Patent Description:
Engine management is an important aspect for increasing efficient energy usage in hybrid vehicles. This importance is magnified during vehicle launch because an engine is not efficient during launch. Additionally, engine management in a single machine parallel hybrid vehicle poses the challenge that a single electric machine needs to provide the necessary starting torque for the engine while at the same time propelling the vehicle.

<CIT> discloses methods for starting an engine of a hybrid vehicle having a torque converter. At vehicle start, this document suggests to disengage the electric motor from the transmission.

<CIT> discloses engine starting methods after vehicle start using the lock-up clutch of a torque converter to simultaneously transmit torque to the wheels.

The invention is defined in the appended independent claims. Advantageous aspects are defined in the dependent claims.

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:.

Referring to <FIG> an example of the present invention is shown. The drive train system of the present invention includes an internal combustion engine <NUM> (the "engine"), coupled to an integrated starter/generator/motor (ISGM) <NUM> by way of a clutch assembly <NUM>. The clutch assembly <NUM> allows the ISGM <NUM> to be disengaged from the engine <NUM> during decelerations and full stops. The clutch assembly <NUM> is controlled by a clutch control assembly <NUM>. The clutch control assembly <NUM> is, for example, a hydraulic solenoid controlling engagement and disengagement of the clutch assembly <NUM> based on the state of the hybrid vehicle. Additionally, the clutch control assembly <NUM> can be pneumatic or mechanical. In the present invention, the clutch assembly <NUM> disengages the engine <NUM> from the ISGM <NUM> during decelerations.

Additionally, a torque converter <NUM> is provided between the ISGM <NUM> and the gearbox <NUM>. The gearbox <NUM> is coupled to drive wheels by way of a drive shaft (not shown).

The ISGM <NUM> is sized to operate efficiently as a traction motor for propelling the vehicle with or without engine assistance up to a cruising velocity. In addition, the ISGM <NUM> is adapted to provide sufficient rotational torque to rotate the engine crankshaft and propel the vehicle simultaneously.

Moreover, the ISGM <NUM> operates as a starter at engine launch and to launch the vehicle, as a generator during vehicle deceleration, and as a traction motor during acceleration and cruising. As a generator, the ISGM <NUM> generates electrical energy during the deceleration process by recuperating from regenerative braking the mechanical energy of the vehicle. The ISGM <NUM> is electrically coupled to an energy storage system <NUM>, which may be batteries or fuel cells or ultra capacitors. Co-pending application entitled a Parallel Hybrid Electric Vehicle Power Management System and Adaptive Power Management Method and Program Therefor assigned to BAE Systems Controls, Inc. , which is incorporated by reference describes a system and method for charging the energy storage system <NUM> only using energy from regenerative braking. The energy storage system <NUM> receives electrical energy from the ISGM <NUM> operating as a generator during deceleration. The energy storage system <NUM> provides electrical energy to the ISGM <NUM> when the ISGM <NUM> is operating as a starter motor and/or traction motor. Torque from the engine <NUM> and ISGM <NUM> is mechanically coupled to the torque converter <NUM>.

A second clutch (<NUM>) is connected in parallel with the torque converter. The second clutch can be a lock-up clutch <NUM> integrally disposed within a torque converter <NUM>. The lock-up clutch <NUM> can be electronically controlled. The lock-up clutch can be engaged and disengaged depending on a velocity.

The engine control unit <NUM> provides control signals for actuating fuel injectors, fuel pumps and other engine components. Additionally, the engine control unit <NUM> monitors engine operating conditions, and may be configured to control operation of the clutch assembly <NUM> and ISGM <NUM> based on sensor signals from accelerator and brake pedals in the vehicle cabin. Moreover, the engine control unit <NUM> provides control signals to the clutch control assembly <NUM>.

Turning to <FIG>, a flow diagram showing an exemplary a vehicle launch process in accordance with the present invention is provided. As shown, the vehicle launch process begins at step <NUM> when a launch event is sensed or detected. A launch event includes a release of the service brakes or a detection of a request for acceleration from a driver, such as a torque command, or the like. The service brake, for purposes of the present invention, can include any mechanical braking mechanisms, such as, but not limited to foot pedal actuated brakes and hand/emergency brakes.

Once a launch event is detected, a controller, such as the engine control unit <NUM>, accelerates the ISGM <NUM> in step <NUM> by transmitting electrical energy from the energy storage system <NUM> to the ISGM <NUM>. The controller can be a separate controller from the engine control unit <NUM>. However, for purposes of the description the controller and engine control unit <NUM> are used interchangeably. At step <NUM>, torque is transmitted to the output shaft. In this example, the torque is transmitted via the torque converter <NUM>. However, as will be described herein later with respect to the other examples not falling under the scope of the claims, the torque can be transmitted via computer or manually operated clutches. Since the ISGM <NUM> is coupled to the torque converter <NUM>, the vehicle begins moving at step <NUM>, instantaneously with the acceleration of the ISGM <NUM>.

At step <NUM>, the ISGM <NUM> is coupled to the engine <NUM>. A portion of the power or output torque of the ISGM <NUM> is coupled to the engine <NUM> by engaging the clutch assembly <NUM> to enable the starting of the engine <NUM> when launching the vehicle.

The ISGM <NUM> is accelerated until the controller determines in step <NUM> that the ISGM <NUM> is operating at a predetermined percentage above the engine idle speed. The coupling of the engine <NUM> and ISGM <NUM> is maintained. For example, the predetermined percentage may be <NUM>% above engine idle speed. In step <NUM>, the controller controls the fuel injection system of the engine <NUM>. At this point, the engine <NUM> is fueled and begins to support vehicle launch. After the starting of the engine <NUM> via the fuel injection system, an output torque from the engine <NUM> is combined with the output torque from the ISGM <NUM> as the combined torques are transmitted through the torque converter and the gear box <NUM> to the output drive shaft to accelerate the launching of the vehicle at step <NUM>.

According to the invention, the lock-up clutch <NUM> is disengaged during the initial launch process shown in <FIG>. The lock-up clutch <NUM> is not engaged until vehicle components are traveling at a predetermined speed, for example, transmission input speed in excess of <NUM> revolutions per minute. The speed as used herein and in the figures can be, but is not limited to, transmission input speed, transmission output speed, ISGM speed or vehicle speed. However, with respect to steps <NUM> and <NUM> as described below, the ISGM speed is not needed. The actually predetermined speed for engaging the lock-up clutch <NUM> can be based upon fuel efficiency and torque characteristics of the engine, and the like. According to the invention, during the initial launch process, the power from the ISGM <NUM> and/or engine <NUM> is directed through the torque converter <NUM> alone to launch the vehicle. As depicted in <FIG>, the engine <NUM> is coupled to the ISGM <NUM> prior to the speed of the ISGM <NUM> reaching a predetermined percentage of the engine idle speed. However, in accordance with the invention, the coupling of the ISGM <NUM> to the engine <NUM> can occur after the speed of the ISGM <NUM> reaches a predetermined percentage of the engine idle speed as illustrated in <FIG>. The order of steps <NUM> and <NUM> is reversed. The remaining steps are the same and will not be described in detail again.

Additionally, a received torque command and the maximum or peak torque for the ISGM <NUM> can be used to determine when to couple the engine <NUM> to the ISGM <NUM> or when to refuel or fuel the engine <NUM>. The peak torque is an ISGM <NUM> specific parameter. The peak torque threshold is a percentage of the peak torque. <FIG> illustrates a flow chart of an exemplary method where the torque command is compared with the peak ISGM torque to determine when the fuel injection system is controlled. At step <NUM>, a determination is made whether the received torque command is greater than a predetermined percentage of the peak ISGM torque. If the torque command is greater than the predetermined percentage of the peak, then the fuel injection system is controlled to fuel or refuel the engine <NUM> at step <NUM>. If not, the system will wait for a new torque command. The remaining steps are the same and will not be described in detail again.

Additionally, a second speed threshold can be used to determine when to refuel or fuel the engine <NUM>. For example, <FIG> illustrates a flow chart of an exemplary method in accordance with the invention where a second speed threshold is used. In <FIG> steps <NUM> and <NUM> are reversed with respect to the method described in <FIG>. The ISGM <NUM> is started and initially accelerated at step <NUM>. After the engine <NUM> is coupled to the ISGM <NUM>, the ISGM <NUM> continues to accelerate at step <NUM>. The ISGM is accelerated until a speed is reached that is greater than a second speed threshold relative to the idle speed of the engine. At step <NUM>, a determination is made as to whether the speed is greater than the second speed threshold. If the speed is greater ("YES" at <NUM>), the fuel injection system supplies the engine <NUM> with fuel or refuels the engine <NUM> at step <NUM>. If not, the ISGM <NUM> is allowed to continue to accelerate <NUM>.

The remaining steps are the same and will not be described in detail again. <FIG> illustrates another exemplary method in accordance with the invention. In the method depicted in <FIG>, both a second speed threshold and a received torque command and the peak torque for the ISGM <NUM> are used in the launch process.

<FIG> illustrates an exemplary deceleration process not falling under the scope of the claimed invention for the system depicted in <FIG>. At step <NUM>, sensors detect negative system torque command. A negative system torque command can be, but is not limited to, an input though an accelerator pedal, brake pedal, combination thereof, or a cruise control device. If the system torque command is negative, the process proceeds to step <NUM>. In step <NUM> the ISGM <NUM> and engine <NUM> are decoupled by disengagement of a clutch assembly <NUM> disposed between the ISGM <NUM> and the engine <NUM>. However, if additional negative torque is needed beyond the retarding torque provided by the ISGM <NUM>, step <NUM> may be skipped, keeping the engine <NUM> coupled to the ISGM <NUM>.

Additionally, since a torque converter <NUM> is not designed to transfer power efficiently from the transmission side, the lock-up clutch <NUM> of the torque converter <NUM> is engaged during in step <NUM>, if not already engaged. The lock-up clutch <NUM> allows more efficient transfer of regenerative power from the drive wheels to the ISGM <NUM>.

In <FIG>, the ISGM <NUM> and engine <NUM> are decoupled before the lock-up clutch <NUM> is engaged. However, step <NUM> and step <NUM> can be switched, with the lock-up clutch <NUM> being engaged prior to the ISGM <NUM> and engine <NUM> being decoupled. The particular order in which steps <NUM> and <NUM> are executed is dependent on speed, battery state of charge, and throttle signal.

The regenerative power is recouped to charge batteries or other energy storage devices (systems), e.g., energy storage system <NUM>, in step <NUM>. During step <NUM>, speeds are monitored by a controller. If monitored speed(s) is/are above a preset threshold speed, in <NUM>, the process determines if the system torque command is non-negative in step <NUM>. As long as the system torque command is negative and speed is above the threshold speed of step <NUM>, the process continues charging the batteries as described in step <NUM>. However, if the speed is above the threshold of step <NUM> but system torque command is no longer negative, the process stops charging the batteries and returns to step <NUM>, awaiting the next detection of negative system torque command. Once the controller determines that the speed is below the threshold speed in step <NUM>, the process proceeds to step <NUM>. In step <NUM>, the lock-up clutch <NUM> is disengaged. When the lock-up clutch <NUM> is disengaged, deceleration energy that would have been regenerative power is dissipated through the torque converter <NUM>. The engine <NUM> may remain disengaged from the ISGM <NUM>, and the engine <NUM> may be allowed to idle or even shut off. The controller maintains the ISGM <NUM> at a threshold RPM in step <NUM>. Optionally, when the speed is below the second threshold, the controller may de-fuel the engine <NUM> in step <NUM>.

The engine <NUM> can be kept at a low idle speed in step <NUM> so that power is provided to conventional power steering and power brake systems even when the engine <NUM> is not providing motive energy to the gearbox <NUM>. Alternatively, the engine <NUM> can be completely de-fueled and powered off to further increase the fuel efficiency of the hybrid vehicle. However, in order to properly operate the hybrid vehicle with the engine <NUM> powered off, the conventional mechanically driven power steering and power brake systems are replaced with electrically driven power steering and power brake systems. Use of the electrically driven systems increase cost to the hybrid vehicle.

Referring to <FIG> an alternative example, not falling under the scope of the claims, is shown in which the automatic transmission, i.e., torque converter <NUM> and gearbox <NUM>, of <FIG> are replaced with a semi-automatic type manual transmission represented by gearbox <NUM>. The drive train system of this example includes an internal combustion engine <NUM> ("engine"), coupled to an integrated starter/generator/motor ("ISGM") <NUM> by way of a clutch assembly <NUM>. The clutch assembly <NUM> allows the ISGM <NUM> to be disengaged from the engine <NUM> during decelerations and full stops. The clutch assembly <NUM> is controlled by a clutch control assembly <NUM>. The clutch control assembly <NUM> is, for example, a hydraulic solenoid controlling engagement and disengagement of the clutch assembly <NUM> based on the state of the hybrid vehicle. As noted above, the clutch control assembly <NUM> can be pneumatic or mechanical. In the example, the clutch assembly <NUM> disengages the engine <NUM> from the ISGM <NUM> during decelerations.

Additionally, the ISGM <NUM> is coupled to the gearbox <NUM>. The gearbox <NUM> is coupled to drive wheels by way of a drive shaft (not shown).

Moreover, the ISGM <NUM> operates as a starter engine launch, as a generator during vehicle deceleration, and as a traction motor during acceleration and cruising. As a generator, the ISGM <NUM> generates electrical energy during the deceleration process by recuperating the mechanical energy of the vehicle. The ISGM <NUM> is electrically coupled to an energy storage system <NUM>, which may be batteries or ultra capacitors. Co-pending application entitled a Parallel Hybrid Electric Vehicle Power Management System and Adaptive Power Management Method and Program Therefor assigned to BAE Systems Controls, Inc. , which is incorporated by reference describes a system and method for charging the energy storage system <NUM> only using energy from regenerative braking. The energy storage system <NUM> receives electrical energy from the ISGM <NUM> operating as a generator during deceleration. The energy storage system <NUM> provides electrical energy to the ISGM <NUM> when the ISGM <NUM> is operating as a starter motor and/or traction motor. Torque from the engine <NUM> and ISGM <NUM> is mechanically coupled to the gearbox <NUM>.

Additionally, an engine control unit <NUM> provides control signals for actuating fuel injectors, fuel pumps and other engine components. Additionally, the engine control unit <NUM> monitors engine-operating conditions, and may be configured to control operation of the clutch assembly <NUM> and ISGM <NUM> based on sensor signals from accelerator and brake pedals in the vehicle cabin. Moreover, the clutch control assembly <NUM> receives control signals from the engine control unit <NUM>.

The vehicle launch process for the additional example shown in <FIG> operates essentially as described above with reference to <FIG>. However, during the initial launch, prior to step <NUM>, the clutch assembly <NUM> can be engaged, disengaged, or in a slip state where the clutch assembly <NUM> allows partial transfer of load to the engine <NUM>.

<FIG> and <FIG> illustrate flow charts of exemplary process for deceleration for the exemplary system depicted in <FIG>. In <FIG>, at step <NUM> a sensor detect negative system torque command. If there is a negative system torque command, the process proceeds to step <NUM>. In step <NUM>, the ISGM <NUM> and engine <NUM> are decoupled by disengagement of a clutch assembly <NUM> disposed between the ISGM <NUM> and the engine <NUM>.

It should be noted that, step <NUM> can be optionally executed depending on speed, battery state of charge, and throttle signal. Thus, step <NUM> is not required in all instances of the deceleration process of <FIG> or <FIG>.

The regenerative power is recouped to charge batteries or other energy storage devices (systems), e.g., energy storage system <NUM> in step <NUM>. During step <NUM>, speeds are monitored by a controller. If the speed(s) is/are above a preset threshold velocity, in <NUM>, the process determines if the system torque command is negative in step <NUM>. As long as the system torque command is negative and speed is above the threshold speed of step <NUM>, the process continues charging the batteries e.g., energy storage system <NUM>, as described in step <NUM>. However, if the speed is above the threshold speed of step <NUM> but system torque command is no longer negative, the process stops charging the batteries and returns to step <NUM>, awaiting the next negative system torque command.

Once the controller determines that the speed is below the threshold speed in step <NUM>, the process proceeds to step <NUM>. The clutch assembly <NUM> between the ISGM <NUM> and the engine <NUM> is engaged in step <NUM>. Even with the assembly clutch <NUM> engaged, regenerative power is recouped to charge the energy storage system <NUM>. The charging will be at a reduced rate due to the engine <NUM> acting as a load. The energy storage system <NUM> can be charged until a state of charge reaches a target level. Alternatively, in step <NUM>, the engine <NUM> may remain disengaged from the ISGM <NUM>, and the engine <NUM> may be allowed to idle or even shut off.

At step <NUM>, a determination is made whether speed is below a second threshold. Optionally, when the speed is below the second threshold in step <NUM>, the controller may de-fuel the engine <NUM> in step <NUM>. At this point, the ISGM <NUM> operates as a torsional damper on the engine <NUM>, in step <NUM>, while the engine <NUM> moves through its first resonance frequency. Thus, the ISGM <NUM> decelerates the engine <NUM> using any remaining regenerative energy. Alternatively, the engine can be de-fueled at step <NUM> if the engine <NUM> remains decoupled throughout the deceleration process.

Several steps of the process or method illustrated in <FIG> are similar to <FIG> and will not be described in detail again, for example, steps <NUM>-<NUM> and steps <NUM>-<NUM>. Step <NUM> is not performed in the process illustrated in <FIG>. After de-fueling the engine at step <NUM>, a determination is made whether the speed is below a third threshold (at step <NUM>). Additionally, a determination as to whether the engine speed (RPMs) is below an engine speed threshold (also at step <NUM>). If both determinations are "YES", then the engine <NUM> is coupled to the ISGM <NUM> at step <NUM>.

Referring to <FIG> a second alternative example is shown in which the automatic transmission, i.e., torque converter <NUM> and gearbox <NUM>, of <FIG> are replaced with a traditional manual transmission represented by gearbox <NUM> and transmission clutch <NUM>, which couples the ISGM <NUM> to the gearbox <NUM>. The drive train system of this example includes an internal combustion engine <NUM> (the "engine"), coupled to the ISGM <NUM> by way of a clutch assembly <NUM>. The clutch assembly <NUM> allows the ISGM <NUM> to be disengaged from the engine <NUM> during decelerations and full stops. The clutch assembly <NUM> is controlled by a clutch control assembly <NUM>. The clutch control assembly <NUM> is, for example, a hydraulic solenoid controlling engagement and disengagement of the clutch assembly <NUM> based on the state of the hybrid vehicle. Additionally, the clutch control assembly <NUM> can be pneumatic or mechanical. In the present example, the clutch assembly <NUM> disengages the engine <NUM> from the ISGM <NUM> during decelerations.

Moreover, the ISGM <NUM> operates as a starter engine launch, as a generator during vehicle deceleration, and as a traction motor during acceleration and cruising. As a generator, the ISGM <NUM> generates electrical energy during the deceleration process by recuperating the mechanical energy of the vehicle. The ISGM <NUM> is electrically coupled to an energy storage system <NUM>, which may be batteries or ultra capacitor. Co-pending application entitled a Parallel Hybrid Electric Vehicle Power Management System and Adaptive Power Management Method and Program Therefor assigned to BAE Systems Controls, Inc. , which is incorporated by reference describes a system and method for charging the energy storage system <NUM> only using energy from regenerative braking. The energy storage system <NUM> receives electrical energy from the ISGM <NUM> operating as a generator during deceleration. The energy storage system <NUM> provides electrical energy to the ISGM <NUM> when the ISGM <NUM> is operating as a starter motor and/or traction motor. Torque from the engine <NUM> and ISGM <NUM> is mechanically coupled to the transmission clutch <NUM>.

The vehicle launch process for the second alterlnative example shown in <FIG> operates essentially as described above with reference to <FIG>. However, during the initial launch, prior to step <NUM>, the clutch assembly <NUM> can be engaged, disengaged, or in a slip state where the clutch assembly <NUM> allows partial transfer of load to the engine <NUM>.

<FIG> and <FIG> illustrate two exemplary deceleration processes for the second alternative example. As depicted in <FIG> or <FIG>, at step <NUM> sensors detect a negative system torque command. If the system torque command is negative, the process proceeds to step <NUM>. In step <NUM>, the ISGM <NUM> and engine <NUM> are decoupled by disengagement of the clutch assembly <NUM> disposed between the ISGM <NUM> and the engine <NUM>.

The process continues to step <NUM> where the transmission clutch <NUM> is engaged between the ISGM <NUM> and the gearbox <NUM>, if the transmission clutch <NUM> is not already engaged. The regenerative power is recouped to charge batteries or other energy storage devices (systems), e.g., energy storage system <NUM> in step <NUM>. During step <NUM>, speeds are monitored by a controller. If a speed is above a preset threshold speed, in <NUM>, the process determines if the system torque command is negative in step <NUM>. As long as the system torque command is negative and the speed is above the threshold speed of step <NUM>, the process continues charging the batteries e.g., energy storage system <NUM>, as described in step <NUM>. However, if the speed is above the threshold speed of step <NUM> but system torque command is not negative, the process stops charging the batteries and returns to step <NUM>, awaiting the next detection of negative system torque command.

Once the controller determines that the speed is below the threshold speed in step <NUM>, the process proceeds to step <NUM>. The transmission clutch <NUM> is disengaged in step <NUM>. Alternatively, in step <NUM>, the ISGM <NUM> may remain engaged to the gearbox <NUM>. The clutch assembly <NUM> between the ISGM <NUM> and the engine <NUM> is engaged in step <NUM>. Alternatively, in step <NUM>, the engine <NUM> may remain disengaged from the ISGM <NUM>, and the engine <NUM> may be allowed to idle or even shut off. For example, <FIG> illustrates the process without coupling the ISGM <NUM> and engine <NUM> via clutch assembly <NUM> at step <NUM>. The controller maintains the ISGM <NUM> at a threshold RPM in step <NUM> until the speed is detected below a second threshold in step <NUM>.

Optionally, when the speed is below the second threshold in step <NUM>, the controller may de-fuel the engine <NUM> in step <NUM>. At this point, the ISGM <NUM> operates as a torsional damper on the engine <NUM>, in step <NUM>, while the engine <NUM> moves through its first resonance frequency. Thus, the ISGM <NUM> decelerates the engine <NUM>. Alternatively, the engine <NUM> can be de-fueled at step <NUM> if the engine <NUM> remains decoupled throughout the deceleration process.

The process illustrated in <FIG> is similar to the process illustrated in <FIG> except that steps <NUM> and <NUM> are omitted. The engine <NUM> and the ISGM <NUM> are not coupled in <FIG>.

The control functions of the present invention may be performed by a single engine control unit or by multiple controllers performing discrete portions of the control functions described above.

Claim 1:
A method of controlling the operation of a parallel hybrid electric vehicle during vehicle start, comprising an engine (<NUM>), a first clutch (<NUM>), an integrated starter/generator/motor (ISGM) (<NUM>) coupled to said engine (<NUM>) in accordance with the operating state of said first clutch (<NUM>), a combination of a torque converter (<NUM>) and a second clutch (<NUM>) connected in parallel therewith, said combination being mechanically coupled between said ISGM (<NUM>) and an output drive shaft that propels the vehicle, and an energy storage device electrically coupled to said ISGM (<NUM>), comprising:
transmitting electrical energy from said energy storage device to said ISGM (<NUM>), wherein said ISGM (<NUM>) functions as a motor having an output torque;
transmitting a portion of the output torque from said ISGM (<NUM>) through said torque converter (<NUM>) to the output drive shaft to launch the vehicle; and
operating said first clutch (<NUM>) to enable a remaining portion of the output torque of said ISGM (<NUM>) to be coupled to said engine (<NUM>) to enable the starting of said engine (<NUM>),
wherein during the transmitting of electrical energy, said ISGM (<NUM>) is accelerated to a predefined percentage above an idle speed of said engine (<NUM>).