JP2007240418A - Hardness tester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hardness tester capable of high precision measurement by imparting a little load for a soft measurement object. <P>SOLUTION: The hardness meter for measuring the hardness of the measurement object by detecting the relative positional change between the measurement object and pressed needle by abutting the press needle to the measurement object, and the hardness of the measurement object is obtained characteristically comprises: the loading mechanism holding the press needle with leaf spring; the movable mechanism for moving the load imparting mechanism; and the driving part of the movable mechanism constituted with the voice coil motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an industrial product such as rubber and plastics, not a hard material such as a metal material, and a hardness measuring instrument used in medical, health and food industries such as skin, muscle, fruit and food. In particular, it is a contact-type hardness tester that performs measurement by bringing a push needle into contact with an object to be measured, and includes a load applying mechanism in which the push needle is held by a leaf spring, and further movable for moving the load applying mechanism. The present invention relates to a hardness meter having a mechanism.

  The measurement principle of the hardness meter is roughly classified into a variable load type and a constant load type, and the present invention is a technique related to the constant load type. In the constant load type, the push needle is first brought into slight contact with the object to be measured, this state is set as the initial position, and then a larger load than that in the initial state is applied to the object to be measured. Is the hardness.

  The mechanism of the antenna device in the prior art will be described with reference to FIG. The voice coil motor 202 is composed of a magnetic circuit unit including a yoke 220 and a magnet 221 attached thereto, and a voice coil 222 which is a movable unit, and generates a magnetic force corresponding to a current supplied to the voice coil 222. It is like that. The contact 201 is attached to a movable part of the voice coil motor 202 and moves up and down so as to contact the object to be measured with a predetermined force. The movable part of the voice coil motor 202 is elastically supported by a parallel plate spring 203 formed of two plate springs, and the parallel plate is generated by the force generated by the voice coil motor 202 and the reaction force received by the contact 201 from the object to be measured. The spring 203 is displaced. On the other hand, the stator of the voice coil motor 202 is attached to the movable portion 205 of the movable mechanism. The housing 206 is attached to a dedicated stand, for example. A strain gauge 209 is attached to the parallel leaf spring 203, and when the parallel leaf spring 203 is displaced to bend, the displacement amount can be detected by the output of the strain gauge 209. A movable portion 205 of the movable mechanism is engaged with a feed screw 210 connected to a rotating shaft of the DC motor 214 at a nut 211, and a large stroke can be moved by the rotation of the DC motor 214. The outside of the nut portion 211 of the movable portion 205 is slidable with respect to a guide 216 fixed to the housing 206 via a linear bearing 212. An angle encoder 215 is attached to the shaft of the DC motor 214 and detects the rotation angle of the DC motor 214. This rotation angle is proportional to the amount of movement of the movable portion 205 of the movable mechanism by the feed screw 210. The dimension of the object to be measured is determined from the sum or difference of the amount of movement of the feed screw 210 and the amount of displacement of the parallel leaf spring 203. (For example, refer to Patent Document 1.)

JP-A-60-119402 (page 15, FIG. 2)

  Since the hardness meter in the prior art uses a DC motor with an encoder connected to a ball screw as the movable mechanism, a steady position error due to step drive occurs, and this error becomes a deformation error of the leaf spring, and the object to be measured An error occurs in the load applied to the. As a result, a difference occurs in the amount of movement of the movable mechanism and appears as an error in the hardness value.

  In addition, in the load application mechanism, when the push needle is suspended from a parallel plate spring in the form of a cantilever, the tip of the push needle moves in the axial direction and moves in the lateral direction. It becomes.

  An object of the present invention is to solve the above-described problems of the prior art and to provide a hardness meter capable of measuring with high accuracy without being affected by the surface state of the measurement surface of the object to be measured.

In order to solve the above problems and achieve the object, the hardness meter according to the present invention detects and detects a relative position change between the push needle and the measured object by bringing the tip of the push needle into contact with the measured object. In a hardness tester that determines the hardness of the object to be measured based on the measured displacement,
A load generation unit that generates a load in response to a load application command, and a first position detection unit that detects a displacement amount of a leaf spring that is deformed when the load is applied to the push needle or the push needle contacts the object to be measured; A load applying mechanism that applies a commanded load to the object to be measured via the push needle, a drive unit that moves the load applying mechanism in the direction of approaching or moving away from the object to be measured, and the amount of movement of the load applying mechanism And a movable mechanism having a second position detection unit for detecting the movement, and the drive unit has a voice coil motor.

  With this configuration, it is possible to drive the movable part without any stationary position error, and it is possible to minimize the load error caused by the deformation of the leaf spring. Therefore, it is possible to provide a highly accurate hardness meter with little measurement error. Can do.

  The load applying mechanism includes a push needle, a support member that supports the push needle, a base that holds the support member so as to be movable along the push needle axis, and a constant interval across the base. A pair of leaf springs disposed opposite to each other, and a first position detection portion disposed between the pair of leaf springs to detect displacement of the push needle, the leaf spring comprising a central spring portion and the central spring portion And a center point of the central spring part is fixed to the support member, a center point of the both side springs is fixed to the base, and a pair of leaf springs is provided for each spring part. The straight lines passing through the center point are arranged so as to form approximately 90 degrees with each other, the push needle is supported via a leaf spring, and the first position detector is located on or near the push needle axis, It is provided at a substantially central position between the leaf springs.

  With this configuration, the pair of leaf springs has strong rigidity against the force from the lateral direction perpendicular to the axial direction of the push needle without using a sliding position holding means such as a bearing or a guide mechanism. Acting as a member, there is almost no lateral movement of the tip of the push needle. Furthermore, the resistance against the action of the lateral force generated by the shape of the contact surface of the push needle of the object to be measured has at least the same resistance against the action from the four directions where the support points of the leaf springs are present. become. Further, when the push needle receives a lateral force, the push needle and the link member connected to the push needle are moved based on the center position between the pair of leaf springs. The variation in direction is minimized. As a result, it is possible to provide a highly accurate hardness meter with little measurement error.

  And since it can give from a very small load to the needle axis direction, an accurate and reproducible measurement result can be obtained.

  The first position detection unit provided in the load applying mechanism includes a differential transformer or a Hall element.

  With this configuration, since the displacement amount of the push needle in the axial direction can be directly obtained, a highly accurate hardness meter with little measurement error can be provided.

  In addition, the drive unit is configured so that the load applying mechanism is positioned with respect to the measured object so that the deformation of the leaf spring maintains the initial state before applying the load in a state where the load is applied to the measured object via the push needle. It is characterized by controlling.

  With this configuration, the load error caused by the deformation of the leaf spring can be minimized, so that a highly accurate hardness meter with little measurement error can be provided.

  According to the present invention, a pair of leaf springs has a strong rigidity against a force from a lateral direction perpendicular to the axial direction of the push needle without using a sliding position holding means such as a bearing or a guide mechanism. It acts as a holding member, and there is almost no lateral movement of the tip of the push needle, and it shows a flexible movement in the axial direction of the push needle. With this configuration, the load generated in the load voice coil motor can be controlled by controlling the movable part with the drive voice coil motor so that the deformation of the leaf spring in the load applying mechanism is in the initial state before the load is applied. Since only the test object is added to the object to be measured, the load accuracy can be improved. As a result, it is possible to provide a hardness meter that can measure with high accuracy with little measurement error.

  Exemplary embodiments of a hardness meter according to the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 are diagrams showing a configuration of a hardness meter according to an embodiment of the present invention. 3 and 4 are views showing the configuration of the spring support portion provided in the load applying mechanism in the embodiment of the present invention. FIG. 5 is a diagram showing the configuration and operation of the hardness meter in the embodiment of the present invention. 6 and 7 are views showing a configuration of position detection provided in the load application mechanism in the embodiment of the present invention. Note that, in the following description of the embodiment and the accompanying drawings, the same reference numerals are given to the same components, and duplicate descriptions are omitted.

FIG. 1 is an exploded perspective view of a hardness meter in the present embodiment. FIG. 2 is a perspective view of the hardness meter in the present embodiment. As shown in FIGS. 1 and 2, the pusher needle 1 is fixed to the support member 2 on the spring support portion 40, and is supported by two leaf springs 4 a and 4 b having different 90 ° directions via the link member 3. The leaf springs 4a and 4b are attached to the base 6 through the support column 5, and a first member for detecting the deformation amount of the leaf springs 4a and 4b on the link member 3 between the two leaf springs 4a and 4b. One position detector 7 (see FIG. 4) is attached. The coil 20 is mounted on the spring support portion 40 and operates in conjunction with the push needle 1. The spring support portion 40 is attached on the cradle 22.
The movable part 60 is provided with cradles 21, 22, and 23. A holder 27 to which a yoke 25 and a magnet 26 are attached is fixed to the cradle 21 with screws. The base 6 of the spring support 40 is fixed to the cradle 22 with screws. The coil 20, the yoke 25, and the magnet 26 constitute a voice coil motor 30. The voice coil motor 30 serves to generate a load on the object to be measured. A load applying mechanism 50 is formed by the spring support 40 and the voice coil motor 30.

  The linear bearing 51 is attached between the movable part 60 and the fixed part 70, and the movable part 60 moves according to the guide of the linear bearing 51. The coil 52 is attached to the movable part 60, and the holder 55 to which the yoke 53 and the magnet 54 are attached is fixed to the fixing part 70 with screws. The coil 52, the yoke 53, and the magnet 54 constitute a voice coil motor 80. The movable part 60 is driven by the voice coil motor 80.

  An optical second position detection unit 90 that detects the amount of movement of the spindle 91 connected to the glass scale is passed through between the light receiving and emitting elements disposed opposite to each other with a glass scale having a slit formed thereon, and is fixed to the fixing unit with a screw. . The tip of the spindle 91 is in contact with the cradle 23, and the position of the movable part 60 is detected by the second position detector 90.

In this way, the movable unit 60, the fixed unit 70, the linear bearing 51, the voice coil motor 80, and the second position detection unit 90 form the movable mechanism 100.
The fixing unit 70 is attached to a stand or the like having a table for placing a measurement object (not shown), and the hardness of the measurement object is measured.

  Next, the shape and deformation | transformation of the leaf | plate spring of the spring support part used for the load provision mechanism in the hardness meter of this embodiment are demonstrated using FIG. The leaf spring 4a and the leaf spring 4b have the same shape and will be described together. As shown in FIG. 3, the leaf springs 4a and 4b are thin plates and have a rectangular shape, and have a pair of symmetrically arranged long holes 12a and 12b extending in parallel with the longitudinal direction thereof. A central spring portion 8 and two side spring portions 9a and 9b, which are divided into three portions with the long holes 12a and 12b as boundaries, are formed. The central spring portion 8 is provided between the pair of long holes 12a and 12b, the double-side spring portions 9a are provided outside the long holes 12a, and the double-side spring portions 9b are provided outside the long holes 12b. Further, a fixing hole 13 is formed at the position of the center point 10 of the central spring portion 8, and fixing holes 14a and 14b are formed at the positions of the center points 11a and 11b of the spring portions 9a and 9b, respectively. ing.

  Next, the deformation state of the leaf springs 4a and 4b formed in this way will be described. The center points 11a and 11b of the two side spring portions 9a and 9b of the leaf springs 4a and 4b are fixed points, the center point 10 of the center spring portion 8 is a movable point, and the center point 10 of the center spring portion 8 is shown in FIG. When a force in the direction of the arrow is applied as shown in b), deformation as shown by the alternate long and short dash line occurs. When a force is applied in the direction of arrow C, the two side spring portions 9a and 9b have a shape in which the planes at both end portions in the longitudinal direction are curved in the direction of arrow C with the center points 11a and 11b as the base points. The portion 8 has a shape curved in a convex shape with the plane at both ends in the longitudinal direction as a base point and the center point 10 as a vertex. On the other hand, when a force is applied in the direction of arrow D, the two side spring portions 9a and 9b have a shape in which the planes at both ends in the longitudinal direction are bent in the direction of arrow D with the center points 11a and 11b as the base points. The central spring portion 8 has a concave curved shape with the center point 10 as the base point with the planes at both ends in the longitudinal direction as the base point.

  Next, the structure of the spring support part used for the load provision mechanism in the hardness meter of this embodiment is demonstrated using FIG. A push needle 1, a support member 2 that holds the push needle 1, a base 6 that holds the support member 2 so as to be movable along the push needle axis, and a fixed interval with the base 6 therebetween. A pair of leaf springs 4a and 4b, and a first position detector 7 that is disposed between the pair of leaf springs 4a and 4b and detects the displacement of the push needle 1. Each of the pair of leaf springs 4a and 4b has a center spring portion 8 and both side spring portions 9a and 9b located on both sides of the center spring portion 8, and the center point 10 (see FIG. 3) of the center spring portion 8 is a link member. The center points 11a and 11b (see FIG. 3) of the springs 9a and 9b are fixed to the base 6 via the support column 5, respectively. Further, the pair of leaf springs 4a and 4b are arranged such that the straight lines A and B passing through the center points 10, 11a and 11b of the respective spring portions 8, 9a and 9b form approximately 90 degrees.

Next, the configuration and operation of the hardness meter according to the present embodiment will be described with reference to FIG. As shown in FIG. 5, in a state where the push needle 1 is not in contact with the object to be measured 110, the output of the Hall element 31 is taken into a circuit unit (not shown), and this value is used as a reference value at the time of control. Next, a current based on a load application command is applied to the coil 20 from a circuit unit (not shown), and a series of members such as the leaf springs 4a and 4b and the push needle 1 connected to the coil 20 move in the direction of arrow E. To do. At this time, the magnet 32 approaches the Hall element 31 side and the output value of the Hall element 31 increases. Next, a current based on a movement command is applied to the coil 52 from a circuit unit (not shown), and the movable unit 60 moves in the direction of arrow F according to the guidance of the linear bearing 51. Then, the push needle 1 comes into contact with the object 110 to be measured, and the push needle 1 is further pushed forward. When the output value of the Hall element 31 coincides with the initial value, the applied current to the coil 52 is held, and the movable portion 60 is moved. Stop. The movement command to the coil 52 works to bring the output value of the Hall element 31 closer to the initial value, and when the output value of the Hall element 31 is higher than the initial value, the amount of current applied to the coil 52 is increased, 1 is the measured object side 110
On the contrary, when the output value of the Hall element 31 is lower than the initial value, the amount of current applied to the coil 52 is reduced, and the push needle 1 is controlled to be pulled away from the object 110 to be measured. Next, a larger current is applied to the coil 52 than from a circuit application (not shown), and the push needle 1 is pushed toward the measured object side 110. At this time, since the magnet 32 approaches the Hall element 31 side, the output value of the Hall element 31 increases. Then, the current applied to the coil 52 is increased in the direction of the arrow F in the direction of returning the output value of the Hall element 31 to the initial value, and the movable portion 60 is moved. When the output value of the Hall element 31 coincides with the initial value, the current applied to the coil 52 is held, and the movable part 60 is stopped. The amount of movement of the spindle 91 of the second position detector 90 (see FIG. 2) at this time is taken as the hardness value of the object 110 to be measured.

  FIG. 6 is a cross-sectional view showing a configuration of a first position detection unit used in the load application mechanism of the hardness meter of the present invention. As shown in FIG. 6, the first position detection unit 7 includes a hall element 31, a magnet 32, and a magnet holding member 33. The hall element 31 is attached to a plane facing the plate spring 4 a of the base 6 directly or via a substrate 34. The magnet holding member 33 is fixed to the link member 3, and the cylindrical magnet 32 is fixed to the magnet holding member 33. The magnet 32 is arranged in such a direction that its cylindrical central axis is parallel to the axial direction of the link member 3 and the cylindrical center of the magnet 32 and the detection unit center of the hall element 31 are aligned. Furthermore, the end surface of the magnet 32 on the Hall element 31 side and the end surface (mold surface) of the Hall element 31 are arranged to face each other with a certain gap.

  According to the first position detector 7 configured in this manner, the distance between the magnet 32 and the Hall element 31 changes as the push needle 1 moves in the axial direction, and the magnetic flux density with respect to the gap is changed. The Hall output voltage changes due to the change of. By this change, the displacement amount of the push needle 1 can be directly detected. As a result, it is possible to provide a highly accurate hardness meter free from measurement errors.

  FIG. 7 is a cross-sectional view showing the configuration of another embodiment of the first position detection unit used in the load application mechanism of the hardness meter of the present invention. As shown in FIG. 7, the position detector 7 is provided at an approximately equal distance from one leaf spring 4a and the other leaf spring 4b, and the outer cylinder portion 43 of the first position detector 7 is a base. 6 is attached to a hole 45 formed in the center of the adhesive 6 by adhesion. The outer cylinder portion 43 incorporates two coils 44a forming a differential transformer. On the other hand, the magnetic material core 44 b is disposed between the core support member 46 and the core fixing member 47. The link member 3 is configured by the core 44b, the core support member 46, and the core fixing member 47, and the core 44b operates in conjunction with the movement of the push needle 1.

  When the core 44b moves to the two coils 44a of the differential transformer in an excited state in which an AC voltage is applied from a circuit unit (not shown), the reactance of the two coils 44a changes, corresponding to the amount of movement of the core 44b. An output voltage is obtained. By this change, the displacement amount of the push needle 1 can be directly detected.

  Further, when the push needle 1 receives a lateral force, the push needle 1 and the link member 3 connected to the push needle 1 are moved based on the positions of substantially equal distances between the leaf springs 4a and 4b. The fluctuation in the vertical direction of the core 44b constituting the position detection unit 7 can be suppressed. As a result, it is possible to provide a highly accurate hardness meter with little measurement error.

It is a disassembled perspective view which shows the hardness meter of this invention. It is a perspective view which shows the hardness meter of this invention. It is a 2nd page figure which shows the spring shape used for the load provision mechanism of the hardness meter of this invention, and a deformation | transformation state. It is a perspective view which shows the structure of the spring support part used for the load provision mechanism of the hardness meter of this invention. It is a side view which shows the structure and operation | movement of a hardness meter of this invention. It is sectional drawing which shows the structure of the 1st position detection part used for the load provision mechanism of the hardness meter of this invention. It is sectional drawing which shows the structure of other embodiment of the 1st position detection part used for the load provision mechanism of the hardness meter of this invention. It is sectional drawing which shows the hardness meter of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Push needle 2 Support member 3 Link member 4a, 4b Leaf spring 5 Strut 6 Base 7 First position detection part 8 Central spring part 9a, 9b Both-side spring part 10, 11a, 11b Center point 12a, 12b Long hole 13, 14a, 14b, 45 Hole 20, 44a, 52 Coil 21, 22, 23 Receiving base 25, 53 Yoke 26, 32, 54 Magnet 27, 55 Holder 30, 80 Voice coil motor 31 Hall element 33 Magnet holding member 34 Substrate 40 Spring Support part 43 Outer cylinder part 44b Core 46 Core support member 47 Core fixing member 50 Load applying mechanism 51 Linear bearing 60 Movable part 70 Fixed part 90 Second position detection part 91 Spindle 100 Movable mechanism 110 Device under test

Claims (4)

In a hardness meter that determines the hardness of the object to be measured based on the detected displacement by contacting the tip of the push needle with the object to be measured and detecting a relative position change between the push needle and the object to be measured.
A load generation unit that generates a load in response to a load application command, and a first position detection unit that detects a displacement amount of a leaf spring that is deformed when the load is applied to the push needle or the push needle contacts the object to be measured; A load applying mechanism that applies a commanded load to the object to be measured via the push needle, a drive unit that moves the load applying mechanism in a direction toward or away from the object to be measured, and the load applying mechanism. A hardness meter, comprising: a movable mechanism having a second position detection unit for detecting a movement amount, wherein the driving unit has a voice coil motor.   The load applying mechanism includes a push needle, a support member that supports the push needle, a base that holds the support member so as to be movable along the push needle axis, and a fixed interval across the base. A pair of leaf springs disposed opposite to each other, and a first position detector disposed between the pair of leaf springs to detect displacement of the push needle, the leaf spring comprising a central spring portion and the central spring portion And a center point of the central spring part is fixed to the support member, a center point of the both side springs is fixed to the base, and the pair of leaf springs is The straight lines passing through the center points of the respective spring portions are arranged so as to form approximately 90 degrees with each other, the push needle is supported via the leaf spring, and the first position detector is located on the push needle axis or It is located in the vicinity thereof and is provided at a substantially central position between the pair of leaf springs. Hardness tester according to claim 1,.   The hardness meter according to claim 1, wherein the first position detection unit includes a differential transformer or a Hall element. In the state where the load is applied to the object to be measured via the push needle, the drive unit applies the load applying mechanism to the object to be measured so that the deformation of the leaf spring maintains the initial state before the load is applied. The hardness meter according to any one of claims 1 to 3, wherein the position is controlled.

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