JP3701581B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine in which an electrophotographic image forming unit and an inkjet image forming unit are arranged in a conveyance path of a recording sheet.
[0002]
[Prior art]
Conventionally, as an image forming apparatus for forming a color image on a recording sheet, an electrophotographic system using toner and an ink jet system using ink exist. However, these methods have the following advantages and disadvantages, and none of the methods can effectively use only the advantages. In other words, the electrophotographic method has an advantage that the image forming process can be speeded up, but since the toner is melted by heating and fixed on the recording paper, the color reproducibility depends on the transparency of the toner and is fixed. There are disadvantages that the hue changes with temperature fluctuations and that the toner layer causes irregularities on the recording paper. On the other hand, the ink jet method has an advantage of excellent color reproducibility of the ink, but has a disadvantage that an image drying process cannot be accelerated because an ink drying time is required.
[0003]
By the way, generally, as image information to be subjected to image forming processing in the image forming apparatus, there is less color image information than monochrome image information. Further, color image information is also a document image that is a monochrome image than full-color image information. A so-called partial color image in which a color image such as a seal stamp, an illustration or a graph is inserted into the part is the mainstream.
[0004]
Therefore, in view of such a usage situation, in order to utilize the advantages of both types, an electrophotographic image forming unit that performs image formation based on monochrome image information and an inkjet method that performs image formation based on color image information are used. An image forming apparatus provided with an image forming unit has been proposed.
[0005]
For example, Japanese Patent Publication No. 8-95463 discloses an image forming apparatus that performs image formation by an ink jet method after image formation by an electrophotographic method. At the time of image formation by both, and at the time of image formation only by the ink jet method, a means for changing the conveyance speed of the recording paper or a means for cooling the recording paper is provided, and the temperature of the recording paper that has passed through the fixing device is always maintained. A configuration is disclosed in which deterioration within an image formed by an inkjet image forming process is suppressed within a certain range.
[0006]
[Problems to be solved by the invention]
However, in a conventional image forming apparatus in which an electrophotographic image forming unit and an ink jet image forming unit are provided together, an ink jet method is used as compared with an image forming process based on monochrome image information in an electrophotographic image forming unit. There has been no consideration of a decrease in reproducibility of a color image due to a low frequency of image forming processing based on color image information in the image forming unit, and waste of ink. In other words, in an ink jet type image forming unit that is not frequently used, the ink in the ink head dries or adheres to dust, resulting in clogging of the nozzles, and the ink is ejected when color image information is formed. There is a problem that the color image cannot be accurately reproduced. In addition, since the maintenance process of the ink head including the ink ejection operation is executed according to the number of times of image formation including the monochrome image forming process in the image forming apparatus, the number of times of image formation is reduced even when only the monochrome image forming process is performed. When the predetermined number is reached, the ink head maintenance process is executed, so that the ink is wasted and the running cost is increased.
[0007]
An object of the present invention is to use an electrophotographic image forming unit that performs a color image forming process in combination with an electrophotographic image forming unit that performs a monochrome image forming process in comparison with an electrophotographic image forming unit. Even when the ink is low, it is possible to maintain the color image reproducibility by preventing the clogging of the nozzles due to the drying of the ink in the ink head and the adhesion of dust, and to perform unnecessary ink head maintenance processing. It is an object of the present invention to provide an image forming apparatus capable of preventing the waste of ink due to the above and realizing a reduction in running cost.
[0008]
[Means for Solving the Problems]
The present invention has the following configuration as means for solving the above problems.
[0009]
  (1) Electrophotographic methodBy monochromeFirst image forming section for performing image formation and inkjet methodBy colorA second image forming unit that performs image formation of the image forming apparatus, and an image forming apparatus that is disposed in a recording paper conveyance path,
  Ink head in the second image forming unitToMaintenance unit for maintenance processingPrepared,
  When the power is turned on, it is determined whether or not the ink head is sealed by the maintenance unit. If the ink head is not sealed, a sealing process is performed to seal the ink head using the maintenance unit. Run,
  When an image formation request is input, it is determined whether or not the image data relating to the image formation request is only monochrome image data. If the image formation request is not only monochrome image data, the image formation request is performed only once. The ink head is unsealed after performing maintenance using the maintenance unit.The control part which performs is provided.
[0010]
  In this configuration, the ink head provided in the ink jet image forming unit provided together with the electrophotographic image forming unit is sealed by the maintenance unit during non-energization and non-image formation during energization. Therefore, the ink head is not exposed to the outside air until it is actually used for image formation, and the nozzles are not clogged due to drying of ink or adhesion of dust.
  In addition, maintenance processing to be executed when an image formation request for the second image forming unit input prior to the image data is confirmed is performed. Accordingly, the maintenance process is started at a timing that is completed before the start of the image forming process in the second image forming unit, and the image forming process is not started after the end of the maintenance process.
[0011]
  (2) The control unitCumulatively counts the number of ink ejections from the ink head, and executes the maintenance process on the condition that the counted value reaches a predetermined numberIt is characterized by doing.
[0012]
  In this configuration,When the cumulative number of ink ejections from the ink head reaches a predetermined number, the ink head maintenance process is executed. Therefore, without considering the number of image formations in the attached electrophotographic image forming unit, the inkjet head maintenance process is performed based on only the number of image formations in the inkjet image forming unit, which is unnecessary. Ink is wasted in the maintenance processThere is nothing.
[0013]
  (3) The aboveThe second image forming unit is disposed in the vicinity of the fixing device in the first image forming unit.It is characterized by that.
[0014]
  In this configuration,The recording paper subjected to the ink jet image forming process in the second image forming unit is dried in advance by heat generated by the fixing device in the first image forming unit, the ink absorbability is improved, and the recording paper is discharged onto the recording paper. Ink drying is promoted.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A digital copying machine will be described below as an example of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing the configuration of a digital copying machine according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration in the vicinity of the second image forming unit in the printer unit of the digital copying machine. The digital copying machine 1 has a substantially U-shaped configuration with a scanner unit 1A at the top, a printer unit 1B at the middle, and a paper feed unit 1C at the bottom.
[0018]
The scanner unit 1A includes a transparent hard glass body platen 15 exposed on the upper surface of the digital copying machine. A light source lamp 11, mirrors 12a to 12c, a lens 13 and a photoelectric conversion element (hereinafter referred to as CCD) are provided below the platen 15. The scanner optical system 10 including 14 is provided. The exposure lamp 11 reciprocates in parallel with the lower surface of the document table 15 together with the mirror 12 a to expose the image surface of the document placed on the upper surface of the document table 15. The mirrors 12b and 12c reciprocate in parallel with the lower surface of the document table 15 at a speed half that of the light source lamp 11 and the mirror 12a, and the light reflected from the image surface of the document by the light source lamp 11 is reflected on the optical path length. The light is distributed to the lens 13 at a constant value. The lens 13 forms an image of the reflected light on the image surface of the document on the light receiving surface of the CCD 14. The CCD 14 outputs a light reception signal corresponding to the amount of light received on the light receiving surface. The light reception signal output from the CCD 14 is converted into digital data by an image processing unit to be described later, subjected to predetermined image processing, and supplied to the printer unit 1B as image data.
[0019]
In this example, the scanner unit of the document fixing method is described in which the image of the document placed on the document table with the position fixed is read by the scanner optical system that moves in parallel to the document table. However, only the document movement method is described. Alternatively, it is possible to use a scanner unit that uses both the document moving method and the document fixing method.
[0020]
The printer unit 1B includes a first image forming unit 20 (first image forming unit of the present invention) that forms a monochrome image by electrophotography and a second image forming unit 50 (color of the present invention) that forms a color image by inkjet method. And a second image forming unit). This makes it possible to form an image by taking advantage of the respective advantages of the electrophotographic method excellent in speeding up and the ink jet method excellent in color image reproducibility.
[0021]
The first image forming unit 20 includes a charger 29, a laser scan unit (hereinafter referred to as LSU) 30, a developing unit 31, and a transfer device 32 around the photosensitive drum 28 along the rotation direction of the photosensitive drum 28. Further, the fixing device 23 is arranged on the downstream side of the main conveyance path 41 between the photosensitive drum 28 and the transfer device 32. At the time of image formation in the first image forming unit 20, after a predetermined charge is uniformly applied from the charger 29 to the surface of the photosensitive drum 28 that rotates at a predetermined process speed in the direction of the arrow, the image data is transferred from the LSU 30. The laser beam modulated by is irradiated. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 28. The developing unit 31 supplies toner to the surface of the photosensitive drum 28 on which the electrostatic latent image is formed via the developing roller 31a, and visualizes the electrostatic latent image into a toner image. The transfer device 32 transfers the toner image carried on the surface of the photosensitive drum 28 to the surface of the recording paper P. The surface of the photosensitive drum 28 that has completed the transfer process is subjected to removal of residual toner and residual charges by a cleaner and a static eliminator (not shown), and is repeatedly used in the image forming process. The fixing device 23 presses the heating roller 23a and the pressure roller 23b with a predetermined pressing force, heats and presses the recording paper P passing between them, and transfers the toner image transferred to the recording paper P under high temperature and high pressure. By being crushed, it is thermally fixed on the recording paper P.
[0022]
The second image forming unit 50 is disposed in the paper discharge conveyance path 42 that is continuous to the downstream side of the main conveyance path 41 in the printer unit 1B. As shown in FIG. 2, the second image forming unit 50 supports a carriage 53 on which an ink head 53 a and an ink tank 53 b are mounted so as to be reciprocally movable in the main scanning direction via a shaft 54. A platen 55 facing the carriage 53 is provided. Further, in the discharge conveyance path 42, conveyance rollers 51a and 52a are supported so as to be rotatable in both forward and reverse directions with a position where the carriage 53 and the platen 55 are opposed to each other. The recording paper P is sandwiched and conveyed between 51b and 52b. The star rollers 51b and 52b reduce the contact area with the image forming surface of the recording paper P on which the ink image is formed in the second image forming unit 50 to prevent bleeding of the image, similarly to the star roller 25b described later. Used for.
[0023]
The carriage 53 moves in the main scanning direction while the recording paper P is stopped between the carriage 53 and the platen 55. During this period, ink is selectively received from a plurality of nozzles of the ink head 53a driven based on the image data. Discharged. When the carriage 53 finishes moving for one line in the main scanning direction, the recording paper P is conveyed by a distance corresponding to the nozzle arrangement range in the ink head 53a by the rotation of the conveying rollers 51a and 52a. By repeating the movement of the carriage 53 with the driving of the ink head 53a in the main scanning direction and the conveyance of the recording paper P, an image of ink is formed on the entire surface of the recording paper P.
[0024]
In addition to the main transport path 41 and the paper discharge transport path 42, a sub transport path 43 is formed in the printer unit 1B. Between the main transport path 41 and the paper discharge transport path 42, a sub transport path 43 is formed. A flapper 56 that opens and closes the transport path 43 is swingably provided.
[0025]
The paper feed unit 1C is placed on a paper feed tray 16 mounted on one side of the main body, a paper feed cassette 17 that houses a plurality of sheets and is detachable from the main body, and a paper feed tray 16. Pickup rollers 18a and 18b for feeding the recording paper P and the recording paper P stored in the paper feed cassette 17 one by one, and a paper feed roller for feeding the recording paper P fed by the pickup roller 18b to the printer unit 1B. 19 is provided. In the sheet feeding unit 1C, sheet feeding conveyance paths 44 and 45 are formed to connect the sheet feeding tray 16 and the sheet feeding cassette 17 to the upstream side of the main conveyance path 41, respectively.
[0026]
In the printer unit 1B, a registration roller 22 is disposed in the main conveyance path 41 in addition to the heating roller 23a and the pressure roller 23b that constitute the fixing device 23. The registration roller 22 temporarily stops the recording paper P fed from the paper feeding unit 1C prior to the rotation of the photosensitive drum 28, and then synchronizes with the rotation of the photosensitive drum 28 and the transfer drum. Lead to 32. That is, the registration roller 22 stops rotating when the recording paper P is fed from the paper feeding unit 1C, and the front end of the recording paper P is located at a position where the photosensitive drum 28 and the transfer device 32 face each other. The rotation is started at a timing coincident with the front end portion of the toner image carried on the photosensitive drum 28.
[0027]
In the digital copying machine 1, a paper discharge tray 39 mounted on one side surface of the printer unit 1B is disposed in a space between the scanner unit 1A and the paper feed unit 1C. A discharge conveyance path 42 formed in the printer unit 1B communicates the downstream end portion of the main conveyance path 41 to the discharge tray 39, and the end portion of the discharge conveyance path 42 on the discharge tray 39 side. The paper discharge roller 25a is provided together with the star roller 25b. The paper discharge roller 25a is rotatable in both forward and reverse directions, like the transport rollers 51a and 52b, and is used together with the transport rollers 51a and 52b to realize a double-sided image forming function in the first image forming unit 20.
[0028]
That is, in the single-sided image forming mode in which the first image forming unit 20 forms an image on one side of the recording paper P, the flapper 56 is positioned in the state indicated by the solid line in FIG. 2, and the transport rollers 51a and 52a and the paper discharge roller 25a. 2 rotates forward in the clockwise direction in FIG. 2, and the recording paper P passing through the fixing device 23 passes through the paper discharge conveyance path 42 and is discharged onto the paper discharge tray 39. On the other hand, when the first side image is formed in the double-sided image forming mode in which images are formed on both sides of the recording paper P, the flapper 56 is broken by a broken line in FIG. 2 when the trailing edge of the recording paper P passes the transport roller 52a. 2, the transport rollers 51a and 52a and the paper discharge roller 25a are rotated in the counterclockwise direction in FIG. 2 so that the recording paper P is guided into the sub-transport path 43, and the entire surface of the recording paper P is sub-transported. When moving into the path 43, the flapper 56 moves to the state indicated by the solid line in FIG. After the recording paper P that has passed through the sub-transport path 43 is guided to the first image forming unit 20 through the upstream side of the main transport path 41 with the front and back surfaces reversed, and after receiving image formation on the second surface. The paper is discharged onto the paper discharge tray 39 by the transport rollers 51a and 52a and the paper discharge roller 25a that rotate in the clockwise direction in FIG.
[0029]
FIG. 3 is a side view showing the configuration of the main part of the second image forming unit in the digital copying machine. FIG. 3 shows a state in which the carriage 53 that is movable in the main scanning direction via the shaft 54 is positioned at the home position before the start of image formation. At this home position, a maintenance unit 70 facing the ink head 53a disposed on the lower surface of the carriage 53 is disposed so as to be movable up and down. During the maintenance process, the maintenance unit 70 rises from the position shown in FIG. 4 and approaches the ink head 53a to clean the ink head 53a. The maintenance unit 70 includes a pump 71 that sucks ink leaked from the nozzles of the ink head 53a and dust attached to the vicinity of the nozzles before cleaning the ink head 53a.
[0030]
FIG. 4 is a sectional view showing an internal structure of a maintenance unit provided in the digital copying machine. The maintenance unit 70 disposed at the home position of the carriage 53 in the second image forming unit 50 of the digital copying machine 1 includes a slider 70d having a brush 70e fixed on the upper part in a case 70a having a housing structure with an open upper surface. The female screw part formed in a part of the case 70a is screwed into the screw screw 70b pivotally supported at the upper part in the case 70a. The rotation of the slider 70d is restricted by contact with the inner surface of the case 70a, and the screw screw 70b is rotated in both forward and reverse directions by the rotational force transmitted through the drive gear 70c fixed to one end. The slider 70d reciprocates along the screw screw 70b.
[0031]
The opening 70f on the upper surface of the case 70a is sized to fit the ink head 53a mounted on the carriage 53. When the maintenance unit 70 rises to the carriage 53 side, the ink head is placed in the opening 70f of the case 70a. 53a is fitted in a state indicated by a two-dot chain line in the figure. As a result, the ink head 53a is capped by the maintenance unit 70 and is airtight with respect to the outside. In addition, the inside of the case 70a communicates with the pump 71 through the pipe 72, and when the pump 71 is driven in a state where the maintenance unit 70 is raised, the ink leaked from the nozzles of the ink head 53a and the vicinity of the nozzles The dust adhering to is sucked by the pump 71.
[0032]
This prevents ink clogging due to ink drying or dust adhesion in the ink head 53a. Further, when rotation in both forward and reverse directions is transmitted to the drive gear 70c while the maintenance unit 70 is raised, the ink head 53a is cleaned by the brush 70e attached to the slider 70d that reciprocates along the screw screw 70b. .
[0033]
The maintenance unit 70 does not perform color image formation processing when the second image forming unit 50 is de-energized and during non-image formation, that is, when the first image forming unit 20 includes a monochrome image. Thus, the ink head 53a is surely prevented from being clogged with ink due to ink drying or dust adhesion. On the other hand, the cleaning process of rotating the screw screw 70b in both the forward and reverse directions via the drive gear 70c is executed only at a predetermined timing.
[0034]
FIG. 5 is a diagram showing the configuration of the control unit of the digital copying machine. The control unit 100 of the digital copying machine 1 is configured by connecting a front surface image storage unit 104, a back surface image storage unit 105, an image processing unit 106, and motor drivers 107 to 109 to a CPU 101 having a ROM 102 and a RAM 103. The CPU 101 corresponds to the control unit of the present invention. Each of the front surface image storage unit 104 and the back surface image storage unit 105 stores the front surface image data and the back surface image data read from each of the front surface and the back surface of one document in the scanner unit 1A.
[0035]
The image processing unit 106 performs predetermined image processing on the image data stored in the front surface image storage unit 104 and the back surface image storage unit 105. Each of the motor drivers 107 to 109 moves a maintenance unit elevating motor M1 for elevating the maintenance unit 70, a screw screw driving motor M2 for rotating the screw screw 70b, and the carriage 53 based on the driving data output from the CPU 101. A drive voltage is applied to each of the carriage drive motors M3 to be driven.
[0036]
FIG. 6 is a flowchart showing the processing procedure of the control unit of the digital copying machine. When the power is turned on, the CPU 101 of the control unit 100 is in a state where the carriage 53 is in the home position, the maintenance unit 70 is in the raised position, and the ink head 53a is capped by the maintenance unit 70. If the ink head 53a is not capped (s1), the maintenance unit 70 is raised with the carriage 53 in the home position to cap the ink head 53a (s2). Then, an input of an image formation request is waited (s3).
[0037]
That is, when the carriage 53 is not at the home position, the CPU 101 moves the carriage 53 to the home position by driving the carriage drive motor M3 via the motor driver 109, and then the maintenance unit via the motor driver 107. The elevating motor M1 is driven to raise the maintenance unit 70.
[0038]
The state in which the ink head 53a is not capped when the power is turned on is a state in which the power is turned on again after the power is turned off during color image formation or replacement of the ink head 53a and the ink tank 53b with respect to the carriage 53. Yes, even if an unauthorized process is performed before the power is turned on by the processes of s1 to s3, the ink head 53a is immediately capped by the maintenance unit 70 after the power is turned on, and is brought into an appropriate state.
[0039]
When an image formation request is input, the CPU 101 determines whether a document on which image formation is to be performed is a single-sided document or a double-sided document (s4, s5). Then, the image of the document is read through the scanner unit 1A (s6), and the read image data is stored in the surface image storage unit 104 (s7), and then the image data stored in the surface image storage unit 104 is imaged. Predetermined image processing is performed via the processing unit 106 (s8). On the other hand, when the document on which image formation is to be performed is a double-sided document, the CPU 101 stores the image data read from the front side of the document via the scanner unit 1A in the front side image storage unit 104 and reads it from the back side of the document. The stored image data is stored in the back image storage unit 105 (s9, s10), and predetermined image processing is performed on the image data stored in the front image storage unit 104 and the back image storage unit 105 via the image processing unit 106. (S11).
[0040]
Next, the CPU 101 determines whether or not the image data stored in the front surface image storage unit 104 and the back surface image storage unit 105 is only monochrome image data (s12). Executes an electrophotographic monochrome image forming process in the first image forming unit 20 (s13). On the other hand, when the image data stored in the front image storage unit 104 and the back image storage unit 105 is not only monochrome image data, a color image formation process using the ink head 53a in the second image forming unit 50 is always performed. Therefore, immediately, the screw screw driving motor M1 is driven through the motor driver 108, and the slider 70d is reciprocated to execute the maintenance process of the inkjet head 53a (s14). When this maintenance process is completed, the cap of the inkjet head 53a by the maintenance unit 70 is released.
[0041]
As described above, when it is determined that the color image data is included in the image data related to the image formation request, the maintenance process of the ink head 53a is started immediately, thereby preventing a delay in the subsequent image formation process. Note that the maintenance process of the ink head 53a in s14 is performed only once for each image forming process related to each image forming request.
[0042]
Further, the CPU 101 determines whether the image data stored in the front surface image storage unit 104 and the back surface image storage unit 105 is only color image data or a mixture of color image data and monochrome image data. Discrimination is performed (s15, s16). The CPU 101 performs ink-jet color image formation processing in the second image forming unit 50 when only the color image data is present (s17), and if the color image data and the monochrome image data are mixed, the CPU 101 executes the first. Both the electrophotographic monochrome image forming process in the one image forming unit 50 and the ink jet color image forming process in the second image forming unit 50 are performed (s18).
[0043]
Thereafter, the CPU 101 determines whether or not it is time to perform maintenance processing on the ink head 53a (s19). If it is time to perform maintenance processing, the screw 101 is rotated to rotate the screw screw drive motor M2. Maintenance processing for the head 53a is executed (s20). Whether or not it is time to perform the maintenance process in s19 is determined by counting the number of ink ejections by the ink head 53a after the image formation request and comparing the counted value with a predetermined number of times set in advance. Can be performed. The CPU 101 repeatedly executes the processes from s4 to s20 for all the documents related to the image formation request (s21 → s4).
[0044]
Next, with respect to the conveyance state of the recording P at the time of image formation in the digital copying machine 1, when an image formation request is made for a document in which a monochrome image and a color image are mixed, the flowcharts and FIGS. 9 and FIG. 10 will be used for explanation.
[0045]
If it is determined in s18 of FIG. 6 that the monochrome image data and the color image data are mixedly stored in the front image storage unit 104 and the back image storage unit 105, the digital copying machine 1 converts the monochrome image data into an electrophotographic image. Both the first image forming unit 20 and the second image forming unit 50 are operated so as to form an image by the method and form an image of color image data by the ink jet method.
[0046]
When an image formation request is made for a single-sided document in which image data is stored only in the front image storage unit 104, the digital copying machine 1 first executes the monochrome image forming process in the first image forming unit 20 (s31 → s33). . Before the monochrome image forming process by the first image forming unit 20, the first image forming unit in the transport path of the recording paper P formed by the main transport path 41 and the paper discharge transport path 42 in the printer unit 1 </ b> B. This is because 20 is arranged on the upstream side of the second image forming unit 50.
[0047]
In the digital copying machine 1, first, the recording paper P is fed one by one from the paper feed tray 16 or the paper cassette 17 to the main transport path 41 via the paper feed transport path 44 or 45 by the operation of the paper feed unit 1C. Then, the recording paper P is guided into the first image forming unit 20 through the registration roller 22 at a timing synchronized with the rotation of the photosensitive drum 28. At the same time, monochrome image data read from the front image storage unit 104 starting from the front end of the image is supplied to the LSU 30 of the first image forming unit 20 and an electrostatic latent image is formed on the photosensitive drum 28. (S33) The electrostatic latent image is visualized as a toner image by the developing unit 31 (s34), and the toner image carried on the photosensitive drum 28 is transferred to the first surface of the recording paper P by the transfer device 32. (S35).
[0048]
As shown in FIG. 9A, the recording paper P having the toner image transferred to the first surface passes between the photosensitive drum 28 and the transfer device 32 in the main transport path 41 and reaches the fixing device 23. Then, the toner image is fixed on the first surface of the recording paper P by heating and pressurizing (s36). The recording paper P that has passed through the fixing device 23 is guided to the paper discharge conveyance path 42 by the flapper 56 positioned in the state indicated by the solid line in FIG. 2 (s37). As shown in FIG. 9B, the rotation of the paper discharge roller 25a is stopped in a state where the rear end of the recording paper P conveyed in the paper discharge conveyance path 42 in the direction of the paper discharge tray 39 is sandwiched (s38). The color image data read from the image storage unit 104 starting from the rear end side of the image is supplied to the ink head 53a (s39).
[0049]
Thereafter, after the flapper 56 is displaced to the state indicated by the broken line in FIG. 2, the paper discharge roller 25a is driven in reverse rotation together with the transport rollers 51a and 52a, and the recording paper P changes the transport direction as shown in FIG. The switchback is performed and the paper is conveyed from the paper discharge conveyance path 42 to the sub conveyance path 43 (s40). After the entire surface of the recording paper P has moved into the sub-transport path 43, the flapper 56 is displaced to the state indicated by the solid line in FIG. 2, and the recording paper P passes through the sub-transport path 43 and is turned upside down. It is guided to the main transport path 41 and is guided from the main transport path 41 to the paper discharge transport path 42 via the first image forming unit 20 (s41). At this time, as shown in FIG. 9D, the first surface on which the toner image of the monochrome image has already been formed on the recording paper P faces the ink head 53 a in the second image forming unit 50. In the second image forming unit 50, the ink head 53a is driven based on the color image data while intermittently driving the transport rollers 51a and 52a, and a color image is formed by an inkjet method (s42 and s43).
[0050]
Since the conveyance direction of the recording paper P at this time is opposite to the conveyance direction at the time of monochrome image formation in the first image forming unit 20, the first surface of the recording paper P is the monochrome image formed by toner. It faces the ink head 53a in order from the rear end side. Therefore, when the ink head 53a is driven based on the color image data, the upstream end in the conveyance direction of the recording paper P is controlled so as to coincide with the rear end position in the image data. The drive data for the ink head 53a is sequentially applied.
[0051]
In this way, the recording paper P on which the monochrome image by the toner and the color image by the ink are formed on the first surface has the face-up state (surface (first surface) facing upward as shown in FIG. 9E. In this state, the sheet discharge roller 25 is rotated and discharged from the sheet discharge path 42 onto the sheet discharge tray 39 (s44).
[0052]
In the above processing, in order to shorten the image forming processing time, the recording paper P for which the image forming processing has been completed is discharged in the face-up state. However, for a plurality of recording papers P in which pages are continuous. In the case where the recording paper P is discharged in the face-down state (the state where the front surface (first surface) faces downward) in order to eliminate the need for rearrangement of the recording paper P after discharging during the image forming process, the second After completion of the color image forming process in the image forming unit 50, the paper discharge roller 25a and the transport rollers 51a and 52a are reversed to switch back the recording paper P and guide it to the sub transport path 43 again. The paper is discharged to the paper discharge tray 39 via the conveyance path 42.
[0053]
When an image formation request is made for a double-sided document in which image data is stored not only in the front-surface image storage unit 104 but also in the back-side image storage unit 105, the digital copying machine 1 causes the paper feed tray 16 or the paper feed by the operation of the paper feed unit 1C. The recording paper P is fed from the paper cassette 17 one by one to the main transport path 41 via the paper feed transport path 44 or 45, and the recording paper P is synchronized with the rotation of the photosensitive drum 28 via the registration roller 22. At this timing, it is guided into the first image forming unit 20. At the same time, the back-side monochrome image data read from the back-side image storage unit 105 starting from the front end side is supplied to the LSU 30 of the first image forming unit 20, and an electrostatic latent image is formed on the photosensitive drum 28. Thereafter (s51), the developing unit 31 visualizes the electrostatic latent image into a toner image (s52), and the toner image carried on the photosensitive drum 28 is transferred to the first surface of the recording paper P by the transfer device 32. (S53).
[0054]
As shown in FIG. 10A, the recording paper P having the back surface monochrome image transferred to the first surface passes between the photosensitive drum 28 and the transfer device 32 in the main transport path 41, and is fixed to the fixing device. 23, the toner image is fixed on the first surface of the recording paper P by heating and pressing (s54). The recording paper P that has passed through the fixing device 23 is guided to the paper discharge conveyance path 42 by the flapper 56 positioned in the state indicated by the solid line in FIG. 2 (s55). As shown in FIG. 10B, the rotation of the discharge roller 25a is stopped in a state where the rear end of the recording paper P conveyed in the discharge tray 39 toward the discharge tray 39 is sandwiched (s56). The color image data for the front surface read from the image storage unit 104 starting from the rear end side is supplied to the ink head 53a (s57).
[0055]
At the same time, after the flapper 56 is displaced to the state indicated by the broken line in FIG. 2, the paper discharge roller 25a is driven reversely together with the transport rollers 51a and 52a, and the recording paper P changes the transport direction as shown in FIG. While being switched back and guided to the sub-transport path 43, the second image forming unit 50 receives an ink jet type image forming process based on the color image data for the front surface with respect to the second surface (s59, s60). The recording paper P on which the back side monochrome image is formed on the first side and the front side color image is formed on the second side is guided to the main transport path 41 via the sub transport path 43 (s61). After the entire surface of the recording paper P has moved into the sub-transport path 43, the flapper 56 is displaced to the state indicated by the solid line in FIG.
[0056]
Further, the monochrome image data for the surface read from the surface image storage unit 104 starting from the rear end side is supplied to the LSU 30 of the first image forming unit 20, and an electrostatic latent image is formed on the photosensitive drum 28. Thereafter (s62), the developing unit 31 visualizes the electrostatic latent image into a toner image (s63), and the toner image carried on the photosensitive drum 28 is transferred onto the second surface of the recording paper P by the transfer device 32. (S64).
[0057]
As shown in FIG. 10E, the recording paper P having the toner image transferred on the second surface passes between the photosensitive drum 28 and the transfer device 32 in the main transport path 41 and reaches the fixing device 23. Then, the toner image is fixed on the first surface of the recording paper P by heating and pressing (s65). At this time, the back side color image data read from the back side image storage unit 105 starting from the rear end side is supplied to the ink head 53a (s66), and the recording paper P passing through the fixing device 23 is shown in FIG. The flapper 56 positioned in the state indicated by the solid line is guided to the paper discharge conveyance path 42 (s67). While the recording paper P passes through the paper discharge conveyance path 42, the second image forming unit 50 receives a color image forming process based on the color image data for the back surface with respect to the first surface (s68, s69). The recording paper P on which the monochrome image and the color image for the back side are formed and the monochrome image for the front side and the color image for the front side are formed on the second side is discharged by the paper discharge roller 25a as shown in FIG. It is discharged onto the tray 39 (s44). At this time, the recording paper P is discharged in a face-down state in which the second surface on which the front image is formed faces downward and the first surface on which the rear image is formed faces upward.
[0058]
As described above, the recording paper P is conveyed and the monochrome image forming process in the first image forming unit 20 and the color image forming process in the second image forming unit 50 are performed, so that an image in which a monochrome image and a color image are mixed is obtained. The configuration of the digital copying machine 1 that performs image forming processing on data can be reduced in size, and the image forming processing can be speeded up.
[0059]
Further, it is necessary to change the conveyance speed of the recording paper P between the monochrome image forming process by the electrophotographic method and the color image forming process by the ink jet method. For this purpose, the first image forming for performing the electrophotographic image forming is performed. The portion 20 and the second image forming portion 50 that performs ink jet image formation must be sufficiently separated from each other. That is, if the rear end of the recording paper P is located in the fixing device 23 of the first image forming unit 20 during the image forming process of the ink jet method in the second image forming unit 50, the rear end of the recording paper P Becomes an overfixed state, causing high-temperature toner offset (transfer of the toner image on the recording paper P to the peripheral surface of the roller of the fixing device 23) and discoloration of the recording paper P.
[0060]
For this reason, after the recording paper P is once transported to the paper discharge roller 25a in the paper discharge direction, the recording paper P is switched back and conveyed into the sub-transport path 43 by the reverse rotation of the paper discharge roller 25a and the transport rollers 51a and 52a. In the meantime, the distance between the first image forming unit 20 and the second image forming unit 50 is sufficiently shortened by performing the image forming process of the ink jet system in the second image forming unit 50, and the digital copying machine 1 is It can be downsized.
[0061]
In the image forming process based on the image data in which the monochrome image and the color image are mixed, the conveying speed during the time when the image forming process is not performed is the fastest, and the conveying speed during the electrophotographic image forming process is set as follows. The image forming process can be executed efficiently by increasing the speed and slowing down the conveyance speed during the ink jet image forming process.
[0062]
Further, as shown in FIG. 2, a discharge cover 42 in which the second image forming unit 50 is disposed on the fixing cover 57 disposed in the vicinity of the heating roller 23 a of the fixing device 23 in the first image forming unit 20. By closely contacting the conveyance guide 42a, the recording paper P subjected to the inkjet image forming process in the second image forming unit 50 is dried in advance by the heat generated by the fixing device 23 to improve the ink absorbability. And drying of the ink discharged on the recording paper P can be accelerated | stimulated.
[0063]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0064]
  (1) By actually sealing an ink head provided in an ink jet type image forming unit, which is provided together with an electrophotographic type image forming unit, with a maintenance unit during non-energization and during non-image formation during energization, By not exposing the ink head to the outside air until it is used for forming, it is possible to reliably prevent nozzle clogging due to ink drying and dust adhesion, and maintain good color image reproducibility. be able to.
  Also, the maintenance process to be executed when the image formation request for the second image forming unit input prior to the image data is confirmed is completed before the image forming process in the second image forming unit is started. Thus, the maintenance process can be started at the timing, and the image formation process time can be shortened without waiting for the end of the maintenance process to start the image formation process.
[0066]
  (2) By performing the ink head maintenance process when the cumulative number of ink ejections in the ink head reaches a predetermined number of times, the ink jet system can be used without considering the number of times of image formation in the electrophotographic image forming unit. The maintenance process of the inkjet head can be performed without excess or deficiency based only on the number of times of image formation in the image forming unit, and the running cost can be reduced by preventing ink from being wasted due to unnecessary maintenance process. it can.
[0067]
  (3)The recording paper subjected to the inkjet image forming process in the second image forming unit can be dried in advance by the heat generated by the fixing device in the first image forming unit, so that the ink absorbability can be improved. It is possible to promote drying of the ink discharged onto the ink.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of a digital copying machine according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration in the vicinity of a second image forming unit in a printer unit of the digital copying machine.
FIG. 3 is a side view showing a configuration of a main part of a second image forming unit in the digital copying machine.
FIG. 4 is a cross-sectional view showing an internal structure of a maintenance unit provided in the digital copying machine.
FIG. 5 is a diagram showing a configuration of a control unit of the digital copying machine.
FIG. 6 is a flowchart showing a processing procedure of a control unit of the digital copying machine.
FIG. 7 is a flowchart for explaining a recording conveyance state when an image is formed on a single-side original in which a monochrome image and a color image are mixed in the digital copying machine.
FIG. 8 is a flowchart illustrating a recording conveyance state during image formation on a double-sided document in which a monochrome image and a color image are mixed in the digital copying machine.
FIG. 9 is a conveyance path diagram illustrating a conveyance state for recording when an image is formed on a single-sided document in which a monochrome image and a color image are mixed in the digital copying machine.
FIG. 10 is a conveyance path diagram illustrating a conveyance state for recording when an image is formed on a double-sided document in which a monochrome image and a color image are mixed in the digital copying machine.
[Explanation of symbols]
1-Digital copier (image forming device)
20-first image forming unit
41-Main transport path
42-Discharge transport path
43-Sub-transport path
50-second image forming unit
53a-Ink head
70-Maintenance unit

Claims (3)

In an image forming apparatus in which a first image forming unit that forms a monochrome image by an electrophotographic method and a second image forming unit that forms a color image by an inkjet method are arranged in a conveyance path of a recording sheet.
Comprising a maintenance unit for maintenance action for Inkuhe' de in the second image forming unit,
When the power is turned on, it is determined whether or not the ink head is sealed by the maintenance unit. If the ink head is not sealed, a sealing process is performed to seal the ink head using the maintenance unit. Run,
When an image formation request is input, it is determined whether or not the image data related to the image formation request is only monochrome image data. An image forming apparatus, comprising: a control unit that releases sealing of the ink head after performing a maintenance process using the maintenance unit. 2. The image formation according to claim 1, wherein the control unit cumulatively counts the number of ink ejections of the ink head and executes the maintenance process on the condition that the counted value has reached a predetermined number. apparatus. The image forming apparatus according to claim 1, wherein the second image forming unit is disposed in the vicinity of the fixing device in the first image forming unit.

Images