JP2006159874A - Liquid tank and image forming apparatus using tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple-structured liquid tank wherein presence or absence of a liquid tank itself, and presence or absence of a liquid in the liquid tank are detected without assembling a plurality of optical elements, and also to provide an image forming apparatus with the ink tank mounted therein. <P>SOLUTION: The ink tank 10 of the present invention is provided with: a case 25 containing ink; a light transparent window member 22 assembled in the case 25 so as to constitute a part of the case 25; light reflecting surfaces 37 and 38 which are formed in the window member 22 so as to face inside of the case 25, and reflects measurement light incident to the window member 22 and emits the light outside the case 25 from the window member 22; and reflected light amount controller sections 39 and 40 provided on the surface of the window member 22 facing outside of the case 25. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid tank that stores liquid supplied to a liquid discharge head, and an image forming apparatus that can detect the presence / absence of liquid stored in the liquid tank and the presence / absence of the liquid tank itself.

  The “print” described in this specification is not only for forming significant information such as characters and figures, but also manifested so that it can be perceived visually by humans, regardless of significance. Regardless of whether or not it is, it includes a case where an image, a pattern, a pattern or the like is widely formed on the print medium, or the print medium is processed such as etching.

  The “print medium” is a sheet-like object that can accept not only a piece of paper used in a general printing apparatus but also a liquid such as a cloth, a resin film, a metal plate, glass, ceramics, wood, and leather. Other three-dimensional solids such as a sphere and a cylinder are also included.

  Furthermore, “liquid” is to be interpreted widely as the definition of “print” above, and by being applied on the print medium, the formation of images, patterns, patterns, etc., processing of the print medium such as etching, Alternatively, it refers to a liquid that can be subjected to ink processing, such as solidification or insolubilization of the colorant in the ink applied to the print medium, and includes any liquid used for printing.

  Electric energy using an electromechanical conversion element such as a piezo element as an ejection energy generating means for ejecting liquid from an ejection port formed in the liquid ejection head, or an electric heat having a heating resistor that heats and boils the liquid 2. Description of the Related Art An inkjet image forming apparatus that uses a conversion element to form a desired image by discharging droplets onto a print medium is known. In this type of image forming apparatus, a liquid discharge head, that is, an ink tank that stores ink to be supplied to an ink jet head is incorporated in a replaceable manner. It is necessary to supply ink to the ink tank. For this reason, this type of ink jet printer has a built-in system for detecting the remaining amount of ink in the ink tank, and if the remaining amount of ink in the ink tank becomes low, the user can replace the ink tank. And the printing operation of the ink jet printer is temporarily interrupted as necessary.

  Conventionally, as a method for detecting the remaining amount of ink in the ink tank, an optical method using light reflection is generally used. For example, as disclosed in Patent Document 1, an ink chamber formed in an ink tank is used. A light reflecting plate is provided to detect the presence or absence of ink, or as disclosed in Patent Document 2 or Patent Document 3, a plurality of light reflecting members are provided to indicate the presence or absence of an ink tank and the remaining amount of ink in the ink tank. It is known to detect this. Patent Document 4 discloses an ink jet printer that can detect the presence or absence of an ink tank and the presence or absence of ink with a single photosensor. Further, Patent Document 5 discloses a technique for determining whether or not the remaining amount of ink is very small based on optically measured data.

  An example of such a conventional ink tank is shown in FIG. 6, and the sectional structure of the bottom is shown in FIG. In order to detect the presence of the ink tank 1 and the prism 2 for detecting the remaining amount of ink stored in the ink tank 1 on the bottom surface of the ink tank 1 formed of a light transmissive material such as polypropylene. Are provided adjacent to the concave reflection surface 3. The light detection unit 4 having a light emitting element and a light receiving element (not shown) is fixed to the chassis side of an ink jet printer (not shown) so as to face the prism 2 and the concave reflecting surface 3, and the light emitting element and the light receiving element are ink tanks. 1 are arranged side by side in a direction perpendicular to the longitudinal direction of 1 (direction perpendicular to the paper surface of FIG. 7).

  The concave reflecting surface 3 having a metal thin film such as aluminum deposited on the surface is formed as a part of an elliptical spherical surface, and the concave reflecting surface 3 of the ink tank 1 is optically detected using a scanning movement mechanism of an ink jet head. In the state of being moved right above the unit 4, the light emitting element and the light receiving element are positioned at the two focal points of the elliptical spherical surface, and the light emitted from the light emitting element is reflected by the concave reflecting surface 3. The light is incident on the light receiving element, whereby the presence or absence of the ink tank 1 can be confirmed. In addition, in a state where the prism 2 of the ink tank 1 is moved immediately above the light detection unit 4, when there is no ink in the ink tank 1, the light emitted from the light emitting element is totally reflected by the prism 2 and received. When incident on the element but the prism 2 is covered with ink in the ink tank 1, light incident on the prism 2 from the light emitting element passes through the prism 2 and travels into the ink in the ink tank 1 to receive light. Since there is no reflection toward the element side, the presence or absence of ink in the ink tank 1 can be determined.

JP-A-8-183183 JP-A-9-174877 Japanese Patent Laid-Open No. 10-323993 JP-A-9-29989 JP 2001-328273 A

  In the conventional detection system shown in FIG. 7, a prism 2 is provided in the ink tank 1 as an optical element for detecting the presence or absence of ink in the ink tank 1, and an optical for detecting the presence or absence of the ink tank 1 itself. A concave reflecting surface 3 is formed in the ink tank 1 as an element. For this reason, when the presence or absence of the ink tank 1 itself or the presence or absence of ink is detected using one light detection unit 4, the ink tank 1 must be moved relative to the light detection unit 4 at least twice. Also, a positioning mechanism for that purpose is required. Further, since it is necessary to arrange the prism 2 and the concave reflecting surface 3 side by side in the ink tank 1 along the relative movement direction with respect to the light detection unit 4, when the ink tank 1 having a small capacity is intended, The dimensions of the optical elements themselves must be reduced, and the relative position between the optical elements and the light detection unit 4 needs to be stricter. As a result, there has been a problem that, together with the strictness of these dimensional accuracy and assembly position accuracy, the manufacturing cost of the ink jet printer is increased.

  With respect to such problems, an early solution is desired in combination with a demand for a variety of liquids to be used and a reduction in the size of the image forming apparatus.

  An object of the present invention is to provide a liquid tank having a simple configuration capable of detecting the presence / absence of the liquid tank itself and the presence / absence of the liquid in the liquid tank without incorporating a plurality of optical elements, and an image forming apparatus on which the liquid tank is mounted. And to provide.

  According to a first aspect of the present invention, a housing that contains a liquid, a light-transmissive window member that is incorporated in the housing and forms a part of the housing, and the window member that faces the housing are provided. A light reflecting surface that is formed and reflects measurement light incident on the window member and emits the light from the window member to the outside of the housing, and the light reflecting surface or the surface of the window member facing the outside of the housing. The liquid tank is provided with a light reflection amount control unit provided.

  In the liquid tank according to the present invention, the light reflection amount control unit is disposed on a part of the light reflecting surface or a part of the surface of the window member facing the outside of the housing, and reflects the measurement light by almost 100%. Good. In this case, it is preferable that a plurality of light reflection amount control units are arranged in a dispersed state on the light reflection surface.

  In the present invention, when the light reflection amount control unit is provided on the light reflection surface, the light incident from the window member and reaching the light reflection surface is one of them when the light reflection surface is covered with the liquid. The part advances from the light reflecting surface into the liquid, and the rest is reflected by the light reflecting surface and guided outside the window member. Further, the light incident on the light reflection amount control unit is also regularly reflected, and most of the light is guided out of the window member. In contrast, when the light reflection surface is not covered with liquid, total reflection occurs at the interface between the light reflection surface and the gap in the liquid tank, and the light incident on the light reflection amount control unit is also regularly reflected. As a result, almost all of the incident light is guided out of the window member.

  On the other hand, when the light reflection amount control unit is disposed on a part of the surface of the window member facing the outside of the housing, the light incident on the light reflection amount control unit is directly reflected and becomes reflected light. In addition, the light that has entered the window member and reached the light reflecting surface partially proceeds from the light reflecting surface into the liquid when the light reflecting surface is covered with the liquid, and the rest of the light reflecting surface. And is guided out of the window member. On the other hand, in a state where the light reflecting surface is not covered with the liquid, total reflection occurs at the interface between the light reflecting surface and the gap in the liquid tank, and almost all of the incident light is guided out of the window member.

  The light reflection amount control unit may be a light transmissive thin film formed over the entire area of the light reflection surface. In this case, it is preferable that the material constituting the light transmissive thin film has a refractive index substantially equal to or smaller than the refractive index of the material constituting the window member with respect to the measurement light.

  In the present invention, a part of the light that has entered the window member and reached the light reflection surface passes through the light reflection amount control unit from the light reflection surface in a state where the light reflection surface is covered with the liquid. The remaining light is reflected by the light reflection surface and / or the light reflection amount control unit, and guided outside the window member. In contrast, when the light reflecting surface is not covered with liquid, total reflection occurs at the interface between the light reflection amount control unit and the gap in the liquid tank, and almost all of the incident light is guided out of the window member. It is burned.

  The window member may be a prism body having at least two light reflecting surfaces.

  According to a second aspect of the present invention, there is provided an image forming apparatus for discharging a liquid from a liquid discharge head to form an image on a print medium, and storing the liquid supplied to the liquid discharge head. A mounting portion of the liquid tank according to the embodiment, a measurement light source for irradiating measurement light toward the window member of the liquid tank mounted on the mounting portion, a photodetector for detecting reflected light from the measurement light source, It is characterized by comprising determination means for determining the presence / absence of a liquid tank and the presence / absence of liquid in the liquid tank in accordance with the amount of light detected by the photodetector.

  In the present invention, the measurement light from the measurement light source is irradiated toward the window member of the liquid tank, the reflected light is detected by the photodetector, and the presence or absence of the liquid tank and the liquid tank are detected according to the detected reflected light amount. The presence / absence of the liquid is determined by the determination means. This determination means determines that there is no liquid tank in the case of the minimum light quantity, determines that there is no liquid in the liquid tank in the case of the maximum light quantity, and in the case of an intermediate light quantity between the minimum light quantity and the maximum light quantity. It is determined that there is liquid in the liquid tank.

  As the form of the image forming apparatus according to the present invention, in addition to what is used as an output terminal of information processing equipment such as a computer or an optical disk apparatus, a copying apparatus combined with a reader, a facsimile apparatus or a textile printing apparatus having a transmission / reception function, Alternatively, it may be in the form of an etching apparatus, and the print medium may be a sheet or long paper or fabric, or a plate-like wood or leather, stone, resin, glass, metal, etc. A three-dimensional solid structure etc. can be mentioned.

  According to the liquid tank of the present invention, a light-transmitting window member that is incorporated in a housing that contains liquid and forms a part of the housing, and the window member is formed so as to face the housing. A light reflecting surface that reflects incident measurement light and emits the light from the window member to the outside of the housing, and a light reflection amount control unit provided on the surface of the light reflecting surface or the window member facing the outside of the housing. Therefore, the minimum amount of light detected when there is no liquid tank, the maximum amount of light detected when there is no liquid in the liquid tank, and the minimum and maximum amounts when there is liquid in the liquid tank. Therefore, the presence or absence of the liquid tank and the presence or absence of the liquid in the liquid tank can be reliably determined even by incorporating a single optical element.

  When the light reflection amount control unit is arranged on a part of the light reflection surface or a part of the surface of the window member facing the outside of the housing and reflects the measurement light almost 100%, the light reflection amount control unit particularly reflects the light. When a plurality of surfaces are distributed in a dispersed state, the ratio of the light reflection amount control unit with respect to the light reflection surface is changed, so that the ratio of the reflected light emitted from the window member when liquid is present in the liquid tank can be easily achieved. Can be adjusted.

  In the case where the light reflection amount control unit is a light-transmitting thin film formed over the entire surface of the light reflecting surface, in particular, the material constituting the light-transmitting thin film is the refractive index of the material constituting the window member with respect to the measurement light. When the refractive index is approximately equal to or smaller than that, the ratio of the measurement light transmitted through the light reflection amount control unit when there is liquid in the liquid tank by changing the thickness of the thin film (transmittance / (Reflectance) can be easily adjusted.

  When the window member is a prism body having at least two light reflecting surfaces, it can be detected using the total reflection of the measurement light that no liquid is present in the liquid tank.

  According to the image forming apparatus of the present invention, the mounting portion of the liquid tank according to the present invention, the measuring light source that irradiates the measuring light toward the window member of the liquid tank mounted on the mounting portion, and the reflected light from the measuring light source And a determination means for determining the presence / absence of the liquid tank and the presence / absence of the liquid in the liquid tank according to the amount of light detected by the photodetector. The presence or absence of the liquid can be reliably determined.

  Embodiments in which the image forming apparatus according to the present invention is applied to a serial scan type ink jet printer will be described in detail with reference to FIGS. 1 to 5, but the present invention is not limited to these embodiments, and these are further described. Combinations and modifications and variations that are encompassed by the concepts of the present invention as set forth in the claims are possible, and of course applicable to other techniques belonging to the spirit of the present invention.

  The external appearance of this embodiment is shown in FIG. 1, the sectional structure of the ink tank is shown in FIG. 2, and the extracted enlarged sectional structure of the window member is shown in FIG. That is, the ink jet printer 10 according to the present embodiment causes ink droplets to be ejected from ejection ports formed in an ink jet head (not shown), and accurately attaches the ink droplets to a predetermined portion of a print medium such as paper (not shown). A desired image is formed on a print medium.

  The ink jet head is detachably connected to an ink tank 11 containing ink to be supplied to the ink jet head, and is detachably mounted on the carriage 12 together with the ink tank 11 in a posture of ejecting ink droplets downward in FIG. Is done. The carriage 12 is slidably supported with respect to the scanning guide shaft 14 fixed to the frame 13 of the inkjet printer 10. Further, both ends of a toothed belt driven by the rotation of the carriage drive motor 15 are connected to the carriage 12, and the carriage 12 is moved along the scanning guide shaft 14 by rotating the carriage drive motor 15 forward and backward. To scan. Printing on the print medium is performed by ejecting ink droplets from the inkjet head while moving the carriage 12.

  A home position is set at one end of the scanning movement region of the carriage 12, and in a state where the carriage 12 is located at the home position, a portion facing an ejection port surface where an ejection port of an inkjet head (not shown) is opened, A head recovery mechanism 16 is provided for maintaining a good ink discharge state from the discharge port of the inkjet head. The head recovery mechanism 16 includes a cap member 17 that covers the discharge port surface of the ink jet head, a wiping member 18 that wipes the discharge port surface of the ink jet head, and a cap member 17 from the discharge port of the ink jet head through the cap member 17. A suction pump (not shown) for sucking ink is included.

  A light detection unit 19 is disposed adjacent to the head recovery mechanism 16. The light detection unit 19 includes a light emitting element 20 using an LED that emits measurement light having a wavelength of about 300 nm, and a light receiving element 21 using a phototransistor for receiving reflected light from the light emitting element 20. However, it is not necessary to provide the light emitting element 20 and the light receiving element 21 as one photodetecting unit 19, and it is also possible to arrange them separately. A determination unit (not shown) is connected to the light detection unit 19. The determination unit determines whether the ink tank 11 is mounted on the carriage 12 according to the amount of light received by the light receiving element 21, and the ink tank 11 mounted on the carriage 12. It is determined whether or not there is ink inside. In the light detection unit 19, when the carriage 12 moves right above, the light emitting element 20 emits light to a window member 22 (to be described later) of the ink tank 11 mounted on the carriage 12. .

  The ink tank 11 in the present embodiment has a housing 25 composed of a main body 23 and a lid 24, and ink that generally has a refractive index of about 1.3 is accommodated in the housing 25. The main body 23 is formed of a light transmissive member, specifically, an optically transparent polypropylene having a refractive index of about 1.5. The inside of the main body 23 is partitioned by a partition wall 26 that partitions into two spaces, and the two spaces are in communication with each other via a communication portion 27 formed at the lower end of the partition wall 26. One of the two spaces is an ink storage chamber 28 that stores ink, and the other is a negative pressure generation chamber 30 that stores an ink holding member 29 that absorbs and holds ink using capillary force. The main body 23 facing the negative pressure generating chamber 30 is provided with an ink supply port 31 for supplying ink to the ink jet head. Further, the ink tank from the outside is consumed as the ink stored in the ink tank 11 is consumed. An atmosphere communication path 32 for introducing the atmosphere into the interior 11 is formed. On the surface of the partition wall 26 facing the negative pressure generation chamber 30, a pressure adjusting groove 33 extending upward from the communication portion 27 is provided in order to promote introduction of air from the negative pressure generation chamber 30 to the ink storage chamber 28. Is formed. Further, around the open end of the atmospheric communication passage 32 that faces the negative pressure generation chamber 30, a buffer portion 35 in which the ink holding member 29 does not exist is formed by a rib 34 that extends downward from the inside of the lid 24.

  Accordingly, the ink in the negative pressure generating chamber 30 held by the ink holding member 29 is consumed as ink is ejected from the inkjet head, and the upper end of the liquid surface, that is, the gas-liquid interface 36 is at the upper end of the pressure adjusting groove 33. When it reaches, air introduced into the negative pressure generating chamber 30 from the atmospheric communication passage 32 thereafter is sucked into the ink containing chamber 28 from the communicating portion 27 via the pressure adjusting groove 33. By introducing the atmosphere into the ink storage chamber 28 in this way, the ink in the ink storage chamber 28 is filled into the ink holding member 29 of the negative pressure generation chamber 30 through the communication portion 27. That is, even if the ink in the negative pressure generating chamber 30 is supplied to the ink jet head side as the ink is consumed by the ink jet head, the ink corresponding to the supply amount is filled from the ink containing chamber 28 into the negative pressure generating chamber 30. As a result, the gas-liquid interface 36 in the negative pressure generating chamber 30 is maintained at a substantially constant height. As a result, the negative pressure on the ink tank 11 side with respect to the ink jet head is kept substantially constant, and stable ink supply to the ink jet head is performed. Is possible.

  A window member 22 is formed integrally with the main body 23 at the bottom of the ink storage chamber 28. In the present embodiment, the window member 22 has a rectangular prism shape in which the angle formed by the pair of light reflecting surfaces 37 and 38 is set to 90 degrees. Have The size of the pair of light reflecting surfaces 37 and 38 of the window member 22 is appropriately set according to the distance between the light emitting element 20 and the light receiving element 21 of the light detection unit 19 described above. Specifically, when the window member 22 is positioned immediately above the light detection unit 19, the center portion of the light detection element 19 in the state where the optical axis of the light emitting element 20 is inclined 45 degrees with respect to the one light reflection surface 37. And the optical axis of the light receiving element 21 passes through the center of the light receiving element 21 with an inclination of 45 degrees with respect to the other light reflecting surface 38, and the measurement light from the light emitting element 20 enters the window member 22 and is reflected in a pair. It is set so that the reflected light that is totally reflected by the surfaces 37 and 38 and finally emitted from the window member 22 enters the light receiving element 21.

  Note that since the ink tank 11 is mounted on the carriage 12, the measurement light from the light emitting element 20 and its reflected light are not shown in the portion of the carriage 12 facing the window member 22 (not shown). An opening is formed.

  A silver thin film 39 as a light reflection amount control unit of the present invention is formed over the entire area of the pair of light reflecting surfaces 37 and 38, and the silver thin film 39 in this embodiment functions as a semitransparent mirror. Have By setting the film thickness of the silver thin film 39 to an appropriate value, when the silver thin film 39 and the light reflecting surfaces 37 and 38 are covered with ink, the ratio of the measurement light reflected here is set to the silver thin film 39. It can be increased compared to the case where there is no at all.

  Accordingly, in a state where the ink tank 11 is not mounted on the carriage 12, the measurement light emitted from the light emitting element 20 of the light detection unit 19 travels straight as it is and is scattered within the ink jet printer 10 and does not return to the light receiving element 21. . The intensity of light received by the light receiving element 21 at this time is A. The light intensity A is basically close to zero, but has a slight amount of background light due to scattered light in the ink jet printer 10 and stray light from the outside.

  On the other hand, when the ink tank 11 in which the ink in the ink storage chamber 28 is emptied is mounted on the carriage 12, the measurement light emitted from the light emitting element 20 is the window member of the ink tank 11 as shown by the arrow in FIG. 22, reaches one light reflecting surface 37, part of the light is reflected by the surface reflection toward the other light reflecting surface 38, and the rest enters the silver thin film 39. Total reflection occurs at the air interface with the storage chamber 28. A similar phenomenon occurs in the other light reflecting surface 38 with respect to the reflected light reflected from the one light reflecting surface 37, and almost all of the measurement light finally incident on the window member 22 becomes reflected light. To the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is B. This light intensity B basically indicates the maximum amount of light received by the light receiving element 21.

  On the other hand, when the ink tank 11 storing ink in the ink storage chamber 28 that is more than enough to cover the light reflecting surfaces 37 and 38 is mounted on the carriage 12, the measurement light emitted from the light emitting element 20 is emitted from the ink tank 11. The light enters the window member 22 and reaches one light reflecting surface 37, part of which is reflected toward the other light reflecting surface 38 by interfacial reflection with the silver thin film 39, and the rest enters the silver thin film 39. Then, part of the light is reflected at the interface with the ink in the ink storage chamber 28, and the rest passes through the silver thin film 39 and proceeds to the ink storage chamber 28. A similar phenomenon occurs in the other light reflecting surface 38 with respect to the reflected light reflected from one light reflecting surface 37. As a result, a part of the measuring light incident on the window member 22 becomes reflected light and the window member 22 is reflected. To the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is C. The light intensity C is larger than the light intensity A described above and smaller than the light intensity B.

The determination unit determines the presence / absence of the ink tank 11 and the presence / absence of ink in the ink tank 11 when the ink tank 11 is mounted on the carriage 12 based on the intensity of the reflected light received by the light receiving element 21. In order to clearly distinguish the light intensities A, B, and C in order to avoid misjudgment by the judging means, the silver thin film 39 needs to function well as a translucent mirror that passes through part of the incident light and reflects the rest. There is. Here, if the incident light quantity with respect to the silver thin film 39 is I, the transmitted light quantity is O, and the extinction coefficient peculiar to the material constituting the light reflection quantity control unit (silver in this embodiment) is k, log (O / I) = − k · t, and it can be seen from the relationship O = I · 10 ^{−k · t that} the transmitted light amount O gradually decreases as the film thickness t of the silver thin film 39 increases.

  Therefore, based on the constituent material of the light reflection amount control unit, the light amount of the light emitting element 20, the sensitivity of the light receiving element 21, the optical path length reaching the light receiving element 21 from the light emitting element 20 through the light reflecting surfaces 37 and 38, etc. It is necessary to set the film thickness t of the quantity control unit appropriately. In this case, the film thickness t of the silver thin film 39 formed on one of the two light reflecting surfaces 37 and 38 may be set to be sufficiently thick so that the light incident thereon is reflected almost 100%. It is only necessary that at least one of the light reflecting surfaces 37 and 38 constitutes a semitransparent mirror.

  When using a dielectric such as magnesium fluoride instead of metal as the light reflection amount control unit, a plurality of dielectric thin films are laminated to form a translucent mirror using light interference. The refractive index, the number of laminated thin films, each film thickness, etc. need to be set appropriately. In the case where there is a possibility that the silver thin film 39 may chemically react with the ink, it is effective to further cover the silver thin film 39 with a protective film that is corrosion resistant to the ink. Needless to say, it is necessary to consider the influence of the measurement light from the film.

  In the above-described embodiment, the window member 22 is formed integrally with the main body 23. However, since only the window member 22 needs to have light transmission, the main body 23 is formed of a light-shielding colored material, and the window The member 22 may be joined to the main body 23 as a separate member.

  The structure of the main part of another embodiment of the liquid tank according to the present invention is shown in FIG. 4, but the same reference numerals are given to the elements having the same functions as those of the previous embodiment, and redundant description is omitted. It shall be. That is, in this embodiment, the window member 22 formed of an optically transparent acrylic resin or the like is fitted into the main body 23 of the ink tank 11 and these are integrally joined. On the pair of light reflection surfaces 37 and 38 of the window member 22, a large number of light reflection films 40 are formed at predetermined intervals as light reflection amount control units. The light reflecting film 40 is formed by evaporating aluminum, silver, or the like on the light reflecting surfaces 37, 38 in a predetermined pattern, and reflects almost 100% of light at the interface with the light reflecting surfaces 37, 38. Each has a film thickness such that

  Therefore, in a state where the ink tank 11 is not mounted on the carriage 12, the measurement light emitted from the light emitting element 20 of the light detection unit 19 goes straight as it is, and is scattered and received in the ink jet printer 10 as in the previous embodiment. It does not return to the element 21. The intensity of light received by the light receiving element 21 at this time is A.

  On the other hand, when the ink tank 11 in which the ink in the ink storage chamber 28 is emptied is mounted on the carriage 12, the measurement light emitted from the light emitting element 20 is the window of the ink tank 11 as shown by the arrow in FIG. The light enters the member 22 and reaches one of the light reflecting surfaces 37, and a part thereof undergoes total reflection at the air interface with the ink containing chamber 28. Further, the measurement light reaching the light reflecting film 40 is reflected toward the other light reflecting surface 38 by the interface reflection. In this way, the same phenomenon occurs in the other light reflecting surface 38 with respect to the reflected light reflected from the one light reflecting surface 37 side, and almost all of the measuring light finally incident on the window member 22 is reflected light. Then, the light is guided from the window member 22 to the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is B.

  On the other hand, when the ink tank 11 storing ink in the ink storage chamber 28 that is more than enough to cover the light reflecting surfaces 37 and 38 is mounted on the carriage 12, the measurement light emitted from the light emitting element 20 is emitted from the ink tank 11. The light enters the window member 22 and reaches one light reflecting surface 37, and a part of the light is reflected toward the other light reflecting surface 38 by interfacial reflection with the light reflecting film 40. In the region where the light reflection film 40 does not exist, a part of the light is reflected according to the difference in refractive index between the ink and the window member 22, and the rest proceeds into the ink in the ink storage chamber 28. In this way, the same phenomenon occurs on the other light reflecting surface 38 side with respect to the reflected light reflected from the one light reflecting surface 37 side. As a result, a part of the measuring light incident on the window member 22 is reflected light. Then, the light is guided from the window member 22 to the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is C. The light intensity C is larger than the light intensity A described above and smaller than the light intensity B.

  The determination unit determines the presence / absence of the ink tank 11 and the presence / absence of ink in the ink tank 11 when the ink tank 11 is mounted on the carriage 12 based on the intensity of the reflected light received by the light receiving element 21. In order to avoid the erroneous determination by the determination means, it is desirable to appropriately set the formation ratio of the light reflection film 40 to the light reflection surfaces 37 and 38 in order to clearly distinguish the light intensities A, B and C.

  It is also effective to reduce the thickness of the light reflecting film 40 according to the present embodiment so as to function as the same translucent mirror as in the above-described embodiment, and substantially the same effect can be obtained. Further, as in the previous embodiment, it is possible to cover the entire area of any one of the light reflecting surfaces 37 and 38 with a light reflecting film that reflects almost 100% of the light incident thereon. The difference between the two light intensities A and B can be clarified.

  In the two embodiments described above, since it is necessary to form the light reflection amount control unit on the light reflection surfaces 37 and 38 of the window member 22, that is, on the inner surface side of the ink tank 11, the window member 22 and the main body 23 of the ink tank 11. However, when the light reflection amount control unit is formed on the surface of the window member 22, that is, outside the ink tank 11, the light reflection amount control unit is more easily performed. Can be formed.

  The structure of the main part of another embodiment of the liquid tank according to the present invention is shown in FIG. 5, but the elements having the same functions as those of the previous embodiment are denoted by the same reference numerals, and redundant description is omitted. It shall be. That is, a light reflection film 40 as a light reflection amount control unit is formed on the surface of the window member 22 so that light incident thereon is reflected by almost 100% and guided to the light receiving element 21. Instead of the light reflecting film 40, a thin film such as a semi-transparent mirror as in the first embodiment can be used. Anyway, it is sufficient if the amount of light incident on the light receiving element 21 is increased. However, a part of the measurement light reaches one light reflecting surface 37 of the window member 22 without going through the light reflection amount control unit, and the reflected light does not go through the light reflection amount control unit from the other light reflecting surface 38. It is preferable that the light reflection amount control unit is formed only at the center of the surface of the window member 22 so that the light can be emitted to the light receiving element 21.

  Therefore, when the ink tank 11 is not mounted on the carriage 12, the measurement light emitted from the light emitting element 20 of the light detection unit 19 goes straight as it is and is scattered in the ink jet printer 10 as in the previous two embodiments. Therefore, it does not return to the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is A.

  On the other hand, when the ink tank 11 in which the ink in the ink storage chamber 28 is emptied is mounted on the carriage 12, a part of the measurement light emitted from the light emitting element 20 is light as shown by the arrow in FIG. The light is reflected directly on the light receiving element 21 by the reflective film 40 and the remainder enters the window member 22 of the ink tank 11 and reaches one light reflecting surface 37, where it is totally reflected at the air interface with the ink containing chamber 28. It is raised and guided to the other light reflecting surface 38 side. A similar phenomenon occurs in the other light reflecting surface 38 with respect to the reflected light reflected from one light reflecting surface 37 in this way, and almost all of the measuring light finally incident on the window member 22 becomes reflected light. Then, the light is guided from the window member 22 to the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is B.

  On the other hand, when the ink tank 11 storing ink in the ink storage chamber 28 that is more than enough to cover the light reflecting surfaces 37 and 38 is mounted on the carriage 12, part of the measurement light emitted from the light emitting element 20 is light. The light is reflected directly on the light receiving element 21 by the reflective film 40, and the remainder enters the window member 22 of the ink tank 11 and reaches one light reflecting surface 37. Here, a part of the light is reflected in accordance with the difference in refractive index between the ink and the window member 22, and the rest proceeds into the ink in the ink storage chamber 28. A similar phenomenon occurs on the other light reflecting surfaces 37 and 38 side with respect to the reflected light reflected from one light reflecting surface 37 in this way, and as a result, part of the measuring light incident on the window member 22 is reflected. Light is guided from the window member 22 to the light receiving element 21. The intensity of light received by the light receiving element 21 at this time is C. The light intensity C is larger than the light intensity A described above and smaller than the light intensity B.

  The determination unit determines the presence / absence of the ink tank 11 and the presence / absence of ink in the ink tank 11 when the ink tank 11 is mounted on the carriage 12 based on the intensity of the reflected light received by the light receiving element 21. In order to avoid the erroneous determination by the determination means, the area of the light reflection film 40 is appropriately set in order to clearly distinguish the light intensities A, B, and C.

  When a material having a small refractive index must be used as the window member 22 because of the material constituting the main body 23, the critical angle for total reflection at the light reflecting surfaces 37 and 38 exceeds 45 degrees. In such a case, it is effective to use a trapezoidal prism having three light reflecting surfaces whose incident angle to the light reflecting surface is 60 degrees. Of course, it is possible to use four or more reflecting surfaces as required.

1 is a three-dimensional projection diagram schematically illustrating an appearance of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view illustrating a schematic structure of an embodiment of a liquid tank according to the present invention mounted on the image forming apparatus illustrated in FIG. 1. FIG. 3 is an enlarged cross-sectional view of a portion of a window member of the liquid tank shown in FIG. 2, schematically showing the liquid tank and the liquid detection principle. It is an expanded sectional view of the part of the window member in other embodiments of the liquid tank by the present invention, and represents the detection principle of a liquid tank and a liquid typically. It is an expanded sectional view of the part of the window member in another embodiment of the liquid tank by the present invention, and represents the detection principle of a liquid tank and liquid typically. It is a three-dimensional projection figure showing the external appearance of the conventional ink tank. FIG. 7 is a cross-sectional view illustrating a bottom portion of the ink tank illustrated in FIG. 6 in an enlarged manner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet printer 11 Ink tank 12 Carriage 13 Frame 14 Scanning guide shaft 15 Carriage drive motor 16 Head recovery mechanism 17 Cap member 18 Wiping member 19 Photodetection unit 20 Light emitting element 21 Light receiving element 22 Window member 23 Main body 24 Lid 25 Housing 26 Partition wall 27 Communication portion 28 Ink storage chamber 29 Ink holding member 30 Negative pressure generating chamber 31 Ink supply port 32 Atmospheric communication path 33 Pressure adjusting groove 34 Rib 35 Buffer portion 36 Gas-liquid interface 37, 38 Light reflecting surface 39 Silver thin film 40 Light reflecting film

Claims (7)

A housing containing the liquid;
A light-transmissive window member that is incorporated in the housing and forms a part of the housing;
A light reflecting surface that is formed on the window member so as to face the housing, reflects the measurement light incident on the window member, and emits the light from the window member to the outside of the housing;
A liquid tank comprising: a light reflection amount control unit provided on the light reflection surface or the surface of the window member facing outside the casing.   The light reflection amount control unit is arranged on a part of the light reflection surface or a part of the surface of the window member facing the outside of the housing, and reflects the measurement light by almost 100%. The liquid tank according to claim 1.   The liquid tank according to claim 2, wherein a plurality of the light reflection amount control units are arranged in a dispersed state on the light reflection surface.   The liquid tank according to claim 1, wherein the light reflection amount control unit is a light-transmitting thin film formed over the entire area of the light reflection surface.   5. The liquid according to claim 4, wherein the material constituting the light transmissive thin film has a refractive index substantially equal to or smaller than the refractive index of the material constituting the window member with respect to the measurement light. tank.   The liquid tank according to any one of claims 1 to 5, wherein the window member is a prism body having at least two light reflecting surfaces. An image forming apparatus for discharging liquid from a liquid discharge head to form an image on a print medium,
The liquid tank mounting portion according to any one of claims 1 to 6, wherein the liquid supplied to the liquid discharge head is stored.
A measurement light source for irradiating measurement light toward the window member of the liquid tank mounted on the mounting unit;
A photodetector for detecting reflected light from the measurement light source;
An image forming apparatus comprising: determination means for determining the presence / absence of a liquid tank and the presence / absence of a liquid in the liquid tank according to the amount of light detected by the photodetector.

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