Methods for increasing the availability of a vehicle including an automatic transmission in the event of transmission failures

Abstract

A method for increasing the availability of a vehicle comprising an automatic transmission in the event of transmission faults, wherein the fault present in the transmission is analyzed, wherein, after determining the existing transmission fault, it is analyzed which gears are still available taking into account the shift logic and possible gear engagement sequences, wherein the available gears are shifted automatically, characterized in that, if a fault dependent on a shifting element is detected, it is first determined whether the affected shifting element is permanently closed or permanently open, or whether it permanently allows a partial torque transmission. wherein, if the affected switching element is permanently not fully closed and transmits part of the torque, the gears enabled by the switching logic are automatically shifted, and wherein a torque limitation is implemented, wherein, if the affected switching element is permanently closed, the gears are automatically switched in which this switching element is required in the closed state, excluding the gears in which, according to the switching logic, positive locking switching elements are supported during insertion or removal by the affected switching element designed as a lamellar switching element, wherein, if the affected switching element is permanently open, the gears are automatically switched where this switching element is not required, excluding the gears where, according to the switching logic, positive locking switching elements are supported during insertion or removal by the affected switching element designed as a lamellar switching element.

Description

[0001] The present invention relates to a method for increasing the availability of a vehicle comprising an automatic transmission in the event of transmission faults or faults in the vehicle system according to the preamble of claim 1.

[0002] It is known from the prior art to make a still-available gear available in the event of a transmission failure. However, this results in a significant limitation of the vehicle's availability; furthermore, the vehicle may become undrivable on steep inclines or when towing a trailer if the gear ratio of the available gear is not high enough.

[0003] Methods that allow the gearbox to still be operated in the event of a gearbox fault are disclosed in the publications DE 10 2017 200 405 A1, DE 10 2007 006 210 A1, DE 10 2011 017 741 A1 and DE 10 2013 221 036 A1.

[0004] From the applicant's DE 44 31 073 A1, an automatic transmission with a hydrodynamic torque converter is disclosed, comprising a first and second clutch arranged on a transmission input shaft, wherein the first clutch is engaged in first gear and the second clutch in second gear, with a downstream planetary gear set whose gear ratio can be selected by means of clutches and brakes controlled by an electronic control unit via electromagnetic actuators. If the electronic control unit detects a fault in the first clutch based on the input signals, the electromagnetic actuators are deactivated via a safety relay, thereby putting the automatic transmission into emergency mode. In this case, the electromagnetic actuators of the second clutch are activated by an additional device, which can be, for example, a switch, transistor, relay, or logic module.

[0005] The term "automatic transmission" as used below refers to all transmissions that can automatically change gear ratios. This includes stepped automatic transmissions with planetary gear sets, with and without hydrodynamic torque converters, continuously variable transmissions (CVTs), and dual-clutch transmissions.

[0006] From EP 0431538 B1 it is known to carry out an emergency program and switch the transmission into a predetermined emergency gear stage in the event of a malfunction of a switching element of an automatic transmission of a motor vehicle.

[0007] Furthermore, it is known from EP 0380214 A2 to implement an emergency program with switchable gears in the event of a malfunction of the electronic transmission control of an automatic transmission of a motor vehicle, as long as the transmission's shift actuator is still functional.

[0008] From DE 10 2015 212 772 A1 of the applicant a method for dealing with multiple faults within a transmission system of a motor vehicle emerges, in which components of the transmission are assigned to independent fault categories, whereby, depending on the type of the first fault occurring in a fault category, it is determined which emergency gear is possible when a second fault occurs.

[0009] The present invention is based on the objective of providing a method for increasing the availability of a vehicle comprising an automatic transmission in the event of transmission faults and faults in the vehicle system that can cause a gear limitation.

[0010] This problem is solved by the features of claim 1. Further embodiments and advantages of the invention are set out in the dependent claims.

[0011] Accordingly, a procedure is proposed to increase the availability of a vehicle, including an automatic transmission, in the event of transmission faults or faults in the vehicle system that could cause gear limiting. This procedure involves analyzing the specific fault in the transmission and, after identifying the fault, analyzing which gears are still available, taking into account the shift logic and possible gear engagement sequences. The available gears are then shifted automatically. Transmission faults are defined here as all faults occurring within the entire transmission system, including not only the power- or torque-carrying components, but also the control unit, hydraulics, and electronics.

[0012] According to further training, depending on the fault, functions of the transmission can be restricted; for example, a torque limitation can be implemented or the available gears can be shifted from position N.

[0013] The situation-dependent limitation of gear selection allows the vehicle to continue driving for as long as possible with minimal necessary restrictions. Information about transmission faults is collected and evaluated in a control unit, and this information about the effects of the faults is then distributed to all relevant software components.

[0014] If a fault dependent on a switching element is detected, it is first determined whether the affected switching element is permanently closed or permanently open, or whether it permanently allows a partial torque transmission.

[0015] If the affected switching element is permanently closed, which can occur, for example, with a claw due to mechanical clamping in the closed position, the gears that require this switching element to be in the closed state are switched automatically. Gears where, according to the switching logic, positive-locking switching elements are supported during insertion or removal by the affected switching element, which is designed as a lamellar switching element, are excluded.

[0016] If the affected switching element is permanently open, which can occur, for example, due to an interruption of the electrical connection to the corresponding actuator, the gears in which this switching element is not required are switched automatically. Gears where positive-locking switching elements are supported in the engagement or disengagement by the affected switching element, which is designed as a lamellar switching element, are excluded.

[0017] If the affected switching element is permanently not fully closed and transmits some of the torque, the gears allowed by the shift logic will be engaged automatically, with torque limitation applied. If the parking lock is engaged, it cannot be disengaged.

[0018] In the event of a turbine speed sensor failure, the current gear is preferably maintained, and no further gear changes are permitted. If the parking lock is engaged, it cannot be disengaged.

[0019] The invention is explained in more detail below with reference to the accompanying figures. Identical reference numerals denote identical components. The figures show: Fig. 1: A shifting diagram of a transmission comprising nine forward gears and one reverse gear and a flowchart to illustrate the possible switchable gears according to the invention in the event that the shifting element F designed as a claw is mechanically jammed in the closed position; Fig. 2: A flowchart illustrating the possible selectable gears according to the invention in the case of a transmission with the in Fig. In the circuit diagram shown in 1, the switching element D, designed as a lamellar switching element, is permanently open due to an interruption of the electrical connection to the corresponding actuator; Fig. 3: A flowchart illustrating the possible selectable gears according to the invention in the case of a transmission with the in Fig. In the circuit diagram shown in Figure 1, the switching element C, designed as a lamellar switching element, is permanently not fully closed due to a mechanical problem and transmits part of the torque; and

[0020] Fig. 4: A flowchart illustrating the possible selectable gears according to the invention in the case of a transmission with the in Fig. The turbine speed sensor shown in the circuit diagram 1 has failed.

[0021] In the figures, the steps relevant to each example are represented by the dashed lines.

[0022] In the example according to Fig. 1. After the fault is detected, the gears are automatically switched where switching element F is required in the closed state, namely the first, second, third and fourth forward gear and the reverse gear.

[0023] In the example according to Fig. 2. After the fault is detected, the gears are automatically shifted where shift element D is required in the open position. The fifth and sixth gears are excluded, as the positive-locking shift element F is assisted by the affected shift element during engagement or disengagement. The gear engagement sequence is performed via shift element E, which is designed as a lamellar shift element.

[0024] In the example according to Fig. 3. Upon detection of the fault, either the second, third, and fourth gears are engaged automatically, with the gear selection process carried out via the multi-plate shift element E and the torque to be transmitted being limited, or the third and fourth gears are engaged, with the gear selection process carried out via the multi-plate shift element E. If the parking lock is engaged, it can no longer be disengaged.

[0025] In the embodiment according to Fig. Error 4 is the identified fault, namely the failure of the turbine speed sensor, independent of any of the transmission's shift elements. In this case, the current gear is preferably held, or fourth gear is engaged via the multi-plate shift element, preventing any further shifting. If the parking lock is engaged, it cannot be disengaged.

Claims

[1] A method for increasing the availability of a vehicle comprising an automatic transmission in the event of transmission failures, wherein the fault in the transmission is analyzed, wherein, after determining the transmission fault present, the gears still available are analyzed taking into account the shift logic and possible gear engagement sequences, wherein the available gears are shifted automatically, characterized by , that if a fault dependent on a switching element is detected, it is first determined whether the affected switching element is permanently closed or permanently open, or whether it permanently allows a partial torque transmission, wherein, if the affected switching element is permanently not fully closed and transmits part of the torque, the gears enabled by the switching logic are automatically shifted, and wherein a torque limitation is implemented, wherein, if the affected switching element is permanently closed, the gears are automatically switched in which this switching element is required in the closed state, excluding the gears in which, according to the switching logic, positive locking switching elements are supported during insertion or removal by the affected switching element designed as a lamellar switching element, wherein, if the affected switching element is permanently open, the gears are automatically switched where this switching element is not required, excluding the gears where, according to the switching logic, positive locking switching elements are supported during insertion or removal by the affected switching element designed as a lamellar switching element. [2] Method according to claim 1, characterized by , that depending on the detected error, functions of the transmission may be restricted. [3] Method according to claim 1 or 2, characterized by, that the information about the gearbox faults is collected and evaluated in a control system, whereby the information about the effects of the gearbox faults is distributed to all participating software components.

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