JP2017072752A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve the sensitivity of a sensor that detects magnetic permeability inside a developer container that stores a two-component developer, while ensuring rigidity necessary for a stirring member inside the developer container.SOLUTION: A magnetic permeability sensor 435 detects the magnetic permeability at a measurement position P0 inside a developer container 4300. A stirring member 432 comprises a rotation shaft 11 including a synthetic resin base part 12 and a metallic reinforcement part 13 formed integrally with the base part 12. The reinforcement part 13 includes a first portion 131 that reinforces a portion excluding a specific intermediate part 12a opposite to the measurement point P0 in the base part 12. The reinforcement part 13 includes a second portion 132 that reinforces the specific intermediate part 12a of the base part 12 and is formed thinner than the first portion 131.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a developing device and an image forming apparatus.

In general, an electrophotographic image forming apparatus includes an image carrier on which an electrostatic latent image is formed,
A developing device for developing the electrostatic latent image on the image carrier.

  The developing device includes a stirring member that stirs the developer in the developing container. In the case where the developer is a two-component developer, the developing device includes a magnetic permeability sensor that detects the magnetic permeability in the developing container. The detected value of the magnetic permeability sensor is an index value of the remaining amount of toner in the developing container.

  In addition, it is known that the stirring member of the developing device includes a plate-like pressurizing portion that protrudes outward from a portion corresponding to the magnetic permeability sensor on the rotation shaft of the stirring member (for example, Patent Literature 1). 1). As the stirring member rotates, the pressurizing unit applies pressure to the two-component developer present between the inner surface of the developing container.

  When the two-component developer is pressurized at a position facing the magnetic permeability sensor in the developing container, the bulk density and the flow state of the two-component developer are stabilized. As a result, the detection result of the magnetic permeability sensor is not easily affected by disturbances such as the bulk density and flow state of the two-component developer.

JP 2009-244534 A

  By the way, in the developing device, the stirring member is mainly composed of a member made of synthetic resin in response to a request for weight reduction and cost reduction. However, the rotating shaft of the stirring member may be reinforced with a metal member. Thereby, the required rigidity of the said rotating shaft is ensured, without forming the said rotating shaft too thickly.

  For example, the rotating shaft may have a metal rod-shaped core member and a synthetic resin portion formed around the core member. In this case, the core member is a reinforcing portion.

  On the other hand, if the metal reinforcing part is present in the detection area of the magnetic permeability sensor, the detection sensitivity of the magnetic permeability sensor is deteriorated.

  An object of the present invention is to provide a developing device capable of improving the sensitivity of a sensor for detecting the magnetic permeability in the developing container while ensuring the necessary rigidity of the stirring member in the developing container containing the two-component developer. An object is to provide an image forming apparatus.

  A developing device according to one aspect of the present invention includes a developing container, a stirring member, and a magnetic permeability sensor. The developing container is a container for storing a two-component developer. The stirring member is a member that rotates in the developing container and stirs the two-component developer. The magnetic permeability sensor is a sensor that is disposed outside the developing container and detects a magnetic permeability at a measurement position in the developing container. The stirring member includes a rotating shaft that is rotatably supported by a pair of opposing side wall portions in the developing container. The measurement position is a position along a specific intermediate portion between both end portions of the rotating shaft of the stirring member. The rotating shaft includes a base portion and a reinforcing portion. The base is a synthetic resin portion formed in a series from one end to the other end of the rotating shaft. The reinforcing portion is a metal portion formed integrally with the base portion. The reinforcing part has a first part and a second part. The first portion is a portion that reinforces a portion excluding the specific intermediate portion facing the measurement position in the base portion. The second portion is a portion that reinforces the specific intermediate portion of the base and is formed thinner than the first portion.

  A developing device according to another aspect of the present invention includes a developing container, a stirring member, and a magnetic permeability sensor. The developing container is a container for storing a two-component developer. The stirring member is a member that rotates in the developing container and stirs the two-component developer. The magnetic permeability sensor is a sensor that is disposed outside the developing container and detects a magnetic permeability at a measurement position in the developing container. The stirring member includes a rotating shaft that is rotatably supported by a pair of opposing side wall portions in the developing container. The measurement position is a position along a specific intermediate portion between both end portions of the rotating shaft of the stirring member. The rotating shaft includes a base portion and a reinforcing portion. The base is a synthetic resin portion formed in a series from one end to the other end of the rotating shaft. The reinforcing portion is a metal portion that is formed integrally with the base portion and reinforces a portion of the base portion excluding the specific intermediate portion that faces the measurement position. The rotating shaft does not have the reinforcing portion made of metal at the specific intermediate portion in the base portion.

  An image forming apparatus according to another aspect of the present invention includes an image carrier and the developing device. The image carrier is a member on which an electrostatic latent image is formed. The developing device develops the electrostatic latent image on the image carrier.

  According to the present invention, a developing device capable of improving the sensitivity of a sensor for detecting the magnetic permeability in the developing container while ensuring the necessary rigidity of the stirring member in the developing container that accommodates the two-component developer, and An image forming apparatus can be provided.

FIG. 1 is a configuration diagram of an image forming apparatus including a developing device according to the first embodiment. FIG. 2 is a configuration diagram of the developing device according to the first embodiment. FIG. 3 is a longitudinal sectional view of a part of the developing device according to the first embodiment. FIG. 4 is a cross-sectional view of a part of the developing device according to the first embodiment. FIG. 5 is a front view of a part of the stirring member provided in the developing device according to the first embodiment. FIG. 6 is a perspective view of the reinforcing portion of the stirring member provided in the developing device according to the first embodiment. FIG. 7 is a longitudinal sectional view of a part of the developing device according to the second embodiment. FIG. 8 is a perspective view of the reinforcing portion of the stirring member according to the application example. FIG. 9 is a graph showing the relationship between the toner ratio of the two-component developer and the magnetic sensor detection result in the evaluation test.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: It does not have the character which limits the technical scope of this invention.

First Embodiment: Schematic Configuration of Image Forming Apparatus 10
First, a schematic configuration of the image forming apparatus 10 according to the first embodiment will be described with reference to FIG.

  The image forming apparatus 10 is an electrophotographic image forming apparatus that forms an image on a sheet 9. The sheet 9 is a sheet-like image forming medium such as paper, coated paper, postcard, envelope, and OHP sheet.

  The image forming apparatus 10 includes a sheet supply unit 2, a sheet conveying unit 3, an image forming unit 4, a control unit 8, and the like in the main body unit 100. The image forming unit 4 includes a developing unit 4x, an optical scanning unit 40, a fixing device 49, and the like.

  An image forming apparatus 10 shown in FIG. 1 is a tandem image forming apparatus and a color printer. Therefore, the image forming unit 4 includes a plurality of developing units 4x corresponding to cyan, magenta, yellow, and black colors.

  Further, the image forming unit 4 includes an intermediate transfer belt 48, a secondary transfer device 481, and a secondary cleaning device 482. The intermediate transfer belt 48 is a belt-like member formed in an annular shape, and rotates in a state of being spanned between two rollers.

  In the sheet supply unit 2, the sheet delivery unit 22 sends out the sheet 9 stored in the sheet cassette 21 to the conveyance path 30.

  The sheet conveyance unit 3 includes a plurality of conveyance rollers 31. Each of the transport rollers 31 transports the sheet 9 supplied from the sheet supply unit 2 along the transport path 30. Further, one transport roller 31 discharges the sheet 9 after image formation from the main body 100 to the discharge tray 101.

  In each developing unit 4x, the drum-shaped photoconductor 41 rotates, and the charging device 42 charges the surface of the photoconductor 41 uniformly. Further, the optical scanning unit 40 writes an electrostatic latent image on the surface of the photoreceptor 41, and the developing device 43 develops the electrostatic latent image formed on the surface of the photoreceptor 41 with the toner 91. As a result, a toner image is formed on the surface of the photoreceptor 41. The photoconductor 41 is an example of an image carrier.

  The toner 91 of each color is supplied to the developing device 43 of each developing unit 4x from a toner replenishing unit 400 provided for each color of cyan, magenta, yellow, and black.

  In each developing unit 4x, the primary transfer device 45 transfers the toner image from the surface of the photoreceptor 41 to the intermediate transfer belt 48. On the intermediate transfer belt 48, the toner image is transferred from each of the plurality of photoconductors 41. As a result, a color image in which the toner images of the respective colors are superimposed is formed on the intermediate transfer belt 48. The primary cleaning device 47 removes the toner 91 remaining on the surface of the photoreceptor 41.

  The secondary transfer device 481 transfers the color image formed on the intermediate transfer belt 48 to the sheet 9 in the conveyance path 30. The secondary cleaning device 482 removes the toner 91 remaining on the intermediate transfer belt 48.

  The fixing device 49 heats the toner image on the sheet 9 in the conveyance path 30 to fix the color image on the sheet 9. The control unit 8 is a processor that controls an electrical device included in the image forming apparatus 10.

  The developing device 43 shown in FIGS. 1 and 2 executes a developing process using a two-component developer 90 including a toner 91 and a carrier 92. That is, the developing device 43 agitates the two-component developer 90 including the toner 91 and the carrier 92 to charge the toner 91 and supplies the charged toner 91 to the photoreceptor 41.

  The carrier 92 is a granular material having magnetism. For example, the carrier 92 may be a granular body including a granular magnetic body and a synthetic resin film such as an epoxy resin coated on the surface of the magnetic body.

  As shown in FIG. 2, the developing device 43 includes a developing container 4300, a developing roller 430, stirring members 432 and 433, a blade 434, and a magnetic permeability sensor 435. Further, the developing device 43 includes a developing magnet 431. The magnet 431 is included in the developing roller 430. The developing roller 430 and the magnet 431 constitute a magnet roller for carrying a two-component developer.

  The developing container 4300 is a container for storing the two-component developer 90. The developing roller 430 and the stirring members 432 and 433 rotate within the developing container 4300. The developing roller 430 is rotatably supported so as to face the photoreceptor 41 in a non-contact state.

  The stirring members 432 and 433 are members that rotate in the developing container 4300 and stir the two-component developer 90. As a result, the toner 91 is charged with a predetermined polarity. Further, the carrier 92 is charged with a polarity opposite to the charging polarity of the toner 91.

  In the present embodiment, the developing device 43 includes two stirring members 432 and 433 arranged in parallel. The first stirring member 432 and the second stirring member 433 stir while transporting the two-component developer 90 in opposite directions. Thereby, the first stirring member 432 and the second stirring member 433 circulate the two-component developer 90 in the developing container 4300.

  The developing roller 430 rotates while carrying the stirred two-component developer 90. The developing roller 430 supplies the charged toner 91 of the carried two-component developer 90 to the photoreceptor 41.

  More specifically, the developing roller 430 carries the two-component developer 90 as a magnetic brush by the action of the magnetic force of the magnet 431 included therein. Further, the developing roller 430 develops the electrostatic latent image into the toner image by bringing the magnetic brush into contact with the outer peripheral surface of the photoreceptor 41.

  The blade 434 limits the thickness of the magnetic brush carried by the developing roller 430. The carrier 92 remaining on the developing roller 430 after the development is collected in the developing container 4300. Accordingly, as the remaining amount of toner 91 in the developing container 4300 decreases, the ratio of the carrier 92 in the two-component developer 90 increases and the ratio of the toner 91 decreases.

  In the following description, the ratio of the weight of the toner 91 to the weight of the carrier 92 in the two-component developer 90 per unit volume at the measurement position P0 is referred to as a toner ratio.

  The magnetic permeability sensor 435 is disposed outside the developing container 4300. The magnetic permeability sensor 435 is a sensor that detects the magnetic permeability at a predetermined measurement position P 0 in the developing container 4300. Accordingly, the detection end 4350 of the magnetic permeability sensor 435 is directed from the outside of the developing container 4300 to the measurement position P0.

  The magnetic permeability sensor 435 is provided for measuring the magnetic permeability of the two-component developer 90 present at the measurement position P0. The detection value of the magnetic permeability sensor 435 changes according to the ratio of the carrier 92 in the two-component developer 90. In other words, the ratio of the toner 91 in the two-component developer 90 appears as a magnetic permeability that is the magnetic resistance of the two-component developer 90 per unit volume. Therefore, the detected value of the magnetic permeability sensor 435 becomes an index value of the remaining amount of toner in the developing container 4300.

  By the way, in the developing device 43, the stirring members 432 and 433 are mainly composed of a synthetic resin member due to a demand for weight reduction and cost reduction. However, the rotating shaft 11 of the stirring members 432 and 433 may be reinforced with a metal member. Thereby, the required rigidity of the rotating shaft 11 is ensured, without the rotating shaft 11 being formed too thickly.

  For example, the rotating shaft 11 may have a metal rod-shaped core member and a synthetic resin portion formed around the core member. In this case, the core member is a reinforcing portion.

  On the other hand, if the metal reinforcing part is present in the detection region of the magnetic permeability sensor 435, the detection sensitivity of the magnetic permeability sensor 435 is deteriorated. In the present embodiment, a part of the rotation shaft 11 of the first stirring member 432 exists in the detection region of the magnetic permeability sensor 435.

  The first stirring member 432 of the developing device 43 has a structure that can improve the sensitivity of the magnetic permeability sensor 435 while ensuring necessary rigidity. Hereinafter, the structure of the first stirring member 432 will be described.

[First stirring member 432]
As shown in FIGS. 3 to 5, the first stirring member 432 includes the rotating shaft 11, the spiral blade 14, and the pressurizing unit 16. FIG. 4 shows a cross section along the II plane shown in FIG.

  As shown in FIG. 3, the rotation shaft 11 of the first stirring member 432 is rotatably supported by the support shaft portions 4302 of the pair of side wall portions 4301 facing each other in the developing container 4300. The measurement position P <b> 0 is a position along an intermediate portion between both end portions of the rotary shaft 11 of the first stirring member 432. Hereinafter, this intermediate portion is referred to as a specific intermediate portion 12a.

  The rotating shaft 11 includes a base portion 12 and a reinforcing portion 13. The base 12 is a synthetic resin portion formed in a series from one end of the rotating shaft 11 to the other end. The specific intermediate portion 12 a of the rotating shaft 11 is a part of the base portion 12. The specific intermediate portion 12a is a portion facing the measurement position P0 in the base portion 12.

  The spiral blade 14 is a portion formed so as to protrude spirally from the base portion 12. That is, the first stirring member 432 is a so-called screw feeder. The base 12 and the spiral blade 14 are synthetic resin integrally molded members.

  As the first stirring member 432 rotates around the rotation shaft 11, the spiral blade 14 conveys the two-component developer 90 in the longitudinal direction of the rotation shaft 11 while stirring the two-component developer 90.

  In the first stirring member 432, a rib 15 protruding from the outer peripheral surface of the base 12 along the longitudinal direction of the rotary shaft 11 is formed in the specific intermediate portion 12 a of the base 12 of the rotary shaft 11. In the first stirring member 432, the base portion 12, the spiral blade 14, and the rib 15 of the rotary shaft 11 are synthetic resin integrally molded members.

  The reinforcing portion 13 is a metal portion formed integrally with the base portion 12. For example, it is conceivable that the reinforcing portion 13 is a metal member mainly composed of stainless steel, iron, aluminum, steel, or the like.

  In the present embodiment, the base portion 12 of the rotating shaft 11 includes a reinforcing portion 13. For example, it is conceivable that the base portion 12, the spiral blade 14 and the rib 15 are synthetic resin members formed by insert molding using the metal reinforcing portion 13 as an insert. It is also conceivable that the reinforcing portion 13 is a member press-fitted into a through hole formed in the base portion 12.

  The reinforcing portion 13 of the first stirring member 432 has a first portion 131 and a second portion 132. The first portion 131 of the reinforcing portion 13 is a portion that reinforces the portion of the base portion 12 excluding the specific intermediate portion 12a. The second portion 132 of the reinforcing portion 13 is a portion that reinforces the specific intermediate portion 12 a of the base portion 12. The second portion 132 is formed thinner than the first portion 131.

  In the first stirring member 432, the pressurizing unit 16 is a non-metallic member attached to the specific intermediate portion 12 a in the base portion 12 of the rotating shaft 11. The pressurizing unit 16 is also a nonmagnetic material. The pressurizing part 16 is formed in a plate shape projecting outside the specific intermediate part 12a. The pressurizing part 16 is formed to protrude further outward than the spiral blade 14.

  The pressurizing unit 16 is a flexible member such as a synthetic leather member. It is also conceivable that the pressure unit 16 is a plate-like member made of a synthetic resin such as polyethylene terephthalate (PET). Also in this case, the pressure unit 16 bends due to the pressure received from the two-component developer 90.

  As the first stirring member 432 rotates, the pressure unit 16 applies pressure to the two-component developer 90 existing between the inner surface 430f of the developing container 4300 (see FIGS. 3 and 4). That is, the two-component developer 90 is pressurized at the measurement position P0 that faces the detection end 4350 of the magnetic permeability sensor 435 in the developing container 4300.

  Here, the magnetic permeability sensor 435 will be described. The magnetic permeability sensor 435 is a resonance type magnetic sensor. The level of the detection signal of the magnetic permeability sensor 435 represents the resonance frequency of the resonance circuit that varies depending on the magnetic permeability at the measurement position P0.

  A generally positive proportional relationship is established between the resonance frequency and the toner ratio. Therefore, the higher the detection signal level of the magnetic permeability sensor 435, the higher the toner ratio.

  On the other hand, the level of the detection signal of the magnetic permeability sensor 435 also varies due to disturbances such as the bulk density and flow state of the two-component developer 90 at the measurement position P0. Therefore, every time the first stirring member 432 makes one rotation, the detection signal of the magnetic permeability sensor 435 periodically varies according to the periodic variation of the disturbance.

  Then, at the timing when the pressurizing unit 16 pressurizes the two-component developer 90 at the measurement position P0, the level of the detection signal of the magnetic permeability sensor 435 becomes a minimum value. Further, the state where the pressurizing unit 16 pressurizes the two-component developer 90 at the measurement position P0 is the state where the influence of the disturbance is the smallest.

  The control unit 8 specifies the minimum value of the detection signal of the magnetic permeability sensor 435 generated in synchronization with the rotation period of the first stirring member 432. Then, the control unit 8 processes the specified minimum value of the detection signal as a detection value representing the toner ratio.

  For example, the control unit 8 performs toner replenishment control when the minimum value of the detection signal of the magnetic permeability sensor 435 falls below a predetermined lower limit value. The toner replenishment control is a process for replenishing the toner 91 from the toner replenishing unit 400 to the developing container 4300 by controlling a toner supply mechanism (not shown).

  When the two-component developer 90 is pressurized at the measurement position P0, the bulk density and the flow state of the two-component developer 90 are stabilized. As a result, the detection result of the magnetic permeability sensor 435 is not easily affected by disturbances such as the bulk density and flow state of the two-component developer 90.

  In the present embodiment, a part on the base side of the pressurizing part 16 is fixed to the rib 15 of the specific intermediate part 12a. For example, it is conceivable that the pressure unit 16 is fixed to the rib 15 by screwing, adhesive, welding, or the like. The pressurizing portion 16 is formed so as to protrude further outward from the rib 15. The rib 15 is a mounting seat for the pressure unit 16 and also a reinforcing part for the base 12 of the rotating shaft 11.

  It is also conceivable that the plurality of ribs 15 are formed on the outer peripheral surface of the specific intermediate portion 12 a of the base portion 12. In this case, the remaining one or more ribs 15 other than the one rib 15 to which the pressurizing unit 16 is attached function as a reinforcing portion of the specific intermediate portion 12 a in the base portion 12.

  In this embodiment, the 2nd part 132 of the reinforcement part 13 is formed in the position biased to the opposite side to the side in which the pressurization part 16 was attached in the base part 12 (refer FIG. 4, 5). For example, as shown in FIGS. 4 to 6, it is conceivable that the first portion 131 of the reinforcing portion 13 has a cylindrical shape, and the second portion 132 of the reinforcing portion 13 has a semi-cylindrical shape. In this case, the semi-cylindrical second portion 132 is formed on the opposite side of the base portion 12 to the side on which the pressurizing portion 16 is attached.

  Therefore, when the pressurizing unit 16 pressurizes the two-component developer 90 at the measurement position P0, the second portion 132 of the reinforcing unit 13 exists at a position farthest from the detection end 4350 of the magnetic permeability sensor 435. .

  In the developing device 43, the specific intermediate portion 12 a of the rotation shaft 11 of the first stirring member 432 is close to the detection region of the magnetic permeability sensor 435. Therefore, the metal member that reinforces the specific intermediate portion 12a deteriorates the detection sensitivity of the magnetic permeability sensor 435.

  In the present embodiment, the second portion 132 of the reinforcing portion 13 that reinforces the specific intermediate portion 12 a of the base portion 12 is thinner than the first portion 131 that reinforces the other portions of the base portion 12. Therefore, the influence which the 2nd part 132 of the reinforcement part 13 has on the detection sensitivity of the magnetic permeability sensor 435 is small.

  Furthermore, the second portion 132 of the reinforcing portion 13 is formed at a position that is biased toward the opposite side of the base portion 12 to the side to which the pressing portion 16 is attached. In this case, when the minimum value of the detection signal of the magnetic permeability sensor 435 is obtained, the second portion 132 of the reinforcing portion 13 exists at a position farthest from the detection end 4350 of the magnetic permeability sensor 435. Accordingly, the influence of the second portion 132 of the reinforcing portion 13 on the detection sensitivity of the magnetic permeability sensor 435 is smaller.

  Further, a portion of the rotating shaft 11 excluding the specific intermediate portion 12a, that is, a portion having a very small influence on the magnetic permeability sensor 435 is reinforced by the first portion 131 of the relatively thick reinforcing portion 13. Furthermore, the specific intermediate portion 12 a of the rotating shaft 11 is also reinforced by the second portion 132 of the reinforcing portion 13. Therefore, the required rigidity of the first stirring member 432 is ensured.

  As described above, when the developing device 43 is employed, the detection sensitivity of the magnetic permeability sensor 435 can be improved while ensuring the necessary rigidity of the entire first stirring member 432.

[Second Embodiment]
Next, the developing device 43A according to the second embodiment will be described with reference to FIG. The developing device 43A differs from the developing device 43 shown in FIGS. 1 to 6 in that the first stirring member 432A having a different reinforcing portion structure is provided.

  7, the same components as those shown in FIGS. 1 to 6 are given the same reference numerals. Hereinafter, differences between the first stirring member 432A and the first stirring member 432 will be described.

  The first stirring member 432A includes a rotating shaft 11A, a spiral blade 14, and a pressure unit 16. The rotating shaft 11A includes a base portion 12 and a reinforcing portion 13A. The base portion 12 of the rotating shaft 11 </ b> A is a synthetic resin portion like the base portion 12 of the rotating shaft 11.

  The reinforcing portion 13A of the first stirring member 432A is a metal portion that reinforces the portion of the base portion 12 excluding the specific intermediate portion 12a. The reinforcing portion 13 </ b> A is formed integrally with the base portion 12.

  The reinforcing portion 13A is formed separately on both sides of the specific intermediate portion 12a. That is, the reinforcing portion 13 </ b> A of the first stirring member 432 </ b> A corresponds to the first portion 131 of the reinforcing portion 13 in the first stirring member 432.

  The rotating shaft 11A of the first stirring member 432A does not have a metal reinforcing portion in the specific intermediate portion 12a of the base portion 12. A synthetic resin rib 15 is formed on the specific intermediate portion 12a of the base portion 12 of the rotating shaft 11A. The specific intermediate portion 12 a is reinforced by the rib 15. Even if such a rotating shaft 11A is employed, sufficient rigidity of the entire first stirring member 432A may be ensured.

  When the developing device 43A is employed, the same effect as that obtained when the developing device 43 is employed can be obtained. In the first stirring member 432A, it is conceivable that the plurality of ribs 15 are formed on the outer peripheral surface of the specific intermediate portion 12a of the base portion 12. In this case, the remaining one or more ribs 15 other than the one rib 15 to which the pressurizing unit 16 is attached function as a reinforcing portion of the specific intermediate portion 12 a in the base portion 12.

[Application example]
Next, the reinforcing portion 13B according to an application example applicable to the first stirring member 432 of the developing device 43 will be described with reference to FIG. The reinforcing portion 13B is a metal member, like the reinforcing portion 13.

  Similarly to the reinforcing portion 13, the reinforcing portion 13 </ b> B also includes a first portion 131 that reinforces a portion of the base portion 12 excluding the specific intermediate portion 12 a and a second portion 132 </ b> B that reinforces the specific intermediate portion 12 a.

  In the reinforcing portion 13B, the second portion 132B is formed thinner than the first portion 131. In the example shown in FIG. 8, the first portion 131 and the second portion 132 </ b> B are columnar shapes having a concentric circular section when viewed from the longitudinal direction.

  In the first stirring member 432, when the reinforcing portion 13B is employed instead of the reinforcing portion 13, the same effect as that when the reinforcing portion 13 is employed is obtained.

  However, when the minimum value of the detection signal of the magnetic permeability sensor 435 is obtained, the second portion 132 of the reinforcing portion 13 is farther from the detection end 4350 of the magnetic permeability sensor 435 than the second portion 132B of the reinforcing portion 13B. Exists in position. Therefore, the reinforcing part 13 has a smaller influence on the detection sensitivity of the magnetic permeability sensor 435 than the reinforcing part 13B.

[Results of evaluation test]
Next, the results of evaluation tests on three examples EX1 to EX3 and one reference example RF0 will be described with reference to FIG. The first embodiment EX1 is an example in which the first stirring member 432 including the reinforcing portion 13 shown in FIGS. The second example EX2 is an example in which the first stirring member 432A including the reinforcing portion 13A shown in FIG. 7 is employed. The third embodiment EX3 is an example in which the first stirring member 432 including the reinforcing portion 13B shown in FIG. 8 is employed. Reference example RF0 is an example in which, in the first stirring member 432 of the developing device 43, a reinforcing portion having a uniform thickness from one end to the other end of the base portion 12 is employed instead of the reinforcing portion 13.

  The thickness and cross-sectional shape of the first portion 131 of the reinforcing portions 13 and 13B in the first embodiment EX1 and the third embodiment EX3, the thickness and cross-sectional shape of the reinforcing portion 13A in the second embodiment EX2, and the reference example RF0 The thickness and cross-sectional shape of the reinforcing part are the same. Their cross-sectional shape is a circle with a diameter of 6 mm.

  In the first embodiment EX1 and the third embodiment EX3, the cross-sectional area of the second portion 132 of the reinforcing portion 13 and the cross-sectional area of the second portion 132B of the reinforcing portion 13B are both the cross-sectional area of the first portion 131. It is half.

  Other conditions are the same in the three examples EX1 to EX3 and the one reference example RF0. For example, the material of the reinforcing portions 13, 13 </ b> A, 13 </ b> B is SUS430. Moreover, the rotational speed of the 1st stirring member 432 is 296 rpm, the diameter of the 1st stirring member 432 is 20 mm, and the diameter of the rotating shaft 11 is 9 mm. The toner 91 is a positively charged toner having a particle size of 6.8 micrometers, and the particle size of the carrier 92 is 36 micrometers.

  In the graph of FIG. 9, the horizontal axis represents the toner ratio, and the vertical axis represents the resonance frequency corresponding to the minimum value of the detected value of the magnetic permeability sensor 435. In addition, description of the specific numerical value of a vertical axis | shaft is abbreviate | omitted.

  The graph of FIG. 9 shows that all of the first example EX1, the second example EX2, and the third example EX3 have higher detection sensitivity of the toner ratio than the reference example RF0. Here, the difference between the detection values of the magnetic permeability sensor 435 when the toner ratio is 4% and 10% is used as an index value of the detection sensitivity of the magnetic permeability sensor 435.

  The index value of the first embodiment EX1 is about 1.9 times the index value dF0 of the reference example RF0. The index value of the second embodiment EX2 is about 2.0 times the index value dF0 of the reference example RF0. The index value of the third embodiment EX3 is about 1.5 times the index value dF0 of the reference example RF0.

  From the result of the evaluation test, when the first example EX1, the second example EX2, and the third example EX3 are adopted, the detection sensitivity of the magnetic permeability sensor 435 is significantly larger than when the reference example RF0 is adopted. It can be seen that it is improved.

  The developing device and the image forming apparatus according to the present invention can be freely combined within the scope of the invention described in each claim, or can be appropriately combined with the above-described embodiments and application examples. It is also possible to configure by deforming or omitting a part.

2: Sheet supply unit 3: Sheet transport unit 4: Image forming unit 4 x: Development unit 8: Control unit 9: Sheet 10: Image forming apparatus 11, 11 A: Rotating shaft 12: Rotating shaft base 12 a: Specific intermediate portion of the base 13, 13A, 13B: Rotating shaft reinforcement 14: Spiral blade 15: Rib 16: Pressurizing unit 21: Sheet cassette 22: Sheet feeding unit 30: Conveying path 31: Conveying roller 40: Optical scanning unit 41: Photoconductor 42 : Charging device 43, 43A: developing device 45: primary transfer device 47: primary cleaning device 48: intermediate transfer belt 49: fixing device 90: two-component developer 91: toner 92: carrier 100: main body 101: discharge tray 131: First part 132, 132B of reinforcing part: Second part of reinforcing part 400: Toner replenishing part 430: Developing roller 430f: Inner surface 431: Magnetic 432, 432A: first stirring member 433: second stirring member 434: blade 435: magnetic permeability sensor 481: secondary transfer device 482: secondary cleaning device 4300: developing container 4301: side wall portion 4302: support shaft portion P0: measurement position

Claims (7)

A developer container containing a two-component developer;
A stirring member that rotates in the developing container and stirs the two-component developer;
A magnetic permeability sensor disposed on the outside of the developing container and detecting a magnetic permeability at a measurement position in the developing container,
The stirring member includes a rotation shaft that is rotatably supported by a pair of opposing side wall portions in the developing container,
The measurement position is a position along a specific intermediate portion between both end portions of the rotating shaft of the stirring member,
The rotation axis is
A synthetic resin base formed in series from one end of the rotating shaft to the other;
A metal reinforcement formed integrally with the base, and
The reinforcing part is
A first portion for reinforcing a portion excluding the specific intermediate portion facing the measurement position in the base portion;
And a second portion that reinforces the specific intermediate portion of the base and is narrower than the first portion. The stirring member includes a non-metallic pressurizing portion that is attached to the specific intermediate portion of the base of the rotating shaft and is formed in a plate shape projecting to the outside of the specific intermediate portion.
The developing device according to claim 1, wherein the pressure member applies pressure to the two-component developer existing between an inner surface of the developing container and the pressure member when the stirring member rotates.   3. The developing device according to claim 2, wherein the second portion of the reinforcing portion is formed at a position biased to an opposite side of the base portion to a side where the pressing portion is attached. A developer container containing a two-component developer;
A stirring member that rotates in the developing container and stirs the two-component developer;
A magnetic permeability sensor disposed on the outside of the developing container and detecting a magnetic permeability at a measurement position in the developing container,
The stirring member includes a rotation shaft that is rotatably supported by a pair of opposing side wall portions in the developing container,
The measurement position is a position along a specific intermediate portion between both end portions of the rotating shaft of the stirring member,
The rotation axis is
A synthetic resin base formed in series from one end of the rotating shaft to the other;
A metal reinforcing portion that is formed integrally with the base portion and reinforces a portion excluding the specific intermediate portion that faces the measurement position in the base portion, and
The rotating shaft is a developing device in which the specific intermediate portion in the base does not have the metal reinforcing portion. The stirring member includes a non-metallic pressurizing portion that is attached to the specific intermediate portion of the base of the rotating shaft and is formed in a plate shape projecting to the outside of the specific intermediate portion.
5. The developing device according to claim 4, wherein the pressure member applies pressure to the two-component developer existing between an inner surface of the developing container and the pressure member when the stirring member rotates.   The rib which protruded from the outer peripheral surface of the said base along the longitudinal direction of the said rotating shaft is formed in the said specific intermediate part in the said base of the said rotating shaft. The developing device according to 1. An image carrier on which an electrostatic latent image is formed on the surface;
An image forming apparatus comprising: the developing device according to claim 1 that develops the electrostatic latent image on the image carrier.

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