JPH0588542A - Developing device - Google Patents

Abstract

PURPOSE:To provide the developing device which can sufficiently supply a developer to a developer carrying member side by agitating means regardless of whether the printing rate of an image is high or low. CONSTITUTION:The agitating means 14, 15 of the developing device in which the internal developer T is supplied toward an developer carrying member 8 by the agitating means 14, 15 rotated at a constant speed in a specified direction are rotated at the speed higher than in an ordinary case if the printing rate of the image is high by the signal from the control means judging the high or low rate of the printing rate of the image. Then, the agitating means 14, 15 are rotated at the high speed and the developer T is supplied more to the developer carrying member 8 side when the printing rate of the image is high and even if the developer around the developer carrying member 8 is rapidly consumed; therefore, the insufficiency of the developer T around the developer carrying member 8 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus such as a copying machine or a laser beam printer which employs an electrophotographic system.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a developer (toner) is supplied to a latent image formed on an image carrier,
Although it is necessary to visualize this latent image as a toner image, such developing work is performed by the developing device.

As shown in FIG. 1, such a developing device has a developing roller 8 as a developer carrying member, and the developing roller 8
Developing unit 7 for supplying the toner T to the image carrier 1 side via the
And the developing unit 7 that holds the toner T inside and is adjacent to each other via the stirring members 14 and 15 that rotate at a constant speed in a fixed direction.
In many cases, it is composed of a developer storage section 13 for supplying the toner T and the like.

In the toner scooping type developing device 2, the toner T in the developer accommodating portion 13 is supplied to the developing portion 7 by an amount corresponding to the rotation speed of the stirring members 14 and 15, but the toner holding amount is A small amount of toner remaining amount detecting means 10 is provided in the developing unit 7, and when the developing unit 7 runs out of toner, a display to that effect is displayed on the panel of the image forming apparatus main body side. There are also many.

[0005]

However, in the developing device 2 of the toner scooping type in which the toner holding amount in the developing unit 7 is small as described above, an image having a high printing rate and a large consumption amount of the toner T such as a solid black image is formed. If the toner T is continuously formed, the toner T may not be supplied from the developer accommodating portion 13 to the developing portion 7 via the stirring members 14 and 15 in time, and the toner T may be insufficient in the developing portion 7. Occurs.

In this case, a white spot (a part where the toner is hardly supplied occurs in a part of the image) occurs before the display of the lack of toner by the remaining toner amount detecting means 10 is displayed on the panel. There was an inconvenience.

The present invention has been made in view of the above problems, and an object thereof is to sufficiently supply the developer to the developer carrying member side by the stirring means regardless of whether the printing rate of the image is high or low. To provide a developing device.

[0008]

In order to achieve the above object, the present invention is directed to a developing device in which a developer inside is supplied to a developer carrying member by a stirring means which is rotated in a fixed direction at a constant speed. When the image printing rate is high, the agitating means is rotated at a higher speed than usual in response to a signal from the control means for judging whether the image printing rate is high or low.

[0009]

In the developer scooping type developing device in which the developer inside is supplied to the developer carrying member side by a predetermined amount by the stirring means, if an image having a high printing rate is continuously formed to some extent, the development by the stirring means is performed. The agent is not supplied in time, and a so-called blank image is formed.

Therefore, the printing rate of the image to be formed is calculated in advance, and when the printing rate is higher than the predetermined value, the stirring means is rotated at a higher speed than usual to supply the developer sufficiently near the developer carrying member. I made it possible. It is possible to increase the rotation speed of the stirring means regardless of the printing rate, but this is not appropriate because the deterioration of the developer is accelerated in this case.

[0011]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.
Will be explained.

First, the overall structure of the process cartridge mounted in the printer body of the laser beam printer will be described with reference to FIG. Reference numeral 1 in the drawing denotes a photosensitive drum which is an electrophotographic photosensitive member (image bearing member), and is rotated in the direction of the arrow in the drawing. Around the photosensitive drum 1, a developing device 2,
A charging roller 3 and a cleaning device 4 are provided, these are incorporated in a cartridge container 5a, and the process cartridge 5 is detachably provided to the printer body. This process cartridge 5 facilitates maintenance by replacing the entire process cartridge 5 when the internal individual equipment reaches the end of its life, such as when the developer (toner) T in the developing device 2 is consumed. It is for the purpose of planning. Reference numeral 6 denotes a drum cover for protecting the photosensitive drum 1, which is opened / closed in accordance with attachment / detachment of the process cartridge 5 to / from the printer body.

That is, the photosensitive drum 1 uniformly charged by the charging roller 3 is exposed to the image light L, and the photosensitive drum 1 is exposed.
When the electrostatic latent image is formed on the electrostatic latent image, the electrostatic latent image is directed toward the developing device 2 as the photosensitive drum 1 rotates, and the developing device 2 supplies the toner T to convert the electrostatic latent image into a toner image. .. The toner image is transferred onto a transfer paper via a transfer charger or a transfer roller (not shown) on the printer body side, the transfer paper carrying the toner image is sent to a fixing device, and the toner image is fixed as a permanent image. To be done. Further, the photosensitive drum 1 after the transfer is cleaned of the residual toner through a cleaning blade 4a of a cleaning device 4 which slides on the outer surface of the photosensitive drum 1, and is prepared for the next image formation.

The developing device 2 is disposed on the photosensitive drum 1 side,
A developing unit 7 for supplying the toner T to the photosensitive drum 1, and a developing unit 7 provided adjacent to the developing unit 7 for holding the toner T therein and supplying the toner T to the developing unit 7 having a small toner holding amount. And a developing agent storage section 13 and the like. The developing unit 7 is rotated with a certain gap from the photosensitive drum 1, and the toner T is magnetically held on the outer peripheral portion of the photosensitive drum 1 by the action of an internal magnet or the like. A developing roller 8 as a developer carrying member to be supplied to the developing roller 8; a rubber blade 9 whose one end rubs against the developing roller 8 to regulate the thickness of the toner T around the developing roller 8 to a constant value;
A toner remaining amount detecting means 10 and the like for detecting the amount of the toner T in the developing unit 7 by detecting the electrostatic capacitance between and are provided.

In the developer accommodating portion 13, rotating shafts 14a, 14a are provided.
Two first and second stirring members 14 and 15 are provided, 5a of which are provided in parallel to the axial direction of the photosensitive drum 1 and the developing roller 8, and the first and second stirring members 14 and 15 are provided therebetween. The toner T in the developer accommodating portion 13 is supplied into the developing portion 7 through the opening 11 between the developer accommodating portion 13 and the developing portion 7. The first and second stirring members 14 and 15 rotate in the direction of the arrow in FIG. 1 at a constant speed, and supply a constant amount of toner corresponding to the rotation speed to the developing unit 7.

A reference numeral 12 in FIG. 1 denotes a seal member, which prevents the toner T in the developer accommodating portion 13 of the developing device 2 from leaking to the outside through the developing portion 7 in the unused process cartridge 5. It is for doing.

That is, when the image forming work is started on the photosensitive drum 1 side, the first and second stirring members 14, 1 of the developing device 2 are started.
5 rotates, and the toner T in the developer accommodating portion 13 is transferred to the developing portion 7
And the developing roller 8 attracts and holds (carries) the toner T on its outer peripheral surface and rotates. Then, the toner T on the developing roller 8 is regulated by the rubber blade 9 into a thin layer having a uniform thickness, and is moved to the photosensitive drum 1 side, and then the developing bias voltage applied to the developing roller 8 applies the photosensitive drum 1 to the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 is made visible as a toner image. Further, the toner T is insufficient in the developer accommodating portion 13, and the sufficient amount of the toner T is not supplied to the developing portion 7.
Is not supplied, the developing unit 7 runs out of toner,
The toner remaining amount detecting means 10 detects the toner shortage and displays a message to that effect on a panel or the like of the printer body.

Now, the toner T in the developer accommodating portion 13 as described above is pumped up to the developing portion 7 side through the first and second stirring members 14 and 15, and the amount of the toner T held in the developing portion 7 is reduced. In the relatively small developing device 2, when images (toner images) having a high printing rate are continuously formed to some extent, the amount of toner T consumed in the developing portion 7 rapidly increases, so that the developer accommodating portion 13 First and second stirring members 1
The supply of the toner T to the developing unit 7 by 4 and 15 is not in time, and the toner shortage occurs in the developing unit 7 (around the developing roller 8).

Here, if the toner T in the developing unit 7 is insufficient, the toner remaining amount detecting means 10 is activated and a message to that effect is displayed on the panel of the printer body, so that the operator can immediately stop the image forming work. However, when the toner consumption amount rapidly increases as described above, a defective image is formed before the detection by the toner remaining amount detecting unit 10, and a so-called blank image (image in which toner is insufficiently supplied) is formed. Will form.
It is also conceivable to rotate the first and second stirring members 14 and 15 at a high speed all the time, but since toner in the developing device 2 is deteriorated in this way, the high speed of the first and second stirring members 14 and 15 is high. In terms of minimizing the rotation time,
It is not appropriate to constantly rotate the second stirring members 14 and 15 at a high speed.

Therefore, in the present invention, the printing rate of the image is calculated before the image forming (developing) work, and if the printing rate is higher than a predetermined value (for example, 30%), the first and second stirring members 1 are
4, 5 are rotated at a rotation speed of 50 rpm (hereinafter referred to as high speed) higher than a normal rotation speed of 20 rpm (hereinafter referred to as low speed) to supply the toner T from the developer storage unit 13 to the development unit 7. Is larger than in the normal case, and the rapid toner shortage around the developing roller 8 in the developing unit 7 as described above is eliminated, and white spots and the like do not occur in the formed image due to the high and low image printing rates. I did it.

That is, in the laser beam printer, as shown in FIG. 3, the image signal S1 from the image reader 24 for the original image is once stored in the computer 25 on the host side, and then this image is transmitted via the computer 25. Since the signal S1 is output to the printer main body 26, the image print ratio is determined by the computer 25 on the host side.
In advance, calculation is made, and it is judged whether the printing rate is higher or lower than a predetermined value (30%), and a high printing rate or low signal S2 from the computer 25 is sent to the controller 27 of the printer main body 26 to develop it. The first of the device 2,
The second stirring members 14 and 15 are rotated at high speed or low speed.

To explain this with reference to FIG. 4, after the image signal from the image reader 24 is stored in the host computer 25 (step 1), the computer 25
Then, the printing rate η for one page of the original image is calculated (step 2), and it is judged whether or not the printing rate η is 30% or more (step 3). If the print ratio η is 30% or more, the determination result is YES, and the high print ratio signal S2 is output to the printer main body 2
6, the first and second stirring members 14 and 15 are rotated at high speed (step 4). If the print rate η is less than 30%, the result is NO, and the low print rate signal S2 is output to the printer main body 2
6, and the first and second stirring members 14 and 15 are rotated at a low speed (step 5). When an image of one page of the original is formed by the developing device 2, the printing rate η becomes 0, for example.
(Step 6), the printing rate η for the next one page of the original image is formed again by the host computer 25, and the same operation is repeated.

Next, a specific method of driving the first and second stirring members 14 and 15 and a method of switching the rotation speed will be described with reference to FIG. Incidentally, FIG. 2A shows the first and second stirring members 1.
4 and 15 show a case where they are rotated at a high speed, and FIG. 7B shows a case where they are rotated at a low speed.

V rotated by the actuator 16
The large and small gears 18a,
First and second stepped gears 1 including 18b, 19a and 19b
The rotary shafts 8 and 19 are pivotally supported, and by the rotation of the joint bar 17, the small gears 18b and 19b of the first and second stepped gears 18 and 19 are rotated by the rotary shaft 1 of the first stirring member 14.
The large gear 18 of the first and second stepped gears 18 and 19 can be meshed with the first gear 20 attached to the 4a.
The a and 19a can mesh with a drum gear 22 attached to the end of the photosensitive drum 1. Also, the first gear 2
Zero meshes with the second gear 21 attached to the rotary shaft 15a of the second stirring member 15 via the idler gear 23.

Here, the large gears 18a and 19a of the first and second stepped gears 18 and 19 have substantially the same number of teeth, but the small gear 19b of the second stepped gear 19 has the same number of teeth. Since the number of teeth of the small gear 18b of the gear 18 is twice or more,
As shown in (a), the large and small gears 19a and 19b of the second stepped gear 19 mesh with the drum gear 22 and the first gear 20, and the second stepped gear 19 is separated from these gears 22 and 20. 2B, the first and second stirring members 14 and 15 rotate at high speed, but as shown in FIG. 2B, the large and small gears 18a and 18b of the first stepped gear 18 are replaced by the drum gear 2
When the second stepped gear 19 is separated from these gears 22 and 20, the first and second agitating members 14 and 15 are rotated at a low speed. ..

That is, in a normal image forming operation having a low printing rate, the actuator 16 operated by the controller 27 causes the joint bar 17 to rotate clockwise as shown in FIG. Stepped gear 1
8 large and small gears 18a and 18b are meshed with the drum gear 22 and the first gear 20. When the photosensitive drum 1 is rotated by a drive source (not shown) on the apparatus body side, the first and second gears 2 are passed through the first stepped gear 18 and the idler gear 23.
0 and 21 are rotated, and the first and second stirring members 14 and 15 are rotated at low speed. When forming an image with a high printing rate, the joint bar 17 rotates counterclockwise as shown in FIG.
The small gears 19a and 19b are connected to the drum gear 22 and the first gear 2.
Mesh with 0. Then, as the photosensitive drum 1 rotates, the first step, the second step, and the second stepped gear 19 and the idler gear 23 are performed.
The gears 20 and 21 are rotated, and the first and second stirring members 14 and
15 is rotated at high speed.

Next, a second embodiment of the present invention will be described with reference to FIG. The same reference numerals are given to those having the same functions as those according to the first embodiment, and the description thereof will be omitted.

In the first embodiment, the image print ratio is calculated by the host computer 25 that sends the image signal S1 to the printer body 26 and operates the printer body 26. However, in the present embodiment, the printer body is calculated. The print rate of the image is calculated on the controller 27 side of 26.

That is, the controller 2 of the printer body 26
A buffer (intermediate storage unit) is provided in the buffer 7, and the image signal S sent from the host computer 25 or the like to the buffer.
For example, the laser ON signal time (indicating a portion where an image is formed by toner) of 10 scans (10 scans of the laser scanner) of 1 is stored. Then, the calculation unit of the controller 27 divides the laser ON signal time by the scanning time of 10 scans to calculate the print ratio of the image for the 10 scans, and the judgment unit has a high print ratio (30% or more). Make them judge whether or not. Then, the controller of the controller 27 rotates the actuator 16 in a predetermined direction in accordance with the increase or decrease of the printing rate, and the first or second stepped gear 18, 1
The first and second stirring members 14 and 15 are rotated at high speed or low speed so that any one of 9 is selected.

FIG. 5 is a flow chart showing the above operation. After storing the laser ON signal for 10 scans (step 11), the printing rate η for 10 scans is calculated (step 12). It is judged whether or not the printing rate η is 30% or more (step 13). If the printing rate η for 7 scans is 30% or more at step 13, YES
Then, the first and second stirring members 14 and 15 are rotated at high speed (step 14), and if the printing rate η is less than 30%, NO is obtained and the first and second stirring members 14 and 15 are rotated at low speed. (Step 15). When the image formation (development) for 10 scans is completed, the printing rate η is reset to, for example, 0 (step 16), the same operation is performed again for the images for the next 7 scans, and finally the original 1 Repeat the same operation for each page. In the last part of one page, the image signal may be less than 10 scans.

As described above, although the printing rate calculating means and the like are different from those of the first embodiment, the same effects as those of the first embodiment can be obtained in this embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG. The same reference numerals are given to those having the same functions as those according to the first embodiment, and the description thereof will be omitted.

In the second embodiment, the print ratio of the image for 10 scans is calculated, and the rotation speed of the first and second stirring members 14 and 15 is controlled to be low or high every time the image is formed for 10 scans. However, in this embodiment, the first and second stirring members 14 and 1 are formed every time one page of the original image is formed.
The rotation speed of 5 was controlled to be low or high. Note that such control is performed by the controller 27 of the printer body 26 as in the second embodiment.

FIG. 6 shows a control flow in such a case, which will be described below. Controller 2
After the laser ON signal for 10 scans is stored in the buffer of 7 (step 21), the print rate η for 7 scans is calculated in the same manner as in the second embodiment (step 22), and the print rate η is calculated. Is judged to be 30% or more (step 23). If the printing rate η is 30% or more, YES is set and the value n1 (initial value 1) indicating the high printing rate is set to n1 + 1 (step 24). If the printing rate is less than 30%, NO is set and the printing rate is low. The indicated value n2 (initial value 1) is set to n2 + 1 (step 25). Then, it is judged whether or not the printing ratios for one page of the original have all been calculated (step 26), and if not calculated, the printing ratio η1 is reset to 0 (NO) (step 27), and the process returns to step 1 again. move on.

If the printing rate for one page is all calculated in step 26, the determination is YES and the printing rate η = n1 / n2 for one page is calculated (step 2
8). Then, it is determined whether or not the printing rate η2 is, for example, 60% or more (step 29). If the printing rate η2 is 60% or more, it is determined that the printing rate is high, and the determination result is YES and the first and second stirring members 14, 15 is rotated at a high speed (step 30), and if the printing rate η2 is less than 60%, it is determined that the printing rate is low, NO is set, and the first and second stirring members 14 and 15 are rotated at a low speed (step 31). And if the image for one page is formed,
The printing rate η2 is reset to 0, and the values n1 and n2 indicating the high and low printing rates for 10 scans are also reset to 1 (step 32). Then, the same operation is repeated for the original image of the next page.

Here, in order to switch the first and second stirring members 14 and 15 to high speed and low speed rotation in this embodiment, FIG.
Without using the actuator 16 or the like as shown in, the rotation speed of the photosensitive drum 1 is switched to a high speed (for example, 2.5 times the normal speed) or a low speed.
The speeds of the second stirring members 14 and 15 are switched. Therefore, the switching of the first and second stirring members 14 and 15 to the high speed rotation is performed at the time when the image forming work is not performed on the photosensitive drum 1 side.

As described above, although the printing rate calculating means and the like are different from those of the first embodiment, the same effects as those of the first embodiment can be obtained in this embodiment. Further, in the present embodiment, when switching the first and second stirring means 14 and 15 to high speed and low speed rotation, no gear switching means is required, so that the apparatus can be simplified and downsized. You can

[0039]

As is apparent from the above description, according to the present invention, since the rotation speed of the stirring means of the developing device is set to be high or low depending on whether the image printing rate is high or low, the image printing rate is high. Regardless of this, it is possible to always supply a sufficient amount of developer to the developer carrying member side. Therefore, even if images having a high printing rate are continuously formed, image defects such as white spots do not occur in the image.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a process cartridge including a developing device according to a first embodiment.

FIG. 2 is a diagram showing a drive mechanism of first and second stirring members of the developing device.

FIG. 3 is a diagram showing an overall configuration of a laser beam printer having the developing device.

FIG. 4 is a flowchart for rotating the first and second stirring members of the developing device at high speed or low speed.

FIG. 5 is a flowchart for rotating the first and second stirring members of the developing device according to the second embodiment at high speed or low speed.

FIG. 6 is a flowchart for rotating the first and second stirring members of the developing device according to the third embodiment at high speed or low speed.

[Explanation of symbols]

 2 developing device 8 developing roller (developer carrying member) 14, 15 first and second stirring means (stirring means) 25 computer (controller)

Claims (1)

[Claims] 1. In a developing device in which a developer inside is supplied toward a developer carrier by a stirring means rotated at a constant speed in a certain direction, a control means for judging whether the printing rate of an image is high or low. The developing device is characterized in that, when the image printing rate is high, the stirring means is rotated at a higher speed than usual in response to the signal.