Patent Publication Number: US-9847192-B2

Title: Push button keyboard device

Description:
PRIORITY CLAIM 
     The present application claims benefit of priority under 35 U.S.C. §§120, 365 to the previously filed Japanese Patent Application No. JP2014-055607 with a priority date of Mar. 18, 2014, which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to keyboard devices in general, and particularly to a keyboard device used in an electronic apparatus. 
     2. Description of Related Art 
     A keyboard device used in an electronic apparatus such as a laptop personal computer (laptop PC) is normally equipped with a base plate, a membrane sheet provided on the upper or lower surface of the base plate, and a key top vertically movably arranged on the upper surface side of the base plate by a pantograph. In such a keyboard device, the corresponding signal is output to a key depressed by making contacting/separating action of the contact of the membrane sheet when the key top is depressed. When the depression of the key top is released, the key top is reset to its original position by the elastic force of a rubber dome (elastic member) provided inside. 
     The keyboard device generates a suitable repulsive force (or biasing force) when a user depresses the key top with a configuration based on the pantograph and the rubber dome and realizes high usability. To make a thinner keyboard device is relatively difficult because of the usage of rubber domes. For one prior art thin keyboard design, an actuator is placed thereinside and a haptic feedback (or vibration) is provided when a key is depressed. One problem with this thin keyboard design is that vibration is different in touch from the “click” of a key, and the usability is degraded with no suitable repulsive force. Consequently, it would be desirable to provide an improved thin keyboard design. 
     SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the present invention, a keyboard device includes a base, a key top, a film actuator, a position sensor, and a controller. The key top is movably arranged on the upper surface side of the base. Disposed between the base and the key top, the film actuator bends according to an applied voltage. Also disposed between the base and the key top, the position sensor detects a position of the key top. The controller applies a voltage to the film actuator in order to generate a repulsive force corresponding to the position of the key top detected by the IC position sensor. 
     All features and advantages of the present disclosure will become apparent in the following detailed written description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a diagram of an electronic apparatus in which a keyboard device according to a preferred embodiment of the present invention can be incorporated; 
         FIG. 2  is a diagram illustrating a repulsive force of a key in a keyboard device; 
         FIG. 3  is a diagram illustrating the principle of a film actuator; 
         FIG. 4A  is a diagram showing a top positions of a key; 
         FIG. 4B  is a diagram showing a bottom positions of a key; 
         FIG. 5  is a diagram illustrating a configuration example of a film actuator control circuit; 
         FIG. 6  is a diagram describing the relationship between a force curve table and the position of a key top at states (a)-(e); 
         FIG. 7  is a flowchart of a method for controlling a repulsive force of a film actuator by a keyboard controller; 
         FIG. 8  is an exploded perspective diagram of a key provided in the keyboard device; 
         FIG. 9  is a perspective diagram of a key where a key top is at a top position; 
         FIG. 9A  is a cross-sectional diagram of the key from  FIG. 9  taken along line A-A; 
         FIG. 9B  is a cross-sectional diagram of the key from  FIG. 9  taken along B-B; 
         FIG. 10  is a perspective diagram of a key where a key top is at a bottom position; 
         FIG. 10A  is a cross-sectional diagram of the key from  FIG. 10  taken along line A-A; and 
         FIG. 10B  is a cross-sectional diagram of the key from  FIG. 10  taken along B-B. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     A keyboard device, a push button device and an electronic apparatus according to the present invention will hereinafter be described in detail based on the accompanying drawings. It will be readily understood that the components of the present invention, as generally illustrated in the figures of the present specification, may be arranged and designed widely in various ways in a variety of different configurations. Thus, the following more detailed description of the embodiments of the device, system and method of the present invention is not intended to limit the scope of the present invention as claimed, but is merely representative of one example of the selected embodiment of the present invention, and is merely illustrative of the selected embodiment related to the device, system and method without inconsistency with the present invention as claimed in the present specification. One skilled in the related art will recognize that the present invention can be practiced even without one or more of the specific details or even with other methods, components and materials. Incidentally, the present invention is not limited by this embodiment. Further, the components in the following embodiments include one that can be assumed easily by one skilled in the related art, or the substantially the same one. The following embodiments and modifications may respectively be practiced independently, or parts or all thereof may be practiced in combination. 
       FIG. 1  is a diagram of a laptop PC  10  to which a keyboard device according to a preferred embodiment of the present invention is applied. As shown, the laptop PC  1 . 0  is equipped with a main body side chassis  14  and a display side chassis  12  both of which are substantially parallelepiped. The main body side chassis  14  and the display side chassis  12  are coupled to each other by a pair of right and left hinges  20  at their ends. The hinges  20  openably/closably support these chassis. 
     The display side chassis  12  is provided with a display  18 . The display  18  is configured by, for example, a touch panel type liquid crystal display device. The main body side chassis  14  accommodates thereinside a substrate (not shown) equipped with various electronic parts such as a keyboard controller (refer to  FIG. 5 ) that controls the operation of the keyboard device  16 , a main controller that controls the entire apparatus, a display controller that controls the display  18 , etc. and includes the keyboard device  16  exposed at the upper surface of the main body side chassis  14 . 
     The keyboard device  16  is an isolation type keyboard device equipped with a plurality of keys (key switches)  22 , and a frame (or isolation frame)  26  that fills a gap surrounding a key top  24  constituting an operation surface of each key  22 . Namely, in the keyboard device  16 , the frame  26  partitions between the key tops  24  and other adjacent key tops  24 , and the partitioned key tops  24  are respectively arranged independently. 
     The frame  26  is a frame body formed with a plurality of holes through which the key tops  24  of the keys  22  are inserted in a sheet of plate-like member formed of a resin or the like. 
     The keyboard device  16  is connected to the keyboard controller. When an operator depresses the key top  24 , a signal corresponding to the key  22  depressed by making contacting/separating action of the contact of a membrane sheet (not shown) (when the key switch is in a state of ON) is output to the keyboard controller. 
     In the present embodiment, in order to generate a repulsive force suitable for a user where the key top  24  is depressed while thinning the keyboard device  16 , a film actuator is used in the keyboard device  16 . 
       FIG. 2  is a diagram showing the repulsive force of the key  22  in the keyboard device  16 . As illustrated in  FIG. 2 , the key  22  is equipped with a key top  24 , a film actuator  31 , a position sensor  32  that detects the position of the key top  24 , a cushion plate  33 , and a base plate  34 . In the same figure, the illustration of a switch mechanism (membrane sheet or the like) is omitted for ease of explanation. 
     The key top  24  has a surface which serves as an operation surface depressed by the operator upon depressing the key  22 . The film actuator  31  applies a repulsive force (biasing force) in the direction to return the key top  24  to its original position when the key top  24  is depressed. Both end sides of the film actuator  31  are fixed to the base plate  34 . 
       FIG. 3  is a diagram showing the principle of the film actuator  31 .  FIG. 4  is a diagram describing the top and bottom positions of the key top  24 . In  FIG. 3 , the film actuator  31  has, for example, a structure made by binding two of a piezoelectric polymer  31   a  and a non-piezoelectric film  31   b  such as a PET film together (e.g., Electrical-Mechanical Polymers (EMP) actuator). The film actuator  31  makes use of the PET film  31   b  being bent by stretching of the piezoelectric polymer  31   a  by the application of a voltage.  FIG. 3 a    illustrates a state in which no voltage is applied to the piezoelectric polymer  31   a , and  FIG. 3 b    illustrates a state in which the voltage is applied to the piezoelectric polymer  31   a.    
     In  FIG. 4 , since the film actuator  31  does not stretch in the state in which no voltage is applied thereto, as illustrated in (bottom position), the key top  24  is at the bottom position without being pushed up. When an initial voltage is applied to the film actuator  31  as illustrated in (top position), the film actuator  31  is bent by its stretching to push the key top  24  upwards, so that the key top  24  is at the top position. This top position is referred to as a reference position (or start position). The position of the key top  24  is set with an X1 direction defined as a plus direction (refer to  FIG. 6 ). 
     The position sensor  32  is for detecting the position of the key top  24  and can use the same material as the film actuator  31 , for example. When the film actuator is bent, the polarization of the piezoelectric polymer  31   a  is aligned in direction to generate a polarization potential. It is therefore possible to detect the position of the key top  24  by measuring the potential. When the film actuator is used as the position sensor  32  (hereinafter referred to as a film sensor  32 ), both end sides of the film sensor  32  are fixed to the base plate  34 , and the position (height) of the key top  24  is set to correspond to the bending of the film sensor  32  one on one. Incidentally, although a description has been made about the example in which the film sensor is used as the position sensor  32 , an electrostatic sensor or a distance sensor may be used. 
       FIG. 5  is a diagram illustrating a configuration example of a film actuator control circuit related to the control of the repulsive force of the film actuator  31 . The film actuator control circuit is equipped with a keyboard controller  40 , a driver  41 , and an amplifier  42  as illustrated in  FIG. 5 . The keyboard controller  40  detects the position of the key top  24 , based on the voltage detected by the film sensor  32  and applies a voltage for generating a repulsive force corresponding to the position of the key top  24  to the film actuator  31 . 
     The keyboard controller  40  is equipped with a key top position calculating table  40   a , a force curve table  40   b , and a film actuator characteristic table  40   c . The key top position calculating table  40   a  is a table that defines the relationship between the detected voltage of the film sensor  32  and the position (or height) of the key top  24 . The force curve table  40   b  is a table that defines the relationship between the position of the key top  24  and the repulsive force generated by the film actuator  31 . The film actuator characteristic table  40   c  is a table that defines the relationship between the repulsive force generated by the film actuator  31  and the drive voltage to be applied to the film actuator  31 . These tables are calculated by experiment, simulation or the like. 
     The driver  41  amplifies the voltage outputted from the keyboard controller  40  and applies the same to the film actuator  31 . The amplifier  42  amplifies the detected voltage of the film sensor  32  and outputs the same to the keyboard controller  40 . 
       FIG. 6  is a diagram showing one example of the relationship between the force curve table  40   b  and the position of the key top  24 . An example of a force curve illustrated in  FIG. 6  is illustrated as a similar force curve as a rubber dome, and the shape of the force curve can be arbitrarily set (programmed). The force carve table  40   b  may change the force curve in the direction (outward path) to depress the key top  24  and the direction (return path) to return the key top  24  or may reduce the repulsive force in the direction to return the key top  24  more than that in the direction to depress the key top  24 . 
     In  FIG. 6 , the start position is in a state (a) in which the initial voltage is applied to the film actuator  31  so that the key top  24  is pushed up to be at the top position (reference position). As the key top  24  is pressed, the repulsive force of the film actuator  31  gradually increases (b). The repulsive force is at the peak (c) in, for example, a position where the key switch assumes a state of ON. After that, the repulsive force is reduced (d), and thereafter the repulsive force is increased again (e) to rise to an end position. 
     Incidentally, a plurality of force curves (e.g., a force curve small in repulsive force, a force curve large in repulsive force, etc.) may be prepared and configured to be selectable according to the preference of the user. 
       FIG. 7  is a flowchart of a method for controlling the repulsive force of the film actuator  31  by the keyboard controller  40 . The keyboard controller  40  repeatedly performs the processing illustrated in the flowchart of  FIG. 7  in a predetermined cycle. In  FIG. 7 , the keyboard controller  40  obtains the detected voltage of the film sensor  32  through the amplifier  42  (Step S 1 ). Since the detected voltage of the film sensor  32  corresponds to the position of the key top  24  as described above, the position of the key top  24  can be detected by detecting the voltage of the film sensor  32 . The keyboard controller  40  calculates the position of the key top  24  corresponding to the thus obtained detected voltage by referring to the key top position calculating table  40   a  (Step S 2 ). 
     The keyboard controller  40  calculates a repulsive force of the film actuator  31  corresponding to the calculated position of the key top  24  by referring to the force curve table  40   b  (Step S 3 ). Subsequently, the keyboard controller  40  calculates a voltage to be applied to the film actuator  31  corresponding to the calculated repulsive force of the film actuator  31  by referring to the film actuator characteristic table  40   c  (Step S 4 ). Afterwards, the keyboard controller  40  applies the calculated voltage to the film actuator via the driver  41  (Step S 5 ). Thus, the repulsive force corresponding to the position of the key top  24  occurs in the film actuator  31 . 
     Incidentally, although the position of the key top  24 , the repulsive force of the film actuator  31  and the voltage applied to the film actuator  31  are calculated using the tables here, they may be calculated using operational expressions. Further, although the voltage for generating the repulsive force of the film actuator  31  corresponding to the position of the key top  24  is calculated using the two two-dimensional tables of the force curve table  40   b  and the film actuator characteristic table  40   c , it may be calculated using a three-dimensional table that defines the relationship among the position of the key top  24 , the repulsive force of the film actuator  31  and the voltage applied to the film actuator  31 . 
     A schematic configuration example of the keyboard device  16  according to the present embodiment will next be described.  FIG. 8  is an exploded perspective diagram of the key  22  provided in the keyboard device  16  as viewed from above.  FIG. 9  is a perspective diagram of the key  22  where the key top  24  is at a top position;  FIG. 9A  illustrates a cross-section taken along line A-A thereof; and  FIG. 9B  illustrates a cross-section taken along line B-B thereof.  FIG. 10  is a perspective diagram of the key  22  where the key top  24  is at a bottom position; and  FIG. 10A  illustrates a cross-section taken along line A-A thereof; and  FIG. 10B  illustrates a cross-section taken along B-B thereof. The illustration of a configuration related to the switch of the key  22  is omitted in  FIG. 8  to  FIG. 10  for simplicity of description. 
     In  FIG. 8  to  FIG. 10 , the key top  24  is formed to be almost rectangular plate-like, and the surface thereof serves as an operation surface depressed by the user. The frame  26  is formed of a resin or the like and is a frame body formed with a hole that inserts the key tops  24  therethrough. 
     A guide mechanism (pantograph)  51  guides the up/down movement of the key top  24  accompanied with its depression operation. In other words, the guide mechanism  51  guides the depression and return movements of the key top  24 . The guide mechanism  51  has a first link member and a second link member. The first link member and the second link member are arranged so as to intersect with each other. The first link member and the second link member are coupled to each other through a shaft  51   a  in the central part of an intersecting portion and rotated about the shaft  51   a . The first link member has one end pivotally supported by an engaging part  34   a  of the base plate  34  and the other end brought into abutment against the back surface of the key top  24 . The second link member has one end pivotally supported by an engaging part  34   b  of the base plate  34  and the other end brought into abutment against the back surface of the key top  24 . 
     The film actuator  31  is laminated with the film sensor  32  of the same shape as that. The film actuator  31  is an elastic member that generates a repulsive force corresponding to the position of the key top  24 . The film actuator  31  has a portion arranged between the base plate  34  and the key top  24  and acting on the key top  24 , which penetrates the inner periphery of the guide mechanism  51 . The film actuator  31  is brought into contact with the lower surface of the key top  24 , and both ends of the portion acting on the key top  24  are fixed to a receiving part  34   c  of the base plate  34 . 
     The base plate  34  is made of a member having rigidity endurable to the key touch of the user, e.g., a metal and is formed approximately like a plate. The engaging parts  34   a  and  34   b  and the receiving part  34   c  are formed on the base plate  34 . 
     Since the film actuator  31  is not stretched in the state in which no voltage is applied to the film actuator  31  as illustrated in  FIG. 10 , the key top  24  is at the bottom position and placed in a lower position to the frame  26 . Further, as illustrated in  FIG. 9 , in the state in which the initial voltage is applied to the film actuator  31 , the film actuator  31  is stretched to push the key top  24  upwards, so that the key top  24  is at the top position and placed in a higher position to the frame  26 . 
     Incidentally, when the keyboard device  16  becomes active (e.g., where the PC main body is reset from a sleep state when the power supply thereof is ON, etc.), the keyboard controller  40  applies the initial applied voltage to the film actuator  31 . When the keyboard device  16  becomes inactive (where a tablet configuration, i.e., configuration in which the keyboard device  16  of the main body side chassis  14  is exposed, is adapted in such a configuration that the display side chassis  12  is rotatable 360° relative to the main body side chassis  14  where the PC main body is in the sleep state when the power supply thereof is OFF, etc.), the keyboard controller  40  may turn OFF the voltage to be applied to the film actuator  31 . 
     According to the present embodiment as described above, the keyboard device is equipped with the base plate  34 , the key top  24  vertically movably arranged on the upper surface side of the base plate  34 , the film actuator  31  arranged between the base plate  34  and the key top  24  and bent according to the applied voltage, the film sensor  32  arranged between the base plate  34  and the key top  24  and for detecting the position of the key top  24 , and the keyboard controller  40  that applies the voltage to the film actuator  31  and generates the repulsive force according to the position of the key top  24  detected by the position sensor. Therefore, with an inexpensive and simple configuration, it is possible to obtain a repulsive force suitable for the user where the key top is depressed, while thinning the keyboard device. Additionally, the keyboard device can be made thinner as compared with the configuration where the rubber dome is used. Further, it is possible to obtain a repulsive force more suitable when the key top is depressed than the case of using vibrations generated by haptic feedback, thereby making it possible to improve usability. Further, the keyboard device can be provided with an inexpensive and simple configuration as compared with the structure of generating a repulsive force by an electromagnetic coil mechanism. 
     Incidentally, in the above embodiment, the mechanism of generating the repulsive force by the film actuator  31  is applied to the keyboard device  16 , but the present invention is not limited by or to this. The present invention can be applied even to a push button device mounted in an electronic apparatus or the like. In this case, the push button device can include as a basic configuration, a configuration equipped with a base, an operating member vertically movably arranged on the upper surface side of the base, a film actuator disposed between the base and the operating member and bent according to a voltage to be applied, a position sensor disposed between the base and the operating member and for detecting the position of the operating member, and control means that applies a voltage to the film actuator to generate a repulsive force corresponding to the position of the operating member detected by the position sensor. 
     As has been described, the present disclosure provides an improved thin keyboard design. 
     While the disclosure has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure.