Control method for limiting engine torque in failure mode of automatic transmission

Abstract

The invention discloses a control method for engine torque limitation in an automatic transmission failure mode, and belongs to the technical field of transmissions. The method comprises the following steps: the gearbox enters a fault state; the gearbox control unit carries out corresponding torque limiting control according to different fault states; after the gearbox completes torque limiting control in different fault states, whether the current real-time torque in the fault states is smaller than the maximum torque threshold value calibrated in a gearbox control unit or not is judged, and if yes, torque limiting control quitting is executed; on the contrary, continuously executing the torque limiting control until the current real-time torque in the fault state is smaller than the maximum torque threshold value calibrated in the gearbox control unit; and after the car customer completes the power-off and power-on operation once, the fault mode exits. The engine torque is limited according to different gearbox fault modes, the gearbox is protected to the maximum extent, and the problems that other elements are damaged, secondary damage of the gearbox is caused, and the whole vehicle maintenance cost of a user is increased are solved.

Description

Technical Field

[0001] The invention relates to a control method for limiting engine torque in an automatic transmission fault mode, and belongs to the technical field of transmissions. Background Art

[0002] In the prior art, when the gearbox enters the fault mode, most of them adopt the basic power-off mechanical limp home mode. Although this mode can temporarily maintain the basic driving ability of the vehicle, it lacks effective control of the engine torque, which may cause the gearbox to continue to bear excessive torque load in the fault state. This situation not only increases the risk of damage to other components of the gearbox, but may also cause more serious secondary damage, thereby significantly increasing the vehicle maintenance cost for the owner. Summary of the invention

[0003] In order to solve the problems existing in the background technology, the present invention provides a control method for limiting engine torque in an automatic transmission fault mode.

[0004] To achieve the above object, the present invention adopts the following technical solution: a control method for engine torque limitation in an automatic transmission fault mode, the method comprising the following steps:

[0005] S1: When the vehicle has a gearbox failure, the gearbox enters a fault state;

[0006] S2: The gearbox control unit performs corresponding torque limiting control according to different fault states;

[0007] The fault states include a clutch speed ratio fault state, a transmission maintaining a single gear fault state, and a transmission entering neutral fault state.

[0008] S3: After the transmission completes the torque limiting control under different fault states, it is determined whether the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit. If so, the torque limiting control is exited; otherwise, the torque limiting control is continued until the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit.

[0009] S4: When the customer completes a power-off and power-on operation, the fault mode exits.

[0010] The control method of the torque limiting control corresponding to the clutch speed ratio fault state comprises the following steps:

[0011] S201: Identify speed ratio fault, and the transmission enters a fault state;

[0012] S202: Find a safe driving gear: While preparing to shift gears, the gearbox control unit performs conventional torque reduction control; and at the same time performs torque limit control to keep the gearbox input torque at 0N, so that the engine output torque is equal to the total friction torque;

[0013] The method of finding a safe driving gear position comprises the following steps:

[0014] S20201: The transmission control unit analyzes the current vehicle driving status;

[0015] S20202: According to the analysis result, select a gear that meets the safety driving requirement from the available gears of the transmission;

[0016] S20203: Determine at least one suitable gear as an alternative and prepare for a gear shift operation.

[0017] S203: Perform a gear shift operation;

[0018] S204: After entering the safety gear, the transmission control unit continues to monitor the transmission speed ratio status and vehicle driving status.

[0019] The control method for torque limiting control corresponding to the single gear fault state of the gearbox comprises the following steps:

[0020] S201: a single gear fault is identified, and the transmission enters a fault state;

[0021] S202: The vehicle maintains a single gear.

[0022] S203: Limit the engine output torque so that the transmission input torque is maintained and does not exceed the maximum torque threshold calibrated in the transmission control unit; if the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

[0023] The control method for torque limiting control corresponding to the gearbox entering a neutral fault state comprises the following steps:

[0024] S201: Identify a neutral gear fault, and the transmission enters a fault state;

[0025] S202: The transmission remains in the N gear mode;

[0026] S203: Depress the accelerator pedal;

[0027] S204: Detect and determine the value of the transmission input torque. If the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention limits the engine torque according to different gearbox failure modes, protects the gearbox to the maximum extent, and prevents damage to other components, which would cause secondary damage to the gearbox and increase the user's vehicle maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of torque limitation under clutch speed ratio failure state of the present invention;

[0031] Figure 2 is a flow chart of torque limitation when the gearbox of the present invention maintains a single gear fault state;

[0032] Figure 3 It is a flow chart of torque limitation when the transmission enters neutral fault state. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] A method for controlling engine torque limitation in an automatic transmission fault mode, the method comprising the following steps:

[0035] S1: When the vehicle is in normal driving state and a gearbox failure occurs suddenly, the gearbox enters the fault state;

[0036] S2: The gearbox control unit performs corresponding torque limiting control according to different fault states;

[0037] S3: After the transmission completes the torque limiting control under different fault states, it is determined whether the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit. If so, the torque limiting control is exited; otherwise, the torque limiting control is continued until the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit.

[0038] S4: When the customer completes a power-off and power-on operation, the fault mode exits.

[0039] The fault state described in S2 includes a clutch speed ratio fault state, a transmission maintaining a single gear fault state, and a transmission entering neutral fault state.

[0040] The control method of the torque limiting control corresponding to the clutch speed ratio fault state comprises the following steps:

[0041] S201: Identify speed ratio fault, and the transmission enters a fault state;

[0042] S20101: During the operation of the automatic transmission, the transmission control unit monitors the speed ratio status of the transmission in real time.

[0043] S20102: When the transmission control unit detects an abnormal speed ratio, it immediately determines it as a speed ratio failure, the transmission enters a fault state, and triggers the corresponding fault handling process.

[0044] S202: Find a safe driving gear: While preparing to shift gears, the gearbox control unit performs conventional torque reduction control to reduce the gearbox input torque. Conventional torque reduction control includes adjusting the engine throttle opening, changing the fuel injection amount, and other measures; and at the same time, torque limit control is increased to further limit the engine output torque. Torque limit control includes adjusting the engine torque output curve, cutting off part of the fuel supply, etc. The gearbox input torque is kept at 0N, so that the engine output torque is equal to the total friction torque;

[0045] The method of finding a safe driving gear position comprises the following steps:

[0046] S20201: After confirming the speed ratio fault, the transmission control unit analyzes the current vehicle driving status (such as speed, acceleration, road conditions, etc.);

[0047] S20202: According to the analysis result, select a gear that meets the safety driving requirement from the available gears of the transmission;

[0048] S20203: Determine at least one suitable gear as an alternative and prepare for a gear shift operation.

[0049] S203: Perform a gear shift operation;

[0050] S204: After entering the safe gear position, the gearbox control unit continues to monitor the gear ratio status of the gearbox and the vehicle driving status to ensure that the gear shifting effect is good and safe.

[0051] When a speed ratio failure occurs in an automatic transmission, according to the normal logic of the transmission control unit, it is necessary to shift gears in sequence under the current fault state to find an available and suitable safe driving gear. During this shifting process, the turbine speed and engine speed cannot be suppressed in time due to clutch slippage, resulting in a runaway phenomenon. At this time, if the torque is still loaded to shift gears, the degree of clutch damage will be aggravated.

[0052] In the process of searching for a safe gear, the present invention adds torque limiting control in addition to conventional torque reduction control, limits the engine output torque, keeps the transmission input torque at 0N to complete such gear shifting, and only allows the engine to output a total torque approximately equal to the friction torque, thereby ensuring safe completion of the gear shift.

[0053] The control method for torque limiting control corresponding to the single gear fault state of the gearbox comprises the following steps:

[0054] S201: a single gear fault is identified, and the transmission enters a fault state;

[0055] S20101: The transmission control unit monitors the operating status of the automatic transmission in real time.

[0056] S20102: When the transmission control unit detects that the transmission is seriously damaged or has a communication failure, causing the transmission control unit to be unable to change gears, the fault handling process is immediately triggered.

[0057] S202: The vehicle maintains a single gear (such as rear D gear) while driving;

[0058] S203: Limit the engine output torque so that the transmission input torque is maintained and does not exceed the maximum torque threshold calibrated in the transmission control unit; if the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

[0059] When the automatic transmission is seriously damaged or has a communication failure with the engine, the transmission control unit lacks the key signal for shifting, which causes the gear to be changed again. When the control unit maintains a single fixed gear unchanged, it is equivalent to the automatic transmission moving with a fixed gear ratio. The present invention limits the engine output torque in this type of fixed single gear driving fault, so that the transmission input torque fluctuates within a fixed range, and the maximum value is not allowed to exceed a certain value, which is the engine friction torque plus a fixed value. At this time, it can be avoided that the vehicle speed continues to increase due to the continuous increase in torque, resulting in the engine speed exceeding the limit at a fixed gear ratio, causing damage to the engine or other hardware.

[0060] In D gear, the engine torque starts to rise after the accelerator is pressed. After exceeding the calibrated value in the transmission control unit, the output will be limited so that the transmission input torque can only reach the calibrated limit. When the accelerator is released, the engine torque starts to decrease. After decreasing to a value slightly smaller than the calibrated value in the transmission control unit (to prevent torque fluctuations from causing continuous torque limiting and exiting torque limiting), the torque limiting is exited.

[0061] The control method for torque limiting control corresponding to the gearbox entering a neutral fault state comprises the following steps:

[0062] S201: Identify a neutral gear fault, and the transmission enters a fault state;

[0063] S202: The transmission remains in the N gear mode;

[0064] S203: Depress the accelerator pedal;

[0065] S204: Detect and determine the value of the transmission input torque. If the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

[0066] When the automatic transmission is seriously damaged, the internal circuit has an open circuit / short power / short ground fault, or there are faults such as power supply and gear inconsistency that make it impossible to drive, the present invention will also limit the engine torque in such a fault state that the transmission cannot drive in neutral, so that the transmission input torque is maintained at a certain positive value, which should not be too large, and can meet the user's requirement that the speed maintains a slow upward trend after stepping on the accelerator. At this time, idling can be prevented from causing the engine speed to rise rapidly.

[0067] When entering this fault state, the transmission always remains in N gear. At this time, the engine torque starts to rise after the accelerator is pressed. After exceeding the calibrated value in the transmission control unit, the output will be limited so that the transmission input torque can only reach the calibrated limit. When the accelerator is released, the engine torque starts to decrease. After decreasing to a value slightly smaller than the value calibrated in the transmission control unit (to prevent torque fluctuations from causing continuous torque limiting and exiting torque limiting), the torque limiting is exited.

[0068] When the gearbox enters a fault mode, the probability of secondary damage to the gearbox due to imperfect strategies is significantly reduced. At the same time, the present invention can also enable the gearbox to perform as many conventional shifting operations as possible when entering a fault state, thereby increasing the driving options and driving experience of car users.

[0069] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0070] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A control method for engine torque limitation in an automatic transmission fault mode, characterized in that: The method comprises the following steps: S1: When the vehicle has a gearbox failure, the gearbox enters a fault state; S2: The gearbox control unit performs corresponding torque limiting control according to different fault states; S3: After the transmission completes the torque limiting control under different fault states, it is determined whether the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit. If so, the torque limiting control is exited; otherwise, the torque limiting control is continued until the current real-time torque under the fault state is less than the maximum torque threshold value calibrated in the transmission control unit. S4: When the customer completes a power-off and power-on operation, the fault mode exits.

2. The control method for limiting engine torque in an automatic transmission fault mode according to claim 1, characterized in that: The fault state described in S2 includes a clutch speed ratio fault state, a transmission maintaining a single gear fault state, and a transmission entering neutral fault state.

3. The control method for limiting engine torque in an automatic transmission fault mode according to claim 2, characterized in that: The control method of the torque limiting control corresponding to the clutch speed ratio fault state comprises the following steps: S201: Identify speed ratio fault, and the transmission enters a fault state; S202: Searching for a safe driving gear: While preparing for gear shifting, the transmission control unit performs conventional torque reduction control; At the same time, torque limiting control is performed to keep the transmission input torque at 0N, so that the engine output torque is equal to the total friction torque; S203: Perform a gear shift operation; S204: After entering the safety gear, the transmission control unit continues to monitor the transmission speed ratio status and vehicle driving status.

4. The control method for limiting engine torque in an automatic transmission fault mode according to claim 3, characterized in that: S202 of searching for a safe driving gear position comprises the following steps: S20201: The transmission control unit analyzes the current vehicle driving status; S20202: According to the analysis result, select a gear that meets the safety driving requirement from the available gears of the transmission; S20203: Determine at least one suitable gear as an alternative and prepare for a gear shift operation.

5. The control method for limiting engine torque in an automatic transmission fault mode according to claim 2, characterized in that: The control method for the torque limiting control corresponding to the single gear fault state of the gearbox comprises the following steps: S201: a single gear fault is identified, and the transmission enters a fault state; S202: The vehicle maintains a single gear. S203: Limit the engine output torque so that the transmission input torque is maintained and does not exceed the maximum torque threshold calibrated in the transmission control unit; if the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

6. The control method for limiting engine torque in an automatic transmission fault mode according to claim 2, characterized in that: The control method for torque limiting control corresponding to the gearbox entering a neutral fault state comprises the following steps: S201: Identify a neutral gear fault, and the transmission enters a fault state; S202: The transmission remains in the N gear mode; S203: Depress the accelerator pedal; S204: Detect and determine the value of the transmission input torque. If the transmission input torque exceeds the maximum torque threshold calibrated in the transmission control unit, the transmission control unit performs conventional torque reduction control so that the transmission input torque can only reach the calibrated limit value.

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