JP2015072189A - Load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load cell which can have improved accuracy in measurement of a load relating to friction.SOLUTION: The load cell includes: an actuator 2 which oscillates in a prescribed excitation direction and of which one end side in the excitation direction is supported by a support member 1; a load sensor 3 which is fixed to the other end side of the actuator 2 to detect a force at least in the excitation direction; an oscillating body 4 which is supported by the support member 1 so as to be movable in the excitation direction and receives oscillation of the actuator 2 to be allowed to oscillate only in the excitation direction; a disk member 5 which is directly or indirectly brought into contact with a side surface of the oscillating body 4 to give resistance to oscillation of the oscillating body 4; an urging part 6 which urges at least one of the support member 1 and the disk member 5 in such a direction that the support member 1 and the disk member 5 are brought closer to each other; and an urging force sensor 7 which detects an urging force of the urging part 6. The load sensor 3 has a contact surface 3b which is brought into contact with the actuator 2 by an in-plane uniform force, and a centroid X of the oscillating body 4 is located on a line parallel with excitation direction, which passes a centroid O of the contact surface 3b.

Description

  The present invention relates to a load measuring device.

  The load measuring device is used, for example, when it is desired to measure the frictional force of a test piece. There is an increasing demand for load measuring devices, particularly in the study of the causes of brake squeal. For example, the relationship between the brake squeal, the friction coefficient of the brake pad, and the rotation speed of the brake rotor can be investigated by a load measuring device. However, the normal load measuring device cannot actively control the vibration of the brake pad (friction material), and it is difficult to further investigate the cause of the brake squeal.

  Therefore, in the apparatus described in Non-Patent Document 1, not only the relationship between the friction coefficient and the rotation speed but also the friction coefficient and the vibration speed (vibration) are obtained by actively applying vibration to the friction material assuming the brake pad by the piezoelectric element. The correlation between the frequency) and the brake noise can be investigated to some extent. This made it possible to further investigate the cause of brake squeal.

D & D Conference 2011 NO. 407 Influence of brake squeal vibration on speed dependence of pad friction coefficient

  However, in the apparatus described in Non-Patent Document 1, the influence of the inertia force (F = ma) on the pad side increases as the vibration frequency increases. The load sensor detected a value including this inertial force, and the noise component was large.

  This invention is made in view of such a situation, and it aims at providing the load measuring device which can improve the measurement precision of the load regarding friction.

  The load measuring apparatus according to aspect 1 of the present invention includes a support member, a vibration unit that vibrates in a predetermined vibration direction and one end side of the vibration direction is supported by the support member, and the other end of the vibration unit A load sensor that is fixed to a side and detects at least the force in the vibration direction, and is supported by the support member so as to be movable in the vibration direction, and receives vibration of the vibration portion and vibrates only in the vibration direction. A resistance is applied to the vibration of the measured vibration body by directly or indirectly contacting an allowable measured vibration body and a side surface of the measured vibration body parallel to the excitation direction. Detecting a resistance applying member, an urging portion that urges at least one of the support member and the resistance applying member in a direction in which the support member and the resistance applying member approach, and a force applied by the urging portion. An urging force sensor, and the load sensor includes the excitation unit and Has a contact surface for contacting the inner uniform force, the center of gravity of the object to be measured side vibrating body is located on a straight line parallel to the vibration direction passes through the center of gravity of the contact surface.

  According to the aspect 1 of the present invention, the center of gravity of the measured vibration body that generates the inertial force is on a straight line parallel to the excitation direction passing through the center of gravity of the contact surface between the load sensor and the excitation unit. , The rotational moment is suppressed. According to aspect 1, the influence of the rotation mode generated on the measured vibration body can be reduced as much as possible, the force (noise) other than the frictional force can be reduced, and the measurement accuracy of the load related to friction can be improved. Can do.

  The load measuring device according to aspect 2 of the present invention is the above-described aspect 1, wherein the center of gravity of the excitation unit, the center of gravity of the load sensor, and the center of gravity of the measured vibration body are on a straight line parallel to the excitation direction. Is located.

  According to the above aspect 2 of the present invention, the measured vibration body vibrates on a straight line passing through the center of gravity of the three members including vibrations (excitation unit, load sensor, measured vibration object). Thus, the influence of the inertial force can be reduced more reliably and stably.

  The load measuring device according to aspect 3 of the present invention further includes a sensor for measuring the acceleration, speed, or displacement of the measured vibration body in the aspect 1 or 2. According to the above aspect 3 of the present invention, the acceleration, speed, or displacement of the measured vibration body itself can be directly measured. According to this, for example, the relationship of the frictional force (friction coefficient) with respect to the vibration speed of the measured vibration body can be accurately investigated.

  In the load measuring device according to aspect 4 of the present invention, in any one of aspects 1 to 3, the load sensor detects only a load in the excitation direction. According to the aspect 4 of the present invention, a uniaxial force sensor is used as a load sensor, and the vibration target can be made smaller and lighter than other sensors (for example, a three-component force sensor). Thereby, the influence of inertia force (F = ma) can be further reduced, and the measurement accuracy can be improved.

It is a right view which shows the structure of the load measuring apparatus of 1st embodiment. It is a perspective view showing composition of a load measuring device of a first embodiment. It is a front view which shows the structure of the load measuring apparatus of 1st embodiment. It is a top view which shows the structure of the load measuring apparatus of 1st embodiment. It is a schematic diagram for demonstrating the actuator of 1st embodiment, a load sensor, and the base part of a vibrating body. It is a schematic diagram for demonstrating the contact surface of the load sensor of 1st embodiment. It is a right view which shows the structure of the load measuring device of 2nd embodiment.

  Next, the present invention will be described in more detail with reference to embodiments. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings. Each figure is a conceptual diagram and does not necessarily define the dimensions of the detailed structure.

<First embodiment>
As shown in FIGS. 1 to 4, the load measuring device according to the first embodiment includes a support member 1, an actuator (corresponding to a “vibration unit”) 2, a load sensor 3, and a vibrating body (“measured” 4, a disc member (corresponding to “resistance applying member”) 5, an urging unit 6, an urging force sensor 7, an acceleration sensor 8, and a control unit 9. ing. 1 will be described as a right side view of the load measuring device, that is, FIG. 3 will be described as a front view (front view) of the load measuring device. 2 to 4 show a load measuring device in which the disk member 5, the urging unit 6, the urging force sensor 7, and the control unit 9 are omitted. In the description, “up and down”, “left and right”, and “front and back” can be translated into “one and the other”.

  The support member 1 is a substantially L-shaped metal member that supports each part, and is arranged to engage with the rail Z so as to be movable in the front-rear direction. Specifically, the support member 1 includes a rectangular parallelepiped first main body 11, a rectangular parallelepiped second main body 12 extending upward from a rear portion of the upper surface of the first main body 11, a fixing portion 13, and a slide guide. Part 14. The fixing portion 13 is provided in a concave shape at a front portion of the upper surface of the first main body portion 11, and is formed so that the lower end portion of the actuator 2 can be fixed to the first main body portion 11. The slide guide portion 14 is provided on the front side surface of the second main body portion 12 and constitutes a rail that protrudes forward and extends vertically. The slide guide part 14 engages with a vibrating body 4 to be described later, and restricts the moving direction of the vibrating body 4 only in the vertical direction.

  The actuator 2 is an actuator that vibrates in the vertical direction and has a lower end bonded and fixed to the fixing portion 13. In the first embodiment, the vertical direction is the excitation direction of the actuator 2. Specifically, the actuator 2 includes a piezoelectric actuator portion 21 having a piezoelectric element, and a sensor fixing portion 22 that is bonded and fixed to one end (upper end) of the piezoelectric actuator portion 21. The piezoelectric actuator portion 21 is formed in a quadrangular prism shape. The piezoelectric actuator unit 21 vibrates in accordance with an electrical signal from a control unit 9 (a driver thereof) described later, and vibrates the vibrating body 4 via the sensor fixing unit 22 and the load sensor 3. An electrical signal (amplitude and frequency) to a driver that drives the piezoelectric actuator unit 21 is controlled by the control unit 9 (of which a function generator). The piezoelectric actuator unit 21 generates minute vibrations with an arbitrary amplitude and frequency.

  As shown in FIG. 5, the sensor fixing portion 22 includes a pedestal portion 221 and a bolt 222. The pedestal portion 221 is a rectangular parallelepiped member having a through hole 221a at the center. Bolts 222 are inserted through the through holes 221a, and the base portions 221 and the bolts 222 are engaged in the radial direction. The lower end surface of the base portion 221 is bonded to the upper end surface of the piezoelectric actuator portion 21. The bolt 222 is engaged with the through hole 221a of the base portion 221 so that the lower side is the head and the upper side is the shaft portion. The shape of the through hole 221a is a stepped shape in which the portion where the head portion of the bolt 222 is accommodated is larger in diameter than the portion where the shaft portion is accommodated. A gap C is formed between the head of the bolt 222 and the upper end surface of the piezoelectric actuator unit 21 so that the contact area does not change when the load sensor 3 receives a force. The load sensor 3 and the pedestal portion 221 are slidable with respect to the bolt 222.

  The load sensor 3 is a sensor for detecting a load, and is a ring-shaped sensor having a through hole 3a in the center. The load sensor 3 of the present embodiment is a uniaxial force sensor that detects only the load in the excitation direction (vertical direction). The load sensor 3 of the present embodiment is a quartz piezoelectric load sensor. Bolts 222 are inserted into the through holes 3a, and the load sensor 3 and the bolts 222 are engaged in the radial direction. The pedestal 221 and the load sensor 3 are fixed coaxially. The lower end surface of the load sensor 3 is in contact with the upper end surface of the pedestal portion 221. That is, the load sensor 3 has the contact surface 3b to which the force generated by the actuator 2 is transmitted.

  The contact surface 3b is a ring-shaped surface as shown in FIG. The contact surface 3b receives the force generated by the actuator 2 with a uniform in-plane (overall surface) force (pressure) by fixing the bolt 222 to the vibrating body 4. That is, the surface pressure of any one part of the contact surface 3b is the same as the surface pressure of any other part of the contact surface 3b. Although the surface pressure value changes during the measurement, the contact surface 3b receives a uniform surface pressure. A configuration that receives a uniform force in a plane is a configuration in which a plane and a plane are in uniform contact, and a similar force is applied to the plane.

  The vibrating body 4 is a member that has an object to be measured and vibrates as a whole with respect to vibration. Specifically, the vibrating body 4 includes a pedestal portion 41, a slide portion 42, and a pad 43. The pedestal portion 41 has a rectangular parallelepiped shape, and has a concave portion 41a that opens to communicate with the front surface and the upper surface. A pad 43 is fixed to the recess 41a. The pedestal portion 41 is fixed to the slide portion 42 (screwed in this embodiment). The pedestal portion 41 is a member that applies a preload to the load sensor 3 and also has a function of holding the slide portion 42 and the pad 43.

  As shown in FIG. 5, a female screw 41 b into which the bolt 222 is screwed is formed at the lower end of the pedestal 41. The female screw 41b is formed such that a straight line passing through the center of gravity X of the vibrating body 4 and parallel to the excitation direction (vertical direction) is the central axis. The load sensor 3 is fixed by being sandwiched between the pedestal portion 221 and the pedestal portion 41 when the bolt 222 is screwed into the female screw 41b.

  As shown in FIG. 4, the slide portion 42 is a rectangular parallelepiped member having a groove portion 42 a that engages with a rail portion of the slide guide portion 14. The slide portion 42 is allowed to move in the vertical direction by the slide guide portion 14 and is prohibited from moving in the left-right direction and the rearward direction. The movement of the slide part 42 in the front-rear direction is also restricted by the support member 1 fixed via the actuator 2. That is, the vibrating body 4 is allowed to vibrate only in the exciting direction (vertical direction).

  The pad 43 is a friction material that assumes a brake pad, and is an object to be measured in the present embodiment. The pad 43 is formed in a rectangular parallelepiped shape, and is fixed to the pedestal portion 41 so that one surface (surface to be measured) is a front surface. A side surface parallel to the excitation direction of the pad 43 (a surface extending in parallel), that is, a front end surface is a surface to be measured that comes into contact with the disk member 5. The vibrating body 4 of the first embodiment is configured to include an object to be measured.

  Here, the center of gravity X of the vibrating body 4 is located on a straight line (virtual straight line) A that passes through the center (center of gravity) O of the contact surface 3b and is parallel to the excitation direction (vertical direction). The position of the center of gravity X can be calculated by considering the density and shape of each part. The position of the center of gravity of each part is obtained from the center of gravity of the main body part of each part excluding wiring. The center O of the contact surface 3b is the center (center of gravity) of the ring (ring) as shown in FIG. Furthermore, in this embodiment, the center of gravity X of the vibrating body 4, the center of gravity X1 of the actuator 2, and the center of gravity X2 of the load sensor 3 are located on a straight line extending in the excitation direction.

  The disk member 5 is a cylindrical member that provides resistance to vibration of the vibrating body 4 by directly or indirectly contacting the front end surface of the vibrating body 4. In this embodiment, the disk member 5 is a disk that assumes a brake rotor. The position of the disk member 5 is fixed with respect to the support member 1. The disk member 5 is rotated by a drive device (for example, a motor) Y capable of rotation control. The disk member 5 is disposed such that the rotation axis extends in the front-rear direction. The measurement is started by bringing the rear end surface of the disk member 5 into contact with the front end surface of the pad 43. In the present embodiment, the disk member 5 rotates and directly contacts the pad 43 (vibrating body 4) to impart resistance against vibration to the pad 43. Although the pad 43 is a composite material, in this embodiment, since the pad 43 is in surface contact with the disk member 5, a measurement result including the characteristics of the composite material is obtained.

  The urging unit 6 is an urging unit that urges the support member 1 toward the disk member 5, and is, for example, an air pressure device. The urging unit 6 presses the support member 1 from behind the support member 1 to advance the support member 1 along the rail Z. The urging unit 6 urges the support member 1 to bring the support member 1 and the disk member 5 closer to each other and bring the pad 43 and the disk member 5 into contact with each other.

  The urging force sensor 7 is a sensor that measures the urging force (load) of the urging unit 6 to the support member 1. The biasing force sensor 7 of the present embodiment is a strain type load sensor. The urging force sensor 7 is disposed between the support member 1 and the urging unit 6. The biasing force sensor 7 detects a load in the front-rear direction.

  The acceleration sensor 8 is a sensor that measures the acceleration of the vibrating body 4. The acceleration sensor 8 is installed on the upper end surface of the pedestal portion 41 and measures the acceleration of the vibrating body 4 in the excitation direction (vertical direction). That is, the acceleration of the vibrating body 4 itself can be directly measured. Based on the acceleration measured by the acceleration sensor 8, the vibration speed, displacement, and the like can be calculated.

  The control unit 9 is a part that exerts control and measurement functions of the load measuring device, and includes various drivers, computers, and measuring instruments. The control unit 9 controls the driving of the actuator 2, the drive device Y, and the urging unit 6 according to the operation of the operator. That is, in this embodiment, the vibration frequency and amplitude of the actuator 2, the number of rotations of the disk member 5, and the pressing force of the pad 43 to the disk member 5 can be freely set. The control unit 9 receives and records information from the various sensors 3, 7, and 8. Then, the control unit 9 calculates and records the frictional force, the friction coefficient, the rotational speed of the disk member, the vibration speed, and the like based on information from the various sensors 3, 7, and 8. The control unit 9 is a general term for the control devices of each unit, and may be any unit that does not have the arithmetic function as long as it can control each unit.

(Operational effects of the first embodiment)
According to the configuration of the first embodiment, the center of gravity X of the vibrating body 4 is located on the straight line A. Thereby, the vibrating body 4 vibrates on the straight line A passing through the center of gravity X, and the fulcrum of the rotational moment of the inertial force due to the mass of the vibrating body 4 is on or near the straight line A, thereby reducing the influence of the inertial force. be able to. In other words, since the center of gravity X of the vibrating body 4 is coaxial with the sensor shafts of the actuator 2 and the load sensor 3, the influence of the rotation mode due to inertia during vibration can be reduced.

  Further, the inertial force increases as the vibration frequency (vibration speed) increases. However, when the vibrating body 4 vibrates on the straight line A, the influence of the rotation mode due to the inertial force can be reduced. That is, according to the present embodiment, with respect to the detection target of the load sensor 3, the force other than the frictional force applied to the pad 43 is reduced, the noise component is reduced, the SN ratio is improved, and accurate load measurement is possible. Become. According to the present embodiment, it is possible to measure frictional force (shear resistance) even under high frequency and large amplitude conditions. Thus, according to this embodiment, the influence of the rotation mode generated in the vibrating body 4 can be reduced as much as possible, and the measurement accuracy of the load related to friction can be improved. According to this embodiment, for example, it is possible to measure the relationship between the friction coefficient and the vibration speed under a constant urging force.

  Furthermore, in 1st embodiment, the gravity center X of the vibrating body 4, the gravity center X1 of the actuator 2, and the gravity center X2 of the load sensor 3 are located on one straight line (straight line A) extended in an excitation direction. Thereby, the vibrating body 4 vibrates on a straight line passing through all the centers of gravity, and the influence of the inertial force can be reduced more reliably and stably. Also, the design is easy.

  Furthermore, in the present embodiment, a uniaxial force sensor that is smaller and lighter than the three-component force sensor is adopted as the load sensor 3, so that the mass of the target (load sensor 3 and vibrating body 4) to which the actuator 2 applies vibrations. Can be reduced. Further, according to the present embodiment, the pedestal portion 41 has both a function of applying a preload to the load sensor 3 and a function of holding the slide portion 42 (slide member) and the pad 43 (measurement object). The mass of the body 4 can be reduced. Thus, in this embodiment, since the mass of the vibration target object of the actuator 2 can be reduced, the influence of inertia force (F = ma) can be further reduced.

  Further, in the pedestal portion 41 of the present embodiment, a female screw 41b is formed on the straight line A, and the actuator 2 (the pedestal portion 221) and the load sensor 3 are fixed to the pedestal portion 41 so as to be able to measure a load with a bolt 222. Thus, the center of gravity X can be easily arranged at a predetermined position (on the straight line A). In the present embodiment, each part can be automatically positioned at a predetermined position simultaneously with the fixing of the load sensor 3 or the like to the vibrating body 4.

<Second embodiment>
In the load measuring device according to the second embodiment, the pad 43 is changed to the metal block 430 and a test piece (measurement object) S is arranged between the metal block 430 and the disk member 5 as compared with the first embodiment. Is different. Therefore, only different parts will be described.

  As shown in FIG. 7, the vibrating body 4 of the second embodiment includes a pedestal portion 41, a slide portion 42, and a metal block 430. The metal block 430 is an iron rectangular parallelepiped member, and is fixed to the pedestal portion 41 like the pad 43. The center of gravity X3 of the vibrating body 4 of the second embodiment is located on the straight line A as in the first embodiment. The size and shape of the metal block 430 may be set so that the center of gravity is at the same position as X1. The metal block 430 is in contact with the disk member 5 through the test piece S, and can be said to be a measured object auxiliary member.

  The test piece S is a plate-like composite material assuming a shim. The test piece S is, for example, a member obtained by coating a plate-shaped iron material with an elastic member such as rubber. The test piece S is sandwiched in surface contact with the metal block 430 and the disk member 5 by the movement of the support member 1. In other words, the vibrating body 4 is in contact with the disk member 5 indirectly via the test piece S. The vibrating body 4 of the second embodiment has a configuration that does not include an object to be measured.

  In the second embodiment, the disk member 5 is fixed so as not to rotate, and an urging force is applied by the urging unit 6 in a state where the test piece S is sandwiched between the metal block 430 and the disk member 5, so that the vibrating body 4 is actuated as an actuator. 2. Shake according to 2. Thereby, the effect similar to 1st embodiment is exhibited, for example, the shearing characteristic of the test piece S can be measured. Note that the force measured by the load sensor 3 is a resultant force of the elastic modulus (spring force) in the shear direction of the test piece S and the viscous resistance force, and therefore, the two can be separated based on the phase information of the vibrating body 4. it can. When acceleration is used as a phase reference (0 degree), a 90-degree lag component is viscous resistance (damping), and a 180-degree lag component is elastic modulus. This acceleration is the acceleration in the excitation direction detected by the acceleration sensor 8.

<Other variations>
The present invention is not limited to the above embodiment. For example, the load sensor 3 may be a three-component force sensor that measures a load in three axial directions. Further, the load sensor 3 is not limited to a ring shape. In the above embodiment, the urging unit 6 urges the support member 1. However, the urging unit 6 may be arranged to urge the disk member 5 toward the support member 1. That is, the urging unit 6 may be any member that urges at least one of the support member 1 and the disk member 5 in the direction in which the support member 1 and the disk member 5 approach each other.

  Further, the bolt 222 may be formed so as to protrude downward from the lower end surface of the vibrating body 4 with the straight line A as the central axis. In this case, an internal thread may be formed at the upper end portion of the base portion 221 of the sensor fixing portion 22. That is, the actuator 2, the load sensor 3, and the vibrating body 4 may be fixed by a fastening member having the straight line A as the central axis so that the load can be measured. The vibrating body 4 has a part to be measured (pad 43) in part or is disposed on the part to be measured (test piece S) side in the load measuring device, and can be said to be a measured side vibrating body. The object to be measured is not limited to the pad 43 or the test piece S. The disc member 5 is not limited to a disc shape, and any member can be used as long as it can impart resistance to the object to be measured.

  Further, the acceleration sensor 8 may be replaced with a speed sensor or a displacement sensor. Even when a sensor such as the acceleration sensor 8 is not arranged, for example, a frictional force (frictional force in a measurement state) with respect to the control (predetermined vibration) of the actuator 2, a state in which vibration is actively applied, and a state in which vibration is not applied The frictional force can be accurately measured (for comparison). Moreover, the urging | biasing part 6 may be urged | biased manually which applies urging | biasing force by, for example, turning a screw or a handle type screw. Various sensors include simple instruments such as load cells.

  The piezoelectric actuator unit 21 may be formed in a cylindrical shape. In this case, by making the diameter of the head portion of the bolt 222 smaller than the inner diameter of the piezoelectric actuator portion 21, it is possible to measure the load with the load sensor 3 without forming the gap C. In the above embodiment, the center (center of gravity) O of the contact surface 3 b is located on the measurement axis of the load sensor 3. In the above embodiment, the center (center of gravity) O of the contact surface 3 b is located on the central axis of the actuator 2.

1: support member, 2: actuator (vibration unit), 21: piezoelectric actuator unit,
22: sensor fixing part, 221: pedestal part, 222: bolt,
3: Load sensor, 3b: Contact surface,
4: Vibrating body (measurement-side vibrating body), 41: base portion, 42: slide portion,
43: Pad, 430: Metal block, 5: Disk member (resistance imparting member),
6: urging unit, 7: urging force sensor, 8: acceleration sensor (sensor), 9: control unit,
X, X1, X2, X3: center of gravity, O: center of the contact surface (center of gravity)

Claims (4)

A support member;
A vibration unit that vibrates in a predetermined vibration direction and has one end side of the vibration direction supported by the support member;
A load sensor that is fixed to the other end of the excitation unit and detects a force in at least the excitation direction;
A measurement-side vibrating body that is supported by the support member so as to be movable in the excitation direction, and that is allowed to vibrate only in the excitation direction by receiving vibration of the excitation unit;
A resistance applying member that provides resistance to vibration of the measured vibration body by directly or indirectly contacting a side surface parallel to the excitation direction of the measured vibration body;
An urging portion that urges at least one of the support member and the resistance applying member in a direction in which the support member and the resistance applying member approach each other;
An urging force sensor for detecting an urging force of the urging unit;
With
The load sensor has a contact surface that is in contact with the excitation unit with a uniform in-plane force,
A load measuring device in which a center of gravity of the measured vibration body is located on a straight line passing through the center of gravity of the contact surface and parallel to the excitation direction. In claim 1,
The center of gravity of the excitation unit, the center of gravity of the load sensor, and the center of gravity of the vibration body to be measured are load measuring devices located on a straight line parallel to the excitation direction. In claim 1 or 2,
A load measuring device further comprising a sensor for measuring an acceleration, a speed, or a displacement of the measured vibration body. In any one of Claims 1-3,
The load sensor is a load measuring device that detects only a load in the excitation direction.

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