JP2013029712A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device configured to stabilize nonmagnetic toner concentration in a container of the developing device that uses two-component developer containing nonmagnetic toner and magnetic carrier, and an image forming apparatus having the same.SOLUTION: A magnetometric sensor S is arranged at the bottom of a developing container 15 of a developing unit 10. It is assumed that, as a sensitivity characteristic of the magnetometric sensor S, toner concentration in the developing container 15 has a linear function of an output voltage value of the magnetometric sensor S. Measurement is carried out at two points in order to determine two constants of the linear function. For the first point, an output voltage value measured from toner concentration in a new developing unit 10 is used. For the second point, an output voltage value measured from toner concentration after a predetermined amount of toner is supplied from the new developing unit is used.

Description

  The present invention relates to a developing device and an image forming apparatus. More specifically, the present invention relates to a developing device and an image forming apparatus that stabilize the concentration of nonmagnetic toner in a container of a developing device in a developing device that uses a two-component developer including a nonmagnetic toner and a magnetic carrier. is there.

  Some image forming apparatuses using an electrophotographic system use a two-component developer containing a non-magnetic toner and a magnetic carrier. In this method, it is desirable to store a certain amount of toner in the developing container. That is, the toner concentration in the developing container is made almost constant. Therefore, when toner is consumed by development, it is preferable to supply the same amount of toner as the amount of consumed toner into the developing container.

  In order to keep the toner concentration in the developing container substantially constant, a sensor for detecting the toner concentration may be provided in the developing container. However, the sensitivity of the sensor varies from production lot to production lot. In addition, the sensor sensitivity may be shifted later. When the sensor is deviated in sensitivity, the amount of toner supplied to the developing container is also deviated based on the measured value of the sensor. That is, it becomes difficult to keep the toner concentration in the developing container substantially constant. If the toner concentration in the developing container deviates from a suitable value, an image having a suitable concentration may not be formed.

  Therefore, a technology for correcting the sensor sensitivity deviation has been developed. For example, in Patent Document 1, a toner density detection sensor is provided in a developing container, and the output value from the toner density detection sensor is compared before and after the image formation, thereby comparing the sensitivity of the toner density detection sensor. The deviation is corrected (see claim 1 and paragraphs [0132] to [0142] of Patent Document 1). Thereby, a suitable amount of toner can be appropriately supplied into the developing container.

JP 2008-261907 A

  However, the amount of toner consumed when a solid image is formed depends on the temperature and humidity environment at that time. Considering this, when a solid image is formed as in the technique described in Patent Document 1, the amount of correction for correcting the sensor sensitivity deviation should be different depending on the temperature and humidity environment. Therefore, it is somewhat difficult to correct the sensor sensitivity shift with high accuracy by the technique described in Patent Document 1. In the technique described in Patent Document 1, it is necessary to form a solid image once. For this reason, in correcting the deviation of the sensitivity of the sensor, the toner for forming a solid image must be wasted.

  The present invention has been made to solve the above-described problems of the prior art. That is, the object is to provide a developing device using a two-component developer containing a non-magnetic toner and a magnetic carrier, and a developing device for stabilizing the concentration of the non-magnetic toner in the container of the developing device, and the same. An image forming apparatus is provided.

  In order to solve this problem, a developing device according to an aspect of the present invention includes a developing container that contains a two-component developer containing non-magnetic toner and a magnetic carrier, receives toner from a toner bottle, and develops. A magnetic detection unit for obtaining an output value corresponding to the magnetic permeability inside the container; and a toner replenishment amount control unit for determining an amount of toner to be replenished to the developing container from the output value detected by the magnetic detection unit. Is. The toner replenishment amount control unit is configured to output the first output value of the magnetic detection unit when the toner concentration of the two-component developer in the developing container is a known first toner concentration, and the two-component developer in the developing container. The sensitivity characteristic of the magnetic detector is obtained from the second output value of the magnetic detection unit when the toner density is a known second toner density that is greater than the first toner density, and at the time of image formation The amount of toner to be replenished to the developing container is determined from the obtained sensitivity characteristics. In such a developing device, the toner density value obtained from the output value of the magnetic detection unit is appropriate. Therefore, a suitable amount of toner can be supplied from the toner bottle to the developing container. Therefore, a toner image suitable for an electrostatic latent image can be formed. The toner replenishment amount control unit may also employ the third output value.

  In the developing device described above, the first toner concentration is lower than the density at the time of image formation, and is a predetermined new toner concentration of the developing device, and the second toner concentration is the first toner concentration. The density may be obtained after a known amount of toner is supplied to a certain developing container. This is because the magnetic detection unit can be calibrated when a new developing device is used or replaced.

  In the developing device described above, the second toner density may be the toner density at the time of image formation. This is because, after the calibration of the magnetic detection unit is completed, the toner concentration inside the developing container is a toner concentration suitable for image formation.

  In the developing device described above, the magnetic detection unit may be disposed at the bottom of the developing container. This is because the detection can be performed in a state where the developer is filled in the detection range of the magnetic detection unit.

  An image forming apparatus according to another aspect of the present invention includes a developing container that contains a two-component developer containing non-magnetic toner and a magnetic carrier, a toner bottle that supplies toner to the developing container, and an interior of the developing container. A magnetic detection unit for obtaining an output value corresponding to the magnetic permeability, and a toner replenishment amount control unit for determining the amount of toner to be replenished to the developing container from the output value detected by the magnetic detection unit. The toner replenishment amount control unit is configured to output the first output value of the magnetic detection unit when the toner concentration of the two-component developer in the developing container is a known first toner concentration, and the two-component developer in the developing container. The sensitivity characteristic of the magnetic detector is obtained from the second output value of the magnetic detection unit when the toner density is a known second toner density that is greater than the first toner density, and at the time of image formation The amount of toner to be replenished to the developing container is determined from the obtained sensitivity characteristics. In such an image forming apparatus, the toner density value obtained from the output value of the magnetic detection unit is appropriate. Therefore, a suitable amount of toner can be supplied from the toner bottle to the developing container. Therefore, a toner image suitable for an electrostatic latent image can be formed. The toner replenishment amount control unit may also employ the third output value.

  In the image forming apparatus described above, the first toner density is lower than the density at the time of image formation, and is a predetermined toner density of a new developing device, and the second toner density is the first toner density. It is good that the density is after a known amount of toner is supplied to the developing container. This is because the magnetic detection unit can be calibrated when a new developing device is used or replaced.

  In the image forming apparatus described above, the second toner density may be the toner density at the time of image formation. This is because, after the calibration of the magnetic detection unit is completed, the toner concentration inside the developing container is a toner concentration suitable for image formation.

  In the image forming apparatus described above, the magnetic detection unit may be disposed at the bottom of the developing container. This is because the detection can be performed in a state where the developer is filled in the detection range of the magnetic detection unit.

  According to the present invention, in a developing device using a two-component developer including a non-magnetic toner and a magnetic carrier, a developing device that stabilizes the concentration of the non-magnetic toner in a container of the developing device and an image forming apparatus including the developing device. A device is provided.

1 is a schematic configuration diagram illustrating a mechanical configuration of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram for explaining a developing unit and a photoreceptor unit of the image forming apparatus according to the embodiment. 1 is a schematic configuration diagram for explaining a developing device and a toner bottle according to an embodiment. 2 is a block diagram illustrating a control system of the image forming apparatus according to the embodiment. FIG. 6 is a graph showing sensitivity characteristics of a standard magnetic sensor in the image forming apparatus according to the embodiment. 6 is a graph (part 1) illustrating sensitivity characteristics of a magnetic sensor in the image forming apparatus according to the embodiment. 6 is a graph (part 2) illustrating sensitivity characteristics of the magnetic sensor in the image forming apparatus according to the embodiment. 6 is a graph (part 3) illustrating sensitivity characteristics of the magnetic sensor in the image forming apparatus according to the embodiment. 5 is a flowchart for explaining a calibration flow of a magnetic sensor in the image forming apparatus according to the embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is embodied in an image forming apparatus using a two-component developer including a non-magnetic toner and a magnetic carrier.

1. Image forming apparatus 1-1. Schematic Configuration of Image Forming Apparatus The image forming apparatus 100 of the present embodiment is a so-called tandem type color copier having an intermediate transfer belt 101 as shown in FIG. The intermediate transfer belt 101 is an endless belt member. Both ends of the intermediate transfer belt 101 are supported by rollers 102 and 103, and are rotated in the direction of arrow D in FIG. Along the lower portion of the intermediate transfer belt 101 in the figure, image forming portions 1Y, 1M, 1C, and 1K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are arranged.

  The image forming units 1Y, 1M, 1C, and 1K for the respective colors have the same configuration. Each has a photoreceptor unit 20, an exposure device 30, and a developing unit 10. The photoconductor unit 20 has a photoconductor drum 21. The exposure device 30 is for drawing an electrostatic latent image on the photosensitive drum 21. The developing unit 10 is a developing device for applying toner to the electrostatic latent image on the photosensitive drum 21 for development. In addition, a primary transfer roller 111 is disposed at a position facing the photosensitive drum 21 with the intermediate transfer belt 101 interposed therebetween. In FIG. 1, the reference numerals of these devices are shown as representatives by the image forming unit 1Y.

  1 is a paper feed cassette 112 that accommodates the paper P. The paper P is sent upward from the paper feed cassette 112 along the paper transport path 114. A secondary transfer roller 115 is disposed at a position facing the roller 103 with the sheet conveyance path 114 interposed therebetween. Further, a fixing device 130 is disposed on the downstream side (upper side in FIG. 1). A paper discharge roller 116 and a paper discharge tray 117 are disposed further downstream of the sheet conveying path 114 from the fixing device 130.

1-2. Basic Operation of Image Forming Apparatus Next, the basic operation of the image forming apparatus 100 of this embodiment will be briefly described. In this image forming apparatus 100, when an image formation instruction is received, image data of each color is generated from the image signal. The generated image data of each color is sent to the corresponding image forming units 1Y, 1M, 1C, and 1K. The image forming units 1Y, 1M, 1C, and 1K for each color form an electrostatic latent image based on the image data. Further, the formed electrostatic latent image is developed to form a toner image.

  The formed toner images are sequentially transferred to the intermediate transfer belt 101 by the primary transfer roller 111 and superimposed. The toner image superimposed on the intermediate transfer belt 101 is transferred onto the paper P by the secondary transfer roller 115. The sheet P carrying the toner image is further conveyed and reaches the fixing device 130, and is heated and pressurized by the fixing device 130. As a result, the toner image is fixed on the paper P. The paper P on which the toner image is fixed is discharged to a paper discharge tray 117 by a paper discharge roller 116. The above is the basic operation of the image forming apparatus 100.

2. Image forming unit 2-1. Photosensitive Unit and Developing Unit FIG. 2 shows the image forming unit 1. As described above, the image forming apparatus 100 includes the image forming units 1Y, 1M, 1C, and 1K for each color. These have the same mechanical structure, although there are differences in the color of the toner contained. Therefore, the following description will be made without distinguishing colors. The image forming unit 1 includes a photoconductor unit 20, a developing unit 10, and an exposure device 30. The photoconductor unit 20 includes a photoconductor drum 21, a cleaner 23, and a charging device 50.

  The photosensitive drum 21 is an image carrier for carrying an electrostatic latent image. The photosensitive drum 21 rotates in the direction of the arrow E in FIG. 2 during image formation. The cleaner 23 is for collecting the development residual toner adhering to the surface of the photosensitive drum 21. The charging device 50 is for uniformly charging the surface of the photosensitive drum 21.

2-2. Developing Unit and Toner Bottle FIG. 3 shows the developing unit 10. The developing unit 10 is a developing device for developing toner by applying toner to the photosensitive drum 21. The developing unit 10 has a developing container 15 for accommodating therein a two-component developer composed of a nonmagnetic toner and a magnetic carrier. Since toner is applied to the electrostatic latent image every time the development is performed, the toner inside the developing container 15 decreases. Therefore, the developing container 15 can receive toner supply from the toner bottle 200. On the other hand, the carrier inside the developing container 15 is not consumed by the development.

  In addition to the developing container 15, the developing unit 10 includes a developing sleeve 11, a supply screw 12, and a stirring screw 13. The developing sleeve 11 is a developing member for applying toner to the electrostatic latent image formed on the photosensitive drum 21. The developing sleeve 11 rotates around the counter (in the direction of arrow F in FIG. 2) with respect to the photosensitive drum 21 during image formation. The supply screw 12 is a supply member for supplying toner to the developing sleeve 11. The stirring screw 13 is a stirring member for stirring the toner inside the developing container 15. The developing unit 10 is connected to the motor M1. The motor M1 is for rotationally driving the supply screw 12 and the stirring screw 13.

  The development unit 10 is provided with a magnetic sensor S as shown in FIG. The magnetic sensor S is a magnetic detection unit for detecting the magnetic permeability of the detection region R. The magnetic sensor S outputs a voltage corresponding to the density of the magnetic carrier in the two-component developer within the detection region R, that is, the magnetic permeability. There is a certain relationship between the output voltage and the detection region R as described later. The detection area R is at least a part of the conveyance path along which the two-component developer is conveyed. In FIG. 3, the detection region R is located at the bottom of the developing container 15. This is for detecting the magnetism of the developer conveyed through the bottom of the developing container 15. The magnetic sensor S detects the magnetic permeability at the bottom of the developing container 15. This is because the bottom of the developing container 15 is always filled with the developer.

  The toner bottle 200 includes a toner container 201 and a supply screw 211. The toner bottle 200 is a toner replenishing device that accommodates toner and appropriately replenishes the developing unit 10 with toner. The toner container 201 is a container for storing non-magnetic toner (T). The replenishing screw 211 is for replenishing toner to the developing unit 10. The toner bottle 200 is connected to the motor M2. The motor M2 is for driving the supply screw 211 to rotate.

3. Control System of Image Forming Apparatus Here, a control system of the image forming apparatus 100 will be described. The control system of the image forming apparatus 100 is shown in the block diagram of FIG. The control system of the image forming apparatus 100 includes a control unit 300 and a storage unit 400. The control unit 300 includes a machine control unit 310 and an image control unit 320.

  The machine control unit 310 is for controlling the mechanical operations of the image forming units 1Y, 1M, 1C, 1K and other units. The machine control unit 310 includes a motor control unit 350 and a toner replenishment amount control unit 360. The motor control unit 350 is for controlling the rotational drive of the motors M1 and M2. The toner replenishment amount control unit 360 is for determining the amount of toner to be replenished by the toner bottle 200 to the developing container 15 from the output value detected by the magnetic sensor S. The image control unit 320 is for processing an image image to be formed. The image controller 320 also adjusts the exposure amount by the exposure device 30.

  The storage unit 400 includes a main body attached storage unit 410 and a unit attached storage unit 420. The main body attached storage unit 410 is for storing information of the main body of the image forming apparatus 100. The unit-attached storage unit 420 is a conceptually extracted drawing of a storage unit attached to the developing unit 10 or the photoconductor unit 20.

4). Amount of toner replenished to the developing container 4-1. The amount of toner inside the developing container The amount of toner inside the developing container 15 is preferably maintained at a predetermined amount. In other words, the toner density should be substantially constant. If the amount of toner is too small, the amount of toner used for development is insufficient. That is, the density of the toner image after development is thin. On the other hand, if the amount of toner is too large, the magnetic carrier may not sufficiently charge the toner. That is, toner charging failure occurs. Alternatively, the toner charge amount varies. This causes a density unevenness of the toner image. Thus, the toner density inside the developing container 15 has a value suitable for image formation. In this embodiment, the preferable toner concentration is 8%. This is merely an example, and other values may be used.

As described above, the two-component developer of this embodiment is composed of a nonmagnetic toner and a magnetic carrier. Therefore, the developer becomes 1 (100%) when the toner concentration and the carrier concentration are added on a weight basis. This can be expressed by the following formula.
TD + CD = 1 (100%) ... (1)
TD: Toner density
CD: Carrier concentration

4-2. Toner replenishment amount The toner in the developing container 15 is consumed by development. Therefore, the toner bottle 200 replenishes the developing container 15 with toner. At this time, the amount of toner supplied to the developing container 15 by the toner bottle 200 is an amount that makes the amount of toner inside the developing container 15 substantially constant. That is, the developing container 15 may be replenished with the same amount of toner as the toner consumed by development. As a result, the toner concentration inside the developing container 15 can be maintained in a state close to 8%, which is a toner concentration suitable for development.

  The toner supply amount control unit 360 determines the toner supply amount. The toner replenishment amount control unit 360 determines the toner replenishment amount to the developing container 15 according to the toner density value input from the magnetic sensor S.

For example, a breakdown of the weight of the two-component developer in the developing container 15 in this embodiment is shown below.
Carrier weight 460g
Toner weight at suitable toner concentration (8%) 40 g
Two-component developer weight at suitable toner concentration (8%) 500 g

Thus, for example, assume that the toner concentration inside the developing container 15 is 7%. Then, the toner amount corresponding to 1% of the toner density may be replenished. The breakdown of the weight of the two-component developer inside the developing container 15 when the toner concentration is 7% is as follows.
Carrier weight 460g
Weight of toner when toner concentration is 7% 35g
Weight of two-component developer when toner concentration is 7% 495 g
That is, when the toner density reaches 7%, 5 g of toner may be supplied from the toner bottle 200 to the developing container 15.

5. Variation in sensitivity of magnetic sensor So far, the magnetic sensor S has been described as indicating the correct toner concentration. However, it is common for the sensitivity of each magnetic sensor S to vary. That is, the magnetic sensor S does not necessarily indicate the correct toner density. Therefore, the following description will be made assuming that a sensitivity shift occurs for each individual magnetic sensor S. In the present embodiment, calibration suitable for the magnetic sensor S that is likely to be displaced is performed. Therefore, in this section, a description will be given of what deviation occurs in the sensitivity of the magnetic sensor S.

5-1. Relationship Between Toner Concentration and Output Voltage of Magnetic Sensor Before describing the variation in sensitivity of the magnetic sensor S, the magnetic sensor S having standard sensitivity characteristics will be described. FIG. 5 is a graph showing the relationship between the output voltage value of the standard magnetic sensor S and the toner density in the detection region R of the magnetic sensor S. As shown by the line L0 in FIG. 5, the lower the toner concentration, the higher the output voltage of the magnetic sensor S. This is because, as shown in the equation (1), the lower the toner concentration, the higher the carrier concentration. Therefore, this is a tendency common to the magnetic sensor S regardless of the variation of each production lot.

5-2. However, the sensitivity characteristics of the magnetic sensor S are generally different for each lot. For this reason, when magnetic sensors S of different lots are used, the toner density value indicated by the magnetic sensor S may deviate from the standard value. This deviation includes a case where the inclination is different (see FIG. 6) and a case where the absolute value is different even if the inclination is the same (see FIG. 7). For example, FIG. 6 shows a line L0 indicating the sensitivity characteristics of a standard magnetic sensor and lines L1 and L2 indicating the sensitivity characteristics of the magnetic sensor S that are deviated therefrom.

  The lines L0, L1, and L2 have different slopes of the lines, that is, the rate of change of the output voltage value with respect to the change in toner density. In the magnetic sensor S showing the sensitivity characteristic of the line L1, the output voltage value does not change much compared to the case of the line L0 even if the toner concentration changes. In the magnetic sensor S showing the sensitivity characteristic of the line L2, when the toner concentration changes, the output voltage value changes relatively compared to the case of the line L0.

  In FIG. 6, the slopes of the lines L0, L1, and L2 are different, but these lines L0, L1, and L2 all pass through a point where the output voltage value is 3 V and the toner density is 8%. FIG. 6 is a diagram in a case where it is assumed that this point (a point where the output voltage value is 3 V and the toner density is 8%) is passed in order to explain the case where the inclination of each line is different.

5-3. Variation in Absolute Value FIG. 7 shows variation in the sensitivity characteristic of the magnetic sensor S due to the absolute value. As shown in FIG. 7, the slope of the line L3 is the same as the slope of the line L0. Therefore, if the amount of decrease in the toner density is the same, the amount of change in the output voltage is the same for both the line L0 and the line L3. However, the absolute value of the output voltage value of the line L3 is smaller than the absolute value of the output voltage value of the line L0.

  As is apparent from FIG. 7, even when 3V is detected as the output voltage value, the sensor showing the sensitivity of the line L0 shows a value of 8%, and the sensor showing the sensitivity of the line L3 shows a value of 6%. It will be. FIG. 7 is a diagram when it is assumed that the slopes of the lines L0 and L3 are the same. Therefore, in practice, both the deviation of the change amount (line inclination) shown in FIG. 6 and the deviation of the absolute value shown in FIG. 7 generally occur.

  When the sensitivity of the individual magnetic sensor S is deviated, it is not known in advance what sensitivity characteristic the magnetic sensor S exhibits. However, as will be described later, if the two points indicating the sensitivity characteristic are known, the sensitivity characteristics as exemplified from the line L0 to the line L3 can be obtained.

6). Magnetic sensor sensitivity correction method (calibration)
Here, a correction method (calibration) of the output value of the magnetic sensor S in this embodiment will be described. The sensitivity characteristics shown from the line L to the line L3 in FIGS. 5 to 7 are unique to the magnetic sensor S and cannot be changed. However, even if the sensitivity characteristic of the magnetic sensor S deviates from the line L0, it is only necessary to know the sensitivity characteristic of the deviated magnetic sensor S. This is because if the sensitivity characteristic is used, the output voltage value can be read as an accurate toner density.

For calibration, in this embodiment, a line indicating the sensitivity characteristic of the magnetic sensor S is assumed to be a linear function. Therefore, the toner density TD can be obtained by the following equation (2).
TD = U × V + W (2)
TD: toner density
U: Change in sensitivity characteristics
V: Output voltage value
W: toner density (intercept) when the output voltage value is 0V

  The values required for calibration are two constants U and W in equation (2). For this purpose, two points may be measured for the combination of the output voltage value of the magnetic sensor S and the toner density at that time. Thereby, the constants U and W can be determined.

In this form,
(1) Initial state (2) Measure output voltage values at two points from the initial state to the state where toner is replenished. As a result, the toner bottle 200 can accurately supply the toner to the developing unit 10 by accurately grasping the sensitivity characteristic of the magnetic sensor S.

6-1. Initial state One of the two points is the initial state. In the initial state of the new development unit 10 in this embodiment, that is, the development unit 10, a predetermined amount of nonmagnetic toner and magnetic carrier are accommodated in the development container 15. That is, the toner density (and carrier density) is known. Therefore, it is only necessary to obtain the output voltage value of the magnetic sensor S at this time. Then, the value of the magnetic sensor S in the initial state is read and stored in any location of the storage unit 400.

In this initial state, that is, the weight of the two-component developer in the new development unit 10 is as follows.
Weight of magnetic carrier in initial state 460 g
Weight of non-magnetic toner in initial state 20g
Weight of two-component developer in the initial state 480 g
The toner density in the developing unit 10 is as follows.
Initial toner density 4%

  Note that the amount of toner contained in the new developing unit 10 in this embodiment is smaller than the amount of toner suitable for image formation. That is, the toner density in the initial state is lower than the toner density suitable for image formation. This is because the toner is further supplied to the developing container 15 from the initial state and the second point is measured, as will be described later.

6-2. After toner replenishment, and after storing the output voltage value of the magnetic sensor S in the initial state, the toner is replenished from the toner bottle 200 to the developing container 15. The toner replenishment amount here is an amount sufficient to reach a suitable toner concentration (8%). That is, 20 g. Of course, this is a known value. Therefore, separately from the initial state, the output voltage value of the magnetic sensor S in a state where the toner density is known can be obtained.

6-3. Specific Example Here, how to obtain a specific sensitivity characteristic of the magnetic sensor S will be described. In other words, assume that two points were actually measured. At that time, it is assumed that values as in Example 1 and Example 2 in Table 1 are obtained. In this embodiment, as described above, the toner concentration in the initial state is 4%, and the toner concentration after toner replenishment is 8%. In the case of Example 1 and Example 2 in Table 1, the sensitivity characteristics of the magnetic sensor S correspond to the lines L0 and L4 in the graph of FIG.

[Table 1]
Example 1 (line L0):
Toner density 4% Output voltage 4V
Toner density 8% Output voltage 3V
Example 2 (line L4):
Toner density 4% Output voltage 3.67V
Toner density 8% Output voltage 3V

Therefore, the sensitivity characteristic of the magnetic sensor S can be obtained from the equation (2). Then, the following equations are obtained for the lines L0 and L4.
Line L0:
TD = −4 × V + 20 (3)
Line L4:
TD = −6 × V + 26 (4)
That is, for the magnetic sensor S showing the sensitivity characteristic of the line L0, the toner density can be obtained by applying the equation (3). For the magnetic sensor S indicating the sensitivity characteristic of the line L4, the toner density can be obtained by applying the equation (4).

  Expressions (3) and (4) are merely examples. In practice, U and W in equation (2) can be determined. Therefore, it is only necessary to store the expression (2) in which the values of U and W thus obtained are substituted. As described above, the toner replenishment amount control unit 360 can obtain the sensitivity characteristic of the magnetic sensor S. Thereby, the calibration of the magnetic sensor S is completed.

6-4. During image formation In accordance with the amount of toner consumed, appropriate toner can be replenished from the toner bottle 200 to the developing container 15 during image formation. Then, in order to determine the toner replenishment amount, the toner density is obtained. Each time, the stored sensitivity characteristic of equation (2) (U, W determined) may be used.

  As described above, from the equation (2), the output voltage value in the initial state (new development unit 10), and the output voltage value after replenishing the toner until a suitable toner density is obtained, the magnetic sensor S Sensitivity characteristics can be obtained. Thus, a developing device and an image forming apparatus that can maintain the toner density inside the developing container 15 at a suitable value even when toner is consumed by image formation are realized.

7). Magnetic Sensor Sensitivity Correction Flow Here, the calibration flow of the magnetic sensor S in this embodiment will be described. FIG. 9 is a flowchart for explaining a flow for correcting a deviation in sensitivity of the magnetic sensor S. First, the unit attached storage unit 420 of the developing unit 10 is read (S101). Next, it is determined based on the read information whether the developing unit 10 is new (S102). Therefore, if the developing unit 10 is new (S102: Yes), the process proceeds to S103. If the developing unit 10 is not new (S102: No), the process is terminated.

  In S103, the output voltage value of the magnetic sensor S is read. Then, a suitable amount of toner is supplied from the output voltage value to the inside of the developing unit 10 (S104). Next, the developer in the developing unit 10 is stirred (S105). Then, the output voltage value of the magnetic sensor S is read (S106). Subsequently, the sensitivity of the magnetic sensor S is detected and corrected (S107). Note that the flowchart of FIG. 9 shows a flow performed in the initial use of the developing unit 10. Therefore, even when this flow is not performed, the toner bottle 200 appropriately supplies toner to the developing unit 10.

8). Modified Example 8-1.2 Linear Function In this embodiment, it is assumed that the sensitivity characteristic of the magnetic sensor S is a linear function. However, it may be assumed that the sensitivity characteristic of the magnetic sensor S is a quadratic function.
^{TD = U1 × V 2 + U2} × V + W1 ......... (8)
In order to determine U1, U2, and W1, three points may be measured. Thereby, the toner density can be measured more accurately.

8-2. When the developing unit is replaced In this embodiment, the magnetic sensor S is calibrated when the developing unit 10 is new. This is not limited to the new image forming apparatus 100. That is, when the used developing unit 10 is taken out from the used image forming apparatus 100 and a new developing unit 10 is newly mounted, the magnetic sensor S of this embodiment may be calibrated. This is because it is possible to correct the deviation of the sensitivity characteristic of the magnetic sensor S that has occurred later by continuing to use the image forming apparatus 100.

8-3. Output value In this embodiment, the output value of the magnetic sensor S is a voltage value. However, this output value may be a current value or other values.

8-4. Selection of two points to be measured In this embodiment, the two cases where the amount of toner inside the developing container 15 is known are the initial state (new) and the case where a known toner having an appropriate toner concentration is supplied. . However, the other two points may be used as the two points used for obtaining the sensitivity characteristics of the magnetic sensor S. That is, any two points from the state in which there is no toner in the developing container 15 to the state in which the toner is filled in the developing container 15 (full tank state) are adopted. However, in this case, it is necessary to prevent toner consumption by performing image formation between the initial state and the full state. This is because the amount of toner becomes unknown.

9. Summary As described above in detail, the image forming apparatus 100 according to the present embodiment supplies toner from the toner bottle 200 to the developing unit 10 according to the amount of toner consumed by development. If there is a sensitivity shift in the magnetic sensor S, the shift is corrected. As a result, a developing device and an image forming apparatus that can make the amount of toner inside the developing container 15 substantially constant are realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. In this embodiment, the image forming apparatus 100 including the developing unit 10 and the photosensitive unit 20 has been described as an example. However, other image forming apparatuses may be used as long as they use a two-component developer and supply toner from the toner supply container to the development container.

  The image forming apparatus may be one-sided printing or two-sided printing. Also, it is not limited to color printing. When color printing is not used, the image quality degradation determination value may be calculated for only one color. The image forming apparatus may be a printer. Further, the present invention can be applied to an image reading apparatus and an image forming apparatus that transmit a read image as a print job through a public line. Of course, it may be a multifunction machine. Also, it can be applied regardless of the type of toner.

DESCRIPTION OF SYMBOLS 1 ... Image forming part 10 ... Developing unit 20 ... Photoconductor unit 21 ... Photoconductor drum 100 ... Image forming apparatus 300 ... Control part 310 ... Machine control part 320 ... Image control part 350 ... Motor control part 360 ... Toner replenishment amount control part 400 ... Storage unit 410 ... Main unit attached storage unit 420 ... Unit attached storage unit
M1 ... Motor
M2 ... Motor

Claims (8)

A developer container containing a two-component developer containing a non-magnetic toner and a magnetic carrier, and receiving toner replenishment from a toner bottle;
A magnetic detector for obtaining an output value corresponding to the magnetic permeability inside the developing container;
A toner replenishment amount control unit for determining an amount of toner to be replenished to the developing container from an output value detected by the magnetic detection unit;
The toner replenishment amount control unit
A first output value of the magnetic detection unit when the toner concentration of the two-component developer in the developing container is a known first toner concentration;
From the second output value of the magnetic detection unit when the toner concentration of the two-component developer in the developer container is a known second toner concentration that is larger than the first toner concentration,
While obtaining the sensitivity characteristics of the magnetic detector,
A developing device characterized in that, at the time of image formation, the amount of toner to be supplied to the developing container is determined from the obtained sensitivity characteristics. The developing device according to claim 1,
The first toner concentration is
This is the toner density of a new developing device that is lower than the density at the time of image formation,
The second toner concentration is
A developing device having a density after a known amount of toner is replenished to the developing container having the first toner density. The developing device according to claim 2,
The second toner concentration is
A developing device having a toner density at the time of image formation. A developing device according to any one of claims 1 to 3, wherein
The magnetic detector is
A developing device arranged at the bottom of the developing container. A developer container containing a two-component developer containing a non-magnetic toner and a magnetic carrier;
A toner bottle for supplying toner to the developer container;
A magnetic detector for obtaining an output value corresponding to the magnetic permeability inside the developing container;
A toner replenishment amount control unit for determining an amount of toner to be replenished to the developing container from an output value detected by the magnetic detection unit;
The toner replenishment amount control unit
A first output value of the magnetic detection unit when the toner concentration of the two-component developer in the developing container is a known first toner concentration;
From the second output value of the magnetic detection unit when the toner concentration of the two-component developer in the developer container is a known second toner concentration that is larger than the first toner concentration,
While obtaining the sensitivity characteristics of the magnetic detector,
An image forming apparatus characterized in that, at the time of image formation, an amount of toner to be replenished to the developing container is determined from the obtained sensitivity characteristics. The image forming apparatus according to claim 5, wherein
The first toner concentration is
This is the toner density of a new developing device that is lower than the density at the time of image formation,
The second toner concentration is
An image forming apparatus having a density after a known amount of toner is replenished to the developing container having the first toner density. The image forming apparatus according to claim 6, wherein
The second toner concentration is
An image forming apparatus having a toner density at the time of image formation. An image forming apparatus according to any one of claims 5 to 7,
The magnetic detector is
An image forming apparatus, wherein the image forming apparatus is disposed at a bottom of the developing container.

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