JPH02226269A - image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

1. The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and is particularly applicable to a multicolor image forming apparatus that obtains multicolor or full color images. .

Currently, various multicolor image forming apparatuses have been proposed. For example, a typical example of an electrophotographic color image forming apparatus is shown in FIG. According to this example, a drum-shaped electrophotographic photosensitive member (photosensitive drum), which is an image carrier, is uniformly charged by a primary charger 4.
1, an image of the original 27 is displayed on the illumination means 25 and the lens 22.
, mirrors 24, 23, 21, and a color separation filter 20, the images are separated into colors and formed into images. By irradiating the light image, a latent image is formed on the photosensitive drum 1 according to the color-separated image. The latent image is formed by a rotary developing device, which is arranged on the side of the photosensitive drum 1, and is constituted by a rotating body 3 carrying a yellow developing unit 2Y, a magenta developing unit) 2M, a cyan developing unit) 2C, and a black developing unit) 2B. In the apparatus, by arranging a developing unit corresponding to the color separation latent image at a developing position, the latent image is developed by a predetermined developing unit for each color separation to form a toner image. Each toner image on the photosensitive drum is superimposed and transferred onto a transfer material on a transfer drum 6 disposed below the photosensitive drum 1. Transfer material is cassette 1
5.16, the sheet is fed by pickup rollers 13.14, and is fed to the transfer drum 6 by the registration roller 12 in synchronization with the toner image on the photosensitive drum, where it is gripped by the gripper means 10 of the transfer drum 6, Wrapped around and held by a transfer drum. The transfer material on which the toner image has been transferred is separated from the transfer drum by the action of a separation charger 8 or the like, passes through a conveying section 17 and a fixing device 18, and is discharged onto a tray 19. After the toner image on the photosensitive drum is transferred, residual toner is removed by a cleaner 5, and the toner image is used for the next image formation. According to the color image forming apparatus having such a configuration, in order to develop each latent image sequentially formed on the photosensitive drum 1 according to color separation, a plurality of developing units) 2Y carried by the rotating body 3 are used.
2B needs to be conveyed to the developing position facing the photosensitive drum 1 by rotating the rotating body 3. Such a rotary developing device requires a considerable amount of installation space inside the machine, and by moving each developing unit,
This caused the developer stored in each developing unit to leak to the outside, and the leaked developer scattered into the machine, contaminating the interior of the machine. Further, as understood from FIG. 19 and the above description, the transfer drum 6 is located below the photosensitive drum 1 and the rotary developing device, and the developer scattered from the developing device adheres to the surface of the transfer drum 6. However, the back side of the transfer material held on the surface of the transfer drum 6 is stained, and if the scattered developer adheres to the surface of the transfer material, the image becomes stained, which is not desirable in any case. . Furthermore, if the rotation of the rotating body 3 of the rotary developing device is increased in order to increase the image forming speed, the leakage of developer from each developing unit will also increase, and there is a limit to the rotational speed of the rotary developing device, which will reduce the image forming speed. It was difficult to make it large. In order to solve the above problem, as shown in Figure 2,
Using a reciprocating developing device 1oo in which developing units) 2M to 2B are mounted on a movable base 120, the developing device 100 is moved tangentially to the photosensitive drum 1 to develop the latent image on the photosensitive drum. An image forming apparatus configured to perform the following has been proposed. In the image forming apparatus having such a configuration, as will be described in detail later, each developing unit is supported so as to be able to swing around a pivot point disposed on the movable base 120, and during the developing operation, the developing unit is biased toward the surface of the photosensitive drum by driving a drive gear from a drive source provided on the movable base. However, the image forming apparatus using such a reciprocating developing device has the following problems. First, in order to cause friction between the toner and the carrier and to impart sufficient triboelectric charge to the toner, it is necessary to stir the developer even during non-developing operation. In addition, with the method that measures toner concentration and controls toner replenishment, a decrease in toner moisture is detected immediately after development is completed,
Toner replenishment may be necessary, and for this reason, it is necessary to perform toner replenishment even during non-developing operation. For this reason, in the reciprocating developing device, as mentioned in L.
It is desirable that the external drive source of the developing device is stacked together with the developing unit on a movable base so that drive can be constantly transmitted not only during developing operation but also during non-developing operation.Furthermore, each developing unit Drive is transmitted to the drive gear of the developing sleeve, which is the developer carrying member, via a gear from a drive source disposed coaxially with the center of rotation of the developing unit. At the meshing portion with the gear from the drive source, a force is generated in a direction in which the developing unit approaches the photosensitive drum when driving is transmitted. Therefore, when the movable base reciprocates during continuous image formation and it becomes necessary to drive a developing unit in a non-developing state for developer agitation or toner replenishment, the following problems occur. That is, when a developing device located at a non-developing operation position other than directly below the photosensitive drum is driven, the developing unit receives an upward force as described above and swings upward, so that the area around the photosensitive drum The developing unit may come close to other members constituting the main body of the apparatus disposed in the main body of the apparatus, and there is a concern that these members may be contaminated with toner, or in the worst case, a part of the developing unit may come into contact with these members. Furthermore, when image formation for the first sheet is completed and moving on to the next image formation, for example, when finishing the final thermal development of the first sheet with four full colors and moving on to magenta development of the next second sheet, The developing unit reciprocates directly under the photosensitive drum, but when the developing unit passes directly under the photosensitive drum during such non-developing operation, if the developing unit is driven for developer agitation or toner replenishment. The stopper of the developing unit may come close to or come into contact with the photosensitive drum that receives the stopper. In this case, unnecessary toner may adhere to the photosensitive drum, or 2. Unnecessary impact will be applied to the photosensitive drum in the developing unit. This is because the frequency of continuous image formation naturally increases.
This also caused a reduction in the life of the photosensitive drum. Furthermore, in a reciprocating developing device, each developing unit is mounted on a movable base so as to be rotatable about a rotational fulcrum, as described above, so when the main body of the device is moved or transported,
If an unexpected impact is applied from the outside, it is conceivable that the developing unit will rotate around the rotational fulcrum and move upward. In such a case, as mentioned above, there is also concern that the members constituting the apparatus main body and the photosensitive drum may be contaminated with toner, or that these members may be scratched or damaged by hitting these members. Furthermore, during maintenance such as replacing the photosensitive drum, it is conceivable that a service person manually lifts the developing unit by rotating it around its fulcrum. A similar problem could occur in such cases as well. Therefore, an object of the present invention is to prevent the developing unit from unnecessarily colliding with the image bearing member during the developing operation and during the non-developing operation, damaging the image bearing member, degrading the quality of the image, and further preventing the developing unit from colliding with the image bearing member. An object of the present invention is to provide an image forming apparatus that can stably obtain high-quality images without causing agents to scatter inside the machine and without reducing the life of an image carrier. The above-mentioned object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier on which a latent image is formed, and at least one image carrier disposed close to the surface of the image carrier to visualize the latent image on the image carrier. In an image forming apparatus having one or more developing units and a movable base that supports and moves the developing units, the developing unit may include a stopper for positioning the developing unit with respect to the image carrier. The image forming apparatus is characterized in that the stopper is configured to engage with a stopper receiver which is fixed to the main body of the apparatus and is separate from the image carrier. Preferably, part or all of the stopper holder is a curved receiving surface having the same center of the vehicle as the curvature of the surface of the image carrier, and the stopper holder is detachable from the main body of the apparatus. Can be fixed to a separate board. A Practical Example Next, the image forming apparatus according to the present invention will be explained in more detail with reference to the drawings. FIG. 2 shows a full-color electrophotographic copying machine which is an embodiment of the image forming apparatus according to the present invention. An image carrier, that is, in this embodiment, a photosensitive drum 1 having an electrophotographic photosensitive layer on its surface is rotationally driven in the direction of arrow X. On the left side of the photosensitive drum 1, a primary charger 4 and a photosensitive drum 1 are installed.
Directly below, there is a developing device 100 that moves in the left-right direction and has a plurality of developing units (in this embodiment, developing units 2M, 2C12Y, and 2B each using a two-component developer containing toner and a magnetic carrier). A transfer device 6 is disposed diagonally above and to the right of the photosensitive drum 1, and a cleaning device 5 is disposed diagonally above and to the left of the photosensitive drum 1, respectively. Further, an optical system 3 is disposed above the copying machine, and is configured to project the original image on the platen 26 onto the photosensitive drum l. Optical system 3 can use any optical system, but
In this embodiment, a first scanning mirror 24, second and third scanning mirrors that move in the same direction at half the speed with respect to the first scanning mirror 24 are used.
Scanning mirror 23, imaging lens 22, color separation B, G, R
It is composed of a filter 35, a CCD 34, a laser scanner unit 31, and fixed mirrors 32 and 33. Here, the scanner unit 31 is a well-known device that deflects laser light using a rotating polygon mirror, and detailed description thereof will be omitted. Further, in the optical system 3, the original illumination light source 25 moves together with the first scanning mirror 24. It is configured as follows. Therefore, the reflected light image of the original scanned by the first to third scanning mirrors 24, 23 passes through the lens 22, is color separated by the BGR color separation filter 35 and the CCD 34, and is converted into an electrical signal. After the signal undergoes information processing such as A/D conversion, it is sent as a video signal to a microprocessor unit (hereinafter referred to as rMPU) that controls the entire copying machine. Based on this signal, the MPU oscillates a laser beam from a laser unit via a laser driver, and this laser beam starts a copying sequence while hitting the photosensitive drum 1 at 0N10FFL. Furthermore, in this embodiment, a fixing device 18 is provided on the right side of the copying machine.
and paper feeding devices 15 and 16 are arranged, and a transfer paper conveyance system 17 is arranged between the transfer drum 6 and the fixing device 18. In the above configuration, each process of charging, exposing, developing, transferring, and cleaning is performed on the photosensitive drum 1 for each separated color by the primary charger 4, the optical system 3, the developing device 1OO1, the transfer device 6, and the cleaning device 5. be done. The developing device lOO will be explained in more detail later, but the developing unit 2M (developing unit) is detachably held on the movable base 120.
magenta developing unit), 2C (cyan developing unit))
, 2Y (yellow developing unit) and 2B (black developing unit), and each color-separated latent image formed on the photosensitive drum is developed into a toner image by the corresponding developing unit. The transfer device 6 is typically a transfer drum that is provided with a transfer material-carrying member on its circumferential surface and is configured to electrostatically hold a transfer material, that is, a transfer paper, on the sheet. The transfer drum 6 grips the transfer material, usually transfer paper, fed at the same timing from the paper feeders 15 and 16, and rotates at the transfer position so as to overlay and transfer the toner images of each color on the photosensitive drum 1. Have it transferred. A transfer charger 7 is placed inside the transfer drum 6 at the transfer position. The transfer paper onto which the toner images of each color have been sequentially transferred is transferred to the transfer drum 6.
It is released from the transfer drum 6 and separated from the transfer drum 6 by the separation charger 8 or the like. The transfer paper is then sent to a fixing device 18 by a transfer paper transport system 17. The toner image on the transfer paper is fixed onto the transfer paper by a fixing device 18, and then the transfer paper is discharged onto a tray 19. Next, the developing device 10 used in the image forming apparatus of the present invention
0 will be explained in more detail. As described above, the developing device 100 is configured to be movable in the left-right direction, but the individual developing units must be arranged directly below the photosensitive drum 1 and close to the photosensitive drum 1 with a predetermined gap therebetween. On the other hand, the developing unit is held at a position retracted from the photosensitive drum l except when it is directly below the photosensitive drum, that is, at the developing operation position. In this example, the developing unit) 2 (2M, 2C12Y
, 2B) have the same configuration, and the only difference is the color of the developer supplied inside. Referring to FIG. 8, the developing unit in this embodiment includes an elongated developing container 106 whose cross section is approximately rectangular.
A developing sleeve 102 having a magnet (not shown) built therein is rotatably supported in the developing container 106. A photosensitive drum 1 is mounted on both end shaft portions of the developing sleeve 102.
A stopper for securing a predetermined gap between the
A butting roller 103 is provided. Also, the developing sleeve 10
The drive gear 1 of the developing sleeve 102 is attached to one shaft end of the developing sleeve 102.
04 is fixed, and the motor 125 is
The driving force (FIGS. 9 and 10) is transmitted to the developing sleeve 102. Further, the magnet within the developing sleeve 102 is positioned at an appropriate position within the developing sleeve 102 by a positioning plate 190 disposed on the other end shaft portion of the developing sleeve 102 . At both ends of the developer container 106, there are rotating support shafts 105F and 105R for mounting and positioning the developing unit 2 on a moving base 120 (FIG. 9), which will be described later.
2 and coaxially parallel to each other. Further, inside the developer container 106, there is a screw (only the shaft part is shown) 107.1 that stirs and transports the developer contained therein.
08, and the screws 107 and 108 are driven by a drive gear 104 of the developing sleeve 102 via a gear train (not shown). The end of one of the screws, the screw 107 in this embodiment, protrudes toward the front from the developer container 106 and passes through a conveying pipe 106a connected to a toner replenishing device (not shown). Conveying pipe 10
A replenishing port 106a' for connecting to a toner replenishing device is opened in the upper part of the toner replenishing device 6a. A guide foot 106b (b
+, bz), 106c (see FIGS. 8 and 13), and are configured to slidably engage with a slide guide 121 attached to a movable base 120, which will be described later. Ru. FIG. 9 is a perspective view of the entire developing device 100 seen from diagonally above and to the left in front of the copying machine. In this figure, each developing unit 2 is omitted. The developing device 100 has a movable base 120 on which each developing unit 2 is loaded and moved, and the base 120 has a slide guide 121 (121M) that engages with and holds the guide legs 106b and 106c of each developing unit 2. , 121C, 12
1Y, 121B) are fixed. As will be described later, cutouts 121M' to 121B' are formed in the middle of each slide kite so that the legs of the developer container can escape when the developer unit swings and approaches the photosensitive drum 1. Further, the base 120 is provided with a back support plate 122 and a front support plate 123 corresponding to each slide guide 121. The back support plate 122 has a hole 122' that fits with the rotation support shaft 105R of the developing unit 2, and the front support plate 123 has a hole 123' that fits with the rotation support shaft 105F of the development unit 2. ing. After inserting the developing unit 2 along the slide guide 121 and fitting the rotation support shaft 105R into the hole 122' of the back support plate 122, the front support plate 123 inserts the rotation support shaft 10.
5F and the hole 123' of the front support plate 123 are fitted, and then screwed to the movable base 120. Here, the back support plate 1 provided for each developing unit of each color.
22 and the holes 122' and 123' of the front support plate 123 are adjusted using a jig or the like during assembly so that they share the same axis parallel to the axis of the photosensitive drum 1. In the wooden embodiment, the back support plate 122 is as shown in FIGS. 10 and 11.
As shown in the figure, the drive board 124 is screwed to a drive board 124 that supports drive gears, clutches, etc., which will be described later.
4 is screwed to the movable base 120. Also, the base 120
A support plate 126 that supports a DC motor 125 is fixed with screws. The movable base 120 is provided with a rail 127 at the rear end of the base 120, and the rail 127 is connected to the bottom plate 60 of the copying machine.
It is slidably engaged with a rail abutment 128 attached to a rear side plate 50a fixed to the rear side plate 50a. On the other hand, the moving base 12
A roller 129 having a built-in bearing is rotatably supported at the front end of the roller 129 via a support plate 130. The rollers 129 are allowed to roll on the bottom plate 60. With this configuration, the movable base 120 is movable with respect to the bottom plate 60 and the rear side plate 50a. The movable base 120 is driven by the driving force of a stepping motor 132 mounted on the bottom plate 60 by suitable support means (not shown) and gears 133 and 134 also mounted on the same support means. .135 to a rack 131 fixed to the moving base 120. According to the present invention, the developing device lOO is moved by the movable base 120 toward the photosensitive drum l in a substantially tangential direction of the photosensitive drum, and is placed at the developing operating position, that is, at a position approximately directly below the photosensitive drum. It is positioned with a predetermined gap relative to the drum. Next, the drive train from the DC motor 125 to the developing sleeve 102 will be explained with reference to FIG. 1θ and FIG. FIG. 11 shows the rack 131 in the direction of arrow D in FIG.
Fig. 1O is a plan view of the drive train as seen from the front direction. The output of the DC motor 125 is rotatably supported by an output gear 150, an idler gear 152 provided on the drive board 124, and further by the drive board 124 and a support plate 155, and the drive is transmitted to the developing sleeve 102 at ON10F. F
is transmitted to clutch gear 153M. Further, the driving force from the clutch gear 153M is transmitted to the gear 157 attached to the drive board 124 via its rotating shaft 154 and output gear 158. On the other hand, as can be better understood by also referring to FIGS. 8 and 9, for example, the magenta developing unit 2
When M is inserted along the slide guide 121M, the rotary support plate 105R on the back side of the developer container 106 moves to the back support plate 1.2.
By fitting into the hole 122' of No. 2, the gear 157 and the drive gear 104 of the developing sleeve 102 mesh with each other, as shown in FIG. Similarly to the above, a drive train including clutch gears 153C, 153Y, and 153B is provided for the other developing units) 2C12Y and 2B, and each drive train is connected to a relay gear 159 provided on the drive board 124. The driving force is transmitted from the DC motor 125. With the above configuration, when the main body of the copying machine is turned on, whether or not the movable base 120 is at the home position can be determined by the light emitting element fixed to the bottom plate 60 and the light receiving element, as shown in FIG. A sensor 181 consisting of an element and a base 12
When the movable base 120 is not at the home position, the stepping motor 132 rotates until the light from the sensor 181 is blocked by the light shielding plate 180, that is,
The moving base 120 is moved until it reaches the home position. FIG. 12 shows an embodiment of a developing unit lifting mechanism for lifting and positioning each developing unit 2 toward the photosensitive drum 1 at the developing operating position. In FIG. 12, the movable base 120 and slide guides 121M, 121C, 121Y, 121
B is omitted. Pair of slide guides 121M, 1 installed in parallel
21C1121Y, 121B, in the middle of the slide guide on one side, as described in connection with FIG. Notches 121M' to 121B' for escape
is provided. Further, in the middle of the other slide guide facing the slide guide in which the notch 121' is formed, there is a pressing member, which will be described later, that presses the container guide foot and lifts the developing unit toward the photosensitive drum, namely, rollers 200M and 200C1200.
Y, 200B are provided. On the back side of the movable base 120, as shown in FIGS. 12 and 13, there are roller support plates 201 (201M, 201C12) that constitute a mechanism for lifting each corresponding developing unit.
01Y, 201B) are arranged, and this roller support plate 201 is rotatably supported by a shaft 202 fixedly provided on the back surface of the movable base 120. A shaft 203 is fixed to the roller support plate 201 through the movable base 120, and the aforementioned rollers 200M to 200B are rotatably supported on the shaft 203. On the other hand, the shaft 203 is connected to the roller support plate 201 on the movable base 120.
A slotted hole (not shown) is provided in the shaft 203 so that the shaft 203 can rotate together with the shaft 203. Further, an L-shaped member 204 is fixed to the back surface of the movable base 120, and a rack 205 is arranged on this L-shaped member. The rack 205 functions to transmit the driving force from the pulse motor to the developing unit lifting mechanism, which will be described in detail later. Next, a description will be given of a configuration in which the developing unit is lifted toward the photosensitive drum by the driving force from the pulse motor. Referring to FIG. 12, the developing unit lifting mechanism is disposed below the movable base 120, and is housed in a region H formed by molding a part of the bottom plate of the apparatus main body into a concave shape. Each member constituting the lifting mechanism is fixed to the bottom plate of the main body of the apparatus via a support plate 206. The lifting mechanism has a drive intermittent member, ie, an electromagnetic clutch 207, equipped with a gear 207a that constantly engages with the rack 205 fixed to the back surface of the movable base 120. The rotating shaft 2O8 of the electromagnetic clutch 207 is rotatably supported at both ends by a support plate 206 and an L-shaped member 209 fixed to the support plate 206 via bearings. Furthermore, the electromagnetic clutch 20
A gear 210 is provided below the rotary shaft 208 . The gear 210 includes a shaft 2 fixed to the support plate 206.
Gear 2 via gear 212 rotatably disposed on 11
13 are engaged. The gear 213 is integrally attached to a shaft 214, and the shaft 214 is rotatably supported at both ends by a support plate 206 and a support base 215 fixed to the support plate via bearings. A U-shaped cam plate 21B is integrally attached to one end of the shaft 214 protruding from the support 215. Further, a shaft 217 is fixedly provided on the cam plate 216 at a position eccentric from the shaft 214 by a predetermined amount. The shaft 217 has a link 2 formed of a slippery member such as resin.
One end of 18 is rotatably fitted. The other end of the link 21B is connected to a shaft 219 attached to one end of the class 221.
It is also rotatably fitted. The class 221 of this child is
It is rotatable around a shaft 220 fixed to the support plate 215. Further, inside the class 221, there is arranged a class 222, which is also rotatably provided on the rotation shaft 220 of the class 221. A biasing member (not shown) such as a spring is stretched between the classes 222 and 221, and the class 222 is moved toward the class 221 in the direction of the arrow in the figure. energized. Class A 222 is regulated at a predetermined position relative to class A 221 by having one end thereof abut against a part of class A 221 . A shaft 223 is fixedly provided at a location away from the rotation shaft 220 of the class 222, and a roller 224 is attached to the shaft 223.
is rotatably provided. This roller 224 comes into contact with the outer surface of the bent portion of the roller support plate 201 formed in the U-shape described above. Next, a description will be given of the operation of lifting the developing unit with respect to the photosensitive drum by the lifting mechanism having the above structure. First, when the main body of the copying apparatus is turned on, the movable base 120 is moved to its home position by the light shielding plate 180 and the sensor 181. In this example, the home position is
The center of the photosensitive drum is located at a position where the distance from directly below the photosensitive drum to the magenta developing unit 2M and the cyan developing unit 2C is equal, that is, at the center position between the magenta developing unit 2M and the cyan developing unit 2C. When the movable base 120 is at the home position, the lifting mechanism installed under the movable base 120 and the movable base 12
FIG. 15 shows the positional relationship with the roller support plate 201 arranged on the back surface of the roller 0 when viewed from above. The roller 224 in the lifting mechanism is located at the center position between the magenta developing unit 2M and the cyan developing unit 2C at the home position, that is, directly below the photosensitive drum, and is located in the center position between the magenta developing unit 2M and the cyan developing unit) 2C, in order to lift the cyan developing unit) 2C. It is in contact with the bent surface of the roller support plate 201C of 2C. Next, a case will be described in which development is performed using the magenta developing unit (2M). When developing using the magenta developing unit 2M, the movable base 120 moves in the direction of arrow B due to the copying (image forming) operation. First move the base 12 by a distance of 4
Where 0 moves, that is, from the development position (view/2) -
An ON signal is sent from the MPU controlling the main body of the device to the electromagnetic clutch 207 in the lifting mechanism at a position just in front of the watch. As a result, as can be understood from FIG. 12, the movement of the movable base 120 is transmitted to the shaft 208 via the rack 205 on the back surface of the movable base 120 and the gear 207a that is always engaged with the rack 205, and the shaft 208 is the moving base 12
It starts rotating with the movement of 0. When the shaft 208 rotates,
A gear 210 fixed to this shaft 208 rotates, and this rotation is transmitted to the shaft 214 via gears 212, 213. The rotation of the shaft 214 causes the cam plate 216 to rotate in the direction of the arrow (FIG. 16). Rotating and rolling link 21 of the cam plate 216
8 to class 221, and class 221 rotates in the direction of arrow F (FIG. 18). At this time, since class 222 is spring-biased so as to butt against class 221, the rotation of class 221 causes the arrow G to move.
direction (Fig. 18). Therefore, the roller 224 pushes the roller support plate 201M of the developing unit 2M arranged on the back surface of the movable base 120, and the roller support plate 201M rotates in the upward direction of the arrow (FIG. 18). When the roller support plate 201M rotates in the direction of arrow H, the rollers 200M on the roller support plate 201M move in the direction of arrow 1 (first
Figure 8). Then, as shown in FIG.
The roller 200M moving in the direction is magenta developing 2)2
Since the legs 106b of M are pushed in the same direction, the magenta developing unit 2M is moved to 105F, 1 on the movable base 120.
While the base 120 is moving about 05R as a rotational fulcrum, it is lifted in the direction of arrow J, that is, in the direction approaching the photosensitive drum. Then, when the magenta developing device moves by 1/2, the aforementioned cam plate 216 rotates exactly half a turn, and the magenta developing unit 2M comes to rest at a position directly below the photosensitive drum 1 and close to the photosensitive drum l. The positional relationship between the developing unit and the photosensitive drum, which will be described in detail later, is set at a predetermined distance by an abutting roller provided on the developing unit, that is, a stopper 103, and a stopper receiver 505 (FIG. 1). In the aforementioned lifting mechanism, the gear train 207
a, 210, 212, and 213 are designed so that the cam plate 216 rotates half a turn and stops when the moving base 120 finishes moving. In other words, the electromagnetic clutch 207 is in the ON state during a distance equal to the distance equal to the number of teeth of the gear 207a. Then, through the rack 205, 9,'/ (Zl /2)r
Rotate by ad. Further, if the number of teeth of the gear 210 integrally provided below the shaft 208 is Zz, and the number of teeth of the gear 213 integrally provided to the shaft 214 of the cam plate 216 is Z3, the rotation of the cam plate 216 is The shaft 214 moves 1'/(Z+/2)X(22/Z) while the movable base 120 moves by
3) 2JL'Zz/Z+ *Z3 (rad)
only rotates. The gear trains Z and -z3 are designed so that 2u'Zz/Z+ ・Zz=π (rad. Also, the home position of the developing device 100 is the magenta developing unit) 2M and the cyan developing unit 2C. There are no particular regulations as long as the center of the photosensitive drum is located between
The timing for turning on the electromagnetic clutch 207 is when the developing unit is placed directly below the photosensitive drum regardless of the home position.1'=tt''Z1
Of course, this is set when the object has moved forward by lIZ 3 / 2 Z z. Further, when the vertical distance between the abutting roller 103 and the photosensitive drum surface, that is, the stopper receiver 505 is d when the developing unit is not lifted, the amount of lifting of the developing unit toward the photosensitive drum surface is equal to the distance between the stopper receiver 505 Because it is necessary to press the roller 103 with a predetermined force, the value becomes d+ when the cam plate 216 rotates half a rotation.
The dimensions of the link member 218 in the lifting mechanism are determined so that α (α: positive number) (FIG. 16). Also, the developing unit is placed directly under the photosensitive drum by the abutting roller 103.
When the stopper receiver 5 is close to the
In addition to receiving a reaction force from 05, the developing unit's own weight is pushed back instead. At this time, as mentioned above, since the class 222 is urged to rotate toward the class 221 by the spring, the class 222 receives the reaction force from the photosensitive drum l and rotates toward the class 221. class 22
It rotates in the direction away from 1 against the force of the spring. When the rotation of the second class 222 stops, the developing unit is urged toward the photosensitive drum 1 with a predetermined force, and as will be explained in more detail later, the abutment roller 103 is fixed to the main body of the apparatus. It will be pressed against the station/pa receiver 505. With the above operations, lifting of the magenta developing unit) 2M is completed. Next, a case will be described in which the cyan developing unit 2C is lifted after magenta development is completed. First, it is necessary to separate the magenta developing unit 2M from the photosensitive drum 1 before lifting the cyan developing unit 2C. At this time, as shown in FIG.
6, the link 218 is at the so-called top dead center position with respect to the cam plate 216. Therefore, in order to retreat from this top dead center position, it is necessary to rotate the cam plate 216 slightly by moving the moving base 120. Therefore, the movable base 120 is moved in the direction C in FIG.
The electromagnetic clutch 207 is kept ON only for a very short period of time at the beginning when the magenta developing unit 2M is transferred to the cyan developing unit 2C. In other words, when the cam plate 216 is slightly rotated to avoid the top dead center, the clutch 2
7 is turned off, the recum plate 216 is then rotated by the weight of the magenta developing unit and returned to its initial position, and the magenta developing unit) 2M is lowered and separated from the photosensitive drum 1. After that, when the cyan developing unit (2C) comes to a position that is a distance in front of the developing position (FIGS. 13 and 17), the electromagnetic clutch 207 is turned ON+, and as the movable base 120 moves, the cam plate 216 moves as shown in the arrow. Rotate in the E direction and remove the magenta developing unit/ ) 2 As in the case of M, press the roller support plate 2.
The roller 200C on the roller 01C moves in the direction of arrow 1 (FIG. 13) and begins to lift the cyan developing unit 2c toward the photosensitive drum l. The lifting movement is completed when the moving base 120 has moved by 1/2. The above-mentioned lifting operation when the magenta developing unit 2M moves in the direction of arrow B (FIG. 16) and the cyan developing unit) 2
The lifting operation when C moves in the direction of arrow C (Fig. 17) is as follows:
The same process is performed for each of the other developing units not described. In other words, according to the lifting mechanism configured in the above embodiment, even if the movable base 120 moves in the left-right direction, that is, in the direction of arrow B or C, each developing unit can be lifted toward the surface of the photosensitive drum in an extremely suitable manner. , positioned. According to the lifting mechanism of this embodiment, as described above, regardless of the movement of the movable base in either the left or right direction, the movement of the movable base is used as a run-up to move each developing unit toward the surface of the photosensitive drum. This eliminates the need for extra movement of the movable base for the run-up, which would be required if the run-up direction for lifting is limited to only one direction. For this reason, it becomes possible to move the developing device between sheets of transfer paper supplied to the transfer drum, and as a result, idle rotation of the transfer drum is not required during continuous image forming operations, and the image forming device The image forming processing capacity of the system can be significantly improved. Further, since it is possible to eliminate idle rotation of the transfer drum or the like during continuous image formation without increasing the outer diameter of the transfer drum or the like, it can also contribute to downsizing of the image forming apparatus. As described above, in the reciprocating developing device, each developing unit is mounted on the movable base 120 rotatably about the pivot point 105.
The photosensitive drum 1 is loaded on the photosensitive drum 1 and is urged toward the photosensitive drum 1, particularly in the developing operation position, and positioned at a predetermined position. Next, the means for positioning the developing unit relative to the photosensitive drum according to the present invention will be explained with reference to FIGS. 1 to 6. 1 and 3, the central axis 50 of the photosensitive drum 1
0 has a bearing 506 on the rear side plate 50a of the device main body and a centering plate 503 detachably attached to the front side plate 50b.
It is rotatably supported via. Also, the central axis 500
rotates under the drive of a drive (not shown) via a gear (not shown) fixed to one end of the central shaft 5.
The photosensitive drum l attached to the photosensitive drum 00 is driven to rotate. A toothed flange 504 is fixed to the front side of the photosensitive drum 1, as shown in FIG. The flange 504 is a gear (not shown) integrated with the transfer drum 6.
Drive is transmitted to the transfer drum 6 by meshing with the transfer drum 6. There is a photosensitive drum l between the rear side plate 50a and the photosensitive drum l.
A stopper receiver 505 is provided separately from the stopper receiver 505. This stopper receiver 505 is fixed with screws or the like to a support plate 507 that is detachably attached to the rear side plate 50a. Third
As understood from the figure, the stopper receiver 505 includes:
When the developing unit is urged toward the photosensitive drum 1 at the developing operating position, a stopper, that is, an abutting roller 103 of the developing unit engages. The support plate 507 has a hole in the center, and the hole is aligned with the central axis 500.
The bearing 506 is fitted into the outer periphery of the bearing 506.
and is positioned and attached to the rear side plate 50a at a specified position. Furthermore, the stopper receiver 505 has a dimension from the center hole of the support plate 507 to the stopper receiver surface within a specified value, so that the stopper/pa 103 of the developing unit does not fit into the stopper receiver 50.
5, the gap between the photosensitive drum 1 and the developing sleeve 102 becomes a predetermined value necessary for development. Similarly, a stopper receiver 505 is also provided between the centering plate 503 attached to the front side plate 50b and the photosensitive drum 1.
is arranged and fixed to the centering plate 503 with screws or the like. Similarly, the receiving surface of the stopper receiver 505 is precisely positioned and fixed to the centering plate 503 using a jig. According to this embodiment, the stopper receiver 505 is fixed to the rear side plate 50a and the front side plate 50b separately from the stopper receiver 505.
8.509.510.511 is provided. The stopper receiver 505 and the stopper receivers 508 to 511 are the movable base 1
Stopper 103 of the developing unit within the reciprocating range of 20
They are arranged close to each other with a small gap so that they can be engaged with each other. Next, the shape of the stopper receiver 505 constructed according to the present invention will be explained. As described above, the position of the receiving surface 505a of the stopper receiver 505 in relation to the surface of the photosensitive drum must be strictly defined by a jig. Furthermore, the movable base 12O that loads the developing unit and moves back and forth has considerable variation in the stopping position due to backlash of the drive gear train of the movable base or the stopping accuracy of the pulse motor. Even if there is a gap between the photosensitive drum l and the developing unit, that is, the developing sleeve 102, it is necessary to set it within a predetermined range. Since the developing device of this embodiment reciprocates in the substantially tangential direction of the photosensitive drum surface, the receiving surface 505a of the stopper receiver 505 is an arcuate surface having the same center of curvature as the photosensitive drum l, as shown in FIG. It is preferable to do so. With this configuration, even if some variation occurs in the stop position of the movable base 120 when it reciprocates, the gap between the photosensitive drum and the developing sleeve can be defined to a predetermined value. The magnitude of the curvature of the arcuate surface 505a of the stopper receiver 505 is preferably the same as the curvature of the photosensitive drum 1, as described above. In other words, when the curvature of the receiving surface 5°5a is made larger than the curvature of the photosensitive drum, the outer diameter of the stopper 1°3 of the developing unit must be made larger in order to maintain a predetermined gap between the photosensitive drum' and the developing sleeve. Therefore, when the developing unit is pulled out of the apparatus main body, the gap between the stopper 103 on the back side of the developing unit and the photosensitive drum 1 becomes smaller.
There is a risk of damaging the photosensitive drum. Conversely, if the curvature of the receiving surface '505a of the stopper receiving surface 505 is made smaller than that of the photosensitive drum l, the outer diameter of the stopper 103 becomes smaller, but the stopper receiving surface 50
5a protrudes from the surface of the photosensitive drum, the gap between the stopper receiving surface 505a and the developing sleeve 102 becomes smaller, and when the developing unit is similarly pulled out of the apparatus main body, Developing sleeve 1
There is a risk of scratching the surface of 02. The stopper receivers 508 to 511 are for restricting the upward rotation of the developing unit at a so-called non-developing operation position, where the developing unit is not below the photosensitive drum. Therefore, unlike the stopper receiver 505, its position does not need to be strictly defined, and installation using a jig or the like is not necessary. These stopper receivers 508 to 511 are connected to the movable base 12.
When 0 moves back and forth, the developing sleeve 1 of the developing unit
02 and other parts of the apparatus main body, or in such a position that an appropriate gap is maintained between the two to prevent toner from adhering to and contaminating such members. It is fine as long as it is provided. Further, the shape of the stopper receiving surfaces of the stopper receivers 508 to 511 does not need to be a curved surface like the receiving surface 505a of the stopper receiver 505, and a simple flat surface can sufficiently exhibit its function. Further, according to this embodiment, the stopper receiver 505 is configured to be attached to the support plate 507 and the centering plate 503, which are separate plates that are detachably attached to the rear side plate 50a and front side plate 50b of the device main body. There is an effect that assembly using a jig is easier than in the case of directly fixing 505 to the front side plate 50a and the rear side plate 50b of the apparatus main body. Furthermore, even if the stopper receiver 505 is damaged in the market, the replacement work will be done if the stopper receiver 505 is damaged on the support plate 5.
This can be done with the centering plate 503 and the centering plate 503 fixed together using a jig, which is very efficient. The shape of the stopper receiver 505 is an arcuate surface 50 having the same center of curvature as the photosensitive drum as shown in FIG.
The range (view) of 5a is made as small as possible within a range that can accommodate variations in the stop position of the movable base 120, and
It is also effective to have flat portions 505b located below the arcuate surface at both ends of the arcuate surface 505a. The stopper receiver 505 having such a shape has the following effects. In other words, in the developing unit lifting mechanism described in FIGS. 9 to 13, when the developing unit is lifted, the cam plate 216 rotates half a turn and the link 218 is at the top dead center position with respect to the cam plate 216. . However, since the electromagnetic clutch 207, which continues to be driven by the pulse motor, has a time delay (so-called connection time) required from receiving a signal to actually connecting, the link 218 is not connected to the cam plate 216. It may happen that the point position is not necessarily located. Of course, the developing unit is sufficiently lifted at this position. Therefore, as shown in FIG. 7, if the lifting operation of the developing unit is completed and development is performed while the link 218 has not moved to its top dead center,
Thereafter, when the cam 216 rotates in the direction of the arrow to lower the developing unit, a further force is applied to the developing unit to lift it up until the link 218 reaches its top dead center position. At this time, if the shape of the stopper receiver 505 is an arc having the same center of curvature as the photosensitive drum, as shown in FIG. The stopper 103 of the developing unit is placed in the stopper receiver 505.
The developing unit temporarily rises along the arc. Usually, as shown in FIGS. 4 to 6, the developer container 1
A cover 109 is provided on the upper surface of the developing sleeve 102 to cover the surface of the developing sleeve 102, and as described above, when the developing unit is raised, this sleeve 109 is brought to the position closest to the photosensitive drum 1 (see FIG. ). Therefore, considering this situation, the size of the cover 109 cannot extend too far over the surface of the developing sleeve. For this reason, there is a concern that the effectiveness of the cover in preventing scattering may be reduced. Therefore, in order to cover the sleeve surface other than the vicinity of the developing position in order to prevent toner scattering from the developing sleeve surface as much as possible, the stopper receiver 505 having the shape shown in FIG. 6 is preferable. In other words, the stopper receiver 505 shown in FIG. It has a shape having flat portions 505b located below the arcuate surface at both ends of the surface. As a result, even if the developing unit tries to be lifted further when moving on to the next development after the lifting is completed and development is performed when the link 218 is not at its top dead center position as described above, the movement is regulated by the flat parts 505b at both ends of the arc of the stopper receiving surface 505a, and as described above, the cover 1
09 is never brought to a position close to the photosensitive drum l. Therefore, the cover 109 can be shaped to cover as much of the surface of the developing sleeve as possible, and can exert a sufficient effect against toner scattering. In the above embodiments, the reciprocating type developing device has been described as one that moves horizontally, but it goes without saying that the present invention can also be applied to cases where the reciprocating developing device moves vertically. Further, in the above embodiment, the stopper receiver is constituted by a plurality of members, the member 505 and the members 508 to 511.
If each member constituting the apparatus main body is arranged at a sufficient distance from the developing unit in the region where the stopper receivers 508 to 511 are arranged, only the member 505 as a stopper receiver is arranged near the photosensitive drum. , other members 50
8 to 511 can be omitted. As explained above, according to the image forming apparatus of the present invention,
Since the abutting roller of the developing unit, that is, the stopper receiver that engages with the stopper 7 and positions the developing unit, is provided on a member separate from the image carrier such as the photosensitive drum, the developing unit is Even if the developing unit is driven upward during the development operation to replenish toner and stir the developer, and this driving force lifts the developing unit upward, the developing unit may collide with the image carrier and cause unnecessary damage to the image carrier. It is possible to avoid giving an impact, hitting other members constituting the main body of the apparatus, or contaminating these members with toner from the developing unit. Therefore, according to the image forming apparatus of the present invention, it is possible to more stably obtain high-quality images, and it is also possible to prevent the life of the image carrier from decreasing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a photosensitive drum and a stopper receiver used in an image forming apparatus according to the present invention. FIG. 2 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a configuration diagram of another embodiment of the image forming apparatus according to the present invention. 3 is a front view showing the photosensitive drum and stopper receiver of FIG. 1. FIG. 4 and 5 are side views illustrating the operations of the photosensitive drum, the developing unit, the stopper, and the stopper receiver. FIG. 6 is a side view showing another embodiment of the stopper receiver. FIG. 7 is a plan view illustrating how the lifting mechanism operates. FIG. 8 is a perspective view of the developing unit. FIG. 9 is a perspective view of the developing device. FIG. 10 is a plan view illustrating how the developing sleeve of the developing unit is driven. 1tg is a front view seen from direction D in FIG. 9. FIG. 12 is a perspective view of the developing unit and the lifting mechanism. FIGS. 13 and 14 are front views illustrating the lifting operation of the developing unit. FIG. 15 is a plan view of the lifting mechanism. FIGS. 16 to 18 are plan views illustrating how the lifting mechanism operates. FIG. 19 is a configuration diagram of a conventional image forming apparatus. : Image carrier: Developing unit: Transfer drum: Developing device: Abutting roller (stopper): Moving base: Core/determining plate: Support plate 508 to 511: Stopper receiver 505,

Claims (1)

[Scope of Claims] 1) An image carrier on which a latent image is formed, and at least one image carrier disposed close to the surface of the image carrier to visualize the latent image on the image carrier. In an image forming apparatus having one or more developing units and a movable base that supports and moves the developing units, the developing unit may include a stopper for positioning the developing unit with respect to the image carrier. An image forming apparatus characterized in that the stopper is provided and engages with a stopper receiver that is fixed to the apparatus main body separately from the image carrier. 2) The image forming apparatus according to claim 1, wherein part or all of the stopper receiver is a curved receiving surface having a center of curvature that is the same as the curvature of the surface of the image carrier. 3) The image forming apparatus according to claim 1, wherein the stopper receiver is fixed to a separate plate that is detachable from the apparatus main body.