JP2021191209A - Displacement expansion mechanism and actuator - Google Patents

Abstract

To provide a displacement expansion mechanism and an actuator that can obtain desired output characteristics.SOLUTION: A displacement expansion mechanism includes an expansion element having capacitive properties, an output unit that is in contact with one end of the expansion element and displaces in a direction different from an expansion direction of the expansion element in response to expansion and contraction of the expansion element, a fixed unit that is in contact with the other end of the expansion element and is not displaced by the expansion and contraction of the expansion element, an external force application unit that applies an external force to the output unit so that the rate of change of a thrust force to an output displacement of the output unit is close to zero, and a restraining unit that restrains the external force application unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to a displacement expanding mechanism and an actuator.

A displacement expansion mechanism that expands and outputs a small displacement of a piezo element (piezoelectric element) is known.

Patent Document 1 describes an expansion / contraction element having a capacitive property, an output unit that comes into contact with one end of the expansion / contraction element and is displaced in a direction different from the expansion / contraction direction of the expansion / contraction element according to the expansion / contraction of the expansion / contraction element. A fixed portion that comes into contact with the other end of the telescopic element and is not displaced by the expansion and contraction of the telescopic element, and an external force applying portion that applies an external force to the output portion so that the rate of change of the thrust with respect to the output displacement of the output portion approaches zero. A displacement expansion mechanism comprising the above is disclosed.

Japanese Unexamined Patent Publication No. 2018-12773

By the way, in the displacement expanding mechanism proposed in Patent Document 1, the central portion of the nonlinear spring as the external force applying portion is also displaced with the displacement of the output portion. Further, as the displacement of the nonlinear spring increases, the nonlinear spring tends to spread in the long axis direction. Therefore, slippage may occur between both ends of the nonlinear spring and the fixed portion, and the desired spring characteristics may not be obtained.

Therefore, an object of the present invention is to provide a displacement expanding mechanism and an actuator that can obtain desired output characteristics.

The displacement expansion mechanism according to one aspect of the present invention is in contact with an elastic element having a capacitive property and one end of the elastic element, and is displaced in a direction different from the expansion / contraction direction of the elastic element according to the expansion / contraction of the elastic element. The output unit is in contact with the other end of the expansion / contraction element, and the fixed portion is not displaced by the expansion / contraction of the expansion / contraction element. It is provided with an external force applying portion for applying an external force and a restraining portion for fixing the external force applying portion to the fixing portion.

According to the present invention, it is possible to provide a displacement expanding mechanism and an actuator that can obtain desired output characteristics.

The figure explaining the schematic structure of the displacement expansion mechanism which concerns on this embodiment. The schematic diagram which shows the schematic structure of the rolling part of the displacement expansion mechanism. The graph which shows the _{displacement Y-thrust fy} characteristic in the displacement expansion mechanism which does not include a preload adjustment spring. Displacement of the preload adjusting spring (deflection amount) _{y p} - a graph showing a load _{f p} characteristics. Y ₌ a graph showing the displacement Y- load _{f POE} characteristics of the preload adjustment spring on the Y-axis to y p _{-y pO.} Graph showing the load f _p characteristics, - a displacement Y- thrust f _y properties without the preload adjusting spring in displacement magnifying mechanism, displacement y _p of the preload adjustment spring 15. Graph showing the displacement Y- thrust F _y characteristics of the displacement magnifying mechanism according to the present embodiment. Graph showing an example of a displacement Y- thrust F _y characteristics of the displacement magnifying mechanism according to the comparative example. A graph showing an example of other characteristics of a nonlinear spring. The figure which shows the displacement of the preload adjustment spring schematically. Graph showing a load f _p characteristics - displacement y _p of the preload adjusting spring in the case of pre-load adjustment spring has a displacement with sliding. The graph which shows _{the displacement y p} -load f _p characteristic of the preload adjustment spring provided with the spring restraint part. Sectional drawing of the displacement expansion mechanism including other spring preload adjustment mechanisms. The graph which shows _{the displacement y p} -load f _p characteristic of the preload adjustment spring explaining the effect of a shim. A graph showing the relationship between shim thickness and spring characteristics.

Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same components may be designated by the same reference numerals and duplicate explanations may be omitted.

The displacement expanding mechanism 10 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of a displacement expanding mechanism 10 according to the present embodiment. FIG. 1A is a perspective view of the displacement expanding mechanism 10 according to the present embodiment. FIG. 1B is a perspective view of the displacement expanding mechanism 10 according to the present embodiment in which one of the spring restraining portions 16 is removed and a part of the outer shell 14 is cut off. FIG. 1 (c) is a cross-sectional view of the displacement expanding mechanism 10 according to the present embodiment.

The displacement expansion mechanism 10 is a mechanism that expands the displacement of the telescopic element having a capacitive property by utilizing the buckling phenomenon. In the present embodiment, the telescopic element having a capacitive property is a piezo element, and is composed of, for example, laminated ceramics. However, the expansion / contraction element may be a magnetostrictive element, a hydraulic cylinder, a pneumatic cylinder, or the like.

The displacement expansion mechanism 10 includes a pair of piezo elements (expandable elements) 11, a pair of fixed portions (also referred to as “side blocks”) 12, an output portion (also referred to as “center block”) 13, and an outer shell (also referred to as “center block”) 13. It also has a "frame") 14, a preload adjusting spring (external force applying portion) 15, a spring restraining portion 16, a spring preload adjusting mechanism 17, and a piezo preload adjusting mechanism 18.

One end of each pair of piezo elements 11 is connected to the fixing portion 12 via a rolling joint, and the other end is connected to the output portion 13 via a rolling joint. Caps 111 and 112 are joined to both end faces in the longitudinal direction of the piezo element 11. In the present embodiment, the caps 111 and 112 exist as separate and independent members from the piezo element 11, but may be integrally formed with the piezo element 11. The rolling joint between the piezo element 11 and the fixed portion 12 is a rolling contact between the end curved surface (rolling surface) of the cap 111 joined to one end of the piezo element 11 and the end curved surface (rolling surface) of the fixed portion 12. It is composed of connections via line contact or point contact). Further, the rolling joint between the piezo element 11 and the output unit 13 is formed by the end curved surface (rolling surface) of the cap 112 joined to the other end of the piezo element 11 and the end curved surface (rolling surface) of the fixed portion 12. It is composed of connections via rolling contact (line contact or point contact).

In the example of the displacement expanding mechanism 10 shown in FIG. 1 (c), the rolling surface of the cap 111 has a cylindrical surface, and the rolling surface of the fixing portion 12 has an inclined surface. Further, the rolling surface of the cap 112 has a cylindrical surface, and the rolling surface of the output unit 13 has an inclined surface. That is, the operation of the rolling joint between the piezo element 11 and the fixing portion 12 is defined by the cylindrical surface and the inclined surface of the cap 111. Further, the operation of the rolling joint between the piezo element 11 and the output unit 13 is defined by the cylindrical surface and the inclined surface of the cap 112.

Each of the pair of piezo elements 11 expands in the longitudinal direction when a voltage is applied to cause a buckling phenomenon, and the output unit 13 is oriented in the direction perpendicular to the longitudinal direction (y-axis direction) with a displacement larger than the extension displacement. Displace to. That is, the expansion / contraction motion of the piezo element 11 is converted into a rotational motion by the rolling joint, and the expansion / contraction displacement is expanded. Then, a linear reciprocating operation in the output unit 13 is brought about. In this way, the displacement expanding mechanism 10 converts the outputs of the pair of piezo elements 11 and urges and displaces the output unit 13 in a predetermined output direction different from the expansion / contraction direction of the piezo elements 11. .. In the following, the displacement of the output unit 13 will be referred to as “enlarged displacement”.

The output unit 13 is a functional element that transmits the output of the displacement expansion mechanism 10 to the outside. In the present embodiment, the end portion on the −y side of the output unit 13 is connected to the preload adjusting spring 15, and the end portion on the + y side is connected to the output joint (not shown).

The outer shell 14 is a functional element that fixes the distance between the pair of fixing portions 12. In the present embodiment, the outer shell 14 is a member formed so as to surround a pair of piezo elements 11, a pair of fixing portions 12, and an output portion 13, and is a pair when a buckling phenomenon occurs in the displacement expanding mechanism 10. Prevents the distance between the fixing portions 12 of the above from increasing.

The preload adjusting spring (also referred to as “PCS (Preload Compensation Spring)”) 15 is an example of an urging means for urging the output unit 13 of the displacement expanding mechanism 10 with a certain characteristic. In the present embodiment, the preload adjusting spring 15 adjusts the expansion displacement-thrust characteristic, which is the relationship between the expansion displacement of the output unit 13 and the thrust caused by the expansion displacement. Specifically, the preload adjusting spring 15 has a central portion 151, both end portions 152, and a connection portion 153. The preload adjusting spring 15 is composed of a leaf spring whose central portion 151 is curved so as to bulge in the −y direction. The central portion 151 is connected to the output portion 13, and the both end portions 152 are connected to the outer shell 14. The preload adjusting spring 15 generates a force in the y-axis direction that offsets the thrust caused by the expanded displacement of the output unit 13. Hereinafter, the force generated by the preload adjusting spring 15 is referred to as an “offset force”. With this configuration, the preload adjusting spring 15 can determine the direction of the expansion and displacement of the output unit 13 and stabilize the behavior of the output unit 13.

In the example shown in FIG. 1, the preload adjusting spring 15 has a plurality of (four in FIG. 1) leaf springs. The central portion 151 of the preload adjusting spring 15 is provided with a through hole (not shown) through which the bolt 191 is inserted. The output unit 13 is provided with a screw hole (not shown) for screwing with the bolt 191. The bolt 191 is screwed into the screw hole of the output portion 13 through the central portion 151 of the preload adjusting spring 15. As a result, the central portion 151 and the output portion 13 are connected. Both ends 152 of the preload adjusting spring 15 are provided with through holes (not shown) through which bolts 194 are inserted. The blocks 192 and 193 are provided with through holes (not shown) through which the bolts 194 are inserted. The outer shell 14 is formed with a screw hole (not shown) for screwing with the bolt 194. The bolt 194 is inserted in the order of the block 192, both ends 152 of the preload adjusting spring 15, and the block 193, and is screwed into the screw hole of the outer shell 14. As a result, both end portions 152 and the outer shell 14 (fixing portion 12) are connected.

The spring restraining portion 16 is a mechanical element that restrains both end portions 152 of the preload adjusting spring 15 from expanding in the longitudinal direction (z-axis direction). In the example shown in FIG. 1, the spring restraint portion 16 is fastened to the outer shell 14 with bolts 195. The end faces of both end portions 152 are in contact with the spring restraint portion 16. This prevents the ends 152 from slipping on the outer shell 14.

The spring preload adjusting mechanism 17 is a mechanism for adjusting the offset force by the preload adjusting spring 15. In the example of FIG. 1 (c), the spring preload adjusting mechanism 17 may be composed of a shim (not shown) arranged between the central portion 151 and the output portion 13. Further, it may be composed of shims (not shown) arranged between both ends 152 and the block 193 and / or between the block 193 and the outer shell 14.

The piezo preload adjusting mechanism 18 is a mechanism for applying and adjusting preload to the four rolling joints in the displacement expanding mechanism 10. In the present embodiment, the piezo preload adjusting mechanism 18 for the piezo element 11 is composed of a shim arranged between the cap 112 and the piezo element 11. Although the piezo preload adjusting mechanism 18 has been described as being arranged at one end of the piezo element 11 (on the side of the fixed portion 12), it may be arranged on the other end of the piezo element 11 (on the side of the output portion 13). ..

The piezo preload adjusting mechanism 18 adjusts the distance between the leftmost contact point and the rightmost contact point so as to be shorter than the natural length. Therefore, the rolling surface of the rolling joint always makes rolling contact with a force (preload) equal to or higher than a predetermined value.

With the above configuration, the displacement expanding mechanism 10 has a characteristic that the displacement of the piezo element 11 can be expanded 100 times or more and the output energy can be transmitted by 70% or more. Further, since it has the characteristics that there is no energy loss due to the maintenance of static thrust and the expansion displacement is relatively large, the displacement expansion mechanism 10 can be applied to, for example, a brake actuator that requires a clamping operation.

<Expanded displacement Y-thrust _fy characteristics>
Next, in the displacement expansion mechanism 10, the expansion displacement Y-thrust _fy characteristic of the output unit 13 will be described with reference to FIGS. 2 to 8.

FIG. 2 is a schematic diagram showing a schematic configuration of a rolling portion of the displacement expansion mechanism 10. FIG. 2A shows the shape of the non-linear spring used as the preload adjusting spring 15. FIG. 2B shows the posture of the rolling portion to which the preload adjusting spring 15 shown in FIG. 2A is assembled at the reference position (Y = 0). FIG. 2C shows the posture at _{the maximum displacement position (Y = Y max} ) of the rolling portion to which the preload adjusting spring 15 shown in FIG. 2A is assembled.

In the displacement expanding mechanism 10 shown in FIG. 2, the rolling surface shapes of the fixing portion 12 and the output portion 13 can be made into a planar shape as shown in FIGS. 2 (b) and 2 (c). _{The plane has an inclination α 0} with respect to the output axis direction (y-axis) after the displacement is expanded. Further, in the design in which the caps 111 and 112 of the piezo element 11 are concentric circles, the angle of the line connecting the contacts of the rolling surface with respect to the z-axis is α ₀ . In the configurations shown in FIGS. 2 (b) and 2 (c). The displacement Y-thrust _fy characteristic is expressed by Eq. (1) in the range where sin α ₀ ≈ α ₀ and cos α _{0 ≈ 1 hold.} However, the equation (1) does not include the rigidity of the preload adjusting spring 15. Incidentally, k _S represents the overall mechanical rigidity of the displacement magnifying mechanism 10 in the direction of displacement of the piezoelectric element 11, k _PZT represents mechanical compression rigidity of the piezoelectric element 11, F _PL is a piezo preload by the piezoelectric preload adjusting mechanism 18 Represented by d is the piezoelectric strain constant, and _VPZT represents the voltage applied to the piezo element 11.

_{Further, the displacement Y-thrust fy characteristics when the voltage V PZT} is applied to the piezo element 11 (state in FIG. 2 (c)) and when no voltage is applied (state in FIG. 2 (b)) are expressed by the equations (state). It is shown in 2) and the formula (3).

From the equations (2) and (3), _{it can be seen that the force generated by applying a voltage f yON} − f _yOFF is expressed by the equation (4) and does not depend on y.

Next, the characteristics of the preload adjusting spring 15 will be described. FIG. 2A shows a schematic diagram of the preload adjusting spring 15. The preload adjusting spring 15 in FIG. 2A is a leaf spring, and as an example of the configuration, both end portions 152 are fixed to the fixing portion 12 of the displacement expanding mechanism 10, and the central portion 151 is the output portion 13 of the displacement expanding mechanism 10. It is fixed. Direction of displacement y _p of the preload adjustment spring 15 corresponds to the output direction Y of the output portion 13 of the displacement enlarging mechanism 10. Preload adjusting spring 15, as shown in FIG. 2 (a), the distance _{y d} is provided between the central portion 151 and both end portions 152 with respect to the Y direction. If y _d = y _d0 in the natural length state, the rigidity does not become a constant value when the central portion 151 of the preload adjusting spring 15 is displaced in the direction of _{y d} < _{yd 0} from the natural length state. shows a load _{f p} characteristics - y _p.

The shape of the preload adjusting spring 15 used as the preload adjusting spring 15 is, for example, a flat plate-shaped central portion 151 orthogonal to the Y direction and both sides of the central portion 151, and is offset _{by y d0 in the Y direction when the natural length is used.} A pair of flat plate-shaped both end portions 152 that are orthogonal to the Y direction as in the central portion 151, and a pair of both end portions 152 that are inclined with respect to the Y direction and are connected to each other. It takes a shape having a pair of connecting portions 153.

FIG. 3 is a graph showing the _{displacement Y-thrust fy} characteristics in the displacement expanding mechanism 10 not including the preload adjusting spring 15. The thick solid line in FIG. 3 is when the maximum voltage V _max is applied to the piezo element 11, the dotted line is when the voltage V _max / 2 is applied to the piezo element 11, and the thin solid line is when the applied voltage to the piezo element 11 is 0. , Each displacement Y-thrust _fy characteristic is shown. The displacement Y-thrust _fy characteristic when V _max / 2 is applied is expressed by the following equation (5) from the equation (1).

4, displacement (deflection amount) of the preload adjusting spring 15 _{y p} - is a graph showing a load _{f p} characteristics. From FIG. 4, the spring rigidity shows a positive value in the range of _{the displacement y p} = 0 to _{y pp} of the preload adjusting spring 15, but the spring rigidity tends to decrease as _{y p increases, and further.} In _{the range of y p} = y _{pp to y pe} , the spring rigidity shows a negative value. Here, the spring stiffness is meant the rate of change of load _{f p} with respect to the displacement _{y p} a _{(df p} / dy p).

In the present embodiment, as shown in FIGS. 3 (b) and 3 (c), the preload adjusting spring 15 having the characteristics of FIG. 4 is displaced in the Y direction between the central portion 151 and the output portion 13. The offset amount y _pO is taken and installed in the displacement expansion mechanism 10. _{In this case, the position of y pO} shown in FIG. 4 indicates the displacement amount of the preload adjusting spring 15 when the output displacement of the actuator is 0. At this time, the displacement range of the preload adjusting spring 15 with respect to the operating range of the actuator is y _p = y _{pO to y pe} . The offset amount y _pO can be appropriately adjusted by, for example, installing a spring preload adjusting mechanism 17 such as a spacer between the central portion 151 and the output portion 13.

Figure 5 _is a graph showing the displacement Y- load _{f POE} characteristics of the preload adjustment spring 15 on the Y-axis to _Y = y p _{-y pO.} That is, FIG. 5 shows the characteristics in a state where the preload adjusting spring 15 having the characteristics shown in FIG. 4 is attached to the output unit 13 _{with a predetermined offset amount y pO.} The characteristics of the preload adjusting spring 15 shown in FIG. 4 are that when the _{spring displacement increases from the displacement y pp at} which the spring load is maximum, the spring load tends to decrease substantially evenly as the displacement increases, and the behavior is close to linear. Will be. In the present embodiment, the offset amount y _pO is set _{to be larger than y pp} , and is adjusted so that the characteristics of the preload adjusting spring 15 can be linearly approximated in the operating range of the output unit 13.

In Figure 5, the linear linear approximation in Y = 0 to y _e is expressed by the following equation (6).

Further, the thrust _{F y} of the output portion 13 of the displacement magnifying mechanism 10, using the thrust _{f POE} by the rigidity of the thrust _{f y} and preload adjustment spring 15 that does not include the rigidity of the preload adjusting spring 15, the following equation (7) expressed.

Further, when the equations (1) and (6) are substituted into the equation (7) and the displacement Y is arranged, it is expressed by the equation (8).

Here, in order to serve the purpose of reducing the change in thrust F _y due to the displacement Y described above, it is required that the coefficient of the first term of equation (8) is close to zero, spring stiffness k _Oe below It is required to satisfy the equation (9) of.

Further, from the second term of the equation (8), the intermediate value of the thrust Fy with respect to the input voltage is determined. For example, in a configuration in which thrust Fy is desired to be obtained in both polarities with the same magnitude, the spring offset load f _pO is required to satisfy the following equation (10).

For formula (8), under the condition that the formula (9) and (10) holds, as a displacement Y- thrust _{F y} characteristics of the actuator including the preload adjusting spring 15, the following equation (11) is obtained.

That is, the thrust _{F y} regardless of the displacement Y, defined by the applied voltage _{V PZT.} Further, in the characteristic of the equation (11), when the applied voltage is V _max / 2, the thrust _Fy = 0, and the thrust in two directions of ± can be obtained.

In this embodiment, the characteristics of the preload adjusting spring 15 are designed so as to be close to the relationship of the equations (9) and (10). 6, a displacement Y- thrust _{f y} properties without the preload adjusting spring 15 in the displacement enlarging mechanism 10, the displacement _{y p} of the preload adjustment spring 15 - is a graph showing a load _{f p} characteristics, a. Figure 7 is a graph showing the displacement Y- thrust F _y characteristics of the displacement magnifying mechanism 10 according to this embodiment obtained by combining those properties. In FIG. 7, the thrust F _{y is expressed as the sum of the thrust f y} not including the spring characteristic and the spring load (thrust f _y + spring load [N]).

Figure 8 is a graph showing an example of a displacement Y- thrust F _y characteristics of the displacement magnifying mechanism according to the comparative example. As shown in FIG. 8, the displacement Y- thrust F _y characteristics of the displacement magnifying mechanism according to the comparative example, since the non-linear relationship variation of thrust is greater at a constant applied voltage, the output enable energy of the displacement magnifying mechanism, The effective range AA becomes much smaller.

In the characteristics shown in FIG. 7, the fluctuation of the thrust at a constant applied voltage is about 25N, which is smaller than the fluctuation of the conventional actuator shown in FIG. Thus, the displacement Y- thrust F _y characteristic relationship thrust force variation depends only on the voltage applied _{(F y = C · V:} C is a coefficient) are able to approach the. As a result, the displacement expansion mechanism 10 of the first embodiment can have a sufficiently large effective range AA with respect to the outputable energy, can effectively use the outputable energy as the effective range AA, and can increase the output. It becomes.

Further, shown in FIG. 7, the slope of the linear approximation curve of displacement Y- thrust _{F y} characteristic curve at a constant applied voltage is as small as 1.7~2.0N / mm, relationship thrust depends only on the voltage applied _{(F y} = C · V: C is a coefficient) It was confirmed that the characteristics close to were obtained. As a result, the ratio of the effective range AA to the theoretical output range of the actuator unit can be increased.

Thus, the displacement enlarging mechanism 10 of the first embodiment, as a non-linear spring to apply a preload adjusting spring 15, further, closer to the rate of change of the thrust F _y with respect to the output displacement Y of the output section 13 to 0, the output also functions as an external force applying portion applying an external force (spring load f _p) to the unit (13). The preload adjusting spring 15, the rate of change of the spring load f _p for deflection amount y _p of spring, it changes to the negative gradually reduced from a positive with the increase of the deflection amount y _p, a negative value of approximately constant It has a non-convergent characteristic (see FIG. 4) that converges.

Further, in the present embodiment, the contact portion with which the piezo element 11 contacts on the surface of the output unit 13 and the contact portion with which the piezo element 11 contacts on the surface of the fixed portion 12 have a planar shape, and the displacement expanding mechanism 10 has a planar shape. Of these, the displacement Y-thrust _fy characteristics excluding the preload adjusting spring 15 are monotonically decreasing linear characteristics as shown in FIG. Further, the preload adjusting spring 15 has a non-linear characteristic in the operating range of the output unit 13 in a region where the rate of change of the spring load with respect to the amount of deflection of the spring is a substantially constant negative value (y _{pO to y p} e in FIG. 4). The amount of deflection (that is, the amount of offset y _pO ) when the output unit 13 is in the initial position is adjusted so as to be within the range).

With these configurations, the slope of the displacement Y- thrust f _y characteristics except preload adjusting spring 15 of the displacement magnifying mechanism 10, the displacement of the preload adjustment spring 15 (deflection amount) y p _- directly opposite the inclination of the load f _p characteristics made for being canceled, as a result, displacement Y- thrust F _y characteristic of the whole of the displacement magnifying mechanism 10, for example, the characteristics shown in FIG. 7, the slope is close to zero, the thrust F fluctuation of _y output displacement Y It becomes less dependent on the fluctuation of. As a result, the effective range AA can be sufficiently large with respect to the outputable energy of the displacement expansion mechanism 10, the outputable energy can be effectively used as the effective range AA, and the output can be increased.

In the description of the above embodiment, a configuration is exemplified in which the rolling surface shapes of the fixed portion 12 and the output portion 13 of the rolling portions are planar shapes as shown in FIGS. 2 (b) and 2 (c). However, other shapes such as a non-cylindrical surface and a partially cylindrical surface may be used.

Further, in the above embodiment, the external force applying unit as (preload adjusting spring 15), the displacement y _p spring stiffness in response to an increase of the spring displacement is changed from positive to negative - non-linear spring (Fig. 4 with a load f _p characteristics has been exemplified a configuration in which using the reference), be close to 0 the gradient of the displacement Y- thrust f _y characteristics except preload adjusting spring 15 (i.e., the rate of change of the thrust F _y for the output displacement Y) of the displacement magnifying mechanism 10 A non-linear spring having other characteristics can be applied as long as it has the characteristics that can be achieved. FIG. 9 is a graph showing an example of other characteristics of the nonlinear spring. As shown in FIG. 9A, a non-linear spring having a characteristic that the spring rigidity (k = df _p / dy _p ) changes from a positively large value to a positively small value according to an increase in spring displacement may be used. However, as shown in FIG. 9B, a non-linear spring having a characteristic that the spring rigidity changes from positive to 0 as the spring displacement increases may be used.

_{Similarly, if the inclination of the displacement Y-thrust fy} characteristic of the displacement expansion mechanism 10 excluding the preload adjusting spring 15 can be brought close to 0, an element other than the non-linear spring, for example, a linear spring having a linear displacement-load characteristic. Can also be used as the preload adjusting spring 15.

Further, in the displacement expanding mechanism 10 shown in FIG. 1, a configuration in which a plurality of preload adjusting springs 15 are combined as an external force applying portion is illustrated, but the configuration is not limited to this. Desired displacement y _p of the external force applying unit - to output a load f _p characteristics may be configured using a single non-linear spring.

Next, the spring restraint portion 16 included in the displacement expanding mechanism 10 according to the present embodiment will be further described. FIG. 10 is a diagram schematically showing the displacement of the preload adjusting spring 15. Specifically, FIG. 10A is a diagram schematically showing the displacement of the preload adjusting spring 15 restrained by the spring restraining portion 16. FIG. 10B is a diagram schematically showing the displacement of the preload adjusting spring 15 accompanied by slippage. The preload adjusting spring 15 before displacement is shown by a two-dot chain line, and the preload adjusting spring 15 after displacement is shown by a solid line.

First, as shown in FIG. 10 (b), due to the displacement of the output unit 13 (indicated by the white arrow in FIG. 10), it slides between both end portions 152 and the outer shell 14 (indicated by the black arrow in FIG. 10). The case of displacement accompanied by) will be described. 11, the displacement y _p of the preload adjustment spring 15 when the preload adjusting spring 15 has the displacement with sliding - is a graph showing a load f _p characteristics. 11, the solid line, the displacement _{y p} of the preload adjusting spring 15 by the measurement results - indicating a load _{f p} characteristics. Dashed line, the displacement _{y p} of the preload adjusting spring 15 by FEM structural analysis - shows a load _{f p} characteristics. As shown in comparison between the measurement result (solid line) and the analysis result (dashed line) in FIG. 11, the spring characteristics of the analysis result are caused by slippage between both ends 152 of the preload adjusting spring 15 and the outer shell 14. The spring characteristics (solid line) of the measurement result deviate greatly from the (broken line). This is because, in the design using the analysis tool, ideal fixing conditions can be set at both ends, but in the actual machine, slippage occurs between both ends 152 of the preload adjustment spring 15 and the outer shell 14. There is a discrepancy in the spring characteristics.

On the other hand, the displacement expanding mechanism 10 of the present embodiment includes a spring restraining portion 16. Here, the output displacement of the output unit 13 increases in the + y direction, and the central portion 151 connected to the output unit 13 is also displaced by the same amount. With the displacement of the preload adjusting spring 15, the preload adjusting spring 15 tends to expand in the major axis direction (z-axis direction). On the other hand, the spring restraint portion 16 is fixed to the outer shell 14. Further, the outer shell 14 has a rigidity capable of generating a binding force that suppresses the expansion of the preload adjusting spring 15. As a result, as shown in FIG. 10A, the spring restraining portion 16 restrains the expansion of the preload adjusting spring 15 to suppress the slip of the preload adjusting spring 15.

12, the displacement y _p of the preload adjustment spring 15 the spring restraining portion 16 is provided - is a graph showing a load f _p characteristics. 12, the solid line, the displacement _{y p} of the preload adjusting spring 15 by the measurement results - indicating a load _{f p} characteristics. Dashed line, the displacement _{y p} of the preload adjusting spring 15 by FEM structural analysis - shows a load _{f p} characteristics. As shown in comparison between the measurement result (solid line) and the analysis result (broken line) in FIG. 12, by providing the spring restraint portion 16, slippage at both end portions 152 of the preload adjustment spring 15 can be suppressed, and analysis can be performed. The spring characteristics (solid line) of the measurement result similar to the spring characteristics (dashed line) of the result can be obtained.

In FIG. 1 (c), the spring preload adjusting mechanism 17 has been described as being composed of a shim (not shown) arranged between the central portion 151 and the output portion 13, but is not limited to this. No. FIG. 13 is a cross-sectional view of a displacement expanding mechanism 10 including another spring preload adjusting mechanism 17.

The displacement expanding mechanism 10 shown in FIG. 13A includes a shim 171 arranged between the spring restraining portion 16 and the preload adjusting spring 15 as the spring preload adjusting mechanism 17. By providing the shim 171 it is possible to adjust (narrow) the distance between the pair of spring restraint portions 16. The displacement expanding mechanism 10 shown in FIG. 13B includes a shim 172 arranged between the spring restraining portion 16 and the outer shell 14 as the spring preload adjusting mechanism 17. By providing the shim 172, the distance between the pair of spring restraint portions 16 can be adjusted (expanded). That is, by providing the shims 171 and 172, it is possible to interpolate the dimensional difference between the distance between the pair of spring restraining portions 16 and the dimension of the preload adjusting spring 15 in the long axis direction.

14, the displacement _{y p} of the preload adjustment spring 15 for describing the effect of the shim 171 - is a graph showing a load _{f p} characteristics. In FIG. 14, the solid line shows the measurement result when the shim 171 is provided. The broken line shows the measurement result when the shim 171 is not provided.

As shown by the broken line in FIG. 14, in the configuration in which the shim 171 is not provided, a hysteresis loop is observed due to friction loss due to slippage. That is, it is considered that there is a slight gap between both ends of the preload adjusting spring 15 and the spring restraint portion 16, and slippage is caused by the gap.

On the other hand, as shown by the solid line in FIG. 14, in the configuration in which the shim 171 is provided, the hysteresis loop is eliminated. That is, the gap between both ends of the preload adjusting spring 15 and the spring restraint portion 16 can be filled, and slippage of the preload adjusting spring 15 can be suppressed.

Further, in FIG. 14, as shown by comparing the solid line and the broken line, the magnitude of the negative rigidity and the maximum load are different. In other words, by inserting the shim 171 the preload is applied in the long axis direction of the preload adjusting spring 15, and the spring characteristics can be adjusted.

The adjustment effect of the shim 171 will be further described with reference to FIG. FIG. 15 is a graph showing the relationship between the thickness of the shim 171 and the spring characteristics. In FIG. 15, the offset position of the spring displacement is shown by the alternate long and short dash line. In (a), the spring displacement-spring load characteristic when the shim 171 is not inserted (total shim thickness = 0) is shown by a thick solid line. (B) shows the spring displacement-spring load characteristics when the total shim thickness of the shims 171 is 0.1 mm by a solid line. In (c), the spring displacement-spring load characteristic when the total shim thickness of the shim 171 is 0.2 mm is shown by a fine solid line.
In addition, a straight line that is linearly approximated is shown by a broken line.

In (a), the spring rigidity, which is the slope of the linearly approximated broken line, is _koea, and the offset load, which is the value of the intersection of the offset position indicated by the alternate long and _{short dash line and the linearly approximated dashed line, is f so} . The total shim thickness, spring rigidity, and offset load in (a) to (c) are shown in the table of FIG.

As shown in the table of FIG. 15, it was confirmed that the spring rigidity and the offset load increased when the total shim thickness of the shims 171 was increased. As described above, the change in the spring characteristics depending on the thickness of the shim enables fine adjustment so as to satisfy the equations (9) and (10).

Further, in a configuration in which the dimension of the preload adjusting spring 15 in the major axis direction is longer than the distance between the pair of spring restraint portions 16, the preload is reduced in the major axis direction of the preload adjustment spring 15 by inserting the shim 172. , Spring characteristics can be adjusted.

Although the displacement expanding mechanism 10 according to the present embodiment has been described above, the present disclosure is not limited to the above-described embodiment and the like, and various types are within the scope of the gist of the present disclosure described in the claims. It can be transformed and improved.

10 Displacement expansion mechanism 11 Piezo element (expansion / contraction element)
111, 112 Cap 12 Fixed part 13 Output part 14 Outer shell 15 Preload adjustment spring (external force application part)
151 Central part 152 Both ends 153 Connection part 16 Spring restraint part (restraint part)
17 Spring preload adjustment mechanism (preload adjustment mechanism)
171,172 Sim 18 Piezo preload adjustment mechanism

Claims (8)

Telescopic elements with capacitive properties and
An output unit that comes into contact with one end of the expansion / contraction element and is displaced in a direction different from the expansion / contraction direction of the expansion / contraction element according to the expansion / contraction of the expansion / contraction element.
A fixed portion that comes into contact with the other end of the telescopic element and is not displaced by the expansion and contraction of the telescopic element.
An external force application unit that applies an external force to the output unit so that the rate of change of the thrust with respect to the output displacement of the output unit approaches 0.
A restraining portion for restraining the external force applying portion, and a restraining portion.
Displacement expansion mechanism. The restraint portion is
Restrains the sliding of the external force applying portion in the long axis direction.
The displacement expansion mechanism according to claim 1. The external force applying portion has a central portion and both end portions that are displaced together with the output portion.
The restraint restrains the slip of both ends.
The displacement expansion mechanism according to claim 1 or 2. A preload adjusting mechanism for adjusting the preload of the external force applying portion is provided.
The displacement expanding mechanism according to any one of claims 1 to 3. The preload adjusting mechanism has a shim arranged between the restraining portion and the external force applying portion.
The displacement expansion mechanism according to claim 4. The preload adjusting mechanism has a shim arranged between the restraining portion and the fixing portion.
The displacement expansion mechanism according to claim 4 or 5. The external force application portion is a non-linear spring.
The non-linear spring has a characteristic that the rate of change of the spring load with respect to the amount of deflection of the spring decreases as the amount of deflection increases.
The displacement expanding mechanism according to any one of claims 1 to 6. The actuator provided with the displacement expanding mechanism according to any one of claims 1 to 7.

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