ENGINE TORQUE SMOOTHING

• US 20170342920A1
• Filed: 08/17/2017
• Published: 11/30/2017
• Est. Priority Date: 01/12/2015
• Status: Active Grant

• Current Assignee: Tula Technology, Incorporated
• Original Assignee: Tula Technology, Incorporated
• Inventors: PIRJABERI, Mohammad R., EISAZADEH-FAR, Kian, CARLSON, Steven E., REN, Ying, VAN ESS, Joel D.
• Granted Patent: US 10,196,995 B2
• Time in Patent Office: Days
• CPC Class Codes: B60K 2006/4825 Electric machine connected or connectable to gearbox input shaft
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2030/206 related or induced by the engine
• CPC Class Codes: F02D 2041/0012 with selective deactivation of cylinders
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2250/28 Control for reducing torsional vibrations, e.g. at acceleration
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: F02D 41/3058 the engine working with a variable number of cycles
• CPC Class Codes: F02D 41/307 to avoid torque shocks
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

Methods, devices, estimators, controllers and algorithms are described for estimating the torque profile of an engine and/or for controlling torque applied to a powertrain by one or more devices other than the engine itself to manage the net torque applied by the engine and other device(s) in manners that reduce undesirable NVH. The described approaches are particularly well suitable for use in hybrid vehicles in which the engine is operated in a skip fire or other dynamic firing level modulation manner—however they may be used in a variety of other circumstances as well. In some embodiments, the hybrid vehicle includes a motor/generator that applies the smoothing torque.

Claims

1. A method of control of a hybrid engine having an internal combustion engine and an auxiliary power source/sink, the method comprising:

determining a torque profile for the internal combustion engine;

determining whether the torque profile provides acceptable NVH;

when the torque profile is determined to provide acceptable NVH, operating the hybrid vehicle solely on the output of the internal combustion engine; and

when the torque profile is determined to provide unacceptable NVH, operating the hybrid vehicle on both the internal combustion engine and the auxiliary power source/sink, wherein the auxiliary power source/sink provides a smoothing torque to reduce NVH to an acceptable level.

2. A method as recited in claim 1 wherein the torque profile is determined by:

determining a normalized torque profile for each stroke of a cylinder in the engine, wherein the normalized torque profile is based on intake manifold pressure;

scaling the normalized torque profile to determine the cylinder torque; and

summing the cylinder torques for all cylinders in the engine to obtain an overall engine torque profile.

3. A method as recited in claim 1 wherein acceptable NVH limit corresponds to a maximum value of instantaneous torque in the torque profile.

4. A method as recited in claim 3 wherein the maximum value of instantaneous torque varies as a function of engine speed and transmission gear.

5. A method as recited in claim 1 wherein acceptable NVH limit corresponds to a weighed RMS vibration threshold.

6. A method as recited in claim 1 performed during skip fire operation of the engine.

7. A method as recited in claim 2 wherein the scaling is based on at least one of engine speed, engine firing history, cylinder firing history, spark timing, valve timing and valve lift.

8. A method comprising:

operating an engine, the engine being part of a powertrain;

estimating an engine generated torque or angular acceleration profile during operation of the engine;

based on the estimated torque or angular acceleration profile, identifying periods where an instantaneous torque or an instantaneous acceleration produced by the engine is expected to exceed a designated threshold, the designated threshold being an instantaneous torque threshold or an instantaneous acceleration threshold; and

applying a counteracting torque to a component of a powertrain from an energy source or sink during the identified periods such that an expected overall powertrain torque does not exceed the designated threshold.

9. A method as recited in claim 8 wherein the designated threshold varies as a function of engine speed and transmission gear.

10. A method as recited in claim 8 wherein the engine is operated in a skip fire manner at a current operational firing fraction having an associated firing opportunity period and each identified period corresponds to no more than the firing opportunity period.

11. A method as recited in claim 8 performed during operation of the engine in a skip fire or firing charge level modulation operational mode.

12. A method as recited in claim 8 wherein a substantial portion of energy drawn from the powertrain is returned to the powertrain within a period corresponding to a cyclic pattern associated with a current operational firing fraction.

13. A method as recited in claim 12 wherein the cyclic pattern is equal to a firing opportunity period associated with the current operational firing fraction times the denominator of the firing fraction.

14. A method of controlling an output of a powertrain that includes an engine configured to apply torque to the powertrain, the method comprising:

determining an expected engine torque profile associated with a sequence of one or more engine firing opportunities;

determining whether the expected engine torque profile predicts the occurrence of one or more torque spikes that exceed a designated torque spike threshold; and

for each predicted torque spike that exceeds the designated torque spike threshold, causing an opposing torque impulse to be applied to the powertrain, the opposing torque impulse being arranged to cause a net torque applied to the powertrain to not exceed the designated torque spike threshold.

15. A method as recited in claim 14 wherein the opposing torque is applied by a motor/generator.

16. A method as recited in claim 14 wherein the designated torque spike threshold varies as a function of engine speed and transmission gear.

17. A method as recited in claim 14 wherein the engine is operated in a skip fire manner at a current operational firing fraction having an associated firing opportunity period and each opposing torque impulse has a duration of less than the firing opportunity period.

18. A method as recited in claim 14 performed during operation of the engine in skip fire or firing charge level modulation operational mode.

19. A method of determining an operational firing fraction for delivering a desired engine output during operation of an engine, the method comprising:

(a) determining an estimated torque profile associated with operating the engine at a candidate firing fraction under current engine operating conditions to deliver the desired engine output;

(b) determining whether a smoothing torque would be required to meet NVH criteria during operation of the engine at the candidate firing fraction under the current engine operating conditions;

(c) determining a fuel efficiency associated with the candidate firing fraction, wherein when a smoothing torque is required;

(d) repeating steps (a)-(c) for each of a plurality of candidate firing fractions; and

(f) selecting one of the candidate firing fractions as the operational firing fraction based at least in part of the determined fuel efficiency of the candidate firing fractions, wherein the fuel efficiency implications of applying the smoothing torque are considered in the determination of the fuel efficiency of each candidate firing fraction that requires a smoothing torque.

20. A method as recited in claim 19 further comprising operating the engine at the selected candidate firing fraction.

21. A method as recited in claim 19 further comprising, when a smoothing torque is required for a particular candidate firing fraction, determining whether it would be practical to apply the smoothing torque, wherein when it would not be practical to apply the smoothing torque, the candidate firing fraction is rejected from consideration as the operational firing fraction.

23. A method as recited in claim 19 wherein:

each torque profile is compared to a torque limit associated with operating the engine under the current operating conditions to determine whether a smoothing torque is required for such torque profile; and

the smoothing torque is a counteracting torque that is expected to prevent torque delivered during operation at the associated candidate firing fraction from exceeding the torque limit

24. A method as recited in claim 19 wherein the method is performed during operation of the engine in a skip fire operational mode.

25. A method as recited in claim 19 wherein the method is performed during operation of the engine in a multi-charge level operational mode.

26. A method as recited in claim 19 wherein the candidate firing fraction selected as the operational firing fraction is the firing fraction candidate having the best fuel economy for delivering the desired engine output.

27. A method as recited in claim 23 wherein the smoothing torque is a filtered version of the torque profile.

22. A method as recited in 19 wherein each torque profile is based at least in part on intake manifold pressure, engine speed, camshaft phase and spark timing.