Electric drive system oil temperature estimation method, device and system and medium

Abstract

The invention provides an electric drive system oil temperature estimation method, device and system and a medium, and the method comprises the steps: according to the oil liquid density, the oil liquid specific heat capacity, the vehicle operation time from vehicle starting to the current moment, the oil temperature of the vehicle electric drive system at the last moment, the second heat generation amount and the third heat generation amount, calculating the oil temperature of the vehicle electric drive system; and the oil temperature at the current moment is obtained through calculation according to one of the fourth heat dissipating capacity and the fifth heat dissipating capacity. According to the invention, the mode of acquiring the oil temperature by using an oil temperature sensor, an oil pump and a corresponding power supply circuit and a detection circuit in the prior art is canceled, the structure of the oil temperature detection system is simplified, the application requirements of water cooling and oil cooling electric drive are met, the oil temperature can be accurately acquired by using an oil temperature estimation method, and the oil temperature detection efficiency is improved. The cost and the fault rate of hardware are reduced, and the robustness is improved.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a method, apparatus, system and medium for estimating oil temperature in an electric drive system. Background Technology

[0002] Transmission systems such as motors and speed reducers inevitably experience some wear during gear meshing and rotation within bearings. To reduce frictional losses and protect transmission components, lubricating oil is typically used to lubricate the surfaces of these components. As the lubricating oil flows across the component surfaces, in addition to reducing wear and providing lubrication, it also carries away heat.

[0003] Excessively high or low oil temperatures can significantly impact lubrication and cooling performance. In extreme cases, the oil itself can even deteriorate at extreme temperatures, affecting the overall lifespan of the lubrication system. Therefore, most mainstream lubrication and cooling oil systems employ oil temperature sensors to monitor oil temperature in real time and provide feedback to the oil pump control unit or main control unit. When the oil temperature is too high or too low, the opening of the oil pump or water pump is adjusted to regulate the oil temperature within the optimal operating range for the system.

[0004] Patents CN116502444A, CN112416030B, and CN113833841A disclose oil temperature estimation models for electric drive systems. These patents primarily target oil-cooled electric drive systems, estimating oil temperature based on the operating status of the oil pump within the oil-cooling system.

[0005] The basic idea of ​​the oil temperature estimation model in CN116502444A is to obtain the oil pump speed in real time. When the oil pump speed is less than the preset threshold, the current oil temperature is estimated by the motor temperature and the oil temperature at the previous moment. When the oil pump speed is greater than or equal to the preset threshold, the current oil temperature is obtained by the oil pump speed, current, voltage and the flow resistance characteristics of the oil circuit.

[0006] CN112416030B discloses an oil temperature estimation method based entirely on the electrical characteristics of the motor, which calculates the oil temperature at the current moment by using the oil pump speed and current and the mapping relationship between these variables and oil temperature.

[0007] CN113833841A introduces an oil temperature estimation model, which calculates the transmission oil temperature by measuring the current value at a reference speed and looking up a table showing the correspondence between current, speed, and oil temperature.

[0008] The above patents are mainly applied to oil-cooled electric drive systems, estimating the oil temperature of the electric drive system based on the electrical characteristics of the oil pump motor. Therefore, two problems exist:

[0009] 1. For water-cooled electric drive systems, the oil temperature of the gearbox cannot be estimated, thus making it impossible to protect the gearbox components; 2. In the event of an oil pump failure, the oil temperature of the electric drive system cannot be estimated, thus making it impossible to protect the components.

[0010] Therefore, how to reduce costs and hardware failure rates while satisfying the oil temperature estimation requirements of water-cooled and oil-cooled electric drives, and improve robustness, is a technical problem that needs to be solved in this field. Summary of the Invention

[0011] In view of this, a summary section is provided to briefly introduce the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0012] The purpose of this application is to provide a method, device, system and medium for estimating oil temperature in an electric drive system, which can reduce costs and hardware failure rates and improve robustness while meeting the requirements for oil temperature estimation in both water-cooled and oil-cooled electric drives.

[0013] To achieve the above objectives, this application provides the following technical solution:

[0014] In a first aspect, embodiments of this application provide a method for estimating the oil temperature of an electric drive system, including:

[0015] Get the oil temperature of the vehicle's electric drive system at the previous moment;

[0016] Based on the first preset dimensionless coefficient, the current motor torque and the current motor speed, the first heat generation of the gearbox and the second heat generation of the motor at the current moment are calculated.

[0017] Based on the second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle electric drive system, and the current outside air temperature, the third heat dissipation of the oil through the electric drive housing and air at the current moment is calculated.

[0018] If the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, the fourth heat dissipation amount of the oil exchanging heat with the coolant through the electric drive housing at the current moment is calculated.

[0019] If the vehicle is an oil-cooled electric drive, then based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated.

[0020] The current oil temperature is calculated based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, the previous oil temperature of the vehicle's electric drive system, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation.

[0021] In one possible implementation, the initial oil temperature at the time of vehicle startup is calculated based on an initial preset dimensionless coefficient, the motor temperature at the time the engine was turned off after the last drive, the motor temperature at the time of vehicle startup, the current outside air temperature, and the oil temperature at the time the engine was turned off after the last drive. Specifically, this is calculated using the following formula:

[0022]

[0023] Among them, T oil@t＝0 The initial oil temperature is given by T, k0 is the initial preset dimensionless coefficient, and T is the initial oil temperature. motor@t＝0 T represents the motor temperature at the time of vehicle startup. motor@t＝N T represents the motor temperature at the time the engine was turned off after the last driving session. air Let T be the current outside air temperature. oil@t＝N The oil temperature was the temperature at the time the engine was turned off after the last driving session.

[0024] In one possible implementation, the third heat dissipation of the oil through the electric drive housing and air at the current moment is calculated based on a second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle's electric drive system, and the current outside air temperature. Specifically, this is calculated using the following formula:

[0025] Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ;

[0026] Among them, T oil@t＝n-1 Q1 represents the oil temperature of the vehicle's electric drive system at the previous moment, Q2 represents the third heat dissipation, and k2, c, and d represent the second preset dimensionless coefficients.

[0027] In one possible implementation, if the vehicle is an oil-cooled electric drive, then based on a fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the current temperature of the coolant flowing through the water-cooled electric drive, the current flow rate of the coolant flowing through the water-cooled electric drive, and the current oil pump speed, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated, specifically using the following formula:

[0028] Q5=-k4(T oil@t＝n-1 -T clnt ) f n g q clnt h ;

[0029] Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is n, the current oil pump speed is q clnt The current flow rate of the coolant flowing through the water-cooled electric drive is denoted as _____.

[0030] Secondly, embodiments of this application provide an oil temperature estimation device for an electric drive system, comprising:

[0031] The acquisition unit is used to acquire the oil temperature of the vehicle's electric drive system at the previous moment.

[0032] The second calculation unit is used to calculate the first heat generation of the gearbox and the second heat generation of the motor at the current moment based on the first preset dimensionless coefficient, the current motor torque and the current motor speed.

[0033] The third calculation unit is used to calculate the third heat dissipation of oil through the electric drive housing and air at the current moment based on the second preset dimensionless coefficient, the motor speed at the current moment, the oil temperature of the vehicle electric drive system at the previous moment, and the outside air temperature at the current moment.

[0034] The fourth calculation unit is used to calculate the fourth heat dissipation of the oil through the electric drive housing and the coolant at the current moment, based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, if the vehicle is a water-cooled electric drive.

[0035] The fifth calculation unit is used to calculate the fifth heat dissipation of the oil through the oil cooler and the coolant at the current moment, based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, if the vehicle is an oil-cooled electric drive.

[0036] The sixth calculation unit is used to calculate the current oil temperature based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, the oil temperature of the vehicle's electric drive system at the previous moment, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation.

[0037] In one possible implementation, it further includes: a first calculation unit, specifically used to calculate the initial oil temperature at the time of vehicle startup using the following formula:

[0038]

[0039] Among them, T oil@t =0 represents the initial oil temperature, k0 represents the initial preset dimensionless coefficient, and T motor@t＝0 The temperature of the motor during vehicle startup is T. motor@t＝N T represents the motor temperature at the time the engine was turned off after the last drive. air Let T be the current outside air temperature. oil@t＝N This is the oil temperature at the time the engine was turned off after the last drive.

[0040] In one possible implementation, the third calculation unit is specifically used to calculate the third heat dissipation using the following formula:

[0041] Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ;

[0042] Among them, T oil@t＝n-1 Q1 represents the oil temperature of the vehicle's electric drive system at the previous moment, Q2 represents the third heat dissipation, and k2, c, and d represent the second preset dimensionless coefficients.

[0043] In one possible implementation, the fifth calculation unit is specifically used to calculate the fifth heat dissipation using the following formula:

[0044] Q5=-k4(T oil@t＝n-1 -T clnt ) f n g q clnt h ;

[0045] Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is n, the current oil pump speed is q clnt The current flow rate of the coolant flowing through the water-cooled electric drive is denoted as _____.

[0046] Thirdly, embodiments of this application provide an oil temperature estimation system for an electric drive system, comprising:

[0047] Memory, used to store computer programs;

[0048] A processor is used to implement the steps of the electric drive system oil temperature estimation method as described above when executing the computer program.

[0049] Fourthly, embodiments of this application provide a computer-readable medium storing a computer program, which, when processed and executed, implements the steps of the electric drive system oil temperature estimation method described above.

[0050] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0051] This application provides a method, apparatus, system, and medium for estimating the oil temperature of an electric drive system. The method includes: acquiring the oil temperature of the vehicle's electric drive system at the previous moment; calculating the first heat generation of the gearbox and the second heat generation of the motor at the current moment based on a first preset dimensionless coefficient, the motor torque at the current moment, and the motor speed at the current moment; calculating the third heat dissipation of the oil through the electric drive housing and air at the current moment based on a second preset dimensionless coefficient, the motor speed at the current moment, the oil temperature of the vehicle's electric drive system at the previous moment, and the outside air temperature at the current moment; if the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the outside air temperature at the current moment... The coolant flow rate through the water-cooled electric drive is used to calculate the fourth heat dissipation of the oil through the electric drive housing and coolant at the current moment. If the vehicle is an oil-cooled electric drive, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment. The current oil temperature is calculated based on the oil density, oil specific heat capacity, the vehicle running time from start-up to the current moment, the oil temperature of the vehicle's electric drive system at the previous moment, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation. This application simplifies the structure of the oil temperature detection system by eliminating the use of oil temperature sensors, oil pumps, and their corresponding power supply circuits and detection circuits to obtain oil temperature in the prior art. It adapts to the application requirements of both water-cooled and oil-cooled electric drives. By using an oil temperature estimation method, the oil temperature can be accurately obtained, reducing costs and hardware failure rates, and improving robustness. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0054] Figure 1 A flowchart of an oil temperature estimation method for an electric drive system provided in an embodiment of this application is shown;

[0055] Figure 2A schematic diagram illustrating the oil energy exchange in an electric drive system according to an embodiment of this application is shown;

[0056] Figure 3 A schematic diagram of an oil temperature estimation device for an electric drive system provided in an embodiment of this application is shown. Detailed Implementation

[0057] It should be noted that the oil temperature estimation method, apparatus, system, and medium for an electric drive system provided by this invention can be applied to the field of vehicle technology. The above are merely examples and do not limit the application areas of the oil temperature estimation method, apparatus, system, and medium for an electric drive system provided by this invention.

[0058] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0059] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0060] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0061] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0062] As described in the background section, the applicant's research has revealed that transmission systems such as motors and reducers inevitably experience wear during gear meshing and rotation within bearings. To reduce frictional losses and protect transmission components, lubricating oil is typically used to lubricate the surface of these components. In addition to reducing wear and providing lubrication, the lubricating oil also carries away heat as it flows across the component surface.

[0063] Excessively high or low oil temperatures can significantly impact lubrication and cooling performance. In extreme cases, the oil itself can even deteriorate at extreme temperatures, affecting the overall lifespan of the lubrication system. Therefore, most mainstream lubrication and cooling oil systems employ oil temperature sensors to monitor oil temperature in real time and provide feedback to the oil pump control unit or main control unit. When the oil temperature is too high or too low, the opening of the oil pump or water pump is adjusted to regulate the oil temperature within the optimal operating range for the system.

[0064] Patents CN116502444A, CN112416030B, and CN113833841A disclose oil temperature estimation models for electric drive systems. These patents primarily target oil-cooled electric drive systems, estimating oil temperature based on the operating status of the oil pump within the oil-cooling system.

[0065] The basic idea of ​​the oil temperature estimation model in CN116502444A is to obtain the oil pump speed in real time. When the oil pump speed is less than the preset threshold, the current oil temperature is estimated by the motor temperature and the oil temperature at the previous moment. When the oil pump speed is greater than or equal to the preset threshold, the current oil temperature is obtained by the oil pump speed, current, voltage and the flow resistance characteristics of the oil circuit.

[0066] CN112416030B discloses an oil temperature estimation method based entirely on the electrical characteristics of the motor, which calculates the oil temperature at the current moment by using the oil pump speed and current and the mapping relationship between these variables and oil temperature.

[0067] CN113833841A introduces an oil temperature estimation model, which calculates the transmission oil temperature by measuring the current value at a reference speed and looking up a table showing the correspondence between current, speed, and oil temperature.

[0068] The above patents are mainly applied to oil-cooled electric drive systems, estimating the oil temperature of the electric drive system based on the electrical characteristics of the oil pump motor. Therefore, two problems exist:

[0069] 1. For water-cooled electric drive systems, the oil temperature of the gearbox cannot be estimated, thus making it impossible to protect the gearbox components; 2. In the event of an oil pump failure, the oil temperature of the electric drive system cannot be estimated, thus making it impossible to protect the components.

[0070] Therefore, how to reduce costs and hardware failure rates while satisfying the oil temperature estimation requirements of water-cooled and oil-cooled electric drives, and improve robustness, is a technical problem that needs to be solved in this field.

[0071] To address the above technical problems, embodiments of this application provide a method, apparatus, system, and medium for estimating oil temperature in an electric drive system. The method includes: acquiring the oil temperature of the vehicle's electric drive system at a previous moment; calculating a first heat generation of the reduction gearbox and a second heat generation of the motor at the current moment based on a first preset dimensionless coefficient, the motor torque at the current moment, and the motor speed at the current moment; calculating a third heat dissipation of the oil through the electric drive housing and air at the current moment based on a second preset dimensionless coefficient, the motor speed at the current moment, the oil temperature of the vehicle's electric drive system at a previous moment, and the outside air temperature at the current moment; if the vehicle is a water-cooled electric drive, then based on a third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at a previous moment, and the coolant temperature flowing through the water-cooled electric drive at the current moment... The system calculates the fourth heat dissipation through heat exchange between the oil and the coolant at the current moment, based on the current temperature and the current flow rate of the coolant flowing through the water-cooled electric drive. If the vehicle is an oil-cooled electric drive, the fifth heat dissipation through heat exchange between the oil and the coolant at the current moment is calculated based on the fourth preset dimensionless coefficient, the previous oil temperature of the vehicle's electric drive system, the current coolant temperature flowing through the water-cooled electric drive, the current coolant flow rate flowing through the water-cooled electric drive, and the current oil pump speed. The current oil temperature is calculated based on the oil density, oil specific heat capacity, the vehicle's running time from start-up to the current moment, the previous oil temperature of the vehicle's electric drive system, the second heat generation, the third heat dissipation, and either the fourth or fifth heat dissipation. This application simplifies the structure of the oil temperature detection system by eliminating the use of oil temperature sensors, oil pumps, and their corresponding power supply and detection circuits in existing technologies. It adapts to the application requirements of both water-cooled and oil-cooled electric drives, and accurately obtains the oil temperature using an oil temperature estimation method, reducing costs and hardware failure rates, and improving robustness.

[0072] Exemplary methods

[0073] See Figure 1 The flowchart shown is a method for estimating oil temperature in an electric drive system according to an embodiment of this application, including:

[0074] S101: Obtain the oil temperature of the vehicle's electric drive system at the previous moment.

[0075] In this embodiment, the oil temperature of the vehicle's electric drive system changes gradually. After the vehicle is turned off following the last drive, the oil temperature gradually decreases until it approaches ambient temperature. After the engine is turned off, the degree of temperature drop will vary depending on the time elapsed, and the heat exchange process is mainly due to natural convection heat exchange with the air.

[0076] The embodiments of this application can obtain the oil temperature of the vehicle's electric drive system at the previous moment, so as to calculate the current oil temperature of the vehicle's electric drive system based on the previous oil temperature.

[0077] Specifically, when the vehicle is first started, the initial oil temperature at that moment needs to be obtained to calculate the oil temperature at each subsequent moment of vehicle operation. The previous oil temperature can be pre-calculated and stored in the vehicle's electronic system. If it is the initial moment of vehicle startup, the initial oil temperature of the vehicle's electric drive system is used as the previous oil temperature of the vehicle's electric drive system for calculating the current oil temperature.

[0078] Therefore, it is first necessary to calculate the initial oil temperature when the vehicle starts, because after the engine is turned off, the oil and the motor stator begin to dissipate heat through natural convection simultaneously. Therefore, in this embodiment, the oil temperature is estimated using the motor temperature and the ambient temperature. The initial oil temperature when the vehicle starts is expressed as:

[0079]

[0080] Among them, T oil@t＝0 The initial oil temperature is given by k, where k0 is the initial preset dimensionless coefficient, and T is the initial oil temperature. motor@t＝0 The temperature of the motor during vehicle startup is T. motor@t＝N T represents the motor temperature at the time the engine was turned off after the last drive. air T represents the current outside air temperature. oil@t＝N This is the oil temperature at the time the engine was turned off after the last drive.

[0081] S102: Based on the first preset dimensionless coefficient, the current motor torque and the current motor speed, calculate the first heat generation of the gearbox and the second heat generation of the motor at the current moment;

[0082] S103: Based on the second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle electric drive system, and the current outside air temperature, calculate the third heat dissipation of the oil through the electric drive housing and the air at the current moment.

[0083] S104: If the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, the fourth heat dissipation amount of the oil exchanging heat with the coolant through the electric drive housing at the current moment is calculated.

[0084] S105: If the vehicle is an oil-cooled electric drive, then based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated.

[0085] S106: The current oil temperature is calculated based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, the previous oil temperature of the vehicle's electric drive system, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation.

[0086] In the embodiments of this application, see Figure 2 The diagram shown is a schematic representation of oil energy exchange in an electric drive system according to an embodiment of this application.

[0087] In an electric drive system, the hydraulic fluid comes into direct / indirect contact with the motor, gears, bearings, oil seals, coolant, and air, resulting in energy exchange between the hydraulic fluid and these components. For water-cooled electric drives, the hydraulic fluid primarily lubricates gearbox components such as gears, bearings, and oil seals, resulting in direct contact and energy exchange between the fluid and these components. While it doesn't directly contact the coolant or air outside the gearbox, energy exchange still occurs between them. For oil-cooled electric drives, the hydraulic fluid simultaneously cools both the gearbox and the motor, exchanging heat with the coolant through an oil cooler. Additionally, there is heat exchange between the fluid and air.

[0088] Specifically, the components and motor inside the gearbox act as heat sources during operation, and their heat generation is related to the motor's torque and speed. Therefore, the heat generated by the gearbox can be described as follows:

[0089] Q1 = f1(Torque, N) speed );

[0090] That is, the first heat generation is the motor torque forque at the current moment and the motor speed N at the current moment. speed The relevant function f1 is calculated.

[0091] In water-cooled electric drives, the heat generated by the motor is dissipated by the coolant. However, in oil-cooled electric drives, the heat generated by the motor is directly dissipated by the oil, which can be described as...

[0092] Q2 = f2(Torque, N) speed );

[0093] That is, the second heat generation is related to the current motor torque Torque and the current motor speed N. speed The relevant function f1 is calculated.

[0094] From a simplified calculation perspective, since the losses of both the gearbox and the motor are related to both the motor's torque and speed, Q1 and Q2 can be combined into one.

[0095] Q 1，2 =k1Torque a N speedb ;

[0096] Where k1 and a, b are the initial preset dimensionless coefficients, which are parameters fitted from the loss models of the gearbox and motor.

[0097] During the operation of an electric drive system, the oil temperature is generally higher than the ambient temperature and the coolant temperature. Therefore, the heat exchange process between the oil and air / coolant is a heat dissipation process. For the heat exchange process between the oil, the electric drive housing, and the air, since the heat exchange between the oil and air in the electric drive system is related to the motor speed (corresponding to the vehicle speed) and the ambient temperature, the third heat dissipation from the oil to the air through the electric drive housing can be expressed as:

[0098] Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ;

[0099] Among them, T oil@t＝n-1 Let Q1 be the oil temperature of the vehicle's electric drive system at the previous moment, Q2 be the third heat dissipation, and k2, c, and d be the second preset dimensionless coefficients. k2, c, and d are dimensionless coefficients extracted from the oil-shell-air convective heat transfer model.

[0100] For a water-cooled electric drive, the heat exchange between the oil and coolant through the casing can be expressed as:

[0101] Q4=-k3(T oil@t＝n-1 -T clnt ) e

[0102] Where Q4 is the fourth heat dissipation, k3 and e are the third preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is given. k3 and e are dimensionless coefficients extracted from the oil-coolant heat exchange model. The current flow rate of the coolant flowing through the water-cooled electric drive is given by q. clnt The amount required to establish a heat exchange model between oil and coolant.

[0103] For oil-cooled electric drives, the heat exchange between oil and coolant through the oil cooler can be represented as follows:

[0104] Q5=-k4(T oil@t＝n-1 -T clnt ) f n g q clnt h ;

[0105] Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and Tclnt q represents the current temperature of the coolant flowing through the water-cooled electric drive, n represents the current oil pump speed, and q represents the current temperature of the coolant. clnt This represents the current flow rate of coolant passing through the water-cooled electric drive.

[0106] If the oil pump malfunctions and cannot operate, then Q5 = 0, meaning that the oil pump malfunction has no impact on the estimation and detection of the oil temperature at the current moment. k4, f, g, and h are dimensionless coefficients extracted through the oil-coolant heat exchange model.

[0107] Then, based on the energy changes of the oil, the temperature change of the oil can be calculated as follows:

[0108] ΔT oil =k×(Q) 1，2 +Q3+Q4)×Δt; (water-cooled electric drive)

[0109] ΔT oil =k×(Q) 1，2 +Q3+Q5)×Δt;(Oil-cooled electric drive)

[0110] Where, ΔT oil Let represent the temperature change of the oil, k represents the reciprocal of the product of the oil density and specific heat capacity, and Δt is the duration of vehicle operation from vehicle startup to the current moment.

[0111] The current oil temperature can be expressed as:

[0112] T oil@t＝n =T oil@t＝n-1 +ΔT oil ,

[0113] T oil@t＝2 This is the current oil temperature. When the vehicle is turned off, the oil temperature and motor temperature at the moment of shutdown need to be recorded so that the initial oil temperature can be calculated when starting the vehicle again.

[0114] The purpose of this invention is to provide a method for estimating the oil temperature of an electric drive system, which can accurately estimate the oil temperature of the electric drive system in real time, without relying on oil temperature sensors or other hardware, thereby reducing the cost of the electric drive and improving its robustness.

[0115] To achieve the above objectives, this invention proposes an oil temperature estimation model based on the law of conservation of energy. By simplifying the calculation of the energy received and lost by the oil in the electric drive system, the accumulated heat in the oil within the current time step is obtained, the change in oil temperature is further obtained, and finally the oil temperature of the electric drive system at the current moment is estimated.

[0116] This application provides a method for estimating the oil temperature of an electric drive system. The method includes: obtaining the oil temperature of the vehicle's electric drive system at the previous moment; calculating the first heat generation of the reduction gearbox and the second heat generation of the motor at the current moment based on a first preset dimensionless coefficient, the current motor torque, and the current motor speed; calculating the third heat dissipation of the oil through the electric drive housing and air at the current moment based on a second preset dimensionless coefficient, the current motor speed, the oil temperature of the vehicle's electric drive system at the previous moment, and the current outside air temperature; if the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the current temperature of the coolant flowing through the water-cooled electric drive, and the current temperature of the coolant flowing through the water-cooled electric drive... The coolant flow rate of the electric drive is used to calculate the fourth heat dissipation of the oil through the electric drive housing and coolant at the current moment. If the vehicle is an oil-cooled electric drive, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment. The current oil temperature is calculated based on the oil density, oil specific heat capacity, the vehicle running time from start-up to the current moment, the oil temperature of the vehicle's electric drive system at the previous moment, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation. This application simplifies the structure of the oil temperature detection system by eliminating the use of oil temperature sensors, oil pumps, and their corresponding power supply circuits and detection circuits to obtain oil temperature in the prior art. It also adapts to the application requirements of both water-cooled and oil-cooled electric drives. By using an oil temperature estimation method, the oil temperature can be accurately obtained, reducing costs and hardware failure rates, and improving robustness.

[0117] Exemplary device

[0118] See Figure 3 The diagram shown is a schematic of an oil temperature estimation device for an electric drive system provided in an embodiment of this application, comprising:

[0119] Acquisition unit 201 is used to acquire the oil temperature of the vehicle's electric drive system at the previous moment;

[0120] The second calculation unit 202 is used to calculate the first heat generation of the gearbox and the second heat generation of the motor at the current moment based on the first preset dimensionless coefficient, the current motor torque and the current motor speed.

[0121] The third calculation unit 203 is used to calculate the third heat dissipation of oil through the electric drive housing and air at the current moment based on the second preset dimensionless coefficient, the motor speed at the current moment, the oil temperature of the vehicle electric drive system at the previous moment, and the outside air temperature at the current moment.

[0122] The fourth calculation unit 204 is used to calculate the fourth heat dissipation of the oil through the electric drive housing and the coolant at the current moment, based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, if the vehicle is a water-cooled electric drive.

[0123] The fifth calculation unit 205 is used to calculate the fifth heat dissipation of the oil through the oil cooler and the coolant at the current moment, based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, if the vehicle is an oil-cooled electric drive.

[0124] The sixth calculation unit 206 is used to calculate the current oil temperature based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, oil temperature of the vehicle electric drive system at the previous moment, the second heat generation and the third heat dissipation, and one of the fourth heat dissipation or the fifth heat dissipation.

[0125] In one possible implementation, it further includes: a first calculation unit, specifically used to calculate the initial oil temperature at the time of vehicle startup using the following formula:

[0126]

[0127] Among them, T oil@t＝0 The initial oil temperature is given by T, k0 is the initial preset dimensionless coefficient, and T is the initial oil temperature. motor@t＝0 The temperature of the motor during vehicle startup is T. motor@t＝N T represents the motor temperature at the time the engine was turned off after the last drive. air Let T be the current outside air temperature. oil@t＝N This is the oil temperature at the time the engine was turned off after the last drive.

[0128] In one possible implementation, the third calculation unit is specifically used to calculate the third heat dissipation using the following formula:

[0129] Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ;

[0130] Among them, T oil@t＝n-1 Q1 represents the oil temperature of the vehicle's electric drive system at the previous moment, Q2 represents the third heat dissipation, and k2, c, and d represent the second preset dimensionless coefficients.

[0131] In one possible implementation, the fifth calculation unit is specifically used to calculate the fifth heat dissipation using the following formula:

[0132] Q5=-k4(T oil@t＝n-1 -T clnt ) f n g q clnt h ;

[0133] Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is n, the current oil pump speed is q clnt The current flow rate of the coolant flowing through the water-cooled electric drive is denoted as _____.

[0134] This application provides an electric drive system oil temperature estimation device. The method applied to this device includes: acquiring the oil temperature of the vehicle's electric drive system at the previous moment; calculating the first heat generation of the reduction gearbox and the second heat generation of the motor at the current moment based on a first preset dimensionless coefficient, the current motor torque, and the current motor speed; calculating the third heat dissipation of the oil through the electric drive housing and air at the current moment based on a second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle's electric drive system, and the current outside air temperature; if the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the previous oil temperature of the vehicle's electric drive system, the current temperature of the coolant flowing through the water-cooled electric drive, and the current outside air temperature... The fourth heat dissipation is calculated based on the coolant flow rate of the water-cooled electric drive, representing the heat exchange between the oil and the coolant through the electric drive housing at the current moment. If the vehicle has an oil-cooled electric drive, the fifth heat dissipation is calculated based on the fourth preset dimensionless coefficient, the previous oil temperature of the vehicle's electric drive system, the current coolant temperature flowing through the water-cooled electric drive, the current coolant flow rate through the water-cooled electric drive, and the current oil pump speed, representing the heat exchange between the oil and the coolant through the oil cooler at the current moment. The current oil temperature is calculated based on the oil density, oil specific heat capacity, the vehicle's running time from start-up to the current moment, the previous oil temperature of the vehicle's electric drive system, the second heat generation, the third heat dissipation, and either the fourth or fifth heat dissipation. This application simplifies the structure of the oil temperature detection system by eliminating the use of oil temperature sensors, oil pumps, and their corresponding power supply and detection circuits in existing technologies. It adapts to the application requirements of both water-cooled and oil-cooled electric drives, and accurately obtains the oil temperature using an oil temperature estimation method, reducing costs and hardware failure rates, and improving robustness.

[0135] Based on the above embodiments, this application provides an oil temperature estimation system for an electric drive system, comprising:

[0136] Memory, used to store computer programs;

[0137] A processor is used to implement the steps of the above-described method for estimating oil temperature in an electric drive system when executing the computer program.

[0138] Based on the above embodiments, this application also provides a computer-readable medium storing a computer program, which, when processed and executed, implements the steps of the above-described electric drive system oil temperature estimation method.

[0139] It should be noted that the computer-readable medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0140] The aforementioned computer-readable medium may be included in the aforementioned system, or it may exist independently and not assembled into the system.

[0141] In particular, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this disclosure include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts.

[0142] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0143] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A method for estimating oil temperature in an electric drive system, characterized in that, include: Get the oil temperature of the vehicle's electric drive system at the previous moment; Based on the first preset dimensionless coefficient, the current motor torque and the current motor speed, the first heat generation of the gearbox and the second heat generation of the motor at the current moment are calculated. Based on the second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle electric drive system, and the current outside air temperature, the third heat dissipation of the oil through the electric drive housing and air at the current moment is calculated. If the vehicle is a water-cooled electric drive, then based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, the fourth heat dissipation amount of the oil exchanging heat with the coolant through the electric drive housing at the current moment is calculated. If the vehicle is an oil-cooled electric drive, then based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated. The current oil temperature is calculated based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, the previous oil temperature of the vehicle's electric drive system, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation.

2. The method according to claim 1, characterized in that, Also includes: Based on the initial preset dimensionless coefficient, the motor temperature when the engine was turned off at the end of the last drive, the motor temperature when the vehicle is started this time, the current outside air temperature, and the oil temperature when the engine was turned off at the end of the last drive, the initial oil temperature when the vehicle is started this time is calculated using the following formula: Among them, T oil@t＝0 The initial oil temperature is given by T, k0 is the initial preset dimensionless coefficient, and T is the initial oil temperature. #otor@t＝0 T represents the motor temperature at the time of vehicle startup. $otor@t＝N T represents the motor temperature at the time the engine was turned off after the last driving session. alr Let T be the current outside air temperature. oil@t＝N The oil temperature was the temperature at the time the engine was turned off after the last driving session.

3. The method according to claim 2, characterized in that, The third heat dissipation of the oil through the electric drive housing and air at the current moment is calculated based on the second preset dimensionless coefficient, the current motor speed, the previous oil temperature of the vehicle's electric drive system, and the current outside air temperature. Specifically, it is calculated using the following formula: Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ; Among them, T oil@t＝n-1 Q1 represents the oil temperature of the vehicle's electric drive system at the previous moment, Q2 represents the third heat dissipation, and k2, c, and d represent the second preset dimensionless coefficients.

4. The method according to claim 3, characterized in that, If the vehicle is an oil-cooled electric drive, then based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the current temperature of the coolant flowing through the water-cooled electric drive, the current flow rate of the coolant flowing through the water-cooled electric drive, and the current oil pump speed, the fifth heat dissipation of the oil through the oil cooler and coolant at the current moment is calculated, specifically using the following formula: Q5=-k4(T oil@t＝n-1 -T clnt )fn g q clnt h ; Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is n, and the current oil pump speed is qcl. n t is the flow rate of coolant flowing through the water-cooled electric drive at the current moment.

5. An oil temperature estimation device for an electric drive system, characterized in that, include: The acquisition unit is used to acquire the oil temperature of the vehicle's electric drive system at the previous moment. The second calculation unit is used to calculate the first heat generation of the gearbox and the second heat generation of the motor at the current moment based on the first preset dimensionless coefficient, the current motor torque and the current motor speed. The third calculation unit is used to calculate the third heat dissipation of oil through the electric drive housing and air at the current moment based on the second preset dimensionless coefficient, the motor speed at the current moment, the oil temperature of the vehicle electric drive system at the previous moment, and the outside air temperature at the current moment. The fourth calculation unit is used to calculate the fourth heat dissipation of the oil through the electric drive housing and the coolant at the current moment, based on the third preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, and the coolant flow rate flowing through the water-cooled electric drive at the current moment, if the vehicle is a water-cooled electric drive. The fifth calculation unit is used to calculate the fifth heat dissipation of the oil through the oil cooler and the coolant at the current moment, based on the fourth preset dimensionless coefficient, the oil temperature of the vehicle's electric drive system at the previous moment, the coolant temperature flowing through the water-cooled electric drive at the current moment, the coolant flow rate flowing through the water-cooled electric drive at the current moment, and the oil pump speed at the current moment, if the vehicle is an oil-cooled electric drive. The sixth calculation unit is used to calculate the current oil temperature based on the oil density, oil specific heat capacity, vehicle running time from vehicle startup to the current moment, the oil temperature of the vehicle's electric drive system at the previous moment, the second heat generation, the third heat dissipation, and one of the fourth or fifth heat dissipation.

6. The apparatus according to claim 5, characterized in that, Also includes: The first calculation unit is specifically used to calculate the initial oil temperature at the time of vehicle startup using the following formula: Among them, T oil@t＝0 The initial oil temperature is given by T, k0 is the initial preset dimensionless coefficient, and T is the initial oil temperature. motor@t＝0 The temperature of the motor during vehicle startup is T. motor@t＝N T represents the motor temperature at the time the engine was turned off after the last drive. air Let T be the current outside air temperature. oil@t＝N This is the oil temperature at the time the engine was turned off after the last drive.

7. The apparatus according to claim 6, characterized in that, The third calculation unit is specifically used to calculate the third heat dissipation using the following formula: Q3=-k2N speed c (T oil@t＝n-1 -T air ) d ; Among them, T oil@t＝n-1 Q1 represents the oil temperature of the vehicle's electric drive system at the previous moment, Q2 represents the third heat dissipation, and k2, c, and d represent the second preset dimensionless coefficients.

8. The apparatus according to claim 7, characterized in that, The fifth calculation unit is specifically used to calculate the fifth heat dissipation using the following formula: Q5=-k4(T oil@t＝n-1 -T clnt ) f n g q clnt h ; Where Q5 is the fifth heat dissipation, k4, f, g, and h are the fourth preset dimensionless coefficients, and T clnt The current temperature of the coolant flowing through the water-cooled electric drive is n, the current oil pump speed is q clnt The current flow rate of the coolant flowing through the water-cooled electric drive is denoted as _____.

9. An oil temperature estimation system for an electric drive system, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the oil temperature estimation method for an electric drive system as described in any one of claims 1-4 when executing the computer program.

10. A computer-readable medium, characterized in that, The computer-readable medium stores a computer program that, when processed and executed, implements the steps of the oil temperature estimation method for an electric drive system as described in any one of claims 1-4.

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