JPH10319672A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operability in changing a color developing device by preventing the fixing of a developing rotary from being released when a position detection means detects that a developing device locking member exists at the position capable of detaching the developing device. SOLUTION: The developing rotary 23 trisected in a peripheral direction is provided with guide rails in an axial direction at the trisected parts, and the respective color developing devices 20Y, 20M and 20C are attached/detached by sliding on the guide rails from the axial direction respectively. A fixing member 40 is movably arranged to be located at the position being away from the notched part 43a of the rotary 23 as shown by a thin line and the position to be engaged with the notched part 43a as shown by a solid line at the attaching/detaching position of the developing devices 20Y, 20M and 20C. The member 40 is arranged in a driving device so as to be moved toward the notched part 43a to be engaged with the notched part 43a according to a signal showing that a reflection type sensor 42 detects the release of a locking lever at the position capable of detaching the developing device 20Y by the locking lever.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type color image forming apparatus such as a color copying machine or a color printer.

[0002]

The present invention is a further development of the prior art described below.

An object of the present invention is to provide a color image forming apparatus provided with a rotary developing device having improved operability of replacing a color developing device.

[0004]

According to a first aspect of the present invention, there is provided an electrophotographic photosensitive drum and a plurality of developing units, wherein a toner image is formed on the electrophotographic photosensitive drum and transferred onto a transfer material. In the color image forming apparatus for creating a color image, each of the developing units is detachable, and each developing unit is located at a position where the latent image on the electrophotographic photosensitive drum is developed opposite to the electrophotographic photosensitive drum. A developing rotary for rotating the developing device and moving any of the developing devices to the attaching / detaching position without facing any of the electrophotographic photosensitive drums; an indexing rotation means of the developing rotary; A fixing means for fixing the developing rotary when the developing rotary is in the mounting / removing position, a position for preventing the developing rotary on the developing rotary from being removed, and a removable position. An imager locking member, position detecting means for detecting the position of the developing device locking member, an opening provided in the image forming apparatus main body for attaching and detaching the developing device to and from a developing rotary, and opening and closing for opening and closing the opening A fixing means for fixing the developing rotary when the developing device is stopped at the attachment / detachment position, and the position detecting means sets the position at which the developing device lock member can remove the developing device. The color image forming apparatus is characterized in that the fixing of the developing rotary is not released when it is detected that

According to a second aspect of the present invention, there is provided a color image forming apparatus according to the first aspect, wherein the position detecting means of the developing device locking member is a non-contact detecting means with respect to the developing device locking member. Device.

A third invention according to the present application is the color image forming apparatus according to the second invention, wherein the position detecting means of the developing device lock member is a reflection type optical sensor.

According to a fourth aspect of the present invention, there is provided the color image forming apparatus according to the first aspect, wherein the driving means of the developing rotary does not operate when the opening / closing member covering the opening is open. is there.

According to a fifth aspect of the present invention, the opening / closing member is attached to a lower edge of the opening and is supported at an open position in the axial direction of the developing rotary, and can support a developing unit to be detached. A color image forming apparatus according to a fourth aspect of the present invention.

A sixth invention according to the present application is the first to fifth inventions wherein the developing rotary includes guide means for detachably mounting a developing device in an axial direction, and the developing device locking member. The color image forming apparatus according to any one of the above.

According to a seventh aspect of the present invention, the developing device lock member is provided at a position operable from an opening of the image forming apparatus main body when the developing rotary is at a mounting / removing position of the developing device. A color image forming apparatus according to a sixth aspect, characterized in that:

An eighth invention according to the present application is the color image forming apparatus according to the sixth or seventh invention, wherein the developing device locking member is a lever.

A ninth invention according to the present application is characterized in that the developing device locking member has a position overlapping the developing device and a position not overlapping when viewed from the axial direction of the developing rotary. A color image forming apparatus according to any one of the aspects of the invention.

According to a tenth aspect of the present invention, in the color image forming apparatus according to the second or third aspect, the position detecting means of the developing device lock member is provided in the image forming apparatus main body. It is.

According to an eleventh aspect of the present invention, the fixing means for the developing rotary includes a notch provided on the circumference of the developing rotary by a number equal to the number of the developing devices, and a position fitted to the notch. The color image forming apparatus according to the first aspect of the present invention is a fixing member provided on the image forming apparatus main body so as to be able to advance and retreat to a position where it does not fit.

According to a twelfth aspect of the present invention, the developing device is a developing cartridge in which a toner container for storing black or color toner and a developing member for supplying the toner to an electrophotographic photosensitive drum are integrated. The color image forming apparatus according to any one of the first to eleventh aspects of the present invention, further comprising a developing rotary detachably mounted.

[0016]

2. Description of the Related Art Conventionally, a color image forming apparatus has a rotary developing device, a plurality of color developing devices are mounted on a developing rotary, indexed and rotated, and one color developing device is provided to a photosensitive drum. The process of developing the latent image on the photoconductor drum and transferring it to the intermediate transfer member was repeated, and yellow and
There is a type in which magenta, cyan, and black toner images are superimposed, and the toner image on the intermediate transfer body is collectively transferred to a recording medium.

In such a color image forming apparatus, when the toner in each developing unit is exhausted, the developing unit formed into a cartridge is replaced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to the present invention will be described below with reference to the drawings.

[Overall Description of Image Forming Apparatus] First, the overall configuration of a color image forming apparatus will be schematically described with reference to FIG. FIG. 1 is an explanatory diagram of the overall configuration of a laser printer which is an embodiment of a color image forming apparatus.

As shown in FIG. 1, the color laser printer includes an image forming section including a photosensitive drum of an image carrier rotating at a constant speed, a fixed black developing device, and three rotatable color developing devices. An intermediate transfer member that holds the color image that has been developed and multi-transferred in the forming section, and further transfers the color image to the transfer material 2 fed from the feeding section. The transfer material 2 onto which the color image has been transferred is then conveyed to the fixing unit 25 to fix the color image on the transfer material 2 and discharged to a discharge tray 37 on the upper surface of the apparatus by a discharge roller. The rotatable color developing device and the fixed black developing device are configured to be individually detachable from the printer main body.

Next, the structure of each section of the image forming apparatus will be described in detail sequentially.

[Process Cartridge] The process cartridge 13 is a container 1 of a cleaning device that also serves as an image carrier (photosensitive drum) 15 and a holder for the photosensitive drum 15.
4 and the process cartridge 13
Is detachably supported by the apparatus main body 24 and is configured to be easily replaceable in accordance with the life of the photosensitive drum 15. Photosensitive drum 1 according to the present embodiment
Reference numeral 5 denotes an aluminum cylinder having a diameter of about 60 mm, which is formed by coating an organic conductive layer on the outside, and is rotatably supported by a container 14 of a cleaning device also serving as a holder for the photosensitive drum 15. A cleaning blade 16 and a primary charging unit 17 are arranged around the photoconductor drum 15, and the driving force of a drive motor (not shown) is transmitted to one end on the rear side of FIG. It is rotated counterclockwise in the figure according to the forming operation.

[Charging Means] The charging means 17 uses a contact charging method.
The surface of the photosensitive drum 15 is uniformly charged by applying a voltage to the conductive roller.

[Exposure Means] Exposure to the photosensitive drum 15 is performed from a scanner unit 30. That is, when an image signal is given to the laser diode, the laser diode emits image light corresponding to the image signal to the polygon mirror 31.
Irradiation. The polygon mirror 31 is rotated at a high speed by a scanner motor, and the image light reflected by the polygon mirror 31 selectively exposes the surface of the photosensitive drum 15 rotating at a constant speed through the imaging lens 32 and the reflection mirror 33 to thereby expose the surface. As a result, an electrostatic latent image is formed on the photosensitive drum 15.

[Developing Means] The developing means comprises three rotary developing devices 20Y, 20M, 20M, and 20M capable of developing each color of yellow, magenta and cyan in order to visualize the electrostatic latent image.
20C, and one black developing device 21B
And developing means 21 having

The black developing device 21B is a fixed developing device. A developing sleeve 21BS is arranged at a position facing the photosensitive drum 15 at a minute interval (about 300 μm) with respect to the photosensitive drum 15. To form a visible image.

The black developing device 21B feeds the toner in the container by a feeding mechanism, and applies a thin layer of toner to the outer periphery of the developing sleeve 21BS rotating clockwise in the figure by an application blade 21BB pressed against the outer periphery of the developing sleeve 21BS. In addition, charge is applied to the toner (frictional charging). Further, by applying a developing bias to the developing sleeve 21BS, toner development is performed corresponding to the electrostatic latent image on the photosensitive drum 15.

Three rotary developing units 20Y, 20M, 20C
Are detachably held by a developing rotary 23 which rotates about a shaft 22. Each of the developing devices 2
0Y, 20M, and 20C rotate around the shaft 22 while being held by the developing rotary 23.
The developing sleeve is stopped at a position facing the photosensitive drum 15 and the developing sleeve is positioned so as to face the photosensitive drum 15 at a small interval (about 300 μm). Form a visible image. At the time of forming a color image, the developing rotary 23 rotates for each rotation of the intermediate transfer member 9, and the yellow developing device 20Y, the magenta developing device 20M, the cyan developing device 20C, and then the black developing device 20
The developing process is performed in the order of B.

FIG. 1 shows a state in which the yellow rotary developing device 20Y is positioned at a position facing the photosensitive drum 15 and is stationary. The yellow developing device 20Y sends the toner in the container to the coating roller 20YR by a feeding mechanism, and the coating roller 20YR rotating clockwise in the drawing and the blade 20 pressed against the outer circumference of the developing sleeve 20YS.
Developing sleeve 20 rotated clockwise by YB
A thin layer of toner is applied to the outer periphery of the YS, and a charge is applied to the toner (frictional charging). By applying a developing bias to the developing sleeve 20YS facing the photosensitive drum 15 on which the latent image is formed, toner development is performed on the photosensitive drum 15 in accordance with the latent image. Magenta developer 20
M and cyan developing units 20C also perform toner development by the same mechanism as described above.

Each of the rotary developing devices 20Y, 20M, 20C
Each of the developing sleeves 20YS, 20MS, and 20CS is connected to a developing high-voltage power supply and a drive provided in the apparatus main body 24 when each developing device is rotated to the developing position.
A voltage is sequentially and selectively applied for each color development, and driving is connected.

The drive rotary 23 is a rotary rotary shaft 2
2 to be rotatably supported. The developing rotary 23 has a guide rail (not shown) extending in the circumferential direction at three equal intervals in the circumferential direction, and each of the developing units 20Y and 20
0M and 20C are respectively attached and detached by sliding from the axial direction. The developing rotary 23 is a driving device (not shown) provided in the apparatus main body 24, and any one of the developing sleeves 20YS, 20MS, and 20CS of the developing units 20Y, 20M, and 20C faces the photosensitive drum 15 to perform predetermined developing. It is indexed and rotated every 120 degrees so as to face each other with a gap. Further, the developing sleeve 20 is rotated by 60 degrees with respect to the indexing position, and takes a position where none of the developing sleeves 20YS, 20MS, and 20CS is opposed to the photosensitive drum 15.

As shown in FIG. 2, the developing sleeve 20YS,
At an indexing position where neither 20MS nor 20CS is opposed to the photosensitive drum 15, the developing rotary 23 is at an axial position of one developing device (in this example, a yellow developing device 20Y), and an opening through which the yellow developing device 20Y can enter and exit. Figure 2,
As shown in FIG. 3, provided on the outer cover 38 of the apparatus main body 24, the developing device attaching / detaching opening 1 of the developing devices 20Y, 20M, and 20C.
8 is set. An opening / closing door 19 is provided at the lower edge of the opening / closing opening 18 which is pivotally connected to the lower side by a hinge (not shown). Have been. When the opening / closing door 19 is opened, the developing devices 20Y, 20M, 2
The direction of attachment / detachment to / from the development rotary 23 of the OC coincides with the plate surface, and the developing units 20Y, 20M and 20C are partially supported to facilitate attachment / detachment.

The outer periphery of the flange 43 of the developing rotary 23 is provided with a notch 43a on which the fixing member 40 can be engaged in three equal parts on the periphery. The notch 43a is provided in the developing device 20.
Y, 20M, 20C developing sleeves 20YS, 20M
Neither S nor 20CS opposes the photosensitive drum 15,
At the position shown in FIG. 2 where any of the developing devices 20Y, 20M, and 20C can be attached to and detached from the developing device attaching / detaching port 18, the fixing member 40 is provided.
Position.

The fixing member 40 is located at a position away from the notch 43a of the developing rotary 23 as shown by a thin line in FIG. 2 and at a position where the developing units 20Y, 20M and 20C are attached and detached as shown by a solid line in FIG. It is movably provided so as to take a position where it fits. When the lock lever 41 is in a position where the developing device 20Y can be removed, the reflection type optical sensor 42 moves toward the notch 43a in accordance with a signal indicating that the lock lever 41 has been released, and is fixed to the notch 43a. It is arranged on a driving device (not shown) so as to match.

The lock lever 41 is rotatably attached to the developing rotary 23 with a pin 41a. The lock lever 41 is in contact with the end plate of the developing device (yellow developing device 20Y in FIG. 2) and the outside of the developing device not in contact with the end plate. It takes a position. When viewed from the axial direction of the developing rotary 23, the developing device and the lock lever 41 take a locked position where the developing device and the lock lever 41 overlap and a non-locking position where the locking lever 41 does not overlap.

Here, the developing rotary 23 is rotated by a driving means such as a motor (not shown), and the developing devices of the respective colors are sequentially moved to positions opposing the photosensitive drum 15.

On the other hand, when the color developing device 20Y is replaced, the developing sleeve 20CS of the color developing device 20C as shown in FIG.

At this time, the opening / closing door 1 that covers the developing device attaching / detaching opening 18
When the shutter 9 is opened, a switch (not shown) that operates in conjunction with the opening / closing door 19 is operated to turn off the power of the rotary drive means and prevent the developing rotary 23 from rotating during the operation of taking out the developing device.

When the opening / closing door 19 is opened, the fixing member 40 of the developing rotary 23 is engaged with the notch 43a of the flange 43 on the outer periphery of the developing rotary 23 at this time. .

Further, the color developing device is fixed to the developing rotary 23 by the lock lever 41, and the color developing device can be taken out only after releasing this. FIG. 3 to FIG.
The side view of arrow A of FIG.

The developing device and the developing rotary 23 are provided with guide strips that engage with each other in the axial direction. The developing device is moved in the axial direction of the developing rotary 23 toward the near side perpendicular to the plane of FIG. Withdraw through 18. Thereafter, a new developing device is mounted in the axial direction of the developing rotary 23 through the developing device attaching / detaching opening 18 and is mounted.

After the replacement of the developing device is completed, the lock lever 41 is returned to the locked position, the opening / closing door 19 is closed, and the developing rotary 23 is moved to the position where the next developing device is taken out, or the developing rotary 23 is operated for normal developing operation. Before the rotation, the fixing member 40 is released. Before that, the position of the lock lever 41 is detected by the reflection type optical sensor 42 disposed in front of the lock lever 41, and if the lock lever 41 is in the unlocked position. If it is 41a, the fixing member 40 is not released, and the user is notified of this by means of a display device or the like (not shown). This reflection type optical sensor 42 is attached to the apparatus main body 24. The detection of the position of the lock lever 41 is not limited to the reflection type optical sensor 42.
Any means may be used as long as it is a non-contact detecting means.

Therefore, when the lock lever 41 is not at the lock position, the developing rotary 23 cannot rotate, so that a failure such as damage to the apparatus due to the developing device falling out during the rotation of the developing rotary 23 can be prevented. .

FIG. 4 is a flowchart showing this series of operations.

[Intermediate Transfer Body] In the intermediate transfer body 9, during the color image forming operation, the toner image on the photosensitive drum 15 visualized by each developing device is printed four times (each image of four colors of Y, M, C, and B). 1) to receive multiple transfer over
5 rotates clockwise in the figure in synchronization with the outer peripheral speed of the transfer member 5, and the intermediate transfer member 9 that has received the multiple transfer sandwiches the transfer material 2 with the transfer roller 10 to which a voltage is applied and conveys the intermediate transfer member 2 to the transfer material 2 Each color toner image on the transfer body 9 is simultaneously multiplex-transferred.

The intermediate transfer member 9 according to the present embodiment has a structure in which an outer periphery of an aluminum cylinder 12 having a diameter of 180 mm is covered with an elastic layer 11 such as a medium resistance sponge or a medium resistance rubber. The intermediate transfer member 9 is driven by a gear (not shown) which is rotatably supported and integrally fixed, and rotates.

[Cleaning Unit] The cleaning unit transfers the toner visualized on the photosensitive drum 15 to the intermediate transfer member 9 by the developing unit.
This is for cleaning the remaining toner, and the cleaned waste toner is stored in the cleaning container 14. The amount of waste toner stored in the container 14 does not fill the container 14 earlier than the life of the photosensitive drum 15, and therefore, the cleaning container 14 is simultaneously replaced when the life of the photosensitive drum 15 is replaced.

[Sheet Feeding Section] The sheet feeding section transfers the transfer material 2 to the image forming section.
From a paper cassette 1 containing a plurality of transfer materials 2, a paper feed roller 3, a feed roller 4, a retard roller 5 for preventing double feed, a paper feed guide plate 6, and a registration roller 8. Mainly composed. At the time of image formation, the paper feed roller 3 is driven and rotated in accordance with the image forming operation, separates and feeds the transfer material 2 in the paper feed cassette 1 one by one, and is guided by the paper feed guide plate 6 to move the transport roller 7. Through the registration roller 8. During the image forming operation, the registration roller 8 performs a non-rotating operation of stopping the transfer material 2 in a standby state and a rotating operation of transporting the transfer material 2 toward the intermediate transfer body 9 in a predetermined sequence, which is the next step. The image and the transfer material 2 at the time of the transfer step are aligned.

[Transfer Section] The transfer section comprises a transfer roller 10 which can swing.

The transfer roller 10 has a metal shaft wound around a medium-resistance foamed elastic material, and can move up and down in the figure and has driving. While forming the four-color toner image on the intermediate transfer member 9, that is, while the intermediate transfer member 9 rotates a plurality of times, the transfer roller 10 is positioned below as shown by a solid line in the drawing so as not to disturb the image. It is separated from the intermediate transfer member 9. After the four color toner images have been formed on the intermediate transfer member 9, the transfer roller 10 is pushed up by a cam member (not shown) to an upper position 10 b shown by a thin line in FIG. Then, it is pressed against the intermediate transfer body 9 via the transfer material 2 with a predetermined pressure. At this time, the toner image on the intermediate transfer body 9 to which the bias is applied to the transfer roller 10 is simultaneously transferred to the transfer material 2. Here, the intermediate transfer member 9
Since the transfer material 2 and the transfer roller 10 are driven respectively, the transfer material 2 sandwiched between them is conveyed at a predetermined speed to the left in the drawing at the same time as the transfer process is performed, and is transferred to the fixing unit 25 which is the next process. Sent to.

[Fixing Unit] The fixing unit 25 is provided with the developing unit 2
The toner image formed on the transfer material 2 is fixed on the transfer material 2 via the intermediate transfer member 9 with the toner image formed by the transfer media 0 and 21. As shown in FIG. A roller 26 and a pressure roller 27 for pressing the transfer material 2 against the fixing roller 26. Each roller is a hollow roller, and has a heater 28, 2 inside.
9 and is configured to be driven to rotate and to simultaneously transfer the transfer material 2.

That is, the transfer material 2 holding the toner image is conveyed by the fixing roller 26 and the pressure roller 27 and is subjected to heat and pressure so that the toner is transferred to the transfer material 2.
Is established.

[Image Forming Operation] Next, the operation in the case where an image is formed by the apparatus configured as described above will be described.

First, the paper feed roller 3 shown in FIG. 1 is rotated to separate one sheet of the transfer material 2 in the paper feed cassette 1 and transported to the registration roller 8.

On the other hand, the photosensitive drum 15 and the intermediate transfer member 9 rotate at the outer peripheral speed V of 75.4 mm / sec (hereinafter referred to as process speed) in the direction of the arrow shown in the figure. 60m diameter
m photoreceptor drum 15 makes one rotation at 60π / 75.4 = 2.5 seconds, and the intermediate transfer member 9 having a diameter of 180 mm is 180π /
One revolution in 75.4 = 7.5 seconds. Also, the photosensitive drum 1
5 and the intermediate transfer member 9 are connected by a gear (not shown), so that when the photosensitive drum 15 makes three rotations, the intermediate transfer member 9 makes one full rotation.

When an arbitrary point on the outer periphery of the intermediate transfer member 9 comes to the position S shown in FIG. 5, the photosensitive drum 15 whose surface is uniformly charged by the charging means 17 is exposed to the laser at the position E shown in FIG. Then, an image is formed. Photoconductor drum 1
5, the distance a from the exposure position E to the contact portion T1 with the intermediate transfer member 9 in the clockwise direction is equal to the distance b from the point S to T1 of the intermediate transfer member 9 in the clockwise direction. E and the point S on the intermediate transfer member 9 coincide at the position of T1. That is, an image is formed counterclockwise with respect to the intermediate transfer member 9 with the point S as a tip. 1: Formation of Yellow Image Laser irradiation of the yellow image is performed by the scanner unit 30 to form a yellow latent image on the photosensitive drum 15.
Simultaneously with the formation of the latent image, the yellow developing device 20Y is driven to apply a voltage having the same polarity and substantially the same potential as the charging polarity of the photoconductor drum 15 so that yellow toner adheres to the latent image on the photoconductor drum 15, and the yellow image is formed. Perform development. At the same time, the yellow toner image on the photosensitive drum 15 is primarily transferred to the outer periphery of the intermediate transfer member 9 at the first transfer position T1 downstream of the developing section. At this time, a voltage having a characteristic opposite to that of the yellow toner is applied to the intermediate transfer body 9 to perform primary transfer.

The image to be formed is the size A of Japanese Industrial Standard paper.
In the case of three sizes, the long side is 420 mm long, and an image is formed from the outer periphery S point of the intermediate transfer body 9 to the L1 point. See the thick line on the outer periphery of the intermediate transfer member 9 in FIG. When the transfer of the yellow toner to the intermediate transfer member 9 is completed, that is, when the point L1 has passed the first transfer position T1, the developing rotary 23 rotates clockwise, and the next magenta developing device 20M rotates.
It is positioned at a position facing the photosensitive drum 15. 2: Formation of Magenta Image Next, when one point S (the tip of the yellow image) on the outer periphery of the intermediate transfer member 9 makes a round and reaches the position shown in FIG. Similarly, a magenta toner image is developed on the latent image on the photosensitive drum 15, and the magenta toner image on the photosensitive drum 15 is similarly transferred onto the intermediate transfer body 9 at the first transfer position T1. When the transfer of the magenta toner to the intermediate transfer member 9 is completed, that is, when the point L1 has passed the first transfer position T1, the developing rotary 23 rotates clockwise, and the next cyan developing device 20C rotates, and the photosensitive drum 20C rotates. 15 are positioned. 3: Formation of Cyan Image Next, when one point S (the leading end of the yellow and magenta images) on the outer periphery of the intermediate transfer member 9 reaches the position shown in FIG. Then, a cyan toner image is developed on the latent image on the photosensitive drum 15 in the same manner as magenta, and the cyan toner on the photosensitive drum 15 is transferred to the intermediate transfer member 9 at the first transfer position T1 by yellow and magenta toner images. And transfer it. When the transfer of the cyan toner to the intermediate transfer member 9 is completed, that is, when the point L1 has passed the first transfer position T1, the developing rotary 23 rotates clockwise by 60 degrees and the position facing the photosensitive drum 15 is moved to the color developing position. There is no vessel. 4: Formation of Black Image Next, when one point S (the leading end of the yellow / magenta / cyan image) on the outer periphery of the intermediate transfer member 9 further makes a round and reaches the position shown in FIG. Is started and then the black developer 2
1B develops the black toner, and the photosensitive drum 1
5 is further superimposedly transferred onto the intermediate transfer body 9 at the first transfer position T1.

The formation of the latent image and the transfer of the toner to the intermediate transfer member 9 are sequentially performed four times in the order of yellow, magenta, cyan, and black, and the four surfaces of yellow, magenta, cyan, and black are formed on the surface of the intermediate transfer member 9. Thus, a full-color image composed of various kinds of toner is formed.

Before the transfer of the black toner to the intermediate transfer member 9 is completed, that is, the image transfer end T of the intermediate transfer member 9 having completed the first transfer of the fourth color black toner and forming a full-color image is the second transfer portion T2. Before the transfer, the transfer material 2 which has been waiting by the above-described registration roller 8 is conveyed and started at the same timing. The above four intermediate transfer members 9
At the time of forming each color image on the upper side, the transfer roller 10 which waits downward and is in a non-contact state with the intermediate transfer body 9 is simultaneously moved upward by a cam (not shown) to move the transfer material 2 to the second side of the intermediate transfer body 9. The full-color image on the intermediate transfer body 9 is simultaneously transferred to the transfer material 2 at a stretch by applying a bias having a characteristic opposite to that of the toner to the transfer roller 10 at the same time as pressing the transfer portion T2. The transfer material 2 that has passed through the second transfer portion T2 is an intermediate transfer member 9
After being separated from the sheet and conveyed to the fixing section 25 to fix the toner, the sheet is discharged onto a discharge tray 37 on the upper portion of the apparatus main body 24 via discharge rollers 34, 35, and 36 with the image surface facing downward, and the image forming operation is performed. finish.

It can be understood that the intermediate transfer member 9 basically requires four rotation operations and a time required for the rotation operation of 30 seconds (7.5 seconds × 4) to produce one full-color image. . Incidentally, the intermediate transfer member 9 and the photosensitive drum 15 whose outer peripheral speed V are driven equally are inversely proportional to the outer shape ratio of the intermediate transfer member 9 for forming one full-color image.
Rotate.

The intermediate transfer body 9 has a diameter of 180 mm and an outer circumference of about 565 mm, and a peripheral length of 420 mm is used for forming an A3-size image. That is, the distance from the outer peripheral point S of the intermediate transfer body 9 to the point L1 in the counterclockwise direction is 420 mm.
It is. See the thick line on the outer periphery of the intermediate transfer member 9 in FIG. That is, of the 565 mm outer circumference of the intermediate transfer member 9, 42
0 mm is used, and the remaining 145 mm is not used for image formation. The intermediate transfer member 9 has a constant process speed V = 75.
Since the image is rotated at 4 mm / sec, a non-image forming time of 145 / 75.4 = 1.92 seconds exists for forming an A3-size full-color image, and the color developing units 20Y, 20M,
20C switching time. Photoconductor drum 15
The actual timing of the time allocated for the developing unit 20Y located between the laser exposure unit E and the first transfer unit T1 to form a visible image and replace the next developing unit 20M is shifted. However, this corresponds to the time from the point L1 of the intermediate transfer member 9 passing through the first transfer portion T1 to the next point S reaching the first transfer portion T1.

In the above embodiment, the color image forming apparatus in which the color developing device is attached and detached in the axial direction of the developing rotary is described. However, the present invention is similarly applied to the case where the developing device is attached and detached in the radial direction of the developing rotary. You. In addition, three color developing units
Although the color image forming apparatus of the type mounted on the developing rotary has been described, the present invention is applied to a color image forming apparatus in which four developing devices of a color developing device and a black developing device are detachably mounted on the developing rotary.

According to the present invention, it is possible to easily replace the color developing device, and it is possible to prevent a failure of the apparatus due to an erroneous operation, thereby improving usability.

[0064]

[Examples] This is also described in the description of the embodiments.

[0065]

According to the present invention, it is possible to easily replace the color developing device, and to prevent a failure of the apparatus due to an erroneous operation, thereby improving usability.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a color laser printer according to the present invention.

FIG. 2 is a front view of a developing rotary.

FIG. 3 is a view taken in the direction of arrow A in FIG. 2;

FIG. 4 is a flowchart illustrating the operation of the present invention.

FIG. 5 is a partially enlarged view of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Paper feed cassette 2 ... Transfer material 3 ... Paper feed roller 4 ... Feed roller 5 ... Retard roller 6 ... Paper feed guide 7 ... Transport roller 8 ... Registration roller 9 ... Intermediate transfer body 10 ... Transfer roller 10b ... Position 11 ... Elasticity Layer 12 Aluminum cylinder 13 Process cartridge 14 Container 15 Photoconductor drum 16 Cleaning blade 17 Charging means 18 Developing unit opening / closing door 20 Opening door 20 Developing unit 20Y Yellow developing unit 20YB Coating blade 2
0YR: coating roller 20YS: developing sleeve 20M: magenta developing device 20MB: coating blade 2
0MS: developing sleeve 20C: cyan developing device 20CB: coating blade 20
CS: developing sleeve 21: developing means 21B: black developing device 21BB: coating blade 21BR: coating roller 21BS: developing sleeve 22: rotary shaft 23: developing rotary 24: apparatus body 25: fixing unit 26: fixing roller 27: pressurizing Rollers 28, 29 Heater 30 Scanner unit 31 Polygon mirror 32 Lens 33 Reflection mirror 34, 35, 36 Discharge roller 37 Discharge tray 38 Exterior cover 40 Fixing member 41 Lock lever 41a Pin 42 Reflection type optical sensor 43 ... Flange 43a ... Notch

Claims (12)

[Claims] 1. A color image forming apparatus having an electrophotographic photosensitive drum and a plurality of developing units, wherein a color image is formed by forming a toner image on the electrophotographic photosensitive drum and transferring the toner image onto a transfer material. Each of the developing units is detachable, and each developing unit is rotationally moved to a position where the developing unit develops a latent image on the electrophotographic photosensitive drum opposite to the electrophotographic photosensitive drum. A developing rotary for moving any of the developing devices to the mounting / removing position without facing the photographic photosensitive drum; an indexing rotation unit of the developing device rotary; and fixing the developing rotary when the developing rotary is at the mounting / removing position of the developing device. Fixing means for fixing the developing device on the developing rotary so that the developing device cannot be removed, a developing device lock member taking a removable position, and a developing device lock. A position detecting means for detecting a position of the member, an opening provided in the image forming apparatus main body for attaching and detaching the developing device to and from the developing rotary, and an opening and closing member for opening and closing the opening, the developing rotary The fixing means operates when the developing device is stopped at the attaching / detaching position to fix the developing rotary, and when the position detecting means detects that the developing device lock member is at a position where the developing device can be removed, the developing device is stopped. A color image forming apparatus, wherein a fixing means of a rotary is not released. 2. The color image forming apparatus according to claim 1, wherein the position detecting means of the developing device locking member is a detecting device that does not contact the developing device locking member. 3. The color image forming apparatus according to claim 2, wherein the position detecting means of the developing device lock member is a reflection type optical sensor. 4. The color image forming apparatus according to claim 1, wherein when the opening / closing member covering the opening is open, the driving means of the developing rotary does not operate. 5. The developing device according to claim 1, wherein the opening and closing member is attached to a lower edge of the opening and is supported at an open position in an axial direction of a developing rotary, and can support a developing unit to be detached. 5. The color image forming apparatus according to 4. 6. The collar according to claim 1, wherein the developing rotary includes guide means for detachably mounting a developing device in an axial direction, and the developing device locking member. Image forming device. 7. The image forming apparatus according to claim 6, wherein the developing device lock member is disposed at a position operable from an opening of the image forming apparatus main body when the developing rotary is at a mounting / removing position of the developing device. 3. The color image forming apparatus according to 1. 8. The color image forming apparatus according to claim 6, wherein said developing device lock member is a lever. 9. The developing device locking member according to claim 6, wherein the developing device locking member has a position overlapping with the developing device when viewed from the axial direction of the developing rotary and a position not overlapping with the developing device.
6. A color image forming apparatus according to any one of the preceding claims. 10. The color image forming apparatus according to claim 2, wherein the position detecting means of the developing device lock member is provided in an image forming apparatus main body. 11. The developing rotary fixing means includes a notch provided in a number equal to the number of developing devices on a circumference of the developing rotary, a position where the notch is fitted, and a position where the notch is not fitted. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a fixing member provided on the image forming apparatus main body so as to be able to advance and retreat. 12. The developing device includes a developing rotary which is detachably mounted as a developing cartridge in which a toner container for storing black or color toner and a developing member for supplying the toner to the electrophotographic photosensitive drum are integrated. The color image forming apparatus according to claim 1, further comprising: