JPH1195556A - Developer blocking preventive mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer blocking preventive mechanism capable of eliminating blocking in an early stage by detecting blocking with a developer in an electrophotographic image duplicating device and informing an operator of the fact. SOLUTION: The developer blocking preventive mechanism is provided with a blocking detecting means 8 for precautionally detecting the occurrence of blocking, in such a manner that the driving current of a motor 4 for driving the magnet roll 3 of a developing unit 1 is detected by a current detecting means 7 and the fact that the current value of the driving current is increased to be a prescribed reference value or more is detected. When the blocking detecting means 8 detects the occurrence of blocking, an alarm means 9 is actuated to inform the operator of the occurrence of blocking with the developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the occurrence of blocking in which a developer supplied from a developing unit of an electrophotographic image copying apparatus becomes jammed between a photosensitive member and a magnet roller of the developing unit. The present invention relates to a developer blocking prevention mechanism capable of eliminating blocking.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image copying apparatus, as shown in a perspective view of FIG. 7, a magnet roll 3 rotating a developer stirred in a developer container 2 of a developing device 1 is used.
The surface of the photoconductor 5 is electrostatically attracted to the photoconductor 5 opposed to the magnet roll 3 after a constant amount of the application is controlled by a doctor blade (not shown) to form a visible image on the photoconductor 5. . Most of the developer that has not been electrostatically attracted to the photoreceptor 5 adheres to the surface of the magnet roll 3 and is collected in the developer container 2, but the remaining part adheres to the photoreceptor 5 and adheres to the paper. The developer remaining on the magnet roll 3 at the time of transfer is collected in a developer collection container different from the developing device 1 by a scraper or the like provided as necessary.

The motor 4 for driving the magnet roll 3 detects the number of revolutions of the motor 4 by an encoder 50 and is feedback-controlled by a drive circuit 6 so as to reach a predetermined number of revolutions.

[0004]

The number of revolutions of the magnet roll 3 may be increased for some reason,
If the gap between the doctor blade 4 and the magnet roll 3 increases due to external pressure or thermal expansion difference on the magnet roll 3 or the doctor blade 4, the amount of developer supplied to the surface of the photoconductor 5 increases, Blocking in which the developer is clogged between the photoreceptor 5 and the magnet roll 3 of the developing device 1 may occur.

[0005] In addition, when the developing gap between the magnet roll 3 and the photoreceptor 5 is reduced due to an external pressure or a difference in thermal expansion, blocking may occur. When blocking occurs, the amount of developer attached to the photoconductor 5 increases,
In addition to the phenomenon that the developer flows out of the developing device 1, the paper may become dirty and the image quality may deteriorate, and in some cases, the developer may become clogged between the photoconductor 5 and the magnet roll 3, and 5 and the magnet roll 3 may stop.

However, in the conventional electrophotographic image copying apparatus, there is no mechanism for automatically detecting such a blocking of the developer, and moreover, a means for automatically eliminating the blocking when it occurs. There is no one with.

An object of the present invention is to provide a developer blocking preventing mechanism which solves the above conventional technical problems, automatically detects occurrence of blocking, and can eliminate the blocking at an early stage. It is intended for.

[0008]

According to the present invention, in order to achieve this object, a current detecting means 7 for detecting a driving current of a motor 4 for driving a magnet roll 3 of a developing device 1, and the current detecting means 7 comprises: A blocking detection unit for comparing the current value of the drive current to be detected with a predetermined critical value and detecting that the drive current value rises above the critical value to thereby detect the occurrence of blocking of the developer beforehand; An alarm means 9 is provided for operating when the blocking detecting means 8 detects the occurrence of the blocking of the developer beforehand, and for predicting the occurrence of the blocking of the developer.

That is, if there is a possibility that blocking occurs, the rotational resistance of the magnet roll 3 of the developing device 1 increases, so that the drive current value of the motor 4 for driving the magnet roll 3 increases as compared with the case where there is no blocking. .
Therefore, according to the present invention, the current detection means 7 detects the drive current of the motor 4 for driving the magnet roll 3, and the blocking detection means 8 detects that the drive current value rises to a predetermined value or more. The occurrence of blocking of the developer can be detected in advance.

When the occurrence of the blocking is detected beforehand, the occurrence of the blocking is predicted by the alarm means 9 so that the surrounding operators can recognize that there is a possibility that the blocking will occur. By taking appropriate measures based on the recognition, the occurrence of blocking can be prevented beforehand, and the generated blocking can be eliminated at an early stage.

In the present invention, the blocking detecting means 8 compares the current value of the driving current detected by the current detecting means 7 with a predetermined critical value, and determines that the driving current value rises above the critical value. Detection is performed to detect the occurrence of blocking of the developer, and is activated together with or instead of the alarm means when the blocking detection means 8 detects the occurrence of blocking to eliminate the blocking. Blocking elimination means can be provided.

Thus, when the current detection means 7 and the blocking detection means 8 automatically detect the occurrence of the blocking, the blocking elimination means is operated to quickly and automatically eliminate the blocking. .

[0013] The blocking elimination means can be roughly classified as follows.
Blocking can be broadly divided into those that eliminate blocking by reducing the amount of developer supplied to the developing gap and those that eliminate blocking by increasing the developing gap.

The blocking eliminating means for eliminating the blocking by reducing the supply amount of the developer to the developing gap when the blocking occurs, includes a rotational speed controlling means for decreasing the rotational speed of the motor when the blocking is detected. In this case, the number of rotations of the motor is reduced at the time of detecting the amount of the developer, and the amount of the developer supplied to the developing gap is reduced.

The blocking elimination means for eliminating the blocking by reducing the amount of the developer supplied to the developing gap when the blocking occurs, includes a method for removing the blocking between the magnet roll and the doctor blade opposed thereto when the blocking is detected. Another example is to provide a height control means for reducing the width of the cutting edge, and reduce the amount of the developing agent to the developing gap by reducing the width of the cutting edge when detecting blocking.

The blocking eliminating means for eliminating the blocking by enlarging the developing gap includes:
Move the magnet roll or the developing device at the time of detection of blocking, or move the photosensitive member facing the magnet roll, to enlarge the developing gap between the magnet roll and the photosensitive member facing the magnet roll, One that eliminates blocking by facilitating the passage of the developer through the development gap can be cited as an example.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mechanism for preventing blocking of a developer according to one embodiment of the present invention will be specifically described with reference to the drawings.

As shown in the block diagram of FIG. 1, a mechanism for preventing developer blocking according to one embodiment of the present invention is a current detector for detecting a drive current of a motor 4 for driving a magnet roll 3 of a developing device 1. And a blocking detection means 8 which compares the current value detected by the current detector 7 with a predetermined critical current value, and determines that there is a risk of occurrence of blocking when the former becomes greater than the latter, and outputs a detection signal. And an alarming means 9 which is activated when the blocking detecting means 8 detects the occurrence of blocking beforehand, to predict that blocking of the developer will occur.

The blocking detecting means 8 includes the developing device 1
An appropriate critical current value corresponding to this temperature is read out from the temperature current table 11 based on the temperature data given from the temperature sensor 10 for detecting the temperature inside, and the current value detected by the current detector 7 and this critical current value Are compared, and when the former is greater than the latter, it is determined that there is a risk of occurrence of blocking, and a detection signal is output.

Thus, at normal temperature, the driving current of the motor 4 is about 6 A during normal operation in which blocking does not occur.
Since the drive current of the motor 4 rises to 11A or more,
If about 10 A is set as the critical current value, the alarm means 9 is activated immediately before the occurrence of the blocking, and the occurrence of the blocking is predicted beforehand.

By the way, more accurate control becomes possible in consideration of the temperature requirement. That is, when the temperature is low, for example, when the temperature of the developer is, for example, about −5 ° C., the fluidity of the developer is reduced, and the driving current is increased to, for example, 8 A or more. Therefore, the driving current may be higher than 10 A even if there is no risk of blocking. Therefore,
As shown in FIG. 1, a temperature-critical current table 11 is created so that the critical current value increases when the temperature of the developer decreases, and based on the output from the temperature sensor 10 that measures the temperature of the developer. The blocking detecting means 8 reads the critical current based on each temperature from the temperature-critical current table 11, and activates the alarm means 9 when the driving current value becomes higher than the critical temperature. This can prevent the occurrence of blocking from being erroneously predicted at low temperatures.

In this embodiment, to control the rotation speed of the magnet roll 3 to be constant, an encoder 50 for detecting the rotation speed of the magnet roll 3 and the motor 4 is provided.
The reference rotation speed of the magnet roll 3 and the motor 4 is compared with the reference rotation speed setting means 12, and the rotation speed of the magnet roll 3 and the motor 4 detected by the encoder 50 is compared with the reference rotation speed set by the reference rotation speed setting device 12. In addition, a magnet roll rotation control means 13 for controlling the number of drive pulses, the drive pulse width, the drive pulse period, and the like of the drive circuit 6 so as to make these coincide with each other is provided.

In another embodiment of the present invention shown in FIG. 2, when the drive current value of the motor 4 rises above the critical value as in the embodiment shown in FIG. 1, a detection signal is output. In this embodiment, there is provided a blocking eliminating means 15 for receiving the detection signal and eliminating the blocking. In this embodiment, the blocking elimination means 15 reduces the rotation speed of the magnet roll when the detection signal is output.

The blocking elimination means 15 includes a normal rotation speed setting unit 12a for setting the rotation speed of the magnet roll 3 in a normal state, and a magnet roll 3 in the blocking state.
Rotation speed setting section 12b for setting the rotation speed of the motor
The switching means 12 c selectively inputs the normal rotation speed and the blocking rotation speed to the rotation control means 13 in accordance with the detection result of the blocking detection means 8.

The motor speed at the time of occurrence of blocking set in the blocking speed setting unit 12b is lower than the normal motor speed set in the normal speed setting unit 12a. When the occurrence of the blocking is detected, the number of rotations of the drive motor of the magnet roller is reduced as compared with the normal case, so that the amount of the developer supplied to the developing gap is reduced, and the blocking is eliminated.

Although the alarm means 9 may be provided in this embodiment, the alarm means 9 is omitted here. Also in this embodiment, the temperature condition can be reflected in the blocking detection.
That is, the critical current according to the temperature is set in the temperature-critical current table 11, and the blocking detecting means 8 selects the target critical value from the temperature-critical current table 11 based on the output from the temperature sensor 10. Can be.

In another embodiment of the present invention shown in the perspective view of FIG. 3 and the block diagram of FIG.
Reference numeral 5 denotes a developing gap adjusting means for enlarging a developing gap between the magnet roll and the photoconductor opposed thereto when a blocking is detected.

The developing gap adjusting means comprises a gap control mechanism 16 and a gap control means 17 for controlling the gap control mechanism 16, as shown in FIG. As shown in FIG. 3, the gap control mechanism 16 includes an elevating cam 16a for elevating and lowering the developing device 1, a gap adjusting motor 16b for driving the elevating cam 16a, and a belt type motor for interlocking the elevating cam 16a with the gap adjusting motor 16b. And a transmission mechanism 16c.

When the blocking detecting means 8 detects the occurrence of the blocking, the gap control means 17 controls the motor driving circuit 16d for a predetermined time after the detection.
A drive pulse for driving the gap adjustment motor 16a to rotate forward is given to the developer container 2 and the magnet roll 3 of the developing device 1 to lower the developing gap, that is, the gap between the magnet roll 3 and the photoconductor 5 Increase spacing. When the blocking detecting means 8 detects the elimination of the blocking, a driving pulse for reversely driving the gap adjusting motor 16a is supplied to the gap adjusting motor 16a via the motor driving circuit 16d for the predetermined time, and the developer container 2 of the developing device 1 is provided.
Then, the magnet roll 3 is raised to operate to return the developing gap to the normal interval.

According to this embodiment, at the time of occurrence of blocking, the developer clogged in the development gap passes through the development gap by expanding the development gap, thereby eliminating the blocking.

In this embodiment, the temperature-critical current table 11 may be provided to reflect the temperature factor in the gap adjustment processing. In another embodiment of the present invention shown in the configuration diagram of FIG. 5 and the block diagram of FIG. 6, a head height control means is provided as the blocking eliminating means 15.

The height control means comprises a gap control mechanism 20 for moving the doctor blade 18 toward and away from the magnet roll 3, and a height control means 21 for controlling the gap control mechanism 20. As shown in FIG. 5, the blade advance / retreat mechanism 20 includes a blade drive motor 2
0a and a link mechanism 20b for linking the doctor blade 18 to the motor 20a.

When the blocking detecting means 8 detects blocking as in the gap controlling means 17, the blade cutting motor 20a
May be rotated forward for a predetermined time (for a predetermined number of pulses) to reduce the gap between the docker blade 18 and the magnet roll. However, another embodiment will be described here.

That is, as shown in FIG. 6, a reference gap corresponding to the normal cutting edge gap between the doctor blade 18 and the magnet roll 3 and a blocking gap (corresponding to the gap reduced for eliminating blocking). More precisely, a gap setting unit 21a is provided for registering the reference gap and the rotation position of the blade drive motor 20a corresponding to the reduced gap. Upon detection, the gap value input to the head-closing gap control means 21d is switched from the reference gap (for example, 1 mm) to the blocking gap (for example, 0.9 mm).

As a result, the blade drive motor 20a is normally rotated via the motor drive circuit 21c, and the position of the doctor blade is adjusted to the reduced gap.

When the operation is continued in this state, and the blocking current detecting means 8 detects the elimination of the blocking, the gap setting section 21a informs the head-cut gap control means 21d that the gap is changed from the gap at the time of blocking to the reference gap. The blade drive motor 20 is switched and input.
a is reversed and returns to the original position.

Thus, when the blocking occurs, the shorting gap is reduced to reduce the amount of the developer supplied to the developing gap, thereby eliminating the blocking. When the blocking is eliminated, the shorting gap is returned to the reference gap. be able to.

Also in this embodiment, the temperature / current table 1
It goes without saying that the temperature element may be reflected by providing 1.

[0039]

As described above, since the present invention is configured as described above, the occurrence of blocking can be predicted to the surroundings by an alarm. In addition, the operator who recognizes the forecast can take appropriate measures to prevent the blocking and to eliminate the generated blocking at an early stage.

As a result, it is possible to prevent the problems associated with blocking, such as the loss of the developer, the contamination of the paper, and the stoppage of the developing device and the photoconductor, thereby reducing the reliability of the electrophotographic image copying apparatus. It can be enhanced.

In the present invention, when the blocking detection means is provided in place of the alarm means and operates when the blocking of the developer is detected to eliminate the blocking, the occurrence of the blocking is automatically controlled. And the blocking is automatically eliminated by the anti-blocking means at an early stage and automatically.

As a result, it is possible to prevent the problems associated with blocking, such as the loss of the developer, the contamination of the paper, and the stoppage of the developing device and the photoconductor, thereby reducing the reliability of the electrophotographic image copying apparatus. It can be enhanced.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a perspective view of a main part of the present invention.

FIG. 4 is a block diagram of another embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of the present invention.

FIG. 6 is a block diagram of another embodiment of the present invention.

FIG. 7 is a perspective view of a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing device 3 Magnet roll 4 Motor 7 Current detecting means 8 Blocking detecting means 9 Alarm means 14 Blocking eliminating means

Claims (6)

[Claims] 1. A current detecting means for detecting a driving current of a motor for driving a magnet roll of a developing device, and a current value of the driving current detected by the current detecting means is compared with a predetermined critical value. Blocking detecting means for detecting the occurrence of the developer blocking by detecting that the value rises above the critical value, and operating when the blocking detecting means detects the occurrence of the developer blocking beforehand. An anti-blocking mechanism for a developer, further comprising alarm means for notifying that blocking of the developer will occur. 2. A current detecting means for detecting a driving current of a motor for driving a magnet roll of a developing device, and a current value of the driving current detected by the current detecting means is compared with a predetermined critical value. Blocking detection means for detecting that the blocking of the developer has occurred by detecting that the value rises above the critical value; and blocking when the blocking detection means detects the occurrence of the blocking of the developer. A blocking preventing mechanism for a developer, comprising a blocking eliminating means for eliminating the blocking. 3. The developer blocking prevention mechanism according to claim 2, wherein said blocking eliminating means includes a rotation number control means for reducing the rotation number of said motor when a blocking is detected. 4. The developer blocking according to claim 2, wherein said blocking eliminating means includes a developing gap control means for expanding a developing gap between said magnet roll and a photosensitive member opposed thereto when a blocking is detected. Prevention mechanism. 5. The developer according to claim 2, wherein said blocking eliminating means includes a head height control means for reducing a head height gap between said magnet roll and a doctor blade opposed thereto when a blocking is detected. Anti-blocking mechanism. 6. A mechanism for preventing developer blocking according to claim 1, further comprising a temperature sensor, wherein a critical value for detecting a possibility of occurrence of blocking is corrected based on a detected value of the temperature sensor. .