Patent Publication Number: US-7905565-B2

Title: Recording apparatus and method for detecting the position of an ink container

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following applications, all of which are filed on the same day and assigned to the same assignee as the present application: 
     “Recording Apparatus for Detecting Position of Ink Tank and Position Detecting Method of the Ink Tank” U.S. application Ser. No. 11/424,944 
     “Recording Apparatus Capable of Checking Positions of Ink Containers, and Method for Checking the Positions” U.S. application Ser. No. 11/424,950 
     “Ink Tank Position Detection Method” U.S. application Ser. No. 11/424,940 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a position checking method, and more particularly to a position checking method in which the mounting positions of ink tanks are specified in a recording apparatus. 
     2. Related Background Art 
     According to recent demands for further improve image quality, not only four popular color inks (black, yellow, magenta, and cyan), but also a light magenta ink and a light cyan ink having low density have been used. Further, the use of so-called special color inks such as red ink and blue ink has also been proposed. When these inks are used, seven or eight ink tanks corresponding to the colors are individually mounted in an inkjet printer. In this case, a mechanism is necessary to prevent the ink tanks from being mounted at wrong positions. Japanese Patent Laid-Open No. 2001-253087 discloses that the engaged portions between a carriage and ink tanks have different shapes. This prevents the ink tanks from being mounted improperly. 
     In order to specify the mounting positions of the ink tanks, the engaged portions between the carriage and the ink tanks have different shapes, as described above. In this case, however, it is necessary to produce ink tanks that have different shapes corresponding to the colors and types of ink. This is disadvantageous in terms of production efficiency and cost. 
     As another method, it is conceivable to separately provide different circuit signal lines of circuits, which are formed by connecting electrical contacts of ink tanks and electrical contacts provided at the mounting positions of the ink tanks in a carriage of a main unit, corresponding to the mounting positions. For example, it is conceivable to respectively provide different signal lines corresponding to the mounting positions in order to read ink color information from the ink tanks, and to control lighting of LEDs. When the color information read from any of the ink tanks does not correspond to the mounting position, it is determined that the ink tank is mounted improperly. 
     However, when the signal lines are thus separately provided corresponding to the ink tanks or the mounting positions, the number of signal lines increases. In particular, there is a tendency to improve image quality by increasing the number of types of inks in recent inkjet printers, as described above. In these printers, particularly, the increase in the number of signal lines increases the cost. A so-called bus connection using a common signal line is effective in reducing the number of signal lines. However, it is apparent that the ink tank or the mounting position of the ink tank cannot be determined by simply using a common signal line like a bus connection. 
     Accordingly, a position checking method is conceivable in which lighting of LEDs at mounting positions of a plurality of ink tanks is controlled by a common signal line, and in which the mounting positions of the ink tanks can be determined. However, the amount of emitted light varies among the LEDs, and therefore, the amount of light received by a light receiver provided in the printer also varies. For this reason, it is sometimes difficult to check the presence or absence of emitted light with reference to a threshold value depending on the amount of received light, and to thereby check the positions of the ink tanks. Although this problem can be solved by reducing the variation in the amount of emitted light, the cost is increased, for example, because there is a need to screen LEDs. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a position checking method that can specify mounting positions of liquid containers, such as ink tanks. 
     According to an aspect of the present invention, a recording apparatus includes a carriage, a plurality of ink containers detachably mounted in the carriage and having respective light emitting portions, a light receiving portion configured to receive light from the light emitting portions, where the position of the plurality of ink containers are determined based on the light that is emitted from the light emitting portions and received by the light receiving portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A ,  1 B,  1 C and  1 D are schematic views showing a position checking procedure according to a first embodiment of the present invention. 
         FIGS. 2A ,  2 B,  2 C and  2 D are schematic views showing the position checking procedure according to the first embodiment of the present invention. 
         FIGS. 3A ,  3 B,  3 C and  3 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 4A ,  4 B,  4 C and  4 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 5A ,  5 B,  5 C and  5 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 6A ,  6 B,  6 C and  6 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 7A ,  7 B,  7 C and  7 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 8A ,  8 B,  8 C and  8 D are schematic views showing the position detecting procedure according to the first embodiment of the present invention. 
         FIGS. 9A and 9B  are schematic views showing a position detecting procedure according to a second embodiment of the present invention. 
         FIGS. 10A ,  10 B and  10 C are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 11A ,  11 B and  11 C are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 12A and 12B  are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 13A and 13B  are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 14A ,  14 B and  14 C are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 15A ,  15 B and  15 C are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIGS. 16A and 16B  are schematic views showing the position detecting procedure according to the second embodiment of the present invention. 
         FIG. 17  is a side view of an ink tank according to an embodiment of the present invention. 
         FIG. 18  is a perspective view of an ink jet printer which effects recording with the ink tank mounted therein. 
         FIG. 19  is a perspective view of the ink jet printer with a main body cover shown in  FIG. 18  detached therefrom. 
         FIG. 20  is a conceptual view showing signal lines for connection between the inkjet printer and the ink tanks in conjunction with substrates of the ink tanks. 
         FIG. 21  is a circuit diagram showing the configurations of a light emitting circuit of the ink tank and a light receiving circuit of a light receiving portion. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     First Embodiment 
       FIG. 17  is a side view showing a form of an ink tank according to a first exemplary embodiment of the present invention. A substrate  100  having an LED  101  mounted thereon is carried on an ink tank  1 . Light emitted from the LED  101  is guided in a light guide  20 , is reflected by an inclined portion  28 , and is emitted toward the right side of the ink tank  1  in  FIG. 17 , thus forming an optical path  111 . 
       FIG. 18  depicts an ink jet printer  200  which effects recording with the above-described ink tank  1  mounted therein, while  FIG. 19  is a perspective view showing a state in which a main body cover  201  shown in  FIG. 18  has been opened. 
     As shown in  FIG. 18 , a main part of the inkjet printer  200  is formed by a mechanism that performs recording by scanning a carriage  205  ( FIG. 19 ) on which recording heads and ink tanks are mounted. The main part is covered with the main body cover  201  and other case portion, sheet discharge trays  203  provided before and behind it, and an automatic sheet feeder (ASF)  202 . The inkjet printer  200  also includes an operating unit  213  having a display that indicates the condition of the inkjet printer  200  in both a state in which the main body cover  201  is closed and a state in which the main body cover  201  is opened, a power supply switch and a reset switch. 
     In the state in which the main cover  201  is opened, as shown in  FIG. 19 , a user can see a range in which the carriage  205  carrying a recording head unit  105  and ink tanks  1 K,  1 C,  1 M and  1 Y (hereinafter these ink tanks are sometimes by the same reference numeral “ 1 ”) mounted thereon moves, and the surroundings of the range. In actuality, when the main cover  201  is opened, a sequence in which the carriage  205  is automatically moved to almost the center position (hereinafter referred to as the “tank interchanging position”) shown in  FIG. 19  is performed. The user can replace each tank at the tank interchanging position. 
     The recording head unit  105  includes chip-shaped recording heads (not shown) corresponding to the ink of each color in the recording head unit  105 . The recording heads are scanned over a recording medium, such as a sheet of paper, by the movement of the carriage  205 , and discharge ink onto the recording medium during the scanning operation to thereby affect recording. That is, the carriage  205  is slidably engaged with a guide shaft  207  that extends in the movement direction thereof and can be moved by a carriage motor and a mechanism for transmitting the driving force from the carriage motor. Therefore, respective recording heads corresponding to K, C, M and Y color inks effect ink discharge on the basis of discharge data sent from a control circuit on a main body side via a flexible cable  206 . A sheet feeding mechanism, including a sheet feeding roller and an ejection roller, is also provided to convey a recording medium (not shown) supplied from the automatic sheet feeder  202  onto the ejection tray  203 . The recording head unit  105 , with which ink tank holders are integrally provided, is detachably mounted on the carriage  205 . The ink tanks  1  are detachably mounted with respect to the recording head unit  105 . 
     During recording, each of the recording heads is scanned while discharging ink onto the recording medium to record in a region having a width corresponding to discharge openings of the recording head. Also, the recording medium is conveyed by a predetermined amount corresponding to the above-described width by the sheet feeding mechanism between scanning operations, so that recording on the recording medium is performed sequentially. A discharging recovery unit, such as a cap, is provided at an end of the range, in which the recording heads are moved by the movement of the carriage  205 , to cover surfaces of the recording heads on which the discharge openings are provided. The recording heads are moved to the recovery unit at predetermined time intervals so as to be subjected to recovery operation such as preliminary discharging. 
     The recording head unit  105  provided with the tank holders for the ink tanks  1  has connectors corresponding the ink tanks  1 , as described above. Each of the connectors is in contact with a pad of the substrate provided on the corresponding ink tank  1 . This allows control of turning on or turning off of each LED  101 . 
     More specifically, at the above-described tank interchanging position, when the amount of ink remaining in each ink tank  1  becomes low, the LED  101  corresponding to the ink tank  1  is turned on or turned off. In this case, the user can observe light guided from the LED  101  in the light guide  20  by viewing the ink tank  1  from above the ink jet printer  200 . 
     A light receiving portion  210  having a light receiving element is provided near the end portion of the movement range of the carriage which is opposite the position at which the above-described recording unit is provided. Thus, when the LED  101  of each ink tank  1  passes the light receiving portion  210  during the movement of the carriage  205 , the LED  101  of each ink tank  1  is turned on (i.e., emits light), and the light emitted by the LED  101  is received by the light receiving portion  210 . Based on the position of the carriage  205  when the light is received, the position of each ink tank  1  on the carriage  205  can be detected. Further, as another example of controlling lighting (i.e., turning on) of the LED  101 , when the ink tank  1  has been properly mounted at the tank interchanging position, the control of turning on the LED  101  of that tank is affected. This control, like the control of ink discharge by the recording heads, is executed according to control data (control signal) transmitted from a control circuit on the main body side to each ink tank through the flexible cable  206 . 
       FIG. 20  shows a wiring structure in the flexible cable  206  for connecting the ink tanks  1  and a control circuit  300  in conjunction with substrates  100  of the ink tanks  1 . 
     As shown in  FIG. 20 , the wiring structure for the four ink tanks  1  is comprised of four signal lines, and is common to the four ink tanks  1  (so-called bus connection). That is, a wiring structure for each respective ink tank  1  comprises four signal lines, i.e., a power supply signal line “VDD”, a ground signal line “GND”, a signal line “DATA”, and a clock signal line “CLK”. The power signal line VDD is concerned with the supply of power for the operation of a function element in an IC package  102  that lights and drives the LED  101  in the ink tank  1 . The signal line DATA transmits control signals (control data) relating operations, such as lighting and flashing of the LED  101 , from the control circuit  300 , as will be described below. While the four signal lines are used in the present exemplary embodiment, the present invention is not limited thereto. For example, the ground signal line “GND” may be omitted by obtaining a ground signal by other methods. It is also possible to combine the signal lines “CLK” and “DATA”. In this case, it is not necessary to provide a signal line “DATA” for each ink tank  1 , and it is possible to reduce the signal wiring in the flexible cable  206 . For example, when a signal line DATA is provided for each of eight color ink tanks in the printer, eleven lines, that is, eight signal lines DATA, a power signal line VDD, a ground signal line GND, and a clock signal line CLK are necessary. This complicates the wiring structure of the flexible cable  206 , and increases the cost. For this reason, the above-described bus connection provides a cost advantage to the printer in which a plurality of color ink tanks are mounted. 
     The control circuit  300  performs data processing and operation control in the printer  200 . For that purpose, the control circuit  300  includes a CPU, a ROM that stores a program for operation control, and a RAM serving as a work area, although they are not shown. 
       FIGS. 1A to 1D  to  FIGS. 4A to 4D  are schematic views showing a position checking procedure according to the first exemplary embodiment of the present invention. The steps shown in  FIGS. 1A to 4C  are performed sequentially. The carriage  205  is movable along the guide shaft  207 , and includes four positions, namely, a black position K, a cyan position C, a magenta position M, and a yellow position Y arranged in that order from the left side. The black ink tank  1 K, the cyan ink tank  1 C, the magenta ink tank  1 M, and the yellow ink tank  1 Y are respectively mounted at the black position K, the cyan position C, the magenta position M, and the yellow position Y. The light receiver  210  is fixed on the main unit (not shown) of the printer  200 . The light receiver  210  is a sensor which can be formed of a phototransistor, and a photocurrent varies depending on the amount of light received by the light receiver  210 . In the present embodiment, a circuit shown in  FIG. 21  detects the change in the photocurrent as a voltage change when an output potential of VDD=3300 mV and load resistance=150 kΩ is used as the reference potential. That is, the amount of received light is expressed as the voltage.  FIGS. 1A to 4D  show a state in which the ink tanks  1  are properly mounted at correct positions in the carriage  205 . Light emission of the light emitting element, detection of a photocurrent in accordance with the amount of received light, movement of the carriage  205 , the checking of the ink tank  1  positions, which will be described below, are controlled according to the program stored in the ROM in the control circuit  300 . 
     In  FIGS. 1A to 1D , the LED  101  of the black ink tank  1 K is first turned on.  FIG. 1A  shows a position in which the light receiving portion  210  faces the black ink tank  1 K. In this case, the amount of light received by the light receiving portion  210  is 563 mV. Next,  FIG. 1B  shows a state in which the carriage  205  has been moved along the guide shaft  207  to the left by a distance corresponding to an ink tank, and the light receiving portion  210  faces the cyan ink tank  1 C. In this case, since the LED  101  of the black ink tank  1 K is turned on, the amount of light that reaches the light receiving portion  210  is 110 mV, which is less than when the light receiving portion  210  faces the black ink tank  1 K. 
     Next,  FIG. 1C  shows a state in which the carriage  205  has been further moved to the left by a distance corresponding to an ink tank  1 , and the light receiving portion  210  faces the magenta ink tank  1 M. In this case, the amount of light received by the light receiving portion  210  is 28 mV. Lastly,  FIG. 1D  shows a position in which the light receiving portion  210  faces the yellow ink tank  1 Y, and the amount of light received by the light receiving portion  210  in this case is 3 mV. 
       FIGS. 2A to 4D  are schematic views showing a case where the above-described operation has been sequentially performed in a state in which the LED  101  of the cyan ink tank  1 C has been turned on, a state in which the LED  101  of the magenta ink tank  1 M has been turned on, and a state in which the LED  101  of the yellow ink tank  1 Y has been turned on. 
     Tables in the figures show the relationship between the lighted ink tank and the amount of light received by the light receiver at the respective ink tank positions. Even when the same current is passed by the same circuit, the amount of emitted light varies among a plurality of LEDs of the ink tanks because of manufacturing error. Consequently, this sometimes leads to variations among the LEDs  101  attached to the ink tanks  1 . Further, the light guide characteristic varies among the light guides of the ink tanks because of manufacturing error, and the amount of light guided in the light guides is sometimes reduced. In addition, soil, such as ink mist, sticks to the ink tanks  1  because of differences in replacement frequency of the ink tanks  1 , and this sometimes reduces the amount of emitted light. For this reason, the amount of emitted light sometimes varies among the ink tanks  1 . 
     In the tables of the present exemplary embodiment for example, when the black ink tank  1 K is turned on and placed at a position such as to face the light receiver  210 , the amount of light received by the light receiver  210  is 563 mV. In contrast, when the cyan ink tank  1 C is turned on and placed at a position such as to face the light receiver  210 , the amount of received light is 62 mV, which is about one-ninth of the amount of light in the above case. 
     A method for checking the positions of the ink tanks  1  will now be described. Data corresponding to the tables shown in the above referenced figures are stored in the memory of the inkjet printer  200 , and the positions are checked on the basis of the data. First, the position of the black ink tank  1 K is checked. The position, where the largest amount of light is received by the light receiving portion  210  when the LED  101  of the black ink tank  1 K is turned on is found. The amount of light at the black position K is 563 mV, which is the largest. Therefore, it is determined that the black ink tank  1 K is mounted at the black position K. In this way, when the color of the lighted ink tank coincides with the color of the position in the carriage  205  where the amount of received light is the largest, it is determined that the ink tank is mounted at a correct position. Likewise, by looking for a maximum value with respect to each color, it can be determined that the cyan ink tank, the magenta ink tank and the yellow ink tank are mounted at a cyan position, a magenta position and a yellow position, respectively. 
     Next, a method for checking the ink tanks  1  that are mounted at wrong positions will be described.  FIGS. 5A to 8D  are schematic views showing the position detecting procedure when in the position detecting procedure described with reference to  FIGS. 1A to 4D , mounting positions of the cyan ink tank  1 C and the magenta ink tank  1 M are reversed. That is, the cyan ink tank  1 C is mounted at the magenta position M and the magenta ink tank  1 M is mounted at the cyan position C. The steps shown in  FIG. 5A  to  FIG. 8D  are performed sequentially. 
     In  FIGS. 5A to 5D , the LED  101  of the black ink tank  1 K is first turned on. In  FIG. 5A , the black ink tank  1 K faces the light receiver  210 , and the amount of light received by the light receiver  210  is about 563 mV. In the state shown in  FIG. 5B , the carriage  205  is moved to the left along the guide shaft  207  by a distance corresponding to one ink tank, and the light receiver  201  faces the magenta ink tank  1 M mounted at the cyan position C. In this case, since the LED  101  of the black ink tank  1 K is turned on, the amount of light that reaches the light receiving portion  210  is 110 mV, which is smaller than when the light receiving portion  210  and the black ink tank  1 K face each other. Next,  FIG. 5C  shows a state in which the carriage is further moved to the left by a distance corresponding to one ink tank  1 , and the light receiving portion  210  faces the cyan ink tank  1 C mounted at the magenta position M. In this case, the amount of light received by the light receiving portion  210  is 28 mV. Lastly,  FIG. 5D  shows a position in which the light receiving portion  210  faces the yellow ink tank  1 Y mounted in the yellow position Y, and the amount of light received by the light receiving portion  210  in this case is 3 mV. 
     In  FIGS. 6A to 6D , the LED  101  of the cyan ink tank  1 C is turned on.  FIG. 6A  shows a position in which the light receiving portion  210  faces the yellow ink tank  1 Y, and the amount of light received by the light receiving portion  210  in this case is 13 mV. Next,  FIG. 6B  shows a state in which the carriage  205  has been moved to the right along the guide shaft  207  by a distance corresponding to one ink tank  1 , and the light receiving portion  210  faces the cyan ink tank  1 C mounted at the magenta position M. In this case, the amount of light received by the light receiving portion  210  is 62 mV. Next,  FIG. 6C  shows a state in which the carriage  205  has been further moved to the right by a distance corresponding to one ink tank  1 , and the light receiving portion  210  faces the magenta ink tank  1 M mounted at the cyan position C. In this case, the amount of light received by the light receiving portion  210  is 14 mV. Lastly,  FIG. 6D  shows a position in which the light receiving portion  210  faces the black ink tank  1 K mounted in the black position K. The amount of light received by the light receiving portion  210  in this case is 1 mV. 
     In  FIGS. 7A to 7D , the LED  101  of the magenta ink tank  1 M is turned on.  FIG. 7A  shows a position in which the light receiving portion  210  faces the black ink tank  1 K and the amount of light received by the light receiving portion  210  in this case is 67 mV. Next,  FIG. 7B  shows a state in which the carriage  205  is moved to the left along the guide shaft  207  by a distance corresponding to one ink tank  1 , and the light receiving portion  210  faces the magenta ink tank  1 M mounted at the cyan position. In this case, the amount of light received by the light receiving portion  210  is 323 mV. Next,  FIG. 7C  shows a state in which the carriage  205  has been further moved to the left by a distance corresponding to one ink tank  1 , and the light receiving portion  210  faces the cyan ink tank  1 C mounted at the magenta position M. In this case, the amount of light received by the light receiving portion  210  is 68 mV. Lastly,  FIG. 7D  shows a position in which the light receiving portion  210  faces the yellow ink tank  1 Y mounted at the yellow position Y, and the amount of light received by the light receiving portion  210  in this case is 3 mV. 
     The steps of  FIGS. 8A to 8D  are similarly performed to acquire data on the amount of received light. Then, the positions of the ink tanks  1  are checked. 
     First, the position of the black ink tank  1 K is checked. The position, where the largest amount of light is received by the light receiver  210  when the LED  101  of the black ink tank  1 K is turned on, is found. The amount of received light is 563 mV, that is, the largest at the black position K. Therefore, it is determined that the black ink tank  1 K is mounted at the black position K. Similarly, the position, where the largest amount of light is received the light receiving portion  210  when the LED  101  of the cyan ink tank  1 C is turned on, is found. The amount of light received by the light receiving portion  210  is 62 mV, that is, the largest at the magenta position M. Therefore, it is determined that the cyan ink tank  1 C is incorrectly mounted at the magenta position M. 
     When the LED  101  of the magenta ink tank  1 M is turned on, the amount of light received by the light receiving portion  210  is 323 mV, that is, the largest at the cyan position C. Finally, when the LED  101  of the yellow ink tank  1 Y is turned on, the amount of light received by the light receiving portion  210  is 663 mV, that is, the largest at the yellow position Y. Thus, it can be determined that the black ink tank  1 K and the yellow ink tank  1 Y are correctly mounted, and the magenta ink tank  1 M and the cyan ink tank  1 C are incorrectly mounted. 
     A description will now be provided of a position detecting procedure when there is the influence of extraneous light. When the inkjet printer  200  is covered with the main body cover  201 , any extraneous light is blocked from reaching the light receiving portion  210 . However, depending on the environment where the inkjet printer  200  is used, extraneous light may enter from the ASF side or the sheet discharge tray  203  side. If this occurs, even though the LED  101  of the ink tank  1  is not turned on, the light receiving portion  210  detects the presence of light. This may result in the undesirable effect that the magnitude of the amount of light emitted by each ink tank  1  may be changed by the influence of the extraneous light, which may cause an incorrect detection. Therefore, the influence of the extraneous light is excluded by a method which is described below. 
     First, with the LED&#39;s  101  of the ink tanks  1  all turned off, the carriage  205  is moved along the guide shaft  207 . At that time, the amount of light received by the light receiving portion  210  at each position is recorded (stored) in the memory as an amount of background light. When the LED  101  of each ink tank  101  is turned on in a state where extraneous light has entered the light receiving portion  210 , the amount of light received by the light receiving portion  210  becomes a combination of the extraneous light plus the light of the LED  101 . 
     When the amount of the extraneous light is the amount of background light, the amount of background light is subtracted from the amount of light received by the light receiving portion  210  during the above described position detection of the ink tanks  1 . Thus it becomes possible to exclude the influence of the extraneous light, and stable position detection of the ink tanks  1  can be achieved. When the extraneous light is greater than the light typically emitted from the LEDs  101 , the background value is large, and the extraneous light plus the amount of light emitted by the LED  101  exceeds a reference voltage of 3300 mV and becomes saturated. That is, the value obtained by subtracting the amount of background light does not exhibit the amount of light emitted from the LED, and there is the possibility of incorrect detection. Therefore, when the background value exceeds a set value, error processing is carried out so that position detection may not take place. 
     In the present embodiment, the LED&#39;s  101  of the respective ink tanks  1  are successively made to emit light one by one in order to detect the position of the ink tank  1  which emitted light, whereafter the LED  101  of the next ink tank  1  is made to emit light to thereby achieve the position detection of that ink tank  1  which has emitted light. 
     Further, detecting the amount of light emitted by each of the ink tanks  1  at the multiple positions enables determination of not only whether an ink tank  1  has been incorrectly mounted, but which ink tank  1  has been incorrectly mounted. In an embodiment where the inkjet printer  200  has a display, it is possible for a user to view the results of the above-described detection procedures. In addition, if the inkjet printer  200  and a personal computer (not shown) are connected, the results of the detection can be viewed on the personal computer&#39;s display. Displaying the results of the detection enables a user to easily solve the problem when ink tanks  1  are incorrectly mounted. 
     Second Embodiment 
     A position checking method, using ink tanks and a printer similar to those in the first embodiment, will now be described with reference to  FIGS. 9A to 16B . 
       FIGS. 9A to 12B  are schematic views showing the position checking procedure when the ink tanks  1  are correctly mounted, where the procedure is performed sequentially from  FIG. 9A  to  FIG. 12B .  FIGS. 13A to 16B  are schematic views showing the position checking procedure when mounting positions of the cyan ink tank  1 C and the magenta ink tank  1 M are reversed. That is, the cyan ink tank  1 C is mounted at the magenta position M and the magenta ink tank  1 M is mounted at the cyan position C. The procedure is performed sequentially from  FIG. 13A  to  FIG. 16B . 
     Also, as in the first embodiment, the following operation is controlled by the control circuit  300 . 
       FIGS. 9A and 9B  show a state in which the carriage  205  has been moved so that the light receiving portion  210  faces a black position K.  FIG. 9A  shows a state in which the LED  101  of the black ink tank  1 K is turned on, and the amount of light received by the light receiving portion  210  is 563 mV.  FIG. 9B  shows a state in which the LED  101  of the black ink  1 K tank is turned off and the LED  101  of the cyan ink tank  1 C is turned on. In this case, the amount of light received by the light receiving portion  210  is 14 mV. 
       FIGS. 10A and 10B  show states in which the carriage  205  is moved to the left by a distance corresponding to one ink tank  1 , that is, the light receiving portion  210  faces the cyan position C. In the state shown in  FIG. 1A , the carriage  205  is moved without turning off the LED  101  of the cyan ink tank  1 C that has been turned on in  FIG. 9B . In this case, the amount of light received by the light receiving portion  210  62 mV. In the state shown in  FIG. 10B , the carriage  205  is not moved, the LED  101  of the cyan ink tank  1 C is turned off, and the LED  101  of the black ink tank  1 K is turned on. In this case, the amount of light received by the light receiving portion  210  is 110 mV. In the state shown in  FIG. 10C , the LED  101  of the black ink tank  1 K is turned off, and an LED  101  of the magenta ink tank  1 M is turned on. In this case, the amount of light received by the light receiving portion  210  at this time is 67 mV. 
     In  FIGS. 11A to 12B , the carriage  205  is moved to the left by a distance corresponding to one ink tank  1 , and the LEDs  101  of the adjacent ink tanks are alternately turned on. Consequently, the amount of light received by the light receiving portion  210  placed in front of the ink tank  1  mounted at a proper position and the amounts of received light obtained at the positions on both sides (only one position on the outermost side) are stored as data in the memory of the inkjet printer  200 . The mounting positions of the ink tanks are checked on the basis of the data. 
     According to the tables in  FIGS. 11A to 12  obtained by the above-described procedure, for example, the mounting position of the magenta ink tank  1 M is checked. When the LED  101  of the magenta ink tank  1 M is turned on, the amount of light received is 323 mV when the light receiving portion  210  faces the magenta position M. When the magenta ink tank  1 M is moved to the cyan position C, the amount of light received is 67 mV when the light receiving portion  210  faces the cyan position C. When the magenta ink tank  1 M is moved to the yellow position Y, the amount of light received by the light receiving portion  210  is 68 mV. By comparing these values, it is found that the amount of received light is the largest at the magenta position M. Therefore, it is determined that the magenta ink tank  1 M is mounted properly. 
     When the ink tank  1  is mounted at a proper position in this way, the amount of received light at the proper position is larger than the amounts of received light at the positions on both sides of the proper position (only one position on the outermost side), that is, the amount of received light at the proper position is the largest. From this, it can be determined that the ink tank  1  is mounted properly. 
     A description will now be given a position checking procedure performed when the cyan ink tank  1 C and the magenta ink tank  1 M are reversed, that is, the cyan ink tank  1 C has been mounted at the magenta position M and the magenta ink tank  1 M has been mounted at the cyan position C. 
       FIGS. 13A and 13B  show states in which the carriage  205  is moved so that the light receiving portion  210  faces the black position K.  FIG. 13A  shows a state in which the LED  101  of the black ink tank  1 K is turned on, and the amount of light received by the light receiving portion  210  is 563 mV.  FIG. 13B  shows a state in which the LED  101  of the black ink tank  1 K is turned off and the LED  101  of the cyan ink tank  1 C is turned on. However, the cyan ink tank  1 C is mounted at the magenta position M, and therefore, the amount of light received by the light receiving portion  210  is 1 mV, which is lower than the 14 mV received when the cyan ink tank  1 C is mounted at the cyan position C. 
     Next,  FIGS. 14A to 14C  show states in which the carriage  205  is moved to the left by a distance corresponding to one ink tank  1 , that is, the light receiving portion  210  faces the cyan position C.  FIG. 14A  shows a state in which the carriage  205  is without turning off the LED  101  of the cyan ink tank  1 C that was turned on in  FIG. 13B , and therefore, the LED  101  of the cyan ink tank  1 C remains lighted. However, the cyan ink tank  1 C is mounted at the magenta position M, and therefore, the 14 mV received by the light receiving portion  210  is lower than the 62 mV received when the cyan ink tank  1 C is mounted at the cyan position C. 
       FIG. 14B  shows a state in which LED  101  of the cyan ink tank  1 C is turned off and the LED  101  of the black ink tank  1 K is turned on.  FIG. 14C  shows a state in which the LED  101  of the black ink tank  1 K is turned off and the LED  101  of the magenta ink tank  1 M is turned on. 
     In  FIGS. 15A to 16B , the carriage  205  is moved to the left by a distance corresponding to one ink tank  1 , and the LEDs  101  of the adjacent ink tanks are alternately turned on. Consequently, according to the above-described procedure, taking the magenta ink tank  1  as an example, in the tables in  FIGS. 15A to 16B , the amount of light received at the light receiving portion  210  when the magenta ink tank  1 M mounted at the cyan position C faces the light receiving portion  210  is 323 mV. When the carriage  205  is moved to a position where the cyan ink tank  1 C mounted at the magenta position M faces the light receiving portion  210 , the amount of received light is 68 mV. When the carriage  205  is moved to a position where the yellow ink tank  1 Y mounted at the yellow position Y faces the light receiving portion  210 , the amount of received light is 8 mV. Since the maximum amount of light is not received when the magenta ink tank  1 M is at the magenta position M, it is determined that the magenta ink tank  1 M is incorrectly mounted. 
     When the ink tank  1  is incorrectly mounted, the amount of light received at the incorrect position is less than the amounts of light received light at the positions on both sides of the correct position (only one position on the outermost side). Thus, when the amount of light received in the central position is not the maximum amount, it can be determined that the ink tank  1  is improperly mounted. 
     Like the first embodiment, the second embodiment also includes a position detecting procedure when there is the influence of extraneous light. Since the procedure in the present embodiment is identical to that previously described, a detailed description is omitted herein. 
     In the present embodiment, the positions of all the ink tanks can be checked only during the movement of the carriage  205  in one direction. This can reduce the time from when the ink tank is replaced to when the printer is restarted. 
     While the position checking method for the printer in which four ink tanks corresponding to four colors are mounted have been described in the first and second embodiments, the number of colors is not limited to four. The above-described position checking method is also applicable to a printer in which ink tanks corresponding to five or more colors are mounted. 
     As described above, in the first and second embodiments, the light emitted by the LEDs  101  of adjacent ink tanks  1  can be used to determine whether ink tanks  1  are correctly mounted. 
     According to the above-described exemplary embodiments, a determination is made whether ink tanks  1  are correctly mounted by sequentially turning on the LEDs  101  of the respective ink tanks  1  at predetermined positions in accordance with the movement of the carriage  205 , resulting in detection of the light emitted by the LEDs  101 . 
     Further, as described in the above exemplary embodiments, in a case where there is some unevenness in the amount of light received by the light receiving portion  210 , a determination can still be made whether the ink tanks  1  are correctly mounted. 
     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 modifications, equivalent structures and functions. 
     This application claims priority from Japanese Patent Application No. 2005-180555 filed Jun. 21, 2005, which is hereby incorporated by reference herein.