JP2012083662A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress influence of environmental variation and detect the residual amount of toner with high accuracy.SOLUTION: The image forming apparatus comprises: a container 21 which has an opening and stores a toner; a toner carrier 25 and a first electrode member 28 which are arranged in the opening of the container; and a toner supply member 24 and a second electrode member 29 which are arranged in the container. The image forming apparatus further comprises: a developing device for supplying the toner in the container to the toner carrier by rotating the toner supply member while being brought into contact with the toner carrier; driving means capable of rotatively driving the toner supply member to first and second directions; detecting means for detecting an electrostatic capacitance Cv1 after the toner supply member has been rotated by the driving means to the first direction for a predetermined time, and detecting an electrostatic capacitance Cv2 after the toner supply member has been rotated by the driving means to the second direction for the predetermined time; and notification means for notifying that residual amount of the toner is lower than a predetermined amount when|Cv1-Cv2| is lower than a threshold value.

Description

  The present invention provides an image forming apparatus having a developing device including a toner carrier and a toner supply member that supplies toner to the toner carrier, and an electrode member provided in the toner carrier and an electrode member provided in the toner supply member The present invention relates to an image forming apparatus including a detection mechanism for detecting a capacitance between

  As a method for detecting the remaining amount of toner contained in a developing device used in an image forming apparatus such as an electrophotographic apparatus, development is performed by detecting the capacitance between two electrodes provided in the developing apparatus. There is a capacitance detection method for obtaining information on the remaining amount of the agent.

  In particular, when a developing device having a developing roller as a toner carrier and a supply roller having a foamed layer as a toner supply member is used, as described in Patent Document 1, the shaft of the development roller, the supply roller There is a method of obtaining information on the remaining amount of toner by detecting the capacitance between the shaft and the other shaft. In this method, since there is a correlation between the remaining amount of toner in the developing device and the capacitance between the shafts, it is possible to measure the remaining amount of toner by detecting the capacitance.

  In addition, in an image forming apparatus that measures the remaining amount of toner by detecting the capacitance provided in the developing device, the capacitance changes when the temperature / humidity environment changes. In some cases, the accuracy is lowered, and it is impossible to accurately notify the user that the remaining amount of toner has fallen below a predetermined amount or the cartridge replacement time. In order to reduce the influence of such environmental changes, it is possible to correct the notification timing by providing a temperature sensor or a humidity sensor, for example, as described in the cited document 2.

JP 2009-9035 A JP 2002-132038 A

  In an image forming apparatus configured to detect capacitance between an electrode member included in a toner carrier and an electrode member included in a toner supply member as described in Patent Document 1, when the temperature / humidity environment changes Since the capacitance is changed, the measurement accuracy of the remaining amount of toner is lowered, and there are cases where it is impossible to accurately notify the user that the remaining amount of toner has fallen below a predetermined amount and the cartridge replacement timing. In order to reduce the influence of such environmental changes, if a temperature sensor and a humidity sensor are provided as described in Patent Document 2, there are restrictions on the arrangement, which reduces design freedom and increases costs. .

  Accordingly, the object of the invention according to the present application is to accurately detect the fact that the remaining amount of toner has fallen below a predetermined amount and the cartridge replacement time even if the temperature / humidity environment changes and the temperature sensor or humidity sensor is not used. An object of the present invention is to provide an image forming apparatus capable of informing.

In order to achieve the above object, a first invention according to the present application is a container having an opening and containing toner, and a toner carrier disposed in the opening of the container. A toner carrying member that carries and conveys toner and supplies the electrostatic latent image to the electrostatic latent image, a toner supply member disposed inside the container, the second electrode member, and the first electrode member A toner supply member having a foam layer around the electrode member, and supplying the toner in the container to the toner carrier by rotating the toner supply member in pressure contact with the toner carrier. A developing device, and a driving unit capable of rotating the toner supply member in first and second directions;
Detection means for detecting an electrostatic capacitance between the first electrode member and the second electrode member, after the toner supply member is rotated in the first direction for a predetermined time by the driving means; Detecting means for detecting electrostatic capacity Cv1, and detecting electrostatic capacity Cv2 after rotating the toner supply member in the second direction for a predetermined time by the driving means; and | Cv1-Cv2 | And an informing means for informing that the remaining amount of toner has fallen below a predetermined amount.

Furthermore, a second invention according to the present application is a container having an opening and containing toner, and a toner carrier disposed in the opening of the container, the first electrode member being provided. A toner carrying member that carries and conveys toner to the electrostatic latent image, a regulating member that regulates the amount of toner carried on the toner carrying member, and a toner supply member that is disposed inside the container. A second electrode member, and a toner supply member having a foam layer around the second electrode member, and the toner supply member is pressed against the toner carrier and rotated. A developing device that supplies toner in the container to the toner carrier, a mounting portion for detachably mounting the developing device, and a drive that can rotationally drive the toner supply member in first and second directions. Means,
Detection means for detecting an electrostatic capacitance between the first electrode member and the second electrode member, after the toner supply member is rotated in the first direction for a predetermined time by the driving means; Detecting means for detecting electrostatic capacity Cv1, and detecting electrostatic capacity Cv2 after rotating the toner supply member in the second direction for a predetermined time by the driving means; and | Cv1-Cv2 | And an informing means for informing the user to replace the developing device when the value is lower than.

  An image forming apparatus capable of accurately informing the user that the remaining amount of toner has fallen below a predetermined amount and the replacement timing of the cartridge even if the temperature / humidity environment changes without using a temperature sensor or a humidity sensor. Can be provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus. 1 is a schematic configuration diagram of a developing device during image formation according to the present invention. 3 is a block diagram of a toner remaining amount measuring device. FIG. It is a flowchart until difference detection sequence execution. 3 is a flowchart of a difference detection sequence in the first embodiment. FIG. 6 is a relationship diagram of a capacitance difference value ΔC with respect to the remaining amount of toner in Embodiment 1. 3 is a flowchart for determining a result of a difference detection sequence in the first embodiment. It is a figure showing the determination method of the timing which performs a next difference detection sequence. 6 is a diagram illustrating electrostatic capacity (toner content) after a first rotation and a second rotation in Embodiment 1. FIG. It is a figure showing the relationship between the electrostatic capacitance (toner content) after the first rotation and after the second rotation in a high temperature and high humidity environment and a low temperature and low humidity environment. 10 is a flowchart for determining a result of a difference detection sequence in the second embodiment. 12 is a flowchart of a difference detection sequence when toner is not notified in Embodiment 2. 12 is a flowchart of a difference detection sequence when toner low notification is completed in Embodiment 2. FIG. 10 is a diagram illustrating electrostatic capacity (toner content) after the first rotation and after the second rotation in each difference detection sequence of Example 2. FIG. 10 is a relationship diagram of a capacitance difference value ΔC with respect to a remaining amount of toner in each difference detection sequence according to the second exemplary embodiment. FIG. 12 is a diagram illustrating a timing determination method for executing a first difference detection sequence O after toner low notification in the second embodiment. It is a figure showing the relationship between the toner amount in a supply roller, and an electrostatic capacitance. 2 is a diagram illustrating attachment and detachment of a developing device with respect to an image forming apparatus main body. It is the schematic which shows the drive transmission means to the image development apparatus to which this invention is applied. FIG. 7 is a diagram illustrating toner movement around a supply roller in each rotation direction.

Example 1
Embodiments of the present invention will be illustrated below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. However, the present invention is not intended to be limited to the following embodiments.

  The configuration of the image forming apparatus of this embodiment is shown in FIG. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier. The photosensitive drum 1 rotates in the direction of arrow R1. Reference numeral 2 denotes a charging roller. 3 is an exposure device, and 4 is a reflection mirror. The laser beam transmitted from the exposure device 3 is arranged so as to reach the exposure position A on the photosensitive drum 1 via the reflection mirror 4. The developing device 5 contains black toner and is configured to be detachable from the main body of the image forming apparatus as shown in FIG. A transfer roller 6 is disposed below the photosensitive drum 1. The transfer material P after the transfer is sent to the fixing device 15. A cleaning device 9 is installed downstream of the transfer position B in the moving direction of the photosensitive drum 1. An attached blade is disposed so as to scrape off the toner on the photosensitive drum 1.

  An image forming operation of the image forming apparatus will be described. The surface of the photosensitive drum 1 rotating at 100 mm / sec in the direction of the arrow R1 is charged to a predetermined potential by the charging roller 2. At the exposure position A, an electrostatic latent image is formed on the photosensitive drum 1 by the laser beam transmitted according to the image signal by the exposure device 3 and the reflection mirror 4. The formed electrostatic latent image is developed by the developing device 5 at the development position C to form a toner image. The toner image formed on the photosensitive drum 1 is transferred to the transfer material P at the transfer position B. The transfer material P to which the toner image has been transferred is sent to the fixing device 15. The fixing device 15 pressurizes and heats the toner image on the transfer material P to fix it on the transfer material P, thereby obtaining a final image.

  The developing device 5 will be described in detail with reference to FIG. The developing device 5 includes a developing container 21 that contains toner, a developing roller 25 that is a toner carrier disposed in an opening of the developing container 21, a regulating blade 27 that is a developer regulating member, and a developing roller inside the developing container 21. And a supply roller 24 which is a toner supply member provided adjacent to the toner supply member 25. The developing roller 25 rotates while in contact with the photosensitive drum 1 during the developing operation. In the developing operation, the developing roller 25 and the supply roller 24 are driven and transmitted from a driving device (not shown) of the main body of the image forming apparatus as the first driving means, so that rotation is started and stopped at the same timing. After completion of the developing operation, the cam 20 shown in FIG. 1 provided in the image forming apparatus main body rotates and pushes the upper portion of the developing container, thereby separating the developing roller 25 from the photosensitive drum 1. After the separation, the rotation drive of the drive device as the first drive means is stopped.

  The developing roller 25 is composed of a conductive shaft 28 of φ8 (mm) as a first electrode member made of stainless steel, aluminum alloy or the like, and a conductive elastic layer based on silicon rubber formed therearound. . The surface layer is coated with an acrylic / urethane rubber layer. The outer diameter of the developing roller 25 is φ13 (mm), and the volume resistance is about 10E5 Ω · cm. During the developing operation, the developing roller 25 is supported by the developing container 21 so as to come into contact with the photosensitive drum 1 at the developing position C described above and to be rotationally driven in the direction of arrow R4 in FIG. During image formation, the peripheral speed of the developing roller is 160 mm / sec, and a developing bias is applied by voltage applying means of the image forming apparatus main body.

  The supply roller 24 includes a φ6 (mm) conductive shaft 29 as a second electrode member made of stainless steel, an aluminum alloy, or the like, and a urethane sponge layer, which is a foam surface layer made of soft open-celled material formed around the conductive shaft 29. Consists of The outer diameter of the supply roller 24 is φ15 (mm), and the volume resistance is about 10E5 Ω · cm. In this embodiment, the distance between the center of the shaft 28 of the developing roller 25 and the center of the shaft 29 of the supply roller 24 (hereinafter referred to as the center distance) is 13 mm, and the surface of the developing roller 25 covers the urethane sponge layer of the supply roller 24. , Installed so as to push in at a depth of about 1.0 mm. Here, the intrusion amount is a length obtained by dividing the sum of the outer diameters of the supply roller 24 and the developing roller 25 by 2 and subtracting the distance between the centers on a line segment connecting the center of the shaft 28 and the center of the shaft 29. It is. The supply roller 24 is supported by the developing container 21 so as to be rotationally driven in both directions of an arrow R5 direction in FIG. 2 and a direction opposite to the arrow R5 direction. The rotation direction of the supply roller is controlled by a driving device provided in the main body, and is changed at a necessary timing. During image formation, the rotation speed (circumferential speed) of the supply roller is 140 mm / sec in the direction of arrow R5. Hereinafter, the direction of the arrow R5, which is the direction of rotation of the supply roller during image formation, will be referred to as the forward direction, and the direction of rotation of the supply roller opposite to the direction of the arrow R5 will be referred to as the reverse direction.

  The regulation blade 27 is made of a phosphor bronze sheet metal having flexibility, one end is fixed to the developing container 21, and the other end is brought into contact with the developing roller 25 with a free end. A smooth surface in the vicinity of the free end is disposed so as to rub against the surface of the developing roller 25 in a direction that is a counter direction with respect to the rotation direction of the developing roller 25.

  In addition, a leakage prevention seal 26 that covers the gap between the developing roller 25 and the developing container 21 is provided.

  Next, driving means for reverse rotation driving to the supply roller will be described with reference to FIG. The developing device is provided with a coupling gear 30 that receives driving from the image forming apparatus. A supply gear 31 for driving the supply roller 24 and a development gear 33 for driving the development roller 25 are provided. First, when the coupling gear 30 receives driving from the image forming apparatus, the gear 31 of the supply roller driven by the coupling gear 30 rotates, and the supply roller 24 rotates. The drive rotation direction of the image forming apparatus main body can be rotated in both the forward direction and the reverse direction, and the supply gear 31 can be rotated in both the forward direction and the reverse direction via the coupling gear 30. The coupling gear 30 also transmits drive to the one-way clutch 32. Only when the one-way clutch 32 rotates in the forward direction of the image forming operation, the one-way clutch 32 engages with the gear 33 of the developing roller, transmits the drive to the developing gear 33, and rotates the developing roller 25. As described above, in this embodiment, the gear that transmits the drive to the developing roller 25 does not mesh in the reverse direction of the arrow R4, and the drive is transmitted to the developing roller when the supply roller 24 rotates in the reverse direction. This prevents toner leakage during reverse rotation. However, as will be described later, a difference detection sequence may be executed in order to accurately detect the time of running out of toner and the replacement time of the developing device, and it is essential that the developing roller is not driven to rotate in the reverse direction of the arrow R4. Absent. In this embodiment, a coupling gear is used for driving transmission to the supply roller. However, as will be described later, in order to measure the capacitance after rotation including the rotation direction of different supply rollers, supply is performed. Any configuration may be used as long as the roller 24 can be driven in reverse rotation. For example, a means for independently driving the supply roller 24 without using a coupling gear may be provided.

  Here, the behavior of the toner dispersed in the urethane sponge layer of the supply roller 24 and the surrounding air when the supply roller 24 rotates in a predetermined rotation direction will be described.

  First, the behavior when the supply roller 24 is rotating in the direction of the arrow R5, which is the positive direction, will be described. When rotating in the forward direction, as shown in FIG. 20 (a), in a region upstream of the supply roller 24 in the rotation direction with respect to the contact position of the supply roller 24 and the developing roller 25 (in the vicinity of X in FIG. 2). The supply roller 24 is compressed and released from the compressed state in the region on the downstream side in the rotation direction (in the vicinity of Y in FIG. 2). Here, in the vicinity of X, since the supply roller 24 is compressed, the toner sucked into the supply roller 24 is discharged together with air. Conversely, in the vicinity of Y, when the supply roller 24 is released from the compressed state and returns to its original shape, the toner dispersed in the air is sucked into the supply roller.

  Next, the toner behavior when the supply roller 24 rotates in the direction of the arrow R6, which is the reverse direction of the arrow R5, will be described. When rotating in the reverse direction, as shown in FIG. 20B, in the region upstream of the supply roller 24 in the rotation direction with respect to the contact position of the supply roller 24 and the developing roller 25 (in the vicinity of Y in FIG. 2). Since the supply roller 24 is compressed and released from the compressed state in the region on the downstream side in the rotation direction (in the vicinity of X in FIG. 2), the toner discharge position and the suction position are opposite to those in the forward rotation. That is, in the vicinity of X, when the supply roller 24 is released from the compressed state and returns to its original shape, the toner dispersed in the air is sucked into the supply roller. Conversely, in the vicinity of Y, the supply roller 24 is compressed, so the toner sucked into the supply roller 24 is discharged together with air.

  As described above, when the forward rotation is performed, the toner is sucked in the Y portion and discharged in the X portion, whereas in the reverse rotation, the toner is sucked in the X portion and discharged in the Y portion. The reverse operation is performed.

  Under the condition that the toner enters and exits smoothly, the pressure of the toner as the powder fluid deposited in the vicinity of the supply roller 24 and the pressure of the toner as the powder fluid in the supply roller 24 are balanced, and the supply roller 24 A certain correlation appears between the amount of toner held inside and the total amount of toner in the developer container. Therefore, the capacitance between the shaft 29 of the supply roller 24 and the developing roller 25 not only indicates the amount of toner held inside the supply roller 24 but also can estimate the total amount of toner in the developer container ( Patent Document 1). The toner enters and exits only when the supply roller 24 rotates, and the supply roller 24 after the rotation stops maintains the amount of toner being rotated. Even if the developing device 5 is moved or the posture is changed in this state, the amount of toner held in the supply roller 24 does not change.

Next, a toner remaining amount measuring method of the developing device in this embodiment will be described.
In this embodiment, when the remaining amount of toner is large, a rough toner usage amount is estimated by using a pixel count counting means (pixel counter) capable of calculating the light emission amount of the exposure means. The amount of toner used per pixel count is stored in the main body memory, and the amount of toner used is estimated from the pixel count integrated value counted by the pixel counter. The pixel count integrated value is stored in a memory 23 that is a storage unit provided in the developing device 5. When the remaining amount of toner becomes relatively small, a difference detection sequence (described in detail later) using electrostatic capacity is executed in order to accurately detect the toner exhaustion time and the development device replacement time.

Hereinafter, the flow of toner remaining amount measurement will be specifically described with reference to FIG.
At the time of image formation, the pixel count is measured (S002). At the end of the image forming operation, the measured pixel count is integrated to calculate an integrated value Pcount (S003). Next, it is determined whether the integrated value Pcount has reached the predetermined value Pth (S004). When it is determined that the integrated value Pcount has reached, the toner remaining amount measurement sequence (difference detection sequence) using the capacitance is started. (S005). If not, normal image formation is continued until Pcount becomes equal to or greater than Pth (S006).

In this embodiment, the execution timing of the first difference detection sequence is set as follows. An integrated value that is 20% less than the pixel count integrated value P0% that would be reached when the remaining toner life is 0% was defined as Pth. (See Equation 1)
Pth = P0% × 0.8 .. Formula 1
As described above, the reason why the execution timing of the first difference detection sequence is set when the remaining amount of toner is larger than the remaining amount of toner at the time of running out of toner is as follows. Due to the variation in the amount of toner used, the remaining amount of toner estimated by the pixel count varies. In consideration of this variation, it is necessary to reliably execute the difference detection sequence before the occurrence of the low density image or the whiteout image. Therefore, the difference detection sequence is executed at a slightly earlier timing than the toner count is estimated to be out of the pixel count.

  For the second and subsequent times, Pth is recalculated by the calculation method described later, and the difference detection sequence is executed when Pth newly provided is reached. In this way, it is possible to detect toner out with a small number of executions. The term “out of toner” does not indicate that there is no toner in the developing device, but indicates the remaining amount of toner that makes it difficult to maintain the level of image quality that is desired to be maintained, and is an amount that is set as appropriate. Hereinafter, toner out is used in the above meaning.

  In this embodiment, the pixel count method is used to estimate the rough toner remaining amount in a short time when the remaining amount of toner is high. However, the toner out time and the development device replacement time can be accurately set. For detection, a difference detection sequence may be executed, and the pixel count method is not essential. For example, the difference detection sequence may be executed every time a predetermined number of images are formed, or the start timing of the difference detection sequence may be determined by another toner remaining amount measurement method.

  Next, a capacitance measurement method necessary for executing the difference detection sequence will be described. First, as a configuration for measuring the capacitance, as shown in FIG. 3, a voltage applying means for detection is connected to the shaft 28, and a detection circuit is connected to the shaft 29. The AC bias for detecting the capacitance was a frequency of 50 KHz and a peak-to-peak voltage Vpp = 200V. When measuring the capacitance, a predetermined AC bias is applied to the shaft 28 of the developing roller 25, and the capacitance between the shafts is detected from the AC voltage induced on the shaft 29 of the supply roller 24 (with the shaft 28). Since the shaft 29 only needs to apply an AC bias to one side and detect the output from the other, the toner remaining amount can be measured from the AC voltage induced on the shaft 28 by applying the AC bias to the shaft 29. I do not care). The AC voltage induced in the shaft 29 is rectified by the detection circuit, and the rectified DC voltage itself or signal information obtained by quantifying the DC voltage is output as an output value. The value output here represents the capacitance between the shaft 28 and the shaft 29, and this capacitance reflects the amount of toner between the shaft 28 and the shaft 29. FIG. 17 shows the relationship between the toner amount in the supply roller and the capacitance between the shaft 28 and the shaft 29. Since the dielectric constant of the toner is about three times that of air, the capacitance between the shaft 28 and the shaft 29 increases as the amount of toner between the shaft 28 and the shaft 29 increases. The relationship is almost linear.

  In this embodiment, when detecting the capacitance, the photosensitive drum 1 and the developing roller 25 are separated from each other and the developing roller 25 is stopped. This reduces the influence of the potential of the photosensitive drum and measures the capacitance in a stable state. However, as will be described later, in order to cancel the influence of the environment on the capacitance by taking the difference in capacitance, it is only necessary to measure the capacitance after an operation including rotation in different rotation directions. For example, the capacitance may be measured in a state where the photosensitive drum 1 and the developing roller 25 are in contact with each other, or in a state where the developing roller 25 and the supply roller 24 are rotated.

  The difference detection sequence that is a feature of the present invention will be described below with reference to FIG. When the pixel count integrated value Pcount of the developing device reaches Pth, a difference detection sequence is executed after the development operation is completed (S005, S100). First, the developing drive can be transmitted (S101), and the supply roller is rotated in the forward direction (in the direction of arrow R5) for a predetermined time (S102). In this embodiment, the rotation time is 15 seconds. The rotation speed used here is the rotation speed normally used for image formation. Here, the toner is discharged from the urethane sponge layer of the supply roller by rotating for a long time, and the amount of toner in the supply roller is stabilized. After the rotation for 15 seconds, the developing roller is separated from the photosensitive drum, and the rotation of the developing roller and the supply roller is stopped (S103). Thereafter, the first capacitance Cv1 is measured (S104).

  Next, the developing drive can be transmitted again (S105), and the second rotation including the rotation of the supply roller in the reverse direction (arrow R6 direction) is performed. In the present embodiment, the rotation was performed for 5 seconds in total in the order of reverse direction, forward direction, reverse direction, forward direction, and reverse direction (S106, S107, S108, S109, S110). The rotation speed used here is the same as the rotation speed used during normal image formation except for the difference in the rotation direction. Here, as will be described later, the toner is contained in the urethane sponge layer of the supply roller more than in the measurement of the capacitance Cv1 by rotating in different directions a plurality of times. After rotating for a predetermined time, in order to measure the remaining amount of toner, the developing roller is separated from the photosensitive drum, and the rotation of the developing roller and the supply roller is stopped (S111). Thereafter, the second capacitance Cv2 is measured (S112).

  When the absolute value | Cv1−Cv2 | of the difference between the electrostatic capacitances Cv1 and Cv2 detected in this way is ΔC, the relationship between ΔC and the remaining amount of toner in the developing device is as shown in FIG. The toner remaining amount measurement is performed in a state where the remaining amount of toner is correspondingly reduced because it is particularly necessary to accurately detect the timing of toner exhaustion. Therefore, “large” and “low” of the remaining amount of toner in the figure are relative expressions in a state where the remaining amount of toner is correspondingly reduced. (In the following FIGS. 8, 9, 10, 14, 15, and 16, “more” and “less” are used in the same meaning.) According to FIG. 6, ΔC and the remaining amount of toner have a correlation. I understand that. Where the remaining amount of toner is large, ΔC is large, but as the remaining amount of toner decreases, ΔC decreases. Therefore, by measuring ΔC, the remaining amount of toner can be measured by using this correlation.

  The operation after Pcount reaches Pth (S200), the difference detection sequence is executed (S201), and ΔC is calculated (S202) will be described with reference to FIG. After calculating ΔC, it is determined whether ΔC is equal to or less than a threshold value ΔCth (S203). When ΔC is equal to or less than the threshold value ΔCth (S203 Yes), a toner out signal is notified (S204). The content of the notification here is a notification that the toner has fallen below a predetermined amount, or that prompts the user to replace the developing device. For example, “Toner is low.” “Toner out.” “Cartridge (Developing device) ) "Is displayed. It is also possible to detect a stepwise toner amount by setting a plurality of threshold values. In this way, it is possible to notify the user of the remaining amount of toner step by step. On the other hand, when ΔC does not reach ΔCth or less (No in S203), a difference ΔD between ΔC and ΔCth is calculated (S205), and Pth is reset (S206). Returning to S000 or S001 in FIG. 4, image formation is continued until the pixel count integrated value Pcount reaches the newly set Pth (S207). When Pth is reached, the second difference detection sequence is executed, and the operation of FIG. 7 is performed again based on the calculated ΔC.

Next, a method for resetting Pth from ΔD will be described. The relationship between the remaining amount of toner and ΔC is as shown in FIG. An approximate straight line is calculated in advance from this relationship, and the approximate straight line data is stored in the storage means of the image forming main body. A toner amount Xg that can be used until the toner runs out is calculated from ΔD and prestored approximate linear data. When the toner amount Xg is used, a pixel count Px that is assumed to be integrated is calculated. Pth ′, which is a value obtained by adding Px to the previous Pth, is reset as a new Pth. When the pixel count integrated value Pcount reaches the reset Pth, the second difference detection sequence is performed. Thereafter, when ΔC has not reached ΔCth or less, the flow from S200 to S203 and from S205 to S207 is repeated, and this operation is repeated until ΔC becomes ΔCth or less.
Here, the physical meaning of the correlation between the difference in capacitance and the amount of toner in the container is inferred based on the observation result in the developing device.

  The inventors have found a phenomenon in which the relationship between the remaining amount of toner and the amount of toner in the supply roller changes by changing the rotation direction of the supply roller. FIG. 9 shows the relationship between the toner content in the supply roller when the rotation (first and second rotations) including different rotation directions of the supply roller is performed with respect to the toner amount in the container. In a state where the amount of toner in the container is large (point A), the toner contains more toner after the second rotation, which is alternately rotated in the forward direction and the reverse direction, and after the first rotation only in the forward direction. The difference in toner content is large. As the amount of toner in the container decreases, the amount of toner in the supply roller decreases both after the first rotation (forward rotation) and after the second rotation (forward and reverse alternating rotation), and the amount of toner in the container is very small. In the state (point B), substantially the same toner content is shown after the first and second rotations.

  It is considered that the above phenomenon is influenced by the fact that the toner suction position and the discharge position of the supply roller are reversed between the forward rotation and the reverse rotation of the supply roller as described above. The mechanism by which the above phenomenon occurs is inferred below.

  From the observation results of the present inventors, when the amount of toner is small to some extent (the amount of toner so that the supply roller is not completely buried in the toner), the amount of toner stored in the X portion is large after the forward rotation. all right. Conversely, it was found that the amount of toner stored in the Y portion was large after the rotation in the reverse direction. This is because the toner discharged from the supply roller to the discharge portion (X portion in the normal rotation) does not get over the top of the supply roller around the supply roller and accumulates without moving to the suction portion (Y portion in the normal rotation). It is. When the rotation direction is changed from this state, the portion that was the discharge position becomes the suction position, so that a large amount of toner is sucked in, and the supply roller contains more toner.

  The above phenomenon occurs not only when the amount of toner is small, but also when the amount of toner is large (the amount of toner such that the supply roller is completely buried in the toner). This is considered to be caused by the change in toner density. That is, the density of the toner in the discharge portion is higher due to the toner discharged from the supply roller, and the toner density in the suction portion is conversely sparse because it is sucked into the supply roller. When the rotation direction is changed from this state, the portion that was the discharge position becomes the suction position, so that a large amount of toner is sucked in, and the supply roller contains more toner. Furthermore, by repeating forward and reverse rotation, the discharge position and the suction position are reversed, and the discharged toner is repeatedly brought to the suction position, so this tendency appears more remarkably. This completes the explanation of the mechanism by which the above phenomenon occurs.

  As a result, in a state where the toner in the container remains to some extent (point A in FIG. 9), after the first rotation after the first rotation, the second rotation after the forward rotation and the reverse rotation are alternately performed. The amount of toner in the supply roller is larger (the electrostatic capacity is larger). Here, the sucked toner is discharged from the discharge position when rotated for a long time. However, if the rotation is performed for a short time that does not reduce the toner amount at the suction position, the toner is included in the supply roller. Therefore, in this embodiment, the rotation direction of the supply roller is changed every second.

When the amount of toner in the container is very small (point B in FIG. 9), the toner in both the suction portion and the discharge portion is almost lost both in the forward rotation and in the reverse rotation. Therefore, it becomes difficult to suck the toner into the supply roller even if the rotation direction of the supply roller is changed. In other words, as the toner amount in the container decreases from point A to point B, the difference in toner amount in the supply roller is less likely to occur after the first rotation and after the second rotation.
From these results, the relationship between the toner amount in the container and the electrostatic capacity is as shown in FIG. 9, and the difference is obtained as shown in FIG.

  Based on the above, the effects of the present invention will be described in detail. FIG. 10A shows a container in a high temperature and high humidity environment (30 ° C./80% RH: hereinafter referred to as H / H) and a low temperature low humidity environment (15 ° C./10% RH: hereinafter referred to as L / L). The relationship between the amount of toner inside and the electrostatic capacity after forward rotation (first rotation) and forward and reverse rotation (second rotation) is shown. It can be seen that the measured value of H / H shows a higher capacitance than the measured value of L / L. However, when the difference in capacitance after each rotation is measured, the result is almost the same between H / H and L / L as shown in FIG. According to the above results, the effects of temperature and humidity on the capacitance are the same even if the rotation direction of the supply roller is changed. If the difference in electrostatic capacity when the toner amount is changed is used, the influence of the environmental change on the electrostatic capacity can be canceled. Therefore, by measuring the remaining amount of toner using the difference detection method of this embodiment, even if the temperature / humidity environment changes, the remaining amount of toner can be measured with high accuracy without using a temperature sensor or a humidity sensor. It becomes possible. As a result, even when the temperature / humidity environment changes, the user can be informed accurately that the remaining amount of toner has fallen below the predetermined amount or the development device replacement time without using the temperature sensor or humidity sensor. it can.

Another effect is as follows.
Conventionally, the output value may fluctuate depending on the previous printing history or toner accumulation state of the toner amount in the foam layer of the supply roller. In response to this problem, when the toner remaining amount is measured as in the present embodiment, a state where the toner amount in the supply roller is stable can be created by rotating the supply roller for a predetermined time. As a result, it is possible to suppress the fluctuation of the output value caused by the print history and to detect the remaining amount of toner with high accuracy.

  In this embodiment, the amount of toner in the supply roller after the second rotation to be rotated thereafter is included rather than the amount of toner in the supply roller after the first rotation in the difference detection sequence. ing. In particular, as in the present embodiment, the difference detection sequence is ended after the forward and reverse rotations are alternately performed, so that the toner can be contained in the supply roller in a subsequent image formation. As a result, even if an image with a high printing rate is output after the difference detection sequence, it is possible to suppress the occurrence of an image with a low density or a whiteout image. However, in order to obtain the effect of the present invention that the remaining amount of toner can be measured with high accuracy even if the temperature / humidity environment changes, the rotation direction of the supply roller should be set in this order. Is not required.

  In this embodiment, in the rotation method (second rotation in this embodiment) in which the toner is included in the supply roller in the difference detection sequence, the toner is further supplied by changing the rotation direction. Included in. As described above, by using the difference between the forward and reverse rotations, the inclination of the capacitance difference ΔC with respect to the toner amount in the container increases. When the slope of the difference ΔC in capacitance increases, the remaining amount of toner becomes smaller than the variation in detecting the difference ΔC, and the remaining amount of toner can be detected with higher accuracy. . From the above, as in this embodiment, the remaining amount of toner can be measured with higher accuracy by rotating the supply roller a plurality of times in different rotation directions in the first rotation or the second rotation. is there.

  In the present embodiment, the flow of FIG. 5 was continuously performed. These flows are desirably performed continuously, but the present invention is not limited to this as long as the environment and the amount of toner in the container have not changed significantly. For example, in the case of an image with a low printing rate, even if several sheets are printed between the Cv1 measurement and the Cv2 measurement, there is no significant influence.

  The present invention is also effective for an image forming apparatus in which a plurality of cartridges having the same form as in this embodiment are arranged to obtain a full color image.

(Example 2)
Embodiments of the present invention will be illustrated below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. However, the present invention is not intended to be limited to the following embodiments.

  The image forming apparatus used in the second embodiment has the same configuration as the image forming apparatus used in the first embodiment, and the developing device 5, the developing roller 25, and the supply roller 24 that are used have the same configuration.

The image forming operation of the image forming apparatus according to the present embodiment is the same as that of the first embodiment.
The peripheral speed of the developing roller during image formation is 160 mm / sec in the direction of arrow R4, and the peripheral speed of the supply roller is 140 mm / sec in the direction of arrow R5. The rotation direction of the supply roller 24 can be changed to both the forward direction and the opposite direction when the arrow R5 direction is the forward direction. The driving means for reverse rotation driving to the supply roller is the same as in the first embodiment.

  Also in this embodiment, as in the first embodiment, the gear for driving transmission to the developing roller is not engaged in the reverse direction of the arrow R4, and is driven to the developing roller when the supply roller 24 rotates in the reverse direction. By not being transmitted, toner leakage during reverse rotation is prevented. However, the difference detection sequence may be executed to accurately detect the toner out time and the development device replacement time, and it is not essential that the developing roller is not driven to rotate in the reverse direction of the arrow R4.

  Next, a toner remaining amount measuring method of the developing device in this embodiment will be described. Since the basic method for measuring the remaining amount of toner is the same as that in the first embodiment, only the characteristic part of this embodiment will be described later.

  In this embodiment, there are two types of difference detection sequences, and the driving method of the difference detection sequence is switched from a place where it is determined that the remaining amount of toner is small to some extent. First, a point in time when the toner is low is detected by a difference detection sequence and notified as a stage before the toner runs out (hereinafter referred to as toner low notification). After the low toner notification, a difference detection sequence using a supply roller rotation method capable of detecting a smaller amount of toner with high accuracy is performed to notify information such as toner exhaustion and development device replacement required. The first difference detection sequence is a difference detection sequence L, and the difference detection sequence performed after it is determined that the toner is low is called a difference detection sequence O.

The basic toner remaining amount measurement flow is the same as that in FIG. In the present embodiment, the execution timing of the difference detection sequence L performed for the first time is set as follows. An integrated value that is 80% less than the pixel count integrated value P0% that would be reached when the remaining toner life is 0% was defined as Pth. (See Equation 2)
Pth = P0% × 0.2... Formula 2
This Pth is reset after the difference detection sequence, as in the first embodiment. When the pixel count integrated value Pcount of the developing device reaches Pth, when the low toner notification is not notified, the difference detection sequence L is executed. If the low toner notification has been completed, the difference detection sequence O is executed.

  The movement during the difference detection sequence in this embodiment will be described. FIG. 12 shows the flow of the difference detection sequence L, and FIG. 13 shows the flow of the difference detection sequence O.

  First, the difference detection sequence L will be described. When the pixel count integrated value Pcount of the developing device reaches Pth, a difference detection sequence is executed after the development operation is completed (S005, S100). First, the developing drive can be transmitted (S301), and the first rotation is performed. Here, the supply roller is rotated in the forward direction (arrow R5 direction) for a predetermined time (S302), and then the supply roller is rotated in the reverse direction (arrow R6 direction) for a predetermined time (S303). In this embodiment, the rotation time in the forward direction is 15 seconds, and the rotation time in the reverse direction is 1 second. The rotation speed used here is the rotation speed normally used for image formation. During normal rotation, the toner is discharged from the urethane sponge layer of the supply roller by rotating for a long time, and the amount of toner in the supply roller is stabilized. After rotating for a predetermined time, in order to measure the remaining amount of toner, the developing roller is separated from the photosensitive drum, and the rotation of the developing roller and the supply roller is stopped (S304). Thereafter, the first capacitance Cv1 is measured (S305).

  Next, the developing drive can be transmitted again (S306), and the second rotation including the rotation of the supply roller in the positive direction (the direction of arrow R5), which is a rotation direction different from the first rotation, is performed. In this embodiment, a total of four rotations are performed in the order of the forward direction, reverse direction, forward direction, and reverse direction (S307, S308, S309, S310), and the rotation time is 1 second. The rotation speed used here is the same as the rotation speed used during normal image formation except for the difference in the rotation direction. Here, as will be described later, the toner is sucked into the urethane sponge layer of the supply roller by rotating in different directions a plurality of times. After the rotation for a predetermined time, in order to measure the remaining amount of toner, the developing roller is separated from the photosensitive drum, and the rotation of the developing roller and the supply roller is stopped (S311). Thereafter, the second capacitance Cv2 is measured (S312).

  The absolute value | Cv1−Cv2 | of the difference between the capacitances Cv1 and Cv2 detected in this way is calculated, and this is set as ΔC. The calculated ΔC is as shown in FIG. FIG. 11 shows the operation after calculating ΔC. ΔCth, which is the threshold value of the difference detection sequence L, is determined based on the target remaining amount for the low toner notification. When ΔC becomes equal to or less than ΔCth (S504 Yes), a low toner notification such as “Toner is low” or “Cartridge (development device) is nearing replacement” is performed (S505). Then, in order to determine the timing of the difference detection sequence O for the next toner exhaustion detection, a difference ΔD between ΔC and ΔCth is calculated (S506), and Pth is reset (S507). The setting method here will be described in detail later. On the other hand, when ΔC has not reached ΔCth or less (No in S504), a value obtained by adding P0% × 0.2 to Pth is reset. As described above, when the toner is used to some extent using the pixel count value, the difference detection sequence is executed again, so that the low toner notification can be performed with simple control. However, the pixel count method is not essential, and other toner remaining amount detection methods may be used. After Pth is reset, the process returns to S000 or S001 in FIG. 4 and image formation is continued until the pixel count integrated value Pcount reaches the newly set Pth (S206). When the toner reaches the Pth, if the low toner notification has not been made (S501 Yes), the second difference detection sequence L is executed. If the low toner notification has been made (S501 No), the difference detection sequence O is executed, and the calculated ΔC is calculated. The operation shown in FIG. 11 is performed again. In the difference detection sequence L, when ΔC has not reached ΔCth or less, the flow from S500 to S504 and S508 to S509 is repeated, and this operation is repeated until ΔC becomes ΔCth or less.

  Next, a method for determining the execution timing of the next difference detection sequence O at the time of low toner notification will be described with reference to FIG. A method for resetting Pth from ΔD will be described. The relationship between the remaining amount of toner and ΔC is as shown in FIG. An approximate straight line is calculated in advance from this relationship, and the approximate straight line data is stored in the storage means of the image forming main body. A toner amount Xg that can be used until the toner runs out is calculated from ΔD and prestored approximate linear data. When the toner amount Xg is used, a pixel count Px that is assumed to be integrated is calculated. Pth ′, which is a value obtained by adding Px to the previous Pth, is reset as a new Pth. When the pixel count integrated value Pcount reaches the reset Pth, the difference detection sequence O is performed.

  Next, the difference detection sequence O will be described. Until the first capacitance measurement, the difference detection sequence in the first embodiment is the same (S401, S402, S403, S404), but the second rotation is limited to one reverse rotation (S405, S406). The rotation time was 1 second, and the rotation speed used here was the same as the rotation speed used during normal image formation except for the difference in the rotation direction. Here, in order to perform the difference detection sequence in a shorter time, the toner is contained in the supply roller by only one reverse rotation. The process from the rotation for a predetermined time to the measurement of the second capacitance Cv2 is the same as that in the first embodiment (S407, S408).

  The absolute value | Cv1−Cv2 | of the difference between the capacitances Cv1 and Cv2 detected in this way is calculated, and this is set as ΔC. The calculated ΔC is as shown in FIG. The operation from the calculation of ΔC to the detection of toner out is the same as that in the first embodiment. Here, the threshold value ΔCth ′ of the difference detection sequence O is a value set separately from the threshold value ΔCth of the difference detection sequence L.

  As shown in FIG. 14, it can be seen that the slope of ΔC of the difference detection sequence O is larger than ΔC of the difference detection sequence L. This is because in the difference detection sequence L, the first rotation with a small amount of toner in the supply roller performs an operation including the toner by reverse rotation once, and the difference is small. However, since the difference detection sequence L does not take a difference from that after the operation of discharging the toner as in the normal rotation of the first embodiment, a more constant linear relationship with a wide range of the remaining amount of toner. Keep. This is because when toner is included in the supply roller in different rotation directions, the toner is always present at the suction position, but in one direction rotation, when the toner is low, the toner is at the suction position, and the supply roller from the discharge position. This is because a phenomenon occurs in which the product is not supplied after overcoming its top.

  As described above, first, in a state where there is a lot of toner, by using the supply roller rotation method of the difference sequence L, it is possible to accurately detect the stage before the toner runs out. Further, by using the supply roller rotation method of the difference detection sequence O for the toner out detection, the inclination of the capacitance difference ΔC with respect to the toner amount in the container increases. That is, the sensitivity of ΔC with respect to the toner amount in the container is increased, and the remaining amount of toner can be detected with higher accuracy. From the above, as in this embodiment, the rotation method in the difference detection sequence is changed according to the remaining amount of toner to be detected, so that it is possible to detect toner out with higher accuracy and to further shorten the rotation time of the supply roller. It is possible to execute the sequence.

  In order to obtain an effect that the remaining amount of toner can be measured with high accuracy even when the temperature / humidity environment changes, which is an effect common to the difference detection sequences of the first and second embodiments, the rotation direction of the supply roller It is necessary to change the amount of toner contained in the foam layer of the supply roller by changing. That is, by detecting the electrostatic capacity Cv1 after rotating the supply roller in the first rotation direction, and then detecting the electrostatic capacity Cv2 after rotating the supply roller in the second rotation direction, | Cv1 It is possible to perform the remaining toner measurement using −Cv2 | as a parameter.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Laser 5 (5a-5d) Developing device 6 Transfer roller 15 Fixing device 20 Cam 21 Developing container 23 Memory 24 Supply roller 25 Developing roller 30 Coupling gear 31 Supply gear 32 One-way clutch 33 Developing gear T Toner P transfer material

Claims (4)

A container having an opening and containing toner, and a toner carrier disposed in the opening of the container, having a first electrode member, carrying and transporting the toner, and electrostatic latent image A toner carrier to be supplied to the container, a toner supply member disposed inside the container, a second electrode member, and a toner supply member having a foam layer around the second electrode member, A developing device for supplying toner in the container to the toner carrier by rotating the toner supply member in pressure contact with the toner carrier; and the toner supply member in first and second directions. Drive means capable of rotationally driving, and detection means for detecting capacitance between the first electrode member and the second electrode member, wherein the toner supply member is moved to the first electrode by the drive means. After rotating for a predetermined time in the direction of Detecting the amount Cv1, further comprising detection means for detecting an electrostatic capacitance Cv2 after said toner supplying member was rotary predetermined time in said second direction by said driving means,
An informing means for informing that, when | Cv1-Cv2 | is below a threshold value, the remaining amount of toner is below a predetermined amount;
An image forming apparatus comprising: A container having an opening and containing toner, and a toner carrier disposed in the opening of the container, having a first electrode member, carrying and transporting the toner, and electrostatic latent image A toner carrier to be supplied to the container, a toner supply member disposed inside the container, a second electrode member, and a toner supply member having a foam layer around the second electrode member, A developing device that supplies the toner in the container to the toner carrier by rotating the toner supply member in pressure contact with the toner carrier; and
A mounting portion for detachably mounting the developing device;
Drive means capable of rotationally driving the toner supply member in first and second directions;
Detection means for detecting an electrostatic capacitance between the first electrode member and the second electrode member, after the toner supply member is rotated in the first direction for a predetermined time by the driving means; Detecting means for detecting electrostatic capacity Cv1, and further detecting electrostatic capacity Cv2 after rotating the toner supply member in the second direction for a predetermined time by the driving means;
An informing means for informing the user to replace the developing device when | Cv1-Cv2 |
An image forming apparatus comprising:   The driving means rotates in the first rotation direction for a predetermined time after rotating in the second direction for a predetermined time and before detecting the capacitance Cv2. The image forming apparatus according to 1 or 2.   2. The drive unit according to claim 1, wherein the drive unit rotates in the second direction for a predetermined time after rotating in the first direction for a predetermined time and before detecting the capacitance Cv1. Or the image forming apparatus according to 2;

Images