JP2013152318A - Concentration detection device and image forming device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentration detection device capable of accurately measuring concentration of a resin component dissolved in a liquid developer and concentration of toner dispersed as solid content and to provide an image forming device equipped with the same.SOLUTION: A QCM sensor 60 having a quartz oscillator and a weight 32 are immersed in a liquid developer LD stored in a concentration detection tank 691. The gravity of the liquid developer LD is detected from buoyancy applied to the weight 32. The oscillation frequency of the quartz oscillator is mainly fluctuated by concentration of a resin component in dissolved in the liquid developer LD. A solution concentration detection device 280 drives less erroneous solution resin concentration CRH and solid content concentration DSH from the oscillation frequency of the quartz oscillator in the QCM sensor 60 and the detected gravity of the liquid developer LD.

Description

  The present invention relates to a density detection apparatus that detects the density of a liquid developer, and an image forming apparatus including the density detection apparatus.

  As an image forming apparatus, a wet type apparatus that forms a toner image using a liquid developer is known. In the liquid developer, toner as a solid content is dispersed in a dielectric liquid serving as a carrier liquid. The wet image forming apparatus includes a photosensitive drum on which a toner image is formed, a developing device that supplies a liquid developer to the photosensitive drum and forms a toner image on the photosensitive drum, and a toner on the photosensitive drum. A transfer unit that transfers the image onto the sheet; and a fixing unit that fixes the toner image on the sheet onto the sheet.

  In order to form a good toner image on a sheet, it is necessary to properly adjust the toner concentration of the liquid developer before the developing device supplies the liquid developer to the photosensitive drum. For this reason, an apparatus for detecting the toner concentration of a liquid developer is known for the purpose of determining whether or not the toner concentration is properly adjusted (Patent Document 1).

  The density detection apparatus of Patent Document 1 utilizes the specific gravity of a liquid developer, and a comparison container enclosing a liquid developer for density comparison is immersed in the liquid developer to be measured. Then, the toner concentration of the liquid developer is detected based on the change in the position of the comparison container due to the buoyancy caused by the specific gravity difference.

  On the other hand, techniques for measuring the concentration of microorganisms in a microorganism suspension using a QCM sensor equipped with a crystal resonator are known (Patent Documents 2 to 5).

  In this technique, an antibody is immobilized on a crystal resonator, and a weight change occurs on the surface of the crystal resonator electrode by binding the antibody and a microorganism. The change in the oscillation frequency of the quartz crystal resonator accompanying the change in weight is measured, and the concentration of microorganisms is calculated.

JP 2007-310122 A JP 62-64934 A Japanese Unexamined Patent Publication No. Sho 63-11835 JP-A-62-288546 JP-A-62-288547

  In recent years, as a liquid developer for an image forming apparatus, as described above, a toner as a solid content is dispersed in a dielectric liquid serving as a carrier liquid, and a resin component is dissolved in the carrier liquid. Exists. The resin component has a function of precipitating on the sheet in the fixing step of image formation and protecting the surface.

  In a liquid developer in which such a resin component is dissolved, the specific gravity of the carrier liquid as a solvent and the specific gravity of the dissolved resin are often approximated. For this reason, it is difficult to detect the concentration of the dissolved resin in an apparatus using the specific gravity of the liquid developer, such as the concentration detection apparatus of Patent Document 1.

  Also, as disclosed in Patent Documents 2 to 5, an apparatus for detecting a microbial concentration using a crystal resonator is known. However, a dissolved resin concentration in a liquid developer is detected using a crystal resonator. As for the technology to do, it was unclear whether or not its detailed application was possible.

  The present invention has been made in view of the above problems, and is a concentration detection apparatus capable of accurately measuring the concentration of a resin component dissolved in a liquid developer and the concentration of toner dispersed as a solid content. And an image forming apparatus including the same.

  A concentration detection apparatus according to one aspect of the present invention includes a storage container for storing a liquid developer including a carrier liquid, solid particles dispersed in the carrier liquid, and a resin component dissolved in the carrier liquid; A specific gravity detecting unit that includes a weight immersed in the liquid developer in the storage container, and detects a specific gravity of the liquid developer based on a buoyancy applied to the weight; and the liquid in the storage container A sensor unit that is immersed in a developer and includes a crystal unit; an oscillation circuit that is connected to the sensor unit and oscillates the crystal unit; a frequency detection unit that detects a vibration frequency of the crystal unit; Based on the specific gravity of the liquid developer detected by the specific gravity detection means and the vibration frequency of the crystal resonator detected by the frequency detection means, the concentration of the solid particles in the liquid developer, or , Characterized by having a a density detection means for detecting the concentration of the dissolved resin component in the liquid developer.

  According to this configuration, the specific gravity detecting means includes the weight immersed in the liquid developer in the storage container. The specific gravity of the liquid developer varies depending on the solid content concentration in the liquid developer. The specific gravity detecting means detects the specific gravity of the liquid developer based on the buoyancy applied to the weight. The sensor unit is immersed in the liquid developer in the storage container and includes a crystal resonator inside. An oscillation circuit that oscillates the crystal resonator is connected to the sensor unit, and the frequency detection means detects the vibration frequency of the crystal resonator. The quartz oscillator vibrates at different frequencies according to the concentration of the resin component in which the liquid developer is dissolved. The concentration detection means detects the concentration of solid particles in the liquid developer or the concentration of the dissolved resin component in the liquid developer based on the specific gravity of the liquid developer and the vibration frequency of the crystal resonator. To do. For this reason, compared to the case where the concentration of solid particles in the liquid developer is detected based only on the specific gravity of the liquid developer, errors caused in the concentration of solid particles due to the dissolved resin component in the liquid developer are reduced. Is done. Further, compared with the case where the concentration of the dissolved resin component in the liquid developer is detected based only on the vibration frequency of the crystal resonator, the dissolved resin in the liquid developer is detected by the solid particles in the liquid developer. Errors that occur in the concentration of components are reduced.

  In the above configuration, the first calibration curve indicating the concentration of the solid particles or the dissolved resin component when the vibration frequency of the crystal resonator and the specific gravity of the liquid developer are respectively changed is stored. A storage unit, wherein the concentration detection unit uses the first calibration to calculate the specific gravity of the liquid developer detected by the specific gravity detection unit and the vibration frequency of the crystal resonator detected by the frequency detection unit. It is preferable to detect the concentration of the solid particles or the dissolved resin component by collating with a line.

  According to this configuration, the first storage unit has the first calibration curve indicating the concentration of the solid particles or the dissolved resin component when the vibration frequency of the crystal unit and the specific gravity of the liquid developer are changed. Remembered. Therefore, it is possible to detect the concentration of the solid particles or the concentration of the dissolved resin component from the specific gravity of the liquid developer detected by the specific gravity detection unit and the vibration frequency of the crystal resonator detected by the frequency detection unit. It becomes. For this reason, compared to the case where the concentration of solid particles in the liquid developer is detected based only on the specific gravity of the liquid developer, errors caused in the concentration of solid particles due to the dissolved resin component in the liquid developer are reduced. Is done. Further, compared with the case where the concentration of the dissolved resin component in the liquid developer is detected based only on the vibration frequency of the crystal resonator, the dissolved resin in the liquid developer is detected by the solid particles in the liquid developer. Errors that occur in the concentration of components are reduced.

  In the above configuration, the second memory storing the second calibration curve indicating the concentration of the solid particles or the dissolved resin component when the viscosity of the liquid developer and the specific gravity of the liquid developer are respectively changed. The density detection means derives the viscosity of the liquid developer based on the vibration frequency of the crystal resonator, and the specific gravity of the liquid developer detected by the specific gravity detection means, and the derivation It is preferable to detect the concentration of the solid particles or the dissolved resin component by comparing the viscosity of the liquid developer thus obtained with the second calibration curve.

  According to this configuration, in the second storage unit, the second calibration curve indicating the concentration of the solid particles or the concentration of the dissolved resin component when the viscosity of the liquid developer and the specific gravity of the liquid developer are changed, respectively. Is memorized. Then, the density detecting means derives the viscosity of the liquid developer based on the vibration frequency of the crystal resonator. Therefore, it is possible to detect the concentration of solid particles or the concentration of the dissolved resin component from the specific gravity of the liquid developer detected by the specific gravity detection means and the derived viscosity of the liquid developer. As a result, compared with the case where the concentration of solid particles in the liquid developer is detected based only on the specific gravity of the liquid developer, errors caused in the concentration of solid particles due to the dissolved resin component in the liquid developer are reduced. Is done. Further, compared with the case where the concentration of the dissolved resin component in the liquid developer is detected based only on the vibration frequency of the crystal resonator, the dissolved resin in the liquid developer is detected by the solid particles in the liquid developer. Errors that occur in the concentration of components are reduced.

  In the above configuration, the storage container includes an injection port for injecting the liquid developer and an exhaust port for discharging the liquid developer, and in the liquid developer in the storage container It is preferable that the weight is immersed above the inlet and below the outlet and the sensor unit.

  According to this configuration, the weight can be easily immersed in the liquid developer. Thereby, the buoyancy acting on the weight can be obtained accurately. In addition, a larger amount of liquid developer is secured around the weight that requires a larger amount of target solution than the sensor unit.

  In the above-described configuration, it may include a regulating member that is immersed in the liquid developer in the storage container, covers the upper part of the sensor unit, and is maintained at a constant distance in the depth direction from the sensor unit. preferable.

  According to this configuration, the regulating member that is immersed in the liquid developer, covers the upper portion of the sensor unit, and is maintained at a constant distance in the depth direction from the sensor unit is disposed in the storage container. . When the sensor unit is immersed in the liquid developer, the vibration frequency at which the crystal resonator oscillates may vary depending on the liquid height of the liquid developer located above the sensor unit. Even in such a case, the height of the liquid developer located above the sensor unit is kept constant by the regulating member. As a result, the vibration of the crystal resonator in the liquid developer is stabilized.

  In the above-described configuration, the load cell further includes a strain body connected to the weight, and a strain gauge installed on the strain body, and the specific gravity detecting means is based on an output from the strain gauge. It is preferable to detect the specific gravity of the liquid developer.

  According to this configuration, the buoyancy acting on the weight is obtained from the gravity acting on the weight and the force acting on the strain body by the weight. And the force which acts on a strain body with a weight is derived | led-out by the output of a strain gauge. For this reason, the buoyancy acting on the weight is stably calculated, and the specific gravity of the liquid developer is easily calculated.

  In the above-described configuration, the semiconductor device further includes a housing that houses the oscillation circuit therein and includes a bottom portion that is immersed in the liquid developer, and the sensor portion is disposed so as to protrude downward from the bottom portion of the housing. Preferably, the oscillation circuit is connected to the sensor portion via the bottom portion, and the restriction member is the bottom portion of the housing.

  According to this configuration, the oscillation circuit is accommodated in the housing, and the liquid developer is prevented from adhering to the oscillation circuit. Further, the sensor unit is disposed so as to protrude downward from the bottom of the housing. For this reason, the bottom part of a housing has a function as a control member. Therefore, the simple structure of the housing stabilizes the vibration of the crystal resonator in the liquid developer. Further, the oscillation circuit can be brought as close to the sensor unit as possible through the bottom of the housing. As a result, electrical noise is prevented from interposing between the sensor unit and the oscillation circuit.

  In the above configuration, the apparatus further includes a liquid temperature detection unit that detects a liquid temperature of the liquid developer in the storage container, and the frequency detection unit adjusts the liquid temperature of the liquid developer detected by the liquid temperature detection unit. Accordingly, it is preferable to correct the vibration frequency.

  According to this configuration, even when the liquid temperature of the liquid developer containing the dissolved resin component is changed and the viscosity of the liquid developer is changed, the fluctuation due to the liquid temperature among the vibration frequencies of the crystal resonator is changed. Minutes can be corrected.

  In the above configuration, liquid development comprising an image carrier on which a toner image is formed, a carrier liquid, solid particles as the toner dispersed in the carrier liquid, and a resin component dissolved in the carrier liquid A developing device for storing the developer and supplying the toner to the image carrier, a developer adjusting unit for adjusting the concentration of the toner and the resin component in the liquid developer, and the solid particles in the liquid developer Alternatively, it is preferable that the liquid developer concentration detecting device according to any one of claims 1 to 8 that detects the concentration of the resin component.

  According to this configuration, compared to the case where the concentration of solid particles in the liquid developer is detected based only on the specific gravity of the liquid developer, the concentration of solid particles is generated by the dissolved resin component in the liquid developer. Errors are reduced. Further, compared with the case where the concentration of the dissolved resin component in the liquid developer is detected based only on the vibration frequency of the crystal resonator, the dissolved resin in the liquid developer is detected by the solid particles in the liquid developer. Errors that occur in the concentration of components are reduced. For this reason, the concentration of the dissolved resin component and the concentration of solid particles in the liquid developer are detected with high accuracy. As a result, in the density adjusting unit, the density of the solid particles in the liquid developer and the density of the dissolved resin component are suitably adjusted, and stable image formation can be executed.

  According to the present invention, a concentration detection device capable of accurately measuring the concentration of a resin component dissolved in a liquid developer and the concentration of toner dispersed as a solid content, and an image forming apparatus including the same Can be provided. In particular, the resin component and the toner are effectively reduced in the amount of error that affects each other's concentration, and the resin component concentration and the concentration of the toner dispersed as a solid component are accurate over a wide range. Measured well.

It is sectional drawing and block diagram of the solution concentration detection apparatus which concerns on embodiment of this invention. It is sectional drawing and the block diagram of the melted resin concentration detection apparatus which concern on embodiment of this invention. It is a partial sectional view of a dissolved resin concentration detection device concerning an embodiment of the present invention. It is (a) top view and (b) side view of the QCM sensor which concerns on embodiment of this invention. It is the figure which showed the relationship between the melted resin density | concentration and output frequency of the melted resin density | concentration detection apparatus concerning embodiment of this invention. It is the figure which showed transition of the output frequency of the melted resin concentration detection apparatus which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating a relationship between a liquid temperature and a viscosity of a liquid developer according to an embodiment of the present invention. It is the figure which showed the relationship between the liquid temperature of a liquid developer, and an output frequency in the dissolved resin concentration detection apparatus which concerns on embodiment of this invention. It is the figure which showed the temperature dependence of the oscillation circuit with which the melt | dissolution resin concentration detection apparatus which concerns on embodiment of this invention is provided. It is a figure which shows typically the structure of the solid content concentration detection apparatus which concerns on this embodiment. It is a figure which shows the density | concentration detection tank and load cell of a solid content concentration detection apparatus, (a) is a top view of a density | concentration detection tank and a load cell, (b) is a side view of a density | concentration detection tank, (c), It is a side view of the density | concentration detection tank seen from the opposite side to (b), (d) is a longitudinal cross-sectional view of a density | concentration detection tank and a load cell. It is a figure which shows the relationship between the solid content density | concentration of a liquid developer, and the specific gravity of a liquid developer. It is a figure which shows the calibration curve produced in advance in order to show the relationship between solid content concentration of a liquid developer, and an amplification voltage value. It is a graph which shows the example which measured the amplified voltage value output from the amplifier circuit with the oscilloscope. It is a graph which shows the result of having measured the pulsation resulting from the conveyance pump of a liquid developer with an oscilloscope. It is a figure which shows that the specific gravity of a liquid developer changes with temperature fluctuations. It is a figure which shows the relationship between the rotation speed of a stirring apparatus, and an amplified voltage value. It is a schematic diagram which shows the positional relationship between a 1st inlet and a 2nd inlet, and a 1st outlet and a 2nd outlet in a cross section. It is a figure which shows typically the positional relationship between a 1st injection port and a 2nd injection port, and a 1st discharge port and a 2nd discharge port when a density | concentration detection tank is seen from upper direction. It is a figure which shows the relationship between the melted resin density | concentration of a liquid developer, and a viscosity. It is a figure which shows the relationship between the melted resin density | concentration of a liquid developer, and a viscosity. It is a figure which shows the relationship between solid content concentration and specific gravity of a liquid developer. It is a figure which shows the relationship between the melted resin density | concentration and solid content density | concentration of a liquid developer, and a viscosity. It is a figure which shows the relationship between the density | concentration of the melted resin density | concentration and solid content of a liquid developer, and specific gravity. It is a flowchart from which a melted resin concentration and a solid content concentration are derived. 1 is an overall schematic cross-sectional view of a color printer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the color printer excluding a liquid developer circulating device. It is sectional drawing which expands and shows one of the image formation parts. It is a block diagram of a liquid developer circulation device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a solution concentration detection device 280 according to this embodiment. The configuration shown in FIG. 1 corresponds to a part of a liquid developer circulating device LY (FIG. 28) described later. The solution concentration detection device 280 is connected to the developer container 272. A carrier tank 274, a toner tank 275, and a varnish tank 279 are connected to the developer container 272. In the carrier tank 274, a carrier liquid C corresponding to the solvent of the liquid developer LD is stored. In the toner tank 275, toner corresponding to the solid content in the liquid developer LD is stored in a dispersed state in the carrier liquid C. The varnish tank 279 stores a resin component R dissolved in the carrier liquid C in the liquid developer LD. From the carrier tank 274, the toner tank 275, and the varnish tank 279 to the developer container 272, respectively, a pure carrier liquid C, a carrier liquid C containing a high concentration toner, and a high concentration resin component R are included. The carrier liquid C is supplied. The developer container 272 is provided with a stirring device 276 that stirs the supplied carrier liquids C having different concentrations. As a result, a liquid developer LD as a solution is generated. The liquid developer LD flows into the solution concentration detection device 280 via the fourth pipe 84. Then, the solution concentration detection device 280 detects the solid content concentration DS and the dissolved resin concentration CR of the liquid developer LD stored in the developer storage container 272. The solid content concentration DS corresponds to the concentration of toner dispersed in the liquid developer LD without being dissolved in the carrier liquid C. The dissolved resin concentration CR corresponds to the concentration of the resin component R dissolved in the carrier liquid C in the liquid developer LD. The components of the liquid developer LD used in this embodiment will be described in detail later.

  The solution concentration detection device 280 includes a dissolved resin concentration detection device 280A, a measurement unit 280B, and a solid content concentration detection device 280C. The dissolved resin concentration detection device 280A is a measurement device that detects the dissolved resin concentration CR, and the solid content concentration detection device 280C is a measurement device that detects the solid content concentration DS. The measurement unit 280B includes an electrical circuit for measurement described later. Further, the measurement unit 280B is finally connected to the dissolved resin concentration detection device 280A and the solid content concentration detection device 280C to derive the dissolved resin concentration CR and the solid content concentration DS.

  Hereinafter, the dissolved resin concentration detection device 280A and the solid content concentration detection device 280C will be described in order.

<About dissolved resin concentration detector 280A>
FIG. 2 is a combination of a sectional view of a dissolved resin concentration detection device 280A according to an embodiment of the present invention and an electrical block diagram of a measurement unit 280B. FIG. 3 is a sectional view of a QCM (Quarts Crystal Microbalance) sensor of the dissolved resin concentration detector 280A. FIG. 4 is a (a) plan view and (b) side view of the QCM sensor.

  The dissolved resin concentration detection device 280A is a device main body that measures the concentration of the resin component dissolved in the liquid developer LD (hereinafter, dissolved resin concentration CR). The dissolved resin concentration detection device 280A includes a QCM sensor 60, a circuit unit 64, a housing 65, a concentration detection tank 691, and a liquid temperature sensor 692.

  The QCM sensor 60 includes a crystal resonator 611 (FIG. 4) inside, and oscillates a vibration frequency according to the dissolved resin concentration CR of the liquid developer LD. The QCM sensor 60 is immersed in the liquid developer LD to be measured. The QCM sensor 60 includes a sensor electrode 61 and a pedestal portion 62. The sensor electrode 61 includes a crystal resonator 611 therein and has a disk shape when viewed from the front. The pedestal 62 is immersed in the liquid developer LD above the sensor electrode 61. The pedestal portion 62 has a disk shape in plan view and includes two through holes (not shown). The pedestal 62 has a function of fixing the first lead 63a and the second lead 63b disposed between the sensor electrode 61 and the circuit unit 64 through the hole. The QCM sensor 60 is disposed below the bottom surface portion 651 of the housing 65 described later so as to protrude from the housing 65.

  With reference to FIG. 4, the sensor electrode 61 of the QCM sensor 60 has a three-layer structure in a side view, and includes a crystal resonator 611, a first electrode portion 612, and a second electrode portion 613. The first electrode portion 612 and the second electrode portion 613 are disposed so as to sandwich the crystal resonator 611 from both sides. By forming a closed circuit using the crystal unit 611 as a part of the circuit, a predetermined voltage is applied to both sides of the crystal unit 611. Then, the crystal resonator 611 oscillates at different vibration frequencies according to the dissolved resin concentration CR in the surrounding liquid developer LD. The relationship between the dissolved resin concentration CR in the liquid developer LD and the vibration frequency will be described in detail later.

  One side regulating member 612A is disposed on one surface of one of the first electrode portion 612 and the second electrode portion 613 sandwiching the crystal resonator 611. In the present embodiment, the single-side regulating member 612A is disposed on the surface of the first electrode 612. The single-side regulating member 612A is disposed so as to cover the surface of the first electrode 612, and is formed by an oil-resistant insulating seal or coating. As a result, the liquid developer LD adheres only to the surface of the second electrode portion 613, and the surface of the first electrode 612 is protected from the liquid developer LD. As a result, a current flows between the first electrode portion 612 and the second electrode portion 613 via the liquid developer LD, thereby preventing a short circuit.

  The circuit unit 64 includes an oscillation circuit 641 that is disposed above the QCM sensor 60 and includes an interface circuit therein. The oscillation circuit 641 is disposed on a wiring board as small as possible so as not to be affected by external electrical noise. The circuit unit 64 includes a connector 642. The circuit unit 64 is electrically connected to the QCM sensor 60 by the first lead portion 63a and the second lead portion 63b (FIG. 3). Further, the circuit unit 64 is electrically connected to the power source 693 by the first wiring portion 694. Further, the circuit unit 64 is electrically connected to a frequency meter 696 described later by the second wiring portion 695. An oscillation circuit 641 in the circuit unit 64 is a circuit for causing the crystal resonator 611 to oscillate. In the present embodiment, a multivibrator oscillation circuit is employed as the oscillation circuit 641. A predetermined drive voltage is supplied from the power source 693 to the circuit unit 64 via the first wiring portion 694. The circuit unit 64 outputs the vibration frequency of the crystal resonator 611 of the QCM sensor 60 to the frequency meter 696 of the measurement unit 280B through the second wiring unit 695 as a clock signal.

  The housing 65 is a substantially cylindrical housing and houses the circuit unit 64 therein. The housing 65 includes a bottom surface portion 651 made of a circular flat plate arranged horizontally. A circular opening (not shown) is formed at the center of the bottom surface 651 of the housing 65. The QCM sensor 60 is inserted through the opening through the internal space of the housing 65. Thereby, the QCM sensor 60 is disposed outside the housing 65 and the circuit unit 64 is accommodated inside the housing 65. The QCM sensor 60 is disposed immediately below the center portion of the bottom surface portion 651 of the housing 65. A seal member (not shown) is disposed in the opening to prevent the liquid developer LD from entering the housing 65. A shield 66 is provided on the inner wall of the housing 65 to protect the circuit unit 64 from surrounding electrical noise. With the housing 65 accommodating the circuit unit 64 therein, the bottom surface portion 651 of the housing 65 is immersed in the liquid developer LD. Thereby, even when the QCM sensor 60 is immersed in the liquid developer LD, the circuit unit 64 can be disposed as close to the QCM sensor 60 as possible. As a result, the lengths of the first lead portion 63a and the second lead portion 63b can be shortened, and electrical noise is caused between the QCM sensor 60 and the oscillation circuit 641 in the circuit unit 64. Deterred.

  The density detection tank 691 stores the liquid developer LD to be measured inside. The QCM sensor 60 is immersed in the liquid developer LD stored in the concentration detection tank 691. A more detailed structure of the concentration detection tank 691 will be described in detail as a solid content concentration detection device 280C described later.

  The liquid temperature sensor 692 measures the liquid temperature T of the liquid developer LD stored in the concentration detection tank 691. The liquid temperature sensor 692 employs various temperature measuring means such as a thermocouple and a platinum resistance thermometer. The liquid temperature T of the liquid developer LD measured by the liquid temperature sensor 692 is used by the concentration calculation unit 698 in the measurement unit 280B to calculate the dissolved resin concentration CR.

  The power source 693 supplies a predetermined drive voltage to the QCM sensor 60. The power source 693 includes a stabilized power circuit (not shown).

  The measuring unit 280B obtains the dissolved resin concentration CR in the liquid developer LD based on the vibration frequency oscillated from the QCM sensor 60. The measurement unit 280B includes a frequency meter 696, a storage unit 697, and a concentration calculation unit 698. The measurement unit 280B includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) that is used as a work area of the CPU, and the like. The measurement unit 280B functions to include a frequency meter 696, a storage unit 697, and a concentration calculation unit 698 by the CPU executing a control program stored in the ROM.

  The frequency meter 696 cuts noise from the clock signal output from the circuit unit 64 according to the vibration of the crystal resonator 611 and calculates the output frequency F of the crystal resonator 611. The output frequency F is used by the concentration calculation unit 698 to calculate the dissolved resin concentration CR. Various arithmetic units may be used instead of the frequency meter 696. Finally, the oscillation frequency of the QCM sensor 60 may be analyzed based on the clock signal output from the circuit unit 64 so that the dissolved resin concentration CR is calculated on the PPM order.

  The storage unit 697 stores various storage information for the calculation of the dissolved resin concentration CR by the concentration calculation unit 698. The storage unit 697 stores a temperature correction value Vt and a converted concentration value Vd described later.

  The concentration calculation unit 698 uses the output frequency F calculated from the frequency meter 696, the temperature correction value Vt stored in the storage unit 697, the converted concentration value Vd, and the liquid temperature T measured by the liquid temperature sensor 692. The dissolved resin concentration CR is calculated.

<Detection of dissolved resin concentration CR>
In the present embodiment, a liquid developer LD is used as a measurement target of the dissolved resin concentration detection device 280A. The liquid developer LD includes an electrically insulating carrier liquid C and colored particles P dispersed in the carrier liquid C. Further, the liquid developer LD contains a resin material R. When used in the image forming apparatus, the concentration of the colored particles P and the concentration of the resin material R in the liquid developer LD are controlled.

  The colored particles P in the liquid developer LD are not dissolved in the carrier liquid C. For this reason, the concentration of the colored particles P is measured as the solid content concentration DS dispersed in the carrier liquid C. The solid content concentration DS is measured by a solid content concentration detection device 280C described later. The resin material R in the liquid developer LD is dissolved in the carrier liquid C. Therefore, the concentration of the resin material R in the liquid developer LD is measured as a dissolved resin concentration CR. The specific gravity of the carrier liquid C and the specific gravity of the dissolved resin material R are approximate. For this reason, even if the dissolved resin concentration CR in the liquid developer LD changes, the overall specific gravity of the liquid developer LD hardly changes. Therefore, it becomes difficult to employ a density measurement technique based on the specific gravity of the liquid to measure the dissolved resin concentration CR in the liquid developer LD.

  Further, the liquid developer LD in which the resin material R is dissolved is colorless or white light and nonpolar. Furthermore, the liquid developer LD in which the resin material R is dissolved has a feature of high viscosity. For this reason, the rotating body is immersed in the liquid developer LD, and the dissolved resin concentration CR in the liquid developer LD is changed using the fact that the torque of the rotating body changes according to the change in the viscosity of the liquid developer LD. A measurement technique can be considered. However, the viscosity of the liquid developer LD varies greatly depending on the dissolved resin concentration CR.

  Table 1 shows the viscosity of the liquid developer LD corresponding to each dissolved resin concentration CR when the dissolved resin concentration CR of the liquid developer LD is changed in advance. Thus, the viscosity of the liquid developer LD varies greatly depending on the dissolved resin concentration CR. For measuring the viscosity of the liquid developer LD, a rotational viscometer based on “JIS-Z8803 Liquid Viscosity—Measurement Method” was used.

  Since there is such a change in the viscosity of the liquid developer LD, in the concentration region where the viscosity is high (torque is large), even if the concentration is detected with the desired accuracy, in the concentration region where the viscosity is low (torque is small). The concentration is not detected with the desired accuracy. Further, in the region where the viscosity is extremely high (the torque is extremely large), the rotational speed of the rotating body is remarkably lowered, and the accuracy of density detection is lowered. Furthermore, if the torque of the rotating body increases too much, the rotation of the rotating body stops, making it difficult to detect the density.

  In the dissolved resin concentration detection device 280A according to the present embodiment, unlike the concentration detection device in which the rotating body rotates, the liquid developer LD does not have a mechanical action, so the viscosity of the liquid developer LD. It becomes possible to cope with the change of. As shown below, the dissolved resin concentration detection device 280A according to this embodiment is also characterized in that it uses a change in the viscosity of the liquid developer LD. Hereinafter, the measurement of the dissolved resin concentration CR by the dissolved resin concentration detection device 280A according to the present embodiment will be described in detail.

  FIG. 5 is a diagram showing the relationship between the dissolved resin concentration CR of the dissolved resin concentration detector 280A and the output frequency F of the frequency meter 696. FIG. 6 is a diagram showing the relationship between the output frequency F of the frequency meter 696 and the immersion depth D3 of the QCM sensor 60 in the dissolved resin concentration detection device 280A. FIG. 7 is a graph showing the relationship between the liquid temperature T of the liquid developer LD and the viscosity η of the liquid developer LD. FIG. 8 is a diagram showing the relationship between the liquid temperature T of the liquid developer LD and the output frequency F of the frequency meter 696. Further, FIG. 9 is a diagram showing the temperature dependence of the oscillation circuit 641 provided in the dissolved resin concentration detection device 280A.

  FIG. 5 shows the output frequency F detected by the frequency meter 696 when the various conditions of the dissolved resin concentration detector 280A are constant and the dissolved resin concentration CR of the liquid developer LD is changed in advance. Thus, it can be seen that the output frequency F of the crystal resonator 611 in the QCM sensor 60 changes according to the dissolved resin concentration CR of the liquid developer LD. As described above, this is because the viscosity of the liquid developer LD varies depending on the dissolved resin concentration CR. A certain correlation exists between the dissolved resin concentration CR and the output frequency F. Therefore, the dissolved resin concentration CR in the liquid developer LD can be detected using the output frequency F of the crystal resonator 611.

  On the other hand, the present inventor has found that the output frequency F of the crystal resonator 611 is affected by the depth of the crystal resonator 611 immersed in the liquid developer LD. FIG. 6 shows a state of the output frequency F when the depth D3 (d in FIG. 6) of the sensor electrode 61 of the QCM sensor 60 is changed in the liquid developer LD having a predetermined dissolved resin concentration CR. The depth D3 of the sensor electrode 61 is shown in FIG. FIG. 6 shows that the output frequency F of the crystal resonator 611 changes according to the depth D3 in which the sensor electrode 61 is immersed even at the same dissolved resin concentration CR. The change in the output frequency F is affected by the height of the liquid developer LD covering the upper side of the sensor electrode 61. This is because if the liquid height above the sensor electrode 61 increases, a large amount of vibration energy of the crystal resonator 611 is required.

  Further, FIG. 7 shows a change in the viscosity η when the liquid temperature T of the liquid developer LD provided with a predetermined dissolved resin concentration CR is changed by a heater or a cooling device (not shown). Thus, when the liquid temperature T of the liquid developer LD changes, the fluidity of the resin material R in the carrier liquid C changes, and the viscosity η of the liquid developer LD changes. Then, as shown in FIG. 8, even if the liquid developer LD has the same dissolved resin concentration CR due to the influence of the viscosity η of the liquid developer LD, the output of the crystal resonator 611 when the liquid temperature T changes. The frequency F changes. Note that the change in the output frequency F may include the temperature dependence of the oscillation circuit 641 in the circuit unit 64. However, as shown in FIG. 9, it was found that the output frequency F detected by the frequency meter 696 hardly changes even when the temperature of the oscillation circuit 641 itself is changed. Therefore, it can be understood that the change in the output frequency F accompanying the change in the liquid temperature T is due to the change in the viscosity η of the liquid developer LD.

  In the present embodiment, based on the above-described problem when the dissolved resin concentration CR in the liquid developer LD is measured using the vibration action of the crystal resonator 611, in the present embodiment, the concentration calculation of the QCM sensor 60 and the concentration calculation unit 698 is performed. Features in the method.

  As described above, the QCM sensor 60 is immersed in the liquid developer LD in the concentration detection tank 691 (FIG. 2). At this time, the bottom surface portion 651 of the housing 65 is disposed immediately above the QCM sensor 60. The pedestal portion 62 of the QCM sensor 60 is disposed so as to contact the bottom surface portion 651. That is, the bottom surface portion 651 covers the upper side of the QCM sensor 60 in the liquid developer LD, and the distance in the depth direction from the QCM sensor 60 is kept constant. Thereby, the distance D1 in the vertical direction between the sensor electrode 61 and the bottom surface portion 651 of the QCM sensor 60 is always kept constant. For this reason, the liquid height of the liquid developer LD covering the upper side of the QCM sensor 60 is always kept constant. As a result, it is possible to suppress fluctuations in the output frequency F due to the immersion depth of the sensor electrode 61. In order to further avoid the influence of the liquid developer existing above the QCM sensor 60, the depth D1 with respect to the bottom surface portion 651 of the immersed QCM sensor 60 in FIG. 2 is preferably 6 mm or more. . Further, regarding the area of the bottom surface portion 651 that covers the QCM sensor 60, it is preferable that the diameter of the bottom surface portion 651 is 34 mm or more. Thereby, the upper part of the QCM sensor 60 is sufficiently covered by the bottom surface part 651.

  The concentration calculation unit 698 converts the output frequency F detected by the frequency meter 696 into a dissolved resin concentration CR. At this time, the concentration calculation unit 698 corrects the fluctuation amount of the dissolved resin concentration CR caused by the liquid temperature T of the liquid developer LD. First, the liquid temperature T of the liquid developer LD detected by the liquid temperature sensor 692 is stored in the storage unit 697. On the other hand, the temperature correction value Vt is stored in the storage unit 697 in advance. The temperature correction value Vt is a correction value calculated based on FIG. 8, and is used to convert the output frequency F at the liquid temperature T to the conversion frequency FC at the reference liquid temperature 25 degrees. The concentration calculation unit 698 derives a conversion frequency FC from the detected liquid temperature T and output frequency F.

  The storage unit 697 stores a density conversion value Vd in advance. The concentration conversion value Vd is used to convert the conversion frequency FC (the output frequency F in FIG. 5) into the dissolved resin concentration CR based on the calibration curve of FIG. For this reason, in this embodiment, the density | concentration conversion value Vd is stored for every predetermined frequency. The concentration calculation unit 698 derives the dissolved resin concentration CR of the liquid developer LD from the converted frequency FC based on the concentration converted value Vd.

  As described above, in the present embodiment, after correcting the influence of the immersion depth D3 (D1) of the QCM sensor 60 immersed in the liquid developer LD and the influence of the liquid temperature T of the liquid developer LD, the liquid It becomes possible to detect the dissolved resin concentration CR of the developer LD.

<About Solid Content Concentration Detector 280C>
Hereinafter, based on the drawings, the solid content concentration detection apparatus 280C according to the embodiment of the present invention will be described in detail. FIG. 10 is a diagram schematically showing the configuration of the solid content concentration detection device 280C according to the present embodiment.

  Referring to FIG. 10, solid content concentration detection device 280C is a device for detecting the concentration of toner in liquid developer LD in which toner as solid content is dispersed in a dielectric liquid serving as carrier liquid C. . More specifically, the solid content concentration detecting device 280C is applied to the developer adjusting unit 27 that adjusts the liquid developer LD supplied to the developing device 14 to be described later. This is used to determine whether or not the toner density is a predetermined density value. The solid content concentration detection device 280C includes a weight 32 and a load cell 33 in addition to the concentration detection tank 691 described above. In addition, the solid content concentration detection device 280C is electrically connected to the measurement unit 280B described above.

  FIG. 11 is a view showing the concentration detection tank 691 and the load cell 33 of the solid content concentration detection device 280C, (a) is a top view of the concentration detection tank 691 and the load cell 33, and (b) is a view of the concentration detection tank 691. It is a side view, (c) is a side view of the density | concentration detection tank 691 seen from the opposite side to (b), (d) is a longitudinal cross-sectional view of the density | concentration detection tank 691 and the load cell 33. FIG. As shown in FIG. 11, the concentration detection tank 691 is a cylindrical container that opens upward, and stores the liquid developer LD. The opening of the concentration detection tank 691 is closed by the lid member 38. The concentration detection tank 691 has an inner wall surface 691a that defines its capacity. The inner wall surface 691a is composed of an inner peripheral surface 691b and an inner bottom surface 691c. The density detection tank 691 is held by a holding member 37 installed at an appropriate position in the wet image forming apparatus.

  The concentration detection tank 691 includes two first inlets 43 and second inlets 44 provided in the lower part thereof, and two first outlets 46 and second outlets 45 provided in the upper part thereof. Have. The liquid developer LD is introduced into the concentration detection tank 691 from the first inlet 43 and the second inlet 44 and discharged from the first outlet 46 and the second outlet 45.

  Each of the first inlet 43 and the second inlet 44 is connected to the upstream side of the fourth pipe 84 (FIG. 9) in order to introduce the liquid developer LD into the concentration detection tank 691. On the other hand, a downstream side of the fourth pipe 84 is connected to each of the first discharge port 46 and the second discharge port 45 in order to discharge the liquid developer LD from the concentration detection tank 691. The fourth pipe 84 is connected to the developer container 272. Therefore, in this embodiment, the liquid developer LD is configured to continuously flow between the concentration detection tank 691 and the developer container 272 in terms of time.

  As shown in FIG. 11, the load cell 33 includes a strain generating body 35 and a strain gauge 36 installed on the strain generating body 35. Although the shape of the strain generating body 35 is not particularly limited, in the present embodiment, the strain generating body 35 has a shape formed in an elongated block shape, and extends above the concentration detection tank 691. The strain generating body 35 is supported at a base end portion thereof by a support block 39 fixed to the upper portion of the concentration detection tank 691. Therefore, the front end portion of the strain generating body 35 is located above the liquid developer LD in the concentration detection tank 691 via the lid member 38. The strain generating body 35 is made of, for example, an aluminum alloy.

  Although the strain gauge 36 is installed on the upper surface of the strain generating body 35 in FIG. 11, the installation position is not limited to the portion shown in FIG. 11, and the strain is the largest in the strain generating body 35 by the weight 32 described later. Set to the location where it occurs. The strain gauge 36 includes, for example, a resistor whose resistance value changes due to expansion and contraction, and a Wheatstone bridge circuit that converts the resistance value change into a voltage, and fluctuates due to distortion of the strain generating body 35. The electrical resistance value is output as a voltage value.

  The weight 32 has a spherical shape made of, for example, SUS. The weight 32 is connected to the distal end portion of the strain generating body 35 by a metal wire 47 that passes through a through hole formed in the lid member 38, and is accommodated in the concentration detection tank 691. The weight 32 is set so that the weight 32 does not protrude from the liquid surface of the liquid developer LD that has flowed into the concentration detection tank 691. Further, the weight 32 is disposed so as to occupy a substantially central position in the concentration detection tank 691 when the concentration detection tank 691 is viewed from above, and on the inner peripheral surface 31b and the inner bottom surface 31c of the concentration detection tank 691. It is arranged not to touch. The material of the weight 32 may be a material having a density difference sufficient for the weight 32 to be immersed in the liquid developer LD, and is appropriately selected in consideration of cost. The member that connects the weight 32 and the tip of the strain generating body 35 does not necessarily need to use the metal wire 47, and may be any member that does not affect the buoyancy acting on the weight 32 by the liquid developer LD. .

  Measurement unit 280B includes an amplifier circuit 53, an A / D converter 55, and a temperature correction unit 58, in addition to the power supply 693, the storage unit 697, and the concentration calculation unit 698 described above.

  The amplification circuit 53 is connected to the strain gauge 36 of the load cell 33 and amplifies the voltage value output from the strain gauge 36. The amplification factor of the voltage value is set as appropriate. The amplifying circuit 53 can cancel the tare weight acting on the strain-generating body 35, that is, the force acting on the strain-generating body 35 by the weight 32 in the state where there is no liquid developer LD in the concentration detection tank 691. Note that the amplifier circuit 53 is electrically separated from an A / D converter 55 and a concentration calculator 698 described later.

  In the solid content concentration detection device 280C, the power source 693 controls the output voltage of the amplifier circuit 53 so that it always becomes a constant value.

  The A / D converter 55 converts the voltage value amplified and output from the amplifier circuit 53 into a digital signal value.

  The temperature correction unit 58 stores in advance a temperature correction value based on the relationship between the liquid temperature T of the liquid developer LD and the specific gravity ρ. The temperature correction value is referred to by the concentration calculation unit 698 when calculating the solid content concentration DS.

In the solid content concentration detection device 280C, the concentration calculation unit 698 obtains the solid content concentration DS (toner concentration) of the liquid developer LD based on the digital signal value. FIG. 12 is a diagram showing the relationship between the specific gravity ρ of the liquid developer LD and the solid content concentration DS. The density calculator 698 changes the specific gravity ρ of the liquid developer LD according to the solid content concentration DS of the liquid developer LD as shown in FIG. 12, and the buoyancy acting on the weight 32 by the liquid developer LD is liquid developed. A characteristic that varies depending on the specific gravity ρ of the agent LD is used. The load Fr acting on the strain body 35 by the weight 32 is based on the Archimedes principle,
Fr = Mg−ρVg (Formula 1)
(M is the mass of the weight 32, g is the acceleration of gravity, ρ is the specific gravity of the liquid developer LD, and V is the volume of the weight 32).

  That is, the load Fr acting on the strain generating body 35 by the weight 32 is obtained by subtracting the buoyancy acting on the weight 32 from the gravity acting on the weight 32. Therefore, in this embodiment, a calibration curve indicating the relationship between the load Fr, that is, the digital signal value corresponding to the amplified voltage value, and the solid content concentration DS of the liquid developer LD is created in advance, and the calibration curve is stored in a ROM or the like. The data is stored in the storage unit 697, and the storage unit 697 is connected to the density calculation unit 698. The calibration curve is shown in FIG. Therefore, the concentration calculation unit 698 can obtain the solid content concentration DS by comparing the actually obtained digital signal value (amplified voltage value) with a calibration curve.

  As shown in the calibration curve of FIG. 13, when the buoyancy acting on the weight 32 is increased by the liquid developer LD and the load Fr acting on the strain generating body 35 is decreased, the voltage value output from the strain gauge 36 is decreased. Become. On the other hand, when the buoyancy decreases and the load Fr increases, the voltage value increases. The toner density increases as the voltage value decreases.

  FIG. 14 is a graph showing an example in which the amplified voltage value output from the amplifier circuit 53 is measured with an oscilloscope. In this example, the solid concentration DS was intentionally increased by 7% while the liquid developer LD was continuously introduced from the developer container 272 into the concentration detection tank 691 in terms of time. As indicated by the arrow, the amplification voltage value decreased corresponding to the increase in the solid content concentration DS of 7%. This change in output appeared in less than 10 seconds, as is apparent from FIG. In the present embodiment, the liquid developer LD is continuously introduced into the concentration detection tank 691 from the developer adjusting unit 27 in terms of time, but as is clear from the example shown in FIG. Even if it changes over time, the solid content concentration DS can be detected quickly and accurately.

  Since the liquid developer LD is introduced into the concentration detection tank 691 by the fourth pump P4, pulsation caused by driving the fourth pump P4 is captured as a noise component. FIG. 15 is a diagram showing the transition of the noise component accompanying the driving of the fourth pump P4. As described above, as long as the fourth pump P4 operates stably, a regular noise component appears in the amplified voltage value. The measurement unit 280B is configured to cancel such a regular noise component when obtaining the solid content concentration DS.

  The solid content concentration detection device 280C can further include a liquid temperature sensor 692 used in the dissolved resin concentration detection device 280A. FIG. 16 is a diagram showing the relationship between the liquid temperature T of the liquid developer LD and the specific gravity ρ. The specific gravity ρ of the liquid developer LD varies depending on the liquid temperature T of the liquid developer LD even under the same solid content concentration DS condition. That is, the specific gravity ρ of the liquid developer LD increases as the temperature increases. For this reason, when the liquid temperature T varies even if the solid content concentration DS does not vary, the buoyancy acting on the weight 32 and, consequently, the load Fr acting on the strain generating body 35 by the weight 32 also varies. Accordingly, when the liquid temperature T of the liquid developer LD is fluctuating, the solid content concentration DS cannot be detected with high accuracy if the voltage value output from the load cell 33 is used as it is.

  Therefore, in the present embodiment, a temperature correction value is created in advance based on the relationship between the liquid temperature T and the specific gravity ρ, and a temperature correction table including the temperature correction value is stored in the temperature correction unit 58. The concentration calculation circuit 56 is connected to the liquid temperature sensor 692 and the temperature correction unit 58. Thereby, the concentration calculation unit 698 can accurately detect the solid content concentration DS by correcting the amplified voltage value with the predetermined temperature correction value based on the liquid temperature T detected by the liquid temperature sensor 692.

  The solid content concentration DS obtained by the concentration calculation unit 698 is transmitted to a control unit (not shown) connected to the developer container 272. When it is determined that the solid content concentration DS obtained by the concentration calculation unit 698 is higher than a predetermined concentration value, the control unit controls the carrier liquid C to be supplied from the carrier tank 274 to the developer storage container 272. . On the other hand, when the control unit determines that the solid content concentration DS obtained by the concentration calculation unit 698 is lower than a predetermined concentration value, the liquid developer T having a high toner concentration from the toner tank 275 enters the developer storage container 272. Control to be supplied. Since the liquid developer LD is continuously supplied to the concentration detection tank 691 in time, the control unit can know the change in the solid content concentration DS that can change over time by the concentration calculation unit 698, The supply of the carrier liquid C or the liquid developer T having a high toner concentration is controlled until the solid content concentration DS of the liquid developer LD reaches a predetermined concentration value.

  Since the developer container 272 includes the stirring device 276, bubbles of a level that is difficult to visually recognize are generated in the liquid developer LD by the stirring of the liquid developer LD by the stirring device 276. It is feared that the buoyancy acting on the water will be affected. However, when the output amplified voltage value was observed while changing the rotation speed of the stirring device 276 in the liquid developer LD having a toner concentration of 30%, the rotation speed of the stirring device 276 was found to be as shown in FIG. Even if it became large, the big fluctuation | variation in an amplification voltage value was not observed. Therefore, it was found that the bubbles generated by the stirring by the stirring device 276 hardly affect the buoyancy acting on the weight 32. Even when a SUS sphere is used as the weight 32, if the bubbles affect the buoyancy, the influence of the bubbles can be canceled by appropriately increasing the weight of the weight 32.

  In the solid content concentration detection device 280C according to the present embodiment described above, (1) the specific gravity ρ of the liquid developer LD varies according to the solid content concentration DS, and (2) the buoyancy acting on the weight 32 is liquid development. Fluctuating according to the specific gravity ρ of the agent LD, (3) the force acting on the strain body 35 by the weight 32 is obtained by subtracting the buoyancy acting on the weight 32 from the gravity acting on the weight 32, Is used to obtain the solid content concentration DS based on the voltage value from the strain gauge 36. Therefore, the solid content concentration detection device 280C can accurately detect the solid content concentration DS, unlike the conventional detection device that uses the light absorption rate, even if the solid content concentration DS is high. . Further, the solid content concentration detection device 280C can reduce the influence of bubbles acting on the weight 32 by appropriately increasing the weight of the weight 32 even if the liquid developer LD has a high viscosity. For this reason, the solid content concentration DS can be detected with high accuracy. Furthermore, the solid content concentration detection device 280C can accurately detect the solid content concentration DS even when the liquid developer LD is flowing. Furthermore, since the solid content concentration detection device 280C uses the load cell 33, unlike a conventional device using conductivity, a power supply with a large output voltage is not required.

  In addition, according to the solid content concentration detection device 280C according to the present embodiment, since the calibration curve indicating the relationship between the solid content concentration DS and the voltage value output from the strain gauge 36 is stored in the storage unit 697, the strain gauge The solid content concentration DS can be easily obtained simply by collating the voltage value output by 36 with a calibration curve.

  Furthermore, according to the solid content concentration detection device 280C according to the present embodiment, the liquid temperature sensor 692 for detecting the temperature of the liquid developer LD in the concentration detection tank 691 is provided, and the concentration calculation unit 698 is a predetermined based on the temperature. The voltage value from the strain gauge 36 is corrected with the temperature correction value to obtain the solid content concentration DS. Thereby, even when the temperature of the liquid developer LD varies and the specific gravity ρ varies, the solid content concentration DS can be accurately detected.

  Furthermore, according to the solid content concentration detection device 280C according to the present embodiment, the liquid developer LD is continuously introduced into the concentration detection tank 691 from the developer storage container 272 in time, so that the solid content concentration DS is Even if it changes over time, the solid content concentration DS can be accurately detected.

  The solid content concentration detection device 280C according to the present embodiment has been described above with reference to FIGS. 10 to 17. In the solid content concentration detection device 280C, the first note is used to improve the detection accuracy of the solid content concentration DS. The positional relationship between the inlet 43 and the second inlet 44 and the first outlet 46 and the second outlet 45 is defined. Hereinafter, the positional relationship will be described with reference to FIGS. 18 and 19. FIG. 18 is a schematic view showing the positional relationship between the first inlet 43 and the second inlet 44 and the first outlet 46 and the second outlet 45 in cross section. FIG. 19 schematically shows the positional relationship between the first inlet 43 and the second inlet 44 and the first outlet 46 and the second outlet 45 when the concentration detection tank 691 is viewed from above. FIG.

  As shown in FIG. 18, the first inlet 43 and the second inlet 44 are provided so as not to be located on the same line as the weight 32 in the horizontal plane. According to this configuration, the flow of the liquid developer LD that has flowed into the concentration detection tank 691 from the first injection port 43 and the second injection port 44 does not directly collide with the weight 32, so that the liquid developer flow is It is possible to avoid the influence of the buoyancy acting on the bulging force and the force acting on the strain generating body 35 by the weight 32. Thereby, it is possible to maintain the detection of the solid content concentration DS with high accuracy.

  As shown in FIG. 18, the first inlet 43 and the second inlet 44 are provided at a position lower than the weight 32, while the first outlet 46 and the second outlet 45 are provided with a weight. It is provided at a position higher than 32. According to this configuration, the weight 32 can be easily immersed in the liquid developer LD. Thereby, the buoyancy acting on the weight 32, and hence the force acting on the strain generating body 35 by the weight 32 can be obtained accurately.

  Further, as shown in FIG. 19, the first inlet 43 is provided approximately 90 ° apart from the second inlet 44, and the first outlet 46 is approximately 90 from the second outlet 45. ° Separated. As shown in FIG. 18, the first inlet 43 is substantially opposite to the first outlet 46 when viewed in the vertical direction, and the second inlet 44 is the second outlet 45 when viewed in the vertical direction. It is almost opposite. By arranging the first inlet 43 and the second inlet 44 and the first outlet 46 and the second outlet 45 in this way, a part of the liquid developer LD stays in the concentration detection tank 691. Can be suppressed. As a result, the solid content concentration DS of the liquid developer LD becomes substantially uniform in the concentration detection tank 691. As a result, the solid content concentration DS can be accurately detected.

  In the present embodiment, as shown in FIG. 1, the solid content concentration detection device 280 </ b> C and the above-described dissolved resin concentration detection device 280 </ b> A are arranged in the concentration detection tank 691. At this time, the weight 32 of the solid content concentration detection device 280C is immersed below the sensor electrode 61 of the QCM sensor 60 of the dissolved resin concentration detection device 280A in the liquid developer LD. This is because the solid content concentration detection device 280C requires more liquid developer LD than the dissolved resin concentration detection device 280A. Thus, by arranging the weight 32 and the sensor electrode 61, it is possible to efficiently detect the dissolved resin concentration CR and the solid content concentration DS.

<Mutual correction of dissolved resin concentration detection device and solid content concentration detection device>
As described above, in the present embodiment, the dissolved resin concentration CR and the solid content concentration DS of the liquid developer LD are suitably detected by the dissolved resin concentration detection device 280A and the solid content concentration detection device 280C. Here, by using the dissolved resin concentration detection device 280A and the solid content concentration detection device 280C, the present inventor can further obtain a highly accurate dissolved resin concentration CRH and solid content concentration DSH with less errors. I found out.

  FIG. 20 is a diagram showing the relationship between the dissolved resin concentration CR and the viscosity η of the liquid developer LD when the solid content concentration DS in the liquid developer LD is changed. FIG. 21 shows the difference in the solid content concentration DS of the liquid developer LD in FIG. 20 as the difference in specific gravity ρ. Further, FIG. 22 is a diagram showing the relationship between the solid content concentration DS and the specific gravity ρ of the liquid developer LD when the viscosity η (dissolved resin concentration CR) of the liquid developer LD is changed.

  20 and 21, even if the dissolved resin concentration CR is the same, the viscosity η is slightly different when the solid content concentration DS is different. In other words, even if the viscosity η is the same, the dissolved resin concentration CR is different when the solid content concentration DS is different. Therefore, in the above-described dissolved resin concentration detection device 280A, when the output frequency F based on the vibration of the crystal resonator 611 is converted into the dissolved resin concentration CR, an error corresponding to the solid content concentration DS of the liquid developer LD is generated. Will occur.

  In FIG. 22, the specific gravity ρ is slightly different when the dissolved resin concentration CR (viscosity η) is different even at the same solid content concentration DS. In other words, even if the specific gravity ρ is the same, if the dissolved resin concentration CR is different, the solid content concentration DS is different. Therefore, in the above-described solid content concentration detection device 280C, when the solid content concentration DS is derived from the voltage value output from the load cell 33 based on the specific gravity ρ of the liquid developer LD, the dissolved resin concentration CR of the liquid developer LD. As much as this, an error will occur. Thus, it was found that the dissolved resin concentration CR and the solid content concentration DS derived from the dissolved resin concentration detection device 280A and the solid content concentration detection device 280C influence each other.

  Therefore, in the present embodiment, the solid content concentration DSH and the dissolved resin concentration CRH are derived in which the errors that contribute to each other between the dissolved resin concentration CR and the solid content concentration DS are removed as much as possible. The derivation process will be described below. In the present embodiment, the solution concentration detection device 280A is used as a frequency detection unit that detects the output frequency F of the crystal resonator 611 that vibrates according to the viscosity η of the liquid developer LD. The solid content concentration detection device 280C is used as specific gravity detection means for detecting the specific gravity ρ of the liquid developer LD.

  FIG. 25 is a flowchart when the dissolved resin concentration CRH and the solid content concentration DSH are derived by the concentration calculation unit 698 (FIG. 1). In the present embodiment, the storage unit 697 stores known constants to be described later. The storage unit 697 stores calibration curve data D1 and D2. The calibration curve data D1 is the actual value obtained by converting the voltage value V output from the strain gauge 36 (FIG. 11) of the load cell 33 into the digital signal VD by the A / D converter 55 in the solid content detector 280C. This is data calibrated with respect to the relationship with the load Fr applied to the strain gauge 36. Further, the calibration curve data D2 is the relationship between the dissolved resin concentration CR and the solid content concentration DS when the specific gravity ρ is a variable and the viscosity η in the liquid developer LD (or the dissolved resin when the viscosity η is a variable). This is calibration data showing the relationship between the concentration CR and the solid content concentration DS and the specific gravity ρ.

  Referring to FIGS. 1 and 25, when liquid developer LD flows into concentration detection tank 691, voltage value V is output from strain gauge 36 (FIG. 11) of load cell 33 of solid content concentration detection device 280C. (Step S001). The voltage value V is amplified by the amplifier circuit 53 and then converted into a digital signal VD by the A / D converter 55.

  The concentration calculation unit 698 converts the digital signal VD into the load Fr based on the calibration curve data D1 stored in advance in the storage unit 697 (step S002).

Next, the density calculation unit 698 derives the specific gravity ρ of the liquid developer LD based on the load F obtained above (step S003). At this time, the concentration calculation unit 698 is based on the above-described (Expression 1).
ρ = (Mg—Fr) / Vg (Formula 2)
Ρ is derived from the relationship (ρ: specific gravity of liquid developer LD, M: mass of weight 32, g: acceleration of gravity, V: volume of weight 32, Fr: load Fr derived in step S002).

  Thereafter, the density calculation unit 698 derives the viscosity η of the liquid developer LD using the specific gravity ρ of the liquid developer LD derived as described above (step S004). At this time, the concentration calculation unit 698 refers to the following equation.

Δf = −f ₀ ^3/2 (ρη / πρ _T μ _T ) ^1/2 (Expression 3)
(Δf: f−f ₀ , f: output frequency F based on vibration of the crystal resonator 611, f ₀ : resonance frequency of the crystal resonator 611 in a state in which no sample is attached to the surface, ρ _T : crystal resonator 611 density, μ _T : shear modulus of the crystal resonator 611.)
(Equation 3) is a known relational expression relating to the viscosity of the viscous fluid and the resonance frequency of the vibrating body. In the above (Formula 3), f0, ρT, and μT are known constants and are stored in the storage unit 697 in advance. The concentration calculation unit 698 derives the viscosity η of the liquid developer LD from f (output frequency F) obtained from the dissolved resin concentration detection device 280A and the specific gravity ρ obtained in step S003.

  Thus, the density calculation unit 698 obtains the specific gravity ρ and the viscosity η of the liquid developer LD that is the measurement target. Then, the concentration calculation unit 698 derives the dissolved resin concentration CRH and the solid content concentration DSH of the liquid developer LD from the calibration curve data D2 stored in the storage unit 697 in advance (step S005). At this time, the calibration curve stored in the storage unit 697 is the same type of information as that shown in FIGS. FIG. 23 and FIG. 24 show examples where the dissolved resin concentration CRH and the solid content concentration DSH are derived as a result of obtaining the specific gravity ρ and the viscosity η of the liquid developer LD.

  Thus, according to the present embodiment, it is possible to individually derive the dissolved resin concentration CRH and the solid content concentration DSH using the two variables of the specific gravity ρ and the viscosity η of the liquid developer LD. For this reason, the dissolved resin concentration CRH and the solid content concentration DSH are derived in a state in which the influences of errors included in the dissolved resin concentration CR and the solid content concentration DS and contributing to each other are suppressed as much as possible. Therefore, compared with the case where the solid content concentration DS in the liquid developer LD is detected based only on the specific gravity ρ of the liquid developer LD, the concentration of solid particles is generated by the dissolved resin component in the liquid developer LD. Errors are reduced. Further, compared to the case where the dissolved resin concentration CR in the liquid developer LD is detected based only on the vibration frequency (output frequency F) of the crystal resonator 611, solid particles (toner) in the liquid developer LD are used. The error generated in the concentration of the dissolved resin component in the liquid developer LD is reduced. As a result, the concentration of the resin material R dissolved in the liquid developer LD and the concentration of the solid particles dispersed in the liquid developer LD are accurately grasped in a wide range, and the concentration adjustment of the liquid developer LD is suitably realized. Is done.

<Embodiment as Image Forming Apparatus>
Next, an image forming apparatus incorporating the solution concentration detection device 280 according to the above embodiment will be described. 26 is a schematic configuration diagram of the color printer 1 (image forming apparatus) in which the solution concentration detection device 280 is incorporated, FIG. 27 is a schematic cross-sectional view of the color printer 1 excluding the liquid developer circulating device, and FIG. FIG. 3 is an enlarged cross-sectional view showing one of image forming units. Although the image forming apparatus shown in FIGS. 26 to 28 is a color printer, a copier, a facsimile machine, a multifunction peripheral (MFP) including these functions, and other devices capable of forming an image on a sheet. It can also be a device.

  As shown in FIG. 26, the color printer 1 is arranged in an upper main body 1A in which various units and parts for image formation are housed, and a lower part of the upper main body 1A, and a liquid developer circulation for each color. It is comprised from the lower main-body part 1B in which apparatus LY, LM, LC, LB is accommodated. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown.

  As shown in FIG. 27, the upper main body 1A is formed by a tandem image forming unit 2 that forms a toner image based on image data, a paper storage unit 3 that stores paper, and an image forming unit 2. A secondary transfer unit 4 that transfers the toner image onto the paper, a fixing unit 5 that fixes the transferred toner image on the paper, a discharge unit 6 that discharges the fixed paper, and a paper storage unit 3. And a paper transport unit 7 for transporting paper from the discharge unit 6 to the discharge unit 6.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22 for the intermediate transfer belt 21, and an image forming unit corresponding to each of yellow (Y), magenta (M), cyan (C), and black (Bk). FY, FM, FC, and FB.

  The intermediate transfer belt 21 is a belt-like member that has conductivity and is wider than the maximum length of paper in the direction perpendicular to the usable paper conveyance direction, and is an endless, ie, loop-shaped belt. In FIG. 27, it is circulated and driven clockwise. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

  The image forming units FY, FM, FC, and FB are arranged in parallel in the vicinity of the intermediate transfer belt 21 and between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but the order of arrangement is preferable in consideration of the influence on the completed image caused by the color mixture of each color.

  The image forming units FY, FM, FC, and FB include a photosensitive drum 10, a charger 11, an LED exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning device 26, and a charge removal device 13. And a carrier liquid removing roller 30. Of the image forming units, the image forming unit FB located closest to the secondary transfer unit 4 is not provided with the carrier liquid removal roller 30, but the other configurations are the same.

  In addition, liquid developer circulating devices LY, LM, LC, and LB are provided corresponding to the image forming units FY, FM, FC, and FB, respectively, and supply and recovery of the liquid developer LD of each color are performed. The liquid developer circulating devices LY, LM, LC, and LB will be described in detail later.

  The photoconductor drum 10 is a cylindrical member, and carries a toner image including toner charged (charged positively in the present embodiment) on the surface thereof. The photosensitive drum 10 is rotated counterclockwise in FIGS. 26 and 27. The charger 11 uniformly charges the surface of the photosensitive drum 10. The LED exposure device 12 has a light source such as an LED, and irradiates light onto the surface of the uniformly charged photoreceptor drum 10 according to image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing device 14 holds the liquid developer LD including the toner and the liquid carrier so as to face the electrostatic latent image on the surface of the photosensitive drum 10, thereby attaching the toner to the electrostatic latent image. Thereby, the electrostatic latent image is developed as a toner image.

  Referring to FIG. 28, the developing device 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a supply roller blade 144, a development cleaning blade 145, a developer recovery device 146, and a developing roller charger 147. Including.

  The developing container 140 is supplied with a liquid developer LD composed of toner particles and a liquid carrier. The liquid developer LD is supplied from the supply nozzle 278 into the developing container 140 in a state where the density adjustment between the toner and the carrier is performed in advance. The liquid developer LD is supplied toward the nip portion between the supply roller 142 and the support roller 143, and the excess part falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer LD is collected by the liquid developer circulating device through the pipe 82 (see FIG. 29).

  The support roller 143 is disposed substantially at the center of the developing container 140 and is brought into contact with the supply roller 142 from below to form a nip portion. The supply roller 142 is arranged not diagonally above the support roller 143 but obliquely above in a direction away from the supply nozzle 278. A groove for holding the liquid developer LD is provided on the peripheral surface of the supply roller 142. As shown by a dotted arrow in FIG. 28, the support roller 143 rotates counterclockwise and the supply roller 142 rotates clockwise.

  The liquid developer LD supplied from the supply nozzle 278 is temporarily retained on the upstream side in the rotation direction of the nip portion. The liquid developer LD is carried upward while being held in the groove of the supply roller 142 as the rollers 142 and 143 rotate. The supply roller blade 144 is pressed against the peripheral surface of the supply roller 142 so that the amount of the liquid developer LD held by the supply roller 142 becomes a predetermined amount. Regulates liquid developer LD. The excess liquid developer LD scraped off by the supply roller blade 144 is received at the bottom of the developing container 140.

  The developing roller 141 is disposed in the upper opening of the developing container 140 so as to be in contact with the supply roller 142. The developing roller 141 is rotated in the same direction as the supply roller 142 (the surface of the developing roller 141 moves in the opposite direction to the surface of the supply roller 142 in the nip portion where the developing roller 141 and the supply roller 142 abut). The liquid developer LD held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. Since the layer thickness of the liquid developer on the supply roller 142 is regulated to a predetermined value, the layer thickness of the liquid developer layer formed on the surface of the developing roller 141 is also maintained at the predetermined value.

  The developing roller charger 147 applies a charging potential having the same polarity as the toner charging polarity on the surface of the developing roller 141. For this reason, the toner in the developer layer carried on the developing roller 141 is moved to the surface side of the developing roller 141, and the development efficiency is improved. The developing roller charger 147 is a peripheral surface of the developing roller 141 on the developing roller 141 on the downstream side in the rotation direction with respect to the contact portion with the supply roller 142 and on the upstream side with respect to the contact portion with the photosensitive drum 10. It arrange | positions so that it may oppose.

  The developing roller 141 is in contact with the photosensitive drum 10. A toner image corresponding to the image data is formed on the surface of the photosensitive drum 10 by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 141.

  The development cleaning blade 145 is disposed so as to contact the downstream side in the rotation direction with respect to the contact portion of the development roller 141 with the photosensitive drum 10, and the development cleaning blade 145 is on the surface of the development roller 141 that has completed the development operation on the photosensitive drum 10. The liquid developer LD is removed.

  The developer recovery device 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer LD to the pipe 81 of the liquid developer circulation device. The liquid developer LD flows down along the surface of the development cleaning blade 145. However, since the viscosity of the liquid developer LD is high, the developer recovery device 146 has a delivery roller (not shown) that assists in feeding the liquid developer LD. Is provided.

  The primary transfer roller 20 is disposed on the back surface of the intermediate transfer belt 21 so as to face the photosensitive drum 10. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). The primary transfer roller 20 applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt 21 and its periphery. The intermediate transfer belt 21 functions as an image carrier that carries a toner image and conveys it to a sheet.

  The cleaning device 26 cleans the liquid developer LD remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21. The cleaning device 26 includes a residual developer conveying screw 261 and a cleaning blade 262. The residual developer conveying screw 261 is a member for conveying the residual developer scraped by the cleaning blade 262 and stored in the cleaning device 26 to the outside of the cleaning device, and is disposed in the cleaning device 26. Yes.

  The cleaning blade 262 is a member for scraping off the liquid developer LD remaining on the surface of the photosensitive drum 10 and is a plate-like member extending in the rotation axis direction of the photosensitive drum 10. The end of the cleaning blade 262 is in sliding contact with the surface of the photosensitive drum 10, and scrapes off the liquid developer LD remaining on the photosensitive drum 10 as the photosensitive drum 10 rotates.

  The static eliminator 13 has a light source for static elimination, and removes the liquid developer LD by the cleaning blade 262 and removes the surface of the photosensitive drum 10 with light from the light source in preparation for image formation in the next round.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier liquid removing roller 30 is disposed on the side where the secondary transfer unit 4 is disposed with respect to the position where the photosensitive drum 10 and the intermediate transfer belt 21 are in contact with each other, and the carrier liquid is removed from the surface of the intermediate transfer belt 21. Remove.

  Referring back to FIG. 27, the paper storage unit 3 is a part for storing paper for fixing a toner image, and is disposed below the upper main body 1A. The paper storage unit 3 has a paper feed cassette that stores paper.

  The secondary transfer unit 4 transfers the toner image formed on the intermediate transfer belt 21 to a sheet. The secondary transfer unit 4 includes a support roller 41 that supports the intermediate transfer belt 21 and a secondary transfer roller 42 that is disposed to face the support roller.

  The fixing unit 5 fixes the toner image on the paper. The fixing unit 5 is disposed on the upper side of the secondary transfer unit 4. The fixing unit 5 includes a heating roller 51 and a pressure roller 52 disposed so as to face the heating roller 51.

  The discharge unit 6 discharges the sheet on which the toner image is fixed by the fixing unit 5. The discharge unit 6 is disposed at the top of the color printer 1. The paper transport unit 7 includes a plurality of transport roller pairs, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4, the fixing unit 5, and the discharge unit 6.

  FIG. 29 is a block diagram showing an outline of the entirety of one liquid developer circulating device LY. The other liquid developer circulating devices LM, LC, LB have the same configuration. This liquid developer circulation device LY supplies the residual developer (mixture of toner and carrier liquid) scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the liquid developer LD to the photosensitive drum 10. It is a device for circulation and reuse.

  The liquid developer circulation device LY includes a residual developer tank 271, a developer container 272, a solid concentration detector 273, a carrier tank 274, a toner tank 275, a varnish tank 279, a stirring device 276, a developer reserve tank 277, and liquid development. An agent supply device 278, a dissolved resin concentration detection device 280, a liquid developer separation device 28, a plurality of pumps P1 to P14, and a control unit 550 are provided.

  The residual developer tank 271 is a tank that is connected to the developing device 14 via the first pipe 81 and the second pipe 82 and can store the liquid developer LD collected from the developing device 14 side. A first pump P1 and a fifth pump P5 are attached in the middle of the first pipe 81 and the second pipe 82, respectively.

  The liquid developer scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the toner to the photosensitive drum 10 is sent to the residual developer tank 271 through the first pipe 81 by driving the first pump P1. It is done. Further, in the developing container 140, the liquid developer LD stored in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 passes through the second pipe 82 by the driving of the fifth pump P5, and remains in the developing process. Sent to the agent tank 271.

  The developer container 272 is connected to the residual developer tank 271. The developer container 272 adds the developer having a solid content concentration DS (toner concentration) higher than the developer used in the developing device 14 or the carrier liquid to the residual developer, so that the solid content concentration DS is in an appropriate range. Adjust to. The liquid developer LD whose solid content concentration DS is adjusted is supplied to the developing device 14. The developer container 272 is connected to the residual developer tank 271 via the third pipe 83. A second pump P2 is attached to the third pipe 83. The liquid developer LD in the residual developer tank 271 is sent to the developer container 272 through the third pipe 83 by driving the second pump P2.

  The solution concentration detector 280 detects the solid content concentration DS (DSH) and the dissolved resin concentration CR (CRH) of the liquid developer LD in the developer container 272. The solution concentration detection device 280 is connected to an annular fourth pipe 84 that is connected to the developer container 272. A fourth pump P4 is attached to the annular fourth pipe 84. The liquid developer LD in the developer container 272 is guided from the inlet end of the fourth pipe 84 to the solution concentration detecting device 280 by the driving of the fourth pump P4, and then the developer from the outlet end of the fourth pipe 84. Returned to the storage container 272.

  The carrier tank 274 stores a carrier liquid. When the solid concentration detector 273 determines that the toner concentration in the developer container 272 is higher than the appropriate range, the carrier liquid is supplied from the carrier tank 274 into the developer container 272, and the container 272 The solid concentration DS of the liquid developer is lowered. The carrier tank 274 and the developer container 272 are connected by a fifth pipe 85, and the supply of the carrier liquid is executed by driving a third pump P3 provided in the middle of the fifth pipe 85.

  The toner tank 275 stores a liquid developer LD having a toner concentration higher than that of the developer used in the developing device 14. When the solid content concentration detection device 273 determines that the solid content concentration DS (DSH) in the developer storage container 272 is lower than the appropriate range, the solid content concentration DS from the toner tank 275 to the developer storage container 272 is determined. Liquid developer LD is supplied, and the solid concentration DS of the liquid developer LD in the container 272 is increased. The toner tank 275 and the developer container 272 are connected by a sixth pipe 86, and the supply of the liquid developer LD is executed by driving an eighth pump P8 provided in the middle of the sixth pipe 86. .

  The varnish tank 279 stores a liquid developer LD having a dissolved resin concentration CR higher than that of the liquid developer LD used in the developing device 14. When the dissolved resin concentration detector 280 determines that the dissolved resin concentration CR (CRH) in the developer container 272 is lower than the appropriate range, the dissolved resin concentration CR is transferred from the varnish tank 279 to the developer container 272. A high liquid developer LD is supplied. As a result, the dissolved resin concentration CR of the liquid developer LD in the developer container 272 is increased. The varnish tank 279 and the developer container 272 are connected by an eleventh pipe 891, and the supply of the liquid developer LD is executed by driving a thirteenth pump P13 provided in the middle of the eleventh pipe 891.

  The stirring device 276 is a member for stirring the liquid developer in the developer container 272. The purpose of this stirring is to allow the toner or carrier liquid introduced into the developer container 272 for density adjustment to be uniformly mixed with the existing liquid developer in the developer container 272. This is to redisperse the toner that may aggregate in the liquid developer LD accommodated in the developer accommodating container 272. The stirring device 276 includes a rotating shaft and a stirring blade attached to the tip of the rotating shaft. A liquid level detecting member 276a is coaxially assembled to the rotating shaft. The liquid level detection member 276a is driven by a motor (not shown), and the amount of liquid developer is detected based on a change in the load of the motor when the liquid level detection member 276a contacts the liquid level of the liquid developer LD. Is done.

  The developer reserve tank 277 is a tank that stores the liquid developer LD to be replenished to the developing device 14. The developer reserve tank 277 is connected to the developer container 272 by a seventh pipe 871. The developer reserve tank 277 is supplied with the liquid developer LD from the developer container 272 by driving a sixth pump P6 provided in the middle of the seventh pipe 871. Further, the developer reserve tank 277 is connected by a carrier tank 274 and a first direct connection pipe 910, and by a toner tank 275 and a second direct connection pipe 920, respectively. Further, the developer reserve tank 277 is connected to the varnish tank 279 through a third direct connection pipe line 930. An eleventh pump P11, a twelfth pump P12, and a fourteenth pump P14 are arranged in the first, second, and third direct connection pipes 910, 920, and 930, respectively, and carrier, toner, and dissolved resin are directly supplied from each tank. The developer can be supplied to the developer reserve tank 277. The carrier, toner, and dissolved resin supply systems from the first, second, and third direct connection pipes 910, 920, and 930 are known at the start of use of the color printer 1 in which no recovered liquid developer has been generated. This is utilized when the liquid developer LD is promptly generated according to the blending ratio.

  The supply nozzle 278 supplies the liquid developer LD stored in the developer reserve tank 277 to the developing device 14 (developing container 140). The supply nozzle 278 and the developer reserve tank 277 are connected by an eighth pipe 872. The supply of the liquid developer LD is executed by driving a seventh pump P7 attached to the eighth pipe 872.

  Further, the liquid developer circulation device LY includes a direct connection conduit 910 extending from the carrier tank 274 to the developer reserve tank 277 and a direct connection conduit 920 extending from the toner tank 275 to the developer reserve tank 277. These direct connection pipes 910 and 920 are used to supply a predetermined amount of carrier and toner to the developer reserve tank 277 before the liquid developer LD is circulated. This makes it possible to start the development process quickly.

  Although not shown, the residual developer tank 271, the carrier tank 274, the toner tank 275, the developer reserve tank 277, and the varnish tank 279 are provided at appropriate positions for detecting the liquid level in these tanks. A liquid level detection device is provided.

  The liquid developer separating device 28 separates the toner from the residual developer collected by the cleaning device 26 and the carrier liquid C in which the resin material R is dissolved, and separately extracts the toner and the carrier liquid C. The cleaning device 26 and the liquid developer separating device 28 are connected by a ninth pipe 881. A ninth pump P9 is attached to the ninth pipe 881. The residual developer in the cleaning device 26 is sent to the liquid developer separating device 28 by driving the ninth pump P9. Further, the liquid developer separating device 28 and the carrier tank 274 are connected by a tenth pipe 882. A tenth pump P10 is attached to the tenth pipe 882. The carrier liquid C extracted by the liquid developer separating device 28 is sent to the carrier tank 274 by driving the tenth pump P10.

  The control unit 550 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores each control program, and a RAM (Random Access Memory) that temporarily stores data such as arithmetic processing and control processing. Etc. The controller 550 controls driving of the first to eleventh pumps P1 to P14, driving of a motor that operates the liquid level detection member 276a, and the like.

  Next, the operation of the color printer 1 will be described. Upon receiving an image formation instruction from a personal computer (not shown) connected to the color printer 1, the color printer 1 converts toner images of each color corresponding to the image data received with the creation instruction into image forming units FY, FM, FC, It is formed using FB. Specifically, an electrostatic latent image based on image data is formed on the photosensitive drum 10, and toner is supplied to the electrostatic latent image from the developing device 14. The images formed by the image forming units FY, FM, FC, and FB in this way are transferred to the intermediate transfer belt 21 and are superimposed on the intermediate transfer belt 21 to form a color toner image.

  In synchronization with the formation of the color toner image, the paper stored in the paper storage unit 3 is taken out from the paper storage unit 3 one by one by a paper feeding device (not shown), and is transported along the paper transport unit 7. . Then, the sheet is fed into the secondary transfer unit 4, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet at the secondary transfer unit 4.

  The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 5 and the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged outside the color printer 1 by the discharge unit 6. The toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning unit 22 of the intermediate transfer belt 21.

  The liquid developer LD remaining on the developing roller 141 without being supplied to the photosensitive drum 10 during the image forming operation is scraped off by the developing cleaning blade 145 and is collected in the residual developer tank 271 through the first pipe 81. The Further, the liquid developer LD recovered in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 is also recovered in the residual developer tank 271 through the second pipe 82. Further, the carrier liquid extracted by the liquid developer separating device 28 from the residual developer recovered by the cleaning device 26 is recovered to the carrier tank 274. In order to execute such liquid circulation, the first, fifth, ninth, and tenth pumps P1, P5, P9, and P10 are driven and controlled by the control unit 550.

  When the liquid developer amount in the developer container 272 is exhausted, the control unit 550 drives the second pump P2. The controller 550 causes the residual developer tank 271 to supply the residual developer to the developer storage container 272. When the developer container 272 is filled with the residual developer, the solution concentration detector 280 detects the solid content concentration DS (DSH) (toner concentration) of the liquid developer LD. In accordance with the detection result, the control unit 550 drives the third pump P3 or the eighth pump P8 to supply a necessary amount of carrier liquid or high-concentration liquid developer to the developer container 272. Thereafter, the solid concentration DS of the liquid developer LD is detected again by the solution concentration detector 280. If the solid content concentration DS is within an appropriate range, the liquid developer LD is supplied to the developer reserve tank 277 as necessary. Similarly, after the dissolved resin concentration CR (CRH) of the liquid developer LD in the developer container 272 is measured by the solution concentration detector 280, a necessary amount of the resin component R is obtained by the controller 550. Adjusted.

  Inside the liquid developer separating device 28, the carrier liquid and the toner particles are separated. That is, the collected liquid developer is introduced into the liquid tank 510 through the ninth pipe 881. The carrier liquid separated by the carrier liquid recovery roller 540 is sent to the carrier tank 274 through the tenth pipe 882. On the other hand, the toner recovered from the toner recovery roller 530 is guided to a waste tank. According to the color printer 1 provided with such a liquid developer separation device 28, the separation speed between the toner and the carrier liquid can be increased, so that it is possible to cope with high-speed printing processing.

<About liquid developer>
Next, the liquid developer LD used as a measurement target of the solution concentration detection device 280 in the above embodiment will be described. As described above, the liquid developer LD includes the electrically insulating carrier liquid C and the colored particles P dispersed in the carrier liquid C. Further, the liquid developer LD contains a resin material R. When used in the image forming apparatus, the liquid developer LD preferably has a viscosity of 30 to 400 mPa · s at a measurement temperature of 25 ° C. More preferably, the viscosity (measurement temperature 25 ° C.) of the liquid developer is 40 to 300 mPa · s, and more preferably 50 to 250 mPa · s.

<Carrier liquid>
The electrically insulating carrier liquid C that plays the role of a liquid carrier enhances the electrical insulation of the liquid developer LD. As the electrically insulating carrier liquid C, for example, an electrically insulating organic solvent having a volume resistance at 25 ° C. of 1012 Ω · cm or more (in other words, conductivity of 1.0 pS / cm or less) is preferable. Further, in addition to the above physical properties, those capable of dissolving a resin material R described later (a resin material R having a relatively high solubility) are preferably used.

  Further, the viscosity, type, and blending amount of the carrier liquid C are appropriately adjusted and selected so that the overall viscosity (measurement temperature 25 ° C.) of the liquid developer LD is 30 to 400 mPa · s. The viscosity of the liquid developer LD also depends on the combination of the organic solvent used as the carrier liquid C and the resin material R described later. Therefore, the type and blending amount of the organic solvent are appropriately determined according to the desired viscosity of the liquid developer LD and the type of the selected resin material R.

  Examples of such an electrically insulating organic solvent include aliphatic hydrocarbons and vegetable oils that are liquid at room temperature.

  As the aliphatic hydrocarbon, for example, liquid n-paraffinic hydrocarbon, iso-paraffinic hydrocarbon, halogenated aliphatic hydrocarbon, branched aliphatic hydrocarbon or a mixture thereof is preferable. For example, n-hexane, n-heptane, n-octane, nonane, decane, dodecane, hexadecane, heptadecane, cyclohexane, perchloroethylene, and trichloroethane are used as the aliphatic hydrocarbon. From the viewpoint of environmental measures (measures against VOC), non-volatile organic solvents and organic solvents with relatively low volatility (for example, those having a boiling point of 200 ° C. or higher) are preferable. Liquid paraffin containing a relatively large amount of hydrogen is preferably used.

  In the above embodiment, as long as the resin material R is dissolved in the carrier liquid C, only the carrier liquid C having a relatively high solubility of the resin material R (good solvent for the resin material R) may be used, or A resin material R having a relatively low solubility (a poor solvent for the resin material R) may be mixed and used.

  The content of the oils in the carrier liquid C depends on the type and content of the resin material R contained in the liquid developer LD. Examples of suitable oil content include 70 to 95% by mass. If it is less than 70 mass%, it will be difficult to dissolve the resin material R well in the carrier liquid C.

  In the embodiment described above, the conductivity of the liquid developer LD is preferably 200 pS / cm or less, for example. The carrier liquid C is an insulating solution by itself, but the liquid developer LD has a predetermined electrical conductivity by dispersing pigments and dispersants that are colored particles. Therefore, liquid development can be achieved by mixing aliphatic hydrocarbons having high electrical resistance with a solution obtained by dissolving resin material R in oils such as tall oil fatty acid (hereinafter referred to as “resin solution”). It is preferable that the electrical conductivity of the agent LD is adjusted to 200 pS / cm or less, for example.

<Colored particles>
In the above embodiment, the pigment itself is used for the colored particles P as the toner. The colored particles P used in the image forming unit FM described above have a magenta hue. The colored particles P used in the image forming unit FC described above have a cyan hue. The colored particles P used in the above-described image forming unit FY have a yellow hue. The colored particles P used in the above-described image forming unit FB have a black hue.

  As a pigment in said embodiment, a conventionally well-known organic pigment and an inorganic pigment are used, for example, without specifically limiting.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. . Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include C.I. I. Pigment Blue 15: 3, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated product, first sky blue, and indanthrene blue BC. Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  The content of the pigment in the liquid developer LD is preferably 1 to 30% by mass. More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more. Moreover, More preferably, it is 20 mass% or less, More preferably, it is 10 mass% or less.

  The average particle diameter of the pigment in the liquid developer LD, that is, the volume-based median diameter (D50) is preferably 0.1 to 1.0 μm. A pigment having an average particle size of less than 0.1 μm causes, for example, a reduction in image density. A pigment having an average particle diameter exceeding 1.0 μm causes, for example, a decrease in fixability. Here, the volume-based median diameter (D50) is generally that the cumulative curve is 50% when the cumulative curve is obtained with the total volume of a group of particles whose particle size distribution is required as 100%. The particle diameter of

<Polymer compound (resin material)>
The resin material R contained in the liquid developer LD according to the above embodiment is an organic polymer compound. As the organic polymer compound having solubility in the carrier liquid C, a material capable of increasing the viscosity of the liquid developer and suppressing the occurrence of bleeding in image formation is selected. Examples of the organic polymer compound include cyclic olefin copolymer, styrene elastomer, cellulose ether, and polyvinyl butyral. Preferably, a styrene elastomer is used as the organic polymer compound. As the resin material R, a single type of organic polymer compound may be used, or a plurality of types of organic polymer compounds may be used.

  In the liquid developer LD according to the above embodiment, the organic polymer compound is dissolved in the carrier liquid C. The organic polymer compound dissolved in the carrier liquid C may be in a gel state. Depending on the type and molecular weight of the organic polymer compound, a gel-like organic polymer compound entangled with each other in the carrier liquid C can be obtained. Gel-like organic polymer compounds have relatively low fluidity. For example, when the concentration of the organic polymer compound is high, when the affinity between the organic polymer compound and the carrier liquid C is low, or when the temperature is low, a gel-like organic polymer compound is easily obtained. On the other hand, the organic polymer compound with little entanglement in the carrier liquid C becomes a solution having relatively high fluidity.

  The content of the organic polymer compound in the liquid developer LD is appropriately determined according to the type of the organic polymer compound. The content of the organic polymer compound is preferably 1 to 10% by mass, for example.

  If the content of the organic polymer compound is less than 1% by mass, sufficient viscosity in the liquid developer LD cannot be obtained, and there is a possibility that the occurrence of bleeding in image formation cannot be sufficiently suppressed. On the other hand, when the content of the organic polymer compound exceeds 10% by mass, the amount of the coating with the organic polymer compound remaining on the surface of the sheet S is excessively increased, and the drying property of the coating is excessively lowered. As a result, the adhesiveness (tackiness) of the film may be excessively increased, and the scratch resistance of the image may be excessively decreased.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, For example, the following modified embodiment can be taken.

  (1) In the above embodiment, in the dissolved resin concentration detection device 280A, the bottom surface portion 651 of the flat housing 65 has been described as being disposed horizontally. However, the present invention is not limited to this. For example, the bottom surface portion 651 may be a surface slightly inclined with respect to a horizontal plane at a predetermined angle in advance. In this case, even if bubbles are generated in the liquid developer LD, the bubbles do not stay at the bottom 651 of the housing 65 and escape along the slope of the bottom 651. Therefore, the bubbles are prevented from affecting the oscillation of the crystal resonator 611.

  (2) In the above-described embodiment, the bottom surface portion 651 of the housing 65 has been described as the restricting member that covers the top of the QCM sensor 60 and keeps the immersion depth of the QCM sensor 60 constant. It is not limited. For example, a configuration in which a member different from the housing 65 (bottom surface portion 651) is disposed above the QCM sensor 60 so as to cover the QCM sensor 60 may be employed.

  (3) In the above embodiment, the solid content concentration detection device 280C and the dissolved resin concentration detection device 280A have been described in the form of detecting the concentration of the liquid developer LD in the same concentration detection tank 691, respectively. However, the present invention is not limited to this, and the solid content concentration detection device 280C and the dissolved resin concentration detection device 280A measure the liquid developer LD collected from the developer container 272 via different pipes, respectively. The solid content concentration DS and the dissolved resin concentration CR may be detected.

  (4) Further, in the above embodiment, in step S004 in which the dissolved resin concentration CRH and the solid content concentration DSH are derived, the formula η is used to derive the viscosity η of the liquid developer LD. explained. However, the derivation of the viscosity η of the liquid developer LD is not limited to this step. In advance, calibration curve data D3 that defines the relationship between Δf (= f−f0) and viscosity η is stored in the storage unit 697 in advance, so that the viscosity η of the liquid developer LD is directly obtained from the calibration curve data D3. It may be a mode in which is derived. Even in this case, by obtaining both the specific gravity ρ and the viscosity η of the liquid developer LD, the dissolved resin concentration CRH and the solid content concentration DSH with reduced errors are derived. In any of the embodiments, without calculating the viscosity η as the characteristic value, the dissolved resin concentration CRH and the solid content are determined by the specific gravity ρ of the liquid developer LD and the vibration frequency (output frequency F) that is an intermediate characteristic value. A partial concentration DSH may be derived. In this case, the storage unit 697 previously stores calibration curve data D4 of the dissolved resin concentration CRH and the solid content concentration DSH for the two variables of the output frequency F and the specific gravity ρ.

  (5) In the above embodiment, when the solution concentration detection device 280 is connected to the developer container 272, the fourth concentration is higher than the solution concentration detection device 280 on the fourth pipe 84. Although it demonstrated in the aspect provided with 4 pumps P4, it is not restricted to this. When the distance between the developer container 272 and the solution concentration detection device 280 is large, in order to improve the circulation performance of the liquid developer LD, it is located at a position downstream of the solution concentration detection device 280. A new pump may be arranged. In this case, the fourth pipe 84 is provided with a pump for transporting the liquid developer LD on the upstream and downstream sides of the solution concentration detection device 280, respectively. Therefore, the liquid developer LD is efficiently introduced into the concentration detection tank 691 in the solution concentration detection device 280, and the liquid developer LD is quickly discharged from the concentration detection tank 691.

1 Color printer (image forming device)
280 Solution concentration detection device 280A Dissolved resin concentration detection device (frequency detection means)
280B measurement unit 280C solid content concentration detection device (specific gravity detection means)
32 Weight 33 Load cell 36 Strain gauge 43 First inlet (inlet)
44 Second inlet (inlet)
45 1st discharge port (discharge port)
46 2nd discharge port (discharge port)
60 QCM sensor 61 Sensor electrode 611 Crystal oscillator 612 First electrode portion 613 Second electrode portion 62 Base portion 63a First lead portion 63b Second lead portion 64 Circuit unit 641 Oscillation circuit 65 Housing 651 Bottom portion (regulating member)
66 Shield 691 Concentration detection tank (storage container)
692 Liquid temperature sensor (liquid temperature detection means)
693 Power supply 694 First wiring section 695 Second wiring section 696 Frequency meter 697 Storage section 698 Concentration calculation section (concentration detection means)

Claims (9)

A storage container for storing a liquid developer containing a carrier liquid, solid particles dispersed in the carrier liquid, and a resin component dissolved in the carrier liquid;
A specific gravity detecting means comprising a weight immersed in the liquid developer in the storage container, and detecting the specific gravity of the liquid developer based on buoyancy applied to the weight;
A sensor unit that is immersed in the liquid developer in the storage container and includes a crystal resonator;
An oscillation circuit connected to the sensor unit and oscillating the crystal resonator;
A frequency detection means for detecting a vibration frequency of the crystal resonator;
Based on the specific gravity of the liquid developer detected by the specific gravity detection means and the vibration frequency of the quartz vibrator detected by the frequency detection means, the concentration of the solid particles in the liquid developer, or Concentration detecting means for detecting the concentration of the dissolved resin component in the liquid developer;
A concentration detection apparatus comprising: A first storage unit that stores a first calibration curve indicating the concentration of the solid particles or the dissolved resin component when the vibration frequency of the crystal resonator and the specific gravity of the liquid developer are changed, respectively; ,
The concentration detection unit collates the specific gravity of the liquid developer detected by the specific gravity detection unit and the vibration frequency of the crystal resonator detected by the frequency detection unit with the first calibration curve. The concentration detection apparatus according to claim 1, wherein the concentration of the solid particles or the dissolved resin component is detected. A second storage unit storing a second calibration curve indicating the concentration of the solid particles or the dissolved resin component when the viscosity of the liquid developer and the specific gravity of the liquid developer are changed, respectively;
The density detection means derives the viscosity of the liquid developer based on the vibration frequency of the crystal resonator, the specific gravity of the liquid developer detected by the specific gravity detection means, and the derived liquid development. The concentration detection apparatus according to claim 1, wherein the concentration of the solid particles or the dissolved resin component is detected by comparing the viscosity of the agent with the second calibration curve. The storage container has an inlet for injecting the liquid developer and an outlet for discharging the liquid developer,
4. The liquid developer in the storage container, wherein the weight is immersed above the injection port and below the discharge port and the sensor unit. The concentration detection apparatus according to any one of the above. The control member according to claim 1, further comprising a regulating member that is immersed in the liquid developer in the storage container, covers an upper portion of the sensor unit, and maintains a constant distance in the depth direction from the sensor unit. 5. The concentration detection apparatus according to any one of 1 to 4. A load cell comprising a strain body connected to the weight and a strain gauge installed on the strain body;
The density detection apparatus according to claim 1, wherein the specific gravity detecting unit detects a specific gravity of the liquid developer based on an output from the strain gauge. The housing further includes a housing that houses the oscillation circuit and is immersed in the liquid developer,
The sensor portion is disposed so as to protrude downward from the bottom portion of the housing,
The oscillation circuit is connected to the sensor unit via the bottom,
The concentration detection apparatus according to claim 5, wherein the restriction member is the bottom portion of the housing. A liquid temperature detecting means for detecting a liquid temperature of the liquid developer in the storage container;
8. The density according to claim 1, wherein the frequency detection unit corrects the vibration frequency according to a liquid temperature of the liquid developer detected by the liquid temperature detection unit. Detection device. An image carrier on which a toner image is formed;
Development for storing a liquid developer containing a carrier liquid, solid particles as the toner dispersed in the carrier liquid, and a resin component dissolved in the carrier liquid, and supplying the toner to the image carrier Equipment,
A developer adjusting unit that adjusts the concentrations of the toner and the resin component in the liquid developer;
The concentration detector according to any one of claims 1 to 8, which detects the concentration of the solid particles or the resin component in the liquid developer.
An image forming apparatus comprising:

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