Method for increasing the availability of a vehicle after the combustion engine stops due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch

Abstract

Method for increasing the availability of a vehicle after the internal combustion engine has stopped owing to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch, characterized in that the internal combustion engine is restarted, the engine speed being monitored while the engine is running and when gear is engaged, and if the engine speed is kept below an applicable threshold during gear engagement, the control pressure in the shift element establishing the frictional connection in the transmission is reduced to the filling pressure or an applicable emergency pressure, thereby preventing the engine from stopping, a corresponding error memory entry and corresponding driver information being generated.

Description

[0001] The invention relates to a method for increasing the availability of a vehicle after the internal combustion engine stops due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch, according to the preamble of patent claim 1.

[0002] In conventional powertrains with automatic transmissions, malfunctions or mechanical / hydraulic defects in the transmission can cause the combustion engine to shut down. However, a combustion engine can also shut down unexpectedly due to engine-related problems / defects.

[0003] In the event of an actual defect or malfunction in the control chain of a torque converter lockup clutch or starting clutch, this can lead to the vehicle becoming immobilized. While a blocked or defective torque converter lockup clutch / starting clutch has less impact on restarting with the transmission not engaged, it would cause the engine to stall again when engaging a gear. This would render the vehicle unusable.

[0004] For example, the document US 2016 / 0 017 988 A1 discloses a further method for increasing the availability of a vehicle after the combustion engine stops due to a defect in a converter clutch.

[0005] The present invention is based on the object of specifying a method for increasing the availability of a vehicle after the internal combustion engine stops due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch.

[0006] This object is achieved by the features of patent claim 1. Further embodiments and advantages emerge from the subclaims. Accordingly, a method is proposed for increasing the availability of a vehicle after the internal combustion engine has stopped due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch. In the context of this method, if the internal combustion engine stops, the internal combustion engine is restarted, wherein the engine speed is monitored when the engine is running and when a gear is engaged, i.e. when gear D or R is selected.

[0007] If the engine speed is kept below an applicable threshold during gear engagement, the control pressure in the switching element that establishes the power connection in the transmission is reduced to the filling pressure or an applicable emergency pressure, thereby preventing the engine from stalling, whereby a corresponding error memory entry, for example "emergency start due to engine speed suppression" and corresponding driver information, e.g. "transmission fault" are generated.

[0008] According to the invention, when a starting request is detected, the starting process is carried out by a controlled closing of the switching element that establishes the power connection in the transmission. Separate parameters are used for the closing process of this switching element to prevent the engine from shutting down. As part of a further development, a predefined number of starting attempts and starting processes can optionally be permitted.

[0009] According to the invention, the number of starting operations can be limited to a certain number before the vehicle is finally immobilized; in this case, a corresponding driver message "x starting operations still possible" can be generated.

[0010] When the vehicle is stopped again, the switching element that establishes the power connection in the transmission can be opened to prevent the combustion engine from stalling again and to enable the vehicle to start moving again.

[0011] According to a further development of the invention, it can be provided that if there is no desire to start, the switching element which establishes the power connection in the transmission is switched on in a pulsating manner, wherein if drops in the engine speed are detected, a defect in the converter lock-up clutch or the starting clutch or a defect in the control chain of the converter lock-up clutch or the starting clutch is verified and a corresponding error entry is generated.

[0012] Advantageously, the pulsating engagement of the switching element that establishes the power connection in the transmission can ensure that the system is put into an operational state in the event of contamination, allowing the emergency functions to be exited.

[0013] A shutdown of the internal combustion engine caused by a defect in a torque converter lock-up clutch or a starting clutch or by a fault in the control chain of the torque converter lock-up clutch or the starting clutch can be detected, for example, by determining, when the internal combustion engine shuts down, whether the shutdown of the internal combustion engine is caused by a known function and whether there is a counter-reaction of the internal combustion engine against shutting down, wherein if the shutdown of the internal combustion engine is not caused by a known function, a fault on the transmission side that is suitable for the shutdown of the internal combustion engine is detected and there is a counter-reaction of the internal combustion engine against shutting down, a malfunction in the control chain of the torque converter lock-up clutch or the starting clutch is detected.

[0014] To determine whether the engine is reacting against stalling, the engine torque, ignition timing, air supply, fuel supply, and idle speed control can be monitored. To ensure that the engine stall is not caused by a known function, all signals that could trigger an engine shutdown are evaluated. This check determines whether the engine shutdown is requested by the start-stop function (MSA) and whether "sailing with engine off" is requested by the strategy. The status of the ignition flag, the status of the start-stop button, and, if present, the status of an emergency engine shutdown switch are checked.

[0015] A transmission-side fault capable of shutting down the internal combustion engine can be detected, for example, by means of symptom recognition of a defect in a torque converter lockup clutch or a starting clutch, or of a fault in the control chain of the torque converter lockup clutch or the starting clutch of a motor vehicle. At the start of an opening ramp for the torque converter lockup clutch or the starting clutch, a timer is started that represents a previously applied maximum time. At the same time, the curve of the differential speed between the engine speed and the turbine speed is monitored within this maximum time. If the differential speed does not reach a previously applied minimum value within the maximum time, a symptom of a defect in the torque converter lockup clutch or the starting clutch, or of a fault in the control chain of the torque converter lockup clutch or the starting clutch, is detected.

[0016] The invention is explained in more detail below using the attached figure, which represents a flow chart.

[0017] With reference to the attached figure, at the beginning of the method, after the internal combustion engine has stopped due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch, the internal combustion engine is restarted, the engine speed being observed when the engine is running and when the gear is engaged, ie when the gear position D or R is selected.

[0018] If the engine speed is kept below an applicable threshold during gear engagement, the control pressure in the switching element that establishes the power connection in the transmission is reduced to the filling pressure or an applicable emergency pressure as part of an emergency start function, thereby preventing the engine from stalling, whereby an error memory entry "Emergency start due to engine pressure" and driver information, e.g. "Transmission fault" are generated.

[0019] When a move-off request is detected, the move-off process is carried out by the controlled closing of the switching element that establishes the power connection in the transmission using separate parameters. A move-off request can be detected, for example, by releasing the brake and increasing the load. This can allow a predefined number of start-off attempts and processes. Furthermore, when the vehicle is stopped again, the switching element that establishes the power connection in the transmission can be opened to prevent the combustion engine from shutting down again, thus enabling a new move-off process.

[0020] In the example shown, if there is no desire to start after the gear has been engaged, the switching element that establishes the power connection in the transmission is switched on in a pulsating manner, whereby if drops in the engine speed are detected, a defect in the torque converter lock-up clutch or the starting clutch or a defect in the control chain of the torque converter lock-up clutch or the starting clutch is verified and a corresponding error entry, for example "problem in the control of the torque converter lock-up clutch / starting clutch", is generated.

Claims

[1] Method for increasing the availability of a vehicle after the internal combustion engine stops due to a defect in a torque converter lock-up clutch or a starting clutch or due to a fault in the control chain of the torque converter lock-up clutch or the starting clutch, characterized by that the internal combustion engine is restarted, the engine speed being monitored when the engine is running and when the gear is engaged, and if the engine speed is kept below an applicable threshold during gear engagement, the control pressure in the switching element which establishes the power connection in the transmission is reduced to the filling pressure or an applicable emergency pressure, thereby preventing the engine from stalling, a corresponding error memory entry and corresponding driver information being generated. [2] Method for increasing the availability of a vehicle according to claim 1, characterized bythat when a drive-off request is detected, the drive-off process is carried out by a controlled closing of the switching element which establishes the power connection in the transmission, whereby separate parameters are used for the closing process of this switching element. [3] Method for increasing the availability of a vehicle according to claim 1 or 2, characterized by that the number of start-up operations is limited to a certain number. [4] Method for increasing the availability of a vehicle according to claim 1, 2 or 3, characterized by that when the vehicle stops again, the switching element which establishes the power connection in the transmission is opened in order to prevent the combustion engine from switching off again and to enable a new starting process. [5] Method for increasing the availability of a vehicle according to claim 1, characterized bythat if there is no desire to start, the switching element which establishes the power connection in the transmission is switched on in a pulsating manner, whereby if drops in the engine speed are detected, a defect in the torque converter lock-up clutch or the start-up clutch or a defect in the control chain of the torque converter lock-up clutch or the start-up clutch is verified and a corresponding error entry is generated. [6] Method for increasing the availability of a vehicle according to claim 5, characterized by that the pulsating activation of the switching element which creates the power connection in the transmission ensures that the system is put into an operational state in the event of contamination.

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