JPH0754410B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus, and in particular, multicolor image formation for obtaining multicolor images such as multicolor or full color. It can be suitably embodied in a device.

2. Description of the Related Art Currently, various multicolor image forming apparatuses have been proposed. For example, a typical example of an electrophotographic color copying machine is No. 15
As shown in the figure.

This copying machine is provided with a transfer drum 5 which holds a transfer sheet P by a gripper 5a or the like on its peripheral surface, a photosensitive drum 1 and a plurality of developing units 101Y, 101M, 101C, 101B above the transfer drum 5.
And a toner supply device 200 for storing toner and supplying toner to the developing units 101Y, 101M, 101C, 101B.

The photosensitive drum 1 and the rotary developing device 100 arranged above the transfer drum 5 are all scattering sources of toner,
Further, carriers (magnetic particles) in the used two-component developer are also scattered. Therefore, the transfer drum 5 existing below
These scattered toners and carriers are easily deposited on the surface of the.

The toner deposited on the surface of the transfer drum 5 causes the backside of the transfer paper P to be soiled, and weakens the electrostatic attraction between the transfer sheet 5b wound around the transfer drum 5 and the transfer paper P.
This results in poor image quality and jams (paper jams)
And also causes various adverse effects such as shortening of the life of the fixing roller.

Therefore, a large-scale device is required to collect and collect the toner and carrier accumulated on the surface of the transfer drum 5 to keep the surface of the transfer drum clean, and these devices become a noise source, and the device price is low. It was hindering low prices.

Further, since the rotary developing device is configured by housing a plurality of developing units in the rotating body, it is inevitable to increase the size of the entire copying machine.

In order to solve the above problem, as shown in FIG.
The reciprocating developing device 100 having the developing units 101M to 101B mounted on a moving base 120 (see FIG. 3) is used, and the developing device 100 is moved in a tangential direction with respect to the photosensitive drum 1. An image forming apparatus has been proposed which is configured to visualize the above latent image.

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 swingable around a rotation fulcrum disposed on the moving base 120, and at the time of developing operation, the developing unit is Was urged in a direction to approach the surface of the photosensitive drum by driving a driving gear from a driving source provided on the moving base.

However, the image forming apparatus using such a reciprocating type developing device has the following problems.

That is, as described above, in the developing device of this image forming apparatus, each developing unit is formed in the developing unit while the moving base 120 is driven by the driving force of the driving source such as the stepping motor. The structure is such that when the foot is pressed, it is lifted toward the photosensitive drum 1. Therefore, the home position of the developing device must be located at the position of the magenta developing unit 101M in FIG. 2, that is, to the left by the run-up distance (L) for lifting from just below the photosensitive drum 1.

If the approach distance L is set to be as large as possible in comparison with the lifting amount, the accuracy of the components forming the lifting mechanism and the stopping accuracy of the stepping motor have less influence on the lifting amount, and accurate lifting movement can be achieved. Further, as shown in the figure, if the run-up distance L of the developing unit is made equal to the distance between the developing units, there is an advantage that the same gear common to the developing units can be used as a gear in the lifting mechanism.

However, since the developing device as a whole is moved to the left side in order to lift the developing unit in this way, the stroke of the lateral movement of the developing device becomes large, which leads to an increase in the size of the entire image forming apparatus.

Further, since each developing unit partially projects outward from the front and rear side plates that form the framework of the image forming apparatus, it is possible to move each developing unit when the moving stroke of the developing apparatus becomes large. Therefore, the holes formed in the front and rear side plates inevitably become large, and this also reduces the strength of the image forming apparatus, which is not preferable. Further, when the moving stroke of the developing device becomes large, the swinging stroke of the replenishing pipe of the toner replenishing device (which will be described later in detail) that engages with the developing unit and swings in conjunction with the movement of the developing device also becomes large. As a result, the length of the supply pipe becomes long, the weight thereof increases, and it is feared that the smooth swinging motion is hindered.

Therefore, an object of the present invention is to reduce the lateral movement stroke of the developing device, thereby minimizing the holes formed in the frame body such as the side plate of the image forming apparatus, improving the strength of the entire apparatus, and extending it. Is to provide an image forming apparatus capable of preventing deterioration of image quality such as image blurring due to insufficient strength.

Another object of the present invention is to provide an image forming apparatus capable of reducing the size of the developing apparatus by eliminating the need to move the developing apparatus to the left by the approach distance required to lift each developing unit.

Means for Solving the Problems The above-described objects are achieved by the image forming apparatus according to the present invention. In summary, the present invention comprises an image carrier on which a latent image is formed, and a developing device for developing the latent image on the image carrier, wherein the developing device is the image carrier. At least two developing units installed close to the surface of the image carrier, and carrying the developing units, and moving the developing units toward the surface of the image carrier in a direction substantially tangential to the surface of the image carrier in the developing operation area. The developing device includes a moving base and positioning means for positioning the developing unit at a predetermined gap with respect to the image carrier when the developing unit is moved to the developing operation position by the base. The home position is set so that the first developing unit is located on one side from directly below the image carrier and the second developing unit is located on the other side from directly below the image carrier. Image forming apparatus characterized by It is.

Embodiment Next, the image forming apparatus according to the present invention will be described 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.

The image carrier, that is, the photosensitive drum 1 having the electrophotographic photosensitive layer on its surface in the present embodiment is rotationally driven in the direction of arrow x. A primary charger 2 is provided on the left side of the photosensitive drum 1, a surface electrometer 3 for measuring the potential of the surface of the photosensitive drum 1 is provided obliquely below the photosensitive drum 1, and a plurality of developing units are provided just below the photosensitive drum 1. Then, the developing units 101M, 101C, 101Y,
A developing device 100 that stacks 101B and moves to the left and right, a transfer device 5 diagonally above the photosensitive drum 1, and a drum of toner remaining on the surface of the photosensitive drum 1 after transfer approximately directly above the photosensitive drum 1. A front static eliminator 6 for reducing the adhesive force of the photosensitive drum 1 to facilitate cleaning, and a cleaning device 7 are disposed diagonally above and to the left of the photosensitive drum 1.

An optical system 10 is arranged above the copying machine, and an original image on the platen 8 is transferred onto the photosensitive drum 1 by an exposure unit 9 located between the primary charger 2 and the surface electrometer 3. Configured to project. The optical system 10 may use any optical system, but in the present embodiment, the first scanning mirror 11 and the second and third scanning mirrors 12 that move in the same direction at half the speed of the first scanning mirror 11. And 13, the imaging lens 14, and B, G,
It is composed of a CCD 15 integrated with an R filter, a laser scanner unit 16, and fixed mirrors 17 and 18. Here, the scanner unit 16 is a well-known device that deflects laser light with a rotary polygon mirror, and detailed description thereof will be omitted.

Further, in the optical system 10, the document illumination light source 20 is configured to move together with the first scanning mirror 11. Therefore, the reflected light image of the document scanned by the first to third scanning mirrors 11, 12 and 13 passes through the lens 14 and is color-separated by the CCD 15 having the BGR4 color separation filter to be converted into an electric signal. This document information signal is subjected to information processing such as A / D conversion and then sent as a video signal to a microprocessor unit (hereinafter referred to as MPU) which controls the entire copying machine. Based on this signal, the MPU oscillates laser light from the laser unit via the laser driver, and this laser light irradiates the photosensitive drum 1.
Start the copy sequence while turning on / off.

Further, in this embodiment, the fixing device 20 and the paper feeding device 30 are arranged on the right side of the copying machine, and the transfer drum 5 and the fixing device are arranged.
Transfer paper conveying systems 25 and 35 are respectively arranged between the paper feeding device 20 and the paper feeding device 30.

In the above configuration, the steps of charging, exposing, developing, transferring, and cleaning are performed on the photosensitive drum 1 for each color separated by the CCD 15, the primary charger 2, the optical system 10, the developing device 4, the transfer device 5, and the cleaning device. Given by 7.

The developing device 100 will be described in more detail later, but the moving table 120
(Fig. 3) Developing unit 101M removably held
(Magenta developing unit), 101C (cyan developing unit), 101Y (yellow developing unit) and 101B (black developing unit) are provided, and the latent images of each color separated are visualized by the corresponding developing units.

The transfer device 5 typically includes a transfer drum 5b having a gripper 5a for holding a transfer material, that is, the transfer paper P on the peripheral surface. The transfer device 5 grips the front end of the transfer paper P fed from the transfer paper cassette 31 or 32 of the paper supply device 30 through the transfer paper transport system 35 with the gripper 5a, and develops a visible image for each color on the photosensitive drum 1. It is rotatably transferred to transfer. Transfer charger 5c in the transfer area
Are arranged inside the transfer drum 5.

The transfer paper P on which the visible images of the respective colors, that is, the toner images are sequentially transferred, is released from the gripper 5a and separated from the transfer drum 5b by the separating charger 8 and the separating 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 on the transfer paper by the fixing device 20, and then the transfer paper is discharged onto the tray 23.

Next, the developing device 100 according to the present invention will be described.

The developing device 100 is configured to be movable in the left-right direction as described above, but it is necessary that each developing unit is disposed immediately below the photosensitive drum 1 and in proximity to the photosensitive drum 1 with a predetermined gap. On the other hand, it is desirable that the developing unit is held immediately below the photosensitive drum, that is, at a position retracted from the photosensitive drum 1 except when in the developing operation position.

The reason is that when each developing unit is moved close to the photosensitive drum 1, even when the developing unit returns to the original position (home position) after the development of all four colors is completed, This is because the toner passes through a position close to 1, so that the toner standing on the developing sleeve in each developing unit contacts the photosensitive drum and unnecessary toner adheres to the photosensitive drum.

If unnecessary toner adheres to the photosensitive drum, the toner adhered to such a photosensitive drum is entirely or not because the transfer paper is not interposed between the photosensitive drum 1 and the transfer drum 5b during non-development. Part of it flies to the transfer drum 5b,
This results in contamination of the transfer drum 5b.

Further, in the vicinity of the developing operation position of the photosensitive drum 1, it is necessary to dispose a surface potential meter 3 and a partition plate for preventing foreign matters such as paper dust from dropping onto the developing sleeve of each developing unit from above. . In order to maintain a predetermined distance between each of these members and the developing sleeve and prevent the two from approaching each other, it is necessary that each developing unit is at a position retracted from the photosensitive drum 1 except during the developing operation.

That is, in the laterally moving developing device 100 configured according to the present invention, each developing unit is brought close to the photosensitive drum 1 only during development (when the developing unit is right below the drum), and retracted from the photosensitive drum 1 during other non-developing periods. It is configured so as to be located at the set position.

Next, referring to FIGS. 1 and 3 to 14, the developing device 10
0 will be described in more detail.

In this embodiment, the developing unit 101 (101M, 101C, 101
Y, 101B) have the same structure, and only the colors of the developers replenished inside are different.

Referring to FIG. 5, the developing unit in this embodiment has an elongated developing container 106 having a substantially horizontal cross section, and the developing container 106 has a magnet (not shown) inside.
A developing sleeve 102 containing therein is rotatably supported.
Abutting rollers 103 for securing a predetermined gap with the photosensitive drum 1 are provided on both end shaft portions of the developing sleeve 102. A drive gear 104 of the developing sleeve 102 is fixed to one shaft end of the developing sleeve 102, and the driving force of a motor 125 (FIG. 10) is transmitted to the developing sleeve 102 by a drive system described later.

Further, the magnet in the developing sleeve 102 is positioned and adjusted to an appropriate position in the developing sleeve 102 by a positioning plate 190 arranged on the other end shaft portion of the developing sleeve.

At both ends of the developing container 106, support shafts 105F and 105R for mounting and positioning the developing unit 101 on a moving base 120 (FIG. 3) described later are provided on the same axis line parallel to the axis line of the developing sleeve 102. It is provided.

Further, in the developing container 106, screws (only the shaft portion is shown) 107 and 108 for stirring and conveying the developer contained therein are provided, and the screws 107 and 108 are geared by a drive gear 104 of the developing sleeve 102. Driven via a column (not shown). Also, one screw, screw 10 in this example.
The end of 7 projects from the developing container 106 to the front side and is internally passed through a conveying pipe 106a connected to a toner replenishing device described later. A toner replenishing device 200 is provided above the transport pipe 106a.
A replenishment port 106a 'for connecting with is formed in the shape of an elongated hole.

That is, as can be seen in FIG.
The supply port 106a 'of the toner supply device 200 is engaged with the supply port 241a of the shutter 241 of the supply pipe 202 of the toner supply device 200. Therefore, when the developing unit 101 moves, the replenishment port 241a follows the lateral movement of the developing unit 101 and the replenishment port 241a
As a result of being guided by a ', the replenishment pipe 202 swings to enable constant replenishment of toner.

An example of such a toner supply device 200 is shown in FIG.

FIG. 7 is a perspective view showing a simplified general view of the toner replenishing device 200 by omitting a detailed portion thereof. The toner replenishing device 200 has containers 201M, 201C, 201Y, and 201B that store developers of respective colors of magenta, cyan, yellow, and black, and supplies toner to the developing units 101M, 101C, 101Y, and 101B from the respective containers. Replenishment pipe 202M-B with a built-in screw for
Is swingably connected to the toner containers 201M-B. As described above, the replenishing port 241a of the shutter 241 of the replenishing pipe 202 is configured to engage with a part of the developing unit, that is, the replenishing port 106a 'to supply the toner to the developing container 106. .

The toner container of the toner replenishing device 200, the replenishing pipe, and other parts constituting the replenishing device are attached to the replenishing support plate 203. Further, the replenishment support plate 203 is supported by a support base 204 fixedly attached to a front side plate (not shown) of the copying machine, while supporting shafts 205a, 205 are provided.
It is rotatably supported by and. During the copying operation, the supply support plate 203 is rotated toward the front side plate, and the end opposite to the rotation fulcrum is fixed to the front side plate with screws or the like.

Returning to the developing device 100 again, the developing container 1 will be described.
Guide feet 106b, 106c (Figs. 5, 11, 11
12 (see FIG. 12) is formed so as to be slidably engaged with a slide guide 121 attached to a moving base 120 described later.

FIG. 3 is a perspective view of the entire developing device 100 as seen from the front of the copying machine, from the upper left. In this figure, each development unit
101 is omitted.

The developing device 100 has a moving base 120 on which the developing units 101 are loaded and moved, and the developing unit 10 is mounted on the base 120.
A slide guide 121 (121M, 121C, 121Y, 121B) that engages with and holds one guide leg 106b, 106c is attached by a step screw (not shown) so as to be slidable in the arrow A direction.

Further, the base 120 is provided with a back side support plate 122 and a front side support plate 123 corresponding to each slide guide 121. Back support plate 122
Has a hole 122 'that fits with the rotation support shaft 105R of the developing unit 101, and the front support plate 123 has a hole 123' that fits with the rotation support shaft 105F of the development unit 101. The front support plate 123 is configured such that the developing unit 101 is inserted along the slide guide 121, the rotation support shaft 105R is fitted into the hole 122 ′ of the back support plate 122, and then the rotation support shaft 105F and the front support plate 123. The holes 123 ′ of 123 are fitted and then screwed to the base 120.

Here, the back side support plate 12 provided for each developing unit of each color
2 and the holes 122 'and 123' of the front support plate 123 are adjusted by using a jig or the like at the time of assembly so as to share the same axis parallel to the axis of the photosensitive drum 1.

In the present embodiment, the rear support plate 122 is screwed to a drive board 124 that supports a drive gear, a clutch, etc., which will be described later, and the drive board 124 is screwed to the base 120. In addition, D on the base 120
The support plate 126 that supports the C motor 125 is screwed.

As can be understood by also referring to FIG. 4, the movable base 120 includes a rail 127 at the rear end of the base 120,
The rail 127 is slidably engaged with a rail abutment 128 mounted on the rear side plate 50 fixed to the bottom plate 60 of the copying machine. On the other hand, a roller 129 having a bearing built therein is rotatably supported at the front end of the base 120 via a support plate 130. The roller 129 can roll on the bottom plate 60.

With this configuration, the moving base 120 can be moved with respect to the bottom plate 60 and the rear side plate 50.

The moving base 120 is driven by the driving force of a stepping motor 132 attached to the bottom plate 60 by an appropriate supporting means (not shown), and a gear 133 also provided on the same supporting means. Base 120 via gear train consisting of 134, 135
It is achieved by transmitting to the rack 131 fixed to the.

According to the present invention, the developing device 100 is moved by the base 120 toward the photosensitive drum 1 in a direction substantially tangential to the photosensitive drum, and the developing device 100 is moved relative to the photosensitive drum at the developing operation position, that is, substantially directly below the photosensitive drum. Positioned with a predetermined gap.

FIG. 1 shows each developing unit constructed according to the present invention.
FIG. 6 is a perspective view showing a developing unit lifting mechanism for positioning the developing unit 101 by lifting it toward the photosensitive drum 1 at the developing operation position. In this figure, in order to facilitate understanding of the arrangement of internal parts, the movable base 120 and the slide guides 121M and 121C for the developing units 101M and 101C are indicated by chain double-dashed lines, and the slide guides 121Y for other developing units are shown. , 121B have been omitted.

Short rack teeth 140C are fixed to the back side of the slide guide 121C.
The slide guides 121Y and 121B of 01Y and 101B are also provided. Further, long rack teeth 141 are fixed to the back side of the base 120.

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

In addition, the rotation shaft 142 has a rack on the back surface of the slide guide 121.
A gear 145 is provided at a position where it meshes with 140C. Here, the number of teeth Z144 of the clutch gear 144 is set smaller than the number of teeth Z145 of the gear 145. The reason for this will be described in detail later.

A ring 146 is fixed to the rotary shaft 142 adjacent to the gear 145, and a coil spring 147 is inserted between the gear 145 and the ring 146. One end of the coil spring 147 has a ring 146.
, And the other end is hooked in a hole 145a formed in the side surface of the gear 145, as shown in FIG. The parallel pin groove 145b is fan-shaped in the gear 145, and the gear 145 is biased by the coil spring 147 in the arrow direction, and one end of the fan-shaped groove is in contact with the parallel pin.

Further, according to the present invention, rack teeth 170 are fixedly provided on the back side of the slide guide 121M of the magenta color developing unit 101M. A gear 171 is provided on the rotary shaft 142 so as to mesh with the rack teeth 170. Like the gear 145, the gear 171 is biased in the same direction as the gear 145 by a coil spring (not shown) so that one end of a fan-shaped groove provided inside the gear 171 abuts on the parallel pin. It is rotatable integrally with the rotary shaft 142.

Next, the drive system from the DC motor 125 to the developing sleeve 102 will be described with reference to FIGS. 9 and 10. 9 is a view of the drive system viewed from the direction of arrow D in FIG. 3, that is, the front direction of the rack 131, and FIG. 10 is a plan view thereof.

The output of the DC motor 125 is the output gear 150 and the drive board 12
4 is transmitted to the idler gear 152 provided on the drive shaft 124, and further, the rotation shaft 154 is rotatably carried by the drive substrate 124 and the support plate 155, and transmitted to the clutch gear 153M that turns ON / OFF the drive transmission to the developing sleeve 102. To be done. Further, the driving force from the clutch gear 153M is transmitted to the gear 157 mounted on the drive board 124 via the rotation shaft 154 and the output gear 158.

On the other hand, as will be better understood by referring to FIGS. 3 and 5 together, for example, a magenta color developing unit 10
When 1M is inserted along the slide guide 121M, the developer container
By fitting the rotary support plate 105R on the rear side of 106 into the hole 122 'of the rear support plate 122, as shown in FIG.
7 and the drive gear 104 of the developing sleeve 102 mesh with each other.

A drive train including clutch gears 153C, 153Y, and 153B is provided for each of the other developing units 101C, 101Y, and 101B, and each drive train is a relay gear 159 provided on the drive board 124. And the driving force is transmitted from the DC motor 125.

Further, when each developing unit 101 is inserted into the slide guide 121, a contact portion (not shown) provided on the base 120 for applying a high voltage to the developing sleeve 102 is also provided in the developing unit 101. The contact point (not shown) provided is electrically conducted and a high voltage is applied to the developing sleeve 102 at the time of development. However, since such a configuration is well known to those skilled in the art, a more detailed description will be given. The description is omitted.

With the above configuration, when the power of the copier body is turned on, the base
As shown in FIG. 3, a sensor 181 including a light emitting element and a light receiving element fixedly provided on the bottom plate 60 and whether the 120 is in the home position or not can be adjusted on the base 120. When the base 120 is not in the home position, the stepping motor 132 rotates and the light of the sensor 181 is blocked by the light shield 180, that is, until the home position is reached. To move.

According to the present invention, as shown in FIGS. 11 and 12, the home position of the moving base 120 is the photosensitive drum 1.
The magenta developing unit 101M is set to a right side as viewed from this side, and is separated by l ₂ from directly below. In Figure 12, l
Reference numeral ₂ indicates a position from the rotary support shaft 105F when the developing sleeve 102 is right under the photosensitive drum 1 to the position of the rotary support shaft 105F in the home position. At the home position, the rack 141 and the clutch gear 144 are engaged with each other.

That is, at the home position, the photosensitive drum 1 moves to the 11th position.
As shown in the figure, it is located between the magenta developing unit 101M and the cyan developing unit 101C, and the home position is set by adjusting the light shielding plate 180.

Next, when the copy button is operated to start the copy operation, the microprocessor unit (MPU) that controls the operation of the copying machine body causes the pulse generator of the stepping motor 132 that drives the base 120 to the magenta developing unit 101M. A signal is sent to move the base 120 at a predetermined speed until the developing sleeve 102 is directly below the photosensitive drum 1.

With the movement of the base 120, the magenta developing unit 101M is lifted upward and approaches the photosensitive drum 1. This lifting operation will be described in detail below with reference to FIGS. 2, 11, and 12.

As described above, at the home position, the rack 141 and the clutch gear 144 are in a meshed state. When the image forming operation, that is, the copy operation is started, the base 120 moves to the left. Further, since the clutch of the clutch gear 144 is turned on prior to this, the rotary shaft 142, the gear 145, and the gear 171 also rotate with the movement of the moving base 120.

When the moving base 120 moves, first, the rack 170 fixed to the bottom of the slide guide 121M of the magenta color developing unit 101M meshes with the rotating gear 171. Here, since the number of teeth Z171 of the gear 171 is set to be smaller than the number of teeth Z144 of the clutch gear 144, as will be understood with reference to FIG. 12, for example, the position where the rack 170 starts to engage with the gear 171 is ₃
Assuming that (l ₃ <l ₂ ), when the moving base 120 moves a distance l ₃ , the clutch gear 144 rotates so that it also moves by l ₃ as measured on the pitch circumference.

When this is converted into the rotation angle α of the rotation shaft 142, α = l ₃ / r144 (rad). r144 is the pitch circle radius of the clutch gear 144.

Therefore, the rotation length of the gear 171 on the pitch circumference, that is, the slide guide 121M integrated with the rack 170 that meshes with the gear 171.
The moving distance l _{4 of} is l ₄ = α × r171 = l ₃ × (r171 / r144). r171 is the pitch circle radius of the gear 171.

Here, since Z171 <Z144, that is, r171 <r144, l ₄
<L ₃ .

Slide guide 121 while that is the movable base 120 l ₃ moves
M moves relative to the moving base 120 by a length of (l ₃ −l ₄ ) in the direction opposite to the moving direction of the moving base 120. Therefore,
As shown in FIG. 12, the slide guide 121M moves the moving base 12
The foot 106b of the developing unit 101M which is rotatable on the fulcrum 105F (105R) as the fulcrum is pressed in the direction of arrow A. As a result, the sleeve 10 of the magenta color developing unit 101M
The reference numeral 2 is lifted in the direction of arrow B during the movement of the moving base 120, and stands still below the photosensitive drum 1 at a position close to the photosensitive drum 1 via the abutting roller 103.

At the time of this lifting, since the foot 106c of the developing container 106 moves so as to come off the slide guide 121M as shown in the drawing,
12 As shown in the figure, the foot 106c
A notch 121M 'and the like are formed in a portion corresponding to.

Further, since the abutting roller 103 needs to be pressed against the photosensitive drum 1 with a predetermined force, when the distance between the abutting roller 103 and the photosensitive drum surface at the home position is d, the developing unit 101M is lifted in the B direction. The amount needs to be d + α (α: positive number), and therefore, the number of teeth of the gear 171 is appropriately determined in relation to the moving distance in order to achieve such a lifting amount.

On the other hand, when the developing unit 101M is directly below the photosensitive drum 1 and is in close proximity via the abutting roller 103, the developing unit 101M receives a reaction force from the photosensitive drum 1 by an amount corresponding to the distance α, and
The self-weight of the developing unit is added to this and pushed back. This force causes the developing unit 101M to rotate its fulcrum 105F,
Since it is rotated clockwise around 105R, the slide guide 121M is pushed to the left (the opposite direction of arrow A) by the foot 106b of the developing container, and the rack 170 engaged with the slide guide 121M is geared. Try to rotate 171 counterclockwise. As described above, the gear 171 is biased in the direction of arrow D (FIG. 8) by the coil spring 147, but until the reaction force from the photosensitive drum 1 and the movement of the developing unit balance with the biasing force of this coil spring, While rotating, the gear 171 is rotated between the fan-shaped parallel pin grooves 145b.

At this time, the coil spring 147 reacts with the reaction force from the photosensitive drum 1, in other words, the abutting members 71, 72 of the abutting roller 103 (first
The wire diameter and the number of windings are appropriately determined so that the pressing force against (to be described later with reference to FIG. 4) has a desired value. The rotating shaft 142 is connected to the stepping motor 132 via the clutch gear 144, the rack 141, and the rack 131, and the self-holding force of the stepping motor 132 acts on the rotating shaft 142. Accurate movement of the base is achieved without being affected by the rotation of the gear 171 described above.

As described above, when the developing unit 101M is lifted, the abutting roller 103 is pressed against the abutting members 71 and 72 corresponding to the surface of the photosensitive drum 1 with a predetermined force as shown in FIG. The sleeve 102 comes close to the photosensitive drum 1 with a required gap.

Here, FIG. 14 is a simplified diagram showing the main body of the copying machine in a transverse section, in which the abutting member 72 is fixed to the main body rear side plate 50, and the abutting member 71 is detachable from the front side plate 73. It is fixedly provided on the centering member 70 of the photosensitive drum 1. From this state, the clutch gear 153M shown in FIG. 10 is turned on at a predetermined timing, so that the developing sleeve 102 is driven by the DC motor 125 via the drive system shown in FIG. 10 to visualize the latent image on the photosensitive drum 1. To do.

Further, as described with reference to FIG. 10, even if the developing unit 101M is rotated about its rotation fulcrums 105F and 105R and lifted, the gear 157 that transmits the drive to the sleeve gear 104 is a fulcrum of fulcrum.
Since it is coaxial with 105F and 105R, it can always be driven by the motor during the lifting operation. Therefore, according to this embodiment, there is an advantage that the timing for rotationally driving the developing sleeve 102 can be freely set regardless of the lifting operation position.

When the magenta color developing process is completed as described above, the clutch gear 144 (Fig. 1) and the clutch gear 153M (Fig. 10) are turned off. As a result, the rotation shaft 142 becomes free of rotation, and the gear 171 integrated with the rotation shaft 142 also becomes free of rotation. Therefore, the reaction force from the photosensitive drum 1 and the developing unit
The slide guide 121 is pushed back to the left by the foot 106b of the developing container 106 due to the weight of the developing unit 101M.
Returns to the lowered position as shown on the right side of FIG. 12 and moves away from the photosensitive drum 1.

As described above, when the magenta developing unit 101M returns to the lowered position and separates from the photosensitive drum 1, the moving base 120
Starts moving rightward, and the cyan developing unit and the developing units of other colors are sequentially lifted in association with the movement of the moving base. Such an operation is similar to the conventional one, and will be briefly described below.

In FIG. 1, short rack teeth 140C are fixed to the back side of the slide guide 121C, and similarly, such rack teeth 140 are also provided on the slide guides 121Y and 121B of each developing unit.

In addition, the rotation shaft 142 has a rack on the back surface of the slide guide 121.
A gear 145 is provided at a position where it meshes with 140C. Here, the number of teeth Z144 of the clutch gear 144 is set smaller than the number of teeth Z145 of the gear 145 for the same reason as described in relation to the magenta developing unit 101M.

A ring 146 is fixed to the rotary shaft 142 adjacent to the gear 145, and a coil spring 147 is inserted between the gear 145 and the ring 146, and has the configuration and function described above with reference to FIG. ing.

Referring to FIG. 13, the cyan developing unit 101C is located right below the photosensitive drum 1 to the left as viewed from the front side (l is the position of the rotary support shaft 105F when the developing sleeve 102 is located directly below the photosensitive drum 1). To the position of the rotation support shaft 105F)).

In FIG. 1, the rack 141 and the clutch gear 14 of the base 120 are shown.
4 is in a meshed state, and the clutch of the clutch gear 144 is turned on immediately before the base 120 starts its movement, so that the rotating shaft 142 and the gear 145 rotate with the movement of the base. Then, 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.

The number of teeth Z144 of the clutch gear 144 is equal to that of the gear 145 as described above.
Since the number of teeth is less than Z145, for example
Let l ₁ (l ₁ <l, the state shown in FIG. 13) start to engage with each other. When the base 120 moves by l ₁ , the clutch gear 144 also rotates by l ₁ on the pitch circumference. When this is converted into the rotation angle of the rotation shaft 142, α = l ₁ / r144 (rad) (r144 is the pitch circle radius of the clutch gear 144).

Therefore, the rotation length of the gear 145 on the pitch circumference, that is,
Slide guide integrated with rack 140 that meshes with gear 145 12
The moving distance l _{2 of} 1C is l ₂ = α × r145 = l ₁ × (r145 / r144) (r145 is the pitch circle radius of the gear 145).

Here, since Z145> Z144, that is, r145 <r144, l ₂
> L ₁ . That is, the slide guide 121C slides relative to the base 120 by a length of (l ₂ −l ₁ ) while the base 120 moves by l ₁ . By moving the slide guide 121C by (l ₂ -l ₁ ) with respect to the base 120, as shown in FIG.
121C pushes the foot 106b of the developing unit 101C, which is rotatable on the base 120 with the fulcrums 105F and 105R as pivotal fulcrums, in the direction of arrow A.

As a result, the cyan developing unit 101C is lifted in the direction of the arrow B during the movement of the base 120 and stands still at a position immediately below the photosensitive drum 1 and close to the photosensitive drum 1 via the abutting roller 103. The manner of lifting the developing unit and the like are the same as those related to the magenta developing unit 10M, and thus detailed description thereof will be omitted.

As described above, when the developing unit 101C is lifted, the abutting roller 103 is pressed against the abutting members 71 and 72 corresponding to the surface of the photosensitive drum 1 with a predetermined force as shown in FIG. The sleeve 102 comes close to the photosensitive drum 1 with a required gap.

In this way, the cyan developing unit 101C is lifted just below the photosensitive drum, and the clutch gear 153 (FIG. 10).
Is turned on and the cyan developing sleeve 102C is rotated to perform cyan developing.

Thereafter, in the same manner, when the development for yellow color and black color and the overlapping transfer onto one transfer sheet of each color image are finished, the transfer sheet is separated from the transfer drum 5 by the separation charger 8 and the separation claw 8 '. Then, the image is fixed by the fixing device 20 and the paper output tray 23
And the copy operation ends.

As can be understood from the above description, according to the present invention, the photosensitive drum 1 is positioned between the magenta developing unit 101M for the first developing and the cyan developing unit 101C for the second developing. Since the home position is set,
When the apparatus main body is stopped, the developing sleeve 102 and the abutting roller 103 are not located directly below the photosensitive drum.

For this reason, when the photosensitive drum or the developing unit is attached or detached by maintenance or the like, there is an advantage that the photosensitive drum and the developing sleeve arranged close to each other are not damaged by the attaching and detaching operation.

Further, according to the present invention, since the home position is set between the magenta developing unit for the first developing and the cyan developing unit for the second developing, the developing units are arranged in the order of magenta, cyan, yellow and black as in the conventional example. The development unit can be replaced in the same time as the replacement, that is, it is not necessary to move the development unit every other or every two units for replacement. This point is not inferior to the conventional device.

Further, in the present embodiment, the abutting roller 103 of the developing unit 101 is configured to directly contact the photosensitive drum, but a member corresponding to the surface of the photosensitive drum is fixedly provided on the main body, and the abutting roller abuts against this. It is also possible to secure a gap between the developing sleeve and the photosensitive drum.

In the above embodiment, a full-color electrophotographic copying machine was described as an example, but it goes without saying that the present invention can also be applied to a mono-color copying machine having two or more developing units.

Further, in the present embodiment, the holding force of the stepping motor is used to hold the state in which the developing unit is positioned with respect to the photosensitive drum, that is, the lifted state. For this purpose, the arm rotatably fixed to the main body can be engaged with the movable base at a predetermined timing by a drive source such as a solenoid.

EFFECTS OF THE INVENTION As described above, according to the image forming apparatus of the present invention, the stroke of the lateral movement of the developing device can be made smaller than that of the conventional device, so that the developing device can be moved. The holes formed in the front and rear side bodies of the image forming apparatus are reduced, the strength of the entire image forming apparatus is improved, and it is possible to prevent deterioration of image quality such as image blur due to insufficient strength.

Further, since it is not necessary to move the developing device to the left side by the approaching distance required for lifting the developing device, which is seen in the conventional device, the device can be downsized.

[Brief description of drawings]

FIG. 1 is a perspective view of a developing unit lifting mechanism according to the present invention. FIG. 2 is a sectional view of a color electrophotographic copying machine showing an embodiment of the image forming apparatus according to the present invention. FIG. 3 is a perspective view of the developing device constructed according to the present invention, and the developing units are omitted. FIG. 4 is a front view seen from the direction of arrow B in FIG. FIG. 5 is a perspective view of the developing unit. FIG. 6 is a perspective view showing a connecting structure of the developing unit and the toner replenishing device. FIG. 7 is a perspective view of the toner supply device. FIG. 8 is a front view showing the driving means of the developing unit lifting mechanism. FIG. 9 is a front view showing the drive system of the developing sleeve.
It is the figure seen from the arrow D direction of a figure. FIG. 10 is a plan view of the drive system for the developing sleeve. 11 and 12 are schematic front views of the developing device for explaining the operation of the magenta developing unit lifting mechanism. FIG. 13 is a schematic front view of the developing device for explaining the operation of the cyan developing unit lifting mechanism. FIG. 14 is a schematic cross-sectional view showing the positional relationship between the photosensitive drum and the developing sleeve. FIG. 15 is a sectional view of a conventional electrophotographic copying machine. 1: image carrier 5: transfer device 100: developing device 101: developing unit 102: developing sleeve 120: moving base 121: slide guide 125: developing sleeve drive motor 132: moving base drive motor

Claims (1)

[Claims] 1. An image carrier having a latent image formed on its surface, and a developing device for visualizing the latent image on the image carrier.
The developing device carries at least two or more developing units installed close to the surface of the image carrier, carrying the developing units, and carrying an image in the developing operation area toward the surface of the image carrier. A moving base for moving the body surface in a substantially tangential direction, and a positioning means for positioning the developing unit with a predetermined gap with respect to the image carrier when the developing unit is moved to a developing operation position by the base. And a home position of the developing device in which the first developing unit is located on one side below the image carrier and the second developing unit is located below the image carrier. An image forming apparatus, wherein the image forming apparatus is set so as to be located on the side.