Abstract:
A display apparatus has: a touch panel of a capacitance type; a detector which detects, as an environmental condition, at least one of temperature, humidity, and pressure; and an adjuster which adjusts the environmental condition based on the result of the detection. The adjuster varies the intensity of adjustment stepwise.

Description:
[0001]    This application is based on Japanese Patent Application No. 2010-042165 filed on Feb. 26, 2010 and Japanese Patent Application No. 2010-171565 filed on Jul. 30, 2010, the contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a display apparatus provided with a touch panel, or to a vending machine provided with such a display apparatus. 
         [0004]    2. Description of Related Art 
         [0005]    Conventionally, touch panels are widely used as an interface in bank ATMs or railway ticket vending machines. Touch panels are available in a wide range of sizes from several inches to over 50 inches. 
         [0006]    In the past, these displays provided with touch panels were mostly installed indoors, but recently they are installed outdoors or semi-outdoors such as at gas stations or in sight-seeing guide boards. 
         [0007]    According to the operation principle, touch panels are classified into a resistive film type, a capacitance type, an ultrasonic type, an infrared type, etc. Since each type of the touch panels have advantages and disadvantages, the appropriate types should be selected for particular uses. As touch panels for 20 inches or larger displays installed outdoors or semi-outdoors, the capacitance type are widely used for example. 
         [0008]    As disclosed in JP 2009-258903 A1 etc., the capacitance type touch panel has sensors which detect changes in capacitance are provided across the panel. The position touched by user&#39;s finger is determined based on the detected capacitance in each position of the panel. 
         [0009]    Capacitance occurs where two conductors are arranged across a dielectric material. The magnitude of capacitance is given by formula (1) below. 
         [0000]        C=E   0   ×E   S   ×S/d    (1)
 
         [0010]    where 
         [0011]    C represents the capacitance (F); 
         [0012]    E 0  represents the dielectric constant of vacuum, which equals 8.854×10 −12  (F/m); 
         [0013]    E S  represents the relative dielectric constant of the dielectric; 
         [0014]    S represents the area of the conductors (m 2 ); and 
         [0015]    d represents the distance between the conductors (m). 
         [0016]    Environmental conditions may affect the performance of a touch panel of the above capacitance type. For example, it may cause a false detection, mistakenly detecting that the finger is touched even though the finger is not actually touched. 
         [0017]    One of the techniques to reduce such false detection is to control the temperature. JP-2009-296105 A1 discloses a display apparatus having a structure in which air is passed between a liquid crystal panel and a front glass using a fan. When such structure is adopted, the temperature of not only the liquid crystal panel but also the touch panel can be lowered, and thus false detections in the touch panel are expected to be reduced. 
         [0018]    However, in such display apparatuses, if the rotation speed of the fan or the intensity of cooling changes drastically or rapidly, the offset in the capacitance may change abruptly. Thus, the deviation of the sensor&#39;s capacitance from its standard value (=the offset in capacitance) varies. Consequently, it may cause the false detection in the touch panel. 
       SUMMARY OF THE INVENTION 
       [0019]    According to the present invention, a display apparatus includes: a touch panel of a capacitance type; a detector which detects, as an environmental condition, at least one of temperature, humidity, and pressure; and an adjuster which adjusts the environmental condition based on the result of the detection, wherein the adjuster varies the intensity of adjustment stepwise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is an external view of a vending machine according to an embodiment of the invention; 
           [0021]      FIG. 2  is a diagram illustrating the arrangement of a display apparatus in the vending machine. 
           [0022]      FIG. 3  is a diagram illustrating a cooling mechanism according to an embodiment of the invention; 
           [0023]      FIG. 4  is a block diagram showing the configuration of the vending machine; 
           [0024]      FIG. 5  is a diagram showing the construction of a display apparatus according to an embodiment of the invention; 
           [0025]      FIG. 6  is a diagram showing the construction of the display apparatus as seen from another direction; 
           [0026]      FIG. 7  is a diagram showing the construction of the display apparatus as seen from yet another direction; and 
           [0027]      FIG. 8  is a flow chart showing temperature adjustment operation. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    The embodiment of the present invention is described below. The following embodiment regards to a vending machine or a display apparatus attached to the vending machine. 
         [0029]    [Structure of the Vending Machine] 
         [0030]      FIG. 1  is an external view of a vending machine  10 .  FIG. 2  is a diagram showing the arrangement of a display apparatus  1  in the machine  10 . As shown in these diagrams, the display  1  is fitted to the body  5  of the machine  10 . 
         [0031]    [Structure of a Cooling Mechanism] 
         [0032]    As shown in  FIG. 3 , the display  1  has a cooling mechanism which cools the display  1  itself. The cooling mechanism cools the display  1  by rotating fans  19  and thereby passes air from outside into the cabinet of the display  1 . 
         [0033]    When the display  1  is installed outdoors, a liquid crystal panel  14  is heated intensely by sunlight. Therefore, it is important to cool the panel  14 , particularly the front-face side thereof. 
         [0034]    To cool the liquid crystal panel  14  efficiently, the display  1  has a structure so that air is passed through a space (SP) between the liquid crystal panel  14  and a front glass  21  provided at the front-face side of the panel  14 . 
         [0035]    When the fans  19  rotate, air passes from inhaling fans  19   a  to exhaust fans  19   b.  As shown in  FIG. 3 , a touch panel  15  is adhered on the front-face side of the front glass  21 . If the fans  19  rotate for purpose of cooling the liquid crystal panel  14 , the temperature on the touch panel  15  changes precipitously. As a result, the offset of the touch panel  15  fluctuates, and a false detection in the panel  15  may occur. Accordingly, in the display  1 , a control is performed so that the air flow produced by the fans is changed stepwise. 
         [0036]    The body  5  is provided with product selection buttons  53  (a portion for which the user select a product to buy), a processing controller  55 , a coin handling mechanism  56 , a product transport mechanism  57 , etc., and is box-shaped. 
         [0037]    A CPU  55  performs various kinds of control processing. 
         [0038]    The coin handling unit  56  handles coins, and includes, a coin inlet  51 , a coin outlet, a coin transporter, a coin storage, and a coin sorter, etc. 
         [0039]    The product transport unit  57  handles products sold by the machine  10 , and has a product outlet  54 , a product storage, and a product transporter, etc. 
         [0040]      FIG. 5  is a diagram showing the structure of the display  1  seen from the top.  FIG. 6  is a diagram showing the structure of the display  1  seen from the right side.  FIG. 7  is a diagram showing the structure of the display  1  seen from the left side. 
         [0041]    As shown in these figures, the display  1  has a housing made of front cabinet FC and a back cabinet BC. The liquid crystal panel  14  is arranged at the front-face side of the BC, and the touch panel  15  is arranged in the FC so that the touch panel  15  overlaps the liquid crystal panel  14 . The inhaling fans  19   a  (fans A, B, and C) are arranged in one side of the BC, and the exhaust fans  19   b  (D, E, and F) are arranged in the other side of the BC. 
         [0042]    The temperature inside the cabinet is affected by the atmospheric temperature at the installation site and the heat generated inside the display  1 . Thus the temperature may vary in a wide range from 0 degrees Celsius or less, to 60 degrees Celsius or more. 
         [0043]    [Processing Performed by the Vending Machine] 
         [0044]      FIG. 4  is a block diagram showing the configuration of the machine  10 . The major process performed by the machine  10  is “product selling process”, “video/audio output process”, “touch operation acceptance process”, “touch panel initialization process”, and “temperature adjustment process”. 
         [0045]    The “product sale process” is a process for selling products based on demand from the user. This process is same as the process performed in common vending machines. This process is executed mainly by the processing controller  55  which controls the units  56  and  57 . 
         [0046]    The controller  55  counts the amount of money fed into the coin inlet  51 . When one of the product selection buttons  53  is pressed, the controller  55  transports the selected product to the outlet  54 . 
         [0047]    The “video/audio output process” is a process for displaying an image and outputting sound based on video/audio signals received by a wireless communication unit  11 . 
         [0048]    The “touch operation acceptance process” is a process for accepting a touch operation made by the user on the touch panel  15 . When the touch operation is made, the signal is fed to the processing controller  55  via a touch operation signal output I/F  20 . I/F  20  is implemented as a USB interface for example. 
         [0049]    Instead of pushing the button  53 , a user can select a product also by a touch operation on the touch panel  15 . 
         [0050]    The “touch panel initialization process” is process for adjusting the threshold value of sensors provided over the touch panel  15  so as to stabilize the detecting function of the touch panel  15 . Via the I/F  20 , offset in capacitance is monitored continuously. 
         [0051]    Based on the result of this monitoring, the unit  18  adjusts the threshold value of the sensors so as to cancel the offset. 
         [0052]    The threshold value may be set at different values for the sensors at different places of the panel  15 . Thereby, the detection can be performed correctly even when the offset is caused by dust or rain attached to the touch panel  15 . 
         [0053]    However, when this initialization process is performed too frequently, it may hamper the detection process. Accordingly, this initialization process is performed at certain time intervals, for example, for a period of ten and several seconds. In this case, when one-half of the period pass, the offset in capacitance is predicted, and the threshold value is adjusted so as to cancel the predicted offset. 
         [0054]    [Temperature Adjustment Process] 
         [0055]    The temperature adjustment process is a process to adjust the temperature of the display  1  by driving the fans  19 . This process is described below with reference to a flow chart in  FIG. 8 . 
         [0056]    A processing control unit  18  continuously acquires the temperature information detected by a temperature sensor  16  and calculates the average of the temperature detected during the predetermined time period Ttemp as an evaluated temperature (step S 1 ). Instead of the average temperature during Ttemp, the temperature at a predetermined time point may be adopted as the evaluated temperature. 
         [0057]    Next, the unit  18  determines whether or not cooling is currently being performed (step S 2 ). If cooling is not being performed (“N” at step S 2 ), the unit  18  determines whether or not the evaluated temperature is higher than a predetermined cooling initiating temperature Temp 1  (step S 3 ). 
         [0058]    When it is determined that the evaluated temperature is higher than Temp 1  (“Y” at step S 3 ), the unit  18  initiates the cooling process (step S 4 ). When it is determined that the evaluated temperature is not higher than the Temp 1  (“N” at step S 3 ), the flow returns to step S 1 . 
         [0059]    At step S 5 , the unit  18  determines whether or not the evaluated temperature is lower than a cooling terminating temperature Temp 2 . In this embodiment Temp 2  is assumed to be lower than Temp 1 , but they may have an equal value. 
         [0060]    When it is determined that the evaluated temperature is lower than Temp 2  (“Y” at step S 5 ), cooling terminating process begins (step S 4 ). When it is determined that the evaluated temperature is not lower than Temp 2  (“N” at step S 5 ), the flow returns to step S 1 . 
         [0061]    Next, the cooling operation at step S 4  mentioned above is described specifically. When cooling operation is initiated, first, the unit  18  begins driving fans A and D only, out of the six fans A to F. A predetermined time thereafter (for example, 20 seconds thereafter), the unit  18  additionally drives fans B and E. 
         [0062]    Another predetermined time (20 seconds) thereafter, fans C and F are additionally driven. As a result, all the fans  19  are being driven. Thereby, the display  1  increases the number of fans driven stepwise during the initiation of the cooling. Thereafter, all the fans are kept being driven until a cooling terminating process begins. 
         [0063]    Next, the cooling terminating operation at step S 6  mentioned above is described specifically. In the cooling terminating operation, first, the unit  18  terminates fans C and F, out of the six fans A to F. A predetermined time thereafter, the unit  18  additionally terminates fans B and E. 
         [0064]    Another predetermined time thereafter, fans A and D is terminated. As a result, all of the fans  19  are not driving, and cooling operation is not being performed. Thereby, the display  1  reduces the number of fans driven stepwise during the cooling terminating process. This state is maintained thereafter until the cooling operation is newly started. 
         [0065]    If the temperature detection period Ttemp mentioned above is set shorter than the period needed for the touch panel initialization process, the initialization of the touch panel is outpaced by the change in temperature caused by driving of the fans. Consequently, the accuracy of the touch panel initialization process may be determined. Accordingly, the temperature detection period Ttemp is set longer than (about three to five times) the period necessary for the touch panel initialization process. 
         [0066]    As described above, when initiating or terminating the cooling, the display  1  changes the number of driving fans stepwise. Thereby, the abrupt change in the temperature inside the display  1  accompanied by the cooling operation is reduced. 
         [0067]    Further, by a touch operation, the user can select content. The display  1  may be configured so that, when content is selected, the corresponding image or sound is replayed. 
         [0068]    The embodiment of the invention specifically described above is in no way meant to limit the invention. The invention may be carried out with many variations and modifications made without departing from the spirit of the invention. 
         [0069]    For example, for the purpose of changing the air flow, other method may be adopted. For example, the air flow may be changed stepwise, instead of by changing the number of fans driven, by changing the rotation speed of the fans stepwise. 
         [0070]    In the embodiment described above the display apparatus is used in a form fitted to the vending machine  10 , the display apparatus may be used in a form fitted to any other device than a vending machine. 
         [0071]    In the embodiment described above, a touch panel  15  is adhered on the front-face side of the front glass  21 , however, the panel  15  may be adhered on the rear-face side of the glass  21  instead.