GB2391325A

GB2391325A - Control system and method for a hybrid vehicle powertrain.

Info

Publication number: GB2391325A
Application number: GB0312524A
Authority: GB
Inventors: La Salle Stephen De; Michael Larsen; Rongjun Zhang; Mathew Breton; Shankar Raman
Original assignee: Visteon Global Technologies Inc
Current assignee: Visteon Global Technologies Inc
Priority date: 2002-07-12
Filing date: 2003-06-02
Publication date: 2004-02-04
Also published as: GB0312524D0; DE10331701A1; JP2004060648A; FR2842145A1

Abstract

The hybrid vehicle comprises an internal combustion engine 50, an electric motor/generator 40, and an energy storage device 42 such as a battery. The system further comprises a detector 43 for detecting the status of the battery and a vehicle deceleration detector 30, both of which are in communication with a controller 32 coupled to the I.C. engine and the electric motor/generator. The controller is adapted to determine deceleration corresponding to a torque braking quantity and the status of the battery. In response to the foregoing values, whereby the status of the battery is capable for regenerative braking, the controller controls the I.C. engine to modulate engine pumping losses so as to selectively control the mass of fresh air passing through the vehicle catalyst system. Alternatively, if the battery status is such that regenerative braking is not required, the generator is operated as a motor.

Description

239 1 325

- 1 CONTROL FOR ENGINE PUMPING LOSSES IN A HYBRID POWERTRAIN

BACKGROUND OF THE INVENTION

5 Field of the Invention

The present invention relates to a hybrid vehicle capable of being driven by the mechanical output from at least one of a internal combustion engine and a motor-generator, and in 10 particular for an apparatus and method for optimizing pumping losses in the internal combustion engine of a parallel hybrid vehicle and controlling a motor generator to provide braking torque. 15 Description of the Prior Art

Hybrid vehicles generally consist of series hybrid vehicles and parallel hybrid vehicles. Parallel hybrid vehicles usually include at least a internal combustion engine and a 20 motor-generator disposed along a vehicle powertrain such that the torques produced by each drive mean" are effectively summed together to drive the vehicle. A typical parallel hybrid vehicle is usually driven directly by the mechanical output of the internal combustion engine. However, when the 25 vehicle must be accelerated or decelerated at a rate that cannot be accomplished by the internal combustion engine alone or if the drive efficiency of the engine would be degraded if only the internal combustion engine were used, the motor-generator, which is mechanically connected to the 30 powertrain, operates as an electric motor (during acceleration) or as an electric generator (during deceleration) to compensate for the limitations or inefficiencies of the internal combustion engine.

- 2 - In a parallel hybrid vehicle the motor-generator can provide rapid acceleration or deceleration. Fluctuation in the internal combustion engine's speed can be suppressed, and 5 thus the parallel hybrid vehicle provides the advantages of reduced fuel consumption and reduced emissions. Since the consumption of the internal combustion engine can be regulated as desired, the parallel hybrid vehicle can be low-

noise, low-emision and low-fuel consumption vehicle. For 10 example, the parallel hybrid vehicle can be driven by only the motor-generator even if the internal combustion engine is stopped, since both the internal combustion engine and the motor-generator are mechanically connected to the driving wheels. A problem that arises in a typical parallel hybrid vehicle occurs when the vehicle has been cruising on the internal combustion engine and it begins to decelerate. Deceleration occurs when the drive demand produces a torque that is less 20 than the vehicle road load, and thus the vehicle experiences a negative adjustment to its momentum. Often, this lose in momentum in transmitted to the internal combustion engine such that an engine load is produced.

25 The engine load is composed of two parts: friction loaves and pumping losses. Friction losses result from the mechanical friction and resultant internal combustion loss of the moving parts within the engine. Pumping losses occur when the internal combustion engine acts as a pneumatic pump. In a 30 typical deceleration, the throttle will remain virtually closed and the engine will continue to pump air from the intake manifold, compress the air, and then pump the air out into the exhaust manifold. The energy expended by the engine

pumping in this manner is not intended to drive the vehicle, and an such, is only useful insofar as it provides a certain feel of deceleration to a vehicle operator.

5 The change in vehicle momentum, however, is also a source of potential energy. In a parallel hybrid configuration, the change in vehicle momentum corresponding to deceleration might be converted into electrical energy by the motor-

generator operating in a generation mode, a process commonly 10 known as regenerative braking.

Regenerative braking is utilized to convert the kinetic energy of the hybrid vehicle into electrical potential energy for powering the motorgenerator. In theory, regenerative 15 braking should significantly reduce the necessity of the internal combustion engine. However, this benefit of a parallel hybrid vehicle is only realized if the internal combustion engine does not squander the vehicle's change in momentum, and hence the vehicle's kinetic energy, through 20 friction and pumping losses. Consequently, many variations of hybrid powertrain" have been developed to maximize the benefits of regenerative braking and minimize the inefficiencies of the internal combustion engine.

25 Several solutions to thin problem are disclosed in the prior art. For example, by decoupling the internal combustion engine from the powertrain during deceleration, the motor-

generator may readily convert the vehicle's kinetic energy into electrical energy. This approach is problematic in that 30 re-coupling the internal combustion engine is a complicated and tedious process and is prone to result in torque disturbances. Generally, a selectively coupled internal

- 4 - ( combustion engine requires a clutch mechanism, which increaser the cost and weight of the hybrid vehicle.

Alternatively, one may attempt to reduce friction losses by 5 operating the internal combustion engine at the lowest possible speed. Although this approach provides advantage", it is not optimal for a parallel hybrid vehicle because it depends too heavily on the type of transmission. Moreover, the process of regulating engine speed is complicated and may 10 result in undesirable surges in both vehicle acceleration and deceleration. Therefore, there is a need in the art for a parallel hybrid vehicle having a powertrain controllable for modulating 15 internal combustion engine pumping losses wherein said motor-

generator is controllable for regulating torque braking and thereby creating a deceleration feel consistent with that of an internal combustion engine.

20 For gasoline engines and traditional three-way catalyst aftertreatment system, it is undesirable to purge the catalyst system with fresh air - an may happen if the engine is allowed to rotate with the throttle plate open. This will result in an excess of oxygen in the catalyst substrate. When 25 engine combustion is eventually reinstated, the excess of oxygen will result in a breakthrough of emissions that are not being adequately converted in the catalyst.

Therefore, there is a need in the art for a method of 30 modulating engine pumping losses and selectively minimizing the mass of fresh air being pumped through the catalyst system.

- 5 - ( BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention includes a system and a method for modulating engine pumping losses and selectively 5 minimizing the mass of fresh air passed through the catalyst system. The present invention is intended for use in a hybrid vehicle powertrain and comprises a drive line including a transmission assembly coupled to drive at least one wheel of the vehicle, an internal combustion engine 10 coupled to the transmission assembly, a motor-generator also coupled to the transmission assembly, and an energy storage device having a storage capacity, such as a battery.

The present invention further comprises a storage capacity 15 detector coupled to the energy storage device and a vehicle deceleration detector detecting vehicle deceleration, both of which are in communication with a controller coupled to the internal combustion engine and to the motorgenerator. The controller is adapted to determine a deceleration mode via a 20 signal provided from the deceleration detector and to determine a torque braking quantity corresponding to the deceleration mode and further adapted to determine available storage capacity of the energy storage device.

25 The control modulates the engine pumping losses by determining if the storage capacity is less than an amount correlated to the torque braking quantity. If this condition is satisfied, the controller controls the internal combustion engine to modulate engine pumping losses and minimize the 30 mass of fresh air being pumped through the catalyst system, and the controller controls the motor-generator to generate electrical energy corresponding to the torque braking

( quantity and deliver the electrical energy to the energy storage device for storage.

Conversely, if the storage capacity is greater than the 5 amount correlated to the torque braking quantity, the controller controls the internal combustion engine to generate a braking torque corresponding to the torque braking quantity and the controller causes the motor-generator to not generate electrical energy in a no-generation mode.

The system of the present invention is adaptable for use in internal combustion engines having distinct valve control mechanisms. In a first embodiment, the controller is adapted for use with an internal combustion engine having an Exhaust 15 Gas Recirculation assembly. In a second embodiment, the controller is adapted for use with an internal combustion engine having a variable valve timing mechanism. In a third embodiment, the controller i" adapted for use with an internal combustion engine having a fully variable valve 20 timing mechanism.

Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the

25 preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 in a block diagram of a parallel hybrid vehicle in which the respective embodiments of the present invention may 5 be used.

Figure 2 is a split schematic diagram showing alternative embodiments of the internal combustion engine of the present invention. Figure 3 is a flowchart illustrating the operation of the controller the present invention.

Figure 4 is a group of flowcharts illustrating the alternate 15 subroutines that the controller may initiate in the present invention. DETAILED DESCRIPTION OF THE INVENTION

20 Figure 1 depicts a parallel hybrid vehicle system 8 embodying the present invention. The system 8 comprises an internal combustion engine 50 mechanically coupled to a drive train 18 by a clutch 20b. The drive train 18 is coupled to a transmission 16, which mechanically controls drive output 25 through a drive axle 14. A drive axle 14 drives a pair of drive wheels 10, wherein the drive wheels 10 may be decelerated by a set of mechanical brakes 12. A motor-

generator 40 is also mechanically coupled to the drive train 18 through a clutch 20a. The motor-generator 40 operates 30 selectively as an electric motor or as an electric generator As a motor, the motor-generator 40 produces a torque output such that the motor-generator 40 and the internal combustion engine 50 cooperatively contribute to the drive torque of the

- 8 - ( hybrid vehicle. The motor-generator 40 is electrically coupled to an energy storage device 42, which is coupled to a storage capacity detector 43 for detecting a storage capacity of the energy "forage device 42. The energy storage device 5 40 stores electrical potential energy generated by the motor-

generator 40 when the motor-generator 40 is in a generator mode as discussed further herein.

The internal combustion engine 50 is of the type having an 10 Exhaust Gas Recirculation (EGR) apparatus, a throttle 58, and a plurality of combustion chambers 70 having intake valves 60a and exhaust valves Gob. The internal combustion engine 50 is further coupled to EGR valve actuator 52, throttle angle control actuator 54, and one of an intake valve control 15 actuator 64 or an intake/exhaut valve control actuator 56.

A controller 32 controls the motor-generator 40 directly and further controls the internal combustion engine 50 through 20 its associated control actuators. The controller 32 may control the motor-generator 40 by directing its operation as a motor for electrically driving the hybrid vehicle, or by directing its operation as a generator for generating electrical energy from the kinetic energy of the hybrid 25 vehicle. Simultaneously, the controller 32 may control the internal combustion engine 50 by determining the position of the throttle 58 through the throttle angle control actuator 54. Controller 32 may also control the positioning of the intake 60a and exhaust 60b valves of the internal combustion 30 engine 50 through the intake/exhaust valve control actuator 56. In an alternate embodiment, the controller 32 may control only the intake valve 60a through the intake valve control actuator 64. Additionally, controller 32 determines

- 9 ( the ratio of exhaust gas to fresh air in the combustion chamber 70 by controlling the EGR valve actuator 52.

The controller 32 executes its control schemes based upon 5 inputs from a vehicle deceleration-speed detector 30 and the energy storage device 42. For example, if the controller 32 receives an input from the vehicle deceleration-speed detector 30 that the system 8 is in a deceleration mode, then the controller 32 will determine and transmit control signals 10 representing a required braking torque of the system 8. The internal combustion engine 50 may provide braking torque through mechanical means, while the motor-generator 40 may provide braking torque by operating in generator mode and electromechanically converting the kinetic energy of the 15 system 8 into electrical energy to charge the energy storage device 42.

The controller 32 also inquires as to the storage capacity of the energy storage device 42. Depending on the storage 20 capacity of the energy storage device 42, the controller 32 will utilize control signals to direct either the internal combustion engine 50, the motor-generator 40, or some combination thereof to deliver the optimal braking torque.

If the storage capacity is below a threshold limitation, then 25 the controller 32 will utilize only the motor-generator 40 to provide the braking torque. Conversely, if the storage capacity in above the threshold limitation, then the controller 32 will utilize only the internal combustion engine 50 and its associated control actuators for providing 30 the braking torque.

Figure 2 is a split schematic diagram of the internal combustion engine 50 and its associated elements in

( accordance with alternate embodiments of the present invention. The left portion of the internal combustion engine 50 is an internal combustion engine having the intake/exhaust valve timing control actuator 56 for implementing a process 5 known as fully variable intake/exhaust valve timing. The right portion of the internal combustion engine 50 is an internal combustion engine having an EGR tube 57, the intake valve control actuator 64, and their associated elements for implementing a pair of processes known as EGR and variable 10 valve timing (VVT) respectively.

The following elements are common to each portion of the internal combustion engine so of Figure 2. The internal combustion engine 50 includes an engine speed detector 51 for 15 detecting the speed of internal combustion engine 50.

Throttle 58 and throttle angle control actuator 54 are control the intake of fresh air into the intake manifold 59.

The intake valve 60a controls the entry of fresh air into the combustion chamber 70. The exhaust valve 60b controls the 20 exit of exhaust gas from the combustion chamber 70 into the exhaust manifold 61.

As depicted in the right portion of Figure 2, the flow of the exhaust gas is dictated by the EGR valve 62 and the EGR valve 25 control actuator 52. The EGR valve 62 generally will either direct the exhaust gas to the exhaust manifold 61, or will recirculate the exhaust gas via the EGR tube 57 towards the intake manifold 59 and the intake valve 60a for recombustion in the combustion chamber 70. The EGR tube 57 includes an 30 EGR pressure sensor 53.

As depicted in the left portion of Figure 2, the flow of exhaust gas in controlled by the intake 60a and exhaust 60b

( valves. The intake/exhaust valve timing control actuator 56 controls the combustion and recombustion process in the combustion chamber 70. This type of exhaust gas control is also known as internal EGR, because it is controlled only by 5 the intake 60a and exhaust 60b valves.

Figure 2 depicts an internal combustion engine 50 having two cylinders in a V-configuration. Alternate cylinder configurations of the internal combustion engine 50 include, lo but are not limited to, engines having between 4 and 12 cylinders, aligned in an in-line, V-configuration, or any other configuration known in the art. The scope of the present invention is not limited in application depending on the type of internal combustion engine employed. Rather, the 15 system and method of the present invention is equally applicable to internal combustion engines having different configurations. FIG. 3 is a detailed flow chart describing how the controller 20 32 implements a control strategy through the internal combustion engine 50 and the motor-generator 40. The system 8 of the present invention is engineered to provide optimal braking torque in a hybrid vehicle configuration.

Accordingly, in step SlOO the controller 32 determines 25 whether the vehicle is in a deceleration mode, which may include releasing the accelerator pedal or an adjustment to a cruise control system. The deceleration mode signal is determined by the vehicle deceleration detector 30 and communicated to the controller 32. If the hybrid vehicle is 30 in a deceleration mode, then step S100 is answered yes, and the controller proceeds to step S101, in which the controller determines a value corresponding to the amount of torque braking required. If the hybrid vehicle is not in a

- 12 ( deceleration mode, then step S100 is answered no, and the controller 32 does not implement a torque braking control strategy. 5 In step S102, the controller assesses the storage capacity of the energy storage device 42, which is determinative of which powertrain element will provide the required torque braking.

Depending on the value of the required torque braking, the controller 32 will decide whether the energy storage device 10 42 has sufficient storage capacity to absorb the electrical energy resulting from the torque braking. If the energy "forage device 42 has Sufficient storage capacity, then the controller 32 will switch the motor-generator 40 to generator mode as shown in step S104 such that it will generate 15 electrical energy and motor torque and engine pumping losses will be modulated to provide the required powertrain braking torque. If the energy storage device 42 does not have sufficient 20 storage capacity, then the controller 32 will switch the motor-generator 40 to a no- generation mode as shown in step S108. Thus, the storage capacity of the energy storage device 42 is the initial determinative factor in how the controller 32 schedules torque braking.

If the motor-generator 40 provides the braking torque, then the controller 32 proceeds to step S105, in which the fuel supply to the internal combustion engine 50 is terminated.

The controller 32 then switches the motor-generator 40 to the 30 generator mode in step S106 such that the motor-generator is prepared to provide the torque braking. In step S110, the controller 32 commands that pumping losses from the internal

- 13 combustion engine 50 must be modulated so am not to drag on the motor-generator 40.

The controller 32 proceeds to step 114, in which it must 5 select the type of valve control that it wishes to implement in order to modulate optimize engine pumping losses and optionally to minimize the mass of fresh air being pumped through the catalyst system. The type of valve control executed by controller 32 will depend upon the type of valve 10 mechanism employed by internal combustion engine 50.

In a first embodiment shown in the right portion of Figure 2, the internal combustion engine 50 has an intake valve 60a that is coupled to the intake manifold 59. The internal 15 combustion engine 50 also has an EGR valve 60 that is coupled to the EGR manifold 57, The internal combustion engine 50 also has a throttle 58 for restricting or permitting fresh airflow to the intake manifold 59.

20 According to the foregoing embodiment, the controller 32 will execute one of two strategies for modulating optimizing engine pumping losses and for selectively minimizing the mass of fresh air being pumped through the catalyst system.

First, the controller 32 may control the EGR valve 62 in 25 accordance with step S116. In doing so, the controller 32 will proceed to Subroutine 1 and execute the respective commands thereof.

Alternatively, the controller 32 may control the intake valve 30 60a in accordance with step S118. In doing so, the controller 32 will proceed to Subroutine 2 and execute the respective commands thereof.

In the second embodiment of the present invention depicted in the left portion of Figure 2, internal combustion engine 50 is equipped with a fully variable intake/exhaust valve timing actuator 56 coupled to both intake valve 60a and exhaust 5 valve 60b as shown in step 118. In this embodiment, the controller 32 proceeds from step S114 to step S120.

Thereafter, the controller 32 selects Subroutine 3 and executes the respective commands thereof.

10 Figure 4 is a series of flowcharts corresponding to Subroutines 1, 2, 3 and 4. In Subroutine 1, following step S116, the controller 32 initializes a sequence to minimize engine pumping losses S130. In doing 80, controller 32 opens the EGR valve S131 through the EGR valve actuator 52.

15 Utilizing the throttle angle control actuator 54, the controller 32 closes the throttle 58 in accordance with step S132. Following implementation of the preceding steps, the controller 32 proceeds to step S140, in which Subroutine 1 is terminated. In Subroutine 2, following step S118, the controller 32 initializes a different control strategy to minimize engine pumping losses S130. In step S133, the controller 32 minimizes the amount of air that can pass through the intake 25 valve 60a via the intake valve control actuator 64. In a preferred embodiment, the intake valve 60a may be fully closed by the intake valve control actuator 64. In step S134, the controller 32 closes the throttle 58 utilizing the throttle angle control actuator 54. During Subroutine 2, the 30 internal combustion engine 50 is pumping burnt gas to and from the exhaust manifold 61 and so minimizing the mass of fresh air being pumped through the catalyst system. Following

- 15 implementation of the preceding steps, the controller 32 proceeds to step S140, in which Subroutine 2 in terminated.

In Subroutine 3, following step S120, the controller 32 5 initializes a different control strategy to minimize engine pumping losses S130. The controller 32 firms determines whether the intake valve 60a may be fully closed in step S135. If the intake valve 60a may be fully cloned, the controller 32 proceeds to step S136. If the intake vale 60a 10 may not be fully cloned, the controller 32 proceeds to step S137. In step S136, the controller 32 actuates the fully variable intake/exhaust valve timing actuator 56 to close both the 15 intake valve 60a and the exhaust valve 60b simultaneously over the engine cycle. In step S138, the controller actuates the throttle angle control actuator 54 to clone the throttle 58. In this iteration of Subroutine 3, the internal combustion engine 50 is behaving as a pneumatic spring with 20 minimal pumping loaves. Because no gas is being pumped through the internal combustion engine 50, the catalyst is not being purged. The controller 32 then proceed" to step S140 corresponding to the conclusion of Subroutine 3.

25 Alternatively, in step S137, the fully intake/exhaust valve timing actuator 56 is used to schedule an intake valve 60a and exhaust valve 60b timing combination such that pumping losses are minimized. In step S139, the controller 32 actuates the throttle angle control actuator S4 to open the 30 throttle 58. During this iteration of Subroutine 3, the pumping losses are controlled as required and, additionally, the mass of fresh air being pumped through the catalyst

- 16 ( system is minimized. The controller 32 then proceeds to step S140 corresponding to the conclusion of Subroutine 3.

Upon the completion of the control scheme for either of the 5 preceding embodiments of the present invention, controller 32 proceeds to the end/return step of the flow chart of Figure 3.

Returning to step 102, if the energy storage device 42 has lo insufficient storage capacity to receive further electrical energy, then the controller 32 will proceed to step 108 in which the motor-generator 40 is switched to a no-generation mode. The controller 32 must then optimize engine pumping losses in accordance with step 110 utilizing only the 15 internal combustion engine 50.

In step 112, the controller 32 optimizes the performance of the internal combustion engine 50 by proceeding to Subroutine 4. In Subroutine 4, the controller minimizes the friction 20 losses incurred by the internal combustion engine 50 as shown in step S150. The controller 32 actuates the transmission actuator 17 to schedule the gears of the transmission 16 to control the speed of internal combustion engine 50 in accordance with step Sl51. Step S151 may be executed in 25 either embodiment of the present invention depicted in Figure 2. The controller 32 then proceeds to step S152 corresponding to the conclusion of Subroutine 4.

Upon completion of any of the alternate control schemes 30 related to the control of the internal combustion engine 50, the controller 32 proceeds to the end/return function of the flow chart of Figure 3.

( It should be apparent to those skilled in the art that the abovedecribed embodiments are merely illustrative of but a few of the many possible specific embodiments of the present invention. Numerous and various other arrangements can be s readily devised by those skilled in the art without departing from the scope of the invention as defined in the following claims. The disclosures in US patent application No. 10/193, 820, from

10 which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.

Claims

- 18 ( CLAIMS

1. A hybrid vehicle powertrain and control system comprising: 5 a drive line including a transmission assembly coupled to drive at least one wheel of the vehicle; an internal combustion engine, said internal combustion engine coupled to said transmission assembly; a motor- generator, maid motor-generator also coupled to 10 maid transmission assembly; an energy storage device having a storage capacity, said energy storage device being coupled to said motor-generator; a storage capacity detector coupled to said energy storage device; 15 a vehicle deceleration detector detecting vehicle deceleration; a controller coupled to said internal combustion engine and to "aid motor-generator, said controller also coupled to said energy storage device and to said vehicle deceleration 20 detector, said controller adapted to determine a deceleration mode via a signal provided from said deceleration detector and to determine a torque braking quantity corresponding to the deceleration mode, said controller also adapted to determine a storage capacity of said energy storage device 25 via said storage capacity detector, and whereby in response to said storage capacity being less than an amount correlated to said torque braking quantity, said controller controls said internal combustion engine to modulate engine pumping loosen and minimize a mass of fresh 30 air being pumped through a catalyst system, and said controller controls said motor-generator to generate electrical energy corresponding to said torque braking

- 19 quantity and deliver said electrical energy to said energy storage device for storage thereby) and whereby in response to said storage capacity being greater than said amount correlated to said torque braking 5 quantity, said controller controls said internal combustion engine to generate a braking torque corresponding to said torque braking quantity and said controller causes said motor-generator to not generate electrical energy in a no-

generation mode.

2. The system of claim 1 wherein said internal combustion engine includes a throttle and an exhaust gas recirculation (EGR) valve, said EGR valve adapted to be opened and "aid throttle adapted to be fully closed by said controller during 15 modulation of pumping losses.

3. The system of claim 2 wherein said internal combustion engine includes a manifold pressure sensor coupled to "aid controller.

4. The system of claim 3 wherein said controller controls said EGR valve in response to a manifold pressure signal received from said manifold pressure sensor.

2S

5. The system of claim 1 wherein said internal combustion engine includes a throttle and an intake valve control actuator coupled to an at least one intake valve, said throttle adapted to be opened and said at least one intake valve adapted to be closed by said controller during 30 modulation of pumping losses.

6. The system of claim l wherein said internal combustion engine includes a fully variable intake/exhaust valve timing

- 20 actuator having at least one intake valve and at leant one exhaust valve, said controller adapted to control maid at least one intake valve and said at least one exhaust valve during modulation of pumping losses much that said at least 5 one intake valve is open for a minimum duration and further such that said at least exhaust valve is closed for a maximum duration.

7. The system of claim 1 wherein said internal combustion lo engine includes a throttle and said controller is adapted to control a position of said throttle in response to a signal received by said controller from an engine speed detector and thereby provide braking torque corresponding to "aid torque braking quantity.

8. The system of claim 1 wherein said controller is coupled to said transmission assembly and is adapted to control said transmission assembly to regulate an engine speed of said internal combustion engine.

9. A method of modulating engine pumping losses and generating braking torque in a hybrid vehicle having an internal combustion engine and a motor-generator, said method comprising the steps of: 25 sensing deceleration of the hybrid vehicle; determining braking torque quantity based on the sensed deceleration; determining available storage capacity of an energy storage device coupled to the motor-generator; 30 comparing the available storage capacity of the energy storage device to the required braking torque quantity;

- 21 ( operating the motor-genera/Or in a generation mode when the available storage capacity of the energy storage device exceeds is less than the braking torque quantity; and modulating engine pumping losses in the internal 5 combustion engine when said motor-generator is operated in the generation mode.

10. The method of claim 9 further comprising the step of utilizing the internal combustion engine to provide braking 10 torque when the storage capacity of the energy storage device is less than greater than the braking torque quantity.

11. The method of claim 9 wherein the modulation step includes the step of closing a throttle of the internal 15 combustion engine and opening an exhaust gas recirculation (EGR) valve.

12. The step of claim 11 wherein the closing of the throttle and the opening of the ERG valve is simultaneous.

13. The method of claim 9 wherein the modulation step includes minimizing the internal combustion engine pumping losses. 25

14. The method of claim 9 wherein the modulation step includes optimizing the internal combustion engine pumping losses such that a braking torque feel is generated.

15. The method of claim 9 wherein the modulation step 30 further comprises the steps of opening a throttle and closing an intake valve of the internal combustion engine.

- 22 (

16. The method of claim 9 wherein the modulation step comprises closing an intake valve and an exhaust valve.

17. The method of claim 9 further comprising controlling a 5 plurality of gears for influencing a speed of said internal combustion engine such that friction losses from the internal combustion engine are minimized.

18. A method of modulating engine pumping losses and 10 generating braking torque in a hybrid vehicle having an internal combustion engine and a motor-generator substantially as herein described with reference to the drawings. 15

19. A hybrid vehicle powertrain and control system substantially as herein described with reference to or as shown in the drawings.