JP2011163816A - Liquid detection sensor and liquid detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid detection sensor and a liquid detection method, dealing with various kinds of inks and preventing erroneous detection of the inks. <P>SOLUTION: The liquid detection sensor 1 is equipped with: light irradiating projection parts 5, 6; a prism 7 which has a refractive index within a prescribed range on the basis of a refractive index of an ink, an incidence plane 7a inputting the light irradiated from the projection parts 5, 6, a reflection plane 7b contacting the ink and reflecting the light incident from the incidence plane 7a, and an emission plane 7c contacting the ink and emitting the light reflected at the reflection plane 7b; and light-receiving parts 5, 6 provided separately from the projection parts 3, 4 and the prism 7 and receiving the light emitted from the emission plane 7c. Existence of the ink in a middle tank 20 is detected from existence of light received by the light-receiving parts 5, 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid detection sensor and a liquid detection method for detecting a liquid such as ink.

  Conventionally, magnetic sensors and optical sensors are known as sensors for detecting ink in an ink tank. For example, a magnetic sensor described in Patent Document 1 incorporates a reed switch provided in a guide shaft disposed in an ink tank and a magnet surrounding the reed switch, and is provided movably along the guide shaft. Provided float. In this magnetic sensor, the position of the float that moves according to the increase or decrease of ink is detected by a reed switch, and the position of the liquid level in the ink tank is detected.

  In addition, the optical sensor described in Patent Document 2 includes a light emitting element that emits light to a light reflecting surface provided in an ink tank made of a transparent member, and a light reflecting surface that is irradiated from the light emitting element. And a light receiving element for receiving the reflected light. In this optical sensor, the presence or absence of ink in the ink tank is detected based on the intensity of light reflected by the light reflecting surface and received by the light receiving element.

JP 2000-203057 A JP 2000-190520 A

  However, the conventional sensor has the following problems. That is, the magnetic sensor described in Patent Document 1 has a problem that the float may stick to the inner wall of the ink tank due to the surface tension of the ink and the like, and stable ink detection cannot be performed. In addition, in the optical sensor described in Patent Document 2, when opaque ink is filled in the ink tank, the intensity of light received by the light receiving element changes due to irregular reflection of the ink coloring material, and the ink is erroneously detected. There is a risk. For this reason, there is a problem that not all ink types can be handled.

  SUMMARY An advantage of some aspects of the invention is to provide a liquid detection sensor and a liquid detection method that can cope with various ink types and prevent erroneous detection of ink.

  In order to solve the above problems, a liquid detection sensor according to the present invention is a liquid detection sensor that is provided in a container and detects liquid in the container, and includes a light projecting unit that irradiates light, and a refractive index of the liquid. With a refractive index within a predetermined range with respect to the incident surface, the incident surface that receives the light emitted from the light projecting unit, the reflective surface that contacts the liquid and reflects the light incident from the incident surface, and the liquid And a reflection portion having an emission surface that emits light reflected by the reflection surface, and a light receiving portion that is provided apart from the light projecting portion and the reflection portion and that receives light emitted from the emission surface. To do.

  The liquid detection sensor includes a light projecting unit that projects light, a reflecting unit that reflects light, and a light receiving unit that receives light emitted from the exit surface of the reflecting unit. In this liquid detection sensor, when there is no liquid in the container, the light emitted from the light projecting unit is totally reflected by the reflecting unit and received by the light receiving unit. On the other hand, when the liquid having transparency is filled in the container, the light emitted from the light projecting unit is radiated to the liquid without being reflected by the reflecting surface of the reflecting unit. Is not received. Further, when the container is filled with a liquid that does not have transparency, the light emitted from the light projecting unit is emitted without being reflected by the reflecting surface of the reflecting unit, and the light is not received by the light receiving unit. Alternatively, even when the light irradiated from the light projecting unit is reflected by the irregular reflection of the liquid on the reflecting surface and travels toward the light receiving unit, the liquid existing between the light receiving unit and the light receiving unit provided apart from the reflecting unit Since the light is shielded, the light is not received by the light receiving unit. As described above, in the liquid detection sensor, when the container is not filled with liquid, light is received by the light receiving unit, and when the container is filled with liquid, light is not received by the light receiving unit. . Therefore, even when the liquid has transparency or does not have transparency, the presence or absence of the liquid can be detected based on the presence or absence of light received at the light receiving unit. Therefore, it can respond to various ink types regardless of whether it is transparent or opaque. Further, unlike the magnetic sensor, the float does not stick into the container, so that the liquid can be detected stably without erroneous detection. As described above, the liquid detection sensor of the present invention can cope with various ink types and can prevent erroneous ink detection.

  Moreover, it is preferable that the optical path from a light projection part to an entrance plane is isolated from the liquid. In this case, it is possible to prevent the light irradiated from the light projecting unit from being blocked by the liquid or the like while reaching the incident surface. Therefore, the liquid can be detected more reliably.

  In addition to being described as the invention of the liquid detection sensor as described above, the present invention can also be described as the invention of the liquid detection method as follows. This is substantially the same invention only in different categories, and has the same operations and effects.

  That is, the liquid detection method according to the present invention is a liquid detection method for detecting a liquid in a container by a liquid detection sensor provided in the container, and the liquid detection sensor includes a light projecting unit that emits light, a liquid An incident surface on which the light irradiated from the light projecting unit is incident, a reflective surface that is in contact with the liquid and reflects the light incident from the incident surface, and a liquid A reflection portion having an emission surface that emits light reflected from the reflection surface and contacting with the reflection surface; and a light receiving portion that is provided apart from the light projecting portion and the reflection portion and receives light emitted from the emission surface; When light is received by the light receiving unit, it is determined that there is no liquid in the optical path from the light projecting unit to the light receiving unit, and when light is not received by the light receiving unit, it is determined that there is liquid in the optical path. Features.

  According to the present invention, it is possible to cope with various ink types and to prevent erroneous detection of ink.

It is a perspective view which shows the liquid detection sensor which concerns on one Embodiment of this invention. It is the figure which looked at the liquid detection sensor shown in FIG. 1 from the top. It is a figure which shows typically the structure of the liquid detection sensor shown in FIG. It is a figure which shows the usage type of a liquid detection sensor. It is a figure explaining liquid detection.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a perspective view showing a liquid detection sensor according to an embodiment of the present invention, FIG. 2 is a top view of the liquid detection sensor shown in FIG. 1, and FIG. 3 is shown in FIG. It is a figure which shows the structure of a liquid detection sensor typically. A liquid detection sensor 1 shown in each figure is a sensor that detects ink in an intermediate tank 20 (see FIG. 4) mounted on an inkjet printer. The liquid detection sensor 1 includes a case 2, light projecting units 3 and 4, light receiving units 5 and 6, and a prism (reflecting unit) 7. The liquid detection sensor 1 is connected to a control unit 30 (see FIG. 5) of an inkjet printer (not shown), and this control unit 30 is placed in the intermediate tank 20 by a signal (current) output from the liquid detection sensor 1. Control the amount of ink supplied.

  The case 2 is a part that houses the light projecting units 3 and 4 and the light receiving units 5 and 6. The case 2 is formed of a permeable member such as PTFE (Polytetrafluoroethylene). The case 2 includes a flange portion 10 and a main body portion 11 that is connected to the flange portion 10. The flange portion 10 has a parallelogram shape and is a portion attached to the intermediate tank 20. The main body portion 11 includes a first housing portion 12 and a second housing portion 13. The 1st accommodating part 12 and the 2nd accommodating part 13 comprise the rod shape, and are mutually extended in parallel. The first housing portion 12 and the second housing portion 13 have a hollow structure, and each house a substrate (not shown) on which light projecting portions 3 and 4 and light receiving portions 5 and 6 described later are disposed. . The 1st accommodating part 12 and the 2nd accommodating part 13 have a predetermined space | interval, and are spaced apart in the width direction of the collar part 10, and the base end side (anchor of the 1st accommodating part 12 and the 2nd accommodating part 13) The part 10 side) and the tip side are connected by connecting members 14 and 15. That is, in the case 2, the opening 16 is formed between the first housing portion 12 and the second housing portion 13.

  In addition, the flange portion 10 of the case 2 is provided with an insertion portion (both not shown) that communicates with the hollow portions of the first housing portion 12 and the second housing portion 13. The lead wires 17 and 18 connected to the parts 3 and 4 protrude on the opposite side of the first receiving part 12 and the second receiving part 13 in the flange part 10.

  The light projecting units 3 and 4 are portions that irradiate the prism 7 with light. The light projecting units 3 and 4 are, for example, LEDs (Light Emitting Diodes), and are provided on a plurality of (here, two) substrates with a predetermined interval in the extending direction of the first housing unit 12. The interval between the light projecting units 3 and 4 is set according to the maximum capacity and the minimum capacity of ink in the intermediate tank 20. That is, the light projecting unit 3 is set to a position where the ink has the maximum capacity in the intermediate tank 20, and the light projecting unit 4 is set to be the position where the ink has the minimum capacity in the intermediate tank 20. The light projecting parts 3 and 4 are attached to the first accommodating part 12 at positions where the openings 16 are provided. As shown in FIG. 3, the light irradiation direction in the light projecting units 3 and 4 is obliquely upward toward the opening 16 with respect to the arrangement direction of the first housing unit 12 and the second housing unit 13. The light projecting units 3 and 4 emit light under the control of the control unit 30.

  The light receiving parts 5 and 6 are parts that receive the light emitted from the light projecting parts 3 and 4. The light receiving parts 5 and 6 are, for example, photodiodes, and are provided on a plurality of (here, two) substrates with a predetermined interval in the extending direction of the second housing part 13. Specifically, the light receiving parts 5 and 6 are respectively provided in the same straight line as the light projecting parts 3 and 4 in the arrangement direction of the first housing part 12 and the second housing part 13. The light receiving portions 5 and 6 face the opening 16 in the arrangement direction of the first housing portion 12 and the second housing portion 13. That is, the light irradiation direction of the light projecting units 3 and 4 and the light receiving units 5 and 6 do not coincide with each other in the arrangement direction of the first storage unit 12 and the second storage unit 13. The light receiving units 5 and 6 output a current corresponding to the received light to the control unit 30 via the lead wire 18.

  Here, as shown in FIG. 3, a light shielding plate 19 is provided on the opening 16 side of the light projecting units 3 and 4. The light emitted from the light projecting units 3 and 4 by the light shielding plate 19 is not directly received by the light receiving units 5 and 6.

  The prism 7 is a part that reflects the light emitted from the light projecting units 3 and 4. The prism 7 is formed of the same PTFE as the case 2, for example, and has a triangular cross section. The prism 7 is integrally formed with the first housing portion 12. Specifically, the prism 7 is provided corresponding to the position where the opening 16 is provided in the first housing part 12, that is, the mounting position of the light projecting parts 3 and 4. The prism 7 includes an incident surface 7a that receives light emitted from the light projecting units 3 and 4, a reflective surface 7b that contacts the ink and reflects light incident from the incident surface 7a, and contacts and reflects the ink. And an exit surface 7c for emitting the light reflected by 7b. The incident surface 7a is in contact with the light projecting units 3 and 4, and the optical path L between the incident surface 7a and the light projecting units 3 and 5 is isolated from the ink. The direction of light emitted from the emission surface 7 c faces the light receiving parts 5 and 6. That is, the light emitted from the light projecting units 3 and 4 is emitted from the emission surface 7 c of the prism 7 and enters the light receiving units 5 and 6.

  The prism 7 having such a configuration has a predetermined refractive index (absolute refractive index), and the refractive index is, for example, 1.35. The refractive index of the prism 7 is in a predetermined range based on the refractive index of the ink, and the refractive index of the ink is, for example, 1.33 to 1.45. When the relative refractive index with the ink boundary surface in contact with the prism 7 is close to “1”, the light irradiated from the light projecting units 3 and 4 passes through the reflecting surface 7 b with almost no reflection. On the other hand, when the relative refractive index with respect to the ink boundary surface in contact with the prism 7 is larger than “1”, the light irradiated from the light projecting units 3 and 4 is totally reflected on the reflection surface 7b, and the emission surface 7c. The light is emitted from the light toward the light receiving parts 5 and 6.

  With the above configuration, the optical path L is formed between the light projecting units 3 and 4, the prism 7 and the light receiving units 5 and 6 in the liquid detection sensor 1. As shown in FIG. 3, the light path L is formed by the light emitted from the light projecting unit 3 being reflected by the reflecting surface 7 b of the prism 7, emitted from the emitting surface 7 c and received by the light receiving unit 5. ing.

  Next, a liquid detection method in the liquid detection sensor 1 will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram illustrating a usage pattern of the liquid detection sensor, and FIG. 5 is a diagram illustrating liquid detection in the liquid detection sensor. As shown in FIG. 4, the liquid detection sensor 5 is attached to an intermediate tank 20 provided between an ink tank (not shown) and an inkjet head 21 that ejects ink. The intermediate tank 20 stores the ink supplied from the ink tank, and supplies the ink to the inkjet head 21 when pressure is applied by, for example, a pump. In FIG. 4, the light receiving unit 3 of the liquid detection sensor 1 is provided at a position where the maximum capacity of ink (High capacity) is obtained in the intermediate tank 20, and the position of the light receiving unit 4 is the minimum capacity of ink in the intermediate tank 20. (Low capacity) is provided at a position. The liquid detection sensor 1 is connected to the control unit 30 as described above, and emits light from the light projecting units 3 and 4 under the control of the control unit 30 and receives light at the light receiving units 5 and 6. The current is output to the control unit 30.

  First, a method for detecting transparent ink (for example, acidic ink) will be described. Here, the term “transparent” means having transparency. As shown in FIG. 5, when the reflective surface 7b of the prism 7 is in contact with the transparent ink, the relative refractive index between the prism 7 and the boundary surface of the transparent ink is, for example, 1.02. The light emitted from the parts 3 and 4 passes through the reflecting surface 7b of the prism 7 and is emitted to the ink. Therefore, the light received from the light projecting units 3 and 4 is not received by the light receiving units 5 and 6. In this case, in the control unit 30, since there is no response from the light receiving units 5 and 6 to the light irradiation from the light projecting units 3 and 4, the mounting positions of the light projecting units 3 and 4 and the light receiving units 5 and 6; That is, it is determined that the ink is present in the intermediate tank 20 on the optical path L from the light projecting units 3 and 4 to the light receiving units 5 and 6.

  On the other hand, when there is no transparent ink at the mounting position of the light projecting units 3 and 4 and the light receiving units 5 and 6, the refractive index of air is smaller than the refractive index of the prism 7. 4 is totally reflected by the reflecting surface 7 b of the prism 7, emitted from the emitting surface 7 c, and received by the light receiving units 5 and 6. In this case, in the control unit 30, since there is a response from the light receiving units 5 and 6 to the irradiation of light from the light projecting units 3 and 4, the mounting positions of the light projecting units 3 and 4 and the light receiving units 5 and 6; That is, it is determined that ink is not present in the intermediate tank 20 on the optical path L from the light projecting units 3 and 4 to the light receiving units 5 and 6.

  Next, a method for detecting opaque ink (for example, sublimation ink) will be described. Note that the term “opaque” as used herein means that there is no transparency and is suspended by particles (coloring material). As shown in FIG. 5, when the reflecting surface 7b of the prism 7 is in contact with the opaque ink, the light emitted from the light projecting units 3 and 4 passes through the reflecting surface 7b of the prism 7 and becomes ink. Radiated. Therefore, the light received from the light projecting units 3 and 4 is not received by the light receiving units 5 and 6. Even when the ink has a high density of particles and is reflected by the irregular reflection of the ink on the reflecting surface 7b of the prism 7 and is emitted from the emitting surface 7c, the light emitted from the emitting surface 7c is the portion of the opening 16 Since the light is absorbed and scattered by the opaque ink existing between the light projecting units 3 and 4 and the light receiving units 5 and 6, the light receiving units 5 and 6 do not receive light. In this case, in the control unit 30, since there is no response from the light receiving units 5 and 6 to the light irradiation from the light projecting units 3 and 4, the mounting positions of the light projecting units 3 and 4 and the light receiving units 5 and 6; That is, it is determined that the ink is present in the intermediate tank 20 on the optical path L from the light projecting units 3 and 4 to the light receiving units 5 and 6.

  On the other hand, when there is no opaque ink at the mounting position of the light projecting units 3 and 4 and the light receiving units 5 and 6, the refractive index of air is smaller than the refractive index of the prism 7. 4 is totally reflected by the reflecting surface 7 b of the prism 7, emitted from the emitting surface 7 c, and received by the light receiving units 5 and 6. In this case, in the control unit 30, since there is a response from the light receiving units 5 and 6 to the irradiation of light from the light projecting units 3 and 4, the mounting positions of the light projecting units 3 and 4 and the light receiving units 5 and 6; That is, it is determined that ink is not present in the intermediate tank 20 on the optical path L from the light projecting units 3 and 4 to the light receiving units 5 and 6.

  As described above, the ink in the intermediate tank 20 is detected in the liquid detection sensor 1. As a result, the control unit 30 adjusts the ink so that the ink fluctuates within the range of the high capacity and the low capacity of the intermediate tank 20 shown in FIG.

  As described above, the liquid detection sensor 1 includes the light projecting units 3 and 4 that project light, the prism 7 that reflects light, and the light receiving unit 5 that receives light emitted from the emission surface 7 c of the prism 7. , 6. In the liquid detection sensor 1, when no ink is present in the intermediate tank 20, the light emitted from the light projecting units 3 and 4 is totally reflected by the prism 7 and received by the light receiving units 5 and 6. On the other hand, when the intermediate tank 20 is filled with transmissive (transparent) ink, the light emitted from the light projecting units 3 and 4 is not reflected on the reflecting surface 7 b of the prism 7 and is not reflected in the ink. Therefore, light is not received by the light receiving portions 5 and 6. When the non-transparent (opaque) ink is filled in the intermediate tank 20, the light emitted from the light projecting units 3 and 4 is radiated without being reflected by the reflecting surface 7 b of the prism 7. Therefore, no light is received by the light receiving portions 5 and 6. Alternatively, even when the light irradiated from the light projecting units 3 and 4 is reflected by the irregular reflection of the ink on the reflecting surface 7 b of the prism 7 and travels toward the light receiving units 5 and 6, the light is projected away from the prism 7. Since the light is shielded by the ink existing between the light receiving portions 5 and 6, the light is not received by the light receiving portions 5 and 6. As described above, in the liquid detection sensor 1, when the intermediate tank 20 is not filled with ink, the light receiving units 5 and 6 receive light, and when the intermediate tank 20 is filled with ink. In the light receiving parts 5 and 6, no light is received. Therefore, the presence or absence of ink can be detected based on whether or not the light is received by the light receiving portions 5 and 6 even when the ink has transparency or does not have transparency. Therefore, it can respond to various ink types regardless of whether it is transparent or opaque. Further, unlike the magnetic sensor, the float does not stick to the container, so that the ink can be detected stably without erroneous detection. As described above, the liquid detection sensor 1 of the present invention can cope with various ink types and can prevent erroneous detection of ink.

  Further, since the light projecting units 3 and 4 are accommodated in the first accommodating unit 12 and the prism 7 is formed integrally with the first accommodating unit 12, the incident surfaces of the light projecting units 3 and 4 and the prism 7 are formed. The optical path L to 7a is isolated from the ink. Thereby, it is possible to prevent the light irradiated from the light projecting units 3 and 4 from being blocked by the ink while reaching the incident surface 7a. Therefore, ink can be detected more reliably.

  The present invention is not limited to the above embodiment. For example, in the said embodiment, although LED is used as the light projection parts 3 and 4, and the photodiode is used as the light-receiving parts 5 and 6, the light projection parts 3 and 4 should just irradiate light, and the light-receiving part 5 , 6 need only receive light.

  In the above embodiment, two light projecting units 3 and 4 and two light receiving units 5 and 6 are provided, but the number of the light projecting units and the light receiving units can be changed as appropriate.

  In the above embodiment, the light projecting units 3 and 4 and the prism 7 (incident surface 7a) are arranged in contact with each other. However, the light projecting units 3 and 4 and the prism 7 are arranged separately from each other. May be. That is, it is only necessary that the light emitted from the light projecting units 3 and 4 is incident on the prism 7, and it is sufficient that the ink does not intervene in the optical path L from the light projecting units 3 and 4 to the incident surface 7 a.

  DESCRIPTION OF SYMBOLS 1 ... Liquid detection sensor, 3, 4 ... Light projection part, 5, 6 ... Light-receiving part, 7 ... Prism (reflection part), 7a ... Incident surface, 7b ... Reflection surface, 7c ... Output surface, L ... Optical path.

Claims (3)

A liquid detection sensor provided in a container for detecting a liquid in the container,
A light projecting unit that emits light;
It has a refractive index within a predetermined range based on the refractive index of the liquid, and enters an incident surface that receives light emitted from the light projecting unit, and contacts the liquid and reflects the light incident from the incident surface. A reflecting portion having a reflecting surface and an emitting surface that comes into contact with the liquid and emits the light reflected on the reflecting surface;
A liquid detection sensor, comprising: a light receiving portion that is provided apart from the light projecting portion and the reflecting portion and receives light emitted from the emission surface.   The liquid detection sensor according to claim 1, wherein an optical path from the light projecting unit to the incident surface is isolated from the liquid. A liquid detection method for detecting a liquid in the container by a liquid detection sensor provided in the container,
The liquid detection sensor is
A light projecting unit that emits light;
It has a refractive index within a predetermined range based on the refractive index of the liquid, and enters an incident surface that receives light emitted from the light projecting unit, and contacts the liquid and reflects the light incident from the incident surface. A reflecting portion having a reflecting surface and an emitting surface that comes into contact with the liquid and emits the light reflected on the reflecting surface;
A light receiving portion that is provided apart from the light projecting portion and the reflecting portion, and that receives light emitted from the emission surface;
When light is received by the light receiving unit, it is determined that there is no liquid in the optical path from the light projecting unit to the light receiving unit,
A liquid detection method, comprising: determining that the liquid is in the optical path when no light is received by the light receiving unit.

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