JPS60233666A - Image forming device - Google Patents

Abstract

PURPOSE:To extend maintenance cycle by changing over automatically a developing device under use to the other developing device when abnormality in developer life, etc. arises in said developing device. CONSTITUTION:A remaining developer quantity detector 1172 detects the remaining quantity of the developer while a permanent magnet 120 attached to an actuator 119 integral with a detecting lever 118 to be turned and displaced according to the remaining quantity of the developer makes access to a reed switch 121 on the outside of a hopper 512 when the quantity of the developer G2 in a hopper 512 of the 2nd developing device 322 decreases to a prescribed value or below. A device similar to the detector 1172 is provided to the hopper of the 1st developing device as well. The rotating quantity (time) of sleeves 441, 442 constituting developing rollers 311, 312 is measured and the integrated time meter as a life display is lighted and displayed on cover bodies 1331, 1332 together with the display for absence of the developer from the remaining quantity detectors 171, 172. A developer replenishing roller 521 or 522 is driven by the signals from developer concn. detectors 421, 422 when the developer density in the developing device decreases to the value below the preset value, by which the automatic replenishment of the developer is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus such as a color copying machine capable of making color copies of a plurality of colors.

[Technical Background of the Invention and Problems Therewith] In recent years, for example, copying machines have become more and more colored, and two-color color copying machines that can obtain images in colors other than black have been put into practical use.

However, in conventional color copying machines of this type, multiple cartridges that integrate a developing device and a photoreceptor are prepared and selectively replaced, which has the problem of being extremely troublesome to operate. .

Recently, however, it has become possible to make color copies of various colors by installing a plurality of removable developing devices each capable of developing different colors, and by selecting one or more of the developing devices. A color copying machine is being considered. In such a copying machine, if an abnormality such as developer life occurs in the developing device in use, another developing device is automatically selected, preferably a developing device containing developer of the same color. If you can switch to that developer,
It is possible to lengthen the maintenance cycle of the developing device and is very convenient.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and its object is to provide an extremely convenient image forming apparatus that can lengthen the maintenance cycle of the developing device.

[Summary of the invention! ! ] In order to achieve the above object, the present invention is designed to automatically switch to another developing device when an abnormality such as developer life occurs in the developing device in use.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a two-color copying machine as an example of an image forming apparatus according to the present invention. That is, 1 is a copying machine main body'', and the upper surface of this main body 1 is
A document table 2 is provided which can freely reciprocate in the direction (direction). Further, a paper feed cassette 3 is attached to the right side of the main body 1, and a paper discharge tray 4 is attached to the left side. The cassette cover 5 of the paper feed cassette 3 serves as a manual feeding table 6 for manually feeding paper P2 as appropriate.

Further, a photosensitive drum 7 is disposed approximately in the center of the main body 1. The photosensitive drum 7 is surrounded by a charging device 8, an optical system 9, and a two-color developing device W to be described later.
110, a transfer charger 11, a peeling charger 12, a cleaning device 13, a static elimination lamp 14, and the like are arranged in this order. Further, in the lower part of the main body 1, paper Pi automatically taken out from the paper feed cassette 3 via the paper feed roller 15 or paper P2 manually fed from the manual feed table 6 is placed between the photoreceptor drum 7 and the charged plate for transfer. Image forming section 16 between the container 11
A paper transport path 17 is formed that leads to the paper discharge tray 4 via the paper. A registration roller 18 is disposed on the upstream side of the image transfer section 16 of the paper conveyance path 17, and a heat roller 19 and a paper discharge roller 20 as a fixing device are disposed on the downstream side.

Here, the optical system 9 has an exposure lamp 22 whose back portion is surrounded by a reflector 21, mirrors 23 to 26, and a lens 27.

The photosensitive drum 7 is driven by a drive mechanism (not shown) in the direction indicated by the arrow in the drawing in synchronization with the document table 2. First, the exposure lamp 2 is uniformly charged by the charging device 8.
2, the image of the document uniformly illuminated with light t14 is transferred to the optical system 9.
An image is formed on the photoreceptor drum 7 to form an electrostatic latent image. This formed electrostatic latent image is developed into a developer image by the developing device M10, and sent to the transfer charger 11 side. On the other hand, paper P fed automatically or manually
1 or P2 is supplied by the registration row 518,
A developer image previously formed on the photoreceptor drum 7 is transferred by a transfer charger 11 .

The paper PI (P2) to which this developer image has been transferred is peeled off from the photoreceptor drum 7 by a peeling charger 12, passes through a paper conveyance path 17, and is guided to a heat roller 19, where the transferred image is melted. After being fixed, the paper is discharged to the paper discharge tray 4 by the paper discharge roller 20.

On the other hand, after the developer image is transferred onto the paper PI (P2), the residual toner remaining on the photoreceptor drum 7 is removed by a cleaning device! 13, and the remaining image on the photosensitive drum 7 is erased by a static elimination lamp 14, in preparation for the next copying operation.

In the main body 1, an upper frame and a lower frame (not shown) are pivotally supported at one end via a support shaft (not shown), and the other ends of both frames are rotated at a desired angle, for example, about 30 degrees. It is configured so that it can be opened to The upper frame includes, around the photoreceptor drum 7, a charging device 8, an optical system 9, an exposure lamp 22, a developing device 10,
Respective devices such as an R mount 13 and a static elimination lamp 14 are attached by appropriate means, and a document table 2 and a paper feed roller 15 are also attached to the upper frame.
It constitutes A. Further, in the lower frame, various mechanisms such as a paper feed cassette 3, a transfer charger 11, a peeling charger 12, a heat roller 19, a paper ejection roller 20, a paper ejection tray 4, a main motor 28, etc. are installed as appropriate means. is attached to constitute the lower unit 1B. and,
After the front 1 cover of the main body 1 is rotated and removed, it can be opened and closed almost along the paper conveyance path 17 of the paper PI (P2) via a housing opening/closing device (not shown).

Further, 29 is a cleaning blade 30 of the cleaning device 13.
This is a blade solenoid for bringing the photoconductor drum 7 into contact with and separating it from the photoreceptor drum 7.

Next, details of the developing device 10 will be explained. Second
As detailed in the figure, the first developing roller 311 and the second developing roller 311
It has a developing roller 312, and these developing rollers 311, 3
12 selectively drives black or one other color,
For example, color development such as red, yellow, blue, and green can be performed.

That is, the developing device 10 includes a first developing device 321 including a first developing row 5311 and a second developing device 321 including a second developing roller 312.
The developing unit 322 is divided into two parts, and these first and second developing units are divided into two parts.
The developing devices 321 and 322 are both detachable from the main body 1. In this case, the first developing device 32s in the upper stage is configured to be easily attached and detached so that the user can pull it out upward in the figure, and the second developing device 322 in the lower stage can be maintained and inspected by a service person. It has a structure that allows it to be overlooked with respect to the main body 1 when performing this. The frequently used black developer is used in the second developing device 322 in the lower stage, and the color developer is used in the first developing device 321 in the upper stage.

The first developing device 32 includes a developing mechanism section 331 and a developer replenishing section 341. Above current ** structure part 33
1 is provided on the upstream side of the developing roller 31s and the photosensitive drum 7 where the developer magnetic brush 351 formed on the surface of the developing roller 311 slides, that is, the developing position 361; and a developer magnetic brush 35 provided on the surface of the developing roller 311 downstream of the developing position 361.
Scrap the village, Ili! Image agent image storage section 381 scraper 391. The developer agitating body 401 accommodated in the developer accommodating portion 381 is housed in a casing 411. Note that the developing roller 3 of the casing 411
A developer concentration detector 421 is attached at a position corresponding to the upper portion of the developer G1 to detect the developer concentration by magnetically detecting changes in the magnetic permeability of the developer G1.

The developing roller 311 is a magnetic roll whose center is located on a straight line L2 that passes through the center of rotation of the photoreceptor drum 7 and forms an angle α (approximately 51°) with respect to the horizontal line L1. 431, and a sleeve 441 that is fitted onto the magnetic roll 431 and rotates clockwise in the figure. The magnetic roll 431 has five magnetic pole parts 451 to 491, of which magnetic pole parts 451 and 47
1.491 is the N pole, and the magnetic pole parts 46t and 48t are the S poles. The angle θ1 between the magnetic pole parts 455 and 461 is approximately 50°, and the angle θ2 between the magnetic pole parts 461 and 471 is Approximately 71°, the angle θ3 between magnetic pole parts 47 and 481 is approximately 6
0°, the angle θ4 between the magnetic pole parts 481 and 491 is approximately 60
° respectively.

Further, the developer replenishment section 341 includes a developer replenishment port 501.
A hopper 511 facing the developer storage section 381 of the developing mechanism section 331, and a developer replenishment roller 5 disposed within the hopper 511 and closing the developer replenishment port 501.
21, and the developer G on the developer supply roller 521 side.
The configuration includes a pair of stirring rollers 53r and 531 that stir the developer Gl in the hopper 511 so as to convey the developer Gl.

Further, the second developing device 322 is similar to the first developing device 322 described above.
It has almost the same basic configuration as 1, and the developer supply section 34
2, the shape of the hopper 512, the arrangement structure of the magnetic poles of the magnetic roll 432 of the developing roller 312, the mounting position of the developer concentration detector 422, and the accompanying narrow width (approximately 50 #II
The difference is that a scraper 54 having an inclination of approximately 20° is added. Therefore, other identical components will be designated by the reference numerals with the letter "1" changed from "1" to "2", and detailed description thereof will be omitted. Note that the magnetic roll 432 of the developing roller 312 has four magnetic pole parts 452 to 4.
82, of which the magnetic pole parts 452 and 472 are N poles,
The magnetic pole part 46'2.482 is an S pole, and the magnetic pole part 4
The angle θ5 between 52 and 462 is approximately 78°, and the magnetic pole portion 46
The angle θ6 between 2 and 472 is about 70°, and the magnetic pole part 472
and 482 are set to approximately 80". Also, the magnetic roll 432
The angle β (approximately 1e
), with the center located on the line l1IL3.

On the other hand, each of the magnetic rolls 431 and 432 of the first developing device 321 and the second developing device 322 is configured to be able to rotate at a rotation angle of approximately 25 degrees. Due to the displacement operation, the developing roller 311.3
Developer magnetic brushes 351 and 352 can be formed on and removed from the surface of 12. and,
By switching the magnetic rolls 431 and 432 of the first developing device 321 and the second developing device 322 to a predetermined position by a magnetic roll driving means described later, the developing device of either the first developing device 321 or the second developing device 322 is operated. roller 3
Developer magnetic brush 351.3 only on the surface of 11,312
52 is formed.

That is, when operating the first developing device 321 side,
As shown in FIG. 2, the magnetic roll 4 on the first developing device 321 side
31 as the magnetic pole part 47! A doctor 37 is placed approximately halfway between the magnetic pole portions 451 and 461 while facing the developing position 361.
1 is positioned, and the magnetic roll 432 on the second developing device 322 side is set so that the magnetic pole portion 452 faces the doctor 372. The developer magnetic brush 351 is formed only on the surface of the developing roller 311 on the first developing device 321 side.

In addition, when operating the second developing device 322 side, the third developing device 322 side is operated.
As shown in the figure, a magnetic roll 431 on the side of the first developing device 321
is rotated approximately 25 degrees clockwise from the position shown in FIG. 2 so that the magnetic pole part 451 faces the doctor 371, and the magnetic roll 432 on the second developing unit 322 is moved counterclockwise from the position shown in FIG. The doctor 372 is rotated approximately 25 degrees so that the doctor 372 is positioned approximately midway between the magnetic pole portions 452 and 462. The developer magnetic brush 35 is formed only on the surface of the developing roller 312 on the second developing device 322 side.

In addition, the magnetic pole portions 451.4 of the magnetic rolls 43s and 432
The reason why the developer magnetic brushes 351, 352 are not formed on the surface of the developing roller 311, 312 when the developer roller 311, 312 is opposed to the doctors 371, 372 made of non-magnetic material is because the tn magnetic brush density is low at the magnetic pole portions 451, 452. This is because the force to adsorb the developers G1 and G2 is weak because they are in a canal state, and therefore they can be easily regulated by the doctor blades 371 and 372. Even when the sleeves 441 and 442 rotate, the developer G1-
9G2 never passes through the doctor part 371 and 372.

By the way, each driving section of the first developing device 321, that is, the sleeve 441 of the developing roller 311, the developer stirring body 401,
A driving force is transmitted to the developer replenishing roller 521 via a first driving force transmission system 61, which will be described later. Further, driving force is transmitted to each drive unit of the second developing device 322, that is, the sleeve 442 of the developing roller 312, and the developer stirring body 402 via a second driving force transmission system 62, which will be described later. . The first and second driving force transmission systems 61.
Reference numeral 62 has a configuration as shown in FIGS. 4 to 6, and a rotatable motor 63 serving as a common driving source rotates forward or reverse.

Only the drive system of one of the first and second developing units 321 and 322 is selectively operated.

Hereinafter, the driving force transmission system will be explained in detail with reference to FIGS. 4 to 6. The first driving force transmission system 61 includes an intermediate gear 65 that meshes with a driving gear 64, a first driven gear 66 that meshes with this intermediate gear 65, an intermediate gear 67 that meshes with this driven gear 66, and this intermediate gear 67. The second meshing with
It has a driven gear 68. Further, the second driving force transmission system 62 includes a third driven gear 69 that meshes with the driving gear 64.
, an intermediate gear 70 that meshes with these six driven gears, and a fourth driven gear 71 that meshes with this intermediate gear 70. Then, when the drive gear 64 rotates normally, that is, in the direction of the solid line arrow in FIG.
71 rotate in the direction of the solid line arrow, and the drive gear 64 rotates in the reverse direction, that is, in the direction of the broken line arrow B in FIG. Each of the gears 69 to 71 of the system 62 rotates in the direction of the dashed arrow.

Further, the first driven gear 66 is connected to the drive shaft 721 that is integrated with the sleeve 441 of the first developing roller 311, and the second driven gear 68
are attached to the drive shafts 731 of the developer stirring body 405 via one-way clutches 74, 74, respectively, and the teeth 166, 68 of each of the drive shafts 721, 731 rotate in the direction of the solid line arrow, that is, drive The driving force is transmitted only when the gear 64 rotates in the normal direction, and the gear 64 rotates in the direction of the dashed line arrow. Further, the third driven gear 69 is connected to the drive shaft 722 that is integrated with the sleeve 442 of the second developing roller 312, and the fourth driven gear 71 is connected to the drive shaft 722 of the developer stirring rod 402.
2 through one-way clutches 75, 75, and each drive shaft 722, 732 is connected to a gear 69.
．． 71 respectively rotate in the direction of the dashed line arrow, that is, only when the drive gear 64 is reversed, the driving force is transmitted and the drive gear 64 rotates in the direction of the dashed-dotted line arrow.

Further, the driving gear 64 has a bearing 7 as shown in FIG.
The drive shaft 78 of the reversible motor 63 is rotatably supported via the gear mechanism 77.
It is attached to a rotating shaft 79 that interlocks with the. That is,
A gear 80 is attached to the rotating shaft 79, and the gear 80 is rotatably mounted on a support shaft 83 installed between a motor mounting frame 81 and a stay 82 integrated therewith via bearings 84, 84. It meshes with the attached gear 85. A gear 86 having a larger diameter than the gear 85 is integrally formed with the gear 85, and the gear 86 is attached to the oscillator motor 63.
The gear 87 is in mesh with the gear 87 attached to the drive shaft 78. Thus, the rotation of the drive shaft 78 of the reversible motor 63 in both forward and reverse directions is transmitted to the rotation shaft 79 via the gears 87, 86, 85, 80.
21.degree. 322 can be selectively operated simply by switching the reversible motor 63 between forward and reverse rotation.

Note that switching between forward and reverse rotation of the reversible motor 63 is performed by pressing a color selection key on the operation panel, which will be described later, and at this time, the non-operating magnetic roll 431. The magnetic pole parts 45t and 452 of 43.2 can be switched to face the doctors 371 and 372.

Further, an intermediate gear 65 that meshes with the driving gear 64 and the first driven gear 66 is rotatably attached to a support shaft 89 via a bearing 88.

The eight supporting shafts are bearings 76°76 that pivotally support the rotating shaft 79.
It is attached to an arm 91 that can swing around a rotation center of a housing 90 that holds the It has become.

Further, one stirring roller 531 of the first developing device 32r is
The stirring roller 531 is intermittently driven via a first operating mechanism 921 shown in FIG.
The other stirring roller 531 and developer replenishing roller 521 are simultaneously driven in conjunction with the movement. That is, the first developing device 32! One stirring roller 53 of
! A ratchet gear 941 is attached to one end of the shaft 931, and this ratchet gear 941 is connected to the solenoid 9.
5! It is intermittently driven by a predetermined amount via a ratchet claw 971 attached to a swinging arm 961 that rotates in conjunction with the on/off operations of the switch. Further, sprockets (not shown) are fitted to the shafts 931.98 of the stirring rollers 531, 531 and the shaft 991 of the developer replenishing roller 521, respectively, and an endless chain (not shown) is strung around them. The stirring roller 531 is connected via this driving force transmission system (not shown).
and developer supply roller 521 are driven together.

Further, the stirring roller 532 and the developer replenishing roller 522 of the second developing device 322 are simultaneously driven intermittently through a second operating mechanism 922 having the same configuration as the first operating mechanism 921 and a driving force transmission system having approximately the same configuration. It is now possible to do so. Note that the same constituent parts as the first actuation mechanism 921 are given the reference numerals with the suffix character changed from "1" to "2", and detailed explanation thereof will be omitted.

Next, a magnetic roll driving means 100r (1002) is used to rotationally displace the magnetic roll 43t (432) in order to form or remove the developer magnetic brush 351 (352) on the surface of the developing roller 311 (312'). The configuration will be explained with reference to FIGS. 7 to 9(a) and (b). The shaft 1011 (101) of the magnetic roll 431 (432)
2) One end 1, the bearing 1 attached to the frame 102
03, and a lever 10 is attached to the tip of the shaft.
4 is installed. The tip 11 of this lever 104,
An arm 10 rotatably mounted via a support shaft 105
It is in a state where it is engaged with the engagement groove 107 of No. 6. Furthermore, a support part 108 formed at the lower part of the pivot end side of the arm 106 is connected to a plunger 110 of a solenoid 109, and one end of a tension spring 112 is connected to a support part 111 formed at the upper part of the pivot end side. ing. , - However, when the solenoid 109 is off, the arm 106 is moved by the biasing force of the tension spring 112.
The magnetic pole portion 451 (452) is moved to the position indicated by the two-dot chain line in the figure, that is, as shown in FIG.
The lever 104 is held in a position facing the lever 72). Therefore, when the solenoid 109 is off, the developer magnetic brush 351 (352) is not formed on the surface of the developing roller 311 (312). Furthermore, when the solenoid 109 is in the ON state, the arm 106 is supported by the biasing force of the tension spring 112! The magnetic pole part 45t (452) is moved by the doctor 371 at the position shown by the solid line in Fig. 8, that is, as shown in Fig. 9(b).
The lever 104 is rotated to a position facing (372). Therefore, solenoid 10
9, a developer magnetic brush 351 (352) is formed on the surface of the developing roller 311 (312).

By the way, as shown in FIGS. 2 and 3, the doctor body 1132 described above includes a doctor body 1132 made of a non-magnetic material, and a magnetic body 114 made of a band-shaped iron plate extending in the longitudinal direction of this doctor body 1132. , doctor body 113
A magnetic body 1152 consisting of an iron plate provided at both ends of the magnetic body 1152.
1152 (only one is shown). The magnetic body 114.1152.1152 has the magnetic pole part 452 facing the doctor 372 and the current roller 3.
Ili on the surface of 12! When removing the developer G2, lines of magnetic force are formed between the magnetic pole part 452 and the developer G2 to be removed more reliably. The doctor 371 also includes a doctor body 1131 made of a non-magnetic material.
And, the magnetic body 115 made of iron plates provided at both ends of this doctor body 1131! , 115t (only one of which is shown), and is configured to prevent the developer G1 from being removed in the same manner as in the case of the doctor 372 described above. This doctor 371 is not provided with a magnetic body along the longitudinal direction of the doctor main body 1131 like the doctor 372 described above, and the developing roller 371 facing the doctor 371 is
1! The magnetic pole part 451 of the developing roller 312 and the magnetic pole part 482 of the developing roller 312
The developer G1 is prevented from being taken out by utilizing lines of magnetic force formed between the two.

Furthermore, a magnetic plate 116 is provided between the developing roller 311 and the developing roller 312, as shown in FIGS. 2 and 3, to control the magnetic flux density and polar distribution of the other magnetic roller 431 (432). This weakens the influence and enables good developer transport operation.

Note that 1172 shown in FIGS. 2 and 3 is a developer remaining amount detection device that detects when the amount of developer G2 in the hopper 512 of the second developing device 322 has fallen below a predetermined value. A configuration in which a permanent magnet 120 attached to an actuator 119 integrated with a detection lever 118 that rotates according to the amount of rotation is activated when it approaches a reed switch 121 as a detector provided outside the hopper 512. It has become. Although not shown, a developer remaining amount detecting device 117 having the same configuration as the developer remaining amount detecting device 1172 is also provided for the hopper 511 of the first developing device 321! is provided.

Further, as shown in FIGS. 2, 3, and 10, a hopper cover 131 that forms part of the upper surface of the main body 1 is provided on the upper surface side of the developing device 10 so as to be openable and closable. When you open it, you will see the first developing device 32! a lid body 1331 that opens and closes a top opening 1321 for replenishing developer, and a top opening 1322 for replenishing developer of the second developing device 322
A lid body 1332 that opens and closes is exposed.

By opening the lids 1331 and 1332, the developer G1. G2 can be easily replenished from the top side. In addition, the above-mentioned lid body 1331.1332
has a color display section 134t.

1342 is provided, and the developer G housed inside.
The colors of 1 and G2 can be easily distinguished to prevent the developer of a different color from being mixed in by mistake.

Further, 135 shown in FIGS. 2 and 3 is a cover opening/closing detection device for detecting opening/closing of the hopper cover 131, and a permanent magnet 13 attached to the tip of the hopper cover 131
6, and a reed switch 137 as a detector which is provided on the main body 1 side and turns on when the magnet 136 approaches when the hopper cover 131 is closed.

Further, as shown in FIGS. 10 and 11(a) and (b), the hoppers 511 of the first and second developing units 32s and 322
．． 512 upper surface 138t, 1382, lid body 1331
．． On both sides of 1332, cumulative time meters 1391 and 139 are used as life indicators to display the developer life.
2, and a developer empty indicator 140 that indicates that the amount of developer in the hopper 511, 51'2 has fallen below a predetermined amount.
1.1402 is provided. The above cumulative time meter 139
1°1392 indicates the life of the developer by measuring the amount of rotation (time) of the sleeves 441 and 442 that constitute the developing rollers 311 and 312, for example, by Fuji Ceramic Branch Co., Ltd. I am using an electrolytic type integrating time meter (trade name: FC Timer) made by Manufacturer.

On the other hand, a first developing device 321 containing color developer G1
is a cartridge type that can be freely attached to and detached from the main body 1, and can be easily removed by pulling up the handle 141 (see FIG. 10) in an upright position. That is, the developer supply section 341 of the first developing device 321
Positioning members 142 and 142 (only one is shown) are attached to both the front and rear walls of the
Both end support portions 144 and 144 of the handle 141 are rotatably attached to the handle 141 via support shafts 143 and 142 at 2.142. Hooks 145 that are rotatable around a support shaft 143 are integrally attached to the support portions 144 and 144 of the handle 141, respectively, as shown in FIGS. 12 and 13(a), (b), and (c). It is configured to engage with a locking pin 146 provided on the main body 1 side to restrict and stop upward movement. Further, the retaining groove 147 as a first positioning part and the end face 148 as a second positioning part formed on the lower end side of the positioning member 142 engage with the positioning pins 149 and 150 provided on the main body 1 side. The first developing device 321 can be held in a predetermined position by making contact with the first developing device 321. When the handle 141 is raised, the hook 145 is opened as shown in FIG. 13(a').
When the handle 141 is disengaged from the locking pin 146 and the handle 141 is tilted to a substantially horizontal position, the hook 145 is engaged with the locking pin 146 as shown in FIG. By pushing the hook 145 and the locking bottle 146 into the first developing device 3, as shown in FIG.
21 is surely engaged in a state where it is pressed downward. However, if the handle 141 is in an upright state, the first developing device 321 can be attached and removed, and if the handle 141 is folded down after the first developing device 321 is inserted, the first developing device 32
1 can be fixed, and the operation is extremely easy.

Next, the developing operation of the developing device 10 will be explained. First, when the first developer 321 side is selected to operate using the color selection key, the magnetic rolls 431 and 432 enter the state shown in FIG. 2, and the reversible motor 63 rotates forward.
The sleeve 441 of the first developing roller 311 rotates clockwise in the state shown in FIG. 2, and a developer magnetic brush 351 is formed on the surface of the sleeve 441. Then, the electrostatic latent image previously formed on the photoreceptor drum 7 is developed with the color developer G1. In this way, when the development of the electrostatic latent image is completed, the magnetic roll 43r is
When the magnetic pole part 451 is rotated by a degree and faces the doctor 371, new formation of the developer magnetic brush 351 on the sleeve 441 is stopped, and in this state, the sleeve 441 is further rotated by a predetermined amount to perform development. The agent magnetic brush 351 is removed. Note that at this time, the developer magnetic brush 352 is not formed on the second developing roller 312 either, so that problems such as color mixing will not occur even if any of the developing devices 321 and 322 is selected next. There is.

Further, when the second developing device 322 is selected for black color development, the magnetic rolls 431 and 432 are brought into the state shown in FIG. 442 rotates clockwise in the state shown in FIG. 3, forming a developer magnetic brush 352 on the surface of the sleeve 442. After the electrostatic latent image on the photosensitive drum 7 is developed to black in the same manner as described above, the developing operation is completed with the developer magnetic brush 352 removed from the surface of the sleeve 442.

Note that the developer stirring body 40t (402) and the stirring roller 53 of the developing device 321 (322) in the developing operation state
1 (532) is always operating, and the developer supply roller 521 (522) is the developer concentration detector 421.
The developer Gl (G2) is appropriately replenished by a control signal based on the output signal of (422), thereby maintaining a good developing operation.

FIG. 14 shows the operation panel, including a copy key 151 for executing a copy operation, an interrupt key 152 for specifying an interrupt mode for interrupt copying, and an interrupt key 152 for specifying an interrupt mode for interrupt copying. 153, a numeric keypad 154 for setting the number of copies, a number display section 155 for displaying the number of copies, a color selection key 156 for selecting the copy color (for example, black, red, blue, green), and the selected color. Color display units 157 to 160 for displaying information, a liquid crystal display unit 161 for displaying operating status, etc., a density setting unit 162 for setting copy density, and the like are provided. In the liquid crystal display section 161, 163 is a symbol for indicating that copying is possible, 164 is a symbol for indicating that copying is not possible, and 165 is a symbol for indicating that copying is not possible. This symbol indicates that there is no developer left in the hopper. Note that the color selection by the color selection key 156 can be alternately selected each time the color selection key 156 is pressed. That is, for example, if the first developing device 321 is red and the second developing device 322 is black, when the power is turned on, the black copy mode is automatically selected, the second developing device 322 is selected, and the color display 157 is displayed. Light. When the color selection key 156 is pressed in this state, the red copy mode is set, the first developing device 321 is selected, and the color display 158 lights up. If the color selection key 156 is pressed again in this state, the black copy mode is set again. In this way, each time the color selection key 156 is pressed, the black copy mode and the red copy mode can be selected alternately.

FIG. 15 shows the overall control circuit.

That is, 171 is a microcomputer (hereinafter simply referred to as microcomputer) as a main control section, which controls the entire copying machine. Inputs to the microcomputer 171 include human switches 173 such as various keys on the operation panel, various other switches necessary for the copying operation, sensors 174, and the developing device 321 through the input interface circuit 172. The developer concentration detector 421 and the remaining developer amount detection device 117s, the developer concentration detector 422 and the remaining developer amount detection device 1172 of the second developing device 322, the cover opening/closing detection device 135, and the like are connected.

Further, a storage device 175 is connected to the microcomputer 171, and this storage device 175 is backed up by a backup power source 176 such as a battery. On the other hand, an output interface circuit 177 is connected to the output of the microcomputer 171.
Display devices 178 such as various indicators and display sections of the operation panel, pole position switching solenoids 109, 109 of the first developer 321 and second developer 322,
The reversible motor 63, the cumulative time meter 1391 of the first developing device 321, the cumulative time meter 1392 of the second developing device 322, the developing bias power source 179, the charging power source 180 of the charging device 8, and the transferring device. A transfer voltage 11181 of the charger 11 and a peeling power source 18 of the peeling charger 12
2. The static elimination lamp 14, the developing device absent indicator 140
5, 1402, the main motor 28, other various solenoids 183, a document table driving device 184 for driving the document table 2, an exposure lamp control circuit 185, etc. are connected. The exposure lamp control circuit 185 controls the exposure lamp 22
an output signal of an automatic exposure sensor 186 that detects light from;
and the exposure lamp 2 in response to signals from the microcomputer 171.
2.

Note that the first developing device 321 and the second developing device 322 each have a developing device presence/absence signal generating means 18 that indicates the presence or absence of the developing device.
71.1872 and identification information generating means 188+, 1882 for generating an identification code unique to the developer (which also represents the color of the stored developer), and signals and identification codes from these are also input to the input interface circuit 172. is inputted to the microcomputer 171 via. The developer presence/absence signal generation means 1871, 1872 and the identification information generation means 1881, 1882 each utilize a developer connector for electrically connecting the developer to the control circuit, as shown in FIG. It is designed to generate a signal and an identification code. That is, 191 is the above-mentioned connector, which is composed of a jack 192 and a plug 193. The jack 192 is provided on the developing device side, and the plug 193 is connected to the control circuit shown in FIG. 15 via a cable. In the jack 192, a terminal 1941 is set as a common terminal, and a developing device presence/absence signal is generated by connecting this terminal 1941 and a terminal 1945.
By connecting 941 and terminals 1942 to 1944 according to the developing device, three identification codes are generated. on the other hand.

In the plug 193, a terminal 1951 is grounded on the control circuit side, and terminals 1952 to 1955 are connected to the input interface circuit 172. Therefore, when the jack 192 and the plug 193 are connected, each terminal is connected correspondingly, and as a result, the terminals 1952 to 1954 of the plug 193 provide 3-bit identification according to the connection state of the terminals in the jack 192. you will get the code,
A developing device presence signal can be obtained from the terminal 1955. Therefore, when the jack 192 and the plug 193 are not connected, the terminal 195s of the plug 193
Since the developer presence signal cannot be obtained from , it can be determined that the developer is not installed (there is no developer).

Further, the storage device 175 is, for example, 0MO8RAM.
(random access memory), which is used as a counter to count the number of copies (number of copy operations).
The details will be explained below. That is, in this example,
For example, a plurality of sheet number counters for each developing product are provided to count the number of sheets for each developing device, and a total sheet number counter is provided for counting the total number of sheets. They are selected by designation, and count data is stored in each of them. The count data of each sheet number counter is composed of, for example, 4 bits x 5, and is stored in a BCD code. In addition, the counting data of the total number of sheets counter mentioned above is
For example, it is composed of 4 bits x 6 and stored in BCD code.

Next, the operation in the above configuration will be explained. First, the operation when the power is turned on will be explained using the flowchart shown in FIG. When the power is turned on, the process proceeds to step Δ1. In step A1, the second developing device 322 containing black developer as a reference color is selected, and the automatic exposure mode is selected, and the process proceeds to step A2. In step A2, the heater lamp of one bee 1 and roller is turned on, and the process proceeds to step A3. In step A3, the pole position switching solenoid 109 of the second developing device 322 is turned off and the reversible motor 63 is reversed, and the process proceeds to step A4. In step A4, the reversible motor 63 is stopped, and the process proceeds to step A5.

In step A5, the pole position switching solenoid 109 of the first developing device 321 is turned off, and the reversible motor 63 is turned off.
Turn forward and proceed to step 86. In step 86, the reversible motor 63 is stopped, and the process proceeds to step A7. In step A7, the main motor 28 is turned on for a certain period of time,
Proceed to step 88. In step 88, it is checked whether or not the warming up of the heat roller 19 has been completed.
63 is turned on to enter a standby state, and in step A9, key operations on the operation panel are accepted.

Next, the process proceeds to step AIO, and it is checked whether or not the interrupt key 152 is turned on. If it is not turned on, the process proceeds to step A11, and if it is turned on, the process proceeds to step AI2. In step AI2, it is checked whether or not the current mode is interrupt mode, and if the mode is not interrupt mode, the process proceeds to step A13. In step A13, the copy conditions immediately before the interrupt key 152 is turned on, that is, the copy density, copy color, and set number of copies, are saved, and the second imager 322 containing black developer and the automatic exposure mode are saved. is selected, the set number of copies is set to "1", the interrupt mode is set, and the process proceeds to step A14. In this manner, when the interrupt mode is set, the immediately preceding copying conditions are saved and the copying mode is switched to black as the reference color. Next, in step A14, the interrupt indicator 153 on the operation panel is turned on, and the process proceeds to step A11. on the other hand,
If the interrupt mode is selected in step A12, the process proceeds to step A15. In step A15, step A
The copying conditions saved in step A13 are restored, and the selection of the developing device and exposure mode is returned to the selection state immediately before the start of the interrupt mode, the interrupt mode is canceled, and the process proceeds to step A16. In step A16, the interrupt indicator 153 on the operation panel is turned off, and the process proceeds to step A11.

In step A11, it is checked whether the second developing device 322 is installed based on the developing device presence/absence signal from the second developing device 322, and if it is not installed, the process advances to step A17. In step A17, it is checked whether or not the first developing device 32 is installed based on the developing device presence/absence signal from the first developing device 321. If it is not installed, step A17 is performed.
Proceed to step 18. In step A18, the color indicators 157 to 160 and the copy permission display symbol 163 on the operation panel are displayed.
turn off and return to standby mode.

In this way, the first developing device 321 and the second developing device 322
is not installed at all, the color indicators 157 to 160
This prohibits the display of colors by On the other hand, in step Δ11, if the second developing device 322 is installed, the process advances to step A19. In step A19,
It is checked whether the first developing device 321 is installed, and if it is installed, the process advances to step A20. Step A
In step A20, it is checked whether the color selection key 156 is turned on, and if it is turned on, the process advances to step A21. In step A21, it is checked whether the second developing device 322 is currently selected, and if it is not selected, the process advances to step A22. In step A22, the second developing device 322
is selected and the process proceeds to step A23. Step A19 above
, if the first developing device 32 is not installed,
Step A20. Jump to A21 and proceed to step A2''2. Further, in step A20, if the color selection key 156 is not turned on, step A21
．． Jump to A22 and proceed to step A23. on the other hand,
If the first developing device 321 is installed in step A17, or if the second developing device 322 is selected in step A21, step A24
Proceed to. In step A24, the first developing device 321 is selected, and the process proceeds to step A23. In this way, the first developing device 3
21 and the second developing device 322, or if either one of them is not installed, selection of that developing device is prohibited. In step A23, the color of the selected developer is displayed.

That is, the color of the stored developer is determined based on the identification code output from the selected developer, and a color indicator on the operation panel corresponding to the determined color is turned on. For example, if the discrimination color is black, the color display 157 is turned on, and if the discrimination color is red, the color display 158 is turned on.

After color display is performed in this way, the process advances to step A25. In step A25, the developer remaining amount detection device 1171.117
2, the first and second developing units 321 and 322
It is checked which of the developing devices is out of developer or not, and if neither is out of developer, the process advances to step A26. In step A26, the first and second developing devices 321, 32
The developer empty indicators 140t and 1402 of No. 2 are turned off, and the process proceeds to step A27. On the other hand, in step A25, if one of the developing devices is out of developer, the process proceeds to step A28. In step A28, it is checked whether the hopper cover 131 of the developer +tio is closed based on the signal from the cover opening/closing detection device 135. If it is closed, the process proceeds to step A26; if not, the process proceeds to step A29.

In step A29, the developer empty indicator 1401 or 1402 of the corresponding developing device (developing device without developer) is turned on, and the process advances to step A27. In this way, the first and second
When the developers Gs and G2 run out in the hoppers 51s and 512 of the developing devices 321 and 322, the upper opening 1
32s, developer-free indicator 140 installed near 1322! , 1402 are turned on. At this time, if the hopper cover 131 is closed, the developer-free indicators 1401 and 1402 are not lit, but are lit only when the hopper cover 131 is opened. In step A27, it is checked whether the developing device selected at this time is out of developer, and if not, the process proceeds to step A30.

In step A30, the symbol 165 for displaying the absence of developer on the operation panel is turned off, and the process proceeds to step A31. On the other hand, in step A27, if the selected developing device is out of developer, the process proceeds to step A32. In step A32, the developer-free display symbol 165 on the operation panel is turned on, and the process proceeds to step A31. In this way, only when the selected developing device runs out of developer, this is displayed on the operation panel.

In step A31, it is checked whether or not there is an abnormality in the copying machine. If there is an abnormality, the abnormality is dealt with, and if there is no abnormality, the process advances to step A33.

In step A33, it is checked whether the mode is a manual paper feed mode using the manual feed table 6, and if it is not the manual paper feed mode, the process proceeds to step A34.

In step A34, it is checked whether or not there is paper P1 in the paper feed cassette 3. If there is not, the process returns to the standby state, and if there is, the process proceeds to step A35. On the other hand, the above step A
33, if the manual paper feed mode is selected, step A3 is selected.
4 and proceed to step A35. Step A3
In step 5, it is checked whether the developer has been attached or detached based on the developer presence/absence signals from the first and second developer units 321 and 322, and if the developer has been attached or detached, the process advances to step A36. Step A
At step 36, it is checked based on the signal from the cover opening/closing detection device 135 whether or not the developing device is securely attached. In this case, the cover opening/closing detection device 135
If it detects that it is closed, it is determined that it is attached. When it is determined that the developing device is attached, the process advances to step A37. Step A
At step 37, the developer on the sleeve of the detached developing device is removed by performing the above-described operations, and the developing device returns to the standby state. In this way, when a developing device is attached or detached while the power is on, the device operates to remove the developer on the sleeve of the detached developing device after the developing device is securely attached. It is. On the other hand, if the developing device is not attached or detached in step A35, the process advances to step A38. In step A38, it is checked whether or not the copy key 151 on the operation panel has been turned on. If it has been turned on, the process proceeds to the copying operation to be described later.
If there is no 1'C, the process advances to step A39. Step A3
In step 9, it is checked whether or not any key operation has been performed for a certain period of time on the operation panel. If any operation has been performed, the system returns to the standby state, and if no operation has been performed, the process proceeds to step A40.Step A40 Then, it is checked whether the current mode is interrupt mode or not, and if the mode is not interrupt mode, the process proceeds to step A41.In step A41, the second developing device 322 containing black developer and the automatic exposure mode are selected. Set the number of copies to 1 and return to standby mode. In this way, if no operation is performed for a certain period of time after the normal copying operation is completed, the mode is switched to the black copying mode as the reference color and the automatic exposure mode. On the other hand, in step A40, if it is the interrupt mode, the process advances to step A42. In step A42, the copying conditions saved when setting the interrupt mode are restored, the interrupt indicator 153 on the operation panel is turned off, and the machine returns to the standby state. In this way, if no operation is performed for a certain period of time after interrupt copying is performed in interrupt mode, the state is returned to the state immediately before starting interrupt mode.

Next, the copying operation will be explained using the flowchart shown in FIG. When the copy key 151 on the operation panel is turned on, the process advances to step B1.

In step B1, the pole position switching solenoid 109 of the selected developing device is turned on, and the process proceeds to step B2. In step B2, the reversible motor 63 is rotated in the direction of the selected developing device, and the process proceeds to step B3. In step B3, the blade solenoid 29 of the cleaning device 13, the static elimination lamp 14, the main motor 28, the transfer power source 181 (transfer charger 11), and the stripping power source 182 (stripping charger 12)
Then, the developing bias power supply 179 is turned on, and the process proceeds to step B4. In step B4, the paper feeding operation from the paper feeding cassette 3 is started, and the process proceeds to step B5. In step B5, it is checked whether or not the original table 2 is in the normal position. If it is not in the normal position, the process proceeds to step B6 and is returned to the normal position. When the original table 2 is returned to the normal position, the process proceeds to step B7. In step B7, the exposure lamp 22 is turned on, and step B
Proceed to step 8. In step B8, the charging power source 180 (charging charger 8) is turned on to start charging the photosensitive drum 7, and at the same time, the document table 2 is advanced to start scanning the document, and the process proceeds to step B9. In step B9, the registration roller 18 is rotated to send the paper P1 to the image transfer section 16,
Proceed to step BIO.

In step 810, the sheet count display section 155 on the operation panel
"1" is subtracted from the display content of the storage device 175.
1 is added to the total number of sheets counter and the number of sheets counter of the selected developing device, and the process proceeds to step B11. In step B11, the charging power source 180 is turned off to stop charging the photosensitive drum 7, and the process proceeds to step B12. In step B12, the exposure lamp 22 is turned off, and the process proceeds to step B13. In step B13, the document table 2 is moved backward, and the process proceeds to step 814. In step 814, it is checked whether the document table 2 has returned to the normal position, and if it has returned to the normal position, the process advances to step B15. In step B15, the rotation of the registration roller 18 is stopped, and the backward movement of the document table 2 is also stopped, and the process proceeds to step B16. Step B
In step B16, it is checked whether or not the set number of copies have been completed, and if the copying has been completed, the process advances to step B17. In step B17, it is checked based on the signal from the developer concentration detector of the selected developer whether the developer concentration in the selected developer is at least the lower limit concentration level, and if it is at least the lower limit concentration level, step 818 Proceed to lower limit? If the level is not higher than 11 degrees, the process advances to step 819. Step B1
In step 9, it is checked whether or not the developer has been continuously replenished for a predetermined period of time. If not, the process returns to step B17 and the above operation is repeated, and when the developer has been replenished for a predetermined period of time, the process proceeds to step 818. In other words, in automatic developer concentration control, there is an appropriate concentration level and a lower limit concentration level for not changing the flow characteristics of the developer. to continue replenishing the developer. Step 818
Then, the pole position switching solenoid 109 is turned off and the process proceeds to step B20. In step B20, the reversible motor 63 is stopped, and the process proceeds to step 821. Step B21
Then, the blade solenoid 29, main motor 28, static elimination lamp 14, transfer power source 181, and peeling NWA 182
# and development bias voltage 111179 are turned off,
Return to standby state.

On the other hand, if the set number of copies have not been completed in step B16, the process advances to step B22. Step B
In step B22, the life of the developer is checked by checking whether the value of the number of difficult-to-cut sheets counter in the storage device 175 is a predetermined value set in advance, and if the life has not expired, step B23 Proceed to. In step 823, it is checked whether there is a color change request by checking whether a color change request flag, which will be described later, is set to 1'', and if there is no color change request (flag - O).
Returning to step B4, the above-described operations are repeated, and if there is a color change request (flag-1), the process proceeds to step B24.

In step 824, the selection of the developing device is changed, and the process proceeds to step B25.

In step B25, the pole position switching solenoid of the previously selected developer is turned off, and the process proceeds to step B26. In step B26, the reversible motor 63 is stopped, and the process returns to step B1 to repeat the above-described operation. In this manner, when there is a request to change the selection of a developer during a copying operation, the developer to be used is switched at least after the development of the image being copied is completed. On the other hand, the step B2
In Step 2, if the life of the developer has expired, proceed to step B2.
Proceed to step 7. In step B27, it is checked whether there is another developer of the same color. If not, the process returns to step B4 and the above-described operation is repeated. If there is another developer of the same color, the process advances to step 828. In step 828, the developer of the same color is selected, and the process proceeds to step B25. In this way, when the developer in the developing device you are using reaches the end of its life,
If there is another developing device, that is, a developing device containing developer of the same color, switching to that developing device is performed preferentially.

Next, interrupt processing will be explained using the flowchart shown in FIG. This interrupt processing is repeated from time to time at regular intervals. Once the interrupt processing is started, the process advances to step C1.

In step C1, it is checked whether the reversible motor 63 is rotating (the developing device is in operation), and if it is rotating, the process advances to step C2. +i,')v In step C2, the integrated time of the selected developing device it 139 s and LJ 1
392, and the process proceeds to step C3. In step C3, it is checked whether the A flag is set to 1°.If it is not set to II III II, the process proceeds to step C4. In step C4, timer A starts counting,
Proceed to step C5. In step C5, the timer A
Checks whether ec has been counted for 5 sec.
Once counted, the process advances to step C6. In step C6, A
1゛ for the flag.

Sera 1~ and proceed to step C7. Step C5 above
In step C6, if 5 seconds have not been counted,
Jump to step C7. On the other hand, if the A flag is 1 in step C3, the process advances to step C8. In step C8, it is checked whether the developer concentration of the selected developer is lower than a predetermined value, based on the signal from the developer concentration detector 421 or 422 of the selected developer. If so, proceed to step C9. In step C9, a developer replenishment operation is performed by driving the developer replenishment roller 521 or 522 of the selected developing device, and the process proceeds to step C7.

In step C8, if the value is higher than the predetermined value, step C9 is jumped and the process proceeds to step C7. In this way, after the start of the copying operation, the supply of developer onto the magnetic rolls 43s and 432 is started, and then the developer
．． 1. After a predetermined time when the flow of developer to 422 becomes stable (
For example, from about 5 seconds the developer concentration sensor 421.4
? The severity is checked based on the output of step 2. In step C7, it is checked whether the color selection key 156 on the operation panel is turned on, and if it is turned on, the process advances to step C10. In step C10, the color change request flag is set to 1, and the process proceeds to step C11. In step C7, if the color selection key 156 is not turned on, step C10 is skipped and step C11 is executed.
Proceed to.

On the other hand, in step C1, the reversible motor 6
If 3 is not rotating, the process advances to step CI2. In step CI2, the flag is set to ``0'', timer A is reset, and power is turned off to the total 11 hour total 1391 or 1392, and the process proceeds to step C11.In step C11, the total number of copies is displayed. It is checked whether there is a request (entered in code using the numeric keypad 154 on the operation panel), and if there is a display request, the process proceeds to step C13.In step C13, the storage device [175
The content of the total number of sheets counter is displayed on the number display 11115'5 on the operation panel, and the process proceeds to step C14. In step C11, if there is no request to display the total number of copies, the process advances to step C15. In step C15, it is checked whether there is a request to display the number of copies made by the first developing device 321 (inputted in code using the numeric keypad 154), and if there is a request to display, the process proceeds to step C16.

In step C16, the first developing device 3 in the storage device 175
The contents of the sheet number counter corresponding to No. 21 are displayed in the sheet number display section 155.
is displayed, and the process proceeds to step C14.

In step C15, if there is no display request, the process advances to step C17. In step C17, the second developing device 3
22 to display the number of copies made (numeric keypad 15)
4) is input in code), and if there is a display request, the process advances to step 01B. In step 018, the contents of the sheet number counter corresponding to the second developing device 322 in the storage device 175 are displayed on the sheet number display section 155, and the process proceeds to step C14. In step C17, if there is no display request, the process advances to step C19.

In step C'19, the normal number of copies is displayed on the number display section 155, and the process proceeds to step C14. Step C14
Now, request to clear the number of copies for each developer (numeric keypad 15).
If there is no clear request, the interrupt process ends here, and if there is a clear request, the process proceeds to step C20. In step C20, the number of sheets and the contents of the counter corresponding to the designated developing device in the storage device 175 are cleared, and the interrupt processing is ended.

With the configuration described above, when the developer in use reaches the end of its developer life, if there is another developer that stores developer of the same color, that developer is given priority. Since it can be switched, the maintenance cycle of the developing device can be extended, and it is also very convenient.

Note that in the above embodiment, when the developing device in use reaches the developer life, the developing device is switched to another developing device.
The present invention is not limited to this, and for example, when the developing device in use runs out of developer, it may be possible to switch to another developing device. In short, when an abnormality occurs in the developing device in use, it is sufficient to switch to another developing device.

Further, in the above embodiments, the case where the invention is applied to a monochromatic color copying machine has been described, but the present invention is not limited thereto. The present invention can be applied to any image forming apparatus that forms an image using a developing device.

[Effects of the Invention] As detailed above, according to the present invention, the maintenance cycle of the developing device 1 can be lengthened, and a very convenient image forming apparatus can be provided.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic configuration diagram of a color copying machine, Fig. 2 is a schematic vertical side view of a developing device, and Fig. 3 shows different operating states of the developing device. 4 to 6 show the configuration of the driving force transmission system, FIG. 4 is a front view showing the meshing state of the gear group, and FIG. 5 is a cross-sectional view showing the developed state. 6 is a sectional view showing the state of driving force transmission to the driving gear, FIG. 7 is a partially sectional plan view of the magnetic roll driving means, and FIG. 8 is a side view of the magnetic roll driving means. FIG. 9 is an explanatory diagram showing the operating state of the magnetic roll driving means, FIG. 10 is a schematic perspective view of the developing device section, FIG. 11 is a plan view showing the top surface of each developing device, and FIG. 12 is a diagram of the developing device. A front view showing the fixing structure, FIG. 13 is an explanatory diagram showing the relationship between the handle and the hook, FIG. 14 is a plan view of the operation panel, and FIG. 15 is a block diagram schematically showing the overall control circuit. , FIG. 16 is an explanatory diagram for explaining the phenomenon device presence/absence signal generation means and the identification information generation means.
7 is a flowchart for explaining the operation at power-on, FIG. 18 is a flowchart for explaining the copying operation, and FIG. 19 is a chart 70-A7 for explaining the interrupt processing operation. PI, P2...Paper, 1...Copy machine body, 2...Document stand, 7...Photoconductor drum 10...・Current *mon gate, 321.322...
...Developer, 156...Color selection key, 15
7-160...Color display, 171...
Microcomputer, 1881', 1882...Identification information generation means. Applicant's agent Patent attorney Takehiko Suzue Figure 7 Figure 8 1υυ 1!9 Figures (a) (b) No. 10! 1ill Figure 11 (a) (b) Figure 16 Figure 17 Figure 17 (C) Figure 17 (d)

Claims (4)

[Claims] (1) A plurality of developing devices; a selection means for selecting a desired developing device from among these developing devices; and image formation for forming an image on an image forming medium using the developing device selected by the selection device. means, a detection means for detecting whether or not an abnormality has occurred in the developing device being used by the image forming means, and a control means for switching the selection to another developing device when the detecting means detects the occurrence of the abnormality. An image forming apparatus comprising: (2) The image forming apparatus according to claim 1, wherein the abnormality is developer life. (3) The image forming apparatus according to claim 1, wherein the plurality of developing units each contain a developer of a different color. (4) The image forming apparatus according to claim 3, wherein the control means switches the selection to the developing device preferentially if there is a developing device containing developer of the same color.