Intake control apparatus for an engine and method

Abstract

An engine intake control apparatus for an engine that comprises at least one combustion chamber operatively connected to an intake port and an intake valve associated with each intake port, wherein the intake valve is adapted to open and close the intake port is disclosed herein. The intake control apparatus comprises a variable valve operating mechanism and a controller. The variable valve operating mechanism is configured and arranged to selectively change a valve closing timing and a valve lift amount of the intake valve. The controller is configured and arranged to control the variable valve operating mechanism when the engine is in a low load condition. The valve closing timing is determined such that an actual compression ratio of the engine is reduced relative to the actual compression ratio when the engine is operating in a high load condition. The valve lift amount is smaller when the engine is in the low load condition relative to the valve lift amount when the engine is in the high load condition. A method for controller an engine is also disclosed.

Description

BRIEF DESCRIPTION OF DRAWINGS

Other features and advantages of the present disclosure will be apparent from the ensuing description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a variable valve operating mechanism.

FIGS. 2A-2B are schematic cross-sectional views illustrating the operation of the variable valve operating mechanism of FIG. 1.

FIG. 3 is a chart illustrating the valve lifting characteristics of intake valves.

FIGS. 4A is a PV (in-cylinder gas pressure/cylinder volume) diagram illustrating the drop in the actual compression ratio associated with the reduction of pumping loss by regulating valve closing timing, and its effects.

FIGS. 4B and 4C illustrate different valve closing times.

FIG. 5A is a partial cross section view of a prior art piston.

FIG. 5B is a partial cross section view of an adiathermic piston.

FIGS. 6A-6B are schematic perspective views of an engine illustrating cooling loss recovery through intake control using a variable valve operating mechanism.

FIG. 7A-7C are schematic cross sectional views of an engine illustrating cooling loss recovery through intake control using a variable valve operating mechanism.

FIG. 8 is a flow chart explaining opening/closing control of intake valves using a variable valve operating mechanism.

FIG. 9A is a schematic perspective view of a prior art piston.

FIG. 9B is a schematic perspective view of a piston according to a second embodiment wherein a portion of a cylinder liner in a second embodiment is cut away.

Claims

1. An engine intake control apparatus for an engine that comprises at least one combustion chamber operatively connected to an intake port and an intake valve associated with each intake port, wherein the intake valve is adapted to open and close the intake port, the intake control apparatus comprising: variable valve operating mechanism configured and arranged to selectively change a valve closing timing and a valve lift amount of the intake valve; andcontroller configured and arranged to control the variable valve operating mechanism when the engine is in a low load condition,wherein the valve closing timing is determined such that an actual compression ratio of the engine is reduced relative to the actual compression ratio when the engine is operating in a high load condition, andwherein the valve lift amount is smaller when the engine is in the low load condition relative to the valve lift amount when the engine is in the high load condition.

2. The intake control apparatus as described in claim 1, wherein at least a portion of the wall surfaces of the combustion chamber is made of a heat insulating material.

3. The engine intake control apparatus as described in claim 2, wherein the heat insulating material is a ceramic material.

4. The engine intake control apparatus as described in claim 2, wherein the heat insulating material is coated on a cylinder liner of the engine.

5. The engine intake control apparatus as described in claim 1, wherein a cylinder wall that forms part of the combustion chamber has a lower thermal conductivity than a portion of the cylinder wall at a bottom dead center side.

6. The engine intake control apparatus as described in claim 5, wherein a top dead center side of the cylinder wall is constructed of a first material, and the bottom dead center side of the cylinder wall is constructed of a second material, and wherein the first material is a heat insulating material and the second material is a conductive material.

7. The engine intake control apparatus as described in claim 5, wherein a first cylinder liner forms the top dead center side of the cylinder wall and is constructed of the first material and a second cylinder liner forms the bottom dead center side of the cylinder wall and is constructed of the second material.

8. The engine intake control apparatus as described in claim 1, wherein the valve lift amount of the intake valves is reduced sufficiently to let an intake air flow into the combustion chamber along the wall surfaces of the combustion chamber when the engine is in the low load condition.

9. The engine intake control apparatus as described in claim 1, wherein the valve closing of the intake valves is set to occur prior to the bottom dead center of an intake stroke when the engine is operating in the low load condition, thereby reducing the actual compression ratio.

10. The engine intake control apparatus as described in claim 1, wherein the variable valve operating mechanism comprises a variable lift mechanism that selectively varies the valve lift amount of the intake valves, and a variable valve closing timing mechanism that selectively varies the valve closing timing of the intake valves.

11. The engine intake control apparatus as described in claim 1, wherein when the engine is in a low load condition, the valve lift amount of the intake valve is increased when a temperature of a combustion chamber wall exceeds a predetermined temperature as compared to when the temperature of the combustion chamber wall is lower than the predetermined temperature.

12. The engine intake control apparatus as described in claim 1, wherein when the engine is in the high load condition, the controller actuates the variable valve operating mechanism to increase the valve lift amount of the intake valves so as to alleviate intake air flow from flowing along the wall surfaces of the combustion chamber.

13. A method for controlling an engine that comprises at least one combustion chamber that is operatively connected to an intake port through an intake valve that selectively and variably opens and closes the intake port, the method comprising: detecting an engine operational condition to determine whether the engine is in a low load condition; andactuating an intake valve with a valve closing timing and a valve lift amount when the engine is in the low load condition;wherein the valve closing timing is determined such that an actual compression ratio of the engine is reduced relative to the actual compression ratio of the engine with the engine is in a high load condition; andwherein the valve lift amount is smaller when the engine is in a low load condition relative to the valve lift amount when the engine is in the high load condition.

14. The method for controlling the engine as described in claim 13, wherein when a temperature of a combustion chamber wall exceeds a predetermined temperature, the valve lift amount is increased relative to the valve lift amount when the temperature of the combustion chamber wall is lower than the predetermined temperature.

15. An intake control apparatus for an engine that comprises at least one combustion chamber operatively connected to an intake port and an intake valve associated with each intake port, wherein the intake valve is adapted to open and close the intake port, the intake control apparatus comprising: variable valve operating means for selectively changing a valve closing timing and a valve lift amount of the intake valve; andcontrol means for controlling the variable valve operating means when the engine is in a low load condition,wherein the valve closing timing is determined such that an actual compression ratio of the engine is reduced relative to the actual compression ratio when the engine is operating in a high load condition, andwherein the valve lift amount is smaller when the engine is in a low load condition relative to the valve lift amount when the engine is in the high load condition.