METHOD FOR CONTROLLING NOISE GENERATION IN A HYBRID POWERTRAIN

Abstract

Method for controlling noise generation in a hybrid powertrain (10) comprising a machine (12) and a first and second electric motor (62, 64) configured to transmit torque through a transmission (14) to a final drive (16), comprising: Determining a transition window (70) associated with compensating for backlash in the transmission (14) that occurs during the transition of the second electric motor (64) between operation in an electrical power-generating mode and operation in a torque-generating mode (140); and Executing a noise reduction control scheme when the output torque of the second electric motor (64) is within the transition window (70) (160), wherein the execution of the noise reduction control scheme includes decoupling the second electric motor (64) from an element (46, 60) of the gearbox (14) when the output torque of the electric motor (64) is within the transition window (70), Reducing the amount of torque (80) generated by the power machine (12) and increasing the torque (84) of the second motor (64) during operation in the transition window (70); and The second electric motor (64) switches between operation in an electrical power generating mode and operation in a torque generating mode (72), and subsequently immediately increases the amount of torque (94) generated by the power machine (12) to compensate for the backlash.

Description

[0001] This disclosure relates to hybrid powertrains.

[0002] A hybrid transmission combines and transfers torque from various torque actuators to a driveline to provide traction for a vehicle. Torque actuators can include internal combustion engines and non-combustion-based systems, including electric motors, hydraulic motors, and mechanical engines. Non-combustion-based systems can be controlled to generate torque or produce storable energy. For example, an electric motor can generate electricity that is used immediately in another electric motor or stored remotely in a battery or high-voltage capacitor.

[0003] Paired electric motors may include a first motor configured to generate torque and a second motor configured to generate electricity. However, both the first and second motors may be capable of generating torque and electricity as needed. Thus, the second motor may operate in a torque-generating mode during operation to provide auxiliary torque to the first motor, thus providing additional traction when torque demands are high.

[0004] Hybrid transmissions may utilize a differential gear set and clutches to manage torque between the torque actuators and the driveline. Through various clutch actuations, the hybrid transmission can operate in one of several fixed-gear modes or in a variable-ratio mode. The differential gear assemblies typically include a sun gear, planetary gears, and a ring gear that mesh and interact to transfer torque.

[0005] Any interaction of meshing gears includes backlash, which is a clearance that occurs between mating components of the gears. Backlash has no effect when the gears are transmitting torque. Backlash may manifest itself as audible noise, such as chatter or knock, when the clearance between mating components of the gears is adjusted during a torque transient. Torque transients include initiating torque transfer from rest, stopping torque transfer during a coast-down, or reversing the direction of torque transfer. Excessive backlash is known to impair gear durability and result in torque transfer delays when the backlash between mating components of the gears is adjusted during a torque transient.

[0006] Audible noise associated with backlash during a torque transition can be noticeable and annoying when an electric motor reverses torque direction. Such audible noise can be generated by engine torque being transferred to the transmission during torque reversal in an electric motor coupled to a transmission.

[0007] DE 11 2009 004 666 T5 teaches a hybrid transmission with an internal combustion engine, two electric motors, a planetary gear, and a reduction gear mechanism. The planetary gear combines the outputs of the internal combustion engine and the two electric motors. In operating states in which the first electric motor operates neither as a motor nor as a generator, but is intended to provide reaction torque, i.e., is not rotating, a locking mechanism is engaged, which secures the rotor of the first electric motor to the transmission housing. This engagement is performed in such a way that the play between the elements of the locking mechanism to be connected is compensated, thus achieving a smooth transition to this operating state.

[0008] JP 2010 100 268 A teaches that when starting an internal combustion engine in a hybrid vehicle by means of a first electric motor, when the vehicle is currently driven by a second electric motor, rattling noise occurring in the transmission can be selected by setting a gear ratio according to a voltage waveform of the first electric motor.

[0009] US 2011 0 028 269 A1 discloses, in a series hybrid system in the operating state of purely electric driving, the use of the clutch located between the internal combustion engine and the motor / generator for drive train damping when play occurs in the drive train as a result of a reversal of the direction of rotation of the motor / generator.

[0010] DE 198 42 452 A1 discloses a hybrid transmission with an internal combustion engine, two electric motors, and a planetary gear system. It shifts the operating point of the internal combustion engine in operating ranges where rattling noises may occur in the transmission, thereby avoiding these operating ranges. If necessary, the speeds of the transmission gears are increased.

[0011] US 2007 0 225 888 A1 discloses a method for controlling play and noise in a drivetrain of a hybrid vehicle. Play in the drivetrain is inferred from torque changes at the output shaft, and if necessary, an active damping strategy is applied using a complex control approach.

[0012] From DE 10 2007 055 727 A1 it is known to change the operating point of an electric motor in a hybrid drive train from an area in which noise is generated to an area without noise.

[0013] From US 2013 / 0 054 064 A1 and the corresponding DE 11 2010 005 327 B4, a control device of a hybrid vehicle power transmission device is known, comprising a first electric motor and a second electric motor, each coupled to a drive shaft. The first electric motor is coupled to a rotary element of a differential mechanism having an input shaft coupled to an internal combustion engine. The second electric motor is coupled to an output shaft of the differential mechanism. The control device executes a method in which, via a processing device, when any of a torque of the drive shaft, a torque of the first electric motor, and a torque of the second electric motor changes and passes through zero, the torque is slowly changed at a change rate preset to suppress gear rattle noise.

[0014] It is the object of the invention to provide an improved method for controlling noise generation in a hybrid powertrain.

[0015] This object is achieved by a method for controlling noise generation in a hybrid powertrain having the features of claim 1.

[0016] Advantageous embodiments are specified in the dependent claims.

[0017] One or more embodiments will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates a hybrid powertrain system configured to provide traction to a vehicle in accordance with the present disclosure; Fig.2 graphically illustrates coincident amounts of engine torque, first motor torque, second motor torque, and corresponding clutch activation associated with operation of a powertrain system during execution of an exemplary noise avoidance control scheme, according to the disclosure; and Fig. 3 schematically illustrates an exemplary flowchart of a noise avoidance control scheme for controlling operation of a hybrid powertrain system according to the present disclosure.

[0018] Referring now to the drawings, in which the representations are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same, Fig.1 schematically illustrates a hybrid powertrain system 10 configured to provide traction for propelling a vehicle. The hybrid powertrain system 10 includes a transmission 14 configured to connect an engine 12, a first motor 62, a second motor 64, and a differential 16. Like reference numerals refer to like elements throughout the description. The hybrid powertrain system 10 may be configured to operate, without limitation, as any of a battery electric (EV) system, an extended-range electric (EREV) system, an electric hybrid system, or another configuration. The embodiment of the hybrid powertrain system 10 is illustrative.

[0019] The engine 12 is preferably a multi-cylinder, direct-fuel-injected internal combustion engine that converts fuel into mechanical power through a combustion process. The engine 12 is equipped with a plurality of sensing devices and actuators configured to monitor operation and deliver fuel to form a combustion charge to produce torque. The engine 12 is configured to execute auto-start and auto-stop control schemes and fuel cut-off (FCO) control schemes during ongoing operation of the hybrid powertrain system 10. The engine 12 is considered to be in an ON state when it is fueled and firing. The engine 12 is considered to be in an OFF state when it is not fueled and not rotating.The engine 12 is considered to be in a state when it is not supplied with fuel but is rotating.

[0020] The first and second motors 62 and 64, respectively, preferably comprise multi-phase electric motor / generators electrically connected to a power converter module. The first and second motors 62 and 64, respectively, are configured to operate in torque-generating modes to convert stored electrical energy into mechanical energy, and in electrical power-generating modes to convert mechanical energy into electrical energy storable in an energy storage device. The first and second torque motors 62 and 64 have limits on output power in terms of torque and speeds.

[0021] The planetary gear set 14 includes an input shaft 17 continuously coupled to the engine 12, a planetary gear assembly 18, and an output shaft 19 continuously coupled to the differential 16. A torque converter may be disposed between the engine 12 and the input shaft 17. If no torque converter is present, a vibration damper may be disposed between the engine 12 and the input shaft 17. The exemplary planetary gear assembly 18 includes three planetary gear sets, including a first planetary gear set 20, a second planetary gear set 30, and a third planetary gear set 40.

[0022] The first planetary gear set 20 includes a sun gear member 22, a ring gear member 24, and a planet carrier assembly member 26. The planet carrier assembly member 26 includes a plurality of planet gears 27 rotatably mounted on a carrier member 29 and interacting with both the sun gear member 22 and the ring gear member 24.

[0023] The second planetary gear set 30 includes a sun gear member 32, a ring gear member 34, and a planet carrier assembly member 36. The planet carrier assembly member 36 includes a plurality of planet gears 37 rotatably mounted on a carrier member 39 and interacting with both the sun gear member 32 and the ring gear member 34.

[0024] The third planetary gear set 40 includes a sun gear member 42, a ring gear member 44, and a planet carrier assembly member 46. The planet carrier assembly member 46 includes a plurality of planet gears 47, 48 rotatably mounted on a carrier member 49. The planet gears 47 interact with the sun gear member 42 and the planet gears 48. The planet gears 48 interact with the ring gear member 44 and the planet gears 47. The third planetary gear set 40 is commonly referred to as a compound planetary gear set.

[0025] The first motor 62 and the second motor 64 are integrated into the transmission to convert between electrical energy and mechanical energy. The first motor 62 is coupled to the transmission 14 at the sun gear member 22 and is selectively coupled to the ring gear member 34, as explained below.

[0026] The second motor 64 is coupled to the transmission 14 at the sun gear member 32 and is selectively coupled to the planetary carrier assembly member 46, as explained below. The first and second motors 62, 64 are capable of providing torque to the transmission 14 independently or in combination with each other and the engine 12.

[0027] The exemplary planetary gear assembly 18 includes five selectable torque-transmitting clutches 50, 52, 54, 56, and 58. The torque-transmitting clutches 52 and 56 are any suitable rotating-type torque-transmitting mechanisms and are typically multi-disk clutch devices arranged in a friction configuration. The torque-transmitting clutches 50, 54, and 58 may be any suitable stationary-type torque-transmitting mechanisms and are commonly called brake or reaction clutches. They may be a selectable one-way clutch (SOWC), which may be a controllable mechanical diode clutch, a selectable roller clutch, or a selectable sprag clutch.

[0028] The input shaft 17 is continuously coupled to the ring gear member 24, and the output shaft 19 is continuously coupled to the ring gear carrier member 29. The ring gear member 22 is selectively connected to the carrier member 29 by activation of the clutch 58. The first motor 62 is selectively connected to the ring gear member 34 by activation of the clutch 56. The ring gear member 34 is selectively connectable to the transmission housing 60 by activation of the brake 54. The second motor 64 is selectively connectable to the planetary carrier assembly 46 by activation of the clutch 52. The planetary carrier assembly member 36 is selectively connectable to the transmission housing 60 by activation of the clutch 50.

[0029] The transmission 14 includes a series of fluid circuits for delivering fluid to appropriate areas of the transmission 14. The fluid circuits supply hydraulic pressure to apply individual ones of the clutches 50, 52, 54, 56, and 58. A hydraulic fluid delivery system 8, commonly referred to as a valve body, is signally connected to a control module 5 for selectively opening and closing a number of valves to provide a selectable flow of fluid into the desired fluid circuit(s) to activate and deactivate individual clutches 50, 52, 54, 56, and 58 and thus produce the commanded result, e.g., an appropriate torque multiplication or reduction.

[0030] The control module 5 is operatively connected to the valve body 8 to activate and deactivate the clutches 50, 52, 54, 56, and 58. The control module 5 is signally and operatively connected to each of the engine 12, the first motor 62, and the second motor 64. The control module 5 monitors an operator torque request 7 and powertrain operating parameters 9, e.g., current engine output torque, wheel speed sensor output, and gear selection, to select an appropriate engine output and clutches 50, 52, 54, 56, and 58 to achieve a selected gear ratio for operation. The selected gear ratio may be selected or calculated from a series of lookup tables based on the operator torque request 7 and powertrain operating parameters 9.

[0031] Control module, module, controller, control unit, processor and similar terms mean any one or various combinations of one or more of an application-specific integrated circuit (ASIC), an electronic circuit, a central processing unit (preferably a microprocessor), and associated memory and storage (read-only memory, programmable read-only memory, random access memory, hard disk memory, etc.).) that executes one or more software or firmware programs or routines, a combinational logic circuit, an input / output circuit and input / output device, suitable signal conditioning and buffering circuitry, and other components to provide the described functionality. Software, firmware, programs, instructions, routines, code, algorithms, and similar terms mean any controller-executable set of instructions, including calibrations and lookup tables. The control module has a set of control routines that execute to provide the desired functions.Routines are executed, for example, by a central processing unit and are operable to monitor inputs from sensing devices and other networked control modules and to execute control and diagnostic routines to manage the operation of actuators. Routines can be executed at regular intervals, for example, every 3.125, 6.25, 12.5, 25, and 100 milliseconds, during ongoing engine and vehicle operation. Alternatively, routines can be executed in response to the occurrence of an event.

[0032] The control module 5 monitors the operator torque request 7 and the powertrain operating parameters 9. The control module 5 calculates a preferred output torque required by each of the engine 12, the first motor 62, and the second motor 64, in conjunction with a preferred gear selection, to control operation of the hybrid powertrain system 10 and thus produce traction torque in response to the operator torque request 7. For example, the control module 5 may select operation in an EV mode, with the first and second motors 62, 64 operating in torque-producing modes to provide output torque and the engine 12 in the OFF state. The control module 5 may select operation in a combustion mode, with only the engine 12 producing traction torque and the first and second motors 62, 64 operating in an electric power-producing mode.The control module 5 may select operation in a combination mode wherein the engine 12 and one or both of the first and second motors 62, 64 operate in the torque-producing mode.

[0033] In one embodiment, the prime mover 12 and the first motor 62 are primarily used to generate traction torque, with the second motor 64 being used to generate electrical power. At low levels of torque demand, in one embodiment, the first motor 62 is used to generate traction torque, and the prime mover is in the OFF state. When the torque demand exceeds a response threshold, the second motor 64 switches from operation in the electrical power-generating mode to operation in the torque-generating mode. The response threshold may be triggered, for example, by an increase in the operator torque demand that exceeds a torque capacity of the first motor 62 or a change in the operating efficiencies of the first and second motors 62, 64.It will be appreciated that the second motor 64 transitions from operation in the torque-producing mode to operation in the electric power-producing mode, with a corresponding effect on meshing interactions of selected gear elements of the first, second, and third planetary gear sets 20, 30, and 40, respectively.

[0034] When the second motor 64 transitions between the electric power producing mode and the torque producing mode and its torque direction is reversed, associated meshing interactions are reversed and backlash is taken up as the meshing gears reverse direction. During the transition between the electric power producing mode and the torque producing mode, audible noise may be generated as the second motor 64 changes the torque direction and backlash in the meshing interactions of selected gear elements is taken up during the torque transition. Vibrations associated with the torque transfer from the prime mover 12 via the input shaft 17 to the gear elements of the planetary gear set 14 may exacerbate the audible noise generated by the backlash being taken up in the meshing gears.The resulting disturbing audible noise is amplified by the gear housing 60.

[0035] Fig. 3 is a flowchart for a noise avoidance control scheme for controlling and managing the operation of a powertrain system in response to an operator torque request to minimize or prevent audible noise caused by gear backlash that occurs with a change in the operation of an electric motor from generating torque in a first direction to generating torque in a second direction. The noise avoidance control scheme is described with reference to the hybrid powertrain system 10, which is illustrated with reference to Fig. 1 was described.

[0036] Table 1 is used as a key to Fig.3 for the flowchart of the noise avoidance control scheme, where the blocks marked with numbers and the corresponding functions are listed as follows. Table 1 BLOCK BLOCK CONTENT 100 Monitor engine output torque 110 Monitor output torque of the first motor 120 Monitor output torque of the second motor 130 Monitor clutch activations 140 Determine boundaries of transition windows 150 Determine when one of the first and second motors is operating within the transition window 160 Execute noise reduction control scheme 170 Determine when one of the first and second motors operates outside the transition window 180 Interrupt noise reduction control scheme

[0037] The noise avoidance control scheme monitors the output torques of the engine (100), the first electric motor (110), and the second electric motor (120). Activations of the transmission clutches are monitored (130).

[0038] Boundaries for transition windows for the first and second electric motors are determined (140). Each transition window is related to positive and negative torque values ​​around a zero output torque transition point for the selected electric motor. The transition point is defined as the point at which the electric motor produces zero torque and indicates a point at which the electric motor transitions between producing torque in a first direction to producing torque in a second direction. Thus, a transition between operation in the electrical energy producing mode and operation in the torque producing mode includes a transition point.

[0039] A transition window is an interval related to the transition point. As the direction of output torque from the electric motor is reversed, associated meshing interactions in the transmission are reversed. Backlash is taken up when the meshing gears begin transmitting torque in the other direction. The transition window is associated with taking up backlash in the meshing interactions of selected gear elements during a torque transition when torque transmission in a first direction is relieved from the meshing gears and torque transmission in a second, reverse direction is applied to the meshing gears by changing the operating mode of the electric motor. The transition window can be defined in terms of positive and negative torque values ​​of the motor around the zero torque transition point.The boundaries for the transition window are preferably determined in advance and stored using lookup tables. One skilled in the art will be able to determine appropriate amounts of positive and negative torque values ​​around a zero-torque transition point for backlash compensation. In one embodiment, the transition window may instead be unilateral and defined as the zero-torque transition point and one of the positive and negative motor torque values ​​around the zero-torque transition point, wherein the one of the positive and negative motor torque values ​​around the zero-torque transition point corresponds to a torque transfer in a second, reverse direction applied to the meshing gears at the end of the transition.

[0040] The output torques of the first electric motor (110) and the second electric motor (120) are monitored to determine when the first electric motor or the second electric motor is operating within their respective transition windows (150). The output torques of the first electric motor (110) and the second electric motor (120) may be monitored using torque commands for the first and second electric motors. Determining whether either the first electric motor or the second electric motor is operating within the transition window may be accomplished using lookup tables and operating parameters including the operator torque request, motor torque commands, motor speeds, or other related operating parameters.

[0041] A noise reduction control scheme is executed when either the first electric motor or the second electric motor is operating within the transition window (160). In one embodiment, the noise reduction control scheme includes a process that includes decoupling the transitioning electric motor from the transmission during the transition window by deactivating one or more clutches that effect torque transfer between the electric motor and the transmission. This operation is described with reference to Fig.2. In one embodiment, decoupling the transitioning electric motor from the transmission during the transition window reverses geared interactions in the transmission without a mechanical connection between the transitioning electric motor and the transmission housing, thereby reducing the transmission of noise through the transmission housing associated with the lash transition. The deactivated clutches are reactivated after the lash has been taken up.

[0042] Alternatively, the noise reduction control scheme includes building a torque reserve from the engine and delivering a torque release to quickly reverse all meshing interactions at once during the transition window. The torque reserve is created by increasing throttle opening to the engine and retarding spark timing upon entering the transition window. The engine increases torque production to take up backlash in the transmission by advancing the retarded spark timing at the end of the transition window after the second electric motor transitions between operation in the electric power producing mode and operation in the torque producing mode. This operation causes immediate backlash takeup in the reverse direction of the second motor. The clutches remain preferentially engaged.Such operation may include a single audible click as the entire play is equalized at once, which may be considered less disturbing than a prolonged rattling or growling noise.

[0043] Alternatively, the noise reduction control scheme includes decreasing the amount of torque generated by the prime mover and increasing the torque of the second motor to provide immediate torque generation and thus compensate for the reduction in torque from the prime mover. The immediate increase in torque from the second motor reverses the gear direction to take up the backlash from each of the gear interactions during the transition window. The clutches preferentially remain engaged. Such operation may include a single audible click as all the backlash is taken up at once, which may be considered less disruptive than a prolonged rattle or growl.

[0044] A single or all noise mitigation control schemes may be applied to a single vehicle. It will be appreciated that any reduction in output torque by the engine or the first motor during the transition can be supplemented by the other, i.e., the engine or the first motor.

[0045] The operation of the respective electric motor is monitored, and the noise reduction control scheme is subsequently interrupted when the respective electric motor exits the transition window (170). The powertrain system then resumes normal operation to transfer torque between the first and second electric motors, the engine, and the transmission in response to the operator torque request (180).

[0046] As can be seen, the noise reduction control scheme operates during a transition of one of the electric motors between an electric power-generating mode and a torque-generating mode. It should also be noted that, although the second motor has been discussed in detail, the methods herein are equally applicable to the first motor.

[0047] Fig.2 graphically shows coincident amounts of engine torque 80, first motor torque 82, and second motor torque 84, and a corresponding clutch activation command 86 in relation to elapsed time 88. The engine torque 80, first motor torque 82, second motor torque 84, and the corresponding clutch activation command 86 are associated with the operation of a powertrain system, e.g., hybrid powertrain system 10, including a transmission 14, engine 12, first motor 62, and second motor 64, as described with reference to Fig. 1. The clutch activation command 86 is associated with clutch 54, which is a fixed-type torque-transmitting mechanism. The amounts of engine torque 80, first motor torque 82, and second motor torque 84 are responsive to an operator torque request for traction power.

[0048] Initially, the powertrain system produces zero torque. In response to an operator torque request, engine torque 80 and first motor torque 82 increase. A portion of the produced torque is consumed by second motor torque 84, indicated by operation in the electric power-generating mode.

[0049] The torque of the second motor 84 then begins to increase, approaching a transition point 72 and transition window 70 associated with the transition between operation in the electric power-generating mode and operation in the torque-generating mode. It should be noted that the transition point 72 and transition window 70 occur with mode transitions in both directions. Backlash occurs in specific ones of the gears of the transmission 14 when the motor transitions between generating electric power and generating traction torque, with an associated risk of generating objectionable noise. The transition window 70 is associated with backlash that must be accommodated in conjunction with unloading torque in the gears in a first rotational direction and applying torque to the gears in a second, opposite rotational direction.

[0050] The transition point 72 may be determined by calculating an estimated rate of torque reduction to reach the transition point 72 or by using predetermined lookup tables. The transition window 70 may be determined as a period of time or a torque range before and after the transition point 72. The transition window 70 may be determined as a torque range surrounding the transition point 72, a speed range around the speed of the subject engine at the torque transition point 72, an estimated time period to accomplish the noise reduction, or another suitable engine operating parameter.

[0051] The engine torque 80 increases from zero through the transition window 70 and reaches a peak torque value 94 after the transition window 70. The torque of the first motor 82 increases from zero to a peak output torque at approximately the end of the transition window 70 and then decreases to a point near zero before the torque is increased again.

[0052] The transition point 72 and the corresponding transition window 70 are shown for the second torque motor as it transitions from generating electrical power to generating traction torque. Before the start of the transition window 70, the state of the clutch enable command 86 is 1, indicating that the associated clutch 54 is activated. During the transition window 72, the clutch enable command 86 switches to 0, indicating that the associated clutch 54 is deactivated, allowing the backlash in the gears of the transmission 14 to be taken up as the second motor transitions from generating electrical power to generating traction torque. Thereafter, operation continues with the second motor generating traction torque.

Claims

[1] A method for controlling noise generation in a hybrid powertrain (10) including an engine (12) and first and second electric motors (62, 64) configured to transmit torque through a transmission (14) to a driveline (16), comprising: Determining a transition window (70) associated with compensating for backlash in the transmission (14) that occurs during the transition of the second electric motor (64) between operation in an electric power generating mode and operation in a torque generating mode (140); and Executing a noise reduction control scheme when the output torque of the second electric motor (64) is within the transition window (70) (160), wherein executing the noise reduction control scheme comprises decoupling the second electric motor (64) from an element (46, 60) of the transmission (14) when the output torque of the electric motor (64) is within the transition window (70), Reducing an amount of torque (80) generated by the engine (12) and increasing the torque (84) of the second motor (64) during operation in the transition window (70); and Transitioning the second electric motor (64) between operation in an electric power producing mode and operation in a torque producing mode (72), and subsequently immediately increasing the amount of torque (94) produced by the prime mover (12) to compensate for the backlash. [2] The method of claim 1, wherein decoupling the second electric motor (64) from the element (46, 60) of the transmission (14) comprises deactivating a clutch element (54) configured to couple the second electric motor (64) to a gear box (60) of the transmission (14) when the output torque of the second electric motor (64) is within the transition window (70).

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