JP5046972B2 - Liquid level detection device and image forming apparatus - Google Patents

Description

  The present invention relates to a liquid level detector and an image forming apparatus.

2. Description of the Related Art Conventionally, a float type device as shown in Patent Document 1 is known as a liquid level detector for detecting the level of a liquid level in a container. In this liquid level detector, a float that floats in the liquid and a guide bar that guides the float are provided, and the float moves up and down along the guide bar according to the liquid level. Yes. The liquid level is detected by detecting the position of the float.
JP 59-126570 A

  However, in the float type liquid level detector as described above, the sensitivity is not good for a highly viscous liquid.

  An object of the present invention is to provide a liquid level detecting device having good sensitivity even for a highly viscous liquid.

  A liquid level detection device according to a first aspect of the invention is a device for detecting the height of a liquid level in a container, and includes a movable member, a drive mechanism, and a liquid detection unit. The movable member has a hole in the surface and is provided so as to be movable in the vertical direction. The drive mechanism moves the movable member so that the hole moves up to a detection position above the predetermined position after the hole has moved down to the predetermined position in the container. The liquid detection unit detects the presence or absence of liquid in the hole at the detection position.

  In this liquid level detection device, the hole of the movable member descends to a predetermined position in the container and then moves to the detection position. At this time, if the liquid detection unit detects that there is liquid in the hole, the liquid is present at the predetermined position. On the contrary, when it is detected by the liquid detection unit that there is no liquid in the hole, no liquid is present at the predetermined position. Thereby, it is possible to detect the liquid level with good sensitivity even for a highly viscous liquid.

  A liquid level detector according to a second aspect of the present invention is the liquid level detector of the first aspect, wherein the drive mechanism repeatedly moves the movable member by changing the height at a predetermined position.

  In this liquid level detector, the lowering of the hole to a predetermined position, the rising to the detection position, and the detection of the presence or absence of liquid in the hole are repeated in order, and the height of the predetermined position is changed. For example, in the order from the top, the first height position, the second height position, and the third height position, the presence of liquid is not detected when the hole is lowered to the first height position and the second height position. Suppose that the presence of the liquid is detected when it is lowered to the third height position. In this case, the liquid level in the container is lower than the second height position and higher than the third height position. Thereby, the height of the liquid level in the container can be detected with higher accuracy.

  A liquid level detection device according to a third aspect of the present invention is the liquid level detection device of the first aspect, wherein a plurality of holes are provided in the vertical direction on the surface of the movable member. And a drive mechanism moves a movable member so that a some hole may pass a detection position in order.

  In this liquid level detection device, the liquid detection unit detects which of the plurality of holes has liquid. For example, assuming that the first hole, the second hole, and the third hole are provided in the movable member in order from the top, the presence of liquid is not detected in the first hole and the second hole, and the liquid is not detected in the third hole. Suppose presence is detected. In this case, the liquid level in the container is lower than the lower limit position where the second hole is lowered and is higher than the lower limit position where the third hole is lowered. Thereby, the height of the liquid level in the container can be detected with higher accuracy. In addition, the number of movements of the movable member can be reduced.

  A liquid level detection apparatus according to a fourth aspect of the present invention is the liquid level detection apparatus according to any one of the first to third aspects, further comprising a liquid removal unit. The liquid removing unit removes the liquid accumulated in the holes.

  In this liquid level detector, the liquid collected in the hole after the liquid level is detected can be removed by the liquid removing unit. Thereby, the detection of the liquid level can be repeated.

  An image forming apparatus according to a fifth aspect includes an image forming unit, a container, and a liquid level detection device. The image forming unit forms an image on the medium using a liquid developer containing toner and carrier liquid. The container stores a liquid developer. The liquid level detection device is a device for detecting the height of the liquid level of the liquid developer in the container, and includes a movable member, a drive mechanism, and a liquid detection unit. The movable member has a hole in the surface and is provided so as to be movable in the vertical direction. The drive mechanism moves the movable member so that the hole rises to a detection position above the predetermined position after the hole is lowered to a predetermined position in the container. The liquid detection unit detects the presence or absence of the liquid developer in the hole at the detection position.

  In this image forming apparatus, the hole of the movable member descends to a predetermined position in the container and then moves to the detection position. At this time, when the liquid detection unit detects that the liquid developer is present in the hole, the liquid developer is present at the predetermined position. On the contrary, when the liquid detection unit detects that there is no liquid developer in the hole, no liquid developer is present at the predetermined position. Thereby, it is possible to detect the liquid level with good sensitivity even for a high-viscosity liquid developer.

  In the present invention, when the liquid detector detects that the liquid developer is present in the hole, the liquid developer is present at the predetermined position. On the contrary, when the liquid detection unit detects that there is no liquid developer in the hole, no liquid developer is present at the predetermined position. Thereby, it is possible to detect the liquid level with good sensitivity even for a high-viscosity liquid developer.

1. 1. Configuration 1.1 Overall Configuration FIG. 1 shows an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is a color printer and includes an image forming unit 2, a sheet storage unit 3, a secondary transfer unit 4, a fixing unit 5, a sheet transport unit 6, and a discharge unit 7. Yes. The image forming unit 2 is of a tandem type that forms a toner image based on image data. The paper storage unit 3 stores paper that is an example of a recording medium. The secondary transfer unit 4 transfers the toner image formed by the image forming unit 2 onto a sheet. The fixing unit 5 fixes the toner image transferred to the paper on the paper. The paper transport unit 6 transports the paper from the paper storage unit 3 to the discharge unit 7. The discharge unit 7 discharges the paper on which fixing has been completed.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22, and a plurality of image forming units FY, FC, FM, and FB.

  The intermediate transfer belt 21 is an electroconductive, endless, ie, loop-shaped belt member. The intermediate transfer belt 21 is driven to circulate clockwise as indicated by an arrow in FIGS. The intermediate transfer belt 21 is wider than the maximum width of paper that can be used in the image forming apparatus 1. Here, the “width” refers to the length in the direction perpendicular to the paper transport direction. Hereinafter, the surface facing the outside in the circulation drive of the intermediate transfer belt 21 is referred to as a front surface, and the other surface is referred to as a back surface. The intermediate transfer belt 21 is stretched around a driving roller 41, a driven roller 23, and a tension roller 24. When the driving roller 41 is rotated by driving a driving motor 85 (not shown), the intermediate transfer belt 21 is driven. When the intermediate transfer belt 21 is driven, the driven roller 23 and the tension roller 24 are driven to rotate with respect to the intermediate transfer belt 21. The tension roller 24 is a member that applies an appropriate tension to the intermediate transfer belt 21 so that the intermediate transfer belt 21 does not loosen.

  The cleaning unit 22 cleans the intermediate transfer belt 21. The cleaning unit 22 includes a cleaning roller 22a and a cleaning blade 22b.

  Four image forming units FY, FM, FC, and FB are arranged near the intermediate transfer belt 21 and arranged between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. The image forming units FY, FM, FC, and FB correspond to yellow (Y), magenta (M), cyan (C), and black (Bk) colors, respectively. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image.

  As shown in FIG. 2, the image forming units FY, FM, FC, and FB include a photosensitive drum 10, a charger 11, an exposure device 12, a developing device 14, a primary transfer roller 20, and a cleaning device 26. And a static elimination device 13 and a carrier liquid removal roller 30. Further, among 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.

  Corresponding to the image forming units FY, FM, FC, and FB, liquid developer circulating devices LY, LM, LC, LB, toner tanks CB, CY, CC, CM, and a carrier tank CCA are provided. The liquid developer of each color is supplied and collected. The liquid developer circulating devices LY, LM, LC, and LB will be described in detail later.

  The photosensitive drum 10 is a cylindrical member, and can carry a toner image including toner charged on its surface (charged positively in this embodiment). The photosensitive drum 10 is a member that can rotate counterclockwise as indicated by a broken-line arrow in FIG.

  The charger 11 is a device that can uniformly charge the surface of the photosensitive drum 10.

  The exposure device 12 has a light source such as an LED and irradiates light onto the surface of the uniformly charged photoreceptor drum 10 in accordance with 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 containing 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.

  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 development roller charger 147.

  The developing container 140 is a container that receives supply of a liquid developer including toner particles and a liquid carrier. As will be described later, the liquid developer 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 has been performed in advance. The liquid developer is supplied toward a portion of the support roller 143 near the nip portion between the supply roller 142 and the support roller 143, and the surplus portion falls below the support roller 143, and the bottom of the developing container 140 Is stored. The stored liquid developer is collected by the liquid developer circulating devices LY, LM, LC, and LB through the flow path R2.

  The support roller 143 is disposed substantially at the center of the developing container 140 and abuts against the supply roller 142 to form a nip portion in a manner of supporting from below. The supply roller 142 is disposed obliquely above the support roller 143, and is displaced from the position directly above the support roller 143 in a direction away from the supply nozzle 278. A groove for holding the liquid developer is provided on the peripheral surface of the supply roller 142. 2, the support roller 143 rotates counterclockwise and the supply roller 142 rotates clockwise.

  The liquid developer supplied from the supply nozzle 278 is temporarily retained on the upstream side in the rotation direction of the nip portion, and is moved upward while being held in the groove of the supply roller 142 as the rollers 142 and 143 rotate. Carried to. The supply roller blade 144 is in pressure contact with the peripheral surface of the supply roller 142 and regulates the amount of liquid developer held by the supply roller 142 to be a predetermined amount. Excess liquid developer 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. That is, at the nip portion where the developing roller 141 and the supply roller 142 abut, the surface of the developing roller 141 moves in the opposite direction to the surface of the supply roller 142. As a result, the liquid developer held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. Here, 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 moves the toner in the liquid developer layer carried on the developing roller 141 to the surface side of the developing roller 141 by applying an electric field having the same polarity as the charging polarity of the toner, thereby improving the developing efficiency. It fulfills the action of The developing roller charger 147 faces the circumferential surface of the developing roller 141 on the downstream side in the rotation direction of the developing roller 141 in contact with the supply roller 142 and on the upstream side in contact with the photosensitive drum 10. It is provided as follows.

  The developing roller 141 is in contact with the photosensitive drum 10, and a toner image corresponding to the image data instructed to form is determined 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. Is formed on the surface of the photosensitive drum 10 (development operation).

  The developing cleaning blade 145 is disposed so as to contact the developing roller 141 on the downstream side in the rotation direction of the contact portion of the developing roller 141 with the photosensitive drum 10 and on the upstream side of the contact portion with the supply roller 142. The liquid developer on the surface of the developing roller 141 that has completed the developing operation on the photosensitive drum 10 is removed.

  The developer recovery device 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer to the flow path R1 of the liquid developer circulation devices LY, LM, LC, and LB. The liquid developer flows down along the surface of the development cleaning blade 145. However, since the viscosity of the liquid developer is high, the developer recovery device 146 is provided with delivery rollers 34 and 35 for assisting the delivery of the liquid developer. ing.

  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). That is, 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 cleaning device 26 is a device for cleaning the liquid developer remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21, and includes a cleaning blade 262 and a residual developer conveying screw 261. .

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

  The residual developer conveying screw 261 is disposed in the cleaning device 26. The residual developer transport screw 261 is scraped off by the cleaning blade 262 and transports the liquid developer stored in the cleaning device 26 to the outside of the cleaning device 26.

  The static eliminator 13 has a light source for static elimination, and neutralizes the surface of the photosensitive drum 10 with light from the light source. The neutralization device 13 performs neutralization after the liquid developer is removed by the cleaning blade 262 in preparation for the next image formation.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate around a rotation axis parallel to the rotation axis of the photosensitive drum 10. The carrier liquid removal roller 30 rotates in the same direction as 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. The member to be removed.

  Returning to FIG. 1, the paper storage unit 3 is a part for storing a paper on which a toner image is fixed, and is disposed in the lower part of the image forming apparatus 1. The paper storage unit 3 includes a paper supply cassette 31 that stores paper, a paper supply roller 32, and a paper separation roller pair 33.

  The secondary transfer unit 4 is a part that transfers the toner image formed on the intermediate transfer belt 21 to a sheet, and is disposed opposite to the driving roller 41 that drives the intermediate transfer belt 21 and the driving roller 41. And a secondary transfer roller 42.

  The fixing unit 5 is a part for fixing the toner image on the sheet, and 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 to face the heating roller 51.

  The paper transport unit 6 includes a plurality of transport roller pairs 61 and registration roller pairs 62, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4 and the discharge unit 6. In FIG. 1, only one pair of transport rollers 61 is shown, but the other transport roller pairs are arranged side by side in a direction perpendicular to the paper surface in FIG.

  The discharge unit 7 is a portion from which the paper on which the toner image has been transferred and fixed by the secondary transfer unit 4 is discharged. The discharge unit 7 includes a plurality of discharge roller pairs 71 and a discharge tray 72 provided on the upper surface of the image forming apparatus 1. Have. In FIG. 1, only the pair of discharge rollers 71 is shown, but the other discharge roller pairs are arranged side by side in a direction perpendicular to the paper surface in FIG.

1.2 Configuration of Liquid Developer Circulation Device LY, LM, LC, LB FIG. 3 shows an outline of the entire liquid developer circulation device LY. The liquid developer circulation device LY is a device for circulating and reusing the liquid developer. Although the structure of the liquid developer circulating device LY will be described here, the other liquid developer circulating devices LM, LC, and LB have the same configuration. Examples of the liquid developer circulated by the liquid developer circulation device LY include a developer (a mixture of toner and carrier liquid) scraped from the surface of the developing roller 141 by the developing cleaning blade 145, and a developing roller from the supply roller 142. There is a developer that has not been supplied to 141, and a developer that has been scraped off from the photosensitive drum 10 by the cleaning device 26.

  The liquid developer circulating device LY includes a residual developer tank 271, a developer container 272, a liquid level detector 80 (see FIG. 4), a solid content detector 273, a carrier tank CCA, and toner. A tank CY, a developer reserve tank 277, a supply nozzle 278, a residual developer recovery container 279, a liquid developer separation and extraction device 28, and a plurality of pumps P1 to P10 are provided.

  The residual developer tank 271 is connected to the developing device 14 via a flow path R1. The residual developer tank 271 is a tank that can store the developer scraped from the surface of the developing roller 141 by the developing cleaning blade 145. Further, one pump P1 is attached between the developing device 14 and the residual developer tank 271. The pump P <b> 1 moves the residual developer scraped from the surface of the developing roller 141 to the residual developer tank 271. The residual developer tank 271 is connected to the bottom of the developing device 14 via a flow path R2, and a pump P5 is connected to the flow path R2. The pump P5 sends the developer from the developer container 140 to the residual developer tank 271.

  The developer storage container 272 is connected to the residual developer tank 271 and is a part for preparing the developer to be replenished to the developing device 14 (toner density adjustment). The developer container 272 is connected to the residual developer tank 271 via a flow path R3, and a pump P2 is connected to the flow path R3.

  The liquid level detector 80 is a device for detecting the liquid level of the liquid developer in the developer container 272. Thereby, it is detected whether or not the liquid level of the liquid developer in the developer container 272 has reached the specified position. The liquid level detector 80 will be described in detail later.

  The solid content concentration detection device 273 is a device for detecting the toner concentration of the liquid developer in the developer storage container 272, and is connected to an annular flow path R4 connected to the developer storage container 272. ing. A pump P4 is attached to the upstream side of the solid concentration detector 273 in the annular flow path R4.

  The carrier tank CCA stores a carrier liquid for reducing the toner concentration in the developer storage container 272. The carrier tank CCA is connected to the developer container 272 by a flow path R5 to which a pump P3 is attached. The carrier tank CCA is used in common for each color, and a single common pipe (not shown) is connected to the carrier tank CCA. A flow path R5, which is a branch pipe for each color, extends from the common pipe to the developer storage container 272 for each color.

  The toner tank CY contains a liquid developer having a high toner concentration for increasing the toner concentration in the developer container 272. The toner concentration of the liquid developer in the toner tank CY is used in the developing device 14. It is higher than the toner concentration of the liquid developer. The toner tank CY is connected to the developer container 272 by a flow path R6 to which a pump P8 is attached.

  The developer reserve tank 277 stores a liquid developer to be replenished to the developing device 14 and is connected to the developer storage container 272 via a flow path R7 to which a pump P6 is attached. Further, the supply nozzle 278 is connected via a flow path R8 to which a pump P7 is attached.

  The supply nozzle 278 is a device for supplying the developer to the developing device 14.

  The residual developer collection container 279 is a container for temporarily storing the developer removed from the photosensitive drum 10 by the cleaning device 26.

  The liquid developer separating and extracting device 28 is a device for separating the liquid developer into toner and carrier liquid and extracting the carrier liquid and toner separately. The liquid developer separating and extracting device 28 is disposed in the middle of the flow paths R9 and R10 connecting the residual developer collecting container 279 and the carrier tank CCA. A pump P9 is provided in the flow path R9, and the liquid developer in the residual developer collection container 279 is sent to the liquid developer separation and extraction device 28. The liquid developer separating and extracting device 28 separates the liquid developer stored in the residual developer collecting container 279 into toner and carrier liquid. The flow path R10 is provided with a pump P10 and sends the separated carrier liquid to the carrier tank CCA.

1.3 Configuration of Liquid Level Detector 80 The liquid level detector 80 detects the liquid level in the developer container 272. Thereby, it is detected whether or not the liquid level of the liquid developer in the developer container 272 has reached the specified position. As shown in FIG. 4, the liquid level detection device 80 includes a movable member 81, a drive mechanism 82 (see FIG. 5), a liquid detection unit 83, and a liquid removal unit 84.

  The movable member 81 is a bar-like member that is long in the vertical direction, and is provided so as to be movable in the vertical direction. A hole 90 is provided in the surface near the lower end of the movable member 81, and the hole 90 penetrates the movable member 81 in the horizontal direction. The diameter of the hole 90 is set to a size that allows the liquid developer to enter and be held in the hole 90 when the hole 90 is immersed in the liquid developer, and is about 2 mm, for example. The diameter of the hole 90 can be appropriately set according to the viscosity of the liquid developer.

  The drive mechanism 82 moves the movable member 81 so that the hole 90 moves down to a predetermined position in the developer container 272 and then moves up to a detection position above the predetermined position. As shown in FIG. 5, the drive mechanism 82 includes a motor 85, a pinion gear 86, and a rack gear 87. The motor 85 rotationally drives the pinion gear 86. The rack gear 87 is fixedly provided on the movable member 81 and moves linearly in the vertical direction as the pinion gear 86 rotates. Thereby, the movable member 81 moves up and down.

  The liquid detector 83 shown in FIG. 4 detects the presence or absence of liquid in the hole 90 at the detection position. The liquid detection unit 83 includes a light projecting device 88 and a light receiving device 89. The light projecting device 88 and the light receiving device 89 are arranged to face each other at a distance in the horizontal direction, and the light receiving device 89 receives light emitted from the light projecting device 88. The position sandwiched between the light receiving device 89 and the light projecting device 88 is the detection position described above. The transmittance of light passing through the hole differs depending on whether or not the liquid developer is present in the hole 90. For this reason, the liquid detection unit 83 can detect the presence or absence of liquid in the hole 90 by detecting the transmittance of light passing through the hole 90 located at the detection position.

  The liquid removal unit 84 is disposed below the liquid detection unit 83 and can blow out air toward the hole 90. Thereby, the liquid removing unit 84 can remove the liquid accumulated in the hole 90.

2. 2. Operation 2.1 Image Forming Operation First, the image forming operation of the image forming apparatus 1 will be described. The image forming apparatus 1 that has received an image forming instruction from a personal computer (not shown) connected to the image forming apparatus 1 outputs toner images of each color corresponding to the image data that has received the generating instruction to the image forming units FY, FM, It is formed using FC and 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 toner images formed in the respective image forming units 2 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 synchronism with the formation of the color toner image, the paper stored in the paper feed cassette 31 of the paper storage unit 3 is taken out from the paper feed cassette 31 by the paper feed roller 32, and one by one by the separation roller pair 33. It is sent to the transport unit 6. The paper is sent to the registration roller pair 62 by the transport roller pair 61 of the paper transport unit 6, the paper transport posture is corrected, and the paper is temporarily stopped. Then, the toner image is fed from the registration roller pair 62 to the secondary transfer unit 4 at the same timing as the primary transfer to the intermediate transfer belt 21, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet by the secondary transfer unit 4. Is done. The sheet on which the color toner image is transferred is sent to the fixing unit 5 and the color toner image is fixed on the sheet by the action of heat and pressure.

  The sheet on which the color toner image is fixed is further sent to the discharge unit 7 and discharged by a discharge roller pair 71 to a discharge tray 72 provided outside the image forming apparatus 1.

  The residual liquid developer remaining on the intermediate transfer belt 21 after the secondary transfer is removed by the cleaning roller 22a and the cleaning blade 22b of the cleaning unit 22 of the intermediate transfer belt 21.

2.2 Liquid Developer Circulation Operation Next, the operation of supplying the liquid developer to the developing device 14, that is, the liquid developer circulation operation will be described.

  The liquid developer 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 collected in the residual developer tank 271 through the flow path R1. Further, the liquid developer received in the developing container 140 is also sent to the residual developer tank 271 through the flow path R2 by the pump P5. When the liquid developer in the developer container 272 runs out, the liquid developer is supplied from the residual developer tank 271 to the developer container 272 by the pump P2 via the flow path R3. At this time, the liquid developer remaining on the photosensitive drum 10 without being developed is scraped off by the cleaning blade 262 and stored in the residual developer collection container 279.

  The liquid developer recovered in the residual developer recovery container 279 is conveyed to the liquid developer separation / extraction device 28 via the flow path R9 by the pump P9 every predetermined amount. In the liquid developer separation / extraction device 28, the toner and the carrier liquid are separated and extracted. The carrier liquid extracted in the liquid developer separating and extracting device 28 is sent to the carrier tank CCA by the pump P10 through the flow path R10.

  On the other hand, the toner concentration of the liquid developer in the developer container 272 is detected by the solid concentration detector 273, and the concentration of the liquid developer in the developer container 272 is adjusted. Here, when the toner concentration is high, the carrier liquid is supplied from the carrier tank CCA to the developer container 272 via the flow path R5 by the pump P3. When the toner concentration is low, a liquid developer having a high toner concentration is supplied from the toner tank CY to the developer container 272 via the flow path R6 by the pump P8.

  Then, the liquid developer whose density is adjusted from the developer container 272 to the developer reserve tank 277 as needed is supplied through the flow path R7 by the pump P6, and the liquid developer stored in the developer reserve tank 277 is supplied. The agent is sent to the supply nozzle 278 via the flow path R8 by the pump P7, and is supplied to the developing device 14 from the supply nozzle 278.

2.3 Liquid Level Height Detection Operation Next, the liquid level height detection operation in the developer container 272 by the liquid level detection device 80 will be described.

  First, as shown in FIG. 6A, the movable member 81 stands by at a standby position above the upper opening of the developer container 272.

  Next, the movable member 81 moves downward until the hole 90 reaches a predetermined position (hereinafter referred to as “first height position”) as shown in FIG.

  When the hole 90 reaches the first height position, the rotation direction of the motor 85 of the drive mechanism 82 is switched to the reverse direction, so that the movable member 81 has the hole 90 at the detection position as shown in FIG. Move up until you reach. And the liquid detection part 83 detects the presence or absence of the liquid in the hole 90 in the state in which the hole 90 is located in a detection position. At this time, when the presence of the liquid is detected, it can be determined that the liquid level of the liquid developer is equal to or higher than the first height position. Conversely, if it is detected that there is no liquid, it can be determined that the liquid level of the liquid developer is lower than the first height position.

  Thus, the liquid level detector 80 can detect the liquid level with a simple configuration. Further, the liquid level detector 80 can detect the liquid level with high sensitivity even for a liquid that is highly viscous and colored like a liquid developer.

  When the presence of the liquid developer is detected, the drive mechanism 82 moves the movable member 81 so that the hole 90 faces the liquid removing unit 84 as shown in FIG. Then, as indicated by an arrow in FIG. 6D, the liquid developer accumulated in the hole 90 is removed from the hole 90 by blowing air from the liquid removing unit 84. Thereby, the detection of the liquid level can be repeated.

  In order to detect the liquid level more accurately, the operation of detecting the liquid developer by changing the height at which the hole 90 is lowered to a height other than the first height position may be repeated. .

  For example, if no liquid is detected even when the hole 90 is lowered to the first height position, the movable member 81 is moved until the hole 90 reaches the second height position below the first height position. Lower. Then, the movable member 81 is raised so that the hole 90 reaches the detection position, and the presence or absence of liquid in the hole 90 is detected again. Here, when it is detected that there is no liquid, the movable member 81 is lowered again until the hole 90 reaches a third height position below the second height position. The movable member 81 is raised until the hole 90 reaches the detection position, and the presence or absence of liquid in the hole 90 is detected again. In this way, the detection operation is repeated by changing the height at which the hole 90 is lowered until the presence of the liquid developer is detected. Thereby, the liquid level in the developer container 272 can be detected with higher accuracy.

  As described above, the lower limit position for moving the hole 90 may be increased instead of being gradually lowered, and the detection operation may be repeated until the presence of liquid is no longer detected.

  Further, in order to detect the presence or absence of the liquid developer at a desired height, the above-described detection operation may be performed by fixing the lower limit position for lowering the hole 90 to the desired height.

3. Other Embodiments As shown in FIG. 7, a movable member 81 in which a plurality of holes 91-95 are provided on the surface in the vertical direction may be used. In this case, the drive mechanism 82 lowers the movable member 81 into the developer container 272, and then raises the movable member 81 so that the predetermined plurality of holes 91-95 sequentially pass through the detection positions. Then, the liquid detector 83 detects which of the plurality of holes 91-95 has the liquid. For example, as shown in FIG. 8, it is assumed that the first to fifth holes 91-95 are provided in the movable member 81 in order from the top. It is assumed that no liquid is detected in the first hole 91 to the third hole 93 and the presence of the liquid developer is detected in the fourth hole 94 and the fifth hole 95. In this case, it is detected that the liquid level is lower than the position of the third hole 93 and higher than the position of the fourth hole 94 when the movable member 81 is moved to the lower limit position (see FIG. 8B). it can.

  In the above embodiment, the drive mechanism 82 is a rack gear and pinion gear type mechanism, but may be another mechanism as long as the movable member 81 can be reciprocated up and down.

  In the above embodiment, the holes 90-95 penetrate the movable member 81. However, the holes 90-95 are not limited to the through holes as long as the liquid developer can be held when immersed in the liquid developer. When a hole that does not penetrate through the movable member 81 is provided, a reflecting member is provided at the bottom of the hole, and the light receiving device 89 receives light reflected at the bottom of the hole.

  In the above embodiment, the liquid removing unit 84 removes the liquid from the holes 90-95 by blowing out air, but other configurations may be applied as long as the liquid can be removed from the holes 90-95. Good.

  In the above-described embodiment, the liquid level detector 80 is used for detecting the liquid level of the liquid developer in the developer container 272. However, for detecting the liquid level of the liquid developer in other containers. May be used. Further, the liquid level is not limited to the liquid developer, and may be used for detecting the liquid level of other liquids.

  The present invention can detect the liquid level in a container with high sensitivity even for a highly viscous liquid, and is useful as a liquid level detector and an image forming apparatus.

1 is a diagram illustrating a configuration of an image forming apparatus. The enlarged view of an image forming unit. The figure which shows the structure of a liquid developer circulation device. The figure which shows the structure of a liquid level detection apparatus. The figure which shows the structure of a drive mechanism and a movable member. The figure which shows the detection operation of a liquid level height. The figure which shows the movable member of the liquid level detection apparatus which concerns on other embodiment. The figure which shows the detection operation of the liquid level height in other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 80 Liquid level height detection apparatus 81 Movable member 82 Drive mechanism 83 Liquid detection part 84 Liquid removal part 272 Developer container (container)

Claims (4)

A device for detecting the height of the liquid level in the container,
A hole is provided on the surface, and a movable member provided to be movable in the vertical direction;
A drive mechanism that moves the movable member so that the hole is raised to a detection position above the predetermined position after the hole is lowered to a predetermined position in the container;
A liquid detector for detecting the presence or absence of liquid in the hole at the detection position;
A liquid removing section for removing the liquid accumulated in the holes;
Equipped with a,
The hole penetrates the movable member in the horizontal direction and extends only in the horizontal direction,
The liquid removing unit blows out air toward the hole,
Liquid level detector. The drive mechanism changes the height of the predetermined position and repeatedly moves the movable member;
The liquid level detector according to claim 1. The surface of the movable member is provided with a plurality of holes arranged in the vertical direction,
The drive mechanism moves the movable member so that the plurality of holes sequentially pass through the detection positions.
The liquid level detector according to claim 1. An image forming unit that forms an image on a medium using a liquid developer containing toner and a carrier liquid;
A container for storing the liquid developer;
An apparatus for detecting the height of the liquid developer level in the container, wherein a hole is provided on the surface and the movable member is provided so as to be movable in the vertical direction, and the hole is provided in the container. a drive mechanism for moving said movable member to said raised from the predetermined position to the upper detection position after lowered to a predetermined position, and the liquid detecting portion for detecting the presence or absence of the liquid developer in the hole at the detection position, wherein A liquid removal unit that removes the liquid accumulated in the holes, and a liquid level detector ,
The hole penetrates the movable member in the horizontal direction and extends only in the horizontal direction,
The liquid removing unit blows out air toward the hole,
Image forming apparatus.

Images