Force sensitive element and axial force sensor

Abstract

A force-sensitive element and an axial force sensor, the force-sensitive element comprising: an annular or circular force-bearing member having a first force-bearing portion, a second force-bearing portion and a boss protruding upward from the first force-bearing portion; the boss is annular or circular and corresponds to the stress piece in shape. The outer wall of the boss protrudes outwards in the radial direction to form a plurality of peninsula-shaped protruding parts which are separated in the circumferential direction. The four sets of strain resistors are attached to the upper side surface of the stress piece in the whole circumferential direction of the stress piece at intervals in an insulating mode and located on the radial inner side of the first stress part, the number of the strain resistors in each set is the same, and at least one strain resistor is arranged in each set; and the strain resistors of the second group of strain resistors and the fourth group of strain resistors are distributed on the upper side surfaces of a plurality of peninsula-shaped protruding parts which are formed by outwards protruding the outer wall of the boss along the radial direction and are separated in the circumferential direction in a one-to-one correspondence manner. By means of the protruding parts which are distributed at intervals in the circumferential direction, a proper area of the stress piece can have negative stress, so that the measurement accuracy of the Wheatstone bridge is improved.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a force-sensitive element and an axial force sensor. Background Art

[0002] CN115931188A and CN116576998A disclose a force sensor, which has four circumferentially spaced apart piezoresistors provided on the upper surface of a metal base as a force-sensitive element. These four piezoresistors form a Wheatstone full bridge to measure the deformation degree of the metal base, and then obtain the magnitude of the axial force. Since the thick film resistors are all provided on its upper surface, the bending stresses on its surface are all positive (i.e., tensile stresses), which also results in poor theoretical accuracy. To improve its theoretical accuracy, two fixed resistors can be provided in the electronic module assembly to form a Wheatstone full bridge together with the piezoresistors, but this will cause the temperatures of the fixed resistors and the piezoresistors to be different, thus generating temperature drift.

[0003] In addition, due to mechanical fit deviations caused by the machining accuracy (flatness, surface roughness) of the metal base itself and the coaxiality with the force-applying member, etc., the increase and decrease degrees of the resistance values on the relative bridge arms are usually not the same, which has a very adverse impact on the measurement accuracy and greatly hinders the practical application. Utility Model Content

[0004] Aiming at the deficiencies of the prior art, this application is committed to providing a force-sensitive element to improve its measurement accuracy.

[0005] To achieve the above object, this application provides the following technical solutions:

[0006] A force-sensitive element, which includes:

[0007] A force-receiving member axially arranged in the up-down direction and being annular or circular, having an annular first force-receiving portion provided on its upper side, an annular second force-receiving portion provided on its lower side, and a boss protruding upward from the first force-receiving portion; the second force-receiving portion is concentrically arranged radially outside the first force-receiving portion and radially outside the boss, and the boss is annular or circular corresponding to the shape of the force-receiving member; a plurality of peninsula-shaped protruding portions separated in the circumferential direction formed by the outer wall of the boss protruding radially outward;

[0008] Four groups of strain resistors are spaced apart circumferentially and insulatedly attached to the upper side surface of the force-bearing member and located radially inside the first force-bearing portion. Each group of strain resistors has the same number and at least one strain resistor. The first group of strain resistors and the third group of strain resistors are circumferentially spaced apart and distributed on the upper side surface of a first annular region of a convex platform protruding upward from the first force-bearing portion. The second group of strain resistors and the fourth group of strain resistors are circumferentially spaced apart and distributed on the upper side surface of a second annular region of the force-bearing member. The second annular region is located outside the first annular region. The strain resistors of the second group of strain resistors and the four groups of strain resistors are correspondingly distributed on the upper side surfaces of a plurality of peninsula-shaped protrusions separated circumferentially formed by the outer wall of the convex platform protruding radially outward.

[0009] Among them, the four groups of strain resistors are respectively correspondingly combined into the four arm resistors of a Wheatstone full bridge. The arm resistors corresponding to the first group of strain resistors and the third group of strain resistors are located on two opposite arms. Each group of strain resistors is combined into the corresponding arm resistor alone or in a parallel, series, or mixed series-parallel manner.

[0010] Preferably, a tangentially extending hole is provided at the lower part of the outer wall of the protrusion.

[0011] Preferably, the hole is a straight hole.

[0012] Preferably, the protrusion is symmetrically arranged about a pair of symmetry midlines extending radially along the force-bearing member, and the strain resistors arranged on the protrusion are arranged on the symmetry midline of the protrusion.

[0013] Preferably, an axially extending concave portion is formed relatively between every two adjacent protrusions in the circumferential direction.

[0014] Preferably, the strain resistors are electrically connected through an external circuit or conductive traces provided on the upper side surface of the force-bearing member to form the corresponding arm resistors.

[0015] Preferably, the strain resistors of the first group of strain resistors and the third group of strain resistors are equally angularly spaced in the circumferential direction, and the strain resistors of the second group of strain resistors and the fourth group of strain resistors are equally angularly spaced in the circumferential direction.

[0016] The present utility model also claims to protect an axial force sensor, which includes:

[0017] The above force-sensitive element;

[0018] An electronic module assembly arranged on the upper side of the force-sensitive element, which is electrically connected to the strain resistors; and

[0019] A housing covering the electronic module assembly and the strain resistors from the upper side, and the first force-bearing portion is located outside the housing.

[0020] Preferably, the force-receiving member and the boss are annular, and the force-receiving member is provided with an axially-through shaft hole at its center; the housing includes an outer cylindrical shell, an inner cylindrical shell which are coaxially arranged inside and outside and axially arranged up and down, and a cover plate connecting the upper ends of the outer cylindrical shell and the inner cylindrical shell. The lower end of the outer cylindrical shell is sealingly fixed to the force-sensitive element; the lower end of the inner cylindrical shell extends into the shaft hole and is sealingly connected to the shaft hole.

[0021] Preferably, the force-receiving member and the boss are circular; the axial force sensor further includes a stepped conductive helical spring in electrical contact with the electronic module assembly at one end, and the conductive helical spring is held in a terminal holder; the upper part of the housing is wound inward to form a clamping portion, and the clamping portion presses the terminal holder downward. Description of the Drawings

[0022] Figure 1 Is a top view of the force-sensitive element of the first embodiment;

[0023] Figure 2 Is the first embodiment of the force-sensitive element along Figure 1 The sectional view taken along A-A shown;

[0024] Figure 3 Is the circuit diagram of the Wheatstone bridge composed of strain resistors of the first embodiment;

[0025] Figure 4 Is the longitudinal sectional view of the axial force sensor of the first embodiment;

[0026] Figure 5 Is a top view of the force-sensitive element of the second embodiment;

[0027] Figure 6 Is the second embodiment of the force-sensitive element along Figure 5 The sectional view taken along B-B shown;

[0028] Figure 7 Is the circuit diagram of the Wheatstone bridge composed of strain resistors of the second embodiment;

[0029] Figure 8 、 Figure 9 Is the stress simulation calculation results of the radial stress σr and the tangential stress σt on the symmetric median line M of the upper surface of the protruding part of the force-sensitive element of the second embodiment without the groove structure;

[0030] Figure 10 、 Figure 11 Is the stress simulation calculation results of the radial stress σr and the tangential stress σt on the symmetric median line M of the upper surface of the protruding part of the force-sensitive element of the second embodiment with the groove structure;

[0031] Figure 12Exploded view of the axial force sensor of the second embodiment;

[0032] Figure 13 Longitudinal sectional view of the axial force sensor of the second embodiment;

[0033] Figure 14 Stereogram of the force-sensitive element of the third embodiment;

[0034] Figure 15 、 Figure 16 Stress simulation calculation results of the radial stress σr and tangential stress σt on the symmetry median line M of the upper side surface of the protrusion of the force-sensitive element of the third embodiment under the non-porous structure;

[0035] Figure 17 、 Figure 18 Stress simulation calculation results of the radial stress σr and tangential stress σt on the symmetry median line M of the upper side surface of the protrusion of the force-sensitive element of the third embodiment under the porous structure;

[0036] Figure 19 Exploded view of the axial force sensor of the third embodiment;

[0037] Figure 20 Longitudinal sectional view of the axial force sensor of the third embodiment;

[0038] Figure 21 Stereogram of the force-sensitive element of the fourth embodiment;

[0039] In the figure: 11a, 11b, 11c, 11d, 21a, 21b, 21c, 21d, 21e, 21f, the first strain resistors; 21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d, 22e, 21f, the first strain resistors; 11, 21, the force-sensitive elements; 100, 200, the axial force sensors; 110, 210, the force-receiving members; 111, 211, the first force-receiving portions; 112, 212, the second force-receiving portions; R1, the first bridge arm resistor; R2, the second bridge arm resistor; R3, the third bridge arm resistor; R4, the fourth bridge arm resistor; 119, the conductive trace; 115, the boss; 113, 213, the protrusions; 118, 218, the insulating layers; 114, the circumferential positioning portion; Z1, the first annular region; Z2, the second annular region; 116, 216, the concave portions; 13, 23, the support members; 14, 24, the electronic module assemblies; 15, 25, the housings; F1, F2, the axial forces; 24a, the flexible circuit board; 12, 22, the sealing rings; 110, 220, the force-receiving members; 113a, the sealing groove; 19, the pin; 16, 26, the terminals; 115a, the groove; 115b, the hole. Detailed implementation manners

[0040] The technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are exemplary and are only used to explain the present application, and cannot be construed as a limitation to the present application. In the following description, the same reference numerals are used to represent the same or equivalent elements, and repeated descriptions are omitted.

[0041] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present application 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 construed as a limitation to the present application.

[0042] In addition, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0043] It should also be further understood that the term "and / or" used in the specification and corresponding claims of the present application refers to any combination of one or more of the listed items and all possible combinations.

[0044] As Figures 1 to 3 shown. In the first embodiment of the present invention, a force-sensitive element 21 is provided. The force-sensitive element 21 includes a circular force-receiving member 210, and the force-receiving member 210 extends axially up and down. The force-receiving member 210 has an annular first force-receiving portion 211 provided on its upper side and an annular second force-receiving portion 212 provided on its lower side. The second force-receiving portion 212 is concentrically provided radially outside the first force-receiving portion 211. The first force-receiving portion 211 is used to receive the downward axial force F1, and the second force-receiving portion is used to receive the downward axial force F2. In the state of static force balance, F1 and F2 are reaction forces to each other, equal in magnitude and opposite in direction. Under the action of the axial force F1 and the axial force F2, a bending stress is generated on the upper surface of the force-sensitive element 21. Since the first strain resistors 21a to 21f and the second strain resistors 22a to 22f are located at different radial distances, under the action of the axial force, the resistance change amounts are different. Therefore, it can also be said that the first strain resistors and the second strain resistors are arranged at different radial distances of different deformation amounts of the force-receiving member 210.

[0045] The force sensitive element 21 further includes twelve strain resistors which are insulatedly attached to the upper surface of the force bearing member 210 and are located radially inward of the first force bearing portion 211. The twelve strain resistors are composed as follows: Figure 2 The Wheatstone full bridge shown. The six first strain resistors 21a-21f are sequentially and spaced apart in the first annular region Z1 on the relatively radial inner side, and the other six second strain resistors 22a-22f are sequentially and spaced apart in the second annular region Z2 on the relatively radial inner side. The six first strain resistors 21a-21f and the six second strain resistors 22a-22f are staggered in the circumferential direction. The upper surface of the force-bearing member 210 may be covered with an insulating layer 218, and the strain resistors are arranged on the upper surface of the insulating layer 218.

[0046] Among them, the three first strain resistors 21a, 21c and 21e are the first group, which are connected in parallel to form the first bridge arm resistor R1; the three second strain resistors 22a, 22c and 22e are the second group, which are connected in parallel to form the second bridge arm resistor R2; the three first strain resistors 21b, 21d and 21f are the third group, which are connected in parallel to form the third bridge arm resistor R3; the three second strain resistors 22b, 22d and 22f are the fourth group, which are connected in parallel to form the fourth bridge arm resistor R4. Among them, the first bridge arm resistor R1 and the second bridge arm resistor R2 are located on the bridge arms on opposite sides, and the second bridge arm resistor R2 and the fourth bridge arm resistor R4 are located on the bridge arms on opposite sides. The Wheatstone full bridge is provided with voltage by the Vc and Vd terminals, and under the balancing action of F1 and F2, the corresponding voltage signals are output by the V1 and V2 terminals, thereby measuring the magnitude of the axial force.

[0047] In the force sensitive element 21 of the embodiment, since each bridge arm resistor of the Wheatstone full bridge serving as the measuring circuit is composed of three circumferentially distributed strain resistors, for a certain degree of matching deviation (such as coaxiality deviation), although the resistance value of a certain strain resistor of the bridge arm on the opposite side changes differently, the overall difference in the bridge arm resistance composed of the above three strain resistors is much smaller. Therefore, the measurement deviation caused by mechanical matching factors such as coaxiality deviation can be eliminated to a large extent, thereby improving the measurement accuracy; and since they are all in the same temperature environment, the temperature drift caused by this is avoided.

[0048] In a further preferred embodiment of this embodiment, the twelve strain resistors are arranged on the upper surface of the force bearing member 210 at an angle interval of 30° in the circumferential direction, and preferably have the same or similar initial resistance values. Figure 2Only every three of the above strain resistors are shown as forming the corresponding arm resistors in parallel. However, in some other variant embodiments, every three of the above strain resistors can also form the corresponding arm resistors in series. In some more complex variant embodiments, the three resistors can also be connected in a hybrid series-parallel manner. For example, two of the strain resistors can be connected in series first and then in parallel with the remaining one, or two of the strain resistors can be connected in parallel first and then in series with the remaining one. In some other more complex variant embodiments, each arm resistor can also be formed by four or more strain resistors in the same manner. In short, configuring the total resistance value of each arm resistor to depend on the combination formed in the same manner by the strain resistors arranged at the same radial distance but evenly distributed at multiple circumferential angles is very beneficial for reducing the error of the force-sensitive element caused by mechanical fitting deviation.

[0049] Among them, the strain resistors of each arm resistor can be connected by means of an external circuit to form a parallel or series or hybrid series-parallel connection.

[0050] Among them, the upper surface of the force-sensitive element 21 can be lifted upward relative to the first force-receiving portion 211 to form a circular boss 215.

[0051] Such as Figure 4As shown in the figure, this embodiment also provides an axial force sensor 200 that applies the above-mentioned force-sensitive element 21. In addition to including the above-mentioned force-sensitive element 21, the axial force sensor 200 further includes a housing 25. The lower part of the housing 25 can be cylindrical, and its lower end can be welded to a first support step surface 217 formed on the inner side of the first force-receiving part 211 of the force-sensitive element 21. The housing 25 surrounds the periphery of the boss 215, and the first force-receiving part 211 is located outside the housing 25. An electronic module assembly 24 is further provided inside the housing 25. The electronic module assembly 24 can be electrically connected to the strain resistor through a flexible circuit board 24a. The electronic module assembly 24 can be fixedly supported on a cylindrical support base 23. The support base 23 is located inside the housing 25, and its lower end can similarly be supported on the first support step surface 217. The electronic module assembly 24 is electrically led out through several terminals 26. Among them, the terminal 26 can be a stepped conductive spiral spring. The conductive spiral spring is held on a terminal holder 26a and is electrically contacted with the electronic module assembly 24 at one end. The upper part of the housing 25 can be rolled inward to form a holding and pressing part (not marked). The holding and pressing part presses the terminal holder 26a downward to the electronic module assembly 24 or the support base 23. A sealing ring 22 can be provided between the terminal holder 26a and the holding and pressing part. In addition to being fixedly supported on a cylindrical support base 23, in some other solutions, the electronic module assembly 24 can also be alternatively directly bonded to the upper side surface of the force-receiving member 110, or directly fixed to the lower end of the terminal holder 26a.

[0052] As Figures 5 to 7 shown. The second embodiment of the present invention provides another force-sensitive element 11 with a different structure. Similar to the first embodiment, the force-sensitive element 11 includes a force-receiving member 110, and the force-receiving member 110 extends axially up and down. Compared with the force-sensitive element 11 of the first embodiment, the force-sensitive element 21 of this embodiment is annular instead of circular, and a shaft hole 131 that penetrates up and down is provided at its center.

[0053] The force-bearing member 110 has an annular first force-bearing portion 111 disposed on its upper side, and an annular second force-bearing portion 112 disposed on its lower side, and the second force-bearing portion 112 is concentrically disposed radially outside the first force-bearing portion 111. The first force-bearing portion 111 is used to receive the downward axial force F1, and the second force-bearing portion is used to receive the downward axial force F2. In a state of static force equilibrium, F1 and F2 are reaction forces to each other, which are equal in magnitude and opposite in direction. Under the action of the axial force F1 and the axial force F2, bending stress is generated on the upper surface of the force sensitive element 11. Since the first strain resistors 11a~11d and the second strain resistors 12a~12d are located at different radial distances, the resistance value changes differently under the action of the axial force. Therefore, it can also be said that the first strain resistor and the second strain resistor are arranged at radial distances of different deformation amounts of the force-bearing member 110.

[0054] The force sensitive element 11 also includes eight strain resistors insulatedly attached to the upper surface of the force-bearing member 110 and located radially inside the first force-bearing portion 111. The eight strain resistors form a Wheatstone full bridge. The four first strain resistors 11a to 11d are sequentially and spaced apart in the first annular area Z3 on the relatively radial inside, and the other four second strain resistors 12a to 12e are sequentially and spaced apart in the second annular area Z4 on the relatively radial inside. The four first strain resistors 21a to 21d and the four second strain resistors 12a to 12d are staggered in the circumferential direction. The upper surface of the force-bearing member 110 may be covered with an insulating layer 118, and the strain resistors are arranged on the upper surface of the insulating layer 118. A circumferential positioning portion 114 for relative positioning with an external setting may be provided on the outer wall of the force-bearing member 110.

[0055] like Figure 7 As shown, two spaced-apart first strain resistors 21a and 21c are the first group, which are connected in parallel to form the first bridge arm resistor R1; two spaced-apart second strain resistors 22a and 22c are the second group, which are connected in parallel to form the second bridge arm resistor R2; two spaced-apart first strain resistors 21b and 21d are the third group, which are connected in parallel to form the third bridge arm resistor R3; two spaced-apart second strain resistors 22b and 22d are the fourth group, which are connected in parallel to form the fourth bridge arm resistor R4. The first bridge arm resistor R1 and the second bridge arm resistor R2 are located on the bridge arms on opposite sides, and the second bridge arm resistor R2 and the fourth bridge arm resistor R4 are located on the bridge arms on opposite sides. The Wheatstone full bridge is provided with voltage by the Vc and Vd terminals, and under the balancing action of F1 and F2, the corresponding voltage signals are output by the V1 and V2 terminals, thereby measuring the magnitude of the axial force. Among them, each strain resistor of the bridge arm resistors R2 and R4 is provided with voltage by an external circuit (for example, through Figure 12The circuits of the electronic module components 14 shown in [figure] are implemented in parallel. The strain resistors of the bridge arm resistors R1 and R3 are connected in parallel through the conductive traces 119 arranged on the upper surface of the force-sensitive element 11. In some other alternative embodiments, the two strain resistors that make up each bridge arm resistor can be connected in series to form the corresponding bridge arm resistor.

[0056] In the force-sensitive element 11 of the embodiment, since each bridge arm resistor of the Wheatstone full bridge as the measurement circuit is composed of two circumferentially distributed strain resistors, for a certain degree of fitting deviation (such as coaxiality deviation), although the resistance values of certain strain resistors on the opposite bridge arms change differently, the difference in the overall bridge arm resistors composed of the above two strain resistors is much smaller. Therefore, the measurement deviation caused by mechanical fitting factors such as coaxiality deviation can be largely eliminated, thereby improving the measurement accuracy; and since they are all in the same temperature environment, the temperature drift caused thereby is avoided.

[0057] In a further preferred embodiment of the present embodiment, the eight strain resistors are arranged on the upper surface of the force-receiving member 110 at an angular interval of 45° in the circumferential direction, and preferably have the same or similar initial resistance values.

[0058] The force-sensitive element 11 in the present embodiment can also have a more optimized structure. Specifically, the upper surface of the force-sensitive element 21 can be lifted upward relative to the first force-receiving portion 211 to form a convex platform 115. The first strain resistors 11a to 11d are located on the upper surface of the convex platform 115 that protrudes upward from the first force-receiving portion 111, and the second strain resistors 12a to 12d are correspondingly arranged on the upper surfaces of a plurality of peninsula-shaped protruding portions 113 formed by the outer wall of the convex platform 115 protruding radially outward. Two circumferentially adjacent protruding portions 113 are separated by an axially extending concave portion 116 in the circumferential direction. A tangentially extending groove 113a is provided at the lower part of the outer wall of the protruding portion 113. By providing such a groove 113a, the resistance value of the second strain resistor can be made opposite to that of the first strain resistor, that is, decreased, under the action of the axial forces F1 and F2, thereby improving the measurement accuracy.

[0059] In the above embodiments, the strain resistors are preferably isotropic resistors, such as thick film resistors, that is, having the same resistance strain coefficient in all directions.

[0060] According to the existing mechanical theory, when the force-sensitive element 11 has no peninsula-shaped protruding portion 113, the stresses at all parts of its upper surface are tensile stresses, and the tensile stress is greater near the radially inner side.

[0061] Figure 8 、 Figure 9The stress simulation calculation results of the radial stress σr and the tangential stress σt on the symmetric center line M of the upper surface of the protrusion 113 of the non-grooved 113a are respectively shown under the condition that the magnitudes of the axes F1 and F2 are both 35 KN. The results show that under the condition that there is a protrusion 113 and there is no groove on the protrusion 113, the radial stress σr has a negative stress (i.e., compressive stress) in a relatively limited radial distance range at the radial outer edge, and its minimum value is approximately -3 MPa. At the same time, the minimum value of the tangential stress σt is approximately 8 Mpa, which also appears at the radial outer edge position. This indicates that by setting the protrusion 13, its stress distribution is changed, so that the total bending stress within a certain radial distance near the edge decreases. The symmetric center line M extends radially along the force-receiving member 110.

[0062] Figure 10 , Figure 11 respectively show Figure 6 the stress simulation calculation results of the radial stress σr and the tangential stress σt on the symmetric center line M of the upper surface of the protrusion 113 with the groove 113a of the force-sensitive element 11 shown in

[0063] under the condition that the magnitudes of the axes F1 and F2 are both 35 KN. The results show that under the condition that there is a protrusion 113 and there is a grooved structure, the absolute value of the negative stress of the radial stress σr at the radial outer edge increases, and its minimum value is -13 MPa. However, at the same time, the tangential stress σt correspondingly has a minimum value of approximately -24 Mpa at a non-edge radial distance (5.7 mm to 6.1 mm radially outward starting from the inner edge of the boss), and the change is faster than that of σr. Therefore, when the radial distance is within an appropriate range (for example, about 5.8 mm), the radial stress σr is approximately 13 Mpa, and the tangential stress σt is approximately -18 MPa. When an isotropic second strain resistor is set here, its resistance value will decrease compared to the initial resistance value. Furthermore, by reducing R2 and R4 composed of the second strain resistors (while R1 and R3 composed of the first strain resistors still increase), the measurement accuracy is greatly improved.

[0064] As Figures 12 to 13As shown in the figure, this embodiment also provides an axial force sensor 100 that applies the above force-sensitive element 11. In addition to including the above force-sensitive element 11, the axial force sensor 100 further includes a housing 15. The lower part of the housing 15 can be an inner and outer double-cylinder shell structure, including an outer cylinder shell 151 and an inner cylinder shell 152 that are coaxially arranged inside and outside and axially arranged up and down, and a cover plate 153 that connects the upper ends of both the outer cylinder shell 151 and the inner cylinder shell 152. Among them, the lower end of the outer cylinder shell 151 can be hermetically fixed to a first support step surface 117 formed on the force-sensitive element 21 and located inside the first force-receiving part 111. The lower end of the inner cylinder shell 152 extends into the shaft hole 131 and can be hermetically connected to the inner wall of the shaft hole 131 through a sealing ring 12. The sealing ring 12 can be arranged in a sealing groove 131a formed on the inner wall of the shaft hole 131. The first force-receiving part 111 is located outside the outer cylinder shell 151.

[0065] The housing 15 and the force-sensitive element 11 enclose an installation cavity (not marked). An electronic module assembly 14 is arranged in the installation cavity. The electronic module assembly 14 can be electrically connected to the strain resistor through leads (not shown). A support seat 13 for supporting the electronic module assembly 14 can also be arranged in the installation cavity. The electronic module assembly 14 can be electrically led outwards through a plurality of terminals 16. The terminals 16 can be pin needles, and one end of which penetrates the housing 15 inward and is electrically connected to the electronic module assembly 14. Among them, the inner side of the terminal 16 can be assisted in fixing through a terminal fixing member 16a fixed to the upper end of the electronic module assembly 14. The electronic module assembly 14 can be positioned with respect to the force-sensitive element 11 through a vertical pin 19. For example, a positioning blind hole (not shown) can be arranged on the force-sensitive element 11, and a positioning hole 19a can be arranged on the electronic module assembly 14. The upper and lower ends of the pin 19 are inserted into the positioning hole 19a and the positioning blind hole.

[0066] Among them, an axially extending concave portion 116 is formed relatively between every two adjacent protruding portions 113 in the circumferential direction. One end of the concave portion 116 can sink to the lower side of the first force-receiving part 111. The positioning blind hole can be arranged at the bottom of the concave portion 116.

[0067] As Figure 14 shown, the third embodiment of the present utility model provides a force-sensitive element 11 obtained by changing on the basis of the second embodiment. Compared with the second embodiment, the force-sensitive element 11 of this embodiment is provided with a tangentially extending hole 113b on its protruding portion 113 to replace the groove 113a. At the same time, the concave portion 116 can be selectively omitted. Among them, for the convenience of processing, the hole 113b is preferably a straight hole.

[0068] Figure 15 、 Figure 16 respectively show Figure 14The stress simulation calculation results of the radial stress σr and tangential stress σt on the symmetric center line M of the upper surface of the non-porous protruding portion 113 of the force-sensitive element in [[]] under the condition that the magnitudes of the axes F1 and F2 are both 30 KN show that: under the condition that the protruding portion 113 is provided and there is no hole in the protruding portion 113, the radial stress σr has a negative stress (i.e., compressive stress) in a relatively limited radial distance range at the radial outer edge, and its minimum value is approximately -19 MPa. At the same time, the minimum value of the tangential stress σt is approximately -3.4 Mpa, which also appears at the radial outer edge position.

[0069] Figure 17 、 Figure 18 respectively show Figure 14 the stress simulation calculation results of the radial stress σr and tangential stress σt on the symmetric center line M of the upper surface of the protruding portion 113 with a hole 113b of the force-sensitive element in [[]] under the condition that the magnitudes of the axes F1 and F2 are both 30 KN. The results show that: under the condition that the protruding portion 113 is provided and there is a hole structure, both the radial stress σr and the tangential stress σt have minimum values at a non-edge radial distance (4.8 mm radially outward starting from the inner edge of the boss), and their minimum values are -15 MPa and -67 MPa respectively. Since the surface radial stress within the first annular region (about 2 mm radially outward starting from the inner edge of the boss) is above 100 MPa, in order to make the decrease value of the second strain resistor as close as possible to the increase value of the first strain resistor, the radial stress σr and the tangential stress σt can be made to take the maximum values as much as possible.

[0070] Combined with the simulation calculation results of the force-sensitive element of the second embodiment, it can be seen that setting a hole 113b on the protruding portion 115 can more effectively reduce the resistance value of the second strain resistor, thereby improving the measurement accuracy compared to setting a groove 113a.

[0071] Please refer to Figure 18 、 Figure 19 For the third embodiment of the present invention, an axial force sensor 100 using the above force-sensitive element 11 is further provided. Compared with the second embodiment, in addition to the different structure of the force-sensitive element 11, the overall structure of the axial force sensor 100 can also be selectively changed as follows: The terminal 16 can be replaced by a cable, and one end thereof passes through the housing 15 inward and is electrically connected to the electronic module assembly; the axial force sensor 100 can also include an annular force transmission member 17, which abuts downward against the first force-receiving portion 111.

[0072] Preferably, the support base 13 may include a vertical cylindrical portion 131 and a horizontal support plate 132 horizontally connected to the proximal end of the upper end of the cylindrical portion 131. The electronic module assembly 14 is supported on the horizontal support plate 132 and surrounded by the upper end of the cylindrical portion 131. More preferably, a positioning notch 133 is formed at the upper end of the cylindrical portion 131, and a part of the electronic module assembly 14 extends circumferentially into the positioning notch 133 to form circumferential positioning. A relief hole 134 allowing the lead to pass through may be formed on the horizontal support plate 132.

[0073] Please refer to Figure 20 , the fourth embodiment of the present invention further provides a relatively inferior force-sensitive element 11. Compared with the force-sensitive element of the second embodiment, the force-sensitive element of this embodiment includes four strain resistors instead of eight strain resistors, that is, two first strain resistors 11a, 11b and two second strain resistors 12a, 12b are staggeredly distributed in the circumferential direction of the force-receiving member 110, and these four strain resistors are distributed at an angular interval of 90° in the circumferential direction. Each strain resistor individually forms an arm resistor of a Wheatstone full bridge as a group, rather than being formed by several strain resistors through parallel connection, series connection or a combination of parallel and series connections. Compared with the prior art solution in which four strain resistors are all arranged on the upper side surface of the force-receiving member 110, due to the presence of the groove 113a, the stress states of the second strain resistor and the first strain resistor are opposite, thereby improving the measurement accuracy.

[0074] A housing 15 covering the electronic module assembly and the strain resistor from above, and the first force-receiving portion 111 is located outside the housing 15.

[0075] In the above embodiments, a protective layer such as protective glaze may be covered on the strain resistor and the conductive trace.

[0076] The scope of the present disclosure is not limited by the detailed description, but is defined by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are construed as being included in the present disclosure.

Claims

1. A force sensitive element (11), characterized in that: include: A force-bearing member (110) is arranged axially in the up-down direction and is annular or circular, and comprises an annular first force-bearing portion (111) arranged on the upper side thereof, an annular second force-bearing portion (112) arranged on the lower side thereof, and a boss (115) protruding upward from the first force-bearing portion (111); the second force-bearing portion (112) is concentrically arranged on the radial outer side of the first force-bearing portion (111) and the radial outer side of the boss (115); the boss (115) is annular or circular corresponding to the shape of the force-bearing member (110); the outer wall of the boss (115) protrudes radially outward to form a plurality of peninsula-shaped protrusions (113) separated in the circumferential direction; Four groups of strain resistors are attached to the upper surface of the force-bearing member (110) at intervals and insulated throughout the circumference of the force-bearing member (110) and are located radially inside the first force-bearing portion (111), each group of strain resistors having the same number and at least one strain resistor, the first group of strain resistors (11a, 11c) and the third group of strain resistors (11b, 11d) are circumferentially spaced and distributed in a first annular area (Z1) on the upper surface of a boss (115) protruding upward from the first force-bearing portion (111), the second group of strain resistors (2 The second group of strain resistors (22a, 22c) and the fourth group of strain resistors (22b, 22d) are circumferentially spaced and distributed in a second annular area (Z2) on the upper surface of the force-bearing member (110), and the second annular area (Z2) is located outside the first annular area (Z1); the strain resistors of the second group of strain resistors (22a, 22c) and the fourth group of strain resistors (22b, 22d) are distributed one by one on the upper surface of a plurality of peninsula-shaped protrusions (113) separated in the circumferential direction and formed by the outer wall of the boss (115) protruding radially outward; Among them, the four groups of strain resistors are respectively combined into four bridge arm resistors (R1, R2, R3, R4) of the Wheatstone full bridge, and the bridge arm resistors corresponding to the first group of strain resistors and the third group of strain resistors are located on the two bridge arms on opposite sides; each group of strain resistors is combined into a corresponding bridge arm resistor individually or in parallel, series or mixed series-parallel.

2. The force sensitive element (11) according to claim 1, characterized in that: A hole (113b) extending tangentially is provided at the lower portion of the outer wall of the protruding portion (113).

3. The force sensitive element (11) according to claim 2, characterized in that: The hole (113b) is a straight hole.

4. The force sensitive element (11) according to claim 1, characterized in that: The protrusion (113) itself is symmetrically arranged about a symmetrical center line (M) extending radially along the force-bearing member, and the strain resistors (12a, 12b, 12c, 12d) arranged on the protrusion (113) are arranged on the symmetrical center line of the protrusion (113).

5. The force sensitive element (11) according to claim 1, characterized in that: An axially extending inner recess (116) is formed between each two circumferentially adjacent protrusions (113).

6. The force sensitive element (11) according to claim 1, characterized in that: The strain resistors are electrically connected via an external circuit or a conductive trace (119) disposed on the upper surface of the force-bearing member (110) to form corresponding bridge arm resistors.

7. The force sensitive element (11) according to claim 1, characterized in that: The strain resistors of the first group of strain resistors (11a, 11c) and the third group of strain resistors (11b, 11d) are distributed at equal angles in the circumferential direction, and the strain resistors of the second group of strain resistors (21a, 21c) and the fourth group of strain resistors (21b, 12d) are distributed at equal angles in the circumferential direction.

8. An axial force sensor, characterized in that: include: A force sensitive element (11) as claimed in any one of claims 1 to 7; An electronic module assembly (14) disposed on the upper side of the force sensitive element (11) and electrically connected to the strain resistor; and A housing (15) is provided outside the electronic module assembly and the strain resistor from the upper side, and the first force-bearing portion (111) is located outside the housing (15).

9. The axial force sensor according to claim 8, characterized in that: The force-bearing member (110) and the boss (115) are annular in shape, and an axial hole (131) is provided at the center of the force-bearing member (110) and passes through the member vertically; the housing (15) comprises an outer cylindrical shell (151), an inner cylindrical shell (152) and a cover plate (153) connecting the upper ends of the outer cylindrical shell (151) and the inner cylindrical shell (152), which are coaxial inside and outside and arranged axially vertically; the lower end of the outer cylindrical shell (151) is sealedly fixed to the force sensitive element (11); the lower end of the inner cylindrical shell (152) extends into the axial hole (131) and is sealedly connected to the axial hole (131).

10. The axial force sensor according to claim 8, characterized in that: The force-bearing member (110) and the boss (115) are circular; the axial force sensor also includes a stepped conductive coil spring, one end of which is in electrical contact with the electronic module assembly (14), and the conductive coil spring is retained in a terminal retaining seat (26a); the upper part of the shell is rolled inward to form a pressing portion, and the pressing portion presses the terminal retaining seat (26a) downward.

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