JPS61235870A - Developing device - Google Patents

Abstract

PURPOSE:To control securely the amount of a developer into a specific range and to obtain stable images having neither fogging nor variation in density by supplying only a specific amount of developer to a developing part when no developer is detected continuously for a specific detection time. CONSTITUTION:When the total of the time when a sensor 8 detects no developer attains to a specific value, a supply roller 7 is rotated for a specific time to supply a developer. The developer is detected and supplied invariably during the rotation of a developing sleeve 4 and if the developing sleeve 4 stops while no developer is detected, a no-developer detection time is stored and then added to the last detection time after the developing sleeve 4 rotates again. Consequently, the fogging of an image and a decrease in density owing to the excessive supply of a developer are eliminated. Further, the developer is detected during the rotation of the developing sleeve at any time, so that developer is detected in an invariably uniform state and the accurate amount of developer is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device for an image forming apparatus such as a copying machine or a laser beam printer.

(Prior Art) Conventionally, the above-mentioned developing device includes a hopper for storing developer, and a sensor detects the developer 1 in the developing section so that the developer 1 in the developing section is always within a certain range. There is also one in which at least two parts of the developer are supplied from a part of the hopper to the developing section.

However, conventionally, when a sensor detects that the developer is running out of developer in the developing section, replenishment is started immediately, and only after a small replenishment is completed for a certain period of time, the developer reaches a predetermined level of 11. Friend to detect if supplied. The above developer replenishment starts while the developing sleeve in the developing section is rotating, and even if the developing sleeve stops rotating during replenishment, replenishment continues, and after replenishing for a certain period of time, even if the developing sleeve is stopped. My friend is doing developer detection.

(Problem to be Solved by the Invention) However, in the case of such conventional technology, replenishment of developer was started as soon as the lack of developer was detected, so the condition of the developer may change due to changes in the environment, etc. However, if there is temporarily no developer on the sensor surface, the sensor will detect that there is no developer even though there is enough developer, and excessive developer will be replenished. In this case, there is a problem that there is too much developer 1 in the developing section, and the developer 1 applied to the developing sleeve is not uniform, causing fogging on the image, and the density becomes thinner. Gaatsu'fc.

Conventionally, a small amount of developer was replenished for a certain period of time, and only when this was finished, the current @μJ was detected to check whether the developer had been replenished to a predetermined value. However, since the condition of the developer is uneven after replenishing the developer, the sensor may detect that there is no developer even though the developer has been sufficiently supplied to the developing area. However, in order to prevent this, the amount of developer replenishment tt was set to be larger than necessary, which caused the problem that the fluctuation of the developer 1 in the developing section became large.

Furthermore, in the past, even if the rotation of the developing sleeve stopped during replenishment, the developer continued to be replenished and the developer was detected after the replenishment was completed. There is a problem that the developer 1 cannot be accurately detected because υ varies from time to time.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to be able to reliably control the amount of developer within a predetermined range, and to prevent fogging and It is an object of the present invention to provide a developing device capable of obtaining stable images without density fluctuations.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention, in the first invention, detects the developer at all times while the developing step 13 + is rotating. This developing device is configured to replenish a predetermined amount of developer to a developing section when the detection of the absence of developer continues for a predetermined detection period. In the second invention, when the detection of the absence of developer continues for a predetermined detection period, the developer is supplied to the developing section for a predetermined period of time, and then the detection of the developer is continued for a predetermined detection period.

(Example) The present invention will be explained below based on the illustrated example. 6th
In the figure, reference numeral 1 denotes a next developing device disposed on one side of the photosensitive drum 2. This developing device 1 generally includes a hopper portion 3 for storing dry component developer, and a developing section 5 equipped with a developing sleeve 4. It consists of A stirring rod 6 is provided in the hopper part 3, and a replenishment roller 7 is arranged at the boundary between the hopper part 3 and the developing part 5 to replenish the developer in the hopper part 3 to the developing part 5. has been done. A piezoelectric sensor 8 as a developer detection means is provided on the side surface of the developing section 5, and a stirring rod 9 and a sensor surface cleaning member 10 are provided inside the developing section 5. The sensor surface cleaning member 10 cleans when the developer in the developing section 5 gradually decreases.
It is for scraping off the developer remaining on the surface of the sensor 80, and is rotationally driven by the same driving means (not shown) as the developing sleeve 4 and the stirring rod 9. The stirring rod 9 also has the function of crushing the developer cavity formed on the front surface of the sensor 8 after the sensor surface cleaning member 10 scrapes off the developer attached to the surface of the sensor 80, and the function of crushing the developer cavity formed in the front surface of the sensor 8.
It has the function of uniformly dispersing the developer.

In the above configuration, the developing device according to the present invention operates as follows.

FIG. 1 is an explanatory diagram showing the sequence of the developing device.

The sequence starts from the time when the sensor 8 detects the absence of developer (point X), and progresses to Y unless the detection of developer emptiness continues for a certain period of time (9 seconds or 9 seconds). Y
When the process reaches this point, it is determined that there is no developer in the hopper part 3, a developer replenishment lamp (not shown) is turned on, and the jitance is completed.

On the way from X to Y, developer bleed is detected for a certain period of time (A
(9 seconds in section B, 9 seconds in section B), the current g
The I-absence detection time is reset and returns to X. Here, the A section is a section until the replenishment of the developer starts, and the B section is the section after the replenishment of the developer starts.

When the total time during which the sensor 8 detects that there is no developer reaches a second, the replenishment roller 7 is rotated for 6 seconds or until the developer gap detection continues for 9 seconds to replenish the developer. Detection of the agent is carried out continuously for ta seconds.

Note that detection and replenishment of the developer are always performed while the developing sleeve 40 rotates.

When the developing sleeve 4 stops while detecting no developer,
The developer-free detection time is stored, and after the developing sleeve 4 rotates again, the developer-free detection time is added to the previous detection time.

The above aO value is determined as follows. Namely.

When a cavity is formed on the surface of the sensor 8 by the sensor surface cleaning member 10, no developer is detected even though there is developer. .

It is sufficient if a≧T (1).

Further, the values of b and C in section B are determined as follows. FIG. 2 shows the change over time in the arrangement of developers in the developing section 5. The solid line represents the developer 1 actually present in the developing section 5.
The dotted line indicates the development position detected by the sensor 8. In this way, the actual developer location and sensor 8
The reason why there is a difference between the amount of developer detected by
This is because it takes time for the developer to reach a steady state after being replenished. When it is desired to control between the developer 1t-sx of the developing section 5 and 82, b is.

b=(S, -8□)/α (II). Here, α is 1 of developer supplied per unit time.

Further, if the maximum time from when the developer is replenished until the sensor 8 starts detecting it is tmax, as is clear from FIG.

b + c = tmax + d (1)
It is. Here, d must be larger than the sum of the period T of the sensor surface cleaning member 10 and the time q required for resetting. The reason for this is that, depending on the position of the sensor surface cleaning member 10, detection of the presence of developer does not always start from step 2, so the time corresponding to the cycle T of the sensor surface cleaning member 10 is required. This is because the reset must be completed by Y.

Therefore, d is.

d > q + T (needs to be IW.

(1), (Formula IV1, C is.

c>Q+tmax-"T (V) Next, the reset conditions p and q in the A section and the B section are determined as follows. FIG. Developer 1 and sensor 8 sensed on the surface of sensor 8
shows the change in output over time. In this way, depending on the image quality and image quality, the period of the sensor surface cleaning member 10 may be
Sensor 8 detects the absence of developer. In addition, the detection time for whether there is developer or not, even if the developer snores,
Variations occur due to changes in the state of the developer.

Figure 4 shows the lowest target S0 for developer 1.
It shows the developer presence detection time and its relative probability of occurrence. In the figure, p' and q' are values of ν (center value) ±3σ when the standard deviation is 0.

Figures 5(a) and 5(t)) show the developer 1 and the relative probability when the developer presence detection times are p' and q' in w and Figure 4, respectively.

As shown in FIG. 5(a), when the developer drop time continues for more than p' seconds, the development RJ deposit is at least as much as Sl, but when p' seconds is shorter, developer 1 is 81 times more deposited than Sl. This means that the amount of developer may be low, and it is necessary to replenish the developer.

Therefore, if the replenishment roller 7 is rotated to replenish the developer when the developer refill detection time lasts only for a short period of p' seconds in the section 1, the developer at the developing section 50 will be filled at the start of replenishment. When th is minimum, it becomes almost SL. This is it, p
teeth.

By setting p=p', it is possible to quickly and reliably detect that the developer 1 becomes 81.

On the other hand, when the developer is in the hopper part 3, the replenishment roller 7 starts rotating and even after a maximum of t,X seconds, the sensor 8
In some cases, only 1, S□, is detected yet.

However, at the time when the sensor 8 detects S□ af: as is clear from FIG. 4, the developer aυ detection time is q' seconds or more.

If the time period exceeds tmlLX seconds even a little, the developer bleed detection time will definitely become longer than 92 seconds. Therefore, q is.

By setting q≦q', if the developer is present in the hopper part 3, it is always reset before Y.

Let 6i be the time required for the sensor surface cleaning member 10 to pass through the sensing area of the sensor 8.

It is necessary to satisfy q>q'. This is the sensor surface cleaning member 1.
This is because the sensor 8 always detects that there is developer even when there is no developer during the q seconds during which the sensor 8 is in contact with the sensing area of the sensor 8.

An actual example of the sequence of this embodiment is as follows.

a=30 C seconds) s1=140 (
jE) b=30 S,=200 #c=
30 p=p'=10# α=2CP/sec)q=(1
'=4 #i=0.5 tma! "40 ' T=15 @7 Figure shows another embodiment of the developing device according to the present invention. In this embodiment, when the developer runs out in the hopper part 3, the developer is immediately replenished. Rather than turning on a lamp, it is designed so that even if part of the hopper 3 runs out of developer during continuous copying or printing, it is possible to continue copying up to a certain number of sheets. be.

That is, when the hopper part 3 runs out of developer, the hopper part 3 is replenished with developer.

Make up for the developer 1- that has decreased by continuously copying a certain number of sheets.
Be sure to allow enough time, 3b seconds, for this purpose. This prevents the developer replenishment lamp from turning on immediately after the developer is replenished into the hopper part 3. By using such a sequence, it is possible to continue copying up to a certain number of copies without turning on the developer replenishment lamp immediately during continuous copying of a large number of copies. Of course, in this case, the number of copies that can be made continuously even when the hopper part 3 runs out of developer is set within a range that does not affect the image quality.

In the above description, a secondary developing device using a dry-type two-component developer is exemplified, but it goes without saying that this embodiment can also be applied to a developing device using a dry-type two-component developer.

(Effect of the invention) The present invention has the above-described configuration and operation.

In the first invention, when the detection of the absence of developer continues for a predetermined detection time, the developer is replenished to the developing section for a predetermined replenishment time, so that the developer 1 in the developing section actually becomes less than the predetermined 1. It is possible to replenish the developer only during summer, and there is no possibility that the developer will be oversupplied and the image will become foggy and the be degree will become thin. Since this is always performed while the developing sleeve is rotating, the developer can be detected while the developer is always uniform, and the developer I can be detected accurately. moreover.

In the second invention, after replenishing the developer, the detection of no developer continues for the predetermined holding time)'t? ``Since developer replenishment is not performed, in addition to the above effects, it is possible to detect when the condition of the developer replenishment lamp becomes uniform, making it possible to prevent developer O over-replenishment. , it is possible to always obtain stable images before and after developer replenishment.

[Brief explanation of the drawing]

FIG. 1 is a sequence diagram of a developing device according to the present invention. Figure 2 is a graph showing the time change of developer 1t(2) in the same device, Figure 3 is a graph showing the time change of the developer meter sensed by the sensor and the sensor output, and Figure 4 is a graph showing the time change of the developer 1t(2) detected by the sensor.
A graph showing the relative probability distribution of the developer presence detection time when . ,
FIG. 6 is a schematic diagram showing one embodiment of the developing device according to the present invention, and FIG. 7 is a sequence diagram showing another embodiment of the developing device according to the present invention. Explanation of symbols 1...Developing device 4...Developing sleeve 5...
-Developing section 7...Replenishment roller 8...Piezoelectric element sensor. Patent applicant Gyanon Co., Ltd. No. 11M X y No. 2em Figure 3 Figure 4 Figure 5

Claims (6)

[Claims] (1) In a developing device that always detects developer while the developing sleeve is rotating, a predetermined amount of developer is supplied to the developing section when the detection of no developer continues for a predetermined detection time. A developing device characterized by: (2) The developing device according to claim 1, wherein the conditions for resetting the developer out detection time are changed before and after replenishment is started. (3) The developing device according to claim 1 or 2, wherein the elapsed time of the developer-free detection time is stored and sequentially added. (4) In a developing device that always detects developer while the developing sleeve is rotating, when the detection of no developer continues for a predetermined detection period, a predetermined amount of developer is replenished into the developing section, and then A developing device characterized in that developer detection is continued for a predetermined detection time. (5) The developing device according to claim 4, wherein the conditions for resetting the developer out detection time are changed before and after replenishment is started. (6) The developing device according to claim 4 or 5, wherein the elapsed time of the developer-free detection time is stored and sequentially added.