JP4363241B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention provides an image forming apparatus having a plurality of developing units, selectively using one of the developing units, and developing a latent image on a latent image carrier to form a toner image. The present invention relates to an image forming method. In particular, the present invention relates to an image forming apparatus and an image forming method in which a plurality of developing devices are divided into a plurality of groups and a developing unit is configured for each group.

  As this type of image forming apparatus, as described in Patent Document 1, for example, an apparatus that forms a color image by superimposing a plurality of color toner images is known. In this conventional apparatus, a laser writing section (latent image writing means) and a rotary developing unit are provided for each of two photosensitive members (latent image carriers). Each rotary development unit is rotated 180 ° to switch the development color. One rotary development unit has development colors of yellow (Y) and magenta (M), and the other rotary development unit Development colors of cyan (C) and black (K) are provided. An intermediate transfer belt is stretched under the two photoconductors so as to be in contact with the surface of each photoconductor. A color image is formed by superimposing the toner images of the respective colors formed on the respective photoconductors on the intermediate transfer belt according to the image information separated into the respective colors.

  Specifically, a latent image corresponding to the first color, for example, yellow (Y), is formed on the surface of one photoconductor by one laser writing unit on the first round of the intermediate transfer belt, and the second color, for example, A latent image corresponding to cyan (C) is formed on the surface of another photoreceptor by another laser writing unit. The latent images formed on the two photoconductors in this way are developed into yellow (Y) and cyan (C) toner images by the respective rotary development units, and then sequentially transferred onto the intermediate transfer belt. Subsequently, a latent image corresponding to the third color, for example, magenta (M), is formed on the surface of one photoconductor by the one laser writing unit on the second round of the belt, and the fourth color, for example, black (K). Is formed on the surface of another photoconductor by another laser writing unit. The latent images formed on the two photoconductors in this way are developed into magenta (M) and black (K) toner images by the respective rotary development units whose development colors have been switched, and then the intermediate transfer belt. The images are sequentially transferred on top of each other. At this point, a total of four color toner images are transferred onto the intermediate transfer belt, thereby forming a single color image.

JP-A-11-212328 (FIG. 19, pages 2 and 3)

  By the way, in the apparatus as described above, image unevenness may occur in the color image formed on the intermediate transfer belt. As one of the causes of such image unevenness, vibration when the rotary developing unit, which is one of the components of the apparatus, rotates to change the development color is caused by the latent image writing means. For example, the accuracy of latent image formation on the body is degraded. Specifically, the vibration when the rotary developing unit provided corresponding to one latent image carrier rotates to change the development color is performed on the other latent image carrier. This affects the latent image formation and degrades the latent image formation accuracy. However, in the prior art, it cannot be said that sufficient countermeasures are taken against the deterioration of the latent image formation accuracy on the latent image carrier due to such vibration, and the technology for improving the latent image formation accuracy. There was a need for improvement.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In an image forming apparatus provided with a plurality of image forming means having a latent image carrier and a rotary developing unit equipped with a plurality of developing devices, each latent image carrier is provided. An object is to obtain a highly accurate image by forming a highly accurate latent image on the body.

  In order to achieve the above object, the present invention achieves the above-mentioned plurality of developing devices by rotating around a predetermined rotation axis while integrally holding a latent image carrier capable of carrying a latent image and a plurality of developing devices. A plurality of image forming units including a rotary developing unit that selectively positions the developing position opposite to the latent image carrier and develops a latent image on the latent image carrier by the developing unit to form a toner image; A latent image writing unit that forms a latent image corresponding to each of the plurality of image forming units on each of the latent image carriers of the plurality of image forming units, and the plurality of image forming units. A rotary movement operation for rotating each of the rotary developing units, and a control means for controlling a latent image forming operation by the latent image writing means. In each of the plurality of image forming means, Rotational speed Can be switched between a first moving speed that is equal to or higher than the critical speed at which a latent image is disturbed when the rotational movement operation and the latent image forming operation are simultaneously performed, and a second moving speed that is lower than the critical speed. The control means does not perform a latent image forming operation on all the image forming means when at least one of the plurality of rotary developing units is rotating at the first moving speed. Each of the plurality of image forming units performs a latent image forming operation when the rotational movement speeds of the plurality of rotary developing units are all equal to or lower than the second movement speed.

  The image forming method according to the present invention also includes a latent image carrier capable of carrying a latent image and a plurality of developing units, and the plurality of developing units are rotated and moved around a predetermined rotation axis while integrally holding the plurality of developing units. A plurality of image forming means having a rotary developing unit that can be selectively positioned at a development position facing the latent image carrier, and a latent image corresponding to each of the latent image carriers of the plurality of image forming means In the image forming apparatus including the latent image writing unit to be formed, in each of the plurality of image forming units, a latent image forming operation for forming a latent image on the latent image carrier by the latent image writing unit, and rotary development An image forming method for performing a rotational movement operation for rotating a unit and a developing operation for developing a latent image on the latent image carrier by the developing device positioned at the developing position to form a toner image, The plurality of image forming hands In each of the above, the rotational movement speed of the rotary developing unit is determined by the first movement speed equal to or higher than the critical speed at which the latent image is disturbed when the rotational movement operation and the latent image forming operation are performed simultaneously, and the critical speed. Can be switched to a low second moving speed. When at least one of the plurality of rotary developing units is rotating at the first moving speed, a latent image is formed by all image forming means. While the forming operation is prohibited, the latent image forming operation in each of the plurality of image forming units is permitted when the rotational movement speeds of the plurality of rotary developing units are all equal to or lower than the second movement speed. .

  In the invention configured as described above, the rotational movement operation and the latent image forming operation can be performed in parallel. However, as the rotational movement speed increases, the influence (for example, vibration) associated with the rotational movement operation may act on the latent image forming operation, resulting in disturbance of the latent image. Here, the minimum value of the rotational speed at which the disturbance of the latent image appears is the critical speed. That is, in order to increase the operation speed of the apparatus, it is desirable to increase the rotational movement speed. However, if the latent image forming operation is performed while the rotary developing unit is rotationally moved at a rotational movement speed higher than the critical speed, the influence is increased. The latent image forming operation is performed, and the latent image is disturbed. On the contrary, if the rotational movement speed is set to be less than the critical speed, the operation speed of the apparatus itself is lowered, and the throughput is inevitably lowered. Therefore, in the present invention, as described above, the rotational movement speed of the rotary developing unit can be switched between the first movement speed higher than the critical speed and the second movement speed lower than the critical speed. When at least one of the plurality of rotary developing units is rotationally moved at the first movement speed, the influence of the rotational movement operation may affect the latent image forming operation. The forming unit is configured not to perform the latent image forming operation. As a result, the influence caused by the high-speed movement of the rotary developing unit is prevented from affecting the latent image, and the deterioration of the latent image forming accuracy is prevented. Further, when the rotational movement speeds of the plurality of rotary developing units are all equal to or lower than the second movement speed, the influence of the rotational movement operation does not affect the latent image forming operation. In each, a latent image forming operation is performed. Therefore, even when the rotational movement operation and the latent image forming operation are executed in parallel, the latent image is formed without being affected by the rotational movement operation. Therefore, since the deterioration of the latent image formation accuracy is prevented, the latent image can be formed with high accuracy. Since the latent image formed with high accuracy is developed, a highly accurate image can be obtained.

  Further, the control unit uses at least one of the plurality of image forming units as an active image forming unit, and at least one of the image forming units other than the active image forming unit among the plurality of image forming units. The latent image forming operation is performed in the active image forming means while performing the rotational movement operation at the second movement speed or partially overlapping with the rotational movement operation at the second movement speed. It is good also as composition which performs. Further, the control means uses at least one of the plurality of image forming means as an active image forming means, while the latent image forming operation is being performed in the active image forming means, or the latent image forming The rotational movement operation at the second moving speed is performed in at least one of the plurality of image forming units other than the active image forming unit at a timing partially overlapping with the operation. Also good. In the invention configured as described above, at least one of the plurality of image forming units is used as the active image forming unit, and at least one of the image forming units other than the active image forming unit is rotated at the second moving speed. The latent image forming operation is performed in the active image forming means during the operation or at a timing partially overlapping with the rotational movement operation at the second movement speed. Further, at least one of the image forming units other than the active image forming unit performs the second operation while the latent image forming operation is performed in the active developing unit or at a timing partially overlapping with the latent image forming operation. A rotational movement operation is performed at a moving speed. As described above, the latent image forming operation in the active image forming unit and the rotational movement operation in the other image forming unit are executed at the same time or partially overlapping, but the rotational movement operation is executed at the second movement speed. Therefore, the vibration caused by the rotational movement of the rotary developing unit is suppressed, and the latent image forming accuracy in the image forming unit is not affected. Therefore, even if the latent image forming operation is being executed in the active image forming means, the rotation unit is executed to position the developing device at the developing position in order to execute the latent image forming operation in the other image forming means. Can do. Therefore, it is not necessary to wait for the completion of the latent image forming operation in the active image forming unit to position the developing unit of the image forming unit other than the active image forming unit at the developing position, so that the accuracy is high. An image can be formed and the throughput of the apparatus can be improved.

  In addition, the control unit positions each of the plurality of image forming units immediately before the developing unit reaches the developing position when positioning one developing unit of the plurality of developing units at the developing position. A first movement mode in which the rotary development unit holding the developing unit is rotated and moved, and then the rotary development unit is decelerated or stopped at the immediately preceding position, and the rotary developing unit is moved from the immediately preceding position to the first movement mode. It is also possible to execute a second movement mode in which the developing device is rotated and moved by a distance smaller than the moving distance at the position where the developing device is positioned at the developing position. In the invention configured as described above, when the developing device is positioned at the developing position, the rotary developing unit that holds the developing device is rotated and moved to the position immediately before the developing device reaches the developing position. A first movement mode for decelerating or stopping and a second movement mode for rotating the rotary developing unit by a distance smaller than the movement distance in the first movement mode so as to position the developing device from the immediately preceding position to the developing position. Executed. For this reason, the inertial force acting on the rotary developing unit immediately before the developing device reaches the developing position is weakened, and the inertial force acting on the rotary developing unit when the developing device is positioned at the developing position can be kept small. it can. Thereby, the vibration received by the latent image carrier during positioning of the rotary developing unit is reduced, and the influence on the latent image formation by the latent image writing means can be reduced. Furthermore, by suppressing the inertial force acting on the rotary developing unit to be small, the developing device can be positioned at the developing position with high accuracy. As a result, an image can be obtained with good image quality.

  Further, a rotary drive unit that generates a rotational drive force may be further provided, and the rotational drive force may be transmitted to the plurality of image forming units so that the rotary developing unit of each image forming unit is rotated. In the invention configured as described above, since all of the plurality of rotary developing units are rotated by receiving the rotational driving force from the rotary driving unit, the configuration of the apparatus is simplified. In addition, when rotating the plurality of rotary developing units, the timing for executing the rotational movement can be controlled more accurately than when the plurality of rotary developing units are rotated by separate driving units.

  Here, the configuration (size, shape, internal mechanism, etc.) of each developing device is not limited, but by making all the developing devices the same configuration, the manufacturing cost and versatility of the developing devices are increased. Can be preferred. Furthermore, if the developing units having the same configuration are configured so that the same number can be held in each developing unit, that is, if all the rotary developing units have the same configuration, the manufacturing cost and versatility of the developing unit are also increased. More preferably. Of course, it goes without saying that the number of developing devices that can be held by each rotary developing unit may be different from each other.

  In addition, the latent image writing unit includes a plurality of latent image writing units arranged in a one-to-one relationship at positions facing each of the latent image carriers provided in the plurality of image forming units. Also good. In the invention configured as described above, since the writing unit is arranged corresponding to each latent image carrier, it is possible to form latent images on all the latent image carriers with one writing unit. Compared to a possible configuration, the writing unit can be reduced in size. Therefore, the apparatus can be reduced in size.

<First Embodiment>
FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This image forming apparatus is a so-called two-tandem color printer, and has a photosensitive member 22a corresponding to yellow (Y) and cyan (C) as a latent image carrier, and photosensitive members corresponding to magenta (M) and black (K). The body 22b is juxtaposed in the apparatus main body 1. Then, the toner images formed on the photoconductors 22a and 22b are overlapped to form a full-color image (color printing mode), or an image that forms a monochrome image (single-color printing mode) using only black (K) toner. Forming device. That is, in the image forming apparatus 1, when a print request signal including an image signal is given from an external device such as a host computer to the main controller 11 via the interface 112, the CPU 111 of the main controller 11 instructs the operation of the engine unit EG. Is converted into job data in a format suitable for the data and sent to the engine controller 10. On the other hand, the engine controller 10 controls each unit of the engine unit EG based on job data from the CPU 111 to selectively execute the color printing mode and the single color printing mode, and forms an image corresponding to the image signal on the sheet S.

  In the engine unit EG, the photoconductors 22a and 22b are rotatably provided in the arrow directions D1a and D1b in FIG. 1 around the rotation shafts 26a and 26b, respectively. Further, charging units 23a and 23b, rotary developing units 41a and 41b, and cleaning units 25a and 25b are arranged around the photosensitive members 22a and 22b along the rotation directions D1a and D1b, respectively. The charging units 23a and 23b receive the application of the charging bias from the charging control unit 103 and uniformly charge the outer peripheral surfaces of the photoconductors 22a and 22b to a predetermined surface potential.

  As described above, the light beams La and Lb are irradiated from the laser exposure unit 6 toward the outer peripheral surfaces of the photosensitive members 22a and 22b charged by the charging units 23a and 23b. This laser exposure unit 6 corresponds to the “latent image writing means” of the present invention, and exposes the light beams La and Lb onto the photosensitive members 22a and 22b in accordance with a control command given from the exposure control unit 102. Thus, an electrostatic latent image corresponding to the image signal is formed. For example, when an image signal is given from an external device such as a host computer to the CPU 111 of the main controller 11 via the interface (I / F) 112, the CPU 101 of the engine controller 10 sends the image signal to the exposure control unit 102 at a predetermined timing. In response to this, the laser exposure unit 6 emits light beams La and Lb onto the photoconductors 22a and 22b, and electrostatic latent images corresponding to the image signals become photoconductors 22a and 22b. Formed on top. Thus, in this embodiment, the photoconductors 22a and 22b correspond to the “latent image carrier” of the present invention.

  The electrostatic latent image formed in this way is developed with toner by the developing means 4 including two rotary developing units 41a and 41b. In this embodiment, a yellow developing unit 43Y and a cyan developing unit 43C are mounted on the rotary developing unit 41a, while a magenta developing unit 43M and a black developing unit 43K are mounted on the rotary developing unit 41b. Yes. Then, the rotary drive mechanism 5 is actuated in accordance with an operation command from the drive control unit 105 at an appropriate timing, whereby both or one of the rotary developing units 41a and 41b is rotated around the rotation shafts 44a and 44b to develop the developing device. Is selectively positioned at a development position facing the photoconductors 22a and 22b. Further, a developing bias is applied from the developing device controller 104 to the developing roller 45 of the developing device positioned at the developing position, so that the developing roller 45 carries the photoconductors 22a and 22b on the surface of the developing roller 45. Toner T is supplied. As a result, the electrostatic latent images on the photoconductors 22a and 22b are visualized with the selected toner color. In this embodiment, the photosensitive member 22a and the rotary developing unit 41a constitute an image forming unit 400a, and the photosensitive member 22b and the rotary developing unit 41b constitute an image forming unit 400b. In this embodiment, the engine controller 10 including the drive control unit 105 and the exposure unit control unit 102 corresponds to the “control unit” of the present invention. The configuration and operation of the developing unit 4 will be described in detail later.

  The toner image developed by the developing means 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer regions TR1a and TR1b. The transfer unit 7 includes an intermediate transfer belt 71 spanned between a plurality of rollers 72a and 72b to 74, and a belt driving unit (shown) that rotates the intermediate transfer belt 71 in a predetermined movement direction D2 by rotationally driving the roller 73. (Omitted). A vertical synchronization sensor 77 is disposed in the vicinity of the roller 74. The vertical synchronization sensor 77 is a sensor for detecting the reference position of the intermediate transfer belt 71 and is a vertical signal for obtaining a synchronization signal output in association with the rotational drive of the intermediate transfer belt 71, that is, a vertical synchronization signal Vsync. Functions as a synchronous sensor. In this apparatus, the operation of each part of the apparatus is controlled based on the vertical synchronization signal Vsync in order to align the operation timing of each part and accurately superimpose the toner images formed in the respective colors. That is, each part of the engine unit EG operates in synchronization with the vertical synchronization signal to rotate the rotary developing units 41a and 41b, and a latent image is formed by the laser exposure unit 6 on the photosensitive members 22a and 22b. A latent image forming step (latent image forming operation), a developing step (developing operation) for developing the latent image by a developing device positioned at a developing position, a transfer step, and the like are executed.

  Of these processes, the “rotation movement process” refers to a rotary development unit 41a, 41b that is rotated and moved to selectively position the developing device at the development position of the corresponding photosensitive member 22a, 22b. This means a step of positioning 41a and 41b at the home position HP. The “developing step” is a step of developing a latent image on the photoconductors 22a and 22b by a developing unit switched to the developing position among the developing units 43Y, 43M, 43C, and 43K to form a toner image. means. Therefore, a toner image of four colors can be obtained by executing the developing process every time the developing devices 43Y, 43M, 43C, and 43K are switched. A color image is formed by superimposing these four toner images on the intermediate transfer belt 71 (color printing mode). A color image is thus formed, and the color image is secondarily transferred onto the sheet S taken out one by one from the cassette 8 and conveyed along the conveyance path F to the secondary transfer region TR2.

  On the other hand, when a monochrome image is transferred to the sheet S, a development process is performed on the black color to form a monochrome image (single color printing mode), and the black image is conveyed to the secondary transfer region TR2 as in the case of a color image. A monochrome image is obtained by transferring to the sheet S.

  In this embodiment, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, as shown in FIG. 1, a gate roller 81 is provided on the transport path F in front of the secondary transfer region TR <b> 2, and the gate roller 81 is synchronized with the circumferential movement timing of the intermediate transfer belt 71. , The sheet S is fed into the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the color image or the monochrome image is thus formed is conveyed to a discharge tray portion 82 provided on the upper surface portion of the main body of the apparatus 1 via a fixing unit 9 and a conveyance roller (not shown).

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  Next, the configuration and operation of the developing means 4 will be described in detail with reference to FIGS. In this embodiment, the developing devices 43Y, 43M, 43C, and 43K constituting the developing unit 4 all have the same configuration, and are configured as follows. That is, each of the developing devices 43Y, 43M, 43C, and 43K has a housing 46 serving as a toner storage portion storing toner T therein and a part of the toner T stored in the toner storage portion at a development position. A developing roller 45 to be conveyed and an agitating member 47 such as an agitator for agitating the toner T in the toner accommodating portion are provided. Then, the toner T is forcibly stirred in the toner storage portion by the rotation operation of the stirring member 47. Further, a part of the toner T is conveyed to the developing position facing the photoconductors 22 a and 22 b while being carried on the surface of the developing roller 45. Note that yellow toner T, magenta toner T, cyan toner T, and black toner T are stored in the housings 46 of the developing units 43Y, 43M, 43C, and 43K, respectively.

  The developing units 43Y, 43M, 43C, and 43K configured as described above are divided into two groups, that is, a group of developing units 43Y and 43C and a group of developing units 43M and 43K, which are attached to the developing units 41a and 41b, respectively. Is done. That is, in both of the developing units 41a and 41b, the support frame 48 is rotatably provided around the rotation shafts 44a and 44b, and the two developing devices are symmetrical with respect to the rotation shafts 44a and 44b. It is held as the center. Thus, in this embodiment, the two rotary developing units 41a and 41b have the same configuration.

  Further, the rotating shafts 44a and 44b of the developing units 41a and 41b are mechanically connected to the rotary drive mechanism 5, and the rotary drive mechanism 5 is operated in accordance with the operation command from the drive control unit 105 as described above. As shown in FIG. 3, the rotary developing units 41a and 41b rotate in the direction of the arrow D3. In this embodiment, a predetermined home position HP (see FIG. 3A) for waiting for a print command is provided as an initial position of the rotary developing units 41a and 41b, and after the print command is given, The developing units 41a and 41b are rotated to each position.

  Next, the operation of the image forming apparatus in this embodiment will be described in detail with reference to FIGS. FIG. 3 is a schematic diagram showing a rotational movement operation and a latent image forming operation, and FIG. 4 is a timing chart showing the operation of the image forming apparatus of FIG. In this embodiment, both developing units 41a and 41b are positioned at the home position HP while waiting for a print command (see FIG. 4). When a print command given from an external device is given, the CPU 111 of the main controller 11 converts the job data into a format suitable for the operation instruction of the engine unit EG, and sends the print command to the engine controller 10. On the other hand, the engine controller 10 controls each part of the engine unit EG based on the print command and executes a print operation. Here, a case where a color print command is given will be described.

  When a print command is given from the main controller 11, the engine controller 10 executes a color print mode based on the vertical synchronization signal Vsync. Specifically, at time t0, t1, t2,..., That is, every round (cycle T0) of the intermediate transfer belt 71, a vertical synchronization signal Vsync is output from the vertical synchronization sensor 77, and these are the operations of each part of the engine unit EG. Used as a reference signal. Note that the time when the first vertical synchronization signal Vsync is output after the print command is given is t0. After the vertical synchronization signal Vsync is output at time t0, the rotary developing unit 41a is rotated at a first movement speed (for example, the average speed is 60 rpm) in the direction of the arrow D3 at an appropriate timing (FIG. 3A). FIG. 4). Here, first, the yellow developing device 43Y of the first color is moved toward the developing position facing the photosensitive member 22a (rotation moving step).

  Next, after the rotational movement process of the rotary developing unit 41a is completed and the rotary developing unit 41a is positioned at the Y developing position, the laser exposure unit 6 performs a latent image forming process on the photosensitive member 22a and the developing unit 43Y. The developing step is performed. Specifically, after the rotary developing unit 41a is positioned at the Y developing position (after the rotational movement process), first, the yellow component (image signal IS1) of the image signal from the main controller 11 is timed after time t1. Y latent image forming operation for forming a latent image corresponding to) on the photosensitive member 22a by the light beam La from the laser exposure unit 6 is started. At this time, the rotary developing unit 41b is rotationally moved in the direction of the arrow D3 at the second moving speed (for example, the average speed is 10 rpm) at a timing partially overlapping with the Y latent image forming operation (FIG. 4B, FIG. 4). That is, the second color magenta developing device 43M is moved toward the developing position facing the photosensitive member 22b. Then, after the rotary movement process of the rotary developing unit 42b is completed and the rotary developing unit 41b is positioned at the M developing position, the laser exposure unit 6 performs a latent image forming process on the photosensitive member 22b and the developing unit 43M. A development process is performed. Specifically, after the rotary developing unit 41b is positioned at the M developing position (after the rotational movement process), the latent image corresponding to the magenta component (image signal IS2) of the image signal is transferred to the light beam from the laser exposure unit 6. An M latent image forming operation to be formed on the photosensitive member 22b by Lb is started.

  Note that as the rotational movement speed increases, the influence (for example, vibration) associated with the rotational movement operation may act on the latent image forming operation to cause disturbance of the latent image. This is a speed that takes into account the effect of this rotational movement. Specifically, the minimum value of the rotational speed at which the disturbance of the latent image appears is defined as the critical speed, the speed higher than the critical speed is defined as the first moving speed, and the speed lower than the critical speed is defined as the second moving speed. For example, as an opportunity to rotate the rotary developing unit at the first moving speed, the rotary developing unit is first moved from the home position HP during the use determination operation of each developing device performed when the power is turned on or when printing is performed. It is possible to rotate the developing position. Further, as an opportunity to rotate the rotary developing unit at the second moving speed, timing for eliminating the influence of vibration or the like caused by the rotational movement, for example, timing for forming a latent image by other image forming means, etc. Can be considered.

  The latent images formed on the photoconductors 22a and 22b in this way are developed as yellow and magenta toner images by the developing units 43Y and 43M positioned at the development positions facing the photoconductors 22a and 22b. 22b is revealed (development process). The toner images formed on the photoreceptors 22a and 22b are sequentially transferred to the intermediate transfer belt 71 and superimposed (transfer process).

  Subsequently, after the Y latent image forming operation (latent image forming step) by the laser exposure unit 6 and the developing step by the developing device 43Y are finished, the rotary developing unit 41a is moved to the arrow D3 at a timing partially overlapping with the M latent image forming operation. Is rotated at the second moving speed at the second moving speed (see FIG. 3C), and the third color cyan developing device 43C is moved toward the developing position facing the photoconductor 22a (rotational moving step). . Next, after the rotational movement process of the rotary developing unit 41a is completed and the rotary developing unit 41a is positioned at the C developing position, the latent image forming process is performed by the laser exposure unit 6 and the developing process by the developing device 43C is performed. Done. Specifically, after the rotary developing unit 41a is positioned at the C developing position (after the rotational movement process), the cyan component (image signal IS1) of the image signal from the main controller 11 at a timing after time t2. A latent image forming operation for forming a latent image corresponding to the above on the photosensitive member 22a by the light beam La from the laser exposure unit 6 is started.

  At this time, the rotary developing unit 41b is rotated at the second moving speed in the direction of the arrow D3 at a timing partially overlapping with the C latent image forming operation (see FIG. 4D). That is, the fourth color black developing device 43K is moved toward the developing position facing the photoreceptor 22b. Then, after the rotary moving process of the rotary developing unit 42b is completed and the rotary developing unit 41b is positioned at the K developing position, the latent image forming process for the photosensitive member 22b is performed by the laser exposure unit 6 and the developing unit 43K. A development process is performed. Specifically, after the rotary developing unit 41b is positioned at the K developing position (after the rotational movement process), the latent image corresponding to the black component (image signal IS2) of the image signal is converted into a light beam from the laser exposure unit 6. The K latent image forming operation to be formed on the photoreceptor 22b is started by Lb.

  The latent images formed on the photoconductors 22a and 22b in this way are developed as cyan and black toner images by the developing devices 43C and 43K positioned at the development positions facing the photoconductors 22a and 22b. Revealed on 22b. The toner images formed on the photoconductors 22a and 22b are sequentially transferred to the intermediate transfer belt 71 and superimposed on the yellow and magenta toner images on the intermediate transfer belt 71. In this way, multiple color images are formed on the intermediate transfer belt 71. When color printing is not performed continuously, the rotary developing unit 41b is then rotated and positioned at the home position HP (not shown).

  As described above, in this embodiment, a latent image formed on the photoconductors 22a and 22b corresponding to each color component of the image signal is intermediated with a toner image developed by a developing device of a color corresponding to the latent image. A color image is formed by superimposing on the transfer belt 71. The rotary developing units 41a and 41b can be switched between a rotational moving speed between a first moving speed higher than the critical speed and a second moving speed lower than the critical speed. When at least one or more of them are rotating at the first moving speed, the latent image forming operation may be affected by the rotation moving operation. Therefore, the latent image forming operation is performed in all the image forming units 400a and 400b. Is not performed (prohibited). As a result, the influence caused by the high-speed movement of the rotary developing units 41a and 41b is prevented from affecting the latent image, and the deterioration of the latent image forming accuracy is prevented. In addition, when the rotational movement speeds of the rotary developing units 41a and 41b are all equal to or lower than the second movement speed, the influence of the rotational movement operation does not affect the latent image forming operation. In each of these, a latent image forming operation is performed (allowed). Therefore, even when the rotational movement operation and the latent image forming operation are executed in parallel, the latent image is formed without being affected by the rotational movement operation. Therefore, since the deterioration of the latent image formation accuracy is prevented, the latent image can be formed with high accuracy. Since the latent image formed with high accuracy is developed, a highly accurate image can be obtained.

  In this embodiment, one image forming unit 400a, (or 400b) is used as an active image forming unit, and the rotational movement operation at the second moving speed is performed in the image forming unit 400b, (or 400a) other than the active image forming unit. The latent image forming operation is performed in the active image forming means at the timing of partial overlap. Further, at the timing partially overlapping with the latent image forming operation in the active image forming unit, the image forming unit 400b (or 400a) other than the active image forming unit performs the rotational movement operation at the second moving speed. As described above, the latent image forming operation in the active image forming unit 400a, (or 400b) and the rotational movement operation in the other image forming unit 400b, (or 400a) are executed at a timing partially overlapping. Since the moving operation is executed at the second moving speed, vibration caused by the rotational movement of the rotary developing unit is suppressed, which affects the latent image forming accuracy in the active image forming means 400a (or 400b). There is no. Therefore, even when the latent image forming operation is being executed in the active image forming means 400a, (or 400b), the rotational movement operation is performed in order to execute the latent image forming operation in the other image forming means 400b, (or 400a). This can be done to position the developer to the development position. Therefore, the latent image forming operation in the active image forming means 400a, (or 400b) is used to position the developing device of the image forming means 400b, (or 400a) other than the active image forming means 400a, (or 400b) to the development position. Therefore, it is not necessary to wait more than necessary for completion of the process, so that a highly accurate image can be formed and the throughput of the apparatus can be improved.

  In this embodiment, all the developing units 43Y, 43M, 43C, and 43K have the same configuration. Further, the developing units 43Y, 43M, 43C, and 43K having the same configuration as described above are configured to be able to hold the same number by the developing units 41a and 41b. That is, the rotary developing units 41a and 41b have the same configuration. Therefore, the manufacturing cost and versatility of the developing device can be increased. Further, the manufacturing cost and versatility of the developing unit can be increased.

Second Embodiment
FIG. 5 is a diagram showing a second embodiment of the operation of the image forming apparatus according to the present invention. The present embodiment is greatly different from the first embodiment described above. When the rotary developing units 41a and 41b are rotationally moved to selectively position the developing device at a predetermined position, the developing device is predetermined. A first movement mode in which the rotary developing units 41a and 41b holding the developing device are rotated and moved to a position immediately before reaching the position, and then stopped at the immediately preceding position, and the developing device is positioned from the immediately preceding position to a predetermined position. And a second movement mode in which the rotary developing unit is rotated and moved by a distance smaller than the movement distance in the first movement mode. Hereinafter, with reference to FIG. 3 and FIG. 5, it demonstrates in detail focusing on a different point from 1st Embodiment mentioned above.

  As shown in FIG. 5, when a print command is given from the main controller 11, the engine controller 10 executes the color print mode based on the vertical synchronization signal Vsync. After the vertical synchronization signal Vsync is output at time t0, the rotary developing unit 41a is rotated at the first movement speed in the direction of the arrow D3 at an appropriate timing (see FIGS. 3A and 5). Then, the yellow developing device 43Y for the first color is stopped at a position immediately before reaching the developing position facing the photoreceptor 22a (first movement mode). Subsequently, the rotary developing unit 41a is again rotated and positioned at the Y developing position (second movement mode). In the subsequent processing, when the developer is selectively positioned at the development position, the developer is positioned at the development position by executing the first movement mode and the second movement mode in the same manner as described above. Is done. Other configurations are the same as those of the first embodiment described above, and the description of the configurations and operations will be omitted.

  In this embodiment, when positioning the developing device to the developing position, the developing units 41a and 41b holding the developing device are rotated to the position immediately before the developing device reaches the developing position, and then stopped at the immediately preceding position. The movement mode and the second movement mode in which the developing units 41a and 41b are rotationally moved by a minute distance so as to position the developing device from the immediately preceding position to the developing position are executed. Therefore, the inertial force acting on the developing units 41a and 41b immediately before the developing unit reaches the developing position is weakened, and the inertial force acting on the developing units 41a and 41b when the developing unit is positioned at the developing position is reduced. It can be kept small. As a result, vibrations received by the photoconductors 22a, 22b and the like when positioning the developing units 41a, 41b are reduced, and the influence of the exposure unit 6 on the formation of the electrostatic latent image can be reduced. Furthermore, the developing device can be positioned at the developing position with high accuracy by suppressing the inertial force acting on the developing units 41a and 41b to be small. As a result, a toner image can be formed with good image quality.

<Third Embodiment>
FIG. 6 is an enlarged view of a main part of the third embodiment of the image forming apparatus according to the present invention. This embodiment differs greatly from the first and second embodiments described above in that the LED exposure units 61a and 61b (corresponding to the photosensitive members 22a and 22b, respectively, instead of the laser exposure unit 6 as latent image writing means). (Corresponding to “writing section” of the present invention). Other configurations are the same as those of the first and second embodiments described above, and the description of the configurations and operations will be omitted.

  In this embodiment, latent images are formed on the photoreceptors 22a and 22b using LED exposure units 61a and 61b instead of the laser exposure unit 6, respectively. Therefore, since the latent image writing means is downsized as compared with the laser exposure unit 6, the image forming apparatus can be designed compactly.

<Others>
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the rotational movement operation of the rotary developing unit 41b and the Y, C latent image forming operation on the photosensitive member 22a, and the rotational movement operation of the rotary developing unit 41a and the M, K latent image on the photosensitive member 22b. The forming operation is executed at a timing that partially overlaps. However, the execution timings of these operations may be executed at completely overlapping timings, or may be executed at different timings. In the apparatus configured as described above, the rotational movement operation at the first movement speed in one image forming unit and the latent image forming operation in the other image forming unit are not performed simultaneously. Further, even when the rotational movement operation and the latent image forming operation are executed in parallel, the latent image is formed without being affected by the rotational movement operation. Therefore, the vibration accompanying the rotational movement operation of the rotary developing unit of one image forming unit does not affect the image formation in the other image forming unit, so that a highly accurate image can be obtained as in the above-described embodiment. be able to.

  Further, as a drive source in the rotary drive mechanism 5, a rotary drive motor (corresponding to the “rotary drive unit” of the present invention) capable of driving both of the rotary developing units 41a and 41b may be further provided. In the apparatus configured as described above, both of the rotary developing units 41a and 41b are rotated by a rotary drive motor. Accordingly, since both the rotary developing units 41a and 41b are rotated and moved only by the rotary drive motor, the apparatus configuration can be simplified. Further, the timing of executing the rotational movement can be accurately adjusted as compared with the case where the rotary developing units 41a and 41b are rotationally moved by separate rotary drive motors.

  In the second embodiment described above, when the developing device is positioned at the developing position, as the first movement mode, the rotary developing unit 41a, which holds the developing device until the position immediately before the developing device reaches the developing position ( Alternatively, the rotary developing unit 41a, (or 42b) is decelerated without stopping at the immediately preceding position as shown in FIG. As a mode, the developing device may be positioned from the immediately preceding position to the developing position. In the invention configured in this way, the inertial force acting on the rotary developing unit 41a (or 42b) is weakened immediately before the developing device reaches the developing position, and the rotary when the developing device is positioned at the developing position. The inertial force acting on the developing unit 41a (or 42b) can be kept small. As a result, it is possible to obtain the same operational effects as the above-described embodiment.

  Further, the operation of the rotary developing unit in the first and second embodiments may be combined. For example, in the operation of the developing unit 41a in FIG. 5, when rotating from the C developing position to the home position HP, it may be positioned at the home position HP without stopping or decelerating at the position immediately before the home position HP.

  In the above embodiment, the agitating member 47 is provided in each of the developing units 43Y, 43M, 43C, and 43K. However, the disposition of the agitating member 47 is not an essential requirement and is optional. This is because, in the above-described embodiment, the developing devices 43Y, 43M, 43C, and 43K are configured so that the toner T is fluidly stirred inside the developing device by rotating the rotating devices 44 around the rotation shaft 44. With this configuration, the apparatus can be simplified and miniaturized, and the apparatus cost can be greatly reduced.

  In the above embodiment, each of the developing units 41a and 41b is configured to hold two developing units, but may be configured to hold three or more developing units. By increasing the number of held developer units in this way, the number of types of toner colors used for color printing can be increased, or the number of specific color developer units can be increased compared to other toner color developer units. Can be increased.

  In the above-described embodiment, the developing device having the same configuration is used. However, a plurality of types of developing devices may be used.

  In the above-described embodiment, the developing units 41a and 41b are configured so that the developing units 41a and 41b have the same rotary diameter. However, the rotary units may be configured to have different rotary diameters. That is, the developing units 41a and 41b may have the same configuration or different configurations. In short, as long as each developing unit can be positioned at the developing position while holding a plurality of developing units, Any one may be used.

  In the above embodiment, the two rotary developing units 41a and 41b are used. However, the number of the rotary developing units is not limited to “2”, and three or more rotary developing units may be provided.

  In the second embodiment, the LED exposure units 61a and 61b are arranged at positions facing the photoconductors 22a and 22b. However, instead of the LED exposure units 61a and 61b, a miniaturized laser exposure unit is exposed. You may arrange | position to the position facing body 22a, 22b. In addition, as long as the latent image can be formed on the photosensitive members 22a and 22b, the configuration of the latent image writing unit is arbitrary.

  In the above-described embodiment, the photosensitive member is used as the latent image carrier of the present invention. However, a latent image carrier other than the photosensitive member is used and the latent image writing unit suitable for the latent image carrier is used for latent image carrier. The present invention can also be applied to an apparatus that performs image formation.

  Further, the present invention is not limited to the configuration of the above-described embodiment. For example, the present invention is also applied to an apparatus including a transfer medium (transfer drum, transfer sheet, etc.) other than the intermediate transfer belt, and also to other image forming apparatuses such as a copying machine and a facsimile machine. The invention can be applied.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. The schematic diagram which shows rotational movement operation | movement and latent image formation operation | movement. 2 is a timing chart illustrating the operation of the image forming apparatus in FIG. 1. FIG. 10 is a diagram illustrating a second embodiment of the operation of the image forming apparatus according to the invention. The principal part enlarged view of 3rd Embodiment of the image forming apparatus concerning this invention. 6 is a timing chart showing another operation of the image forming apparatus according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 22a, 22b ... Photoconductor (latent image carrier, image forming means), 41a, 41b ... Rotary developing unit (image forming means), 43Y, 43M, 43C, 43K ... Developing device, 44a, 44b Rotating shaft 61a, 61b LED exposure unit (latent image writing unit) 10 Engine controller (control unit) 102 Exposure control unit (control unit) 105 Drive control unit (control unit) 400a 400b ... Image forming means

Claims (9)

A latent image carrier capable of carrying a latent image and a plurality of developing units are integrally held and rotated around a predetermined rotation axis so that the plurality of developing units are moved to a development position facing the latent image carrier. A plurality of image forming means having a rotary developing unit for selectively positioning and developing a latent image on the latent image carrier by the developing unit to form a toner image;
Latent image writing means for forming a latent image corresponding to each of the plurality of image forming means on each of the latent image carriers of the plurality of image forming means;
A rotational movement operation for rotating each of the rotary developing units provided in the plurality of image forming means, and a control means for controlling a latent image forming operation by the latent image writing means,
In each of the plurality of image forming units, the rotational movement speed of the rotary developing unit is a first movement speed that is equal to or higher than a critical speed at which a latent image is disturbed when the rotational movement operation and the latent image forming operation are performed simultaneously. And can be switched to a second movement speed lower than the critical speed,
The control means includes
While at least one of the plurality of rotary developing units is rotating at the first moving speed, the latent image forming operation is not performed in all image forming units.
An image forming apparatus, wherein a latent image forming operation is performed in each of the plurality of image forming units when the rotational movement speeds of the plurality of rotary developing units are all equal to or lower than the second movement speed.   The control unit uses at least one of the plurality of image forming units as an active image forming unit, and at least one of the image forming units other than the active image forming unit among the plurality of image forming units. The active image forming means performs the latent image forming operation while performing the rotational movement operation at the second movement speed or at a timing partially overlapping with the rotational movement operation at the second movement speed. The image forming apparatus according to claim 1.   The control means uses at least one of the plurality of image forming means as an active image forming means, while the latent image forming operation is being performed in the active image forming means, or as the latent image forming operation. 2. The rotational movement operation at the second movement speed is performed in at least one of the image forming units other than the active image forming unit among the plurality of image forming units at a partially overlapping timing. Image forming apparatus.   In each of the plurality of image forming units, the control unit positions the developing unit of the plurality of developing units at the developing position up to a position immediately before the developing unit reaches the developing position. A first movement mode for decelerating or stopping the rotary developing unit at the immediately preceding position after rotating the rotary developing unit holding the developing device; and the rotary developing unit in the first moving mode from the immediately preceding position. 4. The image forming apparatus according to claim 1, wherein a second movement mode is performed in which the developing unit is rotated and moved by a distance less than a moving distance to position the developing device at the developing position. 5.   5. The rotary drive unit according to claim 1, further comprising a rotary drive unit that generates a rotational driving force, wherein the rotational driving force is transmitted to the plurality of image forming units and the rotary developing unit of each image forming unit is rotated. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein all of the plurality of developing devices have the same configuration.   The image forming apparatus according to claim 1, wherein both of the rotary developing units of the plurality of image forming units can hold the same number of the developing devices.   2. The latent image writing unit includes a plurality of latent image writing units disposed on a one-to-one basis at positions facing each of the latent image carriers provided in the plurality of image forming units. The image forming apparatus according to claim 7. A latent image carrier capable of carrying a latent image and a plurality of developing units are integrally moved while rotating around a predetermined rotation axis so that the plurality of developing units are moved to a development position facing the latent image carrier. An image comprising a plurality of image forming means having a rotary developing unit that can be selectively positioned, and a latent image writing means for forming a latent image corresponding to each of the latent image carriers of the plurality of image forming means. In the forming apparatus, in each of the plurality of image forming units, a latent image forming operation for forming a latent image on the latent image carrier by the latent image writing unit, a rotational movement operation for rotating a rotary developing unit, and the developing An image forming method for developing a latent image on the latent image carrier by the developing device positioned at a position to form a toner image;
In each of the plurality of image forming units, the rotational movement speed of the rotary developing unit is a first movement speed that is equal to or higher than a critical speed at which a latent image is disturbed when the rotational movement operation and the latent image forming operation are performed simultaneously. And can be switched to a second movement speed lower than the critical speed,
While at least one of the plurality of rotary developing units is rotating at the first moving speed, the image forming unit prohibits the latent image forming operation,
A latent image forming operation in each of the plurality of image forming units is permitted when the rotational movement speeds of the plurality of rotary developing units are all equal to or lower than the second movement speed.

Images