1. Field of the Invention
The present invention relates to an ink remaining amount detecting device that detects the amount of ink remaining in an ink tank, a method for detecting the amount of remaining ink, and an ink jet printing apparatus with an ink remaining amount detecting function.
2. Description of the Related Art
Ink tanks in which ink to be supplied to an ink jet printing apparatus is stored are now known to be in various forms. Examples of forms in which ink is stored in an ink tank include a sponge scheme of storing the ink in the ink tank by allowing the ink to permeate a sponge housed inside the ink tank, a real tank scheme of storing the ink directly inside the ink tank, and a bag scheme of storing the ink in a flexible bag. The sponge scheme involves the sponge placed inside the ink tank and thus a reduced amount of stored ink with respect to the volume. Furthermore, the bag scheme involves the need to protect the bag in which the ink is housed with a casing, thus reducing the amount of stored ink with respect to the overall volume. The real tank scheme has the highest volumetric efficiency. However, even ink tanks adopting the real tank scheme pose the following challenges regarding a function to detect the amount of ink remaining inside the ink tank.
In general, ink jet printing apparatuses have a function to, for example, warn a user or shut down the ink jet printing apparatus when the amount of remaining ink reaches a specified threshold value. Such a warn function, shutdown function, and the like act importantly in preventing possible inappropriate printing caused by a shortage of ink. On the other hand, the function may make a user dissatisfied with the inability to use a certain amount of ink remaining. To avoid such dissatisfaction, a remaining amount detecting device is required which can constantly accurately detect a small amount of ink.
Examples of current remaining amount detecting devices that detect the amount of ink remaining in the ink tank include a dot count scheme, a float scheme, and a prism scheme. The dot count scheme counts the number of ink ejections based on image data to calculate the amount of remaining ink based on the count value, and has the advantage of eliminating the need to add components. However, the ejection amount of nozzles may be varied by a variation in the temperature of a print head, a variation among manufactured products, or the like, resulting in a great difference between actual ink consumption and calculated ink consumption.
Furthermore, the float scheme uses a configuration in which a float migrating according to the level of the ink is placed in the ink tank and in which an optical sensor senses the position of the ink. This configuration disadvantageously requires a large space and is unsuitable for detecting a small amount of ink.
On the other hand, the prism scheme provides a triangle pole-shaped prism formed of a transparent resin member inside the ink tank so that the presence or absence of the ink is detected by detecting the presence or absence of light reflected by the prism to which the light has been delivered. An optical sensor with a light emitting element and a light receiving element irradiates the prism with light and detects reflected light. According to the prism scheme, light delivered toward the prism by the light emitting element enters the interface between the inside of the ink tank and the prism at an angle of 45°. The light entering the interface at an angle of 45° penetrates the interface between the resin and the ink, while being reflected by the interface between the resin and air due to a difference in refractive index. As a result, when an amount of ink is present, the light emitting element fails to detect light. When no ink is present, light is reflected and the reflected light is detected by the light receiving element. Thus, an output signal from the light receiving element allows the presence or absence of ink in the ink tank to be detected.
As described above, the prism scheme directly detects the position of the level and is thus more accurate than the dot count scheme. Moreover, advantageously, the prism itself can be molded integrally with other members using resin, and can thus be appropriately recycled and formed to be small.
However, the prism scheme poses the following problems. That is, if the ink tank is left stationary over a long period, the ink may adhere to the surface of the prism. As a result, even when the ink in the ink tank is exhausted, erroneous detection of the presence of ink may be caused by the ink adhering to the prism surface. To avoid such erroneous detection, emission intensity may be increased. However, disadvantageously, when the amount of remaining ink is detected with the emission intensity kept high, the life of the light emitting element is significantly shortened. Furthermore, a common method for preventing a possible increase in load on the light emitting element is to apply a water repellent to the prism surface in order to smoothly remove the ink that is in contact with the prism surface. However, precisely applying the water repellent to the prism surface is difficult, disadvantageously complicating manufacturing steps and increasing the cost of the ink tank.
Furthermore, as a method of avoiding the use of a water repellent, a technique has been disclosed which forms a groove laterally to the prism so that the capillary force of the groove can draw the ink adhering to the prism surface into the groove for removal (Japanese Patent Laid-Open No. 2000-71471). However, the technique disclosed in Japanese Patent Laid-Open No. 2000-71471 has difficulty molding a fine groove laterally to the prism and thus needs to overcome practicability and accuracy problems.
Moreover, a technique has been disclosed which sets the emission intensity of the light emitting element to a large value so that reflected light from an ink tank with the lowest reflectance can be detected based on information from the light receiving sensor (Japanese Patent Laid-Open No. 2003-89218). However, the technique disclosed in Japanese Patent Laid-Open No. 2003-89218 emits light with a high emission intensity not only to an ink tank with a low reflectance but also to an ink tank with a high reflectance. Thus, disadvantageously, the life of the light emitting element is significantly reduced.
An object of the present invention is to provide an ink remaining amount detecting device which uses a light emitting unit irradiating a reflection surface provided on an ink tank with light and a light receiving unit receiving reflected light from the reflection surface and which can accurately determine whether or not the amount of ink remaining in an ink tank has reached a specified value with a decrease in the life of the light emitting unit suppressed.
In order to accomplish this object, the present invention is configured as follows.
The present invention provides an ink remaining amount detecting device that determines whether an amount of ink remaining in an ink tank is smaller than a predetermined value, the device comprising: a reflector provided in the ink tank and in which an optical reflectance obtained in the case where the amount of ink remaining in the ink tank is smaller than the predetermined value is higher than an optical reflectance obtained in the case where the amount of ink remaining in the ink tank is equal to or larger than the predetermined value; a light emitting unit configured to generate light allowed to enter the refection surface; a light receiving unit configured to receive light reflected by the reflector and outputting an output signal according to an amount of received reflected light; a control unit configured to perform light emission control that switches an emission intensity of the light emitting unit among a plurality of levels; and a determination unit configured to determine whether or not the amount of ink remaining in the ink tank has reached the predetermined value based on the output signal output by the light emitting unit, wherein the determination unit determines whether or not the amount of ink remaining in the ink tank has reached the predetermined value based on a difference between output signals each output by the light receiving unit according to a corresponding each of at least two of the plurality of levels of light emissions from the light emitting unit.
The present invention allows light with the intensity thereof varied among the plurality of levels to enter the reflection surface of the ink tank, and determines whether or not the amount of ink remaining in the ink tank has reached the specified value based on the difference between the amounts of reflected light for the respective levels of emission intensity. Thus, even if the ink is likely to adhere to the reflection surface, whether or not the amount of ink remaining in the ink tank has reached the specified value can be accurately determined, with the emission intensity of the light emitting means suppressed. Thus, the life of the light emitting means can be improved.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment of the present invention will be described below with reference to the drawings.
(i) When the ink in the channel 2 is consumed and air enters the channel 2 to eliminate the water head difference between the level of the ink and the surface of the nozzles, the force of the nozzles acting to hold the ink decreases. Then, the ink may leave the nozzles and stain the conveying path for the print medium or the print medium itself.
(ii) When the ink is continuously ejected with no ink remaining, the ink in the nozzles is also exhausted and heat from the heaters is excessively accumulated, making the heaters defective.
Thus, if the amount of remaining ink decreases to zero, a warning needs to be issued or the printing operation needs to be automatically stopped. To that end, if the amount of ink remaining in the ink tank 24 reaches a predetermined value, this needs to be accurately detected.
To accurately determine whether or not the amount of ink remaining in the ink tank 24 is smaller than a predetermined value, the present embodiment optically detects the amount of remaining ink. Thus, according to the present embodiment, the ink tank is configured as shown in
The liquid chamber 6 includes an inclined surface 7 at the bottom thereof so that the amount of remaining ink is minimized when the printing operation is stopped as a result of detection of an ink exhausted state. The ink is guided to an opening end 8a of the supply pipe 8 arranged inside the ink tank 24. Moreover, to deal with a slight variation in the detection of the ink exhausted state, a recessed portion 7a recessed downward from the inclined surface 7 is formed near the opening end 8a of the supply pipe. Thus, even with a slight variation in the detection of the ink exhausted state, entry of air into the channel can be avoided which may result from consumption of the ink in the recessed portion 7a.
The injection port 9 and the atmospheric communicating port 11 are closed by a slitted rubber stopper 12 during transportation to prevent possible entry of the outside air and leakage of the ink. When the ink tank 24 is installed in the main body section 1 of the printing apparatus, a hollow metal needle-like joint section 17 pushes its way through the slit in the rubber stopper 12 into the ink tank 24 to cancel the closed state of the ink tank 24. When the main body section 1 of the printing apparatus is thus connected to the ink tank 24, the ink is supplied to the print head 25 through the injection port 9 in the ink tank 24 via the needle-like joint section 18. Moreover, the space in the ink tank 24 communicates with the air via the needle-like joint section 18 to admit the air into the ink tank through the atmospheric communicating port 11.
Furthermore, in the ink tank 24, a nonvolatile storage element 15 is provided above the atmospheric communicating port 11. The nonvolatile storage element 15 includes an EEPROM substrate and is bonded to a protective case 16. When the ink tank 24 is installed in the main body section 1, the storage element 15 comes into contact with a read terminal (not shown in the drawings) on the main body section 1 so that a CPU provided in the main body section 1 and described below can write and read information to and from the storage element. The following are written to the storage element 15: information such as the colors of the ink housed in the ink tank 24, the date of manufacture of the ink tank 24, and the manufacturer' serial number of the ink tank 24, as well as data on the consumption of ink transmitted from the main body section 1. The consumption of ink is data calculated using the dot count scheme of counting the cumulative total number of times that ink in each color is ejected based on printed image data. Additionally, the amount of ink consumed during a recovery operation of sucking the ink from the nozzles to recover the ejection performance of the nozzles may be converted into an ejection-equivalent amount, which may then be added to a dot count value for a printing operation. The read terminal contacting the EEPROM and the CPU described below form read means. In addition, the present embodiment performs an operation of recovering the print head 25 by covering the ejection port in the print head 25 with a cap 6 shown in
Now, a general configuration of a control system provided in the ink jet printing apparatus according to the present embodiment will be described based on
In
Now, the configuration and operation of the detecting device that detects the amount of remaining ink according to the present embodiment will be described in detail.
As shown in
Furthermore, an optical sensor 50 with a light emitting element 30 and a light receiving element 40 (see FIG. 7A to
The present embodiment can perform light emission control so as to switch the emission intensity of the light emitting diode 30 among a plurality of levels by switching among the plurality of resistors to allow one of the resistors to be used. For example, a driving circuit for the light emitting diode 30 shown in
Light emitted by the light emitting diode 30 perpendicularly enters the bottom surface of the prism 14 and passes through the interior of the prism 14. As shown in
In general, when light from a substance with a refractive index nB enters a substance with a refractive index nA at an angle θm, the incident light is reflected by an interface between the two substances provided that the following condition holds true.
sin θm=sin θm/sin 90°≧nA/nB (Expression 1)
Here, when the condition according to the present embodiment is applied to Expression 1, since θm=45° and nB=1.46 (the refractive index of resin of the prism), the condition that light having entered the prism 14 is totally reflected by the slope 14a is as shown by:
nA≦nB/sin θm=1.46/sin 45°=1.05 (Expression 2)
Thus, if the substance adjacent to the prism 14 has a refractive index of at most 1.05, the light is reflected in an X direction shown in
If the ink is stored in the ink tank up to a height equal to or greater than the height of the point (light spot) on the reflection surface 14a of the prism 14 where the prism 14 is irradiated with the light from the light emitting element, the incident light is prevented from entering the light receiving element 40 as shown in
Now, a light receiving and detecting circuit for use in the present embodiment will be described based on
The light receiving and detecting circuit for use in the present embodiment includes the light receiving element 40 formed of a phototransistor and a resistor R connected to a collector (C) of the phototransistor 40. A power supply voltage Vcc is applied to between one end of the resistor R and an emitter (E) of the phototransistor 40.
The phototransistor 40 includes a light receiving section positioned so as to be able to receive reflected light from the reflection surface 14b of the prism 14. A current (photoelectric current Ic) flows between the collector and emitter of the phototransistor 40. The power supply voltage Vcc is 3.3 V. The CPU 100 detects a voltage Vo between the collector and the emitter. The detected voltage Vo is the difference in voltage between the power supply voltage Vcc and a voltage drop caused by the resistor R. That is, Vo=Vcc−Ir×R.
However, if the prism 14 is used to detect the presence or absence of ink in the ink tank 24, the presence is erroneously detected depending on the state of the ink in contact with the prism 14. For example, when the ink is fixed to the prism surface to form an ink film, if the ink in the liquid chamber is exhausted, the ink film formed on the prism surface may cause the presence of ink to be erroneously detected. Such a phenomenon is likely to occur when the ink tank 24 is left unattended for a long period or when ink with a low capillary force is stored in the ink tank 24.
Thus, in a situation where an ink film is formed on the surface of the prism 14, the amount of light entering the light receiving section 40a is unstable. A variation in the amount of light received may cause an error in the detection of the amount of remaining ink. That is, the amount of ink entering the light receiving section 40a is smaller when an ink film is formed on the prism 14 than when no ink film is formed on the prism 14. Hence, even with the ink in the ink tank 24 exhausted, the presence of ink may be erroneously detected. The amount of decrease in the amount of light received is significantly affected by the degree of adhesion of the ink film (the thickness of the film and the area of the light spot), the type of the ink (light absorption property), and the amount of light from the light emitting diode 30. In contrast, if both the emission intensity of the light emitting diode 30 and the amount of light received by the light emitting section 40a are increased, then even with an ink film formed on the surface of the prism 14, the amount of light received by the light emitting section 40a can be increased. This enables possible erroneous detection to be prevented. However, the increased emission intensity causes the light emitting diode to be prematurely degraded, reducing the life of the light emitting diode.
Thus, the present embodiment enables the emission intensity of the light emitting diode to be switched among a plurality of levels so that the emission intensity is increased only at the appropriate timing. This prevents erroneous detection caused by an ink film formed on the surface of the prism 14, thus precluding the life of the light emitting diode 30 from being reduced.
If the processing from step S1 to step S7 selects the table 1, Lv1 is selected as the low emission intensity, Lv2 is selected as the medium emission intensity, and Lv3 is selected as the high emission intensity. The emission intensity Lv1 is obtained by setting the forward current IF through the light emitting diode 30 to 10 mA. Furthermore, the emission intensity Lv2 is obtained by setting IF to 20 mA, and the emission intensity Lv3 is obtained by setting IF to 30 mA. An emission intensity Lv4 is obtained by setting IF to 35 mA, and an emission intensity Lv5 is obtained by setting IF to 50 mA. Thus, if the table 1 is selected, currents of 10 mA, 20 mA, and 35 mA are set in order to obtain the three levels of emission intensity, the low, medium, and high emission intensities. Furthermore, if the table 2 is selected, currents of 10 mA, 35 mA, and 50 mA are set in order to obtain the low, medium, and high emission intensities. If the table 3 is selected, currents of 10 mA, 50 mA, and 100 mA are set in order to obtain the low, medium, and high emission intensities. Thus, according to the present embodiment, the higher emission intensities are used for the ink tank with a longer elapsed time. This is because the ink in contact with the prism for a longer period is more likely to adhere to the surface of the prism 14. According to the present embodiment, the amount of light emitted by the light emitting diode 30 in terms of radiant flux is 0.4 mW for Lv1, 0.9 mW for Lv2, 1.5 mW for Lv3, 2.4 mW for Lv4, and 5.2 mW for Lv5. The radiant flux is used as a unit of the amount of light because the light emitting element used in the present invention involves invisible light such as infrared light, so that the use of the radiant flux, the amount of light irrelevant to wavelength, is determined to be more appropriate than the use of a unit such as illuminance, which is affected by visibility.
Now, the detection of the amount of ink remaining in the ink tank 24 during a printing operation will be described.
During a printing operation, the emission intensity of the light emitting diode 30 is switched among the three levels, that is, the low, medium, and high levels as necessary to detect the amount of remaining ink, as shown in a flowchart in
Thereafter, in step S12, the CPU 100 determines whether or not an output voltage from the phototransistor 40 (the voltage between the collector and emitter of the phototransistor 40) is equal to or smaller than a preset threshold value, and if the output voltage is equal to or smaller than the preset threshold value, determines that the ink is exhausted to stop the printing operation (step S13). Furthermore, in step S12, if the detected voltage of the phototransistor 40 exceeds the threshold value, the CPU 100 shifts to step S14.
In step S14, the CPU 100 compares the detected voltage Vo obtained if the emission intensity is low with the detected voltage Vo obtained if the emission intensity is medium to determine whether or not the difference between these detected voltages (voltage difference) has reached a preset specified value (for example, 0.4V). If the voltage difference is smaller than the specified value, the CPU 100 determines that an amount of ink is present in the ink tank to continue the printing operation. Then, the processing in steps S14 and S16 is repeated until in step S14, the voltage difference between the detected voltage Vo obtained if the emission intensity is low and the detected voltage Vo obtained if the emission intensity is medium becomes equal to the specified value.
Furthermore, in step S14, if the voltage difference is determined to be equal to or greater than the specified value, the CPU 100 determines that although the ink is exhausted, that is, the level of the ink is below the light spot of the prism 14, an ink film may be formed on the prism. In this case, in step S15, the CPU 100 sets the emission intensity of the phototransistor 40 to the high level. That is, the forward current IF through the light emitting diode 30 is set according to one of the tables 1, 2, and 3 in
As described above, the present embodiment determines whether or not the voltage difference between the detected voltage Vo obtained if the emission intensity is low and the detected voltage Vo obtained if the emission intensity is medium is equal to the specified value, and according to the result of the determination, determines whether or not an ink film is formed on the surface of the prism. The determination based on the potential difference can be achieved for the following reason.
First, with reference to
As shown in
With reference to
In contrast, in an area where an ink film is formed, when the forward current IF setting the emission intensity of the light emitting diode 30 to the low level is 10 mA, the photoelectric current Ic is 3.7 μA, and the detected voltage Vo is 2.49 V. This indicates the result of a decrease in the amount of reflected light resulting from the formation of an ink film on the surface of the prism 14 as described above. Furthermore, when the forward current IF setting the emission intensity to the medium level is 20 mA, the detected voltage Vo is 1.96 V. In this case, the detected voltage Vo is also lower than in the ink exhausted state, but there is a voltage difference of 0.53 V in detected voltage between the case of IF=10 mA and the case of IF=20 mA. That is, in this case, the detected voltage Vo is outside the saturated region and is thus subjected to a marked voltage difference even with only a slight difference in photoelectric current Ic.
Thus, the difference in detected voltage between the irradiation of the prism 14 with light with the low emission intensity and the irradiation of the prism 14 with light with the medium emission intensity is more significant when an ink film is formed at the spot on the surface of the prism 14 where the prism 14 is irradiated with light from the light emitting diode 30 than when no ink is present on the surface of the prism 14. Thus, the CPU 100 determines that an amount of ink remains in the ink tank 24 if the difference in detected voltage between the case where the emission intensity with respect to the prism 14 is low and the case where the emission intensity with respect to the prism 14 is medium is smaller than the specified value (0.4 V). Furthermore, if the voltage difference is equal to or greater than the specified value (0.4 V), the CPU 100 determines that an ink film adheres to the prism surface.
Now, processing following step S15 will be described with reference to
If the detected voltage Vo obtained at the high emission intensity is equal to or lower than the threshold voltage, the CPU 100 determines that the ink is exhausted to stop the printing operation (step S18). Furthermore, if the detected voltage Vo is equal to or greater than 1.65 V, the CPU 100 determines that an amount of ink is present (step S19). Thereafter, the CPU 100 shifts to step S15 to continue emitting light with the high emission intensity. In this case, the light emission with the high emission intensity is continued in order to carry out quick detection because if the difference in detected voltage between light emission with the low emission intensity and light emission with the medium emission intensity is equal to or greater than 0.3 V, the level of the ink in the ink tank 24 may be positioned at a height such that the level overlaps apart of the spot on the prism surface where the prism is irradiated with light.
In the example of the ink tank 24 with an elapsed time of one month, the forward current IF for light emission with the high emission intensity is 35 mA, and when the detected voltage Vo becomes equal to or lower than 1.65 V, the CPU 100 determines that the ink is exhausted to stop the printing operation. The present embodiment sets the threshold for the voltage difference between the light emission with the low emission intensity and the light emission with the medium emission intensity to 0.4 V. The threshold is set to 0.4 V because when light is emitted at the high emission intensity, for example, the photoelectric current Ic is increased by slight reflection of light having impinged on a surface other than the surfaces of the prism, resulting in a difference of about 0.3 V between the high level light and the low level light when an amount of ink is present.
The example of detection of the amount of ink remaining in the ink tank 24 with an elapsed time of one month from manufacture has been described. However, the table 2 in
As described above, the present embodiment repeats the light emissions with the low and medium emission intensities until the amount of ink remaining in the ink tank 24 becomes equal to or smaller than the specified value, and switches to the light emission with the high emission intensity when the amount becomes equal to or smaller than the specified value. Thus, compared to the conventional technique for detecting the amount of remaining ink which technique constantly provides the light emission with the high emission intensity, the present embodiment significantly extends the life of the light emitting diode 30 and also allows the absence of ink to be accurately detected without causing a marked delay in the detecting operation.
In the new ink tank 24, the ink leaves the prism surface almost simultaneously with a decrease in the level of the ink. Thus, for all of the light emissions with the low, medium, and high emission intensities, the detected voltage Vo varies sharply from the maximum value to the minimum value. According to the present embodiment, the detected voltage corresponding to the light emission with the low emission intensity alternated with the detected voltage corresponding to the light emission with the medium emission intensity, and when a remaining amount A in
As shown in
The above-described measurement results indicate that light emission in the appropriate amount at the appropriate timing according to the present embodiment inhibits a possible delay in detection caused by adhesion of ink to the prism surface and prevents a possible decrease in the life of the light emitting element.
The above-described embodiment sets three of the five levels of emission intensity to be the low, medium, and high emission intensity based on the elapsed time of the ink tank 24 from the date of manufacture to the current time. However, if the ink is unlikely to be altered or a large amount of ink is consumed leading to frequent replacements of the ink tank 24, the three levels of emission intensity, the low, medium, and high emission intensity, may be fixed to certain values. Alternatively, the emission intensity of the light emitting diode 30 may be switched among four or at least six levels. Moreover, the switching of the emission intensity of the light emitting diode 30 is not limited to the switching of the current limiting resistor connected to the light emitting diode 30 as in the case of the above-described embodiment. The switching may be carried out according to a well-known PWM scheme.
Moreover, the present invention is not limited to the switching among the three levels of emission intensity, the low, medium, and high emission intensities, which switching is carried out during the use of the ink tank 24. That is, the presence or absence of ink can be detected by switching the emission intensity among at least four levels of emission intensity. For example, the emission intensity can be switched among four levels, that is, a low emission intensity, a medium low emission intensity, a medium emission intensity, and a high emission intensity. In this case, in the beginning of the use, the following control is repeated: the emission intensity of the light emitting element is sequentially switched among at least two levels, for example, among the low, medium low, and medium emission intensities. Then, when the voltage difference between two of three detected voltages associated with the three levels of emission intensity reaches a specified value, the light emission is switched to the high emission intensity. Possible combinations of two detected voltages for the voltage difference include, for example, a combination of the detected voltage associated with the light emission with the low emission intensity and the detected voltage associated with the light emission with the medium emission intensity and a combination of the detected voltage associated with the light emission with the medium low emission intensity and the detected voltage associated with the light emission with the medium emission intensity. Another possible combination is the detected voltage associated with the detected voltage associate with the light emission with the medium low emission intensity and the detected voltage associated with the light emission with the medium emission intensity. Then, when the voltage difference between at least one combination of the detected voltages reaches a preset value, the light emission is switched to the high emission intensity. This allows more assured switching to the light emission with the high emission intensity to be achieved, resulting in higher reliability.
The above-described embodiment changes the emission intensity of the light emitting element is changed according to the elapsed time of the ink tank 24. However, the emission intensity of the light emitting element may be controlled with conditions other than the elapsed time of the ink tank 25 taken into account.
For example, the emission time of the light emitting element may be measured by the CPU 100 so that the emission intensity of the light emitting element can be increased every time the measured elapsed time increments by a specified value. Moreover, an environment sensor may be provided which detects the environmental temperature around the ink tank 24 or the ink jet printing apparatus so that the emission intensity of the light emitting element can be controlled based on the environmental temperature. Furthermore, when the current posture of the ink tank 24 during use is inclined to the reference posture of the main body section of the printing apparatus or the ink tank 24, the amount of remaining ink may be excessively small when the level corresponding to the ink exhausted state is reached as shown in
As described above, the presence or absence of ink can be more accurately detected by controlling the emission intensity with conditions other than the elapsed time of the ink tank 24 taken into account.
Furthermore, the above-described embodiment determines whether or not the ink in the liquid chamber is exhausted by arranging the reflection surface 14a of the prism 14, serving as a reflector, at the same position as that of the inclined surface 7 forming the bottom of the liquid chamber of the ink tank 24 or a position below the inclined surface 7. However, the present invention is not limited to the detection of the presence or absence of ink in the ink tank 24 or the liquid chamber. That is, the present invention determines whether or not the amount of ink remaining in the ink tank 24 is smaller than a predetermined value and allows the amount of remaining ink serving as reference for detection (predetermined amount) to be varied depending on the position where the reflector is provided. For example, the present invention can determine whether the amount of remaining ink is less than 20%, 30%, or 50% of the volume of the ink tank 24, and the above-described predetermined amount can be optionally set.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2011-155587, filed Jul. 14, 2011, which is hereby incorporated by reference herein in its entirety.
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20130016153 A1 | Jan 2013 | US |