Thermostat failure diagnosis device, engine cooling system, and automobile

Abstract

The application discloses a thermostat fault diagnosis device, an engine cooling system and an automobile. The thermostat fault diagnosis device comprises a first temperature sensor, a second temperature sensor and a controller. Under the condition that a thermostat leakage fault diagnosis condition is met and current electronic water pump flow meets the demand of the thermostat leakage fault diagnosis, the controller judges whether the thermostat has a leakage fault based on current engine outlet cooling liquid temperature and current radiator outlet cooling liquid temperature. Under the condition that the current engine outlet cooling liquid temperature is greater than or equal to a preset first temperature threshold Ta, the controller judges whether the thermostat has an opening failure. The thermostat fault diagnosis precondition is considered, and the influence of cooling liquid flow on the thermostat fault diagnosis is excluded, so that the accuracy of the thermostat fault diagnosis can be improved.

Description

Technical Field

[0001] This invention belongs to the field of automotive engines, specifically relating to a thermostat fault diagnosis device, an engine cooling system, and an automobile. Background Technology

[0002] More and more automakers are adopting hybrid technology, along with smart grilles to reduce wind resistance and lower fuel consumption and emissions. Hybrid engines generally use electric water pumps instead of mechanical water pumps. The electric water pump adjusts its operation according to the engine, reducing the energy consumption of the mechanical water pump, improving its regulation capability, and lowering energy consumption. However, due to relatively low coolant flow under certain operating conditions, there is a possibility that even if the thermostat malfunctions, the low coolant flow may prevent timely detection of the fault. Additionally, while reducing wind resistance, smart grilles also reduce airflow within the engine compartment, preventing heat loss and accelerating engine warm-up. However, smart grilles also bring new challenges to control and diagnostics.

[0003] CN114658530A discloses an engine cooling system, a diagnostic method for a thermostat, and a vehicle. The system includes an engine water jacket, a water pump, a radiator, and a thermostat connected between the engine water jacket and the radiator. The thermostat selectively controls the flow of coolant from the engine water jacket into the radiator. It also includes a first detection element for detecting the temperature of the coolant in the engine water jacket, a second detection element for detecting the temperature of the coolant at the radiator outlet, a third detection element for detecting the ambient temperature, and a controller. The controller is connected to the first, second, and third detection elements. The controller determines whether the thermostat is faulty based on the integral of the temperature difference between the coolant in the engine water jacket and the coolant at the radiator outlet. However, this method does not consider the preconditions for thermostat fault diagnosis. If these preconditions are not met, fault diagnosis is likely to occur. Furthermore, it does not consider the impact of coolant flow rate on thermostat fault diagnosis, resulting in low accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a thermostat fault diagnosis device, an engine cooling system, and an automobile to improve the accuracy of thermostat fault diagnosis.

[0005] The thermostat fault diagnosis device of the present invention includes a first temperature sensor, a second temperature sensor, and a controller. The first temperature sensor is located at the engine outlet and is used to detect the current engine outlet coolant temperature. The second temperature sensor is located at the radiator outlet and is used to detect the current radiator outlet coolant temperature. The controller is connected to the first and second temperature sensors. When the thermostat leakage fault diagnosis conditions are met, and the current electric water pump flow rate meets the thermostat leakage fault diagnosis requirements, the controller determines whether a thermostat leakage fault exists based on the current engine outlet coolant temperature and the current radiator outlet coolant temperature. If the current engine outlet coolant temperature is greater than or equal to a preset first temperature threshold Ta, the controller determines whether the thermostat has a failure to open.

[0006] Preferably, if conditions a through e are simultaneously met, it indicates that the diagnostic conditions for a thermostat leak are met. Condition a is: the radiator is not dissipating heat; condition b is: the current coolant temperature at the engine outlet is less than a preset first temperature threshold Ta; condition c is: the current ambient temperature is within a preset temperature range; condition d is: the first and second temperature sensors are functioning correctly; and condition e is: the high idle time is less than or equal to a first preset time. High idle speed refers to the vehicle idling at a relatively high engine speed (around 2000 rpm).

[0007] Preferably, the change in coolant temperature at the radiator outlet is calculated using the formula: ΔT = T1 - T0. Here, T1 represents the current coolant temperature at the radiator outlet, and T0 represents the coolant temperature at the radiator outlet at the moment of the engine's first start.

[0008] Based on the current ambient temperature, a preset temperature curve is queried to obtain the corresponding second temperature threshold Tb. The preset temperature curve is a curve showing the correspondence between the ambient temperature and the second temperature threshold, obtained through calibration and fitting.

[0009] Determine the relationship between ΔT and Tb: If ΔT < Tb, the current electric water pump flow rate meets the requirements for thermostat leakage fault diagnosis; if ΔT ≥ Tb, after a second preset time delay (controlling the electric water pump), increase the electric water pump flow rate until ΔT < Tb, then maintain the electric water pump flow rate when ΔT < Tb. The electric water pump flow rate when ΔT < Tb meets the requirements for thermostat leakage fault diagnosis.

[0010] Preferably, the controller determines whether there is a leak in the thermostat based on the current engine outlet coolant temperature and the current radiator outlet coolant temperature as follows:

[0011] The time integral of the engine outlet coolant temperature is calculated to obtain the value A.

[0012] The time integral of the coolant temperature at the radiator outlet is used to obtain the value B.

[0013] The ratio k can be calculated using the formula: k = A ÷ B.

[0014] Determine the relationship between k and k': if k ≥ k', the thermostat is determined to have no leakage fault; if k < k', the thermostat is determined to have a leakage fault; where k' is a preset calibration ratio.

[0015] Preferably, the controller determines whether the thermostat has a failure to open as follows: the controller determines whether the coolant temperature at the engine outlet gradually increases and reaches a preset third temperature threshold Tc within a third preset time; if so, it determines that the thermostat has a failure to open; otherwise, it determines that the thermostat does not have a failure to open; wherein, Tc > Ta.

[0016] The engine cooling system of this invention includes an engine, an engine outlet water pipe, a thermostat, a smart grille, a radiator, an engine inlet water pipe, a heating and ventilation (HVAC) pipe, a small circulation pipe, and an electronic water pump. The engine outlet is connected to the engine outlet water pipe, which is also connected to the HVAC pipe. The engine outlet water pipe is connected to the small circulation pipe and the radiator via the thermostat. The smart grille faces the radiator. The HVAC pipe, small circulation pipe, and radiator are connected to the engine inlet water pipe, which is connected to the engine inlet water pipe. The electronic water pump is installed on the engine inlet water pipe. The engine cooling system also includes the aforementioned thermostat fault diagnosis device. The controller is connected to the electronic water pump and controls the flow rate of the electronic water pump by adjusting its rotational speed.

[0017] The automobile described in this invention includes the engine cooling system described above.

[0018] The present invention has the following effects:

[0019] (1) The thermostat leakage fault diagnosis will only be performed if the conditions for thermostat leakage fault diagnosis are met and the current electronic water pump flow rate (corresponding to the coolant flow rate) meets the requirements for thermostat leakage fault diagnosis. This takes into account the preconditions for thermostat fault diagnosis and eliminates the influence of coolant flow rate on thermostat fault diagnosis, thereby improving the accuracy of thermostat fault diagnosis.

[0020] (2) After ruling out thermostat leakage, if the current engine outlet coolant temperature is greater than or equal to the preset first temperature threshold Ta, diagnose whether the thermostat cannot open. The diagnostic results obtained are true and accurate.

[0021] (3) The time integral of the coolant temperature at the engine outlet is compared with the time integral of the coolant temperature at the radiator outlet to identify whether there is a leak in the thermostat. Thermostat leak fault diagnosis is reliable and has a high degree of differentiation between faults and non-faults. Quickly troubleshooting and resolving cooling system problems after a thermostat leak occurs can reduce the time it takes for the engine to reach its optimal operating temperature, accelerate warm-up, and reduce fuel consumption and pollutant emissions.

[0022] (4) When the current electronic water pump flow rate does not meet the requirements for thermostat leakage fault diagnosis, the electronic water pump flow rate (i.e., increase the coolant flow rate) is increased to meet the requirements for thermostat leakage fault diagnosis, thereby improving the temperature signals of the first and second temperature sensors, identifying suspected faults, solving the problem that thermostat leakage faults cannot be reported due to low coolant flow rate, and improving the accuracy of thermostat fault diagnosis. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the engine cooling system in this embodiment.

[0024] Figure 2 This is a schematic diagram of the thermostat fault diagnosis device in this embodiment.

[0025] Figure 3 This is a flowchart of the thermostat fault diagnosis process in this embodiment. Detailed Implementation

[0026] like Figure 2 As shown, the thermostat fault diagnosis device in this embodiment includes a first temperature sensor 2, a second temperature sensor 7, and a controller 11. The first temperature sensor 2 is located at the outlet of the engine 1 to detect the current coolant temperature at the engine outlet. The second temperature sensor 7 is located at the outlet of the radiator 6 to detect the current coolant temperature at the radiator outlet. The controller 11 is connected to the first temperature sensor 2 and the second temperature sensor 7 to obtain fault information for the first temperature sensor 2 and the second temperature sensor 7, as well as the current coolant temperature at the engine outlet and the current coolant temperature at the radiator outlet. The controller 11 can obtain the current ambient temperature, the smart grille status (corresponding to whether the radiator is dissipating heat; the smart grille is open, the radiator is dissipating heat; the smart grille is closed, the radiator is not dissipating heat) and high idle time information from the CAN bus.

[0027] like Figure 1As shown, the engine cooling system in this embodiment includes an engine 1, an engine outlet water pipe 3, a thermostat 4, a smart grille 5, a radiator 6, an engine inlet water pipe 8, a heating and ventilation pipe 9, a small circulation pipe 10, an electronic water pump 12, and the aforementioned thermostat fault diagnosis device. The outlet of engine 1 is connected to the engine outlet water pipe 3, which is connected to the heating and ventilation pipe 9. The engine outlet water pipe 3 is connected to the small circulation pipe 10 and the radiator 6 via the thermostat 4. The smart grille 5 is directly opposite the radiator 6. The heating and ventilation pipe 9, the small circulation pipe 10, and the radiator 6 are connected to the engine inlet water pipe 8, which is connected to the inlet of engine 1. The electronic water pump 12 is installed on the engine inlet water pipe 8. A controller 11 is connected to the electronic water pump 12 to control the flow rate of the electronic water pump.

[0028] The coolant flowing from engine 1 has three main channels: First, the coolant returns to engine 1 through engine outlet pipe 3, HVAC pipe 9, engine inlet pipe 8, and electric water pump 12. Second, the coolant returns to engine 1 through engine outlet pipe 3, thermostat 4, small circulation pipe 10, engine inlet pipe 8, and electric water pump 12; this is the small circulation loop. Third, the coolant returns to engine 1 through engine outlet pipe 3, thermostat 4, radiator 6, engine inlet pipe 8, and electric water pump 12; this is the large circulation loop. A first temperature sensor 2 is located at the outlet of engine 1 to detect the current coolant temperature at the engine outlet, which is also the coolant temperature in the small circulation loop. A second temperature sensor 7 is located at the outlet of radiator 6 to detect the current coolant temperature at the radiator outlet, which is also the coolant temperature in the large circulation loop. The thermostat 4 is used to regulate the flow rate of coolant through the radiator 6 and the small circulation pipe 10.

[0029] When the thermostat 4 is functioning correctly, during a cold start of engine 1, the intelligent grille 5 is closed, preventing ambient air from passing through the radiator 6. The thermostat 4 remains normally closed, and coolant flows back to the engine via the engine outlet pipe 3, small circulation pipe 10, engine inlet pipe 8, and electric water pump 12, bypassing the radiator 6. The coolant temperature at the radiator outlet remains at its initial temperature. As engine 1 runs, the coolant temperature at the engine outlet rises over time, eventually exceeding the radiator outlet temperature. The coolant gradually heats the thermostat 4. When the coolant temperature at the engine outlet reaches a preset first temperature threshold Ta, the thermostat 4 gradually opens, allowing coolant to flow through the radiator 6. The intelligent grille 5 then opens, and the opening of the thermostat 4 increases until it is fully open as the coolant temperature rises further.

[0030] If the thermostat 4 leaks (i.e., opens abnormally) when the engine is started cold, coolant will flow through the radiator 6. The radiator 6 will not dissipate heat, and the coolant temperature at the radiator outlet will be close to the coolant temperature at the engine outlet. Therefore, the presence of a leak in the thermostat 4 can be determined based on the coolant temperatures at the radiator outlet and the engine outlet.

[0031] If the coolant temperature rises to a level greater than or equal to the preset first temperature threshold Ta (e.g., 80°C), and the coolant temperature at the engine outlet continues to gradually increase, and reaches the preset third temperature threshold Tc (e.g., 100°C) within a third preset time, it indicates that the thermostat 4 has a failure to open.

[0032] like Figure 3 As shown, the thermostat fault diagnosis method in this embodiment is executed by the controller 11. When the thermostat leakage fault diagnosis conditions are met and the current electronic water pump flow rate meets the thermostat leakage fault diagnosis requirements, the controller 11 determines whether the thermostat 4 has a leakage fault based on the current engine outlet coolant temperature and the current radiator outlet coolant temperature. When the current engine outlet coolant temperature is greater than or equal to the preset first temperature threshold Ta, the controller 11 determines whether the thermostat has a failure to open.

[0033] Specifically, the steps include the following:

[0034] S1. Determine whether the diagnostic conditions for thermostat leakage are met. If yes, proceed to S2; otherwise, end the process.

[0035] If conditions a through e are met simultaneously, the diagnostic conditions for a thermostat leak are met. Condition a is: the radiator is not dissipating heat (corresponding to the intelligent grille 5 being closed); condition b is: the current coolant temperature at the engine outlet is less than the preset first temperature threshold Ta; condition c is: the current ambient temperature is within the preset temperature range; condition d is: the first temperature sensor 2 and the second temperature sensor 7 are functioning correctly; and condition e is: the high idle time is less than or equal to the first preset time. High idle speed refers to the vehicle idling at a relatively high engine speed (around 2000 rpm).

[0036] S2. Determine whether the current electronic water pump flow rate meets the requirements for thermostat leakage fault diagnosis. If yes, execute S4; otherwise, execute S3.

[0037] The specific judgment method is as follows:

[0038] First, using the formula: ΔT = T1 - T0, calculate the current change in coolant temperature at the radiator outlet, ΔT. T1 represents the current coolant temperature at the radiator outlet, and T0 represents the coolant temperature at the radiator outlet at the moment the engine is first started.

[0039] Then, based on the current ambient temperature, a preset temperature curve is consulted to obtain the corresponding second temperature threshold Tb. The preset temperature curve is a curve showing the correspondence between the ambient temperature and the second temperature threshold, obtained through calibration and fitting.

[0040] Finally, determine the relationship between ΔT and Tb: if ΔT < Tb, it means that the current electric water pump flow rate meets the requirements for diagnosing thermostat leakage faults; if ΔT ≥ Tb, it means that the current electric water pump flow rate does not meet the requirements for diagnosing thermostat leakage faults.

[0041] S3. After a second preset time delay (controlling the electronic water pump), increase the electronic water pump flow rate until ΔT < Tb, maintain the electronic water pump flow rate when ΔT < Tb, and then execute S4. The electronic water pump flow rate when ΔT < Tb meets the requirements for thermostat leakage fault diagnosis.

[0042] S4. Calculate the time integral of the engine outlet coolant temperature to obtain the value A, and then execute S5.

[0043] S5. Calculate the time integral of the coolant temperature at the radiator outlet to obtain the value B, and then execute S6.

[0044] S6. Use the formula: k=A÷B to calculate the ratio k, and then execute S7.

[0045] S7. Determine if k < k'. If yes, execute S8; otherwise, execute S9. Here, k' is the preset calibration ratio.

[0046] S8. Determine that there is a leakage fault in the thermostat, and then end.

[0047] S9. Determine that there is no leakage fault in the thermostat, and then execute S10.

[0048] S10. Determine whether the current engine outlet coolant temperature is greater than or equal to the preset first temperature threshold Ta. If yes, execute S11; otherwise, continue executing S10.

[0049] S11. Determine whether the coolant temperature at the engine outlet gradually increases and reaches the preset third temperature threshold Tc within a third preset time. If yes, execute S12; otherwise, execute S13.

[0050] S12. Determine that the thermostat has a fault that it cannot open, and then end.

[0051] S13. Determine that the thermostat is not present and cannot be opened, then end.

[0052] This embodiment also provides a vehicle that includes the above-described engine cooling system.

Claims

1. A thermostat fault diagnosis device, characterized in that, include: The first temperature sensor (2) is arranged at the outlet of the engine (1) to detect the current coolant temperature at the engine outlet. The second temperature sensor (7) is arranged at the outlet of the radiator (6) to detect the current coolant temperature at the outlet of the radiator. The controller (11) is connected to the first temperature sensor (2) and the second temperature sensor (7). When the conditions for diagnosing thermostat leakage are met and the current flow rate of the electronic water pump meets the requirements for diagnosing thermostat leakage, the controller determines whether there is a leakage fault in the thermostat based on the current coolant temperature at the engine outlet and the current coolant temperature at the radiator outlet. When the current coolant temperature at the engine outlet is greater than or equal to the preset first temperature threshold Ta, the controller determines whether there is a fault in the thermostat that it cannot open. The method for determining whether the current flow rate of the electronic water pump meets the requirements for diagnosing thermostat leakage faults is as follows: Using the formula: ΔT = T1 - T0, the change in coolant temperature at the radiator outlet is calculated as ΔT, where T1 represents the current coolant temperature at the radiator outlet and T0 represents the coolant temperature at the radiator outlet at the moment of the first engine start. Based on the current ambient temperature, the preset temperature curve is queried to obtain the corresponding second temperature threshold Tb. The preset temperature curve is the curve showing the relationship between the ambient temperature and the second temperature threshold obtained through calibration and fitting. If ΔT < Tb, it means that the current flow rate of the electric water pump meets the requirements for diagnosing thermostat leakage faults. If ΔT≥Tb, then after a second preset time delay, increase the flow rate of the electronic water pump until ΔT<Tb, and then maintain the flow rate of the electronic water pump when ΔT<Tb.

2. The thermostat fault diagnosis device according to claim 1, characterized in that: If conditions a through e are met simultaneously, then the diagnostic conditions for a thermostat leak are met; where, Condition a is: The radiator is not dissipating heat; Condition b is: the current coolant temperature at the engine outlet is less than the preset first temperature threshold Ta; Condition c is: the current ambient temperature is within the preset temperature range; Condition d is: the first temperature sensor (2) and the second temperature sensor (7) are fault-free; Condition e is: the high idling time is less than or equal to the first preset time.

3. The thermostat fault diagnosis device according to claim 1, characterized in that: The controller determines whether there is a leak in the thermostat based on the current engine outlet coolant temperature and the current radiator outlet coolant temperature as follows: The time integral of the engine outlet coolant temperature is calculated to obtain the value A. The value B is obtained by calculating the time integral of the coolant temperature at the radiator outlet. The ratio k can be calculated using the formula: k = A ÷ B; If k≥k', the thermostat is determined to have no leakage fault; if k<k', the thermostat is determined to have a leakage fault; where k' is a preset calibration ratio.

4. The thermostat fault diagnosis device according to claim 1, characterized in that: The controller determines whether the thermostat has a failure to open as follows: The controller determines whether the engine outlet coolant temperature gradually increases and reaches a preset third temperature threshold Tc within a third preset time; if so, it determines that the thermostat has a failure to open; otherwise, it determines that the thermostat does not have a failure to open; where Tc > Ta.

5. An engine cooling system comprising an engine (1), an engine outlet water pipe (3), a thermostat (4), a smart grille (5), a radiator (6), an engine inlet water pipe (8), a heating and ventilation pipe (9), a small circulation pipe (10), and an electronic water pump (12), wherein the outlet of the engine (1) is connected to the engine outlet water pipe (3), the engine outlet water pipe (3) is connected to the heating and ventilation pipe (9), the engine outlet water pipe (3) is connected to the small circulation pipe (10) and the radiator (6) through the thermostat (4), the smart grille (5) is directly opposite the radiator (6), the heating and ventilation pipe (9), the small circulation pipe (10), the radiator (6) are connected to the engine inlet water pipe (8), the engine inlet water pipe (8) is connected to the inlet of the engine (1), and the electronic water pump (12) is installed on the engine inlet water pipe (8); characterized in that: It also includes a thermostat fault diagnosis device as described in any one of claims 1 to 4, wherein the controller (11) is connected to the electronic water pump (12) and controls the flow rate of the electronic water pump.

6. A car, characterized in that: Includes the engine cooling system as described in claim 5.

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