JP2009092762A - Developing device, image forming apparatus equipped therewith, and toner supply method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of achieving shortening a time required until toner is supplied after variation of toner concentration is detected, coping with small variation of the toner concentration and suppressing lowering of developing concentration and occurrence of developing irregularities. <P>SOLUTION: The developing device has a developing tank 11, a developing roller 12, a first stirring conveying screw 13 and a second stirring conveying screw 14, a partition plate 15, and a toner concentration sensor 16. The first stirring conveying screw 13 is provided on a side nearer to the developing roller 12 than the second stirring conveying screw 14, and the toner concentration sensor 16 is provided at the end on a downstream side in the conveying direction of the first stirring conveying screw 13 on the side of the first stirring conveying screw 13. A toner supply port 11b is provided in the vicinity of the toner concentration sensor 16 on the side of the second stirring conveying screw 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, an image forming apparatus including the same, and a toner replenishing method.

  In an image forming apparatus using an electrophotographic method, a surface of a photosensitive drum, which is a latent image carrier, is uniformly charged by a charging device, and then a document image such as a laser beam is applied to the charged surface of the photosensitive drum. The electrostatic latent image is formed by projecting the signal light, and the electrostatic latent image is developed by a developing device to be visualized as a toner image. Then, after the toner image is transferred to a recording paper such as paper or an OHP sheet, the toner image is heated and pressurized by a fixing device to be fixed on the recording paper to form a desired image.

  In recent years, the market demand for downsizing of an image forming apparatus has increased, and downsizing of the developing device itself has been attempted. Along with this, the number of developing devices having a structure for supplying toner from one place is increasing, compared to a developing device having a structure for supplying toner consumed by development from the entire longitudinal direction of the developing device.

  FIG. 10 is a diagram showing a typical configuration of a conventional developing device 200. FIG. 10A is a cross-sectional view of a conventional developing device 200, and FIG. 10B is a top view of the conventional developing device 200 with its upper cover removed.

  In the developing device 200, a toner supply port 201 is provided in the vicinity of one end portion in the longitudinal direction of the developing device 200. The toner replenished from the toner hopper 202 through the toner replenishing port 201 is mixed with the developer by the agitating and conveying member such as the first agitating and conveying screw 203 and the second agitating and conveying screw 204 and then to the developing roller 205. The electrostatic latent image conveyed and formed on the surface of the photosensitive drum 206 is developed. The developer whose toner has been consumed by development is circulated and conveyed again by the agitating and conveying member, and mixing and agitation and conveyance with the toner replenished from the toner hopper 202 are repeated. Further, the developing device 200 is provided with a toner concentration sensor 207. The toner concentration sensor 207 detects the toner concentration in the developer, and based on the obtained detection result, the toner is consumed by the amount consumed by the development. The toner is replenished to maintain a constant toner density.

  Hereinafter, in the developing device 200, the side where the first stirring / conveying screw 203 is located across the partition plate 208 is referred to as a first circulation path A, and the side where the second stirring / conveying screw 204 is present is referred to as a second circulation path B. The first circulation path A and the second circulation path B are separated by the partition plate 208 so that both end portions in the longitudinal direction communicate with each other.

  The toner replenished from the toner replenishing port 201 is downstream from the installation position a of the toner replenishing port 201 via the upstream side b of the second agitating and conveying screw 204 in the second circulation path B, as shown in FIG. 10B. Conveyed to side c and mixed with developer. Then, after being conveyed from the upstream side d to the downstream side e of the first stirring and conveying screw 203 in the first circulation path A, it is conveyed so as to repeatedly circulate in the order of b, c, d, and e.

  In such a conventional developing device 200, the toner concentration sensor 207 is disposed at a position away from the developing roller 205 and the toner supply port 201, for example, near the downstream side c of the second agitating and conveying screw 204 in the second circulation path B. Is done. Also in a developing device having a structure in which a toner replenishing port is provided on the entire longitudinal direction of the developing device, a toner density sensor is generally disposed at a position away from the developing roller.

  For example, in the developing device disclosed in Patent Document 1, toner concentration sensors are provided at two locations where the two component developer conveying speeds are different from each other on the developer conveying member side corresponding to the second agitating and conveying screw 204. ing.

  The reason why the toner density sensor 207 is provided at the position as described above is that when the toner density sensor 207 is provided near the developing roller 205, the toner density after development varies greatly depending on the image to be printed. Therefore, it is difficult to obtain an average value of the toner density. Further, since the toner density sensor 207 is provided at a position away from the toner replenishing port 201, it is possible to secure a time for the replenished toner to be uniformly mixed with the developer, and to stabilize the accurate toner density. There is a point that can be obtained.

  Further, in Patent Document 2, a supply conveyance screw that conveys the developer in the axial direction, a recovery conveyance screw that conveys the developer recovered after the development processing in the axial direction, and a middle of the supply conveyance screw from the downstream portion of the recovery conveyance screw. It is configured to convey the collected developer to the section, and is located at the merging position of the supply conveying screw and the collecting and conveying screw, or on the downstream side from the merging position, and faces the supply conveying screw corresponding to the first stirring and conveying screw 203. A developing means having a toner density sensor provided as described above is disclosed.

JP 2006-119354 A JP 2003-302835 A

  When the toner concentration sensor is arranged at a position for detecting the toner concentration in the developer before being consumed by the developing roller as in the developing device disclosed in Patent Document 1, the position of the toner concentration sensor and the toner Since the position with respect to the replenishing port is separated, a long time is required until the toner is replenished after the toner density is detected. For this reason, when a specific image in which a print portion with a large amount of toner consumption is biased is continuously printed, the toner cannot be properly replenished, and development unevenness may occur.

  Further, using the above-described conventional developing device 200, for example, an image in which there are many solid images locally at a position corresponding to the vicinity of the upstream side d of the first stirring and conveying screw 203 in the first circulation path A is printed. In this case, only the toner on the developing roller 205 corresponding to the solid image portion is consumed. In this case, the developer is circulated and conveyed in the order of d, e, b, and c. Therefore, after the developer is circulated and conveyed about one round from the vicinity of d where the toner is consumed, the vicinity of c where the toner density sensor 207 is provided. A decrease in toner density is detected at. Then, after being further circulated and transported for about half a circle, toner is supplied at the installation position a of the toner supply port 201. That is, in the conventional developing device 200, after the toner is consumed, the developer is replenished so that the target toner density is obtained after the developer is circulated and conveyed by about one and a half cycles. Therefore, when the toner density variation continues to be large, development unevenness due to the toner density variation may continue to occur.

  In the developing device disclosed in Patent Document 2, the toner concentration sensor is arranged at a position for detecting the toner concentration in the developer after being consumed by the developing roller. However, the toner supply port is not limited to one location. In addition, since the supply conveyance screw and the recovery conveyance screw have a two-stage structure, the apparatus may become large. Further, in such a developing device, since the toner density is detected as an average value, it is not possible to cope with fine fluctuations in the toner density, which may cause development unevenness.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to be able to perform a short period of time from detection of toner density fluctuation to toner replenishment, and to cope with fine fluctuations in toner density. Accordingly, it is an object of the present invention to provide a developing device, an image forming apparatus including the same, and a toner replenishing method that can suppress the development density decrease and development unevenness.

The present invention is a developing device for developing an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus, using a developer including at least a toner and a carrier,
A developer tank containing a developer and having a toner supply port formed therein;
A developing roller which is rotatably provided to face the latent image carrier in the developing tank, and supplies a developer to the latent image carrier;
A first agitation transport member and a second agitation transport member, which are rotatably provided in the developing tank, agitate and mix the developer and supply the developer to the developing roller;
A partition member provided between the first agitating and conveying member and the second agitating and conveying member, and forming a circulation path for conveying the developer;
Toner density detecting means for detecting the toner density in the developer,
The first agitating and conveying member is provided closer to the developing roller than the second agitating and conveying member, and the toner concentration detecting means is on the first agitating and conveying member side and the conveying direction of the first agitating and conveying member The developing device is provided at the downstream end, and the toner replenishing port is provided on the second stirring and conveying member side and in the vicinity of the toner concentration detecting means.

  The developing device of the present invention is characterized in that the lengths of the first stirring and conveying member and the second stirring and conveying member in the longitudinal direction are longer than the length of the developing roller in the longitudinal direction.

  In the developing device of the present invention, the partition member is configured such that the length in the longitudinal direction is smaller than the length in the longitudinal direction of the developing tank, and the length in the short direction is the same as the depth of the developing tank. It is comprised so that it may become.

  In the developing device of the present invention, the toner supply port is provided outside the circulation path formed by the partition member.

In the developing device of the present invention, the second agitating / conveying member is configured such that the length in the longitudinal direction is larger than the length in the longitudinal direction of the first agitating / conveying member, and one end thereof is the first. Provided so as to protrude from one end of the stirring and conveying member of
The toner replenishing port is provided above one end portion of the second agitating / conveying member protruding from the one end portion of the first agitating / conveying member.

  In the developing device of the present invention, a replenishing toner damming means is provided in the vicinity of the toner replenishing port and where there is no partition member between the first agitating and conveying member and the second agitating and conveying member. It is characterized by that.

The present invention also provides an image forming apparatus comprising the developing device.
The present invention also provides a toner for a developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus by circulating and conveying a developer including at least toner and a carrier. A toner replenishing method for replenishing
According to another aspect of the present invention, there is provided a toner replenishing method that detects toner concentration in a developer immediately after development and replenishes toner in the vicinity of a detection position where the toner concentration is detected based on a detection result.

  According to the present invention, in a developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus using a developer that includes at least a toner and a carrier, A developing tank in which a toner replenishing port is accommodated, a developing roller that faces the latent image carrier in the developing tank, is rotatably provided, a developer roller that supplies developer to the latent image carrier, and a developing tank that is rotatable. A first agitation transport member and a second agitation transport member that are provided and agitated and mixed to supply the developer to the developing roller; and provided between the first agitation transport member and the second agitation transport member; A partition member that forms a circulation path for transporting the developer, and a toner concentration detection unit that detects the toner concentration in the developer are provided.

  The first agitating / conveying member is provided closer to the developing roller than the second agitating / conveying member, and the toner concentration detection means is located on the first agitating / conveying member side, Provided at the end on the downstream side in the transport direction. That is, it is provided at a position where the toner density immediately after development can be detected. Accordingly, it is possible to shorten the time until the detection of the change in the toner density after development, and to shorten the time during which the toner density is lowered. it can. Further, since the toner density immediately after development can be detected, fluctuations in the toner density in the developing tank can be suppressed in response to fine fluctuations in the toner density.

  The toner replenishing port is provided on the second stirring / conveying member side and in the vicinity of the toner concentration detecting means. Accordingly, since the detection of toner density fluctuation to toner replenishment can be performed in a short time, and the time during which the toner density is lowered can be shortened, the occurrence of development density drop and development unevenness can be suppressed. .

  Therefore, the developing device of the present invention can perform from the detection of the toner density fluctuation to the toner replenishment in a short time, and can cope with the fine fluctuation of the toner density. Can be suppressed.

  According to the invention, it is preferable that the length of the first stirring and conveying member in the longitudinal direction is longer than the length of the developing roller in the longitudinal direction. As a result, the distance of the circulation path for transporting the replenished toner and developer becomes longer, so that the developer can be circulated and transported more smoothly. In addition, since the mixing and stirring of the replenished toner and the developer can be performed for a longer time, a uniform toner concentration can be ensured more stably.

  According to the invention, the partition member is configured such that the length in the longitudinal direction is smaller than the length in the longitudinal direction of the developing tank, and the length in the short direction is the same as the depth of the developing tank. It is preferable to be configured as follows. Thereby, it is possible to prevent the developer with insufficient mixing with the replenished toner and uneven toner density from moving to the developing roller side while forming a circulation path for conveying the developer. . Therefore, it is possible to suppress the occurrence of development unevenness caused by uneven toner density.

  According to the invention, the toner supply port is preferably provided outside the circulation path formed by the partition member. As a result, the toner concentration detecting means provided in the circulation path can detect the toner concentration without being affected by the replenished toner, so that the toner concentration can be detected with high accuracy.

  According to the invention, the second agitating and conveying member is configured such that the length in the longitudinal direction is larger than the length in the longitudinal direction of the first agitating and conveying member, and one end thereof is the first agitating and conveying member. Preferably, the toner replenishing port is provided above one end portion of the second agitating / conveying member protruding from the one end portion of the first agitating / conveying member. As a result, the toner concentration detecting means provided in the circulation path can detect the toner concentration without being influenced by the replenished toner, and therefore can detect the toner concentration with higher accuracy.

  Further, according to the present invention, the replenishment toner damming means is provided in the vicinity of the toner replenishing port and in the portion where the partition member between the first agitation conveyance member and the second agitation conveyance member does not exist. Is preferred. As a result, the replenished toner can be prevented from flowing back toward the first agitating and conveying member, so that the toner concentration detecting means can detect the toner concentration without being affected by the replenished toner. The toner density can be detected with higher accuracy.

  According to the present invention, the image forming apparatus of the present invention can form a high-quality image with less development density reduction and development unevenness by providing the developing device.

  Further, according to the present invention, for a developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus by circulating and conveying a developer including at least a toner and a carrier. In the toner replenishing method for replenishing toner, the toner concentration in the developer immediately after development is detected, and toner is replenished near the detection position where the toner concentration is detected based on the detection result.

  As a result, it is possible to shorten the time until the change in toner density is detected, and to shorten the time during which the toner density is lowered, so that it is possible to suppress development density reduction and development unevenness. Further, since the toner density immediately after development can be detected, fluctuations in the toner density in the developing tank can be suppressed in response to fine fluctuations in the toner density.

  In addition, since detection of toner density fluctuation to toner replenishment can be performed in a short time, and the time during which the toner density is reduced can be shortened, the occurrence of development density drop and development unevenness can be suppressed. .

  Therefore, the toner replenishing method of the present invention can perform the process from the detection of the toner density fluctuation to the toner replenishment in a short time, and can cope with the fine fluctuation of the toner density. Occurrence can be suppressed.

  The present invention relates to a developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus using a developer including at least a toner and a carrier. A developing tank in which a toner replenishing port is accommodated, a developing roller that faces the latent image carrier in the developing tank, is rotatably provided, a developer roller that supplies developer to the latent image carrier, and a developing tank that is rotatable. A first agitation transport member and a second agitation transport member that are provided and agitated and mixed to supply the developer to the developing roller; and provided between the first agitation transport member and the second agitation transport member; A partition member that forms a circulation path for transporting the developer, and a toner concentration detection unit that detects the toner concentration in the developer are provided.

  The first agitating / conveying member is provided closer to the developing roller than the second agitating / conveying member, and the toner concentration detection means is located on the first agitating / conveying member side, Provided at the end on the downstream side in the transport direction. Therefore, it is possible to shorten the time until the change in toner density is detected, and it is possible to shorten the time during which the toner density is lowered, so that it is possible to suppress the development density drop and the occurrence of development unevenness. Further, since the toner density immediately after development can be detected, fluctuations in the toner density in the developing tank can be suppressed in response to fine fluctuations in the toner density.

  The toner replenishing port is provided on the second stirring / conveying member side and in the vicinity of the toner concentration detecting means. Accordingly, since the detection of toner density fluctuation to toner replenishment can be performed in a short time, and the time during which the toner density is lowered can be shortened, the occurrence of development density drop and development unevenness can be suppressed. .

  Therefore, the developing device of the present invention can perform from the detection of the toner density fluctuation to the toner replenishment in a short time, and can cope with the fine fluctuation of the toner density. Can be suppressed.

  The present invention will be specifically described below with reference to embodiments, but the present invention is not particularly limited as long as it does not exceed the gist thereof.

[Development equipment]
(First embodiment)
FIG. 1 is a cross-sectional view showing a simplified configuration of the developing device 1 according to the first embodiment of the present invention, and FIG. 2 is a perspective view of the developing device 1 according to the first embodiment of the present invention. FIG. 3 is a top view of the developing device 1 according to the first embodiment of the present invention.

  The developing device 1 develops an electrostatic latent image formed on the surface of a photosensitive drum 121 provided in the image forming apparatus 100 described later by using a two-component developer including toner and a carrier to form a toner image. 1 to 3, the apparatus includes a developing tank 11, a developing roller 12, a first stirring and conveying screw 13, a second stirring and conveying screw 14, a partition plate 15, and a toner concentration sensor 16. .

  The developing tank 11 is a container-like member that is elongated and provided in parallel with the direction in which the rotation axis of the photosensitive drum 121 extends, and accommodates a two-component developer therein. The developing tank 11 is made of, for example, a hard resin such as polyphenylene ether resin (PPE resin).

  An upper lid 11a for opening and closing the upper opening of the developing tank 11 is provided above the developing tank 11, and a toner replenishing port 11b for replenishing toner from the toner hopper 17 is provided in the vicinity of one end in the longitudinal direction of the upper lid 11a. Is formed. The developing tank 11 is formed with a rectangular opening 11c that faces the photosensitive drum 121 and extends elongated in parallel with the direction in which the developing tank 11 extends.

  The developing roller 12 is provided in the developing tank 11 through the opening 11c of the developing tank 11 so as to be able to rotate while facing the photosensitive drum 121 so that the rotational axis thereof is parallel to the rotational axis of the photosensitive drum 121. . The developing roller 12 includes a cylindrical sleeve (not shown) made of a non-magnetic metal material such as stainless steel and formed in a substantially cylindrical shape, and a magnet that holds a number of permanent magnets therein so as not to rotate. Including a frame (not shown), and only the cylindrical sleeve is configured to be rotatable. The developing roller 12 adsorbs the toner carried on the carrier having magnetism onto the outer peripheral surface together with the carrier by the magnetic force of the permanent magnet held by the magnet frame body to form a developer brush called a magnetic brush, A toner image corresponding to the electrostatic latent image is formed by supplying developer to the electrostatic latent image formed on the surface of the photosensitive drum 121 by rotating counterclockwise as indicated by an arrow in FIG. Form. After the toner image is formed, the toner remaining on the developing roller 12 falls from the surface of the developing roller 12 and is collected in the developing tank 11 in the repulsive magnetic field region of the permanent magnet.

  The first agitation and conveyance screw 13 and the second agitation and conveyance screw 14 are spiral screws, and are rotatably provided in the developing tank 11. The developer is agitated and mixed and conveyed to the developing roller 12.

  FIG. 4 is a top view of the developing device 1 according to the first embodiment of the present invention with the upper lid 11a removed. As shown in FIG. 4, the first stirring and conveying screw 13 and the second stirring and conveying screw 14 are arranged in this order from the side closer to the developing roller 12. The first stirring and conveying screw 13 includes a central shaft 13a and a helical fin 13b, and the second stirring and conveying screw 14 includes a central shaft 14a and a helical fin 14b as well.

  The central shafts 13 a and 14 a are round bar-shaped members made of, for example, ABS (Acrylonitrile Butadiene Styrene) resin, and are rotatably provided in the developing tank 11 so as to be parallel to the rotation axis of the developing roller 12. The spiral fins 13b and 14b are members made of, for example, ABS resin and are formed on the outer peripheral portions of the central shafts 13a and 14a so as to be integrated with the central shafts 13a and 14a, respectively.

  The first agitating and conveying screw 13 and the second agitating and conveying screw 14 are opposite to each other as the driving gears 19 and 20 provided so as to engage with each other at one end in the longitudinal direction are rotated by the driving force of the driving means (not shown). It is configured to rotate in synchronization with each direction. In this manner, the first stirring and conveying screw 13 and the second stirring and conveying screw 14 rotate around the central shafts 13a and 14a, thereby stirring the toner and the carrier in the developer stored in the developing tank 11. While mixing, the developer is conveyed in the direction of the rotation axis and supplied to the developing roller 12.

  The length in the longitudinal direction of the first stirring and conveying screw 13 and the second stirring and conveying screw 14 is preferably larger than the length in the longitudinal direction of the developing roller 12. As a result, the distance of the circulation path for transporting the replenished toner and developer becomes longer, so that the developer can be circulated and transported more smoothly. In addition, since the mixing and stirring of the replenished toner and the developer can be performed for a longer time, a uniform toner concentration can be ensured more stably.

  Moreover, in this embodiment, the length of the longitudinal direction of the 2nd stirring conveyance screw 14 is comprised so that it may become larger than the length of the longitudinal direction of the 1st stirring conveyance screw 13. FIG. Then, one end of the first stirring and conveying screw 13 and one end of the second stirring and conveying screw 14 are aligned, that is, the other end of the second stirring and conveying screw 14 protrudes from the other end of the first stirring and conveying screw 13. Placed in. The 1st stirring conveyance screw 13 and the 2nd stirring conveyance screw 14 are equivalent to the 1st stirring conveyance member and the 2nd stirring conveyance member, respectively.

  A partition plate 15 is provided between the first stirring and conveying screw 13 and the second stirring and conveying screw 14. The partition plate 15 is a plate-like member made of, for example, ABS resin and is formed to stand upright from the bottom of the developing tank 11.

  The partition plate 15 is configured such that the length in the longitudinal direction is smaller than the length in the longitudinal direction of the developing tank 11, and the length in the lateral direction is the same as the depth of the developing tank 11. Preferably, it is configured. Thereby, it is possible to prevent the developer with insufficient mixing with the replenished toner and uneven toner density from moving to the developing roller side while forming a circulation path for conveying the developer. . Therefore, it is possible to suppress the occurrence of development unevenness caused by uneven toner density. The partition plate 15 corresponds to a partition member.

  Hereinafter, in the developing tank 11, the side where the first stirring and conveying screw 13 is located across the partition plate 15, that is, the side close to the developing roller 12 is referred to as the first circulation path A, and the side where the second stirring and conveying screw 14 is present, ie The side away from the developing roller 12 is referred to as a second circulation path B. The first circulation path A and the second circulation path B are separated by the partition plate 15 so that both end portions in the longitudinal direction communicate with each other. In this way, the partition plate 15 forms a circulation path to be described later for transporting the developer.

  As shown in FIG. 4, the toner replenished from the toner replenishing port 11b is downstream from the installation position a of the toner replenishing port 11b via the upstream side b of the second agitating and conveying screw 14 in the second circulation path B. Conveyed to side c and mixed with developer. Thereafter, the first agitating and conveying screw 13 in the first circulation path A is conveyed from the upstream side d to the downstream side e, and is then repeatedly circulated in the order of b, c, d, and e. The circulation path formed by the partition plate 15 indicates the circulation path indicated by b, c, d, and e.

  Note that the toner replenished from the toner replenishing port 11b has a specific gravity lighter than that of the developer and is thus on the top of the developer immediately after being replenished. While being mixed, as it moves to the downstream side of the second agitating and conveying screw 14, it is mixed uniformly. Accordingly, the toner concentration is non-uniform on the upstream side b of the second agitating and conveying screw 14, and the toner concentration is uniform on the downstream side c.

  The toner concentration sensor 16 is located at the bottom of the developing tank 11 and near the end of the first circulation path A near the downstream side e of the first stirring and conveying screw 13 so as to face the first stirring and conveying screw 13. That is, it is arranged so that the detection surface faces the inner space side of the developing tank 11. In the present embodiment, the toner concentration sensor 16 is, for example, a differential transformer type magnetic permeability sensor. The toner concentration sensor 16 utilizes the fact that the carrier in the developer has magnetism and the toner does not have magnetism, so that the toner concentration in the developer contained in the developer tank 11 [toner weight / developer weight ( = Toner weight + carrier weight)], and the obtained detection result is input to a control means (not shown) for controlling the operation of the developing device 1. The toner density sensor 13 corresponds to a toner density detection unit.

  As described above, the toner concentration sensor 16 is provided on the first stirring and conveying screw 13 side and at the end of the first stirring and conveying screw 13 on the downstream side in the conveying direction. Therefore, it is possible to shorten the time until the change in toner density is detected, and it is possible to shorten the time during which the toner density is lowered, so that it is possible to suppress the development density drop and the occurrence of development unevenness. Further, since the toner density immediately after development can be detected, fluctuations in the toner density in the developing tank can be suppressed in response to fine fluctuations in the toner density.

  The toner hopper 17 is provided in contact with the developing tank 11 above the toner supply port 11b. The toner hopper 17 includes a toner bottle 17a, an intermediate hopper 17b, and a toner supply path 17c.

  The toner bottle 17a is a container-like member made of, for example, a hard resin such as polyethylene resin (PE resin). The toner bottle 17a accommodates toner, which is one component of a two-component developer, inside, and a toner motor (replenishment motor). The toner to be stored is replenished from the opening to the intermediate hopper 17b by being rotated by the driving force of the driving means (not shown).

  The intermediate hopper 17b is a container-like member made of a hard resin such as high impact polystyrene resin (HIPS resin), for example, and is provided below the toner bottle 17a so as to be connected to the toner bottle 17a. The intermediate hopper 17b temporarily stores the toner supplied from the toner bottle 17a, and discharges the toner from the opening based on the detection result of the toner density sensor 16, so that the toner supply path 17c and the toner supply port 11b are discharged. The toner is appropriately supplied to the developing tank 11 through the above.

  The toner supply path 17c is a cylindrical member made of a hard resin such as high impact polystyrene resin (HIPS resin), for example, and is provided below the intermediate hopper 17b, and the toner in the opening of the intermediate hopper 17c and the developing tank 11 The replenishing port 11b is connected to replenish toner supplied from the intermediate hopper 17b to the developing tank 11 through the toner replenishing port 11b.

  The toner bottle 17a is detachably attached to the intermediate hopper 17b, and is configured to be sequentially replaceable with a new toner bottle 17a when all of the toner contained therein is consumed.

  The toner replenished from the toner hopper 17 to the developing tank 11 is circulated and conveyed through the circulation paths b, c, d, and e by the first agitating and conveying screw 13 and the second agitating and conveying screw 14 as described above, thereby developing the developing tank. The toner concentration in the developer is adjusted to be uniform by being agitated and mixed with the developer previously stored in the developer 11. Thereafter, the developer is supplied to the developing roller 12 by the first stirring and conveying screw 13 and the second stirring and conveying screw 14. The toner hopper 17 corresponds to a toner supply unit.

  Here, the arrangement position of the toner supply port 11b will be described. As shown in FIG. 4, the toner supply port 11 b is provided above one end portion of the second stirring and conveying screw 14 that protrudes from one end portion of the first stirring and conveying screw 13. That is, the installation position a of the toner supply port 11 b is provided outside the circulation paths b, c, d, e formed by the partition plate 15. As a result, the toner concentration sensor 16 provided in the circulation paths b, c, d, and e can detect the toner concentration without being affected by the replenished toner, and therefore detects the toner concentration with high accuracy. be able to.

  Further, as described above, the toner supply port 11b is provided on the second stirring and conveying screw 14 side and in the vicinity of the toner concentration sensor 16, that is, in the vicinity of the end of the second stirring and conveying screw 14 on the upstream side in the conveying direction. Accordingly, since the detection of toner density fluctuation to toner replenishment can be performed in a short time, and the time during which the toner density is lowered can be shortened, the occurrence of development density drop and development unevenness can be suppressed. .

  The layer thickness regulating member 18 is a thin plate member made of an elastic material such as an elastic metal or synthetic resin, for example, and one end in the short direction is supported by the opening 11c of the developing tank 11, and the other end is The free end portion is provided so as to contact the surface of the developing roller 12. The leading end of the free end, which is the other end, is formed in a hook shape that bends outward from the surface of the developing roller 12 at the contact portion with the developing roller 12. The layer thickness regulating member 18 adjusts so that the thickness of the toner layer carried on the surface of the developing roller 12 becomes a desired value.

  The control means (not shown) includes a central processing unit (hereinafter referred to as CPU (Central Processing Unit)) mainly composed of a microcomputer, and the like, and is controlled by the toner hopper 17 based on the detection value of the toner density sensor 16. Toner replenishment, that is, the timing of toner replenishment and the amount of toner to be replenished are controlled.

(Second Embodiment)
The developing device 2 according to the second embodiment of the present invention will be described below. The developing device 2 according to the second embodiment of the present invention has the same configuration as the developing device 1 according to the first embodiment, except that a replenishment toner damming member 21 is provided on the upper lid 11a of the developing tank 11. is there. Hereinafter, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The replenishment toner dampening member 21 corresponds to replenishment toner dampening means.

  FIG. 5A is a side view showing the configuration of the upper lid 11a of the developing tank 11 of the developing device 2 according to the second embodiment of the present invention, and FIG. 5B is the second embodiment of the present invention. It is a top view in the state where the upper cover 11a of developing device 2 which is a form was removed. In the developing device 2, as shown in FIG. 5A, a replenishment toner dampening member 21 is provided on the upper lid 11 a of the developing tank 11. The replenishment toner damming member 21 is a plate-shaped member made of, for example, polyphenylene ether resin (PPE resin), and one end in the short direction is supported by the upper lid 11a, and the other end is a displaceable free end. Configured.

  As shown in FIG. 5B, the position where the replenishment toner damming member 21 is supported on the upper lid 11a is, in the developing tank 11, in the vicinity of the upstream side b of the second agitating and conveying screw 14 in the second circulation path B. Alternatively, the position is in the vicinity of the downstream side e of the first agitating and conveying screw 13 in the first circulation path A and corresponding to a portion where the partition plate 15 does not exist. That is, the replenishing toner damming member 21 is provided in the vicinity of the toner replenishing port 11 b and in a portion where the partition member 15 between the first stirring and conveying screw 13 and the second stirring and conveying screw 14 does not exist. As a result, the replenished toner can be prevented from flowing back to the first stirring and conveying screw 13 side, that is, the developing roller 12 side. Since the toner concentration can be detected without being affected, the toner concentration can be detected with higher accuracy.

  As described above, the developing device 1 (2) of the present invention is provided rotatably with the developer containing the developer and the toner supply port 11 b formed therein, and the photosensitive drum 121 facing the developing tank 11. A developing roller 12 for supplying the developer to the photosensitive drum 121, and a first agitating and conveying screw 13 and a second agitating and conveying screw which are rotatably provided in the developing tank 11 and agitated and mixed with the developer and supplied to the developing roller 12. 14, a partition plate 15 provided between the first stirring and conveying screw 13 and the second stirring and conveying screw 14 and forming a circulation path for conveying the developer, and a toner concentration for detecting the toner concentration in the developer Sensor 16.

  The first agitating and conveying screw 13 is provided closer to the developing roller 12 than the second agitating and conveying screw 14, and the toner concentration sensor 16 is located on the first agitating and conveying screw 13 side and the first agitating and conveying screw 13. The toner replenishing port 11 b is provided on the second stirring and conveying screw 14 side and in the vicinity of the toner concentration sensor 16.

  As a result, the toner density in the developer immediately after development can be detected, and toner can be replenished in the vicinity of the detection position where the toner density is detected based on the detection result.

  Therefore, a developing device that can detect a change in toner density and replenish the toner in a short time, can cope with a fine change in the toner density, and can suppress a decrease in development density and development unevenness. realizable.

[Image forming apparatus]
FIG. 6 is a schematic diagram illustrating an example of the configuration of the image forming apparatus 100 including the developing device 1 of the present invention. Hereinafter, the developing device included in the image forming apparatus 100 will be described using the developing device 1 according to the first embodiment of the present invention as a representative example, but the developing device 2 according to the second embodiment is replaced with the developing device 1. It can also be used.

  The image forming apparatus 100 includes an image reading unit (scanner unit) 110, an image forming unit 120, a paper feed desk unit 130, and a fixing device 140. The image forming apparatus 100 forms a monochrome or full-color image on a recording sheet in accordance with image data obtained by the image reading unit 110 or image data transmitted from the outside such as each terminal device on a network. It is a possible digital multifunction device.

The image reading unit (scanner unit) 110 includes a document table and an optical unit.
The document table is supported with its upper surface openable and closable with respect to the document table, and is provided with a document placement surface on which the document is placed. The placement of the document on the document table may be manually performed by the user or may be performed by an automatic document feeder (not shown).

  The optical unit includes a charge coupled device (CCD) line sensor that is a photoelectric conversion element. The CCD line sensor reads a black and white image or a color image, converts the image information of the image into an electrical signal of each color, and outputs it to an optical unit 122 described later.

  The image reading unit 110 reads image information from a document placed on a document table, converts the image information into electrical signals (image data) for each color, and outputs the electrical signal to the optical unit 122.

  The image forming unit 120 includes three color photosensitive drums 121Y, 121M, and 121C corresponding to the respective colors of yellow (Y), magenta (M), and cyan (C), and a size larger than these color photosensitive drums. And a black (K) photosensitive drum 121K. The photosensitive drums 121Y, 121M, 121C, and 121K (hereinafter, collectively referred to as “photosensitive drum 121”) carry a toner image to be formed.

  Around the photosensitive drums 121Y, 121M, 121C, and 121K, there are a charging device, an optical unit (laser scanner unit, LSU) 122, developing devices 1Y, 1M, 1C, and 1K (hereinafter collectively referred to as “developing device 1”). A transfer device and a cleaning device are provided. The image forming unit 120 includes a transfer belt 123 and a secondary transfer unit 124 together with each member used in the Carlson process.

  The charging device uniformly charges the surface of the photosensitive drum 121 to a predetermined potential. The optical unit (LSU) 122 exposes the surface of the photosensitive drum 121 charged by the charging device in accordance with the image data input to the image forming apparatus 100, and electrostatic latent image on the surface of the photosensitive drum 121. Write an image. The writing of the electrostatic latent image is digitally controlled.

  The developing devices 1Y, 1M, 1C, and 1K contain yellow (Y), magenta (M), cyan (C), and black (K) developers, respectively, of the photosensitive drums 121Y, 121M, 121C, and 121K. The electrostatic latent image formed on the surface is visualized with each color toner. In this embodiment, a two-component developer composed of toner and carrier is used as the developer.

  The developing devices 1Y, 1M, 1C, and 1K include color toner bottles 17a (Y), which are provided above the transfer belt 123 and contain yellow (Y), magenta (M), and cyan (C) toners. 17a (M), 17a (C) and two toner bottles 17a (K) each containing a black (K) toner that is one size larger than the color toner bottle are provided for each color. It is done. Hereinafter, the toner bottles 17a (Y), 17a (M), 17a (C), and 17a (K) may be collectively referred to as “toner bottles 17a”. The toner bottle 17a is for replenishing toner to the corresponding developing device 1.

  In the developing device 1, the developing device 1K corresponding to black (K) is different from the developing devices 1Y, 1M, and 1C corresponding to the other three colors in that two toner bottles 17a (K) are arranged. The structure is slightly different.

  A bias voltage having a polarity opposite to that of the toner is applied to the transfer device, and the formed toner image is transferred to a transfer belt 123 provided so as to be in contact with the photosensitive drums 121Y, 121M, 121C, and 121K. The cleaning device removes and collects the toner remaining on the surface of the photosensitive drum 121 after the development processing in the developing device 1 and the transfer of the toner image formed on the photosensitive drum 121. The transfer of the toner image onto the transfer belt 123 as described above is repeated four times for four colors.

  According to the image forming unit 120, a toner image is formed on the recording paper as follows. That is, after the surface of the photosensitive drum 121 is uniformly charged by the charging device, the surface of the photosensitive drum 121 is exposed by the optical unit (LSU) 122 in accordance with the input image data, and an electrostatic latent image is written. Thereafter, the electrostatic latent image on the surface of the photosensitive drum 121 is developed by the developing device 1 to visualize the toner image, and the visualized toner image is transferred to which a bias voltage having a polarity opposite to that of the toner is applied. The toner images of the respective colors are sequentially transferred onto the transfer belt 123 by the apparatus. Then, the toner image transferred to the transfer belt 123 by the secondary transfer unit 124 is transferred to a recording sheet conveyed by a paper feed desk unit 130 described later.

  The paper feed desk unit 130 includes a paper feed cassette 131, a pickup roller 132, and the like, and sequentially supplies the recording paper to the image forming unit 120 so that the toner image formed by the image forming unit 120 is transferred onto the recording paper. . The paper feed cassette 131 stores a plurality of recording papers. The pickup roller 132 separates a plurality of recording sheets stored in the sheet feeding cassette 131 one by one and supplies the separated recording sheets to the conveyance path toward the image forming unit 120.

  According to the paper feed desk unit 130, the recording paper stored in the paper feed cassette 131 is fed by the pickup roller 132 one by one to the conveyance path toward the image forming unit 120.

  The fixing device 140 includes a fixing roller, applies appropriate heat and pressure to the recording paper, melts the toner, and fixes it to the surface of the recording paper, thereby forming a full-color image.

  According to the fixing device 140, the recording paper on which the toner image has been transferred to the surface through the secondary transfer unit 124 in the image forming unit 120 is conveyed to the fixing device 140 disposed in the front in the conveying direction, and is fixed. By passing the apparatus 140, the toner image is fixed on the surface of the recording paper, and a full-color image is formed.

  The recording paper on which the full-color image is formed in this manner is then discharged into a space provided between the image reading unit 110 and the image forming unit 120, or when double-sided printing is performed, switchback conveyance is performed. Then, it is conveyed again to the secondary transfer unit 124 and the above operation is repeated.

  As described above, the image forming apparatus 100 according to the present invention includes the developing device 1 according to the present invention, thereby forming a high-quality image with less development density reduction and development unevenness.

  In the above configuration, recording paper is used as the recording medium. However, the present invention is not particularly limited to this, and may be, for example, an OHP (overhead projector) film or a postcard.

Examples of the present invention will be described below.
(Test Example 1)
In Test Example 1, the influence of the arrangement position of the toner density sensor 16 on the detection time of the change in the toner density of the toner density sensor 16 was examined.

  Hereinafter, the evaluation method in Test Example 1 will be described. FIG. 7 is a schematic diagram showing a printed document used in Test Example 1. As shown in FIG. 7, in Test Example 1, a print image having a lot of solid images locally at a position corresponding to the vicinity of the upstream side d of the first stirring and conveying screw 13 in the first circulation path A is used. Printing was continuously performed in the developing devices of Example 1 and Comparative Example 1, and the time from the start of printing until the toner concentration sensor 16 indicated that the toner concentration was insufficient (elapsed time) and the toner concentration at that time were measured. The results are shown in Table 1. For printing, a developer having an initial toner concentration of 5% by weight was used.

Example 1
The developing device 1 in which the toner concentration sensor 16 is provided in the vicinity of the downstream side e of the first stirring and conveying screw 13 in the first circulation path A was used.

(Comparative Example 1)
A developing device similar to that in Example 1 was used except that the position of the toner concentration sensor 16 was provided near the downstream side c of the second agitating and conveying screw 14 in the second circulation path B.

  From the results shown in Table 1, in the developing device 1 of Example 1, the toner density sensor 16 is in a position where the toner density in the developer after being consumed by the developing roller 12 can be detected, and in the vicinity of the developing roller 12. Therefore, the time from the start of printing until the toner density sensor 16 indicates that the toner density is insufficient can be shortened, and the time during which the toner density is lowered can be shortened. It can be seen that the occurrence of unevenness can be suppressed.

  On the other hand, in the developing device of Comparative Example 1, the toner density sensor 16 is provided at a position where the toner density in the developer before being consumed by the developing roller 12 can be detected and at a position away from the developing roller 12. The time from the start of printing until the toner density sensor 16 indicates that the toner density is insufficient is long, and the time during which the toner density is lowered is long. Therefore, it is impossible to suppress the development density reduction and the development unevenness.

(Test Example 2)
In Test Example 2, in the developing device 1 of the present invention used in Example 1, as shown in FIG. 4, a new toner concentration sensor is located near the upstream side b of the second stirring and conveying screw 14 in the second circulation path B. 36 was used, and the influence of toner replenishment on the change in toner density was examined using the two toner density sensors 16 and 36. The examination results are shown in FIGS.

  FIG. 8 is a graph showing the relationship between the elapsed time after operation of the developing device 1 and the toner density detected by the toner density sensor 16 before toner replenishment, and FIG. 9 shows the elapsed time and toner density after toner replenishment. 4 is a graph showing a relationship with toner density detected by a sensor.

  The toner density sensors 16 and 36 can measure in the order of 1/1000 second (msec), and the detected value (output value: V) is an output value indicated by an exponent value of 8 bits (0 to 2555). The toner motor (replenishing motor) that rotates the toner bottle 17a is capable of instantaneous rotation control and uses a frequency-controlled motor (trade name: PM35S, manufactured by Minebea Motor Co., Ltd.). )It was used.

  In the graphs shown in FIGS. 8 and 9, the horizontal axis indicates the elapsed time (sec) after the developing device 1 is operated or after toner replenishment, and the vertical axis is the output value indicating the toner density detected by the toner density sensor 16 or 36. (Exponential value). Further, the output values of the toner density sensors 16 and 36 are shown with reference to 128 which is the center value of the index, and the deviation amount from the reference value 128 can be confirmed as the displacement amount.

  In Test Example 2, control is performed so that toner is replenished in a region where the output value of the toner density sensor 16 exceeds 128 which is a reference (portion where a mountain is formed in the graph of FIG. 8).

  As can be seen from the graphs of FIGS. 8 and 9, since the developing device 1 of the present invention is provided with the toner concentration sensor 16 near the toner supply port 11b, it takes a short time from detection of toner concentration fluctuation to toner supply. Even after the toner density sensor 16 passes, the fluctuation of the toner density can be suppressed and the toner density can be kept constant.

  In addition, since the toner density immediately after development can be detected, toner replenishment can be controlled based on fine fluctuations in toner density instead of the average value of toner density, and in response to fine fluctuations in toner density. Variations in the toner concentration in the developing tank can be suppressed.

  Further, the toner replenishing port 11b is provided in an upper part of one end portion of the second stirring and conveying screw 14 protruding from one end portion of the first stirring and conveying screw 13, that is, outside the circulation path formed by the partition plate 15. Therefore, the toner density can be detected with high accuracy without being affected by the replenished toner.

1 is a cross-sectional view showing a simplified configuration of a developing device according to a first embodiment of the present invention. 1 is a perspective view of a developing device according to a first embodiment of the present invention. 1 is a top view of a developing device according to a first embodiment of the present invention. FIG. 3 is a top view of the developing device according to the first embodiment of the present invention in a state where an upper cover is removed. FIG. 5A is a side view showing the configuration of the upper lid of the developing tank of the developing device according to the second embodiment of the present invention, and FIG. 5B is the developing device according to the second embodiment of the present invention. It is a top view in the state where the upper lid was removed. 1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus including a developing device of the present invention. FIG. 3 is a schematic view showing a printed document used in Test Example 1; 7 is a graph showing a relationship between an elapsed time after the developing device 1 is operated and a toner density detected by a toner density sensor before toner replenishment. 6 is a graph showing the relationship between the elapsed time after toner replenishment and the toner density detected by the toner density sensor. It is sectional drawing of the conventional image development apparatus. It is a top view in the state where the upper cover of the conventional developing device was removed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Developing apparatus 11 Developing tank 12 Developing roller 13 1st stirring conveyance screw 14 2nd stirring conveyance screw 15 Partition plate 16 Toner density sensor 17 Toner hopper 18 Layer thickness control member 19, 20 Drive gear 21 Replenishment toner block member 100 Image formation Device 110 Image reading unit 120 Image forming unit 121 Photoconductor drum 122 Optical unit 123 Transfer belt 124 Secondary transfer unit 130 Paper feed desk unit 131 Paper feed cassette 132 Pickup roller 140 Fixing device

Claims (8)

A developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in an image forming apparatus using a developer including at least a toner and a carrier,
A developer tank containing a developer and having a toner supply port formed therein;
A developing roller which is rotatably provided to face the latent image carrier in the developing tank, and supplies a developer to the latent image carrier;
A first agitation transport member and a second agitation transport member, which are rotatably provided in the developing tank, agitate and mix the developer and supply the developer to the developing roller;
A partition member provided between the first agitating and conveying member and the second agitating and conveying member, and forming a circulation path for conveying the developer;
Toner density detecting means for detecting the toner density in the developer,
The first agitating and conveying member is provided closer to the developing roller than the second agitating and conveying member, and the toner concentration detecting means is on the first agitating and conveying member side and the conveying direction of the first agitating and conveying member A developing device provided at a downstream end portion, wherein the toner replenishing port is provided near the toner concentration detecting means on the second stirring and conveying member side.   2. The developing device according to claim 1, wherein the lengths of the first stirring and conveying member and the second stirring and conveying member in the longitudinal direction are larger than the length of the developing roller in the longitudinal direction.   The partition member is configured such that the length in the longitudinal direction is smaller than the length in the longitudinal direction of the developing tank, and the length in the lateral direction is the same as the depth of the developing tank. The developing device according to claim 1, wherein:   The developing device according to claim 1, wherein the toner supply port is provided outside the circulation path formed by the partition member. The second agitating / conveying member is configured such that its length in the longitudinal direction is larger than the length in the longitudinal direction of the first agitating / conveying member, and its one end is from one end of the first agitating / conveying member. Is also provided to protrude,
5. The developing device according to claim 4, wherein the toner replenishing port is provided above one end portion of the second agitating / conveying member protruding from the one end portion of the first agitating / conveying member.   2. A replenishing toner damming means is provided in a vicinity of the toner replenishing port and in a portion where there is no partition member between the first agitating and conveying member and the second agitating and conveying member. The developing device according to any one of?   An image forming apparatus comprising the developing device according to claim 1. A toner that replenishes toner to a developing device that develops an electrostatic latent image formed on the surface of a latent image carrier provided in the image forming apparatus by circulating and conveying a developer including at least toner and a carrier. A replenishment method,
A toner replenishing method comprising: detecting a toner concentration in a developer immediately after development; and replenishing toner in the vicinity of a detection position where the toner concentration is detected based on a detection result.

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