JPH08107684A - Driver - Google Patents

Abstract

PURPOSE: To prevent the generation of the loss of a driver which is caused by a frictional force, by fastening one end of an electromechanical conversion element to a static member, and by fastening a driving member to the other end of the electromechanical conversion element, and further, by engaging variably a moving member in frictionally coupled with the driving member, and moreover, by so supporting both the moving and driving members that they can move respectively in their extending directions. CONSTITUTION: As shown in Fig. A, when a voltage is applied to a piezoelectric element 10, it is extended, and an upward force acts on an inertial member 11 and a downward force acts on a frictional member 5, and further, the frictional member 5 is contacted in a pressed way with a driving shaft 3. But, when the voltage is released from the piezoelectric element 10, the frictional force generated between the frictional member 5 and the driving shaft 3 is reduced. By the utilization of this phenomenon, as shown in Fig. B, when a voltage is applied to a piezoelectric element 2 and the voltage is released from the piezoelectric element 10, the piezoelectric element 2 is extended, and as shown in Fig, C, the driving shaft 3 is displaced rightmost, but the frictional member 5 remains in the place. As shown in Fig. D and Fig. E, when a voltage is applied to the piezoelectric element 10 and the voltage is released from the piezoelectric element 2, the frictional member 5 is displaced leftmost. As mentioned above, by the varying of a frictional force, the frictional force of a suitable value can be given to the frictional member 5.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for driving a driven member using an electromechanical conversion element. For example, in addition to driving a lens in an optical device such as a photographing lens of a camera, a projection lens of an overhead projector, a lens of binoculars, a lens of a copying machine, a plotter or an X
The present invention relates to a drive device generally used in a device having a drive unit such as a device such as a Y drive table.

2. Description of the Related Art Conventionally, techniques in such a field include:
There is one disclosed in Japanese Patent Laid-Open No. 4-69070. The contents will be described with reference to the schematic diagram of FIG. Figure 9 (a)
Is a lens driving device, 101 is a lens barrel that holds the lens, and 103 is a guide bar that supports the lens barrel and guides it in the optical axis direction. The guide bar 103 is the lens barrel 101.
101 formed on a support portion 101e extending from the fork 101
The lens barrel 101 is supported and guided by penetrating f. Reference numeral 117 denotes a lens barrel support member / driving rod, which cooperates with the support portion 101e to support the lens barrel 101 and drive the lens barrel 101 in the axial direction. The drive rod 117 has holes 113b and 113 formed in rising portions 113a and 113c provided on the drive rod support member 113.
It is inserted in d and is movable in the axial direction.
The drive rod 117 has holes 101b and 101d formed at both ends 101a and 101c of a U-shaped portion 101k extending from the lens barrel 101 in the direction opposite to the pointing portion 101e.
Penetrates through. Further, the rear end of the drive rod 117 is fixed to the front end of the piezoelectric element 112. The rear end of the piezoelectric element 112 is fixed to another rising portion 113e of the drive rod support member 113. Further, the leaf spring 114 is fixed by the screws 115 and 116 to both ends 101 of the lens barrel 101.
It is attached to a and 101c from below in the figure. The leaf spring 114 is arranged to be parallel to the drive rod 117. Further, a friction portion 114c protruding upward in the drawing is formed in the substantial center of the leaf spring 114, and this is a driving rod 1
The lens barrel 101 and the drive rod 117
Friction is generated between the lens barrel 101 and the lens barrel 101 and the lens barrel 101 can be driven. The friction is generated by the spring pressure of the leaf spring 114. FIG. 9B shows a voltage waveform applied to the piezoelectric element 112. And in FIG.
9B shows a voltage waveform applied to the piezoelectric element 112 when the lens barrel 101 is moved rightward in FIG. 9A, and FIGS. 14B and 14B show the lens barrel 10 in FIG. 9A.
3 shows a voltage waveform applied to the piezoelectric element 112 when moving 1 to the left. When a voltage waveform as shown in FIGS. 9B and 9A is applied to the piezoelectric element 112, the piezoelectric element 112 abruptly expands at the abrupt rising portion where the voltage A changes to the voltage C. At this time, the drive rod 117 also moves to the left in FIG. 9A by the same amount as the extension amount of the piezoelectric element 112. However, in this case, the lens barrel 101 moves only a little due to inertia. On the contrary, when the voltage C slowly changes to the voltage A, the piezoelectric element 112 contracts slowly, and the frictional force between the lens barrel 101 and the drive rod 117 or the leaf spring 114 and the drive rod 117.
The lens barrel 101 moves to the right in FIG. 9A due to the frictional force between and. When the lens barrel 101 is moved to the left in FIG. 9A, a voltage as shown in FIGS. 14B and 14B is applied to the piezoelectric element 112, and the movement at that time is exactly the same as when driving in the right direction as described above. The opposite is true.

However, in the conventional structure as shown in FIG. 9, even when the piezoelectric element 112 expands and contracts abruptly, the lens barrel 101 and the drive rod 117 are moved by the dynamic frictional force. 101 moves somewhat with the drive rod 117. Therefore, the lens barrel 101 will return in the direction opposite to the direction in which it should be originally moved, resulting in a loss in the amount of movement. Here, this loss increases as the frictional force increases, so conversely, it is considered that the frictional force should be decreased. However, it is actually not preferable to reduce the frictional force under the following conditions.
That is, it is necessary to increase the frictional force as the inertia of the drive system increases. Therefore, if the mass of the driven member increases, the frictional force must be increased,
It is conceivable that it will not be practical without generating a considerably large frictional force. Further, when the driving frequency of the piezoelectric element 112 becomes low, there arises a problem that the generated sound becomes noisy. Therefore, it is considered that the driving frequency should be higher to some extent in practical use. However, if so, even if the piezoelectric element 112 expands and contracts slowly, it will be displaced at a considerable speed. Then, a considerable amount of frictional force is required for the lens barrel 101 to follow the drive rod 117. An object of the present invention is to solve the above problems and to obtain a configuration capable of achieving both the problems of preventing the occurrence of loss and obtaining a configuration suitable for practical use.

To achieve the above object, in the present invention according to claim 1, a stationary member and one end of the stationary member in the direction of expansion and contraction are fixed, and a voltage is applied so as to expand and contract. An electromechanical conversion element that receives the
A drive member fixed to the other end of the electromechanical conversion element in the expansion / contraction direction and frictionally engaged with the drive member supported so as to be movable in the expansion / contraction direction of the electromechanical conversion element, A driving device is constituted by a moving member that is supported so as to be movable in the expansion and contraction direction, and a variable unit that changes a frictional force between the driving member and the moving member. Further, in the present invention according to claim 2, the frictional force is generated by a friction applying member installed on the moving member, and an elastic member that presses the driving member and the moving member through the friction applying member. It is supposed to be generated by. Further, in the present invention according to claim 3, the variable means comprises a second electromechanical conversion element having one end fixed to the friction imparting member and the other end fixed with an inertia member. There is. On the other hand, in the present invention according to claim 4, each electromechanical conversion element is expanded or contracted by applying a signal having a synchronous relationship to the first electromechanical conversion element and the second electromechanical conversion element. It is characterized by having a drive circuit.

In the above structure, when the frictional force is changed by the variable member and the moving member needs to follow the driving member, the frictional force is increased, and when it is unnecessary to follow the driving member, the frictional force is reduced. The moving member moves without loss.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a state in which a unit of a drive device adopting the present invention is disassembled (before assembly). In FIG. 1, 1 is a stationary member. The stationary member 1 is formed in a substantially columnar shape as a whole, and has a first hole 1b and a second hole 1c penetrating in the diametrical direction (vertical direction in the drawing). A bearing hole 1d is formed in the wall portion between the holes 1b and 1c. Further, a bearing hole 1e is provided coaxially with the hole 1d at the end face of the cylinder which constitutes the wall surface of the hole 1c. Further, one end portion of the stationary member 1 including the end surface opposite to the above end surface functions as a fixing margin 1a for fixing the driving device unit when it is attached to a device or the like. The piezoelectric element 2 is installed in the hole 1b. The piezoelectric element 2 is fixed to the portion of the wall surface of the hole 1b opposite to the wall portion where the bearing hole 1d is formed, that is, the portion on the fixing margin side by adhesion. The piezoelectric element 2 expands and contracts in the longitudinal direction of the stationary member 1 when a voltage is applied via the lead wires 2a and 2b. Reference numeral 4 denotes a slider, which is arranged in the hole 1c and is movable in the axial direction of the cylinder by using the longitudinal wall surface forming the hole 1c as a rotation stopper and a guide. The slider 4 has a U-shaped portion extending upward from the main body in the figure, and a pair of through holes 4a extending in the longitudinal direction of the stationary member 1 are formed in the U-shaped portion. A groove 4b having a semicircular cross section is formed on the upper surface of the main body portion so as to connect the through holes 4a, 4a. Further, a mounting portion extends below the body portion so as to form a T shape with the body.
The mounting portion is formed with a screw receiving hole 4c for connecting a driven member. Reference numeral 3 is a drive shaft, and the bearing hole 1e, the through hole 4a, the groove 4b, the through hole 4a, and the bearing hole 1 are externally provided.
It is inserted through d and one end is fixed to the piezoelectric element 2 by adhesion. In this state, the other end of the drive shaft has a bearing hole 1e.
It is a little protruding from the. The piezoelectric element 6 can move in the expansion / contraction direction while being instructed by the two bearing holes 1d, 1e. 7 is a leaf spring, and a screw 9
Is attached to the stationary member 1 so as to hold down the drive shaft 3 slightly protruding from the bearing hole 1e. As a result, the drive shaft 3 is pressed against the piezoelectric element 2 with a certain force. The pressing force can be adjusted by tightening or tightening the screw 9. Reference numeral 5 is a friction member, and a groove 5a having a semicircular cross section is formed on the lower surface, and the drive shaft 3 is sandwiched from above toward the groove 4b. Further, a leaf spring 6 is provided above it to press the friction member 5 and the drive shaft 3 from above. The leaf spring 6 is attached to the tip of the U-shaped portion of the slider 4 with four screws 8.
As a result, a pressing force is generated on the drive shaft 3 via the friction member 5. On the other hand, one end of the second piezoelectric element 10 is fixed to the upper surface of the friction member 5 by adhesion or the like, and the inertial member 11 is fixed to the upper surface of the piezoelectric element 10 by adhesion or the like. The piezoelectric element 10 penetrates a through hole formed in the center of the leaf spring 6, and the inertia member 9 is located above the leaf spring 6. The assembled state is shown in FIG. FIG. 3A is a view of the assembled state seen from the upper surface, and FIG. 3B is a sectional view taken along a plane along the drive shaft 3. FIG. 4 shows an outline of a circuit for expanding and contracting driving the piezoelectric elements 2 and 10 in the present embodiment. The driving circuits for driving the respective piezoelectric elements are connected to a common control circuit and are synchronized. In this state, the piezoelectric elements 2 and 10 are driven. Next, referring to FIGS. 5 to 8, the piezoelectric elements 2 and 1 by the control circuit or the drive circuit described above.
The drive sequence of 0 will be described. 5 and 6 show the state in which the slider 4 is moved to the right, FIG. 5 shows the main part of the drive device at that time, and FIG. 6 shows the state of the drive voltage at that time. 7 and 8 show the state in which the slider 4 is moved to the left, FIG. 7 shows the main part of the drive device at that time, and FIG. 8 shows the state of the drive voltage at that time. Since the slider 4 moves together with the friction member 5, the friction member 5 is shown instead of the slider 4 in FIGS. 5 and 7 for simplification of the drawings, but the operation is the same. In FIGS. 5 and 6A, the initial state is the state indicated by A, and both piezoelectric elements are in the voltage non-application state. In this state, both piezoelectric elements are in the most contracted state. From this state, a voltage is applied in a sin curve shape as shown in A to C of FIG. Then, both piezoelectric elements 2 and 10 gradually start expanding as shown in FIG. 5B. Since the piezoelectric element 10 also expands as the piezoelectric element 2 expands, the inertia member 11 receives an upward force, while the friction member 5 receives a downward force. The force applied to the friction member 5 increases the frictional force between the friction member 5 and the drive shaft 3, and the friction member 5 and the slider 4 follow the movement of the drive shaft 3 to the right. As a result, as shown in C, the friction member 5 and the slider 4 move to the position where the drive shaft 3 has moved to the rightmost. Subsequently, the voltage application is released as shown in C to E of FIG. Then, both piezoelectric elements 2 and 10 shrink. At this time, as the piezoelectric element 2 shrinks, the drive shaft 3
Moves to the left, and the friction member 5 and the slider 4 also try to move accordingly. However, at this time, since the piezoelectric element 10 contracts, the inertial member 11 receives a downward force, while the friction member 5 receives an upward pulling force. Therefore, the frictional force between the friction member 5 and the drive shaft 3 is reduced, and slippage occurs between them, and C in FIG.
As indicated by E to E, the friction member 5 and the slider 4 remain in that position. By repeating the above operations A to E, the slider 4 moves to the right toward the desired position. On the other hand, in FIGS.
As shown in A of (a), the maximum voltage is applied to the piezoelectric element 10. As a result, the piezoelectric element 10 is in a stretched state as shown in A of FIG. At this time, a force acts on the inertia member 11 upwards and a force acts on the friction member 5 downwards.
Presses against the drive shaft 3. From this state, a voltage is applied to the piezoelectric element 2 as shown in B of FIG.
The applied voltage is released from 0. Then, the piezoelectric element 2 expands and the drive shaft 3 moves to the left in FIG. 7, but at this time, the piezoelectric element 10 contracts, so that a force pulling upward acts on the friction member 5 and the drive shaft 3. The frictional force between is reduced. Therefore, the friction member 5 and the slider 4 remain in place. Subsequently, as shown in FIG. 7C, the voltage is applied to the piezoelectric element 10 from the most expanded state of the piezoelectric element 2, while the applied voltage is released from the piezoelectric element 2. Then, the drive shaft 3 moves leftward as the piezoelectric element 2 contracts. At this time, since the force of pressing down the friction member 5 acts on the friction member 5 due to the expansion of the piezoelectric element 10, the friction member 5 and the slider 4 follow the drive shaft 3, and the state of E of FIG. Displace to. By repeating the above operations A to E, the slider 4 moves leftward toward a desired position. Since the maximum voltage is applied to the piezoelectric element 10 after the movement to the desired position is completed, this may be released. The above is the description of the embodiment of the present application.
(A), not limited to the sin curve as shown in FIG. 8 (a),
A linear waveform as shown in FIGS. 6B and 8B may be used. That is, when moving the slider 4 (friction member 5) to the right, a voltage is gradually applied as shown in FIG. 6B, and the applied voltage is rapidly released from the state where the piezoelectric element is most expanded. By repeating this state, the slider 4 moves to the right. If the slider 4 (friction member 5) is moved leftward,
As shown in (b), first, the voltage application is rapidly released from the state where the voltage is applied to the piezoelectric element 10, while the voltage is rapidly applied to the piezoelectric element 2. Then, the applied voltage is gradually released from the most expanded state of the piezoelectric element 2, while the voltage is gradually applied to the piezoelectric element 10. By repeating this state, the slider 4 moves to the left.
In the case where the voltage is linearly applied and the rising / falling characteristics are changed, the s
The frictional force can be set in a more optimal state as compared with the case of driving with an in curve, and driving can be performed efficiently. In addition, it has advantages that position control is easy and minute positioning is easy. On the other hand, when driving with a sin curve, the circuit configuration for applying a voltage is easier and more efficient than when a linear voltage with different rising / falling characteristics is applied. ,
It also has the advantage that it can be easily driven at high frequencies.

As described above, since the drive unit of the present invention is provided with the variable means for changing the frictional force between the driving member and the moving member, a frictional force of an amount suitable for practical use is provided. On the other hand, it is possible to prevent the loss of the moving amount by increasing the frictional force, and to provide a highly practical drive device using the electromechanical conversion element. It is possible.

[Brief description of drawings]

FIG. 1 is an assembly explanatory diagram of an embodiment of the present invention.

FIG. 2 is a perspective view of the embodiment.

3A and 3B are a plan view and a sectional view of the embodiment.

FIG. 4 is an explanatory diagram showing an outline of a circuit of an example.

FIG. 5 is an explanatory diagram showing an operation in the embodiment.

FIG. 6 is an explanatory diagram showing a voltage applied to the electromechanical conversion element in the example.

FIG. 7 is an explanatory diagram showing an operation in the embodiment.

FIG. 8 is an explanatory diagram showing a voltage applied to the electromechanical conversion element in the example.

FIG. 9 is an explanatory diagram showing a conventional example.

[Description of Reference Signs] 1 stationary member 2 electromechanical conversion element 3 driving member 4 moving member 5 friction imparting member 6 elastic member 10 variable means (second electromechanical conversion element) 11 variable means (inertial member)

Claims (4)

[Claims] 1. A stationary member (1), an electromechanical conversion element (2) fixed to the stationary member at one end in the direction of expansion and contraction, and receiving a voltage to expand and contract, and expansion and contraction of the electromechanical conversion element. A drive member (3) fixed to the other end of the electromechanical conversion element and supported so as to be movable in the expansion / contraction direction of the electromechanical conversion element, and frictionally engaged with the drive member to move in the expansion / contraction direction of the electromechanical conversion element. Moving members supported so that they can (4)
And a variable device (10, 11) for changing a frictional force between the driving member and the moving member. 2. The frictional force is generated by a friction applying member (5) installed on the moving member and an elastic member (6) for pressing the driving member and the moving member into pressure contact with each other via the friction applying member. The drive device according to claim 1, wherein the drive device is provided. 3. The variable means comprises a second electromechanical conversion element (10) having one end fixed to the friction imparting member and the other end fixed with an inertia member (11). The drive device according to claim 2. 4. A drive circuit for expanding and contracting each electromechanical conversion element by applying a signal having a synchronous relationship to the electromechanical conversion element and the second electromechanical conversion element. The drive device according to claim 3.