JP2001134073A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a developing roller contact with/separate from a photoreceptor in a state where the developing roller is surely rotated at speed equal to or above specified revolving speed, to restrain vibration and to facilitate initializing work. SOLUTION: At the time of forming an image, a timing belt 18 is always rotated by the driving force of a driving motor. When the developing roller 4a is at a position B by the rotation of a rotary 3, a developing device driving gear 25 is meshed with the tooth of the belt 18, and the rotation of the belt 18 is transmitted to the roller 4a through the gear 25, then the roller 4a is rotated. At such a time, the roller 4a does not reach a position C where it abuts on the photoreceptor 8 yet. When the roller 4a is at a position C being a developing position, the rotary 3 is stopped and development is performed. When the roller 4a is at a succeeding position D where it separates from the photoreceptor 8 by the re-rotation of the rotary 3, the meshing of the gear 25 with the tooth of the belt 18 is released and the rotation of the roller 4a is stopped. Thus, the roller 4a always contacts with/separates from the photoreceptor 8 in a rotating state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as an electrostatic copying machine or a printer, provided with a developing device for performing multicolor development of two or more colors such as full color by a plurality of developing devices mounted on a rotating body. The present invention belongs to the technical field of a forming apparatus, and particularly to the technical field of a contact developing type image forming apparatus that performs development in a state where a developing roller of a developing unit is in contact with a photoconductor.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as an electrostatic copying machine or a printer is provided with a developing device for performing multi-color development of two or more colors such as full color by a plurality of developing devices mounted on a rotating body. Various image forming apparatuses have been developed. In this image forming apparatus, a rotating body is rotated at the time of image formation, and a developing roller of each developing unit is sequentially set to a developing position, and a latent image on a photosensitive body is sequentially developed for each color to form an image. I have.

A conventional image forming apparatus of this type includes a contact developing type image forming apparatus in which a developing roller is normally separated from a photoreceptor and a developing roller is brought into contact with the photoreceptor during development to perform development. is there. In this contact developing type image forming apparatus, the developing roller comes in contact with and separates from the photoconductor, and thus the photoconductor may be damaged by the contact and separation of the developing roller. It is suppressed when the photosensitive member is brought into contact with or separated from the photosensitive member in a rotating state. Therefore, in order to prevent damage to the photoconductor, it is necessary to bring the photoconductor into contact with and separate from the photoconductor while the developing roller is always rotated.

As described above, a method for transmitting the driving force of the drive motor of the developing device to the developing roller in order to rotate the developing roller when the developing roller contacts the photosensitive member is described below.
Conventionally, (a) a method in which a fixed driving gear to which a driving force of a driving motor is transmitted and a movably provided developing roller driving gear on a developing roller side are engaged during development, (b) A method of meshing a drive gear, which is provided to be swingable, to which a driving force of a drive motor is transmitted, and a developing roller drive gear on a developing roller side by swinging the swingable drive gear during development; (c) A method in which a driving gear to which a driving force of a driving motor is transmitted and a developing roller driving gear on a developing roller side are engaged with each other by a rotating force of a rotary member such as a rotary during development.

On the other hand, in such an image forming apparatus, it is necessary to first perform initialization after it is shipped from a factory. In carrying out this initialization, the developing roller is driven at a predetermined developing position. In the contact developing type image forming apparatus, in order to prevent the photosensitive member from being damaged as described above, a dummy toner Is applied to the developing roller, and the damage of the photoconductor is prevented by the lubricating action of the dummy toner.

[0006]

However, in the above-mentioned method (a) for transmitting the driving force of the developing device driving motor to the developing roller, the power transmission is performed only in the range of the operation in which the gears contact or separate from each other. Since it cannot be performed, when there is a nip, the developing roller may come into contact with the photosensitive member before the developing roller does not rotate sufficiently. Also,
In the method of (b), similarly to the method of (a), power can be transmitted only in the range of operation in which the gears come into contact with or separate from each other. There is a risk of contact. Furthermore,
In the method (c), when switching between the rotation of the rotary and the rotation of the developing roller, the rotation of the developing roller is stopped,
Alternatively, the rotation speed may not be higher than the predetermined rotation speed.

As described above, in any of the above-mentioned conventional methods (a) to (c), when the developing roller is not rotating when it comes into contact with or separates from the photosensitive member, or when it is not rotating sufficiently. Therefore, it is difficult to sufficiently and surely prevent damage to the photoconductor when the developing roller contacts and separates from the photoconductor. Also, in any of the methods (a) to (c), vibration occurs when the gears come into contact with or separate from each other, and this vibration adversely affects the image quality and generates noise.

Further, in the above-described conventional image forming apparatus, in order to prevent the photosensitive member from being damaged at the time of initialization, the dummy toner is applied to the developing roller before shipment from the factory. Coating work is required, which not only complicates the work at the time of shipping, but also
There is a problem that a dummy toner is required in addition to the developing toner, and the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to make a developing roller contact with and separate from a photosensitive member while the developing roller is securely rotated. It is an object of the present invention to provide an image forming apparatus capable of bringing a developing roller into and out of contact with a photosensitive member in a state where is set to a predetermined number of rotations or more. Another object of the present invention is to provide an inexpensive image forming apparatus capable of suppressing vibration and simplifying the operation for initialization.

[0010]

In order to solve this problem, an invention according to claim 1 includes a rotating member rotatably provided on a frame, a rotating member mounted on the rotating member, and moving toward and away from the photosensitive member. A plurality of developing devices each having a possible developing roller, wherein the developing roller is separated from the photosensitive member during non-development, and a driving force of a developing device drive motor is provided for each developing device during development. The developing roller is sequentially transmitted to the developing roller via a transmitting unit, and the developing roller is sequentially moved to a developing position in contact with the photoconductor by rotation of the rotating body, and is set to this developing position by stopping rotation of the rotating body. In the image forming apparatus performing multi-color development, the developing device driving force transmitting means is rotatably provided on the frame and is rotated by the driving force of the developing device driving motor. A gear, a predetermined number of idler gears rotatably provided on the frame, and a plurality of idler gears. The gears are wound around the developing device drive motor gear and the predetermined number of idler gears so that the teeth mesh with each other. An endless belt made of an elastic body that is rotated by a driving force of the developing device drive motor transmitted to a motor gear; and a rotatable member provided on the rotating body for each developing device. And a developing device driving gear for transmitting a driving force of a driving motor. The developing roller is configured to perform the developing before the developing roller which is to be brought into contact with the photosensitive member by the rotation of the rotating member reaches the developing position where the developing roller comes into contact with the photosensitive member. A developing device driving gear corresponding to the roller meshed with the teeth of the endless belt, and the developing roller moved from the developing position and separated from the photoconductor. Developing device driving gear corresponding to the developing roller and the teeth of the endless belt is characterized by releasing meshing with.

Further, according to the invention of claim 2, the rotating body is
When the developing device drive gear meshes with the teeth of the endless belt and the developing roller reaches a predetermined number of revolutions or more, the developing roller is set to the developing position and is brought into contact with the photoconductor. Features. Furthermore, the invention according to claim 3 is characterized in that, when the rotating body rotates with the developing device driving gear meshing with the teeth of the endless belt and the developing roller reaches a predetermined number of revolutions or more and a predetermined time elapses, A roller is set at the developing position and is brought into contact with the photoconductor.

Further, according to a fourth aspect of the present invention, the rotator includes:
When the developing device driving gear meshes with the teeth of the endless belt and the developing roller is at a predetermined rotation speed or more, the developing roller is moved from the developing position to be separated from the photoconductor. I have. Further, in the invention according to claim 5, the teeth of the endless belt are provided at least inside the endless belt, and the developing device driving gear meshes with the teeth from inside the endless belt. Or the teeth of the endless belt are provided at least outside the endless belt, and the developing device drive gear meshes with the teeth from outside the endless belt. I have.

Further, according to a sixth aspect of the present invention, one of the developing device driving gears is connected to the endless belt in a state where the rotating member is set at a position where none of the developing rollers comes into contact with the photosensitive member. And supplies the toner to the developing roller corresponding to the one developing device driving gear, and further engages the other developing device driving gear with the teeth of the endless belt in the same manner as described above. The initialization is performed by supplying toner to the developing roller corresponding to the driving gear.

[0014]

In the image forming apparatus according to the first aspect of the present invention, before the developing roller which is to come into contact with the photosensitive member reaches the developing position where the developing roller comes into contact with the photosensitive member, the developing roller is brought into contact with the developing roller. The developing device driving gear meshes with the teeth of the endless belt, and the driving force of the developing device driving motor is reliably transmitted to the developing roller. As a result, the developing roller always comes into contact with the photoreceptor in a state of being reliably rotated.
When contacting the photosensitive member, a toner layer is formed on the developing roller, and the developing roller comes into contact with the photosensitive member via the toner layer. Further, after the developing roller in contact with the photoreceptor moves from the developing position and separates from the photoreceptor, the engagement between the developing device driving gear corresponding to the developing roller and the teeth of the endless belt is released. The transmission of the driving force of the developing device drive motor to the developing device is reliably shut off. As a result, the developing roller is always separated from the photoconductor while being reliably rotated, so that the developing roller is separated from the photoconductor via the toner layer. Therefore, the developing roller always rotates and comes into contact with and separates from the photoconductor in a state where the toner layer is formed. At this time, the toner in the toner layer functions as a lubricant, and the photoconductor is not damaged. Is prevented.

In addition, since the endless belt is made of an elastic material, vibration is effectively absorbed when the teeth of the endless belt mesh with the developing device driving gear. Thereby, the adverse effect on the image quality due to the vibration is prevented, and the noise at the time of the engagement is reduced. Further, since the portion of the power transmission mechanism provided outside the rotating body is constituted by an endless belt, the axial length of the developing unit including a plurality of developing units and the rotating body is reduced.

According to the second aspect of the present invention, the developing roller comes into contact with the photosensitive member in a state where the developing roller is always rotated at a predetermined rotational speed or more. Thus, the developing roller comes into contact with the photoconductor in a state where the toner is more reliably supplied, so that damage to the photoconductor when the developing roller comes into contact is more reliably prevented. Further, according to the third aspect of the present invention, the developing roller comes into contact with the photoreceptor after the predetermined time has elapsed while the developing roller is reliably rotated at a predetermined rotation speed or more. As a result, the toner is uniformly dispersed on the developing roller, the toner layer is uniformly formed on the developing roller, and the fluctuation of the rotation of the developing roller is reduced, so that damage to the photoconductor is more reliably prevented.

Further, according to the present invention, the developing roller is separated from the photosensitive member in a state where the developing roller is always rotated at a predetermined rotational speed or more. As a result, the developing roller is separated from the photoconductor in a state where the toner is more reliably supplied, so that damage to the photoconductor when the developing roller is separated is more reliably prevented. Further, in the invention according to claim 5, the developing device drive gear meshes from the inside of the endless belt or meshes from the outside of the endless belt. When the developing device drive gear meshes from the inside of the endless belt, mounting of the endless belt becomes easy, and when the developing device drive gear meshes from the outside of the endless belt, it is advantageous in terms of space. . Further, in the invention according to claim 6, in a state where none of the developing rollers is in contact with the photoconductor, the driving force of the developing device drive motor is reliably transmitted to each developing roller in order,
The developing roller rotates. Therefore, the image forming apparatus can be easily initialized after shipment from the factory without damaging the photoconductor.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus of the present invention,
FIG. 2 is a left side view in FIG. 1 omits some of the components shown in FIG. 2, and FIG. 2 omits some of the components shown in FIG.

As shown in FIG. 1, the image forming apparatus 1 of this embodiment includes a rotary developing device 2, and the rotary developing device 2 includes a rotatably provided rotary 3,
The rotary unit 3 includes yellow (Y), magenta (M), cyan (C), and black (K) developing units 4, 5, 6, and 7, respectively. Each of these developing units 4, 5,
Reference numerals 6 and 7 are disposed in the circumferential direction of the rotary 3 in this order clockwise and at equal intervals.
a, 5a, 6a, 7a and supply rollers 4b, 5b, 6b, 7b. And when the rotary 3 rotates,
In each of these developing devices 4, 5, 6, and 7, the developing rollers 4a, 5a, 6a, and 7a are sequentially brought into contact with a photoconductor (hereinafter, also referred to as OPC) 8. The arrangement order of the developing units 4, 5, 6, 7 for each color is not limited to the above-mentioned order, but is arbitrarily set. However, in the following description, for the sake of convenience, the developing units 4, 5, and 5 are arranged in the order of the aforementioned colors, that is, in the order of yellow, magenta, cyan, and black.
It is assumed that 6, 7 are provided.

As shown in FIGS. 1 and 2, the image forming apparatus 1 further includes a stepping motor 9 as a rotary drive motor for rotating the rotary 3 and a driving force of the stepping motor 9. Driving force transmitting means 10 for transmitting to the developing devices 4, 5,
A developing device drive motor 11 for rotatingly driving the developing rollers 4a, 5a, 6a, 7a; and developing devices 4, 5, 6, 7
The driving force of the developing device drive motor 11 is provided for each of the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4b, 5
b, 6b, and 7b, which are provided with respective developing unit driving force transmitting means 12Y, 12M, 12C, and 12K.

The stepping motor 9 can be stopped while the supply current to the motor is being supplied by setting the stepping motor 9 to the hold current by current control, whereby the position can be easily set. The stepping motor 9 is connected to a central processing unit (C) of the image forming apparatus 1.
PU). The rotary driving force transmitting means 10 includes a rotary driving gear 10 a which is integrally rotatably mounted on the rotating shaft of the stepping motor 9, a rotary driving intermediate gear 10 b which always meshes with the rotary driving gear 10 a, and a rotary driving gear 3 which is concentric with the rotary 3. And a rotary driving intermediate gear 1 provided integrally with the rotary 3.
0b is provided with a rotary gear 10c which always meshes, and the driving force of the stepping motor 9 is reduced and transmitted to the rotary 3. The rotary shaft 3a of the rotary 3 and the rotary gear 10c is rotatably supported by the frame 13 of the image forming apparatus 1. Similarly, the developing device driving motor 11 is also fixed to the frame 13 and is driven and controlled by the CPU similarly to the stepping motor 9.

Further, each developing device driving force transmitting means 12Y, 1
2M, 12C and 12K all have the same configuration,
A developing device driving motor gear 14 rotatably attached to a rotating shaft of the developing device driving motor 11; three first to third idler gears 15, 16, 17 rotatably supported by a frame 13; The developing device drive gear 14 and the first to third idler gears 15, 16 and 17 are wound around the gears 14 and 1 as shown in FIG.
5, an endless timing belt 18 having internal teeth 18a always meshing with 5, 16, 17 and made of an elastic material such as rubber;
Developing roller driving gears 19 (the developing roller driving gears of the developing rollers 5a, 6a, 7a are not shown) which are respectively rotatably mounted on the respective rotating shafts of the developing rollers 4a, 5a, 6a, 7a; Each of these developing roller driving gears 1
9, each of the first developing device driving intermediate gears 2 always meshing with
0 (the first developing device driving intermediate gears meshed with the developing roller driving gears of the developing rollers 5a, 6a, and 7a are not shown).
And a supply roller drive gear 21 (supply roller 5b, 7b) which is rotatably attached to each rotation shaft of each supply roller 4b, 5b, 6b, 7b and always meshes with each first developing device drive intermediate gear 20. The supply roller drive gears 6b and 7b are not shown) and the second developing device drive intermediate gears 22 (the supply rollers 5b, 6b and 7b of the supply rollers 5b, 6b and 7b) which always mesh with the respective supply roller drive gears 21. Each second developing device driving intermediate gear meshing with the driving gear includes:
(Not shown), and each of these second developing device driving intermediate gears 22.
Of the third developing device driving intermediate gears 23 (supply rollers 5b, 6b, 7b)
The third developing device driving intermediate gears, which are gear-connected to the respective supply roller driving gears via the second developing device driving intermediate gears, are not shown), and these third developing device driving intermediate gears 23 are respectively provided. Each fourth developing device driving intermediate gear 24 that always meshes
(The fourth developing device driving intermediate gears which are gear-connected to the respective supply roller driving gears of the supplying rollers 5b, 6b, 7b via the second and third developing device driving intermediate gears are not shown). Each of the fourth developing device driving intermediate gears 24 is provided concentrically and integrally rotatable with each other.
Developing device drive gear 25 which meshes with internal teeth 18a
And

The developing device drive motor gear 14 and the first to third idler gears 15, 16, and 17 are
Timing belt 1 stretched over 4,15,16,17
A developing device driving gear 25 corresponding to a developing device that performs a developing operation at the time of image formation is attached to the internal teeth 18 a of the timing belt 18.
Are set so that the developing device driving gear 25 corresponding to the developing device which does not perform the developing operation is engaged with the developing device while being elastically bent, and is separated from the timing belt 18.

Next, each of the developing rollers 4a,
5a, 6a, 7a and supply rollers 4b, 5b, 6b, 7
The rotation control of b will be described. In this description, for convenience, the developing roller to be brought into contact with the OPC 8 this time is the developing roller 4a of the yellow developing device 4. In the state shown in FIG. 1, the yellow developing roller 4a is
Although it is already in contact with the PC 8 and in the state of the developing position, that is, in the rotational position C of the rotary 3 (hereinafter, simply referred to as position C, other rotational positions are the same), the control by the timing belt 18 will be described in the following. The developing roller 7a of the container 7 is an OPC
8 at a position C where the yellow developing roller 4a
Is not in this position C. When the developing roller 7a of the black developing device 7 is at the position C, the developing roller 4a of the yellow developing device 4 is at the position A where it does not come into contact with the OPC 8. The developing device driving gear 2 corresponding to the developing roller 7a
5 meshes with the internal teeth 18 a of the timing belt 18 while elastically bending the timing belt 18. Furthermore,
The driving force of the developing device driving motor 11 is transmitted to the developing device driving motor gear 14, and the timing belt 18 rotates in the same direction as the rotating direction of the developing device driving motor gear 14.

In this state, the rotary 3 rotates clockwise as indicated by the arrow, the developing roller 7a of the black developing device 7 which has been in contact with the OPC 8 is separated from the OPC 8, and the developing roller 4a is moved to the position C. To rotate. As will be described later in detail, the developing device drive gear 25 corresponding to the developing roller 7a is separated from the timing belt 18 thereafter.

When the developing roller 4a is rotationally moved to the position B where it does not contact the OPC 8, the developing device driving gear 25 corresponding to the developing roller 4a of the yellow developing device 4 causes the timing belt 18 to elastically bend the timing belt 18. Meshes with the internal teeth 18a. Then, the developing device drive motor 11
Is transmitted to the developing device drive gear 25 corresponding to the developing roller 4a, and the developing device drive gear 25 rotates in the same direction as the rotation direction of the timing belt 18. The rotation of the developing device drive gear 25 is transmitted to the yellow developing roller 4a and the supply roller 4b via the yellow developing device driving force transmitting means 12Y.
Both rollers 4a and 4b start rotating.

When the rotary 3 further rotates in the same direction, FIG.
When the developing roller 4a is rotationally moved to the developing position at the position C where the developing roller 4a contacts the OPC 8, the CPU stops the rotary driving stepping motor 9, and the rotation of the rotary 3 stops. At this time, the developing device driving gear 25 elastically bends the timing belt 18 further elastically, so that the engagement between the developing device driving gear 25 and the internal teeth 18a of the timing belt 18 becomes more reliable, and the developing roller 4a rotates by a predetermined rotation. The rotation is continued at more than the number of rotations. As described above, the developing roller 4a starts rotating before the OPC 8 comes into contact with the developing roller 4a.
In a state where the rotation speed is equal to or higher than the predetermined rotation speed, the rotation position is set to the development position by being brought into contact with the OPC 8 while rotating.

Next, when the stepping motor 9 is driven again at the end of the development of yellow and the rotary 3 rotates again in the same direction, the developing roller 4a is separated from the OPC 8 while rotating at a predetermined rotation speed or more. When the developing roller 4a is rotated to the position D, the developing device drive gear 25 is separated from the timing belt 18, and the rotation of the developing roller 4a is stopped.

Each developing roller 5a, 6a, 7a and each supply roller 5 are driven by the driving force of the developing device drive motor 11 in the magenta developing device 5, cyan developing device 6 and black developing device 7.
The rotation control of b, 6b, 7b is performed in the same manner as in the case of the yellow developing device 4 by each developing device drive gear 25 meshing with the internal teeth 18a of the timing belt 18 in this order. I have.

Next, the operation of the thus formed image forming apparatus 1 of this embodiment during image formation will be described. FIG.
Then, the developing roller 4a of the yellow developing device 4 is
Are shown in contact with the developing devices 4, 5, 6,
The developing rollers 4a, 5a, 6a, and 7a are held at positions separated from the OPC 8 during non-development.
That is, the yellow developing roller 4a is moved between the position A and the position B.
In this state, the rotary 3 is stopped and held, and the couplings 12k are held in a disconnected state.

When the image forming apparatus 1 starts operating for image formation, the CPU drives both the stepping motor 9 and the developing device drive motor 11. Since the developing device driving motor gear 14 is rotated by the driving of the developing device driving motor 11, the timing belt 18 which always meshes with the developing device driving motor gear 14 is rotated. Therefore, during the image forming operation, the developing device drive motor gear 14 and the timing belt 18 are constantly rotating. At the same time, the rotary 3 is rotated clockwise by the driving of the stepping motor 9, and the yellow developing roller 4a is rotated toward the position B.

When the developing roller 4a is at the position B, the yellow developing device drive gear 25 starts to mesh with the internal teeth 18a of the timing belt 18 as described above, and both the developing roller 4a and the supply roller 4b start rotating. As a result, the toner is supplied from the supply roller 4b to the developing roller 4a, and the developing roller 4a is
The formation of a toner layer having a predetermined thickness on the surface of the substrate is started. When the rotary 3 further rotates in the same direction and reaches a position C where the developing roller 4a comes into contact with the OPC 8 which is a developing position after a predetermined time has elapsed, the rotation of the rotary 3 is stopped. A predetermined time elapses from the start of rotation of the developing roller 4a to the developing position, and there is a margin for the rising time of the rotation of the developing roller 4a. Therefore, when the developing roller 4a is at the developing position, the developing roller 4a It is rotating at or above the speed. Therefore, the toner is uniformly dispersed in the developing roller 4a, and a toner layer having a predetermined thickness is surely formed on the surface of the developing roller 4a. Also, when the developing roller 4a comes into contact with the OPC 8, damage to the OPC 8 is prevented. Is done. As a result, the developing roller 4a conveys a predetermined amount of toner toward the OPC 8, and the latent image on the OPC 8 is developed with yellow. O
The developed yellow image on the PC 8 is intermediately transferred to the intermediate transfer medium 26. The yellow developing roller 4
When a is at the position C, the developing roller 4a of the next magenta developing device 5 is at the position A as shown in FIG.

When the development of yellow is completed, the rotary 3 rotates in the same direction again, and the developing roller 4a moves away from the OPC 8 while rotating. When the developing roller 4a comes to the position D, the developing device driving gear 25 separates from the timing belt 18, the meshing between the developing device driving gear 25 and the internal teeth 18a of the timing belt 18 is released, and the developing roller 4a and the supply roller 4b are disengaged. The rotation stops.

When the rotary 3 comes to the position B on the developing roller 5a of the magenta developing device 5, the developing device driving gear 25 is moved to the inside of the timing belt 18 as in the case of the yellow developing device 4 described above. The engagement with the teeth 18a starts, and the magenta developing roller 5a and the supply roller 5b start rotating together. Thereafter, as in the case of the developing operation by the yellow developing device 4, the developing operation by the magenta developing device 5 is performed, whereby the magenta developing is performed on the latent image on the OPC, and the developing process on the OPC is performed. The transferred magenta image is intermediate-transferred to the intermediate transfer medium 14.

Subsequently, in the same manner as the yellow development by the yellow development unit 4, the development unit driving gear 25 corresponding to the cyan development by the cyan development unit 6 and the black development by the black development unit 7 is driven by the timing belt. 18 internal teeth 18a
The developed images are sequentially transferred to the intermediate transfer medium 14 by being engaged with the intermediate transfer medium 14. And
The four-color images intermediate-transferred onto the intermediate transfer medium 14 are color-matched, transferred to transfer paper by a transfer unit (not shown), and fixed by a fixing unit to form a full-color image.

Incidentally, before the user uses the image forming apparatus 1 shipped from the factory, it is necessary to initialize the image forming apparatus 1. When the image forming apparatus 1 is initialized, it is necessary to supply a predetermined amount of toner to the developing roller and form a toner layer on the surface of the developing roller in order to prevent OPC from being damaged by the contact of the developing roller. No.
Therefore, the image forming apparatus 1 of this example further includes a position where the four developing rollers 4a, 5a, 6a, and 7a do not sequentially contact the OPC 8 and the developing device drive gear 25 meshes with the internal teeth 18a of the timing belt 18. , The developing roller 4a, 5a, 6a, 7
a, a predetermined amount of toner is supplied to each developing roller 4.
a, 5a, 6a, and 7a. That is, as shown in FIG. 1, the developing rollers 4a, 5a, 6a, 7a
The initialization position E is set at an arbitrary position where the developing device drive gear 25 does not contact the OPC 8 and the developing device drive gear 25 meshes with the internal teeth 18 a of the timing belt 18.

In order to initialize the image forming apparatus 1 shipped from the factory, first, the stepping motor 9 is driven to rotate the rotary 3, and the developing roller of one developing unit is moved to the initial position E. Then, the CPU stops driving the stepping motor 9 and stops the rotation of the rotary 3. Next, when the developing device drive motor 11 is driven by the CPU to rotate the timing belt 18,
One developing device drive gear 25 rotates, and the developing roller and the supply roller of the developing device rotate, and toner is supplied to the developing roller to form a toner layer having a predetermined thickness on the surface. Next, toner is supplied to the developing rollers of the remaining developing devices in the same manner as described above, and a toner layer having a predetermined thickness is formed on the surface thereof. As a result, the image forming apparatus 1 is initialized in a short time without damaging the OPC 8.

As described above, according to the image forming apparatus 1 of this embodiment, when the developing rollers 4a, 5a, 6a, 7a are respectively brought into contact with the OPC 8, these developing rollers 4a, 5a, 6
a and 7a can be brought into contact with the OPC 8 in a state where they are always rotated.
The a, 5a, 6a, and 7a can be brought into contact with the OPC 8 while being constantly rotated at a predetermined rotation speed or more. When the developing rollers 4a, 5a, 6a, 7a are separated from the OPC 8, respectively, these developing rollers 4a, 5a, 6a, 7a
Can be moved away from the OPC 8 while being constantly rotated, and in that case, the developing rollers 4a, 5a,
OPC while rotating 6a, 7a at a predetermined speed or more
8. Thereby, OPC8
When the developing rollers 4a, 5a, 6a, 7a come and go with respect to
Developing rollers 4a, 5a, 6a, 7a and supply rollers 4c,
Since 5c, 6c, 7c are rotating, the developing rollers 4a,
A toner layer having a predetermined thickness can be formed on the surfaces of 5a, 6a and 7a. Therefore, the developing rollers 4a, 5a, 6a, and 7a can be brought into contact with and separated from the OPC 8 via the toner layer, and the toner functions as a lubricant.
Damage to C8 can be effectively prevented.

By setting the start position of the engagement between the developing device drive gear 25 and the internal teeth 18a of the timing belt 18 as appropriate, the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4c, 5c, 6c, Since the rotational drive position of the developing roller 7c can be freely set, and there is a margin for the developing roller 4a, 5a, 6a, 7a to come into contact with the OPC 8, the developing roller 4a, 5a, 6a, 7a The toner can be uniformly dispersed. In addition, even if there is a load fluctuation in the developing rollers 4a, 5a, 6a, and 7a, the developing rollers 4a, 5a, 6a, and 7a have enough time for the rotation rise time.
Before contact with the developing rollers 4a, 5
The rotation speeds of the a, 6a, and 7a can be obtained more reliably, and the rotation fluctuation of the developing rollers 4a, 5a, 6a, and 7a can be reduced. Therefore, a high-quality image can be formed, and the life of the image forming apparatus 1 can be extended.

Further, since the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4c, 5c, 6c, 7c are rotationally driven only in a predetermined area including the developing position, and in other areas, the rotation is stopped. It is possible to suppress toner scattering due to rotational driving. Further, according to the image forming apparatus 1 of the present embodiment, the power transmission to the developing roller and the supply roller is performed by controlling the engagement between the internal teeth 18a of the timing belt 18 and the developing device drive gear 25, so that the configuration is simple. The developing rollers 4a, 5a, 6a, and 7a can be easily and reliably brought into and out of contact with the OPC 8 in a rotating state. In this case, the developing device drive gear 25 resiliently deflects the timing belt 18 so that the internal teeth 18a and the developer drive gear 25 are engaged with each other. Can engage.

Further, since the timing belt 18 is made of an elastic material such as rubber, vibration can be effectively absorbed when the internal teeth 18a and the developing device driving gear 25 mesh with each other. As a result, it is possible to prevent an adverse effect on the image quality due to the vibration, and to reduce noise at the time of meshing. Further, since the portion of the power transmission mechanism provided outside the rotary is constituted by the timing belt 18, the axial length of the developing device 3 can be reduced. Furthermore, according to the image forming apparatus 1 of this example, since all the gears are arranged inside the timing belt 18, the mounting operation over these gears is simplified.

Further, according to the image forming apparatus 1 of the present embodiment, the developing rollers 4a, 5a,
6a, 7a are sequentially set at positions where they do not abut against the OPC 8,
In addition, by driving the developing roller, a toner layer can be reliably formed on the surface of the developing roller, so that initialization can be performed in a short time without damaging the OPC 8. In addition, the dummy toner, which was conventionally performed at the time of shipment from the factory, can be removed from each developing roller 4a,
Since there is no need to apply it on the surface of 5a, 6a, 7a,
The work of applying the dummy toner at the time of shipment from the factory becomes unnecessary, and the work at the time of shipment is simplified. Further, since the dummy toner is not required, the cost can be reduced, and only the toner for forming an image is used, so that the toner can be recycled.

FIG. 4 is a view similar to FIG. 1 showing another example of the embodiment of the present invention. The same components as those in the above-described example are denoted by the same reference numerals, and detailed description thereof will be omitted. In the above-described example, the developing device driving gear 25
Is arranged inside the timing belt 18 so as to mesh with the internal teeth 18a of the timing belt 18,
In the image forming apparatus 1 of this example, as shown in FIG. 4, the developing device driving gear 25 is disposed outside the timing belt 18 so that the developing device driving gear 25 meshes from the outside of the timing belt 18. That is, as shown in FIG. 3B, an inner tooth 18a and an outer tooth 18b are provided on both inside and outside of the timing belt 18, respectively. The developing device drive motor gear 14 and the first and second idler gears 15 and 16 are always meshed with the internal teeth 18a from the inside of the timing belt 18, and the developing device drive gear 25 is connected from the outside of the timing belt 18 to the outside. Tooth 1
8b. Other configurations of the image forming apparatus 1 of this example are the same as those of the above-described example. The operation of the example image forming apparatus 1 is the same as that of the above-described example. Further, according to the image forming apparatus 1 of this example, the timing belt 18 can be arranged compactly, which is advantageous in terms of space. Other functions and effects of the image forming apparatus 1 of this example are the same as those of the above-described example.

In the above-described example, the present invention is described as applied to a full-color image forming apparatus having an intermediate transfer medium. However, the present invention is applied to a plurality of single-color image forming apparatuses having two or more colors. The present invention can be applied to any image forming apparatus as long as the developing device is mounted on a rotating body and the developing roller contacts the photosensitive member.

[0045]

As is apparent from the above description, according to the image forming apparatus of the present invention, the developing roller is brought into contact with and separated from the photosensitive member while the developing roller is always rotated. When the developing roller contacts and separates from the developing roller, a toner layer can be formed on the surface of the developing roller. Thus, the developing roller can be brought into contact with and separated from the photoconductor via the toner layer, and the toner functions as a lubricant, so that damage to the photoconductor can be effectively prevented. Therefore,
A high quality image can be formed, and the life of the image forming apparatus can be improved.

Moreover, since the endless belt is made of an elastic material, the vibration generated when the teeth of the endless belt mesh with the developing device driving gear can be effectively absorbed. As a result, it is possible to prevent an adverse effect on the image quality due to the vibration, and to reduce noise at the time of meshing. Furthermore, since the portion of the power transmission mechanism provided outside the rotating body is constituted by an endless belt, the axial length of the developing unit including a plurality of developing units and the rotating body can be reduced.

In particular, according to the second aspect of the present invention, since the developing roller is kept in contact with the photosensitive member while being constantly rotated at a predetermined rotation speed or more, it is possible to more reliably supply toner to the developing roller. Thus, damage of the photoconductor at the time of contact of the developing roller can be more reliably prevented. Furthermore, according to the third aspect of the present invention, the developing roller is always brought into contact with the photoreceptor in a state where the developing roller is always rotated at a predetermined rotation speed or more and after a predetermined time has elapsed. In addition to being able to be dispersed, fluctuations in the rotation of the developing roller can be suppressed. Thus, the toner layer can be uniformly formed on the developing roller, and the fluctuation of the rotation of the developing roller can be reduced, so that the damage to the photoconductor can be more reliably prevented. Therefore, a higher quality image can be formed, and the life of the image forming apparatus can be further extended.

According to the fourth aspect of the present invention, since the developing roller is always separated from the photoreceptor while rotating at a predetermined rotation speed or more, it is possible to supply toner to the developing roller more reliably. The developing roller can be separated from the photoconductor,
Damage to the photoconductor when the developing roller is separated can be more reliably prevented. Further, according to the fifth aspect of the present invention, the developing device drive gear meshes from the inside of the endless belt or meshes from the outside of the endless belt. When meshing from the inside, the endless belt can be easily mounted, and when the developing device driving gear meshes from the outside of the endless belt, it is advantageous in terms of space.

Further, according to the present invention, since the developing roller can be rotated without being brought into contact with the photoreceptor, the initial stage of the image forming apparatus after shipment from the factory without damaging the photoreceptor. Can be easily performed in a short time. This eliminates the necessity of applying the dummy toner, which has been performed at the time of shipment from the factory, to the surface of each developing roller, so that the work of applying the dummy toner at the time of shipment from the factory can be omitted, and the work at the time of shipment can be simplified. be able to. Further, since the dummy toner is not required, the cost can be reduced, and only the toner for forming an image is used, so that the toner can be recycled.

[Brief description of the drawings]

FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a left side view in FIG.

3A and 3B partially show the timing belt in FIGS. 1 and 4 and gears that mesh with the timing belt, FIG. 3A is a cross-sectional view partially showing the timing belt in FIG. 1, and FIG. FIG. 4 is a sectional view partially showing the timing belt in FIG. 4.

FIG. 4 is a view similar to FIG. 1 and schematically and partially showing another example of the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Developing apparatus, 3 ... Rotary, 4 ...
Yellow developing device, 5 magenta developing device, 6 cyan developing device, 7 black developing device, 4a, 5a, 6a, 7a developing roller, 4b, 5b, 6b, 7b supply roller, 8 ... Photoreceptor (OPC), 9: stepping motor, 10: rotary driving force transmitting means, 11: developing device driving motor, 12
Y, 12M, 12C, 12K: developing device driving force transmitting means, 1
3 Frame, 14 Developing device drive motor gear, 15 First idler gear, 16 Second idler gear, 17 Third
Idler gear, 18 ... Endless timing belt, 19
... developing roller drive gear, 20 ... first developing device driving intermediate gear, 21 ... supply roller driving gear, 22 ... second developing device driving intermediate gear, 23 ... third developing device driving intermediate gear, 24 ... fourth
Developing device drive intermediate gear, 25: Developing device drive gear, 26: Intermediate transfer medium, C: Contact position of the developing roller with OPC

Claims (6)

[Claims] 1. A developing device comprising: a rotating body rotatably provided on a frame; and a plurality of developing devices each having a developing roller mounted on the rotating body and capable of moving toward and away from a photosensitive member. The roller is separated from the photoconductor, and during development, the driving force of a developing device drive motor is sequentially transmitted to the developing roller via a developing device driving force transmitting unit provided for each developing device, and the rotation of the rotating body is also changed. An image forming apparatus that performs multi-color development by sequentially moving the developing roller to a developing position in contact with the photoconductor and setting the developing roller to the developing position when the rotation of the rotating body is stopped; A developing device driving motor gear rotatably provided on the frame and rotated by a driving force of the developing device driving motor; and a predetermined number of idlers rotatably provided on the frame. And a gear having gears, the developing device driving motor gear and the predetermined number of idler gears are wound around the teeth so as to mesh with each other, and are rotated by the driving force of the developing device driving motor transmitted to the developing device driving motor gear. An endless belt made of an elastic material, and a developing device drive gear that is rotatably provided for each developing device on the rotating body and that transmits a driving force of the developing device drive motor to each of the developing rollers. Before the developing roller that comes into contact with the photoconductor by the rotation of the rotating body reaches the developing position where the developing roller comes into contact with the photoconductor, the developing device driving gear corresponding to the developing roller rotates the teeth of the endless belt. After the developing roller moves from the developing position and separates from the photoreceptor, the developing device driving gear corresponding to the developing roller is connected to the endless bell. Image forming apparatus and the teeth and cancels mesh. 2. The developing device according to claim 1, wherein the rotating member is configured to set the developing roller to the developing position when the developing device driving gear meshes with the teeth of the endless belt and the developing roller reaches a predetermined rotation speed or more. The image forming apparatus according to claim 1, wherein the image forming apparatus is brought into contact with the photoconductor. 3. The developing device according to claim 1, wherein the developing device drive gear engages the teeth of the endless belt to rotate the developing roller at a predetermined rotation speed or more and after a predetermined time elapses. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is set at a position and is brought into contact with the photoconductor. 4. The rotating body moves the developing roller from the developing position when the developing device driving gear meshes with the teeth of the endless belt and the developing roller is at a predetermined rotation speed or more. The image forming apparatus according to claim 1, wherein the image forming apparatus is separated from the photoconductor. 5. The endless belt has teeth provided at least inside the endless belt, and the developing device driving gear meshes with the teeth from inside the endless belt, or 2. The endless belt according to claim 1, wherein teeth of the endless belt are provided at least outside the endless belt, and the developing device driving gear meshes with the teeth from outside the endless belt. 3. Or 4
The image forming apparatus according to any one of the above. 6. When one of the developing device driving gears meshes with the teeth of the endless belt, the rotating body is set at a position where none of the developing rollers is in contact with the photosensitive member. Toner is supplied to a developing roller corresponding to one developing device driving gear, and further another developing device driving gear is sequentially meshed with the teeth of the endless belt, and similarly the developing roller corresponding to each developing device driving gear The image forming apparatus according to claim 1, wherein initialization is performed by supplying toner to the image forming apparatus.