Braking force sensor

Abstract

The present application relates to a braking force sensor comprising: a pressure sensing terminal; the sensitive element is arranged at the top of the pressure sensing terminal and is used for converting a force signal loaded above the sensitive element into an electric signal and outputting the electric signal; the bracket is arranged on the sensitive element; the printed circuit board is fixed on the bracket, is electrically connected with the sensitive element and is used for processing the electric signal output by the sensitive element to obtain an output signal; the flexible circuit board is arranged on the printed circuit board; the shell is arranged on the pressure sensing terminal, and covers the sensitive element, the bracket, the printed circuit board and the flexible circuit board; and the spring PINs are arranged in the shell, the spring PINs are electrically connected with the printed circuit board through the flexible circuit board, and the spring PINs are used for making contact with the outside to generate deformation force which acts on the printed circuit board. The braking force sensor solves the problems that in the prior art, the size is large, the high and low temperature precision is low, temperature compensation is needed, repeatability is poor, and the process difficulty is high.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a braking force sensor. Background Art

[0002] A force sensor is a device that can convert a force load signal into an easily modulated signal such as an electrical signal, and is widely used in fields such as hydraulic control, the automotive industry, and aerospace. In the automotive industry, for example, in a brake-by-wire system, on the one hand, due to the high integration of the system, there are high requirements for the size of the sensor. It is necessary to compress the volume of the sensor as much as possible while ensuring the performance and reliability of the force sensor. On the other hand, automotive sensors require the sensor output signal to be a conditioned digital SENT signal or a 0.5 - 4.5V voltage signal. Therefore, a conditioning circuit must be built into the sensor, and the normal operating temperature range of automotive sensors is -40 to 125°C. The sensor needs to ensure that the output signal meets the corresponding accuracy requirements within this temperature range. In addition, the consumption of automotive sensors is large, so the automotive industry has relatively strict control over the cost of sensors.

[0003] Chinese patent document with publication number CN118168696A discloses a force sensor for pedal force detection and its preparation method. It adopts a spoke structure, and multiple sensitive elements are distributed on a corresponding number of cantilever beams. Its advantages are small non-linearity, low hysteresis, and high accuracy, and it is also the most commonly used force sensor solution in the industrial field at present. However, if it is to be applied to an automotive brake EMB system to detect the clamping force of the brake caliper during braking, the design size of the force sensor will be very large, and the space inside the brake caliper is limited, so it is difficult to meet the assembly requirements.

[0004] Chinese patent document with publication number CN118541591A discloses a force sensor device for an electro-mechanical brake. It adopts a ring structure. On the one hand, a silicon MEMS strain gauge is used as a sensitive element, and four sensitive elements are sintered and mounted on the sensitive surface through a glass micro-melting technology to sense the stress transmitted by the pressure-sensing element. Since the zero position and sensitivity temperature coefficients of the silicon strain gauge are relatively high, its output signal is very sensitive to temperature changes. Therefore, it has low intrinsic high and low temperature accuracy and requires temperature compensation to improve the accuracy. On the other hand, the size of the silicon strain gauge is small and cannot cover the entire strain area. When the external force loading site changes slightly, it will affect the actual perceived stress / strain, resulting in different signal output values for the sensitive element under the same external force, that is, the repeatability of the sensor is relatively poor. In addition, this technology requires complex processes such as high-temperature sintering, aluminum wire ultrasonic bonding, high and low temperature temperature compensation calibration and testing, with a high process difficulty and high production cost.

[0005] In view of the above problems in the prior art, no effective solution has been proposed yet. Summary of the Invention

[0006] To solve the above problems, the present application provides a braking force sensor, which solves the problems of large size, low high and low temperature accuracy, requiring temperature compensation, poor repeatability, and high process difficulty in the prior art.

[0007] Specifically, the following technical solutions are included:

[0008] The present application provides a braking force sensor, including:

[0009] A pressure-sensing terminal, the pressure-sensing terminal is a hollow circular ring-shaped rotating body structure;

[0010] A sensitive element, disposed on the top of the pressure-sensing terminal, for converting the force signal applied above it into an electrical signal for output;

[0011] A bracket, disposed on the sensitive element;

[0012] A printed circuit board, fixed on the bracket, electrically connected to the sensitive element, for processing the electrical signal output by the sensitive element to obtain an output signal;

[0013] A flexible circuit board, disposed on the printed circuit board;

[0014] A housing, disposed on the pressure-sensing terminal, and covering the sensitive element, the bracket, the printed circuit board, and the flexible circuit board inside it;

[0015] Spring PIN pins, several of the spring PIN pins are disposed in the housing, the spring PIN pins are electrically connected to the printed circuit board through the flexible circuit board, and the spring PIN pins are used to contact the outside to generate a deformation force and act on the printed circuit board.

[0016] In an embodiment of the present application, on the side of the pressure-sensing terminal facing the housing, there is a pressure-sensing area for mounting the sensitive element, a multi-stage step structure for connecting the bracket and the housing, and a first force loading area for loading an external force. The pressure-sensing area is a ring-shaped convex structure, the multi-stage step structure is disposed on the outer periphery of the pressure-sensing area, and the first force loading area is annularly disposed at the edge of the side of the pressure-sensing terminal facing the housing; the multi-stage step structure includes an adjacent first step and a second step, the first step is used to connect the bracket, and the second step is used to connect the housing.

[0017] In an embodiment of the present application, a second force loading area and a stress buffer groove are provided on the side of the pressure-sensitive terminal away from the housing. The stress buffer groove is used to release stress, avoid plastic deformation of the pressure-sensitive terminal caused by excessive local stress concentration, and can optimize the force transmission direction. The second force loading area is a circular convex structure, and the second force loading area is located at the middle position of the side of the pressure-sensitive terminal away from the housing. The first force loading area and the second force loading area are used to sense the external clamping force and load the external force.

[0018] In an embodiment of the present application, a plurality of positioning anti-rotation grooves are provided at the edges of the upper surface and the lower surface of the pressure-sensitive terminal, and the positioning anti-rotation grooves on the upper surface of the pressure-sensitive terminal and the positioning anti-rotation grooves on the lower surface of the pressure-sensitive terminal are orthogonally distributed.

[0019] In an embodiment of the present application, an installation groove is provided on the inner wall of the pressure-sensitive terminal, and a sealing ring is installed in the installation groove. The housing and the pressure-sensitive terminal are hermetically connected through the sealing ring.

[0020] In an embodiment of the present application, the sensitive element is a circular thin sheet, which uniformly covers the pressure-sensitive area of the pressure-sensitive terminal. The pressure-sensitive terminal is made of high-strength alloy steel.

[0021] In an embodiment of the present application, the sensitive element is bonded to the pressure-sensitive terminal by glue. The sensitive element and the printed circuit board are connected by wire soldering. The sensitive element adopts a metal strain gauge.

[0022] In an embodiment of the present application, the sensitive element is a three-layer structure, including two layers of substrates and a metal foil located between the two layers of substrates. The substrate material adopts polyimide. The metal foil is selected from constantan, Evan, and Karma alloy.

[0023] In an embodiment of the present application, four resistors are provided on the metal foil, including two outer resistors and two inner resistors, and are connected to the outside through six pads. The outer resistors are radially distributed, and the resistance direction of the outer resistors is parallel to the diameter direction of the circular thin sheet of the sensitive element. The inner resistors are tangentially distributed, and the resistance direction of the inner resistors is perpendicular to the diameter direction of the circular thin sheet of the sensitive element.

[0024] In an embodiment of the present application, a plurality of through holes are provided on the housing, and a sealing sleeve is provided on the plurality of through holes. A plurality of spring PIN pins pass through the sealing sleeve and are inserted into the plurality of through holes one by one.

[0025] Compared with the prior art, the beneficial effects of the present application are:

[0026] 1. The overall structure is adapted to the EMB (electro-mechanical braking) system, which has high dimensional requirements. For example, the overall outer diameter is 40 mm, the thickness is 15 mm, and the force detection range is 0 - 65000 N. The conventional spoke structure cannot meet the requirements, and a force sensor with an annular structure or a similar topological structure provided in this application must be used.

[0027] 2. The sensitive element uses an Evan, Karma or constantan alloy with temperature self-compensation, which can ensure that within the normal operating temperature range of automotive sensors from -40 to 150 °C, the influence of temperature on the output signal is covered within the accuracy requirements, effectively ensuring the output accuracy of the force sensor.

[0028] 3. The signal of the sensitive element does not require additional temperature compensation, which simplifies the production process of the force sensor. There is no need for a force calibration system with temperature or a force testing system with temperature.

[0029] 4. The sensitive element is designed as a circular thin sheet and evenly covers the entire strain pressure sensing area, so it is not easily affected by the offset of the force application site, effectively improving the repeatability of the output signal of the force sensor.

[0030] 5. The induction terminal adopts a positioning anti-rotation groove design with a multi-anti-rotation structure, which can avoid sliding friction between the force sensor and the gasket and bearing during use, prevent the force contact site of the force sensor from being damaged due to friction and causing a decrease in accuracy, and improve its long-term force detection accuracy and service life. The induction terminal has multiple slots and rounded corners; surface slots are provided to concentrate the surface stress; stress buffer grooves are provided to avoid stress concentration in the force transmission area and optimize the force transmission direction; multiple rounded corners are provided to prevent local stress concentration.

[0031] 6. Through a conditioning circuit composed of an ASIC chip mounted on a printed circuit board, etc., the original voltage signal output by the sensitive element is processed, and a corresponding digital SENT signal or analog voltage signal can be output externally. The printed circuit board is electrically connected externally through a spring pin connector such as a POGO-PIN, which can achieve no momentary break or short-term momentary break under the V5 vibration level at the wheel end, ensuring the reliability of the force sensor during actual use.

[0032] 7. The process difficulty of the braking force sensor provided in this application is relatively low compared to force sensors based on silicon MEMS glass micro-melting technology. On the one hand, the sensitive element is bonded to the pressure sensing terminal with glue, and after curing and aging, it can be stably applied at the normal operating temperature range of automotive sensors from -40 to 125 °C, without the need for a glass micro-melting high-temperature process of 500 - 600 °C. On the other hand, the sensitive element is connected to the printed circuit board using a wire welding solution, without the need for professional aluminum wire bonding equipment. In addition, there is no need for a calibration and testing system for temperature compensation. It can effectively reduce the production and manufacturing costs of the sensor. Brief Description of the Drawings

[0033] Figure 1 The explosion diagram of the braking force sensor provided by this application.

[0034] Figure 2 The perspective view of the braking force sensor provided by this application.

[0035] Figure 3 The sectional view of the braking force sensor provided by this application.

[0036] Figure 4 The perspective view of the pressure - sensitive terminal provided by this application.

[0037] Figure 5 The sectional view of the pressure - sensitive terminal provided by this application.

[0038] Figure 6 The top view of the pressure - sensitive terminal provided by this application.

[0039] Figure 7 The bottom view of the pressure - sensitive terminal provided by this application.

[0040] Figure 8 The top view of the sensitive element provided by this application.

[0041] In the figure: 1. Pressure - sensitive terminal; 11. Installation groove; 12. Positioning anti - rotation groove; 13. Pressure - sensitive area; 14. Multi - stage step structure; 141. First step; 142. Second step; 15. First force - loading area; 16. Second force - loading area; 17. Stress buffer groove; 2. Sealing ring; 3. Sensitive element; 31. Outer resistor; 32. Inner resistor; 33. Pad; 4. Bracket; 5. Printed circuit board; 6. Flexible circuit board; 7. Shell; 71. Through - hole; 8. Sealing sleeve; 9. Spring PIN needle. Detailed Description of the Preferred Embodiments

[0042] Next, the technical solutions of this application will be described clearly and completely with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in this application belong to the scope of protection of this application.

[0043] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. These are 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. Therefore, it should not be construed as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0044] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection or a detachable 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.

[0045] As Figures 1 to 8 shown, the present application provides a braking force sensor. In some embodiments, the braking force sensor includes:

[0046] A pressure-sensitive terminal 1, and the pressure-sensitive terminal 1 is a hollow annular rotating body structure;

[0047] A sensitive element 3, which is arranged on the top of the pressure-sensitive terminal 1 and is used to convert the force signal applied above it into an electrical signal for output;

[0048] A bracket 4, which is arranged on the sensitive element 3;

[0049] A printed circuit board 5, which is fixed on the bracket 4 and is electrically connected to the sensitive element 3, and is used to process the electrical signal output by the sensitive element 3 to obtain an output signal;

[0050] A flexible circuit board 6, which is arranged on the printed circuit board 5;

[0051] A housing 7, which is arranged on the pressure-sensitive terminal 1 and covers the sensitive element 3, the bracket 4, the printed circuit board 5 and the flexible circuit board 6 inside it;

[0052] Spring PIN pins 9, several of the spring PIN pins 9 are arranged in the housing 7, the spring PIN pins 9 are electrically connected to the printed circuit board 5 through the flexible circuit board 6, and the spring PIN pins 9 are used to contact the outside to generate a deformation force and act on the printed circuit board 5.

[0053] In some embodiments, an installation groove 11 is provided on the inner wall of the pressure-sensitive terminal 1, and a sealing ring 2 is installed in the installation groove 11. The housing 7 and the pressure-sensitive terminal 1 are hermetically connected through the sealing ring 2 to achieve environmental sealing.

[0054] In some embodiments, the sensitive element 3 is mounted on the pressure-sensitive terminal 1, and the sensitive element 3 uses a metal strain gauge.

[0055] Optionally, the bracket 4 is welded to the pressure-sensitive terminal 1 by laser welding; the pressure-sensitive terminal 1, the bracket 4, and the housing 7 are all made of metal.

[0056] In some embodiments, conditioning chips, resistors, capacitors and other electronic components are mounted on the printed circuit board 5 by reflow soldering to jointly form a conditioning circuit for modulating and calibrating the force sensor signal. Optionally, the printed circuit board 5 is fixed to the bracket 4 by reflow soldering.

[0057] In this embodiment, the raw voltage signal output by the sensitive element 3 is processed by a conditioning circuit composed of an ASIC chip and the like mounted on the printed circuit board 5, and a corresponding digital SENT signal or analog voltage signal can be output externally. The printed circuit board 5 is electrically connected externally through a spring pin connector scheme such as POGO - PIN, which can achieve no momentary break or short - term momentary break at the wheel - end V5 vibration level, ensuring the reliability of the force sensor during actual use.

[0058] In some embodiments, one end of the flexible circuit board 6 is electrically connected to the printed circuit board 5, and the other end is connected to the spring PIN pin 9. The flexible circuit board 6 is used to realize the electrical connection between the spring PIN pin 9 and the printed circuit board 5.

[0059] In some embodiments, a plurality of through - holes 71 are provided on the housing 7, and sealing sleeves 8 are provided on the plurality of through - holes 71. A plurality of spring PIN pins 9 pass through the sealing sleeves 8 and are inserted into the plurality of through - holes 71 one by one.

[0060] In this embodiment, three through - holes 71 are provided on the housing 7, and sealing sleeves 8 are provided at the through - holes 71 to achieve environmental sealing. The sealing sleeve 8 is connected to 3 spring PIN pins 9, and the spring PIN pins 9 are signal input / output interfaces. Optionally, the housing 7 is connected to the pressure - sensitive terminal 1 by laser welding.

[0061] In some embodiments, the pressure - sensitive terminal 1 is an overall hollow circular - ring - shaped rotating body structure. A plurality of positioning anti - rotation grooves 12 are provided at the edges of the upper surface and the lower surface of the pressure - sensitive terminal 1, and the positioning anti - rotation grooves 12 on the upper surface of the pressure - sensitive terminal 1 and the positioning anti - rotation grooves 12 on the lower surface of the pressure - sensitive terminal 1 are orthogonally distributed.

[0062] In this embodiment, four positioning and anti-rotation grooves 12 are provided at the edge of the pressure-sensitive terminal 1. Two of the positioning and anti-rotation grooves 12 are located on the upper surface of the pressure-sensitive terminal 1, and are orthogonally distributed with the other two positioning and anti-rotation grooves 12 located on the lower surface of the pressure-sensitive terminal 1. The positioning and anti-rotation grooves 12 are used to ensure the positioning and anti-rotation of the force sensor during production, assembly, and use.

[0063] Further, on the side of the pressure-sensitive terminal 1 facing the housing 7, there are provided a pressure-sensitive area 13 for mounting the sensitive element 3, a multi-step structure 14 for connecting the bracket 4 and the housing 7, and a first force loading area 15 for loading an external force. The pressure-sensitive area 13 is a circular raised structure. The multi-step structure 14 is provided on the outer periphery of the pressure-sensitive area 13. The first force loading area 15 is annularly provided at the edge of the side of the pressure-sensitive terminal 1 facing the housing 7. The multi-step structure 14 includes a first step 141 and a second step 142 arranged adjacent to each other. The first step 141 is used to connect the bracket 4, and the second step 142 is used to connect the housing 7.

[0064] In this embodiment, the first step 141 is used for welding the bracket 4, and the second step 142 is used for welding the housing 7.

[0065] Further, on the side of the pressure-sensitive terminal 1 away from the housing 7, there are provided a second force loading area 16 and a stress buffer groove 17. The stress buffer groove 17 is used to release stress, avoid local stress concentration leading to plastic deformation of the pressure-sensitive terminal 1, and can optimize the force transmission direction. The second force loading area 16 is a circular raised structure, and the second force loading area 16 is located at the middle position of the side of the pressure-sensitive terminal 1 away from the housing 7. The first force loading area 15 and the second force loading area 16 are used to sense the external clamping force and load the external force.

[0066] Optionally, the pressure-sensitive terminal 1 is made of high-strength alloy steel, such as SUS630, which has a high yield strength and is suitable for force sensor products of small size and high force range like the present invention. Among them, if SUS630 alloy steel is used, heat treatment needs to be performed, and the standard of heat treatment is H900.

[0067] The induction terminal 1 of the braking force sensor provided in this application adopts the design of positioning and anti-rotation grooves 12 with a multi-anti-rotation structure, which can avoid sliding friction between the force sensor and gaskets and bearings during use, prevent the force contact sites of the force sensor from being damaged due to friction and resulting in a decrease in accuracy, and improve its long-term force detection accuracy and service life. The induction terminal 1 has multiple slots and rounded corners; surface slots are provided to concentrate surface stress; the stress buffer groove 17 avoids stress concentration in the force transmission area and optimizes the force transmission direction; multiple rounded corners are provided to prevent local stress concentration.

[0068] Optionally, the sensitive element 3 is a circular thin sheet, which uniformly covers the pressure-sensing area 13 of the pressure-sensing terminal 1.

[0069] In this embodiment, the sensitive element 3 is designed as a circular thin sheet and uniformly covers the entire strain pressure-sensing area 13, so it is not easily affected by the offset of the force application site, and can effectively improve the repeatability of the output signal of the force sensor.

[0070] Optionally, the sensitive element 3 is adhesively bonded to the pressure-sensing terminal 1 with glue; the sensitive element 3 is connected to the printed circuit board 5 by wire soldering.

[0071] In this embodiment, on the one hand, the sensitive element 3 is adhesively bonded to the pressure-sensing terminal 1 with glue, and after curing and aging, it can be stably applied at the normal operating temperature of the automotive sensor, -40 to 125 °C, without the need for a glass micro-melting high-temperature process of 500 to 600 °C; on the other hand, the sensitive element 3 is connected to the printed circuit board 5, and a wire soldering scheme is adopted, without the need for professional aluminum wire bonding equipment. In addition, there is no need for a temperature compensation calibration and test system. It can effectively reduce the production and manufacturing costs of the sensor.

[0072] Further, the sensitive element 3 has a three-layer structure, including two layers of substrates and a metal foil located between the two layers of substrates. The substrate material uses polyimide with a wide temperature resistance range, and the temperature resistance range can cover the automotive sensor range of -40 to 150 °C; the metal foil is the core material of the sensitive element; the compensation of the resistance temperature coefficient needs to be considered to ensure that within the operating temperature range of the automotive sensor, -40 to 150 °C, it has a low resistance temperature coefficient; at the same time, it also needs to have a relatively high strain coefficient; generally, constantan, Evan, and Karma alloy are selected as the metal foil materials of the sensitive element 3, which can ensure that within the normal operating temperature of the automotive sensor, -40 to 150 °C, the influence of temperature on the output signal is covered within the accuracy requirements, and can effectively ensure the output accuracy of the force sensor.

[0073] Further, in order to ensure that the output signal of the sensitive element 3 can be processed by the conditioning circuit, the resistance value of the sensitive element 3 should not be too small, usually > 1 kΩ, preferably about 3 kΩ.

[0074] Further, four resistors are arranged on the metal foil, including two outer resistors 31 and two inner resistors 32, and are connected to the outside through six pads 33; the outer resistors 31 are radially distributed, that is, the resistance direction of the outer resistors 31 is parallel to the diameter direction of the circular thin sheet of the sensitive element 3; the inner resistors 32 are tangentially distributed, that is, the resistance direction of the inner resistors 32 is perpendicular to the diameter direction of the circular thin sheet of the sensitive element 3.

[0075] The direction of the resistor is confirmed according to the stress and strain distribution simulation structure on the pressure-sensitive terminal 1, that is, the tangential strain near the inner side is larger, and the inner resistor 32 is also the resistor that plays a leading role in the output signal among the sensitive elements 3.

[0076] Specifically, in the area of the sensitive element 3 above the pressure-sensitive terminal 1, different directions of stress / strain will be generated when an external force is applied. The stress / strain in the area of the inner resistor 32 is mainly concentrated in the tangential direction, and the magnitude of the stress / strain is about one order of magnitude larger than that in the radial direction. Therefore, the resistance of the inner resistor 32 is tangentially distributed, which can maximize the perception of tangential stress / strain and ensure that the original signal output by the sensitive element 3 has a high sensitivity. Although the stress / strain in the area of the outer resistor 31 is also mainly concentrated in the tangential direction, and the radial stress / strain is about 25% of the tangential direction (the stress / strain signs of the radial / tangential directions are opposite), the direction of the outer resistor 31 needs to be set to radial distribution. This is because the stress / strain signs in the area of the outer resistor 31 are the same as those in the area of the inner resistor 32. If the outer resistor 31 is set to tangential distribution, it will have a negative effect on the sensitivity of the overall Wheatstone bridge formed by the inner resistor 32 / outer resistor 31. Setting it to radial distribution, even if the absolute value of the stress / strain in the radial distribution is small, it will still have a positive effect on the sensitivity of the overall Wheatstone bridge. The sensitivity of the Wheatstone bridge will greatly affect the subsequent calibration process of the product and the accuracy of the final product.

[0077] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A braking force sensor, characterized in that: include: A pressure-sensing terminal (1), wherein the pressure-sensing terminal (1) is a hollow annular rotating body structure; A sensitive element (3), arranged on the top of the pressure-sensing terminal (1), and used for converting a force signal applied thereto into an electrical signal output; A bracket (4) is arranged on the sensitive element (3); A printed circuit board (5) is fixed on the bracket (4), is electrically connected to the sensitive element (3), and is used to process the electrical signal output by the sensitive element (3) to obtain an output signal; A flexible circuit board (6) is arranged on the printed circuit board (5); A housing (7) is arranged on the pressure-sensing terminal (1), and the sensitive element (3), the bracket (4), the printed circuit board (5) and the flexible circuit board (6) are housed therein; A spring PIN pin (9), wherein a plurality of the spring PIN pins (9) are arranged in the housing (7), the spring PIN pin (9) is electrically connected to a printed circuit board (5) via a flexible circuit board (6), and the spring PIN pin (9) is used to contact the outside world to generate a deformation force and act on the printed circuit board (5).

2. A braking force sensor according to claim 1, characterized in that: The pressure-sensing terminal (1) is provided with a pressure-sensing area (13) for mounting a sensitive element (3), a multi-step step structure (14) for connecting a bracket (4) and a bracket (7), and a first force-loading area (15) for loading an external force on a side facing the housing (7); the pressure-sensing area (13) is an annular protrusion structure; the multi-step step structure (14) is arranged on the periphery of the pressure-sensing area (13); the first force-loading area (15) is arranged in an annular shape at the edge of the side of the pressure-sensing terminal (1) facing the housing (7); the multi-step step structure (14) comprises a first step (141) and a second step (142) which are arranged adjacent to each other; the first step (141) is used to connect the bracket (4), and the second step (142) is used to connect the housing (7).

3. A braking force sensor according to claim 2, characterized in that: A second force loading area (16) and a stress buffer groove (17) are provided on a side of the pressure sensing terminal (1) away from the housing (7); the stress buffer groove (17) is used to release stress, so as to avoid excessive concentration of local stress leading to plastic deformation of the pressure sensing terminal (1), and can optimize the force transmission direction; the second force loading area (16) is an annular protrusion structure, and the second force loading area (16) is located in the middle position of a side of the pressure sensing terminal (1) away from the housing (7); the first force loading area (15) and the second force loading area (16) are used to sense external clamping force and load external force.

4. A braking force sensor according to claim 3, characterized in that: A plurality of positioning and anti-rotation grooves (12) are provided at the edge of the upper surface and the edge of the lower surface of the pressure-sensing terminal (1); the positioning and anti-rotation grooves (12) on the upper surface of the pressure-sensing terminal (1) and the positioning and anti-rotation grooves (12) on the lower surface of the pressure-sensing terminal (1) are orthogonally distributed.

5. A braking force sensor according to claim 4, characterized in that: The inner wall of the pressure-sensing terminal (1) is provided with a mounting groove (11), a sealing ring (2) is installed in the mounting groove (11), and the housing (7) and the pressure-sensing terminal (1) are sealed and connected via the sealing ring (2).

6. A braking force sensor according to claim 5, characterized in that: The sensitive element (3) is a circular ring-shaped thin sheet, which evenly covers the pressure-sensing area (13) of the pressure-sensing terminal (1); the pressure-sensing terminal (1) is made of high-strength alloy steel.

7. A braking force sensor according to claim 6, characterized in that: The sensitive element (3) is bonded to the pressure-sensing terminal (1) by glue; the sensitive element (3) is connected to the printed circuit board (5) by wire welding; and the sensitive element (3) is a metal strain gauge.

8. A braking force sensor according to claim 7, characterized in that: The sensitive element (3) has a three-layer structure, including two layers of substrates and a metal foil located between the two layers of substrates. The substrate material is polyimide; the metal foil is selected from constantan, Ivan, and Kama alloy.

9. A braking force sensor according to claim 8, characterized in that: Four resistors are arranged on the metal foil, including two outer resistors (31) and two inner resistors (32), which are connected to the outside via six pads (33); the outer resistors (31) are radially distributed, and the resistance direction of the outer resistors (31) is parallel to the diameter direction of the annular thin sheet of the sensitive element (3); the inner resistors (32) are tangentially distributed, and the resistance direction of the inner resistors (32) is perpendicular to the diameter direction of the annular thin sheet of the sensitive element (3).

10. The braking force sensor according to claim 1, characterized in that: The housing (7) is provided with a plurality of through holes (71), a sealing sleeve (8) is provided on the plurality of through holes (71), and a plurality of spring PIN needles (9) pass through the sealing sleeve (8) and are inserted into the plurality of through holes (71) one by one.

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