JP5089199B2 - Density detector and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to a concentration detection device that detects the concentration of a liquid developer composed of a carrier liquid and toner. The present invention also relates to a wet image forming apparatus for forming an image using a liquid developer on a sheet of a copying machine, a facsimile, a printer, or the like.

  2. Description of the Related Art Conventionally, there are image forming apparatuses (so-called wet image forming apparatuses) such as copying machines and printers that form an image by transferring a liquid developer composed of a carrier liquid and a toner to a sheet by an electrophotographic method. . In this image forming apparatus, the liquid developer remaining on the developing roller after supplying the liquid developer to the electrostatic latent image formed on the photosensitive drum (hereinafter referred to as residual liquid developer) From the viewpoint, it is peeled off and collected.

  It is desirable to reuse the residual liquid developer in consideration of cost and environment. However, since the recovered residual liquid developer cannot be reused as it is, it is necessary to adjust the concentration of the recovered liquid developer. In order to perform accurate density adjustment, it is necessary to detect the concentration of the collected liquid developer.

As an apparatus for detecting the concentration of the liquid developer, an invention described in Patent Document 1 has been proposed. In Patent Document 1, in an image forming apparatus using a liquid developer, a slit capable of expanding and contracting a gap is provided in a liquid developer reservoir, and a concentration detector for liquid developer is disposed in the slit. A liquid developer is sealed in the slit to form a thin layer of the liquid developer, and the light irradiated from the light projecting element passes through the thin layer of the liquid developer in the slit to the light receiving element. A detection device that receives light and detects toner density is disclosed (see Patent Document 1: Claim 1, FIG. 5 and the like).
JP 2005-315948

  Here, when light is transmitted through the liquid developer to detect the toner density, the black (= black) liquid developer absorbs light as compared with the liquid developer of other colors such as yellow. Therefore, it is necessary to form a very thin layer (for example, 30 μm) having a low transmittance. Furthermore, an extremely thin liquid developer layer needs to be uniformly formed in order to improve detection accuracy. Therefore, there is a problem that the members and parts forming the thin layer of the liquid developer must be highly dimensionally managed in assembling and manufacturing.

  However, in the detection device described in Patent Document 1, since the transparent member that faces the bottom surface of the recess (slit) for forming a thin layer moves, the dimensional accuracy and assembly of the components that constitute the moving mechanism Due to accuracy and the like, it is difficult to maintain the parallelism of the transparent member facing the bottom surface of the recess. Further, even if the parallelism can be maintained, it is difficult to form the shape of the recess so as to have a uniform depth of several tens of μm, and there is a problem that the dimensional management is disadvantageous in terms of cost. That is, in the invention of Patent Document 1, there is a problem that the thickness of the thin layer of the liquid developer becomes non-uniform (or a thickness different from a predetermined thickness), and the detection accuracy tends to be lowered.

  In addition, the liquid developer is sealed in the recess (slit) to form a thin layer of the liquid developer, but by simply moving the transparent member facing the recess (slit), the excess liquid developer is It may be sandwiched between the recess and the transparent member. For example, a thin layer is formed slightly thicker than a predetermined liquid developer to be formed, which hinders formation of a uniform thin layer. There is a case. That is, the invention described in Patent Document 1 also has a problem that the detection accuracy can be lowered.

  The present invention has been made in view of the above-described problems, and can provide a density detection apparatus and an image forming apparatus capable of stably forming a thin layer of a liquid developer having a uniform thickness and detecting density with high accuracy. The purpose is to provide.

In order to solve the above-mentioned problems, the invention described in claim 1 is a concentration detection device that detects the concentration of a liquid developer comprising a carrier liquid and a toner by determining the light transmittance of the liquid developer. A base part having a flat part and a moving part having a flat part at a position opposite to the flat part of the base part. And a hole for forming a liquid developer layer having a predetermined thickness, and having a thickness corresponding to the predetermined thickness, the base portion side plane portion and the moving portion side plane portion A plate-like member disposed between and fixed so that either the base part side plane part or the moving part side plane part is in contact with each other, and the base part and the moving part, respectively, Consists of a light projecting member and a light receiving member disposed on one side and the other side, formed on the plate-like member And a density detector that detects the density by receiving the transmitted light, and the moving part includes the base part side plane part and the moving part side plane part. The liquid developer layer having a predetermined thickness is formed in the hole portion by moving the plate-like member until it is pressed.

Furthermore, in the invention according to claim 1, the base portion side plane portion is configured such that, when the base portion side and the moving portion side plane portion are in contact with each other via the plate-like member, the hole portion is formed upward. And a groove portion that forms a passage for the liquid developer .

Further, the moving portion side flat portion is also opposed to the groove portion of the base portion side flat portion, and when the base portion side flat portion, the moving portion side flat portion, and the plate member are in contact with each other, liquid development is performed. It was decided to have a groove that forms a passage for the agent. And the groove part of the base part side plane part and the groove part of the moving part side plane part are liquid from between the hole part, the base part side plane part, the moving part side plane part and the plate member. The developer was allowed to escape.

According to a second aspect of the present invention, in the first aspect of the present invention, the moving part has a swinging part for allowing the moving part side flat part to swing, and the moving part side flat part Is formed integrally with the swinging portion.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising: the density detection apparatus according to the first or second aspect; and the density adjustment for adjusting the density of the liquid developer based on the density of the liquid developer detected by the density detection apparatus. Means.

  According to the first aspect of the present invention, the thickness of the plate-like member having the hole portion is set to a thickness corresponding to the layer thickness of the liquid developer to be formed, and the plate-like member is set to the base side plane portion and the movable side plane. Therefore, a thin layer with a uniform thickness of the liquid developer can be easily formed in the hole. In other words, the process of forming recesses of several tens of μm, such as scraping or engraving members, is not only difficult to process itself, but also strictly controls whether the thickness of the recesses after processing is uniform. It is also necessary to carry out this process, which is a high cost factor. However, according to the present invention, since the thin layer is formed by the plate-like member having a predetermined thickness, it is only necessary to manage the thickness of the plate-like member. Accordingly, stable formation of a thin layer of liquid developer having a uniform thickness can be easily achieved. In addition, it is possible to provide a concentration detection apparatus that stably and highly accurately detects the concentration of the liquid developer.

Also, moving unit is moved to the moving portion-side flat portion and the base portion side flat portion is pressed against through the plate-shaped member, in forming a thin layer of the liquid developer, the excess liquid developer I can escape. Therefore, since the excess liquid developer is not sandwiched between the base portion side plane portion, the moving portion side plane portion, and the plate-like member, the liquid developer layer having a predetermined thickness that is stably uniform. Thus, it is possible to provide a concentration detection device with high density detection accuracy. In addition, since the plate-like member is fixed so that the respective planes are in contact with the base-side plane portion or the moving-unit-side plane portion, it is ensured that any plane portion and the plane of the plate-like member are parallel. A liquid developer layer having a predetermined thickness can be stably formed.

Further, the excess liquid developer can be released by the groove portion of the moving portion side flat surface portion, and a liquid developer layer having a uniform predetermined thickness can be stably formed with high accuracy.

According to the second aspect of the present invention, due to the dimensional accuracy of the members and parts, the assembly accuracy, etc., even if the flat portions and the plate-like member are not parallel, the moving portion swings, While absorbing the error, the flat surfaces can be brought into contact with each other in parallel, and a thin layer of liquid developer having a uniform thickness can be stably formed.

According to the image forming apparatus of the third aspect , since the concentration adjustment of the liquid developer is performed based on the concentration of the liquid developer detected by the density detection device according to any one of the first or second aspect , It is possible to adjust the liquid developer to an accurate density, and it is possible to provide an image forming apparatus having a stable toner density in an image and high image quality.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. Although the case where the image forming apparatus 100 is a wet tandem color printer will be described here, another image forming apparatus 100 may be used. For example, the image forming apparatus 100 may be a wet monochrome printer, or may be a wet copying machine, a facsimile machine, or a multifunction machine. In short, each element such as the configuration and arrangement described in the present embodiment does not limit the scope of the invention.

  First, an outline of an electrophotographic image forming apparatus 100 including a density detection device 7 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view seen from the front showing a schematic configuration of an image forming apparatus 100 according to the first embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 100 includes a sheet supply unit 1, a conveyance path 2, an intermediate transfer unit 3, an image forming unit 4 (4Y, 4C, 4M, 4B), and a developing unit 5 (5Y, 5C, 5M). 5B) A secondary transfer unit 6, a fixing unit 61, and a discharge tray 62 are provided.

  The sheet supply unit 1 is provided at the lowermost part of the image forming apparatus 100, and the sheets are stacked and placed, and sequentially feed the sheets to the conveyance path 2. The conveyance path 2 conveys the sheet sent from the sheet supply unit 1 to a secondary transfer roller 6 a provided in the secondary transfer unit 6. The intermediate transfer unit 3 includes an intermediate transfer belt 31 that is rotated in the direction of an arrow. On the intermediate transfer belt 31, yellow (Y), cyan (C), and magenta are formed by image forming units 4Y, 4C, 4M, and 4B. The toner images of each color of (M) and black (B) are sequentially transferred to form a color image.

  Each of the image forming units 4Y, 4C, 4M, and 4B includes a photoconductive drum 41, and toner images of each color of yellow (4Y), cyan (4C), magenta (4M), and black (4B) are transferred to the photoconductive drum. The intermediate transfer belt 31 is formed on the intermediate transfer belt 31. Since the image forming units 4Y, 4C, 4M, and 4B have substantially the same configuration, in the following description, the image forming units 4Y, 4C, 4M, and 4B are referred to as the image forming unit 4 unless particularly limited.

  The developing units 5Y, 5C, 5M, and 5B are each provided with a developing roller 51, and yellow (5Y), cyan (5C), and magenta (5M) are formed on the photosensitive drum 41 of the image forming unit 4 to form a toner image. , Black (5B) toner is supplied. In addition, a liquid developer collecting means 52 is provided for separating and collecting the liquid developer remaining after supplying the toner to the electrostatic latent image on the photosensitive drum 41 from the developing roller 51 (see FIG. 2). Since the developing units 5Y, 5C, 5M, and 5B have substantially the same configuration, they are referred to as the developing unit 5 in the following description unless otherwise limited.

  A secondary transfer roller 6a provided in the secondary transfer unit 6 supplies a color toner image formed on the intermediate transfer belt 31 to a sheet at a nip formed by the intermediate transfer belt 31 and the secondary transfer roller 6a. Secondary transfer is performed on the sheet conveyed from the section 1 via the conveyance path 2 to form a color image on the sheet. The fixing device 61 presses and heats the color (monochrome) toner image transferred by the secondary transfer unit to fix it on the sheet. Then, the sheet after fixing the toner image is stacked on the discharge tray 62, and the image formation for one sheet is completed.

  Next, with reference to FIG. 2, the liquid developer circulation mechanism 8 including the concentration detection device 7 connected to the developing unit 5 shown in FIG. 1 will be described. FIG. 2 is a configuration diagram showing an example of a schematic configuration of the liquid developer circulation mechanism 8 according to the first embodiment of the present invention.

  The liquid developer circulation mechanism 8 collects the residual liquid developer peeled off from the developing roller 51 after supplying the toner to the photosensitive drum 41, adjusts the density, etc., and adjusts the liquid developer that has been adjusted to the developing unit 5. Supply. As a result, the running cost of the image forming apparatus 100 is reduced. As a configuration for that purpose, the liquid developer circulation mechanism 8 includes a concentration detection device 7, a pipe line 81, a pump 82, a redispersion device 83, a carrier tank 84, a toner tank 85, a reservoir tank 86, and a liquid developer supply device 87. Is provided.

  A plurality of pipes 81 are provided between and connected between the members and apparatuses in the liquid developer circulation mechanism 8 and serve as a path for the liquid developer. A plurality of pumps 82 are provided on a pipe 81 in a section divided by each member and apparatus, and sucks and discharges the liquid developer to circulate the liquid developer. As the pump 82, for example, a tube pump can be used.

  The redispersing device 83 (corresponding to the density adjusting means) collects and stores the liquid developer peeled off from the developing roller 51 and discharged via the conduit 81 and the pump 82. Then, the redispersion device 83 converts the recovered liquid developer, the carrier liquid supplied from the carrier tank 84, and the toner supplied from the toner tank 85 into a liquid based on the detection result of the concentration detection device 7 described later. While agglomerating toner particles in the developer is redispersed, the toner is stirred and mixed by the stirring member 831 to keep the toner concentration of the liquid developer constant.

  The carrier tank 84 stores unused carrier liquid made of, for example, silicon oil, and supplies it to the redispersing device 83 via the pipe line 81 and the pump 82. The toner tank 85 stores unused concentrated toner liquid and supplies it to the redispersing device 83 via the conduit 81 and the pump 82. The reservoir tank 86 preliminarily stores the liquid developer that is adjusted to a predetermined toner concentration and supplied from the redispersing device 83 via the conduit 81 and the pump 82.

  The liquid developer supply device 87 is connected to a liquid developer replenishing port (not shown) of the developing unit 5 and supplies the adjusted liquid developer from the reservoir tank 86 to the developing unit 5 via the conduit 81 and the pump 82. To do. Then, the liquid developer whose density has been adjusted is drawn up to the developing roller 51 by the toner supply roller 53 and used for developing the electrostatic latent image.

  The concentration detection device 7 detects the concentration of the liquid developer composed of the carrier liquid and the toner supplied from the redispersion device 83 via the pipe 81 and the pump 82 by determining the light transmittance of the liquid developer. To do. Specifically, the toner concentration of the liquid developer is detected by an optical sensor (not shown in FIG. 2).

  Next, the outline of the concentration detection apparatus 7 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a perspective view of the concentration detection apparatus 7 according to the first embodiment of the present invention.

  First, the concentration detection device 7 is roughly divided into a moving part 70 (upper side in FIG. 3) and a base part 77 (lower side in FIG. 3). In the present embodiment, a configuration in which the moving unit 70 is disposed above and the base unit 77 is disposed below will be described.

  The moving part 70 is provided with a gap with respect to the base part 77 and has a moving part side plane part 76 (not visible in FIG. 3, see FIG. 9) at a position facing the base part side plane part 78. The base part 77 has a base part side plane part 78 (upper surface of the base part 77 in FIG. 3), and is immersed in the liquid developer so that the plane part is immersed in the liquid developer. A plate-like member 90 for forming a liquid developing layer having a predetermined thickness is disposed between the moving unit 70 and the base unit 77.

  The moving unit 70 includes a driving unit 71, a driving force transmitting unit 72, a moving urging unit 73, an engaging unit 74 (not visible in FIG. 3, see FIG. 4), a swinging unit 75, and a moving unit side plane unit 76. (See FIG. 4 invisible in FIG. 3).

  The drive unit 71 includes a disk-shaped member (a disk-shaped member 711 shown in FIG. 4) that is disposed on the top of the moving unit 70 and is driven to rotate by a motor (not shown). The moving urging unit 73 is moved in the vertical direction via

  The driving force transmission unit 72 is made of a bowl-shaped member, and transmits the driving force from the driving unit 71 to the movement urging unit 73.

  The moving urging portion 73 is arranged and connected below the driving force transmitting portion 72 and is configured to be movable in the vertical direction of FIG. The movement urging unit 73 swings the swinging unit 75 that is driven by the driving unit 71 through the driving force transmitting unit 72 in the vertical direction and is engaged with the lower end through the engaging unit 74. Support freely.

  The swinging part 75 is arranged and connected to the lower side of the moving biasing part 73, and the upper end part is supported by the moving biasing part 73 via the engaging part 74 so as to be swingable. The side plane portion 76 (see FIG. 4) is integrally formed. The swinging part 75 includes a light source 753 (see FIG. 4) as a light projecting member that projects light on the thin layer of the liquid developer at a position above the moving part side plane part 76.

  On the other hand, the base portion 77 has a flat surface on the upper surface, and a light receiving member 772 that receives a light beam that has passed through a layer of liquid developer formed to a predetermined thickness (for example, 30 μm) by the plate-like member 90. (See FIG. 4).

  The plate-like member 90 is provided between the moving part 70 and the base part 77 (between the base part side flat part 78 and the moving part side flat part 76), and has a liquid developer layer having a predetermined thickness. It has a hole 91 for forming, and is formed with a thickness (for example, 30 μm) corresponding to a predetermined thickness. In the present embodiment, the hole 91 is formed in a cross shape.

  Next, the structure of the concentration detection apparatus 7 according to the first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 4 is a diagram showing a state of the concentration detection device 7 when the swinging portion 75 of the concentration detection device 7 according to the first embodiment of the present invention is raised, (a) is a front sectional view, (B) is side sectional drawing. FIG. 5 is a perspective view for explaining the base portion 77 and the plate-like member 90 of the concentration detection apparatus 7 according to the first embodiment of the present invention.

  First, the configuration of the moving unit 70 will be described in detail.

  As shown in FIGS. 4A and 4B, the drive unit 71 includes a disk-shaped member 711, an engagement pin 712, and a motor (not shown). The disk-shaped member 711 is rotationally driven around a point on the outer circumference of the disk by a motor (not shown). The engagement pin 712 has a substantially columnar shape, is connected to the upper end portion of the disk-like member 711, is rotatably inserted into the upper end portion of the shaft 721 of the driving force transmitting portion 72, and The driving force transmission part 72 is driven with rotation.

  The driving force transmission unit 72 includes a shaft 721 and an engagement pin 722. The shaft 721 is a rod-shaped member, and the engagement pin 712 of the drive unit 71 is inserted through the upper end portion, and the engagement pin 722 is rotatably fitted at the lower end portion. The engaging pin 722 transmits the driving force from the driving unit 71 to the moving urging unit 73 via the shaft 721, and moves the moving urging unit 73 in the vertical direction in FIG.

  The moving urging portion 73 includes a rod 731, a cylinder 732, a sliding pin 733, and a spring 734, and a gap portion 735 is formed. The rod 731 is a substantially columnar member, and is inserted into the cylinder 732 and supported by the sliding pin 733 so as to be slidable in the vertical direction and swingable in the direction perpendicular to the paper surface in FIG. Then, it moves up and down via the shaft 721. Further, as shown in FIG. 4, the rod 731 has a sliding pin 733 inserted in a substantially central portion, a spring 734 is wound around the outer periphery below the sliding pin 733, and an engaging portion 74 at the lower end portion. Is inserted. The rod 731 is inserted together with the engaging portion 74 into an opening 754 provided on the upper surface of the swinging portion 75.

  The cylinder 732 is a substantially cylindrical member, and supports the rod 731 through the sliding pin 733 so as to be movable in the vertical direction. The sliding pin 733 is a substantially columnar member, is inserted through the rod 731, and both ends are fitted in guide grooves provided on the inner wall of the cylinder 732, and slides in the vertical direction. The rod 731 moves up and down along a preset locus (axial direction of the cylinder 732) formed by the guide groove by the sliding pin 733.

  The spring 734 is formed of a spiral spring, and its upper end is locked to the rod 731. When the moving part 70 and the base part 77 are spaced apart from each other, that is, when the rod 731 is raised, the other end (lower end) is separated from the swinging part 75, and when the rod 731 is lowered. The other end (lower end) biases the upper end of the swinging portion 75 downward.

  The gap portion 735 is formed between the lower end portion of the spring 734 and the upper end portion of the swinging portion 75 when the rod 731 is raised, and the swinging portion 75 is swingable. (This will be described in detail with reference to FIG. 6). When the rod 731 moving toward the base portion 77 moves down, the gap portion 735 disappears and the swinging portion 75 is biased downward by the spring 734 (see FIG. 7).

  The engaging portion 74 is a substantially columnar member, and is inserted into the lower end portion of the rod 731 and disposed inside the swinging portion 75. That is, it is located below the opening 754 formed at the upper end of the swinging part 75. The engaging portion 74 supports the swinging portion 75 so as to be swingable (details will be described later).

  The swing part 75 includes a storage member 751, a moving part side flat part 76, a light source 753, and an opening part 754, and a gap part 755 is formed in the vertical direction between the swinging part 75 and the rod 731 inserted from the opening part 754. The storage member 751 is formed integrally with the moving unit side plane unit 76 and stores the light source 753 therein. The storage member 751 has a tapered shape on the upper side, and an opening 754 is provided at the most tapered portion. Note that as the moving unit 70 and the base unit 77 approach each other, the upper portion of the storage member 751 enters the cylinder 732 and the gap portion 735 disappears, and the lower end of the cylinder 732 is positioned at the swing portion 75 (storage member 751). Touch the top surface.

  The relationship between the engaging portion 74 and the swinging portion 75 will be described. First, the engaging portion 74 is provided in the lower end portion of the rod 731 and in the swinging portion 75. Since the engaging portion 74 is caught by the tapered portion of the storage member 751 when the moving portion 70 is separated from the base portion 77, the swinging portion 75 is caused by the presence of the gap portion 735 and the gap portion 755. (= The engaging portion 74 is formed longer than the diameter of the opening 754 formed in the storage member 751 and shorter than the diameter of the space at the upper end portion in the storage member 751). On the other hand, when the rod 731 is lowered, the engaging portion 74 is separated from the tapered portion formed in the storage member 751.

  The light source 753 (corresponding to a light projecting member) is made up of an LED or the like, projects light rays toward a thin layer of liquid developer formed on the plate-like member 90, and is below the storage member 751 and on the moving unit side plane unit 76. It is stored and locked in the upper part. The gap portion 755 is a gap formed in the vertical direction between the upper end portion of the storage member 751, the rod 731 and the engagement portion 74 so as to support the swinging portion 75 in a swingable manner (see FIG. 6).

  The moving part side plane part 76 is substantially rectangular and is formed in a flat shape, and the movement of the moving part 70 causes the base part side plane part 78 and the moving part side plane part 76 to pass through the plate-like member 90. Move until pressure contact. That is, a liquid developer layer having a predetermined thickness is formed by sandwiching the plate-like member 90 between the base portion side plane portion 78 and the moving portion side plane portion 76 (details will be described later). Further, the moving unit side plane unit 76 is made of a translucent resin or the like in order to transmit the light beam from the light source 753.

  Furthermore, the moving part side plane part 76 is provided with a total of four groove parts 761 on the lower surface in contact with the plate-like member 90 described later (see FIG. 9). The groove is provided with a constant depth and width from a substantially center of each side of the lower surface of the moving part side plane part 76 and a constant length that does not reach the center of the contact surface. By providing the groove portion 761 in this way, the center portion 762 on the lower surface of the moving portion side plane portion 76 is surrounded by the four groove portions 761 and becomes a pedestal shape. Then, a liquid developer layer having a predetermined thickness is formed facing the central portion 762 (details will be described later). Accordingly, the optical path from the light source 753 (light projecting member) of the swinging part 75 is set so as to pass through the central part 762.

  Next, the base part 77 and the plate-like member 90 will be described.

  As shown in FIGS. 4 and 5, the base portion 77 includes a storage member 771, a light receiving member 772, and a base portion side plane portion 78. And in this embodiment, the plate-shaped member 90 is fixed so that the base part side plane part 78 may mutually contact a plane.

  The storage member 771 is made of resin or the like and stores the light receiving member 772.

  The base part side plane part 78 is provided on the upper surface of the storage member 771 and is formed in a substantially rectangular shape and a planar shape. The base portion side plane portion 78 is brought into pressure contact with the moving portion side plane portion 76 via the plate-like member 90 by the movement of the moving portion 70, and the base portion side plane portion 78 and the moving portion side plane portion 76 are plates. By sandwiching the shaped member 90, a liquid developer layer having a predetermined thickness is formed. The base portion side plane portion 76 is made of a translucent resin or the like, and transmits the light beam projected from the light source 753 and passed through the thin layer of the liquid developer.

  Furthermore, as shown in FIG. 5, the base part side plane part 78 is provided with a total of four groove parts 781 on the upper surface. The groove is provided with a constant depth and width from a substantially center of each side of the upper surface of the base part side plane part 78, with a fixed length that does not reach the center while facing the center. Thus, by providing the groove part 781, the center part 782 of the base part side plane part 78 becomes a base shape. Then, a liquid developer layer having a predetermined thickness is formed facing this central portion 782. Accordingly, the light from the light source 753 (light projecting member) of the swinging part 75 passes through the central part 782, and the light receiving member 772 is arranged so as to receive the passed light.

  As shown in FIG. 4, in this embodiment, the planes of the base portion side plane portion 78 and the moving portion side plane portion 76 are substantially the same size in this embodiment, but are different. Also good. In the present embodiment, the positions and sizes of the four groove portions 761 and 781 correspond to each other, and the respective planes of the base portion side plane portion 78 and the moving portion side plane portion 76 are arranged via the plate-like member 90. Are formed so as to overlap in order to allow the liquid developer to escape quickly. Here, the groove portions 761 and 781 formed in the base portion side plane portion 78 and the moving portion side plane portion 76 are not necessarily formed in the same size, and are limited to four on each plane. It is sufficient that the liquid developer can escape.

  As shown in FIGS. 4 and 5, the plate-like member 90 has a substantially rectangular shape and is a metal thin plate, and is formed of, for example, a stainless steel plate. The plate-like member 90 is provided with a cross-shaped hole 91. The plate-like member 90 is parallel to the base portion side plane portion 78 so that the center portion 910 of the cross-shaped hole portion 91 and the center portion 782 of the base portion side plane portion 78 coincide with each other. It is fixed to the base part 77 by a fixing member 92 such as a screw so as to be in contact with (the direction is shown in FIG. 5). Further, the plate-like member 90 is fixed so that the hole portion 91 of the plate-like member 90 exists above the groove portion 781 provided in the base portion side plane portion 78 (see FIG. 3).

  For measuring the concentration of the liquid developer, the base 77 and the plate-like member 90 are provided in a storage tank 79 for storing the liquid developer as shown in FIG. In the present embodiment, the pipe line 81 provided in the storage tank 79 is connected to the redispersion apparatus 83 in order to detect the concentration of the liquid developer in the redispersion apparatus 83. The liquid developer 83 is circulated by the pump 82. The storage tank 79 is filled with the liquid developer so that the liquid developer surface is positioned above the plate-like member 90. This is because a thin layer of liquid developer is formed on the plate-like member 90.

  As shown in FIG. 4, the light receiving member 772 is disposed below the base portion side plane portion 78 in the housing member 771, and includes, for example, a photodiode, a phototransistor, or the like. Then, the light receiving member 772 emits the light beam transmitted through the thin layer of the liquid developer formed by the light source 753 projecting light and the moving unit side plane unit 76 and the base unit side plane unit 78 sandwiching the plate member 90. Light is received, and the concentration of the liquid developer is detected. That is, the light source 753 and the light receiving member 772 serve as a density detection unit. In this embodiment, the light source 753 as the light projecting member is disposed on the moving unit 70 and the light receiving member 772 is disposed on the base 77, but the light source 753 is disposed on the base 77 and the moving unit. A light receiving member 772 may be disposed on 70. In other words, the light projecting member and the light receiving member 772 may be disposed on one side and the other side of the base unit 77 and the moving unit 70, respectively.

  Next, a mechanism in which the swinging portion 75 is swingably engaged with the moving biasing portion 73 when the moving portion 70 and the base portion 77 are separated (when the rod is raised) will be described with reference to FIG. To do. FIG. 6 is an enlarged cross-sectional view of the vicinity of the engaging portion 74 according to the first embodiment of the present invention. (A) is front sectional drawing, (b) is side sectional drawing.

  As shown in FIG. 6, when the rod 731 is raised, a gap portion 735 is formed between the lower end portion of the spring 734 and the upper end portion of the housing member 751 of the swinging portion 75. Since the gap portion 735 is formed, the swinging portion 75 is swingable with respect to the rod 731 and the engaging portion 74 within the range of the gap portion 735 (= the swinging portion 75 is directed downward by the spring 734). Is not energized and not fixed).

  In addition, a gap 755 is formed between the inner wall at the upper end inside the storage member 751, the rod 731 and the engaging portion 74. Since the gap portion 755 is formed, the swinging portion 75 is swingable with respect to the rod 731 and the engaging portion 74 within the interval of the gap portion 755 (= the rod 731 and the engaging portion 74 are The swinging of the storage member 751 is not restricted). Further, the upper surface of the engaging portion 74 and the lower surface of the opening 754 formed at the upper end of the swinging portion 75 (= housing member 751) abut, and the swinging portion 75 is hung and suspended by the engaging portion 74. Thus, the swinging part 75 can swing.

  Next, the operation of the concentration detection device 7 will be described with reference to FIGS. 4 and 7. FIG. 7 shows a state of the concentration detection device 7 when the moving unit side plane part 76 according to the first embodiment of the present invention contacts the base unit side plane part 78 via the plate-like member 90. It is sectional drawing.

  As shown in FIG. 4, when the moving unit 70 and the driving unit 71 are separated from each other, a gap 735 is formed between the lower end of the spring 734 and the upper end of the storage member 751 of the swinging unit 75, and Since a gap 755 is formed between the upper end portion of the storage member 751, the rod 731 and the engaging portion 74, the swinging portion 75 is swingable with respect to the moving biasing portion 73. It has become.

  From this state, when the disk-shaped member 711 starts to rotate clockwise (counterclockwise) in FIG. 4A by a motor (not shown), the shaft 721 is moved downward via the engagement pin 712, The rod 731 moves downward via the engagement pin 722. As the rod moves downward, the gap portion 735 disappears, the spring comes into contact with the upper surface of the swinging portion 75, and the spring starts to bias the swinging portion 75 downward. As a result, the storage member 751 moves downward. That is, the entire moving unit 70 is lowered.

  As shown in FIG. 7, when the disk-like member 711 is rotated by the motor (not shown) to the position where the engagement pin 712 is at the lowest position, the shaft 721 moves further downward and the rod 731 moves further downward. Moving. Then, the engaging portion 74 and the storage member 751 are separated from each other, and as shown in FIG. 7, the spring 734 is compressed, and the upper surface of the storage member 751 is most strongly biased downward. Finally, as shown in FIG. 7, the moving portion side flat portion 76 disposed at the lower end of the storage member 751 comes into contact with the plate member 90 with the flat surfaces overlapping each other. In other words, the rotational drive of the motor is converted into a linear motion, the moving part 70 moves toward the base part 77, and the plate-like member 90 is sandwiched between the moving part side flat part 76 and the base part side flat part 78. It is.

  From the state in which the moving portion side flat portion 76 disposed at the lower end of the storage member 751 is in contact with the flat surface of the plate member 90 until the spring 734 is in contact with the upper surface of the storage member 751 (= shaft). During the period from when 721 is lowered until the gap 735 disappears, only the own weight (for example, 30 g weight) of the swinging portion 75 acts on the moving portion side plane portion 76. During this time, the swinging part 75 swings, so that the moving part side flat part 76, the base part side flat part 78, and the plate-like member 90 are in parallel with each other while absorbing assembly errors and member accuracy errors. A thin layer of liquid developer having a uniform thickness is formed.

  Next, formation of a thin layer of the liquid developer in the concentration detection apparatus 7 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 8 is a front sectional view for explaining the thin layer formation of the liquid developer of the concentration detection apparatus 7 according to the first embodiment of the present invention. (A) is sectional drawing which shows a state when the moving part side plane part 76 of the rocking | swiveling part 75 contact | abuts to the plate-shaped member 90, (b) is enclosed with the dashed-two dotted line of (a). FIG. Here, FIG. 8 shows a simplified cross-sectional view of the configuration of the moving unit 70 and the base unit 77 for convenience.

  As shown in FIG. 8A, the moving part side plane part 76 is in pressure contact with the base part side plane part 78 via the plate-like member 90. As described above, the moving portion 70 of the moving portion 70 gradually comes into contact with the moving portion 70 so as to be parallel to each other as described above. This is done by pushing the plate-like member 90 while the side plane part 76 applies an equal pressure toward the base part side plane part 78. Specifically, the portions other than the groove portions 761 and 781 of the moving portion side plane portion 76 and the base portion side plane portion 78 face the plate-like member 90, and the moving portion side plane portion 76 and the base portion side plane portion. The parallelism between 78 and the plate-like member 90 is maintained.

  As shown in FIG. 8B, when the moving part side plane part 76 is pressed against the base part side plane part 78 via the plate member 90, in this embodiment, as described above, the moving part side plane part 76 is pressed. Since the plane part 76 and the base part side plane part 78 are formed in substantially the same plane, the movable part side plane part 76 and the base part side plane part 78 are stacked with the same members as shown in FIG. It becomes like this. Since the hole 91 is formed in the plate member 90, a space corresponding to the thickness of the plate member 90 (for example, 30 μm) is formed in the central portion 910 of the hole 91. A space formed in the central portion 910 of the hole portion 91 becomes a uniform thin layer of the liquid developer.

  Therefore, in order to form a uniform thin layer of the liquid developer, the central portion 762 of the moving portion side plane portion 76, the central portion 782 of the base portion side plane portion 78, and the hole portion 91 of the plate-like member 90 are formed. The concentration detection device 7 is assembled so that each member is arranged so that the central portion 910 of the two overlaps in the vertical direction. Then, optical paths of the light source 753 and the light receiving member 772 are set in the central portions 762, 782, and 910, and the amount of light transmitted through the thin layer of the liquid developer is detected.

  In this way, since the thin layer of the liquid developer is formed by the plate-like member 90, the plate is compared with the case where the moving part side plane part 76 or the base part side plane part 78 is cut or digged. It is only necessary to manage the thickness of the shaped member 90, which is easy in terms of accuracy control and processing, and it is easy to form a thin layer of the liquid developer uniformly. Therefore, the measurement of the concentration of the liquid developer becomes highly accurate.

  Further, since the four groove portions 761 and 781 are provided on the moving portion side plane portion 76 and the base portion side plane portion 78 so as to be opposed to each other, the moving portion side plane portion 76 and the base portion are provided. When the part-side plane part 78 and the plate-like member 90 are in pressure contact, four substantially U-shaped spaces, that is, liquid developer passages are formed. Of the U-shape, the lower side portion is a groove portion 781 formed in the base portion side plane portion 78, the upper side portion is a groove portion 761 formed in the moving portion side plane portion 76, and the vertical side portion is the moving portion side. This is a space formed by the groove portion 761 of the flat surface portion 76, the groove portion 781 of the base portion side flat surface portion 78, and the hole portion 91 of the plate-like member 90.

  Due to the presence of the grooves 761 and 781, when the moving part side plane part 76 comes into pressure contact with the base part side plane part 78 via the plate-like member 90, as shown by the broken line arrow in FIG. The liquid developer can be quickly released. By allowing the liquid developer to escape, the liquid developer does not enter the hole portion 91 more than necessary, and more pressure than necessary is applied to the moving portion side plane portion 76, the plate-like member 90, and the base portion side plane portion 78. Does not take. Therefore, this is effective in forming a thin layer of the liquid developer more uniformly. In addition, the liquid developer needs to be filled in the storage tank 79 so that the liquid surface of the liquid developer is positioned above the plate-like member 90.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a perspective view of the moving part side plane part 76 as viewed from below for explaining the fixation of the plate member 90 of the concentration detection apparatus 7 according to the second embodiment of the present invention.

  Here, in the second embodiment, only the fixing method of the plate member 90 is different from that of the first embodiment, and the other parts are the same and have the same effects. Explanation and illustration of the constituent parts are omitted.

  The second embodiment of the present invention is different from the first embodiment in that the plate-like member 90 is fixed to the moving unit side plane unit 76. Specifically, the plate member 90 is fixed so that the upper surface of the plate member 90 and the lower surface of the moving part side plane part 76 are parallel, and the parallelism between the moving part side plane part 76 and the plate member 90 is adjusted. Secure. It should be noted that the optical path of the concentration measurement unit is secured in such a manner that the central part 910 of the plate-like member 90 and the central part 762 of the moving part side plane part 76 overlap. Further, as a fixing method, it is conceivable to fix screws other than the moving portion side plane portion 76, and the fixing method can be appropriately selected.

  Thus, according to the present embodiment, the thickness of the plate-like member 90 having the hole portion 91 is set to a thickness corresponding to the layer thickness of the liquid developer to be formed, and the moving portion 70 moves to move the plate-like member. 90 is sandwiched between the base portion side plane portion 78 and the moving portion plane portion 76, so that a thin layer with a uniform thickness of the liquid developer can be easily formed in the hole portion 91. In other words, the process of forming recesses of several tens of μm, such as scraping or engraving members, is not only difficult to process itself, but also strictly controls whether the thickness of the recesses after processing is uniform. It is also necessary to carry out this process, which is a high cost factor. However, according to the present invention, since the thin layer is formed by the plate-like member 90 having a predetermined thickness, only the thickness of the plate-like member 90 needs to be managed. Accordingly, stable formation of a thin layer of liquid developer having a uniform thickness can be easily achieved. In addition, it is possible to provide the density detection device 7 with high accuracy of density detection of the liquid developer.

  Further, since the groove portion 781 is provided in the base portion side plane portion 78, the moving portion 70 moves until the base portion side plane portion 78 and the moving portion side plane portion 76 are in pressure contact with each other via the plate-like member 90, When forming a thin layer of liquid developer, excess liquid developer can be released. Accordingly, since excess liquid developer is not sandwiched between the base portion side plane portion 78, the moving portion side plane portion 76, and the plate-like member 90, a liquid having a predetermined thickness that is stably uniform. It is possible to provide a density detection device 7 that can form a developer layer and has high density detection accuracy.

  Further, since the groove portion 761 is also provided on the moving portion side plane portion 76, excess liquid developer can be released, and a liquid developer layer having a uniform predetermined thickness can be stably formed with high accuracy.

  In addition, since the plate-like member 90 is fixed so that the respective planes are in contact with the base portion side plane portion 78 or the moving portion side plane portion 76, any plane portion and the plane of the plate member 90 are parallel. And a liquid developer layer having a predetermined thickness which is stable and uniform can be formed.

  Further, since the swinging part 75 of the moving part 70 formed integrally with the moving part side flat part 76 is configured to be swingable, each flat part and the plate-like member 90 have the dimensional accuracy of the member / part. Due to the assembly accuracy and the like, even if they are not parallel, the moving unit 70 can be swung so that the flat surfaces can be brought into contact with each other while absorbing the error, and the liquid development with a uniform thickness can be achieved. A thin layer of the agent can be stably formed.

  Further, since the concentration of the liquid developer is adjusted based on the concentration of the liquid developer detected by the concentration detection device 7, the liquid developer can be adjusted to an accurate concentration, and the toner concentration in the image can be adjusted. It is possible to provide an image forming apparatus 100 having a stable and high image quality.

  The present invention can also be applied to the following forms.

  (1) In the present embodiment, the case where the urging portion is formed of a spiral spring that passes through the rod 731 has been described, but other forms may be employed. For example, the urging portion may be formed of an elastic body such as a cylindrical rubber that passes through the rod 731.

  (2) In the present embodiment, the case where the rod 731 is driven in the vertical direction via the driving force transmission unit 72 by the driving unit 71 including a motor or the like has been described, but the rod 731 is driven in the vertical direction by other methods. It may be a form. For example, the rod 731 may be driven by a pneumatic cylinder, a hydraulic cylinder, or the like.

  (3) In the present embodiment, the case where the engaging portion 74 is locked to the lower end portion of the rod 731 has been described, but the engaging portion 74 may be formed integrally with the rod 731.

1 is a schematic cross-sectional view seen from the front showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a configuration diagram illustrating an example of a schematic configuration of a liquid developer circulation mechanism according to a first embodiment of the present invention. 1 is a perspective view of a concentration detection device according to a first embodiment of the present invention. It is a figure which shows the state of the density | concentration detection apparatus when the rocking | swiveling part of the density | concentration detection apparatus which concerns on the 1st Embodiment of this invention raises, (a) is front sectional drawing, (b) is side sectional drawing. It is. It is a perspective view for demonstrating the base part and plate-shaped member of the density | concentration detection apparatus which concern on the 1st Embodiment of this invention. It is an expanded sectional view of the engaging part 74 vicinity which concerns on the 1st Embodiment of this invention. (A) is front sectional drawing, (b) is side sectional drawing. It is sectional drawing which shows the state of the density | concentration detection apparatus when the moving part side plane part which concerns on the 1st Embodiment of this invention contact | abuts to the base part side plane part via the plate-shaped member. It is a front sectional view for explaining thin layer formation of the liquid developer of the concentration detection apparatus according to the first embodiment of the present invention. (A) is sectional drawing which shows a state when the moving part side plane part of a rocking | swiveling part contact | abuts to a plate-shaped member, (b) is the area | region enclosed with the dashed-two dotted line of (a). FIG. It is the perspective view which looked at the moving part side plane part for demonstrating fixation of the plate-shaped member of the density | concentration detection apparatus which concerns on the 2nd Embodiment of this invention from the downward direction.

Explanation of symbols

7 Density Detection Device 70 Moving Unit 75 Oscillating Unit 753 Light Source (Light Projecting Member / Density Detection Unit)
76 Moving part side plane part 761 Groove part (moving part side plane part 76)
77 Base 772 Light receiving member (concentration detector)
78 Base part side plane part 781 Groove part (Base part side plane part 78)
83 Redispersion device (concentration adjustment means)
90 plate-like member 91 hole 92 fixing member 100 image forming apparatus

Claims (3)

A concentration detector that detects the concentration of a liquid developer comprising a carrier liquid and a toner by determining the light transmittance of the liquid developer,
A base part immersed in a liquid developer and having a flat part;
A moving part that is provided at a distance from the base part and has a flat part at a position facing the flat part of the base part;
It has a hole for forming a liquid developer layer having a predetermined thickness, is formed with a thickness corresponding to the predetermined thickness, and is formed between the base part side plane part and the moving part side plane part. A plate-like member that is arranged and fixed so that either one of the base part side plane part or the moving part side plane part is in contact with each other plane ;
The light that has been projected and transmitted through the liquid developer layer formed on the plate-like member, which includes a light projecting member and a light receiving member disposed on one side and the other side of the base unit and the moving unit, respectively. A concentration detection unit that detects the concentration by receiving light,
The moving part moves until the base part side plane part and the moving part side plane part are pressed against each other via the plate-like member, so that a liquid developer layer having a predetermined thickness is formed in the hole part. And
When the base part side and the moving part side flat part are in contact with each other via the plate-like member, the base part side flat part forms a passage for the liquid developer above the hole. Having a groove to
The moving part side plane part is also opposed to the groove part of the base part side plane part, and when the base part side plane part, the moving part side plane part, and the plate member are in contact, the liquid developer Having a groove forming a passage,
The groove part of the base part side plane part and the groove part of the moving part side plane part are liquid developer from between the hole part, the base part side plane part, the moving part side plane part and the plate member. Concentration detection device characterized by letting go. The moving part has a swinging part for allowing the moving part side plane part to swing,
The concentration detecting apparatus according to claim 1 , wherein the moving unit side plane unit is formed integrally with the swing unit. The concentration detection apparatus according to claim 1 or 2 ,
Density adjusting means for adjusting the density of the liquid developer based on the density of the liquid developer detected by the density detector;
An image forming apparatus comprising:

Images