JP2002119074A - Drive using electromechanical sensing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten an SIDM drive without degrading its driving performance. SOLUTION: In this SIDM drive provided with a supporting base 20 disposed linearly, an electromechanical sensing element 4, and an oscillating rod 5, at least part of the supporting base 20 is extended to the oscillating rod 5 side beyond one end of the electromechanical sensing element 4. The electromechanical sensing element 4 and the supporting base 20 have an overlapped section in the lengthwise direction of the SIDM drive, thus it is possible to shorten the SIDM drive by the quantity of the overlapped section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device (SID) using an electromechanical transducer such as a piezoelectric element (piezo element).
M: Smooth Impact Drive Mechanism).

[0002]

2. Description of the Related Art FIGS. 1 and 2 show, for example, a driving apparatus using an electromechanical transducer such as a piezoelectric element whose length changes (expands or contracts) when a voltage is applied.

This driving device can move a moving body 10 relatively to a support base 1 functioning as a weight member, and can be used, for example, as a lens driving device for a camera. That is, if the moving body 10 is connected to the lens frame, the lens can be moved together with the moving body 10.

The piezoelectric element 4 is formed by laminating a large number of piezoelectric plates. One end 4a in the expansion and contraction direction is fixed to the support table 1 and the other end 4b is fixed to one end 5a of a rod (vibrating member) 5. You.

Although the moving body 10 is illustrated in a simplified manner in FIG. 1, in actuality, as shown in FIG. 7, the moving body 10 is friction-coupled around the rod 5 using a V-groove and a leaf spring.

A voltage control circuit (drive circuit) (not shown) is connected to the piezoelectric element 4. When a pulse voltage represented by a sawtooth waveform as shown in FIG. 4 expands and contracts, and the rod 5 vibrates in the longitudinal direction. Specifically, the piezoelectric element 4 expands relatively slowly in response to the gentle rising slope (b) of the pulse, and the piezoelectric element 4 contracts rapidly in response to the falling slope (c), and the initial state. Return to length.

When a voltage is applied so that the above pulse is continuously repeated, the rod 5 vibrates by repeating a slow movement in the direction A and a sudden movement in the direction B. Here, when the rod 5 moves slowly, the moving body 10
Move with the rod 5, and when the rod 5 moves rapidly, the moving body 10 stops at the spot due to inertia (or moves by a smaller amount than the rod 5). The frictional coupling force on the rod 5 is adjusted. Therefore, while the rod 5 vibrates, the moving body 10
Will move in the direction A relative to the support 1.

When the moving body 10 is moved in the direction of arrow B in FIG. 2, the pulse waveform of the voltage applied to the piezoelectric element is changed to that shown in FIG. What is necessary is just to make it the waveform which has a gentle falling part. Moving body
The ten movement principles are the same as in the above case.

Here, the vibration of the piezoelectric element 4 is actually
The vibration is transmitted not only to the rod 5 but also to the support base 1, and a loss is generated in the expansion and contraction vibration on the rod 5 side. In order to reduce this loss, it is important to use a material having a small elastic deformation and a large mass as the support 1 and to make the support 1 function as a weight member. Specifically, a metal member such as tungsten or stainless steel having a high Young's modulus and a large specific gravity is used.

The above-described SIDM driving device is often applied to small products such as portable devices, taking advantage of its small size and high accuracy. There is no limit to the demand for miniaturization of portable devices and the like, and in that sense, there is a demand for further miniaturization of the SIDM driving device itself. In the SIDM drive device, since the support 1, the piezoelectric element 4, and the rod 5 are arranged in a straight line, the length tends to be larger than the radial dimension.

[0011]

Accordingly, a technical problem to be solved by the present invention is to reduce the length dimension of the SIDM driving device.

[0012]

In order to reduce the size of the SIDM driving device, the length of the rod 5 is determined by the moving stroke of the object to be driven. Since the length of the piezoelectric element 4 directly affects the driving performance of the device, there is a limit to shortening the length. Also, regarding the support base 1 functioning as a weight member, there is a limit to downsizing in order to secure a certain weight or more.

[0013] As described above, there is a limit to reducing the size of each component alone to reduce the size of the SIDM driving device. Therefore, in the present invention, among the components arranged in a straight line, the SID and the support
By providing an overlapping portion in the length direction of the M driving device, the length dimension of the SIDM driving device is reduced without lowering its performance.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 shows an SIDM driving device according to an embodiment of the present invention in comparison with a conventional configuration. FIG. 3A shows a conventional example, and FIG. 3B shows a configuration of the present invention. In FIG. 3, illustration of the moving body is omitted.

In the conventional example, the support 1 is a cylindrical body made of tungsten, and its specific gravity is 19.3 mg / mm ^3.
It is. The dimensions are 2 mm in diameter, 2 mm in length, and 6.28 mm ³ in volume.
mg.

In the configuration of the present invention, the support base 20 has a concave portion 21 formed on one surface of a cylindrical body. The recess 21 includes a peripheral wall and a bottom surface, and one end of the piezoelectric element 4 inserted into the recess is fixed to the bottom surface. FIG. 4 shows the dimensions of the support base 20 shown in FIG. Since the support 20 is made of the same tungsten as the support 1, if the volume is made the same as the volume of the support 1, the same weight (121 mg) can be obtained. That is, the same function can be realized as a support base serving as a weight member. FIG. 5 is a table showing combinations of the dimensions of the support 20 in order to make the volume of the support 20 the same as the volume of the support 1 in the conventional example of FIG. The rightmost column of the table shows an SI in which a 2 mm long piezoelectric element and a 7 mm long rod are arranged in a straight line.
This is a value indicating the total length of the DM driving device, and is equal to t + element length + rod length here.

Here, as can be seen by comparing FIGS. 3A and 3B, when the same piezoelectric element 4 and rod 5 are employed, the depth (L−L) of the concave portion 21 formed in the support base 20 is obtained. It can be seen that the total length of the SIDM driving device is reduced by t).
In FIGS. 3A and 3B, a cylindrical element having a diameter of 1.2 mm and a length of 2 mm is used as the piezoelectric element 4. Since the diameter of the concave portion 21 is 1.3 mm, a slight clearance is secured between the piezoelectric element 4 and the peripheral wall of the concave portion,
Thereby, the expansion and contraction of the piezoelectric element 4 is smoothly increased.

Next, the No. shown in the table of FIG. 1, 4,
8, 10 samples and Modification of sample 8
FIG. 6 shows the result of comparing the performance of the conventional example (FIG. 3A) with respect to (No. 8). No. In a modified example of the sample No. 8, as shown in FIG. 8, the support base 20 is formed by combining two members of a disk body 25 and a cylindrical body 26 instead of being formed integrally. The dimensions after union are N
o. This is the same as the modified example of the sample No. 8. When using a material such as die casting, which is difficult to mold, it is advantageous to form two members as in the example of FIG.

In the performance comparison, the diameter was 1 mm and the length was 7 mm.
A carbon rod 5 having a diameter of 2 mm was employed, and a lens frame 30 having a weight of 2 g was engaged with the carbon rod 5 as a driving target. In particular,
As shown in FIG. 7, the rod 5 was arranged in the V-shaped groove 31 a of the frictional engagement body 31 that supports the ball frame 30, and was frictionally engaged so as to be sandwiched by the leaf spring 32.

FIG. 9 shows a voltage waveform applied to the piezoelectric element in the performance comparison. The table in FIG.
The results of comparing the moving speeds of the lens frame 30 at 20 kHz, 50 kHz, 100 kHz, and 150 kHz are shown. In the table, the average value of the ten measurements is used as the moving speed. As can be seen from the table, the dispersion of the average speed among the samples is small, and almost the same performance is achieved as compared with the conventional SIDM driving device.

In the present invention, at least a part of the support is extended to the vibrating member side beyond the one end of the electromechanical transducer, whereby the weight of the support functioning as the weight member is maintained. The essence is to shorten the overall length of the SIDM driving device. Several modified examples will be described below, but the specific embodiments of the SIDM driving device of the present invention are not limited to those illustrated and described, but include all the embodiments that satisfy the above-mentioned essence.

In the example shown in FIG. 10, two notches 28 are provided in a part of the peripheral wall of the concave portion for accommodating one end of the piezoelectric element 4.
Each notch 28 is used to pass a lead wire 29 from the piezoelectric element 4 to control means (not shown).

In the example shown in FIG. 11, the support 35 includes a flat fixing plate 36 and a protruding portion 37 extending from one edge of the fixing plate 36 toward the rod 5. Such a configuration is also convenient for taking out the lead wire 29 from the piezoelectric element. Generally, the SIDM driving device is fixed at any position on the support base, but in this example, it is preferable to fix the SIDM driving device at the protrusion 37.

FIGS. 12 and 13 show examples in which a hollow cylindrical piezoelectric element 40 is employed as an electromechanical transducer. The support base 50 includes a fixed plate 51 and a protruding portion 52, and the protruding portion 52 extends inside the piezoelectric element 40. As shown in FIG. 14, when the extending portion 53 extending outward from the piezoelectric element 40 is arranged on the peripheral edge of the fixed plate 51, the weight of the support base can be further increased.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a conventional SIDM driving device.

FIG. 2 is an explanatory diagram illustrating a conventional SIDM driving device.

FIG. 3 shows a conventional SIDM driving device and the SIDM of the present invention.
It is explanatory drawing which shows a drive device in comparison.

FIG. 4 is a cross-sectional view illustrating a support stand of the SIDM driving device according to the present invention shown in FIG.

FIG. 5 is a table showing combinations of dimensions in the support table of FIG. 4;

FIG. 6 shows a SIDM driving apparatus of the present invention and a conventional SIDM.
5 is a table showing a performance comparison of a driving device.

FIG. 7 is an explanatory diagram illustrating frictional engagement between a ball frame and a rod in a performance comparison test.

FIG. 8 is a perspective view illustrating a modification of the sample 8 in the table shown in FIG. 6;

FIG. 9 is a diagram illustrating a voltage waveform applied to a piezoelectric element in a performance comparison test.

FIG. 10 is a schematic diagram showing a modified example of the SIDM driving device of the present invention.

FIG. 11 is a schematic diagram showing a modified example of the SIDM driving device of the present invention.

FIG. 12 is a schematic diagram showing a modified example of the SIDM driving device of the present invention.

FIG. 13 is a schematic diagram showing a modified example of the SIDM driving device of the present invention.

FIG. 14 is a schematic view showing a modified example of the SIDM driving device of the present invention.

[Description of Signs] 1 support base (weight member) 4 piezoelectric element 5 rod (vibration member) 10 moving body 20 support base (weight member) 21 concave portion 25 disk body 26 cylindrical body 28 notch 29 lead wire 30 balls Frame 31 Friction coupling body 32 Leaf spring 35 Support (weight member) 36 Fixing plate 37 Projection 40 Piezoelectric element 50 Support (weight member) 51 Fixing plate 52 Projection 53 Extension

Claims (4)

[Claims] An electromechanical transducer fixed at one end to a support base, a vibrating member fixed to the other end of the electromechanical transducer, and a moving body engaged with the vibrating member with a predetermined frictional force. And control means including a drive circuit for applying a drive voltage to the electromechanical transducer, and applying a drive voltage from the drive circuit to give vibrations having different speeds to the electromechanical transducer during reciprocation. A driving device for relatively moving the support and the moving body, wherein at least a part of the support extends beyond the one end of the electromechanical transducer toward the vibration member. apparatus. 2. The drive according to claim 1, wherein a concave portion including a peripheral wall and a bottom surface is formed in the support base, and the one end of the electromechanical transducer is fixed to the bottom surface of the concave portion. apparatus. 3. The drive device according to claim 2, wherein a part of the peripheral wall is cut off. 4. The electromechanical transducer according to claim 1, wherein the electromechanical transducer is a tubular body, and a protruding portion provided on a part of the support stand extends inside the tubular body. The driving device as described.