Tactile presenting device

A tactile presenting device includes a panel presenting a tactile sensation, and a control unit that vibrates the panel in a direction perpendicular to a surface of the panel by magnetic force, the control unit vibrating the panel at a frequency equal to or lower than 50 Hz.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the benefit of priority from Japanese Patent Application Publication No. 2004-259092, filed on Sep. 6, 2004 the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

This invention generally relates to tactile presenting devices, and more particularly, to a tactile presenting device having the function of presenting a tactile sensation by vibrating a panel for presentation of tactile in a direction perpendicular to the plane surface.

2. Description of the Related Art

Recently, a touch panel has widely been used for personal computers, PDA, ATM equipment, POS terminals, car navigation, copying machines and so on. The touch panel has a flat panel, which may be depressed by a pen or finger, and outputs information indicative of the coordinates of a touched position. The conventional touch panels cannot present a tactile sense (click sense) associated with depressing, which may be presented by mechanical switches, and has a difficulty in presenting recognizable depressing.

Japanese Patent Application No. 2003-122507 discloses a method for presenting a tactile (click sense) sensation by vibrating a panel of a touch panel input device.FIG. 1shows the touch panel input device disclosed in this application. A piezoelectric element2is used as a vibration source, which vibrates movable plates3of a touch panel1.

However, the structure shown inFIG. 1has a difficulty in low-voltage driving because of the use of the piezoelectric element2, and needs to boost the ordinary operating voltage for electronic circuits in the range of 3 V to 5 V to hundreds of volts. The piezoelectric element is primarily suitable for high-frequency vibrations, and has small amplitudes of vibration.FIG. 2shows an exemplary waveform for driving the piezoelectric element. The piezoelectric element vibrates at a frequency of approximately 400 Hz, and this vibration can be heard by ears of human being. The vibration is apparently different from a sense such that the button has been depressed.

SUMMARY

The present invention has been made in view of the above circumstances and has an object of providing a tactile presenting device and method capable of a practical depressing sense.

This object of the present invention is achieved by a tactile presenting device including a panel presenting a tactile sensation, and a control unit that vibrates the panel in a direction perpendicular to a surface of the panel by magnetic force, the control unit vibrating the panel at a frequency equal to or lower than 50 Hz.

The above object of the present invention is also achieved by a method of presenting a tactile sensation including the steps of vibrating a panel in a direction perpendicular to a surface of the panel by magnetic force; and controlling vibration of the panel at a frequency equal to or lower than 50 Hz.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A tactile presenting device according to one aspect of the present invention includes a panel for presenting a tactile sensation, and a control unit for vibrating the panel in a direction perpendicular to the plane surface by magnetic force to thus present a tactile sensation. The control unit vibrates the panel at a frequency equal to or lower than 50 Hz. The audible frequency sensed by the ears of the human being ranges from 20 Hz to 20,000 Hz. It may be preferable that the vibration has a frequency of 20 Hz or lower. However, this holds true for a vibration formed by a continuous wave. If a vibration is formed by a one-shot wave of a frequency equal to 20 Hz or lower, it may be difficult to sense the vibration of the panel. It is thus preferable that the one-shot wave has a frequency higher than 20 Hz. However, if a one-shot wave has a frequency higher than 50 Hz, it may be audibly sensed. As a result of the above consideration, it is preferable that the panel is driven by a one-shot wave having a frequency equal to or lower than 50 Hz, as shown inFIG. 3A. In this driving, the panel is vibrated once in only one of the two directions perpendicular to the plane surface of the panel. Preferably, the panel may be driven upwards. InFIG. 3A, the horizontal axis denotes time, and the vertical axis denotes the amplitude of vibration (or the magnitude of driving current).

Instead of the one-shot wave, as shown inFIG. 3B, the panel may be driven so as to successively generate multiple one-shot waves, each having a frequency equal to or lower than 50 Hz. That is, the panel is driven so as to generate multiple times in only one of the two directions perpendicular to the plane surface of the panel. It is also possible to drive the panel once by a pair of waves that have an identical shape but the opposite amplitudes, as shown inFIG. 4. It is also possible to drive the panel multiple times by multiple pairs of waves that have an identical shape but the opposite amplitudes. In this case, the panel is vibrated multiple times on both sides of the plane surface.

Even for the one-shot wave of a frequency equal to or lower than 50 Hz, if the one-shot wave rises quickly, it will contain high-frequency components, and the operator senses an impact shock vibration. Preferably, the one-shot wave gently rises like a wave obtained by squaring a sine wave. Preferably, the vibration of the panel has a wave that does not have any inflection point. The inflection point is defined as follows. That is, x=a is the inflection point of f(x) so that fx is convex upwards for x<a and is convex downwards for x>a, or fx is convex downwards for x<a and is convex upwards for x>a. For the wave rising gently, the operator does not sense an impact shock but purely senses a vibration. Preferably, the amplitude of vibration is equal to 0.2 mm or greater. The panel is driven when a given time elapses after touching of an object to the panel is sensed. This makes it possible for the operator to feel a sense similar to the actual depressing sense.

FIG. 5Ais an exploded perspective view of the fundamental structure of a tactile presenting device according to an embodiment of the present invention, andFIG. 5Bshows a panel driving mechanism used in the tactile presenting device, and is an enlarged view of a portion B shown inFIG. 5A. The tactile presenting device includes a panel10, a coil11and multiple magnetic units12, each of which includes a magnet and a yoke. The magnetic units12function as a control unit that vibrates the panel10in the vertical direction(s) with respect to the plane surface thereof, and thus presents a tactile sensation. The details of the panel10will be described later with reference toFIG. 8. The coil11is supported by the lower surface of the panel10, and is wound along the four sides of the panel10. As shown inFIG. 5B, the coil11is wound so that currents flow in the opposite directions along each side of the panel10. The coil11may be formed by a single wire folded so as to flow the currents in the opposite directions, or may be two coils in which the opposing currents flow. The magnetic unit12includes a yoke18and a magnet19. The yoke18has a substantially C-shaped cross section, and the magnet19is arranged in the central portion of the yoke18. Due to the function of the yoke18and the magnet19, two magnetic circuits are formed. One of the magnetic circuits flows the magnetic flux counterclockwise, and the other magnetic circuit flows the magnetic flux clockwise. The currents that flow in the opposite directions cross the magnetic fluxes of the two magnetic circuits, respectively. Force is exerted on the coil11by the two magnetic circuits and the opposing flows of currents according to the Fleming's left-hand rule. In the orientations of the magnetic poles and currents shown inFIG. 5B, upward force is exerted on the coil11. This force vibrates the panel10.

When currents flow through the coil11so as to form the vibration waveform shown inFIG. 3A, the panel10is vibrated upwards at only one time. When currents flow through the coil11so as to form the vibration waveform shown inFIG. 4, the panel10is vibrated upwards and downwards only once.

FIG. 6is a more detailed exploded perspective view of the tactile presenting device shown inFIG. 5, andFIG. 7is a cross-sectional view of the portion B shown inFIG. 5A. The tactile presenting device includes a frame21, the magnetic units12, suspensions22, a panel printed-circuit board23, the coil11, the panel10, a cover22and a packing member25, these structural parts being stacked in this order from the bottom side. The magnetic units12and the suspension22are mounted on the frame21. The suspensions22are disposed in the vicinity of the four corners of the panel10, and are in contact with the lower surface of the panel10. The suspensions22suppress unwanted vibrations (frequency components over 50 Hz). The suspensions22may be made of an elastic member such as rubber. The elastic members of the suspensions22may have hollows in order to facilitate the efficiency of damping. The coil11is attached to the lower surface of the panel10, and face the magnetic units12made of the yoke and the magnet19. The panel10is supported by the cover24attached to the frame21. The cover24has a sheet-like shape, and the packing member25is provided on the cover24. The packing member25may be made of an elastic member, and is fixed to the peripheral portions of the panel10. The panel printed-circuit board23has a panel drive circuit mounted thereon.

FIG. 8shows a cross section of the panel10. The panel10has a film31that may be made of PET (polyethylene terephthalate), an upper transparent electrode32that may be ITO (indium-tin oxide), a glass plate33, a lower transparent electrode34, and dot spacers35. The upper transparent electrode32is attached to the entire inner surface of the film31. The upper electrode32and the lower electrode34are connected to an analog-to-digital converter, which will be described later. The dot spacers35, which may be made of an insulator, are arranged in a matrix formation. As shown in the lower part ofFIG. 8, when the panel10is depressed from the upper side thereof by a pen or finger36, the film31is deformed and the upper transparent electrode32is brought into contact with the lower transparent electrode34. Several methods for detecting the coordinates of the depressed position are available, and any of these methods may be used. For example, a voltage is applied across the lower transparent electrode34in the X direction (transverse direction on the drawing sheet), and the potential at the depressed position (which corresponds to the X coordinate position) is detected via the upper transparent electrode32. Similarly, a voltage is applied across the lower transparent electrode34in the Y direction (lateral direction on the drawing sheet), and the potential at the depressed position (which corresponds to the Y coordinate position) is detected via the upper transparent electrode32. Analog voltages thus obtained are converted into digital signals, which show the coordinates as position information. Another detecting method applies a voltage across the upper transparent electrode32in the X direction, and detects the potential at the depressed position via the lower transparent electrode34. Similarly, a voltage is applied across the upper transparent electrode32in the Y direction, and the potential at the depressed position is detected via the lower transparent electrode32. In this manner, data showing the XY coordinates of the depressed position can be obtained. When the coordinates data is not needed, only one of the two detection steps may be carried out.

FIG. 9is a block diagram of a panel drive unit, which may be mounted on the panel printed-circuit board23. The analog signals produced by the above-mentioned manner are converted into digital signals by an analog-to-digital converter41. The digital signals are then applied to a control unit42, which detects the position information by the above-mentioned manner. The control unit42may, for example, be a microcomputer, and executes a program, which will be described later. The position information is supplied to an external device to which the tactile presenting device is connected. The external device supplies the tactile presenting device to waveform information. The waveform information describes the waveform, which may be as shown inFIG. 3A,3B or4. An amplifier43generates a current based on the waveform information, and supplies it to the coil11.

FIG. 10is a block diagram of another structure of the panel drive unit, in which parts that are the same as those shown in the previously described figures are given the same reference numerals. The control unit42receives waveform selection information from the external device. The control unit42selects waveform information corresponding to the received waveform selection information from among items of waveform information respectively indicative of the respective waveforms stored in a memory device44. For example, the items of waveform information stored in the memory device44respectively describe the waveforms as shown inFIGS. 3A,3B and4. The waveform information thus selected is applied to a digital-to-analog converter45, which converts the waveform information described in digital fashion into a corresponding analog signal, which is applied to the amplifier43.

FIG. 11is a block diagram of yet another structure of the panel drive unit, which differs from that shown inFIG. 10in that the structure shown inFIG. 11can output tactile presenting information to the external device in addition to the position information, and the control unit42has an ability of selecting the desired waveform information without receiving information from the external device.FIG. 12is a flowchart of an operation of the tactile presenting device shown inFIG. 11. The control unit42acquires the position information indicating the depressed position on the panel (step S1). The control unit42determines whether the position indicated by the position information is within a predetermined button range (step S2). Positions corresponding to buttons on the panel10are predetermined, and the control unit42has position information describing the button ranges. When the determination result of step S2is YES, the control unit42selects the corresponding waveform, and outputs information indicating the tactile selected to the external device (step S3). Simultaneously, the control unit42reads the waveform information about the selected waveform from the memory device44, and outputs it to the digital-to-analog converter45. When the determination result of step S2is NO, the control unit42returns to step S1.

FIG. 13is a flowchart of the detailed operation of the control unit42shown inFIGS. 9 through 11. In the structure shown inFIG. 9, some steps shown inFIG. 13are executed by the external device. In the following, the flowchart ofFIG. 13will be described as the operation of the control unit42of the tactile presenting device shown inFIG. 10. The control unit42prepares detection of touch (step S11).FIG. 14shows lead extraction electrodes51through54provided on each of the upper transparent electrode32and the lower transparent electrode34. At step S11, the control unit42applies a given voltage (indicated as “H” inFIG. 13) to, for example, the extraction electrode52of the lower transparent electrode34, and applies the extraction electrode53of the upper transparent electrode32to the ground potential (indicated as “L” inFIG. 13). Further, the control unit42assigns the extraction electrode54of the lower transparent electrode34to an input electrode (also referred to as a detection electrode). At step S12, the control unit42senses the potential of the input electrode, and checks whether the potential of the input electrode is H at step S13. The control unit42returns to step S11when the determination result of step S13is YES, and proceeds to step S14otherwise. At step S14, the control unit42prepares detection of the X coordinate. More specific, the control unit42sets the extraction electrode52of the upper transparent electrode32to H, and sets the opposing extraction electrode54to L. Further, the control unit42sets the extraction electrode51of the lower transparent electrode34to the input electrode. Thereafter, the control unit42detects the potential of the X coordinate at step S15. When the panel10is depressed, the input electrode is at the potential corresponding to the depressed point. The control unit42receives the digital value of the detected potential via the analog-to-digital converter41. The digital value indicates the X coordinate of the depressed point. At step S16, the control unit42prepares the Y coordinate. More specific, the control unit42sets the extraction electrode52of the lower transparent electrode34to H, and sets the opposing extraction electrode54to L. Further, the control unit42sets the extraction electrode51of the upper transparent electrode32to the input electrode. At step S17, the control unit42detects the Y coordinate.

At step S18, the control unit42determines whether the touched position specified by the X and Y coordinates falls within the range of button #1. When the determination result is YES, the control unit42reads the waveform information associated with button #1from the memory device44, and sends it to the digital-to-analog converter45. Similarly, at step S20, the control unit42determines whether the touched position falls within the range of button #2. When the determination result is YES, the control unit42reads the waveform information associated with button #2from the memory device44, and sends it to the digital-to-analog converter45. Similarly, up to step S22, the control unit42determines whether the touched position falls within the range of any of n buttons. When the determination result is YES, the control unit42reads the corresponding waveform information from the memory device44.

In the structure shown inFIG. 9, the control step42executes steps S11to S17, and the external device executes steps S18to S23.

As described above, the present tactile presenting device can vibrate the panel10with the predetermined waveform associated with the depressed position, and are thus used for various applications. For instance, when the tactile presenting device is applied to an electronic calculator, it is easy to realize a man-machine interface such that numeral keys may be vibrated weakly, and the enter key may be vibrated strongly. When the tactile presenting device is applied to data input for an industrial robot, a waveform having only a single peak (FIG. 3A) is used for correct scan, and another waveform having successive peaks is used for an incorrect operation (for example, an alphabet is incorrectly input in a case where a numerical value is required). In an application in which displayed images change like A, B, C A, B . . . , a strong vibration is used at a switching from image C to image A, and a weak vibration is used at other switching. When the tactile presenting device is applied to an external character editor, a waveform having only a single peak is used when the dot changes from white to black, and another waveform having two peaks is used when the dot changes from black to white.