JP5759173B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser printer.

  A color image forming apparatus using an intermediate transfer member forms a toner image on a photosensitive drum (image carrier) of each color, transfers each toner image on the intermediate transfer member, and uses the toner image as a recording material. A color image is formed by secondary transfer.

  For example, when printing in monochrome, a configuration is used in which the photosensitive drums other than black are prevented from rotating by preventing the photosensitive drums other than black from rotating. In the following description, a state in which each member of the image forming apparatus is set so that a plurality of color toner images can be formed, and printing in that state is referred to as a color mode. An image printed using a plurality of color toner images is called a color image. In contrast, members other than the member that forms a single color toner image, such as black, are set to suppress wear, and each member of the image forming apparatus is set so that the single color toner image can be formed. And the printing in that state is called a mono mode. An image printed using the single color toner image is called a mono image. When the print mode is set to the mono mode, only a mono image can be printed. However, in the color mode, both a mono image and a color image can be printed.

  Since switching of the print mode requires a certain amount of time, depending on the mixed state of the mono image and the color image, the delay due to the change of the print mode increases, and the performance of image formation decreases. For this reason, in Patent Document 1, when the color mode is set, if a predetermined number of mono images are continuously printed, the mono mode is changed, and if not, the mono image is printed in the color mode. Propose to do.

JP 2003-237191 A

  In order to suppress the consumption of members, when printing a mono image, it is preferable to set the mono mode as much as possible. However, if the mono image is always printed in the mono mode, as described above, the image forming performance may be degraded. The configuration described in Patent Document 1 reduces the frequency with which a mono image is printed in the color mode while suppressing a decrease in image formation performance. However, it is desired to further reduce the frequency of printing a mono image in the color mode without reducing the image forming performance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing the frequency of printing a mono image in the color mode without reducing the image forming performance.

An image forming apparatus according to the present invention includes a plurality of image carriers, a plurality of developing units corresponding to each of the plurality of image carriers, and forming an image on the corresponding image carrier with toner, and the plurality of developing units. A first mode in which an image is formed by contacting each of the developing units with a corresponding image carrier, and a second mode in which an image is formed by bringing one of the plurality of developing units into contact with the corresponding image carrier. and control means for controlling said plurality of developing means so as to form an image in either, and wherein the control means includes second following the previous SL first image was formed in the first mode Is determined to be an image that can be formed in any one of the first mode and the second mode, and if possible , the first image is formed after the first image is formed. When the second image formation starts If the switching from the first mode to the second mode is completed before, the plurality of developing units are controlled to switch to the second mode and form the second image. It is characterized by.

  When the first mode is set and the image to be formed next can be printed in the second mode, the control means starts the printing of the image to be formed and sets the second mode. Compare the time to complete the switch. Then, if the switching to the second mode is completed by the timing at which printing is started, the switching to the second mode is performed. Therefore, switching of the print mode based on the conditions does not cause a delay in the image forming process. By determining the timing for starting the next printing and determining whether or not switching is possible before this timing, the present invention can be used even in a situation where printing is performed in the first mode in the prior art. In this case, it is possible to perform printing by switching to the second mode. Therefore, it is possible to suppress unnecessary deterioration of the member and to prevent a decrease in image forming performance due to switching of the printing mode.

The figure explaining color mode and mono mode. The figure which shows a part of component of an image formation part 1 is a block diagram of an image forming apparatus. The timing chart of image formation. 5 is a timing chart of image formation in the first embodiment. 6 is a flowchart of image forming processing executed by an engine control unit. The flowchart of the mode switching process in 1st embodiment. 10 is a timing chart of image formation in the second embodiment. The flowchart of the mode switching process in 2nd embodiment. The flowchart of the mode switching process in 3rd embodiment.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated in detail below using drawing. In the following description, it is assumed that the plurality of colors in the color mode are yellow, magenta, cyan, and black, and the single color in the mono mode is black. That is, it is assumed that the mono image is a monochrome image.

  (First Embodiment) As shown in FIG. 1, the charging units 2a to 2d of the image forming unit of the image forming apparatus charge the surfaces of the corresponding photosensitive drums (image carriers) 1a to 1d, and the exposure units 4a to 4d. 4d exposes the surfaces of the corresponding photosensitive drums 1a to 1d with image data to form an electrostatic latent image. The developing units 3a to 3d supply toner to the corresponding photosensitive drums 1a to 1d to form toner images on the photosensitive drums 1a to 1d. The toner images on the photosensitive drums 1a to 1d are multiple-transferred to the intermediate transfer member 6 by the corresponding primary transfer portions 5a to 5d. The photosensitive drum 1a and the corresponding members form a yellow toner image, and the photosensitive drum 1b and the corresponding members form a magenta toner image. The photosensitive drum 1c and the corresponding members correspond to each other. Each member forms a cyan toner image. The photosensitive drum 1d and the corresponding members form a black toner image.

  The toner image transferred to the intermediate transfer member 6 is transferred to a recording material (not shown) that has been transported on the transport path 17 from the paper feed tray 19 of FIG. The recording material on which the toner image has been transferred is fixed on the toner image in the fixing unit 13. The fixing unit 13 includes a fixing roller 14 and a pressure roller 15, and the toner image is fixed to the recording material when the fixing roller 14 and the pressure roller 15 apply heat and pressure to the recording material. Note that the image forming unit includes a temperature measuring unit 16 such as a thermistor for measuring the temperature of the fixing roller 14 or the like. In addition, a sensor (size detection unit) 18 that detects the size of the recording material is provided.

  The image forming unit is configured to be set to either a color mode (first mode) or a mono mode (second mode). FIG. 1A shows a state in which the image forming unit is set to a color mode that can form toner images of various colors. In the color mode, the photosensitive drums 1a to 1d are brought into contact with the intermediate transfer body 6, and the developing units 3a to 3d are brought into contact with the photosensitive drums 1a to 1d. On the other hand, FIG. 1B shows a state in which the image forming unit is set to the mono mode. In the present embodiment, the photosensitive drums 1a to 1c are separated from the intermediate transfer body 6, and the developing units 3a to 3c are separated from the photosensitive drums 1a to 1c. By setting a monochrome image without driving each member for forming a color toner image by setting in this way, consumption of the members for forming each toner image of yellow, magenta, and cyan is suppressed. be able to. Note that the mono mode state is not limited to the state shown in FIG. 1B as long as it can suppress the consumption of the member for forming the toner image of the unused color.

  Next, the image forming apparatus of the present invention will be described with reference to FIGS. The controller 301 is configured to be able to communicate with the host computer 300 and the engine control unit 302. The controller 301 receives image information and a print command from the host computer 300, analyzes the received image information, and converts it into image data that is bit data. In addition, the controller 301 transmits a print reservation command, a print start command, and image data to the engine control unit 302 via the video interface unit. The print reservation command includes information on whether printing of each page is a monochrome image or a color image. The engine control unit 302 controls the image forming unit 303 described with reference to FIGS. 1 and 2 according to each command received from the controller 301, and executes print processing of image data received from the controller 301.

  As shown in FIG. 4, when receiving a print command and image information from the host computer 300, the controller 301 first transmits a print reservation command to the engine control unit 302 according to the print command. Thereafter, every time the received image information is converted into image data, a print start command for instructing the start of printing is transmitted to the engine control unit 302. When the engine control unit 302 receives the print start command, the engine control unit 302 starts preprocessing for performing a printing operation. Specifically, for example, an actuator that drives a member of the image forming unit 303 is activated, and control is performed such that a predetermined member applies a voltage necessary for image formation.

  After completion of the preprocessing, the engine control unit 302 outputs a / TOP signal serving as a reference timing for image data output to the controller 301. The controller 301 outputs image data to the engine control unit 302 upon receiving the / TOP signal, and the engine control unit 302 controls the image forming unit 303 to perform printing processing for one page. If the next print start command or the like is not received by the timing for performing continuous printing, the engine control unit 302 performs post-processing such as stopping the actuator drive. On the other hand, if the next print start command has been received by the timing for performing continuous printing, the / TOP signal is output to the controller 301 as it is to start print processing for the next page.

  When the engine control unit 302 holds the first threshold value and the image forming unit 303 is set to the color mode, when monochrome images equal to or higher than the first threshold value are continuously printed, the engine control unit 302 Change settings to mode. Even if the number of continuous monochrome images printed is less than the first threshold, the time until the next monochrome image can be printed is longer than the time required to switch the mode, and until the printing is started. When the mode switching is completed, the mode is switched to the mono mode. In the present embodiment, the controller 301 analyzes the image information received from the host computer 300 to determine the time until the next printing can be started. The engine control unit 302 is notified of the time until the determined next printing can be started by a print start notice command.

  Hereinafter, the print mode setting control according to the present embodiment will be described with reference to FIG. As described above, upon receiving a print command and image information from the host computer, the controller 301 transmits a print reservation command and a print start command to the engine control unit 302. Note that the first page is a color image, and therefore the engine control unit 302 sets the image forming unit 303 to the color mode and performs the printing process. The controller 301 transmits a print start notice command indicating that the print start command is transmitted after the time Tp to the engine control unit 302.

  When the engine control unit 302 receives the print start notice command, the engine control unit 302 compares the time Ta until the current print processing is completed with the sum of the time Ts for switching to the mono mode and the time Tp. Here, if the sum of the times Ta and Ts is equal to or less than the time Tp, there is no delay in the printing process due to the switching even if the mode is switched to the mono mode. Therefore, the engine control unit 302 switches to the mono mode regardless of the subsequent continuous printing number of monochrome images. On the other hand, if the sum of the times Ta and Ts is larger than the time Tp, the printing process is delayed by switching to the mono mode. Therefore, the engine control unit 302 compares the subsequent continuous printing number of monochrome images with the first threshold value, and switches to the mono mode if the continuous printing number is equal to or more than the first threshold value. Print monochrome image as is. FIG. 5 shows a state where the printing process is performed by switching to the mono mode because the sum of the times Ta and Ts is equal to or less than the time Tp.

  Next, an image forming process executed by the engine control unit 302 will be described with reference to FIG. After receiving the print reservation command, the engine control unit 302 waits for a print start command from the controller 301 in S1. When receiving the print start command, the engine control unit 302 executes pre-processing in S2. After executing the preprocessing, the engine control unit 302 receives the image data from the controller 301 by transmitting a / TOP signal to the controller 301 in S3, and executes the printing process. In parallel with the printing process or after the end of the printing process, the engine control unit executes a mode switching process to be described later in S4. In the mode switching process, when it is determined that the print mode is switched, the print mode is switched after the print process is completed. Thereafter, the engine control unit 302 confirms whether or not the next print start command is received from the controller 301 in S5. If a print start command has been received, the process returns to S3 to start print processing. If a print start command has not been received, the engine control unit 302 confirms whether or not a print start notice command has been received from the controller 301 in S6. When the print start notice command is received, the engine control unit 302 stands by until the print start command is received. If the print start notice command has not been received, the engine control unit 302 executes post-processing in S7.

  Subsequently, a mode switching process executed by the engine control unit 302 in the present embodiment will be described with reference to FIG. In step S <b> 11, the engine control unit 302 determines whether the current print mode of the image forming unit 303 corresponds to the next image to be printed. Specifically, if the current print mode is a color mode and the next print is a color image, or if the current print mode is a mono mode and the next print is a monochrome image, the process proceeds to S11. The determination is “yes”. If they match, the mode switching is not necessary, so the engine control unit 302 ends the mode switching process.

  If the result of S11 does not match, the engine control unit 302 determines whether or not the next print is a color image in S12. If the next printing is a color image, the mono mode needs to be changed to the color mode, and therefore the engine control unit 302 switches to the color mode in S16. On the other hand, when the next printing is a monochrome image, the engine control unit 302 determines whether printing of the monochrome image continues for a first threshold value or more. The continuous number of sheets is notified from the controller 301 to the engine control unit 302 by a print reservation command. If the monochrome image printing continues for the first threshold or more, the engine control unit 302 switches to the mono mode in S16.

  If the monochrome image printing does not continue for the first threshold or more, the engine control unit 302 confirms whether or not a print start notice command is received from the controller 301 in S14. If not received, the engine control unit 302 ends the mode switching process without switching the mode. If the print start notice command has been received, the engine control unit 302 determines in S15 whether the mode can be switched based on the issue time of the next print start command notified by the print start notice command. judge. Specifically, after completion of the current printing process, if the switching of the printing mode is completed before the timing when the next printing is possible, it is determined that the switching of the printing mode is possible. If it is determined that the print mode can be switched, the engine control unit 302 switches to the mono mode in S16. On the other hand, when determining that the print mode cannot be switched, the engine control unit 302 ends the mode switching process without switching the print mode.

  As described above, in the present embodiment, whether or not the mode can be switched is determined in consideration of the time until the next print start command issuance notified by the controller 301. Therefore, conventionally, even when a monochrome image is printed in the color mode, in this embodiment, it is possible to switch to the mono mode without delaying the image forming process. Accordingly, it is possible to suppress wear of the members while maintaining the image forming performance.

  Second Embodiment The image forming unit 303 has a fixing unit 13 for fixing the toner image transferred to the recording material to the recording material by heat and pressure. When the recording material passes through the fixing unit 13, the heat of the fixing unit 13 is taken away by the recording material. However, when the size of the recording material is small, the heat at the end of the fixing unit 13 is not deprived by the recording material, so that the temperature at the end may rise more than necessary. For this reason, as shown in FIG. 2, the image forming unit 303 includes a temperature measuring unit 16 that measures the temperature of the end of the fixing unit 13 and a size detecting unit 18 that detects the size of the recording material upstream of the fixing unit 13. It has. Then, when the recording material size is equal to or smaller than a predetermined size and the temperature of the end portion of the fixing unit 13 is equal to or higher than the second threshold Tm, the engine control unit 302 ends the end portion of the fixing unit 13. Control is performed to widen the image forming interval so that the temperature becomes below a predetermined temperature. In addition, it is preferable that predetermined temperature shall be below 2nd threshold value Tm.

  In this embodiment, when the image forming interval is widened in order to suppress the temperature rise at the end of the fixing unit 13, the timing for starting the next printing is compared with the print mode switching time to determine whether switching is possible. To do. Hereinafter, the present embodiment will be described with reference to the timing chart of FIG. As in the first embodiment, since the first page is a color image, the engine control unit 302 executes print processing in the color mode.

  During the printing process in the color mode, the engine control unit 302 receives a print start command for the next page. The engine control unit 302 acquires the temperature of the end of the fixing unit 13 from the temperature measurement unit 16 if the size of the recording material to be printed next detected by the size detection unit 18 is smaller than a predetermined size. Then, after the end of the current printing process, a time Tr from when the / TOP signal is transmitted to the controller 301 to start the next printing process is determined. If the next printing is a monochrome image and the time Tr is equal to or longer than the time Ts necessary for the mode switching process, the engine control unit 302 switches the print mode regardless of the continuous number of monochrome images. FIG. 8 shows a state in which printing is performed by switching to the mono mode when the time Tr is equal to or longer than the time Ts necessary for the mode switching process.

  The image forming process in this embodiment is the same as that in the first embodiment described with reference to FIG. In the present embodiment, the use of the print start notice command is an option, and when not used, S6 in FIG. 6 is simply omitted. Subsequently, a mode switching process executed by the engine control unit 302 in the present embodiment will be described with reference to FIG. S21 to S23 are the same as S11 to S13 in FIG.

  In S24, the engine control unit 302 determines whether the recording material to be printed next detected by the size detection unit 18 is equal to or smaller than a predetermined size. If it is not less than the predetermined size, the mode switching process is terminated. If it is equal to or smaller than the predetermined size, the engine control unit 302 determines in S25 whether or not the temperature of the end of the fixing unit 13 measured by the temperature measurement unit 16 is equal to or higher than the second threshold value Tm. If it is less than the second threshold Tm, the engine control unit 302 ends the mode switching process. If it is greater than or equal to the second threshold Tm, the engine control unit 302 determines an image formation interval in S26. As for the image forming interval, for example, a correspondence table of the temperature of the end of the fixing unit 13 and the image forming interval in which the temperature of the end is equal to or less than a predetermined value is prepared in advance, and the engine control unit 302 uses the correspondence table. It can be set as the structure to determine. Alternatively, a function for obtaining the image formation interval from the temperature of the end of the fixing unit 13 may be set in the engine control unit 302 in advance, and the engine control unit 302 may obtain the image formation interval using this function. The engine control unit 302 determines whether or not the mode can be switched based on the image formation interval determined in S26. Specifically, if the mode switching is completed before the timing when the next printing can be started, it is determined that the switching is possible. When it is determined that the mode can be switched, the engine control unit 302 switches to the mono mode in S28. On the other hand, when it is determined that the mode cannot be switched, the engine control unit 302 ends the mode switching process without switching the print mode.

  As described above, in this embodiment, it is determined whether the print mode can be switched in consideration of the image formation interval associated with the temperature control of the fixing unit 13. Therefore, conventionally, even when a monochrome image is printed in the color mode, in this embodiment, it is possible to switch to the mono mode without delaying image formation. Accordingly, it is possible to suppress wear of the members while maintaining the image forming performance.

  (Third Embodiment) When printing on a recording material of a small size, the center of the fixing unit 13 is deprived of heat by the recording material, but the end of the fixing unit 13 is not deprived of heat by the recording material. A temperature difference occurs between the center and the end of the portion 13. If printing is performed on a large-sized recording material in this state, there is a possibility that the recording material may be affected by the temperature difference between the central portion and the end portion of the fixing unit 13. Therefore, when the engine control unit 302 performs printing on a large size recording material after printing on a small size recording material, the temperature difference between the central portion and the end portion of the fixing unit 13 is not more than a predetermined value. In addition, control is performed to widen the image forming interval. The predetermined value is a value that does not affect the recording material.

  In this embodiment, in order to reduce the temperature difference between the central portion and the end portion of the fixing unit 13, when the image forming interval is widened, the time until the next printing process can be started is compared with the mode switching time. This determines whether or not the print mode can be switched.

  The image forming process in this embodiment is the same as that in the first embodiment described with reference to FIG. In the present embodiment, the use of the print start notice command is an option, and when not used, S6 in FIG. 6 is simply omitted. Subsequently, a mode switching process executed by the engine control unit 302 in the present embodiment will be described with reference to FIG. S31 to S33 are the same as S11 to S13 in FIG.

  In S34, the engine control unit 302 determines whether or not the size of the recording material to be printed next detected by the size detection unit 18 is larger than the size of the previous recording material. If not, the engine control unit 302 ends the mode switching process. If the determination in S34 is large, the engine control unit 302 determines the image formation interval in S35. For example, a correspondence table of image formation intervals for a combination of the size of the previous recording material and the recording material to be printed next is created in advance, and the engine control unit 302 determines the image formation interval based on this correspondence table. be able to. Note that the image forming interval is an interval necessary for setting the temperature difference between the central portion and the end portion of the fixing portion 13 to be equal to or lower than a predetermined temperature. Alternatively, the configuration may be determined simply based on the correspondence table between the previous recording material size and the image forming interval. The engine control unit 302 determines whether or not the mode can be switched based on the image formation interval determined in S35. Specifically, if the mode switching is completed by the time when the next printing can be started, it is determined that the switching is possible. When it is determined that the mode can be switched, the engine control unit 302 switches to the mono mode in S37. On the other hand, when it is determined that the mode cannot be switched, the engine control unit 302 ends the mode switching process without switching the print mode.

  As described above, in this embodiment, whether or not the mode can be switched is determined in consideration of the image forming interval associated with the temperature control of the fixing unit 13. Therefore, conventionally, even when a monochrome image is printed in the color mode, in this embodiment, it is possible to switch to the mono mode without delaying image formation. Accordingly, it is possible to suppress wear of the members while maintaining the image forming performance.

  In the second and third embodiments, when the engine control unit 302 determines the next print start timing for temperature control of the fixing unit, the switching of the print mode is completed by the determined timing. Whether or not. However, the present invention is not limited to the temperature control of the fixing unit, and may be applied to all cases in which the engine control unit 302 determines the next print start timing in relation to the control of the image forming unit 303. it can. Also, the first to third embodiments can be combined.

  As described above, when the image formed after the formation of the first image that is a color image or a mono image is the second image that is a mono image, the engine control unit 302 has a timing before the start of the formation of the second image. Then, it is determined whether or not the switching to the mono mode is completed. If the switching to the mono mode is completed before the timing for starting the formation of the second image, the engine control unit 302 switches to the mono mode and performs printing. By determining whether or not switching is possible in consideration of not only the continuous number of second images but also the timing of starting the next printing, conventionally, images that can be printed in the mono mode are printed in the color mode. Even in such a case, in the present invention, printing can be performed by switching to the mono mode. In addition, when the switching to the mono mode is completed before the printing start timing, the switching from the color mode to the mono mode is performed, so that there is no delay in the image forming process due to this switching.

  For example, the timing to start printing is determined by the controller 301 that analyzes image information to be printed and generates image data, and notifies the engine control unit 302 of the determination. Since the controller 301 generates the image data, the processing delay due to the switching can be prevented by performing the switching based on the printing start timing determined by the controller 301.

  Further, for example, the timing for starting printing can be the time determined by the engine control unit 302 for temperature control of the fixing unit 13. In the image forming process, the engine control unit 302 needs to determine the time until the next printing is started so that the temperature of the fixing unit 13 does not rise excessively and further, the temperature does not deviate. If the printing mode can be switched using this time, the printing mode can be switched without causing a processing delay due to the switching. The temperature control of the fixing unit 13 is, for example, control that prevents the temperature at the end of the fixing unit 13 from excessively rising. When the temperature at the end of the fixing unit 13 is equal to or higher than a threshold, the engine control unit 302 determines the timing for starting the next printing. This timing is a timing determined so that the temperature of the end portion of the fixing unit 13 becomes a predetermined value or less. As another example, control is performed so that the temperature of the fixing unit 13 is not biased depending on the location. When the size of the recording material to be printed becomes larger than the size of the recording material printed last time, the engine control unit 302 The timing for starting the next printing is determined. This timing is a timing determined so that the temperature difference between the end portion and the central portion of the fixing unit 13 is equal to or less than a predetermined value.

Claims (6)

A plurality of image carriers;
A plurality of developing means corresponding to each of the plurality of image carriers, and forming an image on the corresponding image carrier with toner;
A first mode in which an image is formed by bringing each of the plurality of developing units into contact with a corresponding image carrier, and an image is formed by bringing one of the plurality of developing units into contact with the corresponding image carrier. Control means for controlling the plurality of developing means so as to form an image in any one of the second modes;
With
Wherein, prior Symbol first second image following the image was formed in the first mode, it is capable of forming images in either mode of the first mode and the second mode In the case where it is possible, the first mode is changed to the second mode before the timing at which the formation of the second image is started after the first image is formed. If the switching is completed, the image forming apparatus controls the plurality of developing units so as to switch to the second mode and form the second image. Whether the second image following the first image formed in the first mode is an image that can be formed in either the first mode or the second mode. in the judgment, if it is possible to, switch the prior timing the formation of the second image is started after the first image has been formed, the second mode from the first mode 2. The image forming apparatus according to claim 1, wherein the plurality of developing units are controlled so that the second image is formed in the first mode if the process is not completed. 3. The control means determines whether or not the switching from the first mode to the second mode is completed before the timing at which the formation of the second image is started after the formation of the first image. 3. The method according to claim 1, wherein the first image formation is determined based on a timing at which the formation of the first image is completed and a time for switching from the first mode to the second mode. Image forming apparatus. A controller for analyzing image information and instructing the control means to start image formation;
It said controller, an image forming apparatus according the timing of formation of the second image is started in any one of claims 1 to 3, characterized in that notifies the control unit. A fixing means for fixing the toner image on the recording material;
The timing of formation is started in the second image, any one of claims 1 to 4, characterized in that the end temperature of the fixing means is a timing determined so as to be less than a predetermined value 2. The image forming apparatus according to item 1. Fixing means for fixing the toner image on the recording material;
It has a detection means to detect the size of the recording material,
The timing at which the formation of the second image is started is such that the size of the recording material on which the second image detected by the detection unit is formed is larger than the size of the recording material on which the first image is formed. when the image of any one of claims 1 to 4, characterized in that the temperature difference between the end portion and the central portion of the fixing means is a timing determined so as to be less than a predetermined value Forming equipment.

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