A car fire point monitoring and recording system

Abstract

The application discloses a kind of automobile fire point monitoring and recording system, including electronic control unit and the detection circuit of multiple monitoring nodes in parallel connection.Each monitoring node is formed by temperature response switch and base resistance in series.When ambient temperature reaches threshold value, switch is closed to access base resistance, so that the total resistance of circuit occurs step change.Electronic control unit accurately locates fire point according to changed resistance value, and determines whether fire spreads centrifugally or centripetally according to time sequence of multiple node triggers.The application converts fire signal into stable resistance step signal through instantaneous action of temperature control switch, effectively solves the problem of large positioning error and unable to determine the direction of spread caused by unstable contact resistance in prior art, and supports cloud data recording and active protection linkage of battery management system.

Description

Technical Field

[0001] This invention belongs to the field of automotive safety technology, specifically relating to an automotive ignition point monitoring and recording system. Background Technology

[0002] With the rapid development of the automotive industry, especially the increasing electrification of new energy vehicles, vehicle fire and electrical safety risks have received growing attention. In the event of a vehicle fire, accurately identifying the ignition point (source of the fire) is crucial for determining liability, insurance claims, and technical improvements by the vehicle manufacturer. However, because fire scenes are often severely damaged, subsequent manual on-site investigations alone are insufficient to accurately reconstruct the initial location and spread of the fire.

[0003] Currently, cable-type heat detectors (linear heat-sensing cables) are commonly used in existing technologies for monitoring vehicle fires. Typical implementations of this technology include: Heat shrink tubing type: Two metal conductors are wrapped in heat shrink tubing. When heated, the tubing shrinks, forcing the conductors to short-circuit. Insulation melting type: Two twisted wires are used. When the external temperature rises, the insulation layer on the surface of the wires is burned and melted, causing the internal metal conductors to come into contact and short-circuit.

[0004] The aforementioned systems typically determine the presence of a fire by monitoring changes in loop resistance (usually a sharp drop in resistance) and using the resistance value of the wire between the short circuit point and the controller to estimate the location of the fire. However, in practical applications, the existing technology has the following major drawbacks, making it difficult to meet the needs of accurate accident analysis: 1. Unstable resistance changes lead to large false alarms and location errors: Whether it's the shrinking of the heat-shrink tubing or the melting of the insulation layer, it's a gradual physical change, not an ideal instantaneous action. When a fire occurs, the two detection wires undergo a transition from insulation to poor contact (arcling, carbonization) and then to complete contact. During this process, the contact resistance is unstable, causing the total circuit resistance to fluctuate irregularly in real time over a period of time, rather than abruptly changing from one constant value to another. Since the system typically relies on resistance values ​​to extrapolate distance, this unstable contact resistance leads to significant deviations in the calculated fire location, making accurate location impossible.

[0005] 2. Difficulty in determining the direction and trend of fire spread: Existing linear short-circuit detection technologies can typically only detect a single state of change from open circuit to short circuit. Once a short circuit occurs at a point on the cable near the detection unit (such as the ECU), the entire circuit often exhibits near-zero impedance. At this point, the current is interrupted, and even if the fire continues to spread further and burns subsequent cables, the detection unit cannot detect the subsequent changes. Conversely, if multiple points on the cable are heated simultaneously, due to the randomness of contact resistance, the system also has difficulty distinguishing between single-point and multi-point fires. Therefore, existing technologies cannot record the movement trajectory of a fire inside the vehicle (i.e., whether it spreads centrifugally or centripetally), making it impossible for accident analysts to reconstruct the temporal sequence and spatial trend of the fire from the data.

[0006] In summary, existing vehicle fire monitoring technologies mainly solve the problem of alarming whether a fire exists, but they are significantly lacking in accurately locating the ignition point and recording the fire spread process. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a vehicle fire point monitoring and recording system that can convert fire signals into stable step signals and effectively record the sequence of actions at multiple points.

[0008] The technical solution adopted in this invention is: a vehicle ignition point monitoring and recording system, comprising: an electronic control unit; And at least one detection loop, which is connected to the electronic control unit via a detection wire; Multiple monitoring nodes are connected in parallel on the detection circuit. Each monitoring node consists of a temperature response switch and a basic resistor connected in series. The temperature response switch is configured to have an open state and a closed active state: under normal conditions, the temperature response switch is in the open state and the detection circuit exhibits high impedance characteristics; when the ambient temperature reaches a threshold, the temperature response switch switches to the closed active state, and the base resistor connected in series with it is connected to the parallel network of the detection circuit. The detection wire is attached to the vehicle wiring harness and is used to transmit the equivalent resistance value of the multiple monitoring nodes connected in parallel to the electronic control unit. The electronic control unit is configured to: monitor the total resistance value of the detection loop in real time, and when a step change in the total resistance value of the loop is detected due to the closing action of the temperature response switch, identify the location of the monitoring node in the closed active state based on the changed resistance value.

[0009] In the above technical solution, the electronic control unit is further configured to record the time sequence of a step change in the total resistance value of the circuit; the electronic control unit determines the direction of fire spread on the vehicle based on the order in which different monitoring nodes enter the closed activation state; the logic for determining the direction of spread is as follows: defining the electrical connection path along the detection wire, nodes that are electrically closer to the electronic control unit are considered near-end nodes, and nodes that are electrically farther from the electronic control unit are considered far-end nodes; if the identified activation sequence is that the near-end node is triggered first, followed by the far-end node, then the fire is determined to be spreading centrifugally; if the identified activation sequence is that the far-end node is triggered first, followed by the near-end node, then the fire is determined to be spreading centripetally.

[0010] In the above technical solution, the temperature response switch is a bimetallic strip temperature control switch or a thermal snap switch; the detection circuit is attached to the outside of the main trunk and branches of the vehicle's low-voltage wiring harness, and the multiple monitoring nodes are located in different physical areas of the vehicle.

[0011] In the above technical solution, the multiple monitoring nodes select temperature response switches with different operating temperature thresholds according to the different normal operating temperatures of the areas in which they are arranged in the vehicle; the first type of monitoring node arranged in the high-temperature area of ​​the vehicle selects a temperature response switch with a first temperature threshold, and the second type of monitoring node arranged in the normal area of ​​the vehicle selects a temperature response switch with a second temperature threshold, wherein the first temperature threshold is higher than the second temperature threshold.

[0012] In the above technical solution, the first temperature threshold is set to 150°C, corresponding to the monitoring area near the engine compartment or exhaust pipe; the second temperature threshold is set to 120°C, corresponding to the monitoring area outside the vehicle body wiring harness or battery pack.

[0013] In the above technical solution, the detection wire itself has a predetermined resistance value per unit length; the electronic control unit internally stores a preset resistance characteristic lookup table; the resistance characteristic lookup table records the theoretical total circuit resistance value after considering the line resistance of the detection wire itself and the basic resistance of different monitoring nodes participating in parallel combination; the electronic control unit determines the combination of monitoring nodes currently in a closed active state by matching the real-time collected total circuit resistance value with the resistance characteristic lookup table.

[0014] In the above technical solution, the base resistor has a non-zero preset resistance value, so that when any monitoring node or a combination of monitoring nodes enters a closed active state, its branch presents a specific impedance rather than a short circuit state; the system is configured to: when any monitoring node or combination of monitoring nodes is in a closed active state, utilize the voltage division effect of the base resistor to maintain a non-zero voltage drop across the detection loop, thereby allowing the electronic control unit to continue to detect further changes in the total resistance value of the loop caused by the parallel connection of subsequent monitoring nodes whose electrical positions are farther or closer to the electronic control unit than the monitoring node or combination of monitoring nodes.

[0015] The above technical solution also includes: vehicle-mounted communication terminal and cloud platform; The electronic control unit is connected to the vehicle communication terminal via the vehicle communication network, and sends the monitored resistance value change data, the identified monitoring node location and the determined fire spread direction to the vehicle communication terminal; the vehicle communication terminal is configured to forward the received data to the cloud platform in real time for remote storage, forming an unalterable fire accident process record.

[0016] In the above technical solution, the system includes multiple independent detection loops, each of which monitors different functional areas of the vehicle and is connected to an independent detection port of the electronic control unit.

[0017] In the above technical solution, the base resistance of each monitoring node in the detection loop is a resistor with the same resistance value; the total parallel resistance value generated by any possible combination of several monitoring nodes closing the temperature response switch at the same time in the detection loop has mathematical uniqueness; The electronic control unit is configured to resolve the specific node combination in the case of simultaneous triggering of multiple points based on the unique resistance value.

[0018] In the above technical solution, a terminating resistor is connected in parallel at the end of the detection circuit via a detection wire, and the resistance of the terminating resistor is significantly greater than the resistance of the base resistor. The electronic control unit stores a preset standby reference resistance value, which corresponds to the sum of the terminal resistance and the resistance of the corresponding detection wire itself. The electronic control unit executes the following circuit integrity diagnostic logic: If the total resistance of the monitored circuit is infinite, it is determined to be an open circuit fault in the detection circuit. If the monitored total resistance value of the circuit is within the preset tolerance range centered on the standby reference resistance value, it is determined that the system is in standby mode and the circuit is intact. If the total resistance value of the monitored circuit is less than the lower limit of the preset tolerance range and is within the preset effective range of fire monitoring, it is determined that a fire has occurred.

[0019] In the above technical solution, the electronic control unit stores the physical path length along the wiring harness between two adjacent monitoring nodes; The electronic control unit is configured to calculate the time difference between two adjacent monitoring nodes entering the closed activation state sequentially. The electronic control unit calculates the fire spread speed along the wiring harness based on the ratio of the physical path length to the time difference, and generates a severe combustion warning signal when the spread speed exceeds a preset threshold.

[0020] In the above technical solution, the temperature response switch and the basic resistor in the monitoring node are encapsulated in the same high-temperature resistant housing to form a two-terminal thermistor module. Alternatively, the monitoring node may be composed of a positive temperature coefficient thermistor ceramic element with step characteristics, which exhibits a high resistance state before reaching the Curie temperature and a predetermined low resistance conduction characteristic after reaching the Curie temperature.

[0021] In the above technical solution, the electronic control unit communicates with the vehicle controller and battery management system via the vehicle CAN bus or LIN bus; When the electronic control unit determines that the ignition point is located in the power battery pack area based on the change in resistance value, or determines that the fire is pointing towards the power battery pack based on the direction of spread, it actively sends the highest priority cut-off command to the battery management system to disconnect the high-voltage relay.

[0022] The present invention also provides a method for detecting the ignition point of an automobile using the system, comprising the following steps: S1: A resistance characteristic comparison table is pre-built, which associates the theoretical total resistance value of the detection circuit with the location of the monitoring node under different switch combinations; S2: The electronic control unit samples the actual total resistance value of the detection circuit at a predetermined frequency; S3: When the actual total resistance value is detected to change abruptly from a high impedance state to the first low resistance value, consult the resistance value characteristic comparison table, lock the monitoring node of the first action, and mark it as the fire ignition point; S4: After the first monitoring node is activated, the actual total resistance value is continuously monitored; when the resistance value is detected to undergo one or more subsequent step changes, showing a subsequent resistance value smaller than the first low resistance value, one or more monitoring nodes that subsequently activated are identified according to the parallel resistance calculation rule and the resistance value characteristic comparison table. S5: Based on the physical location relationships and time differences of all motion monitoring nodes identified in steps S3 and S4, generate a report describing the spread trend of the fire's movement trajectory in the vehicle.

[0023] The beneficial effects of this invention are as follows: This invention utilizes a monitoring node formed by a temperature-responsive switch connected in series with a base resistor, fundamentally solving the problem of unstable contact resistance caused by the melting of the insulation layer or the slow shrinkage process of the heat-shrink tubing in existing technologies. By converting the fire signal into the opening and closing action of the temperature-responsive switch, the system transforms the change in the total circuit resistance value from disordered analog fluctuations into a stable digital step change. This design ensures that the electronic control unit can obtain accurate and stable resistance readings, thereby accurately identifying the location of the fire and greatly reducing the false alarm rate and positioning error caused by random changes in contact resistance.

[0024] Furthermore, by recording the time series of step changes in loop resistance, this invention enables the system to capture the dynamic process of fire spread. Unlike traditional systems that can only detect a single short circuit, this solution can intelligently determine whether a fire spreads centrifugally or centripetally based on the order in which nodes are triggered (near end first, then far end, or vice versa). This provides crucial dynamic trajectory data for post-accident technical analysis, helping analysts reconstruct the fire's initiation and spread paths.

[0025] Furthermore, this invention employs a bimetallic strip or a thermally sensitive trip switch as the temperature sensing element, which, compared to a temperature-sensing cable that melts once, offers advantages such as precise operating temperature, stable physical performance, and resetting capability in non-destructive testing. By attaching the detection circuit to the main trunk and branches of the wiring harness, the monitoring network can closely follow high-risk paths of vehicle electrical fires, achieving full-process, accompanying protection of the vehicle's critical electrical circuits.

[0026] Furthermore, this invention flexibly configures switches with different action thresholds based on the thermal load characteristics of different areas of the vehicle, achieving precise thermal management by zone. This differentiated configuration strategy ensures high sensitivity to abnormal temperature rises in low-temperature areas (such as around the battery pack) while effectively preventing false alarms caused by heat radiation generated during normal vehicle operation in high-temperature areas (such as the engine compartment), significantly improving the system's adaptability to complex automotive environments.

[0027] Furthermore, the specific thresholds set in this invention—150°C for the engine compartment and 120°C for the vehicle body and battery area—are optimized selections based on automotive thermal balance engineering experience. These values ​​cover the majority of early-stage fire characteristic temperatures while maintaining a necessary safety margin with the extreme temperatures under normal operating conditions, thus achieving an optimal balance between sensitivity and anti-interference capability.

[0028] Furthermore, by pre-setting a resistance characteristic lookup table and incorporating the resistance of the probe wire itself, this invention eliminates the resistance error caused by long-distance wiring. Using a lookup table instead of simple real-time calculation not only improves the processor's response speed but also allows for pre-verification of the distinguishability of various resistance combinations during the design phase, ensuring the system's accuracy in matching resistance values ​​during actual operation.

[0029] Furthermore, this invention designs a non-zero resistance base resistor to ensure that after a monitoring node and its components are activated, the branch in which they reside will not experience a short circuit, but rather maintain a specific voltage division state. This unshielded design is crucial, as it ensures that after a node is triggered, the circuit remains open and the voltage drop is minimal, allowing the control unit to continue sensing the actions of subsequent nodes, thus ensuring that no details of fire spread are missed.

[0030] Furthermore, by combining an in-vehicle communication terminal (T-BOX) with a cloud platform, this invention constructs a black box mechanism for fire accident data. Key data such as resistor fluctuations, fire location, and spread direction are uploaded to cloud storage in real time, effectively preventing data loss caused by damage to the local ECU due to severe vehicle fires. This provides immutable objective evidence for subsequent manufacturer liability determination, insurance claims, and forensic identification.

[0031] Furthermore, this invention employs multiple independent detection loops to achieve grid-based independent monitoring of different functional areas of the vehicle. This topology not only reduces the risk of signal attenuation caused by excessively long single loops, but also ensures that line faults or fire damage in one area will not affect the monitoring functions of other areas, thereby improving the fault tolerance and reliability of the overall system.

[0032] Furthermore, this invention employs a unique encoding configuration for the base resistors, ensuring that the total parallel resistance value generated by any combination of switches (including simultaneous triggering at multiple points) in the detection loop is mathematically unique. This effectively solves the signal confusion problem during concurrent multi-point fires, enabling the system to accurately deduce specific and complex fault node combination patterns.

[0033] Furthermore, this invention introduces a terminating resistor and corresponding line integrity diagnostic logic, giving the system self-testing capabilities. The system can clearly distinguish between three states: open circuit (fault), intact line (standby), and reduced resistance (fire), completely eliminating the "false safety" state caused by line aging or breakage, and ensuring that the system is always in an effective standby state.

[0034] Furthermore, this invention utilizes the physical path length and action time difference between nodes to calculate the spread rate, enabling the system to quantitatively assess the intensity of a fire. When a severe fire spread is detected, a warning of intense burning is generated, which can buy valuable time for occupants to escape and provide a higher level of triggering signal for the vehicle's active fire suppression system.

[0035] Furthermore, this invention employs an integrated high-temperature resistant package or a PTC thermistor ceramic element, enhancing the mechanical strength and electrical stability of the monitoring node in harsh automotive environments such as vibration, humidity, and oil contamination. This highly integrated design not only facilitates automated production and assembly in wire harness factories but also ensures consistent heat conduction, further improving monitoring reliability.

[0036] Furthermore, by linking with the vehicle controller and battery management system, this invention extends the monitoring function to active safety control. Once it is determined that a fire threatens the safety of the power battery, the active disconnection of the high-voltage relay can cut off the high-energy circuit at the source, preventing the cascading effect of thermal runaway and secondary damage caused by electrical short circuits, thus minimizing property damage and personal injury risks.

[0037] Furthermore, this invention provides a standardized signal processing and decision-making process. From looking up a table to pinpoint the starting point, to continuously monitoring subsequent step changes, and then generating a spread trend report, this method ensures a logical closed loop for the hardware system's functions, enabling fire monitoring to move beyond single-moment alarms and instead generate a complete spatiotemporal accident analysis report.

[0038] In summary, the automotive fire ignition point monitoring and recording system proposed in this invention, with a series architecture of "temperature control switch + basic resistor" as its core, overcomes the industry pain points of large resistance drift and inability to continuously locate fire points in traditional linear temperature sensing technology. This system not only achieves precise location of the fire point but also depicts the movement and velocity of the fire through a stable resistance step signal. Combined with cloud data synchronization and proactive safety control strategies, it provides a comprehensive automotive thermal safety solution integrating precise monitoring, situational awareness, data preservation, and proactive protection. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the system of the present invention; Figure 2 This is a schematic diagram of the installation of the present invention; Figure 3 This is a schematic diagram of an application scenario for an example. Figure 4 This is a schematic diagram of an application scenario for an example.

[0040] Among them, 1-basic resistor, 2-temperature response switch, 3-detection wire, 4-vehicle low voltage wiring harness. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0042] Example 1 like Figure 1 As shown, the present invention provides a vehicle ignition point monitoring and recording system, including: an electronic control unit; And at least one detection loop, which is connected to the electronic control unit via a detection wire; Multiple monitoring nodes are connected in parallel on the detection circuit. Each monitoring node consists of a temperature response switch and a basic resistor connected in series. The temperature response switch is configured to have an open state and a closed active state: under normal conditions, the temperature response switch is in the open state and the detection circuit exhibits high impedance characteristics; when the ambient temperature reaches a threshold, the temperature response switch switches to the closed active state, and the base resistor connected in series with it is connected to the parallel network of the detection circuit. The detection wire is attached to the vehicle wiring harness and is used to transmit the equivalent resistance value of the multiple monitoring nodes connected in parallel to the electronic control unit. The electronic control unit is configured to: monitor the total resistance value of the detection loop in real time, and when a step change in the total resistance value of the loop is detected due to the closing action of the temperature response switch, identify the location of the monitoring node in the closed active state based on the changed resistance value.

[0043] This embodiment proposes a monitoring system based on the principle of discretized transient change. By arranging bimetallic strip temperature control switches with precision resistors connected in series at key nodes of the vehicle wiring harness, the simulated resistance changes during a fire are converted into digital stepped resistance changes. This not only solves the resistance drift problem in traditional technologies, but also achieves precise spatial location of the fire ignition point and dynamic capture of the fire spread direction (i.e., towards or away from the ECU) through an original parallel resistor logic algorithm.

[0044] like Figure 2 As shown, the hardware architecture of this system aims to achieve full-vehicle thermal monitoring with minimal engineering cost by utilizing the existing low-voltage wiring harness layout of the vehicle. The system mainly consists of an electronic control unit (ECU), detection wires (H), temperature control switches (S), base resistors (R), an on-board communication terminal (T-BOX), a remote terminal, and the vehicle's instrument panel.

[0045] The ECU is the core of the entire system. Its main function is to monitor the equivalent resistance of the detection circuit in real time and distribute the data to other nodes via the CAN bus.

[0046] Inside the ECU, the core of the monitoring circuit is a high-precision analog-to-digital converter (ADC). To achieve accurate measurement of the resistance of the probe loop, the ECU employs a voltage divider circuit topology.

[0047] The ECU is equipped with a precision pull-up resistor. Connect to the reference voltage source Typically a 5V or 3.3V regulated power supply). The probe wire (H) is connected to the ADC input as a pull-down resistor network.

[0048] According to Ohm's law, the voltage at the ADC sampling terminal... Determined by the following formula: ; in, It is the total equivalent resistance of the external probe wire network. Among them, This refers to the pull-up resistor inside the ECU.

[0049] Considering that when the fire spreads, the closure of multiple nodes could lead to... To detect minute changes in parallel resistance, this embodiment uses an ADC with at least 12 bits (4096 quantization levels). A 12-bit ADC, with a 5V reference voltage, theoretically achieves a resolution of 1.22mV, sufficient to distinguish minute voltage drops caused by the resistance of long wires, thus ensuring accuracy in long-distance wire harness monitoring.

[0050] The automotive electrical environment is extremely harsh, with significant voltage fluctuations and electromagnetic interference (EMI). To ensure the reliability of the ECU in the early stages of a fire, a protection circuit must be designed at the ADC input: a 3.3V or 5.1V Zener diode is connected in parallel at the ADC input to prevent damage to the MCU pins if the probe wire is accidentally shorted to the 12V / 24V power line. An RC low-pass filter (such as...) is also used. High-frequency noise and transient pulses are filtered out to ensure the stability of resistance sampling. At the software level, de-jitter logic is added, requiring the resistance value to remain stable within a certain time window (e.g., 100ms) before being considered a valid signal, thus avoiding false alarms due to momentary contact caused by vehicle bumps.

[0051] The core innovation of this system lies in the connection method of the detection loop. Unlike traditional single-point sensors, this embodiment adopts a parallel network structure of series resistor units.

[0052] Each monitoring node consists of two core components connected in series, including: Temperature control switch (S): as a normally open mechanical switch; Base resistor (R): A load with a fixed resistance value.

[0053] All monitoring node units are connected in parallel between the signal line and the ground line of the detection wire (H). The detection wire is attached to the outside of the main trunk and branches of the vehicle's low-voltage wiring harness, physically extending to various potential fire areas of the vehicle (such as the engine compartment, the bottom of the battery pack, the trunk electronic control area, etc.).

[0054] The most fundamental difference between this invention and existing technologies lies in the introduction of a fundamental resistor R. In a pure switch parallel circuit without resistor R (i.e., in the prior art), if the switch near the ECU... When the circuit is closed, the resistance of the loop becomes the resistance of the wire (approximately). At this time, regardless of the remote switch Whether the circuit is closed or not, the total resistance of the circuit is always close to 0, and the ECU cannot sense the remote status. In this embodiment, a series resistor R is used when... When closed, the circuit resistance R1 is (Wire resistance). If subsequently The circuit is also closed, and the loop becomes two parallel branches containing R. The total resistance will follow the parallel formula. The resistance value decreases steadily, but it will never reach zero. The ECU can detect the specific value of the resistance and calculate how many switches are currently closed, and even deduce the position of the closed switches based on the difference in wire resistance.

[0055] This embodiment uses a bimetallic snap-action temperature control switch. It utilizes a bimetallic strip, made of two metals with different coefficients of thermal expansion, which deforms as the temperature rises. When a preset threshold is reached, the internal stress is released instantaneously, pushing the contacts to close. This instantaneous action characteristic converts the heat accumulation process of a fire into a digital signal indicating the on / off state of the circuit.

[0056] To avoid affecting measurement accuracy, the contact resistance after the temperature control switch is closed must be extremely low. This embodiment requires a contact resistance of... Compared to the base resistance R (such as...) The internal resistance of the switch itself can be ignored.

[0057] This embodiment configures switches with different operating temperatures based on the heat load characteristics of different areas of the vehicle: High-temperature areas: such as the engine compartment, near the turbocharger, and around the high-power motor controller. Use a temperature control switch with an operating temperature of 150°C. This temperature is higher than the normal operating temperature (usually <110°C), effectively preventing false alarms, while remaining below the combustion temperature of the wiring harness insulation. Regular areas: such as the passenger compartment, trunk, and door interiors. Use temperature control switches with an operating temperature of 120°C. These areas are more sensitive to heat, and a lower threshold provides earlier warning.

[0058] To preserve the state of the accident scene, a manual reset type or a non-reset type can be selected. However, in this monitoring system, in order to continuously monitor the changes in fire intensity as the temperature decreases (such as after the fire is extinguished), it is also a feasible implementation plan to select an automatic reset type in conjunction with the latching logic of the ECU.

[0059] In this embodiment, the probe wire is not only a transmission medium, but its own resistance is also part of the positioning algorithm; therefore, high-temperature resistant automotive-grade wire is selected. To obtain measurable line resistance for auxiliary positioning, excessively thick wires should not be used.

[0060] If the total length of the detection loop is 10 meters, 0.35mm 2 The wire will be introduced into approximately The parasitic resistance. The ECU needs to include this resistance in its algorithm to improve positioning accuracy.

[0061] The detection wires themselves should have a certain degree of flame retardancy to ensure that the signal can be transmitted back to the ECU in the early stages of a fire. It is recommended to use fire-resistant materials that meet ISO 6722 standards for wrapping or routing the wires.

[0062] The base resistor (R) is a high-precision metal film resistor with high accuracy. Ideally, the temperature drift coefficient should be less than 100ppm / °C to prevent the high temperature at the fire scene from causing a drastic drift in the resistance value and affecting the judgment.

[0063] Considering that the resistor will carry a continuous current after the switch is closed, it is necessary to... Calculate the power. For example, if the system voltage is 5V and the resistance is... Then the power A resistor with a rated power of at least 0.5W should be selected to ensure reliability.

[0064] The T-BOX is the vehicle's external communication gateway. The ECU packages and sends the collected resistance data to the T-BOX via the vehicle's CAN bus (such as CAN-FD or high-speed CAN).

[0065] Protocol Standard: Data encapsulation uses the SAE J1939 protocol. Specific PGNs are defined for fire alarm signals; for example, a private PGN (such as 0xFF00) can be defined to broadcast the resistance values ​​and alarm status of each detection loop. The CAN message contains information such as "Loop ID," "Current Resistance Value," "Alarm Level," and "Trigger Switch ID." The SPN (SuspectParameterNumber) defines the specific data bits.

[0066] T-BOX transmits data to the cloud server in real time via 4G / 5G networks. The cloud platform database records thermal data throughout the vehicle's entire lifecycle. In the event of a dispute, resistance change curves before and after the accident can be retrieved. Due to the use of parallel resistor logic, the data can show whether the fire "erupted instantly" or "spread from a point to a surface," providing data support.

[0067] As a human-machine interface (HMI), the instrument panel alerts the driver through three methods after receiving alarm messages from the ECU: sound (buzzer), light (fault light), and text (pop-up notification).

[0068] The core of this system lies in abstracting the complex physical process of fire into a mathematical solution process of resistive network topology.

[0069] like Figure 3 As shown, the probe wire has an inherent linear resistance, denoted as r (unit: 1000 m³ / h). Let the total length of the detection loop be L. Temperature control switch. They are located at different distances from the ECU. The base resistance of each switch connected in series is R.

[0070] In the absence of a fire and without a terminating resistor, all temperature control switches All are in the disconnected state: .

[0071] At this time, the ECU's ADC measurement voltage is close to (Pull-up voltage). This is the system's reference state, used for self-testing open-circuit faults (if a terminal detection resistor is connected in parallel, the reading is the terminal resistance value).

[0072] Assuming at position A fire broke out at a location where the temperature exceeded 150°C, triggering the temperature control switch. closure.

[0073] At this time, the current path is .

[0074] Total resistance of the circuit for: .

[0075] The ECU detected a resistance value from Mutation Since R and r are known, the ECU can calculate... Accurately calculate This refers to the physical distance between the ignition point and the ECU.

[0076] When the fire spreads and causes multiple switches to operate, the changing trend of the total resistance reveals the direction of the fire's flow, which is explained in the following scenario.

[0077] Scenario 1: The fire spreads away from the ECU (from near to far). Time T0: Closed. Resistance. .

[0078] Time T1: The fire spreads further. . closure.

[0079] The circuit now becomes: branch road and Branch roads are connected in parallel.

[0080] because Compare Further along, its branch includes an additional section of wire resistance. .

[0081] The equivalent circuit structure is: R and (This is a simplified understanding that ignores the influence of common conductor segments; rigorous calculations require the application of Kirchhoff's laws.)

[0082] Because a new branch is connected in parallel, the total resistance... It will decrease further, but the extent of the decrease is limited by the resistance of the wire.

[0083] ECU Record: Resistance (The value decreased slightly).

[0084] Scenario 2: The fire spreads towards the ECU (from far to near). Time T0: Closed. Resistance. .

[0085] Time T1: The fire spreads to nearby areas. . closure.

[0086] At this time, the current arrives Before that, I encountered The diversion point.

[0087] The resistance of the branch is . and The resistance of the wires between them is connected in parallel. This will also lead to a decrease in total resistance. If the base resistance... If the total resistance is large, then... The difference in wire resistance will decrease while maintaining a 2r difference compared to scenario one; if the base resistance... If the value is smaller, then the total resistance is lower. A significant, step-like decline will occur.

[0088] ECU Record: Resistance (The numerical value decreases significantly / or the difference from scenario one remains at 2r decreases).

[0089] The ECU maintains a historical resistance value queue. Whenever a resistance change event occurs, the change in resistance before and after the event is calculated. .

[0090] If the total resistance after the transition event Falling into the low resistance range (or (Larger): This indicates a centripetal spread. It means that the node closer to the ECU has been triggered, the main circuit resistance has been bypassed, and the fire is approaching the ECU.

[0091] If the total resistance after the transition event Falling into the high resistance range (or (Smaller): This is determined to be centrifugal spread. It indicates that the distant node behind the original node was triggered, only increasing the parallel load at the end, and the fire spread towards the end of the vehicle.

[0092] To improve the processing efficiency of the ECU, in practice, the resistance values ​​for all possible states are usually calculated in advance during the development phase and stored in the ECU as a lookup table.

[0093] To illustrate the system principle, the following parameters are preset in this embodiment: Basic resistor (This is for illustrative purposes only; in actual engineering, it is recommended to use a larger value to reduce the current.) Wire resistance: Assume that the resistance of the wires between nodes is equal to that of the conductors. .

[0094] Node distribution: .

[0095] This embodiment demonstrates a general calculation and table creation method. In actual reproduction, technicians need to measure the actual harness length L and unit resistance r, and substitute them into a topology formula similar to Table 1 to generate a vehicle-specific table.

[0096] Table 1 State Derivation Table It should be noted that although the detection circuit described in this embodiment exhibits high impedance (open circuit) characteristics in normal standby mode, in practical engineering applications, in order to monitor the integrity of the detection line, a terminating resistor R0 with a resistance significantly greater than the base resistance R can be connected in parallel at the end of the detection circuit, such as... Figure 4 As shown. With the addition of a terminating resistor, the core principle of this invention—based on a step change in resistance for ignition point location—remains unchanged; however, the resistance calculation model within the ECU needs corresponding modifications. First, the system's standby reference resistance will no longer be infinite, but rather the sum of the terminating resistance and the total resistance of the detection wire. The ECU needs to use this to determine whether the system is in normal standby mode. Second, when the temperature control switch is activated, the actual sampled total circuit resistance will become the parallel value of the activated monitoring node branch and the terminating resistance branch. Since the terminating resistance is much larger than the base resistance, its impact on the low impedance signal after a fire is minimal (usually within the error range allowed by the algorithm or precisely corrected by the parallel formula), and will not affect the positioning accuracy. Finally, this hardware change enables the system to identify line open circuit faults by recognizing infinite resistance values, thereby effectively distinguishing between system standby and line disconnection, eliminating the risk of missed alarms caused by wire harness breakage.

[0097] Specifically, the ECU stores a preset standby reference resistance value, which corresponds to the sum of the terminal resistor and the resistance of its corresponding detection wire. The ECU executes the following circuit integrity diagnostic logic: If the total resistance of the monitored circuit is infinite, it is determined to be an open circuit fault in the detection circuit. If the monitored total resistance value of the circuit is within the preset tolerance range centered on the standby reference resistance value, it is determined that the system is in standby mode and the circuit is intact. If the total resistance value of the monitored circuit is less than the lower limit of the preset tolerance range and is within the preset effective range of fire monitoring, it is determined that a fire has occurred.

[0098] Example 2 This embodiment details the specific methods and steps for implementing fire monitoring, location, and spread direction determination using the aforementioned hardware system. The core of this method lies in mapping changes in the temperature field of the physical world to a topological transformation of the resistance network in the electrical world.

[0099] Step S1: Construct a resistance characteristic comparison table.

[0100] During the vehicle development or production line calibration phase, it is necessary to construct a feature mapping table that can associate resistance values ​​with physical locations.

[0101] Suppose that the detection loop contains N monitoring nodes, which are labeled as follows: ,in Closest to the ECU electrical distance The farthest.

[0102] Measure the physical length of each segment of the conductor. and resistivity per unit length r of the conductor (e.g.) ).

[0103] Determine the base resistance value R for each node connected in series.

[0104] For each possible combination of switch states (single - point closure, double - point closure, etc.), use Kirchhoff's law to calculate the theoretical total resistance .

[0105] For only the i - th node being closed, .

[0106] If nodes i and j are closed simultaneously (i < j, that is, i is close to the ECU and j is far from the ECU), the circuit should be equivalent to: Series part (common main circuit): the double - wire resistance from the ECU to node i ; Parallel part (shunt network): located at node i: Branch 1 (proximal shunt): only includes the basic resistance of node i Branch 2 (distal extension): includes the wire resistance from i to j + the basic resistance of node j .

[0107] Final theoretical total resistance correction formula: .

[0108] The example feature table is shown in Table 1. Store the above Table 1 in the non - volatile memory of the ECU to form a lookup table of Map<Resistance_Range,Node_Status>.

[0109] Step S2: Real - time sampling and filtering.

[0110] The ECU performs ADC sampling on the detection loop at a frequency of 100Hz (that is, once every 10ms). Perform a moving average on the most recent 5 sampling values to filter out the spikes caused by electromagnetic interference.

[0111] Convert the ADC voltage value to a resistance value .

[0112] Step S3: First - node locking and fire determination.

[0113] When the monitored suddenly drops from a high impedance (open - circuit or only terminal detection resistance) to a certain low - resistance range, it is determined as the initial stage of a fire.

[0114] Compare with the feature table constructed in S1.

[0115] For example, if , the ECU locks as the "first - starting node".

[0116] Record the event in internal RAM: {Timestamp:T0,Node:S2,Resistance:12Ω}.

[0117] Immediately send a "Level 1 Fire Alarm" signal to the entire vehicle and display "Inspection Location: Middle of Vehicle" on the dashboard.

[0118] Step S4: Dynamic propagation tracking.

[0119] After the first node is activated, the system enters a high-frequency tracking mode to monitor subsequent step changes in the resistance value.

[0120] The logic for determining centrifugal spread (burning towards distant sites) is as follows: A slight decrease in resistance indicates that the fire has spread to a more distant point S. Because S3 is far away, its branch has a longer conductor resistor in series. According to the parallel circuit formula, adding a larger resistor has a relatively small impact on the total resistance.

[0121] like and If so, the direction of spread is determined to be away from the ECU.

[0122] The logic for determining centripetal spread (burning towards the proximal end) is as follows: A significant drop in resistance indicates that the fire has spread to the closer S1 branch. The S1 branch has short wires and low resistance. Connecting a (relatively) small resistor in parallel will lower the overall resistance of the network.

[0123] like If the spread direction is determined to be approaching the ECU (which usually means approaching the cockpit or the core of the battery pack, the highest level of danger).

[0124] Step S5: Generate a spread report and upgrade the early warning.

[0125] The ECU reads the time difference between the actions of two adjacent nodes. .

[0126] Read the pre-stored physical distance between nodes (For example The wire harness between them is 1 meter long.

[0127] Calculate the spread rate .

[0128] If v > 0.5 m / s, it is determined to be "deflagration", and the VCU is directly requested to cut off the high voltage relay.

[0129] If detected before a fire starts The circuit was determined to be open, and a fault code was reported.

[0130] If detected The system is considered to be in normal standby mode based on the terminal resistance value.

[0131] The complete event sequence (e.g., T0:S2Triggered->T1:S1Triggered->Direction:Inward->Speed:Fast) is packaged and sent to T-BOX via CAN bus, and uploaded to the cloud as an unalterable accident file.

[0132] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A vehicle ignition point monitoring and recording system, characterized in that, include: Electronic control unit; And at least one detection loop, which is connected to the electronic control unit via a detection wire; Multiple monitoring nodes are connected in parallel on the detection circuit. Each monitoring node consists of a temperature response switch and a basic resistor connected in series. The temperature response switch is configured to have an open state and a closed active state: under normal conditions, the temperature response switch is in the open state and the detection circuit exhibits high impedance characteristics; when the ambient temperature reaches a threshold, the temperature response switch switches to the closed active state, and the base resistor connected in series with it is connected to the parallel network of the detection circuit. The detection wire is attached to the vehicle wiring harness and is used to transmit the equivalent resistance value of the multiple monitoring nodes connected in parallel to the electronic control unit. The electronic control unit is configured to: monitor the total resistance value of the detection loop in real time, and when a step change in the total resistance value of the loop is detected due to the closing action of the temperature response switch, identify the location of the monitoring node in the closed active state based on the changed resistance value.

2. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The electronic control unit is also configured to record the time sequence of a step change in the total resistance value of the circuit; the electronic control unit determines the direction of fire spread on the vehicle based on the order in which different monitoring nodes enter the closed activation state; the logic for determining the direction of spread is as follows: defining the electrical connection path along the detection wire, nodes that are electrically closer to the electronic control unit are considered near-end nodes, and nodes that are electrically farther from the electronic control unit are considered far-end nodes; if the identified activation sequence is that the near-end node is triggered first, followed by the far-end node, then the fire is determined to be spreading centrifugally; if the identified activation sequence is that the far-end node is triggered first, followed by the near-end node, then the fire is determined to be spreading centripetally.

3. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The temperature response switch is a bimetallic strip temperature control switch or a thermal snap switch; the detection circuit is attached to the outside of the main trunk and branches of the vehicle's low-voltage wiring harness, and the multiple monitoring nodes are located in different physical areas of the vehicle.

4. The vehicle ignition point monitoring and recording system according to claim 3, characterized in that: The multiple monitoring nodes are selected with temperature response switches having different operating temperature thresholds based on the different normal operating temperatures of the areas in which they are deployed in the vehicle. The first type of monitoring node, located in the high-temperature area of ​​the vehicle, uses a temperature response switch with a first temperature threshold, while the second type of monitoring node, located in the normal area of ​​the vehicle, uses a temperature response switch with a second temperature threshold, wherein the first temperature threshold is higher than the second temperature threshold.

5. The vehicle ignition point monitoring and recording system according to claim 4, characterized in that: The first temperature threshold is set to 150°C, corresponding to the monitoring area near the engine compartment or exhaust pipe; the second temperature threshold is set to 120°C, corresponding to the monitoring area outside the vehicle body wiring harness or battery pack.

6. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The detection wire itself has a predetermined resistance value per unit length; the electronic control unit stores a preset resistance characteristic lookup table; the resistance characteristic lookup table records the theoretical total circuit resistance value after considering the line resistance of the detection wire itself and the basic resistance of different monitoring nodes in parallel combination; the electronic control unit determines the combination of monitoring nodes that are currently in a closed active state by matching the real-time collected total circuit resistance value with the resistance characteristic lookup table.

7. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The base resistor has a non-zero preset resistance value, so that when any monitoring node or a combination of monitoring nodes enters a closed active state, its branch presents a specific impedance rather than a short circuit. The system is configured such that when any monitoring node or combination of monitoring nodes is in a closed active state, the voltage division effect of the base resistor is used to maintain a non-zero voltage drop across the detection loop, thereby allowing the electronic control unit to continue to detect further changes in the total resistance value of the loop caused by the parallel connection of subsequent monitoring nodes whose electrical positions are farther or closer to the electronic control unit than the monitoring node or combination of monitoring nodes.

8. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that, It also includes: in-vehicle communication terminals and cloud platforms; The electronic control unit is connected to the vehicle communication terminal via the vehicle communication network, and sends the monitored resistance value change data, the identified monitoring node location and the determined fire spread direction to the vehicle communication terminal; the vehicle communication terminal is configured to forward the received data to the cloud platform in real time for remote storage, forming an unalterable fire accident process record.

9. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The system comprises multiple independent detection loops, each monitoring different functional areas of the vehicle and connected to an independent detection port of the electronic control unit.

10. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The base resistance of each monitoring node in the detection loop is a resistor with the same resistance value; the total parallel resistance value generated by any possible combination of several monitoring nodes closing the temperature response switch at the same time in the detection loop is mathematically unique; The electronic control unit is configured to resolve the specific node combination in the case of simultaneous triggering of multiple points based on the unique resistance value.

11. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: At the end of the detection circuit, a terminating resistor is connected in parallel via a detection wire. The resistance of the terminating resistor is significantly greater than that of the base resistor. The electronic control unit stores a preset standby reference resistance value, which corresponds to the sum of the terminal resistance and the resistance of the corresponding detection wire itself. The electronic control unit executes the following circuit integrity diagnostic logic: If the total resistance of the monitored circuit is infinite, it is determined to be an open circuit fault in the detection circuit. If the monitored total resistance value of the circuit is within the preset tolerance range centered on the standby reference resistance value, it is determined that the system is in standby mode and the circuit is intact. If the total resistance value of the monitored circuit is less than the lower limit of the preset tolerance range and is within the preset effective range of fire monitoring, it is determined that a fire has occurred.

12. The vehicle ignition point monitoring and recording system according to claim 2, characterized in that: The electronic control unit stores the physical path length between two adjacent monitoring nodes along the wiring harness. The electronic control unit is configured to calculate the time difference between two adjacent monitoring nodes entering the closed activation state sequentially. The electronic control unit calculates the fire spread speed along the wiring harness based on the ratio of the physical path length to the time difference, and generates a severe combustion warning signal when the spread speed exceeds a preset threshold.

13. The vehicle ignition point monitoring and recording system according to claim 1, characterized in that: The temperature response switch and the basic resistor in the monitoring node are encapsulated in the same high-temperature resistant housing to form a two-terminal thermistor module. Alternatively, the monitoring node may be composed of a positive temperature coefficient thermistor ceramic element with step characteristics, which exhibits a high resistance state before reaching the Curie temperature and a predetermined low resistance conduction characteristic after reaching the Curie temperature.

14. The vehicle ignition point monitoring and recording system according to claim 2, characterized in that: The electronic control unit communicates with the vehicle controller and battery management system via the vehicle CAN bus or LIN bus. When the electronic control unit determines that the ignition point is located in the power battery pack area based on the change in resistance value, or determines that the fire is pointing towards the power battery pack based on the direction of spread, it actively sends the highest priority cut-off command to the battery management system to disconnect the high-voltage relay.

15. A method for detecting the ignition point of an automobile using the system described in any one of claims 1-14, characterized in that, Includes the following steps: S1: A resistance characteristic comparison table is pre-built, which associates the theoretical total resistance value of the detection circuit with the location of the monitoring node under different switch combinations; S2: The electronic control unit samples the actual total resistance value of the detection circuit at a predetermined frequency; S3: When the actual total resistance value is detected to change abruptly from a high impedance state to the first low resistance value, consult the resistance value characteristic comparison table, lock the monitoring node of the first action, and mark it as the fire ignition point; S4: After the first monitoring node is activated, the actual total resistance value is continuously monitored; when the resistance value is detected to undergo one or more subsequent step changes, showing a subsequent resistance value smaller than the first low resistance value, one or more monitoring nodes that subsequently activated are identified according to the parallel resistance calculation rule and the resistance value characteristic comparison table. S5: Based on the physical location relationships and time differences of all motion monitoring nodes identified in steps S3 and S4, generate a report describing the spread trend of the fire's movement trajectory in the vehicle.

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