JP2908500B2 - Color developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color developing apparatus in an electrophotographic copying machine, a printer, a facsimile, and the like.

(Prior Art) As one type of a color developing apparatus, a type in which a plurality of developing units are rotatably arranged around a photosensitive drum is known. For example, the apparatus described in JP-A-61-103175 has a plurality of developing units detachably supported on a unit support rotatable about an axis parallel to the rotation axis of the photosensitive drum. In the developing position of the photosensitive drum, developing units accommodating developers of different colors according to an image forming process are sequentially positioned. The developing device of this type is advantageous in reducing the size of the photosensitive drum and the size of the device, and has a feature that operability in maintenance is good by making the developing unit detachable.

The uniformity of the gap between the photosensitive drum and the developing roller, that is, the uniformity of the developing gap, is based on the fact that a visible image formed by superimposing three or four colors of developer on the photosensitive drum is transferred to a transfer paper in one transfer step. In a so-called non-contact flying development method in which a full-color image is transferred by transferring the image to a printer, it is extremely important to obtain uniform image quality. In particular, in a non-contact non-magnetic one-component developing system in which a thin layer of a non-magnetic developer is formed on the surface of a developing roller to perform non-contact development, it is required to maintain gap accuracy for image unevenness and the like.

In the case of a system in which a plurality of developing units are held in a revolver manner by a unit support and the unit support is rotated to replace the developing unit opposed to the photosensitive drum, when the unit support rotates, the developing is performed. There is a problem that the developing roller, part of which protrudes from the unit, comes into contact with the photosensitive drum and the developer drops and scatters. As a technique for dealing with this, there is a technique described in Japanese Patent Application Laid-Open No. 61-59372. In this technique, when the support unit is rotated, the development unit moves the support in a direction away from the photosensitive drum.

The apparatus described in JP-A-61-103175 has a rail on a unit support that detachably holds a developing unit, and a guide groove having a locking groove is provided on this rail.
By providing hook means for locking the guide pins of the developing unit, the developing unit is locked and positioned with respect to the unit support. Furthermore, a ring-shaped pull-out preventing member having the same center as the unit support and having an opening formed in a part thereof is arranged outside the unit support,
The holding roller of the developing unit is engaged with the inner peripheral surface of the stopper member to prevent the developing unit from falling off due to centrifugal force or gravity during rotation of the support. To remove the developing unit, pulling the handle to remove the pin from the hook moves the unit radially outward, and at the same time, the holding roller comes off the opening of the stopper member.

(Problems to be Solved by the Invention) The apparatus described in Japanese Patent Application Laid-Open No. 61-103175 achieves the intended purpose for the time being, but is not suitable for forming a gap between the photosensitive drum and the developing roller. The problem remains. The developing unit is set along the rail of the unit support and is positioned by a hook means. There is a problem that it is difficult to maintain the accuracy gap.

Next, in the apparatus described in Japanese Patent Application Laid-Open No. 61-59372, when the developing unit is switched, the support unit is moved away from the photosensitive drum to prevent the developer from being scattered. There remains a problem that the mechanism for moving the body is complicated, the device becomes bulky, and the cost increases.

When the developing unit is held by the revolver method, the handle of the developing unit is pulled to disengage the pin and the hook, and the developing unit is detached from the unit support. If the unit is inadvertently removed, there is a problem that a part of the developing unit, for example, the developing roller and the photosensitive drum interfere with each other and damage the drum surface.

Therefore, a first object of the present invention is to provide a color developing device which can place a developing unit at a developing position with a simple structure.

A second object of the present invention is to support a plurality of developing units in a detachable manner, maintain a gap between a photosensitive drum and a developing roller with high accuracy, and furthermore, mount and remove a photosensitive drum and a developing roller when attaching / detaching a developing unit. Another object of the present invention is to provide a color developing device capable of preventing damage to a color developing device.

(Means for Solving the Problems) A first object of the present invention is to provide a plurality of unit supports provided on a unit support rotatably provided about a rotation center axis arranged in parallel with the rotation center axis of the photosensitive drum. In a color developing device which detachably supports a developing unit and rotates a predetermined developing unit to a developing position of a photosensitive drum to perform development, the developing unit is provided on the unit support, and the developing unit is A support shaft rotatably supported, a guide rail provided on the unit support in parallel with a rotation center axis of the support, and a detachably supporting each of the developing units; A developing roller rotatably supported, gap maintaining means provided at both ends of each of the developing rollers, and both ends of a rotation center axis of the unit support; The developing unit, which has been rotated to the image position, is provided on the stationary cam and the developing unit, which makes the gap holding means come into contact with the peripheral surface of the photosensitive drum, and comes into contact with the cam. The present invention is achieved by a color developing device including a pressing unit including an elastic member.

A second object of the present invention is to detachably support a plurality of developing units on a unit support rotatably provided about a rotation center axis provided in parallel with the rotation center axis of the photosensitive drum. In a color developing device that performs development by rotating a predetermined developing unit to a developing position of a photosensitive drum, a support shaft provided on the unit support and rotatably supporting the developing unit, A developing roller rotatably supported by each of the developing units; gap holding means for holding a gap between the photosensitive drum and each of the developing rollers; and a unit support or each of the developing units. Pressing means for pressing the developing unit toward the photoconductor drum, and pressing the developing unit and the photoconductor drum through the gap holding means; A guide rail which is provided on the unit support in parallel with the rotation center axis of the support and which detachably supports each of the developing units and allows rotation of each of the developing units; Mounting / dismounting control means for restricting attachment / detachment of the unit support to / from the guide rail and allowing attachment / detachment of the developing unit placed at a position other than the developing position to / from the unit support. This is achieved by a color developing device characterized in that:

(Operation) The developing unit is pressed toward the photosensitive drum by the pressing means, and the developing roller is brought into contact with the peripheral surface of the photosensitive drum via the gap maintaining means to form a gap between the photosensitive drum and the developing roller. Is done.

When the developing unit is rotated to the developing position, an elastic member provided in the unit comes into contact with the cam, presses the unit toward the photosensitive drum, and exposes the developing roller through the gap holding means. Make contact with the drum surface.

The developing unit located at the developing position is restricted from being attached to and detached from the guide rail by the attachment / detachment restricting means, and the developing units located at positions other than the developing position can be attached to and detached from the guide rail.

(Example) Hereinafter, the present invention will be described in detail based on the illustrated example.

1 and 2, reference numeral 1 denotes a photosensitive drum, and reference numeral 2 denotes a color developing device. The photosensitive drum 1 is rotatably supported by a support shaft 3 supported on a front plate 4 and a rear plate 5 of the apparatus main body. A part of the front side plate 4 is detachable from a stationary main body side plate (not shown). Around the photosensitive drum 1, a charging charger 6, an exposing device (only the optical axis is shown) 7, a color developing device 2, a transfer charger 8, a separating charger 9, and a cleaning device 10 are arranged along the rotation direction. Have been. The color developing device 2 faces the photosensitive drum 1 at a developing position A, and transfer paper is fed to a transfer / separation position B of the drum by a registration roller 11. Reference symbol O indicates the path of the transfer paper.

The color developing device 2 includes a support shaft 12 fixed to the front side plate 4.
A unit support 14 rotatably supported by a rotary shaft 13 rotatably supported by the rear side plate 5, and a plurality of developing units 15, 16,
17 and. The support shaft 12 and the rotation shaft 13 are on the same axis, and are disposed in parallel with the support shaft 3 of the photosensitive drum 1. In the case of the illustrated example, the unit support 14 has three support portions 18, 19, 20 extending radially in three directions, and supports the developing units 15, 16, 17 between adjacent support portions, respectively. I have.
Each developing unit contains a developer of a different color.For example, unit 15 is a cyan developing unit containing a cyan developer, unit 16 is a magenta developing unit containing a magenta developer, and unit 17 is a yellow developer. It refers to the yellow developing unit containing the developer. The arrangement order of the developing units is not limited to the illustrated example.

Each developing unit has the same structure except that the stored developer and the mounting position on the support 14 are the same, so the structure of the cyan developing unit 15 will be described as a representative. As shown in FIGS. 1, 3, and 4, the cyan developing unit 15 includes a hopper 21 containing a cyan developer, and end plates 22 (only one is shown) provided at both ends of the hopper. A fulcrum hole 24 which is formed in this end plate and forms a unit rotation center which is fitted to a support shaft 23 inserted through the outer end of the support portion 19, and which is formed in the end plate 22 and has a support portion
A guide groove 26 loosely fitted on a guide rail 25 formed in the axial direction on the guide 19 and a guide groove 28 loosely fitted on a guide rail 27 formed on the support portion 18, and a developer rotatably provided in the hopper 21. A supply roller 29, a developing roller 30 formed of an elastic material such as foamed polyurethane and projecting a part of the peripheral surface from an opening of the hopper, and a developing roller 30 supplied to the developing roller 30 by the developer supply roller 29. A developer thin layer forming blade 31 for forming a developer thin layer by making the thickness of the developer uniform, gap holding rings 32, 32 as gap holding means rotatably provided at both ends of the developing roller 30, and Consists of The gap maintaining rings 32, 32 are for maintaining a gap d between the developing roller 30 and the peripheral surface of the photosensitive drum 1, and
The outer diameter is larger than the diameter of 30 by a predetermined dimension.
In the illustrated embodiment, the support portion 18 of the unit support 14 is provided with a leaf spring 33 as a pressing means for urging and pressing the photosensitive drum 1 against the cyan developing unit 15.
The leaf spring 33 has support portions 19, 33A, 33B as shown by reference numerals 33A, 33B.
Also provided at 20, the magenta developing unit 16 and the yellow developing unit 17 are urged in directions in which the respective developing rollers are brought into contact with the peripheral surface of the photosensitive drum around the respective fulcrums 16a and 17a. .

The cyan developing unit 15 has guide grooves 26 and 28 loosely fitted on guide rails 25 and 27 formed on the unit support 14 and is inserted into the support along the rails. Fitted and rotatably mounted. When the leaf spring 33 elastically contacts the back surface of the cyan developing unit 15, the cyan developing unit 15 is rotated and urged counterclockwise in FIG. 1
Is kept in the gap d between the developing roller 30 and the peripheral surface of the photoconductor. The cyan developing unit 15 pressed by the leaf spring 33 is rotated within a clearance between the guide grooves 26, 28 and the guide rails 25, 27.
The gap retaining rings 32, 32 are, of course, brought into contact with the peripheral surface of the non-image forming portion of the photosensitive drum 1.

As shown in FIG. 2, the rotation shaft 13 of the unit support 14
Is a pulse motor 36 via gears 34 and 35 meshing with each other.
And connected to the output shaft according to the image forming process
A predetermined developing unit is rotated by 120 degrees to move the developing unit to a developing position A.
(See FIG. 1).

Here, the process of image formation will be briefly described. An electrostatic latent image that has been color-separated by the exposure device 7 is formed on the photosensitive drum 1 charged to a predetermined polarity by the charging charger 6. When this electrostatic latent image rotates to the developing position A,
The cyan developer in the developer thin layer formed on the peripheral surface of the developing roller 30 flies toward the electrostatic latent image and visualizes the electrostatic latent image. When the blue development by the cyan developer is completed, the unit support 14
Rotates 120 degrees counterclockwise, and the yellow developing unit 17
Is positioned at the developing position A, exposure and development are performed on the yellow image, and finally, the magenta developing unit 16 is positioned at the developing position A to perform exposure and development on the red color. Therefore, on the photosensitive drum 1, a color image in which three color developers are superimposed is formed. When the development of all colors is completed, a transfer sheet is fed toward the drum surface, and an image is transferred to the sheet by the transfer charger 8. The transfer paper on which the color image has been transferred is separated from the drum surface by the separation charger 9, and the image is fixed by a fixing device (not shown), and then discharged outside the apparatus as a color copy. After the transfer step, the surface of the photosensitive drum 1 is cleaned by the cleaning device 10 to prepare for the next image formation.

When the developing process for each color is repeated, the developing roller 30
The gap holding rings 3 provided at both ends of the developing unit are pressed by the leaf spring 33.
2 and 32 are brought into contact with the peripheral surface of the photosensitive drum 1 so that the gap d with the peripheral surface of the photosensitive drum 1 is always kept constant.

5 to 7, the unit support 14 is rotatably supported by a support shaft 12 fixed to the front side plate 4 and a support shaft 37 fixed to the rear side plate 5. In this case, the unit support 14 is rotatably driven by a drive mechanism (not shown). The support shafts 12, 37 are
Cams 39 and 40 forming a part of the pressing means are fixed to the rotation shafts of the unit support. On the other hand, leaf springs 41 and 42 as elastic members that come into contact with the cams 39 and 40 when the unit is placed at the developing position A are fixed to the rear surface of the cyan developing unit 15. Reference numeral 41 is also used for the magenta developing unit 16 and the yellow developing unit 17.
A leaf spring is provided as shown by A and 41B. The guide groove 28 of the cyan developing unit 15 and the support portion in which the guide groove 28 is loosely fitted.
As shown in FIG. 4, between the 18 and the guide rail 27,
A leaf spring 43 as an urging means provided on one surface of the guide rail 27 is interposed. The leaf spring 43 urges the cyan developing unit 15 in a direction away from the photosensitive drum 1. However, when the unit is rotated by the cam 39 in the direction of arrow a in FIG. Allow the rotation in this direction. That is, the elasticity of the leaf spring 43 is
It is set smaller than that of. Therefore, the magenta developing unit 16 and the yellow developing unit 17 located at positions other than the developing position A are separated from the photoreceptor about the respective fulcrums 16a, 17a by the leaf springs 43A (only one is shown). It is urged to rotate in the direction (see arrow b). This rotation is restricted by the range of the clearance between the guide rail and the guide groove.

The cams 39 and 40 are disposed on the rotation trajectories of the leaf springs 41 and 42, and direct the cyan developing unit 15 placed at the developing position A toward the photosensitive drum 1 as shown in FIG. Pressing. The cyan developing unit 15 placed at the developing position A
The gap holding rings 32 of the developing roller 30 are brought into contact with the peripheral surface of the photosensitive drum 1 to maintain the gap d between the developing roller 30 and the peripheral surface of the photosensitive drum 1 (see FIG. 5). Is done.
The other developing units 16 and 17 are urged in the direction of arrow b by the leaf spring 43A, and do not rattle.
Supported by 14.

When the development with the cyan developer is completed, the unit support 14 is rotated counterclockwise by 120 degrees in FIG. Then, the cyan developing unit 15 is rotated in the direction of arrow b by the leaf spring 43, and the yellow developing unit 17 is positioned at the developing position A. This unit 17 is a leaf spring
The contact of the cam 41 with the cam 41B causes the cam to rotate about the fulcrum 17a against the elasticity of the leaf spring 43, and the gap holding ring 42 abuts on the peripheral surface of the photosensitive drum to secure the gap d. Is done.

In FIGS. 2 and 4, a stopper 44 is fixed to the support shaft 12 of the unit support 14 as attachment / detachment restricting means. The stopper 44 is disposed at a position facing the front end plate 22 (see FIG. 2) of the developing unit located at the developing position A, as shown by a chain line in FIG. The removal of the unit is regulated. In FIG. 1, when the developing unit is to be pulled out from the unit support 14, the magenta developing unit 16 and the yellow developing unit 17 can be pulled out, but the cyan developing unit 15 placed at the developing position A is Stopper
The unit cannot be pulled out because its removal is prevented by 44. In the cyan developing unit 15 located at the developing position, the gap holding ring 32 is in contact with the surface of the photoconductor drum 1, so that when this unit is pulled out, the photoconductor may be damaged. Existence avoids this.

(Effects of the Invention) According to the first aspect, the cam fixed to the rotation center of the unit support presses the developing unit, which has moved to the developing position, toward the photosensitive drum. It is possible to press the developing unit at the developing position without requiring a simple driving mechanism, and it is possible to reduce the size and cost of the apparatus. In addition, since the developing unit placed at a position other than the developing position is urged away from the photoconductor drum, the unit may rattle or vibrate during the rotation of the unit support, causing the developer to fall and scatter. Can be prevented, and the in-machine stain and transfer paper stain due to the developer can be avoided.

According to the second aspect of the present invention, the developing unit detachably mounted on the unit support is rotatably supported around a fulcrum on the unit support and the pressing means for pressing the developing unit toward the photosensitive drum is provided. The developing gap can be formed by bringing the developing roller into contact with the surface of the photosensitive drum via the gap maintaining means by means, and only when the developing unit is not placed at the developing position facing the photosensitive drum, Detachment / restriction control means for attaching and detaching the developing unit to and from the unit support is provided, so that the gap between the developing roller and the photosensitive drum of each developing unit can be stably and accurately provided despite the use of a revolver type developing device. The gap holding means is in contact with the photoreceptor drum while restricting the inadvertent attachment and detachment of the developing unit placed at the developing position. It can prevent damaging the optical surface. In particular, in a developing method in which a non-magnetic one-component developer in a thin layer of developer on the peripheral surface of a developing roller is caused to fly toward a photosensitive drum in a non-contact manner and a plurality of colors of developer are superimposed, a uniform image without developing unevenness is obtained. Quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image forming apparatus to which a color developing device according to an embodiment of the second invention is applied, FIG. 2 is a plan sectional view of the same according to the embodiment of the second invention, and FIG. FIG. 4 is a perspective view showing a main part of the developing unit, FIG. 4 is a perspective view showing a main part of the unit support, FIG. 5 is a plan view showing an embodiment of the first invention, and FIG. FIG. 7 is a front view showing an embodiment of the first invention. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Color developing device, 3 ... Support shaft, 12 ... Support shaft, 13 ... Rotating shaft, 15 ... Cyan developing unit, 16 ... Magenta developing unit, 17 ... Yellow Developing unit, 18, 19, 20 ... Support, 21 ... Hopper,
24 ... fulcrum hole, 25, 27 ... guide rail, 26, 28 ... guide groove, 30 ... developing roller, 32 ... gap retaining ring, 33
…… leaf spring, 37 …… support shaft, 39,40 …… cam, 41,42 ……
Leaf spring, 43 ... Leaf spring, 44 ... Stopper.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/08-15/095

Claims (3)

(57) [Claims] A plurality of developing units are detachably supported on a unit support rotatably provided about a rotation center axis disposed in parallel with a rotation center axis of the photosensitive drum. A color developing device that performs development by rotating the developing unit to a developing position of the photosensitive drum, provided on the unit support, and a support shaft rotatably supporting the developing unit; A guide rail that is provided in parallel with the rotation center axis of the support and that detachably supports each of the developing units; a developing roller rotatably supported by each of the developing units; A gap holding means provided at both ends of the roller; and a developing unit provided at both ends of a rotation center axis of the unit support and rotated to the developing position. And a pressing means provided on the developing unit and comprising an elastic member which comes into contact with the cam and which is provided on the developing unit so that the gap holding means comes into contact with the peripheral surface of the photosensitive drum. A color developing device. 2. A color developing apparatus according to claim 1, wherein said pressing means has an urging means for urging each of said developing units in a direction away from said photosensitive drum. 3. A plurality of developing units are detachably supported on a unit support rotatably provided around a rotation center axis disposed parallel to the rotation center axis of the photosensitive drum. A color developing device that performs development by rotating the developing unit to a developing position of the photosensitive drum, provided on the unit support, and a support shaft rotatably supporting the developing unit; A developing roller rotatably supported on each of the developing rollers; a gap holding unit for holding a gap between the photosensitive drum and each of the developing rollers; and a developing unit provided on the unit support or each of the developing units. Pressing means for pressing the developing unit and the photosensitive drum through the gap holding means; A guide rail provided in parallel with the rotation center axis of the support, and detachably supporting each of the developing units and allowing rotation of the developing units; Mounting / dismounting control means for restricting attachment / detachment of the unit support from the guide rail and allowing attachment / detachment of the developing unit placed at a position other than the developing position to / from the unit support. A color developing device comprising: