Method to reduce powertrain noise and vibration during engine start in hybrid vehicle

A method of controlling a powertrain system of a hybrid vehicle includes detecting a request to start an engine, incrementally applying torque to the powertrain system, and biasing the torque against a static member of the powertrain system, such as a parking pawl of a transmission when the transmission is disposed in a parking position, to remove lash from the powertrain system prior to starting the engine.

TECHNICAL FIELD

The invention generally relates to a method of controlling a hybrid vehicle, and more specifically to a method of controlling a powertrain system of the hybrid vehicle having a transmission that does not include a mechanical neutral for disconnecting an output of the transmission from an engine.

BACKGROUND

Vehicular powertrain systems include a number of different components interfacing together. The various different component interfaces may each introduce lash into the powertrain system, i.e., a looseness or slop between the various component interfaces that allow connecting components to move relative to each other.

Some powertrain systems of strong hybrid vehicles do not include a mechanical neutral for disconnecting an output of the transmission from an engine. Accordingly, the output of the transmission is continuously connected in torque transmitting communication with the engine. Therefore, because the engine is continuously connected to the other components of the powertrain system, when the engine is started and applies torque to the powertrain system, the torque from the engine will suddenly load the powertrain system and take up the lash, often causing undesirable noise and vibration.

SUMMARY

A method of controlling a hybrid vehicle having an output of a transmission that is continuously connected in torque transmitting communication to an engine is provided. The method includes detecting a request to start the engine. Torque is applied to a powertrain system of the hybrid vehicle. The applied torque is biased against a static member to remove lash from the powertrain system prior to starting the engine.

A method of controlling a powertrain system having a transmission that does not include a mechanical neutral for disconnecting an output of the transmission from an engine is also provided. The method includes detecting a request to start the engine. A lash state (positive or negative) of the powertrain system is sensed relative to a horizontal plane (zero lash). A determination is made based upon the sensed position of the powertrain system whether an applied torque will load or unload the powertrain system. Torque is incrementally applied to a component of the powertrain system over a period of time upon a determination that an applied torque will load the powertrain system and remove lash therefrom. The applied torque is biased against a static member to gradually remove lash from the powertrain system over the period of time and prior to starting the engine. The applied torque is incrementally removed from the powertrain system after the lash is removed from the powertrain system.

Accordingly, torque is incrementally applied to the powertrain system and biased against the static member to remove the lash from the powertrain system, i.e., de-lash the powertrain system, prior to starting the engine. As such, when the engine is started and applies torque to the powertrain, the lash in the powertrain is already removed, thereby preventing the torque from the engine from suddenly de-lashing the powertrain system, which prevents or minimizes any undesirable noise and/or vibration caused therefrom.

DETAILED DESCRIPTION

Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., are used descriptively for the figures, and do not represent limitations on the scope of the invention, as defined by the appended claims.

Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a powertrain system is generally shown at20inFIG. 1. The powertrain system20is for a hybrid vehicle, which is generally shown at22inFIG. 1.

Referring toFIG. 1, the powertrain system20may include but is not limited to an engine24, a transmission26, a driveline28, a differential30, an electric motor32, an electric torque converter34, etc. The engine24may include but is not limited to an internal combustion engine24, such as a gasoline engine24or a diesel engine24. The transmission26is operable in different operating positions, such as a reverse drive position, a forward drive position or a park position. The transmission26may include a gearset36, clutches, brakes, etc. capable of defining a plurality of different gear ratios, such as but not limited to a first forward gear ratio, a second forward gear ratio, . . . , a fifth forward gear ratio, etc. The transmission26may further include a parking pawl38that mechanically engages the gearset36to mechanically block rotation of an output of the transmission26. The transmission26may also include a chain drive, which if included, may be a significant contributor of lash into the powertrain system20. The output of the transmission26is coupled to the differential30via the driveline28for driving one or more wheels40. As is common in hybrid vehicles22, the transmission26may not include a mechanical neutral, i.e., a neutral position that is capable of mechanically disconnecting the output of the transmission26from the engine24. Accordingly, the output of the transmission26is continuously connected in torque transmitting communication to the engine24. The powertrain system20is shown inFIG. 1representing a rear wheel drive system for convenience. However, it should be appreciated that the powertrain system20may alternatively be configured as a front wheel drive system.

Referring also toFIG. 2, a method of controlling the hybrid vehicle22, and more specifically the powertrain system20of the hybrid vehicle22, is generally shown at42. The method42may be embodied as a control algorithm operable on a control module. Accordingly, the steps of the below described method may be coded into the control algorithm and performed and/or executed by the control module. As such, it should be appreciated that the control module may include but is not limited to a computer or processor, memory, various sensors configured for sensing data at one or more components of the powertrain system20, a communication system for electronically communicating information between the control module and the various components of the powertrain system20, such as but not limited to the various sensors, and any other software and hardware necessary to communicate and control the various components of the powertrain system20and implement the method disclosed herein.

The method includes detecting a request to start the engine24, generally indicated by box44. The request to start the engine24may be either a key start request, such as but not limited to turning an ignition key to a start position, or an auto-start request, such as but not limited to an automatic request from a control module to start the engine24to perform a vehicular function, such as heat a cabin area.

If no request to start the engine24is detected, indicated at46, then no action is taken, generally indicated by box48. However, if a request to start the engine24is detected, generally indicated at50, a driver requested gear selection position (e.g., a PRNDL position) of the transmission26is sensed to determine if the transmission26is disposed in the park position with the parking pawl38engaged to mechanically block rotation of the output of the transmission26, generally indicated by box52. If the transmission26is not disposed in the park position, generally indicated at54, then no torque is applied and the engine is started, which is generally indicated by box86. However, if the transmission26is disposed in the park position with the parking pawl38engaged, which is generally indicated at58, then torque may be applied to load and de-lash the powertrain system20.

If the transmission26is disposed in the park position, then a lash state of the vehicle22relative to a horizontal plane is sensed, generally indicated by box60. The horizontal plane represents or generates zero lash in the powertrain system20. The position of the lash state may be in either direction relative to the horizontal plane, i.e., may be either negative or positive. The lash state of the vehicle22relative to the horizontal plane is sensed to determine if an applied torque will load or unload the powertrain system20. For example, if the vehicle22is parked on a hill, gravity may pre-load the powertrain system20and automatically de-lash the powertrain system20, i.e., removing the lash from the powertrain. However, if torque is applied to the powertrain system20in a direction that counters the affects of gravity, then the torque may unload the powertrain system20and introduce lash back into the powertrain system20. The lash state of the vehicle22relative to the horizontal plane may be sensed and/or measured in any suitable manner, including but not limited to sensing the orientation of the vehicle22and the powertrain system20with an appropriate sensor. The control module may be configured to receive the information regarding the orientation of the vehicle22relative to the horizontal plane, and make the determination, generally indicated by box62, whether the orientation of the vehicle22is such that torque applied to the powertrain system20in a pre-defined direction would load or unload the powertrain system20, i.e., remove lash from or introduce lash into the powertrain system20.

Upon a determination that an applied torque will unload the powertrain, generally indicated at64, then no torque is applied, generally indicated by box66, and the engine24may be started, generally indicated by box86. Upon a determination that an applied torque will load the powertrain system20and remove lash therefrom, generally indicated at68, torque is applied to the powertrain system20of the hybrid vehicle22, generally indicated by box70. As such, torque is only applied when the applied torque will load the powertrain system20and remove the lash therefrom. Preferably, the torque is applied incrementally over a period of time to gradually increase the value or magnitude of torque applied, i.e., the torque is ramped up over time. For example, the torque may be ramped up over a period of time between the range of 0.1 and 0.5 seconds. The torque is applied to remove the lash from the powertrain system20. The torque may be applied from any suitable power source, such as but not limited to the electric motor32of the hybrid powertrain system20.

In order to remove the lash in the powertrain system20, the applied torque must react against a stationary object or component of the powertrain system20. Accordingly, the applied torque is biased against a static member to remove lash from the powertrain system20prior to starting the engine24, generally indicated by box72. The static member may include any component of the powertrain system20that is fixed to prevent rotation of the powertrain system20. For example, the applied torque may be biased against the parking pawl38of the transmission26when the transmission26is disposed in the park position.

Once torque is applied to the powertrain system20, then the state of lash in the powertrain system20may be sensed to determine if the lash is removed from the powertrain system20, generally indicated by box74. The state of lash may be sensed in any suitable manner, including but not limited to sensing the magnitude of torque applied to the powertrain system20with one or more sensors. The control module may be configured to determine whether the lash is removed or is not removed, generally indicated by box76, based upon the value of the sensed torque. For example, once the sensed torque reaches a pre-defined level, the control module may determine that the lash is removed from the powertrain system20.

Upon a determination that the lash is not removed from the powertrain system20, generally indicated at78, the applied torque is continued and biased against the static member. Upon a determination that the lash is removed from the powertrain system20, generally indicated at80, then the control module may allow the engine24to be started, generally indicated by box86. Because the lash is removed from the powertrain system20, torque from the engine24once started will not cause the various components of the powertrain system20to move, thereby eliminating or minimizing noise and vibration in the powertrain system20upon the engine24start, even though the engine24is continuously connected to the output of the transmission26.

Once the engine24is started, then the control module may determine whether torque was applied to remove driveline lash, generally indicated by box87. If the control module determines that no torque was applied to remove the driveline lash, generally indicated at88, then the control module may allow a Brake Transmission Shift Interlock (BTSI) system to be unlocked, generally indicated by box84, thereby allowing a transmission shift lever to be moved between positions. If the control module determines that torque was applied to remove driveline lash, generally indicated at90, then the applied torque is removed from the powertrain system20, generally indicated by box82. Preferably, the torque is removed incrementally over a period of time to gradually remove the applied torque from the powertrain system20, i.e., applied torque is ramped down. For example, the torque may be ramped up over a period of time between the range of 0.1 and 0.5 seconds.

If torque was applied to remove driveline lash, then the control module continuously monitors the powertrain system20to determine if all of the applied torque has been removed and/or eliminated from the powertrain system20, generally indicated by box92. If the control module determines that all of the applied torque has not been eliminated from the powertrain system20, generally indicated at94, then the control module continues to remove the applied torque, generally indicated by box82. If the control module determines that all of the applied torque has been removed and/or eliminated from the powertrain system20, generally indicated at96, then the control module may allow the Brake Transmission Shift Interlock (BTSI) system to be unlocked, generally indicated by box84, thereby allowing the transmission shift lever to be moved between positions.