JP2850320B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer employing an electrophotographic system, and in particular, temporarily supplies toner in a toner supply mode. The present invention relates to an improvement of an image forming apparatus provided with a two-component developing unit. 2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine adopting an electrophotographic system, there is one as shown in FIG. 11, for example. The latent image carrier 1 such as a photosensitive drum and the latent image carrier 1
A charging device 2 such as a corotron for pre-charging, an optical imaging system 3 for optically guiding a light image from a document (not shown) on the charged latent image carrier 1 to form a latent image, A developing device 4 for developing the latent image formed on the carrier 1 with toner, a transfer device 6 such as a corotron for transferring the toner image formed on the latent image carrier 1 to a transfer sheet 5, And a cleaner 7 for removing the toner remaining on the latent image carrier 1. In FIG. 12, reference numeral 8 denotes a resist roll for feeding the transfer sheet 5 to a transfer site at a predetermined timing, and 9 denotes a separation roller such as a corotron for separating the transfer sheet 5 from the latent image carrier 1 after the transfer process. A static eliminator 10 is a transport belt that transports the transfer sheet 5 that has undergone the transfer process to a fixing device (not shown). Assuming that a two-component developing device 4 is used in such an image forming apparatus, this type of developing device 4 is usually provided with a toner replenishing section 4b in a part of a housing 4a,
4a, a magnet roll 4c that is disposed opposite to the latent image carrier 1 to form a magnetic brush of the developer, an agitator 4d that agitates the toner as the developer and the carrier, and a developer agitated by the agitator 4d. The transport paddle 4e to be supplied to the magnet roll 4c side is stored. [Problems to be Solved by the Invention] When the image density of this type of image forming apparatus is reduced, for example, a toner supply mode switch on a console panel is turned on in a non-image forming cycle. The housing 4a by operating the toner supply section 4b.
The toner in the developing unit 4 is operated for a predetermined time to agitate the supplied toner while the toner is temporarily supplied. At this time, if the latent image carrier 1 is rotated in synchronization with the operation state of the developing device 4, no latent image is formed on the latent image carrier 1, but the latent image carrier 1 rotates with the magnetic brush of the magnet roll 4 c. Since the surface of the image carrier 1 comes into sliding contact with the surface of the image carrier 1,
A situation occurs in which the toner powder T slightly adheres to the latent image carrier 1. In such a state, the toner powder T adhered to the latent image carrier 1 is transferred to the transfer device 6 by the rotation of the latent image carrier 1.
After passing through the stripping neutralizer 9, it reaches the cleaner 7. However, from the viewpoint of preventing damage to the latent image carrier 1 as much as possible, the cleaner 7 has a retractable cleaning blade 7 a, If the cleaning blade 7a is set at the retract position during the non-image forming cycle, the toner powder T adhered to the latent image carrier 1 passes through the cleaner image 7 without being removed by the cleaner 7, and the latent image is removed. It remains on the image carrier 1. Then, in the next image forming cycle, the charging device 2 and the transfer device 6
When the discharger 9 for peeling is operated, the toner powder T adhered on the latent image carrier 1 scatters around the latent image carrier 1 due to the discharge phenomenon or the like, and the image on the transfer sheet 5 is transferred. May be adversely affected on image quality such as being stained by the scattered toner powder. As a means for solving such a problem, it is conceivable to stop the single latent image carrier 1 in the toner supply mode so that the floating toner does not rotate together with the latent image carrier 1. Since the outflow of the floating toner from the toner cannot be prevented, the situation where the floating toner adheres to the latent image carrier 1 is inevitable, and in the next image forming cycle, the latent image is caused by the operation of the transfer device 6 and the removing device 9 for peeling. The problem that the floating toner attached to the carrier 1 scatters cannot be completely avoided. [Means for Solving the Problems] The present invention has been made in view of the above problems, and has an image in which the scattering phenomenon of the toner powder accompanying the toner supply operation is almost completely avoided. A forming apparatus is provided. That is, as shown in FIG. 1, the present invention includes a latent image carrier 1, a toner replenishing section 4b for replenishing toner in a toner replenishing mode, and a developer carrier 4c for forming a magnetic brush. An image forming apparatus including a two-component developing unit 4 for applying a developing bias to the developer carrier 4c in a cycle to develop the latent image formed on the latent image carrier 1 with toner; When the toner replenishing unit 4b replenishes the toner under the condition that the toner replenishment mode is selected in the non-image forming cycle and the auxiliary bias applying unit 11 that applies the toner retaining auxiliary bias Vs to the body 4c, Control means for applying the auxiliary bias Vs to the developer carrier 4c. In such technical means, the latent image carrier 1 may be appropriately selected as long as it can form a latent image, such as a photoreceptor or a dielectric. , Regardless of the shape of the belt. Further, the two-component developing means 4 may be a fixed type or a retractable type. Further, the specific configuration of the developer such as the color, physical properties, type of carrier and the like of the toner used in the two-component developing means 4 may be appropriately selected. As long as toner can be supplied into the developing means 4, a toner box may be directly installed on the upper part of the housing of the developing means 4,
To form a color image, a plurality of developing means are vertically arranged side by side, and in the case of using the developing means 4 on the lower side, a toner box is provided on the side of the housing of the developing means 4. The design may be changed as appropriate, for example, the guide may be guided into the housing of the developing means 4 by an appropriate transport means. In addition, the housing member in the housing may include at least an agitator for stirring the replenishment toner in addition to the developer carrier 4c. Also, the method of applying the developing bias to the developer carrier 4c can be appropriately changed in design using a known method. Further, the auxiliary bias applying means 11 may be appropriately designed and modified as long as it does not form an electric field that causes the toner around the developer carrier 4c to move to the latent image carrier 1 during the toner supply operation. Absent. In this case, as the auxiliary bias Vs of the auxiliary bias applying means 11, it is preferable to form an electric field that positively attracts and holds the toner on the developer carrier 1 side. The bias potential is obtained by applying an appropriate bias having the opposite polarity to the
Those having about 0 to 550 V are particularly preferable. In addition, if a developing bias level is selected as the auxiliary bias Vs, it is possible to adopt a configuration in which the auxiliary bias applying unit 11 and the developing bias applying unit are commonly used.
This is preferable in that the configuration of the device is not complicated. [Operation] According to the technical means described above, the auxiliary bias applying means 11 applies the auxiliary bias Vs for toner holding to the developer carrier 4c when the toner replenishment mode is selected in the non-image forming cycle. As a result, an electric field for transferring the toner around the developer carrier 4c to the latent image carrier 1 is not formed, and the toner does not flow out to the latent image carrier 1 actively. Hereinafter, the present invention will be described in detail based on an embodiment shown in the accompanying drawings. FIG. 2 shows an example in which the present invention is applied to a two-color copying machine for reproducing a two-color original of red and black. In FIG. 1, reference numeral 1 denotes a latent image carrier made of, for example, a photosensitive drum, 2 denotes a charger made of a corotron or the like that pre-charges the latent image carrier 1, 3 denotes an exposure lamp 3a, and an optical path of light reflected from the document 22 A plurality of mirrors 3b, an image forming lens 3c for setting an image forming position on the latent image carrier 1, and an optical filter selectively interposed in an optical path when extracting a red portion of the document 22.
3d, an optical image forming system for forming a light image from the document 22 on the platen 21 on the latent image carrier 1 side, 4 is a two-component developing device capable of supplying black toner, and 4 ' Developing unit 4
, A detachable two-component developing unit which contains a predetermined amount of red toner in advance without planning to supply red toner, 5 is a copy sheet, 6 is a transfer unit made of corotron or the like, 7 is a cleaner, 8 Is a resist roll for feeding the copy sheet 5 to the transfer site at a predetermined timing, 9 is a stripping neutralizer made of corotron or the like for peeling the copy sheet 5 after the transfer step from the latent image carrier 1, and 10 is a transfer step. The transport belt transports the passed copy sheet 5. Reference numeral 23 denotes an eraser disposed after the charger 2 for erasing charges on the surface of the latent image carrier 1 other than the area of the document 22. Reference numeral 24 denotes a multi-stage sheet in which copy sheets 5 of various sizes are stored in advance. A feed tray 25, a sheet feeding mechanism for conveying the copy sheet 5 from the sheet feed tray 24 to the position of the registration roll 8; a fixing device 26 for fixing a toner image on the copy sheet 5 after the transfer process; Is a discharge tray for discharging and housing the copy sheet 5 after fixing, and 28 is a return transport path 29 for transferring the copy sheet 5 after fixing when performing double-sided copying and multiple copying.
A switching member 30 for guiding to the intermediate tray (not shown) for double-sided copying and multiplex copying via the, and a copying member 30 disposed at the subsequent stage of the removing device 9 for peeling and ensuring the copy sheet 5 wrapped around the latent image carrier 1 A console panel as an operation unit provided on a part of the body of the copying machine; 32, a start switch for copying operation provided on the console panel 31; This is a toner supply mode switch that is pressed to select the toner supply mode. In this embodiment, the black developing device 4 uses a two-component developer consisting of a carrier and a black toner that is triboelectrically charged to a negative polarity. As shown in FIG. While a toner replenishing part 4b is provided in a part, a magnet roll 4c forming a magnetic brush of the developer, an agitator 4d for stirring the developer,
The transport paddle 4e that supplies the stirred developer to the magnet roll 4c and a metal trimming bar 4f that regulates a trimming gap of the developer on the magnet roll 4c are stored. Since the red developing device 4 'is disposed above the developing device 4, the toner replenishing section 4b communicates with a hopper-shaped toner box 41 on the side of the housing 4a. At the same time, a dispense roll 42 for adjusting the toner supply amount is provided on the base side of the toner box 41, while the toner supplied from the toner box 41 is uniformly distributed in the housing 4a along the width direction in the housing 4a. The transport auger 43 to be supplied is provided. As shown in FIG. 4, the magnet roll 4c includes, for example, a magnet fixed shaft 44 around which a large number of magnets are embedded, and a rotating sleeve 45 rotatably fitted around the magnet fixed shaft 44. The developing bias (for example, 200 to 550 V) and the auxiliary bias V described later are applied to the magnet fixed shaft 44 of the magnet roll 4c.
bias applying means 50 for applying s (equal to the developing bias in this embodiment) (corresponding to auxiliary bias applying means 11)
Is attached. In this embodiment, the bias applying means 50 includes a bias control power supply 51 for supplying a bias voltage at an appropriate timing, a power supply side connector 52 connected to the bias control power supply 51 via a harness (not shown), and a developing device 4. The power supply side connector arranged on the housing 4a
A developing device side connector 53 detachably connected to 52, a harness 54 having one end connected to the developing device side connector 53 and the other end connected to one end side of a metal trimming bar 4f,
A metal plate 55 attached to the other end of the trimming bar 4f and connected to the support portion 44a of the magnet fixed shaft 44.The bias from the bias control power supply 51 is supplied to the connectors 52 and 53, the harness 54, and the trimming bar. 4f, plate 55
Through the magnet roll 4c. The cleaner 7 is, as shown in FIG.
A retractable blade 7b is provided in the housing 7a, and a retractable toner receiving seal 7c is provided below the blade 7b in conjunction with the blade 7b. A transfer auger 7d is provided to transfer the sheet to the collection section. In this embodiment, the blade 7b is supported via a bracket 62 on a rotating arm 61 that rotates within a predetermined angle range as the electromagnetic actuator 60 advances and retreats. The retracted position P2 is set away from the cleaning position P1 in contact with the carrier 1. On the other hand, the toner receiving seal 7c is urged toward the latent image carrier 1 by a spring means (not shown) and is supported in the housing 7a via a rotatable support arm 63. By engaging the fixed engaging plate 64 with the extended engaging portion 61a of the rotating arm 61, the seal position Q1 and the retract position Q2, the leading ends of which contact the latent image carrier 1 in conjunction with the movement of the blade 7b. And move between them. Further, in this embodiment, the toner supply mode control system is realized by a microcomputer system shown in FIG. In the figure, the selection signal from the toner supply mode switch 33 is input to the CPU 72 via the input interface 71. The CPU 72 executes a toner supply mode program stored in the ROM 73 in advance based on the input data, and exchanges data with the RAM 74. Then, the CPU 72 performs the toner supply operation start signal Sa, the toner stirring operation start signal Sb,
The auxiliary bias application signal Sc, the latent image carrier operation start signal Sd, and the blade operation start signal Se are output via the output interface 75, and as shown in the timing chart of FIG. The drive system 4g, the bias control power supply 51, the power supply 81 of the main motor 80 for driving the latent image carrier 1, and the electromagnetic actuator 60 for driving the blade 7b are controlled. Next, the operation of the image forming apparatus according to this embodiment in the toner mode will be described. If the toner supply mode switch 33 is turned on to supply toner to the developing device 4 in the non-image forming cycle because the image density is low, the CPU 72 sets the toner supply mode switch shown in FIG. After recognizing the ON signal of 33, the above-described toner supply mode program is executed. In this case, first, the CPU 72 executes the toner supply operation start signal S
a to the toner replenishing section 4b, and as shown in FIG. 7 (b), the dispense roll 42 is turned on, and the toner in the toner box 41 is transferred from the dispense roll 42 to the housing 4a via the transport auger 43. Also, a toner stirring operation start signal Sb is sent to the developing device driving system 4g, and the developing device driving system 4g is operated at the timing shown in FIG. 7 (c), and the magnet roll 4c, the agitator 4d and the transport paddle are operated.
4e are simultaneously driven to stir the replenishment toner in the housing 4a. Further, an auxiliary bias application signal Sc is sent to the bias control power supply 51, and the auxiliary bias Vs is applied to the magnet roll 4c at the timing shown in FIG. Apply to In this state, focusing on the periphery of the developing device 4, the third
As shown in FIG. 8 and FIG. 8, since each member in the developing device 4 operates during the toner stirring operation, the housing 4a
When the toner 90 is about to flow out to the latent image carrier 1 through the opening, the auxiliary bias Vs from the bias control power supply 51 is applied to the magnet roll 4c, and the gap between the agnet roll 4c and the latent image carrier 1 Since an electrostatic field S from the latent image carrier 1 side to the magnet roll 4c side is formed, the action of the electrostatic field S causes the negative toner 90 around the carrier 91 to be attracted to the magnet roll 4c side. Thus, the toner 90 is effectively held out of the housing 4a by being held on the magnet roll 4c. Further, in this embodiment, in parallel with the operation of the developing device 4 in the toner supply mode, the CPU 72 sends out the latent image carrier operation signal Sd, and as shown in FIG. The latent image carrier 1 is rotationally driven by rotating 80,
Further, a blade operation signal Se is transmitted, and as shown in FIG. 7 (f), the electromagnetic actuator 60 is turned on to set the blade 7b from the retract position P2 to the cleaning position P1. Therefore, in this embodiment, even if the toner 90 from the developing device 4 floats and adheres to the latent image carrier 1 side, as shown in FIG.
The blade 90 is guided to the cleaner 7 by the rotation of the latent image carrier 1 and then reliably scraped off by the blade 7b set at the cleaning position P1. Therefore, in the next image forming cycle, even if the charger 2 and the transfer unit 6 perform a discharging operation or the like, the toner 90 on the latent image carrier 1 is reliably removed, and the toner 90 is almost not scattered. Completely avoided. Further, in this embodiment, since the magnet roll 4c of the developing device 4 and the latent image carrier 1 are in sliding contact with each other while rotating each other, the frictional resistance between the two is extremely small, and the latent image carrier 1 is improper. It will not be damaged as needed. Thereafter, when the output of each of the control signals Sa to Se from the CPU 72 is stopped at an appropriate timing, the toner supply operation, the toner stirring operation in the developing device 4, the auxiliary bias Vs
Is completed, the rotation of the latent image carrier 1 stops, and the blade 7b returns to the retract position P2. In this embodiment, as shown in FIGS. 10A and 10B, the blade 7b is set to the cleaning position P1 in synchronization with the ON operation signal of the toner supply mode switch 33. In addition to this, as shown in FIG. 10 (c), the charging system common power sources such as the charger 2, the transfer unit 6, and the stripping neutralizer 9 are activated, and as shown in FIG. 10 (d). During the startup period of the charging system common power supply,
Is turned on and is turned off only for a short period of time t.
A band-like latent image portion (high potential portion) on the surface of the latent image carrier 1 corresponding to the timing of turning off the eraser 23 is developed by the toner in the developing device 4, and this toner band is supplied to the blade 7b. Therefore, the toner band functions as a kind of lubricant, and damage between the blade 7b and the latent image carrier 1 can be reduced. [Effects of the Invention] As described above, according to the image forming apparatus of the present invention, the floating toner is caused to flow out of the two-component developing unit by holding the floating toner on the developer carrier in the toner supply mode. Therefore, it is possible to effectively prevent the floating toner from adhering to the latent image carrier. For this reason, the scattering of the toner powder in the image forming apparatus can be substantially completely prevented, and the image quality of the transfer sheet can be kept good.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing the configuration of an image forming apparatus according to the present invention, FIG. 2 is an explanatory view showing an embodiment of the image forming apparatus according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing details of a two-component developing device used in the example, FIG. 4 is a perspective explanatory diagram showing a bias application system of the two-component developing device used in the embodiment, and FIG. 5 is a cleaner used in the embodiment. FIG. 6 is a block diagram showing a specific example for realizing a toner supply mode in the image forming apparatus according to the embodiment, and FIGS. 7 (a) to (f) are images according to the embodiment. FIG. 8 is a timing chart showing an operation state of the forming apparatus in the toner supply mode, FIG. 8 is a schematic diagram showing a state around the developing device in the toner supply mode, and FIG. 9 is an explanation showing a state of the cleaner periphery in the toner supply mode. Fig. 10 (a To (d) are timing charts showing a modification of the operating state of the toner supply mode of the image forming apparatus according to the embodiment, FIG. 11 is an explanatory diagram showing an example of an image forming apparatus in the prior art. [Description of Signs] 1 ... Latent image carrier 4 ... Developer (developing unit) 4b ... Toner supply unit 4c ... Magnet roll (developer carrier) 11 ... Auxiliary bias applying unit

Claims (1)

(57) [Claims] It has a latent image carrier (1), a toner replenishing section (4b) for replenishing toner in a toner replenishing mode, and a developer carrier (4c) for forming a magnetic brush. 4c), a developing bias is applied to the latent image carrier (1), and the latent image formed on the latent image carrier (1) is developed with toner. 4c) Auxiliary bias (V
s) and an auxiliary bias applying unit (11) for applying the toner when the toner replenishment unit (4b) replenishes the toner under the condition that the toner replenishment mode is selected in the non-image forming cycle. An image forming apparatus comprising: control means (71 to 75) for applying the auxiliary bias (Vs) to the body (4c). 2. Auxiliary bias applying means (11) is auxiliary bias (Vs)
2. The image forming apparatus according to claim 1, wherein a developing bias level is selected as a value. 3. The image forming apparatus according to claim 1, wherein the latent image carrier (1) is rotating at the time of the toner supply mode.