Fluid Pressure Actuator

Abstract

To provide a fluid pressure actuator capable of not only advancing / retracting an output shaft, but also rotating it, and suppressing the generation of surging on a spring body.SOLUTION: A fluid pressure actuator 1 is equipped with an output shaft advancing / retracting drive portion 30 that advances / retracts an output shaft 5 in an X-direction with respect to a sleeve 10 by changing a fluid amount supplied to pressure chambers 9a and 9b to change the volume of the pressure chambers 9a and 9b, a rotating portion 53 that is disposed on the outer side in an R-direction of the output shaft 5 so as to generally coaxially rotate with the output shaft 5, and a spring body 70 that is disposed on the outer side in the R-direction of the output shaft 5 so as to generally coaxially expand / contract in the R-direction with the output shaft 5, has a front side end portion 71 fixed to the output shaft 5 and a rear side end portion 72 fixed to the rotating portion 53, and rotates the output shaft 5 in a circumferential direction when the rotating portion 53 is driven to rotate. The fluid pressure actuator 1 satisfies at least either one of a pitch of the spring body 70 being an irregular pitch or the spring body 70 made of a material with a vibration control property.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fluid pressure actuator that axially advances and retreats an output shaft relative to a sleeve based on fluid pressure. [Background technology]

[0002] Conventionally, there is a fluid pressure actuator described in Patent Document 1. This fluid pressure actuator includes a sleeve and an output shaft that advances and retreats relative to the sleeve based on fluid pressure. This fluid pressure actuator also includes a rotating part that is disposed approximately coaxially with the output shaft and is rotatable around the axis of the output shaft, and a spring body that has one end fixed to the output shaft and the other end fixed to the rotating part and transmits the rotational power of the rotating part to the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5812826 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned fluid pressure actuator can not only move the output shaft back and forth, but also rotate the output shaft, which allows not only precise adjustment of the axial position of the fixed body fixed to the tip of the output shaft, but also precise adjustment of the circumferential position of the fixed body, thereby greatly increasing the degree of freedom in positioning the fixed body.

[0005] In the course of conducting repeated tests to collect data on the fluid pressure actuator of the above-described configuration, the inventors of the present application ascertained and discovered for the first time that if an external force having a frequency component close to the natural vibration of the spring body is applied to the spring body, there is a risk of surging, in which the spring body vibrates rapidly, and there is a risk that the axial position of the fixed body cannot be determined with high precision.

[0006] Therefore, an object of the present disclosure is to provide a fluid pressure actuator that can not only move an output shaft back and forth but also rotate it, and that can suppress surging in the spring body. [Means for solving the problem]

[0007] In order to solve the above problem, the fluid pressure actuator according to the present disclosure comprises an output shaft having at least one first pressure receiving surface, a sleeve having an inner circumferential surface portion supporting the output shaft movably in the axial direction, and a second pressure receiving surface which, in cooperation with the first pressure receiving surface, defines at least a portion of a pressure chamber, an output shaft advancement / retraction drive portion which varies the volume of the pressure chamber by changing the amount of fluid supplied to the pressure chamber, thereby advancing and retracting the output shaft in the axial direction relative to the sleeve, a rotating portion which is arranged radially outside of the output shaft and rotatably approximately coaxial with the output shaft, and a spring body which is arranged radially outside of the output shaft and approximately coaxial with the output shaft and capable of expanding and contracting in the axial direction, the spring body having one side end fixed to the output shaft and the other side end fixed to the rotating portion, and which rotates the output shaft in the circumferential direction when the rotating portion is rotationally driven, and which satisfies at least one of the following: the pitch of the spring body is uneven; and the spring body is made of a material having vibration damping properties.

[0008] As described above, the present inventors have discovered for the first time that when an external force having a frequency component close to the natural vibration of the spring body acts on the spring body, there is a risk of surging, in which the spring body vibrates rapidly, and there is a risk that the axial position of the fixed body cannot be determined with high precision.

[0009] In light of this background, the inventors of the present application have discovered that by at least one of making the pitch of the spring body uneven and constructing the spring body from a material having vibration-damping properties, surging is less likely to occur in the spring body regardless of the external force applied to the spring body.

[0010] Therefore, according to the present disclosure, since at least one of the spring body having an uneven pitch and the spring body being made of a material having vibration-damping properties is satisfied, it is possible to suppress the occurrence of surging in the spring body, and therefore it becomes easy to perform both highly accurate axial positioning of the output shaft and highly accurate circumferential positioning of the output shaft regardless of the external force applied to the spring body.

[0011] In the present disclosure, the pitch of the spring body may be unequal, and the pitch on both ends of the spring body may be shorter than the pitch on the central side of the spring body.

[0012] The inventors of the present application have discovered that when the pitch of the spring body is unequal and the pitch at both ends of the spring body is shorter than the pitch at the center of the spring body, the effect of suppressing surging can be increased in a configuration in which the spring body transmits rotational power to the output shaft. Therefore, with this configuration, surging can be effectively suppressed and the axial and circumferential positioning of the output shaft can be performed with even higher accuracy.

[0013] In the present disclosure, the spring body may have an uneven pitch, and the spring body may be configured as a cylinder having a slit.

[0014] According to this configuration, the desired spring body can be manufactured easily and with high precision by simply providing unequal pitch slits in the cylinder. More specifically, the spring body used in the fluid pressure actuator of the present disclosure preferably has a low axial spring constant so that it is difficult to apply axial reaction force to parts of the fluid pressure actuator other than the spring body, and has high torsional rigidity so that the rotational power applied to the spring body can be efficiently transmitted to the output shaft in order to effectively suppress surging and efficiently transmit the rotational power to the output shaft. In this background, according to this configuration, the desired wide spring body with low axial spring constant and high torsional rigidity can be manufactured easily and with high precision by simply adjusting the number, pitch, width, depth, etc. of the unequal pitch slits provided in the cylinder. Therefore, by adopting this configuration, it is easy to manufacture a fluid pressure actuator that can efficiently suppress surging, can perform highly accurate axial positioning of the output shaft, and can also perform highly accurate circumferential positioning of the output shaft.

[0015] In the present disclosure, the spring body may be made of Mn-20Cu-5Ni-2Fe (M2052 alloy), where the numbers in Mn-20Cu-5Ni-2Fe represent the atomic percentage of the composition.

[0016] The inventors of the present application have confirmed through numerous tests that, in a fluid pressure actuator that not only moves the output shaft back and forth but also rotates the output shaft, if the spring body is made of the above-mentioned manganese-based damping alloy among many damping materials, a remarkable surging suppression effect can be obtained. In addition, it has been confirmed that if the spring body is composed of spring bodies with an uneven pitch and made of the above-mentioned manganese-based damping alloy, surging of the spring body can be almost prevented in a fluid pressure actuator that not only moves the output shaft back and forth but also rotates the output shaft. Therefore, according to this configuration, surging of the spring body can be more effectively suppressed, and the axial positioning and circumferential positioning of the output shaft can be performed with even higher accuracy. The M2052 alloy is disclosed in Patent No. 2849698 and is one of many damping materials. Here, the inventors of the present application speculate that the reason why the M2052 alloy has a more significant surging suppression effect in the fluid pressure actuator of the present disclosure compared to other vibration damping materials is that the remarkable twinning action of the M2052 alloy makes it possible to efficiently damp vibrations over a wide range from low to high frequencies. Effect of the Invention

[0017] According to the fluid pressure actuator according to the present disclosure, the output shaft can be rotated as well as moved back and forth, and surging of the spring body can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic axial cross-sectional view of a fluid pressure actuator according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a part of the schematic cross-sectional view taken along line AA in FIG. 1, and is a schematic cross-sectional view for explaining the operation of a servo valve of the fluid pressure actuator for rotating a rotating part. [Diagram 3] FIG. 1 is a perspective view showing a spring body of the fluid pressure actuator. [Figure 4] 3 is a schematic cross-sectional view corresponding to FIG. 2 of a servo valve according to a modified example. FIG. [Diagram 5]FIG. 13 is a perspective view of a spring body according to a modified example. [Figure 6] FIG. 11 is a schematic cross-sectional view in the axial direction of a fluid pressure actuator according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In addition, when multiple embodiments and modified examples are included below, it is assumed from the beginning that new embodiments will be constructed by appropriately combining the characteristic parts of those. In addition, in the following examples, the same configurations in the drawings are given the same symbols, and duplicated explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios of length, width, height, etc. of each member between different drawings do not necessarily match. In addition, when the word "approximately" is used in this specification, it is used in the same sense as the word "roughly speaking", and the requirement of "approximately ~" is met if a person looks roughly ~. For example, the requirement of approximately circular is met if a person looks roughly circular.

[0020] In the following, a gas pressure actuator using gas will be described as the fluid pressure actuator, but a hydraulic actuator or a water pressure actuator using a liquid other than gas may be used. The gas used as the fluid may be general air, dry air, inert gas such as nitrogen or argon, or other gas. In the following description and drawings, the X direction indicates the axial direction of the output shaft 5, 105, the θ direction indicates the circumferential direction of the output shaft 5, 105, and the R direction indicates the radial direction of the output shaft 5, 105. The X direction, the θ direction, and the R direction are mutually orthogonal. In the following description, the X direction side of the output shaft 5, 105 where materials or electronic components (e.g., chips, etc.) are fixed is referred to as the X direction front side, and the opposite side is referred to as the X direction rear side. Among the components described below, components not described in the independent claims showing the highest concept are optional components and are not essential components.

[0021] (First embodiment) Fig. 1 is a schematic axial cross-sectional view of a fluid pressure actuator 1 according to a first embodiment of the present disclosure. This fluid pressure actuator 1 is a material testing machine, and is used, for example, to twist and pull a material fixed to the front end surface of an output shaft 5 in the X direction, and is used to test the resistance of the material. As shown in Fig. 1, the fluid pressure actuator 1 includes an output shaft 5, a sleeve 10, an output shaft advance / retreat drive unit 30, a rotation drive unit 50, a spring body 70, a rotation angle detection sensor 75, and an axial displacement sensor 80.

[0022] The output shaft 5 includes a large diameter shaft portion 5a having a large outer diameter, and a small diameter shaft portion 5b having a smaller diameter than the large diameter shaft portion 5a, connected to the large diameter shaft portion 5a, and extending in the X direction. As will be described in detail later, the spring body 70 is disposed on the outer side of the small diameter shaft portion 5b in the R direction, the rotation angle detection sensor 75 detects the rotation angle (displacement in the θ direction) of the small diameter shaft portion 5b relative to the sleeve 10, and the axial displacement sensor 80 detects the X direction displacement of the small diameter shaft portion 5b relative to the sleeve 10. In the first embodiment, the small diameter shaft portion 5b is screwed to the large diameter shaft portion 5a using the nut 6, but the large diameter shaft portion 5a and the small diameter shaft portion 5b may be integrally configured, and the output shaft 5 may not have the small diameter shaft portion 5b.

[0023] The large diameter shaft portion 5a has a cylindrical shape with a circular cross section, and the small diameter shaft portion 5b has a cylindrical shape with a circular cross section. The output shaft 5 further has a flange portion 5c. The flange portion 5c is an annular protruding portion protruding in the R direction from the large diameter shaft portion 5a, and the tip surface of the flange portion 5c in the R direction is a cylindrical outer circumferential surface 7. As will be described in detail later, annular end surfaces 8a and 8b on both sides of the flange portion 5c in the X direction are first pressure receiving surfaces, which are configured to receive the pressure of air supplied from the output shaft advance / retract drive portion 30.

[0024] The sleeve 10 has a first inner peripheral surface portion 10a that supports the outer peripheral portion of the large diameter shaft portion 5a so as to be slidable in the X direction, and a second inner peripheral surface portion 10b that supports the cylindrical outer peripheral surface 7 of the flange portion 5c so as to be slidable in the X direction. The second inner peripheral surface portion 10b is connected to the first inner peripheral surface portion 10a via annular end faces 10c and 10d, and the X-direction length of the second inner peripheral surface portion 10b is longer than the X-direction length of the flange portion 5c. The annular end faces 10c and 10d of the sleeve 10 have substantially the same R-direction dimension as the end faces 8a and 8b on both sides of the X direction of the flange portion 5c, and face the end faces 8a and 8b of the flange portion 5c in the X direction. As will be described in detail later, the annular end faces 10c and 10d of the sleeve 10 are second pressure receiving surfaces and define a part of the pressure chambers 9a and 9b into which air from the output shaft advance / retract drive portion 30 is filled.

[0025] The output shaft advance / retreat drive unit 30 has a servo valve 31, and a first passage 32a and a second passage 32b provided in the sleeve 10. The first passage 32a communicates between a first discharge / suction port (not shown) of the servo valve 31 and a front end of the second inner circumferential surface portion 10b in the X direction, and the second passage 32b communicates between a second discharge / suction port (not shown) of the servo valve 31 and a rear end of the second inner circumferential surface portion 10b in the X direction. Since the X-direction length of the second inner circumferential surface portion 10b is longer than the X-direction length of the flange portion 5c, a space surrounded by the second inner circumferential surface portion 10b of the sleeve 10, the annular end faces 10c and 10d of the sleeve 10, the large-diameter shaft portion 5a, and the end faces 8a and 8b on both sides in the X direction of the flange portion 5c is formed at least on one side of the flange portion 5c in the X direction. This space becomes pressure chambers 9a and 9b.

[0026] The output shaft advancement / retraction drive unit 30 advances and retreats the output shaft 5 as follows. More specifically, the servo valve 31 of the output shaft advancement / retraction drive unit 30 operates so that when the first discharge / suction port discharges air, the second discharge / suction port sucks in air, and conversely, when the first discharge / suction port sucks in air, the second discharge / suction port discharges air. As a result, when air is supplied from the first passage 32a to the front end of the second inner circumferential surface portion 10b in the X direction, the volume of the first pressure chamber 9a located on the front side of the flange portion 5c in the X direction gradually increases, causing the output shaft 5 to retreat rearward, and conversely, when air is supplied from the second passage 32b to the rear end of the second inner circumferential surface portion 10b in the X direction, the volume of the second pressure chamber 9b located on the rear side of the flange portion 5c in the X direction gradually increases, causing the output shaft 5 to advance forward.

[0027] The fluid pressure actuator 1 has a third passage 32c branching off from the first passage 32a and opening into a portion of the first inner circumferential surface portion 10a that is located forward in the X direction from the first pressure chamber 9a, and a fourth passage 32d having an opening located rearward in the X direction from the opening of the third passage 32c on the first inner circumferential surface portion 10a side, and communicating the first inner circumferential surface portion 10a with the outside. The fluid pressure actuator 1 also has a fifth passage 32e branching off from the second passage 32b and opening into a portion of the first inner circumferential surface portion 10a that is located rearward in the X direction from the second pressure chamber 9b, and a sixth passage 32f having an opening located forward in the X direction from the opening of the fifth passage 32e on the first inner circumferential surface portion 10a side, and communicating the first inner circumferential surface portion 10a with the outside.

[0028] When the first discharge / suction port discharges air and the second discharge / suction port sucks air, the air flows in the direction indicated by the arrow a1 through the third passage 32c, between the first inner circumferential surface portion 10a located forward of the first pressure chamber 9a in the X direction and the large diameter shaft portion 5a, and through the fourth passage 32d, and in the direction indicated by the arrow a2 through the sixth passage 32f, between the first inner circumferential surface portion 10a located rearward of the second pressure chamber 9b in the X direction and the large diameter shaft portion 5a, and through the fifth passage 32e, in that order. Therefore, a hydrostatic bearing can be generated between the first inner circumferential surface portion 10a and the large diameter shaft portion 5a both forward of the first pressure chamber 9a in the X direction and rearward of the second pressure chamber 9b in the X direction.

[0029] Conversely, when the first discharge suction port draws in air and the second discharge suction port discharges air, the air flows in the direction indicated by the arrow b1 through the fourth passage 32d, between the first inner circumferential surface portion 10a located forward of the first pressure chamber 9a in the X direction and the large diameter shaft portion 5a, and through the third passage 32c, and in the direction indicated by the arrow b2 through the fifth passage 32e, between the first inner circumferential surface portion 10a located rearward of the second pressure chamber 9b in the X direction and the large diameter shaft portion 5a, and through the sixth passage 32f. Therefore, even in this case, a hydrostatic bearing can be generated between the first inner circumferential surface portion 10a and the large diameter shaft portion 5a both forward of the first pressure chamber 9a in the X direction and rearward of the second pressure chamber 9b in the X direction. Therefore, when the output shaft 5 advances and retreats in the X direction, the large diameter shaft portion 5a can be supported by the hydrostatic bearing so as to be freely advanced and retreated relative to the first inner circumferential surface portion 10a without coming into contact with the first inner circumferential surface portion 10a.

[0030] In the first embodiment, when the output shaft 5 moves back and forth in the X direction, the large diameter shaft portion 5a is supported by a hydrostatic bearing so as to be freely movable back and forth against the first inner surface portion 10a. However, when the output shaft 5 moves back and forth in the X direction, the large diameter shaft portion 5a may be supported by a sliding bearing so as to be freely movable back and forth against the first inner surface portion 10a, or the large diameter shaft portion 5a does not need to be supported by a bearing against the first inner surface portion 10a when the output shaft 5 moves back and forth in the X direction.

[0031] The rotary drive unit 50 has a servo valve 51 constituting a rotary actuator. Fig. 2 is a part of the schematic cross-sectional view taken along line AA in Fig. 1, and is a schematic cross-sectional view for explaining the operation of the servo valve 51 to rotate the rotating unit 53. As shown in Fig. 2, the servo valve 51 has a cylindrical case 52 and a cylindrical rotating unit 53. The axial center of the cylindrical case 52 approximately coincides with the axial center of the cylindrical rotating unit 53, and a cylindrical inner peripheral surface 52a of the case 52 faces a cylindrical outer peripheral surface 53a of the rotating unit 53 at a distance in the R direction.

[0032] The servo valve 51 further has a protruding portion 54 protruding inward in the R direction from the cylindrical inner peripheral surface 52a and facing the cylindrical outer peripheral surface 53a of the rotating portion 53 with a small gap therebetween, and a vane 55 protruding inward in the R direction from the cylindrical outer peripheral surface 53a of the rotating portion 53 and facing the cylindrical inner peripheral surface 52a with a small gap therebetween. With this configuration, two pressure chambers 56a, 56b are formed in the case 52 with the protruding portion 54 and the vane 55 as boundaries. The servo valve 51 further has discharge and suction ports 57a, 57b for discharging or suctioning air. The discharge and suction ports 57a, 57b are provided at the base of both sides in the θ direction of the protruding portion 54 in a wall portion 58 in the case 52 that is substantially perpendicular to the X direction.

[0033] By discharging air from discharge / suction port 57a located on the right side of protrusion 54 in the plane of Fig. 2 and sucking air from discharge / suction port 57b located on the left side of protrusion 54, vane 55 can be rotated clockwise in the plane of Fig. 2, and as a result, rotating part 53 can be rotated clockwise in the plane of Fig. 2. Conversely, by discharging air from discharge / suction port 57b and sucking air from discharge / suction port 57a, vane 55 can be rotated counterclockwise in the plane of Fig. 2, and as a result, rotating part 53 can be rotated counterclockwise in the plane of Fig. 2.

[0034] 1 again, the rotating part 53 is located on the outer side of the small diameter shaft part 5b in the R direction, and is disposed substantially coaxially with the small diameter shaft part 5b. The outer peripheral surface of the rotating part 53 is rotatably supported on the inner peripheral surface of the sleeve 10 by rolling bearings 59a, 59b at the front and rear of the vane 55 in the X direction. The fluid pressure actuator 1 also includes O-rings 60a, 60b at the front and rear of the vane 55 in the X direction for sealing a gap between the outer peripheral surface of the rotating part 53 and the inner peripheral surface of the sleeve 10. The O-rings 60a, 60b are provided to realize high airtightness of the pressure chambers 56a, 56b (see FIG. 2) and to rotate the vane 55 smoothly.

[0035] The spring body 70 has a front end 71, a rear end 72, and a spring portion 73. The front end 71 is pinned by a plurality of pins 77 arranged at intervals on the end face of the large diameter shaft portion 5a on the rear side in the X direction. The rear end 72 is screwed by a plurality of bolts 79 arranged at intervals on an annular flange portion 65 provided on the rear side of the rotating portion 53 in the X direction so as to protrude inward in the R direction. The spring portion 73 is provided between the front end 71 and the front end 71 to connect the front end 71 and the front end 71. In the first embodiment, both ends of the spring body 70 in the X direction are fixed to the output shaft 5 or the rotating portion 53 by pinning or bolting. However, both ends of the spring body 70 in the X direction may be fixed to the output shaft or the rotating portion by any structure, and may be fixed to the output shaft or the rotating portion by using, in addition to screwing or pinning, adhesive bonding, welding, caulking, or the like.

[0036] The spring body 70 is made of a vibration-damping metal, and is, for example, a vibration-damping alloy such as graphite cast iron, aluminum, or zinc alloy. When the spring body 70 is made of a vibration-damping alloy, the spring body 70 may be made of any type of vibration-damping alloy, such as a composite type, a ferromagnetic type, a dislocation type, or a twin crystal type. Alternatively, the spring body 70 may be made of a vibration-damping steel plate (sandwich steel plate) sandwiched with plastic. The spring body 70 may be made of any vibration-damping metal, but is particularly preferably made of a vibration-damping alloy in which, by atomic weight, manganese accounts for approximately 73%, copper accounts for approximately 20%, nickel accounts for approximately 5%, and iron accounts for approximately 2%. In other words, the spring body 70 is preferably made of Mn-20Cu-5Ni-2Fe (M2052 alloy).

[0037] FIG. 3 is a perspective view showing the spring body 70. As shown in FIG. 3, the spring body 70 is composed of a cylinder 76 having slits 78, and the pitch of the spring portion 73 is unequal. In detail, the pitch of both ends 73a, 73b of the spring portion 73 in the X direction is smaller than the pitch of a central portion 73c in the X direction that connects both ends 73a, 73b of the spring portion 73. The spring portion 73 is substantially symmetrical with respect to a virtual plane that passes through the approximate center in the X direction and is substantially perpendicular to the X direction. The spring constant of both ends 73a, 73b of the spring portion 73 is larger than the spring constant of the central portion 73c.

[0038] 1 again, the rotation angle detection sensor 75 detects the rotation angle (displacement in the θ direction) of the small diameter shaft portion 5b relative to the sleeve 10. The rotation angle detection sensor 75 may be composed of any sensor capable of detecting the rotation angle of the small diameter shaft portion 5b relative to the sleeve 10. The rotation angle detection sensor 75 may be composed of, for example, a digital rotary encoder, and may include an annular pulsar ring in which N stations and S stations are alternately arranged in the θ direction and fitted and fixed to the cylindrical outer circumferential surface of the small diameter shaft portion 5b, and a magnetic detection unit. Alternatively, the rotation angle detection sensor 75 may be composed of an optical detection type rotation angle detection sensor, or may be composed of an electromagnetic induction type rotation angle detection sensor (resolver), etc.

[0039] The axial displacement sensor 80 detects the X-direction displacement of the small diameter shaft portion 5b relative to the sleeve 10. The axial displacement sensor 80 may be composed of any sensor capable of detecting the X-direction displacement of the small diameter shaft portion 5b relative to the sleeve 10. The axial displacement sensor 80 may be composed of, for example, a digital linear encoder, and may include a linear scale in which N-pole and S-pole are alternately arranged on a straight line and fixed to the small diameter shaft portion 5b, and a magnetic detection unit fixed to the inner circumferential surface of the sleeve 10. Alternatively, the axial displacement sensor 80 may be composed of a differential transformer type position detection sensor including a soft magnetic probe and a transformer winding, an optical detection type position detection sensor, or a capacitance detection type position detection sensor.

[0040] The fluid pressure actuator 1 is controlled by a control device 85 arranged externally. The control device 85 is preferably configured by a computer, for example, a microcomputer, and includes a control unit 86 and a storage unit 87. The control unit 86, i.e., the processor, includes, for example, a CPU (Central Processing Unit). The storage unit 87 is configured by a hard disk drive (HDD), a semiconductor memory, etc., and the semiconductor memory is configured by a non-volatile memory such as a ROM (Read Only Memory) or a volatile memory such as a RAM (Random Access Memory). The storage unit 87 may be configured by only one storage medium, or may be configured by a plurality of different storage media. The CPU reads out and executes a control program for the fluid pressure actuator 1 that is stored in advance in the storage unit 87. The non-volatile memory stores the control program, a predetermined threshold value, etc. in advance. The volatile memory temporarily stores the read control program and processing data.

[0041] The control unit 86 includes an axial displacement calculation unit 86a, a rotation angle calculation unit 86b, an advance / retreat drive control unit 86c, and a rotation drive control unit 86d. The axial displacement calculation unit 86a calculates the axial displacement of the output shaft 5 relative to the sleeve 10 based on a signal from the axial displacement sensor 80, and the rotation angle calculation unit 86b calculates the rotation angle of the output shaft 5 relative to the sleeve 10 based on a signal from the rotation angle detection sensor 75.

[0042] The forward / backward drive control unit 86c controls the output-shaft forward / backward drive unit 30 based on the displacement of the output shaft 5 in the X direction relative to the sleeve 10 calculated by the axial displacement calculation unit 86a, and controls the displacement of the output shaft 5 in the X direction relative to the sleeve 10 with high precision. Since the rotating unit 53 is stationary in the X direction relative to the sleeve 10 and the rear end 72 of the spring body 70 is fixed to the rotating unit 53, when the displacement of the output shaft 5 in the X direction relative to the sleeve 10 can be determined, the extension dimension Δx of the spring body 70 toward the front side in the X direction relative to its natural length can be determined. Therefore, if the force on the front side in the X direction applied to the output shaft 5 by the air supplied from the servo valve 31 of the output-shaft forward / backward drive unit 30 to the first and second pressure chambers 9a, 9b is F(S) and the spring constant of the spring body 70 is k, the external force on the front side in the X direction applied to the output shaft 5 is F(S)-k×Δx. The forward / backward drive control unit 86c back-calculates F(S) that realizes the desired X-direction position of the output shaft 5 based on the external force, and controls the amount of air discharged or sucked in from the first and second discharge / suction ports of the servo valve 31 so as to realize the F(S).

[0043] The rotation drive control unit 86d controls the rotation drive unit 50 based on the rotation angle of the output shaft 5 relative to the sleeve 10 calculated by the rotation angle calculation unit 86b, and controls the rotation angle of the output shaft 5 relative to the sleeve 10 with high precision. In detail, since the rear end of the spring body 70 is fixed to the rotating unit 53, if the rotation angle of the output shaft 5 relative to the sleeve 10 can be specified, the degree of torsion in the θ direction of the spring body 70 can be specified based on the rotation angle of the rotating unit 53 relative to the sleeve 10, and the torque T(S) (force in the θ direction) applied by the spring body 70 to the output shaft 5 can be specified. The rotation drive control unit 86d controls the servo valve 51 of the rotation drive unit 50 to control the rotation angle of the rotating unit 53 relative to the sleeve 10, thereby adjusting the torque T(S) with high precision, and controls the rotation angle of the output shaft 5 relative to the sleeve 10 with high precision.

[0044] As described above, the fluid pressure actuator 1 includes the output shaft 5 having at least one annular end face 8a, 8b (first pressure receiving surface), the inner circumferential surface portions 10a, 10b that support the output shaft 5 movably in the X direction, and the sleeve 10 having annular end faces 10c, 10d (second pressure receiving surface) that define at least a part of the first and second pressure chambers 9a, 9b in cooperation with the end faces 8a, 8b. The fluid pressure actuator 1 also includes an output shaft advance / retract drive unit 30 that changes the amount of fluid supplied to the first and second pressure chambers 9a, 9b to vary the volumes of the first and second pressure chambers 9a, 9b, thereby advancing and retracting the output shaft 5 in the X direction relative to the sleeve 10, and a rotating unit 53 that is arranged rotatably approximately coaxially with the output shaft 5 on the outer side of the output shaft 5 in the R direction. The fluid pressure actuator 1 is provided with a spring body 70 that is disposed outside the output shaft 5 in the R direction, approximately coaxially with the output shaft 5 and capable of expanding and contracting in the R direction, has a front end 71 (one side end) fixed to the output shaft 5 and a rear end 72 (the other side end) fixed to the rotating part 53, and rotates the output shaft 5 in the θ direction when the rotating part 53 is rotationally driven. The fluid pressure actuator 1 satisfies at least one of the following requirements: the spring body 70 has an uneven pitch, and the spring body 70 is made of a material having vibration-damping properties.

[0045] In the course of carrying out numerous tests to collect data on a fluid pressure actuator that uses a spring body that is neither made of vibration-damping metal nor has an uneven pitch, the inventors of the present application discovered and ascertained for the first time that when an external force having a frequency component close to the natural vibration of the spring body is applied to the spring body, there is a risk of surging, in which the spring body vibrates in small increments, and there is a risk that the X-direction position of the fixed object (e.g., material or electronic component) cannot be determined with high precision.

[0046] Furthermore, the inventors of the present application have further confirmed that by at least one of making the pitch of the spring body uneven and constructing the spring body from a material having vibration-damping properties, surging is less likely to occur in the spring body regardless of the external force applied to the spring body.

[0047] Therefore, according to the present disclosure, the spring body 70 has an uneven pitch and is made of a material having vibration-damping properties, so that it is possible to suppress surging from occurring in the spring body 70. Therefore, no matter what external force is applied to the spring body 70, it is easy to perform both highly accurate positioning of the output shaft 5 in the X direction and highly accurate positioning of the output shaft 5 in the θ direction.

[0048] Furthermore, the pitch of the spring body 70 may be unequal, and the pitch on both ends of the spring body 70 may be shorter than the pitch on the central side of the spring body.

[0049] The inventors of the present application have discovered that if the pitch of the spring body 70 is unequal and the pitch at both ends of the spring body 70 is shorter than the pitch at the center of the spring body, the effect of suppressing surging can be increased in a configuration in which the spring body 70 transmits rotational power to the output shaft 5. Therefore, with this configuration, surging of the spring body 70 can be effectively suppressed, and the axial positioning and circumferential positioning of the output shaft 5 can be performed with even higher accuracy.

[0050] The inventors of the present application speculate that the reason why surging of spring body 70 can be effectively suppressed when the pitch of spring body 70 is uneven and the pitch at both ends of spring body 70 is shorter than the pitch at the center of the spring body is as follows.

[0051] In detail, when the natural frequency of the spring body 70 is f1 and the spring constant of the spring body 70 is k, f1 ∝ k 1 / 2It is known that, when the natural frequency f1 of the spring body 70 coincides with the frequency f2 of the forced vibration of the spring body 70 caused by an external force, resonance occurs and the spring body 70 causes surging. However, when the pitch of the spring body 70 is unequal, the spring constants of both ends of the spring body 70 and the spring constant of the center of the spring body 70 are different, so that both ends of the spring body 70 and the center of the spring body 70 vibrate differently, and both ends of the spring body 70 and the center of the spring body 70 tend to vibrate so as to cancel the resonance of the entire spring body 70. In addition, when the spring constant of the center of the spring body 70 is smaller than the spring constant of both ends of the spring body 70, the vibration frequency of both ends of the spring body 70 is smaller than the vibration frequency of the center of the spring body 70, so that the vibration of the spring body 70 is not easily transmitted to the output shaft 5 connected to the front end 71 of the spring body 70. Therefore, the inventors of the present application have inferred that surging of spring body 70 can be effectively suppressed when the pitch of spring body 70 is uneven and the pitch at both ends of spring body 70 is shorter than the pitch at the center of spring body 70.

[0052] Moreover, the pitch of the spring body 70 may be non-uniform, and the spring body 70 may be configured as a cylinder 76 having a slit 78 formed therein.

[0053] According to this configuration, the desired spring body 70 can be manufactured easily and with high accuracy by simply providing slits with an uneven pitch in the cylinder 76. More specifically, the spring body 70 used in the fluid pressure actuator 1 of the present disclosure preferably has a low axial spring constant so that it is difficult to apply an axial reaction force to parts of the fluid pressure actuator 1 other than the spring body 70, and has high torsional rigidity so that the rotational power applied to the spring body 70 can be efficiently transmitted to the output shaft 5, in order to effectively suppress surging and efficiently transmit the rotational power to the output shaft. In this background, according to this configuration, the desired wide spring body 70 with a low axial spring constant and high torsional rigidity can be manufactured easily and with high accuracy by simply adjusting the number, pitch, width, depth, etc. of the slits with an uneven pitch provided in the cylinder 76. Therefore, by adopting this configuration, it is easy to manufacture a fluid pressure actuator 1 that can efficiently suppress surging, can perform highly accurate axial positioning of the output shaft, and can also perform highly accurate circumferential positioning of the output shaft 5.

[0054] The spring body 70 may also be made of Mn-20Cu-5Ni-2Fe (M2052 alloy), or may be composed of a vibration-damping alloy having, by atomic weight percentage, approximately 73% manganese, approximately 20% copper, approximately 5% nickel, and approximately 2% iron.

[0055] The inventors of the present application have confirmed through numerous tests that, in a fluid pressure actuator that not only moves the output shaft 5 back and forth but also rotates the output shaft 5, if the spring body 70 is made of the above-mentioned manganese-based damping alloy among many damping materials, a remarkable surging suppression effect can be obtained. In addition, it has been confirmed that if the spring body 70 is made of spring bodies with an uneven pitch and made of the above-mentioned manganese-based damping alloy as in the first embodiment, surging of the spring body 70 can be almost prevented in the fluid pressure actuator 1 that not only moves the output shaft 5 back and forth but also rotates the output shaft 5. Therefore, according to this configuration, surging of the spring body 70 can be more effectively suppressed, and the positioning of the output shaft 5 in the X direction and the θ direction can be performed with even higher accuracy. The inventors of the present application speculate that the reason why the M2052 alloy has a more significant surging suppression effect in the fluid pressure actuator 1 of the present disclosure compared to other vibration-damping materials is because the M2052 alloy has a significant twinning effect that enables it to efficiently damp vibrations over a wide range from low to high frequencies.

[0056] In the first embodiment, the case where the rotary drive unit 50 includes the servo valve 51 having only one vane 55 has been described. However, the rotary drive unit may include a servo valve having two or more vanes. For example, as shown in FIG. 4, that is, a schematic cross-sectional view of a modified servo valve 151 corresponding to FIG. 2, the servo valve 151 of the rotary drive unit 150 may have a cylindrical case 152, a cylindrical rotating unit 153, two protruding parts 154a and 154b, two vanes 155a and 155b, and four discharge and suction ports 157a to 157d. The two protruding parts 154a and 154b extend on the same straight line and face the rotating unit 153 in the R direction, and the two vanes 155a and 155b also extend on the same straight line and face the cylindrical case 152 in the R direction. In addition, discharge / suction port 157a and discharge / suction port 157d perform the same operation (air discharge or suction) at the same timing, and discharge / suction port 157b and discharge / suction port 157c perform the same operation at the same timing but in the opposite direction to discharge / suction ports 157a and 157d (air discharge or suction).

[0057] When the servo valve 151 having two vanes 155a, 155b shown in Fig. 4 is employed, the angle at which the rotating part 153 can rotate is smaller than that of the rotary drive part 50 shown in Fig. 2, but the torque that can be applied to the rotating part 153 can be approximately twice that of the rotary drive part 50 shown in Fig. 2, making it easier to apply a large torque to the output shaft 5. The rotary drive part may have a motor instead of the servo valve. Then, a gear fixed to the output shaft of the motor may be meshed with a gear fixed to the cylindrical outer circumferential surface of the rotating part, thereby transmitting the rotational power of the motor to the rotating part to rotate the rotating part.

[0058] Also, the spring body 70 is configured as a cylinder 76 provided with slits 78, and the pitch on both ends of the spring body 70 is shorter than the pitch on the center side of the spring body. However, as shown in Fig. 5, i.e., a perspective view of a modified spring body 90, the spring body 90 may be configured as a coil spring, and the pitch on both ends 91, 92 of the spring body 90 may be shorter than the pitch on the center side 93 of the spring body 90.

[0059] Alternatively, the fluid pressure actuator of the present disclosure may employ any spring body with an unequal pitch in which the pitch at both ends is not shorter than the pitch at the center. For example, the fluid pressure actuator of the present disclosure may employ a spring body in which the pitch at both ends is longer than the pitch at the center. Alternatively, the fluid pressure actuator of the present disclosure may employ a spring body in which the pitch on the front side of the center in the X direction of the spring body is the same and the pitch on the rear side of the center in the X direction of the spring body is also the same, with the pitch on the front side being different from the pitch on the rear side.

[0060] Also, although the case where the spring body 70 is made of a vibration-damping metal and has an uneven pitch has been described, the spring body provided in the fluid pressure actuator of the present disclosure may be made of a vibration-damping metal, but the pitch of the spring body may not be an uneven pitch. Alternatively, the spring body provided in the fluid pressure actuator of the present disclosure may not be made of a vibration-damping metal, but the pitch of the spring body may be an uneven pitch.

[0061] Second embodiment 6 is a schematic axial cross-sectional view of a fluid pressure actuator 101 according to a second embodiment of the present disclosure. Note that, in the fluid pressure actuator 101 of the second embodiment, explanations of the same operational effects and modified examples as those of the fluid pressure actuator 1 of the first embodiment will be omitted. The fluid pressure actuator 101 of the second embodiment can be used as a chip mounter that presses and mounts an electronic component, for example, a chip, in a predetermined position on wiring in a molten state on a substrate.

[0062] As shown in FIG. 6, the fluid pressure actuator 101 includes an output shaft 105, a sleeve 110, an output shaft advance / retreat drive unit 130, a rotation drive unit 150, a spring body 170, a rotation angle detection sensor 175, an axial displacement sensor 180, and a control device 185.

[0063] In the fluid pressure actuator 101, the first pressure chamber 109a is provided on the front side in the X direction, whereas the second pressure chamber 109b is provided in the peripheral region of the spring body 170 (including the internal space of the spring body 170). Also, the front end 171 of the spring body 170 is attached to the output shaft 105 by pressing it against the end face of the output shaft 105 in the X direction with a washer 162 that moves forward in the X direction by tightening a screw 161, and the rear end 172 of the spring body 170 is attached to the rotating part 153 by tightening a female screw provided on the cylindrical inner circumferential surface of the rear end 172 into a male screw provided at the front end of the cylindrical outer circumferential surface of the rotating part 153.

[0064] The fluid pressure actuator 101 differs from the fluid pressure actuator 1 in which the control device 85 is located externally in that it includes a control device 185. The fluid pressure actuator 101 has a collet 190 at the front end in the X direction. The fluid pressure actuator 101 also has a passage 181 inside the output shaft 105 that is connected to an external vacuum pump 195 and opens to the front end face of the collet 190 in the X direction. With this configuration, an electronic component can be adsorbed onto the collet 190 of the fluid pressure actuator 1 by performing vacuum pumping with the vacuum pump 195, and the electronic component can be detached from the collet 190 by stopping vacuum pumping with the vacuum pump 195.

[0065] In the fluid pressure actuator 101, a hydrostatic bearing is also generated between the output shaft 105 and the sleeve 110 by using the servo valve 131 of the output shaft advance / retract drive unit 130 to flow air in the directions indicated by the arrows c and d, or in the opposite direction. In the fluid pressure actuator 101, the output shaft 105 has a large diameter shaft portion 105a, a small diameter shaft portion 105b having a smaller diameter than the large diameter shaft portion 105a, and a rod-shaped portion 105c, and the large diameter shaft portion 105a and the small diameter shaft portion 105b are connected by the rod-shaped portion 105c. A part (most part) of the rod-shaped portion 105c passes through the internal space of the spring body 170. The axial center of the rod-shaped portion 105c approximately coincides with the axial center of the spring body 170.

[0066] In the fluid pressure actuator 101 of the second embodiment, the spring body 170 has an uneven pitch and is configured as a cylinder having slits. The spring body 170 is also configured of a vibration-damping metal, for example, a vibration-damping alloy containing, by atomic weight percent, approximately 73% manganese, approximately 20% copper, approximately 5% nickel, and approximately 2% iron. As a result, even in the fluid pressure actuator 101 that can be used as a chip mounter, it is possible to substantially prevent the spring body 170 from causing surging during operation, and it is possible to achieve highly accurate positioning of the output shaft 105 in the X direction and highly accurate positioning of the output shaft 105 in the circumferential direction. [Explanation of symbols]

[0067] 1,101 Fluid pressure actuator, 5,105 Output shaft, 5a,105a Large diameter shaft portion, 5b,105b Small diameter shaft portion, 5c Flange portion, 6 Nut, 7 Cylinder outer peripheral surface, 8a,8b End surface, 9a,9b,109a,109b Pressure chamber, 10,110 Sleeve, 10a,10b Inner peripheral surface portion, 10c,10d End surface, 30,130 Output shaft advance / retract drive portion, 31,131 Servo valve of output shaft advance / retract drive portion, 32a First passage, 32b Second passage, 32c Third passage, 32d Fourth passage, 32e Fifth passage, 32f Sixth passage, 50,150 Rotation drive portion, 51,151 Servo valve of rotation drive portion, 52,152 Case, 52a cylindrical inner peripheral surface, 53,153 rotating portion, 53a cylindrical outer peripheral surface, 54,154a,154b protruding portion, 55,155a,155b vane, 56a pressure chamber, 57a,57b,157a,157b,157c,157d discharge suction port, 58 wall portion, 59a,59b rolling bearing, 60a,60b O-ring, 65 flange portion, 70,90,170 spring body, 71 front end portion, 72 rear end portion, 73 spring portion, 73a,73b both ends of spring portion, 73c center portion of spring portion, 75,175 rotation angle detection sensor, 76 cylinder, 77 pin, 78 slit, 80,180 Axial displacement sensor, 85,185 control device, 86 control unit, 86a axial displacement calculation unit, 86b rotation angle calculation unit, 86c forward / backward drive control unit, 86d rotation drive control unit, 87 memory unit, 105c rod-shaped portion, 162 washer, 190 collet, 195 vacuum pump.

Claims

1. an output shaft having at least one first pressure surface; a sleeve having an inner circumferential surface portion that supports the output shaft movably in the axial direction, and a second pressure receiving surface that, together with the first pressure receiving surface, defines at least a portion of a pressure chamber; an output shaft advance / retract drive unit that varies a volume of the pressure chamber by changing an amount of fluid supplied to the pressure chamber to advance / retract the output shaft in the axial direction relative to the sleeve; a rotating portion disposed radially outside the output shaft and rotatably and coaxially with the output shaft; a spring body arranged radially outside the output shaft and substantially coaxially with the output shaft so as to be extendable and contractable in the axial direction, the spring body having one end fixed to the output shaft and the other end fixed to the rotating part, and causing the output shaft to rotate in the circumferential direction when the rotating part is rotationally driven; At least one of the pitch of the spring body being non-uniform and the spring body being made of a material having vibration-damping properties is satisfied, The pitch of the spring body is unequal, When the spring body is used in a twisted state, the spring body can transmit rotational power to the output shaft, A fluid pressure actuator capable of suppressing surging, which occurs when the spring body transmits rotational power to the output shaft and causes the spring body to vibrate in small increments.

2. A fluid pressure actuator as described in claim 1, wherein the pitch at both ends of the spring body is shorter than the pitch at the center of the spring body.

3. an output shaft having at least one first pressure surface; a sleeve having an inner circumferential surface portion that supports the output shaft movably in the axial direction, and a second pressure receiving surface that, together with the first pressure receiving surface, defines at least a portion of a pressure chamber; an output shaft advance / retract drive unit that varies a volume of the pressure chamber by changing an amount of fluid supplied to the pressure chamber to advance / retract the output shaft in the axial direction relative to the sleeve; a rotating portion disposed radially outside the output shaft and rotatably and coaxially with the output shaft; a spring body arranged radially outside the output shaft and substantially coaxially with the output shaft so as to be extendable and contractable in the axial direction, the spring body having one end fixed to the output shaft and the other end fixed to the rotating part, and causing the output shaft to rotate in the circumferential direction when the rotating part is rotationally driven; At least one of the pitch of the spring body being non-uniform and the spring body being made of a material having vibration-damping properties is satisfied, The pitch of the spring body is unequal, The spring body is formed of a cylindrical body having a slit, A fluid pressure actuator, wherein a density of the slits present at ends of the spring body in the axial direction is higher than a density of the slits present at a central portion of the spring body in the axial direction.

4. 4. The fluid pressure actuator according to claim 1, wherein the spring body is made of Mn-20Cu-5Ni-2Fe (M2052 alloy).

5. A fluid pressure actuator described in any one of claims 1 to 4, wherein the spring body, having an uneven pitch, is approximately plane-symmetrical with respect to a virtual plane that passes through the center of the axial direction of the spring body and is approximately perpendicular to the axial direction.

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