Patent Application
20190047547
The present disclosure relates to control systems for hybrid vehicles.
Convention strategies for reducing emissions in a vehicle powered by an internal combustion engine after a cold start include adjusting the spark timing within the engine, the air/fuel ratio, and/or idle speed patterns in order to minimize hydrocarbon feed gas while also minimizing catalyst light-off time of the catalytic converter.
A vehicle includes a powertrain and a controller. The powertrain has an engine and an electric machine. The controller is programmed to, for so long as a catalytic converter temperature is less than a threshold, maintain a steady state engine torque output and adjust an electric machine torque output to satisfy driver demand. The controller is further programmed to, responsive to the catalytic converter temperature exceeding the threshold, permit adjustments of the engine torque output to satisfy the driver demand.
A vehicle includes an engine, an electric machine, an engine exhaust system, and a controller. The engine and the electric machine are each configured generate torque to propel the vehicle. The engine exhaust system has a catalytic converter configured to operate above a threshold temperature. The controller is programmed to, for so long as a temperature of the catalytic converter is less than the threshold temperature, maintain a steady state engine torque output and adjust an electric machine torque output to satisfy a driver demanded torque. The controller is further programmed to, responsive to a desired electric machine torque output being outside an operating range of the electric machine to satisfy driver demand during the maintaining, adjust the electric machine torque output to a limit of the operating range and override the maintaining to adjust the engine torque output to satisfy the driver demand.
A method for controlling a vehicle powertrain includes, for so long as a catalytic converter temperature is less than a threshold, maintaining a predetermined steady state engine torque and adjusting an electric machine torque to satisfy powertrain demanded torque. The method further includes, responsive to the catalytic converter temperature exceeding the threshold, adjusting the engine and electric machine torques to satisfy powertrain demanded torque.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
Referring to
The engine 14 and the M/G 18 are both drive sources for the HEV 10 that are configured to propel the HEV 10. The engine 14 generally represents a power source that may include an internal combustion engine such as a gasoline, diesel, or natural gas powered engine, or a fuel cell. The engine 14 generates an engine power and corresponding engine torque that is supplied to the M/G 18 when a disconnect clutch 26 between the engine 14 and the M/G 18 is at least partially engaged. The M/G 18 may be implemented by any one of a plurality of types of electric machines. For example, M/G 18 may be a permanent magnet synchronous motor. Power electronics condition direct current (DC) power provided by the battery 20 to the requirements of the M/G 18, as will be described below. For example, power electronics may provide three phase alternating current (AC) to the M/G 18.
When the disconnect clutch 26 is at least partially engaged, power flow from the engine 14 to the M/G 18 or from the M/G 18 to the engine 14 is possible. For example, the disconnect clutch 26 may be engaged and M/G 18 may operate as a generator to convert rotational energy provided by a crankshaft 28 and M/G shaft 30 into electrical energy to be stored in the battery 20. The disconnect clutch 26 can also be disengaged to isolate the engine 14 from the remainder of the powertrain 12 such that the M/G 18 can act as the sole drive source for the HEV 10. Shaft 30 extends through the M/G 18. The M/G 18 is continuously drivably connected to the shaft 30, whereas the engine 14 is drivably connected to the shaft 30 only when the disconnect clutch 26 is at least partially engaged.
The M/G 18 is connected to the torque converter 22 via shaft 30. The torque converter 22 is therefore connected to the engine 14 when the disconnect clutch 26 is at least partially engaged. The torque converter 22 includes an impeller fixed to M/G shaft 30 and a turbine fixed to a transmission input shaft 32. The torque converter 22 thus provides a hydraulic coupling between shaft 30 and transmission input shaft 32. The torque converter 22 transmits power from the impeller to the turbine when the impeller rotates faster than the turbine. The magnitude of the turbine torque and impeller torque generally depend upon the relative speeds. When the ratio of impeller speed to turbine speed is sufficiently high, the turbine torque is a multiple of the impeller torque. A torque converter bypass clutch (also known as a torque converter lock-up clutch) 34 may also be provided that, when engaged, frictionally or mechanically couples the impeller and the turbine of the torque converter 22, permitting more efficient power transfer. The torque converter bypass clutch 34 may be operated as a launch clutch to provide smooth vehicle launch. Alternatively, or in combination, a launch clutch similar to disconnect clutch 26 may be provided between the M/G 18 and gearbox 24 for applications that do not include a torque converter 22 or a torque converter bypass clutch 34. In some applications, disconnect clutch 26 is generally referred to as an upstream clutch and launch clutch 34 (which may be a torque converter bypass clutch) is generally referred to as a downstream clutch.
The gearbox 24 may include gear sets (not shown) that are selectively placed in different gear ratios by selective engagement of friction elements such as clutches and brakes (not shown) to establish the desired multiple discrete or step drive ratios. The friction elements are controllable through a shift schedule that connects and disconnects certain elements of the gear sets to control the ratio between a transmission output shaft 36 and the transmission input shaft 32. The gearbox 24 is automatically shifted from one ratio to another based on various vehicle and ambient operating conditions by an associated controller, such as a powertrain control unit (PCU). Power and torque from both the engine 14 and the M/G 18 may be delivered to and received by gearbox 24. The gearbox 24 then provides powertrain output power and torque to output shaft 36.
It should be understood that the hydraulically controlled gearbox 24 used with a torque converter 22 is but one example of a gearbox or transmission arrangement; any multiple ratio gearbox that accepts input torque(s) from an engine and/or a motor and then provides torque to an output shaft at the different ratios is acceptable for use with embodiments of the present disclosure. For example, gearbox 24 may be implemented by an automated mechanical (or manual) transmission (AMT) that includes one or more servo motors to translate/rotate shift forks along a shift rail to select a desired gear ratio. As generally understood by those of ordinary skill in the art, an AMT may be used in applications with higher torque requirements, for example.
As shown in the representative embodiment of
The powertrain 12 further includes an associated controller 50 such as a powertrain control unit (PCU). While illustrated as one controller, the controller 50 may be part of a larger control system and may be controlled by various other controllers throughout the vehicle 10, such as a vehicle system controller (VSC). It should therefore be understood that the powertrain control unit 50 and one or more other controllers can collectively be referred to as a “controller” that controls various actuators in response to signals from various sensors to control functions such as starting/stopping engine 14, operating M/G 18 to provide wheel torque or charge battery 20, select or schedule transmission shifts, etc. Controller 50 may include a microprocessor or central processing unit (CPU) in communication with various types of computer readable storage devices or media. Computer readable storage devices or media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the CPU is powered down. Computer-readable storage devices or media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by the controller in controlling the engine or vehicle.
The controller communicates with various engine/vehicle sensors and actuators via an input/output (I/O) interface (including input and output channels) that may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to the CPU. As generally illustrated in the representative embodiment of
Control logic or functions performed by controller 50 may be represented by flow charts or similar diagrams in one or more figures. These figures provide representative control strategies and/or logic that may be implemented using one or more processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Although not always explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending upon the particular processing strategy being used. Similarly, the order of processing is not necessarily required to achieve the features and advantages described herein, but is provided for ease of illustration and description. The control logic may be implemented primarily in software executed by a microprocessor-based vehicle, engine, and/or powertrain controller, such as controller 50. Of course, the control logic may be implemented in software, hardware, or a combination of software and hardware in one or more controllers depending upon the particular application. When implemented in software, the control logic may be provided in one or more computer-readable storage devices or media having stored data representing code or instructions executed by a computer to control the vehicle or its subsystems. The computer-readable storage devices or media may include one or more of a number of known physical devices which utilize electric, magnetic, and/or optical storage to keep executable instructions and associated calibration information, operating variables, and the like.
An accelerator pedal 52 is used by the driver of the vehicle to provide a demanded torque, power, or drive command to propel the vehicle. In general, depressing and releasing the accelerator pedal 52 generates an accelerator pedal position signal that may be interpreted by the controller 50 as a demand for increased power or decreased power, respectively. A brake pedal 58 is also used by the driver of the vehicle to provide a demanded braking torque to slow the vehicle. In general, depressing and releasing the brake pedal 58 generates a brake pedal position signal that may be interpreted by the controller 50 as a demand to decrease the vehicle speed. Based upon inputs from the accelerator pedal 52 and brake pedal 58, the controller 50 commands the torque to the engine 14, M/G 18, and friction brakes 60. The controller 50 also controls the timing of gear shifts within the gearbox 24, as well as engagement or disengagement of the disconnect clutch 26 and the torque converter bypass clutch 34. Like the disconnect clutch 26, the torque converter bypass clutch 34 can be modulated across a range between the engaged and disengaged positions. This produces a variable slip in the torque converter 22 in addition to the variable slip produced by the hydrodynamic coupling between the impeller and the turbine. Alternatively, the torque converter bypass clutch 34 may be operated as locked or open without using a modulated operating mode depending on the particular application.
To drive the vehicle with the engine 14, the disconnect clutch 26 is at least partially engaged to transfer at least a portion of the engine torque through the disconnect clutch 26 to the M/G 18, and then from the M/G 18 through the torque converter 22 and gearbox 24. The M/G 18 may assist the engine 14 by providing additional power to turn the shaft 30. This operation mode may be referred to as a “hybrid mode” or an “electric assist mode.”
To drive the vehicle with the M/G 18 as the sole power source, the power flow remains the same except the disconnect clutch 26 isolates the engine 14 from the remainder of the powertrain 12. Combustion in the engine 14 may be disabled or otherwise OFF during this time to conserve fuel. The traction battery 20 transmits stored electrical energy through wiring 54 to power electronics 56 that may include an inverter, for example. The power electronics 56 convert DC voltage from the battery 20 into AC voltage to be used by the M/G 18. The controller 50 commands the power electronics 56 to convert voltage from the battery 20 to an AC voltage provided to the M/G 18 to provide positive or negative torque to the shaft 30. This operation mode may be referred to as an “electric only” or “EV” operation mode.
In any mode of operation, the M/G 18 may act as a motor and provide a driving force for the powertrain 12. Alternatively, the M/G 18 may act as a generator and convert kinetic energy from the powertrain 12 into electric energy to be stored in the battery 20. The M/G 18 may act as a generator while the engine 14 is providing propulsion power for the vehicle 10, for example. The M/G 18 may additionally act as a generator during times of regenerative braking in which torque and rotational (or motive) energy or power from spinning wheels 42 is transferred back through the gearbox 24, torque converter 22, (and/or torque converter bypass clutch 34) and is converted into electrical energy for storage in the battery 20.
The battery 20 and the M/G 18 may also be configured to provide electrical power to one or more vehicle accessories 62. The vehicle accessories 62 may include, but are not limited to, air conditioning systems, power steering systems, electric heaters, or any other system or device that is electrically operated.
An integrated starter-generator (ISG) 64 may be coupled to the engine 14 (i.e., may be coupled to the crankshaft 28 of the engine 14). The ISG 64 may be configured to operate as a motor to start the engine 14 during an engine start-up event, or to provide additional torque to the powertrain 12 during vehicle operations. The ISG 64 may also be configured to receiving torque from the engine 14 and operate as a generator. The ISG 64 may be selectively coupled to the engine by a clutch 66, belt 68, and a pair of pulleys 70. If the ISG 64 is coupled to the engine by a belt 68 it may be referred to as a belt integrated starter-generator (BISG). The controller 50 may be configured to transmit signals to the ISG 64 to operate the ISG 64 as either a motor or a generator. The controller may also be configured to transmit signals to the clutch 66 in order to open or close the clutch 66. The ISG 64 will be coupled to the engine 14 when the clutch is in a closed state and decoupled from the engine 14 when the clutch 66 is in an open state. The ISG 64 may be configured to provide electrical energy to charge an accessory battery 72, the traction battery 20, or provide electrical energy to power the vehicle accessories 62 when operating as a generator. The accessory battery 72 may also be configured to power the vehicle accessories 62.
An exhaust system 74 is configured to channel the exhaust produced by the engine 14 away from the vehicle 10. The exhaust system 74 may include a muffler 76 to reduce the noise emitted by the exhaust system 74 and a catalytic converter 78. The catalytic converter 78 may be a three-way catalytic converter that is configured to reduce the amount carbon monoxide (CO), unburned hydrocarbons (HC), and oxides of Nitrogen (NOx) that are released into the atmosphere. The catalyst within the catalytic converter 78 may only be operable above a light-off temperature, which is the temperature at which catalytic reactions within the catalytic converter are initiated.
The controller 50 may be configured to receive various states or conditions of the various vehicle components illustrated in
The input channels and output channels are illustrated as dotted lines in
It should be understood that the schematic illustrated in
Referring to
If the CSER is active, the method 100 moves on to block 108 where an ideal desired (or requested) torque output of the M/G 18 is calculated. The ideal desired torque output of the M/G 18 is based on the driver demanded torque (i.e., the desired total torque output of the engine 14 and M/G 18) and the optimal desired torque output of the engine 14 (or CSER torque), which is input into block 108 from block 110. The optimal desired torque output of the engine 14 is a specified steady state torque that is calculated to provide minimal light-off time of the catalytic converter 78 while also keeping noise, vibration, and harshness (NVH) of the engine 14 low (i.e., below a threshold). The ideal desired torque output of the M/G 18 may be represented by equation (1):
τmtrideal,req=τDD−τCSER (1)
where τmtrideal,req is the ideal desired torque output of the M/G 18, τDD is the driver (or powertrain) mtr demanded torque, and tCSER is the optimal desired torque output of the engine 14.
Once the ideal desired torque output of the M/G τmtrideal,req calculated, the method 100 moves on to block 112, where it is determined if the ideal desired torque output of the M/G τmtrideal,req is within an operating range of the M/G 18 (i.e., within the torque limitations of the M/G 18 based on the mechanical limits of the M/G 18 and the limits of the battery 20 to deliver or receive electrical power to or from the M/G 18). The torque limitations of the M/G 18 may include a maximum torque output limit τmtrmax and a minimum torque output limit τmtrmin. If the ideal desired torque output of the M/G τmtrideal,req is within an operating range of the M/G 18 (e.g., τmtrmax>τmtrideal,req>τmtrmin), the method 100 moves on to blocks 114 and 116. At block 114, a desired engine torque output τengreq is calculated based on the optimal desired torque output of the engine τCSER. At block 116, a desired motor torque output τmtrreq is calculated based on the driver demanded torque τDD and an actual or measured engine torque Tens. The desired engine torque output τengreq may be represented by equation (2) and the desired motor torque output τmtrreq, may be represented by equation (3):
τengreq=τCSER (2)
τmtrreq=τDD−τeng (3)
The method 100 will continue to maintain the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) and adjust the desired motor torque output τmtrreq to satisfy driver demanded torque τDD at blocks 114 and 116 and according to equations (2) and (3) for as long as the temperature of the catalytic converter 78 remains less the threshold temperature or for as long as the ideal desired torque output of the M/G τmtrideal,req remains within an operating range of the M/G 18. Once the temperature of the catalytic converter 78 surpasses the threshold temperature, the method 100 ends at block 106 where the engine 14 torque may be adjusted to satisfy the driver demanded torque τDD (i.e., the engine is no longer required to be maintained at the steady state torque).
On the other hand, if the ideal desired torque output of the M/G τmtrideal,req falls outside of the operating range of the M/G 18 required to satisfy driver demanded torque τDD while the temperature of the catalytic converter 78 remains less the threshold temperature, the method 100 moves on to block 118. The method 100 may transition to block 118 immediately if the desired torque output of the M/G τmtrideal,req is initially outside the operating range of the M/G 18 or may transition to block 118 after controlling the torque of the engine 14 and the torque of the M/G 18 based on blocks 114 and 116 if the desired torque output of the M/G τmtrideal,req transitions from a value within to outside of the operating range of the M/G 18. Once the desired torque output of the M/G τmtrideal,req falls outside of the operating range of the M/G 18 required to satisfy driver demanded torque τDD while the temperature of the catalytic converter 78 remains less the threshold temperature, the torque of the M/G 18 may be adjusted to a limit (maximum or minimum) of the operating range of the M/G 18 while maintaining the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) is overridden such that the torque output of the engine 14 will be adjusted to a value other than the steady state torque in order to satisfy the driver demanded torque τDD
At block 118 it is determined if the ideal desired torque output of the M/G τmtrideal,req is greater than the maximum torque output limit τmtrmax of the M/G 18. If the ideal desired torque output of the M/G τmtrideal,req is greater than the maximum torque output limit τmtrideal,req of the M/G 18, the method 100 moves on to blocks 120 and 122. It should be noted that under such a condition, the driver demanded torque τDD will be greater than a sum of the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) and maximum torque output limit τmtrmax of the M/G 18. Therefore, in order to satisfy driver demanded torque τDD, the desired engine torque output τengreq will need to be increased to a value that is greater than the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER). At block 120, the desired engine torque q output τengreq is calculated based on the driver demanded torque τDD and the maximum torque output limit τmtrmax of the M/G 18. At block 122, the desired motor torque output τmtrreq is again calculated based on the driver demanded torque τDD and the actual or measured engine torque τengact. The desired engine torque output τengreq may be represented by equation (4) and the desired motor torque output τmtrreq may again be represented by equation (3):
τengreq=τDD−τmtrmax (4)
τmtrreq=τDD−τeng (3)
At blocks 120 and 122, the torque output of the M/G 18 will ideally be increased to the maximum torque output limit τmtrmax of the M/G 18 while maintaining the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) will be overridden such that the torque output of the engine 14 will be increased to a value above the steady state torque in order to satisfy the driver demanded torque τDD. The method 100 will continue to control the torque output of the M/G 18 and the torque output of the engine 14 according to blocks 120 and 122 for as long as the temperature of the catalytic converter 78 remains less the threshold temperature or for as long as the ideal desired torque output of the M/G τmtrideal,req remains greater than the maximum torque output limit τmtrmax of the M/G 18. Once the temperature of the catalytic converter 78 surpasses the threshold temperature, the method 100 ends at block 106, as described above.
On the other hand, if the ideal desired torque output of the M/G τmtrideal,req returns to a value that is within the operating range of the M/G 18 (e.g., τmtrmax>τmtrideal,req>τmtrmin), the method 100 may return controlling the torque of the engine 14 and the torque of the M/G 18 based on blocks 114 and 116, or if the if the ideal desired torque output of the M/G τmtrideal,req decreases to a value that is less than the minimum torque output limit τmtrmin of the M/G 18 the method 100 may control the torque of the engine 14 and the torque of the M/G 18 based on blocks 126 and 128, described below. Returning to block 118, if the ideal desired torque output of the M/G τmtrideal,req is not greater than the maximum torque output limit τmtrmax of the M/G 18, the method 100 moves on to block 124.
At block 124 it is determined if the ideal desired torque output of the M/G τmtrideal,req is less than the minimum torque output limit τmtrmin of the M/G 18. If the ideal desired torque output of the M/G τmtrideal,req is less than the minimum torque output limit τmtrmin of the M/G 18, the method 100 moves on to blocks 126 and 128. It should be noted that under such a condition, the driver demanded torque τDD may be less than the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) or may be greater than the steady state torque of the but less than a sum of the steady state torque of the engine and the minimum torque output limit τmtrmin of the M/G 18, depending on whether the minimum torque output limit τmtrmin of the M/G 18 has a negative, positive, or zero value. Therefore, in order to satisfy driver demanded torque τDD, the desired engine torque output τengreq will need to be decreased to a value that is less than the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER). At block 126, the desired engine torque output τengreq is calculated based on the driver demanded torque τDD and the minimum torque output limit τmtrmin of the M/G 18. At block 128, the desired motor torque output τmtrreq is again calculated based on the driver demanded torque τDD and the actual or measured engine torque τengact. The desired engine torque output τengreq may be represented by equation (5) and the desired motor torque output τmtrreq may again be represented by equation (3):
τengreqτDD−τmtrmin (5)
τmtrreq=τDD−τeng (3)
At blocks 126 and 128, the torque output of the M/G 18 will ideally be adjusted to the minimum torque output limit τmtrmin of the M/G 18 while maintaining the steady state torque of the engine (i.e., the optimal desired torque output of the engine τCSER) will be overridden such that the torque output of the engine 14 will be decreased to a value below the steady state torque in order to satisfy the driver demanded torque τDD. The method 100 will continue to control the torque output of the M/G 18 and the torque output of the engine 14 according to blocks 126 and 128 for as long as the temperature of the catalytic converter 78 remains less the threshold temperature or for as long as the ideal desired torque output of the M/G τmtrideal,req remains less than the minimum torque output limit τmtrmin of the M/G 18. Once the temperature of the catalytic converter 78 surpasses the threshold temperature, the method 100 ends at block 106, as described above.
On the other hand, if the ideal desired torque output of the M/G τmtrideal,req returns to a value that is within the operating range of the M/G 18 (e.g., τmtrmax>τmtrideal,req>τmtrmin), the method 100 may return controlling the torque of the engine 14 and the torque of the M/G 18 based on blocks 114 and 116. Alternatively, if the if the ideal desired torque output of the M/G τmtrideal,req increases to a value that is greater than the maximum torque output limit τmtrmax of the M/G 18 the method 100 may return controlling the torque of the engine 14 and the torque of the M/G 18 based on blocks 120 and 122.
It should be understood that the flowchart in
In the scenarios described above, where the ideal desired torque output of the M/G τmtrideal,req is greater than the maximum torque output limit τmtrmax of the M/G 18 by a calibratable value or the ideal desired torque output of the M/G τmtrideal,req is less than the minimum torque output limit τmtrmin of the M/G 18 by a calibratable value, the desired engine torque output τengreq may be ramped slowly to meet the driver demanded torque τDD. Under a scenario where the desired engine torque output τengreq is ramped slowly to meet the driver demanded torque τDD, the desired engine torque output τengreq may be represented by equation (6) and the desired motor torque output τmtrreq may again be represented by equation (3):
τengreq=τDD−τEM (6)
τmtrreq=τDD−τeng (3)
where τEM is the energy management torque. It should be noted that the energy management torque may be set to zero while the CSER is active.
The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.
