Control method for electronic differential limiters that can temporarily increase maximum torque

Abstract

This invention provides a control method for an electronic differential limiting device that can temporarily increase the maximum torque. Even when the maximum torque of the electronic differential limiting device is applied and the wheel slip increases to a certain level or its rate of increase is relatively fast, by temporarily increasing the maximum torque upward to the design margin, the maximum wheel speed difference can be reduced and the time required for the wheel speed difference to converge can be reduced.

Description

Technical Field

[0001] This invention relates to a control method for an electronic differential limiting device, and more specifically, to a control method for an electronic differential limiting device that can temporarily increase the maximum torque. Even when the maximum torque of the electronic differential limiting device is applied and wheel slip increases to a certain level or its rate of increase is relatively fast, by temporarily increasing the maximum torque upward to the design margin, the maximum wheel speed difference can be reduced and the time required for wheel speed difference convergence can be reduced. Background Technology

[0002] When a vehicle starts on a road surface with different friction levels on the left and right sides, if the wheel on the side with lower friction slips, the electronic-limited slip differential (e-LSD) will detect the wheel slip and implement wheel slip control by limiting the left and right differential speeds.

[0003] When driving on surfaces with varying friction levels, if the coefficient of friction of the low-friction surface is very low, or if the vehicle's driving force input to the e-LSD is high, resulting in rapid wheel slippage during initial acceleration, then even with the maximum torque applied by the e-LSD, the wheel speed difference convergence speed will be delayed or fail to converge due to the wheel's moment of inertia. Consequently, when the wheel speed difference convergence is delayed, the clutch work and temperature generated by clutch friction will rise sharply, increasing the likelihood of clutch damage. Summary of the Invention

[0004] Technical problems to be solved The purpose of this invention is to provide a control method for an electronic differential limiting device. Even when the maximum torque of the electronic differential limiting device is applied and the wheel slip increases to a certain level or its rate of increase is relatively fast, the maximum wheel speed difference can be reduced and the time required for the wheel speed difference to converge can be reduced by temporarily increasing the maximum torque upward to the design margin.

[0005] The technical problem to be solved by the present invention is not limited to the technical problem mentioned above. Other technical problems not mentioned can also be clearly understood by those skilled in the art through the following description.

[0006] Solution methods for solving technical problems The present invention aims to solve the aforementioned technical problem by temporarily increasing the maximum torque of the e-LSD upward within the torque range that allows for design margin when wheel slip increases to a certain level or at a relatively rapid rate.

[0007] To solve the aforementioned technical problem, an embodiment of the present invention provides a control method for an electronic differential limiting device. The method includes: a first determination step, determining whether a temporary maximum torque increase is active (on); a second determination step, when the temporary maximum torque increase is active (on) in the first determination step, determining whether a temporary maximum torque increase count is satisfied; a third determination step, when the temporary maximum torque increase is inactive (off) in the first determination step, or when the temporary maximum torque increase count is satisfied in the second determination step, determining whether a lubrication time count is satisfied; and a fourth determination step, when the lubrication time count is satisfied in the third determination step, determining whether a temporary maximum torque increase is allowed to enter condition; wherein, when the temporary maximum torque increase is allowed to enter condition in the fourth determination step, it becomes a temporary maximum torque increase active (on) state; when the lubrication time count is not satisfied in the third determination step or when the temporary maximum torque increase is not allowed to enter condition in the fourth determination step, it becomes a temporary maximum torque increase inactive (off) state.

[0008] According to the embodiment, when it is determined in the second determination step that the temporary maximum torque increase count is satisfied, the temporary maximum torque increase count can be initialized.

[0009] According to the embodiment, when it is determined in the second determination step that the temporary maximum torque increase count is not satisfied, the temporary maximum torque increase count can be increased.

[0010] According to an embodiment, when it is determined in the third determination step that the lubrication time count is satisfied, the lubrication time count can be initialized.

[0011] According to an embodiment, a fifth determination step may also be included, in which if the third determination step determines that the lubrication time count is not met, the fifth determination step determines whether the vehicle speed that can be lubricated is met; if the fifth determination step determines that the vehicle speed that can be lubricated is met, the lubrication time count may be increased.

[0012] According to an embodiment, the temporary maximum torque increase allowable entry conditions may include at least one of the following: allowable driving mode conditions, e-LSD slip control operation conditions, and slip above a certain level or uphill driving conditions.

[0013] According to the embodiment, a sixth determination step may also be included. When the fourth determination step determines that it is a temporary maximum torque increase allowable entry condition, the sixth determination step determines whether it is a temporary maximum torque increase restriction condition. When the temporary maximum torque increase restriction condition is met in the sixth determination step, it can become a temporary maximum torque increase active (on) state. When the temporary maximum torque increase restriction condition is not met in the sixth determination step, it can become a temporary maximum torque increase inactive state.

[0014] According to an embodiment, the temporary maximum torque increase restriction condition may include at least one of the following: a clutch stress below a certain level and a low-speed straight-line driving range condition.

[0015] According to the embodiment, the condition for the clutch stress to be below a certain level can be the condition for the clutch stress to be below 50%, and the low vehicle speed condition can be the condition for the vehicle speed to be below 30 kph.

[0016] According to the embodiment, if it is determined in the second determination step that the temporary maximum torque increase count is not met, the sixth determination step can be performed after increasing the temporary maximum torque increase count.

[0017] Invention Effects According to the present invention, wheel slippage is controlled by temporarily increasing the maximum torque within a region where a design margin is allowed, thereby reducing the generated wheel speed difference and the time required for the wheel speed difference to converge to zero. This reduces driving force loss, improves vehicle traction performance, and reduces clutch work and temperature, thus maintaining clutch durability. In this way, performance can be improved without increasing material costs by using a design margin.

[0018] At this point, repeated use of e-LSD maximum torque increase may have an adverse effect on clutch durability. Therefore, by reflecting the maintenance time and lubrication time of temporary maximum torque increase, as well as the temporary maximum torque increase limit conditions according to the situation, into the temporary maximum torque increase function activation conditions, the side effects of using the temporary maximum torque increase function can be reduced and the e-LSD system can be protected.

[0019] The effects of this invention should not be construed as limited to those described above, but should be understood to include all effects that can be inferred from the specific embodiments of the invention or the invention as described in the claims. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating a control method for an electronic differential limiting device that can temporarily increase maximum torque according to an embodiment of the present invention.

[0021] Figure 2 It is shown in detail Figure 1 A diagram illustrating the fourth and sixth judgment steps.

[0022] Figure 3a This is a graph showing the wheel speed difference based on the maximum torque control of the existing e-LSD when starting on different friction surfaces on the left and right sides.

[0023] Figure 3b This is a graph showing the wheel speed difference controlled by the temporary increase in maximum torque of the e-LSD according to the present invention when starting on a road surface with different friction between the left and right sides. Detailed Implementation

[0024] Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the control method of the electronic differential limiting device of the present invention, which can temporarily increase the maximum torque, will be described.

[0025] Furthermore, the terms used below are defined in consideration of the functions in this invention and may be changed according to the intentions or practices of the user or operator. The following embodiments are not intended to limit the scope of the invention, but are merely exemplary matters of the constituent elements within the scope of the claims of this invention.

[0026] To clearly illustrate the invention, irrelevant details have been omitted, and the same or similar reference numerals are used throughout the specification. Throughout the specification, when a part "includes" a certain element, unless specifically stated otherwise, it does not mean that other elements are excluded, but rather that other elements may be further included.

[0027] Furthermore, throughout this specification, the constituent elements referred to as "~" can be two or more constituent elements combined into one constituent element, or one constituent element differentiated into two or more constituent elements according to more detailed functions. In addition, each constituent element described below, besides its own main function, can also perform some or all of the functions of other constituent elements, and of course, some of the main functions of each constituent element can also be performed by other constituent elements.

[0028] First, refer to Figure 1 and Figure 2 View a control method for an electronic differential limiting device (e-LSD) according to an embodiment of the present invention.

[0029] According to an embodiment of the present invention, the control method of the electronic differential limiting device involves determining the temporary maximum torque increase activation / deactivation (on / off) state and its duration, followed by determining the lubrication time, then determining the temporary maximum torque increase allowable entry condition and the temporary maximum torque increase limiting condition, thereby determining whether the temporary maximum torque increase is activated / deactivated (on / off) or not. The specific steps are detailed below.

[0030] First, it is determined whether the temporary maximum torque increase is active (on) (first determination step; S1). That is, the active / deactivated (on / off) state of the temporary maximum torque increase function of the previous task is determined. If it is determined to be active (on) in the first determination step (S1), then the second determination step (S2) is performed to determine whether the temporary maximum torque increase count is satisfied. Conversely, if it is determined to be deactivated (off) in the first determination step (S1), then the third determination step (S3) is performed as described later.

[0031] In the second judgment step (S2), the duration of the temporary maximum torque increase function being activated (on) is counted using a temporary maximum torque increase counter. When a set benchmark value is reached, the temporary maximum torque increase function is deactivated (off). This prevents the cumulative work done at the moment of damage to the e-LSD clutch from exceeding the total critical point. For example, assuming the maximum duration of the temporary maximum torque increase function is set to 2 seconds, and assuming the control method of this invention is executed once every 10 ms, then when the total temporary maximum torque increase count reaches 200, it can be determined that the condition is met.

[0032] In the second judgment step (S2), if the temporary maximum torque increase count is satisfied, that is, when the maximum maintenance time of the temporary maximum torque increase function is reached, the temporary maximum torque increase function is deactivated (off), and the temporary maximum torque increase count is initialized. After the temporary maximum torque increase count is initialized, the third judgment step (S3) is performed to determine whether the lubrication time count is satisfied.

[0033] Conversely, if in the second determination step (S2) it is determined that the temporary maximum torque increase count is not met, i.e., when the maximum maintenance time of the temporary maximum torque increase function has not yet been reached, the temporary maximum torque increase count is incremented by 1. Then, in this embodiment, the process proceeds to the sixth determination step (S6), which will be described later. If the sixth determination step (S6) is omitted according to the embodiment, then after incrementing the temporary maximum torque increase count by 1, the temporary maximum torque increase activation (on) can be output.

[0034] In the third judgment step (S3), the time for maintaining smooth lubrication is counted by the lubrication time counter to determine whether the clutch cooling of the e-LSD is sufficient after the temporary maximum torque increase. Thus, by considering the lubrication rest time after the temporary maximum torque increase function is deactivated (off), the e-LSD system can be protected when the temporary maximum torque increase function is used. For example, assuming the minimum time for maintaining smooth lubrication after the temporary maximum torque increase function is deactivated (off) is set to 30 seconds, and assuming the control method of the present invention is executed once every 10 ms, it can be determined that the lubrication is satisfied when the total lubrication time count reaches 3000.

[0035] In the third judgment step (S3), if the lubrication time count is satisfied, that is, when the minimum time required to maintain smooth lubrication is met, the lubrication time count is initialized. After the lubrication time count is initialized, the fourth judgment step (S4) is performed to determine whether the temporary maximum torque increase is allowed.

[0036] Conversely, if the lubrication time count is not met in the third judgment step (S3), that is, when the minimum time to maintain smooth lubrication has not been reached, the fifth judgment step (S5) is performed to determine whether the vehicle speed can be lubricated.

[0037] The e-LSD of this invention requires a certain vehicle speed in its mechanical structure to achieve smooth lubrication through oil churning, thereby cooling the overheated clutch. Therefore, lubrication is considered to have occurred only when the vehicle speed required for lubrication is determined to be met in step 5 (S5), the lubrication time count is incremented by 1, and then the temporary maximum torque increase is deactivated (off). Conversely, if the vehicle speed required for lubrication is not determined to be met in step 5 (S5), lubrication is considered not to have occurred, the lubrication time count remains unchanged, and the temporary maximum torque increase is deactivated (off). For example, the vehicle speed required for lubrication can be set to 30 km / h or higher.

[0038] In the fourth determination step (S4), the temporary maximum torque increase allowable entry conditions are determined. At this time, the temporary maximum torque increase allowable entry conditions may include at least one of the following: allowable driving mode conditions, e-LSD slip control operation conditions, and slip conditions of a certain level or above or uphill driving conditions.

[0039] Reference Figure 2 In this embodiment, it is determined that the temporary maximum torque increase can be entered only when all of the above three conditions are met. If any of the above three conditions are not met, it is determined that the temporary maximum torque increase cannot be entered, and the temporary maximum torque increase is deactivated (off).

[0040] Specifically, the fourth judgment step (S4) includes: a fourth-first judgment step (S4-1) to determine whether it is a permissible driving mode that allows temporary increases in maximum torque; a fourth-second judgment step (S4-2) to determine whether e-LSD slip control is in operation; and a fourth-third judgment step (S4-3) to determine whether the slip is above a certain level or whether it is an uphill driving condition. The order of these steps can be changed.

[0041] First, if the driving mode is determined to be permissible in step 4-1 (S4-1), then the next step, step 4-2 (S4-2), is performed. If the driving mode is not permissible, then the temporary maximum torque increase is deactivated (off). The degree of permissible wheel slip may vary depending on the vehicle's driving mode concept. Since the temporary maximum torque increase function is designed to suppress wheel slip, its use is determined based on the driving mode concept. When the driving mode is set to be permissible, it is determined that temporary maximum torque increase can be entered; otherwise, it is determined that temporary maximum torque increase cannot be entered.

[0042] For example, you can set normal and offroad modes, which do not focus on handling, as permitted driving modes, while setting sport mode and other driving modes that focus on handling as prohibited driving modes.

[0043] Next, if it is determined in step 4-2 (S4-2) that the e-LSD slip control is running, then proceed to step 4-3 (S4-3). If it is determined that the e-LSD slip control is not running, then the temporary maximum torque increase is deactivated (off). The temporary maximum torque increase function is only used when slip control is running, i.e., when the speed difference between the left and right wheels at the e-LSD mounting location is large, and the e-LSD controls to eliminate this speed difference. Therefore, step 4-2 (S4-2) determines whether e-LSD slip control is being performed.

[0044] Finally, if the slip is determined to be above a certain level or the vehicle is driving uphill in step 4-3 (S4-3), then step 6 (S6) is performed. If the slip is determined to be below a certain level or the vehicle is not driving uphill, then the temporary maximum torque increase is deactivated (off). This is because the temporary maximum torque increase function aims to temporarily increase the maximum torque to guide the wheel speed difference to decrease, even during slip control, if the wheel speed difference does not decrease, causing the slip to exceed a certain level. For example, when the slip is approximately 3 km / h or more, it can be determined that the slip is above a certain level.

[0045] Alternatively, since more driving force is required to move the vehicle uphill than on flat ground, a temporary maximum torque boost function is used when driving uphill. If driving force is lost due to wheel slippage, the e-LSD is more forcefully controlled to improve the vehicle's traction performance when slippage occurs. Here, uphill driving refers to driving on steep slopes or mountainous terrain.

[0046] In the fourth judgment step (S4), if it is determined that the temporary maximum torque increase is allowed to enter the condition, that is, when all three conditions mentioned above are met, the sixth judgment step (S6) is performed to determine whether it is a temporary maximum torque increase restriction condition. At this time, the temporary maximum torque increase restriction condition may include at least one of the following: the condition that the clutch stress is below a certain level and the condition of low vehicle speed straight-line section.

[0047] Reference Figure 2 In this embodiment, the temporary maximum torque increase is activated (on) only when both of the above two conditions are met. If one of the above two conditions is not met, the temporary maximum torque increase is deactivated (off) because it should be restricted. Here, regardless of the three conditions described in the fourth determination step (S4), the condition for restricting the temporary maximum torque increase function is determined in order to protect the system and prevent any abnormality in vehicle behavior.

[0048] Specifically, the sixth judgment step (S6) includes: a 6-1 judgment step (S6-1) to determine whether the clutch stress is below a certain level, and a 6-2 judgment step (S6-2) to determine whether it is a low-speed straight-ahead section. The order of these steps can be changed.

[0049] First, if the clutch stress is determined to be below a certain level in step 6-1 (S6-1), then the next step, step 6-2 (S6-2), is performed. If the clutch stress is determined to exceed a certain level, then the temporary maximum torque increase is deactivated (off). Here, the clutch stress is set to the clutch thermal load rate at which the clutch failure limit is set. If the temporary maximum torque increase function is used under excessive clutch stress, the clutch stress may increase even more rapidly, which may lead to clutch damage. Therefore, the temporary maximum torque increase function is only allowed when the clutch stress drops below a certain level. In particular, it is preferable to set the temporary maximum torque increase function to be allowed without restriction when the clutch stress is below 50%.

[0050] Next, if the determination step (S6-2) indicates a low-speed straight-line driving range, the temporary maximum torque increase is activated (on); if it indicates a non-low-speed straight-line driving range, the temporary maximum torque increase is deactivated (off). This is because excessive e-LSD torque at high speeds or during turns may cause abnormal vehicle behavior. Therefore, the temporary maximum torque increase function is only allowed at low speeds and in straight-line driving ranges. Specifically, it is preferable to allow the temporary maximum torque increase function without restriction when the vehicle speed is below 30 kph. Furthermore, "straight-line driving range" can refer to the traction range.

[0051] As a result, by determining the on / off state of the temporary maximum torque increase, the duration of the on / off state, the lubrication time, the conditions for allowing the temporary maximum torque increase to enter, and the conditions for limiting the temporary maximum torque increase as described above, the system ultimately decides and outputs whether to activate (on) or deactivate (off) the temporary maximum torque increase function.

[0052] When the temporary maximum torque increase function is inactive (off), the maximum value of the target torque controlled by the e-LSD is set to the maximum torque defined in the e-LSD specification (e.g., 1800 Nm).

[0053] Conversely, when the temporary maximum torque boost function is activated, the maximum value of the target torque for e-LSD control is increased upwards to a value higher than the maximum torque defined in the e-LSD specification (e.g., 2000 Nm), which is within the design margin range. This is likely achieved by applying a greater force to the e-LSD clutch than the clamping force required to achieve the maximum torque defined in the e-LSD specification (e.g., 1800 Nm).

[0054] The driving conditions for the control method of the electronic differential limiting device of the present invention can be the conditions for starting from a stop under road surface conditions with different friction surfaces on the left and right sides.

[0055] Figure 3a The graph shows the wheel speed difference controlled by the maximum torque of the existing e-LSD when starting on roads with different types of friction on the left and right sides. Figure 3b The diagram shows a graph of the wheel speed difference controlled by the temporary increase in maximum torque of the e-LSD according to the present invention when starting on a road surface with different friction between the left and right sides.

[0056] Figure 3aThe diagram illustrates the e-LSD control torque (a) and the RR wheel speed (b) and RL wheel speed (c) as they vary over time. During initial acceleration, the e-LSD preemptively applies torque based on driver input to suppress wheel slip. When wheel slip occurs between the RR wheel speed (b) and the RL wheel speed (c), additional torque is applied to suppress this slip. At this point, the maximum torque applied by the existing e-LSD is 1800 Nm as defined in the specifications. Therefore, the maximum difference between the left and right wheel speeds is 25 km / h, and the time required for the difference to converge is 1 second. Thus, the larger the wheel speed difference or the longer the time required for the difference to converge to zero, the greater the work required by the clutch and the higher the clutch temperature, thereby increasing the risk of clutch damage.

[0057] Figure 3b The diagram also shows the e-LSD control torque (a') and the RR wheel speed (b') and RL wheel speed (c') as they vary over time. Here, additional torque is applied to suppress wheel slippage that occurs between the RR wheel speed (b') and the RL wheel speed (c'). However, compared to... Figure 3a In contrast, when excessive wheel slip occurs, the maximum torque of the e-LSD is temporarily increased to a value greater than the specified 1800 Nm within the design margin range; in this embodiment, it is temporarily increased to 2000 Nm and applied. Therefore, the maximum left-right wheel speed difference is 13 km / h, and the time required for the left-right wheel speed difference to converge is 0.7 seconds.

[0058] In this way, by temporarily increasing the maximum torque for control, the maximum value of the speed difference between the left and right wheels and the time required for the speed difference between the left and right wheels to converge are significantly reduced. This reduces the loss of driving force, improves the traction performance of the vehicle, and reduces the amount of work and temperature of the clutch, thereby maintaining the clutch durability level.

[0059] Furthermore, repeated use of e-LSD maximum torque increase may have an adverse effect on clutch durability. Therefore, as mentioned above, by reflecting the maintenance time and lubrication time of temporary maximum torque increase, as well as the temporary maximum torque increase limitation conditions according to the situation, into the activation conditions of the temporary maximum torque increase function, the side effects of using the temporary maximum torque increase function can be reduced and the e-LSD system can be protected.

[0060] This invention is not limited to the specific embodiments and descriptions described above. Various modifications can be made by those skilled in the art without departing from the spirit of the invention as claimed in the claims, and all such modifications are within the scope of protection of this invention.

[0061] Symbol Explanation S1: First judgment step S2: Second judgment step S3: Third Judgment Step S4: Fourth Judgment Step S4-1: Judgment Step 4-1 S4-2: Judgment Step 4-2 S4-3: Judgment Step 4-3 S5: Fifth Judgment Step S6: 6th Judgment Step S6-1: Judgment Step 6-1 S6-2: Judgment Step 6-2 a、a': e-LSD control torque b, b': RR wheel speed c, c': RL wheel speed

Claims

1. A control method for an electronic differential limiting device, characterized in that, include: The first judgment step is to determine whether the temporary maximum torque increase activation state is active. The second judgment step is to determine whether the temporary maximum torque increase activation state is met when the first judgment step determines that the temporary maximum torque increase count is met. The third judgment step, when the first judgment step determines that the temporary maximum torque increase is inactive, or when the second judgment step determines that the temporary maximum torque increase count is met, then the third judgment step determines whether the lubrication time count is met; and The fourth judgment step is to determine whether the lubrication time count is met in the third judgment step. Specifically, if the condition for allowing the increase of temporary maximum torque is met in the fourth determination step, the state becomes the active state of the increase of temporary maximum torque; if the condition for not meeting the lubrication time count is met in the third determination step, or if the condition for not allowing the increase of temporary maximum torque is met in the fourth determination step, the state becomes the inactive state of the increase of temporary maximum torque.

2. The control method for the electronic differential limiting device according to claim 1, characterized in that, When it is determined in the second determination step that the temporary maximum torque increase count is satisfied, the temporary maximum torque increase count is initialized.

3. The control method for the electronic differential limiting device according to claim 2, characterized in that, If the temporary maximum torque increase count is not met in the second judgment step, the temporary maximum torque increase count is increased.

4. The control method for the electronic differential limiting device according to claim 3, characterized in that, In the third determination step, when it is determined that the lubrication time count is satisfied, the lubrication time count is initialized.

5. The control method for the electronic differential limiting device according to claim 4, characterized in that, It also includes the 5th judgment step, If the lubrication time count is not met in the third judgment step, the fifth judgment step determines whether the vehicle speed is sufficient for lubrication. In the fifth judgment step, if it is determined that the vehicle speed is sufficient for lubrication, the lubrication time count is increased.

6. The control method for the electronic differential limiting device according to claim 1, characterized in that, The conditions under which temporary maximum torque can be increased include: permitted driving mode conditions, slip control operation conditions of electronic differential limiter, and at least one of slip conditions above a certain level or uphill driving conditions.

7. The control method for the electronic differential limiting device according to claim 3, characterized in that, It also includes the 6th judgment step, If the fourth determination step determines that it is a temporary maximum torque increase allowable entry condition, the sixth determination step determines whether it is a temporary maximum torque increase restriction condition. When the temporary maximum torque increase restriction condition is met in the sixth judgment step, the temporary maximum torque increase becomes active; when the temporary maximum torque increase restriction condition is not met in the sixth judgment step, the temporary maximum torque increase becomes inactive.

8. The control method for the electronic differential limiting device according to claim 7, characterized in that, The temporary maximum torque increase restriction conditions include at least one of the following: the clutch stress being below a certain level and the low-speed straight-line driving range conditions.

9. The control method for the electronic differential limiting device according to claim 8, characterized in that, The condition for clutch stress to be below a certain level is that the clutch stress is below 50%, and the low vehicle speed condition is that the vehicle speed is below 30 kilometers per hour.

10. The control method for the electronic differential limiting device according to claim 7, characterized in that, If the temporary maximum torque increase count is not met in the second judgment step, the sixth judgment step is performed after increasing the temporary maximum torque increase count.

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