A pm sensor and a production line thereof

Abstract

The application relates to a PM sensor and a production line thereof, the sensor comprising a ceramic chip body, an electrode lead-out end at the tail end and a sensitive area at the head, the surface of the sensitive area being provided with a measuring electrode, a heating electrode being embedded in the ceramic chip body; an external lead wire being electrically connected with the electrode lead-out end; an outer shell accommodating and protecting the ceramic chip body; a memory alloy lead wire locking assembly being located at the connection between the external lead wire and the electrode lead-out end, the memory alloy lead wire locking assembly comprising a clamping ring made of shape memory alloy and a low-temperature curing encapsulating paste layer for chemically bonding the external lead wire and the electrode lead-out end, the phase transition temperature of the shape memory alloy being lower than the curing temperature of the low-temperature curing encapsulating paste layer. The application has the effect of improving the electrical connection reliability and the product yield.

Description

Technical Field

[0001] This application relates to the technical field of PM sensors, and in particular to a PM sensor and its production line. Background Technology

[0002] With increasingly stringent environmental regulations on vehicle exhaust emissions, the requirements for real-time and accurate monitoring of engine exhaust particulate matter (PM) are constantly rising. PM ​​sensors have become a core component of vehicle exhaust monitoring systems. Existing conventional PM sensors generally adopt a ceramic chip substrate structure, with measuring electrodes arranged on the chip surface and heating electrodes embedded inside. The detection principle is as follows: particulate matter in the exhaust gas is adsorbed onto the surface of the measuring electrodes, causing a change in resistance between the electrodes. The controller detects the concentration of exhaust particulate matter by collecting the resistance signal. When the particulate matter accumulates to a threshold, the built-in heating electrode initiates high-temperature regeneration, burning off the surface carbon particles and restoring the sensor to its initial detection sensitivity.

[0003] Existing technical solutions still have many shortcomings under the harsh conditions of automotive applications, seriously affecting the stability and lifespan of sensors. Firstly, the reliability of lead wire connections is poor, and molding defects are significant. Existing sensor leads and electrode leads mostly use a traditional method of fixing them with metal clamps and slurry encapsulation, which has poor process adaptability: tightening the clamps first will compress the joint gaps, preventing the slurry from penetrating into the micro-interface; applying adhesive first and then tightening will easily squeeze the slurry, causing molding problems such as insufficient adhesive and voids in the joint.

[0004] Secondly, the structure and function are limited, lacking the ability to adaptively regulate airflow. Traditional sensor housings are fixed and static structures, unable to adaptively adjust the internal flow field and ventilation volume according to different working states such as measurement and regeneration. It is difficult to create a heat-insulating environment during the regeneration stage, resulting in increased heat loss, which severely restricts regeneration efficiency and energy-saving performance, and cannot meet the requirements of high-precision and long-life vehicle applications. Summary of the Invention

[0005] To address the problems mentioned in the above technical background, this application provides a PM sensor and its production line.

[0006] This application provides a PM sensor, which adopts the following technical solution: A PM sensor, including A ceramic chip body has an electrode lead-out end at the tail end and a sensitive area at the head end. A measuring electrode is provided on the surface of the sensitive area, and a heating electrode is embedded inside the ceramic chip body. External leads are electrically connected to the electrode leads. A housing that contains and protects the ceramic chip body; The shape memory alloy lead locking assembly is located at the connection between the external lead and the electrode lead. It includes a clamping ring made of shape memory alloy and a low-temperature curing encapsulation slurry layer for chemically bonding the external lead to the electrode lead. The austenitic phase transformation initiation temperature of the shape memory alloy is lower than the curing temperature of the low-temperature curing encapsulation slurry layer. During assembly, the clamping ring, which is in the martensitic phase, is enlarged and fitted outside the external lead. When the slurry is heated for curing, the clamping ring triggers the transformation of the martensitic phase to the austenitic phase and shrinks radially, forming a circumferential enclosure and limiting the external lead and the electrode lead. After curing, the temperature is lowered, the clamping ring returns to the martensitic phase and springs back to expand, automatically detaching from the cured low-temperature curing encapsulation slurry layer.

[0007] Furthermore, the shape memory alloy is a nickel-titanium alloy, with an austenitic phase transformation initiation temperature range of 150℃ to 180℃ and an austenitic phase transformation end temperature not exceeding 180℃. The low-temperature curing encapsulation slurry layer is formed by curing aluminum dihydrogen phosphate-based slurry at a curing temperature of 200℃.

[0008] Furthermore, the inner wall of the clamping ring is uniformly distributed with several discrete positioning fulcrums along the circumference. The positioning fulcrums and the clamping ring are integrally formed. When the clamping ring contracts radially, the top of the positioning fulcrum abuts against the outer circle of the outer lead wire to achieve coaxial centering, and a uniform circumferential slurry accommodating gap is formed between adjacent positioning fulcrums.

[0009] Furthermore, the housing includes a dynamic airflow control mechanism, which comprises: The inner protective tube, with its top end in a closed state, is sleeved and fixed to the outside of the ceramic chip body. Its tube wall is provided with an air inlet and its top end is provided with a pressure relief valve. A sliding outer tube, with its bottom end in a closed state, is coaxially sleeved on the outside of the inner protective tube. A through hole is provided on its tube wall. The sliding outer tube slides along the axial direction of the inner protective tube, and its sliding has a first position and a second position. When in the first position, the through hole on the sliding outer tube is at least partially aligned with the air inlet on the inner protective tube, forming an airflow channel. When in the second position, the sliding outer tube blocks the air inlet on the inner protective tube. The first elastic element, which is a return spring, is disposed between the sliding outer tube and a fixed reference, and provides an elastic force to the sliding outer tube to make it slide to the first position; The drive unit is shut down to provide a driving force to the sliding outer tube, causing it to slide from the first position to the second position. A magnetorheological fluid damper includes a sealed cavity, a piston rod, a piston, and an electromagnetic coil. The sealed cavity is fixedly disposed on one side of the ceramic chip body and is filled with magnetorheological fluid. One end of the piston rod is fixedly connected to the sliding outer tube, and the other end extends into the sealed cavity and is connected to the piston. The piston divides the interior of the sealed cavity and can slide within the cavity. The electromagnetic coil is arranged around the outside of the sealed cavity. The electromagnetic coil is electrically connected to a control unit. When it is necessary to switch from the first position to the second position, the control unit first controls the shut-off drive unit to move the sliding outer tube against the force of the first elastic element to the second position. At the same time or subsequently, the control unit energizes the electromagnetic coil, causing the magnetorheological fluid to become high-viscosity or near-solid, thereby locking the sliding outer tube in the second position. When it is necessary to return from the second position to the first position, the control unit cuts off the current to the electromagnetic coil and controls the shut-off drive unit to stop or reverse its operation. The magnetorheological fluid returns to a low-viscosity state, and the first elastic element drives the sliding outer tube back to the first position.

[0010] Furthermore, the magnetorheological fluid includes a high-temperature resistant ionic liquid, soft magnetic particles uniformly dispersed in the ionic liquid, and additives for preventing the soft magnetic particles from settling.

[0011] Furthermore, the sliding outer tube is fixedly connected to the piston rod via a connector, and the first elastic element is a compression spring sleeved on the piston rod, with one end of the compression spring acting on the sliding outer tube and the other end acting on the sealing cavity.

[0012] This application provides a PM sensor production line, which includes, in sequence, the following processes: S1. Ceramic chip body manufacturing: A ceramic chip body with built-in heating electrodes and metallized areas on the surface is prepared by casting, printing, stacking and co-firing processes; S2. Precision structural processing: Measuring electrodes are formed on the surface of the ceramic chip body using laser processing technology; S3. Integration and synchronous processing of shape memory alloy components: S31. Assemble a functional component made of shape memory alloy into a predetermined position of the ceramic chip body, wherein the functional component is a clamping ring for securing external leads; S32. Apply a low-temperature curing encapsulating slurry to the corresponding area that needs to be encapsulated or fixed; S33. Perform a programmed temperature-controlled heat treatment on the assembled and coated parts. The temperature curve of the heat treatment is set to solidify the encapsulating slurry and simultaneously trigger a phase transformation of the shape memory alloy, thereby simultaneously completing chemical bonding and physical shape memory locking in a single heat treatment process. S4. Assembly and Functional Testing: Complete the electrical connection and housing packaging of the sensor, and test the overall performance of the integrated shape memory alloy functional components and the sensor.

[0013] Furthermore, after step S3 and before step S4, step S3' is also included: fabrication and integration of the magnetorheological fluid damper, which includes: S3'1. Provide a damper housing with a sealed cavity, and assemble the piston rod and piston into the cavity; S3'2. Under vacuum or inert atmosphere protection, a quantitative amount of magnetorheological fluid is injected into the sealed cavity; S3'3. Seal the cavity after injection; S3'4. An electromagnetic coil is mounted around the periphery of the sealed cavity to form a magnetorheological fluid damper module; S3'5. Install the first elastic element and close the drive unit, and mechanically and electrically integrate the magnetorheological fluid damper module with the sliding outer tube and housing substrate of the sensor.

[0014] In summary, the beneficial technical effects of this application are as follows: 1. This solution utilizes circumferentially distributed discrete positioning fulcrums on the inner wall of the shape memory alloy clamping ring. This allows for precise coaxial positioning with external leads and electrode leads during the radial shrinkage of the clamping ring, effectively avoiding shrinkage eccentricity and structural skewing, and ensuring circumferentially uniform and stable slurry containment gaps within the ring. Simultaneously, relying on the positioning fulcrums for limiting and shaping, combined with a temperature sequence design that prioritizes positioning and shaping followed by slurry curing, it eliminates defects such as glue overflow, glue extrusion, insufficient glue, and voids inherent in traditional assembly processes. This ensures that the aluminum dihydrogen phosphate-based slurry fully impregnates the metal interface, resulting in a dense, complete, insulating, and durable composite material after curing. The sealing adhesive layer exhibits excellent corrosion resistance, and the discrete, non-closed-loop fulcrum structure does not hinder the radial contraction and cooling rebound deformation of the clamping ring. This allows the clamping ring to function solely as a process positioning and containment component. After the slurry cures and cools, it automatically detaches from the slurry layer and does not participate in the stress of the finished product, leaving no residual mechanical clamping stress. Ultimately, the lead wire connector achieves an integrated and stable sealing structure relying on the high-temperature resistant slurry layer. This effectively adapts to harsh working conditions such as high-frequency vibration of the exhaust pipe, thermal shock, and acid and alkali corrosion, thoroughly improving problems such as lead wire loosening, insulation cracking, and leakage failure, and significantly enhancing the working stability and service life of the PM sensor. 2. Equipped with a dedicated integrated production line, combining heat treatment processes and vacuum-sealed integrated magnetorheological damping components, simplifying the production process, reducing energy consumption equipment investment, and ensuring high performance consistency of mass-produced products. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of an embodiment of this application; Figure 2 This is a cross-sectional structural diagram of the overall structure of an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the electrode lead-out end, measuring electrode, clamping ring, low-temperature curing encapsulation slurry layer, base and movable blade in the embodiment of this application; Figure 4 This is a schematic diagram of the dynamic airflow control mechanism in the embodiments of this application; Figure 5 yes Figure 2 A magnified structural diagram of part A in the middle.

[0016] Explanation of reference numerals in the attached figures: 1. Control unit; 2. External leads; 3. Ceramic chip body; 31. Electrode lead-out terminal; 32. Measuring electrode; 33. Heating electrode; 4. Outer shell; 5. Shape memory alloy lead locking assembly; 51. Clamping ring; 52. Low-temperature curing encapsulation layer; 7. Dynamic airflow control mechanism; 71. Inner protective tube; 72. Air inlet; 73. Pressure relief valve; 74. Sliding outer tube; 75. Through hole; 76. First elastic element; 77. Closing drive unit; 78. Magnetorheological fluid damper; 781. Sealed cavity; 782. Piston rod; 783. Piston; 784. Electromagnetic coil. Detailed Implementation

[0017] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] This application discloses a PM sensor and its production line. (Refer to...) Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5A PM sensor mainly consists of four core parts: a ceramic chip body 3, an external lead wire 2, a housing 4, and a memory alloy lead wire locking assembly 5. The housing 4 is made of 310S high-temperature resistant stainless steel, which can withstand long-term high-temperature corrosion of exhaust gas. The internal cavity of the housing 4 is filled with high-temperature resistant insulating and thermally conductive ceramic cotton, which not only protects the ceramic chip body 3, but also helps to conduct heat evenly. The ceramic chip body 3 is made of alumina ceramic co-fired molding and is divided into a head sensitive area and a tail electrode lead-out end 31. The head sensitive area is equipped with a measuring electrode 32 for measuring particulate matter in automobile exhaust. The measuring electrode 32 is made of platinum precious metal, which has strong oxidation resistance and can withstand high-temperature regeneration conditions above 800℃. The ceramic chip uses a multi-layer stacked printing process to pre-embed heating electrodes 33. The heating electrodes 33 are made of tungsten-molybdenum high-temperature resistant alloy. After being powered on, they can heat the measuring electrode 32, making it rapidly heat up to 600℃~700℃, realizing high-temperature combustion regeneration of carbon particles adsorbed on the surface of the measuring electrode 32. The tail electrode lead-out end 31 is connected to the external lead 2. The end of the external lead 2 away from the electrode lead-out end 31 is electrically connected to the control unit 1.

[0019] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 The shape memory alloy lead locking assembly 5 is located at the docking position between the electrode lead-out end 31 and the external lead 2. It is a key protective structure for electrical connection. It mainly achieves reliable joint protection through process limiting molding and chemical bonding sealing. It includes a shape memory alloy clamping ring 51 and a low-temperature curing encapsulation slurry layer 52. The shape memory alloy clamping ring 51 is made of nickel-titanium shape memory alloy. The austenitic phase transformation temperature of the alloy is set to 150℃~180℃, and the austenitic phase transformation end temperature is not higher than 180℃, ensuring that the phase transformation shrinkage action is completely earlier than the slurry curing process. The clamping ring 51 is initially in the martensitic phase. After the diameter expansion treatment, the inner diameter of the assembly is larger than the outer diameter of the external lead 2. It can be easily fitted into the lead docking position without any assembly stress and has good assembly convenience. The low-temperature curing encapsulation slurry layer 52 uses aluminum dihydrogen phosphate-based high-temperature resistant insulating slurry with a fixed curing temperature of 200℃. After curing, the insulation resistance is ≥1000MΩ, which can withstand long-term acid and alkali corrosion, high-temperature oxidation and alternating hot and cold shocks of automobile exhaust, and is perfectly adapted to the harsh service conditions of exhaust pipes.

[0020] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5Multiple discrete positioning fulcrums are evenly arranged circumferentially on the inner wall of the clamping ring 51. Each positioning fulcrum is disconnected from the others and does not form a closed ring structure. The root of the fulcrum adopts a rounded corner transition design. The whole is integrally formed with the clamping ring 51 using the same nickel-titanium alloy, which does not change the mechanical properties of the clamping ring 51 and does not hinder the radial shrinkage and springback expansion phase deformation of the clamping ring 51. In the unheated assembly state, the positioning fulcrum expands in diameter synchronously with the clamping ring 51, leaving a gap with the outer periphery of the external lead 2, which does not affect normal insertion and assembly. In the integrated heat treatment process, the furnace temperature first rises to the range of 150℃~180℃. The clamping ring 51 undergoes a rapid austenitic phase transformation, resulting in radial shrinkage deformation. During the shrinkage process, the circumferentially evenly distributed positioning fulcrums first abut against the outer circular surface of the external lead 2, automatically completing the coaxial positioning of the clamping ring 51 with the external lead 2 and the electrode lead-out end 31, completely avoiding the problems of eccentric shrinkage and skew offset, and ensuring uniform gap around the joint. Once the positioning fulcrum abuts against the outer wall of the external lead 2, the clamping ring 51 stops further radial contraction. A circumferentially continuous and uniformly thick annular slurry-accommodating gap is formed between the inner wall of the ring between adjacent positioning fulcrums and the joint between the external lead 2 and the electrode lead-out end 31. This gap stably accommodates the injected low-temperature curing encapsulating slurry. Relying on the confining and limiting effect of the clamping ring 51, the slurry flow is effectively constrained, completely preventing the overflow and loss of uncured slurry, while also eliminating defects such as insufficient adhesive and voids caused by the compression of traditional clamping structures. After the clamping ring 51 has contracted and shaped, and the slurry is filled, the furnace body continues to heat to 200℃ and maintain this temperature. The aluminum dihydrogen phosphate-based slurry is completely cured, forming a dense, void-free insulating adhesive layer that fully fills the microscopic gaps between the external lead 2 and the electrode lead-out end 31, achieving comprehensive chemical bonding and insulating sealing of the joint. After the slurry has fully cured, the entire assembly is cooled. As the temperature decreases, the clamping ring 51 transforms from the austenitic phase back to the martensitic phase, automatically rebounding and expanding. The inner diameter returns to its initial large size during assembly, and the positioning fulcrum simultaneously retracts with the ring body, completely detaching the clamping ring 51 from the cured low-temperature encapsulating slurry layer 52. In this invention, the shape memory alloy clamping ring 51 serves only as a coaxial positioning and slurry containment component during the assembly process and does not participate in the stress on the finished product. The finished product joint relies entirely on the aluminum dihydrogen phosphate-based slurry layer for bonding, fixing, insulation, sealing, and corrosion protection.

[0021] In some existing technologies, mechanical clamping structures such as ordinary metal clamps or clips are used to fix the electrode lead 31 and the external lead 2 at the connection point, attempting to suppress the external lead 2 from loosening due to vibration by relying on mechanical preload. However, when this type of single mechanical clamping structure is applied to the high-temperature exhaust gas sensor lead connector in the exhaust pipe, it has multiple inherent defects, such as process compatibility conflicts, high-temperature performance degradation, insufficient vibration and thermal shock resistance, and lack of sealing and insulation. It cannot meet the long-term use requirements of harsh operating conditions on its own. At the same time, the clamping force of conventional clamps is applied once by manually tightening bolts or fastening clips during assembly. If the clamp is pre-tightened, the joint gap between the electrode lead 31 and the external lead 2 will be rigidly squeezed and closed, making it difficult for the subsequently applied high-temperature insulating slurry to penetrate into the microscopic gaps of the metal joint. The slurry will only remain on the outer surface of the joint, and the internal interface will not be bonded and sealed. If the slurry is applied first and then the clamp is tightened, the uncured slurry will be squeezed out in large quantities from the joint gap during the tightening process, resulting in defects such as insufficient glue, voids, and bubbles inside the joint, forming an internal cavity. During the repeated heating and cooling of the exhaust pipe, the gas inside the cavity expands due to heat, which can easily cause the insulation layer to bubble and crack, and the insulation resistance to drop sharply, ultimately leading to leakage and connection failure of the joint. This structure uses a shape memory alloy clamping ring 51 with circumferential discrete positioning fulcrum to achieve an integrated process of coaxial positioning, stable gap storage, curing and molding, and automatic demolding. It solves the industry pain points of traditional tooling such as glue extrusion, glue overflow, insufficient glue, and eccentricity from the root, ensuring uniform slurry layer thickness, sufficient interface wetting, and no internal void defects. The molded connector relies on a high-temperature resistant aluminum dihydrogen phosphate slurry layer to achieve integrated sealing and bonding. The structure is dense and stable, and under the conditions of high-frequency vibration of the vehicle exhaust pipe and high and low temperature thermal shock, there will be no problems such as loosening of the lead wire, cracking of the insulation layer, or leakage failure, which greatly improves the long-term reliability and service life of the PM sensor lead wire connection.

[0022] Existing particulate matter ceramic sensors generally face two major technical challenges in regeneration and carbon removal operations: Firstly, the regeneration process requires high-temperature heating of the ceramic chip body 3 for carbon removal. If exhaust gas continuously flows into the sensor housing 4, the high-speed flow of exhaust gas will create strong forced convection heat dissipation, carrying away a large amount of heat from the ceramic chip body 3. The actual temperature of the ceramic chip body 3 is difficult to raise to the high temperature required for regeneration, resulting in low carbon removal efficiency, incomplete carbon removal, and a significant increase in heating energy consumption. Secondly, the temperature inside the sensor housing 4 rises sharply during the regeneration stage. The continuous flow of low-temperature exhaust gas interacts with the high-temperature ceramic chip body 3, generating severe thermal shock. The ceramic chip body 3 is prone to thermal cracking, directly causing its failure. If a simple fixed sealing structure is used, the sensor cannot flexibly switch between measurement and regeneration modes. During normal measurement, the exhaust gas passage is continuously blocked, resulting in the loss of normal particulate matter detection function. Therefore, in this embodiment, the sensor housing 4 is structurally upgraded by adding a magnetorheological fluid damping dynamic airflow control mechanism 7. This mechanism is nested and installed outside the ceramic chip body 3 to realize the controllable opening and closing of the air intake passage, which is suitable for the high-flow-rate exhaust gas conditions of large displacement engines.

[0023] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5The dynamic airflow control mechanism 7 is nested and installed outside the ceramic chip body 3. It consists of five modules: an inner protective tube 71, a sliding outer tube 74, a first elastic element 76, a shut-off drive unit 77, and a magnetorheological fluid damper 78. All components can withstand the long-term scouring of high-temperature exhaust gas. The dynamic airflow control mechanism 7 is integrated into the transition cavity at the rear end of the sensor housing 4, away from the high-temperature sensitive area of ​​the front electrode. The rear end of the sensor housing 4 has sufficient axial installation space, without encroaching on the arrangement space of the front particulate matter detection chip. The top of the inner protective tube 71 is closed, fixing and wrapping the ceramic chip body 3. Multiple sets of circular air inlets 72 are evenly opened circumferentially on the tube wall of the inner protective tube 71, ensuring that the exhaust gas flows through the air inlets 72 after passing through the front end of the housing 4 and enters the inner protective tube 71 to reach the measuring electrode 32. The top of the inner protective tube 71 integrates a miniature pressure relief valve 73, which automatically releases pressure when the air pressure in the chamber is too high during the regeneration stage, preventing high pressure in the chamber from damaging the ceramic chip body 3. The bottom end of the sliding outer tube 74 is closed, and it is coaxially sleeved on the outside of the inner protective tube 71. Through holes 75, corresponding one-to-one with the air inlet 72, are opened on the wall of the sliding outer tube 74. An external lead wire 2 passes through the bottom end of the sliding outer tube 74. The sliding outer tube 74 can slide up and down along the axial direction of the inner protective tube 71, and has two working positions: a first position and a second position. When the sliding outer tube 74 slides, the through holes 75 align with the air inlet 72; this is the first position, allowing exhaust gas to smoothly enter the inner protective tube 71, and the measuring electrode 32 can perform normal sampling and detection. When the sliding outer tube 74 slides further, the through holes 75 and the air inlet 72 are misaligned, and the wall of the sliding outer tube 74 blocks the air inlet 72 on the inner protective tube 71, preventing external exhaust gas from entering the inner protective tube 71 and cutting off forced convection cooling; at this time, the regeneration mode can be activated. In summary, this invention features a dynamic airflow control mechanism 7. By sliding the outer tube 74 relative to the inner protective tube 71, the intake passage can be controlled to open and close: under measurement conditions, the intake passage is opened to ensure that the exhaust gas can enter normally to complete particulate matter sampling and detection; under regeneration conditions, the intake passage is closed to cut off the forced convection of the exhaust gas, reduce heat loss, increase the actual regeneration temperature of the ceramic chip body 3, and at the same time isolate the low-temperature exhaust gas from directly blowing onto the ceramic chip body 3, reduce the impact of alternating hot and cold temperatures, protect the ceramic chip body 3, and meet the usage requirements of both normal detection and high-temperature regeneration conditions.

[0024] To achieve automatic switching between the first and second positions and maintain position stability of the sliding outer tube 74, relying solely on pneumatic cylinders or electric push rods for long-term position holding presents significant drawbacks: The pneumatic double-acting cylinder lacks self-locking capability after air cut-off; system pipeline pressure fluctuations and high-frequency vibrations of the exhaust pipe can cause the push rod to move erratically, leading to easy displacement of the sliding outer tube 74; misalignment or partial connection between the air inlet and through-hole can result in sealing failure and heat leakage during the regeneration stage. While a lead screw or mechanical locking structure with self-locking function can achieve position locking, the mechanical locking action involves mechanical clearance and impact wear, making it prone to jamming or incomplete engagement under high-temperature and vibration conditions, resulting in slow response speed. Repeated locking and unlocking cycles exacerbate component wear and reduce the reliability of the mechanism. Furthermore, the large size of the mechanical locking structure makes it difficult to fit into the narrow transition cavity installation space at the rear end of the sensor housing 4. Therefore, this application selects a magnetorheological fluid damper 78 as the position locking component, referring to... Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 A magnetorheological fluid damper 78 is fixedly mounted on the outer casing 4 and spaced apart from the sliding outer tube 74. A first elastic element 76 and a closing drive unit 77 are disposed between the magnetorheological fluid damper 78 and the sliding outer tube 74. The magnetorheological fluid damper 78 includes an annular sealed cavity 781, a piston rod 782, a piston 783, and an electromagnetic coil. An external lead 2 passes through the middle of the annular sealed cavity 781. One end of the piston rod 782 is fixedly connected to the bottom end of the sliding outer tube 74, and the other end extends into the sealed cavity 781 and is connected to the piston 783. The piston 783 divides the interior of the sealed cavity 781, and a through hole is provided on the piston 783 so that the piston 783 can slide within the sealed cavity 781. The first elastic element 76 is a high-temperature resistant stainless steel compression spring, directly sleeved on the outside of the piston rod 782. The lower end of the compression spring abuts against the upper end face of the sealing cavity 781, and the upper end abuts against the lower end face of the sliding outer tube 74. Under normal conditions, it continuously provides a reset force, causing the sliding outer tube 74 to slide to the first position, so that the through hole 75 is aligned with the air inlet 72, ensuring that the sensor automatically returns to the measurement mode after power failure. The closing drive unit 77 can be a pneumatic double-acting cylinder, a non-locking ball screw electric push rod, a non-hydraulic lock double-acting cylinder, etc. In this embodiment, the closing drive unit 77 is a pneumatic double-acting cylinder. The pneumatic double-acting cylinder is electrically connected to the control unit 1. The two ends of the pneumatic double-acting cylinder are respectively connected to the upper end of the sealing cavity 781 and the lower end of the sliding outer tube 74, so that when the air pressure is cut off and the pressure is released, there is no air pressure in the two cavities and the push rod is not locked. At this time, under the action of the first elastic element 76, the sliding outer tube 74 can quickly slide to the first position. After air is supplied to the pneumatic double-acting cylinder, the push rod retracts inward, causing the sliding outer tube 74 to quickly slide to the second position against the elastic force of the first elastic element 76. (Refer to...) Figure 1 , Figure 2 , Figure 3 and Figure 4 The sealed cavity 781 is filled with magnetorheological fluid, which uses a high-temperature resistant ionic liquid as its base liquid to ensure that it does not volatilize or fail under 300℃ operating conditions. It contains 200nm spherical soft magnetic carbonyl iron powder, resulting in a fast magnetic response. Fumed silica is added to prevent iron powder from settling over a long period, ensuring stable performance throughout the damper's lifespan. An electromagnetic coil is positioned around the outside of the sealed cavity 781 and electrically connected to the control unit 1. When switching to regeneration mode, the control unit 1 first activates a pneumatic double-acting cylinder to push the sliding outer tube 74 to the second position, simultaneously energizing the electromagnetic coil. A magnetic field is generated inside the sealed cavity 781, causing the magnetorheological fluid to instantly change from a low-viscosity liquid to a near-solid state. The piston 783 is completely locked, and the sliding outer tube 74 remains stably sealed without displacement or deviation, exhibiting extremely strong thermal stability. After regeneration and carbon removal are completed, control unit 1 cuts off the coil current, the magnetic field disappears, and the magnetorheological fluid returns to a low-viscosity flow state. Control unit 1 cuts off the air supply and releases pressure to the pneumatic double-acting cylinder. The first elastic element 76 drives the sliding outer tube 74 to quickly slide to the first position, and the through hole 75 is realigned with the air inlet 72, restoring exhaust gas flow and entering the measurement mode. The entire mechanism has no mechanical engagement latches, eliminating the risk of mechanical wear and jamming. It has a fast response speed and can be adapted to the narrow cavity of the sensor housing 4. With the high-temperature resistant ionic liquid-based magnetorheological fluid system, it can withstand the high-temperature environment inside the sensor, suppress the sedimentation of magnetic particles, and achieve rapid locking and unlocking cycles throughout its entire life cycle, ensuring stable and controllable airflow path opening and closing.

[0025] This application provides a PM sensor production line, which includes, in sequence, the following processes: S1, Ceramic chip body 3 manufacturing process: Using the mature co-firing process of ceramic electronic components, the following steps are completed in sequence: alumina ceramic casting green body preparation, internal heating electrode 33 tungsten molybdenum paste screen printing, multi-layer ceramic green body precise stacking, and 1600℃ high temperature co-firing molding. Finally, a ceramic chip substrate with no internal layering and stable electrode conduction is obtained. The chip tail is reserved with a standardized electrode lead-out metallization area to meet the requirements of subsequent lead wire welding and locking assembly.

[0026] S2, Precision structure processing: Using ultraviolet laser precision processing equipment with a processing accuracy of ±5μm, high-precision measurement electrodes 32 are etched on the surface of the chip head.

[0027] S3, Shape Memory Alloy Component Integration and Synchronous Processing: This process is the core innovation of this production line. It combines the four traditionally separate processes of component assembly, slurry coating, alloy phase transformation, and slurry curing into a single heat treatment process, reducing two heating processes and lowering production energy consumption.

[0028] S31, Component Assembly: The automated robotic arm places the nickel-titanium alloy clamping ring 51 into the lead wire docking point to complete the precise assembly of the shape memory alloy component. S32, Slurry Coating: An automatic dispensing machine applies a quantitative amount of aluminum dihydrogen phosphate-based low-temperature curing slurry to the lead wire joint, with the dispensing amount error controlled within ±0.01mL; S33, segmented temperature-controlled tunnel furnace heat treatment: Utilizing a continuous tunnel heating furnace with a customized stepped heating curve: The first step involves heating to 170℃ (the phase transformation range of nickel-titanium alloy) at a rate of 3℃ / min, holding for 8 minutes to complete the radial shrinkage and clamping of the clamping ring 51; the second step involves further heating to 200℃ and holding for 15 minutes to complete the complete curing of the low-temperature slurry; the third step involves cooling to room temperature with the furnace at a rate of 5℃ / min. Mechanical locking and chemical bonding are simultaneously completed in a single heating cycle, improving process efficiency by 40%.

[0029] S3', Auxiliary process for the preparation and integration of magnetorheological fluid damper 78: After the heat treatment of the shape memory alloy components is completed and before final assembly, a sealed damper integration station is added. The entire process is carried out under the protection of nitrogen inert atmosphere to avoid oxidation failure of the magnetorheological fluid: First, the piston rod 782 and piston 783 are assembled into a sealed cavity 781; second, magnetorheological fluid is quantitatively injected under vacuum to eliminate air bubbles inside the cavity; then, the interface of the sealed cavity 781 is sealed, and an electromagnetic coil is wound to form an independent damping module; finally, the first elastic element 76 and the closing drive unit 77 are installed, and the damping module is mechanically connected and wired to the sliding outer tube 74 and sensor housing 4 through tooling fixtures.

[0030] S4, Assembly and Functional Testing Process: The sensor housing is packaged in sequence, the internal circuit continuity is tested, the shape memory alloy blade deformation performance is sampled, the airflow control mechanism opening and closing response is tested, and the whole machine high and low temperature vibration durability test is performed. After passing the test, the product is marked and discharged, and unqualified products are automatically sorted and reworked.

[0031] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0032] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A PM sensor, characterized in that, include The ceramic chip body (3) has an electrode lead-out end (31) at the tail end and a sensitive area at the head. The surface of the sensitive area is provided with a measuring electrode (32), and a heating electrode (33) is embedded inside the ceramic chip body (3). External lead (2), which is electrically connected to the electrode lead-out end (31); The outer casing (4) contains and protects the ceramic chip body (3); The shape memory alloy lead locking assembly (5) is located at the connection between the external lead (2) and the electrode lead (31). It includes a clamping ring (51) made of shape memory alloy and a low-temperature curing encapsulation slurry layer (52) for chemically bonding the external lead (2) and the electrode lead (31). The austenitic phase transformation initiation temperature of the shape memory alloy is lower than the curing temperature of the low-temperature curing encapsulation slurry layer (52). During assembly, the clamping ring (51) in the martensitic phase is enlarged and fitted outside the external lead (2). When the slurry is heated for curing, the clamping ring (51) triggers the transformation of the martensitic phase to the austenitic phase and shrinks radially, forming a circumferential enclosure and limiting the external lead (2) and the electrode lead (31). After curing, the temperature is lowered, the clamping ring (51) recovers the martensitic phase and rebounds and expands, automatically detaching from the cured low-temperature curing encapsulation slurry layer (52).

2. The PM sensor and its production line according to claim 1, characterized in that, The shape memory alloy is a nickel-titanium alloy, with an austenitic phase transformation initiation temperature range of 150℃~180℃ and an austenitic phase transformation end temperature not higher than 180℃. The low-temperature curing encapsulation slurry layer (52) is cured from aluminum dihydrogen phosphate-based slurry, with a curing temperature of 200℃.

3. A PM sensor and its production line according to claim 1, characterized in that, The inner wall of the clamping ring (51) is uniformly distributed with several discrete positioning fulcrums along the circumference. The positioning fulcrums and the clamping ring (51) are integrally formed. When the clamping ring (51) contracts radially, the top of the positioning fulcrum abuts against the outer circle of the outer lead wire (2) to achieve coaxial centering. A uniform slurry accommodating gap is formed between adjacent positioning fulcrums.

4. A PM sensor according to claim 1, characterized in that, The outer casing (4) includes a dynamic airflow control mechanism (7), which comprises: The inner protective tube (71) is closed at the top and is fitted and fixed to the outside of the ceramic chip body (3). Its tube wall is provided with an air inlet (72) and a pressure relief valve (73) is provided at the top. A sliding outer tube (74) with its bottom end in a closed state is coaxially sleeved on the outside of the inner protective tube (71). A through hole (75) is provided on its tube wall. The sliding outer tube (74) slides along the axial direction of the inner protective tube (71). The sliding has a first position and a second position. When it is in the first position, the through hole (75) on the sliding outer tube (74) is at least partially aligned with the air inlet (72) on the inner protective tube (71) to form an airflow channel. When it is in the second position, the sliding outer tube (74) blocks the air inlet (72) on the inner protective tube (71). The first elastic element (76), which is a return spring, is disposed between the sliding outer tube (74) and a fixed reference, and provides the sliding outer tube (74) with an elastic force that causes it to slide to the first position; The drive unit (77) is shut down to provide a driving force to the sliding outer tube (74) to slide it from the first position to the second position; A magnetorheological fluid damper (78) includes a sealed cavity (781), a piston rod (782), a piston (783), and an electromagnetic coil. The sealed cavity (781) is fixedly disposed on one side of the ceramic chip body (3) and is filled with magnetorheological fluid. One end of the piston rod (782) is fixedly connected to the sliding outer tube (74), and the other end extends into the sealed cavity (781) and is connected to the piston (783). The piston (783) divides the interior of the sealed cavity (781) and can slide inside the cavity. The electromagnetic coil is arranged around the outside of the sealed cavity (781). The electromagnetic coil is electrically connected to a control unit (1). When it is necessary to switch from the first position to the second position, the control unit (1) first controls the shut-off drive unit (77) to move the sliding outer tube (74) against the force of the first elastic element (76) to the second position. At the same time or subsequently, the electromagnetic coil is energized to make the magnetorheological fluid become high viscosity or near-solid, thereby locking the sliding outer tube (74) in the second position. When it is necessary to return from the second position to the first position, the control unit (1) cuts off the current of the electromagnetic coil and controls the shut-off drive unit (77) to stop or reverse its operation. The magnetorheological fluid returns to a low viscosity state, and the first elastic element (76) drives the sliding outer tube (74) back to the first position.

5. A PM sensor according to claim 4, characterized in that, The magnetorheological fluid comprises a high-temperature resistant ionic liquid, soft magnetic particles uniformly dispersed in the ionic liquid, and additives for preventing the soft magnetic particles from settling.

6. A PM sensor according to claim 4, characterized in that, The sliding outer tube (74) is fixedly connected to the piston rod (782) via a connector. The first elastic element (76) is a compression spring sleeved on the piston rod (782). One end of the compression spring acts on the sliding outer tube (74), and the other end acts on the sealing cavity (781).

7. A production line for producing a PM sensor as described in any one of claims 1-6, characterized in that, The production line includes, sequentially along the process flow: S1. Ceramic chip body (3) manufacturing: A ceramic chip body (3) with built-in heating electrode (33) and metallized area on the surface is prepared by casting, printing, stacking and co-firing processes; S2. Precision structure processing: A measuring electrode (32) is formed on the surface of the ceramic chip body (3) using laser processing technology; S3. Integration and synchronous processing of shape memory alloy components: S31. Assemble a functional component made of shape memory alloy into a predetermined position of the ceramic chip body (3), wherein the functional component is a clamping ring (51) for securing the external lead (2); S32. Apply a low-temperature curing encapsulating slurry to the corresponding area that needs to be encapsulated or fixed; S33. Perform a programmed temperature-controlled heat treatment on the assembled and coated parts. The temperature curve of the heat treatment is set to solidify the encapsulating slurry and simultaneously trigger a phase transformation of the shape memory alloy, thereby simultaneously completing chemical bonding and physical shape memory locking in a single heat treatment process. S4. Assembly and Functional Testing: Complete the electrical connection of the sensor, the housing (4) encapsulation, and test the overall performance of the integrated shape memory alloy functional components and the sensor.

8. The production line according to claim 7, characterized in that, After step S3 and before step S4, step S3' is also included: fabrication and integration of the magnetorheological fluid damper (78), which includes: S3'1. Provide a damper housing (4) with a sealed cavity (781), and assemble the piston (783) rod (782) and piston (783) into the cavity; S3'2. Under vacuum or inert atmosphere protection, a quantitative amount of magnetorheological fluid is injected into the sealed cavity (781); S3'3. Seal the cavity after injection; S3'4. The electromagnetic coil is installed around the periphery of the sealed cavity (781) to form a magnetorheological fluid damper (78) module; S3'5. Install the first elastic element (76) and close the drive unit (77), and mechanically and electrically integrate the magnetorheological damper (78) module with the sliding outer tube (74) and the housing (4) substrate of the sensor.

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