JP2001134094A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make constitution simpler and more inexpensive by making a developing roller come in contact with/separate from a photoreceptor in a state where the developing roller is rotated at a speed equal to or above specified revolving speed. SOLUTION: A driving gear 17 is rocked concentrically with a rotating body 3 and rotated through a gear 14 and a belt 18 by the driving force of a driving motor. When the gear 17 arrives at a specified position in front of a position F by the clockwise rotation of a rotary 3, a coupling is connected by a cam 29, and a developing roller 4a is rotated before it arrives at a position D where it abuts on a photoreceptor 8 by the rotation of the gear 17. When the gear 17 is at a position F, the roller 4a is at the developing position D, the rotary 3 is stopped and development is performed. When the roller 4a is separated from the photoreceptor 8 and the gear 14 is at the specified position being the position G by the re-rotation of the rotary 3, the connection of the coupling is released and the rotation of the roller 4a is stopped. Thus, the roller 4a always comes in contact 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. Further, if only the gear power transmission mechanism is used to transmit the driving force of the driving motor, the number of parts, such as gears, increases, so that not only the configuration becomes complicated, but also the cost increases.

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 further 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. It is another object of the present invention to provide an image forming apparatus which can be formed with a simple structure at a low cost and can simplify the operation for initialization.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising a plurality of developing devices each having a developing roller mounted on a rotating member and capable of coming in contact with and separating from a photosensitive member. During development, the developing roller is separated from the photoreceptor, and during development, the driving force of the developing device drive motor is sequentially transmitted to the developing roller via a developing device driving force transmission unit provided for each developing device. An image forming apparatus that performs multi-color development by moving the developing roller to a developing position in contact with the photoconductor in turn by rotation of the rotating body and setting the developing roller to this developing position when the rotating body stops rotating.
The developing device driving force transmitting means is provided concentrically with the rotating body and rotatably, and a developing device driving motor gear that rotates with the driving force of the developing device driving motor, and an axis concentric with the rotating shaft of the rotating body. A developing device drive gear for transmitting the driving force of the developing device drive motor to a developing roller of each developing device, a developing device drive gear, internal gears, and the developing device drive motor gear and the developing device drive. An endless belt made of an elastic body, which is wound around the gear so that the internal teeth mesh with each other, and transmits the driving force of the developing device drive motor transmitted to the developing device drive motor gear to the developing device drive gear; A developing roller driving gear provided so as to be integrally rotatable with each of the developing rollers, an intermediate power transmission gear mechanism for transmitting power to the developing roller driving gear, and a rotation of the developing device driving gear. And a driven-side coupling member for transmitting rotation to the intermediate power transmission gear mechanism, by disengaging the drive-side and driven-side coupling members. A coupling for connecting and disconnecting the developing device drive gear and the intermediate power transmission gear mechanism, and control means for controlling connection and disconnection of the coupling;
The control means connects the coupling before the developing roller which is to come 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 coupling is released after moving from a position and separating from the photoconductor.

Further, according to the invention of claim 2, the rotating body is
When the control unit connects the coupling to rotate the developing roller at a predetermined rotational speed or more, the control unit sets the developing roller to the developing position and abuts the photosensitive member. Furthermore, the invention according to claim 3 is characterized in that, after the rotating member rotates the developing roller to a predetermined number of revolutions or more and a predetermined time has passed since the control means connects the coupling, the developing roller moves the developing roller to the developing position. And contact the photosensitive member.

Further, according to a fourth aspect of the present invention, the rotator includes:
When the control means connects the coupling to rotate the developing roller at a predetermined number of rotations or more, the control means moves the developing roller from the developing position and separates the developing roller from the photosensitive member. Further, the invention of claim 5 is characterized in that the control means is constituted by an arc-shaped cam concentric with the rotating body.

Further, according to a sixth aspect of the present invention, in one of the driving-side coupling member and the driven-side coupling member, an engagement protrusion is provided, and the driving-side coupling member and the driven-side coupling member are provided. One of the side coupling members is provided with an engagement recess to which the engagement protrusion is fitted and rotatably connected, and further, the engagement protrusion and the engagement recess are fitted to each other. It is characterized in that a guide portion is provided to correct and sometimes correct the relative positional deviation. Further, in the invention according to claim 7, initialization is performed by connecting the coupling by the control means in a state where the rotating body is set at a position where none of the developing rollers comes into contact with the photoconductor. It is characterized by:

[0014]

In the image forming apparatus according to the first aspect of the present invention, the control means controls the coupling before the developing roller which comes into contact with the photosensitive member reaches the developing position where it comes into contact with the photosensitive member. Are connected, so that the driving force of the developing device drive motor is reliably transmitted to the developing roller. As a result, the developing roller always comes into contact with the photoconductor in a state of being reliably rotated.When the developing roller comes into contact with the photoconductor, a toner layer is formed on the developing roller, and the developing roller contacts the photoconductor via this toner layer. Come into contact. Further, the control means causes the coupling of the coupling to be released after the developing roller in contact with the photoconductor is moved from the developing position and separated from the photoconductor, so that the transmission of the driving force of the developing device driving motor to the developing roller is reliably shut off. Will be done. As a result, the developing roller always separates from the photoconductor in a state of being reliably rotated.
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.

Further, since power is transmitted by the endless belt made of an elastic material, vibrations generated when the internal teeth of the endless belt mesh with the developing device driving motor gear and the developing device driving gear are effectively reduced. Become absorbed.
As a result, adverse effects on the image quality due to the vibration are prevented, and noise at the time of meshing is reduced. Furthermore, since the driving force of the developing device drive motor is transmitted to the developing device drive gear using the endless belt, the configuration is simpler than, for example, using a gear power transmission mechanism for this power transmission. At the same time, the image forming apparatus becomes inexpensive.

Further, according to the second aspect of the present invention, the developing roller comes into contact with the photoreceptor with the developing roller always rotating 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. Furthermore, in the fifth aspect of the present invention, since the control means is constituted by a cam, the developing roller can easily and reliably come into contact with and separate from the photosensitive member while the developing roller is rotating. In this case, since the cam is formed in an arc shape concentric with the rotating body, the coupling can be more accurately controlled according to the rotation of the rotating body. Further, in the invention according to claim 6, the driving force of the developing device drive motor is reliably transmitted to each developing roller in a state where none of the plurality of developing rollers is in contact with the photoconductor, so that the developing roller rotates. Become. 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,
The developing device drive motor gear 14 is disposed concentrically on the rotary 3 and is integrally rotatably mounted on the rotation shaft 11a of the development device drive motor 11, and one end of the development device drive motor gear 14 is rotatable relative to the rotation shaft 11a of the development device drive motor 11. , A cam rod 16 slidably supported on the other end side of the developing device drive gear support member 15, and a slidable axially slidable on the cam rod 16. A developing device driving gear 17 rotatably supported by the developing device driving gear support member 15 and rotatably provided on the cam rod 16, and the internal teeth 1 as shown in FIG.
8a and an endless end made of an elastic material such as rubber which is stretched between these gears 14 and 17 so that the internal teeth 18a mesh with the developing device driving motor gear 14 and the developing device driving gear 17. The timing belt 18 and each of the developing roller driving gears 19 (each of the developing roller driving gears of the developing rollers 5a, 6a, and 7a are rotatably attached to the respective rotating shafts of the developing rollers 4a, 5a, 6a, and 7a. (Not shown) and first developing device driving intermediate gears 20 which always mesh with these developing roller driving gears 19 (the first developing device driving gears which mesh with the respective developing roller driving gears of developing rollers 5a, 6a and 7a). The intermediate gear is not shown), and is attached to each rotation shaft of each of the supply rollers 4b, 5b, 6b, and 7b so as to be integrally rotatable, and is always attached to each first developing device driving intermediate gear 20. The supply roller drive gears 21 that mesh with each other (the supply roller drive gears of the supply rollers 5b, 6b, and 7b are not shown), and the second developing device drive intermediate gears that always mesh with the supply roller drive gears 21 respectively. 22 (each second developing device drive intermediate gear meshing with each supply roller drive gear of the supply rollers 5b, 6b, 7b is not shown)
And third developing device driving intermediate gears 23 (constituting each supply roller driving gear of supply rollers 5b, 6b, 7b) concentrically and integrally rotatable with each of these second developing device driving intermediate gears 22. The third developing device driving intermediate gears that are gear-connected via the second developing device driving intermediate gears are not shown), and the fourth developing devices that always mesh with these third developing device driving intermediate gears 23, respectively. The driving intermediate gear 24, the driven coupling members 25 provided on the cam rod 16, and the driven couplings respectively provided on the fourth developing device driving intermediate gears 24, and the driving coupling members 25 are respectively disengageable. Each coupling 27 (developer 5, 6, 7) comprising a member 26 (each driven-side coupling member provided in each fourth developer drive intermediate gear 24 corresponding to the developer 5, 6, 7 is not shown) Corresponding to The coupling is not shown in the figure)
A return spring 28 that constantly urges the drive-side coupling member 25 in a direction in which the drive-side coupling member 25 is disengaged from the driven-side coupling members 26; And a cam 29 for controlling the movement. A first developing device driving intermediate gear 20, a supply roller driving gear 21, a second developing device driving intermediate gear 22, a third developing device driving intermediate gear 23,
The fourth developing device driving intermediate gear 24 constitutes an intermediate power transmission gear mechanism of the present invention.

The developing device drive gear support member 15 can swing independently of the rotating shaft 11a of the developing device drive motor 11 (that is, an axis concentric with the rotating shaft 3a of the rotary 3). Therefore, the cam rod 16, the developing device driving gear 17, and the driving side coupling member 25 supported on the other end of the developing device driving gear supporting member 15 are also concentric with the rotating shaft 11a (that is, the rotating shaft 3a of the rotary 3). About the axis). In this case, since the cam rod 16 penetrates the frame 13, for example, the rotation shaft 1 for enabling the rotation of the cam rod 16 is used.
An opening 30 (shown only in FIG. 2) such as an arc-shaped hole concentric with 1a is formed.

A coil spring 31 is stretched between the developing device driving gear support member 15 and the frame 13.
The developing device drive gear support member 15 is always urged in the counterclockwise direction in FIG. This coil spring 31
Is set such that the rotational driving force of the clockwise rotation of the rotary 3 is larger than the counterclockwise urging force of the developing device drive gear support member 15 due to the spring force.

The rotation of the developing device drive gear 17 is transmitted to the drive side coupling member 25 of the coupling 27 via the cam rod 16. As shown in FIG. 4, the drive-side coupling member 25 has an engagement concave groove 25a provided so as to penetrate in the radial direction, and a conical shape provided at the center of the engagement concave groove 25a. Guide hole 2
5b. In addition, the driven side coupling member 2
6 is provided so as to penetrate in the radial direction, and is provided with an engagement ridge 26a which can be fitted into the engagement concave groove 25a;
6a, and has a conical guide protrusion 26b that can be fitted into the guide hole 25b. The conical guide hole 25b and the conical guide protrusion 26b allow the drive-side coupling member 25 and the driven-side coupling member 26 to have a slight relative displacement when the coupling 27 is connected. , The guide projection 26b is in the guide hole 25
b, the drive-side coupling member 25 and the driven-side coupling member 26
Is corrected, the engagement groove 25a and the engagement ridge 26a are securely fitted, and the coupling 27 is rotationally connected.

Further, stoppers 32 are provided upright at predetermined positions of the rotary 3 near the driven side coupling members 26 provided on the fourth developing device driving intermediate gears 24, respectively. These stoppers 32 are provided so that the driving-side coupling member 25
When the drive coupling member 25 approaches or abuts a predetermined distance or less, the drive coupling member 25 can be brought into contact with the drive side coupling member 25 in the rotational direction of the rotary 3. In a state where the drive-side coupling member 25 is separated from the drive-side coupling member 25 beyond the distance, the drive-side coupling member 25 is set so as not to be able to abut.

As shown in FIG. 1, the cam 29 is formed in an arc shape concentric with the swing center of the belt supporting member 15 (that is, the rotating shaft 11a of the developing device drive motor 11 and the rotating shaft 3a of the rotary 3). I have. As is apparent from FIG. 4, the cam 29 includes a stopper contact setting portion 29a for setting the drive-side coupling member 25 to a state capable of contacting the stopper 32, and an inclined surface, and the drive-side coupling member 2
5 is gradually guided toward each driven side coupling member 26, and each driving side coupling member 25 is connected to each driven side coupling member 2.
6 and the drive-side coupling member 25 is gradually guided and disengaged from the driven-side coupling member 26, respectively, and the engagement is released. And an engagement / disengagement direction guide / stopper non-contactable setting portion 29d which sets the stopper 32 to be in a non-contactable state.

Each coupling 27 is formed by the cam 29.
Are connected, the driving force of the developing device driving motor 11 transmitted to the developing device driving motor gear 14 is transmitted to each of the developing rollers 4a, 5a, via the developing device driving force transmitting means 12Y, 12M, 12C, and 12K. 6a, 7a and each supply roller 4b,
5b, 6b, and 7b, so that these two rollers rotate.

Next, control of connection and disconnection of each coupling 27 by the cam 29 and the developing device drive motor 1
The rotation control of each developing roller 4a, 5a, 6a, 7a and each supply roller 4b, 5b, 6b, 7b by one driving force will be described. In this explanation, for convenience, this time O
The developing roller to be brought into contact with the PC 8 is the developing roller 4a of the yellow developing unit 4. In the state shown in FIG. 1, the yellow developing roller 4a has already contacted the OPC 8 and is in the developing position, that is, at the rotational position D of the rotary 3 (hereinafter, simply referred to as position D, and other rotational positions are the same). The description of the control by the cam 29 starts from a state where the developing roller 7a of the black developing device 7 is at the position D where the developing roller 7a contacts the OPC 8 and the yellow developing roller 4a is not at this position D.

When the developing roller 7a of the black developing device 7 is at the position D, the developing roller 4a of the yellow developing device 4 is at the position A, and the fourth developing device driving intermediate gear 24 of the developing device 4 is It is in position B. Further, the drive side coupling member 25 of the black coupling 27 is
Are set at the position F, the developing device drive gear 17 and the cam rod 16 are also at the position F. At the position F of the cam rod 16, the end of the cam rod 16 is located at the engaging portion 29c of the cam 29 as shown in FIG. 4, and the drive-side coupling member 25 is engaged with the black driven coupling member 26, Are coupled. Further, since the black drive-side coupling member 25 is set at the position F, the belt support member 15 and the timing belt 18 are also at the position F. The couplings 27 corresponding to the developing units 4, 5, and 6 other than the black developing unit are in the disconnected state.

On the other hand, the driving force of the developing device driving motor 11 is transmitted to the developing device driving motor gear 14, and this driving force is further transmitted to the developing device driving gear 17 by a timing belt 18. It is spinning. Therefore, the black developing roller 7a and the supply roller 7b rotate, and the other developing rollers 4a, 5a, 6a
And the supply rollers 4b, 5b, 6b have stopped rotating.

In this state, the rotary 3 rotates clockwise as indicated by the arrow, and 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. At this time, since the developing roller 7a is rotating at a predetermined rotation speed or more, the developing roller 7a is separated from the OPC 8 while rotating. Thereafter, the end of the cam rod 16 moves to the engagement / disengagement direction guide / stopper non-contactable setting portion 29d. Then, the end of the cam rod 16 moves along the slope of the engagement / disengagement direction guide / stopper non-contactable setting portion 29d by the spring force of the return spring 16, so that the drive-side coupling member 25 and the black driven-side coupling member 26, the black coupling 27 is disconnected. As a result, the driving force is not transmitted to the black developing roller 7a and the supply roller 7b, and the rotation of both rollers 7a and 7b is stopped.

When the rotary 3 further rotates, the drive-side coupling member 25 moves further away from the driven-side coupling member 26, and when the cam rod 16 comes to the position G, the drive-side coupling member 25 is moved to the stopper 32. Away from the stopper 32, and comes to a position where the stopper 32 cannot contact the stopper 32. Then, with the spring force of the coil spring 31,
The belt support member 15 quickly rotates in the return direction (counter-clockwise in FIG. 1). With this, the cam rod 1
6, the developing device drive gear 17, the timing belt 18, and the drive side coupling member 25 also rotate in the return direction. At this time, the end of the cam rod 16 extends along the respective cam surfaces of the engagement / disengagement direction guide / stopper non-contact setting portion 29d, the engagement portion 29c, the engagement direction guide portion 29b, and the stopper contact setting portion 29a of the cam 29. To move. When the end of the cam rod 16 moves through the engagement portion 29c, the drive-side coupling member 25 is at a position where it is engaged with the driven-side coupling member 26. At this time, the next driven-side coupling member 26 is still in contact. Therefore, it does not engage with the driven-side coupling member 26. Also,
When the end of the cam rod 16 comes to the stopper contact setting portion 29a, the drive side coupling member 25 is set to a position where it can contact the stopper 32.

On the other hand, since the rotary 3 continues to rotate slowly during this time, the fourth yellow developing device driving intermediate gear 24, its driven-side coupling member 26, and the stopper 32 rotate clockwise. Then, when the belt support member 15 comes to the position C, it comes into contact with the next yellow stopper 32 rotating clockwise. Since the rotational driving force for the clockwise rotation of the rotary 3 is set to be larger than the counterclockwise urging force of the developing device driving gear support member 15 due to the spring force of the coil spring 31, the driving-side coupling member 25 is On the other hand, the stopper 32 is rotated clockwise with the stopper 32. That is, the developing device driving gear support member 15, the cam rod 16, the developing device driving gear 17, the timing belt 18, and the driving side coupling member 25 all rotate clockwise together with the rotary 3.

The clockwise rotation of the cam rod 16 causes the end of the cam rod 16 to move to the engagement direction guide portion 29b and to move along the slope. Then, the drive-side coupling member 25 gradually moves to the next yellow driven-side coupling member 26. With the further rotation of the rotary 3 in the same direction, when the end of the cam rod 16 approaches the engagement portion 29c, the conical guide projection 26b of the driven-side coupling member 26 becomes a conical guide hole of the drive-side coupling member 25. 25b. And even if a slight relative displacement occurs between the driving side coupling member 25 and the driven side coupling member 26,
As described above, while the relative misalignment is corrected by the two conical inclined surfaces of the guide hole 25b and the guide protrusion 26b, the engagement groove 25 of the drive side coupling member 25 is corrected.
a and the engagement ridge 26a of the driven-side coupling member 26 reliably start fitting. Then, the developing device drive motor gear 1
Developing device driving gear 17 to which the driving force of developing device driving motor 11 is transmitted via
Is transmitted to the yellow driven side coupling member 26, and the fourth developing device drive intermediate gear 24 starts rotating. This causes the yellow supply roller 4b and the development roller 4a to start rotating. At this time, the developing roller 4a
The position D in contact with C8 has not yet been reached.

When the end of the cam rod 16 moves to the engaging portion 29c, the engaging concave groove 25a of the driving side coupling member 25
And the engagement protrusion 26a of the driven-side coupling member 26 are completely fitted, and the yellow coupling 27 is connected and held in this connected state. At this time, the developing roller 4a and the supply roller 4b are being rotated by the driving force of the developing device drive motor 11. When the rotary 3 further rotates in the same direction and the developing device driving gear supporting member 15 and the fourth developing device driving intermediate gear 24 rotate to the position F, the developing roller 4a rotates to the developing position at the position D, and the CPU rotates the developing roller 4a. The stepping motor 9 for rotary driving stops, and the rotation of the rotary 3 stops. At this time, the end of the cam rod 16 is kept in contact with the engaging portion 29c, the yellow coupling 27 is held in a connected state, and the developing roller 4a and the supply roller 4b continue to rotate at a predetermined rotational speed or more. . As described above, the developing roller 4a starts rotating before the OPC 8 comes into contact, and comes into contact with the OPC 8 while being rotated at a predetermined rotation speed or more after a predetermined time elapses, and is set to the developing position.

Next, when the development of yellow is completed, the stepping motor 9 is driven again to rotate the rotary 3 again in the same direction, and the yellow development roller 4a is moved to the predetermined position as in the case of the black development roller 7a. Separate from the OPC 8 while rotating at or above the rotation speed. Thereafter, connection and disconnection of the couplings 27 of the magenta developing device 5, cyan developing device 6 and black developing device 7 are controlled, and the developing rollers 5a, 6a, 7a are driven by the driving force of the developing device drive motor 11. The rotation of the supply rollers 5b, 6b, and 7b is controlled by the cam 29 in the same order as in the case of the yellow developing device 4.

Next, the operation of the image forming apparatus 1 according to this embodiment at the time of 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,
7, the developing rollers 4a, 5a, 6a, 7a are held at positions separated from the OPC 8 during non-development, the rotary 3 is stopped, and the couplings 27 are held in a disconnected state. ing.

When the operation of the image forming apparatus 1 for forming an image is started, both the stepping motor 9 and the developing device driving motor 11 are driven by the CPU. Since the developing device driving motor gear 14 is rotated by the driving of the developing device driving motor 11, the developing device driving gear 17, which is always rotationally connected by the timing belt 18, also rotates. Therefore, during the image forming operation, the developing device driving motor gear 14, the timing belt 18, and the developing device driving gear 17 are always rotating. At the same time, the rotary 3 is rotated clockwise by the driving of the stepping motor 9, and the yellow driven side coupling member 26, the fourth developing device intermediate gear 24 and the stopper 3 are rotated.
2 rotates toward position D. When the developing device driving gear supporting member 15 comes to the position C, the developing device driving gear supporting member 15
Then, the drive-side coupling member 25 returned by the counterclockwise rotation abuts against the yellow stopper 32 rotating clockwise, and thereafter the developing device drive gear support member 15 rotates clockwise together with the rotary 3.

By the rotation of the developing device drive gear supporting member 15, the driving side coupling member 25 is engaged with the yellow driven side coupling member 26 by the cam 29, and the yellow coupling is connected to the yellow developing roller 4a. And the supply roller 4b rotates so that the toner is
Supplied to When the developing device driving gear support member 15 comes to the position F after a predetermined time has elapsed from the rotation of the developing roller 4a,
When the developing roller 4a comes to a position D where the developing roller 4a comes into contact with the OPC 8 which is a developing position, the rotation of the rotary 3 stops. 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 on the developing roller 4a, and a toner layer having a predetermined thickness is surely formed on the surface of the developing roller 4a.
When the OPC 8 comes into contact with the PC 8, damage to the OPC 8 is prevented.
As a result, the developing roller 4a applies a predetermined amount of toner to the OPC
8 and the latent image on the OPC 8 is subjected to yellow development. The developed yellow image on the OPC 8 is intermediately transferred to the intermediate transfer medium 33.

The yellow developing roller 4a is moved to the position D.
1, the developing roller 5a of the next magenta developing device 5 is at the position A, and the fourth developing device driving intermediate gear 24 of the magenta developing device 5 is located at the position A as shown in FIG.
And the driven side coupling member 26 of magenta
It has become.

When the development of yellow is completed, the rotary 3 rotates again in the same direction, and the developing roller 4a separates from the OPC 8 while rotating at a predetermined rotation speed or more. Cam rod 16
Is located at a predetermined position of the engagement / disengagement direction guide / stopper non-contactable setting portion 29d of the cam 29, the yellow coupling 27 is disconnected, and the rotation of both the yellow developing roller 4a and the supply roller 4b is stopped. I do.

When the developing device drive gear supporting member 15 comes to the position G by the further rotation of the rotary 3, the drive side coupling member 25 is disengaged from the yellow stopper 32, and is brought into the position where the stopper cannot contact. As a result, the developing device drive gear supporting member 15 is quickly rotated counterclockwise by the spring force of the coil spring 31 and returned.
Comes to the position C, the drive-side coupling member 25 comes into contact with the next magenta stopper 32. Thereafter, the magenta developing operation is performed in the same manner as in the case of the yellow developing operation described above, whereby the magenta developing is performed on the latent image on the OPC, and the developed magenta image on the OPC is intermediate. The intermediate transfer is performed on the transfer medium 33.

Subsequently, similarly, cyan development by the cyan developing unit 6 and black development by the black developing unit 7 are sequentially performed, and each developed image is transferred to the intermediate transfer medium 3.
3 is intermediately transferred. Then, the four-color images intermediate-transferred onto the intermediate transfer medium 33 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 sets the four developing rollers 4a, 5a, 6a, and 7a in a position where the four developing rollers 4a, 5a, 6a, and 7a are not in contact with the OPC 8 and one coupling 27 is connected. By rotating these developing rollers 4a, 5a, 6a, 7a in a stopped state, a predetermined amount of toner is supplied to each of the developing rollers 4a, 5a, 6a, 7a.

That is, as shown in FIG.
At an arbitrary position where a, 5a, 6a, and 7a do not contact the OPC 8 and the coupling 27 is connected, an initialization position E for positioning the developing device drive gear support member 15 when the image forming apparatus 1 is initialized is set. ing. As shown in FIG. 4, this position E is a position where the end of the cam rod 16 abuts on the engaging portion 29c and the coupling 27 is connected.

To initialize the image forming apparatus 1 shipped from the factory, first, the stepping motor 9 is driven, the rotary 3 is rotated, and the developing device driving gear support member 15 is connected to one developing device. When it is pushed by the stopper 32 and reaches the initialization position E, the driving of the stepping motor 9 is stopped by the CPU, and the rotation of the rotary 3 is stopped. Next, the CPU drives the developing device driving motor 11 to rotate the developing device driving gear 17 via the developing device driving motor gear 14 and the timing belt 18. As a result, the developing roller and the supply roller of the developing device rotate via the coupled coupling, the toner is supplied to the developing roller, and a toner layer having a predetermined thickness is formed on the surface. Next, for the remaining developing devices, the developing device drive gear support member 15 is set to the initial position E by the stoppers 32 of the developing devices, so that toner is supplied to the developing rollers in the same manner as described above. A toner layer having a predetermined thickness is formed on the surface. As a result, the image forming apparatus 1
It is initialized in a short time without damaging C8.

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 kept 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 can be separated. 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.

Further, by appropriately setting the installation position of the cam 29, the rotational drive position of the developing rollers 4a, 5a, 6a, 7a and the supply rollers 4c, 5c, 6c, 7c can be set freely. In addition, since there is enough time until the developing rollers 4a, 5a, 6a, and 7a come into contact with the OPC 8, the toner can be uniformly dispersed to the developing rollers 4a, 5a, 6a, and 7a. 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, the rotation is stopped in other areas. It is possible to suppress toner scattering due to rotational driving. Further, according to the image forming apparatus 1 of this embodiment, since the control of each coupling 27 is performed by the cam 29, the developing rollers 4a, 5a, 6a, 7
a can be easily and reliably moved in and out of rotation. In this case, since the cam 29 is formed in an arc shape concentric with the rotary 3, the coupling 27 can be more accurately controlled according to the rotation of the rotary.

Further, according to the image forming apparatus 1 of the present embodiment, the power is transmitted to the developing roller and the supply roller by the engagement of the internal teeth 18a of the timing belt 18, the developing device driving motor gear 14, and the developing device driving gear 17. However, since the timing belt 18 is made of an elastic material such as rubber, vibration can be effectively absorbed when the internal teeth 18a are engaged with the developing device driving motor gear 14 and the developing device driving gear 17. 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 driving force of the developing device driving motor 11 is transmitted to the developing device driving gear 17 by using the endless timing belt 18, for example, a gear power transmitting mechanism is used for this power transmission. Thus, the configuration is simplified and the image forming apparatus 1 can be formed at low cost.

Further, according to the image forming apparatus 1 of the present embodiment, the developing rollers 4a, 5a,
The four developing rollers 4a, 5a, 6a, 7a are driven at positions where none of the 6a, 7a contacts the OPC 8, and a toner layer is formed on the surface of each of the developing rollers 4a, 5a, 6a, 7a. Since it can be reliably formed, OP
Initialization can be performed in a short time without damaging C8. In addition, by this, the dummy toner which was conventionally performed at the time of factory shipment can be removed from the developing rollers 4a, 5a, 6a,
Since there is no need to apply the coating on the surface of the dummy 7a, the operation of applying the dummy toner at the time of shipment from the factory becomes unnecessary, and the operation 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.

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 applicable 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.

[0054]

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.

Further, since the endless belt is made of an elastic material, vibration generated when the teeth of the endless belt mesh with the developing device driving motor gear and 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 driving force of the developing device drive motor is transmitted to the developing device drive gear using an endless belt, the configuration is simpler than, for example, using a gear power transmission mechanism for this power transmission. And the image forming apparatus can be formed at a low cost.

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 separated from the photosensitive member while being constantly rotated at a predetermined rotation speed or more, the toner can be more reliably supplied to the developing roller. 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, since the control means is constituted by a cam, the developing roller can be easily and reliably brought into contact with the photosensitive member in a rotating state.
In this case, since the cam is formed in an arc shape concentric with the rotating body, the coupling can be more accurately controlled according to the rotation of the rotating body. Furthermore, according to the invention of claim 6, the engagement projection of the coupling and the engagement recess which is engaged and rotationally connected with the engagement projection are displaced relative to each other during the engagement. Is provided, and the coupling of the coupling can be ensured.

According to the seventh aspect of the present invention, since the plurality of developing rollers can be rotated without any contact with the photosensitive member, the developing roller is not damaged after shipping from the factory without damaging the photosensitive member. Initialization of the forming apparatus 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.

FIG. 3 is a partial cross-sectional view of the timing belt in FIG.

FIG. 4 is an enlarged view of the cam in FIG. 2;
It is a figure explaining operation of this cam.

[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 Developing device drive gear support member, 16 Cam rod, 17 Developing device drive gear, 18 Endless timing belt, 25
Drive-side coupling member, 26: driven-side coupling member, 27: coupling, 29: cam, 29a: stopper contact setting section, 29a: stopper contact setting section, 29b ...
Engaging direction guide part, 29c ... engaging part, 29d ... engaging / disengaging direction guide / stopper non-contactable setting part, 31 ... coil spring, 32 ... stopper, 33 ... intermediate transfer medium, D ...
Contact position of developing roller to OPC

Continued on front page F-term (reference) 2H077 AD02 AD06 BA01 BA03 BA04 BA07 BA09 DA24 DB18 DB25 GA12 3J103 AA02 FA09 FA15 FA30 GA02 GA52 GA57 GA58

Claims (7)

[Claims] A developing device mounted on a rotating body and having a developing roller capable of coming in contact with and separating from the photosensitive member, wherein the developing roller is separated from the photosensitive member during non-development, A developing device that sequentially transmits the driving force of a driving motor to the developing roller via a developing device driving force transmitting unit provided for each developing device, and that sequentially contacts the developing roller with the photosensitive member by rotation of the rotating body. In the image forming apparatus performing multi-color development by moving to a position and setting the developing position when the rotation of the rotating body is stopped, the developing device driving force transmission unit is rotatable concentrically with the rotating body. A developing device driving motor gear that is provided and rotates by the driving force of the developing device driving motor; and is provided so as to be swingable about an axis that is concentric with the rotation axis of the rotator. A developing device driving gear for transmitting a driving force of a driving motor; and an internal tooth, wherein the developing device driving motor gear and the developing device driving gear are wound around the internal gear so as to mesh with the developing device driving gear. An endless belt made of an elastic body, which transmits a driving force of the developing device driving motor transmitted to a motor gear to the developing device driving gear, and a developing roller driving gear provided so as to be integrally rotatable with each of the developing rollers. An intermediate power transmission gear mechanism for transmitting power to the developing roller drive gear, a drive side coupling member for transmitting rotation of the developing device drive gear, and a driven side coupling member for transmitting rotation to the intermediate power transmission gear mechanism By disengaging the drive side coupling member and the driven side coupling member, the developing device drive gear and the intermediate power transmission gear A coupling for coupling and uncoupling the structure, and control means for controlling coupling and decoupling of the coupling, wherein the control means is adapted to contact the photoreceptor by rotation of the rotating body. Connecting the coupling before the roller comes to the developing position in contact with the photoconductor, and disconnecting the coupling after the developing roller moves from the developing position and separates from the photoconductor. Characteristic image forming apparatus. 2. The image forming apparatus according to claim 1, wherein when the control unit connects the coupling to rotate the developing roller at a predetermined rotation speed or more, the developing unit sets the developing roller to the developing position and causes the photosensitive member to rotate. The image forming apparatus according to claim 1, wherein the image forming apparatus contacts the image forming apparatus. 3. The rotator sets the developing roller to the developing position after the control means connects the coupling to rotate the developing roller at a predetermined rotational speed or more and a predetermined time has elapsed. The image forming apparatus according to claim 1, wherein the image forming apparatus contacts the photosensitive member. 4. The rotating member moves the developing roller from the developing position and separates from the photoreceptor when the control means connects the coupling to rotate the developing roller at a predetermined number of revolutions or more. 2. The method according to claim 1, wherein
The image forming apparatus as described in the above. 5. An image forming apparatus according to claim 1, wherein said control means comprises a cam formed in an arc shape concentric with said rotating body. 6. An engaging projection is provided on one of the drive-side coupling member and the driven-side coupling member, and one of the drive-side coupling member and the driven-side coupling member is provided. On the other hand,
There is provided an engagement recess in which the engagement protrusion is fitted and rotated and connected, and further, the relative displacement of the engagement protrusion and the engagement recess when they are fitted is corrected. The image forming apparatus according to any one of claims 1 to 5, further comprising a guide portion to be fitted and fitted. 7. The initialization is performed by connecting the coupling by the control means in a state where the rotating body is set at a position where none of the developing rollers comes into contact with the photoreceptor. The image forming apparatus according to claim 1, wherein: