Liquid tank and image forming apparatus

Abstract

To provide an image forming device that can accurately sense residual liquid quantities in a container main body, using an electrostatic capacitance sensor.SOLUTION: An image forming device 1 comprises: an enclosure 3; a container main body 31 that stores liquid and is placed on a grounding surface G which is a portion of the enclosure; and an electrostatic capacitance sensor 35 that senses change in liquid quantities in the container main body 31, by sensing change in electrostatic capacitance between a side of the container main body 31 and the grounding surface. A ceiling surface that is a portion of the enclosure 3 is provided above the container main body 31. The ceiling surface is conductively connected to the grounding surface, and a distance D2 between the ceiling surface and the electrostatic capacitance sensor 35 is longer than a distance D1 between the grounding surface G and the electrostatic capacitance sensor 35.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid tank that contains a liquid such as a cleaning liquid, and an image forming apparatus. [Background technology]

[0002] An inkjet image forming apparatus is provided with, for example, a liquid tank that contains cleaning liquid for cleaning the recording head of a head unit. As described in Patent Document 1, such a liquid tank includes a supply liquid tank that contains the liquid, and a detection sensor that detects the remaining amount of liquid in the supply liquid tank.

[0003] The supply liquid tank is provided with an outlet through which the liquid is supplied, and the outlet is positioned below the liquid level when the supply liquid tank is determined to be empty, to prevent air from entering through the outlet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-202729 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a liquid tank containing a cleaning liquid as described above, when the liquid tank is determined to be empty, the entire liquid tank is generally discarded to prevent the intrusion of foreign matter. Therefore, it is preferable that the amount of liquid discarded, i.e., the amount of liquid remaining, be small. However, as described above, the liquid supply tank described in Patent Document 1 has an outlet formed below the liquid level when empty. This results in a problem in that a large amount of liquid remains when the tank is empty, making it difficult to use the liquid efficiently. Generally, a capacitance sensor is often used as the detection sensor.

[0006] In consideration of the above circumstances, the present invention aims to provide an image forming apparatus that can accurately detect the amount of liquid remaining in the container body using a capacitance sensor, and a liquid tank that can reduce the amount remaining when empty. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the image forming apparatus of the present invention comprises a housing, a container body that contains liquid and is placed on a ground surface that is part of the housing, and a capacitance sensor that detects changes in the amount of liquid in the container body by detecting changes in capacitance between the side of the container body and the ground surface, and is characterized in that above the container body there is a ceiling surface that is part of the housing, the ceiling surface is conductive to the ground surface, and the distance between the ceiling surface and the capacitance sensor is longer than the distance between the ground surface and the capacitance sensor, or the ceiling surface and the ground surface are electrically insulated, or the ceiling surface is open.

[0008] In the image forming apparatus of the present invention, the container body may be provided with a supply port formed below the liquid level when empty, at which point the container body is determined to be empty based on the detection results of the capacitance sensor, and the container body may be characterized in that a blank portion that does not contain the liquid is formed below the liquid level when empty.

[0009] In the image forming apparatus of the present invention, the blank portion may be hollow.

[0010] In the image forming apparatus of the present invention, the container body may have a main body portion and legs that are placed on the ground surface, and the blank portion may be formed on the legs.

[0011] In the image forming apparatus of the present invention, the capacitance sensor may be attached to the main body, and the supply port may be formed in the leg.

[0012] In the image forming apparatus of the present invention, the blank portion may penetrate through the leg portion.

[0013] In the image forming apparatus of the present invention, the lowest height of the detection surface of the capacitance sensor may be higher than the height of the liquid surface when the liquid is contained until the supply port is blocked.

[0014] In the image forming apparatus of the present invention, the liquid may be a cleaning liquid for cleaning a recording head of the image forming apparatus.

[0015] The image forming apparatus of the present invention may be characterized by comprising a head unit having a recording head, a transport unit that transports paper, and a cleaning unit that cleans the recording head.

[0016] The liquid tank of the present invention is a liquid tank comprising: a container body that contains liquid and is placed on a ground surface; a capacitance sensor that detects changes in the amount of liquid in the container body by detecting changes in capacitance between the container body and the ground surface; and a supply port formed in the container body below the liquid level when empty, at which point the container body is determined to be empty based on the detection results of the capacitance sensor, and is characterized in that the container body has a blank portion formed below the liquid level when empty, in which no liquid is contained.

[0017] In the liquid tank of the present invention, the blank portion may be hollow.

[0018] In the liquid tank of the present invention, the container body may have a main body portion and a leg portion that is placed on the ground surface, and the blank portion may be formed on the leg portion.

[0019] In the liquid tank of the present invention, the capacitance sensor may be attached to the main body, and the supply port may be formed in the leg.

[0020] In the liquid tank of the present invention, the blank portion may penetrate through the leg portion.

[0021] In the liquid tank of the present invention, the lowest height of the detection surface of the capacitance sensor may be higher than the height of the liquid surface when the liquid is contained until the supply port is blocked.

[0022] In the liquid tank of the present invention, the liquid may be a cleaning liquid for cleaning a recording head of an image forming apparatus.

[0023] The image forming apparatus of the present invention is characterized by comprising a head unit having a recording head, a transport unit that transports paper, a cleaning unit that cleans the recording head, and the liquid tank that contains cleaning liquid that is supplied to the cleaning unit. [Effects of the Invention]

[0024] According to the present invention, a blank portion in which no liquid is contained is formed in the portion where liquid remains when the container is empty, so that the remaining amount of liquid can be reduced by the volume of the blank portion. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a front view schematically illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a cleaning liquid tank according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing a state where the cleaning liquid is full according to an embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view showing the cleaning liquid tank when empty according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] A liquid tank and an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0027] First, the image forming apparatus will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the internal configuration of the image forming apparatus. In the following description, the front side of the paper in Fig. 1 is the front side (front side) of the image forming apparatus. L and R in each figure indicate the left and right sides of the image forming apparatus, respectively.

[0028] The device body 3 (an example of a housing) of the image forming device 1 is provided with a paper feed unit 5, an inkjet image forming unit 7, and a discharge tray 9. Furthermore, the device body 3 is formed with a sheet transport path 11 that runs from the paper feed unit 5 through the image forming unit 7 to the discharge tray 9. The main structural members of the device body 3 are made of metal, and each member is electrically connected to another. The device body 3 is grounded.

[0029] The paper feed section 5 is provided at the bottom of the device main body 3 and includes a plurality of paper feed cassettes 13 that store sheets, and a plurality of paper feed devices 15 that feed sheets S from the paper feed cassettes 13 to the conveying path 11.

[0030] The image forming section 7 is provided on the upper part of the device main body 3, and includes a head unit 21 that performs printing operations, a transport unit 23 that transports paper, and a cleaning unit 25 that cleans the head unit 21.

[0031] The head unit 21 is equipped with recording heads corresponding to four colors of ink, each connected to an ink tank 22 that contains the corresponding color of ink.

[0032] The transport unit 23 includes an endless transport belt that travels in a predetermined direction to transport paper. The transport unit 23 moves up and down between a printing position (see solid line in FIG. 1) where the paper transport surface of the transport belt is located below the head unit 21, and a retracted position (see two-dot chain line in FIG. 1) that is further away from the head unit 21 and below the printing position.

[0033] The cleaning unit 25 includes a cap that covers each recording head of the head unit 21 and a wiper that cleans each recording head. The cleaning unit 25 is movable between a cleaning position below the head unit 21 and a retracted position spaced to the left of the head unit 21. A cleaning liquid tank 31 that contains cleaning liquid for cleaning the recording head is connected to the cleaning unit 25. The cleaning liquid tank 31 is detachably attached to, for example, a storage section provided at the bottom of the device main body 3. The storage section is, for example, a rectangular parallelepiped space surrounded by a ceiling surface, a bottom surface, left and right side surfaces, and a rear surface, and is open at the front. The cleaning liquid tank 31 is an example of a liquid tank of the present invention. The cleaning liquid tank 31 will be described later.

[0034] During image formation, the transport unit 23 rises from the retracted position to the printing position. A sheet fed by the paper feed device 15 from a predetermined paper feed cassette 13 in the paper feed section 5 is transported along the transport path 11 to the image forming section 7. In the image forming section 7, as the sheet passes below the head unit 21, ink is ejected from the recording head of the head unit 21 to form an image on the sheet. The sheet with the image formed is transported along the transport path 11 and discharged to the discharge tray 9.

[0035] When cleaning the recording head of the head unit 21, the transport unit 23 moves from the printing position to the retracted position, and then the cleaning unit 25 moves from the retracted position to the cleaning position. A description of the cleaning operation will be omitted.

[0036] Next, the cleaning liquid tank 31 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view showing the cleaning liquid tank 31, Figure 3 is a cross-sectional view showing the cleaning liquid tank 31 when full, and Figure 4 is a cross-sectional view showing the cleaning liquid tank 31 when empty.

[0037] The cleaning liquid tank 31 includes a container body 33 that contains a liquid (cleaning liquid), and a capacitance sensor 35 that detects the remaining amount of liquid in the container body 33. The capacitance sensor 35 may be provided in the device body 3.

[0038] The container body 33 is a hollow, horizontally elongated rectangle, and includes a main body 41 and two legs 43 provided at both longitudinal ends of the main body 41. The interior of the main body 41 and the interior of the two legs 43 are in communication with each other. The main body 41 and the two legs 43 each have a constant thickness. The container body 33 is attached to and detached from the device body 3 along the longitudinal direction. When the container body 33 is attached to the storage section of the device body 3, the lower surfaces of the two legs 43 rest on the lower surface of the storage section of the device body 3 (see Figures 3 and 4, an example of a ground surface of the present disclosure, hereinafter referred to as ground surface G).

[0039] An injection port 45 is formed at one longitudinal end (the end on the front side in the installation direction) of the upper wall of the main body 41. Liquid is injected into the container main body 33 through this injection port 45. The injection port 45 is closed with a cap 47.

[0040] The two leg portions 43 are horizontally long rectangular, and as shown in FIG. 2, have an upper portion 43a and a lower portion 43b having a larger cross-sectional area than the upper portion. The lower surface of the lower portion 43b is formed flat. When the container body 33 is attached to the storage portion of the device body 3, this lower surface is grounded to the ground surface G (see FIGS. 3 and 4). The upper portions 43a of the two leg portions 43 are provided with through holes 49 that run along the short side of the container body 33. The through holes 49 are horizontally long rectangular along the leg portions 43. The through holes 49 are an example of a blank portion of the present invention.

[0041] A supply port 51 is formed at the lower end of the side wall of the leg 43 formed at the other end in the longitudinal direction (the end on the far side in the installation direction). The supply port 51 is closed by a connecting coupling 53. When the container body 33 is installed in the storage section of the device body 3, the connecting coupling 53 is connected to a connecting section (not shown) of the device body 3, and the supply port 51 opens.

[0042] The capacitance sensor 35 is attached to the container body 33. More specifically, it is attached to the outer surface of the side wall of the body 41 at the rear end in the installation direction so that the lowest height H (see FIG. 4) of the detection surface (within the height range of the sensor 35) is slightly higher than the height of the liquid level LS (the upper surface of the leg 43, the bottom surface of the body 41) when the liquid L is contained up to the lowest height at which the supply port 51 is blocked. The capacitance sensor 35 detects changes in capacitance due to the amount of liquid between the detection surface and the ground surface G. The detection result of the capacitance sensor 35 is sent to the control unit 61 (see FIGS. 3 and 4).

[0043] Based on the detection results of the capacitance sensor 35, the control unit 61 determines that the container body 33 is empty when it determines that the liquid L has filled only the leg portion 43 and the liquid level LS has dropped to the minimum height (the upper surface of the leg portion 43, the bottom surface of the main body portion 41) at which the supply port 51 is blocked by the liquid L, as shown in Figure 4.

[0044] As described above, the capacitance sensor 35 detects a change in capacitance due to the amount of liquid between the detection surface and the ground surface G. When the height of the liquid level LS becomes lower than the lowest height H of the detection surface (see FIG. 4), the measured capacitance always remains the same, and no change in capacitance is detected. Also, as described above, the capacitance sensor 35 is positioned so that the lowest height H of the detection surface is slightly higher than the liquid level LS when the container is empty. In other words, when the liquid L is consumed until the height of the liquid level LS becomes lower than the lowest height H of the detection surface, no change in capacitance is detected. Based on the detection results of the capacitance sensor 35, the control unit 61 determines that the container body 33 is empty when no change in capacitance is detected.

[0045] The following describes the full and empty states of the cleaning liquid tank 31 configured as described above. As described above, the cleaning liquid tank 31 is attached to the storage compartment 2 of the device body, and the lower surfaces of the two legs 43 are grounded to the ground surface G of the storage compartment. In this case, as shown in FIG. 1 , the distance D1 between the capacitance sensor 35 and the ground surface G is shorter than the distance D2 between the capacitance sensor 35 and the ceiling surface. Therefore, the capacitance sensor 35 detects the capacitance between the capacitance sensor 35 and the ground surface G, rather than the capacitance between the capacitance sensor 35 and the ceiling surface. Furthermore, the distance between the capacitance sensor 35 and the ground surface G may be shorter than the distance between the capacitance sensor 35 and surfaces other than the ground surface G (the ceiling surface, left and right side surfaces, and rear surface). In this manner, the capacitance sensor 35 mainly detects the capacitance between the capacitance sensor 35 and the ground surface G.

[0046] When the container is full as shown in FIG. 3, the liquid L is filled in the container body 33 (the body part 41 and the legs 43) until the liquid level LS is close to the upper wall of the body part 41.

[0047] 4, when the liquid L is consumed until the liquid level LS becomes lower than the lowest height H of the detection surface of the capacitance sensor 35, the capacitance measured by the capacitance sensor 35 becomes constant. When the control unit 61 no longer detects a change in the capacitance, it determines that the container body 33 is empty. When the container body 33 is empty, the liquid level LS is above the supply port 51, so it is possible to prevent air from entering through the supply port 51 the next time liquid is supplied.

[0048] When the control unit 61 determines that the container body 33 is empty, it displays a message on the display unit (not shown) indicating that the cleaning liquid tank 31 is empty. When the cleaning liquid tank 31 becomes empty, the entire cleaning liquid tank 31 is replaced to prevent the intrusion of foreign matter. In other words, any liquid remaining in the tank when it is empty is discarded.

[0049] As is clear from the above explanation, the cleaning liquid tank 31 of the present invention has a through hole 49 formed in the leg portion 43 where the liquid L remains when the tank is empty, so that the remaining amount of the liquid L, i.e., the amount of the liquid discarded when the tank is empty, can be reduced by the volume of the through hole 49.

[0050] As described above, the capacitance sensor 35 measures the capacitance between the bottom surfaces of the two legs 43 and the ground surface G. Because the contact area between the two legs 43 and the ground surface G is relatively large, the sensitivity of the capacitance sensor 35 can be increased, allowing the remaining amount to be determined more accurately. In this case, because the distance between the capacitance sensor 35 and the ground surface G is shorter than the distance between the capacitance sensor 35 and surfaces other than the ground surface G (the ceiling, left and right side surfaces, and rear), the capacitance of the space containing the cleaning liquid that exists between the capacitance sensor 35 and the ground surface G can be detected with high accuracy.

[0051] As shown in FIG. 4, the capacitance sensor 35 is positioned so that the lowest height H of the detection surface is slightly higher than the liquid level LS when the container is empty, thereby shortening the distance between the detection surface and the ground surface. This reduces detection errors by the capacitance sensor 35. Furthermore, since the capacitance sensor 35 detects the remaining amount without contact, it is attached to the outer surface of the side wall of the container body 33. This simplifies the management of the electrical wires and signal wires connected to the power source, and is also favorable in terms of durability, etc.

[0052] It is also possible to reduce the remaining amount by making the entire leg 43 solid. However, the thickness of the wall of the cleaning liquid tank 31 affects the capacitance (resistance value) detected by the capacitance sensor 35, and the accuracy of the capacitance sensor 35 increases as the thickness of the cleaning liquid tank 31 decreases. If the leg 43 is solid, the resistance value of the leg 43 affects the detection value of the capacitance sensor 35, thereby reducing the detection accuracy. Therefore, it is preferable that the thickness of the container body 33 be as thin as possible.

[0053] Furthermore, the leg 43 may have a solid portion as the blank portion instead of the through-hole 49. In this case, the remaining amount of liquid can be reduced by the volume of the solid portion. However, in consideration of formability and weight, it is preferable that the blank portion be a through-hole 49 (hollow).

[0054] Furthermore, by providing two legs 43 below the liquid level LS when empty and forming supply ports 51 in the legs 43, the volume of the container body 33 below the liquid level LS can be reduced, thereby further reducing the remaining amount when empty. However, the legs 43 do not necessarily have to be provided. In this case, one or more blank sections are formed below the liquid level LS when empty.

[0055] The ceiling surface of the storage section of the device main body 3 may be electrically insulated from the device main body 3. This includes the case where the ceiling surface is made of an insulating material, or the device main body 3 may not be present above the storage section, and the storage section may be open.

[0056] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0057] 1. Image forming device 3. Device body (casing) 21 Head Unit 23 Transport unit 25 cleaning unit 31 Cleaning liquid tank (liquid tank) 33 Container body 35 Capacitive Sensor 41 Main body 43 Legs 49 Through hole (blank part) 51 Supply port

Claims

1. a container body that contains a liquid and is placed on a ground surface; a capacitance sensor that detects a change in the amount of liquid in the container body by detecting a change in capacitance between the capacitance sensor and the ground surface; a supply port formed in the container body below a liquid level when the container body is determined to be empty based on the detection result of the capacitance sensor, A liquid tank characterized in that the container body has a blank portion formed below the liquid level when empty, in which no liquid is contained.

2. 2. The liquid tank according to claim 1, wherein the blank portion is hollow.

3. the container body has a main body portion and a leg portion placed on the ground surface, 3. The liquid tank according to claim 1, wherein the blank portion is formed on the leg portion.

4. 4. The liquid tank according to claim 3, wherein the capacitance sensor is attached to the main body, and the supply port is formed in the leg.

5. 5. The liquid tank according to claim 3, wherein the blank portion penetrates the leg portion.

6. A liquid tank according to any one of claims 1 to 5, characterized in that the lowest height of the detection surface of the capacitance sensor is higher than the height of the liquid surface when the liquid is contained until the supply port is blocked.

7. 7. The liquid tank according to claim 1, wherein the liquid is a cleaning liquid for cleaning a recording head of an image forming apparatus.

8. a head unit including a recording head; a transport unit that transports paper; a cleaning unit for cleaning the recording head; 8. An image forming apparatus comprising: a liquid tank according to claim 7, which contains cleaning liquid to be supplied to the cleaning unit.

Images