Powder supply device and image forming apparatus

Abstract

To provide a powder supply device and an image forming apparatus that can increase the accuracy in detecting the amount of powder.SOLUTION: A powder supply device such as a toner supply device 60 comprises: a pair of electrodes 92, 93 that are arranged on a powder conveyance path for conveying powder such as toner; and detection means such as a control unit 90 that detects the amount of powder in the powder conveyance path based on a change in the capacitance between the electrodes. The powder conveyance path has a vertical conveyance path 64 for conveying the powder in the vertical direction, and the pair of electrodes are arranged in the vertical conveyance path 64.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a powder supply device and an image forming apparatus.

Background Art

[0002] Conventionally, there has been known a powder supply device including a pair of electrodes disposed in a powder conveyance path for conveying powder, and detection means for detecting the amount of powder in the powder conveyance path based on a change in capacitance between the electrodes.

[0003] Patent Document 1 describes, as the powder supply device, a pair of arc-shaped electrodes arranged in parallel with the powder conveyance direction in a cylindrical horizontal conveyance path for horizontally conveying powder as viewed from the powder conveyance direction.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there has been room for improvement in the detection accuracy of the powder amount.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides a powder supply device including a pair of electrodes disposed in a powder conveyance path for conveying powder, and detection means for detecting the amount of powder in the powder conveyance path based on a change in capacitance between the electrodes, wherein the powder conveyance path has a vertical conveyance path in which the powder is conveyed in the vertical direction by its own weight, the vertical conveyance path is configured such that a specified amount of toner is stored therein, and the pair of electrodes are disposed only on the lower end side of the vertical conveyance path. lead Vertical conveyance path, the powder conveyance path and a first horizontal conveyance path having one end inserted into the powder container, having an opening at the one end for receiving the powder from the powder container, and horizontally conveying the powder received from the opening toward the vertical conveyance path; and a second horizontal conveyance path for horizontally conveying the powder conveyed from the vertical conveyance path and is characterized in that.

Effects of the Invention

[0006] According to the present invention, the detection accuracy of the powder amount can be improved.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the present invention applied to a copying machine (hereinafter referred to as copying machine 500) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of the copying machine 500 according to the present embodiment. The copying machine 500 includes a copying machine apparatus main body (hereinafter referred to as printer unit 100), a paper feed table (hereinafter referred to as paper feed unit 200), and a scanner (hereinafter referred to as scanner unit 400) attached on the printer unit 100.

[0009] In a toner container housing portion 70 provided above the printer unit 100, four developer container corresponding to each color (yellow, magenta, cyan, black), that is, toner containers 32 (Y, M, C, K) which are powder containers are detachably (exchangeably) installed. An intermediate transfer unit 85 is disposed below the toner container housing portion 70.

[0010] The intermediate transfer unit 85 is composed of an intermediate transfer belt 48, four primary transfer bias rollers 49 (Y, M, C, K), a secondary transfer backup roller 82, a plurality of tension rollers, an intermediate transfer cleaning device, and the like. The intermediate transfer belt 48 is stretched and supported by a plurality of roller members, and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of the secondary transfer backup roller 82 which is one of the plurality of roller members.

[0011] In the printer unit 100, four image forming units 46 (Y, M, C, K) which are image forming means corresponding to each color are arranged in parallel so as to face the intermediate transfer belt 48. Further, below the four toner containers 32 (Y, M, C, K), four toner supply devices 60 (Y, M, C, K) corresponding to each are arranged. Then, the toner stored in the toner containers 32 (Y, M, C, K) is supplied (refilled) into the developing device (powder material using unit) which is the developing means of the image forming unit 46 (Y, M, C, K) corresponding to each color by the corresponding toner supply device 60 (Y, M, C, K).

[0012] Also, as shown in FIG. 1, the printer unit 100 includes an exposure device 47 which is latent image forming means below the four image forming units 46. The exposure device 47 exposes the surface of the photoreceptor 41 described later based on the image information of the document image read by the scanner unit 400 or the image information input from an external device such as a personal computer, and forms an electrostatic latent image on the surface of the photoreceptor 41. The exposure device 47 provided in the printer unit 100 uses a laser beam scanner method using a laser diode, but other configurations such as using an LED array may be used as the exposure means.

[0013] FIG. 2 is a schematic diagram showing the schematic configuration of the image forming unit 46Y corresponding to yellow. The image forming unit 46Y includes a drum-shaped photoreceptor 41Y as an image carrier. Further, the image forming unit 46Y is configured such that a charging roller 44Y as a charging means, a developing device 50Y as a developing means, a photoreceptor cleaning device 42Y, a discharging device, etc. are disposed around the photoreceptor 41Y. Then, on the photoreceptor 41Y, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed, and a yellow image is formed on the photoreceptor 41Y.

[0014] Note that the other three image forming units 46 (M, C, K) have substantially the same configuration as the image forming unit 46Y corresponding to yellow, except that the color of the toner used is different. Images of colors corresponding to their respective toners are formed on the respective photoreceptors 41 (M, C, K). Hereinafter, the description of the other three image forming units 46 (M, C, K) will be appropriately omitted, and only the description of the image forming unit 46Y corresponding to yellow will be given.

[0015] The photoreceptor 41Y is rotationally driven in the clockwise direction in FIG. 2 by a drive motor. And at the position facing the charging roller 44Y, the surface of the photoreceptor 41Y is uniformly charged (charging process). Then, the surface of the photoreceptor 41Y reaches the irradiation position of the laser beam L emitted from the exposure device 47, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (exposure process). Then, the surface of the photoreceptor 41Y reaches the position facing the developing device 50Y, and the electrostatic latent image is developed at this position, and a yellow toner image is formed (developing process).

[0016] The four primary transfer bias rollers 49 (Y, M, C, K) of the intermediate transfer unit 85 sandwich the intermediate transfer belt 48 between the photoreceptors 41 (Y, M, C, K) to form a primary transfer nip. And a transfer bias opposite to the polarity of the toner is applied to the primary transfer bias roller 49 (Y, M, C, K).

[0017] On the surface of the photoreceptor 41Y on which the toner image is formed in the developing process, it reaches the primary transfer nip facing the primary transfer bias roller 49Y with the intermediate transfer belt 48 interposed therebetween, and at this primary transfer nip, the toner image on the photoreceptor 41Y is transferred onto the intermediate transfer belt 48 (primary transfer process). At this time, a small amount of untransferred toner remains on the photoreceptor 41Y. The surface of the photoreceptor 41Y on which the toner image has been transferred to the intermediate transfer belt 48 at the primary transfer nip reaches the facing position with the photoreceptor cleaning device 42Y. At this facing position, the untransferred toner remaining on the photoreceptor 41Y is mechanically recovered by the cleaning blade 42a (cleaning process). Finally, the surface of the photoreceptor 41Y reaches the facing position with the charge eliminating device, and at this position, the residual potential on the photoreceptor 41Y is removed. Thus, a series of image forming processes performed on the photoreceptor 41Y is completed.

[0018] Such an image forming process is also performed in the same manner as in the yellow image forming unit 46Y in the other image forming units 46 (M, C, K). That is, the laser beam L based on the image information is irradiated from the exposure device 47 disposed below the image forming units 46 (M, C, K) onto the photoreceptors 41 (M, C, K) of the respective image forming units 46 (M, C, K). Specifically, the exposure device 47 emits the laser beam L from a light source and irradiates each photoreceptor 41 (M, C, K) through a plurality of optical elements while scanning the laser beam L with a polygon mirror driven to rotate. Thereafter, the toner images of respective colors formed on the photoreceptors 41 (M, C, K) through the developing process are transferred onto the intermediate transfer belt 48.

[0019] At this time, the intermediate transfer belt 48 travels in the direction of the arrow in FIG. 1 and sequentially passes through the primary transfer nips of the respective primary transfer bias rollers 49 (Y, M, C, K). As a result, the toner images of respective colors on the photoreceptors 41 (Y, M, C, K) are superposed and primarily transferred onto the intermediate transfer belt 48, and a color toner image is formed on the intermediate transfer belt 48.

[0020] The intermediate transfer belt 48 on which toner images of various colors are superposed and transferred to form a color toner image reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 48 between itself and the secondary transfer roller 89 to form a secondary transfer nip. Then, the color toner image formed on the intermediate transfer belt 48 is transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 48. The intermediate transfer belt 48 that has passed through the secondary transfer nip reaches the position of the intermediate transfer cleaning device, and the untransferred toner on its surface is recovered, and a series of transfer processes performed on the intermediate transfer belt 48 ends.

[0021] Next, the movement of the recording medium P will be described. The recording medium P conveyed to the above-described secondary transfer nip is conveyed from the paper feed tray 26 of the paper feed unit 200 disposed below the printer unit 100 via the paper feed roller 27, the registration roller pair 28, and the like. Specifically, a plurality of recording media P are stacked and stored in the paper feed tray 26. Then, when the paper feed roller 27 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is conveyed toward the roller nip formed by the two rollers of the registration roller pair 28.

[0022] The recording medium P conveyed to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 where the rotational drive has stopped. Then, in accordance with the timing when the color toner image on the intermediate transfer belt 48 reaches the secondary transfer nip, the registration roller pair 28 is rotationally driven, and the recording medium P is conveyed toward the secondary transfer nip. Thereby, a desired color toner image is transferred onto the recording medium P.

[0023] The recording medium P onto which the color toner image is transferred by the secondary transfer nip is conveyed to the position of the fixing device 86. In the fixing device 86, the color toner image transferred onto the surface is fixed onto the recording medium P by the heat and pressure applied by the fixing belt and the pressure roller. The recording medium P that has passed through the fixing device 86 is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 29. The recording medium P discharged outside the apparatus by the paper discharge roller pair 29 is sequentially stacked on the stack unit 30 as an output image. Thus, a series of image forming processes in the copying machine 500 is completed.

[0024] Next, the configuration and operation of the developing device 50 in the image forming unit 46 will be described in more detail. Here, the image forming unit 46Y corresponding to yellow will be taken as an example for the description, but the same applies to the other color image forming units 46 (M, C, K).

[0025] As shown in FIG. 2, the developing device 50Y includes a developing roller 51Y, a doctor blade 52Y, two developer conveying screws 55Y, a toner density detection sensor 56Y, and the like. The developing roller 51Y faces the photoreceptor 41Y, and the doctor blade 52Y faces the developing roller 51Y. The two developer conveying screws 55Y are disposed in two developer storage portions (53Y, 54Y). The developing roller 51Y is composed of a magnet roller fixed inside and a sleeve that rotates around the magnet roller. A two-component developer G composed of a carrier and toner is stored in the first developer storage portion 53Y and the second developer storage portion 54Y. The second developer storage portion 54Y communicates with the toner dropping conveyance path 66Y through an opening formed above it. The toner density detection sensor 56Y detects the toner density in the developer G in the second developer storage portion 54Y.

[0026] The developer G in the developing device 50 is circulated between the first developer storage section 53Y and the second developer storage section 54Y while being agitated by two developer conveyance screws 55Y. The developer G in the first developer storage section 53Y is supplied and carried onto the sleeve surface of the developing roller 51Y by the magnetic field formed by the magnet roller in the developing roller 51Y while being conveyed to one side of the developer conveyance screw 55Y. The sleeve of the developing roller 51Y is rotationally driven in the counterclockwise direction as indicated by the arrow in FIG. 2, and the developer G carried on the developing roller 51Y moves on the developing roller 51Y as the sleeve rotates. At this time, the toner in the developer G is charged to a potential of the opposite polarity to the carrier by frictional charging with the carrier in the developer G, electrostatically adsorbed to the carrier, and carried on the developing roller 51Y together with the carrier attracted by the magnetic field formed on the developing roller 51Y.

[0027] The developer G carried on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the doctor section where the doctor blade 52Y and the developing roller 51Y face each other. The amount of the developer G on the developing roller 51Y is adjusted to an appropriate amount when passing through the doctor section, and then it is conveyed to the developing area which is the facing position with the photoreceptor 41Y. In the developing area, the toner in the developer G is adsorbed to the latent image formed on the photoreceptor 41Y by the developing electric field formed between the developing roller 51Y and the photoreceptor 41Y. The developer G remaining on the surface of the developing roller 51Y after passing through the developing area reaches above the first developer storage section 53Y as the sleeve rotates and is detached from the developing roller 51Y at this position.

[0028] The developer G in the developing device 50Y is adjusted so that the toner concentration is within a predetermined range. Specifically, according to the consumption amount of the toner in the developer G in the developing device 50Y due to development, the toner stored in the toner container 32Y is replenished into the second developer storage section 54Y via a toner replenishing device 60Y described later. The toner replenished into the second developer storage section 54Y is circulated between the first developer storage section 53Y and the second developer storage section 54Y while being mixed and agitated with the developer G by two developer conveyance screws 55Y.

[0029] Next, the toner supply device 60 (Y, M, C, K) will be described. FIG. 3 is a schematic diagram showing a state in which the toner container 32Y is installed in the toner supply device 60Y which is a powder supply device, and FIG. 4 is a schematic perspective view showing a state in which four toner containers 32 (Y, M, C, K) are installed in the toner container housing portion 70.

[0030] The toner in each toner container 32 (Y, M, C, K) installed in the toner container housing portion 70 of the printer unit 100 is appropriately supplied into each developing device 50 (Y, M, C, K) according to the toner consumption in the developing devices 50 (Y, M, C, K) of each color. At this time, the toner in each toner container 32 (Y, M, C, K) is supplied by the toner supply device 60 (Y, M, C, K) provided for each toner color. Note that the four toner supply devices 60 (Y, M, C, K) and the toner containers 32 (Y, M, C, K) have substantially the same structure except that the colors of the toner used in the image forming process are different. For this reason, hereinafter, only the toner supply device 60Y and the toner container 32Y corresponding to yellow will be described, and the description of the toner supply devices 60 (M, C, K) and the toner containers 32 (M, C, K) corresponding to the other three colors will be omitted as appropriate.

[0031] The toner supply device 60 (Y, M, C, K) is composed of a toner container housing portion 70, a toner conveyance path as a powder conveyance path for conveying the toner in the toner container 32 to the developing device 50 (Y, M, C, K) which is a powder supply target device, a first drive unit 91 (Y, M, C, K), etc. The toner conveyance path has a conveyance nozzle 611 (Y, M, C, K) which is a first horizontal conveyance path, a vertical conveyance path 64 (Y, M, C, K), a relay conveyance path 65 (Y, M, C, K) which is a second horizontal conveyance path, and a toner dropping conveyance path 66 (Y, M, C, K).

[0032] When the toner container 32Y as a powder container moves in the direction of arrow Q in Fig. 4 and is attached to the toner container housing portion 70 of the printer unit 100, the conveyance nozzle 611Y of the toner supply device 60Y is inserted from the container tip side of the toner container 32Y in conjunction with the attachment operation. As a result, the inside of the toner container 32Y and the inside of the conveyance nozzle 611Y communicate with each other.

[0033] The toner container 32Y is a substantially cylindrical toner bottle. And it is mainly composed of a container tip side cover 34Y that is non-rotatably held in the toner container housing portion 70, and a container body 33Y in which a container gear 301Y is integrally formed. The container body 33Y is held so as to be rotatable relative to the container tip side cover 34Y.

[0034] The toner container housing portion 70 is mainly composed of a container cover receiving portion 73, a container receiving portion 72, and an insertion port forming portion 71. The container cover receiving portion 73 is a portion for holding the container tip side cover 34Y of the toner container 32Y, and the container receiving portion 72 is a portion for holding the container body 33Y of the toner container 32Y. Also, the insertion port forming portion 71 is a portion that forms an insertion port during the attachment operation of the container receiving portion 72 and the toner container 32Y. When the main body cover installed on the front side of the copying machine 500 (the front side in the direction perpendicular to the paper surface of Fig. 1) is opened, the insertion port forming portion 71 of the toner container housing portion 70 is exposed. Then, with the longitudinal direction of each toner container 32 (Y, M, C, K) being the horizontal direction, the attachment / detachment operation of each toner container 32 (Y, M, C, K) (the attachment / detachment operation with the longitudinal direction of the toner container 32 as the attachment / detachment direction) is performed from the front side of the copying machine 500. Note that the set cover 608Y in Fig. 3 is a part of the container cover receiving portion 73 of the toner container housing portion 70.

[0035] The container receiving portion 72 is formed such that its length in the longitudinal direction is substantially equal to the length of the container body 33Y in the longitudinal direction. Further, the container cover receiving portion 73 is provided on the container tip side in the longitudinal direction (attachment / detachment direction) of the container receiving portion 72, and the insertion port forming portion 71 is provided on one end side in the longitudinal direction of the container receiving portion 72. Therefore, with the attachment operation of the toner container 32Y, after passing through the insertion port forming portion 71, the container tip side cover 34Y slides on the container receiving portion 72 for a while and is then attached to the container cover receiving portion 73.

[0036] In a state where the container tip side cover 34Y is attached to the container cover receiving portion 73, rotational drive is input from the first drive portion 91Y constituted by a drive motor, drive gears, etc. to the container gear 301Y provided in the container body 33Y. As a result, the container body 33Y is rotationally driven in the direction of arrow A in FIG. 3. By the rotation of the container body 33Y itself, the toner accommodated inside the container body 33Y is conveyed from the left side to the right side in FIG. 3 along the longitudinal direction of the container body by the spiral protrusion 302Y formed spirally on the inner peripheral surface of the container body 33Y.

[0037] On the container tip side cover side (right side in the figure) of the container body 33, there is provided a lifting portion that lifts upward the toner conveyed to the container tip side cover side by the rotation of the container body 33. By this lifting portion, the toner is lifted above the conveyance nozzle 611 inserted into the toner container and falls into a nozzle opening 610 such as an opening provided at the toner container side end of the conveyance nozzle 611Y (see FIG. 5), so that the toner is supplied into the conveyance nozzle 611.

[0038] Inside the transfer nozzle 611Y, a transfer screw 614Y is arranged. When rotational drive is input from the first drive unit 91Y to the transfer screw gear 605Y, the transfer screw 614Y rotates to horizontally transfer the toner supplied into the transfer nozzle 611Y. The downstream end in the transfer direction of the transfer nozzle 611Y is connected to the vertical transfer path 64Y, and the toner transferred by the transfer screw 614Y is transferred to the relay transfer path 65Y by self-weight falling through the vertical transfer path 64Y. Inside the relay transfer path 65Y, a transfer screw 615Y is arranged. When rotational drive is input from the second drive unit 80Y, the transfer screw 615Y rotates to horizontally transfer the toner supplied into the relay transfer path 65Y. The downstream end in the transfer direction of the relay transfer path 65Y is connected to the toner falling transfer path 66Y, and the toner transferred by the transfer screw 615Y is replenished into the developing device 50Y (second developer storage unit 54Y) by self-weight falling through the toner falling transfer path 66Y.

[0039] The toner containers 32 (Y, M, C, K) are each replaced with new ones when they reach the end of their life (when almost all of the toner they contain has been consumed and they are empty). A handle portion 303 is provided at an end of the toner container 32 on the side opposite to the container tip side cover 34 in the longitudinal direction of the toner container 32. During replacement, the operator can remove the mounted toner container 32 by grasping and pulling out the handle portion 303.

[0040] Based on the image information used in the exposure apparatus 47 described above, the control unit 90 calculates the toner consumption amount, and there may be a case where the control unit 90 determines that the supply of toner to the developing device 50Y is required. Also, there may be a case where the control unit 90 detects that the toner concentration in the developing device 50Y has decreased based on the detection result of the toner concentration detection sensor 56Y. In these cases, the first drive unit 91Y is rotationally driven under the control of the control unit 90, and the container body 33Y of the toner container 32Y and the conveying screws 614Y and 615Y are rotated for a predetermined time to supply toner to the developing device 50Y. Further, since toner is supplied to the developing device 50Y by rotating the conveying screw 615Y disposed in the relay conveyance path 65Y, the toner supply amount from the toner container 32Y can be accurately calculated by detecting the rotation speed of the conveying screw 615Y.

[0041] This toner supply device 60Y controls the toner supply amount to the developing device 50Y according to the rotation speed of the conveying screw 615Y. Also, a toner storage part such as a toner hopper may be provided, and the toner supply amount to the developing device 50Y may be controlled by controlling the toner conveyance amount from this toner storage part to the developing device 50Y. However, if it is configured not to provide a toner storage part like the toner supply device 60Y of the present embodiment, the toner supply device 60Y can be miniaturized, and the entire copying machine 500 can be miniaturized.

[0042] Also, this toner supply device 60Y is configured to convey the toner in the conveying nozzle 611Y and the relay conveyance path 65Y by the conveying screws 614Y and 615Y, but the configuration for conveying the toner is not limited to the screw member. A configuration that applies a conveying force by means other than the screw member, such as a configuration that generates negative pressure using a powder pump, may also be used.

[0043] As a method for detecting that the toner in the toner container has run out (toner end), there are methods of predicting based on the number of times or the time of the toner discharge operation from the toner container 32Y, or the amount of toner developed from the developing device 50 onto the photoreceptor. Also, a sub-hopper for temporarily storing the toner discharged from the toner container 32Y is provided, and there is also a method of detecting the height of the toner temporarily stored in the sub-hopper with a piezoelectric sensor and determining that the toner in the toner container has run out. However, the method of predicting based on the number of times or the time of the toner discharge operation from the toner container 32Y, or the amount of toner developed from the developing device 50 onto the photoreceptor has poor accuracy because the toner supply amount or the consumption amount varies due to errors such as environmental conditions.

[0044] Also, in the method of determining toner end with a piezoelectric sensor provided in the sub-hopper, the vibration condition changes and the presence or absence of toner is detected by the change in the pressure applied to the sensor part when toner is in contact with the sensor part of the vibrated piezoelectric sensor and when it is not in contact. Then, when the toner in the toner container runs out, toner is no longer supplied to the sub-hopper, and the toner height in the sub-hopper decreases, the piezoelectric sensor detects the absence of toner. Thus, it is possible to detect that the toner in the toner container has run out. However, in toner end detection with a piezoelectric sensor, if toner adheres to the sensor part, the vibration condition changes, and there is a possibility that highly accurate detection cannot be performed. For this reason, there is a problem that it is necessary to clean the sensor part regularly. Also, due to the fluidity of the toner, the pressure applied to the sensor part is different, and the vibration condition changes, so highly accurate detection cannot be performed.

[0045] Also, a technique is known in which a pair of electrodes are arranged in parallel at a predetermined interval with respect to the lower part of the toner container, and the remaining amount of toner in the toner container is detected based on the capacitance between the pair of electrodes. However, when the toner container becomes empty, it is replaced with a full toner container. Therefore, due to the shape error for each toner container, the distance between the pair of electrodes and the toner container fluctuates, and the relationship between the capacitance and the toner amount is different for each toner container to be replaced, and there is a possibility that accurate toner end detection cannot be performed.

[0046] Also, in a configuration where the toner container 32 rotates as in this embodiment, eccentricity may occur during the rotation of the toner container 32. With such eccentricity, the distance between the pair of electrodes and the toner container 32 fluctuates, the relationship between the toner amount and the capacitance fluctuates, and there is a possibility that accurate toner end detection cannot be performed.

[0047] Also, since the toner is a powder, unlike a liquid, there is a possibility that the amount varies in the horizontal direction. Therefore, in a configuration where the capacitance of a part of the toner container is detected by a pair of electrodes, the following false detection may occur. That is, when the toner amount at the location where the capacitance is detected is less than that at other locations, there is a false detection that the toner in the toner container is almost exhausted even though there is sufficient toner in the toner container.

[0048] Therefore, it is also conceivable to detect the capacitance of the entire toner container with a pair of electrodes. However, the toner container has a certain size so that it is not frequently replaced. Therefore, when detecting the capacitance of the entire toner container with a pair of electrodes, the electrodes become larger in size, leading to an increase in cost. Also, the distance between the electrodes may become too large, and there is a possibility that the capacitance cannot be detected sensitively.

[0049] In Patent Document 1, a configuration is formed in which a pair of electrodes are arranged in the conveying nozzle 611Y which is a horizontal conveying path, and the remaining toner amount in the toner container is detected based on the change in the capacitance of the horizontal conveying path. In Patent Document 1, a pair of electrodes having an arc shape when viewed from the toner conveying direction outside the cylindrical conveying nozzle 611Y and having a predetermined length in the toner conveying direction are installed in parallel with the toner conveying direction.

[0050] In Patent Document 1, the conveyance nozzle is kept filled with toner. When the toner in the toner container 32 runs out and the toner supplied to the conveyance nozzle 611 runs out, the amount of toner in the conveyance nozzle decreases. When the amount of toner in the conveyance nozzle decreases, the capacitance in the conveyance nozzle changes. By detecting this change in capacitance in the conveyance nozzle with a pair of electrodes, the toner end is detected.

[0051] However, since the conveyance nozzle 611 is a horizontal conveyance path that conveys toner in the horizontal direction, when the amount of toner in the conveyance nozzle 611 decreases, the toner height decreases in a direction perpendicular to the conveyance direction. In a configuration where a pair of arc-shaped electrodes are arranged, the electric field lines between the electrode ends with the shortest electrode distance become the densest, and the sensitivity to the change in the powder amount becomes the highest. As a result, when the height of the toner changes where the electric field lines between these electrode ends are dense, the capacitance changes greatly, and the amount of toner in the conveyance nozzle can be detected with high sensitivity. However, when the height of the toner changes elsewhere, the capacitance does not change much, and the powder amount cannot be detected with high sensitivity.

[0052] Therefore, in the present embodiment, a pair of electrodes are arranged in the vertical conveyance path 64Y that conveys toner in the vertical direction, and the remaining amount of toner in the toner container 32 is detected based on the change in capacitance of the vertical conveyance path 64Y. Hereinafter, the characteristic parts of the present embodiment will be described with reference to the drawings.

[0053] FIG. 5 is a cross-sectional view of the main part of the toner supply device 60, and FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5. As shown in FIG. 5, outside the cylindrical vertical conveyance path 64, electrodes 92 and 93 having an arc shape when viewed from the vertical direction (see FIG. 6) and having a predetermined length in the vertical direction (see FIG. 5) are installed in parallel with the toner conveyance direction (toner falling direction) of the vertical conveyance path 64. The electrodes 92 and 93 can be made of any material as long as it is a conductive member. As shown in FIG. 6, the electrodes 92 and 93 may be arranged at a predetermined interval with respect to the outer peripheral surface of the vertical conveyance path 64, or the pair of electrodes 92 and 93 may be in close contact with the outer peripheral surface of the vertical conveyance path. When the pair of electrodes 92 and 93 are in close contact with the outer peripheral surface of the vertical conveyance path, a conductive tape may be used as the pair of electrodes 92 and 93.

[0054] As shown in FIG. 6, by arranging the electrodes at a predetermined interval with respect to the outer peripheral surface of the vertical conveyance path 64, even if the vertical conveyance path 64 expands thermally, the distance between the pair of electrodes does not change. It is possible to prevent the capacitance with respect to the toner amount from changing, and it is possible to stably detect the toner end.

[0055] On the other hand, by bringing the pair of electrodes 92 and 93 into close contact with the outer peripheral surface of the conveyance path, the distance between the electrodes can be reduced, and the sensitivity can be increased. Also, when arranging the electrodes 92 and 93 at a predetermined interval with respect to the outer peripheral surface of the vertical conveyance path 64, it is necessary to provide a holder or the like for holding the electrodes 92 and 93, but when bringing the pair of electrodes 92 and 93 into close contact with the outer peripheral surface of the conveyance path, it can be directly held on the vertical conveyance path 64 by adhesion or the like. As a result, the number of parts can be reduced, and cost reduction and the like can be achieved.

[0056] Whether to bring the pair of electrodes 92 and 93 into close contact with the outer peripheral surface of the vertical conveyance path 64 or to arrange them at a predetermined distance from the outer peripheral surface of the vertical conveyance path 64 may be appropriately selected according to the configuration of the apparatus or the like. Also, a part of the vertical conveyance path 64 may be constituted by a pair of electrodes.

[0057] As shown in FIG. 5, the pair of electrodes 92 and 93 are each connected to a control unit 90 which is a detection means. The control unit 90 applies a bias to the electrodes 92 and 93 and measures the capacitance. The capacitance measurement method may be a general method. In this embodiment, it is measured by the charging method (applying a constant voltage or constant current between the electrodes and measuring the capacitance from the relationship between the time to reach the charging point and the voltage or current). The capacitance measured here changes according to the dielectric constant between the electrodes. The toner has a higher dielectric constant than air. Therefore, the dielectric constant changes according to the amount of toner in the vertical conveyance path 64. Thus, the capacitance changes according to the amount of toner in the vertical conveyance path 64. Thereby, by measuring the capacitance, the amount of toner in the vertical conveyance path 64 can be detected.

[0058] In this embodiment, a prescribed amount of toner is stored in the vertical conveyance path 64. Specifically, until the capacitance in the vertical conveyance path 64 detected by the pair of electrodes 92 and 93 becomes equal to or greater than the upper threshold value, the control unit 90 executes a toner supply operation to supply the toner in the toner container 32 to the vertical conveyance path 64. When the toner supply operation is executed, the first drive unit 91 is driven to drive the conveyance screw 614 in the container main body 33 and the conveyance nozzle 611, and the toner in the toner container 32 is supplied to the vertical conveyance path 64. The control unit 90 stops the toner supply operation when the capacitance becomes equal to or greater than the upper threshold value and a predetermined amount or more of toner is stored in the vertical conveyance path 64.

[0059] As described above, when the control unit 90 determines that toner replenishment to the developing device 50 is required, the second drive unit 80 drives the conveyance screw 615 in the relay conveyance path 65 to execute a toner replenishment operation to replenish the developing device 50 with toner. When such a replenishment operation is repeated and the capacitance in the vertical conveyance path 64 detected by the pair of electrodes 92 and 93 falls below the lower threshold value, the control unit 90 performs the above-described toner supply operation. The control unit 90 supplies the toner in the toner container 32 to the vertical conveyance path 64 until the capacitance becomes equal to or greater than the upper threshold value.

[0060] If the capacitance in the vertical conveyance path 64 detected by the pair of electrodes 92 and 93 does not exceed the upper threshold value even when the toner supply operation is performed for a prescribed time, the control unit 90 determines that the toner has ended.

[0061] In the above description, the conveying screw 614 in the conveying nozzle and the conveying screw 615 in the relay conveying path are driven by separate driving units, but they may be driven simultaneously by a single driving unit. When driving simultaneously, the toner conveyance amount of the conveying screw 614 in the conveying nozzle is also increased, as well as the toner conveyance amount of the conveying screw 615 in the relay conveying path. For example, by making the rotation speed of the conveying screw 614 in the conveying nozzle faster than the rotation speed of the conveying screw 615 in the relay conveying path, the toner conveyance amount of the conveying screw 614 in the conveying nozzle and the toner conveyance amount of the conveying screw 615 in the relay conveying path can both be increased.

[0062] In this way, by increasing the toner conveyance amount of the conveying screw 614 in the conveying nozzle and also increasing the toner conveyance amount of the conveying screw 615 in the relay conveying path, toner gradually accumulates in the vertical conveying path 64. When there is sufficient toner in the toner container 32, the capacitance in the vertical conveying path 64 detected by the pair of electrodes 92, 93 increases. Alternatively, when the toner height in the vertical conveying path 64 becomes above the upper ends of the pair of electrodes 92, 93, the capacitance in the vertical conveying path 64 detected by the pair of electrodes 92, 93 reaches the upper limit saturation.

[0063] When there is almost no toner left in the toner container 32, the amount of toner supplied from the conveying nozzle 611 to the vertical conveying path 64 decreases, and the amount of toner in the vertical conveying path 64 decreases. As a result, the capacitance in the vertical conveying path 64 detected by the pair of electrodes 92, 93 decreases. And when the capacitance in the vertical conveying path 64 detected by the pair of electrodes 92, 93 falls below the threshold value, the control unit 90 determines that it is toner end.

[0064] Figure 7 is a graph showing the relationship between the capacitance and the toner amount in the vertical conveying path 64. In the vertical conveying path 64, when the amount of toner in the vertical conveying path 64 decreases, the direction of change in the height of the toner in the vertical conveying path is the toner conveying direction (vertical direction) in the vertical conveying path.

[0065] As shown in Fig. 6, also in this embodiment, the pair of electrodes 92 and 93 are arc-shaped. Similar to Patent Document 1, the distance between the ends of the electrodes is the shortest, and in the region of the dashed line in Fig. 6, the electric lines of force are the densest, and the change in capacitance with respect to the change in toner amount is large. Therefore, in the region of the dashed line in Fig. 6, the change in electrostatic capacitance with respect to the change in toner amount (toner height) becomes large, and the detection sensitivity becomes high.

[0066] Fig. 8 is a diagram showing an example in which a pair of arc-shaped electrodes are arranged in the horizontal conveyance path. As shown in Fig. 8(a), when the pair of electrodes are arranged in the vertical direction, even if the toner height fluctuates in the region indicated by the hatching in the figure, there is no fluctuation in the toner amount in the region with high detection sensitivity indicated by the solid line in the figure. Therefore, the detection sensitivity becomes low in the hatched region in the figure.

[0067] Also, when the pair of electrodes shown in Fig. 8(b) are arranged in the horizontal direction, even if the toner height fluctuates in the region indicated by the hatching in the figure, there is no fluctuation in the toner amount in the region with high detection sensitivity indicated by the solid line in the figure. Therefore, the detection sensitivity becomes low in the hatched region in the figure.

[0068] Also, when the pair of electrodes shown in Fig. 8(c) are arranged in the horizontal direction, even if the toner height fluctuates in the region indicated by the hatching in the figure, there is no fluctuation in the toner amount in the region with high detection sensitivity indicated by the solid line in the figure. Therefore, the detection sensitivity becomes low in the hatched region in the figure.

[0069] Also, in Fig. 8(b) and Fig. 8(c), when the toner height fluctuates outside the hatched region in the figure, there is a fluctuation in the toner amount only in one of the two regions with high detection sensitivity. Therefore, even outside the hatched region, it cannot be said that the detection sensitivity is high.

[0070] Thus, when a pair of arc-shaped electrodes are arranged in the horizontal conveyance path, the direction of change in toner height becomes perpendicular to the toner conveyance direction. Therefore, no matter how the electrodes are arranged, there will be a toner height at which there is no fluctuation in the toner amount in the region with high detection sensitivity. As a result, there will always be a toner height with low detection sensitivity.

[0071] On the other hand, in the vertical conveyance path 64, the direction of change in toner height is the same as the toner conveyance direction in the vertical conveyance path. Since the pair of electrodes 92 and 93 are installed parallel to the toner conveyance direction of the vertical conveyance path 64, the region between the ends of the electrode with high detection sensitivity shown by the solid line in the figure extends in the toner conveyance direction. As a result, in the present embodiment where a pair of electrodes are arranged in the vertical conveyance path 64, in the region sandwiched between the pair of electrodes 92 and 93, no matter what the toner height is, when the toner height fluctuates, the height always fluctuates in the region with high detection sensitivity (between the electrode ends). Therefore, as shown in FIG. 7, in the height range (h2 to h1) of the region sandwiched between the pair of electrodes 92 and 93, no matter what the toner height is, the toner amount can be detected with a certain high sensitivity (large slope). Thus, compared with the case where a pair of electrodes 92 and 93 are arranged in the horizontal conveyance path, the toner amount can be detected better.

[0072] Also, in the horizontal conveyance path, due to the height, a region with high detection sensitivity and a region with low detection sensitivity are generated, so the relationship between the capacitance and the toner amount does not become a proportional relationship. On the other hand, when a pair of electrodes 92 and 93 are arranged in the vertical conveyance path 64, as can be seen from FIG. 7, the relationship between the capacitance and the toner amount can be made a proportional relationship. Thereby, using a linear function, the toner amount can be easily and accurately grasped from the detected capacitance. Thereby, highly accurate toner amount detection can be performed, and the toner end can be detected accurately.

[0073] In order to detect the toner end in the vertical conveyance path 64, this toner supply device 60 stores toner in the vertical conveyance path 64. If too much toner is stored in this vertical conveyance path 64, there is a risk that the toner will be clogged on the lower side of the vertical conveyance path 64 due to the self-weight of the toner. Therefore, as shown in FIG. 7, the pair of electrodes 92 and 93 are preferably arranged on the lower end side of the vertical conveyance path 64 so as not to store too much toner in the vertical conveyance path 64.

[0074] Also, a loosening member 616 as shown in FIG. 9 may be provided in the vertical conveyance path 64. The loosening member 616 shown in Fig. 9 has a coil spring shape in which a wire is wound in a spiral shape, and is made of a non-conductive member (insulating member) so as not to affect the capacitance detected by the pair of electrodes 92 and 93. A crank portion is provided on the conveying screw 614 in the conveying nozzle, and the hook portion 616a of the loosening member 616 is hooked on this crank portion. When the conveying screw 614 rotates, the loosening member 616 moves up and down, and the toner in the vertical conveying path 64 can be loosened. Also, by loosening the toner in the vertical conveying path with the loosening member 616, the height of the toner in the vertical conveying path can be made constant, and the toner amount can be accurately detected by the pair of electrodes 92 and 93.

[0075] A crank portion may be provided on the conveying screw 615 in the relay conveying path 65, and the loosening member 616 may be attached to this crank portion to move the loosening member 616 up and down. However, it is preferable to provide the loosening member 616 on the conveying screw 614 in the conveying nozzle because the loosening member 616 can be held in a suspended form and the posture of the loosening member 616 can be easily maintained. The loosening member 616 only needs to be in a shape that can loosen the toner, and is not limited to the shape shown in Fig. 9.

[0076] In this embodiment, the pair of electrodes 92 and 93 are formed in an arc shape along the outer diameter of the vertical conveying path 64, but the pair of electrodes 92 and 93 may be parallel flat plates. In the case of an arc shape, as described above, a region with high detection sensitivity between the ends of the electrodes with the shortest electrode distance and a region with low detection sensitivity between the centers of the electrodes with the longest electrode distance are generated. Therefore, there is a possibility that a difference occurs between the detected capacitance when the toner height in the vertical conveying path 64 is not uniform and the detected capacitance when the toner height is uniform. Specifically, when the toner height at the location corresponding to the center of the electrode is lower than the toner height at the location corresponding to the ends of the electrode, and when the toner height at the location corresponding to the ends of the electrode is lower than the toner height at the location corresponding to the center of the electrode, even with the same toner amount, the detected capacitance is different.

[0077] In the case of an arc shape, if the distance between the ends of the electrodes deviates even slightly from the specification due to assembly errors, the capacitance will vary significantly. As a result, there is a risk that the difference between the detected capacitance when the toner height in the vertical conveyance path 64 is not uniform and the detected capacitance when the toner height is uniform will increase.

[0078] On the other hand, by using a pair of electrodes 92, 93 as parallel plates, the detection sensitivity becomes constant, and there is an advantage that no difference occurs between the detected capacitance when the toner height in the vertical conveyance path 64 is not uniform and the detected capacitance when the toner height is uniform. Also, even if there are some assembly errors, the capacitance does not vary significantly, and there is an advantage that the pair of electrodes can be assembled roughly compared to the arc shape case.

[0079] On the other hand, by forming the pair of electrodes in an arc shape, there is an advantage that the amount of change in capacitance with respect to the change in toner amount (toner height) is larger than that of parallel plates, and the toner amount can be detected with high sensitivity. Therefore, if assembled accurately and means for making the toner height uniform such as a loosening member are used, very accurate toner end detection can be performed.

[0080] Next, a modified example of the toner supply device 60 will be described.

[0081] [Modified Example 1] FIG. 10 is a schematic configuration diagram of a toner supply device 160 according to Modified Example 1. The toner supply device 160 according to Modified Example 1 has a vertical conveyance path 161 provided with a toner supply port 73W through which toner is supplied from the toner container 32, a horizontal conveyance path 162, and a toner dropping conveyance path 163 as powder conveyance paths.

[0082] The container tip-side cover 34 has a toner discharge port W, and a shutter member 38 for opening and closing this toner discharge port W is attached so as to be slidable within a predetermined range in the insertion direction of the toner container 32.

[0083] When the toner container 32 is attached to the image forming apparatus, in conjunction with the attachment operation, the shutter member 38 of the toner container 32 moves to open the toner discharge port W, and the toner supply port 73W of the toner supply device 160 communicates with the toner discharge port W.

[0084] Similar to the embodiment, by rotationally driving the container body 33 by the first driving unit 91, the toner stored inside the container body 33 is discharged from the toner discharge port W and supplied from the toner supply port 73W of the toner supply device 60 to the vertical conveyance path 161.

[0085] The toner supplied to the vertical conveyance path 161 falls by its own weight in the vertical conveyance path 161 and is conveyed to the horizontal conveyance path 162. The toner conveyed to the horizontal conveyance path 162 is conveyed horizontally by a conveyance screw 162a that is rotationally driven by the second driving unit 80. The toner conveyed by this conveyance screw 162a falls by its own weight in the toner falling conveyance path 163 and is supplied to the developing device 50.

[0086] Regarding this modification 1 as well, a pair of electrodes 92 and 93 are provided in the vertical conveyance path 161. And, similar to the embodiment, the control unit 90 controls the first driving unit 91 and the second driving unit 80 so as to store a prescribed amount of toner in the vertical conveyance path 161. Specifically, until the capacitance in the vertical conveyance path 161 detected by the pair of electrodes 92 and 93 becomes equal to or greater than the upper limit threshold value, the control unit 90 executes a toner supply operation for supplying the toner in the toner container 32 to the vertical conveyance path 161. When the toner supply operation is executed, the first driving unit 91 is driven to drive the container body 33 to supply the toner in the toner container 32 to the vertical conveyance path 161. The control unit 90 stops the toner supply operation when the capacitance becomes equal to or greater than the upper limit threshold value and a predetermined amount or more of toner is stored in the vertical conveyance path 161.

[0087] As described above, when the control unit 90 determines that the toner needs to be replenished to the developing device 50, the second drive unit 80 drives the conveying screw 162a in the horizontal conveyance path 162 to execute a toner replenishment operation for replenishing the toner to the developing device 50. By repeating such a replenishment operation, when the capacitance in the vertical conveyance path 161 detected by the pair of electrodes 92 and 93 falls below the lower threshold value, the control unit 90 performs the toner supply operation described above. Then, the control unit 90 supplies the toner in the toner container 32 to the vertical conveyance path 64 until the capacitance becomes equal to or higher than the upper threshold value.

[0088] If the capacitance in the vertical conveyance path 161 detected by the pair of electrodes 92 and 93 does not exceed the upper threshold value even after performing the toner supply operation for a specified time, the control unit 90 as the detection means determines that the toner has ended.

[0089] Also in the toner replenishing device of this modification example, by disposing a pair of electrodes in the vertical conveyance path 161, it is possible to detect the toner end with higher accuracy compared to the case where they are provided in the horizontal conveyance path.

[0090] [Modification Example 2] FIG. 11 is a schematic configuration diagram of a toner replenishing device 260 according to Modification Example 2. The toner replenishing device 260 according to Modification Example 2 is provided with a toner storage container 261 as a temporary storage unit for temporarily storing the toner supplied from the toner container 32.

[0091] An agitator 261a for stirring the toner in the toner storage container 261 is provided in the toner storage container 261. When the agitator 261a rotates in the direction of the arrow in the figure, the toner in the toner storage container 261 is stirred.

[0092] A horizontal conveyance path 262 provided with a conveyance screw 262a is disposed below the toner storage container 261, and the toner in the toner storage container 261 is conveyed by the rotational drive of the conveyance screw 262a. The toner conveyed by the conveyance screw 262a falls by its own weight through the toner dropping conveyance path 264 and is replenished to the developing device 50.

[0093] A pair of arc-shaped electrodes 92 and 93 are arranged near a cylindrical discharge port that discharges toner from the toner storage container 261 to the horizontal conveyance path 262. Based on the capacitance between this pair of electrodes, the presence or absence of toner in the toner storage container 261 is detected.

[0094] When the capacitance detected by the pair of electrodes 92 and 93 becomes equal to or lower than a lower threshold value, detecting that there is no toner in the toner storage container 261, the toner container 32 is driven for a predetermined time to supply toner to the toner storage container 261. Even if the toner container 32 is driven for a predetermined time and the capacitance is at the lower threshold value, it is detected as toner end.

[0095] As shown in FIG. 11, the pair of electrodes 92 and 93 are provided near the discharge port where the distance between the wall surfaces is the shortest in the toner storage container 261, so that the electric lines of force between the electrodes can be made dense, and the change in capacitance can be detected with high sensitivity.

[0096] Also in this Modification 2, the arc surfaces of the pair of electrodes can be arranged to be parallel in the vertical direction. When the toner height in the toner storage container 261 fluctuates, the height always fluctuates in the highly sensitive region between the ends of the pair of electrodes. Thereby, the presence or absence of toner in the toner storage container 261 can be detected with high sensitivity.

[0097] What has been described above is an example, and each of the following aspects has a specific effect. (Aspect 1) A pair of electrodes 92 and 93 arranged in a powder conveyance path (in this embodiment, composed of a conveyance nozzle 611, a vertical conveyance path 64, a relay conveyance path 65, and a toner dropping conveyance path 66) for conveying powder such as toner, and detection means such as a control unit 90 for detecting the amount of powder in the powder conveyance path based on a change in the capacitance between the electrodes. In a powder supply device such as a toner supply device 60, the powder conveyance path has a vertical conveyance path 64 for conveying powder in the vertical direction, and the pair of electrodes are arranged in the vertical conveyance path 64. Patent Document 1 describes the following. That is, in a configuration where a pair of arc-shaped electrodes are arranged in a cylindrical powder conveyance path, the electric lines of force between the electrode ends with the shortest electrode distance become the densest. When the height of the powder changes where the electric lines of force between these electrode ends are dense, the capacitance changes greatly and the powder amount can be detected with high sensitivity. However, it is described that when the height of the powder changes elsewhere, the capacitance does not change much and the powder amount cannot be detected with high sensitivity. In the horizontal conveyance path, the height of the powder changes in a direction orthogonal to the powder conveyance direction. Thus, when the height of the powder changes in a direction orthogonal to the powder conveyance direction, as described with reference to FIG. 8, regardless of the position on the outer peripheral surface of the powder conveyance path where the position between the electrode ends is located, there always exists a region (the hatched region in FIG. 8) where the powder height changes outside the region where the electric lines of force enclosed by the solid line in FIG. 8 are dense and the sensitivity is high. As a result, depending on the toner height in the conveyance path, there are cases where the powder amount cannot be detected with high sensitivity, and there is room for improvement in the powder detection accuracy. On the other hand, in Embodiment 1, a pair of electrodes are arranged in the vertical conveyance path. The direction of change in the height of the powder in the vertical conveyance path is the powder conveyance direction. Since the pair of electrodes are arranged parallel to the conveyance direction, the region where the ends of the electrodes face each other extends in the conveyance direction. Therefore, regardless of the height of the powder in the vertical conveyance path, when the height of the powder changes, the height of the powder where the electric lines of force between the electrode ends become dense changes. As a result, regardless of the height of the powder in the conveyance path, the powder amount can be detected with high sensitivity, and the powder amount in the powder conveyance path can be detected more accurately than the device described in Patent Document 1.

[0098] (Embodiment 2) In Embodiment 1, the vertical conveyance path 64 is cylindrical, and the pair of electrodes are arc-shaped. According to this, as described in the embodiment, compared with the case where the pair of electrodes are parallel flat plates, the change in capacitance with respect to the change in powder height can be increased, and the sensitivity of powder amount detection can be enhanced.

[0099] (Embodiment 3) In Mode 1, the pair of electrodes are flat plates. According to this, as described in the embodiment, the electric lines of force between the electrodes can be made uniform, and even if there is an assembly error, the capacitance does not vary significantly compared to the case where the pair of electrodes has an arc shape.

[0100] (Mode 4) In any of Modes 1 to 3, the powder conveyance path has an opening such as a nozzle opening 610 that receives powder from a powder container at one end side and is inserted into a powder container such as the toner container 32 at one end side, and a first horizontal conveyance path such as a conveyance nozzle 611 that conveys the powder received from the opening horizontally toward the vertical conveyance path 64, and a second horizontal conveyance path such as a relay conveyance path 65 that conveys the powder conveyed from the vertical conveyance path 64 horizontally. According to this, by controlling the powder conveyance in the second horizontal conveyance path such as the relay conveyance path 65, the powder supply amount to a supply target device such as the developing device 50 can be controlled. Also, by controlling the powder conveyance in the second horizontal conveyance path and the powder conveyance in the first horizontal conveyance path such as the conveyance nozzle 611, a specified amount of powder can be stored in the vertical conveyance path 64, and the amount of powder in the vertical conveyance path can be detected by the pair of electrodes.

[0101] (Mode 5) In any of Modes 1 to 3, the vertical conveyance path 161 has a powder supply port such as a toner supply port 73W from which powder is supplied from a powder discharge port such as a toner discharge port W that discharges the powder of a powder container such as the toner container 32, and the powder conveyance path has a horizontal conveyance path 162 that conveys the powder conveyed from the vertical conveyance path 161 horizontally. According to this, as described with reference to FIG. 10, by controlling the powder conveyance in the horizontal conveyance path 162, the powder supply amount to a supply target device such as the developing device 50 can be controlled. Also, by controlling the powder conveyance in the horizontal conveyance path 162 and the powder supply amount from a powder container such as the toner container 32, a specified amount of powder can be stored in the vertical conveyance path 161, and the amount of powder in the vertical conveyance path can be detected by the pair of electrodes.

[0102] (Mode 6) In a powder supply device such as a toner supply device including a temporary storage unit such as a toner storage container 261 that temporarily stores powder in a powder container, a pair of electrodes are arranged in the temporary storage unit, and based on a change in capacitance between the electrodes, the amount of powder in the temporary storage unit is detected. According to this, as described with reference to FIG. 11, if the arc surfaces of the pair of electrodes are arranged to be parallel in the vertical direction, a height change can be detected in a highly sensitive region between the ends of the pair of electrodes in a temporary storage unit such as the toner storage container 261, and the amount of powder in the temporary storage unit can be detected with high sensitivity.

[0103] (Aspect 7) In an image forming apparatus including an image carrier such as a photoreceptor 41, developing means such as a developing device 50 that develops a latent image on the image carrier using a developer, a developer storage container such as a toner container 32 that stores the developer used in the developing means, and developer supply means such as a toner supply device 60 that supplies the developer in the developer storage container to the developing means, as the developer supply means, a powder supply device according to any one of Aspects 1 to 6 is used. According to this, the remaining amount of the developer in the developer storage container such as the toner container 32 can be detected favorably.

Explanation of Reference Numerals

[0104] 32: Toner container 33: Container body 34: Container tip-side cover 38: Shutter member 41: Photoreceptor 46: Image forming unit 50: Developing device 56: Toner concentration detection sensor 60: Toner supply device 64: Vertical conveyance path 65: Relay conveyance path 66: Toner falling conveyance path 70: Toner container housing part 71: Insertion port forming part 72: Container receiving part 73: Container cover receiving part 73W: Toner supply port 80: Second drive unit 90: Control unit 91: First drive unit 92: Electrode 93: Electrode 160: Toner supply device 161: Vertical conveyance path 162: Horizontal conveyance path 162a: Conveyor screw 163: Toner dropping conveyance path 260: Toner supply device 261: Toner storage container 261a: Agitator 262: Horizontal conveyance path 262a: Conveyor screw 264: Toner dropping conveyance path 500: Copier 610: Nozzle opening 611: Conveyor nozzle 614: Conveyor screw 615: Conveyor screw 616: Loosening member 616a: Hook portion W: Toner discharge port

Prior art documents

Patent documents

[0105]

Patent Document 1

Claims

1. A pair of electrodes disposed in a powder conveying path for conveying powder, and a powder supply device comprising detection means for detecting the amount of powder in the powder conveying path based on a change in capacitance between the electrodes, wherein the powder conveying path includes a vertical conveying path in which the powder is conveyed vertically by its own weight, a first horizontal conveying path having one end inserted into a powder container and having an opening at the one end for receiving the powder from the powder container and conveying the powder received from the opening horizontally toward the vertical conveying path, and a second horizontal conveying path for conveying the powder conveyed from the vertical conveying path horizontally, the vertical conveying path is configured such that a specified amount of toner accumulates therein, the pair of electrodes is disposed only at the lower end side of the vertical conveying path. The powder supply device is characterized by this.

2. In the powder supply device according to claim 1, the vertical conveying path is cylindrical, the pair of electrodes is arc-shaped. The powder supply device is characterized by this.

3. In the powder supply device according to claim 1, the pair of electrodes is a flat plate. The powder supply device is characterized by this.

4. An image carrier, developing means for developing a latent image on the image carrier using a developer, a developer storage container for storing the developer used by the developing means, an image forming apparatus comprising developer supply means for supplying the developer in the developer storage container to the developing means, wherein the image forming apparatus is characterized in that the powder supply device according to any one of claims 1 to 3 is used as the developer supply means.

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