JPH02212864A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the unnecessary adhesion of toner to a photosensitive body accompanied with impressing developing bias by forming a bristle cutting state before the developing bias is impressed on a developing device and before the leading edge of the electrostatic charging part of the photosensitive body reaches a position where the developing device is disposed and maintaining the state until it passes the disposed position of the developing device. CONSTITUTION:An image is formed in electrophotographic copying process in which the developing devices 5 and 6 disposed around the photosensitive body 1 are used. A bristle cutting means 80 performs bristle cutting processing for preventing the developer from adhering to the photosensitive body 1 to the developing devices 5 and 6. A control means 12 controls the action of the bristle cutting means 80 so that the bristle cutting state is formed before the developing bias voltage is impressed on the developing devices 5 and 6 and before the leading edge of the electrostatic charging part of the photosensitive body 1 reaches the position where the developing devices 5 and 6 are disposed and also the bristle cutting state is maintained until the leading edge of the electrostatic charging part of the photosensitive body 1 passes the position where the developing devices 5 and 6 are disposed. Thus, the unnecessary adhesion of the toner in the developer to the photosensitive body 1 accompanied with impressing the developing bias is eliminated and the wasteful consumption of the toner is reduced.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an image forming apparatus that forms images by an electrophotographic process. [Prior Art] Conventionally, electrophotographic processes have been widely used as a method for forming hard copy images in image forming apparatuses such as copying machines, facsimile machines, and optical printers using laser beams, LED arrays, and the like. In an electrophotographic process, a negatively charged photoreceptor is exposed to light in accordance with image information, thereby partially discharging the charged portion and forming a latent image. To develop a latent image, a two-component developer is generally used that triboelectrically charges toner (fine particles made by melting and mixing hot-melt resin, carbon, dye, etc.) and a carrier made of iron powder. A predetermined voltage (developing bias) is applied thereto. By applying a developing bias, the carrier in the developer is electrostatically attracted toward the developing device, and only the toner is attracted onto the photoreceptor. Now, carriers are hard fine particles, and if they adhere to the photoreceptor, a serious problem arises in that the photoreceptor and the blade of the cleaning device are damaged.
The carrier, which is originally a non-consumable item, becomes exhausted and needs to be replenished. Therefore, in conventional image forming apparatuses, immediately after charging starts on an uncharged photoreceptor, the timing at which a developing bias is applied to the developing device is adjusted to match the uncharged area and the charged area on the photoreceptor. This is done before the boundary (the tip of the charging part) reaches the position facing the developing device, to prevent carrier from adhering to the photoreceptor. [Problem to be Solved by the Invention] However, if the timing of applying the developing bias to the developing device is set as described above, carriers are prevented from adhering to the photoreceptor, but instead, the timing of applying the developing bias to the developing device is prevented. Due to the repulsion, the toner adheres to the non-charged portion of the photoreceptor. For this reason, conventional image forming apparatuses have a problem in that toner is wasted. In particular, when a separation belt is used as a separation means for separating recording paper from a photoreceptor, a separation belt is provided so that toner adhering to the photoreceptor always comes into contact with the axial end of the photoreceptor. This may cause contamination of the belt. For this reason,
There is a problem in that toner unrelated to the image adheres to the edge of the paper that is mechanically separated from the photoreceptor by the separation belt, making the paper dirty and unsightly. SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an image forming apparatus that eliminates unnecessary toner adhesion to a photoreceptor due to the application of a developing bias. [Means for Solving the Problem] In order to solve the above-mentioned problem, the invention of claim 1 provides a method in which a developing device containing a developer is disposed around a photoreceptor, and the photoreceptor and the developing device are connected to each other. The image forming apparatus is configured to move relative to each other and form an image by an electrophotographic process, and the developing unit is provided with a cutting process to prevent developer from adhering to the photoreceptor. A panicle cutting means is provided to perform panicle cutting in the developing device, and before a developing bias is applied to the developing device and before the tip of the charged portion of the photoreceptor reaches the arrangement position of the developing device, the developing device is in a panicle cutting state. The apparatus is characterized in that it is provided with a control means for controlling the head-cut state to be maintained until the tip of the charged portion of the photoreceptor passes through the position where the developing device is disposed. The invention according to claim 2 is characterized in that, in addition to the structure of the invention according to claim 1, the control means controls the developing device in which the ear cutting state is maintained not to perform the ear cutting process. Constructed as. According to a third aspect of the invention, a plurality of developing devices containing a developer are arranged around a photoreceptor, and the photoreceptor and the developing device move relatively to form an image by an electrophotographic process. In the image forming apparatus configured as follows, each of the developing units is provided with a panicle cutting unit for performing a panicking process to prevent developer from adhering to the photoreceptor, and each of the developing units Before a developing bias is applied to the photoreceptor and before the tip of the charged portion of the photoreceptor reaches the location of the developer, a panicle state is formed in each developer, and the charging of the photoreceptor is A control means is provided for controlling the cutting process to be sequentially performed on each developing device so as to maintain the cutting state of each developing device until the tip of the developing device passes through the arrangement position of each developing device. It is composed of the following characteristics. According to a fourth aspect of the invention, in addition to the configuration of the third aspect, the control means performs control so that the tip of the charged portion of the photoconductor sequentially forms the panicle state starting from the developing device that reaches first. Constructed as a feature. [Function] The image forming apparatus forms an image by an electrophotographic process using a developing device disposed around a photoreceptor. The ear cutting means performs ear cutting processing on the developing device to prevent developer from adhering to the photoreceptor. The control means is configured to form a cutting state before a developing bias voltage is applied to the developing device and before the tip of the charged portion of the photoreceptor reaches a position where the photoreceptor is disposed, and to control the charging of the photoreceptor. The operation of the ear cutting means is controlled so that the ear cutting state is maintained until the tip of the grain passes through the position where the developing device is disposed. When there are a plurality of developing devices, the control means controls the developing devices in which the cutting state is maintained not to perform the cutting process. Furthermore, control is performed to sequentially perform the ear cutting process for each developing device, and further, the panicle cutting process is performed in order from the developing device to which the tip of the charged portion of the photoreceptor reaches first. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 2 is a front sectional view of laser printer A. Laser printer A prints (hard copy image) based on print data (including image data) input together with control signals from a data processing device (not shown), such as a general-purpose computer, word processor, image reading device, or facsimile device. (printing operation). The box-shaped device main body 21 has a top cover 2 on its top surface.
2, a front cover (not shown) is attached to the front surface so that it can be opened and closed. A photoreceptor drum 1 that rotates counterclockwise is provided approximately at the center of the laser printer A, and around it are a charger 3, a first developer 5, and a third developer for the electrophotographic process. 2 developing devices 6, a transfer charging medium 7, a separation belt 8, a cleaning device 9, and a main eraser lamp 10 are arranged. During the printing operation, after the surface of the photosensitive drum l is uniformly charged to a negative polarity during charging step 3,
The portion corresponding to the image is neutralized by exposure scanning by the laser optical system, and a latent image is formed on the surface of the photosensitive drum 1. The latent image on the photosensitive drum 1 is developed by a developer 5 or 6, and transferred by a transfer charger 7 onto a sheet of paper supplied from a paper feed system P, which will be described later. Thereafter, the surface of the photosensitive drum 10 from which excess toner has been removed by the cleaning device 9 is neutralized by the main eraser lamp 10, and is prepared for the next printing operation. The paper after the transfer is separated from the photosensitive drum 1 by the separation belt 8, sent to the fixing device 11 by the conveyor belt 25, and discharged to the tray 26 after the transferred image is fixed. The paper feeding system P has a manual paper feeding section 27 and paper feeding cassettes 2 and 30 for automatic paper feeding, and the paper fed from any of these is sent to the timing roller 24 by rollers 31 to 34. , the timing is adjusted by the timing roller 24, and then conveyed to the transfer section. In addition, 35 and 36 are size detection sensors that detect the size of paper in each paper feed cassette 2B and 30, 37 and 38 are cassette empty sensors that detect the presence or absence of paper in each paper feed cassette 28 and 30, and 39 is a cassette empty sensor A cover sensor 40, which is turned on when the front cover is closed, is a density sensor for detecting the density of the toner image. The laser optical system 18 includes a semiconductor laser that is driven by a modulated pulse corresponding to a character or image to emit a laser beam, a polygon mirror that deflects the laser beam, various lenses, and the like. The control unit 12 controls the entire operation of the laser printer A including the laser optical system 18 by 111m. The power supply unit I3 is located at the bottom of the laser printer, and
It has a high-voltage transformer and high-voltage power supply circuit for boosting C100 volts, and supplies a predetermined amount of power to each part. 3 is an enlarged view of the developing device 5.6, FIG. 4 is an enlarged sectional view of the developing sleeve 44, and FIG. 5 is a perspective view of the ear cutting shutter 80 of FIG. As shown in the figure,
The first developing device 5 and the second developing device 6 have different shapes due to their arrangement, but have substantially the same mechanism and function. Therefore, in FIGS. 4 and 5, two developing devices 5
．． 6 shows the structure of the developing device sleeve 44 and the ear cutting shutter 80 of one of the developing devices 5, but in the following description, each part of the ear cutting shutter 80 will be described with reference to the structure of the first developing device 5.
The suffix ``a'' is added to the second developing device 6, and the suffix ``rb'' is added to the second developing device 6 to distinguish them. As shown in FIG. 3, a toner supply bottle 41 for replenishing toner is removably attached to the first developing device 5. Toner supply port 41 of toner supply bottle 41
A is connected to one end of a transport pipe 42 extending in the longitudinal direction (direction perpendicular to the plane of FIG. 3) within the developing device 5. In the density adjustment process to be described later, the rotational driving force of a main motor (not shown) that drives the photosensitive drum 1 is transmitted to the toner replenishment bottle 41 via a replenishment clutch (not shown), and the rotation of the toner replenishment bottle 41 is controlled. An amount of toner proportional to the number of toners is sent from the toner supply port 4fa through the transport pipe 42 into the developing device 5. The toner conveyed into the developing device 5 is mixed with the magnetic carrier filled in the developing device 5 in advance by a packet roller 43 rotated by a developing motor (not shown), and is charged to a negative polarity by friction at that time, and is charged to a negative polarity as described above. The developing sleeve 440 is supplied to the surface of the developing sleeve 440 which is rotated by the developing motor. Note that the rotation and stopping of the developing sleeve 44 is performed by a first
Controlled by the developer sleeve clutch. A first bottle presence/absence sensor 45 is installed near the toner replenishment bottle 41 to detect whether or not this toner replenishment bottle 41 is attached. A first bottle empty sensor 46 is installed to detect when the toner runs out. The upper part of the developing device 5 is also marked with toner colors (black, red, yellow,
A magnet group 47 is attached to identify the toner color (blue), and the toner color is determined, for example, as shown in Table 1, by the on/off combination of reed switches 49 and 50 placed opposite to magnet #47. . Regarding the second developing device 6 in Table 1, similarly to the first developing device 5 described above, a toner replenishing bottle 5 having a toner replenishing port 53a
3, transport pipes 54, 55, bucket roller 56, developing sleeve 57, bottle presence/absence sensor 58, bottle empty sensor 60. Magnet group 61, reed switch 63
．． 64 are arranged. Normally, the first developing device 5 stores color toner and the second developing device 6 stores black toner, but they can easily be changed to other colors by replacing the developing device. be able to. As shown in FIG. 4, the developing sleeve 44 is made of a non-magnetic conductive material formed into a cylindrical shape, and minute irregularities are formed on the outer periphery by sandblasting. and facing each other with a developing gap DS. As will be described later, a developing bias VB, which is a negative voltage, is applied to the developing sleeve 44 from the power supply section 13 during development, and a predetermined charge is given to the developing sleeve 44. Further, inside the developing sleeve 44, there is provided a magnet roller 49 having a plurality of magnets extending in the axial direction and capable of rotating at a predetermined angle.The magnetic action of these magnets causes the surface of the developing sleeve 44 to 0M where a magnetic brush consisting of magnetic carriers arranged in a brush shape is formed! Toner is attracted to the magnetic carrier of the air brush. Around the developing sleeve 44, there is a height regulating member 48 that is connected to the developing sleeve 44 with a predetermined height regulating gap.
A magnetic brush on the surface of the developing sleeve 44, that is, a panicle cutting shutter 80 is provided for a panicle cutting process that removes the developer (toner and magnetic carrier). During development, the height of the magnetic brush is adjusted by the height regulating member 48, and as the developing sleeve 44 rotates in the direction of arrow C, the magnetic brush is sequentially sent to the developing position X1. At this time, at the development position χ1, the angular position of the magnet roller 49 is controlled so that the magnetic brush ears stand up, and the tips of the magnetic brush ears come into contact with the photoreceptor drum 1. The toner in the magnetic brush adheres to the neutralized portion (the exposed portion of the latent image) of the photosensitive drum 1, which has a relatively positive potential due to the application of the developing bias VB applied to the developing sleeve 44. , a toner image will be formed. Since the positively charged magnetic carriers are attracted by the developing bias vB, the magnetic carriers that do not adhere to the surface of the photosensitive drum 1 are repeatedly used in the developing device 5. As described above, the laser printer A employs a reversal development method in which toner having the same polarity as the surface charge of the photoreceptor drum l is attached to the exposure section (static elimination section). In the following description, the position where development is performed by the second developing device 6, that is, the position where the developing sleeve 57 and the photosensitive drum l face each other with a minimum distance will be referred to as the developing position X2. As shown in FIG. 5, the ear cutting shutter 80 is made of a flat mylar sheet 82 which has approximately the same length as the developing sleeve 44 and whose longitudinal direction is parallel to the axial direction of the developing sleeve 44. and a solenoid for controlling the ear cutting process by the Mylar sheet 82, and the Mylar sheet 82 is fixed to the movable support member 81. The movable support member 81 is rotatable around a support shaft 87, and a slide bin 83 is fixed to the center of the upper part thereof. The shaft 84 is disposed behind the movable support member 81 so as to be parallel to the developing sleeve 44, and is movable along the axial direction of the developing sleeve 44 and is biased in the direction of arrow M2 by a spring (not shown). It is supported by Also,
A slider 85 fixed to the shaft 84 has a guide groove 86 formed obliquely with respect to the shaft 84, and the guide bin 83 is passed through the guide groove 86. The solenoid 88 is fixed to the main body of the laser printer A, and is connected to one end of a lever 89 that rotates around a fulcrum O. 4Urg of the lever 89 is arranged to abut against the end of the shaft 84. At all times, that is, when the laser printer A is in a standby state or in a developing operation, the solenoid 88 is in an off state. During the ear cutting process, when the solenoid 88 is turned on and the lever 89 rotates in the direction of arrow M3, the slider 85 is pushed by the lever 89 and moves together with the shaft 84 in the direction of arrow M1. Along with this, the bottle 83 moves into the guide groove 86.
As the movable support member 81 rotates in the direction of arrow M5, the tip of the Mylar sheet 82 touches the developing sleeve 4.
4. By rotating the developing sleeve 44 in this state, the portion of the surface of the developing sleeve 44 that has passed through the Mylar sheet 82 is scraped of the developer and becomes a panicle state. When the ear cutting process is completed and the solenoid 88 is turned off,
As the lever 89 rotates in the direction of arrow M4, the shaft 84 moves in the direction of arrow M2 due to the biasing force of a spring not shown, and the movable support member 81 rotates in the direction of arrow M6 to remove the developing sleeve 44 of the Mylar sheet 82. Pressure against is released. FIGS. 1(a) and 1(b) are diagrams for explaining the timing of ear cutting processing. Figure (a) shows a certain time immediately after the printing operation starts.

Positions 1 to L on the surface of the photoreceptor drum 10 at
6 and each developing device 5 and 6,
The surface of the photosensitive drum 1 is developed in a straight line. At time t+ito, position L on the surface of photoreceptor drum I]
is opposed to the developing sleeve 57 of the second developing device 6. In other words, position LX is at development position X2. Further, position 2 is located at the developing position X1, and faces the developing sleeve 44 of the first developing device 5. Position 4 is the tip of the charging section, and position 6 is the tip of the latent image. The times T3 to T6 each represent the time required for a certain position on the surface of the photoreceptor drum 1 to move by the distance indicated by the arrow when the photoreceptor drum 1 is rotating at a constant speed. For example, Time t3 when time T3 has elapsed from time to
In this case, position 3 faces the developing sleeve 44 . FIG. 1(b) is a timing chart with time LO as a reference (t-0). As shown in these figures, the developing bias VB is tl t when the tip of the charging section (position L4) reaches the developing position X1.
4, that is, at time t3 when position 3, which is located on the lower side of position 4 in the rotational direction of photoreceptor drum 1, reaches development position X1, a common voltage is applied to both developing devices 5 and 6. At time t3 when the developing bias VB is applied, the uncharged portion of the photoreceptor drum l is directed to both the developing sleeves 44 and 57. At this time, if the developer adheres to the surface of each developing sleeve 44 and 57, the toner will be transferred to the photoreceptor drum.
It will stick to. Therefore, before time t3, each developing sleeve 44
and 57, at least in the portion facing the photoreceptor drum 1, a panicle cutting state in which there is no developer is formed, and the panicle cutting state is different from the time.

[Must be maintained up to 4. Therefore, the ear cutting process is performed using the ear cutting shutters 80a and 80b as described above during the period from time t1 to time L2 so that the ear cutting state is formed at time t2 before time t3. The ear cutting process for each of the developing sleeves 44 and 57 is performed sequentially at different times or in parallel depending on the driving capacity of the control unit 12, as will be described later. When using the first developing device 5 for developing, the tip of the latent image! At time t6 when the magnetic brush (position 1jL6) faces the developing sleeve 44, the surface state of the developing sleeve 44 must be in a state where the ears of the magnetic brush stand up (stand-up shape B). At time tg before time t5, rotation of the developing sleeve 44 is started with the ear cutting shutter 80a open so that the ear-standing state is formed at time t5. When the developing device 6 is used, since there is a distance between the developing sleeve 44 and the developing sleeve 57, the rotation of the developing sleeve 570 is started at a certain time later than the time tg. By performing such a cutting process, unnecessary toner adhesion between the positions L3 and L4 of the photoreceptor drum 1, which has conventionally been observed, can be eliminated. FIG. 6 is a plan view of the operation panel 70 attached to the top surface of the laser printer. The developing device selection key 74 is a key for manually switching between the first developing device 5 and the second developing device 6. Each time this key is pressed, these two developing devices 5 and 6 are selected alternately. be done. The developer display section 74a or the developer display section 74b lights up when the developer 5 or the developer 6 is selected, respectively. The mode switching key 75 has two modes: a manual switching mode in which when the selected developing device becomes toner empty, the printer is temporarily stopped and the developing device is manually switched using the developing device selection key 74; This key is used to select in advance an automatic switching mode in which the developer is automatically switched to another developing device, and each time this key is pressed, the manual switching mode and the automatic switching mode are alternately selected. The automatic mode display section 75a lights up when the automatic switching mode is selected. The same color limited mode setting key 76 is a key for setting the same color limited mode in which the developer can be selected and switched only when the toner color is the same in the automatic switching mode. The mode is set or canceled. The same color limited mode display section 76a lights up when the same color limited mode is set. The near-empty print mode setting key 77 is used to stop the developer even if the toner color changes when the developer 5 and the developer 6 do not have the same toner color when the automatic switching mode and the same color limited mode are set. This key is used to set the near-empty print mode in which printing is continued by switching to the near-empty print mode. Each time this key is pressed, the near-empty print mode is set or canceled. The near-empty print mode display section 77a lights up when the near-empty print mode is set. The paper feed selection key 78 is a key for selecting either the manual paper feed section 27, the paper feed cassette 2B or 30, and the selected one is displayed on the paper feed display sections 78a-c. The toner empty display section 92 indicates that the printing operation of the printer stops due to toner empty, such as when the selected developing device runs out of toner, or when both developing devices run out of toner in automatic switching mode. It lights up sometimes. The toner near empty display section 93 lights up when the developing device is automatically switched and printing is continued in the automatic switching mode. In addition to the above-mentioned keys and display, there is also a test key 71 for performing test printing, a shift key 72 for "cancel" which forces printing to end when pressed at the same time as test key 71, and a shift key 72 for manually stopping printing. a pause key 73 for printing, a pause display section 73a for indicating the stopped state, an error display section 91, an error code display section 90 for displaying the details of the error as a code, and a ready display section for indicating the printable state. 94, a busy display section 95 indicating that print data is being received from the host computer and printing is in progress, a paper jam display section 96, a paper empty display section 97, a paper near empty display section 98, and a display section indicating that the waste toner is full. A waste toner full display section 99 is provided to indicate that the waste toner is full. FIG. 7 is a block diagram of the control section 12. The control unit 12 includes a CPU 2 consisting of a microcomputer.
01, a driver array group 203 consisting of a plurality of driver arrays for driving each of the above-mentioned display units, various motors, clutches, chargers, etc., a ROM 204 that stores programs, data, etc., and print data received from a data processing device. and other data etc.
It consists of an external interface 206 for communication with the AM 205 and the data processing device, and is connected to various keys and a display section of the operation panel 70, as well as other devices and circuits. The concentration sensor 4 is installed in the A/D input port of the CPU 201.
An output signal of 0 is input, and the input signal is CP
The A/D converter inside U201 converts it into a digital value according to the voltage level. The control unit 12 processes signals input manually from each key and sensor on the operation panel 70, outputs control signals to each display unit and devices of each part, and receives data from the data processing device. It controls the overall operation of the laser printer A, such as outputting print data to the laser optical system 18 based on the data or data input from each key.Next, based on the flowcharts of FIGS. ,
The operation of laser printer A will be explained. FIG. 8 is a main flowchart showing the overall operation of the laser printer. When the power is turned on, the CPU 201 is initialized and the initial settings are made to put the laser printer A into the initial mode (step #l), and the RAM 205 is initialized (step #2).
), which resets various flags. Subsequently, in step #3, an internal timer for defining the length of one routine is started. In step #4, input processing is performed to input signals from sensors and switches arranged in various parts, such as various keys on the operation panel 70 and the concentration detection sensor 40, and step #4 is performed.
At step 5, signals for controlling the display on the display section of the operation panel 7o and each section are output. Next, in step #6, a cutting monitoring process is performed to check whether the cutting state of each development H5 and H6 is maintained, and then a polygon mirror control process is performed to control the rotation of the polygon mirror. 2I (step #7) and main motor control (step #8) for controlling the rotation of the photosensitive drum 1 by turning the main motor on and off (step #8). In the following step #9, each device (!! cut shutter 80a, sob
(including on/off) at appropriate time intervals. In step #lO, a density adjustment process using the AIDC method described later is performed, and in step #11, a paper feeding process is performed to take out the paper from the paper feeding cassette 28 or paper feeding cassette 30 specified by the data processing device. In step #12, a print operation is performed. After executing these processes, in step #13, the previously started internal timer is waited for, and the process returns to step #3. As a result, the length of the routine is kept constant and step #3 is maintained while the IT source is turned on.
~The processing of step #13 is repeated. FIG. 9 is a flowchart of the spear cutting monitoring processing routine of step #6 described above. This routine indicates that when the developing sleeve 44 of the first developing device 5 and the developing sleeve 57 of the second developing device 6 are in operation, they are in the ear cutting state provided for each sleeve. Reset the ear cutting completion flags A and B to "0". First, in step #15, it is checked whether or not the developing sleeve 44 of the first developing device 5 is in the on state. The ear cutting completion flag A indicating that the surface of the sleeve 44 is in the ear cutting state is reset to "o". If no in step #15, the process advances to step #17. In step #17, the developing sleeve 5 of the second developing device 6
7 is in the on state, and if YES, in step #18, the ear cutting completion flag B indicating that the surface of the developing sleeve 57 is in the ear cutting state is reset to "0". If step #15 is NO, the process returns to the main routine. FIGS. 10(a) to 10(d) are flowcharts of the photoreceptor peripheral processing routine of step #9 described above. This routine includes a startup process for transitioning each device around the photosensitive drum 1 from a standby state to a printable state in response to a print request signal from a data processing device, and a print (
After the completion of printing, the laser printer A is returned to the standby state. First, the state is checked in step #90, and the following processing is executed depending on the state. If the state is "0" in step #90, the process proceeds to step #91, where it is determined whether there is a print request from the data processing device, and if yes, the state is set to "]" in step #92. and return to the main routine. If no in step #91, it is checked in step #94 whether or not the front cover of the main body of laser printer A has been opened based on the output signal of the cover sensor 39; if yes here, There is a possibility that developing device 5 or 6 has been replaced, and it is necessary to perform the ear cutting process on both developing devices 5 and 6. Therefore, in step #95 and step #96, the ear cutting completion flags A and 6 are set, respectively. The ear cutting completion flag B is reset to "0" and the process returns to the main routine. If step #94 is NO, the process returns directly. When the state is rlJ in step #90, it is determined in step #IO1 whether or not the rotation of the main motor turned on in the main motor control in step #8 above is stable, and if no, it remains as is. Return to main routine. If YES in step #101, step #102
Then, it is checked whether the first developing device 5 is in the cutting state. That is, if the ear cutting completion flag A is "1", the process proceeds to step #110, sets the state to "2", and returns to the main routine. Step #
If no in 102, the ear cutter shutter 80 of the developing device 5
Turn on the solenoid 88a to press the Mylar sheet 82a against the developing sleeve 44 (Step #1
03), the developing sleeve 44 is turned on, that is, the first developing device sleeve clutch is connected, and the developing sleeve 44 is rotated (step #104), and the ear cutting process of the first developing device 5 is started. Subsequently, in step #105, a later-described ear cutting discrimination processing routine is executed, and in step #106, it is checked whether or not simultaneous ear cutting processing is selected in the ear cutting discrimination processing. If the result in step #106 is NO, the process proceeds to step #109, where the timer TMI that defines the ear cutting processing time in the first developer 5 is set, and the state is set to "2" (step #110), where the main Return to routine. Yes in step #106, that is, both developers 5 and 6
If it is possible to perform the ear cutting process at the same time, the timer TM2 that defines the ear cutting process time in the second developing device 6 is set in step #107, and the state is set to "2" in step #108. After setting, the process moves to step #205 of state "2", which will be described later. When the state is "2", the end of the timer TMI is confirmed in step #201. If the timer TM1 ends, it means that the formation of the ear cutting state in the first developing unit 5 is completed, so the ear cutting is completed. Processing to finish the processing, that is, turning off the developing sleeve 44 (step #20
2) and turning off solenoid 88a (step #203)
and set the ear cutting completion flag A (step #204)
The process then proceeds to step #205. Note that if the timer TMI is not set, it is determined that the timer has ended. If the timer TMI has not ended in step #201, the process directly returns to the main routine. In step #205, it is checked whether the second developing device 6 is in the cutting state. That is, if the ear cutting completion flag B is "1", the developer Fa6 is already in the ear cutting state, so the process advances to step #209 and the state is set to "3".
and return to the main routine. If no in step #205, turn on the solenoid 88b of the ear cutting shutter 80b of the developing device 6 to press the Mylacies 1 to B2b against the developing sleeve 57 (step #206), and turn on the developing sleeve 57. and rotate it (step #207), and the ear cutting process of the second developing device 6 is started. Then, in step #208, the timer TM2 that defines the ear cutting processing time in the second developing device 6 is set to zero (step #2 Q B), and in step #209, the state is set to "3" and the process returns to the main routine. do. In this manner, when Steps #20 to #208 are performed successively, the panicle cutting process for the developing device 6 is started after the panicking process for the developing device 5 is completed. That is, a sequential ear cutting process is performed in which the developing device 5 and the developing device 6 are sequentially processed. On the other hand, following step #108, step #20
When Steps 5 to #208 are performed, the panicle cutting process for the developing device 6 is started during the panicking process for the developing device 5, and the panicking processes for each of the two developing devices 5 and 6 are performed in parallel almost simultaneously. It will be implemented as follows. In other words, simultaneous ear cutting processing is performed. In state "3", C checks the end of timer TM2 in step #301. If YES in step #301, it means that the panicle cutting process in the second developing device 6 has been completed, so the developing sleeve 57 is turned off (step #302) and the solenoid 8 is turned off.
8b (step #303), and set the ear cutting completion flag B to "1" (step #304).
Proceed to step #305. In step #305, it is checked whether or not the simultaneous ear cutting process is selected. If YES, the developing sleeve 44 is turned off (step #305) in order to finish the ear cutting process for the first developing device 5. 306) and turn off the solenoid 88a (step #307), and set the ear cutting completion flag A to "1" (step #308).
. When the panicle cutting process for the developing units 5 and 6 is completed through the above process, the main routine block 10 is turned on in step #309, and the timer TM3 is set (step #310), and the state is set to "4". Set and return to the main routine. In state "4", in step #401, the end of timer TM3 is confirmed, charging 3 is turned on (step #402), and timer TM4 is turned on (step #403), and in step #404, state Set "5" to "5". In state "5", the end of the timer TM4 is confirmed in step #501, and the developing bias VB is applied to both developing devices 5 and 6 in step #502. The time T3 (see Figure 1) measured by the timer TM4 is
Charging is started in step #402 described above, and the time T4 required for the tip of the charged portion on the surface of the rotating photosensitive drum l to reach the developing area Xi of the fourteenth developing device 5 is set to be slightly shorter than the time T4. Therefore, at the time when the tip of the charged portion on the surface of the photosensitive drum 1 reaches the development end area XI,
Since the developing bias VB is applied to both the developing devices 5 and 6, even if the surface of the developing sleeves 44 and 57 is not completely trimmed, the magnetic carrier will not adhere to the photosensitive drum l. do not have. When the developing bias VB is turned on, the activation process of each device around the photoreceptor drum 1 is completed, that is, it becomes possible to form a latent image on the photoreceptor drum 1.
In step #503, the photoconductor peripheral startup completion flag is set to "l".
”, and in step #504, set the state to “C6”.
and return to the main routine. States "6" to "11" are related to termination processing for transitioning each device around the photosensitive drum 1 from a printable state to a standby state.
In "7" to "11", when a new print request is added from the data processing device after the termination process has started, each device surrounding the photoconductor drum is activated to form the latent image as soon as possible. Processing to return to the state is executed. Also, in this termination process, the next photoreceptor drum 1rii
In order to shorten the processing time of the startup process (state ro, ~ "5") of each device in the box, the ear cutting process that is performed in advance before transitioning to the standby state is included. In state "6", it is determined in step #6o1 whether or not a printing operation is in progress. That is, it is checked whether the exposure for forming the latent image has been completed, and if YES in step #601, the process directly returns to the main routine. When the printing operation is completed (in the case of printing multiple pages, the exposure for the last page is completed), a negative determination is made in step #601, and the end process is started. First, in step #602, the photoreceptor peripheral activation completion flag is reset (step #602), the timer TM5 is set (step #603), and the state is set to "7" (step #604). When the state is "7J", the presence or absence of a new print request is checked in step #701, and if YES, the state is returned to "5" in step #712, and the process immediately returns to the main routine. If no in step #701, it is confirmed that the timer TM5 ends in step #702, that is, at least the rear end of the latent image passes through the development 2I area x2, and step #7
In step #703, the process proceeds to step #703, where it is checked whether or not the ear cutting completion flag A is "1". If YES here, the developing device 5 was not used in the previous printing operation, and the surface of the developing sleeve 44 remains in the cut state.
Since ear cutting is not necessary, the process returns with the state set to "8" in step #711. If the result in step #703 is NO, the cutting process for the developing device 5 is started. That is, similarly to steps #103 to #106 in state "1", the solenoid 88a of the ear cutting shutter 80a of the developing device 5 is turned on to press the Mylar sheet 82a against the developing sleeve 44 (step #704), and the developing sleeve 44 is turned on (step #705), and in step #706, the ear cutting determination processing routine is executed. Next, in step #707, it is determined whether simultaneous ear cutting processing is selected in the ear cutting determination process of step #706, and if no in step #707, the process proceeds to step #710, where the first development process is performed. Setting a timer TM6 that defines the ear cutting processing time at the end processing in the vessel 5,
After setting the state to "8" (step #711), the process returns to the main routine. Since the termination process has more time than the start-up process, the time measured by the timer TM6 is equal to the time measured by the timer TMI set at the time of the start-up process in order to cut a wide area of the surface of the developing sleeve 44. It can be set longer. Yes in step #707, that is, both developers 5 and 6
If it is possible to perform simultaneous panicle cutting on
Set the timer TM7 that defines the end cutting process time in the second developing device 6 (step #708).
, After setting the state to "8" in step #7o9, the process moves to step #806 for state "8". In state "8", the presence or absence of a new print request is checked in step #801, and if YES, the developer 5 started in state "7" is checked.
Cancel the ear cutting process at the end of the process. That is, the developing sleeve 44 is turned off (step #811) and the solenoid 8 is turned off.
8a off (step #812) and returns to the main routine with the state set to "5J" in step #813. If no in step #801, the termination process continues. Steps #8o2 to #8o5 So, timer T
After confirming the end of M6, turn off the developing sleeve 44 and the solenoid 88a, and set the ear cutting completion flag A to [l,
Set to . Next, in step #806, it is determined whether or not the second developing device 6 is in the cutting state, and if it is in the cutting state, the state is set to "9" and the process returns. Step #
If the answer is NO in 806, the solenoid 88b is turned on, the developing sleeve 57 is turned on, the timer TM7 is set, the state is set to "F9", and the process returns. In state "9", if YES in step #9o1 of checking whether there is a print request, the developing sleeve 44, solenoid 8
8a, the developing sleeve 57, and the solenoid 88b are turned off in order, and the state is changed to r5.8a in step #917. shall be. If no in step #901, step #902~
At 905, after waiting for the timer TM7 to end, the developing sleeve 57 is turned off, the solenoid 88b is turned off, and the cutting completion flag B is set to "1". And step #
In step 906, it is checked whether or not the cutting process at the end of the developing units 5 and 6 was performed in parallel. If yes, in steps #907 to #909, the developing sleeve 44 is
After the solenoid 88a is turned off, the ear cutting completion flag A is set to rl. This means that the ear cutting process at the end of the reproducing devices 5 and 6 has been completed. Next, in steps #910 and 911, the main routine 10 is turned off and the timer TM8 is set, and in step #9]2, the state is set to "IO" and the process returns to the main routine. In state rlOJ, in step #1001,
Check whether there is a print request or not, and proceed to step #10.
If 01 is yes, go to step #1006,
Turn on main eraser lamp 10 and step #1O0
At step 7, set the state to "5" and return. Step #l If no at 001, step #X0
At O2, confirm the end of timer TM8 and turn off timer T.
When M8 is completed, the charger 3 is turned off (step #1.003) and the timer TM9 is set (step #1004), and the state is set to "11" in step #1005. In state [11], if YES in step #1101, the main eraser lamp 10 is turned on in step #1105, and then step #4 of state
Similarly to steps 402 to 404, the charger 3 is turned on (step #1106) and the timer TM4 is turned on (step #1107), and the state is set to "5" in step #1108. If no in step #1101, step #110
2, confirm the end of timer TM9, and
After step 9 is completed, turn off the developing bias VB in step #
11Q3), set "OJ" in the state and return to the main routine. By executing step #1104, the termination processing of each device around the photosensitive drum 1 is completed, and the laser printer A enters the standby state. The figure shows step #105 and step #70 above.
6 is a flowchart of the ear cutting determination processing subroutine of No. 6; This process is performed by the driver array group 203 of the vJIj section 12.
By detecting the driving status of the driver array 20,
This is to judge whether or not it is possible to simultaneously perform the ear cutting process on the two developing units 5 and 6 in view of the drive capacity of No. 3. That is, in this embodiment, as shown on the right side of FIG. 7, a solenoid 88a for ear cutting processing is used. 88b, two clutches for controlling the rotation of each developing sleeve 44.57, and each toner supply bottle 41.5.
A total of eight loads, including two clutches for controlling the rotation of No. 3 and developer selection display LEDs 74a and 74b, are respectively connected to eight boats of the same driver array in the driver array group 203. has been done. However, this driver array does not have the capacity (temperature capacity) to drive the above-mentioned eight loads simultaneously. The ear cutting process for 5 and the developing device 6
Select the simultaneous ear cutting process in which the ear cutting process is performed in parallel with the ear cutting process for the developing units 5 and 6, and if there is not enough time, select the sequential ear cutting process in which the ear cutting process is performed for each developing device 5 and 6 in sequence at staggered times. do. That is, whether the toner replenishing bottle 41 is being rotated by the steering knob #1201, that is, if the first
It is determined whether or not toner is being replenished to the developing device 5. If YES in step #1201, step #12
In step 05, the selection of the ear cutting process is performed sequentially, and the process returns to the photoreceptor peripheral processing routine. Step #! If no at 201, step #120
In step 2, it is determined whether or not toner is being replenished to the second developing device 6. If YES in step #1202, proceed to step #1205 described above; if NO, proceed to step #1205.
In step 1203, it is checked whether the developing device selection display LED 74a is driven, that is, whether it is lit. If no, the process proceeds to step #1206 and the simultaneous ear cutting process is selected. . If YES in step #1203, then in step #1204 it is checked whether the developer selection display LED 74b is lit. If YES in step #1204, sequential ear cutting processing is selected, and if NO, simultaneous ear cutting processing is selected. Next, the density adjustment process of step #10 in FIG. 8 will be explained. In the laser printer A of this embodiment, the print density is adjusted by the AIDC method. That is, a latent image (mark) of a specific shape is formed on the photoreceptor drum l, and after this latent image is developed in a developing device 5 or 6, the density of the marked portion is detected and toner replenishment control 8 is performed. . FIG. 12 is an enlarged perspective view of the concentration sensor 40. As shown in FIG. The 1 degree sensor 40 is a reflective photoreflector, and includes an infrared light emitting diode 40a, a phototransistor 40b,
and a light shielding portion 40c that shields direct light between them. The light emitted from the infrared light emitting diode 40a is emitted from the photosensitive drum 1.
0 surface, and the reflected light is received by the phototransistor 40b. The output current of the phototransistor 40b is amplified by an amplifier built into the concentration sensor 40, and the concentration sensor 40 outputs a voltage corresponding to the amount of reflected light. The output signal of the m degree sensor 40 is input to the A/D converter boat of the CPU 201 as described above. Note that as the concentration sensor 40, a light modulation type sensor that is not affected by ambient light such as irradiation light or sunlight may be used. In the density adjustment process, first, a mark for detecting the density is formed, for example, between one page of images and the next page of images. The infrared light emitting diode 40a is caused to emit light at a timing opposite to the infrared light emitting diode 40a. Then, the output signal level of the density sensor 40 is compared with a preset reference density discrimination level, and the toner supply bottle 41 or 53 (see FIG. 3) is rotated based on the comparison result. As a result, the amount of toner supplied to the developing device 5 or 6 is adjusted, and the print density is automatically adjusted. The reference concentration discrimination level to be compared with the output of the concentration sensor 40 is set as follows. Data on the difference between the amount of light reflected from the surface of the photoreceptor in a state with no latent image and the amount of light reflected from the toner latent image, which is the boundary for determining density, obtained from an experiment, is stored in advance in the ROM 204 as a correction value. Then, using the ear cutting operation time when the photoreceptor drum 1 is started, the reflected light is detected in a state where no latent image is formed on the photoreceptor drum l, and the detection signal level at this time is set as a reference value. It is stored in the RAM 205 as . Calculations are performed based on the newly stored reference value and the constantly stored correction value, and the reference density discrimination level is set as appropriate. By setting the reference density discrimination level in this way, the window of the density sensor 40 is prevented from becoming dirty due to toner plume, etc.
Even when the maximum level of the detection signal changes over time, the reference density discrimination level is also changed in accordance with the change, so the accuracy of density adjustment can be kept constant. According to the above-mentioned embodiment, in the process around the photoreceptor, when executing the ear cutting process, it is checked whether the surface of the developing sleeve 44 57 is already in the ear cutting state, and the developing sleeve 44 in the ear cutting state is checked. Or for 57, the ear cutting process is omitted, so the ear cutting solenoid 88a,
The lifespan of mechanical parts such as 88b can be extended, and the time required from a print request to when a print operation becomes possible, that is, the first print time can be shortened. In the above-mentioned embodiment, in order to prevent magnetic carrier from adhering to the photoreceptor drum 1, as a consideration when insufficiently cut portions occur on the surfaces of the developing sleeves 44 and 57 of the developing units 5 and 6, , before the tip of the charged portion on the surface of the photoreceptor drum 1 reaches the development position X1, the development bias V is applied.
B is applied. However, if a good ear cutting condition is obtained, the magnetic carrier will not adhere to the charged portion of the photoreceptor drum 1, so the timing of applying the developing bias VB can be delayed. That is, if the application timing of the developing bias VB is before the timing at which the leading edge of the latent image reaches the development area (development start timing), the leading edge of the IT portion is at the developing position x1.
You can also do this after reaching . However, when the tip of the charged part reaches each development position,
The surface condition of each developing sleeve must be in a panicle condition. In addition, as a similar consideration regarding the cutting condition, in order to minimize toner adhesion to the photoreceptor drum 1, a developing bias VB is applied to each developing device immediately before the leading end of the charging section reaches the developing position. The timing of applying the developing bias VB is set later than the timing of turning on the charger 3 so that the developing bias VB is applied. However, if a good panicle cutting condition can be obtained, the developing bias VB may be applied considerably before the tip of the charging section reaches the developing position. Bias VB may be applied; if the charging charger 3 and developing bias VB are controlled at the same timing, the high-voltage power supply circuit can be simplified, making the device smaller and lighter and improving reliability. be able to. In the above embodiment, in order to simplify the configuration, the developing bias VB was generated by one high voltage transformer and the developing bias VB was simultaneously applied to the two developing devices 5 and 6. However, it is possible to use a plurality of transformers. It is also possible to set independent application timing for each developing device 5 or 6 by using the above method. In that case, the application timing to the developing device 6 is set such that the developing bias VB is applied to each developing device immediately before the leading end of the charged portion of the photosensitive drum I reaches the developing area x1 or the developing area X2. By delaying the amount of toner attached to the photosensitive drum 1, the amount of toner adhering to the photosensitive drum 1 can be further reduced compared to the case where the developing bias VB is applied to the two developing devices 5 and 6 at the same time. . In the above-mentioned embodiment, the ear cutting shutter 80a or 80b is provided in both the developing units 5 and 6 of 2(+1) so that the ear cutting process can be performed on either developing unit 5 or 6. If one of the developing devices is used less frequently than the others, the first printing time can be shortened by omitting the cutting process by not providing a cutting means for the developing device that is used less frequently. In the above embodiment, the laser printer A is equipped with two developing devices 5 and 6, but an image forming apparatus with one developing device and a laser printer A with three developing devices, such as a full-color copying machine, can be used. The present invention can also be applied to an image forming apparatus equipped with more than one developing device. [Effects of the Invention] According to the invention of claim 1, the toner in the developer is transferred to the photoreceptor due to the application of a developing bias. I no longer wear unnecessary clothes,
Wasteful consumption of toner can be reduced. According to the second aspect of the invention, unnecessary toner adhesion to the photoreceptor due to application of a developing bias is eliminated while suppressing deterioration and deterioration caused by the operation of the ear cutting means and the control means as much as possible.
Wasteful consumption of toner can be reduced. According to the third aspect of the invention, there is no need to provide a control means with a large driving capacity to control the ear cutting process for a plurality of developing devices, and it is possible to control the application of the developing bias while suppressing cost increases as much as possible. It is possible to eliminate unnecessary toner adhesion to the photoreceptor and reduce wasteful consumption of toner. According to the invention of claim 4, it is necessary to provide a control means with a large drive capacity in order to control the panicle cutting process for a plurality of developing devices (while suppressing cost increases as much as possible and shortening the first printing time). While achieving this, unnecessary toner adhesion to the photoreceptor due to the application of a developing bias can be eliminated, and wasteful consumption of toner can be reduced.

[Brief explanation of the drawing]

The drawings show embodiments of the invention, FIGS. 1(a) and (b)
2 is a front sectional view of the laser printer, FIG. 3 is an enlarged view of the developing device, and FIG. 4 is an enlarged sectional view of the developing sleeve. , FIG. 5 is a perspective view of the ear cutting shutter shown in FIG. 4, FIG. 6 is a plan view of the operation panel attached to the top surface of the laser printer, FIG. 7 is a block diagram of the control unit, and
FIG. 1 is a flow chart showing the operation of the control section, and FIG. 12 is an enlarged perspective view showing the concentration sensor. ■...Photoreceptor drum (photoreceptor), 5...Developer, 6
...Developer, 12...wI door section (control means), 80
a. 80b...Ear cutter 7ri (ear cutting means), L4...
- Charging section tip, A... Laser printer (N image forming device), Xi, X2... Development position (arrangement position). Diagram: Strain diagram

Claims (4)

[Claims] (1) Image formation in which a developing device containing a developer is disposed around a photoreceptor, and an image is formed by an electrophotographic process when the photoreceptor and the developing device move relative to each other. In the apparatus, the developing device is provided with a cutting means for performing a cutting process to prevent developer from adhering to the photoreceptor, and before a developing bias is applied to the developing device, Before the tip of the charged portion of the photoreceptor reaches the placement position of the developing device, a panicle state is formed in the developing device, and the tip of the charged portion of the photoconductor passes through the placement location of the developing device. An image forming apparatus characterized in that the image forming apparatus is further provided with a control means for controlling the ear cutting state to be maintained until then. (2) The image forming apparatus according to claim 1, wherein the control unit controls the developing unit in which the cutting state is maintained so as not to perform the cutting process. (3) A plurality of developing devices containing developer are disposed around a photoreceptor, and the photoreceptor and the developing device are configured to move relative to each other so that an image is formed by an electrophotographic process. In the image forming apparatus, each of the developing devices is provided with a cutting means for performing a cutting process to prevent developer from adhering to the photoreceptor, and a developing bias is applied to each of the developing devices. Before the voltage is applied and before the tip of the charged portion of the photoreceptor reaches the arrangement position of the developing device, a panicle state is formed in each developing device, and the tip of the charged portion of the photoreceptor is placed in each of the developing devices. A control means is provided for sequentially performing the ear cutting process on each of the developing units so as to maintain the ear cutting state of each of the developing units until the developing unit passes the arrangement position of the developing unit. Image forming device. (4) The image forming apparatus according to claim 3, wherein the control means performs control so that the tip of the charged portion of the photoreceptor reaches the developing unit first, and then forms the tip-cut state.