An inert gas based micro-positive pressure closed safety protection system and method for R290 heat pump system

Abstract

The application discloses a kind of micro-positive pressure closed safety protection system and method based on inert gas for R290 heat pump system, the safety protection system includes sealed cavity, R290 heat pump system is arranged inside sealed cavity, pressure sensor for real-time monitoring the air pressure in cavity and R290 concentration sensor for real-time monitoring the R290 concentration in cavity;Sealed cavity is filled with inert gas to micro-positive pressure after being evacuated via inert gas filling port;When the R290 concentration in cavity reaches or exceeds preset concentration threshold, immediately cut off the power supply of compressor of R290 heat pump system.The application constructs inert gas environment in cavity, blocks oxygen, avoids the case that R290 occurs leakage to cause fire and explosion accident;Micro-positive pressure in cavity can prevent external air infiltration;Air pressure, R290 concentration double monitoring and corresponding early warning, safety response can prompt maintenance, ensure the long-term reliability of inert gas environment in cavity, avoid secondary risk.

Description

Technical Field

[0001] This invention relates to a thermal management system for electric vehicles, and more specifically to a micro-positive pressure closed-loop safety protection system and method based on inert gas for R290 heat pump systems. Background Technology

[0002] As a core component of the thermal management system for electric vehicles, heat pump systems are gradually becoming the industry mainstream due to their high energy efficiency ratio and minimal impact on driving range. In terms of refrigerant selection, the industry is undergoing a transition from high GWP (Global Warming Potential) refrigerants (such as R134a and R1234yf) to environmentally friendly natural refrigerants. R290 (propane), as a natural refrigerant, possesses zero ODP (Ozone Depletion Potential), an extremely low GWP (approximately 3), and excellent thermodynamic properties, making it considered an ideal alternative for next-generation electric vehicle heat pump systems.

[0003] However, the flammable and explosive properties of R290 (its explosive concentration range is 2.1% to 9.5%, and its minimum ignition energy is extremely low) pose the greatest safety hazard for its application in vehicles. Electric vehicles have confined interior spaces and contain numerous electrical devices; if R290 refrigerant leaks, it can easily form an explosive gas mixture, which, upon encountering an ignition source such as an electrical spark, could trigger a serious safety accident.

[0004] Currently, the main protective measures against R290 leaks are the "monitoring + ventilation" scheme: when the R290 concentration sensor detects an R290 leak, the ventilation device is immediately activated to dilute the refrigerant and discharge it outside the vehicle. However, this scheme has the following drawbacks: (1) The ventilation measures cannot eliminate the ignition source and can only reduce the local R290 concentration. If the leakage rate is fast or the ventilation is poor, it may still reach the explosion limit; (2) Forced ventilation will spread the locally leaked R290 to the entire compartment or other areas of the vehicle, which will expand the distribution range of the explosive mixture and increase the probability of contact with potential ignition sources, which may lead to an expansion of the risk; (3) There is a response time difference between the sensor detecting the R290 leak and the dilution ventilation. When the R290 concentration instantly reaches the lower explosive limit, a combustion and explosion accident cannot be avoided.

[0005] CN114407603B discloses a system and method for improving the safety of a combustible refrigerant heat pump system in electric vehicles. It uses inert gas as an auxiliary treatment method after a leak. When a gas concentration sensor detects a leak in the combustible refrigerant, inert gas is injected into the housing to dilute the refrigerant, and the temperature of the mixed gas is reduced by spraying. However, there are two problems. First, there is a time lag between the leak signal response and the dilution of the R290 concentration to the target value, making it difficult to guarantee safety. Second, a spraying device is required, which is not only structurally complex and costly, but may also cause damage to electronic components after spraying.

[0006] In summary, the safety hazard of R290 leakage potentially causing combustion and explosion accidents has not been effectively resolved, limiting the application of R290 heat pump systems in electric vehicles. Summary of the Invention

[0007] Purpose of the invention: The first purpose of this invention is to address the safety hazard of potential combustion and explosion accidents caused by leakage of R290 refrigerant in the heat pump system of electric vehicles, and to provide an intrinsically safe micro-positive pressure closed-loop safety protection system based on inert gas; the second purpose of this invention is to provide a safety protection method for the micro-positive pressure closed-loop safety protection system based on inert gas.

[0008] Technical Solution: The present invention provides a micro-positive pressure closed-loop safety protection system based on inert gas for an R290 heat pump system, comprising a sealed cavity, wherein an R290 heat pump system, a pressure sensor for real-time monitoring of the gas pressure inside the cavity, and an R290 concentration sensor for real-time monitoring of the R290 concentration inside the cavity are disposed inside the sealed cavity; an inert gas filling port and a filling valve are provided on the sealed cavity, wherein the inert gas filling port is used for evacuating the sealed cavity and filling it with inert gas to make the cavity a micro-positive pressure state.

[0009] Furthermore, the condenser and evaporator of the R290 heat pump system are sealed to the external coolant circuit via a heat exchanger inlet connection on the sealed cavity. The heat exchanger inlet connection includes an outer tube extending outward from the outer wall of the cavity and an inner tube extending inward from the inner wall of the cavity. The outer tube and the inner tube are connected one-to-one through a channel in the cavity wall, and the outer tube is connected to the external coolant circuit. A pressure plate is provided at the coolant interface of the condenser and evaporator to seal the coolant interface of the condenser and evaporator to the inner tube. An O-ring is provided between the pressure plate and the inner tube.

[0010] Furthermore, the inner tube has a stepped hole structure, the pressure plate has a matching stepped shaft structure, and the inner tube and the pressure plate are inserted and fastened with screws.

[0011] The present invention provides a sealed connection structure based on the inner and outer extension tubes, pressure plate, and gasket, which ensures heat exchange efficiency and maintains the absolute seal of the cavity.

[0012] Furthermore, the sealed cavity has an openable sealed cavity door for the installation and maintenance of internal components.

[0013] Furthermore, the openable sealing cavity door is a sealing cavity cover plate, which is hinged to the sealing cavity body via a hinge; the buckle on the sealing cavity cover plate is fastened to the buckle base plate on the sealing cavity body.

[0014] Furthermore, the sealing cavity is made of aluminum alloy, stainless steel, or acrylic.

[0015] Furthermore, the pressure in the micro-positive pressure state is 0.2~0.4 bar higher than the ambient atmospheric pressure.

[0016] The safety protection method of the inert gas-based micro-positive pressure closed safety protection system for R290 heat pump systems described in this invention cuts off the relay power supply of the compressor of the R290 heat pump system and locks the R290 heat pump system until manual reset when the R290 concentration in the cavity reaches or exceeds a preset concentration threshold; the preset concentration threshold is set to a value lower than the lower limit of R290 explosion concentration; when the gas pressure in the cavity is lower than the lower limit threshold of the micro-positive pressure state (for example, the difference between the pressure and the external atmospheric pressure is less than 0.1 bar), a cavity leakage warning is issued.

[0017] Furthermore, the preset concentration threshold is 60% to 80% of the lower limit of the R290 explosive concentration.

[0018] Furthermore, the preset concentration threshold is 5 / 7 of the lower limit of the R290 explosive concentration.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0020] (1) Fundamentally block the conditions for explosion: By constructing an inert gas environment inside the cavity, oxygen is completely isolated from the outside of the cavity. Even if R290 leaks inside the cavity and reaches the explosive concentration range, or even if it encounters an ignition source such as an electric spark, combustion and explosion cannot occur due to the absence of oxygen, thus achieving intrinsic safety.

[0021] (2) Avoid risk spread: The leaked R290 is confined within the sealed cavity to prevent it from spreading to other areas of the vehicle and threatening the safety of the occupants.

[0022] (3) Advantages of micro-positive pressure protection: The micro-positive pressure inside the cavity can not only prevent external air (including oxygen) from seeping in, but also allow inert gas to seep out preferentially when a small leak occurs in the cavity, forming a gaseous protective barrier and delaying the entry of external air.

[0023] (4) Dual monitoring ensures safety: R290 concentration monitoring ensures that leaks are detected in time, and the concentration threshold is set below the lower explosive limit to provide sufficient safety margin; cavity pressure monitoring can not only warn of physical damage to the cavity itself, but also indirectly reflect the state of inert gas (e.g., if the cavity pressure is low, it indicates that inert gas needs to be added to ensure the long-term reliability of the inert gas environment in the cavity).

[0024] (5) Safety control logic: After detecting R290 leakage, immediately cut off the power supply to the compressor relay and lock the R290 heat pump system until manual reset, to prevent the vehicle from automatically restarting before the fault is eliminated and to avoid secondary risks.

[0025] (6) Cost controllable: The safety protection system has a simple structure and does not require complex ventilation ducts and explosion-proof electrical equipment, thus achieving cost control while ensuring high safety. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the framework of a micro-positive pressure closed safety protection system based on inert gas provided in an embodiment of the present invention;

[0027] Figure 2 This is a three-dimensional structural diagram of the micro-positive pressure closed safety protection system based on inert gas provided in an embodiment of the present invention;

[0028] Figure 3 These are three-dimensional structural diagrams of the sealing cavity in an embodiment of the present invention, wherein (a) and (b) are isometric views of the sealing cavity from different perspectives;

[0029] Figure 4 This is a three-dimensional structural diagram of the heat exchanger inlet connection port in an embodiment of the present invention, wherein (a) is an assembly diagram of the heat exchanger inlet connection port, (b) is a detailed diagram of the inner tube side, and (c) is a detailed diagram of the pressure plate side. Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] Appendix Figures 1 to 4 The accompanying figure labels are as follows:

[0032] 101, Sealed cavity; 102, Vapor-liquid separator; 103, Compressor; 104, Condenser; 105, Electronic expansion valve; 106, Evaporator; 107, Pressure sensor; 108, Condenser-side refrigerant inlet; 109, Condenser-side refrigerant outlet; 110, Evaporator-side refrigerant inlet; 111, Evaporator-side refrigerant outlet; 112, R290 concentration sensor; 113, Charging valve; 114, Controller; 115, Integrated wiring harness sealed outlet; 116, Fastener; 117, Hinge; 118, 119. Hook and loop base plate; 120. Condenser-side refrigerant inlet hydraulic plate connection port; 121. Evaporator-side refrigerant inlet hydraulic plate connection port; 122. Evaporator-side refrigerant outlet hydraulic plate connection port; 123. Condenser-side refrigerant outlet hydraulic plate; 124. Condenser-side refrigerant inlet hydraulic plate; 125. Evaporator-side refrigerant inlet hydraulic plate; 126. Evaporator-side refrigerant outlet hydraulic plate; 127. O-ring seal; 128. Positioning threaded hole on the pressure plate connection port side; 129. Positioning threaded hole on the pressure plate side.

[0033] Example 1: As Figures 1 to 3 As shown, Embodiment 1 provides a micro-positive pressure closed safety protection system based on inert gas for an R290 heat pump system, including a sealed cavity 101 and a controller 114. The sealed cavity 101 is made of a pressure-resistant material (such as aluminum alloy, stainless steel or acrylic).

[0034] The sealed cavity 101 has an openable sealed cavity door for the installation and maintenance of internal components. Specifically, the openable sealed cavity door is a sealed cavity cover plate, which is hinged to the sealed cavity body via a hinge 117. A latch 116 on the sealed cavity cover plate is fastened to a latch base plate 118 on the sealed cavity body.

[0035] The sealed cavity 101 is equipped with an R290 heat pump system, a pressure sensor 107, and an R290 concentration sensor 112. The pressure sensor 107 is used to monitor the gas pressure inside the cavity in real time, and the R290 concentration sensor 112 is used to monitor the R290 concentration inside the cavity in real time.

[0036] The R290 heat pump system consists of a compressor 103, a condenser 104, an electronic expansion valve 105, an evaporator 106, and a vapor-liquid separator 102 connected sequentially via refrigerant piping to form a complete refrigerant circulation loop. The condenser 104 and evaporator 106 are located on the same side inside the sealed cavity 101, allowing for a centralized arrangement of external coolant piping, which simplifies the overall vehicle piping layout and connection complexity.

[0037] The condenser 104 and evaporator 106 are sealed to the external coolant circuit via a heat exchanger inlet connection on the sealed cavity 101. The heat exchanger inlet connection includes an outer extension tube located on the outer wall of the cavity and extending outward, and an inner extension tube located on the inner wall of the cavity and extending inward.

[0038] There are four extension tubes located on the same side of the sealed cavity 101, forming a condenser-side coolant inlet 108, a condenser-side coolant outlet 109, an evaporator-side coolant inlet 110, and an evaporator-side coolant outlet 111, respectively. The extension tubes are connected to the external coolant circuit to realize the introduction and export of coolant.

[0039] The number of inner tubes is also four, located on the same side of the sealing cavity 101, forming four pressure plate connection ports, namely the condenser side coolant inlet hydraulic plate connection port 119, the condenser side coolant outlet hydraulic plate connection port 120, the evaporator side coolant inlet hydraulic plate connection port 121, and the evaporator side coolant outlet hydraulic plate connection port 122.

[0040] The outer and inner tubes are connected one-to-one through channels in the cavity wall: the condenser-side coolant inlet 108 is connected to the condenser-side coolant inlet hydraulic plate connection port 119, which is used to introduce external coolant into the condenser 104; the condenser-side coolant outlet 109 is connected to the condenser-side coolant outlet hydraulic plate connection port 120, which is used to export the coolant after heat exchange in the condenser 104 to the external circuit; the evaporator-side coolant inlet 110 is connected to the evaporator-side coolant inlet hydraulic plate connection port 121, which is used to introduce external coolant into the evaporator 106; the evaporator-side coolant outlet 111 is connected to the evaporator-side coolant outlet hydraulic plate connection port 122, which is used to export the coolant after heat exchange in the evaporator 106 to the external circuit.

[0041] The condenser 104 has two coolant inlets equipped with a condenser-side coolant outlet hydraulic plate 123 and a condenser-side coolant inlet hydraulic plate 124, respectively. The evaporator 106 has two coolant inlets equipped with an evaporator-side coolant inlet hydraulic plate 125 and an evaporator-side coolant outlet hydraulic plate 126, respectively. Pressure plates are used to seal the coolant inlets of the condenser 104 and evaporator 106 to the inner tube.

[0042] Figure 4 The sealing connection structure between the pressure plate and the inner tube is shown. The inner tube has a stepped hole structure: starting from the end face of the inner tube, the first section is a large inner diameter section with an inner diameter of a, extending a first predetermined distance; starting from the end of the first section, the second section is a small inner diameter section with an inner diameter of b, penetrating to the cavity wall channel.

[0043] The pressure plate is a ring-shaped structure with an outwardly extending pressure plate interface on one side. This pressure plate interface adopts a stepped shaft structure: starting from the pressure plate body, the first section is a large outer diameter section with an outer diameter of 'a', extending a second predetermined distance; starting from the end of the first section, the second section is a small outer diameter section with an outer diameter of 'b', extending a third predetermined distance. An O-ring 127 is fitted on the small outer diameter section of the pressure plate.

[0044] In addition, the inner tube has a pressure plate connection port side positioning threaded hole 128 on its wall surface, and a corresponding pressure plate side positioning threaded hole 129 on the pressure plate.

[0045] Assembly and Sealing Principle: During assembly, the smaller outer diameter section of the pressure plate is inserted into the smaller inner diameter section of the inner tube, forming a precise shaft-hole fit; simultaneously, the larger outer diameter section of the pressure plate is accommodated within the larger inner diameter section of the inner tube. At this time, the O-ring 127 is fitted onto the smaller outer diameter section of the pressure plate and located between the end face of the larger outer diameter section of the pressure plate and the end face of the larger inner diameter section of the inner tube. The inner tube and the pressure plate are connected by screws. When the screws are tightened, the pressure plate moves towards the inner wall of the cavity, and the end face of the larger outer diameter section of the pressure plate and the end face of the larger inner diameter section of the inner tube approach each other. The O-ring 127 is squeezed between these two end faces, undergoes elastic deformation, and fills the tiny gap between the end faces.

[0046] The heat exchanger's inlet-type connection port achieves triple sealing protection: end face sealing: the O-ring 127 is compressed between the large outer diameter end face of the pressure plate and the large inner diameter end face of the inner tube, forming the main sealing surface; plug sealing: the small outer diameter section of the pressure plate and the small inner diameter section of the inner tube precisely fit together, forming an auxiliary sealing path; threaded fastening: the screw provides continuous clamping force, ensuring long-term reliable sealing. This sealing connection structure allows the condenser 104 and evaporator 106 inside the cavity to exchange heat with the external coolant circuit, while ensuring that the airtightness of the sealed cavity 101 is not compromised. When disassembly and maintenance are required, simply unscrew the screws to separate the pressure plate from the inner tube, facilitating component inspection or replacement.

[0047] The sealed cavity 101 is provided with an inert gas filling port and a filling valve 113. The inert gas filling port is used to evacuate the sealed cavity 101 and fill it with inert gas (such as nitrogen or argon) to a slightly positive pressure state. The pressure of the slightly positive pressure state is 0.2~0.4 bar higher than the external atmospheric pressure.

[0048] The controller 114 is located outside the sealed cavity 101 and is electrically connected to the compressor 103, the pressure sensor 107 and the R290 concentration sensor 112 respectively. The connecting wires pass through the integrated wire harness sealed outlet 115 on the sealed cavity 101.

[0049] Example 2: Example 2 provides a safety protection method for the inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems described in Example 1, including:

[0050] (a) Normal operating status

[0051] After the internal components of the sealed cavity 101 are installed or maintained, a vacuum is drawn through the inert gas filling port, and then an inert gas (such as nitrogen) is filled to a slightly positive pressure state. At this time, the sealed cavity 101 is filled with inert gas, and oxygen is completely removed. The R290 heat pump system operates normally in an inert gas environment.

[0052] (ii) Leakage monitoring

[0053] When a refrigerant leak occurs in the R290 heat pump system, R290 gas enters the sealed cavity 101. The R290 concentration sensor 112 monitors the R290 concentration inside the cavity in real time and transmits the concentration signal to the controller 114. The pressure sensor 107 monitors the gas pressure inside the sealed cavity 101 in real time and transmits the pressure signal to the controller 114. If the cavity suffers physical damage due to external causes (such as a collision causing the cavity to rupture), the gas pressure inside the cavity will drop and be detected by the pressure sensor 107.

[0054] (III) Hazard Assessment

[0055] The controller 114 simultaneously receives signals from the R290 concentration sensor 112 and the pressure sensor 107, and is pre-configured as follows:

[0056] Pressure Judgment: When the pressure sensor 107 detects that the internal air pressure is lower than the lower limit threshold of the slightly positive pressure state (e.g., 0.1 bar higher than the external atmospheric pressure), it is judged that the cavity may leak (for the sake of rigor, because this condition is a necessary but not sufficient condition for cavity damage, and other factors such as sensor failure may also cause low pressure), and a maintenance warning is issued.

[0057] Concentration exceeding threshold trigger: When the R290 concentration detected by the R290 concentration sensor 112 reaches or exceeds the preset concentration threshold, a leakage hazard is identified, and a safety response action is immediately triggered. The preset concentration threshold is set to a value lower than the lower explosive limit of R290, preferably 60% to 80% of the lower explosive limit of R290, and more preferably 5 / 7 of the lower explosive limit of R290.

[0058] (iv) Safety Response

[0059] Once the R290 concentration reaches or exceeds the preset concentration threshold, the controller 114 immediately executes the following safety response actions:

[0060] Immediately disconnect the power supply to compressor 103: Regardless of the operating state of the R290 heat pump system (cooling, heating, standby, or starting), controller 114 will forcibly disconnect the relay power supply to compressor 103, causing compressor 103 to stop working, thereby terminating the refrigerant cycle and preventing further leakage.

[0061] R290 heat pump system locked: Controller 114 locks the R290 heat pump system, preventing any automatic restart attempts;

[0062] Alarm output: Controller 114 sends a leakage alarm signal to the vehicle control system, alerting the driver and passengers via the instrument panel or in-vehicle display screen.

[0063] (v) Manual reset

[0064] Once the R290 heat pump system enters a locked state, it cannot be restarted by power failure or any automatic means. It must be manually reset by professional maintenance personnel after troubleshooting the leak, cleaning the R290 gas in the sealing cavity 101, re-evacuating and filling with inert gas, and using a diagnostic instrument or other special tools. Only then can the R290 heat pump system resume normal operation.

[0065] In summary, this invention completely isolates oxygen by filling the sealed cavity 101 with inert gas. Even if R290 leaks and reaches a flammable concentration, or even encounters an ignition source such as an electric spark, combustion or explosion will not occur due to the lack of oxygen. The slightly positive pressure state within the sealed cavity 101 prevents external air (containing oxygen) from seeping into the cavity. R290 concentration monitoring and safety response prevent further deterioration of R290 leakage, ensuring safety. Gas pressure monitoring can provide early warning of physical damage to the cavity and also prompt maintenance when the cavity's sealing performance deteriorates, ensuring the long-term reliability of the inert gas environment.

Claims

1. A micro-positive pressure closed-loop safety protection system based on inert gas for R290 heat pump systems, characterized in that, The system includes a sealed cavity (101), which is equipped with an R290 heat pump system, a pressure sensor (107) for real-time monitoring of the gas pressure inside the cavity, and an R290 concentration sensor (112) for real-time monitoring of the R290 concentration inside the cavity. The sealed cavity (101) is provided with an inert gas filling port and a filling valve (113). The inert gas filling port is used to evacuate the sealed cavity (101) and fill it with inert gas to make the cavity have a slightly positive pressure.

2. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 1, characterized in that, The condenser (104) and evaporator (106) of the R290 heat pump system are sealed to the external coolant circuit through the heat exchanger inlet on the sealed cavity (101); the heat exchanger inlet includes an outer tube extending outward from the outer wall of the cavity and an inner tube extending inward from the inner wall of the cavity. The outer tube and the inner tube are connected one-to-one through the channel in the cavity wall. The outer tube is connected to the external coolant circuit; a pressure plate is provided at the coolant interface of the condenser (104) and evaporator (106) to seal the coolant interface of the condenser (104) and evaporator (106) to the inner tube; an O-ring (127) is provided between the pressure plate and the inner tube.

3. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 2, characterized in that, The inner tube has a stepped hole structure, and the pressure plate has a matching stepped shaft structure. The inner tube and the pressure plate are inserted and fastened with screws.

4. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 1, characterized in that, The sealed cavity (101) has an openable sealed cavity door for the installation and maintenance of internal components.

5. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 4, characterized in that, The openable sealing cavity door is a sealing cavity cover plate, which is hinged to the sealing cavity body by a hinge (117); the buckle (116) on the sealing cavity cover plate is fastened to the buckle base plate (118) on the sealing cavity body.

6. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 1, characterized in that, The sealing cavity (101) is made of aluminum alloy, stainless steel or acrylic.

7. The inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 1, characterized in that, The pressure in the micro-positive pressure state is 0.2 to 0.4 bar higher than the ambient atmospheric pressure.

8. A safety protection method for an inert gas-based micro-positive pressure closed-loop safety protection system for an R290 heat pump system, as described in any one of claims 1 to 7, characterized in that, When the R290 concentration in the cavity reaches or exceeds the preset concentration threshold, the relay power supply of the compressor (103) of the R290 heat pump system is cut off and the R290 heat pump system is locked until manual reset; the preset concentration threshold is set to a value lower than the lower limit of R290 explosion concentration; when the gas pressure in the cavity is lower than the lower limit threshold of the slightly positive pressure state, a cavity leakage warning is issued.

9. The safety protection method for the inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 8, characterized in that, The preset concentration threshold is 60% to 80% of the lower explosive concentration limit of R290.

10. The safety protection method for the inert gas-based micro-positive pressure closed-loop safety protection system for R290 heat pump systems according to claim 9, characterized in that, The preset concentration threshold is 5 / 7 of the lower limit of R290 explosive concentration.

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