Vehicle torque limiting method and vehicle

Abstract

The application provides a vehicle torque limiting method and a vehicle, and relates to the field of vehicle control. The method comprises the following steps: if the wheel speed of any wheel is invalid, obtaining the transmission output shaft speed of the vehicle and the driving state of the vehicle; determining the wheel speed difference between the two sides of the axle of the vehicle according to the transmission output shaft speed and the driving state of the vehicle; obtaining a torque limiting coefficient based on the wheel speed difference between the two sides of the axle, the driving state of the vehicle and the internal gasket data of the differential in the vehicle; and performing torque limiting control on the vehicle according to the torque limiting coefficient and the current torque value of the vehicle, so that closed-loop torque limiting control can be realized in the case of abnormal wheel speed signal, gasket ablation and crushing can be effectively avoided, and the differential of the vehicle is protected.

Description

Technical Field

[0001] This application relates to the field of vehicle control technology, and in particular to a vehicle torque limiting method and a vehicle. Background Technology

[0002] As vehicles become increasingly feature-rich, their usage scenarios also expand. In some of these scenarios, problems frequently arise. For example, in desert off-roading, vehicles often get stuck in sand pits. When a vehicle is stuck, the differential lock needs to be engaged to extricate it. However, some inexperienced off-road users may attempt to extricate the vehicle by accelerating at high speed without engaging the differential lock. At this point, the half-shaft gear and differential housing inside the differential in the drive axle assembly spin at high speed. The gasket located between the half-shaft gear and the differential housing experiences a rapid temperature increase under the combined effects of high-speed friction and axial pressure, leading to rapid ablation and collapse. This ablation and collapse causes the half-shaft gear to stick to the differential housing, resulting in the differential losing its differential function and the vehicle being unable to steer or move normally.

[0003] In related technologies, wheel speed difference is typically determined based on the effective wheel speed value, and a torque limiting strategy is triggered based on this wheel speed difference to limit vehicle torque, prevent gasket burning and crushing, and protect the differential in the drive axle assembly. However, in some usage scenarios, such as the aforementioned desert off-road scenario, wheel speed values ​​may fail, making it impossible to determine the wheel speed difference. This results in the inability to trigger the torque limiting strategy. Furthermore, torque limiting strategies generally employ open-loop control, which cannot effectively prevent gasket burning and crushing, allowing differential sintering failure to still occur during off-road driving. Summary of the Invention

[0004] This application provides a vehicle torque limiting method and a vehicle to solve the problem of differential sintering failure in the drive axle assembly.

[0005] In a first aspect, embodiments of this application provide a vehicle torque limiting method, including: If the wheel speed of any wheel fails, the transmission output shaft speed and vehicle driving status of the vehicle are obtained. The wheel speed difference between the two sides of the vehicle axle is determined based on the output shaft speed of the transmission and the driving state of the vehicle. Based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the differential in the vehicle, the torque limiting coefficient is obtained. Based on the torque limiting coefficient and the current torque value of the vehicle, torque limiting control is performed on the vehicle.

[0006] This application, when the wheel speed value of any wheel fails, can determine the axle wheel speed difference based on the vehicle's driving state and the transmission output shaft speed, avoiding the predicament of being unable to calculate the wheel speed difference due to wheel speed sensor failure or removal. Based on this, a torque limiting coefficient is obtained according to the wheel speed difference, vehicle driving state, and differential shim data, allowing the torque limiting coefficient to be adjusted specifically based on the shim data. Finally, closed-loop torque limiting control is achieved based on the torque limiting coefficient and the current torque value. Thus, even under abnormal wheel speed signals, the torque limiting strategy can still be activated normally, and the torque limiting coefficient matches the differential shim data, achieving closed-loop control and effectively preventing shim burning and crushing, thereby protecting the vehicle differential.

[0007] In one possible implementation, the wheel speed difference between the two sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels; Determining the wheel speed difference between the two sides of the vehicle axle based on the output shaft speed of the transmission and the vehicle driving state includes: The differential housing speed is obtained based on the transmission output shaft speed, the vehicle driving state, and the vehicle's final drive ratio. The speed difference between the left and right front wheels is determined based on the rotational speed of the differential housing and the effective wheel speed of the front wheels, and / or the speed difference between the left and right rear wheels is determined based on the rotational speed of the differential housing and the effective wheel speed of the rear wheels.

[0008] When any wheel speed value fails, this application uses the transmission output shaft speed, vehicle driving state, and final drive ratio to calculate the differential housing speed, and then combines the effective wheel speed value to determine the wheel speed difference on both sides of the axle. This allows the wheel speed difference on both sides of the axle to be reliably determined even when the wheel speed sensor is abnormal, so that the torque limiting strategy is not affected by sensor failure, and the robustness and integrity of the torque limiting strategy under abnormal operating conditions are improved.

[0009] In one possible implementation, the vehicle driving state includes two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive. The step of obtaining the differential housing speed based on the transmission output shaft speed, the vehicle driving state, and the vehicle's final drive ratio includes: If the vehicle is in two-wheel drive or high-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio. If the vehicle is in low-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio and the transfer case low-speed four-wheel drive ratio of the vehicle.

[0010] This application differentiates the differential housing speed determination method based on the vehicle's driving state, ensuring that the calculated differential housing speed matches the actual drivetrain deceleration characteristics. Based on this, the wheel speed difference between the two sides of the axle under different vehicle driving states can be accurately calculated, providing reliable input for torque limiting strategies.

[0011] In one possible implementation, determining the speed difference between the left and right front wheels based on the rotational speed of the differential housing and the effective wheel speed of the front wheels includes: If the wheel whose wheel speed has failed is any of the front wheels, then the effective wheel speed of the front wheel whose wheel speed has failed is determined based on the rotational speed of the differential housing and the effective wheel speed of the other front wheel. The speed difference between the left and right front wheels is determined based on the difference in the effective values ​​of the wheel speeds of each front wheel; Determining the speed difference between the left and right rear wheels based on the rotational speed of the differential housing and the effective wheel speed of the rear wheels includes: If the wheel whose wheel speed has failed is any of the rear wheels, then the effective wheel speed value of the rear wheel whose wheel speed has failed is determined based on the rotational speed of the differential housing and the effective wheel speed value of the other rear wheel. The speed difference between the left and right rear wheels is determined based on the difference in the effective values ​​of the wheel speeds of each rear wheel.

[0012] When a single front or rear wheel fails, this application uses the differential housing speed and the effective wheel speed on the other side of the same axle to infer the wheel speed value of the failed wheel, thereby determining the left and right wheel speed difference of the axle. This ensures that even if the wheel speed signal of any wheel is lost, the wheel speed difference between the two sides of the corresponding axle can still be determined, ensuring the normal triggering of the torque limiting strategy.

[0013] In one possible implementation, the differential's internal gasket data includes the maximum heat load that the differential's internal gaskets can withstand; The process of obtaining the torque limiting coefficient based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's center differential includes: If the wheel speed difference between the two sides of the axle is less than the first preset wheel speed difference threshold, then the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value.

[0014] This embodiment calculates the current thermal load value of the differential when the wheel speed difference is small, and then triggers torque limiting, solving the problem that the gasket is also at risk of burning under small wheel speed difference and high torque conditions. When the thermal load exceeds the limit, the torque limiting coefficient is dynamically determined based on the ratio of the limit value to the actual value, realizing precise protection based on the physical tolerance limit of the gasket itself, and avoiding the problem of insufficient protection under small wheel speed difference and high torque conditions.

[0015] In one possible implementation, the vehicle driving state includes two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive, and the wheel speed difference on both sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels. The determination of the current thermal load value of the vehicle's differential based on the wheel speed difference on both sides of the axle and the vehicle's driving state includes: If the vehicle is in two-wheel drive mode, the current heat load value is determined based on the product of the speed difference between the left and right rear wheels or the speed difference between the left and right front wheels, the current torque value of the vehicle, the final drive ratio, and the transmission ratio of the vehicle. If the vehicle is in high-speed four-wheel drive mode, the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels is determined, and the current heat load value is determined based on the product of the maximum value, the final drive ratio and the transmission ratio. If the vehicle is in low-speed four-wheel drive mode, the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels is determined, and the current heat load value is determined based on the product of the maximum value, the final drive ratio, the transmission ratio, and the transfer case low-speed four-wheel drive ratio of the vehicle.

[0016] This embodiment distinguishes the calculation method of the current heat load value according to the vehicle driving state, which can ensure that the calculation of the current heat load value strictly corresponds to the torque distribution ratio and transmission amplification link under each driving state, ensuring that the heat load assessment of the differential shim is true and accurate under all operating conditions, and providing a reliable triggering basis for the torque limiting strategy.

[0017] In one possible implementation, obtaining the torque limiting coefficient based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's differential further includes: If the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, then the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value. When the current heat load value is less than or equal to the maximum heat load value, a wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle, a time torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle and a second preset wheel speed difference threshold, and the torque limiting coefficient is determined according to the wheel speed difference torque limiting coefficient and the time torque limiting coefficient; the second preset wheel speed difference threshold is greater than the first preset wheel speed difference threshold.

[0018] In this embodiment, during the transition range with large wheel speed differences but where the current heat load value has not yet exceeded the limit, a two-factor mechanism of wheel speed difference torque limiting coefficient and time torque limiting coefficient is introduced. The wheel speed difference coefficient responds instantly to the slippage intensity, while the time coefficient progressively tightens the torque limiting based on the duration of high slippage. The combination of the two achieves preventive suppression of the gasket heat accumulation effect, taking into account both power maintenance during brief slippage and progressive protection during continuous slippage, eliminating the risk of ablation failure due to response lag.

[0019] In one possible implementation, obtaining the wheel speed difference limiting torque coefficient based on the wheel speed difference between the two sides of the axle includes: Obtain a preset first lookup table; the first lookup table contains different wheel speed differences on both sides of the axle and the corresponding wheel speed difference torque limiting coefficient; the larger the wheel speed difference on both sides of the axle, the smaller the corresponding wheel speed difference torque limiting coefficient; the wheel speed difference torque limiting coefficient is less than 1. The wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle and the first lookup table.

[0020] This embodiment establishes a mapping relationship between the wheel speed difference on both sides of the axle and the wheel speed difference torque limiting coefficient, so that the torque limiting force can be smoothly adjusted according to the degree of slippage, thus protecting the differential while ensuring driving smoothness.

[0021] In one possible implementation, obtaining the time-limited torque coefficient based on the wheel speed difference between the two sides of the axle and a second preset wheel speed difference threshold includes: When the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold, the duration during which the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold is accumulated; Obtain a preset second lookup table; the second lookup table contains different durations and corresponding time limit coefficients; the longer the duration, the smaller the corresponding time limit coefficient; the time limit coefficient is less than or equal to 1; Based on the duration and the second lookup table, the time limit torque coefficient is obtained.

[0022] This embodiment obtains the time-limiting torque coefficient by looking up a table based on the duration of the friction, thereby gradually tightening the torque limit as the friction time increases. This overcomes the shortcomings of the simple wheel speed difference coefficient, which only reflects the instantaneous intensity and cannot take into account the heat accumulation effect. It constructs a dual-layer protection mechanism of friction intensity and duration, effectively preventing the gasket from slowly overheating and failing due to continuous friction.

[0023] Secondly, embodiments of this application provide a vehicle torque limiting device, including: The acquisition module is used to acquire the vehicle's transmission output shaft speed and vehicle driving status if the wheel speed of any wheel fails. Torque limiting module, used for: The wheel speed difference between the two sides of the vehicle axle is determined based on the output shaft speed of the transmission and the driving state of the vehicle. Based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the differential in the vehicle, the torque limiting coefficient is obtained. The control module is used to perform torque limiting control on the vehicle based on the torque limiting coefficient and the current torque value of the vehicle.

[0024] Thirdly, embodiments of this application provide a vehicle including a memory and a processor. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the vehicle torque limiting method as described in any of the first aspects.

[0025] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the vehicle torque limiting method as described in any of the first aspects.

[0026] It is understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0027] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this specification. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of an application scenario provided by an embodiment of this application; Figure 2 This is a schematic flowchart of a vehicle torque limiting method provided in an embodiment of this application; Figure 3 This is a schematic diagram of the internal structure of a differential provided in an embodiment of this application; Figure 4 This is a schematic diagram of vehicle transmission in a rear-wheel drive state provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of the rear drive axle provided in one embodiment of this application; Figure 6 This is a schematic diagram of vehicle transmission in high-speed four-wheel drive and low-speed four-wheel drive states provided in an embodiment of this application; Figure 7 This is a schematic diagram of the torque limiting process provided in an embodiment of the present application when the wheel speed difference between the two sides of the axle is less than a first preset wheel speed difference threshold and the vehicle is in a rear-wheel drive state. Figure 8 This is a schematic diagram of the torque limiting process provided in an embodiment of the present application when the wheel speed difference between the two sides of the axle is less than a first preset wheel speed difference threshold and the vehicle is in a high-speed four-wheel drive state. Figure 9 This application provides a schematic diagram of the torque limiting process when the wheel speed difference between the two sides of the axle is less than a first preset wheel speed difference threshold and the vehicle is in a low-speed four-wheel drive state. Figure 10 This is a schematic diagram of the torque limiting process provided in an embodiment of the present application when the wheel speed difference between the two sides of the axle is greater than or equal to a first preset wheel speed difference threshold and the vehicle is in a rear-wheel drive state. Figure 11 This is a schematic diagram of the torque limiting process provided in an embodiment of the present application when the wheel speed difference between the two sides of the axle is greater than or equal to a first preset wheel speed difference threshold and the vehicle is in a high-speed four-wheel drive state. Figure 12 This is a schematic diagram of the torque limiting process when the wheel speed difference between the two sides of the axle is greater than or equal to a first preset wheel speed difference threshold and the vehicle is in a low-speed four-wheel drive state, according to an embodiment of this application. Figure 13 This is a schematic diagram of the structure of a vehicle torque limiting device provided in an embodiment of this application; Figure 14 This is a schematic diagram of the structure of a vehicle provided in one embodiment of this application. Detailed Implementation

[0030] The present application will be described more clearly below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the function of the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all fall within the protection scope of the present application.

[0031] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0032] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0033] In the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0035] Furthermore, the term "multiple" mentioned in the embodiments of this application should be interpreted as two or more.

[0036] First, the controllers involved in the embodiments of this application, and the signals transmitted between the controllers, will be described: Automatic transmission control unit (TCU): Used to send the transmission output shaft speed to the power domain controller.

[0037] Electronic Stability Program (ESP): Used to send wheel speed values ​​and the validity of each wheel speed value to the power domain controller.

[0038] Electronic Shift-On-the-Fly (ESOF) system: used to send vehicle driving status to the power and controller.

[0039] The Powertrain Domain Control Unit (PDCU) can serve as the execution entity in this embodiment. It is used to receive parameters such as the transmission output shaft speed, wheel speed values ​​of each wheel, the validity of each wheel speed value, and vehicle driving status, and execute the vehicle torque limiting method based on the above parameters.

[0040] The applicant has discovered that vehicles often become stuck in certain usage scenarios, such as desert off-roading where they frequently get stuck in sand pits. When stuck (e.g., trapped in a sand pit), some inexperienced users may attempt to extricate themselves by applying high throttle without engaging the differential lock. Applying high throttle without engaging the differential lock can easily cause the internal gaskets of the differential in the drive axle assembly to burn and collapse, leading to differential failure and rendering the vehicle unable to steer or move normally.

[0041] During vehicle operation, wheel speed difference is typically determined based on the effective wheel speed value, and a torque limiting strategy is triggered based on this wheel speed difference to limit vehicle torque when the vehicle is stuck, preventing gasket burn-out and crushing. The torque limiting strategy typically works as follows: When no torque limiting request is received from other systems and the wheel speed is determined to be valid, the difference in wheel speed between the two sides of the axle is calculated, and a torque limiting coefficient is determined based on this difference. The product of the vehicle's current torque value and the torque limiting coefficient is calculated, and this product is used to determine a new torque value to limit the vehicle's torque. Once a torque limiting request is received from other systems, or the wheel speed is determined to be invalid, the torque limiting strategy is terminated. These other systems may include, but are not limited to, ESP and the Transmission Control Unit (TCU).

[0042] The torque limiting factor can be the product of the wheel speed difference torque limiting factor and the time torque limiting factor. For example, the wheel speed difference torque limiting factor and the time torque limiting factor can be determined according to Table 1-2 below.

[0043] Table 1

[0044] The wheel speed difference torque limiting coefficient can be determined by interpolation according to Table 1, and the values ​​in Table 1 are all scalable quantities that can be determined according to the actual situation.

[0045] Table 2

[0046] Timing begins when the wheel speed difference is ≥95 km / h, and the duration t for this ≥95 km / h is recorded. When the wheel speed difference is <95 km / h, the duration t is reset to zero. Based on the duration t and Table 2 above, the time-limit torque coefficient can be determined.

[0047] As can be seen from the above torque limiting strategies, on the one hand, these strategies are usually triggered based on wheel speed differences. However, in some usage scenarios (such as off-road scenarios), wheel speed may fail. For example, wheel speed sensors may malfunction, or the user may actively disconnect the wheel speed sensor of one wheel to achieve complete control of the vehicle according to driving intentions, causing wheel speed failure and preventing the torque limiting strategy from being triggered. On the other hand, the above torque limiting strategies are based on open-loop control, limiting vehicle torque only according to wheel speed differences to minimize the risk of differential gasket erosion, but cannot effectively prevent gasket erosion. Therefore, it is necessary to consider a new method to limit vehicle torque to avoid differential sintering failure.

[0048] To prevent the differential's internal gaskets from burning and collapsing, and to protect the differential, in the embodiments of this application, when the wheel speed value of any wheel fails, the axle wheel speed difference can be determined based on the vehicle's driving state and the transmission output shaft speed. This avoids the predicament of being unable to calculate the wheel speed difference due to wheel speed sensor failure or removal. Based on this, a torque limiting coefficient is obtained based on the wheel speed difference, vehicle driving state, and differential internal gasket data. This allows the torque limiting coefficient to be adjusted specifically based on the gasket data. Finally, closed-loop torque limiting control is achieved based on the torque limiting coefficient and the current torque value, which can effectively prevent gasket burning and collapse, thereby protecting the vehicle differential.

[0049] First refer to Figure 1 , Figure 1 A schematic diagram of an application scenario provided according to an embodiment of this application is shown, in which the device involved includes a power source controller 101.

[0050] The application scenario is when the vehicle is stuck (e.g., the vehicle is stuck in a sand pit): When the power source controller 101 determines that the wheel speed signal of any wheel has failed, it obtains the transmission output shaft speed and the vehicle driving state, and determines the wheel speed difference on both sides of the axle based on the transmission output shaft speed and the vehicle driving state. Then, it determines the torque limiting coefficient based on the wheel speed difference on both sides of the vehicle, the vehicle driving state and the shim data inside the differential, and performs torque limiting control based on the torque limiting coefficient and the current torque value of the vehicle to avoid the shims inside the differential burning and crushing.

[0051] Optionally, the devices involved in the application scenario also include ESP102, TCU103, and ESOF104. ESP102, TCU103, and ESOF104 are all communicatively connected to the power source controller 101.

[0052] The ESP102 acquires the wheel speed sensors on each wheel and determines the wheel speed value for each wheel based on these signals. The ESP102 also performs multiple checks on the wheel speed values ​​to determine their validity. The ESP102 sends the wheel speed values ​​and their validity information to the power source controller 101. It is understood that if a wheel speed value is valid, it is considered a valid wheel speed value. If a wheel speed value is invalid, it is considered an invalid wheel speed value.

[0053] The power source controller 101 is communicatively connected to TCU103 and ESOF104, respectively, to obtain the transmission output shaft speed from TCU103 and the vehicle driving status from ESOF104. As for the shim data inside the differential, it can be pre-stored in the power source controller 101.

[0054] The following is combined Figure 1 Application scenarios, refer to Figures 2-12 This application describes a vehicle torque limiting method according to exemplary embodiments thereof. It should be noted that the above application scenarios are shown only to facilitate understanding of the spirit and principles of this application, and the embodiments of this application are not limited in any way. Rather, the embodiments of this application can be applied to any applicable scenario.

[0055] It should be noted that the embodiments of this application can be applied to vehicles, and the vehicle can be a power source controller, that is, the vehicle torque limiting method provided by the exemplary embodiments of this application can be executed on the power source controller.

[0056] For new energy vehicles or hybrid vehicles, the power source controller can be a powertrain domain control unit (PDCU), a vehicle control unit (VCU), or a hybrid control unit (HCU), etc. For gasoline vehicles, the power source controller can be an engine control module (ECM), etc.

[0057] refer to Figure 2 , Figure 2 This is a schematic flowchart illustrating a vehicle torque limiting method provided in an embodiment of this application. Figure 2 As shown, the method in the embodiments of this application may include: Step 201: If the wheel speed of any wheel fails, then obtain the transmission output shaft speed and the vehicle driving state.

[0058] The ESP can send wheel speed signals to the power source controller in real time or periodically. The wheel speed signal can include the wheel speed value of each wheel, as well as the validity of each wheel speed value. If the wheel speed value sent by the ESP is valid, then that wheel speed value is the valid wheel speed value.

[0059] If the wheel speed of any wheel is determined to be faulty, the transmission output shaft speed and vehicle driving state can be obtained for subsequent determination of the wheel speed difference between the two sides of the axle. For example, the ESP can periodically send wheel speed signals to the power source controller. The period duration can be determined according to actual conditions, for example, 10ms.

[0060] Understandably, if all wheel speed values ​​sent by ESP are valid, the wheel speed difference between the two sides of the axle can be determined directly based on the valid wheel speed values, without needing to use the transmission output shaft speed and vehicle driving status to determine the wheel speed difference between the two sides of the axle.

[0061] Step 202: Determine the wheel speed difference between the two sides of the vehicle axle based on the transmission output shaft speed and the vehicle driving state.

[0062] The vehicle's transmission drives the wheels to rotate through a series of transmission mechanisms, and the transmission process differs depending on the vehicle's driving state. If the wheel speed value sent by the ESP for any wheel fails, the embodiments of this application can determine the corresponding transmission process based on the vehicle's driving state, and calculate the wheel speed transmitted to the wheel based on the transmission output shaft speed and the transmission process. This allows the determination of the wheel speed value of the wheel with the failed wheel speed, and the wheel speed value can be used as the effective wheel speed value of the wheel with the failed wheel speed.

[0063] Based on this, and combined with the effective wheel speed values ​​of the remaining wheels, the wheel speed difference between the two sides of the axle can be determined. In this embodiment, the wheel speed difference between the two sides of the axle can include the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels. The speed difference between the left and right front wheels is the absolute value of the difference between the effective wheel speed values ​​of the left and right front wheels. The formula is expressed as: Speed ​​difference between the left and right front wheels = |FLS - FRS|. Where FLS represents the effective wheel speed value of the left front wheel, and FRS represents the effective wheel speed value of the right front wheel.

[0064] Similarly, the speed difference between the left and right rear wheels is the absolute value of the difference between the effective speed values ​​of the left and right rear wheels. The formula is: Speed ​​difference between left and right rear wheels = |RLS - RRS|. Where RLS represents the effective speed value of the left rear wheel, and RRS represents the effective speed value of the right rear wheel.

[0065] Understandably, for the left and right front wheels, if both front wheel speeds are valid, the speed difference between the left and right front wheels can be calculated directly based on the valid wheel speed values ​​sent by the ESP. If the wheel speed value of either front wheel is invalid, the wheel speed value of the invalid front wheel can be estimated based on the transmission output shaft speed and the vehicle's driving state, and this wheel speed value is determined as the valid wheel speed value of the invalid front wheel. Based on this, the speed difference between the left and right front wheels is calculated according to the valid wheel speed values ​​of the left and right front wheels.

[0066] Similarly, for the left and right rear wheels, if both wheel speed values ​​are valid, the speed difference between the left and right rear wheels can be calculated directly based on the valid wheel speed values ​​sent by the ESP. If the wheel speed value of either rear wheel is invalid, the wheel speed value of the invalid rear wheel can be estimated based on the transmission output shaft speed and the vehicle's driving state, and this wheel speed value can be determined as the valid wheel speed value of the invalid rear wheel. Based on this, the speed difference between the left and right rear wheels is calculated according to the valid wheel speed values ​​of the left and right rear wheels.

[0067] Step 203: Based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's differential, obtain the torque limiting coefficient.

[0068] See Figure 3 The root cause of differential sintering failure is that high-speed slippage occurs between the half-shaft gear and the differential housing inside the differential, causing the temperature of the gasket located between them to rise sharply, eventually leading to ablation and crushing. After the gasket ablates and crushes, the half-shaft gear and the differential housing stick together through the gasket (similar to a welding effect), causing the differential to lose its differential function.

[0069] Based on this, the embodiments of this application can use the internal gasket data of the differential as a constraint boundary to dynamically determine the torque limiting coefficient according to the wheel speed difference on both sides of the axle and the vehicle driving state. Here, the wheel speed difference on both sides of the axle and the vehicle driving state jointly affect the heat value transferred to the internal gasket of the differential. The internal gasket data of the differential can reflect the heat resistance of the gasket.

[0070] This application embodiment uses the internal gasket data of the vehicle's center differential as a benchmark, and determines the corresponding torque limiting coefficient based on different driving states and the wheel speed difference on both sides of the axle. This allows the vehicle torque to be always limited within the range that the gasket can withstand, achieving closed-loop torque limiting control and effectively preventing gasket burning and crushing.

[0071] Step 204: Perform torque limiting control on the vehicle based on the torque limiting coefficient and the vehicle's current torque value.

[0072] Here, the torque limiting coefficient reflects the degree of torque limitation of the vehicle. The embodiments of this application can calculate the product of the torque limiting coefficient and the vehicle's current torque value, and use this product as a new torque value. Based on this new torque value, the vehicle's operation is controlled to achieve the purpose of torque limitation.

[0073] In this embodiment, the current torque value of the vehicle can be determined by reading the torque output ratio NT. The current torque value of the vehicle is TC = NT × K1. Where K1 represents the torque reference value of the vehicle. The torque reference value varies for different vehicles. For example, when NT = 20% and K1 = 880 Nm, the current torque value of the vehicle is TC = 20% × 880 = 176 Nm.

[0074] To avoid frequent changes in vehicle torque that could affect driving smoothness, the embodiments of this application can periodically execute the aforementioned vehicle torque limiting method. That is, in each control cycle, the current torque value of the vehicle is obtained, and a corresponding torque limiting coefficient is determined based on the current operating conditions; based on the torque limiting coefficient and the current torque value, an updated torque value is calculated, and the vehicle is controlled with the updated torque value.

[0075] For example, the duration of the control cycle can be 10ms, that is, the above-mentioned vehicle torque limiting method is executed once every 10ms to ensure timely torque limiting response and smooth control process.

[0076] This application, when the wheel speed value of any wheel fails, can determine the axle wheel speed difference based on the vehicle's driving state and the transmission output shaft speed, avoiding the predicament of being unable to calculate the wheel speed difference due to wheel speed sensor failure or removal. Based on this, a torque limiting coefficient is obtained according to the wheel speed difference, vehicle driving state, and differential shim data, allowing the torque limiting coefficient to be adjusted specifically based on the shim data. Finally, closed-loop torque limiting control is achieved based on the torque limiting coefficient and the current torque value. Thus, even under abnormal wheel speed signals, the torque limiting strategy can still be activated normally, and the torque limiting coefficient matches the differential shim data, achieving closed-loop control and effectively preventing shim burning and crushing, thereby protecting the vehicle differential.

[0077] Next, we will elaborate on the specific implementation process of determining the wheel speed difference on both sides of the axle (i.e., step 202 above).

[0078] The embodiments of this application mainly determine the effective wheel speed value of the wheel with wheel speed failure based on the transmission process between the vehicle's transmission and the wheels, and then determine the wheel speed difference between the two sides of the axle.

[0079] Here, we will first introduce the transmission structure between the gearbox and the wheels.

[0080] The vehicle's internal transmission structure is related to the vehicle's driving state. Vehicle driving states include: two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive.

[0081] Two-wheel drive configurations can include front-wheel drive and rear-wheel drive. See also Figure 4When the vehicle is in rear-wheel drive mode, the output shaft of the transmission is connected to the rear drive axle via the rear drive shaft, and then to the left and right rear wheels. The rear drive axle mainly includes a final drive, a differential, a left half-shaft, and a right half-shaft. The final drive consists of a driving gear and a driven gear. The differential includes a differential housing, planetary shafts, planetary gears, and half-shaft gears. See also... Figure 5 The output shaft of the transmission (not shown in the figure) drives the drive gear 1 via the rear drive shaft, and the drive gear 1 meshes with and drives the driven gear 2. The driven gear 2 is fixedly connected to the differential housing 3 to transmit torque. A planetary shaft 4 is installed inside the differential housing 3. Planetary gears 5 are mounted on the planetary shaft 4. The planetary gears 5 mesh with the left and right half-shaft gears 6 on both sides. The planetary gears 5 synchronously drive the left and right half-shaft gears 6 on both sides to drive the corresponding left and right half-shafts (not shown in the figure), thereby driving the left and right rear wheels to rotate. Similarly, when the vehicle is in front-wheel drive mode, the output shaft of the transmission in the vehicle is connected to the front drive axle via the front drive shaft, and then connected to the left and right front wheels to drive the left and right front wheels to rotate.

[0082] When the vehicle is in high-speed four-wheel drive or low-speed four-wheel drive mode, see [link / reference]. Figure 6 The transmission's output shaft is connected to the front and rear drive axles via the front and rear drive shafts, respectively, and then to the left and right front and rear wheels. The front and rear drive axles are symmetrically structured, each including a final drive, differential, left half-shaft, and right half-shaft. The final drive consists of a drive gear and a driven gear meshing together; the differential includes a differential housing, planetary shafts, planetary gears, and half-shaft gears.

[0083] The transmission output shaft synchronously drives the front and rear drive shafts via the transfer case. The front drive shaft drives the front drive axle, which in turn rotates the left and right front wheels. The rear drive shaft drives the rear drive axle, which in turn rotates the left and right rear wheels. See the above for details of the drive process. Figure 5 The description will not be repeated here.

[0084] In some embodiments, the differential housing speed can be obtained first based on the transmission output shaft speed, vehicle driving state, and vehicle final reduction ratio; then, the speed difference between the left and right front wheels can be determined based on the differential housing speed and the effective wheel speed of the front wheels, and / or the speed difference between the left and right rear wheels can be determined based on the differential housing speed and the effective wheel speed of the rear wheels.

[0085] As can be seen from the above transmission structure, in two-wheel drive mode, the transmission output shaft speed is transmitted to the differential housing via the final drive. In high-speed four-wheel drive and low-speed four-wheel drive modes, the transmission output shaft speed is transmitted to the differential housing via the transfer case and the final drive. Therefore, the embodiment of this application can obtain the differential housing speed based on the transmission output shaft speed, the vehicle driving state, and the vehicle's final drive ratio.

[0086] When any wheel speed value fails, this application uses the transmission output shaft speed, vehicle driving state, and final drive ratio to calculate the differential housing speed, and then combines the effective wheel speed value to determine the wheel speed difference on both sides of the axle. This allows the wheel speed difference on both sides of the axle to be reliably determined even when the wheel speed sensor is abnormal, so that the torque limiting strategy is not affected by sensor failure, and the robustness and integrity of the torque limiting strategy under abnormal operating conditions are improved.

[0087] Here, if the wheel speed of any front wheel fails, but the wheel speeds of both rear wheels are valid, the wheel speed of the failed front wheel can be calculated based on the differential housing speed and the valid wheel speed of the other front wheel. This wheel speed is then designated as the valid wheel speed of the failed front wheel, and the speed difference between the left and right front wheels can be calculated. The speed difference between the left and right rear wheels can be calculated based on the valid wheel speeds of the left and right rear wheels sent by the ESP.

[0088] If the wheel speed of any rear wheel fails, but the wheel speeds of both front wheels are valid, the wheel speed of the failed rear wheel can be estimated based on the differential housing speed and the valid wheel speed of the other rear wheel. This wheel speed is then designated as the valid wheel speed of the failed rear wheel, and the speed difference between the left and right rear wheels can be calculated. The speed difference between the left and right front wheels can be calculated based on the valid wheel speeds of the left and right front wheels transmitted by the ESP.

[0089] If the wheel speed of any rear wheel fails, and the wheel speed of any front wheel also fails, the wheel speed of the failed front wheel can be estimated based on the differential housing speed and the effective wheel speed of the other front wheel. This wheel speed is then designated as the effective wheel speed of the failed front wheel, and the speed difference between the left and right front wheels can be calculated. Similarly, the wheel speed of the failed rear wheel can be estimated based on the differential housing speed and the effective wheel speed of the other rear wheel. This wheel speed is then designated as the effective wheel speed of the failed rear wheel, and the speed difference between the left and right rear wheels can be calculated.

[0090] The specific method for determining the differential housing speed is as follows: If the vehicle is in two-wheel drive or high-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio.

[0091] When the vehicle is in two-wheel drive mode, only the front or rear drive axle is operational. The transmission output shaft speed is transmitted to the differential housing in the drive axle via a rotating shaft and the final drive reduction gear in the drive axle. Therefore, in the embodiments of this application, the ratio of the transmission output shaft speed to the final drive reduction ratio can be determined as the differential housing speed. The final drive reduction ratio refers to the speed ratio of the final drive.

[0092] When the vehicle is in high-speed four-wheel drive mode, both the front and rear drive axles are operational. The transmission output shaft speed is transmitted to the differential housing in the front drive axle via the transfer case, front rotating shaft, and final drive in the front drive axle. Furthermore, the transmission output shaft speed is also transmitted to the differential housing in the rear drive axle via the transfer case, rear rotating shaft, and final drive in the rear drive axle.

[0093] It should be noted that the speed ratio of the final drive reduction gear in the front drive axle is the same as that in the rear drive axle, and the transfer case synchronously transmits the transmission output shaft speed to the front and rear drive shafts at a 1:1 ratio. The differential housing speed in the front drive axle is always equal to that in the rear drive axle. Based on this, the ratio of the transmission output shaft speed to the final drive reduction ratio can be determined as the differential housing speed, which applies to both the front and rear drive axles.

[0094] If the vehicle is in low-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio and the transfer case low-speed four-wheel drive ratio.

[0095] When the vehicle is in low-speed four-wheel drive mode, both the front and rear drive axles are engaged. The transfer case switches to the low-speed gear set, reducing the speed of the transmission output shaft and simultaneously increasing torque. The transfer case's low-speed four-wheel drive ratio (denoted as i1) reflects the degree of deceleration; that is, the speed output from the transfer case to the drive shaft is 1 / i1 of the transmission output shaft speed, and the front and rear drive shaft speeds remain synchronized at a 1:1 ratio. The final drive ratios of the front and rear drive axles are the same. Therefore, the differential housings in the front and rear drive axles rotate at the same speed, determined by the transmission output shaft speed, the transfer case's low-speed four-wheel drive ratio, and the final drive ratio.

[0096] Specifically, calculate the product of the transfer case's low-speed four-wheel drive ratio and the final drive ratio. Then, calculate the ratio of the transmission output shaft speed to this product, which is the differential housing speed.

[0097] This application differentiates the differential housing speed determination method based on the vehicle's driving state, ensuring that the calculated differential housing speed matches the actual drivetrain deceleration characteristics. Based on this, the wheel speed difference between the two sides of the axle under different vehicle driving states can be accurately calculated, providing reliable input for torque limiting strategies.

[0098] According to the kinematic formula of the differential, in each drive axle, the following condition holds true: 2 × differential housing speed = left wheel speed + right wheel speed, and the differential housing speeds in the front and rear drive axles are equal. That is, 2 × differential housing speed = left front wheel speed + right front wheel speed = left rear wheel speed + right rear wheel speed.

[0099] Based on the determination of the differential housing speed, this embodiment of the application can combine the effective values ​​of the front wheel speed and the effective values ​​of the rear wheel speed to determine the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels.

[0100] Specifically, if the wheel whose wheel speed fails is any front wheel, the effective wheel speed of the front wheel whose wheel speed fails is determined based on the differential housing rotation speed and the effective wheel speed of the other front wheel; and the speed difference between the left and right front wheels is determined based on the difference between the effective wheel speeds of each front wheel.

[0101] For any front wheel whose wheel speed fails, the effective wheel speed value of that front wheel can be expressed as: Effective wheel speed value = [(2×OSS) / i2 - Effective wheel speed value of the other front wheel]. Based on this, the speed difference between the left and right front wheels can be determined as: Speed ​​difference between the left and right front wheels = |[(2×OSS) / i2] - 2× Effective wheel speed value of the other front wheel|.

[0102] In the formula, i2 represents the final drive ratio, and OSS represents the output shaft speed of the transmission.

[0103] If the wheel whose wheel speed fails is any of the rear wheels, then the effective wheel speed of the rear wheel whose wheel speed fails is determined based on the differential housing rotation speed and the effective wheel speed of the other rear wheel; and the speed difference between the left and right rear wheels is determined based on the difference between the effective wheel speeds of each rear wheel.

[0104] For any rear wheel whose wheel speed fails, the effective wheel speed value of that rear wheel can be expressed as [(2×OSS) / i2 - the effective wheel speed value of the other rear wheel]. Based on this, the speed difference between the left and right rear wheels can be determined as: speed difference between the left and right rear wheels = |[(2×OSS) / i2] - 2× the effective wheel speed value of the other rear wheel|.

[0105] Here, wheel speed sensors can collect the distance traveled by the wheel per unit time to determine the wheel speed. For example, if the wheel travels 100 km / h, the wheel speed is 100 km / h. Alternatively, wheel speed sensors can also collect the number of radians the wheel rotates per unit time to determine the wheel speed. For example, if the wheel rotates 50 radians per second, the wheel speed is 50 rad / s. km / h reflects the linear velocity of the tire, while rad / s reflects the angular velocity. Angular velocity and linear velocity can be converted between each other using the tire radius. For example, when the wheel speed is 100 km / h and the tire radius is 0.35 m, the angular velocity is: 100 / (0.35 × 3.6) = 79.4 rad / s.

[0106] To avoid conversion errors caused by inconsistent units of measurement, this embodiment can pre-obtain the rotation radius of the transmission output shaft and convert the transmission output shaft speed from (rad / s) to (km / h) based on this rotation radius before calculating the difference in speed between the left and right wheels. For example, this embodiment uses km / h as the unit of measurement for wheel speed and wheel speed difference.

[0107] It should be noted that when the vehicle is in two-wheel drive mode, only the front or rear drive axle is active. If the vehicle is in front-wheel drive mode, only the front drive axle is active; the left and right rear wheel speed difference does not activate the vehicle's torque limiting strategy, and the rear wheel speed is ineffective, having no impact on the vehicle's torque limiting. If the vehicle is in rear-wheel drive mode, only the rear drive axle is active; the left and right front wheel speed difference does not activate the vehicle's torque limiting strategy, and the front wheel speed is ineffective, having no impact on the vehicle's torque limiting.

[0108] When a single front or rear wheel fails, this application uses the differential housing rotation speed and the effective wheel speed on the other side of the same axle to infer the wheel speed value of the failed wheel, thereby determining the left and right wheel speed difference of the axle. This ensures that even if the wheel speed signal of any wheel is lost, the wheel speed difference between the two sides of the corresponding axle can still be determined, ensuring the normal triggering of the vehicle torque limiting strategy.

[0109] Based on the determination of the wheel speed difference on both sides of the axle, this application determines the torque limiting coefficient based on the wheel speed difference on both sides of the axle, the vehicle driving state, and the internal shim data of the differential, thereby achieving the purpose of limiting vehicle torque.

[0110] Here, the data for the internal gaskets of the differential includes the maximum heat load that the internal gaskets of the differential can withstand (referred to as the TV value in this embodiment). The TV value reflects the maximum heat load that the gasket can withstand. The TV value is an inherent value of the internal gaskets of the differential, and the amount of heat the gasket can withstand is directly related to the TV value: the larger the TV value, the more heat the gasket can withstand. If the heat cannot be dissipated in time, it will cause the gasket temperature to rise, which may lead to lubrication failure, material softening or even melting, ultimately causing wear or seizing. The TV value of the gasket can be obtained through bench / vehicle testing. For example, the bench test process can be briefly described as follows: In bench tests, by applying different driving torques to the input end of the differential and controlling the left and right half-shaft gears to produce different speed differences, the critical driving torque and critical speed difference when the shim is burned and crushed are monitored, and the product of the critical driving torque and critical speed difference is determined as the TV value of the shim.

[0111] Here, the unit for calculating the rotational speed of the half-shaft gear can be rad / s, and correspondingly, the unit for calculating the critical gear speed difference can also be rad / s. The unit for calculating the critical driving torque can be Nm. The TV value is the product of the critical driving torque and the critical speed difference, and its unit is watts (W).

[0112] In this embodiment, the internal gaskets of the differential refer to a pair of gaskets installed inside the differential, one between the left half-shaft gear and the differential housing, and the other between the right half-shaft gear and the differential housing. Since the differential has a symmetrical left-right structure and the gaskets on both sides are of the same specification, in this embodiment, the TV value of a single gasket is used to refer to the aforementioned internal gasket data.

[0113] The torque limiting strategy in related technologies is only triggered when the wheel speed difference between the two sides of the axle is greater than a set threshold. However, it ignores the problem that when the wheel speed difference is small but the current torque value of the vehicle is too large, the differential will also burn out due to excessive heat power.

[0114] To address this, the embodiments of this application employ different calculation methods to determine the torque limiting coefficient based on whether the wheel speed difference between the two sides of the axle is greater than a first preset wheel speed difference threshold. This enables closed-loop torque limiting to be achieved under different wheel speed differences, thereby covering the torque limiting blind spot of related technologies under small wheel speed difference and large torque conditions. This achieves comprehensive consideration of the differential sintering risk under large and small wheel speed difference conditions.

[0115] In some embodiments, the torque limiting coefficient is determined under small wheel speed difference conditions as follows: If the wheel speed difference between the two sides of the axle is less than the first preset wheel speed difference threshold, the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state; when the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined according to the ratio of the maximum heat load value to the current heat load value.

[0116] When the vehicle is in rear-wheel drive mode, if the speed difference between the left and right rear wheels is less than a first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be less than the first preset wheel speed difference threshold. Conversely, if the speed difference between the left and right rear wheels is greater than or equal to the first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be greater than or equal to the first preset wheel speed difference threshold. When the vehicle is in front-wheel drive mode, if the speed difference between the left and right front wheels is less than the first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be less than the first preset wheel speed difference threshold. Conversely, if the speed difference between the left and right front wheels is greater than or equal to the first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be greater than or equal to the first preset wheel speed difference threshold.

[0117] When the vehicle is in high-speed four-wheel drive or low-speed four-wheel drive mode, first determine the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels. If this maximum value is less than a first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be less than the first preset wheel speed difference threshold. Conversely, if this maximum value is greater than or equal to the first preset wheel speed difference threshold, then the wheel speed difference between the two sides of the axle is determined to be greater than or equal to the first preset wheel speed difference threshold.

[0118] Here, the first preset wheel speed difference threshold is a scalable quantity that can be determined according to actual conditions, and this embodiment does not impose a specific limitation on it. For example, the first preset wheel speed difference threshold can be 100km / h.

[0119] This embodiment calculates the current thermal load value of the differential when the wheel speed difference is small, and then triggers torque limiting, solving the problem that the gasket is also at risk of burning under small wheel speed difference and high torque conditions. When the thermal load exceeds the limit, the torque limiting coefficient is dynamically determined based on the ratio of the limit value to the actual value, realizing precise protection based on the physical tolerance limit of the gasket itself, and avoiding the problem of insufficient protection under small wheel speed difference and high torque conditions.

[0120] The current thermal load value of the differential (i.e., the current thermal load value borne by the gasket) is determined by the torque transmitted to the half-shaft gear and the wheel speed difference on both sides of the axle. The torque transmission process is affected by the vehicle's driving state. Based on this, this embodiment can determine the torque transmitted to the half-shaft gear based on the vehicle's current torque value and driving state, and then determine the current thermal load value by multiplying the torque of the half-shaft gear and the wheel speed difference on both sides of the axle.

[0121] Next, we will introduce the methods for determining the current heat load value for different vehicle driving states.

[0122] If the vehicle is in two-wheel drive mode, the current heat load value is determined based on the product of the speed difference between the left and right rear wheels or the speed difference between the left and right front wheels, the vehicle's current torque value, the final drive ratio, and the vehicle's transmission ratio.

[0123] When the vehicle is in rear-wheel drive mode, the input torque of the transmission is the current torque value TC of the vehicle. After being increased by the transmission ratio i3, the output torque of the transmission is obtained as TC×i3. The output torque of the transmission is transmitted to the rear drive axle final drive via the drive shaft. After being further amplified by the final drive ratio i2, the total input torque of the differential housing is obtained as TC×i3×i2. The differential distributes the total input torque of the housing evenly to the left and right half-shaft gears, thus determining that the torque of the left half-shaft gear = the torque of the right half-shaft gear = (TC×i3×i2) / 2.

[0124] Based on this, the current heat load value under rear-wheel drive condition can be determined as (TC×Vr×i3×i2) / 2. Where i3 represents the transmission gear ratio, i2 represents the final drive ratio, and Vr represents the speed difference between the left and right rear wheels.

[0125] Similarly, the current heat load value of the vehicle in front-wheel drive mode = (TC × Vf × i3 × i2) / 2. Where Vf represents the speed difference between the left and right front wheels.

[0126] If the vehicle is in high-speed four-wheel drive mode, determine the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels, and determine the current heat load value based on the product of the maximum value, the final drive ratio, and the transmission ratio.

[0127] When the vehicle is in high-speed four-wheel drive mode, the transfer case synchronously and evenly distributes the transmission output torque TC×i3 to the front and rear drive axles. Therefore, the input torque of the final drive reducer on each drive axle is (TC×i3) / 2. After being amplified by the final drive reduction ratio i2, the total input torque of the single-axle differential housing is (TC×i3×i2) / 2. The differential then distributes this torque evenly to the half-shaft gears on both sides, with the torque of each half-shaft gear being (TC×i3×i2) / 4.

[0128] Therefore, the current thermal load value under high-speed four-wheel drive condition = (TC × Vmax × i3 × i2) / 4. Among them, Vmax is the maximum value of the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels, so as to ensure that the torque limiting strategy can respond in a timely manner to the slippage conditions of either the front drive axle or the rear drive axle.

[0129] If the vehicle is in low-speed four-wheel drive mode, determine the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels, and determine the current heat load value based on the product of the maximum value, the final drive ratio, the transmission ratio, and the transfer case low-speed four-wheel drive ratio of the vehicle.

[0130] When the vehicle is in low-speed four-wheel drive mode, the transfer case switches to the lower gear set, amplifying the output torque of the transmission. The amplified torque is then synchronously and evenly distributed to the front and rear drive axles.

[0131] The input torque of the transmission is the current torque value TC of the vehicle. After being increased by the transmission ratio i3, the output torque of the transmission is TC×i3. The transmission output torque enters the transfer case and is further amplified by the transfer case's low-speed four-wheel drive ratio i1, resulting in a total transfer case output torque of TC×i3×i1. The transfer case synchronously and evenly distributes this total torque to the front and rear drive axles, so the input torque of the final drive reducer on each drive axle is (TC×i3×i1) / 2. After being further amplified by the final drive reduction ratio i2, the total input torque of the single-axle differential housing is (TC×i3×i1×i2) / 2. The differential evenly distributes the total input torque of the housing to the left and right half-shaft gears, resulting in a torque of (TC×i3×i1×i2) / 4 for each half-shaft gear.

[0132] Therefore, the current thermal load value under low-speed four-wheel drive condition = (TC × Vmax × i3 × i1 × i2) / 4. Similarly, Vmax is taken as the maximum value between the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels to ensure that the torque limiting strategy can respond in a timely manner to unilateral slippage conditions of the front or rear axle.

[0133] To maintain consistent units of measurement, this embodiment pre-converts the units of the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels to rad / s based on the tire radius when calculating the current heat load value. The unit of the current heat load value is watts. Here, i1, i2, and i3 are dimensionless parameters.

[0134] This embodiment distinguishes the calculation method of the current heat load value according to the vehicle driving state, which can ensure that the calculation of the current heat load value strictly corresponds to the torque distribution ratio and transmission amplification link under each driving state, ensuring that the heat load assessment of the differential shim is true and accurate under all operating conditions, and providing a reliable triggering basis for the torque limiting strategy.

[0135] Based on the current heat load value, this embodiment further determines the torque limiting coefficient to trigger vehicle torque limiting.

[0136] See Figure 7 When the vehicle is in rear-wheel drive mode, if the current heat load value is greater than the maximum heat load value TV, this embodiment determines the torque limiting coefficient based on the ratio of the maximum heat load value to the current heat load value, and introduces a safety factor a1. The torque limiting coefficient λ is less than 1, and the larger the current heat load value, the smaller λ is, so as to limit the heat load after torque limiting to below the TV value. The torque limiting coefficient can be expressed as: λ=(TV×a1) / [(TC×Vr×i2×i3) / 2]. In the formula, λ represents the torque limiting coefficient, which is dimensionless, and a1 represents the first safety factor, which is dimensionless. a1 is a scalable quantity. For example, a1 can be 0.95 to reserve a certain safety margin for heat load and prevent the gasket from overheating due to control overshoot.

[0137] Based on the determined torque limiting coefficient, the product of the torque limiting coefficient and the current torque value can be calculated to obtain the new torque value. Tlimit = TC × λ = (2 × TV × a1) / (Vr × i2 × i3). The new torque value is used as the current torque value TC for the next control cycle, and the next cycle is determined accordingly. For example, the duration of each control cycle is 10 ms. Here, the unit of calculation for the new torque value Tlimit and the current torque value TC is both Nm.

[0138] Similar to rear-wheel drive, when the vehicle is in front-wheel drive mode, the torque limiting coefficient can be expressed as: λ = (TV × a1) / [(TC × Vf × i2 × i3) / 2]. Based on this, when the vehicle is in front-wheel drive mode, the new torque value is: Tlimit = TC × λ = (2 × TV × a1) / (Vf × i2 × i3).

[0139] Understandably, if the current heat load value is less than or equal to the maximum heat load value TV, the torque limiting strategy will be exited, and the current torque value will still be maintained to control the vehicle operation.

[0140] See Figure 8 When the vehicle is in high-speed four-wheel drive mode, this embodiment takes the maximum value Vmax between the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels to calculate the current heat load value. If the current heat load value is greater than the maximum heat load value TV, the torque limiting coefficient can be expressed as: λ=(TV×a1) / [(TC×Vmax×i2×i3) / 4].

[0141] Based on the determined torque limiting coefficient, the product of the torque limiting coefficient and the current torque value can be calculated to obtain a new torque value: Tlimit = TC × λ = (4 × TV × a1) / (Vmax × i2 × i3). The new torque value is used as the current torque value TC for the next cycle, and the judgment for the next cycle is performed.

[0142] Similarly, if the current heat load value is less than or equal to the maximum heat load value TV, the torque limiting strategy will be exited, and the current torque value will still be maintained to control the vehicle operation.

[0143] See Figure 9 When the vehicle is in low-speed four-wheel drive mode, this embodiment takes the maximum value Vmax between the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels to calculate the current heat load value. If the current heat load value is greater than the maximum heat load value TV, the torque limiting coefficient can be expressed as: λ=(TV×a1) / [(TC×Vmax×i1×i2×i3) / 4].

[0144] Based on the determined torque limiting coefficient, the product of the torque limiting coefficient and the current torque value can be calculated to obtain a new torque value: T_limit = TC × λ = (4 × TV × a1) / (Vmax × i1 × i2 × i3). The new torque value is used as the current torque value TC for the next cycle, and the judgment for the next cycle is performed.

[0145] Similarly, if the current heat load value is less than or equal to the maximum heat load value TV, the torque limiting strategy will be exited, and the current torque value will still be maintained to control the vehicle operation.

[0146] In some embodiments, the method for determining the torque limiting coefficient under large wheel speed difference conditions is as follows: If the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state; when the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined according to the ratio of the maximum heat load value to the current heat load value.

[0147] See Figure 10When the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, and the vehicle is in rear-wheel drive mode, if the current heat load value is greater than the maximum heat load value TV, the torque limiting coefficient can be expressed as: λ=(TV×a2) / [(TC×Vr×i2×i3) / 2]. In the formula, a2 represents the second safety factor, which is dimensionless and scalable, a2<a1. For example, a2 can be 0.5. It is understood that when the wheel speed difference is large, a larger safety margin can be reserved to prevent gasket overheating failure caused by control delay or model deviation.

[0148] Based on the determined torque limiting coefficient, the new torque value can be expressed as: Tlimit = TC × λ = (2 × TV × a2) / (Vr × i2 × i3). The new torque value is used as the current torque value TC for the next cycle, and the determination for the next cycle is made.

[0149] Similar to rear-wheel drive, when the vehicle is in front-wheel drive mode, the torque limiting coefficient can be expressed as: λ = (TV × a2) / [(TC × Vf × i2 × i3) / 2]. Based on this, when the vehicle is in front-wheel drive mode, the new torque value is: Tlimit = TC × λ = (2 × TV × a2) / (Vf × i2 × i3).

[0150] See Figure 11 When the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, and the vehicle is in high-speed four-wheel drive mode, if the current heat load value is greater than the maximum heat load value TV, the torque limiting coefficient can be expressed as: λ=(TV×a2) / [(TC×Vmax×i2×i3) / 4]. The new torque value can be expressed as: Tlimit=TC×λ=(4×TV×a2) / (Vmax×i2×i3). The new torque value is used as the current torque value TC for the next cycle, and the judgment is made for the next cycle. If the current heat load value is less than or equal to the maximum heat load value TV, the high-speed torque limiting strategy is activated.

[0151] See Figure 12 When the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, and the vehicle is in low-speed four-wheel drive mode, if the current heat load value is greater than the maximum heat load value TV, the torque limiting coefficient can be expressed as: λ=(TV×a2) / [(TC×Vmax×i1×i2×i3) / 4]. The new torque value can be expressed as: Tlimit=TC×λ=(4×TV×a2) / (Vmax×i1×i2×i3). The new torque value is used as the current torque value TC for the next cycle for judgment in the next cycle.

[0152] When the wheel speed difference is large (the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold), it indicates that the wheels have slipped significantly. At this time, the wheels cannot provide effective driving force for the vehicle when spinning freely. Instead, the gaskets inside the differential remain in a state of high slippage, and the rate of heat load accumulation is significantly accelerated.

[0153] Therefore, see Figures 10-12 Even if the current heat load value has not exceeded the maximum heat load value, this embodiment still implements a high-speed torque limiting strategy, thereby proactively limiting the vehicle's torque output in advance to control the rate of increase in heat load. This reduces the risk of instantaneous overheating and erosion of the gaskets under transient impact, achieving preventative protection for the differential. Furthermore, it avoids wheel spin and wasted power.

[0154] The high-speed torque limiting strategy is as follows: When the current heat load is less than or equal to the maximum heat load, a wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference between the two sides of the axle. A time torque limiting coefficient is obtained based on the wheel speed difference between the two sides of the axle and a second preset wheel speed difference threshold. The torque limiting coefficient is then determined based on the wheel speed difference torque limiting coefficient and the time torque limiting coefficient. The second preset wheel speed difference threshold is greater than the first preset wheel speed difference threshold. Here, both the wheel speed difference torque limiting coefficient and the time torque limiting coefficient are dimensionless parameters.

[0155] In some embodiments, a preset first lookup table can be obtained, and the wheel speed difference torque limiting coefficient can be obtained based on the wheel speed difference between the two sides of the axle and the first lookup table. The first lookup table contains different wheel speed differences between the two sides of the axle and the corresponding wheel speed difference torque limiting coefficients. The wheel speed difference torque limiting coefficient is less than 1.

[0156] It should be noted that when the vehicle is in rear-wheel drive mode, the wheel speed difference between the two sides here specifically refers to the speed difference between the left and right rear wheels. When the vehicle is in front-wheel drive mode, the wheel speed difference between the two sides here specifically refers to the speed difference between the left and right front wheels. When the vehicle is in high-speed four-wheel drive or low-speed four-wheel drive mode, the wheel speed difference between the two sides here specifically refers to the maximum value of the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels.

[0157] The greater the wheel speed difference between the two sides of the axle, the faster the relative slippage speed of the gasket, and the higher the risk of ablation and crushing. Correspondingly, a smaller wheel speed difference torque limiting coefficient should be used to limit the overall vehicle torque output, thereby reducing the real-time thermal load on the gasket and effectively controlling the risk of ablation and crushing. Therefore, this embodiment limits the wheel speed difference to a larger value, and the smaller the corresponding wheel speed difference torque limiting coefficient.

[0158] To achieve smooth, stepless torque limiting control of the continuously changing wheel speed difference between the two sides of the axle, this embodiment pre-defines a first lookup table. This table records several discrete wheel speed differences between the two sides of the axle and their corresponding wheel speed difference torque limiting coefficients. After obtaining the actual wheel speed difference between the two sides of the axle, an interpolation method can be used to perform linear interpolation between two adjacent discrete points in the first lookup table to determine the wheel speed difference torque limiting coefficients.

[0159] For example, the first query table can be:

[0160] For example, if the wheel speed difference between the two sides of the axle is 120 km / h, the corresponding wheel speed difference torque limiting coefficient can be determined by interpolation: 0.95 + (0.9 - 0.95) × (120 - 110) / (130 - 110) = 0.925.

[0161] This embodiment establishes a mapping relationship between the wheel speed difference on both sides of the axle and the wheel speed difference torque limiting coefficient, so that the torque limiting force can be smoothly adjusted according to the degree of slippage, thus protecting the differential while ensuring driving smoothness.

[0162] The torque limiting coefficient determined solely by the wheel speed difference can only characterize and respond to the instantaneous sliding wear intensity borne by the gasket. However, the ablation failure of the gasket is the result of the continuous accumulation of frictional heat over time. Even if the instantaneous heat load does not exceed the limit, if the high sliding wear condition continues for a long time, the heat accumulation may still lead to the gasket overheating and failure.

[0163] To address the aforementioned physical defects, this application further introduces a time-limited torque coefficient. This coefficient is dynamically determined based on the duration for which the wheel speed difference remains greater than a threshold. The time-limited torque coefficient and the wheel speed difference torque coefficient together constitute a two-dimensional protection mechanism capable of simultaneously responding to both instantaneous slippage intensity and continuous slippage duration, achieving more comprehensive and precise control over the thermal risk of the gasket.

[0164] The method for determining the time-limit torque coefficient is as follows: When the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold, the duration for which the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold is accumulated; a preset second lookup table is obtained; and based on the duration and the second lookup table, the time limit torque coefficient is obtained.

[0165] Here, the second preset wheel speed difference threshold is greater than the first preset wheel speed difference threshold, used to define a high-speed slippage state. When the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold, it is determined that the gasket is experiencing high-intensity slippage with a significant risk of heat accumulation. The second preset wheel speed difference threshold is scalable and can be determined according to actual conditions. For example, the second preset wheel speed difference threshold can be 150 km / h.

[0166] This embodiment can monitor the wheel speed difference between the two sides of the axle in real time. When the wheel speed difference is greater than or equal to a second preset wheel speed difference threshold, a timer is started to accumulate the duration of the high slippage state. Conversely, when the wheel speed difference is less than a third preset wheel speed difference threshold, it indicates that the high slippage risk has been temporarily relieved, and the duration is reset to zero.

[0167] The third preset wheel speed difference threshold is less than the second preset wheel speed difference threshold. The third preset wheel speed difference threshold is a scalable quantity and can be determined according to actual conditions. For example, the third preset wheel speed difference threshold can be 110 km / h.

[0168] Based on the determined duration, this embodiment determines the time limit torque coefficient according to the duration and a second lookup table. The second lookup table contains different durations and their corresponding time limit torque coefficients; the longer the duration, the smaller the corresponding time limit torque coefficient; the time limit torque coefficient is less than or equal to 1.

[0169] For example, the second lookup table can be represented as:

[0170] This embodiment obtains the time-limiting torque coefficient by looking up a table based on the duration of the friction, thereby gradually tightening the torque limit as the friction time increases. This overcomes the shortcomings of the simple wheel speed difference coefficient, which only reflects the instantaneous intensity and cannot take into account the heat accumulation effect. It constructs a dual-layer protection mechanism of friction intensity and duration, effectively preventing the gasket from slowly overheating and failing due to continuous friction.

[0171] Based on the determination of the time-limited torque coefficient and the wheel speed difference torque coefficient, this embodiment can determine the final torque limit coefficient by multiplying the time-limited torque coefficient and the wheel speed difference torque coefficient. Then, based on the product of this torque limit coefficient and the current torque value of the vehicle, a new torque value is determined, and the vehicle operation is controlled according to the new torque value.

[0172] In this embodiment, during the transition range with large wheel speed differences but where the current heat load value has not yet exceeded the limit, a two-factor mechanism of wheel speed difference torque limiting coefficient and time torque limiting coefficient is introduced. The wheel speed difference coefficient responds instantly to the slippage intensity, while the time coefficient progressively tightens the torque limiting based on the duration of high slippage. The combination of the two achieves preventive suppression of the gasket heat accumulation effect, taking into account both power maintenance during brief slippage and progressive protection during continuous slippage, eliminating the risk of ablation failure due to response lag.

[0173] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0174] Figure 13 This is a schematic diagram of the structure of a vehicle torque limiting device provided in one embodiment of this application. Figure 13 As shown, the vehicle torque limiting device provided in this embodiment may include: an acquisition module 131, a torque limiting module 132, and a control module 133.

[0175] The acquisition module 131 is used to acquire the transmission output shaft speed and vehicle driving status if the wheel speed of any wheel fails.

[0176] Torque limiting module 132 is used for: Determine the wheel speed difference between the two sides of the vehicle axle based on the transmission output shaft speed and the vehicle driving state; The torque limiting coefficient is obtained based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's differential.

[0177] The control module 133 is used to perform torque limiting control on the vehicle based on the torque limiting coefficient and the current torque value of the vehicle.

[0178] Optionally, the wheel speed difference between the two sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels; Torque limiting module 132 is specifically used for: The differential housing speed is obtained based on the transmission output shaft speed, vehicle driving state, and vehicle final reduction ratio. The speed difference between the left and right front wheels is determined based on the differential housing speed and the effective value of the front wheel speed, and / or the speed difference between the left and right rear wheels is determined based on the differential housing speed and the effective value of the rear wheel speed.

[0179] Optionally, the vehicle driving status includes two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive. Torque limiting module 132 is specifically used for: If the vehicle is in two-wheel drive or high-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio. If the vehicle is in low-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio and the transfer case low-speed four-wheel drive ratio.

[0180] Optional, torque limiting module 132, specifically used for: If the wheel whose wheel speed has failed is any of the front wheels, then the effective wheel speed of the front wheel whose wheel speed has failed is determined based on the differential housing rotation speed and the effective wheel speed of the other front wheel. The speed difference between the left and right front wheels is determined based on the difference in the effective values ​​of the wheel speeds of each front wheel. Based on the differential housing rotational speed and the effective value of the rear wheel speed, the speed difference between the left and right rear wheels is determined, including: If the wheel whose wheel speed has failed is any of the rear wheels, then the effective wheel speed of the rear wheel whose wheel speed has failed is determined based on the differential housing speed and the effective wheel speed of the other rear wheel. The speed difference between the left and right rear wheels is determined based on the difference in the effective values ​​of the wheel speeds of each rear wheel.

[0181] Optionally, the differential's internal gasket data includes the maximum heat load that the differential's internal gaskets can withstand; Torque limiting module 132 is specifically used for: If the wheel speed difference between the two sides of the axle is less than the first preset wheel speed difference threshold, the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value.

[0182] Optionally, the vehicle driving state includes two-wheel drive, high-speed four-wheel drive and low-speed four-wheel drive, and the wheel speed difference on both sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels. Torque limiting module 132 is specifically used for: If the vehicle is in two-wheel drive mode, the current heat load value is determined based on the product of the speed difference between the left and right rear wheels or the speed difference between the left and right front wheels, the current torque value of the vehicle, the final drive ratio, and the transmission ratio of the vehicle. If the vehicle is in high-speed four-wheel drive mode, determine the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels, and determine the current heat load value based on the product of the maximum value, the final drive ratio, and the transmission ratio. If the vehicle is in low-speed four-wheel drive mode, determine the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels, and determine the current heat load value based on the product of the maximum value, the final drive ratio, the transmission ratio, and the transfer case low-speed four-wheel drive ratio of the vehicle.

[0183] Optionally, the torque limiting module 132 is also used for: If the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, then the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value; When the current heat load value is less than or equal to the maximum heat load value, the wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle, the time torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle and the second preset wheel speed difference threshold, and the torque limiting coefficient is determined according to the wheel speed difference torque limiting coefficient and the time torque limiting coefficient; the second preset wheel speed difference threshold is greater than the first preset wheel speed difference threshold.

[0184] Optional, torque limiting module 132, specifically used for: Obtain the preset first lookup table; the first lookup table contains different wheel speed differences on both sides of the axle and the corresponding wheel speed difference torque limiting coefficient; the larger the wheel speed difference on both sides of the axle, the smaller the corresponding wheel speed difference torque limiting coefficient; the wheel speed difference torque limiting coefficient is less than 1; Based on the wheel speed difference on both sides of the axle and the first lookup table, the wheel speed difference torque limiting coefficient is obtained.

[0185] Optional, torque limiting module 132, specifically used for: When the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold, the cumulative duration of the wheel speed difference between the two sides of the axle being greater than the second preset wheel speed difference threshold is calculated. Obtain the preset second lookup table; the second lookup table contains different durations and corresponding time limit coefficients; the longer the duration, the smaller the corresponding time limit coefficient; the time limit coefficient is less than or equal to 1; Based on the duration and the second lookup table, the time limit coefficient is obtained.

[0186] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0187] Figure 14 This is a schematic diagram of the structure of a vehicle provided in one embodiment of this application. Figure 14 As shown, the vehicle 14 in this embodiment includes a processor 140 and a memory 141, wherein the memory 141 stores a computer program 142 that can run on the processor 140. When the processor 140 executes the computer program 142, it implements the steps in any of the above-described method embodiments, for example... Figure 2 Steps 201-204 are shown. Alternatively, when processor 140 executes computer program 142, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 13 The functions of modules 131-133 are shown.

[0188] For example, computer program 142 may be divided into one or more modules / units, one or more of which are stored in memory 141 and executed by processor 140 to complete this application. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 142 in vehicle 140.

[0189] Those skilled in the art will understand that Figure 14 This is merely an example of a vehicle and does not constitute a limitation on the vehicle. It may include more or fewer components than shown, or combinations of certain components, or different components, such as input / output devices, network access devices, buses, etc.

[0190] The processor 140 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0191] The memory 141 can be an internal storage unit of the vehicle, such as a hard drive or memory, or an external storage device, such as a plug-in hard drive, smart media card (SMC), secure digital (SD) card, flash card, etc. The memory 141 can also include both internal and external storage devices. The memory 141 is used to store computer programs and other programs and data required by the vehicle. The memory 141 can also be used to temporarily store data that has been output or will be output.

[0192] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0193] An embodiment of this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described vehicle torque limiting method.

[0194] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0195] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0196] In the embodiments provided in this application, it should be understood that the disclosed devices / vehicles and methods can be implemented in other ways. For example, the device / vehicle embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0197] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0198] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0199] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0200] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for limiting torque in a vehicle, characterized in that, include: If the wheel speed of any wheel fails, the transmission output shaft speed and vehicle driving status of the vehicle are obtained. The wheel speed difference between the two sides of the vehicle axle is determined based on the output shaft speed of the transmission and the driving state of the vehicle. Based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the differential in the vehicle, the torque limiting coefficient is obtained. Based on the torque limiting coefficient and the current torque value of the vehicle, torque limiting control is performed on the vehicle.

2. The vehicle torque limiting method according to claim 1, characterized in that, The wheel speed difference on both sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels; Determining the wheel speed difference between the two sides of the vehicle axle based on the output shaft speed of the transmission and the vehicle driving state includes: The differential housing speed is obtained based on the transmission output shaft speed, the vehicle driving state, and the vehicle's final drive ratio. The speed difference between the left and right front wheels is determined based on the rotational speed of the differential housing and the effective wheel speed of the front wheels, and / or the speed difference between the left and right rear wheels is determined based on the rotational speed of the differential housing and the effective wheel speed of the rear wheels.

3. The vehicle torque limiting method according to claim 2, characterized in that, The vehicle driving states include two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive. The step of obtaining the differential housing speed based on the transmission output shaft speed, the vehicle driving state, and the vehicle's final drive ratio includes: If the vehicle is in two-wheel drive or high-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio. If the vehicle is in low-speed four-wheel drive mode, the differential housing speed is determined based on the ratio of the transmission output shaft speed to the final drive ratio and the transfer case low-speed four-wheel drive ratio of the vehicle.

4. The vehicle torque limiting method according to claim 2, characterized in that, Determining the speed difference between the left and right front wheels based on the rotational speed of the differential housing and the effective wheel speed of the front wheels includes: If the wheel whose wheel speed has failed is any of the front wheels, then the effective wheel speed of the front wheel whose wheel speed has failed is determined based on the rotational speed of the differential housing and the effective wheel speed of the other front wheel. The speed difference between the left and right front wheels is determined based on the difference in the effective values ​​of the wheel speeds of each front wheel; Determining the speed difference between the left and right rear wheels based on the rotational speed of the differential housing and the effective wheel speed of the rear wheels includes: If the wheel whose wheel speed has failed is any of the rear wheels, then the effective wheel speed value of the rear wheel whose wheel speed has failed is determined based on the rotational speed of the differential housing and the effective wheel speed value of the other rear wheel. The speed difference between the left and right rear wheels is determined based on the difference in the effective values ​​of the wheel speeds of each rear wheel.

5. The vehicle torque limiting method according to any one of claims 1 to 4, characterized in that, The data on the internal gaskets of the differential includes the maximum heat load that the internal gaskets of the differential can withstand; The process of obtaining the torque limiting coefficient based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's center differential includes: If the wheel speed difference between the two sides of the axle is less than the first preset wheel speed difference threshold, then the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value.

6. The vehicle torque limiting method according to claim 5, characterized in that, The vehicle driving states include two-wheel drive, high-speed four-wheel drive, and low-speed four-wheel drive; the wheel speed difference on both sides of the axle includes the speed difference between the left and right front wheels and the speed difference between the left and right rear wheels. The determination of the current thermal load value of the vehicle's differential based on the wheel speed difference on both sides of the axle and the vehicle's driving state includes: If the vehicle is in two-wheel drive mode, the current heat load value is determined based on the product of the speed difference between the left and right rear wheels or the speed difference between the left and right front wheels, the current torque value of the vehicle, the final drive ratio, and the transmission ratio of the vehicle. If the vehicle is in high-speed four-wheel drive mode, the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels is determined, and the current heat load value is determined based on the product of the maximum value, the final drive ratio and the transmission ratio. If the vehicle is in low-speed four-wheel drive mode, the maximum value of the speed difference between the left and right rear wheels and the speed difference between the left and right front wheels is determined, and the current heat load value is determined based on the product of the maximum value, the final drive ratio, the transmission ratio, and the transfer case low-speed four-wheel drive ratio of the vehicle.

7. The vehicle torque limiting method according to claim 5, characterized in that, The method of obtaining the torque limiting coefficient based on the wheel speed difference between the two sides of the axle, the vehicle driving state, and the internal shim data of the vehicle's center differential also includes: If the wheel speed difference between the two sides of the axle is greater than or equal to the first preset wheel speed difference threshold, then the current heat load value of the differential in the vehicle is determined based on the wheel speed difference between the two sides of the axle and the vehicle driving state. When the current heat load value is greater than the maximum heat load value, the torque limiting coefficient is determined based on the ratio of the maximum heat load value to the current heat load value. When the current heat load value is less than or equal to the maximum heat load value, a wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle, a time torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle and a second preset wheel speed difference threshold, and the torque limiting coefficient is determined according to the wheel speed difference torque limiting coefficient and the time torque limiting coefficient; the second preset wheel speed difference threshold is greater than the first preset wheel speed difference threshold.

8. The vehicle torque limiting method according to claim 7, characterized in that, The step of obtaining the wheel speed difference limiting torque coefficient based on the wheel speed difference on both sides of the axle includes: Obtain a preset first lookup table; the first lookup table contains different wheel speed differences on both sides of the axle and the corresponding wheel speed difference torque limiting coefficient; the larger the wheel speed difference on both sides of the axle, the smaller the corresponding wheel speed difference torque limiting coefficient; the wheel speed difference torque limiting coefficient is less than 1. The wheel speed difference torque limiting coefficient is obtained based on the wheel speed difference on both sides of the axle and the first lookup table.

9. The vehicle torque limiting method according to claim 7, characterized in that, The step of obtaining the time-limited torque coefficient based on the wheel speed difference on both sides of the axle and a second preset wheel speed difference threshold includes: When the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold, the duration during which the wheel speed difference between the two sides of the axle is greater than the second preset wheel speed difference threshold is accumulated; Obtain a preset second lookup table; the second lookup table contains different durations and corresponding time limit coefficients; the longer the duration, the smaller the corresponding time limit coefficient; the time limit coefficient is less than or equal to 1; Based on the duration and the second lookup table, the time limit torque coefficient is obtained.

10. A vehicle comprising a memory and a processor, the memory storing a computer program executable on the processor, characterized in that, When the processor executes the computer program, it implements the vehicle torque limiting method as described in any one of claims 1 to 9.

Images