JP5222810B2 - Electromagnetic actuator and material testing machine - Google Patents

Description

  The present invention relates to an electromagnetic actuator that generates a driving force by an electromagnetic force, and a material testing machine that uses the electromagnetic actuator as a load actuator.

  For example, in a material testing machine that applies a load of an arbitrary waveform to a test piece and performs a fatigue strength test, etc., along with the diversification of test materials, such as parts such as polymer materials and micro machines that are test pieces, There is a demand for increasing the load control accuracy while reducing the absolute value of the load. In such a material testing machine for test pieces, a material tester using an electromagnetic actuator as a load actuator is employed instead of a conventional hydraulic cylinder as a load actuator. As such an electromagnetic actuator, for example, the one described in Patent Document 1 is known.

JP 2004-205337 A

  By the way, in such an electromagnetic actuator, since it is necessary to supply a driving current to the reciprocating coil, a configuration in which the power supply unit and the coil are connected by a lead wire or the like has been conventionally employed. ing. At this time, in a material testing machine that performs a fatigue test by repeatedly applying a load to the test piece, the repeated operation is continued until the test piece is fatigued. It is required to be long.

  Conventionally, such a lead wire has a structure in which the lead wire itself is easily bent by bundling a large number of thin metal wires in a spiral shape or in a straight line shape, and by reducing the stress associated with the metal wire, The one with a long fatigue life is used. However, since such a lead wire is easily bent, there is a problem that a large stress concentration is generated in the connection terminal portion of the lead wire due to the influence of the inertial force due to acceleration when the coil reciprocates at a high frequency. . In particular, a crimp terminal or the like is generally used at the connection portion at one end of the lead wire. In this case, the lead wire near the terminal portion is greatly plastically deformed, and this portion is caused by vibration. Due to the effect of stress, the coil is susceptible to damage as the coil reciprocates.

  In addition, in order to solve such a problem, it is possible to reduce the stress against deformation by adopting a configuration in which the lead wire is spirally wound like, for example, a telephone wire. In addition, the mass of the spiral lead wire itself is increased, and an even greater burden is applied to the terminal portion. To prevent this, the stress concentration is reduced when the lead wire is supported by the holding member in the vicinity of the terminal portion. However, even if such a configuration is adopted, the stress is concentrated near the holding portion. Cannot be resolved.

  In addition, when a lead wire is used, it is generally difficult to estimate the stress distribution on the lead wire, so it is difficult to predict the life of the lead wire itself.

  On the other hand, it is also conceivable to use a thin lead plate having a substantially U-shaped longitudinal cross-section instead of the lead wire. When such a lead plate is used, there is no deformation in the direction perpendicular to the longitudinal section, that is, the direction intersecting the reciprocating direction, and its rigidity is also compared with that of the lead wire. Since it can be made large, the amount of vibration is small, and vibration stress due to its own weight is not received. Therefore, it is possible to prevent stress concentration from occurring near the terminal portion as in the case of using a lead wire.

  However, when such a lead plate is used, it is required that the estimated life can be predicted and that a long-term reliability can be obtained corresponding to the use conditions.

  The present invention has been made to solve the above-described problem, and can predict an estimated life and can set the estimated life to a required value or more, and the electromagnetic actuator as a load actuator. An object is to provide a material testing machine used as the above.

The invention according to claim 1 comprises a main body having a magnet therein, a moving shaft having a coil on the outer periphery thereof and capable of reciprocating relative to the main body, and driving current to the coil. In the electromagnetic actuator for reciprocating the moving shaft with respect to the main body by supplying, a first support portion attached to the main body, a second support portion attached to the moving shaft, and a longitudinal sectional shape thereof Is formed in a substantially U shape, one end of which is attached to the first support part and the other end is attached to the second support part, and the coil is attached to one end of the lead plate. A current supply means for supplying a drive current for supply; and a conductive member for connecting the other end of the lead plate and the coil, wherein the first support portion and the second support portion have the longitudinal sectional shape. Lies in a U-shape A plane that abuts against a straight portion of the plate near the attachment position with respect to the first support portion and the second support portion to prevent vibration of the lead plate near the attachment position with respect to the first support portion and the second support portion. The lead plate thickness t and the lead plate curvature radius R are set so that the fatigue life of the lead plate due to the reciprocating movement of the moving shaft is 10 ⁸ cycles or more. It is characterized by that.

  According to a second aspect of the present invention, in the first aspect of the present invention, the lead plate has a curvature radius R of 20 mm to 50 mm.

  The invention according to claim 3 is the invention according to claim 2, wherein the thickness t of the lead plate is 0.2 mm or less.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the lead plate is made of a copper alloy spring material.

  According to a fifth aspect of the invention, in the invention of the fourth aspect, the lead plate is made of beryllium copper.

A sixth aspect of the present invention is a material testing machine comprising the electromagnetic actuator according to any one of the first to fifth aspects.

  According to the first to fifth aspects of the invention, the estimated life of the lead plate can be predicted, and stress concentration and the influence of vibration are prevented, and the estimated life is greater than the required value. It becomes possible to set to.

Further , the action of the flat contact portion can prevent vibration near the mounting position on the lead plate. For this reason, it becomes possible to prevent the influence of the stress fluctuation resulting from the vibration generated in the vicinity of the mounting portion.

According to the sixth aspect of the present invention, the estimated life of the lead plate can be predicted, and the estimated life can be set to a required value or more by preventing the influence of stress concentration and vibration. As a result, the material test can be performed stably for a long period of time.

It is a schematic diagram of a material testing machine using an electromagnetic actuator according to the present invention as a load actuator. It is a perspective view which decomposes | disassembles and shows the principal part of the electromagnetic actuator which concerns on this invention. FIG. 3 is a schematic diagram showing a lead plate 31 together with first and second support portions 32 and 33, a moving shaft 21 and the like. FIG. 3 is a schematic diagram showing a lead plate 31 together with first and second support portions 32 and 33, a moving shaft 21 and the like. FIG. 3 is a schematic diagram showing a lead plate 31 together with first and second support portions 32 and 33, a moving shaft 21 and the like. It is a graph which shows the swing fatigue characteristic of a beryllium alloy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine using an electromagnetic actuator according to the present invention as a load actuator. FIG. 2 is an exploded perspective view showing a main part of the electromagnetic actuator according to the present invention.

  This material testing machine is for performing a fatigue strength test or the like of the test piece 43 by applying an arbitrary waveform load to the test piece 43.

  The electromagnetic actuator according to the present invention is composed of a lid portion 12, a casing portion 13, and a guide portion 14. The main body 11 is provided with an exciting coil 15 functioning as an electromagnet inside thereof, and is wound around a wheel 22 around its outer peripheral portion. And a moving shaft 21 that can reciprocate relative to the main body 11. The moving shaft 21 can be moved up and down with respect to the main body 11 by being guided by a pair of bearings 17 attached to the lid portion 12 and the casing portion 13 in the main body 11.

  A pair of first support portions 32 are attached to the lid portion 12 of the main body 11 via the attachment portion 16. A pair of second support portions 33 are attached to the upper end of the moving shaft 21. And between these 1st support parts 32 and the 2nd support parts 33, the longitudinal cross-sectional shape comprises a substantially U shape, respectively, while the one end is attached to the 1st support part 32, and others A thin plate-like lead plate 31 having an end attached to the second support portion 33 is disposed.

  The end portion of the lead plate 31 on the first support portion 32 side is connected to the drive current supply portion 52 via the feeder line 37. The drive current supply unit 52 is also connected to the excitation coil 15 described above via the feeder line 38. Further, the end portion on the second support portion side of the lead plate 31 is connected to the coil 23 described above via the conductive member 36.

  The material testing machine using this electromagnetic actuator includes a displacement meter 44 connected to the upper end of the moving shaft 21 of the electromagnetic actuator. The material testing machine further includes an upper grip 41 connected to the lower end of the moving shaft 21. The material testing machine further includes a lower grip 42 that holds the test piece 43 together with the upper grip 41. The lower gripper 42 is connected to the load cell 45.

  The displacement meter 44 and the load cell 45 described above are connected to the control unit 51. The test force loaded on the test piece 43 is detected by the load cell 45. Further, the displacement amount of the test piece 43 is detected by a displacement meter 44. Signals from the load cell 45 and the displacement meter 44 are input to the control unit 51. The control unit 51 transmits a control signal to the drive current supply unit 52 based on signals from the load cell 45 and the displacement meter 44, and the drive current supply unit 52 generates a drive current for the electromagnetic actuator based on the control signal. Create The moving shaft 21 of the electromagnetic actuator reciprocates based on this driving current, and the reciprocating movement of the moving shaft 21 applies repeated stress to the lead plate 31 and its shape is repeatedly deformed.

  3 to 5 are schematic views showing the lead plate 31 together with the first and second support portions 32 and 33, the moving shaft 21, and the like. 3 shows a state in which the first support portion 32 and the second support portion 33 are at the same height, and FIG. 4 shows a state in which the second support portion 33 has moved to a position elevated from the first support portion 32. Further, FIG. 5 shows a state in which the second support portion 33 has moved to a position lowered from the first support portion 32.

  As described above, one end of the lead plate 31 is attached to the first support portion 32 by the fixing screw 35, and the other end is attached to the second support portion 33 by the fixing screw 34. The lead plate 31 is made of a material having electrical conductivity and spring property and having high fatigue strength. As the material of the lead plate 31, beryllium copper is most preferable. Further, as the material of the lead plate 31, a copper alloy spring material such as a phosphor bronze spring material, a white spring spring material, a copper-titanium alloy, a copper-nickel alloy, or a copper-nickel-tin alloy can be used. .

  The thickness t and the curvature radius R of the lead plate 31 are set so that the estimated life due to fatigue accompanying the reciprocating movement of the moving shaft 21 in the electromagnetic actuator becomes a value required in the material testing machine.

  That is, as shown in FIG. 3, the mounting interval of the lead plate 31 by the first support portion 32 and the second support portion 33 is approximately twice the radius of curvature R of the lead plate 31. As shown in FIGS. 4 and 5, when the second support portion 33 moves in the vertical direction, a part of the lead plate 31 is repeatedly deformed from R to infinity. Here, when the Young's modulus of the lead plate 31 is E and the cross-sectional secondary moment is I, the maximum bending moment M acting on the surface of the lead plate 31 is expressed by the following equation.

  M = [E · I] / R

  At this time, the maximum bending stress σmax in the tensile direction acting on the surface of the lead plate 31 is expressed by the following expression when the sectional modulus of the lead plate 31 is Z.

  σmax = M / Z = [E / R] · [I / Z]

  Furthermore, when the thickness of the lead plate 31 is t, since [I / Z] = [t / 2], the maximum bending stress σmax in the tensile direction acting on the surface of the lead plate 31 is expressed by the following equation. Will be represented.

  σmax = [tE / 2R]

  From this equation, it can be seen that the smaller the thickness t of the lead plate 31, the smaller the repeated stress, and the larger the radius of curvature R, the smaller the repeated stress.

  Here, the attachment interval of the lead plate 31 by the first support portion 32 and the second support portion 33 is 50 mm (the radius of curvature R of the lead plate 31 is 25 mm), and the lead plate 31 has a beryllium copper having a thickness t of 0.1 mm. When the Young's modulus is 130 GPa, the maximum bending stress σmax = 260 MPa from the above formula.

  FIG. 6 is a graph showing the swing fatigue characteristics of the beryllium alloy.

In this graph, the horizontal axis indicates the number of repetitions, and the vertical axis indicates the maximum bending stress. And the solid line in this graph has shown the fatigue curve. When the maximum bending stress σmax = 260 MPa obtained based on the above formula is applied to this graph, the bending stress is sufficiently lower than the fatigue curve even in the region where the number of repetitions is 10 ⁸ cycles. fatigue life caused by the reciprocating movement of the moving shaft 21 in the lead plate 31, it can be seen that the ¹⁰⁸ cycles or more.

Thus, in the present invention, the thickness t of the lead plate 31 and the radius of curvature R of the lead plate 31 are set so that the fatigue life due to the reciprocating movement of the moving shaft 21 in the lead plate 31 is 10 ⁸ cycles or more. It is necessary to do. Here, generally, when the fatigue life becomes 1010 ⁸ cycles or more, even if stress due to reciprocating movement is continuously applied to the lead plate 31, a phenomenon such as cutting due to the fatigue life Is known to hardly occur.

  The radius of curvature R of the lead plate 31 is preferably 20 mm to 50 mm. When the curvature radius R is smaller than 20 mm, the maximum bending stress σmax with respect to the lead plate 31 is increased, and a necessary fatigue life cannot be obtained. On the other hand, when the radius of curvature R is greater than 50 mm, the resonance frequency of the lead plate 31 is decreased. For this reason, when the resonance frequency approaches the frequency (usually 200 Hz to 300 Hz) for performing the fatigue test of the test piece 43, a resonance phenomenon occurs, local stress is generated in the lead plate 31, and the fatigue life is adversely affected. Effect.

  Further, the thickness t of the lead plate 31 is preferably 0.2 mm or less in order to obtain a necessary fatigue life. However, the thickness t needs to be greater than the thickness that allows the lead plate 31 to maintain its shape.

  The cross-sectional area of the lead plate 31 is determined based on the drive current value supplied to the coil 23. At this time, since the thickness t of the lead plate 31 is limited based on the required fatigue strength, in order to obtain a necessary cross-sectional area, a method of increasing the width of the lead plate 31 and the number of the lead plates 31 are required. You can choose how to increase. However, when the width of the lead plate 31 is increased, the size of the fixing portion of the lead plate 31 also increases, and the weight of the lead plate 31 hinders the movement of the lead plate 31. For this reason, it is preferable that a plurality of lead plates 31 are stacked and fixed together by the same fixing portion.

  As shown in FIGS. 3 to 5, the first support portion 32 and the second support portion 33 are linear portions near the attachment positions of the lead plate 31 with respect to the first support portion 32 and the second support portion 33 ( A planar abutting portion 39 is provided which abuts against the infinite curvature portion and prevents vibration of the straight portion of the lead plate 31. When such a configuration is adopted, the linear portion near the mounting position of the lead plate 31 is restricted by the contact portion 39 and does not vibrate. It is possible to prevent the influence of stress fluctuations.

  The first support part 32 and the second support part 33 include an abutting part 39 having a length capable of abutting and guiding the linear part near the mounting position of the lead plate 31; and It is necessary to use one having rigidity sufficient to prevent vibration of the lead plate 31.

  In the above-described embodiment, the electromagnetic actuator is provided with the excitation coil 15 functioning as an electromagnet in the main body 11, but a permanent magnet may be used instead of the excitation coil 15. .

DESCRIPTION OF SYMBOLS 11 Main body 12 Cover part 13 Casing part 14 Guide part 15 Excitation coil 21 Moving shaft 22 Wheel 23 Coil 31 Lead plate 32 1st support part 33 2nd support part 36 Conductive member 37 Feed line 38 Feed line 39 Contact part 41 Upper grip Tool 42 Lower gripping tool 43 Test piece 44 Displacement meter 45 Load cell 51 Control unit 52 Drive current supply unit

Claims (6)

A main body having a magnet inside thereof, and a moving shaft having a coil on its outer peripheral portion and capable of reciprocating with respect to the main body, and supplying the driving current to the coil, In the electromagnetic actuator that reciprocates with respect to the main body,
A first support portion attached to the main body;
A second support attached to the moving shaft;
The longitudinal cross-sectional shape is substantially U-shaped, and one end thereof is attached to the first support portion, and the other end is attached to the second support portion.
Current supply means for supplying a drive current for supplying the coil to one end of the lead plate;
A conductive member connecting the other end of the lead plate and the coil;
The first support portion and the second support portion are in contact with a linear portion in the vicinity of an attachment position with respect to the first support portion and the second support portion of a lead plate having a substantially U-shaped longitudinal section, While having a planar contact portion for preventing vibration in the vicinity of the attachment position of the lead plate to the first support portion and the second support portion,
The electromagnetic actuator characterized in that the thickness t of the lead plate and the radius of curvature R of the lead plate are set so that the fatigue life due to the reciprocating movement of the moving shaft in the lead plate is 10 ⁸ cycles or more. . The electromagnetic actuator according to claim 1,
An electromagnetic actuator having a radius of curvature R of the lead plate of 20 mm to 50 mm. The electromagnetic actuator according to claim 2,
An electromagnetic actuator in which the thickness t of the lead plate is 0.2 mm or less. The electromagnetic actuator according to claim 3,
The lead plate is an electromagnetic actuator made of a copper alloy spring material. The electromagnetic actuator according to claim 4, wherein
The lead plate is an electromagnetic actuator made of beryllium copper. A material testing machine comprising the electromagnetic actuator according to any one of claims 1 to 5 .

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