JPS61204661A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a drop in surface potential due to the contact of a developer magnetic brush with an image carrier and to obtain excellent images by providing relays having contacts which open and close a developing bias feed path and making and broking the contacts of the relay according to a selection of a developing device. CONSTITUTION:The 1st developing roller 1311 is connected to the bias voltage 192 through a contact 190a of the 1st relay, and the 2nd developing roller 1312 is connected through the contact of the 2nd relay 191 respectively. Further, the 1st relay 190 and the 2nd relay 191 are connected to a color selection key 104 through a control part 220 to constitute a developing bias cutting means which is switched associatively with the color selecting operation of the color selection key 104. While a selected developing device is in operation, the developing bias to the other developing device is cut to prevent a drop in surface potential due to the contact of the developer magnetic brush 1352 (1352) of the unused developing device with a photosensitive drum 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developing device that can be applied to, for example, a two-color color copying machine.

[Technical background of the invention and its problems]

2. Description of the Related Art In recent years, two-color copying machines capable of producing images in colors other than black have been put into practical use.

However, in conventional two-color color copying machines, etc., multiple cartridges are prepared in which a developing device and a photoreceptor are integrated, and the cartridges are selectively replaced, which makes the operation extremely troublesome. was there.

Therefore, recently, a first developing device and a second developing device are arranged along the moving direction of the image carrier (photoreceptor), and these developing devices are arranged in the same direction as the rotor. A developing device boat was developed and put into practical use in which a developer magnetic brush was rubbed against the image carrier while applying a developing/guinea force to the selected one using the tongue switch operation lever, allowing for the development of a wide variety of colors. .

However, in conventional developing devices of this type, when one developing device is performing development, the other developing device, which is not used for development, remains under development and gusset. . For this reason, if the developer magnetic brush of the unselected developer partially contacts the image carrier for some reason, there is a problem that the surface potential of that part decreases and adversely affects the image.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to arrange a plurality of developing devices, select one of the developing devices, and slide a developer magnetic brush onto an image carrier while applying a developing bias. To obtain a good image by preventing a decrease in surface potential due to contact of a developer magnetic brush of a developing device not used for development with an image carrier, in a developing device that performs development by rubbing, while having a simple configuration. The purpose of the present invention is to provide a developing device that can.

[Summary of the Invention] In order to achieve the above-mentioned object, the present invention provides a relay having a contact for opening and closing a developing bias power supply path corresponding to each developing device, and connects the contact of the relay according to the selection operation of the developing device. By opening and closing the developing device, the developing bias of the developing device not used for development is cut off.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view showing a two-color copying machine of a document table moving type as an example of an image forming apparatus to which the developing device of the present invention is applied, and FIG. 2 is a longitudinal sectional front view. That is, 1 is a copying machine main body, and on the top surface of this copying machine main body I is provided a document table 2 that can freely move back and forth in the left and right direction (in the direction of arrow a in the figure). is provided so that it can be opened and closed freely. In addition, a paper feed cassette 4 is located on the right side of the main body 2.
However, a paper discharge tray 5 is attached to the left side.

The above paper feed cassette 4 is the main body! It can be attached to and detached from the paper feed section 6 provided on the lower right side of the inner portion. In the paper feed section 6, 7 is a paper feed roller that takes out the sheets of paper P1 one by one from the paper feed cassette 4, and 8 is an aligning roller pair that conveys the paper fed from the paper feed roller 7 or the automatic paper feed device 1z. In front of the pair of aligning rollers 8, a detector 9 consisting of a detection lever and a microswitch for detecting paper is provided.

In addition, the cassette cover (top surface) of the paper feed cassette 4 serves as a paper feed tray 10 for manually feeding paper as appropriate (possible when automatic paper feeder Z1 is not installed) or for automatically feeding paper. An automatic paper feeder ZI is provided on the paper tray 10, and a paper width adjustment Iprz is provided on the paper feeder 10 on the paper insertion side of the automatic paper feeder 11.

The automatic paper feeder II is a device that continuously feeds sheets of paper P set on the paper feed tray 10 one by one to the paper feeder 6, and is detachable from the right side of the main body 2. ing.

Furthermore, a photosensitive drum I3 serving as an image carrier is disposed approximately at the center of the main body I. Around this photoreceptor drum 13, an exposure optical system 14 and a charging device I5 are provided.
．． A two-color developing device I6, a transfer charger 17, a peeling charger I8, a cleaning device 19, a static elimination lamp '20, and the like are arranged in sequence along the rotation direction.

Further, the developing device I6 is divided into two parts, a magnetic brush type first developing device 16m and a second developing device 16b, each of which is detachable from the main body 1t/C.

The first developing device I6a and the second developing device 16b are selectively driven by a 9-sipple motor (not shown) that rotates forward or reverse.
This allows black or any other color, such as red,
Color development such as yellow, blue, and green can be selectively performed.

On the other hand, in the lower part of the main body I, a sheet P1 or P is conveyed by a pair of aligning rollers 8.

A paper conveyance path 22 that guides the image to the paper discharge tray 5 through the image transfer section 21'ft between the photoreceptor drum 13 and the transfer charger I7.
is formed. The aligning roller pair 8 is located upstream of the image transfer section 21 in the paper conveyance path 22.
Furthermore, a fixing device 23 and a pair of paper discharge rollers 24 are arranged on the downstream side.

Here, the exposure optical system I4 has a back 7 reflector 25.
an exposure lamp 26 surrounded by mirrors 27 to 30;
and a lens 31 whose position is moved according to the set magnification.

Thus, the photosensitive drum I3 is driven by a drive mechanism (not shown) in the direction indicated by the arrow in the drawing in synchronization with the document table 2.

First, it is uniformly charged by the charging charger 75 and then exposed to
The image of the document uniformly irradiated with light by the lens fzg is formed on the photosensitive drum I3 by the exposure optical system I4, thereby forming an electrostatic latent image. This formed electrostatic latent image is developed by the developing device 16 and turned into a developer image, which is then used as a transfer charger! ? He is sent to the side.

On the other hand, the paper P1 or P fed from the paper feed cassette 4 or the automatic paper feeder II is fed by the aligning roller pair 8, and the developer image formed on the photoreceptor P ram 13 is transferred to the transfer charger. transcribed by 17. The paper p, (Pt) to which this developer image has been transferred is charged by a peeling charger I.
The photoreceptor 9 is peeled off from the ram I3 by 8, passes through the paper transport path 22, and is guided to the fixing device 23, where the transferred image is melted and fixed. is discharged to.

7 On the other hand, after transferring the developer image onto paper p+(pt),
The residual toner remaining on the photoreceptor drum 13J-' is cleaned by the photographing device 19, and the residual image on the photoreceptor drum I3 is erased by the static elimination run f2o, in preparation for the next copying operation.

2, 4I is a toner replenishing device for the first developing device, 42 is a toner replenishing device for the second developing device, 43 and 44 are toner degree detectors, 45 is a paper ejection switch, 46 is a static elimination brush, and 47 is an exhaust fan.

Next, the driving force transmission system will be explained with reference to FIGS. 3 to 5. Figure 3 is the main body of the copying machine! FIG. 4 is a view of the internal mechanism of the automatic paper feeder II as seen from the back side, and FIG. 4 shows a state in which the upper unit 5o is separated from the lower unit 51 and the paper conveyance path 22' is opened. In the figure, 52 is a support shaft that pivots the upper unit 50 and the lower unit 51. Further, 53 is a driving gear directly connected to the main motor 48, and the driving force of this driving gear 53 is transmitted to the r-ram driving gear 57 via driven gears 54-56.

Further, as shown in FIG. 5, the driving force of the driving gear 53 is transmitted to the aligning roller driving gear 63 via the driven gears 58 to 62, and further to the paper feed roller driving gear 65 via the driven gear 64. It is meant to be transmitted.

Further, as shown in FIG.
3, and is further transmitted to the paper feed roller drive gear 65 via the driven gear 64.

In this way, the driving force of the drive gear 53 is transferred to the P ram drive gear 52.
When transmitting the power to the aligning roller driving gear 63, the drum driving power transmission system 66 and the aligning roller driving power transmission system 67 are separated and transmitted independently, so that the power is transmitted to the aligning roller drive gear 63 independently. The impact caused by load fluctuations before and after the start of the drive of 8 is not directly transmitted to the drum drive gear 57, and image blur caused by the impact can be prevented.

Further, the paper feed roller drive gear 65 is always in mesh with a drive gear 69 that meshes with the driven force transmission gear 68 of the automatic paper feeder 11, and the automatic paper feeder 1
1 is configured to obtain a sufficiently large driving force from the copying machine main body l side via a driving force transmission mechanism 70. In addition, compared to a device having its own drive source, it is possible to improve the paper feeding speed, improve the paper separation mechanism, and reduce the size, weight, and cost.

Further, the meshing state between the driven force transmission gear 68 of the automatic paper feeder II and the drive gear 69 on the copying machine main body I side is released when the upper unit 50 is opened as shown in FIG. The power transmission system can be driven by manual operation of the device 11, and paper jam removal, maintenance, inspection, etc. can be easily performed.

Further, reference numeral 71 shown in FIGS. 3 and 4 is a scanning motor, and this scanning motor 7I is decelerated by the ear head and rotates the goulift 2. Here, a wire 74 whose one end is fixed to the tip of the document table 2 and whose other end is supported by a spring (not shown) at the rear end of the document table 2 is applied tension to the wire 74 by the idle goo 975 and the spring 26. It is wound around the relief 2 via a tensi comp pulley 77.

Therefore, as shown in FIG.
When the document table 2 rotates in the direction (clockwise), the document table 2 moves forward in the direction a, and when the magnet 78 attached to the document table 2 is detected by the limit switch 79, the goolif 2 rotates in the direction c2, and the document table 2 moves forward in the direction a. moves back in direction a.

The scanning motor 7I is synchronized with the main motor 48 by an encoder disk 80 and an encoder sensor 8I.

Note that 83 is a magnet attached to the document table 2, 84 is a home switch, and 85 is a paper start switch.

Then, based on the detection signal of the paper start switch 85,
Paper feed roller 7, one row 2 of aligning roller pair 8
operate the clutch mechanism (not shown) built into the
Paper feeding and restart are performed at predetermined timing.

In addition, 86 shown in FIG. 3 and FIG. 4 is a developing device motor gear, 87.88 is a driven gear, 89.90 is a developing device drive gear, 91 is a drive gear for the lower discharge roller, and 92 is a drive for the upper heat roller. It's a gear. Further, 93 is a heater rung.

In addition, the paper feed section 6 side is pivotally supported via the support shaft 52, and the
The upper unit 50, which can be rotated by 0 degrees, includes an optical system I4, a charging device Z5, an exposure run f26, a developing device I6, a cleaning device 19, a static elimination run': f20, etc. around the photosensitive drum I3. It is attached by appropriate means,
Furthermore, the document table 2, paper feed roller 7, aligning roller 8
Upper roller 8a, upper roller 23 of heat roller 23
&, and the upper roller 24a of the paper ejection roller 24 are attached.

The lower unit 51 also includes a paper feed cassette 4, a lower roller 8b of the aligning roller 8, a transfer charger 17, a peeling charger I8, and a lower roller 23b of the heat roller 23.
1 the lower roller 24b of the paper ejection roller 24, the paper ejection tray 5,
A main motor 48 and the like are attached by appropriate means.

After rotating and removing the front force/pull of the main body 1, the paper p is almost opened via a housing opening/closing support device (not shown).
It is configured so that it can be opened and closed along the paper conveyance path 22 that conveys the paper t (pt).

Further, at the upper end of the front side of the main body I, as shown in FIG. 1, there is provided an operation/monitoring channel 200. FIG. Duplicate copy key 101, interrupt mode 9 for interrupt copying
an interrupt key 102 for specifying the number of copies, a numeric keypad 103 for setting the number of copies, etc., a copy color (for example, black, red,
a color selection key 104 for selecting (blue, green), a color display section 105 for displaying available colors for copying, a paper feed selection key for selecting automatic paper feeding by the paper feed cassette 4 or automatic paper feeding by the automatic paper feeder II Iθ6, a total counter 107 for counting the total number of copies, and a liquid crystal display section 10g are provided.

The liquid crystal display section 10g includes a sheet number display section 109 that displays the number of copies, a status display section 110 that displays various operating states such as paper jam and toner replenishment, a warm-up display section 11j, a ready display section 112, and the above-mentioned. Color display section 105
a color indicating section 1 that is provided corresponding to the color indicating the selected color;
13. Cassette paper feeding mode display section 114 that displays the automatic paper feeding mode using the paper feeding cassette 4; Pie/Guss paper feeding mode display section 115 that displays the automatic paper feeding mode using the automatic paper feeding device 11; automatic exposure mode display 116, and a set exposure amount display section 117 in manual exposure mode.

Also, an automatic exposure key 1111 for setting the automatic exposure mode.
, a manual exposure key 119 for manually setting the exposure amount, a magnification setting key 120 for selecting and setting a specific predetermined copying magnification and rate, and a zoom key 1 for setting an arbitrary copying magnification.
21. Magnification display that displays the set magnification, 1f161
22 etc. are also provided.

Further, as shown in FIG. 7, a second exhaust fan (Tf tom fan) 124 is provided at the bottom of the copying machine main body I to exhaust air toward an exhaust port 123 formed at the bottom of the copying machine main body I.
are arranged, and a fixing device 23 and an exposure optical system I
A filter 125 is provided between the two.

And 1. A restricting means 126 is configured to restrict the heat generated from the heater run f93 of the fixing device 23 and the offset prevention silicon vapor applied to the fixing roller 23a from going to the exposure optical system I4 side.

Therefore, the exposure optical system I4 is located near the fixing device 23. Even in this copying machine, the heat generated from the fixing device 23 and the silicon vapor for preventing offset do not flow into the exposure optical system I4, so the mirrors 27 to 30, lenses 31, etc. of the exposure optical system I4 do not flow into the exposure optical system I4. There is no possibility of contamination due to silicone vapor condensed on the copy, and it is possible to reliably prevent copies from becoming partially black or defective.

Note that the heat generated from the exposure lamp 26 of the exposure optical system I4 is actively exhausted outside the copying machine main body I by an exhaust fan 47 disposed in the upper part of the copying machine main body I. It is structured so that it is not crowded.

Next, referring to FIGS. 8 to 24, the developing device I6
The details will be explained below. , as detailed in Figure 8,
A first developing roller 131 serving as a first developing body which is a developer conveying means. and a second developing roller 13I as a second developing body which is a developer conveying means, and these developing rollers 131, . 131. is selectively driven to produce black (first
color) or one other color (second color), such as red, yellow, blue, green, etc., can be developed. That is, the developing device 16 includes a first developing roller 131 . 76
& and second developing roller 131. A second developing unit (second
The developing unit (developing unit) Z6b is divided into two. 2nd current mine 16m, 16. b are both detachable from the main body I. In this case, the first current device I6a on the upper stage is configured to be easily attached and detached so that the user can pull it out upward in the figure, and the second current device 16b on the lower stage is configured to be easily attached and detached.
When service personnel perform maintenance, inspection, etc.,
It has a structure that can be attached to and detached from the t/C. And 1.
Black toner T, which is frequently used, is stored in the lower second developing device 16.
Color toner T is used in the first developing device 16 in the upper stage.
It is designed to be used in a.

The first developer 16m includes a toner replenishing section 133. which constitutes the developing mechanism section Z32° and the toner replenishing device 41. It is composed of. The above-mentioned developing mechanism section Z32. is a casing 741. which will be described later. The developing roller 13 supplies the toner T1 to the photosensitive drum 13 through the opening 141 ml.
2. and the sliding contact portion of the developer magnetic brush l351 formed on the surface of the developing roller 13I with the photosensitive drum I3, that is, the developing position Z36. upstream side, that is, the second
A developer magnetic brush 135. is provided on the developing device 16b side.
a doctor (regulating member) 1371 that regulates the thickness of the image, and a developing position 136 . The roller is also installed on the downstream side, and the developing roller 1
31. Developer magnetic brush I35. Scrape off the developer accommodating portion 43B.

Scraper #139I as a peeling means leading to the developer storage part I38. The development side agitator I40. and is housed in the casing I4!1.

Note that the casing 141. Developing roller! At a position corresponding to the upper part of 3I, developer G, (toner TI+
The toner concentration detector 43, which detects the concentration of the toner T in the developing side G by magnetically detecting the change in the magnetic permeability of the carrier c+), has been replaced.

Further, the developing roller I31. is a horizontal line passing through the center of rotation of photoreceptor drum No. 3, and is at an angle α (approximately 51
A magnetic roll (magnet) 143 whose center is located on a straight line L2 that is attracted to a state where
．． and a sleeve (carrying body) 74 (,) which is fitted onto the magnetic roll I431 and rotates clockwise in the figure.

The magnetic roll 143□ has five magnetic pole parts I45. ~14
9, of which the magnetic pole portion 145. ．． 147. .

I49I is the N pole, magnetic pole part 146. , 148. is the S pole, and the magnetic pole part Z45. and 146. The angle θ between
is approximately 50°, and the magnetic pole portion 146. The angle θ between and 1471
, is about 71', and the magnetic pole part I47. and 148. The angle θ3 between the magnetic pole portion I48. and 149. The angle θ between them is set to approximately 60°.

Further, the toner supply section I33. is toner supply port I5
0. #7511 facing the developer storage section 138 of the developing mechanism section 1321, and the developer replenishing port 150. Toner replenishment roller 152. , and this toner supply roller 152. Place toner T1 on the side/4
151. a pair of stirring rollers 153 for stirring the toner inside
．． ．． 153. It has a configuration with.

Further, the second developing device 16b is the first developing device 16 described above.
It has almost the same basic configuration as the toner replenishing unit I33.a, which constitutes the toner replenishing device 42. Hora I'? 1
51. shape and developing roller 131. magnetic roll I
43. The arrangement structure of the magnetic poles, and the toner concentration detector 44
The mounting position etc. are different. Therefore, other identical components will be designated by symbols with the suffix character changed from "," to "," and detailed explanation will be omitted. Further, the developing roller 137. magnetic roll I43. is the four magnetic pole part I4
5. ~Z48. , of which a magnetic pole portion 145. ,2
47. is the N pole, the magnetic pole part 146. , 14g.

is the S pole, and the magnetic pole part I45. and 146. The angle θ between the magnetic pole part Z46. and 147° is approximately 700, and the magnetic pole portion 147. and 1481, respectively, are set to about 80'.

Moreover, the magnetic roll 143. is provided with its center located above a straight line that passes through the center of rotation of the photosensitive drum I3 and is drawn at an angle β (approximately lO) with respect to the horizontal line.

On the other hand, each magnetic roll 143. of the first developing device 16m and the second developing device 16b. ．． 143° has a configuration that can be rotated to a state where the rotation angle is approximately 30°, and along with this rotational displacement operation, the developing roller 131
．． ．． 131. Developer magnetic brush 1351.13 on the surface of
5! It is now possible to remove the formed parts and remove them.

The magnetic rolls I 431 and 143g of the first developing device 16h and the second developing device 16b act as a magnetic roll driving means 160, which will be described later. ．． 160t, the developing row 2131.K of either the first developing device 16m or the second developing device I6b. ．． 131
．． The developer is applied only to the surface of the magnetic brush 135. ．． 135. is starting to form.

That is, when operating the first developing device 16 & side,
As shown in FIG. 8, the magnetic roll I on the first developing device 16* side
431 is the magnetic pole part (developing magnetic pole) 1471 is the developing position 13
61, that is, located in the opening 141 a+ portion, and the magnetic pole part Z45. and 146. The doctor l371 is positioned approximately midway between the magnetic roll 143 and the magnetic roll 143 on the second developing device 16b side. The magnetic pole part (developing magnetic pole) 747. The opening is 141 m! The casing 141 is located inside the magnetic pole part 145. is Doctor 137! so that they are facing each other. The developing roller 131 on the first developing device 16th side. The developer is applied only to the surface of the magnetic brush 135. K is set so that it is formed.

In addition, when operating the side plate of the second developing unit 16b, the eighth developing unit 16b is operated.
As shown in the figure, the magnetic roll I43 on the side of the first developing device 16h
．． is rotated about 30 degrees clockwise from the position shown in FIG. and facing the magnetic pole part I471 from the opening 141 as in the casing 1.
41. A magnetic roll 143 .located inside and on the second developing device 16b side. is rotated approximately 30 degrees counterclockwise from the position shown in FIG. 8, and the magnetic pole portion I47. is the development position 136
degree, that is, located at the opening 141 at portion, and the magnetic pole portion I45. Dr. 137. and 1461. position.

And the developing roller 13Z on the second developing device 16b side! 135. Apply developer magnetic silica only on the surface of the 135. is starting to form. ,,.

Note that the magnetic roll 1431. 143. magnetic pole part 145
,．． 145. Doctors 137, . . . are made of non-magnetic material. 1
37. When facing the developing roller 131. .

131, developer magnetic brush 1351.135t on the surface of
The reason why the magnetic pole part 145. .

At point 145t, the density of the magnetic gran is in the slant Q state, so the force to attract the developer G, , G is weak, and therefore the doctor 137. , 137. This is because the sleeve can be easily regulated by 144 m.

I44. Even if the developer rotates, the developer Gl+ Gt is doctor 1
371.137. Avoid passing through the section.

Next, the developing roller 131. To form or remove developer magnetic brush r3s, (rss,) on the surface of (Z,?Z,), magnetic roll 143. Magnetic roll drive means 160° (7s o,
) will be explained with reference to FIGS. 10 to 12(a) and (b). The magnetic roll 143, (r 4
One end of the axis rst, (762,) of frame 1
62, and a lever 164 is attached to the tip thereof. The tip of this lever 164 is engaged with an engagement groove 167 of an arm 166 rotatably attached via a support shaft 165. Furthermore, a support part 168 formed at the lower part of the pivot end side of the arm 166 is connected to the glasher 170 of the solenoid P169, and one end of the tension spring 112 is connected to a support part 171 formed at the upper part of the pivot end side. has been done.

Therefore, when the solenoid 169 is off, the arm 166 is moved to the first position by the biasing force of the tension spring 172.
The position shown by the two-dot chain line in Fig. 1, that is, the magnetic pole part 145° (145,) as shown in Fig.
The lever 164 is held in the opposing position. Therefore, the solenoid, 169
When the developing roller 1311 (131,) is turned off, the developer magnetic brush 135t (f35.) is not formed on the surface of the developing roller 1311 (131,). Further, when the solenoid 169 is in the ON state, the arm 166 is
72, the magnetic pole parts r4s, (I4
5. ) to a position facing the doctor rsv1(I3y,)K, and -164 is rotationally displaced. It looks like this. Therefore, when the solenoid 169 is turned on, a developer magnetic brush rss (ZJ5.) is formed on the surface of the developing roller rsl (131).

In addition, 155. shown in FIGS. 8 and 9. is the toner T in the hole 41151 of the second developing device 16b.

This is a toner remaining amount detection device that detects when the amount of toner T has fallen below a predetermined value. It is configured to operate when the permanent magnet 158 comes close to a reed switch 159 as a detector provided on the outside of the hora z41512. Although not shown, the toner remaining amount detection device 155. A toner remaining amount detection device having a similar configuration is provided.

Further, 180 is a permanent magnet constituting the conveying magnetic force line breaking means 1111 disposed near the doctor 137 of the first developing device I6a, and when the first developing roller 1311 is not in operation, the first magnetic pole portion 145m and the 2 magnetic pole part 146. The developer magnetic brush 135. The structure is such that the removal efficiency from the sleeve 144° is increased.

Next, the developing operation of the developing device I6 will be explained. First, when the first developer I6a is selected to operate using the color selection key, the magnetic rolls 143, . 143. is the 8th
When the state shown in the figure is reached, the first roller 131. Sleeve 144. rotates clockwise in the state shown in FIG. 8, and the sleeve I44. developer magnetic brush 135.
form. Then, the electrostatic latent image previously formed on the photoreceptor drum I3 is developed with the color developer G1. In this way, when the development of the electrostatic latent image is completed, the magnetic roll! 43° is rotated by about 30° so that the magnetic pole portion 1451 faces the doctor 137, the developer magnetic brush 135.
The new formation of the sleeve 14 is stopped, and in this state, the sleeve 14 is further formed.
4. rotates a predetermined number of rotations, and the developer magnetic brush I35. is removed. Note that at this time, the second developing roller Z31! Even developer magnetic brush I35! is not formed, so that even if one of the developing units 16m and 16b is selected next, problems such as color mixing will not occur.

Further, when the second developing device 16b is selected to perform black development, the magnetic roll 143. ．． When the angle becomes 143° as shown in FIG. 9, the sleeve I4 of the second developing roller 131
4! rotates clockwise in the state shown in FIG. 9, and the three f144. developer magnetic brush 135. form. After the electrostatic latent image on the photosensitive drum 13 is developed to black in the same manner as described above, the sleeve 144. From the surface of the developer magnetic brush I35. The developing operation ends with the removed.

Next, the structure of the transporting magnetic field line breaking means 181 disposed near the doctor I37° of the first moving device 16 will be explained with reference to FIGS. 13 to 15.

First, the permanent magnet 1 constituting the conveying magnetic force line breaking means I81
80 is as thin as about 1IIII as shown in FIG. 13, and its magnetic lines of force run in the thickness direction as shown in FIG. Moreover, the strength of the magnetic force of this permanent magnet 180 is the same as that of the magnetic pole part 145 for conveyance. , 146. ,14g,,1
49. 500 is set to be larger than 400. At this time, the developing magnetic pole portion I471 is set to 1000 mm.

Then, as shown in FIGS. 8 and 9, the permanent magnet 18
The N pole of 0 is the developing roller 731. Development position 136. and r
The developing device 161 faces the peripheral surface between the lid 13 and the lid 13.
Install horizontally against the

By arranging the permanent magnet 1110 as the first developing device 16hK conveying magnetic field line breaking means 181 in this way, the first developing roller! 311, when the developer magnetic brush 135I is not formed on the first magnetic pole portion I45.311, as shown in FIG. is Doctor 137. Opposed to the sleeve 144. as previously described. When the upper developer magnetic brush 135 is removed, the second magnetic pole portion I46. A line of magnetic force is formed between the S pole of the permanent magnet 180 and the N pole of the permanent magnet 180, and the second magnetic pole part I461 and the first magnetic pole part 14
5I is in a state where the transport magnetic field lines a are destroyed.

Note that during the developing operation, the lines of magnetic force of the permanent magnet 180 and the second
Magnetic pole part 146. Since the lines of magnetic force are perpendicular to each other,
Second magnetic pole part I46. The influence of the permanent magnet 180 on the second magnetic pole portion I46. and the first magnetic pole part 1451
The transporting operation of the developer G is not impaired by destroying the transporting magnetic line of force a between the developer G and the developer G.

In this way, when the developer magnetic brush l351 is removed, the second magnetic pole portion 146. S pole and permanent magnet 111
A line of magnetic force is formed between the N pole of 0 and the second magnetic pole part 14.
6. Since the transport magnetic line of force a between the first magnetic pole portion 145° and the first magnetic pole portion 145° is broken, the developer G can be taken out even if the fluidity of the developer G1 or the magnetization characteristics of the carrier CI change. There is no sleeve 144. The upper developer magnetic brush Gt can be reduced to almost zero.

Therefore, when developing with the second developing device 16b, there is no introduction by the first developing device 16bK, and a high quality image can be obtained.

Further, as shown in FIG. 16, the first developing roller 131
．． The gap d1 between the sleeve I441 and the photoreceptor P ram I3 of the second developing roller 131. Sleeve I44.
and the photoreceptor drum 13 (a).
t>at) is set.

Further, the sleeve 144 of the first developing roller 1311 has a surface 1441m processed to have a smooth surface with a roughness of about 3 μm, and the sleeve I44. The upper developer magnetic brush 1351 can be easily removed. Also,
Three f144 of the second developing roller I31. is its surface 144. The roughness of a' is 10 to 2 by San Pf-7 stroke processing, wire: brush processing, knurling processing, etc.
00 μm rough surface, developer magnetic brush 1
35. - the first developing row 2131
The developer magnetic brush 1351 is set so that it can stand up higher than the developer magnetic brush 1351 formed at m.

Note that the carrier C8 in the developer G1 used in the first developer 16m is spherical, and the carrier C1 in the developer G used in the second developer 1''6b is more spherical than that used in the first developer 16m. It is better to have a less spherical shape or a timeless shape. However, the surface 144 of the sleeve I44 of the first developing roller 1311 is smoothed so that the developer magnetic brush 351 on the sleeve I441 is smoothed. Developer magnetic brush ・I35
．． It is possible to prevent electrostatic latent scratches from leaking due to contact with the surface of the photoreceptor drum 13.

Further, during the developing operation by the first developing device 16h, the developer magnetic brush Z35. of the second developing device 16b. Even if the developer G is not removed reliably and remains on the stripper 144, the gap d between the second developer 16b and the photoreceptor ram 13 is set wide, 1 developing device 16
The upper development surface of the photoreceptor drum j3 developed in step h is not contaminated.

Further, while the selected developing device 16'a (1'6b) is operating, the developing bias of the other developing device 16b (Zgm) is cut by the developing device 16'a (1'6b), which will be described later. The developer magnetic brush rss, (rss,) of the developing device 16b (I6-), which is not used, is designed to prevent a decrease in surface potential due to contact with the photosensitive drum 13 for some reason.

That is, as shown in FIGS. 17(a) and 17(b), the first developing roller 131. is the contact 190 of the first relay 190
Also, the second developing roller 131° is connected to the bias voltage !92 through contact 1 (11) of the second relay 191.

Further, the first relay 190 and the second relay 191 are connected to a control section 220 as shown in FIG. 18, and the color selection key 104 is connected to the control section 220. . And color selection key 704
This configuration constitutes a developing device that is switched in conjunction with the color selection operation.

Then, as shown in FIG. 17(a), the second damage device 1
6b is selected and the developer magnetic brush 135t is formed on the surface of the second developing roller I31°, the first contact 190m is open, the second contact 191m is closed, and the second developing roller 131, K (D only, the developing bias is applied.

Further, as shown in FIG. 17(b), the first developing device I6
Hatake is selected and the first challenger is Roller 131. Developer magnetic plan 135. is formed, the first
contact! The contact 90a is closed, the second contact 191m is open, and only the first developing roller 131.degree.

``In this way, the selected developing device te a (16b
) is operating, the other developer 16 b (1:6'
*Developer 1 is not used because the developing bias of ) is cut.
6b (76m) developer magnetic brush 135. (13
5,) will prevent the surface potential from decreasing due to contact with the photoconductor door 3 for some reason.
'In addition, relay 1
90,191 contact point 190m.

Insulation resistance for 191m is 50MΩ with 1000V megger
It is set above.

Further, as shown in FIGS. 19 and 20, the toner concentration detector 44 of the first and second developing device Z6a is connected to the developer agitator I4.
The detection surface 211g of the head portion 211 is provided so as to face the central portion of the head portion 211 in the longitudinal direction.

The head portion 112 of the toner concentration detector 44 includes a second
As shown in Figure 1, a coil 21 that generates a magnetic field inside
2,212 is built-in, and the magnetic permeability changes depending on the mixing ratio of the developer G flowing on the surface of the detection surface 112*, the carrier C7 which is a magnetic material, and the toner T which is a non-magnetic material. The concentration of the toner T in the developer Gt is detected by converting the change in the magnetic field generated by the coil to the change in the inductance of the coil.

Compared to the conventional probe, in which the toner T is once attached to the probe, the toner T is irradiated with light, and the toner concentration inside the developing side G is detected by the reflected light, a separate drive mechanism is not required. The toner concentration detection device and its associated installation can reduce space, do not require regular maintenance due to dirt on the detection part due to toner scattering, etc., and are not affected by environmental changes. Therefore, stable toner concentration detection can be performed.

Note that the toner concentration detector 43 of the first developing device 16g has a similar configuration. Also, as shown in Figure 22,
Developer stirring body 140 of the second developing device 16m. is sleeve I44. Counterclockwise direction (direction of arrow a) opposite to the direction of rotation of
It rotates to scoop up the developer G downward.

For example, as the number of copies is added to the rotation of the carrier C1, a melt of the toner T is formed, and the flow rate of the developer G changes, causing the toner concentration detector 4
The flow of the developer G in the arrangement part 4 may become poor, or
Scree 4139. Even if the amount of developer G2 is slightly changed due to accumulation on the surface, the entire detection surface 211m of the toner concentration detector 44 is always covered with the developer G2, so that stable toner concentration detection can be performed. It's K.

Furthermore, the sensitivity of the toner concentration detector 44 is determined by the detection surface 21Im of the toner concentration detector 44 and the developer stirring body 140. Although it varies depending on the gap H between the two, based on the experimental data shown in FIG. 23, it is set to 500 or less in order to maintain an appropriate image density, and to ensure stable detection operation.

Note that the developer G is the developer agitator 140. Since the developer G is scraped up in a corrective manner by the detector 44, the flow of the developer G at the detector 44 is not affected by the weight of the developer G, and the control will not go out of order even with a slight change in weight.

Further, as shown in FIG. 24, there is also a scraper plate I39. which separates the developer G from the developing roller 13I. A first inclined portion 1392 is formed in a dogleg shape and separates the developer G.
．． and a second inclined part 139. which has a steeper inclination than this and guides the separated developer G to a developer agitating member 140°K. b.

Further, the rear end of the second inclined portion 139vb is located at the developer stirring body 140. The second inclined portions 139,b and the developer stirring body 1 are positioned above the horizontal line a passing through the center of
40. A V-shaped space A is formed between the second inclined portion 139. b and casing 1
4I, the gap H between them is regulated.

Therefore, the first inclined portion 139□ causes the developing roller I31 to
．． The developer G separated from the second slope 139. is steeper than the second slope 139. b, the developer agitator I40. The developing roller I31. Is the developer G separated from the scrape A? 139 without getting stuck in the developer storage section 1.
38. will be smoothly guided. Also, S(-S A
By forming this, it is possible to lengthen the stirring time between the used developer G and the replenished toner T, and by regulating the gap H, it is possible to prevent the toner T from being insufficiently stirred. Developing roller 131. This makes it possible to prevent the toner T from scattering due to the IIC being drawn out.

Also, Suclay 4139. is not limited to a dogleg shape, but is also a flat plate shape as shown by the two-dot chain line in Fig. 24.
139. ' has the same effect.

Further, as shown in FIG. 24, a gap C of about 5 m is formed between the developing roller 131 and the screen head 139, and the developer magnetic brush I35. Among them, the outer number ■ developer G, which contributes to development, is scraped 1'113
9. The developer agitator Z40. The remaining developer G, which does not contribute to development, is transferred to the unseparated magnetic brush 735.
' as the developing roller 131. It is designed so that it can be rotated while remaining on the surface.

In this way, the unseparated magnetic brush 135. ' If you actively leave this unseparated magnetic brush 135. ' becomes magnetized as it rotates, and the developer storage section 13
The suction force (force in the direction indicated by arrow A) of the developer G from 8□ increases, and the developer G2 is evenly supplied to the developing row 2131.

Therefore, the developing roller 131. By supplying the developer G2 evenly to the surface, it is possible to reliably prevent uneven development due to uneven supply of the developer.

Further, the second developing device 16b stores 500 tons of developer G as standard, toner T, and carrier C.
1 is a weight ratio of toner: carrier = 4:100.
The ratio is .

Further, the carrier C2 has a conventional particle size of 74 μrrL.
~150 μm, the surface is not a coarse crystal, but a fine surface crystal, and the proportion of particles with a particle size of 44 μm or less is 10% by weight or less, and the ferrite carrier has a small particle size with a peak of 44 to 105 μm. , zinc, barium, manganese, etc.).

In addition, FIG. 25 shows the relationship between the number of copies and changes in various items due to the difference in particle size of carrier C2.
It can be seen that the image density and the amount of charge are stabilized by using carrier C1 having a small particle size.

Note that if the proportion of the micro carrier C2 (particle size is 44 μm or less) is increased, the absolute value of the amount of charge of the carrier C1 becomes too large, resulting in a decrease in image density and a shortened life.

Furthermore, as shown in the table below, increasing the proportion of carrier C2 with a particle size of 44 μm or less is undesirable because it causes scratches and black spots on the photoreceptor drum Z3. No black spots were observed even after 40,000 copies were made.

The table also shows that when using the ferrite carrier C3, in which the proportion of fine surface crystals with a particle size of 44 μm or less is 10% by weight or less, and the small particle size has a peak of 44 to 105 μm, the toner has a long life. It has the effect of reducing scattering and providing highly detailed image quality, as well as the second
The standard developer storage amount in the developing device 16b is 500? In contrast, the storage amount of developer G is about 3oot (about 30%)
It was confirmed that even if development was performed in a reduced state, there was no change at all, and good development was performed.

Note that similar results were obtained in the first developing device 16m by using the same carrier C0 as the carrier C6 used in the second developing device 16b.

In addition, FIG. 26 shows the difference in the particle size of the toner, copying,
This graph shows the relationship between the number of sheets and the change in fog. Compared to conventional large particle size toner (12 μrrL to 15 μrrL), by using toner T with a small particle size of 11 μm or less, fog is reduced. Therefore, this small particle size toner TI (Tt) is a small particle size toner in which the ratio of the aforementioned fine surface crystals with a particle size of 44 μm or less is 10% by weight or less, and the peak size is 44 to 105 μm. When used in addition to the particle size of the ferrite carrier CI (Ct), further stability of image density can be obtained. (See Figure 25) The reason for this is that the toner 'r+('rt From a microscopic point of view, the charging of ) is toner T, and one particle of ('rt) is carrier C.
, '(Ct) by rubbing against one crystal on the surface. Therefore, if the surface of the carrier CI (C2) is fine and uniform, the charge imparting area from the carrier CI (C2) to the toner 'r+('rt) will be larger than that of a carrier with normal surface crystals. Due to its small size, toner TI
When a carrier having a normal surface crystal is used, the charging of (Tt) is uniform throughout the KJt, and the absolute value of the charging amount is small.

In this way, if the small particle size carrier C, (ct)K small particle size toner Tl ('rt) is used, the amount of charge will be larger than when using a normal particle size toner, so the letter K Smearing and fogging can be prevented, and since the amount of charge becomes uniform, the image density is stabilized. For 5002, the capacity of developer G is about 300f (about 30%)
It was confirmed that even if development was performed in a reduced state, there was no change at all, and good development was performed.

Note that similar results were obtained for the first current device z6a by using the same carrier C7 as the carrier C7 used for the second current device 16b.

In the above embodiment, a case was explained in which the present invention is applied to a monochromatic color copying machine, but the present invention is not limited to this. Any flaw forming device that forms an image using a developing device can be applied.

〔Effect of the invention〕

As explained above, the present invention provides a relay having a contact point for opening and closing a developing bias power supply path corresponding to each developing device, and opens and closes the contact point of the relay in accordance with the selection operation of the developing device. This is designed to cut off the developing gear from the developing device that is not used for developing. Therefore, in a developing device that has a plurality of developing devices arranged, selects one of these developing devices, and rubs a developer magnetic brush against the image carrier while applying a developing bias, it is possible to perform development while having a simple configuration. When the developer magnetic brush of an unused developer comes into contact with the image carrier, a decrease in surface potential due to K can be prevented, and a developing device capable of obtaining good images can be provided.

[Brief explanation of drawings]

FIG. 1 is an external perspective view of an image forming apparatus to which an embodiment of the developing device of the present invention is applied, FIG. 2 is a schematic longitudinal sectional front view, and FIG.
The figure is a diagram of the internal mechanism seen from the rear side, Figure 4 is a diagram showing the upper unit opened, Figure 5 is an explanatory diagram schematically showing the driving force transmission system, and Figure 6 is an illustration of the operation and control system. Floor plan of flannel,
FIG. 7 is an explanatory diagram schematically showing the exhaust system near the fixing device;
8 to 24 show the developing device, and FIGS. 8 and 9 are longitudinal sectional front views showing different operating states, respectively.
FIG. 10 is a partially sectional plan view of the magnetic roll drive means, FIG. 11 is a side view of the magnetic roll drive mechanism, FIG. 12 is an explanatory diagram showing the operating state of the magnetic roll drive means, and FIG. 13 is a side view of the magnetic roll drive means.
14 is an explanatory diagram showing the magnetic field line direction of the magnet shown in FIG. 13. FIG. 15 is an explanatory diagram showing the operating state of the conveying magnetic force line breaking means. Figure 16 shows the 1st. FIG. 17 is an explanatory diagram showing a state in which a gap is formed between the second developing roller. FIG.
Figure 8 is an explanatory diagram of the developing bias applying means, and Figure 19 is an explanatory diagram of the developing bias applying means.
FIG. 20 is a schematic longitudinal sectional front view of the developing unit; FIG. 21 is a schematic lateral plan view; FIG.
Figure 2 is a side view showing the installation state of the toner concentration detector.
Figure 3 is an explanatory diagram showing the relationship between toner concentration and detector output;
Fig. 24 is an explanatory diagram showing the shape of the scrape/flat and the state of gap formation with respect to the developing roller, Fig. 25 is an explanatory diagram showing the relationship between the number of copies and changes in various items due to differences in carrier particle size, and Fig. 26 FIG. 2 is an explanatory diagram showing the relationship between the number of copies and changes in cover due to differences in toner particle size. I3: Photosensitive drum (image carrier), I6: Developing device, I6: First developing device, 16b: Second developing device,
104...Color selection key, 190, 191...Relay, 190m, 191h...Contact point, 192...Smooth ear insulator pressure, 220...Control unit, 221...Currently current ear cut means. □ Applicant's representative Patent attorney Takehiko Suzue Figure 1' Figure 10 Figure 12 (a) (t)) Figure 15 Figure 16 Figure 17 Figure 1j 1,112 Figure 19 Figure 21) j2i Sad Fig. 24 Fig. 25 Gogoichi Mosquito (f shou) Fig. 26 Gobi Chichichi piece (f uncle J Procedural amendment form

Claims (3)

[Claims] (1) In a developing device in which a plurality of developing devices are arranged, one of these developing devices is selected, and a developer magnetic brush is rubbed against the image carrier while applying a developing bias to develop the image, the developing device is developed in correspondence with each developing device. A developing bias cutting means is provided, which includes a relay having a contact for opening and closing the bias power supply path, and cuts the developing bias of the developing device that is not used for development by opening and closing the contact of the relay according to the selection operation of the developing device. A developing device characterized by: (2) The developing device according to claim 1, wherein the contacts of each relay of the developing bias cut means are configured to be selectively opened and closed by operating a color selection key. (3) The developing device according to claim 1, wherein the insulation resistance between the contacts of the relay is 500 MΩ or more at 1000 V Megger.