Exhaust compound internal combustion engine with controlled expansion

Patent metadata

Field	Value
Publication number	US-9897000-B2
Application number	US-201514736030-A
Country	US
Kind code	B2
Filing date	Jun 10, 2015
Priority date	Nov 2, 2012
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

A piston compound internal combustion engine is disclosed with an expander piston deactivation feature. A piston internal combustion engine is compounded with a secondary expander piston, where the expander piston extracts energy from the exhaust gases being expelled from the primary power pistons. The secondary expander piston can be deactivated and immobilized, or its stroke can be reduced, under low load conditions in order to reduce parasitic losses and over-expansion. Two mechanizations are disclosed for the secondary expander piston's coupling with the power pistons and crankshaft. Control strategies for activation and deactivation of the secondary expander piston are also disclosed. In addition, six-cylinder engine configurations are defined by replicating groups of two power pistons and one expander piston.

First claim

What is claimed is:

1. A piston compound internal combustion engine with expander de-stroking, said engine comprising:
a rotating crankshaft;
two or more groups of three pistons, where each group includes two power pistons coupled to the rotating crankshaft, said power pistons providing engine power as a result of a primary expansion of combustion gases from ignition of a fuel-air mixture, and a secondary expander piston, said expander piston providing additional engine power as a result of a secondary expansion of the combustion gases after the primary expansion by the power pistons;
a de-stroking mechanism for reducing or eliminating a stroke of the expander pistons under certain engine conditions; and
a controller configured to measure engine conditions, establish a desired stroke of the expander pistons based on the engine conditions, and communicate the desired stroke to the de-stroking mechanism.

2. The engine of claim 1 wherein the de-stroking mechanism allows the stroke of the expander pistons to be continuously adjustable from a minimum stroke value to a full stroke value.

3. The engine of claim 2 wherein the de-stroking mechanism is a variable stroke mechanism comprising a stroke adjustment link which adjustably couples the stroke of the expander pistons to a stroke of the power pistons.

4. The engine of claim 1 wherein the de-stroking mechanism allows the expander pistons to be fully activated or fully deactivated.

5. The engine of claim 4 wherein the de-stroking mechanism is a clutch which, when engaged, couples rotation of the crankshaft to rotation of a secondary crankshaft, where the secondary crankshaft is coupled to the expander pistons.

6. The engine of claim 1 wherein the controller deactivates the expander pistons under low-load engine conditions.

7. The engine of claim 6 wherein the controller establishes the desired stroke of the expander piston as zero when an exhaust system temperature is below a temperature threshold value or an engine torque is below a torque threshold value, and the controller establishes the desired stroke of the expander piston as full stroke when the exhaust system temperature is above the temperature threshold value and the engine torque is above the torque threshold value.

8. The engine of claim 6 wherein the controller includes a hysteresis effect when deactivating or reactivating the expander piston.

9. The engine of claim 1 wherein the two or more groups of three pistons includes six pistons in a straight-six configuration, where the four power pistons have a common orientation and operate along centerlines which are coplanar, and the two expander pistons have a common orientation and operate along centerlines which are coplanar.

10. The engine of claim 1 wherein the two or more groups of three pistons includes six pistons in a V-six or a horizontally opposed configuration, with two power pistons and one expander piston in a first cylinder bank and two power pistons and one expander piston in a second cylinder bank.

11. The engine of claim 1 wherein the engine is used to power an automobile.

12. A supercharged piston compound internal combustion engine with expander de-stroking, said engine comprising:
a rotating crankshaft;
two or more groups of three pistons, where each group includes two power pistons coupled to the rotating crankshaft, said power pistons providing engine power for an automobile as a result of a primary expansion of combustion gases from ignition of a fuel-air mixture, and a secondary expander piston, said expander piston providing additional engine power as a result of a secondary expansion of the combustion gases after the primary expansion by the power pistons;
a de-stroking mechanism which couples motion of the expander pistons to motion of the power pistons and which provides for reducing or eliminating a stroke of the expander pistons under certain engine conditions, where the de-stroking mechanism is a variable stroke mechanism comprising a stroke adjustment link which adjustably couples the stroke of the expander pistons to a stroke of the power pistons; and
a controller configured to measure engine conditions, establish a desired stroke of the expander pistons based on the engine conditions, and communicate the desired stroke to the de-stroking mechanism.

13. The engine of claim 12 wherein the variable stroke mechanism allows the stroke of the expander pistons to be continuously adjustable from a minimum stroke value to a full stroke value.

14. The engine of claim 12 wherein the controller uses exhaust system temperature and engine load data to establish the desired stroke of the expander pistons, where the desired stroke of the expander pistons is reduced for lower values of exhaust system temperature and engine load, and the controller further includes a hysteresis effect when deactivating or reactivating the expander pistons.

15. The engine of claim 12 wherein the two or more groups of three pistons includes six pistons in a straight-six configuration, where the four power pistons have a common orientation and operate along centerlines which are coplanar, and the two expander pistons have a common orientation and operate along centerlines which are coplanar.

16. The engine of claim 12 wherein the two or more groups of three pistons includes six pistons in a V-six or a horizontally opposed configuration, with two power pistons and one expander piston in a first cylinder bank and two power pistons and one expander piston in a second cylinder bank.

17. A method for controlling a piston compound internal combustion engine with expander piston de-stroking, said method comprising:
measuring an exhaust system temperature;
determining an engine load;
establishing a desired stroke of the expander piston based on the exhaust system temperature and the engine load, including setting the desired stroke equal to a minimum value when the exhaust system temperature is below a temperature threshold and, if the exhaust system temperature is at or above the temperature threshold, using the engine load to determine the desired stroke; and
controlling a de-stroking mechanism in the engine to achieve the desired stroke of the expander piston.

18. The method of claim 17 wherein the de-stroking mechanism is a variable stroke mechanism comprising a stroke adjustment link which adjustably couples a stroke of the expander piston to a stroke of power pistons in the engine.

19. The method of claim 18 wherein using the engine load to determine the desired stroke includes setting the desired stroke equal to a minimum value when the engine load is less than or equal to a first load threshold, setting the desired stroke equal to full-stroke when the engine load is greater than or equal to a second load threshold, and using a ramp function to determine the desired stroke when the engine load is between the first load threshold and the second load threshold.

20. The method of claim 17 wherein the de-stroking mechanism is a clutch which, when engaged, couples rotation of an engine crankshaft to rotation of a secondary crankshaft which is coupled to the expander piston, and where using the engine load to determine the desired stroke includes setting the desired stroke equal to zero when the engine load is less than or equal to a load threshold and setting the desired stroke equal to full-stroke when the engine load is greater than a load threshold.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Durrett Russell P
• Najt Paul M
• Andruskiewicz Peter P

Classifications

• F02B41/08

  Two-stroke compound engines · CPC title

• F02B75/04 Primary

  Engines with variable distances between pistons at top dead-centre positions and cylinder heads · CPC title