Sensitivity-amplified strain gauge and sensor elastomer stress detection method

Abstract

The invention discloses a sensitivity-amplified strain gauge and a sensor elastomer stress detection method, and belongs to the technical field of sensors, the sensitivity-amplified strain gauge comprises a sensitive part, and the outer side of the sensitive part is connected with a rigid support; the sensitive part comprises a substrate, a piezoresistor and an electrode assembly which are sequentially arranged from bottom to top, the piezoresistor comprises four sensitive grids, the two ends of each sensitive grid are connected with pins, each pin is shared by two adjacent sensitive grids, and the four sensitive grids have the same resistance value and are symmetrically arranged. Sensitivity can be further improved, miniaturization is facilitated, and measurement of local small strain is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a strain gauge with amplified sensitivity and a method for detecting stress of an elastic body of a sensor. Background Art

[0002] Strain gauges can measure the tiny deformation of objects or materials after being subjected to force, and convert mechanical strain (such as pressure, tension, compression, etc.) into electrical signals. According to the principle, they can be divided into metal strain gauges, semiconductor strain gauges, etc. Semiconductor strain gauges are mainly based on the piezoresistive effect of semiconductor materials. When semiconductor materials are subjected to external forces, their lattice structure will change, which will cause the resistivity of the material to change, thereby changing its electrical properties.

[0003] (1) Where R is the resistance value, dR is the resistance change, is the piezoresistance coefficient, The electrical properties of semiconductor strain gauges are very sensitive to mechanical stress. Compared with traditional metal strain gauges, they have the advantages of miniaturization, high precision, and high sensitivity.

[0004] The sensitivity of semiconductor strain gauges is related to the piezoresistance coefficient, which mainly depends on the characteristics of the semiconductor material itself. Once the semiconductor material is selected, the sensitivity is determined, and it cannot be used in scenarios that require higher sensitivity. Ordinary silicon strain gauges can usually measure local stresses in the range of ±10MPa to ±20MPa, and it is difficult to detect smaller stresses.

[0005] When strain gauges measure stress, they must first be attached to the surface of the object being measured and coordinated with the measurement circuit. The commonly used measurement circuit is the Wheatstone bridge, which converts the resistance change of the strain gauge into a voltage or current signal output. The steps are cumbersome, and ordinary strain gauges are usually large in size, making it difficult to measure stress in small areas. Summary of the invention

[0006] The present invention provides a strain gauge with amplified sensitivity and a sensor elastic body stress detection method, which can further improve the sensitivity and realize the measurement of local small strain.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a strain gauge with sensitivity amplification, comprising a sensitive part, wherein a rigid support is connected to the outside of the sensitive part; the sensitive part comprises a substrate, a piezoresistor and an electrode assembly arranged in sequence from bottom to top, the piezoresistor comprises four sensitive grids and four pins, the four pins are arranged rotationally symmetrically, the four sensitive grids are arranged around the outside of the four pins in a rotationally symmetrical manner, each sensitive grid is connected to two pins at both ends, and each pin is connected to the connection between two adjacent sensitive grids; the four sensitive grids have the same resistance value, and the electrode assembly comprises four electrodes respectively located above the four pins.

[0008] Furthermore, the sensitive grid includes a plurality of longitudinal grids and transverse grids, the bending part of the longitudinal grid is a transverse grid, the length of the longitudinal grid is greater than the length of the transverse grid, and the width of the longitudinal grid is less than the width of the transverse grid, and the resistance change of the longitudinal grid under the same strain state is twenty times or more of the resistance change of the transverse grid, and adjacent longitudinal grids are connected in sequence; the center line of each longitudinal grid is the axis of the longitudinal grid, the longitudinal grid axes of relative sensitive grids are parallel, and the longitudinal grid axes of adjacent sensitive grids are perpendicular.

[0009] Furthermore, the sensitive gate is a silicon piezoresistive sensitive gate.

[0010] Furthermore, the electrode is a gold electrode.

[0011] Furthermore, the rigid support includes a protruding portion and a connecting portion that are fixedly connected, and the thickness of the protruding portion is greater than the thickness of the connecting portion.

[0012] Furthermore, the substrate is a semiconductor or metal substrate.

[0013] In a second aspect, the present invention provides a sensor elastic body stress detection method, comprising the following steps: Step 1, placing the strain gauge according to claim 1 according to the known direction of the stress at the position to be measured, and sintering the strain gauge on the elastomer; Step 2: Apply an external load to deform the elastic body, which drives the rigid support to move. Under the force of the rigid support, the sensitive part of the strain gauge is deformed, causing the resistance value of the piezoresistor to change and output voltage. The stress in the strain gauge detection patch area is calculated based on the output voltage.

[0014] Furthermore, in step 1, the strain gauge is bonded to the elastomer by sintering glass paste or by using an organic adhesive.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention comprises a sensitive part and a rigid support connected to the outside of the sensitive part. During measurement, the rigid support part is in direct contact with the object to be measured, and the sensitive part is not in contact with the object to be measured. When the object to be measured is subjected to stress, the object to be measured drives the rigid support to be displaced. Under the action of the rigid support, the sensitive part of the strain gauge is deformed. Since the spacing between the two relatively arranged rigid supports is greater than the length of the sensitive part, according to Hooke's law, the rigid support amplifies the stress on the sensitive part, so that the sensitivity of the strain gauge is doubled, and the overall structure becomes larger, and the arrangement and mounting are convenient. At the same time, all electrodes are arranged on the inner side of the sensitive grid and as large as possible, making full use of the space in the central area, facilitating the subsequent wire bonding, and also making the strain gauge structure compact, which is conducive to miniaturization. The sensitive grid is rotationally symmetrically arranged around and almost fills most of the area except the electrode, so that a longer longitudinal grid length can be obtained, and the longitudinal grid bending is minimized. A longer wire grid length means a larger strain sensing area and a larger resistance value, and the lateral effect is reduced. It can more accurately reflect the actual strain of the object to be measured, and improve the accuracy and reliability of the measurement.

[0016] The above arrangement combined with the rigid support achieves miniaturization while improving sensitivity, and can realize the measurement of tiny strains in a narrow space.

[0017] Furthermore, the sensitive grid includes a plurality of longitudinal grids and transverse grids, the bending part of the longitudinal grid is the transverse grid, the length of the longitudinal grid is greater than the length of the transverse grid, and the width of the longitudinal grid is less than the width of the transverse grid. Under the same strain state, the change in resistance of the longitudinal grid is twenty times or more of the change in resistance of the transverse grid, which is used to reduce the lateral effect of the strain gauge. Adjacent sensitive grid longitudinal grids are connected in sequence; the center line of each longitudinal grid is the axis of the longitudinal grid, the longitudinal grid axes of relative sensitive grids are parallel, and the longitudinal grid axes of adjacent sensitive grids are perpendicular, which is used to measure stress in two perpendicular directions.

[0018] Furthermore, the sensitive gate is a silicon piezoresistive sensitive gate. Silicon is a material that is commonly used in semiconductor strain gauges and has good mechanical and conductive properties after being doped.

[0019] Furthermore, the electrode is a gold electrode. Gold has good conductivity and stability. Compared with other metals such as copper and aluminum, gold supports higher current density and has lower resistance. This enables the gold electrode to reduce energy loss when transmitting current and improve the efficiency and stability of the circuit. In addition, the gold electrode is more stable under the corrosion of some harmful substances such as acid and alkali, allowing the strain gauge to be used in more severe environments.

[0020] Furthermore, the rigid support includes a fixedly connected protrusion and a connecting portion, the thickness of the protrusion is greater than the thickness of the connecting portion, the protrusion is used to contact the object to be detected and support the sensitive part of the strain gauge so that it does not have direct contact with the object to be detected.

[0021] Furthermore, the substrate is a semiconductor substrate, which is used to place the fixed piezoresistive part and maintain good insulation between the parts. In addition, the chemical stability of semiconductor materials is good, and the strain gauge using the semiconductor substrate has good stability and can maintain stable performance in various harsh environments.

[0022] The present invention also provides a stress detection method, in which the rigid support part is in direct contact with the object to be measured, while the sensitive part is not in contact with the object to be measured, and the stress is measured by measuring the resistance change of the sensitive grid. When the object to be measured is subjected to stress, the rigid support will be displaced. Under the action of the rigid support, the sensitive part of the strain gauge is deformed. Since the spacing between the two relatively arranged rigid supports is greater than the length of the sensitive part, the rigid support amplifies the stress on the sensitive part, so that the sensitivity of the strain gauge is doubled, thereby realizing accurate detection of the stress of the elastic body.

[0023] Furthermore, in step 1, the strain gauge is attached to the elastomer by glass sintering or organic adhesive. The glass sintering method has the advantages of strong environmental adaptability, accurate stress transmission, and good long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the front structure of the strain gauge of the present invention; Figure 2 This is a schematic diagram of the back structure of the strain gauge of the present invention; Figure 3 It is a schematic cross-sectional view of the strain gauge of the present invention; Figure 4 Schematic diagram of the planar structure of the electrode; Figure 5 Schematic diagram of the planar structure of piezoresistor; Figure 6 is a schematic diagram of the plane structure of the substrate; Figure 7 It is a schematic diagram of the plane structure of the rigid support; Figure 8 Schematic diagram of the measurement bridge.

[0025] In the accompanying drawings: 1, electrode; 2, piezoresistor; 3, substrate; 4, rigid support; 21, vertical gate; 22, horizontal gate; 23, pin; 4, rigid support; 41, protrusion; 42, connecting part. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. used herein indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0030] The present invention doubles the sensitivity of the strain gauge by a rigid support amplification structure. At the same time, the overall structure becomes larger and the arrangement and mounting are convenient. The compact layout of the strain gauge helps to achieve miniaturization. Combined with the detection method of the present invention, micro-stress detection in a small area of ​​the elastomer can be achieved.

[0031] Example 1 Reference Figures 1 to 3 A strain gauge with amplified sensitivity includes a middle sensitive part of the strain gauge and four rigid supports 4. The middle sensitive part of the strain gauge is composed of an electrode assembly, a piezoresistor 2, and a substrate 3 in sequence from top to bottom. The four rigid supports 4 are located outside the middle sensitive part and are respectively connected to the four side walls of the substrate 3.

[0032] Reference Figure 5The piezoresistor 2 includes four sensitive gates and four pins 23. The four pins 23 are arranged rotationally symmetrically. The four sensitive gates are arranged rotationally symmetrically around the outside of the four pins 23, and the rotation angle is 90°. Both ends of each sensitive gate are connected to two pins 23 respectively, and each pin 23 is connected to the connection point of two adjacent sensitive gates and is shared by the two adjacent sensitive gates.

[0033] Each sensitive grid includes three longitudinal grids 21 and two transverse grids 22. The bending part of adjacent longitudinal grids 21 is transverse grid 22. The longitudinal grids 21 are slender strips, and the transverse grids 22 are short and thick. The resistance of the longitudinal grids 21 is much greater than that of the transverse grids 22. Under the same strain state, the resistance change of the longitudinal grids 21 is more than twenty times that of the transverse grids 22. This design can reduce the lateral effect of the strain gauge. The four sensitive grids have the same resistance and are symmetrical in center. The adjacent sensitive grid longitudinal grids 21 are connected in sequence.

[0034] The center line of each longitudinal grid 21 is the axis of the longitudinal grid 21 , the axes of the longitudinal grids 21 of opposite sensitive grids are parallel, and the axes of the longitudinal grids 21 of adjacent sensitive grids are perpendicular. Each sensitive grid is used to detect stress in the same direction as the axis of its longitudinal grid 21 .

[0035] The main body of the cross section of the pin 23 is a square, and the corner of the square extends obliquely outward for a section.

[0036] Reference Figure 4 The electrode assembly includes four centrally symmetrical electrodes 1, which are respectively located above four pins 23, connected to the pins 23 up and down, similar in shape to the pins 23, and slightly smaller in size than the pins 23, and are used to connect with the lead wire when in use. Since the electrode 1 is similar in shape to the pins 23 and is of similar size, the contact area between the electrode 1 and the pins 23 is as large as possible. Electrodes with large contact areas can capture more signals, thereby having a wider measurement range; secondly, a larger contact area helps to reduce signal loss caused by contact resistance, further improving the sensitivity of the measurement; furthermore, a larger contact area increases the mechanical connection strength between the electrode and the pin, thereby improving the reliability of the connection. In harsh environments such as vibration and impact, electrodes and pins with large contact areas can reduce circuit failures caused by loosening or falling off, and improve the service life of the strain gauge.

[0037] Reference Figure 6 The substrate 3 is square, has a cross section slightly larger than the piezoresistance 2, is located below the piezoresistance 2, and is connected to the piezoresistance 2 from top to bottom.

[0038] Reference Figure 7 The rigid support 4 includes a protruding portion 41 and a connecting portion 42 that are fixedly connected, and the thickness of the protruding portion 41 is greater than the thickness of the connecting portion 42.

[0039] The four rigid supports 4 are respectively located on the four sides of the base 3 and are fixedly connected to the four sides of the base 3 through the connecting parts 42. The side length of the connecting part 42 is equal to the four side lengths of the base 3. A step is protruded from the edge of the rigid support 4 to form a raised part 41 of the rigid support. When in use, only the raised part 41 is in contact with the object to be measured.

[0040] Furthermore, the electrode 1 is a metal electrode, preferably a gold electrode.

[0041] Furthermore, the sensitive gate is a silicon piezoresistive sensitive gate or a metal wire gate, and the piezoresistor 2 is doped with P-type silicon. The piezoresistive effect of silicon material is significant. When external pressure acts on the sensitive gate, its resistance value will change significantly, thereby accurately measuring tiny strain changes. In addition, the silicon piezoresistive sensitive gate has a high frequency response and can quickly respond to changes in external pressure or strain. Therefore, the silicon piezoresistive sensor has excellent performance in dynamic measurement and can accurately capture rapidly changing signals.

[0042] Furthermore, the substrate 3 is a semiconductor or metal substrate, and the semiconductor substrate can be silicon dioxide or silicon.

[0043] Furthermore, the rigid support 4 is a rigid connecting member with relatively large rigidity and is not easily deformed.

[0044] Example 2 This embodiment discloses a method for detecting stress of a sensor elastic body using the strain gauge, the method comprising the following steps: Step 1: Apply glass paste to the position to be tested on the elastomer, place the strain gauge in the direction of the stress at the position to be tested according to the simulation calculation, and stick the strain gauge to the elastomer through glass paste sintering or organic adhesive. The sintering temperature of the glass paste is 300~460℃.

[0045] Step 2: Apply an external load to deform the elastic body, and use the strain gauge to detect the stress in the patch area.

[0046] The working principle of the strain gauge is as follows: When using the strain gauge, only the protrusion 41 of the rigid support 4 is in contact with the elastic body. When the elastic body is deformed, the protrusion 41 is displaced. Under the force of the protrusion 41, the middle sensitive part of the strain gauge is deformed, causing the resistance value of the piezoresistance to change. The strain gauge has completed the self-assembly bridge of the Wheatstone bridge. When the input voltage is connected, the voltage output caused by the strain can be obtained. It is known that the stress at the location to be detected is , the elastic modulus is , the total strain at the patch is ,Depend on Figure 3 It can be seen that the length of the patch is , the deformation of the object at the patch becomes , and because the rigid support part is not easy to deform, the deformation will be concentrated in the middle sensitive part of the strain gauge, that is, the deformation of the middle sensitive part of the strain gauge is also ,Depend on (2) (3) get ,in is the stress on the middle sensitive part of the strain gauge of the present invention, is the elastic modulus of the middle sensitive part of the strain gauge, is the strain of the strain gauge, and the length of the sensitive part in the middle of the strain gauge is .

[0047] When the strain gauge is directly attached to the surface of the object to be measured, the length of the strain gauge is , the stress at the location to be tested is known to be , the elastic modulus is , the total strain at the patch is , the deformation of the object at the patch becomes , is the elastic modulus of the strain gauge, is the strain of the strain gauge. Similarly, (4) (5) get

[0048] in is the stress on a general strain gauge.

[0049] By comparison, it can be seen that the stress on the middle sensitive part of the strain gauge of the present invention is amplified. times, it can be obtained from formula (1) that the resistance change rate is proportional to the stress, that is, the strain gauge of the present invention amplifies the sensitivity times, the strain gauge of the present invention When the sensitivity is doubled, the minimum stress range measured is ±5MPa, and the measuring range is extended to ±5MPa to ±20MPa.

[0050] This example can be used with a bridge to measure strain. Assume that the bridge input voltage is u i , the output voltage is u o , the schematic diagram of the measuring bridge is shown in Figure 8 The four sensitive gates are R 1 , R 2 , R 3 , R 4, the basic circuit of the bridge has been connected, and the output can be obtained by simply connecting the input voltage to the corresponding electrode. 1 =R 2 =R 3 =R 4 , when there is no strain, the output voltage formula of the bridge is (6) Among them, R1 is the resistance value of the resistor R1, R2 is the resistance value of the resistor R2, R3 is the resistance value of the resistor R3, and R4 is the resistance value of the resistor R4.

[0051] At this time, the bridge balance condition is met and the bridge output is 0. When the strain gauge is strained by the external environment, the bridge balance condition is no longer met. (7) in, is the resistance value change of resistor R1, is the resistance value change of resistor R1, is the resistance value change of resistor R1, is the resistance value change of resistor R1.

[0052] Thus, a voltage signal with sensitivity amplification is obtained.

[0053] If it is known that the stress in the measured area is only in one direction, such as parallel to R 1 , R 4 The corresponding stress of the sensitive gate in the longitudinal direction is: (8) According to formula (1), the piezoresistance coefficient is also known , input voltage u i , knowing the output voltage u o , we can find the stress The magnitude of , positive or negative, indicates whether it is tensile stress or compressive stress. 2 , R 3 The corresponding stress in the longitudinal direction of the sensitive grid can also be obtained. size and positive and negative.

[0054] Compared with traditional measurement methods, this strain gauge has achieved self-assembled bridge, without the need for external circuits, and can obtain output signals by simply connecting voltage, making stress detection more convenient.

[0055] The term "consisting of" describing a combination shall include the identified elements, ingredients, parts or steps and other elements, ingredients, parts or steps that do not substantially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, parts or steps herein also contemplates embodiments that consist essentially of these elements, ingredients, parts or steps. By using the term "may", it is intended to illustrate that any of the attributes described that "may" be included are optional.

[0056] Multiple elements, ingredients, parts or steps can be provided by a single integrated element, ingredient, part or step. Alternatively, a single integrated element, ingredient, part or step can be divided into separate multiple elements, ingredients, parts or steps. The disclosure "one" or "an" used to describe an element, ingredient, part or step is not intended to exclude other elements, ingredients, parts or steps.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the foregoing claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A strain gauge with amplified sensitivity, characterized in that: The invention comprises a sensitive part, wherein a rigid support (4) is connected to the outside of the sensitive part; the sensitive part comprises a substrate (3), a piezoresistor (2) and an electrode assembly which are arranged in sequence from bottom to top; the piezoresistor (2) comprises four sensitive grids and four pins (23); the four pins (23) are arranged rotationally symmetrically; the four sensitive grids surround the outside of the four pins (23) in a rotationally symmetrical arrangement; the two ends of each sensitive grid are respectively connected to two pins (23); each pin (23) is connected to the connection point of two adjacent sensitive grids; the four sensitive grids have the same resistance value; and the electrode assembly comprises four electrodes (1) respectively located above the four pins (23).

2. A sensitivity-amplified strain gauge according to claim 1, characterized in that: The sensitive grid comprises a plurality of longitudinal grids (21) and transverse grids (22); the bending portion of the longitudinal grids (21) is the transverse grid (22); the length of the longitudinal grids (21) is greater than the length of the transverse grids (22), and the width of the longitudinal grids (21) is less than the width of the transverse grids (22); under the same strain state, the resistance change of the longitudinal grids (21) is twenty times or more of the resistance change of the transverse grids (22); adjacent longitudinal grids (21) are connected in sequence; the center line of each longitudinal grid (21) is the axis of the longitudinal grid (21); the axes of the longitudinal grids (21) of the relative sensitive grids are parallel, and the axes of the longitudinal grids (21) of the adjacent sensitive grids are perpendicular.

3. A sensitivity-amplified strain gauge according to claim 1 or 2, characterized in that: The sensitive gate is a silicon piezoresistive sensitive gate or a metal wire gate.

4. A sensitivity-amplified strain gauge according to claim 1, characterized in that: The electrode (1) is a gold electrode.

5. The sensitivity-amplified strain gauge according to claim 1, characterized in that: The rigid support (4) comprises a raised portion (41) and a connecting portion (42) which are fixedly connected, and the thickness of the raised portion (41) is greater than the thickness of the connecting portion (42).

6. The sensitivity-amplified strain gauge according to claim 1, characterized in that: The substrate (3) is a semiconductor or a metal substrate.

7. A sensor elastic body stress detection method, characterized in that: The following steps are involved: Step 1, placing the strain gauge according to claim 1 according to the known direction of the stress at the position to be measured, and sintering the strain gauge on the elastomer; Step 2: Apply an external load to deform the elastic body, which drives the rigid support (4) to move. Under the force of the rigid support (4), the sensitive part of the strain gauge is deformed, causing the resistance value of the piezoresistor (2) to change, and output voltage. The stress in the strain gauge detection patch area is calculated based on the output voltage.

8. The sensor elastic body stress detection method according to claim 7, characterized in that: In the step 1, the strain gauge is adhered to the elastomer by sintering glass paste or by using an organic adhesive.

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