Patent Publication Number: US-2023152177-A1

Title: Pressure detection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-187892, filed Nov. 18, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a pressure detection device. 
     BACKGROUND 
     A flexible sheet-type pressure sensor with such a structure that a thin-film transistor (TFT) and a pressure-sensitive layer are installed on a polyimide base layer, has been proposed. When such a sheet-type pressure sensor is curved, the pressure sensor can be easily curved if the curving axis is uniaxial, or even multi-axial if they are parallel to each other. On the other hand, if the curving axis is two axes that are not parallel to each other, it is difficult to curve the pressure sensor biaxially. 
     In order to cope with biaxial curving, methods to increase the elasticity of the pressure sensor itself by using expandable wiring, etc., or to provide a cut or a void, such as in a paper-cut structure, have been proposed, but both methods complicate the manufacturing process and reduce the reliability of the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing a pressure detection device according to a first embodiment. 
         FIG.  2    is a cross-sectional view of the pressure detection device taken along line A-A in  FIG.  1   . 
         FIG.  3    is a cross-sectional view of the pressure detection device taken along line B-B in  FIG.  1   . 
         FIG.  4    is a cross-sectional view of a pressure sensor of the pressure detection device. 
         FIG.  5    is a plan view schematically showing a configuration example of the pressure sensor. 
         FIG.  6    is a cross-sectional view schematically showing the pressure sensor when it is pressed. 
         FIG.  7    is a diagram schematically showing a pressure distribution when a central portion of the pressure detection device is pressed. 
         FIG.  8    is a diagram schematically showing a pressure distribution when a peripheral portion of the pressure detection device is pressed. 
         FIG.  9    is a diagram showing sensed pressure distributions before and after conversion of the pressure detection device. 
         FIG.  10    is a cross-sectional view of a pressure sensor according to a modified example. 
         FIG.  11    is a perspective diagram showing an example of use of the pressure detection device. 
         FIG.  12    is a perspective diagram showing a pressure detection device according to a second embodiment. 
         FIG.  13    is a longitudinal cross-sectional view of the pressure detection device according to the second embodiment. 
         FIG.  14    is a perspective diagram showing an example of use of the pressure detection device according to the second embodiment. 
         FIG.  15    is a perspective diagram showing a modified example of the second embodiment. 
         FIG.  16    is a perspective diagram showing a side of a pressed surface of a pressure detection device according to a third embodiment. 
         FIG.  17    is a perspective diagram showing a side of a pressure sensor of the pressure detection device according to the third embodiment. 
         FIG.  18    is a cross-sectional view of the pressure detection device taken along line D-D of  FIG.  16   . 
         FIG.  19    is a cross-sectional view of the pressure detection device taken along line E-E of  FIG.  16   . 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment, a pressure detection device comprises a buffer layer formed of an elastic material and comprising a press surface including a biaxially curved surface and an installation surface comprising a uniaxially curved surface opposing the press surface with an interval therebetween, and a sheet-like pressure sensor provided in tight contact with the installation surface and uniaxially curved along the installation surface. 
     Note that the disclosure is merely an example, and proper changes within the spirit of the invention, which are easily conceivable by a skilled person, are included in the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same or similar elements as or to those described in connection with preceding drawings or those exhibiting similar functions are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary. 
     First Embodiment 
     A pressure detection device of the first embodiment will now be described in detail. 
       FIG.  1    is a perspective view showing the pressure detection device according to the first embodiment.  FIG.  2    is a cross-sectional view of the pressure detection device taken along line A-A in  FIG.  1   .  FIG.  3    is a cross-sectional view of the pressure detection device taken along line B-B in  FIG.  1   . 
     In the figures, a first direction X, a second direction Y and a third direction Z are three directions orthogonal to each other, but they may intersect at an angle other than 90 degrees. In the following descriptions, a direction forwarding a tip of an arrow indicating the third direction Z is referred to as “upward” or “above” and a direction forwarding oppositely from the tip of the arrow is referred to as “downward” or “below”. 
     In addition, it is assumed that there is an observation position to observe the pressure detection device on a tip side of an arrow in the third direction Z, and viewing from this observation position toward the X-Y plane defined by the first direction X and the second direction Y is referred to as a planar view. 
     Further, in the following descriptions, uniaxially curved surfaces are each defined as a curved surface which is curved around one axis, for example, a 2D surface such as a circular arc surface, cylindrical surface, or triangular pyramid, which becomes a plane when developed. Such uniaxially curved surfaces include curved surfaces each curved around multiple axes that are parallel to each other, that is, for example, curved surfaces curved into an S-shape, wavy shape or the like. Biaxially curved surfaces are each defined as a curved surface that is curved around multiple non-parallel axes, for example, a 3D curved surface such as a spherical surface, a free-form surface, a barrel-shaped surface or the like. 
     As shown in  FIGS.  1  to  3   , the pressure detection device  10  of the first embodiment comprises a buffer layer  20  formed of an elastic material such as a synthetic resin, rubber, elastomer or the like, and a sheet-shaped pressure sensor  50  attached to the buffer layer  20 . 
     The buffer layer  20  includes an outer surface (press surface) SA consisting, for example, of a biaxially curved surface such as a convex spherical surface, and a circular flat bottom surface SC opposing the press surface SA. In a central portion of the bottom surface SC, a semi-cylindrical recess  22  having a central axis extending in the first direction X is formed. The bottom surface of the recess  22  is a uniaxially curved surface formed convex toward the press surface SA, which is, here, a semi-cylindrical installation surface SB. The installation surface SB opposes to be spaced apart from the press surface SA. 
     The pressure sensor  50  is formed into a rectangular sheet shape and includes a pair of rectangular main surfaces (a first main surface and a second main surface) opposing each other. The pressure sensor  50  is disposed within the recess  22 . The pressure sensor  50  is adhered to the installation surface SB of the buffer layer  20  by the entire main surface (the first main surface), thus tightly attached to the entire surface of the installation surface SB. The pressure sensor  50  is uniaxially curved along the installation surface SB to form a uniaxially curved surface identical to the installation surface SB, that is, in this case, in a semi-cylindrical shape. The pressure sensor  50  includes a pair of side edges  50   a  and  50   b , which are aligned with each other to be flush with the bottom surface SC of the buffer layer  20 . 
     The recess  22  is filled with a filling material (a core material)  24 . The core material  24  can be an elastic or metal material having a rigidity higher than that of the buffer layer  20 . The core material  24  is tightly attached to the other main surface (the second main surface) of the pressure sensor  50  and is flush with the bottom surface SC. 
     An example of the pressure sensor  50  will be described.  FIG.  4    shows a cross-sectional view of the pressure sensor, and  FIG.  5    shows a plan view of the circuit configuration of the pressure sensor. 
     As shown in  FIG.  4   , the sheet-shaped pressure sensor  50  comprises an array substrate  51 , a sensor layer (pressure-sensitive layer)  54  opposing to be spaced apart from the array substrate  51 , and a counter electrode CE and a protective layer  60 , stacked in order on the sensor layer  54 . The pressure sensor  50  has a thickness in the stacking direction of about 10 to several hundred μm. The pressure sensor  50  includes a controller  62  connected to the array substrate  51  and the counter electrode CE. The controller  62  measures the pressure value of the pressure applied to the pressure sensor  50  and the location where being pressed. 
     The array substrate  51  is a rectangular-shaped insulating substrate. The array substrate  51  includes a counter-surface  51   a  opposing the sensor layer  54  and a lower surface  51   b  opposing the counter-surface  51   a . On the counter-surface  51   a , a plurality of array electrodes (pixel electrodes) PE are arranged in a matrix. The lower surface  51   b  forms the second main surface of the pressure sensor  50 . 
     As shown in  FIG.  5   , the array substrate  51  includes a plurality of scanning lines GL parallel to each other, a plurality of signal lines SL parallel to each other and extending orthogonal to the scanning lines GL, and a plurality of transistors TR provided respectively at intersections between the scan lines GL and respective signal lines SL, provided on the counter-surface  51   a . The gate electrodes GE of the transistors TR are connected to the scanning lines GL, respectively and the source electrodes SE of the transistors TR are connected to the signal lines SL, respectively. The drain electrodes DE of the transistor TR are connected to the array electrodes PE, respectively. Between the array electrode PE and the counter electrode CE, the sensor layer  54  is disposed. 
     As shown in  FIG.  4   , the sensor layer  54  is a sheet member formed into the same shape as that of the array substrate  51  in planar view. The sensor layer  54  includes a first surface  52   a  and a second surface  52   b  on an opposite side to oppose the first surface. The sensor layer  54  is formed of a material whose resistance value changes when stress is applied, that is, for example, a pressure-sensitive conductive elastomer prepared by conductive microparticles are dispersed in a highly insulative rubber material. In the sensor layer  54 , the conductive microparticles disposed inside the base material are separated from each other. The base material of the sensor layer  54  is made of rubber with low rigidity. Therefore, the sensor layer  54  under normal conditions (when not deformed) exhibits a very high resistance value and is insulative in a thickness direction and in a planer direction. On the other hand, when the sensor layer  54  is pressed from above, the base material depresses at the pressed location toward the array substrate  51 . As a result, conductive microparticles contained in the deformed base material are brought into contact with each other and thus the material becomes conductive in the thickness direction. As described the above, the sensor layer  54  is formed of a pressure-sensitive material whose resistance value changes due to pressure applied from the thickness direction. 
     The first surface  52   a  of the sensor layer  54  opposes approximately parallel to be spaced apart at a predetermined distance from the counter-surface  51   a  of the array substrate  51  and the array electrodes PE. The counter electrode CE is stacked on the second surface  52   b  of the sensor layer  54 . The counter electrode CE is a solid electrode deposited on the entire second surface  52   b  of the sensor layer  54  and is formed into a rectangular shape having a size approximately the same as that of the array substrate  51  in planar view. To the counter electrode CE, a reference voltage is applied from the controller  62 . 
     The protective layer  60  is a sheet material formed into a shape identical to that of the array substrate  51  in planar view. The protective layer  60  is formed of rubber or resin, which has high insulating properties and low rigidity. The protective layer  60  is stacked on the counter electrode CE. The protective layer  60  includes a first surface  60   a  attached to the counter electrode CE and a second surface  60   b  on an opposite side. The second surface  60   b  of the protective layer  60  is equivalent to the first main surface of the pressure sensor  50  and forms a pressure-receiving surface to receive pressure. The counter electrode CE and the protective layer  60  have such a rigidity approximately the same as that of the sensor layer  54 , that only the portion pressed by a finger or the like is depressed. 
     Note that the counter electrode CE may be formed on the first surface  60   a  of the protective layer  60 . In this case, the entire first surface  60   a  of the protective layer  60  and the entire counter electrode CE are attached on the first surface  54   a  of the sensor layer  54 . 
     The controller  40  comprises a gate driver (not shown) connected to the scanning lines GL to sequentially select the array electrodes PE, and a source driver (not shown) connected to the signal lines SL. The controller  62  measures the value of the current which flows to the array electrode PE and, based on the measured current value, detects the location (coordinates) in the sensor layer  54 , which is deformed by the pressure and the pressing force (pressure value). 
     Next, an example of the operation of the pressure sensor  50  will be described. 
       FIG.  6    is a cross-sectional view of the pressure sensor  50  when the first main surface (second surface  60   b ) thereof is pressed. When the second surface  60   b  of the protective layer  60  is not pressed, the thickness of the sensor layer  54  is not reduced at any point. Thus, the sensor layer  54  has insulating properties in the thickness direction and no current (signal) flows from the counter electrode CE to the sensor layer  54 . On the other hand, as shown in  FIG.  6   , when the second surface  60   b  of the protective layer  60  is pressed in the thickness direction, the protective layer  60 , the counter electrode CE and the sensor layer  54  are depressed in the pressing direction (stacking direction). As a result, at the pressing point, the first surface  54   a  of the sensor layer  54  is brought into contact with the corresponding array electrode PE (PEa) and the deformed portion B 1  of the sensor layer  54 , which is depressed, exhibits a low resistance value. Therefore, the current flows from the counter electrode CE through the deformed portion B 1  of the sensor layer  54  to the array electrode PE (PEa). In other words, the deformed portion B 1  of the sensor layer  54  is not electrically connected to each of the other array electrodes PE located around the array electrode PEa in the plane direction. 
     The controller  62  detects that a signal (current) is input to the array electrode PEa and calculates the pressed point (coordinates) and the pressure value. 
     The pressure sensor  50  with the above-described structure is configured as shown in  FIGS.  2  and  3    so that the second surface  60   b  (the first main surface) of the protective layer  60  is attached to the buffer layer  20  to be in tight contact with the installation surface SB of the buffer layer  20  and curved along the installation surface SB, that is, uniaxially curved. 
     In this embodiment, the elastic material which forms the buffer layer  20  has a rigidity approximately the same as that of the protective layer  60  of the pressure sensor  50 . The buffer layer  20  is formed to have a thickness greater than that of the sensor layer  54  of the pressure sensor  50 . 
       FIG.  7    is a diagram schematically showing the pressure distribution when substantially the central portion (where the buffer layer is thickest) of the press surface SA of the buffer layer  20  is pressed, and  FIG.  8    is a diagram schematically showing the pressure distribution when the periphery portion (where the buffer layer is thin) of the press surface SA is pressed. 
     In the case where the press surface SA of the buffer layer  20  is spherical (biaxially curved surface), and the pressure receiving surface  60   b  of the pressure sensor  50  is a semi-cylindrical surface (uniaxially curved), the distance between the press surface SA and the pressure receiving surface  60   b , that is, the thickness of the buffer layer  20  is not uniform over the entire surface, but varies from one place to another. 
     As shown in  FIG.  7   , when substantially the central portion (where the buffer layer is thicker) of the press surface SA of the buffer layer  20  is pressed, the pressing force (pressure) is somewhat dispersed, and therefore, the dispersed force is projected widely on the pressure sensor  50 , that is, the pressure is transmitted to the pressure sensor  50  in a spread manner. 
     As shown in  FIG.  8   , when the peripheral portion (where the buffer layer is thin) of the press surface SA is pressed at an angle, the pressing force (pressure) is transmitted to the pressure sensor  50  without being dispersed, but projected in a small spot on the pressure sensor  50 . 
     Under these circumstances, the controller  62  corrects (converts) the pressure value detected by the pressure sensor  50  according to the biaxially curved surface of the press surface SA, and thus correctly detect the pressure value applied to the press surface SA.  FIG.  9    is a diagram showing a comparison of the pressure-sensitive distribution before and after conversion of the pressure sensor. In  FIG.  9   , the solid line indicates the sensed pressure distribution before the conversion and the dashed line indicates the sensed pressure distribution after the conversion. 
     The way the pressure applied to the spherical surface (press surface SA) is reflected (pressure blur) on the semi-cylindrical surface (the pressure-receiving surface  60   b ) can be easily calculated as a function by a finite element method (FEM) simulation or the like. That is, as shown in  FIG.  9   , using the thickness and shape of the buffer layer  20  and the like, as parameters, a function or conversion table can be calculated such as to more greatly compress the central portion of the press surface SA, and thus a function or conversion table for conversion can be formed in advance. In the pressure detection device  10  of this embodiment, an example of the function is expressed by the following formula. 
     
       
         
           
             
               r 
               ′ 
             
             = 
             
               r 
               - 
               
                 A 
                 × 
                 
                   sin 
                   ⁡ 
                   ( 
                   
                     Π 
                     ⁢ 
                     
                       r 
                       R 
                     
                   
                   ) 
                 
               
             
           
         
       
     
     In the formula, r represents the distance from an image center C to the press position before the conversion, r′ represents the distance from the image center C to the press position after the conversion, R represents the distance from the image center C to a diagonal, and A is a constant. 
     The controller  62  includes a conversion unit which stores the calculated function, which converts the pressure value detected by the pressure sensor  50  by the above-described function to calculate the correct pressure value applied to the spherical surface (press surface SA). 
     Note that the pressure sensor  50  is not limited to the embodiment described above, and various types of pressure sensors can be applied.  FIG.  10    is a cross-sectional view of a pressure sensor according to a modified example. 
     As shown in  FIG.  10   , according to the modified example, a plurality of counter electrodes CE are provided on the first surface  51   a  of the array substrate  51  and are disposed to oppose to the corresponding array electrodes (pixel electrodes) PE, respectively, in the plane direction. According to the pressure sensor  50 , the pressure points on the protective layer  60  and the sensor layer  54  are depressed towards the array substrate  51  side, and the corresponding part of the sensor layer  54  is brought into contact with the array electrode PE and the counter electrode CE. Thus, the corresponding array electrode PE and the respective counter electrode CE are electrically connected to each other and current flows to the array electrode PE. In this manner, the controller  62  can detect that a signal (current) is input to the array electrode PE and calculate out the pressed point (coordinates) and the pressure value. 
     Apart from the above, other pressure sensors can as well be applied, such as pressure sensors which detect capacitance changes, matrix pressure sensors and the like. 
     According to the pressure detection device  10  configured as described above, the pressure sensor  50 , which is uniaxially curved, can detect the pressure applied to the press surface having a biaxially curved surface and also the pressure distribution. Thus, the pressure sensor  50  need not to have a biaxially curved surface, thus making it simplifying the manufacturing process and improving the reliability of the pressure sensor. 
       FIG.  11    is a diagram schematically showing an example of the use of the pressure detection device  10 . As shown in the figure, for example, the pressure detection device  10  is installed in a center console box CB of a vehicle and constitutes a touch panel for operating a display DS. The pressure detection device  10  is disposed so that the bottom surface SC is placed on the center console box CB with the press surface SA side being exposed. When the press surface SA is touched, the pressure detection device  10  detects the input operation based on the detected touch position and touch pressure, and the display DS display is controlled accordingly. Note that the pressure detection device  10  can be operated while wearing gloves or the like. Further, a sheet or plastic exterior may be provided over the press surface SA of the buffer layer  20 . 
     Next, pressure detection devices according to another embodiments will be described. In the another embodiments described below, the structural parts identical to those of the first embodiment described above are designated by the same reference symbols as those of the first embodiment and the detailed descriptions thereof may be omitted or simplified. 
     Second Embodiment 
       FIG.  12    is a diagram schematically showing a pressure detection device of the second embodiment, and  FIG.  13    is a longitudinal cross-sectional view of the pressure detection device. 
     As shown in the figures, according to the second embodiment, the pressure detection device  10  comprises a buffer layer  20  formed into a cylindrical shape, a sheet-shaped pressure sensor  50  attached to the buffer layer  20 , and a controller, not shown, connected to the pressure sensor  50 . The buffer layer  20  is formed of an elastic material such as synthetic resin, rubber, elastomer or the like, and includes an outer circumferential surface (press surface SA) which is an approximately barrel-shaped biaxially curved surface and an inner circumferential surface (installation surface SB) which is a cylindrical uniaxially curved surface. The press surface SA and the installation surface SB have a central axis Cl and are located coaxial with each other. The installation surface SB extends from one axial end of the buffer layer  20  to the other axial end. The installation surface SB opposes the press surface SA with an interval provided therebetween. The interval between the press surface SA and the installation surface SB, that is, the thickness of the buffer layer  20 , is at the greatest in the axial central portion and gradually decreases toward both axial ends. 
     The pressure sensor  50  has a configuration similar to that of the pressure sensor in the first embodiment described above. That is, the pressure sensor  50  is formed into a rectangular sheet having a thickness of about 10 to several hundred μm. The pressure sensor  50  includes a pair of rectangular main surfaces (first and second main surfaces) opposing each other. The pressure sensor  50  is attached by the entire main surface (first main surface), to the installation surface SB of the buffer layer  20 , which is lightly in contact with the entire surface of the installation surface SB. The pressure sensor  50  is uniaxially curved along the installation surface SB to form a uniaxially curved surface, in this case, a cylindrical shape, which is identical to the installation surface SB. Both axial edges of the pressure sensor  50  are aligned with both axial edges of the installation surface SB, respectively. Note that the pressure sensor  50  cylindrically formed may be configured such as to be attached to the installation surface SB. 
     The pressure detection device  10  is used in the state where the pressure sensor  50  is attached to a cylindrical or cylindrically columnar core material which is in tight contact with the second main surface of the pressure sensor  50 . 
     The pressure detection device  10  configured as described above can detect, by the uniaxially curved pressure sensor  50 , the pressure applied to the press surface SA including a biaxially curved surface and the pressure distribution. Thus, the pressure sensor  50  need not be biaxially curved, thereby making it possible to simplify the manufacturing process and improves the reliability of the pressure sensor. 
       FIG.  14    is a perspective diagram showing an example of the use of the pressure detection device  10 . As shown in the figure, for example, the pressure detection device  10  is attached to the frame of a walker  70  and constitutes a grip of the walker  70 . The frame is formed from, for example, a cylindrical pipe and is in tight contact with the second main surface of the pressure sensor  50 . The pressure detection device  10  can measure, when the user grasps the press surface SA, the gripping force and the pressure distribution. Thus, the pressure detection device  10  can measure the gripping force and pressure distribution even when the user is wearing gloves or the like. 
       FIG.  15    is a perspective diagram showing a pressure detection device according to a modified example of the second embodiment. 
     As shown in the figure, the outer circumferential surface (the press surface SA) of the buffer layer  20  may be a biaxially curved surface curved into substantially a bellows shape. The press surface SA has a curved surface shape in which annular convex portions  22   a  and annular concave portions  22   b  are aligned alternately along the axial direction. The inner circumferential surface (installation surface SB) of the buffer layer  20  and the sheet-shaped pressure sensor  50  are formed into a cylindrical uniaxially curved surface. 
     The pressure detection device  10  according to the above-described modified example is suitable for a grip of a bicycle, motorcycle, cane or the like. 
     In addition, the shape of the biaxially curved surface of the press surface SA of the buffer layer  20  is not limited to the barrel shape or bellows shape described above, but can be modified in various ways according to the usage. 
     Third Embodiment 
       FIG.  16    is a perspective diagram showing the side of the press surface of a pressure detection device according to the third embodiment.  FIG.  17    is a perspective diagram showing the side of the pressure sensor of the pressure detection device according to the third embodiment.  FIG.  18    is a cross-sectional view of the pressure detection device taken along line D-D of  FIG.  16   , and  FIG.  19    is a cross-sectional view of the pressure detection device taken along line E-E of  FIG.  16   . 
     As shown in the figures, the pressure detection device  10  of the third embodiment comprises a flat and approximately rectangular buffer layer  20 , a sheet-shaped pressure sensor  50  attached to the buffer layer  20  and a controller (not shown) connected to the pressure sensor  50 . The buffer layer  20  is formed of an elastic material such as synthetic resin, rubber, or elastomer. The buffer layer  20  includes an outer surface (press surface SA) which is a biaxially curved surface and an inner surface (installation surface SB) which is a circular arcuate uniaxially curved surface. The press surface SA is formed into approximately rectangular in planar view and forms a convex arcuate curved surface in the first direction X and a concave arcuate curved surface in the second direction Y. 
     The installation surface SB opposes the press surface SA with an interval therebetween. The installation surface SB is formed into rectangular in planar view and forms a concave arcuate curved surface with respect to the press surface SA. 
     The interval between the press surface SA and the installation surface SB, that is, the thickness of the buffer layer  20  is least in the axial central portion and gradually increases toward both axial ends thereof with respect to the second direction Y. The thickness of the buffer layer  20  is greatest in the axial central portion and gradually decreases toward both axial ends thereof with respect to the first direction X. 
     The pressure sensor  50  has a configuration similar to that of the pressure sensor in the first embodiment described above. That is, the pressure sensor  50  is formed into a rectangular sheet having a thickness of 10 to several hundred μm. The pressure sensor  50  includes a pair of rectangular main surfaces opposing each other. The pressure sensor  50  is attached by one entire main surface (the second surface  60   b  of the protective layer described above) to the installation surface SB of the buffer layer  20  and is in tight contact with the entire installation surface SB. The pressure sensor  50  is curved along the installation surface SB to form a uniaxially curved surface identical to the installation surface SB, in this case, an arcuate curved surface. The four sides of the pressure sensor  50  are aligned with the four sides of the installation surface SB, respectively. 
     The pressure detection device  10  configured as described above can be installed on, for example, a chair seat, a support stand, a sofa or the like, and used as a mat, a seat cushion or the like. In this case, the side of the pressure sensor  50  is placed on the seat surface, support stand or the like. When the user sits on the press surface SA, the pressure detection device  10  measures the value of the pressure applied to the press surface SA and the pressure distribution. 
     In the pressure detection device  10  of the third embodiment configured as described above, the uniaxially curved pressure sensor  50  can detect the pressure applied to the press surface SA including a biaxially curved surface and the pressure distribution. Thus, the pressure sensor  50  need not to be biaxially curved, thereby making it possible to simplify the manufacturing process and improve the reliability of the pressure sensor. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     For example, the shapes of the press surface and the installation surface of the buffer layer are not limited to those of the embodiments described above, but various other shapes can be selected according to the usage and conditions of use of the pressure detection device. The materials and dimensions of the buffer layer and the pressure sensor are not limited to those of the embodiments described above, but can be varied appropriately as needed. In addition, for the curved surfaces, those of biaxially or more curved surface may as well be applied.