Patent Application
20160186730
The present invention relates to an impact actuator, a touch panel, and a drive method, and more specifically relates to, for example, an impact actuator, a touch panel, and a drive method that use a shape memory alloy the shape of which changes by causing an electric current to pass therethrough.
Conventionally, there are known actuators using a shape memory alloy (hereinafter abbreviated by SMA as appropriate), which expands and shrinks depending on a change in temperature. For example, the following Patent Literature 1 describes an actuator that produces vibration of various magnitudes by changing the voltage (peak value) of a pulse signal to be applied to the actuator.
In the actuator described in Patent Literature 1, since the peak value is invariant in the single pulse signal, it is difficult to produce various operation feelings in accordance with the single pulse signal.
Thus, one of objects of the present invention is to provide a novel and useful impact actuator, touch panel, and drive method that can solve the above-described problem.
To solve the above problem, a first aspect of the present invention is, for example, an impact actuator that includes a drive signal output unit for outputting a drive signal in which a voltage of a single pulse signal is changed with time, and a shape memory alloy through which an electric current is caused to pass in a period corresponding to the drive signal.
A second aspect of the present invention is, for example, a touch panel that includes an input unit on which an input operation is performed, a drive signal output unit for outputting a drive signal in which a voltage of a single pulse signal is changed with time in response to the input operation, and a shape memory alloy through which an electric current is caused to pass in a period corresponding to the drive signal.
A third aspect of the present invention is, for example, a drive method of an impact actuator, the method including the steps of: outputting a drive signal in which a voltage of a single pulse signal is changed with time; and causing an electric current to pass through a shape memory alloy in a period corresponding to the drive signal.
According to at least one of embodiments, various operation feelings can be produced.
Embodiments of the present invention will be described below with reference to the drawings. The description is given in the following sequence.
The embodiments and the like described below are preferable concrete examples of the present invention, and do not limit the contents of the present invention. Moreover, effects described below are just examples, and do not limit the interpretation of the contents of the present invention.
First, the structure of a common impact actuator (hereinafter appropriately abbreviated as actuator) will be described for the purpose of ease of understanding of the present invention. In the following description, a structure including a SMA, a drive circuit for switching the SMA between an energized state and a non-energized state, and the like is collectively called an actuator.
A switching element is connected in series to the SMA. The switching element is, for example, an N-channel type MOSFET (metal oxide field effect transistor). The drain (D) of the MOSFET is connected to the SMA. The source (S) of the MOSFET is grounded. To the gate (G) of the MOSFET, a single pulse signal is input to control the switching operation of the MOSFET.
By performing ON/OFF control of the MOSFET, the SMA is switched between the energized state and the non-energized state. For example, while the MOSFET is turned on, the capacitor C1 is discharged, and thereby the SMA is heated by causing an electric current to pass therethrough. The heating by the passage of the electric current shrinks the SMA at a predetermined acceleration. While the MOSFET is turned off, the passage of the electric current through the SMA is stopped, and thereby the SMA expands by cooling with outside air. The shrinkage of the SMA actuates the actuator. The actuation of the actuator can provide an intended operation feeling to the user who has performed the input operation.
As illustrated in
A weight 15 is put on the touch panel 14, and an acceleration sensor 16 is attached on the weight 15. The weight 15 is, for example, 100 g (grams). As the acceleration sensor 16, a well-known sensor can be used. The weight 15 and the acceleration sensor 16 are disposed such that the center lines of the actuator 13, the weight 15, and the acceleration sensor 16 coincide or substantially coincide with each other. The acceleration is measured with such an acceleration measurement jig having the structure described above. More specifically, applying the single pulse signal described below heats the SMA of the actuator 13 by causing the electric current to pass therethrough, and the acceleration sensor 16 measures the acceleration caused by the expansion and shrinkage of the SMA.
In the common actuator, as described above, the SMA can be heated quickly by turning on the MOSFET by the single pulse signal. Thus, the actuator using the SMA has the advantage of increased responsiveness owing to the quick shrinkage of the SMA. In the case of applying the actuator to a touch panel, the touch panel has the advantage of being able to provide a certain vibration or impact (also called click feeling) to a fingertip of a user who has touched an input panel of the touch panel, due to the operation of the actuator. On the other hand, since the voltage of the single pulse signal is invariant with time, there is a problem that various operation feelings are difficult to provide by the operation of the actuator. There is also a problem that an operation sound of the actuator might be more dominant than the feeling that the actuator provides to a fingertip of a user. The embodiments of the present invention, which is made in consideration of above, will be described.
Next, the form of an actuator in the first embodiment of the present invention will be described with reference to
The actuator 100 includes, for example, a movable member 25, a fixed member 26, two terminal fittings 27, and the SMA in the shape of, for example, a string. Both of the movable member 25 and the fixed member 26 are made of an insulating rigid material. A bottom surface of the movable member 25 and a top surface of the fixed member 26 are formed in the shape of convex and concave waves fitted with each other, and the SMA is disposed between the convex and concave surfaces of the both members. Note that, the movable member 25 and the fixed member 26 may be made of a conductive metal material or the like, but in this case, a structure is necessary to prevent shorts between the two terminal fittings 27, such as insulating films provided on the surfaces of the movable member 25 and the fixed member 26, respectively.
The SMA is secured to both ends of the fixed member 26 by the terminal fittings 27. The SMA in this embodiment is made of, for example, a nickel-titanium alloy that has conductivity, predetermined resistance, and the shape of a flexible string with an extremely narrow diameter in an environment around the room temperature. Passing the electric current through the SMA generates heat by the SMA itself, and the heat hardens and shrinks the SMA. It is noted that the SMA is not limited to the nickel-titanium alloy, but may be another metal or alloy as long as it has similar characteristics.
The terminal fittings 27 are fitted onto the respective ends of the fixed member 26 together with ends of the SMA, so as to secure the ends of the SMA with sufficient strength to prevent the SMA from loosening. The terminal fittings 27 are made of a conductive metal, and soldered to a land (not shown) in a predetermined shape provided on the printed wiring board 22. Thus, the fixed member 26 is secured on the printed wiring board 22.
The formative operation of the actuator 100 will be described with reference to
When the electric current stops flowing through the SMA, from the state illustrated in
Note that, the following description describes an example in which the actuator is applied as a vibration device of the touch panel. For example, the input panel is formed on the movable member 25 of the actuator 100, to perform various input operations thereon. Upon detecting the input operation, the single pulse signal (drive signal) having a voltage (high level voltage) changing with time is generated and output. As described later in detail, in a period corresponding to the single pulse signal, the SMA is heated and shrinks by the passage of the electric current therethrough. Using the drive signal that is different from a drive signal used in the common actuator allows the provision of the various operation feelings.
An example of the operation of the actuator 100 will be described. Upon the input operation on the touch panel (for example, a touch of the input panel), the input operation is detected by a not-shown detector. The detector informs the drive signal output unit 31 that the input operation has been performed. In response to the performance of the input operation, the drive signal output unit 31 generates and outputs the single pulse signal, as illustrated in
Since the voltage of the single pulse signal gradually increases, the SMA is heated gradually, instead of rapidly, by the passage of the electric current and shrinks gently. In other words, an acceleration caused by the shrinkage of the SMA can be reduced. Accordingly, the movable member 25 of the actuator 100 is lifted slowly in a vertical direction, thus providing a slow feeling of resistance to the fingertip of the user. Although the acceleration with the operation of the SMA is lower than an acceleration of the SMA in the common actuator, a longer operation time required gives a feeling of operation for long time to the fingertip of the user. Furthermore, reducing the acceleration with the operation of the SMA prevents a break and the like of the SMA, which are likely to occur when the SMA is rapidly heated and shrinks with a high acceleration. Moreover, an operation sound of the actuator can be reduced.
Next, the second embodiment will be described. As described above, the form of the actuator 100 in the first embodiment is applicable as the form of an actuator (actuator 200) in the second embodiment.
An example of the operation of the actuator 200 will be described with reference to
The drain current ID flowing between the drain and the source of the MOSFET gradually increases with increase in the voltage of the single pulse signal. In other words, since the electric current flowing through the SMA can gradually increase, the electric current flowing through the SMA can be changed with time. Thus, the SMA gradually shrinks, and the acceleration increases. The SMA is the most heated by the passage of the electric current in the vicinity of a point (a point indicated with P10 in the vicinity of 5 ms (milliseconds) in
The electric current flowing through the SMA reaches its peak in the course of increase in the voltage of the single pulse signal, and then decreases. This is because the capacity of the capacitor C1 decreases. Thereafter, the electric current flowing through the SMA decreases. In other words, energy to be applied to the SMA decreases. After the capacitor C1 is discharged and the electric current stops flowing through the SMA, the SMA extends by natural cooling by outside air and the like. As a matter of course, increase in the capacity of the capacitor C1 allows increase in the voltage of the single pulse signal, and hence increase in the electric current flowing through the SMA. After the acceleration increases once and becomes zero, the waveform of the acceleration appears. This is variation in the acceleration generated when the movable member 25 returns to the initial position, that is, the acceleration generated by vibration caused by a restoring force and the like occurring around the acceleration sensor, after the SMA shrinks.
As described above, according to the actuator 200, it is possible to control the energy to be applied on a time basis within the single heat shrinkage of the SMA, and control a heating time of the SMA in an arbitrary manner. Thus, the SMA can be shrunk gently or at a shrinkage rate increasing stepwise. By applying the actuator 200 to a vibration driver of a touch panel, it is possible to give a slow operation feeling to a fingertip because the actuator 200 operates gently. To give a strong impact, the same single pulse signal as that of the common actuator is input to the MOSFET. A combination of the above allows providing various operation feelings. In addition, the same effects as the first embodiment, that is, the reduction of the operation sound and the like can be obtained. Furthermore, the actuator of the second embodiment has the same circuit structure as the common actuator, thus eliminating the need for modifying the circuit structure and having a cost advantage.
The embodiment of the present invention is described above in detail. However, the present invention is not limited to the above embodiments but can be variously modified. The modification examples will be described below. It is noted that the matters described in the embodiments can be applicable to the modification examples unless otherwise specified.
In the above embodiments, both of the detector for detecting the input operation and the drive signal output unit may be constituted by the same structure such as the microcomputer. The drive circuit in the above embodiment uses the capacitor C1, but may be a circuit without any capacitor in which the SMA and the like are connected directly to the drive voltage generation unit 2. The capacitor C1 may be an electric double layer capacitor, a secondary battery, or the like. The switching element is not limited to the N-channel type MOSFET, but may be a P-channel type MOSFET or another switching element. The circuit structure and the like are appropriately changeable in accordance with the switching element to be used.
The structures, methods, processes, forms, materials, numerical values, and the like described in the above-described embodiments and modification examples are just examples, and different structures, methods, processes, forms, materials, numerical values and the like from those described are usable as necessary. The structures, methods, processes, forms, materials, numerical values, and the like described in the above embodiments and modification examples can be combined with each other so long as a technical contradiction does not arise. Moreover, the present invention can be realized as, for example, a method, a program, and a recording medium having the program stored therein, instead of apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-262043 | Dec 2014 | JP | national |
The contents of the following Japanese patent application and International patent application are incorporated herein by reference, Japanese Patent Application No. 2014-262043 filed on Dec. 25, 2014, and International Patent Application No. PCT/JP2015/061649 filed on Apr. 9, 2015.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2015/061649 | Apr 2015 | US |
| Child | 14970546 | US |
