JP2811657B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus (for example, a copying machine or a laser printer) using an electrophotographic process, and more particularly to an improvement in toner supply. [Related Art] For example, in an electrophotographic copying machine, a toner concentration in a developer contained in a developing device that develops an electrostatic latent image has a certain appropriate range. The image density decreases. Therefore, conventionally, the toner density and the image density are detected, and the toner is replenished so that the detected toner density always falls within an appropriate toner density range. For example, a magnetic sensor is provided in the developing device to detect a change in the magnetic permeability of the developer due to a change in the toner concentration, or a latent image of a reference pattern is formed on a photoreceptor, and developed to develop a photosensitive image. The density of the toner image formed on the body is detected by an optical sensor, the toner density is detected, and it is determined at a cycle timing whether or not the toner density is lower than a reference value. When the toner density is lower than the reference value, a fixed amount of toner is supplied. Normally, the timing of the determination of the toner density and the timing of replenishment are constant irrespective of the type of the original and the manner of copying. [Problems to be Solved by the Invention] By the way, the above-mentioned toner replenishment is performed at regular intervals at regular intervals, because the toner density in the developing device increases in real time in response to the constant volume of toner replenishment.
One of the reasons is that it is not uniform. Therefore, after the toner is supplied once, after a predetermined time has elapsed, and after the developer has been agitated, the toner can be supplied more accurately based on the toner density detection. However, if the toner replenishment timing is set so that toner replenishment is performed after a certain amount of stirring of the toner, the toner replenishment is performed under the condition of rapid toner consumption, even though the toner consumption is rapidly progressing. Is delayed,
In some cases, toner replenishment is started after the toner density becomes considerably lower than the reference toner density, and as a result, the fluctuation range of the toner density may increase. The present invention has been made in view of the above circumstances,
For example, an object of the present invention is to provide an image forming apparatus in which the fluctuation range of the toner density is small even under rapid toner consumption. Means for Solving the Problems Accordingly, an image forming apparatus according to the present invention forms an electrostatic latent image on a charged photoreceptor, and develops the formed electrostatic latent image with toner using a developing device. An image forming apparatus that forms an image by transferring and fixing the image on a sheet of paper; input means for inputting image forming conditions of the image forming means; A toner concentration detecting means for periodically detecting the toner, a toner replenishing means for replenishing the toner in the developing device, and developing a predetermined amount of toner when the toner concentration detected by the toner concentration detecting means is equal to or less than a reference value. A toner replenishing unit for replenishing the image forming apparatus; a determining unit configured to determine whether an image forming condition input by the input unit corresponds to a condition in which rapid toner consumption is predicted; Image strip It is when the rapid toner consumption is determined to be a condition that is expected, and having a control means for setting short predetermined period for detecting the toner density in the toner concentration detector. Embodiment An embodiment of the present invention will be described below with reference to the drawings, taking as an example a case where the image forming apparatus is a copying machine. FIG. 1 schematically shows a copying machine according to the present embodiment. The main motor M1 is located in the counterclockwise direction at the approximate center of the copying machine.
A photoreceptor drum 1 rotatably driven by the photoreceptor is disposed, and a main eraser lamp 32 and a sub-charger are provided therearound.
33, sub eraser lamp 34, main charging charger 35,
An inter-image eraser 36, a developing device 2, a transfer charger 37, a copy paper separation charger 38, and a blade type cleaning device 39 are provided. The photosensitive drum 1 is provided with a photosensitive layer on the surface.
2, and are uniformly charged by passing through the chargers 33 and 35, and receive image exposure from the optical system 10. The optical system 10 is provided so that the original can be scanned from below the original glass 16, and includes a light source L and movable mirrors 41, 42, 43.
, A lens 44, and a mirror 45. The light source L and the movable mirror 41 are at a speed of v / m (where m: copy magnification) with respect to the peripheral speed (constant here, 150 mm / sec) of the peripheral speed of the photosensitive drum 1 (regardless of the same magnification / variable magnification). Move to the left with
The movable mirrors 42 and 43 are driven by a DC motor M3 so as to move leftward at a speed of v / 2m. The scanning of the original image of the optical system causes the photosensitive drum 1 to undergo image exposure,
An electrostatic latent image is formed. Further, toner is attached to the electrostatic latent image in the developing device 2. The inter-image eraser 36 is formed by arranging a large number of LED elements in the axial direction of the photosensitive drum 1, and removes charges outside the effective image forming area on the photosensitive drum 1 by light irradiation. To prevent wasteful consumption. On the other hand, on the left side of the copier body,
Paper feed units 50 and 52 with 1, 53 are installed, and roller pairs 54 and 5
5, timing roller pair 56, transport belt 57, fixing device 5
8. The discharge roller pair 59 forms a copy paper conveyance path. The timing roller pair 56 feeds the copy paper fed from the paper feed unit to the photosensitive drum 1 side with its leading end aligned with the toner image forming area formed on the photosensitive drum 1. The fed copy sheet is transferred with the toner image by the transfer charger 37, is peeled off from the surface of the photosensitive drum 1 by the separation charger 38, passes through the transport belt 57,
After the toner is fused and fixed by the fixing device 58, the toner is discharged outside the apparatus by a discharge roller pair 59. FIG. 2 is a schematic partial sectional view showing the developing device and the toner replenishing means. As shown in FIG. 2, the developing device 2 includes first screw blades 16 arranged in order from a position farthest from the photosensitive drum 1.
, A bucket roller 11, and a developing sleeve 6 as main constituent members, which are held in a space formed by the casing 3 and the cover 4. A toner replenishing tank 60 serving as a toner replenishing means is provided at a position corresponding to an upper end of one end of the first screw 16. FIG. 3 is a perspective view showing the first screw blade 16 and the bucket roller 11. As shown in FIG. 3, the first screw blade 16 has a semi-spiral shape, and the toner replenished from a toner replenishing tank 60 (not shown) is rotated in a counterclockwise direction in FIG. The developer is mixed with the developer and transported while stirring. In this embodiment, a two-component developer composed of a toner and a magnetic carrier is used as the developer. As shown in FIG. 2, the bucket roller 11 has a second screw blade 13 at an axis portion and an L-shaped blade 14 at an outer peripheral portion.
Are radially arranged in the radial direction. The second screw blade 13 and the L-shaped blade 14 are fixed at both ends in the axial direction, and rotate integrally in a clockwise direction. The first screw blade 16, the bucket roller 11, and the developing sleeve 6 are driven and rotated by a main motor M1. The L-shaped blade 14 rotates to convey the toner picked up in the L-shaped portion to the upper portion of the developing sleeve 6, and the magnetic poles (S ₃ , N ₃ ) above the magnetic roller 7 (described later) incorporated in the developing sleeve 6. ) Makes it possible to increase the height of the developer. Further, the bucket roller not only carries the toner at the upper part but also agitates the developer at the lower part. Further, by the rotation of the second screw blade 13, the developer is transported from the back in the figure to the front. A magnetic sensor 15 for detecting the magnetic permeability of the developer is provided in the casing 3 below the bucket roller 11 to detect the toner concentration in the magnetic carrier. Further, a partition plate 5 is provided between the first screw blade 16 and the bucket roller 11.
Are formed with notches at positions corresponding to both ends of the bucket roller 11 in the axial direction. The first screw blade 16 and the second screw blade 13 of the bucket roller 11 form a circulating transport path for the developer through the notches at both ends of the partition plate 5. That is, the toner is supplied from the toner supply tank 60 to one end of the first screw blade 16 on the near side in the drawing. On the other hand, by the rotation of the second screw blade 13, the developer is transported to the near side in the figure, and is supplied to the first screw blade 16 from the notch on the near side of the partition plate 5. The developer supplied from the bucket roller 11 to the first screw blade 16 supplies the toner consumed in the photosensitive drum 1 while being conveyed in the bucket roller 11 in the axial direction. It is low. Therefore, the first screw blade 16 mixes the developer having the low toner concentration with the newly supplied toner.
While being stirred, it is transported to the depth of the first screw blade 16. Next, the developer conveyed to the depth of the first screw blade 16 passes through the notch on the depth side of the
Is transported to the back in the figure. As described above, the circulation and stirring paths of the developer are formed. The developing sleeve 6 has a built-in magnetic roller 7 provided with a magnetic pole on the outer peripheral portion, holds the developer on the outer peripheral surface by the magnetic force of the magnetic roller, and allows the developer supplied from the bucket roller 11 to face the photosensitive drum 1. The photosensitive drum 1 is transported to a developing area (A) where the photosensitive drum 1 is to be developed. The developing sleeve 6 is formed by forming a nonmagnetic conductive material (for example, aluminum) into a cylindrical shape.
Fine irregularities are formed on the surface by sandblasting,
The photosensitive drum 1 is opposed to the photosensitive drum 1 with an interval of development gap: Ds = 0.6 mm, and can be driven to rotate clockwise at a rotation speed of 143.64 rpm. In addition, the lower part of the developing sleeve 6 is kept at a gap of D = 1.0 mm from the casing 3. The magnetic roller 7 has an outer diameter of 24.5 mm, and magnetic poles (N _{1 to} N ₃ ) and (S _{1 to} S ₄ ) are alternately provided on the outer periphery, and the bucket is disposed on the back side of the development area (A). Magnetic poles (S ₂ ) and (S ₃ ) of the same polarity are provided adjacently above and below the portion closest to the roller 11, the magnetic pole (N ₁ ) is 900 G, and the other magnetic poles (N ₂ , N
_3, S ₁ ~S ₄₎ are as 500-600 g. Therefore, the magnetic force between the magnetic poles (S ₂ ) and (S ₃ ) becomes zero, and the developer cannot be held on the developing sleeve 6. Replace with developer. An ear height restricting member 8 is formed on the upper part of the casing 3 and is located between the developing sleeve 6 and the magnetic poles (S ₃ , N ₃ ) at an interval of the ear height restricting gap Db = 0.5 mm. The developer transporting amount is regulated by cutting the developer conveyed by the developing sleeve 6 at a portion facing the developing sleeve 6. Further, 9 is an anti-smoke mylar, which is made of polyethylene film (0.1 mm thick).
The casing 3 is attached to an upper portion of the casing 3 opposed to the photosensitive drum 1, and prevents the generated smoke toner from being scattered upward from around the developing sleeve 6. The toner replenishing tank 60 is for replenishing the developing device 2 with toner. A stirring rod 61 for preventing a toner cross-linking phenomenon, blocking, and the like is rotatably installed at a central portion slightly below, and a toner replenishing tank is provided at a bottom portion. A replenishing unit 62 is provided for dropping the toner contained in 60. The replenishing section 62 has a rotatable toner replenishing roller 63 provided with a spiral blade 63b on a support shaft. In the center. And below this central part,
A toner supply port 62a is formed. Toner supply roller 6
The stirring rod 61 and the stirring rod 61 are rotated in synchronization with a toner supply motor (not shown), and an amount of toner corresponding to the amount of rotation falls from the toner supply port 62a and is supplied to the first screw blade 16. . The operation panel 100 shown in FIG.
The operation panel 100 is provided with a print start switch 101 for instructing the start of copying, a setting for stopping copying immediately after starting copying or during multi-copying (continuous copying of a plurality of sheets based on the same original). Clear stop switch (c / s key) 102, interrupt copy switch 103, numeric keypad 1 for setting the number of copies of the same image, clearing the number of copies made and returning to standard mode "1"
04, an up switch 105 and a down switch 106 for setting a copy magnification, a density down switch 107 for specifying a developing toner density, a density up switch 108, an automatic density adjustment switch 109, an upper sheet feeding section 50 or a lower sheet feeding section 52. Paper feed unit selection switch 111 for selecting any one of the following, and paper feed unit size display LEDs 112 to 11 for displaying the paper size of the selected paper feed unit
5 mag is provided. In the present embodiment, on the operation panel 100, based on the copy condition formed by the switch operated by the operator,
This is to determine whether rapid toner consumption occurs. In addition, the copy conditions are, for example, after the placed original is automatically fed onto the original glass and the copy is completed, except for the operation panel,
It is also formed by a command from an automatic document feeder that automatically discharges the document. Hereinafter, the copy conditions under which the toner is rapidly consumed will be described. (1) Continuous Copy If the same document is used, the toner consumption per sheet is almost the same. However, in the case of continuous copying, the toner consumption per unit time increases. In a normal copying machine, etc.,
The drive time of the developing unit (the ON time of the main motor M1) is set longer than the copy time per sheet, and the developer is sufficiently stirred. On the other hand, when copying is performed continuously, the driving time of the developing device substantially corresponds to the copying time.
There is a large difference in the degree of agitation of the developer between taking zero copies one by one and taking continuous copies. In particular, in the case of a large amount of toner consumption, toner replenishment becomes frequent, and the difference in the degree of stirring becomes more remarkable. (2) Designation of large-size paper As shown in Table 1, as the paper size increases, the toner consumption increases. (3) Changing the density adjustment to “dark” When the density adjustment is changed to “dark”, the toner consumption per sheet increases even for the same document. (4) Enlarged copy As shown in Table 1, when A4 is enlarged to B4 or A3 and copied, for example, the toner consumption increases. (5) Combination of the above In particular, in the case of large-size copy paper and in the "dark" mode,
In the continuous mode, the toner is rapidly consumed and the toner is frequently replenished. FIG. 5 is a block diagram schematically showing a control circuit of the copying machine. As shown in FIG. 5, this control circuit
The output signal of the magnetic sensor 15,
Key operation signals on the operation panel 100 and other signals such as sensors and switches provided in each part of the copying machine are input to an input port of the CPU. The output port outputs a control signal to the driver of the toner supply motor and other control devices. FIG. 6 is a flowchart showing a main routine of the CPU 200. As shown in FIG. 6, for example, various registers such as power-on and a copy mode are set to an initial state (step S1). Next, an internal timer for keeping the length of one routine constant is started (step S3),
A copy control subroutine (step S5) and other processing subroutines (step S7), which will be described later, are sequentially executed, and the process waits until the internal timer ends (step S9).
Return to S3. FIG. 7 is a flowchart showing details of the copy control subroutine. First, as shown in FIG.
It is determined whether there is an on-edge of the print key 101 (step S10). If there is an on-edge, a toner consumption prediction described later is performed (step S12), and a copy start flag is set to "1" (step S14). ). Next, in step S16, it is determined whether or not the copy start flag is "1" (step S16). If it is "1", the sheet feeding and transport control is sequentially performed (step S1).
8), the optical system control (Step S20), the photosensitive drum rotation control (Step S22), and the toner supply control (Step S24) are performed, and the copy start flag is set to "0" at the end of the copy (Step S28). To return. FIG. 8 is a flowchart showing details of a subroutine for toner consumption prediction. As shown in FIG. 8, in a step S100, it is determined whether or not the flag A is "1". If the flag A is "1", the flag A is set to "0" (step S100).
S102). On the other hand, if the flag A is “0”, step S10
Skip to. Note that this flag A is a flag that becomes “1” when rapid toner consumption is predicted. In steps S104 to S110, when the number of multi-copy sheets is equal to or more than α, when the toner density is in the “dark” mode, when the transfer paper (copied paper to be fed) is A3, If so, the process proceeds to step S112, where the flag A is set to "1". If neither, the process returns. It should be noted that the case where the number of multi-copy is equal to or more than α does not matter the number initially set as the multi-copy,
The problem is the number of uncopied copies. FIG. 9 is a flowchart showing a subroutine of toner supply control. As shown in FIG. 9, it is determined whether or not the flag A is "1" (step S201).
If is "1", the toner supply timing cycle is shortened (step S203). In this embodiment, it is assumed that the toner supply timing is usually one time in one copy time. That is, when the flag A is "1", the cycle is half that in the case where the flag A is "0". Note that this cycle can be arbitrarily set according to the configuration of the developing device, in particular, the developer transport mechanism, the charging characteristics of the developer used, and the like. Next, it is determined in step S205 whether or not it is the toner replenishment timing, and in the case of the toner replenishment timing, it is determined whether or not the toner density Tc is lower than the reference density Tca (step S207). On the other hand, if it is not the toner supply timing, the process skips to step S213. If the toner density is smaller than the reference density, the toner supply motor is turned on, and a timer TM1 for defining this ON state is set (steps S209 and S21).
1). If the toner density is equal to or higher than the reference density, the process returns. When the timer TM1 ends in step S213, the toner supply motor is turned off (steps S213 and S215). FIG. 10 is a graph showing a change in the toner density Tc when the toner is replenished once in one copy time when the toner is rapidly consumed. FIG. 11 is a graph showing the change in the toner concentration when the toner is rapidly consumed. The toner supply timing is 1
9 is a graph illustrating a change in toner density Tc when the copy time is twice. In the figure, A shows the case where Tc becomes highest after toner replenishment, and B shows the case where Tc becomes lowest before toner replenishment. Therefore, the maximum Tc of the A line and the minimum Tc of the B line are the fluctuation widths of the toner density Tc. The toner consumption speeds in FIGS. 10 and 11 are the same. As is apparent from FIGS. 10 and 11, when the toner is rapidly consumed, the shorter the cycle of the toner supply timing, the smaller the fluctuation width of the toner density Tc. [Effect of the Invention] With the above-described configuration, when an image is formed in which rapid toner consumption is predicted, the toner density is detected in a shorter cycle than in a normal case. When the toner replenishment is performed, the followability of the toner replenishment corresponding to the toner consumption increases, and the fluctuation range of the toner density with respect to the reference value decreases.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing a copying machine according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view showing a developing device and a toner replenishing means according to the embodiment. Fig. 3 shows the first screw blade
FIG. 4 is a plan view of the operation panel 100 of the copying machine, FIG. 5 is a schematic configuration diagram of a control circuit of the copying machine, FIGS. 6, 7, and 8. FIG. 9 is a flowchart showing a program in the CPU of the control circuit, and FIGS. 10 and 11 are graphs showing the toner supply timing and the fluctuation range of the oner density. 1. Photoconductor drum 6 Developing sleeve 11 Bucket roller 16 Screw blade 60 Toner supply tank.

Claims (1)

(57) [Claims] An image forming apparatus that forms an electrostatic latent image on a charged photoreceptor, develops the formed electrostatic latent image with toner using a developing device, and transfers and fixes this on paper to form an image. An input unit for inputting an image forming condition of the image forming unit; a toner concentration detecting unit for detecting a toner concentration of a developer in the developing device at a predetermined cycle; and a toner supply unit for replenishing toner in the developing device. A toner replenishing unit, a toner replenishing unit that replenishes a predetermined amount of toner to the developing device when the toner density detected by the toner density detecting unit is equal to or less than a reference value, and an image forming condition input by the input unit is rapidly changed. A determination unit that determines whether or not the toner consumption corresponds to a predicted condition; and if it is determined that the image forming condition input by the input unit is a condition that a rapid toner consumption is predicted, Before Imaging apparatus characterized by and a control means for setting short predetermined period for detecting the toner concentration by the toner concentration detection means. 2. The conditions under which the rapid toner consumption is predicted are at least one of the following conditions: continuous image formation on a predetermined number of sheets or more, image formation on large-size paper, input of image density “dark” on paper, and enlarged copy. The image forming apparatus according to claim 1, wherein: