JP4936193B2 - Load sensor - Google Patents

Description

  The present invention relates to a load sensor capable of detecting a component force in two orthogonal axes.

  Conventionally, various types of load sensors have been proposed as load sensors that can detect two axial force components orthogonal to each other in the same plane. For example, Patent Document 1 discloses that a load sensor is configured by attaching a plurality of strain sensing elements (strain gauges) 51 to a complicated three-dimensional strain generating member 50 as shown in FIG. Patent Document 2 discloses that a load sensor is configured by sticking a plurality of strain sensing elements 61 to a T-shaped strain generating member 60 as shown in FIG.

However, these conventional load sensors require complicated cutting work and fastening work using screws or the like in order to form the strain-generating bodies 50 and 60 having a predetermined shape. Therefore, the conventional load sensor has poor workability and is difficult to provide at a low price.
Japanese Utility Model Publication No. 58-169543 JP 7-209113 A

  The present invention has been invented in view of the above-mentioned problems, and provides a load sensor capable of detecting component forces in two orthogonal axes as having good workability and being inexpensive. It is a task to do.

In order to solve the above-described problems, the load sensor according to the present invention includes a laterally-induced strained body 3 that extends in the orthogonal direction from the other end of the longitudinally-distorted strained body 2 having a fixing portion 12 on one end side. 3, the L-shaped strain generating member 1 formed by forming an action portion 13 on which an external force acts, the front and back of the longitudinal strain body 2 and the front and back of the lateral strain body 3 are substantially the same position. Among the external forces acting on the strain sensing elements 7, 8, 9, 10 and the acting portion 13 of the laterally distorted body 3, the lateral component F3 parallel to the laterally distorted body 3 and the longitudinally distorted body 2 and an arithmetic device that calculates a longitudinal component force F2 parallel to 2 based on the detection results of the strain detection elements 7, 8, 9, and 10. The L-shaped strain generating member 1 is formed by bending a sheet metal having a constant thickness into an L shape, and is supported by penetrating the fixing hole 4 in the thickness direction on one end side of the longitudinally strained body 2. The fixed portion 12 fixed to the body S is formed, and the action portion 13 is formed by penetrating the insertion hole 5 in the thickness direction on the distal end side of the laterally distorted body 3, and an external force is applied to the action portion 13. The external force acting member 15 for making it rotate is connected so that rotation is possible. By doing so, the workability of the load sensor becomes very good, and the component forces F2 and F3 in the orthogonal biaxial directions can be detected with a simple configuration using the L-shaped strain generating member 1 or the like. It becomes possible. Further, it is possible to prevent a bending moment from being generated in the action portion 13 and to accurately detect the external force acting on the action portion 13 via the external force action member 15.

  The calculation device calculates the resultant force F1 based on the lateral component force F3 and the longitudinal component force F2, or calculates the direction of the resultant force F1 based on the lateral component force F3 and the longitudinal component force F2. It is preferable that By doing in this way, it becomes possible to detect the magnitude | size and direction of the resultant force F1 which act on the action part 13. FIG.

  The strain detection elements 7, 8, 9, and 10 are preferably strain gauges, piezoelectric elements, or semiconductor elements. By using these, distortion can be detected accurately.

According to the first aspect of the present invention, a load sensor is formed by extending a laterally distorted body in an orthogonal direction from the other end side of the longitudinally distorted body having a fixing portion on one end side, and on the distal end side of the laterally distorted body. An L-shaped strain-generating member formed with an action portion to which an external force acts, a strain detection element disposed at substantially the same position on the front and back of the longitudinally-distorted portion and approximately the same position on the front and back of the laterally-distorted portion, and the horizontal An operation for calculating a lateral component force parallel to the laterally-induced strain member and a longitudinal component force parallel to the longitudinally-induced strain member among external forces acting on the acting portion of the strain-generating member based on the detection result of the strain sensing element. And device. The L-shaped strain generating member is formed by bending a sheet metal having a constant thickness into an L shape, and is fixed to the support by passing a fixing hole in the thickness direction on one end side of the longitudinal strain body. The fixed portion is formed, and the action portion is formed by penetrating the insertion hole in the thickness direction on the distal end side of the laterally distorted body, and an external force acting member for applying an external force to the action portion is rotated. Connect freely. Therefore, a load sensor capable of detecting a two-axial component force orthogonal to a good processability effects and that can be provided as can be provided at low cost, the working unit via the external force acting portion There is an effect that the acting external force can be accurately detected .

In the invention according to claim 2 , the arithmetic device calculates a resultant force based on a lateral component force and a longitudinal component force. Accordingly, the invention according to claim 2, in addition to the effect of the invention according to claim 1, an effect that it is possible to detect the magnitude of the resultant force acting on the acting portion.

In the invention according to claim 3 , the computing device computes the direction of the resultant force based on the lateral component force and the longitudinal component force. Therefore, in addition to the effect of the invention according to claim 1 or 2 , the invention according to claim 3 has the effect of being able to detect the direction of the resultant force acting on the action portion.

In the invention according to claim 4 , the strain sensing element is a strain gauge, a piezoelectric element or a semiconductor element. Therefore, in addition to the effect of the invention according to any one of claims 1 to 3 , the invention according to claim 4 has the effect of being able to accurately detect strain and thus accurately detect external force. .

  The present invention will be described based on embodiments shown in the accompanying drawings. FIG. 1 shows an example load sensor according to an embodiment of the present invention. This load sensor is formed by attaching two pairs of strain sensing elements 7, 8, 9, and 10 to an L-shaped strain generating member 1 formed by bending a sheet metal having a constant thickness into an L shape. The component force of the component parallel to the L-shaped vertical piece and the component force of the component parallel to the L-shaped horizontal piece among the external forces applied to the tip portion of the L-shaped strain generating member 1 are detected. It is supposed to be. Hereinafter, each configuration will be further described in detail.

  The L-shaped strain-generating member 1 is composed of a plate-shaped longitudinally-distorted strain body 2 that is an L-shaped vertical piece portion and a flat plate-shaped laterally-distorted strain body 3 that is an L-shaped lateral piece portion, Is configured. The longitudinally distorted body 2 and the laterally distorted body 3 are both elastically deformable, and the laterally distorted body 3 extends in the orthogonal direction from the lower end of the longitudinally distorted body 2 in the figure.

  The longitudinally-distorting body 2 of the L-shaped strain-generating member 1 is provided with a fixing portion 12 at one end on the upper side in the figure as a fixed end and the other end on the lower side in the figure as a free end. A plurality of fixing holes 4 for inserting fixing members (not shown) such as screws are passed through the fixing portion 12 in the thickness direction. A hatched portion in FIG. 2 is a support S that supports the entire L-shaped strain generating member 1 in a predetermined posture by fixing the fixing portion 12.

  The laterally-induced strained body 3 of the L-shaped strained member 1 is extended at a right angle from the free end side of the longitudinally-distorted strained body 2, and has an action of applying an external force to be detected to the tip thereof. Part 13 is formed. The action portion 13 is provided with an insertion hole 5 penetrating in the thickness direction, and an external force acting member 15 made of an S-shaped hook is rotatably inserted into the insertion hole 5.

  The structures of the insertion hole 5 and the external force acting member 15 are not particularly limited. However, the external force acting member 15 includes at least a predetermined direction including the longitudinal direction and the lateral direction of the L-shaped strain generating member 1 with respect to the acting portion 13. It is provided so as to be rotatable within a plane (see arrow R in the figure).

  Two pairs of strain sensing elements 7, 8, 9, 10 are arranged in pairs on the longitudinally distorted body 2 side and the laterally distorted body 3 side of the L-shaped strained member 1, respectively. Specifically, the strain detection element 7 is attached to the center of the surface of the laterally-induced strain body 3, and the strain detection element 8 that forms a pair with the strain detection element 7 is attached to the center of the back surface of the laterally-induced strain body 3. I wear it. Further, a strain detecting element 9 is attached to the center of the surface of the longitudinally distorted body 2, and a strain detecting element 10 that is paired with the strain detecting element 9 is attached to the center of the surface of the longitudinally distorted body 2. Yes. The pair of strain sensing elements 7 and 8 are arranged at substantially the same position on the front and back of the laterally-induced strain body 3, and the pair of strain sensing elements 9.10 are also arranged at substantially the same position on the front and back of the longitudinally-induced strain body 2. Yes.

  In this example, the strain detection elements 7, 8, 9, and 10 are configured using strain gauges, but the strain detection is performed using other elements such as piezoelectric elements and semiconductor elements as long as the strain can be detected. Elements 7, 8, 9, and 10 may be configured.

  The strain detection elements 7, 8, 9, and 10 only need to be able to detect the strain generated in the L-shaped strain generating member 1, so that the arrangement location may be the surface of the longitudinal strain body 2 or the lateral strain body 3. It is sufficient and not necessarily limited to the center. In order to detect a minute strain, the strain detection elements 9 and 10 are attached to a position close to the fixing portion 12 side of the longitudinally distorted body 2, while the strain detection elements 7 and 8 are laterally distorted bodies. It is desirable to stick to a position close to the connecting portion side (the side opposite to the action portion 13) of 3 of the longitudinally distorted body 2.

  Regarding the position where each strain sensing element 7, 8, 9, 10 is attached to the L-shaped strain-generating member 1, the magnitude of the external force applied to the L-shaped strain-generating member 1, the dimensional shape of the L-shaped strain-generating member 1 These are determined as appropriate based on the relationship between the dimension and shape of each strain sensing element 7, 8, 9, 10 and the wiring to each strain element 7, 8, 9, 10.

  In the arithmetic device (not shown) provided in the load sensor of this example, the lateral component force F3 and the longitudinal component force F2 are calculated based on the detection results of the two pairs of strain detection elements 7, 8, 9, and 10. To do. The lateral component force F <b> 3 here is a component force that acts in parallel to the laterally distorted body 3 among the external forces that act on the acting portion 13 of the laterally distorted body 3. Further, the longitudinal component force F <b> 2 is a component force that acts in parallel with the longitudinally distorted body 2 among the external forces that act on the acting portion 13 of the laterally distorted body 3.

  Hereinafter, the principle for calculating the lateral component force F3 and the longitudinal component force F2 based on the detection results of the strain detection elements 7, 8, 9, 10 will be described. In FIG. 3, the strain ε 1 detected by the strain detecting element 7 by the lateral component force F 3, the strain ε 2 detected by the strain detecting element 8, the strain ε 3 detected by the strain detecting element 9, and the strain detecting element 10 detect. The strain ε4 is schematically shown. These strains ε1, ε2, ε3, and ε4 are in the relationship of the following equations, respectively. Note that εt1 is a tensile strain generated in the laterally distorted body 3 by the force F3, and εb1 is a bending strain generated in the longitudinally distorted body 2 by the force F3.

ε1 = εt1
ε2 = εt1
ε3 = −εb1
ε4 = εb1
In FIG. 4, the strain ε1 detected by the strain detection element 7 by the longitudinal component force F2, the strain ε2 detected by the strain detection device 8, the strain ε3 detected by the strain detection device 9, and the strain detection device 10 detect. The strain ε4 is schematically shown. These strains ε1, ε2, ε3, and ε4 are in the relationship of the following equations, respectively. Εt2 is a tensile strain generated in the longitudinally distorted body 2 by the longitudinal component force F2, εb2 is a bending strain generated in the laterally distorted body 3 by the longitudinal component force F2, and εb3 is generated in the longitudinally distorted body 2 by the longitudinal component force F2. Bending strain.

ε1 = εb2
ε2 = −εb2
ε3 = −εb3 + εt2
ε4 = εb3 + εt2
Therefore, when the lateral component force F3 and the longitudinal component force F2 act simultaneously (that is, when the resultant force F1 of the transverse component force F3 and the longitudinal component force F2 acts), the strains ε1, ε2, ε3, and ε4 are expressed by the following equations. become that way.

ε1 = εt1 + εb2
ε2 = εt1−εb2
ε3 = −εb1−εb3 + εt2
ε4 = εb1 + εb3 + εt2
Here, when the difference between the detection results of the strain detection elements 7 and 8 that form a pair on the front and back of the laterally distorted body 3 is obtained, the following equation is obtained, and the influence of the lateral component force F3 is eliminated and the longitudinal component force F2 is It can be seen that only bending affects.

ε1-ε2 = εt1 + εb2- (εt1-εb2) = 2εb2 (Equation 1)
Further, if the difference between the detection results of the strain detection elements 9 and 10 that form a pair on the front and back of the longitudinally distorted body 2 is taken, the following equation is obtained, and the bending of the longitudinal component force F2 and the lateral component force F3 is affected. I understand.

ε3-ε4 = -εb1-εb3 + εt2- (εb1 + εb3 + εt2)
= -2 (εb1 + εb3) (Formula 2)
By the way, a general relational expression of stress σ, strain ε, and bending moment M is expressed as follows using Young's modulus E and section modulus Z.

σ = E · ε (Formula 3)
σ = M / Z (Formula 4)
Therefore, the following relationship is obtained from Equation 3 and Equation 4.

M = E · ε · Z (Formula 5)
Here, the bending moment Mv generated by the longitudinal component F2 in the laterally distorted body 3 is expressed by the following equation using the distance X between the action portion 13 and the strain detection elements 7 and 8.

Mv = F2 · X
⇔F2 = Mv / X (Formula 6)
When Expression 6 is transformed using Expression 1 and Expression 5, the following relational expression is obtained.

F2 = E · εb2 · Z / X
= E [(ε1-ε2) / 2] Z / X
= K1 (ε1-ε2) (Expression 7)
Since K1 (= E · Z / 2X) in Equation 7 is a constant specific to the load sensor, it can be obtained from an experiment in advance. The value of (ε1−ε2) in Equation 7 can be obtained using a bridge circuit as shown in FIG. 5, for example. In the figure, the output e of the bridge circuit satisfies the following relationship using the applied voltage Ea and the gauge factor K.

e = 1/4 · Ea · K (ε1-ε2)
Further, the bending moment Mh generated by the lateral component force F3 and the longitudinal component force F2 in the longitudinally distorted body 2 is the vertical distance Y between the action part 13 and the strain detection elements 9, 10, and the action part 13 and the strain detection element. Using the distance L in the horizontal direction from 9 and 10, it is expressed as the following equation.

Mh = F3 ・ Y + F2 ・ L
⇔F3 = (Mh−F2 · L) / Y (Expression 8)
When Expression 8 is transformed using Expression 2 and Expression 5, the following relational expression is obtained.

F3 = [E · (εb1 + εb3) · Z−F2 · L] / Y
= [E ·-(ε3-ε4) 1/2 · Z-F2 · L] / Y
= K2 · (ε3−ε4) + K3 · F2 (Equation 9)
Since K2 (= −E · Z / 2Y) and K3 (= −L / Y) in Equation 9 are constants specific to the load sensor, they can be obtained from experiments in advance. The value of (ε3−ε4) in Equation 9 can be obtained using a bridge circuit as shown in FIG. 6, for example. In the figure, the output e of the bridge circuit satisfies the following relationship using the applied voltage Ea and the gauge factor K.

e = 1/4 · Ea · K (ε3-ε4)
Then, if the lateral component force F3 and the longitudinal component force F2 can be obtained by calculating with the arithmetic unit using Equation 8, Equation 9, etc., the magnitude and angle θ of the resultant force F1 can be obtained by the following equation.

F1 = (F3 ² + F2 ² ) ^1/2 (Expression 10)
TANθ = F3 / F2 (Expression 11)
Therefore, in the load sensor of this example, the component force in the biaxial direction of the external force acting in a predetermined plane can be calculated with the above-described configuration that has good workability and can be provided at low cost. Further, in the load sensor of this example, the magnitude and direction of the resultant force acting in a predetermined plane can be calculated, and the angle / load detection sensor that has good workability and can be provided at a low price. Become.

  Next, various modifications will be described with reference to FIGS. In the following, only the features of each example will be described.

  FIG. 7 shows various modifications of the fixing portion 12 provided to fix the longitudinally distorted body 2 to the support S. In the above-described embodiment shown in FIG. 1 and FIG. 2, the fixing portion 12 extends straight from the longitudinally distorted body 2, but in the modification shown in FIG. 7A, the fixing portion 12 is It extends in a direction orthogonal to the longitudinally distorted body 2. Further, in the modification shown in FIG. 7B, the fixing portion 12 is extended in a direction that forms an angle α that is an acute angle with the longitudinally distorted body 2.

  As described above, by appropriately setting the shape of the fixing portion 12, the posture in which the L-shaped strain generating member 1 is fixed to the support S can be arbitrarily set. Even if the L-shaped strain generating member 1 is fixed in any posture, the lateral component force F3 and the longitudinal component force acting in a predetermined plane including the longitudinal direction and the lateral direction of the L-shaped strain member 1 The magnitude of F2 and the magnitude and angle of the resultant force F1 can be detected.

  FIG. 8 shows various modifications of the action portion 13 for applying an external force to the distal end side of the laterally distorted body 3. In the above embodiment shown in FIG. 1, the action portion 13 is formed by the insertion hole 5 for rotatably locking the external force acting member 15 which is an S-shaped hook metal fitting. In the modification shown to a), the action part 13 is formed by fixing the column-shaped rod member 20 so that the width direction of the L-shaped strain generating member 1 may be the axial direction. The rod member 20 is for hooking a string-like external force acting member (not shown) on both ends in the axial direction so as to be rotatable.

  In the modification shown in FIG. 8B, the action portion 13 is formed by spanning the rod member 20 in the groove portion 22 that is recessed from the distal end side of the laterally-raised strain body 3. The rod member 20 is for hooking and locking one end side of the external force acting member 15 which is an S-shaped hook metal fitting. In the modification shown in FIG. 8 (c), the action portion 13 includes a U-shaped metal fitting 23 fixed to the distal end portion of the laterally distorted body 3, a lever member 24 fixed to the U-shaped metal fitting 23, and a lever member 24. It is formed with a bar member 20 provided at the tip. The rod member 20 is for hooking a string-like external force acting member (not shown) on both ends in the axial direction so as to be rotatable. Further, in the modification shown in FIG. 8D, a U-shaped plate-shaped metal fitting 26 in which the action portion 13 is fixed to the distal end portion of the laterally distorted body 3 and a pair of insertions formed in the plate-shaped metal fitting 26 are provided. It is formed by the holes 5. This insertion hole 5 is for allowing a rod-like external force acting member (not shown) to pass therethrough freely.

  In any of the above-described modifications, the external force acting member 15 is rotatable with respect to the acting portion 13 of the laterally distorted body 3 within a predetermined plane including the longitudinal direction and the lateral direction of the L-shaped distorted member 1. It has become. Thereby, it is possible to prevent a bending moment from being generated in the action portion 13 and to accurately detect an external force acting on the action portion 13 via the external force acting member 15.

It is a perspective view of an example load sensor in an embodiment of the present invention. It is explanatory drawing which shows a mode that external force acts on a load sensor same as the above. It is explanatory drawing which shows a mode that a lateral external force acts on a load sensor same as the above. It is explanatory drawing which shows a mode that a longitudinal external force acts on a load sensor same as the above. It is explanatory drawing of the bridge circuit used in a load sensor same as the above. It is explanatory drawing of the other bridge circuit used in a load sensor same as the above. (A), (b) is explanatory drawing which shows the modification of the fixing | fixed part which a load sensor same as the above has. (A), (b), (c), (d) is explanatory drawing which shows the modification of the action part which a load sensor same as the above has. It is a perspective view of the conventional load sensor. It is a perspective view of the other conventional load sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 L-shaped strain generating member 2 Longitudinal strained body 3 Lateral strained body 7 Strain sensing element 8 Strain sensing element 9 Strain sensing element 10 Strain sensing element 12 Fixing part 13 Acting part 15 External force acting part F1 Combined force F2 Longitudinal component force F3 Lateral force

Claims (4)

A laterally-distorted strain body is extended in the orthogonal direction from the other end side of the longitudinally-induced strain body having a fixing portion on one end side, and an action portion to which an external force acts is formed on the distal end side of the laterally-induced strain body. Of the external force acting on the acting part of the laterally-distorted body, the strain-type straining member, the strain-sensing elements disposed at substantially the same position on the front and back of the longitudinally-induced strained part and the front and back of the laterally-strained strained part anda calculation unit for calculating, based on the detection result of the strain detecting element and a parallel longitudinal component force in the vertical flexure element parallel to the lateral component force to the lateral strain body, the L-shaped raised The strain member is formed by bending a sheet metal having a constant thickness into an L shape, and a fixing portion fixed to the support is formed by penetrating the fixing hole in the thickness direction on one end side of the longitudinally distorted body. Forming and forming an action part by penetrating the insertion hole in the thickness direction on the tip side of the laterally distorted body, Load sensor, characterized in that to connect the external force member for applying a force rotatably. The load sensor according to claim 1, wherein the arithmetic device calculates a resultant force based on a lateral component force and a longitudinal component force. The load sensor according to claim 1, wherein the calculation device calculates a direction of a resultant force based on a lateral component force and a longitudinal component force. The load sensor according to claim 1, wherein the strain detection element is a strain gauge, a piezoelectric element, or a semiconductor element.

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