Compact EGR valve
A compact EGR valve uses a BLDC motor to drive a valve member between a closed position blocking flow of exhaust gases and a range of open positions where exhaust gasses flow through the valve. A drive mechanism includes a nut in a fixed position and a screw arranged to rotate within the nut so that rotation of the screw causes the screw to move axially relative to the nut. The screw is coupled to a valve member and the valve member moves axially and rotationally with the screw. The screw slides along the length of a motor shaft as the screw moves axially relative to the nut and motor. Rotation of the valve member within the valve chamber during axial movement aids in removal of deposits that may accumulate within the valve housing.
1. A valve comprising:
a valve housing defining a valve chamber with an inlet opening communicating with a cylindrical portion of the valve chamber and an outlet opening communicating with the cylindrical portion of the valve chamber;
a valve member within the cylindrical portion of the valve chamber, the valve member having a cylindrical side wall and an annular leading edge, the valve member moveable between a closed position where the cylindrical side wall covers the inlet opening and an open position where the cylindrical side wall does not cover the inlet opening;
a drive mechanism comprising:
a screw coupled to the valve member for axial and rotational movement with the valve member, said screw having a first thread and defining an axial bore;
a nut secured in a fixed position and having a second thread engaged with said first thread so that rotation of the screw moves the screw and the valve member axially relative to the nut while rotating the valve member within the cylindrical portion of the valve chamber;
a motor having a shaft received within the screw, said shaft having a constant non-round configuration along its length, said motor shaft received in the bore defined by the screw,
wherein rotation of the motor shaft rotates the screw relative to the nut to move the screw and valve member axially relative to the nut and motor, said screw sliding along the shaft as the valve member moves axially between the closed position and the open position, said valve member rotating with the motor shaft and screw during axial movement.
2. The valve of claim 1 , wherein said valve chamber includes a hemispherical portion extending from the cylindrical portion, said outlet opening located at least partially in said hemispherical portion.
3. The valve of claim 2 , wherein said valve chamber includes an inward projecting shoulder against which the annular leading edge of the valve member sits when the valve member is in the closed position.
4. The valve of claim 1 , wherein the cylindrical side wall of the valve member has an axial length greater than an axial length of the inlet opening.
5. The valve of claim 1 wherein the motor is a BLDC motor having a rotor and equipped with sensors that allow a control circuit to determined the rotational position of the rotor, from which rotational position the control circuit can determine an axial position of the valve member within the valve chamber.
6. The valve of claim 1 , wherein the motor shaft extends from both ends of a rotor of the motor, said valve comprising a torsion spring coupled to the motor shaft to rotate the motor shaft in a direction that moves the valve member to the closed position when power is removed from the motor.
7. The valve of claim 1 , wherein said valve member is cylindrical and a cylindrical insulator is arranged in a center region of the valve member.
8. The valve of claim 1 , wherein the inlet opening is laterally offset from a longitudinal axis of the cylindrical portion of the valve chamber.
9. The valve of claim 1 , wherein the inlet opening is rectangular and has long edges perpendicular to a longitudinal axis of the cylindrical portion of the valve chamber.
10. The valve of claim 9 , wherein the annular leading edge of the valve member is parallel to the long edges of the inlet opening and one short edge of the inlet opening is coincident with a side surface of the cylindrical portion of the valve chamber.
11. The valve of claim 8 , wherein the outlet is perpendicular to the longitudinal axis of the valve chamber and centered on the longitudinal axis of the valve chamber.
12. The valve of claim 1 , wherein the inlet opening is rectangular and the outlet opening is circular.
13. The valve of claim 1 , wherein the outlet is parallel with the longitudinal axis of the valve chamber and centered on the longitudinal axis of the valve chamber.
14. A method of regulating gas flow through the valve of claim 1 , said method comprising:
simultaneously rotating and moving the valve member in the cylindrical portion of the valve chamber between the closed position and a range of open positions wherein the cylindrical side wall uncovers at least a portion of the inlet opening in the cylindrical portion of the valve chamber;
wherein said annular leading edge removes deposits from an inside surface of the cylindrical portion of the valve chamber as the valve member rotates and moves axially from the range of open positions to the closed position.