JPH08248716A - Developing device - Google Patents

Abstract

PURPOSE: To finish discharging operations in all the developing devices in the shortest time by selecting and driving one or more developing devices within such an extent that the load torque of a driving motor does not exceed a rating torque. CONSTITUTION: The driving motor is provided with the rating torque capable of simultaneously driving two developing devices in developing operation. At the discharging operation time in the developing device, the developing devices 11 and 12 are simultaneously driven. Developer in the developing devices 11 and 12 are carried and discharged by the outer screw 84 of a rotating agitation screw 51. The load torque of the driving motor is reduced in accordance with the discharge of the developer. After a prescribed time T2 from the start of the discharging operation in the developing devices 11 and 12, a developing device 13 is driven together. The time T2 is a time required for reducing the load torque of the driving motor by the amount of the torque for driving one developing device. Besides, after a prescribed time T3 from the start of driving the developing device 13, a developing device 14 is driven together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device having a plurality of developing devices, which is used in an electrophotographic multicolor image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic multicolor image forming apparatus using a powder developer, particularly a two-component developer comprising a mixture of a toner and a carrier, developers having different colors (usually yellow , Magenta, cyan, and black), each of which has a developing drive motor, and the developing operation of each developing device is driven by the corresponding developing drive motor. On the other hand, the discharging operation when discharging the developer deteriorated due to printing endurance from the developing device and replacing the same is performed by one or more discharging driving motors provided separately from the developing motors. A product equipped with a developing device that is driven by a is commercialized.

[0003]

However, in the developing device of the above-mentioned type, in addition to each developing device having a developing drive motor, a separate discharging drive motor is provided, resulting in high cost. In addition, there is a problem in that the size of the apparatus cannot be reduced due to the space saving inside the image forming apparatus.

On the other hand, if a large-torque driving motor that can serve both as the developing driving motor and the discharging driving motor is used, it is possible to drive all the developing devices simultaneously with one motor. However, at the time of development, there is no time to operate three or more developing devices at the same time, so that use efficiency of the motor is wasted. On the other hand, if one driving motor having a small rated torque is used and only the developing device that performs the developing operation is selectively driven, the usage efficiency of the motor can be increased. However, during the discharging operation in this case, since the load torque exceeds the rated torque, it is not possible to drive all the developing devices at the same time to perform the discharging operation all at once. If it is done, there is a problem that it takes time to complete the discharge for all the developing devices.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and all the developing and discharging operations of the developing device are efficiently driven by using one drive motor, and each developing device is driven. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device capable of completing the discharging operation for the above in the shortest time.

[0006]

In order to achieve the above object, the present invention comprises a plurality of developing devices arranged with respect to a photoconductor, each developing device forming an electrostatic latent image formed on the photoconductor. In a developing device that is driven during the developing operation that visualizes the developer and during the discharging operation that discharges the deteriorated developer to the outside of the developing device, up to two developing devices that are in the developing operation can be driven at the same time. Has a high rated torque and serves as a drive source for the developing device in both the developing operation and the discharging operation.
One drive motor and one or more developing devices are selected and driven during the discharging operation so that the load torque of the driving motor does not exceed the rated torque, and the load torque decreases as the developer is discharged. Then, the next developing device is driven together within the range not exceeding the rated torque, and this process is applied to all the developing devices, while the control is performed to sequentially stop the driving from the developing devices that have finished discharging. Means and are provided.

[0007]

The plurality of developing devices of the developing device having the above structure are
It is driven by one drive motor in both the developing operation and the discharging operation. The drive motor has a rated torque capable of simultaneously driving up to two of the plurality of developing devices that are in the developing operation, but three or more developing devices are simultaneously driven during the developing operation. The load torque does not exceed the rated torque of the drive motor because there is no time period.

During the developer discharging operation, the control means turns on the drive motor to first select and drive one or more developing devices. At this time, the load torque of the drive motor is equal to or lower than the rated torque and rises to a predetermined value required to drive the selected developing device. After that, the load torque decreases as the developer is discharged from these developing devices. When the load torque of the drive motor decreases from the predetermined value by the torque required to drive one developing device, the control means also drives another developing device. At this time, the load torque of the drive motor once again rises to the above-mentioned predetermined value, but immediately begins to decrease as the developer is discharged, and when the drive torque of one developing device decreases, the control means Further, the driving of another developing device is started. The above-mentioned control means applies such a process to all the developing devices, while sequentially stopping the driving from the developing devices that have finished discharging the developer, and when the discharging is completed for all the developing devices, the drive motor is turned off. To do. In this way, the number of developing devices that perform discharging operations increases in sequence,
The load torque does not exceed the rated torque of the drive motor, and the discharging operation is completed for all the developing devices in the shortest time when one drive motor having the above rated torque is used.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an electrophotographic multicolor image forming apparatus including a developing device 10 according to an embodiment of the present invention.
That is, a schematic configuration of the multicolor copying machine 1-is shown. The copying machine 1 includes an original platen 2 made of transparent plate glass and an original cover 3 for opening and closing the upper surface of the original platen 2, and the original is placed on the original platen 2 with the image surface to be copied facing downward. It is placed and covered with the opening / closing cover 3. Below the document platen 2, there is provided a scanning optical unit 4 that operates in the direction of the arrow a along the lower surface of the document platen 2 and reads the document image placed on the document platen 2. The read original image is decomposed into four-value (yellow, magenta, cyan, black) image data and stored in the image recording unit 5. The image data stored in the image recording unit 5 is sent to the laser exposure device 6 in the order of yellow, magenta, cyan, and black, and the laser 7 corresponding to each image data is transferred to the electrostatic latent image carrier--that is, the photoconductor 8.
-Is exposed.

The photoconductor 8 is composed of a drum having a photosensitive layer on the outer periphery thereof, and is surrounded by a charging device 9, developing devices 11, 12, 1
There are provided a developing device 10 including 3 and 14, a transfer device 15, a cleaning device 16, and a charge eliminating device 17. When the photoconductor 8 rotates in the direction of the arrow 18, the photoconductive layer on the outer periphery of the photoconductor 8 is uniformly charged by the charger 9, and the charged region is exposed to the laser 7 as described above, so that yellow, magenta, cyan, and black are exposed. Electrostatic latent images corresponding to the image data are sequentially formed. These electrostatic latent images are yellow, magenta,
Developer 1 having cyan and black toners, respectively
The image is developed by 1, 12, 13, and 14 to form a visible image, and is sequentially transferred to a transfer sheet (for example, a sheet) by the transfer device 15 and superposed. The toner not transferred to the transfer sheet is collected by the cleaning device 16. In addition, the photoconductor 8
The residual electric charge is removed by the static eliminator 17 to prepare for the next development.

The transfer device 15 includes a transfer drum 19 which rotates in the direction of arrow 20. The transfer drum 19 is a chucking device 2 that holds the leading end of the transfer sheet on the outer peripheral portion.
1 is provided. A transfer charger 22 is provided in the inner space of the transfer drum 19 so as to face the photoconductor 8. In addition, along the outer circumference or the inner circumference of the transfer drum 19, downstream of the transfer charger 22 with respect to the rotation direction of the transfer drum 19, the first static eliminator 23, the sheet separating device 24,
A second charge removing device 25 and a cleaning device 26 are provided.

The transfer sheet 27 is supplied from a paper feed unit 28, 29, or 30 and held by the chucking device 21 on the outer periphery of the transfer drum 19. Further, when the transfer drum 19 rotates, it is sent to the facing portion (transfer area 31) between the photoconductor 8 and the transfer drum 19, and every time the transfer drum 19 makes one rotation,
The four color toner images are transferred onto the transfer sheet 27 in an overlapping manner. Note that the front end of the transfer sheet 27 is resist-adjusted with each toner image, and all the toner images are superposed without displacement.

When the transfer of all the toner images is completed, the transfer sheet 27 is destaticized by the first destaticizing device 23, separated from the transfer drum 19 by the separating device 24, and the toner is thermally fixed by the fixing device 32, so that the discharge tray is discharged. It is discharged to 33. On the other hand, the transfer drum 19 from which the transfer sheet 27 is removed is the second
The charge is removed by the static eliminator 25, and the cleaning device 26
To remove the residue.

Next, the developing devices 11, 12, 13, 14 provided in the developing device 10 will be described. 4 above
The two developers have basically the same structure. To be more specific with reference to FIG. 2, the housing 34 of each of the developing units 11 to 14 has an opening 35 formed in an upper portion facing the photoconductor. Inside the opening 35, the opening 35
From the developing roller 36, which slightly projects from the photoconductor 8 and faces the photoconductor 8.
Is arranged. A dust prevention sheet 38 is attached to the end of one wall 37 facing the outer peripheral surface of the developing roller 36, and the tip of the dust prevention sheet 38 faces the photoconductor 8 in a non-contact manner. The other wall 39 facing the outer peripheral surface of the developing roller 36
A partition wall 40 is disposed inside the partition wall 40, and between the wall 39 and the partition wall 40, the dust and smoke suction chamber 4 in which the photoconductor facing portion is opened.
1 is formed and is connected to a suction device (not shown).

The developing roller 36 is provided with a magnet body 42 fixed in a non-rotating state, and an arrow 44 attached to the exterior of the magnet body 42.
And a developing sleeve 43 that is rotationally driven in the direction. The developing sleeve 43 is connected to a developing bias power source 45. Below the developing roller 36, a supply roller 46 is provided at a predetermined distance from the developing roller 36. Similar to the developing roller 36, the supply roller 46 is composed of a magnet body 47 fixed in a non-rotating state and a supply sleeve 48 which is exteriorly mounted on the magnet body 47 and is rotationally driven in the direction of arrow 49. The spike-height restricting plate 50 fixed to the outer peripheral surface of the supply sleeve 48 faces the outer peripheral surface of the supply sleeve 48 with a predetermined gap. A developer stirring screw 51 is provided below the supply roller 46 and rotates in the direction of arrow 52 to mix the developer contained in the housing 34, that is, the two-component developer including toner and carrier. It has become so. Further, a toner concentration detection sensor 53 is provided at the bottom of the housing 34 so as to face the stirring screw 51, and the toner concentration contained in the developer can be detected.

A plurality of magnetic poles are formed on the magnet bodies 42 and 47, respectively, as shown in FIG. In the drawings, N and S represent polarities, respectively. More specifically, the developing roller 36 is attached to the magnet body 42 of the developing roller 36.
A magnetic pole N1 is arranged as a developing magnetic pole at a portion facing the photoconductor 8 and. In addition, the sleeve rotation direction (direction of arrow 44) from the closest position between the developing roller 36 and the supply roller 46.
The magnetic pole N2 is disposed on the downstream side of the. The magnetic pole S1 is arranged between the magnetic poles N1 and N2, and the magnetic pole S2 is arranged downstream of the magnetic pole N1 in the rotation direction of the developing sleeve 43. On the other hand, the magnet sleeve 47 of the supply roller 46 is sandwiched between the magnet sleeve 47 and the developing sleeve 43 so as to sandwich the supply sleeve 48.
The magnetic pole S3 is arranged on the upstream side and the magnetic pole S4 having the same polarity is arranged on the downstream side with respect to the rotation direction, and the magnetic pole N3 is arranged on the upstream side in the rotation direction of the supply sleeve 48 from the facing portion of the spike height regulating plate 50.

As shown in FIG. 4, the stirring screw 51 has an inner screw 81 having a plurality of feed blades 80 integrally formed on its rotating shaft 51a, and a screw pipe fixed to the inner screw 81 so as to be exteriorly mounted. 82
It consists of and. The feed blade 80 is formed so as to be inclined with respect to the axial direction of the rotating shaft 51a and the blades are alternately intersected with each other. By rotating the stirring screw 51 in the direction of the arrow 52, the developer inside the screw pipe 82 is mixed and stirred. While having the function of conveying in the direction of arrow 83. The screw pipe 82 has an outer screw 84 composed of a plurality of spirally formed protrusions on the outer peripheral surface of the central region except both ends thereof. The outer screw 84 has a function of pumping up the developer on the outer side of the screw pipe 82 and conveying it in the direction of arrow 85 by rotation in the direction of arrow 52. On both ends of the screw pipe 82, openings 88 and 89 defined by a plurality of axial ribs 86 and 87 are formed. Therefore, the toner newly supplied to the rotating stirring screw 51 from the direction of the arrow 90 is taken into the stirring screw 51 through the opening 88 and mixed and stirred with the existing developer in the direction of the arrow 83. Be transported. And the opening 8
The developer extruded outward from the 9 is the outer screw 8
While being conveyed in the direction of arrow 85 by 4, a part is pumped up and supplied to the supply roller 46, and the rest is taken in again through the opening 88 and is circulated and conveyed between the inside and outside of the stirring screw 51. It

In the developing device having the above construction, the developer contained in the housing 34 is the stirring screw 5.
The toner and carrier are agitated at 1 and charged to a predetermined polarity. Further, the developer drawn up by the stirring screw 51 is supplied to the supply roller 4 in the area facing the magnetic pole N3.
6, and the supply sleeve 4 is supplied by the magnetic force of the magnetic pole N3.
8 is held on the outer circumference. Further, the developer is conveyed in the same direction as the supply sleeve 48 rotates in the direction of the arrow 49, and is regulated by the spike height regulating plate 50 to form a pool. The developer that has passed between the height control plate 50 and the supply roller 46 is supplied to the developing sleeve 43 at the portion where the magnetic pole S3 and the magnetic pole N2 face each other. Next, by the rotation of the developing sleeve 43 in the direction of the arrow 44, the developer passes through the facing portion of the magnetic pole S1 and then the developing magnetic pole N1.
Of the electrostatic latent image is made visible with the toner by contacting the photoconductor 8 there. When the developer that has passed through the developing area passes through the facing portion of the magnetic pole S2, the developer is separated from the developing sleeve 43 by the repulsive magnetic field formed between the magnetic pole S2 and the magnetic pole S4 and falls onto the supply roller 46. Further, due to the repulsive magnetic field, the developing sleeve 43 and the supply sleeve 4
8 is prevented from invading the developer. And
The developer dropped to the supply sleeve 48 drops toward the stirring screw 51, and is stirred again by the stirring screw 51. The dust and smoke toner scattered from the opening 35 facing the photoconductor 8 is prevented from being scattered to the outside by the dust and smoke prevention sheet 38, and is sucked and collected through the dust and smoke suction chamber 41.

Next, with reference to FIGS.
The drive units 1, 12, 13, 14 and the transmission mechanism 68 for transmitting the rotation of the drive motor M to the drive units will be described. As shown in FIG. 5, the rotating shafts 46a and 51a of the supply roller 46 and the stirring screw 51 are respectively connected to the developing devices 11 to 11.
A supply roller drive gear 55 and a stirring screw drive gear 56 are fixed to the ends of the side walls 54 of the housing 34 of FIG. These drive gears 5
An electromagnetic clutch CL is fixed to a side plate 57 attached to the housing 34 so as to cover 5, 56, and an internal gear 59 of the clutch 58 is connected to the two drive gears to turn on the electromagnetic clutch CL. Thus, the rotation is simultaneously transmitted to the supply roller 46 and the stirring screw 51.

The developing roller 36 extending from the inside of the developing device to the outside of the side plate 57 has a rotating shaft, and the developing roller drive gear 6
0 is fixed. The drive gear 60 is provided on the side plate 5
It is connected to an external gear 64 of the electromagnetic clutch CL via idle gears 62 and 63 that are axially supported by a support plate 61 attached to the No. The external gear 64 is connected to the drive gear 65 by mounting the developing device 10 including the developing devices 11 to 14 on the copying machine 1, and the rotation of the drive motor M is transmitted to the drive gear 65 to develop the external gear 64. The devices 11 to 14 are driven. Here, since the developing roller drive gear 60 and the drive gear 65 are connected via the idle gear 62 having gear portions at both ends, the idle gear 63, and the external gear 64 of the electromagnetic clutch CL,
The rotation of the developing sleeve 43 of the developing roller 36 and its stopping are interlocked with the drive gear 65.

As shown in FIG. 6, the drive motor M, which is the only drive source for each of the developing devices 11-14, transmits the rotation to the drive gear 65 of each of the developing devices 11-14 via the transmission mechanism 68. To do. The transmission mechanism 68 includes pulleys 69, 7
It is equipped with a belt 73 wound around 0, 71, 72,
The rotation of the motor gear 74 connected to the drive motor M is transmitted to the pulley 69 via the reduction gear 75, so that the belt 73 moves in the direction of arrow 76. This belt 73
Of the drive gears 65 (Y) and 6 of the developing devices 11 and 12 connected to the transmission gear 77, respectively.
5 (M) and the drive gears 65 (C) and 65 (K) of the developing devices 13 and 14 connected to the transmission gear 78 are rotationally driven, respectively.

By the way, some conventional developing devices include one or a plurality of electromagnetic clutches for controlling the rotation of the developing roller, in addition to the electromagnetic clutch for controlling the rotation of the supply roller and the stirring screw. However, in the developing device 10 of this embodiment, since the developing sleeve 43 is rotated in synchronization with the driving of the drive motor M without providing such an electromagnetic clutch, the cost can be suppressed by reducing the electromagnetic clutch. At the same time, the space for disposing the electromagnetic clutch for the developing roller can be saved. Therefore, there is an effect that the space can be saved by reducing the width of the copying machine 1 in the depth direction (the direction perpendicular to the paper surface in FIG. 1).

The rotation of the drive motor M is transmitted to the drive unit via the transmission mechanism 68 having the above-described structure, and the developing devices 11 to 11 are
It is possible to switch the developing device between the developing state and the non-developing state by driving 14 and controlling the on / off of the electromagnetic clutch CL provided in the drive section. Hereinafter, a specific description will be given with reference to FIGS.
When a certain developing device is in the developing state, as shown in FIG. 7, the electromagnetic clutch CL is turned on while the drive motor M is turned on, and the developing sleeve 43 of the developing roller 36 rotates in the direction of arrow 44. And supply roller 4
6, the supply sleeve 48 and the stirring screw 51 rotate in the directions of arrows 49 and 52, respectively. As a result, the developer drawn up by the stirring screw 51 is supplied to the supply sleeve 48.
Is supplied from the developing sleeve 43 to the developing sleeve 43, and the developer having passed through the developing area is sent back to the stirring screw 51 via the supplying sleeve 48.

When the developing device is switched from the developing state to the non-developing state, the electromagnetic clutch CL is turned off to stop the rotation of the supply sleeve 48 and the stirring screw 51. As described above, the rotation of the stirring screw 51 is stopped at the same time as the supply sleeve 48, and the stirring screw 51 is stirred only in the developing state. Therefore, the stirring screw 51 is driven in cooperation with the developing sleeve 43, compared to the conventional stirring. Time is reduced. This makes it possible to minimize the stress applied to the developer and delay the replacement time due to deterioration, so that the developer can be used efficiently. On the other hand, the developing sleeve 43 is driven by the drive motor M and continues to rotate. As a result, as shown in FIG. 8, the supply of the developer from the stirring screw 51 to the supply sleeve 48 is stopped, but the developer drawn up by the stirring screw 51 is
The magnetic force of the magnetic pole N3 inside the supply sleeve 48 causes the magnetic flux to stay near the height control plate 50. Further, the developer held on the developing sleeve 43 is conveyed in the direction of the arrow 44 by the rotation of the developing sleeve 43 and drops to the supply sleeve 48. Therefore, as shown in FIG. The agent is gone. In this way, the developer that was in contact with the photoconductor 8 in the developing area when the electromagnetic clutch CL was turned off is removed from the developing area, and the developing device is switched to the non-developing state. However, even when the developing sleeve 43 is in the non-developing state, it continues to rotate until the drive motor M is turned off.

When one developing device finishes the development as described above, the other three developing devices successively perform the development. At this time, as in the developing device 11 → 12 → 13 → 14,
In the developing device in which the developing devices on the downstream side in the rotation direction of (1) sequentially perform development, there is no time when the two developing devices are in the developing state at the same time. However, for the purpose of preventing the photoreceptor 8 from rotating excessively and accelerating the deterioration, and shortening the image forming time for one sheet, for example, the developing device 1
As shown in 3 → 12 → 11 → 14, in the developing device in which the developing device on the downstream side in the rotation direction of the photoconductor 8 performs the development, and the developing device located on the upstream side then performs the development. As shown in the timing chart, two developing units (13, 12, 1
There is a time t when 2 and 11) are in the developing state at the same time (during this time t, the developing sleeves 43 of the other two developing devices in the non-developing state are also in the idling state as shown in FIG. .). On the other hand, no matter how the order of the developing devices to be driven is changed, there is no time to drive three or more developing devices simultaneously. It causes waste. Further, the torque required to drive the two developing devices in which the developing sleeve 43 is in the idling state is considerably smaller than the driving torque of one developing device in the developing operation. From this, the drive motor M cannot drive three developing devices at the same time during the developing operation, but selects one having a rated torque capable of driving up to two load motors with a margin in load torque.

Next, with reference to FIGS. 11 to 13, a developer discharging mechanism in each of the developing devices 11 to 14 and its discharging operation will be described. The stirring screw 51 has a total length longer than that of the developing roller 36 and the supply roller 46, and projects outward from the housing 34 on the side opposite to the drive section. The stirring screw 51 covers the projecting portion and the stirring screw 51.
A toner replenishing passage 95 rotatably supporting one end of the rotating shaft 51a is detachably provided on the side wall of the housing 34. A toner replenishing port 96 is formed above the toner replenishing path 95, and new toner is replenished from the replenishing port 96 into the developing device in accordance with the detection value of the toner concentration detection sensor 53. A developer discharge port 97 is formed below the toner supply path 95 facing the toner supply port 96. The discharge port 97 is closed by a shutter 98 that is opened / closed by a driving device (not shown) except when the developing device performs a discharge operation. The shutter 98
May be manually opened and closed by the operator during the discharging operation. Further, below the discharge port 97, a developer container 99 for receiving the discharged developer is installed.

The discharging operation of the developer in each of the developing devices 11 to 14 is driven by the driving motor M which is also the driving source of the developing operation, and its operation control is performed by the CPU 100 as a control means. The CPU 100 has
As shown in FIG. 12, the developer discharge signal is input,
This ejection signal may be automatically input for each predetermined number of printable sheets or for each predetermined period, or may be input based on an operator's instruction. From the CPU 100, a photoconductor motor that drives the photoconductor 8, a charger 9, and a static eliminator 1
7, signals are output to the drive motor M, the electromagnetic clutch CL of each of the developing devices 11 to 14, and the shutter 98 drive device.

The drive motor M is a developing device in the developing operation-that is, when the electromagnetic clutch CL is turned on, the developing sleeve 43, the supply sleeve 48 and the stirring screw 5 are connected.
1 has a rated torque capable of driving up to two developing devices (see FIG. 7) in a rotating state at the same time.
L is turned on to supply sleeve 48 and stirring screw 5
Since 1 is rotated, the load torque at the beginning of the discharging operation required for driving one developing device is the same as that during the developing operation. Therefore, during the discharging operation, the CPU 100 first selects one or more developing devices within a range in which the load torque of the drive motor M does not exceed the rated torque, and the load torque decreases as the developer is discharged. Then, the next developing device is driven together within the range not exceeding the above rated torque, and while this process is applied to all developing devices, it is possible to control the driving to be stopped sequentially from the developing device which has finished discharging the developer. To do. Hereinafter, a specific description will be given with reference to FIG.

When the developer discharge signal is input, the CPU 100 first turns on the shutter driving device to open the discharge port 97, and turns on the photoconductor motor to rotate the photoconductor 8. At the same time, the charger 9 and the static eliminator 17 are turned on. This is to prevent toner from adhering from the developer that has been conveyed to the developing area during the discharging operation.
This is for stabilizing the surface potential of the photoconductor 8. Also,
At the same time, the drive motor M is turned on, but at this time, since the electromagnetic clutch CL of each developing device is in the off state, the load torque T of the drive motor M in this state is four developing sleeves 4.
The torque Ta is required to drive No. 3 in the non-developing state (see FIG. 9).

When the surface potential of the photoconductor 8 is stable,
The electromagnetic clutches CL of the developing devices 11 and 12 are simultaneously turned on to rotate the stirring screw 51 and the like. At this time, the load torque T of the drive motor M is equal to that of the two supply sleeves 4 of the developing device.
8 and the torque required to drive the stirring screw 51 rises to the torque Tb that is added to the torque Ta, but this torque Tb is a value that does not exceed the rated torque. The developer in the developing devices 11 and 12 is conveyed toward the discharge port 97 by the outer screw 84 of the rotating stirring screw 51, and is discharged from the discharge port 97 into the developer container 99. Further, since the resistance decreases as the developer is discharged from the developing device, the load torque of the drive motor M decreases.

After the time T2 has elapsed from the start of the discharging operation of the developing devices 11 and 12, the electromagnetic clutch CL of the developing device 13 is turned on to drive the third developing device together. Immediately before driving the developing device 13, a considerable amount of the developer in the developing devices 11 and 12 is discharged, and the load torque T of the drive motor M is reduced to the torque Tc. By driving, the torque again rises to Tb. Here, the time T2 is
This is the time required for the combined load torque of the developing devices 11 and 12 performing the discharging operation to be reduced by the amount of torque for driving the supply sleeve 48 and the stirring screw 51 of one developing device.

Further, the time T from the start of driving the developing device 13
After the lapse of 3 seconds, the electromagnetic clutch CL of the developing device 14 is turned on to drive the fourth developing device together. Immediately before driving the developing device 14, the load torque T of the drive motor M decreases to the torque Tc as the developer is discharged from the developing devices 11 to 13.
Rise to. Here, the time T3 is the developer 11 to 13
Is the time required to reduce the combined load torque by the torque for driving the supply sleeve 48 and the stirring screw 51 of one developing device.

In the state where the developing devices 11 to 14 are performing the discharging operation, the electromagnetic clutch CL of the developing devices 11 and 12 is turned off and the discharging operation is stopped after the time T1 has elapsed from the start of driving the developing devices 11 and 12. . Here, the time T1 is the time required to discharge 90% or more of the developer inside one developing device. Similarly, for the developing devices 13 and 14, the electromagnetic clutch CL is turned off after a lapse of time T1 from the start of driving of each developing device, and the discharging operation is sequentially stopped. Then, after the supply sleeve 48 of the developing device 14 and the stirring screw 51 have completely stopped rotating, the drive motor M, the photoconductor motor, the charger 9, and the neutralization device 17 are turned off, and at the same time, the shutter drive device is operated. The discharge port 97 is closed, thereby ending the discharge operation.

In the conventional developing device, four to six driving motors are used to drive the developing operation and the developer discharging operation of the four developing devices. For example, it can be driven by one drive motor of about 15 watts.

[0035]

As is apparent from the above description, according to the developing device of the present invention, one drive motor is used as efficiently as possible and the developing operation and the developer discharging operation of a plurality of developing devices are performed. Is driving. Therefore, the cost can be significantly reduced as compared with the case where the above-described operation is driven by using a plurality of drive motors as in the conventional developing device. Further, since the number of drive motors can be reduced, the arrangement space inside the image forming apparatus can be saved, which facilitates downsizing of the apparatus and contributes to space saving.

Further, at the time of the developer discharging operation, the control for sequentially driving each developing device within the range in which the load torque of the drive motor does not exceed the rated torque is performed, so that one drive motor can be used with high efficiency. The discharging operation can be completed in the shortest time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a multicolor copying machine.

FIG. 2 is a cross-sectional view of a developing device.

FIG. 3 is a magnetic field distribution diagram of a developing roller and a supply roller.

FIG. 4 is a partially cutaway side view of a stirring screw.

FIG. 5 is a diagram showing a drive unit of a developing device.

FIG. 6 is a diagram showing a transmission mechanism that transmits drive to each developing device.

FIG. 7 is a diagram illustrating the movement of the developer inside the developing device.

FIG. 8 is a view for explaining the movement of the developer inside the developing device, following FIG. 7.

FIG. 9 is a view for explaining the movement of the developer inside the developing device, following FIG. 8.

FIG. 10 is a diagram showing a driving timing of each developing device.

FIG. 11 is a diagram showing a developer discharging mechanism.

FIG. 12 is an input / output diagram of a CPU that controls a developer discharging operation.

FIG. 13 is a diagram showing a drive timing of each developing device and a variation of a load torque of a drive motor in a discharging operation.

[Explanation of symbols]

8 ... Photosensitive member, 10 ... Developing device, 11-14 ... Developing device, 1
00 ... CPU (control means), M ... drive motor

Claims (1)

[Claims] 1. A developing device comprising a plurality of developing devices arranged with respect to a photoconductor, wherein each developing device visualizes an electrostatic latent image formed on the photoconductor with a developer, and deteriorated development. In a developing device driven by a discharging operation for discharging the developer to the outside of the developing device, the developing device has a rated torque capable of driving up to two developing devices at the same time during the developing operation. In the above case, one driving motor which is a driving source of the developing device and one or more developing devices are selected and driven during the discharging operation within a range in which the load torque of the driving motor does not exceed the rated torque. When the load torque decreases with the discharge of the developer, the next developing device is driven together within the range where the above rated torque is not exceeded, and this process is applied to all the developing devices while discharging the developer. Finished development Developing apparatus is characterized by comprising a control means for controlling to stop the sequential driving from.