JP2800826B2 - 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. 2. Description of the Related Art In an image forming apparatus having an electrophotographic process, a toner concentration in a developer contained in a developing device for developing an electrostatic latent image needs to maintain a certain appropriate range. If the toner density in the inside is too low, the density of the toner image will be low. Therefore, a toner replenishing system that replenishes a predetermined amount of toner when detecting that the toner density or the toner image density in the developer has dropped below a predetermined level, and always keeps the toner density within an appropriate toner density range has been conventionally provided. I have. That is, a magnetic sensor that detects the magnetic permeability of the developer is provided in the developing device, the change in the magnetic permeability of the developer is detected according to the change in the toner concentration, and based on this, when the toner concentration is lower than the reference value, A certain amount of toner is supplied. Alternatively, a latent image of the reference pattern is formed on the photoreceptor, which is developed and the density of the toner image formed on the photoreceptor is detected by an optical sensor, and the density becomes lower than a preset value. At this time, a fixed amount of toner is supplied. The constant amount of toner is replenished many times until the toner density returns to the reference value. At this time, the fixed toner amount to be replenished is relatively multiple.
This is because, when a small amount of toner is supplied, for example, when the image area ratio of a document is large and continuous copying is performed, the toner supply cannot follow the toner consumption and the toner concentration is reduced. is there. [Problems to be Solved by the Invention] However, in a case where a large amount of toner is consumed in a short time and toner replenishment is repeated, the replenished toner is not sufficiently dispersed in the developer, and for example, sufficient friction with the carrier is caused. Poorly charged toner, which cannot be charged, is generated, which may appear as "fogging" on the copy, or may scatter into the apparatus to cause contamination. The present invention has been made in view of the above circumstances,
When performing image formation that is expected to rapidly consume toner,
It is an object of the present invention to provide an image forming apparatus in which the toner density in a developing device does not fall below a reference value. 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; input means for inputting image forming conditions of the image forming means; and detecting a toner concentration of a developer in the developing device. A toner concentration detecting unit, a toner replenishing unit for replenishing toner in the developing device, and when the toner concentration detected by the toner concentration detecting unit is lower than a reference value, First control means for issuing a command to supply toner into the developing device; determining means for determining whether or not the image forming conditions input by the input means correspond to conditions under which rapid toner consumption is predicted; The discriminator When it is determined that the image forming condition is a condition for which rapid toner consumption is predicted, even if the toner concentration is equal to or higher than a reference value, the toner is supplied to the developing device by the toner replenishing means. The second command
And control means. 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 paper is transferred with a toner image by a transfer charger 37, is peeled off from the surface of the photosensitive drum 1 by a separation charger 38, passes through a conveyor belt 57, and melts the toner in a fixing device 58. After the image is fixed, the sheet 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 ) on the upper portion of the porcelain 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 7, and transfers the developer supplied from the bucket roller 11 to the photosensitive drum 1. Conveyed to the opposite developing area (A),
The developing is performed by bringing the photosensitive drum 1 into contact with the electrostatic latent image formed on the photosensitive drum 1. 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. 9 is a smoke-prevention mylar, which is made of a polyethylene film (0.1 mm thick).
The casing 3 is attached to an upper part of the casing 3 facing the photosensitive drum 1, and prevents dust powder generated 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 has a print start switch 101 for instructing the start of transfer, 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 tonneau density, a density up switch 108, an automatic density adjustment switch 109, an upper paper feed unit 50 or a lower paper feed unit 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. Note that the copy conditions may also be determined by a command from a device other than the operation panel, such as an automatic developing device that automatically feeds the placed document onto the document glass and automatically discharges the document after copying is completed. It is formed. 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., 1
The drive time of the developing unit is longer than the copy time per sheet (when the main motor M1 is turned on) Is long, and the developer is sufficiently stirred. On the other hand, when copying is continuously performed, the driving time of the developing device substantially corresponds to the copying time. Therefore, for example, 100 copies are taken one by one and continuous copying is performed.
There is a large difference in the degree of stirring of the developer. 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 the copy is enlarged to A4, B4, or A3, for example, the conner 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 S104
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-copies is equal to or more than α does not mean the number of copies initially set as the multi-copy, but the number of copies that have not been copied. FIG. 9 is a flowchart showing a subroutine of toner supply control. As shown in FIG. 9, it is determined whether or not the toner supply timing has come (step S200). At the toner supply timing, the toner density Tc is changed to the reference toner density.
It is determined whether it is smaller than Tca (step S202).
In this embodiment, the toner supply timing is once per copy. When the toner density Tc is lower than the reference toner density Tca, the toner supply motor is turned on, and a timer TM1 for setting the ON time of the toner supply motor is set (steps S204, S206). The timer TM1 performs toner replenishment (hereinafter, referred to as feedback toner replenishment) when the toner concentration falls below the reference value. When the toner density Tc is equal to or higher than the reference toner density Tca, it is determined whether the flag A is "1" (step S208). If the flag A is "1", the toner supply motor is turned on. Timer TM that defines ON time together with
2 is set (steps S210, S212). This timer TM2
As a result, toner replenishment (hereinafter, referred to as feedforward toner replenishment) according to the image forming conditions is performed. Here, the ratio of the time specified by the timer TM1 to the time specified by the timer TM2 is 10 to 1, and 200 mg / sheet of toner is used according to the time specified by the timer TM1 and 20 mg / sheet is used according to the time specified by the timer TM2. Is supplied. In this embodiment, the amount of feedback toner supply and the amount of feedforward toner supply are adjusted by controlling the on-time of the constant-rotation toner motor. But,
For example, the on-time of the toner motor may be kept constant, and the number of rotations may be varied, or may be varied with the on-time and the number of rotations. Also, the feedforward toner replenishment amount is not desired to be too large because the original image ratio of the document is very small, but continuous copy is considered. For example, the feedback toner replenishment amount, the developer amount, and the toner amount The optimum amount may be determined depending on conditions such as the charging property and the stirring ability of the developer. Thereafter, when both the timer TM1 and the timer TM2 have expired, the toner supply motor is turned off (step
S214, 216, 218). On the other hand, if the timer TM1 has not expired, or if the timer TM2 has not expired, step S21
Skip 8 and return to the main routine. FIG. 10 is a graph showing the number of times of feed-back toner replenishment with and without feed-forward toner replenishment. As shown in FIG. 10, the number of feedback toner replenishments (normal replenishment) in which a large amount of toner is replenished at one time is reduced when feed-forward toner replenishment (quantity replenishment) is not performed. . For this reason, for example, the feedback toner is replenished many times in a short time, and thus the stirring is not sufficiently performed. As a result, the toner is not sufficiently dispersed in the developer, and poorly charged toner is generated. Fogging and Kobore can be prevented beforehand. In the above embodiment, the feedforward toner supply amount is constant. However, the feedforward toner amount may be changed according to image forming conditions. That is, not only is it binaryly determined whether or not the image forming condition causes the toner consumption to be rapid, but also whether or not the image forming condition is more rapid is determined according to the image forming condition. Feedforward toner supply amount. [Effects of the Invention] With the above-described configuration, when an image is formed in which rapid consumption of toner is predicted, toner is forcibly supplied. Therefore, if the toner density in the developing device does not fall below the reference value. Therefore, an image having an appropriate image density can always be obtained.

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 FIG. 10 is a graph showing the number of feedback toner replenishments with and without feedforward toner replenishment. 1 photosensitive drum 6 developing sleeve 11 bucket roller 16 first 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. Input means for inputting image forming conditions of the image forming means; toner concentration detecting means for detecting a toner concentration of a developer in the developing device; and toner replenishing means for replenishing toner in the developing device When the toner density detected by the toner density detecting means is lower than a reference value, a first control means for instructing the toner replenishing means to replenish the toner in the developing device; and Discriminating means for discriminating whether or not the input image forming condition corresponds to a condition in which rapid toner consumption is predicted; and the image forming condition is a condition in which rapid toner consumption is predicted by the discriminating means. And judgment And a second control unit for instructing the toner replenishing unit to replenish the toner into the developing device even if the toner concentration is equal to or higher than a reference value. apparatus. 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: