JP2015004631A - Material testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material testing machine capable of extending service life of the device even testing force is repeatedly applied by driving of a ball screw.SOLUTION: When a second support part 12 is moved by reciprocating movement by predetermined number using a same area on screw shafts 13, 14, a first support part 22 and the second support part 12 are moved to a same direction by distance equal to or more than the distance of reciprocating movement. Thereby a contact area of the screw shafts 13, 14 and a ball on a ball screw becomes an area different from an area where they have contacted repeatedly, so that arrival of fatigue limit of predetermined areas on the screw shafts 13, 14 may get late.

Description

  The present invention relates to a material testing machine that performs a fatigue test by repeatedly applying a test force to a test piece.

  As such a material testing machine, both ends of a test piece are gripped by an upper chuck and a lower chuck, and either one of the upper chuck or the lower chuck is reciprocated by a small distance with respect to the other, thereby moving the test piece against the test piece. The test force is repeatedly applied. Conventionally, a hydraulic cylinder is used as a drive source for reciprocating a small distance with respect to the other of either the upper chuck or the lower chuck.

  However, in order to use the hydraulic cylinder, it is necessary to install an expensive hydraulic source separately from the apparatus main body. In addition, this hydraulic power source must always be operated in order to keep the hydraulic pressure constant, which is contrary to the demand for energy saving, and there is a possibility of polluting the environment with the operation of the hydraulic device. Furthermore, there arises a problem that a large installation space for the hydraulic power source is required.

  On the other hand, a material testing machine that performs a tensile test or a compression test uses a motor as a drive source instead of a hydraulic cylinder. Such a material testing machine includes a table provided with a lower grip for gripping the lower end of a test piece, and a pair of screw shafts erected on the table so as to be rotatable in a vertical direction. And an upper grip for gripping the upper end of the test piece, and a cross head movable along the screw axis. The cross head is connected to a pair of screw shafts via nuts. In addition, a drive transmission mechanism having a speed reducer connected to a motor is disposed at the lower end of each screw shaft, and the pair of screw shafts rotate in synchronization with each other by driving the motor. When performing a tensile test or a compression test using a material testing machine having such a configuration, the pair of screw shafts are rotated by driving the motor while both ends of the test piece are gripped by the upper gripper and the lower gripper. Then, by raising and lowering the crosshead, a test force (tensile load or compressive load) is applied to the test piece (Patent Document 1).

JP 2012-42263 A

  Since a material testing machine that applies a test force to a test piece by moving a crosshead by rotating a screw shaft by a motor as described in Patent Document 1 does not require a hydraulic source, apparatus cost and installation space It is possible to reduce energy consumption and to meet the demands for energy saving and environmental protection. When used for a fatigue test in which a test piece is subjected to a fatigue test, a problem arises that the life of the apparatus is shortened.

  That is, in a material testing machine that performs a fatigue test of a test piece by repeatedly applying a test force to the test piece, the crosshead needs to be reciprocated several million times in a small range of about several μm, for example. Therefore, when a material testing machine using a screw shaft is used for a fatigue test, the same area of the screw shaft in the ball screw will repeatedly contact the ball, and that area will reach the service limit in a short time. The problem of reaching it arises.

  The present invention has been made to solve the above-described problems, and provides a material testing machine capable of extending the life of an apparatus even when a test force is repeatedly applied by driving a ball screw. Objective.

  According to the first aspect of the present invention, both ends of the test piece are gripped by the first chuck and the second chuck, and the second chuck is reciprocated by a small distance with respect to the first chuck. A material testing machine that repeatedly applies a test force to a fatigue test to perform a fatigue test, the first support part supporting the first chuck, the first support part, the first chuck and the second chuck. A moving mechanism that moves in a direction parallel to the direction in which the test force is connected, a second support that supports the second chuck, and a motor that is disposed in a direction parallel to the direction in which the test force is applied. A ball screw comprising: a screw shaft that rotates by driving; a nut that is disposed on the second support portion and is screwed with the screw shaft; and a plurality of balls that are disposed between the screw shaft and the nut; By the motor A contact position control unit that changes a contact position between the screw shaft and the ball when a test force is repeatedly applied to the test piece by controlling rotation of the screw shaft; It is characterized by that.

  According to a second aspect of the present invention, in the first aspect of the present invention, the contact position control unit is a region between a plurality of balls arranged around the screw shaft in the ball screw, and A first contact position changing operation for changing a contact position between the screw shaft and the ball; and the nut is moved by a distance equal to or larger than a size of the ball screw in a direction parallel to the axis of the screw shaft. A second contact position changing operation for changing the contact position between the screw shaft and the ball is performed by moving the screw shaft in the axial direction.

  According to the first aspect of the present invention, the same region of the screw shaft in the ball screw is repeatedly formed by changing the contact position between the screw shaft and the ball when the test force is repeatedly applied to the test piece. Contact with the ball can be reduced. For this reason, even when the test force is repeatedly applied by driving the ball screw, the life of the apparatus can be further extended.

  According to the second aspect of the present invention, the region between the plurality of balls disposed around the screw shaft in the ball screw and a size in a direction parallel to the axis of the screw shaft of the nut in the ball screw is greater than or equal to the size. By using both of the regions separated from each other by distance, it is possible to reduce the same region of the screw shaft in the ball screw from repeatedly contacting the ball.

1 is a schematic diagram of a material testing machine according to a first embodiment of the present invention. FIG. 3 is a partial longitudinal sectional view of a ball screw including a screw shaft 13 and a nut 15. It is a top view for demonstrating arrangement | positioning of the some ball | bowl 10 in a ball screw. 3 is a block diagram showing a functional configuration of a control unit 60. FIG. It is a schematic diagram of the material testing machine which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the material testing machine which concerns on 3rd Embodiment of this invention.

  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 according to a first embodiment of the present invention.

  The material testing machine grips both ends of the test piece 100 with the first chuck 21 and the second chuck 11 and reciprocates the second chuck 11 with respect to the first chuck 21 to move the test piece 100 to the test piece 100. On the other hand, a fatigue test is performed by repeatedly applying a test force. This material testing machine includes a first support portion 22 that supports the first chuck 21, a second support portion 12 that supports the second chuck 11, a drive mechanism 30 for the first support portion 22 and the second support portion 12, and the like. Is provided.

  The first support portion 22 is a pair of screw shafts 23, 24 disposed in a direction parallel to a direction in which a test force is applied to connect the pair of nuts 25, 26 and the first chuck 21 and the second chuck 11. Is movable in a direction parallel to the direction in which the test force is applied. That is, a pair of nuts 25 and 26 are built in both ends of the first support portion 22. A pair of left and right screw shafts 23 and 24 are screwed to the pair of nuts 25 and 26, respectively. A pulley 37 disposed on the screw shaft 23 and a pulley 38 disposed on the screw shaft 24 are connected by a belt 39. The pulley 40 disposed on the screw shaft 24 is connected to a pulley 41 disposed on the rotation shaft of the motor 43 by a belt 46. Further, a rotational position detector 45 of the screw shaft 24 such as a rotary encoder is disposed at the lower end portion of the screw shaft 24. When the pair of screw shafts 23 and 24 rotate in synchronization with the drive of the motor 43, the first support portion 22 moves up and down together with the first chuck 21. Then, the rotational angle position of the screw shaft 24 at that time is detected by the rotational position detector 45, and the position information is transmitted to the control unit 60.

  The second support portion 12 is parallel to the direction in which the test force is applied to connect the first chuck 21 and the second chuck 11 by the action of a ball screw including a pair of nuts 15 and 16 and a pair of screw shafts 13 and 14. It can move in the direction. That is, a pair of nuts 15 and 16 are built in both ends of the second support portion 12. A pair of left and right screw shafts 13 and 14 are screwed to the pair of nuts 15 and 16, respectively. A pulley 31 disposed on the screw shaft 13 and a pulley 32 disposed on the screw shaft 14 are connected by a belt 33. The pulley 34 disposed on the screw shaft 14 is connected to a pulley 35 disposed on the rotation shaft of the motor 42 by a belt 36. Further, a rotational position detector 44 of the screw shaft 14 such as a rotary encoder is disposed at the lower end of the screw shaft 14. When the pair of screw shafts 13, 14 rotate in synchronization with the driving of the motor 42, the second support portion 12 moves up and down together with the second chuck 11. Then, the rotation angle position of the screw shaft 14 at that time is detected by the rotation position detector 44, and the position information is transmitted to the control unit 60.

  FIG. 2 is a partial longitudinal sectional view of a ball screw including the screw shaft 13 and the nut 15, and FIG. 3 is a plan view for explaining the arrangement of the plurality of balls 10.

  This ball screw has a configuration in which a large number of balls 10 are interposed between a screw shaft 13 and a nut 15. As shown in FIG. 3, a large number of balls 10 are arranged at fixed angles θ around the screw shaft 13. In FIG. 3, the angle between the balls 10 is exaggerated. The other ball screw including the screw shaft 14 and the nut 16, the ball screw including the screw shaft 23 and the nut 25, and the ball screw including the screw shaft 24 and the nut 26 also have the same configuration as that in FIGS. 2 and 3.

  FIG. 4 is a block diagram illustrating a functional configuration of the control unit 60.

  As shown in FIG. 1, the material testing machine includes a control unit 60 that controls the entire apparatus. The control unit 60 controls the rotation of the screw shafts 13 and 14 by the motor 42 so that the contact position between the screw shafts 13 and 14 and the ball 10 when the test force is repeatedly applied to the test piece 100. It functions as an abutting position control unit for changing. As a functional configuration, the control unit 60 stores a position calculation unit 61 for calculating a contact position between the screw shafts 13 and 14 and the ball 10, and a contact position between the screw shafts 13 and 14 and the ball 10. And a storage unit 62. The controller 60 is connected to the rotational position detectors 44 and 45 and the motors 42 and 43 described above.

  When the fatigue test is executed by the material testing machine having the above-described configuration, the first chuck 21 and the second chuck 11 have a distance corresponding to the size of the test piece 100 to be subjected to the fatigue test. The distance between the first support portion 22 and the second support portion 12 is changed. At this time, the screw shafts 23 and 24 are rotated by driving the motor 43, and the screw shafts 13 and 14 are rotated by driving the motor 42. Then, both ends of the test piece 100 are gripped by the first chuck 21 and the second chuck 11.

  In this state, the test force is repeatedly applied to the test piece 100 by reciprocating the second chuck 11 with respect to the first chuck 21 by a small distance. In this case, by driving the motor 42, the screw shafts 13 and 14 are rotated in the forward and reverse directions by a minute angle, so that the second support portion 12 that supports the second chuck 11 is raised and lowered by a minute distance. The number of times of raising and lowering is, for example, 1 million times. And this raising / lowering distance is generally a distance not exceeding 1 mm in many cases.

  Here, for example, in order to raise and lower the second support part 12 together with the second chuck 11 by 0.01 mm, when the lead (length moved by one rotation) of the screw shafts 13 and 14 of the ball screw is 5 mm. Means that the screw shafts 13 and 14 repeat [0.01 / 5] rotation, that is, rotation in the forward and reverse directions within a range of 0.72 degrees. For this reason, the screw shafts 13 and 14 and the ball 10 are repeatedly contacted in the same region within a range of 0.72 degrees, and the region of the screw shafts 13 and 14 becomes the fatigue limit in a short time.

  For this reason, in this material testing machine, when the second support part 12 is reciprocated a predetermined number of times using the same region of the screw shafts 13 and 14, the first support part 22 and the second support part 12 are moved. A configuration is adopted in which movement is made in the same direction by a distance greater than or equal to the reciprocation distance. By adopting such a configuration, the contact region between the screw shafts 13 and 14 and the ball 10 becomes a region different from the region that has already repeatedly contacted, and a predetermined region in the screw shafts 13 and 14 becomes a fatigue limit. Can be delayed.

  In this case, the position calculation unit 61 in the control unit 60 calculates the contact area of the screw shafts 13 and 14 with the ball 10 based on the signal from the rotational position detector 44. And the memory | storage part 62 in the control part 60 memorize | stores the contact area | region. Further, the position calculation unit 61 calculates the rotation angles of the screw shafts 13, 14, 23, and 24 that are necessary for making the contact region between the screw shafts 13, 14 and the ball 10 different from the region that has already been repeatedly contacted. To do. Then, the screw shafts 13, 14, 23, and 24 are rotated by driving the motors 42 and 43, and the first support portion 22 and the second support portion 12 are moved in the same direction by a necessary distance.

  The movement of the first support portion 22 and the second support portion 12 may be performed during a material test for one test piece 100 or whenever the material test for one test piece 100 is completed. May be. That is, when the test force is repeatedly applied 1 million times to one test piece 100, the first support portion 22 and the second support portion 12 are provided each time the test force is repeatedly applied 100,000 times. The first support portion 22 and the second support portion 12 may be moved each time the fatigue test on one test piece 100 is completed by repeatedly applying a test force of 1 million times.

  Incidentally, as shown in FIG. 3, in the ball screw, a large number of balls 10 are arranged at fixed angles θ around the screw shaft 13. For this reason, the position calculation unit 61 in the control unit 60 calculates the rotation angle of the screw shafts 13 and 14 so that the contact region between the screw shafts 13 and 14 and the ball 10 is different from the region that has already repeatedly contacted. In this case, it is necessary that the area does not overlap with the contact position by the next ball 10 arranged at a certain angle with each other. Therefore, the position calculation unit 61 in the control unit 60 is a contact position between the screw shafts 13 and 14 and the ball 10 in a region between the plurality of balls 10 arranged around the screw shafts 13 and 14 in the ball screw. The first abutting position changing operation for changing the nut and the nuts 13 and 14 together with the second support portion 12 are screwed together by a distance equal to or larger than the size in the direction parallel to the axis of the screw shafts 13 and 14 of the nuts 15 and 16 in the ball screw. A second contact position changing operation for changing the contact position between the screw shafts 13 and 14 and the ball 10 by moving the shafts 13 and 14 in the axial direction is executed.

  As shown in FIG. 3, the first contact position changing operation is performed when a plurality of balls 10 arranged around the screw shafts 13 and 14 are separated from each other by a distance corresponding to an angle θ. This is an operation of changing the contact position between the screw shafts 13 and 14 and the ball 10 in a region between the angles θ. For example, as shown in FIG. 3, when a large number of balls 10 are arranged at a certain angle θ around the screw shaft 13, the angle θ is set to 7.2 degrees, for example. In the first contact position changing operation, the contact position can be changed 10 times, assuming that the screw shafts 13 and 14 are repeatedly rotated in the forward and reverse directions within a range of 0.72 degrees. Only by this first contact position changing operation, the lifetime of the apparatus can be increased by ten times.

  In the second contact position changing operation, the nuts 15 and 16 are moved in the vertical direction together with the second support portion 12 by a distance equal to or larger than the vertical size of the nuts 15 and 16 disposed on the second support portion 12. This is an operation of changing the contact position between the screw shafts 13 and 14 and the ball 10. For example, when the vertical size of the nuts 15 and 16 disposed on the second support portion 12 is 10 cm, the nuts 15 and 16 are moved together with the second support portion 12 by 10 cm or more in the vertical direction. Accordingly, the contact position between the screw shafts 13 and 14 and the ball 10 can be changed.

  The position calculation unit 61 in the control unit 60 executes the first contact position change operation and the second contact position change operation as described above, whereby the contact position between the screw shafts 13 and 14 and the ball 10. Can be changed efficiently.

  Next, another embodiment of the present invention will be described. FIG. 5 is a schematic diagram of a material testing machine according to the second embodiment of the present invention. In addition, about the member similar to 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the material testing machine which concerns on 1st Embodiment mentioned above, the structure which raises / lowers the 2nd support part 12 with a pair of screw shafts 13 and 14 was employ | adopted. On the other hand, in the material testing machine according to the second embodiment, the frame-shaped second support portion 17 is used, and the nut 19 disposed on the second support portion 17 is screwed. By rotating the screw shaft 18 arranged in a direction parallel to the direction in which the test force connecting the chuck 21 and the second chuck 11 is applied by the motor 42, the frame-shaped second support portion 17 is moved to the second direction. It is configured to move up and down together with the chuck 11.

  Also in the material testing machine according to the second embodiment, the position calculation unit 61 in the control unit 60 has a screw shaft 18 and a ball in a region between a plurality of balls 10 arranged around the screw shaft 18 in the ball screw. The first abutting position changing operation for changing the abutting position with respect to 10 and the screw of the nut 19 together with the second support portion 12 by a distance equal to or larger than the size in the direction parallel to the axis of the screw shaft 18 of the nut 19 in the ball screw. By performing the second contact position changing operation for changing the contact position between the screw shaft 18 and the ball 10 by moving the shaft 18 in the axial direction, the life of the apparatus can be extended. .

  Next, still another embodiment of the present invention will be described. FIG. 6 is a schematic diagram of a material testing machine according to a third embodiment of the present invention. In addition, about the member similar to 2nd Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the material testing machine according to the above-described second embodiment, the screw shaft 18 for raising and lowering the second support portion 17 is rotated by the motor 42 and the screw shafts 23 and 24 for raising and lowering the first support portion 22. The configuration in which the motor 43 is rotated by the motor 43 is employed. In contrast, in the material testing machine according to the third embodiment, the screw shaft 18 for raising and lowering the second support portion 17 and the screw shafts 23 and 24 for raising and lowering the first support portion 22 are provided. A configuration in which the motor is rotated by a single motor 49 is employed.

  In the material testing machine according to the third embodiment, in order to raise and lower the first support portion 22 and the second support portion 17, a drive shaft 55 that faces in a direction parallel to the screw shafts 18, 23, and 24 is disposed. Has been. A pulley 56 disposed on the lower end portion of the drive shaft 55 and a pulley 57 disposed on the rotation shaft of the motor 49 are connected by a belt 58. A pulley 51 is disposed on the upper end portion of the drive shaft 55 via a clutch 53, and a pulley 52 is disposed on a central portion of the drive shaft 55 via a clutch 54.

  Similar to the material testing machine according to the first and second embodiments described above, the pulley 37 disposed on the screw shaft 23 and the pulley 38 disposed on the screw shaft 24 are connected by a belt 39. The pulley 40 disposed on the screw shaft 24 is connected to the drive shaft 55 by a belt 46 and a pulley 52 disposed via a clutch 54. Further, the pulley 34 disposed on the screw shaft 18 is connected to the drive shaft 55 by a belt 36 and a pulley 51 disposed via a clutch 53.

  In the material testing machine according to the third embodiment, the clutch 53 and the clutch 54 selectively connect the pulley 51, the pulley 52, and the drive shaft 55 according to a command from the control unit 60. When the pulley 51 and the drive shaft 55 are connected by the clutch 53, the screw shaft 18 is rotated by driving the motor 49, and the second support portion 17 is moved up and down together with the second chuck 11. On the other hand, when the pulley 52 and the drive shaft 55 are connected by the clutch 54, the screw shafts 23 and 24 are rotated by driving the motor 49, and the first support portion 22 is moved up and down together with the first chuck 21.

  Also in the material testing machine according to the third embodiment, the position calculation unit 61 in the control unit 60 has a screw shaft 18 and a ball in a region between a plurality of balls 10 arranged around the screw shaft 18 in the ball screw. The first abutting position changing operation for changing the abutting position with respect to 10 and the screw of the nut 19 together with the second support portion 12 by a distance equal to or larger than the size in the direction parallel to the axis of the screw shaft 18 of the nut 19 in the ball screw. By performing the second contact position changing operation for changing the contact position between the screw shaft 18 and the ball 10 by moving the shaft 18 in the axial direction, the life of the apparatus can be extended. .

  In the material testing machine according to the third embodiment, the first support portion 22 and the second support portion 17 cannot be raised and lowered simultaneously. For this reason, the movement of the first support portion 22 and the second support portion 17 for changing the contact position between the screw shaft 18 and the ball 10 cannot be performed during a material test on one test piece 100. Therefore, the movement of the first support portion 22 and the second support portion 17 for changing the contact position between the screw shaft 18 and the ball 10 needs to be performed when the material test for one test piece 100 is completed. There is.

  In the above-described embodiments, both the first support part 22 and the second support parts 12 and 17 are lifted and lowered by a ball screw. At this time, the second support parts 12 and 17 that reciprocate accurately by a minute distance need to be lifted and lowered by a ball screw. However, the first support part 22 is provided with other screw mechanisms such as trapezoidal screws and other moving mechanisms. You may employ | adopt the structure which raises / lowers using.

  Further, in the above-described embodiment, the support portion including the chuck that holds the upper end of the test piece 100 is used as the first support portion, and the support portion including the chuck that holds the lower end of the test piece 100 is reciprocated by a minute distance. Although the second support part is used, the support part having a chuck for gripping the lower end of the test piece 100 is used as the first support part, and the support part having the chuck for gripping the upper end of the test piece 100 is reciprocated by a minute distance. It is good also as a 2nd support part.

10 Ball 11 Second Chuck 12 Second Support Part 13 Screw Shaft 14 Screw Shaft 15 Nut 16 Nut 17 Second Support Part 18 Screw Shaft 19 Nut 21 First Chuck 22 First Support Part 23 Screw Shaft 24 Screw Shaft 25 Nut 26 Nut DESCRIPTION OF SYMBOLS 42 Motor 43 Motor 44 Rotation position detector 45 Rotation position detector 49 Motor 60 Control part 61 Position calculating part 62 Memory | storage part 100 Test piece

Claims (2)

While holding both ends of the test piece with the first chuck and the second chuck, the test force is repeatedly applied to the test piece by reciprocating the second chuck with respect to the first chuck by a minute distance. A material testing machine for performing fatigue tests,
A first support part for supporting the first chuck;
A moving mechanism for moving the first support portion in a direction parallel to a direction in which a test force is applied to connect the first chuck and the second chuck;
A second support part for supporting the second chuck;
A screw shaft that is arranged in a direction parallel to the direction in which the test force is applied and that is rotated by driving a motor, a nut that is provided in the second support portion and is screwed with the screw shaft, the screw shaft, and the screw shaft A ball screw comprising a plurality of balls disposed between the nuts;
A contact position control unit that changes the contact position between the screw shaft and the ball when the test force is repeatedly applied to the test piece by controlling the rotation of the screw shaft by the motor;
A material testing machine characterized by comprising: The material testing machine according to claim 1,
The contact position control unit includes:
A first contact position changing operation for changing a contact position between the screw shaft and the ball in a region between a plurality of balls disposed around the screw shaft in the ball screw;
By moving the nut in the axial direction of the screw shaft by a distance equal to or larger than the size of the ball screw in the direction parallel to the axial center of the screw shaft, the screw shaft and the ball come into contact with each other. A second contact position changing operation for changing the position;
Performing material testing machine.

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