JP2006126553A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of realizing high-quality image-forming by making toner on the outer peripheral surface of a developing roller uniform from the beginning in the case of restarting the image-forming even when standby time is short. <P>SOLUTION: In the image forming apparatus equipped with a developing cartridge 37 for developing an electrostatic latent image on a photoreceptor drum 32a, the developing roller 42 of the developing cartridge 37k in which black (K) toner is stored is idly rotated to supply/refresh the toner on its outer peripheral surface 42a after finishing the image forming operation and before starting the next image forming operation when the image data of a final page shows the image formed of the black (K) toner on the rear end side of recording paper. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an image forming apparatus, and more particularly to an apparatus capable of performing high-quality image formation from the beginning of image formation restart.

2. Description of the Related Art Conventionally, an electrophotographic recording type image forming apparatus that exposes and forms an electrostatic latent image on the surface of a carrier made of a photoreceptor is known. In this image forming apparatus, the electrostatic latent image is developed with toner. The toner image on the surface of the carrier carried in this manner is transferred to a recording medium such as recording paper to form an image. The electrostatic latent image is developed by rotating a developing roller facing the surface of the carrier and transferring and adhering toner on the outer peripheral surface of the roller. Then, the toner is supplied by the supply roller rotating in the toner storage space being pressed and rotated.

An image forming apparatus employing this electrophotographic recording system is detachably mounted with a developing cartridge (developing device) having a container for storing toner together with a developing roller and a supply roller facing a carrier. There is also an apparatus configured such that a plurality of the development rotary units can be stored. In this image forming apparatus, the developing cartridge at the developing position where the developing roller faces the carrier can be switched by rotating the developing rotary unit about the rotation axis.

For this reason, such an image forming apparatus is a developing cartridge that contains toner of yellow (Y), magenta (M), cyan (C), and black (K) as a developing cartridge that attaches toner to the surface of the carrier. By configuring the cartridge so that it can be stored (attached) in the developing rotary unit, it is possible to sequentially switch the developing cartridge and form a color image in which the respective color toners are superimposed (see, for example, Patent Document 1). In this configuration, it is needless to say that a monochrome image using a single color toner, for example, a black and white monochrome image (hereinafter also simply referred to as a monochrome image) using black (K) toner can be formed.
JP 2004-126089 A

However, in an image forming apparatus that employs such a conventional electrophotographic recording method, if the standby time after the completion of the image forming operation is long to some extent and the developing roller is left unrotated, the developing is performed. Of the outer peripheral surface of the roller, there is a difference in the state of the toner on the outer peripheral surface between the region facing the surface of the carrier and exposed to the outside and the region located in the container of the developing cartridge. For this reason, when the next image forming operation is resumed, density unevenness corresponding to the exposure area and the in-container area, in other words, coincides with the rotation period of the developing roller occurs in the image, causing a problem in image quality. Could occur.

In order to solve this problem, in the above document, the elapsed time from the end of the previous image forming operation is measured, and when the elapsed time exceeds the set time, the developing roller is idled and refreshed. Thus, it has been proposed to make the toner on the outer peripheral surface of the developing roller uniform quality.

In the image forming apparatus described in the above document, it has been possible to eliminate the deterioration in image quality due to the long standby time, but it is better to take measures even when the standby time is short. found.

First, the developing roller is charged while the toner is repeatedly supplied onto the outer peripheral surface thereof by a supply roller that rotates in the developing cartridge, thereby continuing the developing operation for attaching the toner to the electrostatic latent image on the surface of the carrier. Therefore, the toner on the outer peripheral surface is saturated to a desired charging voltage.

Since the toner on the outer peripheral surface of the developing roller is selectively attached to the electrostatic latent image on the surface of the carrier, unevenness occurs depending on whether or not the portion corresponds to the electrostatic latent image on the surface of the carrier. New toner is replenished so as to eliminate the unevenness. At this time, since the toner to be replenished exists around the supply roller, the toner on the outer peripheral surface of the developing roller is closer to the toner on the outer peripheral surface of the developing roller than during the development operation being repeated. Charged. For this reason, the developing roller can uniformly develop the electrostatic latent image on the surface of the carrier with uniform quality by replenishing the toner on the outer peripheral surface.

However, if the toner on the outer peripheral surface of the developing roller is stopped when the last developing operation is performed, the toner remaining on the outer peripheral surface and the next image formation are developed. When the operation is resumed, there is a difference between the state of the toner replenished so as to eliminate unevenness on the outer peripheral surface of the developing roller. That is, the toner on the outer peripheral surface of the developing roller facing the surface of the carrier is left in an electrically floating state, but the toner in the developing cartridge is in a state where a large amount of other toner exists around it. It is assumed that there is a difference in the degree of charging even if left for a short time. In this state, even if the developing operation is resumed, the electrostatic latent image on the surface of the carrier cannot be developed with uniform quality by the toner on the outer peripheral surface of the developing roller.

This non-uniformity phenomenon of toner tends to vary depending on the characteristics of toners of different colors. Among yellow, magenta, cyan, and black toners, particularly black toners containing carbon are used. Because of its excellent conductivity, it tends to be non-uniform compared to other color toners, and the non-uniformity seems to become more pronounced as the carbon content increases.

Due to the difference in the conductive characteristics, the black toner has a different charging voltage from that of other color toners, and it is necessary to rotate the developing roller more than the case of other color toners until the charging voltage is saturated. There is. For this reason, in the case of black toner, the number of rotations of the developing roller required until the non-uniform phenomenon of the toner is eliminated is, for example, in the case of other color toners.
In the case of black toner, there is a tendency that it is better to perform two or more rotations, where one rotation is sufficient.

Here, as a proposal for preventing the non-uniform phenomenon of the toner from appearing, it is conceivable to increase the charging efficiency (voltage) of the toner on the outer peripheral surface of the developing roller. As a result, developability deteriorates, resulting in image deterioration such as density unevenness, which is not suitable as a countermeasure.

In addition, since the possibility that this toner non-uniformity phenomenon occurs depends on the charging characteristics of the toner, it may also be caused by other factors such as the temperature and humidity of the surrounding environment and the degree of toner deterioration. It becomes easy.

Therefore, the present invention can perform high-quality image formation by making the toner on the outer peripheral surface of the developing roller uniform from the beginning when image formation is resumed even when the standby time is short. An object is to provide a forming apparatus.

According to a first aspect of the present invention, there is provided an image forming apparatus for carrying a toner image on which an electrostatic latent image based on image data is formed and developing the electrostatic latent image, and the surface of the carrier A developing unit that selectively attaches toner to the electrostatic latent image and develops the electrostatic latent image, and a control unit that controls driving of each unit such as a carrier and a developing unit according to received image data; , And an image forming apparatus for forming an image by transferring and fixing a toner image on the surface of the carrier onto a recording medium, wherein the developing device includes a container for storing toner and an outer peripheral surface of the carrier. A developing roller that causes the toner on the outer peripheral surface to adhere to the carrier by rotating while facing the surface, and a supply unit that supplies the toner in the container to the outer peripheral surface of the developing roller when the developing roller rotates. The control unit then receives the final image data received. Is an image formed on the rear end side of the recording medium, at one or both timings after the end of image formation of the final image data or before the start of image formation of image data received after the end of image formation. The developing roller of the developing device is idled.

In the present invention, when an image is formed on the rear end side of the final recording medium before shifting to the standby state, the developing roller is idly rotated after the final image formation is completed or before the next image formation is started. . Therefore, since toner development is performed near the final rotation of the developing roller, the toner on the outer peripheral surface of the developing roller may have uneven thickness and charge amount. Uniform toner can be deposited on the outer peripheral surface of the roller, and the toner can be developed with high quality.

In addition to the specific matters of the first invention, the second invention of the image forming apparatus that solves the above problems
The control unit is characterized in that when the image data is an image formed on the rear end side of the recording medium corresponding to about one round of the outer peripheral surface of the developing roller, the developing roller is idled.

In the present invention, when the image forming operation is stopped by toner development by the rotation of the final developing roller, the developing roller is idly rotated after the final image formation is completed or before the next image formation is started. . Therefore, toner development is performed with the final rotation of the developing roller without idlely rotating the developing roller, and unevenness that affects the quality of the next toner development on the toner thickness and charge amount on the outer peripheral surface of the toner is performed. When the toner is generated, the developing roller can be idled so that the uniform toner is attached, and the toner can be developed with high quality.

According to a third aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matter of the first or second aspect, the control unit is configured to control the surface of the recording medium for an image formed on the rear end side of the recording medium. The developing roller of the developing device is idled when the density of the toner is higher than a preset value.

In the present invention, when a large amount of toner is fixed on the rear end side of the final recording medium to form an image, the developing roller is idled after the final image formation or before the next image formation is started. .
Therefore, development is performed in which a large amount of toner adheres to the carrier in the vicinity of the final rotation of the developing roller without causing the developing roller to idle idly. When unevenness affecting the quality of toner development occurs, the developing roller can be idled so that uniform toner is attached, and toner development can be performed with high quality. be able to.

According to a fourth aspect of the image forming apparatus for solving the above problem, in addition to the specific matter of any one of the first to third aspects, the control unit includes means for acquiring information for deteriorating the toner, The developing roller of the developing unit is idly rotated based on the deterioration information of the toner.

In this invention, the temperature and humidity of the surrounding environment, the number of rotations of the developing roller, etc. exceed a preset value, such as exceeding a threshold value that deteriorates the charging characteristics of the toner, and on the rear end side of the final recording medium. When an image is formed, the developing roller is idly rotated after the final image formation or before the next image formation is started. Therefore, toner development is performed in the vicinity of the final rotation of the developing roller without idlingly rotating the developing roller, and the toner has poor charging characteristics. For example, when unevenness that affects the quality of the next toner development occurs, the developing roller can be idled so that uniform toner is adhered, and toner development is performed with high quality. You can get it.

According to a fifth aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matter of any of the first to fourth aspects, the control unit sets the developing roller of the developing device a preset number of times. It is characterized by only idling.

In the present invention, the developing roller can be idly rotated a set number of times after the final image formation is completed or before the next image formation is started. Therefore, even if unevenness occurs in the toner thickness or charge amount on the outer peripheral surface of the developing roller, the developing roller can be idled more than the number of times that the unevenness can be eliminated. A uniform toner can be deposited on the outer peripheral surface of the toner to make it possible to perform toner development with high quality.

According to a sixth aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matters of the first to fifth aspects, the control unit is configured to control the color of the toner stored in the container of the developing device. A means for acquiring information is provided, and when a preset color of a preset color toner is accommodated in the container, the developing roller of the developing unit is idled.

In the present invention, after the final image formation is completed or before the next image formation is started, only the developing roller of the developing device containing the specific toner can be idly rotated. Therefore, without rotating the developing roller idly, only the developing roller of the color toner whose unevenness such as the toner thickness and charge amount on the outer peripheral surface of the developing roller affects the quality of the next toner development is idled. The toner can be uniformly developed on the outer peripheral surface of the developing roller so that the toner can be developed with high quality.

As described above, according to the present invention, when the toner on the outer peripheral surface of the developing roller during standby is uneven, which affects the quality of the next toner development, the developing roller is idled. A uniform toner can be deposited on the outer peripheral surface of the developing roller. Therefore, even when the standby time is short, the electrostatic latent image on the surface of the carrier can be developed with high quality toner from the beginning of the next image formation, and high-quality image formation can be performed with high reliability.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best embodiment of the invention will be described with reference to the drawings. 1 to 4 are diagrams showing an embodiment of an image forming apparatus according to the present invention.

1 and 2, the image forming apparatus creates and outputs an image such as a character. For example, the image forming apparatus is used by being connected to a personal computer PC, and the control unit 10 connected to the personal computer PC has a paper sheet. By comprehensively controlling the conveyance device 20 and the image recording device 30, an image is formed on a recording sheet (recording medium) and printed out.

The control unit 10 includes a controller unit 11 and an engine control unit 12 which are constructed on a circuit board mounted in the apparatus main body. These units perform various data processing controls and various parts of the apparatus according to a program prepared in advance. The drive control is executed.

Briefly, the controller unit 11 executes various processing procedures according to a processing program stored in a memory by a CPU (not shown), thereby various information such as a print command with a printer driver of the personal computer PC. Are received, and image data such as text to be formed by printing on a recording sheet is received and temporarily stored in a memory (not shown). The controller unit 11 is so-called R (red) in which the image data (image information signal) received from the personal computer PC is red (R), green (G), or blue (B).
Since it is GB data, these are converted into image data of so-called YMCK data of yellow (Y), magenta (M), cyan (C), and black (K) that can be printed, and read out from the memory and engine. Transfer to the control unit 12.

In the engine control unit 12, the CPU 13 receives image data, for example, in units of pages from the controller unit 11 according to a control program stored in the ROM 14, temporarily stores it in the main body memory 15, and uses the RAM 16 as a work area. While exchanging various types of information between the paper transport device 20 and the image recording device 30, an image based on the image data is formed on the recording paper. At this time, when executing this image formation control, the CPU 13 causes each unit of the apparatus to operate optimally by measuring various processing times with a built-in timer function (timer) 13a.

In FIG. 2, the I / O interface 17 connects the controller unit 11, the sheet transport device 20, the image recording device 30, and the engine control unit 12 so that various types of information can be exchanged. The D / A converter 18 and the A / D converter 19 are configured so that the engine control unit 12 can process various information exchanged between the controller unit 11, the sheet conveying device 20, and the image recording device 30, respectively. The digital signal (D) is converted into an analog signal (A), or the analog signal is converted into a digital signal.

The paper transport device 20 includes a paper cassette 21, a paper discharge table 22, and a pickup roller 23.
In addition to the conveying roller pair 24, the registration roller pair 25, the switching roller pair 26, the paper discharge roller pair 27, and the reverse roller pairs 28 and 29, an intermediate transfer belt 34 that is also a component of the image recording apparatus 30, and a transfer The roller 35 and the fixing roller pair 36 are constructed. The sheet conveying apparatus 20 separates and conveys a plurality of recording sheets stacked in the sheet cassette 21 one by one and feeds them to the image recording position P1 by the image recording apparatus 30. After image data such as characters received on one side or both sides is recorded and formed, this image-formed recording paper is carried out of the apparatus and stacked on the paper discharge table 22.

Briefly, the pickup roller 23 pulls out the recording sheet by rotating against the recording sheet loaded on the lifting plate 21a in the sheet cassette 21 and cooperates with a separating means (not shown). The sheets are separated one by one and fed to the conveyance path f. Conveying roller pair 24
Squeezes and conveys the recording paper and abuts the leading end against the nip portion of the registration roller pair 25 on the downstream side to correct the skew. The registration roller pair 25 nipping and feeding the recording sheet to the image recording position P1 so as to synchronize with the operation of the image recording apparatus 30.

At the image recording position P1, the intermediate transfer belt 34 and the transfer roller 35 are transported by rotating while sandwiching the fed recording paper, and the image is formed in an image recording apparatus 30 described later. The toner image primarily transferred to the intermediate transfer belt 34 is secondarily transferred to one side of the recording paper to record and form an image. Also, the fixing roller pair 36
Is conveyed further downstream by rotating while sandwiching the recording paper,
The image is fixed on the recording paper.

Thereafter, the switching roller pair 26 and the discharge roller pair 27 carry the recording paper from the fixing roller pair 36 onto the discharge table 22 and stack it. As a result, the recording sheet is fed to the image recording formation position P1 by the image recording apparatus 30 with one side being the image recording formation surface, and is formed on one side and then discharged onto the discharge table 22. The

At this time, when the engine control unit 12 has instructed the duplex control mode for forming an image on both sides of the recording paper, the paper transport device 20 records the paper discharge roller pair 27 carried onto the paper discharge table 22. After temporarily stopping at a position where the trailing edge of the sheet is sandwiched, the recording sheet on which an image is recorded on one side is sent out to the reverse path r by being reversely driven together with the switching roller pair 26.

Thereafter, the reversing roller pair 28, 29 sandwiches the recording sheet and passes the sheet through the reversing path r.
By carrying the recording sheet, the recording paper with the front and back sides reversed with the trailing edge during the image formation on one side turned to the leading edge is fed again to the conveyance path f and transferred to the registration roller pair 25. As a result, the recording sheet is fed again to the image recording formation position P1 by the image recording apparatus 30 with the other side (one side on which no image recording is formed) as the image recording formation surface, and image formation is performed on both sides. Then, the paper is discharged onto the paper discharge table 22.

On the other hand, the image recording apparatus 30 includes an exposure unit 31, a photosensitive cartridge 32, a development rotary unit 33, an intermediate transfer belt 34, a transfer roller 35, and a fixing roller pair 36.
And. The image recording apparatus 30 records received image data such as characters on one or both sides of a recording sheet conveyed by the sheet conveying apparatus 20 and fed to the image recording formation position P1 by an electrophotographic method. Form.

Briefly, the exposure unit 31 has a photosensitive drum (photosensitive drum) in the photosensitive cartridge 32 (based on image data received by an internal laser beam scanning device (polygon mirror) 31a).
By carrying out exposure scanning by selectively irradiating the surface of the carrier 32a with laser light, an electrostatic latent image based on the image data is formed (imaged) on the surface of the photosensitive drum 32a. The developing rotary unit 33 develops the electrostatic latent image on the photosensitive drum 32a with yellow (Y), cyan (C), magenta (M), and black (K) toners for each color. Inside, 37y, 37c, 37m, and 37k) are detachably accommodated, and a developing cartridge (developing device) 37 corresponding to image data forming an electrostatic latent image is accommodated.
Is positioned at the development position P2 facing the photoconductor drum 32a, and the electrostatic latent image is toner-developed by adhering the accommodated toner.

For example, in the case of a monochrome image, the intermediate transfer belt 34 is primarily transferred with a toner image of black (K) toner formed on the photosensitive drum 32a at the transfer position P3 facing the photosensitive drum 32a. And a toner image (toner image) to be transferred onto the recording paper is held on the belt surface. In the case of a color image, the intermediate transfer belt 34 has yellow (Y), cyan (C), and magenta (M) formed on the photosensitive drum 32a.
) Are sequentially received at the transfer position P3 so as to be superimposed on the belt surface (the order is not limited to this), and a color toner image to be transferred onto the recording paper is formed and held. The transfer roller 35 is between this intermediate transfer belt 34 (image recording position P1).
The toner image is secondarily transferred to the recording paper by being nipped and conveyed so as to sandwich the recording paper fed to the recording paper. The toner transfers from the developing cartridge 37 to the recording paper via the photosensitive drum 32a and the intermediate transfer belt 34 in accordance with the bias voltage between the members.

The fixing roller pair 36 heat-presses the recording paper conveyed from the image recording formation position P1, thereby fixing the toner image developed and transferred at the development position P2 and the transfer position P3, and also fixing the recording paper. Further, it is nipped and conveyed downstream. As a result, the recording paper
A monochrome image or a color image based on the received image data is recorded (fixed) on one side or both sides, and by repeating such an operation, images can be continuously recorded on a plurality of sheets.

Note that the toner remaining on the photosensitive drum 32a after being transferred to the intermediate transfer belt 34 is discharged and collected by a cleaning device (not shown), and thereafter the toner is received from the developing cartridge 37 of the developing rotary unit 33 by a charger. Charged to the potential to be attached. Similarly, the intermediate transfer belt 34 is neutralized and charged to transfer (attach) toner.
The collection is repeated. Further, the toner scattered at the time of collection is collected by a filter 39 a attached to the exhaust duct 39 when the suction fan 38 sucks the apparatus main body side through the exhaust duct 39.

The developing rotary unit 33 stores a plurality of developing cartridges 37 for developing toner on the electrostatic latent image on the surface of the photosensitive drum 32a in a storing position partitioned by a partition frame 33b that rotates about a rotating shaft 33a. It is configured by mounting). The developing rotary unit 33 is rotated around a rotation shaft 33 a based on a print command including image data from the personal computer PC received by the CPU (control unit) 13 of the engine control unit 12 via the controller unit 11. As a result, the developing cartridge 37 at the developing position P2 facing the photosensitive drum 32a is switched to develop the toner image to be transferred onto one or both sides of the recording paper to form an image.

As illustrated in FIG. 3, the developing cartridge 37 includes a container 41, a developing roller 42, and a supply roller 43. The container 41 is a partition frame 3 of the developing rotary unit 33.
The toner T is formed in a similar shape so that it can be stored in each storage space (position) partitioned by 3b.
To accommodate. The developing roller 42 is rotatably supported on the outer peripheral side of the container 41 that is separated from the rotation shaft 33a of the developing rotary unit 33, and causes the toner T delivered from the supply roller 43 to adhere to the photosensitive drum 32a that faces the developing roller 42. The supply roller 43 is rotatably supported by the container 41 so as to be adjacent to the development roller 42 on the rotation shaft 33a side of the development rotary unit 33, and supplies the surrounding toner T by rotating in pressure contact with the development roller 42. To do. The container 41 of the developing cartridge 37 is arranged at a position adjacent to the supply roller 43 at a partition plate 41a.
The partition plate 41a partitions the toner T accommodation space in the container 41 in a state where the space on the rotary shaft 33a side and the upper portion of the installation space of the supply roller 43 are in communication with each other. That is, the supply roller 43 constitutes a general supply unit that supplies the toner T to the outer peripheral surface 42 a of the developing roller 42. Needless to say, the supply means is not limited to such a roller type, and may supply toner T by other methods.

With this configuration, the developing cartridge 37 is a container 41 partitioned by a partition plate 41a.
The toner T in the outer peripheral space is supplied to the developing roller 42 in which the supply roller 43 is pressed and rotated. Further, when the developing rotary unit 33 rotates by 90 degrees counterclockwise in FIG. 1 and rotates 180 degrees, the developing cartridge 37 rotates the rotating shaft 33a of the container 41.
The toner T contained on the side of the supply roller 43 and the supply roller 43 are combined together at the upper part of the partition plate 41a (lower part in FIG. 1), and then rotated 90 degrees to agitate and refresh the toner T contained in the container 41. At the same time, the stored toner T is collected on the supply roller 43 side so as to be supplied to the developing roller 42. That is, the developing rotary unit 33 rotating in this way
In the developing cartridge 37 attached to the toner cartridge, the stored toner T is replenished while being agitated toward the supply roller 43 by the rotation thereof. Apparatus and auger apparatus) can be omitted as appropriate. However, if the adjusting cartridge is omitted, the developing cartridge 37 has, for example, a count value by the toner counter, the number of dots of the image, at least before the toner T supplied to the developing roller 42 runs out of the periphery of the supplying roller 43. Integrated development operation (image formation) time,
When the usage amount of the toner T detected by the accumulated number of developments or the actually measured remaining amount of the toner T exceeds a preset value, the developing rotary unit 33 is rotated to supply and agitate the toner T. Need to do.

Further, the developing cartridge 37 exposes the developing roller 42 from the inside of the container 41 so as to face the photosensitive drum 32a at the developing position P2, and the outer peripheral surface 4 of the developing roller 42 is exposed.
In the gap defined between the opening 2a and the container 41, a sealing member 44 that is urged by the urging member 44a and press-contacts the outer peripheral surface 42a, and is urged by the urging member 45a. A regulating blade 45 that is in pressure contact with the outer peripheral surface 42a is disposed. The seal member 44 prevents the toner T from leaking out of the container 41 and the developing roller 42 that has passed through the developing position.
The toner T on the outer peripheral surface 42a is collected in the container 41 without being scraped off. Further, the regulating blade 45 adjusts the flat portion on the rear end side with respect to the edge on the front end side so as to be in pressure contact with the surface of the outer peripheral surface 42a of the developing roller 42. The thickness is controlled to be constant while scraping off at the side edge. Here, the toner T on the outer peripheral surface 42 a of the developing roller 42 is charged by applying a preset charging voltage to the regulating blade 45, and the supply roller 43 is charged by the developing roller 42.
Even when rotating in pressure contact, frictional charging occurs.

Further, the intermediate transfer belt 34 is formed in an endless belt shape that is wound around a primary transfer pulley 51, a secondary transfer pulley 52, a driven pulley 53, and tension pulleys 54 and 55. The primary transfer pulley 51 is disposed at a transfer position P3 where the developed toner image on the photosensitive drum 32a is primarily transferred to the intermediate transfer belt 34. The primary transfer pulley 51 is placed on the photosensitive drum 32a on the back side of the intermediate transfer belt 34. Face to face. The secondary transfer pulley 52 is disposed at a recording formation position P1 where the toner image on the intermediate transfer belt 34 that has been primarily transferred is secondarily transferred to a recording sheet between the transfer roller 35 and an image is recorded. It faces the transfer roller 35 on the back side of the intermediate transfer belt 34. The driven pulley 53 is disposed on the opposite side of the secondary transfer pulley 52 and is rotated by the rotation of the intermediate transfer belt 34. The tension pulleys 54 and 55 are disposed on both sides of the intermediate transfer belt 34 between the secondary transfer pulley 52 and the driven pulley 53, and tension is applied from the back side thereof so that the intermediate transfer belt 34 does not cause a positional shift or the like. Is multiplied.

The intermediate transfer belt 34 is provided with, for example, a not-shown protruding piece (so-called shim) that protrudes outward in the planar direction on one side, and the sensor 56 detects this protruding piece every rotation. As a result, the CPU 13 of the engine control unit 12 controls the rotation drive so as to synchronize with the rotation of the photosensitive drum 32a and the conveyance of the recording paper. Thereby, the intermediate transfer belt 34 is moved to the transfer roller 35.
The photosensitive drum is rotated so as to face the recording sheet conveyed to the recording formation position P1 of the image facing the drum and to repeatedly circulate through the path between the transfer positions P3 facing the photosensitive drum 32a. The toner images of the respective color toners formed on 32a are received at the transfer position P3 and transferred to the recording paper at the image recording formation position P1.

In this manner, the intermediate transfer belt 34 rotates and rotates, whereas the developing rotary unit 33 develops a toner image, particularly when forming a color image.
Need to be switched sequentially. For this reason, the intermediate transfer belt 34 is set longer than the size of the recording paper on which the color image is formed, and holds the toner image to be transferred to the recording paper, whereas the developing rotary unit 33 It is necessary to complete the switching operation of the developing cartridge 37 while the toner image on the intermediate transfer belt 34 rotates between the trailing edge and the leading edge (between the trailing edge and the leading edge of the recording paper, so-called paper). There is.

The developing cartridge 37 includes a nonvolatile memory 46 and a developing-side connector 47, and a control-side connector 48 is disposed on the developing rotary unit 33 body side. The non-volatile memory 46 can rewrite various information such as the color of toner to be stored, the date of manufacture, and the amount of consumption, in addition to the identification number such as the manufacturing number, in addition to the number of mounting and recycling of the developing cartridge 37 itself. The development-side connector 47 is connected to the nonvolatile memory 46 and reads and rewrites the stored information. The control side connector 48 is
It is installed so as not to move to the inner wall surface of the developing rotary unit 33, and when it faces the developing side connector 47 of any of the developing cartridges 37, various information is exchanged by non-contact communication. Thereby, the engine control unit 12 of the control unit 10 appropriately grasps various information such as the color information of the toner of the developing cartridge 37 together with the presence or absence and position of the developing cartridge 37 stored in the storing position of the developing rotary unit 33. Then, image forming control including optimal switching control of the developing cartridge 37 is executed.

The CPU 13 of the engine control unit 12 executes various control operations according to the control program in the ROM 14 after the power is turned on.
7 is exchanged via the connectors 47 and 48 so that the presence / absence of the developing cartridge 37 at the storage position of the developing rotary unit 33, the number of times it is mounted, the number of recycling, etc. are held (stored) in the main body memory 15. To do. Further, the CPU 13 sequentially reads out various information written in the nonvolatile memory 46 of each developing cartridge 37 via the connectors 47 and 48, and position information for each developing cartridge 37, toner color information and consumption. The amount (remaining amount) is stored in the main body memory 15. Further, the CPU 13 writes various information such as the amount of toner consumed by the image formation into the nonvolatile memory 46 of each developing cartridge 37 via the connectors 47 and 48 during the image forming operation or after the image formation is completed. rewrite.

In other words, each time the CPU 13 receives a print command for image data, the CPU 13 sets each color toner mounted on the development rotary unit 33 according to the type of image based on the image data, the position where the image is formed on the recording paper, and the like. The developing cartridge 37 is appropriately switched to rewrite various information in the nonvolatile memory 46, and the developing roller 42, the supply roller 43, and the like are rotationally driven at a preset driving timing, thereby exposing a uniform toner image. A high quality image is formed on the recording drum through the intermediate transfer belt 34 formed on the body drum 32a.

Specifically, when the CPU 13 receives a print command of image data for recording and forming a color image on a recording sheet from the controller unit 11, an image having a density equal to or higher than a preset density is set at the rear end of the recording sheet of the last page. It is confirmed whether or not the image data is formed using black (K) toner, and the drive timing of the developing cartridge 37k containing the black (K) toner is switched to operate. In short, the developing cartridge 37k has image data when there is no image at the trailing edge of the recording paper, or when it is image data that consumes almost no black (K) toner even if there is an image. After formation (after development of electrostatic latent image)
In general drive control for stopping the developing roller 42 as it is, toner is adhered to the outer peripheral surface 42a of the developing roller 42, which has developed the electrostatic latent image on the photosensitive drum 32a, and refreshed and replenished. Stop in state. On the other hand, in the case of image data that forms an image having a density equal to or higher than the set density at the trailing edge of the recording paper of the last page before shifting to the standby state, the drive operation of all the developing cartridges 37 is controlled equally. In general drive control, rotation of the electrostatic latent image on the photosensitive drum 32a is stopped without causing toner to adhere to the outer peripheral surface 42a of the developing roller 42 of the developing cartridge 37k and developing and replenishing the toner. Therefore, in such a case, the CPU 13 has an outer peripheral surface 4 of the developing roller 42 in such a case.
Drive control for performing an operation of refreshing and replenishing toner on 2a is executed.

For example, when the peripheral length of the developing roller 42 is 40 mm and the developing roller 42 is further rotated by 15 mm after stopping from the area of the photosensitive drum 32 a corresponding to the trailing edge of the recording paper, the CPU 13 stops. Is rotated from the supply roller 43 by black (K
) Includes the image data of the rear end portion of the recording paper developed by the outer peripheral surface 42a of the developing roller 42 for 35 mm to which no toner is supplied, and at the same time, the dot count duty of the image data of the rear end portion is the set value. The outer peripheral surface 42 of the developing roller 42 is 50% or more.
Drive control for refreshing and replenishing toner on a is selected and executed. The threshold for determining whether or not to perform the drive control is not limited to the count duty, and may be determined based on other conditions.
Needless to say, the count duty value may be changed from 50%. Further, the refreshing / replenishment of the toner on the outer peripheral surface 42a of the developing roller 42 is not limited to black (K), and may be executed for the developing cartridge 37 that contains toner of other colors. Not too long.

Then, when the CPU 13 receives the image data for forming an image of the set density or higher using the black (K) toner on the trailing edge of the recording paper of the last page immediately before the standby in this way,
As shown in FIG. 4, the development rotary unit 33 is driven following the start of driving of the photosensitive drum 32a, the intermediate transfer belt 34, and the like. At this time, the CPU 13 develops the electrostatic latent image on the photosensitive drum 32a and transfers the toner image formed by the development onto the recording paper via the intermediate transfer belt 34 (primary / secondary transfer). And a sensor 56 for detecting a protruding piece (shim) of the intermediate transfer belt 34.
The developing roller 42 is driven so as to synchronize the developing operation by the developing cartridge 37k with the sensor signal (Vsync) from and the developing roller 42 is idled at a preset timing. That is, when the CPU 13 forms an image having a density equal to or higher than the set density on the trailing edge of the recording paper of the last page immediately before standby using the black (K) toner, immediately after the end of the image forming operation, and Before the start of the next image forming operation, the developing roller 42 of the developing cartridge 37k is rotated once (set number of times) or more. From the charging efficiency of the black (K) toner, preferably two or more rotations are performed. It is set to idle.

Therefore, without causing the developing roller 42 of the developing cartridges 37y, 37c, and 37m to idle idlely, toner nonuniformity (thickness and charge amount) is difficult to be resolved immediately, and the development quality of black (K) is easily affected. Developing roller 4 of developing cartridge 37k that contains toner
2 can be idly rotated after and before the image forming operation, and can be idly rotated as many times as necessary to make a uniform toner adhere to the outer peripheral surface 42a of the developing roller 42. Further, even in the case of image data using black (K) toner, the developing cartridge 37k is used only when the image has a density equal to or higher than the set density at the trailing edge of the recording paper of the last page immediately before standby.
The developing roller 42 can be idly rotated, and the toner contained therein is prevented from deteriorating due to unnecessary rotation of the developing roller 42 (non-empty idling rotation), and on the outer peripheral surface 42a of the developing roller 42. It is possible to eliminate toner unevenness and to develop the electrostatic latent image on the photosensitive drum 32a with high quality.

In detail, the developing rotary unit 33 sets the developing roller 42 of the developing cartridge 37k containing the black (K) toner to the photosensitive drum 32a when the CPU 13 is in a standby state of the developing operation when the image data is not received from the controller unit 11. Development position P2 facing
The developer roller 37 is rotated counterclockwise by 120 degrees (the developing cartridge 37k is turned upside down), and the developing rollers 42 and the like of all the developing cartridges 37 are positioned at a home position (HP) that is disengaged from a driving gear train (not shown). ing.

When the CPU 13 receives a print command during this standby time, in the image forming operation immediately before the standby time, an image having a set density or higher is formed using the black (K) toner at the rear end of the recording paper. First, when the developing rotary unit 33 rotates counterclockwise from the home position to the developing position P2 where the developing cartridge 37k faces the photosensitive drum 32a, the developing roller 42 and the like mesh with the drive gear train. Then, by starting to rotate before the timing when the electrostatic latent image is formed on the photosensitive drum 32a, the developing roller 42 of the developing cartridge 37k is idled to replenish the toner on the outer peripheral surface 42a.・
Let me refresh.

As a result, even if there is unevenness in the toner thickness or charge amount on the outer peripheral surface 42a of the developing roller 42 of the developing cartridge 37k after the development of the last page of the previous image forming operation, even in a short waiting time, Before starting the image forming operation of the received image data, the developing roller 42 can be idled to eliminate the unevenness of the toner and make it uniform, and on the photosensitive drum 32a from the start of the image forming operation. The electrostatic latent image can be developed with high quality. here,
As will be described later, the developing roller 42 of the developing cartridge 37k completes the developing operation when an image having a set density or higher is formed on the trailing edge of the recording paper of the last page using black (K) toner. Since the idle rotation is performed later, it may be performed only once so that the toner thickness and charge amount on the outer peripheral surface 42a become uniform. However, considering the charging efficiency of the black (K) toner, the time If allowed, it is preferable to make two or more revolutions.

The developing rotary unit 33 performs a general image forming operation as it is after the idling rotation of the developing roller 42 of the developing cartridge 37k. The developing rotary unit 33 uses the developing cartridge 37k to perform development using black (K) toner. When the operation is completed, the developing roller 42 of the developing cartridge 37m that accommodates the next magenta (M) toner is rotated 90 degrees counterclockwise, and the developing roller 42 is positioned at the developing position P2 facing the photosensitive drum 32a. The same operation is repeated. At this time, when the developing cartridge 37m is located at the developing position P2, the developing rotary unit 33 rotates the developing cartridge 37k that has performed the developing operation immediately before by 90 degrees, so that the developing connector 47 is connected to the control side on the main body side. Since the connector 48 faces the connector 48 so that non-contact communication is possible, the CPU 13 rewrites the storage information in the nonvolatile memory 46 by integrating the driving time of the developing roller 42 and the toner consumption.

The developing rotary unit 33 is the last yellow (
Y) the developing roller 42 of the developing cartridge 37y containing the toner of the photosensitive drum 32a.
Even after the developing operation is performed at the developing position P2 facing the surface, the developing side connector 47 and the control side connector 4 are rotated by 90 degrees counterclockwise.
8 and the CPU 13 rewrites the stored information in the nonvolatile memory 46 of the developing cartridge 37y, and then rotates 120 degrees so as to be in the home position (HP) and shifts to a standby state.

At this time, if the CPU 13 has received image data for recording and forming an image of a set density or higher using black (K) toner at the trailing edge of the recording paper of the last page in this image forming operation, In parallel with the rewriting operation of the developing cartridge 37y into the non-volatile memory 46, the developing roller 42 of the developing cartridge 37k that is located at the developing position P2 facing the photosensitive drum 32a and meshes with the drive gear train is driven to rotate (empty). The toner is replenished and refreshed on the outer peripheral surface 42a.

Thus, when the image forming operation is completed and the standby state is entered even for a short time, the toner thickness on the outer peripheral surface 42a of the developing roller 42 of the developing cartridge 37k is developed after the development of the last page of the image forming operation. Even if there is unevenness in the amount of charge or the like, in parallel with the rewriting operation of the nonvolatile memory 46 without specially securing a dedicated time (before receiving image data after waiting and starting the image forming operation) The developing roller 42 can be idled to eliminate the unevenness of the toner to make it uniform, and the electrostatic latent image on the photosensitive drum 32a can be developed with high quality from the start of the image forming operation. . Here, as described above, the developing roller 42 of the developing cartridge 37k waits when an image having a set density or more is formed using the black (K) toner at the rear end portion of the recording paper of the last page. Since the idle rotation is again performed before the start of the next subsequent developing operation, the thickness of the toner on the outer peripheral surface 42a, the charge amount, etc. are made uniform.
It may be merely rotated, but considering the charging efficiency of the black (K) toner, it is preferable to rotate it twice or more if time permits.

As described above, in this embodiment, the developing roller 42 of the developing cartridge 37k does not stop and wait while the toner thickness and the charge amount on the outer peripheral surface 42a are uneven.
The developing roller 42 can be idly rotated after the image forming operation (development operation) in which such unevenness occurs or before the next image forming operation is started. Therefore, the developing roller 42 of the developing cartridge 37k can wait in a state where the toner is evenly charged on the outer peripheral surface 42a and is charged, and can start the next development. Photosensitive drum 3
The electrostatic latent image on 2a can be developed with high quality toner with black (K) toner.

As another aspect of the present embodiment, toner refresh / replenishment as in the present embodiment may be executed according to other conditions. In short, the thickness of the black (K) toner adhering to the outer peripheral surface 42a of the developing roller 42 of the developing cartridge 37k and the unevenness of the charge amount are problems. For example, the ambient temperature and humidity are very high. When the charging characteristics of the toner are reduced (deteriorated), or the toner characteristics are deteriorated by being accommodated in the developing cartridge 37 for a long period of time and repeatedly being pressed between the developing roller 42 and the supply roller 43. In such a case, since such unevenness is likely to occur, when the threshold value of these conditions is exceeded,
The toner refresh and replenishment of this embodiment may be executed, or the set rotation speed of the developing roller 42 in the control operation may be increased.

Specifically, a temperature / humidity sensor is provided, and when the temperature / humidity of the surrounding environment detected by the sensor exceeds a threshold value, or the number of times that the developing cartridge 37k stored in the nonvolatile memory 46 is mounted or recycled Charging characteristics are deteriorated by exceeding the threshold and being exposed to the outside air for a long time and absorbing moisture, or the driving time of the developing roller 42 and the amount of toner consumption are exceeding the threshold and charging characteristics due to friction When the toner is lowered, the CPU 13 executes the idling rotation of the developing roller 42 on the assumption that there is a possibility that uniform toner cannot be deposited on the outer peripheral surface 42a of the developing roller 42.

That is, in this case, the temperature / humidity sensor or the CPU 13 functions as a means for acquiring toner deterioration information, and the developing roller 42 of the developing cartridge 37k can be idled, and the developing roller 42 is idly rotated. When the charging characteristics of the toner are reduced without deteriorating the contained toner, the developing roller 42 is idly rotated so that uniform toner is adhered on the outer peripheral surface 42a, and high-quality toner development is executed. Can do.

Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

For example, in the above-described embodiment, when an image is formed on the rear end side of the recording paper of the last page immediately before standby, the developing roller of the developing cartridge 37k is at both the timing after the end of the image formation and before the start of the next image formation. 42 is idly rotated, but the present invention is not limited to this, and it goes without saying that the developing roller 42 may be idly rotated only at any one timing.

Further, an example of an image forming apparatus in which a plurality of developing cartridges 37 are set in the developing rotary unit 33 and a toner image formed on the photosensitive drum 32a is transferred to a recording sheet via the intermediate transfer belt 34 to form an image. However, the present invention is not limited to this, and it goes without saying that the present invention can also be applied to an apparatus that transfers and forms a toner image directly from a photosensitive drum onto a recording sheet.

Further, in the above-described embodiment, although not specifically described, as described in the above-mentioned document 1, when the toner is left for a long time, the developing roller 42 of the developing cartridge 37 is rotated idly to perform high-quality toner development. Needless to say, this is preferable.

1 is a perspective front view showing a schematic overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a related block diagram explaining the control part. It is a longitudinal cross-sectional view which shows the principal part structure. It is a timing chart explaining the drive control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control unit 11 Controller part 12 Engine control part 15 Main body memory 20 Paper conveyance apparatus 21 Paper cassette 22 Paper discharge table 25 Registration roller pair 30 Image recording apparatus 31 Exposure unit 32a Photosensitive drum 33 Development rotary unit 34 Intermediate transfer belt 35 Transfer roller 36 Fixing roller pair 37, 37c, 37k, 37m, 37y Developing cartridge 41 Container 42 Developing roller 43 Supply roller 44 Sealing member 45 Restricting blade 46 Non-volatile memory 47 Developing side connector 48 Control side connector P1 Recording forming position P2 Developing position P3 Transfer position

Claims (6)

An electrostatic latent image based on the image data is formed on the surface, and a carrier carrying a toner image obtained by developing the electrostatic latent image; and toner is selectively attached to the electrostatic latent image on the surface of the carrier. A developing unit that develops the electrostatic latent image, and a control unit that controls driving of each part of the apparatus such as the carrier and the developing unit according to the received image data, and the toner image on the surface of the carrier is recorded on the recording medium. An image forming apparatus for forming an image by transferring and fixing,
The developing device includes a container for storing toner, a developing roller that causes the toner on the outer peripheral surface to adhere to the carrier by rotating while the outer peripheral surface faces the carrier, and the developing roller when the developing roller rotates. Supply means for supplying toner in the container to the outer peripheral surface of
When the received final image data is an image formed on the rear end side of the recording medium, the control unit performs image formation of the image data received after completion of image formation of the final image data or after completion of image formation. An image forming apparatus, wherein a developing roller of a developing device is idly rotated at one or both timings before starting. 2. The control unit according to claim 1, wherein when the image data is an image formed on the rear end side of the recording medium corresponding to about one round of the outer circumferential surface of the developing roller, the developing roller is idled.
The image forming apparatus described in 1. The control unit idle-rotates the developing roller of the developing device when the density of the image formed on the rear end side of the recording medium occupies the surface of the recording medium is higher than a preset value. The image forming apparatus according to claim 1 or 2. The said control part is provided with a means to acquire the information which degrades a toner, and rotates the developing roller of a developing device idly based on the degradation information of this toner. Image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the controller rotates the developing roller of the developing unit idly for a preset number of times. The control unit includes means for acquiring color information of the toner stored in the container of the developing device, and when the preset color toner is stored in the container, the developing unit 6. The image forming apparatus according to claim 1, wherein the developing roller of the container is idled.

Images