JP2003185406A - Position detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detecting device of non-contact type which detects a position of a moving member on the basis of the capacitance between a fixed electrode and the moving member used as an actuator. <P>SOLUTION: An edge of a piezo-electric element 11 is fixed to a frame 14, and the other edge is fixed to a drive shaft 12 with which the moving member 13 is coupled frictionally. A detecting member 15 is arranged in non-contact with and parallel to the moving member 13 in the moving direction. The detecting member 15, where rugged regions with a constant spacing are formed on a surface opposite to the moving member, makes up an electrode 15a and is spaced at a distance D from the moving member so as to form a capacitor with the capacitance C. Drive pulses output from a drive circuit 18 are applied on the piezo-electric element 11, electric current flows through the electrode 15a being capacitively coupled to the moving member, and the amount (i) of current is detected by a detecting circuit 19 and input to a control circuit 17. When the moving member 13 moves on the electrode 15a, the amount (i) of current is increased or decreased in response to the shape of the rugged region of the electrode 15a, and therefore the position of the moving member 13 is detected based on the amount (i) of current. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device, and more particularly to a driving device using an electromechanical conversion element, in an actuator for moving a moving member on a driving member in a predetermined direction, the moving member or the moving member is coupled to the moving member. The present invention relates to a position detection device that detects the position of a mechanical member.

[0002]

2. Description of the Related Art When a drive pulse having a waveform consisting of a gentle rising portion and a rapid falling portion subsequent thereto is applied to an electromechanical conversion element, for example, a piezoelectric element, the piezoelectric element is gently moved at the gentle rising portion of the driving pulse. Stretch displacement occurs in the thickness direction, and rapid contraction displacement occurs at the rapid trailing edge. Therefore, by utilizing this characteristic, the drive pulse having the above waveform is applied to the piezoelectric element to repeatedly charge and discharge at different speeds, thereby causing the piezoelectric element to vibrate in the thickness direction at different speeds and to be fixed to the piezoelectric element. There is known an actuator that reciprocates the driving member at different speeds and moves the moving member frictionally coupled to the driving member in a predetermined direction (see, for example, Japanese Patent Laid-Open No. 2000-205809).

In a positioning device that uses such an actuator to move a moving member (or a mechanical member coupled to the moving member) to set it at a predetermined position, a position detecting device for accurately detecting the position of the moving member. Is required.

FIG. 16 is a diagram for explaining an example of the configuration of a conventional actuator 100 using a piezoelectric element and a position detecting device for detecting the position of a moving member frictionally coupled to a driving member of the actuator.

In FIG. 16, 101 is a piezoelectric element which is one of electromechanical transducers, 102 is a drive shaft, 103 is a moving member frictionally coupled to the drive shaft 102 by an appropriate frictional force, 1
Reference numeral 10 indicates a frame of the actuator. Piezoelectric element 101
One end of the piezoelectric element 101 is fixed to the frame 110 by means of adhesion or the like, and the drive shaft 102 is fixed to the other end of the piezoelectric element 101 by means of adhesion or the like.

The drive shaft 102 and the moving member 103 are made of a conductive material, and the drive shaft 102 is moved by the moving member 10.
3 is a resistor having electric resistance in the moving direction.
The moving member 103 is also in electrical contact with the drive shaft 102, and the DC voltage E supplied from the power source 109 to both ends of the drive shaft 102 is divided according to the position of the moving member 103 to output the DC voltage V. To do.

A control circuit 1 for controlling the actuator 100
Reference numeral 07 denotes a CPU, which is connected to a drive circuit 104 that supplies a drive pulse to the piezoelectric element 101, and receives the DC voltage V output from the moving member 103 described above.

A DC voltage E is supplied to the drive shaft 102, the distance between the first terminal a and the second terminal b thereof is L, and the current position of the moving member 103 and the second terminal b are between them. Distance x
Then, the DC voltage V output from the moving member 103 is expressed by the following formula (1), and the position X of the moving member 103 on the drive shaft 102 is expressed by the formula (2) in which the formula (1) is rewritten. expressed.

V = E × (X / L) ········ (1) X = (V / E) × L ····· .. (2) That is, the position X of the moving member 103 on the drive shaft 102 is
When the distance between the first terminal a and the second terminal b and the supplied DC voltage E are known, it can be determined by detecting the DC voltage V output from the moving member 103.

The control circuit 107 controls the input DC voltage V
The current position of the moving member 103 determined by the above is compared with the separately input target position of the moving member 103, and the drive circuit 104 is feedback-controlled so that the difference in distance between the moving member 103 and the target position becomes zero. It is a control circuit for controlling.

Next, the actuator 1 by the control circuit 107
The control operation of 00 will be briefly described. The drive circuit 104 is driven based on a command from the control circuit 107, and the piezoelectric element 10
A drive pulse having a waveform having a gentle rising portion and a rapid falling portion following the rising portion is applied to 1. The piezoelectric element 101 gently expands and displaces in the thickness direction at the gently rising portion of the drive pulse, and rapidly contracts and displaces at the rapidly falling portion, and the vibration generated in the piezoelectric element 101 in the thickness direction at different speeds occurs. The drive shaft 102 fixed to the piezoelectric element 101 is reciprocated at different speeds, and the moving member 103 frictionally coupled to the drive shaft 102 moves in a predetermined direction.

The current position X of the moving member 103 on the drive shaft 102 is detected by a DC voltage V indicating the position of the moving member 103. The control circuit 107 compares the current position X of the moving member 103 obtained based on the input DC voltage V with the target position of the moving member 103, which is input separately, and drives so that the difference becomes zero. The waveform and the output of the drive pulse output from the circuit 104 are controlled. As a result, the drive shaft 1
The moving member 103 frictionally coupled to 02 moves in a predetermined direction and is set at a target position.

[0013]

In the actuator using the above-mentioned conventional piezoelectric element, the driving member is an electric resistor and the moving member is placed on the electric resistor in order to detect the current position of the moving member. Since it is used as a sliding intermediate contact, it is necessary to connect a lead wire to the moving member, but there is a disadvantage that the reaction force due to this lead wire becomes a load on the driving member.

Further, in the position detecting method for detecting the position of the moving member based on the electrostatic capacitance between the electrodes, it is necessary to apply a voltage between the electrodes, and a special voltage generator for electrostatic capacitance detection is used. In addition to the necessity, it is necessary to connect the lead wire to the moving member, but there is a disadvantage that the reaction force by the lead wire becomes a load on the driving member.

Further, as a structure for detecting the current position of the moving member, an MR sensor is provided in which the moving member is provided with a magnetoresistive element, and a magnetizing rod having magnetic poles is arranged in parallel with the driving member at constant intervals. Although a method using an optical position detection mechanism or the like can be considered, it has a complicated structure and has a difficulty in downsizing the position detection mechanism.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and is based on the electrostatic capacitance between the moving member and the fixed electrode, in which the fixed electrode is arranged close to the moving member constituting the actuator. It is configured to detect the position of the moving member.

The invention of claim 1 is an electromechanical conversion element,
A drive member fixed to one end of the electromechanical conversion element,
A moving member frictionally coupled to the driving member; and a driving circuit supplying a driving pulse to the electromechanical conversion element,
In the position detecting device of the moving member in the driving device for supplying a driving pulse to the electromechanical conversion element to generate expansion and contraction displacement vibrations having different expansion and contraction speeds to relatively move the driving member and the moving member, An electrode plate facing the moving member, which is arranged in parallel along the moving direction of the moving member, and a capacitance detector for detecting a capacitance between the moving member and the electrode plate are provided, and The position detecting device is characterized in that a position in the moving direction of the moving member is detected based on an electrostatic capacitance detected by applying a drive pulse between the moving member and the electrode plate.

The driving member and the moving member are made of a conductive material, and the electrode of the electromechanical conversion element and the driving member are electrically connected.

The electrode plate facing the moving member is
The electromechanical conversion element is provided on a fixed member that is fixed.

The invention of claim 4 is an electromechanical conversion element,
A drive member fixed to one end of the electromechanical conversion element,
A moving member frictionally coupled to the driving member; and a driving circuit supplying a driving pulse to the electromechanical conversion element,
In the position detecting device of the moving member in the driving device for supplying a driving pulse to the electromechanical conversion element to generate expansion and contraction displacement vibrations having different expansion and contraction speeds to relatively move the driving member and the moving member, A high-frequency voltage generator that applies a high-frequency signal to the driving member, an electrode plate that is arranged in parallel along the moving direction of the moving member and faces the moving member, and a static discharge between the moving member and the electrode plate. A capacitance detector for detecting capacitance is provided, and a high-frequency voltage output from the high-frequency voltage generator is applied between the moving member and the electrode plate based on the capacitance detected, and It is a position detecting device characterized by detecting a position of a moving member in a moving direction.

The electrode plate facing the moving member has a plurality of concave-convex portions formed along the moving direction of the moving member at a pitch less than the minimum detection unit of the moving distance of the moving member. .

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

[First Embodiment] FIG. 1 is a diagram for explaining the basic structure of an actuator 10 according to a first embodiment of the present invention. In FIG. 1, 11 is a piezoelectric element that is one of electromechanical conversion elements, 12 is a drive shaft, and 13 is a drive shaft 12.
A moving member frictionally coupled to the moving member, and 14 is a frame of the actuator. One end of the piezoelectric element 11 is fixed to the frame 14 by means such as adhesion, and the other end of the piezoelectric element 11 has a drive shaft 12
Are fixed by means such as adhesion. Further, reference numeral 15 denotes a detection member, which constitutes a fixed electrode for detecting the position of the moving member 13 based on the electrostatic capacitance, and is arranged in parallel in the moving direction of the moving member 13 in a non-contact state. And is fixed to the frame 14.

The drive shaft 12, the moving member 13, and the detecting member 15 (hereinafter sometimes referred to as the fixed electrode 15) are made of a conductive material. The detection member 15 forms an electrode 15a by forming irregularities on the surface facing the moving member at regular intervals along the moving direction of the moving member.
5a and the moving member 13 face each other with a space D therebetween to form a capacitor having a capacitance C.

A control circuit 17 for controlling the actuator 10.
Is composed of a CPU and is connected to a drive circuit 18 which supplies a drive pulse to the piezoelectric element 11. A drive pulse is output from the drive circuit 18 and applied to the piezoelectric element 11, and the drive pulse is also supplied to the moving member 13 via the drive shaft 12. The drive pulse applied to the moving member 13 flows toward the electrode 15a because the moving member 13 and the electrode 15a are capacitively coupled. Moving member 13 to electrode 15
The current i flowing through a is detected by the detection circuit 19 and input to the control circuit 17.

If the facing area between the moving member 13 and the electrode 15a is S, the air gap between them is D, and the permittivity of air is ε, a capacitor formed between the moving member 13 and the electrode 15a. The capacitance C of is expressed by the following equation (3).

C = ε · S / 4πD (3) The current i flowing from the moving member 13 to the electrode 15a due to this capacitive coupling is expressed by the following equation ( 4).

I = C · de (t) / dt ····· (4) When the moving member 13 is located directly above the convex portion of the uneven portion of the electrode 15a, Since the air gap D is small, the electrostatic capacitance C is large and the current i is also large. On the contrary, when the moving member 13 is located directly above the concave portion of the uneven portion of the electrode 15a, the air gap D is large, the capacitance C is small, and the current i is also small.

When the moving member 13 moves on the electrode 15a at a constant speed, the current i also increases / decreases according to the shape of the uneven portion of the electrode 15a. Therefore, the position of the moving member 13 should be detected based on the current i. You can

That is, one end of the detecting member 15 provided with the electrodes 15a by forming irregularities at regular intervals is set at a reference position, for example, the end of the frame, and is arranged in parallel with the moving direction of the moving member 13. . When the moving member 13 moves on the electrode 15a at a constant speed, the current i also increases or decreases according to the shape of the uneven portion of the electrode 15a. Now, assuming that the moving member 13 starts moving from the reference position and the number of detected peak values of the current i is n, the number of peak values is equal to the number of uneven portions of the electrode 15a. A distance X (X = n × p) from the reference position of the moving member 13 can be obtained by multiplying the number n of peak values of the generated current i by the pitch p (length) of the uneven portion.

The size of the uneven portion of the electrode 15a and the size of the air gap D can be appropriately determined depending on the application of the actuator, but the pitch of the uneven portion is set to a pitch equal to or smaller than the minimum detection unit of the moving distance of the moving member 13. . For example, in this embodiment, the pitch of the uneven portions is 200 μm and the step difference of the uneven portions is
The air gap d is 00 μm and the air gap d is 50 μm. Thereby, the moving distance of the moving member 13 can be detected with an accuracy of 200 μm.

The current i detected by the detection circuit 19 includes the frequency component of the drive pulse for driving the piezoelectric element. However, the detected current i which increases or decreases depending on the shape of the uneven portion of the electrode 15a. Since it is sufficiently higher than the frequency, it does not affect the detection of the peak value of the detection current i.

The control operation of the actuator 10 by the control circuit 17 will be briefly described. The drive circuit 18 is driven based on a command from the control circuit 17, and the piezoelectric element 11 is applied with a drive pulse having a waveform having a gentle rising portion and a rapid falling portion following the rising portion. The piezoelectric element 11 gently expands and displaces in the thickness direction at the gently rising portion of the drive pulse, and rapidly contracts and displaces at the rapidly falling portion, and the vibrations of the piezoelectric element 11 in the thickness direction at different speeds are generated.
The drive shaft 12 fixed to the piezoelectric element 11 is reciprocally moved at different speeds, and the moving member 13 frictionally coupled to the drive shaft 12 moves in a predetermined direction.

The current position X of the moving member 13 on the drive shaft 12
Is detected by the detection circuit 19. The control circuit 17 compares the input current position of the moving member 13 and the separately input target position of the moving member 13, and drives the drive circuit 18 so that the difference becomes zero. As a result, the moving member 13 frictionally coupled to the drive shaft 12 is moved in a predetermined direction and set at the target position.

FIG. 2 is a diagram showing another example of the structure of the electrode 15a described in FIG. 1, in which the electrode 15a is divided into two and the first electrode 1
The pitch p of the uneven portion of the second electrode 15aB is 1 with respect to the moving direction of the moving member 13 with respect to the pitch p of the uneven portion of 5aA.
It is a two-phase configuration in which the / 4 pitch phase is shifted.

In FIG. 2, the first electrode 15aA and the second electrode 15aB are shown as opposed to each other, but this is for explaining the phase shift, and the first electrode 15aA is actually used. The tip of the uneven portion of the second electrode 15aB faces the moving member 13 and is arranged parallel to the moving member 13.

Letting iA be the current flowing from the moving member 13 to the first electrode 15aA and iB be the current flowing to the second electrode 15aB, the detection circuit 19 performs the following calculation: i = (iA-iB) / (iA + iB) By obtaining the peak value of the current i, the position of the moving member 13 can be detected as in the above description.

In addition, the moving electrode 13 has a two-phase detection electrode and detects the phase difference between the detection currents iA and iB.
The moving direction of the moving member 13 can be detected.
It is possible to make the fluctuation of the position detection sensitivity insensitive to the fluctuation of the distance D between the first electrode 15aA and the second electrode 15aB.

[Second Embodiment] A second embodiment of the present invention will be described. The difference from the first embodiment is the configuration of the detection electrode of the detection member that constitutes the fixed electrode for detecting the position of the moving member 13 based on the electrostatic capacitance. Since other configurations are the same as those of the first embodiment, the same members are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 3 is a diagram for explaining the basic configuration of the actuator 20 according to the second embodiment of the present invention. In FIG. 3, 11 is a piezoelectric element which is one of electromechanical conversion elements,
Reference numeral 12 is a drive shaft, 13 is a moving member frictionally coupled to the drive shaft 12, and 14 is a frame of an actuator. Piezoelectric element 1
One end of the piezoelectric element 1 is fixed to the frame 14 by means such as adhesion, and the other end of the piezoelectric element 11 is fixed to the drive shaft 12 by means such as adhesion.

Reference numeral 21 denotes a detection member which constitutes a fixed electrode for detecting the position of the moving member 13 based on the electrostatic capacitance, and which is parallel to the moving direction of the moving member 13 and does not come into contact therewith. It is arranged in a state and fixed to the frame 14. Drive shaft 12, moving member 13, and detection member 21
Is made of a conductive material.

FIG. 4 is a plan view for explaining the details of the detecting member 21. In the detecting member 21, the first electrode 21a and the second electrode 21b of a right triangle are placed on the insulator 21p with their hypotenuses facing each other. Is formed.

A drive pulse is output from the drive circuit 18,
While being applied to the piezoelectric element 11, the drive pulse is also supplied to the moving member 13 via the drive shaft 12. Moving member 13
The driving pulse applied to the moving member 13 and the first electrode 2 is
1a, the moving member 13 and the second electrode 21b are respectively capacitively coupled, so that the first electrode 21a and the second electrode 2
Flow toward 1b. First electrode 21a and second electrode 21
The current i flowing toward b is detected by the detection circuit 19 and input to the control circuit 17.

Now, for example, the moving member 13 is the first electrode 21a.
When moving from the side toward the second electrode 21b in the direction of arrow a, the area of the counter electrode between the moving member 13 and the first electrode 21a gradually decreases, and the capacitance Ca between the two gradually increases. The area of the counter electrode between the moving member 13 and the second electrode 21b decreases gradually, and the capacitance Cb between the two gradually increases. Therefore, from the moving member 13 to the first electrode 2
The current ia flowing through 1a gradually decreases, and the current ib flowing from the moving member 13 through the second electrode 21b gradually increases.

The moving member 13 moves from the second electrode 21b side to the first
When moving in the direction opposite to the arrow a toward the electrode 21a side, the counter electrode area between the moving member 13 and the first electrode 21a gradually increases, and the capacitance Ca between them gradually increases. The area of the counter electrode between the moving member 13 and the second electrode 21b gradually decreases, and the capacitance Cb between the two gradually decreases. The current ia flowing from the moving member 13 to the first electrode 21a gradually increases, and the moving member 13 moves to the second electrode 21b.
The electric current ib flowing through the gate gradually decreases.

By comparing the magnitudes of the current ia and the current ib, the position of the moving member 13 with respect to the detecting member 21 can be obtained, and the moving member can be changed depending on the direction in which the magnitudes of the current ia and the current ib change. The moving directions of 13 can be obtained.

[Third Embodiment] A third embodiment of the present invention will be described. The difference from the first embodiment is that in the first embodiment, the drive pulse for driving the piezoelectric element 11 is also supplied to the moving member 13 via the drive shaft 12, and the position of the moving member 13 can be detected. In contrast to this, in the third embodiment, a high-frequency oscillator is connected to the drive shaft 12, and the output of the high-frequency oscillator detects the position of the moving member 13. Since other configurations are the same as those of the first embodiment, the same members are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 5 is a diagram showing the basic configuration of an actuator 10 according to the third embodiment of the present invention. In FIG. 5, 11 is a piezoelectric element, which is one of electromechanical conversion elements, and 1
Reference numeral 2 is a drive shaft, 13 is a moving member frictionally coupled to the drive shaft 12, and 14 is a frame of an actuator. Piezoelectric element 1
One end of the piezoelectric element 1 is fixed to the frame 14 by means such as adhesion, and the other end of the piezoelectric element 11 is fixed to the drive shaft 12 by means such as adhesion. Further, reference numeral 15 denotes a detection member, which constitutes a fixed electrode for detecting the position of the moving member 13 based on the electrostatic capacitance, and is arranged in parallel in the moving direction of the moving member 13 in a non-contact state. And is fixed to the frame 14.

The drive shaft 12, the moving member 13, and the detecting member 15 are made of a conductive material. The detection member 15 forms an electrode 15a on the surface facing the moving member 13 with a concavo-convex portion at regular intervals, and the moving member 13 and the electrode 15a face each other with a distance D therebetween and have a capacitance. It forms a C capacitor.

Control circuit 17 for controlling the actuator 10
Is composed of a CPU and is connected to a drive circuit 18 which supplies a drive pulse to the piezoelectric element 11.

A high frequency voltage is output from the high frequency oscillator 25 and supplied to the moving member 13 via the drive shaft 12. The high frequency voltage applied to the moving member 13 is capacitively coupled between the moving member 13 and the electrode 15a, so that the moving member 1
The high frequency current i flows from 3 toward the electrode 15a. The high frequency current i is detected by the detection circuit 19 and input to the control circuit 17.

As in the case of the first embodiment, when the moving member 13 moves on the electrode 15a at a constant speed, the high-frequency current i detected also increases or decreases according to the shape of the uneven portion of the electrode 15a. Therefore, the position of the moving member 13 can be detected based on the detected high frequency current i.

[Fourth Embodiment] The fourth embodiment is a lens driving mechanism to which the above-mentioned actuator is applied, and shows the components relating to the detection of the lens position.

FIG. 6 is a perspective view showing an essential part of the lens driving mechanism 30 of the fourth embodiment. 31 is a piezoelectric element, 32 is a drive shaft, 33 is a lens holding frame for holding the lens L, and 34 is a lens. The guide shaft is a guide shaft that prevents rotation of the holding frame 33 and guides it in the optical axis direction. In addition to the function as a guide shaft, it is also a member that forms a condenser that detects the position of the lens L, as described later.

The lens holding frame 33 has a friction coupling portion 33a which frictionally couples to the drive shaft 32 with an appropriate frictional force, and a guide shaft 34.
A fitting portion 33b is formed so that the fitting portion 33b is fitted so as not to loosen and to be relatively movable. The drive shaft 32, the lens holding frame 33, and the fitting portion 33b may be made of a conductive material such as metal.

FIG. 7 is a view for explaining the structure of the guide shaft 34.
As shown in FIGS. 7 (a) and 7 (b), the guide shaft 34 has two end faces of shaft members 34a and 34b made of a metal material, which are bonded and fixed with an insulating adhesive 34c, so that the guide shaft 34 has a circumferential direction. Is formed by forming a dielectric coating 34d on the surface thereof.

As shown in FIG. 7C, when the fitting portion 33b of the lens holding frame 33 is fitted to the guide shaft 34, a capacitor Ca is formed between the fitting portion 33b and the shaft member 34a.
A capacitor Cb is provided between the fitting portion 33b and the shaft member 34b.
Is formed. This structure is the same as that described in the second embodiment with reference to FIG. 4 even though the electrode shape is different.

FIG. 8 shows the relative positions of the fitting portion 33b and the shaft members 34a and 34b, and the capacitor C formed.
8A and 8B are views for explaining the relationship between a and Cb with respect to the capacitance, when the fitting portion 33b moves from the state of FIG. 8A to the state of FIG. As shown, the fitting part 3
The capacitance of the capacitor Ca between 3b and the shaft member 34a decreases, and the capacitance of the capacitor Cb between the fitting portion 33b and the shaft member 34b increases.

Lead wires A and B are connected to the shaft member 34a and the shaft member 34b, respectively, and the lead wire E is connected to the fitting portion 33b.
, The fitting portion 33b, the shaft member 34a, and the shaft member 3
The position of the lens holding frame 33, that is, the position of the lens L can be detected by detecting the capacitance between the lens 4 and 4b, and the direction of the change in the capacitance can be detected to detect the position of the lens L. The moving direction can also be detected.

At this time, the drive shaft 32 and the lens holding frame 3
3 and the fitting portion 33b are made of a conductive material such as metal, the lead wire E is connected to the drive shaft 32 to electrically connect the lead wire E to the fitting portion 33b. Since they are the same, the capacitance between the fitting portion 33b and the shaft members 34a and 34b can be detected.
Thereby, the influence of the reaction force generated by connecting the lead wire to the moving member such as the lens holding frame 33 can be eliminated.

In this embodiment, the fitting portion 33b provided on the lens holding frame 33 has a shaft member 34 by a fitting hole.
a and the shaft member 34b are capacitively coupled,
The fitting portion 33b may be formed in a U shape so as to be capacitively coupled to the shaft member 34a and the shaft member 34b. However, in this case, since the area of the facing portion between the fitting portion 33b and the shaft member 34a and the shaft member 34b is reduced, the capacitance of the formed capacitor is reduced.

[Fifth Embodiment] The fifth embodiment also applies the above-described actuator to a lens driving mechanism and is related to the detection of the lens position. The fifth embodiment is similar to the fourth embodiment, but has two guide shafts and is characterized in that lead wires are attached to the electrodes.

FIG. 9 is a perspective view showing an essential part of the lens driving mechanism 40 of the fifth embodiment. 41 is a piezoelectric element, 42 is a drive shaft, 43 is a lens holding frame for holding the lens L, 44 and 45. Is a guide shaft that prevents the lens holding frame 43 from rotating and guides it in the optical axis direction.

The lens holding frame 43 has a frictional coupling portion 43a which frictionally couples to the drive shaft with an appropriate frictional force, and a fitting portion 43 which fits the guide shafts 44 and 45 in a relatively loose manner.
b is formed. Fitting portion 43b of lens holding frame 43
Shall be made of metal.

FIG. 10 is a sectional view for explaining the structure of the guide shafts 44 and 45, which has the same structure as the guide shaft described in the fourth embodiment, and the guide shaft 44 is made of two metal materials. The shaft members 44a and 44b are bonded and fixed with an insulating adhesive 44c, and a dielectric film 44d is formed on the surface of the shaft in the circumferential direction. The guide shaft 45 has the same structure, and two shaft members 45a and 45b made of a metal material are bonded and fixed with an insulating adhesive 45c, and a dielectric film 45d is formed on the circumferential surface of the shaft. Composed.

When the fitting portion 43b of the lens holding frame 43 is fitted to the guide shafts 44 and 45, the shaft member 44a and the fitting portion 4 are inserted.
3b and the capacitor formed between the fitting portion 43b and the shaft member 45a are connected in series to form a capacitor Ca between the shaft member 44a and the shaft member 45a. It

Further, the capacitor formed between the shaft member 44b and the fitting portion 43b, the fitting portion 43b and the shaft member 45b.
Is connected in series with the capacitor formed between
A capacitor Cb is formed between the shaft member 44b and the shaft member 45b.

Therefore, when the lead wires A1 and A2 are attached to the shaft members 44a and 45a and the lead wires B1 and B2 are connected to the shaft members 44b and 45b, respectively, the lead wire A
Capacitor Ca is connected between 1 and A2, and lead wire B1
A capacitor Cb will be connected between B2 and B2.

FIG. 11 is a diagram for explaining the relationship between the position of the fitting portion 43b and the electrostatic capacitances of the capacitors Ca and Cb to be formed. The fitting portion 43b is changed from the state of FIG. When moved to the state shown in b), the capacitance of the capacitor Ca between the fitting portion 43b and the shaft member 44a and the shaft member 45a (the capacitance between the lead wires A1 and A2) is shown in FIG. As shown, the fitting portion 43b and the shaft member 44 are reduced.
The capacitance of the capacitor Cb between the b and the shaft member 45b (the capacitance between the lead wires B1 and B2) is shown in FIG.
Increase as shown in.

By detecting the electrostatic capacitances of the capacitors Ca and Cb, the position of the lens holding frame 43, that is, the position of the lens L can be detected, and by detecting the direction of change of the electrostatic capacitance, The moving direction of the lens L can also be detected.

In the fifth embodiment, the lens holding frame 43
Since it is not necessary to connect a lead wire to the fitting portion 43b of
The influence of the reaction force generated by connecting the lead wire to the moving member such as the lens holding frame 43 can be eliminated.

[Sixth Embodiment] The sixth embodiment also applies the above-mentioned actuator to a lens driving mechanism and is related to the detection of the lens position. The sixth embodiment is characterized in that a flexible substrate having electrodes is used for detecting the position of the lens holding frame.

FIG. 12 is a perspective view showing an essential part of the lens driving mechanism 50 of the sixth embodiment. Reference numeral 51 is a piezoelectric element, 52 is a drive shaft, and 53 is a lens holding frame for holding the lens L.

The lens holding frame 53 is formed with a friction coupling portion 53a which frictionally couples to the drive shaft 52 with an appropriate frictional force, and the lens holding frame 53 is provided with a slit 54a straddling a flexible substrate 55 described later. Metal block 5
4 is attached.

The lens holding frame 53 is prevented from swinging,
Although a guide shaft for guiding the movement of the drive shaft 52 in the direction is not shown, the swing of the lens holding frame 53 is prevented by devising the cross-sectional shape such as providing a guide groove extending in the drive shaft 52 in the axial direction. Alternatively, a guide shaft may be provided separately.

FIG. 13 is a perspective view for explaining the structure of the flexible substrate 55. The flexible substrate 55 is made of a flexible resin film 55p having a high dielectric constant. The electrodes 55a and 55b are formed, and a resin film 55q having a high dielectric constant is adhered onto the electrodes 55a and 55b. At this time, the electrodes 55a and 55 on the substrate 55p
Both ends of b are connected to the lead wire, and the resin film 55
Do not stick q.

As shown in FIG. 12, when the flexible substrate 55 is inserted into the slit 54a of the metal block 54 attached to the lens holding frame 53, the metal block 54 is inserted.
A capacitor Ca is formed between the electrode 55a and the electrode 55a of the flexible substrate 55, and a capacitor Cb is formed between the metal block 54 and the electrode 55b.

In this structure, even if the electrode shape is different,
Electrically, in the second embodiment described above, the configuration is the same as that described in FIG. 4, and when the metal block 54 moves along the surface of the flexible substrate 55 due to the movement of the lens holding frame 53, the capacitor Since the capacitance of one of Ca and Cb decreases and the capacitance of the other increases,
The position of the lens holding frame 53, that is, the position of the lens L can be detected by detecting the electrostatic capacitances of the capacitors Ca and Cb, and the direction of the electrostatic capacitance change can be detected to detect the position of the lens L. The moving direction can also be detected.

FIG. 14 is a perspective view for explaining a modification of the structure of the flexible substrate 55. The two electrodes 55a and 55b formed on the flexible substrate 55 are the electrode 55aA and the electrode 55aB, the electrode 55bA and the electrode 55bB, respectively.
It is divided into and.

According to this structure, the capacitor formed between the electrode 55aA and the metal block 54 and the capacitor formed between the metal block 54 and the electrode 55aB are connected in series to form the electrode 55aA and the electrode 55aB. And a capacitor Ca formed between the electrode 55bA and the metal block 54 and a capacitor formed between the metal block 54 and the electrode 55bB are connected in series to form an electrode 55bA. A capacitor Cb is formed between the electrode and the electrode 55bB.

In this structure, even if the electrode shape is different,
Electrically, in the above-described fifth embodiment, FIGS.
The lens holding frame 53 has the same configuration as that described in
Movement of the metal block 54 causes the flexible substrate 55 to move.
The capacitance of one of the capacitors Ca and Cb decreases and the capacitance of the other increases when moving along the surface of the lens. Therefore, by detecting the capacitance, the position of the lens holding frame 53, that is, the lens The position of L can be detected,
By detecting the direction of change in capacitance, the moving direction of the lens L can also be detected.

In the sixth embodiment, the lens holding frame 53
Since it is not necessary to connect the lead wire to the metal block 54, the influence of the reaction force generated by connecting the lead wire to the moving member such as the lens holding frame 53 can be eliminated.

[Seventh Embodiment] The seventh embodiment also applies the above-mentioned actuator to a lens driving mechanism and is related to the detection of the lens position. The seventh embodiment also uses a flexible substrate on which electrodes are formed to detect the position of the lens holding frame.

FIG. 15 is a perspective view showing an essential part of the lens driving mechanism 60 of the seventh embodiment. Reference numeral 61 is a piezoelectric element, 62 is a drive shaft, and 63 is a lens holding frame for holding the lens L.

The lens holding frame 63 is formed with a frictional coupling portion 63a which frictionally couples to the drive shaft 62 with an appropriate frictional force, and the intermediate electrode member 6 is provided in an extension portion of the lens holding frame 63.
4 is attached.

Further, in a frame (not shown) of the lens driving mechanism, two flexible substrates 65 and 66 are arranged parallel to the axial direction of the drive shaft 62, that is, the moving direction of the lens L, and the flexible substrates 65 and 66 are arranged. The electrode formed on the above and the intermediate electrode member 64 provided in the extension of the lens holding frame 63 face each other.

The lens holding frame 63 is prevented from swinging,
Although the guide shaft for guiding the movement of the drive shaft 62 in the direction is not shown, the swing of the lens holding frame 63 is prevented by devising a sectional shape such as providing a guide groove extending in the drive shaft 62 in the axial direction. Alternatively, a guide shaft may be provided separately.

The flexible boards 65 and 66 are constructed as follows.
The detailed description is omitted because it is the same as that described in FIG. 13, but the flexible substrate 65 has two electrodes 65a.
And 65b are formed, and two electrodes 66a and 66b are formed on the flexible substrate 66.

The electrodes 65a and 65b formed on the flexible substrate 65, the electrodes 66a and 66b formed on the flexible substrate 66, and the intermediate electrode member 64 provided on the extension of the lens holding frame 63. Are opposed to each other, a capacitor formed between the electrode 65a and the intermediate electrode member 64, the intermediate electrode member 64, and the electrode 66a.
Is connected in series to form a capacitor Ca, and between the capacitor formed between the electrode 65b and the intermediate electrode member 64 and the intermediate electrode member 64 and the electrode 66b. The formed capacitor is connected in series to form the capacitor Cb.

In this structure, even if the electrode shape is different,
Electrically, in the above-described fifth embodiment, FIGS.
The lens holding frame 63 has the same configuration as that described in
Movement of the intermediate electrode member 64 causes the flexible substrate 66 to move.
Moving between the two, the capacitance of one of the capacitors Ca and Cb decreases and the capacitance of the other increases, so by detecting the capacitance, the position of the lens holding frame 63, that is, the lens L In addition to being able to detect the position, the moving direction of the lens L can also be detected by detecting the direction of change in capacitance.

In the seventh embodiment, the lens holding frame 63
Since it is not necessary to connect the lead wire to the intermediate electrode member 64, the influence of the reaction force generated by connecting the lead wire to the moving member such as the lens holding frame 63 can be eliminated.

Although various embodiments of the present invention have been described above, the embodiments described above also include the inventions described below.

The position detecting device according to claim 1 is provided with a guide member for guiding the moving member so as to move only in a predetermined moving direction, and the guiding member and the moving member are electrically capacitively coupled to each other. The position detecting device is characterized in that one side is mechanically slidably inserted into the other side.

[0094]

As described above in detail, in the position detecting device of the present invention, the fixed electrode is arranged close to the moving member of the actuator using the electromechanical conversion element, and between the moving member and the fixed electrode. It is configured to detect the position of the moving member based on the electrostatic capacitance of.

As a result, the position of the moving member can be detected in a non-contact manner, and a load is unnecessarily applied to the driving member by the reaction force generated by connecting the lead wire to the moving member as in the conventional device. Not only is it not applied, but the moving member is not subjected to a load due to the reaction force from the lead wire, so that it is possible to detect the position with high accuracy.

Further, since the structure is simpler than that of the conventional non-contact type position detecting device, the number of parts can be reduced, the manufacturing cost can be reduced, and other remarkable effects can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a basic configuration of an actuator according to a first embodiment.

FIG. 2 is a diagram showing another configuration example of the detection electrode of the actuator described in FIG.

FIG. 3 is a diagram illustrating a basic configuration of an actuator according to a second embodiment.

FIG. 4 is a diagram showing a configuration example of detection electrodes of the actuator described in FIG.

FIG. 5 is a diagram illustrating a basic configuration of an actuator according to a third embodiment.

FIG. 6 is a perspective view showing a main part of a lens driving mechanism according to a fourth embodiment.

7 is a cross-sectional view illustrating a configuration of a guide shaft of the lens driving mechanism illustrated in FIG.

FIG. 8 is a diagram for explaining the relationship between the relative positions of the fitting portion and the two shaft members and the capacitances of the two capacitors formed.

FIG. 9 is a perspective view showing a main part of a lens driving mechanism according to a fifth embodiment.

10 is a cross-sectional view illustrating a configuration of a guide shaft of the lens driving mechanism shown in FIG.

11 is a diagram illustrating the relationship between the relative positions of the fitting portion and the two shaft members of the lens driving mechanism shown in FIG. 10 and the capacitances of the two capacitors formed.

FIG. 12 is a perspective view showing a main part of a lens driving mechanism according to a sixth embodiment.

13 is a perspective view (No. 1) for explaining the configuration of the flexible substrate of the lens driving mechanism shown in FIG.

14 is a perspective view (No. 2) for explaining the configuration of the flexible substrate of the lens driving mechanism shown in FIG.

FIG. 15 is a perspective view showing a main part of a lens driving mechanism according to a seventh embodiment.

FIG. 16 is a diagram illustrating a configuration of an actuator using a conventional piezoelectric element.

[Description of Reference Signs] 10, 20 Actuator 11 Piezoelectric element (electromechanical conversion element) 12 Drive shaft 13 Moving member 14 Frame 15 Detecting member (fixed electrode) 15a Electrode 17 Control circuit 18 Drive circuit 19 Detecting circuit 21 Detecting member (fixed electrode) ) 21a 1st electrode 21b 2nd electrode 25 High frequency oscillator 30, 40, 50, 60 Lens drive mechanism 31, 41, 51, 61 Piezoelectric element 32, 42, 52, 62 Drive shaft 33, 43, 53, 63 Lens holding frame 33a, 43a, 53a, 63a Friction coupling parts 33b, 43b Fitting parts 34, 44, 45 Guide shafts 34a, 34b, 44a, 44b, 45a, 45b Shaft members 54 Metal blocks 54a Slits 55, 65, 66 Flexible boards 55a, 55b, 65a, 65b, 66a, 66b Electrode 64 Intermediate electrode member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoyuki Yuasa             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. F term (reference) 2F063 AA02 BA30 BB02 BD15 CA23                       CA34 DA05 EA02 HA05 HA12                       HA14 HA15 HA18 KA04 KA05                       NA06                 2F077 AA49 CC02 HH02 HH03 HH05                       HH11 NN05 PP01 QQ05 RR02                       RR03 VV02                 2H044 DB04 DC01 DE01 DE06

Claims (5)

[Claims] 1. An electromechanical conversion element, a drive member fixed to one end of the electromechanical conversion element, a moving member frictionally coupled to the drive member, and a drive for supplying a drive pulse to the electromechanical conversion element. A circuit, which supplies a driving pulse to the electromechanical conversion element to generate expansion and contraction displacement vibrations having different expansion and contraction speeds to cause relative displacement between the driving member and the moving member. In the position detection device, an electrostatic capacitance detector that is arranged in parallel along a moving direction of the moving member and that detects an electrostatic capacitance between the electrode plate facing the moving member and the moving member and the electrode plate. And a position detecting device for detecting the position of the moving member in the moving direction based on the electrostatic capacitance detected by applying the drive pulse between the moving member and the electrode plate. . 2. The driving member and the moving member are made of a conductive material, and the electrode of the electromechanical conversion element and the driving member are electrically connected to each other. Position detection device. 3. The position detecting device according to claim 1, wherein the electrode plate facing the moving member is provided on a fixed member to which the electromechanical conversion element is fixed. 4. An electromechanical conversion element, a drive member fixed to one end of the electromechanical conversion element, a moving member frictionally coupled to the drive member, and a drive for supplying a drive pulse to the electromechanical conversion element. And a circuit, wherein a driving pulse is supplied to the electromechanical conversion element to generate expansion and contraction displacement vibrations having different expansion and contraction speeds, and the driving member and the moving member are moved relative to each other. In the position detection device, a high-frequency voltage generator that applies a high-frequency signal to the driving member, an electrode plate that is arranged in parallel along the moving direction of the moving member and faces the moving member, the moving member and the electrode plate. And a capacitance detector for detecting a capacitance between the high frequency voltage generator and the high frequency voltage output between the moving member and the electrode plate. Position detecting device and detecting the position of the moving direction of the moving member based on the capacitance. 5. The electrode plate facing the moving member has a plurality of concavo-convex portions formed along a moving direction of the moving member at a pitch not greater than a minimum detection unit of the moving distance of the moving member. The position detecting device according to claim 1, 2, 3, or 4.