JP2011013638A - Image forming apparatus and developer amount detecting system thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit developer amount detecting accuracy from lowering in a system for detecting a developer amount, in a developer storing part by using two sensors.SOLUTION: The developer amount detecting system includes a first sensor, having a developing roller 2 and a plate antenna 10 in a toner container as a pair of counter electrodes and measuring the capacitance of an area pinched between the pair of electrodes, and a second sensor having the developing roller 2 and a plate antenna 6 in the toner container as a pair of counter electrodes and measuring capacitance of an area pinched between the pair of electrodes, wherein the plate antenna 6 is an electrode within a predetermined area arranged in the area held between the pair of electrodes of the first sensor. The system has a detection means 31 for detecting a toner amount based on the capacitance measured by the first and second sensors, and a switching means 36, making electrical connection between the plate antenna 6 and the detection means 31 to be continuous or shutoff. When the detection means 31 detects the toner amount based on the capacitance measured by the first sensor, the electrical connection between the plate antenna 6 and the detection means 31 is set to off.

Description

  The present invention relates to an image forming apparatus that forms an image using a developer and a developer amount detection system thereof.

  In an image forming apparatus that forms an image using a developer, the user needs to replace the process cartridge or replenish the developer container with the developer when the developer runs out in the developer container. . Therefore, a developer amount detection system has been developed that includes a sensor that outputs a measurement value corresponding to the remaining amount of developer in the developer container and detects the developer amount from the output of the sensor. Some sensors include a pair of input and output electrodes and measure the capacitance between both electrodes. This sensor uses the fact that the dielectric constant of the region sandwiched between the electrode pair changes according to the amount of developer present between the electrodes.

  As a developer amount detection system, Patent Document 1 describes a system using a plate antenna. The plate antenna is a pair of plate-like electrodes installed opposite to each other in the developer container, and a capacitor structure is formed by the electrode pair. The developer container is configured so that the developer is accommodated in a region between the capacitor electrode pair. When an alternating voltage is applied to one electrode, a current is induced in the other electrode, which is measured as a voltage value, and the amount of developer in the developer container is detected from this measured value. Further, in a development type image forming apparatus in which a developing bias is applied to a developing roller provided in the developing device, a plate antenna may be provided at a position facing the developing roller, and an electrode pair may be formed by the developing roller and the plate antenna. . In this case, the developing bias applied to the developing roller for image formation can be used as an applied voltage for detecting the developer amount.

JP 2003-255688 A

  Depending on the size and shape of the developer storage section, a plurality of sensors may be required to sequentially detect the developer amount. For example, an example of a developer amount detection system provided with two sensors in the developer container will be described with reference to FIG. FIG. 7 is a diagram illustrating a schematic configuration of a toner container 4 (developer storage unit) of an image forming apparatus that employs a developing method in which an AC bias is applied to the developing roller 2 (developer carrier). Inside the toner container 4, two sensors, a first sensor formed by the plate antenna 10 and the developing roller 2 and a second sensor formed by the plate antenna 6 and the developing roller 2, are installed. Has been. The electrostatic capacity of the region 15 (region surrounded by the broken line) between the plate antenna 10 and the developing roller 2 is measured by the first sensor, and the toner amount in the region 15 can be detected based on the measured capacitance. The second sensor can measure the electrostatic capacity in the region near the developing roller 2 and detect the toner amount in the region near the developing roller 2 based on the measured capacitance. When the amount of toner in the toner container 4 is large, the amount of toner can be detected using the first sensor. When the toner amount in the toner container 4 is small, the toner amount can be detected using the second sensor.

In this way, in the developer amount detection system including two sensors, a part or all of the electrode pairs constituting one sensor may be arranged in a region sandwiched between electrode pairs constituting another sensor. . In this specification, an electrode in which at least a part thereof is arranged in a region sandwiched by electrode pairs of other sensors is referred to as a predetermined region electrode in this specification. In the example shown in FIG. 7, a plate antenna that is one of the electrode pairs constituting the second sensor in a region 15 sandwiched between the electrode pairs constituting the first sensor (that is, the plate antenna 10 and the developing roller 2). 6 is arranged. Here, the predetermined region is the region 15, and the plate antenna 6 is an electrode in the predetermined region. In this case, the measured value of the capacitance output from the first sensor may decrease due to the influence of electrostatic shielding due to the position and shape of the plate antenna 6. Then, there is a risk that the detection accuracy of the toner amount based on the measurement value by the first sensor may be lowered.

  As described above, in the developer amount detection system that detects the amount of developer in the developer storage section using the two sensors, at least one of the electrode pairs constituting one of the two sensors is an electrode in a predetermined region. In this case, the detection accuracy of the developer amount may be lowered. Accordingly, an object of the present invention is to provide a developer amount detecting system and an image forming apparatus that detect the amount of developer in the developer accommodating portion using two sensors, and a developer capable of suppressing a decrease in developer amount detection accuracy. An amount detection system and an image forming apparatus are provided.

The developer amount detection system according to the present invention has the following configuration. That is,
A developer amount detection system for detecting the amount of developer in a developer storage section for storing a developer,
A first sensor that has a pair of electrode portions facing each other in the developer accommodating portion, and that outputs a measurement value according to the capacitance of a region sandwiched between the pair of electrode portions;
A second sensor that has a pair of electrode portions facing each other in the developer accommodating portion and outputs a measurement value corresponding to the capacitance of a region sandwiched between the pair of electrode portions;
With
At least one electrode portion of the second sensor is an electrode portion in a predetermined region in which at least a part thereof is disposed in a region sandwiched between the pair of electrode portions of the first sensor,
The developer amount detection system includes:
From at least one electrode part of the first sensor and at least the electrode part in the predetermined region of the second sensor, and a measurement value inputted from the first sensor or from the second sensor Detection means for detecting the amount of developer in the developer storage section based on the input measurement value;
Switching means for switching electrical connection between the electrode part in the predetermined area of the second sensor and the detection means to either conduction or interruption;
With
When the detection unit detects the developer amount based on the measurement value input from the first sensor, the switching unit and the electrode portion in the predetermined area of the second sensor and the The electrical connection with the detection means is cut off.

  According to the present invention, when the detection unit detects the developer amount based on the measurement value input from the first sensor, the measurement value output from the first sensor is based on the electrode portion of the second sensor. Unaffected by electrostatic shielding. Accordingly, it is possible to suppress a decrease in the detection accuracy of the developer amount based on the measurement value of the first sensor. Therefore, in the developer amount detection system including two sensors, the developer amount can be accurately detected.

1 is a schematic functional block diagram of a developer amount detection system according to an embodiment. 1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of a process cartridge according to Embodiment 1. FIG. The figure which shows the relationship between a toner amount and the measured value of the electrostatic capacitance by a 1st sensor. FIG. 6 is a relationship diagram between a toner amount and a measured value of capacitance by first and second sensors. FIG. 6 is a schematic sectional view of a process cartridge according to a second embodiment. FIG. 5 is a schematic cross-sectional view of a toner container showing an installation area of a second sensor.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are not intended to limit the present invention according to the claims, and all combinations of features described in the present examples are essential as means for solving the problems of the present invention. Not necessarily.

Example 1
FIG. 2 is a diagram illustrating a schematic configuration of the image forming apparatus according to the present embodiment. An image forming apparatus 14 shown in FIG. 2 is a laser beam printer that receives image information from a host computer, a network, or the like, and outputs the image information onto recording paper using a developer. In this embodiment, an insulating magnetic one-component toner is used as a developer. The image forming apparatus 14 according to the present exemplary embodiment is configured such that the process cartridge A can be attached to and detached from the main body.

  FIG. 3 is a diagram showing a schematic configuration of the process cartridge A. As shown in FIG. 3, the process cartridge A includes a photosensitive member 1 that is a latent image carrier, a charging unit 7 that uniformly charges the photosensitive member 1, and a developing device B that is disposed to face the photosensitive member 1. . The process cartridge A further includes a cleaning unit 8 that removes toner as a developer remaining on the photoconductor 1 from the photoconductor, and a waste toner container 9 that stores the toner removed from the photoconductor 1 by the cleaning unit 8. Prepare. The developing device B includes a developing roller 2 and a toner regulating member 5 serving as a developer carrying member, and a toner container 4 serving as a developer storage unit that stores toner T.

  In the image forming apparatus 14, a laser scanner 11 that irradiates a laser beam L corresponding to image information is installed above the process cartridge A as shown in FIG. Further, below the process cartridge A, a transfer unit 12 facing the photoreceptor 1 is installed. In the image forming apparatus 14 configured as described above, the photosensitive member 1 is uniformly charged by the charging unit 7 in the process cartridge A, and scanning exposure is performed on the surface by the laser light L emitted from the laser scanner 11. Is made. As a result, an electrostatic latent image of target image information is formed on the photoreceptor 1.

  When the toner T in the toner container 4 (in the developer storage portion) is carried and conveyed to the photosensitive member 1 by the action of the developing roller 2 of the developing device B, the toner adheres to the electrostatic latent image on the photosensitive member 1, It is visualized as a toner image. The toner image formed on the photoreceptor 1 is transferred by the transfer unit 12 to the recording paper conveyed from the sheet cassette 26. As the recording paper passes through the fixing means 13, the toner image transferred onto the recording paper is fixed on the recording paper. The recording sheet on which the toner image is fixed is discharged to the main body discharge tray 25. After the toner image is transferred onto the recording paper, the toner remaining on the photoconductor 1 is removed from the photoconductor 1 by the cleaning unit 8. The toner removed by the cleaning means 8 is collected in a waste toner container 9.

  The bottom surface of the toner container 4 has one concave shape as shown in FIG. An area in which the conveying member 3 driven by a motor of the main body (not shown) acts is set corresponding to the shape of the concave portion of the toner container 4, and the conveying member 3 rotates so that the inside of the toner container 4 The toner T is agitated, conveyed to the developing roller 2 and supplied. The conveying member 3 is provided with a stirring blade member 3a, and the rotation radius of the stirring blade member 3a is set so that the tip portion thereof rubs the concave shape of the bottom surface. Thereby, the toner T can be conveyed to the developing roller 2 without leaving the toner T on the bottom surface of the toner container 4.

  The image forming apparatus 14 according to the present exemplary embodiment includes a developer amount detection system that can sequentially detect the toner amount (developer amount) in the toner container 4. Hereinafter, the developer amount detection system according to this embodiment will be described.

  In the toner container 4, two sensors capable of outputting a measurement value corresponding to the amount of toner in the toner container 4 are installed. The first sensor is configured to have the plate antenna 10 and the developing roller 2 installed on the bottom surface of the toner container 4 as a pair of electrode portions. The plate antenna 10 is a conductive metal plate, and is formed in the entire concave portion of the toner container 4 along the longitudinal direction of the developing roller 2. The plate antenna 10 is installed so that a part of the action area of the conveying member 3 is sandwiched between the developing roller 2. The second sensor is configured to have a plate antenna 6 and a developing roller 2 installed in the vicinity of the developing roller 2 in the toner container 4 as a pair of electrode portions. The plate antenna 6 is also a conductive metal plate and is installed along the longitudinal direction of the developing roller 2. The plate antenna 6 is disposed in a region 15 between the plate antenna 10 and the developing roller 2. That is, in this embodiment, the plate antenna 6 is an electrode in a predetermined area. The plate antenna 6 is installed so as to sandwich a part of the action area of the conveying member 3 with the developing roller 2. Both the first sensor and the second sensor share the developing roller 2 as one of the pair of electrode portions. An AC voltage is applied to the developing roller 2 as a developing bias. When a developing bias is applied to the developing roller 2, a current corresponding to the capacitance of the space between the developing roller 2 and the plate antenna 6 is induced in the plate antenna 6 that is the other of the pair of electrode portions. Similarly, when a developing bias is applied to the developing roller 2, a current corresponding to the capacitance of the space between the developing roller 2 and the plate antenna 10 is a plate antenna 10 that is the other of the pair of electrode portions. Induced by

  When the amount of toner existing in the space between the developing roller 2 and the plate antenna 6 changes as the amount of toner in the toner container 4 changes, the dielectric constant of this space changes, and therefore the capacitance of this space changes. Change. The current induced in the plate antenna 6 changes when a developing bias is applied to the developing roller 2 in accordance with the change in capacitance. From this induced current, the capacitance of the space between the developing roller 2 and the plate antenna 6 is measured. By examining the relationship between the amount of toner present in this space and the capacitance in advance, the amount of toner can be detected from the measured capacitance value. Similarly, the toner amount in this space can be detected by applying a developing bias to the developing roller 2 and measuring the capacitance of the space between the developing roller 2 and the plate antenna 10. Using the first sensor, it is possible to detect the amount of toner in a state where the amount of toner in the toner container 4 is relatively large (from the initial use to about 10% to about 80% of the remaining amount of toner). The second sensor can be used to detect the amount of toner in a state where the amount of toner in the toner container 4 is relatively small (from about 10% to about 30% until the toner runs out). As described above, by providing two sensors at different positions in the toner container 4 and independently measuring the toner amount, the toner amount can be sequentially detected from the initial state until the toner runs out.

  FIG. 1 is a block diagram of a developer amount detection system according to this embodiment. The process cartridge A includes a first sensor constituted by the developing roller 2 and the plate antenna 10, a second sensor constituted by the developing roller 2 and the plate antenna 6, a switching means 36 and a storage means 20 described later. The image forming apparatus 14 includes a power supply 34 that applies a developing bias to the developing roller 2, a detecting unit 31 that detects a toner amount from the measurement values of the first and second sensors, and an arithmetic control unit 32 that controls arithmetic processing and the like. A storage means 35 and a display means 33 for displaying the detected toner amount. As the display unit 33, for example, an information display display provided in the image forming apparatus 14 can be used. Further, as a means for displaying the detected toner amount, an external display device 51 of an external terminal such as a personal computer that is communicably connected to the image forming apparatus 14 can be used. Note that both the display means 33 and the external display device 51 are not necessarily provided.

  Between the plate antenna 6 of the second sensor and the detection means 31, there is provided a switching means 36 for switching the electrical connection between the plate antenna 6 and the detection means 31 to either conduction or interruption. In this embodiment, the switching means 36 is constituted by an FET. The gate of the FET is connected to the calculation control means 32, the drain is connected to the plate antenna 6, and the source is connected to the detection means 31. By inputting a voltage exceeding the ON voltage to the gate of the FET from the arithmetic control means 32, a current flows between the drain and source of the FET, and the plate antenna 6 and the detection means 31 are brought into conduction. Further, by making the voltage applied from the arithmetic control means 32 to the gate of the FET lower than the ON voltage, no current flows between the drain and source of the FET, and the electrical connection between the plate antenna 6 and the detection means 31 is cut off. The That is, by controlling the gate voltage input to the FET of the switching means 36 from the arithmetic control means 32, the electrical connection between the plate antenna 6 and the detection means 31 can be switched to either conduction or interruption.

  When a developing bias is applied from the power source 34 to the developing roller 2, a current corresponding to the electrostatic capacity corresponding to the amount of toner existing in the space between the plate antenna 6 and the developing roller 2 is induced in the plate antenna 6. Similarly, when a predetermined developing bias is applied from the power source 34 to the developing roller 2, a current corresponding to the electrostatic capacity corresponding to the amount of toner existing in the space between the plate antenna 10 and the developing roller 2 is applied to the plate antenna 10. Induce. The detection means 31 converts these induced currents into electrostatic capacitances and outputs them to the calculation control means 32. The measured capacitance value is stored in the storage unit 35 of the image forming apparatus 14 via the calculation control unit 32. When a predetermined number of measurement values are obtained, the calculation control unit 32 performs statistical processing such as averaging. By this statistical processing, noise such as a change in capacitance caused by the toner being stirred by the conveying member 3 is removed. Based on the measured value after the statistical processing, the toner amount T1 between the electrodes of the first sensor (between the developing roller 2 and the plate antenna 10) and the electrode between the electrodes of the second sensor (the developing roller 2 and the plate antenna 6) Toner amount T2 is detected. The detected toner amounts T1 and T2 are stored in the storage unit 20 of the process cartridge A.

  In the developer amount detection system according to the present embodiment, the toner amount is detected based on the measurement value of the first sensor in the initial use state. That is, the remaining toner information to be displayed on the display means 33 and / or the external display device 51 is calculated based on the toner amount T1 obtained as described above. When the toner amount detected based on the measurement value by the first sensor falls below a predetermined threshold (20%), the toner amount is detected based on the measurement value by the second sensor. That is, the remaining toner information to be displayed on the display means 33 and / or the external display device 51 is calculated based on the toner amount T2 obtained as described above. As a result, the toner amount can be sequentially detected over a wide toner amount range from the initial use until the toner runs out.

  Here, problems caused by providing two sensors in the toner container 4 will be described with reference to FIGS. FIG. 4 is a diagram illustrating the relationship between the remaining amount of toner in the toner container 4 and the amount of change in the measured value of the capacitance output from the first sensor from the measured value in the initial use state. The scale on the horizontal axis is normalized by assuming that the remaining amount of toner in the initial use state is 100%, and the remaining amount of toner when no toner is used is 0%. The scale on the vertical axis is normalized by assuming that the change amount in the initial use state is 0% and the change value in the initial use state from the measurement value in the initial use state is 100% in a configuration in which the plate antenna 6 does not exist. It is a thing.

In FIG. 4, a solid line graph A shows the relationship between the remaining amount of toner and the measured value of the capacitance by the first sensor in the configuration according to the related art including only the first sensor. The broken line graph B shows the remaining amount of toner and the first amount in the configuration including the first and second sensors and not including the switching unit 36, that is, the configuration according to the related art in which the plate antenna 6 is always in a conductive state. The relationship with the measured value of the electrostatic capacitance by a sensor is shown. The difference in conditions between the graph A and the graph B is the presence or absence of the plate antenna 6 in a conductive state. In the condition (graph B) where the plate antenna 6 in the conductive state exists, the electrostatic force by the first sensor with respect to the change in the remaining amount of toner in the region where the amount of toner is smaller than the condition (graph A) where the plate antenna 6 does not exist. The amount of change in the measured capacitance value is decreasing. Further, in the graph B, there is a portion where the change in the measured value of the capacitance by the first sensor with respect to the change in the remaining amount of toner is not smooth. This is due to the influence of electrostatic shielding caused by the presence of the plate antenna 6, and the measured value of the capacitance by the first sensor is reduced as compared with the case where the plate antenna 6 is not present, and the conductive plate antenna 6 is in a conductive state. Is considered to be a noise source. Therefore, in the configuration in which the plate antenna 6 is present, the detection accuracy of the toner amount based on the measurement value by the first sensor is low particularly in the region where the toner amount is small, compared to the configuration in which the plate antenna 6 is not present.

  FIG. 5 is a diagram illustrating the relationship between the remaining amount of toner in the toner container 4 and the amount of change in the measured capacitance value output from the first sensor from the initial use state, as in FIG. 4. . FIG. 5 also shows the relationship between the remaining amount of toner in the toner container 4 and the amount of change from the initial use state of the measured capacitance value output from the second sensor. The scale on the horizontal axis is standardized by assuming that the remaining amount of toner in the initial use state is 100% and the remaining amount of toner when no toner is used is 0%, as in FIG. The scale for the amount of change in the measured value of the capacitance by the first sensor on the vertical axis is the same as in FIG. In other words, in a configuration in which the plate antenna 6 does not exist, the change amount in the initial use state is normalized as 0%, and the change amount from the measurement value in the initial use state of the measurement value in the state where the toner is exhausted is normalized as 100%. is there. The scale for the amount of change in the measured value of the capacitance by the second sensor on the vertical axis is 0% of the amount of change in the initial use state, and the measurement value in the initial use state of the measurement value in the state where the toner has run out. The amount of change is normalized as 100%.

  In FIG. 5, a broken line graph B shows the remaining amount of toner in the configuration including the first and second sensors and not including the switching unit 36, that is, the configuration according to the related art in which the plate antenna 6 is always in a conductive state. And the measured value of the capacitance by the first sensor. The graph B in FIG. 5 is the same as the graph B in FIG. A solid line graph D represents the relationship between the remaining amount of toner and the measured value of the electrostatic capacitance by the second sensor. The region sandwiched between the electrode pair of the second sensor (developing roller 2 and plate antenna 6) is buried in the toner until the remaining amount of toner reaches about 20%. There is almost no change in the measured value by the second sensor with respect to the change. A slight change may be measured due to the influence of the stirring action of the conveying member 3 or the like. Graph B shows that the change in the measured value of the capacitance by the first sensor with respect to the change in the remaining amount of toner tends to become dull in the region where the remaining amount of toner is small, like graph B in FIG. . Here, as described above, in the developer amount detection system of the present embodiment, the remaining amount of toner is detected based on the measurement value of the first sensor in the initial stage of use, and the detected value of the remaining amount of toner is less than 20%. In this case, switching to toner remaining amount detection based on the measurement value by the second sensor. Therefore, the second sensor is used for detecting the remaining amount of toner in an area where the accuracy of detecting the remaining amount of toner based on the measurement value by the first sensor is low and the remaining amount of toner is low. However, as shown in graph D of FIG. 5, in the vicinity of the remaining amount of toner of 20%, which is a threshold for switching from the first sensor to the second sensor, the second sensor responds to the change in the remaining amount of toner. Similar to the first sensor in the graph B, the change in the measured value is also slow. That is, in the vicinity of 20% of the threshold, there is a problem that it is difficult to detect the remaining amount of toner with high accuracy by either the first sensor or the second sensor.

In contrast, in the developer amount detection system according to the present embodiment, the electrical connection between the plate antenna 6 of the second sensor and the detection unit 31 can be interrupted by the switching unit 36. By cutting off the electrical connection between the plate antenna 6 and the detection means 31 by the switching means 36, the plate antenna 6 that is the electrode portion in the predetermined area can be electrically floated. When the toner amount is detected based on the measurement value by the first sensor, the plate antenna 6 is electrically floated by the switching unit 36, so that the measurement value by the first sensor is changed to the electrostatic value by the plate antenna 6. It is possible to prevent the influence of shielding from appearing.

  In FIG. 4, a one-dot chain line graph C includes the first sensor and the second sensor, and the toner remaining amount when the electrical connection between the plate antenna 6 and the detection unit 31 is interrupted by the switching unit 36. And the measured capacitance value by the first sensor. As shown in FIG. 4, the graph C and the graph A when the plate antenna 6 is not present show the same change with respect to the change in the toner amount. Further, compared with the graph B, the change in the electrostatic capacitance by the first sensor with respect to the change in the remaining amount of toner is smoother. That is, even when the plate antenna 6 exists in the region sandwiched between the electrode pairs of the first sensor, the plate antenna 6 is electrically floated so that the static due to the presence of the plate antenna 6 is obtained. The influence of electric shielding can be suppressed. Thereby, even in a region where the remaining amount of toner is small, it is possible to suppress a decrease in the amount of change in the measured value of the capacitance by the first sensor with respect to the change in the remaining amount of toner. As a result, compared with the conventional configuration in which the electrical connection between the plate antenna 6 and the detection means 31 cannot be interrupted (graph B), the detection accuracy of the remaining amount of toner is improved particularly in a region where the remaining amount of toner is low.

  In FIG. 5, an alternate long and short dash line graph C includes a first sensor and a second sensor, and when the plate antenna 6 is electrically disconnected from the detection unit 31 by the switching unit 36, The relationship with the measured value of the electrostatic capacitance by 1 sensor is represented. As shown in the graph C of FIG. 5, the change in the measured value of the capacitance by the first sensor in the vicinity of the remaining amount of toner of 20%, which is a threshold for switching from the first sensor to the second sensor. However, it has not slowed down like the graph B. Therefore, according to the developer amount detection system according to the present embodiment, the range from the initial use to the time when the toner runs out is wide, including the vicinity of 20% of the remaining amount of toner that is switched from the first sensor to the second sensor. It becomes possible to detect the toner amount with high accuracy in the toner amount range.

(Example 2)
Next, Example 2 will be described with reference to FIG. In the following description, the same names and reference numerals as those in the first embodiment are used for the same components as those in the first embodiment, and the detailed description is omitted. FIG. 6 is a diagram illustrating a schematic configuration of the process cartridge C of the image forming apparatus according to the present embodiment. The developing device according to this embodiment includes an RS roller 47 (Remove and Supply roller) that supplies toner in the toner container 4 to the developing roller 2 and removes toner remaining on the developing roller 2 from the developing roller 2. . The RS roller 47 is a rotating body that is rotatably supported in the vicinity of the developing roller 2 by a conductive rotating shaft 48, and is disposed between the developing roller 2 and the toner container 4. Further, a power supply 46 for applying an AC voltage to the rotating shaft 48 of the RS roller 47 is provided. In the present embodiment, one of the pair of electrode portions constituting the first sensor and the second sensor is used as a rotating shaft 48 of the RS roller 47, and an AC voltage is applied to the rotating shaft 48, whereby the plate antenna 6 and An electric current was induced in the plate antenna 10 to measure the capacitance.

That is, the developer amount detection system according to the present embodiment includes a first sensor having the rotation shaft 48 of the RS roller 47 and the plate antenna 10 as an electrode pair, and the rotation shaft 48 of the RS roller 47 and the plate antenna 6 as an electrode pair. And a second sensor. The plate antenna 10 is a conductive metal plate, and the length of the RS roller 47 extends along the concave shape of the bottom surface of the toner container 4 so that a part of the action area of the conveying member 3 is sandwiched between the plate antenna 10 and the RS roller 47. Installed throughout the direction. The plate antenna 6 is a conductive metal plate and is disposed in the vicinity of the RS roller 47 in the toner container 4 so as to sandwich a part of the working area of the conveying member 3 between the plate antenna 6 and the RS roller 47.
The plate antenna 6 is disposed in a region between the plate antenna 10 and the RS roller 47. That is, the plate antenna 6 is an electrode in a predetermined area.

  The electrostatic capacity between the rotating shaft 48 of the RS roller 47 and the plate antenna 10 changes according to the amount of toner present in the region between the RS roller 47 and the plate antenna 10. When an AC voltage is applied to the rotation shaft 48 of the RS roller 47 from the power supply 46, a current corresponding to the capacitance of the space between the rotation shaft 48 of the RS roller 47 and the plate antenna 10 is induced in the plate antenna 10. Therefore, the capacitance of the space between the RS roller 47 and the plate antenna 10 is measured from the current induced in the plate antenna 10 when an AC voltage is applied to the rotating shaft 48 of the RS roller 47, and this space is based on the measured capacitance. The amount of toner can be detected. Similarly, the capacitance of the space between the rotation shaft 48 of the RS roller 47 and the plate antenna 6 is measured from the current induced in the plate antenna 6 when an AC voltage is applied to the rotation shaft 48 of the RS roller 47, Based on this, the amount of toner in this space can be detected.

  Using the first sensor, it is possible to detect the amount of toner in a state where the amount of toner in the toner container 4 is relatively large (from the initial use to about 10% to about 80% of the remaining amount of toner). Further, the second sensor can be used to detect the amount of toner in a state where the amount of toner in the toner container 4 is relatively small (from about 10% to about 30% until the toner runs out). As in the first embodiment, in the initial stage of use, the toner amount is detected based on the measured capacitance value of the first sensor. When the detected toner amount falls below 20%, the toner amount is detected. The sensor used for the purpose is switched to the second sensor to detect the toner amount.

  The process cartridge C configured as described above includes a switching unit 36 and a storage unit 20 similar to those described in the first embodiment with reference to FIG. Further, the image forming apparatus in which the process cartridge C is configured to be detachable includes a detection unit 31, a calculation control unit 32, a storage unit 35, and a display unit 33. Further, an external display device 51 that displays the detected toner amount may be connected to the image forming apparatus. The switching means 36 according to the present embodiment is composed of an FET as in the first embodiment, and conducts electrical connection between the plate antenna 6 and the detection means 31 in accordance with the voltage applied from the arithmetic control means 32 to the gate electrode. Or shut off.

  When the toner amount is detected based on the measured capacitance value by the first sensor, the electrical connection between the plate antenna 6 of the second sensor and the detecting means 31 is interrupted by the switching means 36. As a result, the plate antenna 6 can be electrically floated. Similarly to the first embodiment, when the electrostatic capacity is measured by the first sensor, the first sensor is affected by the electrostatic shielding by the plate antenna 6. It can suppress that the measured value of an electrostatic capacitance decreases. As a result, even in a region where the amount of toner is small in the vicinity of 20% of the remaining amount of toner, which is a threshold value for switching from the first sensor to the second sensor, the toner is accurately based on the measured capacitance value by the first sensor. The amount can be detected.

In each of the above-described embodiments, the insulating magnetic one-component toner is used as the developer according to the present invention. However, the abundance in the space between the pair of electrode portions is a change in capacitance between the pair of electrode portions. The developer is not limited to this as long as it can be reflected in the above. Further, the sensor according to the present invention is not limited to the configuration having the developing roller and the plate antenna as a pair of electrode portions, or the configuration having the rotation shaft of the RS roller and the plate antenna as a pair of electrode portions. For example, a sensor configured with two plate antennas arranged in a toner container as an electrode pair may be used. In that case, if a part or all of the electrodes constituting the other sensor are arranged in a region between the two plate antennas, the present invention can be applied to improve the remaining toner detection accuracy. It is possible to plan. The electrode to which the AC voltage is applied is not limited to the rotating shaft of the developing roller or the RS roller. In each of the above embodiments, the FET is used as the switching means according to the present invention. However, when the capacitance is measured by the first sensor, the electrical connection between the electrode in the predetermined region of the second sensor and the detection means is performed. It is not limited to this as long as the connection can be cut off. The process cartridge A and the process cartridge C may be configured by removing both or any one of the charging unit 7 and the cleaning unit 8. Further, the toner container may not be integrally formed with the process cartridge. The present invention is applied to an image forming apparatus that is not a process cartridge type as long as it is an apparatus that forms an image using a developer and includes a plurality of sensors that measure electrostatic capacity in the developer container. Thus, the same effect can be obtained. In each of the above embodiments, an example in which the present invention is applied to a configuration in which two sensors are provided in a toner container has been described. However, the number of sensors is not limited thereto. In a configuration provided with three or more sensors, when at least one of the electrode pairs of one sensor is an in-predetermined region electrode disposed in a region sandwiched between electrode pairs of other sensors The problem of the present invention arises. That is, the measured value of the capacitance output from the other sensor is reduced due to the influence of electrostatic shielding due to the presence of the electrode in the predetermined region. Also in this case, when the present invention is applied and the capacitance is measured by the one sensor, the effect of electrostatic shielding is suppressed by electrically floating the electrode in the predetermined area of the other sensor. Thus, it is possible to improve the detection accuracy of the toner amount. The threshold value of the toner amount to be switched from the first sensor to the second sensor depends on the relationship between the toner amount range detectable by the first sensor and the toner amount range detectable by the second sensor. It is determined, and is not limited to 20% employed in the above embodiment.

2 ... developing roller, 6 ... plate antenna, 10 ... plate antenna, 31 ... detecting means, 36 ... switching means

Claims (7)

A developer amount detection system for detecting the amount of developer in a developer storage section for storing a developer,
A first sensor that has a pair of electrode portions facing each other in the developer accommodating portion, and that outputs a measurement value according to the capacitance of a region sandwiched between the pair of electrode portions;
A second sensor that has a pair of electrode portions facing each other in the developer accommodating portion and outputs a measurement value corresponding to the capacitance of a region sandwiched between the pair of electrode portions;
With
At least one electrode portion of the second sensor is an electrode portion in a predetermined region in which at least a part thereof is disposed in a region sandwiched between the pair of electrode portions of the first sensor,
The developer amount detection system includes:
From at least one electrode part of the first sensor and at least the electrode part in the predetermined region of the second sensor, and a measurement value inputted from the first sensor or from the second sensor Detection means for detecting the amount of developer in the developer storage section based on the input measurement value;
Switching means for switching the electrical connection between the electrode section in the predetermined area and the detection means to either conduction or interruption;
With
When the detection means detects the amount of developer based on the measurement value input from the first sensor, the switching means electrically connects the electrode portion in the predetermined area and the detection means. A developer amount detection system characterized in that the connection is cut off.   When the developer amount detected based on the measurement value input from the first sensor falls below a predetermined threshold value, the detection unit is configured to switch the electrode unit in the predetermined region and the detection unit by the switching unit. 2. The developer amount detection system according to claim 1, wherein the developer amount is detected based on a measurement value obtained by the second sensor, with the electrical connection to a conductive state. Applying means for applying an alternating voltage to one of the pair of electrode portions of the first sensor and one of the pair of electrode portions of the second sensor;
The other of the pair of electrode portions of the first sensor and the other of the pair of electrode portions of the second sensor are connected to the detection means;
The first sensor and the second sensor, when an AC voltage is applied by the application unit, output a measurement value corresponding to the capacitance of the region sandwiched between the pair of the electrode portions to the detection unit. Configured and possible
3. The developer amount detection system according to claim 1, wherein the other of the pair of the electrode portions of the second sensor is the electrode portion in the predetermined region.   4. The development according to claim 3, wherein the first sensor and the second sensor share an electrode portion to which an AC voltage is applied by the applying unit in each pair of electrode portions. Dose amount detection system. A photoreceptor carrying a latent image corresponding to image information;
A developer storage unit that stores the developer, and a developer carrier that carries and transports the developer in the developer storage unit to the photosensitive member, and the latent image is attached to the latent image by attaching the developer to the latent image. A developing device for developing the image;
A developer amount detection system according to claim 4, wherein the developer amount detection system according to claim 4 detects the amount of developer in the developer storage portion,
2. The image forming apparatus according to claim 1, wherein an electrode portion shared by the first sensor and the second sensor and applied with an AC voltage by the applying unit is the developer carrying member. The image forming apparatus is an apparatus that forms an image by applying a developing bias to the developer carrier.
6. The image forming apparatus according to claim 5, wherein the AC voltage applied to the developer carrying member by the applying unit is the developing bias. A photoreceptor carrying a latent image corresponding to image information;
A developer storage unit that stores the developer, and a developer carrier that carries and transports the developer in the developer storage unit to the photosensitive member, and the latent image is attached to the latent image by attaching the developer to the latent image. A developing device for developing the image;
A developer amount detection system according to claim 4, wherein the developer amount detection system according to claim 4 detects the amount of developer in the developer storage portion,
The developing device is disposed in the vicinity of the developer carrier, and supplies the developer in the developer container to the developer carrier and removes the developer remaining on the developer carrier. Further comprising
The image forming apparatus is characterized in that an electrode portion shared by the first sensor and the second sensor and to which an AC voltage is applied by the applying means is a rotating shaft having conductivity in the rotating body. apparatus.