Image forming apparatus

Abstract

The objective of the present invention is to suppress a decrease in the detection accuracy of the detection unit. [Solution] An image forming apparatus comprising: a housing section for housing toner and a first magnetic material; a magnetic material unit comprising a permanent magnet including a first end face and a second end face; a second magnetic material having a lower residual magnetic flux density than the permanent magnet; and a sensor that outputs a signal based on a magnetic field, wherein the first end face is one end of the permanent magnet in the first direction, and the second end face is the other end of the permanent magnet opposite to the first end in the first direction; when the permanent magnet is in the closest proximity position to the sensor, the shortest distance between the first end face and the sensor is greater than the shortest distance between the second end face and the sensor; when the permanent magnet is in a proximity position, the shortest distance between the first magnetic material and the second magnetic material is less than the shortest distance between the first magnetic material and the first end face; and, viewed in the first direction, the second magnetic material comprises an overlapping portion that overlaps with the first end face and a non-overlapping portion that does not overlap with the first end face.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background Art]

[0002] The image forming apparatus described in Patent Document 1 includes a magnet and a detection unit that detects a change in a magnetic field formed by the magnet, and detects the remaining amount of toner. [Prior Art Literature] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-286849 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] When a magnetic material exists around a magnet, a magnetic force acts between the magnetic material and the magnet, which may reduce the detection accuracy of the detection unit.

[0005] Accordingly, an object of the present invention is to suppress a decrease in detection accuracy of a detection unit. [Means for Solving the Problem]

[0006] One aspect of the present invention is as follows.

[0007] an accommodating portion that accommodates toner and a first magnetic material; a magnetic unit including a permanent magnet having a first end face and a second end face, and a second magnetic body having a lower residual magnetic flux density than the permanent magnet, the magnetic unit moving inside the accommodating portion in accordance with an amount of toner in the accommodating portion; a sensor that outputs a signal based on a magnetic field formed by the permanent magnet; comprising: When the direction from one magnetic pole of the permanent magnet toward the other magnetic pole is defined as the first direction, the first end face is one end of the permanent magnet in the first direction, and the second end face is the other end of the permanent magnet opposite to the one end in the first direction. The position where the permanent magnet is closest to the sensor is defined as the proximity position, and when the permanent magnet is in the proximity position, the shortest distance between the first end face and the sensor is greater than the shortest distance between the second end face and the sensor. When the permanent magnet is in the proximity position, the shortest distance between the first magnetic material and the second magnetic material is smaller than the shortest distance between the first magnetic material and the first end face. Viewed in the first direction, the second magnetic material comprises an overlapping portion that overlaps with the first end face and a non-overlapping portion that does not overlap with the first end face. An image forming apparatus characterized by the following features. [Effects of the Invention]

[0008] As described above, the present invention makes it possible to suppress a decrease in the detection accuracy of the detection unit. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram of the image forming apparatus according to Example 1. [Figure 2] A schematic diagram of the developing unit and toner cartridge according to Example 1. [Figure 3] A plan view of the image forming apparatus according to Example 1. [Figure 4] A perspective view of the detection unit according to Example 1. [Figure 5] A block diagram illustrating the control unit according to Example 1. [Figure 6] Plan view (a, b) of the image forming apparatus according to Example 1. [Figure 7] Schematic diagrams (a, b) of the magnetic field formed by the permanent magnet according to Example 1. [Figure 8] Plan view of the permanent magnet and yoke member according to Example 1. [Figure 9]1 is a graph showing the magnetic flux density of the magnetic field formed by the permanent magnet according to Example 1. [Figure 10] 1 is a schematic diagram of an image forming apparatus according to Example 2. [Figure 11] 1 is plan views (a, b) of the image forming apparatus according to Example 2. [Figure 12] 1 is a plan view of a permanent magnet and a yoke member according to Modification 1. [Figure 13] 1 is a plan view of a permanent magnet and a yoke member according to Modification 1. [Figure 14] 1 is a graph showing the magnetic flux density of the magnetic field formed by the permanent magnet according to Modification 1. MODE FOR CARRYING OUT THE INVENTION

[0010] Example 1 The image forming apparatus 1 according to Example 1 will be described with reference to FIGS. 1 to 9. Subscripts y, m, c, and k attached to developing units 50y, 50m, 50c, and 50k, toner cartridges 70y, 70m, 70c, and 70k, and the like, which will be described later, indicate toner colors. A plurality of members having the same numbering and differing only in color have a common basic configuration and function. For example, the basic configuration and function of the toner cartridges 70y, 70m, 70c, and 70k are common. Therefore, when there is no need to distinguish them from each other, the subscripts y, m, c, and k are omitted, and the description will be given assuming that any one of them is referred to. For example, when the description is given with reference to the toner cartridge 70, the description applies to any of the toner cartridges 70y, 70m, 70c, and 70k.

[0011] (Overall Configuration of Image Forming Apparatus) The overall configuration of an image forming apparatus 1 will be described. The image forming apparatus 1 is a laser beam printer that forms an image on a sheet S by an electrophotographic method. The image forming apparatus 1 is a color laser beam printer including four developing units 50y, 50m, 50c, and 50k. As the sheet S serving as a recording material (recording medium), various sheet materials having different sizes and materials can be used, including papers such as plain paper and thick paper, plastic films, cloth, sheet materials subjected to surface treatment such as coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0012] The schematic configuration and image forming operation of the image forming apparatus 1 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing a cross-sectional configuration of the image forming apparatus 1. FIG. 2 is a conceptual diagram showing a configuration for supplying toner from a toner cartridge 70 to the developing unit 50. As shown in FIG. 1, the image forming apparatus 1 includes an image forming apparatus main body (hereinafter referred to as an apparatus main body) 1A, and toner cartridges 70y, 70m, 70c, and 70k detachably attachable to the apparatus main body 1A. The apparatus main body 1A of the present embodiment is a portion obtained by removing the toner cartridges 70y, 70m, 70c, and 70k from the image forming apparatus 1. The apparatus main body 1A of the image forming apparatus 1 includes an electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 2 having a drum shape (cylindrical shape) as an image bearing member that bears an electrostatic latent image. Around the photosensitive drum 2, a charging roller 3 and a scanner 4 serving as an exposure device are arranged.

[0013] The charging roller 3 is an example of a charging means or a charging unit for uniformly charging the photosensitive drum 2. The scanner 4 is an exposure means that performs exposure by irradiating the photosensitive drum 2 with laser light corresponding to image information. An electrostatic latent image is formed on the surface of the photosensitive drum 2 by irradiating the charged photosensitive drum 2 with laser light.

[0014] The main body of the apparatus 1A includes a sheet storage section 300, a pickup roller 310, a feed roller 311, a separation roller 312, a transport roller pair 320, a secondary transfer roller 12, a fixing device 40, and an intermediate transfer unit 10. The pickup roller 310 is a feeding means for feeding the sheets S. The feed roller 311 and the separation roller 312 are examples of a separation transport unit that transports the sheets S one by one while separating them by frictional force. The secondary transfer roller 12 is an example of a transfer means for transferring an image from the intermediate transfer unit to the sheets S. The intermediate transfer unit 10 is an example of an intermediate transfer body that carries the image primarily transferred from the photosensitive drum 2 and performs secondary transfer to the sheets S.

[0015] Furthermore, the main body of the device 1A has a rotary body (rotary, rotating body, developing device) 90 having developing units 50y, 50m, 50c, and 50k. The rotary body 90 is rotatable around the axis of rotation (center of rotation) 90C. Toner cartridges 70y, 70m, 70c, and 70k are removable (attachable) to the rotary body 90. The developing units (first to fourth developing units) 50y, 50m, 50c, and 50k are examples of developing means or developing units that develop (reveal) an electrostatic latent image formed on the photosensitive drum 2 into a toner image using toner of the corresponding color. The developing units 50y, 50m, 50c, and 50k are developing members that develop the electrostatic latent image formed on the photosensitive drum 2 using yellow toner, magenta toner, cyan toner, or black toner, respectively. More specifically, the developing component develops the electrostatic latent image formed on the photosensitive drum 2 with the developer contained in the developing frame 53.

[0016] The rotary body 90 is fitted with toner cartridges 70y, 70m, 70c, and 70k, corresponding to the developing units 50y, 50m, 50c, and 50k. Inside the toner cartridges 70y, 70m, 70c, and 70k are yellow toner, magenta toner, cyan toner, and black toner, respectively, to replenish the developing units 50y, 50m, 50c, and 50k. One of the four toners can be called the first toner, one of the remaining three toners can be called the second toner, one of the remaining two toners can be called the third toner, and the last toner can be called the fourth toner. For example, black toner can be an example of the first toner, and magenta toner can be an example of the second toner. These numberings are used for explanatory convenience only, and in principle, they can be rearranged as appropriate.

[0017] A motor M1 (not shown) rotates the rotary body 90 around the rotation axis 90C. By rotating around the rotation axis 90C, the rotary body 90 can assume a developing position in which any of the developing rollers 51y, 51m, 51c, or 51k faces the photosensitive drum 2. The position in which the developing roller 51y faces the photosensitive drum 2 is called the yellow developing position. The position in which the developing roller 51m faces the photosensitive drum 2 is called the magenta developing position. The position in which the developing roller 51c faces the photosensitive drum 2 is called the cyan developing position. The position in which the developing roller 51k faces the photosensitive drum 2 is called the black developing position. In other words, the rotary body 90 can rotate around the rotation axis 90C so that the position of the developing rollers 51y, 51m, 51c, or 51k relative to the photosensitive drum 2 changes. The black developing position is an example of the first developing position, where the first developing roller (developing roller 51k) faces the photosensitive drum 2. The other developing positions are examples of the second developing position, where the second developing rollers (developing rollers 51y~51c) face the photosensitive drum 2. The yellow / magenta / cyan / black developing positions can also be called the first to fourth developing positions. These numberings are used for explanatory convenience only and can be rearranged as appropriate in principle.

[0018] (Image formation process) Next, the image formation operation in this embodiment will be described. First, the photosensitive drum 2 is rotated in the direction of the arrow in Figure 1 (counterclockwise) in synchronization with the rotation of the intermediate transfer unit 10. Then, the surface of the photosensitive drum 2 is uniformly charged by the charging roller 3. When forming a color image on the sheet S, the rotary body 90 rotates in the direction of the arrow in Figure 1 (clockwise) while supporting the developing units 50y, 50m, 50c, and 50k, as shown below. Then, the electrophotographic process is repeated while moving the developing rollers 51y, 51m, 51c, and 51k one by one to the developing position.

[0019] First, the scanner 4 irradiates the photosensitive drum 2 with laser light based on image data corresponding to the yellow image, forming an electrostatic latent image corresponding to the yellow image on the surface of the photosensitive drum 2. In parallel with the formation of this electrostatic latent image, the motor M1 rotates the rotary body 90, causing the rotary body 90 to assume the yellow developing position. When the rotary body 90 is in the yellow developing position, the developing roller 51y is in the developing position and develops the electrostatic latent image formed on the photosensitive drum 2 with yellow toner.

[0020] At the development position, the developing rollers 51y, 51m, 51c, and 51k are in contact with the photosensitive drum 2, and the electrostatic latent image is developed. The yellow toner image on the photosensitive drum 2 is first transferred to the intermediate transfer unit 10. From here on, the rotary body 90 is rotated to move the developing rollers 51m, 51c, and 51k to the development position in sequence, thereby forming toner images of each color. That is, after the yellow toner image is formed on the intermediate transfer unit 10, the rotary body 90 takes the magenta development position, and a magenta toner image is formed on the intermediate transfer belt 10a. After the magenta toner image is formed on the intermediate transfer belt 10a, the rotary body 90 takes the cyan development position, and a cyan toner image is formed on the intermediate transfer belt 10a. After the cyan toner image is formed on the intermediate transfer belt 10a, the rotary body 90 takes the black development position, and a black toner image is formed on the intermediate transfer belt 10a. After a black toner image is formed on the intermediate transfer belt 10a, the rotary body 90 rotates around the rotation axis 90C in the direction of the arrow shown in Figure 1 (clockwise) to return to the yellow developing position. Then, the primary transfer is repeated on the intermediate transfer belt 10a so that the four toner images are superimposed, and a color image is formed on the intermediate transfer belt 10a.

[0021] Meanwhile, the sheets S are fed from the sheet storage section 300 located at the bottom of the main body 1A by the pickup roller 310. The sheets S are separated one by one by the feed roller 311 and the separation roller 312 and sent to the transport roller pair 320. The transport roller pair 320 sends the fed sheets S to the intermediate transfer unit 10 and the transfer section (secondary transfer section), which is the nip of the secondary transfer roller 12. The color image on the intermediate transfer belt 10a is transferred (secondary transfer) to the surface of the transported sheets S. The sheets S with the transferred color image are sent to the fixing device 40. In the fixing device 40, the sheets S are heated and pressurized, and the image is fixed to the sheets S. The sheets S that have passed through the fixing device 40 are discharged outside the image forming apparatus 1 as the finished product. On the other hand, when forming a monochrome image on the sheets S, the rotary body 90 takes the black developing position. In this state, an electrostatic latent image is formed on the surface of the photosensitive drum 2 by charging and exposure. Then, the electrostatic latent image is developed with black toner by the developing roller 51k located at the developing position. The black toner image is first transferred to the intermediate transfer unit 10, and then secondarily transferred to the sheet S. The subsequent steps are the same as for color images.

[0022] (Toner supply) Next, the configuration for supplying toner from the toner cartridge 70 to the developing unit 50 will be explained using Figures 2 and 3. Figure 3 is a plan view of the image forming apparatus 1. The toner cartridge 70 has a toner frame 71. The toner frame 71 includes a toner storage section 71a for storing toner and an outlet opening 71b communicating with the toner storage section 71a. The developing unit 50 has a developing frame (storage frame) 53. Developing units 50y, 50m, 50c, and 50k each have developing frames 53y, 53m, 53c, and 53k, respectively. The developing frame 53 includes a developing-side storage section 53a and a receiving opening 53b communicating with the developing-side storage section (toner supply chamber) 53a. Note that the developing unit 50 has a developing roller 51 and a supply roller 52, but these components are omitted in Figure 2.

[0023] The discharge opening 71b faces the receiving opening 53b, and the toner storage section 71a communicates with the developing-side storage section 53a of the developing unit 50. When toner is supplied from the toner cartridge 70 to the developing unit 50, at least a portion of the receiving opening 53b is positioned below at least a portion of the discharge opening 71b. That is, toner is supplied when the rotary body 90 is positioned such that at least a portion of the receiving opening 53b is positioned below at least a portion of the discharge opening 71b. The toner stored in the toner storage section 71a is then discharged from the discharge opening 71b, and the toner discharged from the discharge opening 71b is stored in the developing-side storage section 53a through the receiving opening 53b. The toner stored in the developing-side storage section 53a is supplied to the developing roller 51 by the supply roller 52. In this manner, the toner stored in the toner storage section 71a is supplied to the developing roller 51.

[0024] The developing roller 51 and the supply roller 52 will be explained using Figure 3. The developing-side housing section 53a houses the developing roller 51 and the supply roller 52. In this embodiment, only a part of the developing roller 51 is housed in the developing-side housing section 53a. The developing roller 51 is a developer carrier that carries toner as a developer and rotates to supply toner to the photosensitive drum 2. The developing roller 51 includes a shaft 51a and a rubber layer 51b that covers the shaft 51a. The developing roller 51 rotates when the shaft 51a receives a driving force from a drive mechanism (not shown). The shaft 51a contains a magnetic material. In the following explanation, a magnetic material refers to a substance that becomes magnetized when placed in a magnetic field. For example, magnetic materials include iron, nickel, and cobalt. Alloys containing magnetic materials are also called magnetic materials. For example, stainless steel containing iron is a magnetic material. The supply roller 52 is a supply member that is positioned in contact with the developing roller 51 and supplies toner to the developing roller 51. The supply roller 52 includes a shaft 52a and a foam layer 52b covering the shaft 52a. The supply roller 52 rotates when the shaft 52a receives a driving force from a drive mechanism (not shown). The shaft 52a contains a magnetic material. The developing roller 51 and the supply roller 52 each rotate inside the developing-side housing 53a and can be called magnetic rollers (rotating bodies) that supply toner. In addition, the shaft 51a or shaft 52a may be referred to as the first magnetic material in the following description.

[0025] (Configuration that detects the remaining amount in the developing compartment) Next, we will describe the configuration for detecting the remaining amount of toner in the developing frame 53. The amount of toner in the toner cartridge 70 decreases each time an image forming operation is performed. When there is little toner in the toner cartridge 70, it is difficult for toner to be supplied from the toner cartridge 70 to the developing frame 53. As a result, the remaining amount of toner in the developing side storage section 53a decreases. If image forming is performed when the remaining amount of toner is low, there is a possibility that image defects will occur in the printed material. Therefore, the image forming apparatus 1 in this embodiment is equipped with a configuration for detecting the remaining amount of toner in the developing frame 53.

[0026] As shown in Figure 3, the developing unit 50 includes a detected unit 103. That is, developing units 50y, 50m, 50c, and 50k each include a detected unit 103y, 103m, 103c, and 103k, respectively. The image forming apparatus 1 also includes a magnetic sensor 102. The detected unit 103 includes a permanent magnet 101 and a yoke member 104. That is, the detected units 103y, 103m, 103c, and 103k each include a permanent magnet 101y, 101m, 101c, and 101k, respectively. More specifically, the permanent magnet 101 is housed in the developing side housing section 53. The detected units 103y, 103m, 103c, and 103k each include a yoke member 104y, 104m, 104c, and 104k, respectively. As shown in Figures 1 and 3, the magnetic sensor 102 is located above the rotary body 90. The magnetic sensor 102 is located opposite the rotary body 90. The magnetic sensor 102 is a detection unit that detects the magnetic field formed by the permanent magnet 101.

[0027] Next, the detected unit 103 will be described. Figure 4 is a perspective view of the detected unit 103. Note that the yoke member 104 is omitted in Figure 4. In the following description, the direction from the rotation center Rm of the rotary body 90 toward the outside of the rotary will be called the first radial direction. The downstream end of the developing frame 53 in the first radial direction will be called the downstream end 53rd of the housing, and the upstream end will be called the upstream end 53ru of the housing. In the first radial direction, the distance between the upstream end 53ru of the housing and the rotary center Rm is smaller than the distance between the downstream end 53rd of the housing and the rotary center Rm. The downstream end 53rd of the housing and the upstream end 53ru of the housing face each other in the first radial direction. The downstream end 53rd of the housing and the upstream end 53ru of the housing extend in a direction intersecting the first radial direction. As shown in Figure 3, the shortest distance between the shaft 52a and the rotation center Rm is shorter than the shortest distance between the permanent magnet 101 and the rotation center Rm.

[0028] As shown in Figure 4, the detected unit 103 is supported by the developing frame 53. More specifically, it is supported at the downstream end 53rd of the housing section. The developing frame 53 houses the holding member 107 and the detected unit 103. That is, the developing frame 53 can be said to comprise the holding member 107 and the detected unit 103. The detected unit 103 comprises a permanent magnet 101, a yoke member 104, a support member 100, and a rotating shaft 106. In the following description, the unit formed by the permanent magnet 101 and the yoke member 104 will be referred to as the magnetic unit 105. The holding member 107 is integral with the developing frame 53 and holds the rotating shaft 106 relative to the developing frame 53. The rotating shaft 106 is rotatably held by the holding member 107. That is, the rotating shaft 106 can be said to be a supported part supported by the developing frame 53 via the holding member 107.

[0029] The support member 100 is integrated with the rotating shaft 106. That is, the support member 100 is held by the holding member 107. The support member 100 is rotatable about the rotating shaft 106. The rotating shaft 106 extends along the direction of the rotation axis of the rotary body 90. As shown in Figure 3, the support member 100 is a support member that supports the yoke member 104. The support member 100 and the yoke member 104 are engaged by an engaging part (not shown). The permanent magnet 101 and the yoke member 104 are bonded together by adhesive tape (adhesive member). With the above configuration, the permanent magnet 101 supported by the support member 100 via the yoke member 104 is also rotatable about the rotating shaft 106. In other words, the rotation axis of the magnetic material 101 extends along the direction of the rotation axis of the rotary body 90.

[0030] Furthermore, it can be said that the detected unit 103 is located inside the developing frame 53 so as to be movable (rotatable) relative to the developing frame 53. In other words, the detected unit 103 is located inside the developing frame 53 so as to be movable (rotatable) relative to the sensor 102.

[0031] The support member 100 includes a paramagnetic or diamagnetic material. Paramagnetic and diamagnetic materials are substances that are not ferromagnetic and are weakly magnetized when placed in an external magnetic field. Paramagnetic and diamagnetic materials are substances that lose their magnetism when the external magnetic field is removed. However, paramagnetic materials are magnetized in the same direction as the external magnetic field, while diamagnetic materials are magnetized in the opposite direction. Examples of paramagnetic materials include aluminum, platinum, and manganese. Examples of diamagnetic materials include resin, copper, and lead. The support member 100 includes at least one of the paramagnetic and diamagnetic materials listed above. This reduces the influence of the support member 100 on the magnetic field formed by the permanent magnet 101 when detecting the remaining toner level, as described later.

[0032] Furthermore, resin has a lower density than metals such as iron and aluminum. Therefore, when the support member 100 is made of resin, the support member 100 is less likely to sink into the toner in the developing side storage section 53a, making it easier for the detection unit 103 to rest on the toner surface, and thus suppressing a decrease in the accuracy of toner level detection.

[0033] (Determination of toner level in the developing unit) Next, a method for determining the amount of toner in the developing-side storage unit 53a will be explained. First, the configuration of the control unit of the image forming apparatus 1 will be explained using Figure 5. Figure 5 is a block diagram showing the configuration of the control unit of the image forming apparatus 1. The image forming apparatus 1 comprises an engine control unit 500, a controller 600, and a display unit 700. The host computer 400 sends a print job to the image forming apparatus 1. When the controller 600 receives a print job from the host computer 400, it causes the engine control unit 500 to control the image forming operation based on the print job. The display unit 700 is a display device capable of displaying information. The display unit is a display device having a display screen, such as a display. The engine control unit 500 also comprises a CPU 510, a ROM 520, and a RAM 530. The ROM 520 is a non-volatile memory that holds and stores control programs and various data. For example, the ROM 520 stores the toner amount determination result determined by the CPU 510. The RAM 530 is a volatile memory that stores temporary data.

[0034] The magnetic sensor 102 outputs a signal to the engine control unit 500 based on the magnetic field formed by the permanent magnet 101. More specifically, the magnetic sensor 102 changes the signal it outputs according to the magnitude of the detected magnetic flux density. Therefore, the magnetic sensor 102 can also be described as a detection unit that detects the magnetic field formed by the permanent magnet 101. The magnetic sensor 102 is a Hall IC sensor that outputs an output voltage linearly. The magnetic sensor 102 may also be a switch-type sensor in which the output reverses when the magnetic flux passing through the magnetic flux detection unit exceeds a predetermined threshold.

[0035] The rotary body 90 rotates due to the image forming operation of the image forming apparatus 1, performs a pre-rotation before the image forming operation, and a post-rotation after the image forming operation. These rotations cause the developing units 50y, 50m, 50c, and 50k to approach the magnetic sensor 102 in sequence. The magnetic sensor 102 is configured to constantly detect the magnetic field during the period when the rotary body 90 rotates and the developing units 50y, 50m, 50c, and 50k pass in front of the magnetic sensor 102 in sequence. Alternatively, the magnetic sensor 102 may detect only when each of the developing units 50y, 50m, 50c, and 50k is in close proximity to the magnetic sensor 102. The magnetic sensor 102 outputs a signal corresponding to the number of magnetic field lines (magnetic flux density) passing through it. The engine CPU 510 of the image forming apparatus 1 determines the remaining toner amount in the developing side storage section 53a based on the signal output by the magnetic sensor 102.

[0036] As the rotary body 90 rotates, the developing-side housing 53 moves closer to and further away from the magnetic sensor 102, causing the detected unit 103 to move closer to and further away from the magnetic sensor 102. More preferably, it is desirable that the magnetic sensor 102 detects the magnetic field of the permanent magnet 101 at the timing when the developing-side housing 53 is closer to the magnetic sensor 102. The line segment L shown in Figure 3 is a hypothetical line segment connecting the rotation center Rm and the magnetic sensor 102 when viewed in the direction of the rotation axis of the rotary body 90. As shown in Figure 3, in this embodiment, the magnetic sensor 102 detects the magnetic field of the permanent magnet 101y when the permanent magnet 101y coincides with the line segment L when viewed in the direction of the rotation axis of the rotary body 90. The magnetic fields of the permanent magnets 101m, 101c, and 101k are detected at similar timings.

[0037] Figure 6(a) shows the state where the developing side storage section 53a is fully filled with toner. The state in Figure 6(a) corresponds to the timing when the permanent magnet 101y described above aligns with the line segment L. Figure 6(b) shows the state where the remaining toner in the developing side storage section 53a falls below a predetermined threshold. The rotary's orientation (rotation phase) is the same in Figure 6(a) and Figure 6(b).

[0038] As the toner level decreases, the toner surface in the developer-side storage section 53a decreases. Here, the toner surface refers to the upper surface formed by the toner. As the toner surface decreases, the position of the detected unit 103, which is supported by the toner surface, also changes. Specifically, the detected unit 103 (magnetic unit 105) rotates to move away from the magnetic sensor 102. In other words, the detected unit 103 (magnetic unit 105) moves inside the developer-side storage section 53a in accordance with the amount of toner in the developer-side storage section 53a. As shown in Figure 6(b), as the distance between the detected unit 103 and the magnetic sensor 102 increases, the magnetic flux density penetrating the magnetic sensor 102 decreases. That is, the signal output by the magnetic sensor 102 changes. When the toner level in the developer-side storage section 53a falls below a predetermined threshold, the engine control unit 500 controls the controller 600 to notify the display unit 700 of information regarding the toner level. The controller 600 causes the display unit 700 to display information regarding the remaining toner level. In other words, the image forming apparatus 1 notifies the user of information regarding the remaining toner level based on the signal output by the magnetic sensor 102. This information regarding the remaining toner level includes, for example, information indicating the amount of toner remaining and information indicating that the toner cartridge needs to be replaced.

[0039] In this way, the image forming apparatus 1 detects the remaining toner amount based on the change in the signal output by the magnetic sensor 102. The orientation of the rotary body 90 in Figure 6(a) is referred to as the first orientation, and the amount of toner in the developing side storage unit 53a is referred to as the first amount. The state of the image forming apparatus 1 in Figure 6(a) is referred to as the first state. The amount of toner in the developing side storage unit 53a shown in Figure 6(b) is referred to as the second amount. The second amount is smaller than the first amount. In Figure 6(b), the rotary body 90 is in the first orientation. The state of the image forming apparatus 1 shown in Figure 6(b) is referred to as the second state. The shortest distance between the permanent magnet 101 and the shaft 52a when the image forming apparatus 1 is in the second state is shorter than the shortest distance between the permanent magnet 101 and the shaft 52a when the image forming apparatus 1 is in the first state.

[0040] (Construction of the yoke member) Next, the configuration of the yoke member will be described. When a magnetic material is present around the permanent magnet 101, a magnetic force (attractive or repulsive force) may act between the magnetic material and the permanent magnet 101. In this embodiment, the shaft 52a of the supply roller 52 and the shaft 51a of the developing roller are made of magnetic material. Therefore, a magnetic force may act between the shafts 52a and 51a and the permanent magnet 101. In this case, the position of the permanent magnet 101 and the magnetic sensor 102 may change due to the influence of the shafts 52a and 51a, which may reduce the detection accuracy of the magnetic sensor 102. Therefore, the image forming apparatus 1 is equipped with a yoke member 104 (second magnetic material).

[0041] The yoke member 104 will now be described. The yoke member 104 contains a soft magnetic material. Soft magnetic materials include, for example, pure iron (Fe), silicon steel (Si-Fe), permalloy, Sendust, and permendur. Soft magnetic materials also include, for example, soft ferrite, amorphous magnetic alloy, and nanocrystal magnetic alloy. For example, the residual magnetic flux density of the yoke member 104 (soft magnetic material) in this embodiment is smaller than that of the permanent magnet 101. Also, for example, the residual magnetic flux density of the yoke member 104 (soft magnetic material) in this embodiment is larger than that of the support member 100.

[0042] Figure 7 is a schematic diagram showing the magnetic field formed by the permanent magnet 101. Figure 7(a) shows the case where the image forming apparatus 1 is equipped with a yoke member 104. On the other hand, Figure 7(b) shows the case where the image forming apparatus 1 is not equipped with a yoke member 104. The permanent magnet 101 includes a south pole surface 101s containing the south pole and a north pole surface 101n containing the north pole. Hereafter, the direction from one magnetic pole of the permanent magnet 101 toward the other magnetic pole will be called the first direction. That is, the first direction includes the direction from the south pole surface 101s toward the north pole surface 101n and the direction from the north pole surface 101n toward the south pole surface 101s. The south pole surface 101s can be called the first end surface, which is one end of the permanent magnet 101 in the first direction. If the south pole surface 101s is called the first end surface, then the north pole surface 101n can be called the second end surface, which is the other end of the permanent magnet 101 opposite to the one end in the first direction. The south pole surface 101s can also be called the second end surface, and the north pole surface 101n can be called the first end surface. Magnetic field lines emanating from the north pole surface 101n enter the south pole surface 101s. Furthermore, the magnetic field lines emanating from the north pole surface 101n penetrate the magnetic sensor 102, causing the magnetic sensor 102 to detect a magnetic field. In this embodiment, the permanent magnet 101 is a neodymium magnet, but other types of permanent magnets may also be used.

[0043] Next, we will describe the arrangement of the permanent magnet 101 and the yoke member 104. In the following explanation, the position of the permanent magnet 101 when it is closest to the magnetic sensor 102 will be called the proximity position. The proximity position is the position in which the shortest distance between the permanent magnet 101 and the magnetic sensor 102 is smallest among the positions that the permanent magnet 101 can take. For example, the permanent magnet 101 shown in Figure 3 and Figure 6(a) is in the proximity position. As shown in Figure 6(a), let D1 be the shortest distance between the first end face (S pole face 101s) and the magnetic sensor 102 when the permanent magnet 101 is in the proximity position. Let D2 be the shortest distance between the second end face (N pole face 101n) and the magnetic sensor 102 when the permanent magnet 101 is in the proximity position. D1 is greater than D2. Let D3 be the distance between the shaft 52 (first magnetic material) and the yoke member 104 (second magnetic material) when the permanent magnet 101 is in the proximity position. Furthermore, let D4 be the shortest distance between shaft 52a (first magnetic material) and the first end face (S pole surface 101s) when the permanent magnet 101 is in close proximity. D3 is smaller than D4. The fact that D3 is smaller than D4 was explained using shaft 52a as an example of the first magnetic material, but the same applies to shaft 51a.

[0044] As shown in Figure 6(a), when the permanent magnet 101 is in close proximity, the shaft 52a, yoke member 104, S pole surface 101s, N pole surface 101n, and magnetic sensor 102 are arranged in that order in the direction from the S pole surface 101s to the N pole surface 101n. Similarly, the shaft 51a, yoke member 104, S pole surface 101s, N pole surface 101n, and magnetic sensor 102 are arranged in that order in the direction from the S pole surface 101s to the N pole surface 101n.

[0045] As shown in Figure 6(a), in the first direction, the length of the permanent magnet 101 is longer than the length of the yoke member 104. Also, as shown in Figure 6(a), in the direction perpendicular to the first direction, the length of the yoke member 104 is less than or equal to twice the length of the permanent magnet 101. By setting the size of the yoke member 104 in this way, the size of the magnetic unit 105 can be reduced.

[0046] Figure 8 shows a plan view of the permanent magnet 101 and the yoke member 104 when viewed in the direction from the south pole surface 101s to the north pole surface 101n (first direction). The area enclosed by the solid line represents the area of ​​the yoke member 104, and the area enclosed by the dashed line represents the area of ​​the south pole surface 101s of the permanent magnet 101. When viewed in the first direction, the yoke member 104 (second magnetic material) includes an overlapping portion 104o that overlaps with the first end surface (south pole surface 101s). Also when viewed in the first direction, the yoke member 104 includes a non-overlapping portion 104s that does not overlap with the first end surface.

[0047] Viewed in the first direction, the non-overlapping portion 104s surrounds the overlapping portion 104o. That is, viewed in the first direction, the overlapping portion 104o and the permanent magnet 101 are positioned inside the outer edge of the yoke member 104.

[0048] The yoke member 104 is attracted to the south pole surface 101s by the magnetic force acting between the yoke member 104 and the permanent magnet 101. Furthermore, as described above, the yoke member 104 and the south pole surface 101s of the permanent magnet 101 are bonded together via adhesive tape. In addition to the magnetic force acting between the yoke member 104 and the permanent magnet 101, the use of adhesive tape prevents misalignment between the permanent magnet 101 and the yoke member 104.

[0049] Next, the effect of providing the yoke member 104 will be explained using Figures 7 and 9. Figure 9 is a graph showing the magnetic flux density of the magnetic field formed by the permanent magnet 101. The imaginary line 101L shown in Figure 7 is an imaginary line that passes through the center of the S pole surface 101s and extends in the first direction. The magnetic flux density shown in Figure 9 is the magnetic flux density on the imaginary line 101L. The horizontal axis shows the distance from the S pole surface 101s in the direction from the S pole surface 101s toward the N pole surface 101n. The vertical axis shows the magnitude of the magnetic flux density. The solid line shows the case where the yoke member 104 is provided (Figure 7(a)). The dashed line shows the case where the yoke member 104 is not provided (Figure 7(b)).

[0050] Regions 303 and 304 shown in Figures 7(a) and 7(b) represent the magnetic flux distribution on the south pole side of the permanent magnet 101. Comparing region 303 and region 304, it can be seen that region 303 has less magnetic flux on the south pole side than region 304. Furthermore, as shown in the graph in Figure 9, the magnetic flux density on the south pole side is smaller when the yoke member 104 is provided than when the yoke member is not provided. This is because, as mentioned above, the yoke member 104 includes a non-overlapping portion 104s. As shown in Figure 7, magnetic field lines emanating from the north pole surface 101n enter the south pole surface 101s by wrapping around to the back of the south pole surface 101s. When the yoke member 104 has a non-overlapping portion 104s, some of the magnetic field lines emanating from the north pole surface 101n enter the non-overlapping portion 104s and therefore do not wrap around to the back of the south pole surface 101s. On the other hand, as shown in Figure 6, the distance between shaft 52a and the south pole surface 101s is shorter than the distance between shaft 52a and the north pole surface 101n. Also, the distance between shaft 51a and the south pole surface 101s is shorter than the distance between shaft 51a and the north pole surface 101n. In other words, since shafts 51a and 52a are positioned on the south pole surface 101s side, they are affected by the magnetic flux on the south pole surface side. Therefore, when the yoke member 104 is provided, the magnetic flux density on the south pole surface side is small, so the magnetic force acting between the magnetic material unit 105 and shaft 51a becomes small. Similarly, the magnetic force acting between the magnetic material unit 105 and shaft 52a becomes small.

[0051] As shown in the graph in Figure 9, the magnetic flux density on the N pole surface 101n side is greater when the yoke member 104 is provided than when the yoke member 104 is not provided. This is also because the yoke member 104 includes a non-overlapping portion 104s. As shown in Figure 7(a), when the yoke member 104 has a non-overlapping portion 104s, the magnetic field lines emanating from the N pole surface 101n enter the non-overlapping portion 104s, so the slope of the magnetic field lines from when they leave the N pole surface 101n until they return to the 101s side becomes gentler. This change in the slope of the magnetic field lines increases the number of magnetic field lines passing through the magnetic sensor 102, making it easier to detect the magnetic field formed by the permanent magnet 101. Therefore, even when the toner level in the developing side storage section 53a decreases and the distance between the magnetic sensor 102 and the permanent magnet 101 increases, the magnetic sensor 102 can still easily detect the magnetic field.

[0052] As explained above, since the image forming apparatus 1 is equipped with a yoke member 104, the magnetic force acting between the magnetic material and the permanent magnet 101 can be reduced, and a decrease in the detection accuracy of the detection unit can be suppressed.

[0053] [Example 2] Next, Example 2 will be described. Example 1 described a rotary-type image forming apparatus 1 as an example. However, the present invention can also be applied to image forming apparatuses other than the rotary type. As an example, a monochrome, direct transfer type image forming apparatus 200 will be described.

[0054] Note that the components of the image forming apparatus 200 that are denoted by the same reference numerals as those of the image forming apparatus 1 in Example 1 are assumed to have the same functions as those described in Example 1, and their descriptions are omitted. However, the arrangement and dimensions of these components are appropriately changed to function in the image forming apparatus 200. For example, the image forming apparatus 200 has a photosensitive drum 2, similar to the image forming apparatus 1, but is configured so that transfer is performed directly onto the recording material by the photosensitive drum 2 and a transfer roller 9 facing the photosensitive drum 2.

[0055] Next, the differences between the image forming apparatus 1 and the image forming apparatus 200 will be explained using Figure 10. Figure 10 is a schematic diagram of the image forming apparatus 200. The image forming apparatus 200 has a toner cartridge 70 that contains black toner that can be attached to and detached from the main body 200A of the image forming apparatus 200. The image forming apparatus 200 also has a toner storage section 201. Toner is supplied from the toner cartridge 70 to the toner storage section 201, and the toner storage section 201 stores the toner. The toner storage section 201 includes a magnet storage section 201a and a developer roller storage section 201b. The magnet storage section 201 and the developer roller storage section 201b are in communication. The toner supplied from the toner cartridge 70 flows to the magnet storage section 201, and then flows from the magnet storage section 201 to the developer roller storage section 201b. The magnet storage section 201 includes a detection unit 203, which will be described later. The developing roller housing section 201b includes a developing roller 51 and a supply roller 52. The developing roller housing section 201b houses a portion of the developing roller 51.

[0056] The image forming apparatus 200 also includes a magnetic sensor 102. The magnetic sensor 102 is mounted so as to be fixed to the magnet housing 201.

[0057] Next, the detected unit 203 will be described. The detected unit 203 comprises a rotating body 203, a support member 202, a permanent magnet 101, and a yoke member 104. As described in Example 1, the permanent magnet 101 and the yoke member 104 can be called the magnetic unit 105. The rotating body 203 is provided in the magnet housing 201. The rotating body 203 includes a shaft 203a (first magnetic material) which is a magnetic material. The shaft 203a rotates by receiving a driving force from a drive mechanism (not shown). The rotating body 203 rotates together with the shaft 203a. One end of the flexible support member 202 is fixed to the rotating body 203, and the other end is fixed to the magnetic unit 105. The support member 202 rotates in conjunction with the rotation of the rotating body 203, stirring the toner inside the magnet housing 201. In other words, the rotating body 203 rotates inside the magnet housing 201 and is a rotating body that supplies toner. As the support member 202 rotates, the magnetic unit 105 also rotates, changing the position of the permanent magnet 101 relative to the magnetic sensor 102.

[0058] The positional relationship between the permanent magnet 101 and the yoke member 104 is the same as in Embodiment 1. That is, the yoke member 104 is bonded to the south pole surface 101s. Furthermore, the magnetic field lines emanating from the north pole surface 101n are configured to penetrate the magnetic sensor 102.

[0059] Next, the method for detecting the remaining toner level in Example 2 will be explained using Figure 11. Figure 11(a) shows the case where the remaining toner level in the magnet housing 201 is low, and Figure 11(b) shows the case where the remaining toner level in the magnet housing 201 is higher than in Figure 11(a). Note that Figure 11 is a view in the axial direction of the rotating body 203. The trajectory 202rb shown in Figure 11(b) shows the trajectory traced by the center of the S pole surface 101s when the magnetic body unit 105 rotates. The trajectory 202ra shown in Figure 11(a) shows the trajectory traced by the center of the S pole surface 101s when the magnetic body unit 105 rotates. As the rotating body 203 rotates, the magnetic body unit 105 completes one rotation. In other words, the magnetic body unit 105 moves closer to or further away from the magnetic sensor 102. Note that point A shown in Figure 11(a) indicates the proximity position of the permanent magnet 101.

[0060] The magnetic sensor 102 detects the magnetic field when the magnetic material unit 105 approaches the magnetic sensor 102. Because the support member 202 is flexible, if there is enough toner inside the magnet housing 201, the permanent magnet 101 rotates to trace the trajectory 202rb. On the other hand, if there is little toner inside the magnet housing 201, the permanent magnet 101 rotates to trace the trajectory 202ra. In other words, the rotation trajectory of the permanent magnet 101 changes according to the amount of toner inside the magnet housing 201. More specifically, the radius of rotation of the support member 202 is smaller when moving through a space with a lot of toner than when moving through a space with little toner. As a result, the magnetic field detected by the magnetic sensor 102 also changes, and the remaining amount of toner can be detected.

[0061] Next, the effect of the yoke member 104 in this embodiment will be explained. When the permanent magnet 101 is in close proximity to the magnetic sensor 102 (Figure 11(b)), the shaft 203a, yoke member 104, S pole surface 101s, N pole surface 101n, and sensor 102 are arranged in that order in the direction from the S pole surface 101s to the N pole surface 101n. As explained in Embodiment 1, by positioning the yoke member 104 on the S pole surface 101s side, the magnetic flux distribution on the S pole side of the permanent magnet 101 can be reduced. Therefore, the magnetic force acting between the magnetic material unit 105 and the shaft 203a can be weakened compared to when the yoke member 104 is not provided.

[0062] As explained above, even in image forming apparatuses other than rotary type, providing the yoke member 104 can reduce the magnetic force acting between the magnetic material and the permanent magnet 101, thereby suppressing a decrease in the detection accuracy of the detection unit.

[0063] [Example 1] Next, Modification 1 will be described. The yoke member 104 in Examples 1 and 2 can be replaced with the shape of the yoke member 404 described in Modification 1. Figure 12 is a cross-sectional view showing the yoke member 404. The yoke member 404 comprises an overlapping portion 404o and a non-overlapping portion 404s. The overlapping portion 404o is the same as the overlapping portion 104o described in Example 1. That is, the positional relationship of the overlapping portion 104o with respect to the permanent magnet 101 is as described in the example, so the description will be omitted. The non-overlapping portion 404s comprises an extended portion 404s1 and a bent portion 404s2. The extended portion 404s1 extends from the overlapping portion 404o and extends along the direction in which the S pole surface 101s extends. The folded portion 404s2 extends from the non-overlapping portion 404s and extends in the direction from the south pole surface 101s toward the north pole surface 101n. That is, the folded portion 404s2 extends from the first end face toward the second end face.

[0064] The permanent magnet 101 has a first surface 101u located between the south pole surface 101s and the north pole surface 101n in the direction from the south pole surface 101s to the north pole surface 101n (first direction). The permanent magnet 101 also has a second surface 101d located between the south pole surface 101s and the north pole surface 101n in the direction from the south pole surface 101s to the north pole surface 101n. The first surface 101u and the second surface 101d are opposing surfaces. The first surface 101u and the second surface 101d extend in the direction from the south pole surface 101s to the north pole surface 101n. The bent portion 404s2 has a first bent portion 404s2u and a second bent portion 404s2d. The first bent portion 404s2u faces the first surface 101u, and the second bent portion 404s2d faces the second surface 101d.

[0065] Figure 13 is a plan view of the permanent magnet 101 and the yoke member 404. Figure 13 is also a view taken in the direction normal to the first side surface 101u. The area enclosed by the dashed line in Figure 13 represents the area of ​​the first side surface 101u and the second side surface 101. The area enclosed by the solid line represents the area of ​​the first bent portion 404s2u and the second bent portion 404s2d. When viewed in the direction normal to the first side surface 101u, the first bent portion 404s2u overlaps with the first side surface 101u. Also, when viewed in a direction perpendicular to the first direction, the first bent portion 404s2u, as part of the yoke member 404, overlaps with the first side surface 101u. Also, when viewed in the direction normal to the first side surface 101u, the second bent portion 404s2d overlaps with the second side surface 101d. Furthermore, if we refer to either the first side surface 101u or the second side surface 101d as the third end surface, then it can be said that the yoke member 404 (second magnetic material) overlaps with the third end surface when viewed in the direction normal to the third end surface.

[0066] Next, the effect of the yoke member 404 will be explained using Figure 14. Figure 14 is a graph showing the magnetic flux density of the magnetic field formed by the permanent magnet 101. The imaginary line 401L shown in Figure 12 is an imaginary line that passes through the center of the S pole surface 101s and extends in the first direction. The magnetic flux density shown in Figure 14 is the magnetic flux density on the imaginary line 401L. The horizontal axis shows the distance from the S pole surface 101s in the direction from the S pole surface 101s toward the N pole surface 101n. The vertical axis shows the magnitude of the magnetic flux density. The solid line shows the case in which the yoke member 104 described in Example 1 is provided (Figure 7(a)). The dashed line shows the case in which the yoke member 404 is provided (Figure 12). As the graph in Figure 14 shows, it can be seen that the magnetic flux density on the S pole surface side is smaller when the yoke member 404 is provided than when the yoke member 104 is provided. Furthermore, it can be seen that the magnetic flux density on the north pole side is greater when the yoke member 404 is provided than when the yoke member 104 is provided. This is because the yoke member 404 includes a bent portion 404s2. The bent portion 404s2 extends from the south pole surface 101s toward the north pole surface 101n. Therefore, the magnetic field lines emanating from the north pole surface 101n enter the bent portion 404s2, resulting in fewer magnetic field lines wrapping around behind the south pole surface 101s compared to when the yoke member 104 is provided. In addition, the inclination of the magnetic field lines entering the bent portion 404s2 is gentler compared to when the yoke member 104 is provided because the magnetic field lines emanating from the north pole surface 101n enter the bent portion 404s2. As a result, the number of magnetic field lines passing through the magnetic sensor 102 increases, making it easier to detect the magnetic field formed by the permanent magnet 101.

[0067] Examples 1, 2, and Modification 1 have been described above. In Examples 1, 2, and Modification 1, the yoke member 404 was attached to the south pole surface 101s of the permanent magnet 101. However, the polarity of the permanent magnet 101 may be reversed. That is, the yoke member 404 may be attached to the north pole surface 101n of the permanent magnet 101. In this case, the magnetic field lines returning to the south pole surface 101s penetrate the magnetic sensor 102, causing the magnetic sensor 102 to detect a magnetic field.

[0068] Furthermore, while the shaft was mentioned as a component with which magnetic force acts between it and the permanent magnet 101, the present invention can also be applied to other magnetic materials within the image forming apparatus to achieve its effects. [Explanation of symbols]

[0069] 53a Developing side storage section 52a First magnetic body 101 Permanent Magnets 101n N-pole surface 101s S pole surface 102 Magnetic Sensor 104 Second magnetic material 104o Overlap section 104s Non-overlapping section

Claims

1. A housing section for housing toner and first magnetic material, A magnetic material unit comprising a permanent magnet including a first end face and a second end face, and a second magnetic material having a lower residual magnetic flux density than the permanent magnet, wherein the magnetic material unit moves inside the storage section according to the amount of toner in the storage section, A sensor that outputs a signal based on the magnetic field formed by the permanent magnet, Equipped with, When the direction from one magnetic pole of the permanent magnet toward the other magnetic pole is defined as the first direction, the first end face is one end of the permanent magnet in the first direction, and the second end face is the other end of the permanent magnet opposite to the one end in the first direction. The position where the permanent magnet is closest to the sensor is defined as the proximity position, and when the permanent magnet is in the proximity position, the shortest distance between the first end face and the sensor is greater than the shortest distance between the second end face and the sensor. When the permanent magnet is in the proximity position, the shortest distance between the first magnetic material and the second magnetic material is smaller than the shortest distance between the first magnetic material and the first end face. Viewed in the first direction, the second magnetic material comprises an overlapping portion that overlaps with the first end face and a non-overlapping portion that does not overlap with the first end face. An image forming apparatus characterized by the following features.

2. The housing further comprises a rotating body that rotates inside the housing, The first magnetic material is a shaft provided by the rotating body. The image forming apparatus according to feature 1.

3. It further includes a developing roller that supplies toner to the photosensitive drum, The rotating body is the developing roller. The image forming apparatus according to feature 2.

4. A developing roller that supplies toner to the photosensitive drum, The system further comprises a supply roller that supplies toner to the developing roller, The rotating body is the supply roller. The image forming apparatus according to feature 2.

5. The permanent magnet has a third end face located between the first end face and the second end face in the first direction. Viewed in a direction perpendicular to the first direction, a portion of the second magnetic material overlaps with the third end face. The image forming apparatus according to feature 1.

6. The rotary further comprises the aforementioned housing section, The magnetic unit moves relative to the housing as the rotary rotates. The image forming apparatus according to feature 2.

7. The shortest distance between the rotating body and the center of rotation of the rotary is shorter than the shortest distance between the permanent magnet and the center of rotation. The image forming apparatus according to feature 6.

8. The position of the rotary when the permanent magnet is in the aforementioned proximity position is defined as the first position. The first state is defined as the rotary being in the first position and the amount of toner in the storage compartment being a first amount. The second state is defined as the rotary being in the first position and the amount of toner in the storage compartment being a second amount, which is less than the first amount. The shortest distance between the permanent magnet and the shaft in the second state is shorter than the shortest distance between the permanent magnet and the shaft in the first state. The image forming apparatus according to feature 6.

9. The toner cartridge that houses the toner is removable. Toner is supplied from the toner cartridge to the storage unit. The image forming apparatus according to any one of claims 1 to 8.

10. The sensor changes the signal it outputs according to the magnitude of the detected magnetic flux density. The image forming apparatus according to any one of claims 1 to 8.

11. Based on the aforementioned signal, information regarding the remaining toner level is notified. The image forming apparatus according to any one of claims 1 to 8.

12. The permanent magnet and the second magnetic material are bonded together via an adhesive member. The image forming apparatus according to any one of claims 1 to 8.

13. The magnetic material unit further comprises a support member that supports the second magnetic material, The support member includes resin, The image forming apparatus according to any one of claims 1 to 8.

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