JP6456435B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine using an electrophotographic system or an electrostatic recording system, and a developer storage unit used in the image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus employing an electrophotographic system is provided with a developing device that forms a developer image by supplying a developer to an electrostatic latent image formed by scanning and exposing an image carrier. ing. In recent years, there are many cases in which a developing device including a developer accommodating portion for accommodating a developer, an image carrier, and other process means (charging member and the like) are integrally accommodated as a process cartridge. In this way, by integrating a plurality of members as a process cartridge and making the process cartridge detachable from the apparatus main body of the image forming apparatus, it is possible to easily supply the developer and perform other maintenance operations.

  In such a process cartridge system, when the developer runs out, the user can replace the cartridge or replenish the developer to form an image again. For this reason, such an image forming apparatus generally includes a means for detecting when the developer is consumed and notifying the user of the replacement time, that is, a developer detecting unit.

  As one of such developer detection units, Patent Document 1 proposes a method that includes a pair of input side and output side electrodes and detects the developer amount by measuring the capacitance between both electrodes. Has been.

  In Patent Documents 2 and 3, by applying an AC bias to the developer carrying member, the developer carrying member is regarded as an input side electrode, and the electrostatic capacity detection member serving as the output side electrode is developed in the developing device. The structure provided in the location facing an agent carrier is proposed.

  Each of Patent Documents 1 to 3 is a method of detecting the amount of developer using a change in capacitance that changes when the amount of developer occupied between a pair of electrodes changes.

JP 2001-117346 A JP 2003-248371 A JP 2007-121646 A

  As for the detection of the developer amount, it is desirable that the change in the developer amount can be detected just before the developer runs out. Therefore, in the method of detecting the developer amount using the change in electrostatic capacity, the arrangement of the electrodes and the shape of the members around the electrodes can be easily detected even when the amount of the developer decreases. It is desirable to optimize the layout. However, in a configuration in which a change in the amount of developer is easily detected even when the amount of developer is reduced, there are cases where it is difficult to achieve both detection of the amount of developer with high accuracy.

  One of the configurations of the invention according to the present application is as follows.

A stirring member that rotates to stir the developer;
A first electrode;
A second electrode disposed at a distance from the first electrode and opposed to the first electrode with an inclination, wherein a minimum part of the distance is from a rotation center of the stirring member And a second electrode disposed such that a remote portion of the gap larger than the minimum portion is positioned above the minimum portion,
A frame that houses the stirring member and the developer, and includes a first wall surface on which the first electrode is disposed and a second wall surface on which the second electrode is disposed. When,
A developer container comprising:
A developer detecting unit that detects an output value corresponding to a capacitance between the first electrode and the second electrode , the capacitance changing according to a developer amount stored in the frame; ,
With
The output value in the first developer amount as a first reference value, the output value of the developer detection unit in the first to have a first differential with respect to the reference value 0% developer amount When the second reference value is used, the first difference corresponding to the second reference value that changes according to the size of the first reference value is obtained using a table,
The developer detection unit is configured to determine the remaining amount of developer corresponding to the output value of the electrostatic capacitance with a third developer amount that is smaller than the first developer amount and greater than the 0% developer amount. information, the a first amount of developer, the said first difference calculated, the image forming apparatus to be detected to said Rukoto based on.

  According to the present invention, it is possible to provide an image forming apparatus capable of improving developer detection accuracy.

Cross section of image forming apparatus Cross section of process cartridge Sectional view of the developing device (developer storage part) Developer amount detection circuit Sectional view of the developing device (developer storage part) Diagram showing changes in developer amount and capacitance Relational diagram of capacitance and detection voltage Illustration of changes in capacitance and capacitance between electrodes Table showing correction values between electrodes Developer amount detection sequence Toner level table example

[Example 1]
(Outline of configuration and operation of image forming apparatus and process cartridge)
FIG. 1 is a schematic view of an image forming apparatus in the present embodiment. This image forming apparatus is an electrophotographic, process cartridge detachable laser beam printer. This image forming apparatus can receive and print image information by connecting an external host device such as a personal computer or an image reading device.

  Reference numeral 1 denotes a printer main body (apparatus main body) in the image forming apparatus, and 2 denotes a process cartridge that can be attached to and detached from the apparatus main body 1. FIG. 2 is a cross-sectional view of the process cartridge according to the first embodiment, and the process cartridge 2 will be described using this.

  Reference numeral 20 denotes a drum-type electrophotographic photosensitive member (photosensitive drum) as an image carrier. In this embodiment, four types of process members, that is, a photosensitive drum 20, a charging member (charging roller) 30, a developing device 40 as a developer container in this embodiment, and a cleaning member (cleaning blade) 50 are provided. Integrated into a process cartridge. The apparatus main body 1 is detachable.

  The photosensitive drum 20 is rotationally driven at a peripheral speed (process speed) of 200 mm / s in the clockwise direction of the arrow R1 based on the print start signal. A charging roller 30 to which a charging bias is applied is brought into contact with the photosensitive drum 20, and the charging roller 30 is driven to rotate following the photosensitive drum 20. The circumferential surface of the rotating photosensitive drum 20 is uniformly charged by the charging roller 30 to a predetermined polarity and potential. In this embodiment, it is charged to a negative predetermined potential.

  The charged surface is subjected to laser scanning exposure of image information by an exposure device (scanner unit) 3. The laser light output from the scanner unit 3 enters the cartridge and exposes the surface of the photosensitive drum 20. The photosensitive drum 20 is grounded, and the potential of the portion irradiated with the laser light (exposed bright portion) is attenuated to form an electrostatic latent image corresponding to the image information on the photosensitive drum. In this embodiment, an image exposure method for exposing the image information portion is used.

  The electrostatic latent image is developed by a developer (toner) T on a developing sleeve (developing roller) 41 as a developer carrying member of the developing device 40.

  On the other hand, at a predetermined control timing, the pickup roller 5 of the sheet tray unit 4 is driven, and one sheet of recording material (paper or the like) that is a recording medium stacked and stored in the sheet tray unit 4 is fed. The recording material passes through the transfer roller 7 via the transfer guide 6. During this time, the toner image on the surface of the photosensitive drum 20 is sequentially electrostatically transferred onto the surface of the recording material. Thereafter, the recording material onto which the toner image has been transferred reaches the fixing device 9. After the toner image is fixed by the fixing device 9, the recording material is discharged to the discharge tray 11. After the recording material is separated, the photosensitive drum is cleaned by removal of transfer residual toner and the like by the cleaning blade 50, and is again used for image formation starting from charging.

  A memory 120 as a storage unit is installed in the process cartridge 2 and stores a table and the like used for development and charging control necessary for image formation. In this embodiment, the memory 120 may be provided on the apparatus main body 1 side. It can also be provided in both the process cartridge 2 and the apparatus main body 1. The memory 120 stores a correction value used for correction at the time of developer detection described later. Details will be described later.

(Developer)
The developing device according to Example 1 will be described with reference to FIG. FIG. 3 is a sectional view of the developing device according to the first embodiment.

  The developing device 40 according to the present exemplary embodiment includes a frame body 40 a that stores the toner T. A partition wall 40b is provided inside the frame body 40a. The partition wall 40b includes a developing chamber 46 in which the developing roller 41 is rotatably accommodated, and a developer accommodating chamber (hereinafter referred to as a developer chamber) 47 in which the toner T and the stirring member 60 are accommodated. It is divided into. The partition wall 40 b is provided with an opening 40 c that allows the developing chamber 46 and the developer chamber 47 to communicate with each other. The developing device 40 of this embodiment is configured as a developing device (developing unit) separate from the cleaning unit including the photosensitive drum 20 and the cleaning blade 50.

  As the toner T, a magnetic one-component pulverized toner is used. It consists of a matrix and an external additive. The matrix has a center particle diameter of 7 μm, a circularity of 0.95, and a specific gravity of 1.8. The external additive uses 0.5% by weight of silica having a small particle diameter from the viewpoint of fluidity and chargeability.

  The toner T in the developer chamber 47 is conveyed by the stirring member 60 from the developer chamber 47 to the development chamber 46 through the opening 40c. The toner T in the developing chamber 46 is attracted to the developing roller 41 by a magnet included in the developing roller 41. On the other hand, a developing blade 42 as a layer thickness regulating member made of an elastic member is in contact with the developing roller 41. The toner T is transported in the direction of the developing blade 42 as the developing roller 41 rotates in the R2 direction, and is given a tribo by the developing blade 42, and the layer thickness is regulated.

  Here, the developing roller 41 is applied with a developing bias obtained by superimposing an AC voltage (peak-to-peak voltage = 1500 Vpp, frequency f = 2400 Hz) on a DC voltage (Vdc = −400 V) from the developing bias power supply 45 of the image forming apparatus main body. The On the other hand, the electrostatic latent image as described above is formed on the surface of the photosensitive drum 20. Since an electric field is generated in a region of the photosensitive drum 20 facing the developing roller 41, the toner T having the above-mentioned tribo is supplied to a portion of the photosensitive drum 20 where the electrostatic latent image is formed. By doing so, the electrostatic latent image on the surface of the photosensitive drum 20 is developed.

(Developer and developer detector)
Next, the developing device in Example 1 will be described in more detail with reference to FIG.

  In this embodiment, a stirring member 60, a planar first electrode 43, and a second electrode 44 are provided in a frame body 40 a that forms the developer chamber 47 (inside the developer chamber 47). A developing bias power source 45 is connected to the second electrode 44 and the developing roller 41. The first electrode 43 is connected to a developer detection unit 70 described later. When a voltage is applied to the second electrode 44 and the developing roller 41, the developer detection unit 70 detects the electrostatic capacitance between the first electrode 43 and the second electrode 44, and the first electrode 43. The developer amount can be detected based on the change in the combined capacitance with the capacitance between the developing roller 41 and the developing roller 41.

  On the wall surface of the frame body 40a (the inner wall surface 40a1 (corresponding to the first wall surface), the inner wall surface 40a2 (corresponding to the second wall surface)), the first electrode 43 forming the electrode pair in this embodiment and The second electrode 44 is disposed. The second electrode 44 is disposed so as to be spaced apart from the first electrode 43 and to face the first electrode 43 while being inclined. The first electrode 43 and the second electrode 44 are formed such that the minimum portion X1 (minimum portion on the wall surface) of the gap between the first electrode 43 and the second electrode 44 is below the rotation center 60a of the stirring member 60 (lower in the gravity direction). Is arranged. Here, the minimum portion X1 is an interval between the lower portion 43a1 of the first electrode 43 and the lower portion 44a1 of the second electrode 44 in the direction of gravity. Further, the remote portion X2 having a larger interval than the minimum portion X1 among the intervals is arranged so as to be formed above the minimum portion X1 (upward in the gravity direction). Here, the remote portion X2 is a distance between the upper portion 43a2 of the first electrode 43 and the upper portion 44a2 of the second electrode 44 in the direction of gravity. In this example, the distance of the minimum portion X1 (the width of the interval of the minimum portion X1) was 7 mm. Furthermore, in the following description, a region sandwiched between the first electrode 43 and the second electrode 44 and connecting the minimum interval portion X1 and the remote portion X2 is referred to as a region A. That is, the region A is a region where the first electrode 43 and the second electrode 44 face each other, and is divided by a line connecting the lower part 43a1 and the lower part 44a1 and a line connecting the upper part 43a2 and the upper part 44a2. It is an area.

  Here, the inner wall surface 40a1 on which the first electrode 43 of the frame 40a is disposed and the inner wall surface 40a2 on which the second electrode 44 is disposed are in a direction away from the minimum portion X1 in the horizontal direction and in the direction of gravity. It is an inclined surface that is inclined in a direction toward the upper side. In the present embodiment, the inner wall surface 40a1 and the inner wall surface 40a2 are curved surfaces. The first electrode 43 and the second electrode 44 are disposed along the inner wall surface 40a1 and the inner wall surface 40a2, and are in contact with the inner wall surface 40a1 and the inner wall surface 40a2. That is, the minimum portion X1 is disposed at the lowermost position in the developer chamber 47, and the bottom portion (the lowest portion in the direction of gravity) of the developer chamber 47 is exposed from the minimum portion X1 toward the inside of the developer chamber 47. Yes. Furthermore, in this embodiment, the minimum portion X1 is provided below (lower in the gravity direction) than the opening 40c and the lowermost portion 46a of the developing chamber 46.

  By setting the first electrode 43, the second electrode 44, and the wall surface of the frame body 40a as described above, the toner T is likely to gather at the minimum portion X1 even when the toner T is little remaining. Further, the area A can be widened, and the developer amount can be detected when the developer amount is large.

  Further, the stirring member 60 includes a flexible sheet-like stirring portion 60b and an axis that rotates in the direction of arrow R3 in the drawing around the rotation center 60a. In the horizontal direction, the rotation center 60a and the position of the minimum portion X1 are arranged so as to overlap each other. In other words, in the horizontal direction, the rotation center 60a is arranged so that the rotation center 60a is included in the minimum portion X1. The rotation center 60a is provided below the opening 40c in the direction of gravity. The stirring unit 60b rotates so as to pass through the aforementioned minimum part X1, and rubs against the wall surface 40d exposed from the minimum part X1. Then, the toner T in the minimum portion X1 is drawn up toward the opening 40c and supplied to the developing chamber 46. When the stirring member 60 further rotates, the toner T on the stirring unit 60b falls from the stirring unit 60b to the inner wall surface 40a1 and the inner wall surface 40a2 due to gravity, and is returned to the minimum portion X1. With such a configuration, the toner T is likely to gather at the minimum portion X1 even when the toner T becomes very small. Further, the toner in the area A including the minimum portion X1 can be positively conveyed by the stirring member 60.

  On the other hand, the first electrode 43 and the second electrode 44 only have to be conductive, and a metal plate can be used, but in this embodiment, a sheet member made of conductive resin is used. Furthermore, in the present embodiment, the first electrode 43 and the second electrode 44 are integrally molded (so-called insert molding) with respect to the frame body 40a. That is, the first electrode 43 and the frame body 40a (inner wall surface 40a1), the second electrode 44 and the frame body 40a (inner wall surface 40a2) are in close contact, and the toner T does not enter between them.

  In the present embodiment, the first electrode 43 and the second electrode 44 are arranged on the inner wall surface of the frame body 40a, but may be arranged outside the frame body 40a.

  Next, the developing device and the developer detecting unit according to the first embodiment will be described with reference to FIG. FIG. 4 is a circuit configuration diagram of the developing device and the developer detection unit according to the first embodiment.

  When a predetermined AC bias is output from the developing bias power supply 45, it is applied to the reference capacitor 54, the developing roller 41, and the second electrode 44. As a result, a voltage V1 is generated in the reference capacitor 54, and a voltage V2 is generated in the first electrode 43 along with a current corresponding to the combined capacitance. The detection circuit 55 generates a detection voltage V3 from the voltage difference between V1 and V2, and outputs the detection voltage V3 to the AD conversion unit 56. That is, V3 is an output value that is output according to the capacitance between the first electrode 43 and the second electrode 44. The AD conversion unit 56 outputs the result of digital conversion of the analog voltage to the control unit 57. The control unit 57 calculates the developer amount from this result, stores the result in the memory 120, and displays the remaining amount on the display unit 13. The display unit 13 may be configured to read and display the result from the memory 120.

  That is, the developer detection unit 70 detects the capacitance between the first electrode 43 and the second electrode 44, and the developer in the developing device 40 (in the developer storage unit) based on this capacitance. It is a developer detection unit that calculates the amount. Further, the developer detection unit 70 in the present embodiment can detect the developer amount when the toner is sufficiently large as the first developer amount and the developer amount when the toner runs out as the second developer amount. is there. Further, it is possible to detect a third developer amount that is smaller than the first developer amount and larger than the second developer amount. That is, the amount of developer that is reduced by using the developing device 40 can be calculated successively. Calculation of the developer amount based on the capacitance will be described later.

  In this embodiment, the member for applying the AC bias for detecting the developer amount is the developing roller 41 and the second electrode 44. However, for example, the effect of this embodiment can be obtained even when no AC bias is applied to the developing roller 41. Further, an AC bias may be applied to the first electrode 43 to generate a voltage on the second electrode 44. In this embodiment, the first electrode 43 is disposed between the developing roller 41 to which an AC bias is applied and the second electrode 44. By doing so, the change in the electrostatic capacity between the developing roller 41 and the first electrode 43, the change in the electrostatic capacity between the second electrode 44 and the first electrode 43, and the change in the composite electrostatic capacity. Can be detected.

  Further, for example, as shown in FIG. 5, a configuration having a plurality of stirring members and a plurality of electrode pairs may be used. In this case, the first electrode 43 and the second electrode 44 are arranged so that the minimum portion X1 and the region A are formed below the stirring member 60. The second electrode 44 extends beyond the inner wall surface 40a2 to the inner wall surface 40a3. Further, the third electrode 84 is disposed on the inner wall surface 40a4 below the stirring member 85. At this time, the distance from the upper portion 44a2 of the second electrode 44 viewed from the upper portion 43a2 of the first electrode 43 is the remote portion X2. Similarly, the distance from the upper portion 44a4 of the second electrode 44 viewed from the upper portion 84a2 of the third electrode 84 is the remote portion Y2. The interval between the lower portion 84a1 of the third electrode 84 and the lower portion 44a3 of the second electrode 44 is the minimum portion Y1. Here, a region B in FIG. 5 is a region defined similarly to the region A. The inner wall surface 40a3 corresponds to the inner wall surface 40a1. The inner wall surface 40a4 corresponds to the inner wall surface 40a2.

  In such a configuration, the toner T is finally collected in the minimum portion X1 by the rotation of the stirring member 60 and the stirring member 85. In the configuration (X1, Y1) having a plurality of minimum portions as described above, if the minimum portion X1 closest to the developing chamber 46 is located on the lower side in the gravity direction with respect to the developing chamber 46 and the opening 40c, It is easy to obtain the effect of collecting toner at the minimum portion X1.

  By doing so, it is possible to detect the developer amount with high accuracy even for a frame having a larger capacity. Further, here, an example is shown in which the developer amount is detected based on the combined capacitance of the first electrode 43 and the third electrode 84, but a plurality of developer detectors 70 are prepared, and the first More detailed developer amount detection can be performed by separately processing the detection values of the electrode 43 and the third electrode 84.

  In the following description, a description will be given using a configuration with a single stirring member and electrode pair.

(Developer amount detection)
Next, the developer amount detection in this embodiment will be described in detail.

  As described above, the developing device 40 includes the stirring member 60 in the present embodiment. The stirring member 60 is disposed so as to pass through the region A sandwiched between the first electrode 43 and the second electrode 44. In this embodiment, when the developer amount changes, the capacitance between the first electrode 43 and the second electrode 44 and the capacitance between the first electrode 43 and the developing roller 41 are reduced. In this configuration, the developer amount is detected by utilizing the change in the combined capacitance. Therefore, when the toner T is moved by the rotation of the stirring member 60, an output as if the amount of developer is changing is obtained even though the amount of developer in the developing device 40 is not changed.

  Therefore, in this embodiment, the output of the capacitance is acquired at regular time intervals (sampling intervals), which is continued for an integral multiple of the rotation period of the stirring member 60 or a sufficiently large time, Get the average value as the output value. On the other hand, the relationship between the output value and the developer amount is obtained in advance and stored in the memory 120 as a table or a conversion formula. Then, based on the output value acquired at the time of image formation, the developer amount is calculated using the table and the conversion formula. That is, the developer amount detection method of this embodiment is a method of calculating the developer amount in the entire developing container based on the state where the toner in the region A is stirred by the stirring member 60.

  The developer amount detection is preferably performed over a wide range from when the toner T in the developing device 40 is large to when it is low. On the other hand, in general, the detection of the developer amount is one of the main purposes for the user to replace the cartridge and the developing device. Therefore, it is preferable that the accuracy is particularly high when the developer amount is small. Therefore, in this embodiment, particularly when the developer amount is small, the change in the electrostatic capacity per unit change amount of the toner is increased, thereby improving the accuracy of detecting the developer amount when the developer amount is small. It is intended.

  As the amount of change in the output value per unit change amount of the developer amount, that is, the amount of change in the capacitance is larger, the developer amount can be detected with higher accuracy. Conversely, for example, when the capacitance changes only slightly even if the developer amount changes, it can be said that the accuracy of the developer amount detection is low. Here, it is known that the relationship between the capacitance C, the area S of the two electrodes, the distance d, and the dielectric constant ε is described as follows.

C = ε × S / d (1)
Of these, the dielectric constant ε varies depending on the amount of developer present between the electrodes, and the dielectric constant ε increases as the amount of developer increases.

  Here, according to Expression (1), even if the dielectric constant is the same, the smaller the distance d, the larger the capacitance. That is, the change in the dielectric constant that occurs in the region where the distance d is small contributes greatly to the change in the overall capacitance. The change in the dielectric constant that occurs in the region where the distance d is large has a small contribution to the change in the overall capacitance.

  Therefore, in the vicinity of the minimum portion X1 shown in FIG. 3, when the dielectric constant ε changes due to the change in the amount of toner T between the electrodes, the contribution to the change in capacitance is large. That is, it is a portion that is sensitive to changes in the amount of toner T. Further, the upper part of the region A is a portion that contributes relatively little to the change in capacitance when the dielectric constant ε changes due to the change in the amount of toner T between the electrodes.

  As described above, in this embodiment, the toner T is likely to gather at the minimum portion X1 when the developer amount is small. In addition, by disposing the minimum portion X1 having a large change in capacitance below the stirring shaft, the toner falls by its own weight near the minimum portion X1 even when the stirring member 60 is operating. For this reason, the capacitance greatly changes with the change in the developer amount.

  Therefore, it is possible to improve the accuracy of detecting the developer amount, particularly in a state where the developer amount is small, while detecting changes in the developer amount in a wide range.

  In the configuration of this embodiment, the minimum portion X1 is disposed so as to be the lowest wall surface in the developer chamber 47, and the capacitance changes greatly even if the amount of toner dropped from the stirring member 60 is very small. This is a more preferable configuration. However, the effect of the present invention can be obtained in the same manner as long as it is below the rotation center 60a even if it is not the lowest.

  FIG. 6 is a graph showing the relationship between the developer amount and the average value of capacitance in this embodiment. As described above, in this embodiment, even when the amount of developer is small, toner is collected and stirred in the minimum portion X1 where the contribution of capacitance is high during the stirring operation. When the remaining amount of toner is sufficiently large relative to the area A, the amount of developer in the area A does not substantially change even if the toner is reduced in accordance with image formation, so that the change in capacitance is small. As the developer amount decreases, the change in capacitance increases. This is because the toner in the region A is reduced by the amount of developer lifted by the stirring member 60. However, when the toner remains in the vicinity of the minimum portion X1 with high detection sensitivity, the amount of change in the electrostatic capacity is still moderate. As the developer amount further decreases, the capacitance changes greatly. This is because the toner near the minimum portion X1 with high detection accuracy decreases.

  As described above, when the developer amount is small, the developer amount can be detected with high accuracy because the capacitance changes greatly with respect to a slight change in the developer amount.

(Effect of variation in developer detection)
Here, the electrostatic capacitance between the first electrode 43 and the second electrode 44 is affected by variations in the arrangement of members and manufacturing variations. Therefore, if the developer amount is directly calculated from the absolute value of the capacitance between the first electrode 43 and the second electrode 44, the developer amount may not be detected accurately. Therefore, the developer detection unit 70 according to the present embodiment uses the electrostatic capacitance detected in a state where the toner remains sufficiently (first developer amount) after the developing device 40 is mounted on the apparatus main body 1. The first reference value is used. Then, the developer amount is calculated based on the amount of change in capacitance from the first reference value. Details will be described later.

  In the embodiment, since the first electrode 43 and the second electrode 44 are integrally formed with the frame body 40a of the developing device 40, the shape of the first electrode 43 and the second electrode 44 is the frame body 40a. Along. Therefore, there is little variation in the distance between the two electrodes due to the shapes of the first electrode 43 and the second electrode 44. The same applies to the case where the first electrode 43 and the second electrode 44 are attached to the frame body 40a.

  However, variations in the positions of the first electrode 43 and the second electrode 44 (variations depending on the molding position and the attachment position) may occur, and this must be taken into consideration.

  If the positions of the first electrode 43 and the second electrode 44 vary, for example, the distance of the minimum portion X1 may vary. When the distance variation of the minimum portion X1 occurs, a difference in capacitance occurs according to the equation (1), and thus the capacitance also varies. In this embodiment, the shape of the developer container and the arrangement of the first electrode 43 and the second electrode 44 are as shown in FIG. ing. However, by reflecting the influence of such variation in the detection of the developer amount, it can be expected that the influence of the variation in the distance of the minimum portion X1 is reduced and further high accuracy is realized.

  In this embodiment, the first electrode 43 and the second electrode 44 are sheet members made of conductive resin. Further, the first electrode 43 and the second electrode 44 are integrally molded (so-called insert molding) with respect to the frame body 40a. In this case, depending on the molding conditions, the sheet member may be extended by the heat of the resin. Therefore, in this case as well, an effect of reflecting the influence of variation, which is a feature of this embodiment, can be expected.

  As described above, the detection sensitivity with respect to the change in the developer amount increases as the distance of the minimum portion X1 becomes closer from Equation (1). That is, in the developing device 40 of the present embodiment, the detection sensitivity of the lower part is high at the upper part and the lower part of the first electrode 43 and the second electrode 44. Similarly, when the minimum portion X1 is small and large, the detection sensitivity when it is small is high. Further, when toner is present, the toner settles toward the lower side in the direction of gravity, and therefore the toner density (the weight of the developer present per unit space) is higher in the lower part of the frame 40a than in the upper part. As described above, the toner density is related to the dielectric constant ε in the formula (1). When the toner density is high, the dielectric constant ε increases and the electrostatic capacity increases.

  That is, in the configuration of the present embodiment, the region where the detection sensitivity is high coincides with the region where the toner density is high. In this embodiment, the detection sensitivity when the amount of the developer is small is increased, but when the distance of the minimum portion X1 is changed, the influence on the detected capacitance is likely to increase. .

  Here, when there is no toner between the first electrode 43 and the second electrode 44, the capacitance is determined according to the distance between the electrodes. That is, when the distance between the electrodes is small, the capacitance is larger than when the distance is large. In particular, the difference in capacitance is large when the minimum portion X1 is close.

  Next, when toner is present, the influence on the capacitance when the distance between the two electrodes fluctuates increases. That is, the difference in detected capacitance when the distance between the two electrodes fluctuates is greater than when no toner is present. Furthermore, in the present embodiment, the minimum portion X1 with high detection sensitivity matches the portion where the toner density tends to be high, so that it is easily affected by this.

  That is, even if the same toner amount changes and the change in the dielectric constant is the same, the change in capacitance is larger when the distance between the electrodes is smaller than when the distance is large.

  In other words, depending on the distance between the electrodes, particularly the distance of the minimum portion X1, the capacitance from the first reference value (for example, the electrostatic capacity when the remaining amount of toner is 100%) to the remaining amount of 0%. There is a difference in the amount of change.

  Therefore, in order to further improve the accuracy of toner remaining amount detection, it is preferable to reflect the relationship between the amount of change in capacitance and the amount of developer according to the distance of the minimum portion X1.

(Reflect the effect of variation in developer detection)
Hereinafter, a method of reflecting the influence of the variation between the electrodes (variation of the interval between the electrodes) (a method of performing correction based on the size of the interval between the electrodes) will be described together with the developer detection method. As described above, the developer detection unit 70 according to the present exemplary embodiment uses the capacitance detected in a state where the toner is sufficiently remaining (first developer amount) as the first reference value as the first reference value. The developer amount is calculated based on the amount of change in capacitance from the reference value.

  In the present embodiment, the capacitance is obtained by measuring the detection voltage V3. In this configuration, due to the relationship of the conversion circuit, the decreasing increase relationship between the capacitance and the detection voltage is the reverse relationship. When the detected capacitance is large, the detection voltage is small, and when the capacitance is small Is set so that the detection voltage increases. FIG. 7 is a schematic diagram showing this relationship. As is clear from FIG. 7, the capacitance obtained by measuring the detection voltage V3 can be used as the output value for detecting the developer amount, or the detection voltage V3 can be used as it is. it can.

  First, the developer detection unit 70 sets the capacitance detected as corresponding to the state where the toner is sufficiently remaining (first developer amount) as the first reference value. This first reference value is called PAF. That is, PAF corresponds to a value indicating the magnitude of the output value in the first developer amount. In this embodiment, PAF is set when the developer amount is approximately 100%. It is desirable to set the PAF at a timing after image formation using the developing device 40 is performed and in a state where the toner in the developing device 40 is stable (a state where there is little bias or the like). Therefore, the capacitance detected at a predetermined timing such as when an unstable region in the initial stage of use of the developing device 40 is removed is set as a PAF corresponding to the first developer amount. Hereinafter, the timing for setting the PAF is referred to as a reference timing. For example, the capacitance detected at the timing when the stirring member 60 is driven for a predetermined time or rotated by a predetermined number can be used as the PAF. Further, the capacitance detected at the timing when a predetermined amount of image forming operation is performed using the developing device 40 can be set as PAF. Therefore, for example, the capacitance detected when the integration of the number of pixels (printing pixels) on which the image forming operation has been performed reaches a certain value can be set as PAF. The PAF is stored in the memory 120, but is not stored when the cartridge of this embodiment is shipped.

  Next, a second reference value serving as a reference for the magnitude of the electrostatic capacity corresponding to the second developer amount (the remaining toner amount is 0% in this embodiment) smaller than the developer amount for which PAF is set is calculated. To do. In this embodiment, the capacitance having a predetermined difference (first difference) δ with respect to PAF is set with PAF as the first reference value. This is referred to as PAE (second reference value serving as a reference for the magnitude of capacitance corresponding to the second developer amount). That is, PAE corresponds to a second reference value indicating the magnitude of the output value at the second developer amount.

  That is, PAE is a value corresponding to the magnitude of the capacitance obtained by subtracting the difference δ from PAF. In the present embodiment, the difference δ is a value stored in the memory 120. δ is a value predicted as the amount of change in capacitance from the PAF set at the reference timing to the remaining amount of toner 0% when the minimum portion X1 is the reference distance.

  Here, the developer detection unit 70 of the present embodiment is smaller than the first developer amount (developer amount when PAF is set) and is smaller than the second developer amount (developer amount indicated by PAE). A large third developer amount can be detected.

  Specifically, first, the electrostatic capacity when detecting the third developer amount is PA (capacitance obtained from the detected voltage V3 detected during the image forming operation). That is, PA corresponds to the output value at the third developer amount. The difference between PA and PAF is taken as the second difference. Then, the third developer amount is detected based on the ratio of the second difference to the difference δ (first difference) between PAF and PAE. The ratio of the second difference with respect to the first difference is called a PA rate. That is, the PA rate is obtained by the following equation (2).

PA rate = (PA−PAF) / (PAE−PAF) (2)
The remaining amount of toner can be obtained by referring to a later-described toner remaining amount table based on the PA rate.

  However, as described above, when the minimum portion X1 deviates from the reference distance (that is, the width of the minimum portion X1 deviates from the reference distance), the amount of change in capacitance from the reference timing to the remaining amount of 0% changes. . FIG. 8 is a graph showing the relationship between the amount of change in capacitance and the developer amount when the minimum portion X1 is near and far. Here, the reference distance is set when the minimum portion X1 is far.

  When the minimum portion X1 is close, the average value of the electrostatic capacity when the remaining amount of toner is 100% is 16.5 pF, and the average value of the electrostatic capacity when the remaining amount of toner is 0% (empty) is 12 pF. The amount of change is 4.5 pF.

  When the minimum part X1 is far, the average value of the electrostatic capacity when the remaining amount of toner is 100% is 13.7 pF, and the average value of the electrostatic capacity when the remaining amount of toner is 0% (empty) is 10 pF. And the amount of change is 3.7 pF.

  Therefore, it can be seen that when the minimum portion X1 is deviated from the reference distance, a difference is generated in the amount of change in capacitance.

  Therefore, it is preferable to obtain the developer amount by varying the difference δ from PAF to PAE according to the distance of the minimum portion X1. By doing so, the accuracy of developer detection can be improved. In this embodiment, the value used at this time is called an interelectrode correction value P (a value used for calculating the second reference value), and the interelectrode correction value P is stored in the memory 120. A change in the PA rate using the interelectrode correction value P is referred to as a PA 'rate. That is, the change amount of the output value from the reference timing to the remaining amount 0% is corrected by the interelectrode correction value P.

  The difference δ in the output value of the electrostatic capacity between the remaining amount of toner 100% and the remaining amount 0% is obtained by subtracting PAF from PAE. The magnitude of the difference δ is varied according to the interelectrode correction value P. Then, the above-described PA rate is obtained as a PA 'rate. That is, the PA ′ rate is obtained as in the following formula (3).

PA ′ rate = (PA−PAF) / ((PAE−PAF) −P) (3)
In this embodiment, the relationship between the PAF and the interelectrode correction value P is obtained in advance, and the correction value is determined with reference to the PAF and interelectrode correction value P table. That is, the table of the interelectrode correction value P when the result as shown in FIG. 8 is obtained is as shown in FIG. 9, for example.

  This will be described in more detail with reference to FIGS. On the basis of the case where the minimum portion X1 is far, the value corresponding to PAF is 13.7 pF (predetermined value). The above difference δ is 3.7 pF. If the inter-electrode correction value P is not used, δ is the same even when the minimum portion X1 is close. Therefore, the PAE when the minimum portion X1 is close is 12.8 pF obtained by subtracting 3.7 pF from 16.5 pF. . However, the capacitance corresponding to actual PAE is 12 pF. Therefore, using the table shown in FIG. 9, when PAF is detected as 16.5 pF, the interelectrode correction value P is corrected to -0.8 pF. As a result of the correction, the amount of change in capacitance from the remaining amount of toner of 100% to 0% (empty) is changed from 3.7 pF to 4.5 pF, and the deviation from the actual change in capacitance is reduced. The remaining amount detection accuracy can be improved by reducing the deviation of the change amount.

  In other words, the developer detection unit 70 sets the capacitance detected as corresponding to the first developer amount at the reference timing as the first reference value (PAF). Then, using the table illustrated in FIG. 9, the interelectrode correction value P is obtained based on the size of the PAF. Then, the magnitude of the difference δ is changed by the interelectrode correction value P to calculate a second reference value (PAE) that serves as a reference for the magnitude of the capacitance corresponding to the second developer amount. Then, based on PAF, PAE, and PA, the second developer amount (toner remaining amount 0%) and the third developer amount up to the second developer amount are detected.

  Further, according to FIG. 9, the developer detection unit 70 predicts that the variation of the difference δ is such that the larger the PAF (the larger the capacitance), the shorter the distance of the minimum portion X1 and the like. Increase the absolute value. Further, the larger the difference in PAF from a predetermined value (in the case of FIG. 9, 13.7 pF) (including the case where the PAF is smaller than 13.7 pF), the larger the difference from the reference difference δ. Fluctuate so that

  In addition to using a table, the method for determining the interelectrode correction value P can be changed as appropriate. For example, a reference PAF value may be stored in advance, and obtained from a deviation from the measured PAF value by a calculation formula. Alternatively, the difference δ may be multiplied or removed. That is, the difference δ may be multiplied by P, or the difference δ may be divided by P.

  Based on the above correction, the developer detection sequence will be described with reference to FIG. This embodiment is based on the case where the minimum portion X1 is far.

  First, the detection voltage V3 is measured (S102). When the PAF value is not stored or when it is the reference timing, V3 is stored as the PAF value (S103 to S106). That is, in S103, it is confirmed whether the PAF is stored in the memory 120. If YES, the process proceeds to S104. If NO, the process proceeds to S105. In this embodiment, the PAF is not stored at the time of shipment of the process cartridge, but a temporary value may be stored at the time of shipment. In S104, it is confirmed whether it is the reference timing, and if YES, the process proceeds to S106. If NO, the process proceeds to S107. Next, the output value difference δ from the PAF to the remaining amount 0% is referred from the memory 120. (S107).

  Next, the interelectrode correction value P is determined from the PAF value with reference to the previously obtained table of the PAF value and interelectrode correction value P (S108). As described above, the interelectrode correction value P is a correction value that varies the difference from PAF to PAE, and is a correction value that increases as the difference in distance from the minimum portion X1 increases.

  Next, the PA 'rate is calculated according to equation (3) (S109). By comparing the calculated PA ′ rate with the developer remaining amount table, the developer remaining amount can be detected (calculated). For example, the toner remaining amount table shown in FIG. 11 is used (S111). The determined developer amount (Y%) is displayed to notify the user of the remaining amount (S112). The developer remaining amount is stored in the memory 120 and the detection is repeated until the remaining amount becomes 0% (until the third developer amount matches the second developer amount and is detected). The remaining amount can be detected (S113 to S114).

  The PA 'rate is a value obtained by correcting the change amount of the output value from the reference timing to the remaining amount of 0% with the interelectrode correction value P according to the distance of the minimum portion X1. By performing the correction, the remaining amount can be detected with the amount of change in the output value corresponding to the distance of the minimum portion X1, and the remaining amount detection accuracy can be improved.

  As described above, the inter-electrode correction value is calculated according to the reference value, and the correction amount is used to correct the relationship between the change amount of the electrostatic capacitance and the developer amount, thereby detecting the developer amount detection accuracy. Was able to improve.

  In the present embodiment, the developing device 40 as shown in FIG. 4 is used. However, the detection accuracy can be improved by applying the present invention as long as the deviation of the toner density and the detection sensitivity matches. For example, even in the configuration as shown in FIG. 5, the same effect can be obtained by applying the present invention.

  It should be noted that PAF and PAE do not necessarily need to match the developer amounts of 100% and 0%. For example, 80% developer amount is PAF, 20% developer amount is PAE, and other sections have different developer detection methods (for example, the remaining amount is estimated from the predicted value of the developer amount consumed for image formation). The developer can also be detected by a calculation method).

  The present embodiment has been described mainly focusing on the influence of the variation in the distance between the electrodes. However, by the method shown in the present embodiment, it is possible to cope with performance variations of parts on the image forming apparatus side where the developing device 40 is used. That is, by reflecting the influence of the variation between the electrodes shown in the present embodiment in the developer detection, the performance variation of the components of the apparatus main body of the image forming apparatus in which the developing device 40 is used is also reflected. Good developer detection.

  In this embodiment, the inter-electrode correction value is used when obtaining the PA 'ratio, but the present invention is not limited to this. For example, the same effect can be expected if the developer remaining amount table is changed by the inter-electrode correction value, as long as the location is related to the detection of the developer amount. Further, the PAE is varied based on the size of the PAF, and the values of the PAE and PA are compared to detect (determine) that the developer is 0% (the second developer amount has been reached). May be.

  In addition, the value shown in this specification is a numerical value limited to the measurement system used by the inventors of the present invention in experiments, etc., but in verifying the effect of the present invention, the relative capacitance change should be compared. Is sufficient, and is used as an example of the effects of the present invention.

  According to the present invention, it is possible to provide a developer storage unit, a developing device, a process cartridge, and an image forming apparatus that can detect the developer amount with high accuracy.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Process cartridge 20 Photosensitive drum 40 Developing apparatus (developer storage part)
40a Frame 40a1, 40a2, 40a3, 40a4 Inner wall (inclined surface)
40b Partition wall 40c Opening 41 Developer carrier (developing roller)
42 Layer thickness regulating member (developing blade)
43 1st electrode 44 2nd electrode 46 Developing chamber 47 Developer chamber 60 Stirring member 60a Center of rotation 70 Developer detecting unit 120 Storage unit (memory)
T Toner P Inter-electrode correction value X1 Minimum part X2 Remote part Y1 Minimum part Y2 Remote part

Claims (19)

A stirring member that rotates to stir the developer;
A first electrode;
A second electrode disposed at a distance from the first electrode and opposed to the first electrode with an inclination, wherein a minimum part of the distance is from a rotation center of the stirring member And a second electrode disposed such that a remote portion of the gap larger than the minimum portion is positioned above the minimum portion,
A frame that houses the stirring member and the developer, and includes a first wall surface on which the first electrode is disposed and a second wall surface on which the second electrode is disposed. When,
A developer container comprising:
A developer detecting unit that detects an output value corresponding to a capacitance between the first electrode and the second electrode , the capacitance changing according to a developer amount stored in the frame; ,
With
The output value in the first developer amount as a first reference value, the output value of the developer detection unit in the first to have a first differential with respect to the reference value 0% developer amount When the second reference value is used, the first difference corresponding to the second reference value that changes according to the size of the first reference value is obtained using a table,
The developer detection unit is configured to determine the remaining amount of developer corresponding to the output value of the electrostatic capacitance with a third developer amount that is smaller than the first developer amount and greater than the 0% developer amount. information, the a first amount of developer, the said first difference calculated, the image forming apparatus to be detected to said Rukoto based on.   The frame corresponding to the minimum part includes a lowermost part in the gravitational direction of the frame, and the stirring member rubs the frame corresponding to the minimum part according to the rotation, The image forming apparatus according to claim 1, wherein the image forming apparatus passes through the image forming apparatus. If the difference between the pre-Symbol third said first reference value and the output value in the amount of developer is a second difference, the developer detection unit, said second difference for said first difference The image forming apparatus according to claim 1, wherein the third developer amount is detected based on the ratio of the third developer.   4. The first difference when the first reference value is large is larger than the first difference when the first reference value is small. 5. The image forming apparatus described in 1.   The amount by which the first difference fluctuates when the difference between the predetermined value and the first reference value is large is the amount when the difference between the predetermined value and the first reference value is small. 5. The image forming apparatus according to claim 1, wherein the first difference is larger than a fluctuating amount. 6.   6. The output value at a timing at which the stirring member is driven for a predetermined time or rotated by a predetermined number is set as the first reference value. The image forming apparatus according to one item.   The image forming apparatus according to claim 1, wherein the output value at a timing when a predetermined amount of image formation is performed is the first reference value.   An AC power supply for applying an AC voltage to one of the first electrode and the second electrode is further provided, and the output value is generated at the other of the first electrode and the second electrode by the AC voltage. The image forming apparatus according to claim 1, wherein the image forming apparatus has a value corresponding to a voltage.   The said 1st wall surface and the said 2nd wall surface are the directions which leave | separate in the horizontal direction with respect to the said minimum part, and are the inclined surfaces which incline upwards, The any one of Claim 1 to 8 characterized by the above-mentioned. The image forming apparatus described in the item.   The image forming apparatus according to claim 9, wherein the inclined surface is a curved surface, and the first electrode and the second electrode are disposed so as to be in contact with the curved surface along the curved surface. .   The image forming apparatus according to claim 9, wherein the stirring member drops a developer on the inclined surface.   The image forming apparatus according to claim 1, wherein the developer storage unit includes a developer carrier that develops an electrostatic latent image formed on the image carrier.   The frame includes a developing chamber in which the developer carrying member is accommodated, a developer chamber in which the agitating member is accommodated, and a partition wall provided with an opening that communicates the developing chamber and the developer chamber. The image forming apparatus according to claim 12, wherein the first wall surface and the second wall surface are disposed in the developer chamber.   The image forming apparatus according to claim 13, wherein the minimum portion is disposed below the developing chamber.   The developer detection unit detects the developer amount from the output value corresponding to the electrostatic capacitance and a combined electrostatic capacitance between the first electrode and the developer carrier. The image forming apparatus according to claim 12, which is possible.   16. The image forming apparatus according to claim 1, wherein a position of a rotation center of the stirring member overlaps with a position of the minimum portion in a horizontal direction.   The said 1st electrode and the said 2nd electrode are electrically conductive resin, and are the sheet | seat members integrally shape | molded with respect to the said frame, The any one of Claim 1 to 16 characterized by the above-mentioned. The image forming apparatus described in 1. The image forming apparatus according to claim 1, further comprising a storage unit that stores a value used for calculating the second reference value. An image forming apparatus in which the developer storage section is detachable,
The image forming apparatus according to claim 18, wherein the storage unit is provided in the developer storage unit.

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