JP2002014609A - Driving circuit for shape memory alloy actuator device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving circuit capable of controlling the driving of respective actuator elements individually while suppressing the increase of the current capacity of power source for heating low, as the driving circuit of an actuator device which is constituted by combining many pieces of shape memory alloy actuator elements. SOLUTION: In the driving circuit of an actuator device in which an actuator element is constituted of a direct acting type actuating pin and differential type shape memory alloy springs driving the actuating pin in the axial direction and which is constituted by combining plural pieces of the actuator elements, after all shape memory alloy springs 6 of respective actuators are connected in series, the driving circuit is connected to a power source for heating Vcc via a power switch 11 and, also, control switches 10 which are allotted for every actuator element and which control the conducting of electricity of the shape memory springs and a control part 12 which controls the switching of ON/OFF of the power source switch and respective control switches based on instructions is provided in the driving circuit. Thus, the driving circuit controls the driving of respective actuator elements individually in accordance with operation instructions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of a shape memory alloy actuator device applied to a braille pin actuator of a braille display for displaying braille.

[0002]

2. Description of the Related Art In recent years, due to the barrier-free for visually impaired persons, necessary information is displayed in braille by being mounted on, for example, a vending machine, a bank ATM machine, or a museum navigator. Research and development of braille display devices are under way.

Here, the display device for braille is shown in FIG. The display device 1 is provided with a touch panel type braille display unit 2 for a plurality of characters arranged in a horizontal line, and each of the braille display units 2 is provided with a plurality (eight) of braille pins 3 which can appear and disappear. The braille pins 3 arranged on the braille display unit 2 are controlled to appear and disappear based on the braille display information given by the control unit, and the information is displayed as braille, and the information can be read by a visually impaired person by tracing his fingertip here. The configuration is as described above.

[0004] Further, a Braille memory spring is used as a drive means of the Braille pin of the Braille display device, and the Braille pin is protruded and retracted from the panel by controlling the heating of the shape memory alloy spring to display Braille. A display device has been proposed by the same applicant as the present invention as Japanese Patent Application No. 11-047473.

Next, taking the Braille pins incorporated in the Braille display device as an example, the configuration of a shape memory alloy actuator element that drives the Braille pins in and out in a direct-acting manner, and the operating principle thereof are shown in FIGS. This will be described in (b). In the figure,
Reference numerals 4 and 5 denote upper and lower panels for guiding an operating pin (braille pin) 3 in the axial direction. The operating pin 3 straddles between holes 4a and 5a opened in the panels 4 and 5, and has the following shape. It is suspended from the upper panel 4 so as to be suspended from the memory alloy spring 6 and supported.

Here, the operating pin 3 has a head 3a at the tip thereof to be touched by a fingertip, and a large diameter portion 3b serving also as an intermediate electrode of the shape memory alloy spring 6 is formed at an intermediate portion of the pin. On the other hand, the shape memory alloy spring 6 is formed by forming a filament of a shape memory alloy such as Ni-Ti into a coil shape and performing a heat treatment for shape memory. After inserting the pin 3, the large diameter portion 3b
The upper and lower ends thereof are fixed to a support metal fitting 7 serving also as a current-carrying electrode, and are stretched between the panels 4 and 5 in a state of being fitted and engaged with an intermediate portion of the spring, and having been extended and deformed from the memorized shape at room temperature. are doing.

Reference numeral 8 denotes a drive circuit in which a heating power supply 9 and a control switch (a switch for switching bidirectional contacts) 10 are combined. The pin 3 is connected to the large intermediate diameter portion 3b.

In this configuration, when the control switch 10 of the drive circuit 8 is switched to the contact a side as shown in FIG.
From the support fitting 7 on the upper panel 4 side to the shape memory alloy spring 6
Flows through the upper half portion 6a and the intermediate large portion 3b, and the upper half portion 6a of the shape memory alloy spring 6 generates Joule heat due to energization (the nominal electric power in the martensitic phase of the shape memory alloy (Ni-Ti)). The resistance is rapidly heated above the M transformation temperature by 80 × 10 ⁻⁶ Ω · cm), and the shape memory alloy spring 6 recovers its shape so as to contract as shown in FIG. The lower half 6b of the spring 6 is extended. As a result, the head 3a of the operating pin 3 projects from the upper panel 4. Even if the power supply from the heating power supply is stopped after switching to this state, only the plastic strain remains in the lower half 6b, and the operating pin 3 maintains the protruding state shown in FIG.

Next, when the control switch 10 of the drive circuit 8 is switched to the contact b side as shown in FIG. 4 (b), a current i flows through the lower half 6b of the shape memory alloy spring 6 in a manner opposite to the above. As a result, the lower half 6b recovers its shape so as to shrink, and the operating pin 3 retreats so that the head 3a is buried from the upper panel 4.

As described above, by controlling the energization so that the current i flowing through the shape memory alloy spring 6 is alternately switched between the upper half 6a and the lower half 6b, the shape memory alloy spring 6
Functions as a differential element, and operates pin 3 in a very short operation time.
Can be moved in two directions, forward and backward. As the shape memory alloy spring 6, a shape memory alloy spring in which the upper half 6a and the lower half 6b are separated may be used.

[0011]

By the way, in a Braille display device or the like, which employs the above-mentioned shape memory alloy actuator element, the number of actuator elements incorporated in the device becomes very large. If the shape memory alloy actuator elements are individually connected in parallel to a heating power supply via a control switch to form a drive circuit, a very large current capacity is required for the power supply section, and a large number of control switches and A power switch is required. Therefore, a simple and rational configuration of the drive circuit of each actuator element is an important issue in miniaturizing the actuator device, facilitating control, and reducing costs.

It is an object of the present invention to reduce the current capacity of a power supply unit or reduce the total number of control switches incorporated in a circuit as a drive circuit for an actuator device which is modularized by combining a large number of shape memory alloy actuator elements. It is another object of the present invention to provide a driving circuit configured so as to achieve the above.

[0013]

According to the present invention, there is provided, in accordance with the present invention, an actuating element in which an actuator element is axially movable, and a differential in which the actuating pin is axially suspended and driven in two directions. A drive circuit of a shape memory alloy actuator device, which is composed of a dynamic shape memory alloy spring and is modularized by combining a plurality of the actuator elements, is configured as follows.

(1) A power switch connected to a heating power supply by connecting all the shape memory alloy springs of each actuator element in series, and a power switch connected to a power supply circuit of the heating power supply;
A control switch assigned to each actuator element for selectively controlling the energization of the shape memory alloy spring; and a power switch and a control switch attached to each actuator element are turned on / off based on an actuator drive command.
An FF and a control unit for switching control are provided, and the drive pins of each actuator element are individually driven and controlled in accordance with the operation pattern command of the actuator given to the control unit.

According to the above-described circuit configuration, a large number of actuator elements are individually driven and controlled without increasing the current capacity of the power supply section of the drive circuit and without causing variations in the operation time of each shape memory alloy actuator element. be able to.

(2) After a plurality of actuator elements are divided into groups, the shape memory alloy springs of the actuator elements arranged in the same order in the group are connected in parallel between the groups, and are assigned to each group. A power switch connected to the heating power circuit and a shape memory alloy spring of the actuator element connected in parallel between the groups are grouped, and each shape memory alloy spring belonging to the group is collectively allocated to each group. An ON / OFF, changeover control switch for selectively controlling energization; and a control unit for controlling the power switch and each set of control switches based on an actuator drive command, and an actuator operation pattern command given to the control unit. The drive pins of the actuator elements of each group are individually driven and controlled in accordance with ( Claim 2).

With this circuit configuration, the number of switches for driving and controlling a large number of shape memory alloy actuator elements can be greatly reduced, and the size and cost of the device can be reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on illustrated embodiments. In the drawings of each embodiment, members corresponding to those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

[Embodiment 1] FIG. 1 shows an embodiment of a driving circuit according to claim 1 of the present invention. In addition, in order to avoid complicating the drawing, in the illustrated example, 4 represented by # 1 to # 4.
The actuator device is configured by combining the shape memory alloy actuator elements.

Here, the shape memory alloy springs 6 of the actuator elements # 1 to # 4 are connected in series with each other, and are heated via a power switch 11 (not shown).
It is connected to the. Further, the control switch (bidirectional contact switch) 10 described in FIG. 4 is assigned to the shape memory alloy spring 6 for each actuator element, and the drive circuit 8 is constituted by these. Reference numeral 12 denotes a control unit that controls ON / OFF and switching of the power switch 11 and the control switch 10 attached to each actuator element based on an actuator drive command.

In this circuit configuration, after the control switches 10 are switched to the states shown in the figure by a command from the control unit 12, when the power switch 11 is turned on, the shape memory alloys of the actuator elements # 1 to # 4 are turned on. With respect to the spring 6, the current flows through the hatched portions (6a and 6b in the figure correspond to the upper and lower halves of the shape memory alloy spring 6 shown in FIG. 4, respectively). Flows. As a result, the operating pins 3 of the shape memory alloy actuator elements # 1 and # 3 are retracted as shown in FIG.
Is in a state in which the operating pin 3 protrudes from the panel as shown in FIG. Moreover, in this case, since the current flows in series through the shape memory alloy springs 6 of the actuator elements # 1 to # 4, the actuator elements # 1 to # 4 can be simultaneously operated at the same timing. Further, the control of the energization time required for heating the shape memory alloy spring 6 to recover the shape by heating is managed by ON / OFF of the power switch 11.

[Embodiment 2] FIG. 2 shows a driving circuit according to a second embodiment of the present invention. In this embodiment, a plurality of (two in the illustrated example) shape memory alloy actuator elements are grouped into groups A, B, C,... To constitute an actuator device.

Here, the shape memory alloy springs 6 for the actuator elements # 1 and # 2 belonging to the group A and the actuator elements # 3 and # 4 belonging to the group B
A diode 13 is connected to both ends of each of the groups so as to prevent an unnecessary current from flowing around, and lead wires drawn from the center of each of the shape memory alloy springs 6 (joining ends of the spring portions 6a and 6b) are connected to the groups A and B. Power switch 11 assigned to each
A and 11B are connected to a heating power supply (not shown).

Of the actuator elements belonging to each of the groups A and B, the shape memory alloy springs of the actuator elements # 1 and # 3 arranged on the left side and the shape memories of the actuator elements # 2 and # 4 arranged on the right side. The alloy springs are vertically divided into groups A and B, and the shape memory alloy springs of actuator elements # 1 and # 3 and the shape memory alloy springs of # 2 and # 4 are provided for each group. Both ends are connected in parallel to a lead wire 14, and the lead wire 14 is connected to a control switch 10 assigned to each group to form a drive circuit 8.

With such a configuration, the switching control of the control switch 10 and the ON / OFF control of the power switches 11A and 11B are selectively performed by a command from the control unit (see FIG. 1) based on the drive command, so that each Group A,
For each of B,..., The operation pins (see FIG. 4) of the actuator elements # 1 to # 4 belonging to the group can be individually driven and controlled in accordance with a specified operation pattern.

The number of power switches 11A and 11B is the same as that of groups A, B,.
The total number of 0s may be the same as the number of actuator elements belonging to each of the groups A and B. Accordingly, in an actuator device configured by combining a large number of shape memory alloy actuator elements, the total number of switches to be incorporated in the drive circuit is determined by the embodiment. In addition to the above, it is possible to reduce the number of times, and it is possible to perform fine drive control in units of groups.

[0027]

As described above, as an actuator device applied to a Braille pin or the like of a Braille display device, a drive circuit in which a number of shape memory alloy actuator elements are combined to individually drive and control each element is described. According to claim 1 of the present invention, the shape memory alloy springs of each actuator element are all connected in series and connected to a heating power supply, and a power switch connected to a power supply circuit of the heating power supply; A control switch for selectively energizing the shape memory alloy spring and controlling the power switch and a control switch attached to each actuator element based on an actuator drive command. Driving each actuator element according to the given actuator operation pattern command With the arrangements to individually drive control emissions, the current capacity of the heating power source without increasing correspondingly the number of actuator elements can be individually driven and controlled individual actuator elements.

According to a second aspect of the present invention, after a plurality of actuator elements are divided into groups, the shape memory alloy springs of the actuator elements arranged in the same order in each group are connected in parallel. In addition, a power switch assigned to each group and connected to the heating power circuit, and a shape memory alloy spring of an actuator element connected in parallel between the groups as a set are assigned to each set and each shape belonging to the set is assigned. An ON / OFF, changeover control switch for selectively selectively energizing the memory alloy spring; and a control unit for controlling the power switch and each set of control switches based on an actuator drive command. The operation pins of each group of actuator elements are individually driven in accordance with the given actuator operation pattern command. With the arrangements to control,
In addition to reducing the total number of switches incorporated in the drive circuit, fine drive control for each group can be performed.

Thus, a drive circuit having a high practical value, which is effective in reducing the size, controllability, and cost of the Braille display device, etc., which is constituted by employing a shape memory alloy actuator device. Can be provided.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram of a shape memory alloy actuator device according to a first embodiment of the present invention.

FIG. 2 is a drive circuit diagram of a shape memory alloy actuator device according to a second embodiment of the present invention.

3A and 3B are schematic diagrams of a braille display device to which the shape memory alloy actuator device of the present invention is applied, wherein FIG. 3A is an external view of the entire device, and FIG. 3B is an enlarged view of a braille display unit in FIG.

4A and 4B are explanatory diagrams of the configuration and operation principle of a shape memory alloy actuator element used in the actuator device of the present invention, wherein FIGS. 4A and 4B show different operation states, respectively.

[Explanation of symbols]

 3 Working Pin 6 Shape Memory Alloy Spring 6a Upper Half of Spring 6b Lower Half of Spring 8 Drive Circuit 9 Heating Power Supply 10 Control Switch 11, 11A, 11B Power Switch A, B Group

Claims (2)

[Claims] An actuator element comprises an operating pin movable in the axial direction, and a differential type shape memory alloy spring for driving the operating pin in two directions by suspending the operating pin in the axial direction. A drive circuit for a shape memory alloy actuator device which is modularized and connected, wherein all the shape memory alloy springs of each actuator element are connected in series and connected to a heating power supply, and a power switch connected to a heating power supply circuit. A control switch that is assigned to each actuator element and selectively controls the energization of the shape memory alloy spring; and a control unit that controls the power switch and a control switch attached to each actuator element based on an actuator drive command. Each actuator in accordance with the actuator operation pattern command given to the control unit. Driving circuit of the shape memory alloy actuator device being characterized in that the drive pin to be individually driven and controlled. 2. An actuator element comprising: an operating pin movable in an axial direction; and a differential shape memory alloy spring for suspending the operating pin in an axial direction and driving the actuator pin in two directions. A drive circuit of a shape memory alloy actuator device that is grouped and modularized, wherein shape memory alloy springs of actuator elements arranged in the same order in each group are connected in parallel between the groups, and each group is A power switch connected and connected to the heating power circuit and a shape memory alloy spring of an actuator element connected in parallel between each group are grouped, and each shape memory alloy spring belonging to the group is collectively allocated to each group. A control switch for selectively controlling energization, a power switch based on an actuator drive command, and each group. A shape memory alloy actuator comprising: a control unit for controlling a control switch, wherein drive pins of actuator elements of each group are individually driven and controlled in accordance with an operation pattern command of the actuator given to the control unit. The drive circuit of the device.