JPH0434471A - Image forming device - Google Patents

Abstract

PURPOSE:To increase a developer filling ratio by operating a developer carrying velocity adjusting means and making the developer carrying velocity of at least either of a 1st developing device and a 2nd developing device higher in the case of detecting the lowering of the image density or the effect that the device is under the condition that the lowering of the image density is brought by an element by a detecting means. CONSTITUTION:In the case of detecting the lowering of the image density or the effect that the device is in the state where the lowering of the image density is brought by the element by the detecting means for detecting the lowering of the image density or the change in the element which influences the image density, the developer carrying velocity adjusting means 40 is operated by a controlling means. Then, the velocity for carrying the developer which is carried to the developing area of either of the 1st developing device and the 2nd developing device is made higher. Thus, the increased density can be kept in an optimum state in accordance with the increase of the developer filling ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic method using a magnetic bluff type developing device.

(Prior Art) Conventionally, as the image forming apparatus, a first developing device and a second developing device containing a developer containing toner of the same color are arranged on the side of a photoconductor, and a sleeve and a photoconductor are connected to each other. JP-A-1-307783 discloses a device in which the developer filling rate of the opposing developing areas is set to be higher in the first developing device than in the second developing device.
It is proposed in the publication.

Note that the developer filling rate is a value obtained by dividing the amount of developer transported to the development area by the distance between the photoreceptor and the development roller.

In this image forming apparatus, when the first developing device and the second developing device are driven almost simultaneously, the electrostatic latent image on the photoreceptor is first developed by the first developing device, and then reproduced by the second developing device. Ru. As a result, it is possible to obtain an image that has an image density equivalent to that of the original image and has excellent reproducibility of fine lines.

(Problem to be Solved by the Invention) However, even in the image forming apparatus, when the toner a degree of the first developing device, which affects the image a degree in particular, decreases,
It becomes difficult to secure a sufficient number of images. Furthermore, even if the toner density is appropriate, if factors that affect image density, such as humidity at the installation location of the image forming apparatus, decrease, the toner charge amount may increase and sufficient density may not be ensured.

(Means for Solving the Problems) Therefore, the present invention provides a magnetic brush type first developer and a second developer having toner of the same color on the side of the photoreceptor, and these developers are connected to the photoreceptor. The amount of developer conveyed per unit time to the opposing developing area is set so that the first developer is larger than the second developer. An image forming apparatus configured to reproduce an electrostatic latent image in a second developing device, comprising: a detection means for detecting an image J degree or a change in an element affecting the image J degree; and a developer conveyed to the development area. a developer transport speed adjusting means for adjusting a transport speed of the developer; and when the pressure detecting means detects that the image density is reduced or that the element is in a condition that causes a reduction in the image density, the developer transport speed adjusting means and a control means for increasing the developer conveyance speed of at least one of the first developing device and the second developing device.

(Function) According to the above configuration, when the detection means detects that the image density has decreased, or that an element that affects the image density is in a state that causes a decrease in the image density, the control means can control the developer transport speed adjusting means. It is operated.

As a result, the speed at which the developer is transported to the development area of at least one of the first developing device and the second developing device is increased, and the image density is maintained at an appropriate level as the developer filling rate increases. .

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 Configuration of image forming device FIG. 1 shows the main parts of an image forming apparatus.

b) Photoconductor 1 Photoconductor 1 is a cylindrical body with a photoconductor position on its outer circumferential surface, and is indicated by arrow a.
It is designed to rotate at a circumferential speed of 1v in the direction.

(11) Charging charger 2 The charging charger 2 has a wire 4 stretched inside a stabilizing plate 3 having a U-shaped cross section, a grid 5 provided in the opening, and the grid 5 facing the photoreceptor l. It is placed parallel to this. Further, the wire 4 and the grid 5 are connected to a power source 6, and the high voltage V, 4. ．． V□ can be applied.

In this example, VF11=6KV, Vot=6
It is 00V.

(iii) Inter-image eraser 7 The inter-image eraser 7 includes light-emitting diodes in multiple stages, which are arranged in parallel with the photoreceptor 1, so that each light-emitting diode can be turned on or off as desired.

(i,) Developing device 10. 20 The first developing device 10 and the second developing device 20 each include a developing roller 12 in an opening 11 facing the photoreceptor l.

The developing roller 12 includes a fixed magnet body 13 having a plurality of magnetic poles on its outer periphery, and a sleeve 14 covered with the magnet body 13.
It is composed of Further, there is a developing gap Ds (D,) between the sleeve 14 and the photoreceptor l.

D sz) is secured, and the regulation plate I5 is attached to the upper outer peripheral surface of the sleeve 14 with regulation gears D, (Db, , D, , ).
are facing each other. Further, the sleeve 14 is rotatably driven in the direction of the arrow by a drive device 40, which will be described later.

A stirring section 6 is formed at the rear (left side in the figure) of the opening 11, and a bucket roller 17 is disposed in this stirring section 16. Further, a magnetic sensor 18 is provided at the bottom of the stirring section 16.

The developing devices 10 and 20 are both equipped with a toner replenishment section 21. This toner replenishing section 21 has a conveyance path 22 provided at the bottom.
The conveyor blade 23 is provided with a conveyor blade 23, and the conveyor blade 23 is rotated by the drive of a motor 24, and toner is supplied from the toner replenishing part 21 to the stirring part 16.

Further, a photosensor 8 is provided on the upper part of the second developing device 20 so as to face the photoreceptor 1, and illuminates the outer peripheral surface of the photoreceptor 1 and detects the reflected light.

(]■) Drive device 40 In the drive device 40, as shown in FIGS. 2 and 3, a drive gear 42 is provided on a drive shaft 41 connected to a drive source (not shown). A large diameter gear 4 is attached to the rotating shaft 43 of the sleeve 14.
4 and a small diameter gear 45 are provided. A plunger 47 of the solenoid 46 is fixed to a connecting member 48, and a large diameter gear 5 is connected to a shaft 49 rotatably provided on the connecting member 48.
1 and a small diameter gear 52 are fixed.

In this drive device 40, when the solenoid 46 is turned on, the drive gear 42 meshes with the gear 51, and the gear 44 of the sleeve rotation shaft 43 meshes with the gear 52, as shown in FIG. Therefore, the driving force is gear 42.51, 52.4
4 to the sleeve rotation shaft 43.

Further, with the twist/right 46 in the OFF state, as shown in FIG.

Once this is done, the driving force is transmitted to the sleeve rotation shaft 43 through gears 42, 51, 45.

Here, the number of teeth 01 of the large diameter gear 44 is greater than the number n of teeth of the small diameter gear 45, and the number n of teeth of the large diameter gear 51.

is greater than the number of teeth n4 of the small diameter gear 52.

Therefore, the sleeve rotational speed VL when the solenoid 46 is turned on (the state shown in FIG. 3) is faster than the sleeve rotational speed VL when the solenoid 46 is turned off (the state shown in FIG. 4).

Further, if the ratio (velocity ratio) of the circumferential speed (V) of the sleeve 14 to the circumferential speed V1 of the photoconductor 1 is θ, then in this embodiment, the high speed state (v, = vH), θ=1.75, and the low speed state (V
*=Vt, ) so that θ-1,25.

(1v) Control device The control device CPU is connected to the above-mentioned photosensor 8 magnetic sensor 18, motor 24, 'lunoid 46, i [6, 70 and operation)' channel 1000, printed switch 101, etc., and the above-mentioned sensors The motors, etc. are each driven and controlled based on these signals.

(2) Multiple development operation A multiple development operation in which the first developing device 10 and the second developing device 20 are driven almost simultaneously to develop the electrostatic latent image on the photoreceptor 1 twice will be described.

Note that in the first developing device IO1 and the second developing device 20, the developing gear knob DSI of the first developing device 10 is set to Q, 5 mm, and the developing gear knob Dst of the second developing device 20 is set to 1.2 mm. Regulatory gear knob of developer unit 10.20.

Both Db++ and Dbt are set to Q and 5 mm.

Also, in the drive device 40 of the first developing unit 10, the solenoid 46 is on, and the sleeve 14! Well, high speed state (θ
= 1.75). On the other hand, in the drive device 40 of the second developing device 20, the eloid 46 is turned off, and the sleeve 14 is set to a low speed state (θ=1.25). However, the speed ratio θ of the first developing device IO may be switched to a low speed state by speed ratio switching control, which will be described later, so that an image of appropriate density can be obtained.

Under these conditions, the photoreceptor 1 rotates in the direction of arrow a, and the charger 2 applies high voltage vH□ to the wire 4.

A high voltage V82 is applied to the pad 5, and the outer peripheral surface of the photoreceptor 1 passing through the charging region X1 is charged to vH2.

Next, the image area of the charged photoreceptor 1 is exposed to image light at exposure position X, and an electrostatic latent image corresponding to the image to be reproduced is formed.

Subsequently, the non-image area of the photoreceptor l is illuminated by the inter-image eraser 7 in the charge-eliminating area X3, and the charges in the area are erased.

Furthermore, the electrostatic latent image on the photoreceptor l is
When passing through the portion facing the developing device 2o, the toner is developed in the developing areas X, , X, respectively.

The following operations are performed in the first developing device 10 and the second developing device 20.

The developer is mixed and agitated by the rotation of the chenotrol roller 17, and the toner and carrier come into frictional contact and are charged to opposite polarities. Further, the developer is scooped up by the care roller I7 and supplied to the developing roller 12.

The developer supplied to the developing roller 12 is held on the outer periphery of the sleeve 14 by the magnetic force of the magnet 13, and is conveyed in the direction of the arrow as the sleeve I4 rotates, and the amount of conveyance is controlled by the regulating portion 15. limited.

Here, the developer regulated by the regulating section 15 flows backward and falls into the stirring section 16 . On the other hand, the regulation gear knob Vb (Db+) between the regulation part 15 and the sleeve 14.

The developer that has passed through Db is conveyed in the direction of the arrow while forming a magnetic brush along the lines of magnetic force formed on the outer periphery of the sleeve by the magnetic force of the magnet body 13, so that the sleeve 14 and the photoreceptor 1 face each other. The outer peripheral surface of the photoreceptor 1 is rubbed in the development areas X, , X5.

The developer that has passed through the development areas X, , X, continues to be conveyed in the direction indicated by the arrow as the sleeve I4 rotates, and is released from the magnetic force of the magnet 13 at the portion facing the bucket roller 17 and falls into the stirring section 16. .

I want to do it now! Photoreceptor l passing through area X,,X,
are in contact with the magnetic plans of the first developer IQ and the second developer 20, respectively, and are connected to the image area potential of the electrostatic latent image and the power source 7.
The bias Vゎ(V
b+, Vbz), the charged toner electrostatically adheres to the electrostatic latent image area.

Here, the development gap DS+ of the first developer 10 is 0.6
mm, development length of the second developing device 20 + '7b Ds.

is set to 1.2 mm, and the developer filling rate in the first developing area X is higher than the developer filling rate in the second developing area X5.

Therefore, in the development area X4, the developer frequently comes into contact with the electrostatic latent image, and sufficient toner adheres to the electrostatic latent image.

However, the toner scraping effect due to contact with the magnetic brush is also large, and most of the toner adhering to the thin line electrostatic latent image is collected by the magnetic brush, resulting in the thin line passing through the first development area The amount of toner adhering to the electrostatic latent image is small. On the other hand, electrostatic latent images such as solid images and ordinary character images have sufficient toner attached to them, and are reproduced with sufficient density even if they are subjected to the scraping action of the magnetic brush.

Next, toner is again supplied to the electrostatic latent image conveyed to the development area X5, and the thin line is again visualized as a toner image.

Here, the developer filling rate of the second development area X is higher than the developer filling rate of the first development area X4.

Therefore, the probability that the magnetic plan will come into contact with the toner on the photoconductor (2) is lower than that in the first development area A faithful reproduction of the original. Furthermore, solid images and character images of normal thickness are reproduced with sufficient density.

(2) Zero Image Density Control Image and density control performed during the multiple development will be described with reference to the attached flowchart.

(i) Main Routine (See Figure 4) In the main routine, when the power is turned on to the image forming apparatus and the program starts, Step 1 starts.

In step #l, the control device CPU is initialized and each component device is set to the initial mode.

In step #2, the internal timer initialized in step #1 is started. This internal timer is used to make the time length of one routine constant regardless of the contents of each of the following subroutines, and the various timers in each subroutine are counted based on the length of this l routine.

In step #3, a copy control subroutine is executed, and if the print switch 101 is pressed, an image forming operation is executed by the subroutine.

In step #4, other processes, such as a subroutine for adjusting the temperature of the fixing device, are called and executed. Since the contents of this subroutine are unrelated to the present invention, a description thereof will be omitted.

In step #5, it is determined whether the internal timer set in step 2 has expired, and after waiting for the internal timer to expire, the process returns to step #2.

(11) Copy control subroutine (see FIG. 5) In this subroutine, in step #10, it is detected whether the print switch 101 of the image forming apparatus is on-edge.

Note that on-edge refers to a state in which the signal input from the print switch 101 to the control device CPU changes from off to on.

When on-edge is detected in step #10, the copy start flag FC5 is set to "l" in step #11,
In step #12, the concentration detection flag FID is set to "1" and the process proceeds to step #13. Note that the copy start flag FCS is a flag for determining whether or not to start a copy operation.

Further, the density detection flag FID is a flag for determining whether or not to execute density detection processing, which will be described later.

On the other hand, if on-edge is not detected in step #10, step #11.
Proceed to step 13.

In step #13, it is determined whether the copy start flag FC5 is "BI" or not, and when the copy start flag FC8 is "1", each step after step #14 is executed, and if the copy start flag FC3 is "O". Returns to the main routine.

Therefore, while waiting until the print switch 101 is pressed, steps #11 and #12 and steps #14 to #21 described below are not executed.

Next, steps #14 to #18 include image density detection,
Controls include speed ratio switching, copy paper feeding and transport, optical system, and photoreceptor surroundings.

Next, in the toner MiHi control subroutine of step #19, the toner concentration is measured by the signal from the magnetic sensor 18, and based on the result, if the toner concentration is less than a predetermined base concentration, the motor 24 is driven to stir the toner. Part 16
Toner is replenished.

Finally, in step #20, it is determined whether or not the copying operation has been completed, and if the copying operation has been completed, step #21
Then, the copy start flag FC5 is reset to "0" and the process returns to the main routine.

(iii) Image density detection subroutine (see Figure 6)
In this subroutine, in step #30, it is determined whether the concentration detection flag FID is "1" or not.
If D is "1", step #31 is executed, and if the density detection flag FID is not set, the process returns to the copy control sub-chin.

In step #31, an fA degree detection processing sub-chin is executed. The details of this process will be described later.

In step #32, it is determined whether the processing of the density detection processing sub-chin has been completed, and if it has not been completed, the process returns to the copy control sub-chin. When the density detection processing sub-chin is completed, the density detection flag FID is reset to "0" in step #33, the speed ratio switching flag FMC is set to "1" in step #34, and the copy control sub-chip is reset to "0". -Return to Chin. This speed ratio switching flag FM
C is a flag for executing switching processing of the speed ratio θ of the first developing device IO.

(iv) A degree detection processing subroutine (FIG. 7 all PCs) In this subroutine, in step #40, the charger 2 is turned on, and a predetermined high voltage is applied to the wire 4, grid, and gate 5 from the power supply 6, The outer peripheral surface of the photoreceptor 1 rotating in the direction of arrow a is charged to a constant potential.

Next, in step #41, the inter-image eraser 7 is turned on and the individual light emitting diodes are blinked to form a pattern latent image of a predetermined size on the outer peripheral surface of the photoreceptor 1 for image detection.

Subsequently, in step #42, the first developing device 10 is driven to convert the pattern latent image to %iL and form a toner pattern image for density detection.

Finally, the photo sensor 8 reads the reflection density (image density) ID of the toner pattern image.

(v) Speed ratio switching subroutine (see Figure 8) In this subroutine, the speed ratio switching flag FMC is set in step #50.
or “l”. This speed ratio switching flag FM
C is set to "1" at step=34, as described above.

If the speed ratio switching flag FMC is not "1", that is, if image 1]D is not detected, or if this speed ratio switching subroutine has ended and the copy operation is being executed, the copy control flag FMC is set to "1". Return to subroutine.

When the speed ratio switching flag FMC is “1”, step #5
1, the image density rD and the first reference density ID are compared.

If ID>ID, and the image density is darker (too dark) than the first reference density, the solenoid 46 in the drive device 40 of the first developing device 10 is turned off (low speed state) in step #52. Determine whether or not there is.

As a result of the determination, if the solenoid 46 is turned off and set to a low speed state, the process returns to the copy control subroutine. Conversely, if the solenoid 46 is turned on without being turned off and set to the high speed state, the solenoid 46 is turned off in step #53 and switched to the low speed state, and then the speed change flag FMC is set to "0'' and returns to the copy control subroutine.

As a result, the developer filling rate in the first development area X4 decreases, and the image density decreases.

If it is determined that the image density is lower than the image density [D or the first reference density ID, Step #55 selects the image density ID or the second base 4 density I. It is determined whether it is lower (too thin) than D2 (<ID,).

If l<ID, it is determined in step #56 whether or not the solenoid 46 is set to the off state (low speed state), and if it is turned on and is set to the high speed state, the process returns to the copy control subroutine.

On the other hand, if the solenoid 46 is turned off and in a low speed state, the solenoid 46 is turned on in step #57 to switch to a high speed state, and in step #57, the solenoid 46 is turned on and switched to a high speed state.
At step 58, the speed switching flag FMC is reset to "0" and the process returns to the copy control subroutine. This increases the developer filling rate in the first development area X4,
Image density increases.

In this manner, when multiple development processing is executed, the first developing device 10 uses the image density ID before performing the multiple development processing.
When the image density ID is higher than the first group 11i density ID, the developer filling rate is lowered, and when the image density ID is lower than the second standard 1 degree 1 island, the developer filling rate is increased, and the image i' JItf
is set between ID and ID.

Therefore, an image with proper a degree can be obtained without dark or light gaps.

■Other Embodiments In the embodiments described above, a toner pattern image is formed on the photoreceptor 1 prior to multiple development, and the first toner pattern image is formed based on the image density.
Although the speed ratio θ of the developing device 10 is changed, as shown in FIG. The sleeve rotation speed may be increased, and conversely, when the humidity falls below the reference value, the sleeve rotation speed may be decreased.

Further, although the speed ratio θ of the first developing device 10 is changed according to the image density, etc., the speed ratio of not only the first developing device 10 but also the second developing device 20 may be changed. , 1st
The speed ratio of the developing device 10 and the second developing device 20 may be changed.

Further, the driving device 4 for the first developing device IO and the second developing device 20
The number of gear teeth at 0 may be changed to change the switching speed ratio of both developing devices 10 and 20.

Furthermore, the means for switching the speed ratio of the developing device is not limited to the above embodiment.

(Effects of the Invention) As is clear from the above description, in the present invention, in an image forming apparatus that simultaneously drives a plurality of developing devices to develop the same electrostatic latent image multiple times, the image density decreases or the image density decreases. When it is detected that the state is set, the first developing unit,
In at least one of the second developing devices, the conveying speed of the developer conveyed to the developing area becomes faster, and the developer filling rate increases.

Therefore, an image with appropriate density and excellent density reproducibility and fine line reproducibility can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross section of main parts and a circuit configuration of an image forming apparatus;
2.3 is a front view of the drive device, FIGS. 4 to 8 are flowcharts showing operation control of the image forming apparatus, FIG. 4 is a main routine, FIG. 5 is a subroutine for copy control, and FIG. 6 is a flowchart showing operation control of the image forming apparatus. 7 is an image density detection subroutine, FIG. 7 is an image detection processing subroutine, and FIG. 8 is a speed ratio switching subroutine. 1... Photoreceptor, 8... Photo sensor, 10... First
Developing device, 20... Second developing device, 40... Drive device,
CPU...control device. Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Haka 1 person 2nd Hosho 1 Figure 3

Claims (1)

[Claims] (1) A magnetic brush type first developer and a second developer having toner of the same color are provided on the side of the photoreceptor, and the number of times per unit time when these developers are conveyed to the development area facing the photoreceptor is The amount of developer in the first developing device is set to be larger than that in the second developing device, so that the electrostatic latent image on the photoreceptor developed by the first developing device is reproduced in the second developing device. In the image forming apparatus according to the present invention, a detection means for detecting an image density or a change in an element affecting the image density; a developer transport speed adjusting means for adjusting a transport speed of the developer transported to the development area; When the detection means detects that the image density has decreased or that the element is under a condition that causes the image density to decrease,
An image forming apparatus comprising: a control means for operating the developer conveyance speed adjusting means to increase the developer conveyance speed of at least one of the first developing device and the second developing device.