JPH0710364Y2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus applicable to, for example, a two-color color copying machine.

[Technical Background of the Invention and its Problems] In recent years, color formation has progressed in image forming apparatuses such as copying machines, and two-color color copying machines and the like have been put into practical use so that color images other than black can be obtained. .

However, in the conventional two-color color copying machine or the like, a plurality of cartridges in which a developing device and a photoconductor are integrated are prepared and selectively replaced.
There was a problem that the operation was extremely troublesome.

[Object of the Invention] The present invention has been made in view of the above circumstances. The object of the present invention is to achieve black development or color development easily and selectively with a simple structure, and yet to achieve color development of a black developer. It is an object of the present invention to provide an image forming apparatus capable of obtaining a clear image while preventing contamination during development as much as possible.

[Outline of the Invention] In order to achieve such an object, the present invention comprises an image carrier composed of a cylindrical rotating body rotating in a predetermined direction, and an image forming means for forming an electrostatic latent image on the image carrier. A first latent image is developed by supplying a color developer other than black to the electrostatic latent image formed on the image carrier by the image forming means.
And a first developing means that is detachable from the main body of the apparatus and is provided downstream of the first developing means in the rotation direction of the image carrier and is formed by the image forming means. A second developing roller for supplying a black developer to the electrostatic latent image on the image carrier, and a second developing means fixed to the apparatus main body. In the first developing means, the rotation center of the first developing roller is above the horizontal line passing through the rotation center of the image carrier in the direction of gravity, and the rotation center of the image carrier and the first developing device are the same. The straight line connecting the center of rotation of the roller is arranged at a position such that a straight line connecting the center of rotation of the image carrier forms a first angle of less than 90 degrees on the upstream side in the direction of rotation of the image carrier, The second developing means is the second
Of the developing roller is higher than the horizontal line passing through the center of rotation of the image carrier in the direction of gravity, and a straight line connecting the center of rotation of the image carrier and the center of rotation of the second developing roller is the image. It is arranged such that it is arranged at a position forming a second angle smaller than the first angle on the upstream side in the rotation direction of the image carrier with respect to a horizontal line passing through the center of rotation of the carrier.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a two-color color copying machine as an image forming apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a copying machine main body. A flexible document table 2 is provided, and an operation panel (not shown) on which a display, a numeric keypad, a color designation button, an exposure setting volume, a print key and the like are arranged is provided at the front edge of the upper surface.

A paper feed cassette 3 is mounted on the right side surface of the apparatus body 1, and a paper discharge tray 4 is mounted on the left side surface. The cassette cover 5 of the paper feeding cassette 3 serves as a manual feed table 6 for manually feeding the paper P '.

A drum-shaped photoconductor 7 is arranged in the central portion of the copying machine body 1. Around the photosensitive member 7, a charging device 8, an optical device 9, a two-color developing device 10, which will be described later, a transfer device 11,
A peeling device 12, a cleaning device 13, and an afterimage erasing device 14 are sequentially arranged.

In the lower part of the copying machine main body 1, the paper P automatically taken out from the paper feeding cassette 3 through the paper feeding roller 15 or the paper P ′ manually fed from the manual feeding stand 6 is provided on the photoconductor 7 and the transfer device 11. A sheet conveying path 17 is formed which leads to the sheet discharge tray 4 through an image transfer portion 16 between Aligning roller pairs 18, 18 are arranged on the upstream side of the image transfer section 16 of the sheet conveying path 17, and fixing device 19 and discharge roller pairs 20, 20 are arranged on the downstream side.

The optical device 9 has an exposure lamp 22 and a lens mirror system 23, the back of which is surrounded by a reflector 21. The photoconductor 7 is driven in synchronization with the document table 2 in the direction of arrow b by a drive mechanism (not shown). First,
A document image uniformly charged by the charging device 8 and uniformly irradiated by the exposure lamp 22 is formed on the photoconductor 7 by the lens mirror system 23 to form an electrostatic latent image. The formed electrostatic latent image is sent as a developer image by the developing device 10 to the transfer device 11 side.

The paper P or P'which is automatically or manually fed is fed by the aligning roller pair 18, 18 and the developer image previously formed on the photoconductor 7 is transferred by the transfer device 11 to the paper P.
Alternatively, it is transferred onto P '. Further, it is peeled off from the photoconductor 7 by the peeling device 12 by AC corona discharge, passes through the conveying path 17, and the fixing device 19 melts and fixes the developer image on the paper P (P ′), and the discharge roller pair 20, 20. It is discharged to the removable tray 4.

On the other hand, the residual toner remaining on the photoconductor 7 after the developer image is transferred onto the paper P (P ') is cleaned by the cleaning device 13.
The afterimage erasing device 14 lowers the potential on the photoconductor 7 to a certain level or lower to make it ready for the next copy operation.

Further, a fan as a cooling device is provided in the main body 1 of the apparatus, and a heat generating portion, an exposure lamp 22 and a fixing device in the apparatus are provided.
The heat generated from 19 is exhausted. 24 is a power switch,
Reference numeral 25 is a door switch, and an exhaust device 28 is also attached to the main motor 27 to cool the heat generated by the power supply 26 and the like.

An upper frame (not shown) and a lower frame (not shown) are pivotally supported in the copying machine body 1 at one end via a support shaft (not shown), and the other ends of both frames are at a desired angle, for example, 30 °.
It is configured to open to. In the upper frame, a charging device 8, a lens mirror system 23,
Exposure lamp 22, developing device 10, cleaning device 13, afterimage erasing device
Each device such as 14 is attached by appropriate means, and a fan as a cooling device, a sheet feeding roller 15 of a sheet feeding device, and a document table 2 are also attached to the upper frame to form an upper unit 1A. Further, the lower frame includes a paper feed cassette 3, a transfer device 11, a peeling device 12, and a conveyance path forming guide plate 3.
0, the fixing device 19, the pair of paper discharge rollers 20, 20, each mechanism such as the tray 4, the main motor 27, the power supply unit 26, etc. are attached by appropriate means to form the lower unit 1B. Then, after rotating and removing the front cover of the copying machine body 1,
It is constructed so that it can be opened and closed substantially along the conveyance path 17 for the paper P (P ') via a housing opening / closing device (not shown). Therefore, even if the paper P (P ') is jammed on the conveying path 17, it can be easily taken out.

Reference numerals 18 and 18 correct the inclination of the front end surface of the paper P that is automatically fed from the paper feed cassette 3 or the paper P ′ that is manually fed, and adjust the timing to the toner image forming operation on the photoconductor 7. Is a pair of aligning rollers for supplying the sheet P or P'to the transfer device 11, and reference numeral 31 is a manual feed detection switch arranged immediately before the pair of aligning rollers 18, 18.

Reference numeral 32 is a paper discharge switch, and 34 is a paper empty switch for detecting that the paper P ...

Further, 35 is a high-voltage transformer, 36 is a static elimination brush, and 38 is an auxiliary reflector.

Further, 39 is a blade solenoid for bringing the cleaning blade 40 of the cleaning device into and out of contact with the photoconductor 7.

As described in detail in FIG. 2, the developing device 10 has a developing roller 50 as a first developing body and a developing roller 51 as a second developing body, and selectively drives these developing rollers 50, 51. Then, a color copy of black or another color such as red, yellow and green can be obtained.

Further, the developing device 10 includes a first developing unit 52 as a color developing unit including a first developing roller 50 and a second developing unit 53 as a black developing unit including a second developing roller 51. The second developing unit 53 in the lower stage is fixedly provided with respect to the copying machine main body 1, and the first developing unit 52 in the upper stage can be pulled out upward in the drawing. Then, the black developer, which is frequently used, is used in the lower second developing unit 53, and the color developer is used in the upper first developing unit 52.

Further, the first developing unit 52 comprises a developing mechanism portion 54 and a developer replenishing portion 55, and the developing mechanism portion 54 includes the developing roller 50.
And a doctor 58 provided on the upstream side of the sliding contact portion of the developer magnetic brush 56 formed on the surface of the developing roller 50 with the photoconductor 7, that is, on the upstream side of the developing position 57, and controlling the thickness of the developer magnetic brush 56. , A scraper 60 which is provided downstream of the developing position 57 and scrapes off the developer magnetic brush 56 on the surface of the developing roller 50 and guides it to the developer accommodating portion 59, and the developer agitation contained in the developer accommodating portion 59. The body 61 and the body 62 are housed in a casing 62. The developing roller of the casing 62
A developer concentration detector 63 for detecting the developer concentration by magnetically detecting the change in the magnetic permeability of the developer 56a is attached to a position corresponding to the upper portion of 50.

Further, the developing roller 50 is provided such that the center thereof is located on a straight line L ₂ drawn through the rotation center of the photoconductor 7 and at an angle α (α = 51 °) with respect to the horizontal line L ₁ .
64 and a sleeve 65 which is fitted onto the magnetic roll 64 and rotates clockwise in the drawing.

The magnetic roll 64 has five magnetic pole portions 66a to 66e,
The first, third, and fifth magnetic pole portions 66a, 66c, 66e are N poles, and the second, fourth magnetic pole portions 66b, 66d are S poles. The first magnetic pole portion 66a and the second magnetic pole portion The angle θ ₁ with 66b is θ ₁ = 50 °, the second
The angle θ ₂ between the magnetic pole portion 66b and the third magnetic pole portion 66c is θ ₂
= 71 °, the angle θ ₃ between the third magnetic pole portion 66c and the fourth magnetic pole portion 66d is θ ₃ = 60 °, the fourth magnetic pole portion 66d and the fifth magnetic pole portion 6
The angle θ ₄ with 6e is set to θ ₄ = 60 °.

Further, the developer replenishing section 55 is provided in a hopper 68 with the developer replenishing port 67 facing the developer accommodating section 59 of the developing mechanism section 54, and in a state where the developer replenishing port 67 is closed in the hopper 68. Developer supply roller 69 and this developer supply roller 69
The developer 56a in the hopper 68 so as to convey the developer 56a to the side.
It is configured to have a pair of stirring rollers 70, 70 for stirring the.

The second developing unit 53 has substantially the same basic structure as the above-described first developing unit 52, and the developer replenishing section 5
Due to the shape of the 5'hopper 68 ', the arrangement of the magnetic poles of the magnetic roll 64' of the developing roller 51, the mounting position of the developer concentration detector 63 'and the accompanying narrow width (about 50 mm), an inclination of about 20 ° is provided. The difference is that a second scraper 80 is added.
The other same components are given the same reference numerals with a dash, and their detailed description is omitted.

The magnetic roller 64 'of the developing roller 51 has four magnetic pole portions 66'.
a to 66'd, and the first and third magnetic pole portions 66'a and 66'c are N
The poles, the second and fourth magnetic pole portions 66'b, 66'd are S poles, and the angle θ ₅ between the first magnetic pole portion 66'a and the second magnetic pole portion 66'b is At θ ₅ = 78 °, the angle θ ₆ between the second magnetic pole portion 66′b and the third magnetic pole portion 66′c is θ ₆ = 70 °, and the angle between the third magnetic pole portion 66′c and the fourth magnetic pole portion 66′c is 4 °. The angle θ ₇ with the magnetic pole portion 66′d is set to θ ₇ = 80 °. Further, the magnetic roll 64 'is provided in a state where the center on the straight line L ₃ to be pulled to a state where an angle β (β = 1 °) with respect to as the horizontal line L ₁ of the center of rotation of the photosensitive member 7 is located There is.

On the other hand, the first developing unit 52 and the second developing unit
Each of the magnetic rolls 64 and 64 'of 53 has a rotation angle of 2
It is structured such that it can be rotationally displaced to a state of about 5 degrees, and the developer magnetic brushes 56, 56 'can be formed on or removed from the surfaces of the developing rollers 50, 51 in accordance with this rotational displacement operation. It is like this.

Then, the magnetic rolls 64, 64 'of the first developing unit 52 and the second developing unit 53 are switched to predetermined positions by a magnetic roll driving means described later, whereby the first developing unit 52 or the second developing unit The developer magnetic brushes 56, 56 'are formed only on the surface of one of the developing rollers 64, 64'.

That is, when operating the first developing unit 52 side, as shown in FIG. 2, the magnetic roll 64 on the first developing unit 52 side is placed in a state in which the third magnetic pole 66c faces the developing position 57. The second developing unit is provided while the doctor 58 is positioned substantially in the middle of the first magnetic pole 66a and the second magnetic pole 66b.
The first magnetic pole 66'a of the magnetic roll 64 'on the 53 side is the doctor 58'.
To face. Then, the first developing unit 52
The developer magnetic brush 56 is formed only on the surface of the developing roller 64 on the side.

When operating the second developing unit 53 side,
As shown in FIG. 3, the magnetic roll 64 on the first developing unit 52 side is rotationally displaced from the position shown in FIG. 2 by about 25 degrees in the clockwise direction so that the first magnetic pole 66a faces the doctor 58 and the second magnetic pole 66a. The magnetic roll 64 'on the side of the developing unit 53 is rotationally displaced counterclockwise by about 25 degrees from the position shown in FIG.
The doctor 58 'is positioned approximately in the middle of 6'a and the second magnetic pole 66'b. The developer magnetic brush 56 'is formed only on the surface of the developing roller 64' on the second developing unit 53 side.

When the first magnetic pole 66a (66'a) of the magnetic rolls 64, (64 ') faces the doctor 58 (58') made of a non-magnetic material, the developer magnetic brush 56 (56) is formed on the surface of the developing roller 50 (51). The reason why the magnetic field 66a (66'a) is not formed is that the magnetic flux density of the magnetic brush is sparse at the magnetic pole 66a (66'a).
This is because the force of adsorbing 6'a) is weak and can be easily regulated by the doctor 58 (58 '). Even if the sleeve 65 (65') rotates, the developer 56a (56'a) does not move to the doctor 58 (58 '). It does not pass through section 58 ').

The driving force is transmitted to each driving portion of the first developing unit 52, that is, the sleeve 65 of the developing roller 50, the developer stirring body 61, and the developer replenishing roller 69 via a first driving force transmission system 85 described later. It has become so. In addition, each drive unit of the second developing unit 53, that is, the sleeve of the developing roller 51.
65 'and developer agitator 61' are the second driving force transmission system described later.
The driving force is transmitted via 86.

The first and second driving force transmission systems 85 and 86 are shown in FIGS.
As shown in the figure, by reversing or reversing the reversible motor 87 as a common drive source, only one drive unit of the first and second developing units 52, 53 is selected. Is designed to work properly. And
In addition to simplifying the mechanism and reducing the number of parts, the developer 56
It is possible to prevent unnecessary deterioration of a (56'b) due to unnecessary stirring and conveyance.

The driving force transmission system will be described below with reference to FIGS. 4 to 6. FIG. 4 shows the first and second driving force transmission systems 85 and 86.
Fig. 5 is a schematic front view showing Fig. 5, and Fig. 5 is a sectional view showing a state in which the first and second driving force transmission systems 85, 86 are expanded around the driving gear 88. The first driving force transmission system 85 includes an intermediate gear 89 that meshes with the driving gear 88, a first driven gear 90 that meshes with the intermediate gear 89, and an intermediate gear 91 that meshes with the first driven gear 90. Second driven gear 92 meshing with intermediate gear 91
And have.

The second driving force transmission system 86 includes a third driven gear 93 that meshes with the driving gear 88, an intermediate gear 94 that meshes with the driven gear 93, and a fourth driven gear that meshes with the intermediate gear 94. 95
And have.

The drive gear 88 rotates in the normal direction, that is, the solid arrow A in FIG.
When rotated in the direction, each gear group 8 of the first drive transmission system 85
9,90,91,92 and gear groups 93,9 of the second driving force transmission system 86
When 4,95 respectively rotate in the direction of the solid arrow and the drive gear 88 rotates in the reverse direction, that is, in the direction of the arrow B in the broken line, the gear groups 89, 90, 91, 92 and the second gear groups of the first driving force transmission system 85 are rotated. Each gear group 93, 94, 95 of the driving force transmission system 86 is adapted to rotate in the direction of the broken arrow.

The first driven gear 90 is connected to the drive shaft 65a which is integral with the sleeve 65 of the first developing roller 50, and the second driven gear 92 is connected to the drive shaft 61a of the developer agitator 61.
In the drive shafts 65a, 61a, the gears 90, 92 rotate in the directions of solid arrows, that is, the drive force is transmitted only when the drive gears 88 rotate in the forward direction, and in the directions indicated by alternate long and short dash lines. It is designed to rotate.

The third driven gear 93 is connected to the drive shaft 65'a integral with the sleeve 65 'of the second developing roller 51, and the fourth driven gear 95 is connected to the drive shaft 61'a of the developer agitator 61'. It is mounted via a one-way clutch 97, and each drive shaft 65'a, 6 '
1'a is designed such that the gears 93 and 95 rotate in the directions of the broken line arrows, that is, the driving force is transmitted only when the drive gear 88 rotates in the reverse direction, and rotates in the direction indicated by the alternate long and short dash line arrow.

Further, as shown in FIG. 6, the drive gear 88 is rotatably supported by bearings 98 ... And a rotary shaft 110 that is interlocked with a drive shaft 87a of the reversible motor 87 via a gear mechanism 99. Installed. That is, a gear 111 is attached to the rotating shaft 110, and the gear 111 is rotatably attached to a motor mounting frame 112 and a support shaft 114 installed between stays 113 integrated with the motor mounting frame via bearings 115 and 115. It meshes with the gear 116. A gear 117 having a larger diameter than this is integrally formed with the gear 116, and this gear 117 is in a state of meshing with a gear 118 attached to a drive shaft 87a of the reversible motor 87. Then, the drive shaft 87a of the reversible motor 87
The rotations in both the forward and reverse directions are transmitted to the rotary shaft 110 via gears 118, 117, 116, 111, and the first and second developing units 52, 53
Can be selectively operated only by a switching operation of the reversible motor 87 between forward rotation and reverse rotation.

The reversible motor 87 is switched between normal rotation and reverse rotation by pressing a color designation button on an operation panel (not shown).
The first magnetic poles 66a, 66'a of the non-operating magnetic rolls 64, 64 'are switched by 0, 100' so as to face the doctors 58, 58 '.

An intermediate gear 89 that meshes with the drive gear 88 and the first driven gear 90 is rotatably attached to the support shaft 121 via a bearing 120. The support shaft 121 is attached to an arm 123 which is swingable around a housing 122 that holds the bearings 98, 98 that support the rotary shaft 110, and a drive gear 88 and a first driven gear 90. The position can be changed so as to surely engage with each other.

Also, the first stirring roller 70 of the first developing unit 52 is
Is intermittently driven via a first actuating mechanism 124 shown in FIG. 4, and the second agitating roller 70 and the developer replenishing roller are interlocked with the movement of the agitating roller 70.
69 are driven at the same time.

That is, the ratchet gear 125 is attached to one end of the shaft 70a of the first stirring roller 70 of the first developing unit 52, and the ratchet gear 125 is an ON-O of the solenoid 126.
It is adapted to be intermittently driven by a predetermined amount via a ratchet pawl 128 attached to an operating arm 127 which is rotationally displaced in association with the FF operation.

Further, sprockets (not shown) are fitted on the shafts 70a, 70b of the first and second stirring rollers 70, 70 and the shaft 69a of the developer replenishing roller 69, respectively, and an endless chain (not shown) is provided.
The stirring rollers 70, 70 and the developer replenishing roller 69 are integrally driven via the driving force transmission system (not shown).

The agitating roller 70 'and the developer replenishing roller 69 of the second developing unit 53 have a second operating mechanism 124' having the same configuration as the first operating mechanism 124 and a driving force transmission system having substantially the same configuration. It is designed to be driven intermittently at the same time via. The same components as those of the first actuating mechanism 124 are denoted by the same reference numerals with a dash, and a detailed description thereof will be omitted.

Next, the developer brush 56 (5
Magnetic roll 64 to form or remove 6 ')
The magnetic roll drive means 100 for rotationally displacing (64 ')
The structure of (100 ') will be described with reference to FIGS. 7 to 9a and 9b. The shafts 64a, (64 ') of the magnetic rolls 64, (64')
One end of a) is pivotally supported through a bearing 131 attached to the frame 130, and a lever 132 is attached to the tip thereof. The tip of the lever 132 is in a state of being engaged with an engagement groove 134a of an arm 134 rotatably attached via a support shaft 133. Further, a first support portion 134b formed on the lower portion of the arm 134 on the pivotal end side is connected to the plunger 135a of the solenoid 135, and a second support portion 134b formed on the upper portion on the pivotal end side.
One end of a tension spring 136 is connected to the support portion 134c.

Then, when the solenoid 135 is in the OFF state, the arm 134 is moved by the urging force of the tension spring 136 to the position shown by the chain double-dashed line in FIG. 8, that is, the first magnetic pole portion as shown in FIG. The lever 132 is held at a position where the 66a (66'a) faces the doctor 58 (58 '). Therefore, when the solenoid 135 is turned off, the developer brushes 56, 56 'are not formed on the surfaces of the developing rollers 50, 51.

When the solenoid 135 is turned on, the arm 1
34 is a position shown by the solid line in FIG. 8 against the urging force of the tension spring 136, that is, as shown in FIG. 9 (b), the first magnetic pole portions 66a, (66'a) are connected to the doctor 58 (58 '). ), The lever 132 is rotationally displaced. Therefore, when the solenoid 135 is turned on, the developer brushes 56, 56 'are formed on the surfaces of the developing rollers 50, 51.

As shown in FIGS. 2 and 3, the doctor 58 'is composed of a doctor body 58'a made of a non-magnetic material, and a strip-shaped iron plate provided along the longitudinal direction of the doctor body 58'a. The first magnetic body 58'b and the second magnetic bodies 58'c, 58'c made of iron plates provided at both ends of the doctor body 58'a.
(Only one is shown). In the first and second magnetic bodies 58'b, 58'c, 58'c, the first magnetic pole portion 66'a faces the doctor 58 ', and the developer 56'a on the surface of the developing roll 51. To remove the first magnetic pole portion 66 '.
A magnetic line of force is formed between the developer a and a, so that the developer 56'a can be more reliably prevented from being taken out.

Further, the doctor 58 is a doctor body 58 made of a non-magnetic material.
a and magnetic members 58c, 58c (only one of which is shown) made of an iron plate provided at both ends of the doctor body 58a, and the developer is formed in the same manner as in the case of the doctor 58 'described above. It is designed to prevent the removal of 56a. Unlike the above-mentioned doctor 58 ', the doctor 58 is not provided with a magnetic body along the longitudinal direction of the doctor body 58a, and the first magnetic pole portion 66a of the developing roll 50 and the developing roll 51 facing the doctor 58 are not provided.
The magnetic lines of force formed between the fourth magnetic pole portion 66'd and the fourth magnetic pole portion 66'd are used to prevent the developer 56a from being taken out.

A magnetic plate 140 is provided between the developing roll 50 and the developing roll 51 as shown in FIGS. 2 and 3.
The influence of the magnetic flux density / pole distribution of the other magnetic roll 64, (64 ') is weakened so that a good developer transport operation can be performed.

Reference numeral 141 shown in FIGS. 2 and 3 is a developer empty detecting means for detecting that the amount of the developer 56'a in the developer hopper 68 'of the second developing unit 53 has decreased. A structure in which a magnet 144 attached to an actuator 143 integrated with a detection lever 142 that is rotationally displaced in accordance with the amount of developer is operated when it comes close to a reed switch 145 as a detector provided outside the hopper 68 '. Has become.

Further, as shown in FIGS. 2, 3, and 10, a cover 150 forming a part of the upper surface of the apparatus main body 1 is provided on the upper surface side of the two-color color developing apparatus 10 so as to be openable and closable. 1
A lid 152 for opening and closing the upper surface opening 151 for supplying the developer of the first developing unit 52 when the opening 50 is opened, and a lid 1 for opening and closing the upper opening 151 'for supplying the developer of the second developing unit 53
52 'is exposed. And these lids
By opening 152, 152 ', the developer 56a, 56'a can be easily replenished from the upper surface side.

Further, the color display portions 153, 153 'are provided on the lids 152, 152'.
And the developer 56'a, 56 'housed inside
The color of a can be easily discriminated and the developer of a different color is prevented from being mistakenly mixed in.

On the other hand, the first developing unit 52 accommodating the color developer 56a is a cartridge type that is attachable to and detachable from the apparatus main body 1, and by pulling up the grip 155 (see FIG. 10) in an upright state. It is designed to be easily removable.

That is, positioning members 156 and 156 (only one is shown) are attached to the front and rear walls of the developer replenishing portion 55 of the first developing unit 52, and the support shaft 15 is attached to these positioning members 156 and 156.
Both ends supporting rod portions 155a, 155a of the handle 155 are rotatably and pivotally attached via 7,157.

As shown in FIGS. 11 and 12, hooks 158 rotatable around a support shaft 157 are integrally attached to the support rods 155a, 155a of the handle 155, respectively, and the apparatus main body 1
The engaging pin 159 provided on the side is engaged to restrict upward movement. Engaging groove 15 as a first positioning portion formed on the lower end side of the positioning member 156.
6a and the end surface 156b serving as the second positioning portion are adapted to engage and abut the positioning pins 160 and 161 provided on the apparatus main body 1 side, so that the first developing unit 52 can be held at a predetermined position. ing. Further, when the handle 155 is erected, the engagement between the hook 158 and the locking pin 159 is released as shown in FIG. 12 (a), and when the handle 155 is tilted to a substantially horizontal state, as shown in FIG. 12 (b). The hook 158 is locked to the pin 159
Then, by pushing in from the horizontal position, the hook 158 and the locking pin 159 are surely engaged so that the developing unit 52 is pressed downward as shown in FIG. 12 (c). It has become.

Therefore, if the handle 155 is set upright, the first developing unit 52 can be attached / detached, and if the handle 155 is tilted after the first developing unit 52 is inserted, the first developing unit 5
2 can be fixed and its operation becomes extremely easy.

In addition, the second developer containing the frequently used black developer 56'a
The capacity of the hopper 68 'of the developing unit 53 of the color developer 56
The capacity is set to be larger than the capacity of the hopper 68 of the first developing unit 52 accommodating a, and the developer replenishment interval is extended to facilitate maintenance. Next, the reason why the first developing unit 52 as the first developing unit and the second developing unit 53 as the second developing unit are arranged at the following positions will be described.

As shown in FIG. 2, in the first developing unit 52 as the first developing means, the rotation center of the first developing roller 50 is from a horizontal line L ₁ passing through the rotation center of the photoconductor 7 as the image carrier. A straight line L ₂ connecting the rotation center of the photoconductor 7 and the rotation center of the first developing roller 50 upward in the direction of gravity is the photoconductor 7.
Is arranged at a position that forms a first angle α of less than 90 degrees on the upstream side in the rotation direction of the photoconductor 7 with respect to the horizontal line L ₁ passing through the rotation center of.

In addition, the second developing unit 53 as the second developing means.
The rotation center of the second developing roller 51 is above the horizontal line L ₁ passing through the rotation center of the photoconductor 7 in the direction of gravity, and
A straight line L ₃ connecting the rotation center of the photoconductor 7 and the rotation center of the second developing roller 51 is located on the upstream side in the rotation direction of the photoconductor 7 with respect to the horizontal line L ₁ passing through the rotation center of the photoconductor 7. It is arranged at a position that forms a second angle β that is less than the angle α.

Since the first developing unit 52 is detachable, the developer easily spills when it is attached and detached, and this spilled developer is prevented from scattering in the machine body.

That is, for example, the first developing roller 50 is a straight line connecting the center of rotation of the photoconductor 7 and the center of rotation of the first developing roller 50.
When L ₂ is 90 degrees or more on the upstream side in the rotation direction of the photoconductor 7 with respect to the horizontal line L ₁ passing through the rotation center of the photoconductor 7, the developer spilled when the first developing unit 52 is attached or detached is Although it falls downward due to gravity, since the second developing unit 53 does not exist in this dropping direction, it cannot be collected by the second developing unit 53, and the inside of the machine is polluted.

In the second developing roller 51, a straight line L ₃ connecting the rotation center of the photoconductor 7 and the rotation center of the second development roller 51 is a photoconductor 7.
When disposed on the downstream side (lower side) in the rotation direction of the photoconductor 7 with respect to the horizontal line L ₁ passing through the rotation center of, the spilled developer drops downward due to gravity from the most overhanging part of the photoconductor in the horizontal direction. However, the dropped developer collects on the casing 62 'which is the housing of the second second developing unit 53, is not collected by the second developing unit 53, and eventually contaminates the inside of the machine body.

Therefore, the second developing roller 51 is in the same quadrant as the first developing roller 50 (above the most protruding portion of the photoconductor in the horizontal direction).
The developer spilled from the removable first developing unit 52 is reliably collected by the second developing unit 53.

Further, the detachable first developing unit 52 located above
Is for color development, and the second developing unit 53 located below is for black development, the developer collected in the second developing unit 53 is a color developer. Even if mixed in, the image quality is not affected.

Next, the developing operation of the developing device 10 will be described. First, when the color designation button is designated to operate the first developing unit 52 side, the magnetic rolls 64, 64 'are brought into the state shown in FIG. 2 and the reversible motor 87 is normally rotated.
The sleeve 65 of the first developing roll 50 rotates clockwise in the state of FIG. 2 to form the magnetic developer brush 56 on the surface of the sleeve 65.

Then, the electrostatic latent image previously formed on the photoconductor 7 is developed with the color developer 56a.

When the development of the electrostatic latent image is completed in this way, the first
Of the magnetic roll 64 of the first magnetic pole 66a
By facing the doctor 58, new formation of the developer magnetic brush 56 on the sleeve 65 is stopped, and in this state, the sleeve 65 further rotates by a predetermined amount and the developer magnetic brush 56 is removed. At this time, the developer magnetic brush 56 'is not formed on the second developing roller 51, so that even if any one of the developing units 52 and 53 is designated next, a problem such as color mixing does not occur. It has become.

When the second developing unit 53 is designated for black development, the magnetic rolls 64 and 64 'are brought into the state shown in FIG. 3 and the reversible motor 87 is rotated in the reverse direction so that the second developing roll 51 The sleeve 65 'of FIG. 3 rotates clockwise in the state shown in FIG. 3, and the developer magnetic brush 56' is attached to the surface of the sleeve 65 '.
To form. Then, after the electrostatic latent image on the photoconductor 7 is black-developed in the same manner as described above, the developing operation is ended with the developer magnetic brush 56 'removed from the surface of the sleeve 65'.

On the other hand, the developer stirring body 61 (61 ') and the stirring mechanism 70 (70') of the developing unit 52 (53) in the developing operation state are always operating, and the developer replenishing roller 69 (69 ') is the developer. Depending on the signal from the density detector 63 (63 '), the developer 56
The replenishing operation of a (56'a) is performed so that the good developing operation is maintained.

By setting the magnetic pole arrangement structure of the magnetic rolls 64, 64 'of the first and second developing rollers as described above, the formation state of the developer magnetic brushes 56, 56' is not damaged.

Further, since the first developing unit 52 for color developing is provided on the upper stage of the second developing unit 53 for black developing, even if the developer is scattered or spilled from the upper stage for some reason, it is the color developer 65a. By the black development in the second developing unit 53, it becomes inconspicuous and the image quality is not greatly impaired.

[Advantages of the Invention] As described above, according to the present invention, black development and color development of a color different from black can be selectively performed, and the image carrier can be rotated more than the first developing unit for black development. Since the color developing means provided upstream in the direction is disposed above, it is possible to prevent the black developer from being mixed in during color development, and it is possible to obtain a clear color image without deterioration of image quality due to black mixing.

Further, since the black developing means located in the lower portion is located above the horizontal line passing through the center of rotation of the image carrier composed of the cylindrical rotating body, the color developing means arranged above this line. The color developer spilled from the developer drops toward the black developing means located at the lower portion and is collected by the black developing means, so that the inside of the machine can be prevented from being contaminated by the color developer. Even if the color developer is slightly mixed with the black developer, the image quality is not affected, and the image forming operation is not impaired.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a copying machine as an image forming apparatus of the present invention, and FIG. 2 is a schematic vertical sectional front view of a developing device which is a main part. FIG. 3 is a schematic vertical sectional front view showing a different operating state of the main part, and FIGS. 4 to 6 show the structure of the driving force transmission system.
FIG. 4 is a front view showing a meshing state of gears, FIG. 5 is a sectional view showing a developed state, FIG. 6 is a sectional view showing a driving force transmission state to a driving gear, and FIG. 7 is a magnetic roll driving means. FIG. 8 is a front view, FIG. 8 is a front view, FIG. 9 (a) and (b) are explanatory views showing the same operating state, and FIG. 10 is a schematic perspective view of the developing device section. FIG. 11 is a front view showing the fixing structure of the developing unit, and FIGS. 12 (a), (b), and (c) are explanatory views showing the engagement / disengagement relationship between the handle and the hook. 10 ... Two color developing device, 52 ... First developing unit (color developing means), 53 ... Second developing unit (black developing means), 56,56 '... Developer magnetic brush, 56a, 5
6'a ... Developer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-87058 (JP, A) JP-A-58-150973 (JP, A) JP-A-57-26881 (JP, A) JP-A-53- 115238 (JP, A) JP 58-195853 (JP, A) Actually developed 58-121040 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. An image carrier comprising a cylindrical rotating body which rotates in a predetermined direction, an image forming means for forming an electrostatic latent image on the image carrier, and the image forming means for forming the electrostatic latent image. A first developing unit which has a first developing roller for developing the electrostatic latent image on the image bearing member by supplying a color developer other than black, and is detachable from the apparatus main body; A second developer which is provided downstream of the first developing means in the rotation direction of the image carrier and supplies a black developer to the electrostatic latent image on the image carrier formed by the image forming means. And a second developing unit fixed to the main body of the apparatus, wherein the first developing unit is the center of rotation of the first developing roller of the image carrier. Above the horizontal line passing through the center of rotation in the direction of gravity, and A straight line connecting the rotation center of the image carrier and the rotation center of the first developing roller is less than 90 degrees on the upstream side in the rotation direction of the image carrier with respect to the horizontal line passing through the rotation center of the image carrier. The second developing means is disposed above the horizontal line where the rotation center of the second developing roller passes through the rotation center of the image carrier and in the direction of gravity, and A straight line connecting the rotation center of the image carrier and the rotation center of the second developing roller is less than the first angle on the upstream side in the rotation direction of the image carrier with respect to the horizontal line passing through the rotation center of the image carrier. The image forming apparatus is arranged at a position that forms a second angle of the.