Method and control device for operating a drive train

Abstract

A method for operating a drive train comprising a drive unit (1), a torque converter (5) as a starting element, an automatic transmission (2), and an output (3), wherein, after starting the drive unit (1), the rotational speed of a turbine (7) of the torque converter (5) is monitored, characterized in that, if it is determined that within a defined initial time period after starting the drive unit (1) the rotational speed of the turbine (7) of the torque converter (5) reaches or exceeds a first limit value, it is concluded that the torque converter (5) is properly filled, whereas, if within the defined initial time period after starting the drive unit (1) the rotational speed of the turbine (7) of the torque converter (5) does not reach or exceed the first limit value, it is concluded that the torque converter (5) is improperly filled or has run dry, wherein, if it is concluded that the torque converter (5) is properly filled,and if, subsequently, within a defined second time period after the start of the drive unit (1), it is determined that the rotational speed of the turbine (7) of the converter (5) reaches or falls below a second limit value when a non-load-engaging switching position of the automatic transmission (2) is selected via a gear selector lever (9), a fault in the automatic transmission (2) is concluded, wherein at least the first limit value is greater than the second limit value or the second time period is greater than the first time period.

Description

[0001] The invention relates to a method for operating a drive train and a control device for carrying out the method.

[0002] Fig. Figure 1 shows a known prior art schematic of a motor vehicle drivetrain with a drive unit 1 and an automatic transmission 2 connected between the drive unit 1 and an output 3, wherein the automatic transmission 2 is designed as an automatic or automated manual transmission and comprises several switching elements 4 configured as clutches and / or brakes. A starting element configured as a torque converter 5 is positioned between the drive unit 1 and the automatic transmission 2, wherein a torque converter lock-up clutch 6 is associated with the torque converter 5. The torque converter 5 is connected to Fig. Figure 1 shows a turbine wheel 7 and a pump wheel 8. Furthermore, it shows Fig. 1 a gear selector lever 9 and a gear control unit 10. The gear control unit 10 controls and / or regulates the operation of the automatic transmission 2, including the torque converter 5 and the torque converter lock-up clutch 6. A shift position for the automatic transmission 2 is selected via the gear selector lever 9, namely at least one of the shift positions N (Neutral), P (Park), D (Drive - Forward), and R (Reverse).

[0003] It is already known in practice to monitor an automatic transmission to see if it unintentionally engages when a non-engaging gear position is selected via the gear selector lever. However, it is not yet possible to reliably perform this monitoring.

[0004] DE 10 2007 002 171 A1 discloses a generic method by which a faulty transmission capability of a torque converter can be detected.

[0005] From DE 10 2007 001 496 A1 a method for determining a gearbox fault based on the evaluation of the gearbox input speed and the engine speed is known.

[0006] Based on this, the present invention aims to create a novel method for operating a drive train and a control device for carrying out the method.

[0007] This problem is solved by a method for operating a drive train according to claim 1.

[0008] After the drive unit starts, the rotational speed of a turbine in the converter is monitored. If it is determined that the rotational speed of the converter's turbine reaches or exceeds a first limit value within a defined initial period after the drive unit starts, it is concluded that the converter is properly filled. Conversely, if the rotational speed of the converter's turbine does not reach or exceed the first limit value within the defined initial period after the drive unit starts, it is concluded that the converter is empty.

[0009] The invention proposes monitoring, immediately after the start of the drive unit and within the initial period, whether the converter is properly filled or has run dry, based on the rotational speed of the converter's turbine. Only after this initial monitoring confirms that the converter is properly filled can it then be used, again based on the rotational speed of the converter's turbine, to monitor whether an unwanted power transmission is developing in the automatic transmission.

[0010] Preferably, the initial time interval is dependent on the transmission oil temperature such that the higher the transmission oil temperature, the shorter the initial time interval is chosen. This allows for a particularly advantageous verification of whether the torque converter is properly filled or empty, as it is adapted to the transmission oil temperature of the automatic transmission.

[0011] If it is determined that the torque converter is properly filled, and if, subsequently, within a defined second time period after the start of the drive unit, it is observed that the torque converter turbine speed reaches or falls below a second limit value when the automatic transmission is in a non-engaged gear position selected via the gear selector lever, then a fault in the automatic transmission is concluded. Checking for a fault in the automatic transmission after verifying whether the torque converter is empty or filled is particularly advantageous.

[0012] According to a further advantageous embodiment, if, when the automatic transmission is in park mode via the gear selector lever, the rotational speed of the torque converter turbine reaches or falls below the second limit value within the defined second time period, an error is inferred indicating an unintended power transmission in the automatic transmission. The invention presented here allows for the reliable verification of whether an unintended power transmission exists in the automatic transmission despite the selected, power-free gear position.

[0013] The invention is based on the understanding that an empty torque converter and an unintended power transmission in the automatic transmission lead to essentially the same fault pattern immediately after the vehicle is started, namely that the rotational speed of the torque converter turbine falls below a certain threshold immediately after the engine starts. To avoid erroneously concluding that an unintended power transmission is present when monitoring the torque converter turbine speed, the system first checks, based on the turbine speed, whether the torque converter is properly filled or empty. Only after confirming that the torque converter is properly filled is the system then used to check whether an unintended power transmission is developing in the transmission.

[0014] In this case, at least the first limit value is greater than the second limit value, or the second time period is greater than the first time period. The ratio of the two limit values ​​is particularly advantageous for checking whether a properly filled or empty converter is present, and for subsequently determining whether an unwanted friction connection builds up in the automatic transmission despite the selected, friction-free switching position.

[0015] Preferably, the second time interval, which is longer than the first, depends on the transmission oil temperature such that the higher the transmission oil temperature, the shorter the second time interval is chosen. This, in turn, makes it possible to optimally adapt the check for unwanted power transmission in the automatic transmission to the specific operating situation, namely the transmission oil temperature of the automatic transmission.

[0016] The control device according to the invention is defined in claim 6.

[0017] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1 a powertrain diagram of a motor vehicle; Fig. 2. A time diagram to illustrate the procedure for operating a drive train.

[0018] The invention presented here relates to a method for operating a drive train of a motor vehicle and a control device for carrying out the method.

[0019] Fig. Figure 1 shows a schematic powertrain diagram of a motor vehicle with a drive unit 1, an automatic transmission 2, and an output 3, wherein the automatic transmission 2, which includes several shift elements 4, is positioned between the drive unit 1 and the output 3, and provides the tractive force of the drive unit 1 at the output 3. The powertrain includes the following as a starting element: Fig. Figure 1 shows a converter 5, in which a turbine wheel 7 and a pump wheel 8 are shown schematically within the converter 5. A converter lock-up clutch 6 is connected in parallel to the converter 5.

[0020] A gear selector lever 9 allows the driver to select a shift position for the automatic transmission 2, at least one of the following positions: N (Neutral), P (Park), D (Drive - Forward), and R (Reverse). The operation of the automatic transmission 2 is controlled and regulated by a transmission control unit 10.

[0021] According to the invention, the rotational speed of the turbine 7 of the converter 5 is monitored immediately after the start of the drive unit 1, in particular beginning with the presence of an activation signal for the ignition of the drive unit 1. This monitoring of the rotational speed of the turbine 7 of the converter 5 is carried out in such a way that it is monitored whether the rotational speed of the turbine 7 reaches or exceeds a first limit value within a defined first time period after the start of the drive unit 1.

[0022] If, within the defined initial time period after the start of the drive unit 1, the rotational speed of the turbine 7 of the converter reaches or exceeds the first limit value, it is concluded that the converter 5 is properly filled. Conversely, if the rotational speed of the turbine 7 of the converter 5 does not reach or exceed the first limit value within the defined initial time period after the start of the drive unit 1, it is concluded that the converter 5 is improperly filled or has run dry.

[0023] In Fig. 2 is the curve of the rotational speed n over time t. T The turbine 7 of the converter 5 is carried out for two different states, wherein at time t0 the drive unit 1 is started, and wherein time t1 defines the defined first time period after the start of the drive unit 1.

[0024] For curve 11, a rotational speed profile of the turbine 7 of the converter 5 is available, in which, within the defined first time interval, the rotational speed nT of the turbine 7 of the converter 5 exceeds the first limit value S1, so that if curve s 11 is available, it can be concluded that the converter 5 is properly filled.

[0025] In contrast, in curve 12, the rotational speed nT of the turbine 7 of the converter 5 remains so low beyond time t1, i.e., beyond the first time period defined after the start of the drive unit 1, that it does not reach or exceed the first limit value S1, so that for curve 12 it is concluded that the converter 5 is not properly filled or has run dry.

[0026] The first time interval, within which the rotational speed of the turbine 7 of the converter 5 must reach or exceed the first limit value S1 to detect a properly filled converter, is preferably dependent on the transmission oil temperature, with the first time interval being chosen to be shorter the higher the transmission oil temperature of the automatic transmission 2. This allows the detection of whether a properly filled or improperly filled converter 5 is present to be optimally adapted to the operating state of the automatic transmission 2 and converter 5.

[0027] According to an advantageous further development of the invention, it is provided that when it is concluded that the converter 5 is properly filled, a second defined time period (in Fig.2 not shown) after the start of the drive unit 1, which is preferably greater than the first defined time interval, the rotational speed of the turbine 7 of the converter 5 is further evaluated, wherein, if it is found that the rotational speed n subsequently T If the turbine 7 of the converter 5 reaches or falls below a second limit value when a non-engaging shift position for the automatic transmission 2 is selected via the gear selector lever 9, a fault in the automatic transmission 2 is inferred, namely an unwanted engagement in the automatic transmission 2.

[0028] In particular, if, when the automatic transmission 2 is in a park position selected via the gear selector lever 9, the speed of the turbine 7 of the torque converter 5 reaches or falls below the second limit value within the defined second time period, assuming the torque converter 5 is properly filled, a fault, namely an unwanted power transmission, in the automatic transmission 2 is concluded.

[0029] The second time period, within which the check for the unwanted power transmission in the automatic transmission 2 takes place, is, like the first time period, within which a conclusion is drawn as to whether the torque converter is properly or improperly filled, preferably dependent on the transmission oil temperature, wherein the second time period is chosen to be shorter the higher the transmission oil temperature.

[0030] As previously explained, monitoring whether the converter 5 is properly or improperly filled involves checking whether the rotational speed of the converter 5's turbine 7 reaches or exceeds a first limit value within the initial period after the drive unit is started. Subsequent monitoring, checking whether an unwanted power transmission occurs in the automatic transmission 2 when the selected, non-power-engaged shift position is selected, involves checking whether the rotational speed of the converter 5's turbine 7 reaches or falls below a second limit value within a second period that is longer than the first. The first limit value is higher than the second limit value.

[0031] With the invention presented here, it is possible to reliably distinguish and reliably detect the fault pattern of an empty or improperly filled converter 5 as well as the fault pattern of an unwanted power transmission in the automatic transmission 2 despite the selected, power-free shift position, both based on the course of the rotational speed of the turbine 7 of the converter 5.

[0032] The present invention further relates to a control device for carrying out the method. This control device is preferably the transmission control direction 10.

[0033] The control device comprises means for carrying out the method according to the invention. These means are hardware-related and software-related.

[0034] The hardware components consist of data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention. Furthermore, the hardware components include a processor and a memory, wherein the memory serves to store data and the processor to process data.

[0035] The software-related means consist of program modules for carrying out the method according to the invention. Reference sign 1 drive unit 2 automatic transmissions 3 Drive 4 switching element 5 converters 6 Torque converter lock-up clutch 7 Turbine wheel 8 Pump wheel 9 Gear selector lever 10 Transmission control unit 11 Curve path 12 Curve path

Claims

A method for operating a drive train comprising a drive unit (1), a torque converter (5) as a starting element, an automatic transmission (2), and an output (3), wherein, after starting the drive unit (1), the rotational speed of a turbine (7) of the torque converter (5) is monitored, characterized in that, if it is determined that within a defined initial time period after starting the drive unit (1) the rotational speed of the turbine (7) of the torque converter (5) reaches or exceeds a first limit value, it is concluded that the torque converter (5) is properly filled, whereas, if within the defined initial time period after starting the drive unit (1) the rotational speed of the turbine (7) of the torque converter (5) does not reach or exceed the first limit value, it is concluded that the torque converter (5) is improperly filled or has run dry, wherein, if it is concluded that the torque converter (5) is properly filled,and if, subsequently, within a defined second time period after the start of the drive unit (1), it is determined that the rotational speed of the turbine (7) of the converter (5) reaches or falls below a second limit value when a non-load-engaging switching position of the automatic transmission (2) is selected via a gear selector lever (9), a fault in the automatic transmission (2) is concluded, wherein at least the first limit value is greater than the second limit value or the second time period is greater than the first time period. Method according to claim 1, characterized in that if, when the automatic transmission (2) is in park position selected via the gear selector lever (9), the rotational speed of the turbine (7) of the converter (5) reaches or falls below the second limit value within the defined second time period, a fault in the automatic transmission (5) is inferred. Method according to claim 2, characterized in that if the rotational speed of the turbine (7) of the converter (5) reaches or falls below the second limit value within the defined second time period, an unintended power transmission in the automatic transmission (2) is inferred. Method according to one of claims 1 to 3, characterized in that the first time interval depends on the transmission oil temperature such that the higher the transmission oil temperature, the shorter the first time interval is chosen. Method according to one of claims 1 to 4, characterized in that the second time interval depends on the transmission oil temperature such that the higher the transmission oil temperature, the shorter the second time interval is chosen. Control device, in particular transmission control device (10), characterized by means for carrying out the method according to one of claims 1 to 5 .

Images