JP2004117593A - Image forming apparatus and its control method, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the density of toner is extremely decreased because the toner end is firstly detected after decreasing the density from 6% to 2%, if the reference voltage of a magnetic permeability sensor is set at 3.0 V in the latter half of the life of the toner. <P>SOLUTION: In an image forming apparatus for forming an image on a recording medium by forming an electrostatic image on an image carrier and by developing the electrostatic image with developer, a reference voltage value is corrected by the durable number of sheets (the printing number of sheets) (S102), the corrected reference voltage value is compared with a voltage value indicating an amount of the developer (S104), and it is determined whether or not the remaining amount of the toner decreases at or below an acceptable remaining amount (S105). If the remaining amount decreases at or below the acceptable remaining amount, it is determined that the remaining amount has reached the toner end (S106) and a warning display is performed (S107). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an electrostatic image on an image carrier and visualizing the image with a developer to form an image on a recording medium, a control method thereof, and a process cartridge.
[0002]
[Prior art]
In an image forming apparatus employing an electrophotographic method, a toner of a charged developer is adsorbed on an electrostatic latent image formed on the surface of an image carrier to form a toner image, and the toner is conveyed so as to contact the image carrier. Transfer the toner image to the transfer paper. Then, a heat fixing process is performed on the transfer paper on which the toner image has been transferred, thereby completing the image formation on the transfer paper. The developer used here is a two-component developer obtained by mixing toner with magnetic powder called a carrier. The toner of this developer is charged, and only the toner is charged on the surface of the image carrier by electrostatic latent. It is designed to be adsorbed on the image.
[0003]
The ratio of the weight of the toner particles to the total weight of the carrier particles and the toner particles (hereinafter, toner concentration), which corresponds to the capacity of the two-component developer, plays a very important role in stabilizing the quality of the output image. ing. Therefore, the toner concentration of the developer is accurately detected by using the developer concentration control means (ATR), and the toner is replenished in accordance with the detected change in the toner concentration. The quality of the output image is stabilized by controlling it to be constant.
[0004]
The developer concentration control means (ATR) generally includes a toner concentration detection means for detecting a toner concentration of the developer, and a toner supply amount control means for processing output data of the toner concentration detection means to determine a toner supply amount. And toner supply means for actually supplying toner based on the toner supply amount determined by the toner supply amount control means. In particular, various types of toner concentration detection means are employed. ing.
[0005]
For example, a toner concentration detection device using an optical sensor that utilizes the fact that the light reflectance of the developer in the developing container or on the developer carrying member varies with the toner concentration, and utilizes the fact that the magnetic permeability of the developer varies with the toner concentration A toner density detecting device using a magnetic permeability sensor that converts magnetic permeability into an electric signal, and indirectly detects a change in light reflectivity of a predetermined patch image formed on the latent image carrier under predetermined conditions. There is a method of estimating the toner concentration of the developer.
[0006]
In an image forming apparatus that forms a digital latent image using a laser scanner or an LED array, the amount of toner consumed per page is compared based on the total number of print pixels (video count) in the image information signal per page. There is also known a developer density control means (hereinafter, referred to as a "video count ATR") which determines the toner replenishment amount in accordance with the estimated consumption amount because it can be accurately estimated. This video count ATR has a great advantage in terms of cost because it does not require a toner density detecting means, but has a drawback that errors in the toner replenishment amount are gradually accumulated. Some means is required, and at present it is difficult to use this video count ATR alone.
[0007]
As described above, it is necessary to install the toner concentration detecting means in the developing device, and at the same time, it is also desired to reduce the size of the developing device. Accordingly, an automatic toner replenishment control device using a toner density detection device using a magnetic permeability sensor, which is advantageous only in the space for installing the magnetic permeability sensor and is advantageous for miniaturization, is often selected. The magnetic permeability sensor is installed in a part of a developer carrying path or the like inside the developing device so that a head part of a sensor including a coil serving as a detection unit is always in a state of being in contact with the developer. . Here, since the strength of the magnetic field generated when a high frequency is applied to the coil inside the head changes according to the magnetic permeability around the head, the self-inductance of the coil itself (or the mutual inductance of another measurement coil) is obtained. Is measured, the magnetic permeability of the developer around the head portion can be converted into an electrical value.
[0008]
The magnetic permeability of the developer changes depending on the mixing ratio of the magnetic carrier and the nonmagnetic toner. For example, when it is detected that the magnetic permeability of the developer has increased, it is determined that the ratio of the carrier in the developer in a certain volume has increased and the toner concentration has decreased. Therefore, in this case, toner supply is started. Conversely, when the magnetic permeability decreases, it is determined that the ratio of the carrier in the developer in a certain volume has decreased and the toner concentration has increased, and the toner concentration is controlled such that toner replenishment is stopped. Will be. This inductance detecting type developer concentration detecting means is suitable because there is no disadvantage that the error of the toner supply amount is gradually accumulated as in the video count ATR as described above. Hereinafter, the developer concentration detecting means of the inductance detecting method is referred to as an inductance detecting method ATR.
[0009]
FIG. 9 is a cross-sectional view of a two-component developing device 100 employing an inductance detection type ATR.
[0010]
In the figure, reference numeral 104 denotes a developing container which contains a developer (toner) 116. Reference numeral 105 denotes a developing sleeve which is a developer carrier. The developing sleeve 105 is a hollow metal sleeve and includes a magnet roller 106 as a magnetic field generating means inside. The developer sent along with the rotation of the developing sleeve 105 in the direction of the arrow is thinned by the developer regulating blade 109 serving as the developer regulating means.
[0011]
An A screw 107 is disposed in the developing container 104 substantially in parallel with the developing sleeve 105, and conveys and agitates the developer in the direction of the arrow. Further, a B screw 108 is arranged on the opposite side of the developing screw 105 from the A screw 107 with a partition wall 130 interposed therebetween. In order to transfer the developer from the side of the A screw 107 to the side of the B screw 108, the partition walls 130 are not provided at both ends in the longitudinal direction but are present at intermediate positions in the longitudinal direction. , 108 are circulated. The developer present on the side of the A screw 107 and used for image formation is sent to the side of the B screw 108 to detect the toner concentration located on the upstream side of the B screw 108 in the developer conveying direction. The toner density is detected by the magnetic susceptibility sensor 125.
[0012]
The toner density is detected by the following method.
[0013]
First, an output voltage value of the magnetic permeability sensor 125 when a desired toner concentration is obtained is determined in advance as a reference value. Alternatively, the output voltage value of the magnetic permeability sensor 125 is checked for a new developer having an initial predetermined toner concentration, and the value is used as a reference value. This reference value is stored in the nonvolatile memory 123 provided in the developing device. Then, during the actual image formation, the output value of the magnetic permeability sensor 125 is checked, and this output voltage value is compared with the above-mentioned reference value. When the output voltage value is larger, it is determined that the toner density is low, and An appropriate amount of toner is supplied from the toner supply mechanism through the toner supply port 110 on the downstream side of the magnetic susceptibility sensor 125. Conversely, if the output voltage value is small, it is determined that the toner density is high, and toner supply is not performed. As a result, the concentration of the toner as the developer is kept constant.
[0014]
Conventionally, this inductance detection method ATR has a problem that the output voltage value of the magnetic permeability sensor 125 corresponding to the apparent magnetic permeability changes due to a change in the bulk density of the developer 116 due to a change in environment. That is, under environmental conditions of low temperature and low humidity, the amount of water contained in the developer decreases, and as a result, the charge amount of the toner due to the contact between the toner and the carrier increases. For this reason, repulsion between the developers is increased, and the bulk density of the developers is reduced. Conversely, in an environment of high temperature and high humidity, the amount of water contained in the developer increases and the charge amount of the toner due to the contact between the toner and the carrier decreases. The density increases. That is, although the toner concentration in the developing container 104 is constant, the output voltage value of the magnetic permeability sensor 125 varies depending on the environment.
[0015]
Therefore, the environment correction is performed so that the output value is constant by changing the voltage input to the magnetic permeability sensor 125 according to the information on such environmental conditions. As a result, even if the bulk density of the developer fluctuates due to the fluctuation of the environment, the toner density can be detected without any problem.
[0016]
When the image forming operation is performed by the automatic toner replenishment control device using the toner density detecting device based on the magnetic permeability sensor 125, the toner is naturally consumed, and the amount of the replenishing toner in the toner replenishing mechanism is reduced. If the image forming operation is continued in the state in which the toner is in the state, the toner concentration of the developer continues to decrease. When the toner density of the developer is low in this manner, the image density is of course low. Therefore, it is necessary to detect a state in which the toner concentration of the developer has decreased, and to urge the user to replace the toner supply mechanism. Such a warning display is generally called a toner end display, and when this display is made, the image forming operation stops.
[0017]
Conventionally, the toner replenishment mechanism is provided with toner end detection to perform toner end detection, or when the output voltage value from the magnetic permeability sensor 125 provided in the developing device reaches a predetermined value. There was one that performed end detection. As described above, when the output voltage value of the sensor reaches a predetermined value, a warning display is displayed to prompt replacement of the toner supply mechanism. However, if the toner replenishment mechanism attempts to detect the toner end, the toner replenishment mechanism itself must be provided with a structure for detecting the toner end, resulting in an increase in the cost of the toner replenishment mechanism. On the other hand, by detecting the toner end using the detection voltage value of the magnetic permeability sensor 125, the toner end can be detected only by the developing device, and the cost of the toner supply mechanism can be reduced. For example, there is a method in which a voltage value for detecting toner end is determined in advance. This toner end detection method will be described below.
[0018]
As shown in FIG. 10, the output characteristic of the magnetic permeability sensor 125 is such that as the toner concentration decreases, the output voltage value gradually increases, and as the toner concentration further decreases, the output voltage value of the magnetic permeability sensor 125 increases. Saturated. Conversely, when the toner concentration increases, the output voltage value of the magnetic permeability sensor 125 gradually decreases, and when the toner concentration increases, the output voltage value saturates at a small value. The toner end is detected using the output characteristics of the magnetic permeability sensor 125. Specifically, the output voltage value of the magnetic permeability sensor 125 is adjusted to be 2.5 V when the toner concentration is the index value of 8%. When the voltage value is around 2.5 V, the output voltage value changes almost linearly with the toner density.
[0019]
FIG. 11 is a diagram illustrating a relationship (linear) between the toner concentration of the developer and the output voltage value of the magnetic permeability sensor 125 when the output voltage value of the magnetic permeability sensor 125 is in the range of 2.0 V to 3.0 V.
[0020]
The toner density becomes 10% with respect to the output voltage value of 2.0 V of the magnetic permeability sensor 125, and the toner density becomes 6% with respect to 3.0V. Assuming that the toner end is detected when the toner density is 6%, the toner end detection is performed when the voltage value detected by the magnetic permeability sensor 125 becomes 3.0V.
[0021]
Next, a change in the toner concentration of the developer from the time of the normal image forming operation to the time when the toner end is detected will be described in detail with reference to FIG.
[0022]
FIG. 12 is a diagram showing how the output voltage value of the magnetic permeability sensor 125 changes until the toner end is detected.
[0023]
In the figure, Va is a reference voltage value of the magnetic permeability sensor 125, and Vb is an output voltage value when it is determined that the toner end is reached. During a normal image forming operation, the output voltage of the magnetic permeability sensor 125 is around 2.5V. If the image forming operation is repeatedly performed with the amount of toner in the toner replenishing mechanism reduced, the toner replenishment is stopped from the point (A) when the toner in the toner replenishing mechanism runs out. Becomes lower. If the image forming operation is continued in such a state, the toner density becomes too low, and the image density becomes too low.
[0024]
Therefore, it is necessary to detect a state in which the toner density has decreased, that is, to detect a toner end so that the image density does not decrease. The toner end is detected based on the output voltage value of the magnetic permeability sensor 125 as described above. For example, when the toner concentration is 8%, the output voltage (Va) of the magnetic permeability sensor 125 is detected at 2.5 V, but when the toner concentration of the developer becomes 6%, the magnetic permeability sensor 125 is detected. When the output voltage (Ve) becomes 3.0 V, it is determined that the toner is exhausted. At this time, Vm = Ve-Va = 0.5 [V] is defined as a margin from the initial reference voltage value until the toner end is detected, and Vm is defined as a limit margin voltage value.
[0025]
As described above, in the toner end detection, a value obtained by adding the limit margin voltage value to the initially set reference voltage value is determined as the toner end detection voltage value Ve. When this toner end detection voltage value Ve is expressed by a mathematical expression, it is as follows.
[0026]
Ve = Va + Vm
It has been proposed until now that the toner end is accurately detected by the method described above, the user is notified that the toner in the toner supply mechanism has run out, and replacement with a new toner supply mechanism is urged.
[0027]
Further, when a long life of the developing device using the above-described conventional magnetic permeability sensor 125 is aimed at, the reference voltage is changed in order to lower the toner concentration with respect to the initial toner concentration. For example, the reference voltage at the initial 2.5V is 8%, and the reference voltage at 3.0V is 6% in the latter half of the endurance. This is because in the latter half of the life of the developer, the deterioration of the developer progresses, the charge amount of the toner decreases, the developability of the toner increases, the density becomes too high, and fog sometimes occurs.
[0028]
Therefore, the reference voltage value is corrected so that the toner concentration is 8% in the initial stage and the toner concentration is 6% in the latter half of the endurance. Specifically, the initial voltage is set to 2.5 V, and the correction is performed so that 3.0 V becomes the reference voltage in the latter half of the durability. In this way, the optimum control of the toner density can be performed from the initial stage to the latter half of the endurance, and a good image can be provided.
[0029]
In this manner, the toner end is detected by detecting the toner end based on the output voltage value of the magnetic permeability sensor 125 described above, and the user is notified that the toner in the toner replenishing mechanism has run out, and a new toner replenishing mechanism is provided. It has been proposed to prompt the exchange.
[0030]
[Problems to be solved by the invention]
However, when such a reference voltage is corrected for durability, the following problem occurs when the toner end detection voltage value (Ve) is set. That is, in the latter half of the endurance, when the correction amount of the reference voltage is large, the density of the output image when the toner end is reached is remarkably low.
[0031]
Regarding this phenomenon, the relationship between the toner concentration and the output voltage value of the magnetic permeability sensor was examined. The result is shown in FIG. From this result, when the reference voltage value of the magnetic permeability sensor is corrected so as to be higher in the latter half of the durability, the linear relationship between the output voltage value of the magnetic permeability sensor and the toner concentration of the developer increases the reference voltage value. The more you raise, the more nonlinear the relationship becomes. Therefore, it has been found that the fluctuation of the output voltage value of the magnetic permeability sensor becomes slow with respect to the fluctuation of the toner concentration of the developer.
[0032]
When the reference voltage of the magnetic permeability sensor is set to 2.5 V, when toner end is detected, the normal toner density is reduced from 8% to 6%, and toner end is detected. However, when the reference voltage of the magnetic permeability sensor is set to 3.0 V in the latter half of the service life, it has been found that the toner end is detected only when the toner concentration is reduced from 6% to 2%, which causes a significant decrease in the concentration. .
[0033]
In order to prevent this problem, for example, it is conceivable to set the margin voltage value to a small value from the beginning in order to prevent a decrease in density at the time of toner end detection in the latter half of the endurance. In spite of the above, a slight change in the toner density causes a problem that a toner end is erroneously detected, and this is not preferable. Therefore, when the reference voltage value is corrected for durability, if the margin voltage value is set to a fixed value, it is possible to prevent a large change in image density at the time of toner end while preventing erroneous detection of toner end during the entire durability. could not.
[0034]
SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and an image forming apparatus that prevents the density of an image to be formed from being reduced and the image quality from being reduced when it is detected that the remaining amount of a developer is reduced. And a control method thereof and a process cartridge.
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus of the present invention has the following configuration. That is,
An image forming apparatus that forms an electrostatic image on an image carrier, visualizes the image with a developer, and forms an image on a recording medium,
Detecting means for detecting the amount of the developer,
Determining means for comparing the detection result of the detecting means with a reference value to determine whether the remaining amount of the developer has become equal to or less than an allowable remaining amount;
Correction means for correcting the reference value based on information related to image formation,
It is characterized by having.
[0035]
In order to achieve the above object, a method for controlling an image forming apparatus according to the present invention includes the following steps. That is,
A control method in an image forming apparatus for forming an electrostatic image on an image carrier, visualizing the image with a developer, and forming an image on a recording medium,
The developer is configured by mixing toner particles with carrier particles having magnetism, is housed in a container, and a detection step of detecting the amount of the developer in the container,
A determination step of comparing the detection result in the detection step with a reference value to determine whether the remaining amount of the developer is equal to or less than an allowable remaining amount;
A correction step of correcting the reference value based on information related to image formation,
It is characterized by having.
[0036]
In order to achieve the above object, a process cartridge of the present invention has the following configuration. That is,
A developer in which toner particles are mixed with carrier particles having magnetism, a developing container that stores the developer, a magnetic permeability sensor that detects the amount of the developer in the developing container as a change in magnetic permeability, and the developer And storage means for storing information relating to the amount of use of the information.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0038]
[Embodiment 1]
FIG. 1 is a diagram illustrating a cross-sectional configuration of an electrophotographic printer (laser beam printer), which is an embodiment of an image forming apparatus according to an embodiment of the present invention.
[0039]
In the figure, an electrophotographic photosensitive drum 1 which is an image carrier which rotates in the direction of arrow A is provided. Around the photosensitive drum 1, a charger 2, a developing unit 4, a transfer charger 11, a cleaning unit 17, and a photosensitive unit An image forming unit including a laser beam scanner and the like provided above the drum 1 is provided. The photosensitive drum 1 has an outer diameter of 30 mm and rotates in the direction of arrow A at a peripheral speed of 100 [mm / s].
[0040]
The developing device 4 develops an electrostatic latent image using a two-component developer containing a non-magnetic toner and a carrier, and supplies the charged toner to the electrostatic latent image on the photosensitive drum 1. This is visualized. Reference numeral 22 denotes a magnetic permeability sensor, which is provided in the developing device 4. Reference numeral 23 denotes a storage unit, which is installed in the developing device 4 and uses a readable / writable EEPROM in the present embodiment. By setting the developing unit 4 in the main body of the printer, the storage unit 23 is electrically connected to the engine controller 24, and can read and write image forming processing information of the developing unit 4 from the printer side.
[0041]
In FIG. 1, a laser beam 3 modulated by an image signal scans on a photosensitive drum 1, and an electrostatic latent image is formed on the drum 1. The toner is transferred to the electrostatic latent image via the developing sleeve 5 of the developing device 4, and the electrostatic latent image is visualized. In synchronization with this image formation, the recording sheet 20 picked up from the paper feed cassette 18 by the rotation of the pickup roller 19 is conveyed to the position of the photosensitive drum 1 via the conveying path, and the transfer charger 11 and the photosensitive drum 1 , And the visualized electrostatic latent image is transferred to the recording sheet 20. The recording sheet 20 transferred in this manner is fixed by the fixing device 14 and then discharged out of the apparatus by rotation of the discharge roller pair 21.
[0042]
FIG. 2 is a sectional view of the developing device 4 as viewed from above. The developing device 4 will be further described with reference to FIG.
[0043]
As shown in FIG. 2, in order to transfer the developer (toner) between the developing chamber 201 and the stirring chamber 202, both ends 4b and 4c of the partition wall 4a in the longitudinal direction are open. The A and B screws 7, 8 rotate clockwise, respectively, so that the toner circulates between the developing chamber 201 and the stirring chamber 202 as shown by the arrow in FIG. In the present embodiment, the A and B screws 7 and 8 having a diameter of 14 mm are used.
[0044]
An opening is provided in a portion of the developing device 4 which is in close proximity to the photosensitive drum 1, and a developing sleeve 5 which is a non-magnetic toner carrier such as aluminum or non-magnetic stainless steel is provided in this opening. ing. The developing sleeve 5 contains a magnet roller as a magnetic field generating means inside. The developing sleeve 5 conveys the toner to the photosensitive drum 1 by rotation. The thin toner layer formed by being regulated by the toner regulating blade 9 provided above the developing sleeve 5 comes into contact with the rotating photosensitive drum 1 as a magnetic brush, and the electrostatic latent image on the photosensitive drum 1 is It is developed with this toner.
[0045]
Above the stirring chamber 202, a toner supply mechanism is provided, and the inside of the toner supply mechanism is filled with toner for supply. A magnetic permeability sensor 22 is provided on the side surface of the stirring chamber 202 and upstream of the B screw 8 in the toner conveying direction. The toner on the developing chamber 201 side used for image formation is sent to the stirring chamber 202, and the toner density is detected by the magnetic permeability sensor 22.
[0046]
Then, based on the toner density detection result by the magnetic permeability sensor 22, an appropriate amount of toner is supplied from the toner supply mechanism through a toner supply port 46 provided above the stirring chamber 202 and downstream of the magnetic permeability sensor 22. You. As a result, the toner density of the developing device 4 is always kept constant.
[0047]
As the toner as a developer, for example, a known toner in which a colorant or a charge controlling agent is added to a binder resin can be used. In the present embodiment, a toner having a volume average particle diameter of 5 to 15 [μm] is used. ing. On the other hand, as the magnetic carrier of the toner, in addition to magnetic particles such as ferrite, for example, magnetic particles having an extremely thin resin coating on the surface are preferably used, and the average particle diameter is 5 to 70 [μm]. Is preferable.
[0048]
The toner according to the exemplary embodiment has a preferable toner concentration (the ratio of the weight of toner particles to the total weight of carrier particles and toner particles; , T / D) having a T / D ratio of 8%.
[0049]
Next, details of the magnetic permeability sensor 22 according to the present embodiment will be described.
[0050]
In the present embodiment, since the developer concentration in the developing device 4 changes due to the development of the electrostatic latent image, the magnetic permeability sensor 22 is installed on the side wall of the stirring chamber 202, and the engine controller 24 The toner concentration is detected based on the detection signal from the reference numeral 22. Then, an automatic toner replenishment control method (ATR) based on an inductance detection method is employed in which replenishment of toner is controlled based on a result of comparison between the detected toner density and a preset reference value.
[0051]
As described above, the toner of the two-component developer contains a magnetic carrier and a non-magnetic toner as main components, and when the T / D ratio of the developer changes, the apparent magnetic permeability due to the mixing ratio of the magnetic carrier and the non-magnetic toner is changed. Change. The apparent magnetic permeability is detected by an inductance sensor, which is the magnetic permeability sensor 22, and is converted into an electric signal.
[0052]
FIG. 3 is a graph showing the relationship between the input voltage and the output voltage of the magnetic permeability sensor 22. In this example, the input voltage (hereinafter referred to as the input voltage for a developer having a T / D ratio of 8% in an environment (23 ° C., 60% RH)) is used. , Control voltage) and the output voltage (output voltage).
[0053]
As shown in the figure, since the change rate of the output voltage is the largest near the control voltage of 12.5 V, in this embodiment, 12.5 V is used as the control voltage under the standard environment, and 2.5 V is used as the standard output voltage. are doing. Note that the relationship between the T / D ratio and the output voltage of the inductance sensor (magnetic permeability sensor 22) changes almost linearly according to the T / D ratio.
[0054]
Basic control of the toner density is performed by the engine controller 24 as follows.
[0055]
When performing the image forming operation, first, the output voltage from the magnetic permeability sensor 22 is detected. This output voltage corresponds to the density of the toner which is a two-component developer of the developing device 4. The output voltage from the magnetic permeability sensor 22 is compared with a reference voltage corresponding to an apparent magnetic permeability at a predetermined toner density, and the toner supply time is corrected and controlled based on the comparison. For example, when the toner density detected by the magnetic permeability sensor 22 is lower than a predetermined value (preset toner density), that is, when the toner amount is insufficient, the engine controller 24 outputs a control signal. The toner replenishing mechanism is operated so as to output and supply the insufficient toner to the developing device 4. As shown in FIG. 2, the toner replenishing mechanism has toner conveying screws 7 and 8 therein, and the screws 7 and 8 are provided only for a time for dropping the toner amount determined according to a control signal from the engine controller 24. To rotate.
[0056]
Further, when the toner density detected by the magnetic permeability sensor 22 is higher than the specified value, that is, when the toner is excessively replenished, in the subsequent image formation, the excessive toner amount is consumed. An image is formed without supplying toner. That is, control is performed such that an image is formed without toner replenishment, the excess toner amount is consumed, and after the excessive toner is consumed, the toner replenishing operation is performed as described above.
[0057]
Next, the relationship between the toner concentration of the developer and the output of the magnetic permeability sensor 22 will be described in detail.
[0058]
FIG. 4 is a graph showing an example of the output voltage of the magnetic permeability sensor 22 according to the present embodiment.
[0059]
In the present embodiment, as shown in FIG. 4, when the toner concentration is the index value 8%, the output voltage value of the magnetic permeability sensor 22 is adjusted to be 2.5V. When the output voltage value is around 2.5 V, the output voltage changes almost linearly with the toner density (linear). Actually, when the output voltage of the magnetic permeability sensor 22 is in the range of 1.96 V to 3.04 V, the relationship between the toner concentration and the output voltage value of the magnetic permeability sensor 22 is substantially linear. Here, when the output voltage of the magnetic permeability sensor 22 is 1.96 V, the toner density is 10%, and when the output voltage of the magnetic permeability sensor 22 is 3.04 V, the toner density is 6%.
[0060]
Next, a method of detecting a toner end (insufficient amount of toner) during a normal image forming operation will be described below. The transition of the toner density until the toner end is detected will be described with reference to FIG.
[0061]
FIG. 5 is a diagram showing how the output voltage of the magnetic permeability sensor 22 changes until the toner end is detected. The output voltage is set on the vertical axis, and the number of prints is set on the horizontal axis.
[0062]
In the figure, Va is a reference voltage value of the magnetic permeability sensor 22, and Ve is an output voltage value when it is detected that the toner is out. During a normal image forming operation, the output voltage of the magnetic permeability sensor 22 is around 2.5V. Thereafter, if the image forming operation is repeatedly performed in a state where the remaining amount of toner in the toner supply mechanism is low, the toner density decreases as the toner is consumed. That is, the ratio of the weight of the toner particles to the total weight of the carrier particles and the toner particles decreases. If the image forming operation is further continued in such a state, the toner density further decreases, and the formed image density does not reach a certain density.
[0063]
Here, the toner end is detected based on the output voltage value of the magnetic permeability sensor 22 as described above. For example, when the toner density is 8%, the output voltage (Va) of the magnetic permeability sensor 22 is 2.50 V (reference voltage), and when the toner density becomes 6%, When the output voltage (Ve) becomes 3.04 V, it is detected that the toner is out. At this time, a limit margin voltage value Vm is defined as a margin from Vm = Ve−Va = 0.54V to the detection of toner end from the initial reference voltage value.
[0064]
As described above, the toner end detection is determined by adding the limit margin voltage value Vm to the initially set reference voltage value Va as the toner end detection voltage value Ve. The voltage value at the time when the toner end is detected is expressed by the following equation.
[0065]
Ve = Va + Vm
The voltage value detected as the toner end is not the output voltage value of the magnetic permeability sensor 22 at the toner density described above, but may be any value that can be detected at the time when the density of the formed image does not decrease so much. In particular, the present invention is not limited to the above-described mathematical expressions and reference voltages.
[0066]
When the life of the toner is in the initial stage, the image forming operation can be performed at the toner density index value of 8%. However, in the latter half of the toner life, there is a possibility that normal image formation may not always be performed based on the initially set index value of 8%. Therefore, it is necessary to increase or decrease the reference voltage value according to the life of the toner to obtain an optimum toner density.
[0067]
Hereinafter, a method according to the present embodiment for detecting the toner end by changing the reference value of the magnetic permeability sensor 22 according to the toner life described above will be specifically described.
[0068]
In the latter half of the toner life (the latter half of the durability), the developing property of the toner increases. Therefore, in the latter half of the endurance, if the toner density is controlled by the initially set reference voltage value at the toner density of 8%, the image density tends to increase, and further, the fog generated on the white background portion due to the increase in the developing property of the toner occurs. A problem arises. Therefore, in order to solve such a problem, the magnetic permeability sensor 22 is configured to reduce the toner density in accordance with the image forming processing information stored in the storage unit 23 of the developing device 4 by the amount corresponding to the increase in the toner developability. Is corrected. However, the image forming processing information may be any information that reflects the life of the toner, such as the number of durable sheets (the number of printed sheets), the number of rotations of the developing sleeve 5, the developing operation time, and the like. The processing information is the number of durable sheets.
[0069]
As shown in FIG. 14, the storage unit 23 is a storage unit that stores image forming processing information. In the present embodiment, the information about the number of rotations of the developing roller, the information about the developing operation time, and the information about the number of printed sheets are provided. Further, areas 231 to 235 are provided for storing information relating to the correction amount of the reference voltage value of the magnetic permeability sensor, which will be described later, and information relating to the toner life (toner amount). The storage unit may be a nonvolatile memory, and for example, a memory such as an EEPROM or a FeRAM (ferroelectric memory) is suitable. Regarding connection with the image forming apparatus, a method of electrically connecting a signal line to the storage unit for communication or a method of wireless communication using radio waves may be used.
[0070]
The correction amount of the reference voltage value of the magnetic permeability sensor 22 is stored in advance in the developing device 4 as information corresponding to the toner life. However, the place where the information relating to the image forming processing information is stored may not necessarily be the developing device 4.
[0071]
In the present embodiment, when the toner life is 50,000 in terms of the number of prints, the correction amount of the reference voltage value is determined according to the number of prints as shown in FIG.
[0072]
As shown in FIG. 6, while the correction amount is “0” when the number of printed sheets is 1000 or less, the reference voltage value is determined so that the toner density is reduced from 1000 sheets.
[0073]
As described above, in the present embodiment, when toner end is detected, the limit margin voltage value Vm is reduced. As described above, when the reference voltage value of the magnetic permeability sensor 22 is corrected to be higher in the latter half of the endurance, the relationship between the output voltage value of the magnetic permeability sensor 22 and the toner density increases as the reference voltage value increases. The reason for this is that the output voltage of the magnetic permeability sensor 22 fluctuates more slowly as the toner density fluctuates.
[0074]
Hereinafter, a specific toner end detection method will be described.
[0075]
When the output voltage value of the magnetic permeability sensor 22 exceeds the toner end detection voltage value (Ve ') three times in succession, it is set so that the toner end is detected.
[0076]
The reference voltage value (Vx) of the magnetic permeability sensor 22 corrected according to the number of durable sheets, the reference voltage value of the magnetic permeability sensor 22 that is initially set is (Va), the limit margin voltage value is (Vm), and the reference voltage value is When the constant is α to reduce the limit margin voltage value by the correction amount (Vx−Va), the toner end detection voltage value (Ve ′) is
Ve ′ = Vx + Vm−α × (Vx−Va) Equation (1)
Is defined.
[0077]
In the equation (1), the constant α is set to “0.5”. Therefore, α × (Vx−Va) acts to reduce the limit margin voltage value when the reference value of the magnetic permeability sensor 22 is corrected (in the example of FIG. 6, the number of printed sheets is 1000 or more). I have. The value of the constant α is not limited to this, but may be any value as long as the toner developability can be secured over the life of the toner and a sufficient image density can be satisfied. When correcting the reference voltage value, the constant α may be set to a constant determined according to the correction amount of the reference voltage value in consideration of the chargeability and developability of the toner.
[0078]
FIG. 7 is a block diagram showing a configuration of the engine controller 24 according to the present embodiment.
[0079]
In the figure, a CPU 240 such as a microprocessor controls the operation of the entire engine controller 24 according to a control program stored in a ROM 241. The ROM 241 also stores the table data shown in FIG. A RAM 242 is used as a work area when the CPU 240 executes the control processing, and is used for temporarily storing various data and variables. An input port 243 receives an output voltage of the magnetic permeability sensor 22, converts the voltage into a digital signal, and outputs the digital signal to the bus 246. Thereby, the CPU 240 can acquire the voltage value output from the magnetic permeability sensor 22. Reference numeral 244 denotes an input / output port to which the above-mentioned storage unit 23 (EEPROM) is connected so that the contents of the EPROM can be read and written. In the storage unit 23, information related to the toner life (toner amount) such as the number of printed sheets, the number of rotations of the developing sleeve 5, and the developing operation time is updated and stored. Reference numeral 245 denotes an output port through which supply of toner to the developing device 4 and development processing can be controlled.
[0080]
FIG. 7 is a flowchart illustrating a method of detecting a toner end by the engine controller 24 according to the present embodiment. A program for executing this process is stored in the ROM 241.
[0081]
First, in step S101, the number of durable sheets (the number of printed sheets) stored in the storage unit 23 is read. Next, the process proceeds to step S102, and based on the read number of durable sheets, a correction amount of the reference voltage value of the magnetic permeability sensor 22 is obtained with reference to the table of FIG. Then, the process proceeds to step S103, and the toner end detection voltage (Ve ') is calculated according to the above-described equation (1).
[0082]
Next, the process proceeds to step S104, where the output voltage value of the magnetic permeability sensor 22 is input via the input port 243, and it is determined whether or not the voltage value exceeds Ve ′ obtained in step S103. If it exceeds, the process proceeds to step S104, and in this embodiment, it is determined that the toner end is reached when the output voltage value of the magnetic permeability sensor 22 exceeds Ve ′ three times in succession. To see if they are over. If it is not three consecutive times, the process returns to step S103 to execute the above-described processing.
[0083]
When the output voltage value of the magnetic permeability sensor 22 exceeds Ve ′ three times in a row, the process proceeds to step S106, and it is determined that the toner is out. Then, the process proceeds to step S107, and a warning is displayed to inform the user that the toner is out.
[0084]
When the first embodiment is applied, for example, when the number of prints is 30,000, the voltage value Ve ′ when the toner end is detected when the above control is performed is 3.31 V. When toner end detection is performed based on the toner end detection voltage value Ve ′ = 3.31 V, the toner density at the time when the toner end is detected is 4%. On the other hand, in the conventional toner end detection method, when the number of prints is 30,000, Ve = 3.5 V, and the toner density when the toner end is detected is reduced to 2%.
[0085]
As described above, according to the first embodiment, it was possible to prevent a decrease in print image density when toner end was detected.
[0086]
As described above, even when the number of prints is equal to or more than the predetermined amount and the correction amount of the reference voltage value is increased, the toner end is determined based on the toner density in the same manner as when the number of prints is equal to or less than the predetermined amount. Can be detected. Then, it is possible to prevent the toner concentration when the toner end is detected from becoming too low, and to accurately detect the toner end.
[0087]
<Embodiment 2>
Further, a second embodiment of the present invention will be described.
[0088]
The toner particles according to Embodiment 2 of the present invention are spherical polymerized toners. The spherical polymerized toner is manufactured by mixing a monomer composition obtained by adding a colorant and a charge control agent to a monomer of the polymerization method in an aqueous medium. Polymerization is carried out so that spherical toner particles can be obtained. This production method is suitable for producing a spherical toner. Note that the method for generating such a spherical toner is not limited to this method. If a spherical toner can be prepared, for example, the toner may be prepared by an emulsion polymerization method or the like, and other additives may be contained.
[0089]
The spherical polymer toner obtained by this method has a shape factor of 100 to 140 for SF-1 and 100 to 120 for SF-2. For the SF-1 and SF-2, FE-SEM (S-800) manufactured by Hitachi, Ltd. was used, and 100 toners were randomly sampled, and the image information was obtained through an interface using an image analysis device (Lusex3, Nicole 3). ) And analyzed, and the values calculated by the following equations are defined as shape factors SF-1 and SF-2 in the present embodiment.
[0090]
SF-1 = (MXLNG) 2 / AREA × (π / 4) × 100
SF-2 = (PERI) 2 / AREA × (π / 4) × 100
Here, AREA indicates the toner projection area, MXLNG indicates the absolute maximum length, and PERI indicates the circumference.
[0091]
The SF-1 indicates a degree of sphere, and when it is larger, the shape gradually becomes irregular from a sphere. SF-2 indicates the degree of unevenness, and when it is larger, the unevenness of the surface area becomes remarkable. As compared to the spherical shape factor, the shape factor of the conventional pulverized toner is 180 to 220 for SF-1 and 180 to 200 for SF-2. This indicates that the spherical polymerized toner has almost a perfect circular shape compared to the conventional pulverized toner. Originally, spherical polymerized toner having a shape close to a perfect circle has little change in shape with respect to pulverized toner, and thus has little change in shape. Further, the crushed toner has a large variation in the shape of the toner particles, so that the porosity and the bulk density change greatly. On the other hand, since the spherical polymerized toner has a small change in the shape of the toner particles as described above, the bulk density change is small, and the detection signal error of the inductance detection type ATR when the toner is left unattended is small.
[0092]
Therefore, in the second embodiment, by using such a spherical polymerization toner, it is possible to suppress an error in the output voltage of the magnetic permeability sensor immediately after the printing process is resumed after being left. As a result, the T / D ratio can be controlled with less error as compared with the pulverized toner.
[0093]
Further, a spherical carrier is used, and 1 × 10 ¹⁰ ~ 1 × 10 ¹⁴ It is preferable to use a material having a high resistance of [Ω · cm]. By making the carrier spherical, the change in the bulk density is reduced. In addition, since the resistance is high, the charge accumulated in the carrier at a time is difficult to escape, and the fluctuation of the charge in the carrier when the toner is left is reduced. For this reason, it can be said that this high-resistance spherical carrier is suitable for an inductance type ATR. Therefore, by combining the toner using the high-resistance spherical carrier with the toner end detecting method according to the first embodiment, the toner end can be detected with higher accuracy.
[0094]
In the present embodiment, a resin magnetic carrier composed of a binder resin and a magnetic metal oxide and a non-magnetic metal oxide is manufactured by a polymerization method, but if the resistance can be adjusted by another manufacturing method. , You can use that carrier.
[0095]
It should be noted that the spherical polymerized toner does not need to be particularly formed by polymerization and toner, and may be formed by another method as long as the spherical toner can be manufactured by another method.
[0096]
In the second embodiment described above, if the same control as the control described in the first embodiment is performed, the case where the reference voltage value is not corrected even when the correction amount of the reference voltage value is increased is increased. The toner end can be detected with the same toner concentration, and the toner concentration of the developer when the toner end is detected does not become too low, so that it is possible to prevent erroneous detection of the toner end detection.
[0097]
[Other embodiments]
Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), the present invention can be applied to an apparatus (for example, a copier, a facsimile device, and the like) including one device. May be applied.
[0098]
Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus to store the storage medium. Needless to say, this can also be achieved by reading out and executing the program code stored in the.
[0099]
In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
[0100]
As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like is used. I can do it.
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that a case where a part of the actual processing is performed and the function of the above-described embodiment is realized by the processing is also included.
[0101]
Further, after the program code read from the storage medium is written into a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes the case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0102]
As described above, according to the present embodiment, it is possible to suppress a decrease in image density when toner end is detected, and to prevent erroneous detection of toner end over the entire toner life.
[0103]
【The invention's effect】
As described above, according to the present invention, when it is detected that the remaining amount of the developer is small, there is an effect that it is possible to prevent the density of an image to be formed from being lowered and the image quality from being lowered.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a cross-sectional configuration of an electrophotographic printer (laser beam printer) which is an embodiment of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the developing device according to the exemplary embodiment as viewed from above.
FIG. 3 is a diagram showing output characteristics of the magnetic permeability sensor according to the present embodiment.
FIG. 4 is a diagram illustrating the relationship between the output voltage of the magnetic permeability sensor and the toner density according to the embodiment.
FIG. 5 is a diagram showing how the output voltage value of the magnetic permeability sensor changes until a toner end is detected in the present embodiment.
FIG. 6 is a diagram illustrating a relationship between the number of prints and a correction amount according to the present embodiment.
FIG. 7 is a block diagram illustrating a configuration of an engine controller according to the present embodiment.
FIG. 8 is a flowchart illustrating toner end detection processing by the engine controller according to the present embodiment.
FIG. 9 is a cross-sectional view of the developing device according to the exemplary embodiment.
FIG. 10 is a diagram illustrating output characteristics of a magnetic permeability sensor.
FIG. 11 is a diagram showing output characteristics of a magnetic permeability sensor.
FIG. 12 is a diagram illustrating a conventional toner end detection method.
FIG. 13 is a diagram showing output characteristics of a conventional magnetic permeability sensor.
FIG. 14 is a diagram illustrating a data configuration of a storage unit according to the present embodiment.

Claims (18)

An image forming apparatus that forms an electrostatic image on an image carrier, visualizes the image with a developer, and forms an image on a recording medium,
Detecting means for detecting the amount of the developer,
Determining means for comparing the detection result of the detecting means with a reference value to determine whether the remaining amount of the developer has become equal to or less than an allowable remaining amount;
Correction means for correcting the reference value based on information related to image formation,
An image forming apparatus comprising: The developer is configured by mixing toner particles with carrier particles having magnetism and housed in a container, and the amount of the developer is the weight of the toner particles with respect to the total weight of the carrier particles and the toner particles. The image forming apparatus according to claim 1, wherein the ratio corresponds to a ratio. The image forming apparatus according to claim 2, wherein the detection unit includes a magnetic permeability sensor that detects a capacity of the developer in the container based on magnetic permeability. The image forming apparatus according to claim 1, wherein the information related to the image formation corresponds to the number of recording media on which an image is formed. The image forming apparatus according to claim 2, wherein the information related to the image formation corresponds to a rotation number of a roller that supplies the developer from the inside of the container to the outside. 2. The image processing apparatus according to claim 1, further comprising storage control means for updating the information relating to the image formation and storing the updated information in a memory, wherein the correction means corrects the reference value based on the information stored in the memory. 5. The image forming apparatus according to claim 1. The image forming apparatus according to claim 2, wherein the shape factor SF-1 of the toner particles is in a range of 100 to 140, and SF-2 is in a range of 100 to 120. The image forming apparatus according to claim 2, wherein the toner particles are formed by a polymerization method. The image forming apparatus according to claim 2, wherein the specific resistance of the carrier particles is 1 × 10 ¹⁰ to 1 × 10 ¹⁴ [Ω · cm]. The image forming apparatus according to claim 2, wherein the carrier particles are a magnetic resin carrier including a binder resin, a metal oxide, and a non-magnetic metal oxide. A developer in which toner particles are mixed with carrier particles having magnetism, a developing container that stores the developer, a magnetic permeability sensor that detects an amount of the developer in the developing container as a change in magnetic permeability, and the developer A storage unit having an area for storing information relating to the amount of use of the process cartridge. The process cartridge according to claim 11, wherein the toner particles are produced by a polymerization method. The process cartridge according to claim 11, wherein the specific resistance of the carrier particles is 1 × 10 ¹⁰ to 1 × 10 ¹⁴ [Ω · cm]. The process cartridge according to claim 11, wherein the carrier particles are a magnetic resin carrier including a binder resin, a metal oxide, and a non-magnetic metal oxide. A control method in an image forming apparatus for forming an electrostatic image on an image carrier, visualizing the image with a developer, and forming an image on a recording medium,
The developer is configured by mixing toner particles with carrier particles having magnetism, is housed in a container, and a detection step of detecting the amount of the developer in the container,
A determination step of comparing the detection result in the detection step with a reference value to determine whether the remaining amount of the developer is equal to or less than an allowable remaining amount;
A correction step of correcting the reference value based on information related to image formation,
A control method comprising: 16. The control method according to claim 15, wherein, in the detecting step, a capacity of the developer in the container is detected by a magnetic permeability sensor. 17. The control method according to claim 15, wherein the information on the image formation corresponds to the number of recording media on which an image has been formed. 17. The control method according to claim 15, wherein the information related to the image formation corresponds to a rotation speed of a roller that supplies the developer to the outside from inside the container.

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