JPS61170758A - Developing device - Google Patents

Abstract

PURPOSE:To drive selectively plural developing bodies by using one driving source, by constituting a titled device so that plural developing bodies can be driven by a switching operation of a driving force transfer switching means. CONSTITUTION:When the first developing device 321 side is selected so as to operate by a color selecting key, a driving means 60 is operated so as to transfer a driving force to the first driving force transfer system 6 side, a sleeve 441 of the first developing roller 311 rotates, and a developer magnetic brush 351 is formed on the surface of a sleeve 441. In this state, an electrostatic latent image which has been formed in advance on a photosensitive drum 7 is developed by a color developer G1. Also, in case when the second developing device 322 has been selected, the driving means 60 is operated so as to transfer a driving force to the second driving force transfer system 62 side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a developing device applicable to, for example, a two-color color copying machine.

C. Technical background of the invention and its problems] In recent years, color copying machines and the like have progressed, and two-color color copying machines capable of producing images in colors other than black have been put into practical use.

In addition, in conventional two-color color copying machines, multiple cartridges that integrate a developer and a photoreceptor are prepared and selectively replaced, making the operation extremely troublesome. There was a problem.

Therefore, in order to solve this problem, a two-color color developing device has been put into practical use in which development can be carried out by selectively driving the first developing body and the second developing body by an operator's button switching operation, etc. Ta.

In this system, when one developing body is being driven for development, it is necessary to stop driving the other developing body.

However, in the past, the first developing body and the second developing body
Each of the developing bodies is driven by a dedicated motor, leading to problems such as an increase in size, weight, and cost of the developing device.

[Purpose of the invention]

The present invention was made based on the above-mentioned circumstances, and its purpose is to be able to selectively drive a plurality of developing bodies using one drive source, thereby making it possible to reduce size, weight, and cost. The purpose of the present invention is to provide a developing device.

[Summary of the invention]

In order to achieve the above object, the present invention provides a developing device that includes a plurality of developing bodies and is capable of selectively driving these developing bodies to perform development, in which a driving force is transmitted to the plurality of developing bodies. A plurality of driving force transmission systems are provided, and a driving force transmission switching means for selectively transmitting the driving force of a common drive source to the plurality of driving force transmission systems is provided, A plurality of developing bodies are selectively driven by a switching operation of a force transmission switching means.

[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 to which a developing device according to the present invention is applied. That is, 1 is a main body of the copying machine, and the upper surface of this main body 1 has a
A document table 2 is provided which can freely reciprocate. 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. Then, the paper feeding force Cera "3(7)7Jt"7"l<-54"1""
There is a manual feeder and a supply stand 6 for feeding NM+"l.

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 10, which will be described later. 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, the paper Pl automatically taken out from the paper feed cassette 3 via the paper feed row 515 or the paper P2 manually fed from the manual feed table 6 is connected to the photoreceptor drum 7 and charged for transfer. A paper conveyance path 17 is formed that leads to the paper discharge tray 4 via the image forming section 16 between the paper feeder 11 and the paper discharge tray 4 . 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.
The image of the document uniformly irradiated with light by the optical system 9 is formed on the photoreceptor drum 7 to form an electrostatic latent image. The formed electrostatic latent image is developed into a developer image by the developing bag [10], and is sent to the transfer charger 11 side. On the other hand, the automatically or manually fed paper P1 or P2 is fed by the registration rollers 18, and the developer image previously formed on the photoreceptor drum 7 is transferred to the transfer band! ! The image is transferred by the container 11.

The paper PL (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 transferring the developer image onto paper PI (P'2),
The residual toner remaining on the photoreceptor drum 7 is cleaned by a cleaning device 13, and the residual image on the photoreceptor 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 On the upper frame, various devices such as a charging device 8, an optical system 9, an exposure lamp 22, a developing device 10, a cleaning device 13, and a static elimination lamp 14 are attached around the photosensitive drum 7 by appropriate means. Furthermore, the document table 2 and paper feed roller 15 are also attached to the upper frame, and the upper unit 1A
It consists of 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 2o, a paper ejection tray 4, a main motor 28, etc. are installed as appropriate means. is attached to constitute the lower unit 1B. After the front cover of the main body 1 is rotated and removed, it is configured so that it can be opened and closed almost along the paper conveyance path 17 of the paper P1 (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 photosensitive drum 7 into and out of contact with 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 5312, 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 is divided into two parts: a first developing device 321 that includes a first developing roller 311 as a developing body, and a second developing device 322 that includes a second developing roller 312 as a developing body. Both the first and second developing devices 32r and 322 are detachably attached to the main body 1. In this case, the user pulls out the upper first developing device 321 in the upward direction in the figure.
The second developing device 322 with 15 degrees and 11 stages is configured so that it can be attached to and detached from the main body 1 when a service person performs maintenance, inspection, etc. , the frequently used black developer is stored in the lower second developing device 322.
The color developer is used in the first developing device 321 on the upper stage.

The first developing device 321 includes a developing mechanism section 331 and a developer replenishing section 341. The developing mechanism section 33
1 is provided at the sliding contact portion between the developing roller 311 and the photosensitive drum 7 of the developer magnetic brush 351 formed on the surface of the developing roller 311, that is, upstream of the developing position 361, and a doctor 371 regulating the thickness of the developer 351; and a developer magnetic brush 35 provided downstream from the development position 361 and on the surface of the development roller 311.
scraper 3 and guide it to the developer storage section 381.
91 and a developer agitating body 401 accommodated in the developer accommodating portion 381 are housed in a casing 411. A developer concentration detector 421 is attached to the casing 411 at a position above the developing roller 311, which detects the developer concentration by magnetically detecting changes in the magnetic permeability of the developer G1. ing.

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 49! of which the magnetic pole part 451°47
r and 49t are north poles, and magnetic pole parts 46t and 48t are south poles, the angle θ1 between the magnetic pole parts 451 and 461 is about 50°, and the angle θ2 between the magnetic pole parts 461 and 471 is about 71°. °, the angle θ3 between the magnetic pole parts 471 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 531 and 53t that stir the developer G1 in the hopper 511 so as to convey the developer G1.

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 resulting narrow width (approximately 50 mm) with an approximately 20° inclination. The difference is that a scraper 54 is added. Therefore, other identical components will be designated by reference numerals with the suffix character changed from "1" to "2", and detailed explanations will be omitted. The developer concentration detector 422 is attached to the rear surface of the casing 412 with its detection surface vertical within the casing 412. Further, the scraper 54 collects the developer scraped off from the developing roller 312 to a developer concentration detector 422.
This is a guide member for guiding the sensor to the detection surface of the sensor. Further, the magnetic roll 432 of the developing roller 312 has four magnetic pole parts 452 to 482, of which magnetic pole parts 452 and 47
2 is a N pole, and 11 pole parts 462 and 482 are S poles, and the angle θ5 between the magnetic pole parts 452 and 462 is about 78°.
The angle θ6 between the magnetic pole portions 462 and 472 is set to approximately 70°, and the angle θ7 between the magnetic pole portions 472 and 482 is set to approximately 80°. Further, the magnetic roll 432 passes through the rotation center of the photoreceptor drum 7 and makes an angle β with respect to the horizontal line L1.
(approximately 1°) so that the center is located on a straight line L3 drawn at an angle of about 1°.

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
Developed on the surface of 12 ``''1fi75235'', 35z''
JE5a°ゞ°゛2° -It is now possible to remove. Then, the first developing device 321 and the second developing device 3
By switching the magnetic rolls 431 and 432 of No. 22 to predetermined positions by magnetic roll driving means (not shown), the developing O-roller 311 and 312 of either the first developing device 321 or the second developing device 322 is switched to a predetermined position. Developer magnetic brushes 351 and 352 are formed only on the surface.

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 with the magnetic pole part 471 facing the development position 361, and a doctor 37 placed approximately halfway between the magnetic pole parts 451 and 461.
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 located approximately midway between the magnetic pole portions 452 and 462. The developer magnetic brush 352 is formed only on the surface of the developing roller 312 on the second developing device 322 side.

In addition, the magnetic pole parts 451.4 of the magnetic rolls 43r and 432
52 is a doctor 37 made of non-magnetic material! , 372, the reason why the developer magnetic brushes 351 and 352 are not formed on the surface of the developing rollers 311 and 312 is that the density of the magnetic brushes is in a slanted state at the magnetic pole portions 451 and 452. ．． This is because the force to adsorb G2 is weak, and therefore it can be easily regulated by the doctor 371, 372, and even if the sleeve 441, 442 rotates, the developer Gs,
G2 never passes through the doctors 37t 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,
The developer replenishment 0-5521 and each driving section of the second developing device 322, that is, the sleeve 442 of the developing roller 312 and the developer stirring body 402, are selectively driven by a driving means 60, which will be described later. Only one of the developing devices 321 and 322 is operated.

Hereinafter, the driving means 60 will be described with reference to FIGS. 4 to 7.
will be explained in detail. The driving means 60 includes a first driving force transmission system 61 that transmits driving force to the first developing device 321, a second driving force transmitting system 62 that transmits the driving force to the second developing device 322, and the first, Second driving force transmission system 61.6
A motor 63 as a common drive source for the motor 6 and the motor 6
3 to the first and second driving force transmission systems 61 and 62.
The structure includes a driving force transmission switching means 64 that selectively transmits the driving force to the driving force.

The first driving force transmission system 61 includes an intermediate gear 65 that meshes with the first driving gear 57, a first driven gear 66 that meshes with the intermediate gear 65, and an intermediate gear 67 that meshes with the driven gear 66. The second driven gear 6 that meshes with this intermediate gear 67
8.

The second driving force transmission system 62 also includes an intermediate gear 59 that meshes with the second drive gear 58, a third driven gear 69 that meshes with this intermediate gear 59, and idle gears 701 and 702 that mesh with this driven gear 69. and a fourth driven gear 71 that meshes with this idle gear 702. And the first
When the drive gear 57 rotates in the six directions shown by the solid line arrows in FIG.
Each of the gears 65 to 68 of the first driving force transmission system 61 rotates in the direction of the solid line arrow, and the second driving gear 58 rotates in the direction of the solid line arrow.
When rotated in the direction of the broken line arrow B in the figure, the second driving force transmission system 6
Each of the gears 59, 69 to 71 of No. 2 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 respectively attached to the drive shaft 731 of the developer agitator 401, and the three 1441 and the developer agitator 40
1 rotates in a predetermined direction with the rotation of gears 66 and J68. Further, the third driven gear 69 is connected to the drive shaft 722 that is integrated with the sleeve 442 of the second developer roller 312, and the fourth driven gear 71 is connected to the developer stirring body 4.
The sleeve 442 and the developer stirring body 402 are attached to the gear 69.7.
1 rotates in a predetermined direction.

Further, the first driving gear 57 and the second driving gear 58 are provided with a driving force transmission switching means 64 shown in FIGS. 6 and 7.
The driving force of the motor 63 is selectively transmitted through the motor 63.

The driving force transmission switching means 64 has the following configuration.

In the figure, 80 is a drive gear driven by the motor 63 of the drive source, and this drive gear 80 is provided with first and second driven gears 81 and 82 facing each other. The first driven gear 81 is attached to a horizontally suspended first rotating shaft 85 via first and second levers 83 and 84,
The second driven gear 82 is attached to a horizontally suspended second rotation shaft 88 via third and fourth levers 86,87.

Further, each lever 83, 84, 86, 87 as a holding member for swingably holding the driven gear 8L 82 is rotatably attached to a common support shaft 89, and
The driven gears 81 and 82 are movable toward and away from the drive gear 80.

Further, a relay gear 90 is attached to the first rotating shaft 85, and when the first driven gear 81 meshes with the drive gear 80, the relay gear 90 meshes with the driving gear 91. ing. Further, a relay gear 92 is attached to the second rotating shaft 88, and when the second driven gear 82 meshes with the drive gear 80, the relay gear 92
2 meshes with the driving gear 93.

On the other hand, each lever 83, 84, 86, 87 is connected to a tension spring 94 as a biasing body, and the first driven gear 81 and the driving gear 80, the relay gear 90 and the driving gear 9
The first and second driven gears 82 and the driving gear 80, and the relay gear 92 and the driving gear 93 are always biased so as to mesh with each other.

Further, a first solenoid 95 as a holding member moving means is connected to the second lever 84, and the first and second levers 83.84 and gears 81.90 are connected to the second lever 84.
The first unit 97 is configured to be able to rotate against the biasing force of the tension springs 94 and 94. Also,
A second solenoid 96 is connected to the fourth lever 87, and the third and fourth levers 86,87
and a second unit 98 having gears 82, 92, respectively, can be rotated against the biasing force of tension springs 94, 94.

The driving gear 91 is interlocked with the driving gear 57 of the first driving force transmission system 61 via the rotating shaft 100, and the driving gear 93 is interlocked with the driving gear 57 of the first driving force transmission system 61 via the rotating shaft 101. It is in a state in which it is interlocked with the drive gear 58 of the force transmission system 62.

When transmitting the driving force to the first driving force transmission system 61, the first solenoid 95 is turned off and the second solenoid 96 is turned on, as shown in FIGS. 4 and 7(a). By doing so, the second unit 98 is separated against the urging force of the tension spring 94.94, and the first unit 98 is moved away from the first unit 98.
Only 7 is biased by tension springs 94 and 94. Then, the first driven gear 81 and the driving gear 80 . By bringing the relay gear 90 and the drive gear 91 into a meshed state, the rotation of the drive gear 80 is transmitted to the drive gear 57 of the first drive force transmission system 61.

In addition, when transmitting the driving force to the second driving force transmission system 62, as shown in FIG. 7(b), the second solenoid 9
5 is turned off and the first solenoid 96 is turned on, the first unit 97 is separated against the biasing force of the tension spring 94.94, and only the second unit 98 is biased by the tension spring 94.94. state. Then, the second driven gear 82 and the drive gear 80, and the relay gear 92 and the driving gear 93 are brought into mesh with each other, so that the drive gear 8
0 rotation is transmitted to the -drive gear 58 of the second drive force transmission system 62.

In addition, the solenoids 95 and 96 of the driving force transmission switching means 64
The switching is performed by pressing a color selection key arranged on an operation panel (not shown), and at this time, the magnetic pole portions 451, 452 of the non-operating magnetic rolls 431, 432 are moved by a magnetic roll driving means (not shown). doctor 37t
, 372.

Note that one stirring roller 531 of the first developing device 321 is
The stirring roller 5531 is intermittently driven via the first operating mechanism 102 shown in FIG. The agent supply roller 521 is configured to be driven at the same time. In addition, the second developing device 32
The second stirring roller 532 and the developer replenishing roller 522 are simultaneously driven intermittently via the second operating mechanism 103 and a driving force transmission system (not shown).

Note that 104 shown in FIGS. 2 and 3 is the second developing device 3.
This is a developer remaining amount detection device that detects when the amount of developer G2 in the hopper 512 of No. 22 has become less than a predetermined value. It is configured to operate when the attached permanent magnet approaches a reed switch as a detector provided outside the hopper 512. Although not shown, a similar developer remaining amount detection device is also provided on the first developing device 321 side.

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.
The sleeve 441 of the first developing roller 311 rotates clockwise in the state shown in FIG. 2, and developer magnetic brush 351 is applied to the surface of the sleeve 441. form. 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 431 is rotated by about 25 degrees and the magnetic pole portion 451 faces the doctor 371, so that the developer magnetic brush 351 is transferred onto the sleeve 441. New formation is stopped, and in this state, the sleeve 441 is further rotated by a predetermined amount to remove the developer magnetic brush 35.
1 is removed. Note that at this time, the second developing roller 312
Since the developer magnetic brush 352 is not formed in either of the developer units 321 and 322, problems such as color mixing will not occur even if any of the developers 321 and 322 is selected next.

Further, when the second developing device 322 is selected to perform black development, the magnetic rolls 431 and 432 are in the state shown in FIG. The second
The sleeve 442 of the developing roller 312 rotates clockwise in the state shown in FIG. 3, forming a developer magnetic brush 352 on the surface of the sleeve 442. Then, the electrostatic latent image on the photoreceptor drum 7 is developed black in the same manner as described above.
The developing operation ends with the developer magnetic brush 352 removed from the surface of the sleeve 442.

Note that the developer stirring body 40t (402>) of the developing device 321 (322) in the developing operation state and the stirring roller 53
1 (532) is always operating, and the developer replenishment roller 521 (522) is connected to the developer concentration detector 4.
21 (422), replenishment of the developer Gl (G2) is performed as appropriate, and a good development operation is maintained.

In the above-mentioned embodiments, an explanation has been given of a case in which two developing bodies are selectively driven, but the present invention is not limited to this, and may be configured to include two or more developing bodies.

In addition, it goes without saying that the present invention can be modified in various ways without departing from the gist of the present invention.

As described above, in the developing device which is capable of selectively driving the first developing member and the second developing member to perform development, the first (7) developing member 1 driving force 8 transmission 111 / A driving force transmission system and a second driving force transmission system that transmits driving force to the second developing body are provided, and the driving force of a drive source common to these first and second driving force transmission systems is transmitted to the first and second developing bodies. ,
A driving force transmission switching means for selectively transmitting the driving force to the second driving force transmission system is provided, and the first and second developing bodies are selectively driven by the switching operation of the driving force transmission means. Developing can be carried out without increasing the size, weight, or cost of the developing device, which would be required if the developing device were driven by a dedicated motor.

In the above embodiments, two developing bodies are used to selectively develop black and red colors, but the present invention is not limited to this, and a structure using two or more developing bodies is described. Of course, it is also possible to do so.

In addition, it goes without saying that the present invention can be modified in various ways without departing from the gist of the invention.

〔Effect of the invention〕

As explained above, the present invention is a developing device capable of selectively driving and developing a plurality of developing bodies, which comprises a plurality of independent driving forces that transmit driving forces to the plurality of developing bodies. A transmission system is provided, and a driving force transmission switching means for selectively transmitting the driving force of a drive source common to the plurality of driving force transmission systems to the plurality of driving force transmission systems is provided, and a switching operation of the driving force transmission means is provided. Accordingly, a plurality of developing bodies are selectively driven. Therefore, a single drive source can drive multiple developing bodies, making the developing device smaller and lighter.
This has the effect of being able to provide a developing device that enables cost reduction.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of a color copying machine employing the developing device of the present invention, FIG. 2 is a schematic longitudinal sectional side view of the developing device, and FIG. 4 is an explanatory view showing the structure of the driving means of the developing device, FIG. 5 is a cross-sectional view showing the meshing state of the gear group, and FIG. FIG. 6 is a perspective view showing the configuration of the driving force transmission switching means which is the main part, and FIG. 7 is an explanatory view showing the switching operation state. 10...Developing device, 311.312...Developing body (developing roller), 57.58,...Drive gear, 60
...Driving means, 61.62...Driving force transmission system, 6
3... Drive source (motor), 64... Drive force transmission switching means, 80... Drive gear, 81.82... Driven gear, 83.84.86.87... Holding member (lever) ), 94... biasing body (spring), 95.96.
...Holding member moving means (solenoid). Applicant's agent Patent attorney Takehiko Suzue Figure 6 Figure 7

Claims (2)

[Claims] (1) A developing device having a plurality of developing bodies and capable of selectively driving these developing bodies to perform development, wherein a plurality of independent driving forces transmit driving force to each of the developing bodies. a transmission system, a drive source common to these drive force transmission systems,
A developing device comprising a driving force transmission switching means for selectively transmitting the driving force of the driving source to each of the driving force transmission systems. (2) The driving force transmission switching means includes a driving gear driven by a driving source, a plurality of driven gears that can transmit driving force to a plurality of driving force transmission systems by meshing with the driving gear, and these driven gears. a retaining member that holds the driven gear; a biasing body that always biases the retaining member in a predetermined direction so that the driven gear meshes with the driving gear; and a holding member moving means for selectively engaging the driven gear with the driving gear by rotating it against the biasing force and transmitting the driving force to any one of the driving force transmission system. A developing device according to claim 1, characterized in that: