JP5239487B2 - Development device - Google Patents

Description

  The present invention relates to an improvement of a developing device in an image forming apparatus that forms an image by electrophotography.

  In an electrophotographic image forming apparatus, a developer carrying member for supplying a developer to a developing region is provided to face an image forming member such as a photoreceptor.

  Further, in order to form a uniform developer layer on the developer carrying member, a plate-like or rod-like developer amount regulating means is provided facing the developer carrying member at a position upstream of the developing region.

  One of the problems in the developing device using the developer amount regulating means is the deterioration of the developer due to stress.

  That is, the developer receives a pressure when passing through the gap formed by the developer carrier and the developer amount regulating means, and the developer deteriorates due to the stress caused by this pressure.

  This deterioration causes a decrease in toner charge amount, a decrease in developer fluidity, and the like. As a result, undesirable phenomena such as uneven stripes, fireflies, and toner scattering occur.

  The stripe unevenness is a stripe-like density unevenness appearing in the image, and the firefly is a density unevenness in which a low-density circular portion is formed around a black spot.

  Another problem is unevenness in the amount of developer supplied to the developing area, which is called screw pitch unevenness, and the like, and uneven transport of the developer supply means for supplying the developer to the developer carrier. It is caused by.

  In Patent Document 1, for the purpose of preventing deterioration of the developer due to stress, an elastic member is provided on the developer carrying member and upstream of the developer amount regulating means, and development is performed at the position of the developer amount regulating means. The stress on the agent is relieved.

Patent Document 2 proposes that a sensor for detecting the pressure of toner is provided between the developing roller and the supply roller, and the supply operation of the supply roller is controlled based on the detection signal of the sensor.
JP 2007-147915 A JP 7-253709 A

  In the developing device disclosed in Patent Document 1, the elastic member is in contact with the developer conveyed by the developer carrier.

  In the configuration in which the elastic member is in contact with the developer conveyed by the developer carrier as in Patent Document 1, in high-speed image formation, that is, in image formation in which development is performed by rotating the developer carrier at high speed, The pressure adjustment function by the elastic member becomes insufficient with respect to fluctuations in the developer supply amount to the developer carrying member, and the developer amount after the regulation by the regulating means is likely to be uneven, and the image density is likely to be uneven.

  In particular, when the amount of the developer supplied to the developer carrying member is locally insufficient, the image density is locally reduced due to the unevenness of conveyance, thereby degrading the image quality.

  In Patent Document 2, the supply amount control in which the supply amount is controlled by the development supply roller cannot sufficiently respond to the fluctuation in the amount of developer conveyed by the developer carrier, and the unevenness in the conveyance amount cannot be eliminated.

  Further, in the method of Patent Document 2, since the time delay is controlled, the stress applied to the developer cannot be reduced.

  The present invention provides a developing device that can relieve stress on a developer, sufficiently suppress deterioration of the developer, and can form a high-quality image over a long period of time without density unevenness. Objective.

  The above object is achieved by the following invention.

1. A developer carrier that carries the developer and conveys the developer to the development area, a developer supply means that supplies the developer onto the developer carrier, and an amount of the developer that is conveyed on the developer carrier In a developing device having a developer amount regulating means for regulating
A developer supply that is disposed between the developer supply means and the developer carrier, supports the developer supplied by the developer supply means, and deposits the developer supplied to the developer carrier. A developer support member that forms a space and forms a developer passage transported toward the developer carrier and a wall that faces the developer support member are formed to form the developer supply space. A pressure adjusting wall that forms a part of the wall and that applies pressure to the developer that is displaceable and passes between the developer carrier and the developer amount regulating means ;
Cooling means for circulating cooling air to the back surface of the pressure adjusting wall opposite to the surface in contact with the developer, and cooling the pressure adjusting wall;
Detecting means for detecting the amount of displacement of the pressure adjusting wall and control means for controlling the developer supplying means based on the detection result of the detecting means;
The developing device according to claim 1, wherein the detecting means detects a displacement amount of the pressure adjusting wall by detecting a wind speed of the cooling air .

  2. 2. The developing device according to claim 1, wherein the pressure adjusting wall forms a ceiling portion of the wall.

  3. The developer supply space is a space defined by the developer support member, the developer supply means, and the pressure adjustment wall, and the pressure adjustment wall faces the developer support member and the developer supply means. 3. The developing device according to 1 or 2, wherein a wall is formed.

  4). The developing device according to any one of claims 1 to 3, wherein the developer supplying means includes a rotating sleeve and a magnetic field generating means provided in the sleeve.

  5. 5. The developing device according to claim 1, wherein the pressure adjusting wall is made of a plate-like member having a stretchability in which a peripheral edge portion is fixed to a fixing portion of the wall.

  According to the present invention, a developer supply space in which developer is deposited is formed between the developer carrying member and the developer supply means, and a pressure adjustment that can displace a part of the wall forming the developer supply space is provided. It is formed with a wall.

  Therefore, the pressure applied to the developer is adjusted between the developer carrying member and the developer amount regulating means, thereby preventing the pressure from protruding.

  As a result, the stress applied to the developer is alleviated and the developer can be prevented from being deteriorated, and the image quality deterioration, toner scattering, and the like caused by the deterioration can be sufficiently prevented.

  Further, the amount of developer conveyed to the development area by the developer carrying member is made uniform, and a high-quality image can be formed over a long period of time.

  Hereinafter, the present invention will be described by way of embodiments of the present invention, but the present invention is not limited to the embodiments.

  FIG. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention.

  The housing of the developing device 2 has a two-part configuration including a lower lower casing 20 and an upper upper casing 21, and can be opened and closed. The developing device 2 is disposed opposite to the photoreceptor 1 as shown.

  In the lower casing 20 of the developing device 2, a developing roller 22 as a developer carrying member, a first developer agitating and conveying member (hereinafter referred to as a first agitating member) 24, and a second developer agitating and conveying member (hereinafter, referred to as “developer roller”) (Referred to as a second stirring member) 25, a developer supply roller 26 as a developer supply means, a developer support member 27, and the like.

  The lower casing 20 includes a developer supply chamber 2A that houses the first stirring member 24 and a developer stirring chamber 2B that houses the second stirring member 25. The developer supply chamber 2 </ b> A and the developer stirring chamber 2 </ b> B are formed on both sides with a partition wall 20 </ b> A standing upright from the bottom of the lower casing 20.

  The developing roller 22 includes a rotatable developing sleeve 22A and a fixed magnetic field generating means (magnet roll) 22B.

  At the opposing proximity point between the developing sleeve 22A and the first stirring member 24, the developing sleeve 22A moves upward from below and the first stirring member 24 moves downward from above.

  A wide space is formed in the ceiling inside the upper casing 21 to form a developer supply space W1.

  The developer supply space W <b> 1 is formed by the developing roller 22, the developer supplying roller 26, the developer supporting member 27, the plate-like member 28, and the developer amount regulating member 23.

  The developing roller 22 is disposed so as to face the photoconductor 1 carrying the electrostatic latent image, and forms a developing interval Q in the developing area.

  The developing sleeve 22A is driven to rotate by a driving source (not shown).

  A developing bias in which an alternating voltage from the alternating current power supply E1 and a direct current voltage from the direct current power supply E2 are superimposed is applied to the developing sleeve 22A.

  The magnetic field generating means 22B is fixedly arranged inside the developing sleeve 22A and has seven magnetic poles N1, N2, N3, N4, S1, S2, and S3. The magnetic pole N1 is a developing main magnetic pole, the magnetic pole N2 is a stripping magnetic pole, and the magnetic pole N3 is a regulating magnetic pole (a pumping magnetic pole) that regulates the amount of developer conveyed on the developing roller 22.

  The tip of the developer amount regulating member 23 as the developer amount regulating means is disposed at a position in the vicinity of the magnetic pole N3 of the magnetic field generating means 22B.

  Two magnetic poles N2 and N3 adjacent to each other among the plurality of magnetic poles of the magnetic field generating means 22B are arranged in the same polarity to form a repulsive magnetic field. The developer stripping magnetic pole N2 strips the developer from the developing sleeve 22A. The magnetic pole N3 for receiving the developer pumps up the developer supplied by the developer supply roller 26 and deposits it on the developing sleeve 22A.

  The first agitating member 24 agitates and conveys the developer conveyed from the second agitating member 25 and supplies it to the developing supply roller 26. The first stirring member 24 and the second stirring member 25 are both helical screw members.

  The second agitating member 25 is disposed in parallel with the first agitating member 24, and mixes and agitates the new toner replenished from the toner replenishing means (not shown) and the developer recirculated from the developing sleeve 22A to the first agitating member 25. It is conveyed to the upstream part of the stirring member 24.

  The first stirring member 24 transports the developer in the direction of the rotation axis and releases the developer in a direction substantially perpendicular to the rotation axis.

  The developer amount regulating member 23 is composed of two metal plates arranged with a magnetic body on the inner side of the developing device and a non-magnetic body on the outer side. The inner magnetic metal plate faces the magnetic pole N3 and is located on the developing sleeve 22A. Regulates developer layer thickness. The developer supply roller 26 includes a rotating sleeve 26A and fixedly arranged five-pole magnetic poles N1, N2,. N3. A magnetic field generation unit 26B having S1 and S2 is provided, and the developer conveyed from the first stirring member 24 is held and conveyed, and is fed into the developer supply space W1.

  In the vicinity of the opposing proximity point between the developing sleeve 22 </ b> A and the first stirring member 24, the developer support member 27 is disposed in an inclined manner. The developer support member 27 separates the lower developer, which is peeled off from the developing sleeve 22A and conveyed in the direction of the white arrow C2 shown in FIG. 2, from the upper developer supplied to the developing sleeve 22A.

  The developer is guided by the developer support member 27 and conveyed to the developing roller 22, and the developer accumulates in the developer supply space W <b> 1 above the developer support member 27.

  The developer support member 27 is formed of a nonmagnetic material, for example, a synthetic resin such as ABS resin, nonmagnetic stainless steel, aluminum alloy, copper alloy, ceramics, or the like.

  The flow of the developer used for development is indicated by C1, but the developer is supplied from the developer support member 27 to the developing roller 22 as indicated by an arrow C1A, and the developer supplied to the developing roller 22 is The developing sleeve 22A is rotated and conveyed on the developing roller 22 as indicated by an arrow C1B.

  The developer scraped up by the rotation of the first agitating member 24 is conveyed by the rotation of the developer supply roller 26 having a built-in magnetic pole, transferred to the developer supply space W1, and then on the developer support member 27. The developing roller 22 is moved in the direction and supplied to the rotating developing roller 22.

  On the developing roller 22, the thickness of the developer layer is regulated by a developer quantity regulating member 23 as a developer quantity regulating means, and the developer is conveyed to the development interval Q.

  Further, when the developer supply space W1 is filled with the developer, the developer supplied excessively from the developer supply roller 26 overflows from the developer supply roller 26 at the entrance of the developer supply space W1 and is first. It is returned to the stirring member 24.

  Reference numeral 28 denotes a plate-like member that forms a displaceable wall.

  The plate-like member 28 is preferably made of a rubber-based stretchable film such as urethane resin, and deforms according to the amount of developer accommodated in the developer supply space W1.

  The peripheral edge of the plate-like member 28 is fixed to the fixing portion of the developing device 2.

  The plate-like member 28 thus forms a displaceable wall, and this displaceable wall constitutes a part of the wall surrounding the developer supply space W1. When the developer amount is large, the plate-like member 28 is pushed up and deformed upward as shown by a dotted line.

  The plate-shaped member 28 forms a wall that defines a developer supply space W1 in which the developer is conveyed toward the developing roller 22 as indicated by an arrow C1A, and the developer supply roller 26 and the developer supporting member 27 It arrange | positions so that it may oppose.

  The displaceable wall may be a wall that can be displaced only without being deformed, in addition to a wall that is displaced by deformation of the wall itself.

  The plate-like member 28 forms a pressure adjusting wall and applies an appropriate pressure to the developer in the developer supply space W1.

  As a result, an appropriate pressure is applied to the developer passing between the developing sleeve 22A and the developer amount regulation 23, and the applied pressure is made uniform.

  The pressure adjusting action of the plate-like member 28 equalizes the pressure not only in the developer conveyance direction but also in the direction perpendicular to the conveyance direction, and the stress applied to the developer is equalized. In addition, a uniform developer layer is formed on the developing roller 22.

  Reference numeral 29 denotes a support member that supports the base of the plate-like member 28, and forms a gap through which the developer passes around the developer supply roller 26 as shown in the figure.

  A developer supply space W <b> 1 is formed below the plate-shaped member 28, and a ventilation space W <b> 2 is formed above the plate-shaped member 28.

  The toner is supplied to the developer stirring chamber 2B and mixed with the developer by the second stirring member 25. In the developer stirring chamber 2B, as shown by the black arrow C1, the developer mixed with the toner passes through the opening provided in the partition wall portion 20A and enters the developer supply chamber 2A.

  In the developer supply chamber 2 </ b> A, the developer is stirred and transported by the first stirring member 24.

  The developer stirred in the developer supply chamber 2A is pumped up by the developer supply roller 26 and supplied onto the developer support member 27 as indicated by an arrow C1.

  The developer conveyed on the developer support member 27 adheres to the peripheral surface of the developing roller 22.

  The developer on the developing roller 22 is regulated by the developer amount regulating member 23, and a developer layer having a constant thickness is formed on the developing roller 22.

  The developer on the developing roller 22 is supplied to a developing interval Q that forms a developing area, and develops the electrostatic latent image on the photoreceptor 1.

  The developer after development passes below the developing roller 22 as shown by the white arrow C2, and returns to the developer supply chamber 2A.

  The developer returned to the developer supply chamber 2A passes through an opening (not shown) provided at the end of the partition wall portion 20A in the width direction (the rotation axis direction of the developing roller 22, the same applies hereinafter), and the developer stirring chamber 2B. To reflux.

  Such developer circulation is continuously performed, and the electrostatic latent image on the photoreceptor 1 is continuously developed.

  In the above developing step, when passing through the developer amount regulating member 23, that is, in the layer forming portion, the developer receives pressure.

  As a result, the stress of the developer increases, causing deterioration such as deterioration in charging performance and fluidity, and lowering the image quality.

  The stress received by the developer in the layer forming portion is affected by the amount of the developer present in the developer supply space W1 on the upstream side of the layer forming portion. That is, when the amount of the developer is large, the pressure in the layer forming portion increases and the developer is subjected to strong stress.

  When the pressure received by the developer supply space W1 increases beyond the appropriate range, the image quality deteriorates due to the deterioration of the developer.

  On the other hand, when the pressure decreases beyond the appropriate value range due to the developer supply space W1, the amount of developer supplied to the development area by the developing roller 22 becomes insufficient. As a result, density unevenness occurs.

  By forming a part of the wall forming the developer supply space W1 with the deformable plate-like member 28, the pressure fluctuation in the layer forming portion is relieved by the developer in the developer supply space W1, and in the layer forming portion The pressure is made uniform within an appropriate range.

  The fluctuation of the pressure in the layer forming portion occurs not only in the developer transport direction but also in the width direction perpendicular to the transport direction.

  When there is a local variation in the developer amount on the developer support member 27, the plate-like member 28 is displaced corresponding to the local developer amount. Local pressure fluctuations are alleviated. The uniform pressure is performed not only in the developer conveyance direction but also in the width direction.

  In this way, the pressure in the layer forming portion is made uniform, and the image quality deterioration due to the stress received by the developer and the density unevenness due to the decrease in the developer supply amount to the development interval Q are sufficiently prevented, and the uniform and high image quality is prolonged. It became possible to maintain over a period of time.

  FIG. 2 is a plan view of the developing device 2 shown in FIG.

  A duct 33 that is long in the direction perpendicular to the width direction is provided continuously to the ventilation space W2 that is long in the width direction.

  The duct 33 is provided with an exhaust fan 31 and a wind speed sensor 32. As the wind speed sensor 32, an ultra-compact wind speed sensor such as QB-5CK manufactured by Tonic Co., Ltd. is used.

  By exhausting with the exhaust fan 31, cooling air flows as shown by the black arrow C3, and the plate-shaped member 28 is cooled. As a result, the developer is cooled.

  When the temperature and humidity of the atmosphere surrounding the developer rises, the developer tends to aggregate, and streaks and fireflies tend to occur.

  The muscle unevenness is a stripe-like concentration unevenness, and the firefly is a white spot-like concentration unevenness surrounding a black dot.

  In addition, the toner charging ability decreases due to a rise in the temperature of the developer, and toner scattering tends to occur.

  Such an undesirable phenomenon due to an increase in temperature and humidity is particularly likely to occur in a low-temperature fixing toner, and when the low-temperature fixing toner is used, the above-described problem becomes particularly significant in a high-temperature and high-humidity environment.

  These problems can be sufficiently prevented by the cooling of the developer shown in the figure.

  As shown in FIG. 1, the volume of the ventilation space W2 changes when the plate-like member 28 is deformed according to the amount of developer in the developer supply space W1.

  As a result, the amount of air passing through the ventilation space W2 changes. This means that the amount of air flowing through the ventilation space W2 changes in response to a change in pressure in the layer forming portion.

  FIG. 3 shows the result of observing the amount of developer in the developer supply space W1 and the wind speed of the air flowing through the ventilation space W2.

  As shown, the wind speed decreases linearly with increasing developer amount. This phenomenon is detected by a wind speed sensor, and the developer supply amount is controlled in accordance with the detected wind speed.

  That is, when the wind speed is high, the developer supply amount from the developer supply roller 26 is increased, and when the wind speed is low, the developer supply amount is decreased.

  By such developer supply control, the amount of developer supplied to the layer forming portion is maintained within an appropriate range.

  Further, since the developer is cooled, the image quality is prevented from being lowered due to the temperature rise.

  FIG. 4 is a block diagram of a control system that performs developer supply control based on wind speed measurement, and FIG. 5 is a flowchart of developer supply control.

  Based on the detection result of the wind speed sensor 32, the control means CR controls the motor MT for driving the developer supply roller 26 as shown in FIG. 5 to control the amount of developer supplied to the developer supply space W1.

  The control shown in FIG. 5 starts with the start of the operation of the developing device 2.

  In step ST1, wind speed detection by the wind speed sensor 32 is performed.

  When the detected wind speed H is a predetermined threshold value H0, for example, 3.47 m / s or more (No in ST2), the process proceeds to step ST4.

  When the detected wind speed is less than the predetermined threshold value H0 (Yes in ST2), in step ST3, the rotation speed is changed to lower the rotation speed of the developer supply roller 26.

  Next, in step ST4, the motor MT is operated for 2 seconds to rotationally drive the developer supply roller 26, so that the developer is supplied.

  In step ST5 following step ST4, it is checked whether or not the developing roller 22 has stopped rotating. If not, the process returns to step ST1 to detect the wind speed.

  When the developing roller 22 is stopped, the control is finished.

  While the developing roller 22 is rotating, steps ST1 to ST4 are repeated.

  As shown in FIG. 5, the developer supply roller 26 is intermittently driven after being driven at a constant speed for a predetermined time (for example, 2 seconds), and the rotation speed of the supply roller in FIG. Is the average rotational speed in one minute.

  FIG. 6 shows an example of control of the developer supply roller 26 based on wind speed detection. As a result of the control shown in FIG. 5, as shown in FIG. 6, when the wind speed is less than 3.47 m / s, the rotation speed of the developer supply roller 26 is greatly reduced.

  By such control, a constant amount of developer always exists in the developer supply space W1, and the pressure applied to the developer in the layer forming portion is kept constant.

  Further, the temperature rise of the developer is suppressed by cooling by ventilation.

  As a result, a high-quality image is formed over a long period of time.

  Development was performed using the developing device having the structure shown in FIGS. 1 and 2 to form an image on the recording paper.

  The following was used as the developing device.

Plate member 28: rubber urethane resin,
Thickness: 0.05mm
Strength at break: 55 MPa or more Cross-sectional area on a plane perpendicular to the airflow in the ventilation space W2 (cross-sectional area when the plate-like member 28 is not deformed):
: 380mm ²
Wind speed: 3-5m / s
As Comparative Example 1, a plate-like member that does not deform is used as the plate-like member 28, and a developing device to which the plate-like member is fixed is used.

  Further, as Comparative Example 2, development was performed using the developing device shown in FIG. 1 of JP-A-2007-147915 to form an image.

  In both Example, Comparative Example 1 and Comparative Example 2, the process speed was 600 mm / sec.

  Table 1 shows the evaluation results for fogging, image roughness, streak unevenness, fireflies, and image density unevenness, and FIG. 7 shows the change in charge amount.

  In the example, good results were obtained in image evaluation regarding image roughness, streak unevenness, fireflies, and density unevenness, and the rate of decrease in charge amount was low. In Comparative Example 1, the image quality increased as the number of printed sheets increased. The above problems occurred, and the amount of charge was greatly reduced.

  Also, in Comparative Example 2, the charge amount was reduced, although not as much as Comparative Example 1. Regarding specific evaluation items of the image, in Comparative Example 1, fogging from 2000 prints, image roughness, and stripe unevenness were observed.

  In Comparative Example 1, fogging and image roughness appeared remarkably from 5000 prints, streak unevenness appeared remarkably from 10,000 prints, and density unevenness was observed in all prints.

  In Comparative Example 1, fireflies were further generated from 10,000 prints.

  In Comparative Example 2, image density unevenness occurred in all printing processes, and fogging and image roughness occurred in 10,000 printing.

1 is a cross-sectional view of a developing device according to an embodiment of the present invention. It is a figure which shows the developing device cooling part in a developing device. It is the graph which showed the result of having observed the quantity of the developer in the developer supply space W1, and the wind speed of the air which flows through the ventilation space W2. It is a control system block for performing developer supply control based on wind speed measurement. It is a flowchart of developer supply control. 6 is a graph showing an example of control of the developer supply roller 26 based on wind speed detection. It is a graph which shows the change of charge amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing apparatus 22 Developing roller 23 Developer amount control member 24 1st stirring member 25 2nd stirring member 26 Developer supply roller 27 Developer support member 28 Plate-shaped member 31 Exhaust fan 32 Air speed sensor 33 Duct CR control means

Claims (5)

A developer carrier that carries the developer and conveys the developer to the development area, a developer supply means that supplies the developer onto the developer carrier, and an amount of the developer that is conveyed on the developer carrier In a developing device having a developer amount regulating means for regulating
A developer supply that is disposed between the developer supply means and the developer carrier, supports the developer supplied by the developer supply means, and deposits the developer supplied to the developer carrier. A developer support member that forms a space and forms a developer passage transported toward the developer carrier and a wall that faces the developer support member are formed to form the developer supply space. A pressure adjusting wall that forms a part of the wall and that applies pressure to the developer that is displaceable and passes between the developer carrier and the developer amount regulating means ;
Cooling means for circulating cooling air to the back surface of the pressure adjusting wall opposite to the surface in contact with the developer, and cooling the pressure adjusting wall;
Detecting means for detecting the amount of displacement of the pressure adjusting wall and control means for controlling the developer supplying means based on the detection result of the detecting means;
The developing device according to claim 1, wherein the detecting means detects a displacement amount of the pressure adjusting wall by detecting a wind speed of the cooling air .   The developing device according to claim 1, wherein the pressure adjusting wall forms a ceiling portion of the wall.   The developer supply space is a space defined by the developer support member, the developer supply means, and the pressure adjustment wall, and the pressure adjustment wall faces the developer support member and the developer supply means. The developing device according to claim 1, wherein a developing wall is formed.   The developing device according to claim 1, wherein the developer supplying unit includes a rotating sleeve and a magnetic field generating unit provided in the sleeve.   5. The developing device according to claim 1, wherein the pressure adjusting wall is formed of a plate-like member having stretchability in which a peripheral edge portion is fixed to a fixing portion of the wall.

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