Systems and methods for providing compression release with continuous variable valve lift

Patent metadata

Field	Value
Publication number	US-11473459-B2
Application number	US-202016922638-A
Country	US
Kind code	B2
Filing date	Jul 7, 2020
Priority date	Jul 7, 2020
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

Methods and systems are provided for providing compression release during a stop/start event in an engine. In one example, a method includes: responsive to a request for a stop/start event in an engine with a continuously variable valve lift (CVVL) system including a compression release hydraulic valve actuator coupled to a valve of a first cylinder, determining a desired stop position of the engine; and prior to restarting the engine during the stop/start event, adjusting the compression release hydraulic valve actuator to open the valve during a compression stroke of the first cylinder. In this way, an amount of torque used to restart the engine may be reduced.

First claim

The invention claimed is:

1. A method, comprising:
responsive to a request for a stop/start event in an engine with a continuously variable valve lift (CVVL) system including a compression release hydraulic valve actuator coupled to a valve of a first cylinder, determining a desired stop position of the engine; and
prior to restarting the engine during the stop/start event, adjusting the compression release hydraulic valve actuator to open the valve before or during a compression stroke of the first cylinder.

2. The method of claim 1 , further comprising:
responsive to a request to restart the engine during the stop/start event, turning a crankshaft of the engine via an electric machine; and
responsive to a rotational speed of the crankshaft exceeding a threshold rotational speed, adjusting the compression release hydraulic valve actuator to not open the valve during the compression stroke of the first cylinder and resuming combustion in the engine.

3. The method of claim 1 , wherein the desired stop position is an engine position in which the first cylinder is before or at a beginning of the compression stroke.

4. The method of claim 1 , wherein the request for the stop/start event is responsive to an amount of driver-demanded torque decreasing below a threshold torque demand while a battery state of charge (SOC) exceeds a threshold SOC.

5. The method of claim 1 , wherein the CVVL system includes additional compression release hydraulic valve actuators coupled to valves of additional cylinders of the engine, and the method further comprises:
prior to restarting the engine during the stop/start event, adjusting the additional compression release hydraulic valve actuators to open the valves of the additional cylinders before or during the compression stroke of the corresponding additional cylinder.

6. The method of claim 1 , wherein the compression release hydraulic valve actuator includes a cam with a first, high-lift lobe and a second, low-lift lobe, the low-lift lobe positioned to open the valve before or during the compression stroke of the first cylinder when a hydraulic pressure in the compression release hydraulic valve actuator exceeds a first threshold hydraulic pressure.

7. The method of claim 6 , wherein adjusting the compression release hydraulic valve actuator to open the valve before or during the compression stroke of the first cylinder includes fully closing a hydraulic control valve to block flow of a hydraulic fluid out of the compression release hydraulic valve actuator.

8. The method of claim 1 , wherein the compression release hydraulic valve actuator includes an accumulator fluidically coupled to a hydraulic cylinder of the valve via an accumulator line having an accumulator valve disposed therein, and wherein adjusting the compression release hydraulic valve actuator to open the valve before or during the compression stroke of the first cylinder includes increasing hydraulic pressure in the hydraulic cylinder of the valve by opening the accumulator valve.

9. The method of claim 1 , wherein the compression release hydraulic valve actuator includes a lift-locking valve fluidically coupled between a hydraulic control valve disposed in a hydraulic supply line to the compression release hydraulic valve actuator and a hydraulic cylinder of the valve, and adjusting the compression release hydraulic valve actuator to open the valve before or during the compression stroke of the first cylinder includes fully closing the lift-locking valve while the valve is open.

10. A method, comprising:
during an engine auto-stop, adjusting a position of a valve of a compression release hydraulic valve mechanism coupled to a cylinder valve of a first cylinder, the cylinder valve configured to open when a hydraulic pressure in the compression release hydraulic valve mechanism at a valve piston of the cylinder valve exceeds a threshold pressure; and
responsive to a request to restart the engine from the engine auto-stop, rotating a crankshaft of the engine via electric motor torque.

11. The method of claim 10 , wherein the compression release hydraulic valve mechanism includes a cam with a first, high-lift lobe positioned to open the cylinder valve during one of an intake stroke and an exhaust stroke and a second, low-lift lobe positioned to open the cylinder valve during at least the compression stroke of the first cylinder.

12. The method of claim 11 , wherein the valve is a hydraulic control valve, and adjusting the position of the valve of the compression release hydraulic valve mechanism includes fully closing the hydraulic control valve during at least the compression stroke of the first cylinder to maintain the hydraulic pressure at the valve piston above the threshold hydraulic pressure.

13. The method of claim 10 , further comprising:
prior to shutting down the engine for the engine auto-stop, determining a desired engine stop position in which a next cylinder to enter a compression stroke is the first cylinder; and stopping the engine at the desired engine stop position.

14. The method of claim 10 , wherein the valve is an accumulator valve positioned to control a flow of hydraulic fluid from a high pressure accumulator to the valve piston, and adjusting the position of the valve of the compression release hydraulic valve mechanism includes opening the accumulator valve to flow the hydraulic fluid from the high pressure accumulator to the valve piston to increase the hydraulic pressure above the threshold pressure.

15. A system, comprising:
an engine including a plurality of cylinders;
an electric machine coupled to a crankshaft of the engine;
a continuously variable valve lift (CVVL) system controlling intake and exhaust valves of each of the plurality of cylinders, including a first compression release hydraulic valve mechanism coupled to an intake valve of a first cylinder of the plurality of cylinders; and
a controller storing executable instructions in non-transitory memory that, when executed, cause the controller to:
while cranking the engine via torque from the electric machine to restart the engine from an auto-stop, open the intake valve of the first cylinder during at least a compression stroke of the first cylinder via the first compression release hydraulic valve mechanism.

16. The system of claim 15 , wherein the first compression release hydraulic valve mechanism includes a cam in contact with a cam piston and a valve piston in contact with the intake valve of the first cylinder, the cam piston positioned within a cam cylinder and the valve piston positioned within a valve cylinder, wherein the cam cylinder is fluidically coupled to the valve cylinder via an inter-cylinder line that is further fluidically coupled to a hydraulic supply line having a hydraulic control valve disposed therein.

17. The system of claim 16 , wherein the cam includes a first, higher-lift lobe positioned to contact the cam piston during an intake stroke of the first cylinder and a second, lower-lift valve positioned to contact the cam piston during the compression stroke of the first cylinder, and wherein to open the intake valve of the first cylinder during at least the compression stroke of the first cylinder via the first compression release hydraulic valve mechanism, the controller fully closes the hydraulic control valve during at least the compression stroke of the first cylinder.

18. The system of claim 16 , wherein the first compression release valve mechanism further includes an accumulator coupled to the inter-cylinder line via an accumulator line h

Assignees

• Ford Global Tech Llc

Inventors

• Vanderwege Brad Alan
• Shelby Michael

Classifications

• F02N11/0818

  Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode · CPC title

• F01L13/08 Primary

  for decompression, e.g. during starting; for changing compression ratio · CPC title

• F02D13/0226

  changing valve lift or valve lift and timing · CPC title

• F02N2200/061

  Battery state of charge [SOC] · CPC title

• F01L1/08 Primary

  Shape of cams · CPC title