System and method for controlling a transmission

The present invention provides a system for controlling a vehicle comprising a prime mover, a first sensor, a transmission, a second sensor, and a transmission controller. The first sensor outputs a first signal that indicates a speed of an input shaft of the transmission and the second sensor outputs a second signal that indicates a speed of the prime mover. The transmission controller includes control logics that control the transmission using the first signal, perform a diagnostic check on the first sensor, determining whether the diagnostic check of the second control logic indicates that the first sensor meets a predefined performance characteristic, instruct the transmission controller to use the second signal of the second sensor to control the transmission if the third control logic indicates that the first sensor does not meet the predefined performance characteristic, and control the transmission using the second signal of the second sensor.

FIELD

The present disclosure relates to methods and systems for controlling a transmission, and more particularly to methods and systems for controlling a transmission after detecting a faulty sensor.

BACKGROUND

Automatic transmissions often employ sensors to detect a shaft input speed to the transmission. The input speed may be used in various ways to improve the quality and performance of transmission shifts between speed ratios of the transmission. Occasionally, the sensor for the transmission input speed may output a faulty or noisy signal. Such faulty or noisy signals are often inadequate for use in controlling the transmission as desired. A transmission with a faulty sensor may exhibit decreased drivability or may be placed into a “limp-home” mode having reduced transmission performance. Accordingly, there is a need in the art to provide a method and system for improving transmission performance when a transmission speed input sensor fails.

SUMMARY

The present invention provides a system for controlling a vehicle comprising a prime mover, a first sensor, a transmission, a second sensor, and a transmission controller. The prime mover includes an output shaft and the second sensor is configured to detect a rotational speed of the output shaft of the prime mover and output a second signal indicative of the speed of the output shaft of the prime mover. The transmission has an input shaft, a clutch assembly, a plurality of gears, a plurality of torque transmitting devices, and an output shaft. The clutch assembly includes a friction clutch that rotationally couples the input shaft with the plurality of gears and the plurality of torque transmitting devices are selectively engageable with the plurality of gears to establish a plurality of speed ratios between the input shaft and the output shaft. The first sensor is configured to detect a rotational speed of the input shaft of the transmission and output a first signal indicative of the speed of the input shaft of the transmission. The transmission controller is in electronic communication with the first and second sensors and is operable to control the transmission by selectively engaging the plurality of torque transmitting devices, wherein the transmission controller includes a first, second, third, fourth, and fifth control logic. The first control logic is for controlling the transmission using the first signal of the first sensor, the second control logic is for performing a diagnostic check on the first sensor, the third control logic is for determining whether the diagnostic check of the second control logic indicates that the first sensor meets a predefined performance characteristic, the fourth control logic is for instructing the transmission controller to use the second signal of the second sensor to control the transmission if the third control logic indicates that the first sensor does not meet the predefined performance characteristic, and the fifth control logic is for controlling the transmission using the second signal of the second sensor.

In another aspect of the present invention, the clutch assembly is a friction launch clutch assembly.

In yet another aspect of the present invention, the first and fifth control logics include instructions for controlling the transmission by commanding the timing and force of engagement of the plurality of torque transmitting devices.

In yet another aspect of the present invention, the control logic further comprises a sixth control logic for returning the transmission controller to the first control logic if the diagnostic check of the third control logic indicates that the first sensor meets the predefined performance characteristic.

In yet another aspect of the present invention, the predefined performance characteristic of the first sensor is a first signal with less than a predefined amount of signal noise.

In yet another aspect of the present invention, the system further includes a flywheel and the input shaft of the transmission is directly rotationally coupled with the flywheel.

In yet another aspect of the present invention, the clutch assembly is a dual clutch assembly including a first friction clutch and a second friction clutch.

In yet another aspect of the present invention, the transmission is a dual clutch transmission, the plurality of gears are co-planar gear sets, and the plurality of torque transmitting devices are synchronizers.

In yet another aspect of the present invention, the synchronizers are selectively engageable to provide at least seven forward speed ratios and at least one reverse speed ratio.

In yet another aspect of the present invention, the prime mover is an internal combustion engine.

In yet another aspect of the present invention, a method for controlling a transmission of a motor vehicle is provided. The method includes the steps of: receiving a first signal from a first sensor that is configured to output the first signal to indicate a rotational speed of an input shaft of the transmission; processing the first signal with a transmission controller; commanding a plurality of torque transmitting devices using the first signal to establish a plurality of speed ratios between the input shaft and an output shaft of the transmission; performing a diagnostic check on the first sensor; determining whether the diagnostic check indicates that the first sensor meets a predefined performance characteristic; instructing the transmission controller to use a second signal of a second sensor to control the transmission if the diagnostic check indicates that the first sensor does not meet the predefined performance characteristic, wherein the second sensor is configured to output the second signal that indicates a speed of a prime mover interconnected with the transmission input shaft; and commanding the plurality of torque transmitting devices using the second signal when the diagnostic check indicates that the first sensor does not meet the predefined performance characteristic.

DETAILED DESCRIPTION

Referring to the drawings, wherein like reference numbers refer to like components, inFIG. 1a system10for controlling a transmission of a vehicle is schematically illustrated and inFIG. 2a lever diagram of an exemplary transmission10′ for use with the system is illustrated. In the embodiment provided, system10includes a prime mover12, a flywheel or vibration absorber14, transmission16, and a transmission controller20with control logic embodied in hardware, software, or a combination of hardware and software within controller20. In the example provided, the prime mover12is an internal combustion engine. It should be appreciated that other prime movers, such as electric motors, may be incorporated without departing from the scope of the present invention. The engine12has an engine output shaft20and an engine speed sensor22. The engine output shaft20is rotatably coupled with the crankshaft of the engine12. The engine speed sensor22outputs a signal that indicates the rotational speed of the engine12and the engine output shaft20. The example provided incorporates an engine speed sensor22that outputs a signal that indicates when a ferrous gear tooth of a gear that is coupled to the engine passes a magnetic sensor. It should be appreciated that the engine speed sensor22may alternatively measure speed using other technologies, such as mechanically or optically, without departing from the scope of the present invention.

The flywheel14reduces torsional vibrations between the engine output shaft20and the transmission16. The flywheel may incorporate springs, weights, pendulums, and other technologies without departing from the scope of the present invention.

The transmission16is an automatic transmission that provides multiple speed ratios between a transmission input shaft30and a transmission output shaft19. The example provided is a dual clutch or automated manual transmission16. The transmission16may be other types of transmissions without departing from the scope of the present invention. The transmission16includes the transmission input shaft30, a transmission input speed sensor32, a clutch assembly34, and a plurality of gears36for establishing the multiple speed ratios. The transmission input shaft30is rotationally coupled with the flywheel14and the clutch assembly34. The transmission input speed sensor32is similar to the engine speed sensor22, however, the transmission input speed sensor32is configured to output a signal that indicates the speed of the transmission input shaft30.

The clutch assembly34includes at least one launch or friction clutch that rotationally connects the transmission input shaft30with the plurality of gears36without a substantial difference between the speed of the engine12and the speed at the clutch assembly34. Therefore, the clutch assembly34is any clutch assembly that does not incorporate a fluid coupling or torque converter. The launch clutch assembly34provided is a dual clutch assembly having a first clutch34A and a second clutch34B. It should be appreciated that a single friction launch clutch may be incorporated without departing from the scope of the present invention.

The plurality of gears36are selectively engageable by a plurality torque transmitting devices (not shown) for selectively transferring power between the plurality of gears and ultimately to the transmission output shaft19. The example provided is a dual clutch transmission16having meshing co-planar gear sets and synchronizers. It should be appreciated that other gear configurations, such as with planetary gear sets, may be incorporated when the clutch assembly34is used.

The transmission controller20generally includes a processor (not shown) in communication with electronic memory storage devices (not shown). Further, control logic is also provided in the controller20and may be implemented in hardware, software, or a combination of hardware and software. For example, a control logic may be in the form of program code that is stored on the electronic memory storage and executable by the processor. The transmission controller30is in electronic communication with both the engine speed sensor22and the transmission input sensor32. In the embodiment provided, the transmission input sensor32is in direct electronic communication with the controller30and the engine speed sensor22is in electronic communication with an engine controller (not shown), which broadcasts the engine speed sensor22signal to the transmission controller30. Under default conditions, the controller20receives the signal from the transmission input and selectively activates a plurality of control devices, such as the torque transmitting devices, to control the operation of the transmission.

For example, a control logic implemented in software program code that is executable by the processor of controller20includes a first control logic for controlling the transmission with the signal from the transmission input speed sensor32, a second control logic for performing diagnostic checks on the transmission input speed sensor32, a third control logic for determining whether the transmission input speed sensor32is faulty, a fourth control logic for instructing the controller20to use the engine speed sensor22to control the transmission16, and a fifth control logic for operating the transmission16using the engine speed sensor22.

Referring now toFIG. 3, a flowchart of a method100for controlling the transmission16is shown, in accordance with an embodiment of the present invention. The method100is initiated at block102. At block104the method100controls operation of the transmission16using the transmission input speed sensor32. For example, the timing of and force of actuation of the torque transmitting mechanisms (not shown) are determined at least in part by the signal from the transmission input speed sensor32.

In step106the controller20performs diagnostic tests on the input speed sensor32. In step107the controller20determines whether the transmission speed input sensor32signal is faulty. For example,FIG. 4illustrates an exemplary first signal108from a faulty transmission input speed sensor and an exemplary second signal110from the engine speed sensor22. In the example provided, the first signal108is noisy and may be inaccurate or difficult to read. The second signal110is not noisy and is indicative of the speed of the transmission input shaft30. If the controller20determines that the first signal108does not indicate a faulty sensor32then the method returns to step104and the signal108from the sensor32is used to control the transmission16.

If the controller20determines that the first signal108is faulty, the method proceeds to step112. In step112the controller20is instructed to use the second signal110from the engine speed sensor22to control the transmission16. In step114the method controls the transmission16using the second signal110from the engine speed sensor22as a replacement for the faulty first signal108from the transmission input speed sensor32. For example, the timing of and force of actuation of the torque transmitting mechanisms (not shown) are now determined at least in part by the signal from the engine speed sensor22. The method ends at block116.

The present invention provides beneficial operation of the transmission when a faulty transmission input speed sensor is detected. Accordingly, shift quality and transmission performance are substantially maintained until the transmission input speed sensor is replaced.

While the best modes for carrying out the invention have been described in detail, it is to be understood that the terminology used is intended to be in the nature of words and description rather than of limitation. Those familiar with the art to which this invention relates will recognize that many modifications of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced in a substantially equivalent way other than as specifically described herein.