JP6767559B2 - Strain gauge and multi-axial force sensor - Google Patents

Description

The present invention relates to a strain gauge and a multiaxial force sensor including the strain gauge.

Multiaxial force sensors equipped with strain gauges are widely used in robots, game machines, various measuring devices, and other devices. Patent Documents 1 and 2 disclose an example of a multi-axial force sensor including a strain gauge.

JP-A-2010-164495 Japanese Patent No. 508188

In a multiaxial force sensor provided with a strain gauge, the existence of a measurement error due to a change in ambient temperature is recognized, and its suppression is desired.

Therefore, an object of the present invention is to provide a strain gauge in which the occurrence of measurement error due to a change in ambient temperature is suppressed, and a multiaxial force sensor including the strain gauge.

According to the first aspect of the present invention,
A load that is attached to a straining member that is distorted by receiving a load and acts in the first direction of the straining member is detected by a first Wheatstone bridge circuit, and in a second direction orthogonal to the first direction of the straining member. A strain gauge used to detect the acting load by the second Wheatstone bridge circuit.
With a flexible substrate
With a circuit pattern formed on the base material,
The base material has a sensitive region attached to a strain-causing region where strain is generated by receiving a load of the strain-causing member, a dead region arranged outside the strain-causing region, and a sensitive region and the dead region. Has a connection area that connects and
The dimension of the connecting region in the orthogonal direction orthogonal to the direction in which the sensitive region and the dead region are connected is smaller than the dimension in the orthogonal direction of the sensitive region and the dead region.
The circuit pattern comprises two first-direction strain-sensitive elements constituting the first Wheatstone bridge circuit, two second-direction strain-sensitive elements constituting the second Wheatstone bridge circuit, and a first Wheatstone bridge circuit. 1st direction fixed resistance element and at least one of 2nd direction fixed resistance elements constituting the 2nd Wheatstone bridge circuit.
At least one of the two first-direction strain-sensitive elements, the two second-direction strain-sensitive elements, and the first-direction fixed resistance element and the second-direction fixed resistance element are made of the same material.
The two first-direction strain-sensitive elements and the two second-direction strain-sensitive elements are formed in the sensitive region.
At least one of the first-direction fixed resistance element and the second-direction fixed resistance element is formed in the dead region.
Strain gauges are provided.

In the strain gauge of the first aspect, the circuit pattern includes two first-direction fixed resistance elements constituting the first Wheatstone bridge circuit and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit. The two first-direction strain-sensitive elements, the two second-direction strain-sensitive elements, the two first-direction fixed resistance elements, and the two second-direction fixed resistance elements may be made of the same material. It may be formed, and the two first-direction fixed resistance elements and the two second-direction fixed resistance elements may be formed in the dead region.

In the strain gauge of the first aspect, the circuit pattern may further include at least one terminal, and the at least one terminal may be formed in the dead region.

In the strain gauge of the first aspect, in the dead region, the at least one terminal is provided on the side opposite to the sensitive region of at least one of the first-direction fixed resistance element and the second-direction fixed resistance element. You may be.

In the strain gauge of the first aspect, a pair of the dead areas may be provided on both sides of the sensitive area.

In the strain gauge of the first aspect, the circuit pattern may further include two third direction strain sensitive elements or two third direction fixed resistance elements, the two third direction strain sensitive elements or 2 The three third-direction fixed resistance elements may connect a first Wheatstone bridge circuit and a second Wheatstone bridge circuit to form a third Wheatstone bridge circuit.

According to the second aspect of the present invention,
The strain plate and
With the load acting part connected to the strain generating plate,
A multiaxial force sensor comprising the strain gauge of the first aspect attached to the strain generating plate is provided.

In the strain sensor of the second aspect, the dead region of the base material of the strain gauge may be attached to the side surface of the strain raising plate.

In the strain gauge of the present invention and the multiaxial force sensor including the strain gauge, the occurrence of measurement error due to a change in ambient temperature is suppressed.

FIG. 1 is a perspective view of a three-axis force sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the triaxial force sensor shown in FIG. 1 cut along a YZ plane including the axis A. FIG. 3 shows the wiring pattern of the strain gauge. FIG. 4 is a circuit diagram corresponding to the wiring pattern of the strain gauge of FIG. 5 (a) and 5 (b) are explanatory views showing a state of measurement in the three-axis force sensor. FIG. 6 shows another example of the strain gauge wiring pattern.

<Embodiment>
Regarding the embodiment of the multi-axial force sensor and the strain gauge of the present invention, FIGS. Will be described with reference to.

As shown in FIGS. 1 and 2, the 3-axis force sensor 100 of the present embodiment has a main body portion 10 that is rotationally symmetrical around the shaft A and a strain gauge 20 attached to the main body portion 10. The main body 10 includes a disk-shaped strain-causing plate (distortion member) 11 having a shaft A as a rotation axis, a load acting portion 12 that stands upright in the axial direction from the center of the surface 11a of the strain-causing plate 11, and strain-causing. A pair of holding plates 13 that stand upright in the axial direction from the peripheral edge of the front surface 11a of the plate 11, a peripheral wall 14 that stands upright in the axial direction from the peripheral edge of the back surface 11b of the strain generating plate 11, and four mounted on the peripheral wall 14. Includes leg 15. The main body 10 is integrally molded with, for example, a synthetic resin material.

In the following description, as shown in FIG. 1, the two orthogonal radial directions of the strain generating plate 11 are defined as the X direction (first direction) and the Y direction (second direction) of the triaxial force sensor 100 and the main body 10. To do. Further, the direction of the axis A orthogonal to the X direction and the Y direction is defined as the Z direction (third direction) of the triaxial force sensor 100 and the main body 10.

The strain generating plate 11 is a disk that is distorted by receiving an external load applied to the main body portion 10 of the triaxial force sensor 100 via the load acting portion 12. The strain in the strain generating plate 11 occurs on the front surface 11a and the back surface 11b of the strain generating plate 11 (upper and lower surfaces orthogonal to the axis A in FIG. 1), and the side surface 11c of the strain generating plate 11 (the circumference parallel to the axis A in FIG. On the surface), it does not occur or is small enough to be ignored. In the present specification, a region of the strain plate 11 that is distorted by receiving an external load, such as the front surface 11a and the back surface 11b of the strain plate 11 in the present embodiment, is referred to as a “distortion region”. The diameter and thickness of the strain generating plate 11 are arbitrary.

The load acting portion 12 is a portion that moves by receiving a load from the outside and causes strain on the strain generating plate 11, for example, a prism having a square cross-sectional shape. The load acting portion 12 is provided on the surface 11a of the straining plate 11 so that the central axis of the prism coincides with the rotation axis (axis A) of the straining plate 11, that is, coaxially with the straining plate 11.

The pair of holding plates 13 is a portion to which a part (dead regions 21n1 and 21n2) of the base material 21 (FIG. 3) of the strain gauge 20 described later is attached. The holding plates 13 face each other so as to sandwich the load acting portion 12 in the Y direction, and stand upright from the surface 11a of the strain generating plate 11, and each has a curved surface along the outer circumference of the strain generating plate 11.

The peripheral wall 14 stands upright from the back surface 11b along the outer circumference of the back surface 11b of the strain generating plate 11 and surrounds the back surface 11b. Further, the peripheral wall 14 is provided with a pair of notched portions 14n so as to sandwich the load acting portion 12 in the Y direction. That is, the pair of notch portions 14n are provided at positions overlapping the pair of holding plates 13 in the circumferential direction of the strain generating body 11. The peripheral wall 14 is used as a guide when the strain gauge 20 is attached to the strain generating plate 11, and the details thereof will be described later.

The legs 15 are pedestals for attaching the three-axis force sensor 100 to the robot hand, and four legs 15 are provided on the peripheral wall 14 at equal intervals.

FIG. 3 shows a state (developed view) before the strain gauge 20 shown in FIG. 1 is attached to the strain generating body 11. As shown in FIG. 3, the strain gauge 20 includes a base material 21 and a circuit pattern CP printed on the surface of the base material 21. The base material 21 has a sensitive region 21s and a dead region 21n1 and 21n2 sandwiching the sensitive region 21s, and the circuit pattern CP has six strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z _2. , Four fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , eight terminals T _{1 to} T _8, and a wiring W connecting them. In the following description, the direction in which the insensitive regions 21n1 and 21n2 sandwich the sensitive region 21s is the y direction (second direction), and the direction orthogonal to the y direction on the surface of the base material 21 is the x direction (first direction). ).

The base material 21 is a flexible resin film, and has a central circular sensation region 21s, a pair of insensitive regions 21n1 and 21n2 sandwiching the sensation region 21s, and a pair of insensitivity regions 21s. It has a pair of connecting regions 21c1 and 21c2 that connect 21n1 and 21n2, respectively. It is desirable to use a resin film that is flexible and highly flexible so that it can be easily bent, and as a specific example, polyester, polyimide, or the like can be used. Further, although it is possible to form the sensitive region 21s, the dead region 21n1, 21n2, and the connecting regions 21c1 and 21c2 from different materials, these are formed from the same material and the temperature characteristics (resistance temperature coefficient) of the entire region are formed. Etc.) should be equal. Further, in this case, the sensitive region 21s, the insensitive regions 21n1, 21n2, and the connecting regions 21c1 and 21c2 are integrally cut out from a nearby portion in the integrally formed material (for example, a sheet of polyester, polyimide, etc.) to form a base material. It is more desirable to form 21. As a result, the temperature characteristics of each region can be made more uniform.

Since the sensitive region 21s is a region attached to the back surface 11b of the strain generating plate 11 of the main body portion 10, it has a diameter equal to or smaller than the back surface 11b of the strain generating plate 11. On one surface of the sensitive region 21s, strain-sensitive elements (first-direction strain-sensitive elements) X ₁ and X ₂ sandwiching the center c in the x direction are sandwiched in the y-direction, and strain-sensitive elements (second). Directional strain-sensitive elements) Y ₁ and Y ₂ are formed, and strain-sensitive elements (third-direction strain-sensitive elements) Z ₁ and Z ₂ are formed along the outer periphery.

The strain-sensitive elements X ₁ and X ₂ are formed parallel to each other with the y direction as the width direction of the grid. The strain-sensitive element X ₁ and the strain-sensitive element X ₂ are formed at equidistant positions from the center c, respectively, and are formed in the x direction between the strain-sensitive element X ₁ and the strain-sensitive element X ₂ . The distance is larger than the width of the load acting portion 12 of the main body portion 10 in the X direction.

The strain-sensitive elements Y ₁ and Y ₂ are formed parallel to each other with the x direction as the width direction of the grid. The strain-sensitive element Y ₁ and the strain-sensitive element Y ₂ are formed at equidistant positions from the center c, respectively, and are formed in the y direction between the strain-sensitive element Y ₁ and the strain-sensitive element Y ₂ . The distance is larger than the width of the load acting portion 12 of the main body portion 10 in the Y direction.

The strain-sensitive elements Z ₁ and Z ₂ are arcuate, respectively, and are formed so as to face each other in the x direction with the circumferential direction of the sensitive region 21s as the width direction of the grid. The strain-sensitive elements Z ₁ and Z ₂ are arranged on the opposite side (outside) of the center c of the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y ₂ .

The pair of dead regions 21n1 and 21n2 sandwich the sensitive region 21s in the y direction, and have a rectangular shape with the x direction as the long side direction and the y direction as the short side direction, respectively.

Fixed resistance elements (first-direction fixed resistance elements) RX ₁ and RX ₂ extending in the x direction are formed side by side in the x direction in a portion on the surface of the dead region 21n1 far from the sensitive region 21s. Four terminals T ₁ , T ₂ , T ₃ , and T ₄ arranged in the x direction are formed in a portion close to the sensitive region 21s. That is, in the dead region 21N1, a fixed resistance element _RX 1, RX ₂ terminal _T 1 through T _4, are disposed on the opposite side of the sensitive region 21s.

Similarly, fixed resistance elements (second-direction fixed resistance elements) RY ₁ and RY ₂ extending in the x direction are formed side by side in the x direction in a portion of the surface of the dead region 21n2 far from the sensitive region 21s. In the portion close to the sensitive region 21s, four terminals T ₅ , T ₆ , T ₇ and T ₈ arranged in the x direction are formed. That is, in the dead region 21n2, the fixed resistance elements RY ₁ and RY ₂ are arranged on the opposite side of the terminals T _{5 to} T ₈ from the sensitive region 21s.

The connecting regions 21c1 and 21c2 connecting the sensitive regions 21s and the insensitive regions 21n1 and 21n2 have dimensions (widths) in the x direction orthogonal to the y direction in which the sensitive regions 21s and the insensitive regions 21n1 and 21n2 are connected, respectively. Is smaller than the dimensions (width) of the sensitive regions 21s and the dead regions 21n1 and 21n2 in the x direction. Therefore, the base material 21 has a constricted shape in the connecting regions 21c1 and 21c2.

As shown in FIGS. 3 and 4, the wiring W constitutes the first bridge circuit (first Wheatstone bridge circuit) BC1 connected strain sensitive elements _X 1, _{X 2,} the fixed resistance element _RX 1, RX ₂ ing. Further, the terminal T ₁ is between the strain-sensitive element X ₁ and the fixed resistance element RX ₁ , the terminal T ₂ is between the strain-sensitive elements X ₁ and X ₂ , and the terminal T ₂ is between the fixed resistance elements RX ₁ and RX ₂ . The terminal T ₃ is connected to the terminal T ₄ between the strain-sensitive element X ₂ and the fixed resistance element RX ₂ .

Similarly, the wiring W connects the strain-sensitive elements Y ₁ and Y ₂ and the fixed resistance elements RY ₁ and RY ₂ to form a second bridge circuit (second Wheatstone bridge circuit) BC2. Terminal T ₈ is between the strain-sensitive element Y ₁ and the fixed resistance element RY ₁ , terminal T ₆ is between the strain-sensitive elements Y ₁ and Y ₂ , and terminal T is between the fixed resistance elements RY ₁ and RY _2. No. ₇ has a terminal T ₅ connected between the strain-sensitive element Y ₂ and the fixed resistance element RY ₂ .

One end of the strain-sensitive element Z ₁ is connected to the first bridge circuit BC1 between the strain-sensitive element X ₁ and the fixed resistance element RX ₁ , and the other end is connected to the strain-sensitive element Y ₁ and the fixed resistance element RY. It is connected to the second bridge circuit BC2 between ₁ and ₁ . Similarly, one end of the strain-sensitive element Z ₂ is connected to the first bridge circuit BC1 between the strain-sensitive element X ₂ and the fixed resistance element RX ₂ , and the other end is fixed to the strain-sensitive element Y _2. It is connected to the second bridge circuit BC2 with the resistance element RY ₂ . Thus, a first bridge circuit BC1 to a pair of opposite sides portion of the second bridge circuit BC2 respectively sensitive elements Z ₁ strain to another pair of opposite side _portions, a third bridge circuit having Z _2, respectively (Third Wheatstone bridge circuit) BC3 is configured.

The strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ , fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , and wiring W included in the circuit pattern CP are made of the same material. , More preferably formed by nearby sites within one material. This material is, for example, a copper alloy such as copper or copper / nickel. The circuit pattern CP can be printed on the base material 21 by photoetching, printing, thin film deposition, sputtering or the like.

As shown in FIGS. 1 and 2, the strain gauge 20 is attached to the main body 10 so that the surface of the base material 21 opposite to the surface on which the circuit pattern CP is formed is in contact with the main body 10. There is.

Specifically, the sensitive region 21s of the base material 21 is a strain generating plate so that the x direction and the y direction coincide with the X direction and the Y direction of the main body 10, respectively, and the center c coincides with the axis A. It is attached to the back surface 11b of 11. As described above, the distance between the strain-sensitive elements X ₁ and X ₂ in the x direction is larger than the dimension of the load acting portion 12 in the X direction, and the distance between the strain-sensitive elements Y ₁ and Y _{2 in} the y direction is It is larger than the dimension of the load acting portion 12 in the Y direction. Therefore, when the sensitive portion 21s of the base material 21 is attached to the strain generating plate 11, the strain sensitive elements X ₁ and X ₂ and the strain sensitive elements Y ₁ and Y ₂ , respectively, are in the X direction and Y, respectively. It is arranged in a region where strain is relatively large, outside the load acting portion 12 in the direction. In FIGS. 3 and 6, the outline of the load acting portion 12 in the state where the base material 21 is attached to the strain generating plate 11 is shown by a broken line, and the load acting portion 12 and the strain sensitive elements X ₁ , X _{2 are shown} . The positional relationship with Y ₁ and Y ₂ is shown.

The pair of dead regions 21n1 and 21n2 of the base material 21 are attached to the side surface 11c of the strain generating plate 11 which is bent and the outer surface of the holding plate 13 extending above the side surface 11c, respectively. Therefore, the terminals T ₁ , T ₂ , T ₃ , T ₄ formed in the dead region 21n1 and the terminals T ₅ , T ₆ , T ₇ , and T ₈ formed in the dead region 21n ₂ are in the radial direction of the strain generating plate 11. It is exposed facing outward.

The pair of connecting portions 21c1 and 21c2 each pass through the notch portion 14n of the peripheral wall 14 and are bent at the connecting portion between the back surface 11b and the side surface 11c of the strain generating plate 11.

When the strain gauge 20 is attached to the base material 21, the peripheral edge of the sensitive region 21s of the base material 21 is brought into contact with the inner peripheral surface of the peripheral wall 14, and the pair of connecting regions 21c1 and 21c2 of the base material 21 are brought into contact with the peripheral wall. By arranging each of the pair of notches 14n of 14, the strain gauge 20 can be easily positioned with respect to the main body 10 and the strain raising plate 11.

Specifically, by bringing the peripheral edge of the sensitive region 21s of the base material 21 into contact with the inner peripheral surface of the peripheral wall 14, the center c of the sensitive region 21s is aligned with the axis A of the main body 10. In addition, the movement of the sensitive region 21s in the X direction and the Y direction is restricted. Next, by arranging the pair of connecting portions 21c1 and 21c2 of the strain gauge 20 in the pair of notched portions 14n of the peripheral wall 14, the strain gauge 20 can be formed by the main body portion 10 and the strain generating plate 11 even in the circumferential direction of the axis A center. Aligned with.

Next, the usage and operation of the three-axis force sensor 100 and the strain gauge 20 of the present embodiment will be described.

When the 3-axis force sensor 100 is used as a tactile sensor of the robot hand, first, the 3-axis force sensor 100 is fixed to the fingertip of the robot hand via the leg portion 15. Then, the terminal _T 1 through T ₈ and the signal processing unit (not shown), respectively, connected with the lead wire _L 1 ~L ₈ (FIG. 2). The terminals T _{1 to} T ₈ and the lead wires L _{1 to} L ₈ can be joined by any method, for example, by using solder or an anisotropic conductive film (ACF).

The terminals T ₁ and T ₅ are connected to the power supply (not shown) of the signal processing unit by the lead wires L ₁ and L ₅ , respectively. Terminals _T 2, _{T 3,} the terminal _T 6, _{T 7,} the terminal _T 4, _{T 8,} respectively, the leads _L 2, _{L 3,} the leads _L 6, _{L 7,} the lead wire _L 4, _{L 8,} signal It is connected to a calculation unit (not shown) in the signal processing unit via an amplifier (not shown) in the processing unit.

3 During operation of the force sensor 100, apply an input voltage Ei between the terminals T ₁ and the terminal T ₅ by the power source. The resistance value of each strain-sensitive element and the resistance value of each fixed resistance element constituting the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 have no deflection in the sensitive region 21s of the base material 21. in the state, a voltage equal between terminals _T 2, _{T 3,} the voltage equal between the terminal _T 6, _{T 7,} is adjusted so that the voltage becomes equal between the terminal _T 4, _{T 8.} Therefore, no cause strain Okoshiibitsuban 11, in a state where there is no deflection in the sensitive region 21s (FIG. 5 (a)), between the terminals _T 2, _{T 3,} between the terminals _T 6, _{T 7,} the terminal There is no potential difference between T ₄ and T ₈ , and the calculation unit does not calculate the strain.

Next, when a load in the X direction is applied to the load acting portion 12, the load acting portion 12 receives the load and moves, causing strain in the strain generating plate 11 (FIG. 5 (b)). At this time, the sensitive region 21s of the substrate 21 of the strain gauge 20 attached to Okoshiibitsuban 11 also strain-generating plate 11 and the flexure together, compressive strain in the strain sensitive elements X ₁ is, strain sensitive elements Elongation strain occurs in X ₂ . Accordingly, the strain sensitive elements _X 1, the resistance value of _{X 2} is changed respectively, a potential difference occurs between the terminals _T 2, _{T 3} of the first bridge circuit BC1 including sensitive elements _X 1, _{X 2} strain. Based on this potential difference, the calculation unit obtains the amount of strain generated in the strain generating plate 11, and obtains the magnitude of the load acting on the load acting unit 12 in the X direction. At this time, no strain is generated on the side surface 11c of the strain generating plate 11 and the holding plate 13, and the resistance values of the fixed resistance elements RX ₁ and RX ₂ are constant. When a load in the Y direction is applied to the load acting portion 12, the magnitude of the applied load in the Y direction is obtained in the same manner.

When a load in the Z direction is applied to the load acting portion 12, the strain-sensitive region 21s of the strain generating plate 11 and the base material 21 is curved so that the center protrudes, so that the strain-sensitive elements X ₁ and X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ all have extended strain. As a result, the combined resistance of the first bridge circuit BC1, the combined resistance of the second bridge circuit BC2, and the resistance values of the strain-sensitive elements Z ₁ and Z ₂ , respectively, change, and the terminals T ₄ and T _{8 of} the third bridge circuit BC 3 change. There is a potential difference between them. Based on this potential difference, the calculation unit obtains the amount of strain generated in the strain generating plate 11, and obtains the magnitude of the load acting on the load acting unit 12 in the Z direction.

Here, the fixed resistance elements RX ₁ and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC ₂ are printed on the base material 21, and the strain sensitive elements X ₁ and X ₂ are printed. , Y ₁ and Y ₂ are made of the same material, and the significance of forming the same material will be described.

(1) By forming the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ in this way, the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are strain-sensitive elements X ₁ , X. It will be formed of the same material as ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ , and at a position close to these. Here, since the resistance temperature coefficient indicating the rate of change of the resistance value with respect to the temperature change is a physical property value depending on the material, the resistance temperature coefficients of the total strain-sensitive element and the total fixed resistance element are equal in the present embodiment. Further, the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed on the base material 21, and are in the vicinity of the strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ . Since it is formed in, the change in ambient temperature that affects the total strain sensitive element and the total fixed resistance element is substantially the same. Therefore, when the ambient temperature changes, the resistance value of the total strain-sensitive element and the resistance value of the total fixed resistance element change at the same rate.

In the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3, when the balance of resistance values changes between the resistance elements (distortion-sensitive element and fixed resistance element) included in each, the terminals between T _{2, T 3,} between the terminals _T 6, _{T 7,} the potential difference between the terminals _T 4, _{T 8} occurs, the strain on the basis of which is detected. Therefore, when the balance between the resistance value of the strain-sensitive element and the resistance value of the fixed resistance element changes due to a change in the ambient temperature, a measurement error may occur due to this change in the balance. However, in the present embodiment, when the ambient temperature changes, the resistance value of the total strain-sensitive element and the resistance value of the total fixed resistance element change at the same rate, so that the ambient temperature changes. Even in this case, the balance of resistance values between the elements does not change, and the occurrence of measurement error is suppressed. When the circuit pattern CP is formed, the strain-sensitive element X ₁ is formed by forming a strain-sensitive element or the like using a portion near the material (copper, copper alloy, etc.) prepared as an integral mass. The temperature coefficient of resistance of X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ , fixed resistance element RX ₁ , RX ₂ , RY ₁ , RY ₂ , and wiring W can be made more uniform, and the occurrence of measurement error is better. It can be suppressed.

(2) As in the present embodiment, the fixed resistance elements RX ₁ and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC ₂ are arranged in the dead regions 21n1 and 21n2 of the base material 21. When the dead regions 21n1 and 21n2 are attached to the portion of the main body 10 where distortion does not occur (outside the strain-causing region), the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed. It can act as a dummy gauge for temperature compensation. Therefore, even if the expansion or contraction occurs in the body portion 10 including a strain generating plate 11 due to a change in ambient temperature, sensitive elements X ₁ strain according to the expansion or _{contraction, X 2, Y 1, Y} 2 of the resistance value It is possible to compensate for the change in the above and suppress the occurrence of measurement error.

(3) The first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 are formed by printing the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ on the base material 21. Each can be formed as a complete closed circuit on the substrate 21.

When the strain-sensitive element constituting the bridge circuit is printed on the base material and the fixed resistance element constituting the bridge circuit is provided outside the base material, for example, in the signal processing unit, the bridge circuit is closed. It is necessary to connect the strain-sensitive element on the base material and the fixed resistance element of the signal processing unit with a lead wire or the like. In this case, the wiring on the base material and the lead wire are connected by joining the lead wire to the electrode provided on the base material, but when a joining resistance occurs at the joint portion between the electrode and the lead wire, this is a bridge. The bonding method is limited to solder bonding in which the bonding resistance is substantially negligible, as it becomes a resistance in the circuit and causes a large strain detection error.

However, in order to perform good solder bonding, it is necessary to provide a relatively large electrode on the base material and secure a pitch between the plurality of electrodes, so that the base material becomes large. Further, in order to perform good solder bonding, it is necessary to pile up the solder with a certain thickness, which hinders the miniaturization of the triaxial force sensor.

In contrast, in the present embodiment, the first bridge circuit BC1, second bridge circuit BC2, the third bridge circuit BC3, respectively, is formed as a closed circuit was completed on the substrate 21, the terminal _T 1 through T The connection between the base material 21 and the signal processing unit via ₈ is merely a connection for connecting the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 to the power supply and the arithmetic unit. Therefore, in the present embodiment, the generation of bonding resistance is allowed at the bonding portion between the terminals T _{1 to} T ₈ and the lead wires L _{1 to} L _8, and any bonding method other than solder bonding, for example, an anisotropic conductive film, is allowed. It is possible to adopt the joining using. By using an anisotropic conductive film, the size of the electrodes, the pitch between the electrodes, and the thickness of the joint can all be suppressed to about 1/10 of that in the case of solder bonding, so that the triaxial force can be suppressed. When it is desired to reduce the size of the sensor 100, bonding with an anisotropic conductive film is advantageous.

The effects of the 3-axis force sensor 100 and the strain gauge 20 of the present embodiment are as follows.

In the strain gauge 20 of the present embodiment, the fixed resistance elements RX ₁ and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC ₂ are formed on the base material 21. The effects of (2) and (3) above can be achieved, and the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are the same as the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y ₂ . Since it is formed of a material, the effect of (1) above can be obtained.

In the strain gauge 20 of the present embodiment, only the strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ are formed in the strain-sensitive region 21s, and the terminals T _{1 to} T are formed. ₈ and the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed in the dead regions 21n1 and 21n2. Therefore, the diameter (dimension) of the sensitive region 21s can be reduced, and the strain generating plate 11 of the triaxial force sensor 100 can be reduced. The miniaturization of the strain generating plate 11 leads to the miniaturization of the 3-axis force sensor 100, which is preferable.

In the strain gauge 20 of the present embodiment, since the electrode _T 1 through T ₈ is provided in the dead region 21N1,21n2, if necessary, without increasing the diameter of the sensitive area 21s, electrodes _T 1 ~ The size of T ₈ can be increased to facilitate the joining work with the lead wire or the like.

Since the base material 21 of the strain gauge 20 of the present embodiment has connecting portions 21c1 and 21c2 narrower than the sensitive regions 21s and the dead regions 21n1 and 21n2 between the sensitive regions 21s and the dead regions 21n1 and 21n2. The sensitive region 21s and the insensitive regions 21n1 and 21n2 can be arranged in various ways without being restricted by the connecting portion with the connecting portion 21c1 and 21c2.

Since the triaxial force sensor 100 of the present embodiment includes the strain gauge 20, the same effect as that of the strain gauge 20 can be obtained.

In the above embodiment, the following modification can also be adopted.

In the strain gauge 20, the strain-sensitive elements Z ₁ and Z ₂ may be formed in the dead region 21n1 and / or the dead region 21n2. In this case, since the deflection in the dead zones 21n1,21n2 does not occur, sensitive elements _Z 1, _{Z 2} strain acts as a substantially fixed resistance element (third direction fixed resistance element).

Even when the strain-sensitive elements Z ₁ and Z ₂ act as fixed resistance elements, the detection of the load in the X direction using the first bridge circuit BC1 and the detection of the load in the Y direction using the second bridge circuit BC2 are carried out as described above. It can be done in the same way as the form. It is also possible to detect the load in the Z direction. When a Z-direction load acts on the load acting unit 12 to change the resistance value of the strain detection elements X ₁ , X ₂ , Y ₁ , and Y ₂ , the combined resistance of the first bridge circuit BC1 and the combined resistance of the second bridge circuit BC2 This is because the combined resistance changes and the balance of the resistance values between the elements of the third bridge circuit BC3 changes even if the resistance values of the strain-sensitive elements Z ₁ and Z ₂ are constant.

The strain gauge 20 does not have to have the strain sensitive elements Z ₁ and Z ₂ . In this case, for example, the first bridge circuit BC1, second bridge circuit BC2 is, instead of the strain sensitive elements _Z 1, _{Z 2,} are connected by two arcuate lines W.

Even when the strain-sensitive elements Z ₁ and Z ₂ are not present, the detection of the load in the X direction using the first bridge circuit BC1 and the detection of the load in the Y direction using the second bridge circuit BC2 are the same as in the above embodiment. It can be carried out. The strain gauge 20 in such a deformed form can be used in a biaxial force sensor. Alternatively, the first Wheatstone bridge and the second Wheatstone bridge of the strain gauge of such a deformation mode are connected by a fixed resistance element formed in the signal processing unit to form a third Wheatstone bridge in the three-axis force sensor. It can also be used.

In the strain gauge 20, the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ formed in the dead regions 21n1 and 21n2 of the base material 21 leave at least one of them on the base material 21 and are based on the other. It may be provided outside the material 21, for example, in a signal processing unit. Even in such an embodiment, at least one of the fixed resistance elements RX ₁ and RX ₂ constituting the first bridge circuit BC ₁ and the fixed resistance elements RY ₁ and RY ₂ constituting the second bridge circuit BC 2 is used as the base material 21. By providing the above dead regions 21n1 and / or 21n2, it is possible to exert the effect of suppressing the temperature error in the strain gauge 20 and the triaxial force sensor 100.

In the dead region 21n1 provided on one side of the sensitive region 21s in the y direction (second direction), the fixed resistance elements RX ₁ and RX ₂ and the terminals T _{1 to} T ₄ are orthogonal to the y direction (second direction). It may be arranged in a row along the x direction (first direction), and the fixed resistance elements RY ₁ and RY may be arranged in the dead region 21n2 provided on the other side of the sensitive region 21s in the y direction (second direction). ₂ and the terminals T _{5 to} T ₈ may be arranged in a row along the x direction (first direction) orthogonal to the y direction (second direction). As a result, the dead areas 21n1 and 21n2 can be attached to a more elongated portion. For example, the holding plate 13 of the main body 10 can be omitted, and the dead areas 21n1 and 21n2 can be attached only to the side surface of the strain raising plate 11. ..

As shown in FIG. 6, the fixed resistance element _RX 1 to a portion close to the sensitive region 21s of the dead region 21n1, RX ₂ may also be the terminal _T 1 through T ₄ to portion distant from the sensitive region 21s are formed. That is, in the dead region 21n1, terminals T _{1 to} T ₄ may be provided on the side opposite to the sensitive region 21s of the fixed resistance elements RX ₁ and RX ₂ . Placement of fixed resistor _RY 1, RY ₂ and the terminal _T 5 through T ₈ in the dead region 21n2 versa. By arranging the terminals T _{1 to} T ₈ on the outside in this way, it becomes easier to join the lead wires and the like to the terminals T _{1 to} T ₈ .

Any one or more of the terminals _T 1 through T ₈ may be formed in the sensitive region 21s. In this case, it is desirable to provide it in the vicinity of the center c, which is attached below the load acting portion 12 and hardly causes strain.

In the strain-sensitive region 21s, the strain-sensitive elements Z ₁ and Z ₂ may be arranged on the center c side (inside) of the strain-sensitive elements X ₁ , X ₂ , Y ₁ and Y ₂ . Further, each of the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y ₂ may be formed in an arc shape so that the width direction of the grid is the circumferential direction of the sensitivity region 21s. Such a strain gauge 20 can be satisfactorily used by attaching the load acting portion 12 to the main body portion 10 having a cylindrical shape centered on the shaft A.

The shape of the base material 21 of the strain gauge 20 is arbitrary, and may be a rectangular shape or an elliptical shape having no connecting portions 21c1 and 21c2, or may have only one of the dead regions 21n1 and 21n2. In the base material 21 having only one of the dead regions 21n1 and 21n2, all of the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , and terminals T _{1 to} T ₈ can be formed in this dead region. In addition, the base material 21 may have an arbitrary shape including a sensitive region attached to the strain generating plate of the multiaxial force sensor and a dead region arranged outside the region.

The holding plate 13 of the main body 10 may be a flat plate extending in parallel with the strain generating plate 11 from the outer circumference of the strain generating plate 11. In this case, the base material 21 of the strain gauge 20 is attached to the strain raising plate 11 and the holding plate 13 without bending. Further, the main body 10 does not have to have the holding plate 13. In this case, the entire area of the dead regions 21n1 and 21n2 can be attached to the side surface 11c of the strain generating plate 11. In addition, the dead areas 21n1 and 21n2 may not be attached to the side surface 11c of the strain generating plate 11, or may not be attached to the main body 10. The arrangement of the dead regions 21n1 and 21n2 in the state where the sensitive region 21s is attached to the back surface 11b of the strain generating plate 11 can be appropriately determined according to the shape of the main body of the multi-axis sensor and the application of the multi-axis sensor. it can.

The strain gauge 20 of the above embodiment can also be used as a strain generating member of any sensor other than the multiaxial force sensor.

As long as the features of the present invention are maintained, the present invention is not limited to the above-described embodiment, and other modes considered within the scope of the technical idea of the present invention are also included within the scope of the present invention. ..

The strain gauge and the multi-axial force sensor of the present invention can suppress the influence of temperature changes in load detection, and can contribute to the improvement of stability and reliability in robots, game machines, various measuring devices, and other devices.

10 Main body 11 Distortion plate (distortion member)
12 Load acting part 13 Holding plate 14 Peripheral wall 15 Leg part 20 Strain gauge 21 Base material 21s Sensitive area 21c1, 21c2 Connecting area 21n1, 21n2 Insensitive area BC1 First bridge circuit (first Wheatstone bridge circuit)
BC2 2nd bridge circuit (2nd Wheatstone bridge circuit)
BC3 3rd bridge circuit (3rd Wheatstone bridge circuit)
RX ₁ and RX ₂ Fixed resistance element (1st direction fixed resistance element)
RY ₁ , RY ₂ fixed resistance element (second direction fixed resistance element)
T _{1 to} T ₈ terminals X ₁ , X ₂ Strain-sensitive element (first-direction strain-sensitive element)
Y ₁ , Y ₂ strain-sensitive element (second-direction strain-sensitive element)
Z ₁ and Z ₂ strain-sensitive elements (third-direction strain-sensitive elements)

Claims (7)

A strain-causing body used for detecting a load acting in the first direction by a first Wheatstone bridge circuit and detecting a load acting in a second direction orthogonal to the first direction by a second Wheatstone bridge circuit.
Distortion member and
It is provided with a circuit pattern provided on the strain-causing member.
The strain-causing member has a strain-causing region in which strain is generated by receiving a load to be detected, and a region different from the strain-causing region.
The circuit pattern comprises two first-direction strain-sensitive elements constituting the first Wheatstone bridge circuit, two second-direction strain-sensitive elements constituting the second Wheatstone bridge circuit, and a first Wheatstone bridge circuit. The first-direction fixed resistance element and the second-direction fixed resistance element constituting the second Wheatstone bridge circuit are included.
At least one of the two first-direction strain-sensitive elements, the two second-direction strain-sensitive elements, and the first-direction fixed resistance element and the second-direction fixed resistance element are made of the same material.
The two first-direction strain-sensitive elements and the two second-direction strain-sensitive elements are provided in the strain-causing region, and at least one of the first-direction fixed resistance element and the second-direction fixed resistance element is provided. A strain-causing body provided in a region different from the strain-causing region. The circuit pattern includes two first-direction fixed resistance elements constituting the first Wheatstone bridge circuit and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit.
The two first-direction strain-sensitive elements, the two second-direction strain-sensitive elements, the two first-direction fixed resistance elements, and the two second-direction fixed resistance elements are made of the same material. ,
The strain-causing body according to claim 1, wherein the two first-direction fixed resistance elements and the two second-direction fixed resistance elements are provided in a region different from the strain-causing region. The circuit pattern further includes at least one terminal.
The strain-causing body according to claim 1 or 2, wherein the at least one terminal is provided in a region different from the strain-causing region. Claim that the at least one terminal is provided on the side opposite to the strain-causing region of at least one of the first-direction fixed resistance element and the second-direction fixed resistance element in a region different from the strain-causing region. The strain-causing body according to 3. The strain-causing body according to any one of claims 1 to 4, wherein a region different from the strain-causing region is provided in pairs on both sides of the strain-causing region. The circuit pattern further includes two third direction strain sensitive elements or two third direction fixed resistance elements.
Claims 1 to 5 that the two third-direction strain-sensitive elements or the two third-direction fixed resistance elements connect a first Wheatstone bridge circuit and a second Wheatstone bridge circuit to form a third Wheatstone bridge circuit. The strain-causing body according to any one of the above items. The strain-causing body according to any one of claims 1 to 6,
A sensor including a load acting portion connected to the strain generating member.

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