Method for controlling the powertrain of a motor vehicle

Abstract

A method for controlling a drive train of a motor vehicle with at least one engine and at least one transmission, wherein the transmission comprises a first sub-transmission (T1) with a first clutch (K1) and with a first forward gear (I) and with at least one further, in particular odd-numbered, forward gear (III, V) and a second sub-transmission (T2) with a second clutch and with a second forward gear (II) and with at least one further, in particular even-numbered, forward gear (IV, VI), wherein the first forward gear (I) is engaged with a freewheel (F1), characterized in that, if no power transmission occurs via the freewheel (F1) when the first forward gear (I) is engaged and / or slippage of the freewheel (F1) is detected, it is determined whether the freewheel (F1) or the first clutch (K1) is defective, wherein, if it is determined that only the freewheel (F1) is defective,only the first forward gear (I) is deactivated and at least one further, in particular odd-numbered, forward gear (III, V) of the first sub-transmission (T1) remains usable.

Description

[0001] The invention relates to a method for controlling a drive train of a motor vehicle according to the features of the preamble of claim 1.

[0002] From EP 0 321 873 A2, a dual-clutch transmission and a method for controlling it are known. The dual-clutch transmission comprises a first sub-transmission with a first clutch, a first forward gear, and at least one further forward gear, and a second sub-transmission with a second clutch, a second forward gear, and at least one further forward gear. Among other features, the first forward gear is also equipped with a selectable freewheel mechanism.

[0003] DE 10 2004 035 534 A1 describes a method for controlling a dual-clutch transmission in which, in the event of a malfunction or emergency operation, only one of the two sub-transmission units is used to maintain the drivability of the vehicle.

[0004] DE 10 2007 027 953 A1 relates to a drive unit for a vehicle in which the driving force is transmitted from an end section of a crankshaft via a primary reduction system and a clutch system to a gear transmission housed in a crankcase of an engine. The invention relates in particular to an improvement of a dual-clutch transmission.

[0005] EP 1 531 292 A2 discloses a method for controlling a dual-clutch transmission, which in particular provides strategies for fault and emergency operation to ensure the drivability of the vehicle even in the event of malfunctions of individual clutch or actuator elements.

[0006] However, the methods known in the prior art for controlling a motor vehicle's drivetrain are not yet optimally developed. For example, if no power transmission occurs via the corresponding freewheel when first forward gear is engaged, or if the freewheel slips, other forward gears of the first sub-transmission that could actually be used are also deactivated, which can lead to a reduction in driving comfort.

[0007] The invention is therefore based on the objective of further developing and refining the aforementioned method for controlling a motor vehicle drive train in such a way that driving comfort can be increased in a simple and cost-effective manner.

[0008] The problem underlying the invention is solved by a method for controlling a drive train of a motor vehicle with the features of claim 1.

[0009] The drivetrain comprises, in particular, at least one engine and at least one transmission. The transmission comprises a first sub-transmission with a first clutch, a first forward gear, and at least one further forward gear (in particular, an odd number), and a second sub-transmission with a second clutch, a second forward gear, and at least one further forward gear (in particular, an even number). The first forward gear is engaged via a freewheel. In particular, the first forward gear may have or be equipped with a freewheel. The freewheel thus replaces, in particular, the synchronizing clutch used in the other even and odd forward gears, which, in particular, connects a loose gear to a shaft in a rotationally fixed manner. The freewheel or the synchronizing clutches are thus, in principle, integrated with the associated first or second forward gear.The second clutch is arranged in series in the torque path between the drive motor and the wheel.

[0010] A defect in the freewheel or first clutch can refer to both a temporary loss of function, for example due to temperature and / or weather influences, and a permanent loss of function, for example due to damage and / or wear of functionally relevant components. In such a case, there is no or only insufficient torque transmission between the drive motor and the wheel, because a transmission or torque connection in the torque path is faulty.

[0011] In this procedure, if no power transmission occurs via the freewheel when engaging first forward gear and / or freewheel slippage is detected, it is determined whether the freewheel or the first clutch is defective. If it is determined that only the freewheel is defective, only first forward gear is deactivated, and at least one other forward gear of the first sub-transmission, particularly an odd-numbered one, remains usable, for example, without restriction. For instance, apart from first forward gear, all other forward gears, particularly odd-numbered ones, and / or other gears of the first sub-transmission can remain usable, for example, without restriction.

[0012] If only the freewheel of the first forward gear is defective, only the first forward gear of the first sub-transmission is deactivated. In this way, only as much "flexibility" of the transmission as necessary is eliminated. The function of the first forward gear of the first sub-transmission can then be taken over, for example, by the second forward gear of the second sub-transmission. While this could result in reduced acceleration and / or starting torque, especially with heavy trailer loads and / or steep inclines, this method leads to fewer limitations and / or increased driving comfort compared to deactivating the entire first sub-transmission or all of its gears, because the other gears of the first sub-transmission remain fully functional.

[0013] In one embodiment, the freewheel is identified as defective if the rotational speed at an output side of the freewheel is lower than the rotational speed at an input side of the first clutch. Specifically, if the rotational speed at the output side of the freewheel is lower than the rotational speed at the input side of the first clutch, the freewheel is assumed to be defective, and a measure with only minor driving restrictions is initiated. Such a diagnostic approach, for example, a cascading one, allows the method to be applied in a particularly simple manner, even without the use of at least one intermediate special speed sensor. The rotational speed at the input side of the first clutch can be calculated from or derived from the engine speed, and the rotational speed at the output side of the freewheel can be calculated, for example, from the wheel speeds.

[0014] In a further embodiment, the rotational speed on the drive side of the first clutch is therefore calculated from the engine speed and / or the rotational speed on the output side of the freewheel is calculated from at least one wheel speed, for example from the wheel speeds.

[0015] In a further, alternative, or additional embodiment, the freewheel is identified as defective if the rotational speed at one of the output sides of the freewheel is lower than the rotational speed at one of the input sides of the freewheel and / or at one of the output sides of the first clutch. Thus, by additionally using at least one speed sensor interposed between the first clutch and the freewheel, it can be directly determined whether the freewheel or the clutch is interrupting the power transmission or is defective.

[0016] Provided that the speed on the drive side of the first clutch is equal to the speed on the output side of the first clutch and / or on the drive side of the freewheel and is equal to the speed on the output side of the freewheel, there is no interruption of the power transmission and / or the freewheel does not slip.

[0017] If the rotational speed on the output side of the first clutch and / or on the drive side of the freewheel is lower than the rotational speed on the drive side of the first clutch, then the first clutch is defective.

[0018] In a specific embodiment, the first clutch is therefore determined to be defective if the rotational speed at the drive side of the freewheel and / or at the output side of the first clutch is less than the rotational speed at the drive side of the first clutch.

[0019] If the rotational speed on the output side of the freewheel is lower than the rotational speed on the output side of the first clutch and / or on the input side of the freewheel, the freewheel is defective.

[0020] In a further embodiment, if it is determined that the freewheel is defective, the second forward gear and at least one other forward gear, particularly an even-numbered one, of the second sub-transmission remain usable. Thus, in the event of a defective freewheel in the first forward gear, all other forward gears can still be used, thereby increasing driving comfort.

[0021] In a further embodiment, if it is determined that the first clutch is defective, all gears of the first sub-transmission, in particular the first forward gear and at least one further forward gear, especially an odd-numbered one, of the first sub-transmission, are deactivated. This prevents damage and / or wear of the gears of the first sub-transmission in the event of a defective clutch.

[0022] Normally, i.e., in the case of an intact freewheel and an intact first clutch, the motor vehicle can always be started via the first forward gear, for example by engaging the first forward gear and closing the first clutch.

[0023] In a further embodiment, however, if, when starting off, the vehicle does not engage the first forward gear and / or slippage of the freewheel is detected, the second forward gear is engaged or selected, particularly for starting off. In this case, starting off in second gear is possible instead of first.

[0024] The transmission can be, in particular, an automatic and / or an automatable transmission.

[0025] In a further highly preferred embodiment, the transmission is designed as a dual-clutch transmission. In this configuration, the first forward gear can be engaged via the first clutch and the second forward gear via the second clutch. For example, one clutch component of the first clutch can be non-rotatably connected to an engine shaft driven by the engine, and another clutch component of the first clutch can be non-rotatably connected to a first transmission input shaft. Similarly, one clutch component of the second clutch can be non-rotatably connected to the engine shaft driven by the engine, while another clutch component of the second clutch can be non-rotatably connected to a second transmission input shaft. The first forward gear can be specifically assigned to the first transmission input shaft, and the second forward gear to the second transmission input shaft.The first transmission input shaft and / or the first forward gear, as well as the second transmission input shaft and / or the second forward gear, can be connected to a transmission output shaft in a rotationally effective manner, possibly via an intermediate shaft.

[0026] For example, the transmission can be designed as an automatic and / or automatable dual-clutch transmission, for example with a manual shift function, such as a so-called "Tiptronic" function. This allows the first gear to be manually controlled and / or selected.

[0027] The first forward gear can be engaged, for example, by a freewheel that transmits traction torque, or it can be configured as a freewheel. A freewheel that transmits traction torque, in particular, can be designed more simply and cost-effectively than a freewheel that can be switched on and off. The freewheel for the first forward gear can, for example, be built into or integrated within the first forward gear itself. It is also conceivable that the freewheel for the first forward gear can be switched on and off.

[0028] The second forward gear, for example, can be designed without a freewheel.

[0029] In a further embodiment, the motor vehicle is designed as an electric vehicle with at least one electric motor.

[0030] In a further embodiment, the motor vehicle is designed as a hybrid vehicle with an internal combustion engine and at least one electric motor.

[0031] The disadvantages mentioned at the beginning are therefore avoided and corresponding advantages are achieved.

[0032] There are now numerous possibilities for advantageously designing and further developing the method according to the invention. For this purpose, reference may first be made to the claims subordinate to claim 1. In the following, some preferred embodiments of the method according to the invention are explained in more detail with reference to the drawing and the accompanying description. The drawing shows: Fig. 1 in a schematic flowchart an embodiment of a method according to the invention, in which, if no power transmission occurs via the freewheel when the first forward gear is engaged and / or slippage of the freewheel is detected, it is then determined whether the freewheel or the first clutch is defective, wherein, if it is determined that only the freewheel is defective, only the first forward gear is deactivated and the at least one further, in particular odd-numbered, forward gear of the first sub-transmission remains usable; and Fig. 2. In a schematic flowchart, a design of the in Fig. 1 embodiment of a method according to the invention, in which a defect of the freewheel and / or the first clutch can be detected, in particular by means of a speed sensor connected between the first clutch and the freewheel.

[0033] Fig. Figure 1 illustrates an embodiment of the inventive method for controlling a drive train of a motor vehicle with at least one engine and at least one transmission, wherein Fig. 2 illustrates a specific embodiment of this.

[0034] The motor vehicle can be, for example, an electric vehicle with at least one electric motor and / or a hybrid vehicle with an internal combustion engine and at least one electric motor.

[0035] The transmission comprises a first sub-transmission T1 with a first clutch K1, a first forward gear I, and at least one further forward gear (III, V, etc.), particularly an odd number, and a second sub-transmission T2 with a second clutch, a second forward gear II, and at least one further forward gear (IV, VI, etc.), particularly an even number. The first forward gear I is engaged via a freewheel F1, for example, a freewheel that transmits (only) traction torque. The transmission can be designed, in particular, as a dual-clutch transmission, in which the first forward gear I is engaged via the first clutch K1 and the second forward gear II is engaged via the second clutch K2.

[0036] In the embodiment of the inventive method and its configuration, if no power transmission occurs via the freewheel F1 when the first forward gear I is engaged and / or selected, and / or slippage of the freewheel F1 is detected, it is determined whether the freewheel F1 or the first clutch K1 is defective.

[0037] If it is determined that only the freewheel F1 is defective, only the first forward gear I of the first sub-transmission T1 will be deactivated. Gears II, IV, VI of the second sub-transmission T2, in particular the second forward gear II and at least one further, especially even-numbered, forward gear IV, VI, for example the fourth and sixth forward gears IV, VI, of the second sub-transmission T2, as well as at least one further, for example odd-numbered, forward gear III and / or V of the first sub-transmission T1, for example the third and fifth forward gears III, V of the first sub-transmission, will remain usable.

[0038] If it is determined that the first clutch K1 is defective, the entire first sub-transmission, namely all gears I, III, V of the first sub-transmission T1, i.e. the first forward gear I and at least one further, in particular odd-numbered, forward gear III and / or V of the first sub-transmission T1, is deactivated.

[0039] If, when starting off the motor vehicle, no power transmission via the freewheel F1 is detected when engaging / selecting the first forward gear I, the second forward gear II can be engaged, especially for starting off.

[0040] The freewheel F1 can be identified as defective in a particularly simple way by measuring a rotational speed (n FA ) on one output side of the freewheel F1 less than a rotational speed (n GK ) on a drive side of the first clutch K1. The rotational speed (n FAThe rotational speed (n) on the output side of the freewheel F1 can be calculated from at least one wheel speed. GK The torque on the drive side of the first clutch K1 can be calculated from the engine speed. This can advantageously be achieved without the use of additional speed sensors.

[0041] In the Fig. In the illustrated embodiment 2, an additional speed sensor is connected between the first clutch K1 and the freewheel F1 to determine a speed n. KF This is used on a drive side of the freewheel F1 and / or on a driven side of the first clutch K1. This allows for a more precise differentiation as to whether the freewheel F1 or the first clutch K1 is defective.

[0042] Fig. Figure 2 shows in particular that the drive train has an input side E, for example a gearbox input, which is coupled to the first clutch K1, wherein the first clutch K1 is in turn coupled via the freewheel F1 to the output side A, for example the driven gear. The following is shown in Fig. The input side E shown in Figure 2 can, for example, be the input side of the dual clutch of a dual-clutch transmission.

[0043] Fig. Figure 2 further shows that both the rotational speed n GK on a drive side of the first clutch K1 as well as the rotational speed n FA The rotational speed is measured both on the output side of the freewheel F1 and via the additional, intermediate speed sensor. KF is determined on the output side of the first clutch K1 or on the input side of the freewheel F1.

[0044] The freewheel F1 is identified as defective if the rotational speed n FAon the output side of the freewheel F1, the rotational speed n is smaller. KF on the output side of the first clutch K1 or on a drive side of the freewheel F1.

[0045] The first clutch K1 is identified as defective if a rotational speed n KF on the output side of the first clutch K1 or on the input side of the freewheel F1, the rotational speed n is smaller than the speed n. GK on the drive side of the first clutch K1.

[0046] As already explained, the rotational speed n can also be adjusted here. GK on the drive side of the first clutch K1 from the engine speed and the speed n FA on the output side of the freewheel F1, determined or calculated from at least one wheel speed.

[0047] In the above-described explanation of the preferred and / or alternative and / or further developed embodiments, the freewheel and / or the clutch is identified as defective, in particular by determining and comparing the respective rotational speeds, as described above. When determining or comparing the respective rotational speeds, any micro-slip at the clutch and / or any intentionally set slip at the clutch is taken into account or "factored out." Any micro-slip / slip inherent in the freewheel is also taken into account or "factored out" when comparing the respective rotational speeds of the drive and driven sides of the freewheel. Or, put another way: The freewheel is identified as defective if the rotational speed n FA The smaller the rotational speed n is on the output side. KFon the drive side and / or when the magnitude of a speed difference between the speed n FA on the output side of the freewheel F1 and the rotational speed n KF A certain minimum speed difference is exceeded on the drive side of the freewheel. In particular, the first clutch K1 is identified as defective if the speed n KF on the output side of the first clutch K1, the rotational speed n is smaller than GK on the drive side of the first clutch K1 and / or if the magnitude of a speed difference between the speed n KF on the output side of the first clutch K1 and the rotational speed n GK A certain minimum speed difference is exceeded on the drive side of the first clutch K1. This should be emphasized again. List of reference symbols T1 first sub-transmission K1 first clutch of the first sub-transmission I first forward gear of the first sub-transmission III third forward gear of the first sub-transmission V fifth forward gear of the first sub-transmission F1 Freewheeling of the first forward gear of the first sub-transmission T2 second sub-transmission II second forward gear of the second sub-transmission IV fourth forward gear of the second sub-transmission VI sixth forward gear of the second sub-transmission E Gearbox input A drive n FA Rotational speed at one output side of the freewheel n GK Speed ​​at the drive side of the first clutch n KF Speed ​​at the drive side of the freewheel and / or output side of the first clutch

Claims

[1] Method for controlling a drive train of a motor vehicle with at least one engine and at least one transmission, wherein the transmission comprises a first sub-transmission (T1) with a first clutch (K1) and with a first forward gear (I) and with at least one further, in particular odd-numbered, forward gear (III, V) and a second sub-transmission (T2) with a second clutch and with a second forward gear (II) and with at least one further, in particular even-numbered, forward gear (IV, VI), wherein the first forward gear (I) is engaged with a freewheel (F1), characterized by, that if, when engaging the first forward gear (I), no power transmission occurs via the freewheel (F1) and / or slippage of the freewheel (F1) is detected, it is determined whether the freewheel (F1) or the first clutch (K1) is defective, whereby if it is determined that only the freewheel (F1) is defective, only the first forward gear (I) is deactivated and at least one further, in particular odd-numbered, forward gear (III, V) of the first sub-transmission (T1) remains usable. [2] Method according to claim 1, characterized by , that the freewheel (F1) is identified as defective when a rotational speed (n FA ) on one output side of the freewheel (F1) less than a rotational speed (n) GK ) on a drive side of the first clutch (K1). [3] Method according to claim 2, characterized by , that the rotational speed (n FA) on the output side of the freewheel (F1) is calculated from at least one wheel speed and / or the rotational speed (n GK ) is calculated from the engine speed on the drive side of the first clutch (K1). [4] Method according to any of the preceding claims, characterized by , that the freewheel (F1) is identified as defective when the rotational speed (n FA ) on the output side of the freewheel (F1) less than a rotational speed (n) KF ) on a drive side of the freewheel (F1) and / or on an output side of the first clutch (K1). [5] Method according to any of the foregoing claims, characterized by , that the first clutch (K1) is identified as defective when the rotational speed (n KF ) on the drive side of the freewheel (F1) and / or on the output side of the first clutch (K1) less than a rotational speed (n) GK ) on a drive side of the first clutch (K1). [6] Method according to any of the foregoing claims, characterized by , that the freewheel (F1) is determined to be defective if the magnitude of a speed difference between the speed (n FA ) on the output side of the freewheel and the speed (n KF ) on the drive side of the freewheel (F1) exceeds a minimum speed difference and / or the first clutch (K1) is determined to be defective if the magnitude of a speed difference between the speed (n KF ) on the output side of the first clutch (K1) and the rotational speed (n GK ) on the drive side of the first clutch (K1) exceeds a minimum speed difference. [7] Method according to any of the foregoing claims, characterized by , that if it is determined that the freewheel (F1) is defective, the second forward gear (II) and at least one further, in particular even-numbered, forward gear (IV, VI) of the second sub-transmission (T2) remain usable. [8] Method according to any of the foregoing claims, characterized by, that if it is determined that the first clutch (K1) is defective, all gears (I, III, V) of the first sub-transmission (T1), in particular the first forward gear (I) and at least one further, in particular odd-numbered, forward gear (III, V) of the first sub-transmission (T1), are disabled. [9] Method according to any of the foregoing claims, characterized by , that if, when starting the motor vehicle, no power transmission occurs via the freewheel (F1) when engaging the first forward gear (I) and / or slippage of the freewheel (F1) is detected, the second forward gear (II) is engaged or selected, especially for starting. [10] Method according to any of the preceding claims, characterized by that the motor vehicle is designed as a hybrid vehicle with an internal combustion engine and at least one electric motor or as an electric vehicle with at least one electric motor.

Images