Force sensor and manufacturing method thereof

Abstract

A force sensor and a manufacturing method, the force sensor comprises: a support sleeve, the top of the support sleeve is provided with a first groove; a sensitive element, sealed and connected in the first groove, the sensitive element is a cylinder, the top of the sensitive element is provided with a truncated cone-shaped pressure head and a groove surrounding the outer periphery of the pressure head, the pressure head protrudes from the top of the support sleeve, the bottom of the sensitive element is a plane, and two strain resistor pairs are provided, the two strain resistor pairs are centrally symmetrically arranged, each strain resistor pair includes two resistors connected in series, the two resistors are arranged along the radial direction of the sensitive element, and the resistors are thin film resistors; a cable, the cable passes through the side wall of the support sleeve and is electrically connected to the resistor. The sensor of the present invention can adapt to various harsh working conditions of aircraft, has high reliability and excellent performance, and has a significant effect on improving the reliability and performance indicators of the aircraft's all-electric brake device.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and more specifically, relates to a force sensor and a manufacturing method thereof. Background Art

[0002] Force sensors are basic mechanical sensors widely used in industrial production, military equipment, aerospace, navigation and other fields. Most of their measurement principles are based on resistance strain gauge technology. The strain caused by the force on the elastic body of the resistance strain gauge is converted into a change in the resistance value of the resistance strain gauge, and then the resistance change is converted into a voltage signal through a Wheatstone bridge. This type of force sensor has a mature process and a clear division of labor in the industrial chain, and can solve most application needs. However, the organic rubber substrate used in the resistance strain gauge itself directly participates in the strain. When it works for a long time or frequently in a repeatedly alternating thermal environment in a wide temperature range, and is superimposed with high vacuum or ultra-high vacuum environmental conditions, there are hidden dangers in reliability and life. Traditional metal resistance strain force sensors are also limited by the manufacturing process and material properties of metal resistance strain gauges. It is usually difficult to make them very small in size, or it must be at the cost of reducing the resistance of the bridge arm resistance, which leads to high self-heating, thermal stability, power consumption and other performance indicators. At the same time, the resistance strain gauges made by the manufacturing process of metal resistance strain gauges also have many deficiencies in the high temperature resistance requirements and wide working temperature range when working for a long time. For example, the common metal resistance strain gauge substrate uses polymer organic materials, which will gradually age when working at high temperature for a long time, resulting in the migration of performance indicators. Although the performance affected by temperature can be compensated, it needs to be compensated within a certain temperature range to achieve better results. In general, the resistance strain gauge process technology cannot meet the application environment requirements of some high reliability, wide working temperature range, and miniaturization requirements in the current aerospace and other fields. For example, in the aircraft's all-electric braking system, the braking force value often reaches several kilonewtons or even more than ten kilonewtons, but due to the volume and weight requirements of the braking system, the volume of the sensor is often limited to the volume range of several one-yuan coins or even dimes superimposed. Due to the characteristics of the space environment, seasonal changes, and the huge heat generated by friction during braking, the working environment faced by the sensor is very harsh. For the aviation field, there are also high requirements for service life, especially fatigue life.

[0003] Therefore, a force sensor is needed to solve at least one of the above problems. Summary of the invention

[0004] The object of the present invention is to provide a force sensor and a manufacturing method thereof, so as to solve the problem that the traditional force sensor is difficult to be very small in size and has a wide operating temperature range.

[0005] In order to achieve the above object, the present invention provides a force sensor, comprising:

[0006] A support sleeve, wherein a first groove is provided on the top of the support sleeve;

[0007] A sensitive element, the sensitive element is sealed and connected in the first groove, the sensitive element is a cylinder, the top of the sensitive element is provided with a truncated cone-shaped pressure head and a groove surrounding the outer circumference of the pressure head, the pressure head protrudes from the top of the support sleeve, the bottom of the sensitive element is a plane, and is provided with two strain resistor pairs, the two strain resistor pairs are centrally symmetrically arranged, each strain resistor pair includes two resistors connected in series, the two resistors are arranged along the radial direction of the sensitive element, and the resistors are thin film resistors;

[0008] A cable passes through the side wall of the support sleeve and is electrically connected to the resistor.

[0009] Preferably, the support sleeve is cylindrical, and the inner wall of the support sleeve is provided with the first groove, the second groove, the third groove, the fourth groove and the fifth groove which are annular, penetrate axially and are connected in sequence from top to bottom, and the cable passes through the side wall of the support sleeve and extends into the fourth groove.

[0010] Preferably, the diameters of the second groove and the fourth groove are the same, and the diameters of the second groove and the fourth groove are smaller than the diameter of the first groove and larger than the diameter of the third groove.

[0011] Preferably, a pad corresponding to the resistor is provided at the bottom of the sensitive element, the force sensor further comprises a circular compensation circuit board, the compensation circuit board is arranged in the fourth groove, a plurality of connection points are provided on the compensation circuit board, the pads corresponding to the resistors of the two strain resistor pairs are electrically connected to the connection points through leads to form an electric bridge, the resistor is a thin film resistor, the electric bridge is a Wheatstone bridge, and the cable is electrically connected to the electric bridge;

[0012] The fourth groove is provided with sealant for sealingly connecting the compensation circuit board to the support sleeve.

[0013] Preferably, at least one compensation resistor is further provided at the bottom of the sensitive element, and the compensation resistor is electrically connected to the bridge and is used for zero point compensation of the bridge.

[0014] Preferably, a harness hole is provided on the side wall of the support sleeve, and the cable passes through the harness hole and extends into the fourth groove; the outer side of the harness hole and the cable are bonded to each other by high temperature resistant epoxy resin glue.

[0015] Preferably, the bottom of the sensitive element is coated with a triple-proof protective layer, and the triple-proof protective layer at least covers the pad and the resistor.

[0016] Preferably, a sealing sheet is further included, which is circular and sealed in the fifth groove. The diameter of the fifth groove is greater than the diameter of the fourth groove.

[0017] Preferably, the support sleeve also includes a sixth groove located at the bottom of the support sleeve and connected to the fifth groove, the diameter of the sixth groove is larger than the diameter of the fifth groove, the sealing sheet and the support sleeve are sealed by a sealing material, the sealing material is located in the sixth groove and is not higher than the bottom end surface of the support sleeve.

[0018] The present invention also provides a method for manufacturing the force sensor, comprising:

[0019] Step 1: manufacturing a sensitive element, and manufacturing a thin film resistor on the sensitive element to form the strain resistor pair;

[0020] Step 2: installing the sensitive element in the first groove of the support sleeve, and sealing the gap between the sensitive element and the support sleeve by welding;

[0021] Step 3: electrically connecting the resistors of the strain resistor pair to form the bridge, and performing three-proof protection on the bottom surface of the sensitive element;

[0022] Step 4: inserting the cable through the side wall of the support sleeve and electrically connecting it to the bridge, and bonding and sealing the cable to the side wall of the support sleeve;

[0023] Step 5: sealing the support sleeve;

[0024] Step 6: Test, inspect and experiment the load cell.

[0025] The present invention relates to a force sensor, which has the beneficial effect that: the end of the sensor of the present invention that is away from the pressure head is fixed on the installation plane, the electrical part is connected by a cable, and the sensor outputs an initial zero signal after power is turned on; when axial pressure is applied to the truncated cone-shaped pressure head of the sensitive element at the other end of the sensor, the sensitive element will deform in the direction of the force, and the resistor in the bridge will be compressed or stretched, generating an output electrical signal change proportional to the change in force value. By adopting the sputtering film process to make the sensitive element, the sensor can achieve a high-precision force measurement of up to 10 kilonewtons on the premise that the diameter does not exceed 20mm and the height does not exceed 11mm, and its repeatability can reach within ±0.1%FS, and within the working temperature range of -55℃~+125℃, without compensation, the temperature is affected by ±1%FS. When the sensor of the present invention is used in the aircraft all-electric brake device, it is of great help to reduce the overall volume and weight of the brake device. At the same time, the sensor of the present invention can adapt to various harsh working conditions of the aircraft, has high reliability and excellent performance, and has a significant effect on improving the reliability and performance indicators of the aircraft all-electric brake device.

[0026] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0028] Figure 1 A schematic structural diagram of a force sensor according to an exemplary embodiment of the present invention is shown;

[0029] Figure 2 A top view of a load cell according to an exemplary embodiment of the present invention is shown;

[0030] Figure 3 A schematic diagram showing the layout of resistors of a sensitive element in a force sensor according to an exemplary embodiment of the present invention is shown;

[0031] Figure 4 A circuit diagram of a bridge in a force sensor according to an exemplary embodiment of the present invention is shown.

[0032] Description of reference numerals:

[0033] 1. Sensitive element; 2. Support sleeve; 3. Compensation circuit board; 4. Sealing sheet; 5. Sealant; 6. Welding seam; 7. Lead wire; 8. Cable; 9. Wire harness hole; 10. Groove; 11. Pressure head; 12. Strain resistor pair; 121. Resistor; 122. Pad; 123. Compensation resistor; 13. Epoxy resin glue. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0035] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0036] In order to solve the problems existing in the prior art, the present invention provides a force sensor, such as Figure 1 and Figure 3 As shown, including:

[0037] A support sleeve 2, wherein a first groove is provided on the top of the support sleeve 2;

[0038] A sensitive element 1 is sealed and connected in the first groove. The sensitive element 1 is a cylinder. A truncated cone-shaped pressure head 11 and a groove 10 surrounding the outer periphery of the pressure head 11 are provided on the top of the sensitive element 1. The pressure head 11 protrudes from the top of the support sleeve 2. The bottom of the sensitive element 1 is a plane and is provided with two strain resistor pairs 12. The two strain resistor pairs 12 are centrally symmetrically arranged. Each strain resistor pair 12 includes two resistors 121 connected in series. The two resistors 121 are arranged along the radial direction of the sensitive element 1. The resistors 121 are thin film resistors.

[0039] The cable 8 passes through the side wall of the support sleeve 2 and is electrically connected to the resistor 121 .

[0040] The force sensor of the present invention fixes one end away from the pressure head 11 on the installation plane, and the electrical part is connected by a cable 8. After power is turned on, the sensor outputs an initial zero signal; when axial pressure is applied to the truncated cone-shaped pressure head 11 of the sensitive element 1 at the other end of the sensor, the sensitive element 1 will deform in the direction of the force, and the resistor 12 in the bridge will be compressed or stretched, generating an output electrical signal change proportional to the change in force value. By adopting the sputtering film process to make the sensitive element 1, the sensor can achieve a high-precision force measurement of up to 10 kN on the premise that the diameter does not exceed 20 mm and the height does not exceed 11 mm, and its repeatability can reach within ±0.1% FS. In the working temperature range of -55℃~+125℃, without compensation, the temperature is affected by ±1% FS. When the sensor of the present invention is used in the aircraft all-electric brake device, it is of great help to reduce the overall volume and weight of the brake device. At the same time, the sensor of the present invention can adapt to various harsh working conditions of the aircraft, has high reliability and excellent performance, and has a significant effect on improving the reliability and performance indicators of the aircraft all-electric brake device.

[0041] In one embodiment of the present invention, Figure 1 and Figure 2 As shown, the support sleeve 2 is cylindrical, and the inner wall of the support sleeve 2 is provided with annular first groove, second groove, third groove, fourth groove and fifth groove connected in sequence from top to bottom along the axial direction, and the cable 8 passes through the side wall of the support sleeve 2 and extends into the fourth groove.

[0042] As a preferred solution, the diameters of the second groove and the fourth groove are the same, and the diameters of the second groove and the fourth groove are smaller than the diameter of the first groove and larger than the diameter of the third groove, so as to maintain diameter consistency and improve linear accuracy and hysteresis accuracy.

[0043] The sensitive element 1 is made of a metal elastic diaphragm, and the materials of the sensitive element 1 and the support sleeve 2 are both martensitic stainless steel. The sensitive element 1 is arranged in the first groove and connected to the support sleeve 2 by laser welding. The weld 6 between the sensitive element 1 and the support sleeve 2 is sealed. The pressure head 11 of the sensitive element 1 and the groove 10 surrounding the pressure head 11 are located within the range of the second groove in the vertical direction. When the pressure head 11 of the sensitive element 1 is pressurized, the annular groove 10 can absorb the pressure deformation of the pressure head 11, and the second groove can absorb the deformation of the sensitive element 1.

[0044] A pad 122 corresponding to the resistor 121 is provided at the bottom of the sensitive element 1. The force sensor also includes a circular compensation circuit board 3. The compensation circuit board 3 is arranged in the fourth groove. A plurality of connection points are provided on the compensation circuit board 3. The pads 122 corresponding to the resistors 121 of the two strain resistor pairs 12 are electrically connected to the connection points through the lead wires 7 to form an electric bridge. The electric bridge is a Wheatstone bridge. The cable 8 is electrically connected to the electric bridge.

[0045] A sealant 5 is provided in the fourth groove for sealingly connecting the compensation circuit board 3 to the support sleeve 2 .

[0046] The compensation circuit board 3 is arranged in the fourth groove. Since the diameter of the third groove is smaller than that of the fourth groove, the compensation circuit board 3 is limited by the fourth groove and the step of the third groove, and is sealed and fixed by pouring glue in the fourth groove. The sealant 5 can be silicone rubber. The potting silicone rubber should completely cover the compensation circuit board 3, and the thickness of the sealant 5 should not be less than 2mm, so as to better play the three anti-sealing and waterproof, dustproof and anti-static functions.

[0047] To prevent wire mixing, lead wire 7 is made of enameled wire, and the specific type is selected according to different national standards of enameled wires according to working conditions such as operating temperature.

[0048] The lead wire 7 extending from the end point of the bridge is generally thin and easy to break. By providing a compensation circuit board 3 and providing a connection point on the compensation circuit board 3, the conversion of the lead wire 7 to the cable 8 is achieved, making the transmission of electrical signals between the bridge and the plug stronger and more reliable; in addition, providing the compensation circuit board 3 can also play a role in temperature compensation.

[0049] In one embodiment of the present invention, at least one compensation resistor 123 is further provided at the bottom of the sensitive element 1. The compensation resistor 123 is electrically connected to the bridge and is used for zero point compensation or temperature compensation of the bridge. The compensation resistor 123 is a thin film resistor. The thin film resistor has good output consistency and temperature consistency, is easy to use, and is easy to manufacture large resistance resistors. In addition, the thin film resistor generates little heat under the working current and can be used directly without preheating.

[0050] In other embodiments of the present invention, the compensation circuit 123 may also be disposed on the compensation circuit board 3 and connected to the bridge by being electrically connected to the connection point.

[0051] like Figure 3 As shown, the strain resistor pair 12 of the sensitive element 1 includes but is not limited to two, each strain resistor pair 12 includes two resistors 121, the two strain resistor pairs 12 are symmetrically arranged with the bottom circle center of the sensitive element 1 as the center, and the two strain resistor pairs 12 are in the same diameter direction, that is, the resistors 121 of each strain resistor pair 12 are along the same radial direction, each strain resistor pair 12 includes two resistors 121 and three pads 122 that connect the two resistors 121 in series, and the resistors 121 and pads 122 of each strain resistor pair 12 form a series circuit, which is then connected in parallel with the series circuit of another strain resistor pair 12 to form an electric bridge, which has output positive and negative poles and power supply positive and negative poles, and the compensation resistor 123 is connected between the two series circuits. The compensation resistor 123 is connected in series with the bridge according to the positive and negative conditions of the initial zero point of the bridge, so as to achieve the purpose of compensating the zero point.

[0052] The two resistor pairs 12 arranged along the diameter direction of the sensitive element 1 form an electric bridge, which can effectively offset the influence of the eccentric load. The two resistor pairs 12 are symmetrically arranged on both sides of the center of the cylindrical surface of the support sleeve 2, which can effectively improve the linearity of the sensor.

[0053] In one embodiment of the present invention, Figure 4 The bridge circuit diagram shown in the figure, wherein point a and point b are the output positive electrode and the output negative electrode respectively, point c and point d are the power supply positive electrode and the power supply negative electrode respectively, the compensation resistor 123 is connected to the output positive electrode a, the bridge is pre-tested according to the actual situation, and the actual situation of the bridge is judged according to the test result, so that the potential between the output positive electrode a and the output negative electrode b of the bridge is close to 0, thereby adjusting the series position of the compensation circuit 123, that is, connecting it in series with one of the two series circuits respectively, thereby adjusting the zero point of the bridge, eliminating the potential difference between the output positive electrode and the output negative electrode, so that the output signal of the sensor is only the signal affected by the pressure.

[0054] Multiple connection points are set on the compensation circuit board 3, some of which are electrically connected to the pads 123, some of which are electrically connected to the end points of the bridge, some of which are electrically connected to the compensation resistor 123, and some of which are electrically connected to each core wire of the cable 8, wherein the connection points are electrically connected to each other through signal lines buried in the compensation circuit board 3.

[0055] The connection points on the compensation circuit board 3 are connected in advance on the compensation circuit board 2 according to the needs of forming an electric bridge. When a part of the specific connection points are connected to the pads 122 on the sensitive element 1, the resistor 121 on the sensitive element 1 can be used to form an electric bridge. The compensation resistor 123 is also connected in series to the bridge to compensate for the potential changes at the two output ends of the bridge caused by temperature changes. Therefore, the series position of the compensation resistor 123 can be adjusted according to actual conditions and tests to make the potential between the output positive electrode a and the output negative electrode of the bridge 0, thereby achieving the compensation bridge zero point or compensation temperature.

[0056] The bottom plane of the sensitive element 1 is fixed on the mounting plane, the cable 8 is electrically connected to the external device, and the sensor outputs an initial zero point signal after power is turned on; when axial pressure is applied to the pressure head 11 of the sensitive element 1, the elastic diaphragm of the sensitive element 1 will deform in the direction of the force, and the resistor 121 in the bridge will be compressed or stretched, generating an output electrical signal change proportional to the change in force value.

[0057] In other embodiments of the present invention, when the internal space of the support sleeve 2 meets the requirements, multiple wiring terminals can be pasted on the inner cylindrical surface of the support sleeve 2 to replace the role of the circular compensation circuit board 3. Specifically, multiple wiring terminals are pasted on the inner cylindrical surface of each support sleeve 2 to replace the circular compensation circuit board 3, each wiring terminal has two connection points, and is in a conducting state, each wiring terminal has a connection point connected to the pad 122 of the resistor pair 12 through a lead to form an electric bridge, and the other connection point of each wiring terminal is electrically connected to the core wire of the corresponding cable 8.

[0058] The side wall of the support sleeve 2 is provided with a harness hole 9, which is a round hole or an oblate hole, and the cable 8 passes through the harness hole 9 and extends into the fourth groove; the outer side of the harness hole 9 and the cable 8 are bonded by a high temperature resistant epoxy resin glue 13. The cable 8 is bonded to the outer cylindrical surface of the harness hole 9 of the support sleeve 2 by using the high temperature resistant epoxy resin glue 13, which can improve the pulling resistance of the cable 8 and improve the reliability. In addition, the bonding by the high temperature resistant epoxy resin glue 13 is simple, convenient and easy to operate. The shape of the glue point is easy to control manually, and it is easy to meet the shape restrictions of the installation position.

[0059] Preferably, a metal capillary may be embedded in the harness hole 9 and welded to the support sleeve 2 , and the cable 8 and the metal capillary may be fixed by a heat shrink tube.

[0060] A thin-walled metal capillary that matches the diameter of the harness hole 9 on the cylindrical surface of the support sleeve 2 is selected and inserted into the harness hole 9. Laser welding is used at the intersection of the outer cylindrical surface of the support sleeve 2 and the metal capillary. The cable 8 is inserted into the metal capillary and welded to the internal wiring point, such as the connection point. A heat shrink tube is used to secure the cable 8 and the metal capillary sleeve. This method is more reliable for long-term use in a high-temperature environment, and has better consistency in appearance and structure, and is more suitable for mass production.

[0061] The bottom of the sensitive element 1 is coated with a three-proof protective layer, which at least covers the pad 122 and the resistor 121 and is used for waterproofing, dustproofing and anti-static.

[0062] In harsh environments, such as heat and humidity, frost pollution, etc., the sensor may be damaged. Therefore, the elastic diaphragm surface of the sensitive element 1, that is, the bottom of the sensitive element 1, the connection point on the surface of the compensation circuit board 3, the lead 7 and the core root of the cable 8 are treated with three-proofing to enable it to achieve high-precision measurement in a long-term and stable manner in harsh environments. The material of the three-proofing protective layer is selected according to the working temperature and specific environment, such as silicone three-proofing paint or polyurethane three-proofing paint. Since the coating thickness of the three-proofing protective layer is relatively high, in addition to the pad 122, it can also cover the resistor 121 on the sensitive element 1.

[0063] The force sensor further comprises a sealing sheet 4 which is circular and is sealed in the fifth groove. The diameter of the fifth groove is greater than the diameter of the fourth groove so as to seal the fourth groove.

[0064] The support sleeve 2 also includes a sixth groove located at the bottom of the support sleeve 2 and connected to the fifth groove. The diameter of the sixth groove is larger than the diameter of the fifth groove. The sealing sheet 4 and the support sleeve 2 are sealed by a sealing material. The sealing material is located in the sixth groove and is not higher than the bottom end surface of the support sleeve 2.

[0065] In one embodiment of the present invention, the sealing sheet 4 is fixed and sealed by laser welding, and the sealing material is a weld 6, wherein the weld 6 does not protrude from the sixth groove to ensure that the bottom surface of the support sleeve 2 is flat, so that the accuracy of the sensor will not be affected by the low surface roughness of the weld when it is working, and the weld 6 itself will not be damaged due to pressure on the weld 6.

[0066] In other embodiments of the present invention, the sealing sheet 4 may also be sealed and bonded in the sixth groove by means of a sealant.

[0067] After the circular sealing sheet 4 is installed on the support sleeve 2, it is fixed and sealed by laser welding, so that the interior of the sensor is sealed, reducing the impact or damage of external humidity and foreign matter, so that the interior of the sensor is protected and the reliability is improved.

[0068] The present invention also provides a method for manufacturing the above-mentioned force sensor, the method comprising:

[0069] Step 1: a sputtering thin film process is used to manufacture a sensitive element 1, and a thin film resistor is manufactured on the sensitive element 1 to form a strain resistor pair 12, and a pad 122 corresponding to the resistor 121 of the strain resistor pair 12 is manufactured;

[0070] Step 2: Install the sensitive element 1 in the first groove of the support sleeve 2, and seal the gap between the sensitive element 1 and the support sleeve 2 by welding, which can be laser welding, electron beam welding or other welding methods;

[0071] Step 3: The resistor 121 of the strain resistor pair 12 is electrically connected to form an electric bridge, and the bottom surface of the sensitive element 1 is provided with three-proof protection;

[0072] Step 4: insert the cable 8 through the side wall of the support sleeve 2 and electrically connect it to the bridge, and bond and seal the cable 8 to the side wall of the support sleeve 2;

[0073] Step 5: Sealing support sleeve 2;

[0074] Step 6: Test, inspect and experiment the load cell.

[0075] Specifically, the technology used in the method for manufacturing a small-sized large-value force sensor of the present invention is mature, convenient and easy, and is very suitable for mass production in the form of mechanization and assembly lines.

[0076] Wherein, step 1 comprises: making a metal elastic diaphragm having a thickness matching the test force value;

[0077] Two or more strain resistor pairs 12 and one or more compensation resistors 123 are manufactured on the elastic diaphragm by using a sputtering thin film process, that is, the sensitive element 1 is manufactured.

[0078] The sputtering thin film process makes it easier to achieve miniaturization, overcoming the contradiction between miniaturization and large force measurement. Under the premise that the diameter of the sensor does not exceed 20mm and the height does not exceed 11mm, the sensor can achieve high-precision force measurement of up to 10 kN, and its repeatability can reach within ±0.1% FS. The sensor made by the sputtering thin film process has a wide operating temperature range, ensuring wide temperature range operation and low temperature drift characteristics. The temperature performance of the entire temperature range is already very good when not compensated. Within the operating temperature range of -55℃ ~ +125℃, the temperature influence is within ±1% FS.

[0079] Step 3 includes: using lead 7 to connect the pad 122 of the resistor 121 on the sensitive element 1 and the connection point of the compensation circuit board 3 to form an electric bridge, and spraying the bottom surface of the sensitive element 1 with three-proof paint for three-proof protection.

[0080] The lead wire 7 from the end point of the bridge is generally thin and easy to break. By providing a compensation circuit board 3 and a connection point on the compensation circuit board 3, the lead wire 7 is converted into a cable 8, making the transmission of electrical signals between the bridge and the plug more robust and reliable.

[0081] Step 3 also includes: placing the compensation circuit board 3 in the fourth groove, and bonding, fixing and sealing the compensation circuit board 3 in the fourth groove by filling and curing the silicone rubber.

[0082] Step 4 includes: inserting the cable 8 through the lead hole 9 on the side wall of the support sleeve 2, and electrically connecting it to the connection point of the compensation circuit board 3, so as to be electrically connected to the bridge; embedding a metal capillary in the harness hole 9, and welding it to the support sleeve 2, fixing the cable 8 and the metal capillary through a heat shrink tube, and bonding the cable 8 to the outer cylindrical surface around the harness hole 9 of the support sleeve 2 with a high temperature resistant epoxy glue;

[0083] Step 5 includes: setting a sealing sheet 4 in the fifth groove, the sealing sheet 4 completely covers the fourth groove, fixing the sealing sheet 4 and the support sleeve 2 by welding and sealing the gap between the sealing sheet 4 and the support sleeve 2, and the weld 6 is located in the sixth groove and does not protrude from the support sleeve 2.

[0084] All the processing and manufacturing methods used in the entire sensor are mature and easy. The sputtering thin film process used in the processing and manufacturing of the sensitive element 1 is very suitable for mechanized and assembly-line mass production. The remaining parts can be realized through traditional mechanical processing technology, printed circuit board technology and integrated circuit packaging, welding and assembly technology. The relative bottleneck is manual welding, assembly, debugging and inspection. The problems of manual welding and assembly can be solved through the electric tools, special tooling and welding equipment that are widely used in mature ordinary sensor production lines. The overall solution can be divided according to the process of mature sensor production process, and an appropriate number of assembly tools and calibration inspection tools can be configured according to the demand scale to achieve batch production.

[0085] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A force sensor, characterized in that: include: A support sleeve (2), wherein a first groove is provided on the top of the support sleeve (2); A sensitive element (1), the sensitive element (1) being sealed and connected in the first groove, the sensitive element (1) being a cylinder, the top of the sensitive element (1) being provided with a truncated cone-shaped pressure head (11) and a groove (10) surrounding the outer circumference of the pressure head (11), the pressure head (11) protruding from the top of the support sleeve (2), the bottom of the sensitive element (1) being a plane, and being provided with two strain resistor pairs (12), the two strain resistor pairs (12) being centrally symmetrically arranged, each strain resistor pair (12) comprising two resistors (121) connected in series, the two resistors (121) being arranged along the radial direction of the sensitive element (1), and the resistors (121) being thin film resistors; A cable (8), wherein the cable (8) passes through the side wall of the support sleeve (2) and is electrically connected to the resistor (121).

2. The force sensor according to claim 1, characterized in that The support sleeve (2) is cylindrical, and the inner wall of the support sleeve (2) is provided with the first groove, the second groove, the third groove, the fourth groove and the fifth groove which are annular and connected in sequence from top to bottom along the axial direction, and the cable (8) passes through the side wall of the support sleeve (2) and extends into the fourth groove.

3. The force sensor according to claim 2, characterized in that: The diameters of the second groove and the fourth groove are the same, and the diameters of the second groove and the fourth groove are smaller than the diameter of the first groove and larger than the diameter of the third groove.

4. The force sensor according to claim 3, characterized in that: A pad (122) corresponding to the resistor (121) is provided at the bottom of the sensitive element (1), the force sensor further comprising a circular compensation circuit board (3), the compensation circuit board (3) being arranged in the fourth groove, the compensation circuit board (3) being provided with a plurality of connection points, the pads (122) corresponding to the resistors (121) of the two strain resistor pairs (12) being electrically connected to the connection points via leads (7) to form an electric bridge, the electric bridge being a Wheatstone bridge, the cable (8) being electrically connected to the electric bridge; The fourth groove is provided with a sealant (5) for sealingly connecting the compensation circuit board (3) to the support sleeve (2).

5. The force sensor according to claim 4, characterized in that: At least one compensation resistor (123) is also provided at the bottom of the sensitive element (1); the compensation resistor (123) is electrically connected to the bridge and is used for zero point compensation of the bridge.

6. The force sensor according to claim 3, characterized in that: The side wall of the support sleeve (2) is provided with a harness hole (9), and the cable (8) passes through the harness hole (9) and extends into the fourth groove; the outer side of the harness hole (9) and the cable (8) are bonded to each other by a high temperature resistant epoxy resin glue (13).

7. The force sensor according to claim 4, characterized in that: The bottom of the sensitive element (1) is coated with a triple-proof protective layer, and the triple-proof protective layer at least covers the solder pad (122) and the resistor (121).

8. The force sensor according to claim 3, characterized in that: It also comprises a sealing sheet (4), which is circular and is sealed in the fifth groove. The diameter of the fifth groove is greater than the diameter of the fourth groove.

9. The force sensor according to claim 8, characterized in that The support sleeve (2) further comprises a sixth groove located at the bottom of the support sleeve (2) and connected to the fifth groove, the diameter of the sixth groove being greater than the diameter of the fifth groove, the sealing sheet (4) and the support sleeve (2) being sealed by a sealing material, the sealing material being located in the sixth groove and not higher than the bottom end surface of the support sleeve (2).

10. A method for manufacturing a force sensor according to any one of claims 1 to 9, characterized in that: The method comprises: Step 1: manufacturing a sensitive element (1), and manufacturing a thin film resistor on the sensitive element (1) to form the strain resistor pair (12); Step 2: installing the sensitive element (1) in the first groove of the supporting sleeve (2), and sealing the gap between the sensitive element (1) and the supporting sleeve (2) by welding; Step 3: electrically connecting the resistors (121) of the strain resistor pair (12) to form an electric bridge, and performing three-proof protection on the bottom surface of the sensitive element (1); Step 4: inserting the cable (8) through the side wall of the support sleeve (2) and electrically connecting it to the bridge, and bonding and sealing the cable (8) to the side wall of the support sleeve (2); Step 5: sealing the support sleeve (2); Step 6: Test, inspect and experiment the load cell.

Images