is made in S40, and the process proceeds to S50.

  When the process proceeds to S50, the count operation of the timer T1 is ended by the instruction of the CPU 81. Then, in response to a command from the CPU 81, the count value of the timer T1, that is, the continuous printing time for duplex printing is stored in the RAM 83.

  Thereafter, the process proceeds to S60. In S60, the timer T2 starts counting in response to a command from the CPU 81. The timer T2 measures the time from the end of double-sided printing to the start of the next printing.

  Then, when the count operation of the timer T2 is started, the process proceeds to S70. In S <b> 70, processing for determining the presence / absence of single-sided print data is performed according to a command from the CPU 81. If the printer 1 has received a print job for single-sided print data during execution of double-sided printing, a YES determination is made in S70.

  If YES is determined in S70, the process proceeds to S80. In S80, the CPU 81 performs processing for determining whether the count value of the timer T2, that is, the elapsed time from the end of double-sided printing, is equal to or greater than a threshold value. The threshold value is a time for which the temperature of the transfer roller 31 naturally falls from the saturation temperature (48 ° C. in this example) to the allowable temperature (45 ° C. in this example) (3 minutes in this example). ).

  As described above, the reason why the elapsed time from the end of double-sided printing is compared with the standby time is that even if the temperature of the transfer roller 31 has reached the saturation temperature at the end of double-sided printing, the time is 3 minutes or longer. This is because if it has elapsed, there is no worry of image quality deterioration and it is not necessary to restrict printing.

  If NO is determined in S80 (when the elapsed time from the end of double-sided printing is less than 3 minutes), the process proceeds to S90. In step S90, the CPU 81 determines whether the print target is the first type of print paper based on the paper size information added to the print data. Hereinafter, each process will be described in different cases depending on the type of printing paper.

  In this embodiment, the determination criterion of the sheet width is set to 200 mm as an example, and “A5” and “B5” printing sheets having a sheet width smaller than 200 mm are set as the first type printing sheet S1. The “A4” or “letter size” printing paper having a sheet width larger than 200 mm is used as the second type printing paper S2.

(A) Single-sided printing of first type printing paper S1 after double-sided printing When the sheet to be printed is first type printing paper (B5 size or A5 size printing paper) S1 with a small sheet width, S100 Migrate to In S100, the CPU 81 performs a process for determining whether the count value of the timer T1 is equal to or greater than a specified value. The specified value is a time period during which the temperature of the transfer roller 31 is assumed to exceed the allowable temperature of 45 ° C. due to continuous printing, and is set to “28 minutes” as an example.

  Therefore, in S100, it is determined whether the count value of the timer T1 is “28 minutes” or more. The intention of performing the process of S100 is to determine whether or not the temperature of the transfer roller 31 exceeds the allowable temperature of 45 ° C. based on the count value of the timer T1 (determination process).

  When the count value T1 of the timer T1 is equal to or greater than “28 minutes”, the process proceeds to S110. In S110, the CPU 81 executes a process for determining whether or not a standby time has elapsed since the end of double-sided printing. The waiting time is the time required for the ambient temperature of the transfer roller 31 to drop from the saturation temperature (for example, 48 ° C.) to the allowable temperature (for example, 45 ° C.) or less, for example “3 minutes”. It is.

  After shifting to S110, the CPU 81 determines whether the standby time has elapsed based on the count value of the timer T2, and waits for the standby time to elapse. The reason for waiting for the elapse of the standby time in S110 is to wait for the ambient temperature of the printing unit 14 to be equal to or lower than the allowable temperature.

  When the standby time has elapsed, a YES determination is made in S110, and the process proceeds to S120. In S120, the first type printing paper S1 is fed from the manual feed tray 50 according to a command from the CPU 81, and single-sided printing is executed. In other words, when the count value of the timer T1 is equal to or greater than the specified value, the process of S110 is performed, so that the first paper feed timing is adjusted late by the waiting time for single-sided printing. Then, while the single-sided printing process is continued, NO is determined in S130. Thereafter, when the single-sided printing process is completed, a YES determination is made in S130, and the process proceeds to S140. In S140, a process for resetting the count values of the timers T1 and T2 is performed.

  On the other hand, when the count value T1 of the timer T1 is less than “28 minutes”, S110 is skipped and the process proceeds to S120. Therefore, when the count value T1 of the timer T1 is less than “28 minutes”, the first-type printing paper S1 starts to be fed and single-sided printing is executed without waiting for the standby time to elapse. As described above, the execution sequence of the series of temperature decrease promotion processing ends.

(B) When the second type printing paper S2 is printed on one side after completion of double-sided printing When the print-scheduled sheet is the second type printing paper (A4 size or letter size printing paper) S2 having a large sheet width , S100 and S110 are skipped, and the process proceeds to S120. For this reason, when the printing-scheduled sheet is the second type of printing paper S2, the second type of printing paper S2 does not wait for the waiting time to elapse, and the second type of printing paper S2 has a normal supply with the temperature of the transfer roller 31 being lower than the allowable temperature. Paper is fed at the same paper feed timing as the paper timing, and single-sided printing is executed. As described above, the execution sequence of the series of temperature decrease promotion processing ends.

(C) When there is no print data after completion of double-sided printing When there is no single-sided print data after completion of double-sided printing, a NO determination is made at S70, and at that point, the execution sequence of a series of temperature decrease promotion processing ends. .

4). Explanation of Effects As described above, in the printer 1, when it is determined that the temperature around the printing unit 14 such as the transfer roller 31 is equal to or higher than the allowable temperature, the next print scheduled sheet to be printed is the first type of printing. In the case of the sheet S1, the printing process is performed by delaying the initial sheet feeding timing by the waiting time by waiting for the waiting time. On the other hand, when the next print-scheduled sheet is the second type of printing paper S2, the printing process is performed at the normal paper feeding timing without waiting for the waiting time to elapse.

  In other words, when the print-scheduled sheet is the first type, priority is given to image quality over productivity, so that deterioration in image quality can be suppressed. On the other hand, when the print-scheduled sheet is of the second type, productivity is prioritized over image quality, so that a decrease in productivity can be suppressed. Therefore, it is possible to achieve both the reduction in productivity and the reduction in image quality.

  In the printer 1, even when it is determined that the temperature of the transfer roller 31 is equal to or higher than the allowable temperature, if the print-scheduled sheet is the second type of printing paper S 2, the waiting time has elapsed. Instead, the printing paper S2 is fed at the normal paper feeding timing (that is, the same paper feeding timing as when the temperature of the transfer roller 31 is within the allowable range). Therefore, when the printing scheduled sheet is the second type of printing paper S2, it is always possible to ensure the same level of productivity as usual.

  The printer 1 determines whether the temperature of the transfer roller 31 has exceeded the allowable temperature based on the continuous printing time of the printing paper. Therefore, even if there is no sensor for detecting the temperature of the transfer roller 31, it can be determined whether or not the temperature of the transfer roller 31 exceeds the allowable temperature (specified level).

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described with reference to FIGS.
In the first exemplary embodiment, whether the temperature of the transfer roller 31 exceeds the allowable temperature based on whether the continuous printing time of double-sided printing is measured using the timer T1 and the count value of the timer T1 exceeds the specified value. Whether or not was determined (S100 in FIG. 5). Then, after printing on both sides, when printing the printing paper S1 with a small sheet width classified as the first type, if the temperature of the transfer roller 31 exceeds the allowable temperature, the waiting time has passed. , Printed. On the other hand, after printing on both sides, when printing the printing sheet S2 having a large sheet width classified as the second type, printing is performed without waiting for the waiting time to pass regardless of the temperature of the transfer roller 31. I did it.

  In the second embodiment, the method of determining whether or not the temperature of the transfer roller 31 exceeds the allowable temperature is different from that of the first embodiment. In the second embodiment, the temperature of the transfer roller 31 is directly measured by the temperature sensor 90. It is measured and it is determined from the detection value of the temperature sensor 90 whether or not the temperature of the transfer roller 31 exceeds the allowable temperature (S105 in FIG. 7).

  The other processes are the same as those in the first embodiment, and when the printing paper S1 with a small sheet width classified as the first type is printed after the double-sided printing, the temperature of the transfer roller 31 exceeds the allowable temperature. If the waiting time elapses, printing is performed. On the other hand, after printing on both sides, when printing the printing sheet S2 having a large sheet width classified as the second type, printing is performed regardless of the temperature of the transfer roller 31.

  Therefore, similarly to the first embodiment, it is possible to achieve both the reduction in productivity and the reduction in image quality. Further, although the temperature of the transfer roller 31 is increased by double-sided printing, the actual temperature has a correlation with the environmental temperature, and therefore the temperature cannot be accurately specified only by the continuous printing time of double-sided printing.

  In this regard, in the second embodiment, since the temperature of the transfer roller 31 is detected by the temperature sensor 90, the temperature of the transfer roller 31 can be accurately determined as compared with the case where the determination is based on the length of continuous printing time. Therefore, it can be accurately determined whether or not the temperature of the transfer roller 31 exceeds the allowable temperature. In the second embodiment, since the continuous printing time for double-sided printing is not counted, the timer T1 is abolished, and the processes of S20 and S50 shown in FIG. 5 are also abolished.

<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 the first and second embodiments, the printer 1 having the configuration in which the paper feed tray 16 and the manual feed tray 50 are provided is illustrated. However, the scope of application of the technology disclosed in the present embodiment is illustrated in the first and second embodiments. For example, as shown in FIG. 8, the present invention can be applied to a printer 100 in which paper feed trays 16A and 16B are arranged in multiple stages.

  That is, the printer 100 in which the paper feed trays 16 are arranged in multiple stages, like the printer 1 having the manual feed tray 50, feeds paper from one of the paper feed trays 16A and performs duplex printing, and then waits for time. In addition, printing can be performed by feeding the printing sheet S1 having a small sheet width classified as the first type from the other sheet feeding tray 16B. Accordingly, there is a case where the first type of printing paper S1 is printed in a state where the temperature of the transfer roller 31 exceeds the allowable temperature due to the double-sided printing, and there is a concern that the image quality is deteriorated. By applying the technique (temperature decrease promotion process) described in this specification to such a printer 100, it is possible to suppress a decrease in image quality.

  (2) In the first and second embodiments, a “monochrome” printer is illustrated as an example of the printer 1. However, the present invention can be applied to any electrophotographic printer and is described in this specification as a “color type” printer. It is also possible to apply the disclosed technique (temperature decrease promotion process).

  (3) In the first and second embodiments, the printer 1 capable of both single-sided printing and double-sided printing has been exemplified. However, the technology disclosed in this specification (temperature decrease promotion processing) is applied to the printer 1 that does not have the double-sided printing function. ) Can also be applied. That is, when it is expected that the temperature of the printing unit such as the transfer roller will rise to an allowable temperature by continuously performing single-sided printing, for example, single-sided printing is performed by the printer 1 that is not provided with a fan that exhausts heat inside the apparatus. In the case of continuously performing the temperature lowering promotion process, it is possible to achieve both the reduction in productivity and the reduction in image quality as in the first and second embodiments.

  (4) In the first and second embodiments, as an example of the temperature lowering promotion process, when it is determined that the temperature around the printing unit 14 exceeds the allowable temperature, if the next print scheduled sheet to be printed is the first type, An example has been described in which printing processing is performed after waiting time has elapsed, and printing processing is performed without waiting for the waiting time to elapse if the next print-scheduled sheet to be printed is the second type.

  The temperature lowering promotion process may be performed when the next printing scheduled sheet to be printed is the first type, as long as the printing scheduled sheet promotes the temperature lowering of the transfer roller 31 as compared with the second type. In the case of one type of printing paper, the standby time may be lengthened, and in the case where the print-scheduled sheet is the second type of printing paper, the standby time may be shortened. That is, when the print-scheduled sheet is the first type of printing paper, priority is given to the suppression of image quality deterioration, and the standby time is set long so that the temperature of the transfer roller 31 is surely lowered to an allowable temperature or less. On the other hand, when the print-scheduled sheet is the second type of printing paper, the productivity is prioritized, and the standby time may be set to a short time such that the temperature of the transfer roller 31 decreases to near the allowable temperature.

  (5) In the first and second embodiments, an example is given in which the time until the temperature of the transfer roller 31 decreases is adjusted by the paper feed timing. In addition to the paper feed timing, the time adjustment method can be adjusted by the transport speed of the printing paper. Instead of delaying the paper feed timing, the transport speed may be slowed. The method for lowering the temperature of the transfer roller 31 is not particularly limited. In addition to the method of waiting for the temperature of the transfer roller 31 to drop naturally as disclosed in this specification, the transfer fan 31 is rotated to perform transfer. The temperature of the roller may be lowered.

  (6) In the first embodiment, whether or not the temperature of the transfer roller exceeds the allowable temperature is determined based on the continuous printing time of double-sided printing. You may make it judge based on.

  (7) In the first embodiment, the control unit 80 is mainly configured by the CPU 81. However, the control unit 80 can be configured by one or more hardware circuits such as an ASIC, and the CPU 81 and the ASIC. It is also possible to configure by combining these hardware circuits. Further, in the first embodiment, an example in which the printing scheduled sheets are classified into the first type and the second type by paying attention to the size of the sheet width has been shown. If there is a difference in the influence of the image quality on the sheet, the printing scheduled sheet may be classified into the first type and the second type by paying attention to the thickness and material of the sheet.

1. Laser printer (printing device)
5. Printing paper (sheet)
DESCRIPTION OF SYMBOLS 12 ... Paper feed part structure 13 ... Conveyance mechanism 14 ... Printing part 15 ... Re-conveyance mechanism 30 ... Photosensitive drum (image carrier)
31. Transfer roller (transfer section)
32 ... Flapper 33 ... Switchback path 40 ... Fixing device 80 ... Control unit 90 ... Temperature sensor

Claims (8)

A printing section for printing an image on a sheet;
A control unit,
The controller is
A determination process for determining whether the temperature around the printing unit exceeds a specified level;
If the print-scheduled sheet that is scheduled to be printed after it is determined that the temperature around the print unit exceeds the specified level is the first type, the print-scheduled sheet has a temperature around the print unit. Compared to the case where the deterioration in image quality when printing is performed in a state exceeding the specified level is the second type, which is less than the first type, the temperature lowering promotion that promotes the temperature decrease around the printing unit. And a printing apparatus that executes processing. The printing unit includes an image carrier and a transfer unit that transfers a developer image formed on the image carrier onto a sheet.
2. The printing apparatus according to claim 1, wherein the first type of sheet is a sheet having a sheet width that is a length in a direction orthogonal to a sheet conveyance direction, which is smaller than the second type of sheet width. . The controller is
In the temperature lowering promotion process, when the print-scheduled sheet is of the first type, the transport of transporting the print-scheduled sheet to the printing unit is greater than when the print-scheduled sheet is of the second type. The printing apparatus according to claim 2, which is a process for delaying timing. The controller is
In the temperature lowering promotion process, when the printing-scheduled sheet is the second type, a sheet printed before determining that the temperature around the printing unit exceeds the specified level is determined as the conveyance timing. Is maintained at the normal transport timing, which is the transport timing for
The printing apparatus according to claim 3, wherein when the print-scheduled sheet is the first type, the conveyance timing is set later than the normal conveyance timing. It has a paper feeder that feeds sheets,
The controller is
5. The power supply system according to claim 3, wherein the conveyance timing is adjusted by a sheet feeding timing at which the sheet to be printed is fed by the sheet feeding unit. The controller is
Execute count processing to count the amount of sheets printed continuously,
6. The determination process according to claim 2, wherein in the determination process, when the amount of sheets counted in the count process exceeds a specified value, it is determined that the temperature around the printing unit exceeds the specified level. The printing apparatus as described. A fixing unit that heat-fixes an image printed on a sheet by the printing unit;
A re-conveying mechanism that re-conveys the sheet on which the image has been heat-fixed by the fixing unit to the printing unit,
The controller is
The printing apparatus according to claim 6, wherein, in the counting process, an amount of sheets continuously re-conveyed by the re-conveyance mechanism is counted. A sensor for detecting a temperature around the printing unit;
The controller is
6. The printing apparatus according to claim 1, wherein in the determination process, it is determined whether a temperature around the printing unit exceeds the specified level based on a detection value of the sensor.

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