A test method for cooling performance of power assembly of passenger car in off-road working condition

Abstract

This invention discloses a test method for the cooling performance of passenger vehicle powertrains under off-road conditions, belonging to the field of automotive performance testing technology. It is used by automakers in a vehicle environmental simulation laboratory to verify the cooling performance of passenger vehicle powertrains, including those employing forced-circulation liquid cooling for components such as engines. This fills the gap in indoor testing methods for the cooling performance of passenger vehicle powertrains under off-road conditions developed by major automakers in China. The test method employs natural environmental conditions covering typical climates and road conditions within China, as well as harsh driving conditions experienced by users. It can encompass the maximum heat load conditions experienced by domestic passenger vehicles under off-road conditions, ensuring the overall development quality of passenger vehicles under off-road conditions. Furthermore, the method is conducted in a vehicle environmental simulation laboratory, reducing testing risks, saving R&D costs, and ensuring verification can be performed at any time and in any weather, effectively shortening the testing cycle.

Description

Technical Field

[0001] This invention belongs to the field of automotive performance testing technology, specifically a method for testing the cooling performance of a passenger vehicle powertrain under off-road conditions. Background Technology

[0002] With the continuous improvement of people's living standards, users' demands for passenger vehicles under off-road conditions are also gradually increasing. Whether it is a regular passenger car or a professional off-road vehicle, the powertrain cooling system often experiences overheating, malfunctions, or even failures on extreme off-road surfaces. Therefore, it is necessary to develop a test method for the cooling performance of passenger vehicle powertrains under off-road conditions to quickly and effectively verify whether the performance of the powertrain cooling system meets the requirements on extreme off-road surfaces. Currently, there are very few domestic inventions and research in this area. Summary of the Invention

[0003] To address the above issues, this invention provides a test method for the cooling performance of passenger vehicle powertrains under off-road conditions. This method allows automakers to verify the cooling performance of passenger vehicle powertrains, including components such as engines, automatic transmissions, power batteries, DC / DC converters, and drive motors, which employ forced-circulation liquid cooling, in a vehicle environmental simulation laboratory. This fills the gap in indoor testing methods for the cooling performance of passenger vehicle powertrains under off-road conditions developed by major automakers in China. The test method employs natural environmental conditions covering typical climates and road conditions within China, as well as demanding driving conditions experienced by users. It can encompass the maximum heat load conditions experienced by domestic passenger vehicles under off-road conditions, ensuring the overall development quality of passenger vehicles under off-road conditions. Furthermore, the method is conducted in a vehicle environmental simulation laboratory, reducing testing risks, saving R&D costs, and ensuring verification can be performed at any time and in any weather, effectively shortening the testing cycle.

[0004] The technical solution of this invention is as follows: a test method for the cooling performance of a passenger vehicle powertrain under off-road conditions, comprising the following steps:

[0005] S1. Preparation of the test vehicle;

[0006] S2, User operating condition data collection;

[0007] S3. Data analysis and environmental simulation laboratory condition conversion;

[0008] S4. Environmental simulation laboratory operating condition verification;

[0009] S5. Confirm the test conditions.

[0010] Further, step S1 specifically involves placing temperature sensors at the passenger vehicle's air intake grille, the center of the engine's inlet / outlet water pipes, the center of the automatic transmission's oil outlet pipe, the center of the intercooler's inlet / outlet air pipes, and the deepest part of the engine's oil dipstick pipe to measure the ambient temperature, engine inlet / outlet water temperature, automatic transmission oil temperature, intercooler inlet / outlet air temperature, and engine oil temperature.

[0011] An acceleration sensor and a slope sensor are simultaneously installed at the center of the vehicle's cab floor to measure the vehicle's acceleration and the road slope while it is moving.

[0012] Connect the above sensors to the test module to measure engine speed, engine torque, and vehicle speed on the power CAN bus; integrate the test module and power CAN bus information synchronously into the software to measure and store the above data in real time.

[0013] Furthermore, step S2 specifically involves driving the passenger vehicle continuously for 5 minutes on various road conditions, including a 70° slope, a V-shaped ditch, a cross-axle, a rocky road, a gravel road, a sandy area, a stepped road, a rocky slope road, a muddy road, and a pebble road. When the engine coolant temperature or the automatic transmission oil temperature reaches equilibrium, the road condition data collection ends. All data from step S1 are recorded during the test.

[0014] Furthermore, the equilibrium state is defined as follows: the temperature difference change value is ≤2℃ within two consecutive minutes, or the temperature difference exhibits periodic fluctuations with a peak change value of ≤2℃.

[0015] Furthermore, step S3 specifically includes:

[0016] S301, Confirm core parameter temperature T t Based on the value T of the moment when the engine outlet water temperature is at its maximum. eo The value T at the moment of maximum automatic transmission oil temperature o Obtain the designed engine coolant temperature limit T from the vehicle development project. wl and automatic transmission oil temperature limit T ol ;

[0017] If T wl -T eo <T ol -T o Then T t =T eo ;

[0018] If T wl -T eo >T ol -T o Then T t =T o ;

[0019] If Twl -T eo =T ol -T o Then compare T wl and T ol The measurement value corresponding to the smaller of the size and limit values ​​is T. t ;

[0020] S302. Take the average value of all measured parameters within 10 seconds before and after the time corresponding to the core parameter temperature confirmed in step S301, i.e., ambient temperature T. c Engine inlet water temperature T wi Engine outlet water temperature T wo Automatic transmission oil temperature T g Engine oil temperature T e Intercooler intake temperature T i The intercooler outlet temperature T0, engine speed n, engine torque T1, vehicle speed V, acceleration a, and road surface gradient i are also present.

[0021] Furthermore, the relationship between vehicle driving force and driving resistance during user operation is collected when the engine or automatic transmission reaches thermal equilibrium, as shown in formula (1):

[0022] (1)

[0023] In the formula:

[0024] T1 — Engine torque, in N;

[0025] n — Engine speed, in r / min;

[0026] V — Vehicle speed, measured in km / h;

[0027] ƒ — Rolling resistance coefficient (dimensionless);

[0028] M — Vehicle mass, in kg;

[0029] g — acceleration due to gravity, in m / s² 2 Take 9.8066 m / s 2；

[0030] a — Vehicle acceleration, in m / s² 2 ;

[0031] C d —Air drag coefficient (dimensionless value);

[0032] ρ — air density, in kg / m³ 3 The laboratory sample was 1.093 kg / m³. 3;

[0033] A — Vehicle's frontal area, in meters (m²) 2 ;

[0034] i — Road gradient, in %

[0035] When a vehicle is traveling on a chassis dynamometer, rolling resistance, acceleration resistance, gradient resistance, and wind resistance are all provided by the resistance between the dynamometer motor and the vehicle tires. Based on experimental experience, the target resistance of the vehicle on the chassis dynamometer is set with friction resistance coefficient and wind resistance coefficient, as shown in formula (2):

[0036] (2)

[0037] F — Target resistance of the vehicle measured by the chassis dynamometer, in N;

[0038] ƒ1 — Friction resistance coefficient of chassis dynamometer (dimensionless value);

[0039] To ensure that the vehicle maintains the same ambient temperature and speed as when the user is driving on the road in the environmental simulation test chamber, while also ensuring that the vehicle's overall driving force, engine speed, and thermal load are consistent with those during road operation, the driving resistance experienced by the user on the road is converted into the resistance of the chassis dynamometer in the environmental simulation test chamber. The road wind resistance in formula (1) can be determined by setting the wind resistance coefficient in formula (2). The road rolling resistance, acceleration resistance, and gradient resistance in formula (1) can all be reflected by setting the friction resistance coefficient of the chassis dynamometer in formula (2). Thus, the target friction resistance coefficient of the chassis dynamometer can be determined. The relationship is as shown in formula (3):

[0040] (3)

[0041] Furthermore, step S4 specifically involves:

[0042] S401, the target friction resistance coefficient of the chassis dynamometer ƒ c Vehicle mass M, drag coefficient C d The vehicle's frontal area A and air density ρ are input into the dynamometer control interface. Then, the test vehicle is fixed in the environmental simulation test chamber, and the ambient temperature is set to the ambient temperature T in step S302. c The vehicle was left stationary in the test chamber for more than 6 hours;

[0043] S402. Set the test vehicle speed to V as in step S302, and drive at a constant speed until the vehicle's core parameter temperature reaches thermal equilibrium. Stop the test at this point, and define the core parameter temperature at thermal equilibrium as T. w ;

[0044] S403, T in step S402 w Compared with the target core parameter temperature T in step S301 t Comparison, if T w ≤T t Then the target friction coefficient ƒ c Increase by 0.005, repeat step S402; if T w >T t Then the target friction resistance coefficient ƒ c Decrease by 0.005, repeat step S402, until the minimum target frictional resistance coefficient is obtained, and T w >T t The target friction resistance coefficient at this point is the chassis dynamometer friction resistance coefficient ƒ required for verification under environmental simulation test conditions. cd .

[0045] Furthermore, step S5 specifically involves calculating the frictional resistance coefficient ƒ of the chassis dynamometer selected in step S4. cd At that time, the values ​​of the vehicle powertrain cooling performance characteristic parameters when the core parameter temperature was balanced during the test were respectively the engine inlet water temperature T. wi1 Engine outlet water temperature T wo1 Automatic transmission oil temperature T g1 Engine oil temperature T e1 Intercooler intake temperature T i1 and intercooler outlet temperature T 01 Compare the result with the result in step S302, and the comparison condition is: T wi1 ≥T wi T wo1 ≥T wo T g1 ≥T g T e1 ≥T e T i1 ≥T i T 01 ≥T0.

[0046] Furthermore, after all four conditions are met, a performance test condition for the cooling system of passenger vehicles under off-road conditions is established, with the ambient temperature set at T. c The vehicle speed is V, and the friction resistance coefficient of the chassis dynamometer is ƒ. cd The vehicle resistance is set as follows: .

[0047] The beneficial effects of this invention are as follows:

[0048] This invention employs natural environmental conditions and demanding driving conditions under typical climates and road conditions within China, encompassing the maximum thermal loads experienced by domestic passenger vehicles under off-road conditions. This ensures the overall vehicle development quality under off-road conditions. Furthermore, the method is conducted in a vehicle environmental simulation laboratory, reducing testing risks, saving R&D costs, and guaranteeing verification at any time and in any weather, effectively shortening the testing cycle. Attached Figure Description

[0049] Figure 1 This is the logic diagram for selecting the core parameter temperature in this invention.

[0050] Figure 2 This is a logic diagram of the target friction resistance coefficient of the vehicle chassis dynamometer of the present invention.

[0051] Figure 3 This is a diagram showing the results of simulating road conditions where the user's powertrain cooling performance characteristic parameter is at a high temperature, as presented in this invention.

[0052] Figure 4 This is a comparison chart showing the results of other characteristic parameters of the vehicle powertrain cooling performance of the present invention.

[0053] Figure 5 for Figure 3 Color illustrations.

[0054] Figure 6 for Figure 4 Color illustrations. Detailed Implementation

[0055] It should be noted that in the description of this invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; a connection can be a mechanical connection or an electrical connection; a link can be a direct connection or an indirect connection through an intermediate medium, and can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] A test method for the cooling performance of a passenger vehicle powertrain under off-road conditions includes the following steps:

[0058] Step 1: Preparation of the test vehicle

[0059] One temperature sensor is installed at the passenger vehicle's air intake grille to measure ambient temperature; one temperature sensor is installed at the center of the engine's inlet / outlet coolant flow lines to measure engine inlet / outlet coolant temperature; one temperature sensor is installed at the center of the automatic transmission oil outlet line to measure automatic transmission oil temperature; one temperature sensor is installed at the center of the intercooler inlet / outlet air lines to measure intercooler inlet / outlet air temperature; one temperature sensor is installed at the deepest point of the engine oil dipstick line to measure engine oil temperature; and one acceleration sensor and one slope sensor are simultaneously installed at the center of the vehicle's cab floor to measure vehicle acceleration and road slope during driving. All installed sensors are connected to the IPTRONIK module. Using DBC files, engine speed, engine torque, vehicle speed, and other vehicle signals are measured on the vehicle's OBD port's CAN bus. The IPTRONIK module and the CAN bus information are synchronously integrated into the IPEmotion software via a CAN card, allowing for real-time measurement and storage of the required data.

[0060] Step 2: User operating condition data collection

[0061] Passenger vehicles were subjected to simulated extreme driving conditions, including over 20 typical off-road scenarios described by the user, such as 70° steep slopes, V-shaped ditches, axle crossings, rocky roads, gravel roads, sandy terrain, stepped roads, rocky slopes, muddy roads, and pebble roads. Under each condition, the engine coolant temperature / automatic transmission oil temperature remained stable or fluctuated frequently within 5 minutes of continuous driving, without an upward trend, reaching a state of equilibrium. This equilibrium was defined as a temperature difference ≤2℃ within two consecutive minutes, or a periodic temperature fluctuation with a peak change ≤2℃. The data collection for the current road condition was terminated when the vehicle reached thermal equilibrium or when an over-temperature alarm for coolant / oil was triggered. The vehicle preparation parameters from step one were recorded throughout the entire test.

[0062] Step 3: Data analysis and conversion of environmental simulation laboratory conditions.

[0063] The collected data was analyzed, and the value T of the engine coolant temperature at the moment of maximum temperature was compared during the entire user operating condition data collection process. eo The value of the automatic transmission oil temperature at its maximum, T o The designed engine coolant temperature limit was obtained from the vehicle development project as T. wl The automatic transmission oil temperature limit is T. olSelect the temperature parameter that is closest to the respective limit among the maximum values ​​of engine coolant temperature or automatic transmission oil temperature as the core parameter temperature for operating condition transition, i.e., compare T. wl -T eo With T ol -T o The smaller of the two values ​​is taken as the core parameter temperature at the moment of maximum temperature, and this temperature is defined as the target core parameter temperature T. t If the values ​​are the same, compare their limits and select the parameter with the smaller limit as the core parameter, temperature. See the details for the logic. Figure 1 .

[0064] The average value of all measured parameters within 10 seconds before and after the time corresponding to the core temperature parameter is taken, i.e., the ambient temperature T. c Engine inlet water temperature T wi Engine outlet water temperature T wo Automatic transmission oil temperature T g Engine oil temperature T e Intercooler intake temperature T i Intercooler outlet temperature T0, engine speed n, engine torque T1, vehicle speed V, acceleration a, and road surface gradient i.

[0065] Based on the collected parameters, the vehicle's driving equations show that the torque generated by the engine is transmitted to the drive wheels through the transmission system to overcome the vehicle's overall driving resistance, thus propelling the vehicle. During the user's operating conditions, when the engine or automatic transmission reaches thermal equilibrium, the relationship between the vehicle's driving force and driving resistance is as follows:

[0066] (1)

[0067] In the formula:

[0068] T1 — Engine torque, in N;

[0069] n — Engine speed, in r / min;

[0070] V — Vehicle speed, measured in km / h;

[0071] ƒ — Rolling resistance coefficient (dimensionless);

[0072] M — Vehicle mass, in kg;

[0073] g — acceleration due to gravity, in m / s² 2 Take 9.8066 m / s 2 .

[0074] a — Vehicle acceleration, in m / s²2 .

[0075] C d —Air drag coefficient (dimensionless value);

[0076] ρ — air density, in kg / m³ 3 The laboratory sample was 1.093 kg / m³. 3 ;

[0077] A — Vehicle's frontal area, in meters (m²) 2 ;

[0078] i — Road gradient, in %

[0079] When a vehicle travels on a chassis dynamometer, rolling resistance, acceleration resistance, gradient resistance, and wind resistance are all provided by the resistance between the dynamometer motor and the vehicle tires. Based on experimental experience, the target resistance of the vehicle on the chassis dynamometer can be set using friction resistance coefficients and wind resistance coefficients, as follows:

[0080] (2)

[0081] F — Target resistance of the vehicle measured by the chassis dynamometer, in N;

[0082] ƒ1 — Friction resistance coefficient of chassis dynamometer (dimensionless value);

[0083] To ensure that the vehicle maintains the same ambient temperature and speed as when the user is driving on the road in the environmental simulation test chamber, while also ensuring that the vehicle's overall driving force, engine speed, and thermal load are consistent with those experienced during road operation, the driving resistance experienced by the user on the road is converted into the chassis dynamometer resistance in the environmental simulation test chamber. The road wind resistance in formula (1) can be determined by setting the wind resistance coefficient in formula (2). The road rolling resistance, acceleration resistance, and gradient resistance in formula (1) can all be reflected by setting the friction resistance coefficient of the chassis dynamometer in formula (2). Therefore, the target friction resistance coefficient of the chassis dynamometer can be determined. The relationship is calculated using the following formula:

[0084] (3)

[0085] Step 4: Environmental simulation laboratory operating condition verification

[0086] First, calculate the target friction resistance coefficient ƒ of the vehicle chassis dynamometer in step three. c And the vehicle's mass M and drag coefficient C d The frontal area A and air density ρ are input into the dynamometer control interface. Then, the test vehicle is fixed in the environmental simulation test chamber, and the ambient temperature is set to the user's ambient temperature T from step three. cAfterward, the vehicle is left to stand still in the test chamber for at least 6 hours to allow the coolant temperature of the vehicle's powertrain system to reach the ambient temperature. Next, the test speed is set to the user's actual vehicle speed V (as selected in step three), and the vehicle is driven at a constant speed. The test is stopped when the core parameter temperature selected in step three reaches thermal equilibrium. The core parameter temperature at this thermal equilibrium state is defined as T. w T w The target core parameter temperature T in step three t Comparison, if T w ≤T t Then the target friction resistance coefficient ƒ c Increase T by 0.005 and proceed to the next round of testing; if T w >T t Then the target friction resistance coefficient ƒ c Reduce the value by 0.005 and conduct the next round of experiments. Finally, find a value when T... w >T t The target frictional resistance coefficient at which the minimum frictional resistance coefficient is reached is the chassis dynamometer frictional resistance coefficient ƒ required for verification under environmental simulation test conditions. cd See the specific logic below. Figure 2 .

[0087] Step 5: Confirm the test conditions

[0088] Calculate the friction resistance coefficient ƒ of the chassis dynamometer selected in step four. cd At that time, the values ​​of the vehicle powertrain cooling performance characteristic parameters when the core parameter temperature was balanced during the test were respectively the engine inlet water temperature T. wi1 Engine outlet water temperature T wo1 Automatic transmission oil temperature T g1 Engine oil temperature T e1 Intercooler intake temperature T i1 Intercooler outlet temperature T 01 Compare the results with those from step three, using the following comparison condition: T wi1 ≥T wi T wo1 ≥T wo T g1 ≥T g T e1 ≥T e T i1 ≥T i T 01 For the above six comparison conditions, depending on the different components of the vehicle's cooling system being tested, it is sufficient to select at least four conditions that are met.

[0089] After the above conditions are met, the performance test conditions for the cooling system of passenger vehicles under off-road conditions are determined as follows, with the ambient temperature T set as follows: c The vehicle speed is V, and the friction resistance coefficient of the chassis dynamometer is ƒ. cd The vehicle resistance is set as follows: .

[0090] During the development of a certain brand's off-road vehicle, this method was used to conduct powertrain cooling performance tests under off-road conditions. It quickly established the testing conditions for the vehicle's cooling system performance in a simulated off-road environment within a laboratory, thus validating the cooling system's development. The testing process is unaffected by weather, climate, environment, or road conditions, effectively shortening the testing cycle, saving R&D costs, and reducing testing risks.

[0091] The specific implementation steps are as follows:

[0092] Step 1, the specific implementation process of test vehicle preparation is as follows:

[0093] One temperature sensor was installed at the air intake grille of the test vehicle to measure ambient temperature; one temperature sensor was installed at the center of the engine inlet / outlet coolant flow lines to measure engine inlet / outlet coolant temperature; one temperature sensor was installed at the center of the automatic transmission oil outlet line to measure automatic transmission oil temperature; one temperature sensor was installed at the center of the intercooler inlet / outlet air lines to measure intercooler inlet / outlet air temperature; and one temperature sensor was installed at the deepest point of the engine oil dipstick line to measure engine oil temperature. All installed sensors were connected to the IPTRONIK module. Using DBC files, vehicle signals such as engine speed, engine torque, and vehicle speed were measured on the power CAN bus at the vehicle's OBD port. The IPTRONIK module and power CAN bus information were synchronously integrated into the IPmotion software via a CAN card, allowing for real-time measurement and storage of the required data.

[0094] Step two, the user operating condition data collection process is as follows:

[0095] The test vehicle was subjected to over 20 typical off-road conditions, including a 70° steep slope, cobblestone roads, V-shaped ditches, axle articulation, and rocky terrain, simulating extreme driving by the user. Measurement parameters installed in step one were collected. Among these, the powertrain cooling performance characteristic parameter was obtained under relatively high road conditions. The temperature data results during the test are as follows: Figure 3 As shown.

[0096] Step 3, Data Analysis: The implementation process of transforming environmental simulation laboratory operating conditions is as follows.

[0097] The collected data was analyzed, and the value T of the moment when the engine coolant temperature was at its maximum on the Guamishi Road was compared during the entire user operating condition data collection process.eo =114.7℃, the value of the automatic transmission oil temperature at the moment of maximum temperature on a 70° incline. o =122.3℃; The engine coolant temperature limit obtained from the project is T wl =123℃, automatic transmission oil temperature limit is T ol =135℃. Therefore, T wl -T eo <T ol -T o Therefore, the engine coolant outlet temperature was chosen as the target core parameter temperature T for this vehicle model. t .

[0098] Calculate the average of all measured parameters within 10 seconds before and after the peak engine coolant temperature on the gravel road, i.e., the ambient temperature T. c =36℃, engine inlet water temperature T wi =106.8℃, engine outlet water temperature T wo =114.5℃, automatic transmission oil temperature T g =115.6℃, engine oil temperature T e =119.3℃, intercooler intake temperature T i =149℃, intercooler outlet temperature T0=68.9℃, engine speed n=2400r / min, engine torque T1=158.4Nm, vehicle speed V=16km / h. From the project, we know the vehicle mass M=2280kg, frontal area A=3.06m2, and drag coefficient C. d =0.395.

[0099] The target friction resistance coefficient ƒ of the chassis dynamometer is calculated according to formula (3). c =0.400.

[0100] Step four, the implementation process of environmental simulation laboratory condition verification is as follows:

[0101] First, the target friction resistance coefficient ƒ of the vehicle chassis dynamometer in step three is determined. c =0.400, and the vehicle mass and drag coefficient C d Calculate the target drag of the chassis dynamometer using the frontal area A and air density ρ: F = 8937.6 + 0.051V 2 The drag coefficient is then input into the dynamometer control interface. The test vehicle is then fixed in the environmental simulation test chamber, and the ambient temperature is set to the user's ambient temperature of 36℃ (as described in step three). The vehicle is then left to stand still for 6 hours for temperature equalization. Afterward, the test vehicle speed is set to 16 km / h, and it is driven at a constant speed until the vehicle's core parameters reach thermal equilibrium, at an equilibrium temperature T. w =120.9℃. This is higher than the target core parameter temperature T.t =114.5℃, according to Figure 2 The logical steps involve conducting four rounds of tests. In the third round, the frictional resistance coefficient of the chassis dynamometer required for the test conditions is obtained.

[0102] ƒ cd =0.385, engine outlet water temperature T w =115.1℃.

[0103] Step 5, confirm the specific implementation process of the test conditions as follows:

[0104] According to step four, the frictional resistance coefficient ƒ of the dynamometer on the test chassis is... cd In the third test with a value of 0.385, when the engine outlet water temperature reached thermal equilibrium, the results of other characteristic parameters of the vehicle powertrain cooling performance were calculated and compared. Figure 4 As shown.

[0105] Depend on Figure 3 It can be seen that, under the simulated operating condition with a drag coefficient of 0.385, the engine inlet water temperature, engine outlet water temperature, engine oil temperature, intercooler inlet air temperature, and intercooler outlet air temperature are all higher than the results obtained by the user on a gravel road, with only the automatic transmission oil temperature result being relatively lower. The results meet the judgment criteria. The performance test condition for the cooling system of a certain vehicle under off-road conditions is determined as follows, with the ambient temperature T set as follows: c =36℃, constant speed driving speed is V=16km / h, chassis dynamometer friction resistance coefficient ƒ cd =0.385, vehicle resistance is set as: F=8602.44+0.051V 2 .

[0106] In this embodiment of the invention, the engine outlet water temperature is selected as the target core parameter temperature T. t Alternatively, other characteristic parameters of powertrain cooling performance, such as automatic transmission oil temperature and power battery temperature, can be selected based on the vehicle model being developed. In this embodiment of the invention, the ambient temperature T set for off-road conditions is... c =36℃, constant speed driving speed is V=16km / h, chassis dynamometer friction resistance coefficient ƒ cd =0.385. The ambient temperature can also be other values ​​depending on the user's location. For example, the ambient temperature for users in the Middle East could be 45℃.

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be included within the scope of protection of the present invention. Furthermore, all content not described in detail in this specification is prior art known to those skilled in the art.

[0108] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

Claims

1. A test method for the cooling performance of a passenger vehicle powertrain under off-road conditions, characterized in that, Includes the following steps: S1. Preparation of the test vehicle; S2. User operating condition data collection; During the user operating condition data collection period, when the engine or automatic transmission reaches thermal equilibrium, the relationship between the vehicle's driving force and driving resistance is as shown in formula (1): (1) In the formula: T1 — Engine torque, in N / m; n — Engine speed, in r / min; V — Vehicle speed, measured in km / h; ƒ — Rolling resistance coefficient (dimensionless); M — Vehicle mass, in kg; g — acceleration due to gravity, in m / s² 2 Take 9.8066 m / s 2 ; a — Vehicle acceleration, in m / s² 2 ; C d —Air drag coefficient (dimensionless value); ρ — air density, in kg / m³ 3， The laboratory sample was 1.093 kg / m³. 3 ; A — Vehicle's frontal area, in meters (m²) 2 ; i — Road gradient, in % When a vehicle is traveling on a chassis dynamometer, rolling resistance, acceleration resistance, gradient resistance, and wind resistance are all provided by the resistance between the dynamometer motor and the vehicle tires. Based on experimental experience, the target resistance of the vehicle on the chassis dynamometer is set with friction resistance coefficient and wind resistance coefficient, as shown in formula (2): (2) F — Target resistance of the vehicle measured by the chassis dynamometer, in N; ƒ1 — Friction resistance coefficient of chassis dynamometer (dimensionless value); To ensure that the vehicle maintains the same ambient temperature and speed as when the user is driving on the road in the environmental simulation test chamber, while also ensuring that the vehicle's overall driving force, engine speed, and thermal load are consistent with those during road operation, the driving resistance experienced by the user on the road is converted into the resistance of the chassis dynamometer in the environmental simulation test chamber. The road wind resistance in formula (1) can be determined by setting the wind resistance coefficient in formula (2). The road rolling resistance, acceleration resistance, and gradient resistance in formula (1) can all be reflected by setting the friction resistance coefficient of the chassis dynamometer in formula (2). Thus, the target friction resistance coefficient of the chassis dynamometer can be determined. The relationship is as shown in formula (3): (3)； S3. Data analysis and conversion of environmental simulation laboratory operating conditions; specifically: S301, Confirm core parameter temperature T t Based on the value T of the moment when the engine outlet water temperature is at its maximum. eo The value T at the moment of maximum automatic transmission oil temperature o Obtain the designed engine coolant temperature limit T from the vehicle development project. wl Automatic transmission oil temperature limit T ol ; If T wl -T eo <T ol -T o Then T t =T eo ; If T wl -T eo >T ol -T o Then T t =T o ; If T wl -T eo =T ol -T o Then compare T wl and T ol The measurement value corresponding to the smaller of the size and limit values ​​is T. t ; S302. Take the average value of all measured parameters within 10 seconds before and after the time corresponding to the core parameter temperature confirmed in step S301, i.e., ambient temperature T. c Engine inlet water temperature T wi Engine outlet water temperature T wo Automatic transmission oil temperature T g Engine oil temperature T e Intercooler intake temperature T i Intercooler outlet temperature T0, engine speed n, engine torque T1, vehicle speed V, acceleration a, and road surface gradient i; S4. Environmental simulation laboratory operating condition verification; S401, the target friction resistance coefficient of the chassis dynamometer ƒ c Vehicle mass M, drag coefficient C d The vehicle's frontal area A and air density ρ are input into the dynamometer control interface. Then, the test vehicle is fixed in the environmental simulation test chamber, and the ambient temperature is set to the ambient temperature T in step S302. c The vehicle was left stationary in the test chamber for more than 6 hours; S402. Set the test vehicle speed to V as in step S302, and drive at a constant speed until the vehicle's core parameter temperature reaches thermal equilibrium. Stop the test at this point, and define the core parameter temperature at thermal equilibrium as T. w ; S403, T in step S402 w Compared with the target core parameter temperature T in step S301 t Comparison, if T w ≤T t Then the target friction coefficient ƒ c Increase by 0.005, repeat step S402; if T w >T t Then the target friction resistance coefficient ƒ c Decrease by 0.005, repeat step S402, until the minimum target frictional resistance coefficient is obtained, and T w >T t The target friction resistance coefficient at this point is the chassis dynamometer friction resistance coefficient ƒ required for verification under environmental simulation test conditions. cd ; S5. Confirm the test conditions, specifically, calculate the friction resistance coefficient ƒ of the chassis dynamometer selected in step S4. cd At that time, the values ​​of the vehicle powertrain cooling performance characteristic parameters when the core parameter temperature was balanced during the test were respectively the engine inlet water temperature T. wi1 Engine outlet water temperature T wo1 Automatic transmission oil temperature T g1 Engine oil temperature T e1 Intercooler intake temperature T i1 and intercooler outlet temperature T 01 Compare the result with the result in step S302, and the comparison condition is: T wi1 ≥T wi T wo1 ≥T wo T g1 ≥T g T e1 ≥T e T i1 ≥T i T 01 After the comparison conditions are met (≥T0), the performance test conditions for the cooling system of passenger vehicles under off-road conditions are determined, and the ambient temperature is set as T. c The vehicle speed is V, and the friction resistance coefficient of the chassis dynamometer is ƒ. cd The vehicle resistance is set as follows: .

2. The test method for cooling performance of a passenger vehicle powertrain under off-road conditions as described in claim 1, characterized in that, Step S1 specifically involves placing temperature sensors at the passenger vehicle's air intake grille, the center of the engine's inlet / outlet water pipes, the center of the automatic transmission's oil outlet pipe, the center of the intercooler's inlet / outlet air pipes, and the deepest part of the engine's oil dipstick pipe to measure the ambient temperature, engine inlet / outlet water temperature, automatic transmission oil temperature, intercooler inlet / outlet air temperature, and engine oil temperature. An acceleration sensor and a slope sensor are simultaneously installed at the center of the vehicle's cab floor to measure the vehicle's acceleration and the road slope while it is moving. Connect the above sensors to the test module to measure engine speed, engine torque, and vehicle speed on the power CAN bus; integrate the test module and power CAN bus information synchronously into the software to measure and store the above data in real time.

3. The test method for cooling performance of a passenger vehicle powertrain under off-road conditions as described in claim 2, characterized in that, Step S2 specifically involves driving the passenger vehicle continuously for 5 minutes on various road conditions, including a 70° slope, a V-shaped ditch, a cross-axle, a rocky road, a gravel road, a sandy area, a stepped road, a rocky slope road, a muddy road, and a pebble road. The road condition data collection ends when the engine coolant temperature or the automatic transmission oil temperature reaches equilibrium. All data from step S1 are recorded during the test.

4. The test method for cooling performance of a passenger vehicle powertrain under off-road conditions as described in claim 3, characterized in that, The equilibrium state is defined as follows: the temperature difference change is ≤2℃ within two consecutive minutes, or the temperature difference exhibits periodic fluctuations with a peak change value ≤2℃.

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