Drive apparatus, drive system, and drive method

• US 20060150627A1
• Filed: 12/05/2005
• Published: 07/13/2006
• Est. Priority Date: 12/06/2004
• Status: Active Grant

• Current Assignee: Konica Minolta Holdings Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta Holdings Incorporated (Konica Minolta Inc.)
• Inventors: Oohara, Masamichi
• Granted Patent: US 7,650,752 B2
• Time in Patent Office: Days
• US Class Current: 60/528
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: F05C 2251/08 Shape memory
• CPC Class Codes: G03B 2205/0015 by displacing one or more optical elements normal to the optical axis
• CPC Class Codes: G03B 2205/0076 using shape memory alloys
• CPC Class Codes: G03B 2217/005 Blur detection

Abstract

An actuator has two shape memory alloys (SMAs) connected in a push-pull arrangement to a movable part. By passing current to each of the SMAs from a drive circuit part, the movable part can be driven. When a target position signal of the movable part is input to the drive circuit part, a current is passed to an SMA of the contraction side on the basis of a drive waveform obtained by adding a voltage according to the target position signal to a bias voltage, and a current is passed to the SMA on the expansion side on the basis of a signal waveform obtained by subtracting the voltage according to the target position signal from the bias voltage. Consequently, the SMA of the expansion side maintains a pre-heat state and is not cooled excessively, so that response delay at the time of the next heating can be prevented. As a result, the response of the actuator can be increased.

Claims

1. A drive apparatus for driving an actuator having two shape memory alloys connected in a push-pull arrangement to a movable part to give a displacement to said movable part on the basis of a displacement target value, comprising:

(a) a feeder that feeds current to a shape memory alloy to be heated on the basis of a drive current signal, thereby making said shape memory alloy perform a regaining operation towards a memorized shape to interlock with said displacement of said movable part; and

(b) a controller that generates a first drive current signal based on said displacement target value for one of said two shape memory alloys, which performs said regaining operation, and generates a second drive current signal to which a signal of a bias current is given for another shape memory alloy which does not perform said regaining operation.

2. The drive apparatus according to claim 1, wherein

said bias current is set to a current value necessary to heat said shape memory alloy to a specific temperature in a temperature range from a transformation start temperature to a transformation end temperature of said shape memory alloy, and

said controller includes:

(b-1) a first generator that generates said first drive current signal by adding a first current signal according to said displacement target value to said signal of said bias current; and

(b-2) a second generator that generates said second drive current signal by subtracting a second current signal according to said displacement target value and a heat radiation characteristic of said shape memory alloy from said signal of said bias current.

3. The drive apparatus according to claim 1, wherein

said bias current is set to a current value necessary to heat said shape memory alloy to a specific temperature in a temperature range from a transformation start temperature to a transformation end temperature of said shape memory alloy, and

said controller includes:

(b-3) a first generator that generates said first drive current signal by adding a first current signal according to said displacement target value to said signal of said bias current; and

(b-4) a second generator that generates said second drive current signal by subtracting said first current signal from said signal of said bias current.

4. The drive apparatus according to claim 2, wherein

said specific temperature is equal to or less than an intermediate temperature between said transformation start temperature and said transformation end temperature.

5. The drive apparatus according to claim 1, wherein

said bias current is set to a current value necessary to heat said shape memory alloy to a transformation start temperature of said shape memory alloy, and

said controller includes:

(b-5) a generator that generates said first drive current signal by adding a first current signal according to said displacement target value to said signal of said bias current; and

(b-6) a setter that sets said signal of said bias current as said second drive current signal.

6. The drive apparatus according to'"'"'claim 2, wherein

said first current signal is an analog signal proportional to said displacement target value.

7. The drive apparatus according to claim 1, wherein

said first drive current signal and/or said second drive current signal are/is subjected to a signal decimation process.

10. The drive apparatus according to claim 1, wherein

said drive apparatus is used for correcting a camera shake of an image capturing apparatus.

8. A drive apparatus for driving an actuator having two shape memory alloys connected in a push-pull arrangement to a movable part to give a displacement to said movable part on the basis of a displacement target value, comprising:

(a) a feeder that feeds current to a shape memory alloy to be heated on the basis of a drive current signal, thereby performing a regaining operation towards a memorized shape to interlock with said displacement of said movable part; and

(b) a controller that generates a first drive current signal based on said displacement target value for one of said two shape memory alloys, which performs said regaining operation, and generates a second drive current signal for another shape memory alloy which does not perform said regaining operation, said first drive current signal being a pulse width modulation signal obtained by adding a first duty ratio according to said displacement target value to a predetermined duty ratio, and said second drive current signal being a pulse width modulation signal obtained by subtracting said first duty ratio from said predetermined duty ratio.

9. The drive apparatus according to claim 8, wherein

said predetermined duty ratio is 50%, and

said first drive current signal and second drive current signal are signals complementary to each other.

11. A drive system for giving a displacement to a movable part on the basis of a displacement target value, comprising:

(a) an actuator having two shape memory alloys connected in a push-pull arrangement to said movable part;

(b) a feeder that feeds current to a shape memory alloy to be heated on the basis of a drive current signal, thereby making said shape memory alloy perform a regaining operation towards a memorized shape to interlock with said displacement of said movable part; and

(c) a controller that generates a first drive current signal based on said displacement target value for one of said two shape memory alloys, which performs said regaining operation, and generates a second drive current signal to which a signal of a bias current is given for another shape memory alloy which does not perform said regaining operation.

12. A drive system for giving a displacement to a movable part on the basis

(a) an actuator having two shape memory alloys connected in a push-pull arrangement to said movable part;

(b) a feeder that feeds current to a shape memory alloy to be heated on the basis of a drive current signal, thereby performing a regaining operation towards a memorized shape to interlock with said displacement of said movable part; and

(c) a controller that generates a first drive current signal based on said displacement target value for one of said two shape memory alloys, which performs said regaining operation, and generates a second drive current signal for another shape memory alloy which does not perform said regaining operation, said first drive current signal being a pulse width modulation signal obtained by adding a duty ratio according to said displacement target value to a predetermined duty ratio, and said second drive current signal being a pulse width modulation signal obtained by subtracting the duty ratio according to said displacement target value from said predetermined duty ratio.

13. A drive method for driving an actuator having two shape memory alloys connected in a push-pull arrangement to a movable part to give displacement to said movable part on the basis of a displacement target value, comprising the steps of:

(a) feeding to a shape memory alloy to be heated on the basis of a drive current signal, thereby making said shape memory alloy perform a regaining operation towards a memorized shape to interlock with said displacement of said movable part; and

(b) generating a first drive current signal based on said displacement target value for one of said two shape memory alloys, which performs said regaining operation, and generating a second drive current signal to which a signal of a bias current is given for another shape memory alloy which does not perform said regaining operation.

14. The drive method according to claim 13, wherein

said bias current is set to a current value necessary to heat said shape memory alloy to a specific temperature in a temperature range from a transformation start temperature to a transformation end temperature of said shape memory alloy, and

said step (b) includes the steps of:

generating said first drive current signal by adding a first current signal according to said displacement target value to said signal of said bias current; and

generating said second drive current signal by subtracting a second current signal according to said displacement target value and a heat radiation characteristic of said shape memory alloy from said signal of said bias current.

15. The drive method according to claim 13, wherein

said bias current is set to a current value necessary to heat said shape memory alloy to a specific temperature in a temperature range from a transformation start temperature to a transformation end temperature of said shape memory alloy, and

said step (b) includes the steps of:

generating said first drive current signal by adding a first current signal according to said displacement target value to said signal of bias current; and

generating said second drive current signal by subtracting said first current signal from said signal of said bias current.