GB2500922A

GB2500922A - A method of performing an electric shift assist in a non-powershift transmission

Info

Publication number: GB2500922A
Application number: GB1206140.4A
Authority: GB
Inventors: Giuseppe Mazzara Bologna; Vincenzo Alfieri; Gianmarco Brunetti
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-04-05
Filing date: 2012-04-05
Publication date: 2013-10-09
Also published as: GB201206140D0

Abstract

A method of performing an electric shift assist in a non-powershift transmission of a hybrid powertrain (100, fig 1), comprising a motor-generator electric unit (500), an internal combustion engine 110, a clutch 700 and a non-powershift gearbox 710. While the clutch 700 is pressed, the method comprises the following steps: comparing a speed of the internal combustion engine 110 with the speed of a gearbox primary shaft 720 and if they are different, actuating the motor-generator electric unit (500), to increase or decrease the internal combustion engine 110 speed, comparing the speed of the primary shaft of the gearbox 720 with the internal combustion engine 110 speed and repeating the previous step until they are equal. Reference is also made to a hybrid powertrain configured to carry out the method, a computer program product on which a computer program for carrying out the method is stored. Also claimed are control apparatus comprising a computer program stored in a memory system (460) connected to an electronic control unit (450) and an electromagnetic signal representing the computer program.

Description

METHOD OF PERFORMING ELECTRIC SHIFT ASSIST IN A HYBRID P0 WER TRAIN

TECHNICAL FIELD

The present disclosure relates to a method of performing an electric shift assist for non-powershift transmissions in a hybrid powertrain.

BACKGROUND

It is known that any motor vehicle is equipped with a powertrain, namely with a group of components and/or devices that are provided for generating mechanical power and for delivering it to the final drive of the motor vehicle, such as for example the drive wheels ofacar.

A hybrid powertrain particularly comprises an internal combustion engine (ICE), such as for example a compression-ignition engine (Diesel engine) or a spark-ignition engine (gasoline or gas engine), and a motor-generator electric unit (MGU). The MGU can operate as an electric motor for assisting or replacing the ICE in propelling the motor vehicle, and can also operate as an electric generator, especially when the motor vehicle is braking, for charging an electrical energy storage device (battery) connected thereto.

Besides, the battery is provided for powering the MGU when it operates as electric motor.

The hybrid powertrain is controlled by an electronic control system according to a dedicated hybrid control strategy. During the traction of the motor vehicle, the hybrid control strategy provides for determining an overall value of mechanical power to be delivered to the wheels of the motor vehicle, for splitting this overall value in a first contributing value of mechanical power to be requested to the ICE and a second contributing value of mechanical power to be requested to the MGU, and then for operating the ICE and the MGU to deliver to the wheels of the motor vehicle the respective contributing value of mechanical power.

In greater details, the splitting of the above mentioned overall power value is conventionally optimized by determining, among the infinite couples of first and second contributing power values whose addition is equal to the overall power value, the couple that minimize the a predetermined polynomial function, usually referred as target function, which quantifies an overall power that is lost due to the operation of the hybrid powertrain, namely a quantity of power that has been supplied to the hybrid powertrain through the ICE fuel, but that has not been delivered to the final drive of the motor vehicle, for example because it has been dissipated due to specific aspect of the hybrid powertrain operation.

As a consequence of this optimization, the first contributing power value is always positive, whereas the second contributing power value may be either positive or negative. If the second contributing power value is positive, the MGU is operated as an electric motor that actually supplies mechanical power to the final drive. If the second contributing power value is negative, the MGU is operated as an electric generator that actually absorbs mechanical power from the final drive.

The fact that, being directly or indirectly connected to the ICE, the MGU can add or subtract torque to ICE, allows to face and solve a technical problem connected with the shifting operations. In fact, with powertrains adopting a non-powershift transmission (i.e. manual or semi-automated transmissions, having power interruption during shifting), during shifting the engine speed decreases according to the engine inertia until idle control occurs, i.e. an engine refueling occurs to avoid stall. Furthermore, up today, there is no feature controlling the engine speed to match the transmission speed during shifting. That is to say, the shift quality is very influenced by the driver ability.

Therefore a need exists for a method that allows to improve the driver feeling during gear shift, using the electric motor to assist shifting. More particularly, by operating the MGU as an electric motor it would be possible to provide torque to the ICE and then to accelerate it, while by operating the MGLJ as an electric generator it would be possible to get torque from the ICE, therefore decelerating it.

An object of an embodiment of the invention is to provide a method for performing an electric shift assist for non-powershift transmissions in a hybrid powertrain.

Another object is to provide an apparatus which allows to perform the above method.

These objects are achieved by a method, by an apparatus, by an engine, by a computer program and computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides a method of performing an electric shift assist for non-powershift transmission of a hybrid powertrain, comprising a motor-generator electric unit, an internal combustion engine, a clutch and a non-powershift gearbox, while the clutch is pressed comprising the following steps: -comparing the speed of the internal combustion engine with the speed of the gearbox primary shaft and if they are different, -actuating the motor-generator electric unit, to increase or decrease the internal combustion engine speed, -comparing the speed of the primary shaft of the gearbox with the internal combustion engine speed, repeating the previous step until they are equal Consequently, an apparatus is disclosed for performing an electric shift assist for non-powershift transmission of a hybrid powertrain, the apparatus comprising: -means for comparing the speed of the internal combustion engine with the speed of the gearbox primary shaft and if they are different, -means for actuating the motor-generator electric unit, to increase or decrease the internal combustion engine speed, -means for comparing the speed of the primary shaft of the gearbox with the internal combustion engine speed, repeating the previous step until they are equal An advantage of this embodiment is that it allows to avoid refueling, since the idle control does not occur. Moreover, shift feeling is improved, due to reduced slippage of the clutch and synchronization work, and the wear of the clutch and the transmission is reduced as well.

According to a further embodiment of the invention, the speed of the gearbox primary shaft is evaluated by means a speed sensor.

An advantage of this embodiment is that it provides a safe way to exactly detect the speed of the gearbox primary shaft without using any prediction model.

According to still another embodiment, the invention relates to a hybrid powertrain, comprising a motor-generator electric unit, an internal combustion engine, a non-powershift transmission having a clutch and a non-powershift gearbox, the hybrid powertrain comprising an electronic control unit configured for carrying out the above method.

An advantage of this embodiment is that it allows to reduce the system complexity of a hybrid power-train and to pursuit integration.

The method according to one of its aspects can be carried out with the help of a computer program comprising a program-code for carrying out afl the steps of the method described above, and in the form of computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier aSsociated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

The method according to a further aspect can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represents a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an internal combustion engine specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 schematically represents a hybrid powertrain of a motor vehicle.

Figure 2 shows in more details an internal combustion engine belonging to the hybrid powertrain of figure 1.

Figure 3 is a section A-A of the internal combustion engine of figure 2.

Figure 4 is a schematic view of a powertrain.

Figure 5 is a flowchart of a method for performing an electric shift assist.

Figure 6 is a scheme depicting the actuation phase of the method of Fig. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Some embodiments may include a motor vehicle's mild hybrid powertrain 100, as shown in Figures 1, that comprises an internal combustion engine (ICE) 110, in this example a diesel engine, a motor-generator electric unit (MGU) 500, an electric energy storage device (battery) 600 electrically connected to the MGU 500, and an electronic control unit (ECU) 450 in communication with a memory system 460.

As shown in Figures 2 and 3, the ICE 110 has an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200.

An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The MGU 500 is an electric machine, namely an electra-mechanical energy converter, which is able either to convert electricity supplied by the battery 600 into mechanical power (i.e., to operate as an electric motor) or to convert mechanical power into electricity that charges the battery 600 (i.e., to operate as electric generator). In greater details, the MGU 500 may comprise a rotor, which is arranged to rotate with respect to a stator, in order to generate or respectively receive the mechanical power. The rotor may comprise means to generate a magnetic field and the stator may comprise electric windings connected to the battery 600, or vice versa. When the MGU 500 operates as electric motor, the battery 600 supplies electric currents in the electric windings, which interact with the magnetic field to set the rotor in rotation. Conversely, when the MGU 500 operates as electric generator, the rotation of the rotor causes a relative movement of the electric wiring in the magnetic field, which generates electrical currents in the electric windings. The MGU 500 may be of any known type, for example a permanent magnet machine, a brushed machine or an induction machine. The MGU 500 may also be either an asynchronous machine or a synchronous machine.

The rotor of the MGU 500 may comprise a coaxial shaft 505, which is mechanically is connected with other components of the hybrid powertrain 100, so as to be able to deliver or receive mechanical power to and from the final drive of the motor vehicle. In this way, operating as an electric motor, the MGIJ 500 can assist or replace the ICE 110 in propelling the motor vehicle, whereas operating as an electric generator. especially when the motor vehicle is braking, the MGU 500 can charge the battery 600. in the present example, the MGU shaft 505 is connected with the ICE crankshaft 145 through a transmission belt 510, similarly to a conventional alternator starter. In order to switch between the motor operating mode and the generator operating mode, the MGU 500 may be equipped with an appropriate internal control system.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110 and equipped with a memory system 460. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110 and the MGU 500.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with the memory system 460 and an interface bus. The memory system 460 may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110 and the MGU 500.

In order to carry out these methods, the ECU 450 is in communication with one or more sensors and/or devices associated with the ICE 110, the MGU 500 and the battery 600.

The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110, the MGU 500 and the battery 600. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant temperature sensor 385, oil temperature sensor 385, a fuel rail pressure sensor 400, a camshaft position sensor 410, a crankshaft position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, a sensor 445 of a position of an accelerator pedal 446, and a measuring circuit 605 capable of sensing the state of charge of the battery 600.

Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110 and the MGU 500, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, the cam phaser 155, and the above mentioned intemal control system of the MGU 500. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

The hybrid powertrain also comprises, see Fig. 4, a transmission system comprising a clutch 700, a gearbox 710, having at least a gearbox primary shaft 720 and a gearbox secondary shaft 730. The powerfiow, as in known systems, goes from the ICE 110 to the gearbox 710 and then to a differential 750 and to the wheel axle 760. Said transmission system is a non-powershift transmission that is to say not a fully automated transmission.

With such configuration, being furthermore the electric motor 500 directly or indirectly connected to the ICE 110, said electric motor 500 could influence the engine speed during gear shifting and therefore the engine speed can match the transmission speed.

In fact, when the driver presses the clutch and shifts gear, knowing the vehicle speed and consequently the speed W2nd of the gearbox secondary shaft 730, by measuring the speed of the gearbox primary shaft 720 to evaluate the gear ratio without relying on

U

any prediction about the driver intentions. Furthermore, the speed 0lst is the target value to be reached by the engine speed 0ICE. This is realized, having verified that the activation conditions (battery power, battery state of charge) are met, by the electric motor 500 which supplies torque to the ICE 110 in order to control its speed. Then, the electric motor 500 accelerate or decelerate the engine speed in order to match the transmission speed, calculated starting from the desired gear ratio and wheel speed.

When the clutch is completely released, the strategy is disabled and the engine runs at the same speed of the transmission.

Turning to Fig. 5, more in detail, the method for performing an electric shift assist for non-powershift transmission of a hybrid powertrain, to be adopted when the clutch 700 is pressed 20, comprises the following steps: -comparing 21 the speed of the internal combustion engine 110 with the speed of the gearbox primary shaft 720 and if they are different, -actuating 22 the motor-generator electric unit 500, to increase or decrease the internal combustion engine 110 speed, -comparing 23 the speed of the primary shaft of the gearbox 720 with the internal combustion engine 110 speed, repeating the previous step until they are equal As soon as the clutch is released 24, the strategy is disabled.

The actuation phase of this method is schematically shown in Fig.6, wherein the closed loop control of the engine speed is realized by ECU 450, by acting on the motor-generator electric unit 500, which will assist the internal combustion engine in increasing or decreasing its speed.

Advantageously, the speed of the gearbox primary shaft 720 can be evaluated by means of a speed sensor 740.

It is interesting to show the trade-off between the electric energy used to control the engine speed vs. the fuel saved, by skipping idle control. In table 1, the results of experimental tests conducted on maneuvers over the New European Driving Cycle (NEDC) are shown.

TABLE I

_____________________________________ Regular operation Electric shift assist Fuel use @ shifting [gfs 0.0440 -Power use shifting [kWJ -1.57 Shifting time [s] 1 1 Number of shifts NEDC 36 36 FC [L/lOOkmJ 3.89 FC gain due to Regen {%] -3.7 FC Total Loss [%] -0.44 -0.46 As can be seen, actuating the method according to the invention, there is no remarkable penalty in term of fuel consumption. Moreover, state-of-art technology includes a control of the engine speed during down-shifts by means of a fuel injection, that, with the above invention, could be avoided leading to a fuel economy advantage.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS block

21 block 22 block 23 block 24 block hybrid powertrain internal combustion engine engine block 125 cylinder cylinder head camshaft piston crankshaft 150 combustion chamber cam phaser fuel injector fuel rail fuel pump 190 fuel source intake manifold 205 air intake pipe 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 DOC 281 [NT 282 DPF 290 VGT actuator 300 exhaust gas recirculation system 305 EGR conduit 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 in-cylinder pressure sensor 380 coolant temperature sensor 385 oil temperature sensor 400 fuel rail pressure sensor 410 camshaft position sensor 420 crankshaft position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor 446 accelerator pedal 450 ECU 460 memory system 500 motor-generator electric unit 505 MGU shaft 510 transmission belt 600 battery 605 measuring circuit 700 clutch 710 gearbox 720 gearbox primary shaft 730 gearbox secondary shaft 740 speed sensor 750 differential 760 wheel axle

Claims

CLAIMS1. Method of performing an electric shift assist for non-powershift transmission of a hybrid powertrain (100), comprising a motor-generator electric unit (500), an internal combustion engine (110), a clutch (700) and a non-powershift gearbox (710), while the clutch is pressed comprising the following steps: -comparing (21) the speed of the internal combustion engine (110) with the speed of a gearbox primary shaft (720) and if they are different, -actuating (22) the motor-generator electric unit (500), to increase or decrease the internal combustion engine (110) speed, -comparing (23) the speed of the primary shaft of the gearbox (720) with the internal combustion engine (110) speed, repeating the previous step until they are equal.
2. Method according to claim 1, wherein the speed of the gearbox primary shaft (720) is evaluated by means of a speed sensor (740).
3. Hybrid powertrain (100), comprising a motor-generator electric unit (500), an internal combustion engine (110), a non-powershift transmission having a clutch (700) and a non-powershift gearbox (710), the hybrid powertrain (100) further comprising an electronic control unit (450) configured for carrying out the method according to claims 1-2.
4. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-2.
5. Computer program product on which the computer program according to claim 4 is stored.
6. Control apparatus for an internal combustion engine, comprising an Electronic Control Unit (450), a data carrier (40) associated to the Electronic Control Unit (450) and a computer program according to claim 4 stored in a memory system (460).
7. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 4.