JPH0385564A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the durability of a rocking mechanism to decrease the blurring of an image, and to improve the image quality by pulling up one edge of an rocking supporting shaft with an elastic member, making the developing unit abut on an image carrier at three supporting points, and when the developing unit is driven, activating the force of the developing unit work in the direction of the image carrier. CONSTITUTION:One edge of the rocking supporting shaft 105R of the developing unit 101 is supported by the developing device so that it is only rotatable, the other edge 105F of the rocking supporting shaft 105 is also rotatable and is supported by the developing device so that it can be moved in the vertical direction energized in the direction coming closer to the image carrier 1 with the elastic member 110. Then by energizing a driving means 125 which drives the developing unit 101, the developing unit 101 receives the force which moves to the direction of the image carrier 1 with the rocking supporting shaft 105 as the center. Thus, the durability of the rocking mechanism can be improved, the blurring of image cause by vibration in rocking can be decreased, and the image can be improved.

Description

[Detailed Description of the Invention] Part 1! The present invention relates to an electrophotographic or electrostatic recording image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus.

A currently commercialized image forming apparatus, such as a full-color electrophotographic copying machine, is illustrated in FIG.

This copying machine includes a transfer drum 5 that holds a transfer paper P on its circumferential surface by a gripper 58 or the like, and above the transfer drum 5 there is a photosensitive drum 1 and a plurality of developing units 101Y, IOIM,
A rotary developing device 1 that accommodates and rotates 10IC and 10IB.
00, and each developing unit 101Y that stores toner.
, 101M, and 10IC1IOIB.

The photosensitive drum 1 and the rotary developing device 100 arranged above the transfer drum 5 are sources of toner scattering, and the carrier (iron powder) in the two-component developer used is also scattered. Therefore, these scattered toners and carriers tend to accumulate on the surface of the transfer drum 5 located below.

The toner deposited on the surface of the transfer drum 5 causes stains on the back side of the transfer paper P, and also weakens the electrostatic attraction between the transfer sheet 5b wound around the transfer drum 5 and the transfer paper P. As a result, it causes various problems such as deterioration of image quality, occurrence of paper jams, and shortened lifespan of the fixing roller.

Therefore, large-scale equipment is required to collect and collect the toner and carrier accumulated on the surface of the transfer drum 5 and keep the surface of the transfer drum clean, and these equipment can become a source of noise and increase the cost of the equipment. This was hindering low prices.

Furthermore, since the rotary developing device is constructed by housing a plurality of developing units in a rotary body, the overall size of the copying machine has inevitably increased.

Therefore, in order to solve the above-mentioned drawbacks of the conventional device,
By arranging toner and carrier scattering sources such as a developing device, a toner replenishing device, and an image bearing member such as a photosensitive drum below or in front of the transfer device, and configuring the developing device to be movable laterally, transfer is possible. Image forming apparatuses have been proposed that can prevent the accumulation of toner and carrier on the surface of the apparatus, thereby solving problems such as deterioration of image quality, occurrence of jams (paper jams), and shortening of the life of the fixing roller. 8th
An example of an image forming apparatus is illustrated in the figure.

FIG. 8 shows a schematic sectional view of a full-color electrophotographic copying machine, and the overall configuration will be explained.

An image carrier, that is, a photosensitive drum 1 having an electrophotographic photosensitive layer on its surface, is rotated in the direction of arrow X. Photosensitive drum 1
A primary charger 2 is located on the left side of the photosensitive drum 1, a surface electrometer 3 that measures the potential on the surface of the photosensitive drum 3 is located diagonally below and to the left of the photosensitive drum 1, and a plurality of developing units, that is, developing units in this embodiment, are located directly below the photosensitive drum 1. tIOIM, l0
A developing device 100 loaded with Ic, 10IY, 101B and moving in the left-right direction, a transfer device 5 diagonally above and to the right of the photosensitive drum 1, and a device approximately directly above the photosensitive drum 1 that remains on the surface of the photosensitive drum 1 after transfer. A pre-static eliminator 6 and a cleaning device 7 are disposed diagonally above and to the left of the photosensitive drum 1, respectively, to reduce the adhesion of toner to the photosensitive drum to facilitate cleaning.

Further, an optical system 10 is disposed in the upper part of the copying machine, and the original image on the platen 8 is transferred to the charger 2 and the surface electrometer 3.
The image is projected onto the photosensitive drum 1 at an exposure section 9 located between the two. Although any optical system can be used as the optical system 10, in this embodiment, the first scanning mirror 11, the first
second and third scanning mirrors 12 and 13 that move in the same direction at half the speed of the scanning mirror 11; an imaging lens 14;
and B, a CCD integrated with a G%R filter 5, a laser scanner unit 16, and a fixed mirror 17.
Consists of 18. Here, the scanner unit 16
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 10, the original illumination light source 20 is configured to move together with the first scanning mirror 11. Therefore, after passing through the lens 14, the reflected light image of the original scanned by the first to third scanning mirrors 11, 12.
The CCD 15 equipped with an R4 color separation filter separates the colors and converts them into electrical signals, and this document information signal is sent to the A/
After undergoing information processing such as D conversion, the video signal is converted into a microprocessor unit (hereinafter referred to as M) that controls the entire copying machine.
PU). 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 i at 0N10FFL.

Further, in this example, a fixing device 20 and a paper feeding device 30 are arranged on the right side of the copying machine, and a transfer paper conveying system is provided between the transfer drum 5 and the fixing device 20 and paper feeding device 30, respectively. 25 and 35 are provided, respectively.

In the above configuration, the photosensitive drum 1 includes a primary charger 2, an optical system 10, a developing device 4, a transfer device 5, and a cleaning device for charging, exposing, developing, transferring, and cleaning processes for each color separated by the CCD 15. Performed by 7.

The developing device 100, which will be described in more detail later, includes a developing unit IOIM (magenta developing unit) 101C (cyan developing unit) 101Y (yellow developing unit) that is detachably held on a movable stage 120 (FIG. 9).
and 101B (black developing unit), and the color-separated latent images of each color are visualized by the corresponding developing units.

The transfer device 5 typically includes a transfer drum 5b equipped with a gripper 5a for gripping a transfer material, that is, a transfer paper P, on its circumferential surface. The transfer device 5 receives the transfer paper P fed from the transfer paper cassette 31 or 32 of the paper feed device 3o via the transfer paper conveyance system 35.
The tip of the photosensitive drum 1 is gripped by a gripper 5a and rotated to transfer a visible image of each color on the photosensitive drum 1. A transfer charger 5C is arranged inside the transfer drum 5 in the transfer area.

The transfer paper P on which the toner image of each color has been sequentially transferred is released from the gripper 5a and peeled off from the transfer drum 5b by the separation charger 8 and the separation claw 8'. Next, the transfer paper P is sent to the fixing device 20 by the transfer paper transport system 25. The toner image on the transfer paper P is fixed onto the transfer paper by the fixing device 20, and then the transfer paper is discharged onto the tray 23.

In FIG. 8, a toner replenishing device is provided on the upper left side of the copying machine, and a detailed explanation of the toner replenishing device will be described later.

Next, the developing device 100 will be explained.

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, it is desirable that the developing unit be held directly below the photosensitive drum, that is, at a position retracted from the photosensitive drum l except when it is in the developing operation position.

This is because when each developing unit is moved close to the photosensitive drum 1, even when returning to its original position (home position) after development of all four colors is completed, each developing unit remains close to the photosensitive drum 1. 1, and as a result, all the toner standing on the developing sleeve in each developing unit comes into contact with the photosensitive drum, causing unnecessary toner to adhere to the photosensitive drum.

If unnecessary toner adheres to the photosensitive drum, all or all of the toner adhered to the photosensitive drum may be removed because there is no transfer paper between the photosensitive drum 1 and the transfer drum 5b during non-development. A part of it flies to the transfer drum 5b, resulting in contamination of the transfer drum 5b.

In addition, near the developing operation position of the photosensitive drum 1, it is necessary to arrange a surface electrometer 3 and a partition plate to prevent foreign matter such as paper dust from falling from above onto the developing sleeve of each developing unit. . In order to maintain a predetermined distance between each of these members and the developing sleeve and to prevent them from coming close to each other, it is necessary that each developing unit is located at a position retracted from the photosensitive drum 1 outside the developing operating position.

In other words, the laterally moving developing device 100 configured according to the present invention brings each developing unit close to the photosensitive drum 1 only during development (when it is directly below the drum), and retreats from the photosensitive drum 1 during other non-development periods. It is configured so that it is located at the position shown in the figure.

Next, the developing device 100 will be described in more detail with reference to FIGS. 9 to 17.

In this example, developing unit lot (IOIMlo
lClIOIY, l0IB) have the same configuration, and the only difference is the color of the developer supplied inside.

Referring to FIG. 11, the developing unit 101 has an elongated developing container 106 whose cross section is approximately rectangular. A sleeve 102 is rotatably supported. Abutment rollers 103 are provided at both end shaft portions of the developing sleeve 102 to ensure a predetermined gap between the developing sleeve 102 and the photosensitive drum 1 . 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 as described later, the developing sleeve drive gear 1' (first
6) meshes with the drive gear 104 to drive 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.

A developing unit 101 is installed at both ends of the developing container 106.
Developing sleeve 1 (
52 and coaxially parallel to it.

Also, inside the developer container 106, only the shaft portion of a screw C that stirs and transports the developer contained therein is shown) 107.1.
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). Further, the end of one of the screws, the screw 107 in this embodiment, protrudes toward the front side from the developer container 106, and is connected to a toner replenishing device 200 (described later).
It passes through a conveying pipe 160a connected to the pipe (FIG. 13). A toner replenishing device 2 is installed above the conveying pipe 160a.
A replenishment port 160a' for connecting to the supply port 160a' is an elongated opening.

That is, as understood from FIG. 12, the replenishment port 160a' of the conveying pipe 160a is
Supply port 2 of shutter 241 of supply pipe 202 of 00
41a. Therefore, when the developing unit 101 moves, the replenishing port 24 follows the lateral movement of the developing unit 101.
1a is guided by the replenishment 0160a' of the developing unit, and the replenishment pipe 202 swings to enable constant replenishment of toner.

An embodiment of such a toner replenishing device 200 is shown in FIG.

FIG. 13 is a perspective view showing a simplified overall view of the toner replenishing device 200 with detailed parts omitted. Toner supply device 200
are containers 201M, 201C, 201Y, and 201 that store developer of each color of magenta, cyan, and yellow black.
B, and the developing unit IOIM, 101C from each container.
, 10IY, and 1oIB, a supply pipe 202M-B having a built-in screw is swingably connected to the toner container 201M-B. As described above, the replenishment port 241a of the shutter 241 of the replenishment pipe 202 is located in a part of the developing unit, that is, the replenishment port 160.
a' and is configured to supply toner to the developer container 106.

The toner container, replenishment pipe, and other components of the toner replenishment device 200 are attached to the replenishment support plate 203 . Further, the supply support plate 203 is attached to the support shaft 2 with respect to the support stand 204 fixedly provided on the front side plate (not shown) of the copying machine.
05a and 205b, it is rotatably supported.

During the copying operation, the supply support plate 203 is rotated toward the front plate, and is fixed to the front plate at the end opposite to the rotational fulcrum with screws or the like and set.

Returning to the developing device 100, guide legs 106b and 106c (see FIG. 10) are formed at the bottom of the developing container 106, and are attached to a movable base 120, which will be described later. It is adapted to be slidably engaged with the slide guide 121.

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 101 is omitted.

The developing device 100 has a movable base 120 on which each developing unit 101 is loaded and moved, and the base 120 has a slide guide 121 (121M) that engages and holds the guide legs 106b and 106c of each developing unit 101. %
121c, 121Y, and 121B) are attached with stepped screws (not shown) so as to be slidable in the six directions of the arrows.

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 is the rotation support shaft 105 of the developing unit 101.
The front support plate 123 has a hole 122' that fits with the rotation support shaft 105F of the developing unit 101.
'have. The front support plate 123 supports the developing unit 10
1 along the slide guide 121, and rotate the pivot shaft 1.
After fitting 05R into the hole 122' of the back support plate 122,
The rotation support shaft 105F and the hole 123' of the front support plate 123 are fitted, and then screwed to the base 120.

As can be understood by referring to FIG. 10, the movable base 120 is provided with a rail 127 at the rear end of the base 120, and the rail 127 is fixed to the bottom plate 60 of the copying machine. It is slidably engaged with a rail support 128 attached to the side plate 50. On the other hand, a roller 129 having a built-in bearing is rotatably supported at the front end of the base 120 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 50.

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 base 120. Further, the stepping motor 132 and the gears 133 to 135 are configured as one unit and are attached to the bottom plate 60.

As described above, according to the electrophotographic copying machine of this example, the developing device 100 is moved toward the photosensitive drum 1 on the base 120 in the substantially tangential direction of the photosensitive drum, and the developing device 100 is moved to the developing operation position, that is, the photosensitive drum The photosensitive drum is positioned approximately directly below the photosensitive drum with a predetermined gap therebetween.

FIG. 14 is a perspective view showing a developing unit lifting mechanism for positioning each developing unit 101 by lifting it toward the photosensitive drum 1 at the developing operating position. In this diagram, to make the internal parts arrangement easier to understand,
The movable base 120 and the slide guide 121M for the developing unit 101M are indicated by two-dot chain lines, and the slide guides 12IC, 121Y for other developing units are
121B is omitted.

There are short rack teeth 14 on the back side of the slide guide 121M.
0M is fixed, and the rack teeth 140 that are also turned down are attached to the slide guides 121 (:,, 121Y) of each developing unit.
, 121B. Furthermore, long rack teeth 141 are fixed to the back side of the base 120.

On the other hand, a rotating shaft 142 rotatably supported by a support plate 143 is provided on the bottom plate 60 . A clutch gear 144 is attached to the rotating shaft 142 at a position that engages with the rack 141 on the back side of the base 120, and when a voltage is applied to the clutch gear 144, the rotation of the gear is transmitted to the shaft 142. ing.

Further, a gear 145 is provided on the rotating shaft 142 at a position that engages with the rack 140M on the back surface of the slide guide 121. Here, the number of teeth Z144 of the clutch gear 144 is set smaller than the number of teeth 2145 of the gear 145.

The reason for this will be explained in detail later.

Adjacent to the gear 145, a ring 1 is attached to the rotating shaft 142.
46 is fixed, and a coil spring 147 is inserted between the gear 145 and the ring (46.
One end of the ring 146 is hooked into a groove (not shown) provided in the ring 146, and the other end is hooked into a hole 145a made in the side surface of the gear 145, as shown in FIG. And the gear 145 has a parallel bin groove 145b.
is fan-shaped, the gear 145 is biased in the direction of the arrow by the coil spring 147, and one end of the fan-shaped groove abuts against the parallel bottle.

Next, the driving mode of the developing sleeve 102 will be explained.

FIG. 16 is a diagram showing the relationship between the developing unit 101 and the photosensitive drum 1 when viewed from the direction of arrow E in FIG. 11.

The developing unit 101 uses a moving support shaft 105F as described later when developing each color.

The abutting roller 103 is oscillated about the oscillation center 105R until it abuts against the photosensitive drum, and is lifted and moved so that the distance between the photosensitive drum 1 and the developing sleeve 102 becomes a predetermined distance. At this time, as mentioned above, the photosensitive drum 1
A developing sleeve driving drum gear l' provided on the flange portion of the developing sleeve 102 and a gear 1 fixed coaxially with the developing sleeve 102.
04, the developing sleeve 102 is also driven by the photosensitive drum 1 and rotates.

With the above configuration, when the main body of the copying machine is turned on, whether or not the base 120 is at the home position can be determined by the light emitting element and light receiving element fixed to the bottom plate 60, as shown in FIG. Detected by a sensor 181 consisting of
When the base 120 is not at the home position, the stepping motor 132 rotates to move the base 120 until the light from the sensor 181 is blocked by the light shielding plate 180, that is, until the base 120 reaches the home position.

To explain further, referring to FIG. 17, the home position is such that the magenta developing unit 101M is located directly below the photosensitive drum 1, and the magenta developing unit 101M is located on the left side when viewed from the front (β is the position where the developing sleeve 102 is directly below the photosensitive drum 1). Swing shaft 1
Swing shaft 1 from the 05F position to the home position
05F, and is located at a distance equal to the interval between each developing unit), and that position is located at a distance from the light shielding plate 18.
It is set by adjusting 0.

Next, when the copy button is operated to start the copying operation, the microprocessor unit (MPU) that controls the operation of the copying machine body sends the pulse generator of the stepping motor 132 that drives the base 120 to the developing unit of the magenta developing unit. A signal is sent to move the base 120 at a predetermined speed until the sleeve 102 is directly below the photosensitive drum 1.

Then, this pulse generator generates a pulse signal corresponding to this moving distance and its speed, and this pulse signal is shaped and distributed by the driver of the stepping motor 132, and a predetermined pulse is sent to each coil of the stepping motor for each pulse. The motor 132 rotates by flowing current in this order.

Here, the stepping motor 132 moves stepwise at a constant angle in accordance with the number of input cavities, and has the feature that the angle error is extremely small. Therefore, the stopping accuracy of the base 120 is very high, and the image may be affected by variations in stopping accuracy. The effect of is negligible.

As the base 120 moves, the magenta developing unit 10
1M is lifted upward and approaches the photosensitive drum 1.

This lifting operation will be explained in detail next.

In FIG. 14, as described above, at the home position of the base 120, the rack 141 and the clutch gear 144 are in an engaged state. Further, since the clutch of the clutch gear 144 is turned ON immediately before the base 120 starts moving, the rotating shaft 142 and the gear 145 rotate as the base moves. While the base 120 is moving, the racks 140 fixed to the bottom of the slide guide 121 are engaged with the rotating gears 145, respectively.

The number of teeth 2144 of the clutch gear 144 is as described above.
Since the number of teeth is smaller than 2145 of the gear 145, for example, the point where the rack 140 starts to mesh with the gear 145! 2. (I
2. <g, the state shown in FIG. 17), when the base 120 moves by 1, the clutch gear 144 also rotates by β1 on the pitch circumference. Converting this into the rotation angle of the rotating shaft 142.

a=ffl/r 1 44 (rad) (I1
44 is the pitch circle radius of the clutch gear 144).

Therefore, the rotational length of the gear 145 on the pitch circumference, that is, the moving path 11i1122 of the slide guide 121M integrated with the rack 140 that meshes with the gear 145 is n2=αXr145 ==12. x (r 145/r 144)
(I145 is the pitch circle radius of gear 145).

Here, since 2145>Z144, that is, I145>I144, I22>I2+. That is, while the base 120 moves 121 times, the slide guide 121M slides relative to the base 120 by a length of (I22J2+). This slide guide 121M is connected to the base 120 (
As shown in FIG. 17, the slide guide 121M moves the leg 106b of the developing unit IOIM, which is rotatable about the supporting points 105F and 105R on the base 120, as shown in FIG. is pushed in the direction of arrow A.

As a result, the magenta developing unit IOIM
0 is lifted in the direction of arrow B and comes to rest at a position directly below the photosensitive drum 1 and close to the photosensitive drum 1 via the abutting roller 103.

During this lifting, the legs 106C of the developer container 106 move away from the slide guide 121M as shown in the figure, so as shown in FIG. Notches 121M' and the like are formed.

Also, since the abutting roller 103 needs to be pressed against the photosensitive drum l with a predetermined force, if the distance between the abutting roller 103 and the surface of the photosensitive drum at the home position is d, then
The lifting amount of the developing unit IOIM in the B direction is d+α
(α: positive number). Therefore, in order to achieve such a lifting amount, the number of teeth of the gears 145 and 144 is appropriately determined from the relationship with the moving distance.

On the other hand, when the developing unit 101M is close to the photosensitive drum 1 via the abutment roller 103 directly below the photosensitive drum 1, it receives a reaction force from the photosensitive drum 1 corresponding to the distance α, and the developing unit's own weight is In addition to this, it will be pushed back. This force causes the developing unit IOIM to rotate clockwise around its pivot points 105F and 105R, so the slide guide 121M is now pushed to the left (in the opposite direction of arrow A) by the feet 106b of the developer container. As a result, the rack 140M engaged with the slide guide 121M tries to rotate the gear 145 counterclockwise. The gear 145 is connected to the coil spring 14 as described above.
Although the photosensitive drum 1 is biased in the direction of the arrow by
The coil spring flexes until the reaction force from the coil spring and the movement of the developing unit balance the biasing force of the coil spring.
45 is rotated between fan-shaped parallel bins 145b.

At this time, the coil spring 147 receives a reaction force from the photosensitive drum l,
In other words, the wire diameter and the number of turns are appropriately determined so that the pressing force of the abutting roller 103 against the photosensitive drum 1 becomes a desired value. Further, the rotating shaft 142 is connected to the clutch gear 1
43, the rack 141 is connected to the stepping motor 132 via the rack 131, and the self-holding force of the stepping motor 132 acts on the rotating shaft 142, so that it is not affected by the rotation of the gear 145 mentioned above. Accurate movement of the base is achieved.

As described above, when the developing unit 101M is lifted up, the abutment roller 103 comes into pressure contact with the photosensitive drum 1 with a predetermined force, and the developing sleeve 102 approaches the photosensitive drum 1 with a required gap.

At this time, as described with reference to FIG. 16, the developing sleeve drive gear 104 and the photosensitive drum gear 1 mesh with each other, so the developing sleeve 102 rotates and the latent image on the photosensitive drum 1 is visualized.

When the magenta developing process is completed as described above, the clutch gear 144 (FIG. 14) is turned off. This results in
Since the rotating shaft 142 becomes free to rotate, the gear 146 integrated therewith also becomes free to rotate, and therefore, the slide guide 121 is moved by the foot of the developer container 106 due to the reaction force from the photosensitive drum 1 and the weight of the developing unit IOIM. 106b
17, the developing unit lOIM returns to the lowered position shown in the left diagram of FIG. 17 and separates from the photosensitive drum l.

Next, the stepping motor 132 rotates by a predetermined amount, the clutch gear 144 is turned ON, and the cyan developing unit 10IC is lifted directly below the photosensitive drum. The developing sleeve receives the drive from the driving drum gear l' and performs cyan color development.

Thereafter, when the development of yellow and black colors and the overlapping transfer of each color image onto a sheet of transfer paper are completed in the same manner, the transfer paper is separated from the transfer drum 5 by the separation charger 8 and the separation claw 8'. The image is fixed by the fixing device 20 and then delivered to the paper output tray 2.
3, and the copying operation ends.

Since the developing device that moves horizontally is placed below the photosensitive drum, it is possible to place the developing device below the transfer drum, and since the developing sleeve is located above the developing container, Compared to conventional full-color electrophotographic copying machines, we were able to reduce toner carrier scattering to a much lower level. Because of this, it has become possible to commercialize a small and inexpensive full-color copying machine because the device for suppressing and cleaning the toner carrier has been removed and there is no large rotating body.

Furthermore, the developing device does not consist of multiple developing units as rotary bodies as in the past, but instead moves horizontally in the left-right direction. The behavior of the developer is stabilized, and as a result, the mixing ratio of toner and carrier (T/C ratio) can be controlled more accurately than before. Therefore, it is possible to always obtain stable image quality, which is of great benefit to the user.

In order to adopt a configuration that has such advantages, it is necessary to have an arrangement and a mechanism in which the developing unit is disposed below the photosensitive drum and the developing unit is brought into contact with the photosensitive drum by a lifting operation. However, the following problems were caused by such an arrangement and mechanism, and these problems were conventionally solved by the methods described below.

That is, in FIG. 16, the developing unit 101 is supported at four locations: the front swinging support shaft 105F, the back swinging support shaft 105R, the front abutment roller 103F, and the rear abutment roller 103R. Double swing support shaft 105F%1
If 05R is fixed, one of the abutment rollers will not abut against the photosensitive drum unless the drum axis and the rotating axis of the developing unit are completely parallel.

Even if the photosensitive drum axis and the rotating axis of the developing unit are set parallel to each other using a jig, they cannot be completely parallel, and it is difficult to reliably obtain a gap between the photosensitive drum 1 and the developing sleeve 102 on the order of several hundred μm. This also caused problems such as deterioration in assembly efficiency and an increase in the number of parts for adjustment.

Furthermore, it is unreasonable to make the developing unit, especially the developing container, flexible in terms of ensuring the performance of the magnetic roller seal and the screw shaft seal, and ensuring a reliable gap between the drum sleeves. In such a case, one method for boat fishing is to make one of the front or rear swinging shafts free. FIG. 18 shows this method. In this example, the front swing support shaft 105F is received by a bearing 109F', and the developing device has an elongated hole 109F'' that expands the bearing 109F'' in the vertical direction. It is configured to be supported by a support plate 123 fixed to the main body of the device.

However, in this method, the present inventors conducted an experiment and found that the swing support shaft 105F on the near side actually lifts up from the lower end of the elongated hole, as schematically shown in FIG. Don't hesitate,
As a result, the abutting roller 103F did not abut against the photosensitive drum. The reason for this is that, as shown in FIG. 20, in the conventional example, the lifting force for the developing unit is applied in the tangential direction of the rotating locus of the developing unit so that the swinging is most efficient. This is because almost no force is exerted to lift the shaft 105F upward. To solve this problem, for example, as shown in FIG. 21, it is necessary to apply upward force sufficient to support the weight of the developing unit near directly below the swing shaft 105F. Since the moving force becomes small, the lifting mechanism must apply a correspondingly large force to the developing unit, which puts strain on the lifting mechanism and is not practical.

Due to this background, this problem has conventionally been dealt with in the following manner.

FIG. 22 shows the method. In this method, the bearing 109F' supporting the front swing support shaft 105F overcomes the weight of the developing unit 101 by the spring 110,
09F". In this case, the front swinging spindle 105F is higher than the back swinging spindle 105R, so as the developing unit swings, the front abutting roller 103F goes first. It hits the photosensitive drum 1.

The force with which the foot 106b is pushed by the slide guide 121 becomes a moment about the pivot shaft 105F, and a force is applied from the abutting roller 103F to the photosensitive drum l, and the developing unit 101 receives the reaction force downward. Become. Due to this downward force, the swinging support shaft 105F moves down against the lifting force of the lifting spring 110, and the abutment roller on the back side is brought to the photosensitive drum at three points: the two back abutment rollers and the swing support shaft. It stops where it is supported by.

By employing such a mechanism, a conventional method has been established in which a horizontally movable developing device is disposed below the photosensitive drum, and each developing unit is brought close to the photosensitive drum by a lifting operation.

However, despite the improvements described so far, the full color electrophotographic copying machine devised by the present applicant still has the following problems.

In other words, in the conventional method, it is necessary to set the spring pressure of the lifting spring 110 that lifts up the swinging shaft of the developing unit to be large, and a large lifting force must be given to the developing unit to overcome this. There wasn't. As a result, the lifting operation becomes uncertain and various other problems occur.

Specifically, it is difficult to obtain accurate spring pressure with a spring 110 bent into a U-shape as shown in FIG. If the predetermined lifting spring pressure is not exerted, the swinging support shaft on the near side will not be fixed, so no matter how much swinging force is applied to the feet 106b of the developing unit, the supporting point will move. The abutting roller 103F may not be able to exert sufficient abutting force, or in the worst case may not come into contact with the drum.

Therefore, in order to ensure reliable lifting, it is necessary to set the spring pressure of the lifting spring 110 to a sufficiently large value with a sufficient safety factor. Further, the position of the front bearing 109F' when the developing unit is lifted according to the inclination of the swinging shaft of the developing unit with respect to the photosensitive drum shaft is the elongated hole 10.
Sometimes it's close to the top of 9F'', sometimes it's close to the bottom,
Even when the bearing 109F' is near the upper end of the elongated hole 109F" and the lifting spring 110 has little extension, it is necessary to ensure that the spring pressure is sufficient. If the extension is large, the force required to extend the spring 110 will be even greater,
From this point of view, the spring pressure of the lifting spring 110 tends to be large.

Now, in the lifting operation of the developing unit as explained in FIG.
The lifting spring 110 is stretched by the moment of the pushing force, and the photosensitive drum axis and the swinging support shaft become parallel. However, as described above, if the spring pressure of the lifting spring 110 is large, the developing unit is swung accordingly. The moving force also increases, and the load on the lifting mechanism increases.

Specifically, in order to ensure the strength of the rack and gears for driving the slide guide 121, strong materials and large tooth widths are required, leading to increased costs and decreased space efficiency.

Furthermore, in this example, the lifting force for the developing unit is received from the drive system of the movable base 120 on which the developing unit is placed and moves, which also increases the load on the drive motor of the base. Furthermore, when the lifting force is increased, the impact when the abutting rollers 103F and 103R of the developing unit abut against the photosensitive drum 1 increases, causing pitch unevenness and color misregistration, which leads to deterioration of image quality and increased noise.

Therefore, an object of the present invention is to simply give one of the fulcrums of the swinging support shaft some play and to lift it upward with an elastic member.
Three-point support is established when the developing unit is brought into contact with the image carrier, and when the developing unit is driven, a force is applied to the developing unit in the swinging direction around the swinging shaft by the driving means. With this structure, the operation of swinging the developing unit and lifting it toward the image carrier is performed with less load on the lifting mechanism, thereby increasing the durability and reliability of the lifting mechanism. It is an object of the present invention to provide an image forming apparatus that can reduce vibrations during rocking of a developing unit, reduce noise during operation, and eliminate blurring of images and obtain high-quality images.

Another object of the present invention is to achieve a rocking operation that reliably abuts the developing unit against the image carrier with three-point support without using any special mechanism, thereby reducing costs, improving reliability, and downsizing the device. An object of the present invention is to provide an image forming apparatus that enables the following.

The above-mentioned objects are achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image bearing member on which a latent image is formed, and an image bearing member disposed below the image bearing member for making the latent image on the image bearing member visible. and a developing device including at least one developing unit that swings toward and away from the image carrier about a swing shaft and is positioned with respect to the image carrier through an abutting member. In the forming device, one end of the swinging support shaft of the developing unit is supported by the developing device so as to be only rotatable, and the other end of the swinging support shaft is rotatable and supported by an elastic member. The developing unit is supported by the developing device so as to be biased in a direction approaching the image carrier and movable in the vertical direction.Furthermore, when a driving means for driving the developing unit is biased, the developing unit moves in the swinging direction. This image forming apparatus is characterized in that it receives a force that moves toward an image carrier around a support shaft.

Practical 1L Example Next, the image forming apparatus according to the present invention will be explained in more detail with reference to the drawings.

The present invention is suitably embodied in the full-color electrophotographic copying machine previously explained with reference to FIG. explain. The overall configuration of the full-color electrophotographic copying machine has been explained above, so a repeated explanation will be omitted.

Since the present invention is particularly characterized by the developing device, the developing device will be described in detail next with particular reference to the parts that are different from the previously described developing device.

1 to 4 show a developing device lOO in a first embodiment of the present invention. In particular, FIG. 2 shows a movable base 120 for the developing unit, and the same parts as in FIG. 9 representing the conventional example are represented by the same symbols, and only the different parts will be explained here.

As understood from FIG. 2, according to this embodiment, the back support plate 124 supports a drive gear, a clutch, etc., which will be described in detail later, and a motor 125 that drives the developing unit.
The support plate 126 carrying the is also fixed.

3 is a view of the drive system viewed from the direction of arrow D in FIG. 2, that is, the front direction of the rack 131, and FIG. 4 is a top view thereof.

Referring to FIGS. 3 and 4, in this embodiment, the output of the motor 125 is transmitted through its output gear 150 and the drive board 1.
The rotation shaft 154 is rotatably supported by the drive board 124 and the support plate 155, and the drive is transmitted to the clutch gear 153M, which turns ON10 F F the drive transmission to the developing sleeve 102. communicated. Further, the driving force from the clutch gear 153M is transmitted to the drive board 12 via its rotating shaft 154 and output gear 158.
The signal is transmitted to a gear 158 attached to 4. gear 158
meshes with the developing unit drive gear 157 to transmit the drive from the motor. At this time, the shaft 156 of the gear 157 is coaxial with the hole 122' formed in the shaft back support plate 122 which is fastened to the back support plate 124.

Furthermore, when the magenta developing unit IOIM is inserted along the slide guide 121M, the swinging shaft 105R of the developing unit 101 is inserted into the hole 122' of the back support plate 122, as shown in the top view of FIG. By fitting, the developing unit driving gear 157 and the driving gear 10 of the developing sleeve 102
4 and mesh with each other with a predetermined backlash.

In the above configuration, FIG. 1 shows how the force is applied when the developing unit 101 is driven, and best represents the features of the present invention.

FIG. 1 shows the developing unit 101 from the direction of the arrow in FIG.
For the sake of explanation, the drive board 124 and drive system gear clutch are omitted, and the developing unit drive gear 15 is shown.
Only 7 is shown.

The developing unit 101 is moved under the photosensitive drum 1 at the development timing, and at the same time is pushed by the slide guide 121 by the force of Fl, and the center of swing 200 (swing shaft 105 in FIG.
It lifts up while swinging around the center (corresponding to R). At the same time, a developing unit driving gear 157 attached to the driving support plate 122 (FIG. 4) coaxially with the swing center 200 transmits drive to the gear 104 provided in the developing unit to rotate the developing sleeve and perform development. . At this time, the positional relationship between the gear 104 and the swing center 200 is arranged as shown in FIG.
4 and at the same horizontal position as or above the center of the gear 104, and furthermore, the direction of rotation is such that the gear 104 rotates counterclockwise in FIG. is the developing unit drive gear 15
7 applies force F2 as shown.

This F2 acts as a clockwise moment around the pivot center 200 in FIG. 1, that is, the pivot shaft 105R, and helps the slide 121 lift the developing unit 101.

In the present invention, the support shaft on the other end side of the swing center (corresponding to the swing support shaft 105F in FIG. 11) has the same structure as that shown in FIG. 22.

Conventionally, as mentioned above, if the lifting spring of the fulcrum on the play side was strengthened as a prerequisite for reliably lifting the developing unit, the fulcrum on the other end would no longer hit the photosensitive drum, so the main It is difficult to properly lift the developing unit as in the embodiment.

As in the present invention, the fulcrum side (swinging shaft 10
Directly transmitting the rocking force on the 5R side) is effective for reliably lifting the developing unit. When the development is finished, the slide guide 121 and the development unit drive gear 157
Since the developing unit 101 becomes free, the developing unit 101 swings under its own weight and lowers to the standby position.

As described above, by adopting the above-described driving mode according to the present embodiment, the lifting force of the lifting mechanism can be reduced relative to the spring pressure of the lifting spring 110 that is sufficient to ensure that the front side hits the object. Therefore, the load on each part of the lifting mechanism is reduced. At the same time, since the impact when lifting is reduced, image shift and pitch unevenness are reduced, and image quality is improved.

Furthermore, noise and vibration during lifting can be reduced.

Other embodiments of the invention are illustrated in FIGS. 5-7.

According to the second embodiment of the present invention, a special mechanism for driving the swinging motion for lifting the developing unit is not provided, and when the developing unit moves to a position facing below the photosensitive drum during the developing operation, The abutting member on the developing unit side abuts against the photosensitive drum or the abutting member positioned relative to the photosensitive drum, and the swinging fulcrum of the developing unit, which had been urged upward, is pushed up, and the reaction force causes the abutting member to abut against the photosensitive drum or the abutting member positioned relative to the photosensitive drum. On the other swinging fulcrum side, which is configured to obtain a sufficient abutting pressure and is supported only so as to be able to swing, the distance between the abutting members on the developing unit side and the photosensitive drum side is set so small that they do not come into contact with each other during non-development. The two are brought into contact with each other by obtaining a swinging force using only the driving force of the developing unit drive gear.

Hereinafter, only the parts different from the first embodiment will be explained using FIGS. 5 to 7.

FIG. 5 is a diagram of the developing unit in the second embodiment seen from the front side (only one of the four developing units is shown for explanation). According to this embodiment, the mechanism for swinging the developing unit such as the slide rail 121 and the rack 140 as shown in FIGS. 2 and 14 is removed from the structure of the first embodiment, and the mechanism is replaced with With this configuration, a stopper 192 is provided to restrict the swinging of the developing unit 101 and keep the abutting roller 103F at a high position. When horizontally moved in the six directions of arrows, the sixth
As shown in the figure, when it comes to the developing position, the front abutting roller 103
F abuts against the abutting member 191F positioned with respect to the photosensitive drum 1, and the swing support shaft 109F' is pushed down.

FIG. 7 is a view of the developing unit viewed from the rear side, contrary to FIGS. 5 and 6. FIG.

As can be understood from FIG. 7, an abutment member 191R is arranged on the back side as well as on the front side, and when the developing unit is allowed to be driven, the abutment member 191R and the abutment roller 103R are slightly away. Swing center 202
(corresponding to the swing support shaft 105R) and the coaxial drive gear 15
When the developing unit is driven by 7, the developing unit swings against its own weight due to the force F2 received from the drive gear 157, and the abutting roller 103R abuts against the abutting member 191R. At this time, the driving torque of the developing unit drive gear 157 needs to be large enough for its swinging force to support the weight of the developing unit.

If the driving torque of the developing unit is not sufficient to lift the developing unit upward, the developing unit may be provided with a mechanical brake to increase the driving torque.

By employing such a configuration, the developing unit can be reliably abutted against the photosensitive drum 1 and accurately positioned without providing a special mechanism for lifting the developing unit.

Note that the path by which the developing unit 101 moves to the position facing the photosensitive drum 1 is not limited to the horizontal direction, but may be from bottom to top, or may be approached while rotating, and can be configured as desired.

Further, in the description of each of the above embodiments, an example in which the present invention is applied to a full-color copying machine has been described, but it goes without saying that the present invention can also be applied to a multi-color copying machine or a mono-color copying machine. Alternatively, the present invention is applicable to all cases in which a plurality of developing units move between a developing position below the photosensitive drum and another non-developing position.

As explained above, the image forming apparatus according to the present invention has a structure in which one of the fulcrums of the oscillating support shaft is supported by being suspended upward by an elastic member with play. By doing so, the developing unit is brought into contact with the image carrier with three-point support, and a swing support is provided so that a force is applied to the developing unit in the direction of the image carrier when the developing unit is driven. The arrangement of the shaft and drive gear assists the deformation of the elastic member when the developing unit swings, reducing the load on the swinging mechanism, thereby increasing the durability and reliability of the swinging mechanism. In addition, the vibration during rocking of the developing unit is reduced, which in turn reduces image blurring, improving image quality and reducing noise during operation.

Further, according to the image forming apparatus of the present invention, when the developing unit moves to a position facing the image carrier, the abutting roller on the swinging shaft side suspended by the spring comes into contact with the abutting member. On the swinging support shaft side that can only swing, the abutment roller is configured to abut the abutment member only by the force received from the development unit drive gear, so the three-point support ensures reliable abutment. This can be done without providing a mechanism for rocking motion, making it possible to reduce costs, improve reliability, and downsize the device.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a manner in which a developing unit is lifted up in an image forming apparatus according to the present invention. FIG. 2 is a perspective view showing the configuration of a movable base of the developing device. FIG. 3 is a diagram showing the drive system of the developing device, viewed from the direction of the arrow in FIG. 1. FIG. 4 is a top view of FIG. 3. FIGS. 5 and 6 are diagrams illustrating how to lift up a developing device according to another embodiment. FIG. 7 is a view from the opposite side of FIG. 6. FIG. 8 is a schematic configuration diagram of an embodiment of an image forming apparatus that can embody the present invention. FIG. 9 is a perspective view of a movable base of a conventional developing device. FIG. 10 is a view seen from the direction of arrow B in FIG. FIG. 11 is a perspective view of the developing unit. FIG. 12 is a partial perspective view of the toner conveying pipe of the toner replenishing device. FIG. 13 is a perspective view of the toner supply device. FIG. 14 is a perspective view illustrating the developing unit lifting mechanism. FIG. 15 is a side view of the developing unit lifting mechanism. FIG. 16 is a diagram showing the relationship between the developing unit and the photosensitive drum. FIG. 17 is a side view illustrating the developing unit lifting mechanism. FIGS. 18 and 19 are diagrams illustrating an example of a mechanism for lifting a developing unit in a conventional image forming apparatus. FIGS. 20 and 21 are diagrams illustrating other examples of a lifting mechanism for a developing unit in a conventional image forming apparatus. FIG. 22 is a diagram illustrating still another example of a lifting mechanism for a developing unit in a conventional image forming apparatus. FIG. 23 is a schematic configuration diagram of a conventional image forming apparatus. 1: Image carrier 100: Developing device 101: Developing unit 103: Abutting roller 104.157: Developing unit drive gear 201.202
: Swing center 140 Figure 4 Figure 5 Figure 10 Figure 106a Figure 13 Figure 18 Figure 19 Figure 20 Figure 21

Claims (1)

[Claims] 1) An image carrier on which a latent image is formed, and a rocking support disposed below the image carrier to visualize the latent image on the image carrier. an image forming apparatus comprising at least one developing unit that swings toward and away from an axis and is positioned with respect to the image carrier through an abutting member; One end of the swinging shaft of the developing unit is supported by the developing device so as to be only rotatable, and the other end of the swinging shaft is rotatable and is brought close to the image carrier by an elastic member. The developing unit is supported by the developing device so as to be biased in the direction and movable in the vertical direction.Furthermore, when the driving means for driving the developing unit is biased, the developing unit rotates the image about the pivot shaft. An image forming apparatus that receives a force that moves toward a carrier.