Driving element and driving device

Abstract

A driving element (1) comprises: a base part (13); a movable part (30) located spaced apart from the base part (13) in a direction parallel to a rotary shaft (R0); a first connecting part (14) and a second connecting part (15) connecting the base part (13) and the movable part (30); a pair of first arm parts (11a), (11b) extending in a first direction parallel to the rotary shaft (R0), sandwiching the rotary shaft (R0) therebetween; a pair of second arm parts (12a), (12b) extending in a second direction which is opposite to the first direction, sandwiching the rotary shaft (R0) therebetween; joining parts (16a), (16b) joining the pair of first arm parts (11a), (11b) and the pair of second arm parts (12a), (12b) to the first connecting part (14) and the second connecting part (15); and piezoelectric drivers (17a), (17b), (27a), (27b) disposed on the pair of first arm parts (11a), (11b) and / or the pair of second arm parts (12a), (12b).

Description

[Technical field]

[0001] The present invention relates to a drive element that rotates a movable part using a piezoelectric driver and a drive device equipped with the drive element, and is suitable for use, for example, in scanning light using a reflective surface arranged on the movable part. [Background technology]

[0002] In recent years, a driving element that rotates a movable part using MEMS (Micro Electro Mechanical System) technology has been developed. In this type of driving element, a reflective surface is arranged on the movable part, so that light incident on the reflective surface can be scanned at a predetermined deflection angle. This type of driving element is mounted on an image projection device such as a head-up display or a head-mounted display. In addition, this type of driving element can also be used in a laser radar that detects an object using laser light.

[0003] For example, the following Patent Document 1 describes a driving element that rotates a movable part using a so-called tuning fork vibrator. Here, a piezoelectric driver is disposed on each of a pair of arms extending along a rotation axis. AC voltages with a phase difference of 180° (opposite phases) are applied to these piezoelectric drivers, causing the pair of arms to expand and contract in opposite directions. This causes the movable part to rotate about the rotation axis, and in conjunction with this, the reflecting surface disposed on the movable part rotates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 087919 Summary of the Invention [Problem to be solved by the invention]

[0005] In the driving element having the above configuration, it is preferable that the deflection angle of the movable part per unit voltage is larger. Furthermore, in this configuration, when the driving element is driven, the stress caused by the bending of the arm part may damage the piezoelectric driving body. This problem becomes more pronounced when the pair of arms are bent more greatly to increase the deflection angle.

[0006] In view of such problems, the present invention aims to provide a drive element and a drive device that can further increase the swing angle of the movable part and suppress damage to the piezoelectric drive body due to stress generated during driving. [Means for solving the problem]

[0007] The driving element according to the first aspect of the present invention includes a base, a movable part spaced apart from the base in a direction parallel to a rotation axis, a connection part connecting the base and the movable part, and a connecting part arranged between the base and the movable part ... And from the base side to the movable part side A pair of first arm portions extending in a first direction sandwich the rotation shaft, from the ends of the pair of first arms on the base side a pair of second arm portions each extending in a second direction opposite to the first direction; At a connection point between the pair of first arm portions and the pair of second arm portions The actuator includes a connecting portion that connects the pair of first arm portions and the pair of second arm portions to the connection portion, and a piezoelectric driver arranged on at least one of the pair of first arm portions and the pair of second arm portions.

[0008] According to the driving element of this aspect, by providing a pair of second arms, it is possible to suppress the torsion and stress generated in the first arm and the second arm when the piezoelectric driver is driven, and further to increase the deflection angle of the movable part when the piezoelectric driver is driven. Therefore, it is possible to suppress damage to the piezoelectric driver due to the stress generated during driving while increasing the deflection angle of the movable part.

[0009] A driving element according to a second aspect of the present invention includes a base, a movable part spaced apart from the base in a direction parallel to a rotation axis, a connection part connecting the base and the movable part, and a connecting part that is disposed between the rotation axis and a connecting part that is parallel to the rotation axis. And from the base side to the movable part side A pair of arms extending in a first direction sandwich the rotation shaft, From the ends of the pair of arms on the base side In a second direction opposite to the first direction each A pair of extending balance adjustment parts; At the connection points of the pair of arm portions and the pair of balance adjustment portions The actuator includes a coupling portion that couples the pair of arm portions and the pair of balance adjustment portions to the connection portion, and a piezoelectric driver disposed on at least one of the pair of arm portions and the pair of balance adjustment portions.

[0010] The driving element according to this aspect can achieve the same effects as the first aspect.

[0011] A drive device according to a third aspect of the present invention comprises the drive element according to the second aspect, and a drive circuit that supplies a drive voltage to the piezoelectric drive body.

[0012] Driving according to this embodiment Device According to this, the same effects as those of the first aspect can be achieved.

[0013] In the above embodiment, "extending in a first direction" broadly includes a state in which the extension direction of the first arm portion includes a component in the first direction, such as a state in which the first arm portion is parallel to the first direction, a state in which the first arm portion is tilted at a predetermined angle from the first direction, etc. Similarly, "extending in a second direction" broadly includes a state in which the extension direction of the second arm portion includes a component in the second direction, such as a state in which the second arm portion is parallel to the second direction, and a state in which the second arm portion is tilted at a predetermined angle from the second direction. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to provide a drive element and a drive device that can increase the deflection angle of the movable part and prevent damage to the piezoelectric drive body due to stress generated during driving.

[0015] The effects and significance of the present invention will become clearer from the following description of the embodiment. However, the embodiment described below is merely an example of how the present invention can be put into practice, and the present invention is not limited to the embodiment described below. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing the configuration of a driving element according to an embodiment. [Diagram 2] FIG. 2 is a plan view showing the configuration of a driving element according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing a waveform of a driving voltage applied to a piezoelectric driving body according to an embodiment. [Figure 4] 4(a) and (b) are diagrams showing the driving state of a movable part when a driving signal is supplied to a piezoelectric driver according to an embodiment. [Diagram 5] FIG. 5 is a diagram showing dimensions of each part used in a simulation of stress occurring during driving according to the embodiment. [Figure 6] Fig. 6(a) is a diagram showing a simulation result of stress distribution according to an embodiment, and Fig. 6(b) is a diagram showing a simulation result of stress distribution according to a comparative example. [Figure 7] Fig. 7(a) is a diagram showing a method for setting conditions for verification 2 according to the embodiment, and Fig. 7(b) is a graph showing verification results of the shake angle characteristics in verification 2 according to the embodiment. [Figure 8] 8(a) and (b) are plan views showing other arrangement methods of the piezoelectric driving body according to the first modified example. [Figure 9] 9(a) to 9(c) are plan views showing the configuration of a drive element according to Modification Example 2 when only a first drive unit is arranged. [Figure 10] 10(a) and 10(b) are plan views showing the configuration of a driving element according to another modified example. [Figure 11] FIG. 11 is a diagram showing the configuration of a driving device including the driving element of FIG. 10(b).

[0017] However, the drawings are for illustrative purposes only and are not intended to limit the scope of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with mutually orthogonal X, Y, and Z axes. The Y-axis direction is parallel to the rotation axis of the drive element, and the Z-axis direction is perpendicular to the reflecting surface disposed on the movable part.

[0019] FIG. 1 is a perspective view showing the configuration of the driving element 1, and FIG. 2 is a plan view showing the configuration of the driving element 1. For convenience, in FIG. 1, parts 13 and 23 of the base (hereinafter, referred to as “base 13”) are shown. 、23 " is illustrated.

[0020] As shown in FIG. 1 and FIG. 2, the driving element 1 includes a first driving unit 10, a second driving unit 20, a movable part 30, and a reflecting surface 40. The first driving unit 10 and the second driving unit 20 rotate the movable part 30 about a rotation axis R0 by a driving signal supplied from a driving circuit (not shown). The reflecting surface 40 is disposed on the upper surface of the movable part 30, and reflects incident light in a direction according to the swing angle of the movable part 30. As a result, the light (e.g., laser light) incident on the reflecting surface 40 is scanned as the movable part 30 rotates. Here, the movable part 30 and the reflecting surface 40 may be formed of the same material.

[0021] The first drive unit 10 includes a pair of first arm portions 11a and 11b, a pair of second arm portions 12a and 12b, a base portion 13, a first connection portion 14, a second connection portion 15, coupling portions 16a and 16b, and piezoelectric actuators 17a and 17b. In a plan view, the first drive unit 10 has a shape symmetrical with respect to the X-axis direction. The piezoelectric actuator 17a extends along the upper surfaces of the first arm portion 11a, the second arm portion 12a, and the coupling portion 16a. The piezoelectric actuator 17b extends along the upper surfaces of the first arm portion 11b, the second arm portion 12b, and the coupling portion 16b.

[0022] The thickness of each part of the first drive unit 10, excluding the piezoelectric drivers 17a and 17b, is constant. However, the thickness of each part does not necessarily have to be constant, and for example, the thickness of the base 13 may be greater than the thickness of the other parts. Each part of the first drive unit 10, excluding the piezoelectric drivers 17a and 17b, is integrally formed, for example, from silicon or the like. However, the material constituting each part is not limited to silicon, and may be other materials. The material constituting each part is preferably a material with high mechanical strength and Young's modulus, such as metal, crystal, glass, or resin. In addition to silicon, titanium, stainless steel, Elinvar, brass alloy, etc. can be used as such a material.

[0023] The pair of first arm portions 11a, 11b are disposed symmetrically with respect to the rotation axis R0 and extend in a first direction (negative Y-axis direction) parallel to the rotation axis R0. The first arm portions 11a, 11b have the same length and cross-sectional area. The first arm portions 11a, 11b have the same width and thickness over their entire length. The cross-sectional shape of the first arm portions 11a, 11b when cut along a plane parallel to the XZ plane is rectangular. The first arm portions 11a, 11b are spaced apart from the rotation axis R0 by the same distance in opposite directions.

[0024] The pair of second arm portions 12a, 12b are disposed symmetrically with respect to the rotation axis R0 and extend in a second direction (positive direction of the Y axis) opposite to the first direction (negative direction of the Y axis). The length and cross-sectional area of ​​the second arm portions 12a, 12b are the same. The width and thickness of the second arm portions 12a, 12b are uniform over their entire length. The cross-sectional shape of the second arm portions 12a, 12b when cut along a plane parallel to the XZ plane is rectangular. The second arm portions 12a, 12b are spaced apart from each other in opposite directions by the same distance from the rotation axis R0.

[0025] The first arm portion 11a and the second arm portion 12a on the positive side of the X-axis are aligned in the same straight line. above The first arm portion 11b and the second arm portion 12b on the negative side of the X-axis are aligned in the same straight line. aboveand have the same cross-sectional shape and cross-sectional area. As described later, the length of second arm portions 12a, 12b is adjusted to a length that can reduce stress and twisting generated in first arm portions 11a, 11b when movable portion 30 is driven and can further increase the swing angle of movable portion 30.

[0026] The base 13 is for connecting the first drive unit 10 to an external structural member. That is, the first drive unit 10 is supported by an external structural member via the base 13. The base 13 and the movable part 30 are aligned linearly in the Y-axis direction at a predetermined distance. The base 13 and the movable part 30 are connected to each other by a first connection part 14 and a second connection part 15.

[0027] The second connection part 15 extends parallel to the Y-axis direction along the rotation axis R0. The cross-sectional shape of the second connection part 15 when cut on a plane parallel to the XZ plane is rectangular. The first connection part 14 extends in the Y-axis negative direction from the end part on the Y-axis negative side of the second connection part 15. The end part on the Y-axis negative side of the first connection part 14 is connected to a side surface of the movable part 30. The cross-sectional shape of the first connection part 14 when cut on a plane parallel to the XZ plane is rectangular. The width of the first connection part 14 in the X-axis direction is several steps smaller than the width of the second connection part 15 in the X-axis direction. The first connection part 14 has a plate-like shape that is long in the Y-axis direction.

[0028] The second connection portion 15 does not necessarily extend linearly along the rotation axis R0, and may, for example, extend in the Y-axis direction while meandering in the X-axis direction. Similarly, the first connection portion 14 does not necessarily extend linearly along the rotation axis R0, and may, for example, extend in the Y-axis direction while meandering in the X-axis direction.

[0029] The piezoelectric drivers 17a and 17b have a layered structure in which electrodes are arranged above and below a piezoelectric body of a predetermined thickness. The piezoelectric body is made of a piezoelectric material with a high piezoelectric constant, such as lead zirconate titanate (PZT). The electrodes are made of a material with low electrical resistance and high heat resistance, such as platinum (Pt). The piezoelectric drivers 17a and 17b are arranged on the upper surfaces of the first arm portions 11a and 11b, the second arm portions 12a and 12b, and the connecting portions 16a and 16b by forming a layered structure including the piezoelectric body and the upper and lower electrodes on the upper surfaces of these portions by a sputtering method or the like.

[0030] The second drive unit 20 includes a pair of first arm portions 21a, 21b, a pair of second arm portions 22a, 22b, a base portion 23, a first connection portion 24, a second connection portion 25, coupling portions 26a, 26b, and piezoelectric actuators 27a, 27b. In a plan view, the second drive unit 20 has a shape symmetrical with respect to the X-axis direction. The piezoelectric actuator 27a extends along the upper surfaces of the first arm portion 21a, the second arm portion 22a, and the coupling portion 26a. The piezoelectric actuator 27b extends along the upper surfaces of the first arm portion 21b, the second arm portion 22b, and the coupling portion 26b.

[0031] The configuration of each part of the second drive unit 20 is similar to the configuration of the corresponding part of the first drive unit 10. The second drive unit 20 is disposed in the opposite direction to the first drive unit 10 so that the first connection part 24 extends from the second connection part 25 in the positive direction of the Y axis. The first connection part 24 extends along the rotation axis R0. In other words, the first connection parts 14, 24 are aligned on the same straight line. The end of the first connection part 24 on the positive side of the Y axis is connected to the side of the movable part 30.

[0032] The movable part 30 has a circular shape in a plan view. Side positions of the movable part 30 that are symmetrical with respect to the central axis of the movable part 30 are connected to the first connection part 14 of the first drive unit 10 and the first connection part 24 of the second drive unit 20, respectively. The thickness of the movable part 30 is the same as that of the first connection parts 14, 24. However, the thickness of the movable part 30 does not necessarily have to be the same as that of the first connection parts 14, 24, and for example, the thickness of the movable part 30 may be greater than that of the first connection parts 14, 24. The movable part 30 is integrally formed with the first connection parts 14, 24.

[0033] The reflecting surface 40 is formed by forming a reflecting film made of a material with high reflectivity on the upper surface of the movable part 30. The material constituting the reflecting film may be selected from, for example, metals such as gold, silver, copper, and aluminum, metal compounds, silicon dioxide, titanium dioxide, and the like. The reflecting film may be a dielectric multilayer film. Alternatively, the reflecting surface 40 may be formed by polishing the upper surface of the movable part 30. The reflecting surface 40 does not necessarily have to be a flat surface, and may be a concave or convex curved surface.

[0034] In a plan view, the driving element 1 is symmetrical in the X-axis direction and in the Y-axis direction. Each part of the driving element 1 except for the piezoelectric drivers 17a, 17b, 27a, and 27b and the reflecting surface 40 is formed, for example, by cutting a silicon substrate of a predetermined thickness into the shape shown in FIG. 2 by etching. The piezoelectric drivers 17a, 17b, 27a, and 27b and the reflecting surface 40 are formed in the corresponding regions by a film forming technique such as sputtering. In this way, the driving element 1 shown in FIGS. 1 and 2 is formed.

[0035] FIG. 3 is a diagram showing waveforms of the driving voltages applied to the piezoelectric drivers 17a, 17b, 27a, and 27b.

[0036] The drive signals S1 and S2 are AC signals with a predetermined frequency that oscillate in the range of +Va and -Va. The periods T of the drive signals S1 and S2 are the same. The drive signals S1 and S2 are out of phase with each other by T / 2. That is, the drive signals S1 and S2 are AC voltages with opposite phases.

[0037] 1 and 2, a drive signal S1 is supplied to the piezoelectric actuators 17a and 27a on the positive side of the X-axis, and a drive signal S2 is supplied to the piezoelectric actuators 17b and 27b on the negative side of the X-axis, causing the movable part 30 and the reflecting surface 40 to rotate around the rotation axis R0 at a predetermined deflection angle.

[0038] 4(a) and (b) are diagrams showing the driving states of the movable portion 30 when the driving signals S1 and S2 shown in FIG. 3 are supplied to the corresponding piezoelectric drivers, respectively.

[0039] When the drive signals S1 and S2 shown in FIG. 3 are supplied to the corresponding piezoelectric actuators, the first arm portions 11a and 21a and the second arm portions 12a and 22a on the X-axis positive side and the first arm portions 11b and 21b and the second arm portions 12b and 22b on the X-axis negative side repeatedly deform in opposite directions in the Z-axis direction. As a result, the connecting portions 16a and 26a on the X-axis positive side and the connecting portions 16b and 26b on the X-axis negative side vibrate in opposite phases, generating torque in the same rotation direction around the rotation axis R0. This torque is transmitted to the first connecting portions 14 and 24, causing the movable portion 30 to vibrate around the rotation axis R0. In this way, the reflecting surface 40 rotates at a predetermined swing angle.

[0040] 4(a), the first arm portions 11a, 21a and the second arm portions 12a, 22a on the positive side of the X-axis are deformed upward, and the first arm portions 11b, 21b and the second arm portions 12b, 22b on the negative side of the X-axis are deformed downward. As a result, a torque Ta is generated around the rotation axis R0, and the movable portion 30 rotates clockwise when viewed in the negative direction of the Y-axis.

[0041] 4(b), the first arm portions 11a, 21a and the second arm portions 12a, 22a on the positive side of the X-axis are deformed downward, and the first arm portions 11b, 21b and the second arm portions 12b, 22b on the negative side of the X-axis are deformed upward. As a result, a torque Tb is generated around the rotation axis R0, and the movable portion 30 rotates counterclockwise when viewed in the negative direction of the Y-axis.

[0042] In this way, the driving element 1 resonates at a predetermined resonance frequency, and the movable part 30 repeatedly rotates in the clockwise and counterclockwise directions at a predetermined deflection angle. Accordingly, the reflecting surface 40 arranged on the movable part 30 repeatedly rotates in the clockwise and counterclockwise directions at a predetermined deflection angle. As a result, the light (laser light, etc.) incident on the reflecting surface 40 is scanned at a predetermined deflection angle.

[0043] In addition, Figure 4 (a) and (b) shows a state in which the first driving unit 10, the second driving unit 20, and the movable part 30 are driven in opposite phases, but it is also possible to control the first driving unit 10, the second driving unit 20, and the movable part 30 to be driven in the same phase.

[0044] Incidentally, when the driving element 1 is used as an optical deflection element as described above, it is preferable that the deflection angle of the movable part 30 is as large as possible. This allows the light to scan a wider range. Furthermore, when the arm parts are deflected to vibrate the movable part 30 as described above, the piezoelectric actuators 17a, 17b, 27a, and 27b may be damaged by stress (torsion) generated in the first arm parts 11a, 11b, 21a, and 21b during driving. This problem becomes more prominent when the pair of first arm parts 11a, 11b, 21a, and 21b are deflected more greatly to increase the deflection angle.

[0045] In contrast, in this embodiment, in addition to the pair of first arm portions 11a, 11b, 21a, and 21b, a pair of second arm portions 12a, 12b, 22a, and 22b are provided. b The pair of second arm portions 12a, 12b, 22a, and 22 b Actions by To As a result, the above two problems are solved at the same time. That is, in this embodiment, the swing angle of the movable part 30 can be increased and the stress (twist) generated in the first arm parts 11a, 11b, 21a, 21b can be suppressed compared to the conventional configuration in which the pair of second arm parts 12a, 12b, 22a, 22b is not arranged. As a result, the swing angle of the movable part 30 can be further increased while suppressing damage to the piezoelectric drivers 17a, 17b, 27a, 27b due to the stress (twist).

[0046] <Verification 1> The inventors conducted simulations to verify the stresses generated in each part of the above-configured driving element 1 when it was driven. In addition, as a comparative example, they conducted simulations to verify the stresses generated in each part when it was driven for a configuration in which the second arm portions 12a, 12b, 22a, and 22b were omitted from the above-configuration.

[0047] FIG. 5 is a diagram showing the dimensions of each part used in the simulation.

[0048] As in the above configuration, the driving element 1 has a shape symmetrical in the Y-axis direction and in the X-axis direction in a plan view. In the verification, the thickness of the driving element 1 excluding the piezoelectric drivers 17a, 17b, 27a, and 27b and the reflecting surface 40 was set to a uniform thickness of 50 μm. Under the conditions of FIG. 5, the stress of each part was obtained by simulation when AC voltages of a predetermined frequency and a predetermined amplitude were applied in opposite phase to the piezoelectric drivers 17a and 27a and the piezoelectric drivers 17b and 27b.

[0049] FIG. 6(a) is a diagram showing the results of a stress distribution simulation according to the embodiment, and FIG. 6(b) is a diagram showing the results of a stress distribution simulation according to a comparative example.

[0050] The simulation results in Figures 6(a) and (b) are color images converted to grayscale. In the actual color images, dark blue is set as the color with the lowest stress, and red is set as the color with the highest stress. In Figures 6(a) and (b), the magnitude of stress is displayed in stages. B0 to B4 indicate the blue range, G indicates the green range, and Y indicates the yellow range. O1 and O2 indicate the orange range, and R indicates the red range. The order of stress is red (highest), orange, yellow, green, and blue (lowest). In the blue range, the order of stress is B4 (highest), B3, B2, B1, and B0 (lowest), and in the orange range, the order of stress is O2 (high) and O1 (low).

[0051] As shown in FIG. 6(b), in the comparative example, the stress is high at the bending portion from the first arm portions 11a and 11b to the connecting portions 16a and 16b. It is also found that the stress distribution is non-uniform at the bending portion, and strong twisting occurs at the bending portion. Furthermore, in the comparative example, the stress is high over almost the entire range of the connecting portions 16a and 16b. From these facts, it is estimated that in the comparative example, high stress and twisting act on the piezoelectric actuator, especially at the bending portion, and the piezoelectric actuator is likely to be damaged. It is also estimated that high stress and twisting act on the piezoelectric actuator at the connecting portions 16a and 16b, and the piezoelectric actuator is likely to be damaged.

[0052] In contrast, in the embodiment, as shown in FIG. 6(a), the stress in the bending portion from the first arm portion 11a, 11b and the second arm portion 12a, 12b to the connecting portion 16a, 16b is significantly small. In addition, it can be seen that the stress distribution in this bending portion is not uneven, and that there is almost no twisting in this bending portion. Furthermore, in the embodiment, the stress is low in almost the entire range of the connecting portion 16a, 16b. From these facts, in the embodiment, it is presumed that the piezoelectric driver does not break in the bending portion, and that the connecting portion 16a, 16b is also unlikely to break. This is presumed to be because, by providing the second arm portion 12a, 12b, the connecting portion 16a, 16b is driven without twisting when the drive unit is driven (so-called pure bending mode drive).

[0053] From the above verification, it was confirmed that in the configuration of the embodiment, by disposing the pair of second arm parts 12a, 12b, the stress generated in each part during driving can be significantly suppressed. In addition, it was confirmed that by setting the length of the second arm parts 12a, 12b to an appropriate value (here, 2000 μm) under the dimensional conditions shown in FIG. 5, it was possible to prevent the occurrence of twisting at the bent part. As a result, it was confirmed that in the configuration of the embodiment, damage to the piezoelectric driver due to stress and twisting during driving can be prevented.

[0054] In order to prevent stress caused by twisting from concentrating on and occurring at the connection parts (the bent parts) between the first arm parts 11a, 11b and the second arm parts 12a, 12b and the connecting parts 16a, 16b and at the connecting parts 16a, 16b during driving, it is necessary to make the torques in the opposite directions (torques parallel to the YZ plane) of the first arm parts 11a, 11b and the second arm parts 12a, 12b generated around these connection parts be in a balanced state with each other. To In addition, by adjusting the two torques in this way, the connection portion moves substantially up and down when driven, so that the movable portion 30 and reflective surface 40 can be rotated at a large swing angle.

[0055] <Verification 2> Next, the inventors conducted an experiment to verify the swing angle characteristics of the movable part 30 when the length L2 of the second arm parts 12a, 12b, 22a, and 22b shown in Fig. 7(a) was changed. In the verification, the dimensions other than the length L2 were set in the same manner as in Fig. 5. In addition, the swing angle characteristics were also verified experimentally for a comparative example similar to the above verification 1.

[0056] FIG. 7B is a graph showing the verification results of the deflection angle characteristics.

[0057] Here, the length L2 of the second arm portions 12a, 12b, 22a, and 22b is set to four types: 1900 μm, 2000 μm, 2100 μm, and 2200 μm. The dashed lines in Fig. 7(b) show the verification results of the swing angle according to the comparative example. The vertical axis of Fig. 7(b) is the swing angle per unit voltage, which is normalized by the swing angle of the comparative example.

[0058] As shown in Fig. 7(b), by setting the length L2 of the second arm portions 12a, 12b, 22a, and 22b to 1900 to 2100 µm, the deflection angle characteristics are improved compared to the comparative example. In particular, when the length L2 of the second arm portions 12a, 12b, 22a, and 22b was set to 2000 µm, a significantly higher deflection angle characteristic of about 1.13 times was obtained compared to the comparative example.

[0059] From the above verification, it was confirmed that in the configuration of the embodiment, by arranging the second arm parts 12a, 12b, 22a, and 22b and optimizing their lengths, it is possible to significantly improve the swing angle characteristics of the movable part 30. Therefore, in the configuration of the embodiment, by arranging the reflecting surface 40 on the movable part 30, it is possible to significantly expand the scanning range of light.

[0060] 7(b), it can be inferred that the length L2 of the second arm portions 12a, 12b, 22a, and 22b that can improve the swing angle characteristics compared to the comparative example is limited to a certain range. Therefore, it can be said that the length L2 of the second arm portions 12a, 12b, 22a, and 22b needs to be set at least within this range.

[0061] <Effects of the embodiment> According to this embodiment, the following effects can be achieved.

[0062] As shown in the above verifications 1 and 2, by providing a pair of second arm portions 12a, 12b, 22a, 22b, it is possible to suppress the twist and stress generated in the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b when the piezoelectric actuators 17a, 17b, 27a, 27b are driven, and further, it is possible to increase the swing angle of the movable portion 30 when the piezoelectric actuators 17a, 17b, 27a, 27b are driven. Therefore, it is possible to suppress the occurrence of damage to the piezoelectric actuators 17a, 17b, 27a, 27b due to the stress generated during driving, while increasing the swing angle of the movable portion 30.

[0063] 1, the piezoelectric actuators 17a, 17b, 27a, and 27b are disposed on both the pair of first arm portions 11a, 11b, 21a, and 21b and the pair of second arm portions 12a, 12b, 22a, and 22b. This makes it possible to generate a larger torque, and to more effectively increase the swing angle of the movable portion 30.

[0064] 1, the piezoelectric actuators 17a, 17b, 27a, and 27b are also disposed on the connecting portions 16a, 16b, 26a, and 26b, so that a larger torque can be generated and the swing angle of the movable portion 30 can be expanded more effectively.

[0065] As shown in the above verification 1, it is preferable that the lengths of the second arm portions 12a, 12b, 22a, and 22b are set so that twisting does not substantially occur in the first arm portions 11a, 11b, 21a, and 21b. This makes it possible to more reliably prevent the piezoelectric actuators 17a, 17b, 27a, and 27b from being damaged by stress generated during driving.

[0066] As shown in the above verification 2, the lengths of the second arm portions 12a, 12b, 22a, and 22b are preferably set so that the swing angle of the movable portion 30 is maximized when the movable portion 30 is vibrated around the rotation axis R0 at the target frequency. This allows the movable portion 30 to vibrate at a larger swing angle, and the driving element 1 to operate most efficiently.

[0067] 1, two drive units, a first drive unit 10 and a second drive unit 20, are arranged facing in opposite directions with a movable part 30 in between, and the first connection parts 14, 24 of each drive unit are connected to the movable part 30. In this way, by supporting and driving the movable part 30 with each drive unit, the movable part 30 can be driven stably with a larger torque.

[0068] 1, a reflecting surface 40 is disposed on the movable part 30. This allows light (e.g., laser light) incident on the reflecting surface 40 to be scanned at a larger deflection angle, thereby widening the scanning range of the light.

[0069] As shown in FIG. 4The width of the second connection parts 15, 25 is set to be larger than that of the first connection parts 14, 25. By designing the torsional rigidity of the second connection parts 15, 25 to be higher than that of the first connection parts 14, 25 in this way, leakage vibrations of the first drive unit 10 and the second drive unit 20 are less likely to be transmitted to the base parts 13, 23, and as a result, the Q value can be increased.

[0070] <Change Example 1> In the above embodiment, piezoelectric drivers 17a, 17b, 27a, 27b are arranged on first arm portions 11a, 11b, 21a, 21b, second arm portions 12a, 12b, 22a, 22b and connecting portions 16a, 16b, 26a, 26b, but the method of arranging piezoelectric drivers 17a, 17b, 27a, 27b is not limited to this.

[0071] 8(a) and (b) are plan views showing other arrangement methods of the piezoelectric drivers 17a, 17b, 27a, and 27b.

[0072] In the arrangement methods of Figures 8(a) and (b), the piezoelectric actuators 17a, 17b, 27a, and 27b are not arranged on the second arm portions 12a, 12b, 22a, and 22b. In Figure 8(a), the piezoelectric actuators 17a, 17b, 27a, and 27b are arranged on the first arm portions 11a, 11b, 21a, and 21b and the connecting portions 16a, 16b, 26a, and 26b, and in Figure 8(b), the piezoelectric actuators 17a, 17b, 27a, and 27b are arranged only on the first arm portions 11a, 11b, 21a, and 21b.

[0073] These arrangements also allow the second arm portions 12a, 12b, 22a, and 22b to function as balancers for the first arm portions 11a, 11b, 21a, and 21b. This prevents uneven and large stress from being generated in the portions that bend from the first arm portions 11a, 11b, 21a, and 21b and the second arm portions 12a, 12b, 22a, and 22b to the connecting portions 16a, 16b, 26a, and 26b during driving. This prevents the piezoelectric actuators 17a, 17b, 27a, and 27b from being damaged by stress and twisting that occurs during driving.

[0074] 8(a) and (b), when the first arm portions 11a, 11b, 21a, and 21b are driven by the piezoelectric actuators 17a, 17b, 27a, and 27b, the second arm portions 12a, 12b, 22a, and 22b are deflected in the vertical direction by the reaction. As a result, torques are generated not only by the first arm portions 11a, 11b, 21a, and 21b but also by the second arm portions 12a, 12b, 22a, and 22b, and these torques cause the movable portion 30 to rotate more. Therefore, in the configurations of FIGS. 8(a) and (b), the swing angle of the movable portion 30 can be increased compared to the comparative example.

[0075] The inventors set the dimensions of each part of the driving element 1 to the dimensions shown in FIG. 5, and then arranged the piezoelectric drivers 17a, 17b, 27a, and 27b as shown in FIG. 8(a), and experimentally verified the deflection angle characteristics of the movable part 30. In this verification, the lengths of the second arm parts 12a, 12b, 22a, and 22b were set to 2000 μm. As a result of the verification, a deflection angle of the movable part 30 was obtained that was about 1.07 times that of the comparative example. Although this deflection angle was about 5% lower than the deflection angle of the configuration of the embodiment in the above verification 2 (1.12 times that of the comparative example), it was significantly higher than the deflection angle related to the comparative example.

[0076] From the results of this verification, it was confirmed that even when the piezoelectric drivers 17a, 17b, 27a, and 27b are arranged as shown in Figures 8(a) and (b) above, the swing angle of the movable part 30 can be significantly increased by the action of the second arm parts 12a, 12b, 22a, and 22b.

[0077] 8(a) and (b), it is preferable to optimize the lengths of the second arm parts 12a, 12b, 22a, and 22b, as in the above embodiment. That is, it is preferable to optimize the lengths of the second arm parts 12a, 12b, 22a, and 22b so that the piezoelectric actuators 17a, 17b, 27a, and 27b are not damaged by stress and twisting that occur during driving, and the swing angle of the movable part 30 at the target frequency is maximized. This makes it possible to significantly expand the scanning range of light (for example, laser light) when the reflecting surface 40 is disposed on the movable part 30.

[0078] In addition, in the configuration examples of Figures 8(a) and (b) above, the areas of the piezoelectric drivers 17a, 17b, 27a, and 27b are smaller than in the configuration example of Figure 1, which has the advantage of reducing power consumption during driving.

[0079] <Change Example 2> In the above embodiment and modified example 1, the first drive unit 10 and the second drive unit 20 are arranged in the drive element 1, but only one of the first drive unit 10 and the second drive unit 20 may be arranged in the drive element 1.

[0080] 9(a) to 9(c) are plan views showing the configuration of the drive element 1 when only the first drive unit 10 is arranged.

[0081] 9(a) to 9(c) are similar to the configurations of the respective parts of the first drive unit 10 in the above embodiment. The movable part 30 is connected to the first connection part 14 only at the end on the Y-axis positive side.

[0082] In this case, similarly to the above embodiment and modified example 1, the piezoelectric actuators 17a and 17b are connected to the first arm portions 11a and 11b as shown in FIG. 1b 9B, the first arm portions 11a and 11b may be disposed on the second arm portions 12a and 12b and the connecting portions 16a and 16b. 1b Piezoelectric actuators 17a and 17b may be disposed on the connecting portions 16a and 16b, and as shown in FIG. 9(c), the first arm portions 11a and 1 1b Piezoelectric actuators 17a and 17b may be disposed only on the first and second electrodes 17a and 17b.

[0083] With these configurations, as in the above embodiment and modified example 1, the first arm portions 11a and 11b are shorter than those in a configuration in which the second arm portions 12a and 12b are omitted. 1b Therefore, the first arm portion 11a, the first arm portion 11b, and the second arm portion 11c can be prevented from being twisted, and the swing angle of the movable portion 30 can be increased. 1bThis can prevent the piezoelectric drivers 17a and 17b from being damaged due to torsion and stress in the piezoelectric actuator 17a, 17b, and can improve the deflection angle characteristic of the movable portion 30.

[0084] Furthermore, the configurations of FIGS. 9(a), (b), and (c) make it possible to reduce the overall size of the driving element 1, which has the advantage that the driving element 1 can be made smaller and less expensive.

[0085] In these configurations, it is preferable to optimize the length of the second arm parts 12a and 12b, as in the above embodiment. That is, it is preferable to optimize the length of the second arm parts 12a and 12b so that the piezoelectric actuators 17a and 17b are not damaged by stress and twisting that occur during driving, and the deflection angle of the movable part 30 at the target frequency is maximized. This makes it possible to significantly expand the scanning range of light (for example, laser light) when the reflecting surface 40 is disposed on the movable part 30.

[0086] <Other changes> In the above embodiment and modified examples 1 and 2, the shape of the movable part 30 is circular, but the shape of the movable part 30 may be other shapes, such as a square. In the above embodiment and modified examples 1 and 2, the first connection parts 14, 24 extend linearly and are connected to the second connection parts 15, 25, but the ends of the first connection parts 14, 24 on the Y-axis positive side may be bifurcated and connected to the second connection parts 15, 25. In addition, the first connection parts 14, 24 do not have to be plate-shaped and may be, for example, rectangular rod-shaped.

[0087] Furthermore, in the above embodiment and modified examples 1 and 2, the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b are arranged in a straight line in the Y-axis direction, but the second arm portions 12a, 12b, 22a, 22b may be arranged in a position slightly offset in the X-axis direction from the first arm portions 11a, 11b, 21a, 21b.

[0088] In the above embodiment and modified examples 1 and 2, the first arm portions 11a, 11b, 21a, and 21b are parallel to the rotation axis R0, but the first arm portions 11a, 11b, 21a, and 21b may be inclined with respect to the rotation axis R0. For example, the first arm portions 11a, 11b, 21a, and 21b may be inclined in the X-axis direction with respect to the rotation axis R0 so that the distance between the first arm portions 11a and 11b increases as they approach the movable portion 30, and the distance between the first arm portions 21a and 21b increases. Similarly, the second arm portions 12a, 12b, 22a, and 22b may be inclined in at least one of the X-axis direction and the Y-axis direction with respect to the rotation axis R0. The extension direction of the first arm portion may include a component in a first direction parallel to the rotation axis R0, and the extension direction of the second arm portion may include a component in a second direction opposite to the first direction.

[0089] The shapes of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b are not limited to those shown in the above embodiment and modified examples 1 and 2. For example, the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b may be trapezoidal in plan view so that the widths of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b become narrower toward the front. In this shape, the swing angle of the movable portion 30 increases as the weight of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b is reduced, but on the other hand, the resonance frequency of the driving element 1 is slightly reduced.

[0090] Alternatively, the widths of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b may increase in a step-like manner, for example, the ends of the second arm portions 12a, 12b, 22a, 22b may increase in a rectangular shape as shown in Fig. 10(a). Also, the widths of the second arm portions 12a, 12b, 22a, 22b may be wider than the widths of the first arm portions 11a, 11b, 21a, 21b, and the thicknesses of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b may be different from each other.

[0091] The shapes of the first arm parts 11a, 11b, 21a, 21b and the second arm parts 12a, 12b, 22a, 22b may be set to a shape that allows the swing angle and resonance frequency of the movable part 30 to be adjusted to a predetermined value. As described above, the second arm parts 12a, 12b, 22a, 22b may act as a balance adjustment part that generates a torque centered on the connection parts between the first arm parts 11a, 11b, 21a, 21b and the second arm parts 12a, 12b, 22a, 22b and the coupling parts 16a, 16b when driven, and brings this torque and the torque generated by the first arm parts 11a, 11b, 21a, 21b closer to a balanced state. This makes it possible to suppress the twisting generated in the connection parts and the coupling parts 16a, 16b, as described above, and to adjust the movable part 30 and reflective surface The swing angle of 40 can be increased.

[0092] In addition, in the above embodiment and modified example 1, the driving element 1 has a symmetrical shape in the X-axis direction and the Y-axis direction in a plan view, but the driving element 1 may have a slightly asymmetrical shape in the X-axis direction or the Y-axis direction in a plan view. Similarly, the driving element 1 according to modified example 2 may have a slightly asymmetrical shape in the X-axis direction.

[0093] The arrangement of the piezoelectric drivers 17a, 17b, 27a, and 27b is not limited to the arrangement shown in the above embodiment and modified examples 1 and 2. For example, the piezoelectric drivers 17a, 17b, 27a, and 27b may be arranged to extend linearly from the first arm portions 11a, 11b, 21a, and 21b to the second arm portions 12a, 12b, 22a, and 22b without being arranged on the connecting portions 26a and 26b. The piezoelectric drivers 17a, 17b, 27a, and 27b may be arranged only on the second arm portions 12a, 12b, 22a, and 22b.

[0094] 10(b), piezoelectric drivers 17a, 17b, 18a, 18b, 27a, 27b, 28a, and 28b may be individually arranged on the first arm portions 11a, 11b, 21a, and 21b and the second arm portions 12a, 12b, 22a, and 22b (balance adjustment portion), respectively. In this case, the torque generated by the first arm portions 11a, 11b, 21a, and 21b and the torque generated by the second arm portions 12a, 12b, 22a, and 22b may be balanced by controlling the driving operation of each piezoelectric driver.

[0095] In this case, the driving device 100 is configured as shown in Fig. 11. The driving device 100 includes the driving element 1 shown in Fig. 10(b), a control circuit 101, and four driving circuits. 102~105 For the sake of convenience, in the configuration of the driving element 1, only the configuration of the piezoelectric drivers 17a, 17b, 18a, 18b, 27a, 27b, 28a, and 28b is shown in Fig. 11.

[0096] The control circuit 101 includes a microcomputer and controls the drive circuits 102 to 105 according to a program stored in advance. The drive circuit 102 supplies drive signals to the piezoelectric actuators 17a and 17b under the control of the control circuit 101, the drive circuit 103 supplies drive signals to the piezoelectric actuators 18a and 18b under the control of the control circuit 101, the drive circuit 104 supplies drive signals to the piezoelectric actuators 27a and 27b under the control of the control circuit 101, and the drive circuit 105 supplies drive signals to the piezoelectric actuators 28a and 28b under the control of the control circuit 101.

[0097] 4(a) and (b), the driving circuits 102 to 105 drive the piezoelectric actuators 17a, 17b, 18a, 18b, 27a, 27b, 28a, and 28b so that the first arm 11a, 21a and the second arm 12a, 22a on the positive side of the X-axis and the first arm 11b, 21b and the second arm 12b, 22b on the negative side of the X-axis are driven in the opposite directions. At this time, the driving circuits 102 to 105 further drive the piezoelectric actuators so that twisting is suppressed at the connection parts between the first arm 11a, 11b, 21a, 21b and the second arm 12a, 12b, 22a, 22b (balance adjustment parts) and the connection parts 16a, 16b, 26a, and 26b, thereby rotating the movable part about the rotation axis R0. 3 That is, the drive circuits 102 to 105 drive the piezoelectric actuators so that the torques in the opposite directions of the first arm portions 11a, 11b, 21a, 21b and the second arm portions 12a, 12b, 22a, 22b, centered on the connection portions, approach a state of equilibrium with each other. This makes it possible to suppress the twisting that occurs in the connection portions and the coupling portions 16a, 16b, as described above, and also to prevent the movable portion 30 and reflective surface The swing angle of 40 can be increased.

[0098] In this configuration, the two torques in opposite directions are brought closer to a balanced state by controlling the drive of each piezoelectric driver, so the length of the second arm portions 12a, 12b, 22a, 22b (balance adjustment portion) does not necessarily have to be set within the preferred range shown in FIG. 7(a).

[0099] In addition, when the driving device 100 includes the driving element 1 shown in the above embodiment and modified examples 1 and 2, the number of driving circuits 102 to 105 in FIG. 11 is changed according to the number of piezoelectric actuators arranged in these driving elements 1. For example, when the driving element 1 included in the driving device 100 has the configuration shown in FIG. 1, the driving circuits 103 and 105 are omitted from the configuration shown in FIG. 11. In this case as well, the driving circuits 102 and 104 drive the piezoelectric actuators 17a, 17b, 27a, and 27b so as to suppress twisting at the above-mentioned connection portions, thereby rotating the movable part about the rotation axis R0. 3 In this configuration, similarly to the above, the length of the second arm portions 12a, 12b, 22a, 22b (balance adjustment portion) does not necessarily have to be set within the preferred range shown in FIG.

[0100] Furthermore, the dimensions of each part of the driving element 1 are not limited to the dimensions shown in Fig. 5 and can be changed as appropriate. When the dimensions of each part are changed, the dimensions of the second arm parts 12a, 12b, 22a, and 22b are accordingly optimized. transformation That should be done.

[0101] Furthermore, when the driving element 1 is used as an element other than an optical deflection element, the movable portion 30 does not need to have the reflecting surface 40 disposed thereon, and a member other than the reflecting surface 40 may be disposed thereon.

[0102] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims. [Explanation of symbols]

[0103] 1 Drive element 10 First drive unit 20 Second drive unit 30 Moving parts 40 reflective surface 11a, 11b, 21a, 21b First arm part 12a, 12b, 22a, 22b Second arm part 13, 23 base 14, 24 First connection part 15, 25 Second connection part 16a, 16b, 26a, 26b connection part 17a, 17b, 27a, 27b Piezoelectric actuator 100 Drive unit

Claims

1. A base and a movable portion spaced apart from the base portion in a direction parallel to the pivot axis; a connection portion that connects the base portion and the movable portion; a pair of first arm portions that sandwich the rotation shaft and extend in a first direction parallel to the rotation shaft and from the base portion side toward the movable portion side; a pair of second arm portions extending from ends of the pair of first arm portions on the base side in a second direction opposite to the first direction, the pair of second arm portions sandwiching the rotation shaft; a coupling portion that couples the pair of first arm portions and the pair of second arm portions to the connection portion at connection points between the pair of first arm portions and the pair of second arm portions; a piezoelectric driver disposed on at least one of the pair of first arm portions and the pair of second arm portions, A driving element characterized by:

2. 2. The driving element according to claim 1, The piezoelectric driver is disposed on both of the pair of first arm portions and the pair of second arm portions. A driving element characterized by:

3. 2. The driving element according to claim 1, the piezoelectric driver is disposed on the pair of first arm portions and is not disposed on the pair of second arm portions; A driving element characterized by:

4. 4. The driving element according to claim 1, The piezoelectric driver is further disposed in the connecting portion. A driving element characterized by:

5. 5. The driving element according to claim 1, The length of the second arm portion is set so that twisting does not substantially occur at least in the first arm portion. A driving element characterized by:

6. 6. The driving element according to claim 1, the length of the second arm portion is set so that a swing angle of the movable portion becomes maximum when the movable portion is vibrated around the rotation axis at a target frequency. A driving element characterized by:

7. 7. The driving element according to claim 1, two drive units each including the base portion, the connection portion, the pair of first arm portions, the pair of second arm portions, the coupling portion and the piezoelectric drive body are disposed in opposite directions with the movable portion interposed therebetween; The connection portion of each of the drive units is connected to the movable portion. A driving element characterized by:

8. 8. The driving element according to claim 1, A reflecting surface is disposed on the movable part. A driving element characterized by:

9. A base and a movable portion spaced apart from the base portion in a direction parallel to the pivot axis; a connection portion that connects the base portion and the movable portion; a pair of arms extending in a first direction parallel to the rotation shaft and from the base portion side toward the movable portion side, the pair of arms sandwiching the rotation shaft; a pair of balance adjustment parts extending from ends of the pair of arms on the base side in a second direction opposite to the first direction, with the rotation shaft between them; a connecting portion that connects the pair of arm portions and the pair of balance adjustment portions to the connecting portion at a connection portion between the pair of arm portions and the pair of balance adjustment portions; a piezoelectric driver disposed on at least one of the pair of arm portions and the pair of balance adjustment portions, A driving element characterized by:

10. 10. The driving element according to claim 9, two drive units each including the base portion, the connection portion, the pair of arm portions, the pair of balance adjustment portions, the coupling portion, and the piezoelectric driver are disposed opposite to each other with the movable portion therebetween; The connection portion of each of the drive units is connected to the movable portion. A driving element characterized by:

11. 11. The driving element according to claim 9, A reflecting surface is disposed on the movable part. A driving element characterized by:

12. A drive element according to any one of claims 9 to 11; A drive circuit that supplies a drive voltage to the piezoelectric drive body. A drive device characterized by:

13. 13. The drive device according to claim 12, the piezoelectric actuator is disposed on each of the pair of arm portions and the pair of balance adjustment portions, the drive circuit drives each of the piezoelectric drivers so as to suppress twisting at a connection portion between the arm portion and the connection portion and between the balance adjustment portion and the coupling portion, thereby rotating the movable portion about the rotation axis. A drive device characterized by:

Images